The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Malcolm D Walkinshaw - One of the best experts on this subject based on the ideXlab platform.
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a molecular dynamics study of allosteric transitions in leishmania mexicana pyruvate kinase
Biophysical Journal, 2015Co-Authors: Ankita Naithani, Paul Taylor, Burak Erman, Malcolm D WalkinshawAbstract:A comparative molecular dynamics analysis of the pyruvate kinase from Leishmania mexicana is presented in the absence and presence of the allosteric effector fructose 2,6-bisphosphate. Comparisons of the simulations of the large 240 kDa apo and holo tetramers show that binding of fructose 2,6-bisphosphate cools the enzyme and reduces dynamic movement, particularly of the B-domain. The reduced dynamic movement of the holo form traps the pyruvate kinase tetramer in its enzymatically active state with the B-domain acting as a lid to cover the active site. The simulations are also consistent with a transition of the mobile active-site α6′ helix, which would adopt a helical conformation in the active R-state and a less structured coil conformation in the inactive T-state. Analysis of the rigid Body motions over the trajectory highlights the concerted anticorrelated rigid Body Rocking motion of the four protomers, which drives the T to R transition. The transitions predicted by these simulations are largely consistent with the Monod-Wyman-Changeux model for allosteric activation but also suggest that rigidification or cooling of the overall structure upon effector binding plays an additional role in enzyme activation.
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allosteric mechanism of pyruvate kinase from leishmania mexicana uses a rock and lock model
Journal of Biological Chemistry, 2010Co-Authors: Hugh P Morgan, I W Mcnae, Matthew W Nowicki, Veronique Hannaert, Paul A M Michels, Linda A Fothergillgilmore, Malcolm D WalkinshawAbstract:Allosteric regulation provides a rate management system for enzymes involved in many cellular processes. Ligand-controlled regulation is easily recognizable, but the underlying molecular mechanisms have remained elusive. We have obtained the first complete series of allosteric structures, in all possible ligated states, for the tetrameric enzyme, pyruvate kinase, from Leishmania mexicana. The transition between inactive T-state and active R-state is accompanied by a simple symmetrical 6° rigid Body Rocking motion of the A- and C-domain cores in each of the four subunits. However, formation of the R-state in this way is only part of the mechanism; eight essential salt bridge locks that form across the C-C interface provide tetramer rigidity with a coupled 7-fold increase in rate. The results presented here illustrate how conformational changes coupled with effector binding correlate with loss of flexibility and increase in thermal stability providing a general mechanism for allosteric control.
I Y Shen - One of the best experts on this subject based on the ideXlab platform.
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Rocking Vibration of Rotating Disk and Spindle Systems With Asymmetric Bearings
Journal of Applied Mechanics, 2003Co-Authors: J. S. Park, I Y ShenAbstract:This note presents how bearing asymmetry affects natural frequencies and mode shapes of a rotating disk/ spindle system through a perturbation analysis. The analysis will focus on Rocking motion of the disk/ spindle system that consists of rigid-Body Rocking of the spindle, one-nodal-diameter modes of each disk, and deformation of spindle bearings.
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closed form forced response of a damped rotating multiple disks spindle system
Journal of Applied Mechanics, 1997Co-Authors: I Y ShenAbstract:This paper is to study forced vibration response of a rotating disk/spindle system consisting of multiple flexible circular disks clamped to a rigid spindle supported by two flexible bearings. In particular, the disk/spindle system is subjected to prescribed translational base excitations and externally applied loads. Because of the bearing flexibility, the rigid spindle undergoes infinitesimal rigid-Body Rocking and translation simultaneously. To model real vibration response that has finite resonance amplitudes, the disks and the bearings are assumed to be viscously damped. Equations of motion are then derived through use of Rayleigh dissipation function and Lagrange's equation. The equations of motion include three sets of matrix differential equations: one for the rigid-Body Rocking of the spindle and one-nodal-diameter disk modes, one for the axial translation of the spindle and axisymmetric disk modes, and one for disk modes with two or more nodal diameters. Each matrix differential equation contains either a gyroscopic matrix or a damping matrix or both. The causal Green's function of each matrix differential equation is determined explicitly in closed form through use of matrix inversion and inverse Laplace transforms. Closed-form forced response of the damped rotating disk/spindle system is then obtained from the causal Green's function and the generalized forces through convolution integrals. Finally, responses ofa disk/spindle system subjected to a concentrated sinusoidal load or an impulsive load are demonstrated numerically as an example.
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Closed-Form Forced Response of a Damped, Rotating, Multiple Disks/Spindle System
Journal of Applied Mechanics, 1997Co-Authors: I Y ShenAbstract:This paper is to study forced vibration response of a rotating disk/spindle system consisting of multiple flexible circular disks clamped to a rigid spindle supported by two flexible bearings. In particular, the disk/spindle system is subjected to prescribed translational base excitations and externally applied loads. Because of the bearing flexibility, the rigid spindle undergoes infinitesimal rigid-Body Rocking and translation simultaneously. To model real vibration response that has finite resonance amplitudes, the disks and the bearings are assumed to be viscously damped. Equations of motion are then derived through use of Rayleigh dissipation function and Lagrange’s equation. The equations of motion include three sets of matrix differential equations: one for the rigid-Body Rocking of the spindle and one-nodal-diameter disk modes, one for the axial translation of the spindle and axisymmetric disk modes, and one for disk modes with two or more nodal diameters. Each matrix differential equation contains either a gyroscopic matrix or a damping matrix or both. The causal Green’s function of each matrix differential equation is determined explicitly in closed form through use of matrix inversion and inverse Laplace transforms. Closed-form forced response of the damped rotating disk/spindle system is then obtained from the causal Green’s function and the generalized forces through convolution integrals. Finally, responses of a disk/spindle system subjected to a concentrated sinusoidal load or an impulsive load are demonstrated numerically as an example.
Matthew S. Goodwin - One of the best experts on this subject based on the ideXlab platform.
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An analysis of stereotypical motor movements and cardiovascular coupling in individuals on the autism spectrum.
Biological psychology, 2019Co-Authors: James Heathers, Kristin H. Gilchrist, Meghan Hegarty-craver, Sonia Grego, Matthew S. GoodwinAbstract:Abstract One of the core diagnostic features of autism spectrum disorder (ASD) is engagement in stereotypical motor movements, although the etiology of this repetitive behavior is unknown. Since the 1960s, it has been hypothesized that stereotypical motor movements serve a homeostatic regulation function, and thereby a putative coupling mechanism to cardiovascular arousal. However, to date, surprisingly few reports explicitly assess cardio-somatic coupling and stereotypical motor movements. The present exploratory study investigates coupling of stereotypical Body Rocking and hand flapping to heart rate and heart rate variability (HRV) in a convenience sample (n = 10) of children and young adults with moderate to profound ASD. Motor movements were recorded via video and three-axis accelerometry, and simultaneous electrocardiographic signals were obtained to determine cardiovascular indices at or around the onset of naturalistically occurring stereotypy. Analysis of the heart rate revealed both repetitive Body Rocking and hand flapping in particular were found to associate with a strikingly similar cardiovascular pattern of acceleration and deceleration unrelated to physical demands associated with the movements themselves. Furthermore, neither type of stereotypical movement provoked directional change in heart rate variability. The implications of these results and opportunities for future research are discussed.
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fast track article detecting stereotypical motor movements in the classroom using accelerometry and pattern recognition algorithms
Pervasive and Mobile Computing, 2012Co-Authors: Fahd Albinali, Matthew S. Goodwin, Stephen S. IntilleAbstract:Individuals with Autism Spectrum Disorders (ASD) frequently engage in stereotyped and repetitive motor movements. Automatically detecting these movements using comfortable, miniature wireless sensors could advance autism research and enable new intervention tools for the classroom that help children and their caregivers monitor, understand, and cope with this potentially problematic class of behavior. We present activity recognition results for stereotypical hand flapping and Body Rocking using accelerometer data collected wirelessly from six children with ASD repeatedly observed by experts in real classroom settings. An overall recognition accuracy of 88.6% (TP: 0.85; FP: 0.08) was achieved using three sensors. We also present pilot work in which non-experts use software on mobile phones to annotate stereotypical motor movements for classifier training. Preliminary results indicate that non-expert annotations for training can be as effective as expert annotations. Challenges encountered when applying machine learning to this domain, as well as implications for the development of real-time classroom interventions and research tools are discussed.
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recognizing stereotypical motor movements in the laboratory and classroom a case study with children on the autism spectrum
Ubiquitous Computing, 2009Co-Authors: Fahd Albinali, Matthew S. Goodwin, Stephen S. IntilleAbstract:Individuals with Autism Spectrum Disorders (ASD) frequently engage in stereotyped and repetitive motor movements. Automatically detecting these movements in real-time using comfortable, miniature wireless sensors could advance autistic research and enable new intervention tools for the classroom that help children and their caregivers monitor and cope with this potentially problematic class of behavior. We present activity recognition results for stereotypical hand flapping and Body Rocking using data collected from six children with ASD repeatedly observed in both laboratory and classroom settings. In the classroom, an overall recognition accuracy of 88.6% (TP: 0.85; FP: 0.08) was achieved using three sensors. Challenges encountered when applying machine learning to this domain, as well as implications for the development of real-time classroom interventions and research tools, are discussed.
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IDC - Sensor-enabled detection of stereotypical motor movements in persons with autism spectrum disorder
Proceedings of the 7th international conference on Interaction design and children - IDC '08, 2008Co-Authors: Matthew S. Goodwin, Stephen S. Intille, Wayne F. Velicer, June GrodenAbstract:Stereotypical motor movements are one of the most common and least understood behaviors occurring in individuals with Autism Spectrum Disorder (ASD). Problems with traditional methods for measuring movement stereotypy make it difficult to accurately determine when and why these behaviors occur. The current research overcomes previous measurement problems by utilizing wireless accelerometers and pattern recognition software to automatically and reliably detect stereotypical motor movements such as Body Rocking and hand flapping in children with ASD.
Stephen S. Intille - One of the best experts on this subject based on the ideXlab platform.
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fast track article detecting stereotypical motor movements in the classroom using accelerometry and pattern recognition algorithms
Pervasive and Mobile Computing, 2012Co-Authors: Fahd Albinali, Matthew S. Goodwin, Stephen S. IntilleAbstract:Individuals with Autism Spectrum Disorders (ASD) frequently engage in stereotyped and repetitive motor movements. Automatically detecting these movements using comfortable, miniature wireless sensors could advance autism research and enable new intervention tools for the classroom that help children and their caregivers monitor, understand, and cope with this potentially problematic class of behavior. We present activity recognition results for stereotypical hand flapping and Body Rocking using accelerometer data collected wirelessly from six children with ASD repeatedly observed by experts in real classroom settings. An overall recognition accuracy of 88.6% (TP: 0.85; FP: 0.08) was achieved using three sensors. We also present pilot work in which non-experts use software on mobile phones to annotate stereotypical motor movements for classifier training. Preliminary results indicate that non-expert annotations for training can be as effective as expert annotations. Challenges encountered when applying machine learning to this domain, as well as implications for the development of real-time classroom interventions and research tools are discussed.
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recognizing stereotypical motor movements in the laboratory and classroom a case study with children on the autism spectrum
Ubiquitous Computing, 2009Co-Authors: Fahd Albinali, Matthew S. Goodwin, Stephen S. IntilleAbstract:Individuals with Autism Spectrum Disorders (ASD) frequently engage in stereotyped and repetitive motor movements. Automatically detecting these movements in real-time using comfortable, miniature wireless sensors could advance autistic research and enable new intervention tools for the classroom that help children and their caregivers monitor and cope with this potentially problematic class of behavior. We present activity recognition results for stereotypical hand flapping and Body Rocking using data collected from six children with ASD repeatedly observed in both laboratory and classroom settings. In the classroom, an overall recognition accuracy of 88.6% (TP: 0.85; FP: 0.08) was achieved using three sensors. Challenges encountered when applying machine learning to this domain, as well as implications for the development of real-time classroom interventions and research tools, are discussed.
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IDC - Sensor-enabled detection of stereotypical motor movements in persons with autism spectrum disorder
Proceedings of the 7th international conference on Interaction design and children - IDC '08, 2008Co-Authors: Matthew S. Goodwin, Stephen S. Intille, Wayne F. Velicer, June GrodenAbstract:Stereotypical motor movements are one of the most common and least understood behaviors occurring in individuals with Autism Spectrum Disorder (ASD). Problems with traditional methods for measuring movement stereotypy make it difficult to accurately determine when and why these behaviors occur. The current research overcomes previous measurement problems by utilizing wireless accelerometers and pattern recognition software to automatically and reliably detect stereotypical motor movements such as Body Rocking and hand flapping in children with ASD.
Gershon Berkson - One of the best experts on this subject based on the ideXlab platform.
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Attitudes Toward Stereotyped Behaviors
Journal of Developmental and Physical Disabilities, 2003Co-Authors: Nilly Mor, Gershon BerksonAbstract:This investigation examined trait inferences that people make of individuals who engage in Body Rocking. In Study 1, participants interacted with either a Rocking or a nonRocking individual. In Study 2, participants observed video-clips of Rocking and nonRocking individuals in various settings. In Study 3, participants observed video-clips of a person engaging in Body-Rocking, head-rolling, or no-stereotyped behavior. Results of the 3 studies suggest that people hold specific negative attitudes toward people who engage in Body-Rocking, and that amplitude of Body-Rocking is a factor in determining these negative attitudes. People tend to attribute Body-Rocking to high-neuroticism and anxiety, and to low-agreeableness.
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Early Development of Stereotyped and Self-Injurious Behaviors: II. Age Trends.
American journal of mental retardation : AJMR, 2002Co-Authors: Gershon BerksonAbstract:Thirty-nine infants who were served in early intervention programs and who engaged in stereotyped or self-injurious behaviors were studied weekly from the time they entered the school until they were 3 years old. The development of these behaviors increased and declined over age more slowly than in typical babies. A few children retained the behaviors for long periods, and some were still showing them when they left the program. The hypothesis that Body-Rocking promotes motor development was not supported. Indeed, Body-Rocking may be a consequence of motor development. Head-banging seemed to be related to tantrums, whereas eye-poking developed early and seemed to be self-stimulatory. Suggestions for early treatment are presented.
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More information on the nature of stereotyped Body-Rocking.
American journal of mental retardation : AJMR, 2001Co-Authors: Gershon Berkson, Tami Andriacchi, Lauren ShermanAbstract:Body-Rocking was exposed to kinematic analysis in two studies. In the first study, amplitude was larger in the natural Body-Rocking of individuals with mental retardation than in the natural Body-Rocking of college students. Variability did not differ. In the second study, natural Body-Rocking of people with mental retardation was compared with their artificial Body-Rocking. Amplitude and variability were larger in the artificial condition. However, this result was not clear. We suggest that group and condition differences might have been a function of practice.
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Early Development of Stereotyped and Self-Injurious Behaviors: I. Incidence
American journal of mental retardation : AJMR, 2001Co-Authors: Gershon Berkson, Megan Tupa, Lauren ShermanAbstract:From five programs with 457 eligible children, 39 children younger than 40 months who had developmental disabilities were studied. Video sampling, observation notes, parent reports, staff reports, and clinical records were the data sources. Twenty-one children, or 4.6% of the total number in the program, exhibited SIBs. Virtually all children in the sample who were motorically capable of it showed Body-Rocking in at least one position. The SIBs were directed mainly toward the head, and Body-Rocking occurred mainly in four-point and seated position.
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Body-Rocking in college students and persons with mental retardation: characteristics, stability, and collateral behaviors.
Research in developmental disabilities, 2000Co-Authors: Gershon Berkson, Tami AndriacchiAbstract:Body-Rocking was analyzed in four studies. The first showed that Rocking chairs are not necessarily preferred by people with mental retardation, and that a Rocking chair produces a higher amplitude of Body-Rocking. A second study demonstrated the stability of various measures of Body-Rocking over a 21-month period. Stable idiosyncratic behaviors accompanying Body-Rocking also were described. The third study showed that, when compared with college students who engage in habitual Body-Rocking, persons with mental retardation engage in more Body-Rocking than college students on various dimensions, and that they also show different collateral behaviors. Finally, in the fourth study, a reanalysis of the data from Study I showed that collateral behaviors do not necessarily occur as part of a Body-Rocking complex.