Parallel Monte Carlo sampling scheme for sphere and hemisphere

The sampling of certain solid angle is a fundamental operation in realistic image synthesis, where the rendering equation describing the light propagation in closed domains is solved. Monte Carlo methods for solving the rendering equation use sampling of the solid angle subtended by unit hemisphere or unit sphere in order to perform the numerical integration of the rendering equation. In this work we consider the problem for generation of uniformly distributed random samples over hemisphere and sphere. Our aim is to construct and study the parallel sampling scheme for hemisphere and sphere. First we apply the symmetry property for partitioning of hemisphere and sphere. The domain of solid angle subtended by a hemisphere is divided into a number of equal sub-domains. Each sub-domain represents solid angle subtended by orthogonal spherical triangle with fixed vertices and computable parameters. Then we introduce two new algorithms for sampling of orthogonal spherical triangles. Both algorithms are based on a transformation of the unit square. Similarly to the Arvo's algorithm for sampling of arbitrary spherical triangle the suggested algorithms accommodate the stratified sampling. We derive the necessary transformations for the algorithms. The first sampling algorithm generates a sample by mapping of the unit square onto orthogonal spherical triangle. The second algorithm directly compute the unit radius vector of a sampling point inside to the orthogonal spherical triangle. The sampling of total hemisphere and sphere is performed in parallel for all sub-domains simultaneously by using the symmetry property of partitioning. The applicability of the corresponding parallel sampling scheme for Monte Carlo and Quasi-D/lonte Carlo solving of rendering equation is discussed.

Psychophysics of emotion: the QUEST for emotional attention

To investigate the mechanisms involved in automatic processing of facial expressions, we used the QUEST procedure to measure the display durations needed to make a gender decision on emotional faces portraying fearful, happy, or neutral facial expressions. In line with predictions of appraisal theories of emotion, our results showed greater processing priority of emotional stimuli regardless of their valence. Whereas all experimental conditions led to an averaged threshold of about 50 ms, fearful and happy facial expressions led to significantly less variability in the responses than neutral faces. Results suggest that attention may have been automatically drawn by the emotion portrayed by face targets, yielding more informative perceptions and less variable responses. The temporal resolution of the perceptual system (expressed by the thresholds) and the processing priority of the stimuli (expressed by the variability in the responses) may influence subjective and objective measures of awareness, respectively.

Elevated atmospheric CO2 and humidity delay leaf fall in Betula pendula, but not in Alnus glutinosa or Populus tremula × tremuloides

Context: Anthropogenic activity has increased the level of atmospheric CO2, which is driving an increase of global temperatures and associated changes in precipitation patterns. At Northern latitudes, one of the likely consequences of global warming is increased precipitation and air humidity. Aims: In this work, the effects of both elevated atmospheric CO2 and increased air humidity on trees commonly growing in northern European forests were assessed. Methods: The work was carried out under field conditions by using Free Air Carbon dioxide Enrichment (FACE) and Free Air Humidity Manipulation (FAHM) systems. Leaf litter fall was measured over 4 years (FACE) or 5 years (FAHM) to determine the effects of FACE and FAHM on leaf phenology. Results: Increasing air humidity delayed leaf litter fall in Betula pendula, but not in Populus tremula × tremuloides. Similarly, under elevated atmospheric CO2, leaf litter fall was delayed in Betula pendula, but not in Alnus glutinosa. Increased CO2 appeared to interact with periods of low precipitation in summer and high ozone levels during these periods to effect leaf fall. Conclusions: This work shows that increased CO2 and humidity delay leaf fall, but this effect is species specific.

On the 'special' status of emotional faces... Comment on Yang, Hong, and Blake (2010)

A wealth of literature suggests that emotional faces are given special status as visual objects: Cognitive models suggest that emotional stimuli, particularly threat-relevant facial expressions such as fear and anger, are prioritized in visual processing and may be identified by a subcortical “quick and dirty” pathway in the absence of awareness (Tamietto & de Gelder, 2010). Both neuroimaging studies (Williams, Morris, McGlone, Abbott, & Mattingley, 2004) and backward masking studies (Whalen, Rauch, Etcoff, McInerney, & Lee, 1998) have supported the notion of emotion processing without awareness. Recently, our own group (Adams, Gray, Garner, & Graf, 2010) showed adaptation to emotional faces that were rendered invisible using a variant of binocular rivalry: continual flash suppression (CFS, Tsuchiya & Koch, 2005). Here we (i) respond to Yang, Hong, and Blake's (2010) criticisms of our adaptation paper and (ii) provide a unified account of adaptation to facial expression, identity, and gender, under conditions of unawareness

Using high-fidelity virtual reality to study perception in freely moving observers

Technological innovations have had a profound influence on how we study the sensory perception in humans and other animals. One example was the introduction of affordable computers, which radically changed the nature of visual experiments. It is clear that vision research is now at cusp of a similar shift, this time driven by the use of commercially available, low-cost, high- fidelity virtual reality (VR). In this review we will focus on: (a) the research questions VR allows experimenters to address and why these research questions are important, (b) the things that need to be considered when using VR to study human perception, (c) the drawbacks of current VR systems, and (d) the future direction vision research may take, now that VR has become a viable research tool.

Optimering av hålltidstabeller vid Normaliseringsugnen

Analyserna av hålltiderna i Normaliseringsugnen visar att i de flesta fall kan hålltiderna förkortas, beroende på om man väljer att godkänna värmebehandlingen vid en temperatur15C° eller 5C° under börvärdet. Om 5C° väljas kan det krävas att vissa ugnstider förlängs. Det finns ingen anledning att hålla övertid på plåtarna i ugnen, vilket kan leda till korntillväxt och ett sprött material. Undersökningen visar att övertiden ökar med plåttjockleken. Temperaturavvikelsediagrammet för värmebehandlingen visar att inom tjockleksintervallet 30mm - 50mm är temperaturdifferensen vid hålltidens slut störst gentemot börvärdet. Man bör dock komma ihåg att pyrometern endast mäter yttemperaturen. Kärntemperaturen är förmodligen något lägre och då krävs en viss övertid för att säkerställa en homogen temperatur genom hela plåten. Vid ett lyckat experiment med att plana en plåt, efter att ha värmt upp den till 650°C, gjordes en simulering i dataprogrammet Steeltemp 2D. Simuleringen visar svalningskurvor för en given analyskod från 600°C för olika plåttjocklekar. Temperaturen på experimentplåten vid inträdet i planmaskinen var 350°C. Resultatet som redovisas i Steeltempdiagrammet visar att det inte finns risk att plåttemperaturen sjunker under 350°C.

Topical 1% Nalbuphine on corneal sensivity and epitheilization after experimental lamellar keratectomy in rabbits

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Warming alters photosynthetic rates of sub-boreal peatland vegetation

Boreal peatlands are important in the global carbon cycle. Despite covering only 3% of the global land area, peatlands store approximately one third of all soil carbon. Temperature is one of the major drivers in peatland carbon cycling as it affects both plant production and CO2 fluxes from soils. However, it is relatively unknown how boreal peatland plant photosynthesis is affected by higher temperatures. Therefore, we measured plant photosynthetic rates under two different warming treatments in a poor fen in Northern Michigan. Eighteen plots were established that were divided into three treatments: control, open-top chamber (OTC) warming and infrared (IR) lamp warming. Previous work at this site has shown that there was a significant increase in canopy and peat temperature with IR warming (5°C and 1.4°C respectively), while the OTC’s had mixed overall warming. Plots were divided equally into lawns and hummocks. We measured mid-day carbon dioxide (CO2) uptake on sedges (Carex utriculata), shrubs (Chamaedaphne calyculata) and Sphagnum mosses. Sphagnum moss net primary production (NPP) was also measured with cranked wires and compared with CO2 uptake. Our results indicate that there was no significant difference in sedge CO2 uptake, while shrub CO2 uptake significantly decreased with warming. A significant increase occurred in Sphagnum moss gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem exchange (NEE). Contrary to the positive CO2 exchange of Sphagnum, overall NPP decreased significantly in hummocks with both warming treatments. The results of the study indicate that temperature partly limits the photosynthetic capacity of plants in sub-boreal peatlands, but not all species respond similarly to higher temperatures.

Allocentric visual cues influence mental transformation of bodies

Identifying a human body stimulus involves mentally rotating an embodied spatial representation of one's body (motoric embodiment) and projecting it onto the stimulus (spatial embodiment). Interactions between these two processes (spatial and motoric embodiment) may thus reveal cues about the underlying reference frames. The allocentric visual reference frame, and hence the perceived orientation of the body relative to gravity, was modulated using the York Tumbling Room, a fully furnished cubic room with strong directional cues that can be rotated around a participant's roll axis. Sixteen participants were seated upright (relative to gravity) in the Tumbling Room and made judgments about body and hand stimuli that were presented in the frontal plane at orientations of 0°, 90°, 180° (upside down), or 270° relative to them. Body stimuli have an intrinsic visual polarity relative to the environment whereas hands do not. Simultaneously the room was oriented 0°, 90°, 180° (upside down), or 270° relative to gravity resulting in sixteen combinations of orientations. Body stimuli were more accurately identified when room and body stimuli were aligned. However, such congruency did not facilitate identifying hand stimuli. We conclude that static allocentric visual cues can affect embodiment and hence performance in an egocentric mental transformation task. Reaction times to identify either hands or bodies showed no dependence on room orientation.

Perceptual learning of motion discrimination by mental imagery.

Perceptual learning can occur when stimuli are only imagined, i.e., without proper stimulus presentation. For example, perceptual learning improved bisection discrimination when only the two outer lines of the bisection stimulus were presented and the central line had to be imagined. Performance improved also with other static stimuli. In non-learning imagery experiments, imagining static stimuli is different from imagining motion stimuli. We hypothesized that those differences also affect imagery perceptual learning. Here, we show that imagery training also improves motion direction discrimination. Learning occurs when no stimulus at all is presented during training, whereas no learning occurs when only noise is presented. The interference between noise and mental imagery possibly hinders learning. For static bisection stimuli, the pattern is just the opposite. Learning occurs when presented with the two outer lines of the bisection stimulus, i.e., with only a part of the visual stimulus, while no learning occurs when no stimulus at all is presented.

VEGF-B-induced vascular growth leads to metabolic reprogramming and ischemia resistance in the heart

Angiogenic growth factors have recently been linked to tissue metabolism. We have used genetic gain- and loss-of function models to elucidate the effects and mechanisms of action of vascular endothelial growth factor-B (VEGF-B) in the heart. A cardiomyocyte-specific VEGF-B transgene induced an expanded coronary arterial tree and reprogramming of cardiomyocyte metabolism. This was associated with protection against myocardial infarction and preservation of mitochondrial complex I function upon ischemia-reperfusion. VEGF-B increased VEGF signals via VEGF receptor-2 to activate Erk1/2, which resulted in vascular growth. Akt and mTORC1 pathways were upregulated and AMPK downregulated, readjusting cardiomyocyte metabolic pathways to favor glucose oxidation and macromolecular biosynthesis. However, contrasting with a previous theory, there was no difference in fatty acid uptake by the heart between the VEGF-B transgenic, gene-targeted or wildtype rats. Importantly, we also show that VEGF-B expression is reduced in human heart disease. Our data indicate that VEGF-B could be used to increase the coronary vasculature and to reprogram myocardial metabolism to improve cardiac function in ischemic heart disease.

The effect of nontemporal stimulus size on perceived duration as assessed by the method of reproduction

Perceived duration is assumed to be positively related to nontemporal stimulus magnitude. Most recently, the finding that larger stimuli are perceived to last longer has been challenged to represent a mere decisional bias induced by the use of comparative duration judgments. Therefore, in the present study, the method of temporal reproduction was applied as a psychophysical procedure to quantify perceived duration. Another major goal was to investigate the influence of attention on the effect of visual stimulus size on perceived duration. For this purpose, an additional dual-task paradigm was employed. Our results not only converged with previous findings in demonstrating a functional positive relationship between nontemporal stimulus size and perceived duration, but also showed that the effect of stimulus size on perceived duration was not confined to comparative duration judgments. Furthermore, the effect of stimulus size proved to be independent of attentional resources allocated to stimulus size; nontemporal visual stimulus information does not need to be processed intentionally to influence perceived duration. Finally, the effect of nontemporal stimulus size on perceived duration was effectively modulated by the duration of the target intervals, suggesting a hitherto largely unrecognized role of temporal context for the effect of nontemporal stimulus size to become evident.