scholarly journals A Ratio-Dependent Model of Replicator-Genetic Parasite Coevolution Demonstrates Instability of the Parasite-Free State

2021 ◽  
Author(s):  
Faina Berezovskaya ◽  
Georgy P. Karev ◽  
Eugene V. Koonin
Keyword(s):  
Mortality Rate ◽  
Carrying Capacity ◽  
Biological Evolution ◽  
Type Model ◽  
Model Parameters ◽  
Volterra Type ◽  
Dependent Model ◽  
Ratio Dependent ◽  
Host Parasite ◽  
Intrinsic Feature

AbstractNearly all organisms on earth are hosts to diverse genetic parasites including viruses and various types of mobile genetic elements. The emergence and persistence of genetic parasites was hypothesized to be an intrinsic feature of biological evolution. Here we examine this proposition by analysis of a ratio-dependent Lotka-Volterra type model of replicator(host)-parasite coevolution where the evolutionary outcome depends on the ratio of the host and parasite numbers. In a large, unbounded domain of the space of the model parameters, which include the replicator carrying capacity, the damage inflicted by the parasite, the replicative advantage of the parasites, and its mortality rate, the parasite-free equilibrium takes the form of a saddle and accordingly is unstable. Therefore, the evolutionary outcome is either the stable coexistence of the replicator and the parasite or extinction of both. Thus, the results of ratio-dependent model analysis are compatible with the hypothesis that genetic parasites are inherent to life.

scholarly journals Noninteractive Macroscopic Reliability Model for Ceramic Matrix Composites With Orthotropic Material Symmetry

1990 ◽  
Vol 112 (4) ◽  
pp. 507-511 ◽  
Author(s):  
S. F. Duffy ◽  
J. M. Manderscheid
Keyword(s):  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Experimental Program ◽  
Type Model ◽  
Model Parameters ◽  
Reliability Model ◽  
Matrix Composites ◽  
Physical Mechanisms ◽  
Weakest Link ◽  
Monolithic Ceramics

A macroscopic noninteractive reliability model for ceramic matrix composites is presented. The model is multiaxial and applicable to composites that can be characterized as orthotropic. Tensorial invariant theory is used to create an integrity basis with invariants that correspond to physical mechanisms related to fracture. This integrity basis is then used to construct a failure function per unit volume (or area) of material. It is assumed that the overall strength of the composite is governed by weakest link theory. This leads to a Weibull-type model similar in nature to the principle of independent action (PIA) model for isotropic monolithic ceramics. An experimental program to obtain model parameters is briefly discussed. In addition, qualitative features of the model are illustrated by presenting reliability surfaces for various model parameters.

The Summary of the Durability of Concrete Parameters Calculation Models

2011 ◽  
Vol 71-78 ◽  
pp. 937-944
Author(s):  
Ping Jie Cheng ◽  
Han Zhou Hu ◽  
Shu Guang Hu
Keyword(s):  
Environmental Effects ◽  
Concrete Structure ◽  
Civil Engineering ◽  
Steel Corrosion ◽  
Type Model ◽  
Model Parameters ◽  
Source Type ◽  
Important Field ◽  
Parameters Calculation ◽  
Durability Of Concrete

The durability of concrete structure has become an important field of civil engineering at home and abroad, and how to determine the environmental effects of typical durability of concrete structure key parameters become the key. Proposed by different domestic and foreign scholars to study durability parameters of concrete structure of different models, different models are different in the source, type, model parameters and applicable conditions. In this paper, some typical models are reviewed and analyzed from two major aspects of the durability of concrete, the deterioration of concrete and the steel corrosion.

Effects of glycine–metal compounds onAscaridia galli-infected chickens expressed by a kinetic model

2004 ◽  
Vol 78 (1) ◽  
pp. 25-32 ◽  
Author(s):  
M. Gabrashanska ◽  
S.E. Teodorova ◽  
M. Galvez-Morros ◽  
M. Mitov
Keyword(s):  
Body Weight Gain ◽  
Biogenic Elements ◽  
Model Parameters ◽  
Ascaridia Galli ◽  
Mineral Deficiency ◽  
Metal Compounds ◽  
High Infection ◽  
Gain Reduction ◽  
Reduction Of Mortality ◽  
Host Parasite

AbstractThe biogenic elements zinc, manganese and cobalt are essential for metabolic processes in animals. Compounds of nGly.Me2+A. mH2O (Me2+=Zn2+, Mn2+, Co2+; A=Cl−, SO42−, n=1, 2; m=2, 5), as supplements in the diet, were used separately on different experimental groups of male Hisex chickens to correct the mineral deficiency caused byAscaridia galliinfections. An amelioration of body weight gain, reduction of mortality and restoration of trace element levels were estimated in infected chickens. A mathematical model has been proposed forA. gallipopulation kinetics in chickens, taking into account the stimulating effect of these elements on the nematodes. The model parameters are considered as phenomenological constants of the host–parasite system. An agreement with experimental data is observed using, for the parametersψ,α,μandμs, values equal to those calculated in previously investigatedA. galli–chicken systems. For parameterν(immunological constant) the same value was obtained as in a previous experiment with high infection. This model is likely to be suitable for a range of host–nematode systems, including varying degrees of infection and treatment with different trace elements.

Turing and Benjamin–Feir instability mechanisms in non-autonomous systems

2020 ◽  
Vol 476 (2238) ◽  
pp. 20200003 ◽  
Author(s):  
Robert A. Van Gorder
Keyword(s):  
Autonomous Systems ◽  
Reaction Diffusion ◽  
Reaction Rates ◽  
Time Dependent ◽  
Model Parameters ◽  
Time Varying ◽  
Reaction Diffusion Systems ◽  
Diffusion Systems ◽  
Dependent Model ◽  
Spatio Temporal

The Turing and Benjamin–Feir instabilities are two of the primary instability mechanisms useful for studying the transition from homogeneous states to heterogeneous spatial or spatio-temporal states in reaction–diffusion systems. We consider the case when the underlying reaction–diffusion system is non-autonomous or has a base state which varies in time, as in this case standard approaches, which rely on temporal eigenvalues, break down. We are able to establish respective criteria for the onset of each instability using comparison principles, obtaining inequalities which involve the in general time-dependent model parameters and their time derivatives. In the autonomous limit where the base state is constant in time, our results exactly recover the respective Turing and Benjamin–Feir conditions known in the literature. Our results make the Turing and Benjamin–Feir analysis amenable for a wide collection of applications, and allow one to better understand instabilities emergent due to a variety of non-autonomous mechanisms, including time-varying diffusion coefficients, time-varying reaction rates, time-dependent transitions between reaction kinetics and base states which change in time (such as heteroclinic connections between unique steady states, or limit cycles), to name a few examples.

Modeling study of solid-particle erosion with consideration of particle velocity dependent model parameters

2016 ◽  
Vol 07 (03) ◽  
pp. 1650026 ◽  
Author(s):  
Shijie Qian ◽  
Kuiying Chen ◽  
Rong Liu ◽  
Ming Liang
Keyword(s):  
Experimental Data ◽  
Solid Particle ◽  
Particle Velocity ◽  
Target Material ◽  
Model Parameters ◽  
Particle Impact ◽  
Erosion Rates ◽  
Proposed Model ◽  
Dependent Model ◽  
Predicted Model

An advanced erosion model that correlates two model parameters—the energies required to remove unit mass of target material during cutting wear and deformation wear, respectively, with particle velocity, particle size and density, as well as target material properties, is proposed. This model is capable of predicting the erosion rates for a material under solid-particle impact over a specific range of particle velocity at the impingement angle between [Formula: see text] and [Formula: see text], provided that the experimental data of erosion rate for the material at a particle velocity within this range and at impingement angles between [Formula: see text] and [Formula: see text] are available. The proposed model is applied on three distinct types of materials: aluminum, perspex and graphite, to investigate the dependence behavior of the model parameters on particle velocity for ductile and brittle materials. The predicted model parameters obtained from the model are validated by the experimental data of aluminum plate under Al2O3 particle impact. The significance and limitation of the model are discussed; possible improvements on the model are suggested.

Eggs-per-recruit model for management of the California market squid (Loligo opalescens) fishery

2005 ◽  
Vol 62 (7) ◽  
pp. 1640-1650 ◽  
Author(s):  
Michael R Maxwell ◽  
Larry D Jacobson ◽  
Ramon J Conser
Keyword(s):  
Mortality Rate ◽  
Egg Laying ◽  
Reference Points ◽  
Model Parameters ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Loligo Opalescens ◽  
Maturation Rate ◽  
Sampling Procedures ◽  
Yield Per Recruit

We develop a per-recruit model for the management of the California market squid (Loligo opalescens) fishery. Based on recent confirmation of determinate fecundity in this species, we describe how catch fecundity (i.e., eggs remaining in the reproductive tracts of harvested females) can be used to simultaneously infer fishing mortality rate along with management reference points such as yield-per-recruit, spawned eggs-per-recruit, and proportional egg escapement. Rates of mortality and egg laying have important effects on these reference points. Somewhat surprisingly, increasing the rate of natural mortality decreased spawned eggs-per-recruit while increasing proportional egg escapement. Increasing the rate of egg laying increased both spawned eggs-per-recruit and egg escapement. Other parameters, such as the maturation rate and gear vulnerability of immature females, affected the reference points. In actual practice, the influence of these parameters for immature squid may go undetected if immature squid are excluded from analysis of the catch. Application of this model to routine management is feasible but requires refinement of sampling procedures, biological assumptions, and model parameters. This model is useful because it is grounded on empirical data collected relatively inexpensively from catch samples (catch fecundity) while allowing for the simultaneous calculation of instantaneous fishing mortality rate and egg escapement.

EFFECT OF ASSET VALUE CORRELATION ON CREDIT-LINKED NOTE VALUES

2002 ◽  
Vol 05 (05) ◽  
pp. 455-478 ◽  
Author(s):  
C. H. HUI ◽  
C. F. LO
Keyword(s):  
Interest Rate ◽  
Credit Risk ◽  
Structural Model ◽  
Credit Spreads ◽  
Model Parameters ◽  
Risk Premiums ◽  
Closed Form Solutions ◽  
Asset Values ◽  
Dependent Model ◽  
Payoff Condition

This paper develops a simple model to study the credit risk premiums of credit-linked notes using the structural model. Closed-form solutions of credit risk premiums of the credit-linked notes derived from the model as functions of firm values and the short-term interest rate, with time-dependent model parameters governing the dynamics of the firm values and interest rate. The numerical results show that the credit spreads of a credit-linked note increase non-linearly with the decrease in the correlation between the asset values of the note issuer and the reference obligor when the final payoff condition depends on the asset values of the note issuer and the reference obligor. When the final payoff condition depends on the recovery rate of the note issuer upon default, the credit spreads could increase with the correlation. In addition, the term structures of model parameters and the correlations involving interest rate are clearly the important factors in determining the credit spreads of the notes.

scholarly journals Numerical Analysis of Test Embankment on Soft Ground Using Multi-Laminate Type Model with Destructuration / Analiza Numeryczna Nasypu Drogowego Posadowionego Na Gruncie Słabonosnym Z Zastosowaniem Modelu Wielopłaszczyznowego Z Destrukturyzacja

2011 ◽  
Vol 57 (1) ◽  
pp. 27-44
Author(s):  
M. Cundi
Keyword(s):  
Constitutive Model ◽  
Constitutive Models ◽  
In Situ Stress ◽  
Type Model ◽  
Model Parameters ◽  
Structural Anisotropy ◽  
Soft Clays ◽  
Stress Induced Anisotropy ◽  
Test Embankment

Abstract A multi-laminate constitutive model for soft soils incorporating structural anisotropy is presented. Stress induced anisotropy of strength, which is present in multi-laminate type constitutive models, is augmented by directionally distributed overconsolidation. The model is presented in the elastic-plastic version in order to simulate strength anisotropy of soft clayey soils and destructuration effects. Performance of the model is shown for some element tests and for the numerical simulation of a trial road embankment constructed on soft clays at Haarajoki, Finland. The numerical calculations are completed with the commercial finite element code capable to perform coupled static/consolidation analysis of soils. Problems related to the initiation of in situ stress state, conditions of preconsolidation, as well as difficulties linked to estimation of the model parameters are discussed. Despite simple assumptions concerning field conditions and non-viscous formulation of the constitutive model, the obtained final results are of a sufficient accuracy for geotechnical practice.

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