574 research outputs found
Shot noise in resonant tunneling through a zero-dimensional state with a complex energy spectrum
We investigate the noise properties of a GaAs/AlGaAs resonant tunneling
structure at bias voltages where the current characteristic is determined by
single electron tunneling. We discuss the suppression of the shot noise in the
framework of a coupled two-state system. For large bias voltages we observed
super-Poissonian shot noise up to values of the Fano factor .Comment: 4 pages, 4 figures, accepted for Phys. Rev.
The composition of Singaporean shopping centres
With its growing population but limited supply of land, Singapore has seen a huge increase in the number and size of shopping centres in recent years. This growth has led to two rather contradictory outcomes - more choice for retailers in their efforts to reach customers but also claims that too many of the centres contain the same types of retailers and contain no real differentiation in their offerings. This paper looks at this trend and reports on a survey of the composition of store types in a wide range of Singaporean shopping centres to consider whether or not these views are based on a full picture of the roles played by these shopping centres
Patient Outcomes at Twelve Months after Early Decompressive Craniectomy for Diffuse Traumatic Brain Injury in the Randomized DECRA Clinical Trial
Functional outcomes at 12 months were a secondary outcome of the randomized DECRA trial of early decompressive craniectomy for severe diffuse traumatic brain injury (TBI) and refractory intracranial hypertension. In the DECRA trial, patients were randomly allocated 1:1 to either early decompressive craniectomy or intensive medical therapies (standard care). We conducted planned secondary analyses of the DECRA trial outcomes at 6 and 12 months, including all 155 patients. We measured functional outcome using the Glasgow Outcome Scale-Extended (GOS-E). We used ordered logistic regression, and dichotomized the GOS-E using logistic regression, to assess outcomes in patients overall and in survivors. We adjusted analyses for injury severity using the International Mission for Prognosis and Analysis of Clinical Trials in TBI (IMPACT) model. At 12 months, the odds ratio (OR) for worse functional outcomes in the craniectomy group (OR 1.68; 95% confidence interval [CI]: 0.96-2.93; p = 0.07) was no longer significant. Unfavorable functional outcomes after craniectomy were 11% higher (59% compared with 48%), but were not significantly different from standard care (OR 1.58; 95% CI: 0.84-2.99; p = 0.16). Among survivors after craniectomy, there were fewer good (OR 0.33; 95% CI: 0.12-0.91; p = 0.03) and more vegetative (OR 5.12; 95% CI: 1.04-25.2; p = 0.04) outcomes. Similar outcomes in survivors were found at 6 months after injury. Vegetative (OR 5.85; 95% CI: 1.21-28.30; p = 0.03) and severely disabled outcomes (OR 2.49; 95% CI: 1.21-5.11; p = 0.01) were increased. Twelve months after severe diffuse TBI and early refractory intracranial hypertension, decompressive craniectomy did not improve outcomes and increased vegetative survivors
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A multispacecraft analysis of a small-scale transient entrained by solar wind streams
The images taken by the Heliospheric Imagers (HIs), part of the SECCHI imaging package onboard the pair of STEREO spacecraft, provide information on the radial and latitudinal evolution of the plasma compressed inside corotating interaction regions (CIRs). A plasma density wave imaged by the HI instrument onboard STEREO-B was found to propagate towards STEREO-A, enabling a comparison between simultaneous remotesensing and in situ observations of its structure to be performed. In situ measurements made by STEREO-A show that the plasma density wave is associated with the passage of a CIR. The magnetic field compressed after the CIR stream interface (SI) is found to have a planar distribution. Minimum variance analysis of the magnetic field vectors shows that the SI is inclined at 54° to the orbital plane of the STEREO-A spacecraft. This inclination of the CIR SI is comparable to the inclination of the associated plasma density wave observed by HI. A small-scale magnetic cloud with a flux rope topology and radial extent of 0.08 AU is also embedded prior to the SI. The pitch-angle distribution of suprathermal electrons measured by the STEREO-A SWEA instrument shows that an open magnetic field topology in the cloud replaced the heliospheric current sheet locally. These observations confirm that HI observes CIRs in difference images when a small-scale transient is caught up in the compression region
Supersymmetrization of Quaternion Dirac Equation for Generalized Fields of Dyons
The quaternion Dirac equation in presence of generalized electromagnetic
field has been discussed in terms of two gauge potentials of dyons.
Accordingly, the supersymmetry has been established consistently and thereafter
the one, two and component Dirac Spinors of generalized quaternion Dirac
equation of dyons for various energy and spin values are obtained for different
cases in order to understand the duality invariance between the electric and
magnetic constituents of dyons.Comment: Key words: Supersymmetry, quaternion, Dirac equation, dyons PACS No.:
11.30.Pb, 14.80.Ly, 03.65.G
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging
We present a measurement of the top quark pair () production cross
section () in collisions at TeV
using 230 pb of data collected by the D0 experiment at the Fermilab
Tevatron Collider. We select events with one charged lepton (electron or muon),
missing transverse energy, and jets in the final state. We employ
lifetime-based b-jet identification techniques to further enhance the
purity of the selected sample. For a top quark mass of 175 GeV, we
measure pb, in
agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let
Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV
We present a study of events with Z bosons and jets produced at the Fermilab
Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV.
The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding
to the integrated luminosity of 0.4 fb-1 collected using the D0 detector.
Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross
section have been measured for n = 1 to 4 jet events. Our measurements are
found to be in good agreement with a next-to-leading order QCD calculation and
with a tree-level QCD prediction with parton shower simulation and
hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
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