Psychophysiological experiments were performed in which imaginary right angles formed by three spots of light were supplemented by distracting line segments. The subjects' task was to restore the orthogonality disturbed by the distractors. Subjects' errors were assessed in relation to the distance between the basal spots and the distractors. The results led to the suggestion that there are specific lateral interaction processes involving local averaging of information on the positions of stimulus components. Quantitative evaluation of the parameters of this interaction was addressed using a simplified mathematical model constructed on the basis of the concept of displacements of the centers of gravity resulting from summation of the corresponding excitation patterns in the neural networks of the visual system. Good consistency between theoretical and experimental data was obtained.

In the present communication, we have developed a computational model related to the conception of positional coding via centers-of-masses (centroids) of the objects' luminance distributions. The model predictions have been tested by the results of our psychophysical study of geometrical illusion of extent evoked by a modified Brentano figure consisting of three separate spots clusters. In experiments, the centroids of the clusters were manipulated by varying the positions of additional non-target spots flanking the stimulus terminators. A good correspondence between the model predictions and the illusion magnitude changes provided convincing evidences in favor of "centroid" explanation of origin of the illusion investigated.

In the present study, a computational model of the automatic centroid extraction based on the processes of local integration of excitatory profiles in the visual pathways has been developed. The model predictions have been compared with the results of our psychophysical examination of the perceptual distortions of the spatial extent. In experiments, the subjects matched two spatial intervals flanked by one of the three types of the contextual objects: either the Müller-Lyer wings, or vertical stripes, or spot pairs. A good resemblance between the theoretical functions and dependencies of the illusions' magnitudes on various spatial parameters of the stimuli has provided evidence that the effects caused by indirect positional coding via centroids are powerful enough to explain the phenomena of the geometric illusions investigated.

The present paper aims at critically reviewing the most outstanding and recent studies regarding the control of body orientation in the vertical space. A first part defines the general concepts used throughout this manuscript. The second part investigates the vertical perception and the main factors which affect it, while trying to overcome the five areas of theoretical and experimental controversies we have identified in the literature. The third part of this review presents the different theoretical models of the vertical perception and body orientation in space. Finally, the last part focuses on the functional coupling between perception of the vertical and orientation of the body in space. It considers more particularly how these two dimensions interact for explaining the observed behaviors.

The truncation of upper-case words can result in a subjective contour along the truncated ends of the letters. We explored this effect in two experiments designed to tease apart the processes responsible: in particular, the possible role of letter recognition. Such a role would indicate an unprecedented involvement of "high-level vision" in the genesis of subjective contours. In experiment 1, we confirmed the basic effect of word truncation in eliciting a subjective contour, using only letters where truncation does not eliminate any critical features. In experiment 2, we showed that the effect is not confined to words/letters but is equally strong for controlled non-letter stimuli that, like words, have many forms that have an inflection or an intersection near the centre. Truncation at one end then introduces proportional imbalance between upper and lower sections of the figures. We conclude from the two experiments that part of the effect is due to vertical shortening per se and the rest to the proportional imbalance introduced by the truncation. The effect of proportional imbalance, a novel determinant of subjective contours, may result from experience with letters, although the effect is not "high level" in requiring the recognition of specific letters.

Early Renaissance painters innovatively attempted to depict realistic three-dimensional scenes. A major problem was to produce the impression of overlap for surfaces that occlude one another in the scene but are adjoined in the picture plane. Much has been written about perspective in art but little about occlusion. Here I examine some of the strategies for depicting occlusion used by early Renaissance painters in relation to ecological considerations and perceptual research. Perceived surface overlap is often achieved by implementing the principle that an occluding surface occludes anything behind it, so that occlusion perception is enhanced by a lack of relationship of occluding contour to occluded contours. Some well-known figure-ground principles are also commonly used to stratify adjoined figures. Global factors that assist this stratification include the placement of figures on a ground plane, a high viewpoint, and figure grouping. Artists of this period seem to have differed on whether to occlude faces and heads, often carefully avoiding doing so. Halos were either eliminated selectively or placed oddly to avoid such occlusions. Finally, I argue that the marked intransitivity in occlusion by architecture in the paintings of Duccio can be related to the issue of perceptual versus cognitive influences on the visual impact of paintings.

INTRODUCTION: While the directionality of tactile motion processing has been studied extensively, tactile speed processing and its relationship to direction is little-researched and poorly understood. We investigated this relationship in humans using the 'tactile speed aftereffect'(tSAE), in which the speed of motion appears slower following prolonged exposure to a moving surface. METHOD: We used psychophysical methods to test whether the tSAE is direction sensitive. After adapting to a ridged moving surface with one hand, participants compared the speed of test stimuli on the adapted and unadapted hands. We varied the direction of the adapting stimulus relative to the test stimulus. RESULTS: Perceived speed of the surface moving at 81 mms(-1) was reduced by about 30% regardless of the direction of the adapting stimulus (when adapted in the same direction, Mean reduction = 23 mms(-1), SD = 11; with opposite direction, Mean reduction = 26 mms(-1), SD = 9). In addition to a large reduction in perceived speed due to adaptation, we also report that this effect is not direction sensitive. CONCLUSIONS: Tactile motion is susceptible to speed adaptation. This result complements previous reports of reliable direction aftereffects when using a dynamic test stimulus as together they describe how perception of a moving stimulus in touch depends on the immediate history of stimulation. Given that the tSAE is not direction sensitive, we argue that peripheral adaptation does not explain it, because primary afferents are direction sensitive with friction-creating stimuli like ours (thus motion in their preferred direction should result in greater adaptation, and if perceived speed were critically dependent on these afferents' response intensity, the tSAE should be direction sensitive). The adaptation that reduces perceived speed therefore seems to be of central origin.

A small region of background presented to only one eye in an otherwise binocular display may, under certain conditions, be resolved in the visual system by interpreting the region as a small gap between two similar objects placed at different depths, with the gap hidden in one eye by parallax. This has been called monocular gap stereopsis. We investigated the electrophysiological correlate of this type of stereopsis by means of sum potential recordings in 12 observers, comparing VEP's for this stimulus ("Gillam Stereo", Author BG has strong reservations about this term) with those for similar stimuli containing disparity based depth and with no depth (flat). In addition we included several control stimuli. The results show a pronounced early negative potential at a latency of around 170 ms (N170) for all stimuli containing non- identical elements, be they a difference caused by binocular disparity or by completely unmatched monocular contours. A second negative potential with latency around 270 ms (N270), on the other hand, is present only with stimuli leading to fusion and the perception of depth. This second component is similar for disparity-based stereopsis and monocular gap, or "Gillam Stereo" although slightly more pronounced for the former. We conjecture that the first component is related to the detection of differences between the images of the two eyes that may then either be fused, leading to stereopsis and the corresponding second potential, or else to inhibition and rivalry without a later trace in the VEP. The finding that that "Gillam Stereo" leads to cortical responses at the same short latencies as disparity based stereopsis indicates that it may partly rely on quite early cortical mechanisms.

Muscle vibration excites muscle spindles and creates illusory movement of a body part in a blindfolded individual. It is followed by an aftereffect, an illusion of return movement when vibration stops. The aftereffect reflects adaptation in the proprioceptive system. This adaptation is susceptible to attentional manipulations (Seizova-Cajic and Azzi in Exp Brain Res 203(1):213-219, 2010), but it is not known whether it is open to cross-modal influences unaided by those manipulations. We attempted to answer this question by allowing vision of the vibrated, stationary arm. We asked our participants (n = 20) to retain focus on the feeling of movement. They reported any illusory movement during 60-s biceps vibration (at 90 Hz), as well as following its offset, when vision of the arm was removed. During vibration, the proprioceptive movement illusion persisted, although the stationary arm was visible, but its duration and strength were much reduced in comparison with the no-vision condition. The movement aftereffect, experienced in total darkness following vibration offset, was also substantially weaker. The results show that proprioceptive adaptation is strongly modulated by vision. We propose that two processes contribute: perceptual (cross-modal binding with conflicting vision reduces the proprioceptive movement signal) and attentional (view of a stationary arm distracts from the proprioceptive movement signal). Our finding that during vibration, participants felt movement in the arm they could see, which was stationary, shows that cross-modal binding partially failed. This happened because the two percepts were too discrepant. However, only one-the visual-appeared real, and we argue that such an outcome is consistent with general principles of intersensory integration.

Static and dynamic observers provided binocular and monocular estimates of the depths between real objects lying well beyond interaction space. On each trial, pairs of LEDs were presented inside a dark railway tunnel. The nearest LED was always 40 m from the observer, with the depth separation between LED pairs ranging from 0 up to 248 m. Dynamic binocular viewing was found to produce the greatest (ie most veridical) estimates of depth magnitude, followed next by static binocular viewing, and then by dynamic monocular viewing.(No significant depth was seen with static monocular viewing.) We found evidence that both binocular and monocular dynamic estimates of depth were scaled for the observation distance when the ground plane and walls of the tunnel were visible up to the nearest LED. We conclude that both motion parallax and stereopsis provide useful long-distance depth information and that motion-parallax information can enhance the degree of stereoscopic depth seen.

Visual processing of basic perceptual attributes depends on attention. This has been well documented since the surprising initial report on attentional modulation of the visual motion aftereffect (Chaudhuri 1990). Here, we investigate proprioception and show for the first time that attention modulates adaptation to perceived limb movement. We used biceps vibration to induce illusory forearm extension in 10 participants and measured the aftereffect-perceived movement in the opposite direction. The aftereffect was largest when participants focused on the illusory extension during the adaptation period. To divert attention away from the illusory extension, a rapid serial visual presentation task was performed during the adaptation. The aftereffect was much smaller in this condition, indicating interference between the visual task and proprioceptive adaptation. In tests of an analogous interaction between audition and vision, earlier research found no effect. We suggest that conscious proprioception requires more attention than conscious processing of visual or auditory input.

We report an improved draft nucleotide sequence of the 2.3-gigabase genome of maize, an important crop plant and model for biological research. Over 32,000 genes were predicted, of which 99.8% were placed on reference chromosomes. Nearly 85% of the genome is composed of hundreds of families of transposable elements, dispersed nonuniformly across the genome. These were responsible for the capture and amplification of numerous gene fragments and affect the composition, sizes, and positions of centromeres. We also report on the correlation of methylation-poor regions with Mu transposon insertions and recombination, and copy number variants with insertions and/or deletions, as well as how uneven gene losses between duplicated regions were involved in returning an ancient allotetraploid to a genetically diploid state. These analyses inform and set the stage for further investigations to improve our understanding of the domestication and agricultural improvements of maize.

We report an aftereffect in perception of the extent (or degree or range) of joint movement, showing for the first time that a prolonged exposure to a passive back-and-forth movement of a certain extent results in a change in judgment of the extent of a subsequently presented movement. The adapting stimulus, movement about the wrist, had an extent of either 30 degrees or 75 degrees , while the test stimulus was a 50 degrees movement. Following a 4-min adaptation period, the estimated magnitudes of the test stimuli were 61 degrees and 36 degrees in the 30 degrees and 75 degrees condition, respectively (t test(6)= 9.6; p < 0.001). The observed effect is an instance of repulsion or contrast commonly described in perception literature, with perceived value of the test stimulus pushed away from the adapting stimulus.

Here we investigated the influence of angular separation between visual and motor targets on concurrent adaptation to two opposing visuomotor rotations. We inferred the extent of generalisation between opposing visuomotor rotations at individual target locations based on whether interference (negative transfer) was present. Our main finding was that dual adaptation occurred to opposing visuomotor rotations when each was associated with different visual targets but shared a common motor target. Dual adaptation could have been achieved either within a single sensorimotor map (i.e. with different mappings associated with different ranges of visual input), or by forming two different internal models (the selection of which would be based on contextual information provided by target location). In the present case, the pattern of generalisation was dependent on the relative position of the visual targets associated with each rotation. Visual targets nearest the workspace of the opposing visuomotor rotation exhibited the most interference (i.e. generalisation). When the minimum angular separation between visual targets was increased, the extent of interference was reduced. These results suggest that the separation in the range of sensory inputs is the critical requirement to support dual adaptation within a single sensorimotor mapping.

When using a driver, the centre of pressure of a golfer shows a pattern that is characteristic of one of two distinct swing styles: the "front foot" style or the "reverse" style. The aim of this study was to establish whether these two swing styles are also evident when using other clubs, and if so, to determine whether golfers use the same swing style when using different clubs. Forty-six professional, amateur, and recreational golfers performed swings to hit a ball into a net placed 3 m away. Ten swings were performed for each of the driver, 3-iron, and 7-iron while standing on two force plates. The position of the golfer's centre of pressure parallel with the line of shot and relative to the feet was quantified at eight swing events that were identified from 200-Hz video. Cluster analysis confirmed that the front foot and reverse styles were evident in all three clubs, and most of the golfers (96%) used the same swing style for all three clubs. Golfers that used the reverse swing positioned their centre of pressure nearer to their toes at ball contact compared with golfers that used the front foot swing.

The dSNAP computer program has been used to classify searches of the Cambridge Structural Database for two ligands:-O-CH(2)-CH(2)-O- and N(CH(2)CH(2)O-)(3) commonly found in metal-organic systems. The clustering method used is based on total geometries (i.e. all the lengths and angles involving all the atoms in the search fragment, whether bonded or not) and proved capable of distinguishing in a wholly automatic, objective way between different types of metal complex purely on the basis of the geometry of the ligand and the relative positions of the O atoms to the metals.

CYP4F22 and CYP4F8 are expressed in epidermis, and mutations of CYP4F22 are associated with lamellar ichthyosis. Epoxyalcohols (HEETs) and epoxides (EETs) of 20:4n-6 appear to be important for the water permeability barrier of skin. Our aim was to study the MS/MS spectra and fragmentation of these compounds and to determine whether they were oxidized by CYP4F22 or CYP4F8 expressed in yeast. HEETs were prepared from 15-hydroperoxyeicosatetraenoic acid (15-HPETE), 12-HPETE, and their [(2)H(8)]labeled isotopomers, and separated by normal phase-HPLC with MS/MS analysis. CYP4F22 oxygenated 20:4n-6 at C-18, whereas metabolites of HEETs could not be identified. CYP4F8 formed omega3 hydroxy metabolites of HEETs derived from 12R-HPETE with 11,12-epoxy-10-hydroxy configuration, but not HEETs derived from 15S-HPETE. 8,9-EET and 11,12-EET were also subject to omega3 hydroxylation by CYP4F8. We conclude that CYP4F8 and CYP4F22 oxidize 20:4n-6 and that CYP4F8 selectively oxidizes 8,9-EET, 11,12-EET, and 10,11R,12R-HEET at the omega3 position.

Groups of frequency chirping modes observed between sawtooth crashes in the Alcator C-Mod tokamak are interpreted as reversed shear Alfvén eigenmodes near the q=1 surface. These modes indicate that a reversed shear q profile is generated during the relaxation phase of the sawtooth cycle. Two important parameters, q_{min} and its radial position, are deduced from comparisons of measured density fluctuations with calculations from the ideal MHD code NOVA. These studies provide valuable constraints for further modeling of the sawtooth cycle.

We present a method to incorporate geometrical uncertainties into dose-volume histogram evaluation: the dose-volume population histogram (DVPH). For each dose-volume point, the probability of the plan DVH meeting the constraint is calculated. The use of DVPH for the target shows that the minimum dose to the PTV might not be representative of the minimum dose to the CTV considering geometrical uncertainties when the PTV extends into the build-up region. For OARs, the DVH obtained from DVPH with 90% confidence level is found to be different to the planning organ at risk volume (PRV) DVH recommended by ICRU 62, especially for parallel organs.

We study the patterns formed on ion sputtered Si surfaces as a function of ion energy and incidence angle, and identify a region in parameter space where the flat surface is stable. The boundaries between the stable and pattern-forming regions represent mathematical bifurcations. Our data set exhibits at least two different bifurcation types. We discuss the constraints imposed by these observations on the correct model of long wavelength dynamics of ion sputtered surfaces.

Sodium oxinate is found to precipitate Be(II) quantitatively in the pH range 7.5-8.2. The complex has the composition Be(2)O(C(9)H(6)NO)(2).2H(2)O, is stable and can be weighed directly after drying at 105-110 degrees . A method for the estimation of Be(II) and its separation from interfering elements is described. The monohydrate has been prepared from the dihydrate and characterized. The results show the presence of hydroxyl bridges in the monohydrate. Methods using various organic reagents for the direct estimation of beryllium in ores and alloys have been examined and it is found that 4-chloro-2,5-dimethoxyacetoacetanilide gives the best results. A method for the determination of be(II) in beryl without prior separation of Fe(III) and Al(III) is described.

A new method for pattern recognition that is invariant under changes of position, orientation, intensity, and scale is presented. The centroids of objects provide unique points that are related to the energy distribution. For obtaining more such unique points a conformal transform can be used to rearrange the energy distribution of the object. By means of the conformal transform many different centroids can be produced from the same object. A useful pattern-recognition and object-registration method that yields a position-, rotation-, intensity-, and scale-invariant feature vector based on these centroids can be created.

A Bayesian methodology for the analysis of inequality constrained models for contingency tables is presented. The problem of interest lies in obtaining the estimates of functions of cell probabilities subject to inequality constraints, testing hypotheses and selection of the best model. Constraints on conditional cell probabilities and on local, global, continuation and cumulative odds ratios are discussed. A Gibbs sampler to obtain a discrete representation of the posterior distribution of the inequality constrained parameters is used. Using this discrete representation, the credibility regions of functions of cell probabilities can be constructed. Posterior model probabilities are used for model selection and hypotheses are tested using posterior predictive checks. The Bayesian methodology proposed is illustrated in two examples.