38,788 research outputs found
Atherosusceptible Shear Stress Activates Endoplasmic Reticulum Stress to Promote Endothelial Inflammation.
Atherosclerosis impacts arteries where disturbed blood flow renders the endothelium susceptible to inflammation. Cytokine activation of endothelial cells (EC) upregulates VCAM-1 receptors that target monocyte recruitment to atherosusceptible regions. Endoplasmic reticulum (ER) stress elicits EC dysregulation in metabolic syndrome. We hypothesized that ER plays a central role in mechanosensing of atherosusceptible shear stress (SS) by signaling enhanced inflammation. Aortic EC were stimulated with low-dose TNFα (0.3 ng/ml) in a microfluidic channel that produced a linear SS gradient over a 20mm field ranging from 0-16 dynes/cm2. High-resolution imaging of immunofluorescence along the monolayer provided a continuous spatial metric of EC orientation, markers of ER stress, VCAM-1 and ICAM-1 expression, and monocyte recruitment. VCAM-1 peaked at 2 dynes/cm2 and decreased to below static TNFα-stimulated levels at atheroprotective-SS of 12 dynes/cm2, whereas ICAM-1 rose to a maximum in parallel with SS. ER expansion and activation of the unfolded protein response also peaked at 2 dynes/cm2, where IRF-1-regulated VCAM-1 expression and monocyte recruitment also rose to a maximum. Silencing of PECAM-1 or key ER stress genes abrogated SS regulation of VCAM-1 transcription and monocyte recruitment. We report a novel role for ER stress in mechanoregulation at arterial regions of atherosusceptible-SS inflamed by low-dose TNFα
Meteorological satellite data: A tool to describe the health of the world's agriculture
Local area coverage data acquired aboard the TIROS-N satellite family by the advanced very high resolution radiometer systems was examined to determine the agricultural information current. Albedo differences between channel 2 and channel 1 of the advanced very high resolution radiometer LAC (called EVI) are shown to be closely correlated to the Ashburn vegetative index produced from LANDSAT multispectral scanner data which have been shown to vary in response to "greenness", soil moisture, and crop production. The statistical correlation between the EVI and the Ashburn Vegetative Index (+ or - 1 deg) is 0.86
Spontaneous creation of non-zero angular momentum modes in tunnel-coupled two-dimensional degenerate Bose gases
We investigate the dynamics of two tunnel-coupled two-dimensional degenerate
Bose gases. The reduced dimensionality of the clouds enables us to excite
specific angular momentum modes by tuning the coupling strength, thereby
creating striking patterns in the atom density profile. The extreme sensitivity
of the system to the coupling and initial phase difference results in a rich
variety of subsequent dynamics, including vortex production, complex
oscillations in relative atom number and chiral symmetry breaking due to
counter-rotation of the two clouds.Comment: 7 pages, 5 figure
Transmission and Reflection of Bose-Einstein Condensates Incident on a Gaussian Potential Barrier
We investigate how Bose-Einstein condensates, whose initial state is either
irrotational or contains a single vortex, scatter off a one-dimensional
Gaussian potential barrier. We find that for low atom densities the vortex
structure within the condensate is maintained during scattering, whereas at
medium and high densities, multiple additional vortices can be created by the
scattering process, resulting in complex dynamics and disruption of the atom
cloud. This disruption originates from two different mechanisms associated
respectively with the initial rotation of the atom cloud and the interference
between the incident and reflected matter waves. We investigate how the
reflection probability depends on the vorticity of the initial state and on the
incident velocity of the Bose-Einstein condensate. To interpret our results, we
derive a general analytical expression for the reflection coefficient of a
rotating Bose-Einstein condensate that scatters off a spatially-varying
one-dimensional potential.Comment: 9 pages, 9 figure
Negative Differential Resistivity and Positive Temperature Coefficient of Resistivity effect in the diffusion limited current of ferroelectric thin film capacitors
We present a model for the leakage current in ferroelectric thin- film
capacitors which explains two of the observed phenomena that have escaped
satisfactory explanation, i.e. the occurrence of either a plateau or negative
differential resistivity at low voltages, and the observation of a Positive
Temperature Coefficient of Resistivity (PTCR) effect in certain samples in the
high-voltage regime. The leakage current is modelled by considering a
diffusion-limited current process, which in the high-voltage regime recovers
the diffusion-limited Schottky relationship of Simmons already shown to be
applicable in these systems
Impact of layer defects in ferroelectric thin films
Based on a modified Ising model in a transverse field we demonstrate that
defect layers in ferroelectric thin films, such as layers with impurities,
vacancies or dislocations, are able to induce a strong increase or decrease of
the polarization depending on the variation of the exchange interaction within
the defect layers. A Green's function technique enables us to calculate the
polarization, the excitation energy and the critical temperature of the
material with structural defects. Numerically we find the polarization as
function of temperature, film thickness and the interaction strengths between
the layers. The theoretical results are in reasonable accordance to
experimental datas of different ferroelectric thin films.Comment: 17 pages, 8 figure
A Spectroscopic Survey of Subarcsecond Binaries in the Taurus-Auriga Dark Cloud with the Hubble Space Telescope
We report the results of a spectroscopic survey of 20 close T Tauri binaries
in the Taurus-Auriga dark cloud where the separations between primaries and
their secondaries are less than the typical size of a circumstellar disk around
a young star. Analysis of low-resolution and medium-resolution STIS spectra
yields the stellar luminosities, reddenings, ages, masses, mass accretion
rates, IR excesses, and emission line luminosities for each star in each pair.
We examine the ability of IR color excesses, H-alpha equivalent widths, [O I]
emission, and veiling to distinguish between weak emission and classical T
Tauri stars. Four pairs have one cTTs and one wTTs; the cTTs is the primary in
three of these systems. This frequency of mixed pairs among the close T Tauri
binaries is similar to the frequency of mixed pairs in wider young binaries.
Extinctions within pairs are usually similar; however, the secondary is more
heavily reddened than the primary in some systems, where it may be viewed
through the primary's disk. Mass accretion rates of primaries and secondaries
are strongly correlated, and H-alpha luminosities, IR excesses, and ages also
correlate within pairs. Primaries tend to have somewhat larger accretion rates
than their secondaries do, and are typically slightly older than their
secondaries according to three different sets of modern pre-main-sequence
evolutionary tracks. Age differences for XZ Tau and FS Tau, systems embedded in
reflection nebulae, are striking; the secondary in each pair is less massive
but more luminous than the primary. The stellar masses of the UY Aur and GG Tau
binaries measured from their rotating molecular disks are about 30% larger than
the masses inferred from the spectra and evolutionary tracks
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