Polysiloxane surfactants for the dispersion of carbon nanotubes in nonpolar organic solvents.

We develop two new amphiphilic molecules that are shown to act as efficient surfactants for carbon nanotubes in nonpolar organic solvents. The active conjugated groups, which are highly attracted to the graphene nanotube surface, are based on pyrene and porphyrin. We show that relatively short (C18) carbon tails are insufficient to provide stabilization. As our ultimate aim is to disperse and stabilize nanotubes in siloxane matrix (polymer and cross-linked elastomer), both surfactant molecules were made with long siloxane tails to facilitate solubility and steric stabilization. We show that the pyrene-siloxane surfactant is very effective in dispersing multiwall nanotubes, while the porphyrin-siloxane makes single-wall nanotubes soluble, both in petroleum ether and in siloxane matrix.

A generalized self-consistent method accounting for fiber section shape

A three-phase confocal elliptical cylinder model is proposed for fiber-reinforced composites, in terms of which a generalized self-consistent method is developed for fiber-reinforced composites accounting for variations in fiber section shapes and randomness in fiber section orientation. The reasonableness of the fiber distribution function in the present model is shown. The dilute, self-consistent, differential and Mori-Tanaka methods are also extended to consider randomness in fiber section orientation in a statistical sense. A full comparison is made between various micromechanics methods and with the Hashin and Shtrikman's bounds. The present method provides convergent and reasonable results for a full range of variations in fiber section shapes (from circular fibers to ribbons), for a complete spectrum of the fiber volume fraction (from 0 to 1, and the latter limit shows the correct asymptotic behavior in the fully packed case) and for extreme types of the inclusion phases (from voids to rigid inclusions). A very different dependence of the five effective moduli on fiber section shapes is theoretically predicted, and it provides a reasonable explanation on the poor correlation between previous theory and experiment in the case of longitudinal shear modulus.

Effect of inclusions and holes on the stiffness and strength of honeycombs

A finite element study has been performed on the effects of holes and rigid inclusions on the elastic modulus and yield strength of regular honeycombs under biaxial loading. The focus is on honeycombs that have already been weakened by a small degree of geometrical imperfection, such as a random distribution of fractured cell walls, as these imperfect honeycombs resemble commercially available metallic foams. Hashin-Shtrikman lower and upper bounds and self-consistent estimates of elastic moduli are derived to provide reference solutions to the finite element calculations. It is found that the strength of an imperfect honeycomb is relatively insensitive to the presence of holes and inclusions, consistent with recent experimental observations on commercial aluminum alloy foams.

La teología ante la física moderna : cuestiones fundamentales para un diálogo posible : 2ª parte: la teología de la creación ante la cosmología científica

Resumen: El descubrimiento de la verdadera naturaleza evolutiva y mutable de este universo en que vivimos ha dado origen a la moderna cosmología científica, que con sus modelos del nacimiento y evolución del cosmos plantea estimulantes cuestiones teológicas como la relación entre creación e inicio del universo, la acción divina en el mundo o la teleología y finalidad última de la Creación.

El redescubrimiento de la filosofía personalista de Jacques Maritain

Resumen: El autor sostiene que la búsqueda de nuevos modelos empresariales y de política económica nos invita a redescubrir la filosofía personalista de Maritain. En el núcleo de la obra Humanismo integral (1936) del filósofo francés aparece la idea de que el hombre es una persona "de naturaleza espiritual, dotada de libre albedrío, y por lo tanto autónoma en relación con el mundo". El artículo estudia la naturaleza del bien común temporal, que para Maritain se relaciona con la vida buena de la toda la comunidad –el bien común o bonum commune– tanto en el sentido material como moral. Este bonum commune no es el objetivo final del orden temporal, sino que está subordinado a lo que trasciende el bienestar temporal de la persona humana –la realización de la libertad y la perfección espiritual. En última instancia, el orden nunca se completa. El balance definitivo o telos nunca se obtiene ya que el hombre está siempre en camino.

Low Temperature Properties of PI/SiO_2 Nanocomposite Films

In this paper, the mechanical properties of PI/Si_O, nanocomposite hybrid films with different silica doping levels are experimentally studied at low temperature. Experimental results show that the coefficient of thermal expansion (CTE) of the PI/Si_O, nanocomposite hybrid films gradually reduces when the ambiance temperature is decreased. At the liquid nitrogen temperature (77 K), the CTE value is about five times less than that at room temperature (287 K). The measured CTEs of hybrid films greatly decrease when doped with inorganic silica, especially when the silica doping level is more than 1 wt.%. However, too high silica contents (more than 10 wt.%) can cause problem to disperse effectively and the specimens become quite opaque. Experimental results also show that the effects of the pre-applied stress levels can be neglected on the CTE testing. When the ambient temperature changes from 287 to 77 K, the measured average values of the films' ultimate tensile strength (UTS) and Young's modulus increase about 60 and 90%, respectively, while the breaking elongation decreases about 42%.

Uniform stability of a particle approximation of the optimal filter derivative

Sequential Monte Carlo methods, also known as particle methods, are a widely used set of computational tools for inference in non-linear non-Gaussian state-space models. In many applications it may be necessary to compute the sensitivity, or derivative, of the optimal filter with respect to the static parameters of the state-space model; for instance, in order to obtain maximum likelihood model parameters of interest, or to compute the optimal controller in an optimal control problem. In Poyiadjis et al. [2011] an original particle algorithm to compute the filter derivative was proposed and it was shown using numerical examples that the particle estimate was numerically stable in the sense that it did not deteriorate over time. In this paper we substantiate this claim with a detailed theoretical study. Lp bounds and a central limit theorem for this particle approximation of the filter derivative are presented. It is further shown that under mixing conditions these Lp bounds and the asymptotic variance characterized by the central limit theorem are uniformly bounded with respect to the time index. We demon- strate the performance predicted by theory with several numerical examples. We also use the particle approximation of the filter derivative to perform online maximum likelihood parameter estimation for a stochastic volatility model.

Preparation And Optical Properties Of Cdte/Cdo Center Dot Nh(2)O Core/Shell Nano-Composites In Aqueous Solution

The deposition of CdO center dot nH(2)O On CdTe nanoparticles was studied in an aqueous phase. The CdTe nanocrystals (NCs) were prepared in aqueous solution through the reaction between Cd2+ and NaHTe in the presence of thioglycolic acid as a stabilizer. The molar ratio of the Cd2+ to Te2- in the precursory solution played an important role in the photoluminescence of the ultimate CdTe NCs. The strongest photoluminescence was obtained under 4.0 of [Cd2+]/[Te2-] at pH similar to 8.2. With the optimum dosage of Cd(II) hydrous oxide deposited on the CdTe NCs, the photoluminescence was enhanced greatly. The photoluminescence of these nanocomposites was kept constant in the pH range of 8.0-10.0, but dramatically decreased with an obvious blue-shifted peak while the pH was below 8.0. In addition, the photochemical oxidation of CdTe NCs with cadmium hydrous oxide deposition was markedly inhibited.

Measurement Of Fracture Toughness And Interfacial Shear Strength Of Hard And Brittle Cr Coating On Ductile Steel Substrate

The fracture toughness and interfacial adhesion properties of a coating on its substrate are considered to be crucial intrinsic parameters determining performance and reliability of coating-substrate system. In this work, the fracture toughness and interfacial shear strength of a hard and brittle Cr coating on a normal medium carbon steel substrate were investigated by means of a tensile test. The normal medium carbon steel substrate electroplated with a hard and brittle Cr coating was quasi-statically stretched to induce an array of parallel cracks in the coating. An optical microscope was used to observe the cracking of the coating and the interfacial decohesion between the coating and the substrate during the loading. It was found that the cracking of the coating initiated at critical strain, and then the number of the cracks of the coating per unit axial distance increased with the increase in the tensile strain. At another critical strain, the number of the cracks of the coating became saturated, i.e. the number of cracks per unit axial distance became a constant after this critical strain. Based on the experiment result, the fracture toughness of the brittle coating can be determined using a mechanical model. Interestingly, even when the whole specimen fractured completely under an extreme strain of the substrate, the interfacial decohesion or buckling of the coating on its substrate was completely absent. The test result is different from that appeared in the literature though the identical test method and the brittle coating/ductile metal substrate system are taken. It was found that this difference can be attributed to an important mechanism that the Cr coating on the steel substrate has a good adhesion, and the ultimate interfacial shear strength between the Cr coating and the steel substrate has exceeded the maximum shear flow strength level of the steel substrate. This result also indicates that the maximum shear flow strength level of the ductile steel substrate can be only taken as a lower bound estimate on the ultimate shear strength of the interface. This estimation of the ultimate interfacial shear strength is consistent with the theoretical analysis and prediction presented in the literature.

Ensayo : acreditación de calidad académica: el desafío de articular la teoría con la práctica en la carrera de Psicología

Un concepto que articula la teoría, la información y la práctica es el concepto de Competencia Profesional entendida como el conjunto de conocimientos, habilidades y actitudes (Roe, 2003) que definen el perfil profesional. La problemática de la articulación entre los contenidos de las materias del Plan de Estudios y la Práctica profesional es un tema básico para que teoría y práctica no estén divorciadas en la realidad de todo futuro profesional. La propuesta de este trabajo es que la articulación entre el Plan de estudios, el Perfil profesional y las Prácticas Preprofesionales brinda una oferta universitaria dentro de esquemas de evaluación y acreditación de calidad académica, que responden al desarrollo personal y al de la sociedad en su conjunto. Este trabajo teórico no pretende ser definitivo ni exhaustivo, sino simplemente una aproximación al tema.

La tortura en las Siete Partidas : la pena, la prueba y la majestad. Un análisis sobre la reinstauración del tormento en la legislación castellana del siglo XIII

Resumen: Nadie, de entre los historiadores del derecho, podría animarse a negar la presencia de fuentes romanas (en especial esa compilación tardía denominada Corpus Iuris Civilis) dentro de Partidas; con particular acento en el caso del Digesto. Por esto, en términos de su materialidad, lo que se presentará aquí será un trabajo de cotejo entre títulos específicos de las obras citadas y que refieren al tópico de la tortura. Por un lado, el título 18 del libro XLVIII del Digesto junto con el título 41 del libro IX del Codex. Del otro lado, el título 30 del libro VII de Partidas. Esta comparación buscará no tanto las equivalencias textuales (que son conscientemente obviadas por los redactores a pesar de conocer a la perfección los sistemas de citado) como el sentido último de introducir estos textos en el corpus legislativo castellano. En este sentido, lo que se buscará será plantear métodos posibles para sortear el problema de la intertextualidad en un mundo sin autores.

Le relativisme idéologique

Abstract: From a general standpoint, current thought is dominated by an ideological relativism which considers that truth depends on whom asserts a certain statement. This stance, related to Protagoras’ perspective, rejects the Enlightenment’s view, especially Kant’s way of thinking, viz. It rejects of all forms of authority, transcendent authority in particular. It also favors the conception of the subject developed by Sartre’s existentialism. However, relativism is the ultimate expression of skepticism which always reflects a painful rational relinquishment of the natural desire for truth. Relativism weakens reason and makes the arrival of ideological and political totalitarianism possible, which the 20th century suffered in its most tragic versions. In order to prevent its consequences and to restore reason’s legitimate confidence in wisdom, modern man ought to find the universal within him and his natural thirst for truth, and his transcendent origin. This demands recognizing and accepting humbly man’s condition as a creature, and his dependence on the Verb, who is Truth and Life.

El origen de la civitas en el Defensor Pacis y la reinterpretación de la causalidad final aristotélica

Resumen: La obra capital de Marsilio de Padua, el Defensor Pacis, comienza con un relato histórico-genético de la Ciudad o comunidad perfecta a partir de las organizaciones más primitivas. El autor explica el probable devenir histórico de las comunidades desembocando en la explicación de las partes funcionales de la comunidad última, con la vista puesta en estudiar cuál es la función y lugar de la parte sacerdotal de la ciudad. Es sugerente que el mismo recurso del relato genético ya había sido utilizado por Aristóteles en el Libro I de su Política, y no parece ser casualidad la similitud dado el evidente interés de Marsilio por dicha obra del Estagirita. El objetivo del trabajo planificado es estudiar las similitudes y diferencias entre los relatos genéticos de la comunidad perfecta presentados por Marsilio y por Aristóteles, con énfasis en el uso teórico que ambos hacen de la causalidad final. Es mi opinión que, mientras que Aristóteles dispone de una causa final con un espectro teórico más amplio, la causa final retomada por Marsilio se limita al aspecto intencional. Una lectura de ambos textos con esta diferencia presente podría explicar las diferencias tanto en los resultados como en los desarrollos de las dos “historias” de la ciudad.

El sacramento del matrimonio : donde el amor divino y humano se encuentran...

“Amor de Dios en el amor humano”. Con estas palabras, Dionisio Borobio expresa la presencia divina en el amor conyugal. De esto justamente, se tratarán estas páginas, al desplegar, con la ayuda del teólogo español, la pregnancia divina del amor humano y la mutua implicación de un amor que busca lo absoluto, y la condescendencia trinitaria de manifestarse allí, en ese amor que anhela un sentido último, más allá de sí, para santificarlo. Para ello, en primer lugar, se describirá la riqueza antropológica del matrimonio. En un segundo momento se delineará su riqueza simbólica y sacramental. Finalmente, se abordarán las consecuencias del encuentro del amor divino y del amor humano en la vida esponsal.