9,477 research outputs found
Millicharged Atomic Dark Matter
We present a simplified version of the atomic dark matter scenario, in which
charged dark constituents are bound into atoms analogous to hydrogen by a
massless hidden sector U(1) gauge interaction. Previous studies have assumed
that interactions between the dark sector and the standard model are mediated
by a second, massive Z' gauge boson, but here we consider the case where only a
massless gamma' kinetically mixes with the standard model hypercharge and
thereby mediates direct detection. This is therefore the simplest atomic dark
matter model that has direct interactions with the standard model, arising from
the small electric charge for the dark constituents induced by the kinetic
mixing. We map out the parameter space that is consistent with cosmological
constraints and direct searches, assuming that some unspecified mechanism
creates the asymmetry that gives the right abundance, since the dark matter
cannot be a thermal relic in this scenario. In the special case where the dark
"electron" and "proton" are degenerate in mass, inelastic hyperfine transitions
can explain the CoGeNT excess events. In the more general case, elastic
transitions dominate, and can be close to current direct detection limits over
a wide range of masses.Comment: 5 pages, 2 figures; v2: added references, and formula for dark
ionization fraction; published versio
Exosome-mediated Transfer of αvβ3 Integrin from Tumorigenic to Nontumorigenic Cells Promotes a Migratory Phenotype.
The αvβ3 integrin is known to be highly upregulated during cancer progression and promotes a migratory and metastatic phenotype in many types of tumors. We hypothesized that the αvβ3 integrin is transferred through exosomes and, upon transfer, has the ability to support functional aberrations in recipient cells. Here, for the first time, it is demonstrated that αvβ3 is present in exosomes released from metastatic PC3 and CWR22Pc prostate cancer cells. Exosomal β3 is transferred as a protein from donor to nontumorigenic and tumorigenic cells as β3 protein or mRNA levels remain unaffected upon transcription or translation inhibition in recipient cells. Furthermore, it is shown that upon exosome uptake, de novo expression of an αvβ3 increases adhesion and migration of recipient cells on an αvβ3 ligand, vitronectin. To evaluate the relevance of these findings, exosomes were purified from the blood of TRAMP mice carrying tumors where the expression of αvβ3 is found higher than in exosomes from wild-type mice. In addition, it is demonstrated that αvβ3 is coexpressed with synaptophysin, a biomarker for aggressive neuroendocrine prostate cancer.
IMPLICATIONS: Overall this study reveals that the αvβ3 integrin is transferred from tumorigenic to nontumorigenic cells via exosomes, and its de novo expression in recipient cells promotes cell migration on its ligand. The increased expression of αvβ3 in exosomes from mice bearing tumors points to its clinical relevance and potential use as a biomarker. Mol Cancer Res; 14(11); 1136-46. ©2016 AACR
Black holes and membranes in AdS_7
We investigate maximal gauged supergravity in seven dimensions and some of
its solitonic solutions. By focusing on a truncation of the gauged SO(5)
R-symmetry group to its U(1)^2 Cartan subgroup, we construct general two charge
black holes that are asymptotically anti-de Sitter. We demonstrate that 1- and
2-charge black holes preserve 1/2 and 1/4 of the supersymmetries respectively.
Additionally, we examine the odd-dimensional self-duality equation governing
the three-form potential transforming as the 5 of SO(5), and provide some
insight on the construction of membrane solutions in anti-de Sitter
backgrounds.Comment: 13 pages, harvmac (big option
Supergravities with Minkowski x Sphere Vacua
Recently the authors have introduced a new gauged supergravity theory with a
positive definite potential in D=6, obtained through a generalised Kaluza-Klein
reduction from D=7. Of particular interest is the fact that this theory admits
certain Minkowski x Sphere vacua. In this paper we extend the previous results
by constructing gauged supergravities with positive definitive potentials in
diverse dimensions, together with their vacuum solutions. In addition, we prove
the supersymmetry of the generalised reduction ansatz. We obtain a
supersymmetric solution with no form-field fluxes in the new gauged theory in
D=9. This solution may be lifted to D=10, where it acquires an interpretation
as a time-dependent supersymmetric cosmological solution supported purely by
the dilaton. A further uplift to D=11 yields a solution describing a pp-wave.Comment: Latex, 26 pages, typos correcte
Anaerobic methanogenesis in wetland ecosystems: do cut emergent aerenchyma of Typha x glauca facilitate increased atmospheric methane emission?
General EcologyAnaerobic methanogensis by bacteria communities is a major source of global atmospheric methane and therefore an important area of concern regarding climate change. This is particularly relevant to wetland ecosystems whose warm, water-logged, oxygen-poor soil conditions are the ideal environment for the fermentation of methane. In addition to relatively slow diffusion of methane through soil and water, and the sudden ebullition of trapped gas pockets, the aerenchyma (vessel-like tubes composed of mostly airspace that transport essential gases throughout the plant) of plants provide a direct route for gases to reach the atmosphere through the aerenchyma. We tested our hypothesis at a wetland site on the coast of Lake Huron in Cheboygan County, MI called Cheboygan Marsh. Five bucket plots pairs were installed where each pair had one bucket with the Typha stems cut below the water (submerged) and the other had stems cut above the water (emerged). Methane emissions were measured from each plot and we concluded that there was a significantly higher methane flux from emergent Typha than submerged Typha.http://deepblue.lib.umich.edu/bitstream/2027.42/89433/1/Green_Dorey_Pedley_Lu_2011.pd
On the third critical field in Ginzburg-Landau theory
Using recent results by the authors on the spectral asymptotics of the
Neumann Laplacian with magnetic field, we give precise estimates on the
critical field, , describing the appearance of superconductivity in
superconductors of type II. Furthermore, we prove that the local and global
definitions of this field coincide. Near only a small part, near the
boundary points where the curvature is maximal, of the sample carries
superconductivity. We give precise estimates on the size of this zone and decay
estimates in both the normal (to the boundary) and parallel variables
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