abst[1]=' '; abst[2]=' '; abst[3]=' '; abst[4]=' '; abst[5]=' '; abst[6]=' '; abst[7]=' '; abst[8]=' '; abst[9]=' '; abst[10]=' '; abst[11]=' '; abst[12]=' '; abst[13]=' '; abst[14]=' '; abst[15]=' '; abst[16]=' '; abst[17]=' '; abst[18]=' '; abst[19]=' '; abst[20]=' '; abst[21]=' '; abst[22]=' '; abst[23]=' '; abst[24]=' '; abst[25]=' '; abst[26]=' '; abst[27]=' '; abst[28]=' '; abst[29]=' '; abst[30]=' '; abst[31]=' '; abst[32]=' '; abst[33]=' '; abst[34]=' '; abst[35]=' '; abst[36]=' '; abst[37]=' '; abst[38]=' '; abst[39]=' '; abst[40]=' '; abst[41]=' '; abst[42]=' '; abst[43]=' '; abst[44]=' '; abst[45]=' '; abst[46]=' '; abst[47]=' '; abst[48]=' '; abst[49]=' '; abst[50]=' '; abst[51]=' '; abst[52]=' '; abst[53]=' '; abst[54]=' '; abst[55]=' '; abst[56]=' '; abst[57]=' '; abst[58]=' '; abst[59]=' '; abst[60]='The concept of fractal has deserved a good deal of attention of many chemists and physicists in the last years, because its potential utilities in describing several real forms of condensed matter. The fractal geometry provides a formalism to study physicochemical processes, such as electrodeposition. Diffusion limited aggregation is a simple model, which is easily implemented on a computer, and that reproduces the natural shapes. Diffusion-controlled electrodeposition onto surfaces has been simulated in two dimensions. The deposits generated have a fractal structure manifested in terms of geometric scaling relationships which characterize the deposits. Electrochemically generated copper deposits were studied under various experimental conditions. The resulting structures were self-similar with fractal dimensions close to those obtained by numerical simulation. '; abst[61]=' '; abst[62]=' '; abst[63]=' '; abst[64]='The electrochemical reduction of mesoxalic acid on polycristalline platinum surfaces has been studied in acid medium. The reaction proceeds through the interaction with adsorbed hydrogen atoms. Malonic acid is proposed as final reaction product. '; abst[65]='The electroplating of zinc-nickel alloys from a chloride bath containing two brighteners (a phenolic derivative and an unsaturated aromatic compound) and a levelling agent (an aromatic carboxylate) has been studied under different plating conditions. The composition and morphology of the alloys depended on the concentration of all the additives and also on the temperature. As a general effect, these additives smooth the deposit and refine the grain size. By means of scanning electron microscopy, it was possible to classify the deposit morphologies according to the type and concentration of the additives. The resistance of the alloys to corrosion was studied by means of a neutral salt-spray test. '; abst[66]='The initial stages of the electrodeposition of nickel onto vitreous carbon from ethanol/water chloride solutions was studied in the presence and absence of some organic compounds. The influence of both additives and metal concentration was investigated by cyclic voltammetry, potential step experiments and differential capacity measurements. The role of the additives in the deposition process related to their adsorption, both on vitreous carbon and on vitreous carbon/nickel deposited electrodes, is also discussed. '; abst[67]='The magnetically induced splay Freedericksz transition is reexamined to look for pattern forming phenomena slightly above or below criticality. By using our traditional scheme of stochastic nematodynamic equations, situations are, respectively, found of transient and permanent predominance of transversal periodicities (wave numbers) along the direction perpendicular to the initial orientation within the sample. The relevance of these predictions in relation with recent observations in the electrically driven splay Freedericksz transition, and in general with other pattern forming phenomena, is stressed. '; abst[68]='Relaxational processes close to a hysteresis limit in the bistable iodate-arsenous chemical system are analyzed under the effect of external fluctuations affecting the flow rate parameter. A dynamical characterization is proposed based on the use of the first-passage-time-distribution (FPTD) technique. Exact numerical results are presented showing the different relaxational behavior above and below marginality. Supplementary, we analytically obtain characteristic scaling laws for the first two moments of the FPTD in terms of a unified description valid on both sides of the hysteresis limit. '; abst[69]='Relaxational processes in bistable potentials close to marginal conditions are studied under the combined effect of additive and multiplicative fluctuations. Characteristic time scales associated with the first-passage-time-distribution are analytically obtained. Multiplicative noise introduces large effects on the characteristic decay times, which is particularly significant when relaxations are mediated by fluctuations, i.e., below marginality and for small noise intensity. The relevance of our approach with respect to realistic chemical bistable systems experimentally operated under external noise influences is mentioned. '; abst[70]='The photochemical behaviour of 3-cyanovinyl-2-aryl(heteroaryl)indoles has been studied in dichloromethane under non-oxidative conditions. The photocyclization-oxidation reaction observed affording carbazoles proceeds, by contrast with the reversible conrotatory ring closure of stilbenes or vinylbiphenyls, through the formation of a substrate-dichloromethane radical ion pair obtained by photoinduced electron transfer from the vinyl compounds to dichloromethane. The phototransformation observed is not an exclusive property of vinylindoles, being chemically productive for the synthesis of heteroaromatic polycyclic systems. '; abst[71]='Experiments are reported on fractal copper electrodeposits. An electrochemical cell was designed in order to obtain a potentiostatic control on the quasi-two-dimensional electrodeposition process. The aim was focused on the analysis of the growth rate of the electrodeposited phase, in particular its dependence on the electrode potential and electrolyte concentration. '; abst[72]='Fractal geometry is finding many applications in materials science, where many structures posses a particular geometrical complexity. The patterns observed in corrosion phenomena display complex ordering in many length scales. The structure of the corrosion pit profiles can be described in terms of fractal dimensions, a concept which is specially useful in understanding the surface structure. In the present communication, a preliminary account on fractal properties of steel corrosion pitting is presented. '; abst[73]='The sensitivity to stirring shown by the oscillatory Belousov-Zhabotinskii (BZ) reaction when carried out in batch mode has been experimentally examined. Different series of experiments were designed in order to test the influence of both the flow rate of a deaerating agent and the reactant initial concentrations on the observed stirring susceptibility. In addition, distinctive stirring effects associated with the different phases of the oscillatory reaction were analyzed. The experimental results indicate that stirring effects strongly depens on the initial concentrations of the BZ mixture and on the detailed chemical dynamics inherent in each phase of the reaction. '; abst[74]='A diffusion-limited-aggregation (DLA) model with two components (A and B species) is presented to investigate the structure of the composite deposits. The sticking probability P(AB) (= P(BA)) between the different species is introduced into the original DLA model. By using computer simulation it is shown that various patterns are produced with varying the sticking probabilities P(AB) (= P(BA)) and P(AA) (= P(BB)), where P(AA) (= P(BB)) is the sticking probability between the same species. Segregated patterns can be analyzed under the condition P(AB) < P(AA), assumed throughout the paper. With decreasing sticking probability P(AB), a clustering of the same species occurs. With sufficiently small values of both sticking probabilities P(AB) and P(AA), the deposit becomes dense and the segregated patterns of the composite deposit show a striped structure. The effect of the concentration on the pattern morphology is also shown. '; abst[75]='A diffusion-limited-aggregation (DLA) model with two immiscible components (A and B atoms) is presented to investigate a phase transition in morphological changes. A segregation occurs where the DLA pattern is constructed by a mixture of trees consisting of only A atoms and trees consisting of only B atoms. Above a critical concentration p(c), trees with only A atoms exceed trees with only B atoms, and the DLA with only A atoms dominates. It is found that a phase transiton between A-DLA and B-DLA occurs at the critical concentration p(c), where A-DLA and B-DLA represent, respectively, DLA with only A atoms and DLA with only B atoms. The phase transition is analyzed by making use of the real-space renormalization-group method. The correlation length xi scales as xi almost-equal-to (p-p(c))-v, where p(c) = 0.5 and v = 1.85 on the square lattice. '; abst[76]='The effect of hydrodynamic flow upon diffusion-limited deposition on a line is investigated using a Monte Carlo model. The growth process is governed by the convection and diffusion field. The convective diffusion field is simulated by the biased-random walker resulting from a superimposed drift that represents the convective flow. The development of distinct morphologies is found with varying direction and strength of drift. By introducing a horizontal drift parallel to the deposition plate, the diffusion-limited deposit changes into a single needle inclined to the plate. The width of the needle decreases with increasing strength of drift. The angle between the needle and the plate is about 45-degrees at high flow rate. In the presence of an inclined drift to the plate, the convection-diffusion-limited deposit leads to the formation of a characteristic columnar morphology. In the limiting case where the convection dominates, the deposition process is equivalent to ballistic deposition onto an inclined surface. '; abst[77]='Hydrodynamic effects in the transient dynamics of the Freedericksz transition in the twist and homeotropic to planar geometries are analyzed. A novel dynamical anisotropic response for the transverse orientational fluctuations of the director at finite wave numbers is described '; abst[78]='A synthetic route that allows to obtain four different multisulfur pi-organic donors based on the tetrathiafulvalene structure is given. The synthesized donors which have one sulphur atom in each of the outer rings, are BTDM-TTF [1], trans-BET-TTF [2], and their aromatic counterparts; i.e., DT-TTF [3] and alpha-T-TTF [2]. Structure of trans-BET-TTF has been confirmed by single crystal X-ray diffraction. Generation and EPR characterizations, both in solution and in the solid state of their cation-radicals are also presented. '; abst[79]='A systematic experimental study of quasi two-dimensional zinc electrodeposition in an electrochemical cell with parallel electrodes is reported. The well-known different growth regimes, from anisotropically dendritic to irregularly disordered fractal, described previously in radial cells, are shown together with a novel mixed texture composed of dendritic backbones with ramified open branches. Experiments conducted by varying the cell thickness and electrode separation show significant effects by the current on the pattern morphology. Finally, the self-similarity of the electrodeposits is examined for two different growth regimes. '; abst[80]='The electro-oxidation of squaric acid (SQA) on basal platinum single-crystal surfaces in aqueous 0.5 M H2SO4 solutions has been studied. Voltammetric results show that two different processes occur in the overall reaction. In the potential range 0.7-0.8 V vs. reversible hydrogen electrode, the oxidation of strongly bonded species formed after adsorption of SQA at less positive potentials takes place. This process is a structure-sensitive reaction and its characteristics allow us to assume that CO-like species are the stable adsorbed residues. At more positive potentials, the direct oxidation of SQA takes place overlapping with the oxidation of the platinum surface; Pt(110) is the most active electrode for this reaction. Its sensitivity to the surface structure indicates that this reaction involves the interaction of SQA molecules with the first platinum surface oxides. Only a slight inhibition effect on the direct oxidation of SQA due to strongly adsorbed CO is observed on Pt(100) and Pt(110) electrodes. '; abst[81]='Morphological transitions are analyzed for a radial multiparticle diffusion-limited aggregation process grown under a convective drift. The introduction of a tangential flow changes the morphology of the diffusion-limited structure, into multiarm structures, inclined opposite to the flow, whose limit consists of single arms, when decreasing density. The case of shear flow is also considered. The anisotropy of the patterns is characterized in terms of a tangential correlation function based analysis. Comparison between the simulation results and preliminary experimental results has been done. '; abst[82]='The scaling properties of the growth probability distribution for fractallike electrodeposits grown two-dimensionally are analysed. The measure is obtained after numerical resolution of Laplace equation. The usual representations based on the scaling indices tau(q), D(q) and spectrum of singularities f(alpha) are computed and favourably compared with existing ones for related experimental situations and DLA patterns. '; abst[83]='An effect of drift is investigated on the segregation pattern in diffusion-limited aggregation (DLA) with two components (A and B species). The sticking probability P(AB) (= P(BA)) between the different species is introduced into the DLA model with drift, where the sticking probability P(AA) (= P(BB)) between the same species equals 1. By using computer simulation it is found that the drift has an important effect on not only the morphology but also the segregation pattern. Under the drift and the small sticking probability, a characteristic pattern appears where elongated clusters of A species and of B species are periodically dispersed. The period decreases with increasing drift. The periodic structure of the deposits is characterized by an autocorrelation function. The shape of the cluster consisting of only A species (or B species) shows a vertically elongated filamentlike structure. Each cluster becomes vertically longer with decreasing sticking probability P(AB). The segregation pattern is distinctly different from that with no drift and a small sticking probability P(AA). The effect of the concentration on the segregation pattern is also shown. '; abst[84]='The anodic oxidation of dipyrrin-1(10H)-ones, biladiene-ac-diones (bilirubins), bilindiones (biliverdins), two 2,3-dihydrobilindiones and phycocyanobilin dimethyl ester were studied by cyclic voltammetry in N,N-dimethylformamide. The cathodic reduction of the bilindiones, the 2,3-dihydrobilindiones and phycocyanobilin dimethyl ester was also studied by voltammetry and polarography. Substituent effects and the influence of bases on the oxidative behaviour of these compounds were studied. The results are discussed in relation to the biological role of bile pigments. Phycocyanobilin dimethyl ester shows a clearly different oxidative behaviour with respect to the bile pigments tested. '; abst[85]='Some specific effects of cell dimensions on the morphology of zinc electrodeposits in a parallel cell are reported. At high concentration values, a transition from mixed to string-like structures is observed as cell thickness is increased. Homogeneous patterns, which are observed at low concentration values, seem to be the most stable against modification of cell parameters. '; abst[86]='Electroanalytical experiments show that overoxidized polypyrrole, especially the corresponding beta,beta′-substituted polymers, poly(3-methoxy-4-methylpyrrole) and poly(3,4-dimethylpyrTole), shows a high affinity for dissolved dioxygen. This interaction occurs after deprotonation of the overoxidized polymer. The overoxidation potentials necessary for this interaction are low (about +0.2 to 0.5 V versus SCE), i.e., lower than the oxidation potentials which lead to the addition of nucleophiles from the solution. '; abst[87]='Analytical results are derived for the effective dispersion of a passive scalar in a stochastic velocity field evolving in a fast time scale. These results are favorably compared with direct computer simulation of stochastic differential equations containing multiplicative space-time correlated noise. '; abst[88]='A Precise and simple computational model to generate well-behaved two-dimensional turbulent flows is presented. The whole approach rests on the use of stochastic differential equations and is general enough to reproduce a variety of energy spectra and spatiotemporal correlation functions. Analytical expressions for both the continuous and the discrete versions, together with simulation algorithms, are derived. Results for two relevant spectra, covering distinct ranges of wave numbers, are given. '; abst[89]='Experimental quasi-two-dimensional Zn electrodeposits are grown under forced convection conditions. Large-scale effects, with preferential growth towards the impinging flow, together with small-scale roughness suppression effects are evidenced and separately analyzed by using two different radial cell configurations. Interpretations are given in terms of primary concepts concerning current and concentration distributions. '; abst[90]='The electrochemical and chemical oxidative alpha,alpha′-coupling of 3-methoxy-4-methyl-2-pyrrolecarboxylic acid (2) and its ethyl ester 4 is compared with that of the corresponding 4-methoxy-2-pyrrolecarboxylates (1 and 3 respectively). The beta-alkoxy substituent exerts a strong directing influence on its vicinal alpha-position, which in the case of compounds 2 and 4 determines the 2,5′-coupling and allows the isolation of the corresponding 1H,2′H-2,2′-bipyrrole 6 in the case of 4. For 2 the polypyrrole can be obtained by exhaustive electrochemical or chemical coupling, whereas in the case of 1 only the corresponding tetramers are formed. The structures of these tetrapyrroles, already described in the literature, here obtained by oxidation of 4-alkoxy-2-pyrrolecarboxylic acid (1), have been reexamined: they are mixtures of tetramers with zwitterionic structure, have at least two substitution patterns and are partially oxidized to the corresponding bipyrrolylidenes. '; abst[91]='Film obtained by the electrolytic polymerization of pyrrole monomer and pyrrole under addition of dipyrrin-1(10H)-ones, which can act as polymer chain end groups, are compared. The effect of the doping anion and of ageing on electrical conductivity are studied. Elemental chemical analysis of the film materials points to the presence of short polymer chains: comparison with similar polymerizations of 3,4-dimethyl pyrrole suggests the presence of beta, beta′ cross-linking in the polypyrrole structure. '; abst[92]='Fractal characterization of zinc electrodeposits obtained in a quasi two-dimensional film cell under suitable applied potential and zinc sulphate concentrations is reported. Our results show that these deposits are formed according to a Laplacian growth mode, and moreover, their self-similar fractal nature allows the generalization of the Cottrell law for diffusion-limited electrochemical processes occurring on these surfaces. '; abst[93]='The theoretical models proposed for the study of electrode processes under diffusion control on rough surfaces are tested using quasi-two-dimensional experimental electrodes obtained by zinc electrodeposition. Exponents of a generalized scaling law similar to the classical Cottrell equation, which depend on the fractal dimension of the mass distribution measure of the electrode, are calculated using Monte Carlo simulation. The validity of the algorithms of the simulation has been tested previously on flat electrodes. '; abst[94]='Some preliminary results to illustrate the effect of turbulent convection on the dynamics of physicochemical systems incorporating reaction, diffusion and convection of chemical species are given. The whole approach rests on the use of stochastic differential equations with spatiotemporal correlated noise. In particular, it is shown how the propagation velocity of a chemically reacting front can be enhanced due to the fluid motion. '; abst[95]='The diffusion of passive scalars convected by turbulent flows is addressed here. A practical procedure to obtain stochastic velocity fields with well-defined energy spectrum functions is also presented. Analytical results are derived, based on the use of stochastic differential equations, where the basic hypothesis involved refers to a rapidly decaying turbulence. These predictions are favorable compared with direct computer simulations of stochastic differential equations containing multiplicative space-time correlated noise. '; abst[96]='The multifractal scaling of the growth probability distribution is analysed for experimentally grown quasi-two-dimensional Zn electrodeposits. Two morphologies are considered: an open-fractal self-similar growth form, and a dense parallel mode whose fractality is limited to its lateral branching texture. Restricting to the less screened regions of the deposits (q greater-than-or-equal-to 0), and appropriately choosing the examined range of length scales, evident features of Laplacian multifractality are detected. '; abst[97]='The electrochemical behaviour of croconic acid at platinum single crystal electrodes with Pt(100) and Pt(2n-1,1,1) orientations has been studied in 0.5 M H2SO4 by cyclic voltammetry. Experiments with croconic acid in solution show two main processes: the oxidation of surface poisons at around O.8 V, and the oxidation of the acid, between 0.9 and 1.25 V. While the currents involved in the first process tend to increase with the terrace width, the process at higher potentials gives maximum current density for short terraces (3-6 atoms width). Adsorption experiments have shown that, although strongly adsorbed species are formed from croconic acid even under open circuit conditions, the application of a polarization significantly increases the amount of poison formed. For each surface, maximum amounts of irreversibly adsorbed species are formed at potentials around 0.4-0.5 V. The greatest amount of strongly adsorbed species is obtained with the Pt (100) electrode, for which adsorbed CO seems to be the only adsorbate. For stepped surfaces, some other intermediates may also be formed. '; abst[98]='A two-dimensional Monte Carlo simulation algorithm is formulated following the tunneling mechanism for localized (pitting) corrosion. Depending on the values of a minimum set of control parameters, easily interpreted in terms of physicochemical variables, the two limiting regimes of stable and unstable corrosion are reproduced. Pits grown under such distinctive-conditions are analyzed from the point of view of both their electrochemical response (current vs time behavior) and their morphology. In this last respect, fractal concepts are advantageously used to describe their exposed profiles as well as their distributions of local currents. '; abst[99]='The title porphyrin shows non ideal cmc with formation of J-aggregates, due to the formation of intermolecularly stabilized zwitterions, which at high concentration also results in H-aggregates. '; abst[100]='The basic concepts of fractal geometry are reviewed and applied to quasi-two-dimensional zinc electrodeposits. Among the different structures developed during zinc electrodeposition, we have identified the open texture (obtained at large zinc sulfate concentration and small applied potential values) as a typical fractal self-similar structure. (C) 1994 John Wiley & Sons, Inc. '; abst[101]='The influence of an inert electrolyte (sodium sulfate) on quasi-two-dimensional copper electrodeposition from a nondeaerated aqueous copper sulfate solution has been analyzed. The different morphologies for a fixed concentration of CuSO4 have been classified in a diagram in terms of the applied potential and the inert electrolyte concentration. The main conclusion is the extension of the well-known Ohmic model for the homogeneous growth regime for copper sulfate solutions with small amounts of sodium sulfate. Moreover, we have observed the formation of fingerlike deposits at large applied potential and inert electrolyte concentration values, before hydrogen evolution becomes the main electrode reaction. '; abst[102]='The cathodic reduction at the mercury electrode of a biliverdin IX alpha-serum albumin complex at physiological pH in an aqueous buffer containing percentages of DMSO ranging from 4% to 20% is studied by cyclic voltametry and controlled potential coulometry. The progression of pigment disappearance and the (stereochemical) nature of the product are monitored by chromatography, UV-visible absorption and circular dichroism spectroscopy. Upon reduction, albumin-bound biliverdin IX alpha, with a slight preference for the P-helicity, affords the corresponding bound bilirubin IX alpha -with an M-chirality conformation. The complex is reduced at -0.64 V (vs. SCE; 8% DMSO), only a little shifted compared to reduction of free biliverdin IX alpha under the same conditions. In contrast, an analogous bilirubin IX alpha-serum albumin complex is essentially inert towards cathodic reduction under conditions where free bilirubin IX alpha is reduced, indicating a better shielding by the protein of the bilirubin IX alpha molecule from the electrode surface. The presence and relative position (as in the biliverdins IX alpha and XIII alpha) or absence (as in mesobiliverdin IX alpha) of vinyl groups in the pigment does not have a significant effect upon its electroreduction behaviour, indicating that the process is not sensitive to the subtle differences imposed by vinyl groups upon the structure of the corresponding biliverdin-albumin complexes. '; abst[103]='Bilanediones can be easily obtained by sodium dithionite reduction of the corresponding alkyl-substituted bilindiones or biladiene-ac-diones. By reduction of vinyl-substituted dipyrrinones with sodium dithionite, the corresponding alkyl-substituted 4,5-dihydrodipyrrinones can be obtained. '; abst[104]='Velocity has been measured as a function of time for propagating crack tips as water is injected into solutions of end-capped associating polymers in a rectanguar Hele-Shaw cell. Measurements were performed for flows with different values of cell gap, channel width, polymer molecular weight, and polymer concentration. The condition for the onset of fracturelike behavior is well described by a Deborah number which uses the shear-thinning shear rate of the polymer solution as a characteristic frequency for network relaxation. At low molecular weight, the onset of fracturelike pattern evolution is accompanied by an abrupt jump in tip velocity, followed by a lower and approximately constant acceleration. At high molecular weight, the transition to fracturelike behavior involves passing through a regime that may be understood in terms of stick-slip dynamics. The crack-tip wanders from side to side and fluctuates (in both speed and velocity along the channel) with a characteristic frequency which depends linearly on the invading fluid injection rate '; abst[105]='Phase separation dynamics in the presence of externally imposed stirring is studied. The stirring is assumed independent of the concentration and it is generated with a well-defined energy spectrum. The domain growth process is either favored or frozen depending on the intensity and correlation length of this advective flow. This behavior is explained by analytical arguments. '; abst[106]='A short review on the morphologies developped in quasi-twodimensional electrodeposition, is presented in relation to the different transport regimes participating in the whole reaction. The ohmic model for homogeneous (dense parallel) patterns and some convection effects are also reviewed. '; abst[107]='Two representations in multifractal analysis, the so-called q and tau representations, are discussed theoretically and computed practically. Complementary to the standard q-representation, the so-called tau-representation is especially suited to resolving the most rarified subsets of the distributed measure. Moreover, these two representations are especially adapted, respectively, to the well known fixed-size and fixed-mass box-counting algorithms. Both strategies are first applied to iteratively constructed mathematical measures. Once tested in this way, we use them to analyse the mass distribution and the growth probability distribution of an experimental electrodeposited pattern. '; abst[108]='The ability of alpha-CD, beta-CD and gamma-CD to break the aggregates in the solution of the title porphyrin (TPPS4) and to form inclusion self-assemblies has been studied by UV/Vis and H-1-NMR (ROESY). The behaviour of TPPS4 in the presence of alpha-CD, beta-CD and gamma-CD has been compared to that of sodium p-toluenesulfonate and sodium benzenesulfonate. TPPS4 in neutral media forms inclusion assemblies, through its meso-phenyl groups, with beta-CD and gamma-CD, but not with alpha-CD. Diprotonated TPPS4, which has a different geometry from the free base, forms an inclusion assembly only with beta-CD. The inclusion assemblies of TPPS4 with beta-CD and gamma-CD show different geometry: introduction of the phenyl substituent through the cyclodexuin secondary face for beta-CD and through the primary face for gamma-CD. '; abst[109]='We study the problem of pattern and velocity selection of morphologically stable two-dimensional fronts propagating in a spatially modulated medium. The generic system is governed by a local equation and evolves towards a non-trivial steady state with a spatial structure which arises from non-local competition effects and does not necessarily mimic the local structure externally fixed by the modulation. The dynamical process leading to this steady state is studied both analytically and numerically. '; abst[110]='We study the effects of external noise in a one-dimensional model of front propagation. Noise is introduced through the fluctuations of a control parameter leading to a. multiplicative stochastic partial differential equation. Analytical and numerical results for the front shape and velocity are presented. The linear-marginal-stability theory is found to increase its range of validity in the presence of external noise. As a consequence noise can stabilize fronts not allowed by the deterministic equation. '; abst[111]='The electrochemical behaviour of croconic acid (CRA) on Pt(111) electrodes has been studied in acid medium by cyclic voltammetry. Its oxidation proceeds via a dual path mechanism. The direct oxidation path takes place at potentials higher than 0.9 V, probably involving incipient surface oxide formation. The formation of strongly adsorbed species upon CRA adsorption is influenced by the concentration of CRA and the adsorption potential. At open circuit, only COads is formed, while at controlled potentials lower than 0.40 V, other adsorbates, probably with more than one carbon atom, exist. These are oxidized to CO in the range 0.4-0.6 V. ?he activity for poison formation at open circuit is much lower for concentrations higher than 1 mM. FTIR experiments clearly indicate that carbon monoxide is not formed at potentials lower than 0.40 V. Linearly- and bridge-bonded CO adspecies appear at potentials higher than 0.40 V, which are oxidized to CO2 before the direct oxidation of CRA begins. A band at 1780 cm(-1) indicates the presence of leuconic acid at potentials between 0.95 and 1.22 V as a product of the latter process, At higher potentials, CRA is completely oxidized to CO2. '; abst[112]='The reduction of mesobiliverdin XIII alpha propan-1,3-diyl diester with NaBH4 affords mesobilirubin XIII alpha propan-1,3-diyl diester. The same reduction of mesobiliverdin XIII alpha methylen diester. The same reduction of mesobiliverdin XIII alpha methylen diester affords 8-(2-carboxyethyl)-3,17-diethyl-12-(3-hydroxypropyl)-2,7,13,17-tetramethylbiladien-ac-1,19-(21H, 24H)-dione (MBR-mc). The UV/Vis and H-1 NMR spectra of MBR-mc show that its structure in solution is similar to that of the natural bilirubins of the a series. '; abst[113]='We observe dendritic patterns in fluid how in an anisotropic Hele-Shaw cell and measure the tip shapes and trajectories of individual dendritic branches under conditions where the pattern growth appears to be dominated by surface tension anisotropy and also under conditions where kinetic effects appear dominant. In each case, the tip position depends on a power law in the time, but the exponent of this power law can vary significantly among how realizations. Averaging many growth exponents alpha yields <(alpha)over bar> = 0.64 +/- 0.09 in the surface tension dominated regime and <(alpha)over bar> = 0.66 +/- 0.09 in the kinetic regime. Restricting the analysis to realizations when alpha is very close to 0.6 shows great regularity across pattern regimes in the coefficient of the temporal dependence of the tip trajectory. '; abst[114]='Several Mn, Cu, and Zn chelates of etiobiliverdin-IV-gamma, mesobiliverdin-IX alpha, and its dimethyl ester are studied. The results show that the chemical constitution of the Cu biliverdin chelate corresponds to a formal metal oxidation state of (II) coordinated to a neutral radical of the NH trideprotonated biliverdin. The reactivity of the Cu(II) bilindione chelates in nucleophilic solvents agrees with that expected for a pi neutral radical structure of the ligand; in CH3OH, they undergo oxidation towards dimethoxybilipurpurins. The magnetic behaviour of Cu(II) etiobiliverdinate-IV-gamma in the solid state shows an intramolecular weak antiferromagnetic coupling d(9)Cu-to-pi-radical (J = -23 cm(-1)) and an intermolecular weak antiferromagnetic coupling pi-radical-to-pi-radical (J = -45 cm(-1)). The analogy of this magnetic behaviour to that of the pi cation radical of metalloporphyrins is discussed. '; abst[115]='The Cu(II) and Zn(II) chelates of 1,2,3,7,9-pentamethyldipyrrin and 1,2,3,7,9-pentamethyl-8-sulfodipyrrin are studied. When metal acetates are used for the formation of the metal complexes, dipyrrinate metal acetates could be detected as precursors of the bis-dipyrrinates. '; abst[116]='The Cu(II) and Zn(II) chelates of 12,14-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one, 12,13-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one, and their sulfonate derivatives are studied. The chelates show the expected structure of an NH dideprotonated ligand chelating the metal ion. However, in the case of the Zn chelate of 12,14-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one the ligand is only monodeprotonated, and the lactam ring is tautomerized to a hydroximino function. '; abst[117]='In this paper we consider diffusion of a passive substance C in a temporarily and spatially inhomogeneous two-dimensional medium. As a realization for the latter we choose a phase-separating medium consisting of two substances A and B, whose dynamics is determined by the Cahn-Hilliard equation. Assuming different diffusion coefficients of C and A and B, we find that the variance of the distribution function of the said substance grows less than linearly in time. We derive a simple identity for the variance using a probabilistic ansatz and are then able to identify the interface between A and B as the main cause for this nonlinear dependence. We argue that, finally, for very large times the here temporarily dependent diffusion ′′constant′′ goes like t(-1/3) to a constant asymptotic value D-x. The latter is calculated approximately by employing the effective-medium approximation and by fitting the simulation data to the said time dependence. '; abst[118]='Electrodeposition experiments conducted in a thin-layer horizontal cell containing a nonbinary aqueous electrolyte prepared with cupric sulfate and sodium sulfate gave rise to fingerlike deposits, a novel and unexpected growth mode in this context. Both the leading instability from which fingers emerge and some distinctive features of their steady evolution are interpreted in terms of a simple model based on the existing theory of fingering in fluids. '; abst[119]='Experimental results on a fractal tree-like antenna are reported. The fractal structure is generated by electrochemical deposition. The antenna presents a multiband behaviour with a denser band distribution than the previously reported Sierpinski fractal antenna. The matched frequencies are related to the length distribution over the fractal shape. '; abst[120]='We consider the kinetics of the two-dimensional, stoichiometric A + B --> O reaction under external flows, for which we use two models: First a Steady flow, which consists of an array-of eddies; second a time-dependent, stochastic flow which mimics turbulent fluid motion. We follow the reaction numerically and detect in both situations complex decay patterns, which obey different power-laws at short, intermediate and long times: While the initial stage of the reaction is dominated by mixing, c(t) proportional to t(-1), the long-time behavior shows fluctuation-dominated kinetics, c(t) proportional to t(-1/2). In the case of the eddy-lattice-flow a very slow intermediate regime, with c(t) proportional to t(-1/4), emerges. This regime is explained in the framework of an analytical model for mixing along closed-flow lines. (C) 1996 American Institute of Physics. '; abst[121]='We consider the distribution of cross sections of clusters and the density-density correlation functions for the A + B --> 0 reaction. We solve the reaction-diffusion equations numerically for random initial distributions of reactants. When both reactant species have the same diffusion coefficients the distribution of cross sections and the correlation functions scale with the diffusion length and obey superuniversal laws (independent of dimension). For different diffusion coefficients the correlation functions still scale, but the scaling functions depend on the dimension and on the diffusion coefficients. Furthermore, we display explicitly the peculiarities of the cluster-size distribution in one dimension. '; abst[122]='We present a detailed study of the chemical reaction A + B --> 0 in two dimensions for different initial distributions of reactants as characterized by the structure function. We argue that the long-wavelength components of the initial fluctuations determine the long-time decay of the reactant density. Numerical simulations of the coarse grained reaction-diffusion dynamics agree with analytical predictions. '; abst[123]='A two-dimensional reaction-diffusion front which propagates in a modulated medium is studied. The modulation consists of a spatial variation of the local front velocity in the transverse direction to that of the front propagation. We study analytically and numerically the final steady-state velocity and shape of the front, resulting from a nontrivial interplay between the local curvature effects and the global competition process between different maxima of the control parameter. The transient dynamics of the process is also studied numerically and analytically by means of singular perturbation techniques. '; abst[124]='The electrochemical behaviour of tetrahydroxy-p-benzoquinone (THQ) on Pt(111), Pt(100) and Pt(110) surfaces has been studied in sulphuric acid solutions by cyclic voltammetry. The experimental results show that THQ is the oxocarbon having a lesser tendency to form CO-like species after adsorption on platinum surfaces. THQ is directly adsorbed on Pt(111) and Pt(100), although it is not stable and undergoes a slow reaction to CO adspecies on Pt(100) surfaces. Clear evidence of CO adspecies has been found only on Pt(100) electrodes. (C) 1997 Elsevier Science S.A. '; abst[125]='The electrochemical behaviour of rhodizonic acid on Pt(111), Pt(100) and Pt(110) surfaces has been studied in sulphuric acid solutions by cyclic voltammetry and in situ FTIR spectroscopy. The direct oxidation process takes place at potentials positive to the desorption of strongly bonded adsorbates. For the three orientations, polyketonic compounds and finally carbon dioxide are the oxidation products. Reduction processes can cake place at lower potentials, leading to the formation of tetrahydroxyquinone and hexahydroxybenzene, also detected by FTIR. These species seem to be adsorption intermediates in the case of Pt(111), transforming from one to another depending on potential. A small amount of carbon monoxide is observed on this orientation. Significantly higher CO adsorptions have been obtained for Pt(110) (linear CO) and Pt(100) (linearly and bridge bonded). Other adsorbates seem to be formed after adsorption experiments, which give no detectable infrared absorption. '; abst[126]='We consider diffusion of a passive substance C in a phase-separating nonmiscible binary alloy under turbulent mixing. The substance is assumed to have different diffusion coefficients in the pure phases A and B, leading to a spatially and temporarily dependent diffusion ′′coefficient′′ in the diffusion equation plus convective term. In this paper we consider especially the effects of a turbulent Row field coupled to both thc Cahn-Hilliard type evolution equation of the medium and the diffusion equation (both, therefore, supplemented by a convective term). It is shown that the formerly observed prolonged anomalous diffusion [H, Lehr, F, Sapues. and J.M. Sancho, Phys. Rev. E 54, 5028 (1996)] is no longer seen if a Row of sufficient intensity is supplied. '; abst[127]='A fingering instability appears in thin-layer electrodeposition experiments from copper sulphate aqueous solutions in the presence of alkaline sulphates. In this case, cuprous oxide rich and highly space filling deposits are obtained. This latter characteristic allows them to manifest the hydrodynamic fingering instability of the concentration boundary layer that separates the copper depleted solution embedding the deposit from the bulk solution. Moreover, different dynamic morphological transitions experienced by these finger-like deposits are interpreted as due to proton and alkaline ion fronts. '; abst[128]='Dynamic morphological transitions in thin-layer electrodeposits obtained from copper sulphate solutions have been studied. The chemical composition of the electrodeposits indicates that they appear as a consequence of the competition between copper and cuprous oxide formation. In addition, the Ohmic control of the process is verified at initial stages of the deposit growth. At higher deposit developments, gravity-induced convection currents play a role in the control of the whole process and affect the position of these transitions. '; abst[129]='A study of a stable front propagating in a turbulent medium is presented. The front is generated through a reaction-diffusion equation, and the turbulent medium is statistically modeled using a Langevin equation. Numerical simulations indicate the presence of two different dynamical regimes. These regimes appear when the turbulent flow either wrinkles a still rather sharp propagating interfase or broadens it. Specific dependences of the propagating velocities on stirring intensities appropriate to each case are found and fitted when possible according to theoretically predicted laws. Different turbulent spectra are considered. (C) 1997 American Institute of Physics. [S1070-6631(97)01212-9]. '; abst[130]='We study front propagation in stirred media using a simplified modelization of the turbulent flow. Computer simulations reveal the existence of the two limiting propagation modes observed in recent experiments with liquid phase isothermal reactions. These two modes respectively correspond to a wrinkled although sharp propagating interface and to a broadened one. Specific laws relative to the enhancement of the front velocity in each regime are confirmed by our simulations. '; abst[131]='We present an analytical scheme, easily implemented numerically, to generate synthetic Gaussian turbulent flows by using a linear Langevin equation, where the noise term acts as a stochastic stirring force. The characteristic parameters of the velocity field are well introduced, in particular the kinematic viscosity and the spectrum of energy. As an application, the diffusion of a passive scalar is studied for two different energy spectra. Numerical results are compared favorably with analytical calculations. (C) 1997 American Institute of Physics. '; abst[132]='We consider the kinetics of the two-dimensional, stoichiometric A+B-->O reaction under confined-scale turbulent mixing and concentrate on the interplay between the kinetic patterns and the spatial organization of the system. We study the properties of the arising clusters and of the reaction zones, both in the presence and in the absence of mixing. We show that the two-point correlation function C-AB(r)=[c(A)(r′+r)c(B)(r′)]/[c(A)(r)](2) is closely related to the effective reaction rate, while the functional form of the quartic correlation function Q(r,t) =[c(A)(r′,t)c(B)(r′,t)c(A)(r′+r,t)c(B)(r′+r.t)]/[c(A)(2)(r,t)c(B)(2)(r,t)] is connected to the geometry of the reaction zones. We pay special attention to the occurrence of time windows of fast (classical) concentration decay even when the reactants show strong segregation. (C) 1997 American Institute of Physics. '; abst[133]='We investigate the effects of stirring on the kinetics of the A + B --> 0 reaction under stoichiometrical conditions in 2D. We consider both a steady eddy-lattice flow and a random flow mimicking turbulence. In both situations complex decay patterns are detected. Only an intermediate stage of the reaction is dominated by mixing. The long-time behavior shows fluctuation-dominated kinetics, c(t) proportional to t(-1/2), governed by effective diffusion. For the case of an eddy-lattice flow a very slow intermediate regime emerges, c(t) proportional to t(-1/4), which is associated with the closed topology of flow lines. '; abst[134]='The propagation of an initially planar front is studied within the framework of the photosensitive Belousov-Zhabotinsky reaction modulated by a smooth spatial variation of the local front velocity in the direction perpendicular to front propagation. Under this modulation, the wave front develops several fingers corresponding to the local maxima of the modulation function. After a transient, the wave front achieves a stationary shape that does not necessarily coincide with the one externally imposed by the modulation. Theoretical predictions for the selection criteria of fingers and steady-state velocity are experimentally validated. '; abst[135]='The electrochemical reduction of oxygen at thin Pt films prepared on titanium substrate has been studied in alkaline solution. Tafel plots with two different slope regions were observed for oxygen reduction in 0.1 M KOH. At low current densities the slope was around - 60 mV dec(-1), whereas at high current densities the slope was varying between - 260 and - 490 mV dec(-1). The oxygen reduction behaviour at Pt/Ti electrodes was qualitatively the same in comparison to that of Pt/GC electrodes. Cyclic-voltammetric experiments revealed that the potential of the hydrogen adsorption-desorption peaks and the platinum oxide reduction peak shifted towards positive potentials with the increasing Pt film thickness in 0.1 M KOH and 0.5 M H2SO4. The coverage of platinum surface with oxygen-containing species (Theta(ox)) was found to be dependent on Pt film thickness. Theta(ox) plays an important role in determining the oxygen reduction kinetics at platinum electrodes. (C) 1997 Elsevier Science Ltd. '; abst[136]='The electroreduction of oxygen has been studied on thin-film platinum using the rotating disk electrode technique. The kinetic parameters of oxygen reduction were determined for Pt films over the range of thickness from 1 to 50 nm. The kinetics of oxygen reduction were found to be slightly influenced by the platinum film thickness. Copyright (C) 1996 Elsevier Science Ltd. '; abst[137]='Propagating reaction-diffusion fronts in a two-variable chemical system, the so-called open unstirred cubic autocatalator, are analyzed. Both situations of stable/metastable and stable/unstable connections are considered. Numerical results for the front velocities and profiles are supplemented with analytical calculations either exact or obtained perturbatively. Special emphasis is devoted to the question of velocity selection. In this respect, abundant use is made of the marginal stability criteria, either in their linear or nonlinear formulations. Finally, some peculiar phenomenologies related to the appearance of double fronts are examined. (C) 1997 American Institute of Physics. '; abst[138]='Irreversible adsorption of oxocarbons on bismuth and selenium modified Pt(lll) electrodes has been examined by cyclic voltammetry and in situ FT-IR spectroscopy. A simple third-body effect is observed in the adsorption of those oxocarbons giving rise to only one adsorbed residue: squaric acid which is dissociatively adsorbed to CO adsorbates and tetrahydroxy-p-benzoquinone which is directly adsorbed on these surfaces. On the other hand, croconic and rhodizonic acids give rise to more than one adsorbed residue (CO adspecies and another adsorbate with more than one carbon atom) and thus, particular effects arising from their stability can be identified, besides the third-body effects appearing at high adatom coverages. Then, bismuth ad-atoms promote the surface cleavage of croconic acid adsorbates to CO adspecies and selenium ad-atoms hinder the adsorption of some reaction intermediate involved in the conversion of this residue to CO adspecies. FT-IR measurements reinforce these voltammetric results. In the ca se of rhodizonic acids, whose adsorption intermediates a re CO and tetrahydroxy-p-benzoquinone, both ad-atoms promote the formation of CO adspecies, being this effect emphasized more on Pt(lll)-Se electrodes. (C) 1998 Elsevier Science S.A. All rights reserved. '; abst[139]='The adsorption of organic residues on Bi-Pt(111) surfaces gives rise to a bismuth adsorption state different from that characterized by the redox couple at 0.62 V. After the stripping of organic adspecies, surface diffusion of bismuth adatoms takes place in order to attain their most stable distribution on the Pt(111) surface. (C) 1998 Elsevier Science Ltd. All rights reserved. '; abst[140]='The interactions of bismuth adlayers with adsorbed organic compounds on Pt(111) surfaces have been examined using voltammetric techniques. Evidence is provided that adsorbed CO affects bismuth adatoms giving rise to different adsorption states. After CO stripping, a potential excursion to negative potentials allows the surface diffusion of bismuth adatoms to take place in order to attain their most stable state on the Pt(111) surface. A similar effect on the bismuth adlayer is also carried out by tetrahydroxy-p-benzoquinone, an organic compound that exhibits a completely different behavior from that observed for CO adspecies on Pt(111) electrodes. (C) 1998 Elsevier Science S.A. All rights reserved. '; abst[141]='The solution structure of two intramolecular diesters (methylene and 1,3-propylidene) of mesobiliverdin-XIII alpha was studied and compared with that of the corresponding dimethyl ester. The UV/Vis absorption spectra, chiral discrimination with ethyl (S)-(-)-lactate, and the H-1 NMR spectra (ROESY) show that the cyclization of the propionate substituents of biliverdins does not significantly affect the helix structure or its (P) reversible arrow (M) interconversion. The internal methylene diester does not show conformational heterogeneity of the propionate substituents and probably exists only in one diastereomeric form. In this case, the results point to a simultaneous racemization of the tetrapyrrole helix and the bridge cycle. The methylene diester of mesoprotoporphyrin was also synthesized. In this case, the geometry of the propionate chains is probably similar to that present in some hemoproteins. '; abst[142]='The effect of cyclization of the propionic acid residues in mesobilirubin XIII alpha propan-1,3-diyl ester on the angle between the dipyrrinone halves has been studied. This compound is shown to dimerize in chloroform solutions, and a conformation is proposed which is similar to that of the corresponding dimethyl ester. The results point to the contribution of pi-pi interactions, besides hydrogen bonding, to the geometry of the dimer. '; abst[143]='Directional growth at a nematic-isotropic liquid crystal interface shows large quantitative discrepancies when described by the Mullins-Sekerka theory for the planar front, which satisfactorily describes other directional solidification systems. We have addressed these unresolved issues and focused on three-dimensional effects. '; abst[144]='We consider the evaporation of periodic arrays of initially equal droplets in two-dimensional systems with open (absorbing) boundaries. Our study is based on the numerical solution of the Cahn-Hilliard equation. We show that due to cooperative effects the droplets which are further from the boundary may evaporate earlier than those in the boundary′s vicinity. The time evolution of the overall amount of matter in the system is also studied. '; abst[145]='We have studied the effect that two different perturbations have on the flow in Hele-Shaw cells. The introduction of geometrical anisotropy in the cell adds a rich variety of new morphologies whose dynamics reveal interesting regularities. The use of viscoelastic materials, on the other hand, has allowed for the observation of a dynamical transition from viscous fingering into fracture-like behaviour, with many intriguing regularities and with several open questions. '; abst[146]='We study scalar diffusion, both from Eulerian and Lagrangian perspectives, advected by two dimensional flows. Emphasis is devoted to the problem of scalar diffusion under a synthetic turbulent flow. We present numerical and analytical results for the turbulent diffusion coefficient either from the influence of the turbulent synthetic field and a periodic array of eddies. Preliminary results concerning Lagrangian dispersion are also reported. '; abst[147]='The effect of quenched disorder on the propagation of autowaves in excitable media is studied both experimentally and numerically in relation to the light-sensitive Belousov-Zhabotinsky reaction. The spatial disorder is introduced through a random distribution with two different levels of transmittance. In one dimension the (time-averaged) wave speed is smaller than the corresponding to a homogeneous medium with the mean excitability. Contrarily, in two dimensions the velocity increases due to the roughening of the front. Results are interpreted using kinematic and scaling arguments. In particular, for d = 2 we verify a theoretical prediction of a power-law dependence for the relative change of the propagation speed on the disorder amplitude. '; abst[148]='The behavior of chemical waves advancing through a disordered excitable medium is investigated in terms of percolation theory and autowave properties in the framework of the light-sensitive Belousov-Zhabotinsky reaction. By controlling the number of sites with a given illumination, different percolation thresholds for propagation are observed; which depend on the relative wave transmittances of the two-state medium considered. '; abst[149]='Propagating reaction-diffusion fronts constitute one of the paradigms in the realm of the nonlinear chemical phenomena. In this paper different situations are considered. Firstly, we discuss the problem of front propagation in a two-variable chemical system exhibiting multiple stationary states. Emphasis is put on the question of velocity selection. In section 3 of our contribution, the question of front propagating in spatially modulated and noisy media is addressed. Finally, we also briefly comment on the problem of reaction-diffusion fronts in non-quiescent media. In this particular scenario we simply aim at introducing the two basic propagation modes, i.e., thin versus distributed reaction fronts, that are identified in our numerical simulations. '; abst[150]='We examine the patterns formed by injecting nitrogen, gas into the center pf a horizontal, radial Hele-Shaw cell filled with paraffin oil. We use smooth plates and etched plates with lattices having different amounts of defects (0-10 %). hi all cases, a quantitative measure of the pattern ramification shows a regular trend with injection rate and ce:ll gap, such that the dimensionless perimeter scales with the dimensionless time. By adding defects to the lattice, we observe increased branching in the pattern morphologies. However, even in this case, the scaling behavior persists. Only the prefactor of the scaling function shows a dependence on the defect density. For different lattice defect densities, we examine the nature of the different morphology phases. [S1063-651X(99)12508-X]. '; abst[151]='We have studied the nucleation and the physical properties of a -1/2 wedge disclination line near the free surface of a confined nematic liquid crystal. The position of the disclination line has been related to the material parameters (elastic constants, anchoring energy, and favored anchoring angle of the molecules at the free surface). The use of a planar model for the structure of the director field (whose predictions have been contrasted to those of a fully three-dimensional model) has allowed us to relate the experimentally observed position of the disclination line to the relevant properties of the liquid crystals. In particular, we have been able to observe the collapse of the disclination line due to a temperature-induced anchoring-angle transition, which has allowed us to rule out the presence of a real disclination line near the nematic/isotropic front in directional growth experiments. [S1063-651X(99)03901-X]. '; abst[152]='We present a study of the evaporation dynamics of a substance undergoing a coarsening process. The system is modeled by the Cahn-Hilliard equation with absorbing boundaries. We have found that the dynamics, although of a diffusive nature, is much slower than the usual one without coarsening; Analytical and simulation results are in reasonable agreement. [S1063-651X(99)05701-3]. '; abst[153]='We consider the spatio-temporal behavior of the A+B --> 0 bimolecular reaction in a system where both reactants tend to segregate into separated phases. Our study is based on the numerical solution of a pair of reaction-diffusion equations appropriate to capture the underlying coarsening dynamics. The interplay between reaction and coarsening leads to a complex pattern of reactants spatial distribution. At short/intermediate times two distinctive dynamical regimes are seen in the decay of overall concentration and droplet number and the behavior of droplet radii. (C) 1999 American Institute of Physics. [S0021-9606(99)50911-2]. '; abst[154]='Diffusion-controlled A + B --> O reactions in constrained geometries are well-known to obey nonconventional dimension-dependent kinetics. We investigate these kinetics in narrow d-dimensional tubes to study the crossovers from early time d-dimensional kinetics to eventual one-dimensional kinetics. We rely on a reaction-diffusion model that leads to analytically verifiable quantitative results. The crossover times are identified as those times at which the kinetic exponent exhibits maximum curvature and are shown to be universally given by t(c) = 0.034W(2)/D where W is the width of the tube along a narrow direction and D is the diffusion coefficient of both species. Our procedure overcomes many of the statistical difficulties inherent in:Monte Carlo simulations of this problem [Ahn, J.; Kopelman, R.; Argyrakis,. J. Chem. Phys. 1999, 110, 2116]. '; abst[155]='The time-dependent transmission coefficient for the Kramers problem exhibits different behaviors in different parameter regimes. In the high friction regime it decays monotonically ("nonadiabatic"), and in the low friction regime it decays in an oscillatory fashion ("energy-diffusion limited"). The generalized Kramers problem with an exponential memory friction exhibits an additional oscillatory behavior in the high friction regime ("caging"). In this paper we consider an oscillatory memory kernel, which can be associated with a model in which the reaction coordinate is linearly coupled to a nonreactive coordinate, which is in turn coupled to a heat bath. We recover the nonadiabatic and energy-diffusion-limited behaviors of the transmission coefficient in appropriate parameter regimes, and find that caging is not observed with an oscillatory memory kernel. Most interestingly, we identify a new regime in which the time-dependent transmission coefficient decays via a series of rather sharp steps followed by plateaus ("stair-like"). We explain this regime and its dependence on the various parameters of the system. (C) 1999 American Institute of Physics. [S0021-9606(99)50226-2]. '; abst[156]='All systems in thermal equilibrium exhibit a spatially variable energy landscape due to thermal fluctuations. Thus at any instant there is naturally a thermodynamically driven localization of energy in parts of the system relative to other parts of the system. The specific characteristics of the spatial landscape such as, for example, the energy variance, depend on the thermodynamic properties of the system and vary from one system to another. The temporal persistence of a given energy landscape, that is, the way in which energy fluctuations (high or low) decay toward the thermal mean, depends on the dynamical features of the system. We discuss the spatial and temporal characteristics of spontaneous energy localization in 1D anharmonic chains in thermal equilibrium. (C) 1999 American Institute of Physics. [S0021-9606(99)51628-0]. '; abst[157]='The aggregation in water of the free bases and the diprotonated forms of p-sulfonatophenyl and phenyl meso-substituted porphyrins [sodium salts of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4), 5,10,15-tris(4-sulfonatophenyl)-20-phenylporphyrin (TPPS3), 5,10-bis(4-sulfonalophenyl)-15,20-diphenylporphyrin (TPPS2A), 5,15-bis(4-sulfonatophenyl)-10,20-diphenylporphyrin (TPPS2O), 5-(4-sulfonatophenyl)-10,15,20-diphenylporphyrin (TPPS1) and 5,15-bis(4-sulfonatophenyl)porphine (DPPS2O)] was studied by UV/Vis, H-1-NMR, fluorescence, polarized fluorescence and resonance light scattering. The presence of hydrophobic phenyl groups favours the aggregation. The free bases TPPS4 and TPPS3 aggregate into stacks of ill-defined geometry. TPPS2A and DPPS2O give H-aggregates. TPPS2O and TPPS3 give J-aggregates through interaction of the hydrophobic phenyl groups, that is their geometry corresponds to edge-to-edge arrangements. All these porphyrins give J-aggregates upon diprotonation, through electrostatic interactions between the positively charged porphyrin ring and the sulfonato group. These J-aggregates give different arrays depending on the meso-substitution pattern. '; abst[158]='The propagation of a pulse in a nonlinear array of oscillators is influenced by the nature of the array and by its coupling to a thermal environment. For example, in some arrays a pulse can be speeded up while in others a pulse can be slowed down by raising the temperature. We begin by showing that an energy pulse (one dimension) or energy front (two dimensions) travels more rapidly and remains more localized over greater distances in an isolated array (microcanonical) of hard springs than in a harmonic array or in a soft-springed array. Increasing the pulse amplitude causes it to speed up in a hard chain, leaves the pulse speed unchanged in a harmonic system, and slows down the pulse in a soft chain. Connection of each site to a thermal environment (canonical) affects these results very differently in each type of array. In a hard chain the dissipative forces slow down the pulse while raising the temperature speeds it up. In a soft chain the opposite occurs: the dissipative forces actually speed up the pulse, while raising the temperature slows it down. In a harmonic chain neither dissipation nor temperature changes affect the pulse speed. These and other results are explained on the basis of the frequency vs energy relations in the various arrays. [S1063-651X(99)11411-9]. '; abst[159]='The behavior of autowaves under the effect of a quenched disorder is studied in the framework of the light-sensitive Belousov-Zhabotinsky reaction. This allows us to introduce spatial disorder on the excitability by projecting patterns of light transmittance. In particular, we have selected a dichotomic random distribution of levels of transmittance. If the two values of transmittance are equally probable and allows wave propagation without breaking the waves, we find an opposite effect on the wave front velocity and shape depending on the considered dimension. On the other hand, if one of the two values of the transmittance distribution is set on the nonexcitable region, percolation phenomena can arise by changing the number of excitable sites. The different addressed situations are analytically interpreted giving theoretical predictions for the experimental and numerical results. '; abst[160]='Using the experimental data of Paret and Tabeling [Phys. Rev. Led. 79, 4162 (1997)] we consider in detail the dispersion of particle pairs by a two-dimensional turbulent flow and its relation to the kinematic properties of the velocity field. We show that the mean square separation of a pair of particles is governed by rather rare, extreme events and that the majority of initially close pairs are not dispersed by the flow. Another manifestation of the same effect is the fact that the dispersion of an initially dense cluster is not the result of homogeneously spreading the particles within the whole system. instead it proceeds through a splining into smaller but also dense clusters. The statistical nature of this effect is discussed, [S1063-651X(93)09804-9]. '; abst[161]='We study fracturelike flow instabilities that arise when water is injected into a Hele-Shaw cell filled with aqueous solutions of associating polymers. We: explore various polymer architectures, molecular weights, and solution concentrations. Simultaneous measurements of the finger tip velocity and of the pressure at the injection point allow us to describe the dynamics of the finger in terms of the "finger mobility," which relates the velocity to the pressure gradient. The flow discontinuities, characterized by jumps in the finger tip velocity, which are observed in experiments with some of the polymer solutions, can be modeled by using a nonmonotonic dependence between a characteristic shear stress and the shear rate at the tip of the finger. A simple model, which is based on a viscosity function containing both a Newtonian and a non-Newtonian component, and which predicts nonmonotonic regions when the non-Newtonian component of the viscosity dominates, is shown to agree with the experimental data. [S1063-651X(99)08910-2]. '; abst[162]='A simple model of a stochastic bistable medium is analytically shown to exhibit pulse propagation sustained by external spatiotemporal noise. In particular, signal transmission is seen to be optimal for a certain nonzero value of the noise intensity, which can be determined theoretically. Numerical simulations confirm the analytical predictions. This property of noise enables the use of the bistable medium as an information channel through which a continuous tin general nonperiodic) string of bits can be transmitted. '; abst[163]='In this article we report our systematic studies of the dependence on the sample thickness of the onset parameters of the instability of the nematic-isotropic interface during directional growth and melting, in homeotropic or planar anchoring. '; abst[164]='We have studied the structural changes that fatty acid monolayers in the Ov phase undergo when a simple shear flow is imposed. A strong coupling is revealed by the changes in domain structure that are observable using Brewster angle microscopy, suggesting the possibility of shear alignment. The dependence of the alignment on the molecular polar tilt proves that the mechanism is different than in nematic liquid crystals. We argue that the degenerate lattice symmetry lines of the underlying pseudohexagonal lattice align in the flow direction, and we explain the observed alignment angle using geometrical arguments. '; abst[165]='The experimental conditions under which the fingering instability is observed in quasi-two dimensional electrodeposition experiments from a non binary electrolyte have been reviewed. The initial instability features are interpreted in terms of a simple model that parallels the instability observed in fluid displacement experiments whereas a phenomenological model accounts for the late stage competition of well developed fingers. Finally, the morphological transitions experimented by these deposits and those obtained from binary electrolytes are interpreted in terms of the modification of the electrochemical reactions due to migration fronts travelling from the anode to the cathode. '; abst[166]='The dynamics of three-dimensional scroll rings with spatiotemporal random excitability is investigated numerically using the FitzHugh-Nagumo model. Depending on the correlation time and length scales of the fluctuations, the lifetime of the ring filament is enlarged and a resonance effect between the time scale of the scroll ring and the time correlation of the noise is observed. Numerical results are interpreted in terms of a simplified stochastic model derived from the kinematical equations for three-dimensional excitable waves. '; abst[167]='We report a systematic study of pattern formation in a thin fluid layer driven by a simple chemical reaction. The hydrodynamic instability arises due to the increase of fluid density in the subsurface layer caused by the O-2 oxidation of glucose to gluconic acid with the methylene blue as a catalyst. We also report independent measurements of the kinetics of the reaction and of the increase in density which gives rise to the instability. '; abst[168]='We study particle dispersion advected by a synthetic turbulent flow from a Lagrangian perspective and focus on the two-particle and cluster dispersion by the flow. It has been recently reported that Richardson′s law for the two-particle dispersion can stem from different dispersion mechanisms, and can be dominated by either diffusive or ballistic events. The nature of the Richardson dispersion depends on the parameters of our flow and is discussed in terms of the values of a persistence parameter expressing the relative importance of the two above-mentioned mechanisms. We support this analysis by studying the distribution of interparticle distances, the relative velocity correlation functions, as well as the relative trajectories. '; abst[169]='We present a model in which the immediate environment of a bistable system is a molecular chain which in turn is connected to a thermal environment of the Langevin form. The molecular chain consists of masses connected by harmonic or by anharmonic springs. The distribution, intensity, and mobility of thermal fluctuations in these chains is strongly dependent on the nature of the springs and leads to different transition dynamics for the activated process. Thus, all else (temperature, damping, coupling parameters between the chain and the bistable system) being the same, the hard chain may provide an environment described as diffusion-limited and more effective in the activation process, while the soft chain may provide an environment described as energy-limited and less effective. The importance of a detailed understanding of the thermal environment toward the understanding of the activation process itself is thus highlighted. (C) 2000 American Institute of Physics. [S0021-9606(00)00723-6]. '; abst[170]='Films were obtained from the evaporation on flat glass substrates of homoassociate water solutions of the title porphyrin. The films of 1 were characterized by UV-VIS and FT-LR spectroscopy, microscopy, X-ray diffraction, thermogravimetry (TG) and differential scanning calorimetry (DSC). The films are composed by a birefrigent organic phase and NaCl crystallites; the organic phase shows an orientated structure. The water content of the film depends directly on the water-vapour pressure of the surrounding atmosphere; a change of structure occurs for p(H2O) > 10 Torr and there is a transition to gel-like material for p(H2O) > 20 Torr. In the organic phase, water, sodium, and chloride ions are placed in layers or channels parallel to the evaporation surface with thickness depending on the water content. (C) 2000 Elsevier Science B.V. All rights reserved. '; abst[171]='A review on the morphologies and corresponding growth dynamics observed in quasi-two-dimensional electrocrystallization is presented. Emphasis is devoted to the understanding of the specific and growth mode-dependent role played by the different transport mechanisms, i.e. diffusion, migration and convection, as well as the chemical processes. The role of chemical reactions is decissive for the understanding of the well-known morphological transitions and is at the origin of the finger-like texture. (C) 2000 Elsevier Science B.V. All rights reserved. '; abst[172]='Spiral chemical waves subjected to a spatiotemporal random excitability are experimentally and numerically investigated in relation to the light-sensitive Belousov-Zhabotinsky reaction. Brownian motion is identified and characterized by an effective diffusion coefficient which shows a rather complex dependence on the time and length scales of the noise relative to those of the spiral. A kinematically based model is proposed whose results are in good qualitative agreement with experiments and numerics. '; abst[173]='We study the erratic displacement of spiral waves forced to move in a medium with random spatiotemporal excitability. Analytical work and numerical simulations are performed in relation to a kinematic scheme, assumed to describe the autowave dynamics for weakly excitable systems. Under such an approach, the Brownian character of this motion is proved and the corresponding dispersion coefficient is evaluated. This quantity shows a nontrivial dependence on the temporal and spatial correlation parameters of the external fluctuations. In particular, a resonantlike behavior is neatly evidenced in terms of the noise correlation time for the particular situation of spatially uniform fluctuations. Actually, this case turns out to be, to a large extent, exactly solvable, whereas a pair of dispersion mechanisms are discussed qualitatively and quantitatively to explain the results for the more general scenario of spatiotemporal disorder. '; abst[174]='A pacemaker, regularly emitting chemical waves, is created out of noise when an excitable photosensitive Belousov-Zhabotinsky medium, strictly unable to autonomously initiate autowaves, is forced with a spatiotemporal patterned random illumination. These experimental observations are also reproduced numerically by using a set of reaction-diffusion equations for an activator-inhibitor model, and further analytically interpreted in terms of genuine coupling effects arising from parametric fluctuations. Within the same framework we also address situations of noise-sustained propagation in subexcitable media. '; abst[175]=' '; abst[176]='Urea adsorption has been studied at Pt(110) and stepped platinum electrodes with orientations vicinal to Pt(111) in the [1 (1) over bar0] and [01 (1) over bar] zones. In situ infrared spectra and cyclic voltammograms obtained in the urea-containing solutions have been analyzed as a function of the (110) or (100) step densities. At the same time, voltammetric data have been combined with charge displacement experiments in order to determine the potential of zero total charge (pztc) in the presence of urea. The variation of the pztc with the step density is similar to that previously observed for the same surfaces in sulfuric acid solutions thus confirming the anion-like behavior of urea molecules at platinum electrodes. Potential-dependent changes in the bonding of urea at the Pt(110) electrode have been found to be similar to those previously reported for Pt(111), with N-bonded and O-bonding urea predominating at low and high coverages, respectively. The same behavior is observed for stepped surfaces containing (111) terraces and (110) steps. On the other hand, urea molecules bonded through the two nitrogen atoms are detected in the whole coverage range at surfaces with a high density of (100) steps. '; abst[177]='The effect of the addition of beta- and gamma -cyclodextrin (beta -CD, gamma -CD) to water solutions (D2O) of the 4′-sulfonato derivatives of meso-tetraphenylporphyrin (TPPS4, TPPS3, TPPS20 and TPPS2a) was studied by H-1 NMR at several temperatures. In all cases the disaggregation of the porphyrin homoassociates was detected, although in most cases it was only partial. Nuclear Overhauser signals (ROESY) show that cyclodextrin inclusion complexes were formed with TPPS4, TPPS3, and TPPS20, but not with TPPS2a. These complexes include the sulfonatophenyl groups as guest, but not the hydrophobic phenyl substituents. The geometry of the complexes corresponds to that in which the sulfonatophenyl substituent is introduced through the secondary face of beta -CD and through the primary face of gamma -CD. In the inclusion complexes the polar sulfonato group is inside the cyclodextrin cavity but near to the hydrophilic interface with the bulk water. This explains the absence of complexation in the case of cationic porphyrins such as 5,10,15,20-tetrakis(N-methylpyridin-4-yl)porphyrin (TMPyP), and the decrease in the solubility when the beta -CD complex of 5,15-bis(4-sulfonatophenyl)porphyrin (DPPS20) forms. Complexes of the cyclodextrins with porphyrin homoassociates were also detected. This indicates that the heteroassociation avoids the formation of staggered stacks of porphyrin homoassociates, but has less effect on the association through the hydrophobic region of the phenyl substituents. This last type of aggregation, which is not significantly affected by the addition of alpha -CD, explains why the hydrophobic phenyl substituents are not complexed by the cyclodextrins. Copyright (C) 2001 John Wiley & Sons, Ltd. '; abst[178]=' '; abst[179]='Point defects of opposite signs can alternately nucleate on the -1/2 disclination line that forms near the free surface of a confined nematic liquid crystal. We show the existence of metastable configurations consisting of periodic repetitions of such defects. These configurations are characterized by a minimal interdefect spacing that is seen to depend on sample thickness and on an applied electric field. The time evolution of the defect distribution suggests that the defects attract at small distances and repel at large distances. '; abst[180]='Liquid crystalline behaviour is generally limited to a select group of specially designed bulk substances. By contrast, it is a common feature of simple molecular monolayers and other quasi-two-dimensional systems(1), which often possess a type of in-plane ordering that results from unbinding of dislocations-a ′hexatic′ liquid crystalline phase. The flow of monolayers is closely related to molecular transport in biological membranes, affects foam and emulsion stability and is relevant to microfluidics research. For liquid crystalline phases, it is important to understand the coupling of the molecular orientation to the flow. Orientationally ordered (nematic) phases in bulk liquid crystals exhibit ′shear aligning′ or ′tumbling′ behaviour under shear, and are described quantitatively by Leslie-Ericksen theory(2). For hexatic monolayers, the effects of flow have been inferred from textures of Langmuir-Blodgett films(3-5) and directly observed at the macroscopic level(6-10). However, there is no accepted model of hexatic flow at the molecular level. Here we report observations of a hexatic Langmuir monolayer that reveal continuous, shear-induced molecular precession, interrupted by occasional jump discontinuities. Although superficially similar to tumbling in a bulk nematic phase, the kinematic details are quite different and provide a possible mechanism for domain coarsening and eventual molecular alignment in monolayers. We explain the precession and jumps within a quantitative framework that involves coupling of molecular orientation to the local molecular hexatic ′lattice′, which is continuously deformed by shear. '; abst[181]='The coupling between the structure of the tilted condensed phases of docosanoic acid monolayers (L-2, L-2′, and Ov) and an external shear flow has been studied using Brewster angle microscopy. Generally, the coupling results in a reorientation of the alkyl tails, although different kinematics are observed depending on the thermodynamic phase, shear rate, and surface pressure. The coupling can result in continuous orientational changes or in abrupt reorientation of the molecular tilt angle. These molecular-level effects are connected to the macroscopic texture as well; shear can result in either domain fragmentation or annealing. A detailed quantitative analysis of phenomena reminiscent of the "flow alignment" and "tumbling" mechanisms found in nematohydrodynamics is presented. The analysis reveals that the kinematics of the reorientation is different from that in nematic liquid crystals. The underlying lattice plays a crucial role, and the observed phenomena can be explained with geometrical arguments. '; abst[182]='Brewster angle microscopy was used to study the microrheological response of fatty acid Langmuir monolayers subjected to shear flow. Slippage of domains past each other was observed during shear, and elastic recovery of domainshape was monitored following the cessation of shear. Experiments were performed as a function of shear rate, total strain, and temperature in two tilted hexatic monolayer phases, L-2 and Ov. Three regimes were found as a function of temperature. At low temperature (T = 17 degreesC), the degree of slippage and recovery was shear rate independent. At high temperature (T greater than or equal to 25 degreesC), the recovery decreased and the slippage increased systematically with increasing shear rate. At an intermediate temperature (T = 21 degreesC), a distinct transition from low-temperature to high-temperature behavior was observed at a shear rate of 0.35 s(-1). These regimes correlated precisely to previous observations of parabolic or triangular velocity profiles in monolayer channel flow. Taking all temperatures and shear rates into account, there was a one-to-one correspondence between slippage and recovery, suggesting that the two are directly related. These results suggest a fundamental correspondence between macroscopic monolayer theology and domain-level processes. '; abst[183]='The turbulent advection of a reacting substance is considered. The existence of two different states, one smooth and the other filamental, is discussed. The transition between these states is characterized in terms of the competition of the stretching and folding mechanism of the turbulent field and the tendency of the scalar field to relax to the non-homogeneous steady state. (C) 2001 Elsevier Science B.V. All rights reserved. '; abst[184]='We study the problem of the advection of passive particles with inertia in a two-dimensional, synthetic, and stationary turbulent flow. The asymptotic analytical result and numerical simulations show the importance of inertial bias in collecting the particles preferentially in certain regions of the flow, depending on their density relative to that of the flow. We also study how these aggregates are affected when a simple chemical reaction mechanism is introduced through a Eulerian scheme. We find that inertia can be responsible for maintaining a stationary concentration pattern even under nonfavorable reactive conditions or destroying it under favorable ones. '; abst[185]='We present the study of discrete breathers moving resonantly in a two-dimensional polymeric hairpin-shaped model with perpendicular onsite potentials. Their motion adapts to the local dynamical environment and move more efficiently in the curve in several cases. This motion is locally governed by conservation of energy. Weak dissipation and thermal noise do not affect these phenomena qualitatively. '; abst[186]='We Study energy relaxation in thermalized one-dimensional nonlinear arrays of the Fermi-Pasta-Ulam type. The ends of the thermalized systems are placed in contact with a zero-temperature reservoir via damping forces. Harmonic arrays relax by sequential phonon decay into the cold reservoir. the lower-frequency modes relaxing first. The relaxation pathway for purely anharmonic arrays involves the degradation of higher-energy nonlinear modes into lower-energy ones. The lowest-energy modes are absorbed by the cold reservoir. but a small amount of energy is persistently left behind in the array in the form of almost stationary low-frequency localized modes. Arrays with interactions that contain both a harmonic and an anharmonic contribution exhibit behavior that involve, the interplay of phonon modes and breather modes. At long times re laxation is extremely slow due to the spontaneous appearance and persistence of energetic high-frequency stationary breathers. Breather behavior is further ascertained by explicitly injecting a localized excitation into the thermalized arrays and observing the relaxation behavior. '; abst[187]='We use temperature tuning to control signal propagation in simple one-dimensional arrays of masses connected by hard anharmonic springs and with no local potentials. In our numerical model a sustained signal is applied at one site of a chain immersed in a thermal environment and the signal-to-noise ratio is measured at each oscillator. We show that raising the temperature can lead to enhanced signal propagation along the chain, resulting in thermal resonance effects akin to the resonance observed in arrays of bistable systems. '; abst[188]=' '; abst[189]='Achiral diprotonated porphyrins, forming homoassociates in aqueous solution, lead to spontaneous chiral symmetry breaking. The unexpected result is that the chirality sign of these homoassociates can be selected by vortex motion during the aggregation process. This result is confirmed by means of circular dichroism spectra. These experimental findings are rationalized in terms of the asymmetric influence of macroscopic forces on bifurcation scenarios and by considering the specific binding characteristics of the porphyrin units to form the homoassociates. '; abst[190]='Homoassociates of the achiral title porphyrins in acid solutions show spontaneous symmetry breaking, which can be detected by circular dichroism (CD). The CD spectra are due to differential scattering and differential absorption contributions, the relative significance of which is related to the shape and size of the homoassociate. When an earlier model, designed for the association of these diprotonated por phyrins (J aggregates with the geometry of stepped sheets of intramolecular-stabilised zwitterions), was applied to an exciton-coupling point-dipole approximation, the folding of the one dimensional homoassociates explained the CD signals detected. An effect of the vortex direction, caused by stirring or rotary evaporation, upon the exciton chirality sign was detected. In the case of H2TPPS3, the number of experiments performed gave a statistical significance to this effect. This vortex effect can be attributed to enhancement of the chirality fluctuations that originate in the diffusion-limited aggregation to high-molecular-weight homoassociates In this sense, the phenomenon could be general for supramolecular systems that are obtained under kinetic control, and its detection would be possible when inherent chiral chromophores were being generated in the association process. '; abst[191]='We present an analytic and numerical study of the effects of external fluctuations in active media. Our analytical methodology transforms the initial stochastic partial differential equations into an effective set of deterministic reaction-diffusion equations. As a result we are able to explain and make quantitative predictions on the systematic and constructive effects of the noise, for example, target patterns created out of noise and traveling or spiral waves sustained by noise. Our study includes the case of realistic noises with temporal and spatial structures. '; abst[192]='We show that external fluctuations induce excitable behavior in a bistable spatially extended system with activator-inhibitor dynamics of the FitzHugh-Nagumo, type. This scan be understood as a mechanism for sustained signal propagation in bistable media. The phase diagram of the stochastic system is analytically obtained and numerically verified. For small-noise intensities, front propagation becomes unstable, and excitable pulses arise as the only possible spatiotemporal behavior of the system. For large-noise intensities, on the other hand. the system enters an effective regime of oscillatory behavior, where it exhibits spontaneous nucleation of pulses and synchronized firing. '; abst[193]='We present numerical evidence and a theoretical analysis of the appearance of anticoherence resonance induced by noise, not predicted in former analysis of coherence resonance. We have found that this phenomenon occurs for very small values of the intensity of the noise acting on an excitable system, and we claim that this is a universal signature of a nonmonotonous relaxational behavior near its oscillatory regime. Moreover, we demonstrate that this new phenomenon is totally compatible with the standard situation of coherence resonance appearing at intermediate values of noise intensity. '; abst[194]='We propose a phenomenological model of fingering dynamics in the presence of an external drift, motivated by recent experiments on quasi-two-dimensional electrodeposition with hydrodynamic convection. We study the dynamical transition between a Laplacian growth regime and a weak finger competition regime. The model proposed defines a wavelength-selection problem of the finger array which is coupled in a nontrivial way to the single-finger selection problem in a channel. The wavelength-selection mechanism proposed is associated to the crossover from a diffusive to a ballistic behavior of the aggregating particles, as the coarsening spatial scale of the pattern matches the appropriate diffusion length. This yields specific predictions for the selected wavelength. The dynamics of the model are studied numerically with boundary-integral methods in the quasistatic approximation and, complementarily, using a biased random walk Monte Carlo scheme on a lattice. Results are in qualitative agreement with the theoretical predictions. (C) 2002 Elsevier Science B.V. All rights reserved. '; abst[195]='We report a quantitative analysis of a series of chemically induced convection patterns for the methylene-blue-glucose system at different experimental conditions. The objective of the study is to get some quantitative knowledge of the phenomenon (for example, the characteristic wavelength and the characteristic time for the pattern to appear). We focus our attention on the initial stages of the pattern appearance just after the instability and at some aspects of the general behavior of the complete pattern evolution. We analyze the effect on length and time scales of the patterns obtained when varying the initial values of three different experimental parameters (viscosity, pH, and layer depth). The results obtained in the "linear growth" regime reproduce the qualitative trends extracted from the linear stability analysis of a theoretical model subject to a pseudo-steady-state approximation. '; abst[196]='A simple kinetic model of a two-component phase-separating Langmuir monolayer with a chemical reaction is proposed. Its analysis and numerical simulations show that nonequilibrium periodic stationary structures and patterns of traveling stripes can spontaneously develop. The nonequilibrium phase diagram of this system is constructed and the properties of the patterns are discussed. '; abst[197]='We consider the binary diffusion-controlled reaction A+B-->0 between nonpassively advected particles. This reactive system under a two-dimensional synthetic stationary turbulent flow leads to a diversity of kinetic regimes that result from the interplay between reaction, advection, and drag forces. Inertial bias collects particles preferentially in certain regions of the flow depending on their density, and this fact strongly determines the overall kinetic behavior and the spatial organization of the reactive mixture. A Eulerian scheme for the equations that describe this problem is developed and implemented, so that we can numerically follow the decay behavior as well as the patterned evolution of the system. Two-point correlation functions are used in order to characterize the aggregation versus segregation phenomena taking place in the system. (C) 2002 American Institute of Physics. '; abst[198]='We carry out a numerical study of the asymptotic dynamics of breathers in finite Fermi-Pasta-Ulam chains at zero and nonzero temperatures. While at zero temperature such breathers remain essentially stationary and decay extremely slowly over wide parameter ranges, thermal fluctuations tend to lead to breather motion and more rapid decay. In both cases the decay is essentially exponential over long time intervals. '; abst[199]='The dynamics of energy relaxation in thermalized one- and two-dimensional arrays with nonlinear interactions depend in detail on the interactions and, in some cases, on dimensionality. We describe and explain these differences for arrays of the Fermi-Pasta-Ulam type. In particular, we focus on the roles of harmonic contributions to the interactions and of breathers in the relaxation process. (C) 2002 Elsevier Science B.V. All rights reserved. '; abst[200]='Analytical and numerical results on the ordering role of external random fluctuations in excitable systems are presented. Our study focuses on a simple model for excitable systems. Regular waves are created and sustained out of noise when the system is forced with random perturbations. Explicit results for the generation and dynamics of rings and targets are presented. '; abst[201]='In thin-layer electrodeposition the dissipated electrical energy leads to a substantial heating of the ion solution. We measured the resulting temperature field by means of an infrared camera. The properties of the temperature field correspond closely with the development of the concentration field. In particular, we find that the thermal gradients at the electrodes act similar to a weak additional driving force to the convection rolls driven by concentration gradients. '; abst[202]='Recently a fingering morphology, resembling the hydrodynamic Saffman-Taylor instability, was identified in the quasi-two-dimensional electrodeposition of copper. We present here measurements of the dispersion relation of the growing front. The instability is accompanied by gravity-driven convection rolls at the electrodes, which are examined using particle image velocimetry. While at the anode the theory presented by Chazalviel [J. Electroanal. Chem. 407, 61 (1996)] describes the convection roll, the flow field at the cathode is more complicated because of the growing deposit. In particular, the analysis of the orientation of the velocity vectors reveals some lag of the development of the convection roll compared to the finger envelope. '; abst[203]='A closed excitable pathway with one point-to-point connection is used to generate a rotating wave both in experiments using the photosensitive Belousov-Zhabotinsky system and numerically with an Oregonator reaction-diffusion model. By varying the excitability and geometrical properties of the medium, propagation can be made unidirectional or bidirectional, giving rise, respectively, to the existence or not of sustained reentrant activity in a closed excitable track. '; abst[204]='The Langmuir monolayers of diacyl glycerol amino acid-based surfactants with different substitution patterns of the glycerol backbone have been studied by means of surface pressure versus molecular area isotherms and Brewster angle microscopy (BAM). The isotherms show that all the studied compounds form stable monolayers on a water subphase. Concerning the compounds with alkyl chains in adjacent positions, the effect of the nature of the headgroup and the length of alkyl chains on their monolayer behavior is similar to what is observed in naturally occurring phospholipids. BAM images of the condensed phase show initially lobulated domains that relax to rounded-shaped structures with a singularity at the center (star defect) or at the boundary of the condensed droplets. The compound with alkyl chains bound to the ends of the glycerol backbone shows a markedly different behavior. Although condensed domains are favored in this case, some hindrance in the interaction between alkyl chains of different molecules leads to the formation of compact and rough growing droplets, reminiscent of those predicted by the Eden model of cluster growth. This hindrance is attributed to the lower hydrophobic interaction between intra-alkyl chains due to the carbon atom separating them. '; abst[205]='The adsorption properties of parabanic acid (PBA) on Pt(111) electrodes are described. The process takes place with charge transfer at potentials higher than 0.175 V. The PBA adlayer is particularly stable against oxidation or CO adsorption but is desorbed upon hydrogen adsorption. Comparison between voltammetric charges and charge displacement experiments, carried out at low potentials, enables the estimation of the PBA contribution to the overall voltammetric charge. Spectroelectroelectrochemical experiments suggest that PBA adsorption takes place through one of its nitrogen atoms, after breaking of the corresponding N-H bond. The kinetics of the PBA adlayer desorption takes place through an instantaneous nucleation and growth mechanism, linked to the adsorption of hydrogen atoms. (C) 2002 Elsevier Science B.V. All rights reserved. '; abst[206]='Winfree turbulence of scroll waves is a special kind of spatiotemporal chaos that exists exclusively in three-dimensional excitable media and is currently considered one of the principal mechanisms of cardiac fibrillation. A chaotic wave pattern develops through the negative-tension instability of vortex filaments, which tend to spontaneously stretch, bend, loop, and produce an expanding tangle that fills up the volume. We demonstrate that such turbulence can readily be controlled by weak nonresonant modulation of the medium excitability. Depending on the forcing frequency, either suppression or induction of turbulence can be achieved. '; abst[207]='The self-assembly of diprotonated phenyl and 4-sulfonatophenyl meso-tetrasubstituted porphyrins gives a spontaneous chiral symmetry breaking, but only for H2TPPS3-, which forms helicoidal colloidal particles; the selection of the resulting chirality sign by the hydrodynamic forces of a stirring vortex can be demonstrated. '; abst[208]='A disclination line populated with point defects that break the translational symmetry forms near a free nematic (N) interface in a confined geometry. The disclination line is, however, absent in the smectic-A phase (SmA). We use this fact to control the formation of point defect distributions on a disclination line by directional melting of the SmA phase in a temperature gradient. A threshold velocity (nu(th)) exists below which a defect-free disclination line is formed. The frequency of nucleation of point defects increases steadily for nu > nu(th), and exhibits a remarkable regularity. We derive an empirical scaling for nu(th) in terms of the experimental tuning parameters. We propose a simple model that allows to understand the formation of the point defects. '; abst[209]='Plankton play an important role in the ecology of the ocean and the climate because of their participation in the global carbon cycle at the base of the food chain. However, damaging plankton blooms can sometimes occur and are initially characterized by sudden transient increases in the phytoplankton population. They are thought to be driven by several effects, such as seasonal variations in temperature and salinity, and nutrient mixing. Furthermore, phytoplankton and zooplankton have different buoyancy properties, leading to a differential response in turbulent environments. In this paper, we investigate this effect in a model of advected plankton dynamics. We find that, over a range of parameter values, flows of marine species subjected to inertial/viscous forces naturally lead to patchiness and, in turn, periodically sustained plankton blooms. '; abst[210]='Breather stability and longevity in thermally relaxing nonlinear arrays depend sensitively on their interactions with other excitations. We review numerical results for the relaxation of breathers in Fermi-Pasta-Ulam arrays, with a specific focus on the different relaxation channels and their dependence on the interparticle interactions, dimensionality, initial condition, and system parameters. (C) 2003 American Institute of Physics. '; abst[211]='We study, both theoretically and experimentally, the dynamical response of Turing patterns to a spatiotemporal forcing in the form of a traveling-wave modulation of a control parameter. We show that from strictly spatial resonance, it is possible to induce new, generic dynamical behaviors, including temporally modulated traveling waves and localized traveling solitonlike solutions. The latter make contact with the soliton solutions of Coullet [Phys. Rev. Lett. 56, 724 (1986)] and generalize them. The stability diagram for the different propagating modes in the Lengyel-Epstein model is determined numerically. Direct observations of the predicted solutions in experiments carried out with light modulations in the photosensitive chlorine dioxide-iodine-malonic acid reaction are also reported. '; abst[212]='The interdisciplinary field of nonlinear chemical dynamics has grown significantly in breadth and depth over the past three decades. Its subject matter and applications encompass all branches of chemistry as well as areas of mathematics, physics, biology and engineering. In this Perspective, we present an overview of some of the key results of nonlinear chemical dynamics, with emphasis on those areas most likely to be of interest to inorganic chemists. We discuss the range of phenomenology from chemical oscillation to chaos to waves and pattern formation, as well as experimental methods, mechanistic considerations, theoretical techniques, and the results of coupling and external forcing. '; abst[213]='We present an analytical scheme, easily implemented numerically, to generate synthetic Gaussian 2D turbulent flows by using linear stochastic partial differential equations, where the noise term acts as a random force of well-prescribed statistics. This methodology leads to a divergence-free, isotropic, stationary and homogeneous velocity field, whose characteristic parameters are well reproduced, in particular the kinematic viscosity and energy spectrum. This practical approach to tailor a turbulent flow is justified by its versatility when analizing different physical processes occurring in advectely mixed systems. Here, we focuss on an application to study the dynamics of Planktonic populations in the ocean. '; abst[214]='Active media are a suitable benchmark to study the constructive role of random fluctuations in pattern forming systems. The mathematical framework to model these pattern forming systems is by using Partial Differential Equations. Due to the presence of realistic noises in the experiments we have to deal with Non-Markovian Stochastic Partial Differential Equations whose treatment is an unsolved problem in the theory of Stochastic Processes. A preliminary analytical approach to this topic is presented. Quantitative and qualitative agreement is found between theoretical and numerical results. '; abst[215]='Scroll waves. in excitable media, described by the Barkley model, are studied. In the parameter region of weak excitability, negative tension of wave filaments is found. It leads to expansion of scroll rings and instability of wave filaments. A circular filament tends to stretch, bend, loop, and produce an expanding tangle that fills up the volume. The filament does not undergo fragmentation before it touches the boundaries. Statistical properties of such Winfree turbulence of scroll waves are numerically investigated. '; abst[216]='Rotating scroll waves are dynamical spatiotemporal structures characteristic of three-dimensional active media. It is well known that, under low excitability conditions, scroll waves develop an intrinsically unstable dynamical regime that leads to a highly disorganized pattern of wave propagation. Such a "turbulent" state bears some resemblance to fibrillation states in cardiac tissue. We show here that this unstable regime can be controlled by using a spatially distributed random forcing superimposed on a control parameter of the system. Our results are obtained from numerical simulations but an explicit analytical argument that rationalizes our observations is also presented. '; abst[217]='We report a reorientational phenomenon that takes place inside confined smectic-C (SmC) domains in a phase-segregated Langmuir film. Observations of texture changes by means of Brewster angle miscroscopy (BAM) refer to an azobenzene derivative whose monolayer behavior depends strongly on its molecular cis/ trans configuration. Well-developed droplets of a trans-rich mesophase adopt mixed bend/splay structures whose splay sign is reversed through complete droplet reordering when varying the surface pressure. Numerical simulations of a simple relaxational model based on a free-energy functional fully reproduce the experimental observations. '; abst[218]='The monolayer behavior of the azobenzene derivative 8Az3COOH is shown to depend significatively on temperature and on the isomeric (trans-cis) composition. For pure trans monolayers, important temperature effects in the mesoseopic organization (as revealed by means of Brewster angle microscopy, BAM) are observed for the low-pressure phase in the studied temperature range (10 degreesC < T < 40 degreesC). Mixed trans-cis monolayers show that both isomers are virtually immiscible, leading to a phase segregation into birefringent, nearly pure trans droplets surrounded by an isotropic, nearly pure cis matrix. The existence of well-defined anchoring conditions at the droplet boundaries leads to highly symmetric textures, amenable of quantitative BAM image analysis, which helps to better visualize mesoscopic changes induced by variations in the control parameters (temperature, surface pressure or irradiation). '; abst[219]='The inner texture and shape of condensed droplets in Langmuir monolayers of the phospholipid dimyristoylphosphatidylethanolamine (DMPE) have been studied by Brewster angle microscopy. We report a strong temperature dependence of the inner texture in the range 15 degreesC less than or equal to T less than or equal to 25 degreesC, with continuous distortions and boojums at low temperatures and segmented textures that include 6-fold star defects at high temperatures. Image analysis of metastable in = 1 textures at low temperatures has yielded important material parameters. At all temperatures, a clockwise bend structure of the c-director is observed. Droplet shapes are typically cardioidlike, becoming more circular for small droplets or high temperatures. This system exemplifies the need for better theoretical models to understand the problem of the formation of complex shapes and textures in condensed Langmuir monolayers. '; abst[220]='We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a striking symmetry-breaking phenomenon of the intrinsic striped patterns giving rise to hexagonal lattices for intermediate values of the forcing velocity. The phenomenon is understood in the framework of the corresponding amplitude equations, which unveils a complex scenario of dynamical behaviors. '; abst[221]='The oxidation of solutions of glucose with methylene-blue as a catalyst in basic media can induce hydrodynamic overturning instabilities, termed chemoconvection in recognition of their similarity to convective instabilities. The phenomenon is due to gluconic acid, the marginally dense product of the reaction, which gradually builds an unstable density profile. Experiments indicate that dominant pattern wavenumbers initially increase before gradually decreasing or can even oscillate for long times. Here, we perform a weakly nonlinear analysis for an established model of the system with simple kinetics, and show that the resulting amplitude equation is analogous to that obtained in convection with insulating walls. We show that the amplitude description predicts that dominant pattern wavenumbers should decrease in the long term, but does not reproduce the aforementioned increasing wavenumber behavior in the initial stages of pattern development. We hypothesize that this is due to horizontally homogeneous steady states not being attained before pattern onset. We show that the behavior can be explained using a combination of pseudo-steady-state linear and steady-state weakly nonlinear theories. The results obtained are in qualitative agreement with the analysis of experiments. '; abst[222]='Droplet smectic-C domains in films of surfactant molecules exhibit different orientational textures. For these systems we formulate a kinetic model based on a free energy functional containing bulk (elastic) and surface interactions. Numerical simulations for the corresponding relaxational equation show the existence of two different equilibrium configurations with a centered defect. In particular, when the elastic terms dominate, bend-shaped textures appear, whereas for strong boundary effects mixed bend/splay conformations are displayed. A variational analysis for the free energy functional confirms the validity of the above numerical results. The stability of textures with centered defects with respect to the formation of periferic defects (boojums) is also discussed qualitatively. The above theoretical predictions are compared with experimental results from Brewster angle microscopy imaging of azobenzene Langmuir monolayers. (C) 2004 American Institute of Physics. '; abst[223]='A model of a phase-separating two-component Langmuir monolayer in the presence of a photoinduced reaction interconverting two components is formulated. An interplay between phase separation, orientational ordering, and reaction is found to lead to a variety of nonequilibrium self-organized patterns, both stationary and traveling. Examples of the patterns, observed in numerical simulations, include flowing droplets, traveling stripes, wave sources, and vortex defects. '; abst[224]='We report on the effect of a spatio-temporal forcing applied on Turing stripe patterns under spatial resonance. Experiments conducted with the photosensitive CDIMA reaction unveil a large variety of dynamical responses of striped patterns, from entrained to waving, when changing the forcing velocity from small to large values. In between, and quite unexpectedly, we also observe a symmetry breaking phenomenon leading to hexagonal lattices, either entrained with the forcing or oscillating. We propose a new set of coupled amplitude equations [1] which provides a theoretical framework where the experimental phenomena can be interpreted. (C) 2004 Elsevier B.V. All rights reserved. '; abst[225]='Our main objective in this review is that of analysing the cooperative interaction between randomness, nonlinearities and spatial coupling in extended systems. We shall report experimental, analytical and numerical evidences that an unexpected ordering influence appears when the intensity of a forcing external noise is increased. Different generic pattern-forming theoretical models will be considered, together with specific realistic scenarios ranging from electronic circuits to chemical reactions. '; abst[226]='In a photoresponsive Langmuir monolayer comprised of smectic-C-like domains of mesogenic trans-azobenzene derivative embedded within an isotropic matrix of its cis isomer counterpart, several structurally differing circular droplets were irradiated with linearly polarized light. This report describes the structural rearrangements that occurred in these droplets upon illumination followed by Brewster angle microscopy analysis. Starting from initial well-characterized and symmetric states, final photoaligned situations were reached in which the azimuth angles of the rod-shaped elongated molecules were found to be perpendicular to the electric component of the excitation light. The dynamical aspects of the photoalignments, including their transient patterns, are captured by a theoretical model that couples a relaxational principle incorporating long-range elastic forces with a kinetic formalism presenting an anisotropic rate law. (c) 2005 American Institute of Physics. '; abst[227]='Monovalent ligand 4 and divalent ligand 8 have been synthesized, and their thermodynamic parameters of complexation to avidin and streptavidin have been analyzed in terms of multivalent binding. '; abst[228]='Preparation of Langmuir monolayers of a mixture of trans- and cis-isomers of an azobenzene derivative, 4-[4-[(4-octylphenyl)azo]phenoxy]butanoic acid, results in the segregation of birefringent trans-isomer domains embedded in an isotropic medium of cis-isomers. Brewster angle microscopy observations allow us to identify different textures inside the domains depending on surface pressure, temperature, and domain size. The evolution of the monolayer in the dark, from initial droplets formed after spreading to a stable stripe texture, is described. The dynamics of domain coalescence and some morphological transitions induced by temperature and surface pressure changes are also discussed. A simple theoretical model is included to supplement some of these experimental observations. '; abst[229]='We present experiments where opposed pairs of planar parallel disclination lines of topological strength s=+/-1 move due to their mutual attraction. Our measurements show that their motion is clearly asymmetric, with +1 defects moving up to twice as fast as -1 ones. This is a clear indication of backflow, given the intrinsic isotropic elasticity of our system. A phenomenological model is able to account for the experimental observations by renormalizing the orientational diffusivity estimated from the velocity of each defect. '; abst[230]='The addition of cyclodextrins (alpha-CD, beta-CD, 2-hydroxopropyl-beta-CD and gamma-CD) to aqueous solutions of representative cationic (MnTMPyP) and anionic (MnTPPS4) water-soluble Mn porphyrins only substantially affect the behavior of the Mn(III)/Mn(II) couple when inclusion complexes (i.e. for MnTPPS4) are formed. The voltammetric responses were interpreted under the assumption that the inclusion complexes are electroactive, which occurs after their adsorption on the electrode surface. In addition, the results point to a higher affinity of the cyclodextrins for (MnTHS4)-T-II than for (MnTPPS4)-T-III. Copyright (C) 2005 Society of Porphyrins & Phthalocyanines. '; abst[231]='The Mn oxidation state of two water soluble Mn porphyrins, MnTMPyP and MnTPPS4, was studied as a function of the aqua or hydroxo ligands of the Mn atom. In NaOH solutions, long-lived O=Mn(IV) species were detected in the presence of O-2. Conversely, the dihydroxo Mn(III) porphyrin reduces spontaneously to the Mn(II) species in the absence of O-2. In alkaline solutions, these Mn porphyrins were able to electrocatalyze the 4-electron reduction of O-2 to H2O on a vitreous carbon electrode. Copyright (C) 2005 Society of Porphyrins & Phthalocyanines. '; abst[232]='We present a nonequlibrium approach for the study of a flexible bilayer whose two components induce distinct curvatures. In turn, the two components are interconverted by an externally promoted reaction. Phase separation of the two species in the surface results in the growth of domains characterized by different local composition and curvature modulations. This domain growth is limited by the effective mixing due to the interconversion reaction, leading to a finite characteristic domain size. In addition to these effects, first introduced in our earlier work [Phys. Rev. E 71, 051906 (2005)], the important new feature is the assumption that the reactive process actively affects the local curvature of the bilayer. Specifically, we suggest that a force energetically activated by external sources causes a modification of the shape of the membrane at the reaction site. Our results show the appearance of a rich and robust dynamical phenomenology that includes the generation of traveling and/or oscillatory patterns. Linear stability analysis, amplitude equations, and numerical simulations of the model kinetic equations confirm the occurrence of these spatiotemporal behaviors in nonequilibrium reactive bilayers. '; abst[233]='A simple kinetic model of a two-component deformable and reactive bilayer is presented. The two differently shaped components are interconverted by a nonequilibrium reaction, and a phenomenological coupling between local composition and curvature is proposed. When the two components are not miscible, linear stability analysis predicts, and numerical simulations show, the formation of stationary nonequilibrium composition/curvature patterns whose typical size is determined by the reactive process. For miscible components, a linearization of the dynamic equations is performed in order to evaluate the correlation function for shape fluctuations from which the behavior of these systems in micropipet aspiration experiments can be predicted. '; abst[234]='We consider a simple model for steady-state luminescence of single polymer chains in a dilute solution in the case when excitation quenching is due to energy transfer between a donor and an acceptor attached to the ends of the chain. We present numerical results for Rouse chains without or with hydrodynamic interactions, which are taken into account in a perturbative manner. We consider the situations of a quiescent solvent as well as the chain in a shear flow and discuss the dependence of the steady-state luminescence intensity on the strength of hydrodynamic interaction and on the shear rate in the flow. '; abst[235]='We report here a photoswitch process that involves collective molecular reorientation in a monolayer of an azobenzene derivative. Using polarized light we force the transition between two clearly distinguishable orientational mesoscopic configurations that can be monitored by reflection optical microscopy. A model that combines thermodynamic and kinetic arguments is proposed, and it is able to reproduce both the two states and the mechanism involved in the transition. We conclude that the phenomenon reported here is essentially different from the usual electric-field-induced molecular alignment often found in liquid crystalline materials and devices. Instead, it involves a photoexcitation concomitant with an H-aggregation process. '; abst[236]='Scroll waves, a characteristic dynamical pattern of three-dimensional excitable media, exhibit an instability under low excitability conditions. This unstable regime can be partially controlled by using random forcing in a clear manifestation of the ordering role of a stochastic external perturbation. Analytical and numerical results confirm this unexpected noise effect. (c) 2004 Elsevier B.V. All rights reserved. '; abst[237]='By simulations of the Barkley model, action of uniform periodic nonresonant forcing on scroll rings and wave turbulence in three-dimensional excitable media is investigated. Sufficiently strong rapid forcing converts expanding scroll rings into the collapsing ones and suppresses the Winfree turbulence caused by the negative tension of wave filaments. Slow strong forcing has an opposite effect, leading to expansion of scroll rings and induction of the turbulence. These effects are explained in the framework of the phenomenological kinematic theory of scroll waves. '; abst[238]='Excitable media support self-organized scroll waves which can be unstable and give rise to three-dimensional wave chaos. Winfree turbulence of scroll waves results from the negative-tension instability of scroll waves; it plays an important role in the cardiac tissue where it may lead to ventricular fibrillation. By numerical simulations of the Oregonator model, we show that this instability and, thus, the Winfree turbulence may also be observed in the Belousov-Zhabotinsky reaction. The region in the parameter space, where the instability takes place, is determined, and a relationship between the negative-tension instability and the meandering behavior of spiral waves is found. The application of global periodic forcing to control such turbulence in the Oregonator model is discussed. '; abst[239]='Langmuir monolayers of an amphiphilic azobenzene derivative exhibit easily perturbable mesophases with long-range orientational order that couples strongly to linearly polarized light, resulting in symmetric photoaligned textures. Controlled rotation of the polarization plane induces continuous collective precession of the molecular field, which reveals the shear-thinning nature of the surface rotational viscosity. The dynamics is controlled by a balance between the strength of the optical coupling and viscous dissipation so that an increase in the rotational velocity results in a dampening of the synchronous anharmonic oscillations of the orientational field, as revealed by a space-time analysis of the Brewster angle microscopy images. '; abst[240]='Continued irradiation of smectic-C-like domains of photosensitive Langmuir monolayers from azobenzene derivatives induces the nucleation and propagation of orientational travelling waves as observed with Brewster angle microscopy (BAM). BAM image analysis has allowed to identify different dynamical behaviors involving the generation and propagation of such waves. A model based on the coupling between an orientational and a composition field proposes a scenario for dynamic self-assembly that accounts for most of the observed phenomena, and allows to pinpoint the relevance of boundary defects in wave-emitting structures. '; abst[241]='Propagation of localized orientational waves, as imaged by Brewster angle microscopy, is induced by low intensity linearly polarized light inside axisymmetric smectic-C confined domains in a photosensitive molecular thin film at the air/water interface (Langmuir monolayer). Results from numerical simulations of a model that couples photoreorientational effects and long-range elastic forces are presented. Differences are stressed between our scenario and the paradigmatic wave phenomena in excitable chemical media. '; abst[242]='Glycoluril derivatives with a carboxylic acid side chain have been synthesized and shown to bind to both avidin and streptavidin. Introduction of a valerate side chain in glycoluril led to an increased binding to both proteins only when the valerate group was bound to a N atom and with the proper stereochemistry [(+)-enantiomer]. On the other hand, introduction of the valerate side chain either on the bridgehead carbon or on the N atom with the opposite stereochemistry [(-)- enantiomer] led to a decrease in binding constant compared with unsubstituted glycoluril. Direct spectrophotometric competitive titration of each protein with a racemic ligand allowed measurement of the enantioselectivity of the ligand - protein complexation, together with the binding constant of the two enantiomers. In the case of the N-substituted glycoluril, the extension of the side chain by one methylene group, from valerate to caproate, led to an increase in the binding constant to both proteins. Docking studies using AutoDock 3.05 have been performed in order to predict the binding modes of these ligands to streptavidin. The effect of the stereochemistry and the position of the side chain on the binding constant to streptavidin is discussed in view of the predicted binding modes. '; abst[243]='We study the interaction between two independent nonlinear oscillators competing through a neutral excitable element. The first oscillator, completely deterministic, acts as a normal pacemaker sending pulses to the neutral element which fires when it is excited by these pulses. The second oscillator, endowed with some randomness, though unable to make the excitable element to beat, leads to the occasional suppression of its firing. The missing beats or errors are registered and their statistics analyzed in terms of the noise intensity and the periods of both oscillators. This study is inspired in some complex rhythms such as a particular class of heart arrhythmia. '; abst[244]='The interaction between Hopf and Turing modes has been the subject of active research in recent years. We present here experimental evidence of the existence of mixed Turing-Hopf modes in a two-dimensional system. Using the photosensitive chlorine dioxide-iodine-malonic acid reaction (CDIMA) and external constant background illumination as a control parameter, standing spots oscillating in amplitude and with hexagonal ordering were observed. Numerical simulations in the Lengyel-Epstein model for the CDIMA reaction confirmed the results. '; abst[245]='To analyze possible generalizations of reaction-diffusion schemes for the case of subdiffusion we discuss a simple monomolecular conversion A -> B. We derive the corresponding kinetic equations for the local A and B concentrations. Their form is rather unusual: The parameters of the reaction influence the diffusion term in the equation for a component A, a consequence of the non-Markovian nature of subdiffusion. The equation for the product contains a term which depends on the concentration of A at all previous times. Our discussion shows that reaction-subdiffusion equations may not resemble the corresponding reaction-diffusion ones and are not obtained by a trivial change of the diffusion operator for a subdiffusion one. '; abst[246]='Gene regulatory networks have been conserved during evolution. The Drosophila wing and the vertebrate hindbrain share the gene network involved in the establishment of the boundary between dorsal and ventral compartments in the wing and adjacent rhombomeres in the hindbrain. A positive feedback-loop between boundary and non-boundary cells and mediated by the activities of Notch and Wingless/Wnt-1 leads to the establishment of a Notch dependent organizer at the boundary. By means of a Systems Biology approach that combines mathematical modeling and both in silico and in vivo experiments in the Drosophila wing primordium, we modeled and tested this regulatory network and present evidence that a novel property, namely refractoriness to the Wingless signaling molecule, is required in boundary cells for the formation of a stable dorsal-ventral boundary. This new property has been validated in vivo, promotes mutually exclusive domains of Notch and Wingless activities and confers stability to the dorsal-ventral boundary. A robustness analysis of the regulatory network complements our results and ensures its biological plausibility. '; abst[247]='We look at bulk-like viscoplastic properties of a metastable Langmuir mono layer of an alkanethiol derivative close to collapse conditions. By performing controlled creep experiments (decrease of molecular area at constant surface pressure) we were able to evidence two regimes of plastic flow, below and above a pseudo two dimensional melting point, with distinctive temperature dependencies. '; abst[248]='The lateral packing properties of phospholipids that surround transmembrane proteins are fundamental in the biological activity of these proteins. In this work, Langmuir monolayers of one such lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), are studied with a combination of pressure-area isotherm analysis, Brewster angle microscopy, and atomic force microscopy of extracted films. The analysis reveals a sequence of phase transitions LE-LC-LC ′ occurring in a narrow packing range. The lateral pressures and area densities of these phases provided meanings for the packing requirements in the annular lipid region of typical transmembrane proteins. '; abst[249]='Condensed matter physics is facing new challenges and opportunities raising from the vast and increasingly attractive field of soft materials and complex fluids. Here, we concentrate on one of the simplest experimental examples by reviewing different structural and dynamical properties of spread (Langmuir) monolayers. Our interest goes beyond an equilibrium description to stress experiments and models oriented to unveil dynamic responses either following relaxation or externally controlled forcing processes. We choose to focus on mesoscopic phenomena that reflect the pattern of self-assembly of the constituent molecules. We start by reviewing basic structural and textural aspects of Langmuir monolayers. Probably the most classical nonequilibriurn phenomena one can envisage when referring to complex fluids concern flow properties. Thus, rheological experiments conducted with Langmuir monolayers are briefly commented next. Finally, new scenarios of collective self-organization are discussed from experiments and models, revealing unexplored dynamic self-assembling capabilities of Langmuir monolayers. (c) 2007 Elsevier B.V. All rights reserved. '; abst[250]='Phosphatidylcholines (PCs) are among the most common phospholipids in plasma membranes. Their structural and dynamic properties are known to be strongly affected by unsaturation of lipid hydrocarbon chains, yet the role of the exact positions of the double bonds is poorly understood. In this work, we shed light on this matter through atomic-scale molecular dynamics simulations of eight different one-component lipid bilayers comprised of PCs with 18 carbons in their acyl chains. By introducing a single double bond in each acyl chain and varying its position in a systematic manner, we elucidate the effects of a double bond on various membrane properties. Studies in the fluid phase show that a number of membrane properties depend on the double bond position. In particular, when the double bond in an acyl chain is located close to the membrane-water interface, the area per lipid is considerably larger than that found for a saturated lipid. Further, when the double bond is shifted from the interfacial region toward membrane center, the area per lipid is observed to increase and have a maximum when the double bond is in the middle of the chain. Beyond this point, the surface area decreases systematically as the double bond approaches membrane center. These changes in area per lipid are accompanied by corresponding changes in membrane thickness and ordering of the chains. Further changes are observed in the tilt angles of the chains, membrane hydration together with changes in the number of gauche conformations, and direct head group interactions. All of these effects can be associated with changes in acyl chain conformations and local effects of the double bond on the packing of the surrounding atoms. '; abst[251]='A reactive system under the influence of a turbulent flow leads to a diversity of kinetic regimes that result from the interplay between reaction, advection and drag forces. Inertial bias collects reactants preferentially in certain regions of the flow depending on their density, and this fact strongly determines the overall kinetic behaviour and the spatial organization of the reactive mixture. We present a Eulerian scheme for the advection terms in a kinetic mean-field model that is better suited to the study of nonpassively advected reactive systems than the original Lagrangian approach. We show two examples of these systems: first, a formal study of the typical binary diffusion-controlled reaction A + B -> 0, when the reactants are nonpassively advected; second, application to the study of plankton dynamics in the ocean that reproduces the well-known periodically sustained plankton blooms. '; abst[252]='Natural systems are undeniably subject to random fluctuations, arising from either environmental variability or thermal effects. The consideration of those fluctuations supposes to deal with noisy quantities whose variance might at times be a sizable fraction of their mean levels. It is known that, under these conditions, noisy fluctuations can interact with the system′s nonlinearities to render counterintuitive behavior, in which an increase in the noise level produces a more regular behavior. In systems with spatial degrees of freedom, this regularity takes the form of spatiotemporal order. An overview is presented of the mechanisms through which noise induces, enhances, and sustains ordered behavior in passive and active nonlinear media, and different spatiotemporal phenomena are described resulting from these effects. The general theoretical framework used in the analysis of these effects is reviewed, encompassing the theory of stochastic partial differential equations and coupled sets of ordinary stochastic differential equations. Experimental observations of self-organized behavior arising out of noise are also described, and details on the numerical algorithms needed in the computer simulation of these problems are given. '; abst[253]='Reaction-diffusion equations deliver a versatile tool for the description of reactions in inhomogeneous systems under the assumption that the characteristic reaction scales and the scales of the inhomogeneities in the reactant concentrations separate. In the present work, we discuss the possibilities of a generalization of reaction-diffusion equations to the case of anomalous diffusion described in terms of continuous-time random walks with decoupled step length and waiting time probability densities, the first being Gaussian or Levy, the second one being an exponential or a power law lacking the first moment. We consider a special case of an irreversible or reversible A -> B conversion and show that only in the Markovian case of an exponential waiting time distribution can the diffusion term and the reaction term be decoupled. In all other cases, the properties of the reaction affect the transport operator, so the form of the corresponding reaction-anomalous diffusion equations does not closely follow the form of the usual reaction diffusion equations. '; abst[254]='We report on experiments with the photosensitive chlorine dioxide- iodine-malonic acid reaction (CDIMA) when forced with a random (spatiotemporally) distributed illumination. Acting on a mixed mode consisting of oscillating spots, close enough to the Hopf and Turing codimension-two bifurcation, we observe attenuation of oscillations while the spatial pattern is preserved. Numerical simulations confirm and extend these results. All together these observations point out to a larger vulnerability of the Hopf with respect to the Turing mode when facing noise of intermediate intensity and small correlation parameters. Copyright (C) EPLA, 2008. '; abst[255]='We study the dynamics of annihilation of point defects in Langmuir monolayers. The absence of hydrodynamic effects allows us to quantitatively relate the asymmetry in defect mobility to the elastic anisotropy of the material, which in turn can be varied through the control of the surface pressure applied to the monolayer. Using the proposed theoretical analysis, we are able to obtain rather elusive equilibrium properties out of relatively simple dynamical measurements. In particular, we measure the elastic constants and their pressure dependence. '; abst[256]='An anomalously long transient is needed to achieve a steady pressurization of a fluid when forced to flow through micronarrowed channels under constant mechanical driving. This phenomenon, known as the "bottleneck effect" is here revisited from a different perspective, by using confined displacements of interfacial fluids. Compared to standard microfluidics, such effect admits in this case a neat quantitative characterization, which reveals intrinsic material characteristics of flowing monolayers and permits to envisage strategies for their controlled micromanipulation. '; abst[257]='Herein we introduce a multicellular network motif that performs as a spatial toggle switch and explains how boundary formation can be faithfully accomplished in developmental processes. Importantly, we show that expression and activity patterns of proteins must be simultaneously characterized for a proper understanding and description of the underlying mechanism. Our in silico experiments, in agreement with in vivo results, evaluate different genetic backgrounds and shed light on the dynamics of boundary formation. In addition, we provide an estimation of relevant biological parameters and a robustness analysis. '; abst[258]='The tautomeric equilibria of 2-(4′-hydroxyphenylazo)benzoic acid (HABA) and 2- (3′,5′-dimethyl4-hydroxyphenylazo)benzoic acid (3′,5′-dimethyl-HABA) have been studied by a combination of spectroscopic and computational methods. For neutral HABA in solvents of different polarity (toluene, chloroform, DMSO, DMF, butanol, and ethanol) the azo tautomer (AT) is largely predominant. For monoanionic HABA, the hydrazone tautomer (HT) is the only detected species in apolar solvents such as toluene and chloroform, while the AT is the only detected species in water and a mixture of both tautomers is detected in ethanol. Comparison of the results obtained for HABA and its 3′,5′-dimethylated derivative shows that dimethylation of the hydroxybenzene ring shifts the tautomeric preferences towards the hydrazone species. These findings have been used to examine the differences in binding affinity to streptavidin, as the lower affinity of HABA can be explained in terms of the larger energetic cost associated with the tautomeric shift to the bioactive hydrazone species. Overall, these results suggest that a balanced choice of chemical substituents, embedding environment, and pH can be valuable for exploitation of the azo-hydrazone tautomerism of HABA biomimetics in biotechnological applications. '; abst[259]='We consider an irreversible autocatalytic conversion reaction A+B -> 2A under subdiffusion described by continuous-time random walks. The reactants′ transformations take place independently of their motion and are described by constant rates. The analog of this reaction in the case of normal diffusion is described by the Fisher-Kolmogorov-Petrovskii-Piskunov equation leading to the existence of a nonzero minimal front propagation velocity, which is really attained by the front in its stable motion. We show that for subdiffusion, this minimal propagation velocity is zero, which suggests propagation failure. '; abst[260]='Phase separation kinetics of two-dimensional ternary mixtures have been studied by means of a Monte Carlo approach. Standard Kawasaki kinetics are impractical to study the late stages of the segregation process at deep quenches. An extension of the accelerated algorithm for binary mixtures proposed by Marko and Barkema [Phys. Rev. E 52, 2522 (1995)] is presented to overcome this problem in a three-component system discretized with two coupled lattices. We study the domain growth and the scaling behavior over a wide range of quench depths. Computer performances of the Kawasaki and the accelerated schemes are compared. '; abst[261]='Lipid rafts, defined as domains rich in cholesterol and sphingolipids, are involved in many important plasma membrane functions. Recent studies suggest that the way cells handle membrane cholesterol is fundamental in the formation of such lateral heterogeneities. We propose to model the plasma membrane as a nonequilibrium phase-separating system where cholesterol is dynamically incorporated and released. The model shows how cellular regulation of membrane cholesterol may determine the nanoscale lipid organization when the lipid mixture is close to a phase separation boundary, providing a plausible mechanism for raft formation in vivo. '; abst[262]='We have employed atomistic molecular dynamics simulations to investigate the effect of double-bond parametrization on lipid membrane properties. As models, we use one-component membranes composed of glycerol-based phosphatidylcholines (PCs) with monounsaturated acyl chains, and we complement these studies by additional PC/cholesterol simulations. We compare differences between double-bond parametrizations by varying the position of the double bond systematically along the lipid hydrocarbon chains. The results give rise for concern: They indicate that the double-bond description may change not only the quantitative but also the qualitative nature of membrane behavior. In particular, we find that the double-bond description which accounts for skew states in the vicinity of a double bond predicts a maximum in membrane disorder, when the double bond resides at the middle of an acyl chain, in agreement with experiments. The more commonly used description which does not accommodate skew states, however, predicts membrane disorder to decrease monotonically as the double bond is shifted from the glycerol backbone to the end of an acyl chain. The results highlight the importance of properly describing double bonds especially in many-component membranes, where the interplay of different molecule types is difficult to predict on intuitive grounds. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2976443] '; abst[263]='The structural and dynamical properties of lipid membranes rich in phospholipids and cholesterol are known to be strongly affected by the unsaturation of lipid acyl chains. We show that not only unsaturation but also the position of a double bond has a pronounced effect on membrane properties. We consider how cholesterol interacts with phosphatidylcholines comprising two 18-carbon long monounsaturated acyl chains, where the position of the double bond is varied systematically along the acyl chains. Atomistic molecular dynamics simulations indicate that when the double bond is not in contact with the cholesterol ring, and especially with the C18 group on its rough beta-side, the membrane properties are closest to those of the saturated bilayer. However, any interaction between the double bond and the ring promotes membrane disorder and fluidity. Maximal disorder is found when the double bond is located in the middle of a lipid acyl chain, the case most commonly found in monounsaturated acyl chains of phospholipids. The results suggest a cholesterol-mediated lipid selection mechanism in eukaryotic cell membranes. With saturated lipids, cholesterol promotes the formation of highly ordered raft-like membrane domains, whereas domains rich in unsaturated lipids with a double bond in the middle remain highly fluid despite the presence of cholesterol. '; abst[264]='We studied the optical properties of a two-dimensional (2D) photonic crystal monolayer made tip of silica submicrospheres, partly covered by a metallic coating. The silica particles, synthesized by the Stober method, had a diameter of about 300 nm, with little size dispersion. They were deposited on glass in a hexagonal pattern by the Langmuir-Blodgett process. The resulting film consisted of a single monolayer of particles. The final step of sample preparation consisted of depositing a discontinuous gold layer oil top of the 2D crystal. In order to evaluate the effects of small compositional and structural changes on the optical properties of the 2D crystal, the gold layer was applied to a thickness of less than 2 urn. Anisotropy in the metallic coating was induced by tilting the deposition angle by 10 degrees from the vertical: a discontinuous layer was obtained oil top of the particles, with elongated shapes pointing towards the source of the evaporation. The shape of the particles and the film structure were characterized by scanning electron microscopy. Ellipsometric measurements were performed in transmission mode in order to assess the sample anisotropy, and the plasmon response of the samples was determined by extinction measurements. The original 2D crystal presented unexpected optical and uniaxial anisotropy which was increased by a factor of 2 after gold coating. (C) 2008 Elsevier B.V. All rights reserved. '; abst[265]='The aim of this study was to evaluate the presence of dense mitral annular calcification as a marker of complex aortic atherosclerosis in patients with stroke of uncertain etiology. One hundred twenty-one patients with stroke of uncertain etiology were evaluated for complex aortic atherosclerotic plaques; their presence and severity were correlated with transthoracic echocardiographic findings, demographic data, and cardiovascular risk factors. Complex plaques in the ascending aorta or aortic arch were found in 72 of the 121 patients (59.5%). The only difference seen in patients with or without plaques was the presence of dense mitral annular calcification (58.3 vs 16.3%; P < 0.001). Dense mitral annular calcification (n = 50) was associated with higher prevalence of complex aortic plaques (84.0% vs 42.3%; P < 0.001), mobile components (28.0% vs 9.9%; P < 0.01), and protruding (80.0% vs 36.6%; P < 0.001), ulcerated (16.0% vs 1.4%; P < 0.01), and multisite complex plaques (46.0% vs 9.0%; P < 0.001). Therefore, in patients with stroke of uncertain etiology dense mitral annular calcification is an important marker of aortic atherosclerosis with high risk of embolism, and this association may explain in part the high prevalence of stroke and peripheral embolism in patients with mitral annular calcification. '; abst[266]='Preferential affinity of cholesterol for saturated rather than unsaturated lipids underlies the thermodynamic process of the formation of lipid nanostructures in cell membranes, that is, of rafts. In this context, phase segregation of two-dimensional ternary lipid mixtures is formally studied from two different perspectives. The simplest approach is based on Monte Carlo simulations of an Ising model corresponding to two interconnected lattices, from which the basic features of the phenomenon are investigated. Then, the coarse-graining mean field procedure of the discrete Hamiltonian is adapted and a Ginzburg-Landau-like free energy expression is obtained. From this latter description, we construct kinetic equations that enable us to perform numerical simulations and to establish analytical phase separation criteria. Application of our formalism in the biological context is also discussed. (c) 2008 American Institute of Physics. '; abst[267]='We consider a linear reversible isomerization reaction A reversible arrow B under subdiffusion described by continuous time random walks (CTRW). The reactants′ transformations take place independently on the motion and are described by constant rates. We show that the form of the ensuing system of mesoscopic reaction-subdiffusion equations is unusual: the equation for time derivative of say A (x,t) contains the terms depending not only on Delta A, but also on Delta B. This mirrors the fact that in subdiffusion the flux of particles at time t is defined by the distributions of the particles′ concentrations at all previous times. Since the particles which jump as A at time t could previously be both A or B, this flux depends on both A and B concentrations. '; abst[268]='We present a theoretical study of the recently observed dynamical regimes of paramagnetic colloidal particles externally driven above a regular lattice of magnetic bubbles [P. Tierno, T. H. Johansen, and T. M. Fischer, Phys. Rev. Lett. 99, 038303 (2007)]. An external precessing magnetic field alters the potential generated by the surface of the film in such a way to either drive the particle circularly around one bubble, ballistically through the array, or in triangular orbits on the interstitial regions between the bubbles. In the ballistic regime, we observe different trajectories performed by the particles phase locked with the external driving. Superdiffusive motion, which was experimentally found bridging the localized and delocalized dynamics, emerge only by introducing a certain degree of randomness into the bubbles size distribution. '; abst[269]='We investigate the collective organization of paramagnetic colloidal particles externally driven above the periodic stripes of a uniaxial ferrimagnetic garnet film. An external field modulation induces vibration of the stripe walls and produces random motion of the particles. Defects in the stripe pattern break the symmetry of the potential and favor particle nucleation into large clusters above a critical density. Mismatch between particle size and pattern wavelength generates assemblies with different morphological order. At even higher field strengths, repulsive dipolar interactions between the particles induce cluster melting. We propose a novel approach to generate and externally control a variety of colloidal assemblies. '; abst[270]='To achieve permanent propulsion of micro-objects in confined fluids is an elusive but challenging goal that will foster future development of microfluidics and biotechnology. Recent attempts based on a wide variety of strategies are still far from being able to design simple, versatile, and fully controllable swimming engines on the microscale. Here we show that DNA-linked anisotropic colloidal rotors, composed of paramagnetic colloidal particles with different or similar size, achieve controlled propulsion when subjected to a magnetic field precessing around an axis parallel to the plane of motion. During cycling motion, stronger viscous friction at the bounding plate, as compared to fluid resistance in the bulk, creates an asymmetry in dissipation that rectifies rotation into a net translation of the suspended objects. The potentiality of the method, applicable to any externally rotated micro/nano-object, is finally demonstrated in a microfluidic platform by guiding the colloidal rotors through microscopic-size channels connected in a simple geometry. '; abst[271]='We show that DNA-linked anisotropic doublets composed of paramagnetic colloidal particles can be endowed with controlled propulsion when floating above a flat plate and subjected to a magnetic field precessing around an axis parallel to the plate. The propulsion mechanism for this artificial swimmer does not involve deformations, and it makes use of the minimal two degrees of freedom needed to propel it at low Reynolds numbers. We combine experimental observations with a theoretical analysis that fully characterizes the propulsion velocity in terms of the strength and frequency of the actuating magnetic field. '; abst[272]='We use a uniaxial garnet film with a magnetic bubble lattice to sort paramagnetic colloidal particles with different diameters, i.e., 1.0 and 2.8 mu m. We apply an external magnetic field which precesses around an axis normal to the film with a frequency Omega=62.8 s(-1) and intensity 3120 A/m < H < 6911 A/m. By varying the component of the field H(z) normal to the film, we observe that particles of one size are localized around magnetic bubbles while the others are transported through the array. We complement the experimental measurements with numerical simulations to explore the sorting capability for particles with different magnetic moments. '; abst[273]='Pattern formation induced by noise is a celebrated phenomenon in diverse reaction-diffusion systems. Here we report numerical simulations with the Lengyel-Epstein model for the chlorine dioxide-iodine-malonic acid reaction when perturbed with an external spatiotemporal stochastic forcing in the vicinity of the Hopf and Turing codimension-two bifurcation. Competition between Turing and Hopf modes gives rise to the generation of transient Turing patterns evolving to stationary global oscillations. This situation is reversed by the introduction of external fluctuations and Turing patterns become dominant in this case. The increase in the spatial coherence is found for intermediate noise intensity and small correlation length. '; abst[274]='We demonstrate a new concept for the propulsions of abiological structures at low Reynolds numbers. The approach is based on the design of flexible, planar polymer structures with a permanent magnetic moment. In the presence of an external, uniform, rotating magnetic field these structures deform into three-dimensional shapes that have helical symmetry and translate linearly through fluids at Re between 10(-1) and 10. The mechanism for the motility of these structures involves reversible deformation that breaks their planar symmetry and generates propulsion. These elastic propellers resemble microorganisms that use rotational mechanisms based on flagella and cilia for their motility in fluids at low Re. '; abst[275]='We present a nonequilibrium approach for the study of a two-dimensional phase-separating ternary mixture. When the component that promotes phase separation is dynamically exchanged with the medium, the separation process is halted and actively maintained finite-size segregation domains appear in the system. In addition to this effect, already reported in our earlier work [J. Gomez, F. Sagues, and R. Reigada, Phys. Rev. E 77, 021907 (2008)], the use of a generic Ginzburg-Landau formalism and the inclusion of thermal fluctuations provide a more dynamic description of the resulting domain organization. Its size, shape, and stability properties are studied. Larger and more circular and stable domains are formed when decreasing the recycling rate, increasing the mobility of the exchanged component, and the mixture is quenched deeper. We expect this outcome to be of applicability in raft phenomenology in plasmatic cell membranes. '; abst[276]='Despite the large number of possible glycerol-based phospholipids, biological membranes contain only a small number of them. For example, double bonds in acyl chains are preferably located in the sn-2 chain. The question that emerges is: Why? We have addressed this question through atomistic simulations by considering pure one-component bilayers comprising monounsaturated glycerophospholipids [1-stearoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (SOPC) and 1-oleoyl-2-stearoyl-sn-glycero-3-phosphatidylcholine (OSPC)] and membranes of these lipids mixed with cholesterol. By considering the cases in which an individual double bond is in either the sn-1 or the sn-2 chain, we elucidated how membrane properties depend on this intrinsic feature. We found small but systematic differences in all structural and dynamic membrane properties that we considered. It turns out that the differences are driven by two factors: the mismatch in the acyl chain lengths and the interaction of the double bond in the acyl chains with the cholesterol off-plane methyl groups. The results highlight the fact that unsaturated sn-2 chains lead to more disordered membranes than systems with unsaturated sn-1 chains. The differences between the two isomers are enhanced when cholesterol is present as a result of the interaction of the off-plane cholesterol methyl groups with the double-bond carbon segments in the lipid acyl chains. '; abst[277]='We report a novel phenomenon of chiral selection in self-assembled condensates of achiral amphiphiles. The handedness of chiral textures, reproducing the collective rotational component of the molecular orientation inside submillimeter circular domains, is correlated with the sign of a vortical stirring in the aqueous subphase. We propose an explanation based on the distinctive kinetics of topological defect annihilation during domain coalescence at the initial coarsening stage of a phase-separating monolayer. '; abst[278]='Large surface area nanopatterning using colloidal lithography (CL) processed by dry-etching was investigated by comparing the effect of the etching angle on the subsequent nanostructured sample. The particles, produced from an alkoxide precursor by sol–gel process, were spherical with a size about 300 nm. They were self-assembled in closed-packed 2D crystal monolayers by means of the Langmuir–Blodgett (LB) technique, which controls the surface compactness of the colloidal crystals as well as the number of the particle layers deposited on the substrate. Afterwards, the structure was transferred on silicon wafers by CL: further nanostructuring of monolayer films was made by etching with Ar+ ion beam at 550 eV, 7 · 10− 2 Pa and room temperature over areas of about 4 cm2 of the particle film. The incident beam angle was fixed at 0° and 45° with respect to the normal of the substrate in order to change the morphology of the etched 2D crystal. The shape of the sub-micron particles was altered and the particle size was reduced but the original close-packed structure was conserved. The etching process affected both the particles and the interstitial uncovered substrate. The substrate etching was more pronounced for long time and high etching angle: this resulted from a higher physical sputtering yield at higher angle. Moreover the oblique incidence of ion beam introduced anisotropy to the sample. The particle shadowing effect accentuated the nanostructuring of the substrate at 45°. '; abst[279]='A photoisomerizable fatty acid (containing an azobenzene unit) was dissolved in a nematic liquid crystal (LC), and adsorbed at the LC/water interface, influencing the anchoring of the LC material. Reorientation of the LC phase was observed upon exposure of the system to different irradiation wavelengths. Homeotropic, tilted, and planar anchoring were all observed under various thermodynamic and illumination conditions. Lateral coexistence between regions displaying different anchoring was often observed, as were dynamic and reversible transitions between the various states. These observations suggest that adsorbed monolayers of the azobenzene-fatty acid (probably in equilibrium with the same surfactant in solution) display a rich binary phase diagram, where the relative fractions of cis and trans isomers are determined by the photostationary state associated with the illumination wavelength. The morphology of these phase diagrams has been determined as a function of three variables-bulk concentration, temperature, and composition (cis-trans ratio) of the dissolved surfactant-and six distinct interfacial phases were identified, including five condensed phases and a dilute interfacial vapor phase. This phase diagram is distinct from the behavior of Langmuir monolayers of the same amphiphile at the air/water interface, which exhibits only two condensed phases. '; abst[280]='We study numerically the autocatalytic irreversible reaction A+B -> 2A on a one-dimensional lattice for the case of subdiffusive reactants performing symmetric continuous-time random walks with the power-law waiting time density function psi(t)proportional to t(-1-alpha) with 0