scholarly journals Evolution, Chance, and Aging

2021 ◽  
Vol 12 ◽  
Author(s):  
Stewart Frankel ◽  
Blanka Rogina
Keyword(s):  
Evolutionary Theory ◽  
Life Histories ◽  
Molecular Data ◽  
Gene Effects ◽  
Genetic Studies ◽  
Body Of Knowledge ◽  
Evolution Of Aging ◽  
Age Structured ◽  
Survival Patterns ◽  
High Level

Aging has provided fruitful challenges for evolutionary theory, and evolutionary theory has deepened our understanding of aging. A great deal of genetic and molecular data now exists concerning mortality regulation and there is a growing body of knowledge concerning the life histories of diverse species. Assimilating all relevant data into a framework for the evolution of aging promises to significantly advance the field. We propose extensions of some key concepts to provide greater precision when applying these concepts to age-structured contexts. Secondary or byproduct effects of mutations are proposed as an important factor affecting survival patterns, including effects that may operate in small populations subject to genetic drift, widening the possibilities for mutation accumulation and pleiotropy. Molecular and genetic studies have indicated a diverse array of mechanisms that can modify aging and mortality rates, while transcriptome data indicate a high level of tissue and species specificity for genes affected by aging. The diversity of mechanisms and gene effects that can contribute to the pattern of aging in different organisms may mirror the complex evolutionary processes behind aging.

scholarly journals Organizational Strategies for End-User Development—A Systematic Literature Mapping

Informatics ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 15
Author(s):  
Augusto S. C. Modesto ◽  
Rejane M. da C. Figueiredo ◽  
Cristiane S. Ramos ◽  
Letícia de S. Santos ◽  
Elaine Venson ◽  
...  
Keyword(s):  
Organizational Strategies ◽  
End User ◽  
Viable Option ◽  
Research Gaps ◽  
Systematic Mapping ◽  
Level Of Evidence ◽  
Body Of Knowledge ◽  
Methods And Techniques ◽  
Literature Mapping ◽  
High Level

In the last few years, several organizations have been looking for strategies to meet the needs of users of Information Technology (IT). The decentralization of IT and the empowerment of nonprofessional users have been a viable option among these strategies. This study aimed to identify the End-User Development (EUD) strategies adopted by organizations. A systematic mapping was performed in order to provide for a structured body of knowledge and find potential research gaps. The results show that EUD methods and techniques are the most common strategies addressed in the literature. Also, most of the EUD strategies identified a focus either on EUD managerial issues, such as risk management, or on more technical elements, such as the implementation of components for EUD applications. The benefits and barriers to the adoption of EUD by organizations are also presented in this study. In general, defining EUD processes is a common gap in EUD surveys. We reinforce the need to carry out more research on the adoption of EUD in organizations, with a high level of evidence to validate the results.

INHERITANCE OF RESISTANCE TO NET BLOTCH IN BARLEY. I. FACTORS AFFECTING THE PENETRANCE AND EXPRESSIVITY OF GENE(S) CONDITIONING HOST RESISTANCE

1969 ◽  
Vol 11 (3) ◽  
pp. 587-591 ◽  
Author(s):  
T. N. Khan
Keyword(s):  
Environmental Conditions ◽  
Net Blotch ◽  
Host Reaction ◽  
Susceptible Parent ◽  
Breeding Programs ◽  
Genetic Studies ◽  
Factors Affecting ◽  
Drechslera Teres ◽  
Resistant Varieties ◽  
High Level

Variability in the host-reaction of barley to infection by Drechslera teres was examined in the parents and progeny of selected crosses under different environmental conditions of testing.The Ethiopian variety C.I. 5791 exhibits a consistently high level of resistance under a range of environmental conditions, which is in contrast to the Manchurian variety C.I. 2330. The sensitivity of the genes for resistance possessed by these varieties to environmental modifications is considered to depend upon their respective genetic backgrounds. Furthermore, variability of host reaction in the progeny of these resistant varieties was shown to be influenced by the genetic background of the susceptible parent used.The implications of these findings in the conduct and interpretation of genetic studies and in backcross breeding programs is discussed.

Mixed embeddedness of Brazilian entrepreneurs in Toronto

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Roberto Pessoa de Queiroz Falcão ◽  
Michel Mott Machado ◽  
Eduardo Picanço Cruz ◽  
Caroline Shenaz Hossein
Keyword(s):  
Service Sector ◽  
The Body ◽  
Structured Interviews ◽  
Immigrant Entrepreneurship ◽  
Content Type ◽  
Brazilian Government ◽  
Body Of Knowledge ◽  
Multi Method Approach ◽  
High Level ◽  
Entrepreneurial Activities

PurposeThe purpose of this article is to investigate how social integration, immigrant networks and barriers to ventureing affect the entrepreneurial activities of Brazilians in Canada, indicating how mixed embeddedness takes place in that context.Design/methodology/approachData were collected in Toronto, through the application of a survey with 74 Brazilian entrepreneur respondents and 42 semi-structured interviews with selected subjects, thus representing a multi-method approach. The analysis included descriptive statistics from the survey data and a qualitative analysis of the trajectories and life stories of Brazilian immigrants.FindingsOur sample comprises respondents with a high level of education and proficiency in English, coming predominantly from the southeast of Brazil, white, aged from 30 to 49. The majority of businesses are small and related to the service sector. The article contributes to the literature by discussing the elements related to mixed embeddedness, including the need for cultural adaptation and for the creation of networks as a crucial element for business venturing.Research limitations/implicationsThe study focuses on entrepreneurs regardless of their businesses sector or formality/informality status. It could be used as an instrument to support Canadian public policies for welcoming Brazilians and for the Brazilian government to prevent the evasion of potential entrepreneurs.Originality/valueThe article contributes to the body of knowledge of immigrant entrepreneurship in Canada and of Brazilian entrepreneurship overseas. The results suggest factors that may be relevant to the expansion of their business, such as social networking, cultural embeddedness and adaptation of the products/services to a wider range of target customers.

scholarly journals Prediction of Mining Conditions in Geotechnically Complex Sites

Mining ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 279-296
Author(s):  
Marc Elmouttie ◽  
Jane Hodgkinson ◽  
Peter Dean
Keyword(s):  
Neural Network ◽  
Historical Data ◽  
Synthetic Data ◽  
Mining Operations ◽  
Body Of Knowledge ◽  
Future Production ◽  
The Neural Network ◽  
Mining Conditions ◽  
Parameter Interactions ◽  
High Level

Geotechnical complexity in mining often leads to geotechnical uncertainty which impacts both safety and productivity. However, as mining progresses, particularly for strip mining operations, a body of knowledge is acquired which reduces this uncertainty and can potentially be used by mining engineers to improve the prediction of future mining conditions. In this paper, we describe a new method to support this approach based on modelling and neural networks. A high-level causal model of the mining operations based on historical data for a number of parameters was constructed which accounted for parameter interactions, including hydrogeological conditions, weather, and prior operations. An artificial neural network was then trained on this historical data, including production data. The network can then be used to predict future production based on presently observed mining conditions as mining proceeds and compared with the model predictions. Agreement with the predictions indicates confidence that the neural network predictions are properly supported by the newly available data. The efficacy of this approach is demonstrated using semi-synthetic data based on an actual mine.

scholarly journals Parallel Universes for Models of X Chromosome Dosage Compensation in Drosophila: A Review

2016 ◽  
Vol 148 (1) ◽  
pp. 52-67 ◽  
Author(s):  
James A. Birchler
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Sex Chromosome ◽  
Fold Increase ◽  
Molecular Data ◽  
X Chromosomes ◽  
Histone Modifiers ◽  
Parallel Universes ◽  
Msl Complex ◽  
High Level

Dosage compensation in Drosophila involves an approximately 2-fold increase in expression of the single X chromosome in males compared to the per gene expression in females with 2 X chromosomes. Two models have been considered for an explanation. One proposes that the male-specific lethal (MSL) complex that is associated with the male X chromosome brings histone modifiers to the sex chromosome to increase its expression. The other proposes that the inverse effect which results from genomic imbalance would tend to upregulate the genome approximately 2-fold, but the MSL complex sequesters histone modifiers from the autosomes to the X to mute this autosomal male-biased expression. On the X, the MSL complex must override the high level of resulting histone modifications to prevent overcompensation of the X chromosome. Each model is evaluated in terms of fitting classical genetic and recent molecular data. Potential paths toward resolving the models are suggested.

Genetic structure of Gahnia radula (Cyperaceae), a key sedge for revegetation

2017 ◽  
Vol 65 (2) ◽  
pp. 128
Author(s):  
Alex Arnold ◽  
Andrea Kodym ◽  
Nancy M. Endersby-Harshman ◽  
John Delpratt ◽  
Ary A. Hoffmann
Keyword(s):  
Genetic Variation ◽  
Adaptive Potential ◽  
Genetic Studies ◽  
Potential Source ◽  
Landscape Processes ◽  
Disturbed Areas ◽  
Eastern Australia ◽  
Genetic Patterns ◽  
Source Populations ◽  
High Level

Genetic studies can help guide effective ecological restoration by identifying potential source populations that contain the genetic variation necessary for adaptive potential, based on past landscape processes. Here we investigate genetic patterns in Gahnia radula (R.Br.) Benth., a sedge from south-eastern Australia that has potential for revegetation of disturbed areas. We developed microsatellite markers for this species and used them to show that it propagates mostly in a clonal manner. Levels of genetic variability differed between populations and the spatial scale of this variability within these populations is identified. A population used in recent restoration efforts and which sets seed has a particularly high level of variability. Recommendations are developed for sourcing material when using this sedge for revegetation.

Reproductive-timing-dependent alternation of offspring life histories in female threespine sticklebacks

1999 ◽  
Vol 77 (8) ◽  
pp. 1314-1321 ◽  
Author(s):  
Toshihiko Saito ◽  
Shigeru Nakano
Keyword(s):  
Life Histories ◽  
Gasterosteus Aculeatus ◽  
Reproductive Timing ◽  
Equivalent Age ◽  
Structured Population ◽  
Otolith Increments ◽  
Threespine Sticklebacks ◽  
Young Of The Year ◽  
Age Structured ◽  
Breeding Seasons

Relationships between reproductive timing of spawners and timing of hatch and age at maturity of their offspring were examined in fluvial threespine sticklebacks, Gasterosteus aculeatus. Some age 2 and all age 3 females matured in this age-structured population, with only a few females reproducing over two successive breeding seasons. Age 2 females spawned over the relatively long breeding season (March-August), whereas age 3 females spawned mainly early in the season (March-June). Although the standard length of mature age 3 females was greater than that of age 2 females, the back-calculated standard lengths of the former were always shorter than those of the latter at an equivalent age, the most distinct differences being apparent in young of the year. Analysis of daily otolith increments showed that the earlier the young of the year were born, the larger they were at the end of the growing season. As a result of these findings, age 3 females can be expected to produce offspring that will mature at age 2, whereas the offspring of late-spawning age 2 females are more likely to mature at age 3. Therefore, a partial alternation of life histories between generations is thought to occur.

Reproductive and Genetic-Studies With a Laboratory Colony of the Dasyurid Marsupial Sminthopsis-Crassicaudata

1989 ◽  
Vol 37 (3) ◽  
pp. 207 ◽  
Author(s):  
JH Bennett ◽  
WG Breed ◽  
DL Hayman ◽  
RM Hope
Keyword(s):  
Reproductive Biology ◽  
Meiotic Chromosome ◽  
Litter Production ◽  
Genetic Studies ◽  
Adult Weight ◽  
Sminthopsis Crassicaudata ◽  
Laboratory Colony ◽  
Marked Disparity ◽  
Marsupial Species ◽  
High Level

The fat-tailed dunnart, Sminthopsis crassicaudata, is a small insectivorous dasyurid (adult weight about 16 g) widely distributed in Australia. A laboratory colony of this marsupial, which has been built up over many years, is providing material for studies of dasyurid reproductive biology and genetics. In the area of reproductive biology, we have found a marked disparity in the age of maturation between the two sexes, and we are currently studying certain aspects of spermatogenesis, sperm transport, fertilisation and early embryonic development. Genetical studies have revealed large differences between the sexes in autosomal linkage values and meiotic chromosome behaviour. In females, we have observed very limited intrachromosomal recombination and this is reflected in the distal localisation of chiasmata on the autosomes. Extreme localisation of chiasmata has not hitherto been found in a mammal, and it will be interesting to see how widely it occurs in other marsupial species. The genetical and cytological findings lead to a number of predictions that are being tested in further experimental work with the colony. Although we have been able to raise litter production to a high level, the very variable and unpredictable nature of male reproductive performance currently limits the wider use of the S. crassicaudata colony. It is clear, however, that this dasyurid has the potential to become a very useful laboratory marsupial and that it will be especially valuable for comparative biomedical studies.

Key risk factors affecting renewable energy independent power producer (IPP) set-up projects in developing countries

2019 ◽  
Vol 17 (6) ◽  
pp. 1340-1355 ◽  
Author(s):  
Michael Nii Addy ◽  
Stephen Akunyumu ◽  
Barbara Simons
Keyword(s):  
Risk Factors ◽  
Renewable Energy ◽  
Value Chain ◽  
The Body ◽  
Content Type ◽  
Factors Affecting ◽  
Body Of Knowledge ◽  
Set Up ◽  
High Level ◽  
Survey Approach

Purpose Sustained access to efficient electricity plays an essential role in improving living conditions of people and contributes to the economic development of the nation as a whole. Volta River Authority (VRA) mainly manages the generation plants (hydropower sources and thermal plants) alongside independent power producers (IPPs). Power generation in the country has been influenced by myriads of factors. Thus, the purpose of this study is to assess the key risk factors affecting renewable energy of IPPs set-up project in Ghana. Design/methodology/approach Quantitative approach was adopted for the study. Empirical investigation was carried out using the survey approach. The likelihood of occurrence of the risk and the degree of impact of same motivated the use of risk significance index to analyze the data and make deductions from the results. Findings From the study, three key risk factors have high level of severity, which include long and complex procedures for authorization of project activities, stability of the policy environment and ease of obtaining rights to land. These risks could be found in the business/strategic risks and policy/regulatory risks categories, respectively. A total of 25 key risk factors had moderate level of severity and 12 key risk factors have low level of severity on renewable energy IPP set up projects. Practical implications Top-ranked risk factors require maximum attention. The identified risks should be alleviated with strategies to reduce levels of severity by targeting either the likelihood of occurrence or the level of impact. This will serve as a catalyze to promoting renewable energy IPP set-up projects in Ghana. Originality/value Key contribution of the paper to the body of knowledge is demonstrated by the empirical evidence of the risks IPPs are likely to encounter in setting up renewable energy plants in Ghana. The distinctive attribute of this study is further demonstrated by the fact that it focused on the set-up stage, which is a critical stage in the renewable energy provision value chain.

Fungi with heteroxenous life histories

1995 ◽  
Vol 73 (S1) ◽  
pp. 1334-1342 ◽  
Author(s):  
David Malloch
Keyword(s):  
Reproductive Success ◽  
Life Histories ◽  
Transmission Efficiency ◽  
Lifetime Reproductive Success ◽  
Population Densities ◽  
Frequency Distributions ◽  
Parasitic Fungi ◽  
Host Life ◽  
High Level ◽  
Dispersal Events

Heteroxenous (multiple host) life histories are characteristic of many groups of parasitic protista and animals, including Zoomastigina, Apicomplexa, Mesozoa, Platyhelminthes, Nematoda, Acanthocephala, Pentastomida, and Arthropoda. Parasitic fungi, including the Chytridiomycota and the Dikaryomycota (ascomycetes and basidiomycetes), may also have heteroxenous life histories and have many features in common with parasites from other groups. In spite of many conceptual similarities, the study of parasitic fungi has occurred in isolation, resulting in the creation of a separate vocabulary and literature. Many of the concepts developed by zoologists are useful to mycologists and allow examination of parasitic fungi from new perspectives. These new perspectives reveal that heteroxenous fungi are not only similar to heteroxenous protistans and animals but that they also have unique characteristics of their own. Chief among these is a high level of endocyclic asexual reproduction, a phenomenon promoting exponential increases of infections in definitive host populations. Heteroxeny appears to have a number of benefits including (i) increased lifetime reproductive success, (ii) increased transmission efficiency (iii) enhanced effectiveness in colonizing ephemeral or periodically appearing hosts and hosts occurring in low population densities, (iv) maintenance or enhancement of overdispersed frequency distributions in host populations, and (v) enhancement of genetic exchange through multiple dispersal events. Key words: fungi, heteroxenous, parasite, life histories.

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