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Sample records for coevolutionary competitive exclusion

  1. Neanderthal Extinction by Competitive Exclusion

    PubMed Central

    Banks, William E.; d'Errico, Francesco; Peterson, A. Townsend; Kageyama, Masa; Sima, Adriana; Sánchez-Goñi, Maria-Fernanda

    2008-01-01

    Background Despite a long history of investigation, considerable debate revolves around whether Neanderthals became extinct because of climate change or competition with anatomically modern humans (AMH). Methodology/Principal Findings We apply a new methodology integrating archaeological and chronological data with high-resolution paleoclimatic simulations to define eco-cultural niches associated with Neanderthal and AMH adaptive systems during alternating cold and mild phases of Marine Isotope Stage 3. Our results indicate that Neanderthals and AMH exploited similar niches, and may have continued to do so in the absence of contact. Conclusions/Significance The southerly contraction of Neanderthal range in southwestern Europe during Greenland Interstadial 8 was not due to climate change or a change in adaptation, but rather concurrent AMH geographic expansion appears to have produced competition that led to Neanderthal extinction. PMID:19107186

  2. 21 CFR 529.469 - Competitive exclusion culture.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Competitive exclusion culture. 529.469 Section 529.469 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Competitive exclusion culture. (a) Specifications. Each packet of lyophilized culture contains either 2,000...

  3. 21 CFR 529.469 - Competitive exclusion culture.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Competitive exclusion culture. 529.469 Section 529... Competitive exclusion culture. (a) Specifications. Each packet of lyophilized culture contains either 2,000 or... contents of one 2,000-dose packet of lyophilized culture. Mix thoroughly. (2) For 5,000-dose packet,...

  4. 21 CFR 529.469 - Competitive exclusion culture.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Competitive exclusion culture. 529.469 Section 529... Competitive exclusion culture. (a) Specifications. Each packet of lyophilized culture contains either 2,000 or... contents of one 2,000-dose packet of lyophilized culture. Mix thoroughly. (2) For 5,000-dose packet,...

  5. Quantifying Competitive Exclusion and Competitive Release in Ecological Communities: A Conceptual Framework and a Case Study.

    PubMed

    Segre, Hila; DeMalach, Niv; Henkin, Zalmen; Kadmon, Ronen

    2016-01-01

    A fundamental notion in community ecology is that local species diversity reflects some balance between the contrasting forces of competitive exclusion and competitive release. Quantifying this balance is not trivial, and requires data on the magnitude of both processes in the same system, as well as appropriate methodology to integrate and interpret such data. Here we present a novel framework for empirical studies of the balance between competitive exclusion and competitive release and demonstrate its applicability using data from a Mediterranean annual grassland where grazing is a major mechanism of competitive release. Empirical data on the balance between competitive exclusion and competitive release are crucial for understanding observed patterns of variation in local species diversity and the proposed approach provides a simple framework for the collection, interpretation, and synthesis of such data. PMID:27536943

  6. Quantifying Competitive Exclusion and Competitive Release in Ecological Communities: A Conceptual Framework and a Case Study

    PubMed Central

    Henkin, Zalmen; Kadmon, Ronen

    2016-01-01

    A fundamental notion in community ecology is that local species diversity reflects some balance between the contrasting forces of competitive exclusion and competitive release. Quantifying this balance is not trivial, and requires data on the magnitude of both processes in the same system, as well as appropriate methodology to integrate and interpret such data. Here we present a novel framework for empirical studies of the balance between competitive exclusion and competitive release and demonstrate its applicability using data from a Mediterranean annual grassland where grazing is a major mechanism of competitive release. Empirical data on the balance between competitive exclusion and competitive release are crucial for understanding observed patterns of variation in local species diversity and the proposed approach provides a simple framework for the collection, interpretation, and synthesis of such data. PMID:27536943

  7. Competitive Exclusion: Comments on Survival and Extinction of Species

    ERIC Educational Resources Information Center

    Jaeger, Robert G.

    1974-01-01

    Examines aspects of competitive exclusion, which develops when two species jointly utilize a vital resource that is in short supply. When this occurs, one of the species will eventually eliminate the other from the habitat where their distributions overlap, unless one or both species evolve differences that reduce competition. (JR)

  8. Coevolutionary aesthetics in human and biotic artworlds.

    PubMed

    Prum, Richard O

    2013-01-01

    This work proposes a coevolutionary theory of aesthetics that encompasses both biotic and human arts. Anthropocentric perspectives in aesthetics prevent the recognition of the ontological complexity of the aesthetics of nature, and the aesthetic agency of many non-human organisms. The process of evaluative coevolution is shared by all biotic advertisements. I propose that art consists of a form of communication that coevolves with its own evaluation. Art and art history are population phenomena. I expand Arthur Danto's Artworld concept to any aesthetic population of producers and evaluators. Current concepts of art cannot exclusively circumscribe the human arts from many forms of non-human biotic art. Without assuming an arbitrarily anthropocentric perspective, any concept of art will need to engage with biodiversity, and either recognize many instances of biotic advertisements as art, or exclude some instances of human art. Coevolutionary aesthetic theory provides a heuristic account of aesthetic change in both human and biotic artworlds, including the coevolutionary origin of aesthetic properties and aesthetic value within artworlds. Restructuring aesthetics, art criticism, and art history without human beings at the organizing centers of these disciplines stimulate new progress in our understanding of art, and the unique human contributions to aesthetics and aesthetic diversity. PMID:23970809

  9. Probiotics, prebiotics and competitive exclusion for prophylaxis against bacterial disease.

    PubMed

    Callaway, T R; Edrington, T S; Anderson, R C; Harvey, R B; Genovese, K J; Kennedy, C N; Venn, D W; Nisbet, D J

    2008-12-01

    The microbial population of the intestinal tract is a complex natural resource that can be utilized in an effort to reduce the impact of pathogenic bacteria that affect animal production and efficiency, as well as the safety of food products. Strategies have been devised to reduce the populations of food-borne pathogenic bacteria in animals at the on-farm stage. Many of these techniques rely on harnessing the natural competitive nature of bacteria to eliminate pathogens that negatively impact animal production or food safety. Thus feed products that are classified as probiotics, prebiotics and competitive exclusion cultures have been utilized as pathogen reduction strategies in food animals with varying degrees of success. The efficacy of these products is often due to specific microbial ecological factors that alter the competitive pressures experienced by the microbial population of the gut. A few products have been shown to be effective under field conditions and many have shown indications of effectiveness under experimental conditions and as a result probiotic products are widely used in all animal species and nearly all production systems. This review explores the ecology behind the efficacy of these products against pathogens found in food animals, including those that enter the food chain and impact human consumers. PMID:19102792

  10. Competitive coexistence and competitive exclusion for a nonlinear community with delay effect and impulsive birth

    NASA Astrophysics Data System (ADS)

    Liu, Yanping; Zhang, Feng; Wei, Jianzhou

    2016-12-01

    By constructing a population model of multi-species competition, a community with nonlinear interaction relationship is investigated, in which the species' response delay and environmental fluctuation effects (i.e., seasonal fluctuation of resource supplies and species' reproductive activities) on population are considered. Firstly, the conditions about competitive coexistence (i.e., persistence of all species) and competitive exclusion (i.e., only partial of species, but not all, keep persistence) of the community are established, and the underlying ecological mechanism of these results are analyzed. Secondly, by some illustrative examples, the interactive effects of nonlinear competition, species' response delay and environmental fluctuation on the structure of community are explored. It is demonstrated that small response delay and slight deviation of nonlinear competition indexes from 1 have little impact on the coexistence of community, but acute changes have distinct negative influence on community coexistence. This reveals to us that parameter perturbations of natural communities should keep in an appropriate range, which is of great significance in conservation and restoration biology.

  11. Coevolutionary Free Lunches

    NASA Technical Reports Server (NTRS)

    Wolpert, David H.; Macready, William G.

    2005-01-01

    Recent work on the foundations of optimization has begun to uncover its underlying rich structure. In particular, the "No Free Lunch" (NFL) theorems [WM97] state that any two algorithms are equivalent when their performance is averaged across all possible problems. This highlights the need for exploiting problem-specific knowledge to achieve better than random performance. In this paper we present a general framework covering most search scenarios. In addition to the optimization scenarios addressed in the NFL results, this framework covers multi-armed bandit problems and evolution of multiple co-evolving agents. As a particular instance of the latter, it covers "self-play" problems. In these problems the agents work together to produce a champion, who then engages one or more antagonists in a subsequent multi-player game In contrast to the traditional optimization case where the NFL results hold, we show that in self-play there are free lunches: in coevolution some algorithms have better performance than other algorithms, averaged across all possible problems. However in the typical coevolutionary scenarios encountered in biology, where there is no champion, NFL still holds.

  12. Competition between Mutually Exclusive Object States in Event Comprehension.

    PubMed

    Solomon, Sarah H; Hindy, Nicholas C; Altmann, Gerry T M; Thompson-Schill, Sharon L

    2015-12-01

    Successful language comprehension requires one to correctly match symbols in an utterance to referents in the world, but the rampant ambiguity present in that mapping poses a challenge. Sometimes the ambiguity lies in which of two (or more) types of things in the world are under discussion (i.e., lexical ambiguity); however, even a word with a single sense can have an ambiguous referent. This ambiguity occurs when an object can exist in multiple states. Here, we consider two cases in which the presence of multiple object states may render a single-sense word ambiguous. In the first case, one must disambiguate between two states of a single object token in a short discourse. In the second case, the discourse establishes two different tokens of the object category. Both cases involve multiple object states: These states are mutually exclusive in the first case, whereas in the second case, these states can logically exist at the same time. We use fMRI to contrast same-token and different-token discourses, using responses in left posterior ventrolateral prefrontal cortex (pVLPFC) as an indicator of conflict. Because the left pVLPFC is sensitive to competition between multiple, incompatible representations, we predicted that state ambiguity should engender conflict only when those states are mutually exclusive. Indeed, we find evidence of conflict in same-token, but not different-token, discourses. Our data support a theory of left pVLPFC function in which general conflict resolution mechanisms are engaged to select between multiple incompatible representations that arise in many kinds of ambiguity present in language. PMID:26284994

  13. 47 CFR 101.1317 - Competitive bidding procedures for mutually exclusive MAS EA applications.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Competitive bidding procedures for mutually exclusive MAS EA applications. 101.1317 Section 101.1317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Multiple Address Systems...

  14. LIFE AFTER COMPETITIVE EXCLUSION: AN ALTERNATIVE STRATEGY FOR A COMPETITIVE INFERIOR

    EPA Science Inventory

    Experimental manipulations in the rocky intertidal have demonstrated that in the absence of predation (Paine 1966, 1974) or physical disturbance (Dayton 1971) a competitive dominant species can monopolize the primary space, thereby excluding competitors. he endpoint of this compe...

  15. In vitro selection of enteric microflora for potential use as a competitive exclusion culture against Campylobacter in poultry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The administration of nonpathogenic microflora in neonatal poultry has been employed to reduce or eliminate the colonization of enteric pathogens. This concept, also called competitive exclusion (CE), although effective against Salmonella, has not consistently worked against Campylobacter. Most CE...

  16. Competitive exclusion principle in ecology and absolute asymmetric synthesis in chemistry.

    PubMed

    Ribó, Josep M; Hochberg, David

    2015-10-01

    The key concepts underlying the Frank model (1953) for spontaneous asymmetric synthesis in chemistry are traced back to the pioneering works of Volterra (1926) and Lotka (1932) on biological species competition. The Lotka-Volterra (L-V) two-species exclusive competition model reduces to the Frank model for the special case of distinguishable but degenerate species (i.e., the enantiomers). The important ecological principle of competitive exclusion, originally derived from the L-V two-competitors model, is a consequence of sufficiently antagonistic interactions between the species competing for limited common resources, or mutual inhibition, as the term is known in the chemical literature on absolute asymmetric synthesis. The L-V and Frank models are described by the same general differential equations, nevertheless a crucial thermodynamic distinction between these models is necessary to correlate ecological selection and chemical selectivity arising from 1) the absence of reversibility in biological transformations, in marked contrast to chemical reactions, and 2) the constraints in chemical scenarios on the reaction rate constants required to fulfill the principle of micro-reversibility. PMID:26301597

  17. Competitive exclusion by autologous antibodies can prevent broad HIV-1 antibodies from arising

    SciTech Connect

    Luo, Shishi; Perelson, Alan S.

    2015-08-31

    The past decade has seen the discovery of numerous broad and potent monoclonal antibodies against HIV type 1 (HIV-1). Eliciting these antibodies via vaccination appears to be remarkably difficult, not least because they arise late in infection and are highly mutated relative to germline antibody sequences. Here, using a computational model, we show that broad antibodies could in fact emerge earlier and be less mutated, but that they may be prevented from doing so as a result of competitive exclusion by the autologous antibody response. We further find that this competitive exclusion is weaker in infections founded by multiple distinct strains, with broadly neutralizing antibodies emerging earlier than in infections founded by a single strain. Our computational model simulates coevolving multitype virus and antibody populations. Broadly neutralizing antibodies may therefore be easier for the adaptive immune system to generate than previously thought. As a result, if less mutated broad antibodies exist, it may be possible to elicit them with a vaccine containing a mixture of diverse virus strains.

  18. Competitive exclusion by autologous antibodies can prevent broad HIV-1 antibodies from arising

    PubMed Central

    Luo, Shishi; Perelson, Alan S.

    2015-01-01

    The past decade has seen the discovery of numerous broad and potent monoclonal antibodies against HIV type 1 (HIV-1). Eliciting these antibodies via vaccination appears to be remarkably difficult, not least because they arise late in infection and are highly mutated relative to germline antibody sequences. Here, using a computational model, we show that broad antibodies could in fact emerge earlier and be less mutated, but that they may be prevented from doing so as a result of competitive exclusion by the autologous antibody response. We further find that this competitive exclusion is weaker in infections founded by multiple distinct strains, with broadly neutralizing antibodies emerging earlier than in infections founded by a single strain. Our computational model simulates coevolving multitype virus and antibody populations. Broadly neutralizing antibodies may therefore be easier for the adaptive immune system to generate than previously thought. If less mutated broad antibodies exist, it may be possible to elicit them with a vaccine containing a mixture of diverse virus strains. PMID:26324897

  19. Competitive exclusion by autologous antibodies can prevent broad HIV-1 antibodies from arising

    DOE PAGESBeta

    Luo, Shishi; Perelson, Alan S.

    2015-08-31

    The past decade has seen the discovery of numerous broad and potent monoclonal antibodies against HIV type 1 (HIV-1). Eliciting these antibodies via vaccination appears to be remarkably difficult, not least because they arise late in infection and are highly mutated relative to germline antibody sequences. Here, using a computational model, we show that broad antibodies could in fact emerge earlier and be less mutated, but that they may be prevented from doing so as a result of competitive exclusion by the autologous antibody response. We further find that this competitive exclusion is weaker in infections founded by multiple distinctmore » strains, with broadly neutralizing antibodies emerging earlier than in infections founded by a single strain. Our computational model simulates coevolving multitype virus and antibody populations. Broadly neutralizing antibodies may therefore be easier for the adaptive immune system to generate than previously thought. As a result, if less mutated broad antibodies exist, it may be possible to elicit them with a vaccine containing a mixture of diverse virus strains.« less

  20. Comparing a Coevolutionary Genetic Algorithm for Multiobjective Optimization

    NASA Technical Reports Server (NTRS)

    Lohn, Jason D.; Kraus, William F.; Haith, Gary L.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    We present results from a study comparing a recently developed coevolutionary genetic algorithm (CGA) against a set of evolutionary algorithms using a suite of multiobjective optimization benchmarks. The CGA embodies competitive coevolution and employs a simple, straightforward target population representation and fitness calculation based on developmental theory of learning. Because of these properties, setting up the additional population is trivial making implementation no more difficult than using a standard GA. Empirical results using a suite of two-objective test functions indicate that this CGA performs well at finding solutions on convex, nonconvex, discrete, and deceptive Pareto-optimal fronts, while giving respectable results on a nonuniform optimization. On a multimodal Pareto front, the CGA finds a solution that dominates solutions produced by eight other algorithms, yet the CGA has poor coverage across the Pareto front.

  1. The influence of lactobacilli on the competitive exclusion of paratyphoid salmonellae in chickens.

    PubMed

    Soerjadi, A S; Stehman, S M; Snoeyenbos, G H; Weinack, O M; Smyser, C F

    1981-01-01

    The competitive exclusion of salmonellae by native gut microflora was investigated by treating chicks with various avian lactobacilli. The evaluation of protection was based on the number of salmonellae adhering to the mucosa of the crop and the cecum, enumeration of salmonellae in fecal droppings, and enrichment of cloacal swabs and fecal droppings using both individual and seeder bird tests. Lactobacilli reduced the number of salmonellae adhering to the crop mucosa by 1 to 2 logs. Treatment with lactobacilli did not lower the number of chickens shedding salmonellae or reduce the number of salmonellae adhering to the mucosa of the cecum. Lactobacilli as a single bacterial treatment played a minor role in protecting the crop, but no protection of the cecum was demonstrated. PMID:7039590

  2. Species colonisation, not competitive exclusion, drives community overdispersion over long-term succession.

    PubMed

    Li, Shao-Peng; Cadotte, Marc W; Meiners, Scott J; Hua, Zheng-Shuang; Jiang, Lin; Shu, Wen-Sheng

    2015-09-01

    Ecological communities often transition from phylogenetic and functional clustering to overdispersion over succession as judged by space-for-time substitution studies. Such a pattern has been generally attributed to the increase in competitive exclusion of closely related species with similar traits through time, although colonisation and extinction have rarely been examined. Using 44 years of uninterrupted old-field succession in New Jersey, USA, we confirmed that phylogenetic and functional clustering decreased as succession unfolded, but the transition was largely driven by colonisation. Early colonists were closely related and functionally similar to residents, while later colonists became less similar to the species present. Extirpated species were generally more distantly related to residents than by chance, or exhibited random phylogenetic/functional patterns, and their relatedness to residents was not associated with time. These results provide direct evidence that the colonisation of distant relatives, rather than extinction of close relatives, drives phylogenetic and functional overdispersion over succession. PMID:26189648

  3. Competitive exclusion and coexistence in a two-strain pathogen model with diffusion.

    PubMed

    Ackleh, Azmy S; Deng, Keng; Wu, Yixiang

    2016-02-01

    We consider a two-strain pathogen model described by a system of reaction-diffusion equations. We define a basic reproduction number R0 and show that when the model parameters are constant (spatially homogeneous), if R0 >1 then one strain will outcompete the other strain and drive it to extinction, but if R0 ≤ 1 then the disease-free equilibrium is globally attractive. When we assume that the diffusion rates are equal while the transmission and recovery rates are heterogeneous, then there are two possible outcomes under the condition R0 < 1: 1) Competitive exclusion where one strain dies out. 2) Coexistence between the two strains. Thus, spatial heterogeneity promotes coexistence. PMID:26776256

  4. Antimicrobial susceptibility patterns of competitive exclusion bacteria applied to newly hatched chickens.

    PubMed

    Wagner, R Doug; Cerniglia, Carl E

    2005-07-25

    Competitive exclusion (CE) products are mixtures of obligate and facultative anaerobic bacteria applied to poultry hatchlings for prevention of Salmonella colonization. These mixtures have the potential to introduce bacteria with undesirable antimicrobial drug resistance traits into the human food supply. Antimicrobial drug susceptibilities of 27 obligate and facultative anaerobes isolated from a commercial CE product were evaluated with a microdilution minimal inhibitory concentration (MIC) assay. Bacteroides distasonis and Bacteroides fragilis isolates were resistant to tetracycline and other antimicrobial drugs. An Escherichia coli isolate was resistant to four antimicrobial drugs: erythromycin, penicillin, vancomycin, and tylosin. Erythromycin-resistant enterococci and vancomycin-resistant Lactococcus lactis isolates in the CE product were detected. These findings suggest that more work needs to be done to assess the potential effects of CE product use in poultry on the food supply. PMID:16014302

  5. Lactobacillus reuteri protects epidermal keratinocytes from Staphylococcus aureus-induced cell death by competitive exclusion.

    PubMed

    Prince, Tessa; McBain, Andrew J; O'Neill, Catherine A

    2012-08-01

    Recent studies have suggested that the topical application of probiotic bacteria can improve skin health or combat disease. We have utilized a primary human keratinocyte culture model to investigate whether probiotic bacteria can inhibit Staphylococcus aureus infection. Evaluation of the candidate probiotics Lactobacillus reuteri ATCC 55730, Lactobacillus rhamnosus AC413, and Lactobacillus salivarius UCC118 demonstrated that both L. reuteri and L. rhamnosus, but not L. salivarius, reduced S. aureus-induced keratinocyte cell death in both undifferentiated and differentiated keratinocytes. Keratinocyte survival was significantly higher if the probiotic was applied prior to (P < 0.01) or simultaneously with (P < 0.01) infection with S. aureus but not when added after infection had commenced (P > 0.05). The protective effect of L. reuteri was not dependent on the elaboration of inhibitory substances such as lactic acid. L. reuteri inhibited adherence of S. aureus to keratinocytes by competitive exclusion (P = 0.026). L. salivarius UCC118, however, did not inhibit S. aureus from adhering to keratinocytes (P > 0.05) and did not protect keratinocyte viability. S. aureus utilizes the α5β1 integrin to adhere to keratinocytes, and blocking of this integrin resulted in a protective effect similar to that observed with probiotics (P = 0.03). This suggests that the protective mechanism for L. reuteri-mediated protection of keratinocytes was by competitive exclusion of the pathogen from its binding sites on the cells. Our results suggest that use of a topical probiotic prophylactically could inhibit the colonization of skin by S. aureus and thus aid in the prevention of infection. PMID:22582077

  6. Control of Listeria monocytogenes in a Biofilm by Competitive-Exclusion Microorganisms

    PubMed Central

    Zhao, Tong; Doyle, Michael P.; Zhao, Ping

    2004-01-01

    Biofilms from drains in food processing facilities with a recent history of no detectable Listeria monocytogenes in floor drains were cultured for microorganisms producing antilisterial metabolites. A total of 413 microbial isolates were obtained from 12 drain biofilm samples and were assayed at 15 and 37°C for activities that were bactericidal or inhibitory to L. monocytogenes, by two agar plate assays. Twenty-one of 257 bacterial isolates and 3 of 156 yeast isolates had antilisterial activity. All 24 isolates which produced metabolites inhibitory to L. monocytogenes were assayed for antilisterial activity in coinoculated broth cultures containing tryptic soy broth with yeast extract (TSB-YE). A five-strain mixture of 103 CFU of L. monocytogenes/ml and 105 CFU of the candidate competitive-exclusion microorganism/ml was combined in TSB-YE and incubated at 37°C for 24 h, 15°C for 14 days, 8°C for 21 days, and 4°C for 28 days. Substantial inhibition of L. monocytogenes growth (4 to 5 log CFU/ml) was observed for nine bacterial isolates at 37°C, two at 15 and 8°C, and three at 4°C. The inhibitory isolates were identified as Enterococcus durans (six isolates), Lactococcus lactis subsp. lactis (two isolates), and Lactobacillus plantarum (one isolate). The anti-L. monocytogenes activity of these isolates was evaluated in biofilms of L. monocytogenes on stainless steel coupons at 37, 15, 8, and 4°C. Results revealed that two isolates (E. durans strain 152 and L. lactis subsp. lactis strain C-1-92) were highly inhibitory to L. monocytogenes (growth inhibition of >5 log10 CFU of L. monocytogenes/cm2). These two bacterial isolates appear to be excellent competitive-exclusion candidates to control L. monocytogenes in biofilms at environmental temperatures of 4 to 37°C. PMID:15240275

  7. Lactobacillus reuteri Protects Epidermal Keratinocytes from Staphylococcus aureus-Induced Cell Death by Competitive Exclusion

    PubMed Central

    Prince, Tessa; McBain, Andrew J.

    2012-01-01

    Recent studies have suggested that the topical application of probiotic bacteria can improve skin health or combat disease. We have utilized a primary human keratinocyte culture model to investigate whether probiotic bacteria can inhibit Staphylococcus aureus infection. Evaluation of the candidate probiotics Lactobacillus reuteri ATCC 55730, Lactobacillus rhamnosus AC413, and Lactobacillus salivarius UCC118 demonstrated that both L. reuteri and L. rhamnosus, but not L. salivarius, reduced S. aureus-induced keratinocyte cell death in both undifferentiated and differentiated keratinocytes. Keratinocyte survival was significantly higher if the probiotic was applied prior to (P < 0.01) or simultaneously with (P < 0.01) infection with S. aureus but not when added after infection had commenced (P > 0.05). The protective effect of L. reuteri was not dependent on the elaboration of inhibitory substances such as lactic acid. L. reuteri inhibited adherence of S. aureus to keratinocytes by competitive exclusion (P = 0.026). L. salivarius UCC118, however, did not inhibit S. aureus from adhering to keratinocytes (P > 0.05) and did not protect keratinocyte viability. S. aureus utilizes the α5β1 integrin to adhere to keratinocytes, and blocking of this integrin resulted in a protective effect similar to that observed with probiotics (P = 0.03). This suggests that the protective mechanism for L. reuteri-mediated protection of keratinocytes was by competitive exclusion of the pathogen from its binding sites on the cells. Our results suggest that use of a topical probiotic prophylactically could inhibit the colonization of skin by S. aureus and thus aid in the prevention of infection. PMID:22582077

  8. Competitive exclusion in a multi-strain immuno-epidemiological influenza model with environmental transmission.

    PubMed

    Dang, Yan-Xia; Li, Xue-Zhi; Martcheva, Maia

    2016-12-01

    In this paper, a multi-strain model that links immunological and epidemiological dynamics across scales is formulated. On the within-host scale, the n strains eliminate each other with the strain having the largest immunological reproduction number persisting. However, on the population scale, we extend the competitive exclusion principle to a multi-strain model of SI-type for the dynamics of highly pathogenic flu in poultry that incorporates both the infection age of infectious individuals and biological age of pathogen in the environment. The two models are linked through the age-since-infection structure of the epidemiological variables. In addition the between-host transmission rate, the shedding rate of individuals infected by strain j and the disease-induced death rate depend on the within-host viral load. The immunological reproduction numbers [Formula: see text] and the epidemiological reproduction numbers [Formula: see text] are computed. By constructing a suitable Lyapunov function, the global stability of the infection-free equilibrium in the system is obtained if all reproduction numbers are smaller or equal to one. If [Formula: see text], the reproduction number of strain j is larger than one, then a single-strain equilibrium, corresponding to strain j exists. This single-strain equilibrium is globally stable whenever [Formula: see text] and [Formula: see text] is the unique maximal reproduction number and all of the reproduction numbers are distinct. That is, the strain with the maximal basic reproduction number competitively excludes all other strains. PMID:27608293

  9. Cost modeling of pseudomonoas fluorescens and pseudomonoas chlororphis biocontrol for competitive exclusion of salmonella enterica on tomatoes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biocontrol measures may enhance postharvest interventions, however; published research on process-based models for biocontrol of foodborne pathogens on produce is limited. The aim of this research was to develop cost model estimates for competitive exclusion process using Pseudomonas fluorescens and...

  10. Competitive Exclusion and Axiomatic Set-Theory: De Morgan's Laws, Ecological Virtual Processes, Symmetries and Frozen Diversity.

    PubMed

    Flores, J C

    2016-03-01

    This work applies the competitive exclusion principle and the concept of potential competitors as simple axiomatic tools to generalized situations in ecology. These tools enable apparent competition and its dual counterpart to be explicitly evaluated in poorly understood ecological systems. Within this set-theory framework we explore theoretical symmetries and invariances, De Morgan's laws, frozen evolutionary diversity and virtual processes. In particular, we find that the exclusion principle compromises the geometrical growth of the number of species. By theoretical extending this principle, we can describe interspecific depredation in the dual case. This study also briefly considers the debated situation of intraspecific competition. The ecological consequences of our findings are discussed; particularly, the use of our framework to reinterpret coupled mathematical differential equations describing certain ecological processes. PMID:26801920

  11. Competitive exclusion in a vector-host model for the dengue fever.

    PubMed

    Feng, Z; Velasco-Hernández, J X

    1997-05-01

    We study a system of differential equations that models the population dynamics of an SIR vector transmitted disease with two pathogen strains. This model arose from our study of the population dynamics of dengue fever. The dengue virus presents four serotypes each induces host immunity but only certain degree of cross-immunity to heterologous serotypes. Our model has been constructed to study both the epidemiological trends of the disease and conditions that permit coexistence in competing strains. Dengue is in the Americas an epidemic disease and our model reproduces this kind of dynamics. We consider two viral strains and temporary cross-immunity. Our analysis shows the existence of an unstable endemic state ('saddle' point) that produces a long transient behavior where both dengue serotypes cocirculate. Conditions for asymptotic stability of equilibria are discussed supported by numerical simulations. We argue that the existence of competitive exclusion in this system is product of the interplay between the host superinfection process and frequency-dependent (vector to host) contact rates. PMID:9145954

  12. Detection of bacteria from a cecal anaerobic competitive exclusion culture with an immunoassay electrochemiluminescence sensor

    NASA Astrophysics Data System (ADS)

    Beier, Ross C.; Young, Colin R.; Stanker, Larry H.

    1999-01-01

    A competitive exclusion (CE) culture of chicken cecal anaerobes has been developed and used in this laboratory for control of Salmonella typhimurium in chickens. The CE culture consists of 29 different species of micro-organisms, and is known as CF3. Detection of one of the CF3 bacteria, Eubacteria, and S. typhimurium were demonstrated using a commercial immunomagnetic (IM) electrochemiluminescence (ECL) sensor, the ORIGENR Analyzer. Analysis was achieved using a sandwich immunoassay. Bacteria were captured on antibody- conjugated 280 micron sized magnetic beads followed by binding of reporter antibodies labelled with ruthenium (II) tris(dipyridyl) chelate [Ru(bpy)32+]. The magnetic beads were then trapped on an electrode in the reaction cell of the ORIGENR Analyzer by a magnet, and the ECL was evoked from Ru(bpy)32+ on the tagged reporter antibodies by an electrical potential at the electrode. Preliminary IM-ECL assays with Eubacteria yielded a detection limit of 105 cfu/mL. Preliminary IM-ECL assays with S. typhimurium yielded a similar detection limit of 105 cfu/mL.

  13. Competitive exclusion in a vector–host epidemic model with distributed delay†

    PubMed Central

    Cai, Li-Ming; Martcheva, Maia; Li, Xue-Zhi

    2013-01-01

    A multi-strain model of a vector-borne disease with distributed delay in the vector and the host is investigated. It is shown that if the reproduction number of the model ℛ0 < 1, the unique disease-free equilibrium is globally asymptotically stable. Without loss of generality, strain one is assumed to have the largest reproduction number. In this case, the dominance equilibrium of strain one is shown to be locally stable. The basic reproduction number for a strain i (ℛ0i) is written as a product of the reproduction number of the vector (ℛvi) and the reproduction number of the host (ℛih), i.e. ℛi0 = ℛihℛvi. The competitive exclusion principle is derived under the somewhat stronger condition that if strain one maximizes both the reproduction number of the host ℛhi < ℛh1, i ≠ 1 and the reproduction number of the vector ℛvi < ℛv1, i ≠ 1, strain one dominance equilibrium is globally asymptotically stable. AMS Subject Classification: 92D30 PMID:23421610

  14. Competitive exclusion within the predator community influences the distribution of a threatened prey species.

    PubMed

    Byholm, Patrik; Burgas, Daniel; Virtanen, Tarmo; Valkama, Jari

    2012-08-01

    While much effort has been made to quantify how landscape composition influences the distribution of species, the possibility that geographical differences in species interactions might affect species distributions has received less attention. Investigating a predator-prey setting in a boreal forest ecosystem, we empirically show that large-scale differences in the predator community structure and small-scale competitive exclusion among predators affect the local distribution of a threatened forest specialist more than does landscape composition. Consequently, even though the landscape parameters affecting Siberian flying squirrel (Pteromys volans) distribution (prey) did not differ between nest sites of the predators Northern Goshawks (Accipiter gentilis) and Ural Owls (Strix uralensis), flying squirrels were heterospecifically attracted by goshawks in a region where both predator species were present. No such effect was found in another region where Ural Owls were absent. These results provide evidence that differences in species interactions over large spatial scales may be a major force influencing the distribution and abundance patterns of species. On the basis of these findings, we suspect that subtle species interactions might be a central reason why landscape models constructed to predict species distributions often fail when applied to wider geographical scales. PMID:22928409

  15. Salmonellae reduction in poultry by competitive exclusion bacteria Lactobacillus salivarius and Streptococcus cristatus.

    PubMed

    Zhang, Guodong; Ma, Li; Doyle, Michael P

    2007-04-01

    The objective of this study was to develop a defined competitive exclusion bacteria (CE) culture that will prevent or substantially reduce Salmonella colonization of poultry. The efficacy of 56 potential CE isolates in preventing or reducing Salmonella colonization in chickens was determined. These potential CE were perorally administered to day-of-hatch chicks at 10(6) to 10(8) CFU per chick, and salmonellae were subsequently administered by gavage 2 days later at 5.5 x 10(3) to 5.0 x 10(4) CFU per chick. Feeding chickens an overnight CE culture of Lactobacillus salivarius strains Salm-9, List40-1,8, or List40-41 reduced Salmonella carriage in cecal contents by 2.10, 2.52, and 2.20 log CFU/g (average of three trials), respectively. The percentages of Salmonella-positive chickens after receiving these treatments were 35, 31, and 35% respectively, compared with 84% for the untreated control. A mixture of these three isolates had a similar effect when compared with the results of the individual isolates. A mixture of Streptococcus cristatus List40-13 and L. salivarius List40-41 reduced Salmonella carriage from 90 to 65% and 88 to 31% in two feeding trials, and by 2.2 and 4 log CFU/g of cecal contents of chickens. In conclusion, CE isolates L. salivarius Salm-9, List40-18, and List40-41 and S. cristatus List40-13 either individually or in combination were effective in significantly preventing Salmonella colonization of chickens. PMID:17477255

  16. Coevolutionary feedbacks between family interactions and life history.

    PubMed

    Stucki, Dimitri; Kölliker, Mathias

    2013-11-01

    Families with parental care show a parent-offspring conflict over the amount of parental investment. To date, the resolution of this conflict was modeled as being driven by either purely within-brood or between-brood competition. In reality the partitioning of parental resources within- versus between-broods is an evolving life history trait, which can be affected by parent-offspring interactions. This coevolutionary feedback between life history and family interactions may influence the evolutionary process and outcome of parent-offspring coadaptation. We used a genetic framework for a simulation model where we allowed parental parity to coevolve with traits that determine parental investment. The model included unlinked loci for clutch size, parental sensitivity, baseline provisioning, and offspring begging. The simulation showed that tight coadaptation of parent and offspring traits only occurred in iteroparous outcomes whereas semelparous outcomes were characterized by weak coadaptation. When genetic variation in clutch size was unrestricted in the ancestral population, semelparity and maximal begging with poor coadaptation evolved throughout. Conversely, when genetic variation was limited to iteroparous conditions, and/or when parental sensitivity was treated as an evolutionarily fixed sensory bias, coadapted outcomes were more likely. Our findings show the influence of a feedback between parity, coadaptation, and conflict on the evolution of parent-offspring interactions. PMID:24152003

  17. Coevolutionary dynamics with clustering behaviors on cyclic competition

    NASA Astrophysics Data System (ADS)

    Dong, Linrong; Yang, Guangcan

    2012-05-01

    We propose a dynamic model for describing clustering behaviors on a cyclic game, in which the same species form a cluster to compete. The rates of consuming the prey depend not only on the individual competing ability v, but also on the two interacting cluster’s sizes. The fragmentation and coagulation rates of the clusters are related to the cohesive strength among the individuals. A new parameter u is introduced to indicate the uniting degree. We find that the probability distribution of the clustering sizes is almost a power law in a large regime specified by the two parameters, which reflects the scale-free behavior in complex systems. In addition, the exponential magnitudes are mostly in the range of real social systems. Our simulation shows that clustering promotes biodiversity. At steady state, the amounts about the three species evolve tempestuously with asymmetric period; the aggregations about big size’s clusters to compete are obvious and on-off intermittence.

  18. Organizational coevolutionary classifiers with fuzzy logic used in intrusion detection

    NASA Astrophysics Data System (ADS)

    Chen, Zhenguo

    2009-07-01

    Intrusion detection is an important technique in the defense-in-depth network security framework and a hot topic in computer security in recent years. To solve the intrusion detection question, we introduce the fuzzy logic into Organization CoEvolutionary algorithm [1] and present the algorithm of Organization CoEvolutionary Classification with Fuzzy Logic. In this paper, we give an intrusion detection models based on Organization CoEvolutionary Classification with Fuzzy Logic. After illustrating our model with a representative dataset and applying it to the real-world network datasets KDD Cup 1999. The experimental result shown that the intrusion detection based on Organizational Coevolutionary Classifiers with Fuzzy Logic can give higher recognition accuracy than the general method.

  19. Coevolutionary networks of reinforcement-learning agents

    NASA Astrophysics Data System (ADS)

    Kianercy, Ardeshir; Galstyan, Aram

    2013-07-01

    This paper presents a model of network formation in repeated games where the players adapt their strategies and network ties simultaneously using a simple reinforcement-learning scheme. It is demonstrated that the coevolutionary dynamics of such systems can be described via coupled replicator equations. We provide a comprehensive analysis for three-player two-action games, which is the minimum system size with nontrivial structural dynamics. In particular, we characterize the Nash equilibria (NE) in such games and examine the local stability of the rest points corresponding to those equilibria. We also study general n-player networks via both simulations and analytical methods and find that, in the absence of exploration, the stable equilibria consist of star motifs as the main building blocks of the network. Furthermore, in all stable equilibria the agents play pure strategies, even when the game allows mixed NE. Finally, we study the impact of exploration on learning outcomes and observe that there is a critical exploration rate above which the symmetric and uniformly connected network topology becomes stable.

  20. Competition.

    PubMed

    Chambers, D W

    1997-01-01

    Our ambivalence toward competition can be traced to an unspoken preference for certain types of competition which give us an advantage over the types we value less. Four types are defined (a) pure (same rules, same objectives), (b) collaborative (same rules, shared objective), (c) market share (different rules, same objectives), and (d) market growth (different rules, value added orientation). The defining characteristics of the four types of competition are respectively: needing a referee, arguing over the spoils, differentiation and substitutability, and customer focus. Dentistry has features of all four types of competition, thus making it difficult to have a meaningful discussion or frame a coherent policy on this topic. PMID:9270222

  1. Sympatric inhibition and niche differentiation suggest alternative coevolutionary trajectories among Streptomycetes

    PubMed Central

    Kinkel, Linda L; Schlatter, Daniel C; Xiao, Kun; Baines, Anita D

    2014-01-01

    Soil bacteria produce a diverse array of antibiotics, yet our understanding of the specific roles of antibiotics in the ecological and evolutionary dynamics of microbial interactions in natural habitats remains limited. Here, we show a significant role for antibiotics in mediating antagonistic interactions and nutrient competition among locally coexisting Streptomycete populations from soil. We found that antibiotic inhibition is significantly more intense among sympatric than allopatric Streptomycete populations, indicating local selection for inhibitory phenotypes. For sympatric but not allopatric populations, antibiotic inhibition is significantly positively correlated with niche overlap, indicating that inhibition is targeted toward bacteria that pose the greatest competitive threat. Our results support the hypothesis that antibiotics serve as weapons in mediating local microbial interactions in soil and suggest that coevolutionary niche displacement may reduce the likelihood of an antibiotic arms race. Further insight into the diverse roles of antibiotics in microbial ecology and evolution has significant implications for understanding the persistence of antibiotic inhibitory and resistance phenotypes in environmental microbes, optimizing antibiotic drug discovery and developing strategies for managing microbial coevolutionary dynamics to enhance inhibitory phenotypes. PMID:24152720

  2. The mechanism for exclusion of Pinus massoniana during the succession in subtropical forest ecosystems: light competition or stoichiometric homoeostasis?

    NASA Astrophysics Data System (ADS)

    Yan, Junhua; Li, Kun; Peng, Xingju; Huang, Zhongliang; Liu, Shizhong; Zhang, Qianmei

    2015-06-01

    Competition for light has traditionally been considered as the main mechanism for exclusion of Pinus massoniana during succession in subtropical forest ecosystems. However, both long-term inventories and a seedling cultivation experiment showed that growth of mature individuals and young seedlings of P. massoniana was not limited by available light, but was strongly influenced by stoichiometric homoeostasis. This is supported by the results of homoeostatic regulation coefficients for nitrogen (HN) and phosphorus (HP) estimated using the measured data from six transitional forests across subtropical China. Among three dominant tree species in subtropical forests, P. massoniana and Castanopsis chinensis had the lowest values of HP and HN, respectively. Therefore P. massoniana cannot survive in the advanced stage due to soil phosphorus limitation and C. chinensis cannot successfully grow in the pioneer stage due to soil nitrogen limitation. Our results support that stoichiometric homeostasis is the main reason for gradual exclusion of P. massoniana from the transitional forest and the eventual elimination from the advanced forest during the subtropical forest succession. Therefore greater attention should be paid to stoichiometric homeostasis as one of the key mechanisms for species exclusion during forest succession.

  3. The mechanism for exclusion of Pinus massoniana during the succession in subtropical forest ecosystems: light competition or stoichiometric homoeostasis?

    PubMed

    Yan, Junhua; Li, Kun; Peng, Xingju; Huang, Zhongliang; Liu, Shizhong; Zhang, Qianmei

    2015-01-01

    Competition for light has traditionally been considered as the main mechanism for exclusion of Pinus massoniana during succession in subtropical forest ecosystems. However, both long-term inventories and a seedling cultivation experiment showed that growth of mature individuals and young seedlings of P. massoniana was not limited by available light, but was strongly influenced by stoichiometric homoeostasis. This is supported by the results of homoeostatic regulation coefficients for nitrogen (HN) and phosphorus (HP) estimated using the measured data from six transitional forests across subtropical China. Among three dominant tree species in subtropical forests, P. massoniana and Castanopsis chinensis had the lowest values of HP and HN, respectively. Therefore P. massoniana cannot survive in the advanced stage due to soil phosphorus limitation and C. chinensis cannot successfully grow in the pioneer stage due to soil nitrogen limitation. Our results support that stoichiometric homeostasis is the main reason for gradual exclusion of P. massoniana from the transitional forest and the eventual elimination from the advanced forest during the subtropical forest succession. Therefore greater attention should be paid to stoichiometric homeostasis as one of the key mechanisms for species exclusion during forest succession. PMID:26046944

  4. Co-occurrence patterns of Bornean vertebrates suggest competitive exclusion is strongest among distantly related species.

    PubMed

    Beaudrot, Lydia; Struebig, Matthew J; Meijaard, Erik; van Balen, S; Husson, Simon; Marshall, Andrew J

    2013-11-01

    Assessing the importance of deterministic processes in structuring ecological communities is a central focus of community ecology. Typically, community ecologists study a single taxonomic group, which precludes detection of potentially important biotic interactions between distantly related species, and inherently assumes competition is strongest between closely related species. We examined distribution patterns of vertebrate species across the island of Borneo in Southeast Asia to assess the extent to which inter-specific competition may have shaped ecological communities on the island and whether the intensity of inter-specific competition in present-day communities varies as a function of evolutionary relatedness. We investigated the relative extent of competition within and between species of primates, birds, bats and squirrels using species presence-absence and attribute data compiled for 21 forested sites across Borneo. We calculated for each species pair the checkerboard unit value (CU), a statistic that is often interpreted as indicating the importance of interspecific competition. The percentage of species pairs with significant CUs was lowest in within-taxon comparisons. Moreover, for invertebrate-eating species the percentage of significantly checkerboarded species pairs was highest in comparisons between primates and other taxa, particularly birds and squirrels. Our results are consistent with the interpretation that competitive interactions between distantly related species may have shaped the distribution of species and thus the composition of Bornean vertebrate communities. This research highlights the importance of taking into account the broad mammalian and avian communities in which species occur for understanding the factors that structure biodiversity. PMID:23736548

  5. Hybrid Co-Evolutionary Motion Planning via Visibility-Based Repair

    NASA Technical Reports Server (NTRS)

    Dozier, Gerry; McCullough, Shaun; Brown, Edward, Jr.; Homaifar, Abdollah; Bikdash, Mar-wan

    1997-01-01

    This paper introduces a hybrid co-evolutionary system for global motion planning within unstructured environments. This system combines the concept of co-evolutionary search along with a concept that we refer to as the visibility-based repair to form a hybrid which quickly transforms infeasible motions into feasible ones. Also, this system makes use of a novel representation scheme for the obstacles within an environment. Our hybrid evolutionary system differs from other evolutionary motion planners in that (1) more emphasis is placed on repairing infeasible motions to develop feasible motions rather than using simulated evolution exclusively as a means of discovering feasible motions, (2) a continuous map of the environment is used rather than a discretized map, and (3) it develops global motion plans for multiple mobile destinations by co-evolving populations of sub-global motion plans. In this paper, we demonstrate the effectiveness of this system by using it to solve two challenging motion planning problems where multiple targets try to move away from a point robot.

  6. Competitiveness

    NASA Astrophysics Data System (ADS)

    Minihan, Charles E.

    1991-03-01

    Competition is defined as a spirited, sometimes ruthless, engagement of rivals such as in a race, a match, or an effort by one person to sell goods or services to customers in the marketplace of another. Sound familiar? If you will bear with me for a few minutes, I would like to examine competitiveness on a more global basis with emphasis on the rules of the game. You may be thinking that more often than not the competitive arena is relatively small and far from global, and its consequences are singularly influential on a trivial document called the P & L. However, with the newly established freedom of a major segment of the world population and with the industrial capability formerly known as Communist moving into what has heretofore been "our" limited arena, the competition could get very brisk. Brisk, and perhaps ruthless, unless we work together to try to establish an international industrial policy that is truly based on equality of competitive opportunity for all.

  7. The co-evolutionary dynamics of directed network of spin market agents

    NASA Astrophysics Data System (ADS)

    Horváth, Denis; Kuscsik, Zoltán; Gmitra, Martin

    2006-09-01

    The spin market model [S. Bornholdt, Int. J. Mod. Phys. C 12 (2001) 667] is generalized by employing co-evolutionary principles, where strategies of the interacting and competitive traders are represented by local and global couplings between the nodes of dynamic directed stochastic network. The co-evolutionary principles are applied in the frame of Bak-Sneppen self-organized dynamics [P. Bak, K. Sneppen, Phys. Rev. Lett. 71 (1993) 4083] that includes the processes of selection and extinction actuated by the local (node) fitness. The local fitness is related to orientation of spin agent with respect to the instant magnetization. The stationary regime is formed due to the interplay of self-organization and adaptivity effects. The fat tailed distributions of log-price returns are identified numerically. The non-trivial model consequence is the evidence of the long time market memory indicated by the power-law range of the autocorrelation function of volatility with exponent smaller than one. The simulations yield network topology with broad-scale node degree distribution characterized by the range of exponents 1.3<γin<3 coinciding with social networks.

  8. Competition between multiple totally asymmetric simple exclusion processes for a finite pool of resources.

    PubMed

    Cook, L Jonathan; Zia, R K P; Schmittmann, B

    2009-09-01

    Using Monte Carlo simulations and a domain-wall theory, we discuss the effect of coupling several totally asymmetric simple exclusion processes (TASEPs) to a finite reservoir of particles. This simple model mimics directed biological transport processes in the presence of finite resources such as protein synthesis limited by a finite pool of ribosomes. If all TASEPs have equal length, we find behavior which is analogous to a single TASEP coupled to a finite pool. For the more generic case of chains with different lengths, several unanticipated regimes emerge. A generalized domain-wall theory captures our findings in good agreement with simulation results. PMID:19905097

  9. Competition between multiple totally asymmetric simple exclusion processes for a finite pool of resources

    NASA Astrophysics Data System (ADS)

    Cook, L. Jonathan; Zia, R. K. P.; Schmittmann, B.

    2009-09-01

    Using Monte Carlo simulations and a domain-wall theory, we discuss the effect of coupling several totally asymmetric simple exclusion processes (TASEPs) to a finite reservoir of particles. This simple model mimics directed biological transport processes in the presence of finite resources such as protein synthesis limited by a finite pool of ribosomes. If all TASEPs have equal length, we find behavior which is analogous to a single TASEP coupled to a finite pool. For the more generic case of chains with different lengths, several unanticipated regimes emerge. A generalized domain-wall theory captures our findings in good agreement with simulation results.

  10. Combination of competitive exclusion and immunisation with a live Salmonella vaccine in newly hatched chickens: Immunological and microbiological effects.

    PubMed

    Braukmann, M; Barrow, P A; Berndt, A; Methner, U

    2016-08-01

    In addition to evaluating the efficacy potential of a combined use of vaccination and competitive exclusion (CE) against Salmonella exposure in chicks at 3-days of age, a live Salmonella Enteritidis vaccine (SE-LV) and a CE culture were tested for their ability to induce parameters of the innate immunity. Whereas the invasive SE-LV induced an influx of granulocytes and macrophages as well as an increased transcription of several cytokines in the caecal mucosa, the CE culture did not demonstrate any differences in these parameters compared to controls. It is therefore highly probable that the effects observed with CE cultures are not due to the rapid stimulation of the immune system. The combined use of both preparations did not result in an additive intestinal exclusion effect of the challenge strain more pronounced than that after single administration of the CE culture. The combined use of the Salmonella live vaccine and the CE culture resulted in an additive protective effect and prevented completely the systemic dissemination of the Salmonella challenge strain. To exploit the potential of combined use of CE and vaccination further and most effectively, live Salmonella vaccines are needed that are despite their attenuation in virulence still capable to induce both intestinal colonisation- and invasion-inhibition effects against Salmonella exposure. PMID:27473972

  11. Exclusion and spatial segregation in the apparent competition between two hosts sharing macroparasites.

    PubMed

    Manica, Mattia; Rosà, Roberto; Pugliese, Andrea; Bolzoni, Luca

    2013-06-01

    In this paper we investigate the spatial dynamics of a deterministic model describing two host species that partially share a common spatial domain, experiencing apparent competition mediated by macroparasites. The aim of this work is to understand the mechanisms underlying apparent competition processes in a spatially structured environment, which have been generally overlooked up to now. First, we analyse the behaviour of a single-host macroparasite partial differential equation (PDE) model, both in the cases of uniform or spatially-dependent vital rates of the host, focusing on the role of spatial diffusion on parasite persistence and host abundance. We obtained the threshold condition for parasite persistence, and (in contrast to what occurs in reaction-diffusion models for an isolated population) we found that, in the case of spatially-dependent vital rates, increasing the host diffusion coefficient results in an increase of the overall host population. Then, a PDE model featuring spatial diffusion and apparent competition mediated via shared macroparasites between two species is analysed in order to understand the role of spatial heterogeneity in host coexistence. We assumed a partial overlap among the habitats of the two species and found that the shared parasites could cause, depending on the values of the diffusion coefficients and differences in induced mortality among host species, a decrease of the realized habitat and, eventually, the extinction of the species less tolerant to parasite infection. This shows that the presence of regulating parasites complicates the effect of dispersal on population dynamics and that the dynamics of apparent competition cannot be adequately understood from spatially-independent models. PMID:23524023

  12. Distance-limited dispersal promotes coexistence at habitat boundaries: reconsidering the competitive exclusion principle.

    PubMed

    Débarre, Florence; Lenormand, Thomas

    2011-03-01

    Understanding the conditions for the stable coexistence of different alleles or species is a central topic in theoretical evolution and ecology. Different causes for stable polymorphism or species coexistence have already been identified but they can be grouped into a limited number of general processes. This article is devoted to the presentation and illustration of a new process, which we call 'habitat boundary polymorphism', and which relies on two key ingredients: habitat heterogeneity and distance-limited dispersal. Under direct competition and with fixed population densities, we show that this process allows for the equilibrium coexistence of more than n types in a n-habitat environment. Distance-limited dispersal indeed creates local maladaptation at habitat edges, which leaves room for the invasion of more generalist alleles or species. This mechanism provides a generic yet neglected process for the maintenance of polymorphism or species coexistence. PMID:21265974

  13. Competitive Exclusion of Epiphytic Bacteria by Ice−Pseudomonas syringae Mutants

    PubMed Central

    Lindow, Steven E.

    1987-01-01

    The growth of ice nucleation-active and near-isogenic ice nucleation-deficient (Ice−) Pseudomonas syringae strains coexisting on leaf surfaces was examined to determine whether competition was sufficient to account for antagonism of phylloplane bacteria. The ice nucleation frequency spectra of 46 Ice−P. syringae mutants, obtained after mutagenesis with ethyl methanesulfonate, differed both quantitatively and qualitatively, but the mutants could be grouped into four distinct phenotypic classes. The numbers of ice nucleation-active bacteria and ice nuclei active at −5°C were reduced on plants colonized with Ice−P. syringae mutant strains before challenge inoculations with an Ice+P. syringae wild-type strain. Frost injury to plants pretreated with Ice−P. syringae strains was also reduced significantly compared with that to control plants and was correlated with the population size of the Ice+P. syringae strain and with the numbers of ice nuclei active at −5°C. An Ice−P. syringae strain colonized leaves, flowers, and young fruit of pears in field experiments and significantly reduced the colonization of these tissues by Ice+P. syringae strains and Erwinia amylovora as compared with untreated trees. PMID:16347468

  14. Host Gut Motility Promotes Competitive Exclusion within a Model Intestinal Microbiota.

    PubMed

    Wiles, Travis J; Jemielita, Matthew; Baker, Ryan P; Schlomann, Brandon H; Logan, Savannah L; Ganz, Julia; Melancon, Ellie; Eisen, Judith S; Guillemin, Karen; Parthasarathy, Raghuveer

    2016-07-01

    The gut microbiota is a complex consortium of microorganisms with the ability to influence important aspects of host health and development. Harnessing this "microbial organ" for biomedical applications requires clarifying the degree to which host and bacterial factors act alone or in combination to govern the stability of specific lineages. To address this issue, we combined bacteriological manipulation and light sheet fluorescence microscopy to monitor the dynamics of a defined two-species microbiota within a vertebrate gut. We observed that the interplay between each population and the gut environment produces distinct spatiotemporal patterns. As a consequence, one species dominates while the other experiences sudden drops in abundance that are well fit by a stochastic mathematical model. Modeling revealed that direct bacterial competition could only partially explain the observed phenomena, suggesting that a host factor is also important in shaping the community. We hypothesized the host determinant to be gut motility, and tested this mechanism by measuring colonization in hosts with enteric nervous system dysfunction due to a mutation in the ret locus, which in humans is associated with the intestinal motility disorder known as Hirschsprung disease. In mutant hosts we found reduced gut motility and, confirming our hypothesis, robust coexistence of both bacterial species. This study provides evidence that host-mediated spatial structuring and stochastic perturbation of communities can drive bacterial population dynamics within the gut, and it reveals a new facet of the intestinal host-microbe interface by demonstrating the capacity of the enteric nervous system to influence the microbiota. Ultimately, these findings suggest that therapeutic strategies targeting the intestinal ecosystem should consider the dynamic physical nature of the gut environment. PMID:27458727

  15. Competitive Exclusion among Fig Wasps Achieved via Entrainment of Host Plant Flowering Phenology

    PubMed Central

    Chen, Yan; Zhang, Jian; Compton, Stephen G.; Chen, Xiao-Yong

    2014-01-01

    Molecular techniques are revealing increasing numbers of morphologically similar but co-existing cryptic species, challenging the niche theory. To understand the co-existence mechanism, we studied phenologies of morphologically similar species of fig wasps that pollinate the creeping fig (F. pumila) in eastern China. We compared phenologies of fig wasp emergence and host flowering at sites where one or both pollinators were present. At the site where both pollinators were present, we used sticky traps to capture the emerged fig wasps and identified species identity using mitochondrial DNA COI gene. We also genotyped F. pumila individuals of the three sites using polymorphic microsatellites to detect whether the host populations were differentiated. Male F. pumila produced two major crops annually, with figs receptive in spring and summer. A small partial third crop of receptive figs occurred in the autumn, but few of the second crop figs matured at that time. Hence, few pollinators were available to enter third crop figs and they mostly aborted, resulting in two generations of pollinating wasps each year, plus a partial third generation. Receptive figs were produced on male plants in spring and summer, timed to coincide with the release of short-lived adult pollinators from the same individual plants. Most plants were pollinated by a single species. Plants pollinated by Wiebesia sp. 1 released wasps earlier than those pollinated by Wiebesia sp. 3, with little overlap. Plants occupied by different pollinators were not spatially separated, nor genetically distinct. Our findings show that these differences created mismatches with the flight periods of the other Wiebesia species, largely ‘reserving’ individual plants for the resident pollinator species. This pre-emptive competitive displacement may prevent long term co-existence of the two pollinators. PMID:24849458

  16. Host Gut Motility Promotes Competitive Exclusion within a Model Intestinal Microbiota

    PubMed Central

    Baker, Ryan P; Schlomann, Brandon H; Ganz, Julia; Eisen, Judith S; Guillemin, Karen; Parthasarathy, Raghuveer

    2016-01-01

    The gut microbiota is a complex consortium of microorganisms with the ability to influence important aspects of host health and development. Harnessing this “microbial organ” for biomedical applications requires clarifying the degree to which host and bacterial factors act alone or in combination to govern the stability of specific lineages. To address this issue, we combined bacteriological manipulation and light sheet fluorescence microscopy to monitor the dynamics of a defined two-species microbiota within a vertebrate gut. We observed that the interplay between each population and the gut environment produces distinct spatiotemporal patterns. As a consequence, one species dominates while the other experiences sudden drops in abundance that are well fit by a stochastic mathematical model. Modeling revealed that direct bacterial competition could only partially explain the observed phenomena, suggesting that a host factor is also important in shaping the community. We hypothesized the host determinant to be gut motility, and tested this mechanism by measuring colonization in hosts with enteric nervous system dysfunction due to a mutation in the ret locus, which in humans is associated with the intestinal motility disorder known as Hirschsprung disease. In mutant hosts we found reduced gut motility and, confirming our hypothesis, robust coexistence of both bacterial species. This study provides evidence that host-mediated spatial structuring and stochastic perturbation of communities can drive bacterial population dynamics within the gut, and it reveals a new facet of the intestinal host–microbe interface by demonstrating the capacity of the enteric nervous system to influence the microbiota. Ultimately, these findings suggest that therapeutic strategies targeting the intestinal ecosystem should consider the dynamic physical nature of the gut environment. PMID:27458727

  17. Promoting cooperation in social dilemmas via simple coevolutionary rules

    NASA Astrophysics Data System (ADS)

    Szolnoki, A.; Perc, M.

    2009-02-01

    We study the evolution of cooperation in structured populations within popular models of social dilemmas, whereby simple coevolutionary rules are introduced that may enhance players abilities to enforce their strategy on the opponent. Coevolution thus here refers to an evolutionary process affecting the teaching activity of players that accompanies the evolution of their strategies. Particularly, we increase the teaching activity of a player after it has successfully reproduced, yet we do so depending on the disseminated strategy. We separately consider coevolution affecting either only the cooperators or only the defectors, and show that both options promote cooperation irrespective of the applied game. Opposite to intuitive reasoning, however, we reveal that the coevolutionary promotion of players spreading defection is, in the long run, more beneficial for cooperation than the likewise promotion of cooperators. We explain the contradictive impact of the two considered coevolutionary rules by examining the differences between resulting heterogeneities that segregate participating players, and furthermore, demonstrate that the influential individuals completely determine the final outcome of the games. Our findings are immune to changes defining the type of considered social dilemmas and highlight that the heterogeneity of players, resulting in a positive feedback mechanism, is a fundamental property promoting cooperation in groups of selfish individuals.

  18. Modeling and convergence analysis of distributed coevolutionary algorithms.

    PubMed

    Subbu, Raj; Sanderson, Arthur C

    2004-04-01

    A theoretical foundation is presented for modeling and convergence analysis of a class of distributed coevolutionary algorithms applied to optimization problems in which the variables are partitioned among p nodes. An evolutionary algorithm at each of the p nodes performs a local evolutionary search based on its own set of primary variables, and the secondary variable set at each node is clamped during this phase. An infrequent intercommunication between the nodes updates the secondary variables at each node. The local search and intercommunication phases alternate, resulting in a cooperative search by the p nodes. First, we specify a theoretical basis for a class of centralized evolutionary algorithms in terms of construction and evolution of sampling distributions over the feasible space. Next, this foundation is extended to develop a model for a class of distributed coevolutionary algorithms. Convergence and convergence rate analyzes are pursued for basic classes of objective functions. Our theoretical investigation reveals that for certain unimodal and multimodal objectives, we can expect these algorithms to converge at a geometrical rate. The distributed coevolutionary algorithms are of most interest from the perspective of their performance advantage compared to centralized algorithms, when they execute in a network environment with significant local access and internode communication delays. The relative performance of these algorithms is therefore evaluated in a distributed environment with realistic parameters of network behavior. PMID:15376831

  19. OPTIMIZING THROUGH CO-EVOLUTIONARY AVALANCHES

    SciTech Connect

    S. BOETTCHER; A. PERCUS

    2000-08-01

    We explore a new general-purpose heuristic for finding high-quality solutions to hard optimization problems. The method, called extremal optimization, is inspired by ''self-organized critically,'' a concept introduced to describe emergent complexity in many physical systems. In contrast to Genetic Algorithms which operate on an entire ''gene-pool'' of possible solutions, extremal optimization successively replaces extremely undesirable elements of a sub-optimal solution with new, random ones. Large fluctuations, called ''avalanches,'' ensue that efficiently explore many local optima. Drawing upon models used to simulate far-from-equilibrium dynamics, extremal optimization complements approximation methods inspired by equilibrium statistical physics, such as simulated annealing. With only one adjustable parameter, its performance has proved competitive with more elaborate methods, especially near phase transitions. Those phase transitions are found in the parameter space of most optimization problems, and have recently been conjectured to be the origin of some of the hardest instances in computational complexity. We will demonstrate how extremal optimization can be implemented for a variety of combinatorial optimization problems. We believe that extremal optimization will be a useful tool in the investigation of phase transitions in combinatorial optimization problems, hence valuable in elucidating the origin of computational complexity.

  20. A field test for competitive effects of Aedes albopictus on A. aegypti in South Florida: differences between sites of coexistence and exclusion?

    PubMed Central

    Juliano, Steven A.; Lounibos, L. Philip; O’Meara, George F.

    2007-01-01

    We tested whether interspecific competition from Aedes albopictus had measurable effects on A. aegypti at the typical numbers of larval mosquitoes found in cemetery vases in south Florida. We also tested whether the effect of interspecific competition from A. albopictus on A. aegypti differed between sites where A. aegypti either persists or went extinct following invasion by A. albopictus. Similar experiments manipulating numbers of A. albopictus in cemetery vases were conducted at three sites of A. aegypti persistence and three sites where A. aegypti was apparently extinct. The experiments were done using numbers of larvae that were determined by observed numbers of larvae for each site, and with resources (leaf detritus) that accumulated in experimental vases placed into each field site. In both the early rainy season (when number of mosquito larvae was low) and the late rainy season (when number of mosquito larvae was high), there was a significant effect of treatment on developmental progress of experimental A. aegypti. In the late rainy season, when numbers of larvae were high, there was also a significant effect of treatment on survivorship of A. aegypti. However, the competition treatment × site type (A. aegypti persists vs extinct) interaction was never significant, indicating that the competitive effect of A. albopictus on A. aegypti did not differ systematically between persistence versus extinction sites. Thus, although competition from A. albopictus is strong under field conditions at all sites, we find no evidence that variation in the impact of interspecific competition is associated with coexistence or exclusion. Interspecific competition among larvae is thus a viable explanation for exclusion or reduction of A. aegypti in south Florida, but variation in the persistence of A. aegypti following invasion does not seem to be primarily a product of variation in the conditions in the aquatic environments of cemetery vases. PMID:15024640

  1. Competition between macroalgae and corals: effects of herbivore exclusion and increased algal biomass on coral survivorship and growth

    NASA Astrophysics Data System (ADS)

    Lirman, D.

    2001-05-01

    Recent declines in coral abundance accompanied by increases in macroalgal cover on Florida reefs highlight the importance of competition for space between these groups. This paper documents the frequency of coral-algal interactions on the Northern Florida Reef Tract and evaluates the effects of grazer exclusions and experimental algal addition on growth and tissue mortality of three coral species, Siderastrea siderea, Porites astreoides, and Montastraea faveolata. The frequency of interactions between corals and macroalgae was high as more than 50% of the basal perimeter of colonies was in contact with macroalgae; turf forms, Halimeda spp., and Dictyota spp. were the most common groups in contact with corals. Decreased grazing pressure resulted in significant increases in algal biomass within cages, and caged corals showed species-specific susceptibility to increased algal biomass. While no effects were detected for S. siderea, significant decreases in growth rates were documented for caged P. astreoides which had growth rates three to four times lower than uncaged colonies. When an algal addition treatment was included to duplicate maximum algal biomass levels documented for reefs in the area, colonies of P. astreoides in the algal addition treatment had growth rates up to ten times lower than uncaged colonies. High susceptibility to algal overgrowth was also found for the reef-building coral M. faveolata, which experienced significant tissue mortality under both uncaged (5.2% decrease in live tissue area per month) and caged (10.2% per month) conditions. The documented effects of increased algal biomass on coral growth and tissue mortality suggest a potential threat for the long-term survivorship and growth of corals in the Florida Reef Tract if present rates of algal growth and space utilization are maintained.

  2. Competitive exclusion of a worldwide invasive pest by a native. Quantifying competition between two phytophagous insect on two host plant species

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High competitive ability is believed to be an important characteristic of invasive species. Many animal studies have compared the competitive ability of invasive species with a native species that is being displaced, but few have looked at systems where an invasive species has failed to establish it...

  3. Competitive exclusion of a worldwide invasive pest by a native. Quantifying competition between two phytophagous insects on two host plant species

    Technology Transfer Automated Retrieval System (TEKTRAN)

    1. High competitive ability is believed to be an important characteristic of invasive species. Many animal studies have compared the competitive ability of invasive species with a native species that is being displaced, but few have looked at systems where an invasive species has failed to establish...

  4. Control of Listeria spp. by Competitive-Exclusion Bacteria in Floor Drains of a Poultry Processing Plant

    PubMed Central

    Zhao, Tong; Podtburg, Teresa C.; Zhao, Ping; Schmidt, Bruce E.; Baker, David A.; Cords, Bruce; Doyle, Michael P.

    2006-01-01

    In previous studies workers determined that two lactic acid bacterium isolates, Lactococcus lactis subsp. lactis C-1-92 and Enterococcus durans 152 (competitive-exclusion bacteria [CE]), which were originally obtained from biofilms in floor drains, are bactericidal to Listeria monocytogenes or inhibit the growth of L. monocytogenes both in vitro and in biofilms at 4 to 37°C. We evaluated the efficacy of these isolates for reducing Listeria spp. contamination of floor drains of a plant in which fresh poultry is processed. Baseline assays revealed that the mean numbers of Listeria sp. cells in floor drains sampled on six different dates (at approximately biweekly intervals) were 7.5 log10 CFU/100 cm2 for drain 8, 4.9 log10 CFU/100 cm2 for drain 3, 4.4 log10 CFU/100 cm2 for drain 2, 4.1 log10 CFU/100 cm2 for drain 4, 3.7 log10 CFU/100 cm2 for drain 1, and 3.6 log10 CFU/100 cm2 for drain 6. The drains were then treated with 107 CE/ml in an enzyme-foam-based cleaning agent four times in 1 week and twice a week for the following 3 weeks. In samples collected 1 week after CE treatments were applied Listeria sp. cells were not detectable (samples were negative as determined by selective enrichment culture) for drains 4 and 6 (reductions of 4.1 and 3.6 log10 CFU/100 cm2, respectively), and the mean numbers of Listeria sp. cells were 3.7 log10 CFU/100 cm2 for drain 8 (a reduction of 3.8 log10 CFU/100 cm2), <1.7 log10 CFU/100 cm2 for drain 1 (detectable only by selective enrichment culture; a reduction of 3.3 log10 CFU/100 cm2), and 2.6 log10 CFU/100 cm2 for drain 3 (a reduction of 2.3 log10 CFU/100 cm2). However, the aerobic plate counts for samples collected from floor drains before, during, and after CE treatment remained approximately the same. The results indicate that application of the two CE can greatly reduce the number of Listeria sp. cells in floor drains at 3 to 26°C in a facility in which fresh poultry is processed. PMID:16672472

  5. The coevolutionary ultimatum game on different network topologies

    NASA Astrophysics Data System (ADS)

    Deng, Lili; Tang, Wansheng; Zhang, Jianxiong

    2011-11-01

    In this paper, a model of ultimatum game is discussed from the coevolutionary perspective, where strategy dynamics and structure dynamics coexist. The interplay between structure dynamics and strategy dynamics leads to overwhelmingly interesting evolved topology and fairness behaviors. It is found that fair division emerges for specific ratios of structure updating probability to strategy updating probability. Furthermore, it is shown that the initial structures have no essentially different effect on the coevolutionary results. In particular, the results for strategy are almost similar whenever the initial structure is set to be the nearest-neighbor coupled network, the ER random network or the scale-free network. Besides, the effects of other spatial factors are also investigated, e.g. the population size has a positive influence on the offer, while the average degree has a negative effect. In addition, one extrinsic factor, the background payoff, is also of great importance in promoting fair divisions. Apart from above, we study the properties of the evolved networks, which have the small-world effect and positive assortative behaviors.

  6. Coevolutionary dynamics between tribe Cercopithecini tetherins and their lentiviruses

    PubMed Central

    Takeuchi, Junko S.; Ren, Fengrong; Yoshikawa, Rokusuke; Yamada, Eri; Nakano, Yusuke; Kobayashi, Tomoko; Matsuda, Kenta; Izumi, Taisuke; Misawa, Naoko; Shintaku, Yuta; Wetzel, Katherine S.; Collman, Ronald G.; Tanaka, Hiroshi; Hirsch, Vanessa M.; Koyanagi, Yoshio; Sato, Kei

    2015-01-01

    Human immunodeficiency virus, a primate lentivirus (PLV), causes AIDS in humans, whereas most PLVs are less or not pathogenic in monkeys. These notions suggest that the co-evolutionary process of PLVs and their hosts associates with viral pathogenicity, and therefore, that elucidating the history of virus-host co-evolution is one of the most intriguing topics in the field of virology. To address this, recent studies have focused on the interplay between intrinsic anti-viral proteins, such as tetherin, and viral antagonists. Through an experimental-phylogenetic approach, here we investigate the co-evolutionary interplay between tribe Cercopithecini tetherin and viral antagonists, Nef and Vpu. We reveal that tribe Cercopithecini tetherins are positively selected, possibly triggered by ancient Nef-like factor(s). We reconstruct the ancestral sequence of tribe Cercopithecini tetherin and demonstrate that all Nef proteins are capable of antagonizing ancestral Cercopithecini tetherin. Further, we consider the significance of evolutionary arms race between tribe Cercopithecini and their PLVs. PMID:26531727

  7. Cyber Security Research Frameworks For Coevolutionary Network Defense

    SciTech Connect

    Rush, George D.; Tauritz, Daniel Remy

    2015-12-03

    Several architectures have been created for developing and testing systems used in network security, but most are meant to provide a platform for running cyber security experiments as opposed to automating experiment processes. In the first paper, we propose a framework termed Distributed Cyber Security Automation Framework for Experiments (DCAFE) that enables experiment automation and control in a distributed environment. Predictive analysis of adversaries is another thorny issue in cyber security. Game theory can be used to mathematically analyze adversary models, but its scalability limitations restrict its use. Computational game theory allows us to scale classical game theory to larger, more complex systems. In the second paper, we propose a framework termed Coevolutionary Agent-based Network Defense Lightweight Event System (CANDLES) that can coevolve attacker and defender agent strategies and capabilities and evaluate potential solutions with a custom network defense simulation. The third paper is a continuation of the CANDLES project in which we rewrote key parts of the framework. Attackers and defenders have been redesigned to evolve pure strategy, and a new network security simulation is devised which specifies network architecture and adds a temporal aspect. We also add a hill climber algorithm to evaluate the search space and justify the use of a coevolutionary algorithm.

  8. Coevolutionary analysis enabled rational deregulation of allosteric enzyme inhibition in Corynebacterium glutamicum for lysine production.

    PubMed

    Chen, Zhen; Meyer, Weiqian; Rappert, Sugima; Sun, Jibin; Zeng, An-Ping

    2011-07-01

    Product feedback inhibition of allosteric enzymes is an essential issue for the development of highly efficient microbial strains for bioproduction. Here we used aspartokinase from Corynebacterium glutamicum (CgAK), a key enzyme controlling the biosynthesis of industrially important aspartate family amino acids, as a model to demonstrate a fast and efficient approach to the deregulation of allostery. In the last 50 years many researchers and companies have made considerable efforts to deregulate this enzyme from allosteric inhibition by lysine and threonine. However, only a limited number of positive mutants have been identified so far, almost exclusively by random mutation and selection. In this study, we used statistical coupling analysis of protein sequences, a method based on coevolutionary analysis, to systematically clarify the interaction network within the regulatory domain of CgAK that is essential for allosteric inhibition. A cluster of interconnected residues linking different inhibitors' binding sites as well as other regions of the protein have been identified, including most of the previously reported positions of successful mutations. Beyond these mutation positions, we have created another 14 mutants that can partially or completely desensitize CgAK from allosteric inhibition, as shown by enzyme activity assays. The introduction of only one of the inhibition-insensitive CgAK mutations (here Q298G) into a wild-type C. glutamicum strain by homologous recombination resulted in an accumulation of 58 g/liter L-lysine within 30 h of fed-batch fermentation in a bioreactor. PMID:21531824

  9. Nonlinear Dynamics of Complex Coevolutionary Systems in Historical Times

    NASA Astrophysics Data System (ADS)

    Perdigão, Rui A. P.

    2016-04-01

    A new theoretical paradigm for statistical-dynamical modeling of complex coevolutionary systems is introduced, with the aim to provide historical geoscientists with a practical tool to analyse historical data and its underlying phenomenology. Historical data is assumed to represent the history of dynamical processes of physical and socio-economic nature. If processes and their governing laws are well understood, they are often treated with traditional dynamical equations: deterministic approach. If the governing laws are unknown or impracticable, the process is often treated as if being random (even if it is not): statistical approach. Although single eventful details - such as the exact spatiotemporal structure of a particular hydro-meteorological incident - may often be elusive to a detailed analysis, the overall dynamics exhibit group properties summarized by a simple set of categories or dynamical regimes at multiple scales - from local short-lived convection patterns to large-scale hydro-climatic regimes. The overwhelming microscale complexity is thus conveniently wrapped into a manageable group entity, such as a statistical distribution. In a stationary setting whereby the distribution is assumed to be invariant, alternating regimes are approachable as dynamical intermittence. For instance, in the context of bimodal climatic oscillations such as NAO and ENSO, each mode corresponds to a dynamical regime or phase. However, given external forcings or longer-term internal variability and multiscale coevolution, the structural properties of the system may change. These changes in the dynamical structure bring about a new distribution and associated regimes. The modes of yesteryear may no longer exist as such in the new structural order of the system. In this context, aside from regime intermittence, the system exhibits structural regime change. New oscillations may emerge whilst others fade into the annals of history, e.g. particular climate fluctuations during

  10. Multiagent Flight Control in Dynamic Environments with Cooperative Coevolutionary Algorithms

    NASA Technical Reports Server (NTRS)

    Colby, Mitchell; Knudson, Matthew D.; Tumer, Kagan

    2014-01-01

    Dynamic environments in which objectives and environmental features change with respect to time pose a difficult problem with regards to planning optimal paths through these environments. Path planning methods are typically computationally expensive, and are often difficult to implement in real time if system objectives are changed. This computational problem is compounded when multiple agents are present in the system, as the state and action space grows exponentially with the number of agents in the system. In this work, we use cooperative coevolutionary algorithms in order to develop policies which control agent motion in a dynamic multiagent unmanned aerial system environment such that goals and perceptions change, while ensuring safety constraints are not violated. Rather than replanning new paths when the environment changes, we develop a policy which can map the new environmental features to a trajectory for the agent while ensuring safe and reliable operation, while providing 92% of the theoretically optimal performance.

  11. Multiagent Flight Control in Dynamic Environments with Cooperative Coevolutionary Algorithms

    NASA Technical Reports Server (NTRS)

    Knudson, Matthew D.; Colby, Mitchell; Tumer, Kagan

    2014-01-01

    Dynamic flight environments in which objectives and environmental features change with respect to time pose a difficult problem with regards to planning optimal flight paths. Path planning methods are typically computationally expensive, and are often difficult to implement in real time if system objectives are changed. This computational problem is compounded when multiple agents are present in the system, as the state and action space grows exponentially. In this work, we use cooperative coevolutionary algorithms in order to develop policies which control agent motion in a dynamic multiagent unmanned aerial system environment such that goals and perceptions change, while ensuring safety constraints are not violated. Rather than replanning new paths when the environment changes, we develop a policy which can map the new environmental features to a trajectory for the agent while ensuring safe and reliable operation, while providing 92% of the theoretically optimal performance

  12. Cell surface-associated aggregation-promoting factor from Lactobacillus gasseri SBT2055 facilitates host colonization and competitive exclusion of Campylobacter jejuni.

    PubMed

    Nishiyama, Keita; Nakazato, Akiko; Ueno, Shintaro; Seto, Yasuyuki; Kakuda, Tsutomu; Takai, Shinji; Yamamoto, Yuji; Mukai, Takao

    2015-11-01

    Campylobacter jejuni, one of the most common causes of gastroenteritis worldwide, is transmitted to humans through poultry. We previously reported that Lactobacillus gasseri SBT2055 (LG2055) reduced C. jejuni infection in human epithelial cells in vitro and inhibited pathogen colonization of chickens in vivo. This suggested that the LG2055 adhesion and/or co-aggregation phenotype mediated by cell-surface aggregation-promoting factors (APFs) may be important for the competitive exclusion of C. jejuni. Here, we show that cell surface-associated APF1 promoted LG2055 self-aggregation and adhesion to human epithelial cells and exhibited high affinity for the extracellular matrix component fibronectin. These effects were absent in the apf1 knockout mutant, indicating the role of APF1 in LG2055-mediated inhibition of C. jejuni in epithelial cells and chicken colonization. Similar to APF1, APF2 promoted the co-aggregation of LG2055 and C. jejuni but did not inhibit C. jejuni infection. Our data suggest a pivotal role for APF1 in mediating the interaction of LG2055 with human intestinal cells and in inhibiting C. jejuni colonization of the gastrointestinal tract. We thus provide new insight into the health-promoting effects of probiotics and mechanisms of competitive exclusion in poultry. Further research is needed to determine whether the probiotic strains reach the epithelial surface. PMID:26239091

  13. Co-evolutionary dynamics between public good producers and cheats in the bacterium Pseudomonas aeruginosa.

    PubMed

    Kümmerli, R; Santorelli, L A; Granato, E T; Dumas, Z; Dobay, A; Griffin, A S; West, S A

    2015-12-01

    The production of beneficial public goods is common in the microbial world, and so is cheating--the exploitation of public goods by nonproducing mutants. Here, we examine co-evolutionary dynamics between cooperators and cheats and ask whether cooperators can evolve strategies to reduce the burden of exploitation, and whether cheats in turn can improve their exploitation abilities. We evolved cooperators of the bacterium Pseudomonas aeruginosa, producing the shareable iron-scavenging siderophore pyoverdine, together with cheats, defective in pyoverdine production but proficient in uptake. We found that cooperators managed to co-exist with cheats in 56% of all replicates over approximately 150 generations of experimental evolution. Growth and competition assays revealed that co-existence was fostered by a combination of general adaptions to the media and specific adaptions to the co-evolving opponent. Phenotypic screening and whole-genome resequencing of evolved clones confirmed this pattern, and suggest that cooperators became less exploitable by cheats because they significantly reduced their pyoverdine investment. Cheats, meanwhile, improved exploitation efficiency through mutations blocking the costly pyoverdine-signalling pathway. Moreover, cooperators and cheats evolved reduced motility, a pattern that likely represents adaptation to laboratory conditions, but at the same time also affects social interactions by reducing strain mixing and pyoverdine sharing. Overall, we observed parallel evolution, where co-existence of cooperators and cheats was enabled by a combination of adaptations to the abiotic and social environment and their interactions. PMID:26348785

  14. Competition, Competitive Repulsion, and Coexistence

    PubMed Central

    Darlington, P. J.

    1972-01-01

    This manuscript is concerned with concepts rather than abstruse details or mathematics. Discussed are: competition; extended competition, proposed for competition in the strict sense, extended and modified by all related interactions including predation, parasitism, disease, and even cooperation, all of which can be “weapons of competition”; competitive repulsion, proposed for the sum of forces that determine spacings, including ecologic spacings, of individuals and populations; Darwin (biotic) equilibriums; competitive extinction, Gause's principle, limited and limiting resources, and single-resource competition; de facto coexistence of competing species, exemplified by green plants competing for sunlight; niche competition; the two concepts of competitive exclusion; devision of resources and of their utilizers; cause and effect in real situations; and niches, niche overlap, and coexistence. Stressed is the complexity of the real world, and the confusion that can and does arise from modeling it too simply. PMID:4508308

  15. The efficacy of a commercial competitive exclusion product on Campylobacter colonization in broiler chickens in a 5-week pilot-scale study

    PubMed Central

    Schneitz, C.; Hakkinen, M.

    2016-01-01

    The efficacy of the commercial competitive exclusion product Broilact against Campylobacter jejuni was evaluated in broiler chickens in a 5-week pilot-scale study. Newly-hatched broiler chicks were brought from a commercial hatchery. After arrival 50 seeder chicks were challenged orally with approximately 103 cfu of C. jejuni, wing marked, and placed back in a delivery box and moved to a separate room. The rest of the chicks (contact chicks) were placed in floor pens, 100 chicks per pen. Birds in two pens were treated orally on the day of hatch with the commercial competitive exclusion (CE) product Broilact, and three pens were left untreated. The following day 10 seeder chicks were introduced into the Broilact treated and untreated control pens. One pen was left both untreated and unchallenged (0-control). Each week the ceca of 10 contact chicks and one seeder chick were examined quantitatively for Campylobacter. The treatment prevented or significantly reduced the colonization of the challenge organism in the ceca during the two first weeks; the percentage of colonized birds being 0% after the first week and 30% after the second week in the Broilact treated groups but was 100% in the control groups the entire 5-week rearing period. During the third rearing week the proportion of Campylobacter positive birds started to increase in the treated pens, being 80% after the third week and 95 and 90% after the fourth and fifth rearing weeks, respectively. Similarly the average count of Campylobacter in the cecal contents of the Broilact treated chicks started to increase, the difference between the treated and control chicks being 1.4 logs at the end of the rearing period. Although the protective effect was temporary and occurred only during the first two weeks of the rearing period, the results of this study support the earlier observations that CE flora designed to protect chicks from Salmonella may also reduce Campylobacter colonization of broiler chickens. PMID

  16. The efficacy of a commercial competitive exclusion product on Campylobacter colonization in broiler chickens in a 5-week pilot-scale study.

    PubMed

    Schneitz, C; Hakkinen, M

    2016-05-01

    The efficacy of the commercial competitive exclusion product Broilact against Campylobacter jejuni was evaluated in broiler chickens in a 5-week pilot-scale study. Newly-hatched broiler chicks were brought from a commercial hatchery. After arrival 50 seeder chicks were challenged orally with approximately 10(3) cfu of C. jejuni, wing marked, and placed back in a delivery box and moved to a separate room. The rest of the chicks (contact chicks) were placed in floor pens, 100 chicks per pen. Birds in two pens were treated orally on the day of hatch with the commercial competitive exclusion (CE) product Broilact, and three pens were left untreated. The following day 10 seeder chicks were introduced into the Broilact treated and untreated control pens. One pen was left both untreated and unchallenged (0-control). Each week the ceca of 10 contact chicks and one seeder chick were examined quantitatively for Campylobacter The treatment prevented or significantly reduced the colonization of the challenge organism in the ceca during the two first weeks; the percentage of colonized birds being 0% after the first week and 30% after the second week in the Broilact treated groups but was 100% in the control groups the entire 5-week rearing period. During the third rearing week the proportion of Campylobacter positive birds started to increase in the treated pens, being 80% after the third week and 95 and 90% after the fourth and fifth rearing weeks, respectively. Similarly the average count of Campylobacter in the cecal contents of the Broilact treated chicks started to increase, the difference between the treated and control chicks being 1.4 logs at the end of the rearing period. Although the protective effect was temporary and occurred only during the first two weeks of the rearing period, the results of this study support the earlier observations that CE flora designed to protect chicks from Salmonella may also reduce Campylobacter colonization of broiler chickens. PMID

  17. Age structure and cooperation in coevolutionary games on dynamic network

    NASA Astrophysics Data System (ADS)

    Qin, Zilong; Hu, Zhenhua; Zhou, Xiaoping; Yi, Jingzhang

    2015-04-01

    Our proposed model imitates the growth of a population and describes the age structure and the level of cooperation in games on dynamic network with continuous changes of structure and topology. The removal of nodes and links caused by age-dependent attack, together with the nodes addition standing for the newborns of population, badly ruins Matthew effect in this coevolutionary process. Though the network is generated by growth and preferential attachment, it degenerates into random network and it is no longer heterogeneous. When the removal of nodes and links is equal to the addition of nodes and links, the size of dynamic network is maintained in steady-state, so is the low level of cooperation. Severe structure variation, homogeneous topology and continuous invasion of new defection jointly make dynamic network unsuitable for the survival of cooperator even when the probability with which the newborn players initially adopt the strategy cooperation is high, while things change slightly when the connections of newborn players are restricted. Fortunately, moderate interactions in a generation trigger an optimal recovering process to encourage cooperation. The model developed in this paper outlines an explanation of the cohesion changes in the development process of an organization. Some suggestions for cooperative behavior improvement are given in the end.

  18. Building toy models of proteins using coevolutionary information

    NASA Astrophysics Data System (ADS)

    Cheng, Ryan; Raghunathan, Mohit; Onuchic, Jose

    2015-03-01

    Recent developments in global statistical methodologies have advanced the analysis of large collections of protein sequences for coevolutionary information. Coevolution between amino acids in a protein arises from compensatory mutations that are needed to maintain the stability or function of a protein over the course of evolution. This gives rise to quantifiable correlations between amino acid positions within the multiple sequence alignment of a protein family. Here, we use Direct Coupling Analysis (DCA) to infer a Potts model Hamiltonian governing the correlated mutations in a protein family to obtain the sequence-dependent interaction energies of a toy protein model. We demonstrate that this methodology predicts residue-residue interaction energies that are consistent with experimental mutational changes in protein stabilities as well as other computational methodologies. Furthermore, we demonstrate with several examples that DCA could be used to construct a structure-based model that quantitatively agrees with experimental data on folding mechanisms. This work serves as a potential framework for generating models of proteins that are enriched by evolutionary data that can potentially be used to engineer key functional motions and interactions in protein systems. This research has been supported by the NSF INSPIRE award MCB-1241332 and by the CTBP sponsored by the NSF (Grant PHY-1427654).

  19. A Multipopulation Coevolutionary Strategy for Multiobjective Immune Algorithm

    PubMed Central

    Shi, Jiao; Gong, Maoguo; Ma, Wenping; Jiao, Licheng

    2014-01-01

    How to maintain the population diversity is an important issue in designing a multiobjective evolutionary algorithm. This paper presents an enhanced nondominated neighbor-based immune algorithm in which a multipopulation coevolutionary strategy is introduced for improving the population diversity. In the proposed algorithm, subpopulations evolve independently; thus the unique characteristics of each subpopulation can be effectively maintained, and the diversity of the entire population is effectively increased. Besides, the dynamic information of multiple subpopulations is obtained with the help of the designed cooperation operator which reflects a mutually beneficial relationship among subpopulations. Subpopulations gain the opportunity to exchange information, thereby expanding the search range of the entire population. Subpopulations make use of the reference experience from each other, thereby improving the efficiency of evolutionary search. Compared with several state-of-the-art multiobjective evolutionary algorithms on well-known and frequently used multiobjective and many-objective problems, the proposed algorithm achieves comparable results in terms of convergence, diversity metrics, and running time on most test problems. PMID:24672330

  20. Coevolutionary Feedbacks between Female Mating Interval and Male Allocation to Competing Sperm Traits Can Drive Evolution of Costly Polyandry.

    PubMed

    Bocedi, Greta; Reid, Jane M

    2016-03-01

    Complex coevolutionary feedbacks between female mating interval and male sperm traits have been hypothesized to explain the evolution and persistence of costly polyandry. Such feedbacks could potentially arise because polyandry creates sperm competition and consequent selection on male allocation to sperm traits, while the emerging sperm traits could create female sperm limitation and, hence, impose selection for increased polyandry. However, the hypothesis that costly polyandry could coevolve with male sperm dynamics has not been tested. We built a genetically explicit individual-based model to simulate simultaneous evolution of female mating interval and male allocation to sperm number versus longevity, where these two sperm traits trade off. We show that evolution of competing sperm traits under polyandry can indeed cause female sperm limitation and, hence, promote further evolution and persistence of costly polyandry, particularly when sperm are costly relative to the degree of female sperm limitation. These feedbacks were stronger, and greater polyandry evolved, when postcopulatory competition for paternity followed a loaded rather than fair raffle and when sperm traits had realistically low heritability. We therefore demonstrate that the evolution of allocation to sperm traits driven by sperm competition can prevent males from overcoming female sperm limitation, thereby driving ongoing evolution of costly polyandry. PMID:26913946

  1. Sorption of TCE by humic-preloaded activated carbon: Incorporating size-exclusion and pore blockage phenomenon in a competitive adsorption model

    SciTech Connect

    Kilduff, J.E.; Wigton, A.

    1999-01-15

    Naturally occurring, macromolecular dissolved organic matter (NOM) is known to foul activated carbon adsorbents, reducing the ability of fixed-bed adsorbers to efficiently remove targeted synthetic organic contaminants (SOCs). An accurate description of the effects of NOM competition on SOC adsorption equilibria is required to develop dynamic models, which have application to process design and analysis. A model was developed, using an approach based on the Ideal Adsorbed Solution Theory (IAST), to predict trichloroethylene (TCE) adsorption by activated carbon preloaded with humic acid. The IAST model was formulated for a bisolute system in which TCE and humic acid single-solute uptakes were described by the Langmuir-Freundlich and Freundlich isotherms, respectively. The humic mixture was modeled as a single component based on previous studies that identified the low-molecular-weight hydrophobic fraction as the most reactive with regard to preloading effects. Isotherms for this fraction, isolated from whole humic acid using ultrafiltration, were measured, and molar concentrations were computed based on an average molecular weight determined using size-exclusion chromatography. The IAST model was modified to reflect the hypothesis that TCE molecules can access adsorption sites which humic molecules cannot and that no competition can occur on these sites. The model was calibrated with data for TCE uptake by carbon preloaded with the low-molecular-weight humic acid fraction and was verified by predicting TCE uptake by carbon preloaded with whole humic acid. Further improvement to the model was possible by accounting for pore blockage as a mechanism which can reduce the effective surface area available in TCE.

  2. Are the metabolomic responses to folivory of closely related plant species linked to macroevolutionary and plant-folivore coevolutionary processes?

    PubMed

    Rivas-Ubach, Albert; Hódar, José A; Sardans, Jordi; Kyle, Jennifer E; Kim, Young-Mo; Oravec, Michal; Urban, Otmar; Guenther, Alex; Peñuelas, Josep

    2016-07-01

    The debate whether the coevolution of plants and insects or macroevolutionary processes (phylogeny) is the main driver determining the arsenal of molecular defensive compounds of plants remains unresolved. Attacks by herbivorous insects affect not only the composition of defensive compounds in plants but also the entire metabolome. Metabolomes are the final products of genotypes and are constrained by macroevolutionary processes, so closely related species should have similar metabolomic compositions and may respond in similar ways to attacks by folivores. We analyzed the elemental compositions and metabolomes of needles from three closely related Pinus species with distant coevolutionary histories with the caterpillar of the processionary moth respond similarly to its attack. All pines had different metabolomes and metabolic responses to herbivorous attack. The metabolomic variation among the species and the responses to folivory reflected their macroevolutionary relationships, with P. pinaster having the most divergent metabolome. The concentrations of terpenes were in the attacked trees supporting the hypothesis that herbivores avoid plant individuals with higher concentrations. Our results suggest that macroevolutionary history plays important roles in the metabolomic responses of these pine species to folivory, but plant-insect coevolution probably constrains those responses. Combinations of different evolutionary factors and trade-offs are likely responsible for the different responses of each species to folivory, which is not necessarily exclusively linked to plant-insect coevolution. PMID:27386082

  3. Use of organic acids and competitive exclusion product as an alternative to antibiotic as a growth promoter in the raising of commercial turkeys.

    PubMed

    Milbradt, E L; Okamoto, A S; Rodrigues, J C Z; Garcia, E A; Sanfelice, C; Centenaro, L P; Andreatti Filho, R L

    2014-07-01

    A study was conducted to investigate the effects of organic acids (OA) and competitive exclusion product (CE) on growth performance, intestinal morphology, and concentration of volatile fatty acids in the cecal content. The experiment lasted for 10 wk. Four hundred twenty 1-d-old female commercial cross turkey poults (British United Turkeys, BUT Big 9) were distributed into 4 treatments with 5 replicates/pen of 21 birds each. The birds were fed a basal diet without growth promoter (control), diet with lincomycin (44 mg/kg), diet with organic acids (2 g/kg), and diet with product of CE (10(9) cfu/kg). Dietary levels of other nutrients, housing, and general management practices were similar for all treatments. On the first week (d 0-7), the BW and BW gain of the birds that fed diets with OA were lower than in the control group. In the fattening phase (d 28-70), the feed intake of the OA-treated group was lower than compared with the control. The birds that received diet with OA and CE product presented higher concentrations of propionic acid, at 14 d, and butyric acid in cecal content at 28, 56, and 70 d, compared with the control. Dietary inclusion of additives had no significant effects on intestinal villus height, crypt depth, and villus:crypt ratio. Organic acids had negative effects either on early gain or feed intake throughout the study. Because the test was conducted under controlled experimental conditions, the additives that showed results similar to those found by using antibiotics should be studied further in commercial farms to obtain results that can be incorporated into practice. PMID:24812241

  4. Coevolutionary dynamics of polyandry and sex-linked meiotic drive.

    PubMed

    Holman, Luke; Price, Thomas A R; Wedell, Nina; Kokko, Hanna

    2015-03-01

    Segregation distorters located on sex chromosomes are predicted to sweep to fixation and cause extinction via a shortage of one sex, but in nature they are often found at low, stable frequencies. One potential resolution to this longstanding puzzle involves female multiple mating (polyandry). Because many meiotic drivers severely reduce the sperm competitive ability of their male carriers, females are predicted to evolve more frequent polyandry and thereby promote sperm competition when a meiotic driver invades. Consequently, the driving chromosome's relative fitness should decline, halting or reversing its spread. We used formal modeling to show that this initially appealing hypothesis cannot resolve the puzzle alone: other selective pressures (e.g., low fitness of drive homozygotes) are required to establish a stable meiotic drive polymorphism. However, polyandry and meiotic drive can strongly affect one another's frequency, and polyandrous populations may be resistant to the invasion of rare drive mutants. PMID:25565579

  5. Optimal satellite formation reconfiguration using co-evolutionary particle swarm optimization in deep space

    NASA Astrophysics Data System (ADS)

    Huang, Haibin; Zhuang, Yufei

    2015-08-01

    This paper proposes a method that plans energy-optimal trajectories for multi-satellite formation reconfiguration in deep space environment. A novel co-evolutionary particle swarm optimization algorithm is stated to solve the nonlinear programming problem, so that the computational complexity of calculating the gradient information could be avoided. One swarm represents one satellite, and through communication with other swarms during the evolution, collisions between satellites can be avoided. In addition, a dynamic depth first search algorithm is proposed to solve the redundant search problem of a co-evolutionary particle swarm optimization method, with which the computation time can be shorten a lot. In order to make the actual trajectories optimal and collision-free with disturbance, a re-planning strategy is deduced for formation reconfiguration maneuver.

  6. Fine-tuned Bee-Flower Coevolutionary State Hidden within Multiple Pollination Interactions

    PubMed Central

    Shimizu, Akira; Dohzono, Ikumi; Nakaji, Masayoshi; Roff, Derek A.; Miller III, Donald G.; Osato, Sara; Yajima, Takuya; Niitsu, Shûhei; Utsugi, Nozomu; Sugawara, Takashi; Yoshimura, Jin

    2014-01-01

    Relationships between flowers and pollinators are generally considered cases of mutualism since both agents gain benefits. Fine-tuned adaptations are usually found in the form of strict one-to-one coevolution between species. Many insect pollinators are, however, considered generalists, visiting numerous kinds of flowers, and many flower species (angiosperms) are also considered generalists, visited by many insect pollinators. We here describe a fine-tuned coevolutionary state of a flower-visiting bee that collects both nectar and pollen from an early spring flower visited by multiple pollinators. Detailed morphology of the bee proboscis is shown to be finely adjusted to the floral morphology and nectar production of the flower. Behavioral observations also confirm the precision of this mutualism. Our results suggest that a fine-tuned one-to-one coevolutionary state between a flower species and a pollinator species might be common, but frequently overlooked, in multiple flower-pollinator interactions. PMID:24496444

  7. Fine-tuned bee-flower coevolutionary state hidden within multiple pollination interactions.

    PubMed

    Shimizu, Akira; Dohzono, Ikumi; Nakaji, Masayoshi; Roff, Derek A; Miller, Donald G; Osato, Sara; Yajima, Takuya; Niitsu, Shûhei; Utsugi, Nozomu; Sugawara, Takashi; Yoshimura, Jin

    2014-01-01

    Relationships between flowers and pollinators are generally considered cases of mutualism since both agents gain benefits. Fine-tuned adaptations are usually found in the form of strict one-to-one coevolution between species. Many insect pollinators are, however, considered generalists, visiting numerous kinds of flowers, and many flower species (angiosperms) are also considered generalists, visited by many insect pollinators. We here describe a fine-tuned coevolutionary state of a flower-visiting bee that collects both nectar and pollen from an early spring flower visited by multiple pollinators. Detailed morphology of the bee proboscis is shown to be finely adjusted to the floral morphology and nectar production of the flower. Behavioral observations also confirm the precision of this mutualism. Our results suggest that a fine-tuned one-to-one coevolutionary state between a flower species and a pollinator species might be common, but frequently overlooked, in multiple flower-pollinator interactions. PMID:24496444

  8. Cooperation, conformity, and the coevolutionary problem of trait associations.

    PubMed

    Van Cleve, Jeremy

    2016-05-01

    In large scale social systems, coordinated or cooperative outcomes become difficult because encounters between kin or repeated encounters between friends are infrequent. Even punishment of noncooperators does not entirely alleviate the dilemma. One important mechanism for achieving cooperative outcomes in such social systems is conformist bias where individuals copy the behavior performed by the majority of their group mates. Conformist bias enhances group competition by both stabilizing behaviors within groups and increasing variance between groups. Due to this group competition effect, conformist bias is thought to have been an important driver of human social complexity and cultural diversity. However, conformist bias only evolves indirectly through associations with other traits, and I show that such associations are more difficult to obtain than previously expected. Specifically, I show that initial measures of population structure must be strong in order for a strong association between conformist bias and cooperative behaviors (cooperation and costly punishment) to evolve and for these traits to reach high frequencies. Additionally, the required initial level of association does not evolve de novo in simulations run over long timescales. This suggests that the coevolution of cooperative behaviors and conformist bias alone may not explain the high levels of cooperation within human groups, though conformist bias may still play an important role in combination with other social and demographic forces. PMID:26907203

  9. The coevolutionary dynamics of obligate ant social parasite systems--between prudence and antagonism.

    PubMed

    Brandt, Miriam; Foitzik, Susanne; Fischer-Blass, Birgit; Heinze, Jürgen

    2005-05-01

    In this synthesis we apply coevolutionary models to the interactions between socially parasitic ants and their hosts. Obligate social parasite systems are ideal models for coevolution, because the close phylogenetic relationship between these parasites and their hosts results in similar evolutionary potentials, thus making mutual adaptations in a stepwise fashion especially likely to occur. The evolutionary dynamics of host-parasite interactions are influenced by a number of parameters, for example the parasite's transmission mode and rate, the genetic structure of host and parasite populations, the antagonists' migration rates, and the degree of mutual specialisation. For the three types of obligate ant social parasites, queen-tolerant and queen-intolerant inquilines and slavemakers, several of these parameters, and thus the evolutionary trajectory, are likely to differ. Because of the fundamental differences in lifestyle between these social parasite systems, coevolution should further select for different traits in the parasites and their hosts. Queen-tolerant inquilines are true parasites that exert a low selection pressure on their host, because of their rarity and the fact that they do not conduct slave raids to replenish their labour force. Due to their high degree of specialisation and the potential for vertical transmission, coevolutionary theory would predict interactions between these workerless parasites and their hosts to become even more benign over time. Queen-intolerant inquilines that kill the host queen during colony take-over are best described as parasitoids, and their reproductive success is limited by the existing worker force of the invaded host nest. These parasites should therefore evolve strategies to best exploit this fixed resource. Slavemaking ants, by contrast, act as parasites only during colony foundation, while their frequent slave raids follow a predator prey dynamic. They often exploit a number of host species at a given site, and

  10. Vulnerability from a co-evolutionary perspective: valuating natural hazards management in the Eastern Alps

    NASA Astrophysics Data System (ADS)

    Thaler, Thomas; Fuchs, Sven

    2014-05-01

    In past decades, we observed a change in natural hazard management from a structural, security-based policy towards an integrated, risk-based management system. Therefore, the concept of vulnerability has become central in the policy debate. In order to assess vulnerability, we need a broader understanding of the term to manage natural hazards and to reduce damages and losses from future events. This paper adopts a co-evolutionary perspective to provide a critical assessment of vulnerability in natural hazard management, taking the Eastern Alps as an example. We discuss the structural, social and institutional vulnerability and governance from an integrated point of view to understand and to analyse the interdependences and interactions between human and physical systems. The aim is to consider the dynamic interactions between multiple conceptualised vulnerabilities in evaluating natural hazard management systems. A co-evolutionary framework widens the explanatory of multiple interactions in vulnerability to provide useful information and concepts to improve risk management. Keywords: vulnerability; co-evolution; natural hazards; Eastern Alps

  11. The evolution of mutation rate in an antagonistic coevolutionary model with maternal transmission of parasites

    PubMed Central

    Greenspoon, Philip B.; M'Gonigle, Leithen K.

    2013-01-01

    By constantly selecting for novel genotypes, coevolution between hosts and parasites can favour elevated mutation rates. Models of this process typically assume random encounters. However, offspring are often more likely to encounter their mother's parasites. Because parents and offspring are genetically similar, they may be susceptible to the same parasite strains and thus, in hosts, maternal transmission should select for mechanisms that decrease intergenerational genetic similarity. In parasites, however, maternal transmission should select for genetic similarity. We develop and analyse a model of host and parasite mutation rate evolution when parasites are maternally inherited. In hosts, we find that maternal transmission has two opposing effects. First, it eliminates coevolutionary cycles that previous work shows select for higher mutation. Second, it independently selects for higher mutation rates, because offspring that differ from their mothers are more likely to avoid infection. In parasites, however, the two effects of maternal transmission act in the same direction. As for hosts, maternal transmission eliminates coevolutionary cycles, thereby reducing selection for increased mutation. Unlike for hosts, however, maternal transmission additionally selects against higher mutation by favouring parasite offspring that are the same as their mothers. PMID:23760645

  12. Coevolutionary diversification creates nested-modular structure in phage–bacteria interaction networks

    PubMed Central

    Beckett, Stephen J.; Williams, Hywel T. P.

    2013-01-01

    Phage and their bacterial hosts are the most diverse and abundant biological entities in the oceans, where their interactions have a major impact on marine ecology and ecosystem function. The structure of interaction networks for natural phage–bacteria communities offers insight into their coevolutionary origin. At small phylogenetic scales, observed communities typically show a nested structure, in which both hosts and phages can be ranked by their range of resistance and infectivity, respectively. A qualitatively different multi-scale structure is seen at larger phylogenetic scales; a natural assemblage sampled from the Atlantic Ocean displays large-scale modularity and local nestedness within each module. Here, we show that such ‘nested-modular’ interaction networks can be produced by a simple model of host–phage coevolution in which infection depends on genetic matching. Negative frequency-dependent selection causes diversification of hosts (to escape phages) and phages (to track their evolving hosts). This creates a diverse community of bacteria and phage, maintained by kill-the-winner ecological dynamics. When the resulting communities are visualized as bipartite networks of who infects whom, they show the nested-modular structure characteristic of the Atlantic sample. The statistical significance and strength of this observation varies depending on whether the interaction networks take into account the density of the interacting strains, with implications for interpretation of interaction networks constructed by different methods. Our results suggest that the apparently complex community structures associated with marine bacteria and phage may arise from relatively simple coevolutionary origins. PMID:24516719

  13. Coevolutionary diversification creates nested-modular structure in phage-bacteria interaction networks.

    PubMed

    Beckett, Stephen J; Williams, Hywel T P

    2013-12-01

    Phage and their bacterial hosts are the most diverse and abundant biological entities in the oceans, where their interactions have a major impact on marine ecology and ecosystem function. The structure of interaction networks for natural phage-bacteria communities offers insight into their coevolutionary origin. At small phylogenetic scales, observed communities typically show a nested structure, in which both hosts and phages can be ranked by their range of resistance and infectivity, respectively. A qualitatively different multi-scale structure is seen at larger phylogenetic scales; a natural assemblage sampled from the Atlantic Ocean displays large-scale modularity and local nestedness within each module. Here, we show that such 'nested-modular' interaction networks can be produced by a simple model of host-phage coevolution in which infection depends on genetic matching. Negative frequency-dependent selection causes diversification of hosts (to escape phages) and phages (to track their evolving hosts). This creates a diverse community of bacteria and phage, maintained by kill-the-winner ecological dynamics. When the resulting communities are visualized as bipartite networks of who infects whom, they show the nested-modular structure characteristic of the Atlantic sample. The statistical significance and strength of this observation varies depending on whether the interaction networks take into account the density of the interacting strains, with implications for interpretation of interaction networks constructed by different methods. Our results suggest that the apparently complex community structures associated with marine bacteria and phage may arise from relatively simple coevolutionary origins. PMID:24516719

  14. Mathematical Physics of Complex Coevolutionary Systems: Theoretical Advances and Applications to Multiscale Hydroclimate Dynamics

    NASA Astrophysics Data System (ADS)

    Perdigão, Rui A. P.

    2016-04-01

    The fundamental stochastic-dynamic coevolution laws governing complex coevolutionary systems are introduced in a mathematical physics framework formally unifying nonlinear stochastic physics with fundamental deterministic interaction laws among spatiotemporally distributed processes. The methodological developments are then used to shed light onto fundamental interactions underlying complex spatiotemporal behaviour and emergence in multiscale hydroclimate dynamics. For this purpose, a mathematical physics framework is presented predicting evolving distributions of hydrologic quantities under nonlinearly coevolving geophysical processes. The functional formulation is grounded on first principles regulating the dynamics of each system constituent and their interactions, therefore its applicability is general and data-independent, not requiring local calibrations. Moreover, it enables the dynamical estimation of hydroclimatic variations in space and time from knowledge at different spatiotemporal conditions, along with the associated uncertainties. This paves the way for a robust physically based prediction of hydroclimatic changes in unsupervised areas (e.g. ungauged basins). Validation is achieved by producing, with the mathematical physics framework, a comprehensive spatiotemporal legacy consistent with the observed distributions along with their statistic-dynamic relations. The similarity between simulated and observed distributions is further assessed with novel robust nonlinear information-theoretic diagnostics. The present study brings to light emerging signatures of structural change in hydroclimate dynamics arising from nonlinear synergies across multiple spatiotemporal scales, and contributes to a better dynamical understanding and prediction of spatiotemporal regimes, transitions, structural changes and extremes in complex coevolutionary systems. This study further sheds light onto a diversity of emerging properties from harmonic to hyper-chaotic in general

  15. Coevolutionary motion and swarming in a niche space model of ecological species interactions

    NASA Astrophysics Data System (ADS)

    Dommar, C. J.; Ryabov, A.; Blasius, B.

    2008-04-01

    Organisms are involved in coevolutionary relationships with their competitors, predators, preys and parasites. In this context, we present a simple model for the co-evolution of species in a common niche space, where the fitness of each species is defined via the network of interactions with all other species. In our model, the sign and type of the pairwise interactions (being either beneficial, harmful or neutral) is given by a pre-determined community matrix, while the interaction strength depends on the niche-overlap, i.e. the pairwise distances between species in niche space. The evolutionary process drives the species toward the places with the higher local fitness along the fitness gradient. This gives rise to a dynamic fitness landscape, since the evolutionary motion of a single species can change the landscape of the others (known as the Red Queen Principle). In the simplest case of only two-species we observe either a convergence/divergence equilibrium or a coevolutionary arms race. For a larger number of species our analysis concentrates on an antisymmetric interaction matrix, where we observe a large range of dynamic behaviour, from oscillations, quasiperiodic to chaotic dynamics. In dependence of the value of a first integral of motion we observe either quasiperiodic motion around a central region in niche space or unbounded movement, characterised by chaotic scattering of species pairs. Finally, in a linear food-chain we observe complex swarming behaviour in which the swarm moves as a whole only if the chain consists of an even number of species. Our results could be an important contribution to evolutionary niche theory.

  16. Molecular evolution of rbcL in three gymnosperm families: identifying adaptive and coevolutionary patterns

    PubMed Central

    2011-01-01

    Background The chloroplast-localized ribulose-1, 5-biphosphate carboxylase/oxygenase (Rubisco), the primary enzyme responsible for autotrophy, is instrumental in the continual adaptation of plants to variations in the concentrations of CO2. The large subunit (LSU) of Rubisco is encoded by the chloroplast rbcL gene. Although adaptive processes have been previously identified at this gene, characterizing the relationships between the mutational dynamics at the protein level may yield clues on the biological meaning of such adaptive processes. The role of such coevolutionary dynamics in the continual fine-tuning of RbcL remains obscure. Results We used the timescale and phylogenetic analyses to investigate and search for processes of adaptive evolution in rbcL gene in three gymnosperm families, namely Podocarpaceae, Taxaceae and Cephalotaxaceae. To understand the relationships between regions identified as having evolved under adaptive evolution, we performed coevolutionary analyses using the software CAPS. Importantly, adaptive processes were identified at amino acid sites located on the contact regions among the Rubisco subunits and on the interface between Rubisco and its activase. Adaptive amino acid replacements at these regions may have optimized the holoenzyme activity. This hypothesis was pinpointed by evidence originated from our analysis of coevolution that supported the correlated evolution between Rubisco and its activase. Interestingly, the correlated adaptive processes between both these proteins have paralleled the geological variation history of the concentration of atmospheric CO2. Conclusions The gene rbcL has experienced bursts of adaptations in response to the changing concentration of CO2 in the atmosphere. These adaptations have emerged as a result of a continuous dynamic of mutations, many of which may have involved innovation of functional Rubisco features. Analysis of the protein structure and the functional implications of such mutations put

  17. Coevolutionary dynamics of opinion propagation and social balance: The key role of small-worldness

    NASA Astrophysics Data System (ADS)

    Chen, Yan; Chen, Lixue; Sun, Xian; Zhang, Kai; Zhang, Jie; Li, Ping

    2014-03-01

    The propagation of various opinions in social networks, which influences human inter-relationships and even social structure, and hence is a most important part of social life. We have incorporated social balance into opinion propagation in social networks are influenced by social balance. The edges in networks can represent both friendly or hostile relations, and change with the opinions of individual nodes. We introduce a model to characterize the coevolutionary dynamics of these two dynamical processes on Watts-Strogatz (WS) small-world network. We employ two distinct evolution rules (i) opinion renewal; and (ii) relation adjustment. By changing the rewiring probability, and thus the small-worldness of the WS network, we found that the time for the system to reach balanced states depends critically on both the average path length and clustering coefficient of the network, which is different than other networked process like epidemic spreading. In particular, the system equilibrates most quickly when the underlying network demonstrates strong small-worldness, i.e., small average path lengths and large clustering coefficient. We also find that opinion clusters emerge in the process of the network approaching the global equilibrium, and a measure of global contrariety is proposed to quantify the balanced state of a social network.

  18. Cry-wolf signals emerging from coevolutionary feedbacks in a tritrophic system.

    PubMed

    Yamauchi, Atsushi; van Baalen, Minus; Kobayashi, Yutaka; Takabayashi, Junji; Shiojiri, Kaori; Sabelis, Maurice W

    2015-11-01

    For a communication system to be stable, senders should convey honest information. Providing dishonest information, however, can be advantageous to senders, which imposes a constraint on the evolution of communication systems. Beyond single populations and bitrophic systems, one may ask whether stable communication systems can evolve in multitrophic systems. Consider cross-species signalling where herbivore-induced plant volatiles (HIPVs) attract predators to reduce the damage from arthropod herbivores. Such plant signals may be honest and help predators to identify profitable prey/plant types via HIPV composition and to assess prey density via the amount of HIPVs. There could be selection for dishonest signals that attract predators for protection from possible future herbivory. Recently, we described a case in which plants release a fixed, high amount of HIPVs independent of herbivore load, adopting what we labelled a 'cry-wolf' strategy. To understand when such signals evolve, we model coevolutionary interactions between plants, herbivores and predators, and show that both 'honest' and 'cry-wolf' types can emerge, depending on the assumed plant-herbivore encounter rates and herbivore population density. It is suggested that the 'cry-wolf' strategy may have evolved to reduce the risk of heavy damage in the future. Our model suggests that eco-evolutionary feedback loops involving a third species may have important consequences for the stability of this outcome. PMID:26538597

  19. Effects of payoff-related velocity in the co-evolutionary snowdrift game

    NASA Astrophysics Data System (ADS)

    Yang, Zhihu; Li, Zhi; Wu, Te; Wang, Long

    2014-01-01

    Previous studies concerning mobile populations seldom distinguish mobility on the individual level. In these models, all individuals have the identical moving speed and this moving speed has not been clearly defined in terms of its relevance to other features intrinsic to individual. Here we investigate the evolution of cooperation with a minimal co-evolutionary snowdrift game in which the payoff-dependent velocity as well as velocity diversity is taken into account. We find that the fate of evolution in such scenarios is precisely ruled both by population mobility and the inherent parameter of the snowdrift game. The outside-in and inside-out like attacks on cooperator clusters (C-clusters) are triggered in the Monte Carlo simulation. The results show that low mobility can lead to a plateau of full cooperation provided the challenge to cooperate is not too high, and also that high mobility always inhibits cooperation. Nevertheless, the phase transition diagram implies moderate population mobility most benefits the survival of cooperators when cooperation faces the greater challenge. Finally, the evolution of strategies seemingly rises superior to selection strength once the mobility intensity is fixed. Our findings may shed new light on the evolution of strategies in mobile systems.

  20. Coevolutionary particle swarm optimization using AIS and its application in multiparameter estimation of PMSM.

    PubMed

    Liu, Zhao-Hua; Zhang, Jing; Zhou, Shao-Wu; Li, Xiao-Hua; Liu, Kan

    2013-12-01

    In this paper, a coevolutionary particle-swarmoptimization (PSO) algorithm associating with the artificial immune principle is proposed. In the proposed algorithm, the wholepopulation is divided into two kinds of subpopulations consisting of one elite subpopulation and several normal subpopulations. The best individual of each normal subpopulation will be memorized into the elite subpopulation during the evolution process. A hybrid method, which creates new individuals by using three different operators, is presented to ensure the diversity of all the subpopulations. Furthermore, a simple adaptive wavelet learning operator is utilized for accelerating the convergence speed of the pbest particles. The improved immune-clonal-selection operator is employed for optimizing the elite subpopulation, while the migration scheme is employed for the information exchange between elite subpopulation and normal subpopulations. The performance of the proposed algorithm is verified by testing on a suite of standard benchmark functions, which shows faster convergence and global search ability. Its performance is further evaluated by its application to multiparameter estimation of permanentmagnet synchronous machines, which shows that its performance significantly outperforms existing PSOs. The proposed algorithm can estimate the machine dq-axis inductances, stator winding resistance, and rotor flux linkage simultaneously. PMID:23757582

  1. Learning tensegrity locomotion using open-loop control signals and coevolutionary algorithms.

    PubMed

    Iscen, Atil; Caluwaerts, Ken; Bruce, Jonathan; Agogino, Adrian; SunSpiral, Vytas; Tumer, Kagan

    2015-01-01

    Soft robots offer many advantages over traditional rigid robots. However, soft robots can be difficult to control with standard control methods. Fortunately, evolutionary algorithms can offer an elegant solution to this problem. Instead of creating controls to handle the intricate dynamics of these robots, we can simply evolve the controls using a simulation to provide an evaluation function. In this article, we show how such a control paradigm can be applied to an emerging field within soft robotics: robots based on tensegrity structures. We take the model of the Spherical Underactuated Planetary Exploration Robot ball (SUPERball), an icosahedron tensegrity robot under production at NASA Ames Research Center, develop a rolling locomotion algorithm, and study the learned behavior using an accurate model of the SUPERball simulated in the NASA Tensegrity Robotics Toolkit. We first present the historical-average fitness-shaping algorithm for coevolutionary algorithms to speed up learning while favoring robustness over optimality. Second, we use a distributed control approach by coevolving open-loop control signals for each controller. Being simple and distributed, open-loop controllers can be readily implemented on SUPERball hardware without the need for sensor information or precise coordination. We analyze signals of different complexities and frequencies. Among the learned policies, we take one of the best and use it to analyze different aspects of the rolling gait, such as lengths, tensions, and energy consumption. We also discuss the correlation between the signals controlling different parts of the tensegrity robot. PMID:25951199

  2. Coevolutionary interactions between farmers and mafia induce host acceptance of avian brood parasites.

    PubMed

    Abou Chakra, Maria; Hilbe, Christian; Traulsen, Arne

    2016-05-01

    Brood parasites exploit their host in order to increase their own fitness. Typically, this results in an arms race between parasite trickery and host defence. Thus, it is puzzling to observe hosts that accept parasitism without any resistance. The 'mafia' hypothesis suggests that these hosts accept parasitism to avoid retaliation. Retaliation has been shown to evolve when the hosts condition their response to mafia parasites, who use depredation as a targeted response to rejection. However, it is unclear if acceptance would also emerge when 'farming' parasites are present in the population. Farming parasites use depredation to synchronize the timing with the host, destroying mature clutches to force the host to re-nest. Herein, we develop an evolutionary model to analyse the interaction between depredatory parasites and their hosts. We show that coevolutionary cycles between farmers and mafia can still induce host acceptance of brood parasites. However, this equilibrium is unstable and in the long-run the dynamics of this host-parasite interaction exhibits strong oscillations: when farmers are the majority, accepters conditional to mafia (the host will reject first and only accept after retaliation by the parasite) have a higher fitness than unconditional accepters (the host always accepts parasitism). This leads to an increase in mafia parasites' fitness and in turn induce an optimal environment for accepter hosts. PMID:27293783

  3. Coevolutionary interactions between farmers and mafia induce host acceptance of avian brood parasites

    PubMed Central

    Hilbe, Christian; Traulsen, Arne

    2016-01-01

    Brood parasites exploit their host in order to increase their own fitness. Typically, this results in an arms race between parasite trickery and host defence. Thus, it is puzzling to observe hosts that accept parasitism without any resistance. The ‘mafia’ hypothesis suggests that these hosts accept parasitism to avoid retaliation. Retaliation has been shown to evolve when the hosts condition their response to mafia parasites, who use depredation as a targeted response to rejection. However, it is unclear if acceptance would also emerge when ‘farming’ parasites are present in the population. Farming parasites use depredation to synchronize the timing with the host, destroying mature clutches to force the host to re-nest. Herein, we develop an evolutionary model to analyse the interaction between depredatory parasites and their hosts. We show that coevolutionary cycles between farmers and mafia can still induce host acceptance of brood parasites. However, this equilibrium is unstable and in the long-run the dynamics of this host–parasite interaction exhibits strong oscillations: when farmers are the majority, accepters conditional to mafia (the host will reject first and only accept after retaliation by the parasite) have a higher fitness than unconditional accepters (the host always accepts parasitism). This leads to an increase in mafia parasites’ fitness and in turn induce an optimal environment for accepter hosts. PMID:27293783

  4. Comparative dating of attine ant and lepiotaceous cultivar phylogenies reveals coevolutionary synchrony and discord.

    PubMed

    Mikheyev, Alexander S; Mueller, Ulrich G; Abbot, Patrick

    2010-06-01

    The mutualistic symbiosis between fungus-gardening ants and their cultivars has made fundamental contributions to our understanding of the coevolution of complex species interactions. Reciprocal specialization and vertical symbiont cotransmission are thought to promote a pattern of largely synchronous coevolutionary diversification in attines. Here we test this hypothesis by inferring the first time-calibrated multigene phylogeny of the lepiotaceous attine cultivars and comparing it with the recently published fossil-anchored phylogeny of the attine ants. While this comparison reveals some possible cases of synchronous origins of ant and fungal clades, there were a number of surprising asynchronies. For example, leaf-cutter cultivars appear to be significantly younger than the corresponding ant genera. Similarly, a clade of fungi interacting with primitive fungus-gardening ants--thought to be ancestral to the more derived leaf-cutter symbionts--appears instead to be a more recent acquisition from free-living stock. These macroevolutionary patterns are consistent with recent population-level studies suggesting occasional acquisition of novel cultivar types from environmental sources and horizontal transmission of cultivars between different ant species. Horizontal transmission events, even if rare, appear to form loose ecological connections between diffusely coevolving ant and fungus lineages that permit punctuated changes in the topology of the mutualistic ant-fungus interaction network. PMID:20415533

  5. Quantitative genetic insights into the coevolutionary dynamics of male and female genitalia.

    PubMed

    Evans, Jonathan P; van Lieshout, Emile; Gasparini, Clelia

    2013-07-22

    The spectacular variability that typically characterizes male genital traits has largely been attributed to the role of sexual selection. Among the evolutionary mechanisms proposed to account for this diversity, two processes in particular have generated considerable interest. On the one hand, females may exploit postcopulatory mechanisms of selection to favour males with preferred genital traits (cryptic female choice; CFC), while on the other hand females may evolve structures or behaviours that mitigate the direct costs imposed by male genitalia (sexual conflict; SC). A critical but rarely explored assumption underlying both processes is that male and female reproductive traits coevolve, either via the classic Fisherian model of preference-trait coevolution (CFC) or through sexually antagonistic selection (SC). Here, we provide evidence for this prediction in the guppy (Poecilia reticulata), a polyandrous livebearing fish in which males transfer sperm internally to females via consensual and forced matings. Our results from a paternal half-sibling breeding design reveal substantial levels of additive genetic variation underlying male genital size and morphology-two traits known to predict mating success during non-consensual matings. Our subsequent finding that physically interacting female genital traits exhibit corresponding levels of genetic (co)variation reveals the potential intersexual coevolutionary dynamics of male and female genitalia, thereby fulfilling a fundamental assumption underlying CFC and SC theory. PMID:23720546

  6. Competition for finite resources

    NASA Astrophysics Data System (ADS)

    Cook, L. Jonathan; Zia, R. K. P.

    2012-05-01

    The resources in a cell are finite, which implies that the various components of the cell must compete for resources. One such resource is the ribosomes used during translation to create proteins. Motivated by this example, we explore this competition by connecting two totally asymmetric simple exclusion processes (TASEPs) to a finite pool of particles. Expanding on our previous work, we focus on the effects on the density and current of having different entry and exit rates.

  7. Sequence of host contact influences the outcome of competition among Aspergillus flavus isolates during host tissue invasion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biological control of aflatoxin contamination by Aspergillus flavus is achieved by competitive exclusion of aflatoxin producers by atoxigenic strains. However, factors dictating the extent to which competitive displacement occurs during host infection are unknown. The role of preemptive exclusion in...

  8. 48 CFR 6.204 - Section 8(a) competition.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false Section 8(a) competition... ACQUISITION PLANNING COMPETITION REQUIREMENTS Full and Open Competition After Exclusion of Sources 6.204 Section 8(a) competition. (a) To fulfill statutory requirements relating to section 8(a) of the...

  9. 48 CFR 6.204 - Section 8(a) competition.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 1 2013-10-01 2013-10-01 false Section 8(a) competition... ACQUISITION PLANNING COMPETITION REQUIREMENTS Full and Open Competition After Exclusion of Sources 6.204 Section 8(a) competition. (a) To fulfill statutory requirements relating to section 8(a) of the...

  10. 48 CFR 6.204 - Section 8(a) competition.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Section 8(a) competition... ACQUISITION PLANNING COMPETITION REQUIREMENTS Full and Open Competition After Exclusion of Sources 6.204 Section 8(a) competition. (a) To fulfill statutory requirements relating to section 8(a) of the...

  11. 48 CFR 6.204 - Section 8(a) competition.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Section 8(a) competition... ACQUISITION PLANNING COMPETITION REQUIREMENTS Full and Open Competition After Exclusion of Sources 6.204 Section 8(a) competition. (a) To fulfill statutory requirements relating to section 8(a) of the...

  12. 48 CFR 6.204 - Section 8(a) competition.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 1 2014-10-01 2014-10-01 false Section 8(a) competition... ACQUISITION PLANNING COMPETITION REQUIREMENTS Full and Open Competition After Exclusion of Sources 6.204 Section 8(a) competition. (a) To fulfill statutory requirements relating to section 8(a) of the...

  13. A Coevolutionary Residue Network at the Site of a Functionally Important Conformational Change in a Phosphohexomutase Enzyme Family

    PubMed Central

    Furdui, Cristina; Beamer, Lesa J.

    2012-01-01

    Coevolution analyses identify residues that co-vary with each other during evolution, revealing sequence relationships unobservable from traditional multiple sequence alignments. Here we describe a coevolutionary analysis of phosphomannomutase/phosphoglucomutase (PMM/PGM), a widespread and diverse enzyme family involved in carbohydrate biosynthesis. Mutual information and graph theory were utilized to identify a network of highly connected residues with high significance. An examination of the most tightly connected regions of the coevolutionary network reveals that most of the involved residues are localized near an interdomain interface of this enzyme, known to be the site of a functionally important conformational change. The roles of four interface residues found in this network were examined via site-directed mutagenesis and kinetic characterization. For three of these residues, mutation to alanine reduces enzyme specificity to ∼10% or less of wild-type, while the other has ∼45% activity of wild-type enzyme. An additional mutant of an interface residue that is not densely connected in the coevolutionary network was also characterized, and shows no change in activity relative to wild-type enzyme. The results of these studies are interpreted in the context of structural and functional data on PMM/PGM. Together, they demonstrate that a network of coevolving residues links the highly conserved active site with the interdomain conformational change necessary for the multi-step catalytic reaction. This work adds to our understanding of the functional roles of coevolving residue networks, and has implications for the definition of catalytically important residues. PMID:22685552

  14. a Study of a Quadruple Co-Evolutionary Model and its Reciprocity Phase for Various Prisoner's Dilemma Game

    NASA Astrophysics Data System (ADS)

    Tanimoto, Jun

    We present and numerically investigate a quadruple co-evolutionary model for 2 × 2 Prisoner's Dilemma games which allows not only for agents to adopt strategy (Cooperation C or Defection D) and for network topology, but also for the probability of link rewiring that controls the speed of network evolution and the updating rule itself. The results of a series of simulations reveal that C agents in a coexisting phase increase their rewiring probability to avoid neighboring D agents' exploitation through the Game Exit Option. This evolutionary process leads most agents to adopt pairwise updating even though Imitation Max update adopted by all agents brings a higher payoff.

  15. Coevolutionary, coexisting learning and teaching agents model for prisoner’s dilemma games enhancing cooperation with assortative heterogeneous networks

    NASA Astrophysics Data System (ADS)

    Tanimoto, Jun

    2013-07-01

    Unlike other natural network systems, assortativity can be observed in most human social networks, although it has been reported that a social dilemma situation represented by the prisoner’s dilemma favors dissortativity to enhance cooperation. We established a new coevolutionary model for both agents’ strategy and network topology, where teaching and learning agents coexist. Remarkably, this model enables agents’ enhancing cooperation more than a learners-only model on a time-frozen scale-free network and produces an underlying assortative network with a fair degree of power-law distribution. The model may imply how and why assortative networks are adaptive in human society.

  16. Coevolutionary modeling of protein sequences: Predicting structure, function, and mutational landscapes

    NASA Astrophysics Data System (ADS)

    Weigt, Martin

    Over the last years, biological research has been revolutionized by experimental high-throughput techniques, in particular by next-generation sequencing technology. Unprecedented amounts of data are accumulating, and there is a growing request for computational methods unveiling the information hidden in raw data, thereby increasing our understanding of complex biological systems. Statistical-physics models based on the maximum-entropy principle have, in the last few years, played an important role in this context. To give a specific example, proteins and many non-coding RNA show a remarkable degree of structural and functional conservation in the course of evolution, despite a large variability in amino acid sequences. We have developed a statistical-mechanics inspired inference approach - called Direct-Coupling Analysis - to link this sequence variability (easy to observe in sequence alignments, which are available in public sequence databases) to bio-molecular structure and function. In my presentation I will show, how this methodology can be used (i) to infer contacts between residues and thus to guide tertiary and quaternary protein structure prediction and RNA structure prediction, (ii) to discriminate interacting from non-interacting protein families, and thus to infer conserved protein-protein interaction networks, and (iii) to reconstruct mutational landscapes and thus to predict the phenotypic effect of mutations. References [1] M. Figliuzzi, H. Jacquier, A. Schug, O. Tenaillon and M. Weigt ''Coevolutionary landscape inference and the context-dependence of mutations in beta-lactamase TEM-1'', Mol. Biol. Evol. (2015), doi: 10.1093/molbev/msv211 [2] E. De Leonardis, B. Lutz, S. Ratz, S. Cocco, R. Monasson, A. Schug, M. Weigt ''Direct-Coupling Analysis of nucleotide coevolution facilitates RNA secondary and tertiary structure prediction'', Nucleic Acids Research (2015), doi: 10.1093/nar/gkv932 [3] F. Morcos, A. Pagnani, B. Lunt, A. Bertolino, D. Marks, C

  17. Phylogenetic diversity and co-evolutionary signals among trophic levels change across a habitat edge.

    PubMed

    Peralta, Guadalupe; Frost, Carol M; Didham, Raphael K; Varsani, Arvind; Tylianakis, Jason M

    2015-03-01

    Incorporating the evolutionary history of species into community ecology enhances understanding of community composition, ecosystem functioning and responses to environmental changes. Phylogenetic history might partly explain the impact of fragmentation and land-use change on assemblages of interacting organisms and even determine potential cascading effects across trophic levels. However, it remains unclear whether phylogenetic diversity of basal resources is reflected at higher trophic levels in the food web. In particular, phylogenetic determinants of community structure have never been incorporated into habitat edge studies, even though edges are recognized as key factors affecting communities in fragmented landscapes. Here, we test whether phylogenetic diversity at different trophic levels (plants, herbivores and parasitoids) and signals of co-evolution (i.e. phylogenetic congruence) among interacting trophic levels change across an edge gradient between native and plantation forests. To ascertain whether there is a signal of co-evolution across trophic levels, we test whether related consumer species generally feed on related resource species. We found differences across trophic levels in how their phylogenetic diversity responded to the habitat edge gradient. Plant and native parasitoid phylogenetic diversity changed markedly across habitats, while phylogenetic variability of herbivores (which were predominantly native) did not change across habitats, though phylogenetic evenness declined in plantation interiors. Related herbivore species did not appear to feed disproportionately on related plant species (i.e. there was no signal of co-evolution) even when considering only native species, potentially due to the high trophic generality of herbivores. However, related native parasitoid species tended to feed on related herbivore species, suggesting the presence of a co-evolutionary signal at higher trophic levels. Moreover, this signal was stronger in

  18. Competitive Intelligence.

    ERIC Educational Resources Information Center

    Bergeron, Pierrette; Hiller, Christine A.

    2002-01-01

    Reviews the evolution of competitive intelligence since 1994, including terminology and definitions and analytical techniques. Addresses the issue of ethics; explores how information technology supports the competitive intelligence process; and discusses education and training opportunities for competitive intelligence, including core competencies…

  19. Information use and resource competition: an integrative framework

    PubMed Central

    Ounsley, James P.

    2016-01-01

    Organisms may reduce uncertainty regarding how best to exploit their environment by collecting information about resource distribution. We develop a model to demonstrate how competition can facilitate or constrain an individual's ability to use information when acquiring resources. As resource distribution underpins both selection on information use and the strength and nature of competition between individuals, we demonstrate interdependencies between the two that should be common in nature. Individuals in our model can search for resources either personally or by using social information. We explore selection on social information use across a comprehensive range of ecological conditions, generalizing the producer–scrounger framework to a wide diversity of taxa and resources. We show that resource ecology—defined by scarcity, depletion rate and monopolizability—determines patterns of individual differences in social information use. These differences suggest coevolutionary processes linking dominance systems and social information use, with implications for the evolutionary demography of populations. PMID:26888031

  20. Information use and resource competition: an integrative framework.

    PubMed

    Lee, Alexander E G; Ounsley, James P; Coulson, Tim; Rowcliffe, J Marcus; Cowlishaw, Guy

    2016-02-24

    Organisms may reduce uncertainty regarding how best to exploit their environment by collecting information about resource distribution. We develop a model to demonstrate how competition can facilitate or constrain an individual's ability to use information when acquiring resources. As resource distribution underpins both selection on information use and the strength and nature of competition between individuals, we demonstrate interdependencies between the two that should be common in nature. Individuals in our model can search for resources either personally or by using social information. We explore selection on social information use across a comprehensive range of ecological conditions, generalizing the producer-scrounger framework to a wide diversity of taxa and resources. We show that resource ecology--defined by scarcity, depletion rate and monopolizability--determines patterns of individual differences in social information use. These differences suggest coevolutionary processes linking dominance systems and social information use, with implications for the evolutionary demography of populations. PMID:26888031

  1. Topology and sizing optimization of discrete structures using a cooperative coevolutionary genetic algorithm with independent ground structures

    NASA Astrophysics Data System (ADS)

    Zhong, Wei; Su, Ruiyi; Gui, Liangjin; Fan, Zijie

    2016-06-01

    This article proposes a method called the cooperative coevolutionary genetic algorithm with independent ground structures (CCGA-IGS) for the simultaneous topology and sizing optimization of discrete structures. An IGS strategy is proposed to enhance the flexibility of the optimization by offering two separate design spaces and to improve the efficiency of the algorithm by reducing the search space. The CCGA is introduced to divide a complex problem into two smaller subspaces: the topological and sizing variables are assigned into two subpopulations which evolve in isolation but collaborate in fitness evaluations. Five different methods were implemented on 2D and 3D numeric examples to test the performance of the algorithms. The results demonstrate that the performance of the algorithms is improved in terms of accuracy and convergence speed with the IGS strategy, and the CCGA converges faster than the traditional GA without loss of accuracy.

  2. Friendly competition.

    PubMed

    Chambers, David W

    2006-01-01

    Competition that is characterized by rules, often informal, agreed among mutually accepted participants, and that gives the competitors a special, advantageous status with others is called friendly competition. Dentists have engaged in it deeply and it is good for the profession. Friendly competition offers the advantages of spillover of commonly useful information and technologies, stimulation of innovation, a united and convenient face to customers and suppliers, and standards that promote growth. Friendly competition increases the size of the pie, regardless of market share. Paradoxically, this is even true for the little guy in the shadow of the giant. If carried to extremes, unfriendly competition leads to destroying competitors, the confusion of multiple rules, and encouragement of disruptive change. PMID:17477218

  3. UK Higher Education: Competitive Forces in the 21st Century.

    ERIC Educational Resources Information Center

    Webber, G. C.

    2000-01-01

    Considers United Kingdom higher education in the context of Michael Porter's book, "Competitive Strategy," which discusses five forces governing competition. Focusing mainly, but not exclusively, on teaching, the monograph identifies critical factors that have influenced the balance of competitive forces in higher education and identifies ways in…

  4. Subinhibitory Antibiotic Concentrations Mediate Nutrient Use and Competition among Soil Streptomyces

    PubMed Central

    Vaz Jauri, Patricia; Bakker, Matthew G.; Salomon, Christine E.; Kinkel, Linda L.

    2013-01-01

    Though traditionally perceived as weapons, antibiotics are also hypothesized to act as microbial signals in natural habitats. However, while subinhibitory concentrations of antibiotics (SICA) are known to shift bacterial gene expression, specific hypotheses as to how SICA influence the ecology of natural populations are scarce. We explored whether antibiotic ‘signals’, or SICA, have the potential to alter nutrient utilization, niche overlap, and competitive species interactions among Streptomyces populations in soil. For nine diverse Streptomyces isolates, we evaluated nutrient utilization patterns on 95 different nutrient sources in the presence and absence of subinhibitory concentrations of five antibiotics. There were significant changes in nutrient use among Streptomyces isolates, including both increases and decreases in the capacity to use individual nutrients in the presence vs. in the absence of SICA. Isolates varied in their responses to SICA and antibiotics varied in their effects on isolates. Furthermore, for some isolate-isolate-antibiotic combinations, competition-free growth (growth for an isolate on all nutrients that were not utilized by a competing isolate), was increased in the presence of SICA, reducing the potential fitness cost of nutrient competition among those competitors. This suggests that antibiotics may provide a mechanism for bacteria to actively minimize niche overlap among competitors in soil. Thus, in contrast to antagonistic coevolutionary dynamics, antibiotics as signals may mediate coevolutionary displacement among coexisting Streptomyces, thereby hindering the emergence of antibiotic resistant phenotypes. These results contribute to our broad understanding of the ecology and evolutionary biology of antibiotics and microbial signals in nature. PMID:24339897

  5. Coevolutionary dynamics of networks and games under birth-death and birth mechanisms

    NASA Astrophysics Data System (ADS)

    Huang, Z.-G.; Wu, Z.-X.; Xu, X.-J.; Guan, J.-Y.; Wang, Y.-H.

    2007-08-01

    There is much interest in studying evolutionary games in structured populations, in order to understand how cooperation emerges in communities of egoistic agents. In this paper, we consider a new mechanism for cooperation to survive on networks. Agents are designed to reproduce offspring in proportion to their fitness, i.e., the aggregate payoffs they collected in the previous Prisoner's Dilemma game with neighbours. The population then evolves either by an individual giving birth to an offspring that takes over a random neighbour (birth-death process dynamics as the competition for resources already occupied by others) or by an individual constructing one new site from unexploited resources for its offspring (birth process dynamics as the competition for the unexploited resources which induces the extension of system). The underlying interaction network thus evolves and expands simultaneously with the population dynamics. The birth process dynamics is proved to be one new route that favours cooperators, under which cooperators can successfully resist the invasion of defectors in spite of large cost. Furthermore, under this “birth-death & birth” mechanism, the resulting network has a scale-free degree distribution, a small-world property, and hierarchical topology.

  6. Sustainability and collapse in a coevolutionary model of local resource stocks and behavioral patterns on a social network

    NASA Astrophysics Data System (ADS)

    Wiedermann, Marc; Donges, Jonathan F.; Heitzig, Jobst; Kurths, Jürgen

    2014-05-01

    When investigating the causes and consequences of global change, the collective behavior of human beings is considered as having a considerable impact on natural systems. In our work, we propose a conceptual coevolutionary model simulating the dynamics of local renewable resources in interaction with simplistic societal agents exploiting those resources. The society is represented by a social network on which social traits may be transmitted between agents. These traits themselves induce a certain rate of exploitation of the resource, leading either to its depletion or sustainable existence. Traits are exchanged probabilistically according to their instantaneous individual payoff, and hence this process depends on the status of the natural resource. At the same time agents may adaptively restructure their set of acquaintances. Connections with agents having a different trait may be broken while new connections with agents of the same trait are established. We investigate which choices of social parameters, like the frequency of social interaction, rationality and rate of social network adaptation, cause the system to end in a sustainable state and, hence, what can be done to avoid a collapse of the entire system. The importance and influence of the social network structure is analyzed by the variation of link-densities in the underlying network topology and shows significant influence on the expected outcome of the model. For a static network with no adaptation we find a robust phase transition between the two different regimes, sustainable and non-sustainable, which co-exist in parameter space. High connectivity within the social network, e.g., high link-densities, in combination with a fast rate of social learning lead to a likely collapse of the entire co-evolutionary system, whereas slow learning and small network connectivity very likely result in the sustainable existence of the natural resources. Collapse may be avoided by an intelligent rewiring, e

  7. EDITORIAL: Physics competitions Physics competitions

    NASA Astrophysics Data System (ADS)

    Jordens, H.; Mathelitsch, L.

    2009-11-01

    1. Physics competitions: aims and realizations One aim of physics competitions is to increase the interest of young students, primarily at upper secondary level, to physics and natural sciences in general. A competition has motivational aspects known usually from sports events or games—comparing one's own ability with others, of course with the desire to be better and to win. If competitions reach nationwide and even international levels, additional stimulation is created. Competitions provide greatest attraction to possible winners, to the group of gifted people in a particular field. This implies that science contests are excellent tools for the promotion of talented students. Traditional teaching has been shown to have problems in supporting this group of students. Very often teachers are overstretched with the demands of teaching both low- and high-level students. Extracurricular activities are therefore a good chance to relieve the teacher, and to give talented students the opportunity for appropriate training and challenge. The competitions, however, have a broader impact and address more young people than one might guess from the statements above. Training courses and selection at school level give a larger group of students extra and, to some extent, complimentary education in physics. The degree of complexity of the tasks corresponds very often to the standards of the next level of education in the school system. Interestingly, many physics competitions have their origin in countries beyond the former Iron Curtain. They started as regional and national tournaments, were joined by neighbouring countries and have grown, in some cases, to events with participants from more than 80 countries. Although the features mentioned above are common to the different competitions, there are distinct differences between them [1]. The International Physics Olympiad (IPhO) is the oldest international physics competition for students at upper secondary level [2]. It dates

  8. Sequence co-evolutionary information is a natural partner to minimally-frustrated models of biomolecular dynamics

    PubMed Central

    Noel, Jeffrey K; Morcos, Faruck; Onuchic, Jose N

    2016-01-01

    Experimentally derived structural constraints have been crucial to the implementation of computational models of biomolecular dynamics. For example, not only does crystallography provide essential starting points for molecular simulations but also high-resolution structures permit for parameterization of simplified models. Since the energy landscapes for proteins and other biomolecules have been shown to be minimally frustrated and therefore funneled, these structure-based models have played a major role in understanding the mechanisms governing folding and many functions of these systems. Structural information, however, may be limited in many interesting cases. Recently, the statistical analysis of residue co-evolution in families of protein sequences has provided a complementary method of discovering residue-residue contact interactions involved in functional configurations. These functional configurations are often transient and difficult to capture experimentally. Thus, co-evolutionary information can be merged with that available for experimentally characterized low free-energy structures, in order to more fully capture the true underlying biomolecular energy landscape. PMID:26918164

  9. A Bird's Eye View of Influenza A Virus Transmission: Challenges with Characterizing Both Sides of a Co-Evolutionary Dynamic.

    PubMed

    Hill, Nichola J; Runstadler, Jonathan A

    2016-08-01

    In nature, wild birds and influenza A viruses (IAV) are continually co-evolving, locked into a back-and-forth of resistance and conquest that has approached a stable equilibrium over time. This co-evolutionary relationship between bird host and IAV may appear stable at the organismal level, but is highly dynamic at the molecular level manifesting in a constant trade-off between transmissibility and virulence of the virus. Characterizing both sides of the host-virus dynamic has presented a challenge for ecologists and virologists alike, despite the potential for this approach to provide insights into which conditions destabilize the equilibrium state resulting in outbreaks or mortality of hosts in extreme cases. The use of different methods that are either host-centric or virus-centric has made it difficult to reconcile the disparate fields of host ecology and virology for investigating and ultimately predicting wild bird-mediated transmission of IAV. This review distills some of the key lessons learned from virological and ecological studies and explores the promises and pitfalls of both approaches. Ultimately, reconciling ecological and virological approaches hinges on integrating scales for measuring host-virus interactions. We argue that prospects for finding common scales for measuring wild bird-influenza dynamics are improving due to advances in genomic sequencing, host-tracking technology and remote sensing data, with the unit of time (months, year, or seasons) providing a starting point for crossover. PMID:27252222

  10. EDITORIAL: Physics competitions Physics competitions

    NASA Astrophysics Data System (ADS)

    Jordens, H.; Mathelitsch, L.

    2009-11-01

    1. Physics competitions: aims and realizations One aim of physics competitions is to increase the interest of young students, primarily at upper secondary level, to physics and natural sciences in general. A competition has motivational aspects known usually from sports events or games—comparing one's own ability with others, of course with the desire to be better and to win. If competitions reach nationwide and even international levels, additional stimulation is created. Competitions provide greatest attraction to possible winners, to the group of gifted people in a particular field. This implies that science contests are excellent tools for the promotion of talented students. Traditional teaching has been shown to have problems in supporting this group of students. Very often teachers are overstretched with the demands of teaching both low- and high-level students. Extracurricular activities are therefore a good chance to relieve the teacher, and to give talented students the opportunity for appropriate training and challenge. The competitions, however, have a broader impact and address more young people than one might guess from the statements above. Training courses and selection at school level give a larger group of students extra and, to some extent, complimentary education in physics. The degree of complexity of the tasks corresponds very often to the standards of the next level of education in the school system. Interestingly, many physics competitions have their origin in countries beyond the former Iron Curtain. They started as regional and national tournaments, were joined by neighbouring countries and have grown, in some cases, to events with participants from more than 80 countries. Although the features mentioned above are common to the different competitions, there are distinct differences between them [1]. The International Physics Olympiad (IPhO) is the oldest international physics competition for students at upper secondary level [2]. It dates

  11. EDITORIAL: Physics competitions Physics competitions

    NASA Astrophysics Data System (ADS)

    Jordens, H.; Mathelitsch, L.

    2010-07-01

    This editorial opens the second special section on physics competitions in European Journal of Physics. In the first section last year, we asked for feedback on the idea of such a section and on the content of the articles. We received no answer whatsoever, which can be interpreted in two ways: the section is not interesting enough to raise motivation for feedback, or the reader is satisfied. Having no indication which scenario is the correct one, we are optimistic and favour the second. The section at hand contains three articles. Again, as last year, the organizer of the annual Olympiad reports on tasks and outcomes of this competition. The Olympiad took place in Merida, Mexico, and was by far the largest event with 316 contestants from 68 countries. Again, the predominance of Asian/Chinese students was manifest, showing how serious the training is taken by both their authorities and students. Unfortunately, the winners of the last International Young Physicists' Tournament (IYPT), the team from Korea, did not accept the offer to report on their prize-winning contribution. We are thankful that two students from Austria, who achieved second place with their team, took over and reported on the task which they presented in the finals of the competition. It connects the fields of sport and physics and explains a special move in skateboarding. The third contribution introduces a different competition, 'International Conference of Young Scientists'. On one hand, as in the Olympiad, it addresses individuals, not teams. On the other, as in the IYPT, students have several months to prepare and also the quality of the presentation is an important element of the judgment. In fact, this competition comes closer to real scientific research compared to the other events. Finally and again, we hope that this section will serve several purposes: To show the competitions as a very important tool in the support of gifted students. To raise awareness amongst university teachers, and

  12. 48 CFR 19.1006 - Exclusions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Exclusions. 19.1006 Section 19.1006 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Small Business Competitiveness Demonstration Program 19.1006...

  13. Resources versus Response Competition: A False Disjunction?

    ERIC Educational Resources Information Center

    Chapman, Michael

    1989-01-01

    Argues that the resources and response competition models discussed by Brainerd and Reyna (in this issue) may not be mutually exclusive, but instead may model different aspects of performance. The problem is not to decide between the two models in general, but rather to determine which aspects of performance are best explained by each. (RH)

  14. Frontier mutualism: coevolutionary patterns at the northern range limit of the leaf-cutter ant–fungus symbiosis

    PubMed Central

    Mueller, Ulrich G.; Mikheyev, Alexander S.; Solomon, Scott E.; Cooper, Michael

    2011-01-01

    Tropical leaf-cutter ants cultivate the fungus Attamyces bromatificus in a many-to-one, diffuse coevolutionary relationship where ant and fungal partners re-associate frequently over time. To evaluate whether ant–Attamyces coevolution is more specific (tighter) in peripheral populations, we characterized the host-specificities of Attamyces genotypes at their northern, subtropical range limits (southern USA, Mexico and Cuba). Population-genetic patterns of northern Attamyces reveal features that have so far not been observed in the diffusely coevolving, tropical ant–Attamyces associations. These unique features include (i) cases of one-to-one ant–Attamyces specialization that tighten coevolution at the northern frontier; (ii) distributions of genetically identical Attamyces clones over large areas (up to 81 000 km2, approx. the area of Ireland, Austria or Panama); (iii) admixture rates between Attamyces lineages that appear lower in northern than in tropical populations; and (iv) long-distance gene flow of Attamyces across a dispersal barrier for leaf-cutter ants (ocean between mainland North America and Cuba). The latter suggests that Attamyces fungi may occasionally disperse independently of the ants, contrary to the traditional assumption that Attamyces fungi depend entirely on leaf-cutter queens for dispersal. Peripheral populations in Argentina or at mid-elevation sites in the Andes may reveal additional regional variants in ant–Attamyces coevolution. Studies of such populations are most likely to inform models of coextinctions of obligate mutualistic partners that are doubly stressed by habitat marginality and by environmental change. PMID:21389026

  15. Malaysian competition

    SciTech Connect

    Jeffs, E.

    1994-11-01

    Two years ago, the first tentative steps were taken to privatize the Malaysian electricity supply industry with the flotation of 25 percent of Tenaga Nasional Bhd. At the same time the terms were defined for independent power generation, and plans were drawn up for six projects. Now, with six independent power producer projects under construction adding more capacity than the partly privatized TNB, the utility`s station managers are concerned they will be at a competitive disadvantage unless they can operate under the same type of power sales agreement.

  16. EDITORIAL: Physics competitions Physics competitions

    NASA Astrophysics Data System (ADS)

    Jordens, H.; Mathelitsch, L.

    2011-07-01

    International tests on competences, such as TIMSS or PISA, and knowledge of young students have revealed low average scores in many countries, often unexpectedly. One effective measure to increase the average standard of a population is to bring the last third of the group to a higher level. Therefore, many nations put some effort into this activity. This brings the danger that not enough attention is paid to students at the other end, those who are talented. Indeed, it is a very difficult task for a teacher to support the less able and at the same time challenge the gifted students, to lead them to the limits of their abilities and provide for a smooth transition to university study. Physics competitions have been proven to fulfil these last demands to a large degree, and therefore are an important additional and, to some extent, complementary tool for the promotion of talented students. This third special section on physics competitions in European Journal of Physics contains three papers, each dealing with a different form of science contest. The first continues the series of presentations of tasks performed at the International Young Physicists' Tournament, which was held in Vienna in 2011. First place went to the team from Singapore, and they have put their investigation on vertical oscillations of coupled magnets into written form (not required by the tournament, where an oral presentation and a defence and discussion are the central aspects). Their paper shows how rich in physics this problem is, and what level of solutions high-school students can already achieve. Sadly, those responsible for the organization of last year's International Physics Olympiad did not provide us with a report on this competition. This is unfortunate, since the Olympiad in Zagreb was very successful and, in particular, the experimental tasks were creative and demanding. Very similar to the aims and the execution of the Physics Olympiad is the International Olympiad on Astronomy

  17. Competition promotes the persistence of populations in ecosystems.

    PubMed

    Wang, Tao; Duan, Jinqiao; Liu, Tong

    2016-01-01

    Competition is one of the most common form in ecological systems, which plays important roles in population dynamics. However, the influences of competition on persistence of populations remain unclear when space effect is included. In this paper, we investigated a predator-prey model with competition and spatial diffusion. Based on pattern formations and time series of populations, we found that competitions induce the persistence of populations, which denies competitive exclusion principle. Moreover, we testify the robustness of these effects. Our results also suggest that space may lead to the emergence of new phenomenon in ecosystems. PMID:27460143

  18. Competition promotes the persistence of populations in ecosystems

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Duan, Jinqiao; Liu, Tong

    2016-07-01

    Competition is one of the most common form in ecological systems, which plays important roles in population dynamics. However, the influences of competition on persistence of populations remain unclear when space effect is included. In this paper, we investigated a predator-prey model with competition and spatial diffusion. Based on pattern formations and time series of populations, we found that competitions induce the persistence of populations, which denies competitive exclusion principle. Moreover, we testify the robustness of these effects. Our results also suggest that space may lead to the emergence of new phenomenon in ecosystems.

  19. Competition promotes the persistence of populations in ecosystems

    PubMed Central

    Wang, Tao; Duan, Jinqiao; Liu, Tong

    2016-01-01

    Competition is one of the most common form in ecological systems, which plays important roles in population dynamics. However, the influences of competition on persistence of populations remain unclear when space effect is included. In this paper, we investigated a predator-prey model with competition and spatial diffusion. Based on pattern formations and time series of populations, we found that competitions induce the persistence of populations, which denies competitive exclusion principle. Moreover, we testify the robustness of these effects. Our results also suggest that space may lead to the emergence of new phenomenon in ecosystems. PMID:27460143

  20. Interference competition and species coexistence.

    PubMed Central

    Amarasekare, Priyanga

    2002-01-01

    Interference competition is ubiquitous in nature. Yet its effects on resource exploitation remain largely unexplored for species that compete for dynamic resources. Here, I present a model of exploitative and interference competition with explicit resource dynamics. The model incorporates both biotic and abiotic resources. It considers interference competition both in the classical sense (i.e. each species suffers a net reduction in per capita growth rate via interference from, and interference on, the other species) and in the broad sense (i.e. each species suffers a net reduction in per capita growth rate via interference from, but can experience an increase in growth rate via interference on, the other species). Coexistence cannot occur under classical interference competition even when the species inferior at resource exploitation is superior at interference. Such a trade-off can, however, change the mechanism of competitive exclusion from dominance by the superior resource exploiter to a priority effect. Now the inferior resource exploiter can exclude the superior resource exploiter provided it has a higher initial abundance. By contrast, when interference is beneficial to the interacting species, coexistence is possible via a trade-off between exploitation and interference. These results hold regardless of whether the resource is biotic or abiotic, indicating that the outcome of exploitative and interference competition does not depend on the exact nature of resource dynamics. The model makes two key predictions. First, species that engage in costly interference mechanisms (e.g. territoriality, overgrowth or undercutting, allelopathy and other forms of chemical competition) should not be able to coexist unless they also engage in beneficial interference mechanisms (e.g. predation or parasitism). Second, exotic invasive species that displace native biota should be superior resource exploiters that have strong interference effects on native species with little

  1. Evolution of angiosperm seed disperser mutualisms: the timing of origins and their consequences for coevolutionary interactions between angiosperms and frugivores.

    PubMed

    Eriksson, Ove

    2016-02-01

    , and many of the originations of fleshy fruits occurred well after the peak in the early Eocene. (vi) During periods associated with environmental change altering coevolutionary networks and opening of niche space, reciprocal coevolution may result in strong directional selection formative for both fruit and frugivore evolution. Further evidence is needed to test this hypothesis. Based on the abundance of plant lineages with various forms of fleshy fruits, and the diversity of frugivores, it is suggested that periods of rapid coevolution in angiosperms and frugivores occurred numerous times during the 80 million years of angiosperm-frugivore evolution. PMID:25530412

  2. Punctuated Equilibrium in Statistical Models of Generalized Coevolutionary Resilience: How Sudden Ecosystem Transitions Can Entrain Both Phenotype Expression and Darwinian Selection

    NASA Astrophysics Data System (ADS)

    Wallace, Rodrick; Wallace, Deborah

    We argue that mesoscale ecosystem resilience shifts akin to sudden phase transitions in physical systems can entrain similarly punctuated events of gene expression on more rapid time scales, and, in part through such means, slower changes induced by selection pressure, triggering punctuated equilibrium Darwinian evolutionary transitions on geologic time scales. The approach reduces ecosystem, gene expression, and Darwinian genetic dynamics to a least common denominator of information sources interacting by crosstalk at markedly differing rates. Pettini's 'topological hypothesis', via a homology between information source uncertainty and free energy density, generates a regression-like class of statistical models of sudden coevolutionary phase transition based on the Rate Distortion and Shannon-McMillan Theorems of information theory which links all three levels. A mathematical treatment of Holling's extended keystone hypothesis regarding the particular role of mesoscale phenomena in entraining both slower and faster dynamical structures produces the result. A main theme is the necessity of a cognitive paradigm for gene expression, mirroring I. Cohen's cognitive approach to immune function. Invocation of the necessary conditions imposed by the asymptotic limit theorems of communication theory enables us to penetrate one layer more deeply before needing to impose an empirically-derived phenomenological system of 'Onsager relation' recursive coevolutionary stochastic differential equations. Extending the development to second order via a large deviations argument permits modeling the influence of human cultural structures on ecosystems as 'farming'.

  3. Competitive science: is competition ruining science?

    PubMed

    Fang, Ferric C; Casadevall, Arturo

    2015-04-01

    Science has always been a competitive undertaking. Despite recognition of the benefits of cooperation and team science, reduced availability of funding and jobs has made science more competitive than ever. Here we consider the benefits of competition in providing incentives to scientists and the adverse effects of competition on resource sharing, research integrity, and creativity. The history of science shows that transformative discoveries often occur in the absence of competition, which only emerges once fields are established and goals are defined. Measures to encourage collaboration and ameliorate competition in the scientific enterprise are discussed. PMID:25605760

  4. Competitive Science: Is Competition Ruining Science?

    PubMed Central

    Casadevall, Arturo

    2015-01-01

    Science has always been a competitive undertaking. Despite recognition of the benefits of cooperation and team science, reduced availability of funding and jobs has made science more competitive than ever. Here we consider the benefits of competition in providing incentives to scientists and the adverse effects of competition on resource sharing, research integrity, and creativity. The history of science shows that transformative discoveries often occur in the absence of competition, which only emerges once fields are established and goals are defined. Measures to encourage collaboration and ameliorate competition in the scientific enterprise are discussed. PMID:25605760

  5. Lunabotics Mining Competition

    NASA Technical Reports Server (NTRS)

    Mueller, Rob; Murphy, Gloria

    2010-01-01

    This slide presentation describes a competition to design a lunar robot (lunabot) that can be controlled either remotely or autonomously, isolated from the operator, and is designed to mine a lunar aggregate simulant. The competition is part of a systems engineering curriculum. The 2010 competition winners in five areas of the competition were acknowledged, and the 2011 competition was announced.

  6. Coevolutionary Free Lunches

    NASA Technical Reports Server (NTRS)

    Wolpert, David H.; Macready, William G.

    2005-01-01

    Recent work on the mathematical foundations of optimization has begun to uncover its rich structure. In particular, the "No Free Lunch" (NFL) theorems state that any two algorithms are equivalent when their performance is averaged across all possible problems. This highlights the need for exploiting problem-specific knowledge to achieve better than random performance. In this paper we present a general framework covering more search scenarios. In addition to the optimization scenarios addressed in the NFL results, this framework covers multi-armed bandit problems and evolution of multiple co-evolving players. As a particular instance of the latter, it covers "self-play" problems. In these problems the set of players work together to produce a champion, who then engages one or more antagonists in a subsequent multi-player game. In contrast to the traditional optimization case where the NFL results hold, we show that in self-play there are free lunches: in coevolution some algorithms have better performance than other algorithms, averaged across all possible problems. We consider the implications of these results to biology where there is no champion.

  7. Competitive spirit

    NASA Astrophysics Data System (ADS)

    2000-01-01

    Leicester University will host the 65 international teams of students who will assemble in July for this year's International Physics Olympiad . The last time the Olympiad came to the UK was in 1986 in London, and it was the notable enthusiasm of the Leicester Physics and Astronomy department which persuaded the Olympiad Committee to give them the chance of organizing the prestigious event. The students taking part from all over the world are studying physics at A-level or an equivalent standard and they will take part in an intellectual marathon of theoretical and practical examinations. Each national team comprises five students selected from three rounds of competition and the teams will receive an official welcome from the city, as well as opportunities to visit some of the important educational and cultural centres of the surrounding region. The finalists will also be able to test their skills and initiative at the Challenger Learning Centre, which forms part of Leicester's new National Space Science Centre. Specific information on the event can be found on the Olympiad-2000 website at www.star.le.ac.uk/IphO-2000 . The Rudolf Ortvay problem solving contest in physics, which takes place in November, is a tradition of Eötvös University in Budapest, Hungary. The competition was first opened to international participants in 1998, enabling students from universities around the world to show their knowledge, ingenuity, problem-solving skills and physical insight into problems that are far beyond routine level. The problems (30 - 35 each year) are chosen from different branches of theoretical as well as applied physics. They have varying levels of difficulty, and every contestant can send solutions for ten problems. The focus is not on school-level problem-solving routines but rather on the `physical' way of thinking, recognition of the heart of the problem and an appropriate choice of mathematics. The majority of the assigned problems are original, few having

  8. Competitive spirit

    NASA Astrophysics Data System (ADS)

    2000-01-01

    Leicester University will host the 65 international teams of students who will assemble in July for this year's International Physics Olympiad . The last time the Olympiad came to the UK was in 1986 in London, and it was the notable enthusiasm of the Leicester Physics and Astronomy department which persuaded the Olympiad Committee to give them the chance of organizing the prestigious event. The students taking part from all over the world are studying physics at A-level or an equivalent standard and they will take part in an intellectual marathon of theoretical and practical examinations. Each national team comprises five students selected from three rounds of competition and the teams will receive an official welcome from the city, as well as opportunities to visit some of the important educational and cultural centres of the surrounding region. The finalists will also be able to test their skills and initiative at the Challenger Learning Centre, which forms part of Leicester's new National Space Science Centre. Specific information on the event can be found on the Olympiad-2000 website at www.star.le.ac.uk/IphO-2000 . The Rudolf Ortvay problem solving contest in physics, which takes place in November, is a tradition of Eötvös University in Budapest, Hungary. The competition was first opened to international participants in 1998, enabling students from universities around the world to show their knowledge, ingenuity, problem-solving skills and physical insight into problems that are far beyond routine level. The problems (30 - 35 each year) are chosen from different branches of theoretical as well as applied physics. They have varying levels of difficulty, and every contestant can send solutions for ten problems. The focus is not on school-level problem-solving routines but rather on the `physical' way of thinking, recognition of the heart of the problem and an appropriate choice of mathematics. The majority of the assigned problems are original, few having

  9. Female competition: causes, constraints, content, and contexts.

    PubMed

    Campbell, Anne

    2004-02-01

    Monogamy tends to equalise mate competition between the sexes. However, women show greater restraint in their use of direct intrasexual aggression, which, I argue, is a result of their higher parental investment and the consequently greater reproductive cost of injury or death. Women usually compete for mates by advertising qualities valued by men (beauty and sexual exclusiveness) and by using indirect means of denigrating rivals (through gossip and stigmatisation). However, where well-resourced men are in short supply, women must find alternative sources of support or escalate their competition for male partners to physical levels. Data from criminology, psychology, evolutionary biology, and anthropology are used to support these proposals. PMID:15216421

  10. Competition in the Marketplace.

    ERIC Educational Resources Information Center

    Schug, Mark C.; And Others

    1984-01-01

    The conceptual introduction to this issue focuses on two questions: why study competition and what is a competitive market. Four instructional units follow, beginning with "Choosing Competitors." This preschool and kindergarten unit involves students in competitive games (naming colors), role playing competitive behaviors, comparing toys, and…

  11. Competition in Education.

    ERIC Educational Resources Information Center

    Rich, John Martin; DeVitis, Joseph L.

    This book discusses various major aspects of competition in education. It identifies competition within educational policies, programs, and practices, as well as the problems that certain forms of competition create. It also traces the influences of American competitive values on education. Chapter 1 provides an introductory overview of the…

  12. The relative importance of seed competition, resource competition and perturbations on community structure

    NASA Astrophysics Data System (ADS)

    Bohn, K.; Dyke, J. G.; Pavlick, R.; Reineking, B.; Reu, B.; Kleidon, A.

    2011-05-01

    While the regional climate is the primary selection pressure for whether a plant strategy can survive, however, competitive interactions strongly affect the relative abundances of plant strategies within communities. Here, we investigate the relative importance of competition and perturbations on the development of vegetation community structure. To do so, we develop DIVE (Dynamics and Interactions of VEgetation), a simple general model that links plant strategies to their competitive dynamics, using growth and reproduction characteristics that emerge from climatic constraints. The model calculates population dynamics based on establishment, mortality, invasion and exclusion in the presence of different strengths of perturbations, seed and resource competition. The highest levels of diversity were found in simulations without competition as long as mortality is not too high. However, reasonable successional dynamics were only achieved when resource competition is considered. Under high levels of competition, intermediate levels of perturbations were required to obtain coexistence. Since succession and coexistence are observed in plant communities, we conclude that the DIVE model with competition and intermediate levels of perturbation represents an adequate way to model population dynamics. Because of the simplicity and generality of DIVE, it could be used to understand vegetation structure and functioning at the global scale and the response of vegetation to global change.

  13. 10 CFR 781.52 - Exclusive and partially exclusive licenses.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Exclusive and partially exclusive licenses. 781.52 Section 781.52 Energy DEPARTMENT OF ENERGY DOE PATENT LICENSING REGULATIONS Types of Licenses and Conditions for Licensing § 781.52 Exclusive and partially exclusive licenses. (a) Availability of licenses. The Department may grant exclusive or...

  14. Higgs central exclusive production

    NASA Astrophysics Data System (ADS)

    Cudell, J. R.; Dechambre, A.; Hernández, O. F.

    2012-01-01

    Using the CHIDe model, we tune the calculation of central exclusive Higgs production to the recent CDF central exclusive dijet data, and predict the cross section for the exclusive production of Higgs boson at the LHC. In this model, due to different choices of the scale in the Sudakov form factor for dijet and Higgs production, it is always below 1 fb, and below 0.3 fb after experimental cuts.

  15. Probiotics, prebiotics, and competitive exclusion for prophylaxis against bacterial disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bacteria that are pathogenic to animals and human consumers can exist in the gastrointestinal tract of our food animal species. The gastrointestinal tract of food animals can be inhabited by bacteria that cause foodborne illnesses in humans, but that do not cause detectable animal illnesses or a de...

  16. Lunar Regolith Excavation Competition

    NASA Technical Reports Server (NTRS)

    Liles, Cassandra

    2009-01-01

    The Lunar Regolith Excavation Competition is a new competition that needs graphics, logos, rules, as well as an arena. Although this is the first year of the competition, the competition is modeled after an existing competition, the Centennial Lunar Excavator Challenge. This competition however is aimed at college students. This makes the challenge identifying key aspects of the original competition and modeling them to fit into an easier task, and creating exciting advertisement that helps encourage participation. By using a youth focus group, young insight, as well as guiding advice from experts in the field, hopefully an arena can be designed and built, rules can be molded and created to fit, and alluring graphics can be printed to bring about a successful first year of the Lunar Regolith Excavation Competition.

  17. Enhanced Information Exclusion Relations

    NASA Astrophysics Data System (ADS)

    Xiao, Yunlong; Jing, Naihuan; Li-Jost, Xianqing

    2016-07-01

    In Hall’s reformulation of the uncertainty principle, the entropic uncertainty relation occupies a core position and provides the first nontrivial bound for the information exclusion principle. Based upon recent developments on the uncertainty relation, we present new bounds for the information exclusion relation using majorization theory and combinatoric techniques, which reveal further characteristic properties of the overlap matrix between the measurements.

  18. Enhanced Information Exclusion Relations.

    PubMed

    Xiao, Yunlong; Jing, Naihuan; Li-Jost, Xianqing

    2016-01-01

    In Hall's reformulation of the uncertainty principle, the entropic uncertainty relation occupies a core position and provides the first nontrivial bound for the information exclusion principle. Based upon recent developments on the uncertainty relation, we present new bounds for the information exclusion relation using majorization theory and combinatoric techniques, which reveal further characteristic properties of the overlap matrix between the measurements. PMID:27460975

  19. Central Exclusive Dijet Production

    SciTech Connect

    Dechambre, A.; Cudell, J. R.; Ivanov, I. P.; Hernandez, O.

    2008-08-29

    The ingredients of central exclusive production cross section include large perturbative corrections and soft quantities that must be parametrized and fitted to data. In this talk, we summarize the results of a study of the uncertainties coming from these ingredients, in the case of exclusive dijet production.

  20. Strategizing for Intense Competition.

    ERIC Educational Resources Information Center

    Hahn, William; Bourgeois, Ernest J., Jr.

    1999-01-01

    Examines trend toward more aggressive student recruiting strategies by colleges and universities, applying a model that assesses five competitive forces-cause and effect of competition, the expanding marketplace, substitute products, buyer power, and supplier power, and examines various strategies for dealing with these competitive forces, such as…

  1. In Defence of Competition.

    ERIC Educational Resources Information Center

    Prvulovich, Zika Rad

    1982-01-01

    Examines objections to competition as presented by educational philosopher Michael Fielding and others. The two major types of criticism of competition are that it is unfair and divisive and that it is selfish and immoral. The author advocates educational experiences which combine self-competition with cooperation. (AM)

  2. Competitive Anxiety in Sport.

    ERIC Educational Resources Information Center

    Martens, Rainer; And Others

    This book is a comprehensive review of competitive anxiety research that has used the Sport Competition Anxiety Test, or SCAT (a trait scale), and the Competitive State Anxiety Inventory-2 (CSAI-2). The book describes the theoretical basis and development procedures for both scales, including detailed information on reliability and validity. In…

  3. The quick and the dead? Sperm competition and sexual conflict in sea.

    PubMed

    Bode, Michael; Marshall, Dustin J

    2007-11-01

    Our view of sperm competition is largely shaped by game-theoretic models based on external fertilizers. External fertilization is of particular interest as it is the ancestral mode of reproduction and as such, relevant to the evolution and maintenance of anisogamy (i.e., large eggs and tiny, numerous sperm). Current game-theoretic models have been invaluable in generating predictions of male responses to sperm competition in a range of internal fertilizers but these models are less relevant to marine broadcast spawners, the most common and archetypal external fertilizers. Broadcast spawners typically have incomplete fertilization due to sperm limitation and/or polyspermy (too many sperm), but the effects of incomplete (<100% fertilization rates) fertilization on game-theoretic predictions are unclear particular with regards to polyspermy. We show that incorporating the effects of sperm concentration on fertilization success changes the predictions of a classic game-theoretic model, dramatically reversing the relationship between sperm competition and the evolutionarily stable sperm release strategy. Furthermore, our results suggest that male and female broadcast spawners are likely to be in conflict at both ends of the sperm environment continuum rather than only in conditions of excess sperm as previously thought. Across the majority of the parameter space we explored, males release either too little to too much sperm for females to achieve complete fertilization. This conflict could result in a coevolutionary race that may have led to the evolution of internal fertilization in marine organisms. PMID:17908245

  4. 47 CFR 25.401 - Satellite DARS applications subject to competitive bidding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Satellite DARS applications subject to...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Competitive Bidding Procedures for DARS § 25.401 Satellite DARS applications subject to competitive bidding. Mutually exclusive initial applications for...

  5. 47 CFR 25.401 - Satellite DARS applications subject to competitive bidding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Satellite DARS applications subject to...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Competitive Bidding Procedures for DARS § 25.401 Satellite DARS applications subject to competitive bidding. Mutually exclusive initial applications for...

  6. 47 CFR 25.401 - Satellite DARS applications subject to competitive bidding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Satellite DARS applications subject to...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Competitive Bidding Procedures for DARS § 25.401 Satellite DARS applications subject to competitive bidding. Mutually exclusive initial applications for...

  7. 47 CFR 25.401 - Satellite DARS applications subject to competitive bidding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Satellite DARS applications subject to...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Competitive Bidding Procedures for DARS § 25.401 Satellite DARS applications subject to competitive bidding. Mutually exclusive initial applications for...

  8. 47 CFR 25.401 - Satellite DARS applications subject to competitive bidding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Satellite DARS applications subject to...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Competitive Bidding Procedures for DARS § 25.401 Satellite DARS applications subject to competitive bidding. Mutually exclusive initial applications for...

  9. 47 CFR 90.1001 - 220 MHz service subject to competitive bidding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false 220 MHz service subject to competitive bidding. 90.1001 Section 90.1001 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND... Service § 90.1001 220 MHz service subject to competitive bidding. Mutually exclusive initial...

  10. 47 CFR 90.1001 - 220 MHz service subject to competitive bidding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false 220 MHz service subject to competitive bidding. 90.1001 Section 90.1001 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND... Service § 90.1001 220 MHz service subject to competitive bidding. Mutually exclusive initial...

  11. 47 CFR 22.228 - Cellular rural service area licenses subject to competitive bidding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Cellular rural service area licenses subject to... Procedures § 22.228 Cellular rural service area licenses subject to competitive bidding. Mutually exclusive initial applications for Cellular Rural Service Area licenses are subject to competitive bidding....

  12. 47 CFR 90.901 - 800 MHz SMR spectrum subject to competitive bidding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false 800 MHz SMR spectrum subject to competitive... Specialized Mobile Radio Service § 90.901 800 MHz SMR spectrum subject to competitive bidding. Mutually exclusive initial applications for 800 MHz band licenses in Spectrum Blocks A through V are subject...

  13. 47 CFR 90.901 - 800 MHz SMR spectrum subject to competitive bidding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false 800 MHz SMR spectrum subject to competitive... Specialized Mobile Radio Service § 90.901 800 MHz SMR spectrum subject to competitive bidding. Mutually exclusive initial applications for 800 MHz band licenses in Spectrum Blocks A through V are subject...

  14. 47 CFR 90.901 - 800 MHz SMR spectrum subject to competitive bidding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false 800 MHz SMR spectrum subject to competitive... Specialized Mobile Radio Service § 90.901 800 MHz SMR spectrum subject to competitive bidding. Mutually exclusive initial applications for 800 MHz band licenses in Spectrum Blocks A through V are subject...

  15. 47 CFR 90.901 - 800 MHz SMR spectrum subject to competitive bidding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false 800 MHz SMR spectrum subject to competitive... Specialized Mobile Radio Service § 90.901 800 MHz SMR spectrum subject to competitive bidding. Mutually exclusive initial applications for 800 MHz band licenses in Spectrum Blocks A through V are subject...

  16. 47 CFR 90.901 - 800 MHz SMR spectrum subject to competitive bidding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false 800 MHz SMR spectrum subject to competitive... Specialized Mobile Radio Service § 90.901 800 MHz SMR spectrum subject to competitive bidding. Mutually exclusive initial applications for 800 MHz band licenses in Spectrum Blocks A through V are subject...

  17. Seed Removal Increased by Scramble Competition with an Invasive Species.

    PubMed

    Minor, Rebecca L; Koprowski, John L

    2015-01-01

    Competition for seeds has a major influence on the evolution of granivores and the plants on which they rely. The complexity of interactions and coevolutionary relationships vary across forest types. The introduction of non-native granivores has considerable potential to alter seed dispersal dynamics. Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As biological invasions continue to rise, it is important to understand mechanisms to build up strategies to mitigate the threat. Our field experiment quantified the impact of introduced Abert's squirrels (Sciurus aberti) on rates of seed removal within the range of critically endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis), which consumes similar foods. In the presence of invasive Abert's squirrels, the time cones were removed was faster than when the invasive was excluded, accounting for a median removal time of cones available to red and Abert's squirrels that is 32.8% less than that of cones available only to the rare native red squirrels. Moreover, in the presence of Abert's squirrels, removal rates are higher at great distance from a territorial red squirrel larderhoard and in more open portions of the forest, which suggests differential patterns of seed dispersal. The impact on food availability as a result of cone removal by Abert's squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Furthermore, the magnitude and differential spatial patterns of seed removal suggest that non-native granivores may have impacts on forest regeneration and structure. PMID:26650073

  18. Seed Removal Increased by Scramble Competition with an Invasive Species

    PubMed Central

    Minor, Rebecca L.; Koprowski, John L.

    2015-01-01

    Competition for seeds has a major influence on the evolution of granivores and the plants on which they rely. The complexity of interactions and coevolutionary relationships vary across forest types. The introduction of non-native granivores has considerable potential to alter seed dispersal dynamics. Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As biological invasions continue to rise, it is important to understand mechanisms to build up strategies to mitigate the threat. Our field experiment quantified the impact of introduced Abert’s squirrels (Sciurus aberti) on rates of seed removal within the range of critically endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis), which consumes similar foods. In the presence of invasive Abert’s squirrels, the time cones were removed was faster than when the invasive was excluded, accounting for a median removal time of cones available to red and Abert’s squirrels that is 32.8% less than that of cones available only to the rare native red squirrels. Moreover, in the presence of Abert’s squirrels, removal rates are higher at great distance from a territorial red squirrel larderhoard and in more open portions of the forest, which suggests differential patterns of seed dispersal. The impact on food availability as a result of cone removal by Abert’s squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Furthermore, the magnitude and differential spatial patterns of seed removal suggest that non-native granivores may have impacts on forest regeneration and structure. PMID:26650073

  19. Approximate kernel competitive learning.

    PubMed

    Wu, Jian-Sheng; Zheng, Wei-Shi; Lai, Jian-Huang

    2015-03-01

    Kernel competitive learning has been successfully used to achieve robust clustering. However, kernel competitive learning (KCL) is not scalable for large scale data processing, because (1) it has to calculate and store the full kernel matrix that is too large to be calculated and kept in the memory and (2) it cannot be computed in parallel. In this paper we develop a framework of approximate kernel competitive learning for processing large scale dataset. The proposed framework consists of two parts. First, it derives an approximate kernel competitive learning (AKCL), which learns kernel competitive learning in a subspace via sampling. We provide solid theoretical analysis on why the proposed approximation modelling would work for kernel competitive learning, and furthermore, we show that the computational complexity of AKCL is largely reduced. Second, we propose a pseudo-parallelled approximate kernel competitive learning (PAKCL) based on a set-based kernel competitive learning strategy, which overcomes the obstacle of using parallel programming in kernel competitive learning and significantly accelerates the approximate kernel competitive learning for large scale clustering. The empirical evaluation on publicly available datasets shows that the proposed AKCL and PAKCL can perform comparably as KCL, with a large reduction on computational cost. Also, the proposed methods achieve more effective clustering performance in terms of clustering precision against related approximate clustering approaches. PMID:25528318

  20. Enhanced Information Exclusion Relations

    PubMed Central

    Xiao, Yunlong; Jing, Naihuan; Li-Jost, Xianqing

    2016-01-01

    In Hall’s reformulation of the uncertainty principle, the entropic uncertainty relation occupies a core position and provides the first nontrivial bound for the information exclusion principle. Based upon recent developments on the uncertainty relation, we present new bounds for the information exclusion relation using majorization theory and combinatoric techniques, which reveal further characteristic properties of the overlap matrix between the measurements. PMID:27460975

  1. Four paths of competition

    SciTech Connect

    Studness, C.M.

    1995-05-01

    The financial community`s focus on utility competition has been riveted on the proceedings now in progress at state regulatory commissions. The fear that something immediately damaging will come out of these proceedings seems to have diminished in recent months, and the stock market has reacted favorably. However, regulatory developments are only one of four paths leading to competition; the others are the marketplace, the legislatures, and the courts. Each could play a critical role in the emergence of competition.

  2. Intramural Gymnastics Competition.

    ERIC Educational Resources Information Center

    Cornelius, William L.

    1981-01-01

    An intramural gymnastic competition, if properly organized, can foster student and community interest in gymnastics. Aspects of organization and essential preplanning include: directing, judging, scoring, and managing. (JN)

  3. Co-evolutionary Analysis of Domains in Interacting Proteins Reveals Insights into Domain–Domain Interactions Mediating Protein–Protein Interactions

    PubMed Central

    Jothi, Raja; Cherukuri, Praveen F.; Tasneem, Asba; Przytycka, Teresa M.

    2006-01-01

    Recent advances in functional genomics have helped generate large-scale high-throughput protein interaction data. Such networks, though extremely valuable towards molecular level understanding of cells, do not provide any direct information about the regions (domains) in the proteins that mediate the interaction. Here, we performed co-evolutionary analysis of domains in interacting proteins in order to understand the degree of co-evolution of interacting and non-interacting domains. Using a combination of sequence and structural analysis, we analyzed protein–protein interactions in F1-ATPase, Sec23p/Sec24p, DNA-directed RNA polymerase and nuclear pore complexes, and found that interacting domain pair(s) for a given interaction exhibits higher level of co-evolution than the noninteracting domain pairs. Motivated by this finding, we developed a computational method to test the generality of the observed trend, and to predict large-scale domain–domain interactions. Given a protein–protein interaction, the proposed method predicts the domain pair(s) that is most likely to mediate the protein interaction. We applied this method on the yeast interactome to predict domain–domain interactions, and used known domain–domain interactions found in PDB crystal structures to validate our predictions. Our results show that the prediction accuracy of the proposed method is statistically significant. Comparison of our prediction results with those from two other methods reveals that only a fraction of predictions are shared by all the three methods, indicating that the proposed method can detect known interactions missed by other methods. We believe that the proposed method can be used with other methods to help identify previously unrecognized domain–domain interactions on a genome scale, and could potentially help reduce the search space for identifying interaction sites. PMID:16949097

  4. Utah Mock Trial Competition.

    ERIC Educational Resources Information Center

    Oswald, Linda, Comp.

    Background materials and guidelines for secondary students and educators in Utah who wish to participate in the state-wide mock trial competition are provided. Many parts of the publication can be used by educators in other states who are using mock trials in their classrooms or who are developing a state-wide mock trial competition. The manual…

  5. Competition: Was Kohn Right?

    ERIC Educational Resources Information Center

    Shields, David Light; Bredemeier, Brenda Light

    2010-01-01

    Alfie Kohn made the case for competition being destructive to education. The truth may be that there are two separate ways to contest: true competition, which is a healthy desire to excel, and decompetition, which is the unhealthy desire merely to beat the opponent. Decompetition leads to the ills that Kohn enumerated. Educators should teach their…

  6. Competitiveness, Technology and Skills.

    ERIC Educational Resources Information Center

    Lall, Sanjaya

    This document examines competitiveness in the developing world. Chapters 1 through 3, which are largely conceptual, examine the following topics: the concept of competitiveness and why it is important; market-stimulating technology policies in developing countries, and the relationship between import liberalization and industrial performance.…

  7. Competitive coexistence of two Pneumocystis species.

    PubMed

    Icenhour, Crystal R; Arnold, Jonathan; Medvedovic, Mario; Cushion, Melanie T

    2006-05-01

    Pneumocystis are fungal pathogens of mammalian lungs that can cause lethal pneumonia in immunocompromised hosts. In some mammals, coinfections of genetically distinct Pneumocystis populations have been identified, but the nature of their interaction and its significance are unknown. Two species that infect rats, Pneumocystis carinii and Pneumocystis wakefieldiae, were studied over a 6-year period, representing approximately 700 generations of Pneumocystis. Population densities of each species were analyzed within the framework of the Lotka-Volterra competition model, which revealed the two species were in competition and predicted competitive exclusion of one species. However, stable coexistence was observed in 460 replicate populations. Selected extrinsic factors that might mitigate the extinction were evaluated. Logistic-regression analyses showed that higher relative humidity and higher organism lung burdens were associated with infections comprised of P. carinii alone, while lower temperatures and an increased rat census were associated with the presence of P. wakefieldiae. PCR and immunofluorescent analysis of rat lung tissue showed that both species were present within the same alveoli, excluding habitat heterogeneity as a mechanism of coexistence. These data suggest that P. carinii and P. wakefieldiae were in competitive coexistence, which was influenced in part by extrinsic factors. To our knowledge, this is the first report to evaluate interactions of pathogenic fungal species within a mammalian host using ecological models. PMID:15949973

  8. Interpopulation divergence in competitive interactions of the mosquito Aedes albopictus

    PubMed Central

    Leisnham, P. T.; Lounibos, L.P.; O’Meara, G.F.; Juliano, S.A.

    2009-01-01

    Geographic variation in species interactions can have major effects on distributions. Effects of such variation can be particularly evident for invasive species, in which variation in competitive ability can influence invasive success and impacts. We tested the hypothesis that coexistence or exclusion of the resident mosquito Aedes aegypti results from variation among local populations of the invasive Aedes albopictus in competitive interactions with A. aegypti. We also examined the role of variation in fecundity-size relationship in these competitive interactions. We compared competitive abilities of nine North American populations of A. albopictus, three populations from each of three site types: extinction of A. aegypti following A. albopictus invasion, coexistence following A. albopictus invasion, and A. albopictus allopatric to A. aegypti. Competition among larvae from each A. albopictus population and a single A. aegypti population was tested in laboratory microcosms in a response-surface design. We found interpopulation differences in competitive ability of A. albopictus, but no strong patterns among site types. Extinction sites had steeper average fecundity-size relationships than coexistence sites and allopatric sites, but this did not translate into superior population performance. Certain individual A. albopictus populations had exceptionally large competitive effects on A. aegypti or poor competitive responses to competition from A. aegypti, but competitive effect and response were not correlated. These results suggest that interpopulation variation in the competitive ability of A. albopictus may only partly explain geographic pattern of coexistence with or extinction of A. aegypti. Environmental differences among regions may affect the competitive ability of A. albopictus and influence its invasion success and impact. PMID:19769119

  9. An ecocultural model predicts Neanderthal extinction through competition with modern humans

    PubMed Central

    Gilpin, William; Feldman, Marcus W.; Aoki, Kenichi

    2016-01-01

    Archaeologists argue that the replacement of Neanderthals by modern humans was driven by interspecific competition due to a difference in culture level. To assess the cogency of this argument, we construct and analyze an interspecific cultural competition model based on the Lotka−Volterra model, which is widely used in ecology, but which incorporates the culture level of a species as a variable interacting with population size. We investigate the conditions under which a difference in culture level between cognitively equivalent species, or alternatively a difference in underlying learning ability, may produce competitive exclusion of a comparatively (although not absolutely) large local Neanderthal population by an initially smaller modern human population. We find, in particular, that this competitive exclusion is more likely to occur when population growth occurs on a shorter timescale than cultural change, or when the competition coefficients of the Lotka−Volterra model depend on the difference in the culture levels of the interacting species. PMID:26831111

  10. An ecocultural model predicts Neanderthal extinction through competition with modern humans.

    PubMed

    Gilpin, William; Feldman, Marcus W; Aoki, Kenichi

    2016-02-23

    Archaeologists argue that the replacement of Neanderthals by modern humans was driven by interspecific competition due to a difference in culture level. To assess the cogency of this argument, we construct and analyze an interspecific cultural competition model based on the Lotka-Volterra model, which is widely used in ecology, but which incorporates the culture level of a species as a variable interacting with population size. We investigate the conditions under which a difference in culture level between cognitively equivalent species, or alternatively a difference in underlying learning ability, may produce competitive exclusion of a comparatively (although not absolutely) large local Neanderthal population by an initially smaller modern human population. We find, in particular, that this competitive exclusion is more likely to occur when population growth occurs on a shorter timescale than cultural change, or when the competition coefficients of the Lotka-Volterra model depend on the difference in the culture levels of the interacting species. PMID:26831111

  11. Spatial variation and density-dependent dispersal in competitive coexistence.

    PubMed Central

    Amarasekare, Priyanga

    2004-01-01

    It is well known that dispersal from localities favourable to a species' growth and reproduction (sources) can prevent competitive exclusion in unfavourable localities (sinks). What is perhaps less well known is that too much emigration can undermine the viability of sources and cause regional competitive exclusion. Here, I investigate two biological mechanisms that reduce the cost of dispersal to source communities. The first involves increasing the spatial variation in the strength of competition such that sources can withstand high rates of emigration; the second involves reducing emigration from sources via density-dependent dispersal. I compare how different forms of spatial variation and modes of dispersal influence source viability, and hence source-sink coexistence, under dominance and pre-emptive competition. A key finding is that, while spatial variation substantially reduces dispersal costs under both types of competition, density-dependent dispersal does so only under dominance competition. For instance, when spatial variation in the strength of competition is high, coexistence is possible (regardless of the type of competition) even when sources experience high emigration rates; when spatial variation is low, coexistence is restricted even under low emigration rates. Under dominance competition, density-dependent dispersal has a strong effect on coexistence. For instance, when the emigration rate increases with density at an accelerating rate (Type III density-dependent dispersal), coexistence is possible even when spatial variation is quite low; when the emigration rate increases with density at a decelerating rate (Type II density-dependent dispersal), coexistence is restricted even when spatial variation is quite high. Under pre-emptive competition, density-dependent dispersal has only a marginal effect on coexistence. Thus, the diversity-reducing effects of high dispersal rates persist under pre-emptive competition even when dispersal is density

  12. Inclusive and Exclusive |Vub|

    SciTech Connect

    Petrella, Antonio; /Ferrara U. /INFN, Ferrara

    2011-11-17

    The current status of the determinations of CKM matrix element |V{sub ub}| via exclusive and inclusive charmless semileptonic B decays is reviewed. The large datasets collected at the B-Factories, and the increased precision of theoretical calculations have allowed an improvement in the determination of |V{sub ub}|. However, there are still significant uncertainties. In the exclusive approach, the most precise measurement of the pion channel branching ratio is obtained by an untagged analysis. This very good precision can be reached by tagged analyses with more data. The problem with exclusive decays is that the strong hadron dynamics can not be calculated from first principles and the determination of the form factor has to rely on light-cone sum rules or lattice QCD calculations. The current data samples allow a comparison of different FF models with data distributions. With further developments on lattice calculations, the theoretical error should shrink to reach the experimental one. The inclusive approach still provides the most precise |V{sub ub}| determinations. With new theoretical calculations, the mild (2.5{sigma}) discrepancy with respect to the |V{sub ub}| value determined from the global UT fit has been reduced. As in the exclusive approach, theoretical uncertainties represent the limiting factor to the precision of the measurement. Reducing the theoretical uncertainties to a level comparable with the statistical error is challenging. New measurements in semileptonic decays of charm mesons could increase the confidence in theoretical calculations and related uncertainties.

  13. Mutually Exclusive, Complementary, or . . .

    ERIC Educational Resources Information Center

    Schloemer, Cathy G.

    2016-01-01

    Whether students are beginning their study of probability or are well into it, distinctions between complementary sets and mutually exclusive sets can be confusing. Cathy Schloemer writes in this article that for years she used typical classroom examples but was not happy with the student engagement or the level of understanding they produced.…

  14. 2000 FIRST Robotics Competition

    NASA Technical Reports Server (NTRS)

    Purman, Richard

    2000-01-01

    The New Horizons Regional Education Center (NHREC) in Hampton, VA sought and received NASA funding to support its participation in the 2000 FIRST Robotics competition. FIRST, Inc. (For Inspiration and Recognition of Science and Technology) is an organization which encourages the application of creative science, math, and computer science principles to solve real-world engineering problems. The FIRST competition is an international engineering contest featuring high school, government, and business partnerships.

  15. Competition for land

    PubMed Central

    Smith, Pete; Gregory, Peter J.; van Vuuren, Detlef; Obersteiner, Michael; Havlík, Petr; Rounsevell, Mark; Woods, Jeremy; Stehfest, Elke; Bellarby, Jessica

    2010-01-01

    A key challenge for humanity is how a future global population of 9 billion can all be fed healthily and sustainably. Here, we review how competition for land is influenced by other drivers and pressures, examine land-use change over the past 20 years and consider future changes over the next 40 years. Competition for land, in itself, is not a driver affecting food and farming in the future, but is an emergent property of other drivers and pressures. Modelling studies suggest that future policy decisions in the agriculture, forestry, energy and conservation sectors could have profound effects, with different demands for land to supply multiple ecosystem services usually intensifying competition for land in the future. In addition to policies addressing agriculture and food production, further policies addressing the primary drivers of competition for land (population growth, dietary preference, protected areas, forest policy) could have significant impacts in reducing competition for land. Technologies for increasing per-area productivity of agricultural land will also be necessary. Key uncertainties in our projections of competition for land in the future relate predominantly to uncertainties in the drivers and pressures within the scenarios, in the models and data used in the projections and in the policy interventions assumed to affect the drivers and pressures in the future. PMID:20713395

  16. Socio-technical transition as a co-evolutionary process: Innovation and the role of niche markets in the transition to motor vehicles

    NASA Astrophysics Data System (ADS)

    Birky, Alicia K.

    2008-10-01

    Significant reductions in greenhouse emissions from personal transportation will require a transition to an alternative technology regime based on renewable energy sources. Two bodies of research, the quasi-evolutionary (QE) model and the multi-level perspective (MLP) assert that processes within niches play a fundamental role in such transitions. This research asks whether the description of transitions based on this niche hypothesis and its underlying assumptions is consistent with the historical U.S. transition to motor vehicles at the beginning of the 20th century. Unique to this dissertation is the combination of the perspective of the entrepreneur with co-evolutionary approaches to socio-technical transitions. This approach is augmented with concepts from the industry life-cycle model and with a taxonomy of mechanisms of learning. Using this analytic framework, I examine specifically the role of entrepreneurial behavior and processes within and among firms in the co-evolution of technologies and institutions during the transition to motor vehicles. I find that niche markets played an important role in the development of the technology, institutions, and the industry. However, I also find that the diffusion of the automobile is not consistent with the niche hypothesis in the following ways: (1) product improvements and cost reductions were not realized in niche markets, but were achieved simultaneously with diffusion into mass markets; (2) in addition to learning-by-doing and learning-by-interacting with users, knowledge spillovers and interacting with suppliers were critical in this process; (3) cost reductions were not automatic results of expanding markets, but rather arose from the strategies of entrepreneurs based on personal perspectives and values. This finding supports the use of a behavioral approach with a micro-focus in the analysis of socio-technical change. I also find that the emergence and diffusion of the motor vehicle can only be understood by

  17. Dynamics of competitive systems with a single common limiting factor.

    PubMed

    Kon, Ryusuke

    2015-02-01

    The concept of limiting factors (or regulating factors) succeeded in formulating the well-known principle of competitive exclusion. This paper shows that the concept of limiting factors is helpful not only to formulate the competitive exclusion principle, but also to obtain other ecological insights. To this end, by focusing on a specific community structure, we study the dynamics of Kolmogorov equations and show that it is possible to derive an ecologically insightful result only from the information about interactions between species and limiting factors. Furthermore, we find that the derived result is a generalization of the preceding work by Shigesada, Kawasaki, and Teramoto (1984), who examined a certain Lotka-Volterra equation in a different context. PMID:25811338

  18. 37 CFR 404.7 - Exclusive, co-exclusive and partially exclusive licenses.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2013-07-01 2013-07-01 false Exclusive, co-exclusive and partially exclusive licenses. 404.7 Section 404.7 Patents, Trademarks, and Copyrights NATIONAL INSTITUTE OF... applicants, on reasonable terms, when necessary to fulfill health or safety needs. (iii) The license shall...

  19. Healthy Competition and Unsound Comparison: Reforming Educational Competition in Singapore

    ERIC Educational Resources Information Center

    Christensen, Søren

    2015-01-01

    It is frequently claimed that the "competition state" responds to external competition by making competition increasingly central to its internal processes as well. This article discusses education reform in Singapore as departing from the opposite position. In Singapore "excessive" competition in education is now targeted by…

  20. Social exclusion in finite populations

    NASA Astrophysics Data System (ADS)

    Li, Kun; Cong, Rui; Wu, Te; Wang, Long

    2015-04-01

    Social exclusion, keeping free riders from benefit sharing, plays an important role in sustaining cooperation in our world. Here we propose two different exclusion regimes, namely, peer exclusion and pool exclusion, to investigate the evolution of social exclusion in finite populations. In the peer exclusion regime, each excluder expels all the defectors independently, and thus bears the total cost on his own, while in the pool exclusion regime, excluders spontaneously form an institution to carry out rejection of the free riders, and each excluder shares the cost equally. In a public goods game containing only excluders and defectors, it is found that peer excluders outperform pool excluders if the exclusion costs are small, and the situation is converse once the exclusion costs exceed some critical points, which holds true for all the selection intensities and different update rules. Moreover, excluders can dominate the whole population under a suitable parameters range in the presence of second-order free riders (cooperators), showing that exclusion has prominent advantages over common costly punishment. More importantly, our finding indicates that the group exclusion mechanism helps the cooperative union to survive under unfavorable conditions. Our results may give some insights into better understanding the prevalence of such a strategy in the real world and its significance in sustaining cooperation.

  1. Social exclusion in finite populations.

    PubMed

    Li, Kun; Cong, Rui; Wu, Te; Wang, Long

    2015-04-01

    Social exclusion, keeping free riders from benefit sharing, plays an important role in sustaining cooperation in our world. Here we propose two different exclusion regimes, namely, peer exclusion and pool exclusion, to investigate the evolution of social exclusion in finite populations. In the peer exclusion regime, each excluder expels all the defectors independently, and thus bears the total cost on his own, while in the pool exclusion regime, excluders spontaneously form an institution to carry out rejection of the free riders, and each excluder shares the cost equally. In a public goods game containing only excluders and defectors, it is found that peer excluders outperform pool excluders if the exclusion costs are small, and the situation is converse once the exclusion costs exceed some critical points, which holds true for all the selection intensities and different update rules. Moreover, excluders can dominate the whole population under a suitable parameters range in the presence of second-order free riders (cooperators), showing that exclusion has prominent advantages over common costly punishment. More importantly, our finding indicates that the group exclusion mechanism helps the cooperative union to survive under unfavorable conditions. Our results may give some insights into better understanding the prevalence of such a strategy in the real world and its significance in sustaining cooperation. PMID:25974550

  2. Health plan competition in local markets.

    PubMed Central

    Grossman, J M

    2000-01-01

    OBJECTIVE: To examine the structure of local health insurance markets and the strategies health plans were using to respond to competitive pressures in local markets in 1996/1997. DATA SOURCES/STUDY SETTING: Community Tracking Study site visits conducted between May 1996 and April 1997 in 12 U.S. markets selected to be nationally representative. STUDY DESIGN: In each site, 36 to 60 interviews on local health system change were conducted with healthcare industry informants representing health plans, providers, and purchasers. DATA COLLECTION/EXTRACTION METHOD: Relevant data for this article were abstracted from standardized protocols administered to multiple respondents in each site. PRINCIPAL FINDINGS: Although the competitive threat from national plans was pervasive, local plans in most sites continued to retain strong, often dominant, positions in historically concentrated markets. In all sites, in response to purchaser pressures for stable premiums and provider choice, and the threat of entry and to plans were using three strategies to increase market share and market power: (1) consolidation/geographic expansion, (2) price competition, and (3) product line/segment diversification that focused on broad networks and open-access products. In most markets, in response to the demand for provider choice, the trend was away from ownership and exclusive arrangements with providers. CONCLUSIONS: Although local plans were moving to become full-service regional players, there was uncertainty about the abilities of all plans to sustain growth strategies at the expense of margins and organizational stability, and to effectively manage care with broad networks. PMID:10778822

  3. Mineralization by Inhibitor Exclusion

    PubMed Central

    Price, Paul A.; Toroian, Damon; Lim, Joo Eun

    2009-01-01

    One of our goals is to understand the mechanisms that deposit mineral within collagen fibrils, and as a first step we recently determined the size exclusion characteristics of the fibril. This study revealed that apatite crystals up to 12 unit cells in size can access the water within the fibril, whereas molecules larger than a 40-kDa protein are excluded. Based on these observations, we proposed a novel mechanism for fibril mineralization: that macromolecular inhibitors of apatite growth favor fibril mineralization by selectively inhibiting crystal growth in the solution outside of the fibril. To test this mechanism, we developed a system in which crystal formation is driven by homogeneous nucleation at high calcium phosphate concentration and the only macromolecule in solution is fetuin, a 48-kDa inhibitor of apatite growth. Our experiments with this system demonstrated that fetuin determines the location of mineral growth; in the presence of fetuin mineral grows exclusively within the fibril, whereas in its absence mineral grows in solution outside the fibril. Additional experiments showed that fetuin is also able to localize calcification to the interior of synthetic matrices that have size exclusion characteristics similar to those of collagen and that it does so by selectively inhibiting mineral growth outside of these matrices. We termed this new calcification mechanism “mineralization by inhibitor exclusion,” the selective mineralization of a matrix using a macromolecular inhibitor of mineral growth that is excluded from that matrix. Future studies will be needed to evaluate the possible role of this mechanism in bone mineralization. PMID:19414589

  4. Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect.

    PubMed

    Borgström, Pernilla; Strengbom, Joachim; Viketoft, Maria; Bommarco, Riccardo

    2016-01-01

    Insect herbivores can shift the composition of a plant community, but the mechanism underlying such shifts remains largely unexplored. A possibility is that insects alter the competitive symmetry between plant species. The effect of herbivory on competition likely depends on whether the plants are subjected to aboveground or belowground herbivory or both, and also depends on soil nitrogen levels. It is unclear how these biotic and abiotic factors interactively affect competition. In a greenhouse experiment, we measured competition between two coexisting grass species that respond differently to nitrogen deposition: Dactylis glomerata L., which is competitively favoured by nitrogen addition, and Festuca rubra L., which is competitively favoured on nitrogen-poor soils. We predicted: (1) that aboveground herbivory would reduce competitive asymmetry at high soil nitrogen by reducing the competitive advantage of D. glomerata; and (2), that belowground herbivory would relax competition at low soil nitrogen, by reducing the competitive advantage of F. rubra. Aboveground herbivory caused a 46% decrease in the competitive ability of F. rubra, and a 23% increase in that of D. glomerata, thus increasing competitive asymmetry, independently of soil nitrogen level. Belowground herbivory did not affect competitive symmetry, but the combined influence of above- and belowground herbivory was weaker than predicted from their individual effects. Belowground herbivory thus mitigated the increased competitive asymmetry caused by aboveground herbivory. D. glomerata remained competitively dominant after the cessation of aboveground herbivory, showing that the influence of herbivory continued beyond the feeding period. We showed that insect herbivory can strongly influence plant competitive interactions. In our experimental plant community, aboveground insect herbivory increased the risk of competitive exclusion of F. rubra. Belowground herbivory appeared to mitigate the influence of

  5. Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect

    PubMed Central

    Strengbom, Joachim; Viketoft, Maria; Bommarco, Riccardo

    2016-01-01

    Insect herbivores can shift the composition of a plant community, but the mechanism underlying such shifts remains largely unexplored. A possibility is that insects alter the competitive symmetry between plant species. The effect of herbivory on competition likely depends on whether the plants are subjected to aboveground or belowground herbivory or both, and also depends on soil nitrogen levels. It is unclear how these biotic and abiotic factors interactively affect competition. In a greenhouse experiment, we measured competition between two coexisting grass species that respond differently to nitrogen deposition: Dactylis glomerata L., which is competitively favoured by nitrogen addition, and Festuca rubra L., which is competitively favoured on nitrogen-poor soils. We predicted: (1) that aboveground herbivory would reduce competitive asymmetry at high soil nitrogen by reducing the competitive advantage of D. glomerata; and (2), that belowground herbivory would relax competition at low soil nitrogen, by reducing the competitive advantage of F. rubra. Aboveground herbivory caused a 46% decrease in the competitive ability of F. rubra, and a 23% increase in that of D. glomerata, thus increasing competitive asymmetry, independently of soil nitrogen level. Belowground herbivory did not affect competitive symmetry, but the combined influence of above- and belowground herbivory was weaker than predicted from their individual effects. Belowground herbivory thus mitigated the increased competitive asymmetry caused by aboveground herbivory. D. glomerata remained competitively dominant after the cessation of aboveground herbivory, showing that the influence of herbivory continued beyond the feeding period. We showed that insect herbivory can strongly influence plant competitive interactions. In our experimental plant community, aboveground insect herbivory increased the risk of competitive exclusion of F. rubra. Belowground herbivory appeared to mitigate the influence of

  6. Utility competition and residential customers

    SciTech Connect

    Studness, C.M.

    1994-11-01

    Residential customers have found themselves either ignored or ill-used by the major participants in the struggle over utility competition. No group is seeking to secure them the benefits of competition, and those who oppose competition have curried their favor by conjuring up misleading horror stories about how competition would harm them. Yet residential customers ultimately stand to gain as much from competition as larger customers.

  7. Advancing Manufacturing Research Through Competitions

    SciTech Connect

    Balakirsky, Stephen; Madhavan, Raj

    2009-01-01

    Competitions provide a technique for building interest and collaboration in targeted research areas. This paper will present a new competition that aims to increase collaboration amongst Universities, automation end-users, and automation manufacturers through a virtual competition. The virtual nature of the competition allows for reduced infrastructure requirements while maintaining realism in both the robotic equipment deployed and the scenarios. Details of the virtual environment as well as the competitions objectives, rules, and scoring metrics will be presented.

  8. Autonomic and Coevolutionary Sensor Networking

    NASA Astrophysics Data System (ADS)

    Boonma, Pruet; Suzuki, Junichi

    (WSNs) applications are often required to balance the tradeoffs among conflicting operational objectives (e.g., latency and power consumption) and operate at an optimal tradeoff. This chapter proposes and evaluates a architecture, called BiSNET/e, which allows WSN applications to overcome this issue. BiSNET/e is designed to support three major types of WSN applications: , and hybrid applications. Each application is implemented as a decentralized group of, which is analogous to a bee colony (application) consisting of bees (agents). Agents collect sensor data or detect an event (a significant change in sensor reading) on individual nodes, and carry sensor data to base stations. They perform these data collection and event detection functionalities by sensing their surrounding network conditions and adaptively invoking behaviors such as pheromone emission, reproduction, migration, swarming and death. Each agent has its own behavior policy, as a set of genes, which defines how to invoke its behaviors. BiSNET/e allows agents to evolve their behavior policies (genes) across generations and autonomously adapt their performance to given objectives. Simulation results demonstrate that, in all three types of applications, agents evolve to find optimal tradeoffs among conflicting objectives and adapt to dynamic network conditions such as traffic fluctuations and node failures/additions. Simulation results also illustrate that, in hybrid applications, data collection agents and event detection agents coevolve to augment their adaptability and performance.

  9. Gene-Culture Coevolutionary Games

    ERIC Educational Resources Information Center

    Blute, Marion

    2006-01-01

    Gene-culture interactions have largely been modelled employing population genetic-type models. Moreover, in the most notable application to date, the "interactive" modes have been one way rather than bidirectional. This paper suggests using game theoretic, fully interactive models. Employing the logic utilized in population ecology for coevolution…

  10. Competitive strategy for providers.

    PubMed

    Hackett, M C

    1996-01-01

    National Health Service (NHS) Trusts are struggling to determine a long-term strategic direction for their organizations in response to the competitive pressures generated by the NHS reforms. The development of long-term strategic direction and the methods to implement this are presenting real challenges to the Trusts which have inherited service configurations based on bureaucratic planning frameworks rather than service configurations suited to a more competitive environment. Examines the strategic choices available to these organizations; explores the importance of identifying positive strategic choices; and discusses the advantages and disadvantages in the context of the NHS internal market. PMID:10164226

  11. Demography and language competition.

    PubMed

    Kandler, Anne

    2009-04-01

    Attempts to describe language competition and extinction in a mathematical way have enjoyed increased popularity recently. In this paper I review recent modeling approaches and, based on these findings, propose a model of reaction-diffusion type. I analyze the dynamics of interactions of a population with two monolingual groups and a group that is bilingual in these two languages. The results show that demographic factors, such as population growth or population dispersal, play an important role in the competition dynamic. Furthermore, I consider the impact of two strategies for language maintenance: adjusting the status of the endangered language and adjusting the availability of monolingual and bilingual educational resources. PMID:19943743

  12. Mutual exclusivity and exclusion: Converging evidence from two contrasting traditions

    PubMed Central

    Huntley, Kenneth R.; Ghezzi, Patrick M.

    1993-01-01

    Mutual exclusivity and exclusion are two terms used by cognitive psychologists and behavior analysts, respectively, to identify essentially the same phenomenon. While cognitive psychologists view mutual exclusivity in terms of a hypothesis that individuals use intuitively while acquiring language, behavior analysts regard exclusion as a derived stimulus relation that bears upon the acquisition and elaboration of verbal behavior. Each research tradition, though at odds with respect to accounting for the phenomenon, employs similar procedures to answer comparable questions. Insofar as both cognitive and behavioral psychologists are studying the same phenomenon, the ground work is established for collaboration between them. PMID:22477081

  13. Human Resources Competitiveness Profile.

    ERIC Educational Resources Information Center

    Council on Competitiveness, Washington, DC.

    This report distills hundreds of indicators from both domestic and international sources to determine how the United States compares to other countries and to its own past performance in competitiveness. It attempts to establish a baseline of some key education and training indicators that, taken together, show where the nation stands and where it…

  14. Cost and competition

    SciTech Connect

    Kahn, E.

    1994-11-01

    The growth of private power is part of the movement away from administrative regulation and toward competitive control of prices for electricity. Despite the substantial success of the private power industry, this process is far from complete. Utility regulators, who preside over the power purchase contracting process, are responsible for assuring that the prices which are presented to them for approval are reasonable.

  15. Growing Competition for Libraries.

    ERIC Educational Resources Information Center

    Gibbons, Susan

    2001-01-01

    Describes the Questia subscription-based online academic digital books library. Highlights include weaknesses of the collection; what college students want from a library; importance of marketing; competition for traditional academic libraries that may help improve library services; and the ability of Questia to overcome barriers and…

  16. Building Camaraderie from Competition

    ERIC Educational Resources Information Center

    Marino, Gordon

    2007-01-01

    Educational institutions have adopted athletics programs to promote character building. Sports help people feel comfortable in their skins and provide unique opportunities to develop qualities such as cooperation, perseverance, and the ability to cope with fear. But the arena can be a hothouse for more primal feelings that emerge in competition.…

  17. Television and Competition.

    ERIC Educational Resources Information Center

    Noll, Roger G.

    The television industry is characterized by numerous imperfections in market competition. The spectrum allocation policy of the Federal Communications Commission (FCC) assures that there will be only three national television networks; consequently in nearly all markets these stations account for 75% to 100% of revenues. These networks in turn…

  18. Competitiveness and Campaign '88.

    ERIC Educational Resources Information Center

    Kernan-Schloss, Adam, Ed.; And Others

    This report profiles the positions of the six Democratic and six Republican 1988 presidential candidates on policy issues affecting U.S. competitiveness in the global economy. Candidate profiles are provided for: Bruce Babbitt, Michael Dukakis, Richard Gephardt, Albert Gore, Jr., Jesse Jackson, and Paul Simon (Democrats); and George Bush, Robert…

  19. Competitiveness Index 1990.

    ERIC Educational Resources Information Center

    Council on Competitiveness, Washington, DC.

    The United States' economic performance in the world economy is compared with that of Canada, France, Germany, Italy, Japan, and the United Kingdom (the Summit 7 countries). Competitiveness is assessed by four economic indicators: standard of living, trade, manufacturing productivity, and investment. The United States continues to outinvest the…

  20. Competition in the Classroom

    ERIC Educational Resources Information Center

    Jameson, Daphne

    2007-01-01

    In this article, the author shares the strategy she adopted to even out the participation among her multicultural students during their classroom discussions. The author realized that her students had different concepts about the classroom and different philosophies about competition. For the Americans and Indians, the classroom was a site of…

  1. A Winning Competition

    ERIC Educational Resources Information Center

    Geddes, Kim; Franchini, Elease

    2012-01-01

    As a high school physics teacher, Kim Geddes is constantly searching for new experiences to challenge, motivate, and engage students. Last year, she incorporated ExploraVision into the energy unit of her school's physics curriculum with the help of their media specialist (Elease Franchini). ExploraVision is a competition offered through a…

  2. Competition in Advertising.

    ERIC Educational Resources Information Center

    Avery, Jim

    1991-01-01

    Discusses five ways (high school newspaper and yearbook advertising, summer jobs, internships, contests, and student-run advertising agencies) students can start to prepare for a career in the competitive field of advertising while still in high school and college. (SR)

  3. The evolution of increased competitive ability, innate competitive advantages, and novel biochemical weapons act in concert for a tropical invader.

    PubMed

    Qin, Rui-Min; Zheng, Yu-Long; Valiente-Banuet, Alfonso; Callaway, Ragan M; Barclay, Gregor F; Pereyra, Carlos Silva; Feng, Yu-Long

    2013-02-01

    There are many non-mutually exclusive mechanisms for exotic invasions but few studies have concurrently tested more than one hypothesis for the same species. Here, we tested the evolution of increased competitive ability (EICA) hypothesis in two common garden experiments in which Chromolaena odorata plants originating from native and nonnative ranges were grown in competition with natives from each range, and the novel weapons hypothesis in laboratory experiments with leachates from C. odorata. Compared with conspecifics originating from the native range, C. odorata plants from the nonnative range were stronger competitors at high nutrient concentrations in the nonnative range in China and experienced far more herbivore damage in the native range in Mexico. In both China and Mexico, C. odorata was more suppressed by species native to Mexico than by species native to China. Species native to China were much more inhibited by leaf extracts from C. odorata than species from Mexico, and this difference in allelopathic effects may provide a possible explanation for the biogeographic differences in competitive ability. Our results indicate that EICA, innate competitive advantages, and novel biochemical weapons may act in concert to promote invasion by C. odorata, and emphasize the importance of exploring multiple, non-mutually exclusive mechanisms for invasions. PMID:23252450

  4. Environmental structure and competitive scoring advantages in team competitions

    NASA Astrophysics Data System (ADS)

    Merritt, Sears; Clauset, Aaron

    2013-10-01

    In most professional sports, playing field structure is kept neutral so that scoring imbalances may be attributed to differences in team skill. It thus remains unknown what impact environmental heterogeneities can have on scoring dynamics or competitive advantages. Applying a novel generative model of scoring dynamics to roughly 10 million team competitions drawn from an online game, we quantify the relationship between the structure within a competition and its scoring dynamics, while controlling the impact of chance. Despite wide structural variations, we observe a common three-phase pattern in the tempo of events. Tempo and balance are highly predictable from a competition's structural features alone and teams exploit environmental heterogeneities for sustained competitive advantage. Surprisingly, the most balanced competitions are associated with specific environmental heterogeneities, not from equally skilled teams. These results shed new light on the design principles of balanced competition, and illustrate the potential of online game data for investigating social dynamics and competition.

  5. Environmental structure and competitive scoring advantages in team competitions.

    PubMed

    Merritt, Sears; Clauset, Aaron

    2013-01-01

    In most professional sports, playing field structure is kept neutral so that scoring imbalances may be attributed to differences in team skill. It thus remains unknown what impact environmental heterogeneities can have on scoring dynamics or competitive advantages. Applying a novel generative model of scoring dynamics to roughly 10 million team competitions drawn from an online game, we quantify the relationship between the structure within a competition and its scoring dynamics, while controlling the impact of chance. Despite wide structural variations, we observe a common three-phase pattern in the tempo of events. Tempo and balance are highly predictable from a competition's structural features alone and teams exploit environmental heterogeneities for sustained competitive advantage. Surprisingly, the most balanced competitions are associated with specific environmental heterogeneities, not from equally skilled teams. These results shed new light on the design principles of balanced competition, and illustrate the potential of online game data for investigating social dynamics and competition. PMID:24166062

  6. 10 CFR 781.52 - Exclusive and partially exclusive licenses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Exclusive and partially exclusive licenses. 781.52 Section 781.52 Energy DEPARTMENT OF ENERGY DOE PATENT LICENSING REGULATIONS Types of Licenses and Conditions... to sublicense the licensed invention to any foreign government pursuant to any existing or...

  7. Demolishing the competition: the longitudinal link between competitive video games, competitive gambling, and aggression.

    PubMed

    Adachi, Paul J C; Willoughby, Teena

    2013-07-01

    The majority of research on the link between video games and aggression has focused on the violent content in games. In contrast, recent experimental research suggests that it is video game competition, not violence, that has the greatest effect on aggression in the short-term. However, no researchers have examined the long-term relationship between video game competition and aggression. In addition, if competition in video games is a significant reason for the link between video game play and aggression, then other competitive activities, such as competitive gambling, also may predict aggression over time. In the current study, we directly assessed the socialization (competitive video game play and competitive gambling predicts aggression over time) versus selection hypotheses (aggression predicts competitive video game play and competitive gambling over time). Adolescents (N = 1,492, 50.8 % female) were surveyed annually from Grade 9 to Grade 12 about their video game play, gambling, and aggressive behaviors. Greater competitive video game play and competitive gambling predicted higher levels of aggression over time, after controlling for previous levels of aggression, supporting the socialization hypothesis. The selection hypothesis also was supported, as aggression predicted greater competitive video game play and competitive gambling over time, after controlling for previous competitive video game play and competitive gambling. Our findings, taken together with the fact that millions of adolescents play competitive video games every day and that competitive gambling may increase as adolescents transition into adulthood, highlight the need for a greater understanding of the relationship between competition and aggression. PMID:23595418

  8. Single elimination competition

    NASA Astrophysics Data System (ADS)

    Fink, T. M. A.; Coe, J. B.; Ahnert, S. E.

    2008-09-01

    We study a simple model of competition in which each player has a fixed strength: randomly selected pairs of players compete, the stronger one wins and the loser is eliminated. We show that the best indicator of future success is not the number of wins but a player's wealth: the accumulated wealth of all defeated players. We calculate the distributions of strength and wealth for two versions of the problem: in the first, the loser is replaced; in the second, the loser is not. The probability of attaining a given wealth is shown to be path-independent. We illustrate our model with the popular game of conkers and discuss an extension to round-robin sports competition.

  9. Designing Competitive Service Models

    NASA Astrophysics Data System (ADS)

    Martinez, Veronica; Turner, Trevor

    The explosives developed in Europe in the late nineteenth and early twentieth ­century by the famous Swede and patron of the world peace prize, Alfred Nobel, were extremely durable and, apart from the introduction of the electric detonator, have remained in use with minor modifications for almost a century (Fig. 5.1a). In the 1970s a new invention started a process of change that has transformed the explosives business from being a supplier of products to a provider of a service. Survival very much depended on the agility of ICI Explosives UK, hereinafter referred to as "ICI Explosives," in adapting to the new competitive environment. Manufacturing excellence was not a solution. Innovative thinking was required to sustain the ­business as changes in technology reduced the complexity that had ­protected the business from serious competition for over a century.

  10. The Literature of Competitive Intelligence.

    ERIC Educational Resources Information Center

    Walker, Thomas D.

    1994-01-01

    Describes competitive intelligence (CI) literature in terms of its location, quantity, authorship, length, and problems of bibliographic access. Highlights include subject access; competitive intelligence research; espionage and security; monographs; and journals. (21 references) (LRW)

  11. Children's Group Nous: Understanding and Applying Peer Exclusion Within and Between Groups

    ERIC Educational Resources Information Center

    Abrams, Dominic; Rutland, Adam; Pelletier, Joseph; Ferrell, Jennifer M.

    2009-01-01

    In Study 1, 167 English children aged 6-8 or 9-11 evaluated peer English or French soccer fans that were loyal or partially disloyal. In Study 2, 149 children aged 5-11 made judgments about generic inclusion norms between and within competitive groups. In both studies, children's understanding of intergroup inclusion/exclusion norms (group nous)…

  12. Competitive Intelligence and Social Advantage.

    ERIC Educational Resources Information Center

    Davenport, Elisabeth; Cronin, Blaise

    1994-01-01

    Presents an overview of issues concerning civilian competitive intelligence (CI). Topics discussed include competitive advantage in academic and research environments; public domain information and libraries; covert and overt competitive intelligence; data diversity; use of the Internet; cooperative intelligence; and implications for library and…

  13. Competitive epidemic spreading over arbitrary multilayer networks

    NASA Astrophysics Data System (ADS)

    Darabi Sahneh, Faryad; Scoglio, Caterina

    2014-06-01

    This study extends the Susceptible-Infected-Susceptible (SIS) epidemic model for single-virus propagation over an arbitrary graph to an Susceptible-Infected by virus 1-Susceptible-Infected by virus 2-Susceptible (SI1SI2S) epidemic model of two exclusive, competitive viruses over a two-layer network with generic structure, where network layers represent the distinct transmission routes of the viruses. We find analytical expressions determining extinction, coexistence, and absolute dominance of the viruses after we introduce the concepts of survival threshold and absolute-dominance threshold. The main outcome of our analysis is the discovery and proof of a region for long-term coexistence of competitive viruses in nontrivial multilayer networks. We show coexistence is impossible if network layers are identical yet possible if network layers are distinct. Not only do we rigorously prove a region of coexistence, but we can quantitate it via interrelation of central nodes across the network layers. Little to no overlapping of the layers' central nodes is the key determinant of coexistence. For example, we show both analytically and numerically that positive correlation of network layers makes it difficult for a virus to survive, while in a network with negatively correlated layers, survival is easier, but total removal of the other virus is more difficult.

  14. 37 CFR 404.7 - Exclusive, co-exclusive and partially exclusive licenses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... subject to any licenses in force at the time of the grant of the exclusive, co-exclusive or partially... or United States industry in foreign commerce will be enhanced; and (iii) The Federal agency has not... with the United States. (ii) The license shall be subject to any licenses in force at the time of...

  15. The role of drought- and disturbance-mediated competition in shaping community responses to varied environments.

    PubMed

    Napier, Joseph D; Mordecai, Erin A; Heckman, Robert W

    2016-06-01

    By altering the strength of intra- and interspecific competition, droughts may reshape plant communities. Furthermore, species may respond differently to drought when other influences, such as herbivory, are considered. To explore this relationship, we conducted a greenhouse experiment measuring responses to inter- and intraspecific competition for two grasses, Schedonorus arundinaceus and Paspalum dilatatum, while varying water availability and simulating herbivory via clipping. We then parameterized population growth models to examine the long-term outcome of competition under these conditions. Under drought, S. arundinaceus was less water stressed than P. dilatatum, which exhibited severe water stress; clipping alleviated this stress, increasing the competitive ability of P. dilatatum relative to S. arundinaceus. Although P. dilatatum competed weakly under drought, clipping reduced water stress in P. dilatatum, thereby enhancing its ability to compete with S. arundinaceus under drought. Supporting these observations, population growth models predicted that P. dilatatum would exclude S. arundinaceus when clipped under drought, while S. arundinaceus would exclude P. dilatatum when unclipped under drought. When the modeled environment varied temporally, environmental variation promoted niche differences that, though insufficient to maintain stable coexistence, prevented unconditional competitive exclusion by promoting priority effects. Our results suggest that it is important to consider how species respond not just to stable, but also to variable, environments. When species differ in their responses to drought, competition, and simulated herbivory, stable environments may promote competitive exclusion, while fluctuating environments may promote coexistence. These interactions are critical to understanding how species will respond to global change. PMID:26893230

  16. Rowing competitions and perspective

    NASA Astrophysics Data System (ADS)

    Flores, Alfinio; Bernhardt, Stephen A.; Shipman, Henry L.

    2015-02-01

    This paper is about integrating the use of graphing technology (specifically, GeoGebra) with principles of motion, principles of perspective, and the concept of vanishing points to model a dynamic event. Students were asked to analyse video images of a rowing competition filmed with a single camera positioned perpendicular to the race. The fixed position of the camera in such races makes it difficult to determine whether a scull closer to the camera is actually overtaking another, more distant scull. The paper illustrates how students in their first year at the university can integrate the use of technology, science, mathematics, and writing to solve a real world problem involving motion.

  17. Attention competition with advertisement

    NASA Astrophysics Data System (ADS)

    Cetin, Uzay; Bingol, Haluk O.

    2014-09-01

    In the new digital age, information is available in large quantities. Since information consumes primarily the attention of its recipients, the scarcity of attention is becoming the main limiting factor. In this study, we investigate the impact of advertisement pressure on a cultural market where consumers have a limited attention capacity. A model of competition for attention is developed and investigated analytically and by simulation. Advertisement is found to be much more effective when the attention capacity of agents is extremely scarce. We have observed that the market share of the advertised item improves if dummy items are introduced to the market while the strength of the advertisement is kept constant.

  18. Attention competition with advertisement.

    PubMed

    Cetin, Uzay; Bingol, Haluk O

    2014-09-01

    In the new digital age, information is available in large quantities. Since information consumes primarily the attention of its recipients, the scarcity of attention is becoming the main limiting factor. In this study, we investigate the impact of advertisement pressure on a cultural market where consumers have a limited attention capacity. A model of competition for attention is developed and investigated analytically and by simulation. Advertisement is found to be much more effective when the attention capacity of agents is extremely scarce. We have observed that the market share of the advertised item improves if dummy items are introduced to the market while the strength of the advertisement is kept constant. PMID:25314476

  19. Anesthesiology and competitive strategy.

    PubMed

    Gross, Wendy L; Gold, Barbara

    2009-03-01

    Whether we like it or not, medicine is big business. The argument is sometimes made that standard management strategies from the business world do not apply to medicine because the economics and practice of medicine are unique--driven by science and rapid rates of change. But an exploding knowledge base, light-speed technological development, and ever-changing reimbursement schemes are not exclusive to medicine and health care. Some fundamental principles of finance, business management, and strategic development have evolved to deal with problems of rapid change. These principles do apply to modern medicine. The business side of anesthesia practice is off-putting to many clinicians. However, knowledge of the market forces at play can help enhance patient care, improve service, expand opportunities, and extend the perimeter of the discipline. The mission and current market position of anesthesiology practice are considered here. PMID:19361778

  20. The effects of competition and competitiveness on cardiovascular activity.

    PubMed

    Harrison, L K; Denning, S; Easton, H L; Hall, J C; Burns, V E; Ring, C; Carroll, D

    2001-07-01

    Cardiovascular activity was measured at resting baseline and in response to a car racing game, undertaken in competition or in cooperation with an experimenter, or individually. Competitiveness and win and goal orientations were assessed by questionnaire. Competition provoked increases in blood pressure and heart rate, and a significant shortening of the preejection period, an index of enhanced beta-adrenergic influences on the heart. The cooperation task was largely without effect, and although the solo task affected cardiovascular activity, it did so to a lesser extent and much less consistently than did the competition task. The three task conditions, then, were largely distinguishable by their capacity to activate beta-adrenergic processes. Participants high in competitiveness and desire to win showed higher blood pressure reactions and greater shortening of the preejection period to competition than those low in these characteristics. PMID:11446573

  1. Making geothermal power competitive

    NASA Astrophysics Data System (ADS)

    Fassbender, L. L.; Bloomster, C. H.

    The near-term supply curve for the electrical applications of geothermal energy is presented, and the impacts of technological improvements are illustrated. The curve is derived using the subsurface temperature, reservoir thickness, and heat content estimates made by the U.S. Geological Survey for the identified high-temperature and intermediate-temperature hydrothermal resources of the western U.S. Each step in the curve is composed of one or more geothermal resources identified by the USGS. Both high- and intermediate-temperature resources were included up to an arbitrary cost ceiling of 100 mills/kWh. Curves are drawn to show the impacts of combinations of technological advances expected to be achieved by 1982 and 1985. It is shown that most of the identified hydrothermal resources could become competitive with conventional energy sources for electrical power production by 1985.

  2. Mapping your competitive position.

    PubMed

    D'Aveni, Richard A

    2007-11-01

    A price-benefit positioning map helps you see, through your customers' eyes, how your product compares with all its competitors in a market. You can draw such a map quickly and objectively, without having to resort to costly, time-consuming consumer surveys or subjective estimates of the excellence of your product and the shortcomings of all the others. Creating a positioning map involves three steps: First, define your market to include everything your customers might consider to be your product's competitors or substitutes. Second, track the price your customers actually pay (wholesale or retail? bundled or unbundled?) and identify what your customers see as your offering's primary benefit. This is done through regression analysis, determining which of the product's attributes (as described objectively by rating services, government agencies, R&D departments, and the like) explains most of the variance in its price. Third, draw the map by plotting on a graph the position of every product in the market you've selected according to its price and its level of primary benefit, and draw a line that runs through the middle of the points. What you get is a picture of the competitive landscape of your market, where all the products above the line command a price premium owing to some secondary benefit customers value, and all those below the line are positioned to earn market share through lower prices and reduced secondary benefits. Using examples as varied as Harley-Davidson motorcycles, Motorola cell phones, and the New York restaurant market, Tuck professor D'Aveni demonstrates some of the many ways the maps can be used: to locate unoccupied or less-crowded spaces in highly competitive markets, for instance, or to identify opportunities created through changes in the relationship between the primary benefit and prices. The maps even allow companies to anticipate--and counter-- rivals' strategies. R eprint RO711G PMID:18159791

  3. Spatial Aspects of Interspecific Competition

    NASA Technical Reports Server (NTRS)

    Durrett, Rick; Levin, Simon

    1998-01-01

    Using several variants of a stochastic spatial model introduced by Silvertown et al., we investigate the effect of spatial distribution of individuals on the outcome of competition. First, we prove rigorously that if one species has a competitive advantage over each of the others, then eventually it takes over all the sites in the system. Second, we examine tradeoffs between competition and dispersal distance in a two-species system. Third, we consider a cyclic competitive relationship between three types. In this case, a nonspatial treatment leads to densities that follow neutrally stable cycles or even unstable spiral solutions, while a spatial model yields a stationary distribution with an interesting spatial structure.

  4. Controls over native perennial grass exclusion and persistence in California grasslands invaded by annuals.

    PubMed

    Mordecai, Erin A; Molinari, Nicole A; Stahlheber, Karen A; Gross, Kevin; D'Antonio, Carla

    2015-10-01

    Despite obvious impacts of nonnative species in many ecosystems, the long-term outcome of competition between native and exotic species often remains unclear. Demographic models can resolve the outcome of competition between native and exotic species and provide insight into conditions favoring exclusion vs. coexistence. California grasslands are one of the most heavily invaded ecosystems in North America. Although California native perennial bunchgrasses are thought to be restricted to a fraction of their original abundance, the eventual outcome of competition with invasive European annual grasses at a local scale (competitive exclusion, stable persistence, or priority effects) remains unresolved. Here, we used a two-species discrete time population growth model to predict the outcome of competition between exotic annual and native perennial grasses in California, and to determine the demographic traits responsible for the outcome. The model is parameterized with empirical data from several field experiments. We found that, once introduced, annual grasses persist stably with little uncertainty. Although perennial grasses are competitively excluded on average, the most likely range of model predictions also includes stable coexistence with annual grasses. As for many other perennial plants, native bunchgrass population growth is highly sensitive to the survival of adults. Management interventions that improve perennial adult survival are likely to be more effective than those that reduce exotic annual seed production or establishment, reduce competition, or increase perennial seedling establishment. Further empirical data on summer survival of bunchgrass adults and competitive effects of annuals on perennials would most improve model predictions because they contribute most to the uncertainty in the predicted outcome for the perennial grass. This work demonstrates how demographic approaches can clarify the outcome of competition between native and exotic species

  5. Mathematics + Competitions = A Winning Formula!

    ERIC Educational Resources Information Center

    Riley, Tracy L.; Karnes, Frances A.

    1998-01-01

    Describes how teachers of the gifted can make the study of mathematics dynamic, innovative, and creative through the exploration of problem-solving skills and real-life applications. Math competitions and general academic competitions that include mathematics for elementary schools, middle schools, and high schools are highlighted. (CR)

  6. Competitive Grading Sabotages Good Teaching.

    ERIC Educational Resources Information Center

    Krumboltz, John D.; Yeh, Christine J.

    1996-01-01

    Competitive grading stresses judging over learning. Assigning competitive grades adversely affects teachers by turning them into students' opponents, justifying inadequate teaching methods, trivializing course content, encouraging evaluation methods that misdirect and inhibit student learning, and rewarding teachers for punishing students. High…

  7. Feature Discovery by Competitive Learning.

    ERIC Educational Resources Information Center

    Rumelhart, David E.; Zipser, David

    1985-01-01

    Reports results of studies with an unsupervised learning paradigm called competitive learning which is examined using computer simulation and formal analysis. When competitive learning is applied to parallel networks of neuron-like elements, many potentially useful learning tasks can be accomplished. (Author)

  8. Higher Education, Employability and Competitiveness

    ERIC Educational Resources Information Center

    Pavlin, Samo; Svetlicic, Marjan

    2012-01-01

    This paper studies the relationship between competitiveness and higher education systems in Europe. It explores whether more competitive countries have developed more labour-market-oriented systems of higher education (HE) that thereby give their graduates greater short term employability potential. Based on and a large-scale survey among 45.000…

  9. An Approach to Competitive Assessment.

    ERIC Educational Resources Information Center

    Green, Petrina M.

    1994-01-01

    Offers a detailed discussion of competitive assessment, an efficient and cost-effective method to evaluate competitive products. Describes its three phases: numerical scoring, building a best-of-breed model, and determining the gap between the best-of-breed model and another product. (SR)

  10. A Learning Software Design Competition.

    ERIC Educational Resources Information Center

    Hooper, Simon; Hokanson, Brad; Bernhardt, Paul; Johnson, Mark

    2002-01-01

    Explains the University of Minnesota Learning Software Design Competition, focusing on its goals and emphasis on innovation. Describes the review process to evaluate and judge the software, lists the winners, identifies a new class of educational software, and outlines plans for future competitions. (Author/LRW)