No abstract

A patient with thrombotic thrombocytopenic purpura (TTP) showed for the first time catastrophic signs and symptoms of CNS involvement immediately after infusion of platelets. Postmortem examination revealed extensive deposits of platelet aggregates within the small blood vessels of the brain, whereas lesions elsewhere in the body consisted of platelets as well as fibrin and were associated with endothelial proliferation and microaneurysm formation. These findings are consistent with the view that the initial event in TTP may be platelet aggregation. The plasma of this patient contained platelet-aggregating activity. We conclude that platelet transfusions in patients with TTP may aggravate the disease process.

Atom trap trace analysis, a laser-based atom counting method, has been applied to analyze atmospheric 39Ar (half-life=269  yr), a cosmogenic isotope with an isotopic abundance of 8×10(-16). In addition to the superior selectivity demonstrated in this work, the counting rate and efficiency of atom trap trace analysis have been improved by 2 orders of magnitude over prior results. The significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.

Studies of 6He beta decay along with tritium can play an important role in testing ab initio nuclear wave-function calculations and may allow for fixing low-energy constants in effective-field theories. Here, we present an improved determination of the 6He half-life to a relative precision of 3×10(-4). Our value of 806.89±0.11(stat)(-0.19syst)(+0.23)  ms resolves a major discrepancy between previous measurements. Calculating the statistical rate function we determined the ft value to be 803.04(-0.23)(+0.26)  s. The extracted Gamow-Teller matrix element agrees within a few percent with ab initio calculations.

Background: The beta decays of 3 H and 6 He can play an important role in testing nuclear wave-function calculations and fixing low-energy constants in effective-field theory approaches. However, there exists a large discrepancy between previous measurements of the 6 He half-life.Purpose: Our measurement aims at resolving this long-standing discrepancy in the 6 He half-life and providing a reliable f t-value and Gamow-Teller matrix element for comparison with theoretical ab-initio calculations.Method: We measured the 6 He half-life by counting the beta-decay electrons with two scintillator detectors operating in coincidence.Results: The measured 6 He half-life is 806.89 ± 0.11stat +0.23 −0.19 syst ms corresponding to a relative precision of 3 × 10 −4 . Calculating the statistical rate function we determined the f t-value to be 803.04 +0.26 −0.23 s. Conclusions: Our result resolves the previous discrepancy by providing a higher-precision result with careful analysis of potential systematic uncertainties. The result provides a reliable basis for future precision comparisons with ab-inito calculations.