9,480 research outputs found
Decay of flux vacua to nothing
We construct instanton solutions describing the decay of flux
compactifications of a gauge theory by generalizing the Kaluza-Klein
bubble of nothing. The surface of the bubble is described by a smooth
magnetically charged solitonic brane whose asymptotic flux is precisely that
responsible for stabilizing the 4d compactification. We describe several
instances of bubble geometries for the various vacua occurring in a
Einstein-Maxwell theory namely, AdS_4 x S^2, R^{1,3} x S^2, and dS_4 x S^2.
Unlike conventional solutions, the bubbles of nothing introduced here occur
where a {\em two}-sphere compactification manifold homogeneously degenerates.Comment: 31 pages, 15 figure
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Controlled release nanoparticulate matter delivery system
A controlled release nanoparticulate matter delivery system includes a plurality of thermoresponsive modules containing a respective nanoparticulate matter. Each thermoresponsive module is selectively operable in at least one of a heating mode that releases the nanoparticulate matter and a cooling mode that inhibits release of the nanoparticulate matter. A control module is in electrical communication with the plurality of thermoresponsive modules. The control module is configured to determine a temperature of each thermoresponsive module and to select the at least one heating mode and cooling mode based on the temperature. The heating and cooling mode may be selected in response to a desired dosing profile and/or a biometric condition.Board of Regents, University of Texas Syste
Diversity and Ecology of Diatoms in Northwest of Algeria: case of El-Hammam stream and Estuary of Cheliff River
P. 37-52Ecological research on algae from Algeria and in particular on freshwater and estuarine diatoms remains insufficient. The aim of our work is to contribute to the taxonomy and ecology of benthic diatoms from freshwaters and estuaries in Algeria. For this purpose, we studied two sites of water courses in north-western Algeria: El-Hammam stream at Mascara and the estuary of Cheliff river at Mostaganem. Our inventory of benthic diatoms during dry season at the middle of El-Hammam stream during April, June and August 2010 led to the identification of 44 cosmopolitan species, while 30 species occurred at the mouth of Cheliff river. 10 taxa were recorded for the first time in Algeria. Diversity values (Species richness, Shannon's index and Equitability index) for the two study sites are generally medium to low. The results of the 17 diatom-based metrics tested show that ROTT trophic index (TID) and the Trophic Diatom Index (TDI) best mirrored water quality, but a revision of taxa autecological values is requiredS
Comparison of charge modulations in LaBaCuO and YBaCuO
A charge modulation has recently been reported in (Y,Nd)BaCuO
[Ghiringhelli {\em et al.} Science 337, 821 (2013)]. Here we report Cu
edge soft x-ray scattering studies comparing the lattice modulation associated
with the charge modulation in YBaCuO with that associated with
the well known charge and spin stripe order in LaBaCuO.
We find that the correlation length in the CuO plane is isotropic in both
cases, and is \AA for LaBaCuO and \AA for YBaCuO. Assuming weak inter-planar correlations of
the charge ordering in both compounds, we conclude that the order parameters of
the lattice modulations in LaBaCuO and
YBaCuO are of the same order of magnitude.Comment: 3 pages, 2 figure
Spatial Curvature Falsifies Eternal Inflation
Inflation creates large-scale cosmological density perturbations that are
characterized by an isotropic, homogeneous, and Gaussian random distribution
about a locally flat background. Even in a flat universe, the spatial curvature
measured within one Hubble volume receives contributions from long wavelength
perturbations, and will not in general be zero. These same perturbations
determine the Cosmic Microwave Background (CMB) temperature fluctuations, which
are O(10^-5). Consequently, the low-l multipole moments in the CMB temperature
map predict the value of the measured spatial curvature \Omega_k. On this basis
we argue that a measurement of |\Omega_k| > 10^-4 would rule out slow-roll
eternal inflation in our past with high confidence, while a measurement of
\Omega_k < -10^-4 (which is positive curvature, a locally closed universe)
rules out false-vacuum eternal inflation as well, at the same confidence level.
In other words, negative curvature (a locally open universe) is consistent with
false-vacuum eternal inflation but not with slow-roll eternal inflation, and
positive curvature falsifies both. Near-future experiments will dramatically
extend the sensitivity of \Omega_k measurements and constitute a sharp test of
these predictions.Comment: 16+2 pages, 2 figure
Anisotropic Power-law Inflation
We study an inflationary scenario in supergravity model with a gauge kinetic
function. We find exact anisotropic power-law inflationary solutions when both
the potential function for an inflaton and the gauge kinetic function are
exponential type. The dynamical system analysis tells us that the anisotropic
power-law inflation is an attractor for a large parameter region.Comment: 14 pages, 1 figure. References added, minor corrections include
Significant differences in incubation times in sheep infected with bovine spongiform encephalopathy result from variation at codon 141 in the PRNP gene
The susceptibility of sheep to prion infection is linked to variation in the PRNP gene, which
encodes the prion protein. Common polymorphisms occur at codons 136, 154 and 171. Sheep
which are homozygous for the A<sub>136</sub>R<sub>154</sub>Q<sub>171</sub> allele are the most susceptible to bovine spongiform
encephalopathy (BSE). The effect of other polymorphisms on BSE susceptibility is unknown. We
orally infected ARQ/ARQ Cheviot sheep with equal amounts of BSE brain homogenate and a
range of incubation periods was observed. When we segregated sheep according to the amino
acid (L or F) encoded at codon 141 of the PRNP gene, the shortest incubation period was
observed in LL141 sheep, whilst incubation periods in FF<sub>141</sub> and LF<sub>141</sub> sheep were significantly
longer. No statistically significant differences existed in the expression of total prion protein or the
disease-associated isoform in BSE-infected sheep within each genotype subgroup. This
suggested that the amino acid encoded at codon 141 probably affects incubation times through
direct effects on protein misfolding rates
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