Angular momentum generation in nuclear fission

When a heavy atomic nucleus splits (fission), the resulting fragments are observed to emerge spinning¹; this phenomenon has been a mystery in nuclear physics for over 40 years^2,3. The internal generation of typically six or seven units of angular momentum in each fragment is particularly puzzling for systems that start with zero, or almost zero, spin. There are currently no experimental observations that enable decisive discrimination between the many competing theories for the mechanism that generates the angular momentum^4-12. Nevertheless, the consensus is that excitation of collective vibrational modes generates the intrinsic spin before the nucleus splits (pre-scission). Here we show that there is no significant correlation between the spins of the fragment partners, which leads us to conclude that angular momentum in fission is actually generated after the nucleus splits (post-scission). We present comprehensive data showing that the average spin is strongly mass-dependent, varying in saw-tooth distributions. We observe no notable dependence of fragment spin on the mass or charge of the partner nucleus, confirming the uncorrelated post-scission nature of the spin mechanism. To explain these observations, we propose that the collective motion of nucleons in the ruptured neck of the fissioning system generates two independent torques, analogous to the snapping of an elastic band. A parameterization based on occupation of angular momentum states according to statistical theory describes the full range of experimental data well. This insight into the role of spin in nuclear fission is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the γ-ray heating problem in nuclear reactors^13,14, for the study of the structure of neutron-rich isotopes^15,16, and for the synthesis and stability of super-heavy elements^17,18.

Histamine and peptic ulcer: influence of sample-taking on the precision and accuracy of fluorometric histamine assay in biopsies of human gastric mucosa

From a methodological point of view the relevance of clinical-biochemical trials depends on the answers to mainly four complexes of questions: (1) the reliability of the assays in the clinical situation to be tested, (2) the precision and accuracy of sample-taking, (3) the qualification of the design and the protocols in the clinical part of the trial and (4) the usefulness of the time concepts in the trial concerning biorhythms, seasonal influences, psychological trauma of diagnostic procedures and treatment. In this study mainly the second complex of questions was studied intensely. The precision of the fluorometric histamine assay in biopsy specimens from human gastric mucosa depended on several conditions: Biochemical technique, sample preparation and removal of biopsies from gastric mucosa via endoscopy. The CV% of the whole procedure was about 8-times higher than that of the biochemical technique. In clinical-biochemical studies on the significance of histamine or any other hormone (such as gastrin) in any disease (uch as duodenal ulcer) it seems therefore useless to describe the precision of an assay only by the variance of the biochemical technique. Calculation of the histamine content as mean of 3 samples reduced the CV% from 27.2 to 14.9% and should therefore be recommended.

[Pollinosis. II. Specific hyposensitization: indications and results of treatment. A study with the allergen preparation Stallergenes-Depot in the pollen season of 1976, 1977 and 1978]

The efficacy of hyposensitization treatment of pollen allergy has been proven by a series of double blind studies. The clinical success of specific treatment with semi-depot extracts amounts, according to retrospective studies, to 70% and 90% in hay fever and seasonal asthma. Our results, with a success quota averaging 75% obtained by 821 courses of treatment between 1976 and 1978, are within the range reported by other authors. Only 1-2% of the patients experienced a worsening of the allergic symptoms during immunotherapy. The success quota in connection with organ manifestation varied between 65.7% to 86.5% for asthma (up to 34% cured), 59,8% to 79% for rhinitis and 70,5% to 84% for conjuncitivitis. The global results of 409 hyposensitization treatments by outside practitioners in pollen season 1976 were not inferior statistically to those obtained by our allergy unit. The results after 2 and 3 courses, with a success quota of 85%, were statistically significantly better than after the first course. The local reactions observed in approximately 27% of patients, and the allergic generalized reactions seen in approximately 7% during hyposensitization, are described and discussed. Guidelines for the indication for hyposensitization treatment of pollinosis, for the composition of the pollen extracts (only a few relevant allergens!) and for practical performance are given.

Effect of selective gastric vagotomy on histamine concentration in gastric mucosa of patients with duodenal ulcer

In a prospective controlled trial, histamine concentrations in human gastric mucosa were determined fluorometrically in 23 patients 6–11 months after selective gastric vagotomy with drainage and in patients who had undergone other types of operation for duodenal ulcer. The study was in two parts: part 1, a synchronous investigation of mucosal histamine concentrations in patients who had undergone vagotomy, in duodenal ulcer patients before operation and in control subjects; part 2, a consecutive study of the same patients before and after vagotomy.

In part 1, patients with Hollander-negative vagotomy were found to have significantly higher mucosal histamine concentrations than ‘healthy’ control subjects or duodenal ulcer, however, had as low mucosal histamine concentrations as duodenal ulcer patients who had not been operated on. In part 2, all duodenal ulcer patients showed an increase in gastric mucosal histamine concentration after vagotomy (P < 0·01). The smallest increase was in a patient with an incomplete vagotomy. Control patients who were not operated on but who underwent endoscopy and biopsy twice in the period of investigation, did not show any increase in mucosal histamine concentration between the times of the first and the second biopsy. The overall results of selective vagotomy and drainage in this study, with respect both to clinical Visick gradings and to radiological and acid secretory findings, were comparable to those reported by other authors. No significant change in numbers of parietal cells was found after vagotomy. Thus, selective gastric vagotomy with a drainage procedure leads to increased concentrations of histamine in the mucosa of the body of the stomach in man. The mechanism is not clear, but might be through inhibition of histamine release from mast cell stores.

Histamine and peptic ulcer: a prospective study of mucosal histamine concentration in duodenal ulcer patients and in control subjects suffering from various gastrointestinal diseases

In a prospective study the histamine content of the mucosa of the body of the stomach was measured in 100 patients consisting of control subjects, patients with duodenal ulcer and patients suffering from various gastrointestinal diseases. The histamine content was found to be 43 mug/g in male control subjects (median) while in duodenal ulcer patients levels attained were significantly lower by about 30 per cent. In all the other groups of patients histamine concentrations in gastric mucosa were found to be "normal". Since in most species it is extremely diffcult to alter the mucosal histamine concentration by any form of treatment, the diminished histamine content of the gastric mucosa in patients with duodenal ulcer seems remarkable. Among several possible explanations offered for this finding we think the most likely is that histamine release is increased in duodenal ulcer disease.

[Surgical preparation planning of hemodialysis candidates]

An early beginning of chronic hemodialysis is postulated to prevent dangerous uremic complications. Subcutaneous arteriovenous fistulas or autologous saphenous vein grafts in cases where multiple attempts to create a sufficiently functioning arteriovenous fistula have failed turned out to be the best procedures to obtain a suitable access to the blood vessels. The problems arising on a total of 57 patients to get an adequate blood flow by the time of first hemodialysis are discussed.