Surface patch binding induced intermolecular complexation and phase separation in aqueous solutions of similarly charged gelatin-chitosan molecules

The formation of selective surface patch binding induced complex coacervates between polyions, chitosan (cationic polyelectrolyte), and alkali-processed gelatin (polyampholyte), both carrying similar net charge, was investigated for two volumetric mixing ratios: r = [chitosan]/[gelatin] = 1:5 and 1:10. Formation of soluble intermolecular complexes between gelatin and chitosan molecules was observed in a narrow range of pH, though these biopolymers had the same kind of net charge, which was evidenced from electrophoretic measurement. This clearly established the role played by selective surface patch binding driven interactions. The temperature sweep measurements conducted on these coacervate samples through rheology and differential scanning calorimetry (DSC) studies yielded two characteristic melting temperatures located at approximately 68 +/- 3 degrees C and 82 +/- 3 degrees C. In the flow mode, the shear viscosity (eta) of the coacervate samples was found to scale with (power-law model) applied shear rate (gamma*) as eta(gamma*) approximately (gamma*)(-k); this yielded k = 0.76 +/- 0.2 (1 s(-1) < gamma* < 100 s(-1)), indicating non-Newtonian behavior. The static structure factor (I(q)) deduced from small angle neutron scattering (SANS) data in the low q (q is the scattering wavevector) (0.018 A(-1) < q < 0.072 A(-1)) region was fitted to the Debye-Bueche regime, I(q) approximately 1/(1 + zeta(2)q(2))2 that yielded a size of zeta approximately 215 +/- 20 A (for r = 1:10) and zeta approximately 260 +/- 20 A (for r = 1:5) samples, implying change in the size of inhomogeneities present with mixing ratio. In the intermediate q region, called the Ornstein-Zernike regime, I(q) approximately 1/(1 + xi(2)q(2)) gave a correlation length of xi approximately 10.0 +/- 2.0 A independent of the mixing ratio. The results taken together imply the existence of a weakly interconnected and heterogeneous network structure inside the coacervate phase separated by domains of polymer-poor regions.     

Some recent developments in SUSY dark matter analyses

A brief summary of some of the recent developments in the analyses of supersymmetric dark matter is given.     

Mach-Zehnder interferometer-based tree architecture for all-optical logic and arithmetic operations

Interferometric devices for optical processing have been of great interest in recent years. Semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer (MZI) has already taken a significant role in the field of ultra-fast all-optical signal processing. Optical tree architecture (OTA) provides important contributions in optical interconnecting networks. In this communication, we have tried to exploit the advantages of both OTA and SOA-based MZI switches. We have proposed SOA-MZI-based tree architecture, a new and alternative scheme, for integrated all-optical logic and arithmetic operations. This architecture can enable one to perform all-optical processing of signals, including two input logic operations, half-adder, full-adder, full-subtractor, one-bit data comparator, etc.     

Ultrasonic study of binary mixtures of acetone with chlorobenzene at different frequencies

The ultrasonic velocity (C) and density (ρ) have been measured at different frequencies (1MHz, 3MHz and 5 MHz) in the binary mixtures of acetone with chlorobenzene over the entire range of mole fraction at temperature 303.16K. The data of C and ρ have been used to evaluate the isentropic compressibility (β), intermolecular free length (L_f) and acoustic impedance (Z) and their excess values to elucidate the molecular association in the mixture. The variation of these parameters with solute (acetone) indicates the nature of interaction present in the binary mixture.     

Studies on ion-pair and triple-ion formation of some tetraalkylammonium salts in binary solvent mixtures of benzene and tetrahydrofuran at 298.15 K

Conductivities of some tetraalkylammonium halides, viz. tetrabutylammonium bromide (Bu₄NBr), tetrapentylammonium bromide (Pen₄NBr), tetrahexylammonium bromide (Hex₄NBr) and tetraheptylammonium bromide (Hep₄NBr) were measured at 298.15 K in THF + C₆H₆ mixtures with 10, 20, 30 and 40 mass% of C₆H₆. A minimum in the conductance values was observed as concentration increases, which dependent both on the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M⁺ + X⁻ ↔ MX, K_P) and triple-ions (2 M⁺ + X⁻ ↔ M₂X⁺; M⁺ + 2X⁻ ↔ MX₂⁻, K_T). A linear relationship between the triple-ion formation constants [log(K_T/K_P)] and the salt concentrations at the minimum conductivity (log C_min) was given for all salts in C₆H₆ + THF mixtures. The formation of triple-ions might be attributed to the ion sizes in solutions in which coulombic interactions and covalent bonding forces act as the main forces between the ions (R₄N⁺ X⁻).     

Lithium antimonite: A new class of anode material for lithium-ion battery

LiSbO₃ has been synthesized by chemical mixing followed by thermal treatment at 800 °C. Field emission scanning electron microscopy revealed bar shaped multifaceted grains, 0.5–4 μm long and 0.5–1 μm wide, that cluster together as soft agglomeration. 2032 type coin cell vs Li/Li⁺ shows a flat charge–discharge plateau together with low Li intercalation/de-intercalation potential (0.2/0.5 V). A high discharge capacity of 580 mA h g^?1 has been obtained in the 1st cycle with 100% Coulombic efficiency. About 96% of the Coulombic efficiency is retained up to the 12th cycle, but at the 15th cycle, the Coulombic efficiency drops down to 88%. AC impedance spectroscopy shows an increase in electrolyte resistance (R_s) from 4.43 Ohm after the initial cycle to 12.4 Ohm after the 15th cycle indicating a probable dissolution of Sb into the electrolyte causing the capacity fading observed.