13,219 research outputs found
Lifetime Measurement of the 8s Level in Francium
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
Corrosion studies of different ferrous alloys for rolling cylinders
peer reviewedThe aim of this work is to study the corrosion behaviour in chloride media of a high chromium iron alloy. The influence of the surface finishing as well as the heat treatment was analysed. The technique employed for measuring the corrosion behaviour was the Electrochemical Impedance Spectroscopy, an electrochemical technique that allows the observation not only of the corrosion rates but also the changes on the corrosion mechanism of the alloy. The results showed that it is worth performing a double tempering and a having smoother surface finishing only for long exposure periods. A comparison between different oxidising conditions was also performed simulating the life in service of the hot rolling cylinders and revealed an increase in the protective properties as the oxidising time increased due to the chromium present on the alloy (18%). (c) 2005 Elsevier Ltd. All rights reserved
Microsolvation of heavy halides
The fundamental question of how intermolecular interactions lead to the stabilization of heavy halides (Br−, I−, At−) microsolvated with up to six explicit water molecules is addressed here. An exhaustive exploration of the potential energy surfaces using a random search algorithm followed by optimization of molecular geometries using pseudopotentials and at the full four component relativistic levels of theory, affords a good number of structures with high probabilities of occurrence, highlighting the important role of local minima to reproduce experimentally measured properties. Sequential hydration enthalpies for astatide are reported here for the first time in the scientific literature. Closed shell (ionic, long range) as well as intermediate character interactions (contributions from closed shell and covalent) are at play stabilizing the clusters. The ability of water molecules to either donate or to accept electron density dictates the nature and strength of the corresponding hydrogen bonds in solvation shells. Binding energies and molecular geometries are shown to be more sensitive to electron correlation than to relativistic effects
Anisotropic spin-orbit induced splitting of intersubband spin plasmons
The anisotropic splitting of intersubband spin plasmons, resulting from spin-orbit coupling, is studied by angle-resolved inelastic light scattering on a [001]-oriented GaAs/AlGaAs quantum well. Confirming theoretical predictions made in [C. A. Ullrich and M. A. Flatte, Phys. Rev. B ´ 68, 235310 (2003)], this splitting is proven to exhibit a characteristic two-fold symmetry with the in-plane orientation, and to increase with increasing modulus of the excitation momentum. This opens the way to a more complete investigation, aiming at evidencing the existence of a collective spin-orbit field driving these excitations.Fil: Baboux, F.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Francia. Centre National de la Recherche Scientifique; FranciaFil: Perez, F. Universite de Paris Vi. Institut Des Nanosciences de Paris; Francia. Centre National de la Recherche Scientifique; FranciaFil: Ullrich, C. A. . University Of Missouri; Estados UnidosFil: D'Amico, I. . University Of York; Reino UnidoFil: Gomez, Javier Enrique. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Centre National de la Recherche Scientifique; Francia. Universite de Paris Vi. Institut Des Nanosciences de Paris; FranciaFil: Bernard, M.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Franci
Relationships between physical activity frequency and self-perceived health, self-reported depression, and depressive symptoms in spanish older adults with diabetes: a cross-sectional study
Diabetes is one of the most prevalent noncommunicable diseases in the world. This disease can affect both physical and mental health in the population. This study analyzed the prevalence of Self-Perceived Health (SPH), self-reported depression, and depressive symptoms in comparison with the Physical Activity Frequency (PAF) reported by Spanish older adults with diabetes. A cross-sectional study was carried out with data from 2799 self-reported diabetic participants, all of whom were residents of Spain, aged 50–79 years, and included in the European Health Surveys carried out in Spain (EHIS) both in 2014 and 2020. The relationships between the variables were analysed with a chi-squared test. A z-test for independent proportions was performed to analyze differences in proportions between the sexes. A multiple binary logistic regression was carried out on the prevalence of depression. Linear regressions were performed on depressive symptoms and SPH. Dependent relationships were found between the SPH, self-reported depression, and depressive symptoms with PAF. Most of the very active participants reported a higher prevalence of self-reported depression. Physical inactivity increased the risk of depression, major depressive symptoms, and negative SPH.info:eu-repo/semantics/publishedVersio
Thermal Effect on TL Response of Single Doped LiF+NaF:RE Polycrystalline Phosphors
In this work, the sintering and annealing effects on the thermoluminescent (TL) behavior of undoped and rare earth (RE)-doped LiF+NaF powder samples (RE = Ce3+, Eu3+, Lu3+ or Tl+, at 0.5 mol%) was analyzed by evaluating the sensitivity to gamma radiation and TL response of the material. The polycrystalline samples were obtained by solid state reaction at 1000°C. The samples were irradiated in a Gammacell-3000 Elan irradiator loaded with 137Cs sources. The glow curves of the LiF+NaF doped with lutetium or thallium show an intense glow peak at about 175°C and 135°C, respectively. When the phosphor was doped with cerium or europium the glow curves were complex in their structure, with TL peaks observed at 155°C and 165°C, respectively. The linear dose-response was between 10 and 50 Gy for cerium, europium or lutetium doped LiF+NaF samples, while for the thallium doped and undoped samples such intervals were 10-100 Gy and 10-500 Gy, respectively. Because the shape of the glow curves were complex, the analysis was carried out in (i) samples without a sintering treatment where the TL response was found insensitive to pre-irradiation annealing treatment, and (ii) sintered samples (300, 350, 400 or 500 °C), in this last case the TL response was dependent on the annealing temperature (100-400 °C), finally (iii) the kinetics parameters of the glow curves were analyzed by assuming a general order kinetics model. The observed glow curves and TL characteristics of the LiF+NaF:RE phosphor make attractive this material to be useful in gamma dose dosimetry
Identificación de nematodos asociados al pasto colosuana (bothriochloa pertusa (l) a. Camus) en el municipio de sampues, departamento de sucre, Colombia
The present objective this study was to identify genera of nematodes associated with colosuana grass (Bothriochloa pertusa (L) A. Camus) in municipality of Sampues of Sucre department. The isolation of nematodes from roots and soils were performed by the Baermann funnel technique and their identification was made by using existing taxonomic keys to nematodes. We identified 10 genera of nematodes found in greater proportion Cephalobus gender (bacterÃvore) with respect to Pratylenchus, Criconemella (phytoparasitic) Dorylaiminae (omnivore), Prionchulus and Tripyla (Predators), Aphelenchoides (micófago) Tylocephalus, Acrobeles and Rhabditis (BacterÃvoros). This is the first report that we have in the colombian Caribbean diversity of nematodes associated with soil and grass roots colosuana.El presente trabajo tuvo como objetivo identificar géneros de nemátodos asociados al pasto colosuana (Bothriochloa pertusa (L) A. Camus) en el municipio de Sampues, departamento de Sucre. El aislamiento de nematodos de raÃces y suelos fueron realizadas por la técnica del embudo de Baermann y su identificación se hizo mediante el empleo de claves taxonómicas existente para nematodos. Se identificaron 10 géneros de nematodos, encontrándose en mayor proporción el género Cephalobus (bacterÃvoro), con relación a Pratylenchus, Criconemella (fitoparásitos), Dorylaiminae (OmnÃvoro), Prionchulus y Tripyla (Predadores), Aphelenchoides (micófago), Tylocephalus, Acrobeles y Rhabditis (BacterÃvoros). Este es el primer reporte que se tiene en el Caribe Colombiano de la diversidad de nematodos asociados a suelo y raÃces del pasto colosuana
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