966 research outputs found
Correcting calf girth discriminates the incidence of falling but not bone mass by broadband ultrasound attenuation in elderly female subjects.
Calf circumference has been cited as an independent risk factor for hip fracture. Correcting this measured girth for subcutaneous adipose tissue or fluid accumulation provides a more valid estimate of lean tissue, but has not been reported in elderly populations. Two hundred eighty-eight randomly selected female volunteers, aged ≥ 70 years, were assessed by quantitative ultrasound (QUS) and clinical risk factors as part of a larger screening study for hip fracture risk. This involved measuring broadband ultrasound attenuation (BUA) and administering a structured risk factor questionnaire that included estimated daily skeletal loading (time standing or walking). Body mass index (BMI) was estimated using current body mass and height at age 25 years. Calf girth was measured using a standard anthropometric tape, the medial calf skinfold (a vertical fold at the point of maximum calf girth) was measured, and corrected calf girth (CCG) was calculated by subtracting the skinfold (in centimeters) multiplied by π from calf girth. Subjects were aged 76.9 ± 5.0 years, had BMIs of 24.3 ± 3.9 kg/m2, and spent an average of 5.5 ± 2.0 h on their feet each day. Age, current body mass, BMI calf girth, and CCG all correlated with BUA (p 0.05). Dividing the sample into tertiles by these correlates of BUA and predicting BUA using stepwise regression revealed different predictors for each tertile. Of the total sample, 93 had fallen in the last 12 months, whereas 195 had not. Independent t-tests showed these groups to be similar in age, BMI, and calf girth (p > 0.05), but fallers spent less time on their feet each day, and had smaller CCG (p < 0.05). This suggests that larger calf muscles may be protective against falling—possibly as a result of enhanced stability or greater neuromuscular control
The Bousso entropy bound in selfgravitating gas of massless particles
The Bousso entropy bound is investigated in a static spherically symmetric
spacetime filled with an ideal gas of massless bosons or fermions. Especially
lightsheets generated by spheres are considered. Statistical description of the
gas is given. Conditions under which the Bousso bound can be violated are
discussed and it is shown that a possible violating region cannot be
arbitrarily large and it is contained inside a sphere of unit Planck radius if
number of independent polarization states is small enough. It is also
shown that central temperature must exceed the Planck temperature to get a
violation of the Bousso bound for not too large.Comment: 14 pages, 4 figures, a paragraph added, version published in Gen.
Rel. Gra
Future non-linear stability for reflection symmetric solutions of the Einstein-Vlasov system of Bianchi types II and VI
Using the methods developed for the Bianchi I case we have shown that a
boostrap argument is also suitable to treat the future non-linear stability for
reflection symmetric solutions of the Einstein-Vlasov system of Bianchi types
II and VI. These solutions are asymptotic to the Collins-Stewart solution
with dust and the Ellis-MacCallum solution respectively. We have thus
generalized the results obtained by Rendall and Uggla in the case of locally
rotationally symmetric Bianchi II spacetimes to the reflection symmetric case.
However we needed to assume small data. For Bianchi VI there is no
analogous previous result.Comment: 30 page
Fluctuations along supersymmetric flat directions during Inflation
We consider a set of scalar fields, consisting of a single flat direction and
one or several non-flat directions. We take our cue from the MSSM, considering
separately D-flat and F-flat directions, but our results apply to any
supersymmetric scenario containing flat directions. We study the field
fluctuations during pure de Sitter Inflation, following the evolution of the
infrared modes by numerically solving the appropriate Langevin equations. We
demonstrate that for the Standard Model U(1), SU(2) or SU(3) gauge couplings,
as well as for large enough Yukawa couplings, the fluctuations along the
non-flat directions effectively block the fluctuations along the flat
directions. The usual expected behaviour \propto N, with N the
number of efolds, may be strongly violated, depending on the coupling
strengths. As a consequence, those cosmological considerations, which are
derived assuming that during inflation flat directions fluctuate freely, should
be revised.Comment: 19 pages, 5 figures, Submitted to JCA
The effect of pitched and vertical ladder ergometer climbing on cardiorespiratory and psychophysical variables.
This study aimed to assess whether modifying the pitch of a 75° ladder ergometer to vertical had a cardiorespiratory or psychophysical effect on climbing. Nine male participants climbed a ladder ergometer at 75° and subsequently at 90°, adjusted for an equivalent vertical climb rate, completing three climbing bouts at different vertical speeds. One participant dropped out being unable to complete the climb under the 90° condition. Each was monitored for heart rate (HR), V˙O2 and rating of perceived exertion (RPE). Results showed vertical climbing induced higher V˙O2 (mean increase 17.3%), higher HR (mean increase 15.8%), and higher RPE at all speeds and that moving from 75° to vertical exacerbates the effect of speed on the cardiorespiratory response to climbing. This may be explained by increased force production required to maintain balance in a vertical climbing position when the body's centre of mass is not above the feet
Time trends in survival and readmission following coronary artery bypass grafting in Scotland, 1981-96: retrospective observational study
Improvements in coronary revascularisation techniques and an increase in the use of percutaneous interventions1 have led to a rise in the number of coronary artery bypass grafting operations in older patients with more severe cardiac disease and worse comorbidity and who have previously undergone revascularisation procedures. 2 3 Advances in surgical and anaesthetic techniques have prevented a worsening risk profile from being translated into an increase in perioperative deaths. 2 3 The aim of our study was to examine time trends in major outcomes up to two years after coronary artery bypass grafting
Pretreatment with beta-blockers and the frequency of hypokalemia in patients with acute chest pain
Plasma potassium concentration was measured at admission in 1234 patients who presented with acute chest pain. One hundred and ninety five patients were on P blockers before admission. The potassium concentrations of patients admitted early (within four hours of onsetof symptoms) were compared with those admitted later (4-18 hours after onset of symptoms). There was a transient fall in plasma potassium concentrations in patients not pre-treated with , B blockers. This was not seen in patients who had been on P blockers before admission. Nonselective, B blockers were more effective than cardioselective agents in maintaining concentrationsof plasma potassium. These findings suggest a mechanism for the beneficial effects of ,B blockers on morbidity and mortality in acute myocardial infarction
Observational constraints on an inflation model with a running mass
We explore a model of inflation where the inflaton mass-squared is generated
at a high scale by gravity-mediated soft supersymmetry breaking, and runs at
lower scales to the small value required for slow-roll inflation. The running
is supposed to come from the coupling of the inflaton to a non-Abelian gauge
field. In contrast with earlier work, we do not constrain the magnitude of the
supersymmetry breaking scale, and we find that the model might work even if
squark and slepton masses come from gauge-mediated supersymmetry breaking. With
the inflaton and gaugino masses in the expected range, and
in the range to (all at the high scale) the model can give
the observed cosmic microwave anisotropy, and a spectral index in the observed
range. The latter has significant variation with scale, which can confirm or
rule out the model in the forseeable future.Comment: Latex, 19 pages, 14 figures, uses epsf.st
Inflation from Susy quantum cosmology
We propose a realization of inverted hybrid inflation scenario in the context
of n=2 supersymmetric quantum cosmology. The spectrum of density fluctuations
is calculated in the de Sitter regimen as a function of the gravitino and the
Planck mass, and explicit forms for the wave function of the universe are found
in the WKB regimen for a FRW closed and flat universes.Comment: 9 pages, one figure, to appear in Phys. Rev.
Particle physics models of inflation
Inflation models are compared with observation on the assumption that the
curvature perturbation is generated from the vacuum fluctuation of the inflaton
field. The focus is on single-field models with canonical kinetic terms,
classified as small- medium- and large-field according to the variation of the
inflaton field while cosmological scales leave the horizon. Small-field models
are constructed according to the usual paradigm for beyond Standard Model
physicsComment: Based on a talk given at the 22nd IAP Colloquium, ``Inflation +25'',
Paris, June 2006 Curve omitted from final Figur
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