Nighttime enhancements in TEC near the crest of northern equatorial ionization anomaly during low solar activity period

Enhancement in nighttime total electron content (TEC) near the crest of equatorial ionization anomaly at Bhopal (Geog. 23.2°N, 77.4°E, and MLAT 14.2°N) has been studied for the solar minimum period March 2005- November 2006. TEC data recorded by GPS Ionospheric Scintillation and TEC Monitor (GISTM) GSV4004A receiver is used for the study and results are presented in the paper. More than 10% increase in TEC with respect to background content is considered for analysis. Out of total 138 enhancements, 65 observed during pre midnight hours and 73 during post midnight hours. It is observed that nighttime enhancement in TEC at Bhopal occurs in all seasons; it is more frequent during summer, less during equinox and least during winter months. The enhancement in nighttime TEC can be observed both in geomagnetic disturbed time and in quiet time. We found that mean peak amplitude for pre-midnight TEC enhancement are more in equinox and less in winter, while in post-midnight TEC enhancement it is highest in summer and less in winter. Post-midnight enhancements have smaller peak amplitude as compared to pre-midnight. Also the most probable values for pre- and post-midnights are 4.4 TECU and 2.17 TECU respectively. The percentage occurrence of nighttime TEC enhancement does not show any dependence on solar activity whereas the peak amplitude depends on solar activity. The percentage occurrence of nighttime TEC enhancement decreases as the magnetic activity increases whereas there is no such dependency found with peak amplitude. It is also observed that majority of nighttime TEC enhancements are occurred without scintillation. The localised nighttime TEC enhancements near the crest of equatorial ionization anomaly region have been observed most of the nights during the period of study.     

Rapidity distribution as a probe for elliptical flow at intermediate energies

The interplay between spectator and participant matter in heavy-ion collisions is investigated within the isospin-dependent quantum molecular dynamics (IQMD) model in terms of the rapidity distribution of light charged particles. The effect of different types and sizes of rapidity distributions is studied in elliptical flow. The elliptical-flow patterns show the important role of nearby spectator matter on the participant zone. This role is further explained on the basis of the passing time of the spectator and the expansion time of the participant zone. The transition from in-plane to out-of-plane emission is observed only when the mid-rapidity region is included into the rapidity bin. Otherwise no transition occurs. The transition energy is found to be highly sensitive to the size of the rapidity bin, while it is only weakly dependent on the type of the rapidity distribution. These theoretical findings are found to be in agreement with experimental results.     

Variation of interband interaction strength in odd-A nuclei

Bandcrossing in 31 rotational bands of 25 different odd-A nuclei in the rare-earth region has been analysed by using a two-band mixing formalism with a constant band interaction within the framework of the effective decoupling picture. The interband interaction strengthV between the one-quasiparticle band and the three-quasiparticle band exhibits a variation with the neutron number which is not different from the oscillatory behaviour observed in even-even nuclei and does not show signs of any appreciable phase shifting as predicted by theory. However, the overall range of variation ofV is greater than that observed in even-even systems.     

Investigation of transition States in bulk and freestanding film polymer glasses

We have performed transition state searches on the potential energy landscape for bulk and freestanding film polymer glasses and identified connected minima. An analysis of the displacements between minima shows that the sites that undergo the greatest displacement are highly localized in space for both the bulk and the thin-film systems studied. In the case of the thin film, the clusters originate at the surface and penetrate into the center of the film thereby coupling the relaxation in the center of the film to the mobile surface layer. Furthermore, the energy barriers between minima are lower in the thin film than in the bulk system. These findings can rationalize the experimentally observed depression of the glass transition temperature in freestanding polymer films.     

Enhanced grain growth in YBa2Cu3O7−δ doped with Ag,Cu, and CuO

Powders of YBa₂Cu₃O_7– were mixed with Ag, Cu, and CuO powders, pressed and sintered in air and oxygen. Grain-growth enhancement has been observed in the doped samples on sintering in oxygen at 980°C and its attributable to a partial melting and decomposition followed by crystallization during cooling. While the mechanisms of the partial melt may differ with dopant, grain growth enhancement appears to be a common feature of partial melt followed by slow cooling. The possibility of using suitable dopants in aiding an aligned grain structure is pointed out.     

Protein recognition using synthetic surface-targeted agents

The design of synthetic agents to disrupt protein-protein interactions has received relatively little attention in recent years. In this review we describe strategies for targeting different types of protein surfaces using mimetics of protein secondary or tertiary structure. In this way strong and selective binding to a protein surface has be achieved and disruption of clinically important protein-protein interactions has been demonstrated in models of human disease.     

Study of the effect of swift heavy Ni ion irradiation on ruby single crystal by using the XANES and EXAFS techniques

We have made the XAFS measurements at the Cr–K-edge on natural Indian ruby single crystals (corundum) and its two irradiated samples with fluence 1×10¹² Ni⁶⁺ and 5×10¹² Ni⁶⁺ ions/cm². Irradiated samples show interesting changes in their physical appearance. XANES measurements show progressive decrease in Δ_oct value on increase of Ni fluence in irradiated samples. EXAFS measurements on these samples show decrease in Cr–O distance on increase of Ni fluence. Lowering of Δ_oct value is correlated with the increase of Cr–O distance.     

Two photon exchange contributions to elastic $\vec{e}+p\rightarrow e+\vec{p}$ process in the non-local field formalism

We compute the two photon exchange contributions to elastic scattering of polarized electrons from target protons. We use a non-local field theory formalism for this calculation. The formalism maintains gauge invariance and provides a systematic procedure for making this calculation. The results depend on one unknown parameter, . We compute the two photon exchange correction to the ratio of electric to magnetic form factors extracted using polarization transfer experiments. The correction is found to be small if . However, for larger values of , the correction can be quite significant. The correction to the polarization transfer results goes in the right direction to explain their difference with the ratio measured by the Rosenbluth separation method. We find that the difference between the two experimental results can be explained for a wide range of values of the parameter . We also find that the corrections due to two photon exchange depend on the photon longitudinal polarization ε. Hence, we predict an ε dependence of the form factor ratio extracted using the polarization transfer technique. Finally, we obtain a limit on by requiring that the non-linearity in ε dependence of the unpolarized reduced cross section is within experimental errors.     

Kinetics of Surfactant-induced Aggregation of Lysozyme Studied by Fluorescence Spectroscopy

The study of protein conformational changes in the presence of surfactants and lipids is important in the context of protein folding and misfolding. In the present study, we have investigated the mechanism of the protein conformational change coupled with aggregation leading to size growth of Hen Egg White Lysozyme (HEWL) in the presence of an anionic detergent such as sodium dodecyl sulphate (SDS) in alkaline pH. We have utilized intrinsic protein fluorescence (tryptophan) and extrinsic fluorescent reporters such as 8-anilinonaphthalene-1-sulfonic acid (ANS), dansyl and fluorescein to follow the protein conformational change in real-time. By analyzing the kinetics of fluorescence intensity and anisotropy of multiple fluorescent reporters, we have been able to delineate the mechanism of surfactant-induced aggregation of lysozyme. The kinetic parameters reveal that aggregation proceeds with an initial fast-phase (conformational change) followed by a slow-phase (self-assembly). Our results indicate that SDS, below critical micelle concentration, induces conformational expansion that triggers the aggregation process at a micromolar protein concentration range.     

Steady State and Time Resolved Spectroscopic Study of CdSe and CdSe/ZnS QDs:FRET Approach

This article highlights some physical studies on the relaxation dynamics and Förster resonance energy transfer (FRET) of semiconductor quantum dots (QDs) to proximal dye molecule and the way these phenomena change with core to core-shell QD is discussed. Efforts to understand the optical and carrier relaxation dynamics of CdSe and CdSe/ZnS QDs are made by using absorption, steady-state fluorescence and time-resolved fluorescence (TCSPC) techniques. Steady-state as well as time-resolved fluorescence measurements were employed to evaluate the QD PL quenching induced by the proximal Rhodamine 101 dye molecule and to examine the influence of deep trap states on energy transfer efficiency. The FRET parameters such as spectral overlap, Förster distance, intermolecular distance for each donor-acceptor pair are determined and variation of these parameters from core to core-shell QD is discussed.