346 research outputs found
Long Term Recovery in Disaster Response and the Role of Non-Profits
The Legal Framework of Disaster Response does not deal as well with long term recovery. In particular, the role of non-profits is unexamined. This paper examines the role of non-profits in disaster recovery and argues for a legal framework acknowledging its important role. El marco legal de las respuestas ante desastres no tiene en cuenta la recuperación a largo plazo. En particular, no se analiza el papel de las organizaciones sin ánimo de lucro. Este artículo estudia el papel de las organizaciones sin ánimo de lucro en la recuperación de desastres, y se muestra a favor de establecer un marco legal que reconozca la importancia de su papel
The Nearby Neutron Star RX J0720.4-3125 from Radio to X-rays
We present radio, optical, ultraviolet, and X-ray observations of the
isolated, thermally-emitting neutron star RX J0720.4-3125 using the Parkes
radio telescope, the Very Large Array, the Hubble Space Telescope, and the
Chandra X-ray Observatory. From these data we show that the optical/UV spectrum
of RX J0720.4-3125 is not well fit by a Rayleigh-Jeans tail as previously
thought, but is instead best fit by either a single non-thermal power-law or a
combination of a Rayleigh-Jeans tail and a non-thermal power-law. Taken
together with the X-ray spectrum, we find the best model for RX J0720.4-3125 to
be two blackbodies plus a power-law, with the cool blackbody implying a radius
of 11-13 km at an assumed distance of 300 pc. This is similar to many middle
aged (10^{5-6} yr) radio pulsars such as PSR B0656+14, evidence supporting the
hypothesis that RX J0720.4-3125 is likely to be an off-beam radio pulsar. The
radio data limit the flux at 1.4 GHz to be <0.24 mJy, or a luminosity limit of
4*pi*d^2*F < 3e25*d_300^2 ergs/s, and we see no sign of extended nebulosity,
consistent with expectations for a pulsar like RX J0720.4-3125.Comment: 13 pages, 9 figures. Uses emulateapj5.sty and onecolfloat5.sty.
Accepted for publication in Ap
Mechanistic underpinning of an insideâout concept for autoimmunity in multiple sclerosis
The neuroinflammatory disease multiple sclerosis is driven by autoimmune pathology in the central nervous system. However, the trigger of the autoimmune pathogenic process is unknown. MS models in immunologically naĂŻve, specificâpathogenâfree bred rodents support an exogenous trigger, such as an infection. The validity of this outsideâin pathogenic concept for MS has been frequently challenged by the difficulty to translate pathogenic concepts developed in these models into effective therapies for the MS patient. Studies in wellâvalidated nonâhuman primate multiple sclerosis models where, just like in humans, the autoimmune pathogenic process develops from an experienced immune system trained by prior infections, rather support an endogenous trigger. Data reviewed here corroborate the validity of this insideâout pathogenic concept for multiple sclerosis. They also provide a plausible sequence of events reminiscent of Wilkinâs primary lesion theory: (i) that autoimmunity is a physiological response of the immune system against excess antigen turnover in diseased tissue (the primary lesion) and (ii) that individuals developing autoimmune disease are (genetically predisposed) high responders against critical antigens. Data obtained in multiple sclerosis brains reveal the presence in normally appearing white matter of myelinated axons where myelin sheaths have locally dissociated from their enwrapped axon (i.e., blistering). The ensuing disintegration of axonâmyelin units potentially causes the excess systemic release of postâtranslationally modified myelin. Data obtained in a unique primate multiple sclerosis model revealed a core pathogenic role of T cells present in the normal repertoire, which hyperâreact to postâtranslationally modified (citrullinated) myelinâoligodendrocyte glycoprotein and evoke clinical and pathological aspects of multiple sclerosis
The XO Project: Searching for Transiting Extra-solar Planet Candidates
The XO project's first objective is to find hot Jupiters transiting bright
stars, i.e. V < 12, by precision differential photometry. Two XO cameras have
been operating since September 2003 on the 10,000-foot Haleakala summit on
Maui. Each XO camera consists of a 200-mm f/1.8 lens coupled to a 1024x1024
pixel, thinned CCD operated by drift scanning. In its first year of routine
operation, XO has observed 6.6% of the sky, within six 7 deg-wide strips
scanned from 0 deg to +63 deg of declination and centered at RA=0, 4, 8, 12,
16, and 20 hours. Autonomously operating, XO records 1 billion pixels per clear
night, calibrates them photometrically and astrometrically, performs aperture
photometry, archives the pixel data and transmits the photometric data to STScI
for further analysis. From the first year of operation, the resulting database
consists of photometry of 100,000 stars at more than 1000 epochs per star with
differential photometric precision better than 1% per epoch. Analysis of the
light curves of those stars produces transiting-planet candidates requiring
detailed follow up, described elsewhere, culminating in spectroscopy to measure
radial-velocity variation in order to differentiate genuine planets from the
more numerous impostors, primarily eclipsing binary and multiple stars.Comment: 29 pages, 12 figures, accepted by PASP for Aug 2005 issu
A Transiting Planet of a Sun-like Star
A planet transits an 11th magnitude, G1V star in the constellation Corona
Borealis. We designate the planet XO-1b, and the star, XO-1, also known as GSC
02041-01657. XO-1 lacks a trigonometric distance; we estimate it to be 200+-20
pc. Of the ten stars currently known to host extrasolar transiting planets, the
star XO-1 is the most similar to the Sun in its physical characteristics: its
radius is 1.0+-0.08 R_Sun, its mass is 1.0+-0.03 M_Sun, V sini < 3 km/s, and
its metallicity [Fe/H] is 0.015+-0.04. The orbital period of the planet XO-1b
is 3.941534+-0.000027 days, one of the longer ones known. The planetary mass is
0.90+-0.07 M_Jupiter, which is marginally larger than that of other transiting
planets with periods between 3 and 4 days. Both the planetary radius and the
inclination are functions of the spectroscopically determined stellar radius.
If the stellar radius is 1.0+-0.08 R_Sun, then the planetary radius is
1.30+-0.11 R_Jupiter and the inclination of the orbit is 87.7+-1.2 degrees. We
have demonstrated a productive international collaboration between professional
and amateur astronomers that was important to distinguishing this planet from
many other similar candidates.Comment: 31 pages, 9 figures, accepted for part 1 of Ap
XO-2b: Transiting Hot Jupiter in a Metal-rich Common Proper Motion Binary
We report on a V=11.2 early K dwarf, XO-2 (GSC 03413-00005), that hosts a
Rp=0.98+0.03/-0.01 Rjup, Mp=0.57+/-0.06 Mjup transiting extrasolar planet,
XO-2b, with an orbital period of 2.615857+/-0.000005 days. XO-2 has high
metallicity, [Fe/H]=0.45+/-0.02, high proper motion, mu_tot=157 mas/yr, and has
a common proper motion stellar companion with 31" separation. The two stars are
nearly identical twins, with very similar spectra and apparent magnitudes. Due
to the high metallicity, these early K dwarf stars have a mass and radius close
to solar, Ms=0.98+/-0.02 Msolar and Rs=0.97+0.02/-0.01 Rsolar. The high proper
motion of XO-2 results from an eccentric orbit (Galactic pericenter, Rper<4
kpc) well confined to the Galactic disk (Zmax~100 pc). In addition, the phase
space position of XO-2 is near the Hercules dynamical stream, which points to
an origin of XO-2 in the metal-rich, inner Thin Disk and subsequent dynamical
scattering into the solar neighborhood. We describe an efficient Markov Chain
Monte Carlo algorithm for calculating the Bayesian posterior probability of the
system parameters from a transit light curve.Comment: 14 pages, 10 Figures, Accepted in ApJ. Negligible changes to XO-2
system properties. Removed Chi^2 light curve analysis section, and simplified
MCMC light curve analysis discussio
Axon-Myelin Unit Blistering as Early Event in MS Normal Appearing White Matter
Objective: Multiple sclerosis (MS) is a chronic neuroinflammatory and neurodegenerative disease of unknown etiology. Although the prevalent view regards a CD4 +-lymphocyte autoimmune reaction against myelin at the root of the disease, recent studies propose autoimmunity as a secondary reaction to idiopathic brain damage. To gain knowledge about this possibility we investigated the presence of axonal and myelinic morphological alterations, which could implicate imbalance of axon-myelin units as primary event in MS pathogenesis. Methods: Using high resolution imaging histological brain specimens from patients with MS and non-neurological/non-MS controls, we explored molecular changes underpinning imbalanced interaction between axon and myelin in normal appearing white matter (NAWM), a region characterized by normal myelination and absent inflammatory activity. Results: In MS brains, we detected blister-like swellings formed by myelin detachment from axons, which were substantially less frequently retrieved in non-neurological/non-MS controls. Swellings in MS NAWM presented altered glutamate receptor expression, myelin associated glycoprotein (MAG) distribution, and lipid biochemical composition of myelin sheaths. Changes in tethering protein expression, widening of nodes of Ranvier and altered distribution of sodium channels in nodal regions of otherwise normally myelinated axons were also present in MS NAWM. Finally, we demonstrate a significant increase, compared with controls, in citrullinated proteins in myelin of MS cases, pointing toward biochemical modifications that may amplify the immunogenicity of MS myelin. Interpretation: Collectively, the impaired interaction of myelin and axons potentially leads to myelin disintegration. Conceptually, the ensuing release of (post-translationally modified) myelin antigens may elicit a subsequent immune attack in MS. ANN NEUROL 2021;89:711â725
Global Health Practice Competencies: Building Health Professionals' Capacity to Work in Global Health Contexts
The Second-Generation Guide Star Catalog: Description and Properties
The GSC-II is an all-sky database of objects derived from the uncompressed
DSS that the STScI has created from the Palomar and UK Schmidt survey plates
and made available to the community. Like its predecessor (GSC-I), the GSC-II
was primarily created to provide guide star information and observation
planning support for HST. This version, however, is already employed at some of
the ground-based new-technology telescopes such as GEMINI, VLT, and TNG, and
will also be used to provide support for the JWST and Gaia space missions as
well as LAMOST, one of the major ongoing scientific projects in China. Two
catalogs have already been extracted from the GSC-II database and released to
the astronomical community. A magnitude-limited (R=18.0) version, GSC2.2, was
distributed soon after its production in 2001, while the GSC2.3 release has
been available for general access since 2007.
The GSC2.3 catalog described in this paper contains astrometry, photometry,
and classification for 945,592,683 objects down to the magnitude limit of the
plates. Positions are tied to the ICRS; for stellar sources, the all-sky
average absolute error per coordinate ranges from 0.2" to 0.28" depending on
magnitude. When dealing with extended objects, astrometric errors are 20% worse
in the case of galaxies and approximately a factor of 2 worse for blended
images. Stellar photometry is determined to 0.13-0.22 mag as a function of
magnitude and photographic passbands (B,R,I). Outside of the galactic plane,
stellar classification is reliable to at least 90% confidence for magnitudes
brighter than R=19.5, and the catalog is complete to R=20.Comment: 52 pages, 33 figures, to be published in AJ August 200
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