1,162 research outputs found
Thermodynamics of Two Dimensional Black Holes
Thermodynamic relations for a class of 2D black holes are obtained
corresponding to observations made from finite spatial distances. We also study
the thermodynamics of the charged version of the Jackiw-Teitelboim black holes
found recently by Lowe and Strominger. Our results corroborate, in appropriate
limits, to those obtained previously by other methods. We also analyze the
stability of these black holes thermodynamically.Comment: 18 pages (One uncoded postscript file for figure appended),
IP/BBSR/94-5
Gravitational lensing in the Kerr-Randers optical geometry
A new geometric method to determine the deflection of light in the equatorial
plane of the Kerr solution is presented, whose optical geometry is a surface
with a Finsler metric of Randers type. Applying the Gauss-Bonnet theorem to a
suitable osculating Riemannian manifold, adapted from a construction by Naz\i
m, it is shown explicitly how the two leading terms of the asymptotic
deflection angle of gravitational lensing can be found in this way.Comment: 7 pages, 1 figure. Accepted by Gen. Rel. Grav. Version 2: change of
notation in sec.
Extensively Drug-Resistant Tuberculosis (XDR-TB) - A Potential Threat in Ireland
We describe a case of a 25 year old female from Lithuania who presented with a productive cough. Chest radiograph demonstrated an infiltrate in the left upper lobe and a cavitating lesion in the right middle lobe. Sensitivity testing of her sputum led to a diagnosis of extensively drug-resistant tuberculosis (XDR-TB). This is the first case in Ireland and highlights the need for physicians to be aware of the possibility of XDR-TB. Moreover it underlines the need for improvement in service provision in terms of a TB reference laboratory and TB clinics
Fast Scramblers, Horizons and Expander Graphs
We propose that local quantum systems defined on expander graphs provide a
simple microscopic model for thermalization on quantum horizons. Such systems
are automatically fast scramblers and are motivated from the membrane paradigm
by a conformal transformation to the so-called optical metric.Comment: 22 pages, 2 figures. Added further discussion in section 3. Added
reference
Chemical stability study of vitamins thiamine, riboflavin, pyridoxine and ascorbic acid in parenteral nutrition for neonatal use
<p>Abstract</p> <p>Background</p> <p>The objective of this work was to study the vitamins B<sub>1</sub>, B<sub>2</sub>, B<sub>6 </sub>and C stability in a pediatric formulation containing high amounts of calcium in the presence of organic phosphate, amino acids, glucose, sodium chloride, magnesium sulfate, pediatric vitamins and trace elements under different conditions using developed and validated analytical methods.</p> <p>Methods</p> <p>The study was carried out during 72 h with formulations packaged in recommended storage temperature (4°C) and 25°C, with and without photoprotection.</p> <p>Results</p> <p>The results showed that the methodologies used for assessing the chemical stability of vitamins B<sub>1</sub>, B<sub>2</sub>, B<sub>6 </sub>and C in the formulation were selective, linear, precise and accurate. The vitamins could be considered stable in the formulation during the three days of study if stored at 4°C. When stored at 25°C vitamin C presented instability after 48 h.</p> <p>Conclusion</p> <p>The pediatric formulation containing high amount of calcium in the presence of organic phosphate, amino acids, glucose, sodium chloride, magnesium sulphate, pediatric vitamins and trace elements packaged in bag-type trilaminate presented a shelf life of the 72 h, when maintained under refrigeration, between 2°C and 8°C. This shelf life was measured considering the vitamins studied. Further studies are needed including all the vitamins present in this formulation.</p
A Closed-Form Solution of the Multi-Period Portfolio Choice Problem for a Quadratic Utility Function
In the present paper, we derive a closed-form solution of the multi-period
portfolio choice problem for a quadratic utility function with and without a
riskless asset. All results are derived under weak conditions on the asset
returns. No assumption on the correlation structure between different time
points is needed and no assumption on the distribution is imposed. All
expressions are presented in terms of the conditional mean vectors and the
conditional covariance matrices. If the multivariate process of the asset
returns is independent it is shown that in the case without a riskless asset
the solution is presented as a sequence of optimal portfolio weights obtained
by solving the single-period Markowitz optimization problem. The process
dynamics are included only in the shape parameter of the utility function. If a
riskless asset is present then the multi-period optimal portfolio weights are
proportional to the single-period solutions multiplied by time-varying
constants which are depending on the process dynamics. Remarkably, in the case
of a portfolio selection with the tangency portfolio the multi-period solution
coincides with the sequence of the simple-period solutions. Finally, we compare
the suggested strategies with existing multi-period portfolio allocation
methods for real data.Comment: 38 pages, 9 figures, 3 tables, changes: VAR(1)-CCC-GARCH(1,1) process
dynamics and the analysis of increasing horizon are included in the
simulation study, under revision in Annals of Operations Researc
How does gender influence the recognition of cardiovascular risk and adherence to self-care recommendations? : a study in polish primary care
Background:
Studies have shown a correlation between gender and an ability to change lifestyle to reduce the risk of disease. However, the results of these studies are ambiguous, especially where a healthy lifestyle is concerned. Additionally, health behaviors are strongly modified by culture and the environment. Psychological factors also substantially affect engagement with disease-related lifestyle interventions. This study aimed to examine whether there are differences between men and women in the frequency of health care behavior for the purpose of reducing cardiovascular risk (CVR), as well as cognitive appraisal of this type of risk. We also aimed to identify the psychological predictors of engaging in recommended behavior for reducing the risk of cardiovascular disease after providing information about this risk in men and women.
Methods:
A total of 134 consecutive eligible patients in a family practice entered a longitudinal study. At initial consultation, the individual’s CVR and associated health burden was examined, and preventive measures were recommended by the physician. Self-care behavior, cognitive appraisal of risk, and coping styles were then assessed using psychological questionnaires. Six months after the initial data collection, the frequency of subjects’ self-care behavior was examined.
Results:
We found an increase in health care behavior after providing information regarding the rate of CVR in both sexes; this increase was greater for women than for men. Women followed self-care guidelines more often than men, particularly for preventive measures and dietary advice. Women were more inclined to recognize their CVR as a challenge. Coping style, cognitive appraisal, age, level of health behaviors at baseline and CVR values accounted for 48% of the variance in adherence to self-care guidelines in women and it was 52% in men. In women, total risk of CVD values were most important, while in men, cognitive appraisal of harm/loss was most important.
Conclusions:
Different predictors of acquisition of health behavior are encountered in men and women. Our results suggest that gender-adjusted motivation models influencing the recognition process need to be considered to optimize compliance in patients with CVR
Quantum Fields and Extended Objects in Space-Times with Constant Curvature Spatial Section
The heat-kernel expansion and -regularization techniques for quantum
field theory and extended objects on curved space-times are reviewed. In
particular, ultrastatic space-times with spatial section consisting in manifold
with constant curvature are discussed in detail. Several mathematical results,
relevant to physical applications are presented, including exact solutions of
the heat-kernel equation, a simple exposition of hyperbolic geometry and an
elementary derivation of the Selberg trace formula. With regards to the
physical applications, the vacuum energy for scalar fields, the one-loop
renormalization of a self-interacting scalar field theory on a hyperbolic
space-time, with a discussion on the topological symmetry breaking, the finite
temperature effects and the Bose-Einstein condensation, are considered. Some
attempts to generalize the results to extended objects are also presented,
including some remarks on path integral quantization, asymptotic properties of
extended objects and a novel representation for the one-loop (super)string free
energy.Comment: Latex file, 122 page
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