50175 research outputs found
Sort by
Ultra-Range Bimetallic Pt-Pd Nanospheres Deposited on Reduced Graphene Sheet as Efficient Electrocatalyst Towards Electrooxidation of Methanol
No full textDirect methanol fuel cells (DMFCs) offers promising possibilities in meeting future energy needs in a most sustainable way. To electro oxidize methanol at anode of DMFCs, till date Pt and Pt-based materials were widely employed. To improve the utilization of precious metals it is highly desirable to disperse them on conductive carbon structures. Here, we synthesized ultra-range bimetallic platinum-palladium (Pt-Pd) nanospheres (NSs) with uniform dispersion on reduced graphene oxide (RGO) sheets by a simple hydrothermal method and studied their efficacies towards methanol oxidation reaction (MOR). From HR-TEM analysis, it was found that the synthesized bimetallic Pt-Pd NSs possess an average particles size of about 5 to 7 nm consistent with XRD data. The MOR electro catalytic activity of bimetallic PtPd-RGO NSs was higher compared to homemade mono metallic Pt-RGO, Pd-RGO catalysts and commercial E-tekPt/C
Zonally symmetric vs asymmetric North Pacific Ocean sea surface temperature influence on Indian summer monsoon through modulation of upper tropospheric circulation
No full textThis study asks the following question: what role the zonal distribution of sea surface temperature (SST) of North Pacific Ocean (NPAC) plays in the general circulation and vertical stability of the atmosphere during boreal summer season. Results here show that while zonally symmetric SST warming of NPAC shifts the upper tropospheric jet northward, zonally asymmetric warming and cooling alter the phase of mid latitude Rossby waves in east-west direction. These changes in circulation modify the vertical static stability of the atmosphere and precipitation, particularly in the Indian region. In particular, warmer SSTs in the western NPAC reduce the stability over Indian region leading to an enhanced monsoon precipitation even when El Nino-Southern Oscillation (ENSO) is not in favorable phase. In conjunction with an ENSO forcing, however, this phenomenon can augment or suppress its impact on Indian summer monsoon. This result is used to derive an index that explains more than 80% of the interannual variance of Indian summer monsoon (ISM) precipitation in June-July. Since June-July contributes about 50% to the total June-September precipitation in this region, this discovery increases the potential predictability of ISM. Finally, using historical simulations from the Coupled Model Intercomparison Project (CMIP5), we show that SST anomalies over NPAC strongly influence the strength of the relationship between ENSO and Indian summer monsoon. The mechanism proposed in this study can be used to diagnose the skill of general circulation models
Mechanics of plastic flow past a narrow-angle wedge indenter
No full textThe indentation of a metal specimen by a narrow-angle wedge produces extreme plastic deformation, with an effect akin to cutting into the metal. Simulation of such processes is challenging, and complicated by the need to model material separation along the indentation symmetry axis. Here we use an Arbitrary Lagrangian Eulerian (ALE) framework to enforce the symmetry boundary conditions (bcs) in their original, `strong' form, as well as conventional Lagrangian FE to impose the bcs in a complementary, `weak' form. Taken together these two cases, representing perfectly strong and perfectly weak interfaces, produce accurate bounds on the mechanical response for indentation by wedges with semi-apical angles as small as 15 degrees, and encompass intermediate cases that would require complicated models of ductile failure. The method accurately predicts the transition from the cutting pattern to the non-cutting (radially compressive) pattern as the apical angle is increased. In combination with Lagrangian particle tracking, the simulations reveal the deformation pattern as well as strain, strain-rate, and velocity fields in narrow angle indentation at high resolution. Interestingly, the strong form predicts a thin (tens of microns), near-wall layer of intense plastic strain, which has been observed recently in indentation experiments. With the exception of this feature, the strong and weak bc solutions are quite similar. The present approach reveals insights about plastic flow past narrow obstacles in a range of related problems including cone penetration and machining, and suggests using narrow-angle indentation as a way to probe material failure
Nanoscale Engineering of Graphene-Viologen Based 3D Covalent Organic Polymer Interfaces Leading to Efficient Charge-Transfer for Pseudocapacitive Energy Storage
No full textViologen based covalent organic polymer (COP) interfaced with graphene at the nanoscale showed pseudocapacitive energy storage associated with redox-active moieties. The positively charged viologen moieties endow charge storage as well as easy wetting of the electrode. The non-conducting COP grown over conducting graphene enhances its performance by extensive interface formation. All the redox states of viologen moieties can be reversibly attained without significant polarization when it is interfaced with graphene. However, the COP (devoid of graphene) shows irreversible/pseudo-reversible behavior due to lack of electron conducting pathways. The intimate and dense conducting pathways in graphene-COP composites facilitates the charge transfer across interface leading to effective and reversible participation of redox moieties across the entire range over 1000 cycles. Also, we show that the strategy being universal in nature and aid in electron transfer in dense 3D networks which lacks traditional pi-pi stacking of 2D crystalline networks (COF)
A novel member of the Hemidactylus brookii complex (Squamata: Gekkonidae) from the Western Ghats of Maharashtra, India
No full textA new rupicolous gecko from the Hemidactylus brookii complex is described from the forests and plateaus of Amboli, in the Western Ghats of Maharashtra. This medium sized (average adult SVL 56.2 +/- 5.0 to at least 62 mm), nocturnal species is superficially similar to other congeners from the `H. brookii' Glade, but can be distinguished from them in having 17 or 18 fairly regular longitudinal rows of enlarged, conical, keeled tubercles at midbody, extending from posterior part of the head to groin; tubercles in parasagittal rows smaller, feebly keeled and more rounded; approximately six rows of tubercles on either side of parasagittal tubercle rows, highly enlarged, remarkably conical and strongly keeled; lamellae divided in a straight transverse series-seven or eight lamellae beneath fourth digit (manus and pes) and five or six beneath first digit (manus and pes). Males with nine or ten (rarely eight) femoral pores separated by four or five poreless scales; supralabials 11-13; infralabials 8-11. Molecular data based on the mitochondrial ND2 gene supports the distinctiveness of this species and helps ascertain its phylogenetic position within the `H. brookii' group of the Indian Hemidactylus radiation
High-velocity H I jet-like feature towards the SNR candidate G351.7-1.2
No full textWe present the H I 21 cm spectral line and continuum observations of the Galactic supernova remnant (SNR) candidate G351.7-1.2 using the upgraded Giant Metrewave Radio Telescope. Strong absorption features are observed towards the H II regions in the star-forming complex associated with G351.7-1.2. Along with H I emission towards the outer periphery of the SNR shell, we distinguish a high-velocity jet-like feature in the velocity range +40 to +52 km s(-1) in H I. This unusual and highly collimated feature, with a projected length of similar to 7 pc and an opening angle of 14.4 degrees, is located towards the interior of the radio shell. This is the first report of a well collimated H I jet-like emission. The peculiar location and the detection of a gamma-ray source towards the central peak of this H I jet suggests its plausible association with the SNR candidate
Competition between High Speed Rail and Conventional Transport Modes: Market Entry Game Analysis on Indian Corridors
No full textThis paper investigates the competition between HSR and the incumbent with vertical service differentiation for Indian corridors. As Indian government plans to invest in this new technology, strategic decisions pertaining to type of corridor, speed of HSR, HSR technology, given the competition scenario on that corridor becomes vital. The strategic interactions between the operators are modelled as a three staged game between the entrant and the incumbent considering the competition over fare and frequency to maximize different objective functions i.e. Profit and Social Welfare. Speed of HSR is taken as a strategic variable in the game with two levels of high speed, {Low-H, High-H}. This model is applied on two corridors of India of different length i.e. Bangalore-Delhi (competition with airlines with length of corridor being 2400 km) and Bangalore-Mysore (competition with bus with length of corridor being 150 km). Revealed and stated preference surveys are conducted for the passengers traveling on these corridors and a discrete choice model was estimated for both the corridors. These models were used to determine the modal share in the new hypothetical scenario which were in turn used in defining objective functions such as profits and social welfare. Various game scenarios characterized by sunk and variable cost of the modes are formulated and equilibrium for all demand levels is computed for both the corridors for these different objective functions. Results demonstrates variation in Nash equilibrium for different game scenarios and hence indicates the importance of incorporating speed as a strategic variable. Changing the objective function to social welfare maximization results in different equilibrium solution for Bangalore-Delhi corridor. Thus, impact of different combinations of demand, cost structures and objective functions are explored on the market equilibrium thereby providing interesting insights in this area
Glutaredoxin1 Diminishes Amyloid Beta-Mediated Oxidation of F-Actin and Reverses Cognitive Deficits in an Alzheimer's Disease Mouse Model
No full textAims: Reactive oxygen species (ROS) generated during Alzheimer's disease (AD) pathogenesis through multiple sources are implicated in synaptic pathology observed in the disease. We have previously shown F-actin disassembly in dendritic spines in early AD (34). The actin cytoskeleton can be oxidatively modified resulting in altered F-actin dynamics. Therefore, we investigated whether disruption of redox signaling could contribute to actin network disassembly and downstream effects in the amyloid precursor protein/presenilin-1 double transgenic (APP/PS1) mouse model of AD. Results: Synaptosomal preparations from 1-month-old APP/PS1 mice showed an increase in ROS levels, coupled with a decrease in the reduced form of F-actin and increase in glutathionylated synaptosomal actin. Furthermore, synaptic glutaredoxin 1 (Grx1) and thioredoxin levels were found to be lowered. Overexpressing Grx1 in the brains of these mice not only reversed F-actin loss seen in APP/PS1 mice but also restored memory recall after contextual fear conditioning. F-actin levels and F-actin nanoarchitecture in spines were also stabilized by Grx1 overexpression in APP/PS1 primary cortical neurons, indicating that glutathionylation of F-actin is a critical event in early pathogenesis of AD, which leads to spine loss. Innovation: Loss of thiol/disulfide oxidoreductases in the synapse along with increase in ROS can render F-actin nanoarchitecture susceptible to oxidative modifications in AD. Conclusions: Our findings provide novel evidence that altered redox signaling in the form of S-glutathionylation and reduced Grx1 levels can lead to synaptic dysfunction during AD pathogenesis by directly disrupting the F-actin nanoarchitecture in spines. Increasing Grx1 levels is a potential target for novel disease-modifying therapies for AD
Search for anomalous electroweak production of vector boson pairs in association with two jets in proton-proton collisions at 13 TeV
No full textA search for anomalous electroweak production of WW, WZ, and ZZ boson pairs in association with two jets in proton-proton collisions at root s = 13 TeV at the LHC is reported. The data sample corresponds to an integrated luminosity of 35.9 fb(-1) collected with the CMS detector. Events are selected by requiring two jets with large rapidity separation and invariant mass, one or two leptons (electrons or muons), and a W or Z boson decaying hadronically. No excess of events with respect to the standard model background predictions is observed and constraints on the structure of quartic vector boson interactions in the framework of dimension-8 effective field theory operators are reported. Stringent limits on parameters of the effective field theory operators are obtained. The observed 95% confidence level limits for the S0, M0, and T0 operators are -2.7 < f(S0)/A(4) < 2.7, -1.0 < f(M0)/A(4) < 1.0, and -0.17 < f(T0)/A(4) < 0.16, in units of TeV-4. Constraints are also reported on the product of the cross section and branching fraction for vector boson fusion production of charged Higgs bosons as a function of mass from 600 to 2000 GeV. The results are interpreted in the context of the Georgi-Machacek model
Measurement of the top quark polarization and t(t)over-barspin correlations using dilepton final states in proton-proton collisions at root s=13 TeV
No full textMeasurements of the top quark polarization and top quark pair (t (t) over bar) spin correlations are presented using events containing two oppositely charged leptons (e(+)e(-), e(+/-)mu(-/+), or mu(+)mu(-)) produced in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9 fb(-1) . A set of parton-level normalized differential cross sections, sensitive to each of the independent coefficients of the spin-dependent parts of the t (t) over bar production density matrix, is measured for the first time at 13 TeV. The measured distributions and extracted coefficients are compared with standard model predictions from simulations at next-to-leading-order (NLO) accuracy in quantum chromodynamics (QCD), and from NLO QCD calculations including electroweak corrections. All measurements are found to be consistent with the expectations of the standard model. The normalized differential cross sections are used in fits to constrain the anomalous chromomagnetic and chromoelectric dipole moments of the top quark to -0.24 < C-tG/Lambda(2) < 0.07 TeV-2 and -0.33 < C-tG(I)/Lambda(2) < 0.20 TeV-2, respectively, at the 95% confidence level