2D Ising Model for Enantiomer Adsorption on Achiral Surfaces: L- and D-Aspartic Acid on Cu(111)

The 2D Ising model is well-formulated to address problems in adsorption thermodynamics. It is particularly well-suited to describing the adsorption isotherms predicting the surface enantiomeric excess, ees, observed during competitive co-adsorption of enantiomers onto achiral surfaces. Herein, we make the direct one-to-one correspondence between the 2D Ising model Hamiltonian and the Hamiltonian used to describe competitive enantiomer adsorption on achiral surfaces. We then demonstrate that adsorption from racemic mixtures of enantiomers and adsorption of prochiral molecules are directly analogous to the Ising model with no applied magnetic field, i.e., the enantiomeric excess on chiral surfaces can be predicted using Onsager’s solution to the 2D Ising model. The implication is that enantiomeric purity on the surface can be achieved during equilibrium exposure of prochiral compounds or racemic mixtures of enantiomers to achiral surfaces.     

Low-Temperature Processing of PZT Thick Film by Seeding and High-Energy Ball Milling and Studies on Electrical Properties

Lead zirconate titanate thick film with molecular formula PbZr_0.52Ti_0.42O₃ (PZT) was prepared by a modified conventional sol–gel method through seeding and high-energy ball milling, resulting in perovskite phase formation at lower temperatures. The ball-milling time was optimized by keeping the seed particle loading (5 wt.%) constant in the sol–gel solution. This methodology helped in reduction of the crystalline phase formation temperature to 300°C, which is much lower than that reported in the literature (450°C). The well-established perovskite phase was confirmed by x-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) of PZT films revealed uniform and crystalline microstructure. Film prepared by this methodology showed higher spontaneous polarization (2.22 μC/cm²), higher capacitance (1.17 nF), and low leakage current density (18 μA/cm²). The results obtained from ferroelectric characterization showed a strong correlation with the XRD and SEM results.     

Effect of guest-host interaction on the dynamics of ethylene glycol in H-ZSM5 zeolite

Dynamics of ethylene glycol (EG) adsorbed in H-ZSM5 zeolite as studied using quasielastic neutron scattering (QENS) technique is reported here. Analysis of QENS data revealed that observed dynamics correspond to isotropic rotational motion of EG. Rotational diffusion coefficient of EG adsorbed in H-ZSM5 zeolite is found to be slower compared to bulk and comparable to that of benzene adsorbed in the same host. Positron Annihilation Spectroscopy (PAS) technique is used to understand the nature of guest-host interaction and the results of both QENS and PAS are found to be consistent with each other.     

Determination of thallium in water samples

This article illustrates the developments of effective preconcentration techniques and highly sensitive detection methods for accurate measurements of Tl species at extremely low concentration in aqueous solutions. The literature on this topic was taken from the Analytical Abstracts in the period 1990-2005.     

Temperature dependence of threshold and electrical characteristics of InGaAsP-InP d.h. lasers

Measurements are reported of the electrical characteristics and temperature dependence of threshold current of InGaAsP-InP d.h. lasers (? = 1.3 ?m). Analysis of the I dV/dI characteristics of these devices indicates that drift leakage of carriers from the active region is not responsible for the high temperature sensitivity of threshold in this material system.     

Effect of structural misalignments on the temperature variation of basal plane electrical conductivity of graphite

The amount and extent of structural misaligments in natural graphite crystals have been determined, and the temperature variation of the basal plane electrical conductivity (σ_⊥) of naturally occurring graphite has also been studied from 300 to 90 K. The conductivity (σ_⊥) has been found to obey a law σ_⊥α($\text{1}\text{T}$) down to a certain temperature θ (θ varying from sample to sample), below which the variation deviates from linearity towards lower values of σ_⊥. This behaviour, which was earlier thought to be a characteristic of graphite and whose origin could not be traced, has been shown to be an effect of the structural misalignments usually present in natural samples of graphite.     

Effects on mass transfer of atomization and dispersion of liquids in the presence of ultrasound

By applying ultrasound at different frequencies and intensities through the bottom of a narrow tube containing liquids of varying physical properties, followed by critical analysis of the experimental data, a systematic study of the effect of these parameters on enhancement in rate of mass transfer has been made and a correlation has been proposed for prediction of such enhancement.