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Crystallization kinetics of Si20Te80-xBix (0 <= x <= 3) chalcogenide glasses
No full textIn this report, we investigate the crystallization kinetics of Si20Te80-xBi(0 <= x <= 3) chalcogenide glassy systems using differential scanning calorimetry (DSC) technique. Systematic studies are carried out in order to understand the variation of thermal parameters such as glass transition temperature (T-g), onset crystallization temperature (T-c) and peak crystallization temperature (T-p) as a function of composition. Activation energy for glass transition (E-g) and crystallization (E-c) has been calculated based on the relevant statistical methods. Furthermore, thermal parameters such as change in specific heat (Delta C-p), fragility index (F), thermal stability (Delta T) & (S), enthalpy (Delta H-c), entropy (Delta S) are deduced to interpret distinct material behaviour as a function of composition. Structural evaluation like thermal devitrification studies elucidate the restricted glass formability of the studied glass system. Conclusively, a relationship has been established between the obtained thermal parameters and electrical switching characteristics
A dynamical motif comprising the interactions between antigens and CD8 T cells may underlie the outcomes of viral infections
No full textSome viral infections culminate in very different outcomes in different individuals. They can be rapidly cleared in some, cause persistent infection in others, and cause mortality from immunopathology in yet others. The conventional view is that the different outcomes arise as a consequence of the complex interactions between a large number of different factors (virus, different immune cells, and cytokines). Here, we identify a simple dynamical motif comprising the essential interactions between antigens and CD8 T cells and posit it as predominantly determining the outcomes. Viral antigen can activate CD8 T cells, which in turn, can kill infected cells. Sustained antigen stimulation, however, can cause CD8 T-cell exhaustion, compromising effector function. Using mathematical modeling, we show that the motif comprising these interactions recapitulates all of the outcomes observed. The motif presents a conceptual framework to understand the variable outcomes of infection. It also explains a number of confounding experimental observations, including the variation in outcomes with the viral inoculum size, the evolutionary advantage of exhaustion in preventing lethal pathology, the ability of natural killer (NK) cells to act as rheostats tuning outcomes, and the role of the innate immune response in the spontaneous clearance of hepatitis C. Interventions that modulate the interactions in the motif may present routes to clear persistent infections or limit immunopathology
Heterodimerization of Mu Opioid Receptor Protomer with Dopamine D-2 Receptor Modulates Agonist-Induced Internalization of Mu Opioid Receptor
No full textThe interplay between the dopamine (DA) and opioid systems in the brain is known to modulate the additive effects of substances of abuse. On one hand, opioids serve mankind by their analgesic properties, which are mediated via the mu opioid receptor (MOR), a Class A G protein-coupled receptor (GPCR), but on the other hand, they pose a potential threat by causing undesired side effects such as tolerance and dependence, for which the exact molecular mechanism is still unknown. Using human embryonic kidney 293T (HEK 293T) and HeLa cells transfected with MOR and the dopamine D-2 receptor (D2R), we demonstrate that these receptors heterodimerize, using an array of biochemical and biophysical techniques such as coimmunoprecipitation (co-IP), bioluminescence resonance energy transfer (BRET1), F0rster resonance energy transfer (FRET), and functional complementation of a split luciferase. Furthermore, live cell imaging revealed that D2LR, when coexpressed with MOR, slowed down internalization of MOR, following activation with the MOR agonist D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO)
A Hybrid 7-Level Inverter Using Low-Voltage Devices and Operation With Single DC-Link
No full textThis paper proposes a new 7-level inverter topology for induction motor drives. It is a hybrid topology formed by cascading a 5-level active neutral-point-clamped inverter with a 3-level T-type converter. It is obtained using low-voltage semiconductor devices with voltage blocking capability of Vdc/3 and Vdc/6. The topology uses three floating capacitors per phase, which are balanced within a pulsewidth modulation (PWM) switching duration using switching-state redundancies for each pole-voltage level. Topology forms two stacks at the front-end, which requires individual symmetrical de source. The analysis of switching loss and conduction loss is performed and compared with some of the existing 7-level multi-level inverters reported in various literatures to show the advantages of the proposed topology. Furthermore, the single dc source operation with two stacked capacitors and closed-loop control of neutral-point voltage using symmetrical six-phase induction motor is proposed. The voltage-control algorithms fin. floating capacitors and dc-link stacked capacitors are proposed, which are independent of load power factor and modulation index. Open-loop V/f and closed-loop rotor field oriented control are performed, and various results at steady and transient states are presented to validate the aforementioned claims
Universal Nature of Collapsibility in the Context of Protein Folding and Evolution
No full textTheory and simulations predicted that the sizes of the unfolded states of globular proteins should decrease as the denaturant concentration is reduced from a high to a low value. However, small angle X-ray scattering (SAXS) data were used to assert the opposite, while interpretation of single molecule Forster resonance energy transfer experiments (FRET) supported the theoretical predictions. The disagreement between the two experiments is the SAXS-FRET controversy. By harnessing recent advances in SAXS and FRET experiments and setting these findings in the context of a general theory and simulations, which do not rely on experimental data, we establish that compaction of unfolded states under native conditions is universal. The theory also predicts that proteins rich in beta-sheets are more collapsible than alpha-helical proteins. Because the extent of compaction is small, experiments have to be accurate and their interpretations should be as model-free as possible. Theory also suggests that collapsibility itself could be a physical restriction on the evolution of foldable sequences, and also provides a physical basis for the origin of multidomain proteins
On compact anisotropic Weingarten hypersurfaces in Euclidean space
No full textWe show that, up to homotheties and translations, the Wulff shape WF is the only compact embedded hypersurface of the Euclidean space satisfying HrF=aHF+b with a0, b>0, where HF and HrF are, respectively, the anisotropic mean curvature and anisotropic r-th mean curvature associated with the function F:Sn?R+. Further, we show that if the L2-norm of HrF-aHF-b is sufficiently close to 0, then the hypersurface is close to the Wulff shape for the W-2,W-2-norm
Glaucoma Pred: Glaucoma prediction based on Myocilin genotype and phenotype information
No full textGlaucoma is the second leading cause of blindness after cataract and is heterogeneous in nature. Employing a genetic approach for the detection of the diseased condition provides an advantage that the gene responsible for the disease can be identified by genetic test. The availability of predictive tests based on the published literature would provide a mechanism for early detection and treatment. The genotype and phenotype information could be a valuable source for predicting the risk of the disease. To this end, a web server has been developed, based on the genotype and phenotype of myocilin mutation, which were identified by familial linkage analysis and case studies. The proposed web server provides clinical data and severity index for a given mutation. The server has several useful options to help clinicians and researchers to identify individuals at a risk of developing the disease
Inter/Intramolecular Bonds in TH5+ (T = C/Si/Ge): H-2 as Tetrel Bond Acceptor and the Uniqueness of Carbon Bonds
No full textAtoms in molecules (AIM), natural bond orbital (NBO), and normal coordinate analysis have been carried out at the global minimum structures of TH5+ (T = C/Si/Ge). All these analyses lead to a consistent structure for these three protonated TH4 molecules. The CH5+ has a structure with three short and two long C-H covalent bonds and no H-H bond. Hence, the popular characterization of protonated methane as a weakly bound CH3+ and H-2 is inconsistent with these results. However, SiH5+ and GeH5+ are both indeed a complex formed between TH3+ and H-2 stabilized by a tetrel bond, with the H-2 being the tetrel bond acceptor. The three-center-two-electron bond (3c-2e) in CH5+ has an open structure, which can be characterized as a V-type 3c-2e bond and that found in SiH5+ and GeH5+ is a T-type 3c-2e bond. This difference could be understood based on the typical C-H, Si-H, Ge-H, and H-H bond and the tetrel bond energies. This analysis explains the trend observed in proton affinity of TH4 which appears counterintuitive, GeH4 > SiH4 > CH4. Carbon is selective in forming a ``tetrel bond'' and when it does, it might be worthwhile to highlight it as a ``carbon bond''
New Occurrence of Sapphirine-spinel-bearing Granulite from NW of Chilka Lake, Eastern Ghats Belt, Odisha
No full textA new locality of sapphirine-spinel-bearing granulites from the Kaithapalli area which lies NW of Chilka Lake, Odisha is reported. The area tectonically forms a northern part of Eastern Ghats belt. It occurs as small enclaves within the khondalite and pelitic granulite. The mineral assemblage includes spinel-sapphirine-garnet-cordierite-orthopyroxene-sillimanite-biotite-k- feldsparplagioclase- quartz. Development of reaction textures and symplectites are common in the sapphirine-spinel granulites which have been used to describe reaction history. The relative X-Mg values among various minerals are as follows: cordierite > biotite > sapphirine > orthopyroxene > garnet > spinel. The P-T evolution of these sapphirine-spinel granulites constrained through the pseudosection modelling in the NCKFMASH model system using Perple_X software indicate conditions of ultra-high temperature (UHT) metamorphism. The P-T estimates computed by isopleths define a retrograde trajectory with decompression of c.2.5 kbar from P-T-max of c.10.5 kbar at c.950 degrees C. The sequence of reactions as deduced from the symplectite assemblages, together with pseudosection modelling, from the Kaithapalli area, offer greater opportunities for providing a better picture of petrological evolution of northern part of the Eastern Ghats Belt (EGB)
A geochemical and Nd, Sr and stable Ca isotopic study of carbonatites and associated silicate rocks from the similar to 65 Ma old Ambadongar carbonatite complex and the Phenai Mata igneous complex, Gujarat, India: Implications for crustal contamination, carbonate recycling, hydrothermal alteration and source-mantle mineralogy
No full textMajor, trace element concentrations and Nd, Sr and Ca stable isotopic compositions (delta Ca-44/40 and delta Ca-44/42 w.r.t. NIST SRM915a) of carbonatites and associated igneous silicate rocks from the -65 Ma old Ambadongar carbonatite complex and the surrounding Phenai Mata igneous complex of western India are reported. Samples of fluorspar from Ambadongar and the Bagh Limestone and Sandstone, which are part of the country rocks at Ambadongar, have also been analysed. The Ambadongar carbonatites are primarily calcio- and ferro-carbonatites while the silicate rocks from these two complexes are alkaline and tholeiitic in composition. The delta Ca-44/40 values of the carbonatites (0.58-1.1 parts per thousand, n = 7) and the associated igneous silicate rocks (0.50-0.92 parts per thousand, n = 14) show a broad range. The low K/Ca values of the carbonatites (<0.2) and silicate rocks (<2) along with their young eruption age (similar to 65 Ma) rule out any effect of radiogenic Ca-40 ingrowth due to decay of K-40 on the delta Ca-44/40 values. The lack of correlations between delta Ca-44/40 and Mg# as well as La/Yb-(N) values suggest that the variability in delta Ca-44/40 is not controlled by the degree of partial melting. The delta Ca-44/40 values of the carbonatites (0.58-1.1%0) overlap with that of the upper mantle/Bulk Silicate Earth and is mostly higher than the delta Ca-44/40 value of the Bagh Limestone (0.66 parts per thousand) suggesting that assimilation of these crustal limestones by the magma is unlikely to have caused the variability in delta Ca-44/40 of the carbonatites. In plots of delta Ca-44/40 versus epsilon Nd-(t) and Sr-87/Sr-86((t)), the igneous silicate rocks from the Ambadongar and Phenai Mata complexes plot on a mixing trend between a primitive (plume) mantle source and the continental crustal basement suggesting the role of continental crustal contamination during eruption of the Reunion plume. While simple binary mixing calculations yield unrealistically high amounts of crustal contamination (40%), assimilation and fractional crystallization (AFC) models suggest up to 20% contribution from a heterogeneous basement for these igneous silicate rocks. The role of continental crustal contamination in the genesis of the igneous silicate rocks is further supported by their unradiogenic epsilon Nd-(t), radiogenic Sr-87/Sr-86((t)) and low Ce/Pb values. In contrast, carbonatites plot away from the mixing trend between a primitive mantle (plume) source and continental crust in Ca-Sr-Nd isotopic diagrams suggesting that the Ca isotopic variability of carbonatites is not caused by continental crustal contamination. In contrast, the isotopic composition of the carbonatites can be explained by mixing of the plume end-member with up to 20% of similar to 160 Ma-old recycled carbonates suggesting their derivation from a highly heterogeneous, recycled carbonate-bearing plume mantle source. The composition of one carbonatite sample showing unusually high delta Ca-44/40 and highly radiogenic Sr-87/Sr-86((t)) is explained by hydrothermal alteration which is also invoked for the formation of massive fluorspar deposits with high delta Ca-44/40 (1.44 parts per thousand) at Ambadongar. In a plot of delta Ca-44/40 versus K/Rb, the carbonatites plot towards the phlogopite end-member (delta Ca-44/40 = 1 parts per thousand, K/Rb = 40-450) while the igneous silicate rocks plot towards the amphibole end-member (delta Ca-44/40 = 0.44 parts per thousand, K/Rb >1000). Phlogopite, especially if F-rich, is stable at greater depths in the mantle compared to amphibole. Hence, the correlated delta Ca-44/40 and K/Rb values of the carbonatites and associated igneous silicate rocks suggest the derivation of these carbonatites from a relatively deeper mantle source compared to the silicate rocks, both within the Reunion mantle plume. The origin of the carbonatites from the F-rich phlogopite-bearing mantle is also consistent with the occurrence of large fluorspar deposits within the Ambadongar carbonatite complex. (C) 2019 Elsevier B.V. All rights reserved