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Influence of substrate heating on optical, morphological and photoemission properties of CsI thin films for imaging application
No full textOptical and morphological properties of semi-transparent Caesium Iodide (CsI) thin films for three different film thicknesses deposited at a substrate temperature of 120 degrees C have been investigated. The photoemission properties were also studied to know the performance of such photocathodes. A comparison between the films deposited by keeping the substrate at room temperature (27 degrees C) and the films deposited at 120 degrees C is presented. Effect of substrate temperature on the morphological, optical and photoemission properties are presented. Optimization requirement of a semi-transparent photocathode for high sensitivity performance is discussed here
Electrical conductivity behavior of Gum Arabic biopolymer-Fe3O4 nanocomposites
No full textPresent work reports a study on the electrical conduction properties of some composites of Gum Arabic biopolymer and magnetite nanoparticles as host and guest, respectively, synthesized in different weight percentages. The nanocomposites are found to be non-extrinsic type of semiconductors with guest content dependent trap distribution of charge carriers. Conductivity of these materials increases with increasing guest content along with a concomitant decrease in the activation energy. Percolation theory has been employed for the analysis of the electrical conductivity results to explore the effect of the guest on the electrical conductivity of the host
Effect of Li, Na, K cations on photoluminescence of GdAlO3:Eu3+ nanophosphor and study of Li cation on its antimicrobial activity
No full textAlkali metal cations such as Li, Na, K (1mol %) co-doped GdAlO3:Eu3+ (1 mol%) nanophosphors were synthesized by solution combustion technique using oxalyldihydrazide (ODH: C2H6N4O2) as fuel. The structural, morphological, luminescence and antimicrobial activity has been employed to the synthesized nanoparticles. All compounds crystallized in the pure orthorhombic phase with no impurity peak. SEM micrographs showed the agglomerated and irregular shaped particles. The average crystallite size was calculated by William-Hall plots and is found to be in the range 30-40 nm. The characteristic emission peaks of Eu3+ ions were recorded and it is due to D-5(0)-> F-7(J) (J = 1, 2, 3, 4) transitions. The PL intensity of GdAlO3:Eu(3+)nano phosphor was improved evidently by alkali metal cation co-doping, due to local distortion of crystal field surrounding the Eu3+ activator. These nanophosphors find potential applications in WLEDs and solid state lighting. Antimicrobial activity of GdAlO3:Eu3+:Li+ nanophosphor against pathogenic microorganisms of both human and plants was carried out by using micro plate dilution technique for bacteria and food poison method for fungi. (C) 2017 Elsevier B.V. All rights reserved
Intramolecular Hydrogen Bonding Appetency for Conformational Penchants in Oxalohydrazide Fluoro Derivatives: NMR, MD, QTAIM, and NCI Studies
No full textThe conformational stability of synthesized diphenyloxalohydrazide and dibenzoyloxalohydrazide fluoro derivatives has been investigated by extensive NMR studies that are ascertained by various levels of theoretical calculations. Two-dimensional H-1-F-19 HOESY NMR experiments revealed the close spatial proximity between two NMR-active nuclei, confirming the hydrogen bond (HB)-mediated interaction between them, further aiding in establishing the probable stable conformations of these molecules. The relaxed potential energy scan disclosed the energy-minimized most stable structure among the several possible multiple conformations, which is in concurrence with NMR interpretations. Atomistic molecular dynamics simulations have been employed to unequivocally establish the conformational stability and the nature of HB formation at varied temperatures. With the possibility of occurrence of a number of probable conformations, the percentage of occurrences of different types of HBs in them was determined by MD simulations. Their population analysis was carried out using a Boltzmann distribution, in addition to deriving their Gibbs free energies. The molecular interactions governing the stable conformations have not only been ascertained by experimental NMR interpretations but also corroborated by other theoretical computations, viz., quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI)
A novel encystation specific protein kinase regulates chitin synthesis in Entamoeba invadens
No full textPhosphorylation is an important post-translational modification of proteins and is involved in the regulation of a variety of cellular events. The proteome of Entamoeba invadens, the reptilian counterpart of Entamoeba histolytica consists of an overwhelming number of putative protein kinases, and some may have a role to play in Entamoeba encystation. In this study, we have identified a novel protein kinase named as EiCSpk (Entamoeba invadens cyst specific protein kinase) which expressed almost exclusively during encystation. It is an active Protein kinase C with a characteristic substrate phosphorylation and auto-phosphorylation property. Gene silencing study has unveiled its role as a regulator of chitin synthesis through transcriptional activation of the chitin synthesis pathway genes along with glycogen phosphorylases that are involved in the influx of glucose from glycogen breakdown for chitin synthesis
Trade-off between synergy and efficacy in combinations of HIV-1 latency-reversing agents
No full textEradicating HIV-1 infection is difficult because of the reservoir of latently infected cells that gets established soon after infection, remains hidden from antiretroviral drugs and host immune responses, and retains the capacity to reignite infection following the cessation of treatment. Drugs called latency-reversing agents (LRAs) are being developed to reactivate latently infected cells and render them susceptible to viral cytopathicity or immune killing. Whereas individual LRAs have failed to induce adequate reactivation, pairs of LRAs have been identified recently that act synergistically and hugely increase reactivation levels compared to individual LRAs. The maximum synergy achievable with LRA pairs is of clinical importance, as it would allow latency-reversal with minimal drug exposure. Here, we employed stochastic simulations of HIV-1 transcription and translation in latently infected cells to estimate this maximum synergy. We incorporated the predominant mechanisms of action of the two most promising classes of LRAs, namely, protein kinase C agonists and histone deacetylase inhibitors, and quantified the activity of individual LRAs in the two classes by mapping our simulations to corresponding in vitro experiments. Without any adjustable parameters, our simulations then quantitatively captured experimental observations of latency-reversal when the LRAs were used in pairs. Performing simulations representing a wide range of drug concentrations, we estimated the maximum synergy achievable with these LRA pairs. Importantly, we found with all the LRA pairs we considered that concentrations yielding the maximum synergy did not yield the maximum latency-reversal. Increasing concentrations to increase latency-reversal compromised synergy, unravelling a trade-off between synergy and efficacy in LRA combinations. The maximum synergy realizable with LRA pairs would thus be restricted by the desired level of latency-reversal, a constrained optimum we elucidated with our simulations. We expect this trade-off to be important in defining optimal LRA combinations that would maximize synergy while ensuring adequate latency-reversal
Thermal Effect of Sulfur Doping for Luminescent Graphene Quantum Dots
No full textThis work presents a comprehensive study of quantum yield in doped graphene quantum dots with a series of sulfur containing compounds ( S-GQDs). The facile hydrothermal method was used to synthesize S-GQDs at different temperatures (similar to 80 degrees C-140 degrees C) with ZnSO4.7H(2)O containing sulfur powder as a reducing agent. High Resolution Transmission Electron Microscope images suggest that the size of S-GQDs vary as a function of temperature during synthesis. Powdered X-Ray Diffraction confirms the crystallinity of all samples. Raman spectroscopy study reveals that the intensity ratio increases with an increase in temperature due to the presence of additional sulfur related defects that create enhanced elastic scattering. Removal of oxygen functional groups was maximized at 140 degrees C and reached to a ID/IG value of similar to 1.14. The photoluminescence measurements of doped GQDs having sulfur containing compounds at temperature of similar to 140 degrees C attributes to violet shift at lower excitation energy and a blueshift at higher excitation energy within the energy gap of S-GQDs due to the strong interaction of GQDs with high defect concentration of sulfur. The S-GQDs formed at similar to 140 degrees C demonstrated a superior fluorescence quantum yield of 51%. This is, therefore, expected to make S-GQDs more suitable for bioimaging and optoelectronic applications. (C) 2018 The Electrochemical Society
Electronic excitation induced modifications in elongated iron nanoparticle encapsulated multiwalled carbon nanotubes under ion irradiation
No full textMulti-wall carbon nanotubes (MWCNT) filled with Fe nanorods were shown to have contracted and deformed under heavy ion irradiation. In this study, 120 MeV Ag and 80 MeV Ni ion irradiation was performed to study the deformation and defects induced in iron filled MWCNT under heavy ion irradiation. The structural modifications induced due to electronic excitation by ion irradiation were investigated employing high-resolution transmission electron microscopy, micro-Raman scattering experiments, and synchrotron-based X-ray absorption and emission spectroscopy. We understand that the ion irradiation causes modifications in the Fe nanorods which result in compressions and expansions of the nanotubes, and in turn leads to the buckling of MWCNT. The G band of the Raman spectra shifts slightly towards higher wavenumber and the shoulder G' band enhances with the increase of ion irradiation fluence, where the buckling wavelength depends on the radius `r' of the nanotubes as exp(r)(0.5)]. The intensity ratio of the D to G Raman modes initially decreases at the lowest fluence, and then it increases with the increase in ion fluence. The electron diffraction pattern and the high resolution images clearly show the presence of ion induced defects on the walls of the tube and encapsulated iron nanorods. Crown Copyright (C) 2017 Published by Elsevier B.V. All rights reserved
Targeting G-quadruplex DNA structures in the telomere and oncogene Promoter regions by benzimidazole-carbazole ligands
No full textRecent studies support the idea that G-quadruplex structures in the promoter regions of oncogenes and telomere DNA can serve as potential therapeutic targets in the treatment of cancer. Accordingly, several different types of organic small molecules that stabilize G-quadruplex structures and inhibit telomerase activity have been discerned. Here, we describe the binding of benzimidazole-carbazole ligands to G-quadruplex structures formed in G-rich DNA sequences containing the promoter regions of human c-MYC, c-KIT1, c-KIT2, VEGF and BCL2 proto-oncogenes. The fluorescence spectroscopic data indicate that benzimidazole-carbazole ligands bind and stabilize the G-quadruplexes in the promoter region of oncogenes. The molecular docking studies provide insights into the mode and extent of binding of this class of ligands to the G-quadruplexes formed in oncogene promoters. The high stability of these G-quadruplex structures was validated by thermal denaturation and telomerase-catalyzed extension of the 3' end. Notably, benzimidazole-carbazole ligands suppress the expression of oncogenes in cancer cells in a dose-dependent manner. We anticipate that benzimidazole-carbazole ligands, by virtue of their ability to stabilize G-quadruplex structures in the promoter regions of oncogenes, might reduce the risk of cancer through the loss of function in the proteins encoded by these genes. (C) 2018 Elsevier Masson SAS. All rights reserved
A spring-mass-damper system dynamics-based driver-vehicle integrated model for representing heterogeneous traffic
No full textThe traditional traffic microscopic simulation models consider driver and vehicle as a single unit to represent the movements of drivers in a traffic stream. Due to this very fact, the traditional car-following models have the driver behavior related parameters, but ignore the vehicle related aspects. This approach is appropriate for homogeneous traffic conditions where car is the major vehicle type. However, in heterogeneous traffic conditions where multiple vehicle types are present, it becomes important to incorporate the vehicle related parameters exclusively to account for the varying dynamic and static characteristics. Thus, this paper presents a driver-vehicle integrated model hinged on the principles involved in physics-based spring-mass-damper mechanical system. While the spring constant represents the driver's aggressiveness, the damping constant and the mass component take care of the stability and size/weight related aspects, respectively. The proposed model when tested, behaved pragmatically in representing the vehicle-type dependent longitudinal movements of vehicles