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)
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
Recommended from our members
A republic of consumers: Jo Littler in discussion with Clive Barnett and Kate Soper
Clive Barnett is a human geographer at the Open University and is part of a team working on a project entitled âGoverning the Subjects and Spaces of Ethical Consumptionâ. Kate Soper, a professor of philosophy and a cultural theorist based at London Metropolitan University, is working with Lyn Thomas on their âAlternative Hedonism and the Theory and Politics of Consumer Cultureâ project.1 Jo Littler interviewed them both about the cultural and political implications of the expansion of green, ethical and anti-consumerism
Vitamin K catabolite inhibition of ovariectomy-induced bone loss: Structureâactivity relationship considerations
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 gammaâcarboxylation of the vitamin Kâdependent bone proteins. We therefore tested the hypothesis that vitamin K catabolites, 5âcarbon (CAN5C) and 7âcarbon carboxylic acid (CAN7C) aliphatic sideâchain 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
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
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 glycerolâwater 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
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
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
In this paper we study the cross section at leading order in for
polarized Drell-Yan scattering at measured lepton-pair transverse momentum
. We find that for a hadron with spin the quark content at leading
order is described by six distribution functions for each flavor, which depend
on both the lightcone momentum fraction , 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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