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https://www.readbyqxmd.com/read/28813876/design-control-and-validation-of-the-variable-stiffness-exoskeleton-flexo
#1
Sariah Mghames, Marco Laghi, Cosimo Della Santina, Manolo Garabini, Manuel Catalano, Giorgio Grioli, Antonio Bicchi
In this paper we present the design of a one degree of freedom assistive platform to augment the strength of upper limbs. The core element is a variable stiffness actuator, closely reproducing the behavior of a pair of antagonistic muscles. The novelty introduced by this device is the analogy of its control parameters with those of the human muscle system, the threshold lengths. The analogy can be obtained from a proper tuning of the mechanical system parameters. Based on this, the idea is to control inputs by directly mapping the estimation of the muscle activations, e...
July 2017: IEEE ... International Conference on Rehabilitation Robotics: [proceedings]
https://www.readbyqxmd.com/read/28808338/a-dynamical-framework-for-complex-fractional-killing
#2
Richard Ballweg, Andrew L Paek, Tongli Zhang
When chemotherapy drugs are applied to tumor cells with the same or similar genotypes, some cells are killed, while others survive. This fractional killing contributes to drug resistance in cancer. Through an incoherent feedforward loop, chemotherapy drugs not only activate p53 to induce cell death, but also promote the expression of apoptosis inhibitors which inhibit cell death. Consequently, cells in which p53 is activated early undergo apoptosis while cells in which p53 is activated late survive. The incoherent feedforward loop and the essential role of p53 activation timing makes fractional killing a complex dynamical challenge, which is hard to understand with intuition alone...
August 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28796509/predicting-thermal-behavior-of-secondary-organic-aerosols
#3
John H Offenberg, Michael Lewandowski, Tadeusz E Kleindienst, Kenneth S Docherty, Mohammed Jaoui, Jonathan Krug, Theran P Riedel, David A Olson
Volume concentrations of secondary organic aerosol (SOA) are measured in 139 steady-state, single precursor hydrocarbon oxidation experiments after passing through a temperature controlled inlet. The response to change in temperature is well predicted through a feedforward Artificial Neural Network. The most parsimonious model, as indicated by Akaike's Information Criterion, Corrected (AIC,C), utilizes 11 input variables, a single hidden layer of 4 tanh activation function nodes, and a single linear output function...
August 10, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28783639/supervised-learning-based-on-temporal-coding-in-spiking-neural-networks
#4
Hesham Mostafa
Gradient descent training techniques are remarkably successful in training analog-valued artificial neural networks (ANNs). Such training techniques, however, do not transfer easily to spiking networks due to the spike generation hard nonlinearity and the discrete nature of spike communication. We show that in a feedforward spiking network that uses a temporal coding scheme where information is encoded in spike times instead of spike rates, the network input-output relation is differentiable almost everywhere...
August 1, 2017: IEEE Transactions on Neural Networks and Learning Systems
https://www.readbyqxmd.com/read/28767379/composite-backstepping-consensus-algorithms-of-leader-follower-higher-order-nonlinear-multiagent-systems-subject-to-mismatched-disturbances
#5
Xiangyu Wang, Shihua Li, Michael Z Q Chen
This paper is devoted to solving the output consensus problem of leader-follower higher-order nonlinear multiagent systems subject to mismatched disturbances. The disturbances are allowed to be in higher-order forms. First, by constructing a generalized proportional-integral observer for each follower, estimates of the disturbances and their derivatives are obtained. At the same time, a distributed observer is also developed for the followers to estimate the leader state information. Second, based on the estimates of the disturbances and the leader state, together with the backstepping technique, a feedforward-feedback composite consensus control scheme is proposed...
July 27, 2017: IEEE Transactions on Cybernetics
https://www.readbyqxmd.com/read/28738310/postural-response-to-predictable-and-nonpredictable-visual-flow-in-children-and-adults
#6
Mark A Schmuckler
Children's (3-5years) and adults' postural reactions to different conditions of visual flow information varying in its frequency content was examined using a moving room apparatus. Both groups experienced four conditions of visual input: low-frequency (0.20Hz) visual oscillations, high-frequency (0.60Hz) oscillations, multifrequency nonpredictable visual input, and no imposed visual information. Analyses of the frequency content of anterior-posterior (AP) sway revealed that postural reactions to the single-frequency conditions replicated previous findings; children were responsive to low- and high-frequency oscillations, whereas adults were responsive to low-frequency information...
November 2017: Journal of Experimental Child Psychology
https://www.readbyqxmd.com/read/28736520/combined-effects-of-feedforward-inhibition-and-excitation-in-thalamocortical-circuit-on-the-transitions-of-epileptic-seizures
#7
Denggui Fan, Lixia Duan, Qian Wang, Guoming Luan
The mechanisms underlying electrophysiologically observed two-way transitions between absence and tonic-clonic epileptic seizures in cerebral cortex remain unknown. The interplay within thalamocortical network is believed to give rise to these epileptic multiple modes of activity and transitions between them. In particular, it is thought that in some areas of cortex there exists feedforward inhibition from specific relay nucleus of thalamus (TC) to inhibitory neuronal population (IN) which has even more stronger functions on cortical activities than the known feedforward excitation from TC to excitatory neuronal population (EX)...
2017: Frontiers in Computational Neuroscience
https://www.readbyqxmd.com/read/28716400/direct-identification-of-generalized-prandtl-ishlinskii-model-inversion-for-asymmetric-hysteresis-compensation
#8
Young-Rae Ko, Yoonkyu Hwang, Minji Chae, Tae-Hyoung Kim
In this study, we present an identification-based direct construction of the inverse generalized Prandtl-Ishlinskii (P-I) model to facilitate inverse model-based feedforward compensation of asymmetric hysteresis nonlinearities. Compared with the derivation of the inverse model analytically from a generalized P-I model, this direct modeling approach has the following advantages. First, direct inverse model identification is formulated as a nonlinear optimization problem, which is not subject to the constraint condition on the generalized P-I model's threshold and density functions, where this is indispensable for the analytical model inversion procedure...
July 14, 2017: ISA Transactions
https://www.readbyqxmd.com/read/28704632/measuring-memory-and-attention-to-preview-in-motion
#9
Richard J Jagacinski, Gordon M Hammond, Emanuele Rizzi
Objective Use perceptual-motor responses to perturbations to reveal the spatio-temporal detail of memory for the recent past and attention to preview when participants track a winding roadway. Background Memory of the recently passed roadway can be inferred from feedback control models of the participants' manual movement patterns. Similarly, attention to preview of the upcoming roadway can be inferred from feedforward control models of manual movement patterns. Method Perturbation techniques were used to measure these memory and attention functions...
August 2017: Human Factors
https://www.readbyqxmd.com/read/28703352/atpds-over-expression-in-tomato-exposing-unique-patterns-of-carotenoid-self-regulation-and-an-alternative-strategy-for-the-enhancement-of-fruit-carotenoid-content
#10
Ryan P McQuinn, Breanna Wong, James J Giovannoni
The regulation of plant carotenogenesis is an active research area for both biological discovery and practical implementation. In tomato (Solanum lycopersicum) we demonstrate additional bottlenecks exist in the poly-cis-transformation of phytoene to lycopene in the context of ripening-induced PSY1 expression and activity, and reveal phytoene desaturase (PDS), as a target for manipulation toward elevated lycopene content in maturing tomato fruit. Over-expression of Arabidopsis PDS, AtPDS, elevated PDS transcript abundance in all aerial tissues resulting in both altered carotenoid accumulation and associated pathway gene expression in a tissue-specific manner...
July 13, 2017: Plant Biotechnology Journal
https://www.readbyqxmd.com/read/28701537/climbing-fibers-predict-movement-kinematics-and-performance-errors
#11
Martha L Streng, Laurentiu S Popa, Timothy J Ebner
Requisite for understanding cerebellar function is a complete characterization of the signals provided by complex spike (CS) discharge of Purkinje cells, the output neurons of the cerebellar cortex. Numerous studies have provided insights into CS function, with the most predominant view being that they are evoked by error events. However, several reports suggest that CSs encode other aspects of movements and do not always respond to errors or unexpected perturbations. Here, we evaluated CS firing during a pseudo-random manual tracking task in the monkey (Macaca mulatta)...
July 12, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28701534/compensating-for-intersegmental-dynamics-across-the-shoulder-elbow-and-wrist-joints-during-feedforward-and-feedback-control
#12
Rodrigo S Maeda, Tyler Cluff, Paul L Gribble, J Andrew Pruszynski
Moving the arm is complicated by mechanical interactions that arise between limb segments. Such intersegmental dynamics cause torques applied at one joint to produce movement at multiple joints. Here, we investigated whether the nervous system accounts for intersegmental limb dynamics across the shoulder, elbow, and wrist joints during self-initiated planar reaching and when countering external mechanical perturbations. Our first experiment tested whether the timing and amplitude of shoulder muscle activity accounts for interaction torques produced during single-joint elbow movements from different elbow initial orientations and over a range of movement speeds...
July 12, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28690340/run-to-run-optimization-control-within-exact-inverse-framework-for-scan-tracking
#13
Ivan L Yeoh, Per G Reinhall, Martin C Berg, Howard J Chizeck, Eric J Seibel
A run-to-run optimization controller uses a reduced set of measurement parameters, in comparison to more general feedback controllers, to converge to the best control point for a repetitive process. A new run-to-run optimization controller is presented for the scanning fiber device used for image acquisition and display. This controller utilizes very sparse measurements to estimate a system energy measure and updates the input parameterizations iteratively within a feedforward with exact-inversion framework...
September 2017: Journal of Dynamic Systems, Measurement, and Control
https://www.readbyqxmd.com/read/28686594/cannabinoids-disrupt-memory-encoding-by-functionally-isolating-hippocampal-ca1-from-ca3
#14
Roman A Sandler, Dustin Fetterhoff, Robert E Hampson, Sam A Deadwyler, Vasilis Z Marmarelis
Much of the research on cannabinoids (CBs) has focused on their effects at the molecular and synaptic level. However, the effects of CBs on the dynamics of neural circuits remains poorly understood. This study aims to disentangle the effects of CBs on the functional dynamics of the hippocampal Schaffer collateral synapse by using data-driven nonparametric modeling. Multi-unit activity was recorded from rats doing an working memory task in control sessions and under the influence of exogenously administered tetrahydrocannabinol (THC), the primary CB found in marijuana...
July 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28681238/impedance-feedback-control-of-microfluidic-valves-for-reliable-post-processing-combinatorial-droplet-injection
#15
Brant Axt, Yi-Fan Hsieh, Divya Nalayanda, Tza-Huei Wang
Droplet microfluidics has found use in many biological assay applications as a means of high-throughput sample processing. One of the challenges of the technology, however, is the ability to control and merge droplets on-demand as they flow through the microdevices. It is in the interest of developing lab-on-chip devices to be able to combinatorically program additive mixing steps for more complex multistep and multiplex assays. Existing technologies to merge droplets are either passive in nature or require highly predictable droplet movement for feedforward control, making them vulnerable to errors during high throughput operation...
September 2017: Biomedical Microdevices
https://www.readbyqxmd.com/read/28652413/dopaminergic-modulation-of-synaptic-integration-and-firing-patterns-in-the-rat-entopeduncular-nucleus
#16
Hagar Lavian, Mara Almog, Ravit Madar, Yocheved Loewenstern, Izhar Bar-Gad, Eitan Okun, Alon Korngreen
Dopamine is known to differentially modulate the impact of cortical input to the striatum between the direct and indirect pathways of the basal ganglia (BG). However, the role of extrastriatal dopamine receptors (DRs) in BG information processing is less clear. To investigate the role of extrastriatal DRs, we studied their distribution and function in one of the output nuclei of the BG of the rodent, the entopeduncular nucleus (EP). qRT-PCR indicated that all DR subtypes were expressed by EP neurons, suggesting that both D1-like receptors (D1LRs) and D2-like receptors (D2LRs) were likely to affect information processing in the EP...
July 26, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28624113/pi-controller-design-for-indirect-vector-controlled-induction-motor-a-decoupling-approach
#17
Jitendra Kr Jain, Sandip Ghosh, Somnath Maity, Pawel Dworak
Decoupling of the stator currents is important for smoother torque response of indirect vector controlled induction motors. Typically, feedforward decoupling is used to take care of current coupling that requires exact knowledge of motor parameters, additional circuitry and signal processing. In this paper, a method is proposed to design the regulating proportional-integral gains that minimize coupling without any requirement of the additional decoupler. The variation of the coupling terms for change in load torque is considered as the performance measure...
June 14, 2017: ISA Transactions
https://www.readbyqxmd.com/read/28617826/cf2-transcription-factor-is-involved-in-the-regulation-of-mef2-rna-levels-nuclei-number-and-muscle-fiber-size
#18
Juan J Arredondo, Jorge Vivar, Sara Laine-Menéndez, Leticia Martínez-Morentin, Margarita Cervera
CF2 and Mef2 influence a variety of developmental muscle processes at distinct stages of development. Nevertheless, the exact nature of the CF2-Mef2 relationship and its effects on muscle building remain yet to be resolved. Here, we explored the regulatory role of CF2 in the Drosophila embryo muscle formation. To address this question and not having proper null CF2 mutants we exploited loss or gain of function strategies to study the contribution of CF2 to Mef2 transcription regulation and to muscle formation...
2017: PloS One
https://www.readbyqxmd.com/read/28611619/hammering-does-not-fit-fitts-law
#19
Tadej Petrič, Cole S Simpson, Aleš Ude, Auke J Ijspeert
While movement is essential to human wellbeing, we are still unable to reproduce the deftness and robustness of human movement in automatons or completely restore function to individuals with many types of motor impairment. To better understand how the human nervous system plans and controls movements, neuromechanists employ simple tasks such as upper extremity reaches and isometric force tasks. However, these simple tasks rarely consider impacts and may not capture aspects of motor control that arise from real-world complexity...
2017: Frontiers in Computational Neuroscience
https://www.readbyqxmd.com/read/28600254/short-and-long-term-learning-of-feedforward-control-of-a-myoelectric-prosthesis-with-sensory-feedback-by-amputees
#20
Matija Strbac, Milica Isakovic, Minja Belic, Igor Popovic, Igor Simanic, Dario Farina, Thierry Keller, Strahinja Dosen
Human motor control relies on a combination of feedback and feedforward strategies. The aim of this study was to longitudinally investigate artificial somatosensory feedback and feedforward control in the context of grasping with myoelectric prosthesis. Nine amputee subjects performed routine grasping trials, with the aim to produce four levels of force during four blocks of 60 trials across five days. The electrotactile force feedback was provided in the second and third block using multipad electrode and spatial coding...
June 6, 2017: IEEE Transactions on Neural Systems and Rehabilitation Engineering
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