5,217 research outputs found
Stretching and twisting of the DNA duplexes in coarse grained dynamical models
Three coarse-grained models of the double-stranded DNA are proposed and
compared in the context of mechanical manipulation such as twisting and various
schemes of stretching. The models differ in the number of effective beads
(between two and five) representing each nucleotide. They all show similar
behavior and, in particular, lead to a torque-force phase diagrams
qualitatively consistent with experiments and all-atom simulations
Effects of non-uniform interstellar magnetic field on synchrotron X-ray and inverse-Compton gamma-ray morphology of SNRs
Observations of SNRs in X-ray and gamma-ray bands promise to contribute with
important information in our understanding on the nature of galactic cosmic
rays. The analysis of SNRs images collected in different energy bands requires
the support of theoretical modeling of synchrotron and inverse Compton (IC)
emission. We develop a numerical code (REMLIGHT) to synthesize, from MHD
simulations, the synchrotron radio, X-ray and IC gamma-ray emission from SNRs
expanding in non-uniform interstellar medium (ISM) and/or non-uniform
interstellar magnetic field (ISMF). As a first application, the code is used to
investigate the effects of non-uniform ISMF on the SNR morphology in the
non-thermal X-ray and gamma-ray bands. We perform 3D MHD simulations of a
spherical SNR shock expanding through a magnetized ISM with a gradient of
ambient magnetic field strength. The model includes an approximate treatment of
upstream magnetic field amplification and the effect of shock modification due
to back reaction of accelerated cosmic rays. From the simulations, we
synthesize the synchrotron radio, X-ray and IC gamma-ray emission with
REMLIGHT, making different assumptions about the details of acceleration and
injection of relativistic electrons. A gradient of the ambient magnetic field
strength induces asymmetric morphologies in radio, X-ray and gamma-ray bands
independently from the model of electron injection if the gradient has a
component perpendicular to the line-of-sight. The degree of asymmetry of the
remnant morphology depends on the details of the electron injection and
acceleration and is different in the radio, X-ray, and gamma-ray bands. The
non-thermal X-ray morphology is the most sensitive to the gradient, showing the
highest degree of asymmetry. The IC gamma-ray emission is weakly sensitive to
the non-uniform ISMF, the degree of asymmetry of the SNR morphology being the
lowest in this band.Comment: 16 pages, 13 Figures; accepted for publication on A&A. Version with
full resolution images can be found at
http://www.astropa.unipa.it/~orlando/PREPRINTS/sorlando_15505.pd
Neutrino-nucleus reactions on ^{12}C and ^{16}O
Exclusive and inclusive cross-sections and
-capture rates are calculated for ^{12}C and ^{16}O using the consistent
random phase approximation (RPA) and pairing model. After a pairing correction
is introduced to the RPA results the flux-averaged theoretical cross-sections and -capture rates in C are
in good agreement with experiment. In particular when one takes into account
the experimental error bars, the recently measured range of values for the
cross-section is in agreement with the present theoretical
results. Predictions of and cross-sections in
^{16}O are also presented.Comment: 13 pages, Revte
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Spring 1958
Dedication of Turf Clippings to Robert Williams (1) Picture - Stockbridge Turf majors (2) Title page and contents (3) Greetings from Dean Sieling - College of Agriculture (4) Outstanding Men in Turfgrass Honored (4) Word From the Editor of Turf Clippings (5) Message From the 1958 Winter School President (6) Summary of 1958 University of Massachusetts Turfgrass Conference - Al Radko (6-9) Importance of Superintendences Associations - Anthony B. Caranci (10) Picture - Turf Grass Interest Stretch from Coast to Coast (11) Picture - 1958 Winter School for Turf Managers (12) Golf Courses in California - James C. Scott (13) The Constant Battle - Joseph Troll (13) Recognition of the Golf Course Superintendent - Frederick Bove (14-15) 1958 Winter School Comments (16) Maintenance of Insurance Grounds - George J. Moore Jr. (17-18) Don\u27t Get Caught Short - Bruce Silven (19-20) We Have had It - They Now Have it - These Two Shall Have it - Orville O. Clapper (21) The Golf Course Superintendent - Prof. L. S. Dickinson (22-23) Picture - Winter School Alumni Meet at Conference (24) Cartoons (25) Cost of Lawn and Golf Course Construction - Geoffrey Cornish (26-27) Turf Club News (28-29) 1957 Horticulture Show Winner (30) Frosting on the Cake (30) Number One Graduate (31) 1957 Stockbridge Turf majors - Work (32) Turf management Club Associate Memberships (32
Evidence for Neutrino Oscillations from Muon Decay at Rest
A search for nu_bar_mu to nu_bar_e oscillations has been conducted at the Los
Alamos Meson Physics Facility using nu_bar_mu from mu+ decay at rest. The
nu_bar_e are detected via the reaction (nu_bar_e,p) -> (e+,n), correlated with
the 2.2 MeV gamma from (n,p) -> (d,gamma). The use of tight cuts to identify e+
events with correlated gamma rays yields 22 events with e+ energy between 36
and 60 MeV and only 4.6 (+/- 0.6) background events. The probability that this
excess is due entirely to a statistical fluctuation is 4.1E-08. A chi^2 fit to
the entire e+ sample results in a total excess of 51.8 (+18.7) (-16.9) (+/-
8.0) events with e+ energy between 20 and 60 MeV. If attributed to nu_bar_mu ->
nu_bar_e oscillations, this corresponds to an oscillation probability (averaged
over the experimental energy and spatial acceptance) of 0.0031 (+0.0011)
(-0.0010) (+/- 0.0005).Comment: 57 pages, 34 figures, revtex, additional information available at
http://nu1.lampf.lanl.gov/~lsnd
Measurement of J/Ï production in association with a W ± boson with pp data at 8 TeV
A measurement of the production of a prompt J/Ï meson in association with a W± boson with W± â ΌΜ and J/Ï â ÎŒ+ÎŒâ is presented for J/Ï transverse momenta in the range 8.5â150 GeV and rapidity |yJ/Ï| < 2.1 using ATLAS data recorded in 2012 at the LHC. The data were taken at a proton-proton centre-of-mass energy of s = 8 TeV and correspond to an integrated luminosity of 20.3 fbâ1. The ratio of the prompt J/Ï plus W± cross-section to the inclusive W± cross-section is presented as a differential measurement as a function of J/Ï transverse momenta and compared with theoretical predictions using different double-parton-scattering cross-sections. [Figure not available: see fulltext.]
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Search for Magnetic Monopoles and Stable High-Electric-Charge Objects in 13 Tev Proton-Proton Collisions with the ATLAS Detector.
A search for magnetic monopoles and high-electric-charge objects is presented using 34.4ââfb^{-1} of 13 TeV pp collision data collected by the ATLAS detector at the LHC during 2015 and 2016. The considered signature is based upon high ionization in the transition radiation tracker of the inner detector associated with a pencil-shape energy deposit in the electromagnetic calorimeter. The data were collected by a dedicated trigger based on the tracker high-threshold hit capability. The results are interpreted in models of Drell-Yan pair production of stable particles with two spin hypotheses (0 and 1/2) and masses ranging from 200 to 4000 GeV. The search improves by approximately a factor of 5 the constraints on the direct production of magnetic monopoles carrying one or two Dirac magnetic charges and stable objects with electric charge in the range 20â€|z|â€60 and extends the charge range to 60<|z|â€100
Cosmological parameters from SDSS and WMAP
We measure cosmological parameters using the three-dimensional power spectrum
P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in
combination with WMAP and other data. Our results are consistent with a
``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt,
tensor modes or massive neutrinos. Adding SDSS information more than halves the
WMAP-only error bars on some parameters, tightening 1 sigma constraints on the
Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter
density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on
neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when
dropping prior assumptions about curvature, neutrinos, tensor modes and the
equation of state. Our results are in substantial agreement with the joint
analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive
consistency check with independent redshift survey data and analysis
techniques. In this paper, we place particular emphasis on clarifying the
physical origin of the constraints, i.e., what we do and do not know when using
different data sets and prior assumptions. For instance, dropping the
assumption that space is perfectly flat, the WMAP-only constraint on the
measured age of the Universe tightens from t0~16.3+2.3-1.8 Gyr to
t0~14.1+1.0-0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running
tilt, neutrino mass and equation of state in the list of free parameters, many
constraints are still quite weak, but future cosmological measurements from
SDSS and other sources should allow these to be substantially tightened.Comment: Minor revisions to match accepted PRD version. SDSS data and ppt
figures available at http://www.hep.upenn.edu/~max/sdsspars.htm
Modeling Molecular Interactions in Water: From Pairwise to Many-Body Potential Energy Functions.
Almost 50 years have passed from the first computer simulations of water, and a large number of molecular models have been proposed since then to elucidate the unique behavior of water across different phases. In this article, we review the recent progress in the development of analytical potential energy functions that aim at correctly representing many-body effects. Starting from the many-body expansion of the interaction energy, specific focus is on different classes of potential energy functions built upon a hierarchy of approximations and on their ability to accurately reproduce reference data obtained from state-of-the-art electronic structure calculations and experimental measurements. We show that most recent potential energy functions, which include explicit short-range representations of two-body and three-body effects along with a physically correct description of many-body effects at all distances, predict the properties of water from the gas to the condensed phase with unprecedented accuracy, thus opening the door to the long-sought "universal model" capable of describing the behavior of water under different conditions and in different environments
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