The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The ...results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.
We report the first measurement of analyzing powers and spin correlation parameters using a storage ring with both beam and internal target polarized. Spin observables were measured for elastic ...scattering of 45 and 198 MeV protons from polarized sup 3He nuclei in a new laser-pumped internal gas target at the Indiana University Cyclotron Facility Cooler Ring. Scattered protons and recoil sup 3He nuclei were detected in coincidence with large acceptance plastic scintillators and silicon detectors. The internal-target technique demonstrated in this experiment has broad applicability to the measurement of spin-dependent scattering in nuclear and particle physics.
We report the measurement of the differential cross section for sup 2H(pisup minus,pisup 0) for laboratory angles 0degree--145degree, at incident pion energies of 164, 263, and 371 MeV. A Faddeev ...calculation at 164 MeV incorporating Pauli-blocking and multiple-scattering effects describes those data well. At the two higher energies the sup 2H(pisup minus,pisup 0) cross section is essentially identical to the sup 1H(pisup minus,pisup 0) cross section, except at forward angles where the former is suppressed by the Pauli principle. This experiment was the first to make use of a major component of the Neutral Meson Spectrometer at the Los Alamos National Laboratory.
OBJECTIVE:Resting CD4 T cells have been recognized as the major cell reservoir of latent HIV-1 during antiretroviral therapy (ART). Using an simian immunodeficiency virus (SIV)/macaque model for AIDS ...and HIV-related neurocognitive disorders we assessed the contribution of the brain to viral latency and reactivation.
DESIGN:Pigtailed macaques were dual inoculated with SIVDeltaB670 and SIV17E-Fr and treated with an efficacious central nervous system-penetrant ART. After 500 days of viral suppression animals were treated with two cycles of latency reversing agents and increases in viral transcripts were examined.
METHODS:Longitudinal plasma and cerebrospinal fluid (CSF) viral loads were analyzed by quantitative and digital droplet PCR. After necropsy, viral transcripts in organs were analyzed by PCR, in-situ hybridization, and phylogenetic genotyping based on env V1 loop sequences. Markers for neuronal damage and CSF activation were measured by ELISA.
RESULTS:Increases in activation markers and plasma and CSF viral loads were observed in one animal treated with latency reversing agents, despite ongoing ART. SIV transcripts were identified in occipital cortex macrophages by in-situ hybridization and CD68 staining. The most abundant SIV genotype in CSF was unique and expanded independent from viruses found in the periphery.
CONCLUSION:The central nervous system harbors latent SIV genomes after long-term viral suppression by ART, indicating that the brain represents a potential viral reservoir and should be seriously considered during AIDS cure strategies.
We report the $p+p$ and $p+d$ differential cross sections measured in the
SeaQuest experiment for $J/\psi$ and $\psi\left(2S\right)$ production at 120
GeV beam energy covering the forward $x$-Feynman ...($x_F$) range of $0.5 < x_F
<0.9$. The measured cross sections are in good agreement with theoretical
calculations based on the nonrelativistic QCD (NRQCD) using the long-distance
matrix elements deduced from a recent global analysis of proton- and
pion-induced charmonium production data. The $\sigma_{\psi\left(2S\right)} /
\sigma_{J/\psi}$ cross section ratios are found to increase as $x_F$ increases,
indicating that the $q \bar{q}$ annihilation process has larger contributions
in the $\psi\left(2S\right)$ production than the $J/\psi$ production. The
$\sigma_{pd}/2\sigma_{pp}$ cross section ratios are observed to be
significantly different for the Drell-Yan process and $J/\psi$ production,
reflecting their different production mechanisms. We find that the
$\sigma_{pd}/2\sigma_{pp}$ ratios for $J/\psi$ production at the forward $x_F$
region are sensitive to the $\bar{d}/ \bar{u}$ flavor asymmetry of the proton
sea, analogous to the Drell-Yan process. The transverse momentum ($p_T$)
distributions for $J/\psi$ and $\psi\left(2S\right)$ production are also
presented and compared with data collected at higher center-of-mass energies.
We report on precision measurements of the elastic cross section for electron-proton scattering performed in Hall C at Jefferson Lab. The measurements were made at 28 distinct kinematic settings ...covering a range in momentum transfer of 0.4<Q{sup 2}<5.5 (GeV/c){sup 2}. These measurements represent a significant contribution to the world's cross section data set in the Q{sup 2} range, where a large discrepancy currently exists between the ratio of electric to magnetic proton form factors extracted from previous cross section measurements and that recently measured via polarization transfer in Hall A at Jefferson Lab. This data set shows good agreement with previous cross section measurements, indicating that if a heretofore unknown systematic error does exist in the cross section measurements, then it is intrinsic to all such measurements.
Evidence is presented that shows very slow intramolecular energy redistribution (IVR) in the acetylenic C−H stretch fundamental of molecules in planar conformations. Each molecule,4-chlorobut-1-yne, ...4-bromobut-1-yne, 4-fluorobut-1-yne, methyl propargyl ether, 1-pentyne, and pent-1-en-4-yne have a planar trans conformer (except for pent-1-en-4-yne where the planar conformer is cis) that is connected to a nonplanar gauche (skew) conformer by rotation about a C−C bond (C−O for methyl propargyl ether). The planar forms (observed for each molecule except methyl propargyl ether) of these molecules exhibit some of the slowest hydride stretch IVR rates measured, with τIVR for the acetylenic C−H stretch ranging from 1 to 3 ns. These results are compared to the IVR lifetimes for the nonplanar conformers of 1-pentyne and methyl propargyl ether (τIVR ≈ 300 ps). Also presented are a series of molecules ((Z)-pent-3-en-1-yne, (E)-pent-3-en-1-yne, 1-butyne, 3-fluorobut-1-yne, and 2-methyl-1-buten-3-yne) that have a single methyl group substituent and do not form different conformations upon rotation about the C−C bond. The barrier to internal rotation of the methyl tops range from 389 to 2016 cm-1; however, the IVR lifetimes of the acetylenic C−H stretch for each is near 100 ps.
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