499 research outputs found
What is the best way to manage GERD symptoms in the elderly?
No evidence supports one method over another in managing uncomplicated gastroesophageal reflux disease (GERD) for patients aged >65 years. For those with endoscopically documented esophagitis, proton pump inhibitors (PPIs) relieve symptoms faster than histamine H2 receptor antagonists (H2RAs) (strength of recommendation [SOR]: B, extrapolation from randomized controlled trials [RCTs]). Treating elderly patients with pantoprazole (Protonix) after resolution of acute esophagitis results in fewer relapses than with placebo (SOR: B, double-blind RCT). Limited evidence suggests that such maintenance therapy for prior esophagitis with either H2RAs or PPIs, at half- and full-dose strength, decreases the frequency of relapse (SOR: B, extrapolation from uncontrolled clinical trial)
Preliminary results on the 233U capture cross section and alpha ratio measured at n_TOF (CERN) with the fission tagging technique
233U is of key importance among the fissile nuclei in the Th-U fuel cycle. A particularity of 233U is its small neutron capture cross-section, which is on average about one order of magnitude lower than the fission cross-section.The accuracy in the measurement of the 233U capture cross-section depends crucially onan efficient capture-fission discrimination, thus a combined set-up of fission and ¿-detectors is needed. A measurement of the 233U capture cross-section and capture-to-fissionratio was performed at the CERN n_TOF facility. The Total Absorption Calorimeter (TAC) of n_TOF was employed as ¿-detector coupled with a novel compact ionization chamber as fission detector. A brief description of the experimental set-up will be given, and essential parts of the analysis procedure as well as the preliminary response of the set-up to capture are presented and discussedPostprint (published version
First Measurement of 72Ge(n,γ) at n_TOF
9th European Summer School on Experimental Nuclear AstrophysicsThe slow neutron capture process (s-process) is responsible for producing about half of the elemental abundances heavier than iron in the universo
Limiting behaviour of Fréchet means in the space of phylogenetic trees
As demonstrated in our previous work on T4, the space of phylogenetic trees with four leaves, the topological structure of the space plays an important role in the non-classical limiting behaviour of the sample Fréchet means in T4. Nevertheless, the techniques used in that paper cannot be adapted to analyse Fréchet means in the space Tm of phylogenetic trees with m(⩾5)m(⩾5) leaves. To investigate the latter, this paper first studies the log map of Tm. Then, in terms of a modified version of this map, we characterise Fréchet means in Tm that lie in top-dimensional or co-dimension one strata. We derive the limiting distributions for the corresponding sample Fréchet means, generalising our previous results. In particular, the results show that, although they are related to the Gaussian distribution, the forms taken by the limiting distributions depend on the co-dimensions of the strata in which the Fréchet means lie
Recent results in nuclear astrophysics at the n_TOF facility at CERN
The neutron time of flight (n_TOF) facility at CERN is a spallation source characterized by a white neutron spectrum. The innovative features of the facility, in the two experimental areas, (20 m and 185 m), allow for an accurate determination of the neutron cross section for radioactive samples or for isotopes with small neutron capture cross section, of interest for Nuclear Astrophysics. The recent results obtained at n_TOF facility are presented
Preliminary results on the 233U capture cross section and alpha ratio measured at n_TOF (CERN) with the fission tagging technique
233U is of key importance among the fissile nuclei in the Th-U fuel cycle. A particularity of 233U is its small neutron capture cross-section, which is on average about one order of magnitude lower than the fission cross-section. The accuracy in the measurement of the 233U capture cross-section depends crucially on an efficient capture-fission discrimination, thus a combined set-up of fission and γ-detectors is needed. A measurement of the 233U capture cross-section and capture-to-fission ratio was performed at the CERN n_TOF facility. The Total Absorption Calorimeter (TAC) of n_TOF was employed as γ-detector coupled with a novel compact ionization chamber as fission detector. A brief description of the experimental set-up will be given, and essential parts of the analysis procedure as well as the preliminary response of the set-up to capture are presented and discussed
Urine drug screening in chronic pain management
This issue of eMedRef provides information to clinicians on the pathophysiology, diagnosis, and therapeutics of urine drug screening in chronic pain management
Wavelength-selected Neutron Pulses Formed by a Spatial Magnetic Neutron Spin Resonator
AbstractWe present a novel type of spatial magnetic neutron spin resonator whose time and wavelength resolution can be de- coupled from each other by means of a travelling wave mode of operation. Combined with a pair of highly efficient polarisers such a device could act simultaneously as monochromator and chopper, able to produce short neutron pulses, whose wavelength, spectral width and duration could be varied almost instantaneously by purely electronic means with- out any mechanical modification of the experimental setup. To demonstrate the practical feasibility of this technique we have designed and built a first prototype resonator consisting of ten individually switchable modules which allows to produce neutron pulses in the microsecond regime. It was installed at a polarised 2.6Å neutron beamline at the 250kW TRIGA research reactor of the Vienna University of Technology where it could deliver pulses of 55μs duration, which is about three times less than the passage time of the neutrons through the resonator itself. In order to further improve the achievable wavelength resolution to about 3% a second prototype resonator, consisting of 48 individual modules with optimised field homogeneity and enlarged beam cross-section of 6 × 6cm2 was developed. We present the results of first measurements which demonstrate the successful operation of this device
Measurement of 73 Ge(n,γ) cross sections and implications for stellar nucleosynthesis
© 2019 The Author(s). Published by Elsevier B.V.73 Ge(n,γ) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT=30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of 73 Ge produced in stars, which would explain the low isotopic abundance of 73 Ge in the solar system.Peer reviewe
The CERN n_TOF facility: a unique tool for nuclear data measurement
The study of the resonant structures in neutron-nucleus cross-sections, and therefore of the compoundnucleus
reaction mechanism, requires spectroscopic measurements to determine with high accuracy the energy of
the neutron interacting with the material under study. To this purpose, the neutron time-of-flight facility n_TOF has
been operating since 2001 at CERN. Its characteristics, such as the high intensity instantaneous neutron flux, the
wide energy range from thermal to few GeV, and the very good energy resolution, are perfectly suited to perform highquality
measurements of neutron-induced reaction cross sections. The precise and accurate knowledge of these cross
sections plays a fundamental role in nuclear technologies, nuclear astrophysics and nuclear physics. Two different
measuring stations are available at the n_TOF facility, called EAR1 and EAR2, with different characteristics of intensity
of the neutron flux and energy resolution. These experimental areas, combined with advanced detection systems lead
to a great flexibility in performing challenging measurement of high precision and accuracy, and allow the investigation
isotopes with very low cross sections, or available only in small quantities, or with very high specific activity. The
characteristics and performances of the two experimental areas of the n_TOF facility will be presented, together with
the most important measurements performed to date and their physics case. In addition, the significant upcoming
measurements will be introduced.Postprint (published version
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