We present the results of our final analysis of the full data set of g(1)(p) (Q(2)), the spin structure function of the proton, collected using CLAS at Jefferson Laboratory in 2000-2001. Polarized ...electrons with energies of 1.6, 2.5, 4.2, and 5.7 GeV were scattered from proton targets ((NH3)-N-15 dynamically polarized along the beam direction) and detected with CLAS. From the measured double spin asymmetries, we extracted virtual photon asymmetries A(1)(p) and A(2)(p) and spin structure functions g(1)(p) and g(2)(p) over a wide kinematic range (0.05 GeV2 < Q(2) < 5 GeV2 and 1.08 GeV< W < 3 GeV) and calculated moments of g(1)(p). We compare our final results with various theoretical models and expectations, as well as with parametrizations of the world data. Our data, with their precision and dense kinematic coverage, are able to constrain fits of polarized parton distributions, test pQCD predictions for quark polarizations at large x, offer a better understanding of quark-hadron duality, and provide more precise values of higher twist matrix elements in the framework of the operator product expansion.
OBJECTIVES: To compare the use of lipid‐lowering drugs in community‐dwelling older adults with and without dementia.
DESIGN: Comparison of lipid‐lowering drug use by demented cases and nondemented ...controls based on secondary analysis of data from a longitudinal epidemiologic study.
SETTING: Longitudinal study of a largely rural, low‐ socioeconomic‐status, community‐based cohort of older persons residing in the mid‐Monongahela Valley of South‐west Pennsylvania (the Monongahela Valley Independent Elders Survey).
PARTICIPANTS: Eight hundred forty‐five individuals of mean ± standard deviation (SD) age of 80.5 ± 4.6, participating in the fifth biennial wave of data collection.
MEASUREMENTS: Demographics; medical history; medication regimen (including examination of prescription bottle labels); self‐report of most recent visit to primary care physician (PCP); and standardized clinical assessment to determine presence of dementia, including Clinical Dementia Rating (CDR).
RESULTS: One hundred seventy participants (20.1% of total subject cohort) had dementia, with a CDR of 0.5 or greater. Mean ages of demented and nondemented individuals were 83.5 ± 5.1 and 79.8 ± 4.2, respectively. Similar proportions, 87.7% and 89.5%, of these groups reported PCP visits in the previous year. Of the total sample, 9.4% (3.5% of the demented and 10.8% of the nondemented) were taking lipid‐lowering drugs. After adjustment for age, sex, education, visit with PCP within the past year, and potential confounding clinical and lifestyle variables (self‐reported heart disease, stroke or transient ischemic attacks, hypertension, smoking, and alcohol consumption), dementia was associated with a lower likelihood of taking a lipid‐lowering drug (odds ratio = 0.39, 95% confidence interval = 0.16–0.95). In post hoc subgroup analyses, similar results were found when restricting lipid‐lowering drugs to statins alone but were not statistically significant. Drug use was not associated with severity of dementia (CDR = 0.5 vs CDR ≥ 1).
CONCLUSIONS: Demented individuals were less likely than their nondemented counterparts to be taking lipid‐lowering drugs. This finding could reflect different prescribing patterns by physicians for demented and nondemented patients or a possible protective effect of these drugs against dementia.
The CLAS12 drift chamber system Mestayer, M.D.; Adhikari, K.; Bennett, R.P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
959, Številka:
C
Journal Article
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The CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12) is located in Hall B, one of the experimental halls at Jefferson Lab. The forward part of CLAS12 is built around a superconducting toroidal ...magnet. The six coils of the toroid divide the detector azimuthally into six sectors. Each sector contains three multi-layer drift chambers for reconstructing the trajectories of charged particles originating from a fixed target.
Each of the 18 planar chambers has two “superlayers” of six layers each, with the wires in the two adjacent superlayers oriented at ±6° stereo angles. Each layer has 112 hexagonal cells spanning a range from about 5° to 40° in polar angle. The six-layer structure provides redundancy in track segment finding and good tracking efficiency even in the presence of some individual wire inefficiency. The design, construction, operation, and calibration methods are described, and estimates of the efficiency and resolution are presented from in-beam measurements.
We present new data on the Bjorken sum Γ‾1p−n(Q2) at 4-momentum transfer 0.021≤Q2≤0.496 GeV2. The data were obtained in two experiments performed at Jefferson Lab: EG4 on polarized protons and ...deuterons, and E97110 on polarized 3He from which neutron data were extracted. The data cover the domain where chiral effective field theory (χEFT), the leading effective theory of the Strong Force at large distances, is expected to be applicable. We find that our data and the predictions from χEFT are only in marginal agreement. This is somewhat surprising as the contribution from the Δ(1232) resonance is suppressed in this observable, which should make it more reliably predicted by χEFT than quantities in which the Δ contribution is important. The data are also compared to a number of phenomenological models with various degrees of agreement.
We measured the g(1) spin structure function of the deuteron at low Q(2), where QCD can be approximated with chiral perturbation theory (chi PT). The data cover the resonance region, up to an ...invariant mass of W approximate to 1.9 GeV. The generalized Gerasimov-Drell-Hearn sum, the moment Gamma(d)(1) and the spin polarizability gamma(d)(0) are precisely determined down to a minimum Q(2) of 0.02 GeV2 for the first time, about 2.5 times lower than that of previous data. We compare them to several chi PT calculations and models. These results are the first in a program of benchmark measurements of polarization observables in the chi PT domain.
In this study, we present the final results for the deuteron spin structure functions obtained from the full data set collected with Jefferson Lab's CLAS in 2000-2001. Polarized electrons with ...energies of 1.6, 2.5, 4.2 and 5.8 GeV were scattered from deuteron (15ND3) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double spin asymmetry, the virtual photon absorption asymmetry Ad1 and the polarized structure function gd1 were extracted over a wide kinematic range (0.05 GeV2 < Q2 < 5 GeV2 and 0.9 GeV < W < 3 GeV). We use an unfolding procedure and a parametrization of the corresponding proton results to extract from these data the polarized structure functions An1 and g1n of the (bound) neutron, which are so far unknown in the resonance region, W < 2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x, a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the Operator Product Expansion.
The ratios of inclusive electron scattering cross sections of 4He, 12C, and 56Fe to 3He have been measured at 1 < xB <. At Q2 > 1.4 GeV2, the ratios exhibit two separate plateaus, at 1.5 < xB < 2 and ...at xB > 2.25. This pattern is predicted by models that include 2- and 3-nucleon short-range correlations (SRC). Relative to A = 3, the per-nucleon probabilities of 3-nucleon SRC are 2.3, 3.1, and 4.4 times larger for A = 4, 12, and 56. This is the first measurement of 3-nucleon SRC probabilities in nuclei.
The CLAS drift chamber system Mestayer, M.D; Carman, D.S; Asavapibhop, B ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2000, Letnik:
449, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Experimental Hall B at Jefferson Laboratory houses the CEBAF Large Acceptance Spectrometer, the magnetic field of which is produced by a superconducting toroid. The six coils of this toroid divide ...the detector azimuthally into six sectors, each of which contains three large multi-layer drift chambers for tracking charged particles produced from a fixed target on the toroidal axis. Within the 18 drift chambers are a total of 35,148 individually instrumented hexagonal drift cells. The novel geometry of these chambers provides for good tracking resolution and efficiency, along with large acceptance. The design and construction challenges posed by these large-scale detectors are described, and detailed results are presented from in-beam measurements.
In this article we review literature to build a broad understanding of what constitutes e-leadership in organizations. We propose a framework based on Adaptive Structuration Theory that could be used ...to study how Advanced Information Technology could influence and is influenced by leadership. According to our framework, the effects of Advanced Information Technology emerge from their interaction with organizational structures of which leadership is a part. Furthermore, organizational structures, including leadership, may themselves be transformed as a result of interactions with Advanced Information Technology. We use our Adaptive Structuration Theory–based framework to pool relevant results and suggestions from a diverse array of literature to provide recommendations for developing a research agenda on e-leadership.
A traditional view of scholarly quality defines rigor as the application of method and assumes an implicit connection with relevance. But as an applied field, public administration requires explicit ...attention to both rigor and relevance. Interpretive scholars' notions of rigor demand an explicit inclusion of relevance as an integral aspect of quality. As one form of interpretive research, narrative inquiry illuminates how this can be done. Appreciating this contribution requires a deeper knowledge of the logic of narrative inquiry, an acknowledgement of the diversity of narrative approaches, and attention to the implications for judging its quality. We use our story about community-based leadership research to develop and illustrate this argument.
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