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Strong Effects (strong + effects)
Selected AbstractsPolitical Partisanship, Voting Abstention and Higher Education: Changing Preferences in a British Youth Cohort in the 1990sHIGHER EDUCATION QUARTERLY, Issue 2 2002Muriel EgertonArticle first published online: 16 DEC 200 This paper focuses on the relationship between education and political partisanship, using the British Household Panel Study (1991,1999). It is known that partisanship has been falling in Britain since the mid,1950s. However, voting abstention rose only gradually until the June 2001 election where the turnout (at 59 per cent) was the lowest since 1918. Partisanship also fell sharply during the 1990s. Although social class and education are associated with turnout in the USA, no relationship has been reported in the UK, and voting seems to have been perceived as a citizen duty. However, in the light of recent changes in voting patterns and educational participation, this paper investigates the role of education, contextualising education effects in social class and gender effects. The preferences of young people are observed in their late teens, before entering the labour market or higher education, and are compared with those of the same young people in their early 20s, after completing higher education courses or gaining labour market experience. The BHPS yielded a sample of about 500 young people with the required data over the time period. It was hypothesised that dissatisfaction with government performance would take different forms for the more and the less educated, with the more educated shifting preferences to minority parties while the less educated shift preferences to voting abstention. The hypothesis was confirmed for young men. Endorsement of abstention was very high for adolescent women who also seemed to be more influenced by their family's social class. However, by early adulthood a lower proportion of young women endorsed abstention than young men. Strong effects of education were still found with more highly educated young women (as with more highly educated young men) being more likely to have party preferences. [source] Incentives for pollution abatement: Regulation, regulatory threats, and non-governmental pressuresJOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 3 2003Kathryn Harrison In the last decade, voluntary efforts by firms to reduce their environmental impacts have received increasing attention from both policymakers and scholars. This article discusses polluters' incentives to reduce their releases. In particular, using data from Canada's National Pollutant Release Inventory, it examines the impacts of conventional regulation, threats of regulation, and non-governmental pressures facilitated by public dissemination of information about pollutant releases. The vast majority of reductions reported to the inventory to date were found not to be voluntary, as has often been assumed, but are, rather, the result of direct regulation of a relatively small number of polluters. Strong effects of federal regulation were found among other sources, as well, with much weaker responses to the mere threat of regulation. However, of concern are the growth of less visible waste streams,such as land disposal and underground injection,as well as transfers of wastes to other communities. Finally, evidence is reported that some waste streams are increasing in toxicity, an effect that may outweigh the benefits of reductions in releases. © 2003 by the Association for Public Policy Analysis and Management. [source] National Culture and the Composition and Leadership Structure of Boards of DirectorsCORPORATE GOVERNANCE, Issue 5 2008Jiatao Li ABSTRACT Manuscript Type: Empirical Research Question/Issue: How and to what extent does national culture influence the composition and leadership structure of the boards of directors of multinational firms? Research Findings/Insights: Societal norms about corporate structure are treated as components of national culture. Hofstede's measures of national culture were shown to predict the board composition and leadership structure of firms based in that culture. The hypotheses were tested with data on 399 multinational manufacturing firms based in 15 industrial countries. The results suggest that national culture can have strong effects on corporate governance and should be considered in any transnational study. Theoretical/Academic Implications: The predictive accuracy of the culture variables provides strong support for the argument that norms embedded in a society's culture affect organizational structure, at least at the board level. The results of the study contribute to our understanding of institutional theory in explaining observed variations in corporate board composition and leadership structure across countries. By linking board composition to the cultural environment, institutional theory provides an explicit framework for analyzing variations in board structure across national boundaries. Practitioner/Policy Implications: When considering board composition and leadership structure, it is important to consider national culture norms. The findings of the study also have important implications for multinational firms setting up boards for their subsidiaries in different countries. [source] Effects of retinoic acid upon eye field morphogenesis and differentiationDEVELOPMENTAL DYNAMICS, Issue 3 2001Gerald W. Eagleson Abstract This study describes a whole embryo and embryonic field analysis of retinoic acid's (RA) effects upon Xenopus laevis forebrain development and differentiation. By using in situ and immunohistochemical analysis of pax6, Xbf1, and tyrosine hydroxylase (TH), gene expression during eye field, telencephalon field, and retinal development was followed with and without RA treatment. These studies indicated that RA has strong effects upon embryonic eye and telencephalon field development with greater effects upon the ventral development of these organ fields. The specification and determination of separate eye primordia occurred at stage-16 when the prechordal plate reaches its most anterior aspect in Xenopus laevis. Differentiation of the dopaminergic cells within the retina was also affected in a distinct dorsoventral pattern by RA treatment, and cell type differentiation in the absence of distinct retinal laminae was also observed. It was concluded that early RA treatments affected organ field patterning by suppression of the upstream elements required for organ field development, and RA's effects upon cellular differentiation occur downstream to these organ determinants' expression within a distinct dorsoventral pattern. © 2001 Wiley-Liss, Inc. [source] The power of time: spatiotemporal scaling of species diversityECOLOGY LETTERS, Issue 8 2003Peter B. Adler Abstract The species,area relationship (SAR) provides the foundation for much of theoretical ecology and conservation practice. However, by ignoring time the SAR offers an incomplete model for biodiversity dynamics. We used long-term data from permanent plots in Kansas grasslands, USA, to show that the increase in the number of species found with increasing periods of observation takes the same power-law form as the SAR. A statistical model including time, area, and their interaction explains 98% of variation in mean species number and demonstrates that while the effect of time depends on area, and vice versa, time has strong effects on species number even at relatively broad spatial scales. Our results suggest equivalence of underlying processes in space and time and raise questions about the diversity estimates currently used by basic researchers and conservation practitioners. [source] Do Peer Groups Matter?ECONOMICA, Issue 277 2003Peer Group versus Schooling Effects on Academic Attainment This paper estimates an educational production function. Educational attainment is a function of peer group, parental input and schooling. Conventional measures of school quality are not good predictors for academic attainment, once we control for peer group effects; parental qualities also have strong effects on academic attainment. This academic attainment is a then a key determinant of subsequent labour market success, as measured by earnings. The main methodological innovation in this paper is the nomination of a set of instruments, very broad regions of birth, which, as a whole, pass close scrutiny for validity and permit unbiased estimation of the production function. [source] Influence of smoking cues in movies on craving among smokersADDICTION, Issue 12 2009Kirsten Lochbuehler ABSTRACT Aims Research has shown that smoking-related cues are important triggers for craving. The objective of the present study was to test whether smoking cues in movies also function as triggers to evoke craving. To accomplish this, we conducted a pilot study in which we examined smokers' reactivity to smoking cues from a particular movie in a common cue,reactivity paradigm using pictures. In the main study, we tested whether smokers who are confronted with smoking characters in a movie segment have a greater desire to smoke than smokers confronted with non-smoking characters. Design Using an experimental design, participants were assigned randomly to one of two movie conditions (smoking versus non-smoking characters). Setting In a laboratory, that reflected a naturalistic setting, participants watched a 41-minute movie segment. Participants A total of 65 young adults who smoked on a daily basis participated in the experiment. Measurements Craving was assessed before and after watching the movie. Findings The pilot study revealed that pictures of smoking characters had strong effects on craving. However, when smokers actually watched a movie segment, no differences in craving were found between those who watched smoking characters and those who watched non-smoking characters. This finding was not affected by baseline craving, the time of the last cigarette smoked and daily smoking habits. Conclusions No effect of smoking cues in movies on craving was found, in contrast with research supporting the cue-craving link. Thus, if replicated, this might indicate that smoking cues in such contexts do not affect smokers' desire to smoke as expected. [source] Genotoxicity of nitrosulfonic acids, nitrobenzoic acids, and nitrobenzylalcohols, pollutants commonly found in ground water near ammunition facilitiesENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2006Tamara Grummt Abstract 2-Amino-4,6-dinitrobenzoic acid (2-A-4,6-DNBA), 4-amino-2,6-dinitrobenzoic acid (4-A-2,6-DNBA), 2,4,6-trinitrobenzoic acid (2,4,6-TNBA), 2-amino-4, 6-dinitrobenzylalcohol (2-A-4,6-DNBAlc), 4-amino-2,6-dinitrobenzylalcohol (4-A-2,6-DNBAlc), 2,4-dinitrotoluol-5-sulfonic acid (2,4-DNT-5-SA), 2,4-dinitrotoluol-3-sulfonic acid (2,4-DNT-3-SA), and 2, 4-dinitrobenzoic acid (2,4-DNBA) are derivatives of nitro-explosives that have been detected in groundwater close to munitions facilities. In the present study, the genotoxicity of these compounds was evaluated in Salmonella/microsome assays (in strains TA100 and TA98, with and without S9 and in TA98NR without S9), in chromosomal aberration (CA) tests with Chinese hamster fibroblasts (V79), and in micronucleus (MN) assays with human hepatoma (HepG2) cells. All compounds except the sulfonic acids were positive in the bacterial mutagenicity tests, with 2,4,6-TNBA producing the strongest response (8023 revertants/,mol in TA98 without S9 activation). 2-A-4,6-DNBA was a direct acting mutagen in TA98, but negative in TA100. The other positive compounds were ,1,3 orders of magnitude less mutagenic than 2,4,6-TNBA in TA98 and in TA100; relatively strong effects (,50,400 revertants/,mol) were produced by the benzylacohols in the two indicator strains. With the exception of 2,4-DNBA, the mutagenic responses were lower in the nitroreductase-deficient strain TA98NR than in the parental strain. 2,4-DNBA produced a marginally positive response in the V79-cell CA assay; the other substances were devoid of activity. Only the benzoic acids were tested for MN induction in HepG2 cells, and all produced positive responses. As in the bacterial assays, the strongest effect was seen with 2,4,6-TNBA (significant induction at ,1.9 ,M). 4-A-2,6-DNBA was positive at 432 ,M; the weakest effect was observed with 2,4,-DNBA (positive at ,920 ,M). The differences in the sensitivity of the indicator cells to these agents can be explained by differences in the activities of enzymes involved in the activation of the compounds. The strong responses produced by some of the compounds in the human-derived cells suggest that environmental exposure to these breakdown products of nitro-explosives may pose a cancer risk in man. Environ. Mol. Mutagen., 2006. © 2005 Wiley-Liss, Inc. [source] Effects of temperature and food quality on anuran larval growth and metamorphosisFUNCTIONAL ECOLOGY, Issue 5 2002D. Álvarez Summary 1Anurans exhibit high levels of growth-mediated phenotypic plasticity in age and size at metamorphosis. Although temperature and food quality exert a strong influence on larval growth, little is known about the interacting effects of these factors on age and size at metamorphosis. 2Plasticity in growth rates, maximum larval mass, mass loss, larval period and size at metamorphosis was examined in Iberian Painted Frogs (Discoglossus galganoi Capula, Nascetti, Lanza, Bullini & Crespo 1985) under different combinations of temperature and diet quality. 3Temperature and diet had strong effects on the maximum size reached by tadpoles throughout the premetamorphic stages. Larval body mass varied inversely with temperature. The effect of diet depended on temperature; larvae fed on a ,carnivorous' diet (rich in protein and lipids) achieved a larger size than larvae offered an ,herbivorous' diet (rich in carbohydrates) at 17 °C but not at 12 or 22 °C. 4Larval period was insensitive to diet composition, and varied only with temperature. Primarily the interacting effects of food quality and temperature affected size at metamorphosis. Size at metamorphosis varied inversely with temperature under the plant- and the animal-based diets. However, the carnivorous diet resulted in bigger metamorphs at 17 and 22 °C, but did not influence final mass at 12 °C. Maximum size over the larval period explained most of the variation in mass loss after the premetamorphic growing phase. [source] Simple estimates of haplotype relative risks in case-control dataGENETIC EPIDEMIOLOGY, Issue 6 2006Benjamin French Abstract Methods of varying complexity have been proposed to efficiently estimate haplotype relative risks in case-control data. Our goal was to compare methods that estimate associations between disease conditions and common haplotypes in large case-control studies such that haplotype imputation is done once as a simple data-processing step. We performed a simulation study based on haplotype frequencies for two renin-angiotensin system genes. The iterative and noniterative methods we compared involved fitting a weighted logistic regression, but differed in how the probability weights were specified. We also quantified the amount of ambiguity in the simulated genes. For one gene, there was essentially no uncertainty in the imputed diplotypes and every method performed well. For the other, ,60% of individuals had an unambiguous diplotype, and ,90% had a highest posterior probability greater than 0.75. For this gene, all methods performed well under no genetic effects, moderate effects, and strong effects tagged by a single nucleotide polymorphism (SNP). Noniterative methods produced biased estimates under strong effects not tagged by an SNP. For the most likely diplotype, median bias of the log-relative risks ranged between ,0.49 and 0.22 over all haplotypes. For all possible diplotypes, median bias ranged between ,0.73 and 0.08. Results were similar under interaction with a binary covariate. Noniterative weighted logistic regression provides valid tests for genetic associations and reliable estimates of modest effects of common haplotypes, and can be implemented in standard software. The potential for phase ambiguity does not necessarily imply uncertainty in imputed diplotypes, especially in large studies of common haplotypes. Genet. Epidemiol. 2006. © 2006 Wiley-Liss, Inc. [source] Effects of soil frost on soil respiration and its radiocarbon signature in a Norway spruce forest soilGLOBAL CHANGE BIOLOGY, Issue 4 2009JAN MUHR Abstract Apart from a general increase of mean annual air temperature, climate models predict a regional increase of the frequency and intensity of soil frost with possibly strong effects on C cycling of soils. In this study, we induced mild soil frost (up to ,5 °C in a depth of 5 cm below surface) in a Norway spruce forest soil by removing the natural snow cover in the winter of 2005/2006. Soil frost lasted from January to April 2006 and was detected down to 15 cm depth. Soil frost effectively reduced soil respiration in the snow removal plots in comparison to undisturbed control plots. On an annual basis 6.2 t C ha,1 a,1 were emitted in the control plots compared with 5.1 t C ha,1 a,1 in the snow removal plots. Only 14% of this difference was attributed to reduced soil respiration during the soil frost period itself, whereas 63% of this difference originated from differences during the summer of 2006. Radiocarbon (,14C) signature of CO2 revealed a considerable reduction of heterotrophic respiration on the snow removal plots, only partly compensated for by a slight increase of rhizosphere respiration. Similar CO2 concentrations in the uppermost mineral horizons of both treatments indicate that differences between the treatments originated from the organic horizons. Extremely low water contents between June and October of 2006 may have inhibited the recovery of the heterotrophic organisms from the frost period, thereby enhancing the differences between the control and snow removal plots. We conclude that soil frost triggered a change in the composition of the microbial community, leading to an increased sensitivity of heterotrophic respiration to summer drought. A CO2 pulse during thawing, such as described for arable soils several times throughout the literature, with the potential to partly compensate for reduced soil respiration during soil frost, appears to be lacking for this soil. Our results from this experiment indicate that soil frost reduces C emission from forest soils, whereas mild winters may enhance C losses from forest soils. [source] Fifteen years of climate change manipulations alter soil microbial communities in a subarctic heath ecosystemGLOBAL CHANGE BIOLOGY, Issue 1 2007RIIKKA RINNAN Abstract Soil microbial biomass in arctic heaths has been shown to be largely unaffected by treatments simulating climate change with temperature, nutrient and light manipulations. Here, we demonstrate that more than 10 years is needed for development of significant responses, and that changes in microbial biomass are accompanied with strong alterations in microbial community composition. In contrast to slight or nonsignificant responses after 5, 6 and 10 treatment years, 15 years of inorganic NPK fertilizer addition to a subarctic heath had strong effects on the microbial community and, as observed for the first time, warming and shading also led to significant responses, often in opposite direction to the fertilization responses. The effects were clearer in the top 5 cm soil than at the 5,10 cm depth. Fertilization increased microbial biomass C and more than doubled microbial biomass P compared to the non-fertilized plots. However, it only increased microbial biomass N at the 5,10 cm depth. Fertilization increased fungal biomass and the relative abundance of phospholipid fatty acid (PLFA) markers of gram-positive bacteria. Warming and shading decreased the relative abundance of fungal PLFAs, and shading also altered the composition of the bacterial community. The long time lag in responses may be associated with indirect effects of the gradual changes in the plant biomass and community composition. The contrasting responses to warming and fertilization treatments show that results from fertilizer addition may not be similar to the effects of increased nutrient mineralization and availability following climatic warming. [source] The effects of exercise and stress on the survival and maturation of adult-generated granule cells,HIPPOCAMPUS, Issue 10 2009Jason S. Snyder Abstract Stress strongly inhibits proliferation of granule cell precursors in the adult dentate gyrus, whereas voluntary running has the opposite effect. Few studies, however, have examined the possible effects of these environmental manipulations on the maturation and survival of young granule cells. We examined the number of surviving granule cells and the proportion of young neurons that were functionally mature, as defined by seizure-induced immediate-early gene (IEG) expression, in 14- and 21-day-old granule cells in mice that were given access to a running wheel, restrained daily for 2 h, or given no treatment during this period. Treatments began 2 days after BrdU injection, to isolate effects on survival from those on cell proliferation. We found a large increase in granule cell survival in running mice when compared with controls at both time points. In addition, running increased the proportion of granule cells expressing the IEG Arc in response to seizures, suggesting that it speeds incorporation into circuits, i.e., functional maturation. Stressed mice showed no change in Arc expression, compared with control animals, but, surprisingly, showed a transient increase in survival of 14-day-old granule cells, which was gone 7 days later. Examination of cell proliferation, using the endogenous mitotic marker PCNA showed an increase in cell proliferation after 12 days of running but not after 19 days of running. The number of proliferating cells was unchanged 24 h after the 12th or 19th episode of daily restraint stress. These findings demonstrate that running has strong effects on survival and maturation of young granule cells as well as their birth and that stress can have positive but short-lived effects on granule cell survival. Published 2009 Wiley-Liss, Inc. [source] Performance and exergetic analysis of vapor compression refrigeration system with an internal heat exchanger using a hydrocarbon, isobutane (R600a)INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2008Ahmet Kabul Abstract Hydrocarbons (HCs) are excellent refrigerants in many ways such as energy efficiency, critical point, solubility, transport and heat transfer properties, but they are also flammable, which causes the need for changes in standards, production and product. There are increasing number of scientists and engineers who believe that an alternative solution, which has been overlooked, may be provided by using HCs. The main objective of this study is to perform energy and exergy analyses for a vapor compression refrigeration system with an internal heat exchanger using a HC, isobutene (R600a). For a refrigeration capacity of 1 kW and cold chamber temperature of 0°C, energy and exergy balances are taken into account to determine the performance of the refrigeration system. Energy and exergy fluxes are determined, and irreversibility rates are calculated for every component of the system. It is seen that the compressor has the highest irreversibility rate, and the heat exchanger has the lowest. Also from the result of the analysis, it is found that condenser and evaporator temperatures have strong effects on energetic and exergetic performances of the system such as coefficient of performance (COP), efficiency ratio (,), exergetic efficiency (,) and irreversibility rate. Copyright © 2008 John Wiley & Sons, Ltd. [source] Thermodynamic analysis of subcooling and superheating effects of alternative refrigerants for vapour compression refrigeration cyclesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2006encan Abstract This paper presents a computer-based first law and exergy analysis applied to vapour compression refrigeration systems for determining subcooling and superheating effects of environmentally safe new refrigerants. Three refrigerants are considered: R134a, R407c and R410a. It is found that subcooling and superheating temperatures directly influence the system performance as both condenser and evaporator temperatures are affected. The thermodynamic properties of the refrigerants are formulated using artificial neural network (ANN) methodology. Six ANNs were trained to predict various properties of the three refrigerants. The training and validation of the ANNs were performed with good accuracy. The correlation coefficient obtained when unknown data were used to the networks were found to be equal or very near to 1 which is very satisfactory. Additionally, the present methodology proved to be much better than the linear multiple regression analysis. From the analysis of the results it is found that condenser and evaporator temperatures have strong effects on coefficient of performance (COP) and system irreversibility. Also both subcooling and superheating affect the system performance. This effect is similar for R134a and R407c, and different for R410a. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effects of predatory ants on lower trophic levels across a gradient of coffee management complexityJOURNAL OF ANIMAL ECOLOGY, Issue 3 2008S. M. Philpott Summary 1Ants are important predators in agricultural systems, and have complex and often strong effects on lower trophic levels. Agricultural intensification reduces habitat complexity, food web diversity and structure, and affects predator communities. Theory predicts that strong top-down cascades are less likely to occur as habitat and food web complexity decrease. 2To examine relationships between habitat complexity and predator effects, we excluded ants from coffee plants in coffee agroecosystems varying in vegetation complexity. Specifically, we studied the effects of eliminating ants on arthropod assemblages, herbivory, damage by the coffee berry borer and coffee yields in four sites differing in management intensification. We also sampled ant assemblages in each management type to see whether changes in ant assemblages relate to any observed changes in top-down effects. 3Removing ants did not change total arthropod densities, herbivory, coffee berry borer damage or coffee yields. Ants did affect densities of some arthropod orders, but did not affect densities of different feeding groups. The effects of ants on lower trophic levels did not change with coffee management intensity. 4Diversity and activity of ants on experimental plants did not change with coffee intensification, but the ant species composition differed. 5Although variation in habitat complexity may affect trophic cascades, manipulating predatory ants across a range of coffee agroecosystems varying in management intensity did not result in differing effects on arthropod assemblages, herbivory, coffee berry borer attack or coffee yields. Thus, there is no clear pattern that top-down effects of ants in coffee agroecosystems intensify or dampen with decreased habitat complexity. [source] The role of trout in stream food webs: integrating evidence from field surveys and experimentsJOURNAL OF ANIMAL ECOLOGY, Issue 2 2006KRISTIAN MEISSNER Summary 1We evaluated the effects of brown trout on boreal stream food webs using field surveys and enclosure/exclosure experiments. Experimental results were related to prey preference of uncaged trout in the same stream, as well as to a survey of macroinvertebrate densities in streams with vs. without trout. Finally, we assessed the generality of our findings by examining salmonid predation on three groups of macroinvertebrate prey (chironomid midges, epibenthic grazers, invertebrate predators) in a meta-analysis. 2In a preliminary experiment, invertebrate predators showed a strong negative response to trout, whereas chironomids benefited from trout presence. In the main experiment, trout impact increased with prey size. Trout had the strongest effect on invertebrate predators and cased caddis larvae, whereas Baetis mayfly and chironomid larvae were unaffected. Trout impact on the largest prey seemed mainly consumptive, because prey emigration rates were low and independent of fish presence. Despite strong effects on macroinvertebrates, trout did not induce a trophic cascade on periphyton. Uncaged trout showed a strong preference for the largest prey items (predatory invertebrates and aerial prey), whereas Baetis mayflies and chironomids were avoided by trout. 3Densities of invertebrate predators were significantly higher in troutless streams. Baetis mayflies also were less abundant in trout streams, whereas densities of chironomids were positively, although non-significantly, related to trout presence. Meta-analysis showed a strong negative impact of trout on invertebrate predators, a negative but variable impact on mobile grazers (mainly mayfly larvae) and a slightly positive impact on chironomid larvae. 4Being size-selective predators, salmonid fishes have a strong impact on the largest prey types available, and this effect spans several domains of scale. Discrepancies between our experimental findings and those from the field survey and meta-analysis show, however, that for most lotic prey, small-scale experiments do not reflect fish impact reliably at stream-wide scales. 5Our findings suggest that small-scale experiments will be useful only if the experimental results are evaluated carefully against natural history information about the experimental system and interacting species across a wide array of spatial scales. [source] Density effects on life-history traits in a wild population of the great tit Parus major: analyses of long-term data with GIS techniquesJOURNAL OF ANIMAL ECOLOGY, Issue 2 2006TEDDY A. WILKIN Summary 1Population density often has strong effects on the population dynamics and reproductive processes of territorial animals. However, most estimates of density-dependent effects use the number of breeding pairs per unit area in a given season and look for correlations across seasons, a technique that assigns the same density score to each breeding pair, irrespective of local spatial variation. 2In this study, we employed GIS techniques to estimate individual breeding densities for great tits breeding in Wytham Woods UK, between 1965 and 1996. We then used linear mixed modelling to analyse the effect of density on reproductive processes. 3The areas of Thiessen polygons formed around occupied nestboxes were used to approximate territory size (necessarily inverse of breeding density). There were significant, independent and positive relationships between clutch size, fledging mass and the number of offspring recruited to the population, and territory size (all P < 0·001), but no effect of territory size on lay-date or egg mass. 4Thiessen polygons are contiguous and cover all of the available area. Therefore, at low nest densities territory polygons were excessively oversized. Using a novel procedure to address this limitation, territory sizes were systematically capped through a range of maxima, with the greatest effect in the models when territories were capped at 0·9,2·3 ha. This figure approximates to the maximum effective territory size in our population and is in close agreement with several field-based studies. This capping refinement also revealed a significant negative relationship between lay-date and territory size capped at 0·9 ha (P < 0·001). 5These density-dependent effects were also detected when analyses were restricted to changes within individual females, suggesting that density effects do not merely result from either increased proportions of low-quality individuals, or increased occupation of poor sites, when population density is high. 6Overall, these results suggest that, in the current population, great tits with territories smaller than c. 2 ha independently lay smaller and later clutches, have lighter fledglings, and recruit fewer offspring to the breeding population. These analyses thus suggest a pervasive and causal role of local population density in explaining individual reproductive processes. [source] Numerical fluctuations in the northern short-tailed shrew: evidence of non-linear feedback signatures on population dynamics and demographyJOURNAL OF ANIMAL ECOLOGY, Issue 2 2002Mauricio Lima Summary 1,We studied a fluctuating population of the northern short-tailed shrew (Blarina brevicauda) in the Appalachian Plateau Province of Pennsylvania, USA, spanning 21 years of monitoring. We analysed the pattern of annual temporal variation fitting both time-series models and capture,mark,recapture (CMR) statistical models for survival and recruitment rates. 2,We determined that non-linear first-order models explain almost 80% of the variation in annual per capita population growth rates. In particular, a non-linear self-excited threshold autoregressive (SETAR) model describes the time-series data well. Average snowfall showed positive and non-linear effects on population dynamics. 3,The CMR statistical models showed that a non-linear threshold model with strong effects of population density was the best one to describe temporal variation in survival rates. On the other hand, population density or climatic variables did not explain temporal variation in recruitment rates. Survival rates were high during the study period. Weekly changes in population size attributable to new recruits entering in the population fluctuate between 21% and 0%, while the changes in population size related to survival fluctuate between 79% and 100%. 4,Two important results arise from this study. First, non-linear models with first-order feedback appear to capture the essential features of northern short-tailed shrew dynamics and demography. Secondly, climate effects represented by snowfall appear to be small and non-linear on this insectivore. The population dynamics of this shrew in the Appalachian Plateau are determined apparently by a strong non-linear first-order feedback process, which is related to survival rates. 5,This study links population dynamics and demography by detecting the underlying demographic mechanisms driving population dynamics. The feedback structure of this shrew suggests the existence of population dynamics dominated by intraspecific competitive interactions, such as aggression, solitary nesting, non-overlapping home ranges and territoriality. [source] Evidence that dingoes limit abundance of a mesopredator in eastern Australian forestsJOURNAL OF APPLIED ECOLOGY, Issue 3 2009Chris N. Johnson Summary 1Aggressive behaviour of top predators may have strong effects on the distribution and abundance of mesopredator species. Such interactions between predator species can reduce the intensity of predation on vulnerable prey. Suppression of mesopredators by top predators is a potentially important process that could protect small prey species from unsustainable predation. 2There is some evidence that in Australia, the dingo Canis lupus suppresses populations of the red fox Vulpes vulpes. This interaction could be significant to biodiversity conservation because while dingoes have been in Australia for several thousand years and coexist with a wide range of small mammals, the fox is a recent arrival which has caused declines and extinctions, and continues to threaten many prey species. 3However the strength of the effect of dingoes on foxes is unclear, and some published data have been interpreted as demonstrating no relationship between abundance of the two species. These data come from forested habitats in eastern Australia, and may suggest that negative relationships of dingoes and foxes do not occur in complex habitats. 4We re-analyse published data on fox vs. wild dog (i.e. dingoes plus, potentially, feral dogs and hybrids) abundance in eastern forests. These data reveal a triangular relationship of fox to wild dog density: when wild dogs are abundant, foxes are consistently rare, while when wild dogs are rare, foxes may be abundant but are not always so. This suggests that the abundance of wild dogs sets an upper limit on the abundance of foxes, but does not fully determine fox abundance. 5Standard regression and correlation methods are not appropriate for analysing such triangular relationships. We apply two statistical methods that can be used to characterize the edges of data distributions, and use these to demonstrate a negative relationship of maximum fox abundance to the abundance of wild dogs. 6Synthesis and applications. Our analysis adds to evidence that dingoes may have negative effects on red foxes in a wide range of habitats, and therefore, that dingoes may be significant to conservation of mammal biodiversity in Australia. It also illustrates problems and solutions in the statistical analysis of abundance of one species as a function of the abundance of another species with which it has a strong interaction. [source] Composition and distribution of vascular epiphytes in a tropical semideciduous forest, GhanaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Patrick Addo-Fordjour Abstract The composition and distribution of vascular epiphytes were studied in two 1-ha plots in the KNUST Botanic garden, Ghana. One-hectare plot each was randomly set up in secondary and cultivated forests for the identification and enumeration of trees and shrubs (,10 cm dbh), and epiphytes. Each tree was carefully examined, noting the presence, positions and life-forms of all epiphytes. Twenty-nine epiphyte (29) species belonging to fourteen genera and eleven families were identified in the study. These were hosted by 48 tree species and occurred in three life-forms: hemi-epiphytes (45%), casual epiphytes (45%) and true epiphytes (10%). The vascular epiphyte species made up 25.7% of all the identified plant species (excluding herbs and climbers) encountered. Host species (P < 0.001), habitat (P = 0.001) and their interaction (P < 0.001) had strong effects on epiphyte composition in the forests. Moraceae was the most dominant family (44.8%), while Nephrolepis undulata J. Sm. and N. biserrata (Sw.) Scott. were the commonest species of epiphytes. In terms of vertical distribution, most epiphytes were located on the trunk, while a few occurred in the canopy. Résumé On a étudié la composition et la distribution d'épiphytes vasculaires dans deux parcelles d'un hectare, dans le Jardin botanique de la KNUST, au Ghana. Chaque parcelle d'un hectare fut créée au hasard dans des forêts secondaire et cultivée pour y identifier et faire la liste des arbres et des arbustes (,10 cm dbh). Chaque arbre fut soigneusement examiné, et l'on a noté la présence, l'emplacement et les formes vivantes de tous les épiphytes. Vingt-neuf (29) espèces d'épiphytes appartenant à 14 genres et à 11 familles ont été identifiées au cours de cette étude. Elles croissaient sur 48 espèces d'arbres et se présentaient sous trois formes vivantes, hémi-épiphytes (45%), épiphytes opportunistes (45%) et épiphytes vrais (10%). Les espèces vasculaires d'épiphytes représentaient 25,7% de toutes les espèces végétales identifiées (à l'exclusion des herbacées et des plantes grimpantes). Les espèces hôtes (P < 0,001), l'habitat (P = 0,001) et leur interaction (P < 0,001) avaient un effet très net sur la composition des épiphytes dans les forêts. Les Moraceae étaient la famille dominante (44,8%) et Nephrolepis undulata J. Sm. et N. biserrata (Sw.) Scott étaient les espèces d'épiphytes les plus communes. En termes de distribution verticale, la plupart des épiphytes se situaient sur les troncs et quelques-uns croissaient dans la canopée. [source] Do egg size and parental care coevolve in fishes?JOURNAL OF FISH BIOLOGY, Issue 6 2005N. Kolm A phenomenon that has attracted a substantial theoretical and empirical interest is the positive relationship between egg size and the extent of parental care in fishes. Interestingly, despite the effort put into solving the causality behind this relationship over the past two decades it remains largely unsolved. Moreover, how general the positive relationship between egg size and parental care is among fishes is also poorly understood. In order to stimulate research exploring egg size and parental care variation in fishes, the potential selective forces from both natural and sexual selection on egg size and parental care are discussed. Recent empirical findings on how oxygen requirements and developmental times may differ between differently sized eggs are incorporated into a critical view of the current theory of this field. Furthermore, it is suggested that the up to now neglected effects of sexual selection, through both mate choice and sexual conflict, can have strong effects on the relationship between egg size and parental care in fishes. In light of the recent developments of comparative and experimental methods, future approaches that may improve the understanding of the relationship between egg size and care in fishes are suggested. [source] Relationship between achievement and students' acceptance of evolution or creation in an upper-level evolution courseJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 1 2006Ella L. Ingram Students often hold strong attitudes regarding topics they encounter during their studies, and many instructors feel that these attitudes can have strong effects on students' performance. We characterized students' attitudes toward evolution and investigated the influence of students' attitudes (pre-course and post-course) regarding evolution on their performance in an evolution course, measured as their final grade. We found our students to hold positive attitudes toward evolution; these attitudes became more positive following the course. The most significant change in attitude occurred in the group of students initially undecided toward evolution. We also found that attitudes prior to the course had little influence on later achievement; however, at the end of the course, students' attitudes were positively related to final grades, although the effect was small. We argue that pedagogical techniques directly addressing students' attitudes help reduce the influence of attitudes (especially prior attitudes) on achievement. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 43: 7,24, 2006 [source] Enhanced Visible-Light Photocatalytic Degradation of Humic Acid by Palladium-Modified Nitrogen-Doped Titanium OxideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Qi Li Palladium-modified nitrogen-doped titanium oxide (TiON/PdO) nanoparticles were synthesized by a sol,gel process, for visible-light-induced photocatalysis using humic acid (HA) as a target. Our work shows that palladium modification has strong effects on the optical and photocatalytic properties of nitrogen-doped titanium oxide (TiON) photocatalysts. TiON/PdO nanoparticles demonstrated an enhanced photocatalytic activity over TiON within a narrow range of palladium concentration. Beyond this range, the adverse effect of palladium modification was observed in the visible-light-induced degradation of HA. The effects of palladium modification are discussed in terms of its role in controlling electron,hole recombination. [source] Functional traits of woody plants: correspondence of species rankings between field adults and laboratory-grown seedlings?JOURNAL OF VEGETATION SCIENCE, Issue 3 2003J.H.C. Cornelissen Castroviejo et al. (1986,2000); Stace (1991) Abstract. Research into interspecific variation in functional traits is important for our understanding of trade-offs in plant design and function, for plant functional type classifications and for understanding ecosystem responses to shifts in species composition. Interspecific rankings of functional traits are a function of, among other factors, ontogenetic or allometric development and environmental effects on phenotypes. For woody plants, which attain large size and long lives, these factors might have strong effects on interspecific trait rankings. This paper is the first to test and compare the correspondence of interspecific rankings between laboratory grown seedlings and field grown adult plants for a wide range of functional leaf and stem traits. It employs data for 90 diverse woody and semiwoody species in a temperate British and a (sub)Mediterranean Spanish flora, all collected according to a strict protocol. For 12 out of 14 leaf and stem traits we found significant correlations between the species ranking in laboratory seedlings and field adults. For leaf size and maximum stem vessel diameter > 50 % of variation in field adults was explained by that in laboratory seedlings. Two important determinants of plant and ecosystem functioning, specific leaf area and leaf N content, had only 27 to 36 and 17 to 31 % of variation, respectively, in field adults explained by laboratory seedlings, owing to subsets of species with particular ecologies deviating from the general trend. In contrast, interspecific rankings for the same traits were strongly correlated between populations of field adults on different geological substrata. Extrapolation of interspecific trait rankings from laboratory seedlings to adult plants in the field, or vice versa, should be done with great caution. [source] Preparation and evaluation of vegetable oil derived biodiesel esters as lubricity additivesLUBRICATION SCIENCE, Issue 2 2001X. Lang Abstract Various vegetable-oil derived esters using methyl, ethyl, butyl, and 2-propyl alcohols were prepared and tested as diesel fuel lubricity additives in a roller-on-cylinder lubricity evaluator. At1% additive treat rate, the canola methyl and 2-propyl esters, the best-performing esters, increased the lubricity number of a reference fuel by 60%. Statistical analyses indicated strong effects of fatty acids and alcohols on the wear, friction, and lubricity number of the fuel. While no single fatty acid was identifiably responsible for the wear reduction, certain non-linoleic compounds correlated with the wear data in a semi-log relationship. The low-temperature behaviour of the biodiesel was studied using differential scanning calorimetry. The major transitional peak temperature of the biodiesel esters changed with the melting points of their primary fatty acids, and decreased with the lengthening and branching of the tail alkyl groups. [source] The role of hybridization in evolutionMOLECULAR ECOLOGY, Issue 3 2001N. H. Barton Abstract Hybridization may influence evolution in a variety of ways. If hybrids are less fit, the geographical range of ecologically divergent populations may be limited, and prezygotic reproductive isolation may be reinforced. If some hybrid genotypes are fitter than one or both parents, at least in some environments, then hybridization could make a positive contribution. Single alleles that are at an advantage in the alternative environment and genetic background will introgress readily, although such introgression may be hard to detect. ,Hybrid speciation', in which fit combinations of alleles are established, is more problematic; its likelihood depends on how divergent populations meet, and on the structure of epistasis. These issues are illustrated using Fisher's model of stabilizing selection on multiple traits, under which reproductive isolation evolves as a side-effect of adaptation in allopatry. This confirms a priori arguments that while recombinant hybrids are less fit on average, some gene combinations may be fitter than the parents, even in the parental environment. Fisher's model does predict heterosis in diploid F1s, asymmetric incompatibility in reciprocal backcrosses, and (when dominance is included) Haldane's Rule. However, heterosis arises only when traits are additive, whereas the latter two patterns require dominance. Moreover, because adaptation is via substitutions of small effect, Fisher's model does not generate the strong effects of single chromosome regions often observed in species crosses. [source] Mechanisms of resistance to invasion in a California grassland: the roles of competitor identity, resource availability, and environmental gradientsOIKOS, Issue 1 2007Meredith A. Thomsen Resistance to the invasion of exotic plants may sometimes result from the strong effects of a relatively small number of resident species. Understanding the mechanisms by which such species resist invasion could provide important insights for the management of invaded ecosystems. Furthermore, the individualistic responses of community members to resource availability and environmental gradients could drive spatial variation in resistance at the local to landscape scales. We tested the resistance of monoculture plots of three native perennial grasses from the California coastal prairie to the invasion of the European perennial grass Holcus lanatus. We also used a watering treatment that increased early summer water availability and a natural elevational gradient in resource availability and soil texture to evaluate how resident identity interacted with abiotic resistance to affect Holcus establishment. Two native species, Festuca rubra and Calamagrostis nutkaensis, exhibited strong resistance, correlated with their negative effects on light availability. A third native grass, Bromus carinatus var. maritimus, had either no effect or a weakly facultative effect on Holcus performance relative to bare plots. Water addition did not alter the resistance of these species, but the elevation gradient did. Holcus invasion increased with improving abiotic conditions towards the slope bottom in bare and Bromus plots, but invasion decreased towards the bottom in Calamagrostis plots, where better conditions favored competitive residents. These results support the idea that resistance to invasion can sometimes be due to a subset of native species, and that the resistance provided by even a single species is likely to vary across the landscape. Identifying the mechanisms by which species resist invasion could facilitate the selection of management strategies that at best increase, or at worst do not decrease, natural resistance. [source] Effects of CO2 and light on tree phytochemistry and insect performanceOIKOS, Issue 2 2000Jep Agrell Direct and interactive effects of CO2 and light on tree phytochemistry and insect fitness parameters were examined through experimental manipulations of plant growth conditions and performance of insect bioassays. Three species of deciduous trees (quaking aspen, Populus tremuloides; paper birch, Betula papyrifera; sugar maple, Acer saccharum) were grown under ambient (387±8 ,L/L) and elevated (696±2 ,L/L) levels of atmospheric CO2, with low and high light availability (375 and 855 ,mol×m,2×s,1 at solar noon). Effects on the population and individual performance of a generalist phytophagous insect, the white-marked tussock moth (Orgyia leucostigma) were evaluated. Caterpillars were reared on experimental trees for the duration of the larval stage, and complementary short-term (fourth instar) feeding trials were conducted with insects fed detached leaves. Phytochemical analyses demonstrated strong effects of both CO2 and light on all foliar nutritional variables (water, starch and nitrogen). For all species, enriched CO2 decreased water content and increased starch content, especially under high light conditions. High CO2 availability reduced levels of foliar nitrogen, but effects were species specific and most pronounced for high light aspen and birch. Analyses of secondary plant compounds revealed that levels of phenolic glycosides (salicortin and tremulacin) in aspen and condensed tannins in birch and maple were positively influenced by levels of both CO2 and light. In contrast, levels of condensed tannins in aspen were primarily affected by light, whereas levels of ellagitannins and gallotannins in maple responded to light and CO2, respectively. The long-term bioassays showed strong treatment effects on survival, development time, and pupal mass. In general, CO2 effects were pronounced in high light and decreased along the gradient aspen birch maple. For larvae reared on high light aspen, enriched CO2 resulted in 62% fewer survivors, with increased development time, and reduced pupal mass. For maple-fed insects, elevated CO2 levels had negative effects on survival and pupal mass in low light. For birch, the only negative CO2 effects were observed in high light, where female larvae showed prolonged development. Fourth instar feeding trials demonstrated that low food conversion efficiency reduced insect performance. Elevated levels of CO2 significantly reduced total consumption, especially by insects on high light aspen and low light maple. This research demonstrates that effects of CO2 on phytochemistry and insect performance can be strongly light-dependent, and that plant responses to these two environmental variables differ among species. Overall, increased CO2 availability appeared to increase the defensive capacity of early-successional species primarily under high light conditions, and of late-successional species under low light conditions. Due to the interactive effects of tree species, light, CO2, and herbivory, community composition of forests may change in the future. [source] Persistent Advantage or Disadvantage?: Evidence in Support of the Intergenerational Drag HypothesisAMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 2 2001William Darity By utilizing the Integrated Public Use Microdata Series (IPUMS) and a measure of occupational prestige (OCCSCORE) as a labor market outcome, the authors examine variations in the degree of labor market discrimination faced by several ethnic and racial groups in the United States between 1880 and 1990. Results demonstrate that the sharpest decline in labor market discrimination against blacks occurred between 1960 and 1980. For black males the extent of labor market discrimination was greater in all census years in IPUMS after 1880 until 1970, evidence contradicting the conventional expectation that market-based discrimination will decline progressively over time by dint of competitive pressure. Finally, after replicating George Borjas' "ethnic capital" exercise, the authors pool the 1880, 1900, and 1910 data to determine the relative magnitude of a group's gains and losses in occupational prestige due to group advantage or disadvantage in human capital endowments and due to favorable or unfavorable treatment (nepotism or discrimination) of those endowments in the labor market. The authors then examine statistically whether the group human capital advantage or disadvantage and group exposure to nepotism or discrimination at the turn of the century affects labor market outcomes for their descendants today. Results indicate strong effects of the past on present labor market outcomes. Hence, the essence of the study is the statistical demonstration that there are significant and detectable effects on current generations of the labor market experiences of their racial/ethnic ancestors. [source] | |||||||||||||||||||||||||||||||