Chitosan-cellulose sulfate acetate complexation in acetic acid solutions

Colloidal and optical properties of dispersions of chitosan-cellulose sulfate acetate interpolyelectrolyte complexes resultant from mixing dilute solutions of the polymers in acetic acid and in acetic acid-based buffer mixtures are investigated. It is established that, in acetic acid, an insoluble complex is formed whose composition corresponds to the unit ratio [chitosan]: [cellulose sulfate acetate] = 1: 1.5, mol/mol. Particle size and concentration are independent of the order of mixing of the solutions of the polymers. In buffer solvents, the particle size is larger and the particle concentration is lower than those in acetic acid. Excess chitosan causes the dissolution of the complex. The addition of low-molecular-weight electrolytes to ionic strengths of 0.2–0.3 also promotes the dissolution of the interpolyelectrolyte complex. The complex becomes completely soluble at ionic strengths of 1.5–2.0.     

Structure of the critical state in a discrete superconductor for different values of the SQUID parameter

The critical state of a 1D multijunction SQUID with intrinsic spatial randomness has been studied. It is shown that the system behavior is independent of the SQUID parameter and the critical state under consideration is self-organized.     

Development of the method of electron-optical in situ monitoring for periodic structures

A series of the basic problems for the development of the method of electron-optical in situ monitoring for periodic structures are considered in this work. In particular, the problem of submicron- and nanosized inhomogeneity online monitoring in large areas of tested microelectronic structures with a typical size of the order of 100 μm is discussed to give individual inhomogeneities in detail. The Riccati equation method has been proposed to solve the problem.     

Assortative and disassortative networks. The effect of the topology of a complex network on the properties of dynamical processes on it

The effect of the structure of a complex network on the properties of avalanche dynamical process on it has been analyzed for the first time. It has been shown that the assortativity (disassortativity) degree, which is a structure characteristic of the network and is numerically characterized by the assortativity coefficient r, is a control parameter governing the properties of the dynamical process on the network. The structure of individual avalanches on networks with various r values has been studied. It has been shown that the number of nodes involved in an avalanche is a periodic function of the time.     

A statistical model for simulating the emission of light particles from excited nuclei

The algorithms and basic equations of a novel evaporation model that have been implemented in the program package EVAP15 are detailed. The level density of an excited nucleus is described by the composite Gilbert–Cameron formula with parameter values as suggested by the IAEA working group RIPL-3. Special attention is paid to the cross sections of inverse reactions and, in particular, to those for the interactions of low-energy neutrons with nuclei and for crossing of the Coulomb barrier by low-energy charged particles. The model predictions are compared with a large volume of experimental data on the spectra of particles emitted in the reactions (n, xn), (n, xp), and (n, xα) induced by neutrons with energy near 14 MeV and on the four spectra for the reaction (p, xp) induced by 62-MeV protons.     

Synthesis of yttrium,lanthanum, neodymium,praseodymium, and lutetium alkoxides and acetylacetonates

A convenient and practical method is proposed for the synthesis of lanthanide and yttrium alkoxides. The method involves dissolving the metals or their hydrides in a solution of dry HCl in the corresponding alcohol, with subsequent dehalogenation of the LnCl₃ solution by an equivalent amount of alkali metal (Na, Li), The rareearth alkoxides are easily converted into acetylacetonates Ln(acac)₃ by the action of acetylacetone.A. N. Nesmeyanov Institute of Elementoorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2490–2493, November, 1992.     

Photostability of complexes based on fluorescent CdSe/ZnS nanoparticles and polyelectrolytes

By means of fluorescence spectroscopy, it has been found that the oscillator strength of the electronic transition in CdSe/ZnS nanoparticles increases when the hydrophilic fluorescent CdSe/ZnS nanoparticles form complexes with cationic and anionic polyelectrolytes. However, an increase in the relative quantum yield and photostability is possible only in the complexes of the anionic shell-covered CdSe/ZnS nanoparticles with polycations. The mechanisms of the effect of ionic interactions on the probabilities and channels of electronic transitions in the nanoparticles are discussed.     

Self-organization and 1/f noise in granular superconductors

The interplay between the widespread phenomena such as 1/f noise and self-organization of the critical state is studied both theoretically and by computer simulation using a model of multijunction SQUID exposed to an external magnetic field. It is demonstrated that the spectra of the average current in the systems of different size exhibit a broad region of 1/f noise limited only by the system size. However, the coexistence of 1/f noise and self-organization of the critical state was observed only in one two-dimensional system.     

Avalanche dynamics of magnetic flux in a two-dimensional discrete superconductor

The critical state of a two-dimensional discrete superconductor in an external magnetic field is studied. This state is found to be self-organized in the generalized sense, i.e., is a set of metastable states that transform to each other by means of avalanches. An avalanche is characterized by the penetration of a magnetic flux to the system. The sizes of the occurring avalanches, i.e., changes in the magnetic flux, exhibit the power-law distribution. It is also shown that the size of the avalanche occurring in the critical state and the external magnetic field causing its change are statistically independent quantities.