2,955 research outputs found
T Cells Use Rafts for Survival
T cell homeostasis must be tightly controlled. In this issue of Immunity, Cho et al. (2010) describe results that begin to define the roles of the T cell receptor, self-peptide-MHC ligands, cytokines, and membrane rafts in this dynamic process
Ambipolar Diffusion-Mediated Thermal Fronts in the Neutral ISM
In a thermally bistable medium, cold, dense gas is separated from warm,
rareified gas by thin phase transition layers, or fronts, in which heating,
radiative cooling, thermal conduction, and convection of material are balanced.
We calculate the steady-state structure of such fronts in the presence of
magnetic fields, including the processes of ion-neutral drift and ion-neutral
frictional heating. We find that ambipolar diffusion efficiently transports the
magnetic field across the fronts, leading to a flat magnetic field strength
profile. The thermal profiles of such fronts are not significantly different
from those of unmagnetized fronts. The near uniformity of the magnetic field
strength across a front is consistent with the flat field strength-gas density
relation that is observed in diffuse interstellar gas.Comment: 17 pages, 12 figures, 1 table, accepted for publication in Ap
Deconstructing therapy outcome measurement with Rasch analysis of a measure of general clinical distress: the Symptom Checklist-90-Revised
Rasch analysis was used to illustrate the usefulness of item-level analyses for evaluating a common therapy outcome measure of general clinical distress, the Symptom Checklist-90-Revised (SCL-90-R; Derogatis, 1994). Using complementary therapy research samples, the instrument's 5-point rating scale was found to exceed clients' ability to make reliable discriminations and could be improved by collapsing it into a 3-point version (combining scale points 1 with 2 and 3 with 4). This revision, in addition to removing 3 misfitting items, increased person separation from 4.90 to 5.07 and item separation from 7.76 to 8.52 (resulting in alphas of .96 and .99, respectively). Some SCL-90-R subscales had low internal consistency reliabilities; SCL-90-R items can be used to define one factor of general clinical distress that is generally stable across both samples, with two small residual factors
Obesity Is A Modifier of Autonomic Cardiac Responses to Fine Metal Particulates
Background: Increasing evidence suggests that obesity may impart greater susceptibility to adverse effects of air pollution. Particulate matter, especially PM (particulate matter with aero-dynamic diameter ≤2.5 μm), is associated with increased cardiac events and reduction of heart rate variability (HRV).Objectives Our goal was to investigate whether particle-mediated autonomic modulation is aggravated in obese individuals.Methods We examined PM-mediated acute effects on HRV and heart rate (HR) using 10 24-hr and 13 48-hr ambulatory electrocardiogram recordings collected from 18 boilermakers (39.5 ± 9.1 years of age) exposed to high levels of metal particulates. Average HR and 5-min HRV [SDNN: standard deviation of normal-to-normal intervals (NN); rMSSD: square-root of mean squared-differences of successive NN intervals; HF: high-frequency power 0.15–0.4 Hz] and personal PM exposures were continuously monitored. Subjects with body mass index ≥ 30 kg/m were classified as obese. Mixed-effect models were used for statistical analyses. Results: Half (50%) of the study subjects were obese. After adjustment for confounders, each 1-mg/m increase in 4-hr moving average PM was associated with HR increase of 5.9 bpm [95% confidence interval (CI), 4.2 to 7.7] and with 5-min HRV reduction by 6.5% (95% CI, 1.9 to 11.3%) for SDNN, 1.7% (95% CI, –4.9 to 8.4%) for rMSSD, and 8.8% (95% CI, –3.8 to 21.3%) for HF. Obese individuals had greater PM-mediated HRV reductions (2- to 3-fold differences) than nonobese individuals, and had more PM-mediated HR increases (9-bpm vs. 4-bpm increase in HR for each 1-mg/m increase in PM; p < 0.001). Conclusions: Our study revealed greater autonomic cardiac responses to metal particulates in obese workers, supporting the hypothesis that obesity may impart greater susceptibility to acute cardiovascular effects of fine particles
MHD Stability of ISM Phase Transition Layers I: Magnetic Field Orthogonal to Front
We consider the scenario of a magnetic field orthogonal to a front separating
two media of different temperatures and densities, such as cold and warm
interstellar gas, in a 2-D plane-parallel geometry. A linear stability analysis
is performed to assess the behavior of both evaporation and condensation fronts
when subject to incompressible, corrugational perturbations with wavelengths
larger than the thickness of the front. We discuss the behavior of fronts in
both super-Alfvenic and sub-Alfvenic flows. Since the propagation speed of
fronts is slow in the ISM, it is the sub-Alfvenic regime that is relevant, and
magnetic fields are a significant influence on front dynamics. In this case we
find that evaporation fronts, which are unstable in the hydrodynamic regime,
are stabilized. Condensation fronts are unstable, but for parameters typical of
the neutral ISM the growth rates are so slow that steady state fronts are
effectively stable. However, the instability may become important if
condensation proceeds at a sufficiently fast rate. This paper is the first in a
series exploring the linear and nonlinear effects of magnetic field strength
and orientation on the corrugational instability, with the ultimate goal of
addressing outstanding questions about small-scale ISM structure.Comment: 18 pages, 3 figures, and 2 tables. To be published in The
Astrophysical Journa
Spin Excitations in BaFe1.84Co0.16As2 Superconductor Observed by Inelastic Neutron Scattering
Superconductivity appears to compete against the spin-density-wave in Fe
pnictides. However, optimally cobalt doped samples show a quasi-two-dimensional
spin excitation centered at the (0.5, 0.5, L) wavevector, "the spin resonance
peak", that is strongly tied to the onset of superconductivity. By inelastic
neutron scattering on single crystals we show the similarities and differences
of the spin excitations in BaFe1.84Co0.16As2, with respect to the spin
excitations in the high-temperature superconducting cuprates. As in the
cuprates the resonance occurs as an enhancement to a part of the spin
excitation spectrum which extends to higher energy transfer and higher
temperature. However, unlike in the cuprates, the resonance peak in this
compound is asymmetric in energy.Comment: 12 pages, 6 figures; PACS # 74.70.-b, 74.20.Mn, 78.70.Nx, 74.25.Ha;
corrected discussion of figures in tex
Regeneración de las células ciliadas auditivas: Un tratamiento potencial para los problemas de oído en el horizonte
Hearing requires good health of the hair cells to ensure that the sound is detected and processed correctly. They degenerate and die due to age or exposition to high intensity sound, among other causes, and usually they do not regenerate. Some research results about possible regeneration of cochlear hair cells that suggest the possibility of treatment for hearing impairment due to this disease are presented in this paper..La audición requiere de la buena salud de las células ciliadas (vello) para garantizar que el sonido se detecte y procese correctamente. Éstas se degeneran y mueren con la edad o por la exposición a sonido intenso, entre otras causas, y normalmente no se regeneran. Se presentan algunos resultados de la investigación sobre la posible regeneración de las células ciliadas cocleares que sugieren que existe la posibilidad de un tratamiento para la discapacidad auditiva debida a esta enfermedad
Interaction of Streptavidin-Based Peptide-MHC Oligomers (Tetramers) with Cell-Surface T Cell Receptors
he binding of oligomeric peptide–MHC (pMHC) complexes to cell surface TCR can be considered to approximate TCR–pMHC interactions at cell-cell interfaces. In this study, we analyzed the equilibrium binding of streptavidin-based pMHC oligomers (tetramers) and their dissociation kinetics from CD8[superscript pos] T cells from 2C-TCR transgenic mice and from T cell hybridomas that expressed the 2C TCR or a high-affinity mutant (m33) of this TCR. Our results show that the tetramers did not come close to saturating cell-surface TCR (binding only 10–30% of cell-surface receptors), as is generally assumed in deriving affinity values (K[subscript D]), in part because of dissociative losses from tetramer-stained cells. Guided by a kinetic model, the oligomer dissociation rate and equilibrium constants were seen to depend not only on monovalent association and dissociation rates (k[subscript off] and k[subscript on]), but also on a multivalent association rate (μ) and TCR cell-surface density. Our results suggest that dissociation rates could account for the recently described surprisingly high frequency of tetramer-negative, functionally competent T cells in some T cell responses.National Institutes of Health (U.S.) (Grant P01 CA097296)National Institutes of Health (U.S.) (Grant R01 GM55767)National Institutes of Health (U.S.) (Grant PO1-AI071195)National Institutes of Health (U.S.). Pioneer Awar
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