DYNAMICS OF THE LINKAGE DISEQUILIBRIUM FUNCTION UNDER MODELS OF GENE-FREQUENCY HITCHHIKING

ABSTRACT The dynamic behavior of the linkage disequilibrium (D) between a neutral and a selected locus is analyzed for a variety of deterministic selection models. The time-dependent behavior of D is governed by the gene frequency at the selected locus (p) and by the selection (s) and recombination (r) parameters. Thomson (1977) showed numerically that D may increase under certain initial conditions. We give exact conditions for D to increase in time, which require that the selection intensity exceed the recombination fraction (s > r) and that p be near zero or one. We conclude from this result that gene frequency hitchhiking is most likely to be important when a new favorable mutant enters a population. We also show that, for what can be a wide range of gene frequencies, D will decay at a faster rate than the neutral rate. Consequently, the hitchhiking effect may quickly diminish as the selected gene becomes more common.—The method of analysis allows a complete qualitative description of the dynamics of D as a function of s and r. Two major findings concern the range of gene frequencies at the selected locus for which D either increases over time or decays at a faster rate than under neutrality. For all models considered, the region where D increases (i) first enlarges then shrinks as selection intensifies, and (ii) steadily shrinks as r increases. In contrast, the region of accelerated decay constantly enlarges as the selection intensity increases. This region will either shrink or enlarge as r increases, depending upon the form of selection in force.

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GENE FLOW AND SELECTION IN A TWO-LOCUS SYSTEM

Genetics ◽

10.1093/genetics/81.4.787 ◽

1975 ◽

Vol 81 (4) ◽

pp. 787-802 ◽

Cited By ~ 1

Author(s):

Montgomery Slatkin

Keyword(s):

Linkage Disequilibrium ◽

Gene Flow ◽

Spatial Pattern ◽

Recombination Fraction ◽

Gene Frequencies ◽

Spatial Changes ◽

Local Selection ◽

Order Of Magnitude ◽

Locus System

ABSTRACT A model of gene flow and selection in two linked loci is analyzed. The problems considered are the effects of linkage on the clines in frequencies at the two loci and the role of gene flow in producing linkage disequilibrium between the loci. Also, the possible significance of linkage as a mechanism for permitting a population of "track" spatial changes in the environment is considered. The results are that when the recombination fraction between the loci is of the same order of magnitude as the selection coefficients or smaller, then linkage is important in determining the gene frequencies and a substantial amount of linkage disequilibrium is present in the cline. Depending on the spatial pattern of selection on the two loci, linkage can either decrease or increase a population's response to local selection.

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The effect of finite population size on models of linked overdominant loci

Genetics Research ◽

10.1017/s0016672300018024 ◽

1978 ◽

Vol 31 (3) ◽

pp. 239-254 ◽

Cited By ~ 13

Author(s):

P. J. Avery

Keyword(s):

Linkage Disequilibrium ◽

Population Size ◽

Genetic Drift ◽

High Probability ◽

Finite Population ◽

Equilibrium Points ◽

Gene Frequencies ◽

Wide Range ◽

Stable Equilibria ◽

Range Of Values

SUMMARYModels of two linked overdominant loci in moderately large, but finite, populations are examined by looking at the variance-covariance matrix of the two gene frequencies and the linkage disequilibrium around stable deterministic equilibrium points. In particular, the effect of genetic drift is examined in cases where, in infinite populations, two stable equilibria with non-zero linkage disequilibrium, D, are maintained. Theoretical formulae are produced and checked by computer simulation. In general, the results show that unless the population size is very large indeed, genetic drift causes the values of D to vary considerably about the equilibrium values and that for many models, where stable equilibria exist at non-zero D values, a wide range of values of D have a high probability. Thus it is very difficult to draw conclusions about the selection regime by measuring Linkage disequilibrium in a finite population.

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THE EFFECT OF A SELECTED LOCUS ON LINKED NEUTRAL LOCI

Genetics ◽

10.1093/genetics/85.4.753 ◽

1977 ◽

Vol 85 (4) ◽

pp. 753-788 ◽

Cited By ~ 8

Author(s):

Glenys Thomson

Keyword(s):

Linkage Disequilibrium ◽

Natural Populations ◽

Recombination Fraction ◽

Gene Frequencies ◽

Order Of Magnitude

ABSTRACT The effects produced on linked neutral loci as a selected locus evolves towards its equilibrium value are considered. Significant effects on the neutral loci arise if the recombination fraction between the neutral and selected loci is smaller than the order of magnitude of the selective differences at the selected locus. The effect on gene frequencies at the neutral loci, that is, the hitchhiking effect, is determined, as well as the linkage disequilibrium generated by this hitchhiking effect. One of the more important findings is that significant disequilibrium can be generated between two neutral loci by the evolution of a linked selected locus. Consideration is given to the problem of determining how the effect of selection operating in natural populations can be detected, the question of the establishment of inversions in populations, and also to the nonequilibrium properties of populations.

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DYNAMICS OF THERMAL LOSSES BY CONVECTION AND RADIATION OF THE SPHERICAL HEAT ACCUMULATOR OF SOLAR PLANTS

Elektrotekhnologii i elektrooborudovanie v APK ◽

10.22314/2658-4859-2020-67-4-57-62 ◽

2020 ◽

Vol 4 (41) ◽

pp. 57-62

Author(s):

SHAVKAT KLYCHEV ◽

◽

BAKHRAMOV SAGDULLA ◽

VALERIY KHARCHENKO ◽

VLADIMIR PANCHENKO ◽

...

Keyword(s):

Boundary Conditions ◽

Heat Loss ◽

Initial Conditions ◽

Water System ◽

Heat Losses ◽

Research Purpose ◽

Heat Accumulator ◽

Water Heaters ◽

Intrinsic Radiation ◽

Over Time

There are needed energy (heat) accumulators to increase the efficiency of solar installations, including solar collectors (water heaters, air heaters, dryers). One of the tasks of designing heat accumulators is to ensure its minimal heat loss. The article considers the problem of determining the distribution of temperatures and heat losses by convection and radiation of the heat insulation-accumulating body (water) system for a ball heat accumulator under symmetric boundary conditions. The problem is solved numerically according to the program developed on the basis of the proposed «gap method». (Research purpose) The research purpose is in determining heat losses by convection and radiation of a two-layer ball heat accumulator with symmetric boundary conditions. (Materials and methods) Authors used the Fourier heat equation for spherical bodies. The article presents the determined boundary and initial conditions for bodies and their surfaces. (Results and discussion) The thickness of the insulation and the volume of the heat accumulator affect the dynamics and values of heat loss. The effect of increasing the thickness of the thermal insulation decreases with increasing its thickness, starting with a certain volume of the heat accumulator or with R > 0.3 meters, the heat losses change almost linearly over time. The dynamics of heat loss decreases with increasing shelf life, but the losses remain large. (Conclusions) Authors have developed a method and program for numerical calculation of heat loss and temperature over time in a spherical two-layer heat accumulator with symmetric boundary conditions, taking into account both falling and intrinsic radiation. The proposed method allows to unify the boundary conditions between contacting bodies.

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Anti-corruption in History

10.1093/oso/9780198809975.001.0001 ◽

2017 ◽

Keyword(s):

Financial Institutions ◽

Global Media ◽

Policy Makers ◽

The Past ◽

Human Wellbeing ◽

Modern Period ◽

Legitimate Power ◽

Wide Range ◽

Scant Attention ◽

Over Time

Anticorruption in History is the first major collection of case studies on how past societies and polities, in and beyond Europe, defined legitimate power in terms of fighting corruption and designed specific mechanisms to pursue that agenda. It is a timely book: corruption is widely seen today as a major problem, undermining trust in government, financial institutions, economic efficiency, the principle of equality before the law and human wellbeing in general. Corruption, in short, is a major hurdle on the “path to Denmark”—a feted blueprint for stable and successful statebuilding. The resonance of this view explains why efforts to promote anticorruption policies have proliferated in recent years. But while the subjects of corruption and anticorruption have captured the attention of politicians, scholars, NGOs and the global media, scant attention has been paid to the link between corruption and the change of anticorruption policies over time and place. Such a historical approach could help explain major moments of change in the past as well as reasons for the success and failure of specific anticorruption policies and their relation to a country’s image (of itself or as construed from outside) as being more or less corrupt. It is precisely this scholarly lacuna that the present volume intends to begin to fill. A wide range of historical contexts are addressed, ranging from the ancient to the modern period, with specific insights for policy makers offered throughout.

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Inferring Linkage Disequilibrium Between a Polymorphic Marker Locus and a Trait Locus in Natural Populations

Genetics ◽

10.1093/genetics/156.1.457 ◽

2000 ◽

Vol 156 (1) ◽

pp. 457-467 ◽

Cited By ~ 1

Author(s):

Z W Luo ◽

S H Tao ◽

Z-B Zeng

Keyword(s):

Linkage Disequilibrium ◽

Allele Frequency ◽

Random Mating ◽

Natural Populations ◽

Polymorphic Marker ◽

Marker Locus ◽

Model Parameters ◽

Phenotypic Variance ◽

Wide Range ◽

Trait Locus

Abstract Three approaches are proposed in this study for detecting or estimating linkage disequilibrium between a polymorphic marker locus and a locus affecting quantitative genetic variation using the sample from random mating populations. It is shown that the disequilibrium over a wide range of circumstances may be detected with a power of 80% by using phenotypic records and marker genotypes of a few hundred individuals. Comparison of ANOVA and regression methods in this article to the transmission disequilibrium test (TDT) shows that, given the genetic variance explained by the trait locus, the power of TDT depends on the trait allele frequency, whereas the power of ANOVA and regression analyses is relatively independent from the allelic frequency. The TDT method is more powerful when the trait allele frequency is low, but much less powerful when it is high. The likelihood analysis provides reliable estimation of the model parameters when the QTL variance is at least 10% of the phenotypic variance and the sample size of a few hundred is used. Potential use of these estimates in mapping the trait locus is also discussed.

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On the generation of internal waves by river plumes in subcritical initial conditions

Scientific Reports ◽

10.1038/s41598-021-81464-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

R. Mendes ◽

J. C. B. da Silva ◽

J. M. Magalhaes ◽

B. St-Denis ◽

D. Bourgault ◽

...

Keyword(s):

Numerical Modeling ◽

Internal Waves ◽

Coastal Waters ◽

Initial Conditions ◽

Spatial Scales ◽

River Plumes ◽

Wide Range ◽

Near Shore ◽

Generation Mechanisms ◽

Douro River

AbstractInternal waves (IWs) in the ocean span across a wide range of time and spatial scales and are now acknowledged as important sources of turbulence and mixing, with the largest observations having 200 m in amplitude and vertical velocities close to 0.5 m s−1. Their origin is mostly tidal, but an increasing number of non-tidal generation mechanisms have also been observed. For instance, river plumes provide horizontally propagating density fronts, which were observed to generate IWs when transitioning from supercritical to subcritical flow. In this study, satellite imagery and autonomous underwater measurements are combined with numerical modeling to investigate IW generation from an initial subcritical density front originating at the Douro River plume (western Iberian coast). These unprecedented results may have important implications in near-shore dynamics since that suggest that rivers of moderate flow may play an important role in IW generation between fresh riverine and coastal waters.

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A Newfangled Collagenase Inhibitor Topical Formulation Based on Ethosomes with Sambucus nigra L. Extract

Pharmaceuticals ◽

10.3390/ph14050467 ◽

2021 ◽

Vol 14 (5) ◽

pp. 467

Author(s):

Ana Henriques Mota ◽

Inês Prazeres ◽

Henrique Mestre ◽

Andreia Bento-Silva ◽

Maria João Rodrigues ◽

...

Keyword(s):

Biological Activities ◽

Scientific Evidence ◽

Release Profile ◽

Health Claims ◽

Topical Formulation ◽

Sambucus Nigra ◽

Western Asia ◽

Wide Range ◽

The Impact ◽

Over Time

Sambucus nigra L. (S. nigra) is a shrub widespread in Europe and western Asia, traditionally used in medicine, that has become popular in recent years as a potential source of a wide range of interesting bioactive compounds. The aim of the present work was to develop a topical S. nigra extract formulation based on ethosomes and thus to support its health claims with scientific evidence. S. nigra extract was prepared by an ultrasound-assisted method and then included in ethosomes. The ethosomes were analyzed in terms of their size, stability over time, morphology, entrapment capacity (EC), extract release profile, stability over time and several biological activities. The prepared ethosomes were indicated to be well defined, presenting sizes around 600 nm. The extract entrapment capacity in ethosomes was 73.9 ± 24.8%, with an interesting slow extract release profile over 24 h. The extract-loaded ethosomes presented collagenase inhibition activity and a very good skin compatibility after human application. This study demonstrates the potential use of S. nigra extract incorporated in ethosomes as a potential cosmeceutical ingredient and on further studies should be performed to better understand the impact of S. nigra compounds on skin care over the time.

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The Impact of Initial Conditions in N-Body Simulations of Debris Discs

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2015.41 ◽

2015 ◽

Vol 32 ◽

Cited By ~ 4

Author(s):

E. Thilliez ◽

S. T. Maddison

Keyword(s):

Numerical Simulations ◽

Initial Conditions ◽

Parent Body ◽

Dust Trapping ◽

Physical Context ◽

Disc Width ◽

Wide Range ◽

Belt Width ◽

New Generation ◽

The Impact

AbstractNumerical simulations are a crucial tool to understand the relationship between debris discs and planetary companions. As debris disc observations are now reaching unprecedented levels of precision over a wide range of wavelengths, an appropriate level of accuracy and consistency is required in numerical simulations to confidently interpret this new generation of observations. However, simulations throughout the literature have been conducted with various initial conditions often with little or no justification. In this paper, we aim to study the dependence on the initial conditions of N-body simulations modelling the interaction between a massive and eccentric planet on an exterior debris disc. To achieve this, we first classify three broad approaches used in the literature and provide some physical context for when each category should be used. We then run a series of N-body simulations, that include radiation forces acting on small grains, with varying initial conditions across the three categories. We test the influence of the initial parent body belt width, eccentricity, and alignment with the planet on the resulting debris disc structure and compare the final peak emission location, disc width and offset of synthetic disc images produced with a radiative transfer code. We also track the evolution of the forced eccentricity of the dust grains induced by the planet, as well as resonance dust trapping. We find that an initially broad parent body belt always results in a broader debris disc than an initially narrow parent body belt. While simulations with a parent body belt with low initial eccentricity (e ~ 0) and high initial eccentricity (0 < e < 0.3) resulted in similar broad discs, we find that purely secular forced initial conditions, where the initial disc eccentricity is set to the forced value and the disc is aligned with the planet, always result in a narrower disc. We conclude that broad debris discs can be modelled by using either a dynamically cold or dynamically warm parent belt, while in contrast eccentric narrow debris rings are reproduced using a secularly forced parent body belt.

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Harmonic hybrid inflation

Journal of High Energy Physics ◽

10.1007/jhep12(2020)161 ◽

2020 ◽

Vol 2020 (12) ◽

Author(s):

Federico Carta ◽

Nicole Righi ◽

Yvette Welling ◽

Alexander Westphal

Keyword(s):

Domain Wall ◽

Symmetry Breaking ◽

Initial Conditions ◽

Scalar Potential ◽

Field Range ◽

Slow Roll ◽

Minimal Form ◽

Wide Range ◽

Hybrid Inflation ◽

Type Iib String Theory

Abstract We present a mechanism for realizing hybrid inflation using two axion fields with a purely non-perturbatively generated scalar potential. The structure of the scalar potential is highly constrained by the discrete shift symmetries of the axions. We show that harmonic hybrid inflation generates observationally viable slow-roll inflation for a wide range of initial conditions. This is possible while accommodating certain UV arguments favoring constraints f ≲ MP and ∆ϕ60 ≲ MP on the axion periodicity and slow-roll field range, respectively. We discuss controlled ℤ2-symmetry breaking of the adjacent axion vacua as a means of avoiding cosmological domain wall problems. Including a minimal form of ℤ2-symmetry breaking into the minimally tuned setup leads to a prediction of primordial tensor modes with the tensor-to-scalar ratio in the range 10−4 ≲ r ≲ 0.01, directly accessible to upcoming CMB observations. Finally, we outline several avenues towards realizing harmonic hybrid inflation in type IIB string theory.

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