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MoS2-graphene-CuNi2S4 nanocomposite an efficient electrocatalyst for the hydrogen evolution reaction
No full textWe present a facile methodology for the synthesis of a novel 2D-MoS2, graphene and CuNi2S4 (MoS2-g-CuNi2S4) nanocomposite that displays highly efficient electrocatalytic activity towards the production of hydrogen. The intrinsic hydrogen evolution reaction (HER) activity of MoS2 nanosheets was significantly enhanced by increasing the affinity of the active edge sites towards H+ adsorption using transition metal (Cu and Ni-2) dopants, whilst also increasing the edge sites exposure by anchoring them to a graphene framework. Detailed XPS analysis reveals a higher percentage of surface exposed S at 17.04%, of which 48.83% is metal bonded S (sulfide). The resultant MoS2-g-CuNi2S4 nanocomposites are immobilized upon screen-printed electrodes (SPEs) and exhibit a HER onset potential and Tafel slope value of - 0.05 V (vs. RHE) and 29.3 mV dec(-1), respectively. These values are close to that of the polycrystalline Pt electrode (near zero potential (vs. RHE) and 21.0 mV dec(-1), respectively) and enhanced over a bare/unmodified SPE (- 0.43 V (vs. RHE) and 149.1 mV dec(-1), respectively). Given the efficient, HER activity displayed by the novel MoS2-g-CuNi2S4/SPE electrochemical platform and the comparatively low associated cost of production for this nanocomposite, it has potential to be a cost-effective alternative to Pt within electrolyser technologies
Upper Bounds via Lamination on the Constrained Secrecy Capacity of Hypergraphical Sources
No full textHypergraphical sources are a natural class of sources for secret key generation, within which different subsets of terminals sharing secrets are allowed to discuss publicly in order to agree upon a global secret key. While their secrecy capacity, i.e., the maximum rate of a secret key that can be agreed upon by the entire set of terminals, is well-understood, what remains open is the maximum rate of a secret key that can be generated when there is a restriction on the overall rate of public discussion allowed. In this paper, we obtain a family of explicitly computable upper bounds on the number of bits of secret key that can be generated per bit of public discussion. These upper bounds are derived using a lamination technique based on the submodularity of the entropy function. In particular, a specific instance of these upper bounds, called the edge-partition bound, is shown to be tight for the pairwise independent network model, a special case of the hypergraphical source when the hypergraph is a graph. The secret key generation scheme achieving this upper bound is the tree-packing protocol of Nitinawarat et al., thereby resolving in the affirmative the discussion rate optimality of the tree-packing protocol
Time-reversal symmetry breaking in topological superconductor Sr0.1Bi2Se3
No full textThe single helical Fermi surface on the surface state of three-dimensional topological insulator Bi2Se3 is constrained by the time-reversal invariant bulk topology to possess a spin-singlet superconducting pairing symmetry. In fact, the Cu-doped and pressure-tuned superconducting Bi2Se3 show no evidence of the time-reversal symmetry (TRS) breaking. We report on the detection of the TRS breaking in the topological superconductor Sr0.1Bi2Se3, probed by zero-field mu SR measurements. The TRS breaking provides strong evidence for the existence of a spin-triplet pairing state. The existence of TRS breaking is also verified by longitudinal-field mu SR measurements, which negates the possibility of magnetic impurities as the source of TRS breaking. The temperature-dependent superfluid density deduced from transverse-field mu SR measurements yields nodeless superconductivity with low superconducting carrier density and penetration depth lambda = 1622(134) nm. From the microscopic theory of unconventional pairing, we find that such a fully gapped spin-triplet pairing channel is promoted by the complex interplay between the structural hexagonal warping and higher order Dresselhaus spinorbit-coupling terms. Based on Ginzburg-Landau analysis, we delineate the mixing of singlet- to triplet-pairing symmetry as the chemical potential is tuned far above from the Dirac cone. Our observation of such spontaneous TRS breaking chiral superconductivity on a helical surface state, protected by the TRS invariant bulk topology, can open avenues for interesting research and applications
Resonance and beating phenomenon in a nonlinear rigid cylindrical acoustic waveguide: The axisymmetric mode
No full textA rigid-walled semi-infinite circular cylindrical waveguide enclosing a weakly nonlinear fluid is considered. A quadratic nonlinear interaction is assumed as a model. A flat rigid piston generates an axisymmetric harmonic pressure that is prescribed as the input at the finite end of the waveguide. The objective is to study the modal interactions of waves. A regular perturbation method is used to separate the linear (primary) and the quasilinear (second harmonic) equations. First, linear solutions are established. Their quasilinear interactions then lead to modal interactions. Typically, the linear wavenumbers at the quasilinear order generate homogenous wavenumbers. Intersections of both these wavenumbers in the wavenumber-frequency plane are considered as resonances since the resulting pressure grows in amplitude in the axial propagating direction. The conditions under which the solutions become resonant or non-resonant are presented. In this last case, a beating phenomenon occurs with distance. It is found that the resonances are rare, except for the plane wave. Generally, the forced linear wavenumbers and the quasilinear generated wavenumbers acquire numerical values close to each other and create the beating phenomenon. (C) 2019 Elsevier Ltd. All rights reserved
Molecular determinants of complex formation between DNA and the AT-rich interaction domain of BAF250a
No full textAT-rich interaction domain (ARID)-containing BAF250a protein is a central DNA-binding subunit of the SWI/SNF chromatin-remodeling complex. ARIDs are found in several eukaryotic proteins that play roles in different aspects of cellular physiology. However, despite their biological importance, ARIDs remain relatively uncharacterized for their dynamics and DNA binding. Here, we have probed the structure and DNA-binding properties of BAF250a ARID. We show that the core BAF250a ARID interacts with DNA sequences with low micromolar affinities. NMR chemical shift perturbation (CSP) results reveal a number of conserved residues in ARID that are involved in DNA binding. An NMR CSP-based docking model of ARID-DNA complexes reveals that BAF250a ARID possesses necessary determinants of specific DNA binding
ESD Reliability of AlGaN/GaN HEMT Technology
No full textThis experimental study reports new aspects of electrostatic discharge (ESD) behavior in AlGaN/GaN HEMTs. The role of Schottky gate and MESA is investigated using special test structures. Influenceof piezoelectricfield, carrier trapping, and self-heating on ESD behavior is studied. A unique power-law-like behavior is found. Linear scaling of failure current with source-drain spacing is reported. Spot measured drain-to-source DC current is realized as an important parameter to monitor degradation. Unique degradation trends are observed for the first time and a correlation between snapback depth and % degradation is established. Cumulative nature of device degradation is discovered. Change from soft to hard failure with an increase in pulsewidth (PW) is reported. Finally, the cause of snapback instability observed in device, at low PW, is discussed
Enhanced spin transport in a ferrite having distributed energy barriers for exchange bias
No full textWe observe an exchange bias at low temperatures in polycrystalline ferrimagnetic MgFe2O4 (MFO) films grown on Si(100), emerging from Antiferromagnetic (AFM)-like interactions at defect sites, concentrated predominantly at the grain boundaries. In this report, we show it is possible to utilize these AFM interactions to get enhanced spin transport utilizing the spin Seebeck effect (SSE). The temperature dependence of the SSE signal in two films with different defect densities allowed us to identify a unique temperature window for both films where an enhanced SSE signal was observed. Such enhancement has been reported in different Ferromagnet (FM)/AFM bilayer systems, but its observation in a single layer hosting both FM-AFM interactions makes our results attractive. Temperature dependent SQUID magnetometry revealed two distinct regions of strong and weak coupling for the FM-AFM interactions. The weak coupling region is characterized by a distribution of AFM energy barriers (Delta E), which can modify the spin conductance across the FM-AFM boundary and hence, affect the spin transport. Indeed, we find that the same functional form fits both the Delta E distribution and the SSE temperature evolution for both films. This study should aid in the understanding of SSE in the large class of polycrystalline materials with inherent growth induced defect densities and illustrate the significance of magnetically disordered phases in spin transport
UV resistant and fire retardant properties in fabrics coated with polymer based nanocomposites derived from sustainable and natural resources for protective clothing application
No full textHerein, UV-blocking and fire resistance cotton fabric was designed by coating polyurethane based MnO2-FeTiO3 (MFT) nanocomposites. The FeTiO3 (FT) nanoparticles were prepared using acid extraction from naturally occurring ilmenite sand and subsequently manganese acetate was added to synthesize the nanocomposite which was then thoroughly characterized. A colloidal suspension of MFT nanocomposite in TPU was prepared using sol-gel approach and subsequently coated onto cotton fabric. The surface morphology and the coverage of MFT on the coated fabric was assessed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The structural changes, and thermal stability of the coated and uncoated fabrics was investigated by Fourier transform Infrared with Attenuated Total Reflectance Spectroscopy (FTIR-ATR), and thermogravimetric (TGA) analysis respectively. The MFT coated cotton fabrics exhibited a strong UV blocking ability and offered fire resistant properties as assessed using limited oxygen index. Furthermore, the coated cotton fabric retained its properties even after ten water-laundering cycles thereby offering durable, sustainable smart fabric for protective clothing application
Oxygen vacancy induced anomalous Raman mode in intrinsic ZnO film
No full textZnO network were prepared by a simple solution procedure due to its simplicity and cost effectiveness that has been calcined at different temperatures. With increasing the calcination temperature the preferred crystal-lographic orientation shifts from < 002 > to < 103 > direction. Additional Raman modes have been accounted in a number of current literatures compacting with intrinsic and doped ZnO layers but no clear justification has been given. Here we propose that disorder-activated Raman scattering commences increasingly growing second order Raman peak, (B-1(high) - B-1(low)) originated by the breakdown of translational equilibrium of the crystal by the O-vacancy induced defects and changes direction from preferred c-axis orientation with I-< 103 >/I-< 002 (>) > 1. At higher calcination temperatures O-vacancies have the inferior formation energy. The high-concentration of O-vacancy defect which assembles the < 103 > crystallographic orientation and the momentous strong anomalous Raman mode are projected to move forward clarification of the mechanisms of defect induced Raman mode and raise the opto-electronic relevance of ZnO matrix
Proteome Based de novo Sequencing of Novel Conotoxins from Marine Molluscivorous Cone Snail Conus amadis and Neurological Activities of Its Natural Venom in Zebrafish Model
No full textBackground: Conus amadis is a carnivorous snail found abundantly in coastal waters of India. Despite its abundance in southern coastal waters of India and the fact that most of the conotoxin act in neuronal system, research work on Conus amadis venom was not much focused. So we have made a brief study on the venom complex of Conus amadis to identify the library of novel conotoxins and to screen the natural venom for neurological function. Objective: De novo sequencing of novel conopeptides from the venom cocktail of Conus amadis and to screen its natural venom for the presence of biological activities in zebrafish model. Methods: Proteome based MALDI-TOF and LC-MS-MS analysis for identification of novel conotoxins and subsequent sequencing. Due to the complex disulfide rich nature of the venom peptides, the study also involves global chemical modification experiments of the venom extract to unambiguously determine the sequence of novel conotoxins. Biological function analysis of natural venom was tested in zebrafish model to ascertain anti-epileptic properties. Results: In this study, we have identified 19 novel conotox ins containing 1, 2 & 3 disulfides, belonging to different classes. Among them, 2 novel contryphans, 3 T-superfamily conotoxins, 2 A-superfamily conotoxins and 2 Mini M-Superfamily conotoxins were sequenced to its amino acid level from the fragmented spectrum of singly and doubly charged parent ions using de novo sequencing strategies. ama1054, a contryphan peptide toxin, possesses post translationally modified bromo tryptophan at its seventh position. Except ama1251, all the sequenced peptide toxins possess modified C-terminal amidation. Crude venom exhibited anticonvulsant properties in pentylenetetrazole-induced seizure in zebrafish larvae, which suggested anti-epileptic property of the venom cocktail. Acetylcholinesterase activity was also identified in the venom complex. Conclusion: Based on the preliminary evidence, if this study is extended further through bioassay guided purification, could possibly yield peptide toxins with anticonvulsant and other neurologically active molecules