Synthesis condition effects on the anti-polyelectrolyte behaviour of poly(acrylamide-co-(4-vinylpyridine)) (AM/4VP)copolymers in aqueous media

We have synthesized new copolymers AM/4VP of acrylamide (AM) and 4-vinylpyridine (4VP) in aqueous solution by radical adiabatic copolymerization. The prepared copolymers were characterised by nuclear magnetic resonance ( 1H NMR and 13C NMR), and UV -visible spectrophotometry. The molecular weights were obtained by size exclusion chromatography (SEC), and by viscosity. The reduced viscosity variation of the copolymers aqueous solutions with its concentration showed an anti-polyelectrolyte behaviour in the presence of NaCl salt. This behaviour was explained by an increase of the reduced viscosity (ηred) in dilute system. Moreover, this phenomenon depended on synthesis conditions, such as the percentage of water and 4-vinylpyridine co-monomer in the mixture at constant values of pH and temperature.

Diffusion of Conserved Charges in Relativistic Heavy Ion Collisions

We discuss the diffusion currents occurring in a dilute system and show that the charge currents do not only depend on gradients in the corresponding charge density, but also on the other conserved charges in the system—the diffusion currents are therefore coupled. Gradients in one charge thus generate dissipative currents in a different charge. In this approach, we model the Navier-Stokes term of the generated currents to consist of a diffusion coefficient matrix, in which the diagonal entries are the usual diffusion coefficients and the off-diagonal entries correspond to the coupling of different diffusion currents. We evaluate the complete diffusion matrix for a specific hadron gas and for a simplified quark-gluon gas, including baryon, electric and strangeness charge. Our findings are that the off-diagonal entries can range within the same magnitude as the diagonal ones.

Concentration dependent phase behavior and collapse dynamics of PNIPAM microgel by dielectric relaxation

Concentration dependent phase behavior of microgel: the dense system underwent a phase transition from colloidal crystal to liquid and to phase separation (above); the dilute system only underwent a transition from liquid to phase separation (below).

TWO-DIMENSIONAL HOLES IN GaAs HIGFETs: FABRICATION METHODS AND TRANSPORT MEASUREMENTS

We present a fabrication process and results of transport measurements of a number of p-channel heterojunction-insulated-gate field-effect transistors (HIGFETs). Without intentional doping in HIGFETs, the disorder is likely to be less than that in the modulation-doped samples. We established a process that eliminates the well-known gate leakage problem. The hole density in our devices can be continuously tuned down to a record low value of 7 × 108 cm -2. Remarkably, such a dilute system (with Fermi wavelength approaching 1 μm) exhibits a non-activated conductivity that grows with temperature approximately as a power law at sufficiently low temperatures. We contrast it with the activated transport found in more disordered samples and discuss possible transport mechanisms in this strongly-interacting regime.

An experimental study of the partial oxidation of ethane to ethylene in a shallow fluidized bed reactor

The partial catalytic oxidation of ethane to ethylene was investigated experimentally in a shallow fluidized bed. The performances of two catalyst types, pure ?-Al2O3 and V2O5/?-Al2O3 particles 1.8 mm in diameter, were analyzed. A pilot fluidized bed reactor with rectangular cross-section of 100mmx100mm was used. The experiments were carried out under atmospheric pressure in a dilute system under oxygen excess conditions. V2O5/?-Al2O3 showed good catalytic performances regarding ethylene selectivity. The influence of the temperature (in the range of 400-600?C) and the contact time (in the range of 35-85 kg s m-3) on the conversion of ethane and the selectivity to ethylene was analyzed. The highest yield of ethylene was 18%. .