scholarly journals Modeling the Electro-chemical Properties of Microbial Opsin ChrimsonR for Application to Optogenetics-based Vision Restoration

2018 ◽  
Author(s):  
Quentin Sabatier ◽  
Corentin Joffrois ◽  
Grégory Gauvain ◽  
Joël Chavas ◽  
Didier Pruneau ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Chemical Properties ◽  
Light Stimulation ◽  
Adaptation Mechanism ◽  
Detailed Model ◽  
Precise Control ◽  
Computer Interfaces ◽  
Slow Adaptation ◽  
Response Onset ◽  
Steady State Amplitude

AbstractOptogenetic activation of neurons [1] have greatly contributed to our understanding of how neural circuits operate, and holds huge promise in the field of neural prosthetics, particularly in sensory restoration. The discovery of new channelrhodopsins, Chrimson — which is 45 nm more red-shifted than any previously discovered or engineered channelrhodopsin — and its mutant ChrimsonR with faster kinetics [2] made this technology available for medical applications. However, a detailed model that would be able to accurately reproduce the membrane potential dynamics in cells transfected with ChrimsonR under light stimulation is missing. We address this issue by developing the first model for the electrochemical behavior of ChrimsonR that predicts its conductance in response to arbitrary light stimulation. Our model captures ON and OFF dynamics of the protein for stimuli with frequencies up to 100 Hz and their relationship with the brightness, as well as its activation curve, the steady-state amplitude of the response as a function of light intensity. Additionally, we capture a slow adaptation mechanism at a timescale at the order of minutes. Our model holds for light intensities covering the whole dynamic range of the channel (from response onset to saturation) and for timescales in the order of up to several minutes. This model is a new step towards modeling the spiking activity of ChrimsonR-expressing neurons, required for the precise control of information transmission in optogenetics-based Brain-Computer Interfaces, and will inform future applications of ChrimsonR based optogenetics.

Nanocrystals: The Preparation, Precise Control and Application Toward the Pharmaceutics and Food Industry

2018 ◽  
Vol 24 (21) ◽  
pp. 2425-2431 ◽  
Author(s):  
Cao Wu ◽  
Zhou Chen ◽  
Ya Hu ◽  
Zhiyuan Rao ◽  
Wangping Wu ◽  
...  
Keyword(s):  
Food Industry ◽  
Chemical Properties ◽  
Preparation Methods ◽  
Precise Control ◽  
Significant Process ◽  
Technology Applications ◽  
And Performance ◽  
Physical And Chemical ◽  
Analytical Technology ◽  
And Chemical Properties

Crystallization is a significant process employed to produce a wide variety of materials in pharmaceutical and food area. The control of crystal dimension, crystallinity, and shape is very important because they will affect the subsequent filtration, drying and grinding performance as well as the physical and chemical properties of the material. This review summarizes the special features of crystallization technology and the preparation methods of nanocrystals, and discusses analytical technology which is used to control crystal quality and performance. The crystallization technology applications in pharmaceutics and foods are also outlined. These illustrated examples further help us to gain a better understanding of the crystallization technology for pharmaceutics and foods.

Construction of the Precision Solution Spraying System Based on Single-Axis Servo Control

2014 ◽  
Vol 940 ◽  
pp. 173-178
Author(s):  
Xiao Long Tang ◽  
Chun Ming Geng
Keyword(s):  
Chemical Properties ◽  
Servo Control ◽  
Industrial Processing ◽  
Precise Control ◽  
Mechanical Structure ◽  
Control Precision ◽  
Control Interface ◽  
Sealing Performance ◽  
Translation Stage ◽  
Physical And Chemical

In modern industrial processing of the materials, the solution spraying technology is widely used. Spraying a layer of special solution plays an important role to change their physical and chemical properties. Based on single-axis servo control, precision solution spraying system is able to spray a very thin and a uniform layer of solution on the surface of materials as required. The spraying system mechanical structure is mainly composed of these parts: housing, single-axis servo translation stage, push-pull syringe, multifunctional nozzle and other components. The servo translation stage is capable of providing precise control of speed and stroke by using a specialized controller and driver. The system is running stably and smoothly throughout the experiments after the completion of the entire system assembly and it can fully comply with the requirements of customers with excellent sealing performance, feature-rich and human-friendly control interface and compact mechanical structure.

scholarly journals Expanding the molecular-ruler process through vapor deposition of hexadecanethiol

2017 ◽  
Vol 8 ◽  
pp. 2339-2344 ◽  
Author(s):  
Alexandra M Patron ◽  
Timothy S Hooker ◽  
Daniel F Santavicca ◽  
Corey P Causey ◽  
Thomas J Mullen
Keyword(s):  
Vapor Phase ◽  
Self Assembly ◽  
Chemical Properties ◽  
Solution Deposition ◽  
Precise Control ◽  
Vapor Phase Deposition ◽  
Great Utility ◽  
Complex Architectures ◽  
Molecular Ruler ◽  
Physical And Chemical

The development of methods to produce nanoscale features with tailored chemical functionalities is fundamental for applications such as nanoelectronics and sensor fabrication. The molecular-ruler process shows great utility for this purpose as it combines top-down lithography for the creation of complex architectures over large areas in conjunction with molecular self-assembly, which enables precise control over the physical and chemical properties of small local features. The molecular-ruler process, which most commonly uses mercaptoalkanoic acids and metal ions to generate metal-ligated multilayers, can be employed to produce registered nanogaps between metal features. Expansion of this methodology to include molecules with other chemical functionalities could greatly expand the overall versatility, and thus the utility, of this process. Herein, we explore the use of alkanethiol molecules as the terminating layer of metal-ligated multilayers. During this study, it was discovered that the solution deposition of alkanethiol molecules resulted in low overall surface coverage with features that varied in height. Because features with varied heights are not conducive to the production of uniform nanogaps via the molecular-ruler process, the vapor-phase deposition of alkanethiol molecules was explored. Unlike the solution-phase deposition, alkanethiol islands produced by vapor-phase deposition exhibited markedly higher surface coverages of uniform heights. To illustrate the applicability of this method, metal-ligated multilayers, both with and without an alkanethiol capping layer, were utilized to create nanogaps between Au features using the molecular-ruler process.

Pump Up the Volume: Could Excessive Neural Gain Explain Tinnitus and Hyperacusis?

2015 ◽  
Vol 20 (4) ◽  
pp. 273-282 ◽  
Author(s):  
Hannah Brotherton ◽  
Christopher J. Plack ◽  
Michael Maslin ◽  
Roland Schaette ◽  
Kevin J. Munro
Keyword(s):  
Auditory System ◽  
Dynamic Range ◽  
Sensory Deprivation ◽  
Acoustic Stimulation ◽  
Neural Firing ◽  
Slow Adaptation ◽  
Health And Disease ◽  
Adaptation Processes ◽  
Perceptual Changes ◽  
Neural Gain

Naturally occurring stimuli can vary over several orders of magnitude and may exceed the dynamic range of sensory neurons. As a result, sensory systems adapt their sensitivity by changing their responsiveness or ‘gain'. While many peripheral adaptation processes are rapid, slow adaptation processes have been observed in response to sensory deprivation or elevated stimulation. This adaptation process alters neural gain in order to adjust the basic operating point of sensory processing. In the auditory system, abnormally high neural gain may result in higher spontaneous and/or stimulus-evoked neural firing rates, and this may have the unintended consequence of presenting as tinnitus and/or sound intolerance, respectively. Therefore, a better understanding of neural gain, in health and disease, may lead to more effective treatments for these aberrant auditory perceptions. This review provides a concise summary of (i) evidence for changes in neural gain in the auditory system of animals, (ii) physiological and perceptual changes in adult human listeners following an acute period of enhanced acoustic stimulation and/or deprivation, (iii) physiological evidence of excessive neural gain in tinnitus and hyperacusis patients, and (iv) the relevance of neural gain in the clinical treatment of tinnitus and hyperacusis.

scholarly journals Two Temporal Phases of Light Adaptation in Retinal Rods

2002 ◽  
Vol 119 (2) ◽  
pp. 129-146 ◽  
Author(s):  
Peter D. Calvert ◽  
Victor I. Govardovskii ◽  
Vadim Y. Arshavsky ◽  
Clint L. Makino
Keyword(s):  
Binding Sites ◽  
Time Course ◽  
Light Adaptation ◽  
Dynamic Range ◽  
Continuous Illumination ◽  
Slow Phase ◽  
Fast Phase ◽  
Slow Adaptation ◽  
Adaptation Phase

Vertebrate rod photoreceptors adjust their sensitivity as they adapt during exposure to steady light. Light adaptation prevents the rod from saturating and significantly extends its dynamic range. We examined the time course of the onset of light adaptation in bullfrog rods and compared it with the projected onset of feedback reactions thought to underlie light adaptation on the molecular level. We found that adaptation developed in two distinct temporal phases: (1) a fast phase that operated within seconds after the onset of illumination, which is consistent with most previous reports of a 1–2-s time constant for the onset of adaptation; and (2) a slow phase that engaged over tens of seconds of continuous illumination. The fast phase desensitized the rods as much as 80-fold, and was observed at every light intensity tested. The slow phase was observed only at light intensities that suppressed more than half of the dark current. It provided an additional sensitivity loss of up to 40-fold before the rod saturated. Thus, rods achieved a total degree of adaptation of ∼3,000-fold. Although the fast adaptation is likely to originate from the well characterized Ca2+-dependent feedback mechanisms regulating the activities of several phototransduction cascade components, the molecular mechanism underlying slow adaptation is unclear. We tested the hypothesis that the slow adaptation phase is mediated by cGMP dissociation from noncatalytic binding sites on the cGMP phosphodiesterase, which has been shown to reduce the lifetime of activated phosphodiesterase in vitro. Although cGMP dissociated from the noncatalytic binding sites in intact rods with kinetics approximating that for the slow adaptation phase, this hypothesis was ruled out because the intensity of light required for cGMP dissociation far exceeded that required to evoke the slow phase. Other possible mechanisms are discussed.

scholarly journals Multi-channel Precision Bias Source for Experiments on Quantum dots

2021 ◽  
Author(s):  
yumei tang ◽  
kefu liu ◽  
haixing sun
Keyword(s):  
Quantum Dots ◽  
Response Time ◽  
High Precision ◽  
Dynamic Range ◽  
Step Response ◽  
Precise Control ◽  
Device Application ◽  
Short Time

To realize precise control of the quantum dots (Qdots) device, multi-channel precision bias source plays the key role. In this paper, the 16-channel high precision bias source with 18-bit resolution for Qdots device was designed. The prototype was made and its performance was tested. The short time fluctuations can reach 50μV. The step response time is less than 3μs. The resolution, stability, linearity and dynamic range of the bias source exhibits good performance. What's more, the bias source can be controlled locally and online. The results show that it is one effective and feasible topology for experiments in Qdots device application.

scholarly journals Magnetic field–driven assembly and reconfiguration of multicomponent supraparticles

2020 ◽  
Vol 6 (19) ◽  
pp. eaba5337 ◽  
Author(s):  
A. Al Harraq ◽  
J. G. Lee ◽  
B. Bharti
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Chemical Properties ◽  
Building Blocks ◽  
Precise Control ◽  
Patchy Particles ◽  
Local Arrangement ◽  
Response To Change ◽  
Biological Complexes ◽  
Physical And Chemical

Suprastructures at the colloidal scale must be assembled with precise control over local interactions to accurately mimic biological complexes. The toughest design requirements include breaking the symmetry of assembly in a simple and reversible fashion to unlock functions and properties so far limited to living matter. We demonstrate a simple experimental technique to program magnetic field–induced interactions between metallodielectric patchy particles and isotropic, nonmagnetic “satellite” particles. By controlling the connectivity, composition, and distribution of building blocks, we show the assembly of three-dimensional, multicomponent supraparticles that can dynamically reconfigure in response to change in external field strength. The local arrangement of building blocks and their reconfigurability are governed by a balance of attraction and repulsion between oppositely polarized domains, which we illustrate theoretically and tune experimentally. Tunable, bulk assembly of colloidal matter with predefined symmetry provides a platform to design functional microstructured materials with preprogrammable physical and chemical properties.

Multi-stage hydrogel rockets with stage dropping-off by thermal/light stimulation

2018 ◽  
Vol 6 (35) ◽  
pp. 16838-16843 ◽  
Author(s):  
Yuling Liang ◽  
Yibin Xu ◽  
Wei Ye ◽  
Dahua Yao ◽  
Yunhua Chen ◽  
...  
Keyword(s):  
Light Stimulation ◽  
Precise Control ◽  
Multi Stage ◽  
Thermal Light

A multi-stage hydrogel rocket with precise control of the step-by-step detachment of the hydrogel stage and tunable cargo release ability was fabricated.

Temporal Coding of Contrast in Primary Visual Cortex: When, What, and Why

2001 ◽  
Vol 85 (3) ◽  
pp. 1039-1050 ◽  
Author(s):  
Daniel S. Reich ◽  
Ferenc Mechler ◽  
Jonathan D. Victor
Keyword(s):  
Visual Cortex ◽  
Firing Rate ◽  
Primary Visual Cortex ◽  
Visual Stimulus ◽  
Dynamic Range ◽  
Temporal Structure ◽  
Temporal Coding ◽  
Firing Rates ◽  
Related Information ◽  
Response Onset

How do neurons in the primary visual cortex (V1) encode the contrast of a visual stimulus? In this paper, the information that V1 responses convey about the contrast of static visual stimuli is explicitly calculated. These responses often contain several easily distinguished temporal components, which will be called latency, transient, tonic, and off. Calculating the information about contrast conveyed in each component and in groups of components makes it possible to delineate aspects of the temporal structure that may be relevant for contrast encoding. The results indicate that as much or more contrast-related information is encoded into the temporal structure of spike train responses as into the firing rate and that the temporally coded information is manifested most strongly in the latency to response onset. Transient, tonic, and off responses contribute relatively little. The results also reveal that temporal coding is important for distinguishing subtle contrast differences, whereas firing rates are useful for gross discrimination. This suggests that the temporal structure of neurons' responses may extend the dynamic range for contrast encoding in the primate visual system.

scholarly journals Calcium entry does not drive fast mechanotransduction adaptation in cochlear hair cells

2019 ◽  
Author(s):  
Giusy A. Caprara ◽  
Andrew A. Mecca ◽  
Yanli Wang ◽  
Anthony J. Ricci ◽  
Anthony W. Peng
Keyword(s):  
Hair Cells ◽  
Time Course ◽  
Dynamic Range ◽  
Calcium Entry ◽  
Hair Bundle ◽  
Adaptation Mechanism ◽  
Calcium Dependent ◽  
Sensory Hair Cells ◽  
Adaptation Response ◽  
Fast Adaptation

AbstractSound detection in auditory sensory hair cells depends on the deflection of the stereocilia hair bundle, which opens mechano-electric transduction (MET) channels. Adaptation is hypothesized to be a critical property of MET that contributes to the wide dynamic range and sharp frequency selectivity of the auditory system. Historically, adaptation was hypothesized to have multiple mechanisms, all of which require calcium entry through MET channels. Our recent work using a stiff probe to displace hair bundles showed that the fastest adaptation mechanism (fast adaptation) does not require calcium entry. Using a fluid-jet stimulus, others obtained data showing only a calcium-dependent fast adaptation response. Here, we identified the source of this discrepancy. Because the hair cell response to a hair bundle stimulus depends critically on the magnitude and time course of the hair bundle deflection, we developed a high-speed imaging technique to quantify this deflection. The fluid jet delivers a force stimulus, and step-like force stimuli lead to a complex time course of hair bundle displacement (mechanical creep), which affects the hair cell’s macroscopic MET current response by masking the time course of the fast adaptation response. Modifying the fluid-jet stimulus to generate a step-like hair bundle displacement produced rapidly adapting currents that did not depend on membrane potential. This indicated that fast adaptation does not depend on calcium entry. We also confirmed the presence of a calcium-dependent slow adaptation process. These results confirm the existence of multiple adaptation processes: a fast adaptation that is not driven by calcium entry and a slower calcium-dependent process.Significance StatementMechanotransduction by sensory hair cells represents a key first step for the sound sensing ability in vertebrates. The sharp frequency tuning and wide dynamic range of sound sensation are hypothesized to require a mechanotransduction adaptation mechanism. For decades, it had been accepted that all adaptation mechanisms require calcium entry into hair cells. However, more recent work indicated that the apparent calcium dependence of the fastest adaptation differs with the method of cochlear hair cell stimulation. Here, we reconcile existing data and show that calcium entry does not drive the fastest adaptation process, independent of the stimulation method.

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