33,320 research outputs found
Gezichtsbedrog onthult hersenwerking in drie-dimensionale waarneming
Gezichtsbedrog biedt een venster op de werking van de hersenen omdat het onderliggende
waarnemings-mechanismen kan onthullen op een manier die niet mogelijk is tijdens
waarheidsgetrouwe waarneming. Hier wordt getoond hoe een klassiek voorbeeld van
gezichtsbedrog inspiratie geeft voor de ontwikkeling van een hersenmodel voor drie-
dimensionale waarneming. Zulke modellen kunnen tal van praktische toepassingen vinden in de
geneeskunde, luchtvaart en robotiek
Perceptual learning without feedback and the stability of stereoscopic slant estimation
Subjects were examined for practice effects in a stereoscopic slant estimation task
involving surfaces that comprised a large portion of the visual field. In most subjects slant
estimation was significantly affected by practice, but only when an isolated surface (an
absolute disparity gradient) was present in the visual field. When a second, unslanted,
surface was visible (providing a second disparity gradient and thereby also a relative
disparity gradient) none of the subjects exhibited practice effects. Apparently,
stereoscopic slant estimation is more robust or stable over time in the presence of a second
surface than in its absence. In order to relate the practice effects, which occurred without
feedback, to perceptual learning, results are interpreted within a cue interaction
framework. In this paradigm the contribution of a cue depends on its reliability. It is
suggested that normally absolute disparity gradients contribute relatively little to
perceived slant and that subjects learn to increase this contribution by utilizing
proprioceptive information. It is argued that---given the limited computational power of
the brain---a relatively small contribution of absolute disparity gradients in perceived
slant enhances the stability of stereoscopic slant perception
INVESTMENT ANALYSIS OF ALTERNATIVE FRUIT TREE SPRAYERS IN MICHIGAN ORCHARDS
Changing orchard sprayer technology and rising pesticide costs to fruit growers raise the need to analyze the profitability of alternative sprayer investments. This study analyzes investments in four orchard sprayers for use in Michigan apple production: an air blast sprayer, a tower boom sprayer, a tower boom sprayer equipped with electronic sensors that activate spray nozzles when foliage is detected, and an air curtain sprayer that targets spray with a layer of forced air. Assuming equal pest control efficacy, the study calculates the annualized net present cost per acre of owning and operating each sprayer for ten years using a baseline discount rate of 10 percent over 200 acres of semi-dwarf apple trees. The analysis found the annualized net present cost per acre, from least to greatest, to be 312 for the tower sprayer with electronic sensors, 391 for the conventional air blast sprayer. Sensitivity analysis revealed that the ranking of these cost results was sensitive to farm size, but not to percentage of funds borrowed, discount rate, loan interest rate, or pesticide costs within the ranges investigated. The air curtain sprayer was lowest cost for orchards of 25 acres or more; the conventional air blast sprayer was lowest cost for 10-acre orchards.Crop Production/Industries,
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Assessment of the direct and indirect effects of MPP+ and dopamine on the human proteasome: implications for Parkinson's disease aetiology
Mitochondrial impairment, glutathione depletion and oxidative stress have been implicated in the pathogenesis of Parkinson’s disease (PD), linked recently to proteasomal dysfunction. Our study analysed how these factors influence the various activities of the proteasome in human SH-SY5Y neuroblastoma cells treated with the PD mimetics MPP+ (a complex 1 inhibitor) or dopamine. Treatment with these toxins led to dose- and time-dependent reductions in ATP and glutathione and also chymotrypsin-like and post-acidic like activities; trypsin-like activity was unaffected. Antioxidants blocked the effects of dopamine, but not MPP+, suggesting that oxidative stress was more important in the dopamine-mediated effects. With MPP+, ATP depletion was a prerequisite for loss of proteasomal activity. Thus in a dopaminergic neuron with complex 1 dysfunction both oxidative stress and ATP depletion will contribute independently to loss of proteasomal function. We show for the first time that addition of MPP+ or dopamine to purified samples of the human 20S proteasome also reduced proteasomal activities; with dopamine being most damaging. As with toxin-treated cells, chymotrypsin-like activity was most sensitive and trypsin-like activity the least sensitive. The observed differential sensitivity of the various proteasomal activities to PD mimetics is novel and its significance needs further study in human cells
Governance units as interstitial organizations: the role of governance organizations in the development and establishment of Building Environmental Assessment Methods (BEAM)
Green Building has been touted as the future of building construction. However, its emergence, due to the fluidity of the green building concept, is sometimes fraught with power struggles in the debate over which standards and practices to be adopted. With the emergence of Building Environmental Assessment Methods, much hope has been put on their associated third-party certification organizations to help forge a common ground for green building. These organizations are boundary spanning, traversing multiple professional jurisdictions, organizational fields, and involving various state and non-state actors. Despite wielding much influence in the development, establishment and promotion of BEAMs, the authority, and legitimacy of governance organizations are being questioned as to whose interest they serve, and whether they promote realistic green building practices. We argue that while the
success of these governance organizations will be their ability to act as neutral ‘brokers” of green building practices, they may end up capitulating the interest of powerful actors. Drawing on the theory fields proposed by Fligstein and McAdam (2012) and the concept of interstitial emergence, we explore the role of governance organizations for BEAMS in the building industry. The case is made that there is a need to examine the activities of governance organizations in the development of BEAMs, and why conceptualizing them as interstitial/boundary-spanning organizations could offer new insights and research directions in the burgeoning researching on BEAMs.postprin
Integration of disease-specific single nucleotide polymorphisms, expression quantitative trait loci and coexpression networks reveal novel candidate genes for type 2 diabetes.
Aims/hypothesisWhile genome-wide association studies (GWASs) have been successful in identifying novel variants associated with various diseases, it has been much more difficult to determine the biological mechanisms underlying these associations. Expression quantitative trait loci (eQTL) provide another dimension to these data by associating single nucleotide polymorphisms (SNPs) with gene expression. We hypothesised that integrating SNPs known to be associated with type 2 diabetes with eQTLs and coexpression networks would enable the discovery of novel candidate genes for type 2 diabetes.MethodsWe selected 32 SNPs associated with type 2 diabetes in two or more independent GWASs. We used previously described eQTLs mapped from genotype and gene expression data collected from 1,008 morbidly obese patients to find genes with expression associated with these SNPs. We linked these genes to coexpression modules, and ranked the other genes in these modules using an inverse sum score.ResultsWe found 62 genes with expression associated with type 2 diabetes SNPs. We validated our method by linking highly ranked genes in the coexpression modules back to SNPs through a combined eQTL dataset. We showed that the eQTLs highlighted by this method are significantly enriched for association with type 2 diabetes in data from the Wellcome Trust Case Control Consortium (WTCCC, p = 0.026) and the Gene Environment Association Studies (GENEVA, p = 0.042), validating our approach. Many of the highly ranked genes are also involved in the regulation or metabolism of insulin, glucose or lipids.Conclusions/interpretationWe have devised a novel method, involving the integration of datasets of different modalities, to discover novel candidate genes for type 2 diabetes
Stability of binocular depth perception with moving head and eyes
We systematically analyse the binocular disparity field under various eye, head
and stimulus positions and orientations. From the literature we know that
certain classes of disparity which involve the entire disparity field (such as
those caused by horizontal lateral shift, differential rotation, horizontal scale
and horizontal shear between the entire half-images of a stereogram) lead to
relatively poor depth perception in the case of limited observation periods.
These classes of disparity are found to be similar to the classes of disparities
which are brought about by eye and head movements. Our analysis supports
the suggestion that binocular depth perception is based primarily (for the
first few hundred milliseconds) on classes of disparity that do not change as a
result of ego-movement
Temporal aspects of stereoscopic slant estimation: An evaluation and extension of Howard and Kaneko's theory
We investigated temporal aspects of stereoscopically perceived slant produced by the
following transformations: horizontal scale, horizontal shear, vertical scale, vertical shear, divergence
and rotation, between the half-images of a stereogram. Six subjects viewed large field stimuli (70 deg
diameter) both in the presence and in the absence of a visual reference. The presentation duration
was: 0.1, 0.4, 1.6, 6.4 or 25.6 s. Without reference we found the following: Rotation and divergence
evoked considerable perceived slant in a number of subjects. This finding violates the recently
published results of Howard and Kaneko. Slant evoked by vertical scale and shear was similar to
slant evoked by horizontal scale and shear but was generally less. With reference we found the
following: Vertical scale and vertical shear did not evoke slant. Slant due to rotation and divergence
was similar to slant due to horizontal scale and shear but was generally less. According to the theory
of Howard and Kaneko, perceived slant depends on the difference between horizontal and vertical
scale and shear disparities. We made their theory more explicit by translating their proposals into
linear mathematical expressions that contain weighting factors that allow for both slant evoked by
rotation or divergence, subject-dependent underestimation of slant and other related phenomena
reported in the literature. Our data for all stimulus durations and for all subjects is explained by this
unequal-weighting extension of Howard and Kaneko's theory
Is there an interaction between perceived direction and perceived aspect ratio in stereoscopic vision?
In monocular vision, the horizontal/vertical aspect ratio (shape) of a fronto-parallel
rectangle can be based upon the comparison of the perceived directions of the rectangle's edges. In
binocular vision of a typical three-dimensional scene (when occlusions are present) this is not the
case: fronto-parallel rectangles would be perceived in a distorted fashion if an observer were to
base perceived aspect ratio on the perceived directions of the rectangle's edges. We
psychophysically investigated stereoscopically perceived aspect ratios of fronto-parallel occluding
and occluded rectangles for various distances and fixation depths. We found that observers did
not perceive the distortions as predicted on the basis of the above-mentioned comparison of the
perceived visual direction of the edges of the rectangle. Our results strongly suggest that the
mechanism that determines perceived aspect ratio is dissociated from the mechanism that
determines perceived direction. The consequences of the findings for the Kanizsa, Poggendorff,
and horizontal/vertical illusions are discussed
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