scholarly journals 12 Contact Location Trajectory on the Fingertip as a Sufficient Requisite for Illusory Perception of Haptic Shape and Effect of Multiple Contacts

2005 ◽  
pp. 189-198 ◽  
Author(s):  
Hanifa Dostmohamed ◽  
Vincent Hayward
Keyword(s):  
Multiple Contacts ◽  
Illusory Perception

A mode I crack with multiple islands of ideal contact between the crack faces: An asymptotic model

2021 ◽  
pp. 108128652110214
Author(s):  
Ivan Argatov
Keyword(s):  
Crack Opening ◽  
Reduction Factor ◽  
Mode I ◽  
Asymptotic Model ◽  
Mode I Crack ◽  
Opening Displacement ◽  
Multiple Contacts ◽  
Scaling Hypothesis ◽  
Penny Shaped Crack ◽  
Crack Faces

The problem of a mode I crack having multiple contacts between the crack faces is considered. In the case of small contact islands of arbitrary shapes, which are arbitrarily located inside the crack, the first-order asymptotic model for the crack opening displacement is constructed using the method of matched asymptotic expansions. The case of a penny-shaped crack has been studied in detail. A scaling hypothesis for the compliance reduction factor is formulated.

scholarly journals Structural basis for the regulation of nucleosome recognition and HDAC activity by histone deacetylase assemblies

2021 ◽  
Vol 7 (2) ◽  
pp. eabd4413
Author(s):  
Jung-Hoon Lee ◽  
Daniel Bollschweiler ◽  
Tillman Schäfer ◽  
Robert Huber
Keyword(s):  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Active Sites ◽  
Chromatin Modification ◽  
Structural Basis ◽  
Amino Terminal ◽  
Cryo Electron Microscopy ◽  
Multiple Contacts ◽  
Lysine Residues ◽  
Nucleosome Binding

The chromatin-modifying histone deacetylases (HDACs) remove acetyl groups from acetyl-lysine residues in histone amino-terminal tails, thereby mediating transcriptional repression. Structural makeup and mechanisms by which multisubunit HDAC complexes recognize nucleosomes remain elusive. Our cryo–electron microscopy structures of the yeast class II HDAC ensembles show that the HDAC protomer comprises a triangle-shaped assembly of stoichiometry Hda12-Hda2-Hda3, in which the active sites of the Hda1 dimer are freely accessible. We also observe a tetramer of protomers, where the nucleosome binding modules are inaccessible. Structural analysis of the nucleosome-bound complexes indicates how positioning of Hda1 adjacent to histone H2B affords HDAC catalysis. Moreover, it reveals how an intricate network of multiple contacts between a dimer of protomers and the nucleosome creates a platform for expansion of the HDAC activities. Our study provides comprehensive insight into the structural plasticity of the HDAC complex and its functional mechanism of chromatin modification.

scholarly journals The Challenge of Illusory Perception of Animals: The Impact of Methodological Variability in Cross-species Investigation

Animals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1618
Author(s):  
Maria Santacà ◽  
Christian Agrillo ◽  
Maria Elena Miletto Petrazzini
Keyword(s):  
Research Field ◽  
Choice Test ◽  
Training Procedure ◽  
Biologically Relevant ◽  
Selective Pressures ◽  
Extensive Training ◽  
Behavioural Research ◽  
Illusory Perception ◽  
Methodological Approaches ◽  
The Impact

Although we live on the same planet, there are countless different ways of seeing the surroundings that reflect the different individual experiences and selective pressures. In recent decades, visual illusions have been used in behavioural research to compare the perception between different vertebrate species. The studies conducted so far have provided contradictory results, suggesting that the underlying perceptual mechanisms may differ across species. Besides the differentiation of the perceptual mechanisms, another explanation could be taken into account. Indeed, the different studies often used different methodologies that could have potentially introduced confounding factors. In fact, the possibility exists that the illusory perception is influenced by the different methodologies and the test design. Almost every study of this research field has been conducted in laboratories adopting two different methodological approaches: a spontaneous choice test or a training procedure. In the spontaneous choice test, a subject is presented with biologically relevant stimuli in an illusory context, whereas, in the training procedure, a subject has to undergo an extensive training during which neutral stimuli are associated with a biologically relevant reward. Here, we review the literature on this topic, highlighting both the relevance and the potential weaknesses of the different methodological approaches.

An experimental study on the influence of multiple contacts and size on contact behavior of marble sphere

2021 ◽  
Vol 23 (2) ◽  
Author(s):  
Yang Ye ◽  
Yawu Zeng ◽  
Hanqing Sun ◽  
Yang Liu ◽  
Xi Chen ◽  
...  
Keyword(s):  
Experimental Study ◽  
Contact Behavior ◽  
Multiple Contacts

Simulation of Large and Complex Structures With Multiple Contacts and Wear

1992 ◽  
Author(s):  
B. S. Bagepalli ◽  
S. Dinc ◽  
B. Jlidi ◽  
I. Imam ◽  
J. Barnes ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Analytical Models ◽  
Contact Friction ◽  
Complex Structures ◽  
Accelerometer Data ◽  
Mechanism Analysis ◽  
Evaluation Tool ◽  
Simulation Code ◽  
Multiple Contacts ◽  
Field Samples

Abstract This paper deals with the simulation methodology of large and complex structures with multiple contacts and wear. The methodology developed is used to evaluate the dynamics and wear of gas turbine combustors. A unified approach of representing multiple rigid/elastic bodies with numerous contacts is developed. Representation is made, too, of the changing nature of these contacts — both geometric and material. The entire methodology is implemented in a generic and easy-to-use simulation code which serves as a useful generic design/analysis evaluation tool MAP (Mechanism Analysis Program). Appropriate analytical models for inter-material constitutive laws — both incremental (contact friction, pressure, damping, etc.) and cumulative (wear theories) — are incorporated in the tool. As applications of this approach, dynamic simulations of two different gas turbine combustor designs are run, and comparisons are made with real systems. Excellent correlations have been obtained, both with respect to laboratory test (accelerometer) data, and wear patterns at various contacts and junctions on field samples.

Parametric Kinematic Tolerance Analysis of Planar Pairs With Multiple Contacts

1996 ◽  
Author(s):  
Elisha Sacks ◽  
Leo Joskowicz
Keyword(s):  
Efficient Algorithm ◽  
Tolerance Analysis ◽  
Parametric Model ◽  
Worst Case ◽  
Multiple Contacts ◽  
Work Cycle ◽  
Computer Aided ◽  
Kinematic Models ◽  
Range Of Variation ◽  
Different Parts

Abstract We present an efficient algorithm for worst-case limit kinematic tolerance analysis of planar kinematic pairs with multiple contacts. The algorithm extends computer-aided kinematic tolerance analysis from mechanisms in which parts interact through permanent contacts to mechanisms in which different parts or part features interact at different stages of the work cycle. Given a parametric model of a pair and the range of variation of the parameters, it constructs parametric kinematic models for the contacts, computes the configurations in which each contact occurs, and derives the sensitivity of the kinematic variation to the parameters. The algorithm also derives qualitative variations, such as under-cutting, interference, and jamming. We demonstrate the algorithm on a 26 parameter model of a Geneva mechanism.

scholarly journals The effect of multiple contacts between crack faces on crack contribution to the effective elastic properties

2019 ◽  
Vol 163 ◽  
pp. 75-86 ◽  
Author(s):  
A. Markov ◽  
S. Abaimov ◽  
I. Sevostianov ◽  
M. Kachanov ◽  
S. Kanaun ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Effective Elastic Properties ◽  
Multiple Contacts ◽  
Crack Faces

scholarly journals Slowed sensory reweighting and postural illusions in older adults: the moving platform illusion

2019 ◽  
Vol 121 (2) ◽  
pp. 690-700 ◽  
Author(s):  
Chesney E. Craig ◽  
Michail Doumas
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Postural Sway ◽  
Age Groups ◽  
Age Group ◽  
Sensory Reweighting ◽  
Perceptual Illusion ◽  
Healthy Older Adults ◽  
Stable Conditions ◽  
Illusory Perception

We investigated whether postural aftereffects witnessed during transitions from a moving to a stable support are accompanied by a delayed perception of platform stabilization in older adults, in two experiments. In experiment 1, postural sway and muscle cocontraction were assessed in 11 healthy young, 11 healthy older, and 11 fall-prone older adults during blindfolded stance on a fixed platform, followed by a sway-referenced platform and then by a fixed platform again. The sway-referenced platform was more compliant for young adults, to induce similar levels of postural sway in both age groups. Participants were asked to press a button whenever they perceived that the platform had stopped moving. Both older groups showed significantly larger and longer postural sway aftereffects during platform stabilization compared with young adults, which were pronounced in fall-prone older adults. In both older groups elevated muscle cocontraction aftereffect was also witnessed. Importantly, these aftereffects were accompanied by an illusory perception of prolonged platform movement. After this, experiment 2 examined whether this illusory perception was a robust age effect or an experimental confound due to greater surface compliance in young adults, which could create a larger perceptual discrepancy between moving and stable conditions. Despite exposure to the same surface compliance levels during sway-reference, the perceptual illusion was maintained in experiment 2 in a new group of 14 healthy older adults compared with 11 young adults. In both studies, older adults took five times longer than young adults to perceive platform stabilization. This supports that sensory reweighting is inefficient in older adults. NEW & NOTEWORTHY This is the first paper to show that postural sway aftereffects witnessed in older adults after platform stabilization may be due to a perceptual illusion of platform movement. Surprisingly, in both experiments presented it took older adults five times longer than young adults to perceive platform stabilization. This supports a hypothesis of less efficient sensory reintegration in this age group, which may delay the formation of an accurate postural percept.

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