922 research outputs found
Influence of shear flow on vesicles near a wall: a numerical study
We describe the dynamics of three-dimensional fluid vesicles in steady shear
flow in the vicinity of a wall. This is analyzed numerically at low Reynolds
numbers using a boundary element method. The area-incompressible vesicle
exhibits bending elasticity. Forces due to adhesion or gravity oppose the
hydrodynamic lift force driving the vesicle away from a wall. We investigate
three cases. First, a neutrally buoyant vesicle is placed in the vicinity of a
wall which acts only as a geometrical constraint. We find that the lift
velocity is linearly proportional to shear rate and decreases with increasing
distance between the vesicle and the wall. Second, with a vesicle filled with a
denser fluid, we find a stationary hovering state. We present an estimate of
the viscous lift force which seems to agree with recent experiments of Lorz et
al. [Europhys. Lett., vol. 51, 468 (2000)]. Third, if the wall exerts an
additional adhesive force, we investigate the dynamical unbinding transition
which occurs at an adhesion strength linearly proportional to the shear rate.Comment: 17 pages (incl. 10 figures), RevTeX (figures in PostScript
Relating the Lorentzian and exponential: Fermi's approximation,the Fourier transform and causality
The Fourier transform is often used to connect the Lorentzian energy
distribution for resonance scattering to the exponential time dependence for
decaying states. However, to apply the Fourier transform, one has to bend the
rules of standard quantum mechanics; the Lorentzian energy distribution must be
extended to the full real axis instead of being bounded from
below (``Fermi's approximation''). Then the Fourier transform
of the extended Lorentzian becomes the exponential, but only for times , a time asymmetry which is in conflict with the unitary group time evolution
of standard quantum mechanics. Extending the Fourier transform from
distributions to generalized vectors, we are led to Gamow kets, which possess a
Lorentzian energy distribution with and have exponential
time evolution for only. This leads to probability predictions
that do not violate causality.Comment: 23 pages, no figures, accepted by Phys. Rev.
Chiral bosonization for non-commutative fields
A model of chiral bosons on a non-commutative field space is constructed and
new generalized bosonization (fermionization) rules for these fields are given.
The conformal structure of the theory is characterized by a level of the
Kac-Moody algebra equal to where is the
non-commutativity parameter and chiral bosons living in a non-commutative
fields space are described by a rational conformal field theory with the
central charge of the Virasoro algebra equal to 1. The non-commutative chiral
bosons are shown to correspond to a free fermion moving with a speed equal to where is the speed of light. Lorentz
invariance remains intact if is rescaled by . The
dispersion relation for bosons and fermions, in this case, is given by .Comment: 16 pages, JHEP style, version published in JHE
The STAR Time Projection Chamber: A Unique Tool for Studying High Multiplicity Events at RHIC
The STAR Time Projection Chamber (TPC) is used to record collisions at the
Relativistic Heavy Ion Collider (RHIC). The TPC is the central element in a
suite of detectors that surrounds the interaction vertex. The TPC provides
complete coverage around the beam-line, and provides complete tracking for
charged particles within +- 1.8 units of pseudo-rapidity of the center-of-mass
frame. Charged particles with momenta greater than 100 MeV/c are recorded.
Multiplicities in excess of 3,000 tracks per event are routinely reconstructed
in the software. The TPC measures 4 m in diameter by 4.2 m long, making it the
largest TPC in the world.Comment: 28 pages, 11 figure
The use of the antifungal agent miconazole as an inhibitor of Blastocystis hominis growth in Entamoeba histolytica/E. dispar cultures
Driving a motor vehicle and psychogenic nonepileptic seizures: ILAE Report by the Task Force on Psychogenic Nonepileptic Seizures
Objectives
This International League Against Epilepsy (ILAE) Report: (a) summarizes the literature about âdriving and psychogenic nonepileptic seizures (PNES)â; (b) presents the views of international experts; and (c) proposes an approach to assessing the ability of persons with PNES (PwPNES) to drive.
Methods
Phase 1: Systematic literature review. Phase 2: Collection of international expert opinion using SurveyMonkeyÂź. Experts included the members of the ILAE PNES Task Force and individuals with relevant publications since 2000. Phase 3: Joint analysis of the findings and refinement of conclusions by all participants using email. As an ILAE Report, the resulting text was reviewed by the Psychiatry Commission, the ILAE Task Force on Driving Guidelines, and Executive Committee.
Results
Eight studies identified by the systematic review process failed to provide a firm evidence base for PNESârelated driving regulations, but suggest that most health professionals think restrictions are appropriate. Twentyâsix experts responded to the survey. Most held the view that decisions about driving privileges should consider individual patient and PNES characteristics and take account of whether permits are sought for private or commercial driving. Most felt that those with active PNES should not be allowed to drive unless certain criteria were met and that PNES should be thought of as âactiveâ if the last psychogenic seizure had occurred within 6 months.
Significance
Recommendations on whether PwPNES can drive should be made at the individual patient level. Until future research has determined the risk of accidents in PwPNES a proposed algorithm may guide decisions about driving advice
Relationship between CD4 T cell turnover, cellular differentiation and HIV persistence during ART
The precise role of CD4 T cell turnover in maintaining HIV persistence during antiretroviral therapy (ART) has not yet been well characterized. In resting CD4 T cell subpopulations from 24 HIV-infected ART-suppressed and 6 HIV-uninfected individuals, we directly measured cellular turnover by heavy water labeling, HIV reservoir size by integrated HIV-DNA (intDNA) and cell-associated HIV-RNA (caRNA), and HIV reservoir clonality by proviral integration site sequencing. Compared to HIV-negatives, ART-suppressed individuals had similar fractional replacement rates in all subpopulations, but lower absolute proliferation rates of all subpopulations other than effector memory (TEM) cells, and lower plasma IL-7 levels (p = 0.0004). Median CD4 T cell half-lives decreased with cell differentiation from naĂŻve to TEM cells (3 years to 3 months, p<0.001). TEM had the fastest replacement rates, were most highly enriched for intDNA and caRNA, and contained the most clonal proviral expansion. Clonal proviruses detected in less mature subpopulations were more expanded in TEM, suggesting that they were maintained through cell differentiation. Earlier ART initiation was associated with lower levels of intDNA, caRNA and fractional replacement rates. In conclusion, circulating integrated HIV proviruses appear to be maintained both by slow turnover of immature CD4 subpopulations, and by clonal expansion as well as cell differentiation into effector cells with faster replacement rates
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