Rearrangement of cluster structure during fission processes

Results of molecular dynamics simulations of fission reactions $Na_{10}^{2+} \to Na_7^+ + Na_3^+$ and $Na_{18}^{2+} \to 2 Na_9^+$ are presented. Dependence of the fission barriers on isomer structure of the parent cluster is analyzed. It is demonstrated that the energy necessary for removing homothetic groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. Importance of rearrangement of the cluster structure during the fission process is elucidated. This rearrangement may include transition to another isomer state of the parent cluster before actual separation of the daughter fragments begins and/or forming a "neck" between the separating fragments

Tc-Mapping and Investigation of Water-Initiated Modification of YBa2Cu3O7-x Thin Films by Low Temperature Scanning Electron Microscopy

The Tc -mapping method using low temperature scanning electron microscopy (LTSEM) has been developed to study the spatial distribution of the critical temperature in high temperature superconducting (HTSC) films with a spatial resolution approaching 2 μm. To achieve so high a spatial resolution, a numerical deconvolution method was applied that eliminated distorting effects associated with the thermal diffusion and with the contribution from the absorbed beam current. The Tc -mapping method was used to investigate modification by water of YBa2Cu3O7-x films grown on (100) MgO and (110) LaAIO3 substrates. The rate of modification of a [110]-oriented YBa2Cu3O7-x/LaAIO3 film is found to be 40 times that of a c-axis oriented YBa2Cu3O7-x/MgO epitaxial film. It is argued that water-initiated modification of the films results from penetration of hydrogen into the films, rather than from out-diffusion of oxygen

Boolean Dynamics with Random Couplings

This paper reviews a class of generic dissipative dynamical systems called N-K models. In these models, the dynamics of N elements, defined as Boolean variables, develop step by step, clocked by a discrete time variable. Each of the N Boolean elements at a given time is given a value which depends upon K elements in the previous time step. We review the work of many authors on the behavior of the models, looking particularly at the structure and lengths of their cycles, the sizes of their basins of attraction, and the flow of information through the systems. In the limit of infinite N, there is a phase transition between a chaotic and an ordered phase, with a critical phase in between. We argue that the behavior of this system depends significantly on the topology of the network connections. If the elements are placed upon a lattice with dimension d, the system shows correlations related to the standard percolation or directed percolation phase transition on such a lattice. On the other hand, a very different behavior is seen in the Kauffman net in which all spins are equally likely to be coupled to a given spin. In this situation, coupling loops are mostly suppressed, and the behavior of the system is much more like that of a mean field theory. We also describe possible applications of the models to, for example, genetic networks, cell differentiation, evolution, democracy in social systems and neural networks.Comment: 69 pages, 16 figures, Submitted to Springer Applied Mathematical Sciences Serie

Growth in total cross section and elastic scattering

A simple expression is proposed for the amplitude of elastic proton- proton scattering which corresponds to a Froissant growth in the total cross section and which satisfactorily describes all the data on the differential cross section obtained on the CERN storage rings. (7 refs)

Investigation of the Spring Thermal Bar Phenomenon Based on Mathematical and Laboratory Modeling

The regularities of the appearance and develop ment of large scale ordered convective motions and natural currents, which are the essence of the thermal bar phenomenon, are studied on basis of the mathe matical and physical (laboratory) modeling. Joint application of these two methods allows us to compen sate for the lack of exact exhaustive mathematical description of this phenomenon, which is cumber some and requires a large amount of the initial data that are difficult to obtain. The main objective of our research is to gain the physical similarity between the phenomena observed in the model conditions and the whole class of the investigated phenomena. Recently, the degree of technogenic anthropogenic impact on the aquatic environment has become a glo bal problem that is particularly topical in the condi tions of the possible variations in the global climate and requires urgent solution. The quality of water in the rivers, lakes, and reservoirs used for drinking water supply is gradually decreasing. Successful solution of this problem requires investigation of the processes responsible for the redistribution of water masses The objective of this work is to study the thermal bar dynamics by means of numerical experiments and laboratory modeling with account for the influence of wind, solar irradiance, and fluxes of latent and sensible heat. The mathematical model is a development of the model elaborated earlie

Incentive Ratios of Fisher Markets

Abstract. In a Fisher market, a market maker sells m items to n potential buyers. The buyers submit their utility functions and money endowments to the market maker, who, upon receiving submitted information, derives market equilibrium prices and allocations of its items. While agents may benefit by misreporting their private information, we show that the percentage of improvement by a unilateral strategic play, called incentive ratio, is rather limited—it is less than 2 for linear markets and at most e 1/e ≈ 1.445 for Cobb-Douglas markets. We further prove that both ratios are tight.

How Profitable Are Strategic Behaviors in a Market?

It is common wisdom that individuals behave strategically in economic environments. We consider Fisher markets with Leontief utilities and study strategic behaviors of individual buyers in market equilibria. While simple examples illustrate that buyers do get larger utilities when behaving strategically, we show that the benefits can be quite limited: We introduce the concept of incentive ratio to capture the extent to which utility can be increased by strategic behaviors of an individual, and show that the incentive ratio of Leontief markets is less than 2. We also reveal that the incentive ratios are insensitive to market sizes. Potentially, the concept incentive ratio can have applications in other strategic settings as well

Peculiarities of Thermal Denaturation of OmpF Porin from Yersinia Ruckeri

Irreversible denaturation of membrane proteins in detergent solutions is similar to unfolding of water-soluble multidomain proteins and represents a complex, multistage process. Pore-forming proteins of Gram-negative bacteria are heat-modifiable proteins, i.e., proteins altering their molecular forms (trimers or monomers), and accordingly, their electrophoretic mobilities depending upon denaturation conditions. There are still some contradictory data on the peculiarities of the conformational changes in the porin structure with temperature. Some authors demonstrated the loss of the porin trimeric structure only after unfolding of monomer subunits. Other researchers initially observed the dissociation of porin oligomers into the folded monomers. Using SDS-PAGE, spectroscopic methods and differential scanning calorimetry, a detailed study of thermally induced changes in the spatial structure of OmpF porin from the fish pathogen Yersinia ruckeri (Yr-OmpF) was carried out. The data obtained allowed us to conclude unambiguously that changes in the spatial structure of the monomers of Yr-OmpF precede the dissociation of the porin trimer