scholarly journals Disruptive coloration and binocular disparity: breaking camouflage

2019 ◽  
Vol 286 (1896) ◽  
pp. 20182045 ◽  
Author(s):  
Wendy J. Adams ◽  
Erich W. Graf ◽  
Matt Anderson
Keyword(s):  
Critical Role ◽  
Three Dimensional ◽  
Stereoscopic Vision ◽  
Dimensional Structure ◽  
Depth Information ◽  
Edge Enhancement ◽  
Depth Cues ◽  
Disruptive Coloration ◽  
True Shape ◽  
Binocular Depth

Many species employ camouflage to disguise their true shape and avoid detection or recognition. Disruptive coloration is a form of camouflage in which high-contrast patterns obscure internal features or break up an animal's outline. In particular, edge enhancement creates illusory, or ‘fake’ depth edges within the animal's body. Disruptive coloration often co-occurs with background matching, and together, these strategies make it difficult for an observer to visually segment an animal from its background. However, stereoscopic vision could provide a critical advantage in the arms race between perception and camouflage: the depth information provided by binocular disparities reveals the true three-dimensional layout of a scene, and might, therefore, help an observer to overcome the effects of disruptive coloration. Human observers located snake targets embedded in leafy backgrounds. We analysed performance (response time) as a function of edge enhancement, illumination conditions and the availability of binocular depth cues. We confirm that edge enhancement contributes to effective camouflage: observers were slower to find snakes whose patterning contains ‘fake’ depth edges. Importantly, however, this effect disappeared when binocular depth cues were available. Illumination also affected detection: under directional illumination, where both the leaves and snake produced strong cast shadows, snake targets were localized more quickly than in scenes rendered under ambient illumination. In summary, we show that illusory depth edges, created via disruptive coloration, help to conceal targets from human observers. However, cast shadows and binocular depth information improve detection by providing information about the true three-dimensional structure of a scene. Importantly, the strong interaction between disparity and edge enhancement suggests that stereoscopic vision has a critical role in breaking camouflage, enabling the observer to overcome the disruptive effects of edge enhancement.

The Role of Motion in Infants' Perception of Solid Shape

Perception ◽  
1983 ◽  
Vol 12 (6) ◽  
pp. 707-717 ◽  
Author(s):  
Cynthia Owsley
Keyword(s):  
Three Dimensional ◽  
Depth Information ◽  
Visual Depth ◽  
Depth Cues ◽  
Kinetic Depth ◽  
Dimensional Shape ◽  
Three Dimensional Shape ◽  
Visual Habituation ◽  
Binocular Depth

Previous research has shown that infants as young as the first few months of life perceive several aspects of the three-dimensional environment. Yet we know relatively little about the visual depth information which serves as a basis for their spatial capacities. A study is reported in which a visual habituation procedure was used to examine what types of optical depth information four-month-old infants find useful in visually perceiving solid (three-dimensional) shape. Results imply that in the absence of binocular depth cues four-month-olds rely on kinetic depth information to perceive solid shape.

An Accelerated Cue Combination Principle Accounts for Multi-cue Depth Perception

2020 ◽  
Vol 3 (1) ◽  
pp. 10501-1-10501-9
Author(s):  
Christopher W. Tyler
Keyword(s):  
Belief Propagation ◽  
Probability Distributions ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Fusion Model ◽  
Cue Combination ◽  
Depth Estimate ◽  
Appropriate Behavior ◽  
Depth Cues ◽  
Bayesian Averaging

Abstract For the visual world in which we operate, the core issue is to conceptualize how its three-dimensional structure is encoded through the neural computation of multiple depth cues and their integration to a unitary depth structure. One approach to this issue is the full Bayesian model of scene understanding, but this is shown to require selection from the implausibly large number of possible scenes. An alternative approach is to propagate the implied depth structure solution for the scene through the “belief propagation” algorithm on general probability distributions. However, a more efficient model of local slant propagation is developed as an alternative.The overall depth percept must be derived from the combination of all available depth cues, but a simple linear summation rule across, say, a dozen different depth cues, would massively overestimate the perceived depth in the scene in cases where each cue alone provides a close-to-veridical depth estimate. On the other hand, a Bayesian averaging or “modified weak fusion” model for depth cue combination does not provide for the observed enhancement of perceived depth from weak depth cues. Thus, the current models do not account for the empirical properties of perceived depth from multiple depth cues.The present analysis shows that these problems can be addressed by an asymptotic, or hyperbolic Minkowski, approach to cue combination. With appropriate parameters, this first-order rule gives strong summation for a few depth cues, but the effect of an increasing number of cues beyond that remains too weak to account for the available degree of perceived depth magnitude. Finally, an accelerated asymptotic rule is proposed to match the empirical strength of perceived depth as measured, with appropriate behavior for any number of depth cues.

scholarly journals Crystal structure of a tankyrase 1–telomere repeat factor 1 complex

2016 ◽  
Vol 72 (4) ◽  
pp. 320-327 ◽  
Author(s):  
Bo Li ◽  
Ruihong Qiao ◽  
Zhizhi Wang ◽  
Weihong Zhou ◽  
Xin Li ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Large Scale ◽  
Sparse Matrix ◽  
Critical Role ◽  
Three Dimensional ◽  
Mitotic Cell ◽  
Ankyrin Repeat ◽  
Dimensional Structure ◽  
Telomere Repeat ◽  
Tankyrase 1

Telomere repeat factor 1 (TRF1) is a subunit of shelterin (also known as the telosome) and plays a critical role in inhibiting telomere elongation by telomerase. Tankyrase 1 (TNKS1) is a poly(ADP-ribose) polymerase that regulates the activity of TRF1 through poly(ADP-ribosyl)ation (PARylation). PARylation of TRF1 by TNKS1 leads to the release of TRF1 from telomeres and allows telomerase to access telomeres. The interaction between TRF1 and TNKS1 is thus important for telomere stability and the mitotic cell cycle. Here, the crystal structure of a complex between the N-terminal acidic domain of TRF1 (residues 1–55) and a fragment of TNKS1 covering the second and third ankyrin-repeat clusters (ARC2-3) is presented at 2.2 Å resolution. The TNKS1–TRF1 complex crystals were optimized using an `oriented rescreening' strategy, in which the initial crystallization condition was used as a guide for a second round of large-scale sparse-matrix screening. This crystallographic and biochemical analysis provides a better understanding of the TRF1–TNKS1 interaction and the three-dimensional structure of the ankyrin-repeat domain of TNKS.

Three-Dimensional Structure of Ribosome-Sec61p Translocation Complexes From Mammals

2000 ◽  
Vol 6 (S2) ◽  
pp. 264-265
Author(s):  
J-F. Ménétret ◽  
D. G. Morgan ◽  
M. Radermacher ◽  
A. Neuhof ◽  
T. A. Rapoport ◽  
...  
Keyword(s):  
Critical Role ◽  
Three Dimensional ◽  
Channel Morphology ◽  
Dimensional Structure ◽  
Central Channel ◽  
Mass Analysis ◽  
Biologically Relevant ◽  
Ribosome Binding ◽  
Physical Mechanisms ◽  
3D Architecture

Co-translational translocation at the endoplasmic reticulum (ER) plays a critical role in the targeting of both soluble and membrane proteins to their correct intra- and intercellular compartments. We are studying the 3D architecture of the ribosome-Sec61p complex (translocon), with the aim of understanding the physical mechanisms of gating and transport. To this end, we are using single particle electron cryo-microscopy and 3D reconstruction of frozen hydrated channel complexes, to obtain interpretable and biologically relevant maps.Previously, we have shown that both co- and post-translational translocation utilize a common central channel comprised of a ring-like Sec61p oligomer. Moreover, this channel morphology is shared with the related Sec YE complex from B. subtilus. Mass analysis, volume calculations and ribosome binding experiments suggest a stoichiometry of 3-4 Sec61p heterotrimers per ring. We currently favor 4 copies of the Sec61p complex per channel, as projection maps demonstrate 4 nearly equi-spaced peaks around the central pore.

scholarly journals A structural insight into the inhibition of human and Leishmania donovani ornithine decarboxylases by 1-amino-oxy-3-aminopropane

2007 ◽  
Vol 405 (2) ◽  
pp. 261-268 ◽  
Author(s):  
Veronica T. Dufe ◽  
Daniel Ingner ◽  
Olle Heby ◽  
Alex R. Khomutov ◽  
Lo Persson ◽  
...  
Keyword(s):  
Leishmania Donovani ◽  
Homology Modelling ◽  
Critical Role ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Irreversible Inhibitor ◽  
Polyamine Biosynthesis ◽  
Oxime Formation ◽  
Large Conformational Change ◽  
Similar Mode

The critical role of polyamines in key processes such as cell growth, differentiation and macromolecular synthesis makes the enzymes involved in their synthesis potential targets in the treatment of certain types of cancer and parasitic diseases. Here we present a study on the inhibition of human and Leishmania donovani ODC (ornithine decarboxylase), the first committed enzyme in the polyamine biosynthesis pathway, by APA (1-amino-oxy-3-aminopropane). The present study shows APA to be a potent inhibitor of both human and L. donovani ODC with a Ki value of around 1.0 nM. We also show that L. donovani ODC binds the substrate, the co-enzyme pyridoxal 5′-phosphate and the irreversible inhibitor α-difluoromethylornithine (a curative agent of West African sleeping sickness) with less affinity than human ODC. We have also determined the three-dimensional structure of human ODC in complex with APA, which revealed the mode of the inhibitor binding to the enzyme. In contrast with earlier reports, the structure showed no indication of oxime formation between APA and PLP (pyridoxal 5′-phosphate). Homology modelling suggests a similar mode of binding of APA to L. donovani ODC. A comparison of the ODC–APA–PLP structure with earlier ODC structures also shows that the protease-sensitive loop (residues 158–168) undergoes a large conformational change and covers the active site of the protein. The understanding of the structural mode of APA binding may constitute the basis for the development of more specific inhibitors of L. donovani ODC.

scholarly journals Depth Estimation for Monocular Image Based on Convolutional Neural Networks

2021 ◽  
Vol 15 ◽  
pp. 533-540
Author(s):  
Binglin Niu ◽  
Mengxia Tang ◽  
Xuelin Chen
Keyword(s):  
Three Dimensional ◽  
Depth Estimation ◽  
Dimensional Structure ◽  
Depth Information ◽  
Pyramid Structure ◽  
Level Information ◽  
Monocular Image ◽  
Feature Pyramid ◽  
Sampling Structure ◽  
Autonomous Movement

Perceiving the three-dimensional structure of the surrounding environment and analyzing it for autonomous movement is an indispensable element for robots to operate in scenes. Recovering depth information and the three-dimensional spatial structure from monocular images is a basic mission of computer vision. For the objects in the image, there are many scenes that may produce it. This paper proposes to use a supervised end-to-end network to perform depth estimation without relying on any subsequent processing operations, such as probabilistic graphic models and other extra fine steps. This paper uses an encoder-decoder structure with feature pyramid to complete the prediction of dense depth maps. The encoder adopts ResNeXt-50 network to achieve main features from the original image. The feature pyramid structure can merge high and low level information with each other, and the feature information is not lost. The decoder utilizes the transposed convolutional and the convolutional layer to connect as an up-sampling structure to expand the resolution of the output. The structure adopted in this paper is applied to the indoor dataset NYU Depth v2 to obtain better prediction results than other methods. The experimental results show that on the NYU Depth v2 dataset, our method achieves the best results on 5 indicators and the sub-optimal results on 1 indicator.

scholarly journals Effects of cortical damage on binocular depth perception

2016 ◽  
Vol 371 (1697) ◽  
pp. 20150254 ◽  
Author(s):  
Holly Bridge
Keyword(s):  
Depth Perception ◽  
Three Dimensional ◽  
Stereoscopic Vision ◽  
Temporal Lobectomy ◽  
Cortical Atrophy ◽  
Retinal Images ◽  
Posterior Cortical Atrophy ◽  
Retinal Input ◽  
The Brain ◽  
Binocular Depth

Stereoscopic depth perception requires considerable neural computation, including the initial correspondence of the two retinal images, comparison across the local regions of the visual field and integration with other cues to depth. The most common cause for loss of stereoscopic vision is amblyopia, in which one eye has failed to form an adequate input to the visual cortex, usually due to strabismus (deviating eye) or anisometropia. However, the significant cortical processing required to produce the percept of depth means that, even when the retinal input is intact from both eyes, brain damage or dysfunction can interfere with stereoscopic vision. In this review, I examine the evidence for impairment of binocular vision and depth perception that can result from insults to the brain, including both discrete damage, temporal lobectomy and more systemic diseases such as posterior cortical atrophy. This article is part of the themed issue ‘Vision in our three-dimensional world’.

scholarly journals Proof of Principle for Direct Reconstruction of Qualitative Depth Information from Turbid Media by a Single Hyper Spectral Image

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2860
Author(s):  
Martin Hohmann ◽  
Damaris Hecht ◽  
Benjamin Lengenfelder ◽  
Moritz Späth ◽  
Florian Klämpfl ◽  
...  
Keyword(s):  
Opposite Effect ◽  
Three Dimensional ◽  
Turbid Media ◽  
Dimensional Structure ◽  
Depth Information ◽  
Medical Applications ◽  
Spectral Image ◽  
Hyper Spectral ◽  
Hyper Spectral Imaging ◽  
Proof Of Principle

In medical applications, hyper-spectral imaging is becoming more and more common. It has been shown to be more effective for classification and segmentation than normal RGB imaging because narrower wavelength bands are used, providing a higher contrast. However, until now, the fact that hyper-spectral images also contain information about the three-dimensional structure of turbid media has been neglected. In this study, it is shown that it is possible to derive information about the depth of inclusions in turbid phantoms from a single hyper-spectral image. Here, the depth information is encoded by a combination of scattering and absorption within the phantom. Although scatter-dominated regions increase the backscattering for deep vessels, absorption has the opposite effect. With this argumentation, it makes sense to assume that, under certain conditions, a wavelength is not influenced by the depth of the inclusion and acts as an iso-point. This iso-point could be used to easily derive information about the depth of an inclusion. In this study, it is shown that the iso-point exists in some cases. Moreover, it is shown that the iso-point can be used to obtain precise depth information.

Judgments of Azimuth and Elevation as a Function of Monoscopic and Binocular Depth Cues Using a Perspective Display

1995 ◽  
Vol 37 (1) ◽  
pp. 173-181 ◽  
Author(s):  
Woodrow Barfield ◽  
Craig Rosenberg
Keyword(s):  
Spatial Information ◽  
Binocular Disparity ◽  
Three Dimensional ◽  
Stereoscopic Display ◽  
Absolute Value ◽  
Depth Cues ◽  
Depth Cue ◽  
Three Dimensional Display ◽  
The Difference ◽  
Binocular Depth

The purpose of this study was to investigate the use of three-dimensional display formats for judgments of spatial information using an exocentric frame of reference. Eight subjects judged the azimuth and elevation that separated two computer-generated objects using either a perspective or stereoscopic display. Errors, which consisted of the difference in absolute value between the estimated and actual azimuth or elevation, were analyzed as the response variable. The data indicated that the stereoscopic display resulted in more accurate estimates of elevation, especially for images aligned approximately orthogonally to the viewing vector. However, estimates of relative azimuth direction were not improved by use of the stereoscopic display. Furthermore, it was shown that the effect of compression resulting from a 45--deg computer graphics eye point elevation produced a response bias that was symmetrical around the horizontal plane of the reference cube, and that the depth cue of binocular disparity provided by the stereoscopic display reduced the magnitude of the compression errors. Implications of the results for the design of spatial displays are discussed.

Structure–specificity relationships in Abp, a GH27 β-L-arabinopyranosidase fromGeobacillus stearothermophilusT6

2014 ◽  
Vol 70 (11) ◽  
pp. 2994-3012 ◽  
Author(s):  
Shifra Lansky ◽  
Rachel Salama ◽  
Hodaya V. Solomon ◽  
Hadar Feinberg ◽  
Hassan Belrhali ◽  
...  
Keyword(s):  
Active Sites ◽  
Critical Role ◽  
Three Dimensional ◽  
Structural Data ◽  
Size Exclusion ◽  
Dimensional Structure ◽  
Structural Basis ◽  
X Ray ◽  
Three Dimensional Structure ◽  
Tim Barrel

L-Arabinose sugar residues are relatively abundant in plants and are found mainly in arabinan polysaccharides and in other arabinose-containing polysaccharides such as arabinoxylans and pectic arabinogalactans. The majority of the arabinose units in plants are present in the furanose form and only a small fraction of them are present in the pyranose form. The L-arabinan-utilization system inGeobacillus stearothermophilusT6, a Gram-positive thermophilic soil bacterium, has recently been characterized, and one of the key enzymes was found to be an intracellular β-L-arabinopyranosidase (Abp). Abp, a GH27 enzyme, was shown to remove β-L-arabinopyranose residues from synthetic substrates and from the native substrates sugar beet arabinan and larch arabinogalactan. The Abp monomer is made up of 448 amino acids, and based on sequence homology it was suggested that Asp197 is the catalytic nucleophile and Asp255 is the catalytic acid/base. In the current study, the detailed three-dimensional structure of wild-type Abp (at 2.28 Å resolution) and its catalytic mutant Abp-D197A with (at 2.20 Å resolution) and without (at 2.30 Å resolution) a bound L-arabinose product are reported as determined by X-ray crystallography. These structures demonstrate that the three-dimensional structure of the Abp monomer correlates with the general fold observed for GH27 proteins, consisting of two main domains: an N-terminal TIM-barrel domain and a C-terminal all-β domain. The two catalytic residues are located in the TIM-barrel domain, such that their carboxylic functional groups are about 5.9 Å from each other, consistent with a retaining mechanism. An isoleucine residue (Ile67) located at a key position in the active site is shown to play a critical role in the substrate specificity of Abp, providing a structural basis for the high preference of the enzyme towards arabinopyranoside over galactopyranoside substrates. The crystal structure demonstrates that Abp is a tetramer made up of two `open-pincers' dimers, which clamp around each other to form a central cavity. The four active sites of the Abp tetramer are situated on the inner surface of this cavity, all opening into the central space of the cavity. The biological relevance of this tetrameric structure is supported by independent results obtained from size-exclusion chromatography (SEC), dynamic light-scattering (DLS) and small-angle X-ray scattering (SAXS) experiments. These data and their comparison to the structural data of related GH27 enzymes are used for a more general discussion concerning structure–selectivity aspects in this glycoside hydrolase (GH) family.

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