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Sample records for landscape separating divergent

  1. Testing evolutionary hypotheses for phenotypic divergence using landscape genetics.

    PubMed

    Funk, W Chris; Murphy, Melanie A

    2010-02-01

    Understanding the evolutionary causes of phenotypic variation among populations has long been a central theme in evolutionary biology. Several factors can influence phenotypic divergence, including geographic isolation, genetic drift, divergent natural or sexual selection, and phenotypic plasticity. But the relative importance of these factors in generating phenotypic divergence in nature is still a tantalizing and unresolved problem in evolutionary biology. The origin and maintenance of phenotypic divergence is also at the root of many ongoing debates in evolutionary biology, such as the extent to which gene flow constrains adaptive divergence (Garant et al. 2007) and the relative importance of genetic drift, natural selection, and sexual selection in initiating reproductive isolation and speciation (Coyne & Orr 2004). In this issue, Wang & Summers (2010) test the causes of one of the most fantastic examples of phenotypic divergence in nature: colour pattern divergence among populations of the strawberry poison frog (Dendrobates pumilio) in Panama and Costa Rica (Fig. 1). This study provides a beautiful example of the use of the emerging field of landscape genetics to differentiate among hypotheses for phenotypic divergence. Using landscape genetic analyses, Wang & Summers were able to reject the hypotheses that colour pattern divergence is due to isolation-by-distance (IBD) or landscape resistance. Instead, the hypothesis left standing is that colour divergence is due to divergent selection, in turn driving reproductive isolation among populations with different colour morphs. More generally, this study provides a wonderful example of how the emerging field of landscape genetics, which has primarily been applied to questions in conservation and ecology, now plays an essential role in evolutionary research.

  2. Comparative Landscape Genetics of Three Closely Related Sympatric Hesperid Butterflies with Diverging Ecological Traits

    PubMed Central

    Engler, Jan O.; Balkenhol, Niko; Filz, Katharina J.; Habel, Jan C.; Rödder, Dennis

    2014-01-01

    To understand how landscape characteristics affect gene flow in species with diverging ecological traits, it is important to analyze taxonomically related sympatric species in the same landscape using identical methods. Here, we present such a comparative landscape genetic study involving three closely related Hesperid butterflies of the genus Thymelicus that represent a gradient of diverging ecological traits. We analyzed landscape effects on their gene flow by deriving inter-population connectivity estimates based on different species distribution models (SDMs), which were calculated from multiple landscape parameters. We then used SDM output maps to calculate circuit-theoretic connectivity estimates and statistically compared these estimates to actual genetic differentiation in each species. We based our inferences on two different analytical methods and two metrics of genetic differentiation. Results indicate that land use patterns influence population connectivity in the least mobile specialist T. acteon. In contrast, populations of the highly mobile generalist T. lineola were panmictic, lacking any landscape related effect on genetic differentiation. In the species with ecological traits in between those of the congeners, T. sylvestris, climate has a strong impact on inter-population connectivity. However, the relative importance of different landscape factors for connectivity varies when using different metrics of genetic differentiation in this species. Our results show that closely related species representing a gradient of ecological traits also show genetic structures and landscape genetic relationships that gradually change from a geographical macro- to micro-scale. Thus, the type and magnitude of landscape effects on gene flow can differ strongly even among closely related species inhabiting the same landscape, and depend on their relative degree of specialization. In addition, the use of different genetic differentiation metrics makes it possible to

  3. Comparative landscape genetics of three closely related sympatric Hesperid butterflies with diverging ecological traits.

    PubMed

    Engler, Jan O; Balkenhol, Niko; Filz, Katharina J; Habel, Jan C; Rödder, Dennis

    2014-01-01

    To understand how landscape characteristics affect gene flow in species with diverging ecological traits, it is important to analyze taxonomically related sympatric species in the same landscape using identical methods. Here, we present such a comparative landscape genetic study involving three closely related Hesperid butterflies of the genus Thymelicus that represent a gradient of diverging ecological traits. We analyzed landscape effects on their gene flow by deriving inter-population connectivity estimates based on different species distribution models (SDMs), which were calculated from multiple landscape parameters. We then used SDM output maps to calculate circuit-theoretic connectivity estimates and statistically compared these estimates to actual genetic differentiation in each species. We based our inferences on two different analytical methods and two metrics of genetic differentiation. Results indicate that land use patterns influence population connectivity in the least mobile specialist T. acteon. In contrast, populations of the highly mobile generalist T. lineola were panmictic, lacking any landscape related effect on genetic differentiation. In the species with ecological traits in between those of the congeners, T. sylvestris, climate has a strong impact on inter-population connectivity. However, the relative importance of different landscape factors for connectivity varies when using different metrics of genetic differentiation in this species. Our results show that closely related species representing a gradient of ecological traits also show genetic structures and landscape genetic relationships that gradually change from a geographical macro- to micro-scale. Thus, the type and magnitude of landscape effects on gene flow can differ strongly even among closely related species inhabiting the same landscape, and depend on their relative degree of specialization. In addition, the use of different genetic differentiation metrics makes it possible to

  4. Habitat Fragmentation, Variable Edge Effects, and the Landscape-Divergence Hypothesis

    PubMed Central

    Laurance, William F.; Nascimento, Henrique E. M.; Laurance, Susan G.; Andrade, Ana; Ewers, Robert M.; Harms, Kyle E.; Luizão, Regina C. C.; Ribeiro, José E.

    2007-01-01

    Edge effects are major drivers of change in many fragmented landscapes, but are often highly variable in space and time. Here we assess variability in edge effects altering Amazon forest dynamics, plant community composition, invading species, and carbon storage, in the world's largest and longest-running experimental study of habitat fragmentation. Despite detailed knowledge of local landscape conditions, spatial variability in edge effects was only partially foreseeable: relatively predictable effects were caused by the differing proximity of plots to forest edge and varying matrix vegetation, but windstorms generated much random variability. Temporal variability in edge phenomena was also only partially predictable: forest dynamics varied somewhat with fragment age, but also fluctuated markedly over time, evidently because of sporadic droughts and windstorms. Given the acute sensitivity of habitat fragments to local landscape and weather dynamics, we predict that fragments within the same landscape will tend to converge in species composition, whereas those in different landscapes will diverge in composition. This ‘landscape-divergence hypothesis’, if generally valid, will have key implications for biodiversity-conservation strategies and for understanding the dynamics of fragmented ecosystems. PMID:17925865

  5. Habitat fragmentation, variable edge effects, and the landscape-divergence hypothesis.

    PubMed

    Laurance, William F; Nascimento, Henrique E M; Laurance, Susan G; Andrade, Ana; Ewers, Robert M; Harms, Kyle E; Luizão, Regina C C; Ribeiro, José E

    2007-10-10

    Edge effects are major drivers of change in many fragmented landscapes, but are often highly variable in space and time. Here we assess variability in edge effects altering Amazon forest dynamics, plant community composition, invading species, and carbon storage, in the world's largest and longest-running experimental study of habitat fragmentation. Despite detailed knowledge of local landscape conditions, spatial variability in edge effects was only partially foreseeable: relatively predictable effects were caused by the differing proximity of plots to forest edge and varying matrix vegetation, but windstorms generated much random variability. Temporal variability in edge phenomena was also only partially predictable: forest dynamics varied somewhat with fragment age, but also fluctuated markedly over time, evidently because of sporadic droughts and windstorms. Given the acute sensitivity of habitat fragments to local landscape and weather dynamics, we predict that fragments within the same landscape will tend to converge in species composition, whereas those in different landscapes will diverge in composition. This 'landscape-divergence hypothesis', if generally valid, will have key implications for biodiversity-conservation strategies and for understanding the dynamics of fragmented ecosystems.

  6. Shared selective pressure and local genomic landscape lead to repeatable patterns of genomic divergence in sunflowers.

    PubMed

    Renaut, Sebastien; Owens, Gregory L; Rieseberg, Loren H

    2014-02-01

    The repeated evolution of traits in organisms facing similar environmental conditions is considered to be fundamental evidence for the role of natural selection in moulding phenotypes. Yet, aside from case studies of parallel evolution and its genetic basis, the repeatability of evolution at the level of the whole genome remains poorly characterized. Here, through the use of transcriptome sequencing, we examined genomic divergence for three pairs of sister species of sunflowers. Two of the pairs (Helianthus petiolaris - H. debilis and H. annuus - H. argophyllus) have diverged along a similar latitudinal gradient and presumably experienced similar selective pressure. In contrast, a third species pair (H. exilis - H. bolanderi) diverged along a longitudinal gradient. Analyses of divergence, as measured in terms of FST, indicated little repeatability across the three pairs of species for individual genetic markers (SNPs), modest repeatability at the level of individual genes and the highest repeatability when large regions of the genome were compared. As expected, higher repeatability was observed for the two species pairs that have diverged along a similar latitudinal gradient, with genes involved in flowering time among the most divergent genes. Genes showing extreme low or high differentiation were more similar than genes showing medium levels of divergence, implying that both purifying and divergent selection contributed to repeatable patterns of divergence. The location of a gene along the chromosome also predicted divergence levels, presumably because of shared heterogeneity in both recombination and mutation rates. In conclusion, repeated genome evolution appeared to result from both similar selective pressures and shared local genomic landscapes.

  7. Interaction of landscape and life history attributes on genetic diversity, neutral divergence and gene flow in a pristine community of salmonids.

    PubMed

    Gomez-Uchida, Daniel; Knight, Thomas W; Ruzzante, Daniel E

    2009-12-01

    Landscape genetics holds promise for the forecasting of spatial patterns of genetic diversity based on key environmental features. Yet, the degree to which inferences based on single species can be extended to whole communities is not fully understood. We used a pristine and spatially structured community of three landlocked salmonids (Salvelinus fontinalis, Salmo salar, and Salvelinus alpinus) from Gros Morne National Park (Newfoundland, Canada) to test several predictions on the interacting effects of landscape and life history variation on genetic diversity, neutral divergence, and gene flow (m, migration rate). Landscape factors consistently influenced multispecies genetic patterns: (i) waterfalls created strong dichotomies in genetic diversity and divergence between populations above and below them in all three salmonids; (ii) contemporary m decreased with waterway distance in all three species, while neutral genetic divergence (theta) increased with waterway distance, albeit in only two taxa; (iii) river flow generally produced downstream-biased m between populations when waterfalls separated these, but not otherwise. In contrast, we expected differential life history to result in a hierarchy of neutral divergence (S. salar > S. fontinalis > S. alpinus) based on disparities in dispersal abilities and population size from previous mark-recapture studies. Such hierarchy additionally matched varying degrees of spatial genetic structure among species revealed through individual-based analyses. We conclude that, whereas key landscape attributes hold power to predict multispecies genetic patterns in equivalent communities, they are likely to interact with species-specific life history attributes such as dispersal, demography, and ecology, which will in turn affect holistic conservation strategies.

  8. Evidence for an intrinsic factor promoting landscape genetic divergence in Madagascan leaf-litter frogs

    PubMed Central

    Wollenberg Valero, Katharina C.

    2015-01-01

    The endemic Malagasy frog radiations are an ideal model system to study patterns and processes of speciation in amphibians. Large-scale diversity patterns of these frogs, together with other endemic animal radiations, led to the postulation of new and the application of known hypotheses of species diversification causing diversity patterns in this biodiversity hotspot. Both extrinsic and intrinsic factors have been studied in a comparative framework, with extrinsic factors usually being related to the physical environment (landscape, climate, river catchments, mountain chains), and intrinsic factors being clade-specific traits or constraints (reproduction, ecology, morphology, physiology). Despite some general patterns emerging from such large-scale comparative analyses, it became clear that the mechanism of diversification in Madagascar may vary among clades, and may be a multifactorial process. In this contribution, I test for intrinsic factors promoting population-level divergence within a clade of terrestrial, diurnal leaf-litter frogs (genus Gephyromantis) that has previously been shown to diversify according to extrinsic factors. Landscape genetic analyses of the microendemic species Gephyromantis enki and its widely distributed, larger sister species Gephyromantis boulengeri over a rugged landscape in the Ranomafana area shows that genetic variance of the smaller species cannot be explained by landscape resistance alone. Both topographic and riverine barriers are found to be important in generating this divergence. This case study yields additional evidence for the probable importance of body size in lineage diversification. PMID:26136766

  9. Evidence for an intrinsic factor promoting landscape genetic divergence in Madagascan leaf-litter frogs.

    PubMed

    Wollenberg Valero, Katharina C

    2015-01-01

    The endemic Malagasy frog radiations are an ideal model system to study patterns and processes of speciation in amphibians. Large-scale diversity patterns of these frogs, together with other endemic animal radiations, led to the postulation of new and the application of known hypotheses of species diversification causing diversity patterns in this biodiversity hotspot. Both extrinsic and intrinsic factors have been studied in a comparative framework, with extrinsic factors usually being related to the physical environment (landscape, climate, river catchments, mountain chains), and intrinsic factors being clade-specific traits or constraints (reproduction, ecology, morphology, physiology). Despite some general patterns emerging from such large-scale comparative analyses, it became clear that the mechanism of diversification in Madagascar may vary among clades, and may be a multifactorial process. In this contribution, I test for intrinsic factors promoting population-level divergence within a clade of terrestrial, diurnal leaf-litter frogs (genus Gephyromantis) that has previously been shown to diversify according to extrinsic factors. Landscape genetic analyses of the microendemic species Gephyromantis enki and its widely distributed, larger sister species Gephyromantis boulengeri over a rugged landscape in the Ranomafana area shows that genetic variance of the smaller species cannot be explained by landscape resistance alone. Both topographic and riverine barriers are found to be important in generating this divergence. This case study yields additional evidence for the probable importance of body size in lineage diversification.

  10. Post-rift influence of small-scale convection on the landscape evolution at divergent continental margins

    NASA Astrophysics Data System (ADS)

    Sacek, Victor

    2017-02-01

    After decades of geological and geophysical data acquisition along with quantitative modeling of the long-term evolution of the landscape at divergent continental margins, the search for an explanation for the formation and evolution of steep escarpments bordering the coast is still a challenging task. One difficult aspect to explain about the evolution of these escarpments is the expressive variability of denudation rate through the post-rift phase observed in many margins. Here I propose that the interaction of small-scale convection in the asthenosphere with the base of the continental lithosphere can create intermittent vertical displacements of the surface with magnitude of a few hundreds of meters at the continental margin. These topographic perturbations are sufficient to produce an expressive variability in the rate of erosion of the landscape through the post-rift phase similar to the exhumation history observed along old divergent margins. I show that the vertical motion of the surface is amplified when a mobile belt is present at the continental margin, with lithospheric mantle less viscous than the cratonic lithosphere and, consequently, more prone to be partially eroded by the convective asthenosphere. I conclude that the influence of small-scale convection is not the primary explanation for the formation of high topographic features at divergent continental margins, but can be an important component contributing to sustain a preexistent escarpment. The present results are based on numerical simulations that combine thermochemical convection in the mantle, flexure of the lithosphere and surface processes of erosion and sedimentation.

  11. Genetic landscapes GIS Toolbox: tools to map patterns of genetic divergence and diversity.

    USGS Publications Warehouse

    Vandergast, Amy G.; Perry, William M.; Lugo, Roberto V.; Hathaway, Stacie A.

    2011-01-01

    The Landscape Genetics GIS Toolbox contains tools that run in the Geographic Information System software, ArcGIS, to map genetic landscapes and to summarize multiple genetic landscapes as average and variance surfaces. These tools can be used to visualize the distribution of genetic diversity across geographic space and to study associations between patterns of genetic diversity and geographic features or other geo-referenced environmental data sets. Together, these tools create genetic landscape surfaces directly from tables containing genetic distance or diversity data and sample location coordinates, greatly reducing the complexity of building and analyzing these raster surfaces in a Geographic Information System.

  12. Divergent-flow isoelectric focusing for separation and preparative analysis of peptides.

    PubMed

    Duša, Filip; Křenková, Jana; Moravcová, Dana; Kahle, Vladislav; Slais, Karel

    2012-07-01

    A divergent-flow isoelectric focusing (DF IEF) technique has been applied for the separation and preparative analysis of peptides. The parameters of the developed DF IEF device such as dimension and shape of the separation bed, selection of nonwoven material of the channel, and separation conditions were optimized. The DF IEF device was tested by the separation of a peptide mixture originating from the tryptic digestion of BSA, cytochrome c, and myoglobin. The pH gradient of DF IEF was created by the autofocusing of tryptic peptides themselves without any addition of carrier ampholytes. The focusing process was monitored visually using colored pI markers, and the obtained fractions were analyzed by RP-HPLC and ESI/TOF-MS. DF IEF operating in the autofocusing mode provides an efficient preseparation of peptides, which is comparable with a commercially available MicroRotofor multicompartment electrolyzer and significantly improves sequence coverage of analyzed proteins. The potential of the DF IEF device as an efficient tool for the preparative scale separations was demonstrated by the isolation of caseinomacropeptide (CMP) from a crude whey solution.

  13. Genetic Landscapes GIS Toolbox: tools to map patterns of genetic divergence and diversity.

    PubMed

    Vandergast, Amy G; Perry, William M; Lugo, Roberto V; Hathaway, Stacie A

    2011-01-01

    The Landscape Genetics GIS Toolbox contains tools that run in the Geographic Information System software, ArcGIS(®), to map genetic landscapes and to summarize multiple genetic landscapes as average and variance surfaces. These tools can be used to visualize the distribution of genetic diversity across geographic space and to study associations between patterns of genetic diversity and geographic features or other geo-referenced environmental data sets. Together, these tools create genetic landscape surfaces directly from tables containing genetic distance or diversity data and sample location coordinates, greatly reducing the complexity of building and analyzing these raster surfaces in a Geographic Information System. Published 2010. This article is a US Government work and is in the public domain in the USA.

  14. Divergent landscape effects on population connectivity in two co-occurring amphibian species.

    PubMed

    Richardson, Jonathan L

    2012-09-01

    The physical and environmental attributes of landscapes often shape patterns of population connectivity by influencing dispersal and gene flow. Landscape effects on movement are typically evaluated for single species. However, inferences from multiple species are required for multi-species management strategies increasingly being applied in conservation. In this study, I compared the spatial genetic patterns of two amphibian species across the northeastern United States and estimated the influence of specific landscape features on the observed genetic structure. The spotted salamander (Ambystoma maculatum) and wood frog (Rana sylvatica) share many ecological attributes related to habitat use, phenology and site fidelity. However, I hypothesized that important differences in their movement patterns and life history would create distinct genetic patterns for each species. Using 14 microsatellite loci, I tested for differences in the level of genetic differentiation between the two species across 22 breeding ponds. The effects of eight landscape features were also estimated by evaluating 32 landscape resistance models. Spotted salamanders exhibited significantly higher genetic differentiation than wood frogs. Different landscape features were also identified as potential drivers of the genetic patterns in each species, with little overlap in model support between species. Collectively, these results provide strong evidence that these two amphibian species interact with the landscape in measurably different ways. The distinct genetic patterns observed are consistent with key differences in movement ability and life history between A. maculatum and R. sylvatica. These results highlight the importance of considering more than one species when assessing the impacts of the landscape matrix on population connectivity, even for ecologically similar species within the same habitats.

  15. Patterns of divergence in fish species separated by the Isthmus of Panama.

    PubMed

    Thacker, Christine E

    2017-05-10

    The Pleistocene closure of Isthmus of Panama, separating the basins of the Eastern Pacific and the Caribbean Sea, created a unique natural experiment that reveals how marine faunas respond to environmental change. To explore how fishes have been affected by this tectonic event, I compare transisthmian patterns in phylogeny and morphology for geminate lineages in two families, Eleotridae (sleepers) and Apogonidae (cardinalfishes). Time-calibrated phylogenies for these families show different diversification patterns. In Eleotridae, several independent shallow instances of transisthmian divergences occur, with one or a few species on either side of the Isthmus. Among Apogonidae, a single clade of Eastern Pacific species is nested within a broad Caribbean radiation that also includes a species known from the Mediterranean. Divergence time estimates for taxa isolated by closure of the Isthmus are broadly congruent. Hypotheses dated with deeper, fossil-based legacy calibrations put the divergences in the Miocene at 7.4-15.1 Ma, while those estimated with a shallow biogeographic calibration of final Isthmus closure range from 5.1 to 9.9 Ma, in the late Miocene/early Pliocene. Eleotridae are more euryhaline than Apogonidae, but do not exhibit shallower transisthmian divergences. In both families, descendent lineages on either side of the Isthmus of Panama exhibit significant shape differences, although that distinction disappears for Apogonidae when I apply a correction for phylogenetic relationships. To evaluate the tempo and mode of continuous character evolution, I fit several single and multiple rate evolutionary models to morphometric data reconstructed on the Apogonidae phylogeny. I find that the most highly favored model, as estimated on both legacy and isthmus calibrated hypotheses, is a multiple rate Ornstein-Uhlbeck model, with a mosaic of rate shifts postulated for shape changes among fishes in the Caribbean and Eastern Pacific. Although many transisthmian

  16. Altered Chromatin Occupancy of Master Regulators Underlies Evolutionary Divergence in the Transcriptional Landscape of Erythroid Differentiation

    PubMed Central

    Ulirsch, Jacob C.; Lacy, Jessica N.; An, Xiuli; Mohandas, Narla; Mikkelsen, Tarjei S.; Sankaran, Vijay G.

    2014-01-01

    Erythropoiesis is one of the best understood examples of cellular differentiation. Morphologically, erythroid differentiation proceeds in a nearly identical fashion between humans and mice, but recent evidence has shown that networks of gene expression governing this process are divergent between species. We undertook a systematic comparative analysis of six histone modifications and four transcriptional master regulators in primary proerythroblasts and erythroid cell lines to better understand the underlying basis of these transcriptional differences. Our analyses suggest that while chromatin structure across orthologous promoters is strongly conserved, subtle differences are associated with transcriptional divergence between species. Many transcription factor (TF) occupancy sites were poorly conserved across species (∼25% for GATA1, TAL1, and NFE2) but were more conserved between proerythroblasts and cell lines derived from the same species. We found that certain cis-regulatory modules co-occupied by GATA1, TAL1, and KLF1 are under strict evolutionary constraint and localize to genes necessary for erythroid cell identity. More generally, we show that conserved TF occupancy sites are indicative of active regulatory regions and strong gene expression that is sustained during maturation. Our results suggest that evolutionary turnover of TF binding sites associates with changes in the underlying chromatin structure, driving transcriptional divergence. We provide examples of how this framework can be applied to understand epigenomic variation in specific regulatory regions, such as the β-globin gene locus. Our findings have important implications for understanding epigenomic changes that mediate variation in cellular differentiation across species, while also providing a valuable resource for studies of hematopoiesis. PMID:25521328

  17. Nonperturbative landscape of the Mott-Hubbard transition: Multiple divergence lines around the critical endpoint

    NASA Astrophysics Data System (ADS)

    Schäfer, T.; Ciuchi, S.; Wallerberger, M.; Thunström, P.; Gunnarsson, O.; Sangiovanni, G.; Rohringer, G.; Toschi, A.

    2016-12-01

    We analyze the highly nonperturbative regime surrounding the Mott-Hubbard metal-to-insulator transition (MIT) by means of dynamical mean field theory (DMFT) calculations at the two-particle level. By extending the results of Schäfer et al. [Phys. Rev. Lett. 110, 246405 (2013), 10.1103/PhysRevLett.110.246405] we show the existence of infinitely many lines in the phase diagram of the Hubbard model where the local Bethe-Salpeter equations, and the related irreducible vertex functions, become singular in the charge as well as the particle-particle channel. By comparing our numerical data for the Hubbard model with analytical calculations for exactly solvable systems of increasing complexity [disordered binary mixture (BM), Falicov-Kimball (FK), and atomic limit (AL)], we have (i) identified two different kinds of divergence lines; (ii) classified them in terms of the frequency structure of the associated singular eigenvectors; and (iii) investigated their relation to the emergence of multiple branches in the Luttinger-Ward functional. In this way, we could distinguish the situations where the multiple divergences simply reflect the emergence of an underlying, single energy scale ν* below which perturbation theory is no longer applicable, from those where the breakdown of perturbation theory affects, not trivially, different energy regimes. Finally, we discuss the implications of our results on the theoretical understanding of the nonperturbative physics around the MIT and for future developments of many-body algorithms applicable in this regime.

  18. Compositional Divergence and Convergence in Local Communities and Spatially Structured Landscapes

    PubMed Central

    Caruso, Tancredi; Powell, Jeff R.; Rillig, Matthias C.

    2012-01-01

    Community structure depends on both deterministic and stochastic processes. However, patterns of community dissimilarity (e.g. difference in species composition) are difficult to interpret in terms of the relative roles of these processes. Local communities can be more dissimilar (divergence) than, less dissimilar (convergence) than, or as dissimilar as a hypothetical control based on either null or neutral models. However, several mechanisms may result in the same pattern, or act concurrently to generate a pattern, and much research has recently been focusing on unravelling these mechanisms and their relative contributions. Using a simulation approach, we addressed the effect of a complex but realistic spatial structure in the distribution of the niche axis and we analysed patterns of species co-occurrence and beta diversity as measured by dissimilarity indices (e.g. Jaccard index) using either expectations under a null model or neutral dynamics (i.e., based on switching off the niche effect). The strength of niche processes, dispersal, and environmental noise strongly interacted so that niche-driven dynamics may result in local communities that either diverge or converge depending on the combination of these factors. Thus, a fundamental result is that, in real systems, interacting processes of community assembly can be disentangled only by measuring traits such as niche breadth and dispersal. The ability to detect the signal of the niche was also dependent on the spatial resolution of the sampling strategy, which must account for the multiple scale spatial patterns in the niche axis. Notably, some of the patterns we observed correspond to patterns of community dissimilarities previously observed in the field and suggest mechanistic explanations for them or the data required to solve them. Our framework offers a synthesis of the patterns of community dissimilarity produced by the interaction of deterministic and stochastic determinants of community assembly in a

  19. Prominent intraspecific genetic divergence within Anopheles gambiae sibling species triggered by habitat discontinuities across a riverine landscape.

    PubMed

    Caputo, B; Nwakanma, D; Caputo, F P; Jawara, M; Oriero, E C; Hamid-Adiamoh, M; Dia, I; Konate, L; Petrarca, V; Pinto, J; Conway, D J; Della Torre, A

    2014-09-01

    The Anopheles gambiae complex of mosquitoes includes malaria vectors at different stages of speciation, whose study enables a better understanding of how adaptation to divergent environmental conditions leads to evolution of reproductive isolation. We investigated the population genetic structure of closely related sympatric taxa that have recently been proposed as separate species (An. coluzzii and An. gambiae), sampled from diverse habitats along the Gambia river in West Africa. We characterized putatively neutral microsatellite loci as well as chromosomal inversion polymorphisms known to be associated with ecological adaptation. The results revealed strong ecologically associated population subdivisions within both species. Microsatellite loci on chromosome-3L revealed clear differentiation between coastal and inland populations, which in An. coluzzii is reinforced by a unusual inversion polymorphism pattern, supporting the hypothesis of genetic divergence driven by adaptation to the coastal habitat. A strong reduction of gene flow was observed between An. gambiae populations west and east of an extensively rice-cultivated region apparently colonized exclusively by An. coluzzii. Notably, this 'intraspecific' differentiation is higher than that observed between the two species and involves also the centromeric region of chromosome-X which has previously been considered a marker of speciation within this complex, possibly suggesting that the two populations may be at an advanced stage of differentiation triggered by human-made habitat fragmentation. These results confirm ongoing ecological speciation within these most important Afro-tropical malaria vectors and raise new questions on the possible effect of this process in malaria transmission. © 2014 John Wiley & Sons Ltd.

  20. Twins and Kindergarten Separation: Divergent Beliefs of Principals, Teachers, Parents, and Twins

    ERIC Educational Resources Information Center

    Gordon, Lynn Melby

    2015-01-01

    Should principals enforce mandatory separation of twins in kindergarten? Do school separation beliefs of principals differ from those of teachers, parents of twins, and twins themselves? This survey questioned 131 elementary principals, 54 kindergarten teachers, 201 parents of twins, and 112 twins. A majority of principals (71%) believed that…

  1. Twins and Kindergarten Separation: Divergent Beliefs of Principals, Teachers, Parents, and Twins

    ERIC Educational Resources Information Center

    Gordon, Lynn Melby

    2015-01-01

    Should principals enforce mandatory separation of twins in kindergarten? Do school separation beliefs of principals differ from those of teachers, parents of twins, and twins themselves? This survey questioned 131 elementary principals, 54 kindergarten teachers, 201 parents of twins, and 112 twins. A majority of principals (71%) believed that…

  2. Adaptive evolution and segregating load contribute to the genomic landscape of divergence in two tree species connected by episodic gene flow.

    PubMed

    Christe, Camille; Stölting, Kai N; Paris, Margot; Fraїsse, Christelle; Bierne, Nicolas; Lexer, Christian

    2017-01-01

    Speciation often involves repeated episodes of genetic contact between divergent populations before reproductive isolation (RI) is complete. Whole-genome sequencing (WGS) holds great promise for unravelling the genomic bases of speciation. We have studied two ecologically divergent, hybridizing species of the 'model tree' genus Populus (poplars, aspens, cottonwoods), Populus alba and P. tremula, using >8.6 million single nucleotide polymorphisms (SNPs) from WGS of population pools. We used the genomic data to (i) scan these species' genomes for regions of elevated and reduced divergence, (ii) assess key aspects of their joint demographic history based on genomewide site frequency spectra (SFS) and (iii) infer the potential roles of adaptive and deleterious coding mutations in shaping the genomic landscape of divergence. We identified numerous small, unevenly distributed genome regions without fixed polymorphisms despite high overall genomic differentiation. The joint SFS was best explained by ancient and repeated gene flow and allowed pinpointing candidate interspecific migrant tracts. The direction of selection (DoS) differed between genes in putative migrant tracts and the remainder of the genome, thus indicating the potential roles of adaptive divergence and segregating deleterious mutations on the evolution and breakdown of RI. Genes affected by positive selection during divergence were enriched for several functionally interesting groups, including well-known candidate 'speciation genes' involved in plant innate immunity. Our results suggest that adaptive divergence affects RI in these hybridizing species mainly through intrinsic and demographic processes. Integrating genomic with molecular data holds great promise for revealing the effects of particular genetic pathways on speciation. © 2016 John Wiley & Sons Ltd.

  3. Separation and divergence: the untold story of James Robertson's and John Bowlby's theoretical dispute on mother-child separation.

    PubMed

    van der Horst, Frank C P; van der Veer, René

    2009-01-01

    The work of Robertson and Bowlby is generally seen as complementary, Robertson being the practically oriented observer and Bowlby focusing on theoretical explanations for Robertson's observations. The authors add to this picture an "untold story" of the collaboration between Robertson and Bowlby: the dispute between the two men that arose in the 1960s about the corollaries of separation and the ensuing personal animosity. On the basis of unique archival materials, this until now little known aspect of the history of attachment theory is extensively documented. The deteriorating relationship between Robertson and Bowlby is described against the background of different currents in psychoanalysis in Britain in the interbellum.

  4. Subexponential Divergence and Diffusive Twist of Turbulent Magnetic Field Lines in the Limit of the Very Short Separations

    NASA Astrophysics Data System (ADS)

    Ragot, B. R.

    2008-08-01

    Turbulent magnetic field lines have long been thought to be diverging from each other (or converging toward each other) at exponential rates known as Lyapunov exponents. It is argued here that in a turbulent magnetized plasma, subexponential divergence (convergence) and diffusive twist better characterize the dispersal of magnetic field lines (MFLs) in the limit of the very small separations ρ than do the usual Lyapunov exponents or exponentiation rates. In that limit of the very small separations, the field-line equations give a variation rate for ln ρ , not ρ, and the implied log-normality of the ρ distribution makes langle (ln ρ/ρ0)2rangle a much better probe of the exponential divergence of core MFLs. A fully nonlinear calculation shows that the separation logarithm, ln ρ , and twist or rotation angle, Δ θ , between pairs of MFLs diffuse with the distance Δ z elapsed along the main field, as soon as Δ z exceeds min (k-1II,ζII) , the minimum of the parallel correlation length k-1II ≡ L∥ ∇ of the turbulent field gradients and of the associated nonlinear scale, ζII ≡ ζ∇, defined as the field-aligned length scale for which the mean cross-field displacement langle (rζ - r0)2rangle1/2 reaches 21/2ξ k-1II ≡ 21/2L⊥ ∇, with kII the wavenumber where the turbulence spectrum becomes steeper than (k2∥ + ξ2k2⊥)-1 and ξ the anisotropy parameter of the turbulence. The average growth of the core field-line separation ρ0elangle (ln ρ/ρ0)2rangle1/2 = epropto (Δ z)1/2 along the direction of fastest growth, being subexponential, is not compatible with the definition of Lyapunov exponents. The largest exponentiation rate of the core MFLs actually decreases with the distance Δ z. Application of the new nonlinear calculation to the solar wind shows a substantial MFL rotation in a plane transverse to the main field.

  5. Patterns of divergence across the geographic and genomic landscape of a butterfly hybrid zone associated with a climatic gradient

    USDA-ARS?s Scientific Manuscript database

    The process of speciation is impacted by the interaction between the genomic architecture of diverging lineages and the environmental context they occupy. Yet, while climate can have a significant impact on this interaction, its role in determining the patterns of geographic and genomic divergence i...

  6. Quaternary origin and genetic divergence of the endemic cactus Mammillaria pectinifera in a changing landscape in the Tehuacán Valley, Mexico.

    PubMed

    Cornejo-Romero, A; Medina-Sánchez, J; Hernández-Hernández, T; Rendón-Aguilar, B; Valverde, P L; Zavala-Hurtado, A; Rivas-Arancibia, S P; Pérez-Hernández, M A; López-Ortega, G; Jiménez-Sierra, C; Vargas-Mendoza, C F

    2014-01-08

    The endemic Mexican cactus, Mammillaria pectinifera, shows low dispersal capabilities and isolated populations within the highly dissected landscape of Tehuacán Valley. These characteristics can restrict gene flow and act upon the genetic divergence and speciation in arid plants. We conducted a phylogeographic study to determine if the origin, current distribution, and genetic structure of M. pectinifera were driven by Quaternary geomorphic processes. Sequences of the plastids psbA-trnH and trnT-trnL obtained from 66 individuals from seven populations were used to estimate genetic diversity. Population differentiation was assessed by an analysis of molecular variance. We applied a stepwise phylogenetic calibration test to determine whether species origin and genetic divergence among haplotypes were temporally concordant with recognizable episodes of geomorphic evolution. The combination of plastid markers yielded six haplotypes, with high levels of haplotype diversity (h = 0.622) and low nucleotide diversity (π = 0.00085). The populations were found to be genetically structured (F(ST) = 0.682; P < 0.00001), indicating that geographic isolation and limited dispersal were the primary causes of genetic population differentiation. The estimated origin and divergence time among haplotypes were 0.017-2.39 and 0.019-1.237 mya, respectively, which correlates with Pleistocene tectonics and erosion events, supporting a hypothesis of geomorphically-driven geographical isolation. Based on a Bayesian skyline plot, these populations showed long term demographic stability, indicating that persistence in confined habitats has been the main response of this species to landscape changes. We conclude that the origin and haplotype divergence of M. pectinifera were a response to local Quaternary geomorphic evolution.

  7. Appliance of Inertial Gas-Dynamic Separation of Gas-Dispersion Flows in the Curvilinear Convergent-Divergent Channels for Compressor Equipment Reliability Improvement

    NASA Astrophysics Data System (ADS)

    Liaposhchenko, O. O.; Sklabinskyi, V. I.; Zavialov, V. L.; Pavlenko, I. V.; Nastenko, O. V.; Demianenko, M. M.

    2017-08-01

    The new methods of vibration and inertial gas-dynamic separation of gas-condensate and dusty flows and the corresponding separation devices are proposed in order to avoid emergencies and premature wear of parts and components of the compressor equipment. The formation of the gas flow and disperse particles in the curvilinear convergent-divergent channels are investigated. The optimizing hydrodynamic profiling of a geometrical configuration of curvilinear separation channels with rigid and flexible walls of baffles is carried out.

  8. Habitat Discontinuities Separate Genetically Divergent Populations of a Rocky Shore Marine Fish

    PubMed Central

    Knutsen, Halvor; Jorde, Per Erik

    2016-01-01

    Habitat fragmentation has been suggested to be responsible for major genetic differentiations in a range of marine organisms. In this study, we combined genetic data and environmental information to unravel the relative role of geography and habitat heterogeneity on patterns of genetic population structure of corkwing wrasse (Symphodus melops), a rocky shore species at the northern limit of its distribution range in Scandinavia. Our results revealed a major genetic break separating populations inhabiting the western and southern coasts of Norway. This genetic break coincides with the longest stretch of sand in the whole study area, suggesting habitat fragmentation as a major driver of genetic differentiation of this obligate rocky shore benthic fish in Scandinavia. The complex fjords systems extending along the western coast of Norway appeared responsible for further regional genetic structuring. Our findings indicate that habitat discontinuities may lead to significant genetic fragmentation over short geographical distances, even for marine species with a pelagic larval phase, as for this rocky shore fish. PMID:27706178

  9. Species-specific separation of lake plankton reveals divergent food assimilation patterns in rotifers

    PubMed Central

    Burian, Alfred; Kainz, Martin J; Schagerl, Michael; Yasindi, Andrew

    2014-01-01

    1. The analysis of functional groups with a resolution to the individual species level is a basic requirement to better understand complex interactions in aquatic food webs. Species-specific stable isotope analyses are currently applied to analyse the trophic role of large zooplankton or fish species, but technical constraints complicate their application to smaller-sized plankton. 2. We investigated rotifer food assimilation during a short-term microzooplankton bloom in the East African soda lake Nakuru by developing a method for species-specific sampling of rotifers. 3. The two dominant rotifers, Brachionus plicatilis and Brachionus dimidiatus, were separated to single-species samples (purity >95%) and significantly differed in their isotopic values (4.1‰ in δ13C and 1.5‰ in δ15N). Bayesian mixing models indicated that isotopic differences were caused by different assimilation of filamentous cyanobacteria and particles <2 μm and underlined the importance of species-specific sampling of smaller plankton compartments. 4. A main difference was that the filamentous cyanobacterium Arthrospira fusiformis, which frequently forms blooms in African soda lakes, was an important food source for the larger-sized B. plicatilis (48%), whereas it was hardly ingested by B. dimidiatus. Overall, A. fusiformis was, relative to its biomass, assimilated to small extents, demonstrating a high grazing resistance of this species. 5. In combination with high population densities, these results demonstrate a strong potential of rotifer blooms to shape phytoplankton communities and are the first in situ demonstration of a quantitatively important direct trophic link between rotifers and filamentous cyanobacteria. PMID:25866422

  10. Divergent gene copies in the asexual class Bdelloidea (Rotifera) separated before the bdelloid radiation or within bdelloid families.

    PubMed

    Mark Welch, David B; Cummings, Michael P; Hillis, David M; Meselson, Matthew

    2004-02-10

    Rotifers of the asexual class Bdelloidea are unusual in possessing two or more divergent copies of every gene that has been examined. Phylogenetic analysis of the heat-shock gene hsp82 and the TATA-box-binding protein gene tbp in multiple bdelloid species suggested that for each gene, each copy belonged to one of two lineages that began to diverge before the bdelloid radiation. Such gene trees are consistent with the two lineages having descended from former alleles that began to diverge after meiotic segregation ceased or from subgenomes of an alloploid ancestor of the bdelloids. However, the original analyses of bdelloid gene-copy divergence used only a single outgroup species and were based on parsimony and neighbor joining. We have now used maximum likelihood and Bayesian inference methods and, for hsp82, multiple outgroups in an attempt to produce more robust gene trees. Here we report that the available data do not unambiguously discriminate between gene trees that root the origin of hsp82 and tbp copy divergence before the bdelloid radiation and those which indicate that the gene copies began to diverge within bdelloid families. The remarkable presence of multiple diverged gene copies in individual genomes is nevertheless consistent with the loss of sex in an ancient ancestor of bdelloids.

  11. Divergent gene copies in the asexual class Bdelloidea (Rotifera) separated before the bdelloid radiation or within bdelloid families

    PubMed Central

    Welch, David B. Mark; Cummings, Michael P.; Hillis, David M.; Meselson, Matthew

    2004-01-01

    Rotifers of the asexual class Bdelloidea are unusual in possessing two or more divergent copies of every gene that has been examined. Phylogenetic analysis of the heat-shock gene hsp82 and the TATA-box-binding protein gene tbp in multiple bdelloid species suggested that for each gene, each copy belonged to one of two lineages that began to diverge before the bdelloid radiation. Such gene trees are consistent with the two lineages having descended from former alleles that began to diverge after meiotic segregation ceased or from subgenomes of an alloploid ancestor of the bdelloids. However, the original analyses of bdelloid gene-copy divergence used only a single outgroup species and were based on parsimony and neighbor joining. We have now used maximum likelihood and Bayesian inference methods and, for hsp82, multiple outgroups in an attempt to produce more robust gene trees. Here we report that the available data do not unambiguously discriminate between gene trees that root the origin of hsp82 and tbp copy divergence before the bdelloid radiation and those which indicate that the gene copies began to diverge within bdelloid families. The remarkable presence of multiple diverged gene copies in individual genomes is nevertheless consistent with the loss of sex in an ancient ancestor of bdelloids. PMID:14747660

  12. Algae separation from urban landscape water using a high density microbubble layer enhanced by micro-flocculation.

    PubMed

    Chen, Shuwen; Xu, Jingcheng; Liu, Jia; Wei, Qiaoling; Li, Guangming; Huang, Xiangfeng

    2014-01-01

    Eutrophication of raw water results in outbreaks of algae, which hinders conventional water treatment. In this study, high density microbubble layers combined with micro-flocculation was adopted to remove algae from urban landscape water, and the effects of pressure, hydraulic loading, microbubble layer height and flocculation dosage on the removal efficiency for algae were studied. The greatest removal efficiency for algae, chemical oxygen demand, nitrogen and phosphorus was obtained at 0.42 MPa with hydraulic loading at 5 m/h and a flocculation dosage of 4 mg/L using a microbubble layer with a height of 130 cm. Moreover, the size, clearance distance and concentration of microbubbles were found to be affected by pressure and the height of the microbubble layer. Based on the study, this method was an alternative for algae separation from urban landscape water and water purification.

  13. Divergent deiodination of thyroid hormones in the separated parts of the fetal and maternal placenta in pigs.

    PubMed

    Krysin, E; Brzezińska-Slebodzińska, E; Slebodziński, A B

    1997-11-01

    Previous work from this laboratory has shown that the thyroid gland of the fetal pig begins to function at about day 46-47 (0.40-0.415 fraction of gestational age). Sera from fetuses contain lower thyroxine (T4), 3,3',5-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) concentrations than maternal sera, except for about 2 weeks before term. The fetal T4 metabolism is dominated by the 5'-monodeiodinating activity (5'-MD). In the present study we measured the iodothyronines content, and the outer (5'-MD) and inner (5-MD) monodeiodinases activity, in homogenates of the placenta. The pig placenta, which is of the epitheliochorial type, was separated into the fetal and the maternal part. The concentrations of T4, T3 and rT3 were lower, and the deiodinating activity of 5'-MD and 5-MD higher, in the fetal than in the maternal placenta. The fetal placenta not only deiodinated more actively T4 to T3 and T4 to rT3, but degraded T3 to 3,3'-diiodothyronine (3,3'-T2) more actively than rT3 to 3,3'-T2. Such divergent deiodinating activity of T4 to T3, T3 to 3,3'-T2 and rT3 to 3,3'-T2 might favor establishing a relatively high and constant rT3 concentrations in fetal and maternal placentas, and a lower T3 in the fetal placenta. The inner ring deiodinating activity (excluding a day before parturition) was always more active in the fetal placenta, while the outer ring deiodinations varied in this respect, depending on the gestation stage. These results support the hypothesis that in the fetal pig, enzymatic deiodination of thyroid hormones forms a barrier which reduces transplacental passage of the hormones and that the fetal part of the placenta is the primary factor in the mechanism regulating the hormonal transfer. In spite of the presence of the barrier, there is an adequate maternal supply of thyroid hormones to the fetus in early gestation, which suggests that the enzymatic mechanism is influenced in some way by the thyroid status of the fetus.

  14. Separating the effects of habitat area, fragmentation and matrix resistance on genetic differentiation in complex landscapes

    Treesearch

    Samuel A. Cushman; Andrew J. Shirk; Erin L. Landguth

    2012-01-01

    Little is known about how variation in landscape mosaics affects genetic differentiation. The goal of this paper is to quantify the relative importance of habitat area and configuration, as well as the contrast in resistance between habitat and non-habitat, on genetic differentiation. We hypothesized that habitat configuration would be more influential than habitat...

  15. Divergent effects of the ‘biased’ 5-HT1A receptor agonists F15599 and F13714 in a novel object pattern separation task

    PubMed Central

    van Goethem, N P; Schreiber, R; Newman-Tancredi, A; Varney, M; Prickaerts, J

    2015-01-01

    Background and Purpose Pattern separation, that is, the formation of distinct representations from similar inputs, is an important hippocampal process implicated in cognitive domains like episodic memory. A deficit in pattern separation could lead to memory impairments in several psychiatric and neurological disorders. Hence, mechanisms by which pattern separation can be increased are of potential therapeutic interest. Experimental approach 5-HT1A receptors are involved in spatial memory. Herein we tested the ‘biased’ 5-HT1A receptor agonists F15599, which preferentially activates post-synaptic heteroreceptors, and F13714, which preferentially activates raphe-located autoreceptors, in rats in a novel spatial task assessing pattern separation, the object pattern separation (OPS) task. Key Results The acetylcholinesterase inhibitor donepezil, which served as a positive control, significantly improved spatial pattern separation at a dose of 1 mg·kg−1, p.o. F15599 increased pattern separation at 0.04 mg·kg−1, i.p., while F13714 decreased pattern separation at 0.0025 mg·kg−1, i.p. The selective 5-HT1A receptor antagonist WAY-100635 (0.63 mg·kg−1, s.c.) counteracted the effects of both agonists. These data suggest that acute preferential activation of post-synaptic 5-HT1A heteroreceptors improves spatial pattern separation, whereas acute preferential activation of raphe-located 5-HT1A autoreceptors impairs performance. Conclusions and Implications We successfully established and validated a novel, simple and robust OPS task and observed a diverging profile of response with ‘biased’ 5-HT1A receptor agonists based on their targeting of receptors in distinct brain regions. Our data suggest that the post-synaptic 5-HT1A receptor consists of a potential novel molecular target to improve pattern separation performance. PMID:25572672

  16. Chromosomal diversity and molecular divergence among three undescribed species of Neacomys (Rodentia, Sigmodontinae) separated by Amazonian rivers

    PubMed Central

    Oliveira Da Silva, Willam; Pieczarka, Julio Cesar; Ferguson-Smith, Malcolm Andrew; O’Brien, Patricia Caroline Mary; Mendes-Oliveira, Ana Cristina; Sampaio, Iracilda; Carneiro, Jeferson

    2017-01-01

    The Neacomys genus (Rodentia, Sigmodontinae) is distributed in the Amazon region, with some species limited to a single endemic area, while others may occur more widely. The number of species within the genus and their geographical boundaries are not known accurately, due to their high genetic diversity and difficulties in taxonomic identification. In this work we collected Neacomys specimens from both banks of the Tapajós River in eastern Amazon, and studied them using chromosome painting with whole chromosome probes of Hylaeamys megacephalus (HME; Rodentia, Sigmodontinae), and molecular analysis using haplotypes of mitochondrial genes COI and Cytb. Chromosome painting shows that Neacomys sp. A (NSP-A, 2n = 58/FN = 68) and Neacomys sp. B (NSP-B, 2n = 54/FN = 66) differ by 11 fusion/fission events, one translocation, four pericentric inversions and four heterochromatin amplification events. Using haplotypes of the concatenated mitochondrial genes COI and Cyt b, Neacomys sp. (2n = 58/FN = 64 and 70) shows a mean divergence of 6.2% for Neacomys sp. A and 9.1% for Neacomys sp. B, while Neacomys sp. A and Neacomys sp. B presents a medium nucleotide divergence of 7.4%. Comparisons were made with other published Neacomys data. The Tapajós and Xingu Rivers act as geographic barriers that define the distribution of these Neacomys species. Furthermore, our HME probes reveal four synapomorphies for the Neacomys genus (associations HME 20/[13,22]/4, 6a/21, [9,10]/7b/[9,10] and 12/[16,17]) and demonstrate ancestral traits of the Oryzomyini tribe (HME 8a and 8b, 18 and 25) and Sigmodontinae subfamily (HME 15 and 24), which can be used as taxonomic markers for these groups. PMID:28763510

  17. Chromosomal diversity and molecular divergence among three undescribed species of Neacomys (Rodentia, Sigmodontinae) separated by Amazonian rivers.

    PubMed

    Oliveira Da Silva, Willam; Pieczarka, Julio Cesar; Ferguson-Smith, Malcolm Andrew; O'Brien, Patricia Caroline Mary; Mendes-Oliveira, Ana Cristina; Sampaio, Iracilda; Carneiro, Jeferson; Nagamachi, Cleusa Yoshiko

    2017-01-01

    The Neacomys genus (Rodentia, Sigmodontinae) is distributed in the Amazon region, with some species limited to a single endemic area, while others may occur more widely. The number of species within the genus and their geographical boundaries are not known accurately, due to their high genetic diversity and difficulties in taxonomic identification. In this work we collected Neacomys specimens from both banks of the Tapajós River in eastern Amazon, and studied them using chromosome painting with whole chromosome probes of Hylaeamys megacephalus (HME; Rodentia, Sigmodontinae), and molecular analysis using haplotypes of mitochondrial genes COI and Cytb. Chromosome painting shows that Neacomys sp. A (NSP-A, 2n = 58/FN = 68) and Neacomys sp. B (NSP-B, 2n = 54/FN = 66) differ by 11 fusion/fission events, one translocation, four pericentric inversions and four heterochromatin amplification events. Using haplotypes of the concatenated mitochondrial genes COI and Cyt b, Neacomys sp. (2n = 58/FN = 64 and 70) shows a mean divergence of 6.2% for Neacomys sp. A and 9.1% for Neacomys sp. B, while Neacomys sp. A and Neacomys sp. B presents a medium nucleotide divergence of 7.4%. Comparisons were made with other published Neacomys data. The Tapajós and Xingu Rivers act as geographic barriers that define the distribution of these Neacomys species. Furthermore, our HME probes reveal four synapomorphies for the Neacomys genus (associations HME 20/[13,22]/4, 6a/21, [9,10]/7b/[9,10] and 12/[16,17]) and demonstrate ancestral traits of the Oryzomyini tribe (HME 8a and 8b, 18 and 25) and Sigmodontinae subfamily (HME 15 and 24), which can be used as taxonomic markers for these groups.

  18. Using landscape history to predict biodiversity patterns in fragmented landscapes.

    PubMed

    Ewers, Robert M; Didham, Raphael K; Pearse, William D; Lefebvre, Véronique; Rosa, Isabel M D; Carreiras, João M B; Lucas, Richard M; Reuman, Daniel C

    2013-10-01

    Landscape ecology plays a vital role in understanding the impacts of land-use change on biodiversity, but it is not a predictive discipline, lacking theoretical models that quantitatively predict biodiversity patterns from first principles. Here, we draw heavily on ideas from phylogenetics to fill this gap, basing our approach on the insight that habitat fragments have a shared history. We develop a landscape 'terrageny', which represents the historical spatial separation of habitat fragments in the same way that a phylogeny represents evolutionary divergence among species. Combining a random sampling model with a terrageny generates numerical predictions about the expected proportion of species shared between any two fragments, the locations of locally endemic species, and the number of species that have been driven locally extinct. The model predicts that community similarity declines with terragenetic distance, and that local endemics are more likely to be found in terragenetically distinctive fragments than in large fragments. We derive equations to quantify the variance around predictions, and show that ignoring the spatial structure of fragmented landscapes leads to over-estimates of local extinction rates at the landscape scale. We argue that ignoring the shared history of habitat fragments limits our ability to understand biodiversity changes in human-modified landscapes.

  19. Using landscape history to predict biodiversity patterns in fragmented landscapes

    PubMed Central

    Ewers, Robert M; Didham, Raphael K; Pearse, William D; Lefebvre, Véronique; Rosa, Isabel M D; Carreiras, João M B; Lucas, Richard M; Reuman, Daniel C

    2013-01-01

    Landscape ecology plays a vital role in understanding the impacts of land-use change on biodiversity, but it is not a predictive discipline, lacking theoretical models that quantitatively predict biodiversity patterns from first principles. Here, we draw heavily on ideas from phylogenetics to fill this gap, basing our approach on the insight that habitat fragments have a shared history. We develop a landscape ‘terrageny’, which represents the historical spatial separation of habitat fragments in the same way that a phylogeny represents evolutionary divergence among species. Combining a random sampling model with a terrageny generates numerical predictions about the expected proportion of species shared between any two fragments, the locations of locally endemic species, and the number of species that have been driven locally extinct. The model predicts that community similarity declines with terragenetic distance, and that local endemics are more likely to be found in terragenetically distinctive fragments than in large fragments. We derive equations to quantify the variance around predictions, and show that ignoring the spatial structure of fragmented landscapes leads to over-estimates of local extinction rates at the landscape scale. We argue that ignoring the shared history of habitat fragments limits our ability to understand biodiversity changes in human-modified landscapes. PMID:23931035

  20. Male competition fitness landscapes predict both forward and reverse speciation.

    PubMed

    Keagy, Jason; Lettieri, Liliana; Boughman, Janette W

    2016-01-01

    Speciation is facilitated when selection generates a rugged fitness landscape such that populations occupy different peaks separated by valleys. Competition for food resources is a strong ecological force that can generate such divergent selection. However, it is unclear whether intrasexual competition over resources that provide mating opportunities can generate rugged fitness landscapes that foster speciation. Here we use highly variable male F2 hybrids of benthic and limnetic threespine sticklebacks, Gasterosteus aculeatus Linnaeus, 1758, to quantify the male competition fitness landscape. We find that disruptive sexual selection generates two fitness peaks corresponding closely to the male phenotypes of the two parental species, favouring divergence. Most surprisingly, an additional region of high fitness favours novel hybrid phenotypes that correspond to those observed in a recent case of reverse speciation after anthropogenic disturbance. Our results reveal that sexual selection through male competition plays an integral role in both forward and reverse speciation.

  1. The Natural Product Resveratrol Inhibits Yeast Cell Separation by Extensively Modulating the Transcriptional Landscape and Reprogramming the Intracellular Metabolome

    PubMed Central

    Shen, Yan; Wang, Yang; Li, Jing; Lv, Hong; Huo, Keke

    2016-01-01

    An increasing number of studies have shown that the promising compound resveratrol treats multiple diseases, such as cancer and aging; however, the resveratrol mode-of-action (MoA) remains largely unknown. Here, by virtue of multiple omics approaches, we adopted fission yeast as a model system with the goal of dissecting the common MoA of the anti-proliferative activity of resveratrol. We found that the anti-proliferative activity of resveratrol is mainly due to its unique role of inhibiting the separation of sister cells, similar phenotype with the C2H2 zinc finger transcription factor Ace2 knock-out strain. Microarray analysis shown that resveratrol has extensive impact on the fission yeast transcription levels. Among the changed gene’s list, 40% of up-regulated genes are Core Environmental Stress Responses genes, and 57% of the down-regulated genes are periodically expressed. Moreover, resveratrol leverages the metabolome, which unbalances the intracellular pool sizes of several classes of amino acids, nucleosides, sugars and lipids, thus reflecting the remodulated metabolic networks. The complexity of the resveratrol MoA displayed in previous reports and our work demonstrates that multiple omics approaches must be applied together to obtain a complete picture of resveratrol’s anti-proliferative function. PMID:26950930

  2. [Landscape and ecological genomics].

    PubMed

    Tetushkin, E Ia

    2013-10-01

    Landscape genomics is the modern version of landscape genetics, a discipline that arose approximately 10 years ago as a combination of population genetics, landscape ecology, and spatial statistics. It studies the effects of environmental variables on gene flow and other microevolutionary processes that determine genetic connectivity and variations in populations. In contrast to population genetics, it operates at the level of individual specimens rather than at the level of population samples. Another important difference between landscape genetics and genomics and population genetics is that, in the former, the analysis of gene flow and local adaptations takes quantitative account of landforms and features of the matrix, i.e., hostile spaces that separate species habitats. Landscape genomics is a part of population ecogenomics, which, along with community genomics, is a major part of ecological genomics. One of the principal purposes of landscape genomics is the identification and differentiation of various genome-wide and locus-specific effects. The approaches and computation tools developed for combined analysis of genomic and landscape variables make it possible to detect adaptation-related genome fragments, which facilitates the planning of conservation efforts and the prediction of species' fate in response to expected changes in the environment.

  3. Sharing a Disparate Landscape

    ERIC Educational Resources Information Center

    Ali-Khan, Carolyne

    2010-01-01

    Working across boundaries of power, identity, and political geography is fraught with difficulties and contradictions. In Tali Tal and Iris Alkaher's, "Collaborative environmental projects in a multicultural society: Working from within separate or mutual landscapes?" the authors describe their efforts to do this in the highly charged…

  4. Sharing a Disparate Landscape

    ERIC Educational Resources Information Center

    Ali-Khan, Carolyne

    2010-01-01

    Working across boundaries of power, identity, and political geography is fraught with difficulties and contradictions. In Tali Tal and Iris Alkaher's, "Collaborative environmental projects in a multicultural society: Working from within separate or mutual landscapes?" the authors describe their efforts to do this in the highly charged…

  5. The evolutionary history of Darwin's finches: speciation, gene flow, and introgression in a fragmented landscape.

    PubMed

    Farrington, Heather L; Lawson, Lucinda P; Clark, Courtney M; Petren, Kenneth

    2014-10-01

    Many classic examples of adaptive radiations take place within fragmented systems such as islands or mountains, but the roles of mosaic landscapes and variable gene flow in facilitating species diversification is poorly understood. Here we combine phylogenetic and landscape genetic approaches to understand diversification in Darwin's finches, a model adaptive radiation. We combined sequence data from 14 nuclear introns, mitochondrial markers, and microsatellite variation from 51 populations of all 15 recognized species. Phylogenetic species-trees recovered seven major finch clades: ground, tree, vegetarian, Cocos Island, grey and green warbler finches, and a distinct clade of sharp-beaked ground finches (Geospiza cf. difficilis) basal to all ground and tree finches. The ground and tree finch clades lack species-level phylogenetic structure. Interisland gene flow and interspecies introgression vary geographically in predictable ways. First, several species exhibit concordant patterns of population divergence across the channel separating the Galápagos platform islands from the separate volcanic province of northern islands. Second, peripheral islands have more admixed populations while central islands maintain more distinct species boundaries. This landscape perspective highlights a likely role for isolation of peripheral populations in initial divergence, and demonstrates that peripheral populations may maintain genetic diversity through outbreeding during the initial stages of speciation. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  6. Divergences in holographic complexity

    NASA Astrophysics Data System (ADS)

    Reynolds, Alan; Ross, Simon F.

    2017-05-01

    We study the UV divergences in the action of the ‘Wheeler-de Witt patch’ in asymptotically AdS spacetimes, which has been conjectured to be dual to the computational complexity of the state of the dual field theory on a spatial slice of the boundary. We show that including a surface term in the action on the null boundaries which ensures invariance under coordinate transformations has the additional virtue of removing a stronger than expected divergence, making the leading divergence proportional to the proper volume of the boundary spatial slice. We compare the divergences in the action to divergences in the volume of a maximal spatial slice in the bulk, finding that the qualitative structure is the same, but subleading divergences have different relative coefficients in the two cases.

  7. Quantum skew divergence

    SciTech Connect

    Audenaert, Koenraad M. R.

    2014-11-15

    In this paper, we study the quantum generalisation of the skew divergence, which is a dissimilarity measure between distributions introduced by Lee in the context of natural language processing. We provide an in-depth study of the quantum skew divergence, including its relation to other state distinguishability measures. Finally, we present a number of important applications: new continuity inequalities for the quantum Jensen-Shannon divergence and the Holevo information, and a new and short proof of Bravyi's Small Incremental Mixing conjecture.

  8. Quantum skew divergence

    NASA Astrophysics Data System (ADS)

    Audenaert, Koenraad M. R.

    2014-11-01

    In this paper, we study the quantum generalisation of the skew divergence, which is a dissimilarity measure between distributions introduced by Lee in the context of natural language processing. We provide an in-depth study of the quantum skew divergence, including its relation to other state distinguishability measures. Finally, we present a number of important applications: new continuity inequalities for the quantum Jensen-Shannon divergence and the Holevo information, and a new and short proof of Bravyi's Small Incremental Mixing conjecture.

  9. The concept of hydrologic landscapes

    USGS Publications Warehouse

    Winter, T.C.

    2001-01-01

    Hydrologic landscapes are multiples or variations of fundamental hydrologic landscape units. A fundamental hydrologic landscape unit is defined on the basis of land-surface form, geology, and climate. The basic land-surface form of a fundamental hydrologic landscape unit is an upland separated from a lowland by an intervening steeper slope. Fundamental hydrologic landscape units have a complete hydrologic system consisting of surface runoff, ground-water flow, and interaction with atmospheric water. By describing actual landscapes in terms of land-surface slope, hydraulic properties of soils and geologic framework, and the difference between precipitation and evapotranspiration, the hydrologic system of actual landscapes can be conceptualized in a uniform way. This conceptual framework can then be the foundation for design of studies and data networks, syntheses of information on local to national scales, and comparison of process research across small study units in a variety of settings. The Crow Wing River watershed in central Minnesota is used as an example of evaluating stream discharge in the context of hydrologic landscapes. Lake-research watersheds in Wisconsin, Minnesota, North Dakota, and Nebraska are used as an example of using the hydrologic-landscapes concept to evaluate the effect of ground water on the degree of mineralization and major-ion chemistry of lakes that lie within ground-water flow systems.

  10. Higher brightness laser diodes with smaller slow axis divergence

    NASA Astrophysics Data System (ADS)

    Sun, Wenyang; Pathak, Rajiv; Campbell, Geoff; Eppich, Henry; Jacob, J. H.; Chin, Aland; Fryer, Jack

    2013-02-01

    The slow axis (SA) divergence of 20% fill-factor, 980nm, laser diodes (LDs) have been investigated under short pulsed (SP) and continuous (CW) operation. By analyzing the data collected under these two modes of operation, one finds that the SA divergence can be separated into two components: an intrinsic divergence and a thermally induced divergence. At low injected current and power, the intrinsic SA divergence is dominant while at high power their magnitudes are approximately equal. The thermal gradient across the broad stripe is negligible under SP operation and, the SA divergence increased at a much slower rate as a function of injected current, thereby increasing the brightness of the LD by 2X. SRL has redesigned microchannel coolers that remove the thermal gradient under CW operation thereby eliminating the thermally induced SA divergence resulting in LDs that are 2X brighter at 300W/bar.

  11. Mars Landscapes

    NASA Image and Video Library

    Spacecraft have studied the Martian surface for decades, giving Earthlings insights into the history, climate and geology of our nearest neighbor, Mars. These images are from "Mars Landscapes," a v...

  12. Sequence landscapes.

    PubMed Central

    Clift, B; Haussler, D; McConnell, R; Schneider, T D; Stormo, G D

    1986-01-01

    We describe a method for representing the structure of repeating sequences in nucleic-acids, proteins and other texts. A portion of the sequence is presented at the bottom of a CRT screen. Above the sequence is its landscape, which looks like a mountain range. Each mountain corresponds to a subsequence of the sequence. At the peak of every mountain is written the number of times that the subsequence appears. A data structure called a DAWG, which can be built in time proportional to the length of the sequence, is used to construct the landscape. For the 40 thousand bases of bacteriophage T7, the DAWG can be built in 30 seconds. The time to display any portion of the landscape is less than a second. Using sequence landscapes, one can quickly locate significant repeats. PMID:3753762

  13. Phylogeographic structure in an Australian freshwater shrimp largely pre-dates the geological origins of its landscape.

    PubMed

    Page, T J; Hughes, J M

    2007-04-01

    The phylogeographic structure of cryptic lineages within the freshwater shrimp Caridina indistincta Calman, 1926 (Decapoda: Atyidae) was investigated in an attempt to unravel any potential genetic influences of Quaternary sea-level oscillations. The study was based on mitochondrial DNA sequences from specimens from lakes and creeks in the sand dune areas of southeast Queensland, eastern Australia. Four divergent lineages were identified, two of which were from Moreton and North (N.) Stradbroke Islands. Lineage 'C1' has been found only on Moreton Island and the western part of N. Stradbroke Island, whereas 'C2' was found on the eastern side of N. Stradbroke Island and a few locations on the mainland. These diverged from each other during the Late Miocene/Pliocene and so are older than the current landscape in which they are found. Small-scale phylogeographic analysis of C1 identified four separate geographic areas, within the two islands, whose divergences date to the Pleistocene (approximately 100-300 thousand years ago ('kya')). The N. Stradbroke Island population of C2 also diverged from the mainland during the Pleistocene, as did a sympatric freshwater fish Rhadinocentrus ornatus Regan, 1914 (Melanotaeniidae). This implies that the ice-age sea-level changes may have structured these populations, although there is little observable influence of the last glacial maximum (approximately 18 kya). Most estimates for the age of the landscape (dunes, lakes) also fall within the Pleistocene and so the effect of sea-level change may be seen both in biology and geology.

  14. Mitochondrial DNA Detects a Complex Evolutionary History with Pleistocene Epoch Divergence for the Neotropical Malaria Vector Anopheles nuneztovari Sensu Lato

    PubMed Central

    Scarpassa, Vera Margarete; Conn, Jan E.

    2011-01-01

    Cryptic species and lineages characterize Anopheles nuneztovari s.l. Gabaldón, an important malaria vector in South America. We investigated the phylogeographic structure across the range of this species with cytochrome oxidase subunit I (COI) mitochondrial DNA sequences to estimate the number of clades and levels of divergence. Bayesian and maximum-likelihood phylogenetic analyses detected four groups distributed in two major monophyletic clades (I and II). Samples from the Amazon Basin were clustered in clade I, as were subclades II-A and II-B, whereas those from Bolivia/Colombia/Venezuela were restricted to one basal subclade (II-C). These data, together with a statistical parsimony network, confirm results of previous studies that An. nuneztovari is a species complex consisting of at least two cryptic taxa, one occurring in Colombia and Venezuela and the another occurring in the Amazon Basin. These data also suggest that additional incipient species may exist in the Amazon Basin. Divergence time and expansion tests suggested that these groups separated and expanded in the Pleistocene Epoch. In addition, the COI sequences clearly separated An. nuneztovari s.l. from the closely related species An. dunhami Causey, and three new records are reported for An. dunhami in Amazonian Brazil. These findings are relevant for vector control programs in areas where both species occur. Our analyses support dynamic geologic and landscape changes in northern South America, and infer particularly active divergence during the Pleistocene Epoch for New World anophelines. PMID:22049039

  15. Assessment of landscape diversity and determination of landscape hotspots - a case of Slovenia

    NASA Astrophysics Data System (ADS)

    Perko, Drago; Ciglič, Rok; Hrvatin, Mauro

    2017-04-01

    Areas with high landscape diversity can be regarded as landscape hotspots, and vice versa areas with low landscape diversity can be marked as landscape coldspots. The main purpose of this paper is to use quantitative geoinformatical approach and identify parts of our test area (the country of Slovenia) that can be described as very diverse according to natural landscapes and natural elements. We used different digital raster data of natural elements and landscape classifications and defined landscape diversity and landscape hotspots. We defined diversity for each raster pixel by counting the number of different unique types of landscape elements and types of landscapes in its neighborhood. Namely, the method was used separately to define diversity according to natural elements (types of relief forms, rocks, and vegetation) and diversity according to existing geographical landscape classifications of Slovenia (types of landscapes). In both cases one-tenth of Slovenia's surface with the highest landscape diversity was defined as landscape hotspots. The same applies to the coldspots. Additionally we tested the same method of counting different types of landscapes in certain radius also for the area of Europe in order to find areas that are more diverse at continental level. By doing so we were able to find areas that have similar level of diversity as Slovenia according to different European landscape classifications. Areas with landscape diversity may have an advantage in economic development, especially in tourism. Such areas are also important for biodiversity, habitat, and species diversity. On the other hand, localities where various natural influences mix can also be areas where it is hard to transfer best practices from one place to another because of the varying responses of the landscapes to human intervention. Thus it is important to know where areas with high landscape diversity are.

  16. Self-organization in irregular landscapes: Detecting autogenic interactions from field data using descriptive statistics and dynamical systems theory

    NASA Astrophysics Data System (ADS)

    Larsen, L.; Watts, D.; Khurana, A.; Anderson, J. L.; Xu, C.; Merritts, D. J.

    2015-12-01

    The classic signal of self-organization in nature is pattern formation. However, the interactions and feedbacks that organize depositional landscapes do not always result in regular or fractal patterns. How might we detect their existence and effects in these "irregular" landscapes? Emergent landscapes such as newly forming deltaic marshes or some restoration sites provide opportunities to study the autogenic processes that organize landscapes and their physical signatures. Here we describe a quest to understand autogenic vs. allogenic controls on landscape evolution in Big Spring Run, PA, a landscape undergoing restoration from bare-soil conditions to a target wet meadow landscape. The contemporary motivation for asking questions about autogenic vs. allogenic controls is to evaluate how important initial conditions or environmental controls may be for the attainment of management objectives. However, these questions can also inform interpretation of the sedimentary record by enabling researchers to separate signals that may have arisen through self-organization processes from those resulting from environmental perturbations. Over three years at Big Spring Run, we mapped the dynamic evolution of floodplain vegetation communities and distributions of abiotic variables and topography. We used principal component analysis and transition probability analysis to detect associative interactions between vegetation and geomorphic variables and convergent cross-mapping on lidar data to detect causal interactions between biomass and topography. Exploratory statistics revealed that plant communities with distinct morphologies exerted control on landscape evolution through stress divergence (i.e., channel initiation) and promoting the accumulation of fine sediment in channels. Together, these communities participated in a negative feedback that maintains low energy and multiple channels. Because of the spatially explicit nature of this feedback, causal interactions could not

  17. Disposable Landscapes

    Treesearch

    Kevin T. Smith

    2008-01-01

    Whether we are a traditionalist or on the cutting edge of landscape care, we need to take a deep breath and think about what we are trying to achieve, before we select a specific treatment or practice for tree care. We should measure that treatment or practice against what we know about the tree system. I say "system" because the recent years of Modern...

  18. Sharing a disparate landscape

    NASA Astrophysics Data System (ADS)

    Ali-Khan, Carolyne

    2010-06-01

    Working across boundaries of power, identity, and political geography is fraught with difficulties and contradictions. In Tali Tal and Iris Alkaher's, " Collaborative environmental projects in a multicultural society: Working from within separate or mutual landscapes?" the authors describe their efforts to do this in the highly charged atmosphere of Israel. This forum article offers a response to their efforts. Writing from a framework of critical pedagogy, I use the concepts of space and time to anchor my analysis, as I examine the issue of power in this Jew/Arab collaborative environmental project. This response problematizes "sharing" in a landscape fraught with disparities. It also looks to further Tal and Alkaher's work by geographically and politically grounding it in the broader current conflict and by juxtaposing sustainability with equity.

  19. Converging or Diverging Lens?

    ERIC Educational Resources Information Center

    Branca, Mario

    2013-01-01

    Why does a lens magnify? Why does it shrink objects? Why does this happen? The activities that we propose here are useful in helping us to understand how lenses work, and they show that the same lens can have different magnification capabilities. A converging lens can also act as a diverging lens. (Contains 4 figures.)

  20. Converging or Diverging Lens?

    ERIC Educational Resources Information Center

    Branca, Mario

    2013-01-01

    Why does a lens magnify? Why does it shrink objects? Why does this happen? The activities that we propose here are useful in helping us to understand how lenses work, and they show that the same lens can have different magnification capabilities. A converging lens can also act as a diverging lens. (Contains 4 figures.)

  1. Disorder-induced genetic divergence: A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Schulz, Michael; Pȩkalski, Andrzej

    2002-10-01

    We present a Monte Carlo simulation of a system composed of several populations, each living in a possibly different habitat. We show the influence of landscape disorder on the genetic pool of finite populations. We demonstrate that a strongly disordered environment generates an increase of the genetic distance between the populations on identical island. The distance becomes permanent for infinitely long times. On the contrary, landscapes with weak disorder offer only a temporarily allelic divergence which vanishes in the long time limit. Similarities between these phenomena and the well-known first-order phase transitions in the thermodynamics are analyzed.

  2. Divergence Boundary Conditions for Vector Helmholtz Equations with Divergence Constraints

    NASA Technical Reports Server (NTRS)

    Kangro, Urve; Nicolaides, Roy

    1997-01-01

    The idea of replacing a divergence constraint by a divergence boundary condition is investigated. The connections between the formulations are considered in detail. It is shown that the most common methods of using divergence boundary conditions do not always work properly. Necessary and sufficient conditions for the equivalence of the formulations are given.

  3. Divergent evolution in fluviokarst landscapes of central Kentucky

    USGS Publications Warehouse

    Phillips, J.D.; Martin, L.L.; Nordberg, V.G.; Andrews, W.A.

    2004-01-01

    Central Kentucky is characterized by a mixture of karst and fluvial features, typically manifested as mosaic of karst-rich/ channel-poor (KRCP) and channel-rich/karst-poor (CRKP) environments. At the regional scale the location and distribution of KRCP and CRKP areas are not always systematically related to structural, lithological, topographic, or other controls. This study examines the relationship of KRCP and CRKP zones along the Kentucky River gorge area, where rapid incision in the last 1??5 million years has lowered local base levels and modified slopes on the edge of the inner bluegrass plateau. At the scale of detailed field mapping on foot within a 4 km2 area, the development of karst and fluvial features is controlled by highly localized structural and topographic constraints, and can be related to slope changes associated with retreat of the Kentucky River gorge escarpment. A conceptual model of karst/fluvial transitions is presented, which suggests that minor, localized variations are sufficient to trigger a karst-fluvial or fluvial-karst switch when critical slope thresholds are crossed. ?? 2004 John Wiley and Sons, Ltd.

  4. Genetic structure and divergence in populations of Lutzomyia cruciata, a phlebotomine sand fly (Diptera: Psychodidae) vector of Leishmania mexicana in southeastern Mexico.

    PubMed

    Pech-May, Angélica; Marina, Carlos F; Vázquez-Domínguez, Ella; Berzunza-Cruz, Miriam; Rebollar-Téllez, Eduardo A; Narváez-Zapata, José A; Moo-Llanes, David; Ibáñez-Bernal, Sergio; Ramsey, Janine M; Becker, Ingeborg

    2013-06-01

    The low dispersal capacity of sand flies could lead to population isolation due to geographic barriers, climate variation, or to population fragmentation associated with specific local habitats due to landscape modification. The phlebotomine sand fly Lutzomyia cruciata has a wide distribution throughout Mexico and is a vector of Leishmania mexicana in the southeast. The aim of this study was to evaluate the genetic diversity, structure, and divergence within and among populations of Lu. cruciata in the state of Chiapas, and to infer the intra-specific phylogeny using the 3' end of the mitochondrial cytochrome b gene. We analyzed 62 sequences from four Lu. cruciata populations and found 26 haplotypes, high genetic differentiation and restricted gene flow among populations (Fst=0.416, Nm=0.701, p<0.001). The highest diversity values were recorded in populations from Loma Bonita and Guadalupe Miramar. Three lineages (100% bootstrap and 7% overall divergence) were identified using a maximum likelihood phylogenetic analysis which showed high genetic divergence (17.2-22.7%). A minimum spanning haplotype network also supported separation into three lineages. Genetic structure and divergence within and among Lu. cruciata populations are hence affected by geographic heterogeneity and evolutionary background. Data obtained in the present study suggest that Lu. cruciata in the state of Chiapas consists of at least three lineages. Such findings may have implications for vector capacity and hence for vector control strategies.

  5. Evolutionary Divergence of Aggregatibacter actinomycetemcomitans.

    PubMed

    Kittichotirat, W; Bumgarner, R E; Chen, C

    2016-01-01

    Gram-negative facultative Aggregatibacter actinomycetemcomitans is an oral pathogen associated with periodontitis. The genetic heterogeneity among A. actinomycetemcomitans strains has been long recognized. This study provides a comprehensive genomic analysis of A. actinomycetemcomitans and the closely related nonpathogenic Aggregatibacter aphrophilus. Whole genome sequencing by Illumina MiSeq platform was performed for 31 A. actinomycetemcomitans and 2 A. aphrophilus strains. Sequence similarity analysis shows a total of 3,220 unique genes across the 2 species, where 1,550 are core genes present in all genomes and 1,670 are variable genes (accessory genes) missing in at least 1 genome. Phylogenetic analysis based on 397 concatenated core genes distinguished A. aphrophilus and A. actinomycetemcomitans. The latter was in turn divided into 5 clades: clade b (serotype b), clade c (serotype c), clade e/f (serotypes e and f), clade a/d (serotypes a and d), and clade e' (serotype e strains). Accessory genes accounted for 14.1% to 23.2% of the A. actinomycetemcomitans genomes, with a majority belonging to the category of poorly characterized by Cluster of Orthologous Groups classification. These accessory genes were often organized into genomic islands (n = 387) with base composition biases, suggesting their acquisitions via horizontal gene transfer. There was a greater degree of similarity in gene content and genomic islands among strains within clades than between clades. Strains of clade e' isolated from human were found to be missing the genomic island that carries genes encoding cytolethal distending toxins. Taken together, the results suggest a pattern of sequential divergence, starting from the separation of A. aphrophilus and A. actinomycetemcomitans through gain and loss of genes and ending with the divergence of the latter species into distinct clades and serotypes. With differing constellations of genes, the A. actinomycetemcomitans clades may have evolved

  6. Common Garden Experiment Reveals Genetic Control of Phenotypic Divergence between Swamp Sparrow Subspecies That Lack Divergence in Neutral Genotypes

    PubMed Central

    Ballentine, Barbara; Greenberg, Russell

    2010-01-01

    Background Adaptive divergence between populations in the face of strong selection on key traits can lead to morphological divergence between populations without concomitant divergence in neutral DNA. Thus, the practice of identifying genetically distinct populations based on divergence in neutral DNA may lead to a taxonomy that ignores evolutionarily important, rapidly evolving, locally-adapted populations. Providing evidence for a genetic basis of morphological divergence between rapidly evolving populations that lack divergence in selectively neutral DNA will not only inform conservation efforts but also provide insight into the mechanisms of the early processes of speciation. The coastal plain swamp sparrow, a recent colonist of tidal marsh habitat, differs from conspecific populations in a variety of phenotypic traits yet remains undifferentiated in neutral DNA. Methods and Principal Findings Here we use an experimental approach to demonstrate that phenotypic divergence between ecologically separated populations of swamp sparrows is the result of local adaptation despite the lack of divergence in neutral DNA. We find that morphological (bill size and plumage coloration) and life history (reproductive effort) differences observed between wild populations were maintained in laboratory raised individuals suggesting genetic divergence of fitness related traits. Conclusions and Significance Our results support the hypothesis that phenotypic divergence in swamps sparrows is the result of genetic differentiation, and demonstrate that adaptive traits have evolved more rapidly than neutral DNA in these ecologically divergent populations that may be in the early stages of speciation. Thus, identifying evolutionarily important populations based on divergence in selectively neutral DNA could miss an important level of biodiversity and mislead conservation efforts. PMID:20419104

  7. Three Divergent Subpopulations of the Malaria Parasite Plasmodium knowlesi

    PubMed Central

    Lin, Lee C.; Rovie-Ryan, Jeffrine J.; Kadir, Khamisah A.; Anderios, Fread; Hisam, Shamilah; Sharma, Reuben S.K.; Singh, Balbir; Conway, David J.

    2017-01-01

    Multilocus microsatellite genotyping of Plasmodium knowlesi isolates previously indicated 2 divergent parasite subpopulations in humans on the island of Borneo, each associated with a different macaque reservoir host species. Geographic divergence was also apparent, and independent sequence data have indicated particularly deep divergence between parasites from mainland Southeast Asia and Borneo. To resolve the overall population structure, multilocus microsatellite genotyping was conducted on a new sample of 182 P. knowlesi infections (obtained from 134 humans and 48 wild macaques) from diverse areas of Malaysia, first analyzed separately and then in combination with previous data. All analyses confirmed 2 divergent clusters of human cases in Malaysian Borneo, associated with long-tailed macaques and pig-tailed macaques, and a third cluster in humans and most macaques in peninsular Malaysia. High levels of pairwise divergence between each of these sympatric and allopatric subpopulations have implications for the epidemiology and control of this zoonotic species. PMID:28322705

  8. Experimental investigation of flow through planar double divergent nozzles

    NASA Astrophysics Data System (ADS)

    Arora, Rajat; Vaidyanathan, Aravind

    2015-07-01

    Dual bell nozzle is one of the feasible and cost effective techniques for altitude adaptation. Planar double divergent nozzle with a rectangular cross section was designed for two different NPR's to simulate and investigate the flow regimes similar to those inside the dual bell nozzle. Measurements involved flow visualization using Schlieren technique and wall static pressure measurements. The flow transition between the two nozzles at the respective inflection points and the formation of recirculation region due to flow separation was analyzed in detail. Cold flow tests were performed on the double divergent nozzle in the over-expanded conditions to study the shock wave characteristics. The results obtained from the two independent double divergent nozzles were compared with those obtained from a single divergent nozzle of the same area ratio. From the experiments it was observed that inflection angle played a key role in defining the type of shock structures existing inside the double divergent nozzles.

  9. PESP Landscaping Initiative

    EPA Pesticide Factsheets

    Landscaping practices can positively or negatively affect local environments and human health. The Landscaping Initiative seeks to enhance benefits of landscaping while reducing need for pesticides, fertilizers, etc., by working with partners.

  10. Local adaptation in Trinidadian guppies alters stream ecosystem structure at landscape scales despite high environmental variability

    USGS Publications Warehouse

    Simon, Troy N.; Bassar, Ronald D.; Binderup, Andrew J.; Flecker, Alex S.; Freeman, Mary C.; Gilliam, James F.; Marshall, Michael C.; Thomas, Steve A.; Travis, Joseph; Reznick, David N.; Pringle, Catherine M.

    2017-01-01

    While previous studies have shown that evolutionary divergence alters ecological processes in small-scale experiments, a major challenge is to assess whether such evolutionary effects are important in natural ecosystems at larger spatial scales. At the landscape scale, across eight streams in the Caroni drainage, we found that the presence of locally adapted populations of guppies (Poecilia reticulata) is associated with reduced algal biomass and increased invertebrate biomass, while the opposite trends were true in streams with experimentally introduced populations of non-locally adapted guppies. Exclusion experiments conducted in two separate reaches of a single stream showed that guppies with locally adapted phenotypes significantly reduced algae with no effect on invertebrates, while non-adapted guppies had no effect on algae but significantly reduced invertebrates. These divergent effects of phenotype on stream ecosystems are comparable in strength to the effects of abiotic factors (e.g., light) known to be important drivers of ecosystem condition. They also corroborate the results of previous experiments conducted in artificial streams. Our results demonstrate that local adaptation can produce phenotypes with significantly different effects in natural ecosystems at a landscape scale, within a tropical watershed, despite high variability in abiotic factors: five of the seven physical and chemical parameters measured across the eight study streams varied by more than one order of magnitude. Our findings suggest that ecosystem structure is, in part, an evolutionary product and not simply an ecological pattern.

  11. Maximizing the Divergence from a Hierarchical Model of Quantum States

    NASA Astrophysics Data System (ADS)

    Weis, Stephan; Knauf, Andreas; Ay, Nihat; Zhao, Ming-Jing

    2015-03-01

    We study many-party correlations quantified in terms of the Umegaki relative entropy (divergence) from a Gibbs family known as a hierarchical model. We derive these quantities from the maximum-entropy principle which was used earlier to define the closely related irreducible correlation. We point out the differences between quantum states and probability vectors which exist in hierarchical models, in the divergence from a hierarchical model and in local maximizers of this divergence. The differences are, respectively, missing factorization, discontinuity and reduction of uncertainty. We discuss global maximizers of the mutual information of separable qubit states.

  12. Cryptic diversity and deep divergence in an upper Amazonian leaflitter frog, Eleutherodactylus ockendeni

    PubMed Central

    Elmer, Kathryn R; Dávila, José A; Lougheed, Stephen C

    2007-01-01

    Background The forests of the upper Amazon basin harbour some of the world's highest anuran species richness, but to date we have only the sparsest understanding of the distribution of genetic diversity within and among species in this region. To quantify region-wide genealogical patterns and to test for the presence of deep intraspecific divergences that have been documented in some other neotropical anurans, we developed a molecular phylogeny of the wide-spread terrestrial leaflitter frog Eleutherodactylus ockendeni (Leptodactylidae) from 13 localities throughout its range in Ecuador using data from two mitochondrial genes (16S and cyt b; 1246 base pairs). We examined the relation between divergence of mtDNA and the nuclear genome, as sampled by five species-specific microsatellite loci, to evaluate indirectly whether lineages are reproductively isolated where they co-occur. Our extensive phylogeographic survey thus assesses the spatial distribution of E. ockendeni genetic diversity across eastern Ecuador. Results We identified three distinct and well-supported clades within the Ecuadorean range of E. ockendeni: an uplands clade spanning north to south, a northeastern and central lowlands clade, and a central and southeastern clade, which is basal. Clades are separated by 12% to 15% net corrected p-distance for cytochrome b, with comparatively low sequence divergence within clades. Clades marginally overlap in some geographic areas (e.g., Napo River basin) but are reproductively isolated, evidenced by diagnostic differences in microsatellite PCR amplification profiles or DNA repeat number and coalescent analyses (in MDIV) best modelled without migration. Using Bayesian (BEAST) and net phylogenetic estimates, the Southeastern Clade diverged from the Upland/Lowland clades in the mid-Miocene or late Oligocene. Lowland and Upland clades speciated more recently, in the early or late Miocene. Conclusion Our findings uncover previously unsuspected cryptic species

  13. Genetics of ecological divergence during speciation

    PubMed Central

    Arnegard, Matthew E.; McGee, Matthew D.; Matthews, Blake; Marchinko, Kerry B.; Conte, Gina L.; Kabir, Sahriar; Bedford, Nicole; Bergek, Sara; Chan, Yingguang Frank; Jones, Felicity C.; Kingsley, David M.; Peichel, Catherine L.; Schluter, Dolph

    2014-01-01

    Ecological differences often evolve early in speciation as divergent natural selection drives adaptation to distinct ecological niches, leading ultimately to reproductive isolation. Though this process is a major generator of biodiversity, its genetic basis remains poorly understood. Here we investigate the genetic architecture of niche differentiation in a sympatric species pair of threespine stickleback fish by mapping the environment-dependent effects of phenotypic traits on hybrid feeding and performance under semi-natural conditions. We show that multiple, unlinked loci act largely additively to determine position along the major niche axis separating these recently diverged species. We also find that functional mismatch between phenotypic traits reduces growth of some stickleback hybrids beyond that expected from an intermediate phenotype, suggesting a role for epistasis between the underlying genes. This functional mismatch might lead to hybrid incompatibilities that are analogous to those underlying intrinsic reproductive isolation but that depend on the ecological context. PMID:24909991

  14. Gluon mass generation without seagull divergences

    NASA Astrophysics Data System (ADS)

    Aguilar, Arlene C.; Papavassiliou, Joannis

    2010-02-01

    Dynamical gluon mass generation has been traditionally plagued with seagull divergences, and all regularization procedures proposed over the years yield finite but scheme-dependent gluon masses. In this work we show how such divergences can be eliminated completely by virtue of a characteristic identity, valid in dimensional regularization. The ability to trigger the aforementioned identity hinges crucially on the particular Ansatz employed for the three-gluon vertex entering into the Schwinger-Dyson equation governing the gluon propagator. The use of the appropriate three-gluon vertex brings about an additional advantage: one obtains two separate (but coupled) integral equations, one for the effective charge and one for the gluon mass. This system of integral equations has a unique solution, which unambiguously determines these two quantities. Most notably, the effective charge freezes in the infrared, and the gluon mass displays power-law running in the ultraviolet, in agreement with earlier considerations.

  15. Weathering instability and landscape evolution

    NASA Astrophysics Data System (ADS)

    Phillips, Jonathan D.

    2005-04-01

    likely; although stability may be present at intermediate temporal scales if weathering-erosion feedbacks are weak. The distinction is important because stability is associated with convergent evolution whereby the effects of initial variations or disturbances are reduced over time as the landscape converges toward a stable equilibrium state. Instability, by contrast, indicates divergent evolution, increasing differentiation over time, and the persistence and growth of disturbance effects and initial variations.

  16. Landscaping for energy efficiency

    SciTech Connect

    1995-04-01

    This publication by the National Renewable Energy Laboratory addresses the use of landscaping for energy efficiency. The topics of the publication include minimizing energy expenses; landscaping for a cleaner environment; climate, site, and design considerations; planning landscape; and selecting and planting trees and shrubs. A source list for more information on landscaping for energy efficiency and a reading list are included.

  17. Degree landscapes in scale-free networks.

    PubMed

    Axelsen, Jacob Bock; Bernhardsson, Sebastian; Rosvall, Martin; Sneppen, Kim; Trusina, Ala

    2006-09-01

    We generalize the degree-organizational view of real-world networks with broad degree distributions in a landscape analog with mountains (high-degree nodes) and valleys (low-degree nodes). For example, correlated degrees between adjacent nodes correspond to smooth landscapes (social networks), hierarchical networks to one-mountain landscapes (the Internet), and degree-disassortative networks without hierarchical features to rough landscapes with several mountains. To quantify the topology, we here measure the widths of the mountains and the separation between different mountains. We also generate ridge landscapes to model networks organized under constraints imposed by the space the networks are embedded in, associated to spatial or in molecular networks to functional localization.

  18. An Exponential Regulator for Rapidity Divergences

    SciTech Connect

    Li, Ye; Neill, Duff; Zhu, Hua Xing

    2016-04-01

    Finding an efficient and compelling regularization of soft and collinear degrees of freedom at the same invariant mass scale, but separated in rapidity is a persistent problem in high-energy factorization. In the course of a calculation, one encounters divergences unregulated by dimensional regularization, often called rapidity divergences. Once regulated, a general framework exists for their renormalization, the rapidity renormalization group (RRG), leading to fully resummed calculations of transverse momentum (to the jet axis) sensitive quantities. We examine how this regularization can be implemented via a multi-differential factorization of the soft-collinear phase-space, leading to an (in principle) alternative non-perturbative regularization of rapidity divergences. As an example, we examine the fully-differential factorization of a color singlet's momentum spectrum in a hadron-hadron collision at threshold. We show how this factorization acts as a mother theory to both traditional threshold and transverse momentum resummation, recovering the classical results for both resummations. Examining the refactorization of the transverse momentum beam functions in the threshold region, we show that one can directly calculate the rapidity renormalized function, while shedding light on the structure of joint resummation. Finally, we show how using modern bootstrap techniques, the transverse momentum spectrum is determined by an expansion about the threshold factorization, leading to a viable higher loop scheme for calculating the relevant anomalous dimensions for the transverse momentum spectrum.

  19. Using Dendritic Heat Maps to Simultaneously Display Genotype Divergence with Phenotype Divergence

    PubMed Central

    Kellom, Matthew; Raymond, Jason

    2016-01-01

    The advancement of techniques to visualize and analyze large-scale sequencing datasets is an area of active research and is rooted in traditional techniques such as heat maps and dendrograms. We introduce dendritic heat maps that display heat map results over aligned DNA sequence clusters for a range of clustering cutoffs. Dendritic heat maps aid in visualizing the effects of group differences on clustering hierarchy and relative abundance of sampled sequences. Here, we artificially generate two separate datasets with simplified mutation and population growth procedures with GC content group separation to use as example phenotypes. In this work, we use the term phenotype to represent any feature by which groups can be separated. These sequences were clustered in a fractional identity range of 0.75 to 1.0 using agglomerative minimum-, maximum-, and average-linkage algorithms, as well as a divisive centroid-based algorithm. We demonstrate that dendritic heat maps give freedom to scrutinize specific clustering levels across a range of cutoffs, track changes in phenotype inequity across multiple levels of sequence clustering specificity, and easily visualize how deeply rooted changes in phenotype inequity are in a dataset. As genotypes diverge in sample populations, clusters are shown to break apart into smaller clusters at higher identity cutoff levels, similar to a dendrogram. Phenotype divergence, which is shown as a heat map of relative abundance bin response, may or may not follow genotype divergences. This joined view highlights the relationship between genotype and phenotype divergence for treatment groups. We discuss the minimum-, maximum-, average-, and centroid-linkage algorithm approaches to building dendritic heat maps and make a case for the divisive “top-down” centroid-based clustering methodology as being the best option visualize the effects of changing factors on clustering hierarchy and relative abundance. PMID:27536963

  20. Segmenting the human genome based on states of neutral genetic divergence.

    PubMed

    Kuruppumullage Don, Prabhani; Ananda, Guruprasad; Chiaromonte, Francesca; Makova, Kateryna D

    2013-09-03

    Many studies have demonstrated that divergence levels generated by different mutation types vary and covary across the human genome. To improve our still-incomplete understanding of the mechanistic basis of this phenomenon, we analyze several mutation types simultaneously, anchoring their variation to specific regions of the genome. Using hidden Markov models on insertion, deletion, nucleotide substitution, and microsatellite divergence estimates inferred from human-orangutan alignments of neutrally evolving genomic sequences, we segment the human genome into regions corresponding to different divergence states--each uniquely characterized by specific combinations of divergence levels. We then parsed the mutagenic contributions of various biochemical processes associating divergence states with a broad range of genomic landscape features. We find that high divergence states inhabit guanine- and cytosine (GC)-rich, highly recombining subtelomeric regions; low divergence states cover inner parts of autosomes; chromosome X forms its own state with lowest divergence; and a state of elevated microsatellite mutability is interspersed across the genome. These general trends are mirrored in human diversity data from the 1000 Genomes Project, and departures from them highlight the evolutionary history of primate chromosomes. We also find that genes and noncoding functional marks [annotations from the Encyclopedia of DNA Elements (ENCODE)] are concentrated in high divergence states. Our results provide a powerful tool for biomedical data analysis: segmentations can be used to screen personal genome variants--including those associated with cancer and other diseases--and to improve computational predictions of noncoding functional elements.

  1. Adaptation with gene flow across the landscape in a dune sunflower.

    PubMed

    Andrew, Rose L; Ostevik, Katherine L; Ebert, Daniel P; Rieseberg, Loren H

    2012-05-01

    Isolation by adaptation increases divergence at neutral loci when natural selection against immigrants reduces the rate of gene flow between different habitats. This can occur early in the process of adaptive divergence and is a key feature of ecological speciation. Despite the ability of isolation by distance (IBD) and other forms of landscape resistance to produce similar patterns of neutral divergence within species, few studies have used landscape genetics to control for these other forces. We have studied the divergence of Helianthus petiolaris ecotypes living in active sand dunes and adjacent non-dune habitat, using landscape genetics approaches, such as circuit theory and multiple regression of distance matrices, in addition to coalescent modelling. Divergence between habitats was significant, but not strong, and was shaped by IBD. We expected that increased resistance owing to patchy and unfavourable habitat in the dunes would contribute to divergence. Instead, we found that landscape resistance models with lower resistance in the dunes performed well as predictors of genetic distances among subpopulations. Nevertheless, habitat class remained a strong predictor of genetic distance when controlling for isolation by resistance and IBD. We also measured environmental variables at each site and confirmed that specific variables, especially soil nitrogen and vegetation cover, explained a greater proportion of variance in genetic distance than did landscape or the habitat classification alone. Asymmetry in effective population sizes and numbers of migrants per generation was detected using coalescent modelling with Bayesian inference, which is consistent with incipient ecological speciation being driven by the dune habitat.

  2. Union of phylogeography and landscape genetics

    PubMed Central

    Rissler, Leslie J.

    2016-01-01

    Phylogeography and landscape genetics have arisen within the past 30 y. Phylogeography is said to be the bridge between population genetics and systematics, and landscape genetics the bridge between landscape ecology and population genetics. Both fields can be considered as simply the amalgamation of classic biogeography with genetics and genomics; however, they differ in the temporal, spatial, and organismal scales addressed and the methodology used. I begin by briefly summarizing the history and purview of each field and suggest that, even though landscape genetics is a younger field (coined in 2003) than phylogeography (coined in 1987), early studies by Dobzhansky on the “microgeographic races” of Linanthus parryae in the Mojave Desert of California and Drosophila pseudoobscura across the western United States presaged the fields by over 40 y. Recent advances in theory, models, and methods have allowed researchers to better synthesize ecological and evolutionary processes in their quest to answer some of the most basic questions in biology. I highlight a few of these novel studies and emphasize three major areas ripe for investigation using spatially explicit genomic-scale data: the biogeography of speciation, lineage divergence and species delimitation, and understanding adaptation through time and space. Examples of areas in need of study are highlighted, and I end by advocating a union of phylogeography and landscape genetics under the more general field: biogeography. PMID:27432989

  3. Infrared divergences in de Sitter space

    SciTech Connect

    Polarski, D. Service d'Astrophysique, CEN Saclay, 91191 Gif-sur-Yvette CEDEX, France)

    1991-03-15

    Infrared divergences in de Sitter space are considered. It is shown that symmetry breaking is unavoidable only when the infrared divergence is strong enough. The static vacuum has no symmetry breaking despite the presence of an infrared divergence.

  4. Convergence with Divergence: A Sound Change in Vernacular Black English.

    ERIC Educational Resources Information Center

    Denning, Keith

    1989-01-01

    Quantitative evidence is presented for a change in vernacular Black English (VBE) that appears to involve increasing similarities between VBE and other varieties. It is suggested that, although Black varieties and White varieties of English remain distinct and undergo certain changes separately, this need not be regarded as absolute divergence.…

  5. Computers and the landscape

    Treesearch

    Gary H. Elsner

    1979-01-01

    Computers can analyze and help to plan the visual aspects of large wildland landscapes. This paper categorizes and explains current computer methods available. It also contains a futuristic dialogue between a landscape architect and a computer.

  6. Isolation-by-distance in landscapes: considerations for landscape genetics

    PubMed Central

    van Strien, M J; Holderegger, R; Van Heck, H J

    2015-01-01

    In landscape genetics, isolation-by-distance (IBD) is regarded as a baseline pattern that is obtained without additional effects of landscape elements on gene flow. However, the configuration of suitable habitat patches determines deme topology, which in turn should affect rates of gene flow. IBD patterns can be characterized either by monotonically increasing pairwise genetic differentiation (for example, FST) with increasing interdeme geographic distance (case-I pattern) or by monotonically increasing pairwise genetic differentiation up to a certain geographical distance beyond which no correlation is detectable anymore (case-IV pattern). We investigated if landscape configuration influenced the rate at which a case-IV pattern changed to a case-I pattern. We also determined at what interdeme distance the highest correlation was measured between genetic differentiation and geographic distance and whether this distance corresponded to the maximum migration distance. We set up a population genetic simulation study and assessed the development of IBD patterns for several habitat configurations and maximum migration distances. We show that the rate and likelihood of the transition of case-IV to case-I FST–distance relationships was strongly influenced by habitat configuration and maximum migration distance. We also found that the maximum correlation between genetic differentiation and geographic distance was not related to the maximum migration distance and was measured across all deme pairs in a case-I pattern and, for a case-IV pattern, at the distance where the FST–distance curve flattens out. We argue that in landscape genetics, separate analyses should be performed to either assess IBD or the landscape effects on gene flow. PMID:25052412

  7. Landscape Management: Field Supervisor.

    ERIC Educational Resources Information Center

    Newton, Deborah; Newton, Steve

    This module is the third volume in a series of instructional materials on landscape management. The materials are designed to help teachers train students in the job skills they will need in landscape occupations. The module contains six instructional units that cover the following topics: orientation; basic landscape design principles; irrigation…

  8. FRAGSTATS: spatial pattern analysis program for quantifying landscape structure.

    Treesearch

    Kevin McGarigal; Barbara J. Marks

    1995-01-01

    This report describes a program, FRAGSTATS, developed to quantify landscape structure. FRAGSTATS offers a comprehensive choice of landscape metrics and was designed to be as versatile as possible. The program is almost completely automated and thus requires little technical training. Two separate versions of FRAGSTATS exist: one for vector images and one for raster...

  9. Bridging the gap between landscape ecologyand natural resource management

    Treesearch

    Monica G. Turner; Thomas R. Crow; Jianguo Liu; Dale Rabe; Charles F. Rabeni; Patricia A. Soranno; William W. Taylor; Kristiina A. Vogt; John A. Wiens

    2002-01-01

    The challenges facing natural resource managers occur over entire landscapes and involve landscape components at many scales. Many resource managers are shifting their approach from managing resources such as fish, wildlife, and water separately to managing for the integrity of entire ecosystems (Christensen et al., 1996). Indeed, nearly all resource...

  10. Gardener and Landscape Worker. Student Material. Competency Based Education Curriculum.

    ERIC Educational Resources Information Center

    Long, Diana

    This secondary-level, competency-based curriculum contains modules for Gardener and Landscape Worker. A companion teacher's guide is available separately--see note. Each module contains a number of West Virginia-validated Gardener and Landscape Worker tasks/competencies with a performance guide listing the steps needed to perform each task,…

  11. Separated Shoulder

    MedlinePlus

    Separated shoulder Overview By Mayo Clinic Staff A separated shoulder is an injury to the ligaments that hold your collarbone (clavicle) to your shoulder blade. In a mild separated shoulder, the ligaments ...

  12. Landscape genetics of plants.

    PubMed

    Holderegger, Rolf; Buehler, Dominique; Gugerli, Felix; Manel, Stéphanie

    2010-12-01

    Landscape genetics is the amalgamation of landscape ecology and population genetics to help with understanding microevolutionary processes such as gene flow and adaptation. In this review, we examine why landscape genetics of plants lags behind that of animals, both in number of studies and consideration of landscape elements. The classical landscape distance/resistance approach to study gene flow is challenging in plants, whereas boundary detection and the assessment of contemporary gene flow are more feasible. By contrast, the new field of landscape genetics of adaptive genetic variation, establishing the relationship between adaptive genomic regions and environmental factors in natural populations, is prominent in plant studies. Landscape genetics is ideally suited to study processes such as migration and adaptation under global change.

  13. Contrasting effects of landscape features on genetic structure in different geographic regions in the ornate dragon lizard, Ctenophorus ornatus.

    PubMed

    Levy, Esther; Tomkins, Joseph L; Lebas, Natasha R; Kennington, W Jason

    2013-08-01

    Habitat fragmentation can have profound effects on the distribution of genetic variation within and between populations. Previously, we showed that in the ornate dragon lizard, Ctenophorus ornatus, lizards residing on outcrops that are separated by cleared agricultural land are significantly more isolated and hold less genetic variation than lizards residing on neighbouring outcrops connected by undisturbed native vegetation. Here, we extend the fine-scale study to examine the pattern of genetic variation and population structure across the species' range. Using a landscape genetics approach, we test whether land clearing for agricultural purposes has affected the population structure of the ornate dragon lizard. We found significant genetic differentiation between outcrop populations (FST  = 0.12), as well as isolation by distance within each geographic region. In support of our previous study, land clearing was associated with higher genetic divergences between outcrops and lower genetic variation within outcrops, but only in the region that had been exposed to intense agriculture for the longest period of time. No other landscape features influenced population structure in any geographic region. These results show that the effects of landscape features can vary across species' ranges and suggest there may be a temporal lag in response to contemporary changes in land use. These findings therefore highlight the need for caution when assessing the impact of contemporary land use practices on genetic variation and population structure.

  14. Semantic search during divergent thinking.

    PubMed

    Hass, Richard W

    2017-09-01

    Divergent thinking, as a method of examining creative cognition, has not been adequately analyzed in the context of modern cognitive theories. This article casts divergent thinking responding in the context of theories of memory search. First, it was argued that divergent thinking tasks are similar to semantic fluency tasks, but are more constrained, and less well structured. Next, response time distributions from 54 participants were analyzed for temporal and semantic clustering. Participants responded to two prompts from the alternative uses test: uses for a brick and uses for a bottle, for two minutes each. Participants' cumulative response curves were negatively accelerating, in line with theories of search of associative memory. However, results of analyses of semantic and temporal clustering suggested that clustering is less evident in alternative uses responding compared to semantic fluency tasks. This suggests either that divergent thinking responding does not involve an exhaustive search through a clustered memory trace, but rather that the process is more exploratory, yielding fewer overall responses that tend to drift away from close associates of the divergent thinking prompt. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. The phylogeography of an alpine leaf beetle: divergence within Oreina elongata spans several ice ages.

    PubMed

    Borer, Matthias; Alvarez, Nadir; Buerki, Sven; Margraf, Nicolas; Rahier, Martine; Naisbit, Russell E

    2010-11-01

    The genetic landscape of the European flora and fauna was shaped by the ebb and flow of populations with the shifting ice during Quaternary climate cycles. While this has been well demonstrated for lowland species, less is known about high altitude taxa. Here we analyze the phylogeography of the leaf beetle Oreina elongata from 20 populations across the Alps and Apennines. Three mitochondrial and one nuclear region were sequenced in 64 individuals. Within an mtDNA phylogeny, three of seven subspecies are monophyletic. The species is chemically defended and aposematic, with green and blue forms showing geographic variation and unexpected within-population polymorphism. These warning colors show pronounced east-west geographical structure in distribution, but the phylogeography suggests repeated origin and loss. Basal clades come from the central Alps. Ancestors of other clades probably survived across northern Italy and the northern Adriatic, before separation of eastern, southern and western populations and rapid spread through the western Alps. After reviewing calibrated gene-specific substitution rates in the literature, we use partitioned Bayesian coalescent analysis to date our phylogeography. The major clades diverged long before the last glacial maximum, suggesting that O. elongata persisted many glacial cycles within or at the edges of the Alps and Apennines. When analyzing additional barcoding pairwise distances, we find strong evidence to consider O. elongata as a species complex rather than a single species.

  16. Evolutionary comparison reveals that diverging CTCF sites are signatures of ancestral topological associating domains borders

    PubMed Central

    Gómez-Marín, Carlos; Tena, Juan J.; Acemel, Rafael D.; López-Mayorga, Macarena; Naranjo, Silvia; de la Calle-Mustienes, Elisa; Maeso, Ignacio; Beccari, Leonardo; Aneas, Ivy; Vielmas, Erika; Bovolenta, Paola; Nobrega, Marcelo A.; Carvajal, Jaime; Gómez-Skarmeta, José Luis

    2015-01-01

    Increasing evidence in the last years indicates that the vast amount of regulatory information contained in mammalian genomes is organized in precise 3D chromatin structures. However, the impact of this spatial chromatin organization on gene expression and its degree of evolutionary conservation is still poorly understood. The Six homeobox genes are essential developmental regulators organized in gene clusters conserved during evolution. Here, we reveal that the Six clusters share a deeply evolutionarily conserved 3D chromatin organization that predates the Cambrian explosion. This chromatin architecture generates two largely independent regulatory landscapes (RLs) contained in two adjacent topological associating domains (TADs). By disrupting the conserved TAD border in one of the zebrafish Six clusters, we demonstrate that this border is critical for preventing competition between promoters and enhancers located in separated RLs, thereby generating different expression patterns in genes located in close genomic proximity. Moreover, evolutionary comparison of Six-associated TAD borders reveals the presence of CCCTC-binding factor (CTCF) sites with diverging orientations in all studied deuterostomes. Genome-wide examination of mammalian HiC data reveals that this conserved CTCF configuration is a general signature of TAD borders, underscoring that common organizational principles underlie TAD compartmentalization in deuterostome evolution. PMID:26034287

  17. Divergence-based vector quantization.

    PubMed

    Villmann, Thomas; Haase, Sven

    2011-05-01

    Supervised and unsupervised vector quantization methods for classification and clustering traditionally use dissimilarities, frequently taken as Euclidean distances. In this article, we investigate the applicability of divergences instead, focusing on online learning. We deduce the mathematical fundamentals for its utilization in gradient-based online vector quantization algorithms. It bears on the generalized derivatives of the divergences known as Fréchet derivatives in functional analysis, which reduces in finite-dimensional problems to partial derivatives in a natural way. We demonstrate the application of this methodology for widely applied supervised and unsupervised online vector quantization schemes, including self-organizing maps, neural gas, and learning vector quantization. Additionally, principles for hyperparameter optimization and relevance learning for parameterized divergences in the case of supervised vector quantization are given to achieve improved classification accuracy.

  18. Graybody Factors and Infrared Divergences

    NASA Astrophysics Data System (ADS)

    Anderson, Paul; Fabbri, Alessandro; Balbinot, Roberto; Parentani, Renaud

    2015-04-01

    A method of computing the gray-body factors for static spherically symmetric and BEC acoustic black holes using a Volterra integral equation is given. The results are used to investigate infrared divergences in the particle number, two-point function, point-split stress-energy tensor and density-density correlation function. Infrared divergences in the particle number and two-point function occur if the gray-body factor approaches a nonzero constant in the zero frequency limit, as happens for Schwarzschild-de Sitter black holes and BEC acoustic black holes. However, no infrared divergences occur in the point-split stress-energy tensor or the density-density correlation function. Supported in part by the National Science Foundation under Grant Nos. PHY-0856050 and PHY-1308325.

  19. Ultracapacitor separator

    DOEpatents

    Wei, Chang; Jerabek, Elihu Calvin; LeBlanc, Jr., Oliver Harris

    2001-03-06

    An ultracapacitor includes two solid, nonporous current collectors, two porous electrodes separating the collectors, a porous separator between the electrodes and an electrolyte occupying the pores in the electrodes and separator. The electrolyte is a polar aprotic organic solvent and a salt. The porous separator comprises a wet laid cellulosic material.

  20. Divergent Thinking and Interview Ratings

    ERIC Educational Resources Information Center

    Batey, Mark; Rawles, Richard; Furnham, Adrian

    2009-01-01

    This study examined divergent thinking (DT) test scores of applicants taking part in a selection procedure for an undergraduate psychology degree (N = 370). Interviewers made six specific (creative intelligence, motivation, work habits, emotional stability, sociability, and social responsibility) and one overall recommendation rating on each…

  1. Divergent Thinking and Interview Ratings

    ERIC Educational Resources Information Center

    Batey, Mark; Rawles, Richard; Furnham, Adrian

    2009-01-01

    This study examined divergent thinking (DT) test scores of applicants taking part in a selection procedure for an undergraduate psychology degree (N = 370). Interviewers made six specific (creative intelligence, motivation, work habits, emotional stability, sociability, and social responsibility) and one overall recommendation rating on each…

  2. Dynamic investigation of static divergence: Analysis and testing

    NASA Astrophysics Data System (ADS)

    Heeg, Jennifer

    2000-10-01

    The phenomenon known as aeroelastic divergence is the focus of this work. The analyses and experiment presented here show that divergence can occur without a structural dynamic mode losing its oscillatory nature. Aeroelastic divergence occurs when the structural restorative capability or stiffness of a structure is overwhelmed by the static aerodynamic moment. This static aeroelastic coupling does not require the structural dynamic system behavior to cease, however. Aeroelastic changes in the dynamic mode behavior are governed not only by the stiffness, but by damping and inertial properties. The work presented here supports these fundamental assertions by examining a simple system: a typical section airfoil with only a rotational structural degree of freedom. Aeroelastic stability analysis is performed in the discrete time domain. The aerodynamic, structural dynamic, and downwash relationships are cast as time-marching equations and combined to form aeroelastic state space equations. The discrete time eigenvalues and eigenvectors of the coupled system are computed. This method is advantageous because the exact roots and the degree of stability of the system are determined, within the framework of the aerodynamic and structural dynamic representations. The discrete-time eigenvalues are transformed into the continuous time domain to facilitate their interpretation. Results from the analysis have identified configurations of a simple model that exhibit different types of dynamic mode behavior as the system encounters divergence. For the simple configuration examined, these results indicate that low inertial properties and elastic axis location near the center of pressure promote divergence while the dynamic mode persists. Large inertias and large separation between elastic axis and center of pressure promote divergence where the dynamic mode becomes a static mode. A wind tunnel model was designed and tested to examine divergence experimentally. The experimental

  3. Another Paper Landscape?

    ERIC Educational Resources Information Center

    Radlak, Ted

    2001-01-01

    Describes the University of Toronto's extensive central campus revitalization plan to create lush landscapes that add to the school's image and attractiveness. Drawings and photographs are included. (GR)

  4. The Bright Side of Tree-Ring Divergence

    NASA Astrophysics Data System (ADS)

    Stine, A.; Huybers, P.

    2012-12-01

    The second half of the twentieth century saw both a decrease in the intensity of solar shortwave radiation reaching the surface of the Earth and a divergence between Arctic temperature and tree-ring reconstructions of that temperature. Arctic vegetation growth is limited not only by temperature but also by light availability, which suggests a causal relationship between these phenomenon. We demonstrate that Arctic tree-ring density is sensitive to changes in light availability across two distinct phenomena: explosive volcanic eruptions, and the recent epoch of global dimming. In each case the dimmest Arctic regions show the greatest tree-ring density response, whereas the brightest show the least. No significant divergence exists in the least light-limited trees. We repeat this analysis separately for each of the seven species for which we have sufficient data and find, once again, that in all cases divergence increases with increasing light limitation and that divergence approaches zero at the lowest level of light limitation. Changes in light availability thus appear an important control upon tree-ring density and a sufficient explanation for the recent divergence from temperature.

  5. Divergent phenological response to hydroclimate variability in forested mountain watersheds.

    PubMed

    Hwang, Taehee; Band, Lawrence E; Miniat, Chelcy F; Song, Conghe; Bolstad, Paul V; Vose, James M; Love, Jason P

    2014-08-01

    Mountain watersheds are primary sources of freshwater, carbon sequestration, and other ecosystem services. There is significant interest in the effects of climate change and variability on these processes over short to long time scales. Much of the impact of hydroclimate variability in forest ecosystems is manifested in vegetation dynamics in space and time. In steep terrain, leaf phenology responds to topoclimate in complex ways, and can produce specific and measurable shifts in landscape forest patterns. The onset of spring is usually delayed at a specific rate with increasing elevation (often called Hopkins' Law; Hopkins, 1918), reflecting the dominant controls of temperature on greenup timing. Contrary with greenup, leaf senescence shows inconsistent trends along elevation gradients. Here, we present mechanisms and an explanation for this variability and its significance for ecosystem patterns and services in response to climate. We use moderate-resolution imaging spectro-radiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data to derive landscape-induced phenological patterns over topoclimate gradients in a humid temperate broadleaf forest in southern Appalachians. These phenological patterns are validated with different sets of field observations. Our data demonstrate that divergent behavior of leaf senescence with elevation is closely related to late growing season hydroclimate variability in temperature and water balance patterns. Specifically, a drier late growing season is associated with earlier leaf senescence at low elevation than at middle elevation. The effect of drought stress on vegetation senescence timing also leads to tighter coupling between growing season length and ecosystem water use estimated from observed precipitation and runoff generation. This study indicates increased late growing season drought may be leading to divergent ecosystem response between high and low elevation forests. Landscape-induced phenological patterns

  6. Extreme mtDNA divergences in a terrestrial slug (Gastropoda, Pulmonata, Arionidae): accelerated evolution, allopatric divergence and secondary contact.

    PubMed

    Pinceel, J; Jordaens, K; Backeljau, T

    2005-09-01

    Extremely high levels of intraspecific mtDNA differences in pulmonate gastropods have been reported repeatedly and several hypotheses to explain them have been postulated. We studied the phylogeny and phylogeography of 51 populations (n = 843) of the highly polymorphic terrestrial slug Arion subfuscus (Draparnaud, 1805) across its native distribution range in Western Europe. By combining the analysis of single stranded conformation polymorphisms (SSCP) and nucleotide sequencing, we obtained individual sequence data for a fragment of the mitochondrial 16S rDNA and a fragment of the nuclear ITS1. Additionally, five polymorphic allozyme loci were scored. Based on the 16S rDNA phylogeny, five monophyletic haplotype groups with sequence divergences of 9-21% were found. Despite this deep mitochondrial divergence, the haplotype groups were not monophyletic for the nuclear ITS1 fragment and haplotype group-specific allozyme alleles were not found. Although there is evidence for an accelerated mtDNA clock, the divergence among the haplotype groups is older than the Pleistocene and their current allopatric ranges probably reflect allopatric divergence and glacial survival in separate refugia from which different post-glacial colonization routes were established. A range-overlap of two mtDNA groups (S1 and S2, 21% sequence divergence) stretched from Central France and Belgium up to the North of the British Isles. The nuclear data suggest that this secondary contact resulted in hybridization between the allopatrically diverged groups. Therefore, it seems that, at least for two of the groups, the deep mtDNA divergence was only partially accompanied by the formation of reproductive isolation.

  7. Multi-sensory landscape assessment: the contribution of acoustic perception to landscape evaluation.

    PubMed

    Gan, Yonghong; Luo, Tao; Breitung, Werner; Kang, Jian; Zhang, Tianhai

    2014-12-01

    In this paper, the contribution of visual and acoustic preference to multi-sensory landscape evaluation was quantitatively compared. The real landscapes were treated as dual-sensory ambiance and separated into visual landscape and soundscape. Both were evaluated by 63 respondents in laboratory conditions. The analysis of the relationship between respondent's visual and acoustic preference as well as their respective contribution to landscape preference showed that (1) some common attributes are universally identified in assessing visual, aural and audio-visual preference, such as naturalness or degree of human disturbance; (2) with acoustic and visual preferences as variables, a multi-variate linear regression model can satisfactorily predict landscape preference (R(2 )= 0.740), while the coefficients of determination for a unitary linear regression model were 0.345 and 0.720 for visual and acoustic preference as predicting factors, respectively; (3) acoustic preference played a much more important role in landscape evaluation than visual preference in this study (the former is about 4.5 times of the latter), which strongly suggests a rethinking of the role of soundscape in environment perception research and landscape planning practice.

  8. Neptunium separations

    SciTech Connect

    Wild, J.F.

    1983-05-09

    Two procedures for the separation of Np are presented; the first involves separation of /sup 239/Np from irradiated /sup 238/U, and the second involves separation of /sup 237/Np from a solution representing that from a dissolved fuel element.

  9. Landscape assessment for tourism

    Treesearch

    Clare A. Gunn

    1979-01-01

    Increased development of landscapes for tourism now creates problems of integrating the many parts. Accomplishments at the site scale have not been matched with equal progress at the regional scale. This concept, and its example of application, shows promise of assisting regions in assessing their potential of landscapes before development. With such a concept, not...

  10. The complete local genotype–phenotype landscape for the alternative splicing of a human exon

    PubMed Central

    Julien, Philippe; Miñana, Belén; Baeza-Centurion, Pablo; Valcárcel, Juan; Lehner, Ben

    2016-01-01

    The properties of genotype–phenotype landscapes are crucial for understanding evolution but are not characterized for most traits. Here, we present a >95% complete local landscape for a defined molecular function—the alternative splicing of a human exon (FAS/CD95 exon 6, involved in the control of apoptosis). The landscape provides important mechanistic insights, revealing that regulatory information is dispersed throughout nearly every nucleotide in an exon, that the exon is more robust to the effects of mutations than its immediate neighbours in genotype space, and that high mutation sensitivity (evolvability) will drive the rapid divergence of alternative splicing between species unless it is constrained by selection. Moreover, the extensive epistasis in the landscape predicts that exonic regulatory sequences may diverge between species even when exon inclusion levels are functionally important and conserved by selection. PMID:27161764

  11. Correlation of fitness landscapes from three orthologous TIM barrels originates from sequence and structure constraints

    PubMed Central

    Chan, Yvonne H.; Venev, Sergey V.; Zeldovich, Konstantin B.; Matthews, C. Robert

    2017-01-01

    Sequence divergence of orthologous proteins enables adaptation to environmental stresses and promotes evolution of novel functions. Limits on evolution imposed by constraints on sequence and structure were explored using a model TIM barrel protein, indole-3-glycerol phosphate synthase (IGPS). Fitness effects of point mutations in three phylogenetically divergent IGPS proteins during adaptation to temperature stress were probed by auxotrophic complementation of yeast with prokaryotic, thermophilic IGPS. Analysis of beneficial mutations pointed to an unexpected, long-range allosteric pathway towards the active site of the protein. Significant correlations between the fitness landscapes of distant orthologues implicate both sequence and structure as primary forces in defining the TIM barrel fitness landscape and suggest that fitness landscapes can be translocated in sequence space. Exploration of fitness landscapes in the context of a protein fold provides a strategy for elucidating the sequence-structure-fitness relationships in other common motifs. PMID:28262665

  12. Contrastive divergence in gaussian diffusions.

    PubMed

    Movellan, Javier R

    2008-09-01

    This letter presents an analysis of the contrastive divergence (CD) learning algorithm when applied to continuous-time linear stochastic neural networks. For this case, powerful techniques exist that allow a detailed analysis of the behavior of CD. The analysis shows that CD converges to maximum likelihood solutions only when the network structure is such that it can match the first moments of the desired distribution. Otherwise, CD can converge to solutions arbitrarily different from the log-likelihood solutions, or they can even diverge. This result suggests the need to improve our theoretical understanding of the conditions under which CD is expected to be well behaved and the conditions under which it may fail. In, addition the results point to practical ideas on how to improve the performance of CD.

  13. Rugged adaptive landscapes shape a complex, sympatric radiation

    PubMed Central

    Pfaender, Jobst; Hadiaty, Renny K.; Schliewen, Ulrich K.; Herder, Fabian

    2016-01-01

    Strong disruptive ecological selection can initiate speciation, even in the absence of physical isolation of diverging populations. Species evolving under disruptive ecological selection are expected to be ecologically distinct but, at least initially, genetically weakly differentiated. Strong selection and the associated fitness advantages of narrowly adapted individuals, coupled with assortative mating, are predicted to overcome the homogenizing effects of gene flow. Theoretical plausibility is, however, contrasted by limited evidence for the existence of rugged adaptive landscapes in nature. We found evidence for multiple, disruptive ecological selection regimes that have promoted divergence in the sympatric, incipient radiation of ‘sharpfin’ sailfin silverside fishes in ancient Lake Matano (Sulawesi, Indonesia). Various modes of ecological specialization have led to adaptive morphological differences between the species, and differently adapted morphs display significant but incomplete reproductive isolation. Individual fitness and variation in morphological key characters show that disruptive selection shapes a rugged adaptive landscape in this small but complex incipient lake fish radiation. PMID:26763702

  14. Rugged adaptive landscapes shape a complex, sympatric radiation.

    PubMed

    Pfaender, Jobst; Hadiaty, Renny K; Schliewen, Ulrich K; Herder, Fabian

    2016-01-13

    Strong disruptive ecological selection can initiate speciation, even in the absence of physical isolation of diverging populations. Species evolving under disruptive ecological selection are expected to be ecologically distinct but, at least initially, genetically weakly differentiated. Strong selection and the associated fitness advantages of narrowly adapted individuals, coupled with assortative mating, are predicted to overcome the homogenizing effects of gene flow. Theoretical plausibility is, however, contrasted by limited evidence for the existence of rugged adaptive landscapes in nature. We found evidence for multiple, disruptive ecological selection regimes that have promoted divergence in the sympatric, incipient radiation of 'sharpfin' sailfin silverside fishes in ancient Lake Matano (Sulawesi, Indonesia). Various modes of ecological specialization have led to adaptive morphological differences between the species, and differently adapted morphs display significant but incomplete reproductive isolation. Individual fitness and variation in morphological key characters show that disruptive selection shapes a rugged adaptive landscape in this small but complex incipient lake fish radiation. © 2016 The Author(s).

  15. Cetacean morbilliviruses are phylogenetically divergent.

    PubMed

    van de Bildt, M W G; Kuiken, T; Osterhaus, A D M E

    2005-03-01

    We performed a phylogenetic comparison of porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV) isolates from porpoises and dolphins respectively according to criteria adopted by the World Health Organization for the phylogenetic comparison of measles viruses. PMV and DMV were more divergent than the most distantly related measles virus strains, thus challenging the classification of PMV and DMV as two strains of a single species, cetacean morbillivirus.

  16. Gluon masses without seagull divergences

    NASA Astrophysics Data System (ADS)

    Papavassiliou, J.

    The study of dynamical gluon mass generation at the level of Schwinger-Dyson equation involves a delicate interplay between various field-theoretic mechanisms The underlying local gauge invariance remains intact by resorting to the well-known Schwinger mechanism, which is assumed to be realized by longitudinally coupled bound state poles, produced by the non-perturbative dynamics of the theory. These poles are subsequently included into the Schwinger-Dyson equation of the gluon propagator through the three-gluon vertex, generating a non-vanishing gluon mass, which, however, is expressed in terms of divergent seagull integrals. In this talk we explain how such divergences can be eliminated completely by virtue of a characteristic identity, valid in dimensional regularization. The ability to trigger this identity depends, in turn, on the details of the three-gluon vertex employed, and in particular, on the exact way the bound state poles are incorporated. A concrete example of a vertex that triggers the aforementioned identity is constructed, the ensuing cancellation of all seagull divergences is explicitly demonstrated, and a finite gluon mass is obtained. Due to the multitude of conditions that must be simultaneously satisfied, this construction appears to be exclusively realized within the PT-BFM framework. The resulting system of integral equations gives rise to a gluon mass that displays power-law running and an effective charge which, due to the presence of the gluon mass, freezes in the infrared at a finite (non-vanishing) value.

  17. Unphysical divergences in response theory.

    PubMed

    Parker, Shane M; Roy, Saswata; Furche, Filipp

    2016-10-07

    Transition densities between excited states are key for nonlinear theoretical spectroscopy and multi-state non-adiabatic molecular dynamics (NAMD) simulations. In the framework of response theory, these transition densities are accessible from poles of the quadratic response function. It was shown recently that the thus obtained transition densities within time-dependent Hartree-Fock (TDHF) and adiabatic time-dependent density functional theory (TDDFT) exhibit unphysical divergences when the difference in excitation energy of the two states of interest matches another excitation energy. This unphysical behavior is a consequence of spurious poles in the quadratic response function. We show that the incorrect pole structure of the quadratic response is not limited to TDHF and adiabatic TDDFT, but is also present in many other approximate many-electron response functions, including those from coupled cluster and multiconfigurational self-consistent field response theory. The divergences appear in regions of the potential energy surface where the ground state is perfectly well behaved, and they are frequently encountered in NAMD simulations of photochemical reactions. The origin of the divergences is traced to an incorrect instantaneous time-dependence of the effective Hamiltonian. The implications for computations of frequency-dependent response properties are considerable and call into question the validity of conventional approximate many-electron response theories beyond linear response.

  18. Planetary Landscape Geography

    NASA Astrophysics Data System (ADS)

    Hargitai, H.

    INTRODUCTION Landscape is one of the most often used category in physical ge- ography. The term "landshap" was introduced by Dutch painters in the 15-16th cen- tury. [1] The elements that build up a landscape (or environment) on Earth consists of natural (biogenic and abiogenic - lithologic, atmospheric, hydrologic) and artificial (antropogenic) factors. Landscape is a complex system of these different elements. The same lithology makes different landscapes under different climatic conditions. If the same conditions are present, the same landscape type will appear. Landscapes build up a hierarchic system and cover the whole surface. On Earth, landscapes can be classified and qualified according to their characteristics: relief forms (morphology), and its potential economic value. Aesthetic and subjective parameters can also be considered. Using the data from landers and data from orbiters we can now classify planetary landscapes (these can be used as geologic mapping units as well). By looking at a unknown landscape, we can determine the processes that created it and its development history. This was the case in the Pathfinder/Sojourner panoramas. [2]. DISCUSSION Planetary landscape evolution. We can draw a raw landscape develop- ment history by adding the different landscape building elements to each other. This has a strong connection with the planet's thermal evolution (age of the planet or the present surface materials) and with orbital parameters (distance from the central star, orbit excentricity etc). This way we can build a complex system in which we use differ- ent evolutional stages of lithologic, atmospheric, hydrologic and biogenic conditions which determine the given - Solar System or exoplanetary - landscape. Landscape elements. "Simple" landscapes can be found on asteroids: no linear horizon is present (not differentiated body, only impact structures), no atmosphere (therefore no atmospheric scattering - black sky as part of the landscape) and no

  19. Divergent Cognitive Styles in Academic Overachievers.

    ERIC Educational Resources Information Center

    Spotts, Nina R.

    This study explored the relationship of two distinctive types of divergent cognitive styles, "cold" creativity and "hot" creativity, to academic overachievement. The "cold" divergent cognitive style was found to be a controlled, problem-solving approach to stimuli, whereas the "hot" divergent cognitive style was a freer, more impulsive response to…

  20. Chiral Separations

    NASA Astrophysics Data System (ADS)

    Stalcup, A. M.

    2010-07-01

    The main goal of this review is to provide a brief overview of chiral separations to researchers who are versed in the area of analytical separations but unfamiliar with chiral separations. To researchers who are not familiar with this area, there is currently a bewildering array of commercially available chiral columns, chiral derivatizing reagents, and chiral selectors for approaches that span the range of analytical separation platforms (e.g., high-performance liquid chromatography, gas chromatography, supercritical-fluid chromatography, and capillary electrophoresis). This review begins with a brief discussion of chirality before examining the general strategies and commonalities among all of the chiral separation techniques. Rather than exhaustively listing all the chiral selectors and applications, this review highlights significant issues and differences between chiral and achiral separations, providing salient examples from specific classes of chiral selectors where appropriate.

  1. Avian Species and Functional Diversity in Agricultural Landscapes: Does Landscape Heterogeneity Matter?

    PubMed

    Lee, Myung-Bok; Martin, James A

    2017-01-01

    While the positive relationship between avian diversity and habitat heterogeneity is widely accepted, it is primarily based on observed species richness without accounting for imperfect detection. Other facets of diversity such as functional diversity are also rarely explored. We investigated the avian diversity-landscape heterogeneity relationship in agricultural landscapes by considering two aspects of diversity: taxonomic diversity (species richness) estimated from a multi-species dynamic occupancy model, and functional diversity (functional evenness [FEve] and divergence [FDiv]) based on traits of occurring species. We also assessed how agricultural lands enrolled in a conservation program managed on behalf of declining early successional bird species (hereafter CP38 fields, an agri-environment scheme) influenced avian diversity. We analyzed breeding bird data collected at CP38 fields in Mississippi, USA, during 2010-2012, and two principal components of environmental variables: a gradient of heterogeneity (Shannon's landscape diversity index) and of the amount of CP38 fields (percent cover of CP38 fields; CP38). FEve did not show significant responses to environmental variables, whereas FDiv responded positively to heterogeneity and negatively to CP38. However, most FDiv values did not significantly differ from random expectations along an environmental gradient. When there was a significant difference, FDiv was lower than that expected. Unlike functional diversity, species richness showed a clear pattern. Species richness increased with increasing landscape heterogeneity but decreased with increasing amounts of CP38 fields. Only one species responded negatively to heterogeneity and positively to CP38. Our results suggest that the relationships between avian diversity and landscape heterogeneity may vary depending on the aspect of diversity considered: strong positive effects of heterogeneity on taxonomic diversity, but weakly positive or non

  2. Avian Species and Functional Diversity in Agricultural Landscapes: Does Landscape Heterogeneity Matter?

    PubMed Central

    2017-01-01

    While the positive relationship between avian diversity and habitat heterogeneity is widely accepted, it is primarily based on observed species richness without accounting for imperfect detection. Other facets of diversity such as functional diversity are also rarely explored. We investigated the avian diversity-landscape heterogeneity relationship in agricultural landscapes by considering two aspects of diversity: taxonomic diversity (species richness) estimated from a multi-species dynamic occupancy model, and functional diversity (functional evenness [FEve] and divergence [FDiv]) based on traits of occurring species. We also assessed how agricultural lands enrolled in a conservation program managed on behalf of declining early successional bird species (hereafter CP38 fields, an agri-environment scheme) influenced avian diversity. We analyzed breeding bird data collected at CP38 fields in Mississippi, USA, during 2010–2012, and two principal components of environmental variables: a gradient of heterogeneity (Shannon’s landscape diversity index) and of the amount of CP38 fields (percent cover of CP38 fields; CP38). FEve did not show significant responses to environmental variables, whereas FDiv responded positively to heterogeneity and negatively to CP38. However, most FDiv values did not significantly differ from random expectations along an environmental gradient. When there was a significant difference, FDiv was lower than that expected. Unlike functional diversity, species richness showed a clear pattern. Species richness increased with increasing landscape heterogeneity but decreased with increasing amounts of CP38 fields. Only one species responded negatively to heterogeneity and positively to CP38. Our results suggest that the relationships between avian diversity and landscape heterogeneity may vary depending on the aspect of diversity considered: strong positive effects of heterogeneity on taxonomic diversity, but weakly positive or non

  3. Battery separators.

    PubMed

    Arora, Pankaj; Zhang, Zhengming John

    2004-10-01

    The ideal battery separator would be infinitesimally thin, offer no resistance to ionic transport in electrolytes, provide infinite resistance to electronic conductivity for isolation of electrodes, be highly tortuous to prevent dendritic growths, and be inert to chemical reactions. Unfortunately, in the real world the ideal case does not exist. Real world separators are electronically insulating membranes whose ionic resistivity is brought to the desired range by manipulating the membranes thickness and porosity. It is clear that no single separator satisfies all the needs of battery designers, and compromises have to be made. It is ultimately the application that decides which separator is most suitable. We hope that this paper will be a useful tool and will help the battery manufacturers in selecting the most appropriate separators for their batteries and respective applications. The information provided is purely technical and does not include other very important parameters, such as cost of production, availability, and long-term stability. There has been a continued demand for thinner battery separators to increase battery power and capacity. This has been especially true for lithiumion batteries used in portable electronics. However, it is very important to ensure the continued safety of batteries, and this is where the role of the separator is greatest. Thus, it is essential to optimize all the components of battery to improve the performance while maintaining the safety of these cells. Separator manufacturers should work along with the battery manufacturers to create the next generation of batteries with increased reliability and performance, but always keeping safety in mind. This paper has attempted to present a comprehensive review of literature on separators used in various batteries. It is evident that a wide variety of separators are available and that they are critical components in batteries. In many cases, the separator is one of the major factors

  4. Water separator

    NASA Technical Reports Server (NTRS)

    Dunn, W. F.; Austin, I. G. (Inventor)

    1964-01-01

    An apparatus for separating liquids from gases or gaseous fluids is described. Features of the apparatus include: (1) the collection and removal of the moisture in the fluid is not dependent upon, or affected by gravity; (2) all the collected water is cyclically drained from the apparatus irrespective of the attitude of the separator; and (3) a fluid actuator is utilized to remove the collected water from the separator.

  5. Geomorphic control of landscape carbon accumulation

    USGS Publications Warehouse

    Rosenbloom, N.A.; Harden, J.W.; Neff, J.C.; Schimel, D.S.

    2006-01-01

    We use the CREEP process-response model to simulate soil organic carbon accumulation in an undisturbed prairie site in Iowa. Our primary objectives are to identify spatial patterns of carbon accumulation, and explore the effect of erosion on basin-scale C accumulation. Our results point to two general findings. First, redistribution of soil carbon by erosion results in a net increase in basin-wide carbon storage relative to a noneroding environment. Landscape-average mean residence times are increased in an eroding landscape owing to the burial/preservation of otherwise labile C. Second, field observations taken along a slope transect may overlook significant intraslope variations in carbon accumulation. Spatial patterns of modeled deep C accumulation are complex. While surface carbon with its relatively short equilibration time is predictable from surface properties, deep carbon is strongly influenced by the landscape's geomorphic and climatic history, resulting in wide spatial variability. Convergence and divergence associated with upland swales and interfluves result in bimodal carbon distributions in upper and mid slopes; variability in carbon storage within modeled mid slopes was as high as simulated differences between erosional shoulders and depositional valley bottoms. The bimodality of mid-slope C variability in the model suggests that a three-dimensional sampling strategy is preferable over the traditional two-dimensional analog or "catena" approach. Copyright 2006 by the American Geophysical Union.

  6. Quasispecies on Fitness Landscapes.

    PubMed

    Schuster, Peter

    2016-01-01

    Selection-mutation dynamics is studied as adaptation and neutral drift on abstract fitness landscapes. Various models of fitness landscapes are introduced and analyzed with respect to the stationary mutant distributions adopted by populations upon them. The concept of quasispecies is introduced, and the error threshold phenomenon is analyzed. Complex fitness landscapes with large scatter of fitness values are shown to sustain error thresholds. The phenomenological theory of the quasispecies introduced in 1971 by Eigen is compared to approximation-free numerical computations. The concept of strong quasispecies understood as mutant distributions, which are especially stable against changes in mutations rates, is presented. The role of fitness neutral genotypes in quasispecies is discussed.

  7. Agri-environmental collaboratives as bridging organisations in landscape management.

    PubMed

    Prager, Katrin

    2015-09-15

    In recent years, landscape and its management has become a focus of policies and academic conceptualisation. Landscape is understood as a concept of interconnected natural and human systems. Its management must take into account the dynamic interdependencies and diverging interests of various stakeholders at different levels. Bridging organisations can provide an arena for trust-building, conflict resolution, learning and collaboration between relevant stakeholders. This paper draws on two strands of literature - landscape governance and co-management of social-ecological systems - to investigate the contributions of agri-environmental collaboratives (AEC) to sustainable landscape management. Based on data from 41 interviews with key informants and AEC members in Germany and the Netherlands, six fields of contributions were identified: policy implementation and service provision; coordination and mediation; awareness raising and behaviour change; care for 'everyday' landscapes; maintenance and protection of landscapes (including species and habitats); and income generation and economic benefits. Some of the contributions evolve around the specific role of AEC as bridging organisations, but other contributions such as economic benefits emerge beyond this analytical lens. The paper therefore emphasises holistic, bottom up assessment of AEC contributions and argues that governments should support such organisations through i) funding for facilitators and ii) funding for impact monitoring and data management.

  8. Landscape genetics and limiting factors

    Treesearch

    Samuel A. Cushman; Andrew J. Shirk; Erin L. Landguth

    2013-01-01

    Population connectivity is mediated by the movement of organisms or propagules through landscapes. However, little is known about how variation in the pattern of landscape mosaics affects the detectability of landscape genetic relationships. The goal of this paper is to explore the impacts of limiting factors on landscape genetic processes using simulation...

  9. Landscape metrics, scales of resolution

    Treesearch

    Samuel A. Cushman; Kevin McGarigal

    2008-01-01

    Effective implementation of the "multiple path" approach to managing green landscapes depends fundamentally on rigorous quantification of the composition and structure of the landscapes of concern at present, modelling landscape structure trajectories under alternative management paths, and monitoring landscape structure into the future to confirm...

  10. Ultraviolet divergences and supersymmetric theories

    SciTech Connect

    Sagnotti, A.

    1984-09-01

    This article is closely related to the one by Ferrara in these same Proceedings. It deals with what is perhaps the most fascinating property of supersymmetric theories, their improved ultraviolet behavior. My aim here is to present a survey of the state of the art as of August, 1984, and a somewhat more detailed discussion of the breakdown of the superspace power-counting beyond N = 2 superfields. A method is also described for simplifying divergence calculations that uses the locality of subtracted Feynman integrals. 74 references.

  11. Phylogenetic relationships and estimation of divergence times among Sisoridae catfishes.

    PubMed

    Yu, Meiling; He, Shunping

    2012-04-01

    Nineteen taxa representing 10 genera of Sisoridae were subjected to phylogenetic analyses of sequence data for the nuclear genes Plagl2 and ADNP and the mitochondrial gene cytochrome b. The three data sets were analyzed separately and combined into a single data set to reconstruct phylogenetic relationships among Chinese sisorids. Both Chinese Sisoridae as a whole and the glyptosternoid taxa formed monophyletic groups. The genus Pseudecheneis is likely to be the earliest diverging extant genus among the Chinese Sisoridae. The four Pareuchiloglanis species included in the study formed a monophyletic group. Glaridoglanis was indicated to be earliest diverging glyptosternoid, followed by Glyptosternon maculatum and Exostoma labiatum. Our data supported the conclusion that Oreoglanis and Pseudexostoma both formed a monophyletic group. On the basis of the fossil record and the results of a molecular dating analysis, we estimated that the Sisoridae diverged in the late Miocene about 12.2 Mya. The glyptosternoid clade was indicated to have diverged, also in the late Miocene, about 10.7 Mya, and the more specialized glyptosternoid genera, such as Pareuchiloglanis, originated in the Pleistocene (within 1.9 Mya). The speciation of glyptosternoid fishes is hypothesized to be closely related with the uplift of the Qinghai-Tibet Plateau.

  12. Populating the whole landscape.

    PubMed

    Brown, Adam R; Dahlen, Alex

    2011-10-21

    Every de Sitter vacuum can transition to every other de Sitter vacuum despite any obstacle, despite intervening anti-de Sitter sinks, despite not being connected by an instanton. Eternal inflation populates the whole landscape. © 2011 American Physical Society

  13. Landscape Water Budget Tool

    EPA Pesticide Factsheets

    WaterSense created the Water Budget Tool as one option to help builders, landscape professionals, and irrigation professionals certified by a WaterSense labeled program meet the criteria specified in the WaterSense New Home Specification.

  14. Short-range phenotypic divergence among genetically distinct parapatric populations of an Australian funnel-web spider.

    PubMed

    Wong, Mark K L; Woodman, James D; Rowell, David M

    2017-07-01

    Speciation involves divergence at genetic and phenotypic levels. Where substantial genetic differentiation exists among populations, examining variation in multiple phenotypic characters may elucidate the mechanisms by which divergence and speciation unfold. Previous work on the Australian funnel-web spider Atrax sutherlandi Gray (2010; Records of the Australian Museum62, 285-392; Mygalomorphae: Hexathelidae: Atracinae) has revealed a marked genetic structure along a 110-kilometer transect, with six genetically distinct, parapatric populations attributable to past glacial cycles. In the present study, we explore variation in three classes of phenotypic characters (metabolic rate, water loss, and morphological traits) within the context of this phylogeographic structuring. Variation in metabolic and water loss rates shows no detectable association with genetic structure; the little variation observed in these rates may be due to the spiders' behavioral adaptations (i.e., burrowing), which buffer the effects of climatic gradients across the landscape. However, of 17 morphological traits measured, 10 show significant variation among genetic populations, in a disjunct manner that is clearly not latitudinal. Moreover, patterns of variation observed for morphological traits serving different organismic functions (e.g., prey capture, burrowing, and locomotion) are dissimilar. In contrast, a previous study of an ecologically similar sympatric spider with little genetic structure indicated a strong latitudinal response in 10 traits over the same range. The congruence of morphological variation with deep phylogeographic structure in Tallaganda's A. sutherlandi populations, as well as the inconsistent patterns of variation across separate functional traits, suggest that the spiders are likely in early stages of speciation, with parapatric populations independently responding to local selective forces.

  15. Landscape evolution (A Review)

    PubMed Central

    Sharp, Robert P.

    1982-01-01

    Landscapes are created by exogenic and endogenic processes acting along the interface between the lithosphere and the atmosphere and hydrosphere. Various landforms result from the attack of weathering and erosion upon the highly heterogeneous lithospheric surface. Landscapes are dynamic, acutely sensitive to natural and artificial perturbation. Undisturbed, they can evolve through a succession of stages to a plain of low relief. Often, the progression of an erosion cycle is interrupted by tectonic or environmental changes; thus, many landscapes preserve vestiges of earlier cycles useful in reconstructing the recent history of Earth's surface. Landforms are bounded by slopes, so their evolution is best understood through study of slopes and the complex of factors controlling slope character and development. The substrate, biosphere, climatic environment, and erosive processes are principal factors. Creep of the disintegrated substrate and surface wash by water are preeminent. Some slopes attain a quasisteady form and recede parallel to themselves (backwearing); others become ever gentler with time (downwearing). The lovely convex/rectilinear/concave profile of many debris-mantled slopes reflects an interplay between creep and surface wash. Landscapes of greatest scenic attraction are usually those in which one or two genetic factors have strongly dominated or those perturbed by special events. Nature has been perturbing landscapes for billions of years, so mankind can learn about landscape perturbation from natural examples. Images

  16. CENTRIFUGAL SEPARATORS

    DOEpatents

    Skarstrom, C.

    1959-03-10

    A centrifugal separator is described for separating gaseous mixtures where the temperature gradients both longitudinally and radially of the centrifuge may be controlled effectively to produce a maximum separation of the process gases flowing through. Tbe invention provides for the balancing of increases and decreases in temperature in various zones of the centrifuge chamber as the result of compression and expansions respectively, of process gases and may be employed effectively both to neutralize harmful temperature gradients and to utilize beneficial temperaturc gradients within the centrifuge.

  17. Stereoisomers Separation

    NASA Astrophysics Data System (ADS)

    Wieczorek, Piotr

    The use of capillary electrophoresis for enantiomer separation and optical purity determination is presented. The contents start with basic information about the nature of stereoizomers and the mechanism of enantioseparation using capillary electrophoresis techniques. The molecules to be separated show identical chemical structure and electrochemical behavior. Therefore, the chiral recognition of enantiomers is possible only by bonding to chiral selector and the separation based on very small differences in complexation energies of diastereomer complexes formed. This method is useful for this purpose due to the fact that different compounds can be used as chiral selectors. The mostly used chiral selectors like cyclodextrins, crown ethers, chiral surfactants, macrocyclic antibiotics, transition metal complexes, natural, and synthetic polymers and their application for this purpose is also discussed. Finally, examples of practical applications of electromigration techniques for enantiomers separation and determination are presented.

  18. Mist separator

    SciTech Connect

    Moran, T.M.

    1984-04-17

    An apparatus for the removal of particulates from a flowing gas stream and a process for its use are provided. A perforated screen separator formed as a plate having parallel rows of perforations formed by pushing alternating strips of the plate material forward and backward from the plane of the plate is used. The perforated screen separator may be used alone or with a fiber bed mist eliminator for increased particulate removal.

  19. Product separator

    DOEpatents

    Welsh, Robert A.; Deurbrouck, Albert W.

    1976-01-20

    A secondary light sensitive photoelectric product separator for use with a primary product separator that concentrates a material so that it is visually distinguishable from adjacent materials. The concentrate separation is accomplished first by feeding the material onto a vibratory inclined surface with a liquid flow, such as a wet concentrating table. Vibrations generally perpendicular to the stream direction of flow cause the concentrate to separate from its mixture according to its color. When the concentrate and its surrounding stream reach the recovery end of the table, a detecting device notes the line of color demarcation and triggers a signal if it differs from a normal condition. If no difference is noted nothing moves on the second separator. However, if a difference is detected in the constant monitoring of the color line's location, a product splitter and recovery unit normally positioned near the color line at the recovery end, moves to a new position. In this manner the selected separated concentrate is recovered at a maximum rate regardless of variations in the flow stream or other conditions present.

  20. Precision cosmology and the landscape

    SciTech Connect

    Bousso, Raphael; Bousso, Raphael

    2006-10-01

    After reviewing the cosmological constant problem -- why is Lambda not huge? -- I outline the two basic approaches that had emerged by the late 1980s, and note that each made a clear prediction. Precision cosmological experiments now indicate that the cosmological constant is nonzero. This result strongly favors the environmental approach, in which vacuum energy can vary discretely among widely separated regions in the universe. The need to explain this variation from first principles constitutes an observational constraint on fundamental theory. I review arguments that string theory satisfies this constraint, as it contains a dense discretuum of metastable vacua. The enormous landscape of vacua calls for novel, statistical methods of deriving predictions, and it prompts us to reexamine our description of spacetime on the largest scales. I discuss the effects of cosmological dynamics, and I speculate that weighting vacua by their entropy production may allow for prior-free predictions that do not resort to explicitly anthropic arguments.

  1. Divergent Thinking and Constructing Episodic Simulations

    PubMed Central

    Addis, Donna Rose; Pan, Ling; Musicaro, Regina; Schacter, Daniel L.

    2014-01-01

    Divergent thinking likely plays an important role in simulating autobiographical events. We investigated whether divergent thinking is differentially associated with the ability to construct detailed imagined future and imagined past events as opposed to recalling past events. We also examined whether age differences in divergent thinking might underlie the reduced episodic detail generated by older adults. The richness of episodic detail comprising autobiographical events in young and older adults was assessed using the Autobiographical Interview. Divergent thinking abilities were measured using the Alternate Uses Task. Divergent thinking was significantly associated with the amount of episodic detail for imagined future events. Moreover, while age was significantly associated with imagined episodic detail, this effect was strongly related to age-related changes in episodic retrieval rather than divergent thinking. PMID:25483132

  2. Divergent thinking and constructing episodic simulations.

    PubMed

    Addis, Donna Rose; Pan, Ling; Musicaro, Regina; Schacter, Daniel L

    2016-01-01

    Divergent thinking likely plays an important role in simulating autobiographical events. We investigated whether divergent thinking is differentially associated with the ability to construct detailed imagined future and imagined past events as opposed to recalling past events. We also examined whether age differences in divergent thinking might underlie the reduced episodic detail generated by older adults. The richness of episodic detail comprising autobiographical events in young and older adults was assessed using the Autobiographical Interview. Divergent thinking abilities were measured using the Alternative Uses Task. Divergent thinking was significantly associated with the amount of episodic detail for imagined future events. Moreover, while age was significantly associated with imagined episodic detail, this effect was strongly related to age-related changes in episodic retrieval rather than divergent thinking.

  3. Reconstruction from divergent ray projections

    NASA Astrophysics Data System (ADS)

    Sastry, C. S.; Singh, Santosh

    2012-03-01

    Despite major advances in x-ray sources, detector arrays, gantry mechanical design and special computer performances, computed tomography (CT) enjoys the filtered back projection (FBP) algorithm as its first choice for the CT image reconstruction in the commercial scanners [1]. Over the years, a lot of fundamental work has been done in the area of finding the sophisticated solutions for the inverse problems using different kinds of optimization techniques. Recent literature in applied mathematics is being dominated by the compressive sensing techniques and/or sparse reconstruction techniques [2], [3]. Still there is a long way to go for translating these newly developed algorithms in the clinical environment. The reasons are not obvious and seldom discussed [1]. Knowing the fact that the filtered back projection is one of the most popular CT image reconstruction algorithms, one pursues research work to improve the different error estimates at different steps performed in the filtered back projection. In this paper, we present a back projection formula for the reconstruction of divergent beam tomography with unique convolution structure. Using such a proposed approximate convolution structure, the approximation error mathematically justifies that the reconstruction error is low for a suitable choice of parameters. In order to minimize the exposure time and possible distortions due to the motion of the patient, the fan beam method of collection of data is used. Rebinning [4] transformation is used to connect fan beam data into parallel beam data so that the well developed methods of image reconstruction for parallel beam geometry can be used. Due to the computational errors involved in the numerical process of rebinning, some degradation of image is inevitable. However, to date very little work has been done for the reconstruction of fan beam tomography. There have been some recent results [5], [6] on wavelet reconstruction of divergent beam tomography. In this paper

  4. Geomorpho-Landscapes

    NASA Astrophysics Data System (ADS)

    Farabollini, Piero; Lugeri, Francesca; Amadio, Vittorio

    2014-05-01

    Landscape is the object of human perceptions, being the image of spatial organization of elements and structures: mankind lives the first approach with the environment, viewing and feeling the landscape. Many definitions of landscape have been given over time: in this case we refer to the Landscape defined as the result of interaction among physical, biotic and anthropic phenomena acting in a different spatial-temporal scale (Foreman & Godron) Following an Aristotelic approach in studying nature, we can assert that " Shape is synthesis": so it is possible to read the land features as the expression of the endogenous and exogenous processes that mould earth surfaces; moreover, Landscape is the result of the interaction of natural and cultural components, and conditions the spatial-temporal development of a region. The study of the Landscape offers results useful in order to promote sustainable development, ecotourism, enhancement of natural and cultural heritage, popularization of the scientific knowledge. In Italy, a very important GIS-based tool to represent the territory is the "Carta della Natura" ("Map of Nature", presently coordinated by the ISPRA) that aims at assessing the state of the whole Italian territory, analyzing Landscape. The methodology follows a holistic approach, taking into consideration all the components of a landscape and then integrating the information. Each individual landscape, studied at different scales, shows distinctive elements: structural, which depend on physical form and specific spatial organization; functional, which depend on relationships created between biotic and abiotic elements, and dynamic, which depend on the successive evolution of the structure. The identification of the landscape units, recognized at different scales of analysis, allows an evaluation of the state of the land, referring to the dual risk/resource which characterizes the Italian country. An interesting opportunity is to discover those areas of unusual

  5. Compound liquid crystal microlens array with convergent and divergent functions.

    PubMed

    Kang, Shengwu; Zhang, Xinyu

    2016-04-20

    Based on the common liquid crystal microlens, a new compound structure for a liquid crystal (LC) microlens array is proposed. The structure consists of two sub LC microlens arrays with properties of light divergence and convergence. The structure has two LC layers: one to form the positive sub lens, one for the negative. The patterned electrode and plane electrode are used in both sub microlens arrays. When two sub microlens arrays are electrically controlled separately, they can diverge or converge the incident light, respectively. As two sub microlens arrays are both applied on the voltage, the focal length of the compound LC microlens becomes larger than that of the LC microlens with a single LC layer. Another feature of a compound LC microlens array is that it can make the target contour become visible under intense light. The mechanisms are described in detail, and the experimental data are given.

  6. Tracing ancient evolutionary divergence in parasites.

    PubMed

    Tinsley, Richard C; Tinsley, Matthew C

    2016-12-01

    For parasitic platyhelminths that generally lack a fossil record, there is little information on the pathways of morphological change during evolution. Polystomatid monogeneans are notable for their evolutionary diversification, having originated from ancestors on fish and radiated in parallel with tetrapod vertebrates over more than 425 million years (My). This study focuses on the genus Polystomoides that occurs almost worldwide on freshwater chelonian reptiles. Morphometric data show a major divergence in structural adaptations for attachment; this correlates with a dichotomy in micro-environmental conditions in habitats within the hosts. Species infecting the urinary tract have attachment organs with large hamuli and small suckers; species in the oro-nasal tract differ fundamentally, having small hamuli and large suckers. Zoogeographical and molecular evidence supports ancient separation of these site-specific clades: a new genus is proposed - Uropolystomoides - containing urinary tract species distinct from Polystomoides sensu stricto in oro-nasal sites. Aside from differences in attachment adaptations, body plans have probably changed little over perhaps 150 My. This case contrasts markedly with polystomatids in other vertebrate groups where major morphological changes have evolved over much shorter timescales; the chelonian parasites show highly stable morphology across their global distribution over a long period of evolution, exemplifying 'living fossils'.

  7. Divergence of optical vortex beams.

    PubMed

    Reddy, Salla Gangi; Permangatt, Chithrabhanu; Prabhakar, Shashi; Anwar, Ali; Banerji, J; Singh, R P

    2015-08-01

    We show, both theoretically and experimentally, that the propagation of optical vortices in free space can be analyzed by using the width [w(z)] of the host Gaussian beam and the inner and outer radii of the vortex beam at the source plane (z=0) as defined in [Opt. Lett.39, 4364 (2014)10.1364/OL.39.004364OPLEDP0146-9592]. We also studied the divergence of vortex beams, considered as the rate of change of inner or outer radius with the propagation distance (z), and found that it varies with the order in the same way as that of the inner and outer radii at z=0. These results may be useful in designing optical fibers for orbital angular momentum modes that play a crucial role in quantum communication.

  8. Pediatric complex divergent elbow dislocation.

    PubMed

    van Wagenberg, Jan-Maarten F; van Huijstee, Pieter J; Verhofstad, Michiel H J

    2011-01-01

    A divergent dislocation of the elbow is a very rare injury, and only a few cases have been described in the literature. It is characterized as a dorsal dislocation of the ulnohumeral joint combined with a lateral dislocation of the proximal radius. All three articulations of the elbow joint are involved. Like in our case, it can be accompanied by an avulsion fracture of the coronoid and a distal radius fracture. For correct understanding of the injury, proper radiographic studies are imperative. In contrast to some earlier reports that advise a conservative approach, we performed a very aggressive operative treatment. To ensure anatomic reconstruction of the elbow, surgical exposure of the various injuries was performed first. After gross reduction of the joint dislocation, definitive osteosynthesis of the distal radius fracture was performed. Subsequently, the coronoid process and lateral collateral ligament could be repaired anatomically, improving the stability of the elbow. An uneventful recovery with excellent elbow motion and stability was achieved.

  9. DISSIPATIVE DIVERGENCE OF RESONANT ORBITS

    SciTech Connect

    Batygin, Konstantin; Morbidelli, Alessandro

    2013-01-01

    A considerable fraction of multi-planet systems discovered by the observational surveys of extrasolar planets reside in mild proximity to first-order mean-motion resonances. However, the relative remoteness of such systems from nominal resonant period ratios (e.g., 2:1, 3:2, and 4:3) has been interpreted as evidence for lack of resonant interactions. Here, we show that a slow divergence away from exact commensurability is a natural outcome of dissipative evolution and demonstrate that libration of critical angles can be maintained tens of percent away from nominal resonance. We construct an analytical theory for the long-term dynamical evolution of dissipated resonant planetary pairs and confirm our calculations numerically. Collectively, our results suggest that a significant fraction of the near-commensurate extrasolar planets are in fact resonant and have undergone significant dissipative evolution.

  10. Guises and disguises of quadratic divergences

    NASA Astrophysics Data System (ADS)

    Cherchiglia, A. L.; Vieira, A. R.; Hiller, Brigitte; Baêta Scarpelli, A. P.; Sampaio, Marcos

    2014-12-01

    In this contribution, we present a new perspective on the control of quadratic divergences in quantum field theory, in general, and in the Higgs naturalness problem, in particular. Our discussion is essentially based on an approach where UV divergences are parameterized, after being reduced to basic divergent integrals (BDI) in one internal momentum, as functions of a cutoff and a renormalization group scale λ. We illustrate our proposal with well-known examples, such as the gluon vacuum self energy of QCD and the Higgs decay in two photons within this approach. We also discuss frameworks in effective low-energy QCD models, where quadratic divergences are indeed fundamental.

  11. Guises and disguises of quadratic divergences

    SciTech Connect

    Cherchiglia, A.L.; Vieira, A.R.; Hiller, Brigitte; Baêta Scarpelli, A.P.; Sampaio, Marcos

    2014-12-15

    In this contribution, we present a new perspective on the control of quadratic divergences in quantum field theory, in general, and in the Higgs naturalness problem, in particular. Our discussion is essentially based on an approach where UV divergences are parameterized, after being reduced to basic divergent integrals (BDI) in one internal momentum, as functions of a cutoff and a renormalization group scale λ. We illustrate our proposal with well-known examples, such as the gluon vacuum self energy of QCD and the Higgs decay in two photons within this approach. We also discuss frameworks in effective low-energy QCD models, where quadratic divergences are indeed fundamental.

  12. Map Separates

    USGS Publications Warehouse

    ,

    2001-01-01

    U.S. Geological Survey (USGS) topographic maps are printed using up to six colors (black, blue, green, red, brown, and purple). To prepare your own maps or artwork based on maps, you can order separate black-and-white film positives or negatives for any color printed on a USGS topographic map, or for one or more of the groups of related features printed in the same color on the map (such as drainage and drainage names from the blue plate.) In this document, examples are shown with appropriate ink color to illustrate the various separates. When purchased, separates are black-and-white film negatives or positives. After you receive a film separate or composite from the USGS, you can crop, enlarge or reduce, and edit to add or remove details to suit your special needs. For example, you can adapt the separates for making regional and local planning maps or for doing many kinds of studies or promotions by using the features you select and then printing them in colors of your choice.

  13. Disorder on the landscape

    SciTech Connect

    Podolsky, Dmitry; Jokela, Niko; Majumder, Jaydeep E-mail: majumder@mnnit.ac.in

    2008-05-15

    Disorder on the string theory landscape may significantly affect dynamics of eternal inflation leading to the possibility for some vacua on the landscape to become dynamically preferable over others. We systematically study effects of a generic disorder on the landscape, starting by identifying a sector with built-in disorder-a set of de Sitter vacua corresponding to compactifications of the type IIB string theory on Calabi-Yau manifolds with a number of warped Klebanov-Strassler throats attached randomly to the bulk part of the Calabi-Yau. Further, we derive a continuum limit of the vacuum dynamics equations on the landscape. Using methods of the dynamical renormalization group we determine the late-time behavior of the probability distribution for an observer to measure a given value of the cosmological constant. We find the diffusion of the probability distribution to significantly slow down in sectors of the landscape where the number of nearest-neighboring vacua for any given vacuum is small. We discuss the relation of this slowdown with the phenomenon of Anderson localization in disordered media.

  14. Tigers of Sundarbans in India: Is the Population a Separate Conservation Unit?

    PubMed Central

    Singh, Sujeet Kumar; Mishra, Sudhanshu; Aspi, Jouni; Kvist, Laura; Nigam, Parag; Pandey, Puneet; Sharma, Reeta; Goyal, Surendra Prakash

    2015-01-01

    The Sundarbans tiger inhabits a unique mangrove habitat and are morphologically distinct from the recognized tiger subspecies in terms of skull morphometrics and body size. Thus, there is an urgent need to assess their ecological and genetic distinctiveness and determine if Sundarbans tigers should be defined and managed as separate conservation unit. We utilized nine microsatellites and 3 kb from four mitochondrial DNA (mtDNA) genes to estimate genetic variability, population structure, demographic parameters and visualize historic and contemporary connectivity among tiger populations from Sundarbans and mainland India. We also evaluated the traits that determine exchangeability or adaptive differences among tiger populations. Data from both markers suggest that Sundarbans tiger is not a separate tiger subspecies and should be regarded as Bengal tiger (P. t. tigris) subspecies. Maximum likelihood phylogenetic analyses of the mtDNA data revealed reciprocal monophyly. Genetic differentiation was found stronger for mtDNA than nuclear DNA. Microsatellite markers indicated low genetic variation in Sundarbans tigers (He= 0.58) as compared to other mainland populations, such as northern and Peninsular (Hebetween 0.67- 0.70). Molecular data supports migration between mainland and Sundarbans populations until very recent times. We attribute this reduction in gene flow to accelerated fragmentation and habitat alteration in the landscape over the past few centuries. Demographic analyses suggest that Sundarbans tigers have diverged recently from peninsular tiger population within last 2000 years. Sundarbans tigers are the most divergent group of Bengal tigers, and ecologically non-exchangeable with other tiger populations, and thus should be managed as a separate “evolutionarily significant unit” (ESU) following the adaptive evolutionary conservation (AEC) concept. PMID:25919139

  15. Tigers of Sundarbans in India: is the population a separate conservation unit?

    PubMed

    Singh, Sujeet Kumar; Mishra, Sudhanshu; Aspi, Jouni; Kvist, Laura; Nigam, Parag; Pandey, Puneet; Sharma, Reeta; Goyal, Surendra Prakash

    2014-01-01

    The Sundarbans tiger inhabits a unique mangrove habitat and are morphologically distinct from the recognized tiger subspecies in terms of skull morphometrics and body size. Thus, there is an urgent need to assess their ecological and genetic distinctiveness and determine if Sundarbans tigers should be defined and managed as separate conservation unit. We utilized nine microsatellites and 3 kb from four mitochondrial DNA (mtDNA) genes to estimate genetic variability, population structure, demographic parameters and visualize historic and contemporary connectivity among tiger populations from Sundarbans and mainland India. We also evaluated the traits that determine exchangeability or adaptive differences among tiger populations. Data from both markers suggest that Sundarbans tiger is not a separate tiger subspecies and should be regarded as Bengal tiger (P. t. tigris) subspecies. Maximum likelihood phylogenetic analyses of the mtDNA data revealed reciprocal monophyly. Genetic differentiation was found stronger for mtDNA than nuclear DNA. Microsatellite markers indicated low genetic variation in Sundarbans tigers (He= 0.58) as compared to other mainland populations, such as northern and Peninsular (Hebetween 0.67- 0.70). Molecular data supports migration between mainland and Sundarbans populations until very recent times. We attribute this reduction in gene flow to accelerated fragmentation and habitat alteration in the landscape over the past few centuries. Demographic analyses suggest that Sundarbans tigers have diverged recently from peninsular tiger population within last 2000 years. Sundarbans tigers are the most divergent group of Bengal tigers, and ecologically non-exchangeable with other tiger populations, and thus should be managed as a separate "evolutionarily significant unit" (ESU) following the adaptive evolutionary conservation (AEC) concept.

  16. From landscape to domain: Soils role in landscape classifications

    USDA-ARS?s Scientific Manuscript database

    Soil landscape classifications are designed to divide landscapes into units with significance for the provisioning and regulating of ecosystem services and the development of conservation plans for natural resources. More specifically, such classifications serve as the basis for stratifying manageme...

  17. Isotope separation

    DOEpatents

    Bartlett, Rodney J.; Morrey, John R.

    1978-01-01

    A method and apparatus is described for separating gas molecules containing one isotope of an element from gas molecules containing other isotopes of the same element in which all of the molecules of the gas are at the same electronic state in their ground state. Gas molecules in a gas stream containing one of the isotopes are selectively excited to a different electronic state while leaving the other gas molecules in their original ground state. Gas molecules containing one of the isotopes are then deflected from the other gas molecules in the stream and thus physically separated.

  18. ISOTOPE SEPARATORS

    DOEpatents

    Bacon, C.G.

    1958-08-26

    An improvement is presented in the structure of an isotope separation apparatus and, in particular, is concerned with a magnetically operated shutter associated with a window which is provided for the purpose of enabling the operator to view the processes going on within the interior of the apparatus. The shutier is mounted to close under the force of gravity in the absence of any other force. By closing an electrical circuit to a coil mouated on the shutter the magnetic field of the isotope separating apparatus coacts with the magnetic field of the coil to force the shutter to the open position.

  19. Separator sub

    SciTech Connect

    Hayatdavoudi, A.

    1984-10-09

    Apparatus and methods are disclosed for drilling a well. A separator sub is used to separate a stream of drilling mud into a less dense first portion and more dense second portion. The less dense first portion of the stream of drilling mud is directed downward to a drill bit so that the drilling mud adjacent the drill bit has a density less than an initial density of the stream of drilling mud. The more dense second portion of the stream of drilling mud is ejected into a well annulus with an upward component of velocity and thereby reduces a hydrostatic drilling mud pressure adjacent the drill bit.

  20. Isotopic separation

    SciTech Connect

    Chen, C.

    1981-03-10

    Method and apparatus for separating isotopes in an isotopic mixture of atoms or molecules by increasing the mass differential among isotopic species. The mixture containing a particular isotope is selectively irradiated so as to selectively excite the isotope. This preferentially excited species is then reacted rapidly with an additional preselected radiation, an electron or another chemical species so as to form a product containing the specific isotope, but having a mass different than the original species initially containing the particular isotope. The product and the remaining balance of the mixture is then caused to flow through a device which separates the product from the mixture based upon the increased mass differential.

  1. Landscapes and fragilities

    NASA Astrophysics Data System (ADS)

    Ruocco, G.; Sciortino, F.; Zamponi, F.; De Michele, C.; Scopigno, T.

    2004-06-01

    The concept of fragility provides a possibility to rank different supercooled liquids on the basis of the temperature dependence of dynamic and/or thermodynamic quantities. We recall here the definitions of kinetic and thermodynamic fragility proposed in the last years and discuss their interrelations. At the same time we analyze some recently introduced models for the statistical properties of the potential energy landscape. Building on the Adam-Gibbs relation, which connects structural relaxation times to configurational entropy, we analyze the relation between statistical properties of the landscape and fragility. We call attention to the fact that the knowledge of number, energy depth, and shape of the basins of the potential energy landscape may not be sufficient for predicting fragility. Finally, we discuss two different possibilities for generating strong behavior.

  2. Landscapes, tourism, and conservation

    PubMed

    Burger

    2000-04-17

    One key aspect of global change is a decrease in ecological integrity as more and more landscapes are developed, leaving a mosaic of intact refuges and degraded patches that may not be sufficient for conserving biodiversity. While increases in human population and shifts in the distribution of people affect land use, the temporary movement of people can have major implications for conservation and biodiversity. Three examples are presented where recreation/tourism can enhance the conservation of land on a landscape scale, leading to habitat protection and biodiversity preservation: (1) Shorebirds often require a matrix of different habitat types during migratory stopovers, and ecotourism can serve as a catalyst for landscape scale protection of habitat. (2) Riparian habitats can serve as corridors to link diverse habitat patches, as well as serving as biodiversity hotspots. (3) Remediation and rehabilitation of contaminated lands, such as those of the US Department of Energy, aimed at developing recreational activities on the uncontaminated portions, can be the most economical form of re-development with no increase in human or ecological risk. Since large areas on many DOE sites have been undisturbed since the Second World War, when they were acquired, they contain unique or valuable ecosystems that serve an important role within their regional landscapes. In all three cases the judicious development of recreational/tourist interests can encourage both the conservation of habitats and the wise management of habitats on a landscape scale. While some species or habitats are too fragile for sustained tourism, many can be managed so that species, ecosystems and ecotourists flourish. By contributing to the economic base of regions, ecotourists/recreationists can influence the protection of land and biodiversity on a landscape scale, contributing to ecosystem management. The human dimensions of land preservation and biodiversity protection are key to long

  3. Plasma separation

    NASA Technical Reports Server (NTRS)

    Steurer, Wolfgang

    1992-01-01

    This process employs a thermal plasma for the separation and production of oxygen and metals. It is a continuous process that requires no consumables and relies entirely on space resources. The almost complete absence of waste renders it relatively clean. It can be turned on or off without any undesirable side effects or residues. The prime disadvantage is its high power consumption.

  4. SEPARATION PROCESS

    DOEpatents

    Stoughton, R.W.

    1961-10-24

    A process for separating tetravalent plutonium from aqueous solutions and from niobium and zirconium by precipitation on lanthanum oxalate is described. The oxalate ions of the precipitate may be decomposed by heating in the presence of an oxidizing agent, forming a plutonium compound readily soluble in acid. (AEC)

  5. Landscape evolutionary genomics.

    PubMed

    Lowry, David B

    2010-08-23

    Tremendous advances in genetic and genomic techniques have resulted in the capacity to identify genes involved in adaptive evolution across numerous biological systems. One of the next major steps in evolutionary biology will be to determine how landscape-level geographical and environmental features are involved in the distribution of this functional adaptive genetic variation. Here, I outline how an emerging synthesis of multiple disciplines has and will continue to facilitate a deeper understanding of the ways in which heterogeneity of the natural landscapes mould the genomes of organisms.

  6. Labyrinthine granular landscapes.

    PubMed

    Caps, H; Vandewalle, N

    2001-11-01

    We have numerically studied a model of granular landscape eroded by wind. We show the appearance of labyrinthic patterns when the wind orientation turns by 90 degrees. The occurrence of such structures is discussed. Moreover, we introduce the density n(k) of "defects" as the dynamic parameter governing the landscape evolution. A power-law behavior of n(k) is found as a function of time. In the case of wind variations, the exponent (drastically) shifts from two to one. The presence of two asymptotic values of n(k) implies the irreversibility of the labyrinthic formation process.

  7. Means for counteracting charged particle beam divergence

    DOEpatents

    Hooper, Jr., Edwin B.

    1978-01-01

    To counteract charge particle beam divergence, magnetic field-generating means are positioned along the edges of a charged particle beam to be controlled, such as to deflect and redirect particles tending to diverge from a desired beam direction. By selective arrangement of the magnetic field-generating means, the entire beam may be deflected and guided into different directions.

  8. Divergent Thinking and Age-Related Changes

    ERIC Educational Resources Information Center

    Palmiero, Massimiliano; Di Giacomo, Dina; Passafiume, Domenico

    2014-01-01

    Aging can affect cognition in different ways. The extent to which aging affects divergent thinking is unclear. In this study, younger and older adults were compared at the performance on the Torrance Test of Creative Thinking in visual and verbal form. Results showed that older adults can think divergently as younger participants, although they…

  9. Divergent Thinking and Age-Related Changes

    ERIC Educational Resources Information Center

    Palmiero, Massimiliano; Di Giacomo, Dina; Passafiume, Domenico

    2014-01-01

    Aging can affect cognition in different ways. The extent to which aging affects divergent thinking is unclear. In this study, younger and older adults were compared at the performance on the Torrance Test of Creative Thinking in visual and verbal form. Results showed that older adults can think divergently as younger participants, although they…

  10. The suffocating embrace of landscape and the picturesque conditioning of ecology

    Treesearch

    A.M. Ellison

    2013-01-01

    What are natural landscapes? Are they “out there,” separate from people, or are they creations of our own perception? An exploration of artistic visions of landscape on the one hand and the development of ecology as a self-conscious science on the other suggests that for nearly 150 years ecology has been conditioned by romantic, picturesque portrayals of landscape....

  11. Adaptive genetic divergence along narrow environmental gradients in four stream insects.

    PubMed

    Watanabe, Kozo; Kazama, So; Omura, Tatsuo; Monaghan, Michael T

    2014-01-01

    A central question linking ecology with evolutionary biology is how environmental heterogeneity can drive adaptive genetic divergence among populations. We examined adaptive divergence of four stream insects from six adjacent catchments in Japan by combining field measures of habitat and resource components with genome scans of non-neutral Amplified Fragment Length Polymorphism (AFLP) loci. Neutral genetic variation was used to measure gene flow and non-neutral genetic variation was used to test for adaptive divergence. We identified the environmental characteristics contributing to divergence by comparing genetic distances at non-neutral loci between sites with Euclidean distances for each of 15 environmental variables. Comparisons were made using partial Mantel tests to control for geographic distance. In all four species, we found strong evidence for non-neutral divergence along environmental gradients at between 6 and 21 loci per species. The relative contribution of these environmental variables to each species' ecological niche was quantified as the specialization index, S, based on ecological data. In each species, the variable most significantly correlated with genetic distance at non-neutral loci was the same variable along which each species was most narrowly distributed (i.e., highest S). These were gradients of elevation (two species), chlorophyll-a, and ammonia-nitrogen. This adaptive divergence occurred in the face of ongoing gene flow (Fst = 0.01-0.04), indicating that selection was strong enough to overcome homogenization at the landscape scale. Our results suggest that adaptive divergence is pronounced, occurs along different environmental gradients for different species, and may consistently occur along the narrowest components of species' niche.

  12. Sympatric speciation revealed by genome-wide divergence in the blind mole rat Spalax

    PubMed Central

    Li, Kexin; Hong, Wei; Jiao, Hengwu; Wang, Guo-Dong; Rodriguez, Karl A.; Buffenstein, Rochelle; Zhao, Yang; Nevo, Eviatar; Zhao, Huabin

    2015-01-01

    Sympatric speciation (SS), i.e., speciation within a freely breeding population or in contiguous populations, was first proposed by Darwin [Darwin C (1859) On the Origins of Species by Means of Natural Selection] and is still controversial despite theoretical support [Gavrilets S (2004) Fitness Landscapes and the Origin of Species (MPB-41)] and mounting empirical evidence. Speciation of subterranean mammals generally, including the genus Spalax, was considered hitherto allopatric, whereby new species arise primarily through geographic isolation. Here we show in Spalax a case of genome-wide divergence analysis in mammals, demonstrating that SS in continuous populations, with gene flow, encompasses multiple widespread genomic adaptive complexes, associated with the sharply divergent ecologies. The two abutting soil populations of S. galili in northern Israel habituate the ancestral Senonian chalk population and abutting derivative Plio-Pleistocene basalt population. Population divergence originated ∼0.2–0.4 Mya based on both nuclear and mitochondrial genome analyses. Population structure analysis displayed two distinctly divergent clusters of chalk and basalt populations. Natural selection has acted on 300+ genes across the genome, diverging Spalax chalk and basalt soil populations. Gene ontology enrichment analysis highlights strong but differential soil population adaptive complexes: in basalt, sensory perception, musculature, metabolism, and energetics, and in chalk, nutrition and neurogenetics are outstanding. Population differentiation of chemoreceptor genes suggests intersoil population's mate and habitat choice substantiating SS. Importantly, distinctions in protein degradation may also contribute to SS. Natural selection and natural genetic engineering [Shapiro JA (2011) Evolution: A View From the 21st Century] overrule gene flow, evolving divergent ecological adaptive complexes. Sharp ecological divergences abound in nature; therefore, SS appears to be

  13. Sympatric speciation revealed by genome-wide divergence in the blind mole rat Spalax.

    PubMed

    Li, Kexin; Hong, Wei; Jiao, Hengwu; Wang, Guo-Dong; Rodriguez, Karl A; Buffenstein, Rochelle; Zhao, Yang; Nevo, Eviatar; Zhao, Huabin

    2015-09-22

    Sympatric speciation (SS), i.e., speciation within a freely breeding population or in contiguous populations, was first proposed by Darwin [Darwin C (1859) On the Origins of Species by Means of Natural Selection] and is still controversial despite theoretical support [Gavrilets S (2004) Fitness Landscapes and the Origin of Species (MPB-41)] and mounting empirical evidence. Speciation of subterranean mammals generally, including the genus Spalax, was considered hitherto allopatric, whereby new species arise primarily through geographic isolation. Here we show in Spalax a case of genome-wide divergence analysis in mammals, demonstrating that SS in continuous populations, with gene flow, encompasses multiple widespread genomic adaptive complexes, associated with the sharply divergent ecologies. The two abutting soil populations of S. galili in northern Israel habituate the ancestral Senonian chalk population and abutting derivative Plio-Pleistocene basalt population. Population divergence originated ∼0.2-0.4 Mya based on both nuclear and mitochondrial genome analyses. Population structure analysis displayed two distinctly divergent clusters of chalk and basalt populations. Natural selection has acted on 300+ genes across the genome, diverging Spalax chalk and basalt soil populations. Gene ontology enrichment analysis highlights strong but differential soil population adaptive complexes: in basalt, sensory perception, musculature, metabolism, and energetics, and in chalk, nutrition and neurogenetics are outstanding. Population differentiation of chemoreceptor genes suggests intersoil population's mate and habitat choice substantiating SS. Importantly, distinctions in protein degradation may also contribute to SS. Natural selection and natural genetic engineering [Shapiro JA (2011) Evolution: A View From the 21st Century] overrule gene flow, evolving divergent ecological adaptive complexes. Sharp ecological divergences abound in nature; therefore, SS appears to be an

  14. Adaptive Genetic Divergence along Narrow Environmental Gradients in Four Stream Insects

    PubMed Central

    Watanabe, Kozo; Kazama, So; Omura, Tatsuo; Monaghan, Michael T.

    2014-01-01

    A central question linking ecology with evolutionary biology is how environmental heterogeneity can drive adaptive genetic divergence among populations. We examined adaptive divergence of four stream insects from six adjacent catchments in Japan by combining field measures of habitat and resource components with genome scans of non-neutral Amplified Fragment Length Polymorphism (AFLP) loci. Neutral genetic variation was used to measure gene flow and non-neutral genetic variation was used to test for adaptive divergence. We identified the environmental characteristics contributing to divergence by comparing genetic distances at non-neutral loci between sites with Euclidean distances for each of 15 environmental variables. Comparisons were made using partial Mantel tests to control for geographic distance. In all four species, we found strong evidence for non-neutral divergence along environmental gradients at between 6 and 21 loci per species. The relative contribution of these environmental variables to each species' ecological niche was quantified as the specialization index, S, based on ecological data. In each species, the variable most significantly correlated with genetic distance at non-neutral loci was the same variable along which each species was most narrowly distributed (i.e., highest S). These were gradients of elevation (two species), chlorophyll-a, and ammonia-nitrogen. This adaptive divergence occurred in the face of ongoing gene flow (Fst = 0.01–0.04), indicating that selection was strong enough to overcome homogenization at the landscape scale. Our results suggest that adaptive divergence is pronounced, occurs along different environmental gradients for different species, and may consistently occur along the narrowest components of species' niche. PMID:24681871

  15. The exact distribution of divergence times.

    PubMed

    Nadarajah, Saralees; Kotz, Samuel

    2008-02-01

    The recent work of Haubold and Wiehe (Mol. Biol. Evol. 18:1157-1160, 2001) considered statistical inference of the divergence time. However, there appears to be a fundamental flaw in the paper since it treated the divergence time as a random variable and not as a parameter. In this note, we derive a valid statistical inference for the divergence time. We derive an estimator for the divergence time as well as explicit expressions for its the probability density function, cumulative distribution function and the means. We also provide a 5-line computer program for computing the associated confidence intervals. We expect that the results presented could be useful for statistical modeling of divergence times.

  16. Vorticity and divergence in the solar photosphere

    NASA Technical Reports Server (NTRS)

    Wang, YI; Noyes, Robert W.; Tarbell, Theodore D.; Title, Alan M.

    1995-01-01

    We have studied an outstanding sequence of continuum images of the solar granulation from Pic du Midi Observatory. We have calculated the horizontal vector flow field using a correlation tracking algorithm, and from this determined three scalar field: the vertical component of the curl; the horizontal divergence; and the horizontal flow speed. The divergence field has substantially longer coherence time and more power than does the curl field. Statistically, curl is better correlated with regions of negative divergence - that is, the vertical vorticity is higher in downflow regions, suggesting excess vorticity in intergranular lanes. The average value of the divergence is largest (i.e., outflow is largest) where the horizontal speed is large; we associate these regions with exploding granules. A numerical simulation of general convection also shows similar statistical differences between curl and divergence. Some individual small bright points in the granulation pattern show large local vorticities.

  17. Racial Definition: Background for Divergence

    ERIC Educational Resources Information Center

    Nelson, William Javier

    1986-01-01

    The racial definitional system in the United States ensures the separation of people. It is a caste-like system of nomenclature which was invented by Whites for their benefit. It is institutionalized and gets renewed through the socialization process. The system is only peripherally concerned with how Blacks define themselves. (VM)

  18. Descriptive approaches to landscape analysis

    Treesearch

    R. Burton Litton Jr.

    1979-01-01

    Descriptive landscape analyses include various procedures used to document visual/scenic resources. Historic and regional examples of landscape description represent desirable insight for contemporary professional inventory work. Routed and areal landscape inventories are discussed as basic tools. From them, qualitative and quantitative evaluations can be developed...

  19. A Forest Landscape Visualization System

    Treesearch

    Tim McDonald; Bryce Stokes

    1998-01-01

    A forest landscape visualization system was developed and used in creating realistic images depicting how an area might appear if harvested. The system uses a ray-tracing renderer to draw model trees on a virtual landscape. The system includes components to create landscape surfaces from digital elevation data, populate/cut trees within (polygonal) areas, and convert...

  20. Mandibular shape and skeletal divergency.

    PubMed

    Ferrario, V F; Sforza, C; De Franco, D J

    1999-04-01

    Pre-treatment lateral cephalograms of 41 skeletal Class I girls aged 11 to 15 were divided according to MP-SN angle: lower than 28 degrees (hypodivergent, 10 girls), between 31 and 34 degrees (normodivergent, 18 girls), or larger than 37 degrees (hyperdivergent, 13 girls). The mandibular outlines were traced and digitized, and differences in shape were quantified using the elliptic Fourier series. Size differences were measured from the areas enclosed by the mandibular outlines. Shape differences were assessed by calculating a morphological distance (MD) between the size-independent mean mathematical reconstructions of the mandibular outlines of the three divergency classes. Mandibular shape was different in the three classes: large variations were found in hyperdivergent girls versus normodivergent girls (MD = 4.61), while smaller differences were observed in hypodivergent girls (MD versus normodivergent 2.91). Mean size-independent mandibular shapes were superimposed on an axis passing through the centres of gravity of the condyle and of the chin. Normodivergent and hyperdivergent mandibles differed mostly at gonion, the coronoid process, sigmoid notch, alveolar process, posterior border of the ramus, and along the mandibular plane. A significant size effect was also found, with smaller mandibles in the hyperdivergent girls.

  1. Divergent routes to oral cancer.

    PubMed

    Hunter, Keith D; Thurlow, Johanna K; Fleming, Janis; Drake, Paul J H; Vass, J Keith; Kalna, Gabriela; Higham, Des J; Herzyk, Pawel; Macdonald, D Gordon; Parkinson, E Ken; Harrison, Paul R

    2006-08-01

    Most head and neck squamous cell carcinoma (HNSCC) patients present with late-stage cancers, which are difficult to treat. Therefore, early diagnosis of high-risk premalignant lesions and incipient cancers is important. HNSCC is currently perceived as a single progression mechanism, resulting in immortal invasive cancers. However, we have found that approximately 40% of primary oral SCCs are mortal in culture, and these have a better prognosis. About 60% of oral premalignancies (dysplasias) are also mortal. The mortal and immortal tumors are generated in vivo as judged by p53 mutations and loss of p16(INK4A) expression being found only in the original tumors from which the immortal cultures were derived. To investigate the relationships of dysplasias to SCCs, we did microarray analysis of primary cultures of 4 normal oral mucosa biopsies, 19 dysplasias, and 16 SCCs. Spectral clustering using the singular value decomposition and other bioinformatic techniques showed that development of mortal and immortal SCCs involves distinct transcriptional changes. Both SCC classes share most of the transcriptional changes found in their respective dysplasias but have additional changes. Moreover, high-risk dysplasias that subsequently progress to SCCs more closely resemble SCCs than nonprogressing dysplasias. This indicates for the first time that there are divergent mortal and immortal pathways for oral SCC development via intermediate dysplasias. We believe that this new information may lead to new ways of classifying HNSCC in relation to prognosis.

  2. Landscape analysis software tools

    Treesearch

    Don Vandendriesche

    2008-01-01

    Recently, several new computer programs have been developed to assist in landscape analysis. The “Sequential Processing Routine for Arraying Yields” (SPRAY) program was designed to run a group of stands with particular treatment activities to produce vegetation yield profiles for forest planning. SPRAY uses existing Forest Vegetation Simulator (FVS) software coupled...

  3. Landscapes. Artists' Workshop Series.

    ERIC Educational Resources Information Center

    King, Penny; Roundhill, Clare

    This instructional resource, designed to be used by and with elementary level students, provides inspiration for landscape painting by presenting the work of six different artists. These include: "Fuji in Clear Weather" (Katsushika Hokusai, 1823-29); "The Tree of Life" (Gustav Klimt, c. 1905-1909); "The Waterlily…

  4. Litigation and landscape esthetics

    Treesearch

    Michael McCloskey

    1979-01-01

    Over the past two decades, the concerns of conservation groups have shifted in and out of the field of landscape esthetics. As the 1960's began, they tended to pursue their interests under the mantle of recreationists. By the mid-1960's, natural beauty became the watch-word, particularly with the national encouragement of Lady Bird Johnson. By the late 1970...

  5. Shaping the Landscape.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Provides background information on various agents that change the landscape. Includes teaching activities on weathering, water, wind and ice erosion, plate tectonics, sedimentation, deposition, mountain building, and determining contour lines. Contains reproducible handouts and worksheets for two of the activities. (TW)

  6. Landscape in Literature.

    ERIC Educational Resources Information Center

    Salter, Christopher L.; Lloyd, William J.

    One of a series of Resource Papers for College Geography, this thematic study guide focuses on literary setting and the personal space of fictional characters as an approach to comparative literary study, and concurrently uses fictional treatments of landscape and place as a means to encourage greater sensitivity to geographical and architectural…

  7. The New Postsecondary Landscape

    ERIC Educational Resources Information Center

    Sandeen, Cathy

    2013-01-01

    In this essay, Cathy Sandeen states that the new postsecondary landscape requires looking at higher education as a system that provides multiple pathways in and through the various parts of the system, all with the goal of helping students complete a postsecondary degree, credential, or certificate. Sandeen observes two strengths in professional…

  8. Landscape Assessment (LA)

    Treesearch

    Carl H. Key; Nathan C. Benson

    2006-01-01

    Landscape Assessment primarily addresses the need to identify and quantify fire effects over large areas, at times involving many burns. In contrast to individual case studies, the ability to compare results is emphasized along with the capacity to aggregate information across broad regions and over time. Results show the spatial heterogeneity of burns and how fire...

  9. Moving into Landscapes

    ERIC Educational Resources Information Center

    Nelson, Cindy

    2008-01-01

    This article describes a lesson, designed for second graders, that begins with the teacher showing and talking about a few landscape fundamentals: horizon line, depth, and the mood or feeling that a work of art inspires. A class discussion ensues about how an artist's images can make one feel, how they can convey calmness, warmth, anxiety, or a…

  10. Shaping the Landscape.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Provides background information on various agents that change the landscape. Includes teaching activities on weathering, water, wind and ice erosion, plate tectonics, sedimentation, deposition, mountain building, and determining contour lines. Contains reproducible handouts and worksheets for two of the activities. (TW)

  11. Diversity in Riparian Landscapes

    Treesearch

    Thomas R. Crow; Matthew E. Baker; Burton V. Barnes

    2000-01-01

    Therefore, in this chapter we focus on ecosystem diversity, defined as the number, kind, and pattern of landscape and waterscape ecosystems in a specified area and the ecological processes that are associated with these patterns (Lapin and Barnes 1995). One can then characterize eeosysterns as to their composition, structure, and function -- the attributes Of...

  12. Landscape Management: Field Operator.

    ERIC Educational Resources Information Center

    Smith, Carole A.

    These materials for a six-unit course were developed to prepare secondary and postsecondary students for entry-level positions in landscape management. The six units are on orientation, hand tools, light power equipment, water and watering techniques, planting and maintaining plant beds, and establishing and maintaining turf. The first section is…

  13. Landscape Designs for Schools.

    ERIC Educational Resources Information Center

    Taylor, Patricia

    This annotated bibliography includes summaries of 15 books and articles dealing with the topic of school landscape design, as well as a brief introduction that comments on recent trends in the field. Most of the publications cited are fairly recent; about two-thirds of them were published after 1970. Annotations range from approximately 125 to 250…

  14. A landscape analysis plan

    Treesearch

    Nancy E. Fleenor

    2002-01-01

    A Landscape Analysis Plan (LAP) sets out broad guidelines for project development within boundaries of the Kings River Sustainable Forest Ecosystems Project. The plan must be a dynamic, living document, subject to change as new information arises over the course of this very long-term project (several decades). Two watersheds, each of 32,000 acres, were dedicated to...

  15. Landscapes. Artists' Workshop Series.

    ERIC Educational Resources Information Center

    King, Penny; Roundhill, Clare

    This instructional resource, designed to be used by and with elementary level students, provides inspiration for landscape painting by presenting the work of six different artists. These include: "Fuji in Clear Weather" (Katsushika Hokusai, 1823-29); "The Tree of Life" (Gustav Klimt, c. 1905-1909); "The Waterlily…

  16. Complexity and valued landscapes

    Treesearch

    Michael M. McCarthy

    1979-01-01

    The variable "complexity," or "diversity," has received a great deal of attention in recent research efforts concerned with visual resource management, including the identification of complexity as one of the primary evaluation measures. This paper describes research efforts that support the hypothesis that the landscapes we value are those with...

  17. Performance Technology Landscape.

    ERIC Educational Resources Information Center

    Addison, Roger M.

    2003-01-01

    Describes a performance technology landscape that has been developed for performance improvement institutes. Defines performance technology, including identification of value; definition of outcomes; performance analysis; valuation of effectiveness; focusing on results; systemic approach; adding value; aligning workers, activity, the organization,…

  18. Biofuels from urban landscapes

    USDA-ARS?s Scientific Manuscript database

    Biomass from urban landscapes is an untapped resource. Lawn thatch and clippings, fallen leaves and tree limbs are all potential sources of biofuels. Most cities already collect and transport these materials to disposal sites; but, alternatively could collect and transport these materials to a loc...

  19. Landscape genetics [Chapter 17

    Treesearch

    Kevin S. McKelvey; Samuel A. Cushman; Michael K. Schwartz

    2009-01-01

    In reading this book, you have observed that the spatial data used in landscape ecology come from many sources and in many forms. For many organisms, these data take the form of presence or absence at a location, or numbers of individuals at that same location. For species such as trees, where huge size differences exist between individuals, indices such as basal area...

  20. Landscape-level changes

    Treesearch

    A. Joel Frandsen

    2008-01-01

    Since European settlement, Utah?s vegetative landscapes have changed. Like other arid states, these wildland systems were depleted and altered. Certain steps were taken through private, community, and finally public efforts, such as establishment of Forest Reserves (National Forests), to stop the slide. Conservation and management actions were taken to restore,...

  1. A Curious Landscape

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 'postcard' from the panoramic camera on the Mars Exploration Rover Opportunity shows the view of the martian landscape southwest of the rover. The image was taken in the late martian afternoon at Meridiani Planum on Mars, where Opportunity landed at approximately 9:05 p.m. PST on Saturday, Jan. 24.

  2. Landscape Management: Field Specialist.

    ERIC Educational Resources Information Center

    Newton, Deborah; Newton, Steve

    This module is the second volume in a series of three publications on landscape management. The module contains five instructional units that cover the following topics: orientation; equipment; irrigation systems and maintenance; plant material identification and pests; and turf identification and pests. Each instructional unit follows a standard…

  3. Landscapes of Learning.

    ERIC Educational Resources Information Center

    Greene, Maxine

    The commitment of educators to human development goals is a major theme of the booklet's 17 essays. Compiled from lectures written by the author during 1974-77, the essays explore individual potential, the cultural significance of various life situations, and personal fulfillment within each individual's particular landscape of work, experience,…

  4. Landscape habitats [Chapter 2

    Treesearch

    C. L. Simmons

    1994-01-01

    This landscape habitat description is based on a ground reconnaissance of the Lost Lake, West Glacier Lake, and East Glacier Lake portions of GLEES conducted during 10 days in July-September 1986 and on subsequent photo interpretation of 1:6000 scale color-infrared photographs. A ground check was conducted in July-August 1987. The classification used is a physiognomic...

  5. Desert landscape irrigation

    SciTech Connect

    Quinones, R.

    1995-06-01

    Industrialization can take place in an arid environment if a long term, overall water management program is developed. The general rule to follow is that recharge must equal or exceed use. The main problem encountered in landscape projects is that everyone wants a lush jungle setting, tall shade trees, ferns, with a variety of floral arrangements mixed in. What we want, what we can afford, and what we get are not always the same. Vegetation that requires large quantities of water are not native to any desert. Surprisingly; there are various types of fruit trees, and vegetables that will thrive in the desert. Peaches, plums, nut trees, do well with drip irrigation as well as tomatoes. Shaded berry plans will also do well, the strawberry being one. In summary; if we match our landscape to our area, we can then design our irrigation system to maintain our landscape and grow a variety of vegetation in any arid or semiarid environment. The application of science and economics to landscaping has now come of age.

  6. LANDSCAPE MANAGEMENT PRACTICES

    EPA Science Inventory

    USDA Conservation Practices are applied at various scales ranging from a portion of a field or a specific farm operation to the watershed or landscape scale. The Conservation Effects Assessment Project is a joint effort of USDA Conservation and Research agencies to determine the...

  7. Gas separating

    DOEpatents

    Gollan, Arye Z.

    1990-12-25

    Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing.

  8. Gas separating

    DOEpatents

    Gollan, Arye

    1988-01-01

    Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing.

  9. Dust separator

    SciTech Connect

    Borow, H.

    1987-01-27

    This patent describes a gas filter apparatus for separating solids from a gas stream comprising a housing having a top, base, and side walls defining a chamber, a partition wall extending across the chamber and separating the chamber into an upper compartment and a lower compartment. A gas inlet conveyor tube in the chamber passes downwardly of the partition and into the lower compartment, the portion of the conveyor tube passing through the upper compartment being impervious and the portion of the conveyor tube extending downwardly into the lower compartment being provided with exit means including exit apertures at least in the area of the conveyor tube adjacent the partition wall. The partition wall is provided with openings surrounding the conveyor tube and communicates the lower compartment with the upper compartment. A filter means in the form of filter tubes covers each opening in the partition wall and extends downwardly in the lower compartment and parallel to the conveyor tube, at least one gas outlet communicating with the upper compartment. A suction means is associated with the gas outlet to provide a reduced pressure within the chamber. A discharge means at the base of the housing is associated with the lower compartment for discharging solid matter separated from the gas stream. The solid laden gas is conveyed into the lower compartment downwardly by the conveying tube and the gas of the stream is drawn from the conveyor tube immediately past the partition, through the surrounding filter tubes in order to prevent the formation of counter gas flows to the gravity discharge of the solids being separated from the gas stream.

  10. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 23 Highways 1 2011-04-01 2011-04-01 false Landscape development. 752.4 Section 752.4 Highways... ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes landscaping... landscaping and environmental design. (b) Landscape development should have provisions for plant establishment...

  11. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false Landscape development. 752.4 Section 752.4 Highways... ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes landscaping... landscaping and environmental design. (b) Landscape development should have provisions for plant establishment...

  12. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 23 Highways 1 2014-04-01 2014-04-01 false Landscape development. 752.4 Section 752.4 Highways... ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes landscaping... landscaping and environmental design. (b) Landscape development should have provisions for plant establishment...

  13. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false Landscape development. 752.4 Section 752.4 Highways... ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes landscaping... landscaping and environmental design. (b) Landscape development should have provisions for plant establishment...

  14. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 23 Highways 1 2013-04-01 2013-04-01 false Landscape development. 752.4 Section 752.4 Highways... ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes landscaping... landscaping and environmental design. (b) Landscape development should have provisions for plant establishment...

  15. Geomorphology of anthropogenic landscapes

    NASA Astrophysics Data System (ADS)

    Sofia, Giulia; Tarolli, Paolo

    2015-04-01

    The construction of urban areas and the development of road networks leave a significant signature on the Earth surface, providing a geomorphological evidence to support the idea that humans are nowadays a geomorphic agent having deep effects on the morphological organization of the landscape. The reconstruction or identification of anthropogenic topographies, therefore, provides a mechanism for quantifying anthropogenic changes to the landscape systems in the Anthropocene. Following this research line, the present study tests the effectiveness of a recently published topographic index, the Slope Local Length of Autocorrelation (SLLAC, Sofia et al. 2014) to portrait anthropogenic geomorphology, focusing in particular on road network density, and urban complexity (UCI). At first, the research considers the increasing of anthropic structures and the resulting changes in the SLLAC and in two derived parameters (mean SLLAC per km2 and SLLAC roughness, or Surface Peak Curvature -Spc). As a second step, considering the SLLAC derived indices, the anthropogenic geomorphology is automatically depicted using a k-means clustering algorithm. In general, the increasing of road network density or of the UCI is positively correlated to the mean SLLAC per km2, while the Spc is negatively correlated to the increasing of the anthropic structures. Areas presenting different road network organization are effectively captured considering multiple combinations of the defined parameters. Landscapes with small scattered towns, and a network with long roads in a dendritic shape (with hierarchical branching) are characterized simultaneously by high mean SLLAC and low Spc. Large and complex urban areas served by rectilinear networks with numerous short straight lines and right angles, have either a maximized mean SLLAC or a minimized Spc or both. In all cases, the anthropogenic landscape identified by the procedure is comparable to the ones identified manually from orthophoto, with the

  16. Separation system

    DOEpatents

    Rubin, Leslie S.

    1986-01-01

    A separation system for dewatering radioactive waste materials includes a disposal container, drive structure for receiving the container, and means for releasably attaching the container to the drive structure. Separation structure disposed in the container adjacent the inner surface of the side wall structure retains solids while allowing passage of liquids. Inlet port structure in the container top wall is normally closed by first valve structure that is centrifugally actuated to open the inlet port and discharge port structure at the container periphery receives liquid that passes through the separation structure and is normally closed by second valve structure that is centrifugally actuated to open the discharge ports. The container also includes coupling structure for releasable engagement with the centrifugal drive structure. Centrifugal force produced when the container is driven in rotation by the drive structure opens the valve structures, and radioactive waste material introduced into the container through the open inlet port is dewatered, and the waste is compacted. The ports are automatically closed by the valves when the container drum is not subjected to centrifugal force such that containment effectiveness is enhanced and exposure of personnel to radioactive materials is minimized.

  17. Component separations.

    PubMed

    Heller, Lior; McNichols, Colton H; Ramirez, Oscar M

    2012-02-01

    Component separation is a technique used to provide adequate coverage for midline abdominal wall defects such as a large ventral hernia. This surgical technique is based on subcutaneous lateral dissection, fasciotomy lateral to the rectus abdominis muscle, and dissection on the plane between external and internal oblique muscles with medial advancement of the block that includes the rectus muscle and its fascia. This release allows for medial advancement of the fascia and closure of up to 20-cm wide defects in the midline area. Since its original description, components separation technique underwent multiple modifications with the ultimate goal to decrease the morbidity associated with the traditional procedure. The extensive subcutaneous lateral dissection had been associated with ischemia of the midline skin edges, wound dehiscence, infection, and seroma. Although the current trend is to proceed with minimally invasive component separation and to reinforce the fascia with mesh, the basic principles of the techniques as described by Ramirez et al in 1990 have not changed over the years. Surgeons who deal with the management of abdominal wall defects are highly encouraged to include this technique in their collection of treatment options.

  18. Velocity field measurements in oblique static divergent vocal fold models

    NASA Astrophysics Data System (ADS)

    Erath, Byron

    2005-11-01

    During normal phonation, the vocal fold cycle is characterized by the glottal opening transitioning from a convergent to a divergent passage and then closing before the cycle is repeated. Under ordinary phonatory conditions, both vocal folds, which form the glottal passage, move in phase with each other, creating a time-varying symmetric opening. However, abnormal pathological conditions, such as unilateral paralysis, and polyps, can result in geometrical asymmetries between the vocal folds throughout the phonatory cycle. This study investigates pulsatile flow fields through 7.5 times life-size vocal fold models with included divergence angles of 5 to 30 degrees, and obliquities between the vocal folds of up to 15 degrees. Flow conditions were scaled to match physiological parameters. Data were taken at the anterior posterior mid-plane using phase-averaged Particle Image Velocimetry (PIV). Viscous flow phenomena including the Coanda effect, flow separation points, and jet "flapping" were investigated. The results are compared to previously reported work of flow through symmetric divergent vocal fold models.

  19. Divergent sexual selection via male competition: ecology is key.

    PubMed

    Lackey, A C R; Boughman, J W

    2013-08-01

    Sexual selection and ecological differences are important drivers of speciation. Much research has focused on female choice, yet the role of male competition in ecological speciation has been understudied. Here, we test how mating habitats impact sexual selection and speciation through male competition. Using limnetic and benthic species of threespine stickleback fish, we find that different mating habitats select differently on male traits through male competition. In mixed habitat with both vegetated and open areas, selection favours two trait combinations of male body size and nuptial colour: large with little colour and small with lots of colour. This matches what we see in reproductively isolated stickleback species, suggesting male competition could promote trait divergence and reproductive isolation. In contrast, when only open habitat exists, selection favours one trait combination, large with lots of colour, which would hinder trait divergence and reproductive isolation. Other behavioural mechanisms in male competition that might promote divergence, such as avoiding aggression with heterospecifics, are insufficient to maintain separate species. This work highlights the importance of mating habitats in male competition for both sexual selection and speciation.

  20. How old is the Hawaiian biota? Geology and phylogeny suggest recent divergence.

    PubMed

    Price, Jonathan P; Clague, David A

    2002-12-07

    This study quantifies long-term landscape changes in the Hawaiian archipelago relating to dispersal, speciation and extinction. Accounting for volcano growth, subsidence and erosion, we modelled the elevations of islands at time intervals of 0.5 Myr for the last 32 Myr; we also assessed the variation in the spacing of volcanoes during this period. The size, spacing and total number of volcanic islands have varied greatly over time, with the current landscape of large, closely spaced islands preceded by a period with smaller, more distantly spaced islands. Considering associated changes in rates of dispersal and speciation, much of the present species pool is probably the result of recent colonization from outside the archipelago and divergence within contemporary islands, with limited dispersal from older islands. This view is in accordance with abundant phylogenetic studies of Hawaiian organisms that estimate the timing of colonization and divergence within the archipelago. Twelve out of 15 multi-species lineages have diverged within the lifetime of the current high islands (last 5 Myr). Three of these, and an additional seven (mostly single-species) lineages, have colonized the archipelago within this period. The timing of colonization of other lineages remains uncertain.

  1. How old is the Hawaiian biota? Geology and phylogeny suggest recent divergence.

    PubMed Central

    Price, Jonathan P; Clague, David A

    2002-01-01

    This study quantifies long-term landscape changes in the Hawaiian archipelago relating to dispersal, speciation and extinction. Accounting for volcano growth, subsidence and erosion, we modelled the elevations of islands at time intervals of 0.5 Myr for the last 32 Myr; we also assessed the variation in the spacing of volcanoes during this period. The size, spacing and total number of volcanic islands have varied greatly over time, with the current landscape of large, closely spaced islands preceded by a period with smaller, more distantly spaced islands. Considering associated changes in rates of dispersal and speciation, much of the present species pool is probably the result of recent colonization from outside the archipelago and divergence within contemporary islands, with limited dispersal from older islands. This view is in accordance with abundant phylogenetic studies of Hawaiian organisms that estimate the timing of colonization and divergence within the archipelago. Twelve out of 15 multi-species lineages have diverged within the lifetime of the current high islands (last 5 Myr). Three of these, and an additional seven (mostly single-species) lineages, have colonized the archipelago within this period. The timing of colonization of other lineages remains uncertain. PMID:12495485

  2. Characterization and comparison of pore landscapes in crystalline porous materials.

    PubMed

    Pinheiro, Marielle; Martin, Richard L; Rycroft, Chris H; Jones, Andrew; Iglesia, Enrique; Haranczyk, Maciej

    2013-07-01

    Crystalline porous materials have many applications, including catalysis and separations. Identifying suitable materials for a given application can be achieved by screening material databases. Such a screening requires automated high-throughput analysis tools that characterize and represent pore landscapes with descriptors, which can be compared using similarity measures in order to select, group and classify materials. Here, we discuss algorithms for the calculation of two types of pore landscape descriptors: pore size distributions and stochastic rays. These descriptors provide histogram representations that encode the geometrical properties of pore landscapes. Their calculation involves the Voronoi decomposition as a technique to map and characterize accessible void space inside porous materials. Moreover, we demonstrate pore landscape comparisons for materials from the International Zeolite Association (IZA) database of zeolite frameworks, and illustrate how the choice of pore descriptor and similarity measure affects the perspective of material similarity exhibiting a particular emphasis and sensitivity to certain aspects of structures. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Landscape genetics and the spatial distribution of chronic wasting disease

    USGS Publications Warehouse

    Blanchong, Julie A.; Samuel, M.D.; Scribner, K.T.; Weckworth, B.V.; Langenberg, J.A.; Filcek, K.B.

    2008-01-01

    Predicting the spread of wildlife disease is critical for identifying populations at risk, targeting surveillance and designing proactive management programmes. We used a landscape genetics approach to identify landscape features that influenced gene flow and the distribution of chronic wasting disease (CWD) in Wisconsin white-tailed deer. CWD prevalence was negatively correlated with genetic differentiation of study area deer from deer in the area of disease origin (core-area). Genetic differentiation was greatest, and CWD prevalence lowest, in areas separated from the core-area by the Wisconsin River, indicating that this river reduced deer gene flow and probably disease spread. Features of the landscape that influence host dispersal and spatial patterns of disease can be identified based on host spatial genetic structure. Landscape genetics may be used to predict high-risk populations based on their genetic connection to infected populations and to target disease surveillance, control and preventative activities. ?? 2007 The Royal Society.

  4. Exploring the conformational energy landscape of proteins

    SciTech Connect

    Nienhaus, G.U. |; Mueller, J.D.; McMahon, B.H.

    1997-04-01

    Proteins possess a complex energy landscape with a large number of local minima called conformational substates that are arranged in a hierarchical fashion. Here we discuss experiments aimed at the elucidation of the energy landscape in carbonmonoxy myoglobin (MbCO). In the highest tier of the hierarchy, a few taxonomic substates exist. Because of their small number, these substates are accessible to detailed structural investigations. Spectroscopic experiments are discussed that elucidate the role of protonations of amino acid side chains in creating the substates. The lower tiers of the hierarchy contain a large number of statistical substates. Substate interconversions are observed in the entire temperature range from below 1 K up to the denaturation temperature, indicating a wide spectrum of energy barriers that separate the substates.

  5. The estimation of genetic divergence

    NASA Technical Reports Server (NTRS)

    Holmquist, R.; Conroy, T.

    1981-01-01

    Consideration is given to the criticism of Nei and Tateno (1978) of the REH (random evolutionary hits) theory of genetic divergence in nucleic acids and proteins, and to their proposed alternative estimator of total fixed mutations designated X2. It is argued that the assumption of nonuniform amino acid or nucleotide substitution will necessarily increase REH estimates relative to those made for a model where each locus has an equal likelihood of fixing mutations, thus the resulting value will not be an overestimation. The relative values of X2 and measures calculated on the basis of the PAM and REH theories for the number of nucleotide substitutions necessary to explain a given number of observed amino acid differences between two homologous proteins are compared, and the smaller values of X2 are attributed to (1) a mathematical model based on the incorrect assumption that an entire structural gene is free to fix mutations and (2) the assumptions of different numbers of variable codons for the X2 and REH calculations. Results of a repeat of the computer simulations of Nei and Tateno are presented which, in contrast to the original results, confirm the REH theory. It is pointed out that while a negative correlation is observed between estimations of the fixation intensity per varion and the number of varions for a given pair of sequences, the correlation between the two fixation intensities and varion numbers of two different pairs of sequences need not be negative. Finally, REH theory is used to resolve a paradox concerning the high rate of covarion turnover and the nature of general function sites as permanent covarions.

  6. The estimation of genetic divergence

    NASA Technical Reports Server (NTRS)

    Holmquist, R.; Conroy, T.

    1981-01-01

    Consideration is given to the criticism of Nei and Tateno (1978) of the REH (random evolutionary hits) theory of genetic divergence in nucleic acids and proteins, and to their proposed alternative estimator of total fixed mutations designated X2. It is argued that the assumption of nonuniform amino acid or nucleotide substitution will necessarily increase REH estimates relative to those made for a model where each locus has an equal likelihood of fixing mutations, thus the resulting value will not be an overestimation. The relative values of X2 and measures calculated on the basis of the PAM and REH theories for the number of nucleotide substitutions necessary to explain a given number of observed amino acid differences between two homologous proteins are compared, and the smaller values of X2 are attributed to (1) a mathematical model based on the incorrect assumption that an entire structural gene is free to fix mutations and (2) the assumptions of different numbers of variable codons for the X2 and REH calculations. Results of a repeat of the computer simulations of Nei and Tateno are presented which, in contrast to the original results, confirm the REH theory. It is pointed out that while a negative correlation is observed between estimations of the fixation intensity per varion and the number of varions for a given pair of sequences, the correlation between the two fixation intensities and varion numbers of two different pairs of sequences need not be negative. Finally, REH theory is used to resolve a paradox concerning the high rate of covarion turnover and the nature of general function sites as permanent covarions.

  7. Niche Divergence versus Neutral Processes: Combined Environmental and Genetic Analyses Identify Contrasting Patterns of Differentiation in Recently Diverged Pine Species

    PubMed Central

    Moreno-Letelier, Alejandra; Ortíz-Medrano, Alejandra; Piñero, Daniel

    2013-01-01

    Background and Aims Solving relationships of recently diverged taxa, poses a challenge due to shared polymorphism and weak reproductive barriers. Multiple lines of evidence are needed to identify independently evolving lineages. This is especially true of long-lived species with large effective population sizes, and slow rates of lineage sorting. North American pines are an interesting group to test this multiple approach. Our aim is to combine cytoplasmic genetic markers with environmental information to clarify species boundaries and relationships of the species complex of Pinus flexilis, Pinus ayacahuite, and Pinus strobiformis. Methods Mitochondrial and chloroplast sequences were combined with previously obtained microsatellite data and contrasted with environmental information to reconstruct phylogenetic relationships of the species complex. Ecological niche models were compared to test if ecological divergence is significant among species. Key Results and Conclusion Separately, both genetic and ecological evidence support a clear differentiation of all three species but with different topology, but also reveal an ancestral contact zone between P. strobiformis and P. ayacahuite. The marked ecological differentiation of P. flexilis suggests that ecological speciation has occurred in this lineage, but this is not reflected in neutral markers. The inclusion of environmental traits in phylogenetic reconstruction improved the resolution of internal branches. We suggest that combining environmental and genetic information would be useful for species delimitation and phylogenetic studies in other recently diverged species complexes. PMID:24205167

  8. [Phylogeny and divergence time estimation of Schizothoracinae fishes in Xinjiang].

    PubMed

    Ayelhan, Haysa; Guo, Yan; Meng, Wei; Yang, Tianyan; Ma, Yanwu

    2014-10-01

    Based on combined data of mitochondrial COI, ND4 and 16S RNA genes, molecular phylogeny of 4 genera, 10 species or subspecies of Schizothoracinae fishes distributed in Xinjiang were analyzed. The molecular clock was calibrated by divergence time of Cyprininae and geological segregation event between the upper Yellow River and Qinghai Lake. Divergence time of Schizothoracinae fishes was calculated, and its relationship with the major geological events and the climate changes in surrounding areas of Tarim Basin was discussed. The results showed that genus Aspiorhynchus did not form an independent clade, but clustered with Schizothorax biddulphi and S. irregularis. Kimura 2-parameter model was used to calculate the genetic distance of COI gene, the genetic distance between genus Aspiorhynchus and Schizothorax did not reach genus level, and Aspiorhynchus laticeps might be a specialized species of genus Schizothorax. Cluster analysis showed a different result with morphological classification method, and it did not support the subgenus division of Schizothorax fishes. Divergence of two groups of primitive Schizothoracinae (8.18Ma) and divergence of Gymnodiptychus dybowskii and Diptychus maculates (7.67Ma) occurred in late Miocene, which might be related with the separation of Kunlun Mountain and north Tianshan Mountain River system that was caused by the uplift of Qinghai-Tibet Plateau and Tianshan Mountain, and the aridification of Tarim Basin. The terrain of Tarim Basin that was affected by Quaternary Himalayan movement was high in west but low in east, as a result, Lop Nor became the center of surrounding mountain rivers in Tarim Basin, which shaped the distribution pattern of genus Schizothorax.

  9. Verbal and visual divergent thinking in aging.

    PubMed

    Palmiero, Massimiliano; Nori, Raffaella; Piccardi, Laura

    2017-04-01

    According to the peak and decline model divergent thinking declines at a specific age (in or after middle age). However, if divergent thinking declines steadily in aging still has to be clarified. In order to explore the age-related changes in verbal and visual divergent thinking, in the present study a sample of 159 participants was divided in five age groups: young adults (18-35 years), middle-aged adults (36-55), young old (56-74), old (75-85) and the oldest-old (86-98). Two divergent thinking tasks were administered: the alternative uses for cardboard boxes, aimed at assessing verbal ideational fluency, flexibility and originality; the completion drawing task, aimed at assessing visual ideational fluency, flexibility and originality. Results showed that after peaking in the young adult group (20-35 years) all components of verbal and visual divergent thinking stabilized in the middle-aged adult group (36-55 years) and then started declining in the young old group (56-75). Interestingly, all components were found to be preserved after declining. Yet, verbal and visual divergent thinking were found at the same extent across age groups, with the exception of visual ideational fluency, that was higher in the young old group, the old group and the oldest-old group than verbal ideational fluency. These results support the idea that divergent thinking does not decline steadily in the elderly. Given that older people can preserve to some extent verbal and visual divergent thinking, these findings have important implications for active aging, that is, divergent thinking might be fostered in aging in order to prevent the cognitive decline.

  10. Gas separating

    DOEpatents

    Gollan, A.Z.

    1990-12-25

    Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing. 3 figs.

  11. Gas separating

    DOEpatents

    Gollan, A.

    1988-03-29

    Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing. 3 figs.

  12. Cognitive attributes and aesthetic preferences in assessment and differentiation of landscapes.

    PubMed

    Sevenant, Marjanne; Antrop, Marc

    2009-07-01

    The increasing pace and scale of landscape changes involve objective measurements in order to estimate the effects of changes on people's landscape preferences in a meaningful way. In the literature, some attempts have been made to provide a more conceptual base related to landscape preferences. These concepts and their indicators need to be tested empirically in different contexts and landscape types. In the present study, different items related to theoretical concepts of both aesthetic preference and cognitive rating were examined. They were combined in an in situ questionnaire, which was conducted among undergraduate students in geography during two different field excursions. Stimuli consisted of 11 landscape vistas selected during the excursions. All vistas represent rather rural landscapes but they vary with regard to relief, degree of urbanisation, and degree of agricultural land use. Statistical analysis of all data yielded significant correlations between aesthetic and cognitive ratings. However, these correlations did not appear to be very strong. When considering landscape vistas separately, the relations between all cognitive ratings seemed to vary. Further, not all cognitive aspects had an equal predicting value for aesthetic preference. Moreover, this predicting value appeared to vary between different landscape vistas. The groups of interrelated cognitive aspects could not be associated consistently with theoretical concepts. The results demonstrated the inconsistencies existing between the contents of the theoretical concepts and the indicators found within the landscape. The findings argued for the necessity to distinguish between different ratings and landscape types instead of using unitary preference measures and generalized data when studying landscape preference.

  13. Marine landscapes and population genetic structure of herring (Clupea harengus L.) in the Baltic Sea.

    PubMed

    Jørgensen, Hanne B H; Hansen, Michael M; Bekkevold, Dorte; Ruzzante, Daniel E; Loeschcke, Volker

    2005-09-01

    Numerically small but statistically significant genetic differentiation has been found in many marine fish species despite very large census population sizes and absence of obvious barriers to migrating individuals. Analyses of morphological traits have previously identified local spawning groups of herring (Clupea harengus L.) in the environmentally heterogeneous Baltic Sea, whereas allozyme markers have not revealed differentiation. We analysed variation at nine microsatellite loci in 24 samples of spring-spawning herring collected at 11 spawning locations throughout the Baltic Sea. Significant temporal differentiation was observed at two locations, which we ascribe to sympatrically spawning but genetically divergent 'spawning waves'. Significant differentiation was also present on a geographical scale, though pairwise F(ST) values were generally low, not exceeding 0.027. Partial Mantel tests showed no isolation by geographical distance, but significant associations were observed between genetic differentiation and environmental parameters (salinity and surface temperature) (0.001 < P < or = 0.099), though these outcomes were driven mainly by populations in the southwestern Baltic Sea, which also exhibits the steepest environmental gradients. Application of a novel method for detecting barriers to gene flow by combining geographical coordinates and genetic differentiation allowed us to identify two zones of lowered gene flow. These zones were concordant with the separation of the Baltic Sea into major basins, with environmental gradients and with differences in migration behaviour. We suggest that similar use of landscape genetics approaches may increase the understanding of the biological significance of genetic differentiation in other marine fishes.

  14. Wildfire and landscape change

    USGS Publications Warehouse

    Santi, P.; Cannon, S.; DeGraff, J.

    2013-01-01

    Wildfire is a worldwide phenomenon that is expected to increase in extent and severity in the future, due to fuel accumulations, shifting land management practices, and climate change. It immediately affects the landscape by removing vegetation, depositing ash, influencing water-repellent soil formation, and physically weathering boulders and bedrock. These changes typically lead to increased erosion through sheetwash, rilling, dry ravel, and increased mass movement in the form of floods, debris flow, rockfall, and landslides. These process changes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Furthermore, development of alluvial fans, debris fans, and talus cones are enhanced. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years.

  15. Simulations of Fluvial Landscapes

    NASA Astrophysics Data System (ADS)

    Cattan, D.; Birnir, B.

    2013-12-01

    The Smith-Bretherton-Birnir (SBB) model for fluvial landsurfaces consists of a pair of partial differential equations, one governing water flow and one governing the sediment flow. Numerical solutions of these equations have been shown to provide realistic models in the evolution of fluvial landscapes. Further analysis of these equations shows that they possess scaling laws (Hack's Law) that are known to exist in nature. However, the simulations are highly dependent on the numerical methods used; with implicit methods exhibiting the correct scaling laws, but the explicit methods fail to do so. These equations, and the resulting models, help to bridge the gap between the deterministic and the stochastic theories of landscape evolution. Slight modifications of the SBB equations make the results of the model more realistic. By modifying the sediment flow equation, the model obtains more pronounced meandering rivers. Typical landsurface with rivers.

  16. Driving the Landscape

    NASA Astrophysics Data System (ADS)

    Haff, P. K.

    2012-12-01

    Technological modification of the earth's surface (e.g., agriculture, urbanization) is an old story in human history, but what about the future? The future of landscape in an accelerating technological world, beyond a relatively short time horizon, lies hidden behind an impenetrable veil of complexity. Sufficiently complex dynamics generates not only the trajectory of a variable of interest (e.g., vegetation cover) but also the environment in which that variable evolves (e.g., background climate). There is no way to anticipate what variables will define that environment—the dynamics creates its own variables. We are always open to surprise by a change of conditions we thought or assumed were fixed or by the appearance of new phenomena of whose possible existence we had been unaware or thought unlikely. This is especially true under the influence of technology, where novelty is the rule. Lack of direct long-term predictability of landscape change does not, however, mean we cannot say anything about its future. The presence of persistence (finite time scales) in a system means that prediction by a calibrated numerical model should be good for a limited period of time barring bad luck or faulty implementation. Short-term prediction, despite its limitations, provides an option for dealing with the longer-term future. If a computer-controlled car tries to drive itself from New York to Los Angeles, no conceivable (or possible) stand-alone software can be constructed to predict a priori the space-time trajectory of the vehicle. Yet the drive is normally completed easily by most drivers. The trip is successfully completed because each in a series of very short (linear) steps can be "corrected" on the fly by the driver, who takes her cues from the environment to keep the car on the road and headed toward its destination. This metaphor differs in a fundamental way from the usual notion of predicting geomorphic change, because it involves a goal—to reach a desired

  17. Dynamic landscape management.

    Treesearch

    Valerie. Rapp

    2003-01-01

    Pacific Northwest forests and all their species evolved with fires, floods, windstorms, landslides, and other disturbances. The dynamics of disturbance were basic to how forests changed and renewed. Disturbance regimes, as scientists call the long-term patterns of these events—what kind of event, how often, how large, and how severe—created the landscape patterns seen...

  18. Astrobiological Landscape and Neocatastrophism

    NASA Astrophysics Data System (ADS)

    Cirkovic, M. M.; Vukotic, B.

    2009-09-01

    We review results of the simple 1-D models of the Galactic Habitable Zone constructed within neocatastrophic paradigm. The emerging astrobiological landscape demonstrates the capability of this theoretical framework to resolve the classical puzzles of Fermi's paradox and Carter's anthropic argument against extraterrestrial intelligence. Preliminary results show that astrobiology offers a clear rationale for the "Copernican" assumption of typicality of the age of the terrestrial biosphere.

  19. Dynamic landscape management

    Treesearch

    Valerie . Rapp

    2002-01-01

    Pacific Northwest forests and all their species evolved with fires, floods, windstorms, landslides, and other disturbances. The dynamics of disturbance were basic to how forests changed and renewed. Disturbance regimes, as scientists call the long-term patterns of these events—what kind of event, how often, how large, and how severe—created the landscape patterns seen...

  20. Appendix E: Research papers. Use of remote sensing in landscape stratification for environmental impact assessment

    NASA Technical Reports Server (NTRS)

    Stanturf, J. A.; Heimbuch, D. G.

    1980-01-01

    A refinement to the matrix approach to environmental impact assessment is to use landscape units in place of separate environmental elements in the analysis. Landscape units can be delineated by integrating remotely sensed data and available single-factor data. A remote sensing approach to landscape stratification is described and the conditions under which it is superior to other approaches that require single-factor maps are indicated. Flowcharts show the steps necessary to develop classification criteria, delineate units and a map legend, and use the landscape units in impact assessment. Application of the approach to assessing impacts of a transmission line in Montana is presented to illustrate the method.

  1. Appendix E: Research papers. Use of remote sensing in landscape stratification for environmental impact assessment

    NASA Technical Reports Server (NTRS)

    Stanturf, J. A.; Heimbuch, D. G.

    1980-01-01

    A refinement to the matrix approach to environmental impact assessment is to use landscape units in place of separate environmental elements in the analysis. Landscape units can be delineated by integrating remotely sensed data and available single-factor data. A remote sensing approach to landscape stratification is described and the conditions under which it is superior to other approaches that require single-factor maps are indicated. Flowcharts show the steps necessary to develop classification criteria, delineate units and a map legend, and use the landscape units in impact assessment. Application of the approach to assessing impacts of a transmission line in Montana is presented to illustrate the method.

  2. Convergence and Divergence in Political Orientations between Blacks and Whites: 1960-1973

    ERIC Educational Resources Information Center

    Schwartz, Sandra Kenyon; Schwartz, David C.

    1976-01-01

    To determine whether or not blacks and whites are increasingly divergent in their political orientations, public opinion data from 13 separate national surveys conducted in 1961, 1963, 1965, 1966, 1967, 1969, 1970, 1971 (4 studies) and 1972 (2 studies) by the Opinion Research Corporation (ORC) of Princeton, New Jersey, were examined. (Author/JM)

  3. Swirling flow states in diverging or contracting pipes

    NASA Astrophysics Data System (ADS)

    Rusak, Zvi; Zhang, Yuxin; Li, Harry; Wang, Shixiao

    2015-11-01

    We study the dynamics of inviscid and incompressible swirling flows in diverging or contracting long circular pipes. The inlet flow is described by the circumferential and axial velocity profiles together with a fixed azimuthal vorticity while the outlet flow is characterized by a zero radial velocity state. We first solve the Squire-Long PDE for steady-state flows in a pipe and determine the bifurcation diagram of the various possible flow states as a function of pipe geometry. These include states with a decelerated axial velocity along the pipe center line, an accelerated axial velocity along the pipe center line, vortex breakdown states with a stagnation zone around the pipe center line, and wall-separation states. Then, we establish a correlation between the outlet state of these solutions and solutions of the columnar (x-independent) Squire-Long ODE. Numerical simulations based on the unsteady stream function-circulation equations shed light on the stability of the various steady states and their domain of attraction in terms of initial conditions. The results show that pipe divergence promotes the appearance of vortex breakdown states while pipe contraction induces the formation of wall-separation states.

  4. Distance-dependent patterns of molecular divergences in tuatara mitogenomes

    PubMed Central

    Subramanian, Sankar; Mohandesan, Elmira; Millar, Craig D.; Lambert, David M.

    2015-01-01

    Population genetic models predict that populations that are geographically close to each other are expected to be genetically more similar to each other compared to those that are widely separate. However the patterns of relationships between geographic distance and molecular divergences at neutral and constrained regions of the genome are unclear. We attempted to clarify this relationship by sequencing complete mitochondrial genomes of the relic species Tuatara (Sphenodon punctatus) from ten offshore islands of New Zealand. We observed a positive relationship that showed a proportional increase in the neutral diversity at synonymous sites (dS), with increasing geographical distance. In contrast we showed that diversity at evolutionarily constrained sites (dC) was elevated in the case of comparisons involving closely located populations. Conversely diversity was reduced in the case of comparisons between distantly located populations. These patterns were confirmed by a significant negative relationship between the ratio of dC/dS and geographic distance. The observed high dC/dS could be explained by the abundance of deleterious mutations in comparisons involving closely located populations, due to the recent population divergence times. Since distantly related populations were separated over long periods of time, deleterious mutations might have been removed by purifying selection. PMID:25731894

  5. Spontaneous divergent elbow dislocation after Sauve-Kapandji procedure.

    PubMed

    Moritomo, Hisao; Izawa, Kazutaka; Murase, Tsuyoshi; Hashimoto, Hideo; Goto, Akira; Masatomi, Takashi

    2003-01-01

    This is a report on an unusual complication of the Sauve-Kapandji procedure in patients with rheumatoid arthritis. Two women with rheumatoid arthritis who previously had an ipsilateral Sauve-Kapandji procedure experienced spontaneous transverse divergent elbow dislocations without evident trauma. Their radiographs showed medial dislocation of the proximal ulna, which was separated from the radial head. The radial head and distal end of the ulnar shaft showed remarkable instability by a pronation and supination motion without the radial and ulnar shafts being separated from each other. Stress radiographic examination showed significant loosening of all ligaments except the medial collateral ligament around the elbow and did not show disruption of the interosseous membrane. A unique chronic twist radioulnar dissociation which consists of gross instability of the radial head and the distal ulna without disruption of the interosseous membrane was considered to cause instability of the humeroulnar joint, which results in medial dislocation of the proximal ulna. This report suggests that there is a direct cause and effect relationship between the residual distal ulnar instability and the development of transverse divergent dislocation of the elbow in patients with rheumatoid arthritis after the Sauve-Kapandji procedure.

  6. Adaptive chromosomal divergence driven by mixed geographic mode of evolution.

    PubMed

    Feder, Jeffrey L; Gejji, Richard; Powell, Thomas H Q; Nosil, Patrik

    2011-08-01

    Chromosomal inversions are ubiquitous in nature and of great significance for understanding adaptation and speciation. Inversions were the first markers used to investigate the genetic structure of natural populations, leading to the concept of coadapted gene complexes and theories concerning founder effects and genetic drift in small populations. However, we still lack elements of a general theory accounting for the origins and distribution of inversions in nature. Here, we use computer simulations to show that a "mixed geographic mode" of evolution involving allopatric separation of populations followed by secondary contact and gene flow generates chromosomal divergence by natural selection under wider conditions than previous hypotheses. This occurs because inversions arising in allopatry contain a full complement of locally adapted genes. Once gene flow ensues, reduced recombination within inversions keeps these favorable genotypic combinations intact, resulting in inverted genomic regions being favored over collinear regions. This process allows inversions to establish to high frequencies. Our model can account for several classic patterns in the geographic distribution of inversions and highlights how selection on standing genetic variation allows rapid chromosomal evolution without the waiting time for new mutations. As inversion differences often separate closely related taxa, mixed modes of divergence could be common. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

  7. Divergent cellular pathways of hippocampal memory consolidation and reconsolidation

    PubMed Central

    Lee, Jonathan L. C.; Hynds, Robert E.

    2013-01-01

    The reconsolidation of memories after their retrieval involves cellular mechanisms that recapitulate much of the initial consolidation process. However, we have previously demonstrated that there are independent cellular mechanisms of consolidation and reconsolidation in the dorsal hippocampus for contextual fear memories. Expression of BDNF was required for consolidation, while Zif268 expression was necessary for reconsolidation. Given the dichotomy between the obvious mechanistic similarity and notable dissociations between consolidation and reconsolidation, we sought to determine whether the separation at the level of gene expression reflected either parallel and independent upstream signalling pathways, or common upstream mechanisms that diverge by the level of transcriptional activation. Here we show that while consolidation and reconsolidation are commonly dependent upon NMDA receptor activation in the dorsal hippocampus there is a double dissociation between the effects of the MEK inhibitor U0126 and the IKK inhibitor sulfasalazine. Moreover, rescue experiments and western blot analyses show that there are functional NMDA receptor–ERK1–BDNF and NMDA receptor–IKKα–Zif268 pathways for consolidation and reconsolidation, respectively. Therefore, there are divergent pathways of hippocampal memory consolidation and reconsolidation, involving commonality at the cell surface, but separable downstream kinase cascades and transcriptional regulation. PMID:23197404

  8. Particle separator

    DOEpatents

    Hendricks, Charles D.

    1990-01-01

    Method and apparatus (10) are provided for separating and classifying particles (48,50,56) by dispersing the particles within a fluid (52) that is upwardly flowing within a cone-shaped pipe (12) that has its large end (20) above its small end (18). Particles of similar size and shape (48,50) migrate to individual levels (A,B) within the flowing fluid. As the fluid is deflected by a plate (42) at the top end of the pipe (12), the smallest particles are collected on a shelf-like flange (40). Ever larger particles are collected as the flow rate of the fluid is increased. To prevent particle sticking on the walls (14) of the pipe (12), additional fluid is caused to flow into the pipe (12) through holes (68) that are specifically provided for that purpose. Sticking is further prevented by high frequency vibrators (70) that are positioned on the apparatus (10).

  9. Particle separation

    DOEpatents

    Moosmuller, Hans [Reno, NV; Chakrabarty, Rajan K [Reno, NV; Arnott, W Patrick [Reno, NV

    2011-04-26

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  10. Particle separation

    NASA Technical Reports Server (NTRS)

    Moosmuller, Hans (Inventor); Chakrabarty, Rajan K. (Inventor); Arnott, W. Patrick (Inventor)

    2011-01-01

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  11. Fitness and structure landscapes for pre-miRNA processing

    NASA Astrophysics Data System (ADS)

    Bundschuh, Ralf; de Meaux, Juliette; Lassig, Michael

    2011-03-01

    The processing from pre-miRNA to mature miRNA in plants involves a mechanism, which depends on an extended stem in the secondary structure of the pre-miRNA. Here, we show how natural selection acts on this secondary structure to produce evolutionary conservation of the processing mechanism together with modularity of the pre-miRNA molecules, making this molecular function independent of others. Our main results are: 1. Selection on miRNA processing can be described by a fitness landscape which depends directly on the secondary structure of the pre-miRNA. 2. This fitness landscape predicts the divergence of the phenotype between orthologous pre-miRNA molecules from different species. 3. Actual pre-miRNA structures are modular: their phenotype is significantly less affected by deleterious mutations in the remainder of the molecule than for random RNA molecules.

  12. Topological microstructure analysis using persistence landscapes

    NASA Astrophysics Data System (ADS)

    Dłotko, Paweł; Wanner, Thomas

    2016-11-01

    Phase separation mechanisms can produce a variety of complicated and intricate microstructures, which often can be difficult to characterize in a quantitative way. In recent years, a number of novel topological metrics for microstructures have been proposed, which measure essential connectivity information and are based on techniques from algebraic topology. Such metrics are inherently computable using computational homology, provided the microstructures are discretized using a thresholding process. However, while in many cases the thresholding is straightforward, noise and measurement errors can lead to misleading metric values. In such situations, persistence landscapes have been proposed as a natural topology metric. Common to all of these approaches is the enormous data reduction, which passes from complicated patterns to discrete information. It is therefore natural to wonder what type of information is actually retained by the topology. In the present paper, we demonstrate that averaged persistence landscapes can be used to recover central system information in the Cahn-Hilliard theory of phase separation. More precisely, we show that topological information of evolving microstructures alone suffices to accurately detect both concentration information and the actual decomposition stage of a data snapshot. Considering that persistent homology only measures discrete connectivity information, regardless of the size of the topological features, these results indicate that the system parameters in a phase separation process affect the topology considerably more than anticipated. We believe that the methods discussed in this paper could provide a valuable tool for relating experimental data to model simulations.

  13. Local fitness landscape of the green fluorescent protein

    PubMed Central

    Sarkisyan, Karen S.; Bolotin, Dmitry A.; Meer, Margarita V.; Usmanova, Dinara R.; Mishin, Alexander S.; Sharonov, George V.; Ivankov, Dmitry N.; Bozhanova, Nina G.; Baranov, Mikhail S.; Soylemez, Onuralp; Bogatyreva, Natalya S.; Vlasov, Peter K.; Egorov, Evgeny S.; Logacheva, Maria D.; Kondrashov, Alexey S.; Chudakov, Dmitry M.; Putintseva, Ekaterina V.; Mamedov, Ilgar Z.; Tawfik, Dan S.; Lukyanov, Konstantin A.; Kondrashov, Fyodor A.

    2016-01-01

    Fitness landscapes1,2, depictions of how genotypes manifest at the phenotypic level, form the basis for our understanding of many areas of biology2–7 yet their properties remain elusive. Studies addressing this issue often consider specific genes and their function as proxy for fitness2,4, experimentally assessing the impact on function of single mutations and their combinations in a specific sequence2,5,8–15 or in different sequences2,3,5,16–18. However, systematic high-throughput studies of the local fitness landscape of an entire protein have not yet been reported. Here, we chart an extensive region of the local fitness landscape of the green fluorescent protein from Aequorea victoria (avGFP) by measuring the native function, fluorescence, of tens of thousands of derivative genotypes of avGFP. We find that its fitness landscape is narrow, with half of genotypes with two mutations showing reduced fluorescence and half of genotypes with five mutations being completely non-fluorescent. The narrowness is enhanced by epistasis, which was detected in up to 30% of genotypes with multiple mutations arising mostly through the cumulative impact of slightly deleterious mutations causing a threshold-like decrease of protein stability and concomitant loss of fluorescence. A model of orthologous sequence divergence spanning hundreds of millions of years predicted the extent of epistasis in our data, indicating congruence between the fitness landscape properties at the local and global scales. The characterization of the local fitness landscape of avGFP has important implications for a number of fields including molecular evolution, population genetics and protein design. PMID:27193686

  14. Local fitness landscape of the green fluorescent protein.

    PubMed

    Sarkisyan, Karen S; Bolotin, Dmitry A; Meer, Margarita V; Usmanova, Dinara R; Mishin, Alexander S; Sharonov, George V; Ivankov, Dmitry N; Bozhanova, Nina G; Baranov, Mikhail S; Soylemez, Onuralp; Bogatyreva, Natalya S; Vlasov, Peter K; Egorov, Evgeny S; Logacheva, Maria D; Kondrashov, Alexey S; Chudakov, Dmitry M; Putintseva, Ekaterina V; Mamedov, Ilgar Z; Tawfik, Dan S; Lukyanov, Konstantin A; Kondrashov, Fyodor A

    2016-05-19

    Fitness landscapes depict how genotypes manifest at the phenotypic level and form the basis of our understanding of many areas of biology, yet their properties remain elusive. Previous studies have analysed specific genes, often using their function as a proxy for fitness, experimentally assessing the effect on function of single mutations and their combinations in a specific sequence or in different sequences. However, systematic high-throughput studies of the local fitness landscape of an entire protein have not yet been reported. Here we visualize an extensive region of the local fitness landscape of the green fluorescent protein from Aequorea victoria (avGFP) by measuring the native function (fluorescence) of tens of thousands of derivative genotypes of avGFP. We show that the fitness landscape of avGFP is narrow, with 3/4 of the derivatives with a single mutation showing reduced fluorescence and half of the derivatives with four mutations being completely non-fluorescent. The narrowness is enhanced by epistasis, which was detected in up to 30% of genotypes with multiple mutations and mostly occurred through the cumulative effect of slightly deleterious mutations causing a threshold-like decrease in protein stability and a concomitant loss of fluorescence. A model of orthologous sequence divergence spanning hundreds of millions of years predicted the extent of epistasis in our data, indicating congruence between the fitness landscape properties at the local and global scales. The characterization of the local fitness landscape of avGFP has important implications for several fields including molecular evolution, population genetics and protein design.

  15. Inflation, dark matter, and dark energy in the string landscape.

    PubMed

    Liddle, Andrew R; Ureña-López, L Arturo

    2006-10-20

    We consider the conditions needed to unify the description of dark matter, dark energy, and inflation in the context of the string landscape. We find that incomplete decay of the inflaton field gives the possibility that a single field is responsible for all three phenomena. By contrast, unifying dark matter and dark energy into a single field, separate from the inflaton, appears rather difficult.

  16. Classical Chinese Landscape Painting and the Aesthetic Appreciation of Nature

    ERIC Educational Resources Information Center

    Turner, Matthew

    2009-01-01

    Recent theories of the aesthetic appreciation of nature or natural environments have done much to clarify what might be essential to such appreciation. Such accounts are incomplete, however, as they depend on a strict separation between works of art and nature itself. This paper shows how classical Chinese landscape painting offers a way to…

  17. Genetic Divergence in Mandible Form in Relation to Molecular Divergence in Inbred Mouse Strains

    PubMed Central

    Atchley, W. R.; Newman, S.; Cowley, D. E.

    1988-01-01

    Genetic divergence in the form of the mandible is examined in ten inbred strains of mice. Several univariate and multivariate genetic distance estimates are given for the morphological data and these estimates are compared to measures of genealogical and molecular divergence. Highly significant divergence occurs among the ten strains in all 11 mandible traits considered individually and simultaneously. Genealogical relationship among strains is highly correlated with genetic divergence in single locus molecular traits. However, the concordance between genealogical relationship and multivariate genetic divergence in morphology is much more complex. Whether there is a significant correlation between morphological divergence and genealogy depends upon the method of analysis and the particular genetic distance statistic being employed. PMID:3220250

  18. Internal Performance of Several Divergent-Shroud Ejector Nozzles with High Divergence Angles

    NASA Technical Reports Server (NTRS)

    Trout, Arthur M.; Papell, S. Stephen; Povolny, John H.

    1957-01-01

    Nine divergent-shroud ejector configurations were investigated to determine the effect of shroud divergence angle on ejector internal performance. Unheated dry air was used for both the primary and secondary flows. The decrease in the design-point thrust coefficient with increasing flow divergence angle (angle measured from primary exit to shroud exit) followed very closely a simple relation involving the cosine of the angle. This indicates that design-point thrust performance for divergent-shroud ejectors can be predicted with reasonable accuracy within the range investigated. The decrease in design-point thrust coefficient due to increasing the flow divergence engle from 120deg to 30deg (half-singles) was approximately 6 percent. Ejector air-handling characteristics and the primary-nozzle flow coefficient were not significantly affected by change in shroud divergence angle.

  19. Reproductive isolation related to mimetic divergence in the poison frog Ranitomeya imitator.

    PubMed

    Twomey, Evan; Vestergaard, Jacob S; Summers, Kyle

    2014-08-27

    In a mimetic radiation--when a single species evolves to resemble different model species--mimicry can drive within-species morphological diversification, and, potentially, speciation. While mimetic radiations have occurred in a variety of taxa, their role in speciation remains poorly understood. We study the Peruvian poison frog Ranitomeya imitator, a species that has undergone a mimetic radiation into four distinct morphs. Using a combination of colour-pattern analysis, landscape genetics and mate-choice experiments, we show that a mimetic shift in R. imitator is associated with a narrow phenotypic transition zone, neutral genetic divergence and assortative mating, suggesting that divergent selection to resemble different model species has led to a breakdown in gene flow between these two populations. These results extend the effects of mimicry on speciation into a vertebrate system and characterize an early stage of speciation where reproductive isolation between mimetic morphs is incomplete but evident.

  20. Incorporating Bioenergy in Sustainable Landscape Designs Workshop Two: Agricultural Landscapes

    SciTech Connect

    Negri, M. Cristina; Ssegane, H.

    2015-08-01

    The Bioenergy Technologies Office hosted two workshops on Incorporating Bioenergy in Sustainable Landscape Designs with Oak Ridge and Argonne National Laboratories in 2014. The second workshop focused on agricultural landscapes and took place in Argonne, IL from June 24—26, 2014. The workshop brought together experts to discuss how landscape design can contribute to the deployment and assessment of sustainable bioenergy. This report summarizes the discussions that occurred at this particular workshop.

  1. Environmental versus anthropogenic effects on population adaptive divergence in the freshwater snail Lymnaea stagnalis.

    PubMed

    Bouétard, Anthony; Côte, Jessica; Besnard, Anne-Laure; Collinet, Marc; Coutellec, Marie-Agnès

    2014-01-01

    Repeated pesticide contaminations of lentic freshwater systems located within agricultural landscapes may affect population evolution in non-target organisms, especially in species with a fully aquatic life cycle and low dispersal ability. The issue of evolutionary impact of pollutants is therefore conceptually important for ecotoxicologists. The impact of historical exposure to pesticides on genetic divergence was investigated in the freshwater gastropod Lymnaea stagnalis, using a set of 14 populations from contrasted environments in terms of pesticide and other anthropogenic pressures. The hypothesis of population adaptive divergence was tested on 11 life-history traits, using Q(ST)-F(ST) comparisons. Despite strong neutral differentiation (mean F(ST) = 0.291), five adult traits or parameters were found to be under divergent selection. Conversely, two early expressed traits showed a pattern consistent with uniform selection or trait canalization, and four adult traits appeared to evolve neutrally. Divergent selection patterns were mostly consistent with a habitat effect, opposing pond to ditch and channel populations. Comparatively, pesticide and other human pressures had little correspondence with evolutionary patterns, despite hatching rate impairment associated with global anthropogenic pressure. Globally, analyses revealed high genetic variation both at neutral markers and fitness-related traits in a species used as model in ecotoxicology, providing empirical support for the need to account for genetic and evolutionary components of population response in ecological risk assessment.

  2. Adaptation to Low Salinity Promotes Genomic Divergence in Atlantic Cod (Gadus morhua L.).

    PubMed

    Berg, Paul R; Jentoft, Sissel; Star, Bastiaan; Ring, Kristoffer H; Knutsen, Halvor; Lien, Sigbjørn; Jakobsen, Kjetill S; André, Carl

    2015-05-20

    How genomic selection enables species to adapt to divergent environments is a fundamental question in ecology and evolution. We investigated the genomic signatures of local adaptation in Atlantic cod (Gadus morhua L.) along a natural salinity gradient, ranging from 35‰ in the North Sea to 7‰ within the Baltic Sea. By utilizing a 12 K SNPchip, we simultaneously assessed neutral and adaptive genetic divergence across the Atlantic cod genome. Combining outlier analyses with a landscape genomic approach, we identified a set of directionally selected loci that are strongly correlated with habitat differences in salinity, oxygen, and temperature. Our results show that discrete regions within the Atlantic cod genome are subject to directional selection and associated with adaptation to the local environmental conditions in the Baltic- and the North Sea, indicating divergence hitchhiking and the presence of genomic islands of divergence. We report a suite of outlier single nucleotide polymorphisms within or closely located to genes associated with osmoregulation, as well as genes known to play important roles in the hydration and development of oocytes. These genes are likely to have key functions within a general osmoregulatory framework and are important for the survival of eggs and larvae, contributing to the buildup of reproductive isolation between the low-salinity adapted Baltic cod and the adjacent cod populations. Hence, our data suggest that adaptive responses to the environmental conditions in the Baltic Sea may contribute to a strong and effective reproductive barrier, and that Baltic cod can be viewed as an example of ongoing speciation.

  3. Enhancer divergence and cis-regulatory evolution in the human and chimp neural crest.

    PubMed

    Prescott, Sara L; Srinivasan, Rajini; Marchetto, Maria Carolina; Grishina, Irina; Narvaiza, Iñigo; Selleri, Licia; Gage, Fred H; Swigut, Tomek; Wysocka, Joanna

    2015-09-24

    cis-regulatory changes play a central role in morphological divergence, yet the regulatory principles underlying emergence of human traits remain poorly understood. Here, we use epigenomic profiling from human and chimpanzee cranial neural crest cells to systematically and quantitatively annotate divergence of craniofacial cis-regulatory landscapes. Epigenomic divergence is often attributable to genetic variation within TF motifs at orthologous enhancers, with a novel motif being most predictive of activity biases. We explore properties of this cis-regulatory change, revealing the role of particular retroelements, uncovering broad clusters of species-biased enhancers near genes associated with human facial variation, and demonstrating that cis-regulatory divergence is linked to quantitative expression differences of crucial neural crest regulators. Our work provides a wealth of candidates for future evolutionary studies and demonstrates the value of "cellular anthropology," a strategy of using in-vitro-derived embryonic cell types to elucidate both fundamental and evolving mechanisms underlying morphological variation in higher primates.

  4. Understanding patchy landscape dynamics: towards a landscape language.

    PubMed

    Gaucherel, Cédric; Boudon, Frédéric; Houet, Thomas; Castets, Mathieu; Godin, Christophe

    2012-01-01

    Patchy landscapes driven by human decisions and/or natural forces are still a challenge to be understood and modelled. No attempt has been made up to now to describe them by a coherent framework and to formalize landscape changing rules. Overcoming this lacuna was our first objective here, and this was largely based on the notion of Rewriting Systems, also called Formal Grammars. We used complicated scenarios of agricultural dynamics to model landscapes and to write their corresponding driving rule equations. Our second objective was to illustrate the relevance of this landscape language concept for landscape modelling through various grassland managements, with the final aim to assess their respective impacts on biological conservation. For this purpose, we made the assumptions that a higher grassland appearance frequency and higher land cover connectivity are favourable to species conservation. Ecological results revealed that dairy and beef livestock production systems are more favourable to wild species than is hog farming, although in different ways. Methodological results allowed us to efficiently model and formalize these landscape dynamics. This study demonstrates the applicability of the Rewriting System framework to the modelling of agricultural landscapes and, hopefully, to other patchy landscapes. The newly defined grammar is able to explain changes that are neither necessarily local nor Markovian, and opens a way to analytical modelling of landscape dynamics.

  5. Understanding Patchy Landscape Dynamics: Towards a Landscape Language

    PubMed Central

    Gaucherel, Cédric; Boudon, Frédéric; Houet, Thomas; Castets, Mathieu; Godin, Christophe

    2012-01-01

    Patchy landscapes driven by human decisions and/or natural forces are still a challenge to be understood and modelled. No attempt has been made up to now to describe them by a coherent framework and to formalize landscape changing rules. Overcoming this lacuna was our first objective here, and this was largely based on the notion of Rewriting Systems, also called Formal Grammars. We used complicated scenarios of agricultural dynamics to model landscapes and to write their corresponding driving rule equations. Our second objective was to illustrate the relevance of this landscape language concept for landscape modelling through various grassland managements, with the final aim to assess their respective impacts on biological conservation. For this purpose, we made the assumptions that a higher grassland appearance frequency and higher land cover connectivity are favourable to species conservation. Ecological results revealed that dairy and beef livestock production systems are more favourable to wild species than is hog farming, although in different ways. Methodological results allowed us to efficiently model and formalize these landscape dynamics. This study demonstrates the applicability of the Rewriting System framework to the modelling of agricultural landscapes and, hopefully, to other patchy landscapes. The newly defined grammar is able to explain changes that are neither necessarily local nor Markovian, and opens a way to analytical modelling of landscape dynamics. PMID:23049935

  6. Rapid Diversity Loss of Competing Animal Species in Well-Connected Landscapes.

    PubMed

    Schippers, Peter; Hemerik, Lia; Baveco, Johannes M; Verboom, Jana

    2015-01-01

    Population viability of a single species, when evaluated with metapopulation based landscape evaluation tools, always increases when the connectivity of the landscape increases. However, when interactions between species are taken into account, results can differ. We explore this issue using a stochastic spatially explicit meta-community model with 21 competing species in five different competitive settings: (1) weak, coexisting competition, (2) neutral competition, (3) strong, excluding competition, (4) hierarchical competition and (5) random species competition. The species compete in randomly generated landscapes with various fragmentation levels. With this model we study species loss over time. Simulation results show that overall diversity, the species richness in the entire landscape, decreases slowly in fragmented landscapes whereas in well-connected landscapes rapid species losses occur. These results are robust with respect to changing competitive settings, species parameters and spatial configurations. They indicate that optimal landscape configuration for species conservation differs between metapopulation approaches, modelling species separately and meta-community approaches allowing species interactions. The mechanism behind this is that species in well-connected landscapes rapidly outcompete each other. Species that become abundant, by chance or by their completive strength, send out large amounts of dispersers that colonize and take over other patches that are occupied by species that are less abundant. This mechanism causes rapid species loss. In fragmented landscapes the colonization rate is lower, and it is difficult for a new species to establish in an already occupied patch. So, here dominant species cannot easily take over patches occupied by other species and higher diversity is maintained for a longer time. These results suggest that fragmented landscapes have benefits for species conservation previously unrecognized by the landscape ecology

  7. Divergence thrust loss calculations for convergent-divergent nozzles: Extensions to the classical case

    NASA Technical Reports Server (NTRS)

    Berton, Jeffrey J.

    1991-01-01

    The analytical derivations of the non-axial thrust divergence losses for convergent-divergent nozzles are described as well as how these calculations are embodied in the Navy/NASA engine computer program. The convergent-divergent geometries considered are simple classic axisymmetric nozzles, two dimensional rectangular nozzles, and axisymmetric and two dimensional plug nozzles. A simple, traditional, inviscid mathematical approach is used to deduce the influence of the ineffectual non-axial thrust as a function of the nozzle exit divergence angle.

  8. The influence of pollinator phylogeography and mate preference on floral divergence in a sexually deceptive daisy.

    PubMed

    de Jager, Marinus L; Ellis, Allan G

    2013-06-01

    Divergent mate preferences and subsequent genetic differentiation between populations has been demonstrated, but its effects on interspecific interactions are unknown. Associated species exploiting these mate preferences, for example, may diverge to match local preferences. We explore this idea in the sexually deceptive, fly-mimicking daisy, Gorteria diffusa, by testing for association between genetic structure in the fly pollinator (a proxy for mate preference divergence) and geographic divergence in floral form. If genetic structure in flies influences interactions with G. diffusa, we expect phylogeographically distinct flies to be associated with different floral forms. Flies associated with forms exploiting only feeding behavior often belonged to several phylogeographic clades, whereas flies associated with forms exploiting male-mating behavior always belonged to distinct clades, indicating the possibility of pollinator-mediated floral divergence through phylogeographic variation in mating preferences of male flies. We tested this hypothesis with reciprocal presentations using male flies from distinct clades associated with separate floral forms. Results show that males from all clades exhibit similar preferences, making pollinator driven divergence through geographic variation in mate preference unlikely. Males, however, showed evidence of learned resistance to deceptive traits, suggesting antagonistic interactions between plants and pollinators may drive deceptive floral trait evolution in G. diffusa.

  9. "Islands of Divergence" in the Atlantic Cod Genome Represent Polymorphic Chromosomal Rearrangements.

    PubMed

    Sodeland, Marte; Jorde, Per Erik; Lien, Sigbjørn; Jentoft, Sissel; Berg, Paul R; Grove, Harald; Kent, Matthew P; Arnyasi, Mariann; Olsen, Esben Moland; Knutsen, Halvor

    2016-04-11

    In several species genetic differentiation across environmental gradients or between geographically separate populations has been reported to center at "genomic islands of divergence," resulting in heterogeneous differentiation patterns across genomes. Here, genomic regions of elevated divergence were observed on three chromosomes of the highly mobile fish Atlantic cod (Gadus morhua) within geographically fine-scaled coastal areas. The "genomic islands" extended at least 5, 9.5, and 13 megabases on linkage groups 2, 7, and 12, respectively, and coincided with large blocks of linkage disequilibrium. For each of these three chromosomes, pairs of segregating, highly divergent alleles were identified, with little or no gene exchange between them. These patterns of recombination and divergence mirror genomic signatures previously described for large polymorphic inversions, which have been shown to repress recombination across extensive chromosomal segments. The lack of genetic exchange permits divergence between noninverted and inverted chromosomes in spite of gene flow. For the rearrangements on linkage groups 2 and 12, allelic frequency shifts between coastal and oceanic environments suggest a role in ecological adaptation, in agreement with recently reported associations between molecular variation within these genomic regions and temperature, oxygen, and salinity levels. Elevated genetic differentiation in these genomic regions has previously been described on both sides of the Atlantic Ocean, and we therefore suggest that these polymorphisms are involved in adaptive divergence across the species distributional range. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  10. Habitat selection in a rocky landscape: experimentally decoupling the influence of retreat site attributes from that of landscape features.

    PubMed

    Croak, Benjamin M; Pike, David A; Webb, Jonathan K; Shine, Richard

    2012-01-01

    Organisms selecting retreat sites may evaluate not only the quality of the specific shelter, but also the proximity of that site to resources in the surrounding area. Distinguishing between habitat selection at these two spatial scales is complicated by co-variation among microhabitat factors (i.e., the attributes of individual retreat sites often correlate with their proximity to landscape features). Disentangling this co-variation may facilitate the restoration or conservation of threatened systems. To experimentally examine the role of landscape attributes in determining retreat-site quality for saxicolous ectotherms, we deployed 198 identical artificial rocks in open (sun-exposed) sites on sandstone outcrops in southeastern Australia, and recorded faunal usage of those retreat sites over the next 29 months. Several landscape-scale attributes were associated with occupancy of experimental rocks, but different features were important for different species. For example, endangered broad-headed snakes (Hoplocephalus bungaroides) preferred retreat sites close to cliff edges, flat rock spiders (Hemicloea major) preferred small outcrops, and velvet geckos (Oedura lesueurii) preferred rocks close to the cliff edge with higher-than-average sun exposure. Standardized retreat sites can provide robust experimental data on the effects of landscape-scale attributes on retreat site selection, revealing interspecific divergences among sympatric taxa that use similar habitats.

  11. Habitat Selection in a Rocky Landscape: Experimentally Decoupling the Influence of Retreat Site Attributes from That of Landscape Features

    PubMed Central

    Croak, Benjamin M.; Pike, David A.; Webb, Jonathan K.; Shine, Richard

    2012-01-01

    Organisms selecting retreat sites may evaluate not only the quality of the specific shelter, but also the proximity of that site to resources in the surrounding area. Distinguishing between habitat selection at these two spatial scales is complicated by co-variation among microhabitat factors (i.e., the attributes of individual retreat sites often correlate with their proximity to landscape features). Disentangling this co-variation may facilitate the restoration or conservation of threatened systems. To experimentally examine the role of landscape attributes in determining retreat-site quality for saxicolous ectotherms, we deployed 198 identical artificial rocks in open (sun-exposed) sites on sandstone outcrops in southeastern Australia, and recorded faunal usage of those retreat sites over the next 29 months. Several landscape-scale attributes were associated with occupancy of experimental rocks, but different features were important for different species. For example, endangered broad-headed snakes (Hoplocephalus bungaroides) preferred retreat sites close to cliff edges, flat rock spiders (Hemicloea major) preferred small outcrops, and velvet geckos (Oedura lesueurii) preferred rocks close to the cliff edge with higher-than-average sun exposure. Standardized retreat sites can provide robust experimental data on the effects of landscape-scale attributes on retreat site selection, revealing interspecific divergences among sympatric taxa that use similar habitats. PMID:22701592

  12. Economic linkages to changing landscapes.

    PubMed

    Peterson, Jeffrey M; Caldas, Marcellus M; Bergtold, Jason S; Sturm, Belinda S; Graves, Russell W; Earnhart, Dietrich; Hanley, Eric A; Brown, J Christopher

    2014-01-01

    Many economic processes are intertwined with landscape change. A large number of individual economic decisions shape the landscape, and in turn the changes in the landscape shape economic decisions. This article describes key research questions about the economics of landscape change and reviews the state of research knowledge. The rich and varied economic-landscape interactions are an active area of research by economists, geographers, and others. Because the interactions are numerous and complex, disentangling the causal relationships in any given landscape system is a formidable research challenge. Limited data with mismatched temporal and spatial scales present further obstacles. Nevertheless, the growing body of economic research on these topics is advancing and shares fundamental challenges, as well as data and methods, with work in other disciplines.

  13. Laryngotracheal separation.

    PubMed

    LeJeune, F E

    1978-12-01

    The popularity of the motorcycle, specifically trail bike riding, in the past several years has produced an increasing incidence of severe "clothesline" injuries to the larynx and trachea. Even at moderately high speed the impact of a horizontal cable with the neck of the rider causes a sudden hyperextension of the neck, and an avulsion of the larynx from the trachea, separating at the relatively rigid fibrous connective tissue between the cricoid cartilage and the first tracheal ring. Interruption of the strap muscles, the recurrent laryngeal nerves, laceration of the esophagus, and compression fracture of the cervical vertebral bodies can occur. The unseated rider requires immediate assistance, airway obstruction being his greatest problem. In the early minutes after the accident he must be transported to an emergency facility where tracheostomy and resuscitation can be provided. Mediastinal infection, tracheoesophageal fistula, subglottic stenosis, and intermittent depression many follow the initial repair. Rehabilitative measures include permanent tracheostomy, the use of neuromuscular pedicle graft, hyoid bone graft, intracordal injection of teflon paste, and carbon dioxide laser excision of webs and cicatricial tissue.

  14. Soil conservation service landscape resource management

    Treesearch

    Sally Schauman; Carolyn Adams

    1979-01-01

    SCS Landscape Resource Management (LRM) is the application of landscape architecture to SCS conservation activities. LRM includes but is not limited to visual resource management. LRM can be summarized in three principles: (1) SCS landscape architecture considers the landscape as a composite of ecological, social and visual resources; (2) SCS landscapes exist in the...

  15. Context Dependent Effect of Landscape on the Occurrence of an Apex Predator across Different Climate Regions

    PubMed Central

    Fujita, Go; Azuma, Atsuki; Nonaka, Jun; Sakai, Yoshiaki; Sakai, Hatsumi; Iseki, Fumitaka; Itaya, Hiroo; Fukasawa, Keita; Miyashita, Tadashi

    2016-01-01

    In studies of habitat suitability at landscape scales, transferability of species-landscape associations among sites are likely to be critical because it is often impractical to collect datasets across various regions. However, limiting factors, such as prey availability, are not likely to be constant across scales because of the differences in species pools. This is particularly true for top predators that are often the target for conservation concern. Here we focus on gray-faced buzzards, apex predators of farmland-dominated landscapes in East Asia. We investigated context dependency of “buzzard-landscape relationship”, using nest location datasets from five sites, each differing in landscape composition. Based on the similarities of prey items and landscape compositions across the sites, we determined several alternative ways of grouping the sites, and then examined whether buzzard-landscape relationship change among groups, which was conducted separately for each way of grouping. As a result, the model of study-sites grouping based on similarities in prey items showed the smallest ΔAICc. Because the terms of interaction between group IDs and areas of broad-leaved forests and grasslands were selected, buzzard-landscape relationship showed a context dependency, i.e., these two landscape elements strengthen the relationship in southern region. The difference in prey fauna, which is associated with the difference in climate, might generate regional differences in the buzzard-landscape associations. PMID:27123930

  16. Context Dependent Effect of Landscape on the Occurrence of an Apex Predator across Different Climate Regions.

    PubMed

    Fujita, Go; Azuma, Atsuki; Nonaka, Jun; Sakai, Yoshiaki; Sakai, Hatsumi; Iseki, Fumitaka; Itaya, Hiroo; Fukasawa, Keita; Miyashita, Tadashi

    2016-01-01

    In studies of habitat suitability at landscape scales, transferability of species-landscape associations among sites are likely to be critical because it is often impractical to collect datasets across various regions. However, limiting factors, such as prey availability, are not likely to be constant across scales because of the differences in species pools. This is particularly true for top predators that are often the target for conservation concern. Here we focus on gray-faced buzzards, apex predators of farmland-dominated landscapes in East Asia. We investigated context dependency of "buzzard-landscape relationship", using nest location datasets from five sites, each differing in landscape composition. Based on the similarities of prey items and landscape compositions across the sites, we determined several alternative ways of grouping the sites, and then examined whether buzzard-landscape relationship change among groups, which was conducted separately for each way of grouping. As a result, the model of study-sites grouping based on similarities in prey items showed the smallest ΔAICc. Because the terms of interaction between group IDs and areas of broad-leaved forests and grasslands were selected, buzzard-landscape relationship showed a context dependency, i.e., these two landscape elements strengthen the relationship in southern region. The difference in prey fauna, which is associated with the difference in climate, might generate regional differences in the buzzard-landscape associations.

  17. Landscape Construction in Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Tang, Ying; Yuan, Ruoshi; Wang, Gaowei; Ao, Ping

    The idea of landscape has been recently applied to study various of biological problems. We demonstrate that a dynamical structure built into nonlinear dynamical systems allows us to construct such a global optimization landscape, which serves as the Lyapunov function for the ordinary differential equation. We find exact constructions on the landscape for a class of dynamical systems, including a van der Pol type oscillator, competitive Lotka-Volterra systems, and a chaotic system. The landscape constructed provides a new angle for understanding and modelling biological network dynamics.

  18. An improved neutral landscape model for recreating real landscapes and generating landscape series for spatial ecological simulations.

    PubMed

    van Strien, Maarten J; Slager, Cornelis T J; de Vries, Bauke; Grêt-Regamey, Adrienne

    2016-06-01

    Many studies have assessed the effect of landscape patterns on spatial ecological processes by simulating these processes in computer-generated landscapes with varying composition and configuration. To generate such landscapes, various neutral landscape models have been developed. However, the limited set of landscape-level pattern variables included in these models is often inadequate to generate landscapes that reflect real landscapes. In order to achieve more flexibility and variability in the generated landscapes patterns, a more complete set of class- and patch-level pattern variables should be implemented in these models. These enhancements have been implemented in Landscape Generator (LG), which is a software that uses optimization algorithms to generate landscapes that match user-defined target values. Developed for participatory spatial planning at small scale, we enhanced the usability of LG and demonstrated how it can be used for larger scale ecological studies. First, we used LG to recreate landscape patterns from a real landscape (i.e., a mountainous region in Switzerland). Second, we generated landscape series with incrementally changing pattern variables, which could be used in ecological simulation studies. We found that LG was able to recreate landscape patterns that approximate those of real landscapes. Furthermore, we successfully generated landscape series that would not have been possible with traditional neutral landscape models. LG is a promising novel approach for generating neutral landscapes and enables testing of new hypotheses regarding the influence of landscape patterns on ecological processes. LG is freely available online.

  19. Comparative landscape genetics of two river frog species occurring at different elevations on Mount Kilimanjaro.

    PubMed

    Zancolli, Giulia; Rödel, Mark-Oliver; Steffan-Dewenter, Ingolf; Storfer, Andrew

    2014-10-01

    Estimating population connectivity and species' abilities to disperse across the landscape is crucial for understanding the long-term persistence of species in changing environments. Surprisingly, few landscape genetic studies focused on tropical regions despite the alarming extinction rates within these ecosystems. Here, we compared the influence of landscape features on the distribution of genetic variation of an Afromontane frog, Amietia wittei, with that of its more broadly distributed lowland congener, Amietia angolensis, on Mt. Kilimanjaro, Tanzania. We predicted high gene flow in the montane species with movements enhanced through terrestrial habitats of the continuous rainforest. In contrast, dispersal might be restricted to aquatic corridors and reduced by anthropogenic disturbance in the lowland species. We found high gene flow in A. wittei relative to other montane amphibians. Nonetheless, gene flow was lower than in the lowland species which showed little population structure. Least-cost path analysis suggested that dispersal is facilitated by stream networks in both species, but different landscape features were identified to influence connectivity among populations. Contrary to a previous study, gene flow in the lowland species was negatively correlated with the presence of human settlements. Also, genetic subdivision in A. wittei did not coincide with specific physical barriers as in other landscape genetic studies, suggesting that factors other than topography may contribute to population divergence. Overall, these results highlight the importance of a comparative landscape genetic approach for assessing the influence of the landscape matrix on population connectivity, particularly because nonintuitive results can alter the course of conservation and management.

  20. Probing the String Landscape

    ScienceCinema

    Keith Dienes

    2016-07-12

    We are currently in the throes of a potentially huge paradigm shift in physics. Motivated by recent developments in string theory and the discovery of the so-called "string landscape", physicists are beginning to question the uniqueness of fundamental theories of physics and the methods by which such theories might be understood and investigated. In this colloquium, I will give a non-technical introduction to the nature of this paradigm shift and how it developed. I will also discuss some of the questions to which it has led, and the nature of the controversies it has spawned.

  1. Stonehenge and its Landscape

    NASA Astrophysics Data System (ADS)

    Ruggles, Clive L. N.

    In the 1960s and 1970s, Stonehenge polarized academic opinion between those (mainly astronomers) who claimed it demonstrated great astronomical sophistication and those (mainly archaeologists) who denied it had anything to do with astronomy apart from the solstitial alignment of its main axis. Now, several decades later, links to the annual passage of the sun are generally recognized as an essential part of the function and meaning not only of Stonehenge but also of several other nearby monuments, giving us important insights into beliefs and actions relating to the seasonal cycle by the prehistoric communities who populated this chalkland landscape in the third millennium BC Links to the moon remain more debatable.

  2. Probing the String Landscape

    SciTech Connect

    Keith Dienes

    2009-12-01

    We are currently in the throes of a potentially huge paradigm shift in physics. Motivated by recent developments in string theory and the discovery of the so-called "string landscape", physicists are beginning to question the uniqueness of fundamental theories of physics and the methods by which such theories might be understood and investigated. In this colloquium, I will give a non-technical introduction to the nature of this paradigm shift and how it developed. I will also discuss some of the questions to which it has led, and the nature of the controversies it has spawned.

  3. Wind-Eroded Landscape

    NASA Technical Reports Server (NTRS)

    2005-01-01

    5 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust-mantled, wind-eroded landscape in the Medusae Sulci region of Mars. Wind eroded the bedrock in this region, and then, later, windblown dust covered much of the terrain.

    Location near: 5.7oS, 160.2oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Southern Spring

  4. Climates, Landscapes, and Civilizations

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-10-01

    Humans are now the dominant driver of global climate change. From ocean acidification to sea level rise, changes in precipitation patterns, and rising temperatures, global warming is presenting us with an uncertain future. However, this is not the first time human civilizations have faced a changing world. In the AGU monograph Climates, Landscapes, and Civilizations, editors Liviu Giosan, Dorian Q. Fuller, Kathleen Nicoll, Rowan K. Flad, and Peter C. Clift explore how some ancient peoples weathered the shifting storms while some faded away. In this interview, Eos speaks with Liviu Giosan about the decay of civilizations, ancient adaptation, and the surprisingly long history of humanity's effect on the Earth.

  5. Editorial: Mapping the Intellectual Landscape of Landscape and Urban Planning

    Treesearch

    Paul H. Gobster; Wei-Ning. Xiang

    2012-01-01

    Maps are central to our understanding of landscapes. When this Editorship began to revise the journal's Aims and Scope for presentation in a forthcoming editorial, we sought ways in which we could identify the core knowledge base and boundaries, however permeable, of what the journal community considers to be Landscape and Urban Planning (LAND). Strategically, we...

  6. Implementation of a Landscape Lighting System to Display Images

    NASA Astrophysics Data System (ADS)

    Sun, Gi-Ju; Cho, Sung-Jae; Kim, Chang-Beom; Moon, Cheol-Hong

    The system implemented in this study consists of a PC, MASTER, SLAVEs and MODULEs. The PC sets the various landscape lighting displays, and the image files can be sent to the MASTER through a virtual serial port connected to the USB (Universal Serial Bus). The MASTER sends a sync signal to the SLAVE. The SLAVE uses the signal received from the MASTER and the landscape lighting display pattern. The video file is saved in the NAND Flash memory and the R, G, B signals are separated using the self-made display signal and sent to the MODULE so that it can display the image.

  7. Mitochondrial sequence divergence among Antarctic killer whale ecotypes is consistent with multiple species.

    PubMed

    LeDuc, Richard G; Robertson, Kelly M; Pitman, Robert L

    2008-08-23

    Recently, three visually distinct forms of killer whales (Orcinus orca) were described from Antarctic waters and designated as types A, B and C. Based on consistent differences in prey selection and habitat preferences, morphological divergence and apparent lack of interbreeding among these broadly sympatric forms, it was suggested that they may represent separate species. To evaluate this hypothesis, we compared complete sequences of the mitochondrial control region from 81 Antarctic killer whale samples, including 9 type A, 18 type B, 47 type C and 7 type-undetermined individuals. We found three fixed differences that separated type A from B and C, and a single fixed difference that separated type C from A and B. These results are consistent with reproductive isolation among the different forms, although caution is needed in drawing further conclusions. Despite dramatic differences in morphology and ecology, the relatively low levels of sequence divergence in Antarctic killer whales indicate that these evolutionary changes occurred relatively rapidly and recently.

  8. Sustainability, Smart Growth, and Landscape Architecture

    EPA Pesticide Factsheets

    Sustainability, Smart Growth, and Landscape Architecture is an overview course for landscape architecture students interested in sustainability in landscape architecture and how it might apply to smart growth principles in urban, suburban, and rural areas

  9. Experimental evidence that phenotypic divergence in predators drives community divergence in prey.

    PubMed

    Palkovacs, Eric P; Post, David M

    2009-02-01

    Studies of adaptive divergence have traditionally focused on the ecological causes of trait diversification, while the ecological consequences of phenotypic divergence remain relatively unexplored. Divergence in predator foraging traits, in particular, has the potential to impact the structure and dynamics of ecological communities. To examine the effects of predator trait divergence on prey communities, we exposed zooplankton communities in lake mesocosms to predation from either anadromous or landlocked (freshwater resident) alewives, which have undergone recent and rapid phenotypic differentiation in foraging traits (gape width, gill raker spacing, and prey size-selectivity). Anadromous alewives, which exploit large prey items, significantly reduced the mean body size, total biomass, species richness, and diversity of crustacean zooplankton relative to landlocked alewives, which exploit smaller prey. The zooplankton responses observed in this experiment are consistent with patterns observed in lakes. This study provides direct evidence that phenotypic divergence in predators, even in its early stages, can play a critical role in determining prey community structure.

  10. Intrinsically Disordered Energy Landscapes

    NASA Astrophysics Data System (ADS)

    Chebaro, Yassmine; Ballard, Andrew J.; Chakraborty, Debayan; Wales, David J.

    2015-05-01

    Analysis of an intrinsically disordered protein (IDP) reveals an underlying multifunnel structure for the energy landscape. We suggest that such ‘intrinsically disordered’ landscapes, with a number of very different competing low-energy structures, are likely to characterise IDPs, and provide a useful way to address their properties. In particular, IDPs are present in many cellular protein interaction networks, and several questions arise regarding how they bind to partners. Are conformations resembling the bound structure selected for binding, or does further folding occur on binding the partner in a induced-fit fashion? We focus on the p53 upregulated modulator of apoptosis (PUMA) protein, which adopts an -helical conformation when bound to its partner, and is involved in the activation of apoptosis. Recent experimental evidence shows that folding is not necessary for binding, and supports an induced-fit mechanism. Using a variety of computational approaches we deduce the molecular mechanism behind the instability of the PUMA peptide as a helix in isolation. We find significant barriers between partially folded states and the helix. Our results show that the favoured conformations are molten-globule like, stabilised by charged and hydrophobic contacts, with structures resembling the bound state relatively unpopulated in equilibrium.

  11. Landscapes Impacted by Light

    NASA Astrophysics Data System (ADS)

    Arellano, B.; Roca, J.

    2016-06-01

    The gradual spread of urbanization, the phenomenon known under the term urban sprawl, has become one of the paradigms that have characterized the urban development since the second half of the twentieth century and early twenty-first century. However, there is no unanimous consensus about what means "urbanization". The plurality of forms of human settlement on the planet difficult to identify the urbanization processes. The arrival of electrification to nearly every corner of the planet is certainly the first and more meaningful indicator of artificialization of land. In this sense, the paper proposes a new methodology based on the analysis of the satellite image of nighttime lights designed to identify the highly impacted landscapes worldwide and to build an index of Land Impacted by Light per capita (LILpc) as an indicator of the level of urbanization. The used methodology allows the identification of different typologies of urbanized areas (villages, cities or metropolitan areas), as well as "rural", "rurban", "periurban" and "central" landscapes. The study identifies 186,134 illuminated contours (urbanized areas). In one hand, 404 of these contours could be consider as real "metropolitan areas"; and in the other hand, there are 161,821 contours with less than 5,000 inhabitants, which could be identify as "villages". Finally, the paper shows that 44.5 % live in rural areas, 15.5 % in rurban spaces, 26.2 % in suburban areas and only 18.4 % in central areas.

  12. Landscape Evolution of Titan

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey

    2012-01-01

    Titan may have acquired its massive atmosphere relatively recently in solar system history. The warming sun may have been key to generating Titan's atmosphere over time, starting from a thin atmosphere with condensed surface volatiles like Triton, with increased luminosity releasing methane, and then large amounts of nitrogen (perhaps suddenly), into the atmosphere. This thick atmosphere, initially with much more methane than at present, resulted in global fluvial erosion that has over time retreated towards the poles with the removal of methane from the atmosphere. Basement rock, as manifested by bright, rough, ridges, scarps, crenulated blocks, or aligned massifs, mostly appears within 30 degrees of the equator. This landscape was intensely eroded by fluvial processes as evidenced by numerous valley systems, fan-like depositional features and regularly-spaced ridges (crenulated terrain). Much of this bedrock landscape, however, is mantled by dunes, suggesting that fluvial erosion no longer dominates in equatorial regions. High midlatitude regions on Titan exhibit dissected sedimentary plains at a number of localities, suggesting deposition (perhaps by sediment eroded from equatorial regions) followed by erosion. The polar regions are mainly dominated by deposits of fluvial and lacustrine sediment. Fluvial processes are active in polar areas as evidenced by alkane lakes and occasional cloud cover.

  13. Norwegian millstone quarry landscapes

    NASA Astrophysics Data System (ADS)

    Heldal, Tom; Meyer, Gurli; Grenne, Tor

    2013-04-01

    Rotary querns and millstones were used in Norway since just after the Roman Period until the last millstone was made in the 1930s. Throughout all this time millstone mining was fundamental for daily life: millstones were needed to grind grain, our most important food source. We can find millstone quarries in many places in the country from coast to mountain. Some of them cover many square kilometers and count hundreds of quarries as physical testimonies of a long and great production history. Other quarries are small and hardly visible. Some of this history is known through written and oral tradition, but most of it is hidden and must be reconstructed from the traces we can find in the landscape today. The Millstone project has put these quarry landscapes on the map, and conducted a range of case studies, including characterization of archaeological features connected to the quarrying, interpretation of quarrying techniques and evolution of such and establishing distribution and trade patterns by the aid of geological provenance. The project also turned out to be a successful cooperation between different disciplines, in particular geology and archaeology.

  14. The oxidation of landscapes

    NASA Astrophysics Data System (ADS)

    Rempe, D.; Hahm, W. J.; Dietrich, W. E.

    2015-12-01

    At the base of the critical zone, fresh rock is transformed through chemical alteration of minerals and fracturing. The resulting hydrologically dynamic weathered bedrock zone strongly influences how mass is routed throughout a landscape. Studies of weathering in a variety of lithologies and climates have documented the role of oxygen in driving the onset of weathering. Porosity is generated through processes such as the formation of sulfuric acid via oxidative pyrite dissolution and strain via iron oxidation in biotite. The transport of meteoric oxygen is therefore a mechanism that links the topographic surface to weathering processes at depth. Here, we present an alternative to the theory that the advance of an oxidation front is driven by downward advection and diffusion of meteoric fluid. We present field data and theory that suggest that the slow drainage of groundwater within fresh bedrock drives the displacement of unreactive pore fluid from low-porosity fresh bedrock. This drainage, and the subsequent introduction of meteoric fluid to fresh rock, is a hillslope scale process driven by channel incision. The resulting distribution of weathered rock across the landscape is thus controlled by the fresh bedrock porosity and permeability and the rate of channel incision.

  15. Intrinsically Disordered Energy Landscapes

    PubMed Central

    Chebaro, Yassmine; Ballard, Andrew J.; Chakraborty, Debayan; Wales, David J.

    2015-01-01

    Analysis of an intrinsically disordered protein (IDP) reveals an underlying multifunnel structure for the energy landscape. We suggest that such ‘intrinsically disordered’ landscapes, with a number of very different competing low-energy structures, are likely to characterise IDPs, and provide a useful way to address their properties. In particular, IDPs are present in many cellular protein interaction networks, and several questions arise regarding how they bind to partners. Are conformations resembling the bound structure selected for binding, or does further folding occur on binding the partner in a induced-fit fashion? We focus on the p53 upregulated modulator of apoptosis (PUMA) protein, which adopts an -helical conformation when bound to its partner, and is involved in the activation of apoptosis. Recent experimental evidence shows that folding is not necessary for binding, and supports an induced-fit mechanism. Using a variety of computational approaches we deduce the molecular mechanism behind the instability of the PUMA peptide as a helix in isolation. We find significant barriers between partially folded states and the helix. Our results show that the favoured conformations are molten-globule like, stabilised by charged and hydrophobic contacts, with structures resembling the bound state relatively unpopulated in equilibrium. PMID:25999294

  16. Cancer Genome Landscapes

    PubMed Central

    Vogelstein, Bert; Papadopoulos, Nickolas; Velculescu, Victor E.; Zhou, Shibin; Diaz, Luis A.; Kinzler, Kenneth W.

    2013-01-01

    Over the past decade, comprehensive sequencing efforts have revealed the genomic landscapes of common forms of human cancer. For most cancer types, this landscape consists of a small number of “mountains” (genes altered in a high percentage of tumors) and a much larger number of “hills” (genes altered infrequently). To date, these studies have revealed ~140 genes that, when altered by intragenic mutations, can promote or “drive” tumorigenesis. A typical tumor contains two to eight of these “driver gene” mutations; the remaining mutations are passengers that confer no selective growth advantage. Driver genes can be classified into 12 signaling pathways that regulate three core cellular processes: cell fate, cell survival, and genome maintenance. A better understanding of these pathways is one of the most pressing needs in basic cancer research. Even now, however, our knowledge of cancer genomes is sufficient to guide the development of more effective approaches for reducing cancer morbidity and mortality. PMID:23539594

  17. Optical rain gauge using a divergent beam.

    PubMed

    Wang, T I; Lawrence, R S; Tsay, M K

    1980-11-01

    We have shown that path-averaged rain rates can be obtained from the raindrop-induced amplitude scintillations of a divergent laser beam (spherical wave case). We found that the rain rate obtained from a divergent beam is less sensitive to drop-size distribution than that from a collimated beam. However, the path-weighting function is heavily weighted toward the receiving end in the spherical wave case, whereas in the plane wave case, it is almost uniformly weighted along the optical path. The theory was confirmed by observations on two optical paths, one using a collimated beam on a 200-m path, the other using a divergent beam on a 1000-m path. The results for the longer path show a saturation effect for rain rates higher than 12 mm/h.

  18. Evolutionary Divergence of Arabidopsis thaliana Classical Peroxidases.

    PubMed

    Kupriyanova, E V; Mamoshina, P O; Ezhova, T A

    2015-10-01

    Polymorphisms of 62 peroxidase genes derived from Arabidopsis thaliana were investigated to evaluate evolutionary dynamics and divergence of peroxidase proteins. By comparing divergence of duplicated genes AtPrx53-AtPrx54 and AtPrx36-AtPrx72 and their products, nucleotide and amino acid substitutions were identified that were apparently targets of positive selection. These substitutions were detected among paralogs of 461 ecotypes from Arabidopsis thaliana. Some of these substitutions are conservative and matched paralogous peroxidases in other Brassicaceae species. These results suggest that after duplication, peroxidase genes evolved under the pressure of positive selection, and amino acid substitutions identified during our study provided divergence of properties and physiological functions in peroxidases. Our predictions regarding functional significance for amino acid residues identified in variable sites of peroxidases may allow further experimental assessment of evolution of peroxidases after gene duplication.

  19. Vibhakti Divergence between Sanskrit and Hindi

    NASA Astrophysics Data System (ADS)

    Shukla, Preeti; Shukl, Devanand; Kulkarni, Amba

    Translation divergence at various levels between languages arises due to the different conventions followed by different languages for coding the information of grammatical relations. Though Sanskrit and Hindi belong to the same Indo-Aryan family and structurally as well as lexically Hindi inherits a lot from Sanskrit, yet divergences are observed at the level of function words such as vibhaktis. Pāṇini in his Aṣṭādhyāyī has assigned a default vibhakti to kārakas alongwith many scopes for exceptions. He handles these exceptions either by imposing a new kāraka role or by assigning a special vibhakti. However, these methods are not acceptable in Hindi in toto. Based on the nature of deviation, we propose seven cases of divergences in this paper.

  20. Discovery of Highly Divergent Repeat Landscapes in Snake Genomes Using High-Throughput Sequencing

    PubMed Central

    Castoe, Todd A.; Hall, Kathryn T.; Guibotsy Mboulas, Marcel L.; Gu, Wanjun; de Koning, A.P. Jason; Fox, Samuel E.; Poole, Alexander W.; Vemulapalli, Vijetha; Daza, Juan M.; Mockler, Todd; Smith, Eric N.; Feschotte, Cédric; Pollock, David D.

    2011-01-01

    We conducted a comprehensive assessment of genomic repeat content in two snake genomes, the venomous copperhead (Agkistrodon contortrix) and the Burmese python (Python molurus bivittatus). These two genomes are both relatively small (∼1.4 Gb) but have surprisingly extensive differences in the abundance and expansion histories of their repeat elements. In the python, the readily identifiable repeat element content is low (21%), similar to bird genomes, whereas that of the copperhead is higher (45%), similar to mammalian genomes. The copperhead's greater repeat content arises from the recent expansion of many different microsatellites and transposable element (TE) families, and the copperhead had 23-fold greater levels of TE-related transcripts than the python. This suggests the possibility that greater TE activity in the copperhead is ongoing. Expansion of CR1 LINEs in the copperhead genome has resulted in TE-mediated microsatellite expansion (“microsatellite seeding”) at a scale several orders of magnitude greater than previously observed in vertebrates. Snakes also appear to be prone to horizontal transfer of TEs, particularly in the copperhead lineage. The reason that the copperhead has such a small genome in the face of so much recent expansion of repeat elements remains an open question, although selective pressure related to extreme metabolic performance is an obvious candidate. TE activity can affect gene regulation as well as rates of recombination and gene duplication, and it is therefore possible that TE activity played a role in the evolution of major adaptations in snakes; some evidence suggests this may include the evolution of venom repertoires. PMID:21572095

  1. Discovery of highly divergent repeat landscapes in snake genomes using high-throughput sequencing.

    PubMed

    Castoe, Todd A; Hall, Kathryn T; Guibotsy Mboulas, Marcel L; Gu, Wanjun; de Koning, A P Jason; Fox, Samuel E; Poole, Alexander W; Vemulapalli, Vijetha; Daza, Juan M; Mockler, Todd; Smith, Eric N; Feschotte, Cédric; Pollock, David D

    2011-01-01

    We conducted a comprehensive assessment of genomic repeat content in two snake genomes, the venomous copperhead (Agkistrodon contortrix) and the Burmese python (Python molurus bivittatus). These two genomes are both relatively small (∼1.4 Gb) but have surprisingly extensive differences in the abundance and expansion histories of their repeat elements. In the python, the readily identifiable repeat element content is low (21%), similar to bird genomes, whereas that of the copperhead is higher (45%), similar to mammalian genomes. The copperhead's greater repeat content arises from the recent expansion of many different microsatellites and transposable element (TE) families, and the copperhead had 23-fold greater levels of TE-related transcripts than the python. This suggests the possibility that greater TE activity in the copperhead is ongoing. Expansion of CR1 LINEs in the copperhead genome has resulted in TE-mediated microsatellite expansion ("microsatellite seeding") at a scale several orders of magnitude greater than previously observed in vertebrates. Snakes also appear to be prone to horizontal transfer of TEs, particularly in the copperhead lineage. The reason that the copperhead has such a small genome in the face of so much recent expansion of repeat elements remains an open question, although selective pressure related to extreme metabolic performance is an obvious candidate. TE activity can affect gene regulation as well as rates of recombination and gene duplication, and it is therefore possible that TE activity played a role in the evolution of major adaptations in snakes; some evidence suggests this may include the evolution of venom repertoires.

  2. An Alternative String Landscape Cosmology: Eliminating Bizarreness

    NASA Astrophysics Data System (ADS)

    Clavelli, L.; Goldstein, Gary R.

    2013-11-01

    In what has become a standard eternal inflation picture of the string landscape there are many problematic consequences and a difficulty defining probabilities for the occurrence of each type of universe. One feature in particular that might be philosophically disconcerting is the infinite cloning of each individual and each civilization in infinite numbers of separated regions of the multiverse. Even if this is not ruled out due to causal separation one should ask whether the infinite cloning is a universal prediction of string landscape models or whether there are scenarios in which it is avoided. If a viable alternative cosmology can be constructed one might search for predictions that might allow one to discriminate experimentally between the models. We present one such scenario although, in doing so, we are forced to give up several popular presuppositions including the absence of a preferred frame and the homogeneity of matter in the universe. The model also has several ancillary advantages. We also consider the future lifetime of the current universe before becoming a light trapping region.

  3. Fantasy Landscapes with a Message

    ERIC Educational Resources Information Center

    D'Amico, Elizabeth

    2005-01-01

    The author of this article describes using a Fantasy Landscapes lesson to get students expressing environmental issues through art. The Fantasy Landscapes lesson is an exploration of art elements and design principles through visual problem solving that links ideas, language, and theory to art. To get students thinking specifically about…

  4. Landscape ecology and forest management

    Treesearch

    Thomas R. Crow

    1999-01-01

    Almost all forest management activities affect landscape pattern to some extent. Among the most obvious impacts are those associated with forest harvesting and road building. These activities profoundly affect the size, shape, and configuration of patches in the landscape matrix. Even-age management such as clearcutting has been applied in blocks of uniform size, shape...

  5. Landscaping With Maintenance in Mind.

    ERIC Educational Resources Information Center

    Sorensen, Randy

    2000-01-01

    Examines school ground landscape design that enhances attractive of the school and provides for easier maintenance. Landscape design issues discussed include choice of grass, trees, and shrubs; irrigation; and safety and access. Other considerations for lessening maintenance problems for facility managers are also highlighted. (GR)

  6. Messy world: managing dynamic landscape.

    Treesearch

    Sally. Duncan

    1999-01-01

    What lessons does historical disturbance hold for the management of future landscapes? Fred Swanson, a researcher at the Pacific Northwest Research Station and John Cissel, research liaison for the Willamette NF, are members of a team of scientists and land managers who are examining the way we think about and manage landscapes.The team found that past...

  7. Complex Landscape Terms in Seri

    ERIC Educational Resources Information Center

    O'Meara, Carolyn; Bohnemeyer, Jurgen

    2008-01-01

    The nominal lexicon of Seri is characterized by a prevalence of analytical descriptive terms. We explore the consequences of this typological trait in the landscape domain. The complex landscape terms of Seri classify geographic entities in terms of their material make-up and spatial properties such as shape, orientation, and merological…

  8. The integrated landscape assessment project

    Treesearch

    Miles A. Hemstrom; Janine Salwasser; Joshua Halofsky; Jimmy Kagan; Cyndi Comfort

    2012-01-01

    The Integrated Landscape Assessment Project (ILAP) is a three-year effort that produces information, models, data, and tools to help land managers, policymakers, and others examine mid- to broad-scale (e.g., watersheds to states and larger areas) prioritization of land management actions, perform landscape assessments, and estimate potential effects of management...

  9. Landscape habitat suitability index software

    Treesearch

    William D. Dijak; Chadwick D. Rittenhouse; Michael A. Larson; Frank R. III Thompson; Joshua J. Millspaugh

    2007-01-01

    Habitat suitability index (HSI) models are traditionally used to evaluate habitat quality for wildlife at a local scale. Rarely have such models incorporated spatial relationships of habitat components. We introduce Landscape HSImodels, a new Microsoft Windowst (Microsoft, Redmond, WA)-based program that incorporates local habitat as well as landscape-scale attributes...

  10. Caribbean landscapes and their biodiversity

    Treesearch

    A. E. Lugo; E. H. Helmer; E. Santiago Valentín

    2012-01-01

    Both the biodiversity and the landscapes of the Caribbean have been greatly modified as a consequence of human activity. In this essay we provide an overview of the natural landscapes and biodiversity of the Caribbean and discuss how human activity has affected both. Our Caribbean geographic focus is on the insular Caribbean and the biodiversity focus is on the flora,...

  11. Ervin Zube and landscape architecture

    Treesearch

    Paul H. Gobster

    2002-01-01

    As he grew in his knowledge about the landscape through his involvemment in it as a person, student, practitioner, teacher, program director, and researcher, Ervin Zube's ideas about what landscape architecture is and should be continually evolved. He was a prolific writer whose publications span a broad range of audiences, and his contributions to ...

  12. Future landscapes: opportunities and challenges

    Treesearch

    John Stanturf

    2015-01-01

    The global magnitude of degraded and deforested areas is best approached by restoring landscapes. Heightened international perception of the importance of forests and trees outside forests (e.g., woodlands, on farms) demands new approaches to future landscapes. The current need for forest restoration is two billion ha; most opportunities are mosaic restoration in the...

  13. Landscape in a Lacquer Box

    ERIC Educational Resources Information Center

    Savage, Martha

    2010-01-01

    A symbolic dry landscape garden of Eastern origin holds a special fascination for the author's middle-school students, which is why the author chose to create a project exploring this view of nature. A dry landscape garden, or "karesansui," is an arrangement of rocks, worn by nature and surrounded by a "sea" of sand, raked into patterns…

  14. Landscape Solutions to School Problems.

    ERIC Educational Resources Information Center

    Spitz, Katherine

    2002-01-01

    Discusses key lessons in school landscape design. Landscapes should: (1) include trees and plants that themselves provide hands-on teaching opportunities; (2) enhance health and safety in a number of ways while performing their other functions; (3) be sensitively designed relative to location to cut energy costs; and (4) be aesthetic as well as…

  15. Complex Landscape Terms in Seri

    ERIC Educational Resources Information Center

    O'Meara, Carolyn; Bohnemeyer, Jurgen

    2008-01-01

    The nominal lexicon of Seri is characterized by a prevalence of analytical descriptive terms. We explore the consequences of this typological trait in the landscape domain. The complex landscape terms of Seri classify geographic entities in terms of their material make-up and spatial properties such as shape, orientation, and merological…

  16. Landscaping With Maintenance in Mind.

    ERIC Educational Resources Information Center

    Sorensen, Randy

    2000-01-01

    Examines school ground landscape design that enhances attractive of the school and provides for easier maintenance. Landscape design issues discussed include choice of grass, trees, and shrubs; irrigation; and safety and access. Other considerations for lessening maintenance problems for facility managers are also highlighted. (GR)

  17. Landscape Solutions to School Problems.

    ERIC Educational Resources Information Center

    Spitz, Katherine

    2002-01-01

    Discusses key lessons in school landscape design. Landscapes should: (1) include trees and plants that themselves provide hands-on teaching opportunities; (2) enhance health and safety in a number of ways while performing their other functions; (3) be sensitively designed relative to location to cut energy costs; and (4) be aesthetic as well as…

  18. Fantasy Landscapes with a Message

    ERIC Educational Resources Information Center

    D'Amico, Elizabeth

    2005-01-01

    The author of this article describes using a Fantasy Landscapes lesson to get students expressing environmental issues through art. The Fantasy Landscapes lesson is an exploration of art elements and design principles through visual problem solving that links ideas, language, and theory to art. To get students thinking specifically about…

  19. Landscape in a Lacquer Box

    ERIC Educational Resources Information Center

    Savage, Martha

    2010-01-01

    A symbolic dry landscape garden of Eastern origin holds a special fascination for the author's middle-school students, which is why the author chose to create a project exploring this view of nature. A dry landscape garden, or "karesansui," is an arrangement of rocks, worn by nature and surrounded by a "sea" of sand, raked into patterns…

  20. Universal portfolios generated by the Bregman divergence

    NASA Astrophysics Data System (ADS)

    Tan, Choon Peng; Kuang, Kee Seng

    2017-04-01

    The Bregman divergence of two probability vectors is a stronger form of the f-divergence introduced by Csiszar. Two versions of the Bregman universal portfolio are presented by exploiting the mean-value theorem. The explicit form of the Bregman universal portfolio generated by a function of a convex polynomial is derived and studied empirically. This portfolio can be regarded as another generalized of the well-known Helmbold portfolio. By running the portfolios on selected stock-price data sets from the local stock exchange, it is shown that it is possible to increase the wealth of the investor by using the portfolios in investment.

  1. Diverging Fluctuations of the Lyapunov Exponents.

    PubMed

    Pazó, Diego; López, Juan M; Politi, Antonio

    2016-07-15

    We show that in generic one-dimensional Hamiltonian lattices the diffusion coefficient of the maximum Lyapunov exponent diverges in the thermodynamic limit. We trace this back to the long-range correlations associated with the evolution of the hydrodynamic modes. In the case of normal heat transport, the divergence is even stronger, leading to the breakdown of the usual single-function Family-Vicsek scaling ansatz. A similar scenario is expected to arise in the evolution of rough interfaces in the presence of suitably correlated background noise.

  2. Diverging Fluctuations of the Lyapunov Exponents

    NASA Astrophysics Data System (ADS)

    Pazó, Diego; López, Juan M.; Politi, Antonio

    2016-07-01

    We show that in generic one-dimensional Hamiltonian lattices the diffusion coefficient of the maximum Lyapunov exponent diverges in the thermodynamic limit. We trace this back to the long-range correlations associated with the evolution of the hydrodynamic modes. In the case of normal heat transport, the divergence is even stronger, leading to the breakdown of the usual single-function Family-Vicsek scaling ansatz. A similar scenario is expected to arise in the evolution of rough interfaces in the presence of suitably correlated background noise.

  3. Colonization from divergent ancestors: glaciation signatures on contemporary patterns of genomic variation in Collared Pikas (Ochotona collaris).

    PubMed

    Lanier, Hayley C; Massatti, Rob; He, Qixin; Olson, Link E; Knowles, L Lacey

    2015-07-01

    Identifying the genetic structure of a species and the factors that drive it is an important first step in modern population management, in part because populations evolving from separate ancestral sources may possess potentially different characteristics. This is especially true for climate-sensitive species such as pikas, where the delimitation of distinct genetic units and the characterization of population responses to contemporary and historical environmental pressures are of particular interest. We combined a restriction site-associated DNA sequencing (RADSeq) data set containing 4156 single nucleotide polymorphisms with ecological niche models (ENMs) of present and past habitat suitability to characterize population composition and evaluate the effects of historical range shifts, contemporary climates and landscape factors on gene flow in Collared Pikas, which are found in Alaska and adjacent regions of northwestern Canada and are the lesser-studied of North America's two pika species. The results suggest that contemporary environmental factors contribute little to current population connectivity. Instead, genetic diversity is strongly shaped by the presence of three ancestral lineages isolated during the Pleistocene (~148 and 52 kya). Based on ENMs and genetic data, populations originating from a northern refugium experienced longer-term stability, whereas both southern lineages underwent population expansion - contradicting the southern stability and northern expansion patterns seen in many other taxa. Current populations are comparable with respect to generally low diversity within populations and little-to-no recent admixture. The predominance of divergent histories structuring populations implies that if we are to understand and manage pika populations, we must specifically assess and accurately account for the forces underlying genetic similarity. © 2015 John Wiley & Sons Ltd.

  4. Fitness Landscapes of Functional RNAs.

    PubMed

    Kun, Ádám; Szathmáry, Eörs

    2015-08-21

    The notion of fitness landscapes, a map between genotype and fitness, was proposed more than 80 years ago. For most of this time data was only available for a few alleles, and thus we had only a restricted view of the whole fitness landscape. Recently, advances in genetics and molecular biology allow a more detailed view of them. Here we review experimental and theoretical studies of fitness landscapes of functional RNAs, especially aptamers and ribozymes. We find that RNA structures can be divided into critical structures, connecting structures, neutral structures and forbidden structures. Such characterisation, coupled with theoretical sequence-to-structure predictions, allows us to construct the whole fitness landscape. Fitness landscapes then can be used to study evolution, and in our case the development of the RNA world.

  5. Fitness Landscapes of Functional RNAs

    PubMed Central

    Kun, Ádám; Szathmáry, Eörs

    2015-01-01

    The notion of fitness landscapes, a map between genotype and fitness, was proposed more than 80 years ago. For most of this time data was only available for a few alleles, and thus we had only a restricted view of the whole fitness landscape. Recently, advances in genetics and molecular biology allow a more detailed view of them. Here we review experimental and theoretical studies of fitness landscapes of functional RNAs, especially aptamers and ribozymes. We find that RNA structures can be divided into critical structures, connecting structures, neutral structures and forbidden structures. Such characterisation, coupled with theoretical sequence-to-structure predictions, allows us to construct the whole fitness landscape. Fitness landscapes then can be used to study evolution, and in our case the development of the RNA world. PMID:26308059

  6. Complete lack of mitochondrial divergence between two species of NE Atlantic marine intertidal gastropods.

    PubMed

    Kemppainen, P; Panova, M; Hollander, J; Johannesson, K

    2009-10-01

    Some mitochondrial introgression is common between closely related species, but distinct species rarely show substantial introgression in their entire distribution range. In this study, however, we report a complete lack of mitochondrial divergence between two sympatric species of flat periwinkles (Littorina fabalis and Littorina obtusata) which, based on previous allozyme studies, diverged approximately 1 Ma. We re-examined their species status using both morphology (morphometric analysis) and neutral genetic markers (microsatellites) and our results confirmed that these species are well separated. Despite this, the two species shared all common cytochrome-b haplotypes throughout their NE Atlantic distribution and no deep split between typical L. fabalis and L. obtusata haplotypes could be found. We suggest that incomplete lineage sorting explains most of the lack of mitochondrial divergence between these species. However, coalescent-based analyses and the sympatric sharing of unique haplotypes suggest that introgressive hybridization also has occurred.

  7. Regulation of cell-to-cell variability in divergent gene expression

    NASA Astrophysics Data System (ADS)

    Yan, Chao; Wu, Shuyang; Pocetti, Christopher; Bai, Lu

    2016-03-01

    Cell-to-cell variability (noise) is an important feature of gene expression that impacts cell fitness and development. The regulatory mechanism of this variability is not fully understood. Here we investigate the effect on gene expression noise in divergent gene pairs (DGPs). We generated reporters driven by divergent promoters, rearranged their gene order, and probed their expressions using time-lapse fluorescence microscopy and single-molecule fluorescence in situ hybridization (smFISH). We show that two genes in a co-regulated DGP have higher expression covariance compared with the separate, tandem and convergent configurations, and this higher covariance is caused by more synchronized firing of the divergent transcriptions. For differentially regulated DGPs, the regulatory signal of one gene can stochastically `leak' to the other, causing increased gene expression noise. We propose that the DGPs' function in limiting or promoting gene expression noise may enhance or compromise cell fitness, providing an explanation for the conservation pattern of DGPs.

  8. The Enigmatic Transient Landscapes of Bhutan

    NASA Astrophysics Data System (ADS)

    Adams, B. A.; Whipple, K. X.; Heimsath, A. M.; van Soest, M. C.; Hodges, K.

    2010-12-01

    The Bhutan Himalaya are quite unlike the better-known Nepal Himalaya. Despite broad similarity in tectonostratigraphic architecture, the physiography and low-temperature thermochronometric history are significantly different, implying a distinct morphotectonic evolution of this region of the orogen. Bhutan is characterized by several isolated low-relief topographic benches, 20-40 km wide, at around 3,000 m elevation. These benches are separated by deep N-S canyons that represent some of the most rugged topography in the Himalaya. Based on apatite fission track and (U-Th)/He data, geologic and geomorphic observations, and our current understanding of transient landscape evolution, there are three plausible hypotheses for the origin of these low-relief surfaces. To satisfy these data, any hypothesis for Bhutan’s transient evolution must explain: (a) fast exhumation until at least 5 Ma, followed by a decline in temporally averaged exhumation rate since then, (b) creation of low-relief landscapes now perched at 3,000 m, and (c) uplift of the low-relief landscapes and incision of deep canyons that dissect and isolate patches of this now-relict landscape. In each of these hypotheses, distinct uplift histories must explain (a), (b), and (c): 1) Climate Hypothesis. Prior to the rise of the Shillong Plateau, very wet conditions drive rapid exhumation of a low-relief landscape (a & b). Since the 5 Ma rise of the Shillong Plateau to the south of Bhutan, a rain shadow decreased erosional efficiency, driving surface uplift (c) (Grujic et al., 2006). Rock uplift rate is constant in this model. 2) Tectonic Hypothesis. A decrease in tectonic uplift rate around 5 Ma led to a reduction in erosion rates, which led to the formation of low-relief surfaces (a & b). This change in uplift rate may have been caused by the transfer of crustal shortening to the Shillong Plateau. The low-relief landscapes were then raised to their current elevation by a return to higher uplift rates (c

  9. Modelling vegetated dune landscapes

    NASA Astrophysics Data System (ADS)

    Baas, A. C. W.; Nield, J. M.

    2007-03-01

    This letter presents a self-organising cellular automaton model capable of simulating the evolution of vegetated dunes with multiple types of plant response in the environment. It can successfully replicate hairpin, or long-walled, parabolic dunes with trailing ridges as well as nebkha dunes with distinctive deposition tails. Quantification of simulated landscapes with eco-geomorphic state variables and subsequent cluster analysis and PCA yields a phase diagram of different types of coastal dunes developing from blow-outs as a function of vegetation vitality. This diagram indicates the potential sensitivity of dormant dune fields to reactivation under declining vegetation vitality, e.g. due to climatic changes. Nebkha simulations with different grid resolutions demonstrate that the interaction between the (abiotic) geomorphic processes and the biological vegetation component (life) introduces a characteristic length scale on the resultant landforms that breaks the typical self-similar scaling of (un-vegetated) bare-sand dunes.

  10. Evolutionary responses of tree phenology to the combined effects of assortative mating, gene flow and divergent selection

    PubMed Central

    Soularue, J-P; Kremer, A

    2014-01-01

    The timing of bud burst (TBB) in temperate trees is a key adaptive trait, the expression of which is triggered by temperature gradients across the landscape. TBB is strongly correlated with flowering time and is therefore probably mediated by assortative mating. We derived theoretical predictions and realized numerical simulations of evolutionary changes in TBB in response to divergent selection and gene flow in a metapopulation. We showed that the combination of the environmental gradient of TBB and assortative mating creates contrasting genetic clines, depending on the direction of divergent selection. If divergent selection acts in the same direction as the environmental gradient (cogradient settings), genetic clines are established and inflated by assortative mating. Conversely, under divergent selection of the same strength but acting in the opposite direction (countergradient selection), genetic clines are slightly constrained. We explored the consequences of these dynamics for population maladaptation, by monitoring pollen swamping. Depending on the direction of divergent selection with respect to the environmental gradient, pollen filtering owing to assortative mating either facilitates or impedes adaptation in peripheral populations. PMID:24924591

  11. Evolutionary responses of tree phenology to the combined effects of assortative mating, gene flow and divergent selection.

    PubMed

    Soularue, J-P; Kremer, A

    2014-12-01

    The timing of bud burst (TBB) in temperate trees is a key adaptive trait, the expression of which is triggered by temperature gradients across the landscape. TBB is strongly correlated with flowering time and is therefore probably mediated by assortative mating. We derived theoretical predictions and realized numerical simulations of evolutionary changes in TBB in response to divergent selection and gene flow in a metapopulation. We showed that the combination of the environmental gradient of TBB and assortative mating creates contrasting genetic clines, depending on the direction of divergent selection. If divergent selection acts in the same direction as the environmental gradient (cogradient settings), genetic clines are established and inflated by assortative mating. Conversely, under divergent selection of the same strength but acting in the opposite direction (countergradient selection), genetic clines are slightly constrained. We explored the consequences of these dynamics for population maladaptation, by monitoring pollen swamping. Depending on the direction of divergent selection with respect to the environmental gradient, pollen filtering owing to assortative mating either facilitates or impedes adaptation in peripheral populations.

  12. Turbulent-flow separation criteria for overexpanded supersonic nozzles

    NASA Technical Reports Server (NTRS)

    Morrisette, E. L.; Goldberg, T. J.

    1978-01-01

    A comprehensive compilation of available turbulent flow separation data for overexpanded supersonic nozzles is presented with a discussion of correlation techniques, and prediction methods. Data are grouped by nozzle types: conical, contoured, and two dimensional wedge. Correlation of conical nozzle separation is found to be independent of nozzle divergence half-angle above the 9 deg, whereas the contoured nozzle data follow a different correlation curve. Zero pressure gradient prediction techniques are shown to predict adequately the higher divergence angle conical separation data, and an empirical equation is given for the contoured nozzle data correlation. Flow conditions for which the correlations are invalid are discussed and bounded. A nozzle boundary layer transition criterion is presented which can be used to show that much of the noncorrelating data in the literature are concerned with nonturbulent separation and which explains the previously reported external flow effects on nozzle separation.

  13. Neutral and Adaptive Drivers of Microgeographic Genetic Divergence within Continuous Populations: The Case of the Neotropical Tree Eperua falcata (Aubl.)

    PubMed Central

    Brousseau, Louise; Foll, Matthieu; Scotti-Saintagne, Caroline; Scotti, Ivan

    2015-01-01

    Background In wild plant populations, genetic divergence within continuous stands is common, sometimes at very short geographical scales. While restrictions to gene flow combined with local inbreeding and genetic drift may cause neutral differentiation among subpopulations, microgeographical variations in environmental conditions can drive adaptive divergence through natural selection at some targeted loci. Such phenomena have recurrently been observed in plant populations occurring across sharp environmental boundaries, but the interplay between selective processes and neutral genetic divergence has seldom been studied. Methods We assessed the extent of within-stand neutral and environmentally-driven divergence in the Neotropical tree Eperua falcate Aubl. (Fabaceae) through a genome-scan approach. Populations of this species grow in dense stands that cross the boundaries between starkly contrasting habitats. Within-stand phenotypic and candidate-gene divergence have already been proven, making this species a suitable model for the study of genome-wide microgeographic divergence. Thirty trees from each of two habitats (seasonally flooded swamps and well-drained plateaus) in two separate populations were genotyped using thousands of AFLPs markers. To avoid genotyping errors and increase marker reliability, each sample was genotyped twice and submitted to a rigorous procedure for data cleaning, which resulted in 1196 reliable and reproducible markers. Results Despite the short spatial distances, we detected within-populations genetic divergence, probably caused by neutral processes, such as restrictions in gene flow. Moreover, habitat-structured subpopulations belonging to otherwise continuous stands also diverge in relation to environmental variability and habitat patchiness: we detected convincing evidence of divergent selection at the genome-wide level and for a fraction of the analyzed loci (comprised between 0.25% and 1.6%). Simulations showed that the levels of

  14. [Landscape classification: research progress and development trend].

    PubMed

    Liang, Fa-Chao; Liu, Li-Ming

    2011-06-01

    Landscape classification is the basis of the researches on landscape structure, process, and function, and also, the prerequisite for landscape evaluation, planning, protection, and management, directly affecting the precision and practicability of landscape research. This paper reviewed the research progress on the landscape classification system, theory, and methodology, and summarized the key problems and deficiencies of current researches. Some major landscape classification systems, e. g. , LANMAP and MUFIC, were introduced and discussed. It was suggested that a qualitative and quantitative comprehensive classification based on the ideology of functional structure shape and on the integral consideration of landscape classification utility, landscape function, landscape structure, physiogeographical factors, and human disturbance intensity should be the major research directions in the future. The integration of mapping, 3S technology, quantitative mathematics modeling, computer artificial intelligence, and professional knowledge to enhance the precision of landscape classification would be the key issues and the development trend in the researches of landscape classification.

  15. Buildings Interoperability Landscape

    SciTech Connect

    Hardin, Dave; Stephan, Eric G.; Wang, Weimin; Corbin, Charles D.; Widergren, Steven E.

    2015-12-31

    Through its Building Technologies Office (BTO), the United States Department of Energy’s Office of Energy Efficiency and Renewable Energy (DOE-EERE) is sponsoring an effort to advance interoperability for the integration of intelligent buildings equipment and automation systems, understanding the importance of integration frameworks and product ecosystems to this cause. This is important to BTO’s mission to enhance energy efficiency and save energy for economic and environmental purposes. For connected buildings ecosystems of products and services from various manufacturers to flourish, the ICT aspects of the equipment need to integrate and operate simply and reliably. Within the concepts of interoperability lie the specification, development, and certification of equipment with standards-based interfaces that connect and work. Beyond this, a healthy community of stakeholders that contribute to and use interoperability work products must be developed. On May 1, 2014, the DOE convened a technical meeting to take stock of the current state of interoperability of connected equipment and systems in buildings. Several insights from that meeting helped facilitate a draft description of the landscape of interoperability for connected buildings, which focuses mainly on small and medium commercial buildings. This document revises the February 2015 landscape document to address reviewer comments, incorporate important insights from the Buildings Interoperability Vision technical meeting, and capture thoughts from that meeting about the topics to be addressed in a buildings interoperability vision. In particular, greater attention is paid to the state of information modeling in buildings and the great potential for near-term benefits in this area from progress and community alignment.

  16. Divergent pathways lead to ESCRT-III-catalyzed membrane fission.

    PubMed

    Peel, Suman; Macheboeuf, Pauline; Martinelli, Nicolas; Weissenhorn, Winfried

    2011-04-01

    Endosomal sorting complexes required for transport (ESCRT) have been implicated in topologically similar but diverse cellular and pathological processes including multivesicular body (MVB) biogenesis, cytokinesis and enveloped virus budding. Although receptor sorting at the endosomal membrane producing MVBs employs the regulated assembly of ESCRT-0 followed by ESCRT-I, -II, -III and the vacuolar protein sorting (VPS)4 complex, other ESCRT-catalyzed processes require only a subset of complexes which commonly includes ESCRT-III and VPS4. Recent progress has shed light on the pathway of ESCRT assembly and highlights the separation of tasks of different ESCRT complexes and associated partners. The emerging picture suggests that among all ESCRT-catalyzed processes, divergent pathways lead to ESCRT-III assembly within the neck of a budding structure catalyzing membrane fission.

  17. NTC Learning System and Divergent Production

    ERIC Educational Resources Information Center

    Gojkov, Grozdanka; Rajovic, Ranko; Stojanovic, Aleksandar

    2015-01-01

    A short presentation of the basic findings of an explorative research, in which the possibility of encouraging the development of critical thinking with the NTC learning system was explored, i.e. only the results of its influence on the development of one aspect--divergent production are presented. This paper is a modest addition to the research…

  18. Scholarly Groups' Choices Yield Diverging Fortunes

    ERIC Educational Resources Information Center

    Berrett, Dan

    2012-01-01

    Scholarly groups have long served as hubs of academic life and the embodiments of their disciplines, but they face uncertain and divergent futures. Some disciplinary associations are struggling to remain relevant and financially viable as demographic and technological changes threaten their traditional sources of revenue. The core of their…

  19. Reinforcement and divergence under assortative mating.

    PubMed Central

    Kirkpatrick, M

    2000-01-01

    Traits that cause assortative mating such as the flowering time in plants and body size in animals can produce reproductive isolation between hybridizing populations. Can selection against unfit hybrids cause two populations to diverge in their mean values for these kinds of traits? Here I present a haploid analytical model of one population that receives gene flow from another. The partial pre-zygotic isolation between the two populations is caused by assortative mating for a trait that is influenced by any number of genes with additive effects. The post-zygotic isolation is caused by selection against genetic incompatibilities that can involve any form of selection on individual genes and gene combinations (epistasis). The analysis assumes that the introgression rate and selection coefficients are small. The results show that the assortment trait mean will not diverge from the immigrants unless there is direct selection on the trait favouring it to do so or there are genes of very large effect. The amount of divergence at equilibrium is determined by a balance between direct selection on the assortment trait and introgression from the other population. Additional selection against hybrid genetic incompatibilities reduces the effective migration rate and allows greater divergence. The role of assortment in speciation is discussed in the light of these results. PMID:11467428

  20. Divergence of Languages as Resources for Theorizing

    ERIC Educational Resources Information Center

    Nguyen, Thi Hong Nhung

    2017-01-01

    This paper investigates the potential of conceptual divergences within and between languages for providing intellectual resources for theorizing. Specifically, it explores the role of multilingual researchers in using the possibilities of the plurality of intellectual cultures and languages they have access to for theorizing International Service…

  1. Mitochondrial Replacement Techniques: Divergence in Global Policy.

    PubMed

    Schandera, Johanna; Mackey, Tim K

    2016-07-01

    In 2015, the UK became the first country permitting the clinical application of mitochondrial replacement techniques (MRT). Here, we explore how MRT have led to diverging international policy. In response, we recommend focused regulatory efforts coupled with United Nations (UN) leadership to build international consensus on the future of MRT.

  2. The Harmonic Series Diverges Again and Again

    ERIC Educational Resources Information Center

    Kifowit, Steven J.; Stamps, Terra A.

    2006-01-01

    The harmonic series is one of the most celebrated infinite series of mathematics. A quick glance at a variety of modern calculus textbooks reveals that there are two very popular proofs of the divergence of the harmonic series. In this article, the authors survey these popular proofs along with many other proofs that are equally simple and…

  3. Controversial Issues Confronting Special Education: Divergent Perspectives.

    ERIC Educational Resources Information Center

    Stainback, William; Stainback, Susan

    This book of 24 papers presents divergent views on 12 issues in special education: organizational strategies, classroom service delivery approaches, maximizing the talents and gifts of students, classification and labeling, assessment, instructional strategies, classroom management, collaboration/consultation, research practices, higher education,…

  4. Controversial Issues Confronting Special Education: Divergent Perspectives.

    ERIC Educational Resources Information Center

    Stainback, William; Stainback, Susan

    This book of 24 papers presents divergent views on 12 issues in special education: organizational strategies, classroom service delivery approaches, maximizing the talents and gifts of students, classification and labeling, assessment, instructional strategies, classroom management, collaboration/consultation, research practices, higher education,…

  5. Geographically multifarious phenotypic divergence during speciation

    PubMed Central

    Gompert, Zachariah; Lucas, Lauren K; Nice, Chris C; Fordyce, James A; Alex Buerkle, C; Forister, Matthew L

    2013-01-01

    Speciation is an important evolutionary process that occurs when barriers to gene flow evolve between previously panmictic populations. Although individual barriers to gene flow have been studied extensively, we know relatively little regarding the number of barriers that isolate species or whether these barriers are polymorphic within species. Herein, we use a series of field and lab experiments to quantify phenotypic divergence and identify possible barriers to gene flow between the butterfly species Lycaeides idas and Lycaeides melissa. We found evidence that L. idas and L. melissa have diverged along multiple phenotypic axes. Specifically, we identified major phenotypic differences in female oviposition preference and diapause initiation, and more moderate divergence in mate preference. Multiple phenotypic differences might operate as barriers to gene flow, as shown by correlations between genetic distance and phenotypic divergence and patterns of phenotypic variation in admixed Lycaeides populations. Although some of these traits differed primarily between species (e.g., diapause initiation), several traits also varied among conspecific populations (e.g., male mate preference and oviposition preference). PMID:23532669

  6. When does seed limitation matter for scaling up reforestation from patches to landscapes?

    PubMed

    Caughlin, T Trevor; Elliott, Stephen; Lichstein, Jeremy W

    2016-12-01

    Restoring forest to hundreds of millions of hectares of degraded land has become a centerpiece of international plans to sequester carbon and conserve biodiversity. Forest landscape restoration will require scaling up ecological knowledge of secondary succession from small-scale field studies to predict forest recovery rates in heterogeneous landscapes. However, ecological field studies reveal widely divergent times to forest recovery, in part due to landscape features that are difficult to replicate in empirical studies. Seed rain can determine reforestation rate and depends on landscape features that are beyond the scale of most field studies. We develop mathematical models to quantify how landscape configuration affects seed rain and forest regrowth in degraded patches. The models show how landscape features can alter the successional trajectories of otherwise identical patches, thus providing insight into why some empirical studies reveal a strong effect of seed rain on secondary succession, while others do not. We show that seed rain will strongly limit reforestation rate when patches are near a threshold for arrested succession, when positive feedbacks between tree canopy cover and seed rain occur during early succession, and when directed dispersal leads to between-patch interactions. In contrast, seed rain has weak effects on reforestation rate over a wide range of conditions, including when landscape-scale seed availability is either very high or very low. Our modeling framework incorporates growth and survival parameters that are commonly estimated in field studies of reforestation. We demonstrate how mathematical models can inform forest landscape restoration by allowing land managers to predict where natural regeneration will be sufficient to restore tree cover. Translating quantitative forecasts into spatially targeted interventions for forest landscape restoration could support target goals of restoring millions of hectares of degraded land and help

  7. Evolution of the SH3 Domain Specificity Landscape in Yeasts

    PubMed Central

    Gkourtsa, Areti; Avula, Teja; Landgraf, Christiane; Mancilla, Victor Tapia; Huber, Aline; Volkmer, Rudolf; Serrano, Luis; Hochstenbach, Frans; Distel, Ben

    2015-01-01

    To explore the conservation of Src homology 3 (SH3) domain-mediated networks in evolution, we compared the specificity landscape of these domains among four yeast species, Saccharomyces cerevisiae, Ashbya gossypii, Candida albicans, and Schizosaccharomyces pombe, encompassing 400 million years of evolution. We first aligned and catalogued the families of SH3-containing proteins in these four species to determine the relationships between homologous domains. Then, we tagged and purified all soluble SH3 domains (82 in total) to perform a quantitative peptide assay (SPOT) for each SH3 domain. All SPOT readouts were hierarchically clustered and we observed that the organization of the SH3 specificity landscape in three distinct profile classes remains conserved across these four yeast species. We also produced a specificity profile for each SH3 domain from manually aligned top SPOT hits and compared the within-family binding motif consensus. This analysis revealed a striking example of binding motif divergence in a C. albicans Rvs167 paralog, which cannot be explained by overall SH3 sequence or interface residue divergence, and we validated this specificity change with a yeast two-hybrid (Y2H) assay. In addition, we show that position-weighted matrices (PWM) compiled from SPOT assays can be used for binding motif screening in potential binding partners and present cases where motifs are either conserved or lost among homologous SH3 interacting proteins. Finally, by comparing pairwise SH3 sequence identity to binding profile correlation we show that for ~75% of all analyzed families the SH3 specificity profile was remarkably conserved over a large evolutionary distance. Thus, a high sequence identity within an SH3 domain family predicts conserved binding specificity, whereas divergence in sequence identity often coincided with a change in binding specificity within this family. As such, our results are important for future studies aimed at unraveling complex specificity

  8. Evolution of the SH3 Domain Specificity Landscape in Yeasts.

    PubMed

    Verschueren, Erik; Spiess, Matthias; Gkourtsa, Areti; Avula, Teja; Landgraf, Christiane; Mancilla, Victor Tapia; Huber, Aline; Volkmer, Rudolf; Winsor, Barbara; Serrano, Luis; Hochstenbach, Frans; Distel, Ben

    2015-01-01

    To explore the conservation of Src homology 3 (SH3) domain-mediated networks in evolution, we compared the specificity landscape of these domains among four yeast species, Saccharomyces cerevisiae, Ashbya gossypii, Candida albicans, and Schizosaccharomyces pombe, encompassing 400 million years of evolution. We first aligned and catalogued the families of SH3-containing proteins in these four species to determine the relationships between homologous domains. Then, we tagged and purified all soluble SH3 domains (82 in total) to perform a quantitative peptide assay (SPOT) for each SH3 domain. All SPOT readouts were hierarchically clustered and we observed that the organization of the SH3 specificity landscape in three distinct profile classes remains conserved across these four yeast species. We also produced a specificity profile for each SH3 domain from manually aligned top SPOT hits and compared the within-family binding motif consensus. This analysis revealed a striking example of binding motif divergence in a C. albicans Rvs167 paralog, which cannot be explained by overall SH3 sequence or interface residue divergence, and we validated this specificity change with a yeast two-hybrid (Y2H) assay. In addition, we show that position-weighted matrices (PWM) compiled from SPOT assays can be used for binding motif screening in potential binding partners and present cases where motifs are either conserved or lost among homologous SH3 interacting proteins. Finally, by comparing pairwise SH3 sequence identity to binding profile correlation we show that for ~75% of all analyzed families the SH3 specificity profile was remarkably conserved over a large evolutionary distance. Thus, a high sequence identity within an SH3 domain family predicts conserved binding specificity, whereas divergence in sequence identity often coincided with a change in binding specificity within this family. As such, our results are important for future studies aimed at unraveling complex specificity

  9. A Novel Acetivibrio cellulolyticus Anchoring Scaffoldin That Bears Divergent Cohesins

    PubMed Central

    Xu, Qi; Barak, Yoav; Kenig, Rina; Shoham, Yuval; Bayer, Edward A.; Lamed, Raphael

    2004-01-01

    Sequencing of a cellulosome-integrating gene cluster in Acetivibrio cellulolyticus was completed. The cluster contains four tandem scaffoldin genes (scaA, scaB, scaC, and scaD) bounded upstream and downstream, respectively, by a presumed cellobiose phosphorylase and a nucleotide methylase. The sequences and properties of scaA, scaB, and scaC were reported previously, and those of scaD are reported here. The scaD gene encodes an 852-residue polypeptide that includes a signal peptide, three cohesins, and a C-terminal S-layer homology (SLH) module. The calculated molecular weight of the mature ScaD is 88,960; a 67-residue linker segment separates cohesins 1 and 2, and two ∼30-residue linkers separate cohesin 2 from 3 and cohesin 3 from the SLH module. The presence of an SLH module in ScaD indicates its role as an anchoring protein. The first two ScaD cohesins can be classified as type II, similar to the four cohesins of ScaB. Surprisingly, the third ScaD cohesin belongs to the type I cohesins, like the seven ScaA cohesins. ScaD is the first scaffoldin to be described that contains divergent types of cohesins as integral parts of the polypeptide chain. The recognition properties among selected recombinant cohesins and dockerins from the different scaffoldins of the gene cluster were investigated by affinity blotting. The results indicated that the divergent types of ScaD cohesins also differ in their preference of dockerins. ScaD thus plays a dual role, both as a primary scaffoldin, capable of direct incorporation of a single dockerin-borne enzyme, and as a secondary scaffoldin that anchors the major primary scaffoldin, ScaA and its complement of enzymes to the cell surface. PMID:15317783

  10. Cuticular hydrocarbon divergence in the jewel wasp Nasonia: Evolutionary shifts in chemical communication channels?

    PubMed Central

    Buellesbach, Jan; Gadau, Jürgen; Beukeboom, Leo W.; Echinger, Felix; Raychoudhury, Rhitoban; Werren, John H.; Schmitt, Thomas

    2013-01-01

    The evolution and maintenance of intraspecific communication channels constitutes a key feature of chemical signaling and sexual communication. However, how divergent chemical communication channels evolve while maintaining their integrity for both sender and receiver is poorly understood. In the present study, we compare male and female cuticular hydrocarbon (CHC) profiles in the jewel wasp genus Nasonia, analyze their chemical divergence, and investigate their role as species-specific sexual signaling cues. Males and females of all four Nasonia species showed unique, non-overlapping CHC profiles unambiguously separating them. Surprisingly, male and female phylogenies based on the chemical distances between their CHC profiles differed dramatically, where only male CHC divergence parallels the molecular phylogeny of Nasonia. In particular, N. giraulti female CHC profiles were the most divergent from all other species and very different from its most closely related sibling species N. oneida. Furthermore, although our behavioural assays indicate that female CHC can generally be perceived as sexual cues attracting males in Nasonia, this function has apparently been lost in the highly divergent female N. giraulti CHC profiles. Curiously, N. giraulti males are still attracted to heterospecific, but not to conspecific female CHC profiles. We suggest that this striking discrepancy has been caused by an extensive evolutionary shift in female N. giraulti CHC profiles, which are no longer used as conspecific recognition cues. Our study constitutes the first report of an apparent abandonment of a sexual recognition cue that the receiver did not adapt to. PMID:24118588

  11. Proteome-wide analysis of functional divergence in bacteria: exploring a host of ecological adaptations.

    PubMed

    Caffrey, Brian E; Williams, Tom A; Jiang, Xiaowei; Toft, Christina; Hokamp, Karsten; Fares, Mario A

    2012-01-01

    Functional divergence is the process by which new genes and functions originate through the modification of existing ones. Both genetic and environmental factors influence the evolution of new functions, including gene duplication or changes in the ecological requirements of an organism. Novel functions emerge at the expense of ancestral ones and are generally accompanied by changes in the selective forces at constrained protein regions. We present software capable of analyzing whole proteomes, identifying putative amino acid replacements leading to functional change in each protein and performing statistical tests on all tabulated data. We apply this method to 750 complete bacterial proteomes to identify high-level patterns of functional divergence and link these patterns to ecological adaptations. Proteome-wide analyses of functional divergence in bacteria with different ecologies reveal a separation between proteins involved in information processing (Ribosome biogenesis etc.) and those which are dependent on the environment (energy metabolism, defense etc.). We show that the evolution of pathogenic and symbiotic bacteria is constrained by their association with the host, and also identify unusual events of functional divergence even in well-studied bacteria such as Escherichia coli. We present a description of the roles of phylogeny and ecology in functional divergence at the level of entire proteomes in bacteria.

  12. Landscape characterization and biodiversity research

    SciTech Connect

    Dale, V.H.; Offerman, H.; Frohn, R.; Gardner, R.H.

    1995-03-01

    Rapid deforestation often produces landscape-level changes in forest characteristics and structure, including area, distribution, and forest habitat types. Changes in landscape pattern through fragmentation or aggregation of natural habitats can alter patterns of abundance for single species and entire communities. Examples of single-species effects include increased predation along the forest edge, the decline in the number of species with poor dispersal mechanisms, and the spread of exotic species that have deleterious effects (e.g., gypsy moth). A decrease in the size and number of natural habitat patches increases the probability of local extirpation and loss of diversity of native species, whereas a decline in connectivity between habitat patches can negatively affect species persistence. Thus, there is empirical justification for managing entire landscapes, not just individual habitat types, in order to insure that native plant and animal diversity is maintained. A landscape is defined as an area composed of a mosaic of interacting ecosystems, or patches, with the heterogeneity among the patches significantly affecting biotic and abiotic processes in the landscape. Patches comprising a landscape are usually composed of discrete areas of relatively homogeneous environmental conditions and must be defined in terms of the organisms of interest. A large body of theoretical work in landscape ecology has provided a wealth of methods for quantifying spatial characteristics of landscapes. Recent advances in remote sensing and geographic information systems allow these methods to be applied over large areas. The objectives of this paper are to present a brief overview of common measures of landscape characteristics, to explore the new technology available for their calculation, to provide examples of their application, and to call attention to the need for collection of spatially-explicit field data.

  13. Comparing the folding and misfolding energy landscapes of phosphoglycerate kinase.

    PubMed

    Agócs, Gergely; Szabó, Bence T; Köhler, Gottfried; Osváth, Szabolcs

    2012-06-20

    Partitioning of polypeptides between protein folding and amyloid formation is of outstanding pathophysiological importance. Using yeast phosphoglycerate kinase as model, here we identify the features of the energy landscape that decide the fate of the protein: folding or amyloidogenesis. Structure formation was initiated from the acid-unfolded state, and monitored by fluorescence from 10 ms to 20 days. Solvent conditions were gradually shifted between folding and amyloidogenesis, and the properties of the energy landscape governing structure formation were reconstructed. A gradual transition of the energy landscape between folding and amyloid formation was observed. In the early steps of both folding and misfolding, the protein searches through a hierarchically structured energy landscape to form a molten globule in a few seconds. Depending on the conditions, this intermediate either folds to the native state in a few minutes, or forms amyloid fibers in several days. As conditions are changed from folding to misfolding, the barrier separating the molten globule and native states increases, although the barrier to the amyloid does not change. In the meantime, the native state also becomes more unstable and the amyloid more stable. We conclude that the lower region of the energy landscape determines the final protein structure. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  14. Field dynamics and tunneling in a flux landscape

    SciTech Connect

    Johnson, Matthew C.; Larfors, Magdalena

    2008-10-15

    We investigate field dynamics and tunneling between metastable minima in a landscape of type IIB flux compactifications, utilizing monodromies of the complex structure moduli space to continuously connect flux vacua. After describing the generic features of a flux-induced potential for the complex structure and type IIB axiodilaton, we specialize to the mirror quintic Calabi-Yau to obtain an example landscape. Studying the cosmological dynamics of the complex structure moduli, we find that the potential generically does not support slow-roll inflation and that in general the landscape separates neatly into basins of attraction of the various minima. We then discuss tunneling, with the inclusion of gravitational effects, in many-dimensional field spaces. A set of constraints on the form of the Euclidean paths through field space are presented, and then applied to construct approximate instantons mediating the transition between de Sitter vacua in the flux landscape. We find that these instantons are generically thick wall and that the tunneling rate is suppressed in the large-volume limit. We also consider examples where supersymmetry is not broken by fluxes, in which case near-Bogomolnyi-Prasad-Sommerfeld thin-wall bubbles can be constructed. We calculate the bubble-wall tension, finding that it scales like a D- or NS-brane bubble, and comment on the implications of this correspondence. Finally, we present a brief discussion of eternal inflation in the flux landscape.

  15. Decision making on fitness landscapes

    NASA Astrophysics Data System (ADS)

    Arthur, R.; Sibani, P.

    2017-04-01

    We discuss fitness landscapes and how they can be modified to account for co-evolution. We are interested in using the landscape as a way to model rational decision making in a toy economic system. We develop a model very similar to the Tangled Nature Model of Christensen et al. that we call the Tangled Decision Model. This is a natural setting for our discussion of co-evolutionary fitness landscapes. We use a Monte Carlo step to simulate decision making and investigate two different decision making procedures.

  16. How soil shapes the landscape

    NASA Astrophysics Data System (ADS)

    Minasny, Budiman; Finke, Peter; Vanwalleghem, Tom Tom; Stockmann, Uta; McBratney, Alex

    2014-05-01

    There has been an increase in interest in quantitative modelling of soil genesis, which can provide prediction of environmental changes through numerical models. Modelling soil formation is a difficult task because soil itself is highly complex with interactions between water, inorganic materials and organic matter. This paper will provide a review on the research efforts of modelling soil genesis, their connection with landscape models and the inexorable genesis of the IUSS soil landscape modelling working group. Quantitative modelling soil formation using mechanistic models have begun in the 1980s such as the 'soil deficit' model by Kirkby (1985), Hoosbeek & Bryant's pedodynamic model (1992), and recently the SoilGen model by Finke (2008). These profile models considered the chemical reactions and physical processes in the soil at the horizon and pedon scale. The SoilGen model is an integration of sub-models, such as water and solute movement, heat transport, soil organic matter decomposition, mineral dissolution, ion exchange, adsorption, speciation, complexation and precipitation. The model can calculate with detail the chemical changes and materials fluxes in a profile and has been successfully applied. While they can simulate soil profile development in detail, there is still a gap how the processes act in the landscape. Meanwhile research in landscape formation in geomorphology is progressing steadily over time, slope development models model have been developed since 1970s (Ahnert, 1977). Soil was also introduced in a landscape, however soil processes are mainly modelled through weathering and transport processes (Minasny & McBratney 1999, 2001). Recently, Vanwalleghem et al. (2013) are able to combine selected physical, chemical and biological processes to simulate a full 3-D soil genesis in the landscape. Now there are research gaps between the 2 approaches: the landscape modellers increasingly recognise the importance of soil and need more detailed soil

  17. Connecting Brabant's cover sand landscapes through landscape history

    NASA Astrophysics Data System (ADS)

    Heskes, Erik; van den Ancker, Hanneke; Jungerius, Pieter Dirk; Harthoorn, Jaap; Maes, Bert; Leenders, Karel; de Jongh, Piet; Kluiving, Sjoerd; van den Oetelaar, Ger

    2015-04-01

    Noord-Brabant has the largest variety of cover sand landscapes in The Netherlands, and probably in Western Europe. During the Last Ice Age the area was not covered by land ice and a polar desert developed in which sand dunes buried the existing river landscapes. Some of these polar dune landscapes experienced a geomorphological and soil development that remained virtually untouched up to the present day, such as the low parabolic dunes of the Strabrechtse Heide or the later and higher dunes of the Oisterwijkse Vennen. As Noord-Brabant lies on the fringe of a tectonic basin, the thickness of cover sand deposits in the Centrale Slenk, part of a rift through Europe, amounts up to 20 metres. Cover sand deposits along the fault lines cause the special phenomenon of 'wijst' to develop, in which the higher grounds are wetter than the boarding lower grounds. Since 4000 BC humans settled in these cover sand landscapes and made use of its small-scale variety. An example are the prehistoric finds on the flanks and the historic towns on top of the 'donken' in northwest Noord-Brabant, where the cover sand landscapes are buried by river and marine deposits and only the peaks of the dunes protrude as donken. Or the church of Handel that is built beside a 'wijst' source and a site of pilgrimage since living memory. Or the 'essen' and plaggen agriculture that developed along the stream valleys of Noord-Brabant from 1300 AD onwards, giving rise to geomorphological features as 'randwallen' and plaggen soils of more than a metre thickness. Each region of Brabant each has its own approach in attracting tourists and has not yet used this common landscape history to connect, manage and promote their territories. We propose a landscape-historical approach to develop a national or European Geopark Brabants' cover sand landscapes, in which each region focuses on a specific part of the landscape history of Brabant, that stretches from the Late Weichselian polar desert when the dune

  18. An experimental investigation of velocity fields in divergent glottal models of the human vocal tract

    NASA Astrophysics Data System (ADS)

    Erath, Byron D.; Plesniak, Michael W.

    2005-09-01

    In speech, sound production arises from fluid-structure interactions within the larynx as well as viscous flow phenomena that is most likely to occur during the divergent orientation of the vocal folds. Of particular interest are the flow mechanisms that influence the location of flow separation points on the vocal folds walls. Physiologically scaled pulsatile flow fields in 7.5 times real size static divergent glottal models were investigated. Three divergence angles were investigated using phase-averaged particle image velocimetry (PIV). The pulsatile glottal jet exhibited a bi-modal stability toward both glottal walls, although there was a significant amount of variance in the angle the jet deflected from the midline. The attachment of the Coanda effect to the glottal model walls occurred when the pulsatile velocity was a maximum, and the acceleration of the waveform was zero. The location of the separation and reattachment points of the flow from the glottal models was a function of the velocity waveform and divergence angle. Acoustic analogies show that a dipole sound source contribution arising from the fluid interaction (Coanda jet) with the vocal fold walls is expected. [Work funded by NIH Grant RO1 DC03577.

  19. An experimentally informed evolutionary model improves phylogenetic fit to divergent lactamase homologs.

    PubMed

    Bloom, Jesse D

    2014-10-01

    Phylogenetic analyses of molecular data require a quantitative model for how sequences evolve. Traditionally, the details of the site-specific selection that governs sequence evolution are not known a priori, making it challenging to create evolutionary models that adequately capture the heterogeneity of selection at different sites. However, recent advances in high-throughput experiments have made it possible to quantify the effects of all single mutations on gene function. I have previously shown that such high-throughput experiments can be combined with knowledge of underlying mutation rates to create a parameter-free evolutionary model that describes the phylogeny of influenza nucleoprotein far better than commonly used existing models. Here, I extend this work by showing that published experimental data on TEM-1 beta-lactamase (Firnberg E, Labonte JW, Gray JJ, Ostermeier M. 2014. A comprehensive, high-resolution map of a gene's fitness landscape. Mol Biol Evol. 31:1581-1592) can be combined with a few mutation rate parameters to create an evolutionary model that describes beta-lactamase phylogenies much better than most common existing models. This experimentally informed evolutionary model is superior even for homologs that are substantially diverged (about 35% divergence at the protein level) from the TEM-1 parent that was the subject of the experimental study. These results suggest that experimental measurements can inform phylogenetic evolutionary models that are applicable to homologs that span a substantial range of sequence divergence.

  20. Megafans and Trumpeter Bird Biodiversity-Psophia Phylogeography and Landscape Evolution in Amazonia

    NASA Technical Reports Server (NTRS)

    Wilkinson, Justin

    2014-01-01

    Based on geomorphic character and mapped geology, geologists have interpreted the landscape surrounding the Andes Mountains as becoming progressively younger to the East. These sedimentary materials filled the late Miocene swampland that formerly occupied central and western Amazonia. Apart from the ancient landscapes of the Guiana Highlands (top right, figure 1a), Zone Ac is the oldest, followed by Zone Aw, within which megafan Jw is older than megafan Je (figure 1a). DNA-based paleogeography of the trumpeters shows that younger clades diverge from parent lineages with increasing distance from the Andes chain. Thus, Psophia napensis diverges from the P. crepitans parent, and P. ochroptera diverges from P. napensis. The P. ochroptera population is confined solely to the Je megafan (figure 1a). The same trend is seen on the south side of the Amazon depression. Since the timing of the events seems to be of exactly the same order [post-Miocene for the land surfaces and trumpeter divergence within the last 3 million years (figure 1d)], it seems reasonable to think that the megafans provided the substrate on which new bird lineages could speciate. Such physical controls of evolution are becoming more important in the understanding of biodiversity.

  1. Effects of landscape composition on edge-sensitive songbirds in a forest-dominated landscape

    SciTech Connect

    McRae, B.

    1995-12-31

    Thirty-eight mature upland forest stands in the Nicolet National Forest were selected to study relationships between abundances of edge-sensitive forest birds within the stands and patterning of vegetation types surrounding the stands. Ten indicator species were examined, and three years of point count data from the Nicolet National Forest Bird Survey formed the basis of the study. Three separate habitat maps were created to quantify landscape structural characteristics in a geographic information system (GIS); the first was compiled from existing vegetation inventory maps maintained by the Nicolet National Forest, the second was based on a Landsat Thematic Mapper satellite image classification, and the third was based on a combination of the first two habitat maps. Abundance of individuals in the indicator species group was related to statistical metrics of landscape pattern and proportions of habitat types surrounding the sites using multiple regression. Best subsets of variables to explain variation in total bird abundance were selected. Relationships between individual species abundances and landscape and site vegetation variables were also examined using univariate tests. The combined habitat mapping method provided the best regression model of songbird abundance, and relationships given by this model were consistent across all species.

  2. Identification of scenically preferred forest landscapes

    Treesearch

    Roberta C. Patey; Richard M. Evans

    1979-01-01

    This study identified manipulated forest landscapes with a low understory shrub density as being esthetic-ally preferred over non-manipulated, dense understory landscapes. This landscape pattern was identified both qualitatively, by preference ratings of respondents, and quantitatively, by measuring the physical components of each landscape. Forest sites were selected...

  3. Landscape genomics: A brief perspective [Chapter 9

    Treesearch

    Michael K. Schwartz; Gordon Luikart; Kevin S. McKelvey; Samuel A. Cushman

    2010-01-01

    Landscape genetics is the amalgamation of population genetics and landscape ecology (see Manel et al. 2003; Storfer et al. 2007). In Chapter 17, we discuss landscape genetics and provide two examples of applications in the area of modeling population connectivity and inferring fragmentation. These examples, like virtually all extant landscape genetic analyses, were...

  4. Nested Levels of Adaptive Divergence: The Genetic Basis of Craniofacial Divergence and Ecological Sexual Dimorphism

    PubMed Central

    Parsons, Kevin J.; Wang, Jason; Anderson, Graeme; Albertson, R. Craig

    2015-01-01

    Exemplary systems for adaptive divergence are often characterized by their large degrees of phenotypic variation. This variation represents the outcome of generations of diversifying selection. However, adaptive radiations can also contain a hierarchy of differentiation nested within them where species display only subtle phenotypic differences that still have substantial effects on ecology, function, and ultimately fitness. Sexual dimorphisms are also common in species displaying adaptive divergence and can be the result of differential selection between sexes that produce ecological differences between sexes. Understanding the genetic basis of subtle variation (between certain species or sexes) is therefore important for understanding the process of adaptive divergence. Using cichlids from the dramatic adaptive radiation of Lake Malawi, we focus on understanding the genetic basis of two aspects of relatively subtle phenotypic variation. This included a morphometric comparison of the patterns of craniofacial divergence between two ecologically similar species in relation to the larger adaptive radiation of Malawi, and male–female morphological divergence between their F2 hybrids. We then genetically map craniofacial traits within the context of sex and locate several regions of the genome that contribute to variation in craniofacial shape that is relevant to sexual dimorphism within species and subtle divergence between closely related species, and possibly to craniofacial divergence in the Malawi radiation as a whole. To enhance our search for candidate genes we take advantage of population genomic data and a genetic map that is anchored to the cichlid genome to determine which genes within our QTL regions are associated with SNPs that are alternatively fixed between species. This study provides a holistic understanding of the genetic underpinnings of adaptive divergence in craniofacial shape. PMID:26038365

  5. Simulating historical landscape dynamics using the landscape fire succession model LANDSUM version 4.0

    Treesearch

    Robert E. Keane; Lisa M. Holsinger; Sarah D. Pratt

    2006-01-01

    The range and variation of historical landscape dynamics could provide a useful reference for designing fuel treatments on today's landscapes. Simulation modeling is a vehicle that can be used to estimate the range of conditions experienced on historical landscapes. A landscape fire succession model called LANDSUMv4 (LANDscape SUccession Model version 4.0) is...

  6. Studying Landforms through Landscape Painting.

    ERIC Educational Resources Information Center

    Glenn, William H.

    1981-01-01

    Using three specific works of art, the author demonstrates how a study of selected landscape paintings can be integrated into units on landforms in secondary school earth science and general science courses. (Author/SJL)

  7. Economic Growth and Landscape Change

    USGS Publications Warehouse

    Prato, Tony; Fagre, Dan

    2007-01-01

    Sustaining Rocky Mountain Landscapes provides a scientific basis for communities to develop policies for managing the growth and economic transformation of the CCE without sacrificing the quality of life and environment for which the land is renowned. This forthcoming edited volume focuses on five aspects of sustaining mountain landscapes in the CCE and similar regions in the Rocky Mountains. The five aspects are: 1) how social, economic, demographic and environmental forces are transforming ecosystem structure and function, 2) trends in use and conditions for human and environmental resources, 3) activating science, policy and education to enhance sustainable landscape management, 4) challenges to sustainable management of public and private lands, and 5) future prospects for achieving sustainable landscapes.

  8. Accidental inflation in the landscape

    NASA Astrophysics Data System (ADS)

    Blanco-Pillado, Jose J.; Gomez-Reino, Marta; Metallinos, Konstantinos

    2013-02-01

    We study some aspects of fine tuning in inflationary scenarios within string theory flux compactifications and, in particular, in models of accidental inflation. We investigate the possibility that the apparent fine-tuning of the low energy parameters of the theory needed to have inflation can be generically obtained by scanning the values of the fluxes over the landscape. Furthermore, we find that the existence of a landscape of eternal inflation in this model provides us with a natural theory of initial conditions for the inflationary period in our vacuum. We demonstrate how these two effects work in a small corner of the landscape associated with the complex structure of the Calabi-Yau manifold P4[1,1,1,6,9] by numerically investigating the flux vacua of a reduced moduli space. This allows us to obtain the distribution of observable parameters for inflation in this mini-landscape directly from the fluxes.

  9. LANDSCAPE CORRELATES TO ESTUARINE CONDITION

    EPA Science Inventory

    Estuaries are important transition zones between land and sea, yet little is known about how landscapes influence these systems. Using broad scale Environmental Monitoring and Assessment Program (EMAP) data collected in small estuaries of the Virginian Biogeographic Province, w...

  10. Greenhouse warming and landscape care

    Treesearch

    Kevin T. Smith

    2009-01-01

    Climate change is one of the few truly planetary processes that influence the assessments and actions of governments and of everyday citizens. Principles and practices of ecological landscaping fit well with concern about hte effects of climate change.

  11. LANDSCAPE CORRELATES TO ESTUARINE CONDITION

    EPA Science Inventory

    Estuaries are important transition zones between land and sea, yet little is known about how landscapes influence these systems. Using broad scale Environmental Monitoring and Assessment Program (EMAP) data collected in small estuaries of the Virginian Biogeographic Province, w...

  12. Energy landscapes for machine learning.

    PubMed

    Ballard, Andrew J; Das, Ritankar; Martiniani, Stefano; Mehta, Dhagash; Sagun, Levent; Stevenson, Jacob D; Wales, David J

    2017-04-03

    Machine learning techniques are being increasingly used as flexible non-linear fitting and prediction tools in the physical sciences. Fitting functions that exhibit multiple solutions as local minima can be analysed in terms of the corresponding machine learning landscape. Methods to explore and visualise molecular potential energy landscapes can be applied to these machine learning landscapes to gain new insight into the solution space involved in training and the nature of the corresponding predictions. In particular, we can define quantities analogous to molecular structure, thermodynamics, and kinetics, and relate these emergent properties to the structure of the underlying landscape. This Perspective aims to describe these analogies with examples from recent applications, and suggest avenues for new interdisciplinary research.

  13. Accidental inflation in the landscape

    SciTech Connect

    Blanco-Pillado, Jose J.; Metallinos, Konstantinos; Gomez-Reino, Marta E-mail: marta.gomez-reino.perez@cern.ch

    2013-02-01

    We study some aspects of fine tuning in inflationary scenarios within string theory flux compactifications and, in particular, in models of accidental inflation. We investigate the possibility that the apparent fine-tuning of the low energy parameters of the theory needed to have inflation can be generically obtained by scanning the values of the fluxes over the landscape. Furthermore, we find that the existence of a landscape of eternal inflation in this model provides us with a natural theory of initial conditions for the inflationary period in our vacuum. We demonstrate how these two effects work in a small corner of the landscape associated with the complex structure of the Calabi-Yau manifold P{sup 4}{sub [1,1,1,6,9]} by numerically investigating the flux vacua of a reduced moduli space. This allows us to obtain the distribution of observable parameters for inflation in this mini-landscape directly from the fluxes.

  14. Planetary landscape: a new synthesis

    NASA Astrophysics Data System (ADS)

    Hargitai, H.

    The elements that build up a landscape on Earth consists of natural (biogenic and abiogenic - lithologic, atmospheric, hydrologic) and artificial (antropogenic) factors. Landscape is a complex system of these different elements, which interact with one another. For example the same lithology makes different landscapes under different climatic conditions. If the same conditions are present, the same landscape type will appear. The mosaic of ecotopes (topical) units, which are the system of homogenous caharacteristic areas of various geotopes makes up different level geochores (chorical unit). Geochores build up a hierarchic system and cover the whole surface.On Earth, landscapes can be qualified according to their characteristics: relief forms (morphology), and its potential economic value. Aesthetic and subjective parameters can also be considered especially when speaking of a residental area. We now propose the determination of "planetary landscape sets" which can potentially occur on the solid surface of a planetary body during its lifetime. This naturally includes landscapes of the present state of planetary bodies and also paleolandscapes from the past of planets, including Earth. Landscapes occur in the boundary of the planets solid and not solid sphere that is on the solid-vacuum, the solid - gas and on the solid - liquid boundary. Thinking this way a landscape can occurs on the ocean floor as well. We found that for the determination of a planetary landscape system, we can use the experiences from the making of the terminology and nomenclature system of Earth undersea topography. [1] The nomenclature system and the terminology used by astrogeologists could be revised. Common names of features should be defined (nova, tessera, volcano, tholus, lobate ejecta crater etc) with a type example for each. A well defined hierarchy for landscape types should be defined. The Moon is the best example, since it uses many names that originates from the 17th century, mixed

  15. Wall Pressure Measurements in a Convergent-Divergent Nozzle with Varying Inlet Asymmetry

    NASA Astrophysics Data System (ADS)

    Senthilkumar, C.; Elangovan, S.; Rathakrishnan, E.

    2016-06-01

    In this paper, flow separation of a convergent-divergent (C-D) nozzle is placed downstream of a supersonic flow delivered from Mach 2.0 nozzle is investigated. Static pressure measurements are conducted using pressure taps. The flow characteristics of straight and slanted entry C-D nozzle are investigated for various NPR of Mach 2.0 nozzle. The effect of asymmetry at inlet by providing 15°, 30°, 45° and 57° cut is analyzed. Particular attention is given to the location of the shock within the divergent section of the test nozzle. This location is examined as a function both NPR of Mach 2.0 nozzle and test nozzle inlet angle. Some of the measurements are favorably compared to previously developed theory. A Mach number ratio of 0.81 across the flow separation region was obtained.

  16. Landscapes of the Digital Baroque.

    PubMed

    Singh, Gary

    2016-01-01

    Alvaro Ocampo traversed many landscapes to arrive at his current space in the digital art landscape. Eventually, the artist then made his way to the digital world, where he is no longer subjected to the tyranny of the one-off. He believes digital art is the new version of traditional etching in the way that it eliminates the idea of the one original piece of art.

  17. Protein evolution on rugged landscapes.

    PubMed Central

    Macken, C A; Perelson, A S

    1989-01-01

    We analyze a mathematical model of protein evolution in which the evolutionary process is viewed as hill-climbing on a random fitness landscape. In studying the structure of such landscapes, we note that a large number of local optima exist, and we calculate the time and number of mutational changes until a protein gets trapped at a local optimum. Such a hill-climbing process may underlie the evolution of antibody molecules by somatic hypermutation. PMID:2762321

  18. PNW Hydrologic Landscape Class

    EPA Pesticide Factsheets

    Work has been done to expand the hydrologic landscapes (HLs) concept and to develop an approach for using it to address streamflow vulnerability from climate change. This work has included development of the HL classification framework and its application to Oregon, use of the HL classes to predict where a simple lumped hydrologic model accurately predicts daily streamflow, use of HL information to model the presence of cold-water patches at tributary confluences, and combining Oregon HL results with temperature and precipitation predictions to examine how HLs would vary as a result of climate change. As a part of the current work, the HL approach has been expanded to the Pacific Northwest (Oregon, Washington, and Idaho) based on a revision of the approach that makes it more broadly applicable. This revised approach has several advantages compared with the original approach: it is not limited to areas that have an aquifer permeability map; it uses a flexible approach to converting a nationally available geospatial dataset into assessment units; and it is more robust. These improvements should allow the revised HL approach to be applied more often in situations requiring hydrologic classification, and allow greater confidence in results. This effort paves the way for a climate change analysis for the Pacific Northwest that is currently underway, as well as expansion into the southwest (California, Arizona, and Nevada). This dataset contains a high resolutio

  19. Embryogenesis of Artificial Landscapes

    NASA Astrophysics Data System (ADS)

    Ashlock, Daniel; Gent, Stephen; Bryden, Kenneth

    This chapter examines the artificial embryogeny of landscapes intended for use with virtual reality which consist of collections of polygons encoded using L-systems. Artificial Embryogeny is the study of indirect representations. A recent survey that attempts to classify different types of artificial embryogeny appears in [18]. A representation is a way of encoding a model or a solution to a problem for use in computation. For example, an array of n real numbers is a representation of the value of a function in n variables. A representation is indirect if it gives a set of directions for constructing the thing it specifies rather than encoding the object directly. The process of following the directions given in the indirect representation to obtain the final object is called expression. Indirect representations require an interpreter to express them and, because of this, are more difficult to understand at the specification or genetic level. There are number of advantages to indirect representations that more than balance this genetic obscurity in many situations. The most general of these advantages is that the transformation from the indirect specification to the final model or solution can incorporate heuristics and domain knowledge. This permits a search of a genetic space that is far smaller than the space in which the expressed objects reside and has a much higher average quality. Another advantage, showcased in this chapter, is compactness of representation. The indirect representations we evolve in this chapter use a few hundred bytes to specify megabyte-sized collections of polygons.

  20. PSEUDO-CODEWORD LANDSCAPE

    SciTech Connect

    CHERTKOV, MICHAEL; STEPANOV, MIKHAIL

    2007-01-10

    The authors discuss performance of Low-Density-Parity-Check (LDPC) codes decoded by Linear Programming (LP) decoding at moderate and large Signal-to-Noise-Ratios (SNR). Frame-Error-Rate (FER) dependence on SNR and the noise space landscape of the coding/decoding scheme are analyzed by a combination of the previously introduced instanton/pseudo-codeword-search method and a new 'dendro' trick. To reduce complexity of the LP decoding for a code with high-degree checks, {ge} 5, they introduce its dendro-LDPC counterpart, that is the code performing identifically to the original one under Maximum-A-Posteriori (MAP) decoding but having reduced (down to three) check connectivity degree. Analyzing number of popular LDPC codes and their dendro versions performing over the Additive-White-Gaussian-Noise (AWGN) channel, they observed two qualitatively different regimes: (i) error-floor sets early, at relatively low SNR, and (ii) FER decays with SNR increase faster at moderate SNR than at the largest SNR. They explain these regimes in terms of the pseudo-codeword spectra of the codes.

  1. Titan Polar Landscape Evolution

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.

    2016-01-01

    With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

  2. Landscape Visualisation on the Internet

    NASA Astrophysics Data System (ADS)

    Imhof, M. P.; Cox, M. T.; Harvey, D. W.; Heemskerk, G. E.; Pettit, C. J.

    2012-07-01

    The Victorian Resources Online (VRO) website (http://www.dpi.vic.gov.au/vro) is the principal means for accessing landscapebased information in Victoria. In this paper we introduce a range of online landscape visualisations that have been developed to enhance existing static web content around the nature and distribution of Victoria's landforms and soils as well as associated processes. Flash is used to develop online visualisations that include interactive landscape panoramas, animations of soil and landscape processes and videos of experts explaining features in the field as well as landscape "flyovers". The use of interactive visualisations adds rich information multimedia content to otherwise static pages and offers the potential to improve user's appreciation and understanding of soil and landscapes. Visualisation is becoming a key component of knowledge management activities associated with VRO - proving useful for both "knowledge capture" (from subject matter specialists) and "knowledge transfer" to a diverse user base. A range of useful visualisation products have been made available online, with varying degrees of interactivity and suited to a variety of users. The use of video files, animation and interactive visualisations is adding rich information content to otherwise static web pages. These information products offer new possibilities to enhance learning of landscapes and the effectiveness of these will be tested as the next phase of development.

  3. Hiking Over Quantum Control Landscapes

    NASA Astrophysics Data System (ADS)

    Rabitz, Herschel

    2008-03-01

    Seeking the best control over a posed quantum dynamic objective entails climbing over the associated control landscape, which is defined as the quantum mechanical observable as a function of the controls. The topology and general structure of quantum control landscapes as input output maps dictate the final attainable yield, the efficiency of the search for an effective control, the possible existence of multiple dynamically equivalent controls, and the robustness of any viable control solution. Normal optimization problems in virtually any area of engineering and science typically have landscape topologies that remain a mystery. Quantum mechanics appears out to be quite special in that the topology of quantum control landscapes can be established generically based on minimal physical assumptions. Various features of these landscapes will be discussed and illustrated for circumstances where the controls are either an external field or the time independent portions of the Hamiltonian; the latter circumstance corresponds to subjecting the material or molecules to systematic variation and hence viewed in the context of being controls. Both theoretical and experimental findings on control landscapes and their consequences will be discussed, including issues of robustness to noise, search algorithm efficiency, existence of multiple control solutions, prospects for identifying reduced sets of control variables, simultaneous control of multiple quantum systems (optimal dynamic discrimination (ODD)), and mechanism analysis.

  4. 14 CFR 29.629 - Flutter and divergence.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction General § 29.629 Flutter and divergence. Each aerodynamic surface of the rotorcraft must be free from flutter and divergence under...

  5. Morphological and niche divergence of pinyon pines.

    PubMed

    Ortiz-Medrano, Alejandra; Scantlebury, Daniel Patrick; Vázquez-Lobo, Alejandra; Mastretta-Yanes, Alicia; Piñero, Daniel

    2016-05-01

    The environmental variables that define a species ecological niche should be associated with the evolutionary patterns present in the adaptations that resulted from living in these conditions. Thus, when comparing across species, we can expect to find an association between phylogenetically independent phenotypic characters and ecological niche evolution. Few studies have evaluated how organismal phenotypes might mirror patterns of niche evolution if these phenotypes reflect adaptations. Doing so could contribute on the understanding of the origin and maintenance of phenotypic diversity observed in nature. Here, we show the pattern of niche evolution of the pinyon pine lineage (Pinus subsection Cembroides); then, we suggest morphological adaptations possibly related to niche divergence, and finally, we test for correlation between ecological niche and morphology. We demonstrate that niche divergence is the general pattern within the clade and that it is positively correlated with adaptation.

  6. Increasing interpersonal trust through divergent thinking.

    PubMed

    Sellaro, Roberta; Hommel, Bernhard; de Kwaadsteniet, Erik W; van de Groep, Suzanne; Colzato, Lorenza S

    2014-01-01

    Interpersonal trust is an essential ingredient of many social relationships but how stable is it actually, and how is it controlled? There is evidence that the degree of trust into others might be rather volatile and can be affected by manipulations like drawing attention to personal interdependence or independence. Here we investigated whether the degree of interpersonal trust can be biased by inducing either a more integrative or a more focused/exclusive cognitive control mode by means of a creativity task requiring divergent or convergent thinking, respectively. Participants then performed the trust game, which provides an index of interpersonal trust by assessing the money units one participant (the trustor) transfers to another (the trustee). As expected, trustors transferred significantly more money to trustees after engaging in divergent thinking as compared to convergent thinking. This observation provides support for the idea that interpersonal trust is controlled by domain-general (i.e., not socially dedicated) cognitive states.

  7. Increasing interpersonal trust through divergent thinking

    PubMed Central

    Sellaro, Roberta; Hommel, Bernhard; de Kwaadsteniet, Erik W.; van de Groep, Suzanne; Colzato, Lorenza S.

    2014-01-01

    Interpersonal trust is an essential ingredient of many social relationships but how stable is it actually, and how is it controlled? There is evidence that the degree of trust into others might be rather volatile and can be affected by manipulations like drawing attention to personal interdependence or independence. Here we investigated whether the degree of interpersonal trust can be biased by inducing either a more integrative or a more focused/exclusive cognitive control mode by means of a creativity task requiring divergent or convergent thinking, respectively. Participants then performed the trust game, which provides an index of interpersonal trust by assessing the money units one participant (the trustor) transfers to another (the trustee). As expected, trustors transferred significantly more money to trustees after engaging in divergent thinking as compared to convergent thinking. This observation provides support for the idea that interpersonal trust is controlled by domain-general (i.e., not socially dedicated) cognitive states. PMID:24936194

  8. Divergent thinking in Alzheimer's and frontotemporal dementia.

    PubMed

    Hart, Robert P; Wade, James B

    2006-01-01

    Twenty-three patients with mild dementia of the Alzheimer's type (DAT) or frontotemporal type (DFT) and age- and education-matched control subjects were administered tests of complex fluency involving divergent thinking and tests of letter, category, and figural fluency. The tests of complex fluency discriminated the dementia patients from control subjects more strongly than did the other fluency tests. The results suggest that divergent thinking as assessed by complex fluency tests is a cognitive domain that is impaired early in the course of dementia. The sensitivity of complex fluency tests compared to that of letter, category, and figural fluency tests may be related to greater demands for conceptualization in relating stimulus attributes to function and greater demands for flexible thinking during self-directed search processes.

  9. Instrumental Divergence and the Value of Control

    PubMed Central

    Mistry, Prachi; Liljeholm, Mimi

    2016-01-01

    A critical aspect of flexible choice is that alternative actions yield distinct consequences: Only when available action alternatives produce distinct outcome states does discrimination and selection between actions allow an agent to flexibly obtain the currently most desired outcome. Here, we use instrumental divergence – the degree to which alternative actions differ with respect to their outcome probability distributions – as an index of flexible instrumental control, and assess the influence of this novel decision variable on choice preference. In Experiment 1, when other decision variables, such as expected value and outcome entropy, were held constant, we found a significant preference for high instrumental divergence. In Experiment 2, we used an “auto- vs. self-play” manipulation to eliminate outcome diversity as a source of behavioral preferences, and to contrast flexible instrumental control with the complete absence of voluntary choice. Our results suggest that flexible instrumental control over decision outcomes may have intrinsic value. PMID:27811969

  10. Carnot efficiency at divergent power output

    NASA Astrophysics Data System (ADS)

    Polettini, Matteo; Esposito, Massimiliano

    2017-05-01

    The widely debated feasibility of thermodynamic machines achieving Carnot efficiency at finite power has been convincingly dismissed. Yet, the common wisdom that efficiency can only be optimal in the limit of infinitely slow processes overlooks the dual scenario of infinitely fast processes. We corroborate that efficient engines at divergent power output are not theoretically impossible, framing our claims within the theory of Stochastic Thermodynamics. We inspect the case of an electronic quantum dot coupled to three particle reservoirs to illustrate the physical rationale.

  11. Incorporating landscape stochasticity into population viability analysis.

    PubMed

    Chisholm, Ryan A; Wintle, Brendan A

    2007-03-01

    The importance of incorporating landscape dynamics into population viability analysis (PVA) has previously been acknowledged, but the need to repeat the landscape generation process to encapsulate landscape stochasticity in model outputs has largely been overlooked. Reasons for this are that (1) there is presently no means for quantifying the relative effects of landscape stochasticity and population stochasticity on model outputs, and therefore no means for determining how to allocate simulation time optimally between the two; and (2) the process of generating multiple landscapes to incorporate landscape stochasticity is tedious and user-intensive with current PVA software. Here we demonstrate that landscape stochasticity can be an important source of variance in model outputs. We solve the technical problems with incorporating landscape stochasticity by deriving a formula that gives the optimal ratio of population simulations to landscape simulations for a given model, and by providing a computer program that incorporates the formula and automates multiple landscape generation in a dynamic landscape metapopulation (DLMP) model. Using a case study of a bird population, we produce estimates of DLMP model output parameters that are up to four times more precise than those estimated from a single landscape in the same amount of total simulation time. We use the DLMP modeling software RAMAS Landscape to run the landscape and metapopulation models, though our method is general and could be applied to any PVA platform. The results of this study should motivate DLMP modelers to consider landscape stochasticity in their analyses.

  12. Aeolian Morphodynamics of Loess Landscapes

    NASA Astrophysics Data System (ADS)

    Mason, J. A.; Hanson, P. R.; Sweeney, M.; Loope, H. M.; Miao, X.; Lu, H.

    2012-12-01

    Striking aeolian landforms characterize loess landscapes of the Great Plains and Upper Mississippi Valley, USA, shaped in Late Pleistocene environments with many characteristics of modern deserts including large active dunefields. Similar aeolian morphodynamics are evident in northern China and the Columbia Basin, USA, and are clearly important for interpreting the paleoenvironmental record of loess. Four zones spanning the upwind margin of thick loess can be defined from landforms and surficial deposits. From upwind to downwind, they are: A) A largely loess-free landscape, with patchy to continuous aeolian sand mantling bedrock. B) Patchy loess deposits, often streamlined and potentially wind-aligned, intermingled with dunes and sand sheets; interbedding of loess and sand may be common. C) Thick, coarse loess with an abrupt upwind edge, with troughs, yardang-like ridges, and/or wind-aligned scarps recording large-scale wind erosion. D) Thinner, finer loess with little evidence of post-depositional wind erosion. The degree of development and spatial scale of these zones varies among the loess regions we studied. To explain this zonation we emphasize controls on re-entrainment of loess by the wind after initial deposition, across gradients of climate and vegetation. The role of saltating sand in dust entrainment through abrasion of fine materials is well known. Using the Portable In situ Wind Erosion Laboratory (PI-SWERL), we recently demonstrated that unvegetated Great Plains loess can also be directly entrained under wind conditions common in the region today (Sweeney et al., 2011, GSA Abstracts with Programs, Vol. 43, No. 5, p. 251). Rainfall-induced crusts largely prevent direct entrainment in fine loess, but appear less effective in coarse loess. We propose that in zone A, any loess deposited was both abraded by saltating sand and directly re-entrained, so none accumulated. Sparse vegetation in this zone was primarily an effect of climate, but the resulting

  13. Magnetohydrodynamic energy conversion by using convexly divergent channel

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki; Okuno, Yoshihiro

    2009-12-01

    We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The quality of MHD power-generating plasma and the energy conversion efficiency in the convexly divergent channel are compared with those from previous linearly divergent channel. The divergence enhancement in the channel upstream is effective for suppressing an excessive increase in static pressure, whereby notably high isentropic efficiency is achieved.

  14. Magnetohydrodynamic energy conversion by using convexly divergent channel

    SciTech Connect

    Murakami, Tomoyuki; Okuno, Yoshihiro

    2009-12-21

    We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The quality of MHD power-generating plasma and the energy conversion efficiency in the convexly divergent channel are compared with those from previous linearly divergent channel. The divergence enhancement in the channel upstream is effective for suppressing an excessive increase in static pressure, whereby notably high isentropic efficiency is achieved.

  15. Ferrofluid separator for nonferrous scrap separation

    NASA Technical Reports Server (NTRS)

    Kaiser, R.; Mir, L.

    1974-01-01

    Behavior of nonmagnetic objects within separator is essentially function of density, and independent of size or shape of objects. Results show close agreement between density of object and apparent density of ferrofluid required to float it. Results also demonstrate that very high separation rates are achievable by ferrofluid sink-float separation.

  16. Polygamy slows down population divergence in shorebirds

    USGS Publications Warehouse

    Jackson, Josephine D'Urban; dos Remedios, Natalie; Maher, Kathryn; Zefania, Sama; Haig, Susan M.; Oyler-McCance, Sara J.; Blomqvist, Donald; Burke, Terry; Bruford, Michael W.; Székely, Tamás; Küpper, Clemens

    2017-01-01

    Sexual selection may act as a promotor of speciation since divergent mate choice and competition for mates can rapidly lead to reproductive isolation. Alternatively, sexual selection may also retard speciation since polygamous individuals can access additional mates by increased breeding dispersal. High breeding dispersal should hence increase gene flow and reduce diversification in polygamous species. Here, we test how polygamy predicts diversification in shorebirds using genetic differentiation and subspecies richness as proxies for population divergence. Examining microsatellite data from 79 populations in 10 plover species (Genus: Charadrius) we found that polygamous species display significantly less genetic structure and weaker isolation-by-distance effects than monogamous species. Consistent with this result, a comparative analysis including 136 shorebird species showed significantly fewer subspecies for polygamous than for monogamous species. By contrast, migratory behavior neither predicted genetic differentiation nor subspecies richness. Taken together, our results suggest that dispersal associated with polygamy may facilitate gene flow and limit population divergence. Therefore, intense sexual selection, as occurs in polygamous species, may act as a brake rather than an engine of speciation in shorebirds. We discuss alternative explanations for these results and call for further studies to understand the relationships between sexual selection, dispersal, and diversification.

  17. Polygamy slows down population divergence in shorebirds.

    PubMed

    D'Urban Jackson, Josephine; Dos Remedios, Natalie; Maher, Kathryn H; Zefania, Sama; Haig, Susan; Oyler-McCance, Sara; Blomqvist, Donald; Burke, Terry; Bruford, Michael W; Székely, Tamás; Küpper, Clemens

    2017-02-24

    Sexual selection may act as a promotor of speciation since divergent mate choice and competition for mates can rapidly lead to reproductive isolation. Alternatively, sexual selection may also retard speciation since polygamous individuals can access additional mates by increased breeding dispersal. High breeding dispersal should hence increase gene flow and reduce diversification in polygamous species. Here we test how polygamy predicts diversification in shorebirds using genetic differentiation and subspecies richness as proxies for population divergence. Examining microsatellite data from 79 populations in ten plover species (Genus: Charadrius) we found that polygamous species display significantly less genetic structure and weaker isolation-by-distance effects than monogamous species. Consistent with this result, a comparative analysis including 136 shorebird species showed significantly fewer subspecies for polygamous than for monogamous species. By contrast, migratory behaviour neither predicted genetic differentiation nor subspecies richness. Taken together, our results suggest that dispersal associated with polygamy may facilitate gene flow and limit population divergence. Therefore, intense sexual selection, as occurs in polygamous species, may act as a brake rather than an engine of speciation in shorebirds. We discuss alternative explanations for these results and call for further studies to understand the relationships between sexual selection, dispersal and diversification. This article is protected by copyright. All rights reserved.

  18. Genetic divergence predicts reproductive isolation in damselflies.

    PubMed

    Sánchez-Guillén, R A; Córdoba-Aguilar, A; Cordero-Rivera, A; Wellenreuther, M

    2014-01-01

    Reproductive isolation is the defining characteristic of a biological species, and a common, but often untested prediction is a positive correlation between reproductive isolation and genetic divergence. Here, we test for this correlation in odonates, an order characterized by strong sexual selection. First, we measure reproductive isolation and genetic divergence in eight damselfly genera (30 species pairs) and test for a positive correlation. Second, we estimate the genetic threshold preventing hybrid formation and empirically test this threshold using wild populations of species within the Ischnura genus. Our results indicate a positive and strong correlation between reproductive isolation and genetic distance using both mitochondrial and nuclear genes cytochrome oxidase II (COII: r = 0.781 and 18S-28S: r = 0.658). Hybridization thresholds range from -0.43 to 1.78% for COII and -0.052-0.71% for 18S-28S, and both F1 -hybrids and backcrosses were detected in wild populations of two pairs of Ischnura species with overlapping thresholds. Our study suggests that threshold values are suitable to identify species prone to hybridization and that positive isolation-divergence relationships are taxonomically widespread.

  19. Split-step eigenvector-following technique for exploring enthalpy landscapes at absolute zero.

    PubMed

    Mauro, John C; Loucks, Roger J; Balakrishnan, Jitendra

    2006-03-16

    The mapping of enthalpy landscapes is complicated by the coupling of particle position and volume coordinates. To address this issue, we have developed a new split-step eigenvector-following technique for locating minima and transition points in an enthalpy landscape at absolute zero. Each iteration is split into two steps in order to independently vary system volume and relative atomic coordinates. A separate Lagrange multiplier is used for each eigendirection in order to provide maximum flexibility in determining step sizes. This technique will be useful for mapping the enthalpy landscapes of bulk systems such as supercooled liquids and glasses.

  20. 14 CFR 29.629 - Flutter and divergence.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Flutter and divergence. 29.629 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction General § 29.629 Flutter and divergence. Each aerodynamic surface of the rotorcraft must be free from flutter and divergence under each...

  1. 14 CFR 29.629 - Flutter and divergence.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Flutter and divergence. 29.629 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction General § 29.629 Flutter and divergence. Each aerodynamic surface of the rotorcraft must be free from flutter and divergence under each...

  2. 14 CFR 29.629 - Flutter and divergence.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Flutter and divergence. 29.629 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction General § 29.629 Flutter and divergence. Each aerodynamic surface of the rotorcraft must be free from flutter and divergence under each...

  3. 14 CFR 29.629 - Flutter and divergence.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Flutter and divergence. 29.629 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction General § 29.629 Flutter and divergence. Each aerodynamic surface of the rotorcraft must be free from flutter and divergence under each...

  4. Isolation with asymmetric gene flow during the nonsynchronous divergence of dry forest birds.

    PubMed

    Oswald, Jessica A; Overcast, Isaac; Mauck, William M; Andersen, Michael J; Smith, Brian Tilston

    2017-03-01

    Dry forest bird communities in South America are often fragmented by intervening mountains and rainforests, generating high local endemism. The historical assembly of dry forest communities likely results from dynamic processes linked to numerous population histories among codistributed species. Nevertheless, species may diversify in the same way through time if landscape and environmental features, or species ecologies, similarly structure populations. Here we tested whether six co-distributed taxon pairs that occur in the dry forests of the Tumbes and Marañón Valley of northwestern South America show concordant patterns and modes of diversification. We employed a genome reduction technique, double-digest restriction site-associated DNA sequencing, and obtained 4407-7186 genomewide SNPs. We estimated demographic history in each taxon pair and inferred that all pairs had the same best-fit demographic model: isolation with asymmetric gene flow from the Tumbes into the Marañón Valley, suggesting a common diversification mode. Overall, we also observed congruence in effective population size (Ne ) patterns where ancestral Ne were 2.9-11.0× larger than present-day Marañón Valley populations and 0.3-2.0× larger than Tumbesian populations. Present-day Marañón Valley Ne was smaller than Tumbes. In contrast, we found simultaneous population isolation due to a single event to be unlikely as taxon pairs diverged over an extended period of time (0.1-2.9 Ma) with multiple nonoverlapping divergence periods. Our results show that even when populations of codistributed species asynchronously diverge, the mode of their differentiation can remain conserved over millions of years. Divergence by allopatric isolation due to barrier formation does not explain the mode of differentiation between these two bird assemblages; rather, migration of individuals occurred before and after geographic isolation.

  5. Adaptation to Low Salinity Promotes Genomic Divergence in Atlantic Cod (Gadus morhua L.)

    PubMed Central

    Berg, Paul R.; Jentoft, Sissel; Star, Bastiaan; Ring, Kristoffer H.; Knutsen, Halvor; Lien, Sigbjørn; Jakobsen, Kjetill S.; André, Carl

    2015-01-01

    How genomic selection enables species to adapt to divergent environments is a fundamental question in ecology and evolution. We investigated the genomic signatures of local adaptation in Atlantic cod (Gadus morhua L.) along a natural salinity gradient, ranging from 35‰ in the North Sea to 7‰ within the Baltic Sea. By utilizing a 12 K SNPchip, we simultaneously assessed neutral and adaptive genetic divergence across the Atlantic cod genome. Combining outlier analyses with a landscape genomic approach, we identified a set of directionally selected loci that are strongly correlated with habitat differences in salinity, oxygen, and temperature. Our results show that discrete regions within the Atlantic cod genome are subject to directional selection and associated with adaptation to the local environmental conditions in the Baltic- and the North Sea, indicating divergence hitchhiking and the presence of genomic islands of divergence. We report a suite of outlier single nucleotide polymorphisms within or closely located to genes associated with osmoregulation, as well as genes known to play important roles in the hydration and development of oocytes. These genes are likely to have key functions within a general osmoregulatory framework and are important for the survival of eggs and larvae, contributing to the buildup of reproductive isolation between the low-salinity adapted Baltic cod and the adjacent cod populations. Hence, our data suggest that adaptive responses to the environmental conditions in the Baltic Sea may contribute to a strong and effective reproductive barrier, and that Baltic cod can be viewed as an example of ongoing speciation. PMID:25994933

  6. The shifting beverage landscape.

    PubMed

    Storey, Maureen

    2010-04-26

    STOREY, M.L. The shifting beverage landscape. PHYSIOL BEHAV, 2010. - Simultaneous lifestyle changes have occurred in the last few decades, creating an imbalance in energy intake and energy expenditure that has led to overweight and obesity. Trends in the food supply show that total daily calories available per capita increased 28% since 1970. Total energy intake among men and women has also increased dramatically since that time. Some have suggested that intake of beverages has had a disproportional impact on obesity. Data collected by the Beverage Marketing Corporation between 1988-2008 demonstrate that, in reality, fewer calories per ounce are being produced by the beverage industry. Moreover, data from the National Cancer Institute show that soft drink intake represents 5.5% of daily calories. Data from NHANES 1999-2003 vs. 2003-06 may demonstrate a shift in beverage consumption for age/gender groups, ages 6 to>60years. The beverages provided in schools have significantly changed since 2006 when the beverage industry implemented School Beverage Guidelines. This voluntary action has removed full-calorie soft drinks from participating schools across the country. This shift to lower-calorie and smaller-portion beverages in school has led to a significant decrease in total beverage calories in schools. These data support the concept that to prevent and treat obesity, public health efforts should focus on energy balance and that a narrow focus on sweetened beverages is unlikely to have any meaningful impact on this complex problem. Copyright 2010 Elsevier Inc. All rights reserved.

  7. Genomic landscape of liposarcoma

    PubMed Central

    Kanojia, Deepika; Nagata, Yasunobu; Garg, Manoj; Lee, Dhong Hyun; Sato, Aiko; Yoshida, Kenichi; Sato, Yusuke; Sanada, Masashi; Mayakonda, Anand; Bartenhagen, Christoph; Klein, Hans-Ulrich; Doan, Ngan B.; Said, Jonathan W.; Mohith, S.; Gunasekar, Swetha; Shiraishi, Yuichi; Chiba, Kenichi; Tanaka, Hiroko; Miyano, Satoru; Myklebost, Ola; Yang, Henry; Dugas, Martin; Meza-Zepeda, Leonardo A.; Silberman, Allan W.; Forscher, Charles; Tyner, Jeffrey W.; Ogawa, Seishi; Koeffler, H. Phillip

    2015-01-01

    Liposarcoma (LPS) is the most common type of soft tissue sarcoma accounting for 20% of all adult sarcomas. Due to absence of clinically effective treatment options in inoperable situations and resistance to chemotherapeutics, a critical need exists to identify novel therapeutic targets. We analyzed LPS genomic landscape using SNP arrays, whole exome sequencing and targeted exome sequencing to uncover the genomic information for development of specific anti-cancer targets. SNP array analysis indicated known amplified genes (MDM2, CDK4, HMGA2) and important novel genes (UAP1, MIR557, LAMA4, CPM, IGF2, ERBB3, IGF1R). Carboxypeptidase M (CPM), recurrently amplified gene in well-differentiated/de-differentiated LPS was noted as a putative oncogene involved in the EGFR pathway. Notable deletions were found at chromosome 1p (RUNX3, ARID1A), chromosome 11q (ATM, CHEK1) and chromosome 13q14.2 (MIR15A, MIR16-1). Significantly and recurrently mutated genes (false discovery rate < 0.05) included PLEC (27%), MXRA5 (21%), FAT3 (24%), NF1 (20%), MDC1 (10%), TP53 (7%) and CHEK2 (6%). Further, in vitro and in vivo functional studies provided evidence for the tumor suppressor role for Neurofibromin 1 (NF1) gene in different subtypes of LPS. Pathway analysis of recurrent mutations demonstrated signaling through MAPK, JAK-STAT, Wnt, ErbB, axon guidance, apoptosis, DNA damage repair and cell cycle pathways were involved in liposarcomagenesis. Interestingly, we also found mutational and copy number heterogeneity within a primary LPS tumor signifying the importance of multi-region sequencing for cancer-genome guided therapy. In summary, these findings provide insight into the genomic complexity of LPS and highlight potential druggable pathways for targeted therapeutic approach. PMID:26643872

  8. Integrative analyses of speciation and divergence in Psammodromus hispanicus (Squamata: Lacertidae)

    PubMed Central

    2011-01-01

    Background Genetic, phenotypic and ecological divergence within a lineage is the result of past and ongoing evolutionary processes, which lead ultimately to diversification and speciation. Integrative analyses allow linking diversification to geological, climatic, and ecological events, and thus disentangling the relative importance of different evolutionary drivers in generating and maintaining current species richness. Results Here, we use phylogenetic, phenotypic, geographic, and environmental data to investigate diversification in the Spanish sand racer (Psammodromus hispanicus). Phylogenetic, molecular clock dating, and phenotypic analyses show that P. hispanicus consists of three lineages. One lineage from Western Spain diverged 8.3 (2.9-14.7) Mya from the ancestor of Psammodromus hispanicus edwardsianus and P. hispanicus hispanicus Central lineage. The latter diverged 4.8 (1.5-8.7) Mya. Molecular clock dating, together with population genetic analyses, indicate that the three lineages experienced northward range expansions from southern Iberian refugia during Pleistocene glacial periods. Ecological niche modelling shows that suitable habitat of the Western lineage and P. h. edwardsianus overlap over vast areas, but that a barrier may hinder dispersal and genetic mixing of populations of both lineages. P. h. hispanicus Central lineage inhabits an ecological niche that overlaps marginally with the other two lineages. Conclusions Our results provide evidence for divergence in allopatry and niche conservatism between the Western lineage and the ancestor of P. h. edwardsianus and P. h. hispanicus Central lineage, whereas they suggest that niche divergence is involved in the origin of the latter two lineages. Both processes were temporally separated and may be responsible for the here documented genetic and phenotypic diversity of P. hispanicus. The temporal pattern is in line with those proposed for other animal lineages. It suggests that geographic isolation and

  9. Markedly Divergent Tree Assemblage Responses to Tropical Forest Loss and Fragmentation across a Strong Seasonality Gradient

    PubMed Central

    Orihuela, Rodrigo L. L.; Peres, Carlos A.; Mendes, Gabriel; Jarenkow, João A.; Tabarelli, Marcelo

    2015-01-01

    We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide. PMID:26309252

  10. Taxonomic and functional divergence of tree assemblages in a fragmented tropical forest.

    PubMed

    Sfair, Julia C; Arroyo-Rodríguez, Víctor; Santos, Bráulio A; Tabarelli, Marcelo

    2016-09-01

    Tropical forests are being exposed to increasing levels of habitat loss and fragmentation, threatening the maintenance of global biodiversity. However, the effect that land-use change may have on the spatial dissimilarities in taxonomic and functional composition of remaining assemblages (i.e., taxonomic/functional β-diversity) remains poorly understood. We examined a large vegetation database from an old and severely fragmented Atlantic forest landscape to test two alternative hypotheses: (1) tree assemblages experience a taxonomic and functional homogenization (reduced β-diversity) between forest fragments and along forest edges, or alternatively, (2) these edge-affected forests show increased taxonomic and functional differentiation (increased β-diversity) when compared to forest interior (reference) stands. Taxonomic and functional β-diversity were examined via novel abundance-based metrics and considering functional traits related to plant dispersion, recruitment, and growth. Overall, taxonomic β-diversity among fragments was significantly higher than among edge and reference plots. Edge plots also showed higher β-diversity than reference plots, but only when considering dominant species. In functional terms, β-diversity among reference plots was also lower than among forest fragments and among edge plots. These patterns support the landscape-divergence hypothesis, which postulates that variable human disturbances among forest fragments and along forest edges can lead to contrasting trajectories of vegetation changes, thus increasing the compositional and functional differentiation of tree communities in these emerging environments. Our results also show that such differentiation can preserve landscape-wide biodiversity, thus overriding negative effects of habitat fragmentation on local (α) diversity. Therefore, our findings demonstrate that forest fragments and forest edges can be more valuable for maintaining species diversity and ecosystem function

  11. Markedly Divergent Tree Assemblage Responses to Tropical Forest Loss and Fragmentation across a Strong Seasonality Gradient.

    PubMed

    Orihuela, Rodrigo L L; Peres, Carlos A; Mendes, Gabriel; Jarenkow, João A; Tabarelli, Marcelo

    2015-01-01

    We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide.

  12. Exploring constrained quantum control landscapes

    NASA Astrophysics Data System (ADS)

    Moore, Katharine W.; Rabitz, Herschel

    2012-10-01

    The broad success of optimally controlling quantum systems with external fields has been attributed to the favorable topology of the underlying control landscape, where the landscape is the physical observable as a function of the controls. The control landscape can be shown to contain no suboptimal trapping extrema upon satisfaction of reasonable physical assumptions, but this topological analysis does not hold when significant constraints are placed on the control resources. This work employs simulations to explore the topology and features of the control landscape for pure-state population transfer with a constrained class of control fields. The fields are parameterized in terms of a set of uniformly spaced spectral frequencies, with the associated phases acting as the controls. This restricted family of fields provides a simple illustration for assessing the impact of constraints upon seeking optimal control. Optimization results reveal that the minimum number of phase controls necessary to assure a high yield in the target state has a special dependence on the number of accessible energy levels in the quantum system, revealed from an analysis of the first- and second-order variation of the yield with respect to the controls. When an insufficient number of controls and/or a weak control fluence are employed, trapping extrema and saddle points are observed on the landscape. When the control resources are sufficiently flexible, solutions producing the globally maximal yield are found to form connected "level sets" of continuously variable control fields that preserve the yield. These optimal yield level sets are found to shrink to isolated points on the top of the landscape as the control field fluence is decreased, and further reduction of the fluence turns these points into suboptimal trapping extrema on the landscape. Although constrained control fields can come in many forms beyond the cases explored here, the behavior found in this paper is illustrative of

  13. Epigenetic Inheritance across the Landscape

    PubMed Central

    Whipple, Amy V.; Holeski, Liza M.

    2016-01-01

    The study of epigenomic variation at the landscape-level in plants may add important insight to studies of adaptive variation. A major goal of landscape genomic studies is to identify genomic regions contributing to adaptive variation across the landscape. Heritable variation in epigenetic marks, resulting in transgenerational plasticity, can influence fitness-related traits. Epigenetic marks are influenced by the genome, the environment, and their interaction, and can be inherited independently of the genome. Thus, epigenomic variation likely influences the heritability of many adaptive traits, but the extent of this influence remains largely unknown. Here, we summarize the relevance of epigenetic inheritance to ecological and evolutionary processes, and review the literature on landscape-level patterns of epigenetic variation. Landscape-level patterns of epigenomic variation in plants generally show greater levels of isolation by distance and isolation by environment then is found for the genome, but the causes of these patterns are not yet clear. Linkage between the environment and epigenomic variation has been clearly shown within a single generation, but demonstrating transgenerational inheritance requires more complex breeding and/or experimental designs. Transgenerational epigenetic variation may alter the interpretation of landscape genomic studies that rely upon phenotypic analyses, but should have less influence on landscape genomic approaches that rely upon outlier analyses or genome–environment associations. We suggest that multi-generation common garden experiments conducted across multiple environments will allow researchers to understand which parts of the epigenome are inherited, as well as to parse out the relative contribution of heritable epigenetic variation to the phenotype. PMID:27826318

  14. Deconstructing a Polygenetic Landscape Using LiDAR and Multi-Resolution Analysis

    NASA Astrophysics Data System (ADS)

    Houser, C.; Barrineau, C. P.; Dobreva, I. D.; Bishop, M. P.

    2015-12-01

    In many earth surface systems characteristic morphologies are associated with various regimes both past and present. Aeolian systems contain a variety of features differentiated largely by morphometric differences, which in turn reflect age and divergent process regimes. Using quantitative analysis of high-resolution elevation data to generate detailed information regarding these characteristic morphometries enables geomorphologists to effectively map process regimes from a distance. Combined with satellite imagery and other types of remotely sensed data, the outputs can even help to delineate phases of activity within aeolian systems. The differentiation of regimes and identification of relict features together enables a greater level of rigor to analyses leading to field-based investigations, which are highly dependent on site-specific historical contexts that often obscure distinctions between separate process-form regimes. We present results from a Principal Components Analysis (PCA) performed on a LiDAR-derived elevation model of a largely stabilized aeolian system in South Texas. The resulting components are layered and classified to generate a map of aeolian morphometric signatures for a portion of the landscape. Several of these areas do not immediately appear to be aeolian in nature in satellite imagery or LiDAR-derived models, yet field observations and historical imagery reveal the PCA did in fact identify stabilized and relict dune features. This methodology enables researchers to generate a morphometric classification of the land surface. We believe this method is a valuable and innovative tool for researchers identifying process regimes within a study area, particularly in field-based investigations that rely heavily on site-specific context.

  15. Divergent natural selection promotes immigrant inviability at early and late stages of evolutionary divergence.

    PubMed

    Ingley, Spencer J; Johnson, Jerald B

    2016-03-01

    Natural selection's role in speciation has been of fundamental importance since Darwin first outlined his theory. Recently, work has focused on understanding how selection drives trait divergence, and subsequently reproductive isolation. "Immigrant inviability," a barrier that arises from selection against immigrants in their nonnative environment, appears to be of particular importance. Although immigrant inviability is likely ubiquitous, we know relatively little about how selection acts on traits to drive immigrant inviability, and how important immigrant inviability is at early-versus-late stages of divergence. We present a study evaluating the role of predation in the evolution of immigrant inviability in recently diverged population pairs and a well-established species pair of Brachyrhaphis fishes. We evaluate performance in a high-predation environment by assessing survival in the presence of a predator, and swimming endurance in a low-predation environment. We find strong signatures of local adaptation and immigrant inviability of roughly the same magnitude both early and late in divergence. We find remarkably conserved selection for burst-speed swimming (important in predator evasion), and selection for increased size in low-predation environments. Our results highlight the consistency with which selection acts during speciation, and suggest that similar factors might promote initial population differentiation and maintain differentiation at late stages of divergence.

  16. Divergence in an obligate mutualism is not explained by divergent climatic factors

    USGS Publications Warehouse

    Godsoe, W.; Strand, Espen; Smith, C.I.; Yoder, J.B.; Esque, T.C.; Pellmyr, O.

    2009-01-01

    Adaptation to divergent environments creates and maintains biological diversity, but we know little about the importance of different agents of ecological divergence. Coevolution in obligate mutualisms has been hypothesized to drive divergence, but this contention has rarely been tested against alternative ecological explanations. Here, we use a well-established example of coevolution in an obligate pollination mutualism, Yucca brevifolia and its two pollinating yucca moths, to test the hypothesis that divergence in this system is the result of mutualists adapting to different abiotic environments as opposed to coevolution between mutualists. ??? We used a combination of principal component analyses and ecological niche modeling to determine whether varieties of Y. brevifolia associated with different pollinators specialize on different environments. ??? Yucca brevifolia occupies a diverse range of climates. When the two varieties can disperse to similar environments, they occupy similar habitats. ??? This suggests that the two varieties have not specialized on distinct habitats. In turn, this suggests that nonclimatic factors, such as the biotic interaction between Y. brevifolia and its pollinators, are responsible for evolutionary divergence in this system. ?? New Phytologist (2009).

  17. Armillaria phylogeny based on tef-1α sequences suggests ongoing divergent speciation within the boreal floristic kingdom

    Treesearch

    Ned B. Klopfenstein; John W. Hanna; Amy L. Ross-Davis; Jane E. Stewart; Yuko Ota; Rosario Medel-Ortiz; Miguel Armando Lopez-Ramirez; Ruben Damian Elias-Roman; Dionicio Alvarado-Rosales; Mee-Sook Kim

    2013-01-01

    Armillaria plays diverse ecological roles in forests worldwide, which has inspired interest in understanding phylogenetic relationships within and among species of this genus. Previous rDNA sequence-based phylogenetic analyses of Armillaria have shown general relationships among widely divergent taxa, but rDNA sequences were not reliable for separating closely related...

  18. A Bioenergetic Basis for Membrane Divergence in Archaea and Bacteria

    PubMed Central

    Sojo, Víctor; Pomiankowski, Andrew; Lane, Nick

    2014-01-01

    Membrane bioenergetics are universal, yet the phospholipid membranes of archaea and bacteria—the deepest branches in the tree of life—are fundamentally different. This deep divergence in membrane chemistry is reflected in other stark differences between the two domains, including ion pumping and DNA replication. We resolve this paradox by considering the energy requirements of the last universal common ancestor (LUCA). We develop a mathematical model based on the premise that LUCA depended on natural proton gradients. Our analysis shows that such gradients can power carbon and energy metabolism, but only in leaky cells with a proton permeability equivalent to fatty acid vesicles. Membranes with lower permeability (equivalent to modern phospholipids) collapse free-energy availability, precluding exploitation of natural gradients. Pumping protons across leaky membranes offers no advantage, even when permeability is decreased 1,000-fold. We hypothesize that a sodium-proton antiporter (SPAP) provided the first step towards modern membranes. SPAP increases the free energy available from natural proton gradients by ∼60%, enabling survival in 50-fold lower gradients, thereby facilitating ecological spread and divergence. Critically, SPAP also provides a steadily amplifying advantage to proton pumping as membrane permeability falls, for the first time favoring the evolution of ion-tight phospholipid membranes. The phospholipids of archaea and bacteria incorporate different stereoisomers of glycerol phosphate. We conclude that the enzymes involved took these alternatives by chance in independent populations that had already evolved distinct ion pumps. Our model offers a quantitatively robust explanation for why membrane bioenergetics are universal, yet ion pumps and phospholipid membranes arose later and independently in separate populations. Our findings elucidate the paradox that archaea and bacteria share DNA transcription, ribosomal translation, and ATP synthase

  19. Highly divergent mussel lineages in isolated Indonesian marine lakes

    PubMed Central

    de Leeuw, Christiaan A.; Knegt, Bram; Maas, Diede L.; de Voogd, Nicole J.; Abdunnur; Suyatna, Iwan; Peijnenburg, Katja T.C.A.

    2016-01-01

    Marine lakes, with populations in landlocked seawater and clearly delineated contours, have the potential to provide a unique model to study early stages of evolution in coastal marine taxa. Here we ask whether populations of the mussel Brachidontes from marine lakes in Berau, East Kalimantan (Indonesia) are isolated from each other and from the coastal mangrove systems. We analyzed sequence data of one mitochondrial marker (Cytochrome Oxidase I (COI)), and two nuclear markers (18S and 28S). In addition, we examined shell shape using a geometric morphometric approach. The Indonesian populations of Brachidontes spp. harbored four deeply diverged lineages (14–75% COI corrected net sequence divergence), two of which correspond to previously recorded lineages from marine lakes in Palau, 1,900 km away. These four lineages also showed significant differences in shell shape and constitute a species complex of at least four undescribed species. Each lake harbored a different lineage despite the fact that the lakes are separated from each other by only 2–6 km, while the two mangrove populations, at 20 km distance from each other, harbored the same lineage and shared haplotypes. Marine lakes thus represent isolated habitats. As each lake contained unique within lineage diversity (0.1–0.2%), we suggest that this may have resulted from in situdivergence due to isolation of founder populations after the formation of the lakes (6,000–12,000 years before present). Combined effects of stochastic processes, local adaptation and increased evolutionary rates could produce high levels of differentiation in small populations such as in marine lake environments. Such short-term isolation at small spatial scales may be an important contributing factor to the high marine biodiversity that is found in the Indo-Australian Archipelago. PMID:27761314

  20. Highly divergent mussel lineages in isolated Indonesian marine lakes.

    PubMed

    Becking, Leontine E; de Leeuw, Christiaan A; Knegt, Bram; Maas, Diede L; de Voogd, Nicole J; Abdunnur; Suyatna, Iwan; Peijnenburg, Katja T C A

    2016-01-01

    Marine lakes, with populations in landlocked seawater and clearly delineated contours, have the potential to provide a unique model to study early stages of evolution in coastal marine taxa. Here we ask whether populations of the mussel Brachidontes from marine lakes in Berau, East Kalimantan (Indonesia) are isolated from each other and from the coastal mangrove systems. We analyzed sequence data of one mitochondrial marker (Cytochrome Oxidase I (COI)), and two nuclear markers (18S and 28S). In addition, we examined shell shape using a geometric morphometric approach. The Indonesian populations of Brachidontes spp. harbored four deeply diverged lineages (14-75% COI corrected net sequence divergence), two of which correspond to previously recorded lineages from marine lakes in Palau, 1,900 km away. These four lineages also showed significant differences in shell shape and constitute a species complex of at least four undescribed species. Each lake harbored a different lineage despite the fact that the lakes are separated from each other by only 2-6 km, while the two mangrove populations, at 20 km distance from each other, harbored the same lineage and shared haplotypes. Marine lakes thus represent isolated habitats. As each lake contained unique within lineage diversity (0.1-0.2%), we suggest that this may have resulted from in situdivergence due to isolation of founder populations after the formation of the lakes (6,000-12,000 years before present). Combined effects of stochastic processes, local adaptation and increased evolutionary rates could produce high levels of differentiation in small populations such as in marine lake environments. Such short-term isolation at small spatial scales may be an important contributing factor to the high marine biodiversity that is found in the Indo-Australian Archipelago.

  1. A bioenergetic basis for membrane divergence in archaea and bacteria.

    PubMed

    Sojo, Víctor; Pomiankowski, Andrew; Lane, Nick

    2014-08-01

    Membrane bioenergetics are universal, yet the phospholipid membranes of archaea and bacteria-the deepest branches in the tree of life-are fundamentally different. This deep divergence in membrane chemistry is reflected in other stark differences between the two domains, including ion pumping and DNA replication. We resolve this paradox by considering the energy requirements of the last universal common ancestor (LUCA). We develop a mathematical model based on the premise that LUCA depended on natural proton gradients. Our analysis shows that such gradients can power carbon and energy metabolism, but only in leaky cells with a proton permeability equivalent to fatty acid vesicles. Membranes with lower permeability (equivalent to modern phospholipids) collapse free-energy availability, precluding exploitation of natural gradients. Pumping protons across leaky membranes offers no advantage, even when permeability is decreased 1,000-fold. We hypothesize that a sodium-proton antiporter (SPAP) provided the first step towards modern membranes. SPAP increases the free energy available from natural proton gradients by ∼60%, enabling survival in 50-fold lower gradients, thereby facilitating ecological spread and divergence. Critically, SPAP also provides a steadily amplifying advantage to proton pumping as membrane permeability falls, for the first time favoring the evolution of ion-tight phospholipid membranes. The phospholipids of archaea and bacteria incorporate different stereoisomers of glycerol phosphate. We conclude that the enzymes involved took these alternatives by chance in independent populations that had already evolved distinct ion pumps. Our model offers a quantitatively robust explanation for why membrane bioenergetics are universal, yet ion pumps and phospholipid membranes arose later and independently in separate populations. Our findings elucidate the paradox that archaea and bacteria share DNA transcription, ribosomal translation, and ATP synthase, yet

  2. Variational divergence in wave scattering theory with Kirchhoffean trial functions

    NASA Technical Reports Server (NTRS)

    Bird, J. F.

    1986-01-01

    In a recent study of variational improvement of the Kirchhoff approximation for electromagnetic scattering by rough surfaces, a key ingredient in the variational principle was found to diverge for important configurations (e.g., backscatter) if the polarization had any vertical component. The cause and a cure of this divergence are discussed here. The divergence is demonstrated to occur for arbitrary perfectly conducting scatterers and its universal characterstics are determined, by means of a general divergence criterion that is derived. A variational cure for the divergence is prescribed, and it is tested successfully on a standard scattering model.

  3. Landscape characterization for watershed management

    SciTech Connect

    Hunsaker, C.T.; Jackson, B.L.; Schwartz, P.M.

    1996-07-01

    Streams and rivers serve as integrators of terrestrial landscape characteristics and as recipients of pollutants from both the atmosphere and the land; thus, large rivers are especially good indicators of cumulative impacts. Landscape ecologists seek to better understand the relationships between landscape structure and ecosystem processes at various spatial scales. Understanding how scale, both data resolution and geographic extent, influences landscape characterization and how terrestrial processes affect water quality are critically important for model development and translation of research results from experimental watersheds to management of large drainage basins. Measures of landscape structure are useful to monitor change and assess the risks it poses to ecological resources. Many studies have shown that the proportion of different land uses within a watershed can account for some of the variability in surface water quality. Hunsaker and Levine showed that both proportion of land uses and the spatial pattern of land uses is important for characterizing and modeling water quality; however, proportion consistently accounted for the most variance (40% to 86%) across a range of watershed sizes (1000 to 1.35 million ha). The U.S. Environmental Protection Agency (EPA) is performing a demonstration of its Environmental Monitoring and Assessment Program (EMAP) for the Mid-Atlantic Region. One activity, the Mid-Atlantic Integrated Assessment, is designed as a collaborative initiative between EPA`s Office of Research and Development and EPA`s Region III.

  4. Isotope separation apparatus and method

    DOEpatents

    Feldman, Barry J.

    1985-01-01

    The invention relates to an improved method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferably substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. Because the molecules in the beam occupy various degenerate energy levels, if the laser beam comprises chirped pulses comprising selected wavelengths, the laser beam will very efficiently excite substantially all unexcited molecules and will cause stimulated emission of substantially all excited molecules of a selected one of the isotopes in the beam which such pulses encounter. Excitation caused by first direction chirped pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning chirped pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement of essentially all the molecules containing the one isotope is accomplished by a large number of chirped pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam.

  5. Isotope separation apparatus and method

    DOEpatents

    Cotter, Theodore P.

    1982-12-28

    The invention relates to a method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferable substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. The laser beam comprises .pi.-pulses of a selected wavelength which excite unexcited molecules, or cause stimulated emission of excited molecules of one of the isotopes. Excitation caused by first direction .pi.-pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning .pi.-pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement is accomplished by a large number of .pi.-pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam.

  6. Two-year-olds can socially learn to think divergently.

    PubMed

    Hoicka, Elena; Powell, Stephanie; Knight, Jenny; Norwood, Megan

    2017-08-09

    This study aimed to discover whether 2-year-olds can socially learn to think divergently. Two-year-olds (N = 22) who saw an experimenter model a high level of divergent thinking on the Unusual Box Test (modelling 25 different actions, once each) went on to demonstrate a higher level of divergent thinking themselves than (N = 22) children who saw a low level of modelling (five different actions, once each), where divergent thinking was measured by the number of different actions children produced that had not been modelled by the experimenter. Additionally, all children in both High and Low Divergence conditions had higher divergent thinking than imitation scores, where imitation involved copying the experimenter's previous actions. This is the first experiment to show that 2-year-olds' divergent thinking can be increased, and that 2-year-olds do so by socially learning to think more divergently. Statement of contribution What is already known on this subject Recent research found that children as young as 1 year can think divergently, and that this is influenced by parents' own divergent thinking. What does this study add? This paper is important as it provides the first method to increase divergent thinking in toddlers. It also shows that social learning can directly affect individual learning processes, which suggests current theories of social and individual learning should be revised to be more iterative. © 2017 The British Psychological Society.

  7. Spacecraft -- Capsule Separation (Animation)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Click on the image for Spacecraft -- Capsule Separation animation

    This animation shows the return capsule separating from the Stardust spacecraft.

  8. [Selection of landscape metrics for urban forest based on simulated landscapes].

    PubMed

    Liu, Chang-Fu; Li, Jing-Ze; Li, Xiao-Ma; He, Xing-Yuan; Chen, Wei

    2009-05-01

    Based on the existing urban forest landscape of Shenyang, four landscape pattern gradients were simulated, and one existing landscape pattern gradient in accordance with the trend of these gradients was selected. By analyzing the responses of 28 landscape metrics for landscape fragmentation and patch shape complexity to various landscape pattern gradients, preference landscape metrics were selected for describing the degree of the two landscape pattern characteristics. The results showed that patch density (PD) and mean patch area (AREA_MN) regularly responded to the change of landscape fragmentation. The increase of landscape fragmentation resulted in an increase of PD value while a decrease of AREA_MN value. Patch shape complexity of area weighted mean perimeter area ratio (PARA_AM) coincided with the gradients of landscape pattern. PARA AM value increased with increasing patch shape complexity, which precisely characterized the degree of patch shape complexity.

  9. Diverging patterns with endogenous labor migration.

    PubMed

    Reichlin, P; Rustichini, A

    1998-05-05

    "The standard neoclassical model cannot explain persistent migration flows and lack of cross-country convergence when capital and labor are mobile. Here we present a model where both phenomena may take place.... Our model is based on the Arrow-Romer approach to endogenous growth theory. We single out the importance of a (however weak) scale effect from the size of the workforce.... The main conclusion of this simple model is that lack of convergence, or even divergence, among countries is possible, even with perfect capital mobility and labor mobility."

  10. Some Divergence Properties of Asset Price Models

    NASA Astrophysics Data System (ADS)

    Stummer, Wolfgang

    2001-12-01

    We consider asset price processes Xt which are weak solutions of one-dimensional stochastic differential equations of the form (equation (2)) Such price models can be interpreted as non-lognormally-distributed generalizations of the geometric Brownian motion. We study properties of the Iα-divergence between the law of the solution Xt and the corresponding drift-less measure (the special case α=1 is the relative entropy). This will be applied to some context in statistical information theory as well as to arbitrage theory and contingent claim valuation. For instance, the seminal option pricing theorems of Black-Scholes and Merton appear as a special case.

  11. Palmar divergent dislocation of scaphoid and lunate.

    PubMed

    Kang, Ho-Jung; Shim, Dong-Joon; Hahn, Soo-Bong; Kang, Eung-Shick

    2003-12-30

    A 28-year-old man presented with a palmar divergent dislocation of the scaphoid and lunate. He was treated with an open reduction and an internal fixation with two Kirschner's wires after the 25th day of trauma due to a neurological injury. The results were satisfactory after 18 months follow up without any evidence of avascular necrosis and traumatic arthritis of the scaphoid and lunate. The patient had no limitation in motion or intermittent wrist pain. We reported this case with a brief review of relevant literatures.

  12. Streptomyces metabolites in divergent microbial interactions.

    PubMed

    Takano, Hideaki; Nishiyama, Tatsuya; Amano, Sho-ichi; Beppu, Teruhiko; Kobayashi, Michihiko; Ueda, Kenji

    2016-03-01

    Streptomyces and related bacteria produce a wide variety of secondary metabolites. Of these, many compounds have industrial applications, but the question of why this group of microorganism produces such various kinds of biologically active substances has not yet been clearly answered. Here, we overview the results from our studies on the novel function and role of Streptomyces metabolites. The diverged action of negative and positive influences onto the physiology of various microorganisms infers the occurrence of complex microbial interactions due to the effect of small molecules produced by Streptomyces. The interactions may serve as a basis for the constitution of biological community.

  13. Bounding the bias of contrastive divergence learning.

    PubMed

    Fischer, Asja; Igel, Christian

    2011-03-01

    Optimization based on k-step contrastive divergence (CD) has become a common way to train restricted Boltzmann machines (RBMs). The k-step CD is a biased estimator of the log-likelihood gradient relying on Gibbs sampling. We derive a new upper bound for this bias. Its magnitude depends on k, the number of variables in the RBM, and the maximum change in energy that can be produced by changing a single variable. The last reflects the dependence on the absolute values of the RBM parameters. The magnitude of the bias is also affected by the distance in variation between the modeled distribution and the starting distribution of the Gibbs chain.

  14. Islands within an island: repeated adaptive divergence in a single population.

    PubMed

    Langin, Kathryn M; Sillett, T Scott; Funk, W Chris; Morrison, Scott A; Desrosiers, Michelle A; Ghalambor, Cameron K

    2015-03-01

    Physical barriers to gene flow were once viewed as prerequisites for adaptive evolutionary divergence. However, a growing body of theoretical and empirical work suggests that divergence can proceed within a single population. Here we document genetic structure and spatially replicated patterns of phenotypic divergence within a bird species endemic to 250 km(2) Santa Cruz Island, California, USA. Island scrub-jays (Aphelocoma insularis) in three separate stands of pine habitat had longer, shallower bills than jays in oak habitat, a pattern that mirrors adaptive differences between allopatric populations of the species' mainland congener. Variation in both bill measurements was heritable, and island scrub-jays mated nonrandomly with respect to bill morphology. The population was not panmictic; instead, we found a continuous pattern of isolation by distance across the east-west axis of the island, as well as a subtle genetic discontinuity across the boundary between the largest pine stand and adjacent oak habitat. The ecological factors that appear to have facilitated adaptive differentiation at such a fine scale--environmental heterogeneity and localized dispersal--are ubiquitous in nature. These findings support recent arguments that microgeographic patterns of adaptive divergence may be more common than currently appreciated, even in mobile taxonomic groups like birds. © 2015 The Author(s).

  15. Long prereproductive selection and divergence by depth in a Caribbean candelabrum coral.

    PubMed

    Prada, Carlos; Hellberg, Michael E

    2013-03-05

    Long-lived corals, the foundation of modern reefs, often follow ecological gradients, so that populations or sister species segregate by habitat. Adaptive divergence maintains sympatric congeners after secondary contact or may even generate species by natural selection in the face of gene flow. Such ecological divergence, initially between alternative phenotypes within populations, may be aided by immigrant inviability, especially when a long period separates larval dispersal and the onset of reproduction, during which selection can sort lineages to match different habitats. Here, we evaluate the strength of one ecological factor (depth) to isolate populations by comparing the genes and morphologies of pairs of depth-segregated populations of the candelabrum coral Eunicea flexuosa across the Caribbean. Eunicea is endemic to the Caribbean and all sister species co-occur. Eunicea flexuosa is widespread both geographically and across reef habitats. Our genetic analysis revealed two depth-segregated lineages. Field survivorship data, combined with estimates of selection coefficients based on transplant experiments, suggest that selection is strong enough to segregate these two lineages. Genetic exchange between the Shallow and Deep lineages occurred either immediately after divergence or the two have diverged with gene flow. Migration occurs asymmetrically from the Shallow to Deep lineage. Limited recruitment to reproductive age, even under weak annual selection advantage, is sufficient to generate habitat segregation because of the cumulative prolonged prereproductive selection. Ecological factors associated with depth can act as filters generating strong barriers to gene flow, altering morphologies, and contributing to the potential for speciation in the sea.

  16. Contemporary evolution of reproductive isolation and phenotypic divergence in sympatry along a migratory divide.

    PubMed

    Rolshausen, Gregor; Segelbacher, Gernot; Hobson, Keith A; Schaefer, H Martin

    2009-12-29

    Understanding the influence of human-induced changes on the evolutionary trajectories of populations is a fundamental problem [1, 2]. The evolution of reproductive isolation in sympatry is rare, relying on strong selection along steep ecological gradients [3-7]. Improved wintering conditions owing to human activities promoted the recent establishment of a migratory divide in Central European blackcaps (Sylvia atricapilla) [8, 9]. Here, we show that differential migratory orientation facilitated reproductive isolation of sympatric populations within <30 generations. The genetic divergence in sympatry exceeds that of allopatric blackcaps separated by 800 km and is associated with diverse phenotypic divergence. Blackcaps migrating along the shorter northwestern route have rounder wings and narrower beaks and differ in beak and plumage color from sympatric southwest-migrating birds. We suggest that distinct wing and beak morphologies are ecomorphological adaptations resulting from divergent, multifarious selection regimes during migration. We hypothesize that restricted gene flow accelerates the evolution of adaptive phenotypic divergence toward the contrasting selection regimes. Similar adaptive processes can occur in more than 50 bird species that recently changed their migratory behavior [10, 11] or in species with low migratory connectivity. Our study thus illustrates how ecological changes can rapidly drive the contemporary evolution of ecotypes.

  17. Horizontal Gene Transfers from Bacteria to Entamoeba Complex: A Strategy for Dating Events along Species Divergence

    PubMed Central

    Romero, Miguel; Ximenez, Cecilia

    2016-01-01

    Horizontal gene transfer has proved to be relevant in eukaryotic evolution, as it has been found more often than expected and related to adaptation to certain niches. A relatively large list of laterally transferred genes has been proposed and evaluated for the parasite Entamoeba histolytica. The goals of this work were to elucidate the importance of lateral gene transfer along the evolutionary history of some members of the genus Entamoeba, through identifying donor groups and estimating the divergence time of some of these events. In order to estimate the divergence time of some of the horizontal gene transfer events, the dating of some Entamoeba species was necessary, following an indirect dating strategy based on the fossil record of plausible hosts. The divergence between E. histolytica and E. nuttallii probably occurred 5.93 million years ago (Mya); this lineage diverged from E. dispar 9.97 Mya, while the ancestor of the latter separated from E. invadens 68.18 Mya. We estimated times for 22 transferences; the most recent occurred 31.45 Mya and the oldest 253.59 Mya. Indeed, the acquisition of genes through lateral transfer may have triggered a period of adaptive radiation, thus playing a major role in the evolution of the Entamoeba genus. PMID:27239333

  18. Long prereproductive selection and divergence by depth in a Caribbean candelabrum coral

    PubMed Central

    Prada, Carlos; Hellberg, Michael E.

    2013-01-01

    Long-lived corals, the foundation of modern reefs, often follow ecological gradients, so that populations or sister species segregate by habitat. Adaptive divergence maintains sympatric congeners after secondary contact or may even generate species by natural selection in the face of gene flow. Such ecological divergence, initially between alternative phenotypes within populations, may be aided by immigrant inviability, especially when a long period separates larval dispersal and the onset of reproduction, during which selection can sort lineages to match different habitats. Here, we evaluate the strength of one ecological factor (depth) to isolate populations by comparing the genes and morphologies of pairs of depth-segregated populations of the candelabrum coral Eunicea flexuosa across the Caribbean. Eunicea is endemic to the Caribbean and all sister species co-occur. Eunicea flexuosa is widespread both geographically and across reef habitats. Our genetic analysis revealed two depth-segregated lineages. Field survivorship data, combined with estimates of selection coefficients based on transplant experiments, suggest that selection is strong enough to segregate these two lineages. Genetic exchange between the Shallow and Deep lineages occurred either immediately after divergence or the two have diverged with gene flow. Migration occurs asymmetrically from the Shallow to Deep lineage. Limited recruitment to reproductive age, even under weak annual selection advantage, is sufficient to generate habitat segregation because of the cumulative prolonged prereproductive selection. Ecological factors associated with depth can act as filters generating strong barriers to gene flow, altering morphologies, and contributing to the potential for speciation in the sea. PMID:23359716

  19. Parallel and non-parallel morphological divergence among foraging specialists in European whitefish (Coregonus lavaretus)

    PubMed Central

    Siwertsson, Anna; Knudsen, Rune; Adams, Colin E; Præbel, Kim; Amundsen, Per-Arne

    2013-01-01

    Parallel phenotypic evolution occurs when independent populations evolve similar traits in response to similar selective regimes. However, populations inhabiting similar environments also frequently show some phenotypic differences that result from non-parallel evolution. In this study, we quantified the relative importance of parallel evolution to similar foraging regimes and non-parallel lake-specific effects on morphological variation in European whitefish (Coregonus lavaretus). We found evidence for both lake-specific morphological characteristics and parallel morphological divergence between whitefish specializing in feeding on profundal and littoral resources in three separate lakes. Foraging specialists expressed similar phenotypes in different lakes in both overall body shape and selected measured morphological traits. The morphology of the two whitefish specialists resembled that predicted from other fish species, supporting the conclusion of an adaptive significance of the observed morphological characteristics. Our results indicate that divergent natural selection resulting from foraging specialization is driving and/or maintaining the observed parallel morphological divergence. Whitefish in this study may represent an early stage of divergence towards the evolution of specialized morphs. PMID:23789070

  20. How pervasive is biotic homogenization in human-modified tropical forest landscapes?

    PubMed

    Solar, Ricardo Ribeiro de Castro; Barlow, Jos; Ferreira, Joice; Berenguer, Erika; Lees, Alexander C; Thomson, James R; Louzada, Júlio; Maués, Márcia; Moura, Nárgila G; Oliveira, Victor H F; Chaul, Júlio C M; Schoereder, José Henrique; Vieira, Ima Célia Guimarães; Mac Nally, Ralph; Gardner, Toby A

    2015-10-01

    Land-cover change and ecosystem degradation may lead to biotic homogenization, yet our understanding of this phenomenon over large spatial scales and different biotic groups remains weak. We used a multi-taxa dataset from 335 sites and 36 heterogeneous landscapes in the Brazilian Amazon to examine the potential for landscape-scale processes to modulate the cumulative effects of local disturbances. Biotic homogenization was high in production areas but much less in disturbed and regenerating forests, where high levels of among-site and among-landscape β-diversity appeared to attenuate species loss at larger scales. We found consistently high levels of β-diversity among landscapes for all land cover classes, providing support for landscape-scale divergence in species composition. Our findings support concerns that β-diversity has been underestimated as a driver of biodiversity change and underscore the importance of maintaining a distributed network of reserves, including remaining areas of undisturbed primary forest, but also disturbed and regenerating forests, to conserve regional biota.

  1. Why some fitness landscapes are fractal.

    PubMed

    Weinberger, E D; Stadler, P F

    1993-07-21

    Many biological and biochemical measurements, for example the "fitness" of a particular genome, or the binding affinity to a particular substrate, can be treated as a "fitness landscape", an assignment of numerical values to points in sequence space (or some other configuration space). As an alternative to the enormous amount of data required to completely describe such a landscape, we propose a statistical characterization, based on the properties of a random walk through the landscape and, more specifically, its autocorrelation function. Under assumptions roughly satisfied by two classes of simple model landscapes (the N-k model and the p-spin model) and by the landscape of estimated free energies of RNA secondary structures, this autocorrelation function, along with the mean and variance of individual points and the size of the landscape, completely characterize it. Having noted that these and other landscapes of estimated replication and degradation rates all have a well-defined correlation length, we propose a classification of landscapes depending on how the correlation length scales with the diameter of the landscape. The landscapes of some of the kinetic parameters of RNA molecules scale similarly to the model landscapes introduced into evolutionary studies from other fields, such as quadratic spin glasses and the traveling salesman problem, but the correlation length of RNA landscapes are considerably smaller. Nevertheless, both the model and some of the RNA landscapes satisfy a test of self-similarity proposed by Sorkin (1988).

  2. Hydrocyclone separation system

    SciTech Connect

    Worrell, J.R.; Wakley, W.D.; Young, G.A.

    1990-05-22

    This patent describes a hydrocyclone separation system for separating a fluid mixture into at least two components having differing densities. It comprises: a first hydrocyclone separator and a second hydrocyclone separator contained within an elongated protective conduit and each being substantially parallel to a longitudinal axis of the conduit, each hydrocyclone separator having a tangential fluid inlet, an overflow fluid outlet and an underflow fluid outlet; and the first hydrocyclone separator and the second hydrocyclone separator being oppositely disposed with respect to each other with the underflow fluid outlet of the first hydrocyclone separator being spaced immediately adjacent to the tangential fluid inlet of the second hydrocyclone separator and the overflow fluid outlet of the first hydrocyclone separator being spaced immediately adjacent the underflow fluid outlet of the second hydrocyclone separator.

  3. [Landscape pattern of Nanjing urban-rural ecotone].

    PubMed

    Chen, Caihong; Hu, Feng; Zhang, Luochen

    2003-08-01

    Landscape ecological characteristics of the urban-rural ecotone of Nanjing City were studied by using remote sensing and geographical information system (GIS) techniques. Two representative study regions with the same area were chosen in the eastern and southern part of the city. The urban-rural fringe of both east (URFE) and south region (URFS) can be divided into three zones: fringe-paraurban zone, transition zone and pararural zone. URFE was basically characterized by low landscape diversity, dominance and fragmentation. The forest patches in URFE had larger area and average perimeter, while their average fractal dimension, average stretched index and separated degree were lower. The average area of vegetable land and paddy land was larger than that of south region. URFS showed higher landscape diversity, dominance and fragmentation, more and higher density of patches. The area and the perimeter of water and architectural patches in URFS were also larger than that of URFE. The relationship between patch area and fractal dimension, stretched index and fractal dimension, patch number and area were discussed. The function and contributing factors of each type of patches, especially forestland, and the landscape characteristics and the ecological significance of corridors including road, river, and city wall of urban-rural fringe were also analyzed.

  4. Local and landscape determinants of amphibian communities in urban ponds.

    PubMed

    Hamer, Andrew J; Parris, Kirsten M

    2011-03-01

    Urbanization is currently responsible for widespread declines of amphibian populations globally through the loss, isolation, and degradation of habitat. However, it is not clear how urbanization affects amphibian communities at both local (pond) and landscape scales. We assessed the breeding distribution of frogs in ponds along an urban-rural gradient in Greater Melbourne, Australia, and examined community relationships with habitat quality and landscape context. We sampled frog larvae at 65 ponds on four separate occasions and collected data on local pond and landscape variables. Using Bayesian Poisson regression modeling we found that species richness decreased at ponds surrounded by high densities of human residents and at ponds with high water conductivity, whereas species richness increased substantially at ponds surrounded by a high proportion of green open space. Ordination of individual species presence-absence data by canonical correspondence analysis largely confirmed these findings. Ordination also highlighted the negative influences of pond shading and density of predatory fish, and the positive influence of aquatic vegetation, on community composition. Individual species' responses to urbanization varied. Urbanization had strong negative effects on species that were associated with well-vegetated, sunny, fish-free ponds. Our study highlights the importance of strategic management actions in urban landscapes to improve terrestrial habitat and connectivity around ponds and other wetlands, and local management actions to improve water quality, remove predatory fish, and plant aquatic vegetation at breeding sites.

  5. Energy landscape of social balance.

    PubMed

    Marvel, Seth A; Strogatz, Steven H; Kleinberg, Jon M

    2009-11-06

    We model a close-knit community of friends and enemies as a fully connected network with positive and negative signs on its edges. Theories from social psychology suggest that certain sign patterns are more stable than others. This notion of social "balance" allows us to define an energy landscape for such networks. Its structure is complex: numerical experiments reveal a landscape dimpled with local minima of widely varying energy levels. We derive rigorous bounds on the energies of these local minima and prove that they have a modular structure that can be used to classify them.

  6. Energy Landscape of Social Balance

    NASA Astrophysics Data System (ADS)

    Marvel, Seth A.; Strogatz, Steven H.; Kleinberg, Jon M.

    2009-11-01

    We model a close-knit community of friends and enemies as a fully connected network with positive and negative signs on its edges. Theories from social psychology suggest that certain sign patterns are more stable than others. This notion of social “balance” allows us to define an energy landscape for such networks. Its structure is complex: numerical experiments reveal a landscape dimpled with local minima of widely varying energy levels. We derive rigorous bounds on the energies of these local minima and prove that they have a modular structure that can be used to classify them.

  7. Separation of Lift-Generated Vortex Wakes Into Two Diverging Parts

    NASA Technical Reports Server (NTRS)

    Rossow, Vernon J.; Brown, Anthony P.

    2010-01-01

    As part of an ongoing study of the spreading rate of lift-generated vortex wakes, the present investigation considers possible reasons as to why segments of lift-generated wakes sometimes depart from the main part of the wake to move rapidly in either an upward or downward direction. It is assumed that deficiencies or enhancements of the lift carry over across the fuselage-shrouded wing are the driving mechanism for departures of wake-segments. The computations presented first indicate that upwardly departing wake segments that were observed and photographed could have been produced by a deficiency in lift carryover across the fuselage-shrouded part of the wing. Computations made of idealized vortex wakes indicate that upward departure of a wake segment requires a centerline reduction in the span loading of 70% or more, whether the engines are at idle or robust thrust. Similarly, it was found that downward departure of wake segments is produced when the lift over the center part of the wing is enhanced. However, it was also found that downward departures do not occur without the presence of robust engine-exhaust streams (i.e., engines must NOT be at idle). In those cases, downward departures of a wake segment occurs when the centerline value of the loading is enhanced by any amount between about 10% to 100%. Observations of condensation trails indicate that downward departure of wake segments is rare. Upward departures of wake segments appears to be more common but still rare. A study to determine the part of the aircraft that causes wake departures has not been carried out. However, even though departures of wake segments rarely occur, some aircraft do regularly shed these wake structures. If aircraft safety is to be assured to a high degree of reliability, and a solution for eliminating them is not implemented, existing guidelines for the avoidance of vortex wakes [1,3] may need to be broadened to include possible increases in wake sizes caused by vertical departures of wake segments. Further study may indicate that it is not possible to modify existing aircraft enough to prevent wake departures. Wake-avoidance guidelines must then be adjusted to provide the desired degree of safety. It appears that steps to avoid upwardly moving wake segments have already been incorporated into the avoidance procedures used for aircraft on approach to runways at the Frankfurt Airport [6,7]. The uncertainty in the prospects for compromises in flight safety caused by rapidly upwardly or downwardly moving wake segments suggest that it be specified that aircraft do not fly above or below each other during operations in the airport vicinity where aircraft are likely to be closely spaced [20].

  8. Landscape genetics: combining landscape ecology and population genetics

    Treesearch

    Stephanie Manel; Michael K. Schwartz; Gordon Luikart; Pierre Taberlet

    2003-01-01

    Understanding the processes and patterns of gene flow and local adaptation requires a detailed knowledge of how landscape characteristics structure populations. This understanding is crucial, not only for improving ecological knowledge, but also for managing properly the genetic diversity of threatened and endangered populations. For nearly 80 years, population...

  9. Landscape preference assessment of Louisiana river landscapes: a methodological study

    Treesearch

    Michael S. Lee

    1979-01-01

    The study pertains to the development of an assessment system for the analysis of visual preference attributed to Louisiana river landscapes. The assessment system was utilized in the evaluation of 20 Louisiana river scenes. Individuals were tested for their free choice preference for the same scenes. A statistical analysis was conducted to examine the relationship...

  10. Genetic connectivity and inter-population seed dispersal of Banksia hookeriana at the landscape scale

    PubMed Central

    He, Tianhua; Lamont, Byron B.; Krauss, Siegfried L.; Enright, Neal J.

    2010-01-01

    Background and Aims Landscape genetics combines approaches from population genetics and landscape ecology, increasing the scope for conceptual advances in biology. Banksia hookeriana comprises clusters of individuals located on dune crests (geographical populations) physically separated by uninhabitable swales, with local extinctions common through frequent fire and/or severe drought. Methods A landscape genetics approach was used to explore landscape-scale genetic connectivity and structure among geographical populations of B. hookeriana on 18 physically separated dunes located within a heterogeneous landscape of 3 × 5 km. These geographical populations were separated by approx. 0·1 to >1 km of unsuitable intervening swale habitat. Using 11 highly variable microsatellite loci, we utilized a Bayesian approach to identify genetic discontinuities within and between these geographical populations. Population allocation tests were then used to detect inter-dune seed dispersal inferred from assignment of individuals to a source population other than that from which they were collected. Key Results For the modal number of genetically distinct clusters (n = 17 genetic populations), two coincided with the geographical (dune) populations, eight spanned two to four geographical populations, and the remaining seven were spread among various parts of the sampled dunes, so that most geographical populations were spatially defined mosaics of individuals (subpopulations) belonging to two or more genetic populations. We inferred 25 inter-dune immigrants among the 582 individuals assessed, with an average distance between sink and source dunes of 1·1 km, and a maximum of 3·3 km. Conclusions The results show that genetic structure in an apparently strongly spatially structured landscape is not solely dependent on landscape structure, and that many physically defined geographical populations were genetic mosaics. More strikingly, there were physically separated individuals and

  11. 40 CFR 247.15 - Landscaping products.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Landscaping products. (a) Hydraulic mulch products containing recovered paper or recovered wood used for hydroseeding and as an over-spray for straw mulch in landscaping, erosion control, and soil reclamation. (b...

  12. 40 CFR 247.15 - Landscaping products.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Landscaping products. (a) Hydraulic mulch products containing recovered paper or recovered wood used for hydroseeding and as an over-spray for straw mulch in landscaping, erosion control, and soil reclamation. (b...

  13. 40 CFR 247.15 - Landscaping products.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Landscaping products. (a) Hydraulic mulch products containing recovered paper or recovered wood used for hydroseeding and as an over-spray for straw mulch in landscaping, erosion control, and soil reclamation. (b...

  14. Imaginative Landscapes: This World and Beyond.

    ERIC Educational Resources Information Center

    Moore, John Noell, Ed.

    2001-01-01

    Describes a variety of books that offer fictional and poetic landscapes--five historical novels set in disparate locales, a book set in medieval Denmark, another addressing the landscape of memory, and a novel about a poet-scientist. (SR)

  15. 40 CFR 247.15 - Landscaping products.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Landscaping products. (a) Hydraulic mulch products containing recovered paper or recovered wood used for hydroseeding and as an over-spray for straw mulch in landscaping, erosion control, and soil reclamation....

  16. 40 CFR 247.15 - Landscaping products.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Landscaping products. (a) Hydraulic mulch products containing recovered paper or recovered wood used for hydroseeding and as an over-spray for straw mulch in landscaping, erosion control, and soil reclamation....

  17. Benefits and Risks Associated with Landscapes

    EPA Pesticide Factsheets

    To fully reap the benefits that lawns and landscapes can provide our urban and suburban communities, these green spaces must be well-maintained. The landscaping initiative helps manage the benefits and risks associated with lawn care.

  18. Fabric stability in oblique convergence and divergence

    NASA Astrophysics Data System (ADS)

    Teyssier, Christian; Tikoff, Basil

    1999-08-01

    Forward modeling of transpression-transtension, assuming homogeneous strain and a direct relationship between finite strain axes and foliation-lineation in tectonites, investigates fields of stability of foliation and lineation orientations in oblique convergence and divergence. Vertical foliation-horizontal lineation (VF-HL) develop for angles of convergence-divergence between 0 and 20°. With increasing finite strain, this narrow window of stability is further reduced; lineation switches to vertical in transpression and foliation switches to horizontal in transtension. If a shear zone contains VF-HL, it either developed as a zone very close to pure wrenching, or recorded low finite strain. The stability of VF-HL at high strain and higher angles of convergence is enhanced by lateral extrusion of material along transpression zones. VF-HL may be stabilized in magmatic bodies that progressively intrude transtension zones, if the wrench component of deformation partitions within them. Alternatively, if these bodies are dike-like, cool fast, and do not record large deformation, they take up the extension component of transtension through anisotropic volume addition, leaving a larger component of wrench deformation in the country rocks; this effect stabilizes VF-HL effectively at low strain, but only marginally so at high strain.

  19. Occurrence of Knudsen minima in diverging microchannels

    SciTech Connect

    Hemadri, Vadiraj; Bhandarkar, Upendra; Agrawal, Amit

    2014-12-09

    Rarefied gas flow is gaining increasing importance with the emergence of Micro Electro Mechanical Systems (MEMS). Knudsen minima is one of the characteristic feature of such rarefied flows and has been observed in uniform cross section channels such as plane channel, cylindrical tube and annulus. However, data pertaining to gaseous flow in varying cross section channel is relatively sparse. Channels of varying cross section are frequently encountered in MEMS devices and are fundamental to the design of micro-scale nozzles and micro-valves. In this context, rarefied gas flow through a diverging microchannel (divergence angle – 12 degree) is studied experimentally with three different gases (argon, nitrogen and oxygen). The experiments are performed over a wide range with the mean Knudsen number varying from slip to the transitional regime (0.07 to 1.2). It is found that the effect of molecular weight of the gas on the non-dimensional mass flow rate is negligible. The Knudsen minima is experimentally observed for the first time in microchannel of non-uniform cross section.

  20. Phylogeny of the Highly Divergent Echinosteliales (Amoebozoa).

    PubMed

    Kretzschmar, Martin; Kuhnt, Andreas; Bonkowski, Michael; Fiore-Donno, Anna Maria

    2016-07-01

    Myxomycetes or plasmodial slime molds are widespread and very common soil amoebae with the ability to form macroscopic fruiting bodies. Even if their phylogenetic position as a monophyletic group in Amoebozoa is well established, their internal relationships are still not entirely resolved. At the base of the most intensively studied dark-spored clade lies the order Echinosteliales, whose highly divergent small subunit ribosomal (18S) RNA genes represent a challenge for phylogenetic reconstructions. This is because they are characterized by unusually long variable helices of unknown secondary structure and a high inter- and infraspecific divergence. Current classification recognizes two families: the monogeneric Echinosteliaceae and the Clastodermataceae with the genera Barbeyella and Clastoderma. To better resolve the phylogeny of the Echinosteliales, we obtained three new small subunit ribosomal (18S) RNA gene sequences of Clastoderma and Echinostelium corynophorum. Our phylogenetic analyses suggested the polyphyly of the family Clastodermataceae, as Barbeyella was more closely related to Echinostelium arboreum than to Clastoderma, while Clastoderma debaryanum was the earliest branching clade in Echinosteliales. We also found that E. corynophorum was the closest relative of the enigmatic Semimorula liquescens, a stalkless-modified Echinosteliales. We discuss possible evolutionary pathways in dark-spored Myxomycetes and propose a taxonomic update. © 2015 The Author(s) Journal of Eukaryotic Microbiology © 2015 International Society of Protistologists.

  1. Generation of low-divergence laser beams

    DOEpatents

    Kronberg, J.W.

    1993-09-14

    Apparatus for transforming a conventional beam of coherent light, having a Gaussian energy distribution and relatively high divergence, into a beam in which the energy distribution approximates a single, non-zero-order Bessel function and which therefore has much lower divergence. The apparatus comprises a zone plate having transmitting and reflecting zones defined by the pattern of light interference produced by the combination of a beam of coherent light with a Gaussian energy distribution and one having such a Bessel distribution. The interference pattern between the two beams is a concentric array of multiple annuli, and is preferably recorded as a hologram. The hologram is then used to form the transmitting and reflecting zones by photo-etching portions of a reflecting layer deposited on a plate made of a transmitting material. A Bessel beam, containing approximately 50% of the energy of the incident beam, is produced by passing a Gaussian beam through such a Bessel zone plate. The reflected beam, also containing approximately 50% of the incident beam energy and having a Bessel energy distribution, can be redirected in the same direction and parallel to the transmitted beam. Alternatively, a filter similar to the Bessel zone plate can be placed within the resonator cavity of a conventional laser system having a front mirror and a rear mirror, preferably axially aligned with the mirrors and just inside the front mirror to generate Bessel energy distribution light beams at the laser source. 11 figures.

  2. Generation of low-divergence laser beams

    DOEpatents

    Kronberg, James W.

    1993-01-01

    Apparatus for transforming a conventional beam of coherent light, having a Gaussian energy distribution and relatively high divergence, into a beam in which the energy distribution approximates a single, non-zero-order Bessel function and which therefore has much lower divergence. The apparatus comprises a zone plate having transmitting and reflecting zones defined by the pattern of light interference produced by the combination of a beam of coherent light with a Gaussian energy distribution and one having such a Bessel distribution. The interference pattern between the two beams is a concentric array of multiple annuli, and is preferably recorded as a hologram. The hologram is then used to form the transmitting and reflecting zones by photo-etching portions of a reflecting layer deposited on a plate made of a transmitting material. A Bessel beam, containing approximately 50% of the energy of the incident beam, is produced by passing a Gaussian beam through such a Bessel zone plate. The reflected beam, also containing approximately 50% of the incident beam energy and having a Bessel energy distribution, can be redirected in the same direction and parallel to the transmitted beam. Alternatively, a filter similar to the Bessel zone plate can be placed within the resonator cavity of a conventional laser system having a front mirror and a rear mirror, preferably axially aligned with the mirrors and just inside the front mirror to generate Bessel energy distribution light beams at the laser source.

  3. History repeats itself: genomic divergence in copepods.

    PubMed

    Renaut, Sébastien; Dion-Côté, Anne-Marie

    2016-04-01

    Press stop, erase everything from now till some arbitrary time in the past and start recording life as it evolves once again. Would you see the same tape of life playing itself over and over, or would a different story unfold every time? The late Steven Jay Gould called this experiment replaying the tape of life and argued that any replay of the tape would lead evolution down a pathway radically different from the road actually taken (Gould 1989). This thought experiment has puzzled evolutionary biologists for a long time: how repeatable are evolutionary events? And if history does indeed repeat itself, what are the factors that may help us predict the path taken? A powerful means to address these questions at a small evolutionary scale is to study closely related populations that have evolved independently, under similar environmental conditions. This is precisely what Pereira et al. (2016) set out to do using marine copepods Tigriopus californicus, and present their results in this issue of Molecular Ecology. They show that evolution can be repeatable and even partly predictable, at least at the molecular level. As expected from theory, patterns of divergence were shaped by natural selection. At the same time, strong genetic drift due to small population sizes also constrained evolution down a similar evolutionary road, and probably contributed to repeatable patterns of genomic divergence. © 2016 John Wiley & Sons Ltd.

  4. World health inequality: convergence, divergence, and development.

    PubMed

    Clark, Rob

    2011-02-01

    Recent studies characterize the last half of the twentieth century as an era of cross-national health convergence, with some attributing welfare gains in the developing world to economic growth. In this study, I examine the extent to which welfare outcomes have actually converged and the extent to which economic development is responsible for the observed trends. Drawing from estimates covering 195 nations during the 1955-2005 period, I find that life expectancy averages converged during this time, but that infant mortality rates continuously diverged. I develop a narrative that implicates economic development in these contrasting trends, suggesting that health outcomes follow a "welfare Kuznets curve." Among poor countries, economic development improves life expectancy more than it reduces infant mortality, whereas the situation is reversed among wealthier nations. In this way, development has contributed to both convergence in life expectancy and divergence in infant mortality. Drawing from 674 observations across 163 countries during the 1980-2005 period, I find that the positive effect of GDP PC on life expectancy attenuates at higher levels of development, while the negative effect of GDP PC on infant mortality grows stronger. Copyright © 2010 Elsevier Ltd. All rights reserved.

  5. Martian Landscapes in Motion

    NASA Astrophysics Data System (ADS)

    Mattson, Sarah; McEwen, Alfred; Kirk, Randolph; Howington-Kraus, Elpitha; Chojnacki, Matthew; Runyon, Kirby; Cremonese, Gabriele; Re, Cristina

    2014-05-01

    RISE orthorectified image sequences makes it possible to conduct accurate change detection studies of active processes on Mars. Some examples of studies of active landscapes on Mars using HiRISE DTMs and orthoimage sequences include: dune and ripple motion (Bridges et al., 2012, Nature), recurring slope lineae (RSL) (McEwen et al., 2011, Science; McEwen et al., 2013, Nature Geoscience), gully activity (Dundas et al., 2012, Icarus), and polar processes (Hansen et al., 2011, Science; Portyankina et al. 2013, Icarus,). These studies encompass images from multiple Mars years and seasons. Sequences of orthoimages make it possible to generate animated gifs or movies to visualize temporal changes (http://www.uahirise.org/sim/). They can also be brought into geospatial software to quantitatively map and record changes. The ability to monitor the surface of Mars at high spatial resolution with frequent repeat images has opened up our insight into seasonal and interannual changes, further increasing our understanding of Mars as an active planet.

  6. Bromine and Chlorine Go Separate Ways

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This graph shows the relative concentrations of bromine and chlorine at various locations on Earth and Mars. Typically, bromine and chlorine stick together in a fixed ratio, as in martian meteorites and Earth seawater. But sometimes the elements split apart and their relative quantities diverge. This separation is usually caused by evaporation processes, as in the Dead Sea on Earth. On Mars, at Meridiani Planum and Gusev Crater, this split has been observed to an even greater degree than seen on Earth. This puzzling result is currently being further explored by Mars Exploration Rover scientists. Data for the Mars locations were taken by the rover's alpha particle X-ray spectrometer.

  7. Bromine and Chlorine Go Separate Ways

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This graph shows the relative concentrations of bromine and chlorine at various locations on Earth and Mars. Typically, bromine and chlorine stick together in a fixed ratio, as in martian meteorites and Earth seawater. But sometimes the elements split apart and their relative quantities diverge. This separation is usually caused by evaporation processes, as in the Dead Sea on Earth. On Mars, at Meridiani Planum and Gusev Crater, this split has been observed to an even greater degree than seen on Earth. This puzzling result is currently being further explored by Mars Exploration Rover scientists. Data for the Mars locations were taken by the rover's alpha particle X-ray spectrometer.

  8. Wildlife disease prevalence in human-modified landscapes.

    PubMed

    Brearley, Grant; Rhodes, Jonathan; Bradley, Adrian; Baxter, Greg; Seabrook, Leonie; Lunney, Daniel; Liu, Yan; McAlpine, Clive

    2013-05-01

    have been based on a one-dimensional comparison between unmodified and modified sites. What is lacking are spatially and temporally explicit quantitative approaches which are required to enable an understanding of the range of key causal mechanisms and the reasons for variability. This is particularly important for replicated studies across different host-pathogen systems. Furthermore, there are few studies that have attempted to separate the independent effects of habitat loss and fragmentation on wildlife disease, which are the major determinants of wildlife population dynamics in human-modified landscapes. There is an urgent need to understand better the potential causal links between the processes of human-induced landscape change and the associated influences of habitat fragmentation, matrix hostility and loss of connectivity on an animal's physiological stress, immune response and disease susceptibility. This review identified no study that had assessed the influence of human-induced landscape change on the prevalence of a wildlife sexually transmitted disease. A better understanding of the various mechanisms linking human-induced landscape change and the prevalence of wildlife disease will lead to more successful conservation management outcomes. © 2012 The Authors. Biological Reviews © 2012 Cambridge Philosophical Society.

  9. Controlling Separation in Turbomachines

    NASA Technical Reports Server (NTRS)

    Evans, Simon; Himmel, Christoph; Power, Bronwyn; Wakelam, Christian; Xu, Liping; Hynes, Tom; Hodson, Howard

    2010-01-01

    Four examples of flow control: 1) Passive control of LP turbine blades (Laminar separation control). 2) Aspiration of a conventional axial compressor blade (Turbulent separation control). 3) Compressor blade designed for aspiration (Turbulent separation control). 4.Control of intakes in crosswinds (Turbulent separation control).

  10. Natural selection and neutral evolution jointly drive population divergence between alpine and lowland ecotypes of the allopolyploid plant Anemone multifida (Ranunculaceae).

    PubMed

    McEwen, Jamie R; Vamosi, Jana C; Rogers, Sean M

    2013-01-01

    Population differentiation can be driven in large part by natural selection, but selectively neutral evolution can play a prominent role in shaping patters of population divergence. The decomposition of the evolutionary history of populations into the relative effects of natural selection and selectively neutral evolution enables an understanding of the causes of population divergence and adaptation. In this study, we examined heterogeneous genomic divergence between alpine and lowland ecotypes of the allopolyploid plant, Anemone multifida. Using peak height and dominant AFLP data, we quantified population differentiation at non-outlier (neutral) and outlier loci to determine the potential contribution of natural selection and selectively neutral evolution to population divergence. We found 13 candidate loci, corresponding to 2.7% of loci, with signatures of divergent natural selection between alpine and lowland populations and between alpine populations (Fst  = 0.074-0.445 at outlier loci), but neutral population differentiation was also evident between alpine populations (FST  = 0.041-0.095 at neutral loci). By examining population structure at both neutral and outlier loci, we determined that the combined effects of selection and neutral evolution are associated with the divergence of alpine populations, which may be linked to extreme abiotic conditions and isolation between alpine sites. The presence of outlier levels of genetic variation in structured populations underscores the importance of separately analyzing neutral and outlier loci to infer the relative role of divergent natural selection and neutral evolution in population divergence.

  11. Natural Selection and Neutral Evolution Jointly Drive Population Divergence between Alpine and Lowland Ecotypes of the Allopolyploid Plant Anemone multifida (Ranunculaceae)

    PubMed Central

    McEwen, Jamie R.; Vamosi, Jana C.; Rogers, Sean M.

    2013-01-01

    Population differentiation can be driven in large part by natural selection, but selectively neutral evolution can play a prominent role in shaping patters of population divergence. The decomposition of the evolutionary history of populations into the relative effects of natural selection and selectively neutral evolution enables an understanding of the causes of population divergence and adaptation. In this study, we examined heterogeneous genomic divergence between alpine and lowland ecotypes of the allopolyploid plant, Anemone multifida. Using peak height and dominant AFLP data, we quantified population differentiation at non-outlier (neutral) and outlier loci to determine the potential contribution of natural selection and selectively neutral evolution to population divergence. We found 13 candidate loci, corresponding to 2.7% of loci, with signatures of divergent natural selection between alpine and lowland populations and between alpine populations (Fst  = 0.074–0.445 at outlier loci), but neutral population differentiation was also evident between alpine populations (FST  = 0.041–0.095 at neutral loci). By examining population structure at both neutral and outlier loci, we determined that the combined effects of selection and neutral evolution are associated with the divergence of alpine populations, which may be linked to extreme abiotic conditions and isolation between alpine sites. The presence of outlier levels of genetic variation in structured populations underscores the importance of separately analyzing neutral and outlier loci to infer the relative role of divergent natural selection and neutral evolution in population divergence. PMID:23874801

  12. Landscape Builder: software for the creation of initial landscapes for LANDIS from FIA data

    Treesearch

    William. Dijak

    2013-01-01

    I developed Landscape Builder to create spatially explicit landscapes as starting conditions for LANDIS Pro 7.0 and LANDIS II landscape forest simulation models from classified satellite imagery and Forest Inventory and Analysis (FIA) data collected over multiple years. LANDIS Pro and LANDIS II models project future landscapes by simulating tree growth, tree species...

  13. Vegetation responsees to landscape structure at multiple scales across a Northern Wisconsin, USA, pine barrens landscape

    Treesearch

    K.D. Brosofske; J. Chen; Thomas R. Crow; S.C. Saunders

    1999-01-01

    Increasing awareness of the importance of scale and landscape structure to landscape processes and concern about loss of biodiversity has resulted in efforts to understand patterns of biodiversity across multiple scales. We examined plant species distributions and their relationships to landscape structure at varying spatial scales across a pine barrens landscape in...

  14. Recombination between diverged clusters of the tomato Cf-9 plant disease resistance gene family

    PubMed Central

    Parniske, Martin; Jones, Jonathan D. G.

    1999-01-01

    The tomato Cf-4 and Cf-9 genes are the founder members of a large gene family of homologues of Cladosporium fulvum resistance gene Cf-9 (Hcr9 genes), several of which confer resistance against C. fulvum through recognition of different pathogen-encoded avirulence determinants. Three loci of tandemly repeated Hcr9 genes—Southern Cross (SC), Milky Way (MW), and Northern Lights (NL)—are located on the short arm of tomato chromosome 1. Comparisons between 2 SC-Hcr9s, 11 from MW, and 5 from NL implicated sequence exchange between gene family members in their evolution. The extent to which novel variants can be generated by recombination depends on the degree of sequence polymorphism available within the gene family. Here we show that physical separation of Hcr9 genes can be associated with elevated sequence divergence. Two diverged subclasses of Hcr9s could be defined. These are physically separated from each other, with members of one class exclusively residing at Northern Lights. One exceptional Hcr9 at Northern Lights carried sequence features specific for Hcr9s at other loci, suggesting a recent transfer of this gene by an interlocus recombination event. As members of diverged subclasses are brought into physical vicinity within a tandem repeat, a larger spectrum of sequence variants can potentially be generated by subsequent interhomologue sequence exchange. PMID:10318973

  15. Separation-individuation theory and attachment theory.

    PubMed

    Blum, Harold P

    2004-01-01

    Separation-individuation and attachment theories are compared and assessed in the context of psychoanalytic developmental theory and their application to clinical work. As introduced by Margaret Mahler and John Bowlby, respectively, both theories were initially regarded as diverging from traditional views. Separation-individuation theory, though it has had to be corrected in important respects, and attachment theory, despite certain limitations, have nonetheless enriched psychoanalytic thought. Without attachment an infant would die, and with severely insecure attachment is at greater risk for serious disorders. Development depends on continued attachment to a responsive and responsible caregiver. Continued attachment to the primary object was regarded by Mahler as as intrinsic to the process of separation-individuation. Attachment theory does not account for the essential development of separateness, and separation-individuation is important for the promotion of autonomy, independence, and identity. Salient historical and theoretical issues are addressed, including the renewed interest in attachment theory and the related decline of interest in separation-individuation theory.

  16. Population divergence in fish elemental phenotypes associated with trophic phenotypes and lake trophic state.

    PubMed

    Tuckett, Quenton M; Kinnison, Michael T; Saros, Jasmine E; Simon, Kevin S

    2016-11-01

    Studies of ecological stoichiometry typically emphasize the role of interspecific variation in body elemental content and the effects of species or family identity. Recent work suggests substantial variation in body stoichiometry can also exist within species. The importance of this variation will depend on insights into its origins and consequences at various ecological scales, including the distribution of elemental phenotypes across landscapes and their role in nutrient recycling. We investigated whether trophic divergence can produce predictable patterns of elemental phenotypes among populations of an invasive fish, the white perch (Morone americana), and whether elemental phenotypes predict nutrient excretion. White perch populations exhibited a gradient of trophic phenotypes associated with landscape-scale variation in lake trophic state. Perch body chemistry varied considerably among lakes (from 0.09 for % C to 0.31-fold for % P) casting doubt on the assumption of homogenous elemental phenotypes. This variation was correlated with divergence in fish body shape and other trophic traits. Elemental phenotypes covaried (r (2) up to 0.84) with lake trophic state. This covariation likely arose in contemporary time since many of these perch populations were introduced in the last century and the trophic state in many of the lakes has changed in the past few decades. Nutrient excretion varied extensively among populations, but was not readily related to fish body chemistry or lake trophic state. This suggests that predictable patterns of fish body composition can arise quickly through trophic specialization to lake conditions, but such elemental phenotypes may not translate to altered nutrient recycling by fish.

  17. Rapid Diversity Loss of Competing Animal Species in Well-Connected Landscapes

    PubMed Central

    Schippers, Peter; Hemerik, Lia; Baveco, Johannes M.; Verboom, Jana

    2015-01-01

    Population viability of a single species, when evaluated with metapopulation based landscape evaluation tools, always increases when the connectivity of the landscape increases. However, when interactions between species are taken into account, results can differ. We explore this issue using a stochastic spatially explicit meta-community model with 21 competing species in five different competitive settings: (1) weak, coexisting competition, (2) neutral competition, (3) strong, excluding competition, (4) hierarchical competition and (5) random species competition. The species compete in randomly generated landscapes with various fragmentation levels. With this model we study species loss over time. Simulation results show that overall diversity, the species richness in the entire landscape, decreases slowly in fragmented landscapes whereas in well-connected landscapes rapid species losses occur. These results are robust with respect to changing competitive settings, species parameters and spatial configurations. They indicate that optimal landscape configuration for species conservation differs between metapopulation approaches, modelling species separately and meta-community approaches allowing species interactions. The mechanism behind this is that species in well-connected landscapes rapidly outcompete each other. Species that become abundant, by chance or by their completive strength, send out large amounts of dispersers that colonize and take over other patches that are occupied by species that are less abundant. This mechanism causes rapid species loss. In fragmented landscapes the colonization rate is lower, and it is difficult for a new species to establish in an already occupied patch. So, here dominant species cannot easily take over patches occupied by other species and higher diversity is maintained for a longer time. These results suggest that fragmented landscapes have benefits for species conservation previously unrecognized by the landscape ecology

  18. Space Strategies for the New Learning Landscape

    ERIC Educational Resources Information Center

    Dugdale, Shirley

    2009-01-01

    The Learning Landscape is the total context for students' learning experiences and the diverse landscape of learning settings available today--from specialized to multipurpose, from formal to informal, and from physical to virtual. The goal of the Learning Landscape approach is to acknowledge this richness and maximize encounters among people,…

  19. Designing landscapes for northern Nevada's arid climate

    Treesearch

    Heidi Kratsch; JoAnne Skelly

    2011-01-01

    Landscape design is both art and organization. Anyone can plant trees or shrubs in a row, but that isn't a designed landscape. Landscape design is placing plants and structures in ways that organize and enrich an outdoor space to have agreeable and useful relationships with the natural environment. A good design makes the best use of the space available and the...

  20. The Changing Landscape of Higher Education

    ERIC Educational Resources Information Center

    Staley, David J.; Trinkle, Dennis A.

    2011-01-01

    The landscape of higher education--the growing variety of higher education institutions, the cultural environment, the competitive ecosystem--is changing rapidly and disruptively. The higher education landscape is metaphorically crossed with fault lines, those fissures in the landscape creating potential areas of dramatic change, and is as…

  1. The social value of English landscapes

    Treesearch

    Edmund C. Penning-Rowsell

    1979-01-01

    Qualitative assessments of landscape resources can best be approached through direct measurement of landscape perceptions. Results from a survey of one District in Hertfordshire, England, show this approach not only to be viable but also to yield much information relevant to plans for landscape improvement and protection. Consensus was high and the socio-economic...

  2. An Analysis of the Landscaping Occupation.

    ERIC Educational Resources Information Center

    Stemple, Lynn L.; Dilley, John E.

    The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the landscape services occupation. Depending on the preparation and abilities of the individual student, he may enter the landscape area as (1) nursery worker, (2) landscape planter, (3) landscape…

  3. Research needs for our national landscapes

    Treesearch

    Elwood L. Shafer

    1979-01-01

    The prevailing research problem for our national landscapes is: How shall we organize, control, and coordinate public and private development so as to protect, maintain, improve, and manage those landscape features that we value most? Research questions discussed include: environmental/political conflicts, taxation and zoning, landscape classification, public...

  4. The Changing Landscape of Higher Education

    ERIC Educational Resources Information Center

    Staley, David J.; Trinkle, Dennis A.

    2011-01-01

    The landscape of higher education--the growing variety of higher education institutions, the cultural environment, the competitive ecosystem--is changing rapidly and disruptively. The higher education landscape is metaphorically crossed with fault lines, those fissures in the landscape creating potential areas of dramatic change, and is as…

  5. Ecosystem services in changing landscapes: An introduction

    Treesearch

    Louis Iverson; Cristian Echeverria; Laura Nahuelhual; Sandra. Luque

    2014-01-01

    The concept of ecosystem services from landscapes is rapidly gaining momentum as a language to communicate values and benefits to scientists and lay alike. Landscape ecology has an enormous contribution to make to this field, and one could argue, uniquely so. Tools developed or adapted for landscape ecology are being increasingly used to assist with the quantification...

  6. Optimization of landscape pattern [Chapter 8

    Treesearch

    John Hof; Curtis Flather

    2007-01-01

    A fundamental assumption in landscape ecology is that spatial patterns have significant influences on the flows of materials, energy, and information while processes create, modify, and maintain spatial patterns. Thus, it is of paramount importance in both theory and practice to address the questions of landscape pattern optimization ... For example, can landscape...

  7. Axion landscape and natural inflation

    NASA Astrophysics Data System (ADS)

    Higaki, Tetsutaro; Takahashi, Fuminobu

    2015-05-01

    Multiple axions form a landscape in the presence of various shift symmetry breaking terms. Eternal inflation populates the axion landscape, continuously creating new universes by bubble nucleation. Slow-roll inflation takes place after the tunneling event, if a very flat direction with a super-Planckian decay constant arises due to the alignment mechanism. We study the vacuum structure as well as possible inflationary dynamics in the axion landscape scenario, and find that the inflaton dynamics is given by either natural or multi-natural inflation. In the limit of large decay constant, it is approximated by the quadratic chaotic inflation, which however is disfavored if there is a pressure toward shorter duration of inflation. Therefore, if the spectral index and the tensor-to-scalar ratio turn out to be different from the quadratic chaotic inflation, there might be observable traces of the bubble nucleation. Also, the existence of small modulations to the inflaton potential is a common feature in the axion landscape, which generates a sizable and almost constant running of the scalar spectral index over CMB scales. Non-Gaussianity of equilateral type can also be generated if some of the axions are coupled to massless gauge fields.

  8. Language's Landscape of the Mind.

    ERIC Educational Resources Information Center

    Tracy, Janet

    2000-01-01

    Describes how the author's 6 middle school students living in a village in the Yukon, 100 miles off the road system just below the arctic circle, enthusiastically wrote stories or poems about their lives. The students shared their works via an online electronic conferencing system with students from the unimaginably different landscape of the…

  9. LANDSCAPING YOUR HOME, TEACHER'S GUIDE.

    ERIC Educational Resources Information Center

    HEDGES, LOWELL E.

    THE PURPOSE OF THIS GUIDE IS TO ASSIST THE VOCATIONAL AGRICULTURE TEACHER TO DEVELOP A UNIT IN THE RELATIVELY SPECIALIZED FIELD OF HOME LANDSCAPING. IT WAS DEVELOPED BY A TEACHER IN CONSULTATION WITH HORTICULTURISTS AND TESTED IN THE CLASSROOM BEFORE PUBLICATION. THE OBJECTIVES OF THE UNIT ARE TO DEVELOP STUDENT ABILITY TO (1) UNDERSTAND THE NEED…

  10. A heuristic for landscape management

    Treesearch

    Martín Alfonso B. Mendoza; Jesús S. Zepeta; Juan José A. Fajardo

    2006-01-01

    The development of landscape ecology has stressed out the importance of spatial and sequential relationships as explanations to forest stand dynamics, and for other natural ambiences. This presentation offers a specific design that introduces spatial considerations into forest planning with the idea of regulating fragmentation and connectivity in commercial forest...

  11. Assessing the New Competitive Landscape.

    ERIC Educational Resources Information Center

    Blustain, Harvey; Goldstein, Philip; Lozier, Gregory

    1998-01-01

    Argues that complex forces (new delivery technologies, changing demographics, emergence of corporate universities, global economy) have created a new, competitive landscape for higher education that forces institutions to think methodically about how to respond. A framework for college planning, incorporating three critical components, is…

  12. Selected Landscape Plants. Slide Script.

    ERIC Educational Resources Information Center

    McCann, Kevin

    This slide script, part of a series of slide scripts designed for use in vocational agriculture classes, deals with commercially important woody ornamental landscape plants. Included in the script are narrations for use with a total of 253 slides illustrating 92 different plants. Several slides are used to illustrate each plant: besides a view of…

  13. Ornamental Landscape Grasses. Slide Script.

    ERIC Educational Resources Information Center

    Still, Steven M.; Adams, Denise W.

    This slide script to accompany the slide series, Ornamental Landscape Grasses, contains photographs of the 167 slides and accompanying narrative text intended for use in the study and identification of commercially important ornamental grasses and grasslike plants. Narrative text is provided for slides of 62 different perennial and annual species…

  14. Eucalyptus as a landscape tree

    Treesearch

    W. Douglas Hamilton

    1983-01-01

    Ninety-two species of Eucalyptus were evaluated at the University of California re- search station in San Jose. The purpose: to find acceptable new street and park trees. Growth rates and horticultural characteristics were noted. Forty-three species were studied in locations statewide to evaluate site adaptation and landscape usefulness; flooded, cold, dry, saline....

  15. Bioenergy in a Multifunctional Landscape

    SciTech Connect

    Watts, Chad; Negri, Cristina; Ssegane, Herbert

    2015-10-23

    How can our landscapes be managed most effectively to produce crops for food, feed, and bioenergy, while also protecting our water resources by preventing the loss of nutrients from the soil? Dr. Cristina Negri and her team at the U.S. Department of Energy’s Argonne National Laboratory are tackling this question at an agricultural research site located in Fairbury, Illinois.

  16. Ornamental Landscape Grasses. Slide Script.

    ERIC Educational Resources Information Center

    Still, Steven M.; Adams, Denise W.

    This slide script to accompany the slide series, Ornamental Landscape Grasses, contains photographs of the 167 slides and accompanying narrative text intended for use in the study and identification of commercially important ornamental grasses and grasslike plants. Narrative text is provided for slides of 62 different perennial and annual species…

  17. Linguistic Landscape and Minority Languages

    ERIC Educational Resources Information Center

    Cenoz, Jasone; Gorter, Durk

    2006-01-01

    This paper focuses on the linguistic landscape of two streets in two multilingual cities in Friesland (Netherlands) and the Basque Country (Spain) where a minority language is spoken, Basque or Frisian. The paper analyses the use of the minority language (Basque or Frisian), the state language (Spanish or Dutch) and English as an international…

  18. Lessons from a flooded landscape.

    Treesearch

    Sally. Duncan

    1998-01-01

    In our first issue, we describe research that reflects our responsiveness to natural events and our ability to address issues over time. Floods can bring tragedy in the wake of their destruction. Floods also are a natural process that has shaped our landscapes. We hope that our scientific information helps people make wise choices that influence floods associated with...

  19. Flowers and Landscape by Serendipity.

    ERIC Educational Resources Information Center

    Pippin, Sandi

    2003-01-01

    Describes an art lesson in which students sketch drawings of flowers and use watercolor paper and other materials to paint a landscape. Explains that the students also learn about impressionism in this lesson. Discusses how the students prepare the paper and create their artwork. (CMK)

  20. Renewable energy from urban landscapes

    USDA-ARS?s Scientific Manuscript database

    Utilizing biomass from urban landscapes could significantly contribute to the nation’s renewable energy needs. In 2007, an experiment was begun to evaluate the biomass potential from a bermudagrass, Cynodon dactylon var. dactylon (L.) Pers., lawn in Woodward, OK and to estimate the potential biomas...