scholarly journals Selection against males in Caenorhabditis elegans under two mutational treatments

2006 ◽  
Vol 274 (1608) ◽  
pp. 417-424 ◽  
Author(s):  
Diogo Manoel ◽  
Sara Carvalho ◽  
Patrick C Phillips ◽  
Henrique Teotónio
Keyword(s):  
Caenorhabditis Elegans ◽  
Mating Systems ◽  
Low Frequency ◽  
Nematode Species ◽  
Mixed Mating ◽  
Low Frequencies ◽  
Deleterious Alleles ◽  
Ethylmethane Sulphonate ◽  
The Cost ◽  
The Relationship

Within populations with mixed mating systems, selfing is expected to be favoured over outcrossing unless a countervailing process such as severe inbreeding depression is present. In this study, we consider the relationship between the expression of deleterious alleles and the maintenance of outcrossing in the nematode species, Caenorhabditis elegans . This species is characterized by an androdioecious breeding system composed of males at low frequency and self-fertilizing hermaphrodites that can only outcross via males. Here, we find that experimentally increasing the mutational load in four different isogenic wild isolates using 10 generations of Ethylmethane sulphonate (EMS) and UV irradiation mutagenesis significantly diminishes the cost of males. Males are maintained at higher frequencies in mutagenized versus non-mutagenized populations. Nevertheless, males still tend to be driven to low frequencies within isolates that are known to be prone to lose males. Further, we determine the viability effects of a single round of mutagen exposure and find that, for EMS, outcrossing overcomes the almost completely recessive and nearly lethal effects generated. We briefly interpret our results in light of current evolutionary theory of outcrossing rates.

Optimally Sensitive and Efficient Compact Loudspeakers for Low Audio Frequencies

2007 ◽  
Vol 38 (7) ◽  
pp. 11-17
Author(s):  
Ronald M. Aarts
Keyword(s):  
Optimality Criterion ◽  
Low Frequency ◽  
Audio Signal ◽  
Design Procedure ◽  
Frequency Range ◽  
Force Factor ◽  
Low Frequencies ◽  
Limited Frequency ◽  
The Cost ◽  
Higher Sensitivity

Conventionally, the ultimate goal in loudspeaker design has been to obtain a flat frequency response over a specified frequency range. This can be achieved by carefully selecting the main loudspeaker parameters such as the enclosure volume, the cone diameter, the moving mass and the very crucial “force factor”. For loudspeakers in small cabinets the results of this design procedure appear to be quite inefficient, especially at low frequencies. This paper describes a new solution to this problem. It consists of the combination of a highly non-linear preprocessing of the audio signal and the use of a so called low-force-factor loudspeaker. This combination yields a strongly increased efficiency, at least over a limited frequency range, at the cost of a somewhat altered sound quality. An analytically tractable optimality criterion has been defined and has been verified by the design of an experimental loudspeaker. This has a much higher efficiency and a higher sensitivity than current low-frequency loudspeakers, while its cabinet can be much smaller.

scholarly journals Sex differences in deleterious genetic variants in a haplodiploid social insect

2021 ◽  
Author(s):  
Sara E. Miller ◽  
Michael J. Sheehan
Keyword(s):  
Genetic Load ◽  
Low Frequency ◽  
Paper Wasp ◽  
Deleterious Mutations ◽  
Wild Populations ◽  
Nonsense Mutations ◽  
Low Frequencies ◽  
Complete Dominance ◽  
Deleterious Alleles ◽  
Population Allele Frequency

AbstractDeleterious variants are selected against but can linger in populations at low frequencies for long periods of time, decreasing fitness and contributing to disease burden in humans and other species. Deleterious variants occur at low frequency but distinguishing deleterious variants from low frequency neutral variation is challenging based on population genetics data. As a result, we have little sense of the number and identity of deleterious variants in wild populations. For haplodiploid species, it has been hypothesized that deleterious alleles will be directly exposed to selection in haploid males, but selection can be masked in diploid females due to partial or complete dominance, resulting in more efficient purging of deleterious mutations in males. Therefore, comparisons of the differences between haploid and diploid genomes from the same population may be a useful method for inferring rare deleterious variants. This study provides the first formal test of this hypothesis. Using wild populations of Northern paper wasps (Polistes fuscatus), we find that males have fewer overall variants, and specifically fewer missense and nonsense variants, than females from the same population. Allele frequency differences are especially pronounced for rare missense and nonsense mutations and these differences lead to a lower genetic load in males than females. Based on these data we estimate that a large number of highly deleterious mutations are segregating in the paper wasp population. Stronger selection against deleterious alleles in haploid males may have implications for adaptation in other haplodiploid insects and provides evidence that wild populations harbor abundant deleterious variants.

Rates of inbreeding in the androdioecious clam shrimp Eulimnadia texana

1999 ◽  
Vol 77 (9) ◽  
pp. 1402-1408 ◽  
Author(s):  
S C Weeks ◽  
N Zucker
Keyword(s):  
Mating System ◽  
Mating Systems ◽  
Mixed Mating ◽  
Mixed Mating System ◽  
Clam Shrimp ◽  
Inbreeding Rate ◽  
Male Frequency ◽  
Relationship Of ◽  
The Relationship ◽  
Mixed Mating Strategy

Populations of the clam shrimp Eulimnadia texana exhibit androdioecy, which is a mixed mating system composed of males and self-compatible hermaphrodites. It has been suggested that such mating systems are evolutionarily unstable, and yet most populations of E. texana appear to exhibit both outcrossing and selfing (a mixed mating strategy). Genetic and sex-ratio features of seven populations of these clam shrimp confirm that the majority of these populations show a mixture of inbreeding and outcrossing modes of reproduction. Additionally, we suggest that the relationship of inbreeding rate with male frequency indicates that mating is not random, as was suggested in a previous model of the mating system of E. texana.

scholarly journals Sperm competition games when males invest in paternal care

2017 ◽  
Vol 284 (1860) ◽  
pp. 20171266 ◽  
Author(s):  
Gustavo S. Requena ◽  
Suzanne H. Alonzo
Keyword(s):  
Sperm Competition ◽  
Mating Systems ◽  
Paternal Care ◽  
Offspring Survival ◽  
Parental Effort ◽  
Integrative Framework ◽  
Female Promiscuity ◽  
Male Care ◽  
The Cost ◽  
The Relationship

Sperm competition games investigate how males partition limited resources between pre- and post-copulatory competition. Although extensive research has explored how various aspects of mating systems affect this allocation, male allocation between mating, fertilization and parental effort has not previously been considered. Yet, paternal care can be energetically expensive and males are generally predicted to adjust their parental effort in response to expected paternity. Here, we incorporate parental effort into sperm competition games, particularly exploring how the relationship between paternal care and offspring survival affects sperm competition and the relationship between paternity and paternal care. Our results support existing expectations that (i) fertilization effort should increase with female promiscuity and (ii) paternal care should increase with expected paternity. However, our analyses also reveal that the cost of male care can drive the strength of these patterns. When paternal behaviour is energetically costly, increased allocation to parental effort constrains allocation to fertilization effort. As paternal care becomes less costly, the association between paternity and paternal care weakens and may even be absent. By explicitly considering variation in sperm competition and the cost of male care, our model provides an integrative framework for predicting the interaction between paternal care and patterns of paternity.

scholarly journals On the efficiency of energy harvesters: A classification of dynamics in miniaturized generators under low-frequency excitation

2019 ◽  
Vol 30 (16) ◽  
pp. 2436-2446 ◽  
Author(s):  
Thijs WA Blad ◽  
Nima Tolou
Keyword(s):  
Low Frequency ◽  
Poor Performance ◽  
Contributing Factors ◽  
Low Frequencies ◽  
Single Degree Of Freedom ◽  
Energy Harvesters ◽  
Frequency Excitation ◽  
Large Motion ◽  
The Cost

Although motion energy harvesting at the small scales has been a research topic for over 20 years, the implementation of such generators remains limited in practice. One of the most important contributing factors here is the poor performance of these devices under low-frequency excitation. In this research, a new metric is proposed to evaluate the performance and bandwidth of generators at low frequencies. For that, a classification based on the dynamics was made. It was found that the highest efficiencies were found in single-degree-of-freedom resonators where a large motion amplification was achieved. Smaller generators can be designed by limiting the motion through end-stops at the cost of a reduced efficiency. Moreover, it was argued that upon miniaturization, resonators could be outperformed by generators using a frequency up-conversion principle.

Deployment of a charging network based on a cost-benefit model and the CFSFDP algorithm

Kybernetes ◽  
2019 ◽  
Vol 48 (9) ◽  
pp. 1989-2005
Author(s):  
Can Zhong Yao ◽  
Jie Luo
Keyword(s):  
Low Frequency ◽  
Cost Benefit ◽  
Growth Potential ◽  
Content Type ◽  
Gas Stations ◽  
Density Peaks ◽  
Use Efficiency ◽  
The Cost ◽  
Charging Stations ◽  
The Relationship

Purpose This research aims to focus on the problem of optimizing the layout of charging stations. Design/methodology/approach The authors estimate the total number of charging stations by the number of existing gas stations using clustering by fast search-and-find of density peaks (CFSFDP) algorithm. Findings This paper reveals the relationship between the distance and the population. Priority should be given to the short-distance and high-frequency travel charging needs in the city, followed by low frequency and travel, which can improve the use efficiency of the whole charging network. Originality/value First, the total number of charging stations is estimated by the number of existing gas stations. This method can fully consider the growth potential of charging vehicles instead of the traditional cars. Besides, the cost-benefit method is proposed to explore the marginal coverage distance of the city’s charging network and can be used to reveal the relationship between the distance and the population.

Petrofabric and dielectric anisotropy in rock

1982 ◽  
Vol 19 (1) ◽  
pp. 36-54 ◽  
Author(s):  
S. Nowina ◽  
D. W. Strangway
Keyword(s):  
Grain Shape ◽  
Dielectric Material ◽  
Low Frequency ◽  
Dielectric Anisotropy ◽  
Low Loss ◽  
Frequency Relaxation ◽  
Wet Rocks ◽  
The Cost ◽  
Aggregate Shape ◽  
The Relationship

There is a systematic relationship between anisotropy in the fabric of rocks and anisotropy in their dielectric properties, although the relationship is difficult to express in any quantitative sense. In general, the dielectric constant K′, the dielectric loss K″, and the real conductivity σ′ are a maximum when measured along the lineation axis (L) of rock, and a minimum when measured along the foliation normal (F). In this study, rocks were measured both vacuum dried and with varying degrees of water present; the anisotropy of wet rocks is greater than when vacuum dried, due presumably to anisotropic distribution of water parallel to the petrofabric. The effects of water, however, can be eliminated by means of measurements in vacuum or, more simply, by heat drying the sample, and subsequent impregnation of the rock with a hydrophobic low-loss dielectric material (paraffin wax). This is particularly significant since it greatly reduces the cost and time involved in this type of study.Dielectric anisotropy is frequency dependent. It was largest at the lowest measurement frequencies (30 Hz) and diminished with increasing frequency. For this and other reasons, dielectric anisotropy in rock is attributed to Maxwell–Wagner effects, which are low frequency relaxation phenomena related to the shape, size, and dielectric anisotropy in rock, reflecting primarily the grain-shape and grain-aggregate-shape fabric.

scholarly journals Fitness effects of thermal stress differ between outcrossing and selfing populations in Caenorhabditis elegans

2016 ◽  
Author(s):  
Agata Plesnar-Bielak ◽  
Marta K. Labocha ◽  
Paulina Kosztyła ◽  
Katarzyna R. Woch ◽  
Woronika M. Banot ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Caenorhabditis Elegans ◽  
Environmental Change ◽  
Environmental Changes ◽  
Nematode Species ◽  
Free Living ◽  
Fitness Effects ◽  
Selective Pressures ◽  
Free Living Nematode ◽  
The Relationship

AbstractThe maintenance of males and outcrossing is widespread, despite considerable costs of males. By enabling recombination between distinct genotypes, outcrossing may be advantageous during adaptation to a novel environments and if so, it should be selected for under environmental challenge. However, a given environmental change may influence fitness of male, female, and hermaphrodite or asexual individuals differently, and hence the relationship between reproductive system and dynamics of adaptation to novel conditions may not be driven solely by the level of outcrossing and recombination. This has important implications for studies investigating the evolution of reproductive modes in the context of environmental changes, and for the extent to which their findings can be generalized. Here, we use Caenorhabditis elegans – a free-living nematode species in which hermaphrodites (capable of selfing but not cross-fertilizing each other) coexist with males (capable of fertilizing hermaphrodites) – to investigate the response of wild type as well as obligatorily outcrossing and obligatorily selfing lines to stressfully increased ambient temperature. We found that thermal stress affects fitness of outcrossers much more drastically than that of selfers. This shows that apart from the potential for recombination, the selective pressures imposed by the same environmental change can differ between populations expressing different reproductive systems and affect their adaptive potential.

Practical High Resolution Microscopy

1968 ◽  
Vol 26 ◽  
pp. 302-303
Author(s):  
P. A. Marsh ◽  
T. Mullens ◽  
D. Price
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Low Frequency ◽  
Resolving Power ◽  
Careful Attention ◽  
Electron Microscopes ◽  
The Relationship ◽  
High Resolution Microscopy ◽  
New Facilities

It is possible to exceed the guaranteed resolution on most electron microscopes by careful attention to microscope parameters essential for high resolution work. While our experience is related to a Philips EM-200, we hope that some of these comments will apply to all electron microscopes.The first considerations are vibration and magnetic fields. These are usually measured at the pre-installation survey and must be within specifications. It has been our experience, however, that these factors can be greatly influenced by the new facilities and therefore must be rechecked after the installation is completed. The relationship between the resolving power of an EM-200 and the maximum tolerable low frequency interference fields in milli-Oerstedt is 10 Å - 1.9, 8 Å - 1.4, 6 Å - 0.8.

The Awareness Level of the Safety and Health of the Operational Level

2017 ◽  
Vol 3 (1) ◽  
pp. 42
Author(s):  
Roshanira Che Mohd Noor ◽  
Nur Atiqah Rochin Demong
Keyword(s):  
Health And Safety ◽  
Health Conditions ◽  
Effective Strategies ◽  
Operational Level ◽  
Safety And Health ◽  
Health Factors ◽  
The Cost ◽  
The Relationship ◽  
Awareness Level

Providing a safe and healthy workplace is one of the most effective strategies in for holding down the cost of doing construction business. It was a part of the overall management system to facilitate themanagement of the occupational health and safety risk that are associated with the business of the organization. Factors affected the awareness level inclusive of safety and health conditions, dangerous working area, long wait care and services and lack of emergency communication werethe contributed factors to the awareness level for the operational level. Total of 122 incidents happened at Telekom Malaysia Berhad as compared to year 2015 only 86 cases. Thus, the main objective of this study was to determine the relationship between safety and health factors and the awareness level among operational workers.The determination of this research was to increase the awareness level among the operational level workerswho committing to safety and health environment.

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