54 research outputs found
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Neutron metrology for SBSS
This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this work is to develop new detector technologies for Science-Based Stockpile Stewardship (SBSS) at the Los Alamos Neutron Scattering Center (LANSCE) using existing expertise and infrastructure from the nuclear and particle physics programs at LANL
Characterization of Implanted Stents through Neointimal Tissue Bioimpedance Simulations
This work describes how is possible the definition
of the light hole or lumen in implanted stents affected by
restenosis processes using the BioImpedance (BI) as biomarker.
The main approach is based on the fact that neointimal tissues
implied in restenosis can be detected and measured thanks to
their respective conductivity and dielectric properties. For this
goal, it is proposed a four-electrode setup for bioimpedance
measurement. The influence of the several involved tissues in
restenosis: fat, muscle, fiber, endothelium and blood, have been
studied at several frequencies, validating the setup and
illustrating the sensitivity of each one. Finally, a real example
using a standard stent, has been analyzed for stable and
vulnerable plaques in restenosis test cases, demonstrating that
the proposed method is useful for the stent obstruction test.
Bioimpedance simulation test has been performed using the
electric physics module in COMSOL Multiphysics®.Junta de Andalucía 2017/TIC-17
Demonstration of a solid deuterium source of ultra-cold neutrons
Ultra-cold neutrons (UCN), neutrons with energies low enough to be confined
by the Fermi potential in material bottles, are playing an increasing role in
measurements of fundamental properties of the neutron. The ability to
manipulate UCN with material guides and bottles, magnetic fields, and gravity
can lead to experiments with lower systematic errors than have been obtained in
experiments with cold neutron beams. The UCN densities provided by existing
reactor sources limit these experiments. The promise of much higher densities
from solid deuterium sources has led to proposed facilities coupled to both
reactor and spallation neutron sources. In this paper we report on the
performance of a prototype spallation neutron-driven solid deuterium source.
This source produced bottled UCN densities of 145 +/-7 UCN/cm3, about three
times greater than the largest bottled UCN densities previously reported. These
results indicate that a production UCN source with substantially higher
densities should be possible
Activated carbons with high nitrogen content by a combination of hydrothermal carbonization with activation
The work was funded by the FCT (Grants PEst-OE/QUI/UI0619/
2011 and SFRH/BD/82696/2011) with National (OE) and European
Union (FEDER, program COMPETE of QREN) funds
Measurements of Ultracold-Neutron Lifetimes in Solid Deuterium
We present the first measurements of the survival time of ultracold neutrons (UCNs) in solid deuterium (SD2). This critical parameter provides a fundamental limitation to the effectiveness of superthermal UCN sources that utilize solid ortho-deuterium as the source material. These measurements are performed utilizing a SD2 source coupled to a spallation source of neutrons, providing a demonstration of UCN production in this geometry and permitting systematic studies of the influence of thermal up-scatter and contamination with para-deuterium on the UCN survival time
The Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a second generation water Cherenkov
detector designed to determine whether the currently observed solar neutrino
deficit is a result of neutrino oscillations. The detector is unique in its use
of D2O as a detection medium, permitting it to make a solar model-independent
test of the neutrino oscillation hypothesis by comparison of the charged- and
neutral-current interaction rates. In this paper the physical properties,
construction, and preliminary operation of the Sudbury Neutrino Observatory are
described. Data and predicted operating parameters are provided whenever
possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and
epsf style files. For additional information about SNO see
http://www.sno.phy.queensu.ca . This version has some new reference
Measurement of the νe and total 8B solar neutrino fluxes with the Sudbury Neutrino Observatory phase-III data set
This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of 3He proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active 8B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54-0.31+0.33(stat.)-0.34+0.36(syst.)×106 cm-2 s-1, consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of Δm2=7.59-0.21+0.19×10 -5eV2 and θ=34.4-1.2+1.3degrees
Adipokines and insulin resistance during pregnancy
Normal pregnancy has been characterized as a "diabetogenic state". On the other hand, the adipose tissue is now considered an active organ, capable of secreting substances such as adipokines, which may play a role in the pathogenesis of insulin resistance. Resistin, leptin serum and placental levels increase as pregnancy progresses, which is in contrast to levels of adiponectin. These levels correlate with the state of reduced insulin sensitivity often developed in the latter stages of pregnancy. The objective of this article is to review recent advances in our understanding of adipokines and insulin resistance during pregnancy. Zapotitlán 2007 Elsevier Ireland Ltd. All rights reserved
Inversión del tiempo en la desintegración de neutrones polarizados: el experimento emiT
The standard electro-weak model predicts negligible violation of time-reversal invariance in light quark processes. We report on an experimental test of time-reversal invariance in the beta decay of polarized neutrons as a search for physics beyond the standard model. The emiT collaboration has measured the time-reversal-violating triple-correlation in neutron beta decay between the neutron spin, electron momentum, and neutrino momentum often referred to as the D coefficient. The first run of the experiment produced 14 million events which are currently being analyzed. However, a second run with improved detectors should provide greater statistical precision and reduced systematic uncertainties
Trophic and stoichiometric consequences of nutrification for the intertidal tropical zoanthid Zoanthus sociatus
Zoanthids are conspicuous and abundant members of intertidal environments, where they are exposed to large environmental fluctuations and subject to increasing loads of anthropogenic nutrients. Here we assess the trophic ecology and stoichiometric consequences of nutrient loading for symbiotic zoanthids inhabiting different intertidal habitats. More specifically, we analysed the stable isotope signature (δ13C and δ15N), elemental composition (C, N and P) and stoichiometry (C:N, C:P, N:P) of Zoanthus sociatus differently exposed to nutrification. Results suggest that autotrophy is the main feeding mode of zoanthids and that the effect water nutrient content differently affects the elemental phenotype of zoanthids depending on tidal habitat. Additionally, habitat effects on Z. sociatus P-related stoichiometric traits highlight functional differences likely associated with variation in Symbiodinium density. These findings provide an innovative approach to assess how cnidarian-dinoflagellate symbioses response to ecosystem changes in environmentally dynamic reef flats, particularly nutrient loading
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