On a branch-and-bound approach for a Huff-like Stackelberg location problem

Modelling the location decision of two competing firms that intend to build a new facility in a planar market can be done by a Huff-like Stackelberg location problem. In a Huff-like model, the market share captured by a firm is given by a gravity model determined by distance calculations to facilities. In a Stackelberg model, the leader is the firm that locates first and takes into account the actions of the competing chain (follower) locating a new facility after the leader. The follower problem is known to be a hard global optimisation problem. The leader problem is even harder, since the leader has to decide on location given the optimal action of the follower. So far, in literature only heuristic approaches have been tested to solve the leader problem. Our research question is to solve the leader problem rigorously in the sense of having a guarantee on the reached accuracy. To answer this question, we develop a branch-and-bound approach. Essentially, the bounding is based on the zero sum concept: what is gain for one chain is loss for the other. We also discuss several ways of creating bounds for the underlying (follower) sub-problems, and show their performance for numerical cases

Examining indices of individual-level resource specialization

The variety of resources that a population exploits is known as the “niche width”. A particular population has a narrow niche if only few kinds of the available resources are exploited by its members. When the individuals of a population exploit many different resources, then the population has a wide niche. From this point of view it seems that the niche is a property of the population as a whole. However, it is well known that many apparently generalist populations are in fact composed of individual specialists, that is, members that use only small subsets of the population’s niche. This approach justifies the definition of indices to measure the individual-level resource specialization. Although this kind of analysis could be applied to any niche variation: oviposition sites, habitat, etc., we focus the discussion in terms of analysis of diet data. So as to measure species niche breadth a comparison between the frequency distribution of the species’ resource use with that of all available resources is carried out. When a measure of individual specialization is considered, then one should compare the population’s total diet with the individual use. In particular, the total niche width of a population should be compared with its two components: within and between-individual variation. In this sense, in the literature several indices of intrapopulation niche variation are proposed. Our goal is to describe, compare and evaluate four of the most relevant indices applied in ecology. In this work we point out how these techniques could be developed in a compositional framework, particularly when these indices are applied to discrete diet data [e.g. frequency of different prey specimen in the diet]

Adaptabilidad al cambio climático en especies forestales: efectos de la sequía sobre el crecimiento y la anatomía de la madera de pino ponderosa creciendo bajo distintos niveles de competencia

More stressful conditions are expected due to climatic change in several regions, including Patagonia, South-America. In this region, there are no studies about the impact of severe drought events on growth and wood characteristics of the most planted forestry species, Pinus ponderosa (Doug. ex-Laws). The objective of this study was to quantify the effect of a severe drought event on annual stem growth and functional wood anatomy of pines growing at different plantation densities aiming to understand how management practices can help to increase their adaptability to climate change. Growth magnitude and period, specific hydraulic conductivity, and anatomical traits (early- and latewood proportion, lumen diameter, cell-wall thickness, tracheid length and bordered pit dimensions) were measured in the ring 2008-2009, which was formed during drought conditions. This drought event decreased annual stem growth by 30-38% and 58-65% respect to previous mean growth, in open vs. closed stand trees, respectively, indicating a higher sensitivity of the latter, which is opposite to reports from the same species growing in managed native forests in USA. Some wood anatomical variables did differ in more water stressed trees (lower cell wall thickness of early wood cells and higher proportion of small-lumen cells in latewood), which in turn did not affect wood function (hydraulic conductivity and resistance to implosion). Other anatomical variables (tracheid length, pit dimensions, early- and latewood proportion, lumen diameter of early wood cells) did not differ between tree sizes and plantation density. The results suggest that severe drought affects differentially the amount but not the function and quality of formed wood in ponderosa pine growing at different competition levels.Los pronósticos de cambio climático indican condiciones de mayores niveles de estrés ambiental para muchas regiones del mundo, incluyendo la Patagonia, Sudamérica. En esta región no existen antecedentes acerca del impacto de eventos de sequía severa sobre el crecimiento y la anatomía funcional de la madera de Pinus ponderosa (Doug. ex-Laws), la especie forestal más plantada. El objetivo de este estudio fue cuantificar el efecto de un evento de este tipo sobre el crecimiento anual en diámetro y la anatomía de la madera de pinos creciendo a densidades de plantación bien diferenciadas, con la intención de entender cómo las prácticas de manejo pueden ayudar a incrementar la adaptabilidad al cambio climático. Se midieron las siguientes variables en el anillo de crecimiento 2008-2009: magnitud y período de crecimiento, conductividad hidráulica específica, proporción de madera temprana y tardía, y morfometría de los elementos de conducción: diámetro de lúmen, grosor de pared y longitud de traqueidas, y dimensiones de las punteaduras entre traqueidas. Este evento de sequía redujo la magnitud del crecimiento en un 30-38% y un 58-65% con respecto a los años previos en árboles creciendo en baja y alta competencia intraespecífica, respectivamente. Esto indica una mayor sensibilidad de los segundos, mientras se había encontrado una tendencia opuesta en bosques nativos de esta especie gestionados en EEUU. Se observaron diferencias en algunas variables anatómicas de los árboles más estresados (menor grosor de pared en traqueidas del leño temprano y células con lúmenes más pequeños en el leño tardío), que sin embargo no tuvieron un efecto en la función de la madera (conductividad hidráulica y resistencia a la implosión). Otras variables anatómicas no difirieron entre ambas densidades de plantación ni tamaño de árboles analizados (largo de traqueidas, dimensiones de punteaduras, proporción de madera temprana y tardía, diámetro de lúmenes de madera temprana). Los resultados sugieren que los eventos de sequía extrema afectan diferencialmente la cantidad pero no la función y calidad de la madera formada en pino ponderosa creciendo bajo distintos niveles de competencia

Lithogeochimical exploration in a Hercynian Tin-bering batholith in the Northwest of the Iberian Península

El Batolito hercinico de Ricobayo, al que se encuentran asociadas genéticamente mineralizaciones de estaño, ha sido objeto de un estudio litogeoquimico con el fin de comprobar la efectividad de tales metodos en la exploración de áreas con mineralizaciones de estaño. Tomando como referencia las rupturas de pendiente que muestran las distribuciones de SiO,, Fe20,, Na20, K20, CaO, MgO, Rb, Sr y Zr en 10s correspondientes gráficos probabilisticos, se ha procedido a determinar 10s mapas de isocontenidos de tales elementos en el Batolito de Ricobayo. La distribución de Ca0 es la única que refleja las áreas con mineralizaciones de estaño y puede utilizarse como indicadora de las áreas de potencial interés asociadas a este tipo de granitosPostprint (published version

Analysis of the Narratives with Characters That Make Ethnic Diversity Visible¿ Miraculous: Tales of Ladybug & Cat Noir

This study follows the line of different authors who examined the visibility of ethnic diversity in children's television series and the psychoeducational implications of these media narratives for children. Specifically, this work analyses the behaviours/actions developed by the model characters of cultural diversity and how these characters promote a perspective on diversity that conditions children. Employing a qualitative methodology, we use content analysis and critical discourse analysis as tools to be able to read, describe and interpret said content. The results highlight that these children's programmes present a culture that reinforces certain values and behaviours. Likewise, the TV programmes analysed present stories marked by models of cultural diversity that contribute to the maintenance of certain social structures and the normalisation of inequality. We believe that educational institutions, through media education, should go deeper and teach students to look critically, deciphering codes of the audiovisual language present in the elements of children's stories. In the complex society of the 21st century, we must consider that the needs of children change depending on how their identity intersects with aspects such as ethnicity, class, gender, etc., in order to equip them with the appropriate tools to deal with these problems. Keywords: digital narratives; cultural diversity; media literac

Toxicidad de la ciclosporina A y efecto de la S-adenodilmetionina

This work was supported in part by grants from Junta de Castilla y Le—n and Europharma S.A. (Madrid, Spain). The authors thank Boehringer-Europharma S.A. and Sandoz A.G. (Basel, Switzerland) for the kind gift of the SAMe and cyclosporine A, respectively. A.I.G. is a Postdoctoral Fellowship of Boehringer-Europharma S.A. (Madrid).We studied the simultaneous changes undergone by the main indicators of hepatotoxicity, nephrotoxicity and diabetogenicity in rats treated with cyclosporine A (CyA) for one, two, three and four weeks, using the dose of 10 and 20 mg/kg/day. The effects of the drug on the biliary excretion of several biliary compounds as well as on the bile flow fractions - dependent and independent- of the biliary secretion of bile acids and glutathione were also studied. A further aim of this research was to evaluate the hepatoprotective effect of S-adenosylmethionine (SAMe) against the action of CyA. Our results show that CyA treatment alters hepatic, renal and pancreatic functions rapidly and simultaneously; the changes were slightly more intense with the higher dose but they did not become more pronounced when the treatment was prolonged for 4 weeks. The cholestatic effect of the drug is a multifactorial phenomena and develops accompanied by simultaneous decreases in the biliary secretion of bile acids, lipid, glutathione and proteins. SAMe plus CyA cotreatment antagonizes the main hepatotoxic effects of CyA in this species. This hepatoprotective effect of SAMe could be related to its regulatory function as regards membrane lipid composition and fluidity and to its key role in promoting the hepatic synthesis of thiol compounds.Hemos estudiado los cambios simultáneos experimentados por los principales indicadores de hepatotoxicidad, nefrotoxicidad y diabetogenicidad en ratas tratadas con ciclosporina A (CyA) durante una, dos, tres y cuatro semanas, utilizando dósis de 10 y 20 mg/kg/día. También fueron estudiados los efectos de la droga sobre la excreción biliar de varios compuestos biliares, así como sobre las fracciones de flujo biliar –dependiente e independiente- de la secreción biliar de ácidos biliares y glutation. Otro objetivo de este estudio fue la evaluación del efecto hepatoprotector de la S-Adenosilmetionina (SAMe) frente a la acción de la CyA. Nuestros resultados mostraron que el tratamiento con CyA alteran las funciones hepática, renal y pancreática rápida y simultáneamente; los cambios cambios fueron ligeramente más intensos con una dosis más alta pero no se volvieron más pronunciados cuando el tratamiento se prolongó hasta las cuatro semanas. El efecto colestático de la droga es un fenómeno multifactorial y se desarrolla junto a una disminución de la secreción biliar de ácidos biliares, lípidos, glutation y proteinas. El tratamiento conjunto de SAMe y CyA antagoniza los principales efectos hepatotóxicos del CyA en estas especies. Este efecto hepatoprotector del SAMe podría estar relacionado con su función reguladora al preservar la composición y fluidez de la membrana lipídica y con su papel clave en la promoción de la síntesis de componentes tiol

La alteración sobrevenida de las circunstancias contractuales y la doctrina rebus sic stantibus. Génesis y evolución de un principio jurídico

El trabajo analiza las implicaciones filosófico-jurídicas de la doctrina de la denominada cláusula rebus sic stantibus que se corresponde con una visión no formalista, dinámica y flexible del Derecho, y de los contratos en particular, como un fenómeno histórico susceptible de evolución y de adaptación a la realidad, a las circunstancias de tiempo y de lugar, profundizando en el necesario equilibrio entre seguridad y justicia, para lo cual se requiere una formulación técnico-jurídica rigurosa de la figura rebus. Desde esta perspectiva se analiza la génesis y evolución de la doctrina y el proceso de progresiva decantación técnica de la misma.The paper analyzes the philosophical-legal implications of the doctrine of the rebus sic stantibus clause. It corresponds to a non-formalist, dynamic and flexible view of law, and contracts in particular, as a historical phenomenon susceptible of evolution and adaptation to reality, to the circumstances of time and place. The paper deeps into the necessity of balance between security and justice, for which a rigorous technical-legal formulation of this legal figure is required.From this perspective we analyze the genesis and evolution of the doctrine and its process of progressive technical decantation