scholarly journals Spatial soft sweeps: patterns of adaptation in populations with long-range dispersal

2018 ◽  
Author(s):  
Jayson Paulose ◽  
Joachim Hermisson ◽  
Oskar Hallatschek
Keyword(s):  
Long Range ◽  
Selection Pressure ◽  
Natural Populations ◽  
Halo Structure ◽  
The Core ◽  
Spreading Dynamics ◽  
Distinctive Structure ◽  
Opposing Effects ◽  
Dispersal Events ◽  
Scaling Arguments

Adaptation in extended populations often occurs through multiple independent mutations responding in parallel to a common selection pressure. As the mutations spread concurrently through the population, they leave behind characteristic patterns of polymorphism near selected loci—so-called soft sweeps—which remain visible after adaptation is complete. These patterns are well-understood in two limits of the spreading dynamics of beneficial mutations: the panmictic case with complete absence of spatial structure, and spreading via short-ranged or diffusive dispersal events, which tessellates space into distinct compact regions each descended from a unique mutation. However, spreading behaviour in most natural populations is not exclusively panmictic or diffusive, but incorporates both short-range and long-range dispersal events. Here, we characterize the spatial patterns of soft sweeps driven by dispersal events whose jump distances are broadly distributed, using lattice-based simulations and scaling arguments. We find that mutant clones adopt a distinctive structure consisting of compact cores surrounded by fragmented “haloes” which mingle with haloes from other clones. As long-range dispersal becomes more prominent, the progression from diffusive to panmictic behaviour is marked by two transitions separating regimes with differing relative sizes of halo to core. We analyze the implications of the core-halo structure for the statistics of soft sweep detection in small genomic samples from the population, and find opposing effects of long-range dispersal on the expected diversity in global samples compared to local samples from geographic subregions of the range. We also discuss consequences of the standing genetic variation induced by the soft sweep on future adaptation and mixing.

Hybrid and Austere Responses to the Problem of Error

2018 ◽  
Author(s):  
Holly M. Smith
Keyword(s):  
Social Welfare ◽  
Long Range ◽  
Moral Life ◽  
Social Cooperation ◽  
False Beliefs ◽  
The Core ◽  
Extended Sense ◽  
Moral Theories ◽  
Long Range Planning ◽  
The Ideal

Chapter 8 explores the Austere and Hybrid Responses to the problem of error. The two types of response are described in both ideal and non-ideal versions. Both are found wanting, but the Austere Response emerges as best. Codes endorsed by the Austere approach cannot be shown to meet the “goal-oriented” desiderata of maximizing social welfare, facilitating social cooperation and long-range planning, or guaranteeing the occurrence of the ideal pattern of actions. But Austere-endorsed codes do satisfy the conceptual desiderata for “usable” moral theories in the core (but not the extended) sense of “usability.” They are usable despite the agent’s false beliefs, and they provide agents with the opportunity to live a successful moral life according to the modest conception of this life. This chapter concludes that the only remedy for the problem of error is an Austere code containing a derivative duty for agents to gather information before acting.

The Core and Halo Structure of the Quasar 4C18.68

Quasars ◽  
1986 ◽  
pp. 187-188
Author(s):  
Ann C. Gower ◽  
J. B. Hutchings
Keyword(s):  
Halo Structure ◽  
The Core

The influence of fractional surface coverage on the core–core separation in ordered monolayers of thiol-ligated Au nanoparticles

Soft Matter ◽  
2019 ◽  
Vol 15 (43) ◽  
pp. 8800-8807 ◽  
Author(s):  
Morgan Reik ◽  
Melanie Calabro ◽  
Sean Griesemer ◽  
Edward Barry ◽  
Wei Bu ◽  
...  
Keyword(s):  
Long Range ◽  
Au Nanoparticles ◽  
Surface Coverage ◽  
Langmuir Monolayers ◽  
Long Range Order ◽  
The Core ◽  
Nanoparticle Surface ◽  
Nanoparticle Interactions ◽  
Fractional Surface Coverage ◽  
Fractional Surface

This study examines the way in which fractional surface coverage on a nanoparticle surface affects nanoparticle interactions and the long-range order of Langmuir monolayers.

scholarly journals Phenotypic, genotypic and biochemical changes during pyrethroid resistance selection in Anopheles gambiae mosquitoes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maxwell G. Machani ◽  
Eric Ochomo ◽  
Daibin Zhong ◽  
Guofa Zhou ◽  
Xiaoming Wang ◽  
...  
Keyword(s):  
Public Health ◽  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Selection Pressure ◽  
Pyrethroid Resistance ◽  
Natural Populations ◽  
Biochemical Changes ◽  
Moderate Intensity ◽  
Agricultural System ◽  
Selection For

Abstract The directional selection for insecticide resistance due to indiscriminate use of insecticides in public health and agricultural system favors an increase in the frequency of insecticide-resistant alleles in the natural populations. Similarly, removal of selection pressure generally leads to decay in resistance. Past investigations on the emergence of insecticide resistance in mosquitoes mostly relied on field survey of resistance in vector populations that typically had a complex history of exposure to various public health and agricultural pest control insecticides in nature, and thus the effect of specific insecticides on rate of resistance emergency or resistance decay rate is not known. This study examined the phenotypic, genotypic, and biochemical changes that had occurred during the process of selection for pyrethroid resistance in Anopheles gambiae, the most important malaria vector in Africa. In parallel, we also examined these changes in resistant populations when there is no selection pressure applied. Through repeated deltamethrin selection in adult mosquitoes from a field population collected in western Kenya for 12 generations, we obtained three independent and highly pyrethroid-resistant An. gambiae populations. Three susceptible populations from the same parental population were generated by removing selection pressure. These two lines of mosquito populations differed significantly in monooxygenase and beta-esterase activities, but not in Vgsc gene mutation frequency, suggesting metabolic detoxification mechanism plays a major role in generating moderate-intensity resistance or high-intensity resistance. Pre-exposure to the synergist piperonyl butoxide restored the susceptibility to insecticide among the highly resistant mosquitoes, confirming the role of monooxygenases in pyrethroid resistance. The rate of resistance decay to become fully susceptible from moderate-intensity resistance took 15 generations, supporting at least 2-years interval is needed when the rotational use of insecticides with different modes of action is considered for resistance management.

Atomic Displacements Around Nitrogen Interstitial Impurities in Ta and Nb

1986 ◽  
Vol 82 ◽  
Author(s):  
S. Rao ◽  
E. J. Savino ◽  
C. R. Houska
Keyword(s):  
Long Range ◽  
Theoretical Calculations ◽  
Attenuation Factor ◽  
Scattering Data ◽  
Elastic Displacement ◽  
Force Model ◽  
The Core ◽  
Atomic Displacements ◽  
The Green Function ◽  
Experimental Findings

ABSTRACTThe core as well as the long range elastic displacements around N octahedral interstitial atoms in Ta and Nb are modelled using the Green Function – Kanzaki force method. The theoretical calculations are compared with experimental attenuation factor and diffuse scattering data, reported in the literature, for both N in Nb and N in Ta [1,2,3]. It is shown that a third neighbor radial Kanzaki force model is needed to explain the experimental findings, and the long range elastic displacement field is non-spherical.

An Experiment On Spacing-Out as a Defence Against Predation

Behaviour ◽  
1967 ◽  
Vol 28 (3-4) ◽  
pp. 307-320 ◽  
Author(s):  
D. Franck ◽  
M. Impekoven ◽  
N. Tinbergen
Keyword(s):  
Selection Pressure ◽  
Standard Sample ◽  
Direct Detection ◽  
Natural Populations ◽  
The Other ◽  
Detection Distance ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Scattered Population ◽  
Dependent Mortality

AbstractThe paper is concerned with the tracing of a selection pressure which would account for the fact (believed to be sufficiently well established) that individuals of many well-camouflaged species live further away from other individuals of their species than the distance from which even bird predators are able to detect them. Artificially camouflaged hens' eggs were laid out in plots of different densities. Wild Carrion Crows were attracted to each plot by a standard "sample egg" which, while painted in the same way as the other eggs on the uppermost half, was laid out in a more conspicuous way. In spite of the fact that the Crows spent more time searching in the "scattered" than in the "crowded" plots, the crowded eggs suffered a much higher mortality. It is concluded that even for individuals of a well-camouflaged species it must be of advantage to live further away from others than the Direct Detection Distance of their predators. However, the experiments do not show that a crowded population as a whole suffers higher predation than a scattered population; experiments to test this and other aspects of the problem are in progress. It is argued that the absolute values of the density dependent mortality scores of the experiments cannot be applied to natural populations, because their density will in most cases be determined by other ultimate factors as well.

scholarly journals Modeling the role of voyaging in the coastal spread of the Early Neolithic in the West Mediterranean

2017 ◽  
Vol 114 (5) ◽  
pp. 897-902 ◽  
Author(s):  
Neus Isern ◽  
João Zilhão ◽  
Joaquim Fort ◽  
Albert J. Ammerman
Keyword(s):  
Long Range ◽  
Simulation Study ◽  
Cultural Interaction ◽  
Early Neolithic ◽  
The West ◽  
The Core ◽  
Core Elements

The earliest dates for the West Mediterranean Neolithic indicate that it expanded across 2,500 km in about 300 y. Such a fast spread is held to be mainly due to a demic process driven by dispersal along coastal routes. Here, we model the Neolithic spread in the region by focusing on the role of voyaging to understand better the core elements that produced the observed pattern of dates. We also explore the effect of cultural interaction with Mesolithic populations living along the coast. The simulation study shows that (i) sea travel is required to obtain reasonable predictions, with a minimum sea-travel range of 300 km per generation; (ii) leapfrog coastal dispersals yield the best results (quantitatively and qualitatively); and (iii) interaction with Mesolithic people can assist the spread, but long-range voyaging is still needed to explain the archaeological pattern.

Defects in Liquid-Crystalline Polymers

MRS Bulletin ◽  
1995 ◽  
Vol 20 (9) ◽  
pp. 23-28 ◽  
Author(s):  
M. Kléman
Keyword(s):  
Long Range ◽  
Short Range ◽  
Liquid Crystalline ◽  
Dislocation Line ◽  
Liquid Crystalline Polymers ◽  
Core Region ◽  
Molecular Order ◽  
Crystalline Polymers ◽  
The Core ◽  
History Of

The properties of imperfections (or defects) of the atomic or molecular order in condensed matter can be conveniently described under two headings: (1) Topological properties—Defects break a specific symmetry of the ordered system at a local scale, that is, along a point defect, a line defect (a dislocation or a disclination), or a surface defect (a wall). (2) Elastic properties—Defects are sources of two types of distortions of the order: long-range distortions, which depend crucially on the broken symmetry but also on the material constants, and short-range distortions in the “core” region of the defect where the order parameter of the ordered phase is broken. These distortions are irreversible in the sense that defects appear during plastic deformation (in solids) or rheological flow (in liquid crystals).To illustrate this classification, let us recall the example of dislocation lines in solids. These defects break translational symmetries (henceforth a dislocation is defined topologically by the translation b it breaks, the so-called Burgers vector). They are at the origin of rather weak, long-range, internal distortions and stresses that depend on the elastic constants (in the region of the good crystal) and rather strong, short-range distortions and stresses in the “core” region, implying a complete rearrangement of the molecular order. These stresses are different in the static and dynamic states, and the shape of the dislocation line, as well as its size, etc., depend on the history of the sample.In this article, we will focus on defects in liquid-crystalline polymers. A synthetic polymer that displays mesomorphic order (intermediate between crystalline and liquid) is usually made of units that are themselves mesogenic and that align coherently when in contact.

scholarly journals Protein-Coding Genes of Helicobacter pylori Predominantly Present Purifying Selection though Many Membrane Proteins Suffer from Selection Pressure: A Proposal to Analyze Bacterial Pangenomes

Genes ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 377
Author(s):  
Alejandro Rubio ◽  
Antonio Pérez-Pulido
Keyword(s):  
Helicobacter Pylori ◽  
Membrane Proteins ◽  
Selection Pressure ◽  
Purifying Selection ◽  
Protein Coding ◽  
Evolutionary Selection ◽  
Protein Coding Genes ◽  
The Core ◽  
Genes Encoding ◽  
Selection For

The current availability of complete genome sequences has allowed knowing that bacterial genomes can bear genes not present in the genome of all the strains from a specific species. So, the genes shared by all the strains comprise the core of the species, but the pangenome can be much greater and usually includes genes appearing in one only strain. Once the pangenome of a species is estimated, other studies can be undertaken to generate new knowledge, such as the study of the evolutionary selection for protein-coding genes. Most of the genes of a pangenome are expected to be subject to purifying selection that assures the conservation of function, especially those in the core group. However, some genes can be subject to selection pressure, such as genes involved in virulence that need to escape to the host immune system, which is more common in the accessory group of the pangenome. We analyzed 180 strains of Helicobacter pylori, a bacterium that colonizes the gastric mucosa of half the world population and presents a low number of genes (around 1500 in a strain and 3000 in the pangenome). After the estimation of the pangenome, the evolutionary selection for each gene has been calculated, and we found that 85% of them are subject to purifying selection and the remaining genes present some grade of selection pressure. As expected, the latter group is enriched with genes encoding for membrane proteins putatively involved in interaction to host tissues. In addition, this group also presents a high number of uncharacterized genes and genes encoding for putative spurious proteins. It suggests that they could be false positives from the gene finders used for identifying them. All these results propose that this kind of analyses can be useful to validate gene predictions and functionally characterize proteins in complete genomes.

Drones to the Rescue

2021 ◽  
pp. 1162-1178
Author(s):  
Peter Tatham
Keyword(s):  
Natural Disaster ◽  
Long Range ◽  
The Core ◽  
The People ◽  
Core Capabilities

This chapter considers the potential operation of long-range drones to support the logistic response to a natural disaster using a case study of Cyclone Pam that struck Tafea Province of Vanuatu in March 2015. It provides an overview of how the core capabilities of such drones might be employed in order to overcome the key challenge facing humanitarian logisticians responding to such disasters – namely that of understanding the 6W problem of “who wants what where when and why.” The chapter then discusses the people, process, and technology issues that would need to be overcome in order to operationalize the concept.

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