922 research outputs found
Photodisintegration of aligned deuterons at astrophysical energies using linearly polarized photons
Following the model independent approach to deuteron photodisintegration with
linearly polarized rays, we show that the measurements of the tensor
analyzing powers on aligned deuterons along with the differential cross section
involve five different linear combinations of the isovector
amplitudes interfering with the isoscalar and amplitudes. This is
of current interest in view of the recent experimental finding
\cite{blackston1} that the three amplitudes are distinct and also the
reported experimental observation \cite{sawatzky} on the front-back (polar
angle) asymmetry in the differential cross section.Comment: 12 page
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A new high-gradient correction quadrupole for the Fermilab luminosity upgrade
Special superconducting correction quadrupoles are needed for the luminosity upgrade of the Fermilab Tevatron Collider. These correctors are part of the low-beta system for the interaction regions at B/phi/ and D/phi/. The requirements are high gradient and low current. A quadrupole has been designed that meets the operating gradient of 0.63 T/cm at 1086 A. The one-layer quadrupole is wound with a cable consisting of five individually insulated rectangular strands. The five strands are overwrapped with Kapton and epoxy impregnated glass tape. The winding, curing and collaring of the magnet is accomplished in the same manner as Tevatron-like magnets using Rutherford style cable. Once the magnet is complete the five strands are connected in series. A prototype quadrupole has been assembled and tested. The magnet reached a plateau current of 1560 A corresponding to a gradient of 0.91 T/cm without training. The measured field harmonics are substantially better than required. 8 refs., 6 figs., 4 tabs
Conformation and self-association of the peptide hormone substance P: Fourier-transform infrared spectroscopic study
Stressor- and Corticotropin releasing Factor-induced Reinstatement and Active Stress-related Behavioral Responses are Augmented Following Long-access Cocaine Self-administration by Rats
Rationale Stressful events during periods of drug abstinence likely contribute to relapse in cocaine-dependent individuals. Excessive cocaine use may increase susceptibility to stressor-induced relapse through alterations in brain corticotropin-releasing factor (CRF) responsiveness.
Objectives This study examined stressor- and CRF-induced cocaine seeking and other stress-related behaviors in rats with different histories of cocaine self-administration (SA).
Materials and methods Rats self-administered cocaine under short-access (ShA; 2 h daily) or long-access (LgA; 6 h daily) conditions for 14 days or were provided access to saline and were tested for reinstatement by a stressor (electric footshock), cocaine or an icv injection of CRF and for behavioral responsiveness on the elevated plus maze, in a novel environment and in the lightâdark box after a 14- to 17-day extinction/withdrawal period.
Results LgA rats showed escalating patterns of cocaine SA and were more susceptible to reinstatement by cocaine, EFS, or icv CRF than ShA rats. Overall, cocaine SA increased activity in the center field of a novel environment, on the open arms of the elevated plus maze, and in the light compartment of a lightâdark box. In most cases, the effects of cocaine SA were dependent on the pattern/amount of cocaine intake with statistically significant differences from saline self-administering controls only observed in LgA rats.
Conclusions When examined after several weeks of extinction/ withdrawal, cocaine SA promotes a more active pattern of behavior during times of stress that is associated with a heightened susceptibility to stressor-induced cocaine-seeking behavior and may be the consequence of augmented CRF regulation of addiction-related neurocircuitry
Cosmic Rays: The Second Knee and Beyond
We conduct a review of experimental results on Ultra-High Energy Cosmic Rays
(UHECR's) including measurements of the features of the spectrum, the
composition of the primary particle flux and the search for anisotropy in event
arrival direction. We find that while there is a general consensus on the
features in the spectrum -- the Second Knee, the Ankle, and (to a lesser
extent) the GZK Cutoff -- there is little consensus on the composition of the
primaries that accompany these features. This lack of consensus on the
composition makes interpretation of the agreed upon features problematic. There
is also little direct evidence about potential sources of UHECRs, as early
reports of arrival direction anisotropies have not been confirmed in
independent measurements.Comment: 46 pages, 30 figures. Topical Review to appear in J. Physics
Highest Energy Cosmic Rays and results from the HiRes Experiment
The status of the field of ultrahigh energy cosmic rays is summarized, from
the point of view of the latest results of the High Resolution Fly's Eye
(HiRes) Experiment. HiRes results are presented, and compared with those of the
Akeno Giant Air Shower Array (AGASA), plus the Telescope Array and Pierre Auger
experiments. The HiRes measurements of the cosmic ray spectrum, and the
observation of the GZK cutoff are presented. HiRes results on composition,
searches for anisotropy, measurement of the proton-air total cross section, and
shapes of shower profiles are presented.Comment: 31 pages, 18 figures, submitted to Journal of Physics
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
Raman spectroscopy: elucidation of biochemical changes in carcinogenesis of oesophagus
Several techniques are under development to diagnose oesophageal adenocarcinoma at an earlier stage. We have demonstrated the potential of Raman spectroscopy, an optical diagnostic technique, for the identification and classification of malignant changes. However, there is no clear recognition of the biochemical changes that distinguish between the different stages of disease. Our aim is to understand these changes through Raman mapping studies. Raman spectral mapping was used to analyse 20-ÎŒm sections of tissue from 29 snap-frozen oesophageal biopsies. Contiguous haematoxylin and eosin sections were reviewed by a consultant pathologist. Principal component analysis was used to identify the major differences between the spectra across each map. Pseudocolour score maps were generated and the peaks of corresponding loads identified enabling visualisation of the biochemical changes associated with malignancy. Changes were noted in the distribution of DNA, glycogen, lipids and proteins. The mean spectra obtained from selected regions demonstrate increased levels of glycogen in the squamous area compared with increased DNA levels in the abnormal region. Raman spectroscopy is a highly sensitive and specific technique for demonstration of biochemical changes in the carcinogenesis of Barrett's oesophagus. There is potential for in vivo application for real-time endoscopic optical diagnosis
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
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