• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 135
  • 97
  • 6
  • 4
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 387
  • 387
  • 219
  • 144
  • 93
  • 60
  • 57
  • 52
  • 45
  • 42
  • 37
  • 35
  • 34
  • 33
  • 32
  • 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.
281

Comparação de rols classificatórios de tratamentos e de estimativas de componentes de variância em grupos de experimentos / Comparison of treatments classicatory rankings and of variance components estimates in experimental groups

Dessotti, Cássio 28 January 2010 (has links)
As análises de grupos de experimentos, de grande importância em melhoramento genético, são indispensáveis quando se pretende investigar o comportamento de alguns tratamentos em diversos locais de interesse do pesquisador. Nestes casos, parte-se das analises de variância individuais em cada local, para o agrupamento de todos os ensaios em uma única analise. Verifica-se então a veracidade da significância da interação tratamentos versus locais - TL, sendo esta não-significativa, pode-se obter conclusões generalizados a respeito do comportamento dos tratamentos. No entanto, o grande interesse esta nos casos de interação significativa, em que dois caminhos de destaque surgem para que se conclua a analise, o primeiro, permite que se considerem os resultados e conclusões das analises individuais, com o resíduo específico de cada local, enquanto o segundo aconselha que se desdobrem os graus de liberdade relativos a tratamentos + interação significativa, visando a interpretação dos tratamentos em estudo dentro de cada um dos locais, utilizando o resíduo médio como testador. Partindo do fato de que componentes de variância são variâncias associadas aos efeitos aleatórios de um modelo matemático, que permitem quantificar a variabilidade de tais efeitos, tem-se por objetivo neste trabalho, em grupos de experimentos reais com interação TL significativa, comparar os componentes de variância obtidos nas analises individuais utilizando os quadrados médios residuais - QMRes de cada ensaio versus os obtidos pós-desdobramento da interação em questão utilizando o quadrado médio do resíduo médio - QMRM. Tal confronto será fundamentado nas estimativas de variâncias das estimativas destes componentes. Finalmente, em grupos de ensaios reais e simulados, o objetivo será voltado para a comparação de rols classificatórios de tratamentos nas analises individuais versus os rols classificatórios de tratamentos obtidos pós-desdobramento da interação em questão. A montagem destes rols será possível a partir do uso do teste de Tukey, ao nível de 5% de significância, para os cálculos das diferenças mínimas significativas - dms ora com resíduos de analises individuais, ora de conjunta. Todos os cálculos deste trabalho serão realizados no software estatístico R. / The experimental groups analysis, of great importance in genetic improvement, are essential when intends to investigate the treatments behaviour in many places from researcher interest. In these cases, starts by the individual variance analysis in each place, to the grouping of all experiments in a single analysis. Examine the truth of the signicant treatments vs. places interaction - TL, being this no-signicant, is possible to obtain generalized conclusions about the treatments behaviour. However, the interest is in the cases when signi cant interaction is found, because two eminence ways appear for the analysis conclusions, the rst one allow that the individual analysis results and conclusions be considered, with the specic residue from each place, while the second one advise, that the degrees of freedom relative to treatments + signicant interaction be unfound, looking at the interpretation of the treatments in study inside each place, using the mean residue how testator. Starting with the fact that variance components are variances associated to the aleatory eects of a mathematical model, that allow the quantifying of such eects, this work objective, in real experimental groups, with signicant interaction TL, is to compare the variance components obtained in individual analysis using the residual mean square - QMRes from each experiment against the obtained after unfolding the interaction in question using the mean residual mean square - QMRM. This confrontation will be based in variance estimations of these components estimations. Finally, in real and simulate experimental groups, the objective will be directed to the comparison of treatments classicatory rankings in individual analysis vs. the treatments classi catory rankings obtained after unfolding of the interaction in question. The construction of these rankings will be possible using the Tukey test, with 5% of signicance, for the calculation of the signicants minimum dierences - dms, a time with individual analysis residual, othertime, conjunct. All the calculations from this work will be realized in the R statistical software.
282

The Relative Efficiencey of the Wechsler Adult Intelligence Scale (WAIS) as a Predictor of College Academic Achievement

Dennis, Ollie 01 April 1978 (has links)
This study examined the predictive validity of the WAIS in an academic setting. Traditional WAIS IQ scores and subtests of 127 male and 163 female college students were correlated with Grade Point Averages at the end of four semesters and within five academic areas. Five groups were examined including the total group, male group, female group, black group, and white group. The academic University's general and Communication of areas investigated corresponded to the education requirements; Organization Ideas, Humanities, Social and Behavioral Studies, Natural Science and Mathematics, and Physical Development. Results indicated that dictor of both semester GPA and five groups. Full Scale IQ was Verbal IQ was the best preacademic area GPA for the the second best overall indicator. Verbal IQ for blacks was a better predictor of success in college than it was for whites. Verbal abilities appeared more important for blacks than whites in terms of how well they did in school. WAIS IQ tended to best predict first semester GPA and the areas of Social and Behavioral Studies, Organization and Communication of Ideas, Natural Sciences and Mathematics, Humanities and Physical Development, in that order. WAIS Verbal subtests were more efficient predictors than were the Performance subtests. The Digit Span and Arithmetic subtests of the Verbal scale and all five of the Performance subtests appeared to be of negligible value in predicting academic achievement. The highest correlations were found in the Vocabulary subtest, then Similarities and Information, and finally Comprehension. The female group had consistently higher correlation coefficients in every Performance subtest across all semesters and in each of the five academic areas.
283

Circadian Variations and Risky Decision Making

Sra, Sana 01 January 2019 (has links)
Over the past decades, decision making under risk has garnered a great amount of attention both in the field of economics and psychology. Although state-dependent variabilities of risk taking are well-documented, little is known about the effects of a person’s preferred time of day, or chronotype, in risky decision making. Under circumstances of circadian mismatch (e.g., when an “early bird” makes decisions in the evening), research suggests that decision making may reflect a greater reliance on heuristics, such as using stereotypes in social judgments. However, the effects of circadian mismatch on heuristics in risky decision making are relatively unexplored. This paper looks into the effects of circadian mismatch on the reflection effect: a behavioral bias in financial decision making, wherein individuals are risk averse when facing potential gains, and risk seeking when facing potential losses. Participants will be randomly assigned to their circadian matched or circadian mismatched conditions and will play a series of financial gambling tasks with real monetary incentives. This study predicts that the reflection effect will be exacerbated in circadian mismatched individuals as compared to matched participants. Exploring such an effect could have real-world implications on decision making under risk by providing critical knowledge about the effects of time of day on our susceptibility to behavioral biases. It could therefore point to the existence of a more optimal time of day to engage in such critical decision making.
284

NEUROBEHAVIORAL MEASUREMENTS OF NATURAL AND OPIOID REWARD VALUE

Smith, Aaron Paul 01 January 2019 (has links)
In the last decade, (non)prescription opioid abuse, opioid use disorder (OUD) diagnoses, and opioid-related overdoses have risen and represent a significant public health concern. One method of understanding OUD is as a disorder of choice that requires choosing opioid rewards at the expense of other nondrug rewards. The characterization of OUD as a disorder of choice is important as it implicates decision- making processes as therapeutic targets, such as the valuation of opioid rewards. However, reward-value measurement and interpretation are traditionally different in substance abuse research compared to related fields such as economics, animal behavior, and neuroeconomics and may be less effective for understanding how opioid rewards are valued. The present research therefore used choice procedures in line with behavioral/neuroeconomic studies to determine if drug-associated decision making could be predicted from economic choice theories. In Experiment 1, rats completed an isomorphic food-food probabilistic choice task with dynamic, unpredictable changes in reward probability that required constant updating of reward values. After initial training, the reward magnitude of one choice subsequently increased from one to two to three pellets. Additionally, rats were split between the Signaled and Unsignaled groups to understand how cues modulate reward value. After each choice, the Unsignaled group received distinct choice-dependent cues that were uninformative of the choice outcome. The Signaled group also received uninformative cues on one option, but the alternative choice produced reward-predictive cues that informed the trial outcome as a win or loss. Choice data were analyzed at a molar level using matching equations and molecular level using reinforcement learning (RL) models to determine how probability, reward magnitude, and reward-associated cues affected choice. Experiment 2 used an allomorphic drug versus food procedure where the food reward for one option was replaced by a self-administered remifentanil (REMI) infusion at doses of 1, 3 and 10 μg/kg. Finally, Experiment 3 assessed the potential for both REMI and food reward value to be commonly scaled within the brain by examining changes in nucleus accumbens (NAc) Oxygen (O2) dynamics. Results showed that increasing reward probability, magnitude, and the presence of reward-associated cues all independently increased the propensity of choosing the associated choice alternative, including REMI drug choices. Additionally, both molar matching and molecular RL models successfully parameterized rats’ decision dynamics. O2 dynamics were generally commensurate with the idea of a common value signal for REMI and food with changes in O2 signaling scaling with the reward magnitude of REMI rewards. Finally, RL model-derived reward prediction errors significantly correlated with peak O2 activity for reward delivery, suggesting a possible neurological mechanism of value updating. Results are discussed in terms of their implications for current conceptualizations of substance use disorders including a potential need to change the discourse surrounding how substance use disorders are modeled experimentally. Overall, the present research provides evidence that a choice model of substance use disorders may be a viable alternative to the disease model and could facilitate future treatment options centered around economic principles.
285

MEASURING GLUTAMATE AND OXYGEN IN BRAIN REWARD CIRCUITS IN ANIMAL MODELS OF COCAINE ABUSE AND DECISION-MAKING

Batten, Seth Richard 01 January 2019 (has links)
Drug-specific reward and associated effects on neural signaling are often studied between subjects, where one group self-administers drug and a separate group self-administers a natural reinforcer. However, exposure to drugs of abuse can cause long-term neural adaptations that can affect how an organism responds to drug reward, natural reward, and their reward-associated stimuli. Thus, to isolate drug-specific effects it is important to use models that expose the same organism to all of the aforementioned. Multiple schedules provide a means of dissociating the rewarding effects of a drug from the rewarding effects of food within a single animal. Further, drug users do not take drugs in isolation; rather, they are often faced with several concurrently available commodities (e.g. monetary goods, social relationships). Thus, using choice measures to assess the relative subjective value of drug reinforcers in both humans and animals promotes a translational understanding of mechanisms that govern drug-associated decision-making. Thus, in order to gain a more translational view of the neurobehavioral mechanisms that underlie drug-associated behavior, in the first study, glutamate was measured in the nucleus accumbens core (NAcC) and prefrontal cortex (PrL) in freely-moving rats as they behaved in a cocaine-food multiple schedule procedure. In the second study, oxygen dynamics were measured in the orbitofrontal cortex (OFC) of freely-moving rats as they behaved in a cocaine/food choice procedure. The results from the first study showed that, in the NAc and PrL, there was an increase in glutamate release when animals earned cocaine. Further, the number of glutamate peaks that occurred per cocaine lever press and per cocaine reinforcer was increased compared to food. In the second study, OFC oxygen dynamics were positively correlated with cocaine/food choice and generally tracked preference. Further, OFC oxygen dynamics were greater to cocaine related events. Taken together, these results showed the feasibility of combining electrochemical measurements with complex drug-related behavioral procedures. These results also highlight the importance of the PrL, NAcC, and OFC in the valuation of drug and non-drug commodities. Overall, these results add to our understanding of the neurobehavioral mechanisms that guide drug-associated behavior and create more precise experimental avenues to research potential treatments.
286

IS PECKING AVERSIVE TO A PIGEON OR IS IT ONLY THE DELAY TO REINFORCEMENT?

Andrews, Danielle M. 01 January 2018 (has links)
The principle of least effort suggests that animals should minimize effort to reinforcement. Thus, not pecking should be preferred over pecking. However, pigeons often peck when it is allowed but not required (e.g., fixed time schedules) but pecking may be adventitiously reinforced. In the present experiment, to better compare a schedule of reinforcement that requires pecking with one that requires the absence of pecking, we compared a fixed-interval (FI) schedule in which reinforcement follows the first peck after the interval has elapsed and a differential-reinforcement-of-other behavior (DRO) schedule which requires pigeons abstain from pecking for a similar interval. The delay to reinforcement was matched on a trial-by-trial basis by extending the duration of the FI to match the DRO schedule that preceded it. Of 12 pigeons, 6 preferred the DRO schedule over the FI schedule and 6 did not show a schedule preference. Those that were indifferent between the schedules had acquired the contingences, as they responded appropriately to the two schedules but had a spatial preference stronger than their schedule preference. Individual differences in the preference of the pigeons may be related to their behavior during the DRO.
287

TARGETING FOOD SELECTIVITY IN YOUNG CHILDREN IN A PRESCHOOL CLASSROOM USING A MULTI-COMPONENT TREATMENT PACKAGE

Hesley, Christina Challed 01 January 2019 (has links)
The purpose of the study was to evaluate the effectiveness of using a video model, graduated exposure (i.e., touch, smell, try, eat), and positive reinforcement to first increase food exploration, and then increase consumption of non-preferred foods in young children that exhibit food selectivity in a school setting. A multiple probe design across behaviors replicated across participants was used to evaluate the effectiveness of a treatment package. The treatment package consisted of a video model of each target behavior (touch, smell, try, eat) and positive reinforcement which included preferred foods and materials. The results indicated that the treatment package was effective in increasing the food exploration and consumption of non-preferred foods for one participant, and was inconclusive for the second participant.
288

Pupil Attitudes Toward School, Peers, and Teachers Under Ability-Grouped and Random-Grouped Systems in Weber and Ogden School Districts

Christensen, Val R. 01 May 1964 (has links)
Attitudes are usually defined as feelings for or against something (Remmers and Gage, 1955). They are very important in the lives of people because they help determine future success in an individual's life. Because of them one works to get the things he wants, one votes for or against certain issues, one joins a cause, opposes something, or attempts to influence others.
289

Análisis experimental en modelo reducido de la consolidación radial y deformación de un suelo blando mejorado con columnas de grava

Cimentada Hernández, Ana Isabel 10 June 2009 (has links)
El estudio del proceso de consolidación radial alrededor de las columna de grava y de la interacción suelo-columna suele realizarse analizando una celda unitaria formada por una columna de grava central y el área de terreno circundante, sobre la cual ejerce su acción de mejora. En esta tesis doctoral se ha modelizado a escala reducida una celda unidad para analizar la transferencia de carga entre la columna y el terreno y el proceso de consolidación que se produce alrededor de la columna, para condiciones de carga vertical rígida.Se han realizado ensayos con columnas de dos diámetros distintos, con el fin de estudiar también la influencia del área de suelo blando reemplazada por la columna. Se presentan los resultados obtenidos en cada ensayo, su interpretación, y la comparación con soluciones teóricas existentes. Todo ello tanto para el análisis de la consolidación radial como para el comportamiento deformacional del conjunto suelo-columna. / The analysis of the radial consolidation process around the column and the column-soil interaction is based on the study of a unit cell approach, which consists of a central column of gravel and the surrounding soil. In this thesis, a unit cell in small scale has been reproduced with the aim of analyzing load transfer between soil and column, settlement reduction and radial consolidation process that happen when a rigid vertical load is applied on surface.Tests with two different geometries are carried out.From the results, some conclusions related to consolidation process, stress concentration factor and settlement reduction have been obtained for each testing geometry.The influence of the replacement area has been studied comparing the results of both geometries.Finally, the results are presented and interpreted using some existing analytical solutions related to consolidation process and stone columns deformation.
290

Reducing Subjectivity: Meditation and Implicit Bias

Ciuca, Diana M 01 January 2015 (has links)
Implicit association of racial stereotypes is brought about by social conditioning (Greenwald & Krieger, 2006). This conditioning can be explained by attractor networks (Sharp, 2011). Reducing implicit bias through meditation can show the effectiveness of reducing the rigidity of attractor networks, thereby reducing subjectivity. Mindfulness meditation has shown to reduce bias from the use of one single guided session conducted before performing an Implicit Association Test (Lueke & Gibson, 2015). Attachment to socially conditioned racial bias should become less prevalent through practicing meditation over time. An experimental model is proposed to test this claim along with a reconceptualization of consciousness based in meditative practice.

Page generated in 0.1136 seconds