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

Quick Analysis of Organic Amendments via Portable X-ray Fluorescence Spectrometry

The determination of heavy metals in soils and organic amendments, such as compost, manure, biofertilizer, and sludge, generally involves the digestion of samples with aqua regia, and the determination of those in the solution using various techniques. Portable X-ray fluorescence (PXRF) has many advantages in relation to traditional analytical techniques. However, PXRF determines the total elemental content and, until now, its use for the analysis of organic amendments has been limited. The objective of this work is the calibration of a PXRF instrument to determine the aqua regia-soluble elemental contents directly in solid samples of organic amendments. Our proposal will avoid the digestion step and the use of other laboratory techniques. Using a training set of samples, calibration functions were obtained that allow the determination of the aqua regia-soluble contents from the PXRF readings of total contents. The calibration functions (obtained by multiple linear regression) allowed the quantitative determination of the aqua regia-soluble contents of Fe, K, P, S, Zn, Cu, Pb, Sr, Cr, and Mn, as well as the organic matter content and a semi-quantitative assessment of Al, Ca, V, Ba, Ni, and As contents. The readings of Si, Fe, Al, Ca, K, or S were used as correction factors, indicating that the calibrations functions found are truly based on the chemical composition of the sample matrix. This study will allow a fast, cheap, and reliable field analysis of organic amendments and of other biomass-based materials.Spanish Ministry of Science, Innovation and Universities, and the European Regional Development Fund, European Union, (AEI/FEDER, UE), grant number CGL2016-78937-R

Tucídides: panorama actual (1986)

Sin resume

Adult coloration of the Bearded Vulture (Gypaetus barbatus) in the Pyrenees: relation to sex, mating system and productivity.

Cosmetic coloration is not a common phenomenon among bird species. Adult Bearded Vultures Gypaetus barbatus typically show orange coloration in head, chest, belly and tarsus feathers that is the result of mud baths in ferruginous substrates. Several non-mutually exclusive visual signalling hypotheses can be proposed to explain this phenomenon. Coloration could be used to signal: (1) dominance towards conspecifics, with darker birds being dominant (status signalling hypothesis); (2) sex (gender signalling hypothesis) because females are usually more intensely coloured; (3) individual quality for mate choice (quality signalling hypothesis); or (4) different reproductive strategies between individuals (e.g. in polyandrous trios). Here we report results from systematic monitoring of breeding Bearded Vultures in the pre-laying period in the central and western Pyrenees (Spain and France) between 2016 and 2020, including 162 individuals from 70 reproductive units (48 pairs and 22 trios). We classified individuals as being white, pale, medium or dark, and analysed the relationship with sex, mating system (pair or trios) and average productivity across years. Our results showed that the most common form was medium (67%), then pale (22%), dark (9%) and white (2%) morphs. Overall, females were darker than males, but with a large overlap in coloration. In trios, dominant males were darker than subordinate males, although differences were not statistically significant. The mating system (pair or trio) did not influence female coloration. A multimodel comparison showed that the number of years of territory occupation, mating system and their combination (but not coloration) were the best predictors of average productivity. Our results do not support the gender signalling hypothesis. The reproductive strategy signalling hypothesis might be supported because beta males were, on average, paler than males in pairs, but this topic requires further investigations because our results were inconclusive. Finally, that females (thought to be dominant because of their slightly larger size) were on average darker than males agrees with the status signalling hypothesis, although an experimental approach would be needed to formally test this hypothesis

Automated procedures for the comparative analysis of HLA class I-bound peptide repertoires

Comunicaciones a congreso

Relationship between rules and technical and tactical contents in minibasket

Las reglas condicionan el desarrollo del juego en cualquier deporte ya que delimita lo que se puede hacer. Se pretende conocer el orden de importancia de las reglas en minibasket, así como los medios técnico-tácticos que se derivan éstas. El método utilizado para la toma de datos ha sido el grupo nominal. Los participantes han sido siete expertos que cumplían unas condiciones mínimas. Con relación a la primera pregunta, el orden de importancia de las reglas ha sido: los pasos, dobles, líneas delimitadoras, faltas, árbitro, reglas de tiempo y puntuación. Con relación a los medios técnico-tácticos que se derivan de las reglas más importantes, a modo de ejemplo, a través de los pasos se aprende el bote, las arrancadas, las paradas, entradas, etc. Estos datos permiten organizar una programación basada en las reglasThe rules determine the development of the game in every sport because they put a limit to what you can do and what not. The aims of the research were to determine the order of importance of the basic basketball rules as well as the technical and tactical contents deriving from these rules. The method used for the data collection was that of the nominal group technique. The nominal group consisted of seven experts who fulfilled the minimum conditions. Regarding the first question, the order of importance of the rules was: steps, double dribble, lines, fouls, referee, rules regarding time limits and score. With regard to the technical and tactical contents deriving from the most important rules, for example, through the steps’ rules, players can learn starts, stops, lay-up, etc. These data allow organizing a program based on the rule

Paleovegetación durante la Edad del Bronce en la Rioja alavesa: Análisis palinológico del yacimiento de Peña Parda ( Laguardia, Álava)

En este trabajo se presenta el estudio palinológico del yacimiento de Peña Parda (Laguardia, Álava). Los resultados obtenidos, en las 13 muestras estudiadas, han aportado interesantes datos sobre el paisaje vegetal existente en la vertiente sur de la Sierra de Cantabria durante la Edad del Bronce, así como sobre las evidencias de antropización

Structural and morphological evolution of powders nanostructured ceramics: transitional aluminas

This work aims with the study of the transformation of boehmite into transitional aluminas. Boehmite was obtained by a sol-gel method from an aluminium hazardous waste. The thermal behaviour of boehmite was followed by thermogravimetry and differential thermal analysis to determine the transformation temperatures.  By calcinations of boehmite at temperatures ranging between 250-1000ºC, transitional aluminas (?, ? , ?-Al2O3)  were synthesized and characterized by XRD, TEM and FTIR. All the transitional aluminas exhibit nanometric crystallite size, ranging from 2.5-15nm. ?-Al2O3 was obtained as a nanostructured material at 500ºC with a cell parameter a=7.923Å. ?-phase stars to appear at 850ºC with a crystallite size of 6nm and cell parameters a=5.672Å and c=24.600Å. For ?-Al2O3 the cell parameters, in Å, were a=11.817, b=2.912, c=5.621 and ?=103.8º. The progressive conversion of the transitional phase ?-Al2O3 into the stable polymorph ?-alumina, takes place gradually and a four-phases region is achieved at 1000ºC, where coexist with other transitional phase such as  ?- and ?-Al2O3