851 research outputs found
Dirac field in topologically massive gravity
We consider a Dirac field coupled minimally to the Mielke-Baekler model of
gravity and investigate cosmological solutions in three dimensions. We arrive
at a family of solutions which exists even in the limit of vanishing
cosmological constant.Comment: 12 pages. Title changed. Conclusion extended. Appendix added. To
appear in Gen. Rel. Gra
Differential effects of tactile high- and low-frequency stimulation on tactile discrimination in human subjects
<p>Abstract</p> <p>Background</p> <p>Long-term potentiation (LTP) and long-term depression (LTD) play important roles in mediating activity-dependent changes in synaptic transmission and are believed to be crucial mechanisms underlying learning and cortical plasticity. In human subjects, however, the lack of adequate input stimuli for the induction of LTP and LTD makes it difficult to study directly the impact of such protocols on behavior.</p> <p>Results</p> <p>Using tactile high- and low-frequency stimulation protocols in humans, we explored the potential of such protocols for the induction of perceptual changes. We delivered tactile high-frequency and low-frequency stimuli (t-HFS, t-LFS) to skin sites of approximately 50 mm<sup>2 </sup>on the tip of the index finger. As assessed by 2-point discrimination, we demonstrate that 20 minutes of t-HFS improved tactile discrimination, while t-LFS impaired performance. T-HFS-effects were stable for at least 24 hours whereas t-LFS-induced changes recovered faster. While t-HFS changes were spatially very specific with no changes on the neighboring fingers, impaired tactile performance after t-LFS was also observed on the right middle-finger. A central finding was that for both t-LFS and t-HFS perceptual changes were dependent on the size of the stimulated skin area. No changes were observed when the stimulated area was very small (< 1 mm<sup>2</sup>) indicating special requirements for spatial summation.</p> <p>Conclusion</p> <p>Our results demonstrate differential effects of such protocols in a frequency specific manner that might be related to LTP- and LTD-like changes in human subjects.</p
Treatment of poorly differentiated neuroendocrine tumours with etoposide and cisplatin
The purpose of this study was to evaluate by a retrospective analysis of 53 patients the efficacy of chemotherapy combining etoposide and cisplatin in the treatment of neuroendocrine tumours. The regimen was a combination of etoposide 100 mg mâ2 dayâ1 for 3 days and cisplatin 100 mg mâ2 on day 1, given by 2-h intravenous infusion, administered every 21 days. Twelve patients had a well-differentiated and 41 a poorly differentiated neuroendocrine tumour. Toxicity of treatment was assessed in 50 patients and efficacy in 52 patients. Among the 11 patients with a well-differentiated tumour evaluable for tumoural response, only one (9.4%) had a partial response for 8.5 months. Forty-one patients with a poorly differentiated tumour showed an objective response rate of 41.5% (four complete and 13 partial responses); the median duration of response was 9.2 months, the median overall survival 15 months and the median progression-free survival 8.9 months. Haematological grade 3â4 toxicity was observed in 60% of the cases with one treatment-related death, digestive grade 3â4 toxicity in 40% and grade 3 alopecia was constant. No severe renal, hearing and neurological toxicities were observed (grade 1 in 6%, 14%, 72% respectively and no grade >1). We confirm that poorly differentiated neuroendocrine tumours are chemosensitive to the etoposide plus cisplatin combination. However, the prognosis remains poor with a 2-year survival lower than 20% confirming that new therapeutic strategies have to be developed. Š 1999 Cancer Research Campaig
Measurement of D-s(+) and D-s(*+) production in B meson decays and from continuum e(+)e(-) annihilation at âs=10.6 GeV
This is the pre-print version of the Article. The official published version can be accessed from the links below. Copyright @ 2002 APSNew measurements of Ds+ and Ds*+ meson production rates from B decays and from qqĚ
continuum events near the ÎĽ(4S) resonance are presented. Using 20.8 fb-1 of data on the ÎĽ(4S) resonance and 2.6 fb-1 off-resonance, we find the inclusive branching fractions B(BâDs+X)=(10.93Âą0.19Âą0.58Âą2.73)% and B(BâDs*+X)=(7.9Âą0.8Âą0.7Âą2.0)%, where the first error is statistical, the second is systematic, and the third is due to the Ds+âĎĎ+ branching fraction uncertainty. The production cross sections Ď(e+e-âDs+X)ĂB(Ds+âĎĎ+)=7.55Âą0.20Âą0.34pb and Ď(e+e-âDs*ÂąX)ĂB(Ds+âĎĎ+)=5.8Âą0.7Âą0.5pb are measured at center-of-mass energies about 40 MeV below the ÎĽ(4S) mass. The branching fractions ÎŁB(BâDs(*)+D(*))=(5.07Âą0.14Âą0.30Âą1.27)% and ÎŁB(BâDs*+D(*))=(4.1Âą0.2Âą0.4Âą1.0)% are determined from the Ds(*)+ momentum spectra. The mass difference m(Ds+)-m(D+)=98.4Âą0.1Âą0.3MeV/c2 is also measured.This work was supported by DOE and NSF (USA), NSERC (Canada), IHEP (China), CEA and CNRS-IN2P3 (France), BMBF (Germany), INFN (Italy), NFR (Norway), MIST (Russia), and PPARC (United Kingdom). Individuals have received support from the Swiss NSF, A. P. Sloan Foundation, Research Corporation, and Alexander von Humboldt Foundation
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
Azimuthal anisotropy of charged particles at high transverse momenta in PbPb collisions at sqrt(s[NN]) = 2.76 TeV
The azimuthal anisotropy of charged particles in PbPb collisions at
nucleon-nucleon center-of-mass energy of 2.76 TeV is measured with the CMS
detector at the LHC over an extended transverse momentum (pt) range up to
approximately 60 GeV. The data cover both the low-pt region associated with
hydrodynamic flow phenomena and the high-pt region where the anisotropies may
reflect the path-length dependence of parton energy loss in the created medium.
The anisotropy parameter (v2) of the particles is extracted by correlating
charged tracks with respect to the event-plane reconstructed by using the
energy deposited in forward-angle calorimeters. For the six bins of collision
centrality studied, spanning the range of 0-60% most-central events, the
observed v2 values are found to first increase with pt, reaching a maximum
around pt = 3 GeV, and then to gradually decrease to almost zero, with the
decline persisting up to at least pt = 40 GeV over the full centrality range
measured.Comment: Replaced with published version. Added journal reference and DO
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