1,689 research outputs found
Thermomechanical effects in uniformly aligned dye-doped nematic liquid crystals
We show theoretically that thermomechanical effects in dye-doped nematic
liquid crystals when illuminated by laser beams, can become important and lead
to molecular reorientation at intensities substantially lower than that needed
for optical Fr\'eedericksz transition. We propose a 1D model that assumes
homogenous intensity distribution in the plane of the layer and is capable to
describe such a thermally induced threshold lowering. We consider a particular
geometry, with a linearly polarized light incident perpendicularly on a layer
of homeotropically aligned dye-doped nematics
Magnetotransport Properties of Antiferromagnetic YBa_2Cu_3O_6.25 Single Crystals
In-plane and out-of-plane magnetoresistivities (MR) of antiferromagnetic
YBa_2Cu_3O_6.25 single crystals were measured in magnetic fields H applied
along the (ab) plane. In-plane MR is a superposition of two components: The
first component is strongly in-plane anisotropic, changing sign from negative
when H is parallel to the electrical current I to positive when H is
perpendicular to I. The second component is positive, quadratic in H, and
isotropic in the (ab)-plane. The out-of-plane MR displays a fourfold symmetry
upon in-plane rotation of the magnetic field, with maxima along the easy axes
of antiferromagnetic spin ordering and minima along unfavorable directions of
spin orientation (45 degrees from the Cu-O-Cu bonds).Comment: 8 pages, 4 figure
THE EFFECT OF CMV INFECTION ON PROGRESSION OF HUMAN-IMMUNODEFICIENCY-VIRUS DISEASE IN A COHORT OF HEMOPHILIC MEN FOLLOWED FOR UP TO 13 YEARS FROM SEROCONVERSION
The effect of prior infection with cytomegalovirus (CMV) on progression of HIV disease in a cohort of 111 men with haemophilia was studied after 13 years followup. The relative hazards associated with CMV positivity on progression to AIDS, death and a CD4 count of 0.05 x 10(9)/l were 2.28, 2.42 and 2.34, respectively. CMV seropositive patients were significantly older than the seronegative and this was controlled for by using a Cox proportional hazards model. The relative hazards for the three endpoints decreased to 1.89, 1.82 and 1.93 respectively and were marginally non-significant (P = 0.05, 0.08 and 0.08 for the three endpoints respectively). We conclude that this cohort continues to show evidence of a 'co-factor' effect associated with prior infection with CMV which is confounded by age but not completely explained by age differences. The potential biological significance of these results is discussed in the context of recent controlled clinical trials which show a survival benefit from long-term high-dose acyclovir, a drug with activity in vivo against CMV and other herpesviruses
Polymeric alkali fullerides are stable in air
Infrared transmission, electron spin resonance, and X-ray diffraction
measurements show unambiguously that RbC and KC are stable in
air, in contrast to RbC which decomposes rapidly upon exposure.
The specimens studied transform into pure C and other byproducts when
heated above 100\dd C, approximately the temperature of the orthorhombic-fcc
phase transition. The stability of these compounds raises the possibility of
applying them as protective layers for the superconducting fullerides.Comment: Scheduled for publication in Appl. Phys. Lett. 66, 20 Feb. 1995,
typeset in REVTEX v3.0 in LaTeX. Postscript file including all figures is
available on WWW http://insti.physics.sunysb.edu/~mmartin/ under my list of
publications, or will be e-mailed by request
The Use of Expert Judgement Methods for Deriving Accident Probabilities in Aviation
Improving safety has always been the top interest in the aviation industry. The outcomes of safety and risk analyses have become much more thorough and sophisticated. They have become an industry standard of safety investigations in many airlines nowadays. In the past, airlines were much more limited in answering the questions about hazardous situations, accident probabilities, and accident rates. Airlines try hard to cope with stricter safety standards. The objective of this paper is to find out and quantify the extent of the expert judgment in helping airlines in the evaluation of the Flight Data Monitoring (FDM) events. On top of that, the paper reveals the method for a careful choice of experts, so that their estimations will maximize the potential of an accurate and useful outcome. Also, the paper provides details of implementation of the classical model into this research, then continues with the calculations and visualization of the outcomes. The outcomes are probability distributions per each aircraft type, then per IATA accident type and finally per FDM event
Statistical Origin of Quantum Mechanics
The one particle quantum mechanics is considered in the frame of a N-body
classical kinetics in the phase space. Within this framework, the scenario of a
subquantum structure for the quantum particle, emerges naturally, providing an
ontological support to the orthodox quantum mechanics. This approach to quantum
mechanics, constitutes a deductive and direct method which, in a
self-consistent scheme of a classical kinetics, allows us: i) to obtain the
probabilistic nature of the quantum description and to interpret the wave
function according to the Copenhagen school; ii) to derive the quantum
potential and then the Schr\"odinger equation; iii) to calculate the values of
the physical observables as mean values of the associated quantum operators;
iv) to obtain the Heisenberg uncertainty principle.Comment: Accepted for publication in Physica
Pattern forming instability induced by light in pure and dye-doped nematic liquid crystals
We study theoretically the instabilities induced by a linearly polarized
ordinary light wave incident at a small oblique angle on a thin layer of
homeotropically oriented nematic liquid crystal with special emphasis on the
dye-doped case. The spatially periodic Hopf bifurcation that occurs as the
secondary instability after the stationary Freedericksz transition is analyzed.Comment: 8 pages, 7 figures, LaTeX, accepted to Phys. Rev.
Magnetic fullerenes inside single-wall carbon nanotubes
C59N magnetic fullerenes were formed inside single-wall carbon nanotubes by
vacuum annealing functionalized C59N molecules encapsulated inside the tubes. A
hindered, anisotropic rotation of C59N was deduced from the temperature
dependence of the electron spin resonance spectra near room temperature.
Shortening of spin-lattice relaxation time, T_1, of C59N indicates a reversible
charge transfer toward the host nanotubes above K. Bound C59N-C60
heterodimers are formed at lower temperatures when C60 is co-encapsulated with
the functionalized C59N. In the 10-300 K range, T_1 of the heterodimer shows a
relaxation dominated by the conduction electrons on the nanotubes
Janossy Densities of Coupled Random Matrices
We explicitly calculate Janossy densities for a special class of finite
determinantal point processes with several types of particles introduced by
Pr\"ahofer and Spohn and, in the full generality, by Johansson in connection
with the analysis of polynuclear growth models. The results of our paper
generalize the theorem we proved earlier with Borodin about the Janossy
densities in biorthogonal ensembles. In particular, our results can be applied
to coupled random matrices.Comment: We revised the introduction and added a couple of new reference
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