1,718 research outputs found
Morphofunctional correlations in the experimental study of myocardiopathies under the stress of forced restraint. Note 2: The influence of adrenal imbalance
Tests were performed with 70 rats to determine the effects of restraint on the functions and structure of the myocardium under varying conditions of adrenal imbalance. Results showed that in rats with adrenal imbalance, fasting and restraint produced the same biochemical alterations as in the controls. The morphologic alteractions, as well as their electric expression, were more varied and evident in the animals with adrenal imbalance. Persistence of the microscopic and electrocardiographic alterations after 72 hours restraint in the animals subjected to unilateral adrenalectomy suggests chronic evolution of the myocardial lesions. This proves the necessity of intact adrenals for a good adaptability to stress
Simulation of guard ring influence on the performance of ATLAS pixel detectors for inner layer replacement
Electric field magnitude and depletion in the bulk of silicon pixel detectors, which influence its breakdown behaviour, was studied using finite-element method to solve the drift-diffusion equation coupled to Poisson's equation in a simplified two dimensional model of the ATLAS pixel sensor. Based on this model, the number of guard rings and dead edges width were modified to investigate their influence on the detector's depletion at the edge and on its internal electrical field distribution. Final ly, the 3 level model was implemented into the simulation to study the behaviour of such detector under different level of irradiation
An Efficient Rank Based Approach for Closest String and Closest Substring
This paper aims to present a new genetic approach that uses rank distance for solving two known NP-hard problems, and to compare rank distance with other distance measures for strings. The two NP-hard problems we are trying to solve are closest string and closest substring. For each problem we build a genetic algorithm and we describe the genetic operations involved. Both genetic algorithms use a fitness function based on rank distance. We compare our algorithms with other genetic algorithms that use different distance measures, such as Hamming distance or Levenshtein distance, on real DNA sequences. Our experiments show that the genetic algorithms based on rank distance have the best results
Photon polarization in light-by-light scattering: Finite size effects
We derive a simple expression for the photon helicity and polarization-flip probabilities in arbitrary background fields, in the low-energy regime. Taking the background to model a focused laser beam, we study the impact of pulse shape and collision geometry on the probabilities and on ellipticity signals of vacuum birefringence. We find that models which do not account for pulse duration can overestimate all signals in near head-on collisions by up to an order of magnitude. Taking pulse duration into account, the flip probability becomes relatively insensitive to both angular incidence and the fine details of the pulse structure
Vacuum refractive indices and helicity flip in strong-field QED
Vacuum birefringence is governed by the amplitude for a photon to flip
helicity or polarisation state in an external field. Here we calculate the flip
and non-flip amplitudes in arbitrary plane wave backgrounds, along with the
induced spacetime-dependent refractive indices of the vacuum. We compare the
behaviour of the amplitudes in the low energy and high energy regimes, and
analyse the impact of pulse shape and energy. We also provide the first
lightfront-QED derivation of the coefficients in the Heisenberg-Euler effective
action.Comment: Version 2: additional results added, including discussion of vacuum
refractive indices, analysis of flip and non-flip ampltidues at high-energy,
additional plots, new title. Now 17 pages, 10 figure
Coulomb oscillations of the Fano-Kondo effect and zero bias anomalies in the double dot meso-transistor
We investigate theoretically the transport properties of the side-coupled
double quantum dots in connection with the experimental study of Sasaki {\it et
al.} Phys.Rev.Lett.{\bf 103}, 266806 (2009). The novelty of the set-up consists
in connecting the Kondo dot directly to the leads, while the side dot provides
an interference path which affects the Kondo correlations. We analyze the
oscillations of the source-drain current due to the periodical Coulomb blockade
of the many-level side-dot at the variation of the gate potential applied on
it. The Fano profile of these oscillations may be controlled by the
temperature, gate potential and interdot coupling. The non-equilibrium
conductance of the double dot system exhibits zero bias anomaly which, besides
the usual enhancement, may show also a suppression (a dip-like aspect) which
occurs around the Fano {\it zero}. In the same region, the weak temperature
dependence of the conductance indicates the suppression of the Kondo effect.
Scaling properties of the non-equilibrium conductance in the Fano-Kondo regime
are discussed. Since the SIAM Kondo temperature is no longer the proper scaling
parameter, we look for an alternative specific to the double-dot. The extended
Anderson model, Keldysh formalism and equation of motion technique are used.Comment: 19 pages, 8 figure
Silicon Photo-Multiplier radiation hardness tests with a beam controlled neutron source
We report radiation hardness tests performed at the Frascati Neutron
Generator on silicon Photo-Multipliers, semiconductor photon detectors built
from a square matrix of avalanche photo-diodes on a silicon substrate. Several
samples from different manufacturers have been irradiated integrating up to
7x10^10 1-MeV-equivalent neutrons per cm^2. Detector performances have been
recorded during the neutron irradiation and a gradual deterioration of their
properties was found to happen already after an integrated fluence of the order
of 10^8 1-MeV-equivalent neutrons per cm^2.Comment: 7 pages, 6 figures, Submitted to Nucl. Inst. Meth.
Infra-red divergences in plane wave backgrounds
We show that the emission of soft photons via nonlinear Compton scattering in
a pulsed plane wave (laser field) is in general infra-red divergent. We give
examples of both soft and soft-collinear divergences, and we pay particular
attention to the case of crossed fields in both classical and quantum theories.Comment: 15 pages, 7 figure
Effects of a 3-month dietary intervention with a lacto-ovo-vegetarian diet on vitamin B<sub>12</sub> levels in a group of omnivores: results from the CARDIVEG (Cardiovascular Prevention with Vegetarian Diet) study
AbstractPrevious studies have suggested that vegetarianism can result in a reduction of vitamin B12 circulating levels. The aim of the present study was to investigate the effects of a 3-month dietary intervention with a lacto-ovo-vegetarian diet (VD) on the levels of circulating vitamin B12 in a group of omnivores. We analysed fifty-four omnivorous subjects who followed a VD as a first dietary intervention within the CARDIVEG (Cardiovascular Prevention with Vegetarian Diet) study, a dietary intervention study. VD resulted in a significant reduction (P<0·001) of 51·2 % of vitamin B12 intake and in a significant reduction (P=0·005) of 6·2 % of the circulating levels of vitamin B12 (–24·5 pg/ml). Changes in vitamin B12 intake were significantly correlated with changes in circulating levels of vitamin B12 (R 0·61, P<0·001). Subgroup analyses showed that reduction in circulating vitamin B12 levels was more evident in participants who were younger, overweight, non-smokers and had hypercholesterolaemia. A logistic regression analysis showed that a reduction in vitamin B12 intake greater than the first quartile of the delta changes obtained in the study population (–28·5 %) conferred a significantly higher risk of experiencing a decrease in circulating vitamin B12 levels (OR 10·1; 95 % CI 1·3, 76·1). In conclusion, a 3-month VD period determined a significant reduction in circulating levels of vitamin B12, being significantly correlated with the reduction in vitamin B12 intake. Although a well-planned VD can provide adequate nutrition across all life stages, special care must be taken to ensure adequate vitamin B12 intake and to help prevent deficiency
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