Ultrashort pulsed neutron source.

We report on a novel compact laser-driven neutron source with an unprecedented short pulse duration (<50 ps) and high peak flux (>10(18) n/cm(2)/s), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (<3 µm) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast and for creating astrophysical conditions of heavy element synthesis in the laboratory.

Enhanced proton acceleration by an ultrashort laser interaction with structured dynamic plasma targets.

We experimentally demonstrate a notably enhanced acceleration of protons to high energy by relatively modest ultrashort laser pulses and structured dynamical plasma targets. Realized by special deposition of snow targets on sapphire substrates and using carefully planned prepulses, high proton yields emitted in a narrow solid angle with energy above 21 MeV were detected from a 5 TW laser. Our simulations predict that using the proposed scheme protons can be accelerated to energies above 150 MeV by 100 TW laser systems.

Hard two-body photodisintegration of 3He.

We have measured cross sections for the γ(3)He → pd reaction at photon energies of 0.4-1.4 GeV and a center-of-mass angle of 90°. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.

Seasonal pattern in the incidence of bleeding caused by peptic ulcer in Israel.

We have reviewed all endoscopies performed in our hospital between 1977 and 1986. During that period, 1337 endoscopies were performed to identify bleeding from peptic ulcers. Excluded were cases in which a predisposing factor was found, such as the use of ulcerogenic drugs. Also excluded were chronic or critically ill patients. The remaining 540 cases were reviewed. In 447 of those cases, the bleeding lesion was a duodenal ulcer, whereas, in 93 cases, a gastric ulcer was found (a ratio of 5:1). The seasonal variation in the incidence of bleeding from peptic ulcers was evaluated. We found a significant difference in bleeding in the cold and hot seasons, the incidence being significantly greater during the cold season (November until February). A similar pattern was found for bleeding from both duodenal and gastric ulcers.

A controlled double blind multicenter study of the effectiveness of 5-aminosalicylic acid in patients with Crohn's disease in remission.

We evaluated the efficacy of an oral formulation of 5-amino-salicylic acid in lowering the relapse rate after remission of Crohn's disease. Included were 59 patients who had proven Crohn's disease of at least 1 year's duration, and who had been in continuous remission for at least 6 months, while taking only 5-aminosalicylic acid or no therapy at all. Remission was defined as a Harvey Bradshaw index score (Softley-Clamp modification) of < 4. Patients were given coded mesalzaine 250 mg or placebo tablets (2 x 2 day). They were seen at 0, 1, and 2 months, and then every 2 months until the end of the study. Trial endpoints were 1 year of follow-up, or clinical relapse results. After randomization, 31 patients were included in the placebo arm, and 28 in the treatment arm. There were no significant differences between the two groups at entry. Ten patients were withdrawn from the trial because of noncompliance, loss of follow-up, or headache. There were more clinical relapses in the placebo arm (15 patients, 55%) than in the treatment arm (6 patients, 27%) (p < 0.05). Mesalazine had a significant advantage over placebo (p < 0.05) only in the subgroups of patients with ileal Crohn's disease and in those older than 30 years. We conclude that mesalazine has a moderate but significant benefit in preventing relapse in Crohn's disease in remission; this occurred only in patients with small-bowel involvement or in those older than 30 years.