4,069 research outputs found
Fluids of hard ellipsoids: Phase diagram including a nematic instability from Percus-Yevick theory
An important aspect of molecular fluids is the relation between orientation
and translation parts of the two-particle correlations. Especially the detailed
knowledge of the influence of orientation correlations is needed to explain and
calculate in detail the occurrence of a nematic phase.
The simplest model system which shows both orientation and translation
correlations is a system of hard ellipsoids. We investigate an isotropic fluid
formed of hard ellipsoids with Percus-Yevick theory.
Solving the Percus-Yevick equations self-consistently in the high density
regime gives a clear criterion for a nematic instability. We calculate in
detail the equilibrium phase diagram for a fluid of hard ellipsoids of
revolution. Our results compare well with Monte Carlo Simulations and density
functional theory.Comment: 7 pages including 4 figure
Bioactive compounds and their impact on protein modification in human cells
Reactive oxygen species (ROS) represent a group of molecules with a signaling role that are involved in regulating human cell proliferation and differentiation. Increased ROS concentrations are often associated with the local nonspecific oxidation of biological macromolecules, especially proteins and lipids. Free radicals, in general, may randomly damage protein molecules through the formation of protein-centered radicals as intermediates that, in turn, decay into several end oxidation products. Malondialdehyde (MDA), a marker of free-radical-mediated lipid oxidation and cell membrane damage, forms adducts with proteins in a nonspecific manner, leading to the loss of their function. In our study, we utilized U-937 cells as a model system to unveil the effect of four selected bioactive compounds (chlorogenic acid, oleuropein, tomatine, and tyrosol) to reduce oxidative stress associated with adduct formation in differentiating cells. The purity of the compounds under study was confirmed by an HPLC analysis. The cellular integrity and changes in the morphology of differentiated U-937 cells were confirmed with confocal microscopy, and no significant toxicity was found in the presence of bioactive compounds. From the Western blot analysis, a reduction in the MDA adduct formation was observed in cells treated with compounds that underlaid the beneficial effects of the compounds tested
On the drawdown of completely asymmetric Levy processes
The {\em drawdown} process of a completely asymmetric L\'{e}vy process
is equal to reflected at its running supremum : . In this paper we explicitly express in terms of the scale function and the
L\'{e}vy measure of the law of the sextuple of the first-passage time of
over the level , the time of the last supremum of
prior to , the infimum \unl X_{\tau_a} and supremum \ovl
X_{\tau_a} of at and the undershoot and
overshoot of at . As application we obtain explicit
expressions for the laws of a number of functionals of drawdowns and rallies in
a completely asymmetric exponential L\'{e}vy model.Comment: applications added, 26 pages, 3 figures, to appear in SP
Design, Implementation and First Measurements with the Medipix Neutron Camera in CMS
The Medipix detector is the first device dedicated to measuring mixed-field
radiation in the CMS cavern and able to distinguish between different particle
types. Medipix2-MXR chips bump bonded to silicon sensors with various neutron
conversion layers developed by the IEAP CTU in Prague were successfully
installed for the 2008 LHC start-up in the CMS experimental and services
caverns to measure the flux of various particle types, in particular neutrons.
They have operated almost continuously during the 2010 run period, and the
results shown here are from the proton run between the beginning of July and
the end of October 2010. Clear signals are seen and different particle types
have been observed during regular LHC luminosity running, and an agreement in
the measured flux rate is found with the simulations. These initial results are
promising, and indicate that these devices have the potential for further and
future LHC and high energy physics applications as radiation monitoring devices
for mixed field environments, including neutron flux monitoring. Further
extensions are foreseen in the near future to increase the performance of the
detector and its coverage for monitoring in CMS.Comment: 15 pages, 16 figures, submitted to JINS
Dark Matter Spin-Dependent Limits for WIMP Interactions on 19-F by PICASSO
The PICASSO experiment at SNOLAB reports new results for spin-dependent WIMP
interactions on F using the superheated droplet technique. A new
generation of detectors and new features which enable background discrimination
via the rejection of non-particle induced events are described. First results
are presented for a subset of two detectors with target masses of F of
65 g and 69 g respectively and a total exposure of 13.75 0.48 kgd. No
dark matter signal was found and for WIMP masses around 24 GeV/c new limits
have been obtained on the spin-dependent cross section on F of
= 13.9 pb (90% C.L.) which can be converted into cross section
limits on protons and neutrons of = 0.16 pb and = 2.60 pb
respectively (90% C.L). The obtained limits on protons restrict recent
interpretations of the DAMA/LIBRA annual modulations in terms of spin-dependent
interactions.Comment: Revised version, accepted for publication in Phys. Lett. B, 20 pages,
7 figure
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