4,932 research outputs found
Identified particle measurements at large transverse momenta from p+p to Au+Au collisions at RHIC
Measurements of various particle species over an extended momentum range
provide a sensitive experimental tool for investigating particle production
mechanisms in hadronic collisions. Comparison of the spectral shapes from
different collision centralities measured with the STAR detector at RHIC allows
one to study the interplay of soft and hard particle production for mesons and
investigate various baryon-meson effects. Systematic studies of identified
particle spectra for various colliding systems and different incident energies
provide additional insights toward the interplay between fragmentation and
non-fragmentation contributions to the particle production. In these
proceedings we present a systematic study of transverse momentum spectra for
charged pions, protons and antiprotons from Au+Au and Cu+Cu data at
sqrt(s_NN)=200 and 62.4 GeV as a function of collision centrality. We compare
those measurements with p+p and d+Au data, investigating the system effects on
energy loss.Comment: 6 pages, 4 figures, proceedings for the Lake Louise Winter Institute
2007, 19th-24th February 2007, Alberta, Canad
System size dependence of freeze-out properties at RHIC
The STAR experiment at RHIC has measured identified pi(+/-), K(+/-) and
p(pbar) spectra and ratios from sqrt(s_NN) = 62.4 and 200 GeV Cu+Cu collisions.
The new Cu+Cu results are studied with hydro-motivated blast-wave and
statistical model frameworks in order to characterize the freeze-out properties
of this system. Along with measurements from Au+Au and p+p collisions, the
obtained freeze-out parameters are discussed as a function of collision energy,
system size, centrality and inferred energy density. This multi-dimensional
systematic study reveals the importance of the collision geometry and furthers
our understanding of the QCD phases.Comment: 6 pages, 6 figures, poster proceedings for the Quark Matter 2006
Conference, Shanghai, China, 14th-20th Novermber 2006, submitted to the
International Journal of Modern Physics
Summary of Workshop to Review an OMB Report on Regulatory Risk Assessment and Management
Summary of the results of an invitational workshop conducted to peer review the 1990 OMB report, CURRENT REGULATORY ISSUES IN Risk ASSESSMENT AND Risk MANAGENMENTIN REGULATORY PROGRAM OF THE UNITED STATES GOVERNMENT, APRIL 1, 1990 - MARCH 31, 1991
Short-term exposure to heat stress attenuates appetite and intestinal integrity in growing pigs 1
Acute heat stress (HS) and heat stroke can be detrimental to the health, well-being, and performance of mammals such as swine. Therefore, our objective was to chronologically characterize how a growing pig perceives and initially copes with a severe heat load. Crossbred gilts (n=32; 63.8±2.9 kg) were subjected to HS conditions (37°C and 40% humidity) with ad libitum intake for 0, 2, 4, or 6 h (n=8/time point). Rectal temperature (Tr), respiration rates (RR), and feed intake were determined every 2 h. Pigs were euthanized at each time point and fresh ileum and colon samples were mounted into modified Ussing chambers to assess ex vivo intestinal integrity and function. Transepithelial electrical resistance (TER) and fluorescein isothiocyanate-labeled dextran (FD4) permeability were assessed. As expected, Tr increased linearly over time (P\u3c0.001) with the highest temperature observed at 6 h of HS. Compared to the 0-h thermal-neutral (TN) pigs, RR increased (230%; P\u3c0.001) in the first 2 h and remained elevated over the 6 h of HS (P\u3c0.05). Feed intake was dramatically reduced due to HS and this corresponded with significant changes in plasma glucose, ghrelin, and glucose-dependent insulinotropic peptide (P\u3c0.050). At as early as 2 h of HS, ileum TER linearly decreased (P\u3c0.01), while FD4 linearly increased with time (P\u3c0.05). Colon TER and FD4 changed due to HS in quadratic responses over time (P=0.050) similar to the ileum but were less pronounced. In response to HS, ileum and colon heat shock protein (HSP) 70 mRNA and protein abundance increased linearly over time (P\u3c0.050). Altogether, these data indicated that a short duration of HS (2-6 h) compromised feed intake and intestinal integrity in growing pigs
Insights into activity-dependent map formation from the retinotectal system: a middle-of-the-brain perspective
ABSTRACT: The development of orderly topographic maps in the central nervous system (CNS) results from a collaboration of chemoaffinity cues that establish the coarse organization of the projection and activity-dependent mechanisms that fine-tune the map. Using the retinotectal projection as a model system, we describe evidence that biochemical tags and patterned neural activity work in parallel to produce topographically ordered axonal projections. Finally, we review recent experiments in other CNS projections that support the proposition that cooperation between molecular guidance cues and activity-dependent processes constitutes a general paradigm for CNS map formation
Hyper-Rayleigh scattering in centrosymmetric systems
Hyper-Rayleigh scattering (HRS) is an incoherent mechanism for optical second harmonic generation. The frequency-doubled light that emerges from this mechanism is not emitted in a laser-like manner, in the forward direction; it is scattered in all directions. The underlying theory for this effect involves terms that are quadratic in the incident field and involves an even-order optical susceptibility (for a molecule, its associated hyperpolarizability). In consequence, HRS is often regarded as formally forbidden in centrosymmetric media. However, for the fundamental three-photon interaction, theory based on the standard electric dipole approximation, representable as E13, does not account for all experimental observations. The relevant results emerge upon extending the theory to include E12M1 and E12E2 contributions, incorporating one magnetic dipolar or electric quadrupolar interaction, respectively, to a consistent level of multipolar expansion. Both additional interactions require the deployment of higher orders in the multipole expansion, with the E12E2 interaction analogous in rank and parity to a four-wave susceptibility. To elicit the correct form of response from fluid or disordered media invites a tensor representation which does not oversimplify the molecular components, yet which can produce results to facilitate the interpretation of experimental observations. The detailed derivation in this work leads to results which are summarized for the following: perpendicular detection of polarization components both parallel and perpendicular to the pump radiation, leading to distinct polarization ratio results, as well as a reversal ratio for forward scattered circular polarizations. The results provide a route to handling data with direct physical interpretation, to enable the more sophisticated design of molecules with sought nonlinear optical properties
Lentiviral vectors with amplified beta cell-specific gene expression.
An important goal of gene therapy is to be able to deliver genes, so that they express in a pattern that recapitulates the expression of an endogenous cellular gene. Although tissue-specific promoters confer selectivity, in a vector-based system, their activity may be too weak to mediate detectable levels in gene-expression studies. We have used a two-step transcriptional amplification system to amplify gene expression from lentiviral vectors using the human insulin promoter. In this system, the human insulin promoter drives expression of a potent synthetic transcription activator (the yeast GAL4 DNA-binding domain fused to the activation domain of the Herpes simplex virus-1 VP16 activator), which in turn activates a GAL4-responsive promoter, driving the enhanced green fluorescent protein reporter gene. Vectors carrying the human insulin promoter did not express in non-beta-cell lines, but expressed in murine insulinoma cell lines, indicating that the human insulin promoter was capable of conferring cell specificity of expression. The insulin-amplifiable vector was able to amplify gene expression five to nine times over a standard insulin-promoter vector. In primary human islets, gene expression from the insulin-promoted vectors was coincident with insulin staining. These vectors will be useful in gene-expression studies that require a detectable signal and tissue specificity
Dietary sulfur concentration has no effect on In Vitro fermentative activity of ruminal mixed microorganisms
Beef Cattle Research, 2011 is known as Cattlemen’s Day, 2011We previously reported that elevated concentrations of dietary sulfur (0.65% sulfur,
dry basis) in finishing diets containing dried distillers grains with solubles decreased dry
matter intake and average daily gains of feedlot cattle. Furthermore, high dietary sulfur
concentrations yielded lower ruminal concentrations of volatile fatty acids, but were
associated with increased ruminal ammonia concentrations and improved total tract
digestibility of the diet. The objective of this study was to investigate, in culture tubes,
effects of added sulfur on in vitro dry matter disappearance, volatile fatty acid profiles,
and ammonia concentrations from substrates containing different sulfur concentrations
when fermented by mixed ruminal microorganisms from a steer fed a diet based
on corn and alfalfa
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