45,240 research outputs found
Freshwater security, conflict and cooperation: the case of the Red Sea-Dead Sea conduit project
This study examines the challenge of freshwater security faced by Israel, Jordan and Palestine, and mechanisms for multilateral collaboration that have been developed in order to create a Red Sea-Dead Sea Conduit. This paper outlines the proposed conduit as a major collaborative project which hinges on the engagement of both state and non-state stakeholders. The argument presented here is that the feasibility and planning process has so far been successful and that the mechanisms for collaboration developed as part of this project are the reason why. Overall conclusions suggest that the importance of freshwater security and the agency of international state and non-state actors are largely responsible for these collaborative successes
Investigation of resolution limits for indirect microwave holographic imaging
This work describes how indirect holography which has previously been applied to the determination of antenna radiation patterns can be adapted for the imaging of passive objects. It provides details of how complex scattered field values can be obtained in a simple and inexpensive manner from sampled scalar intensity measurements taken over a single scanning aperture. This work uses indirect holographic techniques to image a number of simple objects including a rectangular metallic plate, a small metal plate covered by a dielectric sheet and a small metallic circular annulus. This work demonstrates that good quality images can be reconstructed from simple scalar intensity patterns. It demonstrates that clear outlines can be obtained in particular from reconstructed phase patterns and that good images can be obtained from objects with dimensions of the order of a half wavelength
Müller glia activation in response to inherited retinal degeneration is highly varied and disease-specific
Despite different aetiologies, most inherited retinal disorders culminate in photoreceptor loss, which induces concomitant changes in the neural retina, one of the most striking being reactive gliosis by Müller cells. It is typically assumed that photoreceptor loss leads to an upregulation of glial fibrilliary acidic protein (Gfap) and other intermediate filament proteins, together with other gliosis-related changes, including loss of integrity of the outer limiting membrane (OLM) and deposition of proteoglycans. However, this is based on a mix of both injury-induced and genetic causes of photoreceptor loss. There are very few longitudinal studies of gliosis in the retina and none comparing these changes across models over time. Here, we present a comprehensive spatiotemporal assessment of features of gliosis in the degenerating murine retina that involves Müller glia. Specifically, we assessed Gfap, vimentin and chondroitin sulphate proteoglycan (CSPG) levels and outer limiting membrane (OLM) integrity over time in four murine models of inherited photoreceptor degeneration that encompass a range of disease severities (Crb1rd8/rd8, Prph2+/Δ307, Rho-/-, Pde6brd1/rd1). These features underwent very different changes, depending upon the disease-causing mutation, and that these changes are not correlated with disease severity. Intermediate filament expression did indeed increase with disease progression in Crb1rd8/rd8 and Prph2+/Δ307, but decreased in the Prph2+/Δ307 and Pde6brd1/rd1 models. CSPG deposition usually, but not always, followed the trends in intermediate filament expression. The OLM adherens junctions underwent significant remodelling in all models, but with differences in the composition of the resulting junctions; in Rho-/- mice, the adherens junctions maintained the typical rod-Müller glia interactions, while in the Pde6brd1/rd1 model they formed predominantly between Müller cells in late stage of degeneration. Together, these results show that gliosis and its associated processes are variable and disease-dependent
The Dark Matter Distribution in Abell 383: Evidence for a Shallow Density Cusp from Improved Lensing, Stellar Kinematic and X-ray Data
We extend our analyses of the dark matter (DM) distribution in relaxed
clusters to the case of Abell 383, a luminous X-ray cluster at z=0.189 with a
dominant central galaxy and numerous strongly-lensed features. Following our
earlier papers, we combine strong and weak lensing constraints secured with
Hubble Space Telescope and Subaru imaging with the radial profile of the
stellar velocity dispersion of the central galaxy, essential for separating the
baryonic mass distribution in the cluster core. Hydrostatic mass estimates from
Chandra X-ray observations further constrain the solution. These combined
datasets provide nearly continuous constraints extending from 2 kpc to 1.5 Mpc
in radius, allowing stringent tests of results from recent numerical
simulations. Two key improvements in our data and its analysis make this the
most robust case yet for a shallow slope \beta of the DM density profile
\rho_DM ~ r^-\beta on small scales. First, following deep Keck spectroscopy, we
have secured the stellar velocity dispersion profile to a radius of 26 kpc for
the first time in a lensing cluster. Secondly, we improve our previous analysis
by adopting a triaxial DM distribution and axisymmetric dynamical models. We
demonstate that in this remarkably well-constrained system, the logarithmic
slope of the DM density at small radii is \beta < 1.0 (95% confidence). An
improved treatment of baryonic physics is necessary, but possibly insufficient,
to reconcile our observations with the recent results of high-resolution
simulations.Comment: Accepted to ApJ Letter
Lack of association between the rs2294008 polymorphism in the prostate stem cell antigen gene and colorectal neoplasia : a case-control and immunohistochemical study
PMID: 22824379 [PubMed - indexed for MEDLINE] PMCID: PMC3500224 Free PMC ArticlePeer reviewedPublisher PD
Learning through Game Modding.
We seek to understand how modifying, or modding, existing games can lead to various forms of learning
Effects of Rotation on the Minimum Mass of Primordial Progenitors of Pair Instability Supernovae
The issue of which stars may reach the conditions of electron/positron pair
formation instability is of importance to understand the final evolution both
of the first stars and of contemporary stars. The criterion to enter the pair
instability regime in density and temperature is basically controlled by the
mass of the oxygen core. The main sequence masses that produce a given oxygen
core mass are, in turn, dependent on metallicity, mass loss, and convective and
rotationally-induced mixing. We examine the evolution of massive stars to
determine the minimum main sequence mass that can encounter pair-instability
effects, either a pulsational pair instability (PPISN) or a full-fledged
pair-instability supernova (PISN). We concentrate on zero-metallicity stars
with no mass loss subject to the Schwarzschild criterion for convective
instability, but also explore solar metallicity and mass loss and the Ledoux
criterion. As expected, for sufficiently strong rotationally-induced mixing,
the minimum main sequence mass is encountered for conditions that induce
effectively homogeneous evolution such that the original mass is converted
almost entirely to helium and then to oxygen. For this case, we find that the
minimum main sequence mass is ~40 Msun to encounter PPISN and ~65 Msun to
encounter a PISN. When mass-loss is taken into account those mass limits become
~50 Msun for PPISN and ~80 Msun for PISN progenitors. The implications of these
results for the first stars and for contemporary supernovae is discussed.Comment: 23 pages, 8 figure
Molecular gas in nearby powerful radio galaxies
We report the detection of CO(1-0) and CO(2-1) emission from the central
region of nearby 3CR radio galaxies (z 0.03). Out of 21 galaxies, 8 have
been detected in, at least, one of the two CO transitions. The total molecular
gas content is below 10 \msun. Their individual CO emission exhibit, for 5
cases, a double-horned line profile that is characteristic of an inclined
rotating disk with a central depression at the rising part of its rotation
curve. The inferred disk or ring distributions of the molecular gas is
consistent with the observed presence of dust disks or rings detected optically
in the cores of the galaxies. We reason that if their gas originates from the
mergers of two gas-rich disk galaxies, as has been invoked to explain the
molecular gas in other radio galaxies, then these galaxies must have merged a
long time ago (few Gyr or more) but their remnant elliptical galaxies only
recently (last 10 years or less) become active radio galaxies. Instead, we
argue the the cannibalism of gas-rich galaxies provide a simpler explanation
for the origin of molecular gas in the elliptical hosts of radio galaxies (Lim
et al. 2000). Given the transient nature of their observed disturbances, these
galaxies probably become active in radio soon after the accretion event when
sufficient molecular gas agglomerates in their nuclei.Comment: 6 pages, including 2 figures,in "QSO Hosts and Their Environments",
ed. I. Marquez, in pres
Characterization of Microplastics in the Atmosphere
Microplastics (MPs) are defined as small fragments of plastic or synthetic polymer material that are less than 5mm in size. Previous research has primarily focused on MPs in marine and coastal environments; however, characterization of MPs in the atmosphere has been limited. The goal of this study is to investigate MPs in the atmosphere, i.e., their composition, origin, and transport, due to the uncertainties associated with the impacts of MPs on human health upon inhalation. Active and passive sampling is conducted at two diverse locations: Embry-Riddle Aeronautical University in Daytona Beach, Florida and Colorado State University in Fort Collins, Colorado. Active sampling entails using the Tisch High Volume Air Sampler, to collect MPs on filters which are collected daily. On the other hand, passive sampling utilizes a setup devised to hold the filter to collect MPs, on a weekly basis. Post sampling procedures involve submerging the filters in 30% hydrogen peroxide to eliminate any organic material and to ensure that only MPs are being analyzed followed by vacuum filtration where the MPs are transferred to a 10 filter for visual analysis. Optical characterization takes place using a ZEISS Axioscope 7 compound microscope to determine the size distribution of these particles. Fourier transform infrared (FTIR) spectroscopy will be utilized to investigate the chemical properties of MPs. This study has implications for the effects of MPs on human health via inhalation, as well as their effects on water bodies and soil upon deposition
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