1,847 research outputs found

    Validity of the Generalized Second Law of Thermodynamics of the Universe Bounded by the Event Horizon in Brane Scenario

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    In this paper, we examine the validity of the generalized second law of thermodynamics (GSLT) of the universe bounded by the event horizon in brane-world gravity. Here we consider homogeneous and isotropic model of the universe filled with perfect fluid in one case and in another case holographic dark energy model of the universe has been considered. The conclusions are presented point wise.Comment: 8 pages, the paper has been accepted in EPJC for publication. Conclusion has been modified an some references have been adde

    Temporal evolution of mesoscopic structure of some non-Euclidean systems using a Monte Carlo model

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    A Monte Carlo based computer model is presented to comprehend the contrasting observations of Mazumder et al. [Phys. Rev. Lett. 93, 255704 (2004) and Phys. Rev. B 72, 224208 (2005)], based on neutron-scattering measurements, on temporal evolution of effective fractal dimension and characteristic length for hydration of cement with light and heavy water. In this context, a theoretical model is also proposed to elucidate the same.Comment: 31 Pages, 13 Figure

    Bimetallic Cooperativity in Proton Reduction with an Amido‐Bridged Cobalt Catalyst

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    The bimetallic catalyst [CoII2(L1)(bpy)2]ClO4 (1), in which L1 is an [NN′2O2] fused ligand, efficiently reduced H+ to H2 in CH3CN in the presence of 100 equiv of HOAc with a turnover number of 18 and a Faradaic efficiency of 94 % after 3 h of bulk electrolysis at −1.6 V (vs. Ag/AgCl). This observation allowed the proposal that this bimetallic cooperativity is associated with distance, angle, and orbital alignment of the two Co centers, as promoted by the unique Co−Namido−Co environment offered by L1. Experimental results revealed that the parent [CoIICoII] complex undergoes two successive metal‐based 1 e− reductions to generate the catalytically active species [CoICoI], and DFT calculations suggested that addition of a proton to one CoI triggers a cooperative 1 e− transfer by each of these CoI centers. This 2 e− transfer is an alternative route to generate a more reactive [CoII(CoII−H−)] hydride, thus avoiding the CoIII−H− required in monometallic species. This [CoII(CoII−H−)] species then accepts another H+ to release H2

    Spatially and temporally resolved temperature measurements of plasma generated in percussion drilling with a diode-pumped Nd:YAG laser

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    Results of spectroscopic temperature measurements of the laser-induced plasma generated during percussion drilling with a high power diode-pumped, pulsed Nd:YAG laser are presented. SAE 52100 steel was drilled with varying average powers. Helium and oxygen were each used as the shield gas. Emission spectra were collected with a monochrometer and an intensified charge coupled detector connected to the optical multichannel analyzer. The plasma electron temperatures were calculated from the relative intensities of the spectral lines. The spatial and temporal temperature distributions are presented. Both drilling times and spatial distributions indicate energy absorption by the plasma. © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71333/2/JAPIAU-84-8-4122-1.pd

    Rho-omega mixing in asymmetric nuclear matter via QCD sum rule approach

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    We evaluate the operator product expansion (OPE) for a mixed correlator of the isovector and isoscalar vector currents in the background of the nucleon density with intrinsic isospin asymmetry [i.e. excess of neutrons over protons] and match it with its imaginary part, given by resonances and continuum, via the dispersion relation. The leading density-dependent contribution to ρω\rho-\omega mixing is due the scattering term, which turns out to be larger than any density dependent piece in the OPE. We estimate that the asymmetric density of nnnp2.5×102 fm3n_n-n_p \sim 2.5 \times 10^{-2} ~{\rm fm^3} induces the amplitude of ρω\rho-\omega mixing, equal in magnitude to the mixing amplitude in vacuum, with the constructive interference for positive and destructive for negative values of nnnpn_n-n_p. We revisit sum rules for vector meson masses at finite nucleon density to point out the numerical importance of the screening term in the isoscalar channel, which turns out to be one order of magnitude larger than any density-dependent condensates over the Borel window. This changes the conclusions about the density dependence of mωm_\omega, indicating 40\sim 40 MeV increase at nuclear saturation density.Comment: 8 pages, Revte

    Scalar-Tensor Theory of Gravity and Generalized Second Law of Thermodynamics on the Event Horizon

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    In blackhole physics, the second law of thermodynamics is generally valid whether the blackhole is a static or a non-static one. Considering the universe as a thermodynamical system the second law of blackhole dynamics extends to the non-negativity of the sum of the entropy of the matter and the horizon, known as generalized second law of thermodynamics(GSLT). Here, we have assumed the universe to be bounded by the event-horizon or filled with perfect fluid and holographic dark energy in two cases. Thus considering entropy to be an arbitrary function of the area of the event-horizon, we have tried to find the conditions and the restrictions over the scalar field and equation of state for the validity of the GSLT and both in quintessence-era and in phantom-era in scalar tensor theory.Comment: 8 page

    Prevalence and risk factors of gestational diabetes mellitus in Bangladesh: Findings from demographic health survey 2017–2018

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    Gestational diabetes mellitus (GDM) has serious consequences for both maternal and neonatal health. The growing number of noncommunicable diseases and related risk factors as well as the introduction of new World Health Organization (WHO) diagnostic criteria for GDM are likely to impact the GDM prevalence in Bangladesh. Our study aimed to assess the national prevalence and identify the risk factors using the most recent WHO criteria. We used the secondary data of 272 pregnant women (weighted for sampling strategy) from the Bangladesh Demographic and Health Survey 2017–2018. Multivariate logistic regression was performed to determine the risk factors of GDM. The overall prevalence of GDM in Bangladesh was 35% (95/272). Increased odds of GDM were observed among women living in the urban areas (adjusted odds ratio (aOR) 2.74, 95% confidence interval (CI) 1.43–5.27) compared to rural areas and those aged ≥25 years (aOR 2.03, 95% CI 1.13–3.65). GDM rates were less prevalent in the later weeks of pregnancy compared to early weeks. Our study demonstrates that the national prevalence of GDM in Bangladesh is very high, which warrants immediate attention of policy makers, health practitioners, public health researchers, and the community. Context-specific and properly tailored interventions are needed for the prevention and early diagnosis of GDM

    ρ\rho-ω\omega mixing and spin dependent CSV potential

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    We construct the charge symmetry violating (CSV) nucleon-nucleon potential induced by the ρ0\rho^0-\o mixing due to the neutron-proton mass difference driven by the NNNN loop. Analytical expression for for the two-body CSV potential is presented containing both the central and non- central NNNN interaction. We show that the ρ\rhoNNNN tensor interaction can significantly enhance the charge symmetry violating NNNN interaction even if momentum dependent off-shell ρ0\rho^0-ω\omega mixing amplitude is considered. It is also shown that the inclusion of form factors removes the divergence arising out of the contact interaction. Consequently, we see that the precise size of the computed scattering length difference depends on how the short range aspects of the CSV potential are treated.Comment: Accepted for publication in Phys. Rev.

    Generalized Second Law of Thermodynamics on the Event Horizon for Interacting Dark Energy

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    Here we are trying to find the conditions for the validity of the generalized second law of thermodynamics (GSLT) assuming the first law of thermodynamics on the event horizon in both cases when the FRW universe is filled with interacting two fluid system- one in the form of cold dark matter and the other is either holographic dark energy or new age graphic dark energy. Using the recent observational data we have found that GSLT holds both in quintessence era as well as in phantom era for new age graphic model while for holographic dark energy GSLT is valid only in phantom era.Comment: 8 pages, 2 figure
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