competition effects
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Limiting resource is a angular stone of the interactions between species in ecosystems such as competition, prey-predators and food chain systems. In this paper, we propose a planar system as an extension of Lotka-Voterra competition model. This describes? two competitive species for a single resource? which are affected by intra and inter-specific interference. We give its complete analysis for the existence and local stability of all equlibria and some conditions of global stability. The model exhibits a rich set of behaviors with a multiplicity of coexistence equilibria, bi-stability, tri-stability and occurrence of global stability of the exclusion of one species and the coexistence? equilibrium. The asymptotic behavior and the number of coexistence equilibria are shown by a saddle-node bifurcation of the level of resource under conditions on competitive effects relatively to associated growth rate per unit of resource.Moreover, we determine the competition outcome in the situations of Balanced and Unbalanced intra-inter species competition effects. Finally, we illustrate results by numerical simulations.

<p>Some aphasic patients show single word production deficits in some situations where object naming is required (e.g., they perform well when objects are presented in unrelated groups (e.g., Cat, Fork, Bread...), but deteriorate when the same items are presented in semantically related groups (e.g., Cat, Cow, Dog...)) (see Wilshire & McCarthy, 2002). We investigated whether context-sensitive single-word production impairments reflect an impaired ability to resolve lexical competition. Three groups of participants (non-fluent aphasics, fluent aphasics, and older controls) completed four tasks that manipulated lexical competition: 1) A category exemplar task, where a high competition condition involved generating items from broad categories (e.g., Animals: "Cat. Dog" etc.), and a low competition condition involved generating items from narrow categories (e.g., Pets: Cat. Dog" etc); 2) A verb generation task, where participants were presented with objects and were required to generate related verbs. The high competition objects were related to a range of verbs (e.g., Penny: Spend"/"Pay"/"Buy" etc), and the low competition objects were related to one dominant verb (e.g., Scissors: "Cut"); 3) A name agreement task where a high competition condition involved naming low name agreement objects (e.g., Artist/Painter), and a low competition condition involved naming of high name agreement objects (e.g., Anchor), and; 4) A sentence completion task, where extrinsic competition was introduced via presentation of auditory distracters. The low competition distracters did not make sense (e.g., Barry wisely chose to pay the RANGE: "Bill"/"Cashier" etc), whereas the high competition distracters did (e.g., Barry wisely chose to pay the FINE: "Bill"/Cashier" etc). Our first hypothesis was that all participants would show high competition costs in increased response latencies and/or decreased accuracy. At the group level, this hypothesis was supported in all four tasks. At the individual level, there was mixed support as some participants showed predicted effects on the verb generation, name agreement, and sentence completion tasks. The second hypothesis was that exaggerated competition costs would occur in some or all non-fluent aphasics. At the group level this hypothesis was not clearly supported on any task. At the individual level there was mixed support, with some indications that non-fluents may be more likely to show significant competition effects than fluents. The third hypothesis was that non-fluent aphasics with relatively well preserved single word production but relatively impaired sentence production may be most likely to show exaggerated lexical competition effects. There was little support for this hypothesis. It was concluded that the data do not support the hypothesis that context-sensitive single-word production impairments are symptomatic of an impaired ability to resolve lexical competition. However, we have gained information on how heterogeneous aphasics perform on tasks that manipulate lexical competition, and we have gained some insights that may direct future research down a path towards more informative results, and increased knowledge on the complex process of speech production.</p>

<p>Some aphasic patients show single word production deficits in some situations where object naming is required (e.g., they perform well when objects are presented in unrelated groups (e.g., Cat, Fork, Bread...), but deteriorate when the same items are presented in semantically related groups (e.g., Cat, Cow, Dog...)) (see Wilshire & McCarthy, 2002). We investigated whether context-sensitive single-word production impairments reflect an impaired ability to resolve lexical competition. Three groups of participants (non-fluent aphasics, fluent aphasics, and older controls) completed four tasks that manipulated lexical competition: 1) A category exemplar task, where a high competition condition involved generating items from broad categories (e.g., Animals: "Cat. Dog" etc.), and a low competition condition involved generating items from narrow categories (e.g., Pets: Cat. Dog" etc); 2) A verb generation task, where participants were presented with objects and were required to generate related verbs. The high competition objects were related to a range of verbs (e.g., Penny: Spend"/"Pay"/"Buy" etc), and the low competition objects were related to one dominant verb (e.g., Scissors: "Cut"); 3) A name agreement task where a high competition condition involved naming low name agreement objects (e.g., Artist/Painter), and a low competition condition involved naming of high name agreement objects (e.g., Anchor), and; 4) A sentence completion task, where extrinsic competition was introduced via presentation of auditory distracters. The low competition distracters did not make sense (e.g., Barry wisely chose to pay the RANGE: "Bill"/"Cashier" etc), whereas the high competition distracters did (e.g., Barry wisely chose to pay the FINE: "Bill"/Cashier" etc). Our first hypothesis was that all participants would show high competition costs in increased response latencies and/or decreased accuracy. At the group level, this hypothesis was supported in all four tasks. At the individual level, there was mixed support as some participants showed predicted effects on the verb generation, name agreement, and sentence completion tasks. The second hypothesis was that exaggerated competition costs would occur in some or all non-fluent aphasics. At the group level this hypothesis was not clearly supported on any task. At the individual level there was mixed support, with some indications that non-fluents may be more likely to show significant competition effects than fluents. The third hypothesis was that non-fluent aphasics with relatively well preserved single word production but relatively impaired sentence production may be most likely to show exaggerated lexical competition effects. There was little support for this hypothesis. It was concluded that the data do not support the hypothesis that context-sensitive single-word production impairments are symptomatic of an impaired ability to resolve lexical competition. However, we have gained information on how heterogeneous aphasics perform on tasks that manipulate lexical competition, and we have gained some insights that may direct future research down a path towards more informative results, and increased knowledge on the complex process of speech production.</p>

This study uses detailed manufacturing census panel data for 2000 to 2014 to explore the relationship between Ethiopian firms’ global value chain (GVC) participation and markups. We find that GVC firms, defined as firms involved in both exporting and importing intermediate inputs, tend to have lower markups relative to non-trading firms and firms that are involved only in material imports. Moreover, the more intensely a firm is integrated into a GVC (measured by the share of export value added and imported inputs in total sales), the lower its markup is. Finally, we explore competition effects at the industry level and find that firms operating in industries with a relatively high GVC presence and suppliers selling inputs to such industries tend to have lower markups owing to horizontal competition and backward linkages, respectively. All of these findings suggest that GVC participation is associated with greater competition for Ethiopian firms.

AbstractThis paper investigates empirically the competition effects on procurement costs for Europe Aid funded supply tenders in countries benefiting from the EU Pre-accession (IPA) and Neighbourhood (ENI) financial instruments. We use a dataset created and curated by us from supply tender dossiers published by Europe Aid. We determine a reference price for each procured lot based on the contracting authority’s requirement to establish a participation tender guarantee. We estimate controlling for potential endogeneity how the entry of new bidders in the tendering procedure affects procurement cost savings regarding this reference price. Finally, we discuss the expected additional savings in the management of these funds that may be obtained by further promoting competition.