551 research outputs found

    The Individual and Collective Effects of Exact Exchange and Dispersion Interactions on the Ab Initio Structure of Liquid Water

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    In this work, we report the results of a series of density functional theory (DFT) based ab initio molecular dynamics (AIMD) simulations of ambient liquid water using a hierarchy of exchange-correlation (XC) functionals to investigate the individual and collective effects of exact exchange (Exx), via the PBE0 hybrid functional, non-local vdW/dispersion interactions, via a fully self-consistent density-dependent dispersion correction, and approximate nuclear quantum effects (aNQE), via a 30 K increase in the simulation temperature, on the microscopic structure of liquid water. Based on these AIMD simulations, we found that the collective inclusion of Exx, vdW, and aNQE as resulting from a large-scale AIMD simulation of (H2_2O)128_{128} at the PBE0+vdW level of theory, significantly softens the structure of ambient liquid water and yields an oxygen-oxygen structure factor, SOO(Q)S_{\rm OO}(Q), and corresponding oxygen-oxygen radial distribution function, gOO(r)g_{\rm OO}(r), that are now in quantitative agreement with the best available experimental data. This level of agreement between simulation and experiment as demonstrated herein originates from an increase in the relative population of water molecules in the interstitial region between the first and second coordination shells, a collective reorganization in the liquid phase which is facilitated by a weakening of the hydrogen bond strength by the use of the PBE0 hybrid XC functional, coupled with a relative stabilization of the resultant disordered liquid water configurations by the inclusion of non-local vdW/dispersion interactions

    Wigner's little group, gauge transformations and dimensional descent

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    We propose a technique called dimensional descent to show that Wigner's little group for massless particles, which acts as a generator of gauge transformation for usual Maxwell theory, has an identical role even for topologically massive gauge theories. The examples of BFB\wedge F theory and Maxwell-Chern-Simons theory are analyzed in details.Comment: LaTex, revised version shortened to 9 pages; To appear in Jour.Phys.

    Neutrino masses, cosmological bound and four zero Yukawa textures

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    Four zero neutrino Yukawa textures in a specified weak basis, combined with μτ\mu\tau symmetry and type-I seesaw, yield a highly constrained and predictive scheme. Two alternately viable 3×33\times3 light neutrino Majorana mass matrices mνA/mνBm_{\nu A}/m_{\nu B} result with inverted/normal mass ordering. Neutrino masses, Majorana in character and predicted within definite ranges with laboratory and cosmological inputs, will have their sum probed cosmologically. The rate for 0νββ0\nu\beta\beta decay, though generally below the reach of planned experiments, could approach it in some parameter region. Departure from μτ\mu\tau symmetry due to RG evolution from a high scale and consequent CP violation, with a Jarlskog invariant whose magnitude could almost reach 6×1036\times 10^{-3}, are explored.Comment: Published versio

    Gauge invariances of higher derivative Maxwell-Chern-Simons field theory -- a new Hamiltonian approach

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    A new method of abstracting the independent gauge invariances of higher derivative systems, recently introduced in [1], has been applied to higher derivative field theories. This has been discussed taking the extended Maxwell-Chern-Simons model as an example. A new Hamiltonian analysis of the model is provided. This Hamiltonian analysis has been used to construct the independent gauge generator. An exact mapping between the Hamiltonian gauge transformations and the U(1) symmetries of the action has been established.Comment: 16 pages, no figure. Title and abstract modified, new references added. This version to appear in Phys. Rev.

    ASCA Observation of the New Transient X-ray Pulsar XTE J0111.2-7317 in the Small Magellanic Cloud

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    The new transient X-ray pulsar XTE J0111.2-7317 was observed with Advanced Satellite for Cosmology and Astrophysics (ASCA) on 1998 November 18, a few days after its discovery with the Proportional Counter Array onboard the Rossi X-ray Timing Explorer. The source was detected at a flux level of 3.6x10^-10 erg cm^-2 s^-1 in the 0.7--10.0 keV band, which corresponds to the X-ray luminosity of 1.8x10^38 erg s^-1, if a distance of 65 kpc for this pulsar in the Small Magellanic Cloud is assumed. Nearly sinusoidal pulsations with a period of 30.9497 +/- 0.0004 s were unambiguously detected during the ASCA observation. The pulsed fraction is low and slightly energy dependent with average value of \~27%. The energy spectrum shows a large soft excess below ~2 keV when fitted to a simple power-law type model. The soft excess is eliminated if the spectrum is fitted to an ``inversely broken power-law'' model, in which photon indices below and above a break energy of 1.5 keV are 2.3 and 0.8, respectively. The soft excess can also be described by a blackbody or a thermal bremsstrahlung when the spectrum above ~2 keV is modeled by a power-law. In these models, however, the thermal soft component requires a very large emission zone, and hence it is difficult to explain the observed pulsations at energies below 2 keV. A bright state of the source enables us to identify a weak iron line feature at 6.4 keV with an equivalent width of 50 +/- 14 eV. Pulse phase resolved spectroscopy revealed a slight hardening of the spectrum and marginal indication of an increase in the iron line strength during the pulse maximum.Comment: 8 pages, 5 Figures, to be published in ApJ. Also available at http://www-cr.scphys.kyoto-u.ac.jp/member/jun/job

    Non-commutative Quantum Mechanics in Three Dimensions and Rotational Symmetry

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    We generalize the formulation of non-commutative quantum mechanics to three dimensional non-commutative space. Particular attention is paid to the identification of the quantum Hilbert space in which the physical states of the system are to be represented, the construction of the representation of the rotation group on this space, the deformation of the Leibnitz rule accompanying this representation and the implied necessity of deforming the co-product to restore the rotation symmetry automorphism. This also implies the breaking of rotational invariance on the level of the Schroedinger action and equation as well as the Hamiltonian, even for rotational invariant potentials. For rotational invariant potentials the symmetry breaking results purely from the deformation in the sense that the commutator of the Hamiltonian and angular momentum is proportional to the deformation.Comment: 21 page

    'Mu-Tau' symmetry, tribimaximal mixing and four zero neutrino Yukawa textures

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    Within the type-I seesaw framework with three heavy right chiral neutrinos and in the basis where the latter and the charged leptons are mass diagonal, a near `mu-tau' symmetry in the neutrino sector is strongly suggested by the neutrino oscillation data. There is further evidence for a close to the tribimaximal mixing pattern which subsumes `mu-tau' symmetry. On the other hand, the assumption of a (maximally allowed) four zero texture in the Yukawa coupling matrix Y_nu in the same basis leads to a highly constrained and predictive theoretical scheme. We show that the requirement of an exact `mu-tau' symmetry, coupled with observational constraints, reduces the `seventy two' allowed textures in such a `Y_nu' to 'only four' corresponding to just two different forms of the light neutrino mass matrix `m_nu'. The effect of each of these on measurable quantities can be described, apart from an overall factor of the neutrino mass scale, in terms of two real parameters and a phase angle all of which are within very constrained ranges. The additional input of a tribimaximal mixing reduces these three parameters to `only one' with a very nearly fixed value. Implications for both flavored and unflavored leptogenesis as well as radiative lepton flavor violating decays are discussed. We also investigate the stability of these conclusions under small deviations due to renormalization group running from a high scale where the four zero texture as well as `mu-tau' symmetry or the tribimaximal mixing pattern are imposed.Comment: Typographical changes,accepted for publication in JHE

    Quality of Life among Younger Women with Breast Cancer.

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    INTRODUCTION: The diagnosis of breast cancer despite improved overall survival continues to Generate fear and turmoil in the lives of women and their families. Prevalence studies of Psychological distress indicate that one of every three newly diagnosed patients Experiences significant difficulty in adjustment. [1] Further evidence suggests that the Diagnosis of breast cancer generates more anxiety than any other cancer diagnosis. [2] At the time of diagnosis patients experience uncertainty, confusion and distress. Psychological distress can be exacerbated by inadequate information, complex treatment Decisions, and scheduling difficulties with various specialities. As treatment begins, Concerns related to physical functioning, body image, mood, sexuality, family and Vocational pursuits quickly emerge. Surgical options which include lumpectomy, Mastectomy and reconstruction present unique issues as the patient contemplates the Advantages and disadvantages of each procedure. Following surgery adjuvant therapy Generates additional physiological assaults that further affect body image, sexuality and Family life. They require rehabilitative assistance beyond the physical domain. Major Rehabilitation problem areas include physical, psychological, social, sexual, nutritional, Financial and vocational ones. For younger women the physical and psychosocial morbidity associated with Treatments may affect their ability to successfully function in social roles that typify this Age group. Hence we would like to study the quality of life issues in this subset. AIMS : 1. To describe the quality of life among breast cancer women with age less than or Equal to 35 years at the time of diagnosis. 2. To determine the contribution of socio demographic, medical and psychosocial Factors on quality of life. 3. To study the impact of breast conservation treatment and mastectomy on the Quality of life

    Houston SHOCK: A Practical Scoring System Incorporating Cardiogenic Shock Dynamic Changes

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    Cardiogenic shock has an unacceptably high mortality rate and additional tools are needed to improve outcomes. The Society of Cardiovascular Angiography and Interventions (SCAI) shock severity classification has provided a unified definition of shock severity that has proven to be reproducible and predictive of survival. However, cardiogenic shock assessment goes beyond standardizing its severity, and a uniform and practical approach to comprehensive assessment that may guide therapy in a dynamic state is currently lacking. Since cardiogenic shock is a rapidly evolving pathophysiological catastrophe, we propose a new assessment tool – the Houston SHOCK Score – which incorporates dynamic changes. The acronym SHOCK can be used to emphasize five key aspects of patients in cardiogenic shock: Severity, Hemodynamics, Onset, Causes, and Kinetics. We believe this tool provides physicians with vital information that will facilitate appropriate care by incorporating dynamic changes in the patient’s profile
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