985 research outputs found
Issued as a Part of Progress Report No. 13 of The Investigation of Prestressed Reinforced Concrete for Highway Bridges; Project IHR-10, Illinois Cooperative Highway Research Program
The Division of Highways. State of Illinois.The Bureau of Public Roads. U.S. Department of Commerc
Effects of Collective Potentials on Pion Spectra in Relativistic Heavy Ion Collisions
The effect of collective potentials on pion spectra in ultrarelativistic
heavy ion collisions is investigated. We find the effect of these potential to
be very small, too small to explain the observed enhancement at low transverse
momenta. (7 figures, bill be send on request)Comment: 11 page
Referral for specialist follow-up and its association with post-discharge mortality among patients with systolic heart failure (from the National Heart Failure Audit for England and Wales)
For patients admitted with worsening heart failure, early follow-up after discharge is recommended. Whether outcomes can be improved when follow-up is done by cardiologists is uncertain. We aimed to determine the association between cardiology follow-up and risk of death for patients with heart failure discharged from hospital. Using data from the National Heart Failure Audit (England & Wales), we investigated the effect of referral to cardiology follow-up on 30-day and one-year mortality in 68 772 patients with heart failure and a reduced left ventricular ejection fraction (HFREF) discharged from 185 hospitals between 2007 to 2013. The primary analyses used instrumental variable analysis complemented by hierarchical logistic and propensity matched models. At the hospital level, rates of referral to cardiologists varied from 6% to 96%. The median odds ratio (OR) for referral to cardiologist was 2.3 (95% confidence interval [CI] 2.1, 2.5), suggesting that, on average, the odds of a patient being referred for cardiologist follow-up after discharge differed approximately 2.3 times from one randomly selected hospital to another one. Based on the proportion of patients (per region) referred for cardiology follow-up, referral for cardiology follow-up was associated with lower 30-day (OR 0.70; CI 0.55, 0.89) and one-year mortality (OR 0.81; CI 0.68, 0.95) compared with no plans for cardiology follow-up (i.e., standard follow-up done by family doctors). Results from hierarchical logistic models and propensity matched models were consistent (30-day mortality OR 0.66; CI 0.61, 0.72 and 0.66; CI 0.58, 0.76 for hierarchical and propensity matched models, respectively). For patients with HFREF admitted to hospital with worsening symptoms, referral to cardiology services for follow-up after discharge is strongly associated with reduced mortality, both early and late
Coulomb scattering lifetime of a two-dimensional electron gas
Motivated by a recent tunneling experiment in a double quantum-well system,
which reports an anomalously enhanced electronic scattering rate in a clean
two-dimensional electron gas, we calculate the inelastic quasiparticle lifetime
due to electron-electron interaction in a single loop dynamically screened
Coulomb interaction within the random-phase-approximation. We obtain excellent
quantitative agreement with the inelastic scattering rates in the tunneling
experiment without any adjustable parameter, finding that the reported large
( a factor of six) disagreement between theory and experiment arises from
quantitative errors in the existing theoretical work and from the off-shell
energy dependence of the electron self-energy.Comment: 11 pages, RevTex, figures included. Also available at
http://www-cmg.physics.umd.edu/~lzheng
Operator-Algebraic Approach to the Yrast Spectrum of Weakly Interacting Trapped Bosons
We present an operator-algebraic approach to deriving the low-lying
quasi-degenerate spectrum of weakly interacting trapped N bosons with total
angular momentum \hbar L for the case of small L/N, demonstrating that the
lowest-lying excitation spectrum is given by 27 g n_3(n_3-1)/34, where g is the
strength of the repulsive contact interaction and n_3 the number of excited
octupole quanta. Our method provides constraints for these quasi-degenerate
many-body states and gives higher excitation energies that depend linearly on
N.Comment: 7 pages, one figur
Universal quantum logic gates in a scalable Ising spin quantum computer
We consider the model of quantum computer, which is represented as a Ising
spin lattice, where qubits (spin-half systems) are separated by the isolators
(two spin-half systems). In the idle mode or at the single bit operations the
total spin of isolators is 0. There are no need of complicated protocols for
correcting the phase and probability errors due to permanent interaction
between the qubits. We present protocols for implementation of universal
quantum gates with the rectangular radio-frequency pulses.Comment: 9 pages, 1 figure, Conference on Quantum Information and Quantum
Control II, August 7-11, 2006, Canand
Metastable neon collisions: anisotropy and scattering length
In this paper we investigate the effective scattering length of
spin-polarized Ne*. Due to its anisotropic electrostatic interaction, its
scattering length is determined by five interaction potentials instead of one,
even in the spin-polarized case, a unique property among the Bose condensed
species and candidates. Because the interaction potentials of Ne* are not known
accurately enough to predict the value of the scattering length, we investigate
the behavior of as a function of the five phase integrals corresponding to
the five interaction potentials. We find that the scattering length has five
resonances instead of only one and cannot be described by a simple gas-kinetic
approach or the DIS approximation. However, the probability for finding a
positive or large value of the scattering length is not enhanced compared to
the single potential case. The complex behavior of is studied by comparing
a quantum mechanical five-channel numerical calculation to simpler two-channel
models. We find that the induced dipole-dipole interaction is responsible for
coupling between the different |\Omega> states, resulting in an inhomogeneous
shift of the resonance positions and widths in the quantum mechanical
calculation as compared to the DIS approach. The dependence of the resonance
positions and widths on the input potentials turns out to be rather
straightforward. The existence of two bosonic isotopes of Ne* enables us to
choose the isotope with the most favorable scattering length for efficient
evaporative cooling towards the Bose-Einstein Condensation transition, greatly
enhancing the feasibility to reach this transition.Comment: 13pages, 8 eps figures, analytical model in section V has been
remove
SO(10) unified models and soft leptogenesis
Motivated by the fact that, in some realistic models combining SO(10) GUTs
and flavour symmetries, it is not possible to achieve the required baryon
asymmetry through the CP asymmetry generated in the decay of right-handed
neutrinos, we take a fresh look on how deep this connection is in SO(10). The
common characteristics of these models are that they use the see-saw with
right-handed neutrinos, predict a normal hierarchy of masses for the neutrinos
observed in oscillating experiments and in the basis where the right-handed
Majorana mass is diagonal, the charged lepton mixings are tiny.
In addition these models link the up-quark Yukawa matrix to the neutrino
Yukawa matrix Y^\nu with the special feature of Y^\nu_{11}-> 0 Using this
condition, we find that the required baryon asymmetry of the Universe can be
explained by the soft leptogenesis using the soft B parameter of the second
lightest right-handed neutrino whose mass turns out to be around 10^8 GeV. It
is pointed out that a natural way to do so is to use no-scale supergravity
where the value of B ~1 GeV is set through gauge-loop corrections.Comment: 26 pages, 2 figures. Added references, new appendix of a relevant fit
and improved comment
Fermi-edge singularities in linear and non-linear ultrafast spectroscopy
We discuss Fermi-edge singularity effects on the linear and nonlinear
transient response of an electron gas in a doped semiconductor. We use a
bosonization scheme to describe the low energy excitations, which allows to
compute the time and temperature dependence of the response functions. Coherent
control of the energy absorption at resonance is analyzed in the linear regime.
It is shown that a phase-shift appears in the coherent control oscillations,
which is not present in the excitonic case. The nonlinear response is
calculated analytically and used to predict that four wave-mixing experiments
would present a Fermi-edge singularity when the exciting energy is varied. A
new dephasing mechanism is predicted in doped samples that depends linearly on
temperature and is produced by the low-energy bosonic excitations in the
conduction band.Comment: long version; 9 pages, 4 figure
Constraints on R-parity violating supersymmetry from leptonic and semileptonic tau, B_d and B_s decays
We put constraints on several products of R-parity violating lambda lambda'
and lambda' lambda' type couplings from leptonic and semileptonic tau, B_d and
B_s decays. Most of them are one to two orders of magnitude better than the
existing bounds, and almost free from theoretical uncertainties. A significant
improvement of these bounds can be made in high luminosity tau-charm or B
factories.Comment: 14 pages, latex. A few references added, two typos corrected. Version
to be published in Physical Review
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