340 research outputs found
History of depression and survival after acute myocardial infarction
Objective: To compare survival in post-myocardial (MI) participants from the Enhancing Recovery In Coronary Heart Disease (ENRICHD) clinical trial with a first episode of major depression (MD) and those with recurrent MID, which is a risk factor for mortality after acute MI. Recent reports suggest that the level of risk may depend on whether the comorbid MD is a first or a recurrent episode. Methods: Survival was compared over a median of 29 months in 370 patients with an initial episode of MD, 550 with recurrent MD, and 408 who were free of depression. Results: After adjusting for an all-cause mortality risk score, initial Beck Depression Inventory score, and the use of selective serotonin reuptake inhibitor antidepressants, patients with a first episode of MD had poorer survival (18.4% all-cause mortality) than those with recurrent MD (11.8%) (hazard ratio (HR)=1.4; 95% Confidence Interval (CI)=1.0-2.0; p=.05). Both first depression (HR=3.1; 95% CI=1.6-6.1; p=.001) and recurrent MD (HR=2.2; 95% CI=1.1-4.4; p=.03) had significantly poorer survival than did the nondepressed patients (3.4%). A secondary analysis of deaths classified as probably due to a cardiovascular cause resulted in similar HRs, but the difference between depression groups was not significant. Conclusions: Both initial and recurrent episodes of MD predict shorter survival after acute MI, but initial MD episodes are more strongly predictive than recurrent episodes. Exploratory analyses suggest that this cannot be explained by more severe heart disease at index, poorer response to depression treatment, or a higher risk of cerebrovascular disease in patients with initial MD episodes
X-ray Emission Diagnostics from the M87 Jet
We use Chandra, HST and VLA observations of M87 to investigate the physics of
X-ray emission from AGN jets. We find that X-ray hotspots in the M87 jet occur
primarily in regions with hard optical-to-X-ray spectra and lower than average
polarization. Particle injection appears to be required both continuously in
the jet sheath as well as locally at X-ray hotspots.Comment: 4 pages, 2 figures, submitted to "The Physics of Relativistic Jets in
the CHANDRA and XMM Era", Bologna 200
A Study of the Scintillation Induced by Alpha Particles and Gamma Rays in Liquid Xenon in an Electric Field
Scintillation produced in liquid xenon by alpha particles and gamma rays has
been studied as a function of applied electric field. For back scattered gamma
rays with energy of about 200 keV, the number of scintillation photons was
found to decrease by 64+/-2% with increasing field strength. Consequently, the
pulse shape discrimination power between alpha particles and gamma rays is
found to reduce with increasing field, but remaining non-zero at higher fields.Comment: 15 pages, 12 figures, accepted by Nuclear Instruments and Methods in
Physics Research
Non-Abelian dynamics and heavy multiquarks, Steiner-tree confinement in hadron spectroscopy
A brief review is first presented of attempts to predict stable multiquark
states within current models of hadron spectroscopy. Then a model combining
flip-flop and connected Steiner trees is introduced and shown to lead to stable
multiquarks, in particular for some configurations involving several heavy
quarks and bearing exotic quantum numbers.Comment: 8 pages, 5 figures, Invited talk at the 21st European Conference on
Few-Body Problems in Physics, Salamanca, Spain, August 29th--September 3rd,
2010, to appear in the Proceedings, ed.~A.~Valcarce et al., to appear in
Few-Body Syste
Pentaquark as Kaon-Nucleon Resonance
Several recent experiments have reported evidence for a narrow feature in the
K(+)-neutron system, an apparent resonant state ~ 100 MeV above threshold and
with a width < 25 MeV. This state has been labelled as Theta(+) (previously as
Z(*)), and because of the implied inclusion of a anti-strange quark, is
referred to as a pentaquark, that is, five quarks within a single bag. We
present an alternative explanation for such a structure, as a higher angular
momentum resonance in the isospin zero K(+) -N system. One might call this an
exit channel or a molecular resonance. In a non-relativistic potential model we
find a possible candidate for the kaon-nucleon system with relative angular
momentum L=3, while L=1 and 2 states possess centrifugal barriers too low to
confine the kaon and nucleon in a narrow state at an energy so high above
threshold. A rather strong state-dependence in the potential is essential,
however, for eliminating an observable L=2 resonance at lower energies.Comment: 4 page
Confinement and scaling in deep inelastic scattering
We show that parton confinement in the final state generates large
corrections to Bjorken scaling, thus leaving less room for the logarithmic
corrections. In particular, the -scaling violations at large are
entirely described in terms of power corrections. For treatment of these
non-perturbative effects, we derive a new expansion in powers of for
the structure function that is free of infra-red singularities and which
reduces corrections to the leading term. The leading term represents scattering
from an off-mass-shell parton, which keeps the same virtual mass in the final
state. It is found that this quasi-free term is a function of a new variable
, which coincides with the Bjorken variable for . The
two variables are very different, however, at finite . In particular, the
variable depends on the invariant mass of the spectator particles.
Analysis of the data at large shows excellent scaling in the variable , and determines the value of the diquark mass to be close to zero. -scaling allows us to extract the structure function near the elastic
threshold. It is found to behave as . Predictions for the
structure functions based on -scaling are made.Comment: Discussion of target mass corrections is added. Accepted for
publication in Phys. Rev.
Resummation of mass terms in perturbative massless quantum field theory
The neutral massless scalar quantum field in four-dimensional
space-time is considered, which is subject to a simple bilinear
self-interaction. Is is well-known from renormalization theory that adding a
term of the form to the Lagrangean has the formal
effect of shifting the particle mass from the original zero value to m after
resummation of all two-leg insertions in the Feynman graphs appearing in the
perturbative expansion of the S-matrix. However, this resummation is
accompanied by some subtleties if done in a proper mathematical manner.
Although the model seems to be almost trivial, is shows many interesting
features which are useful for the understanding of the convergence behavior of
perturbation theory in general. Some important facts in connection with the
basic principles of quantum field theory and distribution theory are
highlighted, and a remark is made on possible generalizations of the
distribution spaces used in local quantum field theory. A short discussion how
one can view the spontaneous breakdown of gauge symmetry in massive gauge
theories within a massless framework is presented.Comment: 15 pages, LaTeX (style files included), one section adde
Implications of the CP asymmetry in semileptonic B decay
Recent experimental searches for , the CP asymmetry in semileptonic B
decay, have reached an accuracy of order one percent. Consequently, they give
meaningful constraints on new physics. We find that cancellations between the
Standard Model (SM) and new physics contributions to mixing
cannot be as strong as was allowed prior to these measurements. The predictions
for this asymmetry within the SM and within models of minimal flavor violation
(MFV) are below the reach of present and near future measurements. Including
order and corrections we obtain the SM
prediction: . Future
measurements can exclude not only the SM, but MFV as well, if the sign of the
asymmetry is opposite to the SM or if it is same-sign but much enhanced. We
also comment on the CP asymmetry in semileptonic decay, and update the
range of the angle in the SM: .Comment: 16 pages, a sign typo in eq.(11) fixed, to appear in Phys. Rev.
Temperature Dependence of Electric and Magnetic Gluon Condensates
The contribution of Lorentz non-scalar operators to finite temperature
correlation functions is discussed. Using the local duality approach for the
one-pion matrix element of a product of two vector currents, the temperature
dependence of the average gluonic stress tensor is estimated in the chiral
limit to be . At a
normalization point GeV we obtain . Together with the
known temperature dependence of the Lorentz scalar gluon condensate we are able
to infer and separately
in the low-temperature hadronic phase.Comment: 11 pages, TPI-MINN-92/37-
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