6,175 research outputs found
Occupational exposure to crystalline silica and autoimmune disease.
Occupational exposure to silica dust has been examined as a possible risk factor with respect to several systemic autoimmune diseases, including scleroderma, rheumatoid arthritis, systemic lupus erythematosus, and some of the small vessel vasculitidies with renal involvement (e.g., Wegener granulomatosis). Crystalline silica, or quartz, is an abundant mineral found in sand, rock, and soil. High-level exposure to respirable silica dust can cause chronic inflammation and fibrosis in the lung and other organs. Studies of specific occupational groups with high-level silica exposure (e.g., miners) have shown increased rates of autoimmune diseases compared to the expected rates in the general population. However, some clinic- and population-based studies have not demonstrated an association between silica exposure and risk of autoimmune diseases. This lack of effect may be due to the limited statistical power of these studies to examine this association or because the lower- or moderate-level exposures that may be more common in the general population were not considered. Experimental studies demonstrate that silica can act as an adjuvant to nonspecifically enhance the immune response. This is one mechanism by which silica might be involved in the development of autoimmune diseases. Given that several different autoimmune diseases may be associated with silica dust exposure, silica dust may act to promote or accelerate disease development, requiring some other factor to break immune tolerance or initiate autoimmunity. The specific manifestation of this effect may depend on underlying differences in genetic susceptibility or other environmental exposures
Weak Values with Decoherence
The weak value of an observable is experimentally accessible by weak
measurements as theoretically analyzed by Aharonov et al. and recently
experimentally demonstrated. We introduce a weak operator associated with the
weak values and give a general framework of quantum operations to the W
operator in parallel with the Kraus representation of the completely positive
map for the density operator. The decoherence effect is also investigated in
terms of the weak measurement by a shift of a probe wave function of continuous
variable. As an application, we demonstrate how the geometric phase is affected
by the bit flip noise.Comment: 17 pages, 3 figure
The Effect of Headphone Verses Room Music on Aerobic Performance
Please refer to the pdf version of the abstract located adjacent to the title
Mechanical Control of Spin States in Spin-1 Molecules and the Underscreened Kondo Effect
The ability to make electrical contact to single molecules creates
opportunities to examine fundamental processes governing electron flow on the
smallest possible length scales. We report experiments in which we controllably
stretch individual cobalt complexes having spin S = 1, while simultaneously
measuring current flow through the molecule. The molecule's spin states and
magnetic anisotropy were manipulated in the absence of a magnetic field by
modification of the molecular symmetry. This control enabled quantitative
studies of the underscreened Kondo effect, in which conduction electrons only
partially compensate the molecular spin. Our findings demonstrate a mechanism
of spin control in single-molecule devices and establish that they can serve as
model systems for making precision tests of correlated-electron theories.Comment: main text: 5 pages, 4 figures; supporting information attached; to
appear in Science
Measurement of the Far Infrared Magneto-Conductivity Tensor of Superconducting YBaCuO Thin Films
We report measurements of the far infrared transmission of superconducting
YBaCuO thin films from 5 cm to 200 cm in
fields up to 14. A Kramers-Kronig analysis of the magneto-transmission
spectrum yields the magneto-conductivity tensor. The result shows that the
magneto-conductivity of YBaCuO is dominated by three
terms: a London term, a low frequency Lorentzian ( 3 cm) of width 10 cm and a finite frequency Lorentzian of
width 17 cm at 24 cm in the hole
cyclotron resonance active mode of circular polarization.\\Comment: Revised LaTex file (12 pages) + 4 Postscript figures, uuencoded. In
response to referees' comments, we refined the paper a lot; we encourage you
to download this revised versio
Analysis of Integrating Sphere Performance for IR Enhanced DT Layering
Absorbed IR energy can supplement the beta decay energy from DT ice to improve the driving force toward uniform layers. A significant problem with this approach has been to deliver the added IR energy with sufficient uniformity to enhance rather than destroy the uniformity of the ice layers. Computer modeling has indicated that one can achieve {approximately}1% uniformity in the angular variation of the absorbed power using an integrating sphere containing holes large enough to allow external inspection of the ice layer uniformity. The power required depends on the integrating sphere size, a 25 mm diameter sphere requires {approximately}35 mW of IR to deposit as much energy in the ice as the 50 mW/cm{sup 3}(35 pW total) received from tritium decay in DT. Power absorbed in the plastic can cause unacceptable ice-layer non-uniformities for the integrating sphere design considered here
Radial Velocities of Six OB Stars
We present new results from a radial velocity study of six bright OB stars
with little or no prior measurements. One of these, HD 45314, may be a
long-period binary, but the velocity variations of this Be star may be related
to changes in its circumstellar disk. Significant velocity variations were also
found for HD 60848 (possibly related to nonradial pulsations) and HD 61827
(related to wind variations). The other three targets, HD 46150, HD 54879, and
HD 206183, are constant velocity objects, but we note that HD 54879 has
H emission that may originate from a binary companion. We illustrate
the average red spectrum of each target.Comment: Accepted for publication in PASP July 2007 issu
Asymmetric Lineshape due to Inhomogeneous Broadening of the Crystal-Field Transitions in Mn12ac Single Crystals
The lineshape of crystal-field transitions in single crystals of Mn12ac
molecular magnets is determined by the magnetic history. The absorption lines
are symmetric and Gaussian for the non-magnetized state obtained by zero-field
cooling (zfc). In the magnetized state which is reached when the sample is
cooled in a magnetic field (fc), however, they are asymmetric even in the
absence of an external magnetic field. These observations are quantitatively
explained by inhomogeneous symmetrical (Gaussian) broadening of the
crystal-field transitions combined with a contribution of off-diagonal
components of the magnetic susceptibility to the effective magnetic
permeability.Comment: 4 pages, 3 figure
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Maintaining scale as a realiable computational system for criticality safety analysis
Accurate and reliable computational methods are essential for nuclear criticality safety analyses. The SCALE (Standardized Computer Analyses for Licensing Evaluation) computer code system was originally developed at Oak Ridge National Laboratory (ORNL) to enable users to easily set up and perform criticality safety analyses, as well as shielding, depletion, and heat transfer analyses. Over the fifteen-year life of SCALE, the mainstay of the system has been the criticality safety analysis sequences that have featured the KENO-IV and KENO-V.A Monte Carlo codes and the XSDRNPM one-dimensional discrete-ordinates code. The criticality safety analysis sequences provide automated material and problem-dependent resonance processing for each criticality calculation. This report details configuration management which is essential because SCALE consists of more than 25 computer codes (referred to as modules) that share libraries of commonly used subroutines. Changes to a single subroutine in some cases affect almost every module in SCALE! Controlled access to program source and executables and accurate documentation of modifications are essential to maintaining SCALE as a reliable code system. The modules and subroutine libraries in SCALE are programmed by a staff of approximately ten Code Managers. The SCALE Software Coordinator maintains the SCALE system and is the only person who modifies the production source, executables, and data libraries. All modifications must be authorized by the SCALE Project Leader prior to implementation
Composite vortex model of the electrodynamics of high- superconductor
We propose a phenomenological model of vortex dynamics in which the vortex is
taken as a composite object made of two components: the vortex current which is
massless and driven by the Lorentz force, and the vortex core which is massive
and driven by the Magnus force. By combining the characteristics of the
Gittleman-Rosenblum model (Phys. Rev. Lett. {\bf 16}, 734 (1966)) and Hsu's
theory of vortex dynamics (Physica {\bf C 213},305 (1993)), the model provides
a good description of recent far infrared measurements of the
magneto-conductivity tensor of superconducting YBaCuO
films from 5 cm to 200 cm.Comment: LaTex file (12 pages) + 3 Postscript figures, uuencoded. More
information on this paper, please check
http://www.wam.umd.edu/~lihn/newmodel
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