412 research outputs found
Alendroninezuur effectiever dan alfacalcidol voor preventie van osteoporose bij patiënten met een reumatische ziekte die starten met glucocorticoïdtherapie
OBJECTIVE: To compare the effects of alendronate and alfacalcidol in the prevention ofglucocorticoid-related osteoporosis in patients with a rheumatic disease. DESIGN: Randomised, double-blind, double-placebo clinical trial (www. clinicaltrials.gov; number: NCT00138983). METHODS: A total of 201 patients with rheumatic disease who were starting glucocorticoid treatment at a daily dose that was equivalent to at least 7.5 mg of prednisone were randomised to alendronate (10 mg) and a placebo capsule ofalfacalcidol daily (n = 100) or alfacalcidol (1 microg) and a placebo tablet ofalendronate daily (n = 101) for 18 months. Primary outcome was change in lumbar spine bone mineral density at 18 months. The main secondary outcome was the incidence of morphometrically confirmed vertebral deformities. RESULTS: Overall, 163 patients completed the study. The bone mineral density of the lumbar spine increased by 2.1% (95% CI: 1.1-3.1) in the alendronate group and decreased by 1.9% (95% CI: -3.I--0.7) in the alfacalcidol group. At 18 months the mean difference in change in bone mineral density between the two groups was 4.0% (95% CI: 2.4-5-5). Three patients in the alendronate group had a new vertebral deformity, compared with 8 patients in the alfacalcidol group, including 5 symptomatic vertebral fractures in 3 patients; the hazard ratio was 0.4 (95% CI: 0.1-1.4). CONCLUSION: Alendronate was more effective than alfacalcidol in preventing glucocorticoid-induced bone loss during this 18-month trial in patients with rheumatic diseases who were starting glucocorticoid treatment
Critical structure factor in Ising systems
We perform a large-scale Monte Carlo simulation of the three-dimensional
Ising model on simple cubic lattices of size L^3 with L=128 and 256. We
determine the corresponding structure factor (Fourier transform of the
two-point function) and compare it with several approximations and with
experimental results. We also compute the turbidity as a function of the
momentum of the incoming radiation, focusing in particular on the deviations
from the Ornstein-Zernicke expression of Puglielli and Ford.Comment: 16 page
The delta-function-kicked rotor: Momentum diffusion and the quantum-classical boundary
We investigate the quantum-classical transition in the delta-kicked rotor and
the attainment of the classical limit in terms of measurement-induced
state-localization. It is possible to study the transition by fixing the
environmentally induced disturbance at a sufficiently small value, and
examining the dynamics as the system is made more macroscopic. When the system
action is relatively small, the dynamics is quantum mechanical and when the
system action is sufficiently large there is a transition to classical
behavior. The dynamics of the rotor in the region of transition, characterized
by the late-time momentum diffusion coefficient, can be strikingly different
from both the purely quantum and classical results. Remarkably, the early time
diffusive behavior of the quantum system, even when different from its
classical counterpart, is stabilized by the continuous measurement process.
This shows that such measurements can succeed in extracting essentially quantum
effects. The transition regime studied in this paper is accessible in ongoing
experiments.Comment: 8 pages, 4 figures, revtex4 (revised version contains much more
introductory material
Atomic X-ray Spectroscopy of Accreting Black Holes
Current astrophysical research suggests that the most persistently luminous
objects in the Universe are powered by the flow of matter through accretion
disks onto black holes. Accretion disk systems are observed to emit copious
radiation across the electromagnetic spectrum, each energy band providing
access to rather distinct regimes of physical conditions and geometric scale.
X-ray emission probes the innermost regions of the accretion disk, where
relativistic effects prevail. While this has been known for decades, it also
has been acknowledged that inferring physical conditions in the relativistic
regime from the behavior of the X-ray continuum is problematic and not
satisfactorily constraining. With the discovery in the 1990s of iron X-ray
lines bearing signatures of relativistic distortion came the hope that such
emission would more firmly constrain models of disk accretion near black holes,
as well as provide observational criteria by which to test general relativity
in the strong field limit. Here we provide an introduction to this phenomenon.
While the presentation is intended to be primarily tutorial in nature, we aim
also to acquaint the reader with trends in current research. To achieve these
ends, we present the basic applications of general relativity that pertain to
X-ray spectroscopic observations of black hole accretion disk systems, focusing
on the Schwarzschild and Kerr solutions to the Einstein field equations. To
this we add treatments of the fundamental concepts associated with the
theoretical and modeling aspects of accretion disks, as well as relevant topics
from observational and theoretical X-ray spectroscopy.Comment: 63 pages, 21 figures, Einstein Centennial Review Article, Canadian
Journal of Physics, in pres
Percutaneous stereotactic en bloc excision of nonpalpable breast carcinoma: a step in the direction of supraconservative surgery
peer reviewedRecently, the advanced breast biopsy instrumentation (ABBI) system has been introduced as an alternative to conventional breast biopsy techniques. This study was prospectively conducted to evaluate the potential of the ABBI method in locoregional management of a consecutive series of patients with nonpalpable mammographically detected breast carcinomas. Sixty-one consecutive patients underwent an ABBI procedure as a first step before possible surgery for nonpalpable breast lesions that would in any case require complete excision. For the 27 patients in whom the ABBI biopsy revealed malignancy further surgery was recommended, including re-excision of the biopsy site and axillary dissection in cases of infiltrating carcinoma. We calculated the probabilities that the ABBI specimen would have tumor-free margins and that a definitely complete excision had been achieved as a function of the mammographic or pathological diameter of the cancer. For cancer with a pathological diameter less than 10 mm, measured on the ABBI specimen, the probability (92%) of obtaining complete resection was significantly better than for larger lesions (P = 0.01, Fisher's exact test). Although the therapeutic perspectives for the ABBI method are limited at present, we suggest that this approach is a first step in the direction of a surgical strategy that is better adapted to the pathological characteristics peculiar to these small tumors, whose incidence is increasing. (C) 2002 Elsevier Science Ltd. All rights reserved
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
Longitudinal scaling property of the charge balance function in Au + Au collisions at 200 GeV
We present measurements of the charge balance function, from the charged
particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au
collisions at 200 GeV using the STAR detector at RHIC. We observe that the
balance function is boost-invariant within the pseudorapidity coverage [-1.3,
1.3]. The balance function properly scaled by the width of the observed
pseudorapidity window does not depend on the position or size of the
pseudorapidity window. This scaling property also holds for particles in
different transverse momentum ranges. In addition, we find that the width of
the balance function decreases monotonically with increasing transverse
momentum for all centrality classes.Comment: 6 pages, 3 figure
Energy and system size dependence of \phi meson production in Cu+Cu and Au+Au collisions
We study the beam-energy and system-size dependence of \phi meson production
(using the hadronic decay mode \phi -- K+K-) by comparing the new results from
Cu+Cu collisions and previously reported Au+Au collisions at \sqrt{s_NN} = 62.4
and 200 GeV measured in the STAR experiment at RHIC. Data presented are from
mid-rapidity (|y|<0.5) for 0.4 < pT < 5 GeV/c. At a given beam energy, the
transverse momentum distributions for \phi mesons are observed to be similar in
yield and shape for Cu+Cu and Au+Au colliding systems with similar average
numbers of participating nucleons. The \phi meson yields in nucleus-nucleus
collisions, normalised by the average number of participating nucleons, are
found to be enhanced relative to those from p+p collisions with a different
trend compared to strange baryons. The enhancement for \phi mesons is observed
to be higher at \sqrt{s_NN} = 200 GeV compared to 62.4 GeV. These observations
for the produced \phi(s\bar{s}) mesons clearly suggest that, at these collision
energies, the source of enhancement of strange hadrons is related to the
formation of a dense partonic medium in high energy nucleus-nucleus collisions
and cannot be alone due to canonical suppression of their production in smaller
systems.Comment: 20 pages and 5 figure
Measurement of the Bottom contribution to non-photonic electron production in collisions at =200 GeV
The contribution of meson decays to non-photonic electrons, which are
mainly produced by the semi-leptonic decays of heavy flavor mesons, in
collisions at 200 GeV has been measured using azimuthal
correlations between non-photonic electrons and hadrons. The extracted
decay contribution is approximately 50% at a transverse momentum of GeV/. These measurements constrain the nuclear modification factor for
electrons from and meson decays. The result indicates that meson
production in heavy ion collisions is also suppressed at high .Comment: 6 pages, 4 figures, accepted by PR
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