Suchergebnisse

Elasticity of factor substitution is one of the key parameters of any computational general equilibrium model. Despite a wide use of this model in a policy analysis, there are a few estimates of the elasticity, with almost none for transition economies in Europe. To fill this gap, we estimate the elasticity of substitution between Capital, Labour, Energy and Material in the constant elasticity of substitution (CES) production function. We use a non-linear estimation technique to derive these elasticities for the whole economy and for five different sectors, for the EU as a whole and for its two sub-regions. We find that Cobb-Douglas and the Leontief production functions do not fit the data better than more flexible CES specification, and after evaluating several multiple KLEM nesting structures of the CES production function we conclude that KL-E and KL-EM nesting structures fit the data best in both EU regions and for the most economic sectors. The economy-wide factor substitution elasticity complies to the one reported in the literature, however, its magnitude varies across sectors, and it is much larger for the energy-intensive sectors. The elasticities also differ between the EU economies in the West and in the East, although their magnitude is converging in more recent years. We recommend a set of the specific elasticities to be used in the impact modelling and conclude that the estimates based on more recent data and that are region-specific should be used in CGE-based policy applications.

Mixture modeling has gained more attention among practitioners and statisticians in recent years. However, when researchers analyze their data using finite mixture model (FMM), some may assume that the units are independent of each other even though it may not always be the case. This article used simulation studies to examine the impact of ignoring a higher nesting structure in multilevel mixture models. Results indicate that the misspecification results in lower classification accuracy of individuals, less accurate fixed effect estimates, inflation of lower level variance estimates, and less accurate standard error estimates in each subpopulation, the latter result of which in turn affects the accuracy of tests of significance for the fixed effects. The magnitude of the intraclass correlation (ICC) coefficient has a substantial impact. The implication for applied researchers is that it is important to model the multilevel data structure in mixture modeling.

During the past decades a worldwide loss of biodiversity has been identified, and understanding the consequences for biotic interactions and associated ecosystem services has become a major focus. Ecosystem services of substantial importance are for example crop pollination, pest predation or parasitism. The Jena-Experiment, which is based on an experimental manipulation of plant species richness, offers a great opportunity to study the effects of plant diversity per se, because many confounding factors such as management or land-use intensity of descriptive field studies are excluded. We studied invasion success and performance of Centaurea jacea at different plant diversity levels. Further we focused on the effects of plant species richness, on flower visitors, trap-nesting Hymenoptera and plant-pollinator networks. The first part of the thesis describes the impact of plant species richness and plant functional group richness on the survival and performance on the transplanted phytometer species Centaurea jacea in two consecutive years. The survival of transplanted Centaurea jacea into an established plant community decreased with increasing richness of plant species and plant functional groups and in plots, where legume species were present ...

Context. Nest-site selection can influence nesting success, and thus population dynamics, of many species of ground-nesting birds. Despite the economic importance as a game species, populations of northern bobwhites have been declining throughout the southern United States. This paper reports the nesting ecology of northern bobwhites (Colinus virginianus) on Babcock-Webb Wildlife Management Area, Florida, USA, and illustrates the influence of landscape composition and structure on bobwhite nest-site selection and nest fate. Aim. To investigate nest-site selection by bobwhites, to evaluate the influence of landscape composition and structure on nest-site selection, and to identify factors influencing nesting success. Methods. We used distance-based habitat-selection methods and logistic regression to test for nest-site selection and to investigate the influence of landscape characteristics on nesting success. Key results. Bobwhites preferred to establish nests closer to food plots and farther away from water bodies than expected; other habitats were neither preferred nor avoided. Nesting success did not vary across years, differ among habitats or among burn treatments, and none of the habitat and landscape variables we measured significantly influenced the probability that a nest would be successful. Conclusions. Bobwhites preferred to place nests closer to food plots. However, habitat features of nest sites did not influence bobwhite nesting success. These results may indicate that random nest predation by meso-mammalian predators may currently determine fates of bobwhite nests in south Florida, or that population density is low enough that only suitable nesting sites are occupied. Implications. Our results suggest that increasing the density of linear food plots, and maintaining a structurally diverse pine–palmetto and dry prairie habitat that provides adequate nesting cover could contribute to augmenting bobwhite nesting habitat.

Studies of nesting ecology have proven to be extremely important for stingless bee conservation. These studies have rarely been conducted in urban landscapes, and even fewer have compared species diversity and abundances over time. We surveyed native stingless bee nests at the Federal University of Juiz de Fora campus in Minas Gerais, southeastern Brazil, from May 2008 to April 2009. We recorded the number of nests, nest height, species diversity, and nest substrate type (i.e., natural or artificial). We compared our results to those of a similar survey carried out in the same location eight years prior (2000/2001) in order to evaluate how urban expansion on campus has influenced the Meliponini bee community. Stingless bee abundance and richness were greater in the second survey. The use of natural substrates decreased, while the use of artificial substrates increased. This suggests that the increase in man-made structures on the UFJF campus has provided favorable sites for establishment of some stingless bee species.

We propose two complementary ways to deal with a nesting structure in the node set of a network—such a structure may be called a multilevel network, with a node set consisting of several groups. First, within‐group ties are distinguished from between‐group ties by considering them as two distinct but interrelated networks. Second, effects of nodal variables are differentiated according to the levels of the nesting structure, to prevent ecological fallacies. This is elaborated in a study of two repeated observations of a sociability network in seven villages in Senegal, analyzed using the Stochastic Actor‐oriented Model.

1 Preliminaries -- 1.1 The scope of this book -- 1.2 The anatomy of design -- 1.3 The conceptual stage -- 1.4 General aids to design -- 1.5 Combinative methods: tables of options -- 1.6 Repêchage and reviews -- 1.7 Recurrent problems in design -- 1.8 Combination and separation of functions -- 1.9 Summary -- 2 Structures -- 2.1 Introduction -- 2.2 Structural elements: rods, ties and struts -- 2.3 Beams -- 2.4 Plates -- 2.5 Torsion -- 2.6 Thin-walled pressure vessels -- 2.7 Contact stresses -- 2.8 An example: bathroom scales -- 2.9 Bathroom scales: refinements and details -- 2.10 Springs -- 2.11 Structures, springs, energy and stiffness: pertinacity -- 3 Abutments and Joints -- 3.1 Introduction -- 3.2 The form of abutments -- 3.3 Screwed fastenings -- 3.4 Joints -- 3.5 Stator blade fixing -- 3.6 Joint efficiency -- 3.7 Offset bolted joints: lugs -- 3.8 General principles applied to joint design -- 3.9 Register in joints: intersection problems -- 3.10 Alternating loads on bolted joints -- 3.11 Sealing -- 4 Freedom and Constraints: Bearings -- 4.1 Degrees of freedom -- 4.2 Shafts and bearings -- 4.3 The principle of least constraint: kinematic design -- 4.4 Epicyclic gears -- 4.5 Bearings -- 4.6 Hydrostatic bearings -- 4.7 Hydrodynamic bearings: squeeze action -- 4.8 Hydrodynamic bearings: wedge action -- 4.9 Rolling-element bearings -- 5 Various Principles -- 5.1 Insight and abstraction -- 5.2 Biasing -- 5.3 Force paths -- 5.4 A cylinder head joint -- 5.5 Bevel gear mounting -- 5.6 Gear pump -- 5.7 Nesting and stacking -- 5.8 Guiding principles for choosing nesting orders -- 5.9 Other aspects of nesting -- 5.10 Summary of guiding principles for nesting orders -- 5.11 Flexural elements -- 5.12 Easements -- 6 Materials and Manufacturing Methods -- 6.1 Introduction -- 6.2 Materials, manufacture and design philosophies -- 6.3 The effect of density -- 6.4 Choice of material -- 6.5 Figures of merit -- 6.6 The relation between form and manufacturing method -- 6.7 New materials and processes -- 6.8 Aids to material selection -- 7 Pneumatic Quarter-turn Actuators -- 7.1 Introduction -- 7.2 Fundamental considerations -- 7.3 Aspect ratio -- 7.4 Table of options -- 7.5 Studying a combination -- 7.6 Two good designs -- 7.7 Summary -- 8 Epicyclic Gears -- 8.1 The function of the planet carrier -- 8.2 Increasing the stiffness by asymmetry -- 8.3 Local form design -- 8.4 Joint location and design -- 8.5 'Alexandrian' solutions -- 8.6 The choice of embodiment -- 8.7 Another solution -- 8.8 Other aspects of epicyclic gearing -- 9 Hydraulic Pumps -- 9.1 The swash-plate pump -- 9.2 Valve plate design -- 9.3 Eliminating the valve plate -- 9.4 Virtues and limitations of the swash-plate pump -- 9.5 The bent-axis pump -- 9.6 An elegant bent-axis pump -- 9.7 Combining the virtues of swash-plate and bent-axis -- 10 Miscellaneous Examples -- 10.1 Connecting rods -- 10.2 A suitcase handle and a suspension arm -- 10.3 A window stay -- 10.4 The Challenger disaster -- 11 The Principles of Design -- 11.1 An emerging discipline -- 11.2 Least constraint and kinematic design -- 11.3 Separation and combination of functions -- 11.4 Design mating surfaces or abutments -- 11.5 Clarity of function -- 11.6 Short direct force-paths -- 11.7 Matching and disposition -- 11.8 Nesting order and related principles -- 11.9 Avoiding arbitrary decisions: combining good features.

Rotational grazing is being promoted by some land managers, government agencies, and conservation groups as superior to season-long grazing for improving pasture and cattle production, and for grassland bird conservation; however, the assumed benefits have not been comprehensively studied. In 2011 and 2012, I examined the effects of twice-over rotational grazing on the nesting success of grassland songbirds in southwestern Manitoba, Canada. I monitored nesting attempts and collected structural vegetation data for five species of obligate grassland bird (n=110) and one shrub-nesting species (n=41). Nesting analyses were conducted using logistic exposure models. Twice-over grazing had a significantly negative effect on the nesting success of the ground nesting species, including Savannah sparrows (Passerculus sandwichensis). Grazing system did not have an effect on vegetation structure. The results are consistent with other rotational grazing studies, and suggest that twice-over rotational grazing does not benefit grassland songbirds in mixed-grass prairie habitats. ; October 2016

Lesser prairie-chicken (Tympanuchus pallidicinctus) populations have declined since the 1980s. Understanding factors influencing nest-site selection and nest survival are important for conservation and management of lesser prairie-chicken populations. However, >75% of the extant population is in the northern extent of the range where data on breeding season ecology are lacking. We tested factors influencing fine-scale and regional nest-site selection and nest survival across the northern portion of the lesser prairie-chicken range. We trapped and affixed satellite global positioning system and very high frequency transmitters to female lesser prairie-chickens (n = 307) in south-central and western Kansas and eastern Colorado, USA. We located and monitored 257 lesser prairie-chicken nests from 2013 to 2016. We evaluated nest-site selection and nest survival in comparison to vegetation composition and structure. Overall, nest-site selection in relation to vegetation characteristics was similar across our study area. Lesser prairie-chickens selected nest microsites with 75% visual obstruction 2.0-3.5 dm tall and 95.7% of all nests were in habitat with >= 1 dm and <= 4 dm visual obstruction. Nests were located in areas with 6-8% bare ground, on average, avoiding areas with greater percent cover of bare ground. The type of vegetation present was less important than cover of adequate height. Nest survival was maximized when 75% visual obstruction was 2.0-4.0 dm. Nest survival did not vary spatially or among years and generally increased as intensity of drought decreased throughout the study although not significantly. To provide nesting cover considering yearly variation in drought conditions, it is important to maintain residual cover by managing for structural heterogeneity of vegetation. Managing for structural heterogeneity could be accomplished by maintaining or strategically applying practices of the Conservation Reserve Program, using appropriate fire and grazing disturbances in native working grasslands, and establishing site-specific monitoring of vegetation composition and structure. (c) 2018 The Wildlife Society. ; Kansas Wildlife, Parks, and Tourism [KS W-73-R-3]; United States Department of Agriculture (USDA) Farm Services CRP Monitoring, Assessment, and Evaluation [7, KSCFWRU RWO 62]; USDA Natural Resources Conservation Service, Lesser Prairie-Chicken Initiative ; Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the United States Government. We thank the private landowners for allowing us to access their land to conduct this research and all of the technicians who assisted with this research. We thank J. L. Kramer, M. W. Mitchener, J. A. Prendergast, P. G. Kramos, A. A. Flanders, J. H. Reitz, D. K. Dahlgren, and B. S. T. Hyberg for their assistance with the project. B. K. Sandercock, W. A. Boyle, C. Nichols, B. A. Grisham, the Associate Editor, and an anonymous reviewer provided helpful comments on earlier drafts of this manuscript. We appreciate the assistance from M. R. Bain and Smoky Valley Ranch of The Nature Conservancy. Funding for the project was provided by Kansas Wildlife, Parks, and Tourism (Federal Assistance Grant KS W-73-R-3); United States Department of Agriculture (USDA) Farm Services CRP Monitoring, Assessment, and Evaluation (12-IA-MRE CRP TA#7, KSCFWRU RWO 62); and USDA Natural Resources Conservation Service, Lesser Prairie-Chicken Initiative. ; Public domain authored by a U.S. government employee

Social wasps use different substrates for nesting, such as plants, rocks, and human buildings, and may adopt different strategies to protect their colony and brood. Here, we report the nesting behavior of Polistes versicolor in the deciduous forest, Northern Minas Gerais state, Brazil. The occurrences were recorded during fieldwork from February to December 2021. We found 30 colonies in eight plant species. The statistics demonstrate a preference of this social wasp for the plant Cereus jamacaru Cactaceae, which is used for nestings over a large area. Also, we report the first known record of P. versicolor colonies on the Acacia plumosa, Commiphora leptophloeos, Quiabentia zehntneri, and Ziziphus joazeiro, all of them with thorns. From the preference of P. versicolor for plants with thorns, we conclude this study to reinforce the role of these vegetal structures in protecting the colonies.

Population models proposed as a result of independent tagging programs of nesting Caretta caretta in
Queensland are in disagreement about the size of discrete breeding units. An electrophoretic survey was
conducted to assess the relevance of genetic variation as revealed by electrophoresis to the investigation
of Caretta caretta population breeding structure. Low level electrophoretic variability (H*L(obs) = 0.016)
was found. The geographical distribution of alleles, when compared with tag-recapture data and other
aspects of life history, indicated that discrete breeding populations of C. caretta in Queensland are
larger than previously thought. C. caretta nesting on the mainland beaches and on the cays of the
Capricornia Section of the Great Barrier Reef Marine Park form a panmictic population. The data
indicate that those nesting on the Swain Reefs cays do not interbreed with the mainland-Capricornia
breeding population.