We report on a study of the radiative decay of fission fragments populated via neutronless fission of Cf252 ( sf ) . Applying the double-energy method a perfect mass identification is achieved for ...these rare events. In the specific case of the Cd120/Sn132 cold fragmentation, we find that Sn132 is produced in its ground state. We can therefore directly measure the excitation energy of the complementary fragment, Cd120 . The reproduction of the γ -ray spectrum, measured in coincidence with the neutronless fission events, is sensitive to the angular momentum distribution of the studied primary fragment. The latter estimated using a time-dependent collective Hamiltonian model, allows us to constrain for the first time the deformation ( β2≃0.4 ) of the studied fission fragment at scission. The present work demonstrates the high potential of the understudied neutronless fission channel for extracting detailed information on both fission fragments and process.
Abstract
Due to the current climate crisis, there is an urgent need to reduce greenhouse gas emissions. Improving façades’ energy performance can significantly reduce the cooling and heating demand ...of a building. More and more, in warm and mild climates, ventilated façade are given the function of avoiding overheating due to solar radiation and thus reducing the cooling demand of the building. However, this system’s energy performance is not easy to estimate. This study aims to assess the influence of some defining parameters of the ventilated façade on its energy performance. These parameters are not considered in the usual evaluation systems and can be relevant to the envelope’s energy performance. A calculation system has been developed so that architects can use it during the design process to know how their design decisions influence energy performance. Once validated with comparisons with measured values, the calculation system is applied to analyse the influence of some defining parameters of the façade during a warm day in Barcelona: the outer surface’s colour and the dimensions of the ventilation channel. For the studied cases, the change of these parameters implies an important variation in the daily average energy flow traversing the façade. In some cases, it even reverses the direction of the flow, changing from heat gains to heat losses. This concludes that these parameters are relevant to the energy performance of the ventilated façade and that the developed calculation system is a suitable tool to compute it.
Objective Patients with Cushing’s syndrome (CS) have increased mortality. The aim of this study was to evaluate the causes and time of death in a large cohort of patients with CS and to establish ...factors associated with increased mortality. Methods In this cohort study, we analyzed 1564 patients included in the European Registry on CS (ERCUSYN); 1045 (67%) had pituitary-dependent CS, 385 (25%) adrenal-dependent CS, 89 (5%) had an ectopic source and 45 (3%) other causes. The median (IQR) overall follow-up time in ERCUSYN was 2.7 (1.2–5.5) years. Results Forty-nine patients had died at the time of the analysis; 23 (47%) with pituitary-dependent CS, 6 (12%) with adrenal-dependent CS, 18 (37%) with ectopic CS and two (4%) with CS due to other causes. Of 42 patients whose cause of death was known, 15 (36%) died due to progression of the underlying disease, 13 (31%) due to infections, 7 (17%) due to cardiovascular or cerebrovascular disease and 2 due to pulmonary embolism. The commonest cause of death in patients with pituitary-dependent CS and adrenal-dependent CS were infectious diseases (n = 8) and progression of the underlying tumor (n = 10) in patients with ectopic CS. Patients who had died were older and more often males, and had more frequently muscle weakness, diabetes mellitus and ectopic CS, compared to survivors. Of 49 deceased patients, 22 (45%) died within 90 days from start of treatment and 5 (10%) before any treatment was given. The commonest cause of deaths in these 27 patients were infections (n = 10; 37%). In a regression analysis, age, ectopic CS and active disease were independently associated with overall death before and within 90 days from the start of treatment. Conclusion Mortality rate was highest in patients with ectopic CS. Infectious diseases were the commonest cause of death soon after diagnosis, emphasizing the need for careful clinical vigilance at that time, especially in patients presenting with concomitant diabetes mellitus.
Reliable neutron-induced-reaction cross sections of unstable nuclei are essential for nuclear astrophysics and applications but their direct measurement is often impossible. The surrogate-reaction ...method is one of the most promising alternatives to access these cross sections. In this work, we successfully applied the surrogate-reaction method to infer for the first time both the neutron-induced fission and radiative capture cross sections of 239Pu in a consistent manner from a single measurement. This was achieved by combining simultaneously measured fission and γ-emission probabilities for the 240Pu (4He, 4He′) surrogate reaction with a calculation of the angular-momentum and parity distributions populated in this reaction. While other experiments measure the probabilities for some selected γ-ray transitions, we measure the γ-emission probability. This enlarges the applicability of the surrogate-reaction method.
Gamma-decay probabilities of 173Yb and 176Lu have been measured using the surrogate reactions 174Yb(3He,αγ)173Yb* and 174Yb(3He,pγ)176Lu*, respectively. For the first time, the gamma-decay ...probabilities have been obtained with two independent experimental methods based on the use of C6D6 scintillators and Germanium detectors. Our results for the radiative-capture cross sections are several times higher than the corresponding neutron-induced data. To explain these differences, we have used our gamma-decay probabilities to extract rather direct information on the spin distributions populated in the transfer reactions used. They are about two times wider and the mean values are 3 to 4 ℏ higher than the ones populated in the neutron-induced reactions. As a consequence, in the transfer reactions neutron emission to the ground and first excited states of the residual nucleus is strongly suppressed and gamma-decay is considerably enhanced.
Background Surgery is the definitive treatment of Cushing’s syndrome (CS) but medications may also be used as a first-line therapy. Whether preoperative medical treatment (PMT) affects postoperative ...outcome remains controversial. Objective (1) Evaluate how frequently PMT is given to CS patients across Europe; (2) examine differences in preoperative characteristics of patients who receive PMT and those who undergo primary surgery and (3) determine if PMT influences postoperative outcome in pituitary-dependent CS (PIT-CS). Patients and methods 1143 CS patients entered into the ERCUSYN database from 57 centers in 26 countries. Sixty-nine percent had PIT-CS, 25% adrenal-dependent CS (ADR-CS), 5% CS from an ectopic source (ECT-CS) and 1% were classified as having CS from other causes (OTH-CS). Results Twenty per cent of patients took PMT. ECT-CS and PIT-CS were more likely to receive PMT compared to ADR-CS (P < 0.001). Most commonly used drugs were ketoconazole (62%), metyrapone (16%) and a combination of both (12%). Median (interquartile range) duration of PMT was 109 (98) days. PIT-CS patients treated with PMT had more severe clinical features at diagnosis and poorer quality of life compared to those undergoing primary surgery (SX) (P < 0.05). Within 7 days of surgery, PIT-CS patients treated with PMT were more likely to have normal cortisol (P < 0.01) and a lower remission rate (P < 0.01). Within 6 months of surgery, no differences in morbidity or remission rates were observed between SX and PMT groups. Conclusions PMT may confound the interpretation of immediate postoperative outcome. Follow-up is recommended to definitely evaluate surgical results.
Prompt fission neutron spectra (PFNS) are crucial to any neutronic simulation of critical nuclear systems. An experimental setup dedicated to the measurements of PFNS of very high accuracy was ...developed at the Los Alamos Neutron Science Center (LANSCE) some ten years ago. It allows for the measurement of PFNS for neutron induced fission at the Weapon Neutron Research (WNR) neutron source of the LANSCE. A measurement of the PFNS from the 235U(n,f) reaction was realized recently and is currently analyzed. Preliminary results are presented here and are compared to present nuclear data evaluations.
Cross sections for neutron-induced reactions of short-lived nuclei are essential for nuclear astrophysics since these reactions in the stars are responsible for the production of most heavy elements ...in the universe. These reactions are also key in applied domains like energy production and medicine. Nevertheless, neutron-induced cross-section measurements can be extremely challenging or even impossible to perform due to the radioactivity of the targets involved. Indirect measurements through the surrogate-reaction method can help to overcome these difficulties. The surrogate-reaction method relies on the use of an alternative reaction that will lead to the formation of the same excited nucleus as in the neutron-induced reaction of interest. The decay probabilities (for fission, neutron and gamma-ray emission) of the nucleus produced via the surrogate reaction allow one to constrain models and the prediction of the desired neutron cross sections. We propose to perform surrogate reaction measurements in inverse kinematics at heavy-ion storage rings, in particular at the CRYRING@ESR of the GSI/FAIR facility. We present the conceptual idea of the most promising setup to measure for the first time simultaneously the fission, neutron and gamma-ray emission probabilities. The results of the first simulations considering the 238U(d,d') reaction are shown, as well as new technical developments that are being carried out towards this set-up.
We present the results of two experiments where we have measured for the first time simultaneously the fission and gamma-decay probabilities induced by different surrogate reactions. In particular, ...we have investigated the 238U(d,p), 238U(3He,t) and 238U(3He,4He) reactions as surrogates for the neutron-induced n + 238U, n + 237Np and n + 236U reactions, respectively. In the region where gamma emission, neutron emission and fission compete, our results for the fission probabilities agree fairly well with the neutron-induced data, whereas our gamma-decay probabilities are significantly higher than the neutron-induced data. The interpretation of these results is not obvious and is discussed within the framework of the statistical model with preliminary results for calculated spin-parity distributions populated in surrogate reactions. We also present future plans for surrogate-reaction studies in inverse kinematics with radioactive-ion beams at storage rings.
PDF
