507 research outputs found
Test of Lorentz Invariance in Electrodynamics Using Rotating Cryogenic Sapphire Microwave Oscillators
We present the first results from a rotating Michelson-Morley experiment that
uses two orthogonally orientated cryogenic sapphire resonator-oscillators
operating in whispering gallery modes near 10 GHz. The experiment is used to
test for violations of Lorentz Invariance in the frame-work of the photon
sector of the Standard Model Extension (SME), as well as the isotropy term of
the Robertson-Mansouri-Sexl (RMS) framework. In the SME we set a new bound on
the previously unmeasured component of
, and set more stringent bounds by up to a factor of 7
on seven other components. In the RMS a more stringent bound of
on the isotropy parameter, is set, which is more than a factor of 7 improvement. More detailed
description of the experiment and calculations can be found in: hep-ph/0506200Comment: Final published version, 4 pages, references adde
Large-scale periodicity in the distribution of QSO absorption-line systems
The spatial-temporal distribution of absorption-line systems (ALSs) observed
in QSO spectra within the cosmological redshift interval z = 0.0--4.3 is
investigated on the base of our updated catalog of absorption systems. We
consider so called metallic systems including basically lines of heavy
elements. The sample of the data displays regular variations (with amplitudes ~
15 -- 20%) in the z-distribution of ALSs as well as in the eta-distribution,
where eta is a dimensionless line-of-sight comoving distance, relatively to
smoother dependences. The eta-distribution reveals the periodicity with period
Delta eta = 0.036 +/- 0.002, which corresponds to a spatial characteristic
scale (108 +/- 6) h(-1) Mpc or (alternatively) a temporal interval (350 +/- 20)
h(-1) Myr for the LambdaCDM cosmological model. We discuss a possibility of a
spatial interpretation of the results treating the pattern obtained as a trace
of an order imprinted on the galaxy clustering in the early Universe.Comment: AASTeX, 13 pages, with 9 figures, Accepted for publication in
Astrophysics & Space Scienc
Associations between nutrient intake and gastrointestinal symptoms in autism spectrum disorder
Many children and adolescents with autism spectrum disorder (ASD) have significant gastrointestinal (GI) symptoms, but the etiology is not well understood. Studies have shown conflicting evidence on whether there are nutritional deficiencies in the various diets of individuals with ASD. However, little is known about the relationship between dietary intake and GI symptomatology in ASD. The goal of the present study was to assess for potential relationships between GI symptoms and nutrient intake from diet in the same sample of individuals from the previous study, and to determine whether dietary differences might have contributed to our previously observed findings of a relationship between stress responses and GI functioning in ASD
Strange new worlds: comparative planetology of exoplanets and the Solar System
This is the final version. Available on open access from the American Astronomical Society via the DOI in this record This whitepaper discusses the striking diversity of exoplanets that could be detected by future observations and highlights the potential for comparative planetology to be performed with Solar System planets in the upcoming era of large, space-based flagship missions
Response of Solidago canadensis clones to competition
Transplants of ten Solidago canadensis clones were grown under high and low competition in the field to determine whether clones differed in survival, growth, and reproduction under natural conditions. Transplants had higher probability of survival and flowering and were larger in all measures of size when competition was experimentally reduced. Clones differed in almost all these measures of success, but only when variance among transplants within clones was reduced by excluding transplants that experienced heavy herbivore damage. Differences among clones were more apparent under low competition than under high competition, despite higher coefficients of variation within clones under low competition. Adjusting transplant size for initial size (parent ramet rhizome mass) did not change these results, although clones did differ in parent rhizome mass. All of these results suggest that there is little potential for selection to discriminate among these clones. Despite the strong differences in transplant performance between the competition treatments and among clones, the clones did not differ in competitive ability-almost none of the clone x competition interactions were significant. In addition, the measures of success of each clone were usually positively correlated between the high and low competition treatments, suggesting there were no tradeoffs between performance under high and low competition for these clones.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47776/1/442_2004_Article_BF00378042.pd
Constraining the mass of dark photons and axion-like particles through black-hole superradiance
Ultralight bosons and axion-like particles appear naturally in different
scenarios and could solve some long-standing puzzles. Their detection is
challenging, and all direct methods hinge on unknown couplings to the Standard
Model of particle physics. However, the universal coupling to gravity provides
model-independent signatures for these fields. We explore here the superradiant
instability of spinning black holes triggered in the presence of such fields.
The instability taps angular momentum from and limits the maximum spin of
astrophysical black holes. We compute, for the first time, the spectrum of the
most unstable modes of a massive vector (Proca) field for generic black-hole
spin and Proca mass. The observed stability of the inner disk of stellar-mass
black holes can be used to derive \emph{direct} constraints on the mass of dark
photons in the mass range . By including also higher azimuthal modes, similar
constraints apply to axion-like particles in the mass range
.
Likewise, mass and spin distributions of supermassive BHs --~as measured
through continuum fitting, K iron line, or with the future space-based
gravitational-wave detector LISA~-- imply indirect bounds in the mass range
approximately , for both axion-like particles and dark photons. Overall,
superradiance allows to explore a region of approximately orders of
magnitude in the mass of ultralight bosons
Characterisation of the muon beams for the Muon Ionisation Cooling Experiment
A novel single-particle technique to measure emittance has been developed and used to characterise seventeen different muon beams for the Muon Ionisation Cooling Experiment (MICE). The muon beams, whose mean momenta vary from 171 to 281 MeV/c, have emittances of approximately 1.2–2.3 π mm-rad horizontally and 0.6–1.0 π mm-rad vertically, a horizontal dispersion of 90–190 mm and momentum spreads of about 25 MeV/c. There is reasonable agreement between the measured parameters of the beams and the results of simulations. The beams are found to meet the requirements of MICE
HIV-1 Tat protein alter the tight junction integrity and function of retinal pigment epithelium: an in vitro study
<p>Abstract</p> <p>Background</p> <p>How HIV-1 enter into the eyes remains obscure. We postulated that HIV-1 Tat protein can alter the expression of specific tight-junction proteins and disturb the blood retinal barrier, and contributes to HIV trafficking into the eyes. This study is to determine the effects of HIV-1 Tat proteins on the barrier function and tight-junction protein expression of retinal pigment epithelial cell (RPE).</p> <p>Methods</p> <p>A human RPE cell line (D407) cultured on microporous filter-supports was used. After treating with HIV-1 Tat protein, transepithelial electrical resistance (TER) of confluent RPE cells was measured by epithelial voltmeter. The permeability of the RPE cells to sodium fluorescein was measured. The expressions of the occludin and claudins were determined by real-time polymerase chain reaction, immunofluorescence, and Western blot analysis. Activation of ERK1/2 was detected by Western blot analysis with specific antiphospho protein antibodies. NF-κB DNA binding activity was determined by transcription factor assay. Specific pharmacologic inhibitors directed against the MAPKs were used to analyze the signaling involved in barrier destruction of RPE cells exposed to HIV-1 Tat.</p> <p>Results</p> <p>Treating cultured human retinal pigment epithelial cells with 100 nM Tat for 24 hours increased the permeability and decreased the TER of the epithelial monolayer. HIV-1 Tat also disrupted and downregulated the tight-junction proteins claudin-1, claudin-3, and claudin-4 in these cells, whereas claudin-2 was upregulated, and the expression of occludin was unaffected. HIV-1 Tat protein also induced activation of ERK1/2 and NF-κB. HIV-1 Tat protein induced barrier destruction, changes in expression of TJs, and activation of ERK1/2 and NF-κB were abrogated by inhibitor of ERK1/2 and NF-κB.</p> <p>Conclusion</p> <p>HIV-1 Tat protein causes increases in the paracellular permeability of RPE cells in vitro concomitant with changes in expression of certain transmembrane proteins associated with the tight junction. The effects of HIV-1 Tat on barrier function of the RPE may be mediated by ERK MAPK and NF-κB activation, which may represent potential targets for novel therapeutic approaches for the retinopathy induced by HIV infection.</p
Qualitative Release Assessment to Estimate the Likelihood of Henipavirus Entering the United Kingdom
The genus Henipavirus includes Hendra virus (HeV) and Nipah virus (NiV), for which fruit bats (particularly those of the genus Pteropus) are considered to be the wildlife reservoir. The recognition of henipaviruses occurring across a wider geographic and host range suggests the possibility of the virus entering the United Kingdom (UK). To estimate the likelihood of henipaviruses entering the UK, a qualitative release assessment was undertaken. To facilitate the release assessment, the world was divided into four zones according to location of outbreaks of henipaviruses, isolation of henipaviruses, proximity to other countries where incidents of henipaviruses have occurred and the distribution of Pteropus spp. fruit bats. From this release assessment, the key findings are that the importation of fruit from Zone 1 and 2 and bat bushmeat from Zone 1 each have a Low annual probability of release of henipaviruses into the UK. Similarly, the importation of bat meat from Zone 2, horses and companion animals from Zone 1 and people travelling from Zone 1 and entering the UK was estimated to pose a Very Low probability of release. The annual probability of release for all other release routes was assessed to be Negligible. It is recommended that the release assessment be periodically re-assessed to reflect changes in knowledge and circumstances over time
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