192 research outputs found
Silene patagonica (Speg.) Bocquet
valle de la Laguna BlancapublishedVersio
Superallowed 0+ to 0+ nuclear beta decays: A new survey with precision tests of the conserved vector current hypothesis and the standard model
A new critical survey is presented of all half-life, decay-energy and
branching-ratio measurements related to 20 0+ to 0+ beta decays. Compared with
our last review, there are numerous improvements: First, we have added 27
recently published measurements and eliminated 9 references; of particular
importance, the new data include a number of high-precision Penning-trap
measurements of decay energies. Second, we have used the recently improved
isospin symmetry-breaking corrections. Third, our calculation of the
statistical rate function now accounts for possible excitation in the daughter
atom. Finally, we have re-examined the systematic uncertainty associated with
the isospin symmetry-breaking corrections by evaluating the radial-overlap
correction using Hartree-Fock radial wave functions and comparing the results
with our earlier calculations, which used Saxon-Woods wave functions; the
provision for systematic uncertainty has been changed as a consequence. The new
corrected Ft values are impressively constant and their average, when combined
with the muon liftime, yields the up-down quark-mixing element of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix, V_{ud} = 0.97425(22). The unitarity
test on the top row of the matrix becomes |V_{ud}|^2 + |V_{us}|^2 + |V_{ub}|^2
= 0.99995(61). Both V_{ud} and the unitarity sum have significantly reduced
uncertainties compared with our previous survey, although the new value of
V_{ud} is statistically consistent with the old one. From these data we also
set limits on the possible existence of scalar interactions, right-hand
currents and extra Z bosons. Finally, we discuss the priorities for future
theoretical and experimental work with the goal of making the CKM unitarity
test even more definitive.Comment: 36 pages, 11 tables, 9 figure
Alternative mRNA Editing in Trypanosomes Is Extensive and May Contribute to Mitochondrial Protein Diversity
The editing of trypanosome mitochondrial mRNAs produces transcripts necessary for mitochondrial functions including electron transport and oxidative phosphorylation. Precursor-mRNAs are often extensively edited by specific uridine insertion or deletion that is directed by small guide RNAs (gRNAs). Recently, it has been shown that cytochrome c oxidase subunit III (COXIII) mRNAs can be alternatively edited to encode a novel mitochondrial membrane protein composed of a unique hydrophilic N-terminal sequence of unknown function and the C-terminal hydrophobic segment of COXIII. To extend the analysis of alternative editing in Trypanosoma brucei we have constructed libraries with over 1100 full-length mitochondrial cDNAs and the sequences of over 1200 gRNA genes. Using this data, we show that alternative editing of COXIII, ATPase subunit 6 (A6), and NADH dehydrogenase subunits 7, 8 and 9 (ND7, 8, 9) mRNAs can produce novel open reading frames (ORFs). Several gRNAs potentially responsible for the alternative editing of these mRNAs were also identified. These findings show that alternative editing of mitochondrial mRNAs is common in T. brucei and expands the diversity of mitochondrial proteins in these organisms
High Precision Measurement of the Superallowed 0^+ to 0^+ Beta Decay of ^{22}Mg
The half-life, 3.8755(12) s, and superallowed branching ratio, 0.5315(12),
for ^{22}Mg beta-decay have been measured with high precision. The latter
depended on gamma-ray intensities being measured with an HPGe detector
calibrated for relative efficiencies to an unprecedented 0.15%. Previous
precise measurements of 0^+ to 0^+ transitions have been restricted to the nine
that populate stable daughter nuclei. No more such cases exist, and any
improvement in a critical CKM unitarity test must depend on precise
measurements of more exotic nuclei. With this branching-ratio measurement, we
show those to be possible for T_z = -1 parents. We obtain a corrected Ft-value
of 3071(9) s, in good agreement with expectations.Comment: 4 pages, 2 figures, revtex
Superallowed nuclear beta decays: A critical survey with tests of CVC and the standard model
A complete and critical survey is presented of all half-life, decay-energy
and branching-ratio measurements related to 20 superallowed decays; no
measurements are ignored, though some are rejected for cause and others
updated. A new calculation of the statistical rate function is described and
experimental ft values determined. The associated theoretical corrections
needed to convert these results into Ft values are discussed, and careful
attention is paid to the origin and magnitude of their uncertainties. As an
exacting confirmation of the conserved vector current hypothesis, the Ft values
are seen to be constant to 3 parts in 10^4. These data are also used to set new
limits on any possible scalar interactions or right-hand currents. The average
Ft value obtained from the survey, when combined with the muon lifetime, yields
the CKM matrix element Vud = 0.9738(4); and the unitarity test on the top row
of the matrix becomes |Vud|^2 + |Vus|^2 + |Vub|^2 = 0.9966(14) using the PDG's
currently recommended values for Vus and Vub. We discuss the priorities for
future theoretical and experimental work with the goal of making the CKM
unitarity test more definitive.Comment: 64 pages, 4 postscript figure
Impact of Extended-Duration Shifts on Medical Errors, Adverse Events, and Attentional Failures
BACKGROUND: A recent randomized controlled trial in critical-care units revealed that the elimination of extended-duration work shifts (≥24 h) reduces the rates of significant medical errors and polysomnographically recorded attentional failures. This raised the concern that the extended-duration shifts commonly worked by interns may contribute to the risk of medical errors being made, and perhaps to the risk of adverse events more generally. Our current study assessed whether extended-duration shifts worked by interns are associated with significant medical errors, adverse events, and attentional failures in a diverse population of interns across the United States. METHODS AND FINDINGS: We conducted a Web-based survey, across the United States, in which 2,737 residents in their first postgraduate year (interns) completed 17,003 monthly reports. The association between the number of extended-duration shifts worked in the month and the reporting of significant medical errors, preventable adverse events, and attentional failures was assessed using a case-crossover analysis in which each intern acted as his/her own control. Compared to months in which no extended-duration shifts were worked, during months in which between one and four extended-duration shifts and five or more extended-duration shifts were worked, the odds ratios of reporting at least one fatigue-related significant medical error were 3.5 (95% confidence interval [CI], 3.3–3.7) and 7.5 (95% CI, 7.2–7.8), respectively. The respective odds ratios for fatigue-related preventable adverse events, 8.7 (95% CI, 3.4–22) and 7.0 (95% CI, 4.3–11), were also increased. Interns working five or more extended-duration shifts per month reported more attentional failures during lectures, rounds, and clinical activities, including surgery and reported 300% more fatigue-related preventable adverse events resulting in a fatality. CONCLUSIONS: In our survey, extended-duration work shifts were associated with an increased risk of significant medical errors, adverse events, and attentional failures in interns across the United States. These results have important public policy implications for postgraduate medical education
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