The delayed rectifier potassium conductance in the sarcolemma and the transverse tubular system membranes of mammalian skeletal muscle fibers.

A two-microelectrode voltage clamp and optical measurements of membrane potential changes at the transverse tubular system (TTS) were used to characterize delayed rectifier K currents (IK(V)) in murine muscle fibers stained with the potentiometric dye di-8-ANEPPS. In intact fibers, IK(V) displays the canonical hallmarks of K(V) channels: voltage-dependent delayed activation and decay in time. The voltage dependence of the peak conductance (gK(V)) was only accounted for by double Boltzmann fits, suggesting at least two channel contributions to IK(V). Osmotically treated fibers showed significant disconnection of the TTS and displayed smaller IK(V), but with similar voltage dependence and time decays to intact fibers. This suggests that inactivation may be responsible for most of the decay in IK(V) records. A two-channel model that faithfully simulates IK(V) records in osmotically treated fibers comprises a low threshold and steeply voltage-dependent channel (channel A), which contributes ∼31% of gK(V), and a more abundant high threshold channel (channel B), with shallower voltage dependence. Significant expression of the IK(V)1.4 and IK(V)3.4 channels was demonstrated by immunoblotting. Rectangular depolarizing pulses elicited step-like di-8-ANEPPS transients in intact fibers rendered electrically passive. In contrast, activation of IK(V) resulted in time- and voltage-dependent attenuations in optical transients that coincided in time with the peaks of IK(V) records. Normalized peak attenuations showed the same voltage dependence as peak IK(V) plots. A radial cable model including channels A and B and K diffusion in the TTS was used to simulate IK(V) and average TTS voltage changes. Model predictions and experimental data were compared to determine what fraction of gK(V) in the TTS accounted simultaneously for the electrical and optical data. Best predictions suggest that K(V) channels are approximately equally distributed in the sarcolemma and TTS membranes; under these conditions, >70% of IK(V) arises from the TTS

Catch Efficiency in the Chilean Pelagic Fishery: Does size matter ?

This paper examines the determinants of technical efficiency for a sample of 204 industrial vessels operating in the Southern-Central pelagic fishery of Chile during the 1985-95 period. Data on vessel's annual landings and fishing effort, vessel's size, age, fishing experience and vessel's controlling firm are analysed considering a Translog stochastic frontier model à-la Battese-Coelli (1995), which includes a vessel-specific inefficiency model. Yearly averages for vessel efficiency vary from 50% to 86%. Close to 90% of the residuals' total variance is accounted by the inefficiency term, suggesting a significant disparity in vessels' catch performance. Vessel age and scale of operation are found to be significant in explaining efficiency. Larger vessels tend to be the most efficient and the ones showing least variance in their efficiency. Smaller vessels, which on average are also the oldest in the fleet, show greater dispersion and lower efficiency scores. We confirm prior results suggesting vessel-level economies of scale at this fishery, related to fishing effort intensity. Explanatory variables aggregated at the ship-owner level, which aim at controlling the firm's operating scale, are also significant as a whole when explaining vessel-level efficiency. We find positive search externalities associated to the number of vessels under control of a given firm, as well as external diseconomies related to each firm's fleet use. Overall, we report significant productive heterogeneity in the fleet under study where control variables associated to 'size effects' do indeed play a significant role.

Downward Adjustments in a Cyclical Environment: The Case of Chilean Pelagic Fisheries

Often the scale of production of many industrial fisheries in the world shows rigidity vis à vis declines in fish abundance, which on occasions has generated fishing collapse. This paper studies the two fisheries with the greatest volume of landings in Chile, and which are also characterized by strong variability in their abundance. Production-side aspects that affect the incentives to adjust towards lower fishing efforts are analyzed. To do so, production functions for industrial fleets at each fishery are estimated by resorting to panel data. Two main results are obtained. First, we confirm the empirical relevance of Translog harvest technologies. This contradicts a frequent practice in bioeconomic models, which considers harvest-inputs elasticities as being constant and independent from the scale of production. Second, a set of production-side effects are identified that weaken the incentives to adjust towards lower fishing efforts: increasing returns in the use of variable inputs, which are also strengthened by external economies associated to the aggregate searching effort for fish, and catch yields sensitive to changes in abundance, but where the strength of this effect decreases as abundance declines.

'El Niño' Effects and Biomass Endogeneity in a Harvest Function: The Chilean Jack Mackerel Fishery

The main goal of this paper consists in estimating the input parameters of an annual harvest function for the Chilean jack mackerel stock; particularly, the effects of biomass on catch. One of the main problems faced is that the biomass variable is possibly endogenous, which would bias the estimators if the problem remains unsolved. Our empirical strategy consists in estimating a per vessel harvest function using panel data, which allows us to control for vessels' unobserved heterogeneity, and episodes of 'El Niño' phenomenon as valid instrumental variable for biomass, which allows us to control for the potential biomass endogeneity. This strategy produces consistent estimates of the biomass coefficient. The results, using a panel of industrial vessels operating in the central-southern region of Chile during the period 1985-2002, show that the endogeneity of the biomass variable biases upwardly the magnitude of its coefficient in a Cobb-Douglas harvest function. In the case of our data, the endogeneity bias even changes the sign of the catch-to-biomass elasticity. A first contribution of the paper is to address the endogeneity of biomass in a harvest function, an issue often underestimated in the empirical literature. A second contribution is related to 'El Niño' effects on the Chilean jack mackerel stock. The results show that an oceanic 'El Niño' episode not only has negative contemporaneous effects on jack mackerel biomass but also negative biomass effects lasting for at least two additional years.El Niño phenomenon; pelagic fisheries; Chilean jack mackerel; Instrumental variable estimation; marginal stock effects; endogenous biomass

Cursillo: fundamentos epistemológicos para la enseñanza aprendizaje de las series de Fourier

El propósito de esta charla es socializar con la comunidad matemática, los resultados de una investigación que hemos realizado con el objetivo de diseñar un modelo didáctico que explique como los estudiantes de ingeniería de la Universidad del Atlántico se apropian y usan los fundamentos epistemológicos de la serie de Fourier

Debates sobre Cuotas Individuales Transferibles:¿"Privatizando" el mar? Subsidios? ¿Muerte anunciada de la pesca extractiva en Chile?

Sectores de pesca industrial y artesanal en Chile requieren consolidar esquemas de administración pesquera que promuevan la racionalización de sus esfuerzos de pesca, ajustándolos en general hacia recursos marinos menos abundantes. Argumentamos que un sistema basado en cuotas individuales transferibles (CITs) es la mejor opción disponible, especialmente para el sector industrial. Asignaciones individuales favorecen el coordinar soluciones colectivas para racionalizar los esfuerzos de pesca. Mientras que su transferibilidad promueve soluciones económicamente eficientes al problema de capacidad de pesca excedente. Proponemos una asignación inicial de CITs con base en presencia histórica, condicionando el derecho de uso de las CITs al pago de patentes anuales que permitan financiar los costos de administrar y fiscalizar el sistema de CITs. Por otro lado, defendemos el asignar inicialmente las CITs como derechos de uso transitorios, aunque con un período de validez razonablemente largo (por ejemplo 15 o 20 años). Postulamos que esto favorece la viabilidad política de poder a futuro continuar perfeccionando este sistema de administración pesquera. También proponemos entregar a Asociaciones de Pescadores Artesanales, que consoliden una representatividad local relevante, facultades para decidir y administrar la distribución y uso (entre sus miembros) de la cuota asignada por la autoridad, incluyendo la posibilidad de transferir las asignaciones individuales. Por último, proponemos que pescadores artesanales tengan la facultad legal de realizar transacciones con intereses industriales, de forma que alguna proporción de la cuota industrial pueda ser capturada dentro de las primeras 5 millas, por ejemplo usando embarcaciones artesanales para estos efectos.

Escritura académica y enseñanza de portugués como lengua extranjera: como escribir reseñas en portugués

Anais do VI Encontro de Iniciação Científica e II Encontro Anual de Iniciação ao Desenvolvimento Tecnológico e Inovação – EICTI 2017 - 04 a 06 de outubro de 2017- temática Linguística, Letras e ArtesLa investigación que realizamos en el transcurso de este proyecto busca concentrar sus esfuerzos para dos objetivos: establecer investigaciones que puedan contribuir para el perfil egresado visado por el curso de Letras Portugués e Español como Lenguas Extranjeras – LEPLE – profesionales aptos a la promoción y difusión global de las lenguas portuguesa y española; contribuir para la misión institucional de la UNILA en la integración transregional del continente latino-americano. En ese contexto, en el ámbito de la enseñanza de Portugués como Lengua Extranjera para hispano-hablantes, investigamos propuestas de enseñanza que atendieran a las necesidades lingüísticas de estudiantes universitarios en contextos institucionales, sobretodo en el que toca la dimensión de la compresión y producción de géneros académicos, áreas fundamentales para el desarrollo satisfactorio de las actividades realizadas por los estudiantes en la universidadUniversidade Federal da Integração Latino-Americana (Unila); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação Araucária; Parque Tecnológico Itaipu (PTI) e Companhia de Saneamento do Paraná (SANEPAR

Adicción a las redes sociales y habilidades sociales en estudiantes de una institución educativa privada

This research aims to determine the relationship between addiction to social networks and social skills in students of a private educational centre. A correlational descriptive study where the sample was represented by 205 students from 1st to 5th grade of junior high school was conducted. Two instruments were used: “Goldstein Social Skills Checklist” and “Scale of Attitudes toward Social Networks”, this was adapted and validated for the population. It is concluded that addiction to social networks of the Internet has a significant relationship (p <.01) with social skills, indicating that the greater the addiction to social networks is, a low level of social skills in adolescents is perceived.El presente trabajo de investigación tiene como propósito determinar la relación que existe entre la adicción a las redes sociales y las habilidades sociales en estudiantes de una institución educativa privada. Se realizó un estudio descriptivo correlacional, donde la muestra estuvo representada por 205 estudiantes del 1ero al 5to grado de secundaria. Se utilizaron dos instrumentos: Lista de Chequeo de Habilidades Sociales - Goldstein y Escala de Actitudes hacia las redes sociales. Esta fue adaptada y validada para la población. Se concluye que la adicción a las redes sociales del Internet tiene una relación significativa (p<.01) con las habilidades sociales, lo que indica que, a mayor adicción a las redes sociales, se demuestra un bajo nivel de las habilidades sociales en los adolescentes