50175 research outputs found
Sort by
Understanding the Chemical Nature of the Buried Nanostructures in Low Thermal Conductive Sb-Doped SnTe by Variable-Energy Photoelectron Spectroscopy
No full textNanoprecipitates embedded in a matrix of thermoelectric materials decrease the lattice thermal conductivity significantly by extensive heat carrying phonon scattering. Recently, two-dimensional layered intergrowth nanostructures of SnmSb2nTe3n+m embedded in SnTe matrix have provided record low lattice thermal conductivity in SnTe, but an understanding of the chemical nature of these layered nanostructures is still not clear. Herein, we studied the chemical nature of the intergrowth nanostructures of a series Sb-doped SnTe by variable-energy X-ray photoelectron spectroscopy at synchrotron, which is well known to probe buried interfaces and embedded nanostructures. The primary oxidation states of Sb, Sn, and Te in these intergrowth structures are found to be in +3, +2, and -2, respectively, which is expected from the composition. However, both the Sn and Sb are found to be slightly oxidized in the surface. From the intensity variation with photon energy, we have found a thin layer of SnO2 (similar to 4.5 nm) on the sample surfaces and the thickness decreases with Sb doping. Te is also found in 0 oxidation states, which corroborates with the variation of Sn vacancies with Sb doping. The valence band features near the edge do not change significantly with Sb doping. This understanding of the chemical nature of low lattice thermal conductive Sb-doped SnTe will help further to design the thermoelectric materials with their surface phenomenon
Photocytotoxic oxovanadium(IV) complexes of ferrocenyl-terpyridine and acetylacetonate derivatives (vol 92, pg 332, 2015)
No full textBioinformatic and mutational studies of related toxin-antitoxin pairs in Mycobacterium tuberculosis predict and identify key functional residues
No full textMycobacterium tuberculosis possesses an unusually large representation of type II toxin-antitoxin (TA) systems, whose functions and targets are mostly unknown. To better understand the basis of their unique expansion and to probe putative functional similarities among these systems, here we computationally and experimentally investigated their sequence relationships. Bioinformatic and phylogenetic investigations revealed that 51 sequences of the VapBC toxin family group into paralogous sub-clusters. On the basis of conserved sequence fingerprints within paralogues, we predicted functional residues and residues at the putative TA interface that are useful to evaluate TA interactions. Substitution of these likely functional residues abolished the toxin's growth-inhibitory activity. Furthermore, conducting similarity searches in 101 mycobacterial and approximate to 4500 other prokaryotic genomes, we assessed the relative conservation of the M. tuberculosis TA systems and found that most TA orthologues are well-conserved among the members of the M. tuberculosis complex, which cause tuberculosis in animal hosts. We found that soil-inhabiting, free-living Actinobacteria also harbor as many as 12 TA pairs. Finally, we identified five novel putative TA modules in M. tuberculosis. For one of them, we demonstrate that overexpression of the putative toxin, Rv2514c, induces bacteriostasis and that co-expression of the cognate antitoxin Rv2515c restores bacterial growth. Taken together, our findings reveal that toxin sequences are more closely related than antitoxin sequences in M. tuberculosis. Furthermore, the identification of additional TA systems reported here expands the known repertoire of TA systems in M. tuberculosis
Statistics of work done in a degenerate parametric amplification process
No full textWe study statistics of work done by two classical electric-field pumps (two-photon and one-photon resonant pumps) on a quantum optical oscillator. We compute the moment generating function for the energy change of the oscillator, interpreted as work done by the classical drives on the quantum oscillator starting out in a thermalized Boltzmann state. The moment generating function is inverted, analytically when only one of the pumps is turned on and numerically when both the pumps are turned on, to get the probability function for the work. The resulting probability function for the work done by the classical drive is shown to satisfy transient detailed and integral work fluctuation theorems. Interestingly, we find that, in order for the work distribution function to satisfy the fluctuation theorem in the presence of both the drivings, the relative phases of drivings need to be shifted by pi, which is related to the broken time-reversal symmetry of the Hamiltonian
Gradient plastic strain accommodation and nanotwinning in multi-pass laser shock peened 321 steel
No full textIn this study gradient plastic strain accommodation and nanotwinning are investigated in detail using electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM) techniques in AISI 321 steel after laser shock peening without applying surface protective coatings, employing multiple zigzag peening passes (3 times and 5 times). On the peened specimens, three regions, as identified by residual stress and hardness results, namely, thermally affected region (from top peened surface to 20 mu m), severe plastically deformed region (beneath 20 mu m up to 100 mu m depth) and minor plastically deformed region (beneath 100 mu m up to 180 mu m depth) were observed. Significant grain orientation spread and increased low-angle grain boundaries were noticed in severe plastically deformed region. The accommodation of plastic strain after laser peening gradually decreased from 20 mu m from peened surface. Nanotwins of varying width, in particular, multiple twinning within twin-matrix after 5 times laser peening passes were observed after peening. Interestingly nanotwins were bundled within an austenitic grain after peening with 5 passes
Search for Narrow H gamma Resonances in Proton-Proton Collisions at root s=13 TeV
No full textA search for heavy, narrow resonances decaying to a Higgs boson and a photon (Hy) has been performed in proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb-1 collected with the CMS detector at the LHC in 2016. Events containing a photon and a Lorentz-boosted hadronically decaying Higgs boson reconstructed as a single, large-radius jet are considered, and the y jet invariant mass spectrum is analyzed for the presence of narrow resonances. To increase the sensitivity of the search, events are categorized depending on whether or not the large-radius jet can be identified as a result of the merging of two jets originating from b quarks. Results in both categories are found to agree with the predictions of the standard model. Upper limits on the production rate of Hy resonances are sct as a function of their mass in the range of 720-3250 GeV, representing thc most stringent constraints to date
Editorial: The National Organic Symposium Trust-Shaping Organic Chemistry in India for Over 30 Years
No full textRisk Analysis of Permeable Layer in Pavement Subsurface Drainage System
No full textThe paper presents a framework to predict and consider the risks associated with the permeable layer in a pavement subsurface drainage system and suggests strategies to reduce the risks and improve the performance of the system. The performance of the system is dependent on the inflow characteristics, aggregate gradation, drainage characteristics of unsaturated soils, and geometry of the pavement section. The demand on the system is considered as the required permeability, which is estimated on the basis of total inflow into the pavement system plus the geometric section properties. The discharge capacity of the layer is dependent on the permeability of the drainage layer. The design of the system is examined in terms of capacity-demand models, and a rational design methodology considering variations in demand through rainfall characteristics and capacity in the form of permeability of the permeable layer is presented. Because determination of the exact demand and capacity of the system is a complex and stochastic process, the evaluation of its performance in light of uncertainty is a more realistic process, which should include consideration of the probability of failure and associated risks. The performance measure is analyzed by considering the sensitivity of the design to different variables. The performance of the system can be increased optimally by increasing the layer thickness and/or providing coarser gradation with stabilization
A Dicationic Bismuth(III) Lewis Acid: Catalytic Hydrosilylation of Olefins
No full textInvited for the cover of this issue is Ajay Venugopal from the Indian Institute of Science Education and Research Thiruvananthapuram. The cover image shows dication Tp(Me2)Bi](2+) catalyzing olefin hydrosilylation under mild conditions
Heat conduction model based on percolation theory for thermal conductivity of composites with high volume fraction of filler in base matrix
No full textIn this article, we propose a computational heat conduction model to estimate the thermal conductivity of composites with high volume fraction of filler particles distributed randomly in the base matrix. Most of the presently available models used for estimating the thermal conductivity of the composite materials fail after a certain volume fraction of the filler due to the effect of percolation i.e. the formation of `heat transfer paths' formed by the filler particles within the composite. The proposed model accounts for this percolation effect and estimates the thermal conductivity of a composite material with Aluminium as the filler in the Epoxy matrix. The algorithm for the proposed model is developed using MATLAB program and is used to obtain the thermal conductivity of the composite by entering the specifications of the parent components of the composite. The proposed model is able to predict the thermal conductivity of composites of high volume fraction of filler over the temperature range of 50 K-300 K and the results obtained are in good agreement with the experimental data