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Hot deformation behaviour of Mo-TZM and understanding the restoration processes involved
No full textHot deformation behaviour of Mo-TZM alloy over a temperature range of 1400-1700 degrees C and strain rate range of 0.001-10.0 s(-1) was investigated. The microstructure after deformation was characterized at each deformation condition using electron back scatter diffraction technique. The high strain rate sensitivity domain was found to be in the strain rate range of 10(-2) - 10(-3) s(-1) and in temperature range of 1480-1650 degrees C. The flow stress behaviour of the material indicated dynamic recovery as well as recrystallization of the material during deformation. Microstructural investigation confirmed the occurrence of continuous dynamic recrystallization from 1400 to 1500 degrees C. At higher temperature (1600-1700 degrees C) and low strain rates (10(-2) - 10(-3) s(-1)) grain growth was dominant. At high strain rates (0.1-10 s(-1)) and high temperature (1600-1700 degrees C) dynamic recrystallization was not observed. Based on the experimental observations a schematic model of the microstructure evolution of TZM during deformation at high temperatures was proposed. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Sporosarcina pasteurii can form nanoscale calcium carbonate crystals on cell surface
No full textThe bacterium Sporosarcina pasteurii (SP) is known for its ability to cause the phenomenon of microbially induced calcium carbonate precipitation (MICP). We explored bacterial participation in the initial stages of the MICP process at the cellular length scale under two different growth environments (a) liquid culture (b) MICP in a soft agar (0.5%) column. In the liquid culture, ex-situ imaging of the cellular environment indicated that S. pasteurii was facilitating nucleation of nanoscale crystals of calcium carbonate on bacterial cell surface and its growth via ureolysis. During the same period, the meso-scale environment (bulk medium) was found to have overgrown calcium carbonate crystals. The effect of media components (urea, CaCl2), presence of live and dead in the growth medium were explored. The agar column method allows for in-situ visualization of the phenomena, and using this platform, we found conclusive evidence of the bacterial cell surface facilitating formation of nanoscale crystals in the microenvironment. Here also the bulk environment or the meso-scale environment was found to possess overgrown calcium carbonate crystals. Extensive elemental analysis using Energy dispersive X-ray spectroscopy (EDS) and X-ray powder diffraction (XRD), confirmed that the crystals to be calcium carbonate, and two different polymorphs (calcite and vaterite) were identified. Active participation of S. pasteurii cell surface as the site of calcium carbonate precipitation has been shown using EDS elemental mapping with Scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM)
Investigation on the structure and thermoelectric properties of CuxTe binary compounds
No full textCu2Te is a superionic conductor that belongs to the Phonon Liquid Electron Crystal class of thermoelectric (TE) materials. Despite the simple chemical formula, the crystal structures and phases in the Cu2Te system have not been understood properly. In this work, we study the structural and TE properties of Cu2Te (CT2), Cu1.6Te (CT1.6) and Cu1.25Te (CT1.25). The samples were synthesized via a solid-state reaction method. Powder X-ray diffraction analysis revealed that the samples have different crystal structures depending upon the Cu : Te stoichiometry. The elemental compositional analysis showed that all the samples are copper deficient. This is due to the precipitation of metallic copper on the surface of the ingot arising from the thermal dissociation of Cu2Te. The transport properties were measured in the temperature range 300 K-600 K. The electrical conductivity (sigma) decreases with an increase in temperature indicating a metal-like behaviour for all the samples. The positive Seebeck coefficients (S) for all the samples indicates that majority charge carriers are holes. The sample CT2 has a higher S (29.5 mu V K (1) at 573 K) and a lower sigma (2513 S cm(-1) at 573 K) due to a lower carrier (hole) concentration compared to the other two samples. With the increase in Cu deficiency, the hole concentration increases, and this leads to higher electronic thermal conductivity in the samples CT1.6 and CT1.25. The maximum thermoelectric figure of merit of 0.03 at 524 K is achieved for the sample CT2 owing to its higher power factor (0.24 mW m(-1) K-2) and lower thermal conductivity (3.8 W m(-1) K-1). The present study bridges the gap between the theoretical predictions and experimental observations involving the various possible structures in this system. Furthermore, we have shown that the Cu vacancies are detrimental to the thermoelectric performance of Cu2Te
Arthropod venoms: Biochemistry, ecology and evolution
No full textComprising of over a million described species of highly diverse invertebrates, Arthropoda is amongst the most successful animal lineages to have colonized aerial, terrestrial, and aquatic domains. Venom, one of the many fascinating traits to have evolved in various members of this phylum, has underpinned their adaptation to diverse habitats. Over millions of years of evolution, arthropods have evolved ingenious ways of delivering venom in their targets for self-defence and predation. The morphological diversity of venom delivery apparatus in arthropods is astounding, and includes extensively modified pedipalps, tail (telson), mouth parts (hypostome), fangs, appendages (maxillulae), proboscis, ovipositor (stinger), and hair (urticating bristles). Recent investigations have also unravelled an astonishing venom biocomplexity with molecular scaffolds being recruited from a multitude of protein families. Venoms are a remarkable bioresource for discovering lead compounds in targeted therapeutics. Several components with prospective applications in the development of advanced lifesaving drugs and environment friendly bio-insecticides have been discovered from arthropod venoms. Despite these fascinating features, the composition, bioactivity, and molecular evolution of venom in several arthropod lineages remains largely understudied. This review highlights the prevalence of venom, its mode of toxic action, and the evolutionary dynamics of venom in Arthropoda, the most speciose phylum in the animal kingdom
Revisiting integer factorization using closed timelike curves
No full textClosed timelike curves are relativistically valid objects allowing time travel to the past. Treating them as computational objects opens the door to a wide range of results which cannot be achieved using non-relativistic quantum mechanics. Recently, research in classical and quantum computation has focused on effectively harnessing the power of these curves. In particular, Brun (Found Phys Lett 16:245-253, 2003) has shown that CTCs can be utilized to efficiently solve problems like factoring and quantified satisfiability problem. In this paper, we find a flaw in Brun's algorithm and propose a modified algorithm to circumvent the flaw
Quantum error correction using weak measurements
No full textThe standard quantum error correction protocols use projective measurements to extract the error syndromes from the encoded states. We consider the more general scenario of weak measurements, where only partial information about the error syndrome can be extracted from the encoded state. We construct a feedback protocol that probabilistically corrects the error based on the extracted information. Using numerical simulations of one-qubit error correction codes, we show that our error correction succeeds for a range of the weak measurement strength, where (a) the error rate is below the threshold beyond which multiple errors dominate, and (b) the error rate is less than the rate at which weak measurement extracts information. We observe that error correction based on projective measurements is always superior to that based on weak measurements; so the latter is worthwhile only if the former is unavailable due to some reason, and error correction with too small a measurement strength should be avoided
Novel insights into the properties of AgBiO3 photocatalyst and its application in immobilized state for 4-nitrophenol degradation and bacteria inactivation
No full textThis study focuses on the synthesis of novel AgBiO3 nanoparticles by the hydrothermal route and investigating its properties responsible for waste water treatment. The temperature and time of hydrothermal reaction was optimized to 150 degrees C and 24 h to obtain highly active crystalline nanoparticles, as determined by XRD. The oxidation state of each element in the material was determined from XPS analysis. The morphology and size of the nanoparticles was obtained from SEM and TEM analysis. The optical and electrochemical properties of the material were studied by UPS and Mott Schottky plot. AgBiO3 was found to have a low band gap that facilitates the absorption of higher wavelength range as confirmed by Tauc plots and UV-vis DRS analysis. The excellent photocatalytic activity of the immobilized material towards the degradation of 4-nitrophenol and inactivation of E. coil was confirmed from kinetic studies and stability tests. A maximum degradation of 90% was achieved for 4-NP and a 5-log reduction was observed for viable E. coli cells in 5 h and 1 h respectively. Scavenger studies were performed to identify that superoxide radicals were responsible for the photocatalytic activity of the material. To eliminate the cost of separation and ease the reusability of the material, the nanoparticles were immobilized on cellulose acetate. Leaching of Ag and Bi ions from immobilized as well as free AgBiO3 nanoparticles into water was obtained via ICP-MS analysis. The results indicated that the leaching of Ag and Bi was controlled to a considerable extent due to immobilization on cellulose acetate matrix
Topology of electron density and electrostatic potential of HIV reverse transcriptase inhibitor zidovudine from high resolution X-ray diffraction and charge density analysis
No full textAzidothymidine (AZT) is a first anti-HIV drug namely Zidovudine used for HIV treatment, which binds to the viral DNA primer and inhibits the HIV reverse transcription. The side effects of this powerful drug are severe and the detailed understanding of its electronic structure helps to design new drugs from the AZT molecule. Present study aims to determine the structure of AZT at electronic level from the experimental charge density analysis as well as the solid state DFT calculations. AZT was crystallized and low temperature high resolution X-ray diffraction intensity data has been measured up to sin (theta/lambda)(max) = 1.1 angstrom(-1) at 100.0 (2) K. The crystal structure of AZT was determined, which reveals the information that the AZT compound crystallizes with two molecules in the asymmetric unit which are conformationally different and linked through strong hydrogen bonding interactions (dimer). The Hirshfeld surface of both molecules shows the locations of weak and strong interactions. Further, a multipole model refinement was carried out using Hansen-Coppens multipole formalism. The experimental topological properties of electron density of AZT molecules were determined and compared with the results of theoretical DFT calculations based on solid state and gas phase studies. The charge density distribution of the two molecules in the asymmetric unit is unequal and shows some difference. The topological properties of O-H center dot center dot center dot O, O-H center dot center dot center dot N, C-H center dot center dot center dot N, H center dot center dot center dot H and azide center dot center dot center dot azide group interactions are also determined. The electrostatic potential (ESP) surface of both AZT molecules in the crystal exhibits high electronegative regions around the O, N atoms and also around the azide group, however, ESP regions of molecules (I) and (II) are not similar. (C) 2018 Elsevier B.V. All rights reserved
Mycobacterium tuberculosis Rv0366c-Rv0367c encodes a non-canonical PezAT-like toxin-antitoxin pair
No full textToxin-antitoxin (TA) systems are ubiquitously existing addiction modules with essential roles in bacterial persistence and virulence. The genome of Mycobacterium tuberculosis encodes approximately 79 TA systems. Through computational and experimental investigations, we report for the first time that Rv0366c-Rv0367c is a non-canonical PezAT-like toxin-antitoxin system in M. tuberculosis. Homology searches with known PezT homologues revealed that residues implicated in nucleotide, antitoxin-binding and catalysis are conserved in Rv0366c. Unlike canonical PezA antitoxins, the N-terminal of Rv0367c is predicted to adopt the ribbon-helix-helix (RHH) motif for deoxyribonucleic acid (DNA) recognition. Further, the modelled complex predicts that the interactions between PezT and PezA involve conserved residues. We performed a large-scale search in sequences encoded in 101 mycobacterial and 4500 prokaryotic genomes and show that such an atypical PezAT organization is conserved in 20 other mycobacterial organisms and in families of class Actinobacteria. We also demonstrate that overexpression of Rv0366c induces bacteriostasis and this growth defect could be restored upon co-expression of cognate antitoxin, Rv0367c. Further, we also observed that inducible expression of Rv0366c in Mycobacterium smegmatis results in decreased cell-length and enhanced tolerance against a front-line tuberculosis (TB) drug, ethambutol. Taken together, we have identified and functionally characterized a novel non-canonical TA system from M. tuberculosis
Correlation of abrin-mediated inhibition of protein synthesis and apoptosis
No full textThe plant toxin, abrin, a type-II ribosome inactivating protein, is extremely lethal, the human fatal dose being similar to 1 mu g/kg body weight. Abrin has been classified as an agent for bioterrorism, which is of concern. Conversely, the high toxic property of abrin has been employed in generating immunotoxins, whereas its toxin moiety is conjugated to cell surface marker-specific antibodies for cell-targeted killing. Different cell types exhibit variable levels of sensitivity to abrin toxicity; therefore, adequate knowledge of the molecular mechanism that governs the activity of the protein would be a safeguard. To gain insights into this, two cell lines requiring strikingly different concentrations of abrin for inactivating ribosomes were studied. Employing conjugates of the wild-type and active site mutant of abrin A chain with the ricin B chain, it was found that abrin-induced apoptosis was dependent on inhibition of protein synthesis (PSI) leading to ER-stress in Ovcar-3 cells, but not in KB cells. Abrin was also observed to cause direct DNA damage in KB cells, while in Ovcar-3 cells abrin-induced DNA damage was found to be dependent on caspases. Overall, the study demonstrates that the correlation of abrin-mediated PSI and apoptosis is cell-specific and abrin can induce more than one pathway to cause cell death. (c) 2018 IUBMB Life, 71(3):357-363, 201