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Mechanisms
Kinds of Mechanisms Terms modified by Mechanisms Selected AbstractsDESIGN OF AN ITERATIVE MULTI-ITEM DOUBLE-AUCTION MECHANISMCOMPUTATIONAL INTELLIGENCE, Issue 1 2008Dong H. Roh There have been many multi-item auction mechanisms. As it is not allowed for both sellers and buyers to submit bids and offers in nearly all existing multi-item auction mechanisms, the impartial profit distribution for both sellers and buyers cannot be realized in those mechanisms. Although it is possible for both sellers and buyers to submit bids and offers in a combinatorial exchange, the impartial profit distribution for all individual participants cannot be realized due to its pricing mechanism that focuses only on enforcing budget balance. This paper proposes an iterative multi-item unit-demand and unit-supply double-auction mechanism with a new winner determination and pricing mechanism for distributing profit impartially from the viewpoints of individual participants regardless of whether they are buyers or sellers. It also analyzes the theoretical features of the proposed auction mechanism, including those related to its strategic behavior and efficiency. [source] TRIGGER-POINT MECHANISM AND CONDITIONAL COMMITMENT: IMPLICATIONS FOR ENTRY, COLLUSION, AND WELFARECONTEMPORARY ECONOMIC POLICY, Issue 2 2007LARRY D. QIU When fixed, sunk investment costs are high, firms may not have sufficient incentive to enter the market unless future entry is constrained. In this case, the government faces a dilemma between a full commitment and noncommitment of restricted future entry. A way out is to consider a commitment conditional on the realization of the uncertain parameters, such as the trigger-point mechanism (TPM) that sets conditions on current production level, excess capacity, and demand growth under which future entry will be allowed. This article shows that the TPM facilitates the incumbents' collusion but may improve social welfare under certain circumstances. (JEL L13, L43, L50, H10, H54) [source] HEMODYNAMIC MECHANISM OF ESOPHAGEAL VARICESDIGESTIVE ENDOSCOPY, Issue 1 2006Katsutoshi Obara We investigated the correlation between the collaterals around the esophagus and recurrence of esophageal varices in patients with portal hypertension who had undergone endoscopic injection sclerotherapy (EIS). In patients with portal hypertension, many types of collaterals around the esophagus were visualized by endoscopic ultrasonography (EUS). The collaterals outside the esophageal wall detected by EUS were divided into two groups according to the location of the veins: peri-esophageal collateral veins (peri-ECV) and para-esophageal collateral veins (para-ECV) Perforating veins are those that have penetrated the esophageal wall and have connected with either peri-ECV or para-ECV. We demonstrated that severe peri-ECV and large perforating veins play an important role in the development of esophageal varices in untreated patients with portal hypertension. The results of our investigation have shown that detection of peri-ECV and perforating veins by EUS and treatment of them by EIS appears to be important for the treatment of esophageal varices. The disappearance of peri-ECV by EIS is essential for reducing the recurrence rate of esophageal varices. To prevent variceal recurrence, a mucosal fibrosing method using argon plasma coagulation has been widely performed in Japan. If EUS abnormalities are associated with variceal recurrence, we recommend the use of the mucosal fibrosing method. In conclusion, the presence of severe peri-ECV and large perforating veins in the esophageal wall strongly correlate with the recurrence of esophageal varices in patients with portal hypertension. An understanding of these EUS abnormalities on the basis of hemodynamics around the esophagus is important for the management of esophageal varices in patients with portal hypertension. [source] 3 ISCHEMIC MITRAL VALVE REPAIR: THE IMPACT OF THE MECHANISM OF MITRAL REGURGITATION ON LATE POSTOPERATIVE RESULTSECHOCARDIOGRAPHY, Issue 1 2004E. Ereminien Aim: The aim of our study was to establish the anatomical-functional mechanisms of ischemic mitral regurgitation (MR) and to analyse its impact on late results after mitral valve (MV) reconstructive surgery. Methods: The study included 53 patients with ischemic MR, who underwent CABG and MV repair. MV surgery consisted of subvalvular apparatus repair and/or annuloplasty. 2D Doppler investigations performed pre-, 10,14 days, and 12 months after surgery included evaluation of MV and left ventricular (LV) geometry and function. Results: Analysis of the mechanisms of ischemic MR permitted dividing patients into two groups: group 1,29 patients with inferobasal scar and posterior papillary muscle (PM) displacement, including 22 patients with PM infarction and 7 patients without it, and group 2,24 patients with isolated mitral annulus (MA) dilation. In the case of PM infarction two different mechanisms of MR were stated: (a) P3 restriction and A3 prolapse due to chordal tethering, (b) A3 P3 (commissural) prolapse due to chordal papillary elongation. Preoperatively LV geometry and function were better preserved in group 1 and late MV repair results were better versus (vs.) group 2: LV end-systolic diameter index decreased from 22.9 ± 3.1 mm/m2 to 20.9 ± 3.6 mm/m2 at 1 year, p < 0.05, LV ejection fraction increased from 34.9 ± 8.4 to 41.8 ± 8.1%, respectively, p < 0.05. No significant changes in LV geometry and function were noted in group 2. Conclusions: The underlying mechanism of ischemic MR has an impact on MV repair results. In patients with MR due to posterobasal infarction MV repair resulted in more favorable postoperative effect-marked improvement in LV geometry and function late after surgery versus MR due to isolated MA dilation. [source] PEAK SHIFT DISCRIMINATION LEARNING AS A MECHANISM OF SIGNAL EVOLUTIONEVOLUTION, Issue 6 2005Spencer K. Lynn Abstract "Peak shift" is a behavioral response bias arising from discrimination learning in which animals display a directional, but limited, preference for or avoidance of unusual stimuli. Its hypothesized evolutionary relevance has been primarily in the realm of aposematic coloration and limited sexual dimorphism. Here, we develop a novel functional approach to peak shift, based on signal detection theory, which characterizes the response bias as arising from uncertainty about stimulus appearance, frequency, and quality. This approach allows the influence of peak shift to be generalized to the evolution of signals in a variety of domains and sensory modalities. The approach is illustrated with a bumblebee (Bombus impatiens) discrimination learning experiment. Bees exhibited peak shift while foraging in an artificial Batesian mimicry system. Changes in flower abundance, color distribution, and visitation reward induced bees to preferentially visit novel flower colors that reduced the risk of flower-type misidentification. Under conditions of signal uncertainty, peak shift results in visitation to rarer, but more easily distinguished, morphological variants of rewarding species in preference to their average morphology. Peak shift is a common and taxonomically widespread phenomenon. This example of the possible role of peak shift in signal evolution can be generalized to other systems in which a signal receiver learns to make choices in situations in which signal variation is linked to the sender's reproductive success. [source] BIOACTIVITIES AND MECHANISM OF SPIRO ENOL ETHER ANALOGUES AGAINST PIERIS RAPAEINSECT SCIENCE, Issue 1 2004Zhi-xiang Zhang Abstract, Nineteen kinds of spiro enol ether analogues were screened with larvae of Pieris rapae for antifeedant activity. The results showed that the antifeedant activity of compounds No.20 and No. 12 was higher than others. In non-choice test, AFC50 values within 24 h of compounds No.20 and No. 12 against 3rd instar larvae of P. rapae were 226.93 ,g/mL and 370.00 ,g/mL, and that in choice test against 4th larvae were 280.54 ,g/mL and 398.88 ,g/mL, respectively. Compd. No.20 could prolong the eggs hatch time and reduce the haemolymph content and the protein content in haemolymph of 4th instar larvae obviously. Compd. No.20 could protect tested leaves and control larvae of P. rapae effectively. [source] EQUILIBRIUM LENDING MECHANISM AND AGGREGATE ACTIVITY,INTERNATIONAL ECONOMIC REVIEW, Issue 3 2010Cheng Wang We construct a model of the credit market where financial contracting is subject to costly state verification and moral hazard. The economy's aggregate activity and its equilibrium lending mechanism are determined jointly. We analyze how changes in the model's exogenous variables, including the returns of the economy's investment projects and the supply of loans, affect the economy's aggregate output and the types of the credit through which investment is funded. [source] MONEY AS A MECHANISM IN A BEWLEY ECONOMY*INTERNATIONAL ECONOMIC REVIEW, Issue 2 2005Edward J. Green We investigate the efficiency property of a monetary economy with spot trade. We prove a conjecture that is essentially due to Bewley (Models of Monetary Economics (1980); Econometrica 51 (1983), 1485,504). The gist is that monetary spot trading is nearly efficient ex ante in an environment where very patient agents can accumulate large enough money stocks to be completely self-insured. We also study examples where a nonmonetary mechanism is preferred ex ante to any monetary mechanism in a stationary environment, and where an inflationary monetary mechanism is preferred ex ante to a laissez-faire or deflationary monetary mechanism in an environment with impatient agents. [source] Success factors for the effective implementation of renewable energy options for rural electrification in India,Potentials of the CLEAN DEVELOPMENT MECHANISMINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2008Gudrun Elisabeth Benecke Abstract Developing countries as well as international development assistance have for a long time aspired to combat energy poverty in rural areas of developing countries. However, until now a major part of national and international public and private attempts to provide affordable and stable energy supply have failed due to various economic, political, social and institutional obstacles. This situation is reflected in case of India where in comparison with other South Asian states the status of rural electrification and of energy supply are in a dismal state despite the promotion of renewable energy and rural electrification as early as from the 1960s. Embedded in the global context of the international climate change regime, the Clean Development Mechanism (CDM) of the Kyoto Protocol has now emerged as a new option to facilitate investment in climate change mitigating projects. In this respect, promoting the deployment of renewable energy through this project-based mechanism opens new avenues for rural electrification. The main objective of this paper is, hence, to examine the context conditions and factors determining the effective application of renewable energy options for rural electrification in a developing country context, namely India. Understanding contextual requirements for renewable energy investment has proved imminently important in order to appreciate the potentials provided by new market-based mechanisms such as the CDM for rural poverty alleviation. Comparative political science case study research methods are applied to the analysis of CDM biomass projects in the context of the four Indian states of Tamil Nadu, Maharashtra, Punjab and Andhra Pradesh. This allows for the conclusion that socio-political and historic framework conditions matter for the implementation of new renewable energy options. Copyright © 2008 John Wiley & Sons, Ltd. [source] MONETARY TRANSMISSION MECHANISM IN CENTRAL AND EASTERN EUROPE: SURVEYING THE SURVEYABLEJOURNAL OF ECONOMIC SURVEYS, Issue 2 2009Balázs Égert Abstract This paper surveys recent advances in empirical studies of the monetary transmission mechanism, with special attention to Central and Eastern Europe (CEE). Our results indicate that the strength of the exchange rate pass-through substantially declined over time mainly due to a fall in inflation rates and to some extent due to the so-called composition effect. The asset price channel is weak and is likely to remain weak because of shallow stock and private bond markets and because of low stock and bond holdings of domestic households. House prices may become an exception with booming mortgage lending and with high owner occupancy ratios. While the credit channel could be a powerful channel of monetary transmission , as new funds raised on capital markets are close to zero in CEE , it is actually not, as both commercial banks and non-financial corporations can escape domestic monetary conditions by borrowing from their foreign mother companies. The moderately good news, however, is that those banks and firms are influenced by monetary policy in the euro area because their parent institutions are themselves subjected to the credit channel in the euro area. [source] FILM FORMING MECHANISM AND MECHANICAL AND THERMAL PROPERTIES OF WHEY PROTEIN ISOLATE-BASED EDIBLE FILMS AS AFFECTED BY PROTEIN CONCENTRATION, GLYCEROL RATIO AND PULLULAN CONTENTJOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2010MAHAMADOU ELHADJI GOUNGA ABSTRACT Tensile strength (TS), elongation at break (EAB) and elastic modulus (EM) of edible films prepared from 5, 7 and 9% whey protein isolate (WPI) plasticized with different levels of glycerol (Gly) (WPI : Gly = 3.6:1, 3:1 and 2:1) were investigated in order to completely characterize WPI-Gly films. On increasing protein concentration an increase in TS and EAB was observed. On the other hand, increasing Gly led to a decrease in TS and EM, while EAB increased. The addition of pullulan (Pul) into the film forming solution (FFS) increased EAB while TS, EM and thermal properties were reduced. This suggested that Pul had a similar effect as plasticizers. Films with higher Pul content showed lighter protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fourier transform infrared spectroscopy showed that hydrogen bonding was high in WPI : Pul films as compared with the control. This is attributed to the protein-polysaccharide interactions brought about by the dominance of Pul in the FFS. PRACTICAL APPLICATIONS This work describes some physical properties of films based on blends of whey protein isolate (WPI) and pullulan (Pul), made after a previous study on some characteristics of films based on pure WPI plasticized by glycerol. The most studied proteins in the edible films technology being gluten and WPI, the use of Pul in mixture with WPI is considered as a new investigation to explore the utilization of WPI-Pul in edible film and coating materials applied to food products. Furthermore, the use of WPI-Pul films and coatings could potentially extend the shelf life and improve the stability of the coated products as shown by the resultant properties in this investigation and previous works. [source] TEMPERATURE-VISCOSITY RELATIONS OF BOWHEAD WHALE BLOOD: A POSSIBLE MECHANISM FOR MAINTAINING COLD BLOOD FLOWMARINE MAMMAL SCIENCE, Issue 2 2004Robert Elsner [source] RANDOM PENALTIES AND RENEWABLE RESOURCES: A MECHANISM TO REACH OPTIMAL LANDINGS IN FISHERIESNATURAL RESOURCE MODELING, Issue 3 2009FRANK JENSEN Abstract Recent literature considers illegal landings a moral hazard problem that arises because individual landings are unobservable. The literature proposes incentive schemes to solve the information problem. However, most of the proposed schemes raise huge information requirements and social budget balance is not secured. In this paper, we suggest a random penalty mechanism that reduces the information requirements and secures budget balance in the case of a given number of licensed vessels. In the random penalty mechanism, aggregate landings are measured through stock sizes and the natural growth function. If aggregate landings are below optimal landings, each fisherman receives a subsidy. If aggregate catches are above optimal landings, the mechanism works such that either the fisherman is randomly selected and pays a fine or the fisherman is not selected and receives a subsidy. The fine and subsidy can be designed such that budget balance is secured. Provided risk aversion is sufficiently large and the fine is high enough, the random penalty mechanism will generate optimal individual landings. The budget balance combined with risk aversion drives the result for this advanced tax/subsidy system that does not exhaust the resource rents. The budget balance creates interdependence between fishermen that secure optimality. [source] BEYOND NOTIONS OF DIPLOMACY AND LEGALISM: BUILDING A JUST MECHANISM FOR WTO DISPUTE RESOLUTIONAMERICAN BUSINESS LAW JOURNAL, Issue 3 2003Lawrence D. Roberts First page of article [source] AN EXPLORATION OF MEMBER ROLES AS A MULTILEVEL LINKING MECHANISM FOR INDIVIDUAL TRAITS AND TEAM OUTCOMESPERSONNEL PSYCHOLOGY, Issue 2 2005GREG L. STEWART We use data from 220 individuals in 45 teams to examine team member roles as a cross-level linking mechanism between personality traits and team-level outcomes. At the individual level, peer ratings of task role behavior relate positively with Conscientiousness and negatively with Neuroticism and Extraversion. Peer ratings of social role behavior relate positively with Agreeableness and negatively with Openness to Experience. At the team level, a composition process of aggregation operates such that the mean for social roles corresponds with social cohesion. Compilation processes of aggregation also occur, as the variance of social roles corresponds negatively with task performance, and the variance of task roles corresponds negatively with cohesion. Skew of the distribution for social roles within each team,a measure of critical mass of members individually enacting the role,also correlates with social cohesion. [source] PIOGLITAZONE INHIBITS HOMOCYSTEINE-INDUCED MIGRATION OF VASCULAR SMOOTH MUSCLE CELLS THROUGH A PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR ,-INDEPENDENT MECHANISMCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 12 2008Li Li SUMMARY 1Peroxisome proliferator-activated receptor (PPAR)-, agonists have been demonstrated to exert protective effects against homocysteine (Hcy)-induced pathogenesis. However, the effects of PPAR-, agonists on Hcy-induced migration are unknown. In the present study, we examined the effect of pioglitazone on the migration of vascular smooth muscle cells (VSMC) induced by Hcy and the possible mechanism involved. 2Vascular smooth muscle cells were isolated from the thoracic aortas of male Sprague-Dawley rats. The migration of VSMC was examined using a transwell technique. The generation of intracellular reactive oxygen species (ROS) was measured using the ROS-sensitive fluoroprobe 2,,7,-dichlorodihydrofluorescein diacetate. The activity of NAD(P)H oxidase was assessed by lucigenin enhanced chemiluminescence. Activation of p38 mitogen-activated protein kinase (MAPK) was determined by western blotting. 3The results showed that pioglitazone dose-dependently inhibited the migration of VSMC induced by Hcy. This was not reversed by the PPAR-, antagonist GW9662. In addition, pretreatment with the NAD(P)H oxidase inhibitor diphenylene iodonium (DPI), the free radical scavenger N -acetylcysteine and the p38 MAPK inhibitor SB202190 blocked Hcy-induced VSMC migration. Furthermore, we observed that pioglitazone suppressed Hcy-induced intracellular ROS production; similar effects were observed with DPI and NAC. Pioglitazone attenuated Hcy-induced activation of NAD(P)H oxidase. Moreover, pioglitazone blocked Hcy-induced p38 MAPK phosphorylation; similar effects were observed for DPI, NAC and SB202190. 4The data demonstrate that pioglitazone inhibits Hcy-induced VSMC migration that is independent of PPAR-,. Furthermore, part of the biological effect of pioglitazone involves a decrease in the levels of NAD(P)H oxidase derived-ROS and p38 MAPK activation. [source] PROTECTION BY AND ANTI-OXIDANT MECHANISM OF BERBERINE AGAINST RAT LIVER FIBROSIS INDUCED BY MULTIPLE HEPATOTOXIC FACTORSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2008Ben-Jian Zhang SUMMARY 1The aim of the present study was to investigate the effect and mechanism of berberine, an alkaloid extracted from the traditional Chinese medicine coptis, on rat liver fibrosis induced by multiple hepatotoxic factors. 2Male Wistar rats were separated into five groups, a normal control group, a fibrotic control group and fibrotic groups treated with three different doses of berberine. The fibrotic models were established by introduction of multiple hepatotoxic factors, including CCl4, ethanol and high cholesterol. Rats in the treatment groups were administered 50, 100 or 200 mg/kg berberine, intragastrically, daily for 4 weeks. Serum levels of alanine aminotransferase (ALT) and serum aspartate aminotransferase (AST), hepatic activity of superoxide dismutase (SOD) and hepatic malondialdehyde (MDA) and hepatic hydroxyproline (Hyp) content were determined. Liver biopsies were obtained for histological and immunohistochemical studies to detect the expressions of a-smooth muscle actin (SMA) and transforming growth factor (TGF)-b1. 3The results showed that, compared with the fibrotic control group, serum levels of ALT and AST and hepatic content of MDA and Hyp were markedly decreased, but the activity of hepatic SOD was significantly increased in berberine-treated groups in a dose-dependent manner. In addition, histopathological changes, such as steatosis, necrosis and myofibroblast proliferation, were reduced and the expression of a-SMA and TGF-b1 was significantly downregulated in the berberine-treated groups (P < 0.01). 4These results suggest that berberine could be used to prevent experimental liver fibrosis through regulation of the anti-oxidant system and lipid peroxidation. [source] THE TIMING AND MECHANISMS OF THE OFFENDING-DEPRESSION LINK,CRIMINOLOGY, Issue 3 2007SONJA E. SIENNICK Why is juvenile delinquency associated with depression in young adulthood? One possibility is that delinquency interferes with socioeco-nomic attainment and disrupts entry into adult roles, perhaps because of official labeling processes or adolescent socialization into deviance, and these repercussions of delinquency lead to depression. Another possibility is that grown delinquents may show high levels of depression because they tend to offend in adulthood, and adult offenders tend to be depressed. I use data from the National Longitudinal Study of Adolescent Health to examine the timing and mechanisms of the offending-depression relationship. The results suggest that delinquency is negatively associated with later status attainment and that the status attainment deficits of grown delinquents are not fully explained by justice system contacts or by adolescent delinquent peer influence. A portion of the longitudinal delinquency-depression link is explained by the low levels of education of grown delinquents and by their involvement with the justice system. Still, young adult depression is more closely tied to recent offending than it is to juvenile delinquency, official labeling, or the status attainment consequences of delinquency. [source] MINDFULNESS,SPECIFIC OR GENERIC MECHANISMS OF ACTIONADDICTION, Issue 10 2010CARLO C. DICLEMENTE No abstract is available for this article. [source] [Commentary] EARLY PUBERTAL MATURATION AND DRUG USE: UNDERLYING MECHANISMSADDICTION, Issue 1 2009RUTGER C. M. E. ENGELS No abstract is available for this article. [source] EVOLUTION OF CHARACTER DISPLACEMENT IN SPADEFOOT TOADS: DIFFERENT PROXIMATE MECHANISMS IN DIFFERENT SPECIESEVOLUTION, Issue 8 2010David W. Pfennig Character displacement occurs when two species compete, and those individuals most dissimilar from the average resource-use phenotypes of the other species are selectively favored. Few studies have explored the sequence of events by which such divergence comes about. We addressed this issue by studying two species of spadefoot toads that have undergone ecological character displacement with each other. Previous research revealed that phenotypic shifts between sympatric and allopatric populations of one species, Spea multiplicata, reflect a condition-dependent maternal effect. Here, we show that analogous shifts in the other species, S. bombifrons, cannot similarly be explained by such a maternal effect, and that these shifts instead appear to be underlain by allelic differences. We hypothesize that these two species have evolved different mechanisms of character displacement because they differ in duration in sympatry. Specifically, because they occur at the edge of a range expansion, populations of S. bombifrons have been exposed to S. multiplicata for a longer period. Consequently, S. bombifrons have likely had more time to accumulate genetic changes that promote character displacement. Generally, character displacement may often progress through an initial phase in which trait differences are environmentally induced to one in which they are constitutively expressed. [source] LATITUDINAL VARIATION IN SPECIATION MECHANISMS IN FROGSEVOLUTION, Issue 2 2010Xia Hua Speciation often has a strong geographical and environmental component, but the ecological factors that potentially underlie allopatric and parapatric speciation remain understudied. Two ecological mechanisms by which speciation may occur on geographic scales are allopatric speciation through niche conservatism and parapatric or allopatric speciation through niche divergence. A previous study on salamanders found a strong latitudinal pattern in the prevalence of these mechanisms, with niche conservatism dominating in temperate regions and niche divergence dominating in the tropics, and related this pattern to Janzen's hypothesis of greater climatic zonation between different elevations in the tropics. Here, we test for latitudinal patterns in speciation in a related but more diverse group of amphibians, the anurans. Using data from up to 79 sister-species pairs, we test for latitudinal variation in elevational and climatic overlap between sister species, and evaluate the frequency of speciation via niche conservatism versus niche divergence in relation to latitude. In contrast to salamanders, we find no tendency for greater niche divergence in the tropics or for greater niche conservatism in temperate regions. Although our results support the idea of greater climatic zonation in tropical regions, they show that this climatic pattern does not lead to straightforward relationships between speciation, latitude, and niche evolution. [source] SEX-RATIO CONFLICT BETWEEN QUEENS AND WORKERS IN EUSOCIAL HYMENOPTERA: MECHANISMS, COSTS, AND THE EVOLUTION OF SPLIT COLONY SEX RATIOSEVOLUTION, Issue 12 2005Ken R. Helms Abstract Because workers in the eusocial Hymenoptera are more closely related to sisters than to brothers, theory predicts that natural selection should act on them to bias (change) sex allocation to favor reproductive females over males. However, selection should also act on queens to prevent worker bias. We use a simulation approach to analyze the coevolution of this conflict in colonies with single, once-mated queens. We assume that queens bias the primary (egg) sex ratio and workers bias the secondary (adult) sex ratio, both at some cost to colony productivity. Workers can bias either by eliminating males or by directly increasing female caste determination. Although variation among colonies in kin structure is absent, simulations often result in bimodal (split) colony sex ratios. This occurs because of the evolution of two alternative queen or two alternative worker biasing strategies, one that biases strongly and another that does not bias at all. Alternative strategies evolve because the mechanisms of biasing result in accelerating benefits per unit cost with increasing bias, resulting in greater fitness for strategies that bias more and bias less than the population equilibrium. Strategies biasing more gain from increased biasing efficiency whereas strategies biasing less gain from decreased biasing cost. Our study predicts that whether queens or workers evolve alternative strategies depends upon the mechanisms that workers use to bias the sex ratio, the relative cost of queen and worker biasing, and the rates at which queen and worker strategies evolve. Our study also predicts that population and colony level sex allocation, as well as colony productivity, will differ diagnostically according to whether queens or workers evolve alternative biasing strategies and according to what mechanism workers use to bias sex allocation. [source] POSTMATING SEXUAL SELECTION: ALLOPATRIC EVOLUTION OF SPERM COMPETITION MECHANISMS AND GENITAL MORPHOLOGY IN CALOPTERYGID DAMSELFLIES (INSECTA: ODONATA)EVOLUTION, Issue 2 2004A. Cordero Rivera Abstract Postmating sexual selection theory predicts that in allopatry reproductive traits diverge rapidly and that the resulting differentiation in these traits may lead to restrictions to gene flow between populations and, eventually, reproductive isolation. In this paper we explore the potential for this premise in a group of damselflies of the family Calopterygidae, in which postmating sexual mechanisms are especially well understood. Particularly, we tested if in allopatric populations the sperm competition mechanisms and genitalic traits involved in these mechanisms have indeed diverged as sexual selection theory predicts. We did so in two different steps. First, we compared the sperm competition mechanisms of two allopatric populations of Calopteryx haemorrhoidalis (one Italian population studied here and one Spanish population previously studied). Our results indicate that in both populations males are able to displace spermathecal sperm, but the mechanism used for sperm removal between both populations is strikingly different. In the Spanish population males seem to empty the spermathecae by stimulating females, whereas in the Italian population males physically remove sperm from the spermathecae. Both populations also exhibit differences in genital morphometry that explain the use of different mechanisms: the male lateral processes are narrower than the spermathecal ducts in the Italian population, which is the reverse in the Spanish population. The estimated degree of phenotypic differentiation between these populations based on the genitalic traits involved in sperm removal was much greater than the differentiation based on a set of other seven morphological variables, suggesting that strong directional postmating sexual selection is indeed the main evolutionary force behind the reproductive differentiation between the studied populations. In a second step, we examined if a similar pattern in genital morphometry emerge in allopatric populations of this and other three species of the same family (Calopteryx splendens, C. virgo and Hetaerina cruentata). Our results suggest that there is geographic variation in the sperm competition mechanisms in all four studied species. Furthermore, genitalic morphology was significantly divergent between populations within species even when different populations were using the same copulatory mechanism. These results can be explained by probable local coadaptation processes that have given rise to an ability or inability to reach and displace spermathecal sperm in different populations. This set of results provides the first direct evidence of intraspecific evolution of genitalic traits shaped by postmating sexual selection. [source] UNSTEADY STATE DISPERSION OF AIR POLLUTANTS UNDER THE EFFECTS OF DELAYED AND NONDELAYED REMOVAL MECHANISMSNATURAL RESOURCE MODELING, Issue 4 2009MANJU AGARWAL Abstract In this paper, we present a two-dimensional time-dependent mathematical model for studying the unsteady state dispersion of air pollutants emitted from an elevated line source in the atmosphere under the simultaneous effects of delayed (slow) and nondelayed (instantaneous) removal mechanisms. The wind speed and coefficient of diffusion are taken as functions of the vertical height above the ground. The deposition of pollutants on the absorptive ground and leakage into the atmosphere at the inversion layer are also included in the model by applying appropriate boundary conditions. The model is solved numerically by the fractional step method. The Lagrangian approach is used to solve the advection part, whereas the Eulerian finite difference scheme is applied to solve the part with the diffusion and removal processes. The solutions are analyzed to observe the effects of coexisting delayed and nondelayed removal mechanisms on overall dispersion. Comparison of delayed and nondelayed removal processes of equal capacity shows that the latter (nondelayed) process is more effective than the former (delayed removal) in the removal of pollutants from the atmosphere. [source] REVISITING INTERVIEW,COGNITIVE ABILITY RELATIONSHIPS: ATTENDING TO SPECIFIC RANGE RESTRICTION MECHANISMS IN META-ANALYSISPERSONNEL PSYCHOLOGY, Issue 4 2007CHRISTOPHER M. BERRY This study revisits the relationship between interviews and cognitive ability tests, finding lower magnitudes of correlation than have previous meta-analyses; a finding that has implications for both the construct and incremental validity of the interview. Our lower estimates of this relationship than previous meta-analyses were mainly due to (a) an updated set of studies, (b) exclusion of samples in which interviewers potentially had access to applicants' cognitive test scores, and (c) attention to specific range restriction mechanisms that allowed us to identify a sizable subset of studies for which range restriction could be accurately accounted. Moderator analysis results were similar to previous meta-analyses, but magnitudes of correlation were generally lower than in previous meta-analyses. Findings have implications for the construct and incremental validity of interviews, and meta-analytic methodology in general. [source] PATIENTS ARE A VIRTUE: WHAT STUDIES OF CLINICAL AND NEUROLOGICAL PATIENTS REVEAL ABOUT PHYSIOLOGICAL MECHANISMS OF EMOTIONPSYCHOPHYSIOLOGY, Issue 2008Article first published online: 12 AUG 200 No abstract is available for this article. [source] NEURAL MECHANISMS OF EMOTION ELICITATION AND REGULATIONPSYCHOPHYSIOLOGY, Issue S1 2005Article first published online: 15 AUG 200 No abstract is available for this article. [source] II,Naomi Eilan ON THE ROLE OF PERCEPTUAL CONSCIOUSNESS IN EXPLAINING THE GOALS AND MECHANISMS OF VISION: A CONVERGENCE ON ATTENTION?ARISTOTELIAN SOCIETY SUPPLEMENTARY VOLUME, Issue 1 2006Naomi Eilan ABSTRACT The strong sensorimotor account of perception gives self-induced movements two constitutive roles in explaining visual consciousness. The first says that self-induced movements are vehicles of visual awareness, and for this reason consciousness ,does not happen in the brain only'. The second says that the phenomenal nature of visual experiences is consists in the action-directing content of vision. In response I suggest, first, that the sense in which visual awareness is active should be explained by appeal to the role of attention in visual consciousness, rather than self-induced movements; and second, that the sense in which perceptual consciousness does not happen in the brain only should be explained by appeal to the relational nature of perceptual consciousness, appeal to which also shows why links with action cannot exhaust phenomenal content. [source] EOSINOPHIL APOPTOSIS: MECHANISMS and CLINICAL RELEVANCE IN ASTHMATIC and ALLERGIC INFLAMMATIONBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2000Garry M. Walsh First page of article [source] | |||||||||||||||||||||||||||||||||||||||||||||||||