Random processes with random transitions between stable states

2019 ◽  
pp. 82-93
Author(s):  
V. I. Khimenko
Keyword(s):  
Probabilistic Analysis ◽  
Information Structure ◽  
Physical Nature ◽  
Random Processes ◽  
High Threshold ◽  
Transition Flow ◽  
Stable States ◽  
Spectral Correlation ◽  
Random Transition ◽  
Wide Range

Introduction: Studying random processes with several stable states and random transitions between them is important because it opens a wide range of practical problems. The detailed information structure is not studied well enough, and there is no unified approach to the description and probabilistic analysis of such processes.Purpose: Studying the main probabilistic characteristics of random processes with two stable states, and probabilistic analysis of control over chaotic transitions under various control actions.Results: We show the ways to represent and preliminarily analyze random processes with two stable states on the phase plane and in the pseudophase space. A general probabilistic model for the processes in question is proposed in the form of a two-component probabilistic «mixture» of distributions. A probabilistic analysis was carried out for the principles of control over random transitions between different states. We have defined the basic probabilistic characteristics for the processes in a management action with a variety of spectral-correlation properties and a changeable threshold for random transitions. The Poisson model of a random transition flow is analyzed with an example of «high» threshold levels.Practical relevance: The methods of visual, qualitative and analytical research in studying dynamic systems with several stable states can be combined. The proposed probabilistic models, regardless of the physical nature of the processes under consideration, can be used in problems of probabilistic analysis, control over probabilistic structure of random transitions, and simulation of physical, technical or biological systems with random switching.

Simulation of Local Surface Modification in STM by ab initio Quantum Chemistry

1998 ◽  
Vol 05 (02) ◽  
pp. 493-499 ◽  
Author(s):  
V. S. Gurin
Keyword(s):  
Surface Modification ◽  
Ab Initio ◽  
Physical Nature ◽  
Atomic Scale ◽  
Level Shift ◽  
Electrical Field ◽  
High Electrical Field ◽  
Wide Range ◽  
Energy Level Shift ◽  
Ab Initio Approach

Surface modification by means of STM has became a well-known method for the artificial formation of nanometer and atomic scale structures. The physical nature of surface modification can consist in a wide range of phenomena (from mechanical indentation up to specific tip-induced chemistry). The high electrical field at the STM tip is considered to be the main feature of STM modification experiments. The field strength is comparable with intramolecular ones and can influence the chemical bonding in surface structures. The model of STM-stimulated modification is considered using the quantum-chemical ab initio approach for a surface cluster in the high electrical field. The destabilization effect, energy level shift, and bond polarization under the STM tip field occur and can show the atomistic nature of surface transformations in STM.

scholarly journals Hierarchical Matching and Regression with Application to Photometric Redshift Estimation

2016 ◽  
Vol 12 (S325) ◽  
pp. 145-155
Author(s):  
Fionn Murtagh
Keyword(s):  
Information Structure ◽  
Data Analytics ◽  
A Priori ◽  
Sloan Digital Sky Survey ◽  
Photometric Redshifts ◽  
Merging Galaxies ◽  
Photometric Redshift ◽  
Sky Survey ◽  
Wide Range ◽  
Regression Problems

AbstractThis work emphasizes that heterogeneity, diversity, discontinuity, and discreteness in data is to be exploited in classification and regression problems. A global a priori model may not be desirable. For data analytics in cosmology, this is motivated by the variety of cosmological objects such as elliptical, spiral, active, and merging galaxies at a wide range of redshifts. Our aim is matching and similarity-based analytics that takes account of discrete relationships in the data. The information structure of the data is represented by a hierarchy or tree where the branch structure, rather than just the proximity, is important. The representation is related to p-adic number theory. The clustering or binning of the data values, related to the precision of the measurements, has a central role in this methodology. If used for regression, our approach is a method of cluster-wise regression, generalizing nearest neighbour regression. Both to exemplify this analytics approach, and to demonstrate computational benefits, we address the well-known photometric redshift or ‘photo-z’ problem, seeking to match Sloan Digital Sky Survey (SDSS) spectroscopic and photometric redshifts.

Differential Expression of Three Distinct Potassium Currents in the Ventral Cochlear Nucleus

2003 ◽  
Vol 89 (6) ◽  
pp. 3070-3082 ◽  
Author(s):  
Jason S. Rothman ◽  
Paul B. Manis
Keyword(s):  
Differential Expression ◽  
Cochlear Nucleus ◽  
Nerve Fibers ◽  
Delayed Rectifier ◽  
High Threshold ◽  
Type I ◽  
Acoustic Environment ◽  
Ventral Cochlear Nucleus ◽  
Wide Range ◽  
Slope Factor

In the ventral cochlear nucleus (VCN), neurons transform information from auditory nerve fibers into a set of parallel ascending pathways, each emphasizing different aspects of the acoustic environment. Previous studies have shown that VCN neurons differ in their intrinsic electrical properties, including the K+ currents they express. In this study, we examine these K+ currents in more detail using whole cell voltage-clamp techniques on isolated VCN cells from adult guinea pigs at 22°C. Our results show a differential expression of three distinct K+ currents. Whereas some VCN cells express only a high-threshold delayed-rectifier-like current ( IHT), others express IHT in combination with a fast inactivating current ( IA) and/or a slow-inactivating low-threshold current ( ILT). IHT, ILT, and IA, were partially blocked by 1 mM 4-aminopyridine. In contrast, only ILT was blocked by 10–100 nM dendrotoxin-I. A surprising finding was the wide range of levels of ILT, suggesting ILT is expressed as a continuum across cell types rather than modally in a particular cell type. IA, on the other hand, appears to be expressed only in cells that show little or no ILT, the Type I cells. Boltzmann analysis shows IHT activates with 164 ± 12 (SE) nS peak conductance, -14.3 ± 0.7 mV half-activation, and 7.0 ± 0.5 mV slope factor. Similar analysis shows ILT activates with 171 ± 22 nS peak conductance, -47.4 ± 1.0 mV half-activation, and 5.8 ± 0.3 mV slope factor.

scholarly journals Stability analysis of a signaling circuit with dual species of GTPase switches

2020 ◽  
Author(s):  
Lucas Martins Stolerman ◽  
Pradipta Ghosh ◽  
Padmini Rangamani
Keyword(s):  
Stability Analysis ◽  
Feedback Loop ◽  
Network Motif ◽  
Bound State ◽  
Steady States ◽  
Eukaryotic Cells ◽  
Nucleotide Exchange ◽  
Organelle Biogenesis ◽  
Stable States ◽  
Wide Range

GTPases are molecular switches that regulate a wide range of cellular processes, such as organelle biogenesis, position, shape, and function, vesicular transport between organelles, and signal transduction. These hydrolase enzymes operate by toggling between an active "ON") guanosine triphosphate (GTP)-bound state and an inactive ("OFF") guanosine diphosphate (GDP)-bound state; such a toggle is regulated by GEFs (guanine nucleotide exchange factors) and GAPs (GTPase activating proteins). Here we propose a model for a network motif between monomeric (m) and trimeric (t) GTPases assembled exclusively in eukaryotic cells of multicellular organisms. We develop a system of ordinary differential equations in which these two classes of GTPases are interlinked conditional to their ON/OFF states within a motif through coupling and feedback loops. We provide explicit formulae for the steady states of the system and perform classical local stability analysis to systematically investigate the role of the different connections between the GTPase switches. Interestingly, a coupling of the active mGTPase to the GEF of the tGTPase was sufficient to provide two locally stable states: one where both active/inactive forms of the mGTPase can be interpreted as having low concentrations and the other where both m- and tGTPase have high concentrations. Moreover, when a feedback loop from the GEF of the tGTPase to the GAP of the mGTPase was added to the coupled system, two other locally stable states emerged, both having the tGTPase inactivated and being interpreted as having low active tGTPase concentrations. Finally, the addition of a second feedback loop, from the active tGTPase to the GAP of the mGTPase, gives rise to a family of steady states that can be parametrized by a range of inactive tGTPase concentrations. Our findings reveal that the coupling of these two different GTPase motifs can dramatically change their steady state behaviors and shed light on how such coupling may impact signaling mechanisms in eukaryotic cells.

scholarly journals Performance of Air-Cooled Heat Exchanger with Laminar, Transitional, and Turbulent Tube Flow

2018 ◽  
Vol 240 ◽  
pp. 02012
Author(s):  
Dawid Taler
Keyword(s):  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Flow ◽  
Friction Factor ◽  
Flow Rate ◽  
Empirical Relationship ◽  
Heat Flow Rate ◽  
Transition Flow ◽  
Water Side ◽  
Wide Range

Some air-cooled heat exchangers, especially in air conditioning and heating installations, heat pumps, as well as car radiators, work in a wide range of loads when the liquid flow in the tubes can be laminar, transitional or turbulent. In this paper, a semi-empirical and empirical relationship for the Nusselt number on the liquid-side in the transitional and turbulent range was derived. The friction factor in the transition flow range Rew,trb ≤ Rew ≤ Rew,tre was calculated by linear interpolation between the values of the friction factor for Rew,trb =2,100 and Rew,tre =3,000. Based on experimental data for a car radiator, empirical heat transfer relationships for the air and water-side were found by using the least squares method. The water temperature at the outlet of the heat exchanger was calculated using P-NTU (effectiveness-number of transfer units) method. The heat flow rate from water to air was calculated as a function of the water flow rate to compare it with the experimental results. The theoretical and empirical correlation for the water-side Nusselt number developed in the paper were used when determining the heat flow rate. The calculation results agree very well with the results of the measurements.

Onset of cellular convection in a salinity gradient due to a lateral temperature gradient

1974 ◽  
Vol 63 (3) ◽  
pp. 563-576 ◽  
Author(s):  
C. F. Chen
Keyword(s):  
Salinity Gradient ◽  
Critical Rayleigh Number ◽  
Time Dependent ◽  
Field Equations ◽  
Stable States ◽  
Critical Wavelength ◽  
Wide Range ◽  
Random Disturbances ◽  
Dependent Flow ◽  
The Stability

We consider the two-dimensional problem of a linearly stratified salt solution contained between two infinite vertical plates. The fluid and the plates are initially at the same temperature. At t = 0, one of the plates is given a step increase in temperature, while the other is maintained at the initial temperature. A time-dependent basic flow is thus generated. The stability of such a time-dependent flow is analysed using an initial value problem approach to the linear stability equations. The method consists of initially distributing small random disturbances of given vertical wavelength throughout the fluid. The disturbances may be in the vorticity, temperature or salinity. The linearized field equations are integrated numerically. The growth or decay of the kinetic energy of the perturbation delineates unstable and stable states. Results have been obtained for a wide range of gap widths. The critical wavelength and the critical Rayleigh number compare favourably with those obtained previously in both physical and numerical experiments.

Information Structure and Presupposition

2015 ◽  
Author(s):  
Kjell Johan Sæbø
Keyword(s):  
Information Structure ◽  
The Core ◽  
Wide Range ◽  
Focus Marking ◽  
Core Points ◽  
The Relationship

This article surveys and discusses the core points of contact between notions of information structure and notions of presupposition. Section 1 is devoted to the ‘weak’ presuppositional semantics for focus developed by Mats Rooth, describing its properties with regard to verification and accommodation and showing that it can successfully account for a wide range of phenomena. Section 2 examines the stronger thesis that focus–background structures give rise to existential presuppositions, and finds the counterarguments that have been raised to carry considerable weight. Section 3 looks into the relationship between Givenness and run-of-the-mill presuppositions, finding that this relationship is looser than might be expected, mainly because a presupposition may be in need of focus marking instead of givenness marking.

scholarly journals Modeling of Natural Convection in Electronic Enclosures

2005 ◽  
Vol 128 (2) ◽  
pp. 157-165 ◽  
Author(s):  
Peter M. Teertstra ◽  
M. Michael Yovanovich ◽  
J. Richard Culham
Keyword(s):  
Natural Convection ◽  
Numerical Data ◽  
Composite Model ◽  
Circuit Board ◽  
Flow Conditions ◽  
Transition Flow ◽  
Cfd Simulations ◽  
Wide Range ◽  
Using Data ◽  
Good Agreement

An analytical model is developed for natural convection from a single circuit board in a sealed electronic equipment enclosure. The circuit card is modeled as a vertical isothermal plate located at the center of an isothermal, cuboid shaped enclosure. A composite model is developed based on asymptotic solutions for three limiting cases: pure conduction, laminar boundary layer convection, and transition flow convection. The conduction shape factor and natural convection models are validated using data from CFD simulations for a wide range of enclosure geometries and flow conditions. The model is shown to be in good agreement, to within 10% RMS, with the numerical data for all test configurations.

Nonlinear stability of mixed convection flow under non-Boussinesq conditions. Part 2. Mean flow characteristics

1999 ◽  
Vol 398 ◽  
pp. 87-108 ◽  
Author(s):  
S. A. SUSLOV ◽  
S. PAOLUCCI
Keyword(s):  
Mixed Convection ◽  
Mass Flux ◽  
Flow Characteristics ◽  
Vertical Channel ◽  
Physical Nature ◽  
Reynolds Numbers ◽  
Convection Flow ◽  
Mixed Convection Flow ◽  
Mean Flow ◽  
Wide Range

Based on amplitude expansions developed in Part 1 (Suslov & Paolucci 1999), we examine the mean flow characteristics of non-Boussinesq mixed convection flow of air in a vertical channel in the vicinity of bifurcation points for a wide range of temperature differences between the walls, and Grashof and Reynolds numbers. The constant mass flux and constant pressure gradient formulations are shown to lead to qualitatively similar, but quantitatively different, results. The physical nature of the distinct shear and buoyancy disturbances is investigated, and detailed mean flow and energy analyses are presented. The variation of the total mass of fluid in a flow domain as disturbances develop is discussed. The average Nusselt number and mass flux are estimated for supercritical regimes for a wide range of governing parameters.

scholarly journals Computing wide range of protein/peptide features from their sequence and structure

2019 ◽  
Author(s):  
Akshara Pande ◽  
Sumeet Patiyal ◽  
Anjali Lathwal ◽  
Chakit Arora ◽  
Dilraj Kaur ◽  
...  
Keyword(s):  
Amino Acid ◽  
Information Structure ◽  
Complete Information ◽  
Low Complexity ◽  
Residue Level ◽  
Amino Acid Sequences ◽  
Evolutionary Information ◽  
Post Translational Modification ◽  
Link Type ◽  
Wide Range

AbstractMotivationIn last three decades, a wide range of protein descriptors/features have been discovered to annotate a protein with high precision. A wide range of features have been integrated in numerous software packages (e.g., PROFEAT, PyBioMed, iFeature, protr, Rcpi, propy) to predict function of a protein. These features are not suitable to predict function of a protein at residue level such as prediction of ligand binding residues, DNA interacting residues, post translational modification etc.ResultsIn order to facilitate scientific community, we have developed a software package that computes more than 50,000 features, important for predicting function of a protein and its residues. It has five major modules for computing; composition-based features, binary profiles, evolutionary information, structure-based features and patterns. The composition-based module allows user to compute; i) simple compositions like amino acid, dipeptide, tripeptide; ii) Properties based compositions; iii) Repeats and distribution of amino acids; iv) Shannon entropy to measure the low complexity regions; iv) Miscellaneous compositions like pseudo amino acid, autocorrelation, conjoint triad, quasi-sequence order. Binary profile of amino acid sequences provides complete information including order of residues or type of residues; specifically, suitable to predict function of a protein at residue level. Pfeature allows one to compute evolutionary information-based features in form of PSSM profile generated using PSIBLAST. Structure based module allows computing structure-based features, specifically suitable to annotate chemically modified peptides/proteins. Pfeature also allows generating overlapping patterns and feature from whole protein or its parts (e.g., N-terminal, C-terminal). In summary, Pfeature comprises of almost all features used till now, for predicting function of a protein/peptide including its residues.AvailabilityIt is available in form of a web server, named as Pfeature (https://webs.iiitd.edu.in/raghava/pfeature/), as well as python library and standalone package (https://github.com/raghavagps/Pfeature) suitable for Windows, Ubuntu, Fedora, MacOS and Centos based operating system.

Sign in / Sign up

Export Citation Format

Share Document