Thermodynamic properties of non-electrolyte solutions

Experimental densities (ρ) and ultrasonic sound velocities (u) for the binary mixtures of toluene, o-chlorotoluene, m-chlorotoluene, and p-chlorotoluene with 1-octanol were measured over the entire composition range at T = (298.15, 303.15, and 308.15) K and at a pressure of 0.1 MPa. Excess volumes (V ^E), isentropic compressibilities $ (\kappa_{\text{s}} ) $ , and excess isentropic compressibilities $ (\kappa_{\text{s}}^{\text{E}} ) $ were calculated using the measured experimental densities and ultrasonic sound velocities of the pure liquids and their mixtures. The experimental data were discussed in terms of intermolecular interactions between component molecules. The measured excess properties were correlated with the Redlich–Kister polynomial equation.     

PEG-grafted chitosan as an injectable thermoreversible hydrogel

PEG-grafted chitosan was formulated such that its solution undergoes a thermally reversed phase transition from an injectable free-flowing solution at low temperature to a gel at body temperature. Aqueous solutions of PEG-grafted chitosan can be prepared at physiological pH values, thereby allowing safe incorporation of bioactive molecules. This injectable thermoreversible hydrogel is potentially suitable for a wide range of biomedical applications, particularly in sustained in vivo drug release and tissue engineering. An aqueous solution of PEG-grafted chitosan polymer is injectable at low temperatures but forms a gel at body temperature.     

Townsend's First Ionization Coefficients and Sparking Potentials in Crossed Electric and Magnetic Fields

Townsend's first ionization coefficients have been measured in corssed electric and magnetic fields for values of B/p ranging from 0.013 TESLA. TORR-1 to 0.064 TESLA.TORR-1 and for 103 x 102? E/p? 331 x 102 V.M-1. TORR-1 in oxygen and for 122 x 102? E/p?488 x 102 V.M-1.TORR-1 for dry air. The values of effective collision frequencies determined from the equivalent pressure (pe) concept generally increase with E/p at constant B/p and decrease with increasing B/p at constant E/p. Effective collision frequencies determined from measured sparking potentials at high values of E/p increase with decreasing E/pe. The drift velocity and mean energy of electrons in oxygen in crossed electric and magnetic fields have been derived.     

Pasch geometric spaces inducing finite projective planes

Summary A geometric space over a geometric sfield of dimension three induces a protective plane. A relation between the order of the projective plane and that of the geometric sfield is obtained. For a particular order of the sfield, the induced projective plane is shown to be desarguesian.     

Phase transformation and electrical resistivity of tetracyanoethylene under pressure

This paper reports the phase transformation behaviour of tetracyanoethylene (TCNE) under pressure as revealed by AC electrical resistivity, its time evolution and X-ray diffraction studies. An irreversible transformation from monoclinic to cubic phase occurs at 2.1±0.1 GPa and is indicated by a sharp resistivity drop at this pressure. The time evolution of resistivity studies indicate that this transformation occurs via an intermediate phase having resistivity higher than either of the two crystalline phases. Finally, the kinetics of phase transformations obtained by time evolution of resistivity is compared with the X-ray studies on the pressure quenched TCNE.     

Study of EIT resonances in an anti-relaxation coated Rb vapor cell

We study the sign of resonances obtained in electromagnetically induced transparency (EIT). Resonances of both kinds—bright (corresponding to enhanced absorption) and dark (corresponding to reduced absorption)—are obtained when the frequency of a probe beam is scanned. The experimental results, presented earlier, use magnetic sublevels of a hyperfine transition in the D₁ line of ⁸⁷Rb along with a magnetic field of 27 G. The atoms are contained in a vapor cell at room temperature, and with anti-relaxation coating on the walls. A quantitative theoretical model, which reproduces the experimental results quite well, is presented for the first time. The model solves the density matrix of the sublevels involved, and uses two regions—one with both the light and magnetic field, and the second without light and just a magnetic field. This ability to have both bright and dark resonances promises applications in sub- and super-luminal propagation of light.     

High pressure investigations on amorphous selenium

We report the diamond anvil cell (DAC) high pressure powder X-ray diffraction studies on amorphous selenium (a-Se) under truly hydrostatic pressure condition up to 20 GPa. Amorphous selenium exhibits a sharp and irreversible transition to a hexagonal structure at 10.6 ± 0.1 GPa. It is also known that metallization occurs in a-Se around this pressure. Some plausible arguments are provided to suggest that the amorphous to crystalline transition may be driven by metallization.     

Magnetohydrodynamic unsteady free convection past a hot vertical plate

The free convection flow of an electrically conducting liquid from an infinite plate has been studied in the presence of a uniform magnetic field. General expressions for the velocity field, induced magnetic field, skin-friction and temperature distribution have been obtained when the plate is a perfect conductor and its temperature varies with the law t ⁿ e ^at . The results have been presented through some graphs and tables with the magnetic Prandtl number unity as its value.