Magnetism in Atomic-Sized Palladium Contacts and Nanowires

We have investigated Pd nanowires theoretically, and found that, unlike either metallic or free atomic Pd, they exhibit Hund's rule magnetism. In long, monoatomic wires, we find a spin moment of 0.7 Bohr magnetons per atom, whereas for short, monoatomic wires between bulk leads, the predicted moment is about 0.3 Bohr magnetons per wire atom. In contrast, a coaxial (6,1) wire was found to be nonmagnetic. The origin of the wire magnetism is analyzed.Comment: 6 pages, including 4 figure

Bias in little owl population estimates using playback techniques during surveys

Problemas en las estimas poblacionales de mochuelos cuando se realizan censos con reclamos Se desarrollaron dos estudios diferentes para probar la eficiencia de los censos por medio de reclamos de mochuelos (Athene noctua): (1) un seguimiento intensivo de las respuestas a los reclamos de mochuelos radio–marcados en una pequeña área, (2) un estudio extensivo utilizando reclamos para estimar la eficiencia del método como herramienta para detectar la presencia de mochuelos. En el primer caso, se detectaron 8,12 mochuelos de media en un periodo de censo de 30′, número cercano al tamaño de población real; además, se detectaron esplazamientos significativos de los mochuelos desde la posición inicial (antes de conectar el reclamo) a las posiciones siguientes durante la ejecución del reclamo. Sin embargo, tan sólo se detectó una media de 2,25 y 5,37 mochuelos en los primeros 5′ y 10′ respectivamente. En el segundo caso, se detectaron 137 territorios de mochuelos en 105 unidades de muestreo positivas. La tasa de ocupación fue de 0,35, la ocupación estimada de 0,393 y la probabilidad de detección de 0,439. La probabilidad acumulada estimada de detección sugiere que se precisarían de al menos cuatro muestreos en un estudio extensivo si se pretende detectar el 95% de las áreas ocupadas por mochuelos. Palabras clave: Mochuelo común, Métodos de censo, Programa Presence, Eficacia de detección, Actividad vocal.To test the efficiency of playback methods to survey little owl (Athene noctua) populations we carried out two studies: (1) we recorded the replies of radio–tagged little owls to calls in a small area; (2) we recorded call broadcasts to estimate the effectiveness of the method to detect the presence of little owl. In the first study, we detected an average of 8.12 owls in the 30' survey period, a number that is close to the real population; we also detected significant little owl movements from the initial location (before the playback) to the next locations during the survey eriod. However, we only detected an average of 2.25 and 5.37 little owls in the first 5' and 10', respectively, of the survey time. In the second study, we detected 137 little owl territories in 105 positive sample units. The occupation rate was 0.35, the estimated occupancy was 0.393, and the probability of detection was 0.439. The estimated cumulative probability of detection suggests that a minimum of four sampling times would be needed in an extensive survey to detect 95% of the areas occupied by little owls. Key words: Little owl, Survey methods, Presence Program, Detection efficiency, Vocal activity.Problemas en las estimas poblacionales de mochuelos cuando se realizan censos con reclamos Se desarrollaron dos estudios diferentes para probar la eficiencia de los censos por medio de reclamos de mochuelos (Athene noctua): (1) un seguimiento intensivo de las respuestas a los reclamos de mochuelos radio–marcados en una pequeña área, (2) un estudio extensivo utilizando reclamos para estimar la eficiencia del método como herramienta para detectar la presencia de mochuelos. En el primer caso, se detectaron 8,12 mochuelos de media en un periodo de censo de 30′, número cercano al tamaño de población real; además, se detectaron esplazamientos significativos de los mochuelos desde la posición inicial (antes de conectar el reclamo) a las posiciones siguientes durante la ejecución del reclamo. Sin embargo, tan sólo se detectó una media de 2,25 y 5,37 mochuelos en los primeros 5′ y 10′ respectivamente. En el segundo caso, se detectaron 137 territorios de mochuelos en 105 unidades de muestreo positivas. La tasa de ocupación fue de 0,35, la ocupación estimada de 0,393 y la probabilidad de detección de 0,439. La probabilidad acumulada estimada de detección sugiere que se precisarían de al menos cuatro muestreos en un estudio extensivo si se pretende detectar el 95% de las áreas ocupadas por mochuelos. Palabras clave: Mochuelo común, Métodos de censo, Programa Presence, Eficacia de detección, Actividad vocal

Shell and supershell structures of nanowires: A quantum-mechanical analysis

The stability of sodium nanowires is studied by modeling them as infinite uniform jellium cylinders and solving self-consistently for the electronic structure. The total energy per unit length oscillates as a function of the wire radius giving a shell structure. The amplitude of the energy oscillations attenuates regularly, reflecting a supershell structure. We compare our theoretical results with recent experiments [A. I. Yanson et al., Nature 400, 144 (1999); Phys. Rev. Lett. 84, 5832 (2000)] performed by the mechanically controllable break junctions (MCB) technique. The comparison clarifies the origin of the observed shell structure and especially the formation of the quantum beats of the supershell structure and supports the conclusions based on an earlier semiclassical model. The comparison is also a quantitative test for the reliability of the simple stabilized-jellium model as well as for the accuracy of the equation used to relate the conductivity and the area of the narrowest point of the constriction.Peer reviewe

On the Use of the Theory of Critical Distances with Mesh Control for Fretting Fatigue Lifetime Assessment

This work analyses the viability of the theory of critical distances (TCD) using mesh control for fretting fatigue lifetime assessment. More than seven hundred sets of simulations were performed by taking seventy different experimental tests reported previously in the literature. The outcome of the present study suggests that the TCD mesh control method can be extended to fretting fatigue problems by the reasonable assumption of setting the right element size proportional to critical distance. In this study, a significant computational time reduction of up to 97% was obtained. Thus, this study provides a simple method to design complex 3D industrial components subjected to fretting fatigue phenomena using finite element analysis efficiently without requiring complex remeshing techniques

Fish assemblages across the Mediterranean Sea and the effects of protection from fishing = I Popolamenti ittici nel Mediterraneo e gli effetti della protezione dall’impatto della pesca

Several studies have assessed the effectiveness of individual marine protected areas (MPAs) in protecting fish assemblages, but regional assessments of multiple parks are scarce. Here fish surveys using visual census were done in marine parks and fished areas at 31 locations across the Mediterranean Sea. Fish species richness, diversity and biomass (especially of top predators) were higher in MPAs compared to fished areas, and community structure differed significantly between MPAs and fished areas. Results suggest that MPAs are generally effective means to protect and recover fish populations and assemblages

Formación de líderes solidarios para el fortalecimiento de la convivencia en las instituciones niño Jesús de Praga y sagrada familia de Ibagué

Fotografías, imágenes, Tablas, Graficas, InstrumentosEl presente trabajo de investigación es titulado “Formación de líderes solidarios para el fortalecimiento de la convivencia en las Instituciones Niño Jesús de Praga y Sagrada Familia de Ibagué”, su principal objetivo fue formar líderes solidarios para el fortalecimiento de la convivencia en la Institución Educativa Niño Jesús de Praga grado seis dos jornada mañana e Institución Educativa Sagrada Familia grado seis siete jornada tarde de Ibagué Tolima. Para este estudio se utilizó un enfoque mixto e investigación aplicada, con la aplicación de instrumentos que fueron esenciales en este proceso de investigación como son encuesta de caracterización, diario de campo, test de liderazgo solidario y encuesta de convivencia, esto permitió indagar acerca de la convivencia, la solidaridad y el liderazgo en las instituciones educativas. Es así, que al realizar el respectivo análisis de los instrumentos se encontró que existen problemas de convivencia tales como acoso escolar evidenciado a través de maltrato psicológico, verbal y físico. Por otra parte, los estudiantes consideran que el liderazgo y la solidaridad son esenciales en su vida cotidiana tanto en el contexto educativo, familiar y en la parte social. En este sentido, se aplicaron talleres formativos donde se obtuvieron resultados óptimos mejorando e incrementando la solidaridad y el liderazgo en el aula, las relaciones interpersonales, la comunicación asertiva, el trabajo en equipo, este proyecto permitió trabajar un tema de interés para el fortalecimiento de la convivencia en los grados 6-2 y 6-7 de las dos Instituciones educativas.This research paper is entitled "Leadership training for strengthening solidarity coexistence Institutions Infant Jesus of Prague and Ibague holy Family", the main objective was to train leaders for strengthening solidarity coexistence Child Educational Institution Jesus of Prague degree-six-two hours morning and Holy Family Educational Institution grade seven six hours later in Ibague Tolima. For this study we used a mixed approach and applied research, with the application of tools that were essential to this research process such as characterization survey, field notes, supportive leadership test and survey of living, this allowed to inquire about the coexistence, solidarity and leadership in educational institutions. Thus, to the analysis made by the respective instruments found that there are problems such as bullying coexistence evidenced by psychological abuse, verbal and physical. Moreover, students consider that leadership and solidarity are essential in their daily lives both in the context of education, family and social part. In this sense, training workshops were applied where best results were obtained by improving and increasing solidarity and leadership in the classroom, interpersonal relationships, assertive communication, teamwork, this project allowed work on a topic of interest for strengthening coexistence in grades 6-2 and 6-7 of the two educational institutions

Inelastic scattering of fast electrons in nanowires: A dielectric formalism approach

The excitations produced by fast electrons impinging perpendicularly on both metallic and semiconductor cylindrical nanowires are investigated within the framework of dielectric theory. The dependence of the electron energy-loss spectra (EELS) on the nanowire radius is studied in detail, and so is the spatial extension of the induced-charge fluctuations associated to the modes that are excited during the loss process. The limits of applicability of dielectric theory to nanowires are discussed. In particular, comparison between the present theory and EELS measurements performed with silicon nanofibers support the use of dielectric theory at the scale of a few nanometers in diameter, and it is shown that this positive result is justified in terms of the longitudinal pattern of the induced surface plasmons. Finally, the effect of nanowire termination on the electron energy-loss probability for electrons passing near the edge is calculated using the boundary charge method, showing that the range of this effect can extend up to tens of nanometers for low-energy m=0 modes.Support from the Basque government and Basque Country University is acknowledged. One of the authors E.O. also acknowledges the Spanish Ministerio de Educacion y Cultura for financial support under Contract No. PB98-0780-C02.Peer reviewe

The effect of sodium fluorescein angiography on erythrocyte properties

© 1998 – IOS Press. All rights reservedSodium fluorescein angiography is a widely used routine ophthalmological diagnostic procedure which enables the study of chorioretinal microcirculation and consists of the injection of sodium fluorescein into the systemic bloodstream. The aim of the present study was to evaluate whether or not fluorescein interferes with erythrocyte properties during the angiographic procedure. In a group of 37 patients, 26 with non-insulin-dependent diabetes mellitus (DM) with and without retinopathy, and 11 without diabetes mellitus (non-DM) although affected by other ophthalmological diseases, all undergoing routine angiography, blood samples were drawn before (T0) and 30 min (T30) after fluorescein injection. The erythrocyte aggregation index (EAI), membrane lipid fluidity and erythrocyte acetylcholinesterase activity were determined in both groups. After fluorescein injection there was no statistical change in EAI and erythrocyte membrane fluidity in either group. Erythrocyte acetylcholinesterase activity, a marker of membrane protein integrity, decreased significantly (p < 0:01) in the DM group. Membrane lipid fluidity did not change with fluorescein injection, however, (i) in the DM group erythrocyte membranes became more rigid than in the non-DM (DPH: p < 0:01); (ii) EAI and membrane lipid fluidity became significantly correlated (r = 0:6263, p < 0:05) in non-DM patients at T30. In conclusion, fluorescein administration for angiographic procedures seems to interact with erythrocyte membrane, namely, in diabetic patients, which may interfere with the blood flow in the microcirculation

Magnetic phenomena in 5d transition metal nanowires

We have carried out fully relativistic full-potential, spin-polarized, all-electron density-functional calculations for straight, monatomic nanowires of the 5d transition and noble metals Os, Ir, Pt and Au. We find that, of these metal nanowires, Os and Pt have mean-field magnetic moments for values of the bond length at equilibrium. In the case of Au and Ir, the wires need to be slightly stretched in order to spin polarize. An analysis of the band structures of the wires indicate that the superparamagnetic state that our calculations suggest will affect the conductance through the wires -- though not by a large amount -- at least in the absence of magnetic domain walls. It should thus lead to a characteristic temperature- and field dependent conductance, and may also cause a significant spin polarization of the transmitted current.Comment: 7 pages, 5 figure

Excited states of Na nanoislands on the Cu(111) surface

Electronic states of one monolayer high Na nanoislands on the Cu(111) surface are studied as a function of the nanoisland size. Properties of nanoislands such as one-electron states, the electron density, and the associated potential are obtained self-consistently within the density-functional formalism using a one-dimensional pseudopotential for the Cu(111) substrate and the jellium model for Na. A wave packet propagation method is used to study the energies and lifetimes of quasistationary states localized at Na islands. For very large islands, island-localized states merge into the two-dimensional continuum of the Na quantum well state. Thus, we assign the quasistationary states studied as arising from the quantization of the two-dimensional quantum well continuum due to the finite island size. The scattering at the island boundaries results in the energy-conserving resonant electron transfer into the continuum of the substrate states broadening the island-localized states into resonances.Peer reviewe