[en] This work investigates the structural and electrical properties of both bulk and rf magnetron sputtered thin films of spinel structured Ni_xMn_3-xO_4+δ material system. The distribution of the LDOS of the thin films is also studied using STS. A rf magnetron sputtering system capable of reactive sputtering in a range of argon/oxygen ambients was designed, constructed and commissioned in the first phase of this work. The system was optimised in terms of the effect of various process parameters on the growth rate using factorial experimental design technique. Incident power, substrate to target distance and oxygen percentage in the ambient was found to be the most significant. The effect of different sintering temperatures was investigated for five different compositions of the Ni_xMn_3-xO_4+δ material system. Monophase material could not be prepared without prolonged annealing at 800 deg C after sintering at higher temperatures. This was in contradiction with the published phase diagram of the material and hence a modified scheme was proposed. The lattice parameter of the spinel phase increased with decreasing nickel content. Grain growth was found to be exponentially dependent on the sintering temperature. The R-T characteristics below 300K followed the Shklovskii and Efros VRH model (T₀ ∼2 x 10⁵ K) and a change to the NNH model (ΔE ∼330 meV) was observed above 300K. The resistivity of the material was dependent on both the ratio of Ni:Mn and the oxygen stoichiometry (varying from 1.2 Kohm-cm up to 30 Kohm-cm). The as-deposited films showed poor crystallinity, hence post deposition annealing at 800 deg C was required. The microstructure and the degree of preferred orientation were found to be dependent on the substrate temperature and post deposition annealing. The lattice parameter of the films was lower than the target. The NNH model best described the R-T characteristics of the films deposited at low oxygen content <2.5% (ΔE ∼360 meV) whereas films deposited at higher oxygen content could be better described by the Shklovskii and Efros VRH model (T₀ ∼2.4 x 10⁵ K). The resistivity of the films decreased with increasing oxygen in the ambient in the as-deposited state, however after annealing the resistivity of all the films became similar and much lower than the target. The distribution of the LDOS of the films, using STS, was found to be parabolic and in agreement with the assumption in the Shklovskii and Efros VRH model. Additional features were observed in the LDOS with increasing temperatures (∼±0.15 eV and ∼+1.6 eV) however the changes were completely reversible with temperature. (author)

[en] Wetlands are the most productive and fertile ecosystem in the world and play a vital role in nutrient absorption and control flood and erosion. East Calcutta wetlands is such an ecosystem where usage of city sewage for traditional practices of fisheries and agriculture is practiced. East Calcutta wetlands happens to be the largest ensemble of sewage fed ponds in the world. We investigated the seasonal changes and effects of some physico-chemical variables of some managed and unmanaged ponds at East Calcutta wetlands (ECW) on the primary productivity during winter and summer seasons of 2009. We also studied the alpha radioactivity, as the radioactive elements decay alpha radiation continues to be released into ground water as well as surface water of water-bodies. The GPP showed variation from 247.5 to 700.6 mg/cm³/hr while the NPP varied from 152.5 to 496.25 mg/cm³/hr. The alpha radioactivity ranged from 20.0 to 92.3 bq/L in the studied ponds. The study revealed high alkalinity (162.6 ppm) and high total hardness (270.0 ppm) levels of ponds at ECW. The correlation between primary productivity and different water parameters (temperature, pH, dissolved oxygen, free CO₂, total alkalinity, total hardness, Ca²⁺, Mg²⁺, chloride, H₂S, transparency, TDS, organic carbon of soil) were also determined to observe the influence of those parameters on primary productivity. (author)

[en] The problem of analytical integration involving powers and derivatives of the Fermi function is frequently encountered in many theoretical analyses. To tide over this difficulty, an alternative model for the F.D. distribution function has been proposed. The model is apparently more convenient, because using this model one can now analytically evaluate the integrals much easily, and that too without incurring significant errors in the subsequent results. To assess the extent of validity of the assumed distribution function, the proposed model has been compared with the exact F.D function. The result seems to be satisfactory and motivate us for further analysis of low temperature electron transport in semiconductors using the proposed distribution function. The energy domain is divided into three regions, demarcated on both the sides of the Fermi energy, and the Fermi function is approximated for each regime. (author)

[en] Ebola virus glycoprotein (EGP) has been implicated for the induction of cytotoxicity and injury in vascular cells. On the other hand, EGP has also been suggested to induce massive cell rounding and detachment from the plastic surface by downregulating cell adhesion molecules without causing cytotoxicity. In this study, we have examined the cytotoxic role of EGP in primary endothelial cells by transduction with a replication-deficient recombinant adenovirus expressing EGP (Ad-EGP). Primary human cardiac microvascular endothelial cells (HCMECs) transduced with Ad-EGP displayed loss of cell adhesion from the plastic surface followed by cell death. Transfer of conditioned medium from EGP-transduced HCMEC into naive cells did not induce loss of adhesion or cell death, suggesting that EGP needs to be expressed intracellularly to exert its cytotoxic effect. Subsequent studies suggested that HCMEC death occurred through apoptosis. Results from this study shed light on the EGP-induced anoikis in primary human cardiac endothelial cells, which may have significant pathological consequences

[en] The membrane proteins of viruses play critical roles in the virus life cycle and are attractive targets for therapeutic intervention. Virus-like particles (VLP) present the possibility to study the biochemical and biophysical properties of viral membrane proteins in their native environment. Specifically, the VLP constructs contain the entire protein sequence and are comprised of native membrane components including lipids, cholesterol, carbohydrates and cellular proteins. In this study we prepare VLP containing full-length hemagglutinin (HA) or neuraminidase (NA) from influenza and characterize their interactions with small molecule inhibitors. Using HA-VLP, we first show that VLP samples prepared using the standard sucrose gradient purification scheme contain significant amounts of serum proteins, which exhibit high potential for non-specific interactions, thereby complicating NMR studies of ligand-target interactions. We then show that the serum contaminants may be largely removed with the addition of a gel filtration chromatography step. Next, using HA-VLP we demonstrate that WaterLOGSY NMR is significantly more sensitive than Saturation Transfer Difference (STD) NMR for the study of ligand interactions with membrane bound targets. In addition, we compare the ligand orientation to HA embedded in VLP with that of recombinant HA by STD NMR. In a subsequent step, using NA-VLP we characterize the kinetic and binding properties of substrate analogs and inhibitors of NA, including study of the H274Y-NA mutant, which leads to wide spread resistance to current influenza antivirals. In summary, our work suggests that VLP have high potential to become standard tools in biochemical and biophysical studies of viral membrane proteins, particularly when VLP are highly purified and combined with control VLP containing native membrane proteins.

[en] In the present work, we report giant negative differential resistance action in probably the simplest molecular nanoelectronic device comprising of carbon chain placed between two ferromagnetic electrodes named as graphitic carbon nitride (g-C₄N₃). The negative differential resistance action is spin polarized and only evident at spin down channel. Spin polarized quantum transport studies using Keldysh non-equilibrium Green's function based density functional theory reports very high negative differential resistance over the bias range of ±0.1 V to ±0.3 V. This symmetric negative differential resistancec feature has been explained by an analysis of transmission spectrum across the Fermi energy level and Molecular Projected Self-Consistent Hamiltonian states (MPSH) of the system. Role of in-phase and out of phase electron waves in ensuring negative differential resistance feature has been justified through transmission pathways of the system. The simplicity of the molecular system added with robust spin polarized negative differential action added with experimental relevance certainly establishes the uniqueness of the device in respect of modern spintronic research. (paper)