821 resultados para Theoretical Models


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O principal objetivo deste estudo foi testar a integração de dois modelos teóricos motivacionais (teoria da autodeterminação e a teoria dos objetivos de realização), com o intuito de analisar o impacto do clima motivacional nas necessidades psicológicas básicas e na perceção de esforço dos atletas. Participaram neste estudo 460 atletas (n = 460), da modalidade de futebol, todos do género masculino, do nível distrital e nacional, das categorias de iniciados, juvenis, juniores e seniores, com uma média de idades de 17,42 (SD=4,37) anos. A análise dos dados foi realizada através de técnicas estatísticas multivariadas, nomeadamente, a análise de equações estruturais. Os resultados encontrados suportam a adequação do modelo (S-Bχ² = 171.79; df = 100; p =0.000; S-Bχ²/df = 1.71; SRMR =0.053; TLI = 0.930; CFI = 0.942; RMSEA = 0.042; 90%IC RMSEA = 0.029-0.049), evidenciando que um clima motivacional orientado para a tarefa tem um efeito positivo significativo sobre as necessidades psicológicas básicas, por outro lado, um clima motivacional orientado para o ego tem um efeito positivo mas não significativo sobre as necessidades psicológicas básicas. Por sua vez, as necessidades psicológicas básicas apresentam um efeito positivo e significativo sobre a perceção de esforço dos atletas.

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We investigated spatial and temporal changes in quantity, quality and bioavailability of organic matter in abyssal sediments of the northeastern Atlantic. Sediment samples were collected in the Porcupine Abyssal Plain (PAP, 4800 m depth) during 6 oceanographic cruises from September 1996 to October 1998 down to a depth of 15 cm. Sedimentary proteins, carbohydrates and lipids, and their enzymatically hydrolysable fractions showed significant temporal changes, but different biochemical classes displayed different temporal patterns. Total proteins, carbohydrates and lipids displayed high concentrations, whereas the potentially hydrolysable fractions accounted for only about 10% of their total pools. From September 1996 to October 1998, bioavailable organic carbon concentration in the sediments decreased about 10 gC/m**2 indicating that this benthic system was not steady state. Hydrolysed proteins and carbohydrates were characterised by different vertical patterns. Carbohydrates increased their relative significance with depth in the sediment indicating a shift of organic matter bioavailability with important trophodynamic implications for subsurface consumers. Vertical profiles of reactive and refractory organic carbon in PAP sediments indicate that organic matter bioavailability in deeper sediment layers is higher than expected from previous theoretical models.

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During Legs 127 and 128, we found a systematic error in the index property measurements, in that the wet bulk density, grain density, and porosity did not satisfy well-established interrelationships. We have found that an almost constant difference exists between the weight of water lost during drying and the volume of water lost. This discrepancy is independent of volume or water content of the sample. The water losses should be equal because the density of water is close to 1.0 g/cm**3. The pycnometer wet volume measurement has been identified as the source of the systematic error. The wet volume on average is 0.2 cm**3 too low. For the rare cases when the water content is negligible, there is no offset. The source of the wet volume error results from the partial vapor pressure of water in the pycnometer cell. Newly corrected tables of index properties measured during Legs 127 and 128 are included. The corrected index properties are internally consistent. The data are in better agreement with theoretical models that relate the index properties to other physical properties, such as thermal conductivity and acoustic velocity. In future, a standard volume sampler should be used, or the wet volume should be calculated from the dry volume and the water loss by weight.

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Thesis (Ph.D.)--University of Washington, 2016-06

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The most commonly asked question about cooperative interactions is how they are maintained when cheating is theoretically more profitable [1]. In cleaning interactions, where cleaners remove parasites from apparently cooperating clients, the classical question asked is why cleaner fish can clean piscivorous client fish without being eaten, a problem Trivers [2] used to explain reciprocal altruism. Trivers [2] suggested that predators refrain from eating cleaners only when the repeated removal of parasites by a particular cleaner results in a greater benefit than eating the cleaner. Although several theoretical models have examined cheating behavior in clients [3,4], no empirical tests have been done (but see Darcy [5]). It has been observed that cleaners are susceptible to predation [6, 7]. Thus, cleaners should have evolved strategies to avoid conflict or being eaten. In primates, conflicts are often resolved with conflict or preconflict management behavior [8]. Here, I show that cleaner fish tactically stimulate clients while swimming in an oscillating dancing manner (tactile dancing) more when exposed to hungry piscivorous clients than satiated ones, regardless of the client's parasite load. Tactile dancing thus may function as a preconflict management strategy that enables cleaner fish to avoid conflict with potentially dangerous clients.

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Background: Understanding how environmental attributes can influence particular physical activity behaviors is a public health research priority. Walking is the most common physical activity behavior of adults; environmental innovations may be able to influence rates of participation. Method: Review of studies on relationships of objectively assessed and perceived environmental attributes with walking. Associations with environmental attributes were examined separately for exercise and recreational walking, walking to get to and from places, and total walking. Results: Eighteen Studies were identified. Aesthetic attributes, convenience of facilities for walking (sidewalks, trails); accessibility of destinations (stores, park, beach); and perceptions about traffic and busy roads were found to be associated with walking for particular purposes. Attributes associated with walking for exercise were different front those associated with walking to get to and from places. Conclusions: While few studies have examined specific environment-walking relationships, early evidence is promising. Key elements of the research agenda are developing reliable and valid measures of environmental attributes and walking behaviors, determining whether environment-behavior relationships are causal, and developing theoretical models that account for environmental influences and their interactions with other determinants. (C) 2004 American Journal of Preventive Medicine.

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This article reviews empirical research on the role of follower self-conception in leader-ship effectiveness. and specifies an agenda for future research in this area. The review shows that several aspects of follower self-conception (i.e., self-construal, self-efficacy, self-esteem, and self-consistency) may be affected by leadership. and may mediate the effects of leadership on follower behavior. There also is consistent evidence that follower self-construal moderates the impact of leadership on follower attitudes and behavior. Two key themes for future research are defined. First, future research should focus on the development of theory about the role of relational self-construal in the leadership process. Second, it seems particularly valuable to develop theory about the interplay of different aspects of follower self-conception in leadership effectiveness. including the interactive effects of these aspects of self Working backwards from these theoretical models of follower self-conception, specific leader behavior relevant to these aspects of self should then be identified. (C) 2004 Elsevier Inc. All rights reserved.

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Background: The purpose of the present study was to describe a profile of Australian paediatric occupational therapy practice in terms of theories, assessments and interventions used with the most frequently seen client groups. Methods: An ex post facto survey design was utilised. A purpose-designed survey was mailed to 600 occupational therapists identified by OT Australia as working in paediatrics. Results: The response rate was 55% (n = 330). Respondents in the sample worked chiefly with children with developmental delays, learning disabilities, neurological impairments, and infants/toddlers. Theoretical models used by paediatric clinicians that were common to the most frequently seen client groups focused on sensory integration/multisensory approaches, occupational performance, and client-centred practice. Assessment tools most frequently used were the Test of Visual Motor Integration, Sensory Profile, Bruininks-Oseretsky Test of Motor Proficiency, Handwriting Speed Test, and Motor-Free Visual Perception Test. The most often used treatment methods across the four most frequently seen client groups were parent/caregiver education, sensory integration/stimulation techniques, and managing activities of daily living. Conclusions: Paediatric occupational therapists appeared to draw on a range of theoretical models. With the exception of the Sensory Profile, the assessment and treatment methods most frequently used are not congruent with the most commonly used theoretical models. It is critical that the assessment and treatment methods used are conceptually consistent with the theoretical models that guide practice. Occupational therapists need to examine the evidence and determine whether their clinical practice is grounded in the best contemporary theoretical models, assessments and interventions.

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Considerable emphasis has been placed upon cognitive neuropsychological explanations of awareness disorders in brain injury and Alzheimer's disease (AD), with relatively few models acknowledging the role of psychosocial factors. The present paper explores clinical presentations of unawareness in brain injury and AD, reviews the evidence for the influence of psychosocial factors alongside neuropsychological changes, and considers a number of key issues that theoretical models need to address, before going on to discuss some recently-developed models that offer the potential for developing a comprehensive biopsychosocial account. Building on these developments, we present a framework designed to assist clinicians to identify the specific factors contributing to an individual's presentation of unawareness, and illustrate its application with a case example.

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Wildlife feeding is a wide-spread and controversial practice that can pose serious threats to the safety of both wildlife and visitors. The design and effectiveness of warning signs in recreational areas varies considerably and is rarely the product of theoretical models or scientific research. This study uses front-end and formative evaluation to design and test the perceived effectiveness of warning signs relating to bird feeding. Stage One examined visitors' beliefs, attitudes and bird feeding behaviour and found significant differences between feeders and non-feeders. Stage Two involved designing and evaluating three signs that built on the beliefs, knowledge and mis/conceptions identified in Stage One. Respondents thought the sign that focused on the birds' health and safety would be the most persuasive, however, elements of the other two signs were also positively evaluated. The article concludes with recommendations for the wording of future bird feeding warning signs. (c) 2004 Elsevier Ltd. All rights reserved.

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This paper discusses critical findings from a two-year EU-funded research project involving four European countries: Austria, England, Slovenia and Romania. The project had two primary aims. The first of these was to develop a systematic procedure for assessing the balance between learning outcomes acquired in education and the specific needs of the labour market. The second aim was to develop and test a set of meta-level quality indicators aimed at evaluating the linkages between education and employment. The project was distinctive in that it combined different partners from Higher Education, Vocational Training, Industry and Quality Assurance. One of the key emergent themes identified in exploratory interviews was that employers and recent business graduates in all four countries want a well-rounded education which delivers a broad foundation of key business knowledge across the various disciplines. Both groups also identified the need for personal development in critical skills and competencies. Following the exploratory study, a questionnaire was designed to address five functional business areas, as well as a cluster of 8 business competencies. Within the survey, questions relating to the meta-level quality indicators assessed the impact of these learning outcomes on the workplace, in terms of the following: 1) value, 2) relevance and 3) graduate ability. This paper provides an overview of the study findings from a sample of 900 business graduates and employers. Two theoretical models are proposed as tools for predicting satisfaction with work performance and satisfaction with business education. The implications of the study findings for education, employment and European public policy are discussed.

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Background: As Internet use grows, health interventions are increasingly being delivered online. Pioneering researchers are using the networking potential of the Internet, and several of them have evaluated these interventions. Objective: The objective was to review the reasons why health interventions have been delivered on the Internet and to reflect on the work of the pioneers in this field in order to inform future research. Methods: We conducted a qualitative systematic review of peer-reviewed evaluations of health interventions delivered to a known client/patient group using networked features of the Internet. Papers were reviewed for the reasons given for using the Internet, and these reasons were categorized. Results: We included studies evaluating 28 interventions plus 9 interventions that were evaluated in pilot studies. The interventions were aimed at a range of health conditions. Reasons for Internet delivery included low cost and resource implications due to the nature of the technology; reducing cost and increasing convenience for users; reduction of health service costs; overcoming isolation of users; the need for timely information; stigma reduction; and increased user and supplier control of the intervention. A small number of studies gave the existence of Internet interventions as the only reason for undertaking an evaluation of this mode of delivery. Conclusions: One must remain alert for the unintended effects of Internet delivery of health interventions due to the potential for reinforcing the problems that the intervention was designed to help. Internet delivery overcomes isolation of time, mobility, and geography, but it may not be a substitute for face-to-face contact. Future evaluations need to incorporate the evaluation of cost, not only to the health service but also to users and their social networks. When researchers report the outcomes of Internet-delivered health care interventions, it is important that they clearly state why they chose to use the Internet, preferably backing up their decision with theoretical models and exploratory work. Evaluation of the effectiveness of a health care intervention delivered by the Internet needs to include comparison with more traditional modes of delivery to answer the following question: What are the added benefits or disadvantages of Internet use that are particular to this mode of delivery? © Griffiths, Frances, Lindenmeyer, Antje, Powell, John, Thorogood, Margaret.

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This paper describes physics of nonlinear ultra-short laser pulse propagation affected by plasma created by the pulse itself. Major applications are also discussed. Nonlinear propagation of the femtosecond laser pulses in gaseous and solid transparent dielectric media is a fundamental physical phenomenon in a wide range of important applications such as laser lidars, laser micro-machining (ablation) and microfabrication etc. These applications require very high intensity of the laser field, typically 1013–1015 TW/cm2. Such high intensity leads to significant ionisation and creation of electron-ion or electron-hole plasma. The presence of plasma results into significant multiphoton and plasma absorption and plasma defocusing. Consequently, the propagation effects appear extremely complex and result from competitive counteraction of the above listed effects and Kerr effect, diffraction and dispersion. The theoretical models used for consistent description of laser-plasma interaction during femtosecond laser pulse propagation are derived and discussed. It turns out that the strongly nonlinear effects such self-focusing followed by the pulse splitting are essential. These phenomena feature extremely complex dynamics of both the electromagnetic field and plasma density with different spatio-temporal structures evolving at the same time. Some numerical approaches capable to handle all these complications are also discussed. ©2006 American Institute of Physics

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It is known that distillation tray efficiency depends on the liquid flow pattern, particularly for large diameter trays. Scale·up failures due to liquid channelling have occurred, and it is known that fitting flow control devices to trays sometirr.es improves tray efficiency. Several theoretical models which explain these observations have been published. Further progress in understanding is at present blocked by lack of experimental measurements of the pattern of liquid concentration over the tray. Flow pattern effects are expected to be significant only on commercial size trays of a large diameter and the lack of data is a result of the costs, risks and difficulty of making these measurements on full scale production columns. This work presents a new experiment which simulates distillation by water cooling. and provides a means of testing commercial size trays in the laboratory. Hot water is fed on to the tray and cooled by air forced through the perforations. The analogy between heat and mass transfer shows that the water temperature at any point is analogous to liquid concentration and the enthalpy of the air is analogous to vapour concentration. The effect of the liquid flow pattern on mass transfer is revealed by the temperature field on the tray. The experiment was implemented and evaluated in a column of 1.2 m. dia. The water temperatures were measured by thennocouples interfaced to an electronic computerised data logging system. The "best surface" through the experimental temperature measurements was obtained by the mathematical technique of B. splines, and presented in tenos of lines of constant temperature. The results revealed that in general liquid channelling is more imponant in the bubbly "mixed" regime than in the spray regime. However, it was observed that severe channelling also occurred for intense spray at incipient flood conditions. This is an unexpected result. A computer program was written to calculate point efficiency as well as tray efficiency, and the results were compared with distillation efficiencies for similar loadings. The theoretical model of Porter and Lockett for predicting distillation was modified to predict water cooling and the theoretical predictions were shown to be similar to the experimental temperature profiles. A comparison of the repeatability of the experiments with an errors analysis revealed that accurate tray efficiency measurements require temperature measurements to better than ± 0.1 °c which is achievable with conventional techniques. This was not achieved in this work, and resulted in considerable scatter in the efficiency results. Nevertheless it is concluded that the new experiment is a valuable tool for investigating the effect of the liquid flow pattern on tray mass transfer.

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It is important to maintain a uniform distribution of gas and liquid in large diameter packed columns to maintain mass transfer efficiency on scaling up. This work presents measurements and methods of evaluating maldistributed gas flow in packed columns. Little or no previous work has been done in this field. A gas maldistribution number, F, was defined, based on point to point velocity variations in the gas emerging from the top of packed beds. f has a minimum value for a uniformly distributed flow and much larger values for maldistributed flows. A method of testing the quality of vapour distributors is proposed, based on "the variation of f with packed height. A good gas distributor requires a short packed depth to give a good gas distribution. Measurements of gas maldistribution have shown that the principle of dynamic similarity is satisfied if two geometrically similar beds are operated at the same Reynold's number. The validity of f as a good measure of gas maldistribution, and the principle of dynamic similarity are tested statistically by Multi-Factor Analysis of the variance, and visually by the response "surfaces technique. Pressure distribution has been measured in a model of a large diameter packed bed, and shown to be associated with the velocity of the gas in a tangential feed pipe. Two simplified theoretical models are proposed to describe the flow of gases through packed beds and to support the principle of dynamic similarity. These models explain why the packed bed itself causes the flow of gas to become more uniformly distributed. A 1.2m. diameter scaled-down model was constructed geometrically similar to a 7.3m. diameter vacuum crude distillation column. The previously known internal cylinder gas distributor was tested. Three new distributors suitable for use in a large diameter column were developed and tested, these are: Internal Cylinder with Slots and Cross Baffles, Internal Cylinder with Guides in the Annulus, Internal Cylinder with Internal Cross Baffles - It has been shown that this is an excellent distributor.