914 resultados para alternative reproductive strategies


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Customers’ long-term brand relations are crucial drivers of a service brand’s sustainable competitive advantage. This research empirically examines the quality of customer-service brand relationships in the context of an airline’s frequent flyer program. The authors show that service brand relationship quality (BRQ) involves both a hot (based on emotions) and a cold (based on objectrelevant beliefs) component. They find that these two components have different implications for a service brand’s performance and are at least partially driven by different antecedents whose relative importance changes over time. Specifically, cold BRQ is important for word-of-mouth behavior and is strongly driven by partner quality (i.e., the generalized assessment of the brand in its role as a relationship counterpart). Hot BRQ, on the other hand, has a stronger impact on willingness to pay a price premium and consideration set size. In early stages of a customer-brand relationship hot BRQ is more strongly driven by self-congruence (i.e., consumer’s perception of the fit between his/her self and the brand’s personality), in later stages partner quality becomes more relevant. The authors discuss the implications of their findings for the development of BRQ and the implementation of alternative growth strategies in a services context.

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Malignant brain tumors are one of the most challenging cancers affecting society today. In a recent survey, an estimated 17,000 annual cases were recorded with a staggering total of 13,300 deaths. A unique degree of heterogeneity typifies glial tumors and presents a challenge for solitary anti-neoplastic treatments. Tumors subsist as heterogeneous masses that progress through dysplasia to astrocytomas, mixed glioma and glioblastoma multiforme. Although traditional therapeutic approaches have provided increments of success, the median survival time remains 12 months. The urgency to improve upon current clinical protocols has encouraged alternative experimental strategies such as p53 adenoviral gene therapy (Ad-p53). This study addresses the efficacy of Ad-p53 for the treatment of glioma. Our model presents a tumor response that is unique among human cancers. Ad-p53 effectively induces apoptosis in mutant p53 expressing cells yet fails to do so in those with wildtype p53. In order to adopt Adp53 as a standard anti-cancer modality, we characterized the role of the tumor suppressor gene p53 in mediating apoptosis. We demonstrate that altering cellular p53 status through the introduction of a dominant negative mutant p53 (175H, 248W, 273H) sensitized cells to Ad-p53. We discovered that wild-type p53 expressing glioma cells retain the apoptotic machinery necessary to accomplish cell death, but have developed mechanisms that interfere with p53 signaling. Earlier studies have not addressed the mechanisms of Ad-p53 apoptosis nor the resistance exhibited by wild-type p53 glioma. To explain the divergent phenotypes, we identified apoptotic pathways activated and effectors of the response. We illustrated that modulation of the death receptor Fas/APO-1 is a principal means of Ad-p53 signaling that is impaired in wild-type p53 glioma. Moreover, the apoptotic response was found to be a multi-faceted process that engaged several caspases, most notably caspases -1, -3 and -8. Lastly, we assessed the ability of anti-apoptotic molecules Bcl-2 and CrmA to inhibit Ad-p53 apoptosis. These studies revealed that Ad-p53 is a powerful tool for inducing apoptosis that can be delayed but not inhibited by anti-apoptotic means. This work is critical for understanding the development of glioma and the phenotypic and genotypic alterations that account for tumor resistance. ^

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El trabajo estudia las migraciones regionales e internacionales en un contexto de economías campesinas de frontera, que comprende los actuales municipios de Los Toldos (Salta, Argentina) y Padcaya (Tarija, Bolivia). El valle de Los Toldos perteneció a Bolivia hasta 1938, año en el que se oficializó su traspaso hacia Argentina. Si bien, hasta esa fecha, el área de estudio conformaba una misma región, la diferente pertenencia estatal fue marcando ciertas diferencias entre ambos sectores, principalmente debido a la influencia de las políticas que fue adoptando cada nación. Mediante un estudio etnográfico y, especialmente, el análisis comparado de 110 encuestas semi-estructuradas a unidades domésticas, se observa la movilidad espacial de sus integrantes. Diferentes tipos de migración se constituyen en función de las estrategias reproductivas de tales unidades. Dada la creciente subdivisión de las tierras las migraciones permanentes se entienden como un mecanismo compensatorio en la etapa de redistribución de los medios de producción entre los descendientes. Mientras que las migraciones temporarias se constituyen en una actividad más, que se suma a las actividades económicas convencionales.

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En este trabajo se presenta el dispositivo metodológico de un estudio de casos múltiple realizado a productores agropecuarios familiares del Litoral Oeste de Uruguay. El estudio, de tipo etnográfico, integra los aportes de los enfoques biográficos y de la metodología Enfoque Global de la Explotación Agropecuaria (metodología EGEA). Se describe como fue diseñada la muestra teórica y la etapa de relevamiento de información para cada caso, que implicó visitas a dieciséis familias de productores agropecuarios ubicados en cuatro contextos territoriales diferentes. Esta línea de investigación tiene como referencia a Pierre Bourdieu, su teoría de la práctica y su sistema de conceptos fundamentales. A partir del análisis de los modelos de funcionamiento estratégico de los casos estudiados, se profundiza en los sistemas de reglas estratégicas comunes y específicas de acuerdo a trayectorias y ciclos familiares. Se presentan resultados preliminares del estudio realizado y algunas consideraciones metodológicas sobre la potencialidad y complementariedad de los enfoques utilizados

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El trabajo estudia las migraciones regionales e internacionales en un contexto de economías campesinas de frontera, que comprende los actuales municipios de Los Toldos (Salta, Argentina) y Padcaya (Tarija, Bolivia). El valle de Los Toldos perteneció a Bolivia hasta 1938, año en el que se oficializó su traspaso hacia Argentina. Si bien, hasta esa fecha, el área de estudio conformaba una misma región, la diferente pertenencia estatal fue marcando ciertas diferencias entre ambos sectores, principalmente debido a la influencia de las políticas que fue adoptando cada nación. Mediante un estudio etnográfico y, especialmente, el análisis comparado de 110 encuestas semi-estructuradas a unidades domésticas, se observa la movilidad espacial de sus integrantes. Diferentes tipos de migración se constituyen en función de las estrategias reproductivas de tales unidades. Dada la creciente subdivisión de las tierras las migraciones permanentes se entienden como un mecanismo compensatorio en la etapa de redistribución de los medios de producción entre los descendientes. Mientras que las migraciones temporarias se constituyen en una actividad más, que se suma a las actividades económicas convencionales.

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En este trabajo se presenta el dispositivo metodológico de un estudio de casos múltiple realizado a productores agropecuarios familiares del Litoral Oeste de Uruguay. El estudio, de tipo etnográfico, integra los aportes de los enfoques biográficos y de la metodología Enfoque Global de la Explotación Agropecuaria (metodología EGEA). Se describe como fue diseñada la muestra teórica y la etapa de relevamiento de información para cada caso, que implicó visitas a dieciséis familias de productores agropecuarios ubicados en cuatro contextos territoriales diferentes. Esta línea de investigación tiene como referencia a Pierre Bourdieu, su teoría de la práctica y su sistema de conceptos fundamentales. A partir del análisis de los modelos de funcionamiento estratégico de los casos estudiados, se profundiza en los sistemas de reglas estratégicas comunes y específicas de acuerdo a trayectorias y ciclos familiares. Se presentan resultados preliminares del estudio realizado y algunas consideraciones metodológicas sobre la potencialidad y complementariedad de los enfoques utilizados

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En este trabajo se presenta el dispositivo metodológico de un estudio de casos múltiple realizado a productores agropecuarios familiares del Litoral Oeste de Uruguay. El estudio, de tipo etnográfico, integra los aportes de los enfoques biográficos y de la metodología Enfoque Global de la Explotación Agropecuaria (metodología EGEA). Se describe como fue diseñada la muestra teórica y la etapa de relevamiento de información para cada caso, que implicó visitas a dieciséis familias de productores agropecuarios ubicados en cuatro contextos territoriales diferentes. Esta línea de investigación tiene como referencia a Pierre Bourdieu, su teoría de la práctica y su sistema de conceptos fundamentales. A partir del análisis de los modelos de funcionamiento estratégico de los casos estudiados, se profundiza en los sistemas de reglas estratégicas comunes y específicas de acuerdo a trayectorias y ciclos familiares. Se presentan resultados preliminares del estudio realizado y algunas consideraciones metodológicas sobre la potencialidad y complementariedad de los enfoques utilizados

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El trabajo estudia las migraciones regionales e internacionales en un contexto de economías campesinas de frontera, que comprende los actuales municipios de Los Toldos (Salta, Argentina) y Padcaya (Tarija, Bolivia). El valle de Los Toldos perteneció a Bolivia hasta 1938, año en el que se oficializó su traspaso hacia Argentina. Si bien, hasta esa fecha, el área de estudio conformaba una misma región, la diferente pertenencia estatal fue marcando ciertas diferencias entre ambos sectores, principalmente debido a la influencia de las políticas que fue adoptando cada nación. Mediante un estudio etnográfico y, especialmente, el análisis comparado de 110 encuestas semi-estructuradas a unidades domésticas, se observa la movilidad espacial de sus integrantes. Diferentes tipos de migración se constituyen en función de las estrategias reproductivas de tales unidades. Dada la creciente subdivisión de las tierras las migraciones permanentes se entienden como un mecanismo compensatorio en la etapa de redistribución de los medios de producción entre los descendientes. Mientras que las migraciones temporarias se constituyen en una actividad más, que se suma a las actividades económicas convencionales.

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In the mid-long-term after a nuclear accident, the contamination of drinking water sources, fish and other aquatic foodstuffs, irrigation supplies and people?s exposure during recreational activities may create considerable public concern, even though dose assessment may in certain situations indicate lesser importance than for other sources, as clearly experienced in the aftermath of past accidents. In such circumstances there are a number of available countermeasure options, ranging from specific chemical treatment of lakes to bans on fish ingestion or on the use of water for crop irrigation. The potential actions can be broadly grouped into four main categories, chemical, biological, physical and social. In some cases a combination of actions may be the optimal strategy and a decision support system (DSS) like MOIRA-PLUS can be of great help to optimise a decision. A further option is of course not to take any remedial actions, although this may also have significant socio-economic repercussions which should be adequately evaluated. MOIRA-PLUS is designed to allow for a reliable assessment of the long-term evolution of the radiological situation and of feasible alternative rehabilitation strategies, including an objective evaluation of their social, economic and ecological impacts in a rational and comprehensive manner. MOIRA-PLUS also features a decision analysis methodology, making use of multi-attribute analysis, which can take into account the preferences and needs of different types of stakeholders. The main functions and elements of the system are described summarily. Also the conclusions from end-user?s experiences with the system are discussed, including exercises involving the organizations responsible for emergency management and the affected services, as well as different local and regional stakeholders. MOIRAPLUS has proven to be a mature system, user friendly and relatively easy to set up. It can help to better decisionmaking by enabling a realistic evaluation of the complete impacts of possible recovery strategies. Also, the interaction with stakeholders has allowed identifying improvements of the system that have been recently implemented.

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Los lenguajes de programación son el idioma que los programadores usamos para comunicar a los computadores qué queremos que hagan. Desde el lenguaje ensamblador, que traduce una a una las instrucciones que interpreta un computador hasta lenguajes de alto nivel, se ha buscado desarrollar lenguajes más cercanos a la forma de pensar y expresarse de los humanos. Los lenguajes de programación lógicos como Prolog utilizan a su vez el lenguaje de la lógica de 1er orden de modo que el programador puede expresar las premisas del problema que se quiere resolver sin preocuparse del cómo se va a resolver dicho problema. La resolución del problema se equipara a encontrar una deducción del objetivo a alcanzar a partir de las premisas y equivale a lo que entendemos por la ejecución de un programa. Ciao es una implementación de Prolog (http://www.ciao-lang.org) y utiliza el método de resolución SLD, que realiza el recorrido de los árboles de decisión en profundidad(depth-first) lo que puede derivar en la ejecución de una rama de busqueda infinita (en un bucle infinito) sin llegar a dar respuestas. Ciao, al ser un sistema modular, permite la utilización de extensiones para implementar estrategias de resolución alternativas como la tabulación (OLDT). La tabulación es un método alternativo que se basa en memorizar las llamadas realizadas y sus respuestas para no repetir llamadas y poder usar las respuestas sin recomputar las llamadas. Algunos programas que con SLD entran en un bucle infinito, gracias a la tabulación dán todas las respuestas y termina. El modulo tabling es una implementación de tabulación mediante el algoritmo CHAT. Esta implementación es una versión beta que no tiene implementado un manejador de memoria. Entendemos que la gestión de memoria en el módulo de tabling tiene gran importancia, dado que la resolución con tabulación permite reducir el tiempo de computación (al no repetir llamadas), aumentando los requerimientos de memoria (para guardar las llamadas y las respuestas). Por lo tanto, el objetivo de este trabajo es implementar un mecanismo de gestión de la memoria en Ciao con el módulo tabling cargado. Para ello se ha realizado la implementación de: Un mecanismo de captura de errores que: detecta cuando el computador se queda sin memoria y activa la reinicialización del sitema. Un procedimiento que ajusta los punteros del modulo de tabling que apuntan a la WAM tras un proceso de realojo de algunas de las áreas de memoria de la WAM. Un gestor de memoria del modulo de tabling que detecta c realizar una ampliación de las áreas de memoria del modulo de tabling, realiza la solicitud de más memoria y realiza el ajuste de los punteros. Para ayudar al lector no familiarizado con este tema, describimos los datos que Ciao y el módulo de tabling alojan en las áreas de memoria dinámicas que queremos gestionar. Los casos de pruebas desarrollados para evaluar la implementación del gestor de memoria, ponen de manifiesto que: Disponer de un gestor de memoria dinámica permite la ejecución de programas en un mayor número de casos. La política de gestión de memoria incide en la velocidad de ejecución de los programas. ---ABSTRACT---Programming languages are the language that programmers use in order to communicate to computers what we want them to do. Starting from the assembly language, which translates one by one the instructions to the computer, and arriving to highly complex languages, programmers have tried to develop programming languages that resemble more closely the way of thinking and communicating of human beings. Logical programming languages, such as Prolog, use the language of logic of the first order so that programmers can express the premise of the problem that they want to solve without having to solve the problem itself. The solution to the problem is equal to finding a deduction of the objective to reach starting from the premises and corresponds to what is usually meant as the execution of a program. Ciao is an implementation of Prolog (http://www.ciao-lang.org) and uses the method of resolution SLD that carries out the path of the decision trees in depth (depth-frist). This can cause the execution of an infinite searching branch (an infinite loop) without getting to an answer. Since Ciao is a modular system, it allows the use of extensions to implement alternative resolution strategies, such as tabulation (OLDT). Tabulation is an alternative method that is based on the memorization of executions and their answers, in order to avoid the repetition of executions and to be able to use the answers without reexecutions. Some programs that get into an infinite loop with SLD are able to give all the answers and to finish thanks to tabulation. The tabling package is an implementation of tabulation through the algorithm CHAT. This implementation is a beta version which does not present a memory handler. The management of memory in the tabling package is highly important, since the solution with tabulation allows to reduce the system time (because it does not repeat executions) and increases the memory requirements (in order to save executions and answers). Therefore, the objective of this work is to implement a memory management mechanism in Ciao with the tabling package loaded. To achieve this goal, the following implementation were made: An error detection system that reveals when the computer is left without memory and activate the reinizialitation of the system. A procedure that adjusts the pointers of the tabling package which points to the WAM after a process of realloc of some of the WAM memory stacks. A memory manager of the tabling package that detects when it is necessary to expand the memory stacks of the tabling package, requests more memory, and adjusts the pointers. In order to help the readers who are not familiar with this topic, we described the data which Ciao and the tabling package host in the dynamic memory stacks that we want to manage. The test cases developed to evaluate the implementation of the memory manager show that: A manager for the dynamic memory allows the execution of programs in a larger number of cases. Memory management policy influences the program execution speed.

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This PhD dissertation is framed in the emergent fields of Reverse Logistics and ClosedLoop Supply Chain (CLSC) management. This subarea of supply chain management has gained researchers and practitioners' attention over the last 15 years to become a fully recognized subdiscipline of the Operations Management field. More specifically, among all the activities that are included within the CLSC area, the focus of this dissertation is centered in direct reuse aspects. The main contribution of this dissertation to current knowledge is twofold. First, a framework for the so-called reuse CLSC is developed. This conceptual model is grounded in a set of six case studies conducted by the author in real industrial settings. The model has also been contrasted with existing literature and with academic and professional experts on the topic as well. The framework encompasses four building blocks. In the first block, a typology for reusable articles is put forward, distinguishing between Returnable Transport Items (RTI), Reusable Packaging Materials (RPM), and Reusable Products (RP). In the second block, the common characteristics that render reuse CLSC difficult to manage from a logistical standpoint are identified, namely: fleet shrinkage, significant investment and limited visibility. In the third block, the main problems arising in the management of reuse CLSC are analyzed, such as: (1) define fleet size dimension, (2) control cycle time and promote articles rotation, (3) control return rate and prevent shrinkage, (4) define purchase policies for new articles, (5) plan and control reconditioning activities, and (6) balance inventory between depots. Finally, in the fourth block some solutions to those issues are developed. Firstly, problems (2) and (3) are addressed through the comparative analysis of alternative strategies for controlling cycle time and return rate. Secondly, a methodology for calculating the required fleet size is elaborated (problem (1)). This methodology is valid for different configurations of the physical flows in the reuse CLSC. Likewise, some directions are pointed out for further development of a similar method for defining purchase policies for new articles (problem (4)). The second main contribution of this dissertation is embedded in the solutions part (block 4) of the conceptual framework and comprises a two-level decision problem integrating two mixed integer linear programming (MILP) models that have been formulated and solved to optimality using AIMMS as modeling language, CPLEX as solver and Excel spreadsheet for data introduction and output presentation. The results obtained are analyzed in order to measure in a client-supplier system the economic impact of two alternative control strategies (recovery policies) in the context of reuse. In addition, the models support decision-making regarding the selection of the appropriate recovery policy against the characteristics of demand pattern and the structure of the relevant costs in the system. The triangulation of methods used in this thesis has enabled to address the same research topic with different approaches and thus, the robustness of the results obtained is strengthened.

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Prairie voles (Microtus ochrogaster) are monogamous rodents that form pair bonds characterized by a preference for a familiar social partner. In male prairie voles, exposure to either the stress of swimming or exogenous injections of corticosterone facilitate the development of a social preference for a female with which the male was paired after injection or swimming. Conversely, adrenalectomy inhibits partner preference formation in males and the behavioral effects of adrenalectomy are reversed by corticosterone replacement. In female prairie voles, swim stress interferes with the development of social preferences and corticosterone treatments inhibit the formation of partner preferences, while adrenalectomized females form preferences more quickly than adrenally intact controls. Because sex differences in both behavior and physiology are typically reduced in monogamous species, we initially predicted that male and female prairie voles would exhibit similar behavioral responses to corticosterone. However, our findings suggest an unanticipated sexual dimorphism in the physiological processes modulating social preferences. This dimorphic involvement of stress hormones in pair bonding provides a proximate mechanism for regulating social organization, while permitting males and females to adapt their reproductive strategies in response to environmental challenges.

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Over the past 30 years, numerous attempts to understand the relationship between offspring size and fitness have been made, and it has become clear that this critical relationship is strongly affected by environmental heterogeneity. For marine invertebrates, there has been a long-standing interest in the evolution of offspring size, but there have been very few empirical and theoretical examinations of post-metamorphic offspring size effects, and almost none have considered the effect of environmental heterogeneity on the offspring size/fitness relationship. We investigated the post-metamorphic effects of offspring size in the field for the colonial marine invertebrate Botrylloides violaceus. We also examined how the relationship between offspring size and performance was affected by three different types of intraspecific competition. We found strong and persistent effects of offspring size on survival and growth, but these effects depended on the level and type of intraspecific competition.. Generally, competition strengthened the advantages of increasing maternal investment. Interestingly, we found that offspring size determined the outcome of competitive interaction: juveniles that had more maternal investment were more likely to encroach on another juvenile's territory. This suggests that mothers have the previously unrecognized potential to influence the outcome of competitive interactions in benthic marine invertebrates. We created a simple optimality model, which utilized the data generated from our field experiments, and found that increasing intraspecific competition resulted in an increase,in predicted optimal size. Our results suggest that the relationship between offspring size and fitness is highly variable in the marine environment and strongly dependent on the density of conspecifics.

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We measured plasma androgen (combined testosterone and 5 alpha-dihydrotestosterone) (A) and corticosterone (B) in the promiscuous green turtle (Chelonia mydas) during courtship in the southern Great Barrier Reef. This study examined if reproductive behaviors and intermale aggression induced behavioral androgen and adrenocortical responses in reproductively active male and female green turtles. Associations between reproductive behavior and plasma steroids were investigated in green turtles across the population and within individuals. Levels across a range of both asocial and social behaviors were compared including (a) free swimming behavior; (b) initial courtship interactions; (c) mounted behavior (male and female turtles involved in copulatory activities); (d) intermale aggression (rival males that physically competed with another male turtle or mounted males recipient to these aggressive interactions); and (e) extensive courtship damage (male turtles that had accumulated excessive courtship damage from rival males). Behavioral androgen responses were detected in male turtles, in that plasma A was observed to increase with both attendant and mounted behavior. Male turtles who had been subjected to intermale aggression or who had accumulated severe courtship damage exhibited significantly lower plasma A than their respective controls. No pronounced adrenocortical response was observed after either intermale aggression or accumulation of extensive courtship damage. Female turtles exhibited a significant increase in plasma B during swimming versus mounted behavior, but no change in plasma A. We discuss our results in terms of how scramble polygamy might influence behavioral androgen interactions differently from more typical combative and territorial forms Of male polygamy. (C) 1999 Academic Press.

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In this thesis, we consider four different scenarios of interest in modern satellite communications. For each scenario, we will propose the use of advanced solutions aimed at increasing the spectral efficiency of the communication links. First, we will investigate the optimization of the current standard for digital video broadcasting. We will increase the symbol rate of the signal and determine the optimal signal bandwidth. We will apply the time packing technique and propose a specifically design constellation. We will then compare some receiver architectures with different performance and complexity. The second scenario still addresses broadcast transmissions, but in a network composed of two satellites. We will compare three alternative transceiver strategies, namely, signals completely overlapped in frequency, frequency division multiplexing, and the Alamouti space-time block code, and, for each technique, we will derive theoretical results on the achievable rates. We will also evaluate the performance of said techniques in three different channel models. The third scenario deals with the application of multiuser detection in multibeam satellite systems. We will analyze a case in which the users are near the edge of the coverage area and, hence, they experience a high level of interference from adjacent cells. Also in this case, three different approaches will be compared. A classical approach in which each beam carries information for a user, a cooperative solution based on time division multiplexing, and the Alamouti scheme. The information theoretical analysis will be followed by the study of practical coded schemes. We will show that the theoretical bounds can be approached by a properly designed code or bit mapping. Finally, we will consider an Earth observation scenario, in which data is generated on the satellite and then transmitted to the ground. We will study two channel models, taking into account one or two transmit antennas, and apply techniques such as time and frequency packing, signal predistortion, multiuser detection and the Alamouti scheme.