2,319 research outputs found

    Lifetime Measurement of the 8s Level in Francium

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    We measure the lifetime of the 8s level on a magneto-optically trapped sample of ^{210}Fr atoms with time-correlated single-photon counting. The 7P_{1/2} state serves as the resonant intermediate level for two-photon excitation of the 8s level completed with a 1300 nm laser. Analysis of the fluorescence decay through the the 7P_{3/2} level gives 53.30 +- 0.44 ns for the 8s level lifetime.Comment: 4 pages, 4 figure

    Beta-delayed-neutron studies of 135,136^{135,136}Sb and 140^{140}I performed with trapped ions

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    Beta-delayed-neutron (β\betan) spectroscopy was performed using the Beta-decay Paul Trap and an array of radiation detectors. The β\betan branching ratios and energy spectra for 135,136^{135,136}Sb and 140^{140}I were obtained by measuring the time of flight of recoil ions emerging from the trapped ion cloud. These nuclei are located at the edge of an isotopic region identified as having β\betan branching ratios that impact the r-process abundance pattern around the A~130 peak. For 135,136^{135,136}Sb and 140^{140}I, β\betan branching ratios of 14.6(11)%, 17.6(28)%, and 7.6(28)% were determined, respectively. The β\betan energy spectra obtained for 135^{135}Sb and 140^{140}I are compared with results from direct neutron measurements, and the β\betan energy spectrum for 136^{136}Sb has been measured for the first time

    Oral direct anticoagulants in the treatment of nonvalvular atrial fibrillation. Results of the daily clinical practice.

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    Atrial fibrillation (AF) is the most common arrhythmia. It leads to significant morbidity and mortality. The new oral anticoagulants (NOAC) represent an improvement compared with standard treatment (vitamin K antagonists (AVK)) in the prevention of thromboembolic complications in patients with non-valvular AF.N

    Determination of the Axial-Vector Weak Coupling Constant with Ultracold Neutrons

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    A precise measurement of the neutron decay β\beta-asymmetry A0A_0 has been carried out using polarized ultracold neutrons (UCN) from the pulsed spallation UCN source at the Los Alamos Neutron Science Center (LANSCE). Combining data obtained in 2008 and 2009, we report A0=−0.11966±0.00089−0.00140+0.00123A_0 = -0.11966 \pm 0.00089_{-0.00140}^{+0.00123}, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon gA/gV=−1.27590−0.00445+0.00409g_A/g_V = -1.27590_{-0.00445}^{+0.00409}.Comment: 5 pages, 2 figure

    New result for the neutron β\beta-asymmetry parameter A0A_0 from UCNA

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    The neutron β\beta-decay asymmetry parameter A0A_0 defines the correlation between the spin of the neutron and the momentum of the emitted electron, which determines λ=gAgV\lambda=\frac{g_{A}}{g_{V}}, the ratio of the axial-vector to vector weak coupling constants. The UCNA Experiment, located at the Ultracold Neutron facility at the Los Alamos Neutron Science Center, is the first to measure such a correlation coefficient using ultracold neutrons (UCN). Following improvements to the systematic uncertainties and increased statistics, we report the new result A0=−0.12054(44)stat(68)systA_0 = -0.12054(44)_{\mathrm{stat}}(68)_{\mathrm{syst}} which yields λ≡gAgV=−1.2783(22)\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2783(22). Combination with the previous UCNA result and accounting for correlated systematic uncertainties produces A0=−0.12015(34)stat(63)systA_0=-0.12015(34)_{\mathrm{stat}}(63)_{\mathrm{syst}} and λ≡gAgV=−1.2772(20)\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2772(20).Comment: 9 pages, 7 figures, updated to as-published versio

    Recoil-ion detection efficiency for complex β decays studied using the Beta-decay Paul Trap

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    Beta-delayed neutron emission is being studied by detecting the β particles and recoiling ions emerging from the Beta-decay Paul Trap. For β decays to the ground state or γ-emitting states of the daughter nucleus, the fraction of recoiling ions which reach the ion detector in coincidence with a β particle has been determined for 134, 135Sb, 137, 138, 140I, and 144, 145Cs. This value is needed for the determination of the β-delayed neutron emission branching ratio solely from the recoil-ion time-of-flight (TOF) spectrum. The β-particle energy and recoil-ion TOF spectra were used to constrain a simple decay model, which can be used to determine the detection efficiency. The method is compared to simulations to estimate the uncertainty introduced by incomplete knowledge of the decay pattern. By fitting the simulation results to several β-ion coincidence properties measured during the experiment, the fraction of ions which reach the microchannel plate detector can be determined to within ±4%. This result opens the possibility of using the recoil-ion TOF spectra for high precision β-delayed neutron branching-ratio measurements

    Accuracy and Precision of the COSMED K5 Portable Analyser

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    The main aims of this study were to determine the accuracy of the portable metabolic cart K5 by comparison with a stationary metabolic cart (Vyntus CPX), to check on the validity of Vyntus CPX using a butane combustion test, and to assess the reliability of K5 during prolonged walks in the field. For validation, measurements were consecutively performed tests with both devices at rest and during submaximal exercise (bicycling) at low (60 W) and moderate intensities (130–160 W) in 16 volunteers. For the reliability study, 14 subjects were measured two times during prolonged walks (13 km, at 5 km/h), with the K5 set in mixing chamber (Mix) mode. Vyntus measured the stoichiometric RQ of butane combustion with high accuracy (error <1.6%) and precision (CV <0.5%), at VO2 values between 0.788 and 6.395 L/min. At rest and 60 W, there was good agreement between Vyntus and K5 (breath-by-breath, B×B) in VO2, VCO2, RER, and energy expenditure, while in Mix mode the K5 overestimated VO2 by 13.4 and 5.8%, respectively. Compared to Vyntus, at moderate intensity the K5 in B×B mode underestimated VO2, VCO2, and energy expenditure by 6.6, 6.9, and 6.6%, respectively. However, at this intensity there was an excellent agreement between methods in RER and fat oxidation. In Mix mode, K5 overestimated VO2 by 5.8 and 4.8%, at 60 W and the higher intensity, respectively. The K5 had excellent reliability during the field tests. Total energy expenditure per Km was determined with a CV for repeated measurements of 4.5% (CI: 3.2–6.9%) and a concordance correlation coefficient of 0.91, similar to the variability in VO2. This high reproducibility was explained by the low variation of FEO2 measurements, which had a CV of 0.9% (CI: 0.7–1.5%) combined with a slightly greater variability of FECO2, VE, VCO2, and RER. In conclusion, the K5 is an excellent portable metabolic cart which is almost as accurate as a state-of-art stationary metabolic cart, capable of measuring precisely energy expenditure in the field, showing a reliable performance during more than 2 h of continuous work. At high intensities, the mixing-chamber mode is more accurate than the B×B mode

    Conservation of the endemic dwarf carnivores of Cozumel Island, Mexico.

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    Cozumel Island, Mexico, harbours two endemic species of dwarf procyonids: the Pygmy Raccoon Procyon pygmaeus and the Dwarf Coati Nasua nelsoni. Both species are Critically Endangered, and are among the world&rsquo;s most threatened Carnivora. Here we summarise the research we have been conducting on their ecology, evolution, genetics, and conservation. We also summarise the conservation initiatives we have been undertaking and promoting in order to advance the conservation of these unique species and their habitats. This effort illustrates the importance of an interdisciplinary approach in conservation science and action in maximising effectiveness. Nevertheless, the precarious status of the species make it imperative to continue and expand the work we have carried out in Cozumel to prevent two imminent global extinctions.<br /
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