How spatial heterogeneity shapes multiscale biochemical reaction network dynamics

Spatial heterogeneity in cells can be modelled using distinct compartments connected by molecular movement between them. In addition to movement, changes in the amount of molecules are due to biochemical reactions within compartments, often such that some molecular types fluctuate on a slower timescale than others. It is natural to ask the following questions: how sensitive is the dynamics of molecular types to their own spatial distribution, and how sensitive are they to the distribution of others? What conditions lead to effective homogeneity in biochemical dynamics despite heterogeneity in molecular distribution? What kind of spatial distribution is optimal from the point of view of some downstream product? Within a spatially heterogeneous multiscale model, we consider two notions of dynamical homogeneity (full homogeneity and homogeneity for the fast subsystem), and consider their implications under different timescales for the motility of molecules between compartments. We derive rigorous results for their dynamics and long-term behaviour, and illustrate them with examples of a shared pathway, Michaelis–Menten enzymatic kinetics and autoregulating feedbacks. Using stochastic averaging of fast fluctuations to their quasi-steady-state distribution, we obtain simple analytic results that significantly reduce the complexity and expedite simulation of stochastic compartment models of chemical reactions.

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Spatial Distribution of Local Permeabilities in Fibrous Networks

Textile Research Journal ◽

10.1177/004051759206200306 ◽

1992 ◽

Vol 62 (3) ◽

pp. 151-161 ◽

Cited By ~ 14

Author(s):

Susan M. Montgomery ◽

Bernard Miller ◽

Ludwig Rebenfeld

Keyword(s):

Spatial Distribution ◽

Spatial Heterogeneity ◽

Heterogeneous Networks ◽

Flow Direction ◽

Time Dependent ◽

Dependent Development ◽

Fabric Structure ◽

Elliptical Flow ◽

Fluid Boundary ◽

Liquid Flows

The shape of a developing radial fluid boundary in the plane of a fabric is a reflection of the structure of the fabric. Homogeneous fabrics, with permeabilities independent of position, yield circular or elliptical flow fronts, depending on the existence of a universally preferred flow direction. Heterogeneous networks yield flow fronts that deviate from this elliptical shape due to spatial variations in permeability. The time-dependent development of the fluid front that occurs when liquid flows radially in the plane of a fabric may be analyzed using Darcy's law to calculate local fabric permeabilities. The resulting spatial distribution of permeabilities is representative of the spatial heterogeneity of the fabric structure. Sample permeability distributions of geotextile fabrics are discussed.

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Trailing back from quasi decentralisation to centralisation. Municipal reform in Hungary

Wschodnioznawstwo ◽

10.4467/20827695wsc.20.007.13335 ◽

2020 ◽

Vol 14 ◽

pp. 117-137

Author(s):

László Kákai

Keyword(s):

Spatial Distribution ◽

Public Administration ◽

Service Provision ◽

Point Of View ◽

Direct Impact ◽

Municipal Reform ◽

Distribution Of Power ◽

State Organization ◽

Centralization And Decentralization

Trailing back from quasi decentralisation to centralisation. Municipal reform in Hungary It is very difficult to group countries and state structures according to the extent of their decentralization or the model they follow in the spatial distribution of power. The bounds of responsibility of local government and the state, the distribution of the roles and tasks between the two stakeholders and the question of centralization and decentralization are issues regularly debated in recent years and today. This topic is not merely a public administration, financial or state organization issue since these decisions have a direct impact on citizens’ lives through public services. In my study I wish to introduce this process via Hungary’s example. I also examine how and what those concerned by the financial and political changes, i.e. the population perceived of this most important structural transformation of the period since the transition in 1989. Can it be verified from the consumers’ point of view that the transformation of the local municipal system improves the quality of service provision?

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Building reaction kinetic models for amiloid fibril growth

BIOMATH ◽

10.11145/j.biomath.2016.07.311 ◽

2016 ◽

Vol 5 (1) ◽

pp. 1607311 ◽

Cited By ~ 1

Author(s):

Svetoslav Marinov Markov

Keyword(s):

Computer Algebra ◽

Computer Algebra System ◽

Reaction Kinetic ◽

Growth Models ◽

Reaction Network ◽

Network Models ◽

Point Of View ◽

Logistic Growth ◽

Sigmoidal Functions ◽

Methodological Aspects

In this work we discuss some methodological aspects of the creation and formulation of mathematical models describing the growth of species from the point of view of reaction kinetics. Our discussion is based on familiar examples of growth models such as logistic growth and enzyme kinetics. We propose several reaction network models for the amiloid fibrillation processes in the citoplasm. The solutions of the models are sigmoidal functions graphically visualized using the computer algebra system Mathematica.

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Modeling of spatial distribution of passenger traffi c on interurban bus routes

Innotrans ◽

10.20291/2311-164x-2020-4-31-36 ◽

2020 ◽

pp. 31-36

Author(s):

Alexander V. Martynenko ◽

◽

Alexander A. Shevtsov ◽

Keyword(s):

Spatial Distribution ◽

Quantitative Description ◽

Point Of View ◽

Practical Point ◽

Ticket Price ◽

Passenger Traffic ◽

Correlation And Regression Analysis ◽

Classical Gravity ◽

Bus Service

This paper is devoted to the quantitative description of the spatial distribution of passenger traffic based on the classical gravity model on the example of interurban bus service between Yekaterinburg and other cities of the Sverdlovsk region. The influence of factors such as population, distance between localities, and ticket price on the volume of passenger traffic was studied. As a result of the correlation and regression analysis, it was found that both the distance between localities and the ticket price can be used as a measure of the remoteness of localities. However, the quality of the resulting regression model does not change. The spatial distribution of interurban bus passenger traffic depends on the measure of distance of localities from each other and the size of their population. Moreover, the size of the population is a much more significant factor than the measure of distance. From a practical point of view, this means that when predicting passenger traffic, demographic factors must first be taken into account.

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Identification of Dominant Factors Affecting Soil Erosion and Water Yield within Ecological Red Line Areas

Remote Sensing ◽

10.3390/rs12030399 ◽

2020 ◽

Vol 12 (3) ◽

pp. 399 ◽

Cited By ~ 2

Author(s):

Jiangbo Gao ◽

Yuan Jiang ◽

Huan Wang ◽

Liyuan Zuo

Keyword(s):

Land Use ◽

Spatial Distribution ◽

Soil Erosion ◽

Spatial Heterogeneity ◽

Remote Sensing Data ◽

Vegetation Coverage ◽

Water Yield ◽

Land Use Type ◽

Functional Areas ◽

Red Line

Soil conservation and water retention are important metrics for designating key ecological functional areas and ecological red line (ERL) areas. However, research on the quantitative identification of dominant environmental factors in different ecological red line areas remains relatively inadequate, which is unfavorable for the zone-based management of ecological functional areas. This paper presents a case study of Beijing’s ERL areas. In order to objectively reflect the ecological characteristics of ERL areas in Beijing, which is mainly dominated by mountainous areas, the application of remote sensing data at a high resolution is important for the improvement of model calculation and spatial heterogeneity. Based on multi-source remote sensing data, meteorological and soil observations as well as soil erosion and water yield were calculated using the revised universal soil loss equation (RUSLE) and integrated valuation of ecosystem services and tradeoffs (InVEST) model. Combining the influencing factors, including slope, precipitation, land use type, vegetation coverage, geomorphological type, and elevation, a quantitative attribution analysis was performed on soil erosion and water yield in Beijing’s ERL areas using the geographical detector. The power of each influencing factor and their interaction factors in explaining the spatial distribution of soil erosion or water yield varied significantly among different ERL areas. Vegetation coverage was the dominant factor affecting soil erosion in Beijing’s ERL areas, explaining greater than 30% of its spatial heterogeneity. Land use type could explain the spatial heterogeneity of water yield more than 60%. In addition, the combination of vegetation coverage and slope was found to significantly enhance the spatial distribution of soil erosion (>55% in various ERL areas). The superposition of land use type and slope explained greater than 70% of the spatial distribution for water yield in ERL areas. The geographical detector results indicated that the high soil erosion risk areas and high water yield areas varied significantly among different ERL areas. Thus, in efforts to enhance ERL protection, focus should be placed on the spatial heterogeneity of soil erosion and water yield in different ERL areas.

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Production of highly ionized plasma by micro-dot array irradiation and its application to compact X-ray lasers

Laser and Particle Beams ◽

10.1017/s026303460220110x ◽

2002 ◽

Vol 20 (1) ◽

pp. 73-77 ◽

Cited By ~ 3

Author(s):

NAOHIRO YAMAGUCHI ◽

CHIEMI FUJIKAWA ◽

KAZUNOBU OKASAKA ◽

TAMIO HARA

Keyword(s):

Spatial Distribution ◽

Spatial Structure ◽

Pulse Train ◽

Production Method ◽

Point Of View ◽

Rapid Expansion ◽

Laser Generation ◽

Plasma Production ◽

X Ray ◽

Laser Gain

A plasma production method using the irradiation of an array of small spots has been investigated from the point of view of soft X-ray laser generation in the recombining plasma scheme pumped by a pulse-train laser. The expansion geometry of highly ionized ions produced by the micro-dot array irradiation method has been measured and compared with that by a simple line irradiation. Spatial distribution of gain coefficients of the Li-like Al ion transition lines have also been measured for both irradiation methods. Highly ionized ions were observed to spread wider in the micro-dot array irradiation method. It is expected that rapid expansion and efficient cooling are achieved in plasmas produced by the micro-dot array irradiation method, which is consistent with the experimental results on the spatial structure of the X-ray laser gain region.

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Identification of spatial magnetic inhomogeneities by nuclear forward scattering of synchrotron radiation

Journal of Synchrotron Radiation ◽

10.1107/s1600577519005344 ◽

2019 ◽

Vol 26 (4) ◽

pp. 1310-1315

Author(s):

Vlastimil Vrba ◽

Vít Procházka ◽

Marcel Miglierini

Keyword(s):

Spatial Distribution ◽

Magnetic Moments ◽

Theoretical Description ◽

Forward Scattering ◽

Point Of View ◽

Experimental Point ◽

Nuclear Forward Scattering ◽

Magnetic Inhomogeneities ◽

Geometric Arrangements ◽

Scattering Time

Spatially confined magnetic inhomogeneities were revealed by measuring nuclear forward scattering time spectra on the same sample in two different geometric arrangements. They differ by 180° rotation of the sample around one of the polarization axes. A basic theoretical description of this phenomenon and its relation to a spatial distribution of nuclei featuring different magnetic moments is provided. From an experimental point of view, the violation of rotational invariance was observed for an inhomogeneous Fe81Mo8Cu1B10 metallic glass. The development of magnetic inhomogeneities and their relation to the evolution of time spectra was studied during thermal annealing.

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