738 resultados para perceived location
Resumo:
This paper studies the success of the renovation of the Neonatal Intensive Care Unit at St. Louis Children's Hospital in reducing noise levels and improving the work environment.
Resumo:
Cue combination rules have often been applied to the perception of surface shape but not to judgements of object location. Here, we used immersive virtual reality to explore the relationship between different cues to distance. Participants viewed a virtual scene and judged the change in distance of an object presented in two intervals, where the scene changed in size between intervals (by a factor of between 0.25 and 4). We measured thresholds for detecting a change in object distance when there were only 'physical' (stereo and motion parallax) or 'texture-based' cues (independent of the scale of the scene) and used these to predict biases in a distance matching task. Under a range of conditions, in which the viewing distance and position of the tarte relative to other objects was varied, the ration of 'physical' to 'texture-based' thresholds was a good predictor of biases in the distance matching task. The cue combination approach, which successfully accounts for our data, relies on quite different principles from those underlying geometric reconstruction.
Resumo:
We report evidence for a major ice stream that operated over the northwestern Canadian Shield in the Keewatin Sector of the Laurentide Ice Sheet during the last deglaciation 9000-8200 (uncalibrated) yr BP. It is reconstructed at 450 km in length, 140 km in width, and had an estimated catchment area of 190000 km. Mapping from satellite imagery reveals a suite of bedforms ('flow-set') characterized by a highly convergent onset zone, abrupt lateral margins, and where flow was presumed to have been fastest, a remarkably coherent pattern of mega-scale glacial lineations with lengths approaching 13 km and elongation ratios in excess of 40:1. Spatial variations in bedform elongation within the flow-set match the expected velocity field of a terrestrial ice stream. The flow pattern does not appear to be steered by topography and its location on the hard bedrock of the Canadian Shield is surprising. A soft sedimentary basin may have influenced ice-stream activity by lubricating the bed over the downstream crystalline bedrock, but it is unlikely that it operated over a pervasively deforming till layer. The location of the ice stream challenges the view that they only arise in deep bedrock troughs or over thick deposits of 'soft' fine-grained sediments. We speculate that fast ice flow may have been triggered when a steep ice sheet surface gradient with high driving stresses contacted a proglacial lake. An increase in velocity through calving could have propagated fast ice flow upstream (in the vicinity of the Keewatin Ice Divide) through a series of thermomechanical feedback mechanisms. It exerted a considerable impact on the Laurentide Ice Sheet, forcing the demise of one of the last major ice centres.
Resumo:
During deglaciation of the North American Laurentide Ice Sheet large proglacial lakes developed in positions where proglacial drainage was impeded by the ice margin. For some of these lakes, it is known that subsequent drainage had an abrupt and widespread impact on North Atlantic Ocean circulation and climate, but less is known about the impact that the lakes exerted on ice sheet dynamics. This paper reports palaeogeographic reconstructions of the evolution of proglacial lakes during deglaciation across the northwestern Canadian Shield, covering an area in excess of 1,000,000 km(2) as the ice sheet retreated some 600 km. The interactions between proglacial lakes and ice sheet flow are explored, with a particular emphasis on whether the disposition of lakes may have influenced the location of the Dubawnt Lake ice stream. This ice stream falls outside the existing paradigm for ice streams in the Laurentide Ice Sheet because it did not operate over fined-grained till or lie in a topographic trough. Ice margin positions and a digital elevation model are utilised to predict the geometry and depth of proglacial takes impounded at the margin at 30-km increments during deglaciation. Palaeogeographic reconstructions match well with previous independent estimates of lake coverage inferred from field evidence, and results suggest that the development of a deep lake in the Thelon drainage basin may have been influential in initiating the ice stream by inducing calving, drawing down ice and triggering fast ice flow. This is the only location alongside this sector of the ice sheet where large (>3000 km(2)), deep lakes (similar to120 m) are impounded for a significant length of time and exactly matches the location of the ice stream. It is speculated that the commencement of calving at the ice sheet margin may have taken the system beyond a threshold and was sufficient to trigger rapid motion but that once initiated, calving processes and losses were insignificant to the functioning of the ice stream. It is thus concluded that proglacial lakes are likely to have been an important control on ice sheet dynamics during deglaciation of the Laurentide Ice Sheet. (C) 2004 Elsevier B.V. All rights reserved.
Resumo:
The response to painful stimulation depends not only on peripheral nociceptive input but also on the cognitive and affective context in which pain occurs. One contextual variable that affects the neural and behavioral response to nociceptive stimulation is the degree to which pain is perceived to be controllable. Previous studies indicate that perceived controllability affects pain tolerance, learning and motivation, and the ability to cope with intractable pain, suggesting that it has profound effects on neural pain processing. To date, however, no neuroimaging studies have assessed these effects. We manipulated the subjects' belief that they had control over a nociceptive stimulus, while the stimulus itself was held constant. Using functional magnetic resonance imaging, we found that pain that was perceived to be controllable resulted in attenuated activation in the three neural areas most consistently linked with pain processing: the anterior cingulate, insular, and secondary somatosensory cortices. This suggests that activation at these sites is modulated by cognitive variables, such as perceived controllability, and that pain imaging studies may therefore overestimate the degree to which these responses are stimulus driven and generalizable across cognitive contexts. [References: 28]
Resumo:
The degree to which perceived controllability alters the way a stressor is experienced varies greatly among individuals. We used functional magnetic resonance imaging to examine the neural activation associated with individual differences in the impact of perceived controllability on self-reported pain perception. Subjects with greater activation in response to uncontrollable (UC) rather than controllable (C) pain in the pregenual anterior cingulate cortex (pACC), periaqueductal gray (PAG), and posterior insula/SII reported higher levels of pain during the UC versus C conditions. Conversely, subjects with greater activation in the ventral lateral prefrontal cortex (VLPFC) in anticipation of pain in the UC versus C conditions reported less pain in response to UC versus C pain. Activation in the VLPFC was significantly correlated with the acceptance and denial subscales of the COPE inventory [Carver, C. S., Scheier, M. F., & Weintraub, J. K. Assessing coping strategies: A theoretically based approach. Journal of Personality and Social Psychology, 56, 267–283, 1989], supporting the interpretation that this anticipatory activation was associated with an attempt to cope with the emotional impact of uncontrollable pain. A regression model containing the two prefrontal clusters (VLPFC and pACC) predicted 64% of the variance in pain rating difference, with activation in the two additional regions (PAG and insula/SII) predicting almost no additional variance. In addition to supporting the conclusion that the impact of perceived controllability on pain perception varies highly between individuals, these findings suggest that these effects are primarily top-down, driven by processes in regions of the prefrontal cortex previously associated with cognitive modulation of pain and emotion regulation.
Resumo:
Previous research has shown that people's evaluations of explanations about medication and their intention to comply with the prescription are detrimentally affected by the inclusion of information about adverse side effects of the medication. The present study (Experiment 1) examined which particular aspects of information about side effects (their number, likelihood of occurrence, or severity) are likely to have the greatest effect on people's satisfaction, perception of risk, and intention to comply, as well as how the information about side effects interacts with information about the severity of the illness for which the medication was prescribed. Across all measures, it was found that manipulations of side effect severity had the greatest impact on people's judgements, followed by manipulations of side effect likelihood and then number. Experiments 2 and 3 examined how the severity of the diagnosed illness and information about negative side effects interact with two other factors suggested by Social Cognition models of health behaviour to affect people's intention to comply: namely, perceived benefit of taking the prescribed drug, and the perceived level of control over preventing or alleviating the side effects. It was found that providing people with a statement about the positive benefit of taking the medication had relatively little effect on judgements, whereas informing them about how to reduce the chances of experiencing the side effects had an overall beneficial effect on ratings.
Resumo:
In April–July 2008, intensive measurements were made of atmospheric composition and chemistry in Sabah, Malaysia, as part of the "Oxidant and particle photochemical processes above a South-East Asian tropical rainforest" (OP3) project. Fluxes and concentrations of trace gases and particles were made from and above the rainforest canopy at the Bukit Atur Global Atmosphere Watch station and at the nearby Sabahmas oil palm plantation, using both ground-based and airborne measurements. Here, the measurement and modelling strategies used, the characteristics of the sites and an overview of data obtained are described. Composition measurements show that the rainforest site was not significantly impacted by anthropogenic pollution, and this is confirmed by satellite retrievals of NO2 and HCHO. The dominant modulators of atmospheric chemistry at the rainforest site were therefore emissions of BVOCs and soil emissions of reactive nitrogen oxides. At the observed BVOC:NOx volume mixing ratio (~100 pptv/pptv), current chemical models suggest that daytime maximum OH concentrations should be ca. 105 radicals cm−3, but observed OH concentrations were an order of magnitude greater than this. We confirm, therefore, previous measurements that suggest that an unexplained source of OH must exist above tropical rainforest and we continue to interrogate the data to find explanations for this.
Resumo:
The relation between the Agulhas Current retroflection location and the magnitude of Agulhas leakage, the transport of water from the Indian to the Atlantic Ocean, is investigated in a high-resolution numerical ocean model. Sudden eastward retreats of the Agulhas Current retroflection loop are linearly related to the shedding of Agulhas rings, where larger retreats generate larger rings. Using numerical Lagrangian floats a 37 year time series of the magnitude of Agulhas leakage in the model is constructed. The time series exhibits large amounts of variability, both on weekly and annual time scales. A linear relation is found between the magnitude of Agulhas leakage and the location of the Agulhas Current retroflection, both binned to three month averages. In the relation, a more westward location of the Agulhas Current retroflection corresponds to an increased transport from the Indian Ocean to the Atlantic Ocean. When this relation is used in a linear regression and applied to almost 20 years of altimetry data, it yields a best estimate of the mean magnitude of Agulhas leakage of 13.2 Sv. The early retroflection of 2000, when Agulhas leakage was probably halved, can be identified using the regression.
Resumo:
Although consuming adequate amounts of fruits and vegetables reduces the risk of developing chronic diseases, it is widely recognized that young adults’ intakes are currently well below the Department of Health’s recommended five portions a day, with men consuming even less than women. One approach in the UK has been to introduce health campaigns such as the 5 A DAY programme; however, little is currently known about how well their messages are understood amongst young adults. This study examined current knowledge of the 5 A DAY message in young adults, as well as the perceived benefits and remaining barriers towards consuming more fruits and vegetables. In total, four focus groups were conducted using male (n = 22) and female (n = 18) students at the University of Reading. Content analysis revealed that while participants were aware of the 5 A DAY recommendation, there was widespread confusion regarding the detail. In addition, men were less accepting of the message than women, reporting greater disbelief and a lack of motivation to increase intake. Finally, a range of barriers was reported by participants of both genders, despite the perceived beneficial effects for health and appearance. The results illustrate a considerable gap between awareness and knowledge of the 5 A DAY message, and underscore the challenge that changing behaviour in young adults represents. As well as stepping up education- and skill-based health campaigns, more targeted gender specific interventions will be needed to achieve sustained increases in fruit and vegetable intake.
Resumo:
The stated benefits and perceived risks of genetic modification (GM) cover very diverse issues, such as food safety, world food security, and the environment, that may differentially affect consumer acceptance. In this research, we hypothesize that consumers perceive up to eight dimensions: risks to business (farmers, agribusiness, etc.), benefits to business, risks and benefits to the environment, risks and benefits to the developing world, and risks and benefits to self and family. Moral concerns are also recognized. Using data collected in 2002 in the United States, France, and the UK, we investigate these different dimensions. Second, we analyze the extent to which the dimensions of risk-benefit perceptions can be explained by general attitudes widely used to explain food purchase behavior (such as general attitude to the environment, to technology, etc.), as well as by perceived knowledge of GM, level of education, and trust in various sources of information. In all locations, the majority of consumers only perceive a medium level of risk from GM products. Attitude to technology is the most important attitude variable—those with a positive attitude to technology in general also have a positive attitude to GM technology. More Americans than Europeans fall into this category. Those who trust government and the food industry tend to think GM technology is less risky, whereas those who trust activists believe the opposite. Americans are more trusting of the former, Europeans of the latter. Level of education is positively associated with benefit perceptions and negatively associated with moral concerns. Location continues to play a limited independent role in explaining perceptions even after these factors have been taken into account.
Resumo:
A Bayesian approach to analysing data from family-based association studies is developed. This permits direct assessment of the range of possible values of model parameters, such as the recombination frequency and allelic associations, in the light of the data. In addition, sophisticated comparisons of different models may be handled easily, even when such models are not nested. The methodology is developed in such a way as to allow separate inferences to be made about linkage and association by including theta, the recombination fraction between the marker and disease susceptibility locus under study, explicitly in the model. The method is illustrated by application to a previously published data set. The data analysis raises some interesting issues, notably with regard to the weight of evidence necessary to convince us of linkage between a candidate locus and disease.