838 research outputs found
Dissipative Quantum Ising model in a cold atomic spin-boson mixture
Using cold bosonic atoms with two (hyperfine) ground states, we introduce a
spin-boson mixture which allows to implement the quantum Ising model in a
tunable dissipative environment. The first specie lies in a deep optical
lattice with tightly confining wells and forms a spin array; spin-up/down
corresponds to occupation by one/no atom at each site. The second specie forms
a superfluid reservoir. Different species are coupled coherently via laser
transitions and collisions. Whereas the laser coupling mimics a transverse
field for the spins, the coupling to the reservoir sound modes induces a
ferromagnetic (Ising) coupling as well as dissipation. This gives rise to an
order-disorder quantum phase transition where the effect of dissipation can be
studied in a controllable manner.Comment: 4 pages, 2 figures, 1 table; Title modified and cosmetic change
On the acoustic diffraction by the edges of benthic shells
Author Posting. © Acoustical Society of America, 2004. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 116 (2004): 239-244, doi:10.1121/1.1675813.Recent laboratory measurements of acoustic backscattering by individual benthic shells have isolated the edge-diffracted echo from echoes due to the surface of the main body of the shell. The data indicate that the echo near broadside incidence is generally the strongest for all orientations and is due principally to the surface of the main body. At angles well away from broadside, the echo levels are lower and are due primarily to the diffraction from the edge of the shell. The decrease in echo levels from broadside incidence to well off broadside is shown to be reasonably consistent with the decrease in acoustic backscattering from normal incidence to well off normal incidence by a shell-covered seafloor. The results suggest the importance of the edge of the shell in off-normal-incidence backscattering by a shell-covered seafloor. Furthermore, when considering bistatic diffraction by edges, there are implications that the edge of the shell (lying on the seafloor) can cause significant scattering in many directions, including at subcritical angles.This research was supported by the U.S. Office of Naval
Research (Grant No. N00014-02-1-0095) and the Woods
Hole Oceanographic Institution (WHOI), Woods Hole, MA
Abdominal functional electrical stimulation to improve respiratory function after spinal cord injury: a systematic review and meta-analysis
Objectives: Abdominal functional electrical stimulation (abdominal FES) is the application of a train of electrical pulses to the abdominal muscles, causing them to contract. Abdominal FES has been used as a neuroprosthesis to acutely augment respiratory function and as a rehabilitation tool to achieve a chronic increase in respiratory function after abdominal FES training, primarily focusing on patients with spinal cord injury (SCI). This study aimed to review the evidence surrounding the use of abdominal FES to improve respiratory function in both an acute and chronic manner after SCI.
Settings: A systematic search was performed on PubMed, with studies included if they applied abdominal FES to improve respiratory function in patients with SCI.
Methods: Fourteen studies met the inclusion criteria (10 acute and 4 chronic). Low participant numbers and heterogeneity across studies reduced the power of the meta-analysis. Despite this, abdominal FES was found to cause a significant acute improvement in cough peak flow, whereas forced exhaled volume in 1 s approached significance. A significant chronic increase in unassisted vital capacity, forced vital capacity and peak expiratory flow was found after abdominal FES training compared with baseline.
Conclusions: This systematic review suggests that abdominal FES is an effective technique for improving respiratory function in both an acute and chronic manner after SCI. However, further randomised controlled trials, with larger participant numbers and standardised protocols, are needed to fully establish the clinical efficacy of this technique
Improved Measurements of Partial Rate Asymmetry in B -> h h Decays
We report improved measurements of the partial rate asymmetry (Acp) in B -> h
h decays with 140fb^-1 of data collected with the Belle detector at the KEKB
e+e- collider. Here h stands for a charged or neutral pion or kaon and in total
five decay modes are included: K-+ pi+-, K0s pi-+, K-+ pi0, pi-+ pi0 and K0s
pi0. The flavor of the last decay mode is determined from the accompanying B
meson. Using a data sample 4.7 times larger than that of our previous
measurement, we find Acp(K-+ pi+-) -0.088+-0.035+-0.013, 2.4 sigma from zero.
Results for other decay modes are also presented.Comment: 9 pages, 1 figur
Measurements of the masses and widths of the and baryons
We present measurements of the masses and decay widths of the baryonic states
and using a data sample
corresponding to an integrated luminosity of 711 fb collected with the
Belle detector at the KEKB asymmetric-energy collider operating at
the resonance. We report the mass differences with respect to
the baryon MeV/, MeV/,
MeV/, MeV/, and the decay widths
MeV/,
MeV/,
MeV/,
MeV/,
where the first uncertainties are statistical and the second are systematic.
The isospin mass splittings are measured to be
MeV/ and
MeV/. These results are the most precise to date.Comment: 13 pages, 4 figures, Submitted to PRD(RC
Observation of and search for violation in radiative charm decays
We report the first observation of the radiative charm decay and the first search for violation in decays , , and , using a data sample of
943 fb collected with the Belle detector at the KEKB asymmetric-energy
collider. The branching fraction is measured to be , where the first
uncertainty is statistical and the second is systematic. The obtained
asymmetries, , , and
, are consistent with no violation. We also present an improved
measurement of the branching fractions and
Search for a massive invisible particle in and decays
We present a search for a non-Standard-Model invisible particle in the
mass range in and
decays. The results are obtained from a data sample that corresponds to pairs,
collected at the resonance with the Belle detector at the KEKB
collider. One meson is fully reconstructed in a hadronic mode to
determine the momentum of the lepton of the signal decay in the rest frame of
the recoiling partner meson. We find no evidence of a signal and set upper
limits on the order of .Comment: 8 pages, 4 figures, 3 table
Search for composite and exotic fermions at LEP 2
A search for unstable heavy fermions with the DELPHI detector at LEP is
reported. Sequential and non-canonical leptons, as well as excited leptons and
quarks, are considered. The data analysed correspond to an integrated
luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV
and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172
GeV and 161 GeV. The search for pair-produced new leptons establishes 95%
confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2,
depending on the channel. The search for singly produced excited leptons and
quarks establishes upper limits on the ratio of the coupling of the excited
fermio
Search for charginos in e+e- interactions at sqrt(s) = 189 GeV
An update of the searches for charginos and gravitinos is presented, based on
a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector
in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was
found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a
centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by
combining the chargino searches with neutralino searches at the Z resonance
implies a limit on the mass of the lightest neutralino which, for a heavy
sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.Comment: 22 pages, 8 figure
Observation of Mixing in Collisions
We observe mixing in the decay
using a data sample of integrated luminosity 976 fb collected with the
Belle detector at the KEKB asymmetric-energy collider. We measure the
mixing parameters and and the ratio of doubly Cabibbo-suppressed to
Cabibbo-favored decay rates , where the
uncertainties are statistical and systematic combined. Our measurement excludes
the no-mixing hypothesis at the 5.1 standard deviation level.Comment: 6 pages, 4 figure
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