Structural Constraints: Further Evidence from Apparent Motion in Depth

Perception ◽  
1993 ◽  
Vol 22 (3) ◽  
pp. 323-334 ◽  
Author(s):  
Maurice Hershenson
Keyword(s):  
Apparent Motion ◽  
Three Dimensional ◽  
Structural Constraints ◽  
Motion Patterns ◽  
Motion In Depth ◽  
Point Patterns ◽  
Light Point ◽  
Rigidity Constraint ◽  
Second Category ◽  
Perceived Motion

The three-dimensional (3-D) apparent motion of lines, outline triangles, and light points was studied in four experiments. The stimulus sequences were beginning and end patterns of 3-D motions of a line and a triangle. Light-point patterns corresponded to the ends of the lines and the vertices of the triangles. Perceived motion of lines and light-point pairs resembled the distal motions that were used to construct the proximal patterns. The correspondence was striking for configurations that appeared to move in depth. Outline triangles and light-point triplets produced a strong correspondence between distal and perceived motions when the three sides appeared to be translating in depth. The correspondence was reasonably good for the other motion patterns when scoring included an appropriate second category. The results support the conception of structural or internalized constraints: light points were processed as if they were connected (unity constraint) and proximal change in linear size (or distance between light points) was perceived as rigid 3-D motion (rigidity constraint).

Inferring Structure from Motion in Two-View and Multiview Displays

Perception ◽  
1993 ◽  
Vol 22 (12) ◽  
pp. 1441-1465 ◽  
Author(s):  
Jeffrey C Liter ◽  
Myron L Braunstein ◽  
Donald D Hoffman
Keyword(s):  
Relative Motion ◽  
Apparent Motion ◽  
Structure From Motion ◽  
Three Dimensional ◽  
Rigid Motion ◽  
Parameter Family ◽  
Image Motion ◽  
Heuristic Analysis

Five experiments were conducted to examine constraints used to interpret structure-from-motion displays. Theoretically, two orthographic views of four or more points in rigid motion yield a one-parameter family of rigid three-dimensional (3-D) interpretations. Additional views yield a unique rigid interpretation. Subjects viewed two-view and thirty-view displays of five-point objects in apparent motion. The subjects selected the best 3-D interpretation from a set of 89 compatible alternatives (experiments 1–3) or judged depth directly (experiment 4). In both cases the judged depth increased when relative image motion increased, even when the increased motion was due to increased simulation rotation. Subjects also judged rotation to be greater when either simulated depth or simulated rotation increased (experiment 4). The results are consistent with a heuristic analysis in which perceived depth is determined by relative motion.

scholarly journals FingerprintContacts: Predicting Alternative Conformations of Proteins from Coevolution

2020 ◽  
Author(s):  
Jiangyan Feng ◽  
Diwakar Shukla
Keyword(s):  
Ligand Binding ◽  
Structure Prediction ◽  
De Novo ◽  
Three Dimensional ◽  
Sequence Information ◽  
Structural Constraints ◽  
Complex Signals ◽  
Residue Contacts ◽  
Small Clusters ◽  
Functional Mechanisms

AbstractProteins are dynamic molecules which perform diverse molecular functions by adopting different three-dimensional structures. Recent progress in residue-residue contacts prediction opens up new avenues for the de novo protein structure prediction from sequence information. However, it is still difficult to predict more than one conformation from residue-residue contacts alone. This is due to the inability to deconvolve the complex signals of residue-residue contacts, i.e. spatial contacts relevant for protein folding, conformational diversity, and ligand binding. Here, we introduce a machine learning based method, called FingerprintContacts, for extending the capabilities of residue-residue contacts. This algorithm leverages the features of residue-residue contacts, that is, (1) a single conformation outperforms the others in the structural prediction using all the top ranking residue-residue contacts as structural constraints, and (2) conformation specific contacts rank lower and constitute a small fraction of residue-residue contacts. We demonstrate the capabilities of FingerprintContacts on eight ligand binding proteins with varying conformational motions. Furthermore, FingerprintContacts identifies small clusters of residue-residue contacts which are preferentially located in the dynamically fluctuating regions. With the rapid growth in protein sequence information, we expect FingerprintContacts to be a powerful first step in structural understanding of protein functional mechanisms.

A General Correspondence Approach to Apparent Motion

Perception ◽  
1993 ◽  
Vol 22 (2) ◽  
pp. 185-192 ◽  
Author(s):  
Terry Caelli ◽  
Mark Manning ◽  
David Finlay
Keyword(s):  
Apparent Motion ◽  
Constraint Satisfaction ◽  
General Framework ◽  
Feature Weights ◽  
General Correspondence ◽  
Perceived Motion

A general framework is considered for how different features of image parts determine the perceived direction of apparent motion between these parts as a function of their internalized feature weights. It is shown how the compatibility and constraints between pairwise part correspondences also play important roles in the types of perceived motion between parts; this process is modelled via a multivariate constraint-satisfaction procedure.

Breakdown of Apparent Motion under Stereoscopic Viewing

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 55-55
Author(s):  
S Yukumatsu ◽  
K Bingushi
Keyword(s):  
Apparent Motion ◽  
Binocular Disparity ◽  
Three Dimensional ◽  
The Other ◽  
Bilateral Condition ◽  
Everyday Experiences ◽  
Cumulative Time

To study the effect of binocular disparity on apparent motion, we measured the cumulative time of its breakdown during a 30 s fixation viewing period. Two light spots, both on the left side of the fixation point, were alternately presented one by one on a CRT display (unilateral condition). These spots were binocularly disparate and viewed through a stereoscope. While one spot near the fixation point was presented on a zero disparity plane, the other spot (more peripheral) was either on a zero, uncrossed, or crossed disparity plane, so that three-dimensional motion could be seen depending on disparity values. We found that the duration of the breakdown of apparent motion was longer when uncrossed and zero-disparity spots were paired to produce apparent motion, and it was shorter when crossed and zero-disparity spots were paired. However, such disparity-specific tendencies were not obtained when the two spots were presented on both sides of the fixation point (bilateral condition). The disparity-specific tendencies in the unilateral condition can be explained by assuming that three-dimensional apparent motion that is consistent with the motion perspective may be stable because we experience it more frequently. Thus, we assume that perception of motion, both apparent and real, may develop through everyday experiences of moving to and fro in the environment rather than seeing objects move.

scholarly journals Golgi Structure in Three Dimensions: Functional Insights from the Normal Rat Kidney Cell

1999 ◽  
Vol 144 (6) ◽  
pp. 1135-1149 ◽  
Author(s):  
Mark S. Ladinsky ◽  
David N. Mastronarde ◽  
J. Richard McIntosh ◽  
Kathryn E. Howell ◽  
L. Andrew Staehelin
Keyword(s):  
Golgi Complex ◽  
Rat Kidney ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Structural Constraints ◽  
Vesicular Traffic ◽  
Golgi Region ◽  
Normal Rat ◽  
Em Tomography ◽  
Cis And Trans

Three-dimensional reconstructions of portions of the Golgi complex from cryofixed, freeze-substituted normal rat kidney cells have been made by dual-axis, high-voltage EM tomography at ∼7-nm resolution. The reconstruction shown here (∼1 × 1 × 4 μm3) contains two stacks of seven cisternae separated by a noncompact region across which bridges connect some cisternae at equivalent levels, but none at nonequivalent levels. The rest of the noncompact region is filled with both vesicles and polymorphic membranous elements. All cisternae are fenestrated and display coated buds. They all have about the same surface area, but they differ in volume by as much as 50%. The trans-most cisterna produces exclusively clathrin-coated buds, whereas the others display only nonclathrin coated buds. This finding challenges traditional views of where sorting occurs within the Golgi complex. Tubules with budding profiles extend from the margins of both cis and trans cisternae. They pass beyond neighboring cisternae, suggesting that these tubules contribute to traffic to and/or from the Golgi. Vesicle-filled “wells” open to both the cis and lateral sides of the stacks. The stacks of cisternae are positioned between two types of ER, cis and trans. The cis ER lies adjacent to the ER-Golgi intermediate compartment, which consists of discrete polymorphic membranous elements layered in front of the cis-most Golgi cisterna. The extensive trans ER forms close contacts with the two trans-most cisternae; this apposition may permit direct transfer of lipids between ER and Golgi membranes. Within 0.2 μm of the cisternae studied, there are 394 vesicles (8 clathrin coated, 190 nonclathrin coated, and 196 noncoated), indicating considerable vesicular traffic in this Golgi region. Our data place structural constraints on models of trafficking to, through, and from the Golgi complex.

scholarly journals Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades

2003 ◽  
Vol 9 (6) ◽  
pp. 385-391
Author(s):  
Jörg Bergner ◽  
Dietmar K. Hennecke ◽  
Martin Hoeger ◽  
Karl Engel
Keyword(s):  
Mechanical Stability ◽  
Three Dimensional ◽  
Stability Limit ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Structural Constraints ◽  
Transonic Compressor ◽  
Aero Engines ◽  
The Impact

For Darmstadt University of Technology's axial singlestage transonic compressor rig, a new three-dimensional aft-swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.To avoid the hazard of rubbing at the blade tip, which is found especially at off-design operating conditions close to the stability limit of the compression system, aft-sweep was introduced together with excessive backward lean.This article reports an investigation of the impact of various amounts of lean on the aerodynamic behavior of the compressor stage on the basis of steady-state Navier-Stokes simulations. The results indicate that high backward lean promotes an undesirable redistribution of mass flow and gives rise to a basic change in the shock pattern, whereas a forward-leaning geometry results in the development of a highly back-swept shock front. However, the disadvantage is a decrease in shock strength and efficiency.

The Effect of Two-Dimensional and Three-Dimensional Distance on Apparent Motion

Perception ◽  
1983 ◽  
Vol 12 (3) ◽  
pp. 305-312 ◽  
Author(s):  
Kathleen Mutch ◽  
Isabel M Smith ◽  
Albert Yonas
Keyword(s):  
Motion Perception ◽  
Apparent Motion ◽  
Three Dimensional ◽  
Spatial Separation ◽  
Three Dimensions ◽  
Correspondence Problem ◽  
Two Dimensional ◽  
Motion Display ◽  
Specific Concern ◽  
Actual Depth

The problem of how the visual system matches corresponding inputs from one instant to the next to produce the perception of motion has been experimentally examined. The specific concern was whether this correspondence problem is solved prior to the interpretation of three-dimensional distance. Observers judged the degree of apparent motion between pairs of lights in a conflicting motion display. Spatial separation of the lights was varied in two and three dimensions in order to assess whether retinal distance, actual depth, or some combination of these provided critical information for correspondence. The results support Ullman's contention that only two-dimensional (retinal) distances are used in establishing correspondence in motion perception.

scholarly journals A Linear Theory of Three-Dimensional Land–Sea Breezes

2012 ◽  
Vol 69 (6) ◽  
pp. 1890-1909 ◽  
Author(s):  
Qingfang Jiang
Keyword(s):  
Gravity Waves ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Early Morning ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Motion Patterns ◽  
Sea Breezes ◽  
Differential Heating ◽  
Downwind Side

Abstract Land–sea breezes (LSBs) induced by diurnal differential heating are examined using a three-dimensional linear model employing fast Fourier transform with emphasis on the complex coastline shape and geometry, the earth’s rotation, and background wind effects. It has been demonstrated that the low-level vertical motion associated with LSB can be significantly enhanced over a bay (peninsula) because of convergence of perturbations induced by differential heating along a seaward concave (convex) coastline. The dependence of surface winds and vertical motion patterns and their evolutions on the coastline geometries such as the width and the aspect ratio of the bay, the earth’s rotation, and the background winds are investigated. The LSB induced by an isolated tropical island is characterized by onshore flow and ascent over the island in the afternoon to early evening, with a reversal of direction from midnight to early morning. The diurnal heating–induced vertical motion is greatly enhanced over the island and weakened offshore because of the convergence and divergence of perturbations. In the presence of background flow, stronger diurnal perturbations are found at the downwind side of the island, which can extend far downstream associated with inertia–gravity waves.

STRUCTURE SIMULATIONS OF LIQUID S AND LIQUID Te BY UNCONSTRAINED REVERSE MONTE CARLO METHOD

1996 ◽  
Vol 10 (25) ◽  
pp. 1267-1276 ◽  
Author(s):  
M. ANDRECUT
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Three Dimensional ◽  
Distribution Model ◽  
Dimensional Structure ◽  
Angle Distribution ◽  
Structural Constraints ◽  
Reverse Monte Carlo ◽  
Three Body ◽  
Reverse Monte Carlo Method

A spatial atomic distribution model of liquid S (L-S) and liquid Te (L-Te) was generated by using the experimental diffraction data and reverse Monte Carlo method without applying structural constraints. The obtained models have been analysed in terms of near-atomic-neighbour, bond-angle distribution, three-body correlations and chain statistics. The analysis of the generated models has shown that the three-dimensional structure of the investigated liquids can be well described as a network of short chains.

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