Cross-section measurements for short-lived isotopes of Ti-46, As-75 and Mo-92 at the neutron energies from 13.6 to 14.9 MeV

Cross-sections were measured at neutron energies from 13.6 to 14.9 MeV for the reactions Ti-46(n,p) Sc-46m, As-75(n,p) Ge-75m and Mo-92(n,2n) Mo-91m leading to short-lived products. Corrections were made for the effects of gamma ray attenuation, coincidence summing, pulse pile-up, dead time, neutron flux fluctuations and scattered low energy neutrons. Statistical model calculations taking into account precompound effects were also performed. (C) 2000 Elsevier Science Ltd. All rights reserved

Measurement of formation cross sections for very short lived isotopes at the neutron energies from 13.6 to 14.9 MeV

Neutron activation cross sections were measured for the Ti-46(n,p)(SC)-S-44m, As-75(n,p)Ge-75m, Mo-97(n,p)Nb-97m and Mo-92(n,2n)Mo-91m reactions leading to short-lived nuclei at the neutron energies from 13.6 to 14.9 MeV. Corrections were made for the effects of gamma ray attenuation, coincidence summing, puls pile-up, dead time, neutron flux fluctuations and scattered neutrons. Statistical model calculations taking into account precompound effects were also performed for all the reactions investigated

O-16(n,p)N-16 reaction cross sections around 14 MeV

The (n,p) reaction cross sections of O-16 in the neutron energy range from 13.6 to 14.9 MeV were measured by the activation method. The gamma-ray counting technique was applied, and the cross sections were determined relative to the Al-27(n,p)Mg-27 reaction cross sections. The neutrons were produced via the H-3(d, n)He-4 reaction on a SAMES T-400 neutron generator, and the induced gamma activities were measured by a high-purity germanium (HPGe) detector. The efficiency calibration of the HPGe detector for gamma-ray energies above 6 MeV was determined by means of gamma rays emitted from the decay of Be-11. An automated fast sample transport system was combined with the neutron generator in order to carry out the measurements in cyclic mode. The experimental method is described and the sources of systematic errors are discussed. The results obtained are compared with the experimental data in the available literature and recent evaluations

Measurement of Ti-50(n, alpha)Ca-47 reaction cross sections for 13.6- to 14.9-MeV neutrons

Experimental setup and related measurements for determining precise neutron energy and flux and methods utilized for data acquisition and reduction with the recent results of Ti-50(n, alpha)Ca-47 cross-section measurements performed between 13.6 and 14.9 MeV are presented. The results are also compared with calculations based on the statistical model

(n,alpha) reaction cross sections of Ca-44, Sc-45, and V-51 nuclei from 13.6 to 14.9 MeV

Cross sections were measured for the Ca-44(n, alpha)Ar-41, Sc-45(n, alpha)K-42, and V-51(n, alpha)Sc-48 reactions at neutron energies from 13.6 to 14.9 MeV. The neutrons were produced via the H-3(d, n)He-4 reaction on a neutron generator using a solid TiT target. The activation technique was used, and induced gamma activities were measured by a high-resolution gamma-ray spectrometer. Corrections were made for the effects of gamma-ray attenuation, random coincidence (pulse pileup), coincidence summing, dead time, neutron flux fluctuations, and low-energy neutrons. Statistical model calculations taking into account precompound effects were performed for all the reactions investigated, and the experimental results were reproduced well except for the (n, alpha) reaction on the Sc-45 target. Also, comparisons with the recent experimental data showed good agreement

The effects of a low international normalized ratio on thromboembolic and bleeding complications in patients with mechanical mitral valve replacement

Background: Mechanical heart valve replacement has an inherent risk of thromboembolic events (TEs). Current guidelines recommend an international normalized ratio (INR) of at least 2.5 after mechanical mitral valve replacement (MVR). This study aimed to evaluate the effects of a low INR (2.0-2.5) on thromboembolic and bleeding complications in patients with mechanical MVR on warfarin therapy. Methods: One hundred and thirty-five patients who underwent mechanical MVR were enrolled in this study. The end points of this study were defined as TEs (valve thrombosis, transient ischemic attack, stroke) and bleeding (all minor and major bleeding) complications. Patients were followed up for a mean of 39.6 months and the mean INR of the patients was calculated. After data collection, patients were divided into 3 groups according to their mean INR, as follows: group 1 (n = 34), INR 2.5. Results: A total of 22 events (10 [7.4%] thromboembolic and 12 [8.8%] bleeding events) occurred in the follow-up period. The mean INR was an independent risk factor for the development of TEs. Mean INR and neurological dysfunction were independent risk factors for the development of bleeding events. A statistically significant positive correlation was found between the log mean INR and all bleeding events, and a negative correlation was found between the log mean INR and all TEs. The total number of events was significantly lower in group 2 than in groups 1 and 3 (P = 0.036). Conclusions: This study showed that a target INRs of 2.0-2.5 are acceptable for preventing TEs and safe in terms of bleeding complications in patients with mechanical MVR