Electrical and memory properties of Si3N4 MIS structures with embedded Si nanocrystals.

Memory structures with an embedded sheet of separated Si nanocrystals were prepared by low pressure chemical vapour deposition using a Si3N4 control layer and different Si2O2 or Si3N4 tunnel layers. It was obtained that Si nanocrystals improve the charging behaviour of the MNOS structures. Memory window width of 1.

Phase transitions induced by variation of invasion rates in spatial cyclic predator-prey models with four or six species.

Cyclic predator-prey models with four or six species are studied on a square lattice when the invasion rates are varied. It is found that the cyclic invasions maintain a self-organizing pattern as long as the deviation of the invasion rate(s) from a uniform value does not exceed a threshold value. For larger deviations, the system exhibits a continuous phase transition into a frozen distribution of odd (or even) label species.

Segregation process and phase transition in cyclic predator-prey models with an even number of species.

We study a spatial cyclic predator-prey model with an even number of species (for n=4, 6, and 8) that allows the formation of two defensive alliances consisting of the even and odd label species. The species are distributed on the sites of a square lattice. The evolution of spatial distribution is governed by iteration of two elementary processes on neighboring sites chosen randomly: if the sites are occupied by a predator-prey pair then the predator invades the prey's site; otherwise the species exchange their sites with a probability X .

The hypervariable D3 domain of Salmonella flagellin is an autonomous folding unit.

The hypervariable D3 domain of Salmonella flagellin, composed of the 190-285 segment, is the major determinant of flagellar antigenicity. D3 was cloned and overexpressed in E. coli.

Transmission electron microscope specimen preparation for exploring the buried interfaces in plan view.

A relatively easy and convenient process for the preparation of transmission electron microscope specimens of buried interfaces is described. The method is based on the alignment and realignment of the specimen rotation centre during ion milling. The ion-milling time interval in which good samples are obtained is substantially extended in this way.

Wing scale microstructures and nanostructures in butterflies--natural photonic crystals.

The aim of our study was to investigate the correlation between structural colour and scale morphology in butterflies. Detailed correlations between blue colour and structure were investigated in three lycaenid subfamilies, which represent a monophylum in the butterfly family Lycaenidae (Lepidoptera): the Coppers (Lycaeninae), the Hairstreaks (Theclinae) and the Blues (Polyommatinae). Complex investigations such as spectral measurements and characterization by means of light microscopy, scanning electron microscopy and transmission electron microscopy enabled us to demonstrate that: (i) a wide array of nanostructures generate blue colours; (ii) monophyletic groups use qualitatively similar structures; and (iii) the hue of the blue colour is characteristic for the microstructure and nanostructure of the body of the scales.

Gleaming and dull surface textures from photonic-crystal-type nanostructures in the butterfly Cyanophrys remus.

Photonic-crystal-type nanostructures occurring in the scales of the butterfly Cyanophrys remus were investigated by optical and electron microscopy (scanning and transmission electron microscopy), reflectance measurements (specular, integrated, and goniometric), by fast Fourier transform analysis of micrographs, by modeling, and by numerical simulation of the measured reflectance data. By evaluating the collected data in a cross-correlated way, we show that the metallic blue dorsal coloration originates from scales which individually are photonic single crystals of 50 x 120 microm2 , while the matt pea-green coloration of the ventral side arises from the cumulative effect of randomly arranged, bright photonic crystallites (blue, green, and yellow) with typical diameters in the 3-10-mum range. Both structures are based on a very moderate refractive index contrast between air and chitin.

Ellipsometry of silica nanoparticulate Langmuir-Blodgett films for the verification of the validity of effective medium approximations.

The validity of various effective medium approximations (EMAs) (Bruggeman, Maxwell-Garnett) was studied for nanostructured systems, where the scale of inhomogeneities is comparable to the wavelength. Langmuir-Blodgett (LB) layers of Stöber silica nanospheres of diameters between 40 and 129 nm are excellent model structures for the experimental verification of the validity of the EMA methods in spectroscopic ellipsometry (SE) evaluation. Nanostructured mono- and multilayered silica films were investigated by SE and reflectance spectroscopy.

Apparent diameter of carbon nanotubes in scanning tunnelling microscopy measurements.

Geometric effects influencing scanning tunnelling microscopy (STM) image formation of single wall carbon nanotubes (SWCNTs) were studied within the framework of a simple model potential. We focused on the geometrical effects which may influence the tunnelling probabilities and lead to discrepancies between the apparent height of the nanotubes measured by STM and their real geometrical diameter. We found that there are two main factors responsible for the underestimation of nanotubes diameter by measuring their height in STM images: (1) the curvature of the nanotube affects the cross sectional shape of the tunnelling channel; (2) the decay rate of tunnelling probabilities inside the tunnel gap increases with increasing curvature of the electrodes.

Phase transition of triplet reaction-diffusion models.

The phase transitions classes of reaction-diffusion systems with multiparticle reactions are an open challenging problem. Large scale simulations are applied for the 3A --> 4A, 3A --> 2A and the 3A --> 4A, 3A --> [formula : see text] triplet reaction models with site occupation restriction in one dimension. Static and dynamic mean-field scaling are observed with signs of logarithmic corrections suggesting d(c) = 1 upper critical dimension for this family of models.

Critical behavior of an even-offspringed branching and annihilating random-walk cellular automaton with spatial disorder.

A stochastic cellular automaton exhibiting a parity-conserving class transition has been investigated in the presence of quenched spatial disorder by large-scale simulations. Numerical evidence has been found that weak disorder causes irrelevant perturbation for the universal behavior of the transition and the absorbing phase of this model. This opens up the possibility for experimental observation of the critical behavior of a nonequilibrium phase transition to absorbing state.

Calculation of the charge-carrier mobility of polyguanylic acid: the simultaneous effect of stretching and twisting.

Charge-carrier (electron and hole) mobilities of polyguanylic acid have been computed using the deformation-potential approximation from ab initio Hartree-Fock band structure. Mobilities resulting from electron scattering on torsional acoustic phonons are calculated and compared to those obtained from a previous calculation [F. B.

Phase diagrams for an evolutionary prisoner's dilemma game on two-dimensional lattices.

The effects of payoffs and noise on the maintenance of cooperative behavior are studied in an evolutionary prisoner's dilemma game with players located on the sites of different two-dimensional lattices. This system exhibits a phase transition from a mixed state of cooperators and defectors to a homogeneous one where only the defectors remain alive. Using Monte Carlo simulations and the generalized mean-field approximations we have determined the phase boundaries (critical points) separating the two phases on the plane of the temperature (noise) and temptation to choose defection.

Cluster mean-field study of the parity-conserving phase transition.

The phase transition of the branching and annihilating random walk with even offspring is studied by N-cluster mean-field approximations on one-dimensional lattices. By allowing the system to reach zero branching rate a phase transition can be seen for any N < or = 12. Coherent anomaly extrapolations applied for the series of approximations results in nu(perpendicular) = 1.

Growth model for arc-deposited fullerene-like CNx nanoparticles.

Multiwall CNx nanotubes, nanoonions, and amorphous nanoballs were formed by carbon DC arc evaporation in a nitrogen atmosphere. The samples were investigated by conventional and high-resolution transmission electron microscopy. We propose a fragment-by-fragment growth mechanism for the formation of the nanoparticles.

Consistent indexing of a (set of) single crystal SAED pattern(s) with the ProcessDiffraction program.

A computer program called "ProcessDiffraction" helps indexing a set of single crystal selected area electron diffraction (SAED) patterns by determining which of the presumed structures can fit all the measured patterns simultaneously. Distances and angles are measured in the digitalized patterns with a graphical tool by clicking on the two shortest non-collinear vectors (spots), using user-supplied calibration data. Centers of the spots and center of the pattern are optionally refined by the program.

Three-state Potts model in combination with the rock-scissors-paper game.

We study a three-state Potts model extended by allowing cyclic dominance between the states as exemplified in the rock-scissors-paper game. Monte Carlo simulations are performed on a square lattice while varying the temperature and the strength of cyclic dominance. It is shown that the critical phase transition from the disordered state to the ordered one is destroyed by the cyclic dominance, which yields a self-organizing pattern even at low temperatures.

Role of diffusion in branching and annihilation random walk models.

Different branching and annihilating random walk models are investigated by the cluster mean-field method and simulations in one and two dimensions. In the case of the A-->2A , 2A--> 0 model the cluster mean-field approximations show diffusion dependence in the phase diagram as was found recently by the nonperturbative renormalization group method [Phys. Rev.

Phase transitions for rock-scissors-paper game on different networks.

Monte Carlo simulations and dynamical mean-field approximations are performed to study the phase transitions in the rock-scissors-paper game on different host networks. These graphs are originated from lattices by introducing quenched and annealed randomness simultaneously. In the resulting phase diagrams three different stationary states are identified for all structures.

Vertex dynamics during domain growth in three-state models.

Topological aspects of interfaces are studied by comparing quantitatively the evolving three-color patterns in three different models, such as the three-state voter, Potts, and extended voter models. The statistical analysis of some geometrical features allows us to explore the role of different elementary processes during distinct coarsening phenomena in the above models.

Critical behavior of the two-dimensional 2A-->3A, 4A--> phi binary system.

The phase transitions of the recently introduced 2A-->3A, 4A--> phi reaction-diffusion model [G. Odor, Phys. Rev.

Phase transitions of the binary production 2A-->3A, 4A--> X model.

Phase transitions of the 2A-->3A, 4A--> X reaction-diffusion model is explored by dynamical, N-cluster approximations and by simulations. The model exhibits site occupation restriction and explicit diffusion of isolated particles. While the site mean-field approximation shows a single transition at zero branching rate introduced by Odor [G.

Cooperation for volunteering and partially random partnerships.

Competition among cooperative, defective, and loner strategies is studied by considering an evolutionary prisoner's dilemma game for different partnerships. In this game each player can adopt one of its coplayer's strategy with a probability depending on the difference of payoffs coming from games with the corresponding coplayers. Our attention is focused on the effects of annealed and quenched randomness in the partnership for fixed number of coplayers.

Phase transition and selection in a four-species cyclic predator-prey model.

We study a four-species ecological system with cyclic dominance whose individuals are distributed on a square lattice. Randomly chosen individuals migrate to one of the neighboring sites if it is empty or invade this site if occupied by their prey. The cyclic dominance maintains the coexistence of all four species if the concentration of vacant sites is lower than a threshold value.

Phase transition classes in triplet and quadruplet reaction-diffusion models.

Phase transitions of reaction-diffusion systems with site occupation restriction and with particle creation that requires n=3,4 parents, whereas explicit diffusion of single particles (A) is present are investigated in low dimensions by the mean-field approximation and simulations. The mean-field approximation of general nA-->(n+k)A, mA-->(m-l)A type of lattice models is solved and a different kind of critical behavior is pointed out. In d=2 dimensions, the 3A-->4A, 3A-->2A model exhibits a continuous mean-field type of phase transition, that implies d(c)<2 upper critical dimension.