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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Time in Mind: Understanding the Role of Episodic Future Thinking in Intertemporal Choice

Kinley, Isaac January 2024 (has links)
Humans and other animals systematically discount the value of future rewards as a function of their delay, and individual differences in the steepness of this ``delay discounting'' are predictive of a range of important real-world outcomes. Episodic future thinking, the mental simulation of episodes in the personal future, is one means by which to curb delay discounting. This thesis seeks to contribute to our understanding of how this effect occurs. The account that predominates in the literature is that episodic future thinking simulates the experience of future rewards, enabling their undiscounted value to be appreciated in the present. This thesis takes this account as a starting point, formalizing it in a mathematical model and carrying out several experimental studies to test its predictions. We find that key predictions are not borne out and develop an alternative account in which simulated experience plays a less central role. / Thesis / Doctor of Philosophy (PhD) / Pursuing our goals for the future usually means sacrificing immediate gratification, yet we often make decisions that are not in our best interest over the long term. This is because we assign lower subjective value to future rewards the further they are from the present. Individuals differ in how much they devalue future rewards, and these differences are related to many real-world outcomes. Our tendency to devalue future rewards is reduced when we vividly imagine the future in a process called ``episodic future thinking,'' and this thesis seeks to understand how this effect occurs. The most obvious explanation would seem to be that episodic future thinking ``simulates'' the experience of future rewards and allows us to recognize their value in the present. However, using results from several experimental studies, I argue that this may not be the best explanation after all, and I develop an alternative.
42

Slave to habit?

Horstmann, Annette, Dietrich, Anja, Mathar, David, Pössel, Maria, Villringer, Arno, Neumann, Jane 29 January 2016 (has links) (PDF)
The motivational value of food is lower during satiety compared to fasting. Dynamic changes in motivational value promote food seeking or meal cessation. In obesity this mechanism might be compromised since obese subjects ingest energy beyond homeostatic needs. Thus, lower adaptation of eating behaviour with respect to changes in motivational value might cause food overconsumption in obesity. To test this hypothesis, we implemented a selective satiation procedure to investigate the relationship between obesity and the size of the behavioural devaluation effect in humans. Lean to obese men (mean age 25.9, range 19–30 years; mean BMI 29.1, range 19.2–45.1 kg/m2) were trained on a free operant paradigm and learned to associate cues with the possibility to win different food rewards by pressing a button. After the initial training phase, one of the rewards was devalued by consumption. Response rates for and wanting of the different rewards were measured pre and post devaluation. Behavioural sensitivity to reward devaluation, measured as the magnitude of difference between pre and post responses, was regressed against BMI. Results indicate that (1) higher BMI compared to lower BMI in men led to an attenuated behavioural adjustment to reward devaluation, and (2) the decrease in motivational value was associated with the decrease in response rate between pre and post. Change in explicitly reported motivational value, however, was not affected by BMI. Thus, we conclude that high BMI in men is associated with lower behavioural adaptation with respect to changes in motivational value of food, possibly resulting in automatic overeating patterns that are hard to control in daily life.
43

Stress und modellbasiertes Entscheidungsverhalten

Radenbach, Christoph 31 May 2017 (has links) (PDF)
Moderne Theorien der Verhaltenskontrolle unterscheiden zwei Systeme, wobei das Handeln gesunder Individuen von beiden geprägt ist: Das retrospektiv agierende habituelle, sog. modellfreie Verhalten zeichnet sich durch Wiederholung zuvor belohnter Entscheidungen aus. Es passt sich nur langsam an möglicherweise veränderte Umweltbedingungen an. Die verstärkte Nutzung des habituellen Systems gilt als assoziiert mit verschiedenen psychischen Erkrankungen. Dem gegenüber steht das zielgerichtete, sog. modellbasierte Verhalten, das sich durch vorausschauende Entscheidungen auszeichnet. Hierbei werden die möglichen Konsequenzen einer Handlung berücksichtigt, um ein gewünschtes Ergebnis zu erreichen. Dazu wird ein „mentales“ Modell der Umwelt- bedingungen erstellt. In einer Verhaltensstudie mit 39 Versuchspersonen wurde untersucht, ob biopsychologischer Stress zu einer Reduktion von modellbasiertem hin zu mehr modellfreiem Verhalten führt. Dazu absolvierten 39 Versuchspersonen eine sequentielle Entscheidungsaufgabe, nachdem sie psychosozialem Stress ausgesetzt wurden. Subjektive und physiologische Stress-Parameter wurden über das Experiment hinweg wiederholt erhoben. Ein direkter Effekt von akutem Stress auf das Gleichgewicht modellfreien vs. modellbasierten Verhaltens konnte nicht beobachtet werden. Allerdings zeigten diejenigen Versuchspersonen, die in den letzten zwei Jahren eine hohe Anzahl an stressbehafteten Lebensereignissen aufwiesen (chronischer Stress), signifikant weniger modellbasiertes Verhalten nach der Exposition von akutem Stress als in der Kontrollbedingung. Darüber hinaus korrelierte physiologische Stressreaktivität (stressbedingte Cortisol- Ausschüttung) negativ mit modellbasiertem Entscheidungsverhalten, während subjektive Stressreaktivität (basierend auf Fragebögen) positiv mit modellbasiertem Verhalten assoziiert war. Der in der Forschung beschriebene Einfluss von akutem und chronischem Stress auf die Entstehung und Aufrechterhaltung psychischer Erkrankungen könnte demnach teilweise über ein solches Ungleichgewicht der beiden Entscheidungsstrategien vermittelt sein.
44

A prefrontal–temporal network underlying state changes between Stimulus-Driven and Stimulus-Independent Cognition / Un réseau temporo-frontal soutenant des états cognitifs indépendant des stimulus ou induite par les stimulus

Ossandon Valdes, Tomas 14 December 2010 (has links)
Le cerveau présente des fluctuations de son activité qui reflètent différents niveaux d’engagement avec le monde extérieur. Le traitement des stimuli externes n’est pas seulement associé avec une augmentation du métabolisme cérébrale, mais également avec une désactivation importante dans un ensemble des structures spécifiques connus sous le nom de ‘Default-Mode Network’ (DMN, réseau par défaut). Le rôle du DMN reste énigmatique en partie parce que ses corrélats électrophysiologiques et sa dynamique temporelle sont encore mal compris. En utilisant des enregistrements éléctrophysiologiques intracrânien chez le patient épileptique, nous démontrons que la population neuronale de ce réseau montre des suppressions de l’activité gamma (60-140 Hz). Plus important, nous montrons de quelle manière le profil temporale (en millisecondes) et l’amplitude de cette désactivation sont étroitement corrélés avec la difficulté de la tâche et la performance individuelle. Les résultats mettent également en évidence que pendant une tâche attentionnelle, une activation soutenue dans le temps de la bande gamma est présente dans un large réseau, alors que des activations transitoires sont spécifiques aux régions temporale et occipitale. Nos résultats révèlent ainsi un rôle essentiel des mécanismes d’activation et de désactivation des oscillations large bande gamma dans l’exécution d’un comportement orienté vers un but. / The brain displays moment-to-moment activity fluctuations that reflect various levels of engagement with the outside world. Processing external stimuli is not only associated with increased brain metabolism but also with prominent deactivation in specific structures, collectively known as the default-mode network (DMN). The role of the DMN remains enigmatic partly because its electrophysiological correlates and temporal dynamics are still poorly understood. Using unprecedented wide-spread depth recordings in epileptic patients, undergoing intracranial EEG during pre-surgical evaluation, we reveal that DMN neural populations display task-related suppressions of gamma (60-140 Hz) power and, critically, we show how millisecond temporal profile and amplitude of gamma deactivation tightly correlate with task demands and subject performance. The results show also that during an attentional task, sustained activations in the gamma band power are presented across large cortical networks, while transient activations are mostly specific to occipital and temporal regions. Our findings reveal a pivotal role for broadband gamma modulations in the interplay between activation and deactivation networks mediating efficient goal-directed behavior
45

Flexibilité du contrôle moteur dans les mouvements complexes dirigés / Motor flexibility in complex goal directed movements

Fautrelle, Lilian 04 November 2011 (has links)
L’objectif général de cette thèse est d’étudier dans les mouvements complexes, les propriétés psychophysiques de flexibilité d’un programme moteur suite à une perturbation inattendue et certaines de ses bases neurales. Pour ce faire, trois études comportementales et une étude en imagerie par résonance magnétique fonctionnelles ont été menées. (1)Les principaux résultats de notre première étude démontrent que lors de la réalisation de mouvements complexes, après un déplacement inattendu de la cible visuelle, des corrections motrices peuvent apparaître très rapidement en une centaine de millisecondes dans les muscles de la jambe et du bras. De telles latences pourraient indiquer que les corrections motrices rapides à partir des entrées visuelles pourraient être générées grâce à des boucles corticales de bas niveaux. (2) Lors d’un déplacement imprévu de la cible visuelle pendant l’exécution d’un mouvement complexe dirigé, les temps de correction sont significativement corrélés entre certaines paires de muscles, indépendamment de leur localisation anatomique ou de leur ordre d’apparition dans la séquence temporelle de recrutement musculaire. Ces résultats suggèrent que le système nerveux central est capable d’utiliser des synergies motrices fonctionnelles et complexes lors de la génération de corrections motrices. (3) Lorsque la taille de la cible est modifiée de manière imprévisible pendant l’exécution du plan moteur initial, la durée du mouvement augmente, indépendamment de la variabilité de la précision terminale du mouvement de pointage. Ce résultat suggère que les retours sensori-moteurs et une représentation en (quasi) temps réel de la vitesse de l’effecteur sont utilisés pour générer et contrôler le déplacement de la main. (4) Enfin, lors d’une tâche de rattrapés de balles répétitifs, en manipulant les conditions de prédiction a priori de la masse des balles utilisées, la dernière étude de ce travail expérimental démontre qu’un réseau cérébelleux bilatéral, impliquant les lobules IV, V et VI, est très majoritairement impliqué dans les processus de calcul de l’erreur sensori-motrice. Dans les boucles corticales classiques impliquées dans la flexibilité motrice, le cervelet est engagé dans la génération de l’erreur sensori-motrice. Néanmoins, il semblerait que d’autres boucles de plus bas niveaux puissent être également employées afin de générer des corrections motrices très rapides. La coordination entre ces différentes boucles reste à être étudiée plus précisément. / The main objective of this thesis is to study the motor flexibility in complex movements when an unexpected event makes the initial motor plan inefficient. In this way, three kinematic and electromyographic studies and a fourth with functional magnetic resonance imaging were realized. (1)The main result of the first study clearly demonstrate that during complex movements express motor corrections in the upper and lower limbs, with latency responses of less than 100 ms, were revealed by contrasting electromyographic activities in perturbed and unperturbed trials. Such findings could indicate that visual on-going movement corrections may be accomplished via fast loops at the level of the upper and lower limbs and may not require cortical involvement. (2) When an unexpected target jump occurred, correction times were strongly correlated together for some pairs of muscles independently of their occurrences during the motor sequence and independently of the location of the muscles at the anatomical level. This second study suggests that the CNS re-programs a new motor synergy after the target jumps in order to correct the on going reaching movement. (3) When the target size is varied during the initial motor plan execution, the movement duration can increase independently of the variability of the final endpoint. These results suggests that when the speed-accuracy trade-off is unexpectedly modified, terminal feedbacks based on intermediate representations of the endpoint velocity are used to monitor and control the hand displacement. (4) Finally, when catching a falling ball and the possibility of prediction about the ball weight was manipulated, the last study of this thesis showed that both the right and left cerebellum is engaged in processing sensory–motor errors, and more particularly the lobules IV, V and VI. For classical loops involved in motor flexibility, sensory-motor errors are processed within the cerebellum. However, some shorter sub-cortical loops seem also to be involved for faster motor corrections. The coordination between these different loops needs to be explained more precisely.
46

Estudo randomizado para avaliação da terapia guiada por metas em cirurgia cardíaca de alto risco / A randomized controlled trial to evaluate goal directed therapy in high-risk patients undergoing cardiac surgery

Osawa, Eduardo Atsushi 11 November 2015 (has links)
Introdução: O objetivo do estudo foi avaliar os efeitos da terapia guiada por metas (TGM) sobre desfechos em pacientes de alto risco submetidos à cirurgia cardíaca. Métodos: Estudo prospectivo randomizado que avaliou 126 pacientes submetidos às cirurgias de revascularização do miocárdio ou valvar internados na Unidade de Terapia Intensiva Cirúrgica (UTI) do Instituto do Coração da Faculdade de Medicina da Universidade de São Paulo. Os pacientes foram randomizados para um algoritmo de terapia guiada por metas (grupo TGM, n=62) ou grupo controle (n=64). No grupo TGM, um índice cardíaco superior a 3 L/min/m2 foi utilizado como alvo através de fluidos, inotrópicos e transfusão de concentrado de hemácias, com início após desmame da circulação extracorpórea e com término após 8 horas de admissão na UTI. Resultados: O desfecho primário foi um composto de mortalidade e complicações maiores em 30 dias. Os pacientes do grupo TGM receberam maior volume (mediana e intervalo interquartílico) de fluidos em relação ao grupo controle [1000 (625 - 1500) vs. 500 (500 - 1000) mL (P < 0,001)], e não houve diferença na administração de inotrópicos ou hemotransfusão. A incidência do desfecho primário foi menor no grupo TGM (27,4 vs. 45,3%, p=0,037). O grupo TGM apresentou menor incidência de infecção (12,9 vs. 29,7%, P=0,002) síndrome do baixo débito cardíaco (6,5 vs. 26,6%, P=0.002). Foram também observados menor dose acumulada de dobutamina (12 vs. 19 mg/Kg, P=0,003), menor tempo de internação na UTI (3 [3-4] vs. 5 [4-7] dias; P < 0,001) e no hospital (9 [8-16] vs. 12 [9-22] dias, P=0,049) no grupo TGM comparado ao grupo controle. Não houve diferença nas taxas de mortalidade em 30 dias. (4,8% vs. 9,4%, respectivamente; P = 0,492). Conclusão: A estratégia de terapia guiada por metas através de fluidos, inotrópicos e transfusão sanguínea reduziu a incidência de complicações maiores em 30 dias em pacientes de alto risco submetidos a cirurgia cardíaca / Introduction: The objective of the study was to evaluate the effects of goal-directed therapy on outcomes in high-risk patients undergoing cardiac surgery. Methods: A prospective randomized controlled trial that evaluated 126 patients undergoing coronary artery bypass or valve repair in a Surgical Intensive Care Unit (ICU) of the Heart Institute/Faculty of Medicine of University of Sao Paulo. Patients were randomized to a cardiac output-guided hemodynamic therapy algorithm (GDT group, n=62) or to usual care (n=64). In the GDT arm, a cardiac index of greater than 3 L/min/m2 was targeted with intravenous fluids, inotropes and red blood cell transfusion starting from cardiopulmonary bypass and ending eight hours after arrival to the ICU. Results: The primary outcome was a composite endpoint of 30-day mortality and major postoperative complications. Patients from the GDT group received a greater median (interquartile range) volume of intra-venous fluids than the usual care group [1000 (625 - 1500) vs. 500 (500 - 1000) mL (P<0.001)], with no differences in the administration of either inotropes or red blood cell transfusions. The primary outcome was reduced in the GDT group (27.4 vs. 45.3%, p=0.037). The GDT group had a lower incidence of infection (12.9 vs. 29.7%, P=0.002) and low cardiac output syndrome (6.5 vs. 26.6%, P=0.002). We also observed lower ICU cumulative dosage of dobutamine (12 vs. 19 mg/Kg, P=0.003) and a shorter ICU (3 [3-4] vs. 5 [4-7] days; P < 0.001) and hospital length of stay (9 [8-16] vs. 12 [9-22] days, P=0.049) in the GDT compared to the usual care group. There were no differences in 30-day mortality rates (4.8% vs. 9.4%, respectively; P = 0.492). Conclusions: Goal directed therapy using fluids, inotropes and blood transfusion reduced 30-day major complications in high-risk patients undergoing cardiac surgery
47

Terapia hemodinâmica guiada por saturação venosa central contínua em pacientes pediátricos submetidos à cirurgia cardíaca ensaio clínico randomizado / Hemodynamic therapy guided by continuous central venous oxygen saturation in pediatric patients undergoing cardiac surgery: a clinical randomized study

Ferreira, Flavio Mauá Chaves 21 May 2018 (has links)
Introdução: A terapia hemodinâmica perioperatória baseada em metas modificou a evolução dos pacientes pediátricos cirúrgicos de alto risco, demonstrando ser eficaz na redução de complicações. O objetivo deste estudo foi avaliar o efeito de um protocolo perioperatório guiado por metas baseado na adequação da saturação venosa central mensurada de forma contínua na perfusão tecidual e nas complicações pós-operatórias de pacientes pediátricos submetidos a cirurgia cardíaca. Métodos: Estudo prospectivo, randomizado, e controlado, realizado no Instituto do Coração do Hospital das Clínicas da Faculdade de Medicina de Universidade de São Paulo(Incor-HCFMUSP). Pacientes pediátricos submetidos a cirurgia cardíaca eletiva foram randomizados para grupo terapia hemodinâmica baseado na monitorização da saturação venosa contínua pelo cateter PediaSat (grupo intervenção) ou para grupo padrão. O grupo intervenção foi tratado no intraoperatório e nas primeiras 24 horas de pós-operatório de acordo com um protocolo guiado por metas, baseado na adequação da saturação venosa central (SvcO2 >= 65% nas cardiopatias acianóticas e >= 55% nas cardiopatias cianóticas). O desfecho primário foi a depuração do lactato nas primeiras 24 horas de pós-operatório. Os desfechos secundários foram a ocorrência de complicações pós-operatórias durante a internação hospitalar (insuficiência renal, vasoplegia, baixo débito cardíaco, arritmia, infecção, sangramento e reoperação), tempo de ventilação mecânica, tempo de uso de inotrópicos e de vasopressores e tempo de internação na unidade de terapia intensiva e no hospital e mortalidade operatória. Também foram analisados dados hemodinâmicos e variáveis de perfusão tecidual dos pacientes no período perioperatório. Resultados: No período de julho de 2014 a março de 2016, 65 pacientes foram incluídos no estudo. O número de pacientes que apresentou depuração dos níveis de lactato maior que 30% foi semelhante nos dois grupos (60% no grupo padrão e 59,4% no grupo intervenção, P=0,919). Não houve diferenças em relação a quantidade de dobutamina ou de transfusão de hemácias entre os grupos durante o protocolo. Em relação aos desfechos secundários, o grupo intervenção apresentou menor tempo de ventilação mecânica em comparação como grupo padrão (24,59 h ± 19,69 vs. 85,63 h ± 86,54, P < 0.001), menor tempo de uso de vasopressor [0 h (0-0) vs. 0 h (0-54), P = 0,021], e menor tempo de internação na unidade de terapia intensiva [6 dias (4-10) vs. 8 dias (6-21), p = 0,030 ]. Não houve diferenças entre os grupos em relação aos outros desfechos. Conclusões: Em crianças submetidas a cirurgia cardíaca, uma estratégia de terapia hemodinâmica guiada tendo como alvo a adequação da saturação venosa central de oxigênio não teve impacto na depuração dos níveis de lactato em 24 horas. Entretanto, a estratégia de terapia hemodinâmica guiada foi associada a redução do tempo de ventilação mecânica, da necessidade de vasopressores e do tempo de internação na unidade de terapia intensiva / Introduction: Perioperative hemodynamic therapy through defined goals improves outcomes in high surgical risk patients. The aim of this study was to evaluate whether the use of a perioperative hemodynamic protocol based on the optimisation of the continuous oxygen central venous saturation reduces complications in children undergoing cardiac surgery. Methods: This was a randomized clinical study, performed at the Instituto do Coração do Hospital das Clínicas da Faculdade de Medicina de Universidade de São Paulo. Pediatric patients undergoing cardiac surgery were randomized to hemodynamic therapy based on continous monitorization of central venous saturation of oxgen through the PediaSat catheter (intervention group) or to usual care group. The intervention group during the intraoperative and in the first 24 hours of postoperative were submitted to a hemodynamic protocol of care based on the optimization of central venous saturation (SvcO2 >= 65% in acyanotic disorders and >= 55% in cyanotic disorders). The primary outcome was lactate clearance in 24 hours of postoperative. Secondary outcomes were postoperative complications during hospital stay (acute kidney injury, vasoplegic shock, low cardiac output syndrome, arrhythmia, infection, bleeding and reoperation), duration of mechanical ventilation, duration of inotropes and vasopressors, length of intensive care unit and hospital stay) and death. We also evaluated hemodynamic data and perfusion tissue markers in patients during perioperative care. Results: In the period of July 2014 to March 2016, 65 patients were included in the study. The number of patients presenting lactate clearance higher than 30% in 24 hours was not different between groups (60.6% in the usual care group and 59.4% in the intervention group, P=0.919). There was no difference between groups in the use of dobutamine and in the number of transfused red blood cells units during the protocol. The intervention group had a lower duration of mechanical ventilation when compared to usual care group (24.59 h ± 19.69 s. 85.63 h ± 86.54, P < 0.001). The intervention group had also lower duration of vasopressor therapy [0 h (0-0) vs. 0 h (0-54), P = 0,021], and reduced length of intensive care unit stay [6 days (4-10) vs. 8 days (6-21), p = 0,030].There was no differences between groups in other outcomes. Conclusions: In pediatric patients undergoing cardiac surgery, a strategy of hemodynamic optimization aiming to adequate central venous saturation of oxygen had no influence in lactate clearance. However, hemodynamic therapy was associated with a lower duration of mechanical ventilation, less needing of vasopressors and shorter length of intensive care unit stay
48

Eye, hand and space representations and causal interference in bihemispheric pulvinar-parietal circuitry

Arabali, Danial 14 June 2018 (has links)
No description available.
49

Acurácia diagnóstica da variação da pressão de pulso mensurada em artéria periférica para predição de diferentes aumentos do volume sistólico em resposta ao desafio volêmico em cães

Dalmagro, Tábata Larissa. January 2019 (has links)
Orientador: Francisco José Teixeira-Neto / Resumo: Objetivo – Determinar a acurácia diagnóstica da variação da pressão de pulso (ΔPP) mensurada em artéria periférica na predição de diferentes aumentos no volume sistólico induzidos por um desafio volêmico em cães. Metodologia – Foram incluídos 39 cães, fêmeas (19,3 ± 3,6 kg) submetidas à ovariohisterectomia eletiva. A anestesia foi mantida com isoflurano sob ventilação mecânica controlada a volume (volume corrente 12 mL/kg; pausa inspiratória durante 40% do tempo inspiratório; relação inspiração:expiração 1:1,5). O débito cardíaco foi obtido através da técnica de termodiluição transpulmonar (cateter na artéria femoral) e o ΔPP foi mensurado através de um cateter posicionado na artéria podal dorsal. A fluido-responsividade (FR) foi avaliada através da administração de um (n = 21) ou dois (n = 18) desafios volêmicos com solução de Ringer Lactato (RL, 20 mL/kg durante 15 minutos), antes do procedimento cirúrgico. A análise da curva “receiver operating characteristics” (ROC) e a zona de incerteza diagnóstica (“gray zone”) do ΔPP foram empregadas para avaliar a habilidade do índice preditivo em discriminar os respondedores ao último desafio volêmico. A fluido-reponsividade foi definida por diferentes porcentagens de aumento no índice de volume sistólico (IVS) mensurado pela técnica de termodiluição transpulmonar (IVS>10%, IVS>15%, IVS>20% e IVS>25%). Resultados – O número de respondedores ao último desafio volêmico foi de 25 (IVS>10%), 21 (IVS>15%), 18 (IVS>20%) e 14 (IVS>25%). A á... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Objective – To determine the accuracy of pulse pressure variation (PPV) measured from a peripheral artery to predict different percent increases in stroke volume induced by a fluid challenge in dogs. Methods – Were included 39 adult bitches (19.3 ± 3.6 kg) undergoing ovariohysterectomy. Anesthesia was maintained with isoflurane under volumecontrolled ventilation (tidal volume 12 mL kg-1 ; inspiratory pause during 40% of inspiratory time; inspiration:expiration ratio 1:1.5). Cardiac output was obtained by transpulmonary thermodilution (femoral artery catheter) and PPV was measured from a dorsal pedal artery catheter. Fluid responsiveness (FR) was evaluated by a fluid challenge with lactated Ringer´s solution (LRS, 20 mL kg-1 over 15 minutes) administered once (n = 21) or twice (n = 18) before surgery. Receiver operating characteristics (ROC) curve analysis and the zone of diagnostic uncertainty (gray zone) of PPV cutoff thresholds were employed to evaluate the ability of PPV to discriminate responders to the last fluid challenge, defined by different percentage increases in stroke volume index (SVI) measured by transpulmonary thermodilution (SVI>10% to SVI> 25%, with 5 % increments). Results – Number of responders to the last fluid challenge were 25 (SVI>10%), 21 (SVI>15%), 18 (SVI>20%), and 14 (SVI>25%). The area under the ROC curve (AUROC) of PPV was 0.897 (SVI>10%), 0.968 (SVI>15%), 0.923 (SVI>20%), and 0.891 (SVI>25%) (p <0.0001 from AUROC = 0.5). Gray zones of PPV cutoff ... (Complete abstract click electronic access below) / Mestre
50

L'intention d'achat des produits biologiques dans un marché en voie de développement : le cas du Liban. / The intention of purchase of organic products in a developing market : the case of the Lebanon

Wolley, Farah 05 October 2015 (has links)
Notre travail de thèse s'intéresse à la consommation de produits biologiques, et plus particulièrement, à I'identification des variables déterminantes à I'intention d'achat. Si de nombreuses études se sont penchées sur ce sujet, il reste néanmoins des zones d'ombre que I'on se donne comme objectif d'éclaircir. Tout d'abord, il apparait qu'il existe des différences notables en terme de motivation d'achat des produits biologiques selon le degré de maturité du marché. Ensuite, le cadre rationnel de la théorie du comportement planifié, souvent utilisé dans les recherches précédentes, a maintes fois été critiqué. En effet, I'absence de prise en compte des émotions ainsi que du désir réduisent son pouvoir prédictif. Nous choisissons donc comme cadre théorique de notre étude le modèle d'implémentation des buts de Bagozzi et Perugini, que nous étudions dans le cadre de la consommation de produits biologiques au Liban, marché en voie de développement. Les résultats obtenus confirment une distinction de motivations d'achat entre marchés développés et marchés en voie de développement. Par ailleurs, les résultats démontrent le rôle du désir et des émotions dans la consommation de produits biologiques. D'autres variables spécifiques au contexte d'études sont identifiées et leur rôle avéré: le health Locus of Control et I'authenticité perçue des produits. / Our thesis focuses on the consumption of organic products, and more particularly, in the dentification of the variables that influence purchase intention. lf numerous studies dealt with this subject, there are nevertheless shadow zones which we give as objective to clear up. First of all, it seems that there are notable differences in term of motivation of purchase of organic products according to the degree of maturity of the market. Then, the rational frame of the theory of planned behavior, often used in previous researches, was criticized many a time. lndeed, the absence of consideration of variables such as emotions and desire reduces its predictive power. We thus choose as theoretical framework of our study the model of goal directed model (Bagozzi and Perugini, 2001, 2004) to study organic products purchase intention in Lebanon, a developing market. The obtained results confirm a distinction of motivations of purchase between developed and developing markets. Besides, the results prove the role of desire and emotions in the purchase intention of organic products. Other variables specific to our context of studies are identified and their role proven: the health Locus of Control and the perceived authenticity of organic products.

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