scholarly journals Competition and fixation of cohorts of adaptive mutations under Fisher geometrical model

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2256 ◽  
Author(s):  
Jorge A. Moura de Sousa ◽  
João Alpedrinha ◽  
Paulo R.A. Campos ◽  
Isabel Gordo
Keyword(s):  
Geometric Model ◽  
Theoretical Models ◽  
Geometrical Model ◽  
Simultaneous Increase ◽  
Frequency Change ◽  
Clonal Interference ◽  
Adaptive Mutations ◽  
Experimental Adaptation ◽  
Asexual Populations ◽  
Adaptive Walk

One of the simplest models of adaptation to a new environment is Fisher’s Geometric Model (FGM), in which populations move on a multidimensional landscape defined by the traits under selection. The predictions of this model have been found to be consistent with current observations of patterns of fitness increase in experimentally evolved populations. Recent studies investigated the dynamics of allele frequency change along adaptation of microbes to simple laboratory conditions and unveiled a dramatic pattern of competition between cohorts of mutations, i.e., multiple mutations simultaneously segregating and ultimately reaching fixation. Here, using simulations, we study the dynamics of phenotypic and genetic change as asexual populations under clonal interference climb a Fisherian landscape, and ask about the conditions under which FGM can display the simultaneous increase and fixation of multiple mutations—mutation cohorts—along the adaptive walk. We find that FGM under clonal interference, and with varying levels of pleiotropy, can reproduce the experimentally observed competition between different cohorts of mutations, some of which have a high probability of fixation along the adaptive walk. Overall, our results show that the surprising dynamics of mutation cohorts recently observed during experimental adaptation of microbial populations can be expected under one of the oldest and simplest theoretical models of adaptation—FGM.

scholarly journals A geometrical model for the evolution of spherical planetary nebulae based on thin-shell formalism

2021 ◽  
pp. 2150191
Author(s):  
Ibrahim Gullu ◽  
S. Habib Mazharimousavi ◽  
S. Danial Forghani
Keyword(s):  
Energy Density ◽  
Planetary Nebula ◽  
Thin Shell ◽  
Energy Momentum Tensor ◽  
Geometric Model ◽  
Geometrical Model ◽  
Momentum Tensor ◽  
Evolution Pattern ◽  
Simple Power Function ◽  
Curvature Tensors

A spherical planetary nebula is described as a geometric model. The nebula itself is considered as a thin-shell, which is visualized as a boundary of two spacetimes. The inner and outer curvature tensors of the thin-shell are found in order to get an expression of the energy-momentum tensor on the thin-shell. The energy density and pressure expressions are derived using the energy-momentum tensor. The time evolution of the radius of the thin-shell is obtained in terms of the energy density. The model is tested by using a simple power function for decreasing energy density and the evolution pattern of the planetary nebula is attained.

scholarly journals The Glory of the Past and Geometrical Concurrency

10.29007/klcl ◽  
2018 ◽  
Author(s):  
Cristian Prisacariu
Keyword(s):  
Modal Logic ◽  
Geometric Model ◽  
Expressive Power ◽  
Geometrical Model ◽  
Geometrical Aspect ◽  
Fine Grained ◽  
The Past ◽  
Action Refinement ◽  
Higher Dimensional ◽  
Natural Way

This paper contributes to the general understanding of the "geometrical model of concurrency" that was named higher dimensional automata (HDAs) by Pratt and van Glabbeek. In particular we provide some understanding of the modal logics for such models and their expressive power in terms of the bisimulation that can be captured.The geometric model of concurrency is interesting from two main reasons: its generality and expressiveness, and the natural way in which autoconcurrency and action refinement are captured.Logics for this model, though, are not well investigated, where a simple, yet adequate, modal logic over HDAs was only recently introduced.As this modal logic, with two existential modalities, "during" and "after", captures only split bisimulation, which is rather low in the spectrum of van Glabbeek and Vaandrager, the immediate question was what small extension of this logic could capture the more fine-grained hereditary history preserving bisimulation (hh)?In response, the work in this paper provides several insights. One is the fact that the geometrical aspect of HDAs makes it possible to use for capturing the hh-bisimulation, a standard modal logic that does not employ event variables, opposed to the two logics (over less expressive models) that we compare with. The logic that we investigate here uses standard backward-looking modalities (i.e., past modalities) and extends the previously introduced logic (called HDML) that had only forward, action-labelled, modalities.Since the direct proofs are rather intricate, we try to understand better the above issues by introducing a related model that we call ST-configuration structures, which extend the configuration structures of van Glabbeek and Plotkin. We relate this model to HDAs, and redefine and prove the earlier results in the light of this new model. These offer a different view on why the past modalities and geometrical concurrency capture the hereditary history preserving bisimulation.Additional correlating insights are also gained.

scholarly journals Clonal Interference, Multiple Mutations and Adaptation in Large Asexual Populations

Genetics ◽  
2008 ◽  
Vol 180 (4) ◽  
pp. 2163-2173 ◽  
Author(s):  
Craig A. Fogle ◽  
James L. Nagle ◽  
Michael M. Desai
Keyword(s):  
Clonal Interference ◽  
Asexual Populations

Geometric Model of the Interaction of the Grinding Wheel and Workpiece during Surface Grinding with the Periphery of a Straight Wheel

2015 ◽  
Vol 756 ◽  
pp. 41-46 ◽  
Author(s):  
Aleksandr A. Dyakonov ◽  
Leonid V. Shipulin
Keyword(s):  
Geometric Model ◽  
Translational Motion ◽  
Geometrical Model ◽  
Surface Grinding ◽  
Polished Surface ◽  
Grinding Wheel ◽  
Experimental Check ◽  
Basic Parameters

Results of development of geometrical model of a shaping of a polished surface at surface grinding by the periphery of a wheel are presented in article. The developed model allows to predict a roughness of the processed surface depending on basic parameters of operation: speeds of rotation of the tool and translational motion of workpiece, wheel parameters – granularity and structure, depth of cutting and other parameters. Results of experimental check of the developed model are given in article.

VOID PROBABILITY ENHANCED MULTIPLICITY DISTRIBUTION OF PRODUCED HADRONS IN p–p COLLISION AT LHC ENERGIES

2012 ◽  
Vol 27 (26) ◽  
pp. 1250145 ◽  
Author(s):  
S. DUTTA ◽  
A. H. CHAN ◽  
C. H. OH
Keyword(s):  
Upper Bound ◽  
Collision Energy ◽  
Multiplicity Distribution ◽  
Negative Binomial ◽  
Geometric Distribution ◽  
Geometric Model ◽  
Theoretical Models ◽  
Text Data

This paper studies the multiplicity distribution of hadrons produced in p–p collisions at 0.9 and 2.36 TeV using ALICE as a detector. The multiplicity distribution exhibits enhanced void probability. They are also found to satisfy the void probability scaling. The scaling of χ with [Formula: see text] is studied using the generalized hypergeometric model. The variation of the parameter "a" of the hyper geometric model with energy and type of events is also studied. The parameter "a" distinguishes between various theoretical models, e.g. Lorentz/Catalan, negative binomial, geometric distribution etc. Finally a comparison is made with the [Formula: see text] collisions at 200, 546 and 900 GeV. It is observed both for p–p and [Formula: see text] data, the value of "a" decreases with increase in collision energy and approach towards the upper bound or the NB model of the void probability scaling.

Vehicle detection and tracking for visual understanding of road environments

Robotica ◽  
2009 ◽  
Vol 28 (6) ◽  
pp. 847-860 ◽  
Author(s):  
Arturo de la Escalera ◽  
Jose Maria Armingol
Keyword(s):  
Likelihood Function ◽  
Geometric Model ◽  
Weather Conditions ◽  
Geometrical Model ◽  
Cruise Control ◽  
Driver Assistance Systems ◽  
Vehicle Detection And Tracking ◽  
Visual Understanding ◽  
Shadow It ◽  
Parameter Values

SUMMARYMany of the advanced driver assistance systems have the goal of perceiving the surroundings of a vehicle. One of them, adaptive cruise control, takes charge of searching for other vehicles in order to detect and track them with the aim of maintaining a safe distance and to avoid dangerous maneuvers. In the research described in this article, this task is accomplished using an on board camera. Depending on when the vehicles are detected the system analyzes movement or uses a vehicle geometrical model to perceive them. After, the detected vehicle is tracked and its behavior established. Optical flow is used for movement while the geometric model is associated with a likelihood function that includes information of the shape and symmetry of the vehicle and the shadow it casts. A genetic algorithm finds the optimum parameter values of this function for every image. As the algorithm receives information from a road detection module some geometric restrictions are applied. Additionally, a multiresolution approach is used to speed up the algorithm. Examples of real image sequences under different weather conditions are shown to validate the algorithm.

Theoretical analysis of braiding strand trajectories and simulation of three-dimensional parametric geometrical models for multilayer interlock three-dimensional tubular braided preforms

2019 ◽  
Vol 89 (19-20) ◽  
pp. 4306-4322 ◽  
Author(s):  
Zhipeng Wang ◽  
Guoli Zhang ◽  
Youxin Zhu ◽  
Liqing Zhang ◽  
Xiaoping Shi ◽  
...  
Keyword(s):  
Mathematical Models ◽  
Three Dimensional ◽  
Theoretical Models ◽  
Geometrical Model ◽  
Design Parameters ◽  
Braided Composites ◽  
3D Braided Composites ◽  
Interlaminar Shear ◽  
Braided Structure ◽  
Propeller Blades

Multilayer interlock three-dimensional (3D) tubular braided composites have been widely used in propeller blades, high pressure pipelines, rocket nose cones and engine nozzles owing to prominent interlaminar shear properties, reliable damage tolerance and outstanding torsion performance. The prediction of the mechanical properties and the design of the fabric structures for the 3D braided composites are dependent on the trajectory distribution of strands and the geometrical model of the braided structure. This paper aims to build theoretical models for the braiding strand trajectories and presents a creative method to establish the parametric geometrical models for the multilayer interlock 3D tubular braided structures. Firstly, mathematical models of braiding strand trajectories are derived based on the analysis for the characteristics of carrier paths, the interlacing and interlocking of braided structures and the motion of braiding strands. The mathematical models are then developed to establish parametric expressions for multilayer interlock 3D tubular braided structures by the advanced development of UG NX®. In addition, the models of corresponding braiding strand trajectories and braiding structures can be obtained automatically in the simulation environment with the modification of design parameters. Finally, the established models are compared with the carbon fiber braided specimen. The results show that the innovative parametric geometric models of the multilayer interlock 3D tubular braided structures accurately describe the key characteristics of the preform.

scholarly journals Geometrical Model of the Manufacturing Surface of the Equivalent Working Surface of the Fine Tooth Dolbyak

2019 ◽  
Author(s):  
С. Рязанов ◽  
S. Ryazanov ◽  
Михаил Решетников ◽  
Mihail Reshetnikov
Keyword(s):  
Computer Modeling ◽  
Geometric Modeling ◽  
Dimensional Space ◽  
Geometric Model ◽  
Three Dimensional ◽  
Geometrical Model ◽  
Analytic Description ◽  
Computer Algorithms ◽  
Gear Cutting ◽  
Working Surface

Existing mathematical models for calculating gearing are quite complex and do not always make it possible to quickly and accurately obtain the desired result. A simpler way to find a suitable gear option that satisfies the task is to use computer modeling and computer graphics methods, and in particular solid-state modeling algorithms. The use of geometric modeling techniques to simulate the process of shaping the working surface of gearing is based on the relative movement of intersecting objects in the form of a “workpiece-tool” system. This allows you to obtain the necessary geometric model that accurately reproduces the geometric configuration of the surfaces of the teeth of spatial gears, taking into account the technological features of their production on gear cutting machines. This information allows you to perform on the computer imitation control the movement of the cutting tool. Ultimately, this boils down to the problem of analytic description and computer representation of curves and surfaces in three-dimensional space. As the gear cutting tools, the most widely used are disk and worm modular mills (shaver), gear cutting heads, dolbyaki and lath tools. At the moment there are no computer algorithms for obtaining the “dolbyak” producing surfaces, which are obtained by a tool with a modified producing surface. A change in the geometric shape of the tool producing surface will lead to a change in its working surfaces, which may lead to an improvement in their contact. This article shows the application of the developed methods and algorithms of geometric and computer modeling, which are intended for shaping the working surfaces of the Dolbyak tool. Their application will speed up the process of calculating intermediate adjustments of machines used for cutting gears, bypassing complex mathematical calculations that, under conditions of aging of the gear-cutting machines, their wear and the inevitable reduction in the accuracy of their kinematic chains.

scholarly journals Molecular signatures of resource competition: clonal interference drives the emergence of ecotypes

2020 ◽  
Author(s):  
Massimo Amicone ◽  
Isabel Gordo
Keyword(s):  
Evolutionary Dynamics ◽  
Resource Competition ◽  
Ecological Model ◽  
De Novo ◽  
Clonal Interference ◽  
Microbial Ecosystems ◽  
Difficult Challenge ◽  
Asexual Populations ◽  
Analytical Approaches ◽  
Different Levels

AbstractMicrobial ecosystems harbor an astonishing diversity that can persist for long times. To understand how such diversity is generated and maintained, ecological and evolutionary processes need to be integrated at similar timescales, but this remains a difficult challenge. Here, we extend an ecological model of resource competition to allow for evolution via de novo mutation, focusing on large and rapidly adapting asexual populations. Through numerical and analytical approaches, we characterize adaptation and diversity at different levels and show how clonal interference – the interaction between simultaneously emerging lineages – shapes the eco-evolutionary dynamics. We find that large mutational inputs can foster diversification under sympatry, increasing the probability that phenotypically and genetically distinct clusters arise and stably coexist, constituting an initial form of community. Our findings have implications beyond microbial populations, providing novel insights about the interplay between ecology and evolution in clonal populations.

Sign in / Sign up

Export Citation Format

Share Document