Viscoelasticity and Stokes-Einstein relation in repulsive and attractive colloidal glasses

We report a numerical investigation of the visco-elastic behavior in models for steric repulsive and short-range attractive colloidal suspensions, along different paths in the attraction-strength vs packing fraction plane. More specifically, we study the behavior of the viscosity (and its frequency dependence) on approaching the repulsive glass, the attractive glass and in the re-entrant region where viscosity shows a non monotonic behavior on increasing attraction strength. On approaching the glass lines, the increase of the viscosity is consistent with a power-law divergence with the same exponent and critical packing fraction previously obtained for the divergence of the density fluctuations. Based on mode-coupling calculations, we associate the increase of the viscosity with specific contributions from different length scales. We also show that the results are independent on the microscopic dynamics by comparing newtonian and brownian simulations for the same model. Finally we evaluate the Stokes-Einstein relation approaching both glass transitions, finding a clear breakdown which is particularly strong for the case of the attractive glass.Comment: 12 pages; sent to J. Chem. Phy

Trace elements based classification on clinkers. Application to Spanish clinkers

[EN]The qualitative identification to determine the origin (i.e. manufacturing factory) of Spanish clinkers is described. The classification of clinkers produced in different factories can be based on their trace element content. Approximately fifteen clinker sorts are analysed, collected from 11 Spanish cement factories to determine their Mg, Sr, Ba, Mn, Ti, Zr, Zn and V content. An expert system formulated by a binary decision tree is designed based on the collected data. The performance of the obtained classifier was measured by ten-fold cross validation. The results show that the proposed method is useful to identijy an easy-to-use expert system that is able to determine the origin of the clinker based on its trace element content.[ES]En el presente trabajo se describe el procedimiento de identificación cualitativa de clínkeres españoles con el objeto de determinar su origen (fábrica). Esa clasificación de los clínkeres se basa en el contenido de sus elementos traza. Se analizaron 15 clínkeres diferentes procedentes de 11 fábricas de cemento españolas, determinándose los contenidos en Mg, Sr, Ba, Mn, Ti, Zr, Zn y V. Se ha diseñado un sistema experto mediante un árbol de decisión binario basado en los datos recogidos. La clasificación obtenida fue examinada mediante la validación cruzada de 10 valores. Los resultados obtenidos muestran que el modelo propuesto es válido para identificar, de manera fácil, un sistema experto capaz de determinar el origen de un clínker basándose en el contenido de sus elementos traza.Peer reviewe

Las bibliotecas públicas cubanas en el período 1959-1976

The phenomena influencing on the creation, functioning and development of public libraries in Cuba are analyzed, the work done in the analysis of public libraries as a whole is fundamented, and a chronological approach to the development of public libraries as a system is made. The topic is dealt with from the point of view of the library as a vehicle for cultural promotion and not just as an information source; besides, the existence and development of public libraries are linked to the social, political and cultural advance of our country and its population

Spatially resolved integral field spectroscopy of the ionized gas in IZw18

We present a detailed 2D study of the ionized ISM of IZw18 using new PMAS-IFU optical observations. IZw18 is a high-ionization galaxy which is among the most metal-poor starbursts in the local Universe. This makes IZw18 a local benchmark for understanding the properties most closely resembling those prevailing at distant starbursts. Our IFU-aperture (~ 1.4 kpc x 1.4 kpc) samples the entire IZw18 main body and an extended region of its ionized gas. Maps of relevant emission lines and emission line ratios show that higher-excitation gas is preferentially located close to the NW knot and thereabouts. We detect a Wolf-Rayet feature near the NW knot. We derive spatially resolved and integrated physical-chemical properties for the ionized gas in IZw18. We find no dependence between the metallicity-indicator R23 and the ionization parameter (as traced by [OIII]/[OII]) across IZw18. Over ~ 0.30 kpc^2, using the [OIII]4363 line, we compute Te[OIII] values (~ 15000 - 25000 K), and oxygen abundances are derived from the direct determinations of Te[OIII]. More than 70% of the higher-Te[OIII] (> 22000 K) spaxels are HeII4686-emitting spaxels too. From a statistical analysis, we study the presence of variations in the ISM physical-chemical properties. A galaxy-wide homogeneity, across hundreds of parsecs, is seen in O/H. Based on spaxel-by-spaxel measurements, the error-weighted mean of 12 + log(O/H) = 7.11 +/- 0.01 is taken as the representative O/H for IZw18. Aperture effects on the derivation of O/H are discussed. Using our IFU data we obtain, for the first time, the IZw18 integrated spectrum.Comment: Accepted for publication in MNRAS, 13 pages, 10 figures, 4 table

Exact R\'enyi entropies of DD-dimensional harmonic systems

The determination of the uncertainty measures of multidimensional quantum systems is a relevant issue \textit{per se} and because these measures, which are functionals of the single-particle probability density of the systems, describe numerous fundamental and experimentally accessible physical quantities. However, it is a formidable task (not yet solved, except possibly for the ground and a few lowest-lying energetic states) even for the small bunch of elementary quantum potentials which are used to approximate the mean-field potential of the physical systems. Recently, the dominant term of the Heisenberg and R\'enyi measures of the multidimensional harmonic system (i.e., a particle moving under the action of a $D$-dimensional quadratic potential, $D > 1$) has been analytically calculated in the high-energy (i.e., Rydberg) and the high-dimensional (i.e., pseudoclassical) limits. In this work we determine the exact values of the R\'enyi uncertainty measures of the $D$-dimensional harmonic system for all ground and excited quantum states directly in terms of $D$, the potential strength and the hyperquantum numbers.Comment: Accepted in EPJ-S