1,858 research outputs found

    Comment on "Oxygen as a Site Specific Probe of the Structure of Water and Oxide Materials", PRL 107, 144501 (2011)

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    A recent paper by Zeidler et al. (PRL 107, 144501 (2011)) describes a neutron scattering experiment on water in which oxygen isotope substitution is successfully achieved for the first time. Differences between scattering patterns with different oxygen isotopes give a combination of the O-O and O-H (or O-D) structure factors, and the method elegantly minimizes some of the problematic inelasticity effects associated with neutron scattering from hydrogen. Particular conclusions of the new work are that the OH bond length in the light water molecule is about 0.005A longer than the same bond in heavy water, and that the hydrogen bond peaks in both liquids are at about the same position. Notwithstanding the substantial progress demonstrated by the new work, the comparison with our own results (PRL, 101, 065502 (2008)) by Zeidler et al. is in our opinion misleading.Comment: 2 pages, 1 figure

    Vitamin K catabolite inhibition of ovariectomy-induced bone loss: Structure–activity relationship considerations

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    The potential benefit of vitamin K as a therapeutic in osteoporosis is controversial and the vitamin K regimen being used clinically (45 mg/day) employs doses that are many times higher than required to ensure maximal gamma‐carboxylation of the vitamin K‐dependent bone proteins. We therefore tested the hypothesis that vitamin K catabolites, 5‐carbon (CAN5C) and 7‐carbon carboxylic acid (CAN7C) aliphatic side‐chain derivatives of the naphthoquinone moiety exert an osteotrophic role consistent with the treatment of osteoporosis

    On the relationship between instability and Lyapunov times for the 3-body problem

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    In this study we consider the relationship between the survival time and the Lyapunov time for 3-body systems. It is shown that the Sitnikov problem exhibits a two-part power law relationship as demonstrated previously for the general 3-body problem. Using an approximate Poincare map on an appropriate surface of section, we delineate escape regions in a domain of initial conditions and use these regions to analytically obtain a new functional relationship between the Lyapunov time and the survival time for the 3-body problem. The marginal probability distributions of the Lyapunov and survival times are discussed and we show that the probability density function of Lyapunov times for the Sitnikov problem is similar to that for the general 3-body problem.Comment: 9 pages, 19 figures, accepted for publication in MNRA

    Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K

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    The structure of liquid water is defined by its molecular association through hydrogen bonding. Two different structures have been proposed for liquid water at low temperatures: low-density liquid (LDL) and high-density liquid (HDL) water. Here, we demonstrate a platform that can be exploited to experimentally probe the structure of liquid water in equilibrium at temperatures down to 238 K. We make use of a cryoprotectant molecule, glycerol, that, when mixed with water, lowers the freezing temperature of the solution nonmonotonically with glycerol concentration. We use a combination of neutron diffraction measurements and computational modeling to examine the structure of water in glycerol–water liquid mixtures at low temperatures from 285 to 238 K. We confirm that the mixtures are nanosegregated into regions of glycerol-rich and water-rich clusters. We examine the water structure and reveal that, at the temperatures studied here, water forms a low-density water structure that is more tetrahedral than the structure at room temperature. We postulate that nanosegregation allows water to form a low-density structure that is protected by an extensive and encapsulating glycerol interface

    Two-hadron interference fragmentation functions. Part I: general framework

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    We investigate the properties of interference fragmentation functions measurable from the distribution of two hadrons produced in the same jet in the current fragmentation region of a hard process. We discuss the azimuthal angular dependences in the leading order cross section of two-hadron inclusive lepton-nucleon scattering as an example how these interference fragmentation functions can be addressed separately.Comment: RevTeX, 7 figures, first part of a work split in two, second part forthcoming in few day

    Partons and Jets at the LHC

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    I review some issues related to short distance QCD and its relation to the experimental program of the Large Hadron Collider (LHC) now under construction in Geneva.Comment: Talk at the conference QCD2002 at IIT Kanpur, India, November 2002. Ten pages with 12 figure

    Intrinsic transverse momentum and the polarized Drell-Yan process

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    In this paper we study the cross section at leading order in 1/Q1/Q for polarized Drell-Yan scattering at measured lepton-pair transverse momentum QTQ_T. We find that for a hadron with spin 1/21/2 the quark content at leading order is described by six distribution functions for each flavor, which depend on both the lightcone momentum fraction xx, and the quark transverse momentum \bbox{k}_T^2. These functions are illustrated for a free-quark ensemble. The cross sections for both longitudinal and transverse polarizations are expressed in terms of convolution integrals over the distribution functions.Comment: 25 pages, REVTEX 3.0 (3 figures included in separate LATEX file using feynman.tex), NIKHEF-94-P1 (Revised version
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