scholarly journals Evolution arrests invasions of cooperative populations

2015 ◽  
Author(s):  
Kirill S Korolev
Keyword(s):  
Tumor Growth ◽  
Competitive Advantage ◽  
Native Species ◽  
Analytical Expression ◽  
Exact Analytical Expression ◽  
Fitness Advantage ◽  
New Strategies

Population expansions trigger many biomedical and ecological transitions, from tumor growth to invasions of non-native species. Although population spreading often selects for more invasive phenotypes, we show that this outcome is far from inevitable. In cooperative populations, mutations reducing dispersal have a competitive advantage. Such mutations then steadily accumulate at the expansion front bringing invasion to a halt. Our findings are a rare example of evolution driving the population into an unfavorable state and could lead to new strategies to combat unwelcome invaders. In addition, we obtain an exact analytical expression for the fitness advantage of mutants with different dispersal rates.

Effect of phenology on agonistic competitive interactions between invasive and native sheet-web spiders

2016 ◽  
Vol 94 (6) ◽  
pp. 427-434 ◽  
Author(s):  
Jeremy D. Houser ◽  
Adam H. Porter ◽  
Howard S. Ginsberg ◽  
Elizabeth M. Jakob
Keyword(s):  
Competitive Advantage ◽  
Native Species ◽  
Negative Impact ◽  
Relative Size ◽  
Agonistic Interactions ◽  
Resident Species ◽  
The Third ◽  
Linyphia Triangularis ◽  
Size Interaction ◽  
Very High

The phenologies of introduced relative to native species can greatly influence the degree and symmetry of competition between them. The European spider Linyphia triangularis (Clerck, 1757) (Linyphiidae) reaches very high densities in coastal Maine (USA). Previous studies suggest that L. triangularis negatively affects native linyphiid species, with competition for webs as one mechanism. We documented phenological differences between L. triangularis and three native species that illustrate the potential for the reversal of size-based competitive advantage over the course of the year. To test whether relative size influences interaction outcome, we allowed a resident spider to build a web and then introduced an intruder. We examined whether the outcomes of agonistic interactions over the webs were influenced by the species of the resident (invasive or native), the relative size of the contestants, and the species × size interaction. We found that the importance of relative size differed among species. In interactions between L. triangularis and each of two native species, size played a greater role than resident species on the outcome of interactions, suggesting that competitive advantage reverses over the season based on phenology-related size differences. Linyphia triangularis had a negative impact on the third species regardless of relative size.

scholarly journals Logistics outsourcing by manufacturers in South Africa

2011 ◽  
Vol 5 (1) ◽  
Author(s):  
Beverley Waugh ◽  
Rose Luke
Keyword(s):  
South Africa ◽  
Competitive Advantage ◽  
South African ◽  
Customer Service ◽  
Questionnaire Survey ◽  
Logistics Outsourcing ◽  
Potential Problems ◽  
Insufficient Time ◽  
New Strategies

As organisations find themselves in an increasingly dynamic and competitive world they are seeking new strategies to ensure their competitive advantage and profitability. Logistics presents an area in which these organisations can improve customer service and reduce costs, and strategies in support thereof such as the outsourcing of logistics activities, should be considered. However, it is critical that logistics outsourcing is done diligently to avoid potential problems for the organisation and to achieve the best possible benefits. In South Africa little research has been done regarding current outsourcing practices of local manufacturers. In this article literature on international logistics outsourcing as well as research on some of the logistics outsourcing practices of South African manufacturers is discussed. The findings of a questionnaire survey of South African manufacturers provided information on their logistics outsourcing practices and problems. Prominent issues seem to include inadequate managerial involvement in the logistics outsourcing process, as well as insufficient time spent on many of the important aspects of the outsourcing agreement, the transitioning of resources and ongoing management of the outsourced relationship. It is concluded that a thorough outsourcing process should be followed in order to achieve the benefits of logistics outsourcing.

Exact analytical expression of the hemispherical irradiance on a sloped plane from the Perez sky

Solar Energy ◽  
2014 ◽  
Vol 99 ◽  
pp. 267-271 ◽  
Author(s):  
E. Matagne ◽  
R. El Bachtiri
Keyword(s):  
Analytical Expression ◽  
Exact Analytical Expression

scholarly journals Implementation of the lean ergonomics approach to process performance improvement

2019 ◽  
pp. 10-21
Author(s):  
Mauricio López-Acosta ◽  
Susana García-Vilches ◽  
José Manuel Velarde-Cantú ◽  
Allán Chacara-Montes
Keyword(s):  
Competitive Advantage ◽  
Performance Improvement ◽  
Cycle Time ◽  
Risk Identification ◽  
Value Stream Mapping ◽  
Process Performance ◽  
Manual Lifting ◽  
Value Stream ◽  
Constant Change ◽  
New Strategies

Actually market is subject to constant change which forces organizations to innovate with new strategies that provide greater productivity to maintain a competitive advantage, one of the flexible tools used are Lean systems. However, in most of the improvements registered in these systems, the non-ergonomic elements have not been considered as waste, which have high costs for companies. This document presents an approach to integrating Lean systems with Ergonomics, the main tools used were Value Stream Mapping, SIPOC, Kaizen, REBA Method and NIOSH. As a result, a risk identification was obtained in 86% of the 26 activities of three processes analyzed, mainly by postures, manual lifting of loads and repetitiveness, with the improvements developed, the 25 controlled risks were reduced high to medium or low and obtained an average reduction of 32% in the cycle time of operations, making each process more efficient.

scholarly journals Interplay of Driver, Mini-Driver, and Deleterious Passenger Mutations on Cancer Progression

2016 ◽  
Author(s):  
Xin Li ◽  
D. Thirumalai
Keyword(s):  
Tumor Growth ◽  
Cancer Progression ◽  
Evolutionary Model ◽  
Mutation Rates ◽  
Fitness Advantage ◽  
Dissipative Dynamical Systems ◽  
Passenger Mutations ◽  
The Relationship ◽  
Surprising Finding ◽  
Stochastic Evolutionary Model

Cancer is caused by the accumulation of a critical number of somatic mutations (drivers) that offer fitness advantage to tumor cells. Moderately deleterious passengers, suppressing cancer progression, and mini-drivers, mildly beneficial to tumors, can profoundly alter the cancer evolutionary landscape. This observation prompted us to develop a stochastic evolutionary model intended to probe the interplay of drivers, mini-drivers and deleterious passengers in tumor growth over a broad range of fitness values and mutation rates. Below a (small) threshold number of drivers tumor growth exhibits a plateau (dormancy) with large burst occurring when a driver achieves fixation, reminiscent of intermittency in dissipative dynamical systems. The predictions of the model, in particular the relationship between the average number of passenger mutations versus drivers in a tumor, is in accord with clinical data on several cancers. When deleterious drivers are included, we predict a non-monotonic growth of tumors as the mutation rate is varied with shrinkage and even reversal occurring at very large mutation rates. This surprising finding explains the paradoxical observation that high chromosomal instability (CIN) correlates with improved prognosis in a number of cancers compared with intermediate CIN.

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