scholarly journals A Computational Model of Phosphene Appearance for Epiretinal Prostheses

2021 ◽  
Author(s):  
Jacob Granley ◽  
Michael Beyeler
Keyword(s):  
Computational Model ◽  
Phenomenological Model ◽  
Retinal Prosthesis ◽  
Fiber Bundles ◽  
Degenerative Diseases ◽  
Stimulus Amplitude ◽  
Visual Effects ◽  
Wide Range ◽  
Temporal Aspects ◽  
Electrical Stimuli

Retinal neuroprostheses are the only FDA-approved treatment option for blinding degenerative diseases. A major outstanding challenge is to develop a computational model that can accurately predict the elicited visual percepts (phosphenes) across a wide range of electrical stimuli. Here we present a phenomenological model that predicts phosphene appearance as a function of stimulus amplitude, frequency, and pulse duration. The model uses a simulated map of nerve fiber bundles in the retina to produce phosphenes with accurate brightness, size, orientation, and elongation. We validate the model on psychophysical data from two independent studies, showing that it generalizes well to new data, even with different stimuli and on different electrodes. Whereas previous models focused on either spatial or temporal aspects of the elicited phosphenes in isolation, we describe a more comprehensive approach that is able to account for many reported visual effects. The model is designed to be flexible and extensible, and can be fit to data from a specific user. Overall this work is an important first step towards predicting visual outcomes in retinal prosthesis users across a wide range of stimuli.

Study on Application of CAD Used in Visual Advertising Design

2014 ◽  
Vol 571-572 ◽  
pp. 768-771
Author(s):  
Jun Liu
Keyword(s):  
Computer Aided Design ◽  
Television Advertising ◽  
Paper Study ◽  
Application Technology ◽  
Visual Effects ◽  
3D Technology ◽  
Wide Range ◽  
Computer Aided ◽  
Visual Impact ◽  
Aided Design

The 3D technology currently has in various engineering fields have a wide range of applications, all the 3D visual effects technology can bring us visual impact, the use of 3D technology produced by the television advertising more easily accepted by the audience, this paper study on the 3D computer-aided design advertising design application technology.

scholarly journals Simulation of P2X-mediated calcium signaling in microglia

2018 ◽  
Author(s):  
Ben Chun ◽  
Bradley D. Stewart ◽  
Darin Vaughan ◽  
Adam D. Bachstetter ◽  
Peter M. Kekenes-Huskey
Keyword(s):  
Computational Model ◽  
Purinergic Receptor ◽  
Receptor Activation ◽  
Quantitative Model ◽  
Published Data ◽  
Transcriptional Responses ◽  
Extracellular Adenosine ◽  
Wide Range ◽  
Intracellular Ca

AbstractMicroglia function is orchestrated through highly-coupled signaling pathways that depend on calcium (Ca2+). In response to extracellular adenosine triphosphate (ATP), transient increases in intracellular Ca2+ driven through the activation of purinergic receptors, P2X and P2Y, are sufficient to promote cytokine synthesis and potentially their release. While steps comprising the pathways bridging purinergic receptor activation with transcriptional responses have been probed in great detail, a quantitative model for how these steps collectively control cytokine production has not been established. Here we developed a minimal computational model that quantitatively links extracellular stimulation of two prominent ionotropic puriner-gic receptors, P2X4 and P2X7, with the graded production of a gene product, namely the tumor necrosis factor α (TNFα) cytokine. In addition to Ca2+ handling mechanisms common to eukaryotic cells, our model includes microglia-specific processes including ATP-dependent P2X4 and P2X7 activation, activation of NFAT transcription factors, and TNFα production. Parameters for this model were optimized to reproduce published data for these processes, where available. With this model, we determined the propensity for TNFα production in microglia, subject to a wide range of ATP exposure amplitudes, frequencies and durations that the cells could encounter in vivo. Furthermore, we have investigated the extent to which modulation of the signal transduction pathways influence TNFα production. Our key findings are that TNFα production via P2X4 is maximized at low ATP when subject to high frequency ATP stimulation, whereas P2X7 contributes most significantly at millimolar ATPranges. Given that Ca2+ homeostasis in microglia is profoundly important to its function, this computational model provides a quantitative framework to explore hypotheses pertaining to microglial physiology.

A New Magnetorheological Mount for Vibration Control

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
David York ◽  
Xiaojie Wang ◽  
Faramarz Gordaninejad
Keyword(s):  
Vibration Control ◽  
Phenomenological Model ◽  
Dynamic Performance ◽  
Small Displacement ◽  
Rectilinear Motion ◽  
Single Degree Of Freedom ◽  
Sdof System ◽  
Single Degree ◽  
Performance Predictions ◽  
Wide Range

In this study, the performance of a new controllable mount design utilizing a magnetorheological material encapsulated in an elastomer matrix is investigated. A magnetorheological fluid-elastomer (MRF-E) mount is designed and fabricated, and its dynamic performance is studied under harmonic oscillatory vibrations for a wide range of frequencies and various applied magnetic fields. Also, a theoretical analysis is conducted by proposing a three-element phenomenological model for replicating the dynamic behavior of the MRF-E mount under oscillation loadings, and the results are compared with the experimental data. In order to further evaluate the effectiveness of the MRF-E mount for vibration control, a single degree-of-freedom (SDOF) system incorporated with this device is developed. Theoretically, the equation of motion utilizing the proposed phenomenological model is derived to provide performance predictions on the effectiveness of the semiactive device at suppressing unwanted vibrations. Experimentally, a SDOF system constrained to rectilinear motion and composed of a mass, four linear springs, and the MRF-E mount is designed and manufactured. This work demonstrates the performance of the proposed MRF-E mount and its capability in attenuating undesirable system vibrations for a range of small-displacement amplitudes and frequencies.

Application of Advertising Based on Computer Aided Visual Design

2014 ◽  
Vol 889-890 ◽  
pp. 125-129
Author(s):  
Wei Xiao
Keyword(s):  
Computer Technology ◽  
Computer Aided Design ◽  
Paper Analysis ◽  
Visual Design ◽  
Visual Effects ◽  
Wide Range ◽  
Computer Aided ◽  
Visual Impact ◽  
Technical Features ◽  
Aided Design

The 3D computer technology has a wide range of applications currently, with various engineering fields. All 3D visual effects can bring us visual impact, the use of 3D computer technology produced by advertising more easily accepted by the audience, this paper discuss the 3D computer-aided design advertising and its application. The paper analysis 3D advertising purposes and applications range scale, the application of technical features and style.

Propeller Cavitation Breakdown Analysis

2005 ◽  
Vol 127 (5) ◽  
pp. 995-1002 ◽  
Author(s):  
Jules W. Lindau ◽  
David A. Boger ◽  
Richard B. Medvitz ◽  
Robert F. Kunz
Keyword(s):  
Multiphase Flow ◽  
Computational Model ◽  
Navier Stokes ◽  
Water Tunnel ◽  
Computational Results ◽  
Cavity Size ◽  
Size And Shape ◽  
Wide Range ◽  
Reynolds Averaged Navier Stokes ◽  
Thrust And Torque

A Reynolds-averaged Navier-Stokes computational model of homogeneous multiphase flow is presented. Cavitation driven thrust and torque breakdown over a wide range of advance ratios is modeled for an open propeller. Computational results are presented as a form of validation against water tunnel measured thrust and torque breakdown for the propeller. Successful validation of the computational model is achieved. Additional observations are made with regards to cavity size and shape as well as cavitation breakdown behavior.

Application of Computer-Aided Visual in Advertising Design

2013 ◽  
Vol 475-476 ◽  
pp. 1517-1521
Author(s):  
Qing Gang Yang ◽  
Meng Zhang ◽  
Chang Xiao
Keyword(s):  
Computer Technology ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Television Advertising ◽  
Application Technology ◽  
Visual Effects ◽  
Wide Range ◽  
Computer Aided ◽  
Visual Impact ◽  
Aided Design

The three-dimensional computer technology currently has in various engineering fields have a wide range of applications, all the three-dimensional visual effects technology can bring us visual impact, the use of three-dimensional computer technology produced by the television advertising more easily accepted by the audience, this thesis in the three-dimensional computer-aided design advertising design application technology.

scholarly journals Responses of Cat Auditory Nerve Fibers to Biphasic Electrical Current Pulses

1987 ◽  
Vol 96 (1_suppl) ◽  
pp. 26-30 ◽  
Author(s):  
E. Javel ◽  
Y. C. Tong ◽  
R. K. Shepherd ◽  
G. M. Clark
Keyword(s):  
Auditory Nerve ◽  
Electrical Response ◽  
Nerve Fibers ◽  
Response Threshold ◽  
Stimulus Pulse ◽  
Current Pulses ◽  
Wide Range ◽  
Auditory Nerve Fibers ◽  
Ganglion Neurons ◽  
Electrical Stimuli

Discharge patterns of single auditory nerve fibers were recorded from normal-hearing cats implanted with a 12-band intracochlear electrode array. Stimuli were biphasic current pulses of specifiable width, amplitude, and rate. Acoustic tuning curves were obtained to determine the cochlear positions of the fibers. Response latencies to electrical stimuli formed two groups. Short latency (0.3 to 0.7 ms) responses were attributed to direct activation of spiral ganglion neurons. At high stimulus intensities, these often exhibited abrupt shifts toward even shorter latencies. Long latency (> 1.5 ms) responses were probably caused by electrophonic activation of functional hair cells. Response thresholds to electrical stimuli depended on a fiber's proximity to the stimulating electrodes, and they did not depend on a fiber's acoustic response threshold or spontaneous discharge rate. High intensity (> 1.5 mA) stimuli could excite fibers over a wide range of characteristic frequencies, even for the narrowest (0.45 mm) electrode separations. Response threshold was an exponentially decreasing function of pulse width for widths up to 300 μs/phase. Fiber discharges were highly phase-locked at all suprathreshold intensities, and saturation discharge rates usually equaled stimulus pulse rates for rates up to at least 800 pulses/s. Dynamic ranges were small (1 to 6 dB), increased with pulse rate, and were uncorrelated with electrical response threshold. Within the dynamic range, shapes of poststimulus time and interspike interval histograms resembled those obtained in response to acoustic stimuli. Depolarization block caused fiber activity to cease in 2 to 5 seconds for sustained stimuli presented at high (> 600 pulses/s) pulse rates and intensities.

scholarly journals Network analysis reveals a distinct axis of macrophage activation in response to conflicting inflammatory cues

2019 ◽  
Author(s):  
Xiaji Liu ◽  
Jingyuan Zhang ◽  
Angela C. Zeigler ◽  
Anders R. Nelson ◽  
Merry L. Lindsey ◽  
...  
Keyword(s):  
Computational Model ◽  
Macrophage Activation ◽  
Expression Profiles ◽  
Interleukin 4 ◽  
Cytokine Signaling ◽  
Arginase 1 ◽  
M2 Polarization ◽  
Wide Range ◽  
Polarization Axis

AbstractMacrophages are subject to a wide range of cytokine and pathogen signals in vivo, which contribute to differential activation and modulation of inflammation. Understanding the response to multiple, often conflicting, cues that macrophages experience requires a network perspective. Here, we integrate data from literature curation and mRNA expression profiles to develop a large-scale computational model of the macrophage signaling network. In response to stimulation across all pairs of 9 cytokine inputs, the model predicted activation along the classic M1-M2 polarization axis but also a second axis of macrophage activation that distinguishes unstimulated macrophages from a mixed phenotype induced by conflicting cues. Along this second axis, combinations of conflicting stimuli, interleukin 4 (IL4) with lipopolysaccharide (LPS), interferon-γ (IFNγ), IFNβ, or tumor necrosis factor-α (TNFα), produced mutual inhibition of several signaling pathways, e.g. nuclear factor κB (NFκB) and signal transducer and activator of transcription 6 (STAT6), but also mutual activation of the phosphoinositide 3-kinases (PI3K) signaling module. In response to combined IFNγ and IL4, the model predicted genes whose expression was mutually inhibited, e.g. inducible nitric oxide synthase (iNOS) and arginase 1 (Arg1), or mutually enhanced, e.g. IL4 receptor-α (IL4Rα) and suppressor of cytokine signaling 1 (SOCS1), which was validated by independent experimental data. Knockdown simulations further predicted network mechanisms underlying functional crosstalk, such as mutual STAT3/STAT6-mediated enhancement of IL4Rα expression. In summary, the computational model predicts that network crosstalk mediates a broadened spectrum of macrophage activation in response to mixed pro- and anti-inflammatory cytokine cues, making it useful for modeling in vivo scenarios.Summary sentenceNetwork modeling of macrophage activation predicts responses to combinations of cytokines along both the M1-M2 polarization axis and a second axis associated with a mixed macrophage activation phenotype.

scholarly journals Interactions among mTORC, AMPK, and SIRT: A Computational Model for Cell Energy Balance and Metabolism

2020 ◽  
Author(s):  
Mehrshad Sadria ◽  
Anita T. Layton
Keyword(s):  
Computational Model ◽  
Chronic Stress ◽  
Metabolic Stress ◽  
Signalling Pathways ◽  
Degenerative Diseases ◽  
Health Span ◽  
Environmental Signals ◽  
Complex Interactions ◽  
Cellular Ageing

AbstractKey proteins such as mTORC, AMPK, and sirtuins are known to play an essential role in the management of metabolic stress and ageing mechanisms. An impairment in these mechanisms is commonly associated with cellular ageing and degenerative diseases. To understand the complex interactions of ageing□related signalling pathways and environmental signals, and the impacts on lifespan and health-span, we developed a computational model of ageing signalling pathways. The model includes (i) the insulin/IGF-1 pathway, which couples energy and nutrient abundance to the execution of cell growth and division, (ii) mTORC1 and amino acid sensors, (iii) the Preiss-Handler and salvage pathways, which regulate the metabolism of NAD+ and the NAD+-consuming factor SIRT1, (iv) the energy sensor AMPK, and (v) transcription factors FOXO and PGC-1α. Key findings include the clinically important role of PRAS40, sestrin2, and diet in the treatment of cancers and other diseases, and a potential link between SIRT1-activating compounds and premature autophagy. The model can be used as an essential component to simulate gene manipulation, therapies (e.g., rapamycin and wortmannin), calorie restrictions, and chronic stress, and to assess their functional implications on longevity and ageing□related diseases.Author SummaryIn cellular ageing, mitochondrial function declines over time, which affects normal mechanisms of cells and organisms and leads to myriad of degenerative diseases and other health problems. To investigate the mechanisms that affect the ageing process, we focus on pathways that play a key role in the management of metabolic stress: the mTORC, AMPK, and sirtuins pathways. Our goal is to understand the complex interactions of ageing and metabolism related signalling pathways and environmental signals, and the impacts on lifespan and health-span. To accomplish that goal, we developed a computational model of signalling pathways related to ageing and metabolism. By conducting model simulations, we have unraveled the clinically important role of PRAS40, sestrin2, and diet in the treatment of cancers and other diseases, and a double-edged sword effect of SIRT1-activating compounds in their use as a health remedy. We view this model as an essential step towards a tool for studying metabolism, longevity, and ageing-related diseases. By extending the present model as appropriate, we can simulate gene manipulation, therapies (e.g., rapamycin and wortmannin), calorie restrictions, and chronic stress,.

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