Towards Neutron Capture on Exotic Nuclei: Demonstrating (d,pγ) as a Surrogate Reaction for (n,γ).

The neutron-capture reaction plays a critical role in the synthesis of the elements in stars and is important for societal applications including nuclear power generation and stockpile-stewardship science. However, it is difficult-if not impossible-to directly measure neutron capture cross sections for the exotic, short-lived nuclei that participate in these processes. In this Letter we demonstrate a new technique which can be used to indirectly determine neutron-capture cross sections for exotic systems. This technique makes use of the (d,p) transfer reaction, which has long been used as a tool to study the structure of nuclei. Recent advances in reaction theory, together with data collected using this reaction, enable the determination of neutron-capture cross sections for short-lived nuclei. A benchmark study of the ^{95}Mo(d,p) reaction is presented, which illustrates the approach and provides guidance for future applications of the method with short-lived isotopes produced at rare isotope accelerators.

Key

Detection of nuclear-decay γ rays provides a sensitive thermometer of nova nucleosynthesis. The most intense γ-ray flux is thought to be annihilation radiation from the ß^{+} decay of ^{18}F, which is destroyed prior to decay by the ^{18}F(p,α)^{15}O reaction. Estimates of ^{18}F production had been uncertain, however, because key near-threshold levels in the compound nucleus, ^{19}Ne, had yet to be identified. We report the first measurement of the ^{19}F(^{3}He,tγ)^{19}Ne reaction, in which the placement of two long-sought 3/2^{+} levels is suggested via triton-γ-γ coincidences. The precise determination of their resonance energies reduces the upper limit of the rate by a factor of 1.5-17 at nova temperatures and reduces the average uncertainty on the nova detection probability by a factor of 2.1.

Gastric bypass for morbid obesity.

Failure of conservative methods of control of gross obesity has led to the adoption of surgical measures. The operation of intestinal bypass, may be associated with the number of unpleasant complications. As a result there has been recent interest in the operation of gastric bypass involving an 80 to 90 percent gastric exclusion procedure. We report on the results of our first 19 patients undergoing this operation, a six to 15 month follow-up. The early results would suggest that gastric bypass in the treatment of morbid obesity is likely to prove superior to the various forms of intestinal bypass.

Pancreatitis following intestinal bypass for obesity.

Three out of 24 patients undergoing intestinal bypass in the treatment of morbid obesity have developed acute pancreatitis in the postoperative period. All three had undergone end-to-end jejunoileal bypass. This serious postoperative complication has been infrequently recorded. Its significance and possible aetiological factors are discussed.