Electrodiffusion of ions inside living cells

Electrodiffusion of ions, both inside and outside biologicalcells, are of utmost importance to proper cellular functions.Experiments indicate that both ion concentrations and electropotentialcan jump discontinuously across the cell membranes. We studya system of nonlinear partial differential equations modellingsuch phenomena. Jump conditions for species concentrations andelectropotential across cell membranes are imposed. Under zero-fluxboundary conditions for one-dimensional domains, the solutionsare proved to exist for all times. With further assumptions,these transient solutions will converge to the unique steady-statesolution. Numerical experiments in one- and two-dimensionaldomains are also performed in order to study some unresolvedtheoretical issues.     

NMR investigation of the short-chain ionic surfactant-water systems

The structure and dynamics of surfactant molecules [CH3(CH2)7COOK] in heavy water solutions were investigated by 1H and 2H NMR. A double-exponential attenuation of the spin-echo amplitude in a Carr-Purcell-Meiboom-Gill experiment was found. We expect correspondence to both bounded and monomeric states. At high concentrations in the NMR self-diffusion measurements also a double-exponential decay of the spin-echo signal versus the square of the dc magnetic gradient was observed. The slow component of the diffusion process is caused by micellar aggregates, while the fast component is the result of the self-diffusion of the monomers through the micelles. The self-diffusion studies indicate that the form of micelles changes with increasing total surfactant concentration. The critical temperature range for self-association is reflected in the 1H transverse relaxation.     

13C NMR study of the influence of the Aerosil surface charge on the short-chain surfactant adsorption

¹³C NMR chemical shift measurements have been used to study the adsorption of short-chain ionic surfactants on the Aerosil surface from aqueous solutions. The investigations were carried out in a wide concentration range above and below the critical micelle concentration value. The values and the character of the chemical shift changes of Δδ are mainly determined by the surface charge, which is generally assumed to change with the initial pH value of the silica aqueous dispersion. Most sensitive to changes of the surface charge are the ¹³C NMR parameters of the first and second carbon atoms in the hydrophobic chain of the surfactant molecules. This allows investigating the influence of the Aerosil surface charge on the structure of the adsorbed aggregates.     

K +-meson production inpBe interactions atT p=2.9 GeV

The production ofK ⁺ andπ ⁺ mesons and protons inpBe collisions atT _p=2.9 GeV has been studied at the ITEP proton synchrotron. Ejectiles with a momentum ofp=545 MeV/c were observed under an emission angle ?=17°. The detectors which have been developed for the identification of kaons out of a six orders of magnitude more intense background of pions and protons are described. A cross-section ratio d²σ _K ⁺/dΩdp: d² σ _p /dΩdp: d²σ _p /dΩdp of (1±0.34):(85±1):(31±1) has been measured. Normalization with existing pion data yields an invariant differential cross sectionE·d³σ _K ⁺/d³ p=(3.1±1.2) mbGeV^?2c³sr^?1 and a total cross section of σ_tot(pBe)=(3.7±1.5) mb. These cross sections are compared with existing data and theoretical predictions. TheA dependence ofK ⁺ production in the few-GeV range is analyzed.