258 research outputs found
Capacitance mass sensing of boiling propellants
Capacitance mass sensing of boiling propellant
Measurements at low energies of the polarization-transfer coefficient Kyy' for the reaction 3H(p,n)3He at 0 degrees
Measurements of the transverse polarization coefficient Kyy' for the reaction
3H(p,n)3He are reported for outgoing neutron energies of 1.94, 5.21, and 5.81
MeV. This reaction is important both as a source of polarized neutrons for
nuclear physics experiments, and as a test of theoretical descriptions of the
nuclear four-body system. Comparison is made to previous measurements,
confirming the 3H(p,n)3He reaction can be used as a polarized neutron source
with the polarization known to an accuracy of approximately 5%. Comparison to
R-matrix theory suggests that the sign of the 3F3 phase-shift parameter is
incorrect. Changing the sign of this parameter dramatically improves the
agreement between theory and experiment.Comment: 12 pages, RevTeX, 5 eps figures, submitted to Phys. Rev.
New measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission
Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both
calculable from first principles using various theoretical approaches and of
interest for the understanding of a wide range of questions in many body
physics. Unfortunately, the pair correlation function inferred from
neutron scattering measurements of the differential cross section from different measurements reported in the literature are
inconsistent. We have measured the energy dependence of the total cross section
and the scattering cross section for slow neutrons with energies between
0.43~meV and 16.1~meV on liquid hydrogen at 15.6~K (which is dominated by the
parahydrogen component) using neutron transmission measurements on the hydrogen
target of the NPDGamma collaboration at the Spallation Neutron Source at Oak
Ridge National Laboratory. The relationship between the neutron transmission
measurement we perform and the total cross section is unambiguous, and the
energy range accesses length scales where the pair correlation function is
rapidly varying. At 1~meV our measurement is a factor of 3 below the data from
previous work. We present evidence that these previous measurements of the
hydrogen cross section, which assumed that the equilibrium value for the ratio
of orthohydrogen and parahydrogen has been reached in the target liquid, were
in fact contaminated with an extra non-equilibrium component of orthohydrogen.
Liquid parahydrogen is also a widely-used neutron moderator medium, and an
accurate knowledge of its slow neutron cross section is essential for the
design and optimization of intense slow neutron sources. We describe our
measurements and compare them with previous work.Comment: Edited for submission to Physical Review
LGD-4033 and MK-677 Use Impacts Body Composition, Circulating Biomarkers, and Skeletal Muscle Androgenic Hormone and Receptor Content: A Case Report
LGD-4033, a selective androgen receptor modulator, and MK-677, a growth hormone secretagogue, are being used increasingly amongst recreationally active demographics. However, limited data exist describing their effects on health- and androgen-related biomarkers. The purpose of this case study was to determine changes in body composition and biomarkers during and after continued co-administration of LGD-4033 and MK-677. We also aimed to examine muscular strength and intramuscular androgen-associated biomarkers relative to non-users. A 25-year-old male ingested LGD-4033 (10 mg) and MK-677 (15 mg) daily for 5 weeks. Blood and body composition metrics were obtained pre-, on- and post-cycle. One-repetition maximum leg and bench press, in addition to intramuscular androgens and androgen receptor content, were analysed on-cycle. We observed pre- to on-cycle changes in body composition (body mass, +6.0%; total lean body mass, +3.1%; trunk lean body mass, +6.6%; appendicular lean body mass, +4.3%; total fat mass, +15.4%; trunk fat mass, +2.8%; and appendicular fat mass, +14.8%), bone (bone mineral content, â3.60%; area, â1.1%; and bone mineral density, â2.1%), serum lipid-associated biomarkers (cholesterol, +14.8%; triglycerides, +39.2%; low-density lipoproteinâcholesterol, +40.0%; and high-density lipoproteinâcholesterol, â36.4%), liver-associated biomarkers (aspartate aminotransferase, +95.8%; and alanine aminotransferase, +205.0%) and androgen-associated biomarkers (free testosterone, â85.7%; total testosterone, â62.3%; and sex hormone-binding globulin, â79.6%); however, all variables returned to pre-cycle values post-cycle, apart from total fat mass, appendicular fat mass, bone area, total cholesterol and low-density lipoproteinâcholesterol. Follicle-stimulating hormone was below clinical reference values on- (1.2 IU/L) and post-cycle (1.3 IU/L). Intramuscular androgen receptor (â44.6%), testosterone (+47.8%) and dihydrotestosterone (+34.4%), in addition to one-repetition maximum leg press and bench press (+39.2 and +32.0%, respectively), were different in the case subject compared with non-users. These data demonstrate that LGD-4033 and MK-677 increase several body composition parameters, whilst negatively impacting bone and several serum biomarkers. Given the sparsity of data in recreationally using demographics, further research is warranted to elucidate the acute and chronic physiological effects of these anabolic agents
Neutron Beta Decay Studies with Nab
Precision measurements in neutron beta decay serve to determine the coupling
constants of beta decay and allow for several stringent tests of the standard
model. This paper discusses the design and the expected performance of the Nab
spectrometer.Comment: Submitted to Proceedings of the Conference CIPANP12, St.Petersburg,
Florida, May 201
Qweak: A Precision Measurement of the Proton's Weak Charge
The Qweak experiment at Jefferson Lab aims to make a 4% measurement of the
parity-violating asymmetry in elastic scattering at very low of a
longitudinally polarized electron beam on a proton target. The experiment will
measure the weak charge of the proton, and thus the weak mixing angle at low
energy scale, providing a precision test of the Standard Model. Since the value
of the weak mixing angle is approximately 1/4, the weak charge of the proton
is suppressed in the Standard Model, making it
especially sensitive to the value of the mixing angle and also to possible new
physics. The experiment is approved to run at JLab, and the construction plan
calls for the hardware to be ready to install in Hall C in 2007. The
theoretical context of the experiment and the status of its design are
discussed.Comment: 5 pages, 2 figures, LaTeX2e, to be published in CIPANP 2003
proceeding
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Estimated use of explosives in the mining industries of Egypt, Jordan, Syria, Tunisia, and Turkey
First Observation of -odd Asymmetry in Polarized Neutron Capture on Hydrogen
We report the first observation of the parity-violating 2.2 MeV gamma-ray
asymmetry in neutron-proton capture using polarized cold
neutrons incident on a liquid parahydrogen target at the Spallation Neutron
Source at Oak Ridge National Laboratory. isolates the , \mbox{} component of the weak
nucleon-nucleon interaction, which is dominated by pion exchange and can be
directly related to a single coupling constant in either the DDH meson exchange
model or pionless EFT. We measured , which implies a DDH weak coupling of
and a pionless
EFT constant of MeV. We describe the experiment, data
analysis, systematic uncertainties, and the implications of the result.Comment: 6 pages, 5 figure
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