932 research outputs found
Van der Waals torque induced by external magnetic fields
We present a method for inducing and controlling van der Waals torques
between two parallel slabs using a constant magnetic field. The torque is
calculated using the Barash theory of dispersive torques. In III-IV
semiconductors such as , the effect of an external magnetic field is to
induce an optical anisotropy, in an otherwise isotropic material, that will in
turn induce a torque.
The calculations of the torque are done in the Voigt configuration, with the
magnetic field parallel to the surface of the slabs. As a case study we
consider a slab made of calcite and a second slab made of . In the
absence of magnetic field there is no torque. As the magnetic field increases,
the optical anisotropy of increases and the torque becomes different
from zero, increasing with the magnetic field. The resulting torque is of the
same order of magnitude as that calculated using permanent anisotropic
materials when the magnetic fields is close to 1 T.Comment: to appear in Journal of Applied Physic
Generalidades de la familia Filoviridae y el virus del Ébola: una actualización de sus implicaciones en la población humana
Characteristics of the family Filoviridae and the Ebola virus: an update of its implications in the human population The family Filoviridae is integrated by a group of filamentous RNA viruses that cause severe hemorrhagic fevers in primates and other mammals, including humans, mainly in the African continent. Ebolavirus, arburgrvirus and Lloviu cuevavirus are the members of this family, and their main reservoirs are bats from the family Pteropodidae. The present review describes the main characteristics of the Filoviruses, pathophysiology and epidemiology on the human population, with a focus on the Ebolavirus, a pathogen of great epidemiological importance responsible for the death of 13 293 people since 1976. The Ebola outbreak of 2014-2016 was the largest in history, with 28 652 cases, representing more than 90% of the total number of cases reported since the origin of the disease (31 685). The transmission of the virus between humans can happen directly, through ontaminated fluids, or indirectly, by parenteral transmission and fomites. The incubation period ranges from 2 to 21 days and the symptomatology is divided in four phases: a febrile phase with nonspecific symptoms, a phase characterized by gastrointestinal symptoms, and two with the presence of critical symptoms. Although there is no specific treatment for the Ebola virus disease, the development of potential vaccines is currently underway, and some have showed positive results in animal models. This could lead to the appearance of an effective treatment that increases the survival of infected patients, and better epidemiological control
Liver transplantation for arteriohepatic dysplasia (Alagille's syndrome)
Thirteen out of 268 children (<18 years old) underwent hepatic transplantation (OLT) for end-stage liver disease (ESLD) associated with arteriohepatic dysplasia (AHD). Seven children are alive and well with normal liver function. Six children died, four within 11 days of the operation and the other two at 4 and 10 months after the OLT. Vascular complications with associated septicemia were responsible for the deaths of three children. Two died of heart failure and circulatory collapse, secondary to pulmonary hypertension and congenital heart disease. The remaining patient died of overwhelming sepsis not associated with technical complications. Seven patients had a portoenterostomy or portocholecystostomy early in life; five of these died after the OLT. Severe cardiovascular abnormalities in some of our patients suggest that complete hemodynamic monitoring with invasive studies should be performed in all patients with AHD, especially in cases of documented hypertrophy of the right ventricle. The improved quality of life in our surviving patients confirms the validity of OLT as a treatment of choice in cases of ESLD due to AHD. © 1992 Springer-Verlag
Nonlocal impedances and the Casimir entropy at low temperatures
The problem with the temperature dependence of the Casimir force is
investigated. Specifically, the entropy behavior in the low temperature limit,
which caused debates in the literature, is analyzed. It is stressed that the
behavior of the relaxation frequency in the limit does not play a
physical role since the anomalous skin effect dominates in this range. In
contrast with the previous works, where the approximate Leontovich impedance
was used for analysis of nonlocal effects, we give description of the problem
in terms of exact nonlocal impedances. It is found that the Casimir entropy is
going to zero at only in the case when polarization does not
contribute to the classical part of the Casimir force. However, the entropy
approaching zero from the negative side that, in our opinion, cannot be
considered as thermodynamically satisfactory. The resolution of the negative
entropy problem proposed in the literature is analyzed and it is shown that it
cannot be considered as complete. The crisis with the thermal Casimir effect is
stressed.Comment: Accepted in Phys. Rev.
Computation of Casimir forces for dielectrics or intrinsic semiconductors based on the Boltzmann transport equation
The interaction between drifting carriers and traveling electromagnetic waves
is considered within the context of the classical Boltzmann transport equation
to compute the Casimir-Lifshitz force between media with small density of
charge carriers, including dielectrics and intrinsic semiconductors. We expand
upon our previous work [Phys. Rev. Lett. {\bf 101}, 163203 (2008)] and derive
in some detail the frequency-dependent reflection amplitudes in this theory and
compute the corresponding Casimir free energy for a parallel plate
configuration. We critically discuss the the issue of verification of the
Nernst theorem of thermodynamics in Casimir physics, and explicity show that
our theory satisfies that theorem. Finally, we show how the theory of drifting
carriers connects to previous computations of Casimir forces using spatial
dispersion for the material boundaries.Comment: 9 pages, 2 figures; Contribution to Proceedings of "60 Years of the
Casimir Effect", Brasilia, June 200
Casimir-like tunneling-induced electronic forces
We study the quantum forces that act between two nearby conductors due to
electronic tunneling. We derive an expression for these forces by calculating
the flux of momentum arising from the overlap of evanescent electronic fields.
Our result is written in terms of the electronic reflection amplitudes of the
conductors and it has the same structure as Lifshitz's formula for the
electromagnetically mediated Casimir forces. We evaluate the tunneling force
between two semiinfinite conductors and between two thin films separated by an
insulating gap. We discuss some applications of our results.Comment: 8 pages, 3 figs, submitted to Proc. of QFEXT'05, to be published in
J. Phys.
Causes of death after liver transplantation in children treated with cyclosporine and steroids
Two-hundred-and-twenty-seven children underwent orthotopic liver transplantation between March 1980 and March 1986. Seventy (31%) patients died during the study period. Four patients who died within 24 hours of the initial liver transplant and 5 patients who died outside of our institution were excluded from the analysis. Liver failure, related to either thrombosis of the hepatic artery, primary non-function of the graft or rejection accounted for 25 of the remaining 61 deaths. In 21 patients death was related to overwheming sepsis while 7 patients died from excessive bleeding. Eight of the deaths were due to a miscellaneous group of causes. Twenty percent of the 150 patients who received a single liver transplant died compared to a death rate of 50% in patients who underwent three transplants. Eighty-five percent of the deaths occurred within 6 months after the initial liver transplant. Liver failure was the cause in the majority of the early deaths whereas the later deaths were more likely to be due to sepsis. This detailed analysis of the causes of death after pediatric liver transplantation in a large group of patients has revealed that advances in certain areas could lead to even better results
Vacuum fluctuation force on a rigid Casimir cavity in a gravitational field
We discuss the possibility of verifying the equivalence principle for the
zero-point energy of quantum electrodynamics, by evaluating the force, produced
by vacuum fluctuations, acting on a rigid Casimir cavity in a weak
gravitational field. The resulting force has opposite direction with respect to
the gravitational acceleration; the order of magnitude for a multi-layer cavity
configuration is derived and experimental feasibility is discussed, taking into
account current technological resources.Comment: 13 pages, Latex. In the revised version, the presentation has been
improve
Causas de muerte posterior al trasplante hepatico en ninos tratados con ciclosporina y esteroides
Evaluation of multiple protein docking structures using correctly predicted pairwise subunits
<p>Abstract</p> <p>Background</p> <p>Many functionally important proteins in a cell form complexes with multiple chains. Therefore, computational prediction of multiple protein complexes is an important task in bioinformatics. In the development of multiple protein docking methods, it is important to establish a metric for evaluating prediction results in a reasonable and practical fashion. However, since there are only few works done in developing methods for multiple protein docking, there is no study that investigates how accurate structural models of multiple protein complexes should be to allow scientists to gain biological insights.</p> <p>Methods</p> <p>We generated a series of predicted models (decoys) of various accuracies by our multiple protein docking pipeline, Multi-LZerD, for three multi-chain complexes with 3, 4, and 6 chains. We analyzed the decoys in terms of the number of correctly predicted pair conformations in the decoys.</p> <p>Results and conclusion</p> <p>We found that pairs of chains with the correct mutual orientation exist even in the decoys with a large overall root mean square deviation (RMSD) to the native. Therefore, in addition to a global structure similarity measure, such as the global RMSD, the quality of models for multiple chain complexes can be better evaluated by using the local measurement, the number of chain pairs with correct mutual orientation. We termed the fraction of correctly predicted pairs (RMSD at the interface of less than 4.0Å) as <it>fpair </it>and propose to use it for evaluation of the accuracy of multiple protein docking.</p
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