3,052 research outputs found
Wide parameter search for isolated pulsars using the Hough transform
We use the Hough transform to analyze data from the second science run of the
LIGO interferometers, to look for gravitational waves from isolated pulsars. We
search over the whole sky and over a large range of frequencies and spin-down
parameters. Our search method is based on the Hough transform, which is a
semi-coherent, computationally efficient, and robust pattern recognition
technique. We also present a validation of the search pipeline using hardware
signal injections.Comment: Presented at GWDAW-9 in Annecy, France (Dec. 2004). 11 pages, 5
Figures. To appear in Classical and Quantum Gravit
Untangling the Recombination Line Emission from HII Regions with Multiple Velocity Components
HII regions are the ionized spheres surrounding high-mass stars. They are
ideal targets for tracing Galactic structure because they are predominantly
found in spiral arms and have high luminosities at infrared and radio
wavelengths. In the Green Bank Telescope HII Region Discovery Survey (GBT HRDS)
we found that >30% of first Galactic quadrant HII regions have multiple
hydrogen radio recombination line (RRL) velocities, which makes determining
their Galactic locations and physical properties impossible. Here we make
additional GBT RRL observations to determine the discrete HII region velocity
for all 117 multiple-velocity sources within 18deg. < l < 65deg. The
multiple-velocity sources are concentrated in the zone 22deg. < l < 32deg.,
coinciding with the largest regions of massive star formation, which implies
that the diffuse emission is caused by leaked ionizing photons. We combine our
observations with analyses of the electron temperature, molecular gas, and
carbon recombination lines to determine the source velocities for 103 discrete
H II regions (88% of the sample). With the source velocities known, we resolve
the kinematic distance ambiguity for 47 regions, and thus determine their
heliocentric distances.Comment: 44 pages, 5 figures, 16 pages of tables; Accepted by ApJ
Structural Evidence for a Copper-Bound Carbonate Intermediate in the Peroxidase and Dismutase Activities of Superoxide Dismutase
Copper-zinc superoxide dismutase (SOD) is of fundamental importance to our understanding of oxidative damage. Its primary function is catalysing the dismutation of superoxide to O2 and H2O2. SOD also reacts with H2O2, leading to the formation of a strong copper-bound oxidant species that can either inactivate the enzyme or oxidise other substrates. In the presence of bicarbonate (or CO2) and H2O2, this peroxidase activity is enhanced and produces the carbonate radical. This freely diffusible reactive oxygen species is proposed as the agent for oxidation of large substrates that are too bulky to enter the active site. Here, we provide direct structural evidence, from a 2.15 Å resolution crystal structure, of (bi)carbonate captured at the active site of reduced SOD, consistent with the view that a bound carbonate intermediate could be formed, producing a diffusible carbonate radical upon reoxidation of copper. The bound carbonate blocks direct access of substrates to Cu(I), suggesting that an adjunct to the accepted mechanism of SOD catalysed dismutation of superoxide operates, with Cu(I) oxidation by superoxide being driven via a proton-coupled electron transfer mechanism involving the bound carbonate rather than the solvent. Carbonate is captured in a different site when SOD is oxidised, being located in the active site channel adjacent to the catalytically important Arg143. This is the probable route of diffusion from the active site following reoxidation of the copper. In this position, the carbonate is poised for re-entry into the active site and binding to the reduced copper. © 2012 Strange et al
Rupture process of the June 28, 1992 Big Bear Earthquake
The June 28, 1992 Big Bear earthquake in southern California was assumed to have ruptured along a northeast-trending plane, as suggested by long-term aftershock distribution. No surface rupture was found, however, and mainshock locations determined from both strong motion and TERRAscope data are mutually consistent and do not lie on the assumed fault plane. An integrated study involving waveform modeling, directivity and seismicity analyses suggests a complex rupture pattern, with significant short- and long-period energy propagating northwest along the presumed conjugate fault-plane
Alignment procedure for the VIRGO Interferometer: experimental results from the Frascati prototype
A small fixed-mirror Michelson interferometer has been built in Frascati to
experimentally study the alignment method that has been suggested for VIRGO.
The experimental results fully confirm the adequacy of the method. The minimum
angular misalignment that can be detected in the present set-up is 10
nrad/sqrt{Hz}Comment: 10 pages, LaTex2e, 4 figures, 5 tables. Submitted to Phys. Lett.
Reproducibility of acute steroid hormone responses in men to short-duration running
PURPOSE: Progressively overloading the body to improve physical performance may lead to detrimental states of overreaching/overtraining syndrome (OTS). Blunted cycling-induced cortisol and testosterone concentrations have been suggested to indicate overreaching following intensified-training periods. However, a running-based protocol is yet to be developed or demonstrated reproducible. This study develops two 30-min running protocols: (i) 50/70 (based on individualised physical capacity) and (ii) RPETP (self-paced) and measures the reproducibility of plasma cortisol and testosterone responses. METHODS: Thirteen recreationally active, healthy males completed each protocol (50/70 and RPETP) on three occasions. Venous blood was drawn Pre-, Post- and 30 min Post-Exercise. RESULTS: Cortisol was unaffected (both p > 0.05; 50/70: η2 = 0.090; RPETP: η2 = 0.252) whilst testosterone was elevated (both p < 0.05; 50/70: 35%, η2 = 0.714; RPETP: 42%, η2 = 0.892,) with low intra-individual coefficients of variation (CVi) as mean ± standard deviation (50/70: 7 ± 5%; RPETP: 12 ± 9%). Heart rate (50/70: ES = 0.39; RPETP: ES = -0.03), speed (RPETP: ES = -0.09) and rating of perceived exertion (50/70: ES = -0.06) were unchanged across trials (all CVi < 5%, p < 0.05). RPETP showed greater physiological strain (p < 0.01). CONCLUSIONS: Both tests elicited reproducible physiological and testosterone responses, but RPETP induced greater testosterone changes (likely due to increased physiological strain) and could therefore be considered a more sensitive tool to potentially detect OTS. Advantageously for the practitioner, RPETP does not require a priori exercise-intensity determination, unlike the 50/70, enhancing its integration into practice
A Catalog of Background Stars Reddened by Dust in the Taurus Dark Clouds
Normal field stars located behind dense clouds are a valuable resource in
interstellar astrophysics, as they provide continua in which to study phenomena
such as gas-phase and solid-state absorption features, interstellar extinction
and polarization. This paper reports the results of a search for highly
reddened stars behind the Taurus Dark Cloud complex. We use the Two Micron All
Sky Survey (2MASS) Point Source Catalog to survey a 50 sq deg area of the cloud
to a limiting magnitude of K = 10.0. Photometry in the 1.2-2.2 micron passbands
from 2MASS is combined with photometry at longer infrared wavelengths (3.6-12
micron) from the Spitzer Space Telescope and the Infrared Astronomical
Satellite to provide effective discrimination between reddened field stars and
young stellar objects (YSOs) embedded in the cloud. Our final catalog contains
248 confirmed or probable background field stars, together with estimates of
their total visual extinctions, which span the range 2-29 mag. We also identify
the 2MASS source J04292083+2742074 (IRAS 04262+2735) as a previously
unrecognized candidate YSO, based on the presence of infrared emission greatly
in excess of that predicted for a normal reddened photosphere at wavelengths >5
microns
The calcilytic agent NPS 2143 rectifies hypocalcemia in a mouse model with an activating calcium-sensing-receptor (CaSR) mutation:relevance to autosomal dominant hypocalcemia type 1 (ADH1)
Autosomal dominant hypocalcemia type 1 (ADH1) is caused by germline gain-of-function mutations of the calcium-sensing receptor (CaSR) and may lead to symptomatic hypocalcemia, inappropriately low serum parathyroid hormone (PTH) concentrations and hypercalciuria. Negative allosteric CaSR modulators, known as calcilytics, have been shown to normalise the gain-of-function associated with ADH-causing CaSR mutations in vitro and represent a potential targeted therapy for ADH1. However, the effectiveness of calcilytic drugs for the treatment of ADH1-associated hypocalcemia remains to be established. We have investigated NPS 2143, a calcilytic compound, for the treatment of ADH1 by in vitro and in vivo studies involving a mouse model, known as Nuf, which harbors a gain-of-function CaSR mutation, Leu723Gln. Wild-type (Leu723) and Nuf mutant (Gln723) CaSRs were expressed in HEK293 cells and the effect of NPS 2143 on their intracellular calcium responses determined by flow cytometry. NPS 2143 was also administered as a single intraperitoneal bolus to wild-type and Nuf mice and plasma concentrations of calcium and PTH, and urinary calcium excretion measured. In vitro administration of NPS 2143 decreased the intracellular calcium responses of HEK293 cells expressing the mutant Gln723 CaSR in a dose-dependent manner, thereby rectifying the gain-of-function associated with the Nuf mouse CaSR mutation. Intraperitoneal injection of NPS 2143 in Nuf mice led to significant increases in plasma calcium and PTH without elevating urinary calcium excretion. These studies of a mouse model with an activating CaSR mutation demonstrate NPS 2143 to normalize the gain-of-function causing ADH1, and improve the hypocalcemia associated with this disorder
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