5,840 research outputs found
Measurement of Sivers Asymmetries for Di-jets in \sqrt{s}=200 GeV pp Collisions at STAR
Measurement of the transverse spin dependence of the di-jet opening angle in
pp collisions at sqrt{s}=200 GeV has been performed by the STAR collaboration.
An analyzing power consistent with zero has been observed over a broad range in
pseudorapidity sum of the two jets with respect to the polarized beam
direction. A non-zero (Sivers) correlation between transverse momentum
direction of partons in the initial state and transverse spin orientation of
the parent proton has been previously observed in semi-inclusive deep inelastic
scattering (SIDIS).
The present measurements are much smaller than deduced from predictions made
for STAR di-jets based on non-zero quark Sivers functions deduced from SIDIS,
and furthermore indicate that gluon Sivers asymmetries are comparably small.Comment: 4 pages, 3 figures, talk presented at SPIN 2006, Kyoto, October 200
Antibody responses to a Cryptosporidium parvum rCP15/60 vaccine
Cryptosporidium parvum is a zoonotic apicomplexa-protozoan pathogen that causes gastroenteritis and diarrhoea in mammals worldwide. The organism is transmitted by ingestion of oocysts, which are shed in faeces, and completes its lifecycle in a single host.^1^ C. parvum is ubiquitous on dairy operations worldwide and is one of the leading causes of diarrhoea in calves on these farms.^2,3^ Here, for the first time, we describe the antibody response in a large group of cows to a recombinant C. parvum oocyst surface protein (rCP15/60) vaccine and the antibody response in calves fed rCP15/60-immune colostrum produced by these vaccinated cows. Results of recent genotype surveys indicate that calves are the only major reservoir for C. parvum infections in humans.^4^ Human C. parvum infections are particularly prevalent and often fatal in neonates in developing countries and to immunocompromised people, such as AIDs patients.^4^ Drug therapy against cryptosporidiosis is limited and not wholly efficacious in either humans or calves^5^, making development of an effective vaccine of paramount importance. To date, there is no commercially available effective vaccine against C. parvum, although passive immunization utilizing different zoite surface (glyco)proteins has showed promise.^6-9^ All cows we vaccinated produced an antibody response to the rCP15/60 vaccine and the magnitude of response correlated strongly with the subsequent level of antibody in their colostrum. All calves fed rCP15/60-immune colostrum showed a dose-dependent absorption of antibody. Our results demonstrate that vaccination of cows with rCP15/60 successfully induces antibodies against CP15/60 in their serum and colostrum and that these antibodies are then well absorbed when fed to neonatal calves. With further research, this C. parvum vaccine may well be a practical method of conferring passive protection to calves against cryptosporidiosis. Furthermore, a specifically targeted immune-colostrum may be valuable in protection and treatment of immunocompromised human patients with cryptosporidiosis
The effects of job embeddedness on organizational citizenship, job performance, volitional absences, and voluntary turnover
This study extends theory and research on job embeddedness, which was disaggregated into its two major subdimensions, on-the-job and off-the-job embeddedness. As hypothesized, regression analyses revealed that off-the-job embeddedness was significantly predictive of subsequent voluntary turnover and volitional absences, whereas on-the-job embeddedness was not. Also as hypothesized, on-the-job embeddedness was significantly predictive of organizational citizenship and job performance, whereas off-the-job embeddedness was not. In addition, embeddedness moderated the effects of absences, citizenship, and performance on turnover. Implications are discussed
Hybrid Ion-Detector/Data-Acquisition System for a TOF-MS
A modified ion-detector/data-acquisition system has been devised to increase the dynamic range of a time-of-flight mass spectrometer (TOF-MS) that, previously, included a microchannel-plate detector and a data-acquisition system based on counting pulses and time-tagging them by use of a time-to-digital converter (TDC). The dynamic range of the TOF-MS was limited by saturation of the microchannel plate detector, which can handle no more than a few million counts per second. The modified system includes (1) a combined microchannel plate/discrete ion multiplier and (2) a hybrid data-acquisition system that simultaneously performs analog current or voltage measurements and multianode single-ion-pulse-counting time-of-flight measurements to extend the dynamic range of a TDC into the regime in which a mass peak comprises multiple ions arriving simultaneously at the detector. The multianode data are used to determine, in real time, whether the detector is saturated. When saturation is detected, the data-acquisition system selectively enables circuitry that simultaneously determines the ion-peak intensity by measuring the time profile of the analog current or voltage detector-output signal
Molecular line mapping of the giant molecular cloud associated with RCW 106 - II. Column density and dynamical state of the clumps
We present a fully sampled C^{18}O (1-0) map towards the southern giant
molecular cloud (GMC) associated with the HII region RCW 106, and use it in
combination with previous ^{13}CO (1-0) mapping to estimate the gas column
density as a function of position and velocity. We find localized regions of
significant ^{13}CO optical depth in the northern part of the cloud, with
several of the high-opacity clouds in this region likely associated with a
limb-brightened shell around the HII region G333.6-0.2. Optical depth
corrections broaden the distribution of column densities in the cloud, yielding
a log-normal distribution as predicted by simulations of turbulence.
Decomposing the ^{13}CO and C^{18}O data cubes into clumps, we find relatively
weak correlations between size and linewidth, and a more sensitive dependence
of luminosity on size than would be predicted by a constant average column
density. The clump mass spectrum has a slope near -1.7, consistent with
previous studies. The most massive clumps appear to have gravitational binding
energies well in excess of virial equilibrium; we discuss possible
explanations, which include magnetic support and neglect of time-varying
surface terms in the virial theorem. Unlike molecular clouds as a whole, the
clumps within the RCW 106 GMC, while elongated, appear to show random
orientations with respect to the Galactic plane.Comment: 17 pages, to appear in MNRA
Stellar Proper Motions in the Galactic Bulge from deep HST ACS/WFC Photometry
We present stellar proper motions in the Galactic bulge from the Sagittarius
Window Eclipsing Extrasolar Search (SWEEPS) project using ACS/WFC on HST.
Proper motions are extracted for more than 180,000 objects, with >81,000
measured to accuracy better than 0.3 mas/yr in both coordinates. We report
several results based on these measurements: 1. Kinematic separation of bulge
from disk allows a sample of >15,000 bulge objects to be extracted based on
>6-sigma detections of proper motion, with <0.2% contamination from the disk.
This includes the first detection of a candidate bulge Blue Straggler
population. 2. Armed with a photometric distance modulus on a star by star
basis, and using the large number of stars with high-quality proper motion
measurements to overcome intrinsic scatter, we dissect the kinematic properties
of the bulge as a function of distance along the line of sight. This allows us
to extract the stellar circular speed curve from proper motions alone, which we
compare with the circular speed curve obtained from radial velocities. 3. We
trace the variation of the {l,b} velocity ellipse as a function of depth. 4.
Finally, we use the density-weighted {l,b} proper motion ellipse produced from
the tracer stars to assess the kinematic membership of the sixteen transiting
planet candidates discovered in the Sagittarius Window; the kinematic
distribution of the planet candidates is consistent with that of the disk and
bulge stellar populations.Comment: 71 pages, 30 figures, ApJ Accepte
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