scholarly journals Synaptic mechanisms for motor variability in a feedforward network

2020 ◽  
Vol 6 (25) ◽  
pp. eaba4856
Author(s):  
Guo Zhang ◽  
Ke Yu ◽  
Tao Wang ◽  
Ting-Ting Chen ◽  
Wang-Ding Yuan ◽  
...  
Keyword(s):  
State Transition ◽  
Behavioral Variability ◽  
Noise Levels ◽  
Feedforward Network ◽  
Rhythmic Motor ◽  
System A ◽  
Synaptic Noise ◽  
Variable Activity ◽  
Transition Points ◽  
Synaptic Mechanisms

Behavioral variability often arises from variable activity in the behavior-generating neural network. The synaptic mechanisms underlying this variability are poorly understood. We show that synaptic noise, in conjunction with weak feedforward excitation, generates variable motor output in the Aplysia feeding system. A command-like neuron (CBI-10) triggers rhythmic motor programs more variable than programs triggered by CBI-2. CBI-10 weakly excites a pivotal pattern-generating interneuron (B34) strongly activated by CBI-2. The activation properties of B34 substantially account for the degree of program variability. CBI-10– and CBI-2–induced EPSPs in B34 vary in amplitude across trials, suggesting that there is synaptic noise. Computational studies show that synaptic noise is required for program variability. Further, at network state transition points when synaptic conductance is low, maximum program variability is promoted by moderate noise levels. Thus, synaptic strength and noise act together in a nonlinear manner to determine the degree of variability within a feedforward network.

scholarly journals A biomimetic accelerometer inspired by the cricket's clavate hair

2014 ◽  
Vol 11 (97) ◽  
pp. 20140438 ◽  
Author(s):  
H. Droogendijk ◽  
M. J. de Boer ◽  
R. G. P. Sanders ◽  
G. J. M. Krijnen
Keyword(s):  
Resonance Frequency ◽  
Microelectromechanical Systems ◽  
Dynamic Range ◽  
Detection Threshold ◽  
Gravitational Acceleration ◽  
Noise Levels ◽  
Short Term ◽  
Directional Response ◽  
System A ◽  
Short Term Adaptation

Crickets use so-called clavate hairs to sense (gravitational) acceleration to obtain information on their orientation. Inspired by this clavate hair system, a one-axis biomimetic accelerometer has been developed and fabricated using surface micromachining and SU-8 lithography. An analytical model is presented for the design of the accelerometer, and guidelines are derived to reduce responsivity due to flow-induced contributions to the accelerometer's output. Measurements show that this microelectromechanical systems (MEMS) hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 ms −2 and a dynamic range of more than 35 dB. The accelerometer exhibits a clear directional response to external accelerations and a low responsivity to airflow. Further, the accelerometer's physical limits with respect to noise levels are addressed and the possibility for short-term adaptation of the sensor to the environment is discussed.

scholarly journals Dynamic optimal control for groundwater optimization management with covariates

2011 ◽  
Vol 14 (2) ◽  
pp. 386-394 ◽  
Author(s):  
Furong Yu ◽  
Wenxi Lu ◽  
Ping Li ◽  
Xin Xin ◽  
Jun Li
Keyword(s):  
Groundwater Management ◽  
State Transition ◽  
Optimization Methods ◽  
Management Model ◽  
Groundwater System ◽  
Management Models ◽  
System A ◽  
Optimization Management ◽  
Groundwater Management Model ◽  
Programming Algorithms

It is well known that obtaining optimal solutions for groundwater management models with covariates is a challenging task, especially for dynamic planning and management. Here, a theory and method of dealing with mutual-feed joint variation in groundwater management models is described. Specifically, an equation expressing the inherent connection between covariates and groundwater level was developed. This equation was integrated into a mathematical simulation model of groundwater, after which a groundwater dynamic optimization management model with covariates was constructed using the state transition equation method and solved with differential dynamic programming algorithms. Finally, the above theory and method were applied to a hypothetical groundwater system. For the same groundwater system, a groundwater management model with covariates was developed and the results of the two optimization methods were found to be nearly identical, which validated the theory and methods put forth here.

scholarly journals Necessary Conditions for Reliable Representation of Asynchronous Spikes Through a Single-layered Feedforward Network

2019 ◽  
Author(s):  
Milad Lankarany
Keyword(s):  
Firing Rate ◽  
Network Model ◽  
Mean Squared Error ◽  
Time Windows ◽  
Model Neuron ◽  
Network Size ◽  
Feedforward Network ◽  
Synaptic Noise ◽  
Reliable Representation ◽  
Short Time

AbstractReliable propagation of firing rate – specifically slow modulation of asynchronous spikes in fairly short time windows [20-500]ms across multiple layers of a feedforward network (FFN) receiving background synaptic noise has proven difficult to capture in spiking models. We, in this paper, explore how information of asynchronous spikes disrupted in the first layer of a typical FFN, and which factors can enable reliable information representation. Our rationale is that the reliable propagation of information across layers of a FFN is likely if that information can be preserved in the first layer of the FFN. In a typical FFN, each layer comprises a certain number (network size) of excitatory neurons – leaky integrate and fire (LIF) model neuron in this paper – receiving correlated input (common stimulus from the upstream layer) plus independent background synaptic noise. We develop a reduced network model of FFN which captures main features of a conventional all-to-all connected FFN. Exploiting the reduced network model, synaptic weights are calculated using a closed-form optimization framework that minimizes the mean squared error between reconstructed stimulus (by spikes of the first layer of FFN) and the original common stimulus. We further explore how representation of asynchronous spikes in a FFN changes with respect to other factors like the network size and the level of background synaptic noise while synaptic weights are optimized for each scenario. We show that not only synaptic weights but also the network size and the level of background synaptic noise are crucial to preserve a reliable representation of asynchronous spikes in the first layer of a FFN. This work sheds light in better understanding of how information of slowly time-varying fluctuations of the firing rate can be transmitted in multi-layered FFNs.

NOISE-ENHANCED PERFORMANCE IN A CORTICAL ASSOCIATIVE MEMORY MODEL

1995 ◽  
Vol 06 (01) ◽  
pp. 19-29 ◽  
Author(s):  
H. LILJENSTRÖM ◽  
X.-B. WU
Keyword(s):  
Associative Memory ◽  
Biological Significance ◽  
State Transitions ◽  
Noise Levels ◽  
Attractor State ◽  
Temporal Noise ◽  
Recall Time ◽  
Synaptic Noise ◽  
Neural Information ◽  
Neural Information Processing

Spontaneous neuronal activity and synaptic noise are well-known phenomena, but their biological significance has not yet been assessed. Using a computer model of the olfactory cortex we show that such activity, expressed as temporal noise in the model, can reduce recall time in associative memory tasks. We investigate both additive and multiplicative noise, and find optimal noise levels for which the recall time reaches a minimum. In addition, we demonstrate that noise can induce state transitions, such that the system is pushed from one attractor state to another. For high enough noise levels the dynamics can change dramatically and, for example, switch from an oscillatory to a chaos-like behavior. We discuss these findings in light of their significance for neural information processing.

On Stability and Stabilization of Mechanical Structures Under Nonlinear Time-Varying Perturbations

1991 ◽  
Vol 58 (2) ◽  
pp. 527-535
Author(s):  
Chun-Liang Lin ◽  
Bor-Sen Chen ◽  
Fei-Bin Hsiao
Keyword(s):  
Asymptotic Stability ◽  
State Transition ◽  
Time Varying ◽  
Bibo Stability ◽  
Perturbed System ◽  
System A ◽  
Stability And Stabilization ◽  
Norm Bound ◽  
Bounded Input ◽  
Modal Space

Asymptotic stability and bounded-input, bounded-output (BIBO) stability of a class of underdamped mechanical structures with nonlinear time-varying perturbations are studied. An upper norm-bound of the state transition matrix of a normal mode system is derived. We provide a sufficient condition which guarantees both asymptotic stability and BIBO stability for the perturbed system. A straightforward extension to a robust modal-space control is also briefly introduced. Finally, simple illustrative examples are presented for demonstrating the applications of our results

scholarly journals Calprotectin-mediated zinc chelation inhibits Pseudomonas aeruginosa protease activity in cystic fibrosis sputum

2021 ◽  
Author(s):  
Danielle M Vermilyea ◽  
Alex W. Crocker ◽  
Alex H Gifford ◽  
Deborah A. Hogan
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Metal Binding ◽  
Large Fraction ◽  
Zinc Metalloprotease ◽  
System A ◽  
Variable Activity ◽  
Zinc Concentrations ◽  
Zinc Metalloproteases ◽  
Zinc Chelation

Pseudomonas aeruginosa induces pathways indicative of low zinc availability in the cystic fibrosis (CF) lung environment. To learn more about P. aeruginosa zinc access in CF, we grew P. aeruginosa strain PAO1 directly in expectorated CF sputum. The P. aeruginosa Zur transcriptional repressor controls the response to low intracellular zinc, and we used the NanoString methodology to monitor levels of Zur-regulated transcripts including those encoding a zincophore system, a zinc importer, and paralogs of zinc containing proteins that do not require zinc for activity. Zur-controlled transcripts were induced in sputum-grown P. aeruginosa compared to control cultures, but not if the sputum was amended with zinc. Amendment of sputum with ferrous iron did not reduce expression of Zur-regulated genes. A reporter fusion to a Zur-regulated promoter had variable activity in P. aeruginosa grown in sputum from different donors, and this variation inversely correlated with sputum zinc concentrations. Recombinant human calprotectin (CP), a divalent-metal binding protein released by neutrophils, was sufficient to induce a zinc-starvation response in P. aeruginosa grown in laboratory medium or zinc-amended CF sputum indicating that CP is functional in the sputum environment. Zinc metalloproteases comprise a large fraction of secreted zinc-binding P. aeruginosa proteins. Here we show that recombinant CP inhibited both LasB-mediated casein degradation and LasA-mediated lysis of Staphylococcus aureus, which was reversible with added zinc. These studies reveal the potential for CP-mediated zinc chelation to post-translationally inhibit zinc metalloprotease activity and thereby impact the protease-dependent physiology and/or virulence of P. aeruginosa in the CF lung environment.

The Reliability Research of the Good Receipting and being Put in Storage Process of X City's Tobacco Logistics Distribution Center

2013 ◽  
Vol 444-445 ◽  
pp. 1665-1671
Author(s):  
Jie Jin ◽  
Wei Ping Yang
Keyword(s):  
Discrete Model ◽  
State Transition ◽  
Distribution Center ◽  
Analysis Method ◽  
Storage Process ◽  
Logistics System ◽  
Logistics Distribution ◽  
Availability Analysis ◽  
Markov State ◽  
System A

In this paper,X city's tobacco logistics distribution center is taken as a research subject.Firstly,the author used the availability analysis method to do the reliability analysis of the good receipting and being put in the storage process of this logistics system,a discrete model of the system's reliability based on the Markov process was being put forward .Then, the Markov state transition matrix was being worked out in order to get the computational formulas used to work out the steady state effectiveness and the failure rate of this system.Meanwhile, it also evaluated the reliability of this system and gave the improvement suggestions.

Predicting Acoustical Noise Generation in Complex Mechanical Systems

1979 ◽  
Vol 101 (2) ◽  
pp. 199-209 ◽  
Author(s):  
N. D. Perreira ◽  
S. Dubowsky
Keyword(s):  
Analytical Procedure ◽  
Mechanical Systems ◽  
Design Guidelines ◽  
Noise Generation ◽  
Noise Levels ◽  
Fundamental Study ◽  
Acoustic Design ◽  
System A ◽  
Modal Power ◽  
Complex Mechanical Systems

A fundamental study of noise generation in complex mechanical systems is undertaken. The objective of the study is the development of design guidelines for the prediction of mechanical system noise levels. Recently developed dynamical procedures are used to obtain the motions of linked mechanical systems with elastic elements and connection clearances. An analytical procedure for modeling the acoustical noise generated by complex mechanical systems is applied to a typical linked system, a four-bar mechanism. The far field acoustic pressure distribution is calculated and shown to be a function of many of the parameters under the control of the system designer. To aid the designer in producing quieter systems, acoustic design functions are developed. In particular, the system sound power and modal power efficiencies are found to be promising design tools.

Sound Power and Pressure Level Measurements in the Inlet and Outlet of an HRSG Duct

1995 ◽  
Vol 117 (2) ◽  
pp. 259-265
Author(s):  
D. E. Jungbauer ◽  
J. F. Unruh ◽  
S. Rose ◽  
P. J. Pantermuehl
Keyword(s):  
Heat Recovery ◽  
Sound Pressure ◽  
Design Stage ◽  
Pressure Probe ◽  
Noise Attenuation ◽  
Noise Levels ◽  
Steam Generators ◽  
Acoustic Intensity ◽  
Noise Abatement ◽  
System A

The ever-increasing size of cogeneration facilities has mandated the need for noise abatement in the design stage. Many noise projection models are available to the industry for predicting noise levels in and adjacent to new installations. However, the models all require accurate source noise information if valid noise predictions are to be expected. As a consequence of designing one of the world’s largest cogeneration installations involving eight Model W-701 turbine units and their Heat Recovery Steam Generators (HRSGs), it became apparent that the attention between the exhaust of the turbine and the outlet of the HRSGs was not well known. Not having this information posed potentially expensive noise abatement modifications during the design and construction phases. In order to verify the adequacy of scaling studies from a W-501 turbine and HRSG to the W-701 system, a comprehensive field test of an existing W-501 installation was conducted. This paper describes the design of an acoustic intensity and sound pressure probe to operate inside the high-temperature ductwork, the access engineering required, data acquisition, and final results concerning noise attenuation across the HRSG.

New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

1971 ◽  
Vol 29 ◽  
pp. 44-45
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Electron Diffraction ◽  
Water Vapor Pressure ◽  
Biological Materials ◽  
Thin Membrane ◽  
Reliable System ◽  
System A ◽  
Water Films ◽  
Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

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