Virial series for fluids of hard hyperspheres in odd dimensions

A recently derived method [R. D. Rohrmann and A. Santos, Phys. Rev. E. {\bf 76}, 051202 (2007)] to obtain the exact solution of the Percus-Yevick equation for a fluid of hard spheres in (odd) $d$ dimensions is used to investigate the convergence properties of the resulting virial series. This is done both for the virial and compressibility routes, in which the virial coefficients $B_j$ are expressed in terms of the solution of a set of $(d-1)/2$ coupled algebraic equations which become nonlinear for $d \geq 5$. Results have been derived up to $d=13$. A confirmation of the alternating character of the series for $d\geq 5$, due to the existence of a branch point on the negative real axis, is found and the radius of convergence is explicitly determined for each dimension. The resulting scaled density per dimension $2 \eta^{1/d}$, where $\eta$ is the packing fraction, is wholly consistent with the limiting value of 1 for $d \to \infty$. Finally, the values for $B_j$ predicted by the virial and compressibility routes in the Percus-Yevick approximation are compared with the known exact values [N. Clisby and B. M. McCoy, J. Stat. Phys. {\bf 122}, 15 (2006)]Comment: 9 pages, 6 figure

Key insights on the structural characterization of textured Er2O3–ZrO2 nano-oxides prepared by a surfactant-free solvothermal route

Zirconia-mixed oxides can exhibit cubic fluorite and pyrochlore structure. Their discrimination is not easy in nanooxides with a crystal size close to that of a few unit cells. In this work, high resolution transmission electron microscopy (HRTEM) has been employed to provide key insights on the structural characterization of a nanometric and porous mixed Er2O3–ZrO2 oxide. The material was prepared by a simple template-free solvothermal route that provided nanocrystalline powders at low temperature (170 °C) with spherical morphology, and high surface area (∼280 m2 g−1). The porosity was mainly originated from the assembling of organic complexing agents used in the synthesis to limit the crystal growth and to control hydrolysis and condensation reaction rates. The samples were characterized by thermal analysis, X-ray diffraction, scanning electron microscopy and N2 adsorption measurements. A detailed study by HRTEM was conducted on microtomed samples. It was observed that the material was made of nanocrystals packed into spherical agglomerates. HRTEM simulations indicated that it is not possible to identify the pyrochlore phase in nanoparticles with diameter below 2 nm. In our samples, the analysis of the HRTEM lattice images by means of fast Fourier transform (FFT) techniques revealed well defined spots that can be assigned to different planes of a cubic fluorite-type phase, even in the raw material. Raman spectroscopy was also a powerful technique to elucidate the crystalline phase of the materials with the smallest nanoparticles. HREM and Raman results evidenced that the material is constituted, irrespective of the temperature of the final calcination step, by an ensemble of randomly oriented nanocrystals with fluorite structure. This study opens new perspectives for the design of synthetic approaches to prepare nanooxides (fluorites and pyrochlores) and the analysis of their crystalline structure

Retirement, education and quality of life

[ES] El presente artículo trata de analizar la jubilación contrastando la perspectiva negativa tradicional con visiones mucho más positivas, que ponen el acento en las posibilidades del trabajo educativo para conseguir una jubilación de calidad que pueda extrapolarse más allá del ámbito personal, proyectándose al ámbito comunitario. En este sentido, en el artículo se apuesta por metodologías participativas que tengan en los procesos comunicativos grupales su estrategia más importante. [EN] This article attempts to analyze the retirement contrasting the traditional negative outlook with much more positive views, which emphasize the possibilities of educational work to achieve a quality retirement that could be extrapolated beyond the personal level, projecting towards the community level. In this sense, this work bets on participative methodologies that to use communication processes like its more important strategy of group

About the presence of the grass carp <i>Ctenopharyngodon idella</i> (Valenciennes, 1844) in Cordoba province (Argentina)

Si bien existe evidencia empírica acerca de la presencia de la carpa herbívora Ctenopharyngodon idella en diferentes ambientes de la provincia de Córdoba, no ha sido hasta el momento oficialmente registrada como parte de su ictiofauna. El objetivo del presente trabajo es confirmar la presencia de C. idella en dos lagos urbanos de la ciudad de Río Cuarto. De esta manera, se incorporan nuevos aportes sobre la presencia de este ciprínido dentro de la ictiofauna de Córdoba.Even though the presence of the grass carp Ctenopharyngodon idella in different environments of Córdoba province was recognized by empirical evidence, this species has not been recorded in previous publications as belonging to the ichthyofauna of this province. The objective of this contribution is to confirm the presence of C. idella in two urban lakes of Río Cuarto city. This way, new records of the presence of this cyprinid into the Córdoba ichthyofauna are added.Facultad de Ciencias Naturales y Muse

Using the ℓ1-norm for Image-based tomographic reconstruction

This paper introduces an ℓ1-norm model based on Total Variation Minimization for tomographic reconstruction. The reconstructions produced by the proposed model are more accurate than those obtained with classical reconstruction models based on the ℓ2-norm. This model can be linearized and solved by linear programming techniques. Furthermore, the complementary slackness conditions can be exploited to reduce the dimension of the resulting formulation by removing unnecessary variables and constraints. Since the efficacy of the reduced formulation strongly depends on the quality of the dual-multipliers used when applying the reduction method, Lagrangian relaxation is used to obtain near-optimal multipliers. This allows solving larger instances in an efficient way

Combining Deep Learning and Compressed SensingMethods for the 3D Characterization of Ultra-ThinEpitaxial Layers Grown on Controlled-Shape Nano-Oxides

Using a nanostructured platform (a controlled-shape nano-oxide) and conventional wet impregnation techniques, powder-type materials have been prepared in which atomically thin surface layers are deposited under very mild conditions. More importantly, an advanced methodology, combining energy dispersive X-ray spectroscopy-scanning transmission electron tomography (STEM-EDX ET) and deep learning denoising techniques, has been developed for the 3D compositional characterization of these unique nanosystems. The complex case of LaOx-coated CeO2 nanocubes is illustrated. For these, aberration corrected 2D STEM-EDX evidence that ceria nanocubes become covered with a 2–4 atom-thick layer of a La, Ce-mixed oxide with spatially varying composition. However, STEM-EDX ET reveals that this layer distributes unevenly, patching most of the available nanocube surface. The large flexibility and spread availability of the involved synthetic techniques enables, using the tools here developed, a wide exploration of the wealth of questions and applications of these intriguing, atomically thin, surface oxide phases10 página

On the relation between virial coefficients and the close-packing of hard disks and hard spheres

The question of whether the known virial coefficients are enough to determine the packing fraction $\eta_\infty$ at which the fluid equation of state of a hard-sphere fluid diverges is addressed. It is found that the information derived from the direct Pad\'e approximants to the compressibility factor constructed with the virial coefficients is inconclusive. An alternative approach is proposed which makes use of the same virial coefficients and of the equation of state in a form where the packing fraction is explicitly given as a function of the pressure. The results of this approach both for hard-disk and hard-sphere fluids, which can straightforwardly accommodate higher virial coefficients when available, lends support to the conjecture that $\eta_\infty$ is equal to the maximum packing fraction corresponding to an ordered crystalline structure.Comment: 10 pages, 6 figures; v2: discussion about hard-square and hard-hexagon systems on a lattice added; five new reference

Las actividades acuáticas en la enseñanza secundaria en la Región de Murcia. Un estudio cualitativo

The work presented results from an investigation about the presence and development of aquatic activities in the subject Physical Education in Secondary Education and about the educational nature of these activities, from the point of view of specialist teachers. It was done in educational centres of the Region of Murcia, under the promotion of the Department of Education of the Region of Murcia. It was developed through a qualitative study based on 30 semistructured interviews. The results show insufficient training in the specialists, how positive aquatic activities are for holistic training, and the markedly educational nature of these activities. Results also highlight the difficulties for including these activities in the curriculum,the low status they are given, and that Lorca and Cehegín are the towns where these activities are more developed and the city of Murcia and Jumilla where they are done less frequently. Some of the findings are: the need for teacher basic and further training, the recognition of a higher status for aquatic activities as compared with other physical education activities and theovercome of the drawbacks that appear in the implementation of these activities.El trabajo que se presenta es fruto de una investigación sobre la presencia y desarrollo de actividades acuáticas en la asignatura de Educación Física en la enseñanza secundaria y sobre el carácter educativo de dichas actividades, desde la perspectiva del profesorado de la especialidad. Se realizó en centros educativos de la Región de Murcia, bajo la cobertura de la Concejalía de Educación de la Comunidad Autónoma, y se desarrolló mediante un estudio cualitativo basado en 30 entrevistas semiestructuradas. Entre los resultados destacan la insuficiente formación en la especialidad, lo positivas que son las actividades acuáticas para la formación integral y su carácter marcadamente educativo, pero también las dificultades para su inclusión en el currículum y el escaso estatus reconocido, así como que Lorca y Cehegín son las localidades donde más se desarrollan y Murcia capital y Jumilla destacan por todo lo contrario. Entre las conclusiones destacan: necesidad de formación básica y continua adecuada para el profesorado, reconocer mayor estatus a las actividades acuáticas en relación con otras actividades de educación física y paliar los inconvenientes que aparecen en la implementación de esas actividades