RESUMEN
Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV (J^{π}=1^{+}, T=1) stateâground state (J^{π}=0^{+}, T=0) and the isoscalar magnetic dipole 18.15 MeV (J^{π}=1^{+}, T=0) stateâground state transitions in ^{8}Be. Significant enhancement relative to the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of >5σ. This observation could possibly be due to nuclear reaction interference effects or might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of 16.70±0.35(stat)±0.5(syst) MeV/c^{2} and J^{π}=1^{+} was created.
RESUMEN
Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca â (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe â (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.
RESUMEN
The ß feeding probability of (102,104,105,106,107)Tc, 105Mo, and 101Nb nuclei, which are important contributors to the decay heat in nuclear reactors, has been measured using the total absorption technique. We have coupled for the first time a total absorption spectrometer to a Penning trap in order to obtain sources of very high isobaric purity. Our results solve a significant part of a long-standing discrepancy in the γ component of the decay heat for 239Pu in the 4-3000 s range.
RESUMEN
OBJECTIVE: To study the usefulness of the Second Acute Physiology and Chronic Health Evaluation (APACHE II) scoring system for prognostication of in-hospital mortality in patients with acute myocardial infarction treated with thrombolysis. DESIGN: A prospective validation study was conducted at a medical intensive care unit at a university hospital. Over a 3-year period, 1714 patients with acute myocardial infarction were studied (mean age 72+/-10 years). Thrombolytic therapy was the prescribed treatment for 316 patients and total hospital mortality was 16%. RESULTS: The patients who received thrombolysis were younger, had higher blood pressure, lower heart and respiratory rates and higher Glasgow Coma Scale scores. Total in-hospital mortality was 9.5% in patients treated with thrombolysis and 17.1% in untreated patients (p < 0.01). Corresponding APACHE II predictions of mortality were 11.8 and 15.8% (p < 0.01). There was no significant difference between observed and predicted mortality. When a decision rule of 50% predicted risk of death was employed, sensitivity was 20% and specificity 99% in the thrombolytic group, while the corresponding figures in the nonthrombolytic group were 31% and 97%, respectively. CONCLUSIONS: In-hospital mortality in groups of patients treated with or without thrombolysis for acute myocardial infarction could be predicted with the APACHE II scoring system. Prognostication in individual patients is not possible with the APACHE II system.