During a finite developmental phase – the brain growth spurt – the brain grows and matures at an accelerated rate. During this period the brain is more sensitive to harmful substances such as ethanol and environmental toxins than before or after. This period extends from the last trimester to the second year in humans and occurs postnatally in the mice used for these studies. The aims of this thesis were; to investigate common anaesthetics ability to promote acute apoptosis and late persistant behavioural aberrations measured with spontaneous behaviour in a novel home environment, learning in a radial arm maze and anxiety-like behaviour in an elevated plus maze, to measure alterations in BDNF, CaMKII, GAP-43, synaptophysin and tau after anaesthesia exposure, to evaluate clonidine as a potentially protecting agent and examine if theophylline, a chemically unrelated compound, causes similar effects as anaesthetics. Some of the results are: combinations of anaesthetics acting on the GABAA receptor (propofol or pentothal) and NMDA receptor (ketamine) exhibit more apoptosis and behavioural alterations than single anaesthetics. Ketamine, but not propofol, alters the content of CaMKII and GAP-43 proteins important in brain development. Propofol exposure alters the content of BDNF (brain derived neurotrophic factor) in hippocampus, frontal and parietal cortex. Neonatal propofol exposure leads to less sensitiveness to diazepam in adult age as measured with induced spontaneous behaviour and an elevated plus maze. Clonidine, an alpha2 adrenergic agonist does not cause any aberrations and appears to prevent apoptosis and behavioural alterations after ketamine. Theophylline, used as apnoea treatment in neonates, also increases apoptosis and alters normal behaviour. Thus, alterations both in neuronal survival, function and protein expression is apparent after neonatal exposure to anaesthetics. This is also shown in studies of Rhesus monkeys. However, it is still difficult to assess how these findings should extrapolate to humans. Epidemiological studies give conflicting results. Insufficient anaesthesia is not a solution as pain and stress cause even more pronounced problems. Minimizing anaesthetic exposure, delaying procedures until after the sensitive phase and finding protective agents, such as clonidine, are possible strategies. Evaluation of other substances that infants are exposed to is needed.

Maternal and fetal stressors during development can permanently alter various physiological functions and impact long-term health. These alterations are said to be programmed because they persist long after the original insult. Current evidence indicates that iron deficiency (ID) during pregnancy can induce a host of long-term programming effects, including cardiovascular complications and behavioural deficits. Despite the relevance of ID as a model of developmental programming, these effects have not been extensively studied. The purpose of the present series of experiments was to develop a model of maternal ID throughout pregnancy to study its long-term cardiovascular and behavioural consequences in neonatal and adult offspring. Female rats were fed either a low iron diet (3 mg/kg or 10 mg/kg Fe) or a control diet (> 225 mg/kg Fe) prior to and throughout gestation. At birth, all dams were fed a control diet (270 mg/kg Fe). This treatment caused altered growth trajectories which persisted in adulthood. Adult perinatal ID (PID) offspring, despite showing no signs of anemia at that time, had persistent elevations in arterial pressure (AP), as well as enhanced responsiveness of AP to high and low sodium intake. These animals also had altered responsiveness of renal medullary blood flow to changes in AP. PID offspring also had altered function of intrarenal and vascular nitric oxide signaling. Similar studies performed in acute ID animals revealed opposite trends in intrarenal and vascular NOS function, as well as in effects on the cardiovascular system. In addition to the cardiovascular effects, adult PID male offspring exhibited a number of behavioural changes, as assessed by monitoring locomotor activity in their home cages (by radiotelemetry) as well as in a novel environment. PID male offspring also performed poorly in a Morris water maze compared to controls. These differences were not observed in female PID animals. In summary, these studies provide evidence that ID during gestation has deleterious effects on various aspects of the offspring’s physiology. Given the global incidence of ID, as well as its propensity to afflict pregnant women, developmental programming from this condition could have profound implications on global health. / Thesis (Ph.D, Pharmacology & Toxicology) -- Queen's University, 2009-01-22 23:32:40.931

In the theoretical part the thesis focus on consumer behavior and marketing research. Describes three models of buyer behaviour, main factors influencing the behaviour and the purchase decision-making proces. The second part of the thesis presents results of the primary marketing research.

The thesis is focused on retail marketing and its main goal is to analyse consumer's attitudes to the various retailing formats. First part is dedicated to some theoretical terms of retailing, stores typology, consumer behaviour, segmentation and specifics of retail marketing. Next part analyses available information from public researches, articles and MML database to reveal present situation and trends on retail market. In the last part is executed own primary research with aim to discover consumer behaviour and attitudes to the retailing formats and its perception.

The comprehension of the viscoelastic behaviour of metals is of high interest as these materials are subjected to dynamic loads in most of their structural applications, and also because it enables a deeper understanding of several technologically essential properties, like mechanical damping and yielding. Thus, research on this field is needed not only because it may lead to new potential applications of metals, but also because predictability of the fatigue response may be greatly enhanced. Indeed, fatigue is the consequence of microstructural effects induced in a material under dynamic loading, while the viscoelastic behaviour is also intimately linked to the microstructure. Accordingly, the characterization of the viscoelastic response of a material offers an alternative method for analysing its microstructure and ultimately its fatigue behaviour. This research is aimed at the identification, characterization and modelling of the effects of temperature, excitation frequency and microstructure/phase transformations (when present) on the viscoelastic behaviour of aluminium alloys AA 7075-T6 and AA 2024-T3, and of pure aluminium in the H24 temper. The identification of the mechanical relaxation processes taking place and the relation between the viscoelastic response of AA 7075-T6 and AA 2024-T3 and the fatigue behaviour will be attempted for all these materials. Finally, we intend to investigate possible influences of the dynamic loading frequency on fatigue, and especially the existence of a threshold frequency marking the transition from a static-like response of the material to the advent of fatigue problems. AA 7075-T6 and AA 2024-T3 were selected for this study because these alloys are key representatives of their important families and are highly suitable to a number of industrial applications in the aerospace sector and transport industry. Pure aluminium was selected because of the inherent interest of this metal, for comparison purposes and for discussing the phenomena observed for the alloys. To accomplish the objectives, the viscoelastic response of the materials was measured experimentally with a Dynamic- Mechanical Analyser (DMA). The results were combined with Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC). An analytical model was proposed which fits the storage modulus up to 300 ºC. The model takes into account the effect of temperature, the excitation frequency and the concentration of some precipitates for the alloys. This allows us to test models proposed for the reaction rates of the associated microstructural transformations, to determine their kinetic parameters and to characterize their influence on the viscoelastic behaviour, showing that the DMA is a good tool for studying the material microstructure, phase transformation kinetics and the influence of transformations on the viscoelastic properties of materials. The Time-Temperature Superposition (TTS) principle has been successfully applied to the DMA data, providing master curves for the storage and loss moduli. Also, it is proposed that the decrease of yield and fatigue strength with temperature observed in some aluminium alloys may be due to the internal friction increase with temperature. Finally, the existence of a threshold frequency is suggested, below which materials subjected to dynamic loading exhibit a static-like, elastic response, such that creep mechanisms dominate and deterioration due to fatigue may be neglected. A procedure to estimate this transition frequency is proposed. / La comprensión del comportamiento visco-elástico de los metales es de gran interés ya que estos están sometidos a cargas dinámicas en la mayoría de sus aplicaciones estructurales, y también porque posibilita un conocimiento más profundo de varias propiedades esenciales tecnológicamente, como el amortiguamiento mecánico y el límite elástico. Así, la investigación en este campo es necesaria no sólo porque puede conducir hacia nuevas aplicaciones potenciales de los metales, sino también porque la capacidad de predecir el comportamiento en fatiga de los mismos puede verse ampliamente mejorada. De hecho, la fatiga de los metales es consecuencia de efectos microestructurales inducidos en el material bajo cargas dinámicas, y el comportamiento visco-elástico está también íntimamente relacionado con la microestructura. Así, la caracterización de la respuesta visco-elástica de un material ofrece un método alternativo para analizar su microestructura y, en último término, su respuesta en fatiga. Este trabajo tiene por objetivos la identificación, caracterización y modelización de los efectos de la temperatura, la frecuencia de excitación y la microestructura/transformaciones de fase en el comportamiento visco-elástico de las aleaciones de aluminio AA 7075-T6 y AA 2024-T3, y de aluminio puro en estado H24. Se aborda también la identificación de los procesos de relajación mecánicos que tienen lugar en estos materiales y la identificación de la relación entre el comportamiento visco-elástico de AA 7075-T6 y 2024-T3 y su respuesta en fatiga. Finalmente, se intentará investigar posibles influencias de la frecuencia de la carga dinámica en la fatiga, y en especial la existencia de una frecuencia umbral que marque la transición desde una respuesta cuasi-estática del material hacia la aparición de problemas de fatiga. AA 7075-T6 y AA 2024-T3 fueron seleccionadas porque son representantes clave de sus importantes familias de aleaciones, y son altamente adecuadas para un gran número de aplicaciones en los sectores aeroespacial y del transporte. El aluminio puro fue seleccionado para este estudio por su interés inherente, y para realizar comparaciones y discutir algunos de los fenómenos observados en las aleaciones. Para cumplir los objetivos, el comportamiento visco-elástico de los materiales fue medido experimentalmente con un Dynamic-Mechanical Analyser (DMA). Los resultados se combinaron con microscopía electrónica y calorimetría. Se propuso un modelo analítico que ajusta la componente real del módulo elástico dinámico (el storage modulus) hasta 300 ºC. El modelo toma en consideración los efectos de la temperatura, la frecuencia de la carga dinámica y la concentración de ciertos precipitados para el caso de las aleaciones. Esto permitió testear modelos propuestos para las velocidades de reacción de las transformaciones microestructurales asociadas, determinar sus parámetros cinéticos y caracterizar su influencia en el comportamiento visco-elástico, demostrando que el DMA es una buena herramienta para estudiar la microestructura del material, la cinética de las transformaciones de fase y la influencia de las transformaciones en las propiedades visco-elásticas de los materiales. El principio de superposición de tiempo y temperatura ha sido aplicado con éxito, proporcionando curvas maestras para las componentes del módulo elástico dinámico. Asimismo, se sugiere que el descenso en el límite elástico y la resistencia a fatiga con la temperatura observado en algunas aleaciones de aluminio puede ser debido al incremento de la fricción interna con la temperatura. Finalmente, se propone la existencia de una frecuencia umbral, por debajo de la cual los materiales sometidos a cargas dinámicas exhiben una respuesta cuasi-estática y elástica, de tal modo que mecanismos de termofluencia son dominantes y el deterioro del material debido a fatiga puede ser despreciado. Se propone un procedimiento para estimar esta frecuencia de transición.

Physikalische und chemische Charakterisierung von Lithiumionenzellen

Physikalische und chemische Charakterisierung von Lithiumionenzellen