Melting behavior of large disordered sodium clusters

The melting-like transition in disordered sodium clusters Na_N, with N=92 and 142 is studied by using a first-principles constant-energy molecular dynamics simulation method. Na_142, whose atoms are distributed in two (surface and inner) main shells with different radial distances to the center of mass of the cluster, melts in two steps: the first one, at approx. 130 K, is characterized by a high intrashell mobility of the atoms, and the second, homogeneous melting, at approx. 270 K, involves diffusive motion of all the atoms across the whole cluster volume (both intrashell and intershell displacements are allowed). On the contrary, the melting of Na_92 proceeds gradually over a very wide temperature interval, without any abrupt step visible in the thermal or structural melting indicators. The occurrence of well defined steps in the melting transition is then shown to be related to the existence of a distribution of the atoms in shells. Thereby we propose a necessary condition for a cluster to be considered rigorously amorphouslike (totally disordered), namely that there are no space regions of the cluster where the local value of the atomic density is considerably reduced. Na_92 is the only cluster from the two considered that verifies this condition, so its thermal behavior can be considered as representative of that expected for amorphous clusters. Na_142, on the other hand, has a discernible atomic shell structure and should be considered instead as just partially disordered. The thermal behavior of these two clusters is also compared to that of icosahedral (totally ordered) sodium clusters of the same sizes.Comment: LaTeX file. 7 pages with 12 picture

Bases científicas para el tratamiento del desgarro muscular : movilización versus inmovilización

Se exponen las bases científicas del tratamiento del desgarro muscular, haciendo una valoración de la reparación biológica de las lesiones en músculo estriado. Se estudia el «callo» muscular bajo las perspectivas de «lo conjuntivo» y «lo mioblástico». Se sacan consecuencias de orden terapéutico.The scientific basis for treatment of muscular injury arc considered trying to enlight the regeneration and biological repair of skeletal muscle. Muscular «callus» is studied under the perspectives of the connective and the mioblastic tissues. Some important derived consequence should be taken with account when treating this type of lesions

Migration Patterns in Male Great Bustards (Otis tarda)

5 paginas, 1 figura y 1 tableThe Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards.This study is a contribution to DGICYT-project PB94–0068.Peer reviewe

Evaluation of captive breeding as a method to conserve threatened Great Bustard populations.

6 paginas y 1 tableThe recent Great Bustard Action Plan summarizes de main recommended lines of action to preserve current populations and their habitats in Europe. Among others, captive breeding is mentioned as a method to save clutches found in the field whose hatching success probability is suspected to be low for any reason. Birds hatched from these clutches have been used to either build up small captive-breeding flocks that ensure preservation of the genetic pool of seriously threatened populations once these may be extinct, or to be released into the natural populations as juveniles. In this paper we evaluate the viability of captive breeding in the light of new results of a recent study of juvenile Great Bustards during their maternal dependence period, family break-up and dispersal. The few data available on survival of captive-bred young after being released suggest that they suffer a high mortality, probably due to the lack of the experience acquired in natural conditions from their mothers. The negative effects of imprinting by their human keepers, particularly in relation with display and mating, has not been sufficiently investigated. These and other aspects make captive breeding questionable as an effective method, as compared with habitat protection measures.PB94-0068 of the Dirección General de Investigacion Cientifica y TecnicaPeer reviewe

Migration Patterns in Male Great Bustards (Otis tarda)

5 paginas, 1 figura y 1 tableThe Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards.This study is a contribution to DGICYT-project PB94–0068.Peer reviewe

Labor demand and information technologies: evidence for Spain, 1980-2005

Utilizando la base de datos EU KLEMS, se contrasta la hipótesis de complementariedad entre habilidad y capital en los distintos sectores productivos en España en el periodo 1980-2005. Se analizan tres tipos de trabajadores clasificados según su nivel de habilidad sea alto, medio o bajo. Los activos de capital se van a clasificar entre activos TIC (tecnologías de la información y la comunicación) y activos no-TIC. La adquisición y el uso de activos TIC son costosos pero ha ido disminuyendo en el periodo en consideración en términos relativos a otros activos y al factor trabajo. El principal resultado que se obtiene es que existe un grado de sustituibilidad entre los trabajadores y los activos TIC a medida que la habilidad del trabajador va aumentando. De hecho, los activos TIC son muy complementarios con los trabajadores de alta habilidad. A lo largo del periodo analizado, la fracción de trabajadores con habilidad media y alta ha crecido un 21% y un 12%, respectivamente, en detrimento de los trabajadores de baja habilidad. Después de descomponer estos cambios, se descubre que existe un ajuste dentro de los sectores más que un ajuste del trabajo entre sectores.capital-skill complementarity, ICT, translog cost function, elasticity of substitution.

Artroplastia total de cadera no cementada : resultados a corto plazo con los componentes femorales de los modelos poro-palcar y PCA

Se presentan los resultados clínicos y radiológicos, a corto plazo, referentes al componente femoral de una serie de 62 artroplastias totales de cadera no cementadas. Treinta y tres correspondían al modelo PORO-PALCAR y 29 al modelo PCA. La edad media de los pacientes fue de 62 años (ds = 9,6). El tiempo medio de seguimiento postoperatorio ha sido 2 años (1,5-3). En la valoración clínica se ha utilizado el Test de Harris. La puntuación final total alcanzó 88,7 puntos (ds = 6,9) para el modelo PCA y 83,5 puntos (ds = 13,2) para el POROPALCAR. Los resultados clínicos fueron excelentes (80 a 100 puntos) en el 93 % de los implantes PCA y en el 67% PORO-PALCAR (p<0,01), con una remisión completa del dolor en más del 90% de los casos para ambos modelos. La mejoría funcional fue significativamente mayor para el modelo PCA. En cuanto a los resultados radiológicos, el modelo PORO-PALCAR presentó un hundimiento medio de 1,73 mm (p < 0,05). El 80% de los vástagos PCA y el 48% de los PORO-PALCAR no presentaban líneas radiolucientes en las zonas porosas (p<0,01). En las zonas inferiores, en más del 75% de los modelos PORO-PALCAR aparecieron líneas de hasta 2 mm de espesor y en el 21,2% líneas mayores de 2 mm en el vértice del vástago. Dos vástagos del modelo PORO-PALCAR presentaron signos de aflojamiento aséptico. Por lo tanto, el componente femoral del modelo PCA presentó una mejor fijación y osteointegración que el modelo PORO-PALCAR.The clinical and roentgenographic short-term results regarding femoral component of 62 non cemented total hip arthroplasties were evaluated. In 33 cases PORO-PALCAR model were implanted and in 29 cases PCA model were implanted. The average age of patients was 62 years (sd = 9,6). The average follow-up was 2 years, ranging from 1,5 to 3 years. Clinical assesment was performed using the Harris' score. The total end score reached 88,7 points (sd = 6,9) for the PCA model and 83,5 points (sd = 13,2) for the PORO-PALCAR model. Excellent clinical results (80 to 100 points) were found in 93 % of the patients with PCA model and in 67% of those with the PORO-PALCAR model (p<0,01). Pain was removed in more than 90% of the cases independently of the femoral model implanted. As for radiologic results, PORO-PALCAR model presented an average vertical subsidence of 1,73 mm (p<0,05). Radiolucent lines were not detected in 80% of PCA models and in 48% of PORO-PALCAR models around porous-surfaced (p < 0,01). In more of 75% of PORO-PALCAR models were observed radiolucent lines untill 2 mm of density in lower zones, and in 21% of cases radiolucent lines was greater than 2 mm around of stem apex. Two cases of PORO-PALCAR stem presented sings of aseptic loosening. Fixation and osteointegration seems to be better for the femoral component of PCA model than for the PORO-PALCAR stem

Componentes acetabulares no cementados: resultados preliminares con los modelos PCA y Poro-palcar

Se comparan los resultados clínicos y radiológicos a corto plazo referente s al component e acetabula r de 62 artroplastia s totale s de cader a no cementadas. Treinta y tres implante s correspondían al modelo Poro-palcar y 29 al modelo PCA. La edad media en el momento de la intervención fue de 62 años (ds=9.6). El tiempo medio de seguimient o postoperatorio fue de un año y siet e mese s (máximo 3 años y mínimo un año). Para la valoración clínica se utiliza el test de Harris. La puntuación final total alcanza 88.7 puntos (ds=6.9) para el modelo PCA y 83.5 puntos (ds=13.2) para el poropalear. Los resultados clínicos fueron excelente s (80-100 puntos) en el 93% de los implante s PCA y en el 67% poro-palear (p<0.01), con una remisión completa del dolor en más del 90% de los casos para ambos modelos. La mejoría de la capacidad funcional fue significativament e mayo r en los enfermo s intervenido s con e l model o PCA. En cuanto a los resultados radiológicos, no hubo signos significativos de migración acetabular en ninguno de los modelos. Respecto a la aparición de radiolucencias, no se detectaron en el 72% de las copas PCA y en 60% de las copas poro-palear, presentando el resto radiolucencias de hasta 2 mm, lo cual indica una mejor osteointegración de las copas PCA respecto de las poro-palear.The clinical and roentgenographi c short-term results regarding the acetabular component wer e aveluated in a series of 62 noncemented total hip arthroplastie s in whic h eithe r the PCA cup (29 cases) or the poro-palcar mode l (33 cases) wer e implanted. At the time of surgery, the mean age of patients wa s 62 year s (ds=9.6). The average follow-up wa s 1 year and 7 months, ranging from 1 to 3 years. Clinical assesment wa s performed usin g the Harris'score . At review, the total scor e reache d 88.7 points (ds=6.9) for the PCA model and 83.5 (ds+13.2) for the poro-palcar cup. Excellent clinical results (80-100points) wer e found in 93% of the patients operated on wich the PCA cup and in 67% of those with the poro-palcar model (p<0.01). Pain was removed in more than 90% of the case s independently of the cup model used. The improvement of function was significantly better in patients receiving the PCA cup. There was not acetabular migration in any of the groups. Periacetabular radiolucent images wer e not detected in 72% of PCA case s an in 60% of the poro-palcar group. In case s with radiolucent images, these don't exceded more than 2 mm. Osteointegration seens to be better for the PCA cups than for the poro-palcar models

Labor Demand and Information Technologies: Evidence for Spain, 1980-2005

Using the EU KLEMS dataset we test the capital-skill complementarity hypothesis in a cross-section of sectors in Spain between 1980 and 2005. We analyze three groups of workers, who are classed according to skill level: high, medium and low. Capital assets have been broken down into ICT (information and communication technologies) assets and non-ICT assets. Acquisition and usage costs of ICT assets declined throughout the period studied, both in absolute terms and relative to the other capital assets and workers. Our principal finding is that the substitutibility between workers and ICT assets falls as worker skill level rises. In fact, the ICT assets were strongly complement with highly skilled workers and were not substitutive with them. Throughout the period analyzed, the fraction of employed medium- and high-skill workers rose by 21% and 12%, respectively, to the disadvantage of low-skill workers. After decomposing these changes, we found that the latter were dominated by an ajustment within sectors more than by a composition effect or adjustment between sectors. These adjustments may be explained by reference to the estimated elasticities of substitution.capital-skill complementarity, ICT, translog cost function, elasticity of substitution.