3,381 research outputs found
The Case for a 700+ GeV WIMP: Cosmic Ray Spectra from PAMELA, Fermi and ATIC
Multiple lines of evidence indicate an anomalous injection of high-energy e+-
in the Galactic halo. The recent fraction spectrum from the Payload for
Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) shows a
sharp rise up to 100 GeV. The Fermi Gamma-ray Space Telescope has found a
significant hardening of the e+e- cosmic ray spectrum above 100 GeV, with a
break, confirmed by HESS at around 1 TeV. The Advanced Thin Ionization
Calorimeter (ATIC) has also detected detected a similar excess, falling back to
the expected spectrum at 1 TeV and above. Excess microwaves towards the
galactic center in the WMAP data are consistent with hard synchrotron radiation
from a population of 10-100 GeV e+- (the WMAP ``Haze''). We argue that dark
matter annihilations can provide a consistent explanation of all of these data,
focusing on dominantly leptonic modes, either directly or through a new light
boson. Normalizing the signal to the highest energy evidence (Fermi and HESS),
we find that similar cross sections provide good fits to PAMELA and the Haze,
and that both the required cross section and annihilation modes are achievable
in models with Sommerfeld-enhanced annihilation. These models naturally predict
significant production of gamma rays in the galactic center via a variety of
mechanisms. Most notably, there is a robust inverse-Compton scattered (ICS)
gamma-ray signal arising from the energetic electrons and positrons, detectable
at Fermi/GLAST energies, which should provide smoking gun evidence for this
production.Comment: 28 pages; v2 plots corrected, references added; v3 included Fermi
electron data at reviewer request, references adde
I-Brane Inflow and Anomalous Couplings on D-Branes
We show that the anomalous couplings of -brane gauge and gravitational
fields to Ramond-Ramond tensor potentials can be deduced by a simple anomaly
inflow argument applied to intersecting -branes and use this to determine
the eight-form gravitational coupling.Comment: 8 pages, harvmac, no figure
SiC/SiC Ceramic Matrix Composites Developed for High-Temperature Space Transportation Applications
Researchers at the NASA Glenn Research Center have been developing durable, high-temperature ceramic matrix composites (CMCs) with silicon carbide (SiC) matrices and SiC or carbon fibers for use in advanced reusable launch vehicle propulsion and airframe applications in the Next Generation Launch Technology (NGLT) Program. These CMCs weigh less and are more durable than competing metallic alloys, and they are tougher than silicon-based monolithic ceramics. Because of their high specific strength and durability at high temperatures, CMCs such as C/SiC (carbon- fiber-reinforced silicon carbide) and SiC/SiC (silicon-carbide-fiber-reinforced silicon carbide) may increase vehicle performance and safety significantly and reduce the cost of transporting payloads to orbit
Characterization of a far-red analog of ghrelin for imaging GHS-R in P19-derived cardiomyocytes.
Ghrelin and its receptor, the growth hormone secretagogue receptor (GHS-R), are expressed in the heart, and may function to promote cardiomyocyte survival, differentiation and contractility. Previously, we had generated a truncated analog of ghrelin conjugated to fluorescein isothiocyanate for the purposes of determining GHS-R expression in situ. We now report the generation and characterization of a far-red ghrelin analog, [Dpr(3)(octanoyl), Lys(19)(Cy5)]ghrelin (1-19), and show that it can be used to image changes in GHS-R in developing cardiomyocytes. We also generated the des-acyl analog, des-acyl [Lys(19)(Cy5)]ghrelin (1-19) and characterized its binding to mouse heart sections. Receptor binding affinity of Cy5-ghrelin as measured in HEK293 cells overexpressing GHS-R1a was within an order of magnitude of that of fluorescein-ghrelin and native human ghrelin, while the des-acyl Cy5-ghrelin did not bind GHS-R1a. Live cell imaging in HEK293/GHS-R1a cells showed cell surface labeling that was displaced by excess ghrelin. Interestingly, Cy5-ghrelin, but not the des-acyl analog, showed concentration-dependent binding in mouse heart tissue sections. We then used Cy5-ghrelin to track GHS-R expression in P19-derived cardiomyocytes. Live cell imaging at different time points after DMSO-induced differentiation showed that GHS-R expression preceded that of the differentiation marker aMHC and tracked with the contractility marker SERCA 2a. Our far-red analog of ghrelin adds to the tools we are developing to map GHS-R in developing and diseased cardiac tissues
Mapping Distances Across the Perseus Molecular Cloud Using CO Observations, Stellar Photometry, and Gaia DR2 Parallax Measurements
We present a new technique to determine distances to major star-forming
regions across the Perseus Molecular Cloud, using a combination of stellar
photometry, astrometric data, and spectral-line maps.
Incorporating the Gaia DR2 parallax measurements when available, we start by
inferring the distance and reddening to stars from their Pan-STARRS1 and 2MASS
photometry, based on a technique presented in Green et al. 2014; Green et al.
2015 and implemented in their 3D "Bayestar" dust map of three-quarters of the
sky. We then refine the Green et al. technique by using the velocity slices of
a CO spectral cube as dust templates and modeling the cumulative distribution
of dust along the line of sight towards these stars as a linear combination of
the emission in the slices. Using a nested sampling algorithm, we fit these
per-star distance-reddening measurements to find the distances to the CO
velocity slices towards each star-forming region. This results in distance
estimates explicitly tied to the velocity structure of the molecular gas. We
determine distances to the B5, IC348, B1, NGC1333, L1448, and L1451
star-forming regions and find that individual clouds are located between
pc, with typical combined uncertainties of . We
find that the velocity gradient across Perseus corresponds to a distance
gradient of about 25 pc, with the eastern portion of the cloud farther away
than the western portion. We determine an average distance to the complex of
pc, about 60 pc higher than the distance derived to the western
portion of the cloud using parallax measurements of water masers associated
with young stellar objects. The method we present is not limited to the Perseus
Complex, but may be applied anywhere on the sky with adequate CO data in the
pursuit of more accurate 3D maps of molecular clouds in the solar neighborhood
and beyond.Comment: Accepted for publication in The Astrophysical Journa
Persistent enteric murine norovirus infection is associated with functionally suboptimal virus-specific CD8 T cell responses
Norovirus (NV) gastroenteritis is a major contributor to global morbidity and mortality, yet little is known about immune mechanisms leading to NV control. Previous studies using the murine norovirus (MNV) model have established a key role for T cells in MNV clearance. Despite these advances, important questions remain regarding the magnitude, location, and dynamics of the MNV-specific T cell response. To address these questions, we identified MNV-specific major histocompatibility complex (MHC) class I immunodominant epitopes using an overlapping peptide screen. One of these epitopes (amino acids 519 to 527 of open reading frame 2 [ORF2(519-527)]) was highly conserved among all NV genogroups. Using MHC class I peptide tetramers, we tracked MNV-specific CD8 T cells in lymphoid and mucosal sites during infection with two MNV strains with distinct biological behaviors, the acutely cleared strain CW3 and the persistent strain CR6. Here, we show that enteric MNV infection elicited robust T cell responses primarily in the intestinal mucosa and that MNV-specific CD8 T cells dynamically regulated the expression of surface molecules associated with activation, differentiation, and homing. Furthermore, compared to MNV-CW3 infection, chronic infection with MNV-CR6 resulted in fewer and less-functional CD8 T cells, and this difference was evident as early as day 8 postinfection. Finally, MNV-specific CD8 T cells were capable of reducing the viral load in persistently infected Rag1(−/−) mice, suggesting that these cells are a crucial component of NV immunity. Collectively, these data provide fundamental new insights into the adaptive immune response to two closely related NV strains with distinct biological behaviors and bring us closer to understanding the correlates of protective antiviral immunity in the intestine
Services just for men? Insights from a national study of the well men services pilots.
Men continue to have a lower life expectancy in most countries compared to women. Explanations of this gendered health inequality tend to focus on male risk taking, unhealthy lifestyle choices and resistance to seeking help from health services. In the period 2005-2008 the Scottish Government funded a nationwide community health promotion programme aimed at improving men's health, called Well Men Service Pilots (henceforth WMS)
Linked MRI signatures of the brain\u27s acute and persistent response to concussion in female varsity rugby players
Acute brain changes are expected after concussion, yet there is growing evidence of persistent abnormalities well beyond clinical recovery and clearance to return to play. Multiparametric MRI is a powerful approach to non-invasively study structure-function relationships in the brain, however it remains challenging to interpret the complex and heterogeneous cascade of brain changes that manifest after concussion. Emerging conjunctive, data-driven analysis approaches like linked independent component analysis can integrate structural and functional imaging data to produce linked components that describe the shared inter-subject variance across images. These linked components not only offer the potential of a more comprehensive understanding of the underlying neurobiology of concussion, but can also provide reliable information at the level of an individual athlete. In this study, we analyzed resting-state functional MRI (rs-fMRI) and diffusion tensor imaging (DTI) within a cohort of female varsity rugby players (n = 52) through the in-and off-season, including concussed athletes (n = 21) who were studied longitudinally at three days, three months and six months after a diagnosed concussion. Linked components representing co-varying white matter microstructure and functional network connectivity characterized (a) the brain\u27s acute response to concussion and (b) persistent alterations beyond clinical recovery. Furthermore, we demonstrate that these long-term brain changes related to specific aspects of a concussion history and allowed us to monitor individual athletes before and longitudinally after a diagnosed concussion
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