1,010 research outputs found
SIV Infection Induces Accumulation of Plasmacytoid Dendritic Cells in the Gut Mucosa
Multiple studies suggest that plasmacytoid dendritic cells (pDCs) are depleted and dysfunctional during human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) infection, but little is known about pDCs in the gut—the primary site of virus replication. Here, we show that during SIV infection, pDCs were reduced 3-fold in the circulation and significantly upregulated the gut-homing marker α4β7, but were increased 4-fold in rectal biopsies of infected compared to naive macaques. These data revise the understanding of pDC immunobiology during SIV infection, indicating that pDCs are not necessarily depleted, but instead may traffic to and accumulate in the gut mucosa
SIV Infection Induces Accumulation of Plasmacytoid Dendritic Cells in the Gut Mucosa
Multiple studies suggest that plasmacytoid dendritic cells (pDCs) are depleted and dysfunctional during human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) infection, but little is known about pDCs in the gut—the primary site of virus replication. Here, we show that during SIV infection, pDCs were reduced 3-fold in the circulation and significantly upregulated the gut-homing marker α4β7, but were increased 4-fold in rectal biopsies of infected compared to naive macaques. These data revise the understanding of pDC immunobiology during SIV infection, indicating that pDCs are not necessarily depleted, but instead may traffic to and accumulate in the gut mucosa
The influence of mobile copper ions on the glass-like thermal conductivity of copper-rich tetrahedrites
Tetrahedrites are promising p-type thermoelectric materials for energy recovery. We present here the first investigation of the structure and thermoelectric properties of copper-rich tetrahedrites, Cu12+xSb4S13 (0 0 consist of two tetrahedrite phases. In-situ neutron diffraction data demonstrate that on heating, the two tetrahedrite phases coalesce into a single tetrahedrite phase at temperatures between 493 and 553 K, and that this transition shows marked hysteresis on cooling. Our structural data indicate that copper ions become mobile above 393 K. Marked changes in the temperature dependence of the electrical and thermal transport properties of the copper-rich phases occur at the onset of copper mobility. Excess copper leads to a significant reduction in the total thermal conductivity, which for the nominal composition Cu14Sb4S13 reaches a value as low as 0.44 W m-1K-1 at room temperature, and to thermoelectric properties consistent with phonon liquid electron crystal (PLEC) behaviour
Solid Friction from stick-slip to pinning and aging
We review the present state of understanding of solid friction at low
velocities and for systems with negligibly small wear effects.
We first analyze in detail the behavior of friction at interfaces between
wacroscopic hard rough solids, whose main dynamical features are well described
by the Rice-Ruina rate and state dependent constitutive law. We show that it
results from two combined effects : (i) the threshold rheology of
nanometer-thick junctions jammed under confinement into a soft glassy structure
(ii) geometric aging, i.e. slow growth of the real arrea of contact via
asperity creep interrupted by sliding.
Closer analysis leads to identifying a second aging-rejuvenation process, at
work within the junctions themselves. We compare the effects of structural
aging at such multicontact, very highly confined, interfaces with those met
under different confinement levels, namely boundary lubricated contacts and
extended adhesive interfaces involving soft materials (hydrogels, elastomers).
This leads us to propose a classification of frictional junctions in terms of
the relative importance of jamming and adsoprtion-induced metastability.Comment: 28 page
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The accessible chromatin landscape of the human genome
DNaseI hypersensitive sites (DHSs) are markers of regulatory DNA and have underpinned the discovery of all classes of cis-regulatory elements including enhancers, promoters, insulators, silencers, and locus control regions. Here we present the first extensive map of human DHSs identified through genome-wide profiling in 125 diverse cell and tissue types. We identify ~2.9 million DHSs that encompass virtually all known experimentally-validated cis-regulatory sequences and expose a vast trove of novel elements, most with highly cell-selective regulation. Annotating these elements using ENCODE data reveals novel relationships between chromatin accessibility, transcription, DNA methylation, and regulatory factor occupancy patterns. We connect ~580,000 distal DHSs with their target promoters, revealing systematic pairing of different classes of distal DHSs and specific promoter types. Patterning of chromatin accessibility at many regulatory regions is choreographed with dozens to hundreds of co-activated elements, and the trans-cellular DNaseI sensitivity pattern at a given region can predict cell type-specific functional behaviors. The DHS landscape shows signatures of recent functional evolutionary constraint. However, the DHS compartment in pluripotent and immortalized cells exhibits higher mutation rates than that in highly differentiated cells, exposing an unexpected link between chromatin accessibility, proliferative potential and patterns of human variation
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
Measuring global ocean heat content to estimate the earth energy imbalance
The energy radiated by the Earth toward space does not compensate the incoming radiation from the Sun leading to a small positive energy imbalance at the top of the atmosphere (0.4–1 Wm–2). This imbalance is coined Earth’s Energy Imbalance (EEI). It is mostly caused by anthropogenic greenhouse gas emissions and is driving the current warming of the planet. Precise monitoring of EEI is critical to assess the current status of climate change and the future evolution of climate. But the monitoring of EEI is challenging as EEI is two orders of magnitude smaller than the radiation fluxes in and out of the Earth system. Over 93% of the excess energy that is gained by the Earth in response to the positive EEI accumulates into the ocean in the form of heat. This accumulation of heat can be tracked with the ocean observing system such that today, the monitoring of Ocean Heat Content (OHC) and its long-term change provide the most efficient approach to estimate EEI. In this community paper we review the current four state-of-the-art methods to estimate global OHC changes and evaluate their relevance to derive EEI estimates on different time scales. These four methods make use of: (1) direct observations of in situ temperature; (2) satellite-based measurements of the ocean surface net heat fluxes; (3) satellite-based estimates of the thermal expansion of the ocean and (4) ocean reanalyses that assimilate observations from both satellite and in situ instruments. For each method we review the potential and the uncertainty of the method to estimate global OHC changes. We also analyze gaps in the current capability of each method and identify ways of progress for the future to fulfill the requirements of EEI monitoring. Achieving the observation of EEI with sufficient accuracy will depend on merging the remote sensing techniques with in situ measurements of key variables as an integral part of the Ocean Observing System
Empirical modelling of the BLASTPol achromatic half-wave plate for precision submillimetre polarimetry
A cryogenic achromatic half-wave plate (HWP) for submillimetre astronomical polarimetry
has been designed, manufactured, tested and deployed in the Balloon-borne Large-Aperture
Submillimeter Telescope for Polarimetry (BLASTPol). The design is based on the five-slab
Pancharatnam recipe and itworks in thewavelength range 200–600 μm, making it the broadestband
HWP built to date at (sub)millimetre wavelengths. The frequency behaviour of the HWP
has been fully characterized at room and cryogenic temperatures with incoherent radiation
from a polarizing Fourier transform spectrometer. We develop a novel empirical model, complementary
to the physical and analytical ones available in the literature, that allows us to
recover the HWP Mueller matrix and phase shift as a function of frequency and extrapolated
to 4 K. We show that most of the HWP non-idealities can be modelled by quantifying one
wavelength-dependent parameter, the position of the HWP equivalent axes, which is then readily
implemented in a map-making algorithm. We derive this parameter for a range of spectral
signatures of input astronomical sources relevant to BLASTPol, and provide a benchmark
example of how our method can yield improved accuracy on measurements of the polarization
angle on the sky at submillimetre wavelengths
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