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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

    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 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

  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. 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.

  14. 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.

  15. 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…

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. [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.

  6. 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…

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Mars Landscapes

    NASA Video Gallery

    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...

  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. 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

  15. 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.)

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.…

  17. 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…

  18. 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,…

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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…

  5. 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 ...

  6. 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)

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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. 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

  15. 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

  16. 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…

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Enhancement Through Landscaping.

    ERIC Educational Resources Information Center

    Lindley, Charles

    1985-01-01

    Landscaping can make the school environment more attractive, thus encouraging students' intellectual, emotional, and physical development. Guidelines are offered for comprehensive site planning, tree and plant selection, and grounds maintenance. (MLF)

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Adaptive filters: stable but divergent

    NASA Astrophysics Data System (ADS)

    Rupp, Markus

    2015-12-01

    The pros and cons of a quadratic error measure in the context of various applications have often been discussed. In this tutorial, we argue that it is not only a suboptimal but definitely the wrong choice when describing the stability behavior of adaptive filters. We take a walk through the past and recent history of adaptive filters and present 14 canonical forms of adaptive algorithms and even more variants thereof contrasting their mean-square with their l 2-stability conditions. In particular, in safety critical applications, the convergence in the mean-square sense turns out to provide wrong results, often not leading to stability at all. Only the robustness concept with its l 2-stability conditions ensures the absence of divergence.

  16. 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.

  17. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  19. 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

  20. 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.

  1. 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.

  2. 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…

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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)

  13. 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.

  14. 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)

  15. 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…

  16. 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…

  17. 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…

  18. 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…

  19. 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.

  20. 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,…

  1. 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.

  2. 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...

  3. 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…

  4. 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…

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. [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.

  18. 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)

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  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. 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.

  15. 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.

  16. 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.

  17. 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…

  18. 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.

  19. 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.

  20. 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.

  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. 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.

  3. 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.

  4. 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

  5. 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.

  6. Antagonistic selection factors induce a continuous population divergence in a polymorphism

    PubMed Central

    Takahashi, Y; Nagata, N; Kawata, M

    2014-01-01

    Understanding the relative importance of selection and stochastic factors in population divergence of adaptive traits is a classical topic in evolutionary biology. However, it is difficult to separate these factors and detect the effects of selection when two or more contrasting selective factors are simultaneously acting on a single locus. In the damselfly Ischnura senegalensis, females exhibit color dimorphism and morph frequencies change geographically. We here evaluated the role of selection and stochastic factors in population divergence of morph frequencies by comparing the divergences in color locus and neutral loci. Comparisons between population pairwise FST for neutral loci and for the color locus did not detect any stochastic factors affecting color locus. Although comparison between population divergence in color and neutral loci using all populations detected only divergent selection, we detected two antagonistic selective factors acting on the color locus, that is, balancing and divergent selection, when considering geographical distance between populations. Our results suggest that a combination of two antagonistic selective factors, rather than stochastic factors, establishes the geographic cline in morph frequency in this system. PMID:24281546

  7. 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.

  8. 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.

  9. 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.

  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. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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)

  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. 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…

  17. 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…

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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…

  5. 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.

  6. 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…

  7. 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

  8. 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

  9. 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,…

  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. 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

  13. 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.

  14. Domestication and Divergence of Saccharomyces cerevisiae Beer Yeasts.

    PubMed

    Gallone, Brigida; Steensels, Jan; Prahl, Troels; Soriaga, Leah; Saels, Veerle; Herrera-Malaver, Beatriz; Merlevede, Adriaan; Roncoroni, Miguel; Voordeckers, Karin; Miraglia, Loren; Teiling, Clotilde; Steffy, Brian; Taylor, Maryann; Schwartz, Ariel; Richardson, Toby; White, Christopher; Baele, Guy; Maere, Steven; Verstrepen, Kevin J

    2016-09-08

    Whereas domestication of livestock, pets, and crops is well documented, it is still unclear to what extent microbes associated with the production of food have also undergone human selection and where the plethora of industrial strains originates from. Here, we present the genomes and phenomes of 157 industrial Saccharomyces cerevisiae yeasts. Our analyses reveal that today's industrial yeasts can be divided into five sublineages that are genetically and phenotypically separated from wild strains and originate from only a few ancestors through complex patterns of domestication and local divergence. Large-scale phenotyping and genome analysis further show strong industry-specific selection for stress tolerance, sugar utilization, and flavor production, while the sexual cycle and other phenotypes related to survival in nature show decay, particularly in beer yeasts. Together, these results shed light on the origins, evolutionary history, and phenotypic diversity of industrial yeasts and provide a resource for further selection of superior strains. PAPERCLIP.

  15. [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.

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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...

  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. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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...

  3. 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.

  4. 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.

  5. Phenotypic plasticity and divergence in gene expression.

    PubMed

    Healy, Timothy M; Schulte, Patricia M

    2015-07-01

    The extent to which phenotypic plasticity, or the ability of a single genotype to produce different phenotypes in different environments, impedes or promotes genetic divergence has been a matter of debate within evolutionary biology for many decades (see, for example, Ghalambor et al. ; Pfennig et al. ). Similarly, the role of evolution in shaping phenotypic plasticity remains poorly understood (Pigliucci ). In this issue of Molecular Ecology, Dayan et al. () provide empirical data relevant to these questions by assessing the extent of plasticity and divergence in the expression levels of 2272 genes in muscle tissue from killifish (genus Fundulus) exposed to different temperatures. F. heteroclitus (Fig. A) and F. grandis are minnows that inhabit estuarine marshes (Fig. B) along the coasts of the Atlantic Ocean and Gulf of Mexico in North America. These habitats undergo large variations in temperature both daily and seasonally, and these fish are known to demonstrate substantial phenotypic plasticity in response to temperature change (e.g. Fangue et al. ). Furthermore, the range of F. heteroclitus spans a large latitudinal gradient of temperatures, such that northern populations experience temperatures that are on average ~10°C colder than do southern populations (Schulte ). By comparing gene expression patterns between populations of these fish from different thermal habitats held in the laboratory at three different temperatures, Dayan et al. () address two important questions regarding the interacting effects of plasticity and evolution: (i) How does phenotypic plasticity affect adaptive divergence? and (ii) How does adaptive divergence affect plasticity?

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. Shoulder separation - aftercare

    MedlinePlus

    Separated shoulder - aftercare; Acromioclavicular joint separation - aftercare; A/C separation - aftercare ... Most shoulder separation injuries are caused by falling onto the shoulder. This causes a tear in the tissue that connects the ...

  17. 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

  18. 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.

  19. 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).

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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."

  11. 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.

  12. [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.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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).

  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. 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.

  2. [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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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....

  10. 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....

  11. 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)

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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].

  19. 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…

  20. 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)

  1. 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.

  2. 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…

  3. 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…

  4. 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…

  5. Discovery Learning in Landscape Archaeology.

    ERIC Educational Resources Information Center

    O'Brien, Colm; Wheeler, Hazel

    1979-01-01

    A method of discovery learning in which students learn the technique of observing and formulating questions is applied to landscape archaeology. This method demands that the relationship between tutor and student be adjusted so that the tutor becomes a fellow researcher rather than a conveyor of information. (Author/CSS)

  6. 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…

  7. 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…

  8. 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

  9. Separation Anxiety (For Parents)

    MedlinePlus

    ... Old Feeding Your 1- to 2-Year-Old Separation Anxiety KidsHealth > For Parents > Separation Anxiety Print A ... help both of you get through it. About Separation Anxiety Babies adapt pretty well to other caregivers. ...

  10. How divergence mechanisms influence disassortative mixing property in biology

    NASA Astrophysics Data System (ADS)

    Xu, Chunsui; Liu, Zengrong; Wang, Ruiqi

    2010-02-01

    The duplication-divergence mechanism of network growth has been widely investigated, especially in gene and protein networks. Both the duplication and divergence have a key role in biological network evolution. However, the relative roles of these mechanisms in the influence of disassortative property in protein interaction networks remain to be clarified. It has been shown that duplication can indeed make protein networks evolve towards disassortative networks. To make the relationship between the disassortative property and the duplication-divergence mechanism more clear, we further discuss how the divergence mechanism influences the disassortative property. We tested four different divergence mechanisms, i.e., node deletion, edge deletion, edge addition, and edge rewiring to study their effects on disassortative property. Our study highlights the crucial roles of different divergence evolution mechanisms.

  11. Studies of morphological and molecular phylogenetic divergence in spiders (Araneae: Homalonychus) from the American southwest, including divergence along the Baja California Peninsula.

    PubMed

    Crews, Sarah C; Hedin, Marshal

    2006-02-01

    Comparative phylogenetic and phylogeographic analyses have revealed a pervasive midpeninsular divergence in the mitochondrial genealogies of numerous vertebrate taxa distributed on the Baja California Peninsula. In this study, we extend the investigation of regional vicariance in Baja California to an arthropod taxon by examining patterns of phylogenetic and morphological divergence in the spider genus Homalonychus (Araneae, Homalonychidae). We analyzed data from two mtDNA genes (16S rRNA and NADH dehydrogenase subunit (1) and a nuclear gene (28S rRNA) using maximum parsimony and Bayesian phylogenetic analyses, and also conducted geometric morphometric analyses employing landmark data on male and female genitalia. Genes and morphology both reveal a deep split across the Colorado River and Gulf of California, separating Homalonychus selenopoides on the east side of river from its congener Homalonychus theologus on the west side of the river, including the Baja California Peninsula. Along the north-south axis of the Baja Peninsula, an apparently more recent midpeninsular phylogenetic break is evident within H. theologus in the mitochondrial genome and in female genitalia. However, there is no measurable divergence between northern and southern populations in either nuclear DNA or male genitalia. We suggest that this discordance between datasets reflects either a difference in rates of evolution between male versus female systems, or that male-based nuclear gene flow is obscuring a phylogenetic split that is fixed in the female-based systems. Our findings provide additional support for a midpeninsular Baja divergence event, although the timing and geological evidence for such an event remain elusive.

  12. Characterization of a Diverging Cusped Field Thruster Operating on Krypton

    DTIC Science & Technology

    2014-11-04

    Charts 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Characterization of a Diverging Cusped Field Thruster Operating on Krypton 5a. CONTRACT...Tuesday, November 4, 2014 Characterization of a  Diverging Cusped Field Thruster  Operating on  Krypton DISTRIBUTION A: Approved for public release...distribution unlimited. AFTC/PA Clearance No. 14511 Outline • Motivation for using krypton • Diverging Cusped Field Thruster (DCFT) – Operation on krypton

  13. Multiwavelets on the interval and divergence-free wavelets

    NASA Astrophysics Data System (ADS)

    Lakey, Joseph D.; Pereyra, M. Cristina

    1999-10-01

    This manuscript gives a construction of divergence-free multiwavelets which combines the Hardin-Marasovich (HM) construction with a recipe of Strela for increasing or decreasing regularity of biorthogonal wavelets. Strela's process preserves symmetry of the HM wavelets. This enables the divergence-free wavelets to be suitably adapted to the analysis of divergence-free vector fields whose boundary traces are tangent vectors.

  14. Transformation-associated recombination between diverged and homologous DNA repeats is induced by strand breaks

    SciTech Connect

    Larionov, V.; Kouprina, N. |; Edlarov, M. |; Perkins, E.; Porter, G.; Resnick, M.A.

    1993-12-31

    Rearrangement and deletion within plasmid DNA is commonly observed during transformation. We have examined the mechanisms of transformation-associated recombination in the yeast Saccharomyces cerevisiae using a plasmid system which allowed the effects of physical state and/or extent of homology on recombination to be studied. The plasmid contains homologous or diverged (19%) DNA repeats separated by a genetically detectable color marker. Recombination during transformation for covalently closed circular plasmids was over 100-fold more frequent than during mitotic growth. The frequency of recombination is partly dependent on the method of transformation in that procedures involving lithium acetate or spheroplasting yield higher frequencies than electroporation. When present in the repeats, unique single-strand breaks that are ligatable, as well as double-strand breaks, lead to high levels of recombination between diverged and identical repeats. The transformation-associated recombination between repeat DNA`s is under the influence of the RADS2, RADI and the RNCI genes,

  15. Assimilation and contrast are on the same scale of food anticipated-experienced pleasure divergence.

    PubMed

    Davidenko, Olga; Delarue, Julien; Marsset-Baglieri, Agnès; Fromentin, Gilles; Tomé, Daniel; Nadkarni, Nachiket; Darcel, Nicolas

    2015-07-01

    Consumption of a product is preceded by an anticipation of its qualities by the consumer, which can itself modify the consumption experience. Improved knowledge of anticipation would allow better manipulation of it, for example to enhance the acceptance of healthier foods. According to the Assimilation-Contrast theory, the size of anticipation-reality divergence determines how anticipation influences consumers' satisfaction. For small divergences, experienced pleasure is the same as the anticipated pleasure (Assimilation); for large ones, the effect of surprise provokes an even larger discordance with that which was anticipated (Contrast). Few studies have attempted to observe both effects simultaneously, or to consider the anticipation-reality divergence quantitatively rather than qualitatively; these were the study's objectives. A range of 10 flavored drinks was developed to vary progressively in intensity. Ninety healthy young men consumed samples during two separate sessions. In session 1, hedonic and sensory scores of all drinks were recorded during blind tasting. In session 2, three drinks were chosen as references for taste intensity, and associated with neutral symbols that served as labels. Subjects then consumed 36 drink samples, each one bearing a label. For half of the samples drinks did not correspond to labels, creating a range of anticipation-reality divergence. By predicting session 2 scores using linear modeling with session 1 blind ratings as input, it was confirmed that both Assimilation and Contrast effects on hedonic ratings were present (Assimilation (t(89) = 5.645, p < 0.0001) and Contrast (t(89) = 3.186, p = 0.002 or t(89) = 2.494, p = 0.015, depending on the drink-label combination)). This study was the first to position Assimilation and Contrast within a quantitative context using controlled divergence variation rather than products from distinct categories.

  16. Comparative phylogeography of two marine species of crustacean: Recent divergence and expansion due to environmental changes.

    PubMed

    Zhang, Daizhen; Ding, Ge; Ge, Baoming; Zhang, Huabin; Tang, Boping; Yang, Guang

    2014-10-15

    Environmental changes, such as changes in the coastal topography due to Eurasian plate movements, climate oscillation during the Pleistocene, and alteration of ocean currents, have complicated the geographical structure of marine species and deepened their divergence between populations. As two widely distributed species of crustacean (Oratosquilla oratoria and Eriocheir japonica), weak differences were expected due to their high dispersal potential of planktonic larvae with ocean currents. However, results showed a significant genetic divergence between north of China and south of China in the study. In addition, the estimated north-south divergence time (27-30.5 Myr) of mantis shrimp was near the time of the Himalayan movement, and the China-Japan clade divergence time (10.5-11.9 Myr) of mitten crabs was also coincident with the time of the opening of the Sea of Japan. Thus, we hypothesized that environmental changes in the coastal topography contributed to the marine species divergence. Furthermore, based on phylogenetic analysis, network analysis and haplotype distribution, we surmised that mitten crabs originated from a population with the oldest haplotype (H6) and then divided into the north and south populations due to the recent Eurasian plate movements and ocean currents. And lineage of Japan originated from the north population for the opening of the Sea of Japan. While O. oratoria was guessed to originate from two separate populations in the China Sea. The results of "star-like" network, negative values in neutral test, and Tajima's D statistics of two marine species supported a recent rapid population expansion event after the Pleistocene glaciations.

  17. 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.

  18. Genetic divergence of orangutan subspecies (Pongo pygmaeus).

    PubMed

    Zhang, Y; Ryder, O A; Zhang, Y

    2001-06-01

    Microsatellites and mitochondrial DNA sequences were studied for the two subspecies of orangutans (Pongo pygmaeus), which are located in Borneo (P. p. pygmaeus) and Sumatra (P. p. abelii), respectively. Both subspecies possess marked genetic diversity. Genetic subdivision was identified within the Sumatran orangutans. The genetic differentiation between the two subspecies is highly significant for ND5 region but not significant for 16s rRNA or microsatellite data by exact tests, although FST estimates are highly significant for these markers. Divergence time between the two subspecies is approximately 2.3 +/- 0.5 million years ago (MYA) estimated from our data, much earlier than the isolation of their geological distribution. Neither subspecies underwent a recent bottleneck, though the Sumatran subspecies might have experienced expansion approximately 82,000 years ago. The estimated effective population sizes for both subspecies are on the order of 104. Our results contribute additional information that may be interpreted in the context of orangutan conservation efforts.

  19. Transonic Shocks in Multidimensional Divergent Nozzles

    NASA Astrophysics Data System (ADS)

    Bae, Myoungjean; Feldman, Mikhail

    2011-07-01

    We establish existence, uniqueness and stability of transonic shocks for a steady compressible non-isentropic potential flow system in a multidimensional divergent nozzle with an arbitrary smooth cross-section, for a prescribed exit pressure. The proof is based on solving a free boundary problem for a system of partial differential equations consisting of an elliptic equation and a transport equation. In the process, we obtain unique solvability for a class of transport equations with velocity fields of weak regularity (non-Lipschitz), an infinite dimensional weak implicit mapping theorem which does not require continuous Fréchet differentiability, and regularity theory for a class of elliptic partial differential equations with discontinuous oblique boundary conditions.

  20. Dating Tips for Divergence-Time Estimation.

    PubMed

    O'Reilly, Joseph E; dos Reis, Mario; Donoghue, Philip C J

    2015-11-01

    The molecular clock is the only viable means of establishing an accurate timescale for Life on Earth, but it remains reliant on a capricious fossil record for calibration. 'Tip-dating' promises a conceptual advance, integrating fossil species among their living relatives using molecular/morphological datasets and evolutionary models. Fossil species of known age establish calibration directly, and their phylogenetic uncertainty is accommodated through the co-estimation of time and topology. However, challenges remain, including a dearth of effective models of morphological evolution, rate correlation, the non-random nature of missing characters in fossil data, and, most importantly, accommodating uncertainty in fossil age. We show uncertainty in fossil-dating propagates to divergence-time estimates, yielding estimates that are older and less precise than those based on traditional node calibration. Ultimately, node and tip calibrations are not mutually incompatible and may be integrated to achieve more accurate and precise evolutionary timescales.

  1. Landscape changes have greater effects than climate changes on six insect pests in China.

    PubMed

    Zhao, Zihua; Sandhu, Hardev S; Ouyang, Fang; Ge, Feng

    2016-06-01

    In recent years, global changes are the major causes of frequent, widespread outbreaks of pests in mosaic landscapes, which have received substantial attention worldwide. We collected data on global changes (landscape and climate) and economic damage caused by six main insect pests during 1951-2010 in China. Landscape changes had significant effects on all six insect pests. Pest damage increased significantly with increasing arable land area in agricultural landscapes. However, climate changes had no effect on damage caused by pests, except for the rice leaf roller (Cnaphalocrocis medinalis Guenee) and armyworm (Mythimna separate (Walker)), which caused less damage to crops with increasing mean temperature. Our results indicate that there is slight evidence of possible offset effects of climate changes on the increasing damage from these two agricultural pests. Landscape changes have caused serious outbreaks of several species, which suggests the possibility of the use of landscape design for the control of pest populations through habitat rearrangement. Landscape manipulation may be used as a green method to achieve sustainable pest management with minimal use of insecticides and herbicides.

  2. Pastoral wildfires in the Mediterranean: understanding their linkages to land cover patterns in managed landscapes.

    PubMed

    Ruiz-Mirazo, Jabier; Martínez-Fernández, Jesús; Vega-García, Cristina

    2012-05-15

    The pastoral use of fire to regenerate rangelands is a major cause of wildfires in many Mediterranean countries. Despite producing important environmental impacts, this phenomenon has hardly ever been studied separately from other wildfire ignition causes. As extensive livestock breeding relies on the available pasture resources, we hypothesised that a higher rate of pastoral wildfire ignitions could be associated with land cover patterns, as these reflect the spatial arrangement of human activities in managed landscapes. To investigate these patterns, we studied landscape structure and the pastoral wildfires recorded between 1988 and 2000 in 24 Nature Park landscapes in Andalusia (Spain). The CORINE Land Cover map was reclassified according to five levels of grazing use and landscape metrics were calculated. Neural networks were developed to model the relationship between landscape metrics and pastoral wildfires, obtaining a set of significant variables which are discussed in the frame of land and livestock management in the region. We conclude that pastoral wildfire ignitions are more likely in landscapes where the pattern of being dominated by a matrix composed of several large patches of low to moderate grazing use, and having abundant small and elongated patches of higher grazing use, is more extreme. This pattern could be reflecting the persistence of numerous small livestock farms within an increasingly abandoned agrarian landscape. To prevent pastoral wildfires, land management could attempt to enlarge and merge those small patches of higher grazing use, reducing the amount of interface and their intermixture with the surrounding poorer pasture resources.

  3. Structural Analysis of an Evolved Transketolase Reveals Divergent Binding Modes

    PubMed Central

    Affaticati, Pierre E.; Dai, Shao-Bo; Payongsri, Panwajee; Hailes, Helen C.; Tittmann, Kai; Dalby, Paul A.

    2016-01-01

    The S385Y/D469T/R520Q variant of E. coli transketolase was evolved previously with three successive smart libraries, each guided by different structural, bioinformatical or computational methods. Substrate-walking progressively shifted the target acceptor substrate from phosphorylated aldehydes, towards a non-phosphorylated polar aldehyde, a non-polar aliphatic aldehyde, and finally a non-polar aromatic aldehyde. Kinetic evaluations on three benzaldehyde derivatives, suggested that their active-site binding was differentially sensitive to the S385Y mutation. Docking into mutants generated in silico from the wild-type crystal structure was not wholly satisfactory, as errors accumulated with successive mutations, and hampered further smart-library designs. Here we report the crystal structure of the S385Y/D469T/R520Q variant, and molecular docking of three substrates. This now supports our original hypothesis that directed-evolution had generated an evolutionary intermediate with divergent binding modes for the three aromatic aldehydes tested. The new active site contained two binding pockets supporting π-π stacking interactions, sterically separated by the D469T mutation. While 3-formylbenzoic acid (3-FBA) preferred one pocket, and 4-FBA the other, the less well-accepted substrate 3-hydroxybenzaldehyde (3-HBA) was caught in limbo with equal preference for the two pockets. This work highlights the value of obtaining crystal structures of evolved enzyme variants, for continued and reliable use of smart library strategies. PMID:27767080

  4. When divergent life histories hybridize: insights into adaptive life-history traits in an annual weed.

    PubMed

    Campbell, Lesley G; Snow, Allison A; Sweeney, Patricia M

    2009-12-01

    *Colonizing weed populations face novel selective environments, which may drive rapid shifts in life history. These shifts may be amplified when colonists are hybrids of species with divergent life histories. Selection on such phenotypically diverse hybrids may create highly fecund weeds. We measured the phenotypic variation, strength of natural selection and evolutionary response of hybrid and nonhybrid weeds. *We created F(1) hybrids of wild radish, an early flowering, small-stemmed weed, and its late-flowering, large-stemmed, crop relative (Raphanus spp.). Replicate wild and hybrid populations were established in an agricultural landscape in Michigan, USA. The consequences of three generations of natural selection were measured in a common garden experiment. *Hybrid populations experienced strong selection for larger, earlier flowering plants whereas selection was relatively weak on wild populations. Large plant size evolved two to three times faster in the hybrid populations than in wild populations, yet hybrid populations did not evolve earlier flowering. Strong selection on size and phenotypic correlations between age at reproduction and size may have limited the response of flowering phenology. *Our findings demonstrate hybridization between species with divergent life histories may catalyse the rapid evolution of certain adaptive, weedy traits while tradeoffs limit the evolution of others.

  5. Scl binds to primed enhancers in mesoderm to regulate hematopoietic and cardiac fate divergence

    PubMed Central

    Org, Tõnis; Duan, Dan; Ferrari, Roberto; Montel-Hagen, Amelie; Van Handel, Ben; Kerényi, Marc A; Sasidharan, Rajkumar; Rubbi, Liudmilla; Fujiwara, Yuko; Pellegrini, Matteo; Orkin, Stuart H; Kurdistani, Siavash K; Mikkola, Hanna KA

    2015-01-01

    Scl/Tal1 confers hemogenic competence and prevents ectopic cardiomyogenesis in embryonic endothelium by unknown mechanisms. We discovered that Scl binds to hematopoietic and cardiac enhancers that become epigenetically primed in multipotent cardiovascular mesoderm, to regulate the divergence of hematopoietic and cardiac lineages. Scl does not act as a pioneer factor but rather exploits a pre-established epigenetic landscape. As the blood lineage emerges, Scl binding and active epigenetic modifications are sustained in hematopoietic enhancers, whereas cardiac enhancers are decommissioned by removal of active epigenetic marks. Our data suggest that, rather than recruiting corepressors to enhancers, Scl prevents ectopic cardiogenesis by occupying enhancers that cardiac factors, such as Gata4 and Hand1, use for gene activation. Although hematopoietic Gata factors bind with Scl to both activated and repressed genes, they are dispensable for cardiac repression, but necessary for activating genes that enable hematopoietic stem/progenitor cell development. These results suggest that a unique subset of enhancers in lineage-specific genes that are accessible for regulators of opposing fates during the time of the fate decision provide a platform where the divergence of mutually exclusive fates is orchestrated. PMID:25564442

  6. Divergent Integrals of QED in Krein Space Quantization

    SciTech Connect

    Payandeh, F.

    2010-06-15

    The usual quantum field theory leads to an ultraviolet divergence in the vacuum energies and an infrared divergence in the two-point functions. It has been shown that the presence of unphysical negative-frequency states (Krein space quantization) plays the role of an automatic renormalization tool for the theory of quantized fields. In the standard QED, the divergent quantities are found in the self-energy, vacuum polarization, and vertex graphs. It seems as if evaluating divergent integrals of QED in Krein space leads to convergent values.

  7. Gray Box Optimization for Mk Landscapes (NK Landscapes and MAX-kSAT).

    PubMed

    Whitley, L Darrell; Chicano, Francisco; Goldman, Brian W

    2016-01-01

    This article investigates Gray Box Optimization for pseudo-Boolean optimization problems composed of M subfunctions, where each subfunction accepts at most k variables. We will refer to these as Mk Landscapes. In Gray Box Optimization, the optimizer is given access to the set of M subfunctions. We prove Gray Box Optimization can efficiently compute hyperplane averages to solve non-deceptive problems in [Formula: see text] time. Bounded separable problems are also solved in [Formula: see text] time. As a result, Gray Box Optimization is able to solve many commonly used problems from the evolutional computation literature in [Formula: see text] evaluations. We also introduce a more general class of Mk Landscapes that can be solved using dynamic programming and discuss properties of these functions. For certain type of problems Gray Box Optimization makes it possible to enumerate all local optima faster than brute force methods. We also provide evidence that randomly generated test problems are far less structured than those found in real-world problems.

  8. Informational landscapes in art, science, and evolution.

    PubMed

    Cohen, Irun R

    2006-07-01

    An informational landscape refers to an array of information related to a particular theme or function. The Internet is an example of an informational landscape designed by humans for purposes of communication. Once it exists, however, any informational landscape may be exploited to serve a new purpose. Listening Post is the name of a dynamic multimedia work of art that exploits the informational landscape of the Internet to produce a visual and auditory environment. Here, I use Listening Post as a prototypic example for considering the creative role of informational landscapes in the processes that beget evolution and science.

  9. Steepened channels upstream of knickpoints: Controls on relict landscape response

    NASA Astrophysics Data System (ADS)

    Berlin, Maureen M.; Anderson, Robert S.

    2009-09-01

    The morphology of a relict landscape provides important insight into erosion rates and processes prior to base level fall. Fluvial knickpoints are commonly thought to form a leak-proof moving boundary between a rejuvenated landscape below and a relict landscape above. We argue that fluvial rejuvenation may leak farther upstream, depending on the rate and style of knickpoint migration. The outer margin of a relict landscape should therefore be used with caution in tectonic geomorphology studies, as channel steepening upstream of knickpoints could reduce the relict area. We explore the response of the Roan Plateau to knickpoint retreat triggered by late Cenozoic upper Colorado River incision. Multiple knickpoints (100-m waterfalls) separate a low-relief, upper landscape from incised canyons below. Two digital elevation model data sets (10-m U.S. Geological Survey and 1-m Airborne Laser Swath Mapping) indicate steeper channels above waterfalls relative to concave channels farther upstream. The steepened reaches are several kilometers long, correspond to doubling of slope, and exhibit channel narrowing and an increase in hillslope angle. We compare two mechanisms for generating steepened reaches. The first uses a recent model for erosion amplification due to flow acceleration at the waterfall lip. The second acknowledges that waterfall lips may be limited to the outcrop of a resistant formation. Subtle structural warping of the stratigraphy can lead to lowering of the waterfall lip as it retreats, thus lowering base level for upstream channels. Results of numerical modeling experiments suggest the latter mechanism is more consistent with our observations of long, mildly steepened reaches.

  10. 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.

  11. 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.

  12. Evolution of pollination niches and floral divergence in the generalist plant Erysimum mediohispanicum

    PubMed Central

    Gómez, J. M.; Muñoz-Pajares, A. J.; Abdelaziz, M.; Lorite, J.; Perfectti, F.

    2014-01-01

    Background and Aims How generalist plants diverge in response to pollinator selection without becoming specialized is still unknown. This study explores this question, focusing on the evolution of the pollination system in the pollination generalist Erysimum mediohispanicum (Brassicaceae). Methods Pollinator assemblages were surveyed from 2001 to 2010 in 48 geo-referenced populations covering the entire geographic distribution of E. mediohispanicum. Bipartite modularity, a complex network tool, was used to find the pollination niche of each population. Evolution of the pollination niches and the correlated evolution of floral traits and pollination niches were explored using within-species comparative analyses. Key Results Despite being generalists, the E. mediohispanicum populations studied can be classified into five pollination niches. The boundaries between niches were not sharp, the niches differing among them in the relative frequencies of the floral visitor functional groups. The absence of spatial autocorrelation and phylogenetic signal indicates that the niches were distributed in a phylogeographic mosaic. The ancestral E. mediohispanicum populations presumably belonged to the niche defined by a high number of beetle and ant visits. A correlated evolution was found between pollination niches and some floral traits, suggesting the existence of generalist pollination ecotypes. Conclusions It is conjectured that the geographic variation in pollination niches has contributed to the observed floral divergence in E. mediohispanicum. The process mediating this floral divergence presumably has been adaptive wandering, but the adaptation to the local pollinator faunas has been not universal. The outcome is a landscape where a few populations locally adapted to their pollination environment (generalist pollination ecotypes) coexist with many populations where this local adaptation has failed and where the plant phenotype is not primarily shaped by pollinators. PMID

  13. The Highly Similar Arabidopsis Homologs of Trithorax ATX1 and ATX2 Encode Proteins with Divergent Biochemical Functions[W

    PubMed Central

    Saleh, Abdelaty; Alvarez-Venegas, Raul; Yilmaz, Mehtap; Oahn-Le; Hou, Guichuan; Sadder, Monther; Al-Abdallat, Ayed; Xia, Yuannan; Lu, Guoqinq; Ladunga, Istvan; Avramova, Zoya

    2008-01-01

    Gene duplication followed by functional specialization is a potent force in the evolution of biological diversity. A comparative study of two highly conserved duplicated genes, ARABIDOPSIS TRITHORAX-LIKE PROTEIN1 (ATX1) and ATX2, revealed features of both partial redundancy and of functional divergence. Although structurally similar, their regulatory sequences have diverged, resulting in distinct temporal and spatial patterns of expression of the ATX1 and ATX2 genes. We found that ATX2 methylates only a limited fraction of nucleosomes and that ATX1 and ATX2 influence the expression of largely nonoverlapping gene sets. Even when coregulating shared targets, ATX1 and ATX2 may employ different mechanisms. Most remarkable is the divergence of their biochemical activities: both proteins methylate K4 of histone H3, but while ATX1 trimethylates it, ATX2 dimethylates it. ATX2 and ATX1 provide an example of separated K4 di from K4 trimethyltransferase activity. PMID:18375658

  14. [Vertical zonation of mountain landscape: a review].

    PubMed

    Sun, Ran-Hao; Chen, Li-Ding; Zhang, Bai-Ping; Fu, Bo-Jie

    2009-07-01

    Vertical gradient of mountain landscape is about 1000 times of its horizontal gradient, and hence, only using landscape pattern index is quite difficult to reflect the landscape regularity along vertical gradient. Mountain altitudinal belt is a kind of classic geographic models representing the vertical differentiation of landscape, being of significance in geographic and ecological researches. However, the discrete expression pattern and the inaccuracy of the borderlines of mountain vertical belts limit the roles of mountain vertical belt in accurately describing landscape pattern in regional scale and in explaining ecological processes. This paper reviewed the research progress and existing problems on mountain altitudinal belt, put forward a suggestion of using modern information technology to establish a comprehensive and continuous mountain landscape information chart, and discussed the framework and prospect of the establishment of the chart, which would have reference value for accurately describing mountain landscape pattern and explaining specific ecological processes, and promote the further improvement of the methodology for mountain ecological research.

  15. Convergence Insufficiency/Divergence Insufficiency Convergence Excess/Divergence Excess: Some Facts and Fictions.

    PubMed

    Khawam, Edward; Abiad, Bachir; Boughannam, Alaa; Saade, Joanna; Alameddine, Ramzi

    2015-01-01

    Great discrepancies are often encountered between the distance fixation and the near-fixation esodeviations and exodeviations. They are all attributed to either anomalies of the AC/A ratio or anomalies of the fusional convergence or divergence amplitudes. We report a case with pseudoconvergence insufficiency and another one with pseudoaccommodative convergence excess. In both cases, conv./div. excess and insufficiency were erroneously attributed to anomalies of the AC/A ratio or to anomalies of the fusional amplitudes. Our purpose is to show that numerous factors, other than anomalies in the AC/A ratio or anomalies in the fusional conv. or divergence amplitudes, can contaminate either the distance or the near deviations. This results in significant discrepancies between the distance and the near deviations despite a normal AC/A ratio and normal fusional amplitudes, leading to erroneous diagnoses and inappropriate treatment models.

  16. Evaluation of Landsat Multispectral Scanner data for mapping vegetated soil landscapes

    USGS Publications Warehouse

    Thompson, D. R.; Haas, Robert H.; Milford, M. H.

    1981-01-01

    Landsat multispectral scanner data for Brazos County, Texas, were evaluated in terms of effectiveness for classifying soils on vegetated landscapes at three times during the year: a time of normally adequate soil water, a time of expected soil water deficit, and a time when soil water is normally being replenished. Six test sites were used to evaluate LARSYS supervised and unsupervised classification of vegetated soil landscapes. Open grassland soils were best separated in the fall during a period when soil moisture was being replenished after the summer period of soil water deficit. Woodland soils were separated by Landsat data in late spring when adequate moisture was available. However, a high degree of accuracy was not achieved using Landsat for separating soil map units. Accurate separation of soil mapping units on vegetated landscapes was not possible during late summer when soil water was deficient. Selected soil properties important to plant growth were separable on the test sites using June and October Landsat data. Particle size and soil moisture regime were separated at both dates. Soils with argillic horizons were separated from soils without argillic horizons.

  17. Landscape genetic approaches to guide native plant restoration in the Mojave Desert.

    PubMed

    Shryock, Daniel F; Havrilla, Caroline A; DeFalco, Lesley A; Esque, Todd C; Custer, Nathan A; Wood, Troy E

    2017-03-01

    Restoring dryland ecosystems is a global challenge due to synergistic drivers of disturbance coupled with unpredictable environmental conditions. Dryland plant species have evolved complex life-history strategies to cope with fluctuating resources and climatic extremes. Although rarely quantified, local adaptation is likely widespread among these species and potentially influences restoration outcomes. The common practice of reintroducing propagules to restore dryland ecosystems, often across large spatial scales, compels evaluation of adaptive divergence within these species. Such evaluations are critical to understanding the consequences of large-scale manipulation of gene flow and to predicting success of restoration efforts. However, genetic information for species of interest can be difficult and expensive to obtain through traditional common garden experiments. Recent advances in landscape genetics offer marker-based approaches for identifying environmental drivers of adaptive genetic variability in non-model species, but tools are still needed to link these approaches with practical aspects of ecological restoration. Here, we combine spatially explicit landscape genetics models with flexible visualization tools to demonstrate how cost-effective evaluations of adaptive genetic divergence can facilitate implementation of different seed sourcing strategies in ecological restoration. We apply these methods to Amplified Fragment Length Polymorphism (AFLP) markers genotyped in two Mojave Desert shrub species of high restoration importance: the long-lived, wind-pollinated gymnosperm Ephedra nevadensis, and the short-lived, insect-pollinated angiosperm Sphaeralcea ambigua. Mean annual temperature was identified as an important driver of adaptive genetic divergence for both species. Ephedra showed stronger adaptive divergence with respect to precipitation variability, while temperature variability and precipitation averages explained a larger fraction of adaptive

  18. Landscape genetic approaches to guide native plant restoration in the Mojave Desert

    USGS Publications Warehouse

    Shryock, Daniel F.; Havrilla, Caroline A.; DeFalco, Lesley; Esque, Todd; Custer, Nathan; Wood, Troy E.

    2016-01-01

    Restoring dryland ecosystems is a global challenge due to synergistic drivers of disturbance coupled with unpredictable environmental conditions. Dryland plant species have evolved complex life-history strategies to cope with fluctuating resources and climatic extremes. Although rarely quantified, local adaptation is likely widespread among these species and potentially influences restoration outcomes. The common practice of reintroducing propagules to restore dryland ecosystems, often across large spatial scales, compels evaluation of adaptive divergence within these species. Such evaluations are critical to understanding the consequences of large-scale manipulation of gene flow and to predicting success of restoration efforts. However, genetic information for species of interest can be difficult and expensive to obtain through traditional common garden experiments. Recent advances in landscape genetics offer marker-based approaches for identifying environmental drivers of adaptive genetic variability in non-model species, but tools are still needed to link these approaches with practical aspects of ecological restoration. Here, we combine spatially-explicit landscape genetics models with flexible visualization tools to demonstrate how cost-effective evaluations of adaptive genetic divergence can facilitate implementation of different seed sourcing strategies in ecological restoration. We apply these methods to Amplified Fragment Length Polymorphism (AFLP) markers genotyped in two Mojave Desert shrub species of high restoration importance: the long-lived, wind-pollinated gymnosperm Ephedra nevadensis, and the short-lived, insect-pollinated angiosperm Sphaeralcea ambigua. Mean annual temperature was identified as an important driver of adaptive genetic divergence for both species. Ephedra showed stronger adaptive divergence with respect to precipitation variability, while temperature variability and precipitation averages explained a larger fraction of adaptive

  19. Understanding the genetic effects of recent habitat fragmentation in the context of evolutionary history: Phylogeography and landscape genetics of a southern California endemic Jerusalem cricket (Orthoptera: Stenopelmatidae: Stenopelmatus)

    USGS Publications Warehouse

    Vandergast, A.G.; Bohonak, A.J.; Weissman, D.B.; Fisher, R.N.

    2007-01-01

    Habitat loss and fragmentation due to urbanization are the most pervasive threats to biodiversity in southern California. Loss of habitat and fragmentation can lower migration rates and genetic connectivity among remaining populations of native species, reducing genetic variability and increasing extinction risk. However, it may be difficult to separate the effects of recent anthropogenic fragmentation from the genetic signature of prehistoric fragmentation due to previous natural geological and climatic changes. To address these challenges, we examined the phylogenetic and population genetic structure of a flightless insect endemic to cismontane southern California, Stenopelmatus 'mahogani' (Orthoptera: Stenopelmatidae). Analyses of mitochondrial DNA sequence data suggest that diversification across southern California began during the Pleistocene, with most haplotypes currently restricted to a single population. Patterns of genetic divergence correlate with contemporary urbanization, even after correcting for (geographical information system) GIS-based reconstructions of fragmentation during the Pleistocene. Theoretical simulations confirm that contemporary patterns of genetic structure could be produced by recent urban fragmentation using biologically reasonable assumptions about model parameters. Diversity within populations was positively correlated with current fragment size, but not prehistoric fragment size, suggesting that the effects of increased drift following anthropogenic fragmentation are already being seen. Loss of genetic connectivity and diversity can hinder a population's ability to adapt to ecological perturbations commonly associated with urbanization, such as habitat degradation, climatic changes and introduced species. Consequently, our results underscore the importance of preserving and restoring landscape connectivity for long-term persistence of low vagility native species. Journal compilation ?? 2006 Blackwell Publishing Ltd.

  20. Understanding the genetic effects of recent habitat fragmentation in the context of evolutionary history: phylogeography and landscape genetics of a southern California endemic Jerusalem cricket (Orthoptera: Stenopelmatidae: Stenopelmatus).

    PubMed

    Vandergast, Amy G; Bohonak, Andrew J; Weissman, David B; Fisher, Robert N

    2007-03-01

    Habitat loss and fragmentation due to urbanization are the most pervasive threats to biodiversity in southern California. Loss of habitat and fragmentation can lower migration rates and genetic connectivity among remaining populations of native species, reducing genetic variability and increasing extinction risk. However, it may be difficult to separate the effects of recent anthropogenic fragmentation from the genetic signature of prehistoric fragmentation due to previous natural geological and climatic changes. To address these challenges, we examined the phylogenetic and population genetic structure of a flightless insect endemic to cismontane southern California, Stenopelmatus'mahogani' (Orthoptera: Stenopelmatidae). Analyses of mitochondrial DNA sequence data suggest that diversification across southern California began during the Pleistocene, with most haplotypes currently restricted to a single population. Patterns of genetic divergence correlate with contemporary urbanization, even after correcting for (geographical information system) GIS-based reconstructions of fragmentation during the Pleistocene. Theoretical simulations confirm that contemporary patterns of genetic structure could be produced by recent urban fragmentation using biologically reasonable assumptions about model parameters. Diversity within populations was positively correlated with current fragment size, but not prehistoric fragment size, suggesting that the effects of increased drift following anthropogenic fragmentation are already being seen. Loss of genetic connectivity and diversity can hinder a population's ability to adapt to ecological perturbations commonly associated with urbanization, such as habitat degradation, climatic changes and introduced species. Consequently, our results underscore the importance of preserving and restoring landscape connectivity for long-term persistence of low vagility native species.

  1. A landscape of field theories

    NASA Astrophysics Data System (ADS)

    Maxfield, Travis; Robbins, Daniel; Sethi, Savdeep

    2016-11-01

    Studying a quantum field theory involves a choice of space-time manifold and a choice of background for any global symmetries of the theory. We argue that many more choices are possible when specifying the background. In the context of branes in string theory, the additional data corresponds to a choice of supergravity tensor fluxes. We propose the existence of a landscape of field theory backgrounds, characterized by the space-time metric, global symmetry background and a choice of tensor fluxes. As evidence for this landscape, we study the supersymmetric six-dimensional (2, 0) theory compactified to two dimensions. Different choices of metric and flux give rise to distinct two-dimensional theories, which can preserve differing amounts of supersymmetry.

  2. Reserves, resilience and dynamic landscapes.

    PubMed

    Bengtsson, Janne; Angelstam, Per; Elmqvist, Thomas; Emanuelsson, Urban; Folke, Carl; Ihse, Margareta; Moberg, Fredrik; Nyström, Magnus

    2003-09-01

    In a world increasingly modified by human activities, the conservation of biodiversity is essential as insurance to maintain resilient ecosystems and ensure a sustainable flow of ecosystem goods and services to society. However, existing reserves and national parks are unlikely to incorporate the long-term and large-scale dynamics of ecosystems. Hence, conservation strategies have to actively incorporate the large areas of land that are managed for human use. For ecosystems to reorganize after large-scale natural and human-induced disturbances, spatial resilience in the form of ecological memory is a prerequisite. The ecological memory is composed of the species, interactions and structures that make ecosystem reorganization possible, and its components may be found within disturbed patches as well in the surrounding landscape. Present static reserves should be complemented with dynamic reserves, such as ecological fallows and dynamic successional reserves, that are part of ecosystem management mimicking natural disturbance regimes at the landscape level.

  3. Landscape dynamics of northeastern forests

    NASA Technical Reports Server (NTRS)

    Canham, Charles D.; Silander, John A., Jr.; Civco, Daniel L.

    1994-01-01

    This project involves collaborative research with Stephen W. Pacala and Simon A. Levin of Princeton University to calibrate, test, and analyze models of heterogeneous forested landscapes containing a diverse array of habitats. The project is an extension of previous, NASA-supported research to develop a spatially-explicit model of forest dynamics at the scale of an individual forest stand (hectares to square kilometer spatial scales). That model (SORTIE) has been thoroughly parameterized from field studies in the modal upland environment of western Connecticut. Under our current funding, we are scaling-up the model and parameterizing it for the broad range of upland environments in the region. Our most basic goal is to understand the linkages between stand-level dynamics (as revealed in our previous research) and landscape-level dynamics of forest composition and structure.

  4. Making molehills out of mountains: landscape genetics of the Mojave desert tortoise

    USGS Publications Warehouse

    Hagerty, Bridgette E.; Nussear, Kenneth E.; Esque, Todd C.; Tracy, C. Richard

    2010-01-01

    Heterogeneity in habitat often influences how organisms traverse the landscape matrix that connects populations. Understanding landscape connectivity is important to determine the ecological processes that influence those movements, which lead to evolutionary change due to gene flow. Here, we used landscape genetics and statistical models to evaluate hypotheses that could explain isolation among locations of the threatened Mojave desert tortoise (Gopherus agassizii). Within a causal modeling framework, we investigated three factors that can influence landscape connectivity: geographic distance, barriers to dispersal, and landscape friction. A statistical model of habitat suitability for the Mojave desert tortoise, based on topography, vegetation, and climate variables, was used as a proxy for landscape friction and barriers to dispersal. We quantified landscape friction with least-cost distances and with resistance distances among sampling locations. A set of diagnostic partial Mantel tests statistically separated the hypotheses of potential causes of genetic isolation. The best-supported model varied depending upon how landscape friction was quantified. Patterns of genetic structure were related to a combination of geographic distance and barriers as defined by least-cost distances, suggesting that mountain ranges and extremely low-elevation valleys influence connectivity at the regional scale beyond the tortoises' ability to disperse. However, geographic distance was the only influence detected using resistance distances, which we attributed to fundamental differences between the two ways of quantifying friction. Landscape friction, as we measured it, did not influence the observed patterns of genetic distances using either quantification. Barriers and distance may be more valuable predictors of observed population structure for species like the desert tortoise, which has high dispersal capability and a long generation time.

  5. Using remote sensing products to classify landscape. A multi-spatial resolution approach

    NASA Astrophysics Data System (ADS)

    García-Llamas, Paula; Calvo, Leonor; Álvarez-Martínez, José Manuel; Suárez-Seoane, Susana

    2016-08-01

    The European Landscape Convention encourages the inventory and characterization of landscapes for environmental management and planning actions. Among the range of data sources available for landscape classification, remote sensing has substantial applicability, although difficulties might arise when available data are not at the spatial resolution of operational interest. We evaluated the applicability of two remote sensing products informing on land cover (the categorical CORINE map at 30 m resolution and the continuous NDVI spectral index at 1 km resolution) in landscape classification across a range of spatial resolutions (30 m, 90 m, 180 m, 1 km), using the Cantabrian Mountains (NW Spain) as study case. Separate landscape classifications (using topography, urban influence and land cover as inputs) were accomplished, one per each land cover dataset and spatial resolution. Classification accuracy was estimated through confusion matrixes and uncertainty in terms of both membership probability and confusion indices. Regarding landscape classifications based on CORINE, both typology and number of landscape classes varied across spatial resolutions. Classification accuracy increased from 30 m (the original resolution of CORINE) to 90m, decreasing towards coarser resolutions. Uncertainty followed the opposite pattern. In the case of landscape classifications based on NDVI, the identified landscape patterns were geographically structured and showed little sensitivity to changes across spatial resolutions. Only the change from 1 km (the original resolution of NDVI) to 180 m improved classification accuracy. The value of confusion indices increased with resolution. We highlight the need for greater effort in selecting data sources at the suitable spatial resolution, matching regional peculiarities and minimizing error and uncertainty.

  6. Bioenergy in a Multifunctional Landscape

    ScienceCinema

    Watts, Chad; Negri, Cristina; Ssegane, Herbert

    2016-11-02

    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.

  7. Sneutrino chaotic inflation and landscape

    NASA Astrophysics Data System (ADS)

    Murayama, Hitoshi; Nakayama, Kazunori; Takahashi, Fuminobu; Yanagida, Tsutomu T.

    2014-11-01

    The most naive interpretation of the BICEP2 data is the chaotic inflation by an inflaton with a quadratic potential. When combined with supersymmetry, we argue that the inflaton plays the role of right-handed scalar neutrino based on rather general considerations. The framework suggests that the right-handed sneutrino tunneled from a false vacuum in a landscape to our vacuum with a small negative curvature and suppressed scalar perturbations at large scales.

  8. Divergent selection for muscle color in broilers.

    PubMed

    Harford, I D; Pavlidis, H O; Anthony, N B

    2014-05-01

    One consumer-related physiological abnormality that is a recent concern for the poultry industry is atypical meat quality. Currently in the processing plant, meat is characterized on appearance such as tears, bruises, discoloration, or missing parts. Unfortunately, this method ignores physical properties such as palatability, texture, tenderness, taste, color, pH, and water-holding capacity (WHC). The growing demand for a convenient, economical, and palatable product has shifted the market toward value-added poultry products. The effect of a meat's physical properties on its marketability and versatility has become apparent to processors attempting to utilize poor quality meat. After 8 generations of divergent selection for muscle color or lightness (L*) in broilers, muscle quality parameters were investigated. The 2 broiler lines divergently selected for high (HMC) and low (LMC) muscle color along with their randombred control line (RBC) were included in the study. Heritability estimates for L* were 0.47 ± 0.05 and 0.51 ± 0.05 in the HMC and LMC lines, respectively. For generation 8, the mean L* for the HMC, RBC, and LMC lines were 53.91, 49.70, and 46.86, respectively. Selection for increased L* was found to result in increased breast fillet yellowness (b*), whereas selection for decreased L* resulted in an increase in breast fillet redness (a*). Selection for increased L* has resulted in increased rate of pH decline over time, whereas selection for decreased L* has resulted in a decreased rate of pH decline. The HMC line exhibited a higher percentage fillet drip loss than both the LMC and RBC lines, which did not differ from each other. Overall selection for L* was effective in modifying breast muscle color as well as correlated responses associated with atypical poultry meat such as drip loss and postmortem muscle pH. These selected lines can serve as resource populations for the study of PSE and DFD-like meat in poultry and demonstrate that L* selection

  9. Convergent and Divergent Thinking in the Context of Narrative Mysteries

    ERIC Educational Resources Information Center

    Wenzel, William G.; Gerrig, Richard J.

    2015-01-01

    This project demonstrates how narrative mysteries provide a context in which readers engage in creative cognition. Drawing on the concepts of convergent and divergent thinking, we wrote stories that had either convergent or divergent outcomes. For example, one story had a character give his girlfriend a ring (a convergent outcome), whereas the…

  10. Some Effects of Testing Procedure on Divergent Thinking

    ERIC Educational Resources Information Center

    Nicholls, John G.

    1971-01-01

    Game-like and test-like methods of divergent thinking assessment were compared with 10-year olds. Effects of method on score correlates were sufficient to allow the possibility that method may be implicated in outcomes of many studies of divergent thinking. (Author)

  11. Analyzing Collaborative Interactions: Divergence, Shared Understanding and Construction of Knowledge

    ERIC Educational Resources Information Center

    Puntambekar, Sadhana

    2006-01-01

    One of the most important facets of collaborative learning is the interaction between individual and collaborative learning activities--between divergent perspectives and shared knowledge building. Individuals bring divergent ideas into a collaborative environment. While individuals bring their own unique knowledge and perspectives, the second…

  12. Properties of classical and quantum Jensen-Shannon divergence

    SciTech Connect

    Brieet, Jop; Harremoees, Peter

    2009-05-15

    Jensen-Shannon divergence (JD) is a symmetrized and smoothed version of the most important divergence measure of information theory, Kullback divergence. As opposed to Kullback divergence it determines in a very direct way a metric; indeed, it is the square of a metric. We consider a family of divergence measures (JD{sub {alpha}} for {alpha}>0), the Jensen divergences of order {alpha}, which generalize JD as JD{sub 1}=JD. Using a result of Schoenberg, we prove that JD{sub {alpha}} is the square of a metric for {alpha} is an element of (0,2], and that the resulting metric space of probability distributions can be isometrically embedded in a real Hilbert space. Quantum Jensen-Shannon divergence (QJD) is a symmetrized and smoothed version of quantum relative entropy and can be extended to a family of quantum Jensen divergences of order {alpha} (QJD{sub {alpha}}). We strengthen results by Lamberti and co-workers by proving that for qubits and pure states, QJD{sub {alpha}}{sup 1/2} is a metric space which can be isometrically embedded in a real Hilbert space when {alpha} is an element of (0,2]. In analogy with Burbea and Rao's generalization of JD, we also define general QJD by associating a Jensen-type quantity to any weighted family of states. Appropriate interpretations of quantities introduced are discussed and bounds are derived in terms of the total variation and trace distance.

  13. Dynamic Investigation of Static Divergence: Analysis and Testing

    NASA Technical Reports Server (NTRS)

    Heeg, Jennifer

    2000-01-01

    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. Analytical results identified configurations that exhibit different types of dynamic mode behavior as the system encounters divergence. A wind tunnel model was designed and tested to examine divergence experimentally. The experimental results validate the analytical calculations and explicitly examine the divergence phenomenon where the dynamic mode persists. Three configurations of the wind tunnel model were tested. The experimental results agree very well with the analytical predictions of subcritical characteristics, divergence velocity, and behavior of the noncritical dynamic mode at divergence.

  14. Divergent Thinking and Creative Ideation of High School Students

    ERIC Educational Resources Information Center

    Ramzan, Shaikh Imran; Perveen, Shaheen

    2011-01-01

    Divergent thinking is an integral process in creativity. Openness to experience is a personality trait that relates to divergent thinking and, therefore, is hypothesized to be related to creative performance among the students. The effects of openness to experience are likely to be partially mediated by an individual's attitude toward divergent…

  15. Divergent Thinking and Evaluation Skills: Do They Always Go Together?

    ERIC Educational Resources Information Center

    Grohman, Magdalena; Wodniecka, Zofia; Klusak, Marcin

    2006-01-01

    The aim of the present study was to explore the hypothesized relationship between divergent thinking (DT) and two types of evaluation: interpersonal (judgments about others' ideas) and intrapersonal (judgments about one's own ideas). Divergent thinking and evaluation skills were measured by means of a GenEva (Generation and Evaluation) task. There…

  16. The Relationship Between Lateral Dominance and Divergent Cognitive Thought.

    ERIC Educational Resources Information Center

    Williams, Barbara B.

    This study was designed to explore the relationship of lateral dominance to divergent cognitive thought. According to the screening results of the Harris Tests of Lateral Dominance, 36 subjects ranging from 9-12 years were divided equally into three groups of left, right, and mixed lateral dominance. In order to measure divergent cognitive…

  17. Vacuum selection on axionic landscapes

    SciTech Connect

    Wang, Gaoyuan; Battefeld, Thorsten E-mail: tbattefe@astro.physik.uni-goettingen.de

    2016-04-01

    We compute the distribution of minima that are reached dynamically on multi-field axionic landscapes, both numerically and analytically. Such landscapes are well suited for inflationary model building due to the presence of shift symmetries and possible alignment effects (the KNP mechanism). The resulting distribution of dynamically reached minima differs considerably from the naive expectation based on counting all vacua. These differences are more pronounced in the presence of many fields due to dynamical selection effects: while low lying minima are preferred as fields roll down the potential, trajectories are also more likely to get trapped by one of the many nearby minima. We show that common analytic arguments based on random matrix theory in the large D-limit to estimate the distribution of minima are insufficient for quantitative arguments pertaining to the dynamically reached ones. This discrepancy is not restricted to axionic potentials. We provide an empirical expression for the expectation value of such dynamically reached minimas' height and argue that the cosmological constant problem is not alleviated in the absence of anthropic arguments. We further comment on the likelihood of inflation on axionic landscapes in the large D-limit.

  18. Energy landscapes and persistent minima

    SciTech Connect

    Carr, Joanne M.; Wales, David J.; Mazauric, Dorian; Cazals, Frédéric

    2016-02-07

    We consider a coarse-graining of high-dimensional potential energy landscapes based upon persistences, which correspond to lowest barrier heights to lower-energy minima. Persistences can be calculated efficiently for local minima in kinetic transition networks that are based on stationary points of the prevailing energy landscape. The networks studied here represent peptides, proteins, nucleic acids, an atomic cluster, and a glassy system. Minima with high persistence values are likely to represent some form of alternative structural morphology, which, if appreciably populated at the prevailing temperature, could compete with the global minimum (defined as infinitely persistent). Threshold values on persistences (and in some cases equilibrium occupation probabilities) have therefore been used in this work to select subsets of minima, which were then analysed to see how well they can represent features of the full network. Simplified disconnectivity graphs showing only the selected minima can convey the funnelling (including any multiple-funnel) characteristics of the corresponding full graphs. The effect of the choice of persistence threshold on the reduced disconnectivity graphs was considered for a system with a hierarchical, glassy landscape. Sets of persistent minima were also found to be useful in comparing networks for the same system sampled under different conditions, using minimum oriented spanning forests.

  19. Landscape influences on dispersal behaviour: a theoretical model and empirical test using the fire salamander, Salamandra infraimmaculata.

    PubMed

    Kershenbaum, Arik; Blank, Lior; Sinai, Iftach; Merilä, Juha; Blaustein, Leon; Templeton, Alan R

    2014-06-01

    When populations reside within a heterogeneous landscape, isolation by distance may not be a good predictor of genetic divergence if dispersal behaviour and therefore gene flow depend on landscape features. Commonly used approaches linking landscape features to gene flow include the least cost path (LCP), random walk (RW), and isolation by resistance (IBR) models. However, none of these models is likely to be the most appropriate for all species and in all environments. We compared the performance of LCP, RW and IBR models of dispersal with the aid of simulations conducted on artificially generated landscapes. We also applied each model to empirical data on the landscape genetics of the endangered fire salamander, Salamandra infraimmaculata, in northern Israel, where conservation planning requires an understanding of the dispersal corridors. Our simulations demonstrate that wide dispersal corridors of the low-cost environment facilitate dispersal in the IBR model, but inhibit dispersal in the RW model. In our empirical study, IBR explained the genetic divergence better than the LCP and RW models (partial Mantel correlation 0.413 for IBR, compared to 0.212 for LCP, and 0.340 for RW). Overall dispersal cost in salamanders was also well predicted by landscape feature slope steepness (76%), and elevation (24%). We conclude that fire salamander dispersal is well characterised by IBR predictions. Together with our simulation findings, these results indicate that wide dispersal corridors facilitate, rather than hinder, salamander dispersal. Comparison of genetic data to dispersal model outputs can be a useful technique in inferring dispersal behaviour from population genetic data.

  20. Niche divergence accelerates evolution in Asian endemic Procapra gazelles

    PubMed Central

    Hu, Junhua; Jiang, Zhigang; Chen, Jing; Qiao, Huijie

    2015-01-01

    Ecological niche divergence and adaptation to new environments are thought to play important roles in driving speciation. Whether recently evolved species show evidence for niche divergence or conservation is vital towards understanding the role of ecology in the process of speciation. The genus Procapra is an ancient, monophyletic lineage endemic to Asia that contains three extant species (P. gutturosa, P. przewalskii and P. picticaudata). These species mainly inhabit the Qinghai-Tibetan and Mongolian Plateaus, and today have primarily allopatric distributions. We applied a series of geographic information system–based analyses to test for environmental variation and niche divergence among these three species. We found substantial evidence for niche divergence in species’ bioclimatic preferences, which supports the hypothesis that niche divergence accelerates diversification in Procapra. Our results provide important insight into the evolutionary history of ungulates in Asia and help to elucidate how environmental changes accelerate lineage diversification. PMID:25951051

  1. Applying landscape genetics to the microbial world.

    PubMed

    Dudaniec, Rachael Y; Tesson, Sylvie V M

    2016-07-01

    Landscape genetics, which explicitly quantifies landscape effects on gene flow and adaptation, has largely focused on macroorganisms, with little attention given to microorganisms. This is despite overwhelming evidence that microorganisms exhibit spatial genetic structuring in relation to environmental variables. The increasing accessibility of genomic data has opened up the opportunity for landscape genetics to embrace the world of microorganisms, which may be thought of as 'the invisible regulators' of the macroecological world. Recent developments in bioinformatics and increased data accessibility have accelerated our ability to identify microbial taxa and characterize their genetic diversity. However, the influence of the landscape matrix and dynamic environmental factors on microorganism genetic dispersal and adaptation has been little explored. Also, because many microorganisms coinhabit or codisperse with macroorganisms, landscape genomic approaches may improve insights into how micro- and macroorganisms reciprocally interact to create spatial genetic structure. Conducting landscape genetic analyses on microorganisms requires that we accommodate shifts in spatial and temporal scales, presenting new conceptual and methodological challenges not yet explored in 'macro'-landscape genetics. We argue that there is much value to be gained for microbial ecologists from embracing landscape genetic approaches. We provide a case for integrating landscape genetic methods into microecological studies and discuss specific considerations associated with the novel challenges this brings. We anticipate that microorganism landscape genetic studies will provide new insights into both micro- and macroecological processes and expand our knowledge of species' distributions, adaptive mechanisms and species' interactions in changing environments.

  2. Modern warfare as a significant form of zoogeomorphic disturbance upon the landscape

    NASA Astrophysics Data System (ADS)

    Hupy, Joseph P.; Koehler, Thomas

    2012-07-01

    The damage exerted by warfare on the physical landscape is one, of many, anthropogenic impacts upon the environment. Bombturbation is a term that describes the impacts of explosive munitions upon the landscape. Bombturbation, like many other forms of zoogeomorphology, is a disruptive force, capable of moving large amounts of sediments, and denuding landscapes to the point where changes in micro and mesotopography have long-term implications. The long term implication of bombturbative actions depends on the type and duration of explosive device that rendered the disturbance, and the geographic context of the landscape disturbed; i.e. cultural and physical factors. Recovery from bombturbative activity, in the context of this research, is measured by vegetative regrowth and soil development in cratered disturbances. A comparison and contrast between the two battlefields of Verdun, France and Khe Sanh, Vietnam show that bombturbative actions have significantly altered the topography at each location, thus influencing surface runoff and processes of soil development. Principals of the Runge pedogenic model, or the energy of water moving through the soil profile, best explain how the varying climate and parent material at each location influence post disturbance soil development rates. Whereas the data collected at Verdun suggest that explosive munitions have put that landscape on diverging path of development, thus rendering it much different post-disturbance landscape, Khe Sanh displays much different recovery patterns. Preliminary research at Khe Sanh indicates that reforestation and soil development following disturbance are not so much influenced by bombturbative patterns as land use activities in the area of study.

  3. Genetic effects of landscape, habitat preference and demography on three co-occurring turtle species.

    PubMed

    Reid, Brendan N; Mladenoff, David J; Peery, M Zachariah

    2017-02-01

    Expanding the scope of landscape genetics beyond the level of single species can help to reveal how species traits influence responses to environmental change. Multispecies studies are particularly valuable in highly threatened taxa, such as turtles, in which the impacts of anthropogenic change are strongly influenced by interspecific differences in life history strategies, habitat preferences and mobility. We sampled approximately 1500 individuals of three co-occurring turtle species across a gradient of habitat change (including varying loss of wetlands and agricultural conversion of upland habitats) in the Midwestern USA. We used genetic clustering and multiple regression methods to identify associations between genetic structure and permanent landscape features, past landscape composition and landscape change in each species. Two aquatic generalists (the painted turtle, Chrysemys picta, and the snapping turtle Chelydra serpentina) both exhibited population genetic structure consistent with isolation by distance, modulated by aquatic landscape features. Genetic divergence for the more terrestrial Blanding's turtle (Emydoidea blandingii), on the other hand, was not strongly associated with geographic distance or aquatic features, and Bayesian clustering analysis indicated that many Emydoidea populations were genetically isolated. Despite long generation times, all three species exhibited associations between genetic structure and postsettlement habitat change, indicating that long generation times may not be sufficient to delay genetic drift resulting from recent habitat fragmentation. The concordances in genetic structure observed between aquatic species, as well as isolation in the endangered, long-lived Emydoidea, reinforce the need to consider both landscape composition and demographic factors in assessing differential responses to habitat change in co-occurring species.

  4. Conserving tigers in working landscapes.

    PubMed

    Chanchani, Pranav; Noon, Barry R; Bailey, Larissa L; Warrier, Rekha A

    2016-06-01

    Tiger (Panthera tigris) conservation efforts in Asia are focused on protected areas embedded in human-dominated landscapes. A system of protected areas is an effective conservation strategy for many endangered species if the network is large enough to support stable metapopulations. The long-term conservation of tigers requires that the species be able to meet some of its life-history needs beyond the boundaries of small protected areas and within the working landscape, including multiple-use forests with logging and high human use. However, understanding of factors that promote or limit the occurrence of tigers in working landscapes is incomplete. We assessed the relative influence of protection status, prey occurrence, extent of grasslands, intensity of human use, and patch connectivity on tiger occurrence in the 5400 km(2) Central Terai Landscape of India, adjacent to Nepal. Two observer teams independently surveyed 1009 km of forest trails and water courses distributed across 60 166-km(2) cells. In each cell, the teams recorded detection of tiger signs along evenly spaced trail segments. We used occupancy models that permitted multiscale analysis of spatially correlated data to estimate cell-scale occupancy and segment-scale habitat use by tigers as a function of management and environmental covariates. Prey availability and habitat quality, rather than protected-area designation, influenced tiger occupancy. Tiger occupancy was low in some protected areas in India that were connected to extensive areas of tiger habitat in Nepal, which brings into question the efficacy of current protection and management strategies in both India and Nepal. At a finer spatial scale, tiger habitat use was high in trail segments associated with abundant prey and large grasslands, but it declined as human and livestock use increased. We speculate that riparian grasslands may provide tigers with critical refugia from human activity in the daytime and thereby promote tiger occurrence

  5. Development of hydrologic landscape regions for classifying hydrologic permanace and hydrological-ecological interactions

    EPA Science Inventory

    In a 2001 paper, Winter proposed the concept of the hydrologic landscape unit as a fundamental unit composed of an upland and lowland separated by a steeper slope. Winter suggested that this concept could be useful for hydrologic research, data analysis, and comparing hydrologic...

  6. Divergent clonal selection dominates medulloblastoma at recurrence

    PubMed Central

    Morrissy, A. Sorana; Garzia, Livia; Shih, David J. H.; Zuyderduyn, Scott; Huang, Xi; Skowron, Patryk; Remke, Marc; Cavalli, Florence M. G.; Ramaswamy, Vijay; Lindsay, Patricia E.; Jelveh, Salomeh; Donovan, Laura K.; Wang, Xin; Luu, Betty; Zayne, Kory; Li, Yisu; Mayoh, Chelsea; Thiessen, Nina; Mercier, Eloi; Mungall, Karen L.; Ma, Yusanne; Tse, Kane; Zeng, Thomas; Shumansky, Karey; Roth, Andrew J. L.; Shah, Sohrab; Farooq, Hamza; Kijima, Noriyuki; Holgado, Borja L.; Lee, John J. Y.; Matan-Lithwick, Stuart; Liu, Jessica; Mack, Stephen C.; Manno, Alex; Michealraj, K. A.; Nor, Carolina; Peacock, John; Qin, Lei; Reimand, Juri; Rolider, Adi; Thompson, Yuan Y.; Wu, Xiaochong; Pugh, Trevor; Ally, Adrian; Bilenky, Mikhail; Butterfield, Yaron S. N.; Carlsen, Rebecca; Cheng, Young; Chuah, Eric; Corbett, Richard D.; Dhalla, Noreen; He, An; Lee, Darlene; Li, Haiyan I.; Long, William; Mayo, Michael; Plettner, Patrick; Qian, Jenny Q.; Schein, Jacqueline E.; Tam, Angela; Wong, Tina; Birol, Inanc; Zhao, Yongjun; Faria, Claudia C.; Pimentel, José; Nunes, Sofia; Shalaby, Tarek; Grotzer, Michael; Pollack, Ian F.; Hamilton, Ronald L.; Li, Xiao-Nan; Bendel, Anne E.; Fults, Daniel W.; Walter, Andrew W.; Kumabe, Toshihiro; Tominaga, Teiji; Collins, V. Peter; Cho, Yoon-Jae; Hoffman, Caitlin; Lyden, David; Wisoff, Jeffrey H.; Garvin, James H.; Stearns, Duncan S.; Massimi, Luca; Schüller, Ulrich; Sterba, Jaroslav; Zitterbart, Karel; Puget, Stephanie; Ayrault, Olivier; Dunn, Sandra E.; Tirapelli, Daniela P. C.; Carlotti, Carlos G.; Wheeler, Helen; Hallahan, Andrew R.; Ingram, Wendy; MacDonald, Tobey J.; Olson, Jeffrey J.; Van Meir, Erwin G.; Lee, Ji-Yeoun; Wang, Kyu-Chang; Kim, Seung-Ki; Cho, Byung-Kyu; Pietsch, Torsten; Fleischhack, Gudrun; Tippelt, Stephan; Ra, Young Shin; Bailey, Simon; Lindsey, Janet C.; Clifford, Steven C.; Eberhart, Charles G.; Cooper, Michael K.; Packer, Roger J.; Massimino, Maura; Garre, Maria Luisa; Bartels, Ute; Tabori, Uri; Hawkins, Cynthia E.; Dirks, Peter; Bouffet, Eric; Rutka, James T.; Wechsler-Reya, Robert J.; Weiss, William A.; Collier, Lara S.; Dupuy, Adam J.; Korshunov, Andrey; Jones, David T. W.; Kool, Marcel; Northcott, Paul A.; Pfister, Stefan M.; Largaespada, David A.; Mungall, Andrew J.; Moore, Richard A.; Jabado, Nada; Bader, Gary D.; Jones, Steven J. M.; Malkin, David; Marra, Marco A.; Taylor, Michael D.

    2016-01-01

    The development of targeted anti-cancer therapies through the study of cancer genomes is intended to increase survival rates and decrease treatment-related toxicity. We treated a transposon–driven, functional genomic mouse model of medulloblastoma with ‘humanized’ in vivo therapy (microneurosurgical tumour resection followed by multi-fractionated, image-guided radiotherapy). Genetic events in recurrent murine medulloblastoma exhibit a very poor overlap with those in matched murine diagnostic samples (<5%). Whole-genome sequencing of 33 pairs of human diagnostic and post-therapy medulloblastomas demonstrated substantial genetic divergence of the dominant clone after therapy (<12% diagnostic events were retained at recurrence). In both mice and humans, the dominant clone at recurrence arose through clonal selection of a pre-existing minor clone present at diagnosis. Targeted therapy is unlikely to be effective in the absence of the target, therefore our results offer a simple, proximal, and remediable explanation for the failure of prior clinical trials of targeted therapy. PMID:26760213

  7. Radar imaging of intense nonlinear Ekman divergence

    NASA Astrophysics Data System (ADS)

    Liu, Guoqiang; Perrie, William; Kudryavtsev, Vladimir; He, Yijun; Shen, Hui; Zhang, Biao; Hu, Haibo

    2016-09-01

    In general, given an oceanic thermal front, there is a strong positive correlation between sea surface temperature (SST) gradients and surface winds, and the marine atmospheric boundary layer is unstable over the warm side of the oceanic thermal front. The Gulf Stream is a notable example of an oceanic thermal front, and its warm side is often detected as enhanced backscatter in synthetic aperture radar (SAR) images. However, in some "anomalous" SAR images, low backscatter is sometimes observed on the warm side of the front, which seems inconsistent. Therefore, we propose a mechanism to interpret the generation of the low backscatter, based on interactions between ocean surface wind waves and intense nonlinear Ekman divergence. This mechanism is verified by showing that patterns in an observed anomalous SAR image are in good agreement with those in the simulated radar signature. In addition, this methodology and analysis demonstrate that SAR is potentially important for detecting and diagnosing small scale air-sea interactions and upper ocean dynamics with strong vertical transports induced by submesoscale processes.

  8. Divergent Synthesis of Heparan Sulfate Oligosaccharides

    PubMed Central

    2015-01-01

    Heparan sulfates are implicated in a wide range of biological processes. A major challenge in deciphering their structure and activity relationship is the synthetic difficulties to access diverse heparan sulfate oligosaccharides with well-defined sulfation patterns. In order to expedite the synthesis, a divergent synthetic strategy was developed. By integrating chemical synthesis and two types of O-sulfo transferases, seven different hexasaccharides were obtained from a single hexasaccharide precursor. This approach combined the flexibility of chemical synthesis with the selectivity of enzyme-catalyzed sulfations, thus simplifying the overall synthetic operations. In an attempt to establish structure activity relationships of heparan sulfate binding with its receptor, the synthesized oligosaccharides were incorporated onto a glycan microarray, and their bindings with a growth factor FGF-2 were examined. The unique combination of chemical and enzymatic approaches expanded the capability of oligosaccharide synthesis. In addition, the well-defined heparan sulfate structures helped shine light on the fine substrate specificities of biosynthetic enzymes and confirm the potential sequence of enzymatic reactions in biosynthesis. PMID:26574650

  9. Diversity and Divergence of Dinoflagellate Histone Proteins.

    PubMed

    Marinov, Georgi K; Lynch, Michael

    2015-12-08

    Histone proteins and the nucleosomal organization of chromatin are near-universal eukaroytic features, with the exception of dinoflagellates. Previous studies have suggested that histones do not play a major role in the packaging of dinoflagellate genomes, although several genomic and transcriptomic surveys have detected a full set of core histone genes. Here, transcriptomic and genomic sequence data from multiple dinoflagellate lineages are analyzed, and the diversity of histone proteins and their variants characterized, with particular focus on their potential post-translational modifications and the conservation of the histone code. In addition, the set of putative epigenetic mark readers and writers, chromatin remodelers and histone chaperones are examined. Dinoflagellates clearly express the most derived set of histones among all autonomous eukaryote nuclei, consistent with a combination of relaxation of sequence constraints imposed by the histone code and the presence of numerous specialized histone variants. The histone code itself appears to have diverged significantly in some of its components, yet others are conserved, implying conservation of the associated biochemical processes. Specifically, and with major implications for the function of histones in dinoflagellates, the results presented here strongly suggest that transcription through nucleosomal arrays happens in dinoflagellates. Finally, the plausible roles of histones in dinoflagellate nuclei are discussed.

  10. Divergent Plasticity of Prefrontal Cortex Networks

    PubMed Central

    Moghaddam, Bita; Homayoun, Houman

    2010-01-01

    The ‘executive’ regions of the prefrontal cortex (PFC) such as the dorsolateral PFC (dlPFC) and its rodent equivalent medial PFC (mPFC) are thought to respond in concert with the ‘limbic’ regions of the PFC such as the orbitofrontal (OFC) cortex to orchestrate behavior that is consistent with context and expected outcome. Both groups of regions have been implicated in behavioral abnormalities associated with addiction and psychiatric disorders, in particular, schizophrenia and mood disorders. Theories about the pathophysiology of these disorders, however, incorporate abnormalities in discrete PFC regions independently of each other or assume they are one and the same and, thus, bunch them under umbrella of ‘PFC dysfunction.’ Emerging data from animal studies suggest that mPFC and OFC neurons display opposing patterns of plasticity during associative learning and in response to repeated exposure to psychostimulants. These data corroborate clinical studies reporting different patterns of activation in OFC versus dlPFC in individuals with schizophrenia or addictive disorders. These suggest that concomitant but divergent engagement of discrete PFC regions is critical for learning stimulus-outcome associations, and the execution of goal-directed behavior that is based on these associations. An atypical interplay between these regions may lead to abnormally high or low salience assigned to stimuli, resulting in symptoms that are fundamental to many psychiatric and addictive disorders, including attentional deficits, improper affective response to stimuli, and inflexible or impulsive behavior. PMID:17912252

  11. Clock gene evolution and functional divergence.

    PubMed

    Tauber, Eran; Last, Kim S; Olive, Peter J W; Kyriacou, C P

    2004-10-01

    In considering the impact of the earth's changing geophysical conditions during the history of life, it is surprising to learn that the earth's rotational period may have been as short as 4 h, as recently as 1900 million years ago (or 1.9 billion years ago). The implications of such figures for the origin and evolution of clocks are considerable, and the authors speculate on how this short rotational period might have influenced the development of the "protoclock" in early microorganisms, such as the Cyanobacteria, during the geological periodsin which they arose and flourished. They then discuss the subsequent duplication of clock genes that took place around and after the Cambrian period, 543 million years ago, and its consequences. They compare the relative divergences of the canonical clock genes, which reveal the Per family to be the most rapidly evolving. In addition, the authors use a statistical test to predict which residues within the PER and CRY families may have undergone functional specialization.

  12. On the divergences of inflationary superhorizon perturbations

    SciTech Connect

    Enqvist, K; Nurmi, S; Podolsky, D; Rigopoulos, G I E-mail: sami.nurmi@helsinki.fi E-mail: gerasimos.rigopoulos@helsinki.fi

    2008-04-15

    We discuss the infrared divergences that appear to plague cosmological perturbation theory. We show that, within the stochastic framework, they are regulated by eternal inflation so that the theory predicts finite fluctuations. Using the {Delta}N formalism to one loop, we demonstrate that the infrared modes can be absorbed into additive constants and the coefficients of the diagrammatic expansion for the connected parts of two-and three-point functions of the curvature perturbation. As a result, the use of any infrared cutoff below the scale of eternal inflation is permitted, provided that the background fields are appropriately redefined. The natural choice for the infrared cutoff would, of course, be the present horizon; other choices manifest themselves in the running of the correlators. We also demonstrate that it is possible to define observables that are renormalization-group-invariant. As an example, we derive a non-perturbative, infrared finite and renormalization point-independent relation between the two-point correlators of the curvature perturbation for the case of the free single field.

  13. Remarkable ancient divergences amongst neglected lorisiform primates

    PubMed Central

    Nekaris, K. Anne‐Isola; Perkin, Andrew; Bearder, Simon K.; Pimley, Elizabeth R.; Schulze, Helga; Streicher, Ulrike; Nadler, Tilo; Kitchener, Andrew; Zischler, Hans; Zinner, Dietmar; Roos, Christian

    2015-01-01

    Lorisiform primates (Primates: Strepsirrhini: Lorisiformes) represent almost 10% of the living primate species and are widely distributed in sub‐Saharan Africa and South/South‐East Asia; however, their taxonomy, evolutionary history, and biogeography are still poorly understood. In this study we report the largest molecular phylogeny in terms of the number of represented taxa. We sequenced the complete mitochondrial cytochrome b gene for 86 lorisiform specimens, including ∼80% of all the species currently recognized. Our results support the monophyly of the Galagidae, but a common ancestry of the Lorisinae and Perodicticinae (family Lorisidae) was not recovered. These three lineages have early origins, with the Galagidae and the Lorisinae diverging in the Oligocene at about 30 Mya and the Perodicticinae emerging in the early Miocene. Our mitochondrial phylogeny agrees with recent studies based on nuclear data, and supports Euoticus as the oldest galagid lineage and the polyphyletic status of Galagoides. Moreover, we have elucidated phylogenetic relationships for several species never included before in a molecular phylogeny. The results obtained in this study suggest that lorisiform diversity remains substantially underestimated and that previously unnoticed cryptic diversity might be present within many lineages, thus urgently requiring a comprehensive taxonomic revision of this primate group. © 2015 The Linnean Society of London PMID:26900177

  14. Divergence and Convergence in Enzyme Evolution*

    PubMed Central

    Galperin, Michael Y.; Koonin, Eugene V.

    2012-01-01

    Comparative analysis of the sequences of enzymes encoded in a variety of prokaryotic and eukaryotic genomes reveals convergence and divergence at several levels. Functional convergence can be inferred when structurally distinct and hence non-homologous enzymes show the ability to catalyze the same biochemical reaction. In contrast, as a result of functional diversification, many structurally similar enzyme molecules act on substantially distinct substrates and catalyze diverse biochemical reactions. Here, we present updates on the ATP-grasp, alkaline phosphatase, cupin, HD hydrolase, and N-terminal nucleophile (Ntn) hydrolase enzyme superfamilies and discuss the patterns of sequence and structural conservation and diversity within these superfamilies. Typically, enzymes within a superfamily possess common sequence motifs and key active site residues, as well as (predicted) reaction mechanisms. These observations suggest that the strained conformation (the entatic state) of the active site, which is responsible for the substrate binding and formation of the transition complex, tends to be conserved within enzyme superfamilies. The subsequent fate of the transition complex is not necessarily conserved and depends on the details of the structures of the enzyme and the substrate. This variability of reaction outcomes limits the ability of sequence analysis to predict the exact enzymatic activities of newly sequenced gene products. Nevertheless, sequence-based (super)family assignments and generic functional predictions, even if imprecise, provide valuable leads for experimental studies and remain the best approach to the functional annotation of uncharacterized proteins from new genomes. PMID:22069324

  15. Social and natural sciences differ in their research strategies, adapted to work for different knowledge landscapes.

    PubMed

    Jaffe, Klaus

    2014-01-01

    Do different fields of knowledge require different research strategies? A numerical model exploring different virtual knowledge landscapes, revealed two diverging optimal search strategies. Trend following is maximized when the popularity of new discoveries determine the number of individuals researching it. This strategy works best when many researchers explore few large areas of knowledge. In contrast, individuals or small groups of researchers are better in discovering small bits of information in dispersed knowledge landscapes. Bibliometric data of scientific publications showed a continuous bipolar distribution of these strategies, ranging from natural sciences, with highly cited publications in journals containing a large number of articles, to the social sciences, with rarely cited publications in many journals containing a small number of articles. The natural sciences seem to adapt their research strategies to landscapes with large concentrated knowledge clusters, whereas social sciences seem to have adapted to search in landscapes with many small isolated knowledge clusters. Similar bipolar distributions were obtained when comparing levels of insularity estimated by indicators of international collaboration and levels of country-self citations: researchers in academic areas with many journals such as social sciences, arts and humanities, were the most isolated, and that was true in different regions of the world. The work shows that quantitative measures estimating differences between academic disciplines improve our understanding of different research strategies, eventually helping interdisciplinary research and may be also help improve science policies worldwide.

  16. Social and Natural Sciences Differ in Their Research Strategies, Adapted to Work for Different Knowledge Landscapes

    PubMed Central

    Jaffe, Klaus

    2014-01-01

    Do different fields of knowledge require different research strategies? A numerical model exploring different virtual knowledge landscapes, revealed two diverging optimal search strategies. Trend following is maximized when the popularity of new discoveries determine the number of individuals researching it. This strategy works best when many researchers explore few large areas of knowledge. In contrast, individuals or small groups of researchers are better in discovering small bits of information in dispersed knowledge landscapes. Bibliometric data of scientific publications showed a continuous bipolar distribution of these strategies, ranging from natural sciences, with highly cited publications in journals containing a large number of articles, to the social sciences, with rarely cited publications in many journals containing a small number of articles. The natural sciences seem to adapt their research strategies to landscapes with large concentrated knowledge clusters, whereas social sciences seem to have adapted to search in landscapes with many small isolated knowledge clusters. Similar bipolar distributions were obtained when comparing levels of insularity estimated by indicators of international collaboration and levels of country-self citations: researchers in academic areas with many journals such as social sciences, arts and humanities, were the most isolated, and that was true in different regions of the world. The work shows that quantitative measures estimating differences between academic disciplines improve our understanding of different research strategies, eventually helping interdisciplinary research and may be also help improve science policies worldwide. PMID:25426723

  17. A Holistic Landscape Description Reveals That Landscape Configuration Changes More over Time than Composition: Implications for Landscape Ecology Studies

    PubMed Central

    Mimet, Anne; Pellissier, Vincent; Houet, Thomas; Julliard, Romain; Simon, Laurent

    2016-01-01

    Background Space-for-time substitution—that is, the assumption that spatial variations of a system can explain and predict the effect of temporal variations—is widely used in ecology. However, it is questionable whether it can validly be used to explain changes in biodiversity over time in response to land-cover changes. Hypothesis Here, we hypothesize that different temporal vs spatial trajectories of landscape composition and configuration may limit space-for-time substitution in landscape ecology. Land-cover conversion changes not just the surface areas given over to particular types of land cover, but also affects isolation, patch size and heterogeneity. This means that a small change in land cover over time may have only minor repercussions on landscape composition but potentially major consequences for landscape configuration. Methods Using land-cover maps of the Paris region for 1982 and 2003, we made a holistic description of the landscape disentangling landscape composition from configuration. After controlling for spatial variations, we analyzed and compared the amplitudes of changes in landscape composition and configuration over time. Results For comparable spatial variations, landscape configuration varied more than twice as much as composition over time. Temporal changes in composition and configuration were not always spatially matched. Significance The fact that landscape composition and configuration do not vary equally in space and time calls into question the use of space-for-time substitution in landscape ecology studies. The instability of landscapes over time appears to be attributable to configurational changes in the main. This may go some way to explaining why the landscape variables that account for changes over time in biodiversity are not the same ones that account for the spatial distribution of biodiversity. PMID:26959363

  18. Climate and landscape controls on chemical weathering - regional to pedon-scale analysis (Invited)

    NASA Astrophysics Data System (ADS)

    Rasmussen, C.; Lybrand, R.; Jardine, A. B.; Heidbuechel, I.; Troch, P. A.; Chorover, J.

    2010-12-01

    Understanding the linkages among climate, erosion and weathering is central to quantifying pedogenesis and critical zone evolution. We approach these linkages through a combination of regional scale synthesis of climate, erosion and regolith geochemical data for upland terrain, in addition to detailed studies on climate and landscape position controls on local- and pedon-scale regolith weathering patterns across the steep semiarid climate gradient encompassed by the Santa Catalina Mountain (SCM) Critical Zone Observatory in southern Arizona, USA. The regional analysis indicated strong correlation between regolith plagioclase depletion and total Na mass loss with both total precipitation and the annual water balance as quantified using a humidity index (precipitiaton/potential evapotranspiration). Plagioclase depletion increased exponentially with water availability for sites with annual temperature greater than 5°C and erosion rates greater than 10 g/m2/yr, suggesting second order control of temperature and erosion on plagioclase weathering. The local- and pedon-scale SCM study sites span a steep environmental gradient on granitic and metamorphic parent materials: mean annual air temperature decreases (20-10°C) and mean annual precipitation increases (25-95 cm) with elevation, with concomitant changes in vegetation from desert-scrub to mixed conifer forest. We sampled full regolith profiles from each vegetation community across the climate gradient on spatially coupled divergent and convergent landscape positions. Pedon geochemical and mineralogical data, when coupled with cosmogenic nuclide derived denudation rates, indicated strong linkages among water availability, regolith mass loss and mineral weathering reactions. Specifically, divergent landscape positions demonstrated a pattern similar to that noted in the regional scale synthesis of increasing weatherable mineral mass loss with greater water availability. In contrast, convergent landscape positions

  19. [Wetland landscape ecological classification: research progress].

    PubMed

    Cao, Yu; Mo, Li-jiang; Li, Yan; Zhang, Wen-mei

    2009-12-01

    Wetland landscape ecological classification, as a basis for the studies of wetland landscape ecology, directly affects the precision and effectiveness of wetland-related research. Based on the history, current status, and latest progress in the studies on the theories, indicators, and methods of wetland landscape classification, some scientific wetland classification systems, e.g., NWI, Ramsar, and HGM, were introduced and discussed in this paper. It was suggested that a comprehensive classification method based on HGM and on the integral consideration of wetlands spatial structure, ecological function, ecological process, topography, soil, vegetation, hydrology, and human disturbance intensity should be the major future direction in this research field. Furthermore, the integration of 3S technologies, quantitative mathematics, landscape modeling, knowledge engineering, and artificial intelligence to enhance the automatization and precision of wetland landscape ecological classification would be the key issues and difficult topics in the studies of wetland landscape ecological classification.

  20. Divergence thresholds and divergent biodiversity estimates: can metabarcoding reliably describe zooplankton communities?

    PubMed Central

    Brown, Emily A; Chain, Frédéric J J; Crease, Teresa J; MacIsaac, Hugh J; Cristescu, Melania E

    2015-01-01

    DNA metabarcoding is a promising method for describing communities and estimating biodiversity. This approach uses high-throughput sequencing of targeted markers to identify species in a complex sample. By convention, sequences are clustered at a predefined sequence divergence threshold (often 3%) into operational taxonomic units (OTUs) that serve as a proxy for species. However, variable levels of interspecific marker variation across taxonomic groups make clustering sequences from a phylogenetically diverse dataset into OTUs at a uniform threshold problematic. In this study, we use mock zooplankton communities to evaluate the accuracy of species richness estimates when following conventional protocols to cluster hypervariable sequences of the V4 region of the small subunit ribosomal RNA gene (18S) into OTUs. By including individually tagged single specimens and “populations” of various species in our communities, we examine the impact of intra- and interspecific diversity on OTU clustering. Communities consisting of single individuals per species generated a correspondence of 59–84% between OTU number and species richness at a 3% divergence threshold. However, when multiple individuals per species were included, the correspondence between OTU number and species richness dropped to 31–63%. Our results suggest that intraspecific variation in this marker can often exceed 3%, such that a single species does not always correspond to one OTU. We advocate the need to apply group-specific divergence thresholds when analyzing complex and taxonomically diverse communities, but also encourage the development of additional filtering steps that allow identification of artifactual rRNA gene sequences or pseudogenes that may generate spurious OTUs. PMID:26078859

  1. The limits of the nuclear landscape.

    PubMed

    Erler, Jochen; Birge, Noah; Kortelainen, Markus; Nazarewicz, Witold; Olsen, Erik; Perhac, Alexander M; Stoitsov, Mario

    2012-06-27

    In 2011, 100 new nuclides were discovered. They joined the approximately 3,000 stable and radioactive nuclides that either occur naturally on Earth or are synthesized in the laboratory. Every atomic nucleus, characterized by a specific number of protons and neutrons, occupies a spot on the chart of nuclides, which is bounded by 'drip lines' indicating the values of neutron and proton number at which nuclear binding ends. The placement of the neutron drip line for the heavier elements is based on theoretical predictions using extreme extrapolations, and so is uncertain. However, it is not known how uncertain it is or how many protons and neutrons can be bound in a nucleus. Here we estimate these limits of the nuclear 'landscape' and provide statistical and systematic uncertainties for our predictions. We use nuclear density functional theory, several Skyrme interactions and high-performance computing, and find that the number of bound nuclides with between 2 and 120 protons is around 7,000. We find that extrapolations for drip-line positions and selected nuclear properties, including neutron separation energies relevant to astrophysical processes, are very consistent between the models used.

  2. Toward a comprehensive landscape vegetation monitoring framework

    NASA Astrophysics Data System (ADS)

    Kennedy, Robert; Hughes, Joseph; Neeti, Neeti; Larrue, Tara; Gregory, Matthew; Roberts, Heather; Ohmann, Janet; Kane, Van; Kane, Jonathan; Hooper, Sam; Nelson, Peder; Cohen, Warren; Yang, Zhiqiang

    2016-04-01

    Blossoming Earth observation resources provide great opportunity to better understand land vegetation dynamics, but also require new techniques and frameworks to exploit their potential. Here, I describe several parallel projects that leverage time-series Landsat imagery to describe vegetation dynamics at regional and continental scales. At the core of these projects are the LandTrendr algorithms, which distill time-series earth observation data into periods of consistent long or short-duration dynamics. In one approach, we built an integrated, empirical framework to blend these algorithmically-processed time-series data with field data and lidar data to ascribe yearly change in forest biomass across the US states of Washington, Oregon, and California. In a separate project, we expanded from forest-only monitoring to full landscape land cover monitoring over the same regional scale, including both categorical class labels and continuous-field estimates. In these and other projects, we apply machine-learning approaches to ascribe all changes in vegetation to driving processes such as harvest, fire, urbanization, etc., allowing full description of both disturbance and recovery processes and drivers. Finally, we are moving toward extension of these same techniques to continental and eventually global scales using Google Earth Engine. Taken together, these approaches provide one framework for describing and understanding processes of change in vegetation communities at broad scales.

  3. Magnetic separation of algae

    SciTech Connect

    Nath, Pulak; Twary, Scott N.

    2016-04-26

    Described herein are methods and systems for harvesting, collecting, separating and/or dewatering algae using iron based salts combined with a magnetic field gradient to separate algae from an aqueous solution.

  4. Separation anxiety in children

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/001542.htm Separation anxiety in children To use the sharing features on this page, please enable JavaScript. Separation anxiety in children is a developmental stage in ...

  5. Ionene membrane battery separator

    NASA Technical Reports Server (NTRS)

    Moacanin, J.; Tom, H. Y.

    1969-01-01

    Ionic transport characteristics of ionenes, insoluble membranes from soluble polyelectrolyte compositions, are studied for possible application in a battery separator. Effectiveness of the thin film of separator membrane essentially determines battery lifetime.

  6. Clustering and Phase Transitions on a Neutral Landscape

    NASA Astrophysics Data System (ADS)

    Scott, Adam; King, Dawn; Maric, Nevena; Bahar, Sonya

    2012-02-01

    The problem of speciation and species aggregation on a neutral landscape, subject to random mutational fluctuations rather than selective drive, has been a focus of research since the seminal work of Kimura on genetic drift. These ideas have received increased attention due to the more recent development of a neutral ecological theory by Hubbell. De Aguiar et al. recently demonstrated, in a computational model, that speciation can occur under neutral conditions; this study bears some comparison with more mathematical studies of clustering on neutral landscapes in the context of branching and annihilating random walks. Here, we show that clustering can occur on a neutral landscape where the dimensions specify the simulated organisms' phenotypes. Unlike the De Aguiar et al. model, we simulate sympatric speciation: the organisms cluster phenotypically, but are not spatially separated. Moreover, we find that clustering occurs not only in the case of assortative mating, but also in the case of asexual fission. Clustering is not observed in a control case where organisms can mate randomly. We find that the population size and the number of clusters undergo phase-transition-like behavior as the maximum mutation size is varied.

  7. LANDSCAPE INFLUENCES ON LAKE CHEMISTRY OF SMALL DIMICTIC LAKES IN THE HUMAN DOMINATED SOUTHERN WISCONSIN LANDSCAPE

    EPA Science Inventory

    Changes in landscape heterogeneity, historic landcover change, and human disturbance regimes are governed by complex interrelated landscape processes that modify lake water quality through the addition of nutrients, sediment, anthropogenic chemicals, and changes in major ion conc...

  8. LanDPro: Landscape Dynamics Program

    DTIC Science & Technology

    2012-09-18

    making. These same types of sites were rarely found on landscapes formed on deposits derived from coarse-grained igneous rock sources, such as granite...grained igneous rocks . Our premise is that if our conceptual model were applied at the U.S. Army Yuma Proving Ground (YPG) it would indicate a dominance...of sites on the most stable landscape units developed on deposits derived from fine-grained igneous rocks . At YPG, these landscape units would be

  9. Genetic structure is associated with phenotypic divergence in floral traits and reproductive investment in a high-altitude orchid from the Iron Quadrangle, southeastern Brazil.

    PubMed

    Leles, Bruno; Chaves, Anderson V; Russo, Philip; Batista, João A N; Lovato, Maria Bernadete

    2015-01-01

    Knowledge of the role of Neotropical montane landscapes in shaping genetic connectivity and local adaptation is essential for understanding the evolutionary processes that have shaped the extraordinary species diversity in these regions. In the present study, we examined the landscape genetics, estimated genetic diversity, and explored genetic relationships with morphological variability and reproductive strategies in seven natural populations of Cattleya liliputana (Orchidaceae). Nuclear microsatellite markers were used for genetic analyses. Spatial Bayesian clustering and population-based analyses revealed significant genetic structuring and high genetic diversity (He = 0.733 ± 0.03). Strong differentiation was found between populations over short spatial scales (FST = 0.138, p < 0.001), reflecting the landscape discontinuity and isolation. Monmonier´s maximum difference algorithm, Bayesian analysis on STRUCTURE and principal component analysis identified one major genetic discontinuity between populations. Divergent genetic groups showed phenotypic divergence in flower traits and reproductive strategies. Increased sexual reproductive effort was associated with rock outcrop type and may be a response to adverse conditions for growth and vegetative reproduction. Here we discuss the effect of restricted gene flow, local adaptation and phenotypic plasticity as drivers of population differentiation in Neotropical montane rock outcrops.

  10. The development of quick, robust, quantitative phenotypic assays for describing the host–nonhost landscape to stripe rust

    PubMed Central

    Dawson, Andrew M.; Bettgenhaeuser, Jan; Gardiner, Matthew; Green, Phon; Hernández-Pinzón, Inmaculada; Hubbard, Amelia; Moscou, Matthew J.

    2015-01-01

    Nonhost resistance is often conceptualized as a qualitative separation from host resistance. Classification into these two states is generally facile, as they fail to fully describe the range of states that exist in the transition from host to nonhost. This poses a problem when studying pathosystems that cannot be classified as either host or nonhost due to their intermediate status relative to these two extremes. In this study, we investigate the efficacy of the Poaceae-stripe rust (Puccinia striiformis Westend.) interaction for describing the host–nonhost landscape. First, using barley (Hordeum vulgare L.) and Brachypodium distachyon (L.) P. Beauv. We observed that macroscopic symptoms of chlorosis and leaf browning were associated with hyphal colonization by P. striiformis f. sp. tritici, respectively. This prompted us to adapt a protocol for visualizing fungal structures into a phenotypic assay that estimates the percent of leaf colonized. Use of this assay in intermediate host and intermediate nonhost systems found the frequency of infection decreases with evolutionary divergence from the host species. Similarly, we observed that the pathogen’s ability to complete its life cycle decreased faster than its ability to colonize leaf tissue, with no incidence of pustules observed in the intermediate nonhost system and significantly reduced pustule formation in the intermediate host system as compared to the host system, barley-P. striiformis f. sp. hordei. By leveraging the stripe rust pathosystem in conjunction with macroscopic and microscopic phenotypic assays, we now hope to dissect the genetic architecture of intermediate host and intermediate nonhost resistance using structured populations in barley and B. distachyon. PMID:26579142

  11. Recent ecological divergence despite migration in sockeye salmon (Oncorhynchus nerka)

    USGS Publications Warehouse

    Pavey, Scott A.; Nielsen, Jennifer L.; Hamon, Troy R.

    2010-01-01

    Ecological divergence may result when populations experience different selection regimes, but there is considerable discussion about the role of migration at the beginning stages of divergence before reproductive isolating mechanisms have evolved. However, detection of past migration is difficult in current populations and tools to differentiate genetic similarities due to migration versus recent common ancestry are only recently available. Using past volcanic eruption times as a framework, we combine morphological analyses of traits important to reproduction with a coalescent-based genetic analysis of two proximate sockeye salmon (Oncorhynchus nerka) populations. We find that this is the most recent (~500 years, 100 generations) natural ecological divergence recorded in a fish species, and report that this divergence is occurring despite migration. Although studies of fish divergence following the retreat of glaciers (10,000–15,000 years ago) have contributed extensively to our understanding of speciation, the Aniakchak system of sockeye salmon provides a rare example of the initial stages of ecological divergence following natural colonization. Our results show that even in the face of continued migration, populations may diverge in the absence of a physical barrier.

  12. Diverging Wave Volumetric Imaging Using Subaperture Beamforming.

    PubMed

    Santos, Pedro; Haugen, Geir Ultveit; Lovstakken, Lasse; Samset, Eigil; D'hooge, Jan

    2016-12-01

    Several clinical settings could benefit from 3-D high frame rate (HFR) imaging and, in particular, HFR 3-D tissue Doppler imaging (TDI). To date, the proposed methodologies are based mostly on experimental ultrasound platforms, making their translation to clinical systems nontrivial as these have additional hardware constraints. In particular, clinically used 2-D matrix array transducers rely on subaperture (SAP) beamforming to limit cabling between the ultrasound probe and the back-end console. Therefore, this paper is aimed at assessing the feasibility of HFR 3-D TDI using diverging waves (DWs) on a clinical transducer with SAP beamforming limitations. Simulation studies showed that the combination of a single DW transmission with SAP beamforming results in severe imaging artifacts due to grating lobes and reduced penetration. Interestingly, a promising tradeoff between image quality and frame rate was achieved for scan sequences with a moderate number of transmit beams. In particular, a sparse sequence with nine transmissions showed good imaging performance for an imaging sector of 70 (°)×70 (°) at volume rates of approximately 600 Hz. Subsequently, this sequence was implemented in a clinical system and TDI was recorded in vivo on healthy subjects. Velocity curves were extracted and compared against conventional TDI (i.e., with focused transmit beams). The results showed similar velocities between both beamforming approaches, with a cross-correlation of 0.90 ± 0.11 between the traces of each mode. Overall, this paper indicates that HFR 3-D TDI is feasible in systems with clinical 2-D matrix arrays, despite the limitations of SAP beamforming.

  13. Divergent and Convergent Evolution of Fungal Pathogenicity

    PubMed Central

    Shang, Yanfang; Xiao, Guohua; Zheng, Peng; Cen, Kai; Zhan, Shuai; Wang, Chengshu

    2016-01-01

    Fungal pathogens of plants and animals have multifarious effects; they cause devastating damages to agricultures, lead to life-threatening diseases in humans, or induce beneficial effects by reducing insect pest populations. Many virulence factors have been determined in different fungal pathogens; however, the molecular determinants contributing to fungal host selection and adaptation are largely unknown. In this study, we sequenced the genomes of seven ascomycete insect pathogens and performed the genome-wide analyses of 33 species of filamentous ascomycete pathogenic fungi that infect insects (12 species), plants (12), and humans (9). Our results revealed that the genomes of plant pathogens encode more proteins and protein families than the insect and human pathogens. Unexpectedly, more common orthologous protein groups are shared between the insect and plant pathogens than between the two animal group pathogens. We also found that the pathogenicity of host-adapted fungi evolved multiple times, and that both divergent and convergent evolutions occurred during pathogen–host cospeciation thus resulting in protein families with similar features in each fungal group. However, the role of phylogenetic relatedness on the evolution of protein families and therefore pathotype formation could not be ruled out due to the effect of common ancestry. The evolutionary correlation analyses led to the identification of different protein families that correlated with alternate pathotypes. Particularly, the effector-like proteins identified in plant and animal pathogens were strongly linked to fungal host adaptation, suggesting the existence of similar gene-for-gene relationships in fungus–animal interactions that has not been established before. These results well advance our understanding of the evolution of fungal pathogenicity and the factors that contribute to fungal pathotype formation. PMID:27071652

  14. A computational framework for generalized moving windows and its application to landscape pattern analysis

    NASA Astrophysics Data System (ADS)

    Hagen-Zanker, Alex

    2016-02-01

    Land cover products based on remotely sensed data are commonly investigated in terms of landscape composition and configuration; i.e. landscape pattern. Traditional landscape pattern indicators summarize an aspect of landscape pattern over the full study area. Increasingly, the advantages of representing the scale-specific spatial variation of landscape patterns as continuous surfaces are being recognized. However, technical and computational barriers hinder the uptake of this approach. This article reduces such barriers by introducing a computational framework for moving window analysis that separates the tasks of tallying pixels, patches and edges as a window moves over the map from the internal logic of landscape indicators. The framework is applied on data covering the UK and Ireland at 250 m resolution, evaluating a variety of indicators including mean patch size, edge density and Shannon diversity at window sizes ranging from 2.5 km to 80 km. The required computation time is in the order of seconds to minutes on a regular personal computer. The framework supports rapid development of indicators requiring little coding. The computational efficiency means that methods can be integrated in iterative computational tasks such as multi-scale analysis, optimization, sensitivity analysis and simulation modelling.

  15. Incorporating bioenergy into sustainable landscape designs

    SciTech Connect

    Dale, Virginia H.; Kline, Keith L.; Buford, Marilyn A.; Volk, Timothy A.; Smith, C. Tattersall; Stupak, Inge

    2015-12-30

    In this paper, we describe an approach to landscape design that focuses on integrating bioenergy production with other components of environmental, social and economic systems. Landscape design as used here refers to a spatially explicit, collaborative plan for management of landscapes and supply chains. Landscape design can involve multiple scales and build on existing practices to reduce costs or enhance services. Appropriately applied to a specific context, landscape design can help people assess trade-offs when making choices about locations, types of feedstock, transport, refining and distribution of bioenergy products and services. The approach includes performance monitoring and reporting along the bioenergy supply chain. Examples of landscape design applied to bioenergy production systems are presented. Barriers to implementation of landscape design include high costs, the need to consider diverse land-management objectives from a wide array of stakeholders, up-front planning requirements, and the complexity and level of effort needed for successful stakeholder involvement. A landscape design process may be stymied by insufficient data or participation. An impetus for coordination is critical, and incentives may be required to engage landowners and the private sector. In conclusion, devising and implementing landscape designs for more sustainable outcomes require clear communication of environmental, social, and economic opportunities and concerns.

  16. Planning Construction Research of Modern Urban Landscape

    NASA Astrophysics Data System (ADS)

    Xiao, Z. Q.; Chen, W.

    With the development and expansion of the city's traditional urban landscape planning methods have been difficult to adapt to the requirements of modern urban development, in the new urban construction, planning what kind of urban landscape is a new research topic. The article discusses the principles of modern urban landscape planning and development, promote the adoption of new concepts and theories, building more regional characteristics, more humane, more perfect, more emphasis on urban landscape pattern natural ecological protection and construction can sustainable development of urban living environment, and promote the development and construction of the city.

  17. Multi-scale forest landscape pattern characterization

    NASA Astrophysics Data System (ADS)

    Wang, Jialing

    The purpose of this dissertation is to examine several important issues in landscape pattern analysis, including the identification of important landscape metrics, the impact of the modifiable areal unit problem (MAUP) in landscape pattern analysis, the linkage between pattern and process, and the application of landscape pattern analysis. A theoretical framework of hierarchical patch dynamics paradigm and a technical framework of GIS and remote sensing integration are employed to address these questions. The Red Hills region of southwestern Georgia and northern Florida is chosen as the study area. Land use/cover (LULC) and longleaf pine distribution maps were generated through satellite image classification. Sub-watersheds were used as the main analysis units. Principal component analysis (PCA) was conducted on 43 sub-watersheds at three hierarchical LULC levels to identify important landscape metrics. At both landscape- and class-levels, the measurement of fragmentation was identified as the most important landscape dimension. Other dimensions and important metrics varied with different scales. Hexagons were used as an alternative zoning system to examine the MAUP impact in landscape pattern analysis. The results indicated that landscape pattern analyses at class level and at broader scales were more sensitive to MAUP than at landscape level and at finer scales. Local-scale pattern analysis based on moving window analysis greatly reduced the impact of MAUP at class level, but had little effects at landscape level. An examination of the relationship between landscape pattern variables and biophysical/socio-economic variables was undertaken by using statistical analysis. The biophysical variables of soil drainage and mean slope and the socio-economic variables of road density, population density, distance to Tallahassee, Florida, and plantation amount were found to be closely correlated to the landscape patterns in this region. However, a large amount of variation

  18. Incorporating bioenergy into sustainable landscape designs

    DOE PAGES

    Dale, Virginia H.; Kline, Keith L.; Buford, Marilyn A.; ...

    2015-12-30

    In this paper, we describe an approach to landscape design that focuses on integrating bioenergy production with other components of environmental, social and economic systems. Landscape design as used here refers to a spatially explicit, collaborative plan for management of landscapes and supply chains. Landscape design can involve multiple scales and build on existing practices to reduce costs or enhance services. Appropriately applied to a specific context, landscape design can help people assess trade-offs when making choices about locations, types of feedstock, transport, refining and distribution of bioenergy products and services. The approach includes performance monitoring and reporting along themore » bioenergy supply chain. Examples of landscape design applied to bioenergy production systems are presented. Barriers to implementation of landscape design include high costs, the need to consider diverse land-management objectives from a wide array of stakeholders, up-front planning requirements, and the complexity and level of effort needed for successful stakeholder involvement. A landscape design process may be stymied by insufficient data or participation. An impetus for coordination is critical, and incentives may be required to engage landowners and the private sector. In conclusion, devising and implementing landscape designs for more sustainable outcomes require clear communication of environmental, social, and economic opportunities and concerns.« less

  19. Meniscus Membranes For Separation

    DOEpatents

    Dye, Robert C.; Jorgensen, Betty; Pesiri, David R.

    2005-09-20

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  20. Meniscus membranes for separations

    DOEpatents

    Dye, Robert C.; Jorgensen, Betty; Pesiri, David R.

    2004-01-27

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  1. Separation in Binary Alloys

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Facemire, B. R.; Kaukler, W. F.; Witherow, W. K.; Fanning, U.

    1986-01-01

    Studies of monotectic alloys and alloy analogs reviewed. Report surveys research on liquid/liquid and solid/liquid separation in binary monotectic alloys. Emphasizes separation processes in low gravity, such as in outer space or in free fall in drop towers. Advances in methods of controlling separation in experiments highlighted.

  2. Lineage divergence in Odorrana graminea complex (Anura: Ranidae: Odorrana).

    PubMed

    Xiong, Rongchuan; Li, Cheng; Jiang, Jianping

    2015-05-26

    The confusing and unstable taxonomy of Odorrana livida (Rana livida) since its first record has made it a focal frog complex for systematics. In China, four species, Odorrana nebulosa, O. graminea, O. sinica, O. leporipes, were described to closely resemble O. livida or O. chloronota based on their morphological similarities, accompanied by much taxonomic confusion because of ambiguities in the wide distribution and morphological variations. Currently O. graminea is being used as the name of a provisional monotypic species group to include all the populations in China that closely resemble O. livida or O. chloronota. Here, we conducted a range-wide molecular phylogeographic analysis of the large green odorous frog (Odorrana graminea) complex across the majority of its range in China, based on 2780 bp DNA sequences of three mitochondrial genes (12S, 16S, ND2) in 107 samples from 20 sites. Our data recognized three distinct phylogeographic lineages of the Odorrana graminea (lato sensu) complex in China, and they together with a Thailand lineage formed a monophyletic group. Among the four lineages within O. graminea complex, the average genetic distances based on the concatenated sequences of 12S, 16S and ND2 were 7.5-8.8% and those based on 16S rRNA alone were 4.2-5.5%. Furthermore, canonical discriminant functions in morphometric analyses showed significant separations of all the paired lineage comparisons in China. The aforementioned genetic divergence and mismatched phenotypes among the lineages within the Odorrana graminea complex, in addition to their non-overlapping geographic distributions, imply extensive lineage diversification. However, precise taxonomic status of these lineages needs more studies based on adequate type information and more thorough species delimitation based on analysis of differentiation in bioacoustic and nuclear genetic characters especially regarding gene flow and admixture in geographical contact zones.

  3. Modeling Forest Understory Fires in an Eastern Amazonian Landscape

    NASA Technical Reports Server (NTRS)

    Alencar, A. A. C.; Solorzano, L. A.; Nepstad, D. C.

    2004-01-01

    Forest understory fires are an increasingly important cause of forest impoverishment in Ammonia, but little is known of the landscape characteristics and climatic phenomena that determine their occurrence. We developed empirical functions relating the occurrence of understory fires to landscape features near Paragominas, a 35- yr-old ranching and logging center in eastern Ammonia. An historical sequence of maps of forest understory fire was created based on field interviews With local farmers and Landsat TM images. Several landscape features that might explain spatial variations in the occurrence of understory fires were also mapped and co-registered for each of the sample dates, including: forest fragment size and shape, forest impoverishment through logging and understory fires, source of ignition (settlements and charcoal pits), roads, forest edges, and others. The spatial relationship between forest understory fire and each landscape characteristic was tested by regression analyses. Fire probability models were then developed for various combinations of landscape characteristics. The analyses were conducted separately for years of the El Nino Southern Oscillation (ENSO), which are associated with severe drought in eastern Amazonia, and non-ENS0 years. Most (91 %) of the forest area that burned during the 10-yr sequence caught fire during ENSO years, when severe drought may have increased both forest flammability and the escape of agricultural management fires. Forest understory fires were associated with forest edges, as reported in previous studies from Ammonia. But the strongest predictor of forest fire was the percentage of the forest fragment that had been previously logged or burned. Forest fragment size, distance to charcoal pits, distance to agricultural settlement, proximity to forest edge, and distance to roads were also correlated with forest understory fire. Logistic regression models using information on fragment degradation and distance to ignition

  4. Pseudoknots in RNA folding landscapes

    PubMed Central

    Kucharík, Marcel; Hofacker, Ivo L.; Stadler, Peter F.; Qin, Jing

    2016-01-01

    Motivation: The function of an RNA molecule is not only linked to its native structure, which is usually taken to be the ground state of its folding landscape, but also in many cases crucially depends on the details of the folding pathways such as stable folding intermediates or the timing of the folding process itself. To model and understand these processes, it is necessary to go beyond ground state structures. The study of rugged RNA folding landscapes holds the key to answer these questions. Efficient coarse-graining methods are required to reduce the intractably vast energy landscapes into condensed representations such as barrier trees or basin hopping graphs (BHG) that convey an approximate but comprehensive picture of the folding kinetics. So far, exact and heuristic coarse-graining methods have been mostly restricted to the pseudoknot-free secondary structures. Pseudoknots, which are common motifs and have been repeatedly hypothesized to play an important role in guiding folding trajectories, were usually excluded. Results: We generalize the BHG framework to include pseudoknotted RNA structures and systematically study the differences in predicted folding behavior depending on whether pseudoknotted structures are allowed to occur as folding intermediates or not. We observe that RNAs with pseudoknotted ground state structures tend to have more pseudoknotted folding intermediates than RNAs with pseudoknot-free ground state structures. The occurrence and influence of pseudoknotted intermediates on the folding pathway, however, appear to depend very strongly on the individual RNAs so that no general rule can be inferred. Availability and implementation: The algorithms described here are implemented in C++ as standalone programs. Its source code and Supplemental material can be freely downloaded from http://www.tbi.univie.ac.at/bhg.html. Contact: qin@bioinf.uni-leipzig.de Supplementary information: Supplementary data are available at Bioinformatics online. PMID

  5. River Capture in Disequilibrium Landscapes

    NASA Astrophysics Data System (ADS)

    McCoy, S. W.; Perron, J.; Willett, S.; Goren, L.

    2013-12-01

    The process of river piracy or river capture has long drawn interest as a potential mechanism by which drainage basins large and small evolve towards an equilibrium state. River capture transfers both drainage area and drainage lines from one river basin to another, which can cause large, abrupt shifts in network topology, drainage divide positions, and river incision rates. Despite numerous case studies in which river capture has been proposed to have occurred, there is no general, mechanistic framework for understanding the controls on river capture, nor are there quantitative criteria for determining if capture has occurred. Here we use new metrics of landscape disequilibrium to first identify landscapes in which drainage reorganization is occurring. These metrics are based on a balance between an integral of the contributing drainage area and elevation. In an analysis of rivers in the Eastern United States we find that many rivers are in a state of disequilibrium and are experiencing recent or ongoing area exchange between basins. In these disequilibrium basins we find widespread evidence for network rearrangement via river capture at multiple scales. We then conduct numerical experiments with a 2-D landscape evolution model to explore the conditions in which area exchange among drainage basins is likely to occur as discrete capture events as opposed to continuous divide migration. These experiments indicate that: (1) capture activity increases with the degree of disequilibrium induced by persistent spatial gradients in tectonic forcing or by temporal changes in climate or tectonic forcing; (2) capture activity is strongly controlled by the initial planform drainage network geometry; and (3) capture activity scales with the fluvial incision rate constant in the river power erosion law.

  6. Different atmospheric moisture divergence responses to extreme and moderate El Niños

    NASA Astrophysics Data System (ADS)

    Xu, Guangzhi; Osborn, Timothy J.; Matthews, Adrian J.; Joshi, Manoj M.

    2016-07-01

    On seasonal and inter-annual time scales, vertically integrated moisture divergence provides a useful measure of the tropical atmospheric hydrological cycle. It reflects the combined dynamical and thermodynamical effects, and is not subject to the limitations that afflict observations of evaporation minus precipitation. An empirical orthogonal function (EOF) analysis of the tropical Pacific moisture divergence fields calculated from the ERA-Interim reanalysis reveals the dominant effects of the El Niño-Southern Oscillation (ENSO) on inter-annual time scales. Two EOFs are necessary to capture the ENSO signature, and regression relationships between their Principal Components and indices of equatorial Pacific sea surface temperature (SST) demonstrate that the transition from strong La Niña through to extreme El Niño events is not a linear one. The largest deviation from linearity is for the strongest El Niños, and we interpret that this arises at least partly because the EOF analysis cannot easily separate different patterns of responses that are not orthogonal to each other. To overcome the orthogonality constraints, a self-organizing map (SOM) analysis of the same moisture divergence fields was performed. The SOM analysis captures the range of responses to ENSO, including the distinction between the moderate and strong El Niños identified by the EOF analysis. The work demonstrates the potential for the application of SOM to large scale climatic analysis, by virtue of its easier interpretation, relaxation of orthogonality constraints and its versatility for serving as an alternative classification method. Both the EOF and SOM analyses suggest a classification of "moderate" and "extreme" El Niños by their differences in the magnitudes of the hydrological cycle responses, spatial patterns and evolutionary paths. Classification from the moisture divergence point of view shows consistency with results based on other physical variables such as SST.

  7. Divergence and diversity: lessons from an arctic-alpine distribution (Pardosa saltuaria group, Lycosidae).

    PubMed

    Muster, Christoph; Berendonk, Thomas U

    2006-09-01

    The relationship of interpopulation genetic divergence and within-population diversity has been studied for many temperate species in Europe, but not for the cold-adapted fauna. Here we present the first European-wide phylogeographical study of an arctic-alpine distribution in invertebrates, focusing on wolf spiders of the Pardosa saltuaria group. One hundred twenty-seven (127) specimens from 14 populations were examined. Within Europe, these populations were distributed among six high mountain ranges and Scandinavia. We sequenced the whole 921 base pair mitochondrial (mt) ND1 gene. The resulting 55 unique haplotypes form three monophyletic phylogroups of deep divergence: a Pyrenean, a Balkan and a 'northern' clade. Genetic distances (3.6-4.0%) between the major clades indicate that the arctic-alpine range disjunction was initiated by vicariance events, which precede the four major Alpine glaciations. However, low divergence and incomplete lineage sorting within the 'northern clade' suggest a late Pleistocene separation of the Alpine, Scandinavian, Carpathian and Sudetian populations. Thus, we provide evidence for a multiglacial origin of arctic-alpine distributions in Europe, i.e. the current disjunction results from range fragmentation in several glacial cycles. The pattern of genetic diversity within populations seems predominantly determined by historical factors, but is modified by contemporary aspects. Overall, diversity and divergence are negatively correlated. We suggest that low diversity values might result from (i) ancient bottlenecking during warm interglacial periods, as seen in the Pyrenees and Balkans; (ii) recent bottlenecking in small modern areas, as seen in the Giant Mountains and Bohemian Forest; and (iii) dispersal bottlenecking in northern Scandinavia.

  8. Martian Arctic Landscape Panorama Video

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for animation

    Typical view if you were standing on Mars and slowly turned around for a look. Starting at the north, SSI sees its shadow and turns its head viewing solar arrays, the lander deck and landscape. Note very few rocks on the hummocky terrain and network of troughs, typical of polar surfaces here on Earth.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  9. Landscape genetics, historical isolation and cross-Andean gene flow in the wax palm, Ceroxylon echinulatum (Arecaceae).

    PubMed

    Trénel, Philipp; Hansen, Michael M; Normand, Signe; Borchsenius, Finn

    2008-08-01

    Knowledge of the role of landscapes in shaping genetic connectivity and divergence is essential for understanding patterns of biogeography and diversity. This is particularly relevant for the Andes region, a major biodiversity hotspot of relatively recent origin. We examined the phylogeography and landscape genetics of the Andean wax palm Ceroxylon echinulatum (Arecaceae) that occurs in two narrow bands of montane forests on each side of the Andes in Ecuador and northeastern Peru. First, we tested the hypothesis of C. echinulatum being a geographic cline species crossing the Andes in the Amotape-Huancabamba zone (AHZ) of southern Ecuador/northern Peru, as indicated by observations on fruit morphology. Second, we assessed the timeframe of cross-Andean divergence, and third, we investigated the impact of contemporary and historical landscape features on observed spatio-genetic patterns. Individual-based Bayesian clustering (BC) identified a northeastern, southeastern, southwestern, and northwestern cluster, with areas of genetic discontinuity coinciding with the Andes and the Giron-Paute deflection. F-statistics derived from BC suggested an east-to-west dispersal history. Population-based analyses revealed strong genetic structuring at both small and large geographic scales. Interpopulation relationships and Mantel tests strongly supported the cline model with cross-Andean dispersal in the AHZ. Along the cline, gene flow measured as F(ST) was mainly limited by distance, with less but significant impact of climatic friction. Coalescent analysis revealed that cross-Andean divergence took place during the Quaternary. Significant historical isolation (R(ST) > F(ST)) was found in the southwestern population. The current study illustrates a joint effect of founder dynamics, divergence by distance and historical isolation on patterns of Andean diversity and distribution.

  10. The explosive divergence in iterative maps of matrices

    NASA Astrophysics Data System (ADS)

    Navickas, Zenonas; Ragulskis, Minvydas; Vainoras, Alfonsas; Smidtaite, Rasa

    2012-11-01

    The effect of explosive divergence in generalized iterative maps of matrices is defined and described using formal algebraic techniques. It is shown that the effect of explosive divergence can be observed in an iterative map of square matrices of order 2 if and only if the matrix of initial conditions is a nilpotent matrix and the Lyapunov exponent of the corresponding scalar iterative map is greater than zero. Computational experiments with the logistic map and the circle map are used to illustrate the effect of explosive divergence occurring in iterative maps of matrices.

  11. Observations of velocity divergence in Shelikof Strait, Alaska

    NASA Astrophysics Data System (ADS)

    Reed, R. K.; Stabeno, P. J.

    1993-02-01

    Direct observations of horizontal velocity divergence and relative vorticity were made in Shelikof Strait, Alaska during May 1990 with Loran-C buoys and satellite-tracked drifters. These kinematic properties typically had values of 2 × 10 -5s -1. Some of the observations indicated a cyclic divergence which appeared to be linked to the rise and fall of the pycnocline driven by an internal, semidaily tide. The data also suggested that the net divergence over several days was quite small; thus larval concentration models can ignore this effect.

  12. Discharge Competence and Pattern Formation in Peatlands: A Meta-Ecosystem Model of the Everglades Ridge-Slough Landscape

    PubMed Central

    Heffernan, James B.; Watts, Danielle L.; Cohen, Matthew J.

    2013-01-01

    Regular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrophic loss in response to changing landscape drivers. The central Everglades (Florida, USA) historically exhibited regular, linear, flow-parallel orientation of high-elevation sawgrass ridges and low-elevation sloughs that has degraded due to hydrologic modification. In this study, we use a meta-ecosystem approach to model a mechanism for the establishment, persistence, and loss of this landscape. The discharge competence (or self-organizing canal) hypothesis assumes non-linear relationships between peat accretion and water depth, and describes flow-dependent feedbacks of microtopography on water depth. Closed-form model solutions demonstrate that 1) this mechanism can produce spontaneous divergence of local elevation; 2) divergent and homogenous states can exhibit global bi-stability; and 3) feedbacks that produce divergence act anisotropically. Thus, discharge competence and non-linear peat accretion dynamics may explain the establishment, persistence, and loss of landscape pattern, even in the absence of other spatial feedbacks. Our model provides specific, testable predictions that may allow discrimination between the self-organizing canal hypotheses and competing explanations. The potential for global bi-stability suggested by our model suggests that hydrologic restoration may not re-initiate spontaneous pattern establishment, particularly where distinct soil elevation modes have been lost. As a result, we recommend that management efforts should prioritize maintenance of historic hydroperiods in areas of conserved pattern over restoration of hydrologic regimes in degraded regions. This study illustrates the value of simple meta-ecosystem models for investigation of spatial processes. PMID:23671708

  13. Safety shutdown separators

    DOEpatents

    Carlson, Steven Allen; Anakor, Ifenna Kingsley; Farrell, Greg Robert

    2015-06-30

    The present invention pertains to electrochemical cells which comprise (a) an anode; (b) a cathode; (c) a solid porous separator, such as a polyolefin, xerogel, or inorganic oxide separator; and (d) a nonaqueous electrolyte, wherein the separator comprises a porous membrane having a microporous coating comprising polymer particles which have not coalesced to form a continuous film. This microporous coating on the separator acts as a safety shutdown layer that rapidly increases the internal resistivity and shuts the cell down upon heating to an elevated temperature, such as 110.degree. C. Also provided are methods for increasing the safety of an electrochemical cell by utilizing such separators with a safety shutdown layer.

  14. Divergence in age patterns of mortality change drives international divergence in lifespan inequality.

    PubMed

    Gillespie, Duncan O S; Trotter, Meredith V; Tuljapurkar, Shripad D

    2014-06-01

    In the past six decades, lifespan inequality has varied greatly within and among countries even while life expectancy has continued to increase. How and why does mortality change generate this diversity? We derive a precise link between changes in age-specific mortality and lifespan inequality, measured as the variance of age at death. Key to this relationship is a young-old threshold age, below and above which mortality decline respectively decreases and increases lifespan inequality. First, we show for Sweden that shifts in the threshold's location have modified the correlation between changes in life expectancy and lifespan inequality over the last two centuries. Second, we analyze the post-World War II (WWII) trajectories of lifespan inequality in a set of developed countries-Japan, Canada, and the United States-where thresholds centered on retirement age. Our method reveals how divergence in the age pattern of mortality change drives international divergence in lifespan inequality. Most strikingly, early in the 1980s, mortality increases in young U.S. males led to a continuation of high lifespan inequality in the United States; in Canada, however, the decline of inequality continued. In general, our wider international comparisons show that mortality change varied most at young working ages after WWII, particularly for males. We conclude that if mortality continues to stagnate at young ages yet declines steadily at old ages, increases in lifespan inequality will become a common feature of future demographic change.

  15. Numerical study of the spontaneous nucleation of self-rotational moist gas in a converging-diverging nozzle

    NASA Astrophysics Data System (ADS)

    Ma, Qing-Fen; Hu, Da-Peng; Jiang, Jing-Zhi; Qiu, Zhong-Hua

    2010-01-01

    Spontaneous nucleation is the primary way of droplet formation in the supersonic gas separation technology, and the converging-diverging nozzle is the condensation and separation unit of supersonic gas separation devices. A three-dimensional geometrical model for the generation of self-rotational transonic gas flow is set up, based on which, the spontaneous nucleation of self-rotational transonic moist gas in the converging-diverging nozzle is carried out using an Eulerian multi-fluid model. The simulated results of the main flow and nucleation parameters indicate that the spontaneous nucleation can occur in the diverging part of the nozzle. However, different from the nucleation flow without self-rotation, the distributions of these parameters are unsymmetrical about the nozzle axis due to the irregular flow form caused by the self-rotation of gas flow. The nucleation region is located on the position where gas flows with intense rotation and the self-rotation impacts much on the nucleation process. Stronger rotation delays the onset of spontaneous nucleation and yields lower nucleation rate and narrow nucleation region. In addition, influences of other factors such as inlet total pressure p 0, inlet total temperature T 0, the nozzle-expanding ratio Ȧ and the inlet relative humidity ф 0 on the nucleation of self-rotational moist gas flow in the nozzle are also discussed.

  16. Acoustofluidic bacteria separation

    NASA Astrophysics Data System (ADS)

    Li, Sixing; Ma, Fen; Bachman, Hunter; Cameron, Craig E.; Zeng, Xiangqun; Huang, Tony Jun

    2017-01-01

    Bacterial separation from human blood samples can help with the identification of pathogenic bacteria for sepsis diagnosis. In this work, we report an acoustofluidic device for label-free bacterial separation from human blood samples. In particular, we exploit the acoustic radiation force generated from a tilted-angle standing surface acoustic wave (taSSAW) field to separate Escherichia coli from human blood cells based on their size difference. Flow cytometry analysis of the E. coli separated from red blood cells shows a purity of more than 96%. Moreover, the label-free electrochemical detection of the separated E. coli displays reduced non-specific signals due to the removal of blood cells. Our acoustofluidic bacterial separation platform has advantages such as label-free separation, high biocompatibility, flexibility, low cost, miniaturization, automation, and ease of in-line integration. The platform can be incorporated with an on-chip sensor to realize a point-of-care sepsis diagnostic device.

  17. The effects of landscape fragmentation on pollination dynamics: absence of evidence not evidence of absence.

    PubMed

    Hadley, Adam S; Betts, Matthew G

    2012-08-01

    Animal-mediated pollination is essential for both ecosystem services and conservation of global biodiversity, but a growing body of work reveals that it is negatively affected by anthropogenic disturbance. Landscape-scale disturbance results in two often inter-related processes: (1) habitat loss, (2) disruptions of habitat configuration (i.e. fragmentation). Understanding the relative effects of such processes is critical in designing effective management strategies to limit pollination and pollinator decline. We reviewed existing published work from 1989 to 2009 and found that only six of 303 studies considering the influence of landscape context on pollination separated the effects of habitat loss from fragmentation. We provide a synthesis of the current landscape, behavioural, and pollination ecology literature in order to present preliminary multiple working hypotheses explaining how these two landscape processes might independently influence pollination dynamics. Landscape disturbance primarily influences three components of pollination interactions: pollinator density, movement, and plant demography. We argue that effects of habitat loss on each of these components are likely to differ substantially from the effects of fragmentation, which is likely to be more complex and may influence each pollination component in contrasting ways. The interdependency between plants and animals inherent to pollination systems also has the possibility to drive cumulative effects of fragmentation, initiating negative feedback loops between animals and the plants they pollinate. Alternatively, due to their asymmetrical structure, pollination networks may be relatively robust to fragmentation. Despite the potential importance of independent effects of habitat fragmentation, its effects on pollination remain largely untested. We postulate that variation across studies in the effects of 'fragmentation' owes much to artifacts of the sampling regimes adopted, particularly (1

  18. Individual dispersal, landscape connectivity and ecological networks.

    PubMed

    Baguette, Michel; Blanchet, Simon; Legrand, Delphine; Stevens, Virginie M; Turlure, Camille

    2013-05-01

    Connectivity is classically considered an emergent property of landscapes encapsulating individuals' flows across space. However, its operational use requires a precise understanding of why and how organisms disperse. Such movements, and hence landscape connectivity, will obviously vary according to both organism properties and landscape features. We review whether landscape connectivity estimates could gain in both precision and generality by incorporating three fundamental outcomes of dispersal theory. Firstly, dispersal is a multi-causal process; its restriction to an 'escape reaction' to environmental unsuitability is an oversimplification, as dispersing individuals can leave excellent quality habitat patches or stay in poor-quality habitats according to the relative costs and benefits of dispersal and philopatry. Secondly, species, populations and individuals do not always react similarly to those cues that trigger dispersal, which sometimes results in contrasting dispersal strategies. Finally, dispersal is a major component of fitness and is thus under strong selective pressures, which could generate rapid adaptations of dispersal strategies. Such evolutionary responses will entail spatiotemporal variation in landscape connectivity. We thus strongly recommend the use of genetic tools to: (i) assess gene flow intensity and direction among populations in a given landscape; and (ii) accurately estimate landscape features impacting gene flow, and hence landscape connectivity. Such approaches will provide the basic data for planning corridors or stepping stones aiming at (re)connecting local populations of a given species in a given landscape. This strategy is clearly species- and landscape-specific. But we suggest that the ecological network in a given landscape could be designed by stacking up such linkages designed for several species living in different ecosystems. This procedure relies on the use of umbrella species that are representative of other species

  19. Honeybee foraging in differentially structured landscapes.

    PubMed Central

    Steffan-Dewenter, Ingolf; Kuhn, Arno

    2003-01-01

    Honeybees communicate the distance and location of resource patches by bee dances, but this spatial information has rarely been used to study their foraging ecology. We analysed, for the first time to the best of the authors' knowledge, foraging distances and dance activities of honeybees in relation to landscape structure, season and colony using a replicated experimental approach on a landscape scale. We compared three structurally simple landscapes characterized by a high proportion of arable land and large patches, with three complex landscapes with a high proportion of semi-natural perennial habitats and low mean patch size. Four observation hives were placed in the centre of the landscapes and switched at regular intervals between the six landscapes from the beginning of May to the end of July. A total of 1137 bee dances were observed and decoded. Overall mean foraging distance was 1526.1 +/- 37.2 m, the median 1181.5 m and range 62.1-10037.1 m. Mean foraging distances of all bees and foraging distances of nectar-collecting bees did not significantly differ between simple and complex landscapes, but varied between month and colonies. Foraging distances of pollen-collecting bees were significantly larger in simple (1743 +/- 95.6 m) than in complex landscapes (1543.4 +/- 71 m) and highest in June when resources were scarce. Dancing activity, i.e. the number of observed bee dances per unit time, was significantly higher in complex than in simple landscapes, presumably because of larger spatial and temporal variability of resource patches in complex landscapes. The results facilitate an understanding of how human landscape modification may change the evolutionary significance of bee dances and ecological interactions, such as pollination and competition between honeybees and other bee species. PMID:12769455

  20. The Landscape of the Gibbet

    PubMed Central

    Tarlow, Sarah; Dyndor, Zoe

    2015-01-01

    ABSTRACT From the Murder Act of 1752 until the Anatomy Act of 1832 it was forbidden to bury the bodies of executed murderers unless they had first been anatomised or ‘hung in chains’ (gibbeted). This paper considers some of the observations of the Wellcome-funded project ‘Harnessing the Power of the Criminal Corpse’ as they relate to the practice of gibbeting. The nature of hanging in chains is briefly described before an extensive discussion of the criteria by which gibbets, which often remained standing for many decades, were selected. These are: proximity to the scene of crime, visibility, and practicality. Exceptions, in the forms of those sentenced by the Admiralty Courts, and those sentenced in and around London, are briefly considered. Hanging in chains was an infrequent punishment (anatomical dissection was far more frequently practised) but it was the subject of huge public interest and attracted thousands of people. There was no specified time for which a body should remain hanging, and the gibbet often became a known landmark and a significant place in the landscape. There is a remarkable contrast between anatomical dissection, which obliterates and anonymises the body of the individual malefactor, and hanging in chains, which leaves a highly personalised and enduring imprint on the actual and imaginative landscape. PMID:27335506

  1. Calculation of the Relative Density and the Crossing Time Through the Fitness Barrier in AN Asymmetric Sharply-Peaked Landscape

    NASA Astrophysics Data System (ADS)

    Lee, Kwang Sung; Gill, Wonpyong

    We have calculated the relative density and crossing time through the fitness barrier by switching on an asymmetric sharply-peaked landscape, from the initial state which is the quasispecies in a sharply-peaked landscape. It is found that the increment of the relative density with the reversal sequence is a linearly increasing function of time unless a new stationary state in an asymmetric sharply-peaked landscape is reached. It is also found that the relative density with the reversal sequence at the new stationary state X*L is in inverse proportion to the asymmetric parameter when the asymmetric parameter is greater than the saturation asymmetric parameter. We have derived the approximate formulae for the relaxation time, the saturation asymmetric parameter, and the relative density with the reversal sequence X*L, which nicely fit computer simulation results. It is found that the crossing time diverges at the critical fitness parameter in the asymmetric sharply-peaked landscape, in contrast with the symmetric sharply-peaked landscape where the crossing time scales as a power law in the fitness parameter. It is also found that the critical fitness parameter decreases as the asymmetric parameter and sequence length increase.

  2. An Opportunity for Divergent Thinking in the Classroom.

    ERIC Educational Resources Information Center

    Schuster, Edgar H.

    1984-01-01

    Asking gifted students to find inconsistencies, half truths, and un-truths in their textbooks can help promote creative divergent thinking. Examples are cited from an English textbook with internal inconsistencies and inadequate definitions and rules. (CL)

  3. Role of mantle flow in Nubia-Somalia plate divergence

    NASA Astrophysics Data System (ADS)

    Stamps, D. S.; Iaffaldano, G.; Calais, E.

    2015-01-01

    Present-day continental extension along the East African Rift System (EARS) has often been attributed to diverging sublithospheric mantle flow associated with the African Superplume. This implies a degree of viscous coupling between mantle and lithosphere that remains poorly constrained. Recent advances in estimating present-day opening rates along the EARS from geodesy offer an opportunity to address this issue with geodynamic modeling of the mantle-lithosphere system. Here we use numerical models of the global mantle-plates coupled system to test the role of present-day mantle flow in Nubia-Somalia plate divergence across the EARS. The scenario yielding the best fit to geodetic observations is one where torques associated with gradients of gravitational potential energy stored in the African highlands are resisted by weak continental faults and mantle basal drag. These results suggest that shear tractions from diverging mantle flow play a minor role in present-day Nubia-Somalia divergence.

  4. Molecular estimation of eulipotyphlan divergence times and the evolution of "Insectivora".

    PubMed

    Douady, Christophe J; Douzery, Emmanuel J P

    2003-08-01

    "Insectivores" are one of the key groups in understanding mammalian origins. For years, systematics of "Lipotyphla" taxa remained extremely unstable and challenged. Today, with the application of molecular techniques, "Lipotyphla" appears to be a paraphyletic assemblage that encompasses hedgehogs, shrews, and moles (i.e., Eulipotyphla-a member of Laurasiatheria), and golden moles and tenrecs (i.e., Afrosoricida-a member of Afrotheria). Based on nuclear genes and on this well-established phylogenetic framework, we estimated Bayesian relaxed molecular clock divergence times among major lineages of "Lipotyphla." Crown placental mammals are shown to diversify 102+/-6 million years ago (Mya; mean+/-one standard-deviation), followed by Boreoeutheria (94+/-6 Mya), Laurasiatheria (85+/-5 Mya), and Eulipotyphla (73+/-5), with moles separating from hedgehogs+shrews just at the K/T boundary (65+/-5 Mya). During the Early and Middle Eocene, all extant eulipotyphlan subfamilies originated: Uropsilinae (52+/-5 Mya), and Desmaninae, Talpinae, Erinaceinae, Hylomyinae, Soricinae, and Crocidurinae (38-42+/-5 Mya). Afrosoricida separated from Macroscelidae 69+/-5 Mya, golden moles from tenrecs 63+/-5 Mya, and the diversification within tenrecs occurred 43+/-5 Mya. Divergence times are shown to be in reasonably good agreement with the fossil record of eulipotyphlans, but not with the one of afrosoricid "insectivores." Eulipotyphlans diversification might have been sculpted by variations in paleoclimates of the cenozoic era.

  5. The dynamics of axisymmetric swirling flows in a diverging or contracting circular pipe

    NASA Astrophysics Data System (ADS)

    Rusak, Zvi; Wang, Shixiao

    2009-11-01

    This paper describes a study of the effect of pipe divergence and contraction on the stability and breakdown of axisymmetric swirling flows in a long, finite-length, circular pipe. The work extends the theory of Wang & Rusak (1997). The approach is based on a rigorous analysis of the axisymmetric, steady and inviscid flow equations with non-periodic boundary conditions. The analysis firmly establishes the global bifurcation of flow states in the pipe (solutions of the Squire-Long PDE) by relating it to the bifurcation of solutions of the columnar flow problem (solutions of the resulting ODE) and using a new flow force relationship between the inlet and outlet states. This technique provides a simple, yet exact, method of analyzing the complex flow behavior including transitions from near-columnar vortex states to flow fields with large separation (stagnation) zones along the pipe centerline (breakdown states) or along the pipe wall (swirl induced wall separation). Bifurcation diagrams for base vortex models including the solid- body rotation and the Burgers vortex are presented. The stability characteristics of the various branches of solutions and the flow dynamics in the pipe under various perturbations are discussed. Results show that pipe divergence or contraction significantly modify the global flow behavior in a straight pipe and shed light on the effect of pipe geometry on the mechanism of vortex breakdown.

  6. Multiple-channel, total-reflection optic with controllable divergence

    DOEpatents

    Gibson, David M.; Downing, Robert G.

    1997-01-01

    An apparatus and method for providing focused x-ray, gamma-ray, charged particle and neutral particle, including neutron, radiation beams with a controllable amount of divergence are disclosed. The apparatus features a novel use of a radiation blocking structure, which, when combined with multiple-channel total reflection optics, increases the versatility of the optics by providing user-controlled output-beam divergence.

  7. Multiple-channel, total-reflection optic with controllable divergence

    DOEpatents

    Gibson, D.M.; Downing, R.G.

    1997-02-18

    An apparatus and method for providing focused x-ray, gamma-ray, charged particle and neutral particle, including neutron, radiation beams with a controllable amount of divergence are disclosed. The apparatus features a novel use of a radiation blocking structure, which, when combined with multiple-channel total reflection optics, increases the versatility of the optics by providing user-controlled output-beam divergence. 11 figs.

  8. Negative ion source with low temperature transverse divergence optical system

    DOEpatents

    Whealton, J.H.; Stirling, W.L.

    1985-03-04

    A negative ion source is provided which has extremely low transverse divergence as a result of a unique ion focusing system in which the focal line of an ion beam emanating from an elongated, concave converter surface is outside of the ion exit slit of the source and the path of the exiting ions. The beam source operates with a minimum ion temperature which makes possible a sharply focused (extremely low transverse divergence) ribbon like negative ion beam.

  9. Negative ion source with low temperature transverse divergence optical system

    DOEpatents

    Whealton, John H.; Stirling, William L.

    1986-01-01

    A negative ion source is provided which has extremely low transverse divergence as a result of a unique ion focusing system in which the focal line of an ion beam emanating from an elongated, concave converter surface is outside of the ion exit slit of the source and the path of the exiting ions. The beam source operates with a minimum ion temperature which makes possible a sharply focused (extremely low transverse divergence) ribbon like negative ion beam.

  10. Experiencing Landscape: Orkney Hill Land and Farming

    ERIC Educational Resources Information Center

    Lee, Jo

    2007-01-01

    This paper is about how rural landscape is experienced according to combinations of practical engagements with land and the ways meaning is made in relation to it. It presents the case of the ambiguous position of the Orkney Islands within categorisations of Highland and Lowland landscapes in Scotland. Through a discussion of the physical and…

  11. How to Cut Landscape Maintenance Costs.

    ERIC Educational Resources Information Center

    Brickman, Dick

    1982-01-01

    A landscape architect explains how maintenance requirements and costs are affected by landscape design, the physical demands of the site, and the relative use of grass, ground cover, shrubs, and trees. The relationship of these factors to initial and ongoing maintenance costs, including staff requirements, is discussed. (MLF)

  12. Comparative Rural Landscapes: A Conceptual Geographic Model.

    ERIC Educational Resources Information Center

    Steinbrink, John E.

    The geography unit is designed for use in upper elementary grades. The unit objective is to help the student learn facts about the landscapes of the United States, the Netherlands, Australia, Russia, and Central Africa, and acquire generic ideas which he can apply to the analysis and comparison of other landscapes. The unit is an attempt to apply…

  13. DYNAMIC LANDSCAPES, STABILITY AND ECOLOGICAL MODELING

    EPA Science Inventory

    The image of a ball rolling along a series of hills and valleys is an effective heuristic by which to communicate stability concepts in ecology. However, the dynamics of this landscape model have little to do with ecological systems. Other landscape representations, however, are ...

  14. Oregon Hydrologic Landscapes: A Classification Framework

    EPA Science Inventory

    There is a growing need for hydrologic classification systems that can provide a basis for broad-scale assessments of the hydrologic functions of landscapes and watersheds and their responses to stressors such as climate change. We developed a hydrologic landscape (HL) classifica...

  15. Assessing Landscapes to Support Watershed Management

    EPA Science Inventory

    As we change the face of the landscape in the United States with urban development and agriculture practices, the alterations can cause stormwater runoff, soil erosion and water pollution. Therefore, evaluating or assessing natural landscapes and providing the tools to do the...

  16. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RIGHT-OF-WAY AND ENVIRONMENT LANDSCAPE AND... periods of a duration sufficient for expected survival in the highway environment. Normal 1-year plant..., such as junkyard screening or urban landscaping projects. (c) In urban areas new and...

  17. Eliminating the "divergence problem" at Alaska's northern treeline

    NASA Astrophysics Data System (ADS)

    Wilmking, M.; Singh, J.

    2008-06-01

    Recently, an increasing off-set between tree-ring based temperature reconstructions and measured temperatures at high latitudes has been reported, the so called "divergence problem" (here "divergence effect"). This "divergence effect" seriously questions the validity of tree-ring based climate reconstructions, since it seems to violate the assumption of a stable response of trees to changing climate over time. In this study we eliminated the "divergence effect" in northern Alaska by careful selection of individual trees with consistently significant positive relationships with climate (17% of sample) and successfully attempted a divergence-free climate reconstruction using this sub-set. However, the majority of trees (83%) did not adhere to the uniformitarian principle as usually applied in dendroclimatology. Our results thus support the notion, that factors acting on an individual tree basis are the primary causes for the "divergence effect" (at least in northern Alaska). Neither different detrending methods nor factors acting on larger scales such as global dimming or an increase in UV-B radiation could explain our results. Our results also highlight the necessity to adapt the methods of paleoreconstruction using tree rings to account for non-stable climate growth relationships as these are found in the vast majority of sampled trees and seem to be the norm rather than the exception.

  18. Multimodal registration of remotely sensed images based on Jeffrey's divergence

    NASA Astrophysics Data System (ADS)

    Xu, Xiaocong; Li, Xia; Liu, Xiaoping; Shen, Huanfeng; Shi, Qian

    2016-12-01

    Entropy-based measures (e.g., mutual information, also known as Kullback-Leiber divergence), which quantify the similarity between two signals, are widely used as similarity measures for image registration. Although they are proven superior to many classical statistical measures, entropy-based measures, such as mutual information, may fail to yield the optimum registration if the multimodal image pair has insufficient scene overlap region. To overcome this challenge, we proposed using the symmetric form of Kullback-Leiber divergence, namely Jeffrey's divergence, as the similarity measure in practical multimodal image registration tasks. Mathematical analysis was performed to investigate the causes accounting for the limitation of mutual information when dealing with insufficient scene overlap image pairs. Experimental registrations of SPOT image, Landsat TM image, ALOS PalSAR image, and DEM data were carried out to compare the performance of Jeffrey's divergence and mutual information. Results indicate that Jeffrey's divergence is capable of providing larger feasible search space, which is favorable for exploring optimum transformation parameters in a larger range. This superiority of Jeffrey's divergence was further confirmed by a series of paradigms. Thus, the proposed model is more applicable for registering image pairs that are greatly misaligned or have an insufficient scene overlap region.

  19. Epigenetic divergence as a potential first step in darter speciation.

    PubMed

    Smith, Tracy A; Martin, Michael D; Nguyen, Michael; Mendelson, Tamra C

    2016-04-01

    Recent studies show that epigenetic variation in the form of DNA methylation may serve as a substrate for selection. Theory suggests that heritable epigenetic marks that increase fitness should increase in frequency in a population, and these changes may result in novel morphology, behaviour, or physiology, and ultimately reproductive isolation. Therefore, epigenetic variation might provide the first substrate for selection during the course of evolutionary divergence. This hypothesis predicts that populations in the earliest stages of divergence will differentiate in their methylome prior to any genetic differentiation. While several studies have investigated natural epigenetic variation, empirical studies that test predictions about its role in speciation are surprisingly scarce. Here, we investigate DNA methylation variation using an isoschizomeric digest method, Methyl-Sensitive Amplified Polymorphism, across multiple stages of evolutionary divergence in natural populations of North American stream fishes. We show that epigenetic differentiation between methylomes is greater than genetic divergence among closely related populations across two river drainages. Additionally, we demonstrate that epigenetic divergence is a stronger predictor of the strength of behavioural reproductive isolation and suggest that changes in the methylome could influence the evolution of reproductive isolation between species. Our findings suggest a role for epigenetics not only in the initiation of divergence, but also in the maintenance of species boundaries over greater evolutionary timescales.

  20. Wildlife tradeoffs based on landscape models of habitat

    USGS Publications Warehouse

    Loehle, C.; Mitchell, M.S.

    2000-01-01

    It is becoming increasingly clear that the spatial structure of landscapes affects the habitat choices and abundance of wildlife. In contrast to wildlife management based on preservation of critical habitat features such as nest sites on a beach or mast trees, it has not been obvious how to incorporate spatial structure into management plans. We present techniques to accomplish this goal. We used multiscale logistic regression models developed previously for neotropical migrant bird species habitat use in South Carolina (USA) as a basis for these techniques. Based on these models we used a spatial optimization technique to generate optimal maps (probability of occurrence, P = 1.0) for each of seven species. To emulate management of a forest for maximum species diversity, we defined the objective function of the algorithm as the sum of probabilities over the seven species, resulting in a complex map that allowed all seven species to coexist. The map that allowed for coexistence is not obvious, must be computed algorithmically, and would be difficult to realize using rules of thumb for habitat management. To assess how management of a forest for a single species of interest might affect other species, we analyzed tradeoffs by gradually increasing the weighting on a single species in the objective function over a series of simulations. We found that as habitat was increasingly modified to favor that species, the probability of presence for two of the other species was driven to zero. This shows that whereas it is not possible to simultaneously maximize the likelihood of presence for multiple species with divergent habitat preferences, compromise solutions are possible at less than maximal likelihood in many cases. Our approach suggests that efficiency of habitat management for species diversity can by maximized for even small landscapes by incorporating spatial context. The methods we present are suitable for wildlife management, endangered species conservation, and

  1. Dynamic landscape models of coevolutionary games.

    PubMed

    Richter, Hendrik

    2017-02-24

    Players of coevolutionary games may update not only their strategies but also their networks of interaction. Based on interpreting the payoff of players as fitness, dynamic landscape models are proposed. The modeling procedure is carried out for Prisoner's Dilemma (PD) and Snowdrift (SD) games that both use either birth-death (BD) or death-birth (DB) strategy updating. The main focus is on using dynamic fitness landscapes as a mathematical model of coevolutionary game dynamics. Hence, an alternative tool for analyzing coevolutionary games becomes available, and landscape measures such as modality, ruggedness and information content can be computed and analyzed. In addition, fixation properties of the games and quantifiers characterizing the interaction networks are calculated numerically. Relations are established between landscape properties expressed by landscape measures and quantifiers of coevolutionary game dynamics such as fixation probabilities, fixation times and network properties.

  2. The Contribution of Vegetation and Landscape Configuration for Predicting Environmental Change Impacts on Iberian Birds

    PubMed Central

    Triviño, Maria; Thuiller, Wilfried; Cabeza, Mar; Hickler, Thomas; Araújo, Miguel B.

    2011-01-01

    Although climate is known to be one of the key factors determining animal species distributions amongst others, projections of global change impacts on their distributions often rely on bioclimatic envelope models. Vegetation structure and landscape configuration are also key determinants of distributions, but they are rarely considered in such assessments. We explore the consequences of using simulated vegetation structure and composition as well as its associated landscape configuration in models projecting global change effects on Iberian bird species distributions. Both present-day and future distributions were modelled for 168 bird species using two ensemble forecasting methods: Random Forests (RF) and Boosted Regression Trees (BRT). For each species, several models were created, differing in the predictor variables used (climate, vegetation, and landscape configuration). Discrimination ability of each model in the present-day was then tested with four commonly used evaluation methods (AUC, TSS, specificity and sensitivity). The different sets of predictor variables yielded similar spatial patterns for well-modelled species, but the future projections diverged for poorly-modelled species. Models using all predictor variables were not significantly better than models fitted with climate variables alone for ca. 50% of the cases. Moreover, models fitted with climate data were always better than models fitted with landscape configuration variables, and vegetation variables were found to correlate with bird species distributions in 26–40% of the cases with BRT, and in 1–18% of the cases with RF. We conclude that improvements from including vegetation and its landscape configuration variables in comparison with climate only variables might not always be as great as expected for future projections of Iberian bird species. PMID:22216263

  3. statement of significance, location map, site plan, landscape plan, site ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    statement of significance, location map, site plan, landscape plan, site sections, evolution of cemetery landscape. - San Francisco National Cemetery, 1 Lincoln Boulevard, San Francisco, San Francisco County, CA

  4. [Separation anxiety. Theoretical considerations].

    PubMed

    Blandin, N; Parquet, P J; Bailly, D

    1994-01-01

    The interest in separation anxiety is nowadays increasing: this disorder appearing during childhood may predispose to the occurrence of anxiety disorders (such as panic disorder and agoraphobia) and major depression into adulthood. Psychoanalytic theories differ on the nature of separation anxiety and its place in child development. For some authors, separation anxiety must be understood as resulting from the unconscious internal conflicts inherent in the individuation process and gradual attainment of autonomy. From this point of view, the fear of loss of mother by separation is not regarded as resulting from a real danger. However, Freud considers the primary experience of separation from protecting mother as the prototype situation of anxiety and compares the situations generating fear to separation experiences. For him, anxiety originates from two factors: the physiological fact is initiated at the time of birth but the primary traumatic situation is the separation from mother. This point of view may be compared with behavioral theories. Behavioral theories suggest that separation anxiety may be conditioned or learned from innate fears. In Freud's theory, the primary situation of anxiety resulting from the separation from mother plays a role comparable to innate fears. Grappling with the problem of separation anxiety, Bowlby emphasizes then the importance of the child's attachment to one person (mother or primary caregiver) and the fact that this attachment is instinctive. This point of view, based on the watch of infants, is akin to ethological theories on behaviour of non human primates. Bowlby especially shows that the reactions of infant separated from mother evolve on three stages: the phase of protestation which may constitute the prototype of adulthood anxiety, the phase of desperation which may be the prototype of depression, and the phase of detachment. He emphasizes so the role of early separations in the development of vulnerability to depression

  5. Isotope separation by photochromatography

    DOEpatents

    Suslick, K.S.

    1975-10-03

    A photochromatographic method for isotope separation is described. An isotopically mixed molecular species is adsorbed on an adsorptive surface, and the adsorbed molecules are irradiated with radiation of a predetermined wavelength which will selectively excite desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thus separate them from the undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes. (BLM)

  6. Isotope separation by photochromatography

    DOEpatents

    Suslick, Kenneth S.

    1977-01-01

    An isotope separation method which comprises physically adsorbing an isotopically mixed molecular species on an adsorptive surface and irradiating the adsorbed molecules with radiation of a predetermined wavelength which will selectively excite a desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thereby separate them from the unexcited undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes.

  7. Membrane separation systems

    SciTech Connect

    Baker, R.W.; Cussler, E.L.; Eykamp, W.; Koros, W.J.; Riley, R.L.; Strathman, R.H.

    1991-01-01

    This book discusses developments and future directions in the field of membrane separation systems. It describes research needed to bring energy-saving membrane separation processes to technical and commercial readiness for commercial acceptance within the next 5 to 20 years. The assessment was conducted by a group of six internationally known membrane separations experts who examined the worldwide status of research in seven major membrane areas. These encompassed four mature technology areas: reverse osmosis, microfiltration, ultrafiltration, and electrodialysis; two developing areas: gas separation and pervaporation; and one emerging technology; facilitated transport.

  8. The ADvanced SEParation (ADSEP)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The ADvanced SEParation (ADSEP) commercial payload is making use of major advances in separation technology: The Phase Partitioning Experiment (PPE); the Micorencapsulation experiment; and the Hemoglobin Separation Experiment (HSE). Using ADSEP, commercial researchers will attempt to determine the partition coefficients for model particles in a two-phase system. With this information, researchers can develop a higher resolution, more effective cell isolation procedure that can be used for many different types of research and for improved health care. The advanced separation technology is already being made available for use in ground-based laboratories.

  9. Using nonlocal means to separate cardiac and respiration sounds

    NASA Astrophysics Data System (ADS)

    Rudnitskii, A. G.

    2014-11-01

    The paper presents the results of applying nonlocal means (NLMs) approach in the problem of separating respiration and cardiac sounds in a signal recorded on a human chest wall. The performance of the algorithm was tested both by simulated and real signals. As a quantitative efficiency measure of NLM filtration, the angle of divergence between isolated and reference signal was used. It is shown that for a wide range of signal-to-noise ratios, the algorithm makes it possible to efficiently solve this problem of separating cardiac and respiration sounds in the sum signal recorded on a human chest wall.

  10. The interplay between local ecology, divergent selection, and genetic drift in population divergence of a sexually antagonistic female trait.

    PubMed

    Green, Kristina Karlsson; Svensson, Erik I; Bergsten, Johannes; Härdling, Roger; Hansson, Bengt

    2014-07-01

    Genetically polymorphic species offer the possibility to study maintenance of genetic variation and the potential role for genetic drift in population divergence. Indirect inference of the selection regimes operating on polymorphic traits can be achieved by comparing population divergence in neutral genetic markers with population divergence in trait frequencies. Such an approach could further be combined with ecological data to better understand agents of selection. Here, we infer the selective regimes acting on a polymorphic mating trait in an insect group; the dorsal structures (either rough or smooth) of female diving beetles. Our recent work suggests that the rough structures have a sexually antagonistic function in reducing male mating attempts. For two species (Dytiscus lapponicus and Graphoderus zonatus), we could not reject genetic drift as an explanation for population divergence in morph frequencies, whereas for the third (Hygrotus impressopunctatus) we found that divergent selection pulls morph frequencies apart across populations. Furthermore, population morph frequencies in H. impressopunctatus were significantly related to local bioclimatic factors, providing an additional line of evidence for local adaptation in this species. These data, therefore, suggest that local ecological factors and sexual conflict interact over larger spatial scales to shape population divergence in the polymorphism.

  11. Water and the martian landscape.

    PubMed

    Baker, V R

    2001-07-12

    Over the past 30 years, the water-generated landforms and landscapes of Mars have been revealed in increasing detail by a succession of spacecraft missions. Recent data from the Mars Global Surveyor mission confirm the view that brief episodes of water-related activity, including glaciation, punctuated the geological history of Mars. The most recent of these episodes seems to have occurred within the past 10 million years. These new results are anomalous in regard to the prevailing view that the martian surface has been continuously extremely cold and dry, much as it is today, for the past 3.9 billion years. Interpretations of the new data are controversial, but explaining the anomalies in a consistent manner leads to potentially fruitful hypotheses for understanding the evolution of Mars in relation to Earth.

  12. Dark matter in axion landscape

    NASA Astrophysics Data System (ADS)

    Daido, Ryuji; Kobayashi, Takeshi; Takahashi, Fuminobu

    2017-02-01

    If there are a plethora of axions in nature, they may have a complicated potential and create an axion landscape. We study a possibility that one of the axions is so light that it is cosmologically stable, explaining the observed dark matter density. In particular we focus on a case in which two (or more) shift-symmetry breaking terms conspire to make the axion sufficiently light at the potential minimum. In this case the axion has a flat-bottomed potential. In contrast to the case in which a single cosine term dominates the potential, the axion abundance as well as its isocurvature perturbations are significantly suppressed. This allows an axion with a rather large mass to serve as dark matter without fine-tuning of the initial misalignment, and further makes higher-scale inflation to be consistent with the scenario.

  13. Probabilistic divergence time estimation without branch lengths: dating the origins of dinosaurs, avian flight and crown birds.

    PubMed

    Lloyd, G T; Bapst, D W; Friedman, M; Davis, K E

    2016-11-01

    Branch lengths-measured in character changes-are an essential requirement of clock-based divergence estimation, regardless of whether the fossil calibrations used represent nodes or tips. However, a separate set of divergence time approaches are typically used to date palaeontological trees, which may lack such branch lengths. Among these methods, sophisticated probabilistic approaches have recently emerged, in contrast with simpler algorithms relying on minimum node ages. Here, using a novel phylogenetic hypothesis for Mesozoic dinosaurs, we apply two such approaches to estimate divergence times for: (i) Dinosauria, (ii) Avialae (the earliest birds) and (iii) Neornithes (crown birds). We find: (i) the plausibility of a Permian origin for dinosaurs to be dependent on whether Nyasasaurus is the oldest dinosaur, (ii) a Middle to Late Jurassic origin of avian flight regardless of whether Archaeopteryx or Aurornis is considered the first bird and (iii) a Late Cretaceous origin for Neornithes that is broadly congruent with other node- and tip-dating estimates. Demonstrating the feasibility of probabilistic time-scaling further opens up divergence estimation to the rich histories of extinct biodiversity in the fossil record, even in the absence of detailed character data.

  14. Probabilistic divergence time estimation without branch lengths: dating the origins of dinosaurs, avian flight and crown birds

    PubMed Central

    2016-01-01

    Branch lengths—measured in character changes—are an essential requirement of clock-based divergence estimation, regardless of whether the fossil calibrations used represent nodes or tips. However, a separate set of divergence time approaches are typically used to date palaeontological trees, which may lack such branch lengths. Among these methods, sophisticated probabilistic approaches have recently emerged, in contrast with simpler algorithms relying on minimum node ages. Here, using a novel phylogenetic hypothesis for Mesozoic dinosaurs, we apply two such approaches to estimate divergence times for: (i) Dinosauria, (ii) Avialae (the earliest birds) and (iii) Neornithes (crown birds). We find: (i) the plausibility of a Permian origin for dinosaurs to be dependent on whether Nyasasaurus is the oldest dinosaur, (ii) a Middle to Late Jurassic origin of avian flight regardless of whether Archaeopteryx or Aurornis is considered the first bird and (iii) a Late Cretaceous origin for Neornithes that is broadly congruent with other node- and tip-dating estimates. Demonstrating the feasibility of probabilistic time-scaling further opens up divergence estimation to the rich histories of extinct biodiversity in the fossil record, even in the absence of detailed character data. PMID:28336787

  15. Retroposon analysis and recent geological data suggest near-simultaneous divergence of the three superorders of mammals

    PubMed Central

    Nishihara, Hidenori; Maruyama, Shigenori; Okada, Norihiro

    2009-01-01

    As a consequence of recent developments in molecular phylogenomics, all extant orders of placental mammals have been grouped into 3 lineages: Afrotheria, Xenarthra, and Boreotheria, which originated in Africa, South America, and Laurasia, respectively. Despite this advancement, the order of divergence of these 3 lineages remains unresolved. Here, we performed extensive retroposon analysis with mammalian genomic data. Surprisingly, we identified a similar number of informative retroposon loci that support each of 3 possible phylogenetic hypotheses: the basal position for Afrotheria (22 loci), Xenarthra (25 loci), and Boreotheria (21 loci). This result indicates that the divergence of the placental common ancestor into the 3 lineages occurred nearly simultaneously. Thus, we examined whether these molecular data could be integrated into the geological context by incorporating recent geological data. We obtained firm evidence that complete separation of Gondwana into Africa and South America occurred 120 ± 10 Ma. Accordingly, the previous reported time frame (division of Pangea into Gondwana and Laurasia at 148–138 Ma and division of Gondwana at 105 Ma) cannot be used to validate mammalian divergence order. Instead, we use our retroposon results and the recent geological data to propose that near-simultaneous divisions of continents leading to isolated Africa, South America, and Laurasia caused nearly concomitant divergence of the ancient placental ancestor into 3 lineages, Afrotheria, Xenarthra, and Boreotheria, ≈120 Ma. PMID:19286970

  16. Searching the clinical fitness landscape.

    PubMed

    Eppstein, Margaret J; Horbar, Jeffrey D; Buzas, Jeffrey S; Kauffman, Stuart A

    2012-01-01

    Widespread unexplained variations in clinical practices and patient outcomes suggest major opportunities for improving the quality and safety of medical care. However, there is little consensus regarding how to best identify and disseminate healthcare improvements and a dearth of theory to guide the debate. Many consider multicenter randomized controlled trials to be the gold standard of evidence-based medicine, although results are often inconclusive or may not be generally applicable due to differences in the contexts within which care is provided. Increasingly, others advocate the use "quality improvement collaboratives", in which multi-institutional teams share information to identify potentially better practices that are subsequently evaluated in the local contexts of specific institutions, but there is concern that such collaborative learning approaches lack the statistical rigor of randomized trials. Using an agent-based model, we show how and why a collaborative learning approach almost invariably leads to greater improvements in expected patient outcomes than more traditional approaches in searching simulated clinical fitness landscapes. This is due to a combination of greater statistical power and more context-dependent evaluation of treatments, especially in complex terrains where some combinations of practices may interact in affecting outcomes. The results of our simulations are consistent with observed limitations of randomized controlled trials and provide important insights into probable reasons for effectiveness of quality improvement collaboratives in the complex socio-technical environments of healthcare institutions. Our approach illustrates how modeling the evolution of medical practice as search on a clinical fitness landscape can aid in identifying and understanding strategies for improving the quality and safety of medical care.

  17. Adventures in maceral separation

    SciTech Connect

    Dyrkacz, G.R.

    1994-02-01

    Progress has been made in recent years in the science of maceral separation. However, there are many areas that can be improved and new areas investigated. Power of density gradient centrifugation to physically resolve macerals and submaceral species coupled with other instrumental techniques is attractive for defining the limits of coal heterogeneity as well as investigating the ability of other separation methods.

  18. Method for separating isotopes

    DOEpatents

    Jepson, B.E.

    1975-10-21

    Isotopes are separated by contacting a feed solution containing the isotopes with a cyclic polyether wherein a complex of one isotope is formed with the cyclic polyether, the cyclic polyether complex is extracted from the feed solution, and the isotope is thereafter separated from the cyclic polyether.

  19. URANIUM SEPARATION PROCESS

    DOEpatents

    McVey, W.H.; Reas, W.H.

    1959-03-10

    The separation of uranium from an aqueous solution containing a water soluble uranyl salt is described. The process involves adding an alkali thiocyanate to the aqueous solution, contacting the resulting solution with methyl isobutyl ketons and separating the resulting aqueous and organic phase. The uranium is extracted in the organic phase as UO/sub 2/(SCN)/sub/.

  20. Vanguard Satellite Separation Mechanisms

    NASA Technical Reports Server (NTRS)

    Baumann, Robert C.

    1961-01-01

    Early in the Vanguard program it became apparent that a thoroughly reliable means of separating the satellite packages from the third-stage rocket would be required. A completely self -contained standard mechanism was developed with redundant firing circuits for use on both test vehicles and satellite-launching vehicles. A change in the experimental objectives of the test-vehicle payload units necessitated modification of some of the standard separation mechanisms. A strap, pull-pin, girth-ring separation device was developed which employed the basic actuation of the standard mechanisms. Evidence of residual burning of the third stage made it necessary to delay separation longer than the time designed into the long-delay separation device. The standard separation mechanism was modified and integrated with the satellite command receiver system so that a ground command after third-stage burnout would cause separation. Flight performance of the various separation mechanisms proved their reliability; they performed without failure in all Vanguard launchings.

  1. Working with Separation

    ERIC Educational Resources Information Center

    Krugman, Dorothy C.

    1971-01-01

    Discusses the role of the caseworker in providing support to children experiencing separation from their families and emphasizes the need to recognize that there are differences between those separation experiences dictated by the needs of children and those dictated by arbitrary or noncasework factors. (AJ)

  2. Overview of membrane separations

    SciTech Connect

    Noble, R.D.

    1987-01-01

    The field of membrane separations is discussed. The major membrane types and applications are outlined. The outlook with respect to research activities and commercial applications is surveyed. The advantages and disadvantages of this separation process are discussed. Certain applications where membranes may save energy and improve productivity are also discussed.

  3. Effects of habitat and landscape fragmentation on humans and biodiversity in densely populated landscapes.

    PubMed

    Di Giulio, Manuela; Holderegger, Rolf; Tobias, Silvia

    2009-07-01

    Landscape fragmentation has often been seen as an only ecological problem. However, fragmentation also has a societal perspective, namely, in how humans perceive landscape fragmentation and in how landscape fragmentation potentially influences human well-being. These latter aspects have rarely been addressed so far. The inter-relationship of ecological and human dimensions of landscape fragmentation becomes especially evident when looking at the landscape where most people in industrial countries live, namely in suburban and urban areas. In these areas, landscape planners and environmental managers are confronted with the problem that landscapes should fulfill various functions, often with conflicting goals, e.g. nature reserves to enhance species richness vs. recreational areas for city-dwellers. We reviewed the ecological and sociological literature relevant for fragmentation in suburban and urban landscapes. In an interdisciplinary approach, we evaluated whether there are similarities and dissimilarities between the ecological and the human aspects of landscape fragmentation. We found important similarities. An example is that for both, humans and biodiversity, the loss of semi-natural areas has more drastic effects than the fragmentation of these areas per se. However, there are also relevant differences. We concluded that in densely populated landscapes a shift from responsive planning to an intentional design of environments is therefore needed.

  4. The chromatin landscape of Drosophila: comparisons between species, sexes, and chromosomes.

    PubMed

    Brown, Emily J; Bachtrog, Doris

    2014-07-01

    The chromatin landscape is key for gene regulation, but little is known about how it differs between sexes or between species. Here, we study the sex-specific chromatin landscape of Drosophila miranda, a species with young sex chromosomes, and compare it with Drosophila melanogaster. We analyze six histone modifications in male and female larvae of D. miranda (H3K4me1, H3K4me3, H3K36me3, H4K16ac, H3K27me3, and H3K9me2), and define seven biologically meaningful chromatin states that show different enrichments for transcribed and silent genes, repetitive elements, housekeeping, and tissue-specific genes. The genome-wide distribution of both active and repressive chromatin states differs between males and females. In males, active chromatin is enriched on the X, relative to females, due to dosage compensation of the hemizygous X. Furthermore, a smaller fraction of the euchromatic portion of the genome is in a repressive chromatin state in males relative to females. However, sex-specific chromatin states appear not to explain sex-biased expression of genes. Overall, conservation of chromatin states between male and female D. miranda is comparable to conservation between D. miranda and D. melanogaster, which diverged >30 MY ago. Active chromatin states are more highly conserved across species, while heterochromatin shows very low levels of conservation. Divergence in chromatin profiles contributes to expression divergence between species, with ∼26% of genes in different chromatin states in the two species showing species-specific or species-biased expression, an enrichment of approximately threefold over null expectation. Our data suggest that heteromorphic sex chromosomes in males (that is, a hypertranscribed X and an inactivated Y) may contribute to global redistribution of active and repressive chromatin marks between chromosomes and sexes.

  5. Separators for flywheel rotors

    DOEpatents

    Bender, D.A.; Kuklo, T.C.

    1998-07-07

    A separator forms a connection between the rotors of a concentric rotor assembly. This separator allows for the relatively free expansion of outer rotors away from inner rotors while providing a connection between the rotors that is strong enough to prevent disassembly. The rotor assembly includes at least two rotors referred to as inner and outer flywheel rings or rotors. This combination of inner flywheel ring, separator, and outer flywheel ring may be nested to include an arbitrary number of concentric rings. The separator may be a segmented or continuous ring that abuts the ends of the inner rotor and the inner bore of the outer rotor. It is supported against centrifugal loads by the outer rotor and is affixed to the outer rotor. The separator is allowed to slide with respect to the inner rotor. It is made of a material that has a modulus of elasticity that is lower than that of the rotors. 10 figs.

  6. Separators for flywheel rotors

    DOEpatents

    Bender, Donald A.; Kuklo, Thomas C.

    1998-01-01

    A separator forms a connection between the rotors of a concentric rotor assembly. This separator allows for the relatively free expansion of outer rotors away from inner rotors while providing a connection between the rotors that is strong enough to prevent disassembly. The rotor assembly includes at least two rotors referred to as inner and outer flywheel rings or rotors. This combination of inner flywheel ring, separator, and outer flywheel ring may be nested to include an arbitrary number of concentric rings. The separator may be a segmented or continuous ring that abuts the ends of the inner rotor and the inner bore of the outer rotor. It is supported against centrifugal loads by the outer rotor and is affixed to the outer rotor. The separator is allowed to slide with respect to the inner rotor. It is made of a material that has a modulus of elasticity that is lower than that of the rotors.

  7. Substituted polyacetylene separation membrane

    DOEpatents

    Pinnau, I.; Morisato, Atsushi

    1998-01-13

    A separation membrane is described which is useful for gas separation, particularly separation of C{sub 2+} hydrocarbons from natural gas. The invention encompasses the membrane itself, methods of making it and processes for using it. The membrane comprises a polymer having repeating units of a hydrocarbon-based, disubstituted polyacetylene, having the general formula shown in the accompanying diagram, wherein R{sub 1} is chosen from the group consisting of C{sub 1}-C{sub 4} alkyl and phenyl, and wherein R{sub 2} is chosen from the group consisting of hydrogen and phenyl. In the most preferred embodiment, the membrane comprises poly(4-methyl-2-pentyne) [PMP]. The membrane exhibits good chemical resistance and has super-glassy properties with regard to separating certain large, condensable permeant species from smaller, less-condensable permeant species. The membranes may also be useful in other fluid separations. 4 figs.

  8. Substituted polyacetylene separation membrane

    DOEpatents

    Pinnau, Ingo; Morisato, Atsushi

    1998-01-13

    A separation membrane useful for gas separation, particularly separation of C.sub.2+ hydrocarbons from natural gas. The invention encompasses the membrane itself, methods of making it and processes for using it. The membrane comprises a polymer having repeating units of a hydrocarbon-based, disubstituted polyacetylene, having the general formula: ##STR1## wherein R.sub.1 is chosen from the group consisting of C.sub.1 -C.sub.4 alkyl and phenyl, and wherein R.sub.2 is chosen from the group consisting of hydrogen and phenyl. In the most preferred embodiment, the membrane comprises poly(4-methyl-2-pentyne) ›PMP!. The membrane exhibits good chemical resistance and has super-glassy properties with regard to separating certain large, condensable permeant species from smaller, less-condensable permeant species. The membranes may also be useful in other fluid separations.

  9. Isothermal separation processes

    NASA Technical Reports Server (NTRS)

    England, C.

    1982-01-01

    The isothermal processes of membrane separation, supercritical extraction and chromatography were examined using availability analysis. The general approach was to derive equations that identified where energy is consumed in these processes and how they compare with conventional separation methods. These separation methods are characterized by pure work inputs, chiefly in the form of a pressure drop which supplies the required energy. Equations were derived for the energy requirement in terms of regular solution theory. This approach is believed to accurately predict the work of separation in terms of the heat of solution and the entropy of mixing. It can form the basis of a convenient calculation method for optimizing membrane and solvent properties for particular applications. Calculations were made on the energy requirements for a membrane process separating air into its components.

  10. Landscape co-evolution and river discharge.

    NASA Astrophysics Data System (ADS)

    van der Velde, Ype; Temme, Arnaud

    2015-04-01

    Fresh water is crucial for society and ecosystems. However, our ability to secure fresh water resources under climatic and anthropogenic change is impaired by the complexity of interactions between human society, ecosystems, soils, and topography. These interactions cause landscape properties to co-evolve, continuously changing the flow paths of water through the landscape. These co-evolution driven flow path changes and their effect on river runoff are, to-date, poorly understood. In this presentation we introduce a spatially distributed landscape evolution model that incorporates growing vegetation and its effect on evapotranspiration, interception, infiltration, soil permeability, groundwater-surface water exchange and erosion. This landscape scale (10km2) model is calibrated to evolve towards well known empirical organising principles such as the Budyko curve and Hacks law under different climate conditions. To understand how positive and negative feedbacks within the model structure form complex landscape patterns of forests and peat bogs that resemble observed landscapes under humid and boreal climates, we analysed the effects of individual processes on the spatial distribution of vegetation and river peak and mean flows. Our results show that especially river peak flows and droughts decrease with increasing evolution of the landscape, which is a result that has direct implications for flood management.

  11. Metapopulation capacity of evolving fluvial landscapes

    NASA Astrophysics Data System (ADS)

    Bertuzzo, Enrico; Rodriguez-Iturbe, Ignacio; Rinaldo, Andrea

    2015-04-01

    The form of fluvial landscapes is known to attain stationary network configurations that settle in dynamically accessible minima of total energy dissipation by landscape-forming discharges. Recent studies have highlighted the role of the dendritic structure of river networks in controlling population dynamics of the species they host and large-scale biodiversity patterns. Here, we systematically investigate the relation between energy dissipation, the physical driver for the evolution of river networks, and the ecological dynamics of their embedded biota. To that end, we use the concept of metapopulation capacity, a measure to link landscape structures with the population dynamics they host. Technically, metapopulation capacity is the leading eigenvalue λM of an appropriate "landscape" matrix subsuming whether a given species is predicted to persist in the long run. λM can conveniently be used to rank different landscapes in terms of their capacity to support viable metapopulations. We study how λM changes in response to the evolving network configurations of spanning trees. Such sequence of configurations is theoretically known to relate network selection to general landscape evolution equations through imperfect searches for dynamically accessible states frustrated by the vagaries of Nature. Results show that the process shaping the metric and the topological properties of river networks, prescribed by physical constraints, leads to a progressive increase in the corresponding metapopulation capacity and therefore on the landscape capacity to support metapopulations—with implications on biodiversity in fluvial ecosystems.

  12. Do geographically isolated wetlands influence landscape functions?

    USGS Publications Warehouse

    Cohen, Matthew J.; Creed, Irena F.; Alexander, Laurie C.; Basu, Nandita; Calhoun, Aram J. K.; Craft, Christopher; D’Amico, Ellen; DeKeyser, Edward S.; Fowler, Laurie; Golden, Heather E.; Jawitz, James W.; Kalla, Peter; Kirkman, L. Katherine; Lane, Charles R.; Lang, Megan; Leibowitz, Scott G.; Lewis, David Bruce; Marton, John; McLaughlin, Daniel L.; Mushet, David M.; Raanan-Kiperwas, Hadas; Rains, Mark C.; Smith, Lora; Walls, Susan C.

    2015-01-01

    Geographically isolated wetlands (GIWs), those surrounded by uplands, exchange materials, energy, and organisms with other elements in hydrological and habitat networks, contributing to landscape functions, such as flow generation, nutrient and sediment retention, and biodiversity support. GIWs constitute most of the wetlands in many North American landscapes, provide a disproportionately large fraction of wetland edges where many functions are enhanced, and form complexes with other water bodies to create spatial and temporal heterogeneity in the timing, flow paths, and magnitude of network connectivity. These attributes signal a critical role for GIWs in sustaining a portfolio of landscape functions, but legal protections remain weak despite preferential loss from many landscapes. GIWs lack persistent surface water connections, but this condition does not imply the absence of hydrological, biogeochemical, and biological exchanges with nearby and downstream waters. Although hydrological and biogeochemical connectivity is often episodic or slow (e.g., via groundwater), hydrologic continuity and limited evaporative solute enrichment suggest both flow generation and solute and sediment retention. Similarly, whereas biological connectivity usually requires overland dispersal, numerous organisms, including many rare or threatened species, use both GIWs and downstream waters at different times or life stages, suggesting that GIWs are critical elements of landscape habitat mosaics. Indeed, weaker hydrologic connectivity with downstream waters and constrained biological connectivity with other landscape elements are precisely what enhances some GIW functions and enables others. Based on analysis of wetland geography and synthesis of wetland functions, we argue that sustaining landscape functions requires conserving the entire continuum of wetland connectivity, including GIWs.

  13. Do geographically isolated wetlands influence landscape functions?

    PubMed

    Cohen, Matthew J; Creed, Irena F; Alexander, Laurie; Basu, Nandita B; Calhoun, Aram J K; Craft, Christopher; D'Amico, Ellen; DeKeyser, Edward; Fowler, Laurie; Golden, Heather E; Jawitz, James W; Kalla, Peter; Kirkman, L Katherine; Lane, Charles R; Lang, Megan; Leibowitz, Scott G; Lewis, David Bruce; Marton, John; McLaughlin, Daniel L; Mushet, David M; Raanan-Kiperwas, Hadas; Rains, Mark C; Smith, Lora; Walls, Susan C

    2016-02-23

    Geographically isolated wetlands (GIWs), those surrounded by uplands, exchange materials, energy, and organisms with other elements in hydrological and habitat networks, contributing to landscape functions, such as flow generation, nutrient and sediment retention, and biodiversity support. GIWs constitute most of the wetlands in many North American landscapes, provide a disproportionately large fraction of wetland edges where many functions are enhanced, and form complexes with other water bodies to create spatial and temporal heterogeneity in the timing, flow paths, and magnitude of network connectivity. These attributes signal a critical role for GIWs in sustaining a portfolio of landscape functions, but legal protections remain weak despite preferential loss from many landscapes. GIWs lack persistent surface water connections, but this condition does not imply the absence of hydrological, biogeochemical, and biological exchanges with nearby and downstream waters. Although hydrological and biogeochemical connectivity is often episodic or slow (e.g., via groundwater), hydrologic continuity and limited evaporative solute enrichment suggest both flow generation and solute and sediment retention. Similarly, whereas biological connectivity usually requires overland dispersal, numerous organisms, including many rare or threatened species, use both GIWs and downstream waters at different times or life stages, suggesting that GIWs are critical elements of landscape habitat mosaics. Indeed, weaker hydrologic connectivity with downstream waters and constrained biological connectivity with other landscape elements are precisely what enhances some GIW functions and enables others. Based on analysis of wetland geography and synthesis of wetland functions, we argue that sustaining landscape functions requires conserving the entire continuum of wetland connectivity, including GIWs.

  14. Genomic diversity in switchgrass (Panicum virgatum): from the continental scale to a dune landscape

    PubMed Central

    Morris, Geoffrey P.; Grabowski, Paul; Borevitz, Justin O.

    2011-01-01

    Connecting broad-scale patterns of genetic variation and population structure to genetic diversity on a landscape is a key step towards understanding historical processes of migration and adaptation. New genomic approaches can be used to increase the resolution of phylogeographic studies while reducing locus sampling effects and circumventing ascertainment bias. Here, we use a novel approach based on high-throughput sequencing to characterize genetic diversity in complete chloroplast genomes and >10,000 nuclear loci in switchgrass, across a continental and landscape scale. Switchgrass is a North American tallgrass species, which is widely used in conservation and perennial biomass production, and shows strong ecotypic adaptation and population structure across the continental range. We sequenced 40.9 billion base pairs from 24 individuals from across the species’ range and 20 individuals from the Indiana Dunes. Analysis of plastome sequence revealed 203 variable SNP sites that define eight haplogroups, which are differentiated by 4 to 127 SNPs and confirmed by patterns of indel variation. These include three deeply divergent haplogroups, which correspond to the previously described lowland-upland ecotypic split and a novel upland haplogroup split that dates to the mid-Pleistoscene. Most of the plastome haplogroup diversity present in the northern switchgrass range, including in the Indiana Dunes, originated in the mid- or upper-Pleistocene prior to the most recent postglacial recolonization. Furthermore, a recently colonized landscape feature (~150 ya) in the Indiana Dunes contains several deeply divergent upland haplogroups. Nuclear markers also support a deep lowland-upland split, followed by limited gene flow, and show extensive gene flow in the local population of the Indiana Dunes. PMID:22060816

  15. The Aeroacoustics of Slowly Diverging Supersonic Jets

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Leib, S. J.

    2008-01-01

    This paper is concerned with utilizing the acoustic analogy approach to predict the sound from unheated supersonic jets. Previous attempts have been unsuccessful at making such predictions over the Mach number range of practical interest. The present paper, therefore, focuses on implementing the necessary refinements needed to accomplish this objective. The important effects influencing peak supersonic noise turn out to be source convection, mean flow refraction, mean flow amplification, and source non-compactness. It appears that the last two effects have not been adequately dealt with in the literature. The first of these because the usual parallel flow models produce most of the amplification in the so called critical layer where the solution becomes singular and, therefore, causes the predicted sound field to become infinite as well. We deal with this by introducing a new weakly non parallel flow analysis that eliminates the critical layer singularity. This has a strong effect on the shape of the peak noise spectrum. The last effect places severe demands on the source models at the higher Mach numbers because the retarded time variations significantly increase the sensitivity of the radiated sound to the source structure in this case. A highly refined (non-separable) source model is, therefore, introduced in this paper.

  16. Feedbacks in human-landscape systems

    NASA Astrophysics Data System (ADS)

    Chin, Anne

    2015-04-01

    As human interactions with Earth systems intensify in the "Anthropocene", understanding the complex relationships among human activity, landscape change, and societal responses to those changes is increasingly important. Interdisciplinary research centered on the theme of "feedbacks" in human-landscape systems serves as a promising focus for unraveling these interactions. Deciphering interacting human-landscape feedbacks extends our traditional approach of considering humans as unidirectional drivers of change. Enormous challenges exist, however, in quantifying impact-feedback loops in landscapes with significant human alterations. This paper illustrates an example of human-landscape interactions following a wildfire in Colorado (USA) that elicited feedback responses. After the 2012 Waldo Canyon Fire, concerns for heightened flood potential and debris flows associated with post-fire hydrologic changes prompted local landowners to construct tall fences at the base of a burned watershed. These actions changed the sediment transport regime and promoted further landscape change and human responses in a positive feedback cycle. The interactions ultimately increase flood and sediment hazards, rather than dampening the effects of fire. A simple agent-based model, capable of integrating social and hydro-geomorphological data, demonstrates how such interacting impacts and feedbacks could be simulated. Challenges for fully capturing human-landscape feedback interactions include the identification of diffuse and subtle feedbacks at a range of scales, the availability of data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, and the varied metrics and data needed to represent both the physical and human systems. By collaborating with social scientists with expertise in the human causes of landscape change, as well as the human responses to those changes, geoscientists could more fully recognize and anticipate the coupled

  17. Landscape genetics of high mountain frog metapopulations

    USGS Publications Warehouse

    Murphy, M.A.; Dezzani, R.; Pilliod, D.S.; Storfer, A.

    2010-01-01

    Explaining functional connectivity among occupied habitats is crucial for understanding metapopulation dynamics and species ecology. Landscape genetics has primarily focused on elucidating how ecological features between observations influence gene flow. Functional connectivity, however, may be the result of both these between-site (landscape resistance) landscape characteristics and at-site (patch quality) landscape processes that can be captured using network based models. We test hypotheses of functional connectivity that include both between-site and at-site landscape processes in metapopulations of Columbia spotted frogs (Rana luteiventris) by employing a novel justification of gravity models for landscape genetics (eight microsatellite loci, 37 sites, n = 441). Primarily used in transportation and economic geography, gravity models are a unique approach as flow (e.g. gene flow) is explained as a function of three basic components: distance between sites, production/attraction (e.g. at-site landscape process) and resistance (e.g. between-site landscape process). The study system contains a network of nutrient poor high mountain lakes where we hypothesized a short growing season and complex topography between sites limit R. luteiventris gene flow. In addition, we hypothesized production of offspring is limited by breeding site characteristics such as the introduction of predatory fish and inherent site productivity. We found that R. luteiventris connectivity was negatively correlated with distance between sites, presence of predatory fish (at-site) and topographic complexity (between-site). Conversely, site productivity (as measured by heat load index, at-site) and growing season (as measured by frost-free period between-sites) were positively correlated with gene flow. The negative effect of predation and positive effect of site productivity, in concert with bottleneck tests, support the presence of source-sink dynamics. In conclusion, gravity models provide a

  18. Landscape genetics of high mountain frog metapopulations.

    PubMed

    Murphy, Melanie A; Dezzani, R; Pilliod, D S; Storfer, A

    2010-09-01

    Explaining functional connectivity among occupied habitats is crucial for understanding metapopulation dynamics and species ecology. Landscape genetics has primarily focused on elucidating how ecological features between observations influence gene flow. Functional connectivity, however, may be the result of both these between-site (landscape resistance) landscape characteristics and at-site (patch quality) landscape processes that can be captured using network based models. We test hypotheses of functional connectivity that include both between-site and at-site landscape processes in metapopulations of Columbia spotted frogs (Rana luteiventris) by employing a novel justification of gravity models for landscape genetics (eight microsatellite loci, 37 sites, n = 441). Primarily used in transportation and economic geography, gravity models are a unique approach as flow (e.g. gene flow) is explained as a function of three basic components: distance between sites, production/attraction (e.g. at-site landscape process) and resistance (e.g. between-site landscape process). The study system contains a network of nutrient poor high mountain lakes where we hypothesized a short growing season and complex topography between sites limit R. luteiventris gene flow. In addition, we hypothesized production of offspring is limited by breeding site characteristics such as the introduction of predatory fish and inherent site productivity. We found that R. luteiventris connectivity was negatively correlated with distance between sites, presence of predatory fish (at-site) and topographic complexity (between-site). Conversely, site productivity (as measured by heat load index, at-site) and growing season (as measured by frost-free period between-sites) were positively correlated with gene flow. The negative effect of predation and positive effect of site productivity, in concert with bottleneck tests, support the presence of source-sink dynamics. In conclusion, gravity models provide a

  19. DAST in Flight Showing Diverging Wingtip Oscillations

    NASA Technical Reports Server (NTRS)

    1980-01-01

    normal stiffness. This was done because stiffness requires structural weight but ensures freedom from flutter-an uncontrolled, divergent oscillation of the structure, driven by aerodynamic forces and resulting in structural failure. The program used refined theoretical tools to predict at what speed flutter would occur. It then designed a high-response control system to counteract the motion and permit a much lighter wing structure. The wing had, in effect, 'electronic stiffness.' Flight research with this concept was extremely hazardous because an error in either the flutter prediction or control system implementation would result in wing structural failure and the loss of the vehicle. Because of this, flight demonstration of a sub-scale vehicle made sense from the standpoint of both safety and cost. The program anticipated structural failure during the course of the flight research. The Firebee II was a supersonic drone selected as the DAST testbed because its wing could be easily replaced, it used only tail-mounted control surfaces, and it was available as surplus from the U. S. Air Force. It was capable of 5-g turns (that is, turns producing acceleration equal to 5 times that of gravity). Langley outfitted a drone with an aeroelastic, supercritical research wing suitable for a Mach 0.98 cruise transport with a predicted flutter speed of Mach 0.95 at an altitude of 25,000 feet. Dryden and Langley, in conjunction with Boeing, designed and fabricated a digital flutter suppression system (FSS). Dryden developed an RPRV (remotely piloted research vehicle) flight control system; integrated the wing, FSS, and vehicle systems; and conducted the flight program. In addition to a digital flight control system and aeroelastic wings, each DAST drone had research equipment mounted in its nose and a mid-air retrieval system in its tail. The drones were originally launched from the NASA B-52 bomber and later from a DC-130. The DAST vehicle's flight was monitored from the sky by an F

  20. Formally Verified Practical Algorithms for Recovery from Loss of Separation

    NASA Technical Reports Server (NTRS)

    Butler, Ricky W.; Munoz, Caesar A.

    2009-01-01

    In this paper, we develop and formally verify practical algorithms for recovery from loss of separation. The formal verification is performed in the context of a criteria-based framework. This framework provides rigorous definitions of horizontal and vertical maneuver correctness that guarantee divergence and achieve horizontal and vertical separation. The algorithms are shown to be independently correct, that is, separation is achieved when only one aircraft maneuvers, and implicitly coordinated, that is, separation is also achieved when both aircraft maneuver. In this paper we improve the horizontal criteria over our previous work. An important benefit of the criteria approach is that different aircraft can execute different algorithms and implicit coordination will still be achieved, as long as they all meet the explicit criteria of the framework. Towards this end we have sought to make the criteria as general as possible. The framework presented in this paper has been formalized and mechanically verified in the Prototype Verification System (PVS).

  1. Landscape predictions from cosmological vacuum selection

    SciTech Connect

    Bousso, Raphael; Bousso, Raphael; Yang, Sheng

    2007-04-23

    In Bousso-Polchinski models with hundreds of fluxes, we compute the effects of cosmological dynamics on the probability distribution of landscape vacua. Starting from generic initial conditions, we find that most fluxes are dynamically driven into a different and much narrower range of values than expected from landscape statistics alone. Hence, cosmological evolution will access only a tiny fraction of the vacua with small cosmological constant. This leads to a host of sharp predictions. Unlike other approaches to eternal inflation, the holographic measure employed here does not lead to staggering, an excessive spread of probabilities that would doom the string landscape as a solution to the cosmological constant problem.

  2. Sandwiched Rényi divergence satisfies data processing inequality

    NASA Astrophysics Data System (ADS)

    Beigi, Salman

    2013-12-01

    Sandwiched (quantum) α-Rényi divergence has been recently defined in the independent works of Wilde et al. ["Strong converse for the classical capacity of entanglement-breaking channels," preprint arXiv:1306.1586 (2013)] and Müller-Lennert et al. ["On quantum Rényi entropies: a new definition, some properties and several conjectures," preprint arXiv:1306.3142v1 (2013)]. This new quantum divergence has already found applications in quantum information theory. Here we further investigate properties of this new quantum divergence. In particular, we show that sandwiched α-Rényi divergence satisfies the data processing inequality for all values of α > 1. Moreover we prove that α-Holevo information, a variant of Holevo information defined in terms of sandwiched α-Rényi divergence, is super-additive. Our results are based on Hölder's inequality, the Riesz-Thorin theorem and ideas from the theory of complex interpolation. We also employ Sion's minimax theorem.

  3. Concrete ensemble Kalman filters with rigorous catastrophic filter divergence

    PubMed Central

    Kelly, David; Majda, Andrew J.; Tong, Xin T.

    2015-01-01

    The ensemble Kalman filter and ensemble square root filters are data assimilation methods used to combine high-dimensional, nonlinear dynamical models with observed data. Ensemble methods are indispensable tools in science and engineering and have enjoyed great success in geophysical sciences, because they allow for computationally cheap low-ensemble-state approximation for extremely high-dimensional turbulent forecast models. From a theoretical perspective, the dynamical properties of these methods are poorly understood. One of the central mysteries is the numerical phenomenon known as catastrophic filter divergence, whereby ensemble-state estimates explode to machine infinity, despite the true state remaining in a bounded region. In this article we provide a breakthrough insight into the phenomenon, by introducing a simple and natural forecast model that transparently exhibits catastrophic filter divergence under all ensemble methods and a large set of initializations. For this model, catastrophic filter divergence is not an artifact of numerical instability, but rather a true dynamical property of the filter. The divergence is not only validated numerically but also proven rigorously. The model cleanly illustrates mechanisms that give rise to catastrophic divergence and confirms intuitive accounts of the phenomena given in past literature. PMID:26261335

  4. Concrete ensemble Kalman filters with rigorous catastrophic filter divergence.

    PubMed

    Kelly, David; Majda, Andrew J; Tong, Xin T

    2015-08-25

    The ensemble Kalman filter and ensemble square root filters are data assimilation methods used to combine high-dimensional, nonlinear dynamical models with observed data. Ensemble methods are indispensable tools in science and engineering and have enjoyed great success in geophysical sciences, because they allow for computationally cheap low-ensemble-state approximation for extremely high-dimensional turbulent forecast models. From a theoretical perspective, the dynamical properties of these methods are poorly understood. One of the central mysteries is the numerical phenomenon known as catastrophic filter divergence, whereby ensemble-state estimates explode to machine infinity, despite the true state remaining in a bounded region. In this article we provide a breakthrough insight into the phenomenon, by introducing a simple and natural forecast model that transparently exhibits catastrophic filter divergence under all ensemble methods and a large set of initializations. For this model, catastrophic filter divergence is not an artifact of numerical instability, but rather a true dynamical property of the filter. The divergence is not only validated numerically but also proven rigorously. The model cleanly illustrates mechanisms that give rise to catastrophic divergence and confirms intuitive accounts of the phenomena given in past literature.

  5. Collective Dynamics Differentiates Functional Divergence in Protein Evolution

    PubMed Central

    Glembo, Tyler J.; Farrell, Daniel W.; Gerek, Z. Nevin; Thorpe, M. F.; Ozkan, S. Banu

    2012-01-01

    Protein evolution is most commonly studied by analyzing related protein sequences and generating ancestral sequences through Bayesian and Maximum Likelihood methods, and/or by resurrecting ancestral proteins in the lab and performing ligand binding studies to determine function. Structural and dynamic evolution have largely been left out of molecular evolution studies. Here we incorporate both structure and dynamics to elucidate the molecular principles behind the divergence in the evolutionary path of the steroid receptor proteins. We determine the likely structure of three evolutionarily diverged ancestral steroid receptor proteins using the Zipping and Assembly Method with FRODA (ZAMF). Our predictions are within ∼2.7 Å all-atom RMSD of the respective crystal structures of the ancestral steroid receptors. Beyond static structure prediction, a particular feature of ZAMF is that it generates protein dynamics information. We investigate the differences in conformational dynamics of diverged proteins by obtaining the most collective motion through essential dynamics. Strikingly, our analysis shows that evolutionarily diverged proteins of the same family do not share the same dynamic subspace, while those sharing the same function are simultaneously clustered together and distant from those, that have functionally diverged. Dynamic analysis also enables those mutations that most affect dynamics to be identified. It correctly predicts all mutations (functional and permissive) necessary to evolve new function and ∼60% of permissive mutations necessary to recover ancestral function. PMID:22479170

  6. Neural networks application to divergence-based passive ranging

    NASA Technical Reports Server (NTRS)

    Barniv, Yair

    1992-01-01

    The purpose of this report is to summarize the state of knowledge and outline the planned work in divergence-based/neural networks approach to the problem of passive ranging derived from optical flow. Work in this and closely related areas is reviewed in order to provide the necessary background for further developments. New ideas about devising a monocular passive-ranging system are then introduced. It is shown that image-plan divergence is independent of image-plan location with respect to the focus of expansion and of camera maneuvers because it directly measures the object's expansion which, in turn, is related to the time-to-collision. Thus, a divergence-based method has the potential of providing a reliable range complementing other monocular passive-ranging methods which encounter difficulties in image areas close to the focus of expansion. Image-plan divergence can be thought of as some spatial/temporal pattern. A neural network realization was chosen for this task because neural networks have generally performed well in various other pattern recognition applications. The main goal of this work is to teach a neural network to derive the divergence from the imagery.

  7. Sandwiched Rényi divergence satisfies data processing inequality

    SciTech Connect

    Beigi, Salman

    2013-12-15

    Sandwiched (quantum) α-Rényi divergence has been recently defined in the independent works of Wilde et al. [“Strong converse for the classical capacity of entanglement-breaking channels,” preprint http://arxiv.org/abs/arXiv:1306.1586 (2013)] and Müller-Lennert et al. [“On quantum Rényi entropies: a new definition, some properties and several conjectures,” preprint http://arxiv.org/abs/arXiv:1306.3142v1 (2013)]. This new quantum divergence has already found applications in quantum information theory. Here we further investigate properties of this new quantum divergence. In particular, we show that sandwiched α-Rényi divergence satisfies the data processing inequality for all values of α > 1. Moreover we prove that α-Holevo information, a variant of Holevo information defined in terms of sandwiched α-Rényi divergence, is super-additive. Our results are based on Hölder's inequality, the Riesz-Thorin theorem and ideas from the theory of complex interpolation. We also employ Sion's minimax theorem.

  8. Decompositions of information divergences: Recent development, open problems and applications

    NASA Astrophysics Data System (ADS)

    Stehlík, M.

    2012-11-01

    What is the optimal statistical decision? And how it is related to the statistical information theory? By trying to answer these difficult questions, we will illustrate the necessity of understanding of structure of information divergences. This may be understand in particular through deconvolutions, leading to an optimal statistical inference. We will illustrate deconvolution of information divergence in the exponential family, which will gave us an optimal tests (optimal in the sense of Bahadur (see [3, 4]). We discuss about the results on the exact density of the I-divergence in the exponential family with gamma distributed observations (see [28]). Since the considered I-divergence is related to the likelihood ratio (LR) statistics, we deal with the exact distribution of the likelihood ratio tests and discuss the optimality of such exact tests. The both tests, the exact LR test of the homogeneity and the exact LR test of the scale parameter, are asymptotically optimal in the Bahadur sense when the observations are distributed exponentially. We also discuss decompositions from a broader perspective. We recall relationship between f-divergence and statistical information in the sense of DeGroot, which was shown in [17]. We formulate an open problem of its generalization. Applications in reliability testing and hydrological prediction are mentioned.

  9. Gut microbiota may predict host divergence time during Glires evolution.

    PubMed

    Li, Huan; Qu, Jiapeng; Li, Tongtong; Yao, Minjie; Li, Jiaying; Li, Xiangzhen

    2017-01-29

    The gut microbial communities of animals play key roles in host evolution. However, the possible relationship between gut microbiota and host divergence time remains unknown. Here, we investigated the gut microbiota of eight Glires species (four lagomorpha species and four rodent species) distributed throughout the Qinghai-Tibet plateau and Inner Mongolia grassland. Lagomorphs and rodents had distinct gut microbial compositions. Three out of four lagomorpha species were dominated by Firmicutes, while rodents were dominated by Bacteroidetes in general. The alpha diversity values (Shannon diversity and evenness) exhibited significant differences between any two species within lagomorphs, whereas there were no significant differences among rodents. The structure of the gut microbiota between lagomorphs and rodents showed significant differences. In addition, we calculated host phylogeny and divergence times, and used a phylogenetic approach to reconstruct how the animal gut microbiota has diverged from their ancestral species. Some core bacterial genera (e.g. Prevotella and Clostridium) shared by more than nine-tenths of all the Glires individuals associated with plant polysaccharide degradation showed marked changes within lagomorphs. Differences in Glires gut microbiota (based on weighted UniFrac and Bray-Curtis dissimilarity metrics) were positively correlated with host divergence time. Our results thus suggest the gut microbial composition is associated with host phylogeny, and further suggest that dissimilarity of animal gut microbiota may predict host divergence time.

  10. Convergence and Divergence in the Evolution of Cat Skulls: Temporal and Spatial Patterns of Morphological Diversity

    PubMed Central

    Sakamoto, Manabu; Ruta, Marcello

    2012-01-01

    Background Studies of biological shape evolution are greatly enhanced when framed in a phylogenetic perspective. Inclusion of fossils amplifies the scope of macroevolutionary research, offers a deep-time perspective on tempo and mode of radiations, and elucidates life-trait changes. We explore the evolution of skull shape in felids (cats) through morphometric analyses of linear variables, phylogenetic comparative methods, and a new cladistic study of saber-toothed cats. Methodology/Principal Findings A new phylogenetic analysis supports the monophyly of saber-toothed cats (Machairodontinae) exclusive of Felinae and some basal felids, but does not support the monophyly of various saber-toothed tribes and genera. We quantified skull shape variation in 34 extant and 18 extinct species using size-adjusted linear variables. These distinguish taxonomic group membership with high accuracy. Patterns of morphospace occupation are consistent with previous analyses, for example, in showing a size gradient along the primary axis of shape variation and a separation between large and small-medium cats. By combining the new phylogeny with a molecular tree of extant Felinae, we built a chronophylomorphospace (a phylogeny superimposed onto a two-dimensional morphospace through time). The evolutionary history of cats was characterized by two major episodes of morphological divergence, one marking the separation between saber-toothed and modern cats, the other marking the split between large and small-medium cats. Conclusions/Significance Ancestors of large cats in the ‘Panthera’ lineage tend to occupy, at a much later stage, morphospace regions previously occupied by saber-toothed cats. The latter radiated out into new morphospace regions peripheral to those of extant large cats. The separation between large and small-medium cats was marked by considerable morphologically divergent trajectories early in feline evolution. A chronophylomorphospace has wider applications in

  11. Transforming river basins: Post-livelihood transition agricultural landscapes and implications for natural resource governance.

    PubMed

    Sreeja, K G; Madhusoodhanan, C G; Eldho, T I

    2015-08-15

    The agricultural and livelihood transitions post globalization are redefining resource relations and redrawing landscapes in the Global South and have major implications for nascent natural resource governance regimes such as Integrated River Basin Management (IRBM). A mosaic of divergent reciprocations in resource relations were noticed due to livelihood transitions in the rural areas where previous resource uses and relations had been primarily within agriculture. The reconstitution of rural spaces and the attendant changes in the resource equations are observed to be creating new sites of conformity, contestation and conflicts that often move beyond local spaces. This paper critically reviews studies across the Global South to explore the nature and extent of changes in resource relations and agricultural landscapes post livelihood diversification and the implication and challenges of these changes for natural resource governance. Though there is drastic reduction in agricultural livelihoods throughout the Global South, changes in agricultural area are found to be inconsistent and heterogeneous in the region. Agriculture continues in the countrysides but in widely differentiated capacities and redefined value systems. The transformed agrarian spaces are characterized by a mosaic of scenarios from persistence and sustainable subsistence to differentiation and exploitative commercial practices to abandonment and speculation. The reconfigured resource relations, emergent multiple and multi-scalar interest groups, institutional and policy changes and altered power differentials in these diversified landscapes are yet to be incorporated into natural resource governance frameworks such as IRBM.

  12. Crossing fitness valleys: empirical estimation of a fitness landscape associated with polymorphic mimicry

    PubMed Central

    Arias, Mónica; le Poul, Yann; Chouteau, Mathieu; Rosser, Neil; Théry, Marc; Llaurens, Violaine

    2016-01-01

    Characterizing fitness landscapes associated with polymorphic adaptive traits enables investigation of mechanisms allowing transitions between fitness peaks. Here, we explore how natural selection can promote genetic mechanisms preventing heterozygous phenotypes from falling into non-adaptive valleys. Polymorphic mimicry is an ideal system to investigate such fitness landscapes, because the direction of selection acting on complex mimetic colour patterns can be predicted by the local mimetic community composition. Using more than 5000 artificial butterflies displaying colour patterns exhibited by the polymorphic Müllerian mimic Heliconius numata, we directly tested the role of wild predators in shaping fitness landscapes. We compared predation rates on mimetic phenotypes (homozygotes at the supergene controlling colour pattern), intermediate phenotypes (heterozygotes), exotic morphs (absent from the local community) and palatable cryptic phenotypes. Exotic morphs were significantly more attacked than local morphs, highlighting predators' discriminatory capacities. Overall, intermediates were attacked twice as much as local homozygotes, suggesting the existence of deep fitness valleys promoting strict dominance and reduced recombination between supergene alleles. By including information on predators' colour perception, we also showed that protection on intermediates strongly depends on their phenotypic similarity to homozygous phenotypes and that ridges exist between similar phenotypes, which may facilitate divergence in colour patterns. PMID:27122560

  13. Landscape heterogeneity and marine subsidy generate extensive intrapopulation niche diversity in a large terrestrial vertebrate.

    PubMed

    Darimont, Chris T; Paquet, Paul C; Reimchen, Thomas E

    2009-01-01

    1. Inquiries into niche variation within populations typically focus on proximate ecological causes such as competition. Here we examine how landscape heterogeneity and allochthonous (marine) subsidy might ultimately generate intrapopulation niche diversity. 2. Using stable isotope analysis, we detected extensive terrestrial-marine isotopic niche variation among subpopulations, social groups, and individual grey wolves (Canis lupus) that occupy a spatially heterogeneous landscape in coastal British Columbia comprising a mainland area and adjacent archipelago. 3. The inner island subpopulation exhibited the widest isotopic niche in the population, consuming extensive terrestrial and marine resources. Mainland and outer island subpopulations occupied comparatively narrow and primarily terrestrial, and primarily marine, niches respectively. Within these biogeographical subpopulations, social groups also diverged in niche. 4. To support examination at the individual level, we used an isotopic approach to test Van Valen's (1965) niche variation hypothesis. Consistent with the hypothesis, we observed that among-individual variation increased with subpopulation niche width. 5. Patterns at all levels related to how a spatially heterogeneous coastal landscape structured the competitive environment, which in turn mediated the availability and use of terrestrial and marine resources. Broadly, our results suggest that spatial heterogeneity and allochthonous subsidy--both widespread but commonly subject to contemporary anthropogenic change--might provide novel opportunities for examination and conservation of ecological variation within populations.

  14. Individual Differences and Age-Related Changes in Divergent Thinking in Toddlers and Preschoolers

    ERIC Educational Resources Information Center

    Bijvoet-van den Berg, Simone; Hoicka, Elena

    2014-01-01

    Divergent thinking shows the ability to search for new ideas, which is an important factor contributing to innovation and problem solving. Current divergent thinking tests allow researchers to study children's divergent thinking from the age of 3 years on. This article presents the first measure of divergent thinking that can be used with children…

  15. Process for phase separation

    DOEpatents

    Comolli, Alfred G.

    1979-01-01

    This invention provides a continuous process for separating a gaseous phase from a hydrocarbon liquid containing carbonaceous particulates and gases. The liquid is fed to a cylindrical separator, with the gaseous phase being removed therefrom as an overhead product, whereas the hydrocarbon liquid and the particulates are withdrawn as a bottoms product. By feeding the liquid tangentially to the separator and maintaining a particulate-liquid slurry downward velocity of from about 0.01 to about 0.25 fps in the separator, a total solids weight percent in the slurry of from about 0.1 to about 30%, a slurry temperature of from about 550.degree. to about 900.degree. F., a slurry residence time in the separator of from about 30 to about 360 seconds, and a length/diameter ratio for the separator of from about 20/1 to about 50/1, so that the characterization factor, .alpha., defined as ##STR1## DOES NOT EXCEED ABOUT 48 (.degree.R sec.sup.2)/ft, the deposit of carbonaceous materials on the interior surface of the separator may be substantially eliminated.

  16. Participatory Planning, Monitoring and Evaluation of Multi-Stakeholder Platforms in Integrated Landscape Initiatives.

    PubMed

    Kusters, Koen; Buck, Louise; de Graaf, Maartje; Minang, Peter; van Oosten, Cora; Zagt, Roderick

    2017-03-21

    Integrated landscape initiatives typically aim to strengthen landscape governance by developing and facilitating multi-stakeholder platforms. These are institutional coordination mechanisms that enable discussions, negotiations, and joint planning between stakeholders from various sectors in a given landscape. Multi-stakeholder platforms tend to involve complex processes with diverse actors, whose objectives and focus may be subjected to periodic re-evaluation, revision or reform. In this article we propose a participatory method to aid planning, monitoring, and evaluation of such platforms, and we report on experiences from piloting the method in Ghana and Indonesia. The method is comprised of three components. The first can be used to look ahead, identifying priorities for future multi-stakeholder collaboration in the landscape. It is based on the identification of four aspirations that are common across multi-stakeholder platforms in integrated landscape initiatives. The second can be used to look inward. It focuses on the processes within an existing multi-stakeholder platform in order to identify areas for possible improvement. The third can be used to look back, identifying the main outcomes of an existing platform and comparing them to the original objectives. The three components can be implemented together or separately. They can be used to inform planning and adaptive management of the platform, as well as to demonstrate performance and inform the design of new interventions.

  17. Differential effects of habitat isolation and landscape composition on wasps, bees, and their enemies.

    PubMed

    Schüepp, Christof; Herrmann, John D; Herzog, Felix; Schmidt-Entling, Martin H

    2011-03-01

    Habitat loss and fragmentation are major threats to biodiversity and ecosystem functioning. Effects of these usually intercorrelated processes on biodiversity have rarely been separated at a landscape scale. We studied the independent effects of amount of woody habitat in the landscape and three levels of isolation from the next woody habitat (patch isolation) on trap nesting bees, wasps, and their enemies at 30 farmland sites in the Swiss plateau. Species richness of wasps was negatively affected by patch isolation and positively affected by the amount of woody habitat in the landscape. In contrast, species richness of bees was neither influenced by patch isolation nor by landscape composition. Isolation from woody habitats reduced species richness and abundance of natural enemies more strongly than of their hosts, so that parasitism rate was lowered by half in isolated sites compared to forest edges. Thus, population regulation of the hosts may be weakened by habitat fragmentation. We conclude that habitat amount at the landscape scale and local patch connectivity are simultaneously important for biodiversity conservation.

  18. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, Frederick T.

    1981-01-01

    Intermetallic compounds with the CaCu.sub.5 type of crystal structure, particularly LaNiCo.sub.4 and CaNi.sub.5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  19. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, F.T.

    Intermetallic compounds with the CaCu/sub 5/ type of crystal structure, particularly LaNiCo/sub 4/ and CaNi/sub 5/, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen cn produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  20. Asymmetric gas separation membranes

    SciTech Connect

    Malon, R. F.; Zampini, A.

    1984-12-04

    Asymmetric gas separation membranes of materials having selective permeation of at least one gas of a gaseous mixture over that of one or more remaining gases of the gaseous mixture, exhibit significantly improved permeation selectivities for the at least one gas when the asymmetric membrane is contacted on one or both surfaces with an effective amount of a Lewis acid. The improved asymmetric gas separation membranes, process for producing the improved membrane, and processes utilizing such membranes for selectively separating at least one gas from a gaseous mixture by permeation are disclosed.