299 research outputs found
Liquid Crystal Polarimetry for Metastability Exchange Optical Pumping of 3He
We detail the design and operation of a compact, discharge light polarimeter
for metastability exchange optical pumping of 3He gas near 1 torr under a low
magnetic field. The nuclear polarization of 3He can be discerned from its
electron polarization, measured via the circular polarization of 668 nm
discharge light from an RF excitation. This apparatus measures the circular
polarization of this very dim discharge light using a nematic liquid crystal
wave retarder (LCR) and a high-gain, transimpedance amplified Si photodiode. We
outline corrections required in such a measurement, and discuss contributions
to its systematic error
Electron-Ion Collider: The next QCD frontier
This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on âGluons and quark sea at high energiesâ at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the usersâ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.United States. Department of Energy (Grant DE-AC05-06OR23177
A helical-shape scintillating fiber trigger and tracker system for the DarkLight experiment and beyond
The search for new physics beyond the Standard Model has interesting
possibilities at low energies. For example, the recent 6.8 anomaly
reported in the invariant mass of pairs from nuclear
transitions and the discrepancy between predicted and measured values of muon
g-2 give strong motivations for a protophobic fifth-force model. At low
energies, the electromagnetic interaction is well understood and produces
straightforward final states, making it an excellent probe of such models.
However, to achieve the required precision, an experiment must address the
substantially higher rate of electromagnetic backgrounds. In this paper, we
present the results of simulation studies of a trigger system, motivated by the
DarkLight experiment, using helical-shape scintillating fibers in a solenoidal
magnetic field to veto electron-proton elastic scattering and the associated
radiative processes. We also assess the performance of a tracking detector for
lepton final states using scintillating fibers in the same setup
Spin-Dependent Electron Scattering from Polarized Protons and Deuterons with the BLAST Experiment at MIT-Bates
The Bates Large Acceptance Spectrometer Toroid (BLAST) experiment was operated at the MIT-Bates Linear Accelerator Center from 2003 until 2005. The experiment was designed to exploit the power of a polarized electron beam incident on polarized targets of hydrogen and deuterium to measure, in a systematic manner, the neutron, proton, and deuteron form factors as well as other aspects of the electromagnetic interaction on few-nucleon systems. We briefly describe the experiment, and present and discuss the numerous results obtained.United States. Dept. of EnergyNational Science Foundation (U.S.
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A histological method for quantifying Plasmodium falciparum in the brain in fatal paediatric cerebral malaria
Background: The sequestration of Plasmodium falciparum-infected erythrocytes in brain microvasculature through cytoadherence to endothelium, is the hallmark of the definitive diagnosis of cerebral malaria and plays a critical role in malaria pathogenesis. The complex pathophysiology, which leads each patient to the final outcome of cerebral malaria, is multifaceted and thus, metrics to delineate specific patterns within cerebral malaria are needed to further parse patients. Methods: A method was developed for quantification utilizing counts of capillary contents (early-stage parasites, late-stage parasites and fibrin) from histological preparations of brain tissue after death, and compared it to the standard approach, in which the percentage of parasitized vessels in cross-section is determined. Results: Within the initial cohort of 50 patients, two different observers agreed closely on the percentage of vessels parasitized, pigmented parasites and pigment globules (ICC = 0.795-0.970). Correlations between observers for correct diagnostic classification were high (Kendallâs tau-b = 0.8779, Kappa = 0.8413). When these methods were applied prospectively to a second set of 50 autopsy samples, they revealed a heterogeneous distribution of sequestered parasites in the brain with pigmented parasites and pigment globules present in the cerebellum > cortex > brainstem. There was no difference in the distribution of early stages of parasites or in the percentage of vessels parasitized across the same sites. The second cohort of cases was also used to test a previously published classification and regression tree (CART) analysis; the quantitative data alone were able to accurately classify and distinguish cerebral malaria from non-cerebral malaria. Classification errors occurred within a subclassification of cerebral malaria (CM1 vs CM2). A repeat CART analysis for the second cohort generated slightly different classification rules with more accurate subclassification, although misclassification still occurred. Conclusions: The traditional measure of parasite sequestration in falciparum malaria, the percentage of vessels parasitized, is the most reliable and consistent for the general diagnosis of cerebral malaria. Methods that involve quantitative measures of different life cycle stages are useful for distinguishing patterns within the cerebral malaria population; these subclassifications may be important for studies of disease pathogenesis and ancillary treatment
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