Very long-range attractive and repulsive forces in Model Colloidal Dispersions

Experiments with polymer latex solutions show the coexistence of order-disorder structures of macroions. Because of the large macroions' sizes, this order-disorder phase coexistence imply the existence of very long-range attractive and repulsive forces, which can not be explained in terms of conventional direct interaction potentials, which are short-range. Here we apply an integral equations theory to a simple model for colloidal dispersions, at finite concentrations, calculate the particles distribution functions and the involved effective forces. We find very long-range attractive and repulsive forces among the like-charged macroions. The distribution functions are in qualitative agreement with experimental results. The origin of these forces are discussed in terms of an energy-entropy balance.Comment: 16 pages, seven figures. ECIS-201

Comunidad Mapuche, Sociedad Winka y el “Tercero Incluido”: Los Porma de Paicaví Durante los Siglos XIX y XX

This paper attempts a historical and structural reconstruction of Paicaví rewe and its leaders during the 19th and 20th centuries. By analyzing several dynamics emerging from various socio-historical contexts of the Mapuche-State relationship, we visualize certain stability in the role of the leader and its implications regarding the community. From both historical and ethnographical data, we construe leadership in terms of what we call the ‘included third’, a person who is mediating and reproducing the Mapuche/winka distinction, and who is legitimated by a ‘gift pact’.Este artículo intenta una reconstrucción histórico-estructural del rewe Paicaví y sus líderes durante los siglos XIX y XX. A través del análisis de las distintas dinámicas que emergen en los diferentes contextos socio-históricos de la relación mapuche Estado, se delinea una cierta continuidad en cuanto al papel del líder y sus implicancias con respecto a la comunidad. A partir de datos tanto históricos como etnográficos, se visualiza el liderazgo en función de lo que llamamos el “tercero incluido”, un mediador y reproductor de la distinción mapuche/winka, que se legitima a través de un pacto dónico

Sobre la tradición latinoamericanista

¿Qué hay en la tradición latinoamericanista que pueda hacer de la operación de pensar adhiriendo algo productivo o, al menos, promisorio? O, para decirlo con las palabras de Manuel Ugarte que llamaron la atención de Arturo Andrés Roig y que presiden, en calidad de epígrafe, el artículo: ¿qué puede ser lo amable entre nosotros? El ensayo introduce, para comenzar, una decena de hipótesis concatenadas. En las dos secciones subsecuentes procura avanzar esclareciendo los términos implicados en el entramado hipotético, en buena medida por la vía de un diálogo con aportes de otros autores y que desemboca en el recentramiento de la categoría de ethos. La intención no es otra que la de someter a debate un dispositivo conceptual en construcción. Observación: como puede verse en el sitio web y en la versión del artículo que va adjunta, el ISSN de los Cuadernos del CEL está en trámite.Fil: Kozel, Gabriel Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín; ArgentinaFil: González, Marcelo. Universidad Nacional de San Martin. Escuela de Humanidades. Centro de Estudios Latinoamericanos; Argentin

Video Theraphy: The use of audiovisual media for therapeutic purposes

Este artículo aborda la experiencia del taller de Vídeo Terapia, que se realiza desde el año 2008 en el Servicio de Hospital de Día del Hospital Psicoasistencial Interdisciplinario José T. Borda, en la ciudad de Buenos Aires- Argentina. De esta manera, se busca plantear los principales aspectos teóricos que han servido de base para nuestro trabajo. Destacando las características específicas que hacen al contexto en que se desenvuelve el taller de Video Terapia, nuestras experiencias con los pacientes y la metodología de trabajo.This article is about the experience of the workshop of Video therapy, which is carried out since 2008 in the Day Hospital Service at the Hospital Psicoasistencial interdisciplinary José T. Borda, in the city of Buenos Aires, Argentina. In it we consider the main theoretical aspects that have served as the basis for our work, the specific characteristics that make the context which it operates our workshop, our experiences with patients and work methodology

Políticas de renovación urbana y apropiación del espacio público: El caso de la calle La Ronda en el centro histórico de Quito

El presente estudio se inscribe en el proyecto de investigación-acción participación en el centro histórico de Quito, de la línea de trabajo en psicología ambiental comunitaria del Grupo de Investigaciones Psicosociales de la Carrera de Psicología de la Universidad Politécnica Salesiana. Destacamos la pertinencia de este esfuerzo investigativo puesto que contribuye a identificar disciplinas. Nos referimos a pensar la relación entre políticas urbanas y las formas de apropiación del espacio público de centralidad para generar un diálogo conceptual entre la ciencia política y la psicología ambiental comunitaria. Tanto la gestión política del territorio como las formas de apropiación del espacio urbano co-construyen subjetividades sociales que dotan de sentido a un lugar histórico. Este estudio aporta con un conocimiento empírico y crítico en torno a la necesaria problematización de los procesos de renovación urbana en el centro histórico de Quito, que se fundamenta en el discurso del patrimonio cultural y del fortalecimiento de identidades. Logramos sostener la hipótesis de que la implementación de políticas de renovación urbana basadas en un enfoque de gobernanza jerárquica produce un tipo excluyente y privatizados de apropiación del espacio público urbano. Convocamos al lector y la lectora a revisar este interesante estudio cuyo enfoque indaga sobre novedosas perspectivas de entendimiento de la política, la subjetividad y el espacio urbano

Activation energy in particle suspensions

Assuming that the molar activation energy in a fluid is interpreted as a measure of the potential energy barrier required for the molecular movement [1], the viscosity of a fluid depends on the actual size of the molecules, and the presence of solid particles in a suspension increases the dissipation of energy when the system flows, therefore it is expected that the viscosity of the suspension is higher than that of the pure solvent at a given temperature. The dependence of the viscosity of some silica/glycol suspensions with the temperature can be fitted using an empirical function analogous to the Arrhenius equation, ln⁡η=E/RT-ln⁡C, where η is the viscosity, C is a system-dependent constant, E is the molar activation energy for the viscous flow, T is the absolute temperature and R is the gas universal constant. When the temperature of the suspension decreases two effects are observed. First, larger aggregates of particles are formed due to the reduction of the thermal agitation and, second, the number of links among the molecules of the liquid phase increases. These two effects give place to a higher increase in the viscosity with the temperature compared to the pure solvent. Assuming that a higher viscosity value is due to a smaller free volume available for the molecular movement, and taking into account that the free suspension volume is limited only to the liquid fraction [2], it should be expected that the viscosity of the suspension is less sensitive to temperature than that of the pure solvent. In this work the dependence on the temperature of the viscosity values of the silica/glycol suspensions is compared to that of the liquid media. The results have shown a lower activation energy when the solid volume fraction increases, which has been explained with a scheme that assumes that the particle links are less sensitive to thermal energy absorption than the joining bonds among the solvent molecules. Our conclusion is that, for a given mechanical energy applied to the system, the thermal energy absorbed by the system is mainly used in the rupture of bonds between the solvent molecules. This study can be useful to understand the mechanisms that govern the differences in the activation energy values found between samples of foods, in which many factors are connected with sample composition [3]. [1] Briscoe B, Luckham P, Zhu S. Rheological properties of poly (ethylene oxide) aqueous solutions. J Appl Polym Sci 70 (1998) 419-429. [2] Shenoy AV. Rheology of filled polymer systems. Kluwer Acad Pub, 1999, The Netherlands. [3] Alvarez MD, Canet W. Time-independent and time-dependent rheological characterization of vegetable-based infant purees. J Food Eng 114 (2013) 449-464.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech

A first assessment of atresia in the Chilean jack mackerel Trachurus murphyi (Teleostei, Carangidae) from the South-eastern Pacific Ocean

The Chilean jack mackerel Trachurus murphyi support an important fishery in the South-eastern Pacific Ocean and has declined considerably over time. T. murphyi have asynchronous ovarian development with an oceanic spawning (September to January). Despite the economic importance of this resource critical issue such as characteristics and dynamics of atresia, which affect the reproductive output, are unknown. Females of T. murphyi caught in different spawning seasons were analysed to describe patterns of prevalence and intensity of atresia. General linear models (GLM) were performed by using prevalence and intensity atresia as response variables and gonadosomatic index, condition factor, sea surface temperature, postovulatory follicles and month/year as explanatory variables. The batch fecundity and relative fecundity were compared between females showing atresia, postovulatory follicles and non-atretic females. The stages of atresia identified were alpha, beta and gamma. The GLM showed that variations in the prevalence and intensity of atresia were explained for all variables, except condition factor for prevalence, and gonadosomatic index for intensity of atresia. According to our results, the dynamic of alpha and beta atresia could be considered a potential proxy for any disruption of spawning season. The batch fecundity and relative fecundity were lowest compared with other Trachurus spp. This is the first assessment comparing fecundity between atretic and not atretic females for this species

Effects of cardiorespiratory exercise on cognition in older women exposed to air pollution

The aim was to analyze the effects of cardiorespiratory exercise and air pollution on cognition and cardiovascular markers in four groups of older women: the active/clean air group (AC), the active/polluted air group (AP), the sedentary/clean air group (SC), and the sedentary/polluted air group (SP). Active groups performed a training task based on progressive walking. Prior to and after the experiment, the following parameters were assessed: cognition, by Mini Mental State Examination (MMSE); maximum oxygen uptake (VO2max), estimated by the Six-Minute Walk Test (6mWT); heart rate (HR); and oxygen saturation (SpO2). There were significant differences (p < 0.05) between the AC and the SP in all the MMSE dimensions except “Registration”, and in all the physiological variables (VO2max, SpO2, HR). Aerobic exercise may be a protective factor against the effects that pollution have on cognition and on the mechanisms of oxygen transport