scholarly journals Calcium Activation of Ryanodine Receptor Channels—Reconciling RyR Gating Models with Tetrameric Channel Structure

2005 ◽  
Vol 126 (5) ◽  
pp. 515-527 ◽  
Author(s):  
Ivan Zahradník ◽  
Sándor Györke ◽  
Alexandra Zahradníková
Keyword(s):  
Experimental Data ◽  
Binding Sites ◽  
Linear Models ◽  
Experimental Studies ◽  
Calcium Sensitivity ◽  
Channel Structure ◽  
Calcium Dependence ◽  
Calcium Dependent ◽  
Monomer Composition ◽  
The Best Approximation

Despite its importance and abundance of experimental data, the molecular mechanism of RyR2 activation by calcium is poorly understood. Recent experimental studies involving coexpression of wild-type (WT) RyR2 together with a RyR2 mutant deficient in calcium-dependent activation (Li, P., and S.R. Chen. 2001. J. Gen. Physiol. 118:33–44) revealed large variations of calcium sensitivity of the RyR tetramers with their monomer composition. Together with previous results on kinetics of Ca activation (Zahradníková, A., I. Zahradník, I. Györke, and S. Györke. 1999. J. Gen. Physiol. 114:787–798), these data represent benchmarks for construction and testing of RyR models that would reproduce RyR behavior and be structurally realistic as well. Here we present a theoretical study of the effects of RyR monomer substitution by a calcium-insensitive mutant on the calcium dependence of RyR activation. Three published models of tetrameric RyR channels were used either directly or after adaptation to provide allosteric regulation. Additionally, two alternative RyR models with Ca binding sites created jointly by the monomers were developed. The models were modified for description of channels composed of WT and mutant monomers. The parameters of the models were optimized to provide the best approximation of published experimental data. For reproducing the observed calcium dependence of RyR tetramers containing mutant monomers (a) single, independent Ca binding sites on each monomer were preferable to shared binding sites; (b) allosteric models were preferable to linear models; (c) in the WT channel, probability of opening to states containing a Ca2+-free monomer had to be extremely low; and (d) models with fully Ca-bound closed states, additional to those of an Monod-Wyman-Changeaux model, were preferable to models without such states. These results provide support for the concept that RyR activation is possible (albeit vanishingly small in WT channels) in the absence of Ca2+ binding. They also suggest further avenues toward understanding RyR gating.

Diagnostics of metal samples using the results of experimental and theoretical study of positively charged microparticles formed upon sample destruction

2018 ◽  
Vol 84 (10) ◽  
pp. 23-28
Author(s):  
D. A. Golentsov ◽  
A. G. Gulin ◽  
Vladimir A. Likhter ◽  
K. E. Ulybyshev
Keyword(s):  
Experimental Data ◽  
Early Stage ◽  
Experimental Studies ◽  
Material Model ◽  
Total Charge ◽  
Cross Sectional ◽  
Practical Applications ◽  
Mechanical And Electrical Properties ◽  
Order Of Magnitude ◽  
Using Data

Destruction of bodies is accompanied by formation of both large and microscopic fragments. Numerous experiments on the rupture of different samples show that those fragments carry a positive electric charge. his phenomenon is of interest from the viewpoint of its potential application to contactless diagnostics of the early stage of destruction of the elements in various technical devices. However, the lack of understanding the nature of this phenomenon restricts the possibility of its practical applications. Experimental studies were carried out using an apparatus that allowed direct measurements of the total charge of the microparticles formed upon sample rupture and determination of their size and quantity. The results of rupture tests of duralumin and electrical steel showed that the size of microparticles is several tens of microns, the particle charge per particle is on the order of 10–14 C, and their amount can be estimated as the ratio of the cross-sectional area of the sample at the point of discontinuity to the square of the microparticle size. A model of charge formation on the microparticles is developed proceeding from the experimental data and current concept of the electron gas in metals. The model makes it possible to determine the charge of the microparticle using data on the particle size and mechanical and electrical properties of the material. Model estimates of the total charge of particles show order-of-magnitude agreement with the experimental data.

An investigation of effects of level density models and gamma ray strength functions on cross-section calculations for the production of 90Y, 153Sm, 169Er, 177Lu and 186Re therapeutic radioisotopes via (n,γ) reactions

2019 ◽  
Vol 108 (1) ◽  
pp. 11-17
Author(s):  
Mert Şekerci ◽  
Hasan Özdoğan ◽  
Abdullah Kaplan
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Production Cross Section ◽  
Gamma Ray ◽  
Production Cross ◽  
Level Density ◽  
Experimental Studies ◽  
Level Density Models ◽  
Strength Functions ◽  
Cancer Diseases

Abstract One of the methods used to treat different cancer diseases is the employment of therapeutic radioisotopes. Therefore, many clinical, theoretical and experimental studies are being carried out on those radioisotopes. In this study, the effects of level density models and gamma ray strength functions on the theoretical production cross-section calculations for the therapeutic radioisotopes 90Y, 153Sm, 169Er, 177Lu and 186Re in the (n,γ) route have been investigated. TALYS 1.9 code has been used by employing different level density models and gamma ray strength functions. The theoretically obtained data were compared with the experimental data taken from the literature. The results are presented graphically for better interpretation.

Microemulsion Phase Behavior Observations, Thermodynamic Essentials, Mathematical Simulation

1981 ◽  
Vol 21 (06) ◽  
pp. 747-762 ◽  
Author(s):  
Karl E. Bennett ◽  
Craig H.K. Phelps ◽  
H. Ted Davis ◽  
L.E. Scriven
Keyword(s):  
Experimental Data ◽  
Phase Behavior ◽  
Experimental Studies ◽  
Mathematical Framework ◽  
Alkyl Aryl Sulfonate ◽  
Phase Volume ◽  
Displacement Efficiency ◽  
Alkyl Aryl ◽  
Theoretical Understanding ◽  
Tie Lines

Abstract The phase behavior of microemulsions of brine, hydrocarbon, alcohol, and a pure alkyl aryl sulfonate-sodium 4-(1-heptylnonyl) benzenesulfonate (SHBS or Texas 1) was investigated as a function of the concentration of salt (NaCl, MgCl2, or CaCl2), the hydrocarbon (n-alkanes, octane to hexadecane), the alcohol (butyl and amyl isomers), the concentration of surfactant, and temperature. The phase behavior mimics that of similar systems with the commercial surfactant Witco TRS 10–80. The phase volumes follow published trends, though with exceptions.A mathematical framework is presented for modeling phase behavior in a manner consistent with the thermodynamically required critical tie lines and plait point progressions from the critical endpoints. Hand's scheme for modeling binodals and Pope and Nelson's approach to modeling the evolution of the surfactant-rich third phase are extended to satisfy these requirements.An examination of model-generated progressions of ternary phase diagrams enhances understanding of the experimental data and reveals correlations of relative phase volumes (volume uptakes) with location of the mixing point (overall composition) relative to the height of the three-phase region and the locations of the critical tie lines (critical endpoints and conjugate phases). The correlations account, on thermodynamic grounds, for cases in which the surfactant is present in more than one phase or the phase volumes change discontinuously, both cases being observed in the experimental study. Introduction The phase behavior of a surfactant-based micellar formulation is one of the major factors governing the displacement efficiency of any chemical flooding process employing that formulation. Knowledge of phase behavior is, thus, important for the interpretation of laboratory core floods, the design of flooding processes, and the evaluation of field tests. Phase behavior is connected intimately with other determinants of the flooding process, such as interfacial tension and viscosity. Since the number of equilibrium phases and their volumes and appearances are easier to measure and observe than phase compositions, viscosities, and interfacial tensions, there is great interest in understanding the phase-volume/phase-property relationships. Commercial surfactants, such as Witco TRS 10-80, are sulfonates of crude or partially refined oil. While they seem to be the most economically practicable surfactants for micellar flooding, their behavior, particularly with crude oils and reservoir brines, can be difficult to interpret, the phases varying with time and from batch to batch. Phase behavior studies with a small number of components, in conjunction with a theoretical understanding of phase behavior progressions, can aid in understanding more complex behavior. In particular, one can begin to appreciate which seemingly abnormal experimental observations (e.g., surfactant present in more than one phase or a discontinuity in phase volume trends) are merely features of certain regions of any phase diagram and which are peculiar to the specific crude oil or commercial surfactant used in the study.We report here experimental studies of the phase behavior of microemulsions of a pure sulfonate surfactant (Texas 1), a single normal alkane hydrocarbon, a simple brine, and a small amount of a suitable alcohol as cosurfactant or cosolvent. The controlled variables are hydrocarbon chain length, alcohol, salinity, salt type (NaCl, MgCl2, or CaCl2), surfactant purity, surfactant concentration, and temperature. Many of these experimental data were presented earlier. SPEJ P. 747^

Quantitative Models of Motor Responses Subject to Longitudinal, Lateral, and Preview Constraints

1978 ◽  
Vol 20 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Tarald O. Kvålseth
Keyword(s):  
Experimental Data ◽  
Motor Control ◽  
Linear Models ◽  
Movement Time ◽  
Arm Movements ◽  
Second Order ◽  
Motor Responses ◽  
First Order ◽  
Different Types ◽  
Index Of Difficulty

First- and second-order linear models of mean movement time for serial arm movements aimed at a target and subject to preview constraints and lateral constraints were formulated as extensions of the so-called Fitts's law of motor control. These models were validated on the basis of experimental data from five subjects and found to explain from 80% to 85% of the variation in movement time in the case of the first-order models and from 93% to 95% of such variation for the second-order models. Fitts's index of difficulty (ID) was generally found to contribute more to the movement time than did either the preview ID or the lateral ID defined. Of the different types of errors, target overshoots occurred far more frequently than undershoots.

Hybrid Analysis of Gas Annular Seals With Energy Equation

2013 ◽  
Author(s):  
Patrick J. Migliorini ◽  
Alexandrina Untaroiu ◽  
William C. Witt ◽  
Neal R. Morgan ◽  
Houston G. Wood
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Energy Equation ◽  
Flow Analysis ◽  
Experimental Studies ◽  
Rotor System ◽  
Bulk Flow ◽  
Outlet Temperature ◽  
Cfd Analysis ◽  
Annular Seals

Annular seals are used in turbomachinery to reduce secondary flow between regions of high and low pressure. In a vibrating rotor system, the non-axisymmetric pressure field developed in the small clearance between the rotor and the seal generate reactionary forces that can affect the stability of the entire rotor system. Traditionally, two analyses have been used to study the fluid flow in seals, bulk-flow analysis and computational fluid dynamics (CFD). Bulk-flow methods are computational inexpensive, but solve simplified equations that rely on empirically derived coefficients and are moderately accurate. CFD analyses generally provide more accurate results than bulk-flow codes, but solution time can vary between days and weeks. For gas damper seals, these analyses have been developed with the assumption that the flow can be treated as isothermal. Some experimental studies show that the difference between the inlet and outlet temperature temperatures is less than 5% but initial CFD studies show that there can be a significant temperature change which can have an effect on the density field. Thus, a comprehensive analysis requires the solution of an energy equation. Recently, a new hybrid method that employs a CFD analysis for the base state, unperturbed flow and a bulk-flow analysis for the first order, perturbed flow has been developed. This method has shown to compare well with full CFD analysis and experimental data while being computationally efficient. In this study, the previously developed hybrid method is extended to include the effects of non-isothermal flow. The hybrid method with energy equation is then compared with the isothermal hybrid method and experimental data for several test cases of hole-pattern seals and the importance of the use of energy equation is studied.

Effect of Boundary Layer Suction on Aerodynamic Performance of High-Turning Compressor Cascade

2013 ◽  
Author(s):  
Longxin Zhang ◽  
Shaowen Chen ◽  
Hao Xu ◽  
Jun Ding ◽  
Songtao Wang
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Parameter Distribution ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
End Wall ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

Compared with suction slots, suction holes are (1) flexible in distribution; (2) alterable in size; (3) easy to fabricate and (4) high in strength. In this paper, the numerical and experimental studies for a high turning compressor cascade with suction air removed by using suction holes in the end-wall at a low Mach numbers are carried out. The main objective of the investigation is to study the influence of different suction distributions on the aerodynamic performance of the compressor cascade and to find a better compound suction scheme. A numerical model was first made and validated by comparing with the experimental results. The computed flow visualization and exit parameter distribution showed a good agreement with experimental data. Second, the model was then used to simulate the influence of different suction distributions on the aerodynamic performance of the compressor cascade. A better compound suction scheme was obtained by summarizing numerical results and tested in a low speed wind tunnel. As a result, the compound suction scheme can be used to significantly improve the performance of the compressor cascade because the corner separation gets further suppressed.

The search of CAR, AhR, ESRs binding sites in promoters of intronic and intergenic microRNAs

2018 ◽  
Vol 16 (01) ◽  
pp. 1750029 ◽  
Author(s):  
Vladimir Y. Ovchinnikov ◽  
Denis V. Antonets ◽  
Lyudmila F. Gulyaeva
Keyword(s):  
Transcriptional Activation ◽  
Binding Sites ◽  
In Silico ◽  
Target Genes ◽  
Nuclear Translocation ◽  
Regulation Of Gene Expression ◽  
Experimental Studies ◽  
Transcriptional Level ◽  
Aryl Hydrocarbon ◽  
Exogenous Compounds

MicroRNAs (miRNAs) play important roles in the regulation of gene expression at the post-transcriptional level. Many exogenous compounds or xenobiotics may affect microRNA expression. It is a well-established fact that xenobiotics with planar structure like TCDD, benzo(a)pyrene (BP) can bind aryl hydrocarbon receptor (AhR) followed by its nuclear translocation and transcriptional activation of target genes. Another chemically diverse group of xenobiotics including phenobarbital, DDT, can activate the nuclear receptor CAR and in some cases estrogen receptors ESR1 and ESR2. We hypothesized that such chemicals can affect miRNA expression through the activation of AHR, CAR, and ESRs. To prove this statement, we used in silico methods to find DRE, PBEM, ERE potential binding sites for these receptors, respectively. We have predicted AhR, CAR, and ESRs binding sites in 224 rat, 201 mouse, and 232 human promoters of miRNA-coding genes. In addition, we have identified a number of miRNAs with predicted AhR, CAR, and ESRs binding sites that are known as oncogenes and as tumor suppressors. Our results, obtained in silico, open a new strategy for ongoing experimental studies and will contribute to further investigation of epigenetic mechanisms of carcinogenesis.

Photobiological safety of lamps and lamp systems in agriculture

2021 ◽  
Vol 1 (106) ◽  
pp. 34-41
Author(s):  
A. Semenov ◽  
T. Sakhno ◽  
Y. Sakhno
Keyword(s):  
Experimental Data ◽  
Design Methodology ◽  
Risk Group ◽  
Experimental Studies ◽  
Safety Measures ◽  
Safety Requirements ◽  
Labor Safety ◽  
Uv Lamps ◽  
Practical Implications ◽  
Additional Safety

Purpose: The article aims to study the photobiological safety of ultraviolet radiation of UV lamps in agriculture. Design/methodology/approach: The research and analysis of the lighting characteristics of samples of LUF 80 and LE 30 lamps, which are the most widely used in the agrarian complex. Findings: Experimental studies have shown that the photobiological safety of LUF 80 lamps belongs to the low-risk group RG1, while LE 30 lamps show high risk and are thus assigned to group RG3. Research limitations/implications: It is advisable to continue studying the characteristics of lamps and lamp systems for various fields of agriculture on the market in Ukraine to assess their compliance with safety requirements. Practical implications: The application of the proposed approach allows increasing the level of labor safety in commercial greenhouses or any other industry by choosing the suitable lamps for agriculture that at present are not regulated by additional safety measures. Originality/value: The originality of the article is showing the results of the experimental data of the studies of light-technical characteristics of ultraviolet lamps for agriculture.

Concentration Dependence of the Surface Tension of Three and Four-Component Systems with Peculiarities in the Surface Tension Isotherms of Lateral Binary Melts

2021 ◽  
Vol 1022 ◽  
pp. 194-202
Author(s):  
R.Kh. Dadashev ◽  
R.A. Kutuev
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Concentration Dependence ◽  
Experimental Error ◽  
Binary Systems ◽  
Experimental Studies ◽  
Study Results ◽  
Component Systems ◽  
Minimum Depth ◽  
Surface Tension Isotherms

The experimental study results of the melts concentration dependence of the surface tension of the four-component indium-tin-lead-bismuth system and its constituent binary systems of indium-tin, indium-lead, indium-bismuth, tin-lead, tin-bismuth, lead-bismuth are presented in the paper. It is shown that the concentration dependence of the melts surface tension of the In-Sn-Pb-Bi four-component system can be predicted from the data on ST (surface tension) values of lateral binary systems. Features in the ST isotherms in the form of a minimum are observed only in the indium-tin lateral system from all lateral binaries. A distinctive feature of the detected minimum is that the minimum depth slightly exceeds the experimental error. Therefore, in addition to the fact that the area of average compositions was studied more thoroughly, we carried out the surface tension measurements by two independent methods. The experimental data obtained by both methods coincide within the experimental error and indicate the extremum availability on ST isotherms. Thus, ST experimental studies by two independent methods confirmed the presence of a flat minimum on ST isotherms of the indium-tin binary system increasing the reliability of the obtained data. The obtained outcomes and their comparison with experimental data have shown that the considered models for predicting surface properties based on data due to similar properties of lateral binary systems adequately reflect the experimental dependences. However, the prediction model based on Kohler's method of excess values describes the experimental curves more accurately.

Kinetics of hypso anhydrites dissolution in water. Experimental studies

2019 ◽  
pp. 93-96
Author(s):  
A. L. Lebedev ◽  
I. V. Avilina
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Riccati Equation ◽  
Balance Equation ◽  
Experimental Studies ◽  
Common Ion ◽  
The Common ◽  
Common Ion Effect ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

Experimental study of kinetics of dissolution of hypso anhydrites at 25 ᵒC made it possible to formulate model of the process in the form of a balance equation for the kinetics of dissolution of gypsum, anhydrite (first and second orders, respectively) and kinetics of precipitation of gypsum (second order). The processing of the experimental data were carried out on the basis of the solution of the Riccati equation. When taking into account the common-ion effect on the solubility of gypsum and anhydrite, the calculated values turned out to be more comparable with the experimental ones.

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