The title compound methyl(2E)-2-{N-(2-formylphenyl) (4-methylbenzene)sulfonamidomethyl}-3-(4-fluorophenyl) prop-2-enoate (MFMSF) has been synthesized and single crystals were grown by slow ...evaporation solution growth technique at room temperature. The grown crystals were characterized by FTIR, 1H NMR, 13C NMR, and single crystal X-ray diffraction. In the crystal, molecules are linked by intermolecular C–H…O hydrogen bonds forming a two-dimensional supramolecular network along 110 direction. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6-311G (d,p) basis set in ground state and compared with the experimental data. The entire vibrational assignments of wave numbers were made on the basis of potential energy distribution (PED) by VEDA 4 programme. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. In addition, NLO, MEP, Mulliken, thermodynamic properties, HOMO and LUMO energy gap were theoretically predicted. The global chemical reactivity descriptors are calculated for MFMSF and used to predict their relative stability and reactivity. The antibacterial activity of the compound was also tested against various pathogens. The molecular docking studies concede that title compound may exhibit PBP-2X inhibitor activity.
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•The structure has been studied by SCXRD and DFT.•NBO, NLO and MEP distribution of the molecule were theoretically predicted.•Thermo dynamical properties at different temperatures were calculated.•Antibacterial activity and molecular docking studies were reported.
Gas diffusion layer (GDL) is subjected to compressive stress at high temperature along with polymer electrolyte membrane in the fabrication process and in assembling the fuel cell stacks. Compressive ...stress decreases the thickness of GDL, electrical conductivity, permeability, and affects the pores. Carbon cloth based GDL withstands higher strain level when compared to carbon paper and the pore structure is also disrupted to a greater extent in cloth based GDL. In the present paper, we have addressed the effects of stress on pore structure of cloth based GDL. An optimum GDL must offer low mass transport resistance in an operating PEM fuel cell. The pore size analysis of pristine GDL and GDLs pressed at different pressure levels (200, 600 & 1000 kg cm−2) and their characteristics are evaluated using capillary flow porometry. The compressive stress affects the three types of pores in GDL called bubble point pore, mean flow pore and smallest pore. The change in electrical resistance, wetting behavior and surface morphology is also examined as a function of compressive stress. The fuel cell performances using these GDLs pressed at different compressive stresses are also evaluated and presented. The highest PEMFC performance is achieved at a compressive stress of 200 kg cm−2, which could be attributed to the combined effect of reduced ohmic resistance and optimized pore structure. The order of increasing performance in terms of current density is observed to be j200 > jPristine > j600 > j1000 at 0.15 V. The thicknesses and pore sizes of custom made GDL for optimum fuel cell performance are recommended.
•Effects of stress on the GDL's porosity were studied using capillary flow porometry•The optimum compressive stress was determined for improved fuel cell performance•The optimum pore structure and its corresponding applied stress were recommended
Abstract
Dual phase xenon detectors are widely used in experimental
searches for galactic dark matter particles. The origin of single
electron backgrounds following prompt scintillation and ...proportional
scintillation signals in these detectors is not fully understood,
although there has been progress in recent years. In this paper, we
describe single electron backgrounds in
83m
Kr
calibration events and their correlation with drift and extraction
fields, using the Particle Identification in Xenon at Yale (PIXeY)
dual-phase xenon time projection chamber. The single electron
background induced by the Fowler-Nordheim (FN) effect is measured,
and its electric field dependence is quantified. The photoionization
of grids and impurities by prompt scintillation and proportional
scintillation also contributes to the single electron background.
The title compound methyl(2E)-2-{N-(2-formylphenyl)(4-methylbenzene)sulfonamido methyl}-3-(2-methoxyphenyl)prop-2-enoate (MFMSM) has been synthesized and single crystals were grown by slow ...evaporation solution growth technique at room temperature. XRD, FT-IR and NMR spectra of MFMSM in the solid phase were recorded and analyzed. The optimized geometry and vibrational wave numbers were computed using DFT method. The NLO, Mulliken, MEP, HOMO-LUMO energy gap and thermodynamic properties were theoretically predicted. The NBO analysis explained the intramolecular hydrogen bonding. The global chemical reactivity descriptors are calculated for MFMSM and used to predict their relative stability and reactivity. All the calculations were carried out by B3LYP/6-311G (d,p) method. MFMSM has been screened for its antimicrobial activity and found to exhibit antifungal and antibacterial effects. Docking simulation has been performed.
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•Structural and spectral investigations of MFMSM were carried out.•NBO analysis, HOMO and LUMO energies and MEP distribution of the molecule were theoretically predicted.•Thermo dynamical properties at different temperatures were calculated.•In vitro antimicrobial activity and Molecular docking studies were reported.
The Nafion membrane used as an electrolyte in the Polymer Electrolyte Membrane Fuel Cell (PEMFC) needs hydration to retain the proton conductivity. In PEMFC operation the reactant gas needs to be ...humidified either externally or internally. To reduce the cost, weight and complexities of the PEMFC system, it is beneficial to operate the PMEFC without humidification of the reactant gases because it eliminates the need for a complex gas-humidification sub-system. In recent years, worldwide R&D efforts have been made to remove the external humidifying unit from the PEMFC system by endowing the membrane electrode assembly (MEA) with self-humidifying ability. Efforts have been made to minimize humidification of the ionic polymer by introducing SiO2 either in the catalyst layer or on the gas diffusion layer or on the membrane directly. In-house has made two silica powders, 1. Aerogel silica, surface area is 582 m2/g and 2. Silica powder with surface area of 45 m2/g is incorporated in the fuel cell electrode. This improves the hydrophilic and protonation properties of the SiO2 powders when treated with H2SO4. Initial experiments under humidified conditions showed that the Silica powder, which was not treated with H2SO4, gave marginally lower performance compared to the H2SO4 treated sample. The polarization behaviors of the electrode with and without SiO2 in the catalyst layer were studied. The PEMFC was also studied under different humidity conditions. The electrodes and the PEMFC were characterized by different electrochemical techniques like cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS). The results are presented in this paper.
Prompt scintillation signals from 83mKr calibration sources are a useful metric to calibrate the spatial variation of light collection efficiency and electric field magnitude of a two phase ...liquid-gas xenon time projection chamber. Because 83mKr decays in two steps, there are two prompt scintillation pulses for each calibration event, denoted S1a and S1b. We study the ratio of S1b to S1a signal sizes in the Particle Identification in Xenon at Yale (PIXeY) experiment and its dependence on the time separation between the two signals (Δt), notably its increase at low Δt. In PIXeY data, the Δt dependence of S1b/S1a is observed to exhibit two exponential components: one with a time constant of 0.05±0.02 μs, which can be attributed to processing effects and pulse overlap and one with a time constant of 10.2±2.2 μs that increases in amplitude with electric drift field, the origin of which is not yet understood.
A portable monoenergetic 24 keV neutron source based on the 124Sb-9Be photoneutron reaction and an iron filter has been constructed and characterized. The coincidence of the neutron energy from SbBe ...and the low interaction cross-section with iron (mean free path up to 29 cm) makes pure iron specially suited to shield against gamma rays from 124Sb decays while letting through the neutrons. To increase the 124Sb activity and thus the neutron flux, a >1 GBq 124Sb source was produced by irradiating a natural Sb metal pellet with a high flux of thermal neutrons in a nuclear reactor. The design of the source shielding structure makes for easy transportation and deployment. A hydrogen gas proportional counter is used to characterize the neutrons emitted by the source and a NaI detector is used for gamma background characterization. At the exit opening of the neutron beam, the characterization determined the neutron flux in the energy range 20–25 keV to be 6.00±0.30 neutrons per cm2 per second and the total gamma flux to be 245±8 gammas per cm2 per second (numbers scaled to 1 GBq activity of the 124Sb source). A liquid scintillator detector is demonstrated to be sensitive to neutrons with incident kinetic energies from 8 to 17 keV, so it can be paired with the source as a backing detector for neutron scattering calibration experiments. This photoneutron source provides a good tool for in-situ low energy nuclear recoil calibration for dark matter experiments and coherent elastic neutrino-nucleus scattering experiments.
We investigate scintillation linearity of a commercial high pressure 4He gas detector using monoenergetic 2.8 MeV neutrons from a deuterium-deuterium fusion neutron generator. The scintillation ...response of the detector was measured for a range of recoil energies between 83 keV and 626 keV by tagging neutrons scattering into fixed angles with a far-side organic scintillator detector. Detailed Monte Carlo simulations were compared to experimental data to determine the linearity of the detector response by comparing the scaling of the energy deposits in the simulations to the detector output. In this analysis, a linear scintillation response corresponds to a consistent value for the scaling factor between simulated energy deposits and experimental data for several different scattering angles. We demonstrate that the detector can be used to detect fast neutron interactions down to 83 keV recoil energies and can be used to characterize low-energy neutron sources, one of its potential applications.
The scattering of dark matter (DM) particles with sub-GeV masses off nuclei is difficult to detect using liquid xenon-based DM search instruments because the energy transfer during nuclear recoils is ...smaller than the typical detector threshold. However, the tree-level DM-nucleus scattering diagram can be accompanied by simultaneous emission of a bremsstrahlung photon or a so-called "Migdal" electron. These provide an electron recoil component to the experimental signature at higher energies than the corresponding nuclear recoil. The presence of this signature allows liquid xenon detectors to use both the scintillation and the ionization signals in the analysis where the nuclear recoil signal would not be otherwise visible. We report constraints on spin-independent DM-nucleon scattering for DM particles with masses of 0.4-5 GeV/c^{2} using 1.4×10^{4} kg day of search exposure from the 2013 data from the Large Underground Xenon (LUX) experiment for four different classes of mediators. This analysis extends the reach of liquid xenon-based DM search instruments to lower DM masses than has been achieved previously.
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