A ubiquitous problem for all foragers is the trade-off between acquiring food energy while simultaneously avoiding the risk of predation. In central montane Alberta I modelled how ungulate forage changes with succession within cutblocks and the implications for forage availability to ungulates under current harvest regimes. Because cutblocks are discrete patches in space, I developed a dynamic state variable model for an ungulate to explore under what conditions an individual forager could (1) behaviourally avoid predation within a patch through inactivity, (2) overcome patch isolation when confronted with predation during transit between patches, and (3) alter patch use across a home range to optimize fitness. The model includes the requirement to process forage into energy through rumination behaviour that constrains foraging, and compares outcomes under a time-minimizing (sigmoid) and energy maximizing (linear) fitness functions. When an ungulate is in high energetic state, inactivity provides an effective behavioural refuge, or animals prioritize safety over energy gain, individuals avoid predation within patches reducing the need to move between patches. When energy acquisition is prioritized, individuals are at a low energetic state, or within patch anti-predator behaviours are ineffective, individuals move among patches to avoid predators in space, and configuration of the patches influences fitness. When model results were qualitatively compared to activity patterns and cutblock use of female, GPS-collared elk appear to follow a time minimizing strategy in their patch use across the home range and with their activity within riskier patches. I discuss the implications of these findings for the management of elk and cutblocks in west central Alberta.

Aggregative feeding is widespread in Lepidopteran larvae suggesting that this behavior serves on adaptive function. Many studies of the potential benefits of aggregative feeding in Lepidopteran larvae have been conducted. However, no studies have directly examined the benefits of cryptic larvae being both chemically defended and gregarious. Group feeding occurs disproportionately more in chemically defended larvae than in larvae that have no chemical defense. Most of these larvae are cryptic when they are most highly aggregated and most vulnerable to predation. In this study, the benefits of group feeding in terms of decreased predation were explored in first instar larvae of pipevine swallowtail larvae, Battus philenor, a species that exhibits chemical sequestration. Contrary to our expectation, we found that groups of larvae fed a diet with high levels of the toxin aristolochic acid, which they sequester naturally and use as a defense against natural enemies, had significantly lower survivorship due to predation in both the field and in the laboratory experiments compared to groups of larvae fed a diet with low aristolochic acid content. We also found that aristolochic acid does not deter the generalist predator Hippodamia convergens, the ladybird beetle, suggesting that this compound is not a universal predator deterrent as previously assumed. Thus, instead of finding a benefit to group feeding and chemical defense in cryptic larvae, we have found a negative impact of group feeding in this population of B. philenor. Based on this evidence, we speculate that other benefits of group feeding might be outweighing the negative consequences of increased predation during the first instar. Future research on chemical defense, aposematism, and aggregative feeding should take into consideration that chemical defenses might not be universally effective against all natural enemies.

Uppsats behandlar företags kapitalstruktur d v s fördelning mellan främmande och eget kapital. Det finns teorier kring ämnet som menar att ett företags värde påverkas av sammansättningen mellan skulder och eget kapital. Detta föranledde vår problemformulering om att närbesläktade verksamheter uppvisar en likartad skuldsättning. Syftet var att jämföra skuldsätt-ningsgraden mellan kapitalintensiva branscher och kapitaltunna branscher. Utifrån detta ställdes vår hypotes upp om att kapitalkrävande branscherna fastighet och tunga maskiner har en högre skuldsättningsgrad än branscherna läkemedel och tjänster. Vår studie omfattar 52 företag noterade på Stockholmsbörsen. Vi har utgått från en kvantitativ ansats och empirin är hämtad från företagens årsredovisningar samt en enkätundersökning. Med hjälp av teorier som Modigliani och Millers berömda proposition MMI och MMII, Trade Off och Pecking order har vi försökt finna orsakerna till företagens skuldsättningsgrad. Resultaten i vår under-sökning kunde inte stärka vår hypotes, varpå den förkastades. Vidare kunde inget mönster urskiljas i skuldsättningen för de valda branscherna.

This thesis is an attempt to describe how different environmental factors influence life history traits in different populations, sexes and developmental stages in the moor frog, Rana arvalis. The studied populations are located along 1100 km latitudinal gradient, with pH varying between 4.0 and 8.5. I have used data from both natural populations and common garden experiments. Reproducing moor frogs were larger and older at high latitudes, indicating a selective advantage of large size at high latitudes and/or earlier reproduction at low latitudes. When controlling for age I found that frogs were older and smaller at low pH, which may be a result of a reduced growth rate due to acid stress. The both sexes respond differently to different environments, with the lowest sexual dimorphism in body size found in the acid environments. This is possibly caused by a trade-off between growth and reproduction. Being large is considered to be advantageous, in females due to increased fecundity, and in males due to higher ability to compete for mates, while the cost of high growth is a reduced possibility to survive until the next mating season. Moor frog embryos originating from an acid population survived better under acid stress than embryos from a neutral population. Using quantitative genetic techniques I found strong maternal effects and small additive genetic variation for the traits in acid and non acid populations. The variation in acid stress tolerance owed largely to non-genetic effects. Females from acid localities lay larger eggs, which probably improves the performance of tadpoles under acid conditions. The trade-off between egg size and fecundity was stronger in acid populations indicating that females in acid populations reduced fecundity to increase offspring size. Finally, frogs from acidified environments were more asymmetric in skeletal traits further indicating the developmental stress created by acidification.

For ectotherms living in seasonal environments, time available for development and growth is often constrained by the length of the growth season. Declining season length towards higher latitudes often select for latitudinal clines in development and growth rates, exhibiting increasing growth and developmental rates towards the north. However, the physiological and ecological factors enabling these clines are poorly understood. Our study system included eight populations of Rana temporaria along a 1500 km latitudinal gradient. We found increased growth rates in populations at higher latitudes to be the result of higher growth efficiency, partly due to increased relative gut length. Populations with higher growth rates also exhibited lower standard metabolic rates, implying that fast-growing individuals are able to achieve high growth rates by spending less energy on maintenance metabolism under low activity conditions. Predator densities, and antipredatory defenses in prey, are assumed to decrease towards higher latitudes. While all study populations responded to predator presence by decreasing activity and foraging, high latitude populations maintained higher activity levels in the presence of the predator. In trials with a free-ranging predator, high latitude tadpoles experienced higher mortality than those from the low latitudes. The higher activity level in the northern populations increases mortality under predation risk, but is probably needed to maintain high growth and development rates. When competing over resources, tadpoles from the low latitude population were inferior competitors, as indicated by their longer development time when raised together with high latitude tadpoles. We found no effect of latitude on size-corrected burst speed. The general effect of predator presence on burst speed depended on food availability, with well fed tadpoles being faster in the absence, and food restricted being faster in the presence of a predator.

Ett företags kapitalstruktur och i förlängningen dess val av finansiering för strategiska investeringar omgärdas av motstridiga uppfattningar och teorier. Vi har genomfört en fallstudie av Home Properties AB, ett renodlat hotellfastighetsägarbolag noterat på Stockholmsbörsens lista för medelstora bolag. Uppsatsens syfte är att beskriva hur Home Properties agerar och resonerar vid finansiering av strategiska investeringar och jämföra beskrivningen med Åkerbloms hypotes om sär- och samfinansiering, pecking order teorin och static trade-off modellen. I syftet ingår också att ge förslag på vidare forskning. Enligt pecking order teorin prioriterar företag internt kapital framför externt. Vid finansiering av strategiska investeringar väljer Home Properties emellertid inteckningslån först. I Home Properties fall förklaras företagets val av finansieringskällor bättre av static trade-off modellen och Åkerbloms hypotes om sär- och samfinansiering. Anledningen är delvis att Home Properties strävar efter ett soliditetsmål för att åstadkomma en optimal kapitalstruktur vilket inte överensstämmer med pecking order teorin. Home Properties val av finansiering kan inte helt och hållet förklaras av vare sig pecking order teorin, static trade-off modellen eller Åkerbloms hypotes om sär- och samfinansiering. Efter utförd fallstudie kan vi konstatera att Home Properties vid finansiering av strategiska investeringar i regel vänder sig till (1) särfinansiering (2) internt kapital (3) gemensamt låneutrymme och (4) nytt eget kapital/ lån/ hybrid. En viktig förutsättning för denna ordnings giltighet är att soliditetsmålet inte störs långsiktigt.

Vi undersöker huruvida de två teorierna Pecking order och Trade-off gemensamt kan förklara utformning av kapitalstruktur och hur beslut gällande denna ser ut hos svenska börsnoterade företag. Vi menar att den aktuella kapitalstrukturen är en konsekvens av den historiska utvecklingen inom företag, där tidigare års finansiella över-/underskott leder till dagens kapitalstruktur och att asymmetrisk information och transaktionskostnader gör att intern finansiering är att föredra framför extern. Företag ser dock fördelar med viss skuldsättning, vilket bidrar till att företag sätter upp en målkapitalstruktur i början av aktuell period. Företags benägenhet att justera sin kapitalstruktur mot denna målkapitalstruktur varierar beroende på vilken situation företaget befinner sig i och olika anpassningshastigheter uppstår till följd av att vissa situationer föredras framför andra. Vi undersöker sambandet mellan målkapitalstruktur och finansiella över-/underskott och hur detta påverkar företags förändring i kapitalstruktur. Våra resultat visar att företag är som mest benägna att förändra sin kapitalstruktur när de har ett finansiellt underskott med en kapitalstruktur över sin målkapitalstruktur och minst benägna att förändra sin kapitalstruktur när de har ett finansiellt överskott och en kapitalstruktur under sin målkapitalstruktur. Både Pecking order och Trade-off har inflytande vid förklaring av företags kapitalstruktursförändring, dock har den ena teorin större betydelse än den andra beroende på vilken situation företag befinner sig i.

Las demandas y expectativas de los usuarios y operadores móviles crecen sin parar y, consecuentemente, los nuevos estándares han incorporado tecnologías de acceso de radio cada vez más eficientes. Las especificaciones IMT-Advanced para la cuarta generación (4G) de redes móviles de banda ancha requieren, entre otras cosas, tasas más altas de transmisión de datos, del orden de 100 Mbps a 1 Gbps, dependiendo del nivel de movilidad. Para conseguir éstas tasas se ha escogido como tecnología de acceso el Acceso Múltiple por División de Frecuencias Ortogonal (OFDMA), y se han considerado femtoceldas para mejorar la cobertura de espacios interiores. Para explorar completamente la flexibilidad de estas tecnologías y utilizar los escasos recursos radio de la manera más eficiente posible se requieren técnicas de Gestión de Recursos Radio (RRM) adaptativas e inteligentes. En el ámbito de los sistemas celulares basados en OFDMA, uno de los problemas todavía no resuelto es el compromiso que existe entre la eficiencia en la utilización de los recursos y la equidad en su distribución entre los usuarios de la red. El compromiso entre eficiencia y equidad aparece cuando los recursos radio asignados dan lugar a diferentes indicadores de eficiencia con respecto a los distintos usuarios de red (diversidad multi-usuario). El uso de una asignación de recursos oportunista, para explorar estas diversidades y maximizar la capacidad, causa situaciones de desigualdad en la distribución de los recursos. Por otro lado, los esquemas de RRM que propician equidad absoluta consideran un escenario de peor caso, penalizando a los usuarios con mejores condiciones y reduciendo la capacidad del sistema. En esta tesis, se han propuesto varias políticas y técnicas de RRM para balancear este compromiso en el contexto de redes macrocelulares y femtocelulares. En el caso particular de sistemas macrocelulares, proponemos un nuevo paradigma de gestión de red basado en el control del índice de equidad de la celda en escenarios con servicios de tiempo no-real y de tiempo real. Se han estudiado dos enfoques para el control de la equidad: control instantáneo (a corto plazo) utilizando técnicas de RRM de adaptación de tasa y equidad, y control promediado (a mediano plazo) utilizando estructuras de RRM basadas en la Teoría de la Utilidad. En el caso de las femtoceldas, se ha formulado una nueva técnica para evitar la interferencia capaz de balancear el compromiso entre eficiencia espectral y la equidad entre los puntos de acceso de las femtoceldas. Esta estrategia de RRM se basa en una planificación a mediano/largo plazo de las frecuencias disponibles, que toma en consideración la topología de interferencia de grupos de femtoceldas vecinas. Las técnicas de RRM consideradas en esta tesis se han evaluada utilizando de forma sistemática técnicas de simulación numéricas a nivel de sistema. En el caso del escenario macrocelular, se demuestra que las técnicas adaptativas de RRM propuestas son, para los operadores móviles una, herramienta valiosa porqué, además de ser una generalización de estrategias clásicas bien conocidas, son capaces de garantizar de forma eficiente diferentes niveles de equidad en el sistema, y controlar el compromiso entre eficiencia y equidad. Además, se concluye que las estrategias basadas en la teoría de utilidad, que hacen un control promedio de la equidad, muestran resultados tan buenos ó incluso mejores que los presentados por las técnicas basadas en optimización instantánea de la adaptación de la tasa y la equidad, utilizando menores recursos computacionales. Finalmente, se demuestra que la técnica propuesta para evitar interferencia en redes de femtoceldas puede garantizar una coexistencia sin degradaciones entre punto de acceso vecinos para cualquier topología de interferencia. Esta técnica puede ser implementada mediante arquitecturas de red distribuidas ó centralizadas, presentando en ambos casos unos requisitos de señalización muy bajos. / User and cellular operator requirements and expectations have been continuously evolving, and consequently, advanced radio access technologies have emerged. The International Mobile Telecommunications - Advanced (IMT-Advanced) specifications for mobile broadband Fourth Generation (4G) networks state, among other requirements, that enhanced peak data rates of 100 Mbps and 1 Gbps for high and low mobility should be provided. In order to achieve this challenging performance, Orthogonal Frequency Division Multiple Access (OFDMA) has been chosen as the access technology, and femtocells have been considered for improving indoor coverage. In order to fully explore the flexibility of these technologies and use the scarce radio resources in the most efficient way possible, intelligent and adaptive Radio Resource Management (RRM) techniques are crucial. There are many open RRM problems in wireless networks in general and OFDMA-based cellular systems in particular. One of such problems is the fundamental trade-off that exists between efficiency in the resource usage and fairness in the resource distribution among network players. Several opportunistic RRM algorithms, which dynamically allocate the resources to the network players that present the highest efficiency indicator with regard to these resources, have been proposed to maximize the efficiency in the resource usage. The trade-off between efficiency and fairness appears when the resources have different efficiency indicators to different network players (multi-user or multi-cell diversity). The use of opportunistic resource allocation to explore these diversities causes unfair situations in the resource distribution. On the other hand, schemes that provide absolute fairness deal with the worst case scenario, penalizing players with better condition and reducing the system capacity. In this thesis, several RRM policies and techniques are proposed to balance this compromise in macrocell and femtocell networks. In the particular case of macrocell systems, we propound a new network management paradigm based on the control of a cell fairness index in scenarios with Non-Real Time (NRT) or Real Time (RT) services. Two fairness control approaches are studied: instantaneous (short-term) control by means of generalized fairness/rate adaptive RRM techniques and average (mid-term) control using utility-based frameworks. For femtocell networks, a novel interference avoidance technique able to balance the trade-off between spectral efficiency in the femtocell tier and fairness among the Femtocell Access Points (FAPs) is formulated. This RRM strategy is based on a high-level, mid/long-term frequency planning that takes into account the topology of groups of neighboring FAPs. The RRM techniques considered in this thesis are evaluated by means of extensive system-level and/or numerical simulations. Regarding the macrocell scenario, it is shown that the proposed adaptive RRM techniques are valuable tools for the mobile operators, because they are generalizations of well-known classic strategies found in the literature and they can effectively guarantee different fairness levels in the system and control the trade-off between efficiency and fairness. Furthermore, it is concluded that the utility-based strategies that perform an average fairness control can provide performance results as good as the fairness/rate adaptive techniques, which are based on instantaneous optimization, using less computational resources. Finally, it is demonstrated that the proposed interference avoidance technique for femtocell networks can guarantee a seamless coexistence between neighboring FAPs in any interference topology. Furthermore, this technique can be implemented in both centralized and distributed network architectures and generates very low signaling overhead.

There have been increased efforts to develop methods for improving attention across a range of tasks including those assessing sustained attention. Using a variety of techniques, researchers have reported modest reductions in errors on sustained attention tasks. However, published reports often have not documented changes in response times (RTs) that might accompany error reductions, which is problematic given that the error reductions could be mediated by a slowing strategy (i.e., speed-accuracy trade-off). In three studies, I explored the effects of speed-accuracy trade-offs in a sustained attention task (The Sustained Attention to Response Task; SART). In Study 1, I examined the effects of changing SART instructions from the double-edged "be fast and accurate" to the more conceptually accurate goal of maintaining high accuracy by responding slowly and carefully, and found that instructions to respond slowly and accurately resulted in both significantly longer RTs and fewer SART errors. In Studies 2 and 3, I developed a modified version of the SART that allowed me to experimentally manipulate RTs and found that errors were a systematic function of manipulated differences in RT independent of individual differences in response strategies. The results of these experiments indicate that it is possible that any technique that alters RT might indirectly alter error rates independently of improvements in sustained attention. I therefore conclude that investigators need to carefully attend to, control for, and report any changes in RT that accompany improvements in accuracy of performance, or alternatively employ tasks controlling for RT.

Skuldsättningsgraden ökar värdet på ett företags aktier genom skatteskölden, samtidigt som den ökar sannolikheten för finansiella problem och dess kostnader. För att uppnå en optimal kapitalstruktur måste skatteskölden balanseras mot de potentiella kostnaderna för finansiella problem. Det finns ingen matematiskt formel som förklarar hur denna optimering bör ske, det finns dock fyra viktiga faktorer som ledningen på ett företag bör ta hänsyn till när de bestämmer skuldsättningsgraden –företagets lönsamhet, storlek, tillgångsstruktur och affärsrisk. Syftet med denna studie är att testa vilka oberoende variabler som påverkar skuldsättningsgraden hos de största svenska börsnoterade företagen och genom detta kunna dra slutsatser om huruvida de tillämpar en optimal kapitalstruktur enligt Trade off teorin. Korrelation-samt den multipla regressionsanalysen visar att det inte finns något samband mellan skuldsättningsgraden och de oberoende variablerna. Vi kan därmed dra slutsatsen att företagen i populationen inte har en optimal kapitalstruktur.