RESUMEN
We investigated decays of ^{51,52,53}K at the ISOLDE Decay Station at CERN in order to understand the mechanism of the ß-delayed neutron-emission (ßn) process. The experiment quantified neutron and γ-ray emission paths for each precursor. We used this information to test the hypothesis, first formulated by Bohr in 1939, that neutrons in the ßn process originate from the structureless "compound nucleus." The data are consistent with this postulate for most of the observed decay paths. The agreement, however, is surprising because the compound-nucleus stage should not be achieved in the studied ß decay due to insufficient excitation energy and level densities in the neutron emitter. In the ^{53}K ßn decay, we found a preferential population of the first excited state in ^{52}Ca that contradicted Bohr's hypothesis. The latter was interpreted as evidence for direct neutron emission sensitive to the structure of the neutron-unbound state. We propose that the observed nonstatistical neutron emission proceeds through the coupling with nearby doorway states that have large neutron-emission probabilities. The appearance of "compound-nucleus" decay is caused by the aggregated small contributions of multiple doorway states at higher excitation energy.
RESUMEN
OBJECTIVES: a) To find the prevalence of anti-tetanus vaccination in a health district, and b) to detect difficulties in the implementation of corrective measures, after the appearance of three cases of tetanus in 6 months. DESIGN: An observational descriptive crossover study. SETTING: Primary care. Rural health district with 18266 inhabitants. PARTICIPANTS: People of both sexes over 14 from the 3 population nuclei, which had the best records of attendance and vaccination in the health district. INTERVENTIONS: Vaccination coverage at the start and end of the intervention for 328 people chosen by systematic randomised sampling. SOURCE OF DATA: clinical records. MAIN MEASUREMENTS AND RESULTS: At the start of the intervention there was less vaccination coverage among males, over-50s and people living in small nuclei of population. During the study period vaccination coverage increased more in the nuclei where there had been a tetanus case. Vaccines were lacking at the start of the intervention. CONCLUSIONS: A low use of clinical records in the health district was detected, which posed difficulties for the research. Except for one of the population nuclei, very few people at the start of the study were recorded as correctly vaccinated. It is seen that the health service responded slowly to such serious cases as these. It is suggested that primary health care activities should be programmed more in accord with the health problems prevailing in each area. With an illness like tetanus we should not wait for a case to occur before acting.
