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Sample records for dissimilar spatial genetic

  1. Effects of Spatial Frequency Similarity and Dissimilarity on Contour Integration.

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    Malte Persike

    Full Text Available We examined the effects of spatial frequency similarity and dissimilarity on human contour integration under various conditions of uncertainty. Participants performed a temporal 2AFC contour detection task. Spatial frequency jitter up to 3.0 octaves was applied either to background elements, or to contour and background elements, or to none of both. Results converge on four major findings. (1 Contours defined by spatial frequency similarity alone are only scarcely visible, suggesting the absence of specialized cortical routines for shape detection based on spatial frequency similarity. (2 When orientation collinearity and spatial frequency similarity are combined along a contour, performance amplifies far beyond probability summation when compared to the fully heterogenous condition but only to a margin compatible with probability summation when compared to the fully homogenous case. (3 Psychometric functions are steeper but not shifted for homogenous contours in heterogenous backgrounds indicating an advantageous signal-to-noise ratio. The additional similarity cue therefore not so much improves contour detection performance but primarily reduces observer uncertainty about whether a potential candidate is a contour or just a false positive. (4 Contour integration is a broadband mechanism which is only moderately impaired by spatial frequency dissimilarity.

  2. Hybrid performance in taro (Colocasia esculenta) in relation to genetic dissimilarity of parents.

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    Quero-García, José; Letourmy, P; Ivancic, A; Feldmann, P; Courtois, B; Noyer, J L; Lebot, V

    2009-07-01

    Taro (Colocasia esculenta) breeding, as other root crop breeding, is based on the production and evaluation of large numbers of hybrids. The selection of parents is based on their phenotypic value in the absence of information concerning general combining ability (GCA), specific combining ability (SCA), or genetic distances between varieties. By combining data from heritability trials and from genetic diversity studies conducted with AFLP and SSR markers, we aimed at studying the relationship between hybrid vigour and genetic dissimilarity between parents. The traits studied included number of suckers, corm weight, corm dimensions, and dry matter content. Correlation coefficients between hybrid gain and dissimilarity values were calculated. The prediction of hybrid performance based on the mid-parent value was compared to the prediction based on a modified expression that takes into account the genetic relationships between parents. Correlations were all but one positive but not statistically significant for all traits, with the exception of the number of suckers, when using SSR markers for dissimilarity calculations. Accordingly, the genetic dissimilarities in the prediction of hybrid performances did not increase the correlation between predicted and observed hybrid vigour values. However, large differences were observed among the residual means from the regression between predicted and observed values when using AFLP or SSR markers, mainly due to the much higher polymorphism revealed by the latter. Models need to be further adapted to the type of molecular marker used, since their ability to reveal different rates of polymorphism will have a direct incidence on the calculation of genetic dissimilarities between genotypes. Nevertheless, since SSR markers are more polymorphic and more informative than AFLP markers, they should be preferentially used for these studies. Low genetic dissimilarity of parents yielded weak heterosis effects and future studies need to be

  3. Genetic dissimilarity among sweet potato genotypes using morphological and molecular descriptors

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    Elisângela Knoblauch Viega de Andrade

    2017-08-01

    Full Text Available This study aimed to evaluate the genetic dissimilarity among sweet potato genotypes using morphological and molecular descriptors. The experiment was conducted in the Olericulture Sector at Federal University of Jequitinhonha and Mucuri Valleys (UFVJM and evaluated 60 sweet potato genotypes. For morphological characterization, 24 descriptors were used. For molecular characterization, 11 microsatellite primers specific for sweet potatoes were used, obtaining 210 polymorphic bands. Morphological and molecular diversity was obtained by dissimilarity matrices based on the coefficient of simple matching and the Jaccard index for morphological and molecular data, respectively. From these matrices, dendrograms were built. There is a large amount of genetic variability among sweet potato genotypes of the germplasm bank at UFVJM based on morphological and molecular characterizations. There was no duplicate suspicion or strong association between morphological and molecular analyses. Divergent accessions have been identified by molecular and morphological analyses, which can be used as parents in breeding programmes to produce progenies with high genetic variability.

  4. Genetic dissimilarity among jabuticaba trees native to southwestern Paraná, Brazil

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    Moeses Andrigo Danner

    2011-06-01

    Full Text Available Knowledge on the genetic diversity within and between genotype groups is of great importance for breeding programs. The purpose of this study was to estimate the genetic dissimilarity among 36 native jabuticaba trees (Plinia cauliflora from five sites in the southwestern region of Paraná, Brazil. Sixteen fruit traits were analyzed, based on multivariate techniques (canonical variables, Tocher and UPGMA, using Mahalanobis' distance as dissimilarity measure. By the techniques of clustering and graphic dispersion, together with the comparison of means, the genetic diversity among native jabuticaba trees was efficiently identified, indicating a high potential of these genotypes for breeding programs. The traits of greatest importance for dissimilarity were percentage of pulp and of skin, which are easily measured. The clustering structure is related to the collection sites and for breeding programs, genotypes from different sites should be crossed to generate progenies to be tested. Genotypes 'CV5' and 'VT3' should be conserved in genebanks, due to its important agronomic traits.

  5. Statistical methods in spatial genetics

    DEFF Research Database (Denmark)

    Guillot, Gilles; Leblois, Raphael; Coulon, Aurelie

    2009-01-01

    The joint analysis of spatial and genetic data is rapidly becoming the norm in population genetics. More and more studies explicitly describe and quantify the spatial organization of genetic variation and try to relate it to underlying ecological processes. As it has become increasingly difficult...... to keep abreast with the latest methodological developments, we review the statistical toolbox available to analyse population genetic data in a spatially explicit framework. We mostly focus on statistical concepts but also discuss practical aspects of the analytical methods, highlighting not only...

  6. Adaptive Multidimensional Scaling : The Spatial Representation of Brand Consideration and Dissimilarity Judgments

    NARCIS (Netherlands)

    Bijmolt, T.H.A.; Wedel, M.; DeSarbo, W.S.

    2002-01-01

    We propose Adaptive Multidimensional Scaling (AMDS) for simultaneously deriving a brand map and market segments using consumer data on cognitive decision sets and brand dissimilarities.In AMDS, the judgment task is adapted to the individual respondent: dissimilarity judgments are collected only for

  7. Genetic dissimilarity for resistance to Mononychellus tanajoa (bondar (Acari, Tetranychidae among domesticated and wild Manihot species

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    Verônica de Jesus Boaventura

    2015-10-01

    Full Text Available The aim of this study was to evaluate the genetic dissimilarity among wild and domesticated species of Manihot for resistance to cassava green mite during the insect life cycle. Nine accessions of wild Manihot species, M. esculenta ssp. flabellifolia, M. esculenta ssp. peruviana, and M. carthaginensis ssp. glaziovii, and two clones of M. esculenta (Cigana Preta and Sacaí were evaluated under laboratory conditions at 25 ± 1°C, 70 ± 10% RH, and a 12-h photophase. Daily observations during the mite life cycle stages (larva-adult were recorded. The data were subjected to an analysis of variance, a Scott-Knott test (5%, and Singh criterion, cluster, and principal component analyses. The larval-adult period ranged from 5.53 to 7.01 days: the longest period was observed on an M. glaziovii accession (GLA-19-DF and the shortest on an M. flabellifolia accession (FLA-025V. The UPGMA method allowed the division of the genotypes into six groups, with the greatest distance between the FLA-025V and GLA-19-DF accessions. The first two main components explained 77.50% of the total accumulated variation. The association of the longest cycle duration of M. tanajoa with the lowest larval-adult viability suggests that GLA-19-DF is less favorable to mite development compared to the other accessions. Significant variability among the genotypes was observed.

  8. Dissimilaridade genética entre genótipos de aveia Genetic dissimilarity among oat genotypes

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    Volmir Sergio Marchioro

    2003-04-01

    Full Text Available Dezoito genótipos de aveia foram testados quanto à dissimilaridade genética, com e sem o controle de moléstias da parte aérea. As variáveis avaliadas foram rendimento de grãos desaristados, peso de mil grãos, peso do hectolitro, estatura de planta e dias da emergência à floração. Foram empregados análises por variáveis canônicas e técnicas de agrupamento por meio dos métodos de otimização de Tocher e o método hierárquico do vizinho mais próximo, tendo como medida de dissimilaridade a distância generalizada de Mahalanobis. Pelos resultados, constatou-se significativa dissimilaridade genética entre os genótipos, indicando a existência de variabilidade para os caracteres avaliados. O método de Tocher e o método do vizinho mais próximo permitiram a separação dos genótipos em grupos distintos, possibilitando a identificação de futuros genitores que possam ser utilizados em cruzamentos artificiais que produzam progênies com maior heterose. Os caracteres que mais contribuíram para a dissimilaridade genética foram o peso do hectolitro e a estatura de planta.Eighteen oat genotypes were tested for genetic dissimilarity, with and without shoot disease control. The evaluated variables were grain yield, weight of one thousand grains, test weight, plant stature and days from emergence to flowering. Cannonical variables and clustering methods by Tocher's optimization test and the hierarchical method of nearest neighbor were employed, having as a measure of dissimilarity the general distance of Mahalanobis. The results showed a significant genetic dissimilarity among the genotypes, indicating the presence of genetic variability for the evaluated traits. Tocher's and nearest neighbor methods allowed the separation of genotypes in distinct groups, enabling the identification of potential parents for artificial crosses to obtain progenies with higher heterosis. The major traits contributing to genetic dissimilarity in our study

  9. Multispecies genetic objectives in spatial conservation planning.

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    Nielsen, Erica S; Beger, Maria; Henriques, Romina; Selkoe, Kimberly A; von der Heyden, Sophie

    2016-12-07

    The growing threats to biodiversity and global alteration of habitats and species distributions make it increasingly necessary to consider evolutionary patterns in conservation decision-making. Yet there is no clear-cut guidance on how genetic features can be incorporated into conservation planning processes, with multiple molecular markers and several genetic metrics for each marker type to choose from. Genetic patterns also differ between species, but the potential trade-offs amongst genetic objectives for multiple species in conservation planning are currently understudied. This study compares spatial conservation prioritizations derived from two metrics of both genetic diversity (nucleotide and haplotype diversity) and genetic isolation (private haplotypes and local genetic differentiation) for mitochondrial DNA for five marine species. The findings show that conservation plans based solely on habitat representation noticeably differ from those additionally including genetic data, with habitat-based conservation plans selecting fewer conservation priority areas. Furthermore, all four genetic metrics selected approximately similar conservation priority areas, which is likely a result of prioritizing genetic patterns across a genetically diverse array of species. Largely, the results suggest that multi-species genetic conservation objectives are vital to create protected area networks that appropriately preserve community-level evolutionary patterns. This article is protected by copyright. All rights reserved.

  10. Latent spatial models and sampling design for landscape genetics

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    Hanks, Ephraim M.; Hooten, Mevin B.; Knick, Steven T.; Oyler-McCance, Sara J.; Fike, Jennifer A.; Cross, Todd B.; Schwartz, Michael K.

    2016-01-01

    We propose a spatially-explicit approach for modeling genetic variation across space and illustrate how this approach can be used to optimize spatial prediction and sampling design for landscape genetic data. We propose a multinomial data model for categorical microsatellite allele data commonly used in landscape genetic studies, and introduce a latent spatial random effect to allow for spatial correlation between genetic observations. We illustrate how modern dimension reduction approaches to spatial statistics can allow for efficient computation in landscape genetic statistical models covering large spatial domains. We apply our approach to propose a retrospective spatial sampling design for greater sage-grouse (Centrocercus urophasianus) population genetics in the western United States.

  11. CDPOP: A spatially explicit cost distance population genetics program

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    Erin L. Landguth; S. A. Cushman

    2010-01-01

    Spatially explicit simulation of gene flow in complex landscapes is essential to explain observed population responses and provide a foundation for landscape genetics. To address this need, we wrote a spatially explicit, individual-based population genetics model (CDPOP). The model implements individual-based population modelling with Mendelian inheritance and k-allele...

  12. Plant genetics shapes inquiline community structure across spatial scales.

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    Crutsinger, Gregory M; Cadotte, Marc W; Sanders, Nathan J

    2009-04-01

    Recent research in community genetics has examined the effects of intraspecific genetic variation on species diversity in local communities. However, communities can be structured by a combination of both local and regional processes and to date, few community genetics studies have examined whether the effects of instraspecific genetic variation are consistent across levels of diversity. In this study, we ask whether host-plant genetic variation structures communities of arthropod inquilines within distinct habitat patches--rosette leaf galls on tall goldenrod (Solidago altissima). We found that genetic variation determined inquiline diversity at both local and regional spatial scales, but that trophic-level responses varied independently of one another. This result suggests that herbivores and predators likely respond to heritable plant traits at different spatial scales. Together, our results show that incorporating spatial scale is essential for predicting the effects of genetically variable traits on different trophic levels and levels of diversity within the communities that depend on host plants.

  13. Genetic Drift Suppresses Bacterial Conjugation in Spatially Structured Populations

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    Freese, Peter D.; Korolev, Kirill S.; Jiménez, José I.; Chen, Irene A.

    2014-02-01

    Conjugation is the primary mechanism of horizontal gene transfer that spreads antibiotic resistance among bacteria. Although conjugation normally occurs in surface-associated growth (e.g., biofilms), it has been traditionally studied in well-mixed liquid cultures lacking spatial structure, which is known to affect many evolutionary and ecological processes. Here we visualize spatial patterns of gene transfer mediated by F plasmid conjugation in a colony of Escherichia coli growing on solid agar, and we develop a quantitative understanding by spatial extension of traditional mass-action models. We found that spatial structure suppresses conjugation in surface-associated growth because strong genetic drift leads to spatial isolation of donor and recipient cells, restricting conjugation to rare boundaries between donor and recipient strains. These results suggest that ecological strategies, such as enforcement of spatial structure and enhancement of genetic drift, could complement molecular strategies in slowing the spread of antibiotic resistance genes.

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

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    Blanchong, Julie A; Samuel, Michael D; Scribner, Kim T; Weckworth, Byron V; Langenberg, Julia A; Filcek, Kristine B

    2008-02-23

    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.

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

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    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.

  16. Genetic dissimilarity between primary colorectal carcinomas and their lymph node metastases: ploidy, p53, bcl-2, and c-myc expression--a pilot study.

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    Zalata, Khaled Refaat; Elshal, Mohamed Farouk; Foda, Abd AlRahman Mohammad; Shoma, Ashraf

    2015-08-01

    The current paradigm of metastasis proposes that rare cells within primary tumors acquire metastatic capability via sequential mutations, suggesting that metastases are genetically dissimilar from their primary tumors. This study investigated the changes in the level of expression of a well-defined panel of cell proliferation, differentiation, and apoptosis markers between the primary colorectal cancer (CRC) and the corresponding synchronous lymph node (LN) metastasis from the same patients. DNA flow cytometry and immunostaining of p53, bcl-2, and c-myc were carried out on 36 cases of CRC radical resection specimens with their corresponding LN metastases. There was very low probability that the histological patterns of primary tumors and LN metastases are independent (p < 0.001). Metastatic tumors were significantly more diffusely positive for p53 than the primary tumors (p < 0.001). Conversely, primary tumors were significantly more diffusely positive for c-myc than metastatic tumors (p = 0.011). No significant difference was found between the LNs and the primary tumors in bcl-2 positivity (p = 0.538) and DNA aneuploidy (p = 0.35), with a tendency towards negative bcl-2 and less aneuploidy in LN metastases than primary tumors. In conclusion, LN metastatic colorectal carcinomas have a tendency of being less differentiated, with a higher incidence of diffuse p53 staining, lower incidence of bcl-2 staining, and less aneuploidy in comparison to their primary counterparts suggesting a more aggressive biological behavior, which could indicate the necessity for more aggressive adjuvant therapy.

  17. Genetic hitchhiking under heterogeneous spatial selection pressures.

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    Kristan A Schneider

    Full Text Available During adaptive evolutionary processes substantial heterogeneity in selective pressure might act across local habitats in sympatry. Examples are selection for drug resistance in malaria or herbicide resistance in weeds. In such setups standard population-genetic assumptions (homogeneous constant selection pressures, random mating etc. are likely to be violated. To avoid misinferences on the strength and pattern of natural selection it is therefore necessary to adjust population-genetic theory to meet the specifics driving adaptive processes in particular organisms. We introduce a deterministic model in which selection acts heterogeneously on a population of haploid individuals across different patches over which the population randomly disperses every generation. A fixed proportion of individuals mates exclusively within patches, whereas the rest mates randomly across all patches. We study how the allele frequencies at neutral markers are affected by the spread of a beneficial mutation at a closely linked locus (genetic hitchhiking. We provide an analytical solution for the frequency change and the expected heterozygosity at the neutral locus after a single copy of a beneficial mutation became fixed. We furthermore provide approximations of these solutions which allow for more obvious interpretations. In addition, we validate the results by stochastic simulations. Our results show that the application of standard population-genetic theory is accurate as long as differences across selective environments are moderate. However, if selective differences are substantial, as for drug resistance in malaria, herbicide resistance in weeds, or insecticide resistance in agriculture, it is necessary to adapt available theory to the specifics of particular organisms.

  18. Genetic structure of spatial and verbal working memory.

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    Ando, J; Ono, Y; Wright, M J

    2001-11-01

    Working memory (WM) encompasses both short-term memory (storage) and executive functions that play an essential role in all forms of cognition. In this study, the genetic structure of storage and executive functions engaged in both a spatial and verbal WM span task is investigated using a twin sample. The sample consists of 143 monozygotic (MZ) and 93 dizygotic (DZ) Japanese twin pairs, ages 16 to 29 years. In 155 (87 MZ, 62 DZ) of these pairs, cognitive ability scores from the Kyodai Japanese IQ test are also obtained. The phenotypic relationship between WM and cognitive ability is confirmed (r = 0.26-0.44). Individual differences in WM storage and executive functions are found to be significantly influenced by genes, with heritability estimates all moderately high (43%-49%), and estimates for cognitive ability comparable to previous studies (65%). A large part of the genetic variance in storage and executive functions in both spatial and verbal modalities is due to a common genetic factor that accounts for 11% to 43% of the variance. In the reduced sample, this common genetic factor accounts for 64% and 26% of the variance in spatial and verbal cognitive ability, respectively. Additional genetic variance in WM (7%-30%) is due to modality specific factors (spatial and verbal) and a storage specific factor that may be particularly important for the verbal modality. None of the variance in cognitive ability is accounted for by the modality and storage genetic factors, suggesting these may be specific to WM.

  19. Spread of pedigree versus genetic ancestry in spatially distributed populations.

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    Kelleher, J; Etheridge, A M; Véber, A; Barton, N H

    2016-04-01

    Ancestral processes are fundamental to modern population genetics and spatial structure has been the subject of intense interest for many years. Despite this interest, almost nothing is known about the distribution of the locations of pedigree or genetic ancestors. Using both spatially continuous and stepping-stone models, we show that the distribution of pedigree ancestors approaches a travelling wave, for which we develop two alternative approximations. The speed and width of the wave are sensitive to the local details of the model. After a short time, genetic ancestors spread far more slowly than pedigree ancestors, ultimately diffusing out with radius ∼ t rather than spreading at constant speed. In contrast to the wave of pedigree ancestors, the spread of genetic ancestry is insensitive to the local details of the models. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  20. Genetic algorithm-based evaluation of spatial straightness error

    Institute of Scientific and Technical Information of China (English)

    崔长彩; 车仁生; 黄庆成; 叶东; 陈刚

    2003-01-01

    A genetic algorithm ( GA ) -based approach is proposed to evaluate the straightness error of spatial lines. According to the mathematical definition of spatial straightness, a verification model is established for straightness error, and the fitness function of GA is then given and the implementation techniques of the proposed algorithm is discussed in detail. The implementation techniques include real number encoding, adaptive variable range choosing, roulette wheel and elitist combination selection strategies, heuristic crossover and single point mutation schemes etc. An application example is quoted to validate the proposed algorithm. The computation result shows that the GA-based approach is a superior nonlinear parallel optimization method. The performance of the evolution population can be improved through genetic operations such as reproduction, crossover and mutation until the optimum goal of the minimum zone solution is obtained. The quality of the solution is better and the efficiency of computation is higher than other methods.

  1. Joining of dissimilar materials

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    Tucker, Michael C; Lau, Grace Y; Jacobson, Craig P

    2012-10-16

    A method of joining dissimilar materials having different ductility, involves two principal steps: Decoration of the more ductile material's surface with particles of a less ductile material to produce a composite; and, sinter-bonding the composite produced to a joining member of a less ductile material. The joining method is suitable for joining dissimilar materials that are chemically inert towards each other (e.g., metal and ceramic), while resulting in a strong bond with a sharp interface between the two materials. The joining materials may differ greatly in form or particle size. The method is applicable to various types of materials including ceramic, metal, glass, glass-ceramic, polymer, cermet, semiconductor, etc., and the materials can be in various geometrical forms, such as powders, fibers, or bulk bodies (foil, wire, plate, etc.). Composites and devices with a decorated/sintered interface are also provided.

  2. Genetic Diversity and Spatial Genetic Structure of the Grassland Perennial Saxifraga granulata along Two River Systems.

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    Sascha van der Meer

    Full Text Available Due to changes in land use, the natural habitats of an increasing number of plant species have become more and more fragmented. In landscapes that consist of patches of suitable habitat, the frequency and extent of long-distance seed dispersal can be expected to be an important factor determining local genetic diversity and regional population structure of the remaining populations. In plant species that are restricted to riparian habitats, rivers can be expected to have a strong impact on the dynamics and spatial genetic structure of populations as they may enable long-distance seed dispersal and thus maintain gene flow between fragmented populations. In this study, we used polymorphic microsatellite markers to investigate the genetic diversity and the spatial genetic structure of 28 populations of Saxifraga granulata along two rivers in central Belgium. We hypothesized that rivers might be essential for gene flow among increasingly isolated populations of this species. Genetic diversity was high (HS = 0.68, which to a certain extent can be explained by the octoploid nature of S. granulata in the study area. Populations along the Dijle and Demer rivers were also highly differentiated (G"ST = 0.269 and 0.164 and DEST = 0.190 and 0.124, respectively and showed significant isolation-by-distance, indicating moderate levels of gene flow primarily between populations that are geographically close to each other. Along the river Demer population genetic diversity was higher upstream than downstream, suggesting that seed dispersal via the water was not the primary mode of dispersal. Overall, these results indicate that despite increasing fragmentation populations along both rivers were highly genetically diverse. The high ploidy level and longevity of S. granulata have most likely buffered negative effects of fragmentation on genetic diversity and the spatial genetic structure of populations in riparian grasslands.

  3. Genetic Diversity and Spatial Genetic Structure of the Grassland Perennial Saxifraga granulata along Two River Systems.

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    van der Meer, Sascha; Jacquemyn, Hans

    2015-01-01

    Due to changes in land use, the natural habitats of an increasing number of plant species have become more and more fragmented. In landscapes that consist of patches of suitable habitat, the frequency and extent of long-distance seed dispersal can be expected to be an important factor determining local genetic diversity and regional population structure of the remaining populations. In plant species that are restricted to riparian habitats, rivers can be expected to have a strong impact on the dynamics and spatial genetic structure of populations as they may enable long-distance seed dispersal and thus maintain gene flow between fragmented populations. In this study, we used polymorphic microsatellite markers to investigate the genetic diversity and the spatial genetic structure of 28 populations of Saxifraga granulata along two rivers in central Belgium. We hypothesized that rivers might be essential for gene flow among increasingly isolated populations of this species. Genetic diversity was high (HS = 0.68), which to a certain extent can be explained by the octoploid nature of S. granulata in the study area. Populations along the Dijle and Demer rivers were also highly differentiated (G"ST = 0.269 and 0.164 and DEST = 0.190 and 0.124, respectively) and showed significant isolation-by-distance, indicating moderate levels of gene flow primarily between populations that are geographically close to each other. Along the river Demer population genetic diversity was higher upstream than downstream, suggesting that seed dispersal via the water was not the primary mode of dispersal. Overall, these results indicate that despite increasing fragmentation populations along both rivers were highly genetically diverse. The high ploidy level and longevity of S. granulata have most likely buffered negative effects of fragmentation on genetic diversity and the spatial genetic structure of populations in riparian grasslands.

  4. Avaliação da dissimilaridade genética em genótipos de bananeira (Musa spp. via marcadores RAPD Evaluation of genetics dissimilarity in banana tree genotypes (Musa spp. by means of RAPD markers

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    Carolina Maria Palácios de Souza

    2008-06-01

    Full Text Available A bananicultura possui grande importância econômica e social. A UENF, por meio do Laboratório de Melhoramento Genético Vegetal iniciou um trabalho de introdução de cultivares de bananeira. Foram introduzidas cultivares com procedência da Embrapa Mandioca e Fruticultura e Embrapa Amazônia Ocidental. O objetivo deste trabalho foi realizar um estudo de diversidade genética entre 21 cultivares e obter a correta identificação de possíveis genótipos introduzidos na UENF. Foram avaliados os seguintes genótipos: Fhia 18, Prata-Anã, UENF 1526, Pacovan, Caipira, Maçã, UENF 1527, Nanicão, Thap Maeo, UENF 1528, UENF 1529, Grande Naine, Ambrósia, Bucaneiro, Calipso, PV42-68, PV42-85, PV42-142, ST12-31, Calcutta e BB da França. A análise de divergência genética foi feita com base na caracterização molecular, utilizando-se da técnica RAPD. Para serem obtidas marcas moleculares RAPD, foram utilizados 31 "primers", gerando um total de 94 marcas totais. Os resultados mostraram que os marcadores moleculares RAPD foram eficazes em revelar a existência de diversidade genética entre os 21 genótipos de bananeira. Na interpretação das análises moleculares, foi utilizado o complemento aritmético do Índice de Jaccard. Com base nas análises de agrupamento hierárquicas UPGMA e o método de otimização de Tocher, essa diversidade pôde ser observada pela presença de genótipos similares e divergentes.Banana is a very important social and economic crop. The introduction of of banana cultivars was initiated through the Plant Genetics Laboratory at UENF. Cultivars from Embrapa Cassava and Tropical Fruits and Western Amazon were introduced. The objective of the present work was to analyze the genetic dissimilarity between 21 cultivars and obtain the correct identification of the possible genotypes introduced at UENF. The following genotypes were evaluated: Fhia 18, Prata Anã, UENF 1526, Pacovan, Caipira, Maçã, UENF 1527, Nanicão, Thap

  5. Female rose bitterling prefer MHC-dissimilar males: experimental evidence.

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    Martin Reichard

    Full Text Available The role of genetic benefits in female mate choice remains a controversial aspect of sexual selection theory. In contrast to "good allele" models of sexual selection, "compatible allele" models of mate choice predict that females prefer mates with alleles complementary to their own rather than conferring additive effects. While correlative results suggest complementary genetic effects to be plausible, direct experimental evidence is scarce. A previous study on the Chinese rose bitterling (Rhodeus ocellatus demonstrated a positive correlation between female mate choice, offspring growth and survival, and the functional dissimilarity between the Major Histocompatibility Complex (MHC alleles of males and females. Here we directly tested whether females used cues associated with MHC genes to select genetically compatible males in an experimental framework. By sequentially pairing females with MHC similar and dissimilar males, based on a priori known MHC profiles, we showed that females discriminated between similar and dissimilar males and deposited significantly more eggs with MHC dissimilar males. Notably, the degree of dissimilarity was an important factor for female decision to mate, possibly indicating a potential threshold value of dissimilarity for decision making, or of an indirect effect of the MHC.

  6. Eliciting spatial statistics from geological experts using genetic algorithms

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    Walker, Matthew; Curtis, Andrew

    2014-07-01

    A new method to obtain the statistics of a geostatistical model is introduced. The method elicits the statistical information from a geological expert directly, by iteratively updating a population of vectors of statistics, based on the expert's subjective opinion of the corresponding geological simulations. Thus, it does not require the expert to have knowledge of the mathematical and statistical details of the model. The process uses a genetic algorithm to generate new vectors. We demonstrate the methodology for a particular geostatistical model used to model rock pore-space, which simulates the spatial distribution of matrix and pores over a 2-D grid, using multipoint statistics specified by conditional probabilities. Experts were asked to use the algorithm to estimate the statistics of a given target pore-space image with known statistics; thus, their numerical rates of convergence could be calculated. Convergence was measured for all experts, showing that the algorithm can be used to find appropriate probabilities given the expert's subjective input. However, considerable and apparently irreducible residual misfit was found between the true statistics and the estimates of statistics obtained by the experts, with the root-mean-square error on the conditional probabilities typically >0.1. This is interpreted as the limit of the experts' abilities to distinguish between realizations of different spatial statistics using the algorithm. More accurate discrimination is therefore likely to require complementary elicitation techniques or sources of information independent of expert opinion.

  7. Spatial genetic structure of a symbiotic beetle-fungal system: toward multi-taxa integrated landscape genetics.

    Directory of Open Access Journals (Sweden)

    Patrick M A James

    Full Text Available Spatial patterns of genetic variation in interacting species can identify shared features that are important to gene flow and can elucidate co-evolutionary relationships. We assessed concordance in spatial genetic variation between the mountain pine beetle (Dendroctonus ponderosae and one of its fungal symbionts, Grosmanniaclavigera, in western Canada using neutral genetic markers. We examined how spatial heterogeneity affects genetic variation within beetles and fungi and developed a novel integrated landscape genetics approach to assess reciprocal genetic influences between species using constrained ordination. We also compared landscape genetic models built using Euclidean distances based on allele frequencies to traditional pair-wise Fst. Both beetles and fungi exhibited moderate levels of genetic structure over the total study area, low levels of structure in the south, and more pronounced fungal structure in the north. Beetle genetic variation was associated with geographic location while that of the fungus was not. Pinevolume and climate explained beetle genetic variation in the northern region of recent outbreak expansion. Reciprocal genetic relationships were only detectedin the south where there has been alonger history of beetle infestations. The Euclidean distance and Fst-based analyses resulted in similar models in the north and over the entire study area, but differences between methods in the south suggest that genetic distances measures should be selected based on ecological and evolutionary contexts. The integrated landscape genetics framework we present is powerful, general, and can be applied to other systems to quantify the biotic and abiotic determinants of spatial genetic variation within and among taxa.

  8. Converting genetic network oscillations into somite spatial patterns

    Science.gov (United States)

    Mazzitello, K. I.; Arizmendi, C. M.; Hentschel, H. G. E.

    2008-08-01

    The segmentation of vertebrate embryos, a process known as somitogenesis, depends on a complex genetic network that generates highly dynamic gene expression in an oscillatory manner. A recent proposal for the mechanism underlying these oscillations involves negative-feedback regulation at transcriptional translational levels, also known as the “delay model” [J. Lewis Curr. Biol. 13, 1398 (2003)]. In addition, in the zebrafish a longitudinal positional information signal in the form of an Fgf8 gradient constitutes a determination front that could be used to transform these coupled intracellular temporal oscillations into the observed spatial periodicity of somites. Here we consider an extension of the delay model by taking into account the interaction of the oscillation clock with the determination front. Comparison is made with the known properties of somite formation in the zebrafish embryo. We also show that the model can mimic the anomalies formed when progression of the determination wave front is perturbed and make an experimental prediction that can be used to test the model.

  9. Phenotypic and genetic evidence for a unifactorial structure of spatial abilities.

    Science.gov (United States)

    Rimfeld, Kaili; Shakeshaft, Nicholas G; Malanchini, Margherita; Rodic, Maja; Selzam, Saskia; Schofield, Kerry; Dale, Philip S; Kovas, Yulia; Plomin, Robert

    2017-03-07

    Spatial abilities encompass several skills differentiable from general cognitive ability (g). Importantly, spatial abilities have been shown to be significant predictors of many life outcomes, even after controlling for g. To date, no studies have analyzed the genetic architecture of diverse spatial abilities using a multivariate approach. We developed "gamified" measures of diverse putative spatial abilities. The battery of 10 tests was administered online to 1,367 twin pairs (age 19-21) from the UK-representative Twins Early Development Study (TEDS). We show that spatial abilities constitute a single factor, both phenotypically and genetically, even after controlling for g This spatial ability factor is highly heritable (69%). We draw three conclusions: (i) The high heritability of spatial ability makes it a good target for gene-hunting research; (ii) some genes will be specific to spatial ability, independent of g; and (iii) these genes will be associated with all components of spatial ability.

  10. Isolation by oceanic distance and spatial genetic structure in an overharvested international fishery

    NARCIS (Netherlands)

    Truelove, Nathan K.; Box, Stephen J.; Aiken, Karl A.; Blythe-Mallett, Azra; Boman, Erik M.; Booker, Catherine J.; Byfield, Tamsen T.; Cox, Courtney E.; Davis, Martha H.; Delgado, Gabriel A.; Glazer, Bob A.; Griffiths, Sarah M.; Kitson-Walters, Kimani; Kough, Andy S.; Pérez Enríquez, Ricardo; Preziosi, Richard F.; Roy, Marcia E.; Segura-García, Iris; Webber, Mona K.; Stoner, Allan W.

    2017-01-01

    Aim: A detailed understanding of spatial genetic structure (SGS) and the factors driving contemporary patterns of gene flow and genetic diversity are fundamental for developing conservation and management plans for marine fisheries. We performed a detailed study of SGS and genetic diversity

  11. Spatial sorting and range shifts: consequences for evolutionary potential and genetic signature of a dispersal trait

    NARCIS (Netherlands)

    Cobben, Marleen; Verboom, J.; Opdam, P.F.M.; Hoekstra, R.F.; Jochem, R.; Smulders, M.J.M.

    2015-01-01

    Species are shifting their ranges under climate change, with genetic and evolutionary consequences. As a result, the spatial distribution of genetic diversity in a species’ range can show a signature of range expansion. This genetic signature takes time to decay after the range stops expanding and

  12. Genetic Geostatistical Framework for Spatial Analysis of Fine-Scale Genetic Heterogeneity in Modern Populations: Results from the KORA Study

    Directory of Open Access Journals (Sweden)

    A. N. Diaz-Lacava

    2015-01-01

    Full Text Available Aiming to investigate fine-scale patterns of genetic heterogeneity in modern humans from a geographic perspective, a genetic geostatistical approach framed within a geographic information system is presented. A sample collected for prospective studies in a small area of southern Germany was analyzed. None indication of genetic heterogeneity was detected in previous analysis. Socio-demographic and genotypic data of German citizens were analyzed (212 SNPs; n=728. Genetic heterogeneity was evaluated with observed heterozygosity (HO. Best-fitting spatial autoregressive models were identified, using socio-demographic variables as covariates. Spatial analysis included surface interpolation and geostatistics of observed and predicted patterns. Prediction accuracy was quantified. Spatial autocorrelation was detected for both socio-demographic and genetic variables. Augsburg City and eastern suburban areas showed higher HO values. The selected model gave best predictions in suburban areas. Fine-scale patterns of genetic heterogeneity were observed. In accordance to literature, more urbanized areas showed higher levels of admixture. This approach showed efficacy for detecting and analyzing subtle patterns of genetic heterogeneity within small areas. It is scalable in number of loci, even up to whole-genome analysis. It may be suggested that this approach may be applicable to investigate the underlying genetic history that is, at least partially, embedded in geographic data.

  13. Spatial-genetic associations of tapering traps in the Mesozoic of West Siberia

    Energy Technology Data Exchange (ETDEWEB)

    Sidorenkov, A.I.; Yasovich, G.S.

    1982-01-01

    It is indicated that in a number of regions in the Mesozoic deposits, tapering traps of different genesis which are spatially closely interlinked are encountered. It is suggested that their spatial-genetic associations be revealed. This has forecasting value for the sections which have been poorly studied.

  14. Using IBMs to Investigate Spatially-dependent Processes in Landscape Genetics Theory

    Science.gov (United States)

    Much of landscape and conservation genetics theory has been derived using non-spatialmathematical models. Here, we use a mechanistic, spatially-explicit, eco-evolutionary IBM to examine the utility of this theoretical framework in landscapes with spatial structure. Our analysis...

  15. Using IBMs to Investigate Spatially-dependent Processes in Landscape Genetics Theory

    Science.gov (United States)

    Much of landscape and conservation genetics theory has been derived using non-spatialmathematical models. Here, we use a mechanistic, spatially-explicit, eco-evolutionary IBM to examine the utility of this theoretical framework in landscapes with spatial structure. Our analysis...

  16. Nonequilibrium Conditions Explain Spatial Variability in Genetic Structuring of Little Penguin (Eudyptula minor).

    Science.gov (United States)

    Burridge, Christopher P; Peucker, Amanda J; Valautham, Sureen K; Styan, Craig A; Dann, Peter

    2015-01-01

    Factors responsible for spatial structuring of population genetic variation are varied, and in many instances there may be no obvious explanations for genetic structuring observed, or those invoked may reflect spurious correlations. A study of little penguins (Eudyptula minor) in southeast Australia documented low spatial structuring of genetic variation with the exception of colonies at the western limit of sampling, and this distinction was attributed to an intervening oceanographic feature (Bonney Upwelling), differences in breeding phenology, or sea level change. Here, we conducted sampling across the entire Australian range, employing additional markers (12 microsatellites and mitochondrial DNA, 697 individuals, 17 colonies). The zone of elevated genetic structuring previously observed actually represents the eastern half of a genetic cline, within which structuring exists over much shorter spatial scales than elsewhere. Colonies separated by as little as 27 km in the zone are genetically distinguishable, while outside the zone, homogeneity cannot be rejected at scales of up to 1400 km. Given a lack of additional physical or environmental barriers to gene flow, the zone of elevated genetic structuring may reflect secondary contact of lineages (with or without selection against interbreeding), or recent colonization and expansion from this region. This study highlights the importance of sampling scale to reveal the cause of genetic structuring. © The American Genetic Association 2015.

  17. Explaining spatial heterogeneity in population dynamics and genetics from spatial variation in resources for a large herbivore.

    Science.gov (United States)

    Contasti, Adrienne L; Tissier, Emily J; Johnstone, Jill F; McLoughlin, Philip D

    2012-01-01

    Fine-scale spatial variation in genetic relatedness and inbreeding occur across continuous distributions of several populations of vertebrates; however, the basis of observed variation is often left untested. Here we test the hypothesis that prior observations of spatial patterns in genetics for an island population of feral horses (Sable Island, Canada) were the result of spatial variation in population dynamics, itself based in spatial heterogeneity in underlying habitat quality. In order to assess how genetic and population structuring related to habitat, we used hierarchical cluster analysis of water sources and an indicator analysis of the availability of important forage species to identify a longitudinal gradient in habitat quality along the length of Sable Island. We quantify a west-east gradient in access to fresh water and availability of two important food species to horses: sandwort, Honckenya peploides, and beach pea, Lathyrus japonicas. Accordingly, the population clusters into three groups that occupy different island segments (west, central, and east) that vary markedly in their local dynamics. Density, body condition, and survival and reproduction of adult females were highest in the west, followed by central and east areas. These results mirror a previous analysis of genetics, which showed that inbreeding levels are highest in the west (with outbreeding in the east), and that there are significant differences in fixation indices among groups of horses along the length of Sable Island. Our results suggest that inbreeding depression is not an important limiting factor to the horse population. We conclude that where habitat gradients exist, we can anticipate fine-scale heterogeneity in population dynamics and hence genetics.

  18. Representing genetic variation as continuous surfaces: An approach for identifying spatial dependency in landscape genetic studies

    Science.gov (United States)

    Melanie A. Murphy; Jeffrey S. Evans; Samuel A. Cushman; Andrew Storfer

    2008-01-01

    Landscape genetics, an emerging field integrating landscape ecology and population genetics, has great potential to influence our understanding of habitat connectivity and distribution of organisms. Whereas typical population genetics studies summarize gene flow as pairwise measures between sampling localities, landscape characteristics that influence population...

  19. Sampling strategy for wild soybean (Glycine soja) populations based on their genetic diversity and fine-scale spatial genetic structure

    Institute of Scientific and Technical Information of China (English)

    ZHU Weiyue; ZHOU Taoying; ZHONG Ming; LU Baorong

    2007-01-01

    A total of 892 individuals sampled from a wild soybean population in a natural reserve near the Yellow River estuary located in Kenli of Shandong Province (China) were investigated.Seventeen SSR (simple sequence repeat) primer pairs from cultivated soybeans were used to estimate the genetic diversity of the population and its variation pattern versus changes of the sample size (sub-samples),in addition to investigating the fine-scale spatial genetic structure within the population.The results showed relatively high genetic diversity of the population with the mean value of allele number (A) being 2.88,expected heterozygosity (He) 0.431,Shannon diversity index (/) 0.699,and percentage of polymorphic loci (P) 100%.Sub-samples of different sizes (ten groups) were randomly drawn from the population and their genetic diversity was calculated by computer simulation.The regression model of the four diversity indexes with the change of sample sizes was computed.As a result,27-52 individuals can reach 95% of total genetic variability of the population.Spatial autocorrelation analysis revealed that the genetic patch size of this wild soybean population is about 18 m.The study provided a scientific basis for the sampling strategy of wild soybean populations.

  20. Considering spatial and temporal scale in landscape-genetic studies of gene flow.

    Science.gov (United States)

    Anderson, Corey Devin; Epperson, Bryan K; Fortin, Marie-Josée; Holderegger, Rolf; James, Patrick M A; Rosenberg, Michael S; Scribner, Kim T; Spear, Stephen

    2010-09-01

    Landscape features exist at multiple spatial and temporal scales, and these naturally affect spatial genetic structure and our ability to make inferences about gene flow. This article discusses how decisions about sampling of genotypes (including choices about analytical methods and genetic markers) should be driven by the scale of spatial genetic structure, the time frame that landscape features have existed in their current state, and all aspects of a species' life history. Researchers should use caution when making inferences about gene flow, especially when the spatial extent of the study area is limited. The scale of sampling of the landscape introduces different features that may affect gene flow. Sampling grain should be smaller than the average home-range size or dispersal distance of the study organism and, for raster data, existing research suggests that simplifying the thematic resolution into discrete classes may result in low power to detect effects on gene flow. Therefore, the methods used to characterize the landscape between sampling sites may be a primary determinant for the spatial scale at which analytical results are applicable, and the use of only one sampling scale for a particular statistical method may lead researchers to overlook important factors affecting gene flow. The particular analytical technique used to correlate landscape data and genetic data may also influence results; common landscape-genetic methods may not be suitable for all study systems, particularly when the rate of landscape change is faster than can be resolved by common molecular markers.

  1. Dissimilaridade genética entre genótipos de trigo avaliados em cultivo hidropônico sob estresse por alumínio Genetic dissimilarity among wheat genotypes evaluated in hydroponic culture under aluminum stress

    Directory of Open Access Journals (Sweden)

    Ivandro Bertan

    2006-01-01

    Full Text Available O conhecimento da distância genética entre genótipos é importante ferramenta utilizada na escolha de genitores que vão dar origem às populações segregantes. Essa informação serve como parâmetro para indicação de cruzamentos que possibilitem recuperar recombinantes superiores para o caráter desejado. O principal objetivo do estudo foi promover informações de dissimilaridade genética para o caráter tolerância ao alumínio tóxico em genótipos de trigo da Região Sul do Brasil, avaliados em cultivo hidropônico sob estresse por alumínio em nível tóxico, utilizando diferentes técnicas de agrupamento e visualização gráfica. Entre os 23 genótipos testados, foi constatada a presença de variabilidade genética para tolerância ao alumínio, verificada pela formação de diferentes classes na média das variáveis consideradas bem como agrupamentos distintos. As técnicas de agrupamento e dispersão gráfica utilizadas juntamente com a comparação de médias permitiram identificar de modo eficiente os genótipos promissores na formação de populações segregantes superiores para o caráter estudado. Os genótipos ICAT 01338, ICAT 011, ICA 2, ICA 5, CD 106, CEP 24, CD 103, CD 105, IPR 85, IPR 110 e ICAT 012 são indicados para cruzamentos na expectativa de incremento de tolerância ao alumínio nas progênies formadas.The quantification of genetic distance among genotypes is an important tool for the choice of parents originating the segregating populations. This information serves as a parameter for directing crosses that increase the probability of recover superior recombinants for the desired character. The main object of this study was to provide information recording the genetic dissimilarity for the character tolerance to toxic aluminum in wheat genotypes from the Southern Region of Brazil, evaluated in hydroponic culture under aluminum stress, using different clustering and graphic techniques. It was observed the

  2. Spatial sorting and range shifts: consequences for evolutionary potential and genetic signature of a dispersal trait.

    Science.gov (United States)

    Cobben, M M P; Verboom, J; Opdam, P F M; Hoekstra, R F; Jochem, R; Smulders, M J M

    2015-05-21

    Species are shifting their ranges under climate change, with genetic and evolutionary consequences. As a result, the spatial distribution of genetic diversity in a species' range can show a signature of range expansion. This genetic signature takes time to decay after the range stops expanding and it is important to take that lag time into account when interpreting contemporary spatial patterns of genetic diversity. In addition, the return to spatial equilibrium on an ecologically relevant timescale will depend on migration of genetic diversity across the species' range. However, during a range shift alleles may go extinct at the retracting range margin due to spatial sorting. Here we studied the spatial pattern of genotypes that differ in dispersal rate across the species range before, during and after a range shift, assessed the effect of range retraction on this pattern, and quantified the duration of the ephemeral genetic signature of range expansion for this trait. We performed simulation experiments with an individual-based metapopulation model under several contemporary climate change scenarios. The results show an increase of the number of individuals with high dispersal rate. If the temperature increased long enough the allele coding for low dispersal rate would go extinct. The duration of the genetic signature of range expansion after stabilisation of the species' distribution lasted up to 1200 generations after a temperature increase for 60 years at the contemporary rate. This depended on the total displacement of the climate optimum, as the product of the rate of temperature increase and its duration. So genetic data collected in the field do not necessarily reflect current selection pressures but can be affected by historic changes in species distribution, long after the establishment of the current species' range. Return to equilibrium patterns may be hampered by loss of evolutionary potential during range shift.

  3. Comparative spatial genetics and epigenetics of plant populations: heuristic value and a proof of concept.

    Science.gov (United States)

    Herrera, Carlos M; Medrano, Mónica; Bazaga, Pilar

    2016-04-01

    Despite the recent upsurge of interest on natural epigenetic variation of nonmodel organisms, factors conditioning the spatial structure of epigenetic diversity in wild plant populations remain virtually unexplored. We propose that information on processes shaping natural epigenetic variation can be gained using the spatial structure of genetic diversity as null model. Departures of epigenetic isolation-by-distance (IBD) patterns from genetic IBD patterns for the same sample, particularly differences in slope of similarity-distance regressions, will reflect the action of factors that operate specifically on epigenetic variation, including imperfect transgenerational inheritance and responsiveness to environmental factors of epigenetic marks. As a proof of concept, we provide a comparative analysis of spatial genetic and epigenetic structure of 200 mapped individuals of the perennial herb Helleborus foetidus. Plants were fingerprinted using nuclear microsatellites, amplified fragment length polymorphisms (AFLP) and methylation-sensitive AFLP markers. Expectations from individual-level IBD patterns were tested by means of kinship-distance regressions. Both genetic and epigenetic similarity between H. foetidus individuals conformed to theoretical expectations under individual-level IBD models. Irrespective of marker type, there were significant negative linear relationships between the kinship coefficient for plant pairs and their spatial separation. Regression slopes were significantly steeper for epigenetic markers. Epigenetic similarity between individuals was much greater than genetic similarity at shortest distances, such epigenetic 'kinship excess' tending to decrease as plant separation increased. Results suggest that moderate-to-high heritability and responsiveness to local environments are major drivers of epigenetic spatial structure in H. foetidus, and illustrate the heuristic value of comparing genetic and epigenetic spatial structure for formulating

  4. Modelling the loss of genetic diversity in vole populations in a spatially and temporally varying environment

    DEFF Research Database (Denmark)

    Topping, Christopher John; Østergaard, Siri; Pertoldi, Cino

    2003-01-01

    a genetically explicit individual-based model (IBM) coupled to a dynamic landscape model was used to obtain measures for the genetic status of simulated vole populations. The rate of loss of expected heterozygosity (He) was calculated for simulated populations using two levels of spatial and temporal...... heterogeneity. Results showed that both spatial and temporal heterogeneity exerted an influence on the rate of loss of genetic diversity, but the precise effect was a balance between the effects of population sub-structuring, the frequency of founder effects and population size. These were in turn related...... of heterozygosity was corrected for the harmonic mean of the population size, the rate of loss was almost identical in the four scenarios. Unlike classical genetic models, IBMs are flexible enough to mimic real population processes under a range of environmental and behavioural conditions. We conclude that IBMs...

  5. Local topography shapes fine-scale spatial genetic structure in the Arkansas Valley evening primrose, Oenothera harringtonii (Onagraceae).

    Science.gov (United States)

    Rhodes, Matthew K; Fant, Jeremie B; Skogen, Krissa A

    2014-01-01

    Identifying factors that shape the spatial distribution of genetic variation is crucial to understanding many population- and landscape-level processes. In this study, we explore fine-scale spatial genetic structure in Oenothera harringtonii (Onagraceae), an insect-pollinated, gravity-dispersed herb endemic to the grasslands of south-central and southeastern Colorado, USA. We genotyped 315 individuals with 11 microsatellite markers and utilized a combination of spatial autocorrelation analyses and landscape genetic models to relate life history traits and landscape features to dispersal processes. Spatial genetic structure was consistent with theoretical expectations of isolation by distance, but this pattern was weak (Sp = 0.00374). Anisotropic analyses indicated that spatial genetic structure was markedly directional, in this case consistent with increased dispersal along prominent slopes. Landscape genetic models subsequently confirmed that spatial genetic variation was significantly influenced by local topographic heterogeneity, specifically that geographic distance, elevation and aspect were important predictors of spatial genetic structure. Among these variables, geographic distance was ~68% more important than elevation in describing spatial genetic variation, and elevation was ~42% more important than aspect after removing the effect of geographic distance. From these results, we infer a mechanism of hydrochorous seed dispersal along major drainages aided by seasonal monsoon rains. Our findings suggest that landscape features may shape microevolutionary processes at much finer spatial scales than typically considered, and stress the importance of considering how particular dispersal vectors are influenced by their environmental context.

  6. Low genetic diversity and intrapopulation spatial genetic structure of the Atlantic Forest tree, Esenbeckia leiocarpa Engl. (Rutaceae

    Directory of Open Access Journals (Sweden)

    G. Forti

    2014-12-01

    Full Text Available Studies on population genetics are the key to designing effective in situ management plans for tree species, in particular, those subjected to pressure from anthropogenic processes, such as forest fragmentation and logging. To investigate genetic diversity, inbreeding and intrapopulation spatial genetic structure (SGS in a fragmented population of the insect-pollinated tropical tree, Esenbeckia leiocarpa, we developed specific microsatellite markers for this species and mapped and sampled 100 individuals in a forest plot. Two issues were addressed in particular: (i the level of genetic diversity, inbreeding and effective population size, (ii whether intrapopulation spatial genetic structure exists. Among the 14 loci developed, we only used the three that presented polymorphism to estimate the genetic parameters. Genetic diversity was low, whereby the average number of alleles per locus (A was 3.3 and observed (H0 and expected heterozygosities (He were 0.336 and 0.298, respectively. The average fixation index was significantly higher than zero (F = 0.112, suggesting inbreeding. Significant SGS was found up to 7 m and between 31 to 38 m, indicating that trees growing within these distances may be related. Estimates of the effective population size indicated that the 100 sampled trees correspond to 14 individuals that are neither related nor inbred. Our results suggest that the microsatellite markers developed in this study are suitable for studies on geneticdiversity and structure, mating systems, gene flow and SGS in this species.

  7. Low genetic diversity and intrapopulation spatial genetic structure of the Atlantic Forest tree, Esenbeckia leiocarpa Engl. (Rutaceae

    Directory of Open Access Journals (Sweden)

    G. Forti

    2014-12-01

    Full Text Available Studies on population genetics are the key to designing effective in situ management plans for tree species, in particular, those subjected to pressure from anthropogenic processes, such as forest fragmentation and logging. To investigate genetic diversity, inbreeding and intrapopulation spatial genetic structure (SGS in a fragmented population of the insect-pollinated tropical tree, Esenbeckia leiocarpa, we developed specific microsatellite markers for this species and mapped and sampled 100 individuals in a forest plot. Two issues were addressed in particular: (i the level of genetic diversity, inbreeding and effective population size, (ii whether intrapopulation spatial genetic structure exists. Among the 14 loci developed, we only used the three that presented polymorphism to estimate the genetic parameters. Genetic diversity was low, whereby the average number of alleles per locus (A was 3.3 and observed (H0 and expected heterozygosities (He were 0.336 and 0.298, respectively. The average fixation index was significantly higher than zero (F = 0.112, suggesting inbreeding. Significant SGS was found up to 7 m and between 31 to 38 m, indicating that trees growing within these distances may be related. Estimates of the effective population size indicated that the 100 sampled trees correspond to 14 individuals that are neither related nor inbred. Our results suggest that the microsatellite markers developed in this study are suitable for studies on geneticdiversity and structure, mating systems, gene flow and SGS in this species.

  8. Spatial pattern and genetic diversity estimates are linked in stochastic models of population differentiation

    Directory of Open Access Journals (Sweden)

    Diniz-Filho José Alexandre Felizola

    2000-01-01

    Full Text Available In the present study, we used both simulations and real data set analyses to show that, under stochastic processes of population differentiation, the concepts of spatial heterogeneity and spatial pattern overlap. In these processes, the proportion of variation among and within a population (measured by G ST and 1 - G ST, respectively is correlated with the slope and intercept of a Mantel's test relating genetic and geographic distances. Beyond the conceptual interest, the inspection of the relationship between population heterogeneity and spatial pattern can be used to test departures from stochasticity in the study of population differentiation.

  9. Mapping genetic diversity of cherimoya (Annona cherimola Mill.: application of spatial analysis for conservation and use of plant genetic resources.

    Directory of Open Access Journals (Sweden)

    Maarten van Zonneveld

    Full Text Available There is a growing call for inventories that evaluate geographic patterns in diversity of plant genetic resources maintained on farm and in species' natural populations in order to enhance their use and conservation. Such evaluations are relevant for useful tropical and subtropical tree species, as many of these species are still undomesticated, or in incipient stages of domestication and local populations can offer yet-unknown traits of high value to further domestication. For many outcrossing species, such as most trees, inbreeding depression can be an issue, and genetic diversity is important to sustain local production. Diversity is also crucial for species to adapt to environmental changes. This paper explores the possibilities of incorporating molecular marker data into Geographic Information Systems (GIS to allow visualization and better understanding of spatial patterns of genetic diversity as a key input to optimize conservation and use of plant genetic resources, based on a case study of cherimoya (Annona cherimola Mill., a Neotropical fruit tree species. We present spatial analyses to (1 improve the understanding of spatial distribution of genetic diversity of cherimoya natural stands and cultivated trees in Ecuador, Bolivia and Peru based on microsatellite molecular markers (SSRs; and (2 formulate optimal conservation strategies by revealing priority areas for in situ conservation, and identifying existing diversity gaps in ex situ collections. We found high levels of allelic richness, locally common alleles and expected heterozygosity in cherimoya's putative centre of origin, southern Ecuador and northern Peru, whereas levels of diversity in southern Peru and especially in Bolivia were significantly lower. The application of GIS on a large microsatellite dataset allows a more detailed prioritization of areas for in situ conservation and targeted collection across the Andean distribution range of cherimoya than previous studies could

  10. Mapping Genetic Diversity of Cherimoya (Annona cherimola Mill.): Application of Spatial Analysis for Conservation and Use of Plant Genetic Resources

    Science.gov (United States)

    van Zonneveld, Maarten; Scheldeman, Xavier; Escribano, Pilar; Viruel, María A.; Van Damme, Patrick; Garcia, Willman; Tapia, César; Romero, José; Sigueñas, Manuel; Hormaza, José I.

    2012-01-01

    There is a growing call for inventories that evaluate geographic patterns in diversity of plant genetic resources maintained on farm and in species' natural populations in order to enhance their use and conservation. Such evaluations are relevant for useful tropical and subtropical tree species, as many of these species are still undomesticated, or in incipient stages of domestication and local populations can offer yet-unknown traits of high value to further domestication. For many outcrossing species, such as most trees, inbreeding depression can be an issue, and genetic diversity is important to sustain local production. Diversity is also crucial for species to adapt to environmental changes. This paper explores the possibilities of incorporating molecular marker data into Geographic Information Systems (GIS) to allow visualization and better understanding of spatial patterns of genetic diversity as a key input to optimize conservation and use of plant genetic resources, based on a case study of cherimoya (Annona cherimola Mill.), a Neotropical fruit tree species. We present spatial analyses to (1) improve the understanding of spatial distribution of genetic diversity of cherimoya natural stands and cultivated trees in Ecuador, Bolivia and Peru based on microsatellite molecular markers (SSRs); and (2) formulate optimal conservation strategies by revealing priority areas for in situ conservation, and identifying existing diversity gaps in ex situ collections. We found high levels of allelic richness, locally common alleles and expected heterozygosity in cherimoya's putative centre of origin, southern Ecuador and northern Peru, whereas levels of diversity in southern Peru and especially in Bolivia were significantly lower. The application of GIS on a large microsatellite dataset allows a more detailed prioritization of areas for in situ conservation and targeted collection across the Andean distribution range of cherimoya than previous studies could do, i.e. at

  11. The genetic diversity and spatial genetic structure of the Corso-Sardinian endemic Ferula arrigonii Bocchieri (Apiaceae).

    Science.gov (United States)

    Dettori, C A; Sergi, S; Tamburini, E; Bacchetta, G

    2014-09-01

    Corsica and Sardinia represent major hotspots of plant diversity in the Mediterranean area and are priority regions for conservation due to their high number of endemic plant species. However, information supporting human decision-making on the conservation of these species is still scarce, especially at the genetic level. In this work, the first assessment is reported of the species-wide spatial genetic structure and diversity of Ferula arrigonii Bocchieri, a Corso-Sardinian endemic located in a few coastal sites and on small islands. Nine populations covering the entire natural range of the species were investigated by means of AFLP (amplified fragment length polymorphism) markers. Results indicate that this species is characterised by high levels of genetic polymorphism (92% polymorphic fragments) and of genetic diversity (H(w) = 0.317) and by relatively low differentiation among populations (F(st) = 0.057). PCoA, Bayesian analysis and neighbour-joining clustering were also employed to investigate the genetic structure of this species. Three genetically distinct groups were detected, although with considerable overlap between populations.

  12. Population genetics of the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis across multiple spatial scales.

    Directory of Open Access Journals (Sweden)

    Shem D Unger

    Full Text Available Conservation genetics is a powerful tool to assess the population structure of species and provides a framework for informing management of freshwater ecosystems. As lotic habitats become fragmented, the need to assess gene flow for species of conservation management becomes a priority. The eastern hellbender (Cryptobranchus alleganiensis alleganiensis is a large, fully aquatic paedamorphic salamander. Many populations are experiencing declines throughout their geographic range, yet the genetic ramifications of these declines are currently unknown. To this end, we examined levels of genetic variation and genetic structure at both range-wide and drainage (hierarchical scales. We collected 1,203 individuals from 77 rivers throughout nine states from June 2007 to August 2011. Levels of genetic diversity were relatively high among all sampling locations. We detected significant genetic structure across populations (Fst values ranged from 0.001 between rivers within a single watershed to 0.218 between states. We identified two genetically differentiated groups at the range-wide scale: 1 the Ohio River drainage and 2 the Tennessee River drainage. An analysis of molecular variance (AMOVA based on landscape-scale sampling of basins within the Tennessee River drainage revealed the majority of genetic variation (∼94-98% occurs within rivers. Eastern hellbenders show a strong pattern of isolation by stream distance (IBSD at the drainage level. Understanding levels of genetic variation and differentiation at multiple spatial and biological scales will enable natural resource managers to make more informed decisions and plan effective conservation strategies for cryptic, lotic species.

  13. Spatial genetic structuring of baobab (Adansonia digitata, Malvaceae) in the traditional agroforestry systems of West Africa.

    Science.gov (United States)

    Kyndt, Tina; Assogbadjo, Achille E; Hardy, Olivier J; Glele Kakaï, Romain; Sinsin, Brice; Van Damme, Patrick; Gheysen, Godelieve

    2009-05-01

    This study evaluates the spatial genetic structure of baobab (Adansonia digitata) populations from West African agroforestry systems at different geographical scales using AFLP fingerprints. Eleven populations from four countries (Benin, Ghana, Burkina Faso, and Senegal) had comparable levels of genetic diversity, although the two populations in the extreme west (Senegal) had less diversity. Pairwise F(ST) ranged from 0.02 to 0.28 and increased with geographic distance, even at a regional scale. Gene pools detected by Bayesian clustering seem to be a byproduct of the isolation-by-distance pattern rather than representing actual discrete entities. The organization of genetic diversity appears to result essentially from spatially restricted gene flow, with some influences of human seed exchange. Despite the potential for relatively long-distance pollen and seed dispersal by bats within populations, statistically significant spatial genetic structuring within populations (SGS) was detected and gave a mean indirect estimate of neighborhood size of ca. 45. This study demonstrated that relatively high levels of genetic structuring are present in baobab at both large and within-population level, which was unexpected in regard to its dispersal by bats and the influence of human exchange of seeds. Implications of these results for the conservation of baobab populations are discussed.

  14. Quantification of network structural dissimilarities

    Science.gov (United States)

    Schieber, Tiago A.; Carpi, Laura; Díaz-Guilera, Albert; Pardalos, Panos M.; Masoller, Cristina; Ravetti, Martín G.

    2017-01-01

    Identifying and quantifying dissimilarities among graphs is a fundamental and challenging problem of practical importance in many fields of science. Current methods of network comparison are limited to extract only partial information or are computationally very demanding. Here we propose an efficient and precise measure for network comparison, which is based on quantifying differences among distance probability distributions extracted from the networks. Extensive experiments on synthetic and real-world networks show that this measure returns non-zero values only when the graphs are non-isomorphic. Most importantly, the measure proposed here can identify and quantify structural topological differences that have a practical impact on the information flow through the network, such as the presence or absence of critical links that connect or disconnect connected components.

  15. Spatial and genetic epidemiology of hookworm in a rural community in Uganda.

    Directory of Open Access Journals (Sweden)

    Rachel L Pullan

    Full Text Available There are remarkably few contemporary, population-based studies of intestinal nematode infection for sub-Saharan Africa. This paper presents a comprehensive epidemiological analysis of hookworm infection intensity in a rural Ugandan community. Demographic, kinship, socioeconomic and environmental data were collected for 1,803 individuals aged six months to 85 years in 341 households in a cross-sectional community survey. Hookworm infection was assessed by faecal egg count. Spatial variation in the intensity of infection was assessed using a Bayesian negative binomial spatial regression model and the proportion of variation explained by host additive genetics (heritability and common domestic environment was estimated using genetic variance component analysis. Overall, the prevalence of hookworm was 39.3%, with the majority of infections (87.7% of light intensity (spatial clustering: the range of spatial correlation was estimated to be 82 m and was reduced by a half over a distance of 19 m. Heritability of hookworm egg count was 11.2%, whilst the percentage of variance explained by unidentified domestic effects was 17.8%. In conclusion, we suggest that host genetic relatedness is not a major determinant of infection intensity in this community, with exposure-related factors playing a greater role.

  16. Multicollinearity in spatial genetics: separating the wheat from the chaff using commonality analyses.

    Science.gov (United States)

    Prunier, J G; Colyn, M; Legendre, X; Nimon, K F; Flamand, M C

    2015-01-01

    Direct gradient analyses in spatial genetics provide unique opportunities to describe the inherent complexity of genetic variation in wildlife species and are the object of many methodological developments. However, multicollinearity among explanatory variables is a systemic issue in multivariate regression analyses and is likely to cause serious difficulties in properly interpreting results of direct gradient analyses, with the risk of erroneous conclusions, misdirected research and inefficient or counterproductive conservation measures. Using simulated data sets along with linear and logistic regressions on distance matrices, we illustrate how commonality analysis (CA), a detailed variance-partitioning procedure that was recently introduced in the field of ecology, can be used to deal with nonindependence among spatial predictors. By decomposing model fit indices into unique and common (or shared) variance components, CA allows identifying the location and magnitude of multicollinearity, revealing spurious correlations and thus thoroughly improving the interpretation of multivariate regressions. Despite a few inherent limitations, especially in the case of resistance model optimization, this review highlights the great potential of CA to account for complex multicollinearity patterns in spatial genetics and identifies future applications and lines of research. We strongly urge spatial geneticists to systematically investigate commonalities when performing direct gradient analyses.

  17. Fine-scale spatial genetic dynamics over the life cycle of the tropical tree Prunus africana.

    Science.gov (United States)

    Berens, D G; Braun, C; González-Martínez, S C; Griebeler, E M; Nathan, R; Böhning-Gaese, K

    2014-11-01

    Studying fine-scale spatial genetic patterns across life stages is a powerful approach to identify ecological processes acting within tree populations. We investigated spatial genetic dynamics across five life stages in the insect-pollinated and vertebrate-dispersed tropical tree Prunus africana in Kakamega Forest, Kenya. Using six highly polymorphic microsatellite loci, we assessed genetic diversity and spatial genetic structure (SGS) from seed rain and seedlings, and different sapling stages to adult trees. We found significant SGS in all stages, potentially caused by limited seed dispersal and high recruitment rates in areas with high light availability. SGS decreased from seed and early seedling stages to older juvenile stages. Interestingly, SGS was stronger in adults than in late juveniles. The initial decrease in SGS was probably driven by both random and non-random thinning of offspring clusters during recruitment. Intergenerational variation in SGS could have been driven by variation in gene flow processes, overlapping generations in the adult stage or local selection. Our study shows that complex sequential processes during recruitment contribute to SGS of tree populations.

  18. Spatial heterogeneity as a genetic mixing mechanism in highly philopatric colonial seabirds.

    Science.gov (United States)

    Cristofari, Robin; Trucchi, Emiliano; Whittington, Jason D; Vigetta, Stéphanie; Gachot-Neveu, Hélène; Stenseth, Nils Christian; Le Maho, Yvon; Le Bohec, Céline

    2015-01-01

    How genetic diversity is maintained in philopatric colonial systems remains unclear, and understanding the dynamic balance of philopatry and dispersal at all spatial scales is essential to the study of the evolution of coloniality. In the King penguin, Aptenodytes patagonicus, return rates of post-fledging chicks to their natal sub-colony are remarkably high. Empirical studies have shown that adults return year after year to their previous breeding territories within a radius of a few meters. Yet, little reliable data are available on intra- and inter-colonial dispersal in this species. Here, we present the first fine-scale study of the genetic structure in a king penguin colony in the Crozet Archipelago. Samples were collected from individual chicks and analysed at 8 microsatellite loci. Precise geolocation data of hatching sites and selective pressures associated with habitat features were recorded for all sampling locations. We found that despite strong natal and breeding site fidelity, king penguins retain a high degree of panmixia and genetic diversity. Yet, genetic structure appears markedly heterogeneous across the colony, with higher-than-expected inbreeding levels, and local inbreeding and relatedness hotspots that overlap predicted higher-quality nesting locations. This points towards heterogeneous population structure at the sub-colony level, in which fine-scale environmental features drive local philopatric behaviour, while lower-quality patches may act as genetic mixing mechanisms at the colony level. These findings show how a lack of global genetic structuring can emerge from small-scale heterogeneity in ecological parameters, as opposed to the classical model of homogeneous dispersal. Our results also emphasize the importance of sampling design for estimation of population parameters in colonial seabirds, as at high spatial resolution, basic genetic features are shown to be location-dependent. Finally, this study stresses the importance of

  19. Spatial heterogeneity as a genetic mixing mechanism in highly philopatric colonial seabirds.

    Directory of Open Access Journals (Sweden)

    Robin Cristofari

    Full Text Available How genetic diversity is maintained in philopatric colonial systems remains unclear, and understanding the dynamic balance of philopatry and dispersal at all spatial scales is essential to the study of the evolution of coloniality. In the King penguin, Aptenodytes patagonicus, return rates of post-fledging chicks to their natal sub-colony are remarkably high. Empirical studies have shown that adults return year after year to their previous breeding territories within a radius of a few meters. Yet, little reliable data are available on intra- and inter-colonial dispersal in this species. Here, we present the first fine-scale study of the genetic structure in a king penguin colony in the Crozet Archipelago. Samples were collected from individual chicks and analysed at 8 microsatellite loci. Precise geolocation data of hatching sites and selective pressures associated with habitat features were recorded for all sampling locations. We found that despite strong natal and breeding site fidelity, king penguins retain a high degree of panmixia and genetic diversity. Yet, genetic structure appears markedly heterogeneous across the colony, with higher-than-expected inbreeding levels, and local inbreeding and relatedness hotspots that overlap predicted higher-quality nesting locations. This points towards heterogeneous population structure at the sub-colony level, in which fine-scale environmental features drive local philopatric behaviour, while lower-quality patches may act as genetic mixing mechanisms at the colony level. These findings show how a lack of global genetic structuring can emerge from small-scale heterogeneity in ecological parameters, as opposed to the classical model of homogeneous dispersal. Our results also emphasize the importance of sampling design for estimation of population parameters in colonial seabirds, as at high spatial resolution, basic genetic features are shown to be location-dependent. Finally, this study stresses the

  20. Strong spatial genetic structure reduces reproductive success in the critically endangered plant genus Pseudomisopates.

    Science.gov (United States)

    Amat, María E; Silvertown, Jonathan; Vargas, Pablo

    2013-01-01

    Clonal growth can be a double-edged sword for endangered species, because the short-term insurance against extinction may incur a longer-term hazard of creating small inbred populations with low fecundity. In the present study, we quantify the advantages and disadvantages of clonal growth regarding the fitness of the central Iberian monotypic endangered genus Pseudomisopates. Preliminary studies showed that the species is self-incompatible and exhibits extensive clonal growth with plants flowering profusely. However, seeds at many sites seemed to be unviable, and no seedlings have been observed in the field. A fully replicated nested sampling design (n = 100) was conducted to explore genetic (using seven SSR loci) and environmental factors potentially affecting seed viability, such as: 1) clonal and genetic diversity, 2) spatial genetic structure, and 3) environmental factors (shrub cover and grazing). Generalized Linear Mixed Models were fitted relating genetic and environmental variables to reproductive variables (seed viability and flower display). Our results indicate that the relatively low genotypic diversity of the population (PD = 0.23), as quantified by SSRs, and the strong spatial genetic structure observed are congruent with intense clonal growth. This clonal growth is enhanced by unfavorable environmental conditions, such as canopy closure and grazing. Under these circumstances, both flower display and mate availability decrease, thus hindering sexual reproduction. Indeed, a mixed reproductive system (clonal and sexual) to escape environmental stochasticity is crucial for the survival of Pseudomisopates, a species inhabiting a disturbance-prone ecosystem.

  1. Temporal and spatial genetic differentiation in the crab Liocarcinus depurator across the Atlantic-Mediterranean transition

    Science.gov (United States)

    Pascual, Marta; Palero, Ferran; García-Merchán, Víctor Hugo; Macpherson, Enrique; Robainas-Barcia, Aymée; Mestres, Francesc; Roda, Tania; Abelló, Pere

    2016-01-01

    Spatial genetic studies often require sampling broadly separated areas, difficult to access simultaneously. Although comparing localities surveyed at different time periods might result in spurious genetic differentiation, there is a general believe on the stability of genetic structure through time, particularly if sampled localities are isolated or very distant. By analysing spatial and temporal genetic differentiation of the portunid crab Liocarcinus depurator we assessed the contribution of historical and contemporary processes on population connectivity patterns across three main oceanographic discontinuities along the Atlantic-Mediterranean transition: Gibraltar Strait, Almeria-Oran Front and Ibiza Channel. A partial fragment of the cytochrome oxidase I gene was sequenced in 366 individuals collected from localities at both sides of each discontinuity during three time periods. Although localities showed genetic fluctuations through time, a significant gradient was detected along the coast for all sampling periods. Significant inter-annual differences identified within the Alicante area, north of the Almeria-Oran Front, were associated with shifts in the relative contribution of Atlantic and Mediterranean water masses. The persistence of a clinal pattern in the Atlantic-Mediterranean transition area together with local fluctuations suggests a complex balance of dispersal and selection. PMID:27431989

  2. Bottlenecks drive temporal and spatial genetic changes in alpine caddisfly metapopulations

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    Jokela Jukka

    2011-09-01

    Full Text Available Abstract Background Extinction and re-colonisation of local populations is common in ephemeral habitats such as temporary streams. In most cases, such population turnover leads to reduced genetic diversity within populations and increased genetic differentiation among populations due to stochastic founder events, genetic drift, and bottlenecks associated with re-colonisation. Here, we examined the spatio-temporal genetic structure of 8 alpine caddisfly populations inhabiting permanent and temporary streams from four valleys in two regions of the Swiss Alps in years before and after a major stream drying event, the European heat wave in summer 2003. Results We found that population turnover after 2003 led to a loss of allelic richness and gene diversity but not to significant changes in observed heterozygosity. Within all valleys, permanent and temporary streams in any given year were not differentiated, suggesting considerable gene flow and admixture between streams with differing hydroperiods. Large changes in allele frequencies after 2003 resulted in a substantial increase in genetic differentiation among valleys within one to two years (1-2 generations driven primarily by drift and immigration. Signatures of genetic bottlenecks were detected in all 8 populations after 2003 using the M-ratio method, but in no populations when using a heterozygosity excess method, indicating differential sensitivity of bottleneck detection methods. Conclusions We conclude that genetic differentiation among A. uncatus populations changed markedly both temporally and spatially in response to the extreme climate event in 2003. Our results highlight the magnitude of temporal population genetic changes in response to extreme events. More specifically, our results show that extreme events can cause rapid genetic divergence in metapopulations. Further studies are needed to determine if recovery from this perturbation through gradual mixing of diverged populations by

  3. Spatial genetic structure and mitochondrial DNA phylogeography of Argentinean populations of the grasshopper Dichroplus elongatus.

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    Natalia Rosetti

    Full Text Available Many grasshopper species are considered of agronomical importance because they cause damage to pastures and crops. Comprehension of pest population dynamics requires a clear understanding of the genetic diversity and spatial structure of populations. In this study we report on patterns of genetic variation in the South American grasshopper Dichroplus elongatus which is an agricultural pest of crops and forage grasses of great economic significance in Argentina. We use Direct Amplification of Minisatellite Regions (DAMD and partial sequences of the cytochrome oxydase 1 (COI mitochondrial gene to investigate intraspecific structure, demographic history and gene flow patterns in twenty Argentinean populations of this species belonging to different geographic and biogeographic regions. DAMD data suggest that, although genetic drift and migration occur within and between populations, measurable relatedness among neighbouring populations declines with distance and dispersal over distances greater than 200 km is not typical, whereas effective gene flow may occur for populations separated by less than 100 km. Landscape analysis was useful to detect genetic discontinuities associated with environmental heterogeneity reflecting the changing agroecosystem. The COI results indicate the existence of strong genetic differentiation between two groups of populations located at both margins of the Paraná River which became separated during climate oscillations of the Middle Pleistocene, suggesting a significant restriction in effective dispersion mediated by females and large scale geographic differentiation. The number of migrants between populations estimated through mitochondrial and DAMD markers suggest that gene flow is low prompting a non-homogeneous spatial structure and justifying the variation through space. Moreover, the genetic analysis of both markers allows us to conclude that males appear to disperse more than females, reducing the chance of the

  4. Dissimilarity Representations in Lung Parenchyma Classification

    DEFF Research Database (Denmark)

    Sørensen, Lauge Emil Borch Laurs; de Bruijne, Marleen

    2009-01-01

    are built in this representation. This is also the general trend in lung parenchyma classification in computed tomography (CT) images, where the features often are measures on feature histograms. Instead, we propose to build normal density based classifiers in dissimilarity representations for lung...... parenchyma classification. This allows for the classifiers to work on dissimilarities between objects, which might be a more natural way of representing lung parenchyma. In this context, dissimilarity is defined between CT regions of interest (ROI)s. ROIs are represented by their CT attenuation histogram...

  5. Genetic structure, spatial organization, and dispersal in two populations of bat-eared foxes

    OpenAIRE

    Kamler, Jan F.; Gray, Melissa M; Oh, Annie; Macdonald, David W.

    2013-01-01

    We incorporated radio-telemetry data with genetic analysis of bat-eared foxes (Otocyon megalotis) from individuals in 32 different groups to examine relatedness and spatial organization in two populations in South Africa that differed in density, home-range sizes, and group sizes. Kin clustering occurred only for female dyads in the high-density population. Relatedness was negatively correlated with distance only for female dyads in the high-density population, and for male and mixed-sex dyad...

  6. Uncertain spatial reasoning of environmental risks in GIS using genetic learning algorithms.

    Science.gov (United States)

    Shad, Rouzbeh; Shad, Arefeh

    2012-10-01

    Modeling the impact of air pollution is one of the most important approaches for managing damages to the ecosystem. This problem can be solved by sensing and modeling uncertain spatial behaviors, defining topological rules, and using inference and learning capabilities in a spatial reasoning system. Reasoning, which is the main component of such complex systems, requires that proper rules be defined through expert judgments in the knowledge-based part. Use of genetic fuzzy capabilities enables the algorithm to learn and be tuned to proper rules in a flexible manner and increases the preciseness and robustness of operations. The main objective of this paper was to design and evaluate a spatial genetic fuzzy system, with the goal of assessing environmental risks of air pollution due to oil well fires during the Persian Gulf War. Dynamic areas were extracted and monitored through images from NOAA, and the data were stored in an efficient spatial database. Initial spatial knowledge was determined by expert consideration of the application characteristics, and the inference engine was performed with genetic learning (GL) algorithms. Finally, GL (0.7 and 0.03), GL (0.7 and 0.08), GL (0.98 and 0.03), GL (0.98 and 0.08), and Cordon learning methods were evaluated with test and training data related to samples extracted from Landsat thematic mapper satellite images. Results of the implementation showed that GL (0.98, 0.03) was more precise than the other methods for learning and tuning rules in the concerned application.

  7. Population genetic structuring in Opisthorchis viverrini over various spatial scales in Thailand and Lao PDR.

    Science.gov (United States)

    Laoprom, Nonglak; Sithithaworn, Paiboon; Andrews, Ross H; Ando, Katsuhiko; Laha, Thewarach; Klinbunga, Sirawut; Webster, Joanne P; Petney, Trevor N

    2012-01-01

    Khon Kaen Province in northeast Thailand is known as a hot spot for opisthorchiasis in Southeast Asia. Preliminary allozyme and mitochondrial DNA haplotype data from within one endemic district in this Province (Ban Phai), indicated substantial genetic variability within Opisthorchis viverrini. Here, we used microsatellite DNA analyses to examine the genetic diversity and population structure of O. viverrini from four geographically close localities in Khon Kaen Province. Genotyping based on 12 microsatellite loci yielded a mean number of alleles per locus that ranged from 2.83 to 3.7 with an expected heterozygosity in Hardy-Weinberg equilibrium of 0.44-0.56. Assessment of population structure by pairwise F(ST) analysis showed inter-population differentiation (Pviverrini over a small spatial scale which is similar to that found at a larger scale. This provides the basis for the investigation of the role of parasite genetic diversity and differentiation in transmission dynamics and control of O. viverrini.

  8. Phylogeographic analysis reveals significant spatial genetic structure of Incarvillea sinensis as a product of mountain building

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    Chen Shaotian

    2012-04-01

    Full Text Available Abstract Background Incarvillea sinensis is widely distributed from Southwest China to Northeast China and in the Russian Far East. The distribution of this species was thought to be influenced by the uplift of the Qinghai-Tibet Plateau and Quaternary glaciation. To reveal the imprints of geological events on the spatial genetic structure of Incarvillea sinensis, we examined two cpDNA segments ( trnH- psbA and trnS- trnfM in 705 individuals from 47 localities. Results A total of 16 haplotypes was identified, and significant genetic differentiation was revealed (GST =0.843, NST = 0.975, P  Conclusions The results revealed that the uplift of the Qinghai-Tibet Plateau likely resulted in the significant divergence between the lineage in the eastern Qinghai-Tibet Plateau and the other one outside this area. The diverse niches in the eastern Qinghai-Tibet Plateau created a wide spectrum of habitats to accumulate and accommodate new mutations. The features of genetic diversity of populations outside the eastern Qinghai-Tibet Plateau seemed to reveal the imprints of extinction during the Glacial and the interglacial and postglacial recolonization. Our study is a typical case of the significance of the uplift of the Qinghai-Tibet Plateau and the Quaternary Glacial in spatial genetic structure of eastern Asian plants, and sheds new light on the evolution of biodiversity in the Qinghai-Tibet Plateau at the intraspecies level.

  9. Positive dissimilarity attitudes in multicultural organizations

    DEFF Research Database (Denmark)

    Lauring, Jakob; Selmer, Jan

    2012-01-01

    attitudes, namely openness to linguistic, visible and informational diversity. Contradicting our predictions, language diversity had positive associations with all variables portraying positive dissimilarity attitudes. The implications of these findings are discussed in detail. Originality/value – Few prior......Purpose – The purpose of this study is to contribute to the field of diversity studies with novel insights on how language diversity and communication frequency influence dissimilarity attitudes. Design/methodology/approach – The authors examine language diversity and communication frequency...... as group-level antecedents for positive dissimilarity attitudes by use of questionnaire responses from 489 members of academic culturally diverse departments. Findings – The results showed that communication frequency has strong positive relationships with three variables depicting positive dissimilarity...

  10. Population genetics at three spatial scales of a rare sponge living in fragmented habitats

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    Uriz Maria J

    2010-01-01

    Full Text Available Abstract Background Rare species have seldom been studied in marine habitats, mainly because it is difficult to formally assess the status of rare species, especially in patchy benthic organisms, for which samplings are often assumed to be incomplete and, thus, inappropriate for establishing the real abundance of the species. However, many marine benthic invertebrates can be considered rare, due to the fragmentation and rarity of suitable habitats. Consequently, studies on the genetic connectivity of rare species in fragmented habitats are basic for assessing their risk of extinction, especially in the context of increased habitat fragmentation by human activities. Sponges are suitable models for studying the intra- and inter-population genetic variation of rare invertebrates, as they produce lecitotrophic larvae and are often found in fragmented habitats. Results We investigated the genetic structure of a Mediterranean sponge, Scopalina lophyropoda (Schmidt, using the allelic size variation of seven specific microsatellite loci. The species can be classified as "rare" because of its strict habitat requirements, the low number of individuals per population, and the relatively small size of its distribution range. It also presents a strong patchy distribution, philopatric larval dispersal, and both sexual and asexual reproduction. Classical genetic-variance-based methods (AMOVA and differentiation statistics revealed that the genetic diversity of S. lophyropoda was structured at the three spatial scales studied: within populations, between populations of a geographic region, and between isolated geographic regions, although some stochastic gene flow might occur among populations within a region. The genetic structure followed an isolation-by-distance pattern according to the Mantel test. However, despite philopatric larval dispersal and fission events in the species, no single population showed inbreeding, and the contribution of clonality to the

  11. Ancient Humans Influenced the Current Spatial Genetic Structure of Common Walnut Populations in Asia.

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    Paola Pollegioni

    Full Text Available Common walnut (Juglans regia L is an economically important species cultivated worldwide for its wood and nuts. It is generally accepted that J. regia survived and grew spontaneously in almost completely isolated stands in its Asian native range after the Last Glacial Maximum. Despite its natural geographic isolation, J. regia evolved over many centuries under the influence of human management and exploitation. We evaluated the hypothesis that the current distribution of natural genetic resources of common walnut in Asia is, at least in part, the product of ancient anthropogenic dispersal, human cultural interactions, and afforestation. Genetic analysis combined with ethno-linguistic and historical data indicated that ancient trade routes such as the Persian Royal Road and Silk Road enabled long-distance dispersal of J. regia from Iran and Trans-Caucasus to Central Asia, and from Western to Eastern China. Ancient commerce also disrupted the local spatial genetic structure of autochthonous walnut populations between Tashkent and Samarkand (Central-Eastern Uzbekistan, where the northern and central routes of the Northern Silk Road converged. A significant association between ancient language phyla and the genetic structure of walnut populations is reported even after adjustment for geographic distances that could have affected both walnut gene flow and human commerce over the centuries. Beyond the economic importance of common walnut, our study delineates an alternative approach for understanding how the genetic resources of long-lived perennial tree species may be affected by the interaction of geography and human history.

  12. Spatial structure of morphological and neutral genetic variation in Brook Trout

    Science.gov (United States)

    Kazyak, David C.; Hilderbrand, Robert H.; Keller, Stephen R.; Colaw, Mark C.; Holloway, Amanda E.; Morgan, Raymond P.; King, Timothy L.

    2015-01-01

    Brook Trout Salvelinus fontinalis exhibit exceptional levels of life history variation, remarkable genetic variability, and fine-scale population structure. In many cases, neighboring populations may be highly differentiated from one another to an extent that is comparable with species-level distinctions in other taxa. Although genetic samples have been collected from hundreds of populations and tens of thousands of individuals, little is known about whether differentiation at neutral markers reflects phenotypic differences among Brook Trout populations. We compared differentiation in morphology and neutral molecular markers among populations from four geographically proximate locations (all within 24 km) to examine how genetic diversity covaries with morphology. We found significant differences among and/or within streams for all three morphological axes examined and identified the source stream of many individuals based on morphology (52.3% classification efficiency). Although molecular and morphological differentiation among streams ranged considerably (mean pairwise FST: 0.023–0.264; pairwise PST: 0.000–0.339), the two measures were not significantly correlated. While in some cases morphological characters appear to have diverged to a greater extent than expected by neutral genetic drift, many traits were conserved to a greater extent than were neutral genetic markers. Thus, while Brook Trout exhibit fine-scale spatial patterns in both morphology and neutral genetic diversity, these types of biological variabilities are being structured by different ecological and evolutionary processes. The relative influences of genetic drift versus selection and phenotypic plasticity in shaping morphology appear to vary among populations occupying nearby streams.

  13. Fine-scale spatial genetic structure in the frankincense tree Boswellia papyrifera (Del.) Hochst. and implications for conservation

    NARCIS (Netherlands)

    Addisalem, A.B.; Duminil, J.; Wouters, D.; Bongers, F.; Smulders, M.J.M.

    2016-01-01

    The fine-scale genetic structure and how it varies between generations depends on the spatial scale of gene dispersal and other fundamental aspects of species’ biology, such as the mating system. Such knowledge is crucial for the design of genetic conservation strategies. This is particularly

  14. Fine-scale spatial genetic structure in the frankincense tree Boswellia papyrifera (Del.) Hochst. and implications for conservation

    NARCIS (Netherlands)

    Bekele, Addisalem; Duminil, J.; Wouters, D.; Bongers, F.; Smulders, M.J.M.

    2016-01-01

    The fine-scale genetic structure and how it varies between generations depends on the spatial scale of gene dispersal and other fundamental aspects of species’ biology, such as the mating system. Such knowledge is crucial for the design of genetic conservation strategies. This is particularly rel

  15. Color-Biased Dispersal Inferred by Fine-Scale Genetic Spatial Autocorrelation in a Color Polymorphic Salamander.

    Science.gov (United States)

    Grant, Alexa H; Liebgold, Eric B

    2017-07-01

    Behavioral traits can be influenced by predation rates of color morphs, potentially leading to reduced boldness or increased escape behaviors in one color morph. The red-backed salamander, Plethodon cinereus, is a small terrestrial salamander whose color morphs have different diets and select different microhabitats, but little is known about potential differences in dispersal behaviors. We used fine-scale genetic spatial autocorrelation to examine 122 P. cinereus in a color-polymorphic population at 10 microsatellite loci in order to generate estimates of spatial genetic structure for each color morph. Differences in spatial genetic structure have been used extensively to infer within-population sex-biased dispersal but have never been used to test for dispersal differences between other groups within populations such as color morphs. We found evidence for color-biased dispersal, but not sex-biased dispersal. Striped salamanders had significant positive genetic structure in the shortest distance classes indicating philopatry. In contrast, unstriped salamanders showed a lack of spatial genetic structure at shorter distances and higher than expected genetic similarity at further distances, as expected if they are dispersing from their natal site. These results show that genetic methods typically used for sex-biased dispersal can be used to investigate differences in dispersal between morphs that vary discretely in polymorphic populations, such as color morphs. © The American Genetic Association 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  16. Spatial Genetic Structure of the Abundant and Widespread Peatmoss Sphagnum magellanicum Brid.

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    Magni Olsen Kyrkjeeide

    Full Text Available Spore-producing organisms have small dispersal units enabling them to become widespread across continents. However, barriers to gene flow and cryptic speciation may exist. The common, haploid peatmoss Sphagnum magellanicum occurs in both the Northern and Southern hemisphere, and is commonly used as a model in studies of peatland ecology and peatmoss physiology. Even though it will likely act as a rich source in functional genomics studies in years to come, surprisingly little is known about levels of genetic variability and structuring in this species. Here, we assess for the first time how genetic variation in S. magellanicum is spatially structured across its full distribution range (Northern Hemisphere and South America. The morphologically similar species S. alaskense was included for comparison. In total, 195 plants were genotyped at 15 microsatellite loci. Sequences from two plastid loci (trnG and trnL were obtained from 30 samples. Our results show that S. alaskense and almost all plants of S. magellanicum in the northern Pacific area are diploids and share the same gene pool. Haploid plants occur in South America, Europe, eastern North America, western North America, and southern Asia, and five genetically differentiated groups with different distribution ranges were found. Our results indicate that S. magellanicum consists of several distinct genetic groups, seemingly with little or no gene flow among them. Noteworthy, the geographical separation of diploids and haploids is strikingly similar to patterns found within other haploid Sphagnum species spanning the Northern Hemisphere. Our results confirm a genetic division between the Beringian and the Atlantic that seems to be a general pattern in Sphagnum taxa. The pattern of strong genetic population structuring throughout the distribution range of morphologically similar plants need to be considered in future functional genomic studies of S. magellanicum.

  17. Spatial Impairment and Memory in Genetic Disorders: Insights from Mouse Models

    Directory of Open Access Journals (Sweden)

    Sang Ah Lee

    2017-02-01

    Full Text Available Research across the cognitive and brain sciences has begun to elucidate some of the processes that guide navigation and spatial memory. Boundary geometry and featural landmarks are two distinct classes of environmental cues that have dissociable neural correlates in spatial representation and follow different patterns of learning. Consequently, spatial navigation depends both on the type of cue available and on the type of learning provided. We investigated this interaction between spatial representation and memory by administering two different tasks (working memory, reference memory using two different environmental cues (rectangular geometry, striped landmark in mouse models of human genetic disorders: Prader-Willi syndrome (PWScrm+/p− mice, n = 12 and Beta-catenin mutation (Thr653Lys-substituted mice, n = 12. This exploratory study provides suggestive evidence that these models exhibit different abilities and impairments in navigating by boundary geometry and featural landmarks, depending on the type of memory task administered. We discuss these data in light of the specific deficits in cognitive and brain function in these human syndromes and their animal model counterparts.

  18. Spatial Impairment and Memory in Genetic Disorders: Insights from Mouse Models

    Science.gov (United States)

    Lee, Sang Ah; Tucci, Valter; Vallortigara, Giorgio

    2017-01-01

    Research across the cognitive and brain sciences has begun to elucidate some of the processes that guide navigation and spatial memory. Boundary geometry and featural landmarks are two distinct classes of environmental cues that have dissociable neural correlates in spatial representation and follow different patterns of learning. Consequently, spatial navigation depends both on the type of cue available and on the type of learning provided. We investigated this interaction between spatial representation and memory by administering two different tasks (working memory, reference memory) using two different environmental cues (rectangular geometry, striped landmark) in mouse models of human genetic disorders: Prader-Willi syndrome (PWScrm+/p− mice, n = 12) and Beta-catenin mutation (Thr653Lys-substituted mice, n = 12). This exploratory study provides suggestive evidence that these models exhibit different abilities and impairments in navigating by boundary geometry and featural landmarks, depending on the type of memory task administered. We discuss these data in light of the specific deficits in cognitive and brain function in these human syndromes and their animal model counterparts. PMID:28208764

  19. Spatial genetic structure in two congeneric epiphytes with different dispersal strategies analysed by three different methods.

    Science.gov (United States)

    Snall, T; Fogelqvist, J; Ribeiro, P J; Lascoux, M

    2004-08-01

    Three different approaches were used to assess the kinship structure of two epiphytic bryophytes, Orthotrichum speciosum and O. obtusifolium, that have different dispersal strategies. The two species were sampled in a 200 ha landscape where species occurrence and host trees had been mapped previously. Local environmental conditions at sampled trees were recorded and kinship between individuals was calculated based on amplified fragment length polymorphism (AFLP)-marker data. We did not detect any association between AFLP-markers and investigated environmental conditions. In both species, significant kinship coefficients were found between individuals up to 300-350 m apart which shows that both species have a restricted dispersal range. The spatial kinship structure was detected with both autocorrelation analysis and generalized additive models (GAMs), but linear regression failed to detect any structure in O. speciosum. Although the dioecious O. obtusifolium is currently the more common species it may, none the less, due to its restricted dispersal range and reproduction mode, become threatened in the future by current silvicultural practices which enhance the distance between host trees and decrease their life span. Finally, GAMs seem most appropriate for analysing spatial genetic structure because the effects of local environmental conditions and spatial structure can be analysed simultaneously, no assumption of a parametric form between kinship coefficient and distance is required, and spatial data resolution is not lost in the arbitrary choice of distance classes characterizing autocorrelation analysis.

  20. Population genetic structuring in Opisthorchis viverrini over various spatial scales in Thailand and Lao PDR.

    Directory of Open Access Journals (Sweden)

    Nonglak Laoprom

    Full Text Available Khon Kaen Province in northeast Thailand is known as a hot spot for opisthorchiasis in Southeast Asia. Preliminary allozyme and mitochondrial DNA haplotype data from within one endemic district in this Province (Ban Phai, indicated substantial genetic variability within Opisthorchis viverrini. Here, we used microsatellite DNA analyses to examine the genetic diversity and population structure of O. viverrini from four geographically close localities in Khon Kaen Province. Genotyping based on 12 microsatellite loci yielded a mean number of alleles per locus that ranged from 2.83 to 3.7 with an expected heterozygosity in Hardy-Weinberg equilibrium of 0.44-0.56. Assessment of population structure by pairwise F(ST analysis showed inter-population differentiation (P<0.05 which indicates population substructuring between these localities. Unique alleles were found in three of four localities with the highest number observed per locality being three. Our results highlight the existence of genetic diversity and population substructuring in O. viverrini over a small spatial scale which is similar to that found at a larger scale. This provides the basis for the investigation of the role of parasite genetic diversity and differentiation in transmission dynamics and control of O. viverrini.

  1. Hierarchical spatial structure of genetically variable nucleopolyhedroviruses infecting cyclic populations of western tent caterpillars.

    Science.gov (United States)

    Cooper, Dawn; Cory, Jenny S; Myers, Judith H

    2003-04-01

    The cyclic population dynamics of western tent caterpillars, Malacosoma californicum pluviale, are associated with epizootics of a nucleopolyhedrovirus, McplNPV. Given the dynamic fluctuations in host abundance and levels of viral infection, host resistance and virus virulence might be expected to change during different phases of the cycle. As a first step in determining if McplNPV virulence and population structure change with host density, we used restriction fragment length polymorphism (RFLP) analysis to examine the genetic diversity of McplNPV infecting western tent caterpillar populations at different spatial scales. Thirteen dominant genetic variants were identified in 39 virus isolates (individual larvae) collected from field populations during one year of low host density, and another distinct variant was discovered among nine additional isolates in two subsequent years of declining host density. The distribution of these genetic variants was not random and indicated that the McplNPV population was structured at several spatial levels. A high proportion of the variation could be explained by family grouping, which suggested that isolates collected within a family were more likely to be the same than isolates compared among populations. Additionally, virus variants from within populations (sites) were more likely to be the same than isolates collected from tent caterpillar populations on different islands. This may indicate that there is limited mixing of virus among tent caterpillar families and populations when host population density is low. Thus there is potential for the virus to become locally adapted to western tent caterpillar populations in different sites. However, no dominant genotype was observed at any site. Whether and how selection acts on the genetically diverse nucleopolyhedrovirus populations as host density changes will be investigated over the next cycle of tent caterpillar populations.

  2. Selection and Penalty Strategies for Genetic Algorithms Designed to Solve Spatial Forest Planning Problems

    Directory of Open Access Journals (Sweden)

    Matthew P. Thompson

    2009-01-01

    Full Text Available Genetic algorithms (GAs have demonstrated success in solving spatial forest planning problems. We present an adaptive GA that incorporates population-level statistics to dynamically update penalty functions, a process analogous to strategic oscillation from the tabu search literature. We also explore performance of various selection strategies. The GA identified feasible solutions within 96%, 98%, and 93% of a nonspatial relaxed upper bound calculated for landscapes of 100, 500, and 1000 units, respectively. The problem solved includes forest structure constraints limiting harvest opening sizes and requiring minimally sized patches of mature forest. Results suggest that the dynamic penalty strategy is superior to the more standard static penalty implementation. Results also suggest that tournament selection can be superior to the more standard implementation of proportional selection for smaller problems, but becomes susceptible to premature convergence as problem size increases. It is therefore important to balance selection pressure with appropriate disruption. We conclude that integrating intelligent search strategies into the context of genetic algorithms can yield improvements and should be investigated for future use in spatial planning with ecological goals.

  3. Fine-scale spatial genetic structure and clonal distribution of the cold-water coral Lophelia pertusa

    Science.gov (United States)

    Dahl, M. P.; Pereyra, R. T.; Lundälv, T.; André, C.

    2012-12-01

    Determining the spatial genetic structure within and among cold-water coral populations is crucial to understanding population dynamics, assessing the resilience of cold-water coral communities and estimating genetic effects of habitat fragmentation for conservation. The spatial distribution of genetic diversity in natural populations depends on the species' mode of reproduction, and coral species often have a mixed strategy of sexual and asexual reproduction. We describe the clonal architecture of a cold-water coral reef and the fine-scale population genetic structure (Asexual reproduction was found to be a highly important mode of reproduction for L. pertusa: 35 genetic individuals were found on the largest reef, with the largest clone covering an area of nearly 300 m2.

  4. Distribution and fine-scale spatial-genetic structure in British wild cherry (Prunus avium L.).

    Science.gov (United States)

    Vaughan, S P; Cottrell, J E; Moodley, D J; Connolly, T; Russell, K

    2007-05-01

    Insights into the within-population spatial-genetic structure (SGS) of forest tree species, where little is known regarding seed and pollen dispersal patterns, enhance understanding of their ecology and provide information of value in conservation and breeding. This study utilised 13 polymorphic simple sequence repeat loci to investigate the impact of asexual recruitment, management regime and tree size on the development of SGS in wild cherry (Prunus avium L). Only 246 genotypes were identified in the 551 trees sampled, reflecting significant levels of clonal reproduction in both managed and unmanaged populations. Naturally regenerated wild cherry was spatially aggregated under both management regimes. However, in the managed population, sexually derived trees accounted for a greater proportion of the smaller size classes, whereas vegetatively produced trees dominated the smaller size classes in the unmanaged population. High overall SGS values (Sp 0.030-Sp 0.045) were observed when considering only sexually derived genets and kinship coefficients were significant up to the 120 m distance class for both populations. The inclusion of clonal ramets in the analysis significantly increased the overall SGS (Sp 0.089-Sp 0.119) as well as kinship coefficients in the 40-80 m distance classes, illustrating the dramatic impact of vegetative propagation on SGS in this species. Increased spatial aggregation and regeneration appeared to be concomitant with increased SGS in the 40 m distance class in the unmanaged population. Neighbourhood size estimates were relatively small for both populations and kinship coefficients were found to decline with distance under both management regimes, suggesting that common mechanisms may restrict gene dispersal in wild cherry.

  5. Genetic structure, spatial organization, and dispersal in two populations of bat-eared foxes.

    Science.gov (United States)

    Kamler, Jan F; Gray, Melissa M; Oh, Annie; Macdonald, David W

    2013-09-01

    We incorporated radio-telemetry data with genetic analysis of bat-eared foxes (Otocyon megalotis) from individuals in 32 different groups to examine relatedness and spatial organization in two populations in South Africa that differed in density, home-range sizes, and group sizes. Kin clustering occurred only for female dyads in the high-density population. Relatedness was negatively correlated with distance only for female dyads in the high-density population, and for male and mixed-sex dyads in the low-density population. Home-range overlap of neighboring female dyads was significantly greater in the high compared to low-density population, whereas overlap within other dyads was similar between populations. Amount of home-range overlap between neighbors was positively correlated with genetic relatedness for all dyad-site combinations, except for female and male dyads in the low-density population. Foxes from all age and sex classes dispersed, although females (mostly adults) dispersed farther than males. Yearlings dispersed later in the high-density population, and overall exhibited a male-biased dispersal pattern. Our results indicated that genetic structure within populations of bat-eared foxes was sex-biased, and was interrelated to density and group sizes, as well as sex-biases in philopatry and dispersal distances. We conclude that a combination of male-biased dispersal rates, adult dispersals, and sex-biased dispersal distances likely helped to facilitate inbreeding avoidance in this evolutionarily unique species of Canidae.

  6. Regulatory Status of Dissimilar Metal Weld (DMW)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K. C.; Hong, J. K.; Shin, H. S.; Kang, S. S.; Song, M. H.; Chung, H. D. [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2009-05-15

    In this technical article, the regulatory status for Dissimilar Metal Water (DMW) was discussed. In order to decide the regulatory direction of DMW, the USA's accidents of PWSCC and their regulatory directions were reviewed. By reviewing their experiences, the Korean DMW regulation approach was decided.

  7. Consequences of frugivore-mediated seed dispersal for the spatial and genetic structures of a neotropical palm.

    Science.gov (United States)

    Choo, Juanita; Juenger, T E; Simpson, B B

    2012-02-01

    The idiosyncratic behaviours of seed dispersers are important contributors to plant spatial associations and genetic structures. In this study, we used a combination of field, molecular and spatial studies to examine the connections between seed dispersal and the spatial and genetic structures of a dominant neotropical palm Attalea phalerata. Field observation and genetic parentage analysis both indicated that the majority of A. phalerata seeds were dispersed locally over short distances (10 m) from maternal palms. Seedlings were also spatially aggregated with juveniles. These patterns are probably associated with the dispersal of seeds by rodents and the survival of recruits at specific microsites or neighbourhoods over successive fruiting periods. Our cross-cohort analyses found palms in older cohorts and cohort pairs were associated with a lower proportion of offspring and sibling neighbours and exhibited weaker spatial and genetic structures. Such patterns are consistent with increased distance- and density-dependent mortality over time among palms dispersed near maternal palms or siblings. The integrative approaches used for this study allowed us to infer the importance of seed dispersal activities in maintaining the aggregated distribution and significant genetic structures among A. phalerata palms. We further conclude that distance- and density-dependent mortality is a key postdispersal process regulating this palm population.

  8. Hanseniaspora uvarum from winemaking environments show spatial and temporal genetic clustering

    Directory of Open Access Journals (Sweden)

    Warren eAlbertin

    2016-01-01

    Full Text Available Hanseniaspora uvarum is one of the most abundant yeast species found on grapes and in grape must, at least before the onset of alcoholic fermentation which is usually performed by Saccharomyces species. The aim of this study was to characterise the genetic and phenotypic variability within the H. uvarum species. One hundred and fifteen strains isolated from winemaking environments in different geographical origins were analysed using 11 microsatellite markers and a subset of 47 strains were analysed by AFLP. H. uvarum isolates clustered mainly on the basis of their geographical localisation as revealed by microsatellites. In addition, a strong clustering based on year of isolation was evidenced, indicating that the genetic diversity of Hanseniaspora uvarum isolates was related to both spatial and temporal variations. Conversely, clustering analysis based on AFLP data provided a different picture with groups showing no particular characteristics, but provided higher strain discrimination. This result indicated that AFLP approaches are inadequate to establish the genetic relationship between individuals, but allowed good strain discrimination. At the phenotypic level, several extracellular enzymatic activities of enological relevance (pectinase, chitinase, protease, β-glucosidase were measured but showed low diversity. The impact of environmental factors of enological interest (temperature, anaerobia and copper addition on growth was also assessed and showed poor variation. Altogether, this work provided both new analytical tool (microsatellites and new insights into the genetic and phenotypic diversity of H. uvarum, a yeast species that has previously been identified as a potential candidate for co-inoculation in grape must, but whose intraspecific variability had never been fully assessed.

  9. Greater Genetic Diversity in Spatially Restricted Coral Reef Fishes Suggests Secondary Contact among Differentiated Lineages

    Directory of Open Access Journals (Sweden)

    M. Julian Caley

    2011-09-01

    Full Text Available The maintenance of genetic diversity is a central goal of conservation. It is the raw material for evolutionary change and if lost, can accelerate extinction of species. According to theory, total genetic diversity should be less in species with restricted ranges and in populations on the margins of distributional ranges, making such species or populations more vulnerable to environmental perturbations. Using mtDNA and nuclear Inter Simple Sequence Repeat (ISSR data we investigated how the genetic diversity and structure of three con-generic species pairs of coral reef fishes (Pomacentridae was related to species’ range size and position of populations within these ranges. Estimates of genetic structure did not differ significantly among species, but mtDNA and nucDNA genetic diversities were up to 10 times greater in spatially restricted species compared to their widespread congeners. In two of the three species pairs, the distribution of genetic variation indicated secondary contact among differentiated lineages in the spatially restricted species. In contrast, the widespread species displayed a typical signature of population expansion suggesting recent genetic bottlenecks, possibly associated with the (re colonization of the Great Barrier Reef. These results indicate that historical processes, involving hybridization and founder effects, possibly associated with Pleistocene sea level fluctuations, have differentially influenced the widespread and spatially restricted coral reef damselfish species studied here.

  10. Serial founder effects during range expansion: a spatial analog of genetic drift.

    Science.gov (United States)

    Slatkin, Montgomery; Excoffier, Laurent

    2012-05-01

    Range expansions cause a series of founder events. We show that, in a one-dimensional habitat, these founder events are the spatial analog of genetic drift in a randomly mating population. The spatial series of allele frequencies created by successive founder events is equivalent to the time series of allele frequencies in a population of effective size ke, the effective number of founders. We derive an expression for ke in a discrete-population model that allows for local population growth and migration among established populations. If there is selection, the net effect is determined approximately by the product of the selection coefficients and the number of generations between successive founding events. We use the model of a single population to compute analytically several quantities for an allele present in the source population: (i) the probability that it survives the series of colonization events, (ii) the probability that it reaches a specified threshold frequency in the last population, and (iii) the mean and variance of the frequencies in each population. We show that the analytic theory provides a good approximation to simulation results. A consequence of our approximation is that the average heterozygosity of neutral alleles decreases by a factor of 1-1/(2ke) in each new population. Therefore, the population genetic consequences of surfing can be predicted approximately by the effective number of founders and the effective selection coefficients, even in the presence of migration among populations. We also show that our analytic results are applicable to a model of range expansion in a continuously distributed population.

  11. Image dissimilarity-based quantification of lung disease from CT

    DEFF Research Database (Denmark)

    Sørensen, Lauge; Loog, Marco; Lo, Pechin

    2010-01-01

    In this paper, we propose to classify medical images using dissimilarities computed between collections of regions of interest. The images are mapped into a dissimilarity space using an image dissimilarity measure, and a standard vector space-based classifier is applied in this space. The classif...

  12. Microsatellite genetic diversity and fine-scale spatial genetic structure within a natural stand of Liriodendron chinense (Magnoliaceae in Lanmushan, Duyun City, Guizhou Province

    Directory of Open Access Journals (Sweden)

    Aihong Yang

    2014-05-01

    Full Text Available The Chinese tulip tree (Liriodendron chinense, an endangered species scattered throughout subtropical China and northern Vietnam, suffers from severe habitat fragmentation. Understanding the genetic diversity and fine-scale spatial genetic structure (SGS of fragmented populations is critical for developing successful conservation strategies for endangered species. In this study, we investigated the population genetic diversity and fine-scale spatial genetic structure in a wild, fragmented population of L. chinense using 13 polymorphic microsatellite loci. No significant differences in genetic diversity were found among habitat fragments or age classes (P > 0.05. Two genetically heterogeneous subpopulations were revealed through Bayesian assignment analysis and Principal Coordinates Analysis (PCoA. Significant SGS was found within the whole population within 200 m, while weak spatial aggregation of related individuals in the two subpopulations was found within 20 m. SGS intensity was weak in this population (Sp = 0.0090, and it was stronger in the village subpopulation (Sp = 0.0067 than in the hill subpopulation (Sp = 0.0053. Liriodendron chinense is a predominantly outcrossing tree and its winged seeds are wind-dispersed, a fact that may reduce SGS intensity in the species. Furthermore, low population density and flat hypsography also likely influence the SGS of L. chinense. The presence of significant heterozygote deficiency in the population (FIS = 0.099, P < 0.01 suggests a genetic signal of habitat fragmentation. Therefore, measures for promoting pollen flow should be taken for in situ conservation. For ex situ conservation, individuals should be sampled at 20 m apart to efficiently capture genetic diversity of wild populations.

  13. Spatial genetic structure of Salvia japonica Thunb. population (Labiatae in Botanical Garden of Osaka City University, Kisaichi, Osaka Prefecture, Japan

    Directory of Open Access Journals (Sweden)

    SUDARMONO

    2005-10-01

    Full Text Available Salvia japonica Thunb. (Japan: Aki-no-Tamurasou was a perennial herb, protandry insect-pollinated, and self-incompatible with water-flow dispersed seed. We used allozyme loci to know genetic structure of a S. japonica population. We examined spatial autocorrelation of individuals within five distance class with Moran`s I statistics. The area of observation was in plot 5x5 m2 in Botanical Garden of Osaka City University, Kisaichi, Katano, Osaka Prefecture. The 8 loci examined were polymorphic, namely Aat-1, Aat-2, Pgi, Mnr, Pgm-1, Pgm-2, Idh, and 6-Pgd. Low levels of genetic diversity were found for 29 individuals. Ninety-two percent cases for all of distance class were similar and only 8% (8 of 105 cases were significant differences. This result indicated that the spatial genetic distributions in all of distance classes were all similar and no spatial autocorrelation of genotypes. Only in distance class 2 had one significantly positive cases (0.15 in Pgm-1c, indicating that spatial genetic structure in the study population was weak at most. In the other word that spatial pattern of the individuals within S. japonica population was random. Overall of the result was indicating that genotype among individuals of S. japonica changed distantly and tended to isolation in distance by seed dispersed.

  14. CDFISH: an individual-based, spatially-explicit, landscape genetics simulator for aquatic species in complex riverscapes

    Science.gov (United States)

    Erin L. Landguth,; Muhlfeld, Clint C.; Luikart, Gordon

    2012-01-01

    We introduce Cost Distance FISHeries (CDFISH), a simulator of population genetics and connectivity in complex riverscapes for a wide range of environmental scenarios of aquatic organisms. The spatially-explicit program implements individual-based genetic modeling with Mendelian inheritance and k-allele mutation on a riverscape with resistance to movement. The program simulates individuals in subpopulations through time employing user-defined functions of individual migration, reproduction, mortality, and dispersal through straying on a continuous resistance surface.

  15. Spatial and Temporal Population Genetics at Deep-Sea Hydrothermal Vents Along the East Pacific Rise and Galapagos Rift

    Science.gov (United States)

    2008-09-01

    Rift id’s population density and mean dispersal distances (O. Puebla , OSM 2008). Models of dispersal in all marine habitats should integrate larval...Inference of population structure using multilocus genotype data. Genetics, 155, 945-959. Puebla O (2008) Genetic signature of the spatial scale...in concert with other population processes (O. Puebla , OSM 2008; North et al. 2008; also see Denny et al. 2004 for discussion of scale in ecology

  16. Genetic differentiation across multiple spatial scales of the Red Sea of the corals Stylophora pistillata and Pocillopora verrucosa

    KAUST Repository

    Monroe, Alison

    2015-12-01

    Observing populations at different spatial scales gives greater insight into the specific processes driving genetic differentiation and population structure. Here we determined population connectivity across multiple spatial scales in the Red Sea to determine the population structures of two reef building corals Stylophora pistillata and Pocillopora verrucosa. The Red sea is a 2,250 km long body of water with extremely variable latitudinal environmental gradients. Mitochondrial and microsatellite markers were used to determine distinct lineages and to look for genetic differentiation among sampling sites. No distinctive population structure across the latitudinal gradient was discovered within this study suggesting a phenotypic plasticity of both these species to various environments. Stylophora pistillata displayed a heterogeneous distribution of three distinct genetic populations on both a fine and large scale. Fst, Gst, and Dest were all significant (p-value<0.05) and showed moderate genetic differentiation between all sampling sites. However this seems to be byproduct of the heterogeneous distribution, as no distinct genetic population breaks were found. Stylophora pistillata showed greater population structure on a fine scale suggesting genetic selection based on fine scale environmental variations. However, further environmental and oceanographic data is needed to make more inferences on this structure at small spatial scales. This study highlights the deficits of knowledge of both the Red Sea and coral plasticity in regards to local environmental conditions.

  17. Genetic Geostatistical Framework for Spatial Analysis of Fine-Scale Genetic Heterogeneity in Modern Populations: Results from the KORA Study

    OpenAIRE

    Diaz-Lacava, A. N.; Walier, M; D. Holler; Steffens, M; Gieger, C; C. Furlanello; Lamina, C; Wichmann, H E; Becker, T

    2015-01-01

    Aiming to investigate fine-scale patterns of genetic heterogeneity in modern humans from a geographic perspective, a genetic geostatistical approach framed within a geographic information system is presented. A sample collected for prospective studies in a small area of southern Germany was analyzed. None indication of genetic heterogeneity was detected in previous analysis. Socio-demographic and genotypic data of German citizens were analyzed (212 SNPs; n = 728). Genetic heterogeneity was ev...

  18. Genetic Diversity and Spatial Genetic Structure of an Epiphytic Bromeliad in Costa Rican Montane Secondary Forest Patches

    NARCIS (Netherlands)

    Cascante-Marín, A.; Oostermeijer, G.; Wolf, J.; Fuchs, E.J.

    2014-01-01

    Information on genetic variation and its distribution in tropical plant populations relies mainly on studies of ground-rooted species, while genetic information of epiphytic plants is still limited. Particularly, the effect of forest successional condition on genetic diversity and structure of

  19. The effect of sex-biased dispersal on opposite-sexed spatial genetic structure and inbreeding risk.

    Science.gov (United States)

    Blyton, Michaela D J; Banks, Sam C; Peakall, Rod

    2015-04-01

    Natal sex-biased dispersal has long been thought to reduce the risk of inbreeding by spatially separating opposite-sexed kin. Yet, comprehensive and quantitative evaluations of this hypothesis are lacking. In this study, we quantified the effectiveness of sex-biased dispersal as an inbreeding avoidance strategy by combining spatially explicit simulations and empirical data. We quantified the extent of kin clustering by measuring the degree of spatial autocorrelation among opposite-sexed individuals (FM structure). This allowed us to systematically explore how the extent of sex-biased dispersal, generational overlap, and mate searching distance, influenced both kin clustering, and the resulting inbreeding in the absence of complementary inbreeding avoidance strategies. Simulations revealed that when sex-biased dispersal was limited, positive FM genetic structure developed quickly and increased as the mate searching distance decreased or as generational overlap increased. Interestingly, complete long-range sex-biased dispersal did not prevent the development of FM genetic structure when generations overlapped. We found a very strong correlation between FM genetic structure and both FIS under random mating, and pedigree-based measures of inbreeding. Thus, we show that the detection of FM genetic structure can be a strong indicator of inbreeding risk. Empirical data for two species with different life history strategies yielded patterns congruent with our simulations. Our study illustrates a new application of spatial genetic autocorrelation analysis that offers a framework for quantifying the risk of inbreeding that is easily extendable to other species. Furthermore, our findings provide other researchers with a context for interpreting observed patterns of opposite-sexed spatial genetic structure.

  20. Understanding the Spatial Scale of Genetic Connectivity at Sea: Unique Insights from a Land Fish and a Meta-Analysis.

    Directory of Open Access Journals (Sweden)

    Georgina M Cooke

    Full Text Available Quantifying the spatial scale of population connectivity is important for understanding the evolutionary potential of ecologically divergent populations and for designing conservation strategies to preserve those populations. For marine organisms like fish, the spatial scale of connectivity is generally set by a pelagic larval phase. This has complicated past estimates of connectivity because detailed information on larval movements are difficult to obtain. Genetic approaches provide a tractable alternative and have the added benefit of estimating directly the reproductive isolation of populations. In this study, we leveraged empirical estimates of genetic differentiation among populations with simulations and a meta-analysis to provide a general estimate of the spatial scale of genetic connectivity in marine environments. We used neutral genetic markers to first quantify the genetic differentiation of ecologically-isolated adult populations of a land dwelling fish, the Pacific leaping blenny (Alticus arnoldorum, where marine larval dispersal is the only probable means of connectivity among populations. We then compared these estimates to simulations of a range of marine dispersal scenarios and to collated FST and distance data from the literature for marine fish across diverse spatial scales. We found genetic connectivity at sea was extensive among marine populations and in the case of A. arnoldorum, apparently little affected by the presence of ecological barriers. We estimated that ~5000 km (with broad confidence intervals ranging from 810-11,692 km was the spatial scale at which evolutionarily meaningful barriers to gene flow start to occur at sea, although substantially shorter distances are also possible for some taxa. In general, however, such a large estimate of connectivity has important implications for the evolutionary and conservation potential of many marine fish communities.

  1. PARADOX SOLUTION ON ELASTIC WEDGE DISSIMILAR MATERIALS

    Institute of Scientific and Technical Information of China (English)

    姚伟岸; 张兵茹

    2003-01-01

    According to the Hellinger-Reissner variational principle and introducing proper transformation of variables, the problem on elastic wedge dissimilar materials can be led to Hamiltonian system, so the solution of the problem can be got by employing the separation of variables method and symplectic eigenfunction expansion under symplectic space, which consists of original variables and their dual variables. The eigenvalue - 1 is a special one of all symplectic eigenvalue for Hamiltonian system in polar coordinate. In general, the eigenvalue - is a single eigenvalue, and the classical solution of an elastic wedge dissimilar materials subjected to a unit concentrated couple at the vertex is got directly by solving the eigenfunction vector for eigenvalue - 1 . But the eigenvalue - 1 becomes a double eigenvalue when the vertex angles and modulus of the materials satisfy certain definite relationships and the classical solution for the stress distribution becomes infinite at this moment, that is, the paradox should occur. Here the Jordan form eigenfunction vector for eigenvalue - 1 exists, and solution of the paradox on elastic wedge dissimilar materials subjected to a unit concentrated couple at the vertex is obtained directly by solving this special Jordan form eigenfunction. The result shows again that the solutions of the special paradox on elastic wedge in the classical theory of elasticity are just Jordan form solutions in symplectic space under Hamiltonian system.

  2. The spatial scale of genetic subdivision in populations of Ifremeria nautilei, a hydrothermal-vent gastropod from the southwest Pacific

    Directory of Open Access Journals (Sweden)

    Thaler Andrew D

    2011-12-01

    Full Text Available Abstract Background Deep-sea hydrothermal vents provide patchy, ephemeral habitats for specialized communities of animals that depend on chemoautotrophic primary production. Unlike eastern Pacific hydrothermal vents, where population structure has been studied at large (thousands of kilometres and small (hundreds of meters spatial scales, population structure of western Pacific vents has received limited attention. This study addresses the scale at which genetic differentiation occurs among populations of a western Pacific vent-restricted gastropod, Ifremeria nautilei. Results We used mitochondrial and DNA microsatellite markers to infer patterns of gene flow and population subdivision. A nested sampling strategy was employed to compare genetic diversity in discrete patches of Ifremeria nautilei separated by a few meters within a single vent field to distances as great as several thousand kilometres between back-arc basins that encompass the known range of the species. No genetic subdivisions were detected among patches, mounds, or sites within Manus Basin. Although I. nautilei from Lau and North Fiji Basins (~1000 km apart also exhibited no evidence for genetic subdivision, these populations were genetically distinct from the Manus Basin population. Conclusions An unknown process that restricts contemporary gene flow isolates the Manus Basin population of Ifremeria nautilei from widespread populations that occupy the North Fiji and Lau Basins. A robust understanding of the genetic structure of hydrothermal vent populations at multiple spatial scales defines natural conservation units and can help minimize loss of genetic diversity in situations where human activities are proposed and managed.

  3. The female perspective of mating in A. femoralis, a territorial frog with paternal care--a spatial and genetic analysis.

    Directory of Open Access Journals (Sweden)

    Eva Ringler

    Full Text Available The adaptive significance of sequential polyandry is a challenging question in evolutionary and behavioral biology. Costs and benefits of different mating patterns are shaped by the spatial distribution of individuals and by genetic parameters such as the pairwise relatedness between potential mating partners. Thus, females should become less choosy as costs of mating and searching for mates increase. We used parentage assignments to investigate spatial and genetic patterns of mating across a natural population of the Neotropical frog Allobates femoralis, a species characterized by male territoriality and care and female iteroparity. There was no correlation between genetic and spatial distances between adult individuals across the population. In 72% of cases, females mated with males available within a radius of 20 m. Mean pairwise relatedness coefficients of successful reproducers did not differ from random mating but had a lower variance than expected by chance, suggesting maximal reproductive output at intermediate genetic divergence. We also found evidence for selection in favor of more heterozygous individuals between the embryo and adult stage. The level of sequential polyandry significantly increased with the number of spatially available males. Females that had more candidate males also produced more adult progeny. We hypothesize that the benefits associated with female multiple mating outweigh the costs of in- and outbreeding depression, and consequently precluded the evolution of 'choosy' mate selection in this species.

  4. The female perspective of mating in A. femoralis, a territorial frog with paternal care--a spatial and genetic analysis.

    Science.gov (United States)

    Ringler, Eva; Ringler, Max; Jehle, Robert; Hödl, Walter

    2012-01-01

    The adaptive significance of sequential polyandry is a challenging question in evolutionary and behavioral biology. Costs and benefits of different mating patterns are shaped by the spatial distribution of individuals and by genetic parameters such as the pairwise relatedness between potential mating partners. Thus, females should become less choosy as costs of mating and searching for mates increase. We used parentage assignments to investigate spatial and genetic patterns of mating across a natural population of the Neotropical frog Allobates femoralis, a species characterized by male territoriality and care and female iteroparity. There was no correlation between genetic and spatial distances between adult individuals across the population. In 72% of cases, females mated with males available within a radius of 20 m. Mean pairwise relatedness coefficients of successful reproducers did not differ from random mating but had a lower variance than expected by chance, suggesting maximal reproductive output at intermediate genetic divergence. We also found evidence for selection in favor of more heterozygous individuals between the embryo and adult stage. The level of sequential polyandry significantly increased with the number of spatially available males. Females that had more candidate males also produced more adult progeny. We hypothesize that the benefits associated with female multiple mating outweigh the costs of in- and outbreeding depression, and consequently precluded the evolution of 'choosy' mate selection in this species.

  5. Fine-scale spatial genetic structure of a fungal parasite of coffee scale insects.

    Science.gov (United States)

    Jackson, Doug; Zemenick, Ash T; Malloure, Brian; Quandt, C Alisha; James, Timothy Y

    2016-09-01

    The entomopathogenic fungus Lecanicillium lecanii persists in a highly dynamic network of habitat patches (i.e., a metapopulation) formed by its primary host, the green coffee scale Coccus viridis. Lecanicillium lecanii is an important biological control of both C. viridis and the coffee rust, Hemileia vastatrix. Successfully managing this biocontrol agent will depend on an increased understanding of the characteristics of its dispersal, as migration between occupied and unoccupied patches is essential for the persistence of this metapopulation. In the present study, we employ a population genetics approach, and show that in our study system, a coffee farm in the Soconusco region of southern Mexico, L. lecanii is characterized by clear spatial genetic structure among plots within the farm but a lack of apparent structure at smaller scales. This is consistent with dispersal dominated by highly localized transport, such as by insects or rain splash, and less dependence on longer distance dispersal such as wind transport. The study site was dominated by a few multi-locus microsatellite genotypes, and their identities and large-scale locations persist across both study years, suggesting that local epizootics (outbreaks) are initiated each wet season by residual propagules from the previous wet season, and not by long-distance transport of propagules from other sites. The index of association, a measure of linkage disequilibrium, indicates that epizootics are primarily driven by asexual, clonal reproduction, which is consistent with the apparent lack of a teleomorph in the study site and the presence of only a single mating type across the site (MAT-1-2-1). Although the same predominant clonal genotypes were found across years, a drastic difference in genotypic diversity was witnessed across two sites between the two years, suggesting that interclonal selection was occurring. In light of the dispersal limitation of L. lecanii, spatial structure may be an essential axis

  6. Fragmentation reduces regional-scale spatial genetic structure in a wind-pollinated tree because genetic barriers are removed

    Science.gov (United States)

    Wang, Rong; Compton, Stephen G; Shi, Yi-Su; Chen, Xiao-Yong

    2012-01-01

    Gene flow strongly influences the regional genetic structuring of plant populations. Seed and pollen dispersal patterns can respond differently to the increased isolation resulting from habitat fragmentation, with unpredictable consequences for gene flow and population structuring. In a recently fragmented landscape we compared the pre- and post-fragmentation genetic structure of populations of a tree species where pollen and seed dispersal respond differentially to forest fragmentation generated by flooding. Castanopsis sclerophylla is wind-pollinated, with seeds that are dispersed by gravity and rodents. Using microsatellites, we found no significant difference in genetic diversity between pre- and post-fragmentation cohorts. Significant genetic structure was observed in pre-fragmentation cohorts, due to an unknown genetic barrier that had isolated one small population. Among post-fragmentation cohorts this genetic barrier had disappeared and genetic structure was significantly weakened. The strengths of genetic structuring were at a similar level in both cohorts, suggesting that overall gene flow of C. sclerophylla has been unchanged by fragmentation at the regional scale. Fragmentation has blocked seed dispersal among habitats, but this appears to have been compensated for by enhanced pollen dispersal, as indicated by the disappearance of a genetic barrier, probably as a result of increased wind speeds and easier pollen movement over water. Extensive pollen flow can counteract some negative effects of fragmentation and assist the long-term persistence of small remnant populations. PMID:23139883

  7. Inferring recruitment history from spatial genetic structure within populations of the colonizing tree Albizia julibrissin (Fabaceae).

    Science.gov (United States)

    Pardini, E A; Hamrick, J L

    2008-06-01

    Comparative analyses of spatial genetic structure (SGS) among species, populations, or cohorts give insight into the genetic consequences of seed dispersal in plants. We analysed SGS of a weedy tree in populations with known and unknown recruitment histories to first establish patterns in populations with single vs. multiple founders, and then to infer possible recruitment scenarios in populations with unknown histories. We analysed SGS in six populations of the colonizing tree Albizia julibrissin Durazz. (Fabaceae) in Athens, Georgia. Study sites included two large populations with multiple, known founders, two small populations with a single, known founder, and two large populations with unknown recruitment histories. Eleven allozyme loci were used to genotype 1385 individuals. Insights about the effects of colonization history from the SGS analyses were obtained from correlograms and Sp statistics. Distinct differences in patterns of SGS were identified between populations with multiple founders vs. a single founder. We observed significant, positive SGS, which decayed with increasing distance in the populations with multiple colonists, but little to no SGS in populations founded by one colonist. Because relatedness among individuals is estimated relative to a local reference population, which usually consists of those individuals sampled in the study population, SGS in populations with high background relatedness, such as those with a single founder, may be obscured. We performed additional analyses using a regional reference population and, in populations with a single founder, detected significant, positive SGS at all distances, indicating that these populations consist of highly related descendants and receive little seed immigration. Subsequent analyses of SGS in size cohorts in the four large study populations showed significant SGS in both juveniles and adults, probably because of a relative lack of intraspecific demographic thinning. SGS in populations

  8. Contrasting impacts of pollen and seed dispersal on spatial genetic structure in the bird-pollinated Banksia hookeriana.

    Science.gov (United States)

    Krauss, S L; He, T; Barrett, L G; Lamont, B B; Enright, N J; Miller, B P; Hanley, M E

    2009-03-01

    In plants, pollen- and seed-dispersal distributions are characteristically leptokurtic, with significant consequences for spatial genetic structure and nearest-neighbour mating. However, most studies to date have been on wind- or insect-pollinated species. Here, we assigned paternity to quantify effective pollen dispersal over 9 years of mating, contrasted this to seed dispersal and examined their effects on fine-scale spatial genetic structure, within the bird-pollinated shrub Banksia hookeriana (Proteaceae). We used 163 polymorphic amplified fragment length polymorphism markers to assess genetic structure and pollen dispersal in a spatially discrete population of 112 plants covering 0.56 ha. Spatial autocorrelation analysis detected spatial genetic structure in the smallest distance class of 0-5 m (r=0.025), with no significant structure beyond 8 m. Experimentally quantified seed-dispersal distances for 337 seedlings showed a leptokurtic distribution around a median of 5 m, reaching a distance of 36 m. In marked contrast, patterns of pollen dispersal for 274 seeds departed strikingly from typical near-neighbour pollination, with a distribution largely corresponding to the spatial distribution of plants. We found very high multiple paternity, very low correlated paternity and an equal probability of siring for the 50 closest potential mates. Extensive pollen carryover was demonstrated by multiple siring in 83 of 86 (96.5%) two-seeded fruits. Highly mobile nectar-feeding birds facilitate this promiscuity through observed movements that were effectively random. As the incidence of bird-pollination is markedly greater in the Southwest Australian Floristic Region than elsewhere, our results have broad and novel significance for the evolution and conservation for many species in Gondwanan lineages.

  9. Caracterização morfológica e dissimilaridade genética entre variedades crioulas de melão Morphological characterization and genetic dissimilarity in melon landraces

    Directory of Open Access Journals (Sweden)

    Raquel Silviana Neitzke

    2009-12-01

    Full Text Available Variedades crioulas de melão (Cucumis melo são cultivadas no Sul do Brasil para consumo familiar e também para comercialização dos frutos. No entanto, existe uma carência de trabalhos relativos a sua caracterização. Este trabalho teve por objetivo caracterizar e avaliar a variabilidade genética de variedades crioulas de melão do Sul do Brasil mantidos no Banco Ativo de Germoplasma de Cucurbitáceas da Embrapa Clima Temperado. Foram caracterizados 14 acessos utilizando 26 descritores morfológicos de fruto. Os dados foram analisados pelos métodos de agrupamento de Tocher e hierárquico UPGMA. Os métodos de agrupamento foram parcialmente concordantes. O acesso C88 possui características distintas, ficando isolado dos demais, pois é o único entre todos os avaliados que apresenta formato piriforme e sem gomos, cor de epicarpo creme, cor de polpa branca e ruptura profunda no fruto. Existe grande variabilidade genética, para caracteres de frutos, nas variedades crioulas de melão conservadas nesse Banco Ativo de Germoplasma, com potencial para uso no melhoramento genético, destacando-se o acesso C71 por possuir sabor adocicado e polpa de cor laranja e o C72, por apresentar elevados valores de peso de fruto e espessura de polpa.Melon landraces (Cucumis melo are cultivated in South of Brazil for family consumption and also for marketing fruits. However, there is a lack of works related to characterization of these landraces. The objective of this work was to characterize and evaluate genetic variability of melon landraces from South of Brazil which are maintained in the Cucurbitaceae Genebank at Embrapa Clima Temperado, trough morphological characterization. Fourteen accessions were characterized in 26 morphological fruit descriptors. Data were analyzed by Tocher grouping method and UPGMA hierarchical. The two methods agreed partially. The accession C88 has unique characteristics, being isolated when compared to the other accessions, it

  10. Genetic, household and spatial clustering of leprosy on an island in Indonesia: a population-based study

    Directory of Open Access Journals (Sweden)

    Oskam Linda

    2005-11-01

    Full Text Available Abstract Background It is generally accepted that genetic factors play a role in susceptibility to both leprosy per se and leprosy type, but only few studies have tempted to quantify this. Estimating the contribution of genetic factors to clustering of leprosy within families is difficult since these persons often share the same environment. The first aim of this study was to test which correlation structure (genetic, household or spatial gives the best explanation for the distribution of leprosy patients and seropositive persons and second to quantify the role of genetic factors in the occurrence of leprosy and seropositivity. Methods The three correlation structures were proposed for population data (n = 560, collected on a geographically isolated island highly endemic for leprosy, to explain the distribution of leprosy per se, leprosy type and persons harbouring Mycobacterium leprae-specific antibodies. Heritability estimates and risk ratios for siblings were calculated to quantify the genetic effect. Leprosy was clinically diagnosed and specific anti-M. leprae antibodies were measured using ELISA. Results For leprosy per se in the total population the genetic correlation structure fitted best. In the population with relative stable household status (persons under 21 years and above 39 years all structures were significant. For multibacillary leprosy (MB genetic factors seemed more important than for paucibacillary leprosy. Seropositivity could be explained best by the spatial model, but the genetic model was also significant. Heritability was 57% for leprosy per se and 31% for seropositivity. Conclusion Genetic factors seem to play an important role in the clustering of patients with a more advanced form of leprosy, and they could explain more than half of the total phenotypic variance.

  11. Life-stage differences in spatial genetic structure in an irruptive forest insect: implications for dispersal and spatial synchrony

    Science.gov (United States)

    Patrick M.A. James; Barry Cooke; Bryan M.T. Brunet; Lisa M. Lumley; Felix A.H. Sperling; Marie-Josee Fortin; Vanessa S. Quinn; Brian R. Sturtevant

    2015-01-01

    Dispersal determines the flux of individuals, energy and information and is therefore a key determinant of ecological and evolutionary dynamics. Yet, it remains difficult to quantify its importance relative to other factors. This is particularly true in cyclic populations in which demography, drift and dispersal contribute to spatio-temporal variability in genetic...

  12. Large-scale spatial and temporal genetic diversity of feline calicivirus.

    Science.gov (United States)

    Coyne, Karen P; Christley, Rob M; Pybus, Oliver G; Dawson, Susan; Gaskell, Rosalind M; Radford, Alan D

    2012-10-01

    Feline calicivirus (FCV) is an important pathogen of domestic cats and a frequently used model of human caliciviruses. Here we use an epidemiologically rigorous sampling framework to describe for the first time the phylodynamics of a calicivirus at regional and national scales. A large number of FCV strains cocirculated in the United Kingdom at the national and community levels, with no strain comprising more than 5% and 14% of these populations, respectively. The majority of strains exhibited a relatively restricted geographical range, with only two strains (one field virus and one vaccine virus) spreading further than 100 km. None of the field strains were identified outside the United Kingdom. Temporally, while some strains persisted locally for the majority of the study, others may have become locally extinct. Evolutionary analysis revealed a radial phylogeny with little bootstrap support for nodes above the strain level. In most cases, spatially and temporally diverse strains intermingled in the phylogeny. Together, these data suggest that current FCV evolution is not associated with selective competition among strains. Rather, the genetic and antigenic landscape in each geographical location is highly complex, with many strains cocirculating. These variants likely exist at the community level by a combination of de novo evolution and occasional gene flow from the wider national population. This complexity provides a benchmark, for the first time, against which vaccine cross-protection at both local and national levels can be judged.

  13. Mean Shift Registration Algorithm for Dissimilar Sensors

    Institute of Scientific and Technical Information of China (English)

    QI Yong-qing; JING Zhong-liang; HU Shi-qiang; ZHAO Hai-tao

    2009-01-01

    The mean shift registration (MSR) algorithm is proposed to accurately estimate the biases for multiple dissimilar sensors. The new algorithm is a batch optimization procedure. The maximum likelihood estimator is used to estimate the target states, and then the mean shift algorithm is implemented to estimate the sensor biases. Monte Carlo simulations show that the MSR algorithm has significant improvement in performance with reducing the standard deviation and mean of sensor biased estimation error compared with the maximum likelihood registration algorithm. The quantitative analysis and the qualitative analysis show that the MSR algorithm has less computation than the maximum likelihood registration method.

  14. Dissimilarity-based multiple instance learning

    DEFF Research Database (Denmark)

    Sørensen, Lauge; Loog, Marco; Tax, David M. J.

    2010-01-01

    classifier. This approach is less restrictive than kernel-based approaches and therefore allows for the usage of a wider range of proximity measures. Two conceptually different types of dissimilarity measures are considered: one based on point set distance measures and one based on the earth movers distance...... between distributions of within- and between set point distances, thereby taking relations within and between sets into account. Experiments on five publicly available data sets show competitive performance in terms of classification accuracy compared to previously published results....

  15. Review on electromagnetic welding of dissimilar materials

    Science.gov (United States)

    Shanthala, K.; Sreenivasa, T. N.

    2016-12-01

    Electromagnetic welding (EMW) is a highspeed joining technique that is used to join similar or dissimilar metals, as well as metals to non-metals. This technique uses electromagnetic force to mainly join conductive materials. Unlike conventional joining processes, the weld interface does not melt, thus keeping the material properties intact. Extremely high velocity and strain rate involved in the process facilitate extending the EMW technique for joining several materials. In this paper, the research and progress in electromagnetic welding are reviewed from various perspectives to provide a basis for further research.

  16. [Study of genetic diversity and spatial structure of the wild soybean (Glycine soja Sieb. & Zucc.) population from the Ekaterinovka in the south of Primorskii krai].

    Science.gov (United States)

    Tikhonov, A V; Nedoluzhko, A V; Martynov, V V; Dorokhov, D B

    2011-03-01

    Data are presented on the genetic diversity and spatial structure of the natural wild soybean population from the neighborhood of the settlement of Ekaterinovka in Primorskii krai and on the relationship between the genetic structure of this population and its spatial organization. These data are discussed in comparison with the results of studies of wild soybean populations in the Far East region of the Russian Federation and China. Recommendations are given concerning the collection of genetic wild soybean resources.

  17. Geostatistics for spatial genetic structures: study of wild populations of perennial ryegrass.

    Science.gov (United States)

    Monestiez, P; Goulard, M; Charmet, G

    1994-04-01

    Methods based on geostatistics were applied to quantitative traits of agricultural interest measured on a collection of 547 wild populations of perennial ryegrass in France. The mathematical background of these methods, which resembles spatial autocorrelation analysis, is briefly described. When a single variable is studied, the spatial structure analysis is similar to spatial autocorrelation analysis, and a spatial prediction method, called "kriging", gives a filtered map of the spatial pattern over all the sampled area. When complex interactions of agronomic traits with different evaluation sites define a multivariate structure for the spatial analysis, geostatistical methods allow the spatial variations to be broken down into two main spatial structures with ranges of 120 km and 300 km, respectively. The predicted maps that corresponded to each range were interpreted as a result of the isolation-by-distance model and as a consequence of selection by environmental factors. Practical collecting methodology for breeders may be derived from such spatial structures.

  18. Friction Buttering: A New Technique for Dissimilar Welding

    Science.gov (United States)

    Karthik, G. M.; Mastanaiah, P.; Janaki Ram, G. D.; Kottada, Ravi Sankar

    2017-02-01

    This work offers a fresh perspective on buttering, a technique often considered for fusion welding of dissimilar metals. For the first time, buttering was attempted in solid state using friction deposition. Using this new "friction buttering" technique, fusion welding of two different dissimilar metal pairs (austenitic stainless steel/borated stainless steel and Al-Cu-Mg/Al-Zn-Mg-Cu) was successfully demonstrated. The results show that friction buttering can simplify a tough dissimilar welding problem into a routine fusion welding task.

  19. [Mathematical modeling of the spatial distribution of the pollen produced by genetically modified crops].

    Science.gov (United States)

    Medvinskiĭ, A B; Rusakov, A V; Chakraborty, A; Li, B- L-; Marchenko, A I; Sokolov, M S

    2009-01-01

    We represent and analyze the results of mathematical simulation of pollen dispersion from the origin, a field sowed by genetically modified plants. Factors responsible for the genetic isolation of such fields are discussed.

  20. The interplay between genetic and bioelectrical signaling permits a spatial regionalisation of membrane potentials in model multicellular ensembles.

    Science.gov (United States)

    Cervera, Javier; Meseguer, Salvador; Mafe, Salvador

    2016-10-12

    The single cell-centred approach emphasises ion channels as specific proteins that determine individual properties, disregarding their contribution to multicellular outcomes. We simulate the interplay between genetic and bioelectrical signals in non-excitable cells from the local single-cell level to the long range multicellular ensemble. The single-cell genetic regulation is based on mean-field kinetic equations involving the mRNA and protein concentrations. The transcription rate factor is assumed to depend on the absolute value of the cell potential, which is dictated by the voltage-gated cell ion channels and the intercellular gap junctions. The interplay between genetic and electrical signals may allow translating single-cell states into multicellular states which provide spatio-temporal information. The model results have clear implications for biological processes: (i) bioelectric signals can override slightly different genetic pre-patterns; (ii) ensembles of cells initially at the same potential can undergo an electrical regionalisation because of persistent genetic differences between adjacent spatial regions; and (iii) shifts in the normal cell electrical balance could trigger significant changes in the genetic regulation.

  1. Solid State Joining of Dissimilar Titanium Alloys

    Science.gov (United States)

    Morton, Todd W.

    Solid state joining of titanium via friction stir welding and diffusion bonding have emerged as enablers of efficient monolithic structural designs by the eliminations fasteners for the aerospace industry. As design complexity and service demands increase, the need for joints of dissimilar alloys has emerged. Complex thermomechanical conditions in friction stir weld joints and high temperature deformation behavior differences between alloys used in dissimilar joints gives rise to a highly variable flow pattern within a stir zone. Experiments performed welding Ti-6Al-4V to beta21S show that mechanical intermixing of the two alloys is the primary mechanism for the generation of the localized chemistry and microstructure, the magnitude of which can be directly related to pin rotation and travel speed weld parameters. Mechanical mixing of the two alloys is heavily influenced by strain rate softening phenomena, and can be used to manipulate weld nugget structure by switching which alloy is subjected to the advancing side of the pin. Turbulent mixing of a weld nugget and a significant reduction in defects and weld forces are observed when the beta21S is put on the advancing side of the weld where higher strain rates are present. Chemical diffusion driven by the heat of weld parameters is characterized using energy dispersive x-ray spectroscopy (EDS) and is shown to be a secondary process responsible for generating short-range chemical gradients that lead to a gradient of alpha particle structures. Diffusion calculations are inconsistent with an assumption of steady-state diffusion and show that material interfaces in the weld nugget evolve through the break-down of turbulent interface features generated by material flows. A high degree of recrystallization is seen throughout the welds, with unique, hybrid chemistry grains that are generated at material interfaces in the weld nugget that help to unify the crystal structure of dissimilar alloys. The degree of

  2. Analysing spatial trends in referral patterns to cancer genetics services: a preliminary investigation of regional variations in Wales.

    Science.gov (United States)

    McDonald, Kevin; Higgs, Gary; Iredale, Rachel; Tempest, Vanessa; Gray, Jonathon

    2004-11-01

    This paper discusses spatial trends in referral patterns to a cancer genetics service. It presents a literature review outlining the paucity of existing research, a preliminary analysis at the Unitary Authority level in Wales and advances a programme of further research to be conducted at a more detailed spatial level. The preliminary analysis shows a weak negative relationship between referral rates from primary care and social deprivation by Unitary Authority (Spearman rank correlation coefficient, sigma = -0.38). There is also a weak positive relationship between average settlement size and referral rates (sigma = +0.28), which taken together may indicate that primary care practices in affluent urban areas are more likely to refer than those in poorer rural areas. Future research will be conducted at a finer spatial scale, and will take into account characteristics of primary care practices and the patients being referred, amongst other variables.

  3. Phase-specific brain change of spatial working memory processing in genetic and ultra-high risk groups of schizophrenia.

    Science.gov (United States)

    Choi, Jung-Seok; Park, Ji-Young; Jung, Myung Hun; Jang, Joon Hwan; Kang, Do-Hyung; Jung, Wi Hoon; Han, Ji Yeon; Choi, Chi-Hoon; Hong, Kyung Sue; Kwon, Jun Soo

    2012-11-01

    Spatial working memory (WM) processing has 3 distinct phases: encoding, maintenance, and retrieval and its dysfunction is a core feature in schizophrenia. We examined phase-specific brain activations associated with spatial WM in first-degree relatives of schizophrenia (genetic high risk, GHR), ultra-high risk (UHR) subjects, patients with schizophrenia, and healthy controls. We used an event-related functional magnetic resonance imaging in 17 GHR subjects, 21 UHR subjects, 15 clinically stable patients with schizophrenia and 16 healthy controls, while subjects were performing a spatial delayed-response task. During the encoding phase, the GHR group showed increased activation in the fronto-parietal regions, whereas the UHR and schizophrenia groups showed significantly less activation in these regions than did the healthy control group. Especially, frontal activation was strongest in GHR subjects, followed by healthy controls, and occurred to a lesser degree in the UHR group, with the least activation occurring in the schizophrenia group. During the maintenance phase, the thalamus showed a differential activation, similar to frontal activation pattern during the encoding phase. During the retrieval phase, no prominent differential activations were found. Increased activations were observed in the superior temporal gyrus during the encoding and maintenance phases in the GHR, UHR, and schizophrenia groups relative to healthy controls. Our findings suggest that functional deficits associated with spatial WM processing emerge in the UHR before the onset of schizophrenia and compensatory neural processes exist in the GHR with genetic liability to schizophrenia.

  4. Spatial and temporal genetic variation of green mussel, Perna viridis in the Gulf of Thailand and implication for aquaculture.

    Science.gov (United States)

    Prakoon, Warangkana; Tunkijjanukij, Suriyan; Nguyen, Thuy T T; Na-Nakorn, Uthairat

    2010-10-01

    The culture of green mussel (Perna viridis) in the Gulf of Thailand depends on natural spat which are believed to come from spawning grounds adjacent to major river mouths. In the present paper, genetic diversity of spatial and temporal populations of green mussel in the Gulf of Thailand was investigated using five microsatellite loci. The results showed moderate genetic variation of all 11 populations (averaged number of alleles per locus, A = 10.4-12.2; effective number of alleles per locus, A(e) = 5.36-6.59; mean allelic richness, A(r) = 10.23-12.06; observed heterozygosity, H(o) = 0.52-0.63, and expected heterozygosity, H(e) = 0.66-0.73) without significant differences among populations. No sign of bottleneck or genetic disequilibrium was observed. Genetic differentiation among spatial populations was low (F (ST) = 0.0046, CI(0.95) = 0.0020-0.0083 for the samples collected in January, 2007, and F (ST) = 0.0088, CI(0.95) = 0.0010-0.0162 for the samples collected in July, 2007) while temporal variation was significant as revealed by the analysis of molecular variance. Multidimensional scaling separated temporal population groups with minor exception. The assignment test revealed that most of the recruits were from other populations.

  5. A spatial entropy reflecting distribution of spatial objects

    Institute of Scientific and Technical Information of China (English)

    Youn-Kyung Jang; Byeong-Seob You; Ho-Seok Kim; Kyoung-Bae Kim; Hae-Young Bae

    2007-01-01

    Decision trees are mainly used to classify data and predict data classes. A spatial decision tree has been designed using Euclidean distance between objects for reflecting spatial data characteristic. Even though this method explains the distance of objects in spatial dimension, it fails to represent distributions of spatial data and their relationships. But distributions of spatial data and relationships with their neighborhoods are very important in real world. This paper proposes decision tree based on spatial entropy that represents distributions of spatial data with dispersion and dissimilarity. The rate of dispersion by dissimilarity presents how related distribution of spatial data and non-spatial attributes. The experiment evaluates the accuracy and building time of decision tree as compared to previous methods and it shows that the proposed method makes efficient and scalable classification for spatial decision support.

  6. Spatially explicit genetic structure in the freshwater sponge Ephydatia fluviatilis (Linnaeus, 1759 within the framework of the monopolisation hypothesis

    Directory of Open Access Journals (Sweden)

    Livia Lucentini

    2013-02-01

    Full Text Available An apparent paradox is known for crustaceans, rotifers and bryozoans living in inland small water bodies: a potential for wide distribution due to the presence of resting stages is coupled with marked genetic differences between nearby water bodies, with enclave distributions masking clear phylogeographic patterns. According to the monopolisation hypothesis, this is due to the accumulation of resting stages, monopolising each water body. Freshwater sponges could represent a useful system to assess the generality of the mo- nopolisation hypothesis: these organisms i live in the same habitats as crustaceans, rotifers and bryozoans, ii produce resting stages that can accumulate, and iii have indeed a wide distribution. Currently, no studies on spatially explicit genetic differentiation on fresh- water sponges are available. The aim of the present study is to provide additional empirical evidence in support of the generality of the scenario for small aquatic animals with resting stages by analysing genetic diversity at different spatial scales for an additional model system, the freshwater sponge ephydatia fluviatilis (Linnaeus, 1759. We expected that system genetic variability would follow enclave distributions, no clear phylogeographical patterns would be present, and nearby unconnected water bodies would show markedly different populations for this new model too. We analysed the ribosomal internal transcribed spacer regions 5.8S-ITS2-28S, the D3 domain of 28S subunit, the mitochondrial Cytochrome c Oxidase I (COI and ten specific microsatellite markers of nine Italian and one Hungarian populations. Mitochondrial and nuclear sequences showed no or very low genetic polymorphism, whereas high levels of differentiation among populations and a significant polymorphism were observed using microsatellites. Microsatellite loci also showed a high proportion of private alleles for each population and an overall correlation between geographic and genetic

  7. Spatial and temporal genetic structure of Symbiodinium populations within a common reef-building coral on the Great Barrier Reef.

    Science.gov (United States)

    Howells, Emily J; Willis, Bette L; Bay, Line K; van Oppen, Madeleine J H

    2013-07-01

    The dinoflagellate photosymbiont Symbiodinium plays a fundamental role in defining the physiological tolerances of coral holobionts, but little is known about the dynamics of these endosymbiotic populations on coral reefs. Sparse data indicate that Symbiodinium populations show limited spatial connectivity; however, no studies have investigated temporal dynamics for in hospite Symbiodinium populations following significant mortality and recruitment events in coral populations. We investigated the combined influences of spatial isolation and disturbance on the population dynamics of the generalist Symbiodinium type C2 (ITS1 rDNA) hosted by the scleractinian coral Acropora millepora in the central Great Barrier Reef. Using eight microsatellite markers, we genotyped Symbiodinium in a total of 401 coral colonies, which were sampled from seven sites across a 12-year period including during flood plume-induced coral bleaching. Genetic differentiation of Symbiodinium was greatest within sites, explaining 70-86% of the total genetic variation. An additional 9-27% of variation was explained by significant differentiation of populations among sites separated by 0.4-13 km, which is consistent with low levels of dispersal via water movement and historical disturbance regimes. Sampling year accounted for 6-7% of total genetic variation and was related to significant coral mortality following severe bleaching in 1998 and a cyclone in 2006. Only 3% of the total genetic variation was related to coral bleaching status, reflecting generally small (8%) reductions in allelic diversity within bleached corals. This reduction probably reflected a loss of genotypes in hospite during bleaching, although no site-wide changes in genetic diversity were observed. Combined, our results indicate the importance of disturbance regimes acting together with limited oceanographic transport to determine the genetic composition of Symbiodinium types within reefs.

  8. Increased fire frequency promotes stronger spatial genetic structure and natural selection at regional and local scales in Pinus halepensis Mill.

    Science.gov (United States)

    Budde, Katharina B; González-Martínez, Santiago C; Navascués, Miguel; Burgarella, Concetta; Mosca, Elena; Lorenzo, Zaida; Zabal-Aguirre, Mario; Vendramin, Giovanni G; Verdú, Miguel; Pausas, Juli G; Heuertz, Myriam

    2017-04-01

    The recurrence of wildfires is predicted to increase due to global climate change, resulting in severe impacts on biodiversity and ecosystem functioning. Recurrent fires can drive plant adaptation and reduce genetic diversity; however, the underlying population genetic processes have not been studied in detail. In this study, the neutral and adaptive evolutionary effects of contrasting fire regimes were examined in the keystone tree species Pinus halepensis Mill. (Aleppo pine), a fire-adapted conifer. The genetic diversity, demographic history and spatial genetic structure were assessed at local (within-population) and regional scales for populations exposed to different crown fire frequencies. Eight natural P. halepensis stands were sampled in the east of the Iberian Peninsula, five of them in a region exposed to frequent crown fires (HiFi) and three of them in an adjacent region with a low frequency of crown fires (LoFi). Samples were genotyped at nine neutral simple sequence repeats (SSRs) and at 251 single nucleotide polymorphisms (SNPs) from coding regions, some of them potentially important for fire adaptation. Fire regime had no effects on genetic diversity or demographic history. Three high-differentiation outlier SNPs were identified between HiFi and LoFi stands, suggesting fire-related selection at the regional scale. At the local scale, fine-scale spatial genetic structure (SGS) was overall weak as expected for a wind-pollinated and wind-dispersed tree species. HiFi stands displayed a stronger SGS than LoFi stands at SNPs, which probably reflected the simultaneous post-fire recruitment of co-dispersed related seeds. SNPs with exceptionally strong SGS, a proxy for microenvironmental selection, were only reliably identified under the HiFi regime. An increasing fire frequency as predicted due to global change can promote increased SGS with stronger family structures and alter natural selection in P. halepensis and in plants with similar life history traits.

  9. Femtosecond fiber laser welding of dissimilar metals.

    Science.gov (United States)

    Huang, Huan; Yang, Lih-Mei; Bai, Shuang; Liu, Jian

    2014-10-01

    In this paper, welding of dissimilar metals was demonstrated for the first time, to the best of our knowledge, by using a high-energy high-repetition-rate femtosecond fiber laser. Metallurgical and mechanical properties were investigated and analyzed under various processing parameters (pulse energy, repetition rate, and welding speed). Results showed that the formation of intermetallic brittle phases and welding defects could be effectively reduced. Strong welding quality with more than 210 MPa tensile strength for stainless steel-aluminum and 175 MPa tensile strength for stainless steel-magnesium has been demonstrated. A minimal heat affected zone and uniform and homogenous phase transformation in the welding region have been demonstrated. This laser-welding technique can be extended for various applications in semiconductor, automobile, aerospace, and biomedical industries.

  10. Picosecond laser bonding of highly dissimilar materials

    Science.gov (United States)

    Carter, Richard M.; Troughton, Michael; Chen, Jianyong; Elder, Ian; Thomson, Robert R.; Lamb, Robert A.; Esser, M. J. Daniel; Hand, Duncan P.

    2016-10-01

    We report on recent progress in developing an industrially relevant, robust technique to bond dissimilar materials through ultra-fast microwelding. This technique is based on the use of a 5.9ps, 400kHz Trumpf laser operating at 1030nm. Tight focusing of the laser radiation at, or around, the interface between two materials allows for simultaneous absorption in both. This absorption rapidly, and locally, heats the material forming plasma from both materials. With suitable surface preparation this plasma can be confined to the interface region where it mixes, cools and forms a weld between the two materials. The use of ps pulses results in a short interaction time. This enables a bond to form whilst limiting the heat affected zone (HAZ) to a region of only a few hundred micrometres across. This small scale allows for the bonding of materials with highly dissimilar thermal properties, and in particular coefficients of thermal expansion e.g. glass-metal bonding. We report on our results for a range of material combinations including, Al-Bk7, Al-SiO2 and Nd:YAG-AlSi. Emphasis will be laid on the technical requirements for bonding including the required surface preparation of the two materials and on the laser parameters required. The quality of the resultant bonds are characterized through shear force measurements (where strengths equal to and exceeding equivalent adhesives will be presented). The lifetime of the welds is also discussed, paying particular attention to the results of thermal cycling tests.

  11. Dissimilarity-Based Sparse Subset Selection.

    Science.gov (United States)

    Elhamifar, Ehsan; Sapiro, Guillermo; Sastry, S Shankar

    2016-11-01

    Finding an informative subset of a large collection of data points or models is at the center of many problems in computer vision, recommender systems, bio/health informatics as well as image and natural language processing. Given pairwise dissimilarities between the elements of a 'source set' and a 'target set,' we consider the problem of finding a subset of the source set, called representatives or exemplars, that can efficiently describe the target set. We formulate the problem as a row-sparsity regularized trace minimization problem. Since the proposed formulation is, in general, NP-hard, we consider a convex relaxation. The solution of our optimization finds representatives and the assignment of each element of the target set to each representative, hence, obtaining a clustering. We analyze the solution of our proposed optimization as a function of the regularization parameter. We show that when the two sets jointly partition into multiple groups, our algorithm finds representatives from all groups and reveals clustering of the sets. In addition, we show that the proposed framework can effectively deal with outliers. Our algorithm works with arbitrary dissimilarities, which can be asymmetric or violate the triangle inequality. To efficiently implement our algorithm, we consider an Alternating Direction Method of Multipliers (ADMM) framework, which results in quadratic complexity in the problem size. We show that the ADMM implementation allows to parallelize the algorithm, hence further reducing the computational time. Finally, by experiments on real-world datasets, we show that our proposed algorithm improves the state of the art on the two problems of scene categorization using representative images and time-series modeling and segmentation using representative models.

  12. Dissimilarity-based classification of anatomical tree structures

    DEFF Research Database (Denmark)

    Sørensen, Lauge; Lo, Pechin Chien Pau; Dirksen, Asger

    2011-01-01

    A novel method for classification of abnormality in anatomical tree structures is presented. A tree is classified based on direct comparisons with other trees in a dissimilarity-based classification scheme. The pair-wise dissimilarity measure between two trees is based on a linear assignment betw...

  13. Ultrasonic echo signal fetures of dissimilar material bonding joints

    Institute of Scientific and Technical Information of China (English)

    GANG Tie(刚铁); Yasuo TAKAHASHI

    2004-01-01

    An ultrasonic evaluation method of echo feature of diffusion bond joint between two dissimilar materials is presented. The echo signal was acquired by an automatic ultrasonic C-scan test system. It is found that the intensity of echo and its phase can be used to evaluate the joint quality, and interface products of dissimilar materials bonding can be evaluated by ultrasonic method.

  14. Genetic Relationships and Spatial Genetic Structure Among Populations of Rhodnius prolixus (Hemiptera: Reduviidae) in Colombia and Venezuela Based on Mitochondrial Cytochrome-b Sequences.

    Science.gov (United States)

    Luna-Marín, K P; Angulo-Silva, V M; Hernández-Torres, J; Ruiz-García, M

    2016-11-26

    One hundred twenty Rhodnius prolixus (Stal) (Hemiptera: Reduviidae) specimens from 6 Colombian Departments and 1 Venezuelan State had 594-bp of the mitochondrial cytochrome-b gene sequenced to improve the understanding of evolutionary processes that shape the main vector of Chagas disease. The levels of genetic diversity for this species were low-medium with reference to other bugs. The genetic heterogeneity among the populations was very limited which means there has been extensive gene flow and/or very recent split processes. The overall sample as well as some individual populations showed evidence of recent population expansions (with the exception of Arauca, which yielded evidence of a bottleneck for a mismatch distribution). This expansion (11,000 or 2000-25,000 year ago depending of two procedures employed) coincides with the ending of the last intense glacial conditions during the Pleistocene and the beginning of the Holocene that had a warmer and wetter climate. Some of our autocorrelation analyses (AIDA and Genetic Landscape Interpolation Analysis) indicated local patches of high genetic similarity but no globally significant spatial structure. We did show an original haplotype distributed throughout the entirety of the geographical area studied.

  15. Complex spatial dynamics maintain northern leopard frog (Lithobates pipiens) genetic diversity in a temporally varying landscape

    Science.gov (United States)

    Mushet, David M.; Euliss, Ned H.; Chen, Yongjiu; Stockwell, Craig A.

    2013-01-01

    In contrast to most local amphibian populations, northeastern populations of the Northern Leopard Frog (Lithobates pipiens) have displayed uncharacteristically high levels of genetic diversity that have been attributed to large, stable populations. However, this widely distributed species also occurs in areas known for great climatic fluctuations that should be reflected in corresponding fluctuations in population sizes and reduced genetic diversity. To test our hypothesis that Northern Leopard Frog genetic diversity would be reduced in areas subjected to significant climate variability, we examined the genetic diversity of L. pipiens collected from 12 sites within the Prairie Pothole Region of North Dakota. Despite the region's fluctuating climate that includes periods of recurring drought and deluge, we found unexpectedly high levels of genetic diversity approaching that of northeastern populations. Further, genetic structure at a landscape scale was strikingly homogeneous; genetic differentiation estimates (Dest) averaged 0.10 (SD = 0.036) across the six microsatellite loci we studied, and two Bayesian assignment tests (STRUCTURE and BAPS) failed to reveal the development of significant population structure across the 68 km breadth of our study area. These results suggest that L. pipiens in the Prairie Pothole Region consists of a large, panmictic population capable of maintaining high genetic diversity in the face of marked climate variability.

  16. Modelling the loss of genetic diversity in vole populations in a spatially and temporally varying environment

    DEFF Research Database (Denmark)

    Topping, Christopher John; Østergaard, Siri; Pertoldi, Cino

    2003-01-01

    incorporating explicit genetics provide a promising new approach to the evaluation of the effect of animal behaviour, and random and man-induced events on the genetic composition of populations. They also provide a new platform from which to investigate the implication of real world deviations from assumptions...

  17. Spatial arrangement of genetic variation in the marine bivalve Macoma balthica (L.)

    NARCIS (Netherlands)

    Luttikhuizen, Pieternella Christina

    2003-01-01

    Phenotypic similarities come in two kinds: those that are partially based on genetic differences and those that are not. Genetic variation is inherently heritable and without it, evolution by means of natural selection could not occur. It is therefore important to understand the origin and maintenan

  18. Spatial genetic and morphologic structure of wolves and coyotes in relation to environmental heterogeneity in a Canis hybrid zone.

    Science.gov (United States)

    Benson, John F; Patterson, Brent R; Wheeldon, Tyler J

    2012-12-01

    Eastern wolves have hybridized extensively with coyotes and gray wolves and are listed as a 'species of special concern' in Canada. However, a distinct population of eastern wolves has been identified in Algonquin Provincial Park (APP) in Ontario. Previous studies of the diverse Canis hybrid zone adjacent to APP have not linked genetic analysis with field data to investigate genotype-specific morphology or determine how resident animals of different ancestry are distributed across the landscape in relation to heterogeneous environmental conditions. Accordingly, we studied resident wolves and coyotes in and adjacent to APP to identify distinct Canis types, clarify the extent of the APP eastern wolf population beyond the park boundaries and investigate fine-scale spatial genetic structure and landscape-genotype associations in the hybrid zone. We documented three genetically distinct Canis types within the APP region that also differed morphologically, corresponding to putative gray wolves, eastern wolves and coyotes. We also documented a substantial number of hybrid individuals (36%) that were admixed between 2 or 3 of the Canis types. Breeding eastern wolves were less common outside of APP, but occurred in some unprotected areas where they were sympatric with a diverse combination of coyotes, gray wolves and hybrids. We found significant spatial genetic structure and identified a steep cline extending west from APP where the dominant genotype shifted abruptly from eastern wolves to coyotes and hybrids. The genotypic pattern to the south and northwest was a more complex mosaic of alternating genotypes. We modelled genetic ancestry in response to prey availability and human disturbance and found that individuals with greater wolf ancestry occupied areas of higher moose density and fewer roads. Our results clarify the structure of the Canis hybrid zone adjacent to APP and provide unique insight into environmental conditions influencing hybridization dynamics between

  19. Consequences of severe habitat fragmentation on density, genetics, and spatial capture-recapture analysis of a small bear population.

    Science.gov (United States)

    Murphy, Sean M; Augustine, Ben C; Ulrey, Wade A; Guthrie, Joseph M; Scheick, Brian K; McCown, J Walter; Cox, John J

    2017-01-01

    Loss and fragmentation of natural habitats caused by human land uses have subdivided several formerly contiguous large carnivore populations into multiple small and often isolated subpopulations, which can reduce genetic variation and lead to precipitous population declines. Substantial habitat loss and fragmentation from urban development and agriculture expansion relegated the Highlands-Glades subpopulation (HGS) of Florida, USA, black bears (Ursus americanus floridanus) to prolonged isolation; increasing human land development is projected to cause ≥ 50% loss of remaining natural habitats occupied by the HGS in coming decades. We conducted a noninvasive genetic spatial capture-recapture study to quantitatively describe the degree of contemporary habitat fragmentation and investigate the consequences of habitat fragmentation on population density and genetics of the HGS. Remaining natural habitats sustaining the HGS were significantly more fragmented and patchier than those supporting Florida's largest black bear subpopulation. Genetic diversity was low (AR = 3.57; HE = 0.49) and effective population size was small (NE = 25 bears), both of which remained unchanged over a period spanning one bear generation despite evidence of some immigration. Subpopulation density (0.054 bear/km2) was among the lowest reported for black bears, was significantly female-biased, and corresponded to a subpopulation size of 98 bears in available habitat. Conserving remaining natural habitats in the area occupied by the small, genetically depauperate HGS, possibly through conservation easements and government land acquisition, is likely the most important immediate step to ensuring continued persistence of bears in this area. Our study also provides evidence that preferentially placing detectors (e.g., hair traps or cameras) primarily in quality habitat across fragmented landscapes poses a challenge to estimating density-habitat covariate relationships using spatial capture

  20. A genetic polymorphism affecting reliance on personal versus public information in a spatial learning task in Drosophila melanogaster.

    Science.gov (United States)

    Foucaud, Julien; Philippe, Anne-Sophie; Moreno, Celine; Mery, Frederic

    2013-06-07

    Organisms that face behavioural challenges can use different types of information to guide their decisions. First, they can use the personal information they sample in their environment. Second, they can use the inadvertent social information provided by the behaviour of conspecifics or heterospecifics (i.e. public information). Currently, little is known about the interaction between genetic variation and the use of personal versus public information in natural populations. Here, we investigated whether a natural genetic polymorphism affects the use of personal versus public information in a spatial learning task in Drosophila melanogaster. We found that genetic variation at the foraging locus interacts with social context during spatial learning. While both allelic variants are able to use personal and public information to improve their navigation during 10 training trials, a probe trial revealed that individuals carrying the for(R) (rover) allele rely mainly on personal information, whereas individuals carrying the for(s) (sitter) allele either use or display more public information than rovers. Accordingly, transfer of social information is more important in groups of sitters than in groups of rovers. These results suggest that a positive feedback loop can occur between alleles promoting group living, such as for(s), and the use and/or display of public information, ultimately providing the opportunity for the joint evolution of sociality and cultural traits.

  1. Understanding the genetic diversity, spatial genetic structure and mating system at the hierarchical levels of fruits and individuals of a continuous Theobroma cacao population from the Brazilian Amazon

    Science.gov (United States)

    Silva, C R S; Albuquerque, P S B; Ervedosa, F R; Mota, J W S; Figueira, A; Sebbenn, A M

    2011-01-01

    Understanding the mating patterns of populations of tree species is a key component of ex situ genetic conservation. In this study, we analysed the genetic diversity, spatial genetic structure (SGS) and mating system at the hierarchical levels of fruits and individuals as well as pollen dispersal patterns in a continuous population of Theobroma cacao in Pará State, Brazil. A total of 156 individuals in a 0.56 ha plot were mapped and genotyped for nine microsatellite loci. For the mating system analyses, 50 seeds were collected from nine seed trees by sampling five fruits per tree (10 seeds per fruit). Among the 156 individuals, 127 had unique multilocus genotypes, and the remaining were clones. The population was spatially aggregated; it demonstrated a significant SGS up to 15 m that could be attributed primarily to the presence of clones. However, the short seed dispersal distance also contributed to this pattern. Population matings occurred mainly via outcrossing, but selfing was observed in some seed trees, which indicated the presence of individual variation for self-incompatibility. The matings were also correlated, especially within (r̂p(m)=0.607) rather than among the fruits (r̂p(m)=0.099), which suggested that a small number of pollen donors fertilised each fruit. The paternity analysis suggested a high proportion of pollen migration (61.3%), although within the plot, most of the pollen dispersal encompassed short distances (28 m). The determination of these novel parameters provides the fundamental information required to establish long-term ex situ conservation strategies for this important tropical species. PMID:21139632

  2. Local-scale patterns of genetic variability, outcrossing, and spatial structure in natural stands of Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Kirsten Bomblies

    2010-03-01

    Full Text Available As Arabidopsis thaliana is increasingly employed in evolutionary and ecological studies, it is essential to understand patterns of natural genetic variation and the forces that shape them. Previous work focusing mostly on global and regional scales has demonstrated the importance of historical events such as long-distance migration and colonization. Far less is known about the role of contemporary factors or environmental heterogeneity in generating diversity patterns at local scales. We sampled 1,005 individuals from 77 closely spaced stands in diverse settings around Tübingen, Germany. A set of 436 SNP markers was used to characterize genome-wide patterns of relatedness and recombination. Neighboring genotypes often shared mosaic blocks of alternating marker identity and divergence. We detected recent outcrossing as well as stretches of residual heterozygosity in largely homozygous recombinants. As has been observed for several other selfing species, there was considerable heterogeneity among sites in diversity and outcrossing, with rural stands exhibiting greater diversity and heterozygosity than urban stands. Fine-scale spatial structure was evident as well. Within stands, spatial structure correlated negatively with observed heterozygosity, suggesting that the high homozygosity of natural A. thaliana may be partially attributable to nearest-neighbor mating of related individuals. The large number of markers and extensive local sampling employed here afforded unusual power to characterize local genetic patterns. Contemporary processes such as ongoing outcrossing play an important role in determining distribution of genetic diversity at this scale. Local "outcrossing hotspots" appear to reshuffle genetic information at surprising rates, while other stands contribute comparatively little. Our findings have important implications for sampling and interpreting diversity among A. thaliana accessions.

  3. Residual stress determination in a dissimilar weld overlay pipe by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Wanchuck, E-mail: chuckwoo@kaeri.re.kr [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Em, Vyacheslav [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Hubbard, Camden R. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Lee, Ho-Jin [Nuclear Materials Research Center, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Park, Kwang Soo [Corporate R and D Institute, Doosan Heavy Industries and Construction, Changwon 641-792 (Korea, Republic of)

    2011-10-15

    Highlights: {yields} Determined residual stress distribution in a dissimilar weld overlay pipe. {yields} Consists of a ferritic (SA508), austenitic (F316L) steels, Alloy 182 consumable. {yields} Measured significant compression (-600 MPa) near the inner wall of overlay. {yields} Validate integrity of the inner wall for the pressurized nozzle nuclear structure. - Abstract: Residual stresses were determined through the thickness of a dissimilar weld overlay pipe using neutron diffraction. The specimen has a complex joining structure consisting of a ferritic steel (SA508), austenitic steel (F316L), Ni-based consumable (Alloy 182), and overlay of Ni-base superalloy (Alloy 52M). It simulates pressurized nozzle components, which have been a critical issue under the severe crack condition of nuclear power reactors. Two neutron diffractometers with different spatial resolutions have been utilized on the identical specimen for comparison. The macroscopic 'stress-free' lattice spacing (d{sub o}) was also obtained from both using a 2-mm width comb-like coupon. The results show significant changes in residual stresses from tension (300-400 MPa) to compression (-600 MPa) through the thickness of the dissimilar weld overlay pipe specimen.

  4. Welded joints integrity analysis and optimization for fiber laser welding of dissimilar materials

    Science.gov (United States)

    Ai, Yuewei; Shao, Xinyu; Jiang, Ping; Li, Peigen; Liu, Yang; Liu, Wei

    2016-11-01

    Dissimilar materials welded joints provide many advantages in power, automotive, chemical, and spacecraft industries. The weld bead integrity which is determined by process parameters plays a significant role in the welding quality during the fiber laser welding (FLW) of dissimilar materials. In this paper, an optimization method by taking the integrity of the weld bead and weld area into consideration is proposed for FLW of dissimilar materials, the low carbon steel and stainless steel. The relationships between the weld bead integrity and process parameters are developed by the genetic algorithm optimized back propagation neural network (GA-BPNN). The particle swarm optimization (PSO) algorithm is taken for optimizing the predicted outputs from GA-BPNN for the objective. Through the optimization process, the desired weld bead with good integrity and minimum weld area are obtained and the corresponding microstructure and microhardness are excellent. The mechanical properties of the optimized joints are greatly improved compared with that of the un-optimized welded joints. Moreover, the effects of significant factors are analyzed based on the statistical approach and the laser power (LP) is identified as the most significant factor on the weld bead integrity and weld area. The results indicate that the proposed method is effective for improving the reliability and stability of welded joints in the practical production.

  5. Hierarchical spatial genetic structure in a distinct population segment of greater sage-grouse

    Science.gov (United States)

    Oyler-McCance, Sara J.; Casazza, Michael L.; Fike, Jennifer A.; Coates, Peter S.

    2014-01-01

    Greater sage-grouse (Centrocercus urophasianus) within the Bi-State Management Zone (area along the border between Nevada and California) are geographically isolated on the southwestern edge of the species’ range. Previous research demonstrated that this population is genetically unique, with a high proportion of unique mitochondrial DNA (mtDNA) haplotypes and with significant differences in microsatellite allele frequencies compared to populations across the species’ range. As a result, this population was considered a distinct population segment (DPS) and was recently proposed for listing as threatened under the U.S. Endangered Species Act. A more comprehensive understanding of the boundaries of this genetically unique population (where the Bi-State population begins) and an examination of genetic structure within the Bi-State is needed to help guide effective management decisions. We collected DNA from eight sampling locales within the Bi-State (N = 181) and compared those samples to previously collected DNA from the two most proximal populations outside of the Bi-State DPS, generating mtDNA sequence data and amplifying 15 nuclear microsatellites. Both mtDNA and microsatellite analyses support the idea that the Bi-State DPS represents a genetically unique population, which has likely been separated for thousands of years. Seven mtDNA haplotypes were found exclusively in the Bi-State population and represented 73 % of individuals, while three haplotypes were shared with neighboring populations. In the microsatellite analyses both STRUCTURE and FCA separate the Bi-State from the neighboring populations. We also found genetic structure within the Bi-State as both types of data revealed differences between the northern and southern part of the Bi-State and there was evidence of isolation-by-distance. STRUCTURE revealed three subpopulations within the Bi-State consisting of the northern Pine Nut Mountains (PNa), mid Bi-State, and White Mountains (WM) following a

  6. The rural-urban effect on spatial genetic structure of type II Toxoplasma gondii strains involved in human congenital toxoplasmosis, France, 2002-2009.

    Science.gov (United States)

    Ajzenberg, Daniel; Collinet, Frédéric; Aubert, Dominique; Villena, Isabelle; Dardé, Marie-Laure; Devillard, Sébastien

    2015-12-01

    Congenital toxoplasmosis involves Toxoplasma gondii type II strains in 95% of cases in France. We used spatial principal component analysis (sPCA) and 15 microsatellite markers to investigate the spatial genetic structure of type II strains involved in 240 cases of congenital toxoplasmosis in France from 2002 through 2009. Mailing addresses of patients were geo-referenced a posteriori in decimal degrees and categorized into urban or rural areas of residence. No spatial genetic structure was found for type II strains that infected mothers who were living in urban areas, but a global spatial genetic structure was found for those that infected mothers who were living in a rural environment. Our results suggest that sources of infection by T. gondii are different in rural and urban areas in France, and advocate for targeted messages in the prevention of toxoplasmosis according to the type of residence of susceptible people.

  7. Genetics

    Science.gov (United States)

    ... Inheritance; Heterozygous; Inheritance patterns; Heredity and disease; Heritable; Genetic markers ... The chromosomes are made up of strands of genetic information called DNA. Each chromosome contains sections of ...

  8. Fine scale spatial genetic structure in Pouteria reticulata (Engl. Eyma (Sapotaceae, a dioecious, vertebrate dispersed tropical rain forest tree species

    Directory of Open Access Journals (Sweden)

    John W. Schroeder

    2014-08-01

    Full Text Available Dioecious tropical tree species often have small flowers and fleshy fruits indicative of small-insect pollination and vertebrate seed dispersal. We hypothesize that seed mediated gene flow should be exceed pollen-mediated gene flow in such species, leading to weak patterns of fine scale spatial genetic structure (SGS. In the present study, we characterize novel microsatellite DNA markers and test for SGS in sapling (N=100 and adult trees (N=99 of the dioecious canopy tree Pouteria reticulata (Sapotaceae in a 50 ha forest dynamics plot on Barro Colorado Island (BCI, Panama. The five genetic markers contained between five and 15 alleles per locus, totaling 51 alleles in the sample population. Significant SGS at local spatial scales (<100m was detected in the sapling (dbh≈1cm and adult (dbh≥20cm size classes, but was stronger in the former (sapling Sp=0.010±0.004, adult Sp=0.006±0.002, suggesting demographic thinning. The degree of SGS was lower than the value expected for non-vertebrate dispersed tropical trees (Sp=0.029, but similar to the average value for vertebrate dispersed tropical trees (Sp=0.009 affirming the dispersal potential of vertebrate dispersed tropical trees in faunally intact forests.

  9. Joining Technology of Dissimilar Materials for Automotive Components(Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    Meung Ho Rhee; Jong Ho Song; Woo Young Chung; Young Myoung Kim

    2004-01-01

    Joining techniques of dissimilar materials for lightweight multi-material automotive body structure were discussed. The joining of 1 .4 mm thickness steel and 2 mm thickness of Al were performed by the new method that is hybrid laser welding system. After aluminum and steel were welded by laser hybrid welding process, the micro-structure investment and the micro-hardness test were carried out. Hybrid laser welding promises a bright future in joining technology of dissimilar materials for automotive components.

  10. Micro-scale spatial expansion of microbial cells and mobile genetic elements

    DEFF Research Database (Denmark)

    Smets, Barth F.; Kreft, Jan-Ulrich; Or, Dani;

    Microbes can actively explore their local spatial environment when sufficiently hydrated pathways are present - mobile gene elements can also travel in local environments when cellular density is sufficient. In this presentation, I will present our efforts at predicting the dynamics of these two ...

  11. Spatial genetic structure of the Sea Sandwort on Surtsey: an immigrant's journey

    Directory of Open Access Journals (Sweden)

    S. H. Árnason

    2014-06-01

    Full Text Available Sea Sandwort (Honckenya peploides is one of the first plants to successfully colonize and reproduce on the volcanic island Surtsey, formed in 1963 off the southern coast of Iceland. Using amplified fragment length polymorphic (AFLP markers we examined levels of genetic variation and differentiation among populations of H. peploides on Surtsey in relation to populations on the nearby island Heimaey and from the southern coast of Iceland. Selected populations from Denmark and Greenland were used for comparison. In addition, we tested whether the effects of isolation by distance can be seen in the Surtsey populations. Using two primer combinations, we obtained 173 AFLP markers from a total of 347 plant samples. The resulting binary matrix was then analyzed statistically. Main results include the followings: (i Surtsey has the highest proportion of polymorphic markers as well as a comparatively high genetic diversity (55.5% PLP; 0.1974 HE and Denmark the lowest (31.8% PLP; 0.132 HE, indicating rapid expansion during an early stage of population establishment on Surtsey and/or multiple origins of immigrants; (ii the total genetic differentiation (FST among Surtsey (0.0714 and Heimaey (0.055 populations was less than half of that found among the mainland populations in Iceland (0.1747, indicating substantial gene flow on the islands; (iii most of the genetic variation (79%, pH. peploides most likely immigrated from the nearby island of Heimaey and directly from the southern coast of Iceland.

  12. Japanese quail's genetic background modulates effects of chronic stress on emotional reactivity but not spatial learning.

    Directory of Open Access Journals (Sweden)

    Agathe Laurence

    Full Text Available Chronic stress is known to enhance mammals' emotional reactivity and alters several of their cognitive functions, especially spatial learning. Few studies have investigated such effects in birds. We investigated the impact of a two-week stress on Japanese quail's emotional reactivity and spatial learning. Quail is an avian model widely used in laboratory studies and for extrapolation of data to other poultry species. As sensitivity to chronic stress can be modulated by intrinsic factors, we tested juvenile female Japanese quail from three lines, two of them divergently selected on tonic immobility duration, an indicator of general fearfulness. The different emotional reactivity levels of quail belonging to these lines can be revealed by a large variety of tests. Half of the birds were submitted to repeated unpredictable aversive events for two weeks, whereas the other half were left undisturbed. After this procedure, two tests (open field and emergence tests evaluated the emotional reactivity of treated and control quails. They were then trained in a T-maze for seven days and their spatial learning was tested. The chronic stress protocol had an impact on resting, preening and foraging in the home cage. As predicted, the emotional reactivity of treated quails, especially those selected for long tonic immobility duration, was higher. Our spatial learning data showed that the treatment enhanced acquisition but not memorization. However, intrinsic fearfulness did not seem to interact with the treatment in this test. According to an inverted U-shaped relationship between stress and cognition, chronic stress can improve the adaptability of birds to a stressful environment. We discussed the mechanisms possibly implied in the increase of emotional reactivity and spatial abilities.

  13. Rapid recovery of genetic diversity of stomatopod populations on Krakatau: temporal and spatial scales of marine larval dispersal.

    Science.gov (United States)

    Barber, P H; Moosa, M K; Palumbi, S R

    2002-08-07

    Although the recovery of terrestrial communities shattered by the massive eruption of Krakatau in 1883 has been well chronicled, the fate of marine populations has been largely ignored. We examined patterns of genetic diversity in populations of two coral reef-dwelling mantis shrimp, Haptosquilla pulchella and Haptosquilla glyptocercus (Stomatopoda: Protosquillidae), on the islands of Anak Krakatau and Rakata. Genetic surveys of mitochondrial cytochrome oxidase c (subunit 1) in these populations revealed remarkably high levels of haplotypic and nucleotide diversity that were comparable with undisturbed populations throughout the Indo-Pacific. Recolonization and rapid recovery of genetic diversity in the Krakatau populations indicates that larval dispersal from multiple and diverse source populations contributes substantially to the demographics of local populations over intermediate temporal (tens to hundreds of years) and spatial scales (tens to hundreds of kilometres). Natural experiments such as Krakatau provide an excellent mechanism to investigate marine larval dispersal and connectivity. Results from stomatopods indicate that marine reserves should be spaced no more than 50-100 km apart to facilitate ecological connectivity via larval dispersal.

  14. Fine-scale spatial genetic structure in predominantly selfing plants with limited seed dispersal: A rule or exception?

    Directory of Open Access Journals (Sweden)

    Sergei Volis

    2016-04-01

    Full Text Available Gene flow at a fine scale is still poorly understood despite its recognized importance for plant population demographic and genetic processes. We tested the hypothesis that intensity of gene flow will be lower and strength of spatial genetic structure (SGS will be higher in more peripheral populations because of lower population density. The study was performed on the predominantly selfing Avena sterilis and included: (1 direct measurement of dispersal in a controlled environment; and (2 analyses of SGS in three natural populations, sampled in linear transects at fixed increasing inter-plant distances. We found that in A. sterilis major seed dispersal is by gravity in close (less than 2 m vicinity of the mother plant, with a minor additional effect of wind. Analysis of SGS with six nuclear SSRs revealed a significant autocorrelation for the distance class of 1 m only in the most peripheral desert population, while in the two core populations with Mediterranean conditions, no genetic structure was found. Our results support the hypothesis that intensity of SGS increases from the species core to periphery as a result of decreased within-population gene flow related to low plant density. Our findings also show that predominant self-pollination and highly localized seed dispersal lead to SGS at a very fine scale, but only if plant density is not too high.

  15. Spatial genetic structure and restricted gene flow in bed bugs (Cimex lectularius) populations in France.

    Science.gov (United States)

    Akhoundi, Mohammad; Kengne, Pierre; Cannet, Arnaud; Brengues, Cécile; Berenger, Jean-Michel; Izri, Arezki; Marty, Pierre; Simard, Frederic; Fontenille, Didier; Delaunay, Pascal

    2015-08-01

    Bed bugs (Cimex lectularius) are resurgent blood-sucking ectoparasites that are currently increasing at a rapid rate, particularly in industrialized countries, such as France. Despite the rapid spread of bed bugs, there is a lack of knowledge concerning the population structure and gene flow among C. lectularius populations in France. To fill this gap, a genetic study was conducted using 183 C. lectularius from 14 populations of bed bugs collected in a hotel and in individual apartments in the French Riviera and in the Saint Ouen suburb of Paris. The samples were genotyped using an isolated set of six polymorphic microsatellite loci, including five new loci which were newly isolated and chosen based on prior successful amplification, and one previously described loci (bb15b). The low genetic diversity observed in the samples (of one to five alleles) suggested that most of prospected populations were established by only a few individuals, possibly from a single mated female. The overall genetic differentiation was high and statistically significant (FST=0.556, plectularius populations in France; however, the available information should be expanded in further studies.

  16. The spatial genetic differentiation of the legume pod borer, Maruca vitrata F. (Lepidoptera: Crambidae) populations in West Africa

    KAUST Repository

    Agunbiade, Tolulope A.

    2012-04-17

    The legume pod borer, Maruca vitrata, is an endemic insect pest that causes significant yield loss to the cowpea crop in West Africa. The application of population genetic tools is important in the management of insect pests but such data on M. vitrata is lacking. We applied a set of six microsatellite markers to assess the population structure of M. vitrata collected at five sites from Burkina Faso, Niger and Nigeria. Observed polymorphisms ranged from one (marker 3393) to eight (marker 32008) alleles per locus. Observed and expected heterozygosities ranged from 0.0 to 0.8 and 0.0 to 0.6, respectively. Three of the loci in samples from Nigeria and Burkina Faso deviated significantly from Hardy-Weinberg Equilibrium (HWE), whereas no loci deviated significantly in samples from Niger. Analysis of molecular variance (AMOVA) indicated that 67.3% level of the genetic variation was within individuals compared to 17.3% among populations. A global estimate of F ST=0.1 (ENA corrected F ST=0.1) was significant (Pa=0.05) and corroborated by pairwise F ST values that were significant among all possible comparisons. A significant correlation was predicted between genetic divergence and geographic distance between subpopulations (R2=0.6, P=0.04), and cluster analysis by the program STRUCTURE predicted that co-ancestry of genotypes were indicative of three distinct populations. The spatial genetic variance among M. vitrata in West Africa may be due to limited gene flow, south-north seasonal movement pattern or other reproductive barriers. This information is important for the cultural, chemical and biological control strategies for managing M. vitrata. Copyright © 2012 Cambridge University Press.

  17. Spatial genetic structure of the mountain pine beetle (Dendroctonus ponderosae) outbreak in western Canada: historical patterns and contemporary dispersal.

    Science.gov (United States)

    Gayathri Samarasekera, G D N; Bartell, Nicholas V; Lindgren, B Staffan; Cooke, Janice E K; Davis, Corey S; James, Patrick M A; Coltman, David W; Mock, Karen E; Murray, Brent W

    2012-06-01

    Environmental change has a wide range of ecological consequences, including species extinction and range expansion. Many studies have shown that insect species respond rapidly to climatic change. A mountain pine beetle epidemic of record size in North America has led to unprecedented mortality of lodgepole pine, and a significant range expansion to the northeast of its historic range. Our goal was to determine the spatial genetic variation found among outbreak population from which genetic structure, and dispersal patterns may be inferred. Beetles from 49 sampling locations throughout the outbreak area in western Canada were analysed at 13 microsatellite loci. We found significant north-south population structure as evidenced by: (i) Bayesian-based analyses, (ii) north-south genetic relationships and diversity gradients; and (iii) a lack of isolation-by-distance in the northernmost cluster. The north-south structure is proposed to have arisen from the processes of postglacial colonization as well as recent climate-driven changes in population dynamics. Our data support the hypothesis of multiple sources of origin for the outbreak and point to the need for population specific information to improve our understanding and management of outbreaks. The recent range expansion across the Rocky Mountains into the jack/lodgepole hybrid and pure jack pine zones of northern Alberta is consistent with a northern British Columbia origin. We detected no loss of genetic variability in these populations, indicating that the evolutionary potential of mountain pine beetle to adapt has not been reduced by founder events. This study illustrates a rapid range-wide response to the removal of climatic constraints, and the potential for range expansion of a regional population. © 2012 Blackwell Publishing Ltd.

  18. Spatial genetic structure in natural populations of Phragmites australis in a mosaic of saline habitats in the Yellow River Delta, China.

    Directory of Open Access Journals (Sweden)

    Lexuan Gao

    Full Text Available Determination of spatial genetic structure (SGS in natural populations is important for both theoretical aspects of evolutionary genetics and their application in species conservation and ecological restoration. In this study, we examined genetic diversity within and among the natural populations of a cosmopolitan grass Phragmites australis (common reed in the Yellow River Delta (YRD, China, where a mosaic of habitat patches varying in soil salinity was detected. We demonstrated that, despite their close geographic proximity, the common reed populations in the YRD significantly diverged at six microsatellite loci, exhibiting a strong association of genetic variation with habitat heterogeneity. Genetic distances among populations were best explained as a function of environmental difference, rather than geographical distance. Although the level of genetic divergence among populations was relatively low (F'(ST =0.073, weak but significant genetic differentiation, as well as the concordance between ecological and genetic landscapes, suggests spatial structuring of genotypes in relation to patchy habitats. These findings not only provided insights into the population dynamics of common reed in changing environments, but also demonstrated the feasibility of using habitat patches in a mosaic landscape as test systems to identify appropriate genetic sources for ecological restoration.

  19. Phenotyping the Genetic Diversity of Wild Agave Species that Coexist in the Same Spatial Region

    Directory of Open Access Journals (Sweden)

    Elí Secundino PORRAS-RAMÍREZ

    2016-12-01

    Full Text Available Phenotypic characteristics are important to identify species and provide valuable information for the uses in plant breeding. The aim of this study was to characterize through morphological traits the genetic diversity of the Agave genus under wild and semi-wild culture conditions in Maguey Largo region in Oaxaca, Mexico. Through field trips, eleven morphological characteristics of the Agave species were recorded. Principal component analysis (PCA, phylogenetic trees, and correlation analyses, were performed. Seven wild species were identified: Agave potatorum Zucc., A. seemanniana, A. nussaviorum subsp. nussaviorum, A. angustifolia Haw., A. marmorata Roezl., A. karwinskii Zucc. and A. americana var. Americana. Also, a semi-wild unclassified specie Agave sp. was found. The values of the first four principal components in the PCA explain more than 89% of the total morphological variance. The dendrogram of the agglomerative hierarchical clustering (AHC shown a high similarity between the species and divide them in two main cluster with one unassociated specie (A. karwinskii Miahuatlán shape. Following the different analyses done, we observed a very close relationship between A. potatorum and A. nussaviorum, and dissociated from A. seemanniana, which are belonging to the “Tobala” complex and never described before. The results obtained in this work suggest a great genetic diversity expressed in a wide morphological variety of agaves in Oaxaca; which can be used in futures molecular studies.

  20. The Split Decomposition of a k-Dissimilarity Map

    CERN Document Server

    Herrmann, Sven

    2010-01-01

    A k-dissimilarity map on a finite set X is a function D: \\binom X k -> R assigning a real value to each subset of X with cardinality k. Such functions arise naturally in the area of phylogenetics, where they are commonly used to reconstruct evolutionary trees or networks. In this paper, we show how regular subdivisions of the kth hypersimplex can be used to obtain a canonical decomposition of a k-dissimilarity map into the sum of simpler k-dissimilarity maps arising from bipartitions or splits of X. In the special case k=2, this decomposition is the well-known split decomposition of a distance due to Bandelt and Dress [Adv. Math. 92 (1992), 47-105]. Furthermore, we characterise those sets of splits that may occur in the resulting decompositions of k-dissimilarity maps. As a corollary, we also give a new proof of a theorem of Pachter and Speyer [Appl. Math. Lett. 17 (2004), 615-621] for recovering k-dissimilarity maps from trees.

  1. Modeling the spatial distribution of wolf (Canis lupus pallipes attacks on human using genetic algorithm (GARP in Hamedan province

    Directory of Open Access Journals (Sweden)

    N Behdarvand

    2012-06-01

    Full Text Available In recent decades due to steady human population growth coupled with increased use of resources and habitat degradation, conflicts between humans and carnivores have greatly been expanded. In order to mitigate these conflicts based on a clear understanding of conflict patterns, applying the species distribution models as helpful methods has been suggested. Occurring the recent conflict between wolves and local communities in Hamedan province is a clear case of this problem. In this study, capabilities of the genetic algorithm (GARP were assessed in the modeling spatial distribution of wolf attacks in Hamedan province during 2006-2012. The area under the receiver operating characteristic curve (ROC was used to evaluate performance of the model. Findings indicated that the applied modelingapproach has a very good performance (area under curve=0.856 inpredicting the spatial distribution of wolf attacks on humans. In addition, based on the results of sensitivity analysis, land-cover t ype, human population density and distance from main road were the most effective parameters. Findings of the present study can be applied in formulation of an adaptive management plan for wolf conservation and mitigation of the conflicts with local communities.

  2. Spatial Interpolation of Annual Runoff in Ungauged Basins Based on the Improved Information Diffusion Model Using a Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Mei Hong

    2017-01-01

    Full Text Available Prediction in Ungauged Basins (PUB is an important task for water resources planning and management and remains a fundamental challenge for the hydrological community. In recent years, geostatistical methods have proven valuable for estimating hydrological variables in ungauged catchments. However, four major problems restrict the development of geostatistical methods. We established a new information diffusion model based on genetic algorithm (GIDM for spatial interpolating of runoff in the ungauged basins. Genetic algorithms (GA are used to generate high-quality solutions to optimization and search problems. So, using GA, the parameter of optimal window width can be obtained. To test our new method, seven experiments for the annual runoff interpolation based on GIDM at 17 stations on the mainstream and tributaries of the Yellow River are carried out and compared with the inverse distance weighting (IDW method, Cokriging (COK method, and conventional IDMs using the same sparse observed data. The seven experiments all show that the GIDM method can solve four problems of the previous geostatistical methods to some extent and obtains best accuracy among four different models. The key problems of the PUB research are the lack of observation data and the difficulties in information extraction. So the GIDM is a new and useful tool to solve the Prediction in Ungauged Basins (PUB problem and to improve the water management.

  3. WEIGHT FUNCTIONS FOR INTERFACE CRACKS IN DISSIMILAR ANISOTROPIC MATERIALS

    Institute of Scientific and Technical Information of China (English)

    MA Lifeng; CHEN Yiheng

    2004-01-01

    Bueckner's work conjugate integral customarily adopted for linear elastic materials is established for an interface crack in dissimilar anisotropic materials. The difficulties in separating Stroh's six complex arguments involved in the integral for the dissimilar materials are overcome and then the explicit function representations of the integral are given and studied in detail. It is found that the pseudo-orthogonal properties of the eigenfunction expansion form (EEF) for a crack presented previously in isotropic elastic cases, in isotopic bimaterial cases, and in orthotropic cases are also valid in the present dissimilar arbitrary anisotropic cases. The relation between Bueckner's work conjugate integral and the J-integral in these cases is obtained by introducing a complementary stressdisplacement state. Finally, some useful path-independent integrals and weight functions are proposed for calculating the crack tip parameters such as the stress intensity factors.

  4. The electron beam welding of dissimilar materials - case study

    Science.gov (United States)

    Munteanu, A.

    2016-11-01

    The modalities to realize the welding workpieces are multiple. The electron beam welding is one of them. One can weld two different types of materials that give the possibility to reduce the cost of workpiece, if the active part is realised of rich materials welded on components with inferior phisico-mecanical characteristics. The procedure provides great flexibility to the product designs through efficient use of each type of material. So this aspects lead to the necessity to join dissimilar metals. Different tables are given in the specific literature regarding the possible combination. Conflicts may arise by the compromises required for to the optimum heat control of the two dissimilar materials used. But nowadays, more and more frequently are meet the welding of dissimilar metals, thus, the objective of this article is to provide information regarding the particular case of welding between stainless steel and copper without the filler material use.

  5. Local gene density predicts the spatial position of genetic loci in the interphase nucleus.

    Science.gov (United States)

    Murmann, Andrea E; Gao, Juntao; Encinosa, Marissa; Gautier, Mathieu; Peter, Marcus E; Eils, Roland; Lichter, Peter; Rowley, Janet D

    2005-11-15

    Specific chromosomal translocations are hallmarks of many human leukemias. The basis for these translocation events is poorly understood, but it has been assumed that spatial positioning of genes in the nucleus of hematopoietic cells is a contributing factor. Analysis of the nuclear 3D position of the gene MLL, frequently involved in chromosomal translocations and five of its translocation partners (AF4, AF6, AF9, ENL and ELL), and two control loci revealed a characteristic radial distribution pattern in all hematopoietic cells studied. Genes in areas of high local gene density were found positioned towards the nuclear center, whereas genes in regions of low gene density were detected closer to the nuclear periphery. The gene density within a 2 Mbp window was found to be a better predictor for the relative positioning of a genomic locus within the cell nucleus than the gene density of entire chromosomes. Analysis of the position of MLL, AF4, AF6 and AF9 in cell lines carrying chromosomal translocations involving these genes revealed that the position of the normal genes was different from that of the fusion genes, and this was again consistent with the changes in local gene density within a 2 Mbp window. Thus, alterations in gene density directly at translocation junctions could explain the change in the position of affected genes in leukemia cells.

  6. Friction stir welding tool and process for welding dissimilar materials

    Science.gov (United States)

    Hovanski, Yuri; Grant, Glenn J; Jana, Saumyadeep; Mattlin, Karl F

    2013-05-07

    A friction stir welding tool and process for lap welding dissimilar materials are detailed. The invention includes a cutter scribe that penetrates and extrudes a first material of a lap weld stack to a preselected depth and further cuts a second material to provide a beneficial geometry defined by a plurality of mechanically interlocking features. The tool backfills the interlocking features generating a lap weld across the length of the interface between the dissimilar materials that enhances the shear strength of the lap weld.

  7. The effect of interlayers on dissimilar friction weld properties

    Science.gov (United States)

    Maldonado-Zepeda, Cuauhtemoc

    The influence of silver interlayers on the metallurgical and mechanical properties of dissimilar aluminium alloy/stainless steel friction welds are investigated. An elastic contact model is proposed that explains the conditions at and close to the contact surface, which produce Al2O3 particle fracture in dissimilar MMC/AISI 304 stainless steel friction welds. Intermixed (IM) and particle dispersed (PD) regions are formed in Ag-containing dissimilar friction welds. These regions form very early in the joining operation and both contain Ag3Al. Therefore, an interlayer (Ag) introduced with the specific aim of preventing FexAly compound formation in MMC/AISI 304 stainless steel friction welds promotes the formation of another intermetallic phase at the bondline. Since IM and PD regions are progressively removed as the friction welding operation proceeds thinner intermetallic layers are produced when long friction welding times are applied. This type of behavior is quite different from that observed in silver-free dissimilar MMC/AISI 304 stainless steel welds. Nanoparticles of silver are formed in dissimilar MMC/Ag/AISI 304 stainless steel welds produced using low friction pressures. Nanoparticle formation in dissimilar friction welds has never been previously observed or investigated. The introduction of silver interlayers decreases heat generation during welding, produces narrower softened zone regions and improved notch tensile strength properties. All research to-date has assumed per se that joint mechanical properties wholly depend on the mechanical properties and width of the intermetallic layer formed at the dissimilar joint interface. However, it is shown in this thesis that the mechanical properties of MMC/AISI 304 stainless steel joints are determined by the combined effects of intermetallic formation at the bondline and softened zone formation in MMC base material immediately adjacent to the joint interface. A methodology for calculating the notch tensile

  8. Dissimilarity-based classification of anatomical tree structures

    DEFF Research Database (Denmark)

    Sørensen, Lauge Emil Borch Laurs; Lo, Pechin Chien Pau; Dirksen, Asger

    2011-01-01

    A novel method for classification of abnormality in anatomical tree structures is presented. A tree is classified based on direct comparisons with other trees in a dissimilarity-based classification scheme. The pair-wise dissimilarity measure between two trees is based on a linear assignment...... by including anatomical features in the branch feature vectors. The proposed approach is applied to classify airway trees in computed tomography images of subjects with and without chronic obstructive pulmonary disease (COPD). Using the wall area percentage (WA%), a common measure of airway abnormality in COPD...

  9. Congruence between morphological and molecular markers inferred from the analysis of the intra-morphotype genetic diversity and the spatial structure of Oxalis tuberosa Mol.

    Science.gov (United States)

    Pissard, Audrey; Arbizu, Carlos; Ghislain, Marc; Faux, Anne-Michèle; Paulet, Sébastien; Bertin, Pierre

    2008-01-01

    Oxalis tuberosa is an important crop cultivated in the highest Andean zones. A germplasm collection is maintained ex situ by CIP, which has developed a morphological markers system to classify the accessions into morphotypes, i.e. groups of morphologically identical accessions. However, their genetic uniformity is currently unknown. The ISSR technique was used in two experiments to determine the relationships between both morphological and molecular markers systems. The intra-morphotype genetic diversity, the spatial structures of the diversity and the congruence between both markers systems were determined. In the first experience, 44 accessions representing five morphotypes, clearly distinct from each other, were analyzed. At the molecular level, the accessions exactly clustered according to their morphotypes. However, a genetic variability was observed inside each morphotype. In the second experiment, 34 accessions gradually differing from each other on morphological base were analyzed. The morphological clustering showed no geographical structure. On the opposite, the molecular analysis showed that the genetic structure was slightly related to the collection site. The correlation between both markers systems was weak but significant. The lack of perfect congruence between morphological and molecular data suggests that the morphological system may be useful for the morphotypes management but is not appropriate to study the genetic structure of the oca. The spatial structure of the genetic diversity can be related to the evolution of the species and the discordance between the morphological and molecular structures may result from similar selection pressures at different places leading to similar forms with a different genetic background.

  10. Essential genetic interactors of SIR2 required for spatial sequestration and asymmetrical inheritance of protein aggregates.

    Directory of Open Access Journals (Sweden)

    Jia Song

    2014-07-01

    Full Text Available Sir2 is a central regulator of yeast aging and its deficiency increases daughter cell inheritance of stress- and aging-induced misfolded proteins deposited in aggregates and inclusion bodies. Here, by quantifying traits predicted to affect aggregate inheritance in a passive manner, we found that a passive diffusion model cannot explain Sir2-dependent failures in mother-biased segregation of either the small aggregates formed by the misfolded Huntingtin, Htt103Q, disease protein or heat-induced Hsp104-associated aggregates. Instead, we found that the genetic interaction network of SIR2 comprises specific essential genes required for mother-biased segregation including those encoding components of the actin cytoskeleton, the actin-associated myosin V motor protein Myo2, and the actin organization protein calmodulin, Cmd1. Co-staining with Hsp104-GFP demonstrated that misfolded Htt103Q is sequestered into small aggregates, akin to stress foci formed upon heat stress, that fail to coalesce into inclusion bodies. Importantly, these Htt103Q foci, as well as the ATPase-defective Hsp104Y662A-associated structures previously shown to be stable stress foci, co-localized with Cmd1 and Myo2-enriched structures and super-resolution 3-D microscopy demonstrated that they are associated with actin cables. Moreover, we found that Hsp42 is required for formation of heat-induced Hsp104Y662A foci but not Htt103Q foci suggesting that the routes employed for foci formation are not identical. In addition to genes involved in actin-dependent processes, SIR2-interactors required for asymmetrical inheritance of Htt103Q and heat-induced aggregates encode essential sec genes involved in ER-to-Golgi trafficking/ER homeostasis.

  11. Spatial genetic analyses reveal cryptic population structure and migration patterns in a continuously harvested grey wolf (Canis lupus population in north-eastern Europe.

    Directory of Open Access Journals (Sweden)

    Maris Hindrikson

    Full Text Available Spatial genetics is a relatively new field in wildlife and conservation biology that is becoming an essential tool for unravelling the complexities of animal population processes, and for designing effective strategies for conservation and management. Conceptual and methodological developments in this field are therefore critical. Here we present two novel methodological approaches that further the analytical possibilities of STRUCTURE and DResD. Using these approaches we analyse structure and migrations in a grey wolf (Canislupus population in north-eastern Europe. We genotyped 16 microsatellite loci in 166 individuals sampled from the wolf population in Estonia and Latvia that has been under strong and continuous hunting pressure for decades. Our analysis demonstrated that this relatively small wolf population is represented by four genetic groups. We also used a novel methodological approach that uses linear interpolation to statistically test the spatial separation of genetic groups. The new method, which is capable of using program STRUCTURE output, can be applied widely in population genetics to reveal both core areas and areas of low significance for genetic groups. We also used a recently developed spatially explicit individual-based method DResD, and applied it for the first time to microsatellite data, revealing a migration corridor and barriers, and several contact zones.

  12. Mechanical property variation within Inconel 82/182 dissimilar metal weld between low alloy steel and 316 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Changheui [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)], E-mail: chjang@kaist.ac.kr; Lee, Jounghoon [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Sung Kim, Jong; Eun Jin, Tae [Korea Power Engineering Company, 360-9 Mabuk-ri, Guseong-eup, Yongin-si, Gyeonggi-do 449-713 (Korea, Republic of)

    2008-09-15

    In several locations of pressurized water reactors, dissimilar metal welds using Inconel welding wires are used to join the low alloy steel components to stainless-steel pipes. Because of the existence of different materials and chemistry variation within welds, mechanical properties, such as tensile and fracture properties, are expected to show spatial variation. For design and integrity assessment of the dissimilar welds, these variations should be evaluated. In this study, dissimilar metal welds composed of low alloy steel, Inconel 82/182 weld, and stainless steel were prepared by gas tungsten arc welding and shielded metal arc welding techniques. Microstructures were observed using optical and electron microscopes. Typical dendrite structures were observed in Inconel 82/182 welds. Tensile tests using standard and mini-sized specimens and micro-hardness tests were conducted to measure the variation in strength along the thickness of the weld as well as across the weld. In addition, fracture toughness specimens were taken at the bottom, middle, and top of the welds and tested to evaluate the spatial variation along the thickness. It was found that while the strength is about 50-70 MPa greater at the bottom of the weld than at the top of the weld, fracture toughness values at the top of the weld are about 70% greater than those at the bottom of the weld.

  13. Conservation priorities for Prunus africana defined with the aid of spatial analysis of genetic data and climatic variables.

    Directory of Open Access Journals (Sweden)

    Barbara Vinceti

    Full Text Available Conservation priorities for Prunus africana, a tree species found across Afromontane regions, which is of great commercial interest internationally and of local value for rural communities, were defined with the aid of spatial analyses applied to a set of georeferenced molecular marker data (chloroplast and nuclear microsatellites from 32 populations in 9 African countries. Two approaches for the selection of priority populations for conservation were used, differing in the way they optimize representation of intra-specific diversity of P. africana across a minimum number of populations. The first method (S1 was aimed at maximizing genetic diversity of the conservation units and their distinctiveness with regard to climatic conditions, the second method (S2 at optimizing representativeness of the genetic diversity found throughout the species' range. Populations in East African countries (especially Kenya and Tanzania were found to be of great conservation value, as suggested by previous findings. These populations are complemented by those in Madagascar and Cameroon. The combination of the two methods for prioritization led to the identification of a set of 6 priority populations. The potential distribution of P. africana was then modeled based on a dataset of 1,500 georeferenced observations. This enabled an assessment of whether the priority populations identified are exposed to threats from agricultural expansion and climate change, and whether they are located within the boundaries of protected areas. The range of the species has been affected by past climate change and the modeled distribution of P. africana indicates that the species is likely to be negatively affected in future, with an expected decrease in distribution by 2050. Based on these insights, further research at the regional and national scale is recommended, in order to strengthen P. africana conservation efforts.

  14. Conservation priorities for Prunus africana defined with the aid of spatial analysis of genetic data and climatic variables.

    Science.gov (United States)

    Vinceti, Barbara; Loo, Judy; Gaisberger, Hannes; van Zonneveld, Maarten J; Schueler, Silvio; Konrad, Heino; Kadu, Caroline A C; Geburek, Thomas

    2013-01-01

    Conservation priorities for Prunus africana, a tree species found across Afromontane regions, which is of great commercial interest internationally and of local value for rural communities, were defined with the aid of spatial analyses applied to a set of georeferenced molecular marker data (chloroplast and nuclear microsatellites) from 32 populations in 9 African countries. Two approaches for the selection of priority populations for conservation were used, differing in the way they optimize representation of intra-specific diversity of P. africana across a minimum number of populations. The first method (S1) was aimed at maximizing genetic diversity of the conservation units and their distinctiveness with regard to climatic conditions, the second method (S2) at optimizing representativeness of the genetic diversity found throughout the species' range. Populations in East African countries (especially Kenya and Tanzania) were found to be of great conservation value, as suggested by previous findings. These populations are complemented by those in Madagascar and Cameroon. The combination of the two methods for prioritization led to the identification of a set of 6 priority populations. The potential distribution of P. africana was then modeled based on a dataset of 1,500 georeferenced observations. This enabled an assessment of whether the priority populations identified are exposed to threats from agricultural expansion and climate change, and whether they are located within the boundaries of protected areas. The range of the species has been affected by past climate change and the modeled distribution of P. africana indicates that the species is likely to be negatively affected in future, with an expected decrease in distribution by 2050. Based on these insights, further research at the regional and national scale is recommended, in order to strengthen P. africana conservation efforts.

  15. Functionally dissimilar neighbors accelerate litter decomposition in two grass species.

    Science.gov (United States)

    Barbe, Lou; Jung, Vincent; Prinzing, Andreas; Bittebiere, Anne-Kristel; Butenschoen, Olaf; Mony, Cendrine

    2017-02-16

    Plant litter decomposition is a key regulator of nutrient recycling. In a given environment, decomposition of litter from a focal species depends on its litter quality and on the efficiency of local decomposers. Both may be strongly modified by functional traits of neighboring species, but the consequences for decomposition of litter from the focal species remain unknown. We tested whether decomposition of a focal plant's litter is influenced by the functional-trait dissimilarity to the neighboring plants. We cultivated two grass species (Brachypodium pinnatum and Elytrigia repens) in experimental mesocosms with functionally similar and dissimilar neighborhoods, and reciprocally transplanted litter. For both species, litter quality increased in functionally dissimilar neighborhoods, partly as a result of changes in functional traits involved in plant-plant interactions. Furthermore, functional dissimilarity increased overall decomposer efficiency in one species, probably via complementarity effects. Our results suggest a novel mechanism of biodiversity effects on ecosystem functioning in grasslands: interspecific functional diversity within plant communities can enhance intraspecific contributions to litter decomposition. Thus, plant species might better perform in diverse communities by benefiting from higher remineralization rates of their own litter.

  16. Visualizing Proportions and Dissimilarities by Space-filling Maps

    DEFF Research Database (Denmark)

    Carrizosa, Emilio; Guerrero, Vanesa; Morales, Dolores Romero

    2017-01-01

    In this paper we address the problem of visualizing a set of individuals, which have attached a statistical value given as a proportion, and a dissimilarity measure. Each individual is represented as a region within the unit square, in such a way that the area of the regions represent the proport...

  17. Typology of Empirical Attributes: Dissimilarity Linkage Analysis (DLA).

    Science.gov (United States)

    Dubin, Robert; Champoux, Joseph E.

    Dissimilarity Linkage Analysis (DLA) is an extremely simple procedure for developing a typology from empirical attributes that permits the clustering of entities. First the procedure develops a taxonomy of types from empirical attributes possessed by entities in the sample. Second, the procedure assigns entities to one, and only one, type in the…

  18. Altitudinal gradients, biogeographic history and microhabitat adaptation affect fine-scale spatial genetic structure in African and Neotropical populations of an ancient tropical tree species.

    Science.gov (United States)

    Torroba-Balmori, Paloma; Budde, Katharina B; Heer, Katrin; González-Martínez, Santiago C; Olsson, Sanna; Scotti-Saintagne, Caroline; Casalis, Maxime; Sonké, Bonaventure; Dick, Christopher W; Heuertz, Myriam

    2017-01-01

    The analysis of fine-scale spatial genetic structure (FSGS) within populations can provide insights into eco-evolutionary processes. Restricted dispersal and locally occurring genetic drift are the primary causes for FSGS at equilibrium, as described in the isolation by distance (IBD) model. Beyond IBD expectations, spatial, environmental or historical factors can affect FSGS. We examined FSGS in seven African and Neotropical populations of the late-successional rain forest tree Symphonia globulifera L. f. (Clusiaceae) to discriminate the influence of drift-dispersal vs. landscape/ecological features and historical processes on FSGS. We used spatial principal component analysis and Bayesian clustering to assess spatial genetic heterogeneity at SSRs and examined its association with plastid DNA and habitat features. African populations (from Cameroon and São Tomé) displayed a stronger FSGS than Neotropical populations at both marker types (mean Sp = 0.025 vs. Sp = 0.008 at SSRs) and had a stronger spatial genetic heterogeneity. All three African populations occurred in pronounced altitudinal gradients, possibly restricting animal-mediated seed dispersal. Cyto-nuclear disequilibria in Cameroonian populations also suggested a legacy of biogeographic history to explain these genetic patterns. Conversely, Neotropical populations exhibited a weaker FSGS, which may reflect more efficient wide-ranging seed dispersal by Neotropical bats and other dispersers. The population from French Guiana displayed an association of plastid haplotypes with two morphotypes characterized by differential habitat preferences. Our results highlight the importance of the microenvironment for eco-evolutionary processes within persistent tropical tree populations.

  19. Altitudinal gradients, biogeographic history and microhabitat adaptation affect fine-scale spatial genetic structure in African and Neotropical populations of an ancient tropical tree species

    Science.gov (United States)

    Torroba-Balmori, Paloma; Budde, Katharina B.; Heer, Katrin; González-Martínez, Santiago C.; Olsson, Sanna; Scotti-Saintagne, Caroline; Sonké, Bonaventure; Dick, Christopher W.

    2017-01-01

    The analysis of fine-scale spatial genetic structure (FSGS) within populations can provide insights into eco-evolutionary processes. Restricted dispersal and locally occurring genetic drift are the primary causes for FSGS at equilibrium, as described in the isolation by distance (IBD) model. Beyond IBD expectations, spatial, environmental or historical factors can affect FSGS. We examined FSGS in seven African and Neotropical populations of the late-successional rain forest tree Symphonia globulifera L. f. (Clusiaceae) to discriminate the influence of drift-dispersal vs. landscape/ecological features and historical processes on FSGS. We used spatial principal component analysis and Bayesian clustering to assess spatial genetic heterogeneity at SSRs and examined its association with plastid DNA and habitat features. African populations (from Cameroon and São Tomé) displayed a stronger FSGS than Neotropical populations at both marker types (mean Sp = 0.025 vs. Sp = 0.008 at SSRs) and had a stronger spatial genetic heterogeneity. All three African populations occurred in pronounced altitudinal gradients, possibly restricting animal-mediated seed dispersal. Cyto-nuclear disequilibria in Cameroonian populations also suggested a legacy of biogeographic history to explain these genetic patterns. Conversely, Neotropical populations exhibited a weaker FSGS, which may reflect more efficient wide-ranging seed dispersal by Neotropical bats and other dispersers. The population from French Guiana displayed an association of plastid haplotypes with two morphotypes characterized by differential habitat preferences. Our results highlight the importance of the microenvironment for eco-evolutionary processes within persistent tropical tree populations. PMID:28771629

  20. Measuring the dissimilarity of multiplex networks: An empirical study of international trade networks

    Science.gov (United States)

    Zhang, Xiaohang; Cui, Huiyuan; Zhu, Ji; Du, Yu; Wang, Qi; Shi, Wenhua

    2017-02-01

    In recent years, multiplex networks are becoming a research focus in the domain of complex networks. Discovering significant correlations between layers in multiplex networks can provide an insight to their structures. In this study, we propose some methods to measure the dissimilarities of different layers in directed and weighted multiplex networks. The dissimilarity is defined on two levels: node level and layer level. The node dissimilarity is computed based on the distance of the probability distribution of its link weights vectors in different layers; and the layer-level dissimilarity is the weighted sum of the nodes' dissimilarities. Furthermore, the dissimilarity is disintegrated into the connection-based dissimilarity and the weight-based dissimilarity, which represent the topological structure changes and the link weight changes, respectively. The proposed methods are applied to international trade networks.

  1. Genetic, spatial, and social relationships among adults in a group of howler monkeys (Alouatta palliata) from Barro Colorado Island, Panama

    DEFF Research Database (Denmark)

    Milton, Katharine; Nolin, David A.; Ellis, Kelsey

    2016-01-01

    Kinship plays an important role in the social behavior of many primate species, including patterns of intra-group affiliation and cooperation. Within social groups, kinship is strongly affected by dispersal patterns, with the degree of relatedness among group-mates expected to decrease as the ten......Kinship plays an important role in the social behavior of many primate species, including patterns of intra-group affiliation and cooperation. Within social groups, kinship is strongly affected by dispersal patterns, with the degree of relatedness among group-mates expected to decrease...... as the tendency to disperse increases. In primate species characterized by bisexual dispersal, relatedness among adult group-mates is predicted to be low, with social interactions shaped largely by factors other than kinship. To date, however, few studies have examined the role of kinship in social interactions...... in bisexually dispersing species. Accordingly, we collected genetic, spatial and behavioral data on all adult members (three males, six females) in a group of free-ranging mantled howler monkeys (Alouatta palliata) - a bisexually dispersing species of atelid primate - from Barro Colorado Island (BCI), Panama...

  2. Image dissimilarity-based quantification of lung disease from CT

    DEFF Research Database (Denmark)

    Sørensen, Lauge; Loog, Marco; Lo, Pechin Chien Pau

    2010-01-01

    In this paper, we propose to classify medical images using dissimilarities computed between collections of regions of interest. The images are mapped into a dissimilarity space using an image dissimilarity measure, and a standard vector space-based classifier is applied in this space. The classif...

  3. Present spatial diversity patterns of Theobroma cacao L. in the neotropics reflect genetic differentiation in pleistocene refugia followed by human-influenced dispersal.

    Directory of Open Access Journals (Sweden)

    Evert Thomas

    Full Text Available Cacao (Theobroma cacao L. is indigenous to the Amazon basin, but is generally believed to have been domesticated in Mesoamerica for the production of chocolate beverage. However, cacao's distribution of genetic diversity in South America is also likely to reflect pre-Columbian human influences that were superimposed on natural processes of genetic differentiation. Here we present the results of a spatial analysis of the intra-specific diversity of cacao in Latin America, drawing on a dataset of 939 cacao trees genotypically characterized by means of 96 SSR markers. To assess continental diversity patterns we performed grid-based calculations of allelic richness, Shannon diversity and Nei gene diversity, and distinguished different spatially coherent genetic groups by means of cluster analysis. The highest levels of genetic diversity were observed in the Upper Amazon areas from southern Peru to the Ecuadorian Amazon and the border areas between Colombia, Peru and Brazil. On the assumption that the last glaciation (22,000-13,000 BP had the greatest pre-human impact on the current distribution and diversity of cacao, we modeled the species' Pleistocene niche suitability and overlaid this with present-day diversity maps. The results suggest that cacao was already widely distributed in the Western Amazon before the onset of glaciation. During glaciations, cacao populations were likely to have been restricted to several refugia where they probably underwent genetic differentiation, resulting in a number of genetic clusters which are representative for, or closest related to, the original wild cacao populations. The analyses also suggested that genetic differentiation and geographical distribution of a number of other clusters seem to have been significantly affected by processes of human management and accompanying genetic bottlenecks. We discuss the implications of these results for future germplasm collection and in situ, on farm and ex situ

  4. Present spatial diversity patterns of Theobroma cacao L. in the neotropics reflect genetic differentiation in pleistocene refugia followed by human-influenced dispersal.

    Science.gov (United States)

    Thomas, Evert; van Zonneveld, Maarten; Loo, Judy; Hodgkin, Toby; Galluzzi, Gea; van Etten, Jacob

    2012-01-01

    Cacao (Theobroma cacao L.) is indigenous to the Amazon basin, but is generally believed to have been domesticated in Mesoamerica for the production of chocolate beverage. However, cacao's distribution of genetic diversity in South America is also likely to reflect pre-Columbian human influences that were superimposed on natural processes of genetic differentiation. Here we present the results of a spatial analysis of the intra-specific diversity of cacao in Latin America, drawing on a dataset of 939 cacao trees genotypically characterized by means of 96 SSR markers. To assess continental diversity patterns we performed grid-based calculations of allelic richness, Shannon diversity and Nei gene diversity, and distinguished different spatially coherent genetic groups by means of cluster analysis. The highest levels of genetic diversity were observed in the Upper Amazon areas from southern Peru to the Ecuadorian Amazon and the border areas between Colombia, Peru and Brazil. On the assumption that the last glaciation (22,000-13,000 BP) had the greatest pre-human impact on the current distribution and diversity of cacao, we modeled the species' Pleistocene niche suitability and overlaid this with present-day diversity maps. The results suggest that cacao was already widely distributed in the Western Amazon before the onset of glaciation. During glaciations, cacao populations were likely to have been restricted to several refugia where they probably underwent genetic differentiation, resulting in a number of genetic clusters which are representative for, or closest related to, the original wild cacao populations. The analyses also suggested that genetic differentiation and geographical distribution of a number of other clusters seem to have been significantly affected by processes of human management and accompanying genetic bottlenecks. We discuss the implications of these results for future germplasm collection and in situ, on farm and ex situ conservation of cacao.

  5. Spatial genetic structure in Beta vulgaris subsp. maritima and Beta macrocarpa reveals the effect of contrasting mating system, influence of marine currents, and footprints of postglacial recolonization routes.

    Science.gov (United States)

    Leys, Marie; Petit, Eric J; El-Bahloul, Yasmina; Liso, Camille; Fournet, Sylvain; Arnaud, Jean-François

    2014-05-01

    Understanding the factors that contribute to population genetic divergence across a species' range is a long-standing goal in evolutionary biology and ecological genetics. We examined the relative importance of historical and ecological features in shaping the present-day spatial patterns of genetic structure in two related plant species, Beta vulgaris subsp. maritima and Beta macrocarpa. Using nuclear and mitochondrial markers, we surveyed 93 populations from Brittany (France) to Morocco - the southern limit of their species' range distribution. Whereas B. macrocarpa showed a genotypic structure and a high level of genetic differentiation indicative of selfing, the population genetic structure of B. vulgaris subsp. maritima was consistent with an outcrossing mating system. We further showed (1) a strong geographic clustering in coastal B. vulgaris subsp. maritima populations that highlighted the influence of marine currents in shaping different lineages and (2) a peculiar genetic structure of inland B. vulgaris subsp. maritima populations that could indicate the admixture of distinct evolutionary lineages and recent expansions associated with anthropogenic disturbances. Spatial patterns of nuclear diversity and differentiation also supported a stepwise recolonization of Europe from Atlantic-Mediterranean refugia after the last glacial period, with leading-edge expansions. However, cytoplasmic diversity was not impacted by postglacial recolonization: stochastic long-distance seed dispersal mediated by major oceanic currents may mitigate the common patterns of reduced cytoplasmic diversity observed for edge populations. Overall, the patterns we documented here challenge the general view of reduced genetic diversity at the edge of a species' range distribution and provide clues for understanding how life-history and major geographic features interact to shape the distribution of genetic diversity.

  6. Comparative epigenetic and genetic spatial structure of the perennial herb Helleborus foetidus: Isolation by environment, isolation by distance, and functional trait divergence.

    Science.gov (United States)

    Herrera, Carlos M; Medrano, Mónica; Bazaga, Pilar

    2017-08-16

    Epigenetic variation can play a role in local adaptation; thus, there should be associations among epigenetic variation, environmental variation, and functional trait variation across populations. This study examines these relationships in the perennial herb Helleborus foetidus (Ranunculaceae). Plants from 10 subpopulations were characterized genetically (AFLP, SSR markers), epigenetically (MSAP markers), and phenotypically (20 functional traits). Habitats were characterized using six environmental variables. Isolation-by-distance (IBD) and isolation-by-environment (IBE) patterns of genetic and epigenetic divergence were assessed, as was the comparative explanatory value of geographical and environmental distance as predictors of epigenetic, genetic, and functional differentiation. Subpopulations were differentiated genetically, epigenetically, and phenotypically. Genetic differentiation was best explained by geographical distance, while epigenetic differentiation was best explained by environmental distance. Divergence in functional traits was correlated with environmental and epigenetic distances, but not with geographical and genetic distances. Results are compatible with the hypothesis that epigenetic IBE and functional divergence reflected responses to environmental variation. Spatial analyses simultaneously considering epigenetic, genetic, phenotypic and environmental information provide a useful tool to evaluate the role of environmental features as drivers of natural epigenetic variation between populations. © 2017 Botanical Society of America.

  7. Combination of genetics and spatial modelling highlights the sensitivity of cod (Gadus morhua) population diversity in the North Sea to distributions of fishing

    DEFF Research Database (Denmark)

    Heath, Michael R.; Culling, Mark A.; Crozier, Walter W.

    2014-01-01

    Conserving genetic diversity in animal populations is important for sustaining their ability to respond to environmental change. However, the “between-population” component of genetic diversity (biocomplexity) is threatened in many exploited populations, particularly marine fish, where harvest...... North Sea (Viking) unit by the more widespread (Dogger) unit, and its premature extinction under some spatial patterns of fishing. Fishery catch limits for cod are set at the scale of the whole North Sea without regard to such subpopulation dynamics. Our model offers a method to quantify adjustments...

  8. Failure analysis of dissimilar single-lap joints

    Directory of Open Access Journals (Sweden)

    F.A. Stuparu

    2016-03-01

    Full Text Available Single-lap joints made of aluminium and carbon fibre adherends of different thickness are tested to understand better the behaviour of such dissimilar joints. The overlap length and the thickness of the adhesive are kept constant. Local deformation fields are onitored by using the digital image correlation method. Peeling and shearing strains are investigated, emphasizing that peeling is important in the region where failure is initiated, towards an extremity of the overlap region. The use of only carbon fibre adherends is not recommended for a smaller thickness as an additional interface failure is produced and compromises the integrity of the lap joint. However, a dissimilar joint (aluminium-carbon with smaller thickness adherends succeeds to maintain the stiffness of the assembly, but its strength is diminished. The obtained results are suggesting that a complete monitoring of the failure processes in the overlap region can be fully understood only if local deformation measurements are possible.

  9. Picosecond laser welding of similar and dissimilar materials.

    Science.gov (United States)

    Carter, Richard M; Chen, Jianyong; Shephard, Jonathan D; Thomson, Robert R; Hand, Duncan P

    2014-07-01

    We report picosecond laser welding of similar and dissimilar materials based on plasma formation induced by a tightly focused beam from a 1030 nm, 10 ps, 400 kHz laser system. Specifically, we demonstrate the welding of fused silica, borosilicate, and sapphire to a range of materials including borosilicate, fused silica, silicon, copper, aluminum, and stainless steel. Dissimilar material welding of glass to aluminum and stainless steel has not been previously reported. Analysis of the borosilicate-to-borosilicate weld strength compares well to those obtained using similar welding systems based on femtosecond lasers. There is, however, a strong requirement to prepare surfaces to a high (10-60 nm Ra) flatness to ensure a successful weld.

  10. Full-search-equivalent pattern matching with incremental dissimilarity approximations.

    Science.gov (United States)

    Tombari, Federico; Mattoccia, Stefano; Di Stefano, Luigi

    2009-01-01

    This paper proposes a novel method for fast pattern matching based on dissimilarity functions derived from the Lp norm, such as the Sum of Squared Differences (SSD) and the Sum of Absolute Differences (SAD). The proposed method is full-search equivalent, i.e. it yields the same results as the Full Search (FS) algorithm. In order to pursue computational savings the method deploys a succession of increasingly tighter lower bounds of the adopted Lp norm-based dissimilarity function. Such bounding functions allow for establishing a hierarchy of pruning conditions aimed at skipping rapidly those candidates that cannot satisfy the matching criterion. The paper includes an experimental comparison between the proposed method and other full-search equivalent approaches known in literature, which proves the remarkable computational efficiency of our proposal.

  11. Similarity or dissimilarity in the relations between human service organizations.

    Science.gov (United States)

    Bruynooghe, Kevin; Verhaeghe, Mieke; Bracke, Piet

    2008-01-01

    Exchange theory and homophily theory give rise to counteracting expectations for the interaction between human service organizations. Based on arguments of exchange theory, more interaction is expected between dissimilar organizations having complementary resources. Based on arguments of homophily theory, organizations having similar characteristics are expected to interact more. Interorganizational relations between human service organizations in two regional networks in Flanders are examined in this study. Results indicate that human service organizations tend to cooperate more with similar organizations as several homophily effects but not one effect of dissimilarity were found to be significant. The results of this study contribute to the understanding of interorganizational networks of human service organizations and have implications for the development of integrated care.

  12. Spatial and temporal assessment of pollen- and seed-mediated gene flow from genetically engineered plum Prunus domestica.

    Science.gov (United States)

    Scorza, Ralph; Kriss, Alissa B; Callahan, Ann M; Webb, Kevin; Demuth, Mark; Gottwald, Tim

    2013-01-01

    Pollen flow from a 0.46 ha plot of genetically engineered (GE) Prunus domestica located in West Virginia, USA was evaluated from 2000-2010. Sentinel plum trees were planted at distances ranging from 132 to 854 m from the center of the GE orchard. Plots of mixed plum varieties and seedlings were located at 384, 484 and 998 m from the GE plot. Bee hives (Apis mellifera) were dispersed between the GE plum plot and the pollen flow monitoring sites. Pollen-mediated gene flow from out of the GE plum plot to non-GE plums under the study conditions was low, only occurring at all in 4 of 11 years and then in only 0.31% of the 12,116 seeds analyzed. When it occurred, gene flow, calculated as the number of GUS positive embryos/total embryos sampled, ranged from 0.215% at 132 m from the center of the GE plum plot (28 m from the nearest GE plum tree) to 0.033-0.017% at longer distances (384-998 m). Based on the percentage of GUS positive seeds per individual sampled tree the range was 0.4% to 12%. Within the GE field plot, gene flow ranged from 4.9 to 39%. Gene flow was related to distance and environmental conditions. A single year sample from a sentinel plot 132 m from the center of the GE plot accounted for 65% of the total 11-year gene flow. Spatial modeling indicated that gene flow dramatically decreased at distances over 400 m from the GE plot. Air temperature and rainfall were, respectively, positively and negatively correlated with gene flow, reflecting the effects of weather conditions on insect pollinator activity. Seed-mediated gene flow was not detected. These results support the feasibility of coexistence of GE and non-GE plum orchards.

  13. Spatial and temporal assessment of pollen- and seed-mediated gene flow from genetically engineered plum Prunus domestica.

    Directory of Open Access Journals (Sweden)

    Ralph Scorza

    Full Text Available Pollen flow from a 0.46 ha plot of genetically engineered (GE Prunus domestica located in West Virginia, USA was evaluated from 2000-2010. Sentinel plum trees were planted at distances ranging from 132 to 854 m from the center of the GE orchard. Plots of mixed plum varieties and seedlings were located at 384, 484 and 998 m from the GE plot. Bee hives (Apis mellifera were dispersed between the GE plum plot and the pollen flow monitoring sites. Pollen-mediated gene flow from out of the GE plum plot to non-GE plums under the study conditions was low, only occurring at all in 4 of 11 years and then in only 0.31% of the 12,116 seeds analyzed. When it occurred, gene flow, calculated as the number of GUS positive embryos/total embryos sampled, ranged from 0.215% at 132 m from the center of the GE plum plot (28 m from the nearest GE plum tree to 0.033-0.017% at longer distances (384-998 m. Based on the percentage of GUS positive seeds per individual sampled tree the range was 0.4% to 12%. Within the GE field plot, gene flow ranged from 4.9 to 39%. Gene flow was related to distance and environmental conditions. A single year sample from a sentinel plot 132 m from the center of the GE plot accounted for 65% of the total 11-year gene flow. Spatial modeling indicated that gene flow dramatically decreased at distances over 400 m from the GE plot. Air temperature and rainfall were, respectively, positively and negatively correlated with gene flow, reflecting the effects of weather conditions on insect pollinator activity. Seed-mediated gene flow was not detected. These results support the feasibility of coexistence of GE and non-GE plum orchards.

  14. Spatial vs. temporal effects on demographic and genetic structures: the roles of dispersal, masting and differential mortality on patterns of recruitment in Fagus sylvatica.

    Science.gov (United States)

    Oddou-Muratorio, Sylvie; Klein, Etienne K; Vendramin, Giovanni G; Fady, Bruno

    2011-05-01

    Trees' long lifespan, long-distance dispersal abilities and high year-to-year variability in fecundity are thought to have pervasive consequences for the demographic and genetic structure of recruited seedlings. However, we still lack experimental studies quantifying the respective roles of spatial processes such as restricted seed and pollen dispersal and temporal processes such as mast seeding on patterns of regeneration. Dynamics of European beech (Fagus sylvatica) seedling recruitment was monitored in three plots from 2004 to 2006. Six polymorphic microsatellite genetic markers were used to characterize seedlings and their potential parents in a 7.2-ha stand. These seedlings were shown to result from 12 years of recruitment, with one predominant year of seedling recruitment in 2002 and several years without significant recruitment. Using a spatially explicit mating model based on parentage assignment, short average dispersal distances for seed (δ(s) = 10.9 m) and pollen (43.7 m < δ(p) <57.3 m) were found, but there was also a non-negligible immigration rate from outside the plot (m(s) = 20.5%; 71.6% < m(p) < 77.9%). Hierarchical analyses of seedling genetic structure showed that (i) most of the genetic variation was within plots; (ii) the genetic differentiation among seedling plots was significant (F(ST) = 2.6%) while (iii) there was no effect of year-to-year seed rain variation on genetic structure. In addition, no significant effect of genetic structure on mortality was detected. The consequences of these results for the prediction of population dynamics at ecological timescales are discussed.

  15. MINERVA, qualification of dissimilar welds for HTR-application

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, B.; Gnirss, G.; Neureuther, H.; Schneider, K.

    1989-03-01

    The component test ''MINERVA'' is part of an overall concept to qualify dissimilar welds in pipings of advanced gas-cooled high temperature reactors. ''MINERVA'' is designed for a testing time of 20000 h. The experiment started in January 1987. The paper describes the concept, the manufacuring parameters including the basis of selection of materials and welding procedures. The experiment MINERVA and the operating conditions are described.

  16. Ecological dissimilarity among land-use/land-cover types improves a heterogeneity index for predicting biodiversity in agricultural landscapes.

    Science.gov (United States)

    Yoshioka, Akira; Fukasawa, Keita; Mishima, Yoshio; Sasaki, Keiko; Kadoya, Taku

    2017-06-01

    Land-use/land-cover heterogeneity is among the most important factors influencing biodiversity in agricultural landscapes and is the key to the conservation of multi-habitat dwellers that use both terrestrial and aquatic habitats. Heterogeneity indices based on land-use/land-cover maps typically do not integrate ecological dissimilarity between land-use/land-cover types. Here, we applied the concept of functional diversity to an existing land-use/land-cover diversity index (Satoyama index) to incorporate ecological dissimilarity and proposed a new index called the dissimilarity-based Satoyama index (DSI). Using Japan as a case study, we calculated the DSI for three land-use/land-cover maps with different spatial resolutions and derived similarity information from normalized difference vegetation index values. The DSI showed better performance in the prediction of Japanese damselfly species richness than that of the existing index, and a higher correlation between the index and species richness was obtained for higher resolution maps. Thus, our approach to improve the land-use/land-cover diversity index holds promise for future development and can be effective for conservation and monitoring efforts.

  17. Genetics

    DEFF Research Database (Denmark)

    Christensen, Kaare; McGue, Matt

    2016-01-01

    The sequenced genomes of individuals aged ≥80 years, who were highly educated, self-referred volunteers and with no self-reported chronic diseases were compared to young controls. In these data, healthy ageing is a distinct phenotype from exceptional longevity and genetic factors that protect...

  18. More reliable inference for the dissimilarity index of segregation.

    Science.gov (United States)

    Allen, Rebecca; Burgess, Simon; Davidson, Russell; Windmeijer, Frank

    2015-02-01

    The most widely used measure of segregation is the so-called dissimilarity index. It is now well understood that this measure also reflects randomness in the allocation of individuals to units (i.e. it measures deviations from evenness, not deviations from randomness). This leads to potentially large values of the segregation index when unit sizes and/or minority proportions are small, even if there is no underlying systematic segregation. Our response to this is to produce adjustments to the index, based on an underlying statistical model. We specify the assignment problem in a very general way, with differences in conditional assignment probabilities underlying the resulting segregation. From this, we derive a likelihood ratio test for the presence of any systematic segregation, and bias adjustments to the dissimilarity index. We further develop the asymptotic distribution theory for testing hypotheses concerning the magnitude of the segregation index and show that the use of bootstrap methods can improve the size and power properties of test procedures considerably. We illustrate these methods by comparing dissimilarity indices across school districts in England to measure social segregation.

  19. Ocean-to-Ocean Dissimilarities of Salty Subtropical Surface Water

    Science.gov (United States)

    Gordon, A. L.

    2014-12-01

    Each ocean basin displays its own 'personality', reflecting its degree of isolation or connectivity to the global ocean, its place in the interocean exchange network and associated ocean overturning circulation systems, as well as regional circulation and air-sea exchange patterns. While dissimilarities are most notable in the northern hemisphere (the salty North Atlantic vs the fresher North Pacific; as well as the salty Arabian and the fresher Bay of Bengal, a miniature Atlantic/Pacific analog?) far removed from the grand equalizing interocean link of the circum-Antarctic belt, and where large continental blocks impose contrasting forcing, the southern hemisphere ocean basins also display differences. Ocean to ocean dissimilarities are evident in the dry subtropical climate belt, marked by deserts on land and salty surface ocean water. The subtropical sea surface salinity maximum (SSS-max) patterns of 5 the subtropical regimes (the North and South Atlantic, North and South Pacific, and the southern Indian Ocean) display significant dissimilarities in their relative position within their ocean basin, in the structure and seasonality of the SSS-max pattern. The near synoptic coverage of Aquarius and Argo profilers are further defining interannual variability. The South Atlantic SSS-max is pressed against the western boundary, whereas in the other regimes the SSS-max falls within the eastern half of the ocean basin, though the western South Pacific displays a secondary SSS-max. For further details see: A. Gordon, C. Giulivi, J. Busecke, F. Bingham, submitted to the SPURS Oceanography special issue.

  20. PARENT Program for DMW(Dissimilar Metal Weld) Reliability Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Sung Sik; Kim, Kyung Jo; Jung, Hae Dong [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2010-10-15

    Some cracks were found in dissimilar metal welds (DMW), which are connected with major components of nuclear power plants. Usually, the dissimilar metal welds are consisted of Alloy 600, carbon steel and stainless steel. Since 2000s, most of the cracks are found in welds, especially dissimilar metal welds such as pressurizer safety relief nozzle, reactor head penetration, reactor bottom mounted instrumentation (BMI), and reactor nozzles. Since the cracks are revealed as a primary water stress corrosion cracking (PWSCC), the reliability of non destructive evaluation (NDE) technique becomes more important. To cope with the NDE reliability, PINC (program for inspection of nickel alloy components) international cooperation was organized. The aim of the project was 1) to fabricate representative NDE mock-ups with flaws to simulate PWSCCs, 2) to identify and quantitatively assess NDE methods for accurately detecting, sizing and characterizing PWSCCs, 3) to document the range of locations and morphologies of PWSCCs and 4) to incorporate results with other results of ongoing PWSCC research programs, as appropriate. Since the last KNS autumn meeting, the PINC program was finalized and the next program PARENT (Program to Assess Reliability for Emerging NDE Technique) is started on June this year. In this study, as part of the PINC project, international RRT (round robin test) results for DMW will be introduced and the status of new PARENT program will be introduced

  1. Development of Dissimilar Metal Weld Performance Demonstration System

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Sik; Yoon, Byung Sik; Yang, Seung Han; Guon, Kee Il [KEPCO Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    In the early 1980s, many leaks in the piping systems of boiling water reactors in the USA were discovered in piping weld area which had been examined ultrasonically and found to be defect free. To enhance the reliability of ultrasonic testing system, ASME B and PV code section XI adopted the performance demonstration requirements (Appendix VIII) for the ultrasonic examination of nuclear power plant piping weld in the 1989 winter addenda for the first time. MOST Bulletin 2004-13 was published at 2004.6. Following the MEST Bulletin 2009-37 which was published at 2009.9(formerly MOST Bulletin 2004-13), all nuclear power plants in Korea shall implement performance demonstration of dissimilar metal weld. The object of this study is to develop the performance demonstration system for dissimilar metal weld ultrasonic testing of nuclear power plant in order to meet ASME Sec. XI Appendix VIII requirements and MEST Bulletin 2009-37. This paper describes the status of the development of dissimilar metal weld performance demonstration system in Korea

  2. GO-based Functional Dissimilarity of Gene Sets

    Directory of Open Access Journals (Sweden)

    Aguilar-Ruiz Jesús S

    2011-09-01

    Full Text Available Abstract Background The Gene Ontology (GO provides a controlled vocabulary for describing the functions of genes and can be used to evaluate the functional coherence of gene sets. Many functional coherence measures consider each pair of gene functions in a set and produce an output based on all pairwise distances. A single gene can encode multiple proteins that may differ in function. For each functionality, other proteins that exhibit the same activity may also participate. Therefore, an identification of the most common function for all of the genes involved in a biological process is important in evaluating the functional similarity of groups of genes and a quantification of functional coherence can helps to clarify the role of a group of genes working together. Results To implement this approach to functional assessment, we present GFD (GO-based Functional Dissimilarity, a novel dissimilarity measure for evaluating groups of genes based on the most relevant functions of the whole set. The measure assigns a numerical value to the gene set for each of the three GO sub-ontologies. Conclusions Results show that GFD performs robustly when applied to gene set of known functionality (extracted from KEGG. It performs particularly well on randomly generated gene sets. An ROC analysis reveals that the performance of GFD in evaluating the functional dissimilarity of gene sets is very satisfactory. A comparative analysis against other functional measures, such as GS2 and those presented by Resnik and Wang, also demonstrates the robustness of GFD.

  3. Conservation genetics of threatened Hippocampus guttulatus in vulnerable habitats in NW Spain: temporal and spatial stability of wild populations with flexible polygamous mating system in captivity.

    Directory of Open Access Journals (Sweden)

    Almudena López

    Full Text Available This study was focused on conservation genetics of threatened Hippocampus guttulatus on the Atlantic coast of NW Iberian Peninsula. Information about spatial structure and temporal stability of wild populations was obtained based on microsatellite markers, and used for monitoring a captive breeding program firstly initiated in this zone at the facilities of the Institute of Marine Research (Vigo, Spain. No significant major genetic structure was observed regarding the biogeographical barrier of Cape Finisterre. However, two management units under continuous gene flow are proposed based on the allelic differentiation between South-Atlantic and Cantabrian subpopulations, with small to moderate contemporary effective size based on single-sample methods. Temporal stability was observed in South-Atlantic population samples of H. guttulatus for the six-year period studied, suggesting large enough effective population size to buffer the effects of genetic drift within the time frame of three generations. Genetic analysis of wild breeders and offspring in captivity since 2009 allowed us to monitor the breeding program founded in 2006 in NW Spain for this species. Similar genetic diversity in the renewed and founder broodstock, regarding the wild population of origin, supports suitable renewal and rearing processes to maintain genetic variation in captivity. Genetic parentage proved single-brood monogamy in the wild and in captivity, but flexible short- and long-term mating system under captive conditions, from strict monogamy to polygamy within and/or among breeding seasons. Family analysis showed high reproductive success in captivity under genetic management assisted by molecular relatedness estimates to avoid inbreeding. This study provides genetic information about H. guttulatus in the wild and captivity within an uncovered geographical range for this data deficient species, to be taken into account for management and conservation purposes.

  4. Population genetic structure of Aedes (Stegomyia aegypti (L. at a micro-spatial scale in Thailand: implications for a dengue suppression strategy.

    Directory of Open Access Journals (Sweden)

    Phanthip Olanratmanee

    Full Text Available BACKGROUND: The genetic population structure of Aedes (Stegomyia aegypti (L., the main vector of dengue virus, is being investigated in areas where a novel dengue suppression program is to be implemented. The aim of the program is to release and establish mosquito populations with impaired virus transmission capabilities. To model effects of the release and devise protocols for its implementation, information about the genetic structure of populations at a range of spatial scales is required. METHODOLOGY/PRINCIPAL FINDINGS: This study investigates a potential release site in the Hua Sam Rong Subdistrict of Plaeng Yao District, Chachoengsao Province, in eastern Thailand which comprises a complex of five villages within a 10 km radius. Aedes aegypti resting indoors was sampled at four different times of year from houses within the five villages. Genetic markers were used to screen the mosquitoes: two Exon Primed Intron Crossing (EPIC markers and five microsatellite markers. The raw allele size was determined using several statistical software packages to analyze the population structure of the mosquito. Estimates of effective population size for each village were low, but there was no evidence of genetic isolation by geographic distance. CONCLUSIONS: The presence of temporary genetic structure is possibly caused by genetic drift due to large contributions of adults from a few breeding containers. This suggests that the introduction of mosquitoes into an area needs to proceed through multiple releases and targeting of sites where mosquitoes are emerging in large numbers.

  5. Spatial Genetic Structure within and among Seed Stands of Pinus engelmannii Carr. and Pinus leiophylla Schiede ex Schltdl. & Cham, in Durango, Mexico

    Directory of Open Access Journals (Sweden)

    María Elena Ortiz-Olivas

    2017-01-01

    Full Text Available Studies of spatial genetic structure (SGS are important because they offer detailed insights into historical demographic and evolutionary processes and provide important information regarding species conservation and management. Pinus engelmannii and P. leiophylla var. leiophylla are two important timber tree species in Mexico, covering about 2.5 and 1.9 million hectares, respectively. However, studies in relation to population genetics are unfortunately scant. The aim of this research was to use amplified fragment length polymorphisms (AFLP analysis to identify potential differences in spatial genetic structure within and among seven Pinus engelmannii and nine P. leiophylla var. leiophylla seed stands in Durango, Mexico. Within the 16 seed stands of the two tested pine species, no significant SGS was detected, although SGS was detected among the seed stands. We concluded that the collection of seed in only some seed stands should not significantly alter the degree of genetic differentiation within the (collected seed. Distances between seed orchards and pollen propagators of more than 24 km for P. engelmannii and 7 km for P. leiophylla may be sufficient to limit contamination. Finally, local seeds should be used for (reforestation.

  6. Beta Diversity in a Highly Heterogeneous Area: Disentangling Species and Taxonomic Dissimilarity for Terrestrial Vertebrates.

    Science.gov (United States)

    Calderón-Patrón, Jaime M; Goyenechea, Irene; Ortiz-Pulido, Raúl; Castillo-Cerón, Jesús; Manriquez, Norma; Ramírez-Bautista, Aurelio; Rojas-Martínez, Alberto E; Sánchez-Rojas, Gerardo; Zuria, Iriana; Moreno, Claudia E

    2016-01-01

    Quantifying differences in species composition among communities provides important information related to the distribution, conservation and management of biodiversity, especially when two components are recognized: dissimilarity due to turnover, and dissimilarity due to richness differences. The ecoregions in central Mexico, within the Mexican Transition Zone, have outstanding environmental heterogeneity and harbor huge biological richness, besides differences in the origin of the biota. Therefore, biodiversity studies in this area require the use of complementary measures to achieve appropriate information that may help in the design of conservation strategies. In this work we analyze the dissimilarity of terrestrial vertebrates, and the components of turnover and richness differences, among six ecoregions in the state of Hidalgo, central Mexico. We follow two approaches: one based on species level dissimilarity, and the second on taxonomic dissimilarity. We used databases from the project "Biodiversity in the state of Hidalgo". Our results indicate that species dissimilarity is higher than taxonomic dissimilarity, and that turnover contributes more than richness differences, both for species and taxonomic total dissimilarity. Moreover, total dissimilarity, turnover dissimilarity and the dissimilarity due to richness differences were positively related in the four vertebrate groups. Reptiles had the highest values of dissimilarity, followed by mammals, amphibians and birds. For reptiles, birds, and mammals, species turnover was the most important component, while richness differences had a higher contribution for amphibians. The highest values of dissimilarity occurred between environmentally contrasting ecoregions (i.e., tropical and temperate forests), which suggests that environmental heterogeneity and differences in the origin of biotas are key factors driving beta diversity of terrestrial vertebrates among ecoregions in this complex area.

  7. Recent range expansion and agricultural landscape heterogeneity have only minimal effect on the spatial genetic structure of the plant pathogenic fungus Mycosphaerella fijiensis.

    Science.gov (United States)

    Rieux, A; De Lapeyre De Bellaire, L; Zapater, M-F; Ravigne, V; Carlier, J

    2013-01-01

    Understanding how geographical and environmental features affect genetic variation at both the population and individual levels is crucial in biology, especially in the case of pathogens. However, distinguishing between these factors and the effects of historical range expansion on spatial genetic structure remains challenging. In the present study, we investigated the case of Mycosphaerella fijiensis-a plant pathogenic fungus that has recently colonized an agricultural landscape characterized by the presence of potential barriers to gene flow, including several commercial plantations in which disease control practises such as the use of fungicides are applied frequently, and low host density areas. We first genotyped 300 isolates sampled at a global scale on untreated plants in two dimensions over a 50 × 80-km area. Using two different clustering algorithms, no genetic structure was detected in the studied area, suggesting expansion of large populations and/or no influence of potential barriers. Second, we investigated the potential effect of disease control practises on M. fijiensis diversity by comparing populations sampled in commercial vs food-crop plantations. At this local scale, we detected significantly higher allelic richness inside commercial plantations compared with the surrounding food-crop plantation populations. Analysis of molecular variance indicated that 99% of the total genetic variance occurred within populations. We discuss the suggestion that high population size and/or high migration rate between populations might be responsible for the absence of any effect of disease control practises on genetic diversity and differentiation.

  8. Investigating chemical and microstructural evolution at dissimilar metal welds

    OpenAIRE

    Clark, John William Gordon

    2015-01-01

    Dissimilar metal welds (DMWs) are widely used in steam vessels in thermal power stations to join low-temperature alloys, such as steels, to high temperature alloys, such as nickel-based alloys. This provides a cost-effective manufacturing solution. However, there is a history of DMWs failing due to creep in service environments. Many investigations have been performed on weld systems and failures in the traditional 2.25Cr-1Mo (P22) steels, but fewer have been performed on newer 9Cr-1Mo steels...

  9. Investigation of dissimilar metal welds by energy-resolved neutron imaging

    Science.gov (United States)

    Tremsin, Anton S.; Ganguly, Supriyo; Meco, Sonia M.; Pardal, Goncalo R.; Shinohara, Takenao; Feller, W. Bruce

    2016-01-01

    A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participating alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al–steel weld is clearly resolved and could be used to optimize the welding process. A highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption. PMID:27504075

  10. Investigation of dissimilar metal welds by energy-resolved neutron imaging.

    Science.gov (United States)

    Tremsin, Anton S; Ganguly, Supriyo; Meco, Sonia M; Pardal, Goncalo R; Shinohara, Takenao; Feller, W Bruce

    2016-08-01

    A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participating alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al-steel weld is clearly resolved and could be used to optimize the welding process. A highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption.

  11. Spatial dependence of genetic data related to human health and livestock disease resistance: a role for geography to support the One Health approach

    Directory of Open Access Journals (Sweden)

    Stéphane Joost

    2017-06-01

    Full Text Available The spatial dependence of located health and/or genetic data can be used to detect clusters likely to reveal disease prevalence or signatures of adaptation possibly associated with characteristics of the local environment (high temperatures, air or water pollution, be it in humans or animals (Murtaugh et al. 2017. Most often, geographic maps are produced to represent health data. Medical information is transmitted through thematic choropleth maps. For instance administrative units are colored according to the variable of interest. But it is key to analyse health and/or genetic data by explicitly including geographic characteristics (distances, co-location and also the potential and power of spatial statistics to detect specific patterns in the geographic distribution of disease occurrences (“make visible the invisible”. A classic example using clusters is the map produced by John Snow (Snow 1855 showing the number of deaths caused by a cholera outbreak in London. Looking at a detail of Snow's original map, it is possible to realize how he graphically represented the number of deaths, with short bold lines representing death occurrences (frequencies forming a kind of histogram placed on the street at the addresses where it happened - what we currently name georeferencing. A cluster of death people is an effect observed on the territory, and the existence of such a cluster depends on an infected water pump located at the same place (the cause. How can this spatial dependence be detected and measured? It is possible to identify spatial patterns in the geographic space by means of spatial statistics. We need to determine whether the variable of interest is randomly distributed or spatially dependent, and to check if the patterns observed are robust to random permutations. We also need to explore the data, to find out what is the range of influence of this spatial dependence. Here we focus on the functioning of one among several measures of

  12. A Review: Welding Of Dissimilar Metal Alloys by Laser Beam Welding & Friction Stir Welding Techniques

    Directory of Open Access Journals (Sweden)

    Ms. Deepika Harwani

    2014-12-01

    Full Text Available Welding of dissimilar metals has attracted attention of the researchers worldwide, owing to its many advantages and challenges. There is no denial in the fact that dissimilar welded joints offer more flexibility in the design and production of the commercial and industrial components. Many welding techniques have been analyzed to join dissimilar metal combinations. The objective of this paper is to review two such techniques – Laser welding and Friction stir welding. Laser beam welding, a high power density and low energy-input process, employs a laser beam to produce welds of dissimilar materials. Friction stir welding, a solid-state joining process, is also successfully used in dissimilar welding applications like aerospace and ship building industries. This paper summarizes the trends and advances of these two welding processes in the field of dissimilar welding. Future aspects of the study are also discussed.

  13. Joining Dissimilar Materials Using Friction Stir Scribe Technique

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Piyush [Pacific Northwest National Laboratory, Richland 99352, WA e-mail: piyush.upadhyay@pnnl.gov; Hovanski, Yuri [Pacific Northwest National Laboratory, Richland 99352, WA; Jana, Saumyadeep [Pacific Northwest National Laboratory, Richland 99352, WA; Fifield, Leonard S. [Pacific Northwest National Laboratory, Richland 99352, WA

    2016-10-03

    Development of a robust and cost-effective method of joining dissimilar materials could provide a critical pathway to enable widespread use of multi-material designs and components in mainstream industrial applications. The use of multi-material components such as steel-aluminum and aluminum-polymer would allow design engineers to optimize material utilization based on service requirements and could often lead to weight and cost reductions. However, producing an effective joint between materials with vastly different thermal, microstructural, and deformation responses is highly problematic using conventional joining and/or fastening methods. This is especially challenging in cost sensitive, high volume markets that largely rely on low cost joining solutions. Friction stir scribe technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like magnesium and aluminum to high temperature materials like steel and titanium. Viable joints between polymer composites and metal can also be made using this method. This paper will present the state of the art, progress made, and challenges associated with this innovative derivative of friction stir welding in reference to joining dissimilar metals and polymer/metal combinations.

  14. How Do Users Map Points Between Dissimilar Shapes?

    KAUST Repository

    Hecher, Michael

    2017-07-25

    Finding similar points in globally or locally similar shapes has been studied extensively through the use of various point descriptors or shape-matching methods. However, little work exists on finding similar points in dissimilar shapes. In this paper, we present the results of a study where users were given two dissimilar two-dimensional shapes and asked to map a given point in the first shape to the point in the second shape they consider most similar. We find that user mappings in this study correlate strongly with simple geometric relationships between points and shapes. To predict the probability distribution of user mappings between any pair of simple two-dimensional shapes, two distinct statistical models are defined using these relationships. We perform a thorough validation of the accuracy of these predictions and compare our models qualitatively and quantitatively to well-known shape-matching methods. Using our predictive models, we propose an approach to map objects or procedural content between different shapes in different design scenarios.

  15. JOINING DISSIMILAR MATERIALS USING FRICTION STIR SCRIBE TECHNIQUE

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Piyush; Hovanski, Yuri; Jana, Saumyadeep; Fifield, Leonard S.

    2016-09-01

    Development of robust and cost effective method of joining dissimilar materials can provide a critical pathway to enable widespread use of multi-material design and components in mainstream industrial applications. The use of multi-material components such as Steel-Aluminum, Aluminum-Polymer allows design engineers to optimize material utilization based on service requirements and often lead weight and cost reductions. However producing an effective joint between materials with vastly different thermal, microstructural and deformation response is highly problematic using conventional joining and /or fastening methods. This is especially challenging in cost sensitive high volume markets that largely rely on low–cost joining solutions. Friction Stir Scribe technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like Magnesium and Aluminum to high temperature materials like Steels and Titanium. Additionally viable joints between polymer composites and metal can also be made using this method. This paper will present state of the art, progress made and challenges associated with this innovative derivative of Friction Stir welding in reference to joining dissimilar metals and polymer/metal combinations.

  16. Genetic ablation of the mammillary bodies in the Foxb1 mutant mouse leads to selective deficit of spatial working memory.

    Science.gov (United States)

    Radyushkin, Konstantin; Anokhin, Konstantin; Meyer, Barbara I; Jiang, Qiuhong; Alvarez-Bolado, Gonzalo; Gruss, Peter

    2005-01-01

    Mammillary bodies and the mammillothalamic tract are parts of a classic neural circuitry that has been implicated in severe memory disturbances accompanying Korsakoff's syndrome. However, the specific role of mammillary bodies in memory functions remains controversial, often being considered as just an extension of the hippocampal memory system. To study this issue we used mutant mice with a targeted mutation in the transcription factor gene Foxb1. These mice suffer perinatal degeneration of the medial and most of the lateral mammillary nuclei, as well as of the mammillothalamic bundle. Foxb1 mutant mice showed no deficits in such hippocampal-dependent tasks as contextual fear conditioning and social transmission of food preference. They were also not impaired in the spatial reference memory test in the radial arm maze. However, Foxb1 mutants showed deficits in the task for spatial navigation within the Barnes maze. Furthermore, they showed impairments in spatial working memory tasks such as the spontaneous alternation and the working memory test in the radial arm maze. Thus, our behavioural analysis of Foxb1 mutants suggests that the medial mammillary nuclei and mammillothalamic tract play a role in a specific subset of spatial tasks, which require combined use of both spatial and working memory functions. Therefore, the mammillary bodies and the mammillothalamic tract may form an important route through which the working memory circuitry receives spatial information from the hippocampus.

  17. Complex patterns of population genetic structure of moose, Alces alces, after recent spatial expansion in Poland revealed by sex-linked markers.

    Science.gov (United States)

    Swisłocka, Magdalena; Czajkowska, Magdalena; Duda, Norbert; Danyłow, Jan; Owadowska-Cornil, Edyta; Ratkiewicz, Mirosław

    2013-01-01

    In recent years, human activity directly and indirectly influenced the demography of moose in Poland. The species was close to extinction, and only a few isolated populations survived after the Second World War; then, unprecedented demographic and spatial expansions had occurred, possibly generating a very complex pattern of population genetic structure at the present-day margins of the species range in Poland. Over 370 moose from seven populations were collected from Poland, and partial sequences of the mitochondrial control region (mtDNA-cr; 607 bp) were obtained. In addition, the entire mtDNA cytochrome b gene (1,140 bp) and Y-chromosome markers (1,982 bp in total) were studied in a chosen set of individuals. Twelve mtDNA haplotypes that all belonged to the European moose phylogroup were recorded. They could be divided into two distinct clades: Central Europe and the Ural Mountains. The first clade consists of three distinct groups/branches: Biebrza, Polesie, and Fennoscandia. The Biebrza group has experienced spatial and demographic expansion in the recent past. Average genetic differentiation among moose populations in Poland at mtDNA-cr was great and significant (ΦST = 0.407, p moose that colonized Poland from the east (Lithuania, Belarus, and Ukraine) and the north (former East Prussia). Among all the sequenced Y-chromosome markers, polymorphisms were found in the DBY14 marker in three populations only; four haplotypes were recorded in total. No significant differentiation was detected for this Y-linked marker among moose populations in Poland. Our mtDNA study revealed that a variety of different factors-bottleneck, the presence of relict, autochthonous populations, translocations, limited female dispersal, and the colonization from the east and north-are responsible for the observed complex pattern of population genetic structure after demographic and spatial expansion of moose in Poland.

  18. Genetic differentiation and spatial structure of Geosmithia morbida, the causal agent of thousand cankers disease in black walnut (Juglans nigra).

    Science.gov (United States)

    Hadziabdic, Denita; Vito, Lisa M; Windham, Mark T; Pscheidt, Jay W; Trigiano, Robert N; Kolarik, Miroslav

    2014-05-01

    The main objectives of this study were to evaluate genetic composition of Geosmithia morbida populations in the native range of black walnut and provide a better understanding regarding demography of the pathogen. The fungus G. morbida, and the walnut twig beetle, Pityophthorus juglandis, have been associated with a disease complex of black walnut (Juglans nigra) known as thousand cankers disease (TCD). The disease is manifested as branch dieback and canopy loss, eventually resulting in tree death. In 2010, the disease was detected in black walnut in Tennessee, and subsequently in Virginia and Pennsylvania in 2011 and North Carolina in 2012. These were the first incidences of TCD east of Colorado, where the disease has been established for more than a decade on indigenous walnut species. A genetic diversity and population structure study of 62 G. morbida isolates from Tennessee, Pennsylvania, North Carolina and Oregon was completed using 15 polymorphic microsatellite loci. The results revealed high haploid genetic diversity among seven G. morbida populations with evidence of gene flow, and significant differentiation among two identified genetic clusters. There was a significant correlation between geographic and genetic distance. Understanding the genetic composition and demography of G. morbida can provide valuable insight into recognizing factors affecting the persistence and spread of an invasive pathogen, disease progression, and future infestation predictions. Overall, these data support the hypotheses of two separate, highly diverse pathogen introductions into the native range of black walnut.

  19. Nonstationary patterns of isolation-by-distance: inferring measures of local genetic differentiation with Bayesian kriging.

    Science.gov (United States)

    Duforet-Frebourg, Nicolas; Blum, Michael G B

    2014-04-01

    Patterns of isolation-by-distance (IBD) arise when population differentiation increases with increasing geographic distances. Patterns of IBD are usually caused by local spatial dispersal, which explains why differences of allele frequencies between populations accumulate with distance. However, spatial variations of demographic parameters such as migration rate or population density can generate nonstationary patterns of IBD where the rate at which genetic differentiation accumulates varies across space. To characterize nonstationary patterns of IBD, we infer local genetic differentiation based on Bayesian kriging. Local genetic differentiation for a sampled population is defined as the average genetic differentiation between the sampled population and fictive neighboring populations. To avoid defining populations in advance, the method can also be applied at the scale of individuals making it relevant for landscape genetics. Inference of local genetic differentiation relies on a matrix of pairwise similarity or dissimilarity between populations or individuals such as matrices of FST between pairs of populations. Simulation studies show that maps of local genetic differentiation can reveal barriers to gene flow but also other patterns such as continuous variations of gene flow across habitat. The potential of the method is illustrated with two datasets: single nucleotide polymorphisms from human Swedish populations and dominant markers for alpine plant species.

  20. Patterns of spatial genetic structuring in the endangered limpet Patella ferruginea: implications for the conservation of a Mediterranean endemic.

    Science.gov (United States)

    Casu, Marco; Rivera-Ingraham, Georgina A; Cossu, Piero; Lai, Tiziana; Sanna, Daria; Dedola, Gian Luca; Sussarellu, Rossana; Sella, Gabriella; Cristo, Benedetto; Curini-Galletti, Marco; García-Gómez, José Carlos; Espinosa, Free

    2011-10-01

    Patella ferruginea Gmelin, 1791 is an endangered marine gastropod endemic to the Western Mediterranean. Its range is restricted to the Sardinian-Corsican region (SCR), North Africa, a few scattered sites in Southern Spain, and Sicily. Inter-simple sequence repeat (ISSR) markers and three different mitochondrial DNA (mtDNA) regions, Cytochrome c Oxidase subunit I, 12S (small-subunit ribosomal RNA gene) and 16S (large-subunit ribosomal RNA gene), were used to investigate the presence of genetic population structuring. The mtDNA sequences showed very low levels of genetic differentiation. Conversely, ISSRs showed the presence of two main genetic groups, corresponding to Spain, North Africa and Sicily and the SCR. The SCR was further split into two subgroups. The ISSR results suggest that, on a regional scale, the genetic structure of P. ferruginea is mainly determined by the restriction of gene flow by dispersal barriers. On a more local scale human harvesting may play a crucial role in population structuring by increasing the effect of genetic drift.

  1. Mnemonic networks in the hippocampal formation: from spatial maps to temporal and conceptual codes

    NARCIS (Netherlands)

    Milivojevic, B.; Doeller, C.F.

    2013-01-01

    The hippocampal formation has been associated with a wide variety of functions including spatial navigation and planning, memory encoding and retrieval, relational processing, novelty detection, and imagination. These functions are dissimilar in terms of their behavioral consequences and modality of

  2. Mnemonic networks in the hippocampal formation: from spatial maps to temporal and conceptual codes

    NARCIS (Netherlands)

    Milivojevic, B.; Doeller, C.F.

    2013-01-01

    The hippocampal formation has been associated with a wide variety of functions including spatial navigation and planning, memory encoding and retrieval, relational processing, novelty detection, and imagination. These functions are dissimilar in terms of their behavioral consequences and modality of

  3. Spatial and temporal genetic structure of a river-resident Atlantic salmon (Salmo salar) after millennia of isolation.

    Science.gov (United States)

    Sandlund, Odd Terje; Karlsson, Sten; Thorstad, Eva B; Berg, Ole Kristian; Kent, Matthew P; Norum, Ine C J; Hindar, Kjetil

    2014-05-01

    The river-resident Salmo salar ("småblank") has been isolated from other Atlantic salmon populations for 9,500 years in upper River Namsen, Norway. This is the only European Atlantic salmon population accomplishing its entire life cycle in a river. Hydropower development during the last six decades has introduced movement barriers and changed more than 50% of the river habitat to lentic conditions. Based on microsatellites and SNPs, genetic variation within småblank was only about 50% of that in the anadromous Atlantic salmon within the same river. The genetic differentiation (F ST) between småblank and the anadromous population was 0.24. This is similar to the differentiation between anadromous Atlantic salmon in Europe and North America. Microsatellite analyses identified three genetic subpopulations within småblank, each with an effective population size Ne of a few hundred individuals. There was no evidence of reduced heterozygosity and allelic richness in contemporary samples (2005-2008) compared with historical samples (1955-56 and 1978-79). However, there was a reduction in genetic differentiation between sampling localities over time. SNP data supported the differentiation of småblank into subpopulations and revealed downstream asymmetric gene flow between subpopulations. In spite of this, genetic variation was not higher in the lower than in the upper areas. The meta-population structure of småblank probably maintains genetic variation better than one panmictic population would do, as long as gene flow among subpopulations is maintained. Småblank is a unique endemic island population of Atlantic salmon. It is in a precarious situation due to a variety of anthropogenic impacts on its restricted habitat area. Thus, maintaining population size and avoiding further habitat fragmentation are important.

  4. Study the Factors Effecting on Welding Joint of Dissimilar Metals

    Directory of Open Access Journals (Sweden)

    Esam J. Ebraheam

    2011-01-01

    Full Text Available The aim of this work is to study the factors that affect the welding joint of dissimilar metals. Austenitic stainless steel-type AISI (316L with a thickness of (2mm was welded to carbon steel (1mm using an MIG spot welding. The filler metal is a welding wire of the type E80S-G (according to AWS is used with (1.2mm diameter and CO2 is used as shielding gas with flow rate (7L/min for all times was used in this work. The results indicate that the increase of the welding current tends to increase the size of spot weld, and also increases the sheer force. Whereas the sheer force increased inversely with the time of welding. Furthermore, the results indicate that increasing the current and time of welding increases the diameter of weld zone, and decreases the sheer force.

  5. Development of Welding Procedures for NPP Dissimilar Metal Weld

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jang Wook; Cho, Hong Seok; Lee, Dong Min; Park, Yu Deog; Choi, Sang Hoon [Korea Plant Service and Engineering Co., Seongnam (Korea, Republic of)

    2008-05-15

    Nuclear primary system consists of various materials according to the function. Recently, concern about the integrity on Dissimilar Metal Weld (DMW) which was made of inconel material such as alloy 600/82/182 has arisen from industry. Leak from hot leg nozzle weld at V.C Summer and axial cracks in hot leg nozzle welds at Ringhals 3 and 4 were took placed at the DMW zone, which is major degradation mechanism known as Primary Water Stress Corrosion Cracking (PWSCC). In order to ensure operational ability of nuclear power plants, it is necessary to obtain measures against unexpected risks. KPS has developed the DMW technology, Narrow Groove Welding (NGW) system and field implementation procedures for alloy 600 since March 2005.

  6. AN INTERFACE INCLUSION BETWEEN TWO DISSIMILAR PIEZOELECTRIC MATERIALS

    Institute of Scientific and Technical Information of China (English)

    高存法; 樊蔚勋

    2001-01-01

    The generalized two- dimensional problem of a dielectric rigid line inclusion, atthe interface between two dissimilar piezoelectric media subjected to piecewise uniform loads at infinity, is studied by means of the Stroh theory. The problem was reduced to a Hilbert problem, and then closed-form expressions were obtained, respectively, for the complex potentials in piezoelectric media, the electric field inside the inclusion and the tip fields near the inclusion. It is shown that in the media, all field variables near the inclusion-tip show square root singularity and oscillatory singularity, the intensity of which is dependent on the material constants and the strains at infinity. In addition, it is found that the electric field inside the inclusion is singular and oscillatory too, when approaching the inclusion-tips from inside the inclusion.

  7. A weighted dissimilarity index to isolate faults during alarm floods

    CERN Document Server

    Charbonnier, S; Gayet, P

    2015-01-01

    A fault-isolation method based on pattern matching using the alarm lists raised by the SCADA system during an alarm flood is proposed. A training set composed of faults is used to create fault templates. Alarm vectors generated by unknown faults are classified by comparing them with the fault templates using an original weighted dissimilarity index that increases the influence of the few alarms relevant to diagnose the fault. Different decision strategies are proposed to support the operator in his decision making. The performances are evaluated on two sets of data: an artificial set and a set obtained from a highly realistic simulator of the CERN Large Hadron Collider process connected to the real CERN SCADA system.

  8. Genetic and environmental factors affecting growth of Nile tilapia (Oreochromis niloticus) juveniles: modelling spatial correlations between hapas

    NARCIS (Netherlands)

    Charo-Karisa, H.; Komen, J.; Rezk, M.A.; Reynolds, S.; Ponzoni, R.W.; Bovenhuis, H.

    2006-01-01

    The aim of this study was to quantify the environmental and genetic effects on early growth of Nile tilapia, Oreochromis niloticus, in hapa-in-earthen pond systems. In a pilot study, we grew swim-up fry with or without supplementary feed in hapas suspended in fertilized ponds at 5, 10, 15, and 20 fr

  9. Socio-spatial organization and kin structure in ocelots from integration of camera trapping and noninvasive genetics

    NARCIS (Netherlands)

    Rodgers, T.W.; Giacalone, J.; Heske, E.J.; Janecka, J.E.; Jansen, P.A.; Phillips, C.A.; Schooley, R.L.

    2015-01-01

    Kin selection theory predicts that under certain conditions animals will tolerate related individuals in their home ranges. We examined the relationship between spatiotemporal overlap and genetic relatedness in ocelots (Leopardus pardalis) to determine if kin selection plays a role in structuring

  10. Socio-spatial organization and kin structure in ocelots from integration of camera trapping and noninvasive genetics

    NARCIS (Netherlands)

    Rodgers, T.W.; Giacalone, J.; Heske, E.J.; Janecka, J.E.; Jansen, P.A.; Phillips, C.A.; Schooley, R.L.

    2015-01-01

    Kin selection theory predicts that under certain conditions animals will tolerate related individuals in their home ranges. We examined the relationship between spatiotemporal overlap and genetic relatedness in ocelots (Leopardus pardalis) to determine if kin selection plays a role in structuring oc

  11. E-commerce Website Recommender System Based on Dissimilarity and Association Rule

    OpenAIRE

    MingWang Zhang; ShuWen Yang; LiFeng Zhang

    2013-01-01

    By analyzing the current electronic commerce recommendation algorithm analysis, put forward a kind to use dissimilarity clustering and association recommendation algorithm, the algorithm realized web website shopping user data clustering by use of the dissimilarity, and then use the association rules algorithm for clustering results of association recommendation, experiments show that the algorithm compared with traditional clustering association algorithm of iteration times decrease, improve...

  12. Early diagnosis of dementia based on intersubject whole-brain dissimilarities

    DEFF Research Database (Denmark)

    Klein, S.; Loog, M.; Lijn, F. van der;

    2010-01-01

    . A kNN classifier was trained on the dissimilarity matrix and the performance was tested in a leave-one-out experiment. A classification accuracy of 81% was attained (spec. 83%, sens. 79%). This demonstrates the potential of whole-brain intersubject dissimilarities to aid in early diagnosis of dementia....

  13. Spatial heterogeneity of cyanobacterial communities and genetic variation of Microcystis populations within large, shallow eutrophic lakes (Lake Taihu and Lake Chaohu, China)

    Institute of Scientific and Technical Information of China (English)

    Yuanfeng Cai; Fanxiang Kong; Limei Shi; Yang Yu

    2012-01-01

    Cyanobacteria,specifically Microcystis,usually form massive blooms in eutrophic freshwater lakes.Cyanobacterial samples were collected from eight sites of both Lake Taihu and Lake Chaohu in late summer to determine the diversity and distribution pattern of cyanobacteria and Microcystis in large,shallow,entropic lakes with significant spatial heterogeneity and long-term Microcystis bloom.Molecular methods based on denaturing gradient gel electrophoresis and clone library analysis were used.A similar heterogeneous distribution pattern of cyanobacteria in both lakes was observed.Most parts of these two lakes with high trophic level were dominated by Microcystis.However,in the regions with low trophic levels as well as low concentrations of chlorophyll a,Synechococcus occupied a considerable percentage.Different morphospecies and genotypes dominated the bloom-forming Microcystis populations in these two lakes.Microcystis viridis and Microcystis novacekii were dominant in Lake Chaohu,whereas Microcystis flos-aquae was dominant in Lake Taihu.Only 2 of thel3 Microcystis operational taxonomic units were shared between these two lakes.Analysis of molecular variance based on 16S to 23S internal transcribed spacer sequences indicated the significant genetic differentiation of Microcystis between these two lakes (Fst =0.19,p < 0.001).However,only 19.46% of the genetic variability was explained by the population variation between lakes,whereas most (80.54%) of the genetic variability occurred within the lakes.Phylogenetic analysis revealed no phylogeographic structure of Microcystis population in these two lakes,as illustrated by their cosmopolitan nature.Our results revealed that spatial heterogeneity within lakes has more impact on the cyanobacterial diversity than geographical isolation in a local scale.

  14. Assessment of spatial discordance of primary and effective seed dispersal of European beech (Fagus sylvatica L.) by ecological and genetic methods.

    Science.gov (United States)

    Millerón, M; López de Heredia, U; Lorenzo, Z; Alonso, J; Dounavi, A; Gil, L; Nanos, N

    2013-03-01

    Spatial discordance between primary and effective dispersal in plant populations indicates that postdispersal processes erase the seed rain signal in recruitment patterns. Five different models were used to test the spatial concordance of the primary and effective dispersal patterns in a European beech (Fagus sylvatica) population from central Spain. An ecological method was based on classical inverse modelling (SSS), using the number of seed/seedlings as input data. Genetic models were based on direct kernel fitting of mother-to-offspring distances estimated by a parentage analysis or were spatially explicit models based on the genotype frequencies of offspring (competing sources model and Moran-Clark's Model). A fully integrated mixed model was based on inverse modelling, but used the number of genotypes as input data (gene shadow model). The potential sources of error and limitations of each seed dispersal estimation method are discussed. The mean dispersal distances for seeds and saplings estimated with these five methods were higher than those obtained by previous estimations for European beech forests. All the methods show strong discordance between primary and effective dispersal kernel parameters, and for dispersal directionality. While seed rain was released mostly under the canopy, saplings were established far from mother trees. This discordant pattern may be the result of the action of secondary dispersal by animals or density-dependent effects; that is, the Janzen-Connell effect. © 2013 Blackwell Publishing Ltd.

  15. A software tool to model genetic regulatory networks. Applications to the modeling of threshold phenomena and of spatial patterning in Drosophila.

    Directory of Open Access Journals (Sweden)

    Rui Dilão

    Full Text Available We present a general methodology in order to build mathematical models of genetic regulatory networks. This approach is based on the mass action law and on the Jacob and Monod operon model. The mathematical models are built symbolically by the Mathematica software package GeneticNetworks. This package accepts as input the interaction graphs of the transcriptional activators and repressors of a biological process and, as output, gives the mathematical model in the form of a system of ordinary differential equations. All the relevant biological parameters are chosen automatically by the software. Within this framework, we show that concentration dependent threshold effects in biology emerge from the catalytic properties of genes and its associated conservation laws. We apply this methodology to the segment patterning in Drosophila early development and we calibrate the genetic transcriptional network responsible for the patterning of the gap gene proteins Hunchback and Knirps, along the antero-posterior axis of the Drosophila embryo. In this approach, the zygotically produced proteins Hunchback and Knirps do not diffuse along the antero-posterior axis of the embryo of Drosophila, developing a spatial pattern due to concentration dependent thresholds. This shows that patterning at the gap genes stage can be explained by the concentration gradients along the embryo of the transcriptional regulators.

  16. Spatial genetic structure of Long-tailed Ducks (Clangula hyemalis) among Alaskan, Canadian, and Russian breeding populations

    Science.gov (United States)

    Wilson, Robert E.; Gust, J R; Petersen, Margaret; Talbot, Sandra

    2016-01-01

    Arctic ecosystems are changing at an unprecedented rate. How Arctic species are able to respond to such environmental change is partially dependent on the connections between local and broadly distributed populations. For species like the Long-tailed Duck (Clangula hyemalis), we have limited telemetry and band-recovery information from which to infer population structure and migratory connectivity; however, genetic analyses can offer additional insights. To examine population structure in the Long-tailed Duck, we characterized variation at mtDNA control region and microsatellite loci among four breeding areas in Alaska, Canada, and Russia. We observed significant differences in the variance of mtDNA haplotype frequencies between the Yukon-Kuskokwim Delta (YKD) and the three Arctic locations (Arctic Coastal Plain in Alaska, eastern Siberia, and central Canadian Arctic). However, like most sea duck genetic assessments, our study found no evidence of population structure based on autosomal microsatellite loci. Long-tailed Ducks use multiple wintering areas where pair formation occurs with some populations using both the Pacific and Atlantic Oceans. This situation provides a greater opportunity for admixture across breeding locales, which would likely homogenize the nuclear genome even in the presence of female philopatry. The observed mtDNA differentiation was largely due to the presence of two divergent clades: (A) a clade showing signs of admixture among all breeding locales and (B) a clade primarily composed of YKD samples. We hypothesize that the pattern of mtDNA differentiation reflects some degree of philopatry to the YKD and isolation of two refugial populations with subsequent expansion and admixture. We recommend additional genetic assessments throughout the circumpolar range of Long-tailed Ducks to further quantify aspects of genetic diversity and migratory connectivity in this species.

  17. Genetic diversity and spatial correlation patterns unravel the biogeographical history of the European sweet vernal grasses (Anthoxanthum L., Poaceae).

    Science.gov (United States)

    Pimentel, Manuel; Sahuquillo, Elvira; Catalán, Pilar

    2007-08-01

    Different processes have contributed to shaping the present distribution of the European biotas. Up to three different tertiary- to quaternary-time-scale evolutionary scenarios have been proposed to interpret the divergence and genetic structuring of plant species in Europe. In the present study, the Amplified Fragment Length Polymorphisms technique has been used to unravel the species and regional phylogeography of the European sweet vernal grasses (Anthoxanthum L. Poaceae). Forty-six populations belonging to all seven European species of Anthoxanthum and covering a broad geographical and ecological range were selected. Different phylogeography and population genetics diversity and structure estimates indicated a clear divergence of old Messinian Mediterranean lineages, followed by a pre-Pliocene split between Mediterranean annuals and Eurosiberian perennials and a more recent Pleistocene differentiation of Arctic-Alpine, Atlantic and Submediterranean diploid to polyploid landraces. Regional and population correlation tests between geographical and genetic distances allowed to postulate distinct pre- and post-glacial colonization pathways across Europe for the taxa of this widespread genus.

  18. Spatial genetic structure of bristle-thighed curlews (Numenius tahitiensis): breeding area differentiation not reflected on the non-breeding grounds

    Science.gov (United States)

    Sonsthagen, Sarah A.; Tibbitts, T. Lee; Gill, Robert E.; Williams, Ian S.; Talbot, Sandra L.

    2015-01-01

    Migratory birds occupy geographically and ecologically disparate areas during their annual cycle with conditions on breeding and non-breeding grounds playing separate and important roles in population dynamics. We used data from nuclear microsatellite and mitochondrial DNA control region loci to assess the breeding and non-breeding spatial genetic structure of a transoceanic migrant shorebird, the bristle-thighed curlew. We found spatial variance in the distribution of allelic and haplotypic frequencies between the curlew's two breeding areas in Alaska but did not observe this spatial structure throughout its non-breeding range on low-lying tropical and subtropical islands in the Central Pacific (Oceania). This suggests that the two breeding populations do not spatially segregate during the non-breeding season. Lack of migratory connectivity is likely attributable to the species' behavior, as bristle-thighed curlews exhibit differential timing of migration and some individuals move among islands during non-breeding months. Given the detrimental impact of many past and current human activities on island ecosystems, admixture of breeding populations in Oceania may render the bristle-thighed curlew less vulnerable to perturbations there, as neither breeding population will be disproportionally affected by local habitat losses or by stochastic events. Furthermore, lack of migratory connectivity may enable bristle-thighed curlews to respond to changing island ecosystems by altering their non-breeding distribution. However, availability of suitable non-breeding habitat for curlews in Oceania is increasingly limited on both low-lying and high islands by habitat loss, sea level rise, and invasive mammalian predators that pose a threat to flightless and flight-compromised curlews during the molting period.

  19. Substitution and pooling in visual crowding induced by similar and dissimilar distractors.

    Science.gov (United States)

    Ester, Edward F; Zilber, Emma; Serences, John T

    2015-01-08

    Visual crowding refers to a phenomenon whereby objects that appear in the periphery of the visual field are more difficult to identify when embedded within clutter. Pooling models assert that crowding results from an obligatory averaging or other combination of target and distractor features that occurs prior to awareness. One well-known manifestation of pooling is feature averaging, with which the features of target and nontarget stimuli are combined at an early stage of visual processing. Conversely, substitution models assert that crowding results from binding a target and nearby distractors to incorrect spatial locations. Recent evidence suggests that substitution predominates when target-flanker feature similarity is low, but it is unclear whether averaging or substitution best explains crowding when similarity is high. Here, we examined participants' orientation report errors for targets crowded by similar or dissimilar flankers. In two experiments, we found evidence inconsistent with feature averaging regardless of target-flanker similarity. However, the observed data could be accommodated by a probabilistic substitution model in which participants occasionally "swap" a target for a distractor. Thus, we conclude that-at least for the displays used here-crowding likely results from a probabilistic substitution of targets and distractors, regardless of target-distractor feature similarity. © 2015 ARVO.

  20. Cryptic female choice favours sperm from major histocompatibility complex-dissimilar males.

    Science.gov (United States)

    Løvlie, Hanne; Gillingham, Mark A F; Worley, Kirsty; Pizzari, Tommaso; Richardson, David S

    2013-10-22

    Cryptic female choice may enable polyandrous females to avoid inbreeding or bias offspring variability at key loci after mating. However, the role of these genetic benefits in cryptic female choice remains poorly understood. Female red junglefowl, Gallus gallus, bias sperm use in favour of unrelated males. Here, we experimentally investigate whether this bias is driven by relatedness per se, or by similarity at the major histocompatibility complex (MHC), genes central to vertebrate acquired immunity, where polymorphism is critical to an individual's ability to combat pathogens. Through experimentally controlled natural matings, we confirm that selection against related males' sperm occurs within the female reproductive tract but demonstrate that this is more accurately predicted by MHC similarity: controlling for relatedness per se, more sperm reached the eggs when partners were MHC--dissimilar. Importantly, this effect appeared largely owing to similarity at a single MHC locus (class I minor). Further, the effect of MHC similarity was lost following artificial insemination, suggesting that male phenotypic cues might be required for females to select sperm differentially. These results indicate that postmating mechanisms that reduce inbreeding may do so as a consequence of more specific strategies of cryptic female choice promoting MHC diversity in offspring.

  1. Anatomical Directional Dissimilarities in Tri-axial Swallowing Accelerometry Signals.

    Science.gov (United States)

    Movahedi, Faezeh; Kurosu, Atsuko; Coyle, James L; Perera, Subashan; Sejdic, Ervin

    2017-05-01

    Swallowing accelerometry is a noninvasive approach currently under consideration as an instrumental screening test for swallowing difficulties, with most current studies focusing on the swallowing vibrations in the anterior-posterior (A-P) and superior-inferior (S-I) directions. However, the displacement of the hyolaryngeal structure during the act of swallowing in patients with dysphagia involves declination of the medial-lateral (M-L), which suggests that the swallowing vibrations in the M-L direction have the ability to reveal additional details about the swallowing function. With this motivation, we performed a broad comparison of the swallowing vibrations in all three anatomical directions. Tri-axial swallowing accelerometry signals were concurrently collected from 72 dysphagic patients undergoing videofluoroscopic evaluation of swallowing (mean age: 63.94 ± 12.58 years period). Participants swallowed one or more thickened liquids with different consistencies including thin-thick liquids, nectar-thick liquids, and pudding-thick liquids with either a comfortable self-selected volume from a cup or a controlled volume by the examiner from a 5-ml spoon. Swallows were grouped based on the viscosity of swallows and the participant's stroke history. Then, a comprehensive set of features was extracted in multiple signal domains from 881 swallows. The results highlighted inter-axis dissimilarities among tri-axial swallowing vibrations including the extent of variability in the amplitude of signals, the degree of predictability of signals, and the extent of disordered behavior of signals in time-frequency domain. First, the upward movement of the hyolaryngeal structure, representing the S-I signals, were actually more variable in amplitude and showed less predictable behavior than the sideways and forward movements, representing the A-P and M-L signals, during swallowing. Second, the S-I signals, which represent the upward movement of the hyolaryngeal structure

  2. Perceived Deep-Level Dissimilarity: Personality Antecedents and Impact on Overall Job Attitude, Helping, Work Withdrawal, and Turnover

    Science.gov (United States)

    Liao, Hui; Chuang, Aichia; Joshi, Aparna

    2008-01-01

    The current research extends three research areas in relational demography: considering deep-level dissimilarity in theory building, assessing dissimilarity perceptions directly in theory testing, and examining the antecedents of dissimilarity perceptions. The results, based on two field studies using diverse samples, demonstrate the effects of…

  3. Genetic assessment of meiobenthic community composition and spatial distribution in coastal sediments along northern Gulf of Mexico.

    Science.gov (United States)

    Brannock, Pamela M; Wang, Lei; Ortmann, Alice C; Waits, Damien S; Halanych, Kenneth M

    2016-08-01

    Meiobenthic (meiofauna and micro-eukaryotes) organisms are important contributors to ecosystem functioning in aquatic environments through their roles in nutrient transport, sediment stability, and food web interactions. Despite their ecological importance, information pertaining to variation of these communities at various spatial and temporal scales is not widely known. Many studies in the Gulf of Mexico (GOM) have focused either on deep sea or continental shelf areas, while little attention has been paid to bays and coastal regions. Herein, we take a holistic approach by using high-throughput sequencing approaches to examine spatial variation in meiobenthic communities within Alabama bays and the coastal northern GOM region. Sediment samples were collected along three transects (Mississippi Sound: MS, FOCAL: FT, and Orange Beach: OB) from September 2010 to April 2012 and community composition was determined by metabarcoding the V9 hypervariable region of the nuclear18S rRNA gene. Results showed that Stramenopiles (diatoms), annelids, arthropods (copepods), and nematodes were the dominate groups within samples, while there was presence of other phyla throughout the dataset. Location played a larger role than time sampled in community composition. However, samples were collected over a short temporal scale. Samples clustered in reference to transect, with the most eastern transect (OB) having a distinct community composition in comparison to the other two transects (MS and FT). Communities also differed in reference to region (Bay versus Shelf). Bulk density and percent inorganic carbon were the only measured environmental factors that were correlated with community composition.

  4. Genetic Differentiation and Spatial Structure of Phellinus noxius, the Causal Agent of Brown Root Rot of Woody Plants in Japan.

    Directory of Open Access Journals (Sweden)

    Mitsuteru Akiba

    Full Text Available Phellinus noxius is a pathogenic fungus that causes brown root rot disease in a variety of tree species. This fungus is distributed in tropical and sub-tropical regions of Southeast and East Asia, Oceania, Australia, Central America and Africa. In Japan, it was first discovered on Ishigaki Island in Okinawa Prefecture in 1988; since then, it has been found on several of the Ryukyu Islands. Recently, this fungus was identified from the Ogasawara (Bonin Islands, where it has killed trees, including rare endemic tree species. For effective control or quarantine methods, it is important to clarify whether the Japanese populations of P. noxius are indigenous to the area or if they have been introduced from other areas. We developed 20 microsatellite markers from genome assembly of P. noxius and genotyped 128 isolates from 12 of the Ryukyu Islands and 3 of the Ogasawara Islands. All isolates had unique genotypes, indicating that basidiospore infection is a primary dissemination method for the formation of new disease foci. Genetic structure analyses strongly supported genetic differentiation between the Ryukyu populations and the Ogasawara populations of P. noxius. High polymorphism of microsatellite loci suggests that Japanese populations are indigenous or were introduced a very long time ago. We discuss differences in invasion patterns between the Ryukyu Islands and the Ogasawara Islands.

  5. Hierarchical structure of genetic distances: Effects of matrix size, spatial distribution and correlation structure among gene frequencies

    Directory of Open Access Journals (Sweden)

    Flávia Melo Rodrigues

    1998-06-01

    Full Text Available Geographic structure of genetic distances among local populations within species, based on allozyme data, has usually been evaluated by estimating genetic distances clustered with hierarchical algorithms, such as the unweighted pair-group method by arithmetic averages (UPGMA. The distortion produced in the clustering process is estimated by the cophenetic correlation coefficient. This hierarchical approach, however, can fail to produce an accurate representation of genetic distances among populations in a low dimensional space, especially when continuous (clinal or reticulate patterns of variation exist. In the present study, we analyzed 50 genetic distance matrices from the literature, for animal taxa ranging from Platyhelminthes to Mammalia, in order to determine in which situations the UPGMA is useful to understand patterns of genetic variation among populations. The cophenetic correlation coefficients, derived from UPGMA based on three types of genetic distance coefficients, were correlated with other parameters of each matrix, including number of populations, loci, alleles, maximum geographic distance among populations, relative magnitude of the first eigenvalue of covariance matrix among alleles and logarithm of body size. Most cophenetic correlations were higher than 0.80, and the highest values appeared for Nei's and Rogers' genetic distances. The relationship between cophenetic correlation coefficients and the other parameters analyzed was defined by an "envelope space", forming triangles in which higher values of cophenetic correlations are found for higher values in the parameters, though low values do not necessarily correspond to high cophenetic correlations. We concluded that UPGMA is useful to describe genetic distances based on large distance matrices (both in terms of elevated number of populations or alleles, when dimensionality of the system is low (matrices with large first eigenvalues or when local populations are separated

  6. Inter-specific relationships and hierarchical spatial genetic structuring in Nervilia nipponica, an endangered orchid in Japan.

    Science.gov (United States)

    Gale, Stephan W; Maeda, Ayako; Chen, Chen-I; Yukawa, Tomohisa

    2010-09-01

    An understanding of the extent to which reproductive strategy and seed dispersal lead to the structuring of genetic diversity in space is required when planning measures towards the conservation of endangered plant species. In this study, genetic structure in the endangered terrestrial orchid Nervilia nipponica was investigated using amplified fragment length polymorphisms following extensive sampling throughout the species' range in Japan and intensive sampling at a single population. Limited diversity was found within the species as a whole, but significant structuring was detected between populations. One genotype was common to two widely separated sites, possibly indicative of long-range dispersal. Significant structure was also detected at the intensively sampled site, as a result of the presence of two distinct putative clones. These findings are consistent with observations of the species' ability to set seed autogamously and propagate vegetatively. Given the strong colonising capability inferred for the species, attention should focus on identifying and securing habitat conditions conducive to seed germination and seedling establishment in the development of a conservation strategy. As presently circumscribed, N. nipponica is shown to comprise two polyphyletic taxa, both endemic to Japan, and both distinct from N. taiwaniana, a species that some authors have considered conspecific.

  7. Genetic Differentiation and Spatial Structure of Phellinus noxius, the Causal Agent of Brown Root Rot of Woody Plants in Japan.

    Science.gov (United States)

    Akiba, Mitsuteru; Ota, Yuko; Tsai, Isheng J; Hattori, Tsutomu; Sahashi, Norio; Kikuchi, Taisei

    2015-01-01

    Phellinus noxius is a pathogenic fungus that causes brown root rot disease in a variety of tree species. This fungus is distributed in tropical and sub-tropical regions of Southeast and East Asia, Oceania, Australia, Central America and Africa. In Japan, it was first discovered on Ishigaki Island in Okinawa Prefecture in 1988; since then, it has been found on several of the Ryukyu Islands. Recently, this fungus was identified from the Ogasawara (Bonin) Islands, where it has killed trees, including rare endemic tree species. For effective control or quarantine methods, it is important to clarify whether the Japanese populations of P. noxius are indigenous to the area or if they have been introduced from other areas. We developed 20 microsatellite markers from genome assembly of P. noxius and genotyped 128 isolates from 12 of the Ryukyu Islands and 3 of the Ogasawara Islands. All isolates had unique genotypes, indicating that basidiospore infection is a primary dissemination method for the formation of new disease foci. Genetic structure analyses strongly supported genetic differentiation between the Ryukyu populations and the Ogasawara populations of P. noxius. High polymorphism of microsatellite loci suggests that Japanese populations are indigenous or were introduced a very long time ago. We discuss differences in invasion patterns between the Ryukyu Islands and the Ogasawara Islands.

  8. Spatial and temporal population genetic structure of four northeastern Pacific littorinid gastropods: the effect of mode of larval development on variation at one mitochondrial and two nuclear DNA markers.

    Science.gov (United States)

    Lee, Hyuk Je; Boulding, Elizabeth G

    2009-05-01

    We investigated the effect of development mode on the spatial and temporal population genetic structure of four littorinid gastropod species. Snails were collected from the same three sites on the west coast of Vancouver Island, Canada in 1997 and again in 2007. DNA sequences were obtained for one mitochondrial gene, cytochrome b (Cyt b), and for up to two nuclear genes, heat shock cognate 70 (HSC70) and aminopeptidase N intron (APN54). We found that the mean level of genetic diversity and long-term effective population sizes (N(e)) were significantly greater for two species, Littorina scutulata and L. plena, that had a planktotrophic larval stage than for two species, Littorina sitkana and L. subrotundata, that laid benthic egg masses which hatched directly into crawl-away juveniles. Predictably, two poorly dispersing species, L. sitkana and L. subrotundata, showed significant spatial genetic structure at an 11- to 65-km geographical scale that was not observed in the two planktotrophic species. Conversely, the two planktotrophic species had more temporal genetic structure over a 10-year interval than did the two direct-developing species and showed highly significant temporal structure for spatially pooled samples. The greater temporal genetic variation of the two planktotrophic species may have been caused by their high fecundity, high larval dispersal, and low but spatially correlated early survivorship. The sweepstakes-like reproductive success of the planktotrophic species could allow a few related females to populate hundreds of kilometres of coastline and may explain their substantially larger temporal genetic variance but lower spatial genetic variance relative to the direct-developing species.

  9. Mechanical Properties and Microstructure of Dissimilar Material Welded Joints

    Directory of Open Access Journals (Sweden)

    Ziewiec A.

    2014-10-01

    Full Text Available The paper presents results of the mechanical testing and the microstructure analysis of dissimilar welded joint of the R350HT steel and the high-manganese (Hadfield cast steel using Cr-Ni cast steel spacer. The simulation tests of the welded joint surface deformation were carried out. The macroscopic and microscopic investigation were made using light microscopy (LM and scanning electron microscopy (SEM. Content of the magnetic phase was measured using magnetoscope. The quantitative metallographic investigation was used for assessment of ferrite and martensite contents and X-ray diffraction phase analysis was carried out. The results showed that during cooling of the spacer after welding, the transformation of metastable austenite into martensite proceeded. In addition to work hardening, the phase transformation of austenite into martensite occurs during the process of the superficial deformation of the spacer while simulated exploitation. This leads to a substantial increase of hardness, and at the same time, causes the increase of wear resistance of the welded joints of crossovers.

  10. Direct bonding for dissimilar metals assisted by carboxylic acid vapor

    Science.gov (United States)

    Song, Jenn-Ming; Huang, Shang-Kun; Akaike, Masatake; Suga, Tadatomo

    2015-03-01

    This study developed a low-temperature low-vacuum direct bonding process for dissimilar metals via surface modification with formic acid vapor. Robust Cu/Ag and Cu/Zn bonding with a shear strength higher than 25 MPa can be achieved by thermal compression at 275 and 300 °C, respectively. CuZn5 and Cu5Zn8 formed at the interface of Cu/Zn joints, while no distinct interdiffusion layers appeared at the Cu/Ag interface. At elevated temperatures, the shear strength of Cu/Zn joints decreased significantly and turned to be weaker than Cu/Ag at 250 °C due to the softening of Zn. All the joints performed well subjected to thermal cycling up to 1000 times. However, compared with Cu/Ag joints with stable mechanical performance suffering aging at 250 °C, the shear strength of Cu/Zn degraded drastically up to 200 h, and after that it remained almost constant, which can be ascribed to the competitive growth between CuZn5 and Cu5Zn8, resulting in collapse and oxidation of CuZn5.

  11. Ultrasonic Evaluation of Two Dissimilar Metal Weld Overlay Specimens

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Susan L.; Cinson, Anthony D.; Prowant, Matthew S.; Moran, Traci L.; Anderson, Michael T.

    2012-06-30

    Two dissimilar metal weld (DMW) pipe-to-nozzle specimens were implanted with thermal fatigue cracks in the 13% to 90% through-wall depth range. The specimens were ultrasonically evaluated with phased-array probes having center frequencies of 0.8, 1.0, 1.5, and 2.0 megahertz (MHz). An Alloy 82/182 weld overlay (WOL) was applied and the specimens were ultrasonically re-evaluated for flaw detection and characterization. The Post-WOL flaw depths were approximately 10% to 56% through-wall. This study has shown the effectiveness of ultrasonic examinations of Alloy 82/182 overlaid DMW specimens. Phased-array probes with center frequency in the 0.8- to 1.0-MHz range provide a strong coherent signal but the greater ultrasonic wavelength and larger beam spot size prevent the reliable detection of small flaws. These small flaws had nominal through-wall depths of less than 15% and length in the 50-60 mm (2-2.4 in.) range. Flaws in the 19% and greater through-wall depth range were readily detected with all four probes. At the higher frequencies, the reflected signals are less coherent but still provide adequate signal for flaw detection and characterization. A single inspection at 2.0 MHz could provide adequate detection and sizing information but a supplemental inspection at 1.0 or 1.5 MHz is recommended.

  12. Phase Space Dissimilarity Measures for Structural Health Monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Bubacz, Jacob A [ORNL; Chmielewski, Hana T [ORNL; Pape, Alexander E [ORNL; Depersio, Andrew J [ORNL; Hively, Lee M [ORNL; Abercrombie, Robert K [ORNL; Boone, Shane [ORNL

    2011-11-01

    A novel method for structural health monitoring (SHM), known as the Phase Space Dissimilarity Measures (PSDM) approach, is proposed and developed. The patented PSDM approach has already been developed and demonstrated for a variety of equipment and biomedical applications. Here, we investigate SHM of bridges via analysis of time serial accelerometer measurements. This work has four aspects. The first is algorithm scalability, which was found to scale linearly from one processing core to four cores. Second, the same data are analyzed to determine how the use of the PSDM approach affects sensor placement. We found that a relatively low-density placement sufficiently captures the dynamics of the structure. Third, the same data are analyzed by unique combinations of accelerometer axes (vertical, longitudinal, and lateral with respect to the bridge) to determine how the choice of axes affects the analysis. The vertical axis is found to provide satisfactory SHM data. Fourth, statistical methods were investigated to validate the PSDM approach for this application, yielding statistically significant results.

  13. Development of Weld Overlay Technology for Dissimilar Welds in Pressurizer Nozzles

    Energy Technology Data Exchange (ETDEWEB)

    Park, K. S.; Byeon, J. G.; Lee, J. B. [Doosan Heavy Industries and Construction Co., Daejeon (Korea, Republic of)

    2009-10-15

    As a result of Primary Water Stress Corrosion Cracking (PWSCC) in alloy 600, leaks in dissimilar metal welds of pressurizer nozzles were discovered recently in several US plants. The involved companies developed advanced repair techniques to prevent or repair PWSCC applying weld overlay procedures to dissimilar metal welds such as those between pipes and nozzles. Within 2 or 3 years, more than half of the nuclear power plants in Korea will have been in operation for more than 20 years. From this background, a weld overlay procedure has been developed in Korea for the dissimilar metal welds of pressurizer nozzles.

  14. Applying electron backscattering diffraction to macroscopic residual stress characterisation in a dissimilar weld

    OpenAIRE

    Abburi Venkata, K.; Truman, C.E.; Coules, H.E.; Warren, A D

    2017-01-01

    Dissimilar metal welds are complicated in nature because of the complex microstructure characteristics in the weld fusion zone. It is often necessary to know the phase distribution in a dissimilar metal weld especially at the interface such as fusion zone and heat affected zone to be able to predict the behaviour of the joint and its fitness for service. In this paper, a dissimilar metal weld made between ferritic/martensitic modified 9Cr-1Mo steel (P91) and austenitic AISI 316LN stainless st...

  15. Development of Weld Overlay System for Dissimilar Metal Alloy 82/182 Butt Welds

    Energy Technology Data Exchange (ETDEWEB)

    Park, K. S.; Byeon, J. G.; Kim, Y. J. [Doosan Heavy Industries and Construction Co., Ltd., Changwon (Korea, Republic of)

    2008-10-15

    As a result of the alloy 600 PWSCC(Primary Water Stress Corrosion Cracking), leak in the dissimilar welds in pressurizer nozzle was discovered recently in several US plants and the advanced companies had developed repair techniques. 2 or 3 years from now, more than half of the nuclear power plants in the country will be operated more than 20 years. Therefore, we need to develop repair techniques of dissimilar welds in pressurizer nozzle. With above backgrounds, we have developed a Prototype of Repair System for dissimilar welds in pressurizer nozzle.

  16. Illumination of the Spatial Order of Intracellular pH by Genetically Encoded pH-Sensitive Sensors

    Directory of Open Access Journals (Sweden)

    Mojca Benčina

    2013-12-01

    Full Text Available Fluorescent proteins have been extensively used for engineering genetically encoded sensors that can monitor levels of ions, enzyme activities, redox potential, and metabolites. Certain fluorescent proteins possess specific pH-dependent spectroscopic features, and thus can be used as indicators of intracellular pH. Moreover, concatenated pH-sensitive proteins with target proteins pin the pH sensors to a definite location within the cell, compartment, or tissue. This study provides an overview of the continually expanding family of pH-sensitive fluorescent proteins that have become essential tools for studies of pH homeostasis and cell physiology. We describe and discuss the design of intensity-based and ratiometric pH sensors, their spectral properties and pH-dependency, as well as their performance. Finally, we illustrate some examples of the applications of pH sensors targeted at different subcellular compartments.

  17. Genetically engineered plants, endangered species, and risk: a temporal and spatial exposure assessment for Karner blue butterfly larvae and Bt maize pollen.

    Science.gov (United States)

    Peterson, Robert K D; Meyer, Steven J; Wolf, Amy T; Wolt, Jeffrey D; Davis, Paula M

    2006-06-01

    Genetically engineered maize (Zea mays) containing insecticidal endotoxin proteins from Bacillus thuringiensis (Bt) delta-endotoxin proteins has been adopted widely in the Midwestern United States. The proteins are toxic to several lepidopteran species and because a variety of maize tissues, including pollen, may express the endotoxins, the probability of exposure to nontarget species, including endangered species, needs to be understood. The objective of this study was to assess the potential temporal and spatial exposure of endangered Karner blue butterfly larvae (Lycaeides melissa samuelis) to Bt maize pollen in Wisconsin using probabilistic exposure techniques and geographic information systems analysis. Based on degree-day modeling of butterfly phenology and maize pollen shed, there is some potential for temporal exposure of larvae to maize pollen. However, in the majority of years and locations, maize pollen shed most likely will occur after the majority of larval feeding on wild lupine (Lupinus perennis). The spatial analysis indicates that some Karner blue butterfly populations occur in close proximity to maize fields, but in the vast majority of cases the butterfly's host plant and maize fields are separated by more than 500 m. A small number of potential or existing Karner blue butterfly sites are located near maize fields, including sites in two of the four counties where temporal overlap is most likely. The exposure assessment indicates that these two counties should receive the highest priority to determine if Karner blue butterfly larvae are actually at risk and then, if needed, to reduce or prevent exposure.

  18. Wide variation in spatial genetic structure between natural populations of the European beech (Fagus sylvatica) and its implications for SGS comparability.

    Science.gov (United States)

    Jump, A S; Rico, L; Coll, M; Peñuelas, J

    2012-06-01

    Identification and quantification of spatial genetic structure (SGS) within populations remains a central element of understanding population structure at the local scale. Understanding such structure can inform on aspects of the species' biology, such as establishment patterns and gene dispersal distance, in addition to sampling design for genetic resource management and conservation. However, recent work has identified that variation in factors such as sampling methodology, population characteristics and marker system can all lead to significant variation in SGS estimates. Consequently, the extent to which estimates of SGS can be relied on to inform on the biology of a species or differentiate between experimental treatments is open to doubt. Following on from a recent report of unusually extensive SGS when assessed using amplified fragment length polymorphisms in the tree Fagus sylvatica, we explored whether this marker system led to similarly high estimates of SGS extent in other apparently similar populations of this species. In the three populations assessed, SGS extent was even stronger than this previously reported maximum, extending up to 360 m, an increase in up to 800% in comparison with the generally accepted maximum of 30-40 m based on the literature. Within this species, wide variation in SGS estimates exists, whether quantified as SGS intensity, extent or the Sp parameter. Consequently, we argue that greater standardization should be applied in sample design and SGS estimation and highlight five steps that can be taken to maximize the comparability between SGS estimates.

  19. Spatial Genetic Structure of Coffee-Associated Xylella fastidiosa Populations Indicates that Cross Infection Does Not Occur with Sympatric Citrus Orchards.

    Science.gov (United States)

    Francisco, Carolina S; Ceresini, Paulo C; Almeida, Rodrigo P P; Coletta-Filho, Helvécio D

    2017-04-01

    Xylella fastidiosa, an economically important plant-pathogenic bacterium, infects both coffee and citrus trees in Brazil. Although X. fastidiosa in citrus is well studied, knowledge about the population structure of this bacterium infecting coffee remains unknown. Here, we studied the population structure of X. fastidiosa infecting coffee trees in São Paulo State, Brazil, in four regions where citrus is also widely cultivated. Genotyping of over 500 isolates from coffee plants using 14 genomic microsatellite markers indicated that populations were largely geographically isolated, as previously found with populations of X. fastidiosa infecting citrus. These results were supported by a clustering analysis, which indicated three major genetic groups among the four sampled regions. Overall, approximately 38% of isolates showed significant membership coefficients not related to their original geographical populations (i.e., migrants), characterizing a significant degree of genotype flow among populations. To determine whether admixture occurred between isolates infecting citrus and coffee plants, one site with citrus and coffee orchards adjacent to each other was selected; over 100 isolates were typed from each host plant. No signal of natural admixture between citrus- and coffee-infecting isolates was found; artificial cross-infection assays with representative isolates also yielded no successful cross infection. A comparison determined that X. fastidiosa populations from coffee have higher genetic diversity and allelic richness compared with citrus. The results showed that coffee and citrus X. fastidiosa populations are effectively isolated from each other and, although coffee populations are spatially structured, migration has an important role in shaping diversity.

  20. Spatial Pattern of the Mitochondrial and Chloroplast Genetic Variation in Poland as a Result of the Migration of Abies alba Mill. from Different Glacial Refugia

    Directory of Open Access Journals (Sweden)

    Monika Litkowiec

    2016-11-01

    Full Text Available Currently, the information on the gene pool of silver fir (Abies alba Mill. at the northeastern edge of its distribution in Poland is scarce and insufficient. Using the advantage provided by markers with different modes of inheritance, a hypothesis that gene flow via both seeds and pollen contributed to the genetic structure across the entire analyzed region was investigated. The geographic distribution of maternally inherited mitochondrial DNA (mtDNA, nad5-4 and paternally inherited chloroplast DNA (cpDNA, psbC variation was studied in 81 Polish populations and three reference populations from Ukraine and Romania. The spatial pattern of mtDNA haplotypes (dispersed via seeds indicated that the Apennine Peninsula was the only maternal glacial refugium for the entire territory of Poland and also the Ukraine no 1 population, whereas the other two populations—Ukraine no 2 and Romania—had the haplotype representing the Balkan origin. By contrast, the cpDNA haplotypes (dispersed via pollen from all studied Polish and reference populations showed that A. alba colonized the current natural range from two genetically distinct glacial refugia located on the Apennine and Balkan peninsulas. The occurrence of cpDNA haplotypes varied among the studied populations. Additionally, statistical analyses were used to infer the genetic structure of examined populations. Two distinct groups of A. alba populations were identified showing the postglacial geographic distribution of haplotypes of both mtDNA and cpDNA. A. alba is an important ecological and economic component of forest ecosystems in Europe. An understanding of the Holocene history of this species is relevant for planning sustainable forest management, and acquired data can contribute to strategies of conservation and restoration.

  1. Within-population spatial genetic structure in four naturally fragmented species of a neotropical inselberg radiation, Alcantarea imperialis, A. geniculata, A. glaziouana and A. regina (Bromeliaceae).

    Science.gov (United States)

    Barbará, T; Lexer, C; Martinelli, G; Mayo, S; Fay, M F; Heuertz, M

    2008-09-01

    Studies of organisms on 'terrestrial islands' can improve our understanding of two unresolved issues in evolutionary genetics: the likely long-term effects of habitat fragmentation and the genetic underpinnings of continental species radiations in island-like terrestrial habitats. We have addressed both issues for four closely related plant species of the adaptive radiation Bromeliaceae, Alcantarea imperialis, A. geniculata, A. regina and A. glaziouana. All four are adapted to ancient, isolated inselberg rock outcrops in the Brazilian Atlantic rainforest and are thus long-term fragmented by nature. We used eight nuclear microsatellites to study within-population spatial genetic structure (SGS) and historical gene dispersal in nine populations of these species. Within-population SGS reflected known between-species differences in mating systems. The strongest SGS observed in A. glaziouana (Sp=0.947) was stronger than literature estimates available for plants. Analysis of short- and long-distance components of SGS identified biparental inbreeding, selfing and restricted seed dispersal as main determinants of SGS, with restricted pollen dispersal by bats contributing in some localities. The ability of Alcantarea spp. to colonize isolated inselbergs probably stems from their flexible mating systems and an ability to tolerate inbreeding. Short-ranging gene dispersal (average sigma=7-27 m) is consistent with a loss of dispersal power in terrestrial island habitats. Population subdivision associated with sympatric colour morphs in A. imperialis is accompanied by between-morph differences in pollen and seed dispersal. Our results indicate a high potential for divergence with gene flow in inselberg bromeliads and they provide base-line data about the long-term effects of fragmentation in plants.

  2. Spatial Genetic Structure of Two HIV-I-resistant Polymorphisms (CCR2-64Ⅰand SDF1-3'A) Alleles in Population of Shandong Province, China

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Objective To explore the spatial genetic structure of two HIV-I-resistant polymorphisms (CCR2-64Ⅰand SDF1-3'A) alleles in the population of Shandong Province, China. Methods Using the techniques of spatial stratified sampling and spatial statistics, the spatial genetic structure of the locus (CCR2-64Ⅰand SDF1-3'A), which was shown to be important co-receptor for HIV infection, was quantified from the populations of 36 sampled counties of Shandong Province, and a total of 3147 and 3172 samples were taken for testing CCR2-64I and SDF1-3'A respectively from individuals without known history of HIV-I infection and AIDS symptoms. Results There were significantly spatial genetic structures of the two alleles at different spatial distance classes on the scale of populations, but on the scale of individuals, no spatial structure was found in either the whole area of Shandong Province or the area of each sampled county. Although the change of frequencies of the two alleles with geographic locations in Shandong Province both showed gradual increase trends, their changing directions were inverse. The frequency of CCR2-64I allele gradually increased from the southwest to the northeast, while the frequency of SDF1-3'A allele gradually increased from the northeast to the southwest. However the RH to AIDS of combined types of their different genotypes did not represent obvious geographic diversity on the whole area of the Province. Conclusion The frequency of allele usually has some spatial genetic structures or spatial autocorrelation with different spatial distance classes, but the genotypes of individuals have random distribution in the same geographic area. Evaluating spatial distribution of the genetic susceptibility of HIV (AIDS) to CCR2-64I and SDF1-3'A alleles, should focus on the frequencies of combined genotypes of CCR2 and SDF1 based on the two-locus genotypes of each individual rather than the frequencies of CCR2-64I and SDF1-3'A alleles.

  3. Contrasting patterns of spatial genetic differentiation in two east asian five-needle pine species, Pinus koraiensis and P. armandii

    Directory of Open Access Journals (Sweden)

    Belokon M.-M.

    2008-09-01

    Full Text Available Two species of East Asian five-needle pines of the section Strobus, Korean pine, Pinus koraiensis Sieb. et Zucc. and Armand's pine, Pinus armandii Franch are traditionally placed in two different subsections, Cembrae and Strobi, respectively.However, data on similarity of these pines in needle anatomy and pollen structure are reported. By means of starch gel electrophoresis we studied allozyme variation within populations of these species and between the two species. Among 30 studied loci we selected 17 polymorphic loci with reliable interpretation of allele correspondencebetween species. Allozyme patterns were similar in both species with respect to number of loci and predominant alleles at most loci. Intra-specific differentiation among 12 populations of Pinus koraiensis from Russia, Northeast China and South Korea was low, FST (proportion of among population variation in total variation was as low as 0.019, DN (Nei's genetic distance varied between 0.001 and 0.006. This genetic uniformity can be explained by a common gene pool of this species within virtually continuous range under similar ecological conditions. Common vectors of selection, natural gene flow through pollen and seed dispersal as well as mixing of genetic material between regions by humans (at least in Russian forestry practice are putative factors responsible for low differentiation in Korean stone pine. We estimated the same parameters in Pinus armandii from continental China (Guizhou, Shaanxi, Shenyan where its range is highly fragmented, and found differentiation in this species to be much more pronounced (FST = 0.067, DN = 0.011-0.029. By adding a sample from Taiwan both FST (0.338 and DN (up to 0.232 were substantially higher indicating high level of differences between continental and Taiwanese P. armandii, putatively due to longer isolation time. Maximal contribution was fromloci Adh-1, Got-3, Mdh-1, 6-Pgd-3, Pgm-2 and Skdh-2. Differences were mainly caused by allelic

  4. Contrasting patterns of spatial genetic differentiation in two east asian five-needle pine species, Pinus koraiensis and P. armandii

    Directory of Open Access Journals (Sweden)

    M.M. Belokon

    2013-12-01

    Full Text Available Two species of East Asian five-needle pines of the section Strobus, Korean pine, Pinus koraiensis Sieb. et Zucc. and Armand's pine, Pinus armandii Franch are traditionally placed in two different subsections, Cembrae and Strobi, respectively. However, data on similarity of these pines in needle anatomy and pollen structure are reported. By means of starch gel electrophoresis we studied allozyme variation within populations of these species and between the two species. Among 30 studied loci we selected 17 polymorphic loci with reliable interpretation of allele correspondence between species. Allozyme patterns were similar in both species with respect to number of loci and predominant alleles at most loci. Intra-specific differentiation among 12 populations of Pinus koraiensis from Russia, Northeast China and South Korea was low, FST (proportion of among population variation in total variation was as low as 0.019, DN (Nei's genetic distance varied between 0.001 and 0.006. This genetic uniformity can be explained by a common gene pool of this species within virtually continuous range under similar ecological conditions. Common vectors of selection, natural gene flow through pollen and seed dispersal as well as mixing of genetic material between regions by humans (at least in Russian forestry practice are putative factors responsible for low differentiation in Korean stone pine. We estimated the same parameters in Pinus armandii from continental China (Guizhou, Shaanxi, Shenyan where its range is highly fragmented, and found differentiation in this species to be much more pronounced (FST = 0.067, DN = 0.011-0.029. By adding a sample from Taiwan both FST (0.338 and DN (up to 0.232 were substantially higher indicating high level of differences between continental and Taiwanese P. armandii, putatively due to longer isolation time. Maximal contribution was from loci Adh-1, Got-3, Mdh-1, 6-Pgd-3, Pgm-2 and Skdh-2. Differences were mainly caused by

  5. Genetic and physiological evidence that oligodendrocyte gap junctions contribute to spatial buffering of potassium released during neuronal activity.

    Science.gov (United States)

    Menichella, Daniela M; Majdan, Marta; Awatramani, Rajeshwar; Goodenough, Daniel A; Sirkowski, Erich; Scherer, Steven S; Paul, David L

    2006-10-25

    Mice lacking the K+ channel Kir4.1 or both connexin32 (Cx32) and Cx47 exhibit myelin-associated vacuoles, raising the possibility that oligodendrocytes, and the connexins they express, contribute to recycling the K+ evolved during neuronal activity. To study this possibility, we first examined the effect of neuronal activity on the appearance of vacuoles in mice lacking both Cx32 and Cx47. The size and number of myelin vacuoles was dramatically increased when axonal activity was increased, by either a natural stimulus (eye opening) or pharmacological treatment. Conversely, myelin vacuoles were dramatically reduced when axonal activity was suppressed. Second, we used genetic complementation to test for a relationship between the function of Kir4.1 and oligodendrocyte connexins. In a Cx32-null background, haploinsufficiency of either Cx47 or Kir4.1 did not affect myelin, but double heterozygotes developed vacuoles, consistent with the idea that oligodendrocyte connexins and Kir4.1 function in a common pathway. Together, these results implicate oligodendrocytes and their connexins as having critical roles in the buffering of K+ released during neuronal activity.

  6. Informational dissimilarity and organizational citizenship behavior : The role of intrateam interdependence and team identification

    NARCIS (Netherlands)

    Van der Vegt, GS; Van de Vliert, E; Oosterhof, A

    2003-01-01

    A questionnaire study of 129 members of 20 multidisciplinary project teams examined the relationship between informational dissimilarity and both team identification and organizational citizenship behavior (OCB) for individuals working under different interdependence configurations. Results revealed

  7. Evaluation of similar metal weld effects on residual stress of nozzle dissimilar metal weld

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Seung Cheon; Jeong, Jae Uk; Chang, Yoon Suk; Kim, Young Jin [Sungkyunkwan Univ., Seoul (Korea, Republic of)

    2008-07-01

    Determination of weld-induced residual stress has been an important issue in nuclear power industry because several failures were reported in dissimilar metal weld parts due to primary water stress corrosion cracking. In this context, a couple of remarkable round robin analyses were conducted to quantify the welding simulation variables and to establish optimized numerical analysis process. The purpose of the present research is to introduce welding simulation results for a safety and relief nozzle, which has a dissimilar metal weld part as well as a similar metal weld part. First, finite element analyses are carried out to calculate residual stresses at the inside of nozzle considering only dissimilar metal welding. Subsequently, residual stresses taking into account both the dissimilar and similar metal welding are computed. The similar metal weld effect is evaluated by comparing these analysis results and technical findings derived from the evaluation are fully discussed.

  8. USAGE OF DISSIMILARITY MEASURES AND MULTIDIMENSIONAL SCALING FOR LARGE SCALE SOLAR DATA ANALYSIS

    Data.gov (United States)

    National Aeronautics and Space Administration — USAGE OF DISSIMILARITY MEASURES AND MULTIDIMENSIONAL SCALING FOR LARGE SCALE SOLAR DATA ANALYSIS Juan M Banda, Rafal Anrgyk ABSTRACT: This work describes the...

  9. Phase-space dissimilarity measures for industrial and biomedical applications

    Science.gov (United States)

    Protopopescu, V. A.; Hively, L. M.

    2005-12-01

    its various points, corresponding to the baseline DF. Condition change is established by comparing the base line DFs to subsequent test case DFs via new, phase space dissimilarity measures (PSDM), namely the distance and - square statistics between two DFs. A clear trend in the dissimilarity measures over time indicates substantial departure from the baseline dynamics, thus signaling condition change. The severity of this departure can be interpreted as a "normal" fluctuation, abnormal behavior, impending failure, or complete breakdown. We illustrate the new approach on an assortment of machinery and biomedical examples. The machine data were collected during laboratory tests on industrial equipment, for diverse failure modes, via seeded faults and accelerated failures. The biomedical applications involve detection of physiological changes, such as epileptic seizures from EEG; ventricular fibrillation, fainting, and sepsis onset from ECG; and breathing difficulty from chest sounds. The PSDM show a consistent discrimination of normal-to-abnormal transitions, allowing earlier, more accurate, and more robust detection of the dynamical change for all of these applications in comparison to TNM.

  10. Thermal Recovery of Plastic Deformation in Dissimilar Metal Weld

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Dongxiao [Tsinghua Univ., Beijing (China); Yu, Xinghua [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhang, Wei [The Ohio State Univ., Columbus, OH (United States); Crooker, Paul [Electric Power Research Inst. (EPRI), Palo Alto, CA (United States); David, Stan A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Feng, Zhili [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-05-23

    Stainless steel has been widely used in challenging environments typical to nuclear power plant structures, due its excellent corrosion resistance. Nickel filler metals containing high chromium concentration, including Alloy 82/182, are used for joining stainless steel to carbon steel components to achieve similar high resistance to stress corrosion cracking. However, the joint usually experience weld metal stress corrosion cracking (SCC), which affects the safety and structural integrity of light water nuclear reactor systems. A primary driving force for SCC is the high tensile residual stress in these welds. Due to large dimension of pressure vessel and limitations in the field, non-destructive residual stress measurement is difficult. As a result, finite element modeling has been the de facto method to evaluate the weld residual stresses. Recent studies on this subject from researchers worldwide report different residual stress value in the weldments [5]. The discrepancy is due to the fact that most of investigations ignore or underestimate the thermal recovery in the heat-affect zone or reheated region in the weld. In this paper, the effect of heat treatment on thermal recovery and microhardness is investigated for materials used in dissimilar metal joint. It is found that high equivalent plastic strains are predominately accumulated in the buttering layer, the root pass, and the heat affected zone, which experience multiple welding thermal cycles. The final cap passes, experiencing only one or two welding thermal cycles, exhibit less plastic strain accumulation. Moreover, the experimental residual plastic strains are compared with those predicted using an existing weld thermo-mechanical model with two different strain hardening rules. The importance of considering the dynamic strain hardening recovery due to high temperature exposure in welding is discussed for the accurate simulation of weld residual stresses and plastic strains. In conclsuion, the

  11. Partner dissimilarity in life satisfaction: Stability and change, correlates, and outcomes.

    Science.gov (United States)

    Schade, Hannah M; Hülür, Gizem; Infurna, Frank J; Hoppmann, Christiane A; Gerstorf, Denis

    2016-06-01

    Dissimilarities between partners in prominent domains of functioning are often thought to be a risk factor for compromised relationship quality and relationship dissolution. However, the nature, correlates, and consequences of developmental trajectories of within-couple dissimilarities in key quality-of-life indicators such as life satisfaction are not well understood. In the current study, we applied multilevel growth models to up to 31-wave annual longitudinal data from 13,714 romantic partners in the German Socio-Economic Panel (age at baseline: M = 43 years, SD = 15, range 17-92 years). Partner dissimilarity was calculated at the within-couple level and indicated considerable differences in life satisfaction between partners within a given couple (0.64 SD or 1.14 units on an 11-point scale). Over time, partner dissimilarity slightly increased among partners who remained together. Examining individual and relationship correlates indicated that dissimilarity was greatest for couples who were older, had children, or had a shorter relationship history. Also, dissimilarity was greater when individual life satisfaction or satisfaction with family life was low, particularly among wives, as well as among couples who later separated. Examining consequences, larger levels of and increases in partner dissimilarity were independently predictive of lower satisfaction with family life at the end of the study, over and above individual life satisfaction of either partner as well as key individual and relationship correlates. Our discussion focuses on the advantages of investigating (developmental trajectories of) within-couple dissimilarity and its implications for individual and partner development. (PsycINFO Database Record

  12. Variance, genetic control and spatial phenotypic plasticity of morphological and phenological traits in Prunus spinosa and its large fruited forms (P. x fruticans

    Directory of Open Access Journals (Sweden)

    Kristine Vander Mijnsbrugge

    2016-11-01

    Full Text Available Prunus spinosa is a highly esteemed shrub in forest and landscape plantings. Shrubs with larger organs occur often and are considered either as large fruited forms of P. spinosa or as P. x fruticans, involving a hybridization process with the ancient cultivated P. insititia (crop-to-wild gene flow. As climate change may augment hybridization processes in the future, a hybrid origin is important to detect. In addition, studying crop-to-wild gene flow can give insights in putative consequences for the wild populations. We studied the P. spinosa – P. x fruticans group, focusing on morphology and phenology in three experimental plantations. Two plantings harbored cuttings of P. spinosa (clone plantations. A third plantation comprised of a half-sib offspring from a population with both P. spinosa and P. x fruticans (family plantation. Several results point to a hybridization process as the origin of P. x fruticans. The clone plantation revealed endocarp traits to be more genetically controlled than fruit size, while this was the opposite in the family plantation, suggesting the control of fruit size being derived from the putative P. insititia parent. Bud burst, flower opening and leaf fall were genetically controlled in the clone plantation, whereas in the family plantation intrafamily variability was remarkably large for the bud burst and leaf fall, but not for the flower opening. This suggests there is a reduced genetic control for the first two phenophases, possibly caused by historic hybridization events. Pubescence on the long shoot leaves in the family plantation deviated from the short shoot leaves on the same plants and from long and short shoot leaves in the clone plantation, suggesting again a P. insititia origin. Finally, we quantified spatial phenotypic plasticity, indicating how P. spinosa may react in a changing environment. In contrast to the bud burst and leaf fall, flower opening did not demonstrate plasticity. The fruit size was

  13. Mechanical properties of a dissimilar aluminum alloy joint welded by hybrid laser-MIG welding

    Science.gov (United States)

    Wang, Qiuying; Chen, Hui; Zhu, Zongtao; Cui, Yunlong

    2017-07-01

    Two dissimilar Al alloys, 5083-H111 and 6005A-T6, were joined by hybrid laser-MIG welding method. Mechanical properties of the welded joint were investigated and compared. The results show that the tensile strength of the dissimilar joint is 219.8 MPa, 11.7% higher than that of 6005A-T5 joint. After statistical analysis of the fatigue data, the P-S-N curves of the dissimilar joint were obtained. The mean fatigue strength at Nf = 107 of the dissimilar joint is 112.5 MPa. The fatigue strength at Nf = 107 of the dissimilar joint for a given 10% probability of failure, at a confidence level of 95%, is 101.4 MPa. The fatigue strength at Nf = 107 of the dissimilar joint is almost same as that of the 6005A-T6 joint. In welded structure designing, different P-S-N curves should be chosen according to the different service conditions and reliability requirements.

  14. Microstructure and high temperature properties of the dissimilar weld between ferritic stainless steel and carbon steel

    Science.gov (United States)

    Kim, Jeong Kil; Hong, Seung Gab; Kang, Ki Bong; Kang, Chung Yun

    2009-10-01

    Dissimilar joints between STS441, a ferritic stainless steel, and SS400, a carbon steel, were welded by GMAW (Gas Metal Arc Welding) using STS430LNb as a welding wire. The fracture behavior of the dissimilar weld was analyzed by a microstructural observation and thermo-mechanical tests. Martensite was formed at the region between SS400 and the weld metal because the Cr and Nb content in this region decreased due to the dilution of SS400 carbon steel during welding. According to results from a high temperature tensile test with a specimen aged at 900 °C, it was found that the tensile strength of the dissimilar weld at high temperature was equal to that of STS441 base metal and the formation of martensite had little influence on tensile strength of the dissimilar weld at high temperature. However, in the case of thermal fatigue resistance, the dissimilar weld had an inferior thermal fatigue life to STS441 because of the presence of martensite and the softened region around the interface between the dissimilar weld metal and SS400.

  15. Inbreeding in stochastic subdivided mating systems: the genetic consequences of host spatial structure, aggregated transmission dynamics and life history characteristics in parasite populations

    Indian Academy of Sciences (India)

    Guha Dharmarajan

    2015-03-01

    Inbreeding in parasite populations can have important epidemiological and evolutionary implications. However, theoretical models have predominantly focussed on the evolution of parasite populations under strong selection or in epidemic situations, and our understanding of neutral gene dynamics in parasite populations at equilibrium has been limited to verbal arguments or conceptual models. This study focusses on how host–parasite population dynamics affects observed levels of inbreeding in a random sample of parasites from an infinite population of hosts by bridging traditional genetic and parasitological processes utilizing a backward–forward branching Markov process embedded within a flexible statistical framework, the logarithmic-poisson mixture model. My results indicate that levels of inbreeding in parasites are impacted by demographic and/or transmission dynamics (subdivided mating, aggregated transmission dynamics and host spatial structure), and that this inbreeding is poorly estimated by ‘equilibrium’ levels of inbreeding calculated assuming regular systems of mating. Specifically, the model reveals that at low levels of inbreeding ( ≤ 0.1), equilibrium levels of inbreeding are lower than those observed, while at high levels of inbreeding the opposite pattern occurs. The model also indicates that inbreeding could have important epidemiological implications (e.g., the spread of recessive drug resistance genes) by directly impacting the observed frequency of rare homozygotes in parasite populations. My results indicate that frequencies of rare homozygotes are affected by aggregated transmission dynamics and host spatial structure, and also that an increase in the frequency of rare homozygotes can be caused by a decrease in effective population size solely due to the presence of a subdivided breeding system.

  16. Through-Thickness Measurements of Residual Stresses in an Overlay Dissimilar Weld Pipe using Neutron Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Wan Chuck; EM, Vyacheslav; Lee, Ho Jin; Kim, Kang Soo; Kang, Mi Hyun; Joo, Jong Dae; Seong, Baek Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Byeon, Jin Gwi; Park, Kwang Soo [Doosan Heavy Industries and Construction Co., Changwon (Korea, Republic of)

    2010-10-15

    The distribution of residual stresses in dissimilar material joints has been extensively studied because of the wide applications of the dissimilar welds in many inevitable complex design structures. Especially the cracking of dissimilar welding has been a long standing issue of importance in many components of the power generation industries such as nuclear power plant, boiling pressure system, and steam generators. In particular, several failure analysis and direct observations have shown that critical fractures have frequently occurred in one side of the dissimilar welded parts. For example, the heat-affected zone on the ferrite steel side is known to critical in many dissimilar welding pipes when ferrite (low carbon steel) and austenite (stainless) steels are joined. The main cause of the residual stresses can be attributed to the mismatch in the coefficient of thermal expansion between the dissimilar metals (ferrite and austenite). Additional cladding over circumferential welds is known to reinforce the mechanical property due to the beneficial compressive residual stress imposed on the weld and heat-affected zone. However, science-based quantitative measurement of the through thickness residual stress distribution is very limited in literature. The deep penetration capability of neutrons into most metallic materials makes neutron diffraction a powerful tool to investigate and map the residual stresses of materials throughout the thickness and across the weld. Furthermore, the unique volume averaged bulk characteristic of materials and mapping capability in three dimensions are suitable for the engineering purpose. Thus, the neutron-diffraction measurement method has been selected as the most useful method for the study of the residual stresses in various dissimilar metal welded structures. The purpose of this study is to measure the distribution of the residual stresses in a complex dissimilar joining with overlay in the weld pipe. Specifically, we measured

  17. Landscape genomics of Sphaeralcea ambigua in the Mojave Desert: a multivariate, spatially-explicit approach to guide ecological restoration

    Science.gov (United States)

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

    2015-01-01

    Local adaptation influences plant species’ responses to climate change and their performance in ecological restoration. Fine-scale physiological or phenological adaptations that direct demographic processes may drive intraspecific variability when baseline environmental conditions change. Landscape genomics characterize adaptive differentiation by identifying environmental drivers of adaptive genetic variability and mapping the associated landscape patterns. We applied such an approach to Sphaeralcea ambigua, an important restoration plant in the arid southwestern United States, by analyzing variation at 153 amplified fragment length polymorphism loci in the context of environmental gradients separating 47 Mojave Desert populations. We identified 37 potentially adaptive loci through a combination of genome scan approaches. We then used a generalized dissimilarity model (GDM) to relate variability in potentially adaptive loci with spatial gradients in temperature, precipitation, and topography. We identified non-linear thresholds in loci frequencies driven by summer maximum temperature and water stress, along with continuous variation corresponding to temperature seasonality. Two GDM-based approaches for mapping predicted patterns of local adaptation are compared. Additionally, we assess uncertainty in spatial interpolations through a novel spatial bootstrapping approach. Our study presents robust, accessible methods for deriving spatially-explicit models of adaptive genetic variability in non-model species that will inform climate change modelling and ecological restoration.

  18. Phased Array Ultrasonic Examination of Reactor Coolant System (Carbon Steel-to-CASS) Dissimilar Metal Weld Mockup Specimen

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, S. L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cinson, A. D. [US Nuclear Regulatory Commission (NRC), Washington, DC (United States); Diaz, A. A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Anderson, M. T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-11-23

    In the summer of 2009, Pacific Northwest National Laboratory (PNNL) staff traveled to the Electric Power Research Institute (EPRI) NDE Center in Charlotte, North Carolina, to conduct phased-array ultrasonic testing on a large bore, reactor coolant pump nozzle-to-safe-end mockup. This mockup was fabricated by FlawTech, Inc. and the configuration originated from the Port St. Lucie nuclear power plant. These plants are Combustion Engineering-designed reactors. This mockup consists of a carbon steel elbow with stainless steel cladding joined to a cast austenitic stainless steel (CASS) safe-end with a dissimilar metal weld and is owned by Florida Power & Light. The objective of this study, and the data acquisition exercise held at the EPRI NDE Center, were focused on evaluating the capabilities of advanced, low-frequency phased-array ultrasonic testing (PA-UT) examination techniques for detection and characterization of implanted circumferential flaws and machined reflectors in a thick-section CASS dissimilar metal weld component. This work was limited to PA-UT assessments using 500 kHz and 800 kHz probes on circumferential flaws only, and evaluated detection and characterization of these flaws and machined reflectors from the CASS safe-end side only. All data were obtained using spatially encoded, manual scanning techniques. The effects of such factors as line-scan versus raster-scan examination approaches were evaluated, and PA-UT detection and characterization performance as a function of inspection frequency/wavelength, were also assessed. A comparative assessment of the data is provided, using length-sizing root-mean-square-error and position/localization results (flaw start/stop information) as the key criteria for flaw characterization performance. In addition, flaw signal-to-noise ratio was identified as the key criterion for detection performance.

  19. No evidence for leaf-trait dissimilarity effects on litter decomposition, fungal decomposers, and nutrient dynamics.

    Science.gov (United States)

    Frainer, André; Moretti, Marcelo S; Xu, Wenjing; Gessner, Mark O

    2015-02-01

    Biodiversity and ecosystem-functioning theory suggest that litter mixtures composed of dissimilar leaf species can enhance decomposition due to species trait complementarity. Here we created a continuous gradient of litter chemistry trait variability within species mixtures to assess effects of litter dissimilarity on three related processes in a natural stream: litter decomposition, fungal biomass accrual in the litter, and nitrogen and phosphorus immobilization. Litter from a pool of eight leaf species was analyzed for chemistry traits affecting decomposition (lignin, nitrogen, and phosphorus) and assembled in all of the 28 possible two-species combinations. Litter dissimilarity was characterized in terms of a range of trait-diversity measures, using Euclidean and Gower distances and dendrogram-based indices. We found large differences in decomposition rates among leaf species, but no significant relationships between decomposition rate of individual leaf species and litter trait dissimilarity, irrespective of whether decomposition was mediated by microbes alone or by both microbes and litter-consuming invertebrates. Likewise, no effects of trait dissimilarity emerged on either fungal biomass accrual or changes during decomposition of nitrogen or phosphorus concentrations in individual leaf species. In line with recent meta-analyses, these results provide support for the contention that litter diversity effects on decomposition, at least in streams, are less pronounced than effects on terrestrial primary productivity.

  20. Comparison of Residual Stress Distributions of Similar and Dissimilar Thick Butt-Weld Plates

    Science.gov (United States)

    Suzuki, Hiroshi; Katsuyama, Jinya; Morii, Yukio

    Residual stress distributions of 35 mm thick dissimilar metal butt-weld between A533B ferritic steel and Type 304 austenitic stainless steel (304SS) with Ni alloy welds and similar metal butt-weld of 304SS were measured using neutron diffraction. Effects of differences in thermal expansion coefficients (CTEs) and material strengths on the weld residual stress distributions were discussed by comparison of the residual stress distributions between the similar and dissimilar metal butt-welds. Residual stresses in the similar metal butt-weld exhibited typical distributions found in a thick butt-weld and they were distributed symmetrically on either side of the weld line. Meanwhile, asymmetric residual stress distributions were observed near the root of the dissimilar metal butt-weld, which was caused by differences in CTEs and yield strengths among both parent materials and weld metals. Transverse residual stress distribution of the dissimilar metal butt-weld was similar trend to that of the similar metal butt-weld, since effect of difference in CTEs were negligible, while magnitude of the transverse residual stress near the root depended on the yield strengths of each metal. In contrast, the normal and longitudinal residual stresses in the dissimilar metal butt-weld distributed asymmetrically on either side of weld line due to influence of differences in CTEs.

  1. Children's perceptions of dissimilarity in parenting styles are associated with internalizing and externalizing behavior.

    Science.gov (United States)

    Berkien, Myra; Louwerse, Anneke; Verhulst, Frank; van der Ende, Jan

    2012-02-01

    The purpose of this study was to examine the relationship between children's perception of dissimilarity in parenting styles, and internalizing and externalizing problems in children. Children from the general population (n = 658) reported on the level of emotional warmth, rejection, and overprotection of both parents by filling out the child version of the Egna Minnen Beträffande Uppfostran (EMBU-C) and mothers completed the child behavior checklist (CBCL). Intraclass correlations were computed as measures of dissimilarity between parenting styles of mothers and fathers. Children's perceived dissimilarity in parental emotional warmth is associated with internalizing and externalizing problems (β = 0.092, p parents' overprotection is associated with externalizing problems (β = 0.097, p parenting styles is associated with externalizing and internalizing problems, over and above the effects of the level of the parenting styles. The results highlight the negative consequences of perceived dissimilarity between parents. To conclude, children have more internalizing and externalizing problems when they perceive their parents as more dissimilar in parenting styles.

  2. Prepulse inhibition predicts spatial working memory performance in the inbred Roman high- and low-avoidance rats and in genetically heterogeneous NIH-HS rats: relevance for studying pre-attentive and cognitive anomalies in schizophrenia

    Directory of Open Access Journals (Sweden)

    Ignasi eOliveras

    2015-08-01

    Full Text Available Animal models of schizophrenia-relevant symptoms are increasingly important for progress in our understanding of the neurobiological basis of the disorder and for discovering novel and more specific treatments. Prepulse inhibition (PPI and working memory, which are impaired in schizophrenic patients, are among the symptoms/processes modeled in those animal analogues. We have evaluated whether a genetically-selected rat model, the Roman high-avoidance inbred strain (RHA-I, displays PPI deficits as compared with its Roman low-avoidance (RLA-I counterpart and the genetically heterogeneous NIH-HS rat stock. We have investigated whether PPI deficits predict spatial working memory impairments (in the Morris water maze; MWM in these three rat types (Experiment 1, as well as in a separate sample of NIH-HS rats stratified according to their extreme (High, Medium, Low PPI scores (Experiment 2. The results from Exp. 1 show that RHA-I rats display PPI and spatial working memory deficits compared to both RLA-I and NIH-HS rats. Likewise, in Exp. 2, Low-PPI NIH-HS rats present significantly impaired working memory with respect to Medium-PPI and High-PPI NIH-HS subgroups. Further support to these results comes from correlational, factorial and multiple regression analyses, which reveal that PPI is positively associated with spatial working memory performance. Conversely, cued learning in the MWM was not associated with PPI. Thus, using genetically-selected and genetically heterogeneous rats, the present study shows, for the first time, that PPI is a positive predictor of performance in a spatial working memory task. These results may have translational value for schizophrenia symptom research in humans, as they suggest that either by psychogenetic selection or by focusing on extreme PPI scores from a genetically heterogeneous rat stock, it is possible to detect a useful (perhaps at risk phenotype to study cognitive anomalies linked to schizophrenia.

  3. Prepulse inhibition predicts spatial working memory performance in the inbred Roman high- and low-avoidance rats and in genetically heterogeneous NIH-HS rats: relevance for studying pre-attentive and cognitive anomalies in schizophrenia.

    Science.gov (United States)

    Oliveras, Ignasi; Río-Álamos, Cristóbal; Cañete, Toni; Blázquez, Gloria; Martínez-Membrives, Esther; Giorgi, Osvaldo; Corda, Maria G; Tobeña, Adolf; Fernández-Teruel, Alberto

    2015-01-01

    Animal models of schizophrenia-relevant symptoms are increasingly important for progress in our understanding of the neurobiological basis of the disorder and for discovering novel and more specific treatments. Prepulse inhibition (PPI) and working memory, which are impaired in schizophrenic patients, are among the symptoms/processes modeled in those animal analogs. We have evaluated whether a genetically-selected rat model, the Roman high-avoidance inbred strain (RHA-I), displays PPI deficits as compared with its Roman low-avoidance (RLA-I) counterpart and the genetically heterogeneous NIH-HS rat stock. We have investigated whether PPI deficits predict spatial working memory impairments (in the Morris water maze; MWM) in these three rat types (Experiment 1), as well as in a separate sample of NIH-HS rats stratified according to their extreme (High, Medium, Low) PPI scores (Experiment 2). The results from Experiment 1 show that RHA-I rats display PPI and spatial working memory deficits compared to both RLA-I and NIH-HS rats. Likewise, in Experiment 2, "Low-PPI" NIH-HS rats present significantly impaired working memory with respect to "Medium-PPI" and "High-PPI" NIH-HS subgroups. Further support to these results comes from correlational, factorial, and multiple regression analyses, which reveal that PPI is positively associated with spatial working memory performance. Conversely, cued learning in the MWM was not associated with PPI. Thus, using genetically-selected and genetically heterogeneous rats, the present study shows, for the first time, that PPI is a positive predictor of performance in a spatial working memory task. These results may have translational value for schizophrenia symptom research in humans, as they suggest that either by psychogenetic selection or by focusing on extreme PPI scores from a genetically heterogeneous rat stock, it is possible to detect a useful (perhaps "at risk") phenotype to study cognitive anomalies linked to schizophrenia.

  4. Research progress for fragmentation, spatial genetic structure of clonal plant%克隆植物的裂断、空间遗传结构的研究进展

    Institute of Scientific and Technical Information of China (English)

    滕小华; 洪锐民; 乌云娜

    2011-01-01

    Fragmentation of clonal plants is reputed as pervasive functional behavior in plant kingdom that can cause the growth,reproduction and spreading of clonal plant. The paper discussed fragmentation phenomenon, fragmentation behavior, fragmentation fate, genetic variation, and spatial genetics of clonal plant, and introduced clonal architecture, cloning structure, genetic structure, and spatial genetic structure of divisional clone fragmented, observed meaning and foreground of fragmentation studying, divisional clone fragmented, clonal architecture, and genetic evolution in depth. In addition, the paper had made the forecast to fragmentation fate research.%植物克隆分株集群的裂断是植物界普遍存在的功能行为,裂断可以引发克隆植物生长、繁殖和散布.文章论述了克隆植物裂断现象、裂断行为、裂断命运、遗传变异和空间遗传的研究,介绍了裂断分克隆的克隆构型、克隆结构、遗传结构以及空间遗传结构,较深入地评述了研究裂断、裂断分克隆、克隆构型和遗传演化的意义及其前景,并对裂断命运研究作了展望.

  5. EDL configuration on a dissimilarly charged protrusion array via double Fourier series and perturbation method.

    Science.gov (United States)

    Lin, Sung-Hwa; Hsu, Jyh-Ping; Tseng, Shiojenn; Kuo, Yung-Chih; Liu, Bo-Tau

    2011-11-01

    In this study, through the extension of an one-dimensional, dissimilarly charged protrusions surface model set up in our previous work, a novel dissimilarly charged protrusion array (DCPA) model immersed in an electrolyte solution, which could simulate realistically both the surface morphology and the surface charged condition profoundly concerned on a biological cell membrane, or on the surface of a micro-scale, modified particle used in biomedical engineering and water treatment, is proposed. Considering the condition of small protrusions, the electrical potential field due to the electrical double layer (EDL) on DCPA model is solved semi-analytically using both the double Fourier series and the perturbation method. The analysis from the numerical result reveals that, a small, dissimilarly charged protrusion can lead to a steep variation in the local EDL configuration, especially compared with that in the condition when the charged surface is taken roughly as a flat surface using a lumped, mean surface charge density.

  6. Visual Encoding of Dissimilarity Data via Topology-Preserving Map Deformation.

    Science.gov (United States)

    Bouts, Quirijn W; Dwyer, Tim; Dykes, Jason; Speckmann, Bettina; Goodwin, Sarah; Riche, Nathalie Henry; Carpendale, Sheelagh; Liebman, Ariel

    2016-09-01

    We present an efficient technique for topology-preserving map deformation and apply it to the visualization of dissimilarity data in a geographic context. Map deformation techniques such as value-by-area cartograms are well studied. However, using deformation to highlight (dis)similarity between locations on a map in terms of their underlying data attributes is novel. We also identify an alternative way to represent dissimilarities on a map through the use of visual overlays. These overlays are complementary to deformation techniques and enable us to assess the quality of the deformation as well as to explore the design space of blending the two methods. Finally, we demonstrate how these techniques can be useful in several-quite different-applied contexts: travel-time visualization, social demographics research and understanding energy flowing in a wide-area power-grid.

  7. In-situ neutron diffraction measurement of stress redistribution in a dissimilar joint during heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Dodge, M.F., E-mail: michael.dodge@twi.co.uk [TWI Ltd., Great Abington, Cambridge CB21 6AL (United Kingdom); Gittos, M.F. [TWI Ltd., Great Abington, Cambridge CB21 6AL (United Kingdom); Dong, H. [Department of Engineering, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Zhang, S.Y.; Kabra, S.; Kelleher, J.F. [ISIS, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom)

    2015-03-11

    Neutron diffraction is routinely used to monitor stress redistribution before and after heat treatment in dissimilar joints. However there remains a paucity of information concerning the evolution of strain throughout the process of heat treatment itself. Due to different mechanical properties between opposing sides, a competitive strain redistribution process occurs. Consequently, a novel in-situ measurement approach has been developed: strains at multiple points in a dissimilar joint have been measured during heat treatment. Thus, the described work elucidates areas within the thermal cycle in which competitive strain redistribution occurs, and where high residual stresses remain, following PWHT. The method may be used to characterise comparable material combinations, with a view to optimising the thermal cycles, and ultimately, the structural integrity of dissimilar joints.

  8. Tensile and Fatigue Properties of Single and Multiple Dissimilar Welded Joints of DP980 and HSLA

    Science.gov (United States)

    Cui, Q. L.; Parkes, D.; Westerbaan, D.; Nayak, S. S.; Zhou, Y.; Saha, D. C.; Liu, D.; Goodwin, F.; Bhole, S.; Chen, D. L.

    2017-01-01

    The present study focused on single and multiple dissimilar joints between DP980 and high-strength low-alloy (HSLA) galvanized steels. The tensile properties of the dissimilar joint between the strong DP980 and the relatively soft HSLA reflected only the properties of HSLA with plastic deformation, and final fracture took place entirely in HSLA. The fatigue properties of the dissimilar joints were more intriguing, with the strong DP980 outperforming at high stress amplitude and the ductile HSLA outperforming at low stress amplitude. For different load amplitudes, fatigue failure occurred in different materials and at different locations. The fatigue strength of DP980 was more negatively impaired by weld defects than that of HSLA.

  9. Distribution Characteristics of Weld Residual Stress on Butt Welded Dissimilar Metal Plate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyoung Soo; Park, Chi Yong [KEPCO Research Institute, Daejeon (Korea, Republic of); Kim, Maan Won [Korea Hydro and Nuclear Power Co., Seoul (Korea, Republic of); Park, Jai Hak [Chungbuk National University, Cheongju (Korea, Republic of)

    2010-09-15

    In this study, the weld residual stress distribution at a dissimilar-metal welded plate of low alloy carbon steel and stainless steel, which are widely used in nuclear power plants, was characterized. A plate mock-up with butt welding was fabricated using SA 508 low alloy steel and Type 304 stainless steel plates and the residual stresses were measured by the X-ray diffraction method after electrolytic polishing of the plate specimen. Finite element analysis was carried out in order to simulate the butt welding of dissimilar metal plate, and the calculated weld residual stress distribution was compared with that obtained from the measured data. The characteristics of the three-dimensional residual stress distribution in a butt weld of dissimilar metal plates were investigated by comparing the measured and calculated residual stress data.

  10. Mixture toxicity of three toxicants with similar and dissimilar modes of action to Daphnia magna.

    Science.gov (United States)

    Syberg, Kristian; Elleby, Anders; Pedersen, Henrik; Cedergreen, Nina; Forbes, Valery E

    2008-03-01

    Mixture toxicity of similar- and dissimilar-acting toxicants can be predicted by the models concentration addition (CA) and independent action (IA) using single substance toxicity data. Knowledge of the toxicants mode of action is thus required in order to use the models. In order to test the predictive capability of the models, we conducted Daphnia magna 48 h immobilization experiments with three toxicants with known modes of action (dimethoate, pirimicarb and linear alkyl benzene sulfonate) singly, and in binary and ternary mixtures. Our results indicate that CA and IA predict binary mixtures of similar- and dissimilar-acting toxicants equally well. CA and IA also equally predicted the ternary mixture consisting of both similar- and dissimilar-acting chemicals. The paper discusses the concept of mode of action and the implications the definition of mode of action has on the choice of reference model for mixture toxicity studies.

  11. E-commerce Website Recommender System Based on Dissimilarity and Association Rule

    Directory of Open Access Journals (Sweden)

    MingWang Zhang

    2013-07-01

    Full Text Available By analyzing the current electronic commerce recommendation algorithm analysis, put forward a kind to use dissimilarity clustering and association recommendation algorithm, the algorithm realized web website shopping user data clustering by use of the dissimilarity, and then use the association rules algorithm for clustering results of association recommendation, experiments show that the algorithm compared with traditional clustering association algorithm of iteration times decrease, improve operational efficiency, to prove the method by use of the actual users purchase the recommended, and evidence of the effectiveness of the algorithm in recommendation.  

  12. Residual stress analysis of an overlay weld on a dissimilar metal weld

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kang Soo; Lee, Ho Jin; Lee, Bong Sang (Korea Atomic Energy Research Institute, Daejeon (Korea)); Jung, I.C.; Byeon, J.G.; Park, K.S. (Doosan Heavy Industries and Construction Co., Changwon (Korea)), e-mail: kskim5@kaeri.re.kr

    2009-07-01

    In recent years, a dissimilar metal, Alloy 82/182 welds used to connect stainless steel piping and low alloy steel or carbon steel components in nuclear reactor piping system have experienced a cracking due to a primary water stress corrosion (PWSCC). It is well known that one reason for the cracking is the residual stress by the weld. But, it is difficult to estimate the weld residual stress exactly due to many parameters of a welding. In this paper, the analysis of 3 FEM models is performed to estimate the weld residual stress on a dissimilar metal weld exactly

  13. Inertia Friction Welding of Dissimilar Superalloys Mar-M247 and LSHR

    Science.gov (United States)

    Senkov, Oleg N.; Mahaffey, David W.; Semiatin, S. Lee; Woodward, Christopher

    2014-11-01

    The solid state inertia friction welding (IFW) process was used for the first time to join two dissimilar Ni-based superalloys, LSHR, a powder metallurgy alloy, and Mar-M247, a directionally solidified alloy. Extensive studies of the microstructure, phase composition, re-distribution of the alloying elements between the welded alloys, microhardness, and welding defects were conducted at different distances from the weld interface, and the results were correlated with the loading and friction conditions during IFW. Possible reasons leading to the formation of the welding defects were discussed and directions for the further improvement of the quality of the IFW of these two dissimilar alloys were outlined.

  14. Creep Strength of Dissimilar Welded Joints Using High B-9Cr Steel for Advanced USC Boiler

    Science.gov (United States)

    Tabuchi, Masaaki; Hongo, Hiromichi; Abe, Fujio

    2014-10-01

    The commercialization of a 973 K (700 °C) class pulverized coal power system, advanced ultra-supercritical (A-USC) pressure power generation, is the target of an ongoing research project initiated in Japan in 2008. In the A-USC boiler, Ni or Ni-Fe base alloys are used for high-temperature parts at 923 K to 973 K (650 °C to 700 °C), and advanced high-Cr ferritic steels are planned to be used at temperatures lower than 923 K (650 °C). In the dissimilar welds between Ni base alloys and high-Cr ferritic steels, Type IV failure in the heat-affected zone (HAZ) is a concern. Thus, the high B-9Cr steel developed at the National Institute for Materials Science, which has improved creep strength in weldments, is a candidate material for the Japanese A-USC boiler. In the present study, creep tests were conducted on the dissimilar welded joints between Ni base alloys and high B-9Cr steels. Microstructures and creep damage in the dissimilar welded joints were investigated. In the HAZ of the high B-9Cr steels, fine-grained microstructures were not formed and the grain size of the base metal was retained. Consequently, the creep rupture life of the dissimilar welded joints using high B-9Cr steel was 5 to 10 times longer than that of the conventional 9Cr steel welded joints at 923 K (650 °C).

  15. The Empirical Versus DSM-Oriented Approach of the Child Behavior Checklist Similarities and Dissimilarities

    NARCIS (Netherlands)

    de Wolff, Marianne S.; Vogels, Anton G. C.; Reijneveld, Sijmen A.

    2014-01-01

    The DSM-oriented approach of the Child Behavior Checklist (CBCL) is a relatively new classification of problem behavior in children and adolescents. Given the clinical and scientific relevance of the CBCL, this study examines similarities and dissimilarities between the empirical and the

  16. The empirical versus DSM-oriented approach of the child behavior checklist: Similarities and dissimilarities

    NARCIS (Netherlands)

    Wolff, M.S. de; Vogels, A.G.C.; Reijneveld, S.A.

    2014-01-01

    The DSM-oriented approach of the Child Behavior Checklist (CBCL) is a relatively new classification of problem behavior in children and adolescents. Given the clinical and scientific relevance of the CBCL, this study examines similarities and dissimilarities between the empirical and the

  17. Effects of skill dissimilarity and task interdependence on helping in work teams

    NARCIS (Netherlands)

    van der Vegt, G.S.; Van de Vliert, E.

    2005-01-01

    This study examined the effects of perceived skill dissimilarity and task interdependence on individual team members' helping behavior in a panel study of senior business students enrolled in a management game. The students were randomly assigned to 20 teams and functioned as a firm's top management

  18. Nondestructive testing of austenitic casting and dissimilar metal welds; Kaksimetalliliitosten ja austeniittisten valujen testaustekniikoiden vertailu

    Energy Technology Data Exchange (ETDEWEB)

    Lahdenperae, K. [VTT Manufacturing Technology, Espoo (Finland)

    1995-01-01

    The publication is a literature study of nondestructive testing of dissimilar metal welds and cast austenitic components in PWR and BWR plants. A major key to the successful testing is a realistic mockup made of the materials to be tested. The inspectors must also be trained and validated using suitable mockups. (42 refs., 27 figs., 10 tabs.).

  19. Quantum Watermarking by Frequency of Error when Observing Qubits in Dissimilar Bases

    CERN Document Server

    Worley, G G

    2004-01-01

    We present a so-called fuzzy watermarking scheme based on the relative frequency of error in observing qubits in a dissimilar basis from the one in which they were written. Then we discuss possible attacks on the system and speculate on how to implement this watermarking scheme for particular kinds of messages (images, formated text, etc.).

  20. On Difference of Convex Optimization to Visualize Statistical Data and Dissimilarities

    DEFF Research Database (Denmark)

    Carrizosa, Emilio; Guerrero, Vanesa; Morales, Dolores Romero

    2016-01-01

    In this talk we address the problem of visualizing in a bounded region a set of individuals, which has attached a dissimilarity measure and a statistical value. This problem, which extends the standard Multidimensional Scaling Analysis, is written as a global optimization problem whose objective ...

  1. Mixture toxicity of three toxicants with similar and dissimilar modes of action to Daphnia magna

    DEFF Research Database (Denmark)

    Syberg, K.; Engell-Kofoed, Anders Elleby; Pedersen, H.;

    2008-01-01

    Mixture toxicity of similar- and dissimilar-acting toxicants can be predicted by the models concentration addition (CA) and independent action (IA) using single substance toxicity data. Knowledge of the toxicants mode of action is thus required in order to use the models. In order to test the pre...

  2. Investigation on dissimilar laser welding of advanced high strength steel sheets for the automotive industry

    Energy Technology Data Exchange (ETDEWEB)

    Rossini, M., E-mail: matteo.rossini@unibz.it [Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano (Italy); Spena, P. Russo, E-mail: pasquale.russospena@unibz.it [Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano (Italy); Cortese, L., E-mail: luca.cortese@unibz.it [Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano (Italy); Matteis, P., E-mail: paolo.matteis@polito.it [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Firrao, D., E-mail: donato.firrao@polito.it [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)

    2015-03-25

    To support the use of advanced high strength steels in car body design and fabrication, an investigation was carried out on dissimilar butt laser welding between TWinning Induced Plasticity (TWIP) steels, Dual Phase (DP) steels, hot stamping boron (22MnB5) steels, and TRansformation Induced Plasticity (TRIP) steels. The base materials and the weldments were fully characterized by means of metallography, microhardness, and tensile tests. Digital image analysis was also used to provide additional information on the local strain field in the joint during the tensile tests. Fractographic examination was finally performed on the fracture surfaces of the tensile samples. The dissimilar joints between the DP, 22MnB5, and TRIP steels exhibit good resistance properties. On the contrary, the dissimilar joints encompassing the TWIP steel exhibit poor mechanical strength and fail along the weld seam by intergranular fracture, probably due to presence of Mn segregations. Therefore, the laser welding of TWIP steel with other advanced high strength steels is not recommended without the use of proper metal fillers. Dissimilar laser welding of DP, TRIP and 22MnB5 combinations, on the contrary, can be a solution to assemble car body parts made of these steel grades.

  3. Method development for impurity profiling in SFC: The selection of a dissimilar set of stationary phases.

    Science.gov (United States)

    Galea, Charlene; Mangelings, Debby; Heyden, Yvan Vander

    2015-01-01

    Supercritical fluid chromatography (SFC) is drawing considerable interest as separation technique in the pharmaceutical industry. The technique is already well established in chiral separations both analytically and on a preparative scale. The use of SFC as a technique for drug impurity profiling is examined here. To define starting conditions in method development for drug impurity profiling, a set of dissimilar stationary phases is screened in parallel. The possibility to select a set of dissimilar columns using the retention factors (k-values) for a set of 64 drugs measured on 27 columns in SFC was examined. Experiments were carried out at a back-pressure of 150 bar and 25 °C with a mobile phase consisting of CO2 and methanol with 0.1% isopropylamine (5-40% over 10 min) at a flow rate of 3 mL/min. These k-values were then used to calculate correlation coefficients on the one hand and to perform a principal component analysis on the other. The Kennard and Stone algorithm, besides dendrograms and correlation-coefficient colour maps were used to select a set of 6 dissimilar stationary phases. The stationary phase characterization results from this study were compared to those from previous studies found in the literature. Retention mechanisms for compounds possessing different properties were also evaluated. The dissimilarity of the selected subset of 6 stationary phases was validated using mixtures of compounds with similar properties and structures, as one can expect in a drug impurity profile.

  4. Effects of attitude dissimilarity and time on social integration : A longitudinal panel study

    NARCIS (Netherlands)

    Van der Vegt, GS

    2002-01-01

    A longitudinal panel study in 25 work groups of elementary school teachers examined the effect of attitudinal dissimilarity and time on social integration across a 9-month period. In line with the prediction based on both the similarity-attraction approach and social identity theory, cross-lagged re

  5. On Difference of Convex Optimization to Visualize Statistical Data and Dissimilarities

    DEFF Research Database (Denmark)

    Carrizosa, Emilio; Guerrero, Vanesa; Morales, Dolores Romero

    2016-01-01

    In this talk we address the problem of visualizing in a bounded region a set of individuals, which has attached a dissimilarity measure and a statistical value. This problem, which extends the standard Multidimensional Scaling Analysis, is written as a global optimization problem whose objective ...

  6. Implicit Learning of Musical Timbre Sequences: Statistical Regularities Confronted With Acoustical (Dis)Similarities

    Science.gov (United States)

    Tillmann, Barbara; McAdams, Stephen

    2004-01-01

    The present study investigated the influence of acoustical characteristics on the implicit learning of statistical regularities (transition probabilities) in sequences of musical timbres. The sequences were constructed in such a way that the acoustical dissimilarities between timbres potentially created segmentations that either supported (S1) or…

  7. Prediction of welding residual stress of dissimilar metal weld of nozzle using finite element analyses

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Nam Su; Kim, Jong Wook; Choi, Suhn; Kim, Tae Wan [KAERI, Daejeon (Korea, Republic of)

    2008-07-01

    The Primary Water Stress Corrosion Cracking (PWSCC) of dissimilar metal weld based on Alloy 82/182 is one of major issues in material degradation of nuclear components. It is well known that the crack initiation and growth due to PWSCC is influenced by material's susceptibility to PWSCC and distribution of welding residual stress. Therefore, modeling the welding residual stress is of interest in understanding crack formation and growth in dissimilar metal weld. Currently in Korea, a numerical round robin study is undertaken to provide guidance on the welding residual stress analysis of dissimilar metal weld. As a part of this effort, the present paper investigates distribution of welding resisual stress of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two-dimensional thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed design and fabrication data. The present results are compared with those from other participants, and more works incorporating physical measurements are going to be performed to quantify the uncertainties relating to modelling assumptions.

  8. FEM Analysis and Measurement of Residual Stress by Neutron Diffraction on the Dissimilar Overlay Weld Pipe

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kang Soo; Lee, Ho Jin; Woo, Wan Chuck; Seong, Baek Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Byeon, Jin Gwi; Park, Kwang Soo; Jung, In Chul [Doosan Heavy Industries and Construction Co., Changwon (Korea, Republic of)

    2010-10-15

    Much research has been done to estimate the residual stress on a dissimilar metal weld. There are many methods to estimate the weld residual stress and FEM (Finite Element Method) is generally used due to the advantage of the parametric study. And the X-ray method and a Hole Drilling technique for an experimental method are also usually used. The aim of this paper is to develop the appropriate FEM model to estimate the residual stresses of the dissimilar overlay weld pipe. For this, firstly, the specimen of the dissimilar overlay weld pipe was manufactured. The SA 508 Gr3 nozzle, the SA 182 safe end and SA376 pipe were welded by the Alloy 182. And the overlay weld by the Alloy 52M was performed. The residual stress of this specimen was measured by using the Neutron Diffraction device in the HANARO (High-flux Advanced Neutron Application ReactOr) research reactor, KAERI (Korea Atomic Energy Research Institute). Secondly, FEM Model on the dissimilar overlay weld pipe was made and analyzed by the ABAQUS Code (ABAQUS, 2004). Thermal analysis and stress analysis were performed, and the residual stress was calculated. Thirdly, the results of the FEM analysis were compared with those of the experimental methods

  9. Children's perceptions of dissimilarity in parenting styles are associated with internalizing and externalizing behavior

    NARCIS (Netherlands)

    M. Berkien (Myra); I. Louwerse (Ilse); F.C. Verhulst (Frank); J. van der Ende (Jan)

    2012-01-01

    textabstractThe purpose of this study was to examine the relationship between children's perception of dissimilarity in parenting styles, and internalizing and externalizing problems in children. Children from the general population (n = 658) reported on the level of emotional warmth, rejection, and

  10. Person-group dissimilarity in involvement in bullying and its relation with social status

    NARCIS (Netherlands)

    Sentse, Miranda; Scholte, Ron; Salmivalli, Christina; Voeten, Marinus

    2007-01-01

    This study tested a person-group dissimilarity model for the relation between peer preference on the one hand, and bullying and victimization on the other. This model accounts for both individual and group (i.e., classroom) factors and postulates that children will be rejected by their peers when th

  11. Evaluation of near-surface stress distributions in dissimilar welded joint by scanning acoustic microscopy.

    Science.gov (United States)

    Kwak, Dong Ryul; Yoshida, Sanichiro; Sasaki, Tomohiro; Todd, Judith A; Park, Ik Keun

    2016-04-01

    This paper presents the results from a set of experiments designed to ultrasonically measure the near surface stresses distributed within a dissimilar metal welded plate. A scanning acoustic microscope (SAM), with a tone-burst ultrasonic wave frequency of 200 MHz, was used for the measurement of near surface stresses in the dissimilar welded plate between 304 stainless steel and low carbon steel. For quantitative data acquisition such as leaky surface acoustic wave (leaky SAW) velocity measurement, a point focus acoustic lens of frequency 200 MHz was used and the leaky SAW velocities within the specimen were precisely measured. The distributions of the surface acoustic wave velocities change according to the near-surface stresses within the joint. A three dimensional (3D) finite element simulation was carried out to predict numerically the stress distributions and compare with the experimental results. The experiment and FE simulation results for the dissimilar welded plate showed good agreement. This research demonstrates that a combination of FE simulation and ultrasonic stress measurements using SAW velocity distributions appear promising for determining welding residual stresses in dissimilar material joints.

  12. Measures of precision for dissimilarity-based multivariate analysis of ecological communities.

    Science.gov (United States)

    Anderson, Marti J; Santana-Garcon, Julia

    2015-01-01

    Ecological studies require key decisions regarding the appropriate size and number of sampling units. No methods currently exist to measure precision for multivariate assemblage data when dissimilarity-based analyses are intended to follow. Here, we propose a pseudo multivariate dissimilarity-based standard error (MultSE) as a useful quantity for assessing sample-size adequacy in studies of ecological communities. Based on sums of squared dissimilarities, MultSE measures variability in the position of the centroid in the space of a chosen dissimilarity measure under repeated sampling for a given sample size. We describe a novel double resampling method to quantify uncertainty in MultSE values with increasing sample size. For more complex designs, values of MultSE can be calculated from the pseudo residual mean square of a permanova model, with the double resampling done within appropriate cells in the design. R code functions for implementing these techniques, along with ecological examples, are provided. © 2014 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.

  13. Acoustic and categorical dissimilarity of musical timbre: Evidence from asymmetriesbetween acoustic and chimeric sounds

    Directory of Open Access Journals (Sweden)

    Kai eSiedenburg

    2016-01-01

    Full Text Available This paper investigates the role of acoustic and categorical information in timbre dissimilarity ratings. Using a Gammatone-filterbank-based sound transformation, we created tones that were rated as less familiar than recorded tones from orchestral instruments and that were harder to associate with an unambiguous sound source (Exp. 1. A subset of transformed tones, a set of orchestral recordings, and a mixed set were then rated on pairwise dissimilarity (Exp. 2A. We observed that recorded instrument timbres clustered into subsets that distinguished timbres according to acoustic and categorical properties. For the subset of cross-category comparisons in the mixed set, we observed asymmetries in the distribution of ratings, as well as a stark decay of inter-rater agreement. These effects were replicated in a more robust within-subjects design (Exp. 2B and cannot be explained by acoustic factors alone. We finally introduced a novel model of timbre dissimilarity based on partial least-squares regression that compared the contributions of both acoustic and categorical timbre descriptors. The best model fit (R^2 = .88 was achieved when both types of descriptors were taken into account. These findings are interpreted as evidence for an interplay of acoustic and categorical information in timbre dissimilarity perception.

  14. Implicit Learning of Musical Timbre Sequences: Statistical Regularities Confronted With Acoustical (Dis)Similarities

    Science.gov (United States)

    Tillmann, Barbara; McAdams, Stephen

    2004-01-01

    The present study investigated the influence of acoustical characteristics on the implicit learning of statistical regularities (transition probabilities) in sequences of musical timbres. The sequences were constructed in such a way that the acoustical dissimilarities between timbres potentially created segmentations that either supported (S1) or…

  15. Acoustic and Categorical Dissimilarity of Musical Timbre: Evidence from Asymmetries Between Acoustic and Chimeric Sounds.

    Science.gov (United States)

    Siedenburg, Kai; Jones-Mollerup, Kiray; McAdams, Stephen

    2015-01-01

    This paper investigates the role of acoustic and categorical information in timbre dissimilarity ratings. Using a Gammatone-filterbank-based sound transformation, we created tones that were rated as less familiar than recorded tones from orchestral instruments and that were harder to associate with an unambiguous sound source (Experiment 1). A subset of transformed tones, a set of orchestral recordings, and a mixed set were then rated on pairwise dissimilarity (Experiment 2A). We observed that recorded instrument timbres clustered into subsets that distinguished timbres according to acoustic and categorical properties. For the subset of cross-category comparisons in the mixed set, we observed asymmetries in the distribution of ratings, as well as a stark decay of inter-rater agreement. These effects were replicated in a more robust within-subjects design (Experiment 2B) and cannot be explained by acoustic factors alone. We finally introduced a novel model of timbre dissimilarity based on partial least-squares regression that compared the contributions of both acoustic and categorical timbre descriptors. The best model fit (R (2) = 0.88) was achieved when both types of descriptors were taken into account. These findings are interpreted as evidence for an interplay of acoustic and categorical information in timbre dissimilarity perception.

  16. Exposure assessment of the cumulative intake of pesticides with dissimilar mode of action

    DEFF Research Database (Denmark)

    Jensen, Bodil Hamborg; Petersen, Annette; Christiansen, Sofie

    . In this study the effects of combined exposure from four endocrine disrupting pesticides have been investigated (procymidone, mancozeb, tebuconazole, and prochloraz). The four pesticides have dissimilar mode of actions. On the background of the potency for each pesticide to a given effect, a relative potency...

  17. Toxicity of mixtures of nephrotoxicants with similar or dissimilar mode of action

    NARCIS (Netherlands)

    Jonker, D.; Woutersen, R.A.; Feron, V.J.

    1996-01-01

    The toxicity of mixtures of chemicals with the same target organ was examined in rats using nephrotoxicants with similar or dissimilar modes of action. In a 4-wk feeding study, lysinoalanine, mercuric chloride, hexachloro-1,3-butadiene and d-limonene, each affecting renal proximal tubular cells but

  18. A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    Liming Liu

    2014-05-01

    Full Text Available Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from different perspectives. Welding of dissimilar Mg and Al is challenging due to the formation of brittle intermetallic compound (IMC such as Mg17Al12 and Mg2Al3. In order to increase the joint strength, three main research approaches were used to eliminate or reduce the Mg-Al intermetallic reaction layer. First, solid state welding techniques which have a low welding temperature were used to reduce the IMCs. Second, IMC variety and distribution were controlled to avoid the degradation of the joining strength in fusion welding. Third, techniques which have relatively controllable reaction time and energy were used to eliminate the IMCs. Some important processing parameters and their effects on weld quality are discussed, and the microstructure and metallurgical reaction are described. Mechanical properties of welds such as hardness, tensile, shear and fatigue strength are discussed. The aim of the report is to review the recent progress in the welding of dissimilar Mg and Al to provide a basis for follow-up research.

  19. Children's perceptions of dissimilarity in parenting styles are associated with internalizing and externalizing behavior

    NARCIS (Netherlands)

    M. Berkien (Myra); I. Louwerse (Ilse); F.C. Verhulst (Frank); J. van der Ende (Jan)

    2012-01-01

    textabstractThe purpose of this study was to examine the relationship between children's perception of dissimilarity in parenting styles, and internalizing and externalizing problems in children. Children from the general population (n = 658) reported on the level of emotional warmth, rejection, and

  20. Regulation of the demographic structure in isomorphic biphasic life cycles at the spatial fine scale.

    Directory of Open Access Journals (Sweden)

    Vasco Manuel Nobre de Carvalho da Silva Vieira

    Full Text Available Isomorphic biphasic algal life cycles often occur in the environment at ploidy abundance ratios (Haploid:Diploid different from 1. Its spatial variability occurs within populations related to intertidal height and hydrodynamic stress, possibly reflecting the niche partitioning driven by their diverging adaptation to the environment argued necessary for their prevalence (evolutionary stability. Demographic models based in matrix algebra were developed to investigate which vital rates may efficiently generate an H:D variability at a fine spatial resolution. It was also taken into account time variation and type of life strategy. Ploidy dissimilarities in fecundity rates set an H:D spatial structure miss-fitting the ploidy fitness ratio. The same happened with ploidy dissimilarities in ramet growth whenever reproductive output dominated the population demography. Only through ploidy dissimilarities in looping rates (stasis, breakage and clonal growth did the life cycle respond to a spatially heterogeneous environment efficiently creating a niche partition. Marginal locations were more sensitive than central locations. Related results have been obtained experimentally and numerically for widely different life cycles from the plant and animal kingdoms. Spore dispersal smoothed the effects of ploidy dissimilarities in fertility and enhanced the effects of ploidy dissimilarities looping rates. Ploidy dissimilarities in spore dispersal could also create the necessary niche partition, both over the space and time dimensions, even in spatial homogeneous environments and without the need for conditional differentiation of the ramets. Fine scale spatial variability may be the key for the prevalence of isomorphic biphasic life cycles, which has been neglected so far.

  1. A dynamic fuzzy clustering method based on genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yan; ZHOU Chunguang; LIANG Yanchun; GUO Dongwei

    2003-01-01

    A dynamic fuzzy clustering method is presented based on the genetic algorithm. By calculating the fuzzy dissimilarity between samples the essential associations among samples are modeled factually. The fuzzy dissimilarity between two samples is mapped into their Euclidean distance, that is, the high dimensional samples are mapped into the two-dimensional plane. The mapping is optimized globally by the genetic algorithm, which adjusts the coordinates of each sample, and thus the Euclidean distance, to approximate to the fuzzy dissimilarity between samples gradually. A key advantage of the proposed method is that the clustering is independent of the space distribution of input samples, which improves the flexibility and visualization. This method possesses characteristics of a faster convergence rate and more exact clustering than some typical clustering algorithms. Simulated experiments show the feasibility and availability of the proposed method.

  2. Life time assessment and repair of dissimilar metal welds. Part 1; Livslaengdsbedoemning och reparation av blandsvetsskarvar. Etapp 1

    Energy Technology Data Exchange (ETDEWEB)

    Storesund, Jan; Borggreen, Kjeld

    2005-04-01

    Research on the performance of dissimilar metal welds in high temperature plant has been performed for many years. Nevertheless damages are frequent in such welds. In order to decrease the damage problems and make it possible to estimate residual lifetimes of dissimilar metal welds in our Nordic countries it is first essential to i) collect the knowledge in the literature and ii) map current dissimilar metal welds and their condition in Swedish and Danish plants. The present report describes this first part of the work. There is a comprehensive literature of she subject. Most work has been performed on ferritic/austenitic dissimilar welds. In Swedish and Danish plants the dominating type is ferritic/martensitic dissimilar welds. The damage mechanisms are about the same in the two types, creep is the dominating mechanism, but plant experience indicates that the ferritic/austenitic combination is more prone to damage than the ferritic/martensitic one. An important difference between the two types is that Ni-base weld metal generally prolongs the lifetime for ferritic/austenitic dissimilar welds whereas it shows an opposite effect in ferritic/martensitic ones. In the latter case use of a 5 % Cr weld metal seems to be the best choice but the experiences of such welds are limited. The mapping of dissimilar welds indicates that there are predominantly special kinds of welds which fail whereas ordinary butt welds and branch welds are relatively free from damage.

  3. Three-dimensional finite element analysis for estimation of the weld residual stress in the dissimilar butt weld piping

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyoung Soo; Kim, Man Won; Lee, Sung Ho [KHNP Central Research Institute, Daejeon (Korea, Republic of)

    2013-01-15

    Numerous dissimilar metal welds are used to connect carbon steel and stainless steel in nuclear power plants. Recently, some cracks have occurred in the dissimilar metal welds, and welding residual stress is considered as a contributing factor to the cracks. In this study, welding residual stresses in dissimilar butt weld piping were evaluated by the 3-dimensional (3-D) finite element method. Welding residual stresses along the circumference of heat affected zones as well as weld regions were obtained through the analysis, which could not be obtainable with 2-dimensional (2-D) analysis. The differences between 2-D analysis and 3-D analysis are presented in this paper.

  4. Mechanical and microstructural characterization of 6061 aluminum alloy strips severely deformed by Dissimilar Channel Angular Pressing

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Evren, E-mail: etan@metu.edu.tr [Middle East Technical University, Metallurgical and Materials Eng. Dept., 06531, Ankara (Turkey); Kibar, Alp Aykut, E-mail: alpaykut@gmail.com [Scientific and Technological Research Council of Turkey, 06100, Ankara (Turkey); Guer, C. Hakan, E-mail: chgur@metu.edu.tr [Middle East Technical University, Metallurgical and Materials Eng. Dept., 06531, Ankara (Turkey)

    2011-04-15

    Dissimilar Channel Angular Pressing (DCAP) is a severe plastic deformation technique to improve the mechanical properties of flat products by producing ultrafine grains. In this study, the changes in the microstructure and mechanical properties of 6061 Al-alloy strips deformed by various numbers of DCAP passes were investigated. Some DCAPed samples were also held at 200 deg. C and 350 deg. C to investigate the effect of post-annealing. Mechanical properties were determined by hardness and tension tests; and microstructural changes were investigated by TEM analysis. Up to a critical level of plastic strain, remarkable improvements have been observed in the strength and hardness of the severely deformed strips; and the improvements have been explained by variations in grain size, dislocation structure, and formation of subgrains. - Research Highlights: {yields}Dissimilar Channel Angular Pressing (DCAP). {yields}Severe plastic deformation (SPD). {yields}Transmission Electron Microscopy of the 6061 Al alloy. {yields}Mechanical Properties of 6061 Al alloy.

  5. Numerical simulation and experimental investigation of laser dissimilar welding of carbon steel and austenitic stainless steel

    Science.gov (United States)

    Nekouie Esfahani, M. R.; Coupland, J.; Marimuthu, S.

    2015-07-01

    This study reports an experimental and numerical investigation on controlling the microstructure and brittle phase formation during laser dissimilar welding of carbon steel to austenitic stainless steel. The significance of alloying composition and cooling rate were experimentally investigated. The investigation revealed that above a certain specific point energy the material within the melt pool is well mixed and the laser beam position can be used to control the mechanical properties of the joint. The heat-affected zone within the high-carbon steel has significantly higher hardness than the weld area, which severely undermines the weld quality. A sequentially coupled thermo-metallurgical model was developed to investigate various heat-treatment methodology and subsequently control the microstructure of the HAZ. Strategies to control the composition leading to dramatic changes in hardness, microstructure and service performance of the dissimilar laser welded fusion zone are discussed.

  6. Thermo-mechanical Modeling for Residual Stresses of Friction Stir Welding of Dissimilar Alloys

    Directory of Open Access Journals (Sweden)

    ABDUL ARIF

    2013-06-01

    Full Text Available Friction stir welding is an advanced joining process that has been used for high production since 1996. FSW produces a weld that is strong than the base material because melting does not occur and joining takes place below the melting temperature of the material. FSW produces no fumes and can join aluminum alloys, magnesium, steels, copper and titanium. In this study, a thermo-mechanical model with improved potential is developed to study the formation of residual stress field in dissimilar materials. The model predictions were confirmed with experimental data obtained by Jamshidi et al. on dissimilar aluminum alloys AA6061 to AA5086. A commercial finite element software ANSYS® is used for simulation of friction stir welding. Longitudinal and transverse residual stresses are obtained when AA5086-O on the advancing side and AA6061- T6 on the retreating side after 15sec.

  7. Joining of dissimilar metals by diffusion bonding. Titanium alloy with aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Akca, Enes [International Univ. of Sarajevo (Bosnia and Herzegovina). Research and Development Center; International Univ. of Sarajevo (Bosnia and Herzegovina). Dept. of Mechanical Engineering; Gursel, Ali [International Univ. of Sarajevo (Bosnia and Herzegovina). Dept. of Mechanical Engineering

    2017-05-01

    This paper presents a novel diffusion bonding process of commercially pure aluminum to Ti-6Al-4V alloy at 520, 560, 600 and 640 C for 30, 45 and 60 minutes under argon gas shielding without the use of interlayer. The approach is to overcome the difficulties in fusion welding of dissimilar alloys. Diffusion bonding is a dissimilar metal welding process which can be applied to the materials without causing any physical deformations. Processed samples were metallographically prepared, optically examined followed by Vickers microhardness test and subjected to tensile test in order to determine joint strength. Scanning electron microscopy and energy dispersive spectroscopy were used in this work to investigate the compositional changes across the joint region. Elemental composition of the region has been successfully defined between titanium alloy and aluminum. The maximum tensile strength was obtained from the samples bonded at the highest temperatures of 600 and 640 C.

  8. Combination of Evidence with Different Weighting Factors: A Novel Probabilistic-Based Dissimilarity Measure Approach

    Directory of Open Access Journals (Sweden)

    Mengmeng Ma

    2015-01-01

    Full Text Available To solve the invalidation problem of Dempster-Shafer theory of evidence (DS with high conflict in multisensor data fusion, this paper presents a novel combination approach of conflict evidence with different weighting factors using a new probabilistic dissimilarity measure. Firstly, an improved probabilistic transformation function is proposed to map basic belief assignments (BBAs to probabilities. Then, a new dissimilarity measure integrating fuzzy nearness and introduced correlation coefficient is proposed to characterize not only the difference between basic belief functions (BBAs but also the divergence degree of the hypothesis that two BBAs support. Finally, the weighting factors used to reassign conflicts on BBAs are developed and Dempster’s rule is chosen to combine the discounted sources. Simple numerical examples are employed to demonstrate the merit of the proposed method. Through analysis and comparison of the results, the new combination approach can effectively solve the problem of conflict management with better convergence performance and robustness.

  9. Feature selection using feature dissimilarity measure and density-based clustering: Application to biological data

    Indian Academy of Sciences (India)

    Debarka Sengupta; Indranil Aich; Sanghamitra Bandyopadhyay

    2015-10-01

    Reduction of dimensionality has emerged as a routine process in modelling complex biological systems. A large number of feature selection techniques have been reported in the literature to improve model performance in terms of accuracy and speed. In the present article an unsupervised feature selection technique is proposed, using maximum information compression index as the dissimilarity measure and the well-known density-based cluster identification technique DBSCAN for identifying the largest natural group of dissimilar features. The algorithm is fast and less sensitive to the user-supplied parameters. Moreover, the method automatically determines the required number of features and identifies them. We used the proposed method for reducing dimensionality of a number of benchmark data sets of varying sizes. Its performance was also extensively compared with some other well-known feature selection methods.

  10. EFFECT OF PROCESS PARAMETERS ON THE TENSILE STRENGTH OF FRICTION STIR WELDED DISSIMILAR ALUMINUM JOINTS

    Directory of Open Access Journals (Sweden)

    R. PADMANABAN

    2015-06-01

    Full Text Available Friction stir welding is one of the recent solid state joining processes that has drawn the attention of the metal joining community. In this work the effects of tool rotation speed (TRS and welding speed (WS on the tensile strength of dissimilar friction stir welded AA2024-AA7075 joints are investigated. Response surface methodology is used for developing a mathematical model for the tensile strength of the dissimilar aluminum alloy joints. The model is used to investigate the effect of TRS and WS on the tensile strength of the joints. It is seen that the tensile strength of the joint increases with the increase in TRS up to a limit of 1050 rpm and decreases thereafter. The tensile strength of the joints is also seen increasing with the WS up to 15 mm/min. Further increase in WS results in a reduction of the tensile strength of the joints.

  11. Cracking behavior in a dissimilar weld between high silicon nodular cast iron and ferritic stainless steel

    Science.gov (United States)

    Kim, Sanghoon; Lee, Sangchul; Han, Kyutae; Hong, Seunggab; Lee, Changhee

    2010-06-01

    In this work, the microstructural evolution and cracking behavior of a dissimilar weld between high silicon nodular cast iron and ferritic stainless steel was investigated. An austenitic filler metal (Y309) was employed to produce the dissimilar weld. Microstructural analysis revealed that cracking formed at the unmixed zone (UMZ) and propagated into the partially melted zone (PMZ) in the bond line between the cast iron and the Y309, with hard layers formed around the bond line. The cracking behavior was strongly related to the difference in the melting points of cast iron and the Y309 filler metal, the local liquation of the laves phase, and the constitutional liquation between the graphite and austenite phases in the PMZ.

  12. Development of Temper Bead Welding Process for Weld Overlay of Dissimilar Welds

    Energy Technology Data Exchange (ETDEWEB)

    Byeon, J. G.; Park, K. S.; Kim, Y. J. [Doosan Heavy Industries and Construction Co., Ltd., Seoul (Korea, Republic of)

    2008-10-15

    In recent years, the dissimilar weld metal used to connect stainless steel piping and low alloy steel or carbon steel components have experienced cracking in nuclear reactor piping systems. The cracking has been observed in several Pressurized Water Reactors in overseas. In Several cases, the cracking was repaired using structural weld overlays, a repair technique that has been in use in the U.S. in Boiling Water Reactors for over twenty years. Although weld overlays have been used primarily as a repair for flawed piping, they can also be applied at locations that have not yet exhibited any cracking, but are considered susceptible to cracking. The purpose of this research is to develop the temper bead weld process for the weld overlay of the dissimilar weld pipe. We developed equipment for the overlay system, applied Procedure Qualification(PQ) for the temper bead welding process.

  13. Analysis of overlay weld effect on preventing PWSCC in dissimilar metal weld

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Gun; Oh, Chang Kyun; Jin, Tae Eun [Korea Power Engineering Co., Inc., Yongin (Korea, Republic of); Kim, Yong Tae [Korea Plant Service and Engineering Co., Ltd., Seongnam (Korea, Republic of); Yoo, Sung Soo [Korea Hydro and Nuclear Power Co., Ltd., Seoul (Korea, Republic of)

    2009-07-01

    PWSCC(Primary Stress Corrosion Cracking) in Alloy 82/182 butt welds is the problem affecting safety and integrity of nuclear power plant. PWSCC can be occurred in high magnitude of tensile residual stress, such as Alloy 82/182 dissimilar metal welds in Pressurizer(PZR) nozzles. There have been related incidents recently at the dissimilar metal welds in overseas nuclear power plants. Overlay weld is the one of the effective methods to decrease tensile residual stress of inside surface, which will result in preventing PWSCC. In this paper, overlay weld conditions on the purpose of preventing PWSCC was explained and the benefit of the overlay weld was confirmed performing finite element analysis.

  14. Investigation and Analysis of Weld Induced Residual Stresses in Two Dissimilar Pipes by Finite Element Modeling

    Science.gov (United States)

    Nadimi, S.; Khoushehmehr, R. J.; Rohani, B.; Mostafapour, A.

    In the present study, Manual Metal Arc Welding (MMAW) of austenitic stainless steel to carbon steel were studied. The Schaeffler diagram were used in determining suitable filler metal for this process and then the finite element analysis of residual stresses in butt welding of two dissimilar pipes is performed with the commercial software ANSYS, which includes moving heat source, material deposit, temperature dependant material properties, metal plasticity and elasticity, transient heat transfer and mechanical analysis. The residual stresses distribution and magnitude in the hoop and axial directions in the inner and outer surfaces of two dissimilar pipes were obtained. Welding simulation considered as a sequentially coupled thermo-mechanical analysis and the element birth and death technique was employed for simulation of filler metal deposition.

  15. Analysis of Overlay Weld Effect on Preventing PWSCC in Dissimilar Metal Weld

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Gun; Oh, Chang Kyun; Park, Heung Bae; Jin, Tae Eun [Korea Power Engineering Company, Daejeon (Korea, Republic of)

    2010-01-15

    PWSCC(Primary Stress Corrosion Cracking) in Alloy 82/182 butt welds is the problem affecting safety and integrity of nuclear power plant. PWSCC can be occurred in the area that is at high magnitude of tensile residual stress, such as Alloy 82/182 dissimilar metal welds in PZR(pressurizer) nozzles. There have been a number of incidents recently at the dissimilar metal welds in overseas nuclear power plants. Overlay weld is the one of the effective methods to decrease tensile residual stress of inside surface, which will result in preventing PWSCC. In this paper, overlay weld conditions on the purpose of preventing PWSCC was explained and the benefit of the overlay weld was confirmed performing finite element analysis.

  16. Low Cycle and Thermo-Mechanical Fatigue of Friction Welded Dissimilar Superalloys Joint

    Science.gov (United States)

    Sakaguchi, Motoki; Sano, Atsushi; Tran, Tra Hung; Okazaki, Masakazu; Sekihara, Masaru

    The high temperature strengths of the dissimilar friction welded superalloys joint between the cast polycrystalline Mar-M247 and the forged IN718 alloys have been investigated under low cycle and thermo-mechanical fatigue loadings, in comparison with those of the base metals. The experiments showed that the lives of the dissimilar joints were significantly influenced by the test conditions and loading modes. Not only the lives themselves but also the failure positions and mechanisms were sensitive to the loading mode. The fracture behaviors depending on the loading modes and test conditions were discussed, based on the macroscopic elastic follow-up mechanism and the microstructural inhomogeneity in the friction weld joint.

  17. Long-Term Monitoring of Field Trial Sites with Genetically Modified Oilseed Rape (Brassica napus L. in Saxony-Anhalt, Germany. Fifteen Years Persistence to Date but No Spatial Dispersion

    Directory of Open Access Journals (Sweden)

    Anke Belter

    2016-01-01

    Full Text Available Oilseed rape is known to persist in arable fields because of its ability to develop secondary seed dormancy in certain agronomic and environmental conditions. If conditions change, rapeseeds are able to germinate up to 10 years later to build volunteers in ensuing crops. Extrapolations of experimental data acted on the assumption of persistence periods for more than 20 years after last harvest of rapeseed. Genetically-modified oilseed rape—cultivated widely in Northern America since 1996—is assumed not to differ from its conventional form in this property. Here, experimental data are reported from official monitoring activities that verify these assumptions. At two former field trial sites in Saxony-Anhalt genetically-modified herbicide-resistant oilseed rape volunteers are found up to fifteen years after harvest. Nevertheless, spatial dispersion or establishment of GM plants outside of the field sites was not observed within this period.

  18. Spatial planning

    OpenAIRE

    Dimitrov, Nikola; Koteski, Cane

    2016-01-01

    The professional book ,, Space planning "processed chapters on: space, concept and definition of space, space as a system, spatial economics, economic essence of space, space planning, social determinants of spatial planning, spatial planning as a process, factors development and elements in spatial planning, methodology, components and content of spatial planning stages and types of preparation of spatial planning, spatial planning and industrialization, industrialization, urbanization and s...

  19. Spatial planning

    OpenAIRE

    Dimitrov, Nikola; Koteski, Cane

    2016-01-01

    The professional book ,, Space planning "processed chapters on: space, concept and definition of space, space as a system, spatial economics, economic essence of space, space planning, social determinants of spatial planning, spatial planning as a process, factors development and elements in spatial planning, methodology, components and content of spatial planning stages and types of preparation of spatial planning, spatial planning and industrialization, industrialization, urbanization and s...

  20. Thermo-mechanical Modeling for Residual Stresses of Friction Stir Welding of Dissimilar Alloys

    OpenAIRE

    ABDUL ARIF; ABHISHEK; K. N. Pandey

    2013-01-01

    Friction stir welding is an advanced joining process that has been used for high production since 1996. FSW produces a weld that is strong than the base material because melting does not occur and joining takes place below the melting temperature of the material. FSW produces no fumes and can join aluminum alloys, magnesium, steels, copper and titanium. In this study, a thermo-mechanical model with improved potential is developed to study the formation of residual stress field in dissimilar ...

  1. Method to Identify Similarity and Dissimilarity between Systems Engineering and Neighboring Disciplines

    Institute of Scientific and Technical Information of China (English)

    Yang Tianshe; Dong Xiaoshe; Li Jisheng; Sun Yanhong

    2007-01-01

    Systems engineering is not a new discipline. However, up to now, there is little consensus on its exact definition and scope. The scopes of several disciplines (neighboring disciplines of systems engineering) overlap with that of systems engineering. In this paper, the methods to identify similarities and dissimilarities between systems engineering and its neighboring disciplines are discussed .The research of this paper is expected to be helpful for clarifying the definition and scope of systems engineering.

  2. Gradient descent approach for minimizing dissimilarity measure in log-polarimagery

    Institute of Scientific and Technical Information of China (English)

    JIN Yong-jun; JIANG You-yi

    2006-01-01

    Log-polar mapping has been proposed as a very appropriate space-variant imaging model in active vision applications.There is no doubt about the importance of translation estimation in active visual tracking.In this paper an approach is presented,and its performances are evaluated.The approach uses a gradient descent for minimizing a dissimilarity measure.The experimental results reveal that this method is efficient for approaching active image translations.

  3. Fracture assessment for a dissimilar metal weld of low alloy steel and Ni-base alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Takuya, E-mail: takuya4.ogawa@toshiba.co.jp [Toshiba Corporation Power Systems Company, Power and Industrial Systems Research and Development Center, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan); Itatani, Masao; Saito, Toshiyuki; Hayashi, Takahiro; Narazaki, Chihiro; Tsuchihashi, Kentaro [Toshiba Corporation Power Systems Company, Power and Industrial Systems Research and Development Center, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan)

    2012-02-15

    Recently, instances of SCC in Ni-base alloy weld metal of light water reactor components have been reported. Despite the possibility of propagation of SCC crack to the fusion line between low alloy steel (LAS) of pressure vessel and Ni-base alloy of internal structure, a fracture assessment method of dissimilar metal welded joint has not been established. The objective of this study is to investigate a fracture mode of dissimilar metal weld of LAS and Ni-base alloy for development of a fracture assessment method for dissimilar metal weld. Fracture tests were conducted using two types of dissimilar metal weld test plates with semi-elliptical surface crack. In one of the test plates, the fusion line lies around the surface points of the surface crack and the crack tips at the surface points have intruded into LAS. Material ahead of the crack tip at the deepest point is Ni-base alloy. In the other, the fusion line lies around the deepest point of the surface crack and the crack tip at the deepest point has intruded into LAS. Material ahead of the crack tip at the deepest point is LAS. The results of fracture tests using the former type of test plate reveal that the collapse load considering the proportion of ligament area of each material gives a good estimation for fracture load. That is, fracture assessment based on plastic collapse mode is applicable to the former type of test plate. It is also understood that a fracture assessment method based on the elastic-plastic fracture mode is suitable for the latter type of test plate.

  4. CHARACTERISATION OF SPOT WELD GROWTH ON DISSIMILAR JOINTS WITH DIFFERENT THICKNESSES

    OpenAIRE

    Nachimani Charde

    2012-01-01

    A sound weld from spot welding is what most manufacturers desire and prefer for mechanical assemblies in their systems. The robustness is mainly attributed to the joining mechanism of mechanical parts. This paper focuses on the effect of parametric changes for dissimilar joints using 304 austenitic stainless steel and carbon steel of two different thicknesses. A pneumatic-based spot welder was used to accomplish the entire welding process. The parameters varied during the experiments are the...

  5. Premature failure of dissimilar metal weld joint at intermediate temperature superheater tube

    OpenAIRE

    Al Hajri, Mohammed; Anees U. Malik; MEROUFEL, Abdelkader; Al-Muaili, Fahd

    2015-01-01

    Dissimilar metal weld (DMW) joint between alloyed steel (AS) and stainless steel (SS) failed at one of intermediate temperature superheater (ITSH) tube in steam/power generation plant boiler. The premature failure was detected after a relatively short time of operation (8 years) where the crack propagated circumferentially from AS side through the ITSH tube. Apart from physical examination, microstructural studies based on optical microscopy, SEM and EDX analysis were performed. The results o...

  6. Application of a second-gradient model of ductile fracture on a Dissimilar Metal Weld

    OpenAIRE

    Yang Jun; Lacroix Rémi; Bergheau Jean-Michel; Leblond Jean-Baptiste; Perrin Gilles

    2016-01-01

    A “micromorphic”, second-gradient model applicable to ductile porous materials has been proposed, as an improvement from the fundamental work of Gurson that take into account the physical mechanisms responsible for ductile damage. The model has been applied to the study of fracture of the decarburized layer of a Dissimilar Metal Weld. The model successfully reproduces the crack path experimentally observed in a notched tensile sample extracted from this weld, different from the one predicted ...

  7. Stress field near interface crack tip of double dissimilar orthotropic composite materials

    Institute of Scientific and Technical Information of China (English)

    LI Jun-lin; ZHANG Shao-qin; YANG Wei-yang

    2008-01-01

    In this paper, double dissimilar orthotropic composite materials interracial crack is studied by constructing new stress functions and employing the method of com- posite material complex. When the characteristic equations' discriminants △1 >0 and △2 > 0, the theoretical formula of the stress field and the displacement field near the mode I interface crack tip are derived, indicating that there is no oscillation and inter- embedding between the interfaces of the crack.

  8. THE ELASTIC FIELD CASED BY TWO INCLUSIONS WITH UNI-FORM DILATATIONAL EIGENSTRAINS IN DISSIMILAR MEDIA

    Institute of Scientific and Technical Information of China (English)

    俞家欢; 匡震邦

    2001-01-01

    The displacement and the stress states cased by single inclusion are achieved from the fundamental solutions such as nuclei of strain in bimaterals. The elastic field induced by multiple inclusions in dissimilar media could be found from the superstition of that of individual precipitate. In this paper, the effect of the planner interface with parameters of depth from the interface, both pairs of elastic moduli and also shapes of the inclusion are also given, which are of great significance in physical applications.

  9. Which is Easier, Adjusting to a Similar or to a Dissimilar Culture?

    DEFF Research Database (Denmark)

    Selmer, Jan

    2007-01-01

    The intuitively paradoxical research proposition that it could be as difficult for business expatriates to adjust to a similar as to a dissimilar host culture is tested in this exploratory study. Based on data from a mail survey, a comparison of American business expatriates in Canada and Germany...... expatriates adjust is fundamental. Implications for theory, practice and future research of these findings are discussed in detail.  ...

  10. Dissimilar Al/steel friction stir welding lap joints for automotive applications

    Science.gov (United States)

    Campanella, D.; Spena, P. Russo; Buffa, G.; Fratini, L.

    2016-10-01

    A widespread usage of aluminum alloys for the fabrication of car-body parts is conditional on the employment of appropriate welding methods, especially if dissimilar welding must be performed with automotive steel grades. Dissimilar welding of aluminum alloys and steel grades poses some issues concerning the formation of brittle intermetallic compounds, difference in physical and chemical properties of the parent metals, and poor wetting behavior of aluminum. Friction stir welding is considered to be a reasonable solution to obtain sound aluminum/steel joints. A study on the join quality of dissimilar lap joints of steel and aluminum alloy sheets after friction stir welding is proposed here. A low carbon steel is joined with AA6016 aluminum alloy to study preliminarily the feasibility to assembly car-body parts. The joints, welded with tool rotation and feed rate varying in a wide range, have been studied from a visual examination and microstructural point of view. Optical microscopy has been used to characterize the microstructure of the examined sheets in as-received and welded conditions. Micro-hardness measurements have been carried out to quantitatively analyze the local hardness of the welded joints. Set welding process parameters are identified to assemble without the presence of macroscopic defects the examined steel and aluminum welded parts.

  11. A computational approach for thermomechanical fatigue life prediction of dissimilarly welded superheater tubes

    Energy Technology Data Exchange (ETDEWEB)

    Krishnasamy, Ram-Kumar; Seifert, Thomas; Siegele, Dieter [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany)

    2010-07-01

    In this paper a computational approach for fatigue life prediction of dissimilarly welded superheater tubes is presented and applied to a dissimilar weld between tubes made of the nickel base alloy Alloy617 tube and the 12% chromium steel VM12. The approach comprises the calculation of the residual stresses in the welded tubes with a multi-pass dissimilar welding simulation, the relaxation of the residual stresses in a post weld heat treatment (PWHT) simulation and the fatigue life prediction using the remaining residual stresses as initial condition. A cyclic fiscoplasticity model is used to calculate the transient stresses and strains under thermocyclic service loadings. The fatigue life is predicted with a damage parameter which is based on fracture mechanics. The adjustable parameters of the model are determined based on LCF and TMF experiments. The simulations show, that the residual stresses that remain after PWHT further relax in the first loading cycles. The predicted fatigue lives depend on the residual stresses and, thus, on the choice of the loading cycle in which the damage parameter is evaluated. It the first loading cycle, where residual stresses are still present, is considered, lower fatigue lives are predicted compared to predictions considering loading cycles with relaxed residual stresses. (orig.)

  12. Laser welding of dissimilar materials for lightweight construction and special applications

    Science.gov (United States)

    Schimek, Mitja; Springer, André; Pfeifer, Ronny; Kaierle, Stefan

    2013-02-01

    Against the background of climate objectives and the desired reduction of CO2-emissions, optimization of existing industrial products is needed. To counter rising raw material costs, currently used materials are substituted. This will places new requirements on joining technologies for dissimilar material classes. The main difficulty lies in joining these materials cohesively without changing the properties of the base materials. Current research work at the LZH on joining dissimilar materials is being carried out for the automotive sector and for solar absorbers. For the automotive industry, a laser welding process for joining steel and aluminum without using additives is being investigated, equipped with a spectroscopic welding depth control to increase tensile strength. With a specially constructed laser processing head, it is possible to regulate welding penetration depth in the aluminum sheet, reducing the formation of intermetallic phases. Flat plate solar collectors are favorable devices for generating heat from solar energy. The solar absorber is the central part of a collector, consisting of an aluminum sheet and a copper tube which is attached to the aluminum sheet. Research on new laser welding processes aims at reducing the amount of energy required for production of these solar absorbers. In the field of joining dissimilar materials, laser joining processes, especially for special applications, will complement established joining techniques.

  13. Effect of tool rotational speed and penetration depth on dissimilar aluminum alloys friction stir spot welds

    Directory of Open Access Journals (Sweden)

    Joaquín M. Piccini

    2017-03-01

    Full Text Available In the last years, the automotive industry is looking for the use of aluminum parts in replace of steel parts in order to reduce the vehicles weight. These parts have to be joined, for instance, by welding processes. The more common welding process in the automotive industry is the Resistance Spot Welding (RSW technique. However, RSW of aluminum alloys has many disadvantages. Regarding this situation, a variant of the Friction Stir Welding process called Friction Stir Spot Welding (FSSW has been developed, showing a strong impact in welding of aluminum alloys and dissimilar materials in thin sheets. Process parameters affect the characteristics of the welded joints. However, the information available on this topic is scarce, particularly for dissimilar joints and thin sheets. The aim of this work was to study the effect of the rotational speed and the tool penetration depth on the characteristics of dissimilar FSS welded joints. Defects free joints have been achieved with higher mechanical properties than the ones reported. The maximum fracture load was 5800 N. It was observed that the effective joint length of the welded spots increased with the tool penetration depth, meanwhile the fracture load increased and then decreased. Finally, welding at 1200 RPM produced welded joints with lower mechanical properties than the ones achieved at 680 and 903 RPM.

  14. Expertise dissimilarity and creativity: the contingent roles of tacit and explicit knowledge sharing.

    Science.gov (United States)

    Huang, Xu; Hsieh, J J Po-An; He, Wei

    2014-09-01

    In this study, we investigated whether team-level knowledge sharing moderates the effects of individual-level expertise dissimilarity on individual employees' creativity in research and development (R&D) project teams. Expertise dissimilarity--defined as the difference in expertise and knowledge between a focal team member and her or his fellow team members--was operationalized in terms of the research department to which each member belonged. In Study 1, multilevel analyses of data collected from 200 members of 40 R&D project teams in a telecommunications company revealed that a team member with expertise dissimilar to that of her or his teammates was more likely to exhibit creativity when the project team as a whole engaged in higher levels of tacit, rather than explicit, knowledge sharing. In contrast, a member whose expertise was similar to that of her or his teammates was more likely to exhibit creative behavior when the team engaged in higher levels of explicit, rather than tacit, knowledge sharing. These findings were largely replicated in Study 2 using data collected from 82 members of 25 project teams from another telecommunications company.

  15. Similarity-dissimilarity plot for visualization of high dimensional data in biomedical pattern classification.

    Science.gov (United States)

    Arif, Muhammad

    2012-06-01

    In pattern classification problems, feature extraction is an important step. Quality of features in discriminating different classes plays an important role in pattern classification problems. In real life, pattern classification may require high dimensional feature space and it is impossible to visualize the feature space if the dimension of feature space is greater than four. In this paper, we have proposed a Similarity-Dissimilarity plot which can project high dimensional space to a two dimensional space while retaining important characteristics required to assess the discrimination quality of the features. Similarity-dissimilarity plot can reveal information about the amount of overlap of features of different classes. Separable data points of different classes will also be visible on the plot which can be classified correctly using appropriate classifier. Hence, approximate classification accuracy can be predicted. Moreover, it is possible to know about whom class the misclassified data points will be confused by the classifier. Outlier data points can also be located on the similarity-dissimilarity plot. Various examples of synthetic data are used to highlight important characteristics of the proposed plot. Some real life examples from biomedical data are also used for the analysis. The proposed plot is independent of number of dimensions of the feature space.

  16. Stereopositional Outcome in the Packing of Dissimilar Aromatics in Designed β-Hairpins.

    Science.gov (United States)

    Makwana, Kamlesh Madhusudan; Mahalakshmi, Radhakrishnan

    2016-03-14

    A popular strategy in the de novo design of stable β-sheet structures for various biomedical applications is the incorporation of aromatic pairs at the non-hydrogen-bonding (NHB) position. However, it is important to explicitly understand how aryl pair packing at the NHB region is coordinated with backbone structural rearrangements, and to delineate the benefits and drawbacks associated with stereopositional choice of dissimilar aromatic pairs. Here, we probe the consequences of flipped Trp/Tyr pairs by using engineered permutants at the NHB position of dodecapeptide β-hairpins, proximal and distal to the turn. Extensive conformational analysis of these peptides using NMR and CD spectroscopy reveal that a classic Edge-to-Face and Face-to-Edge geometry at the proximal and distal aromatic pairs, respectively, in YW-WY, is the most stabilizing. Such a preferred packing geometry in YW-WY results in a highly twisted β-sheet backbone, with Trp always providing a 'Face' orientation to its dissimilar aromatic partner Tyr. Flipping the proximal and/or distal aromatic pair distorts the ideal T-shaped geometry, and results in alternate aryl arrangements that can adversely affect strand twist and β-sheet stability. Our study reveals the existence of a strong stereopositional influence on the packing of dissimilar aromatic pairs. Our findings highlight the importance of modeling physical interaction forces while designing protein and peptide structures for functional applications.

  17. Study on weld pool behaviors and ripple formation in dissimilar welding under pulsed laser

    Science.gov (United States)

    Liang, Rong; Luo, Yu

    2017-08-01

    A three-transient numerical model is developed to study the dissimilar metal welding under pulsed laser. The melting, resolidification and vaporization inducing recoil pressure are considered in this model. Their effects on molten pool dynamic and the weld bead formation are studied. The similar metal welding and dissimilar metal welding under pulsed laser are respectively simulated by using this model. It is found that surface ripples are caused mainly by the periodical laser and molten pool solidification. In the first, this model is validated by the weld bead geometry comparison between the simulated and experimental results in similar metal welding. Then, this model is applied to simulate the dissimilar metal welding under pulsed laser. The results show that the distributions of the temperature, melt-flow velocity and surface ripples are asymmetric due to the differences in physical properties of the materials. The higher pulse overlapping factor decreases the solidification rate, leading to the more uniform penetration depths and the finer ripples. Good agreements between the experimental observations and simulation results are obtained by the proposed model.

  18. International Round-Robin Test Results for Dissimilar Metal Weld (DMW)

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Sung Sik; Kim, Kyung Jo; Jung, Hae Dong [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2009-10-15

    In nuclear power plant, there are many joints to connect pipes, nozzles and structural components. Most of them are welding joint, and it may be a weak point for leakage and cracks. Some cracks were found in dissimilar metal welds (DMW), which are connected with major components of nuclear power plants. Usually, the dissimilar metal welds are consisted of Alloy 600, carbon steel and stainless steel. Since 2000s, most of the cracks are found in welds, especially dissimilar metal welds such as pressurizer safety relief nozzle, reactor head penetration, reactor bottom mounted instrumentation (BMI), and reactor nozzles. Since the cracks are revealed as a primary water stress corrosion cracking (PWSCC), the reliability of non destructive evaluation (NDE) technique becomes more important. To cope with the NDE reliability, PINC (program for inspection of nickel alloy components) international cooperation was organized. The aim of the project was 1) to fabricate representative NDE mock-ups with flaws to simulate PWSCCs, 2) to identify and quantitatively assess NDE methods for accurately detecting, sizing and characterizing PWSCCs, 3) to document the range of locations and morphologies of PWSCCs and 4) to incorporate results with other results of ongoing PWSCC research programs, as appropriate. In this study, as part of the PINC project, international RRT (round robin test) results for DMW will be introduced.

  19. Residual stress analysis of an Overlay weld and a repair weld on the dissimilar Butt weld

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kang Soo, E-mail: kskim5@kaeri.re.k [Korea Atomic Energy Research Institute, 150, Dukjin-dong, Daejeon 305-353 (Korea, Republic of); Lee, Ho Jin; Lee, Bong Sang [Korea Atomic Energy Research Institute, 150, Dukjin-dong, Daejeon 305-353 (Korea, Republic of); Jung, In Chul; Park, Kwang Soo [Doosan Heavy Industries and Construction Co., 555 Gwigok Dong, Changwon 641-792 (Korea, Republic of)

    2009-12-15

    Both the experiment and FE analysis were performed to estimate the residual stresses at the parts of the dissimilar metal welds. The specimen of the dissimilar Butt welds was manufactured, and the residual stresses of this specimen were measured by the X-ray method and a Hole Drilling Technique. The values measured by two experimental methods showed a big deviation at the SUS 316L plate. Consequently, the experimental methods to estimate the residual stresses are not a superior method. The Butt FEM Model on this specimen was developed and analyzed by the ABAQUS Code. The results of the FE analysis were compared with those of the experimental methods. As a whole, the values of the Butt FEM Model showed a trend which was in agreement with the experimental values and the values of FE analysis were found reasonable. The Repair FEM Model and the Overlay FEM Model were developed and analyzed by the ABAQUS Code. The values of these results were also found reasonable data even if the experimental methods be not performed. Therefore, the residual stresses for the dissimilar metal welds can be estimated by an analysis with an appropriate FEM Model without the experimental methods.

  20. Tensor dissimilarity based adaptive seeding algorithm for DT-MRI visualization with streamtubes

    Science.gov (United States)

    Weldeselassie, Yonas T.; Hamarneh, Ghassan; Weiskopf, Daniel

    2007-03-01

    In this paper, we propose an adaptive seeding strategy for visualization of diffusion tensor magnetic resonance imaging (DT-MRI) data using streamtubes. DT-MRI is a medical imaging modality that captures unique water diffusion properties and fiber orientation information of the imaged tissues. Visualizing DT-MRI data using streamtubes has the advantage that not only the anisotropic nature of the diffusion is visualized but also the underlying anatomy of biological structures is revealed. This makes streamtubes significant for the analysis of fibrous tissues in medical images. In order to avoid rendering multiple similar streamtubes, an adaptive seeding strategy is employed which takes into account similarity of tensors in a given region. The goal is to automate the process of generating seed points such that regions with dissimilar tensors are assigned more seed points compared to regions with similar tensors. The algorithm is based on tensor dissimilarity metrics that take into account both diffusion magnitudes and directions to optimize the seeding positions and density of streamtubes in order to reduce the visual clutter. Two recent advances in tensor calculus and tensor dissimilarity metrics are utilized: the Log-Euclidean and the J-divergence. Results show that adaptive seeding not only helps to cull unnecessary streamtubes that would obscure visualization but also do so without having to compute the culled streamtubes, which makes the visualization process faster.

  1. Efficient Measurement of Shape Dissimilarity between 3D Models Using Z-Buffer and Surface Roving Method

    Directory of Open Access Journals (Sweden)

    In Kyu Park

    2002-10-01

    Full Text Available Estimation of the shape dissimilarity between 3D models is a very important problem in both computer vision and graphics for 3D surface reconstruction, modeling, matching, and compression. In this paper, we propose a novel method called surface roving technique to estimate the shape dissimilarity between 3D models. Unlike conventional methods, our surface roving approach exploits a virtual camera and Z-buffer, which is commonly used in 3D graphics. The corresponding points on different 3D models can be easily identified, and also the distance between them is determined efficiently, regardless of the representation types of the 3D models. Moreover, by employing the viewpoint sampling technique, the overall computation can be greatly reduced so that the dissimilarity is obtained rapidly without loss of accuracy. Experimental results show that the proposed algorithm achieves fast and accurate measurement of shape dissimilarity for different types of 3D object models.

  2. Quantifying the Degree of Movement Dissimilarity between Two Distinct Action Scenarios: An Exploratory Approach with Procrustes Analysis

    Directory of Open Access Journals (Sweden)

    Pedro Passos

    2017-04-01

    Full Text Available Game consoles allow subjects to perform movements which are visually similar to the movements performed in ‘real’ world scenarios. Beyond entertainment, virtual reality devices are being used in several domains: sports performance; motor rehabilitation; training of risk professions. This article presents the Procrustes method to measure the degree of dissimilarity between movements performed in ‘real’ and ‘virtual’ scenarios. For this purpose, the 501 darts game and a video darts game played on a console were used. The participants’ arm throwing movements were video recorded and digitized. The matrices of x and y coordinates of the movements of the wrist, elbow, and shoulder in both performance scenarios were subjected to the Procrustes method. The wrist displays the most extreme dissimilarity values (higher than elbow and shoulder. Results also revealed smaller dissimilarity values for movements performed under the same conditions (e.g., real–real and larger dissimilarity values between movements performed in different scenarios.

  3. Historical assemblage distinctiveness and the introduction of widespread non-native species explain worldwide changes in freshwater fish taxonomic dissimilarity

    NARCIS (Netherlands)

    Toussaint, A.; Beauchard, O.; Oberdorff, T.; Brosse, S.; Villéger, S.

    2014-01-01

    Aim
    Taxonomic dissimilarity between assemblages can result from two processes - the replacement of species (turnover) and differences in richness - but it remains unclear how anthropogenic drivers (introductions and extirpations) affect these processes. Here, we investigate how historical pattern

  4. Crack growth analysis due to PWSCC in dissimilar metal butt weld for reactor piping considering hydrostatic and normal operating conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hwee Sueng; Huh, Nam Su [Seoul Nat' l Univ., Seoul (Korea, Republic of); Lee, Seung Gun; Park, Heung Bae [KEPCO Engineering and Construction Company, Gyeonggi (Korea, Republic of); Lee, Sung Ho [KHNP Central Research Institute, Daejeon (Korea, Republic of)

    2013-01-15

    This study investigates the crack growth behavior due to primary water stress corrosion cracking (PWSCC) in the dissimilar metal butt weld of a reactor piping using Alloy 82/182. First, detailed finite element stress analyses were performed to predict the stress distribution of the dissimilar metal butt weld in which the hydrostatic and the normal operating loads as well as the weld residual stresses were considered to evaluate the stress redistribution due to mechanical loadings. Based on the stress distributions along the wall thickness of the dissimilar metal butt weld, the crack growth behavior of the postulated axial and circumferential cracks were predicted, from which the crack growth diagram due to PWSCC was proposed. The present results can be applied to predict the crack growth rate in the dissimilar metal butt weld of reactor piping due to PWSCC.

  5. Utility of computer simulations in landscape genetics

    Science.gov (United States)

    Bryan K. Epperson; Brad H. McRae; Kim Scribner; Samuel A. Cushman; Michael S. Rosenberg; Marie-Josee Fortin; Patrick M. A. James; Melanie Murphy; Stephanie Manel; Pierre Legendre; Mark R. T. Dale

    2010-01-01

    Population genetics theory is primarily based on mathematical models in which spatial complexity and temporal variability are largely ignored. In contrast, the field of landscape genetics expressly focuses on how population genetic processes are affected by complex spatial and temporal environmental heterogeneity. It is spatially explicit and relates patterns to...

  6. Dissimilarity between temperature-humidity in the atmospheric surface layer and implications for estimates of evaporation

    Science.gov (United States)

    Cancelli, D. M.; Dias, N. L.; Chamecki, M.

    2012-12-01

    In several methods used in water resources to estimate evaporation from land and water surfaces, a fundamental assumption is that temperature (T) and specific humidity (q) fluctuations behave similarly in the atmospheric surface layer (ASL). In the Energy-Budget Bowen Ratio method it is assumed that both eddy diffusivities are equal, while in the variance method it is often assumed that all the Monin-Obukhov Similarity (MOS) functions for the two scalars are equal. However, it is well-known that the T-q similarity does not always hold and that the dissimilarity found in practice can significantly impact the estimates of evaporation. Given the frequent dissimilarity between temperature and humidity, two important problems arise. The first one is related to the choice of the function used to characterize scalar similarity, given that not all commonly used functions are equally capable of identifying scalar dissimilarity. The second problem is associated with the identification of the physical mechanisms behind scalar dissimilarity in each particular case: local advection, nonstationarity, surface heterogeneity, active/passive roles of the scalars, entrainment fluxes at the top of the atmospheric boundary layer are typically cited as possible causes, but seldom a convincing argument is presented. In this work we combine experimental data and numerical simulations to study similarity between T and q in the ASL. Data measured over a lake in Brazil suggests a strong relationship between scalar similarity and the balance between local production and dissipation of scalar variance, which is in practice related to the strength of the surface forcing. Scalar variance and covariance budgets are used to derive a set of dimensionless Scalar Flux numbers that are capable of diagnosing the balance between gradient production and molecular dissipation of scalar variance and covariance. Experimental data shows that these Scalar Flux numbers are good predictors of scalar (dis)similarity

  7. Effect of Thermal and Diffusion Processes on Formation of the Structure of Weld Metal in Laser Welding of Dissimilar Materials

    Science.gov (United States)

    Turichin, G. A.; Klimova, O. G.; Babkin, K. D.; Pevzner, Ya. B.

    2014-01-01

    The thermal and diffusion processes in laser welding of dissimilar materials are simulated. The active LaserCAD model for welding of dissimilar materials is amended. The developed model is verified for the Fe - Cu system. The microstructure of a weld of tin bronze and low-carbon steel is studied and the elements in the diffusion zone are analyzed. The computed and experimental data for laser and electron-beam welding are shown to agree well.

  8. Genetic evidence of multiple matrilines and spatial disruption of kinship bonds in mass strandings of long-finned pilot whales, Globicephala melas.

    Science.gov (United States)

    Oremus, Marc; Gales, Rosemary; Kettles, Helen; Baker, C Scott

    2013-01-01

    Mass strandings of whales and dolphins have puzzled biologists since Aristotle. Although environmental factors are often assumed to initiate strandings, social forces must also influence the dynamics of many of these events, particularly for the primary species involved in mass strandings, the long-finned pilot whales (Globicephala melas). Here, we test two hypotheses derived from common assumptions about the social dynamics of long-finned pilot whales by identifying maternal lineages from mtDNA haplotypes and inferring kinship from microsatellite genotypes of 490 individuals from 12 stranding events. Contrary to the "extended matriline" hypothesis, we found that multiple maternal lineages were present in at least 9 of the 12 mass strandings. Contrary to the "kinship cohesion" hypothesis, we found no correlation between spatial distribution and kinship along the stranding beach. Most notably, we documented the spatial disruption of the expected proximity between mothers and their dependent calves. These results challenge the common assumption that kinship-based behavior, such as care-giving, are a primary factor in these mass strandings. We suggest instead that disruption of kinship bonds could result from interactions among unrelated social groups during feeding or mating aggregations, perhaps playing a causal role in these events. Our finding that dependent calves were often spatially separated or absent from their mothers has important implications for humane management of rescue efforts. To improve our understanding of the social causes and consequences of mass strandings, future documentation of strandings should include exhaustive DNA sampling, with accompanying spatial and temporal records.

  9. Spatially-Explicit Assessments of Genetic Biodiversity and Dispersal in Gopher Tortoises for Evaluation of Habitat Fragmentation at DoD Sites

    Science.gov (United States)

    2008-10-01

    crocodilian population genetics questions. J. Herpetology . 35: 541-544. Diemer JE. 1992. Home range and movements of the tortoise Gopherus...polyphemus in northern Florida. Journal of Herpetology 26:158–162 Diffendorfer JE. 1998. Testing models of source-sink dynamics and balanced dispersal...associated with tortoise (Gopherus polyphemus) burrows in four habitats in south-central Florida. Journal of Herpetology 25:477-481. Luikart G, Cornuet J-M

  10. The presence of a culturally similar or dissimilar social partner affects neural responses to emotional stimuli

    Directory of Open Access Journals (Sweden)

    Kate A. Woodcock

    2013-06-01

    Full Text Available Background: Emotional responding is sensitive to social context; however, little emphasis has been placed on the mechanisms by which social context effects changes in emotional responding. Objective: We aimed to investigate the effects of social context on neural responses to emotional stimuli to inform on the mechanisms underpinning context-linked changes in emotional responding. Design: We measured event-related potential (ERP components known to index specific emotion processes and self-reports of explicit emotion regulation strategies and emotional arousal. Female Chinese university students observed positive, negative, and neutral photographs, whilst alone or accompanied by a culturally similar (Chinese or dissimilar researcher (British. Results: There was a reduction in the positive versus neutral differential N1 amplitude (indexing attentional capture by positive stimuli in the dissimilar relative to alone context. In this context, there was also a corresponding increase in amplitude of a frontal late positive potential (LPP component (indexing engagement of cognitive control resources. In the similar relative to alone context, these effects on differential N1 and frontal LPP amplitudes were less pronounced, but there was an additional decrease in the amplitude of a parietal LPP component (indexing motivational relevance in response to positive stimuli. In response to negative stimuli, the differential N1 component was increased in the similar relative to dissimilar and alone (trend context. Conclusion: These data suggest that neural processes engaged in response to emotional stimuli are modulated by social context. Possible mechanisms for the social-context-linked changes in attentional capture by emotional stimuli include a context-directed modulation of the focus of attention, or an altered interpretation of the emotional stimuli based on additional information proportioned by the context.

  11. Measuring dissimilarity between respiratory effort signals based on uniform scaling for sleep staging.

    Science.gov (United States)

    Long, Xi; Yang, Jie; Weysen, Tim; Haakma, Reinder; Foussier, Jérôme; Fonseca, Pedro; Aarts, Ronald M

    2014-12-01

    Polysomnography (PSG) has been extensively studied for sleep staging, where sleep stages are usually classified as wake, rapid-eye-movement (REM) sleep, or non-REM (NREM) sleep (including light and deep sleep). Respiratory information has been proven to correlate with autonomic nervous activity that is related to sleep stages. For example, it is known that the breathing rate and amplitude during NREM sleep, in particular during deep sleep, are steadier and more regular compared to periods of wakefulness that can be influenced by body movements, conscious control, or other external factors. However, the respiratory morphology has not been well investigated across sleep stages. We thus explore the dissimilarity of respiratory effort with respect to its signal waveform or morphology. The dissimilarity measure is computed between two respiratory effort signal segments with the same number of consecutive breaths using a uniform scaling distance. To capture the property of signal morphological dissimilarity, we propose a novel window-based feature in a framework of sleep staging. Experiments were conducted with a data set of 48 healthy subjects using a linear discriminant classifier and a ten-fold cross validation. It is revealed that this feature can help discriminate between sleep stages, but with an exception of separating wake and REM sleep. When combining the new feature with 26 existing respiratory features, we achieved a Cohen's Kappa coefficient of 0.48 for 3-stage classification (wake, REM sleep and NREM sleep) and of 0.41 for 4-stage classification (wake, REM sleep, light sleep and deep sleep), which outperform the results obtained without using this new feature.

  12. Multiphysical Modeling of Transport Phenomena During Laser Welding of Dissimilar Steels

    Science.gov (United States)

    Métais, A.; Matteï, S.; Tomashchuk, I.; Gaied, S.

    The success of new high-strength steels allows attaining equivalent performances with lower thicknesses and significant weight reduction. The welding of new couples of steel grades requires development and control of joining processes. Thanks to high precision and good flexibility, laser welding became one of the most used processes for joining of dissimilar welded blanks. The prediction of the local chemical composition in the weld formed between dissimilar steels in function of the welding parameters is essential because the dilution rate and the distribution of alloying elements in the melted zone determines the final tensile strength of the weld. The goal of the present study is to create and to validate a multiphysical numerical model studying the mixing of dissimilar steels in laser weld pool. A 3D modelling of heat transfer, turbulent flow and transport of species provides a better understanding of diffusion and convective mixing in laser weld pool. The present model allows predicting the weld geometry and element distribution. The model has been developed based on steady keyhole approximation and solved in quasi-stationary form in order to reduce the computation time. Turbulent flow formulation was applied to calculate velocity field. Fick law for diluted species was used to simulate the transport of alloying elements in the weld pool. To validate the model, a number of experiments have been performed: tests using pure 100 μm thick Ni foils like tracer and weld between a rich and poor manganese steels. SEM-EDX analysis of chemical composition has been carried out to obtain quantitative mapping of Ni and Mn distributions in the melted zone. The results of simulations have been found in good agreement with experimental data.

  13. Linear-fitting-based similarity coefficient map for tissue dissimilarity analysis in -w magnetic resonance imaging

    Science.gov (United States)

    Yu, Shao-De; Wu, Shi-Bin; Wang, Hao-Yu; Wei, Xin-Hua; Chen, Xin; Pan, Wan-Long; Hu, Jiani; Xie, Yao-Qin

    2015-12-01

    Similarity coefficient mapping (SCM) aims to improve the morphological evaluation of weighted magnetic resonance imaging However, how to interpret the generated SCM map is still pending. Moreover, is it probable to extract tissue dissimilarity messages based on the theory behind SCM? The primary purpose of this paper is to address these two questions. First, the theory of SCM was interpreted from the perspective of linear fitting. Then, a term was embedded for tissue dissimilarity information. Finally, our method was validated with sixteen human brain image series from multi-echo . Generated maps were investigated from signal-to-noise ratio (SNR) and perceived visual quality, and then interpreted from intra- and inter-tissue intensity. Experimental results show that both perceptibility of anatomical structures and tissue contrast are improved. More importantly, tissue similarity or dissimilarity can be quantified and cross-validated from pixel intensity analysis. This method benefits image enhancement, tissue classification, malformation detection and morphological evaluation. Project supported in part by the National High Technology Research and Development Program of China (Grant Nos. 2015AA043203 and 2012AA02A604), the National Natural Science Foundation of China (Grant Nos. 81171402, 61471349, and 81501463), the Innovative Research Team Program of Guangdong Province, China (Grant No. 2011S013), the Science and Technological Program for Higher Education, Science and Research, and Health Care Institutions of Guangdong Province, China (Grant No. 2011108101001), the Natural Science Foundation of Guangdong Province, China (Grant No. 2014A030310360), the Fundamental Research Program of Shenzhen City, China (Grant No. JCYJ20140417113430639), and Beijing Center for Mathematics and Information Interdisciplinary Sciences, China.

  14. Nano-structural and Nano-chemical analysis of dissimilar metal weld interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kyoung Joon; Shin, Shang Hoon; Kim, Jong Jin; Jung, Ju Ang; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2011-10-15

    Dissimilar metal weld is generally applied to nuclear power plant for manufacturing and machining in structural components such as RPV and Pressurizer nozzles. Alloy 152 is used frequently as filler metal in the manufacture of dissimilar metal welds (DMWs) in light water reactors (LWR) to join the low alloy steel (LAS) pressure vessel nozzles and steam generator nozzles to nickel-based wrought alloy or austenitic stainless steel components. The thermal expansion coefficient of the alloy lies between those of ferrite steel and austenitic stainless steel, and it also significantly retards the carbon diffusion from the ferrite base metal to the weld metal. However, in recent years cracking phenomena have been observed in the welded joints. A concern has been raised about the integrity and reliability in the joint transition zone due to the high susceptibility of heat affected zone (HAZ) and fusion zone (FZ) to stress corrosion cracking (SCC). The dissimilar metal joints which were welded between Inconel 690, Ni-based alloy and A533B, low alloy steel with Inconel 152, filler metal were investigated. This study shows microstructural and chemical analysis between Inconel 152 and A533B by using optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), secondary ion mass spectrometry (SIMS) and 3 dimension atom probe (3D AP). In the root region, OM and SEM analysis show the microstructure which contains the interface of Inconel 152 and A533B near the rooter region. And it shows unidentified band structure which is formed along weld interface. AP and TEM/EDS analyses show the chemical gradient containing higher Fe but lower Mn, Ni and Cr than Inconel 152 and the unidentified band

  15. Structure-property relationships of dissimilar friction stir welded aluminum alloys

    Science.gov (United States)

    Quinones, Rogie Irwin Rodriguez

    In this work, the relationship between microstructure and mechanical properties of dissimilar friction stir welded AA6061-to-AA7050 aluminum alloys were evaluated. Experimental results from this study revealed that static strength increased with the tool rotational speed and was correlated with the material intermixing. Fully-reversed low cycle fatigue experimental results showed an increase in the strain hardening properties as well as the number of cycles-to-failure as the tool rotational speed was increased. Furthermore, under both static and cyclic loading, fracture of the joint was dominated by the AA6061 alloy side of the weld. In addition, inspection of the fatigue surfaces revealed that cracks initiated from intermetallic particles located near the surface. In order to determine the corrosion resistance of the dissimilar joint, corrosion defects were produced on the crown surface of the weld by static immersion in 3.5% NaCl for various exposure times. Results revealed localized corrosion damage in the thermo-mechanically affected and heat affected zones. Results demonstrated a decrease in the fatigue life, with evidence of crack initiation at the corrosion defects; however, the fatigue life was nearly independent of the exposure time. This can be attributed to total fatigue life dominated by incubation time. Furthermore, two types of failure were observed: fatigue crack initiation in the AA6061 side at high strain amplitudes (>0.3%); and fatigue crack initiation in the AA7050 side at low strain amplitudes (friction stir welded joints in order to capture the crack initiation and propagation in as-welded and pre-corroded conditions. Good correlation between experimental fatigue results and the model was achieved based on the variation in the initial defect size, microstructure, and mechanical properties of the dissimilar friction stir welded AA6061-to-AA7050 aluminum alloys.

  16. SPATIAL STABILITY

    OpenAIRE

    Pascal Mossay

    2004-01-01

    We consider a continuous spatial economy consisting of pure exchange local economies. Agents are allowed to change their location over time as a response to spatial utility differentials. These spatial adjustments toward higher utility neighborhoods lead the spatial economy to converge to a spatially uniform allocation of resources, provided that the matrix of price effects is quasi-negative definite. Furthermore our model provides a real time interpretation of the tâtonnement story. Also, sp...

  17. On the Temperature and Humidity Dissimilarity in the Marine Surface Layer

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo; Kelly, Mark C.; Sempreviva, Anna Maria

    2014-01-01

    The dissimilarity of temperature and humidity transfer in the marine surface layer (MSL) is investigated through the relative transport efficiency and correlation coefficient of these two scalars. We examine their variability and relationship with mean values, as well as spectral characteristics...... there is an efficient latent heat transfer but negligible sensible heat transfer. Our data suggest that parametrization of humidity fluxes via similarity theory could still be reliable when the correlation coefficient >0.5, and in near-neutral conditions the humidity flux can be estimated without use of the sensible...

  18. A review on TIG welding for optimizing process parameters on dissimilar joints

    Directory of Open Access Journals (Sweden)

    Prashant Kumar Singh

    2015-02-01

    Full Text Available Tungsten Inert Gas Welding (TIG is relatively high strength welding technique. This technique are mostly used in fabrication and other industries to join the either similar or dissimilar materials. In particular, it can be used to join high-quality strength of metal and alloys.In this paper we discuss abouttheTungsten Inert Gas welding of joining heat treatableof stainless steel and mild steel.These welded joints have higher tensile strength to weight ratio and finer micro structure. Tungsten Inert Gas Weldingofdissimilar material such as stainless steel and mild steel have the potential to hold good mechanical and metallurgical properties.

  19. Dissimilarity maps on trees and the representation theory of $GL_n(\\C)$

    CERN Document Server

    Manon, Christopher

    2011-01-01

    We revisit the representation theory in type $A$used previously to establish that the dissimilarity vectors of phylogenetic trees are points on the tropical Grassmannian variety. We use a different version of this construction to show that the space of phylogenetic trees $K_n$ maps to the tropical varieties of every flag variety of $GL_n(\\C).$ Using this map, we interpret the tropicalization of the semistandard tableaux basis of an irreducible representation of $GL_n(\\C)$ as combinatorial invariants of phylogenetic trees.

  20. Application of a second-gradient model of ductile fracture on a Dissimilar Metal Weld

    Directory of Open Access Journals (Sweden)

    YangJun

    2016-01-01

    Full Text Available A “micromorphic”, second-gradient model applicable to ductile porous materials has been proposed, as an improvement from the fundamental work of Gurson that take into account the physical mechanisms responsible for ductile damage. The model has been applied to the study of fracture of the decarburized layer of a Dissimilar Metal Weld. The model successfully reproduces the crack path experimentally observed in a notched tensile sample extracted from this weld, different from the one predicted by the first gradient model.

  1. The role of similarity and dissimilarity focus in sequential judgments of physical attractiveness.

    Science.gov (United States)

    Cypryanska, Marzena; Bedynska, Sylwia; De Zavala, Agnieszka Golec

    2012-01-01

    The present results indicate that procedurally priming comparison focus can change the contrast effect in judgments of physical attractiveness (Kenrick & Gutierres, 1980). Participants were primed to search for similarities vs. differences between target and standard of comparison in a task using material irrelevant to the subsequent physical attractiveness judgment. Focusing participants on similarities testing produced the assimilation effect: evaluation of target and comparison standard as being similar. Focusing participants on dissimilarity testing produced the contrast effect: evaluating the target as different from the standard of comparison.

  2. Improvement of bonding properties of laser transmission welded, dissimilar thermoplastics by plasma surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hopmann, Ch.; Weber, M.; Schöngart, M.; Sooriyapiragasam, S.; Behm, H.; Dahlmann, R. [Institute of Plastics Processing (IKV), RWTH Aachen University, Pontstrasse 49, 52062 Aachen (Germany)

    2015-05-22

    Compared to different welding methods such as ultrasonic welding, laser transmission welding is a relatively new technology to join thermoplastic parts. The most significant advantages over other methods are the contactless energy input which can be controlled very precisely and the low mechanical loads on the welded parts. Therefore, laser transmission welding is used in various areas of application, for example in medical technology or for assembling headlights in the automotive sector. However, there are several challenges in welding dissimilar thermoplastics. This may be due to different melting points on the one hand and different polarities on the other hand. So far these problems are faced with the intermediate layer technique. In this process a layer bonding together the two components is placed between the components. This means that an additional step in the production is needed to apply the extra layer. To avoid this additional step, different ways of joining dissimilar thermoplastics are investigated. In this regard, the improvement in the weldability of the dissimilar thermoplastics polyamide 6 (PA 6) and polypropylene (PP) by means of plasma surface modification and contour welding is examined. To evaluate the influence of the plasma surface modification process on the subsequent welding process of the two dissimilar materials, the treatment time as well as the storage time between treatment and welding are varied. The treatment time in pulsed micro wave excited oxygen plasmas with an electron density of about 1x10{sup 17} m{sup −3} is varied from 0.5 s to 120 s and the time between treatment and welding is varied from a few minutes up to a week. As reference, parts being made of the same polymer (PP and PA 6) are welded and tested. For the evaluation of the results of the welding experiments, short-time tensile tests are used to determine the bond strength. Without plasma treatment the described combination of PA 6/PP cannot be welded with

  3. Exposure assessment of the cumulative intake of pesticides with dissimilar mode of action

    DEFF Research Database (Denmark)

    Jensen, Bodil Hamborg; Petersen, Annette; Christiansen, Sofie

    Risk assessment of pesticides is currently based on the no observed adverse effect levels (NOAELs) for effects of single compounds. However, humans might be exposed to a mixture of pesticides at the same time and the exposure could occur from more pesticides with endocrine disrupting effects....... In this study the effects of combined exposure from four endocrine disrupting pesticides have been investigated (procymidone, mancozeb, tebuconazole, and prochloraz). The four pesticides have dissimilar mode of actions. On the background of the potency for each pesticide to a given effect, a relative potency...... factor and the cumulative acute exposure of the pesticides have been estimated....

  4. Multiple moving interfacial cracks between two dissimilar piezoelectric layers under electromechanical loading

    Science.gov (United States)

    Nourazar, Mahsa; Ayatollahi, Mojtaba

    2016-07-01

    The dynamic problem of several moving cracks at the interface between two dissimilar piezoelectric materials is analyzed. The combined out-of-plane mechanical and in-plane electrical loads are applied to the layers. Fourier transforms are used to reduce the problem to a system of singular integral equations with simple Cauchy kernel. The integral equations are solved numerically by converting to a system of linear algebraic equations and by using a collocation technique. The results presented consist of the stress intensity factors and the electric displacement intensity factors. It is found that generally the field intensity factors increase with increasing crack propagation speed.

  5. Strain analysis of a bonded, dissimilar, composite material T-joint using moiré interferometry

    Science.gov (United States)

    Gascoigne, H. E.; Abdallah, M. G.

    High-sensitivity moiré interferometry and finite-element analysis are used to analyze the state of deformation and stress in the region of contact between a plane orthotropic rectangular punch bonded to a foundation with dissimilar elastic properties which models a highly loaded region of a composite material rocket motor casing. Stress distributions are presented for the contact region and an estimate of the maximum shear stress in the foundation is given. The displacement components show good qualitative agreement between analysis and experiment. The lack of quantitative agreement between the experimental and the finite-element analysis is attributed to uncertainty of the material properties.

  6. Growth of lamellar pearlite in the weld zone between dissimilar steels

    Science.gov (United States)

    Nikulina, A. A.; Smirnov, A. I.; Bataev, I. A.; Bataev, A. A.; Popelyukh, A. I.

    2016-01-01

    Transmission electron microscopy is used to study the welds between high-carbon pearlitic and chromium-nickel austenitic steel workpieces performed by flash butt welding. It has been established that lamellar pearlite colonies alloyed with chromium and nickel are formed in the weld zones between dissimilar steels. Thin austenite interlayers have been detected in the center of ferrite plates. The structure formed presents the C-F-A-F-C-F-A-F (and so on) sequence of three plate-shaped phases. The ferrite-cementite structure in alloyed-pearlite colonies is finer than that in unalloyed pearlite.

  7. Rate sensitivity of mixed mode interface toughness of dissimilar metallic materials: Studied at steady state

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Niordson, Christian Frithiof

    2012-01-01

    the SSV model [Suo, Z., Shih, C., Varias, A., 1993. A theory for cleavage cracking in the presence of plastic flow. Acta Metall. Mater. 41, 1551–1557] embedded in a steady state finite element formulation, here assuming plane strain conditions and small-scale yielding. Results are presented for a wide...... of the macroscopic fracture toughness under mixed Mode I/II loading. Moreover, special cases of joined similar rate dependent materials, as well as dissimilar materials where one substrate remains either elastic or approaches the rate independent limit is also included. The numerical analysis is carried out using...

  8. Welding repair of a dissimilar weld and respective consequences for other German plants

    Energy Technology Data Exchange (ETDEWEB)

    Brummer, G. [High Energy Weapons (United States); Dauwel, W.; Wesseling, U. [Framatome ANP GmbH-NBTT, Erlangen (Germany); Ilg, U. [EnBW, Milano (Italy); Lauer, P.; Widera, M. [E.ON Kernkraft (Germany); Wachter, O. [RWE Power (Germany)

    2002-07-01

    During a regular refueling outage in a German nuclear power plant in year 2000, additional non-destructive examinations have been performed on request of the Authority, to fulfill some recommendations of the independent experts with regard to the retrospective application of the Basic Safety Concept for the ferritic main coolant piping of this plant. During these inspections, indications were found in a dissimilar weld between one of the fifteen MCL (main coolant lines) nozzles and the ECC (emergency core cooling) system piping. By means of on-site metallography and laboratory investigations on three boat samples taken from this weld, it could be shown that the indications were due to hot cracking in the surface layer of the weld. In the course of these investigations, at three locations at the circumference of the weld, dis-bonding defects were found between the ferritic base metal of the nozzle and the austenitic weld butter, which has been applied to join the nozzle to the austenitic safe-end. According to the results of the extensive investigations, the dis-bonding occurred during the manufacturing process after stress-relief heat-treatment of the buttering during the welding of the austenitic safe-end to the butter material. There was no evidence for any crack growth during operation of the plant. Due to the large size of the boat-samples, a weld repair was mandatory. This repair has been performed using the so-called temper-bead technique as specified in the ASME Code, without subsequent stress relief heat treatment, using an advanced automatic orbital TIG welding process. The welding has been successfully performed without the need of further repair work. For those dissimilar welds, all other plants, except one, had used Inconel welding material for buttering the ferritic nozzle instead of stainless steel welding metal. For metallurgical reasons, dis-bonding along the fusion line for Inconel buttered dissimilar welds is unlikely to occur. Nevertheless all

  9. Cultural dissimilarity and intermarriage. a longitudinal study of immigrants in Sweden, 1990–2005.

    Science.gov (United States)

    Dribe, Martin; Lundh, Christer

    2011-01-01

    Intermarriage with natives is a key indicator of immigrant integration. This article studies intermarriage for 138 immigrant groups in Sweden, using longitudinal individual level data. It shows great variation in marriage patterns across immigrant populations, ranging from over 70 percent endogamy in some immigrants groups to below 5 percent in other groups. Although part of this variation is explained by human capital and the structure of the marriage market, cultural factors (values, religion, and language) play an important role as well. Immigrants from culturally more dissimilar countries are less likely to intermarry with natives, and instead more prone to endogamy.

  10. Procedure for Computing Residual Stresses from Neutron Diffraction Data and its Application to Multi-Pass Dissimilar Weld

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei [ORNL; Feng, Zhili [ORNL; Crooker, Paul [Electric Power Research Institute (EPRI)

    2011-01-01

    Neutron diffraction is a powerful tool for non-destructive measurement of internal residual stresses of welded structures. The conventional approach for determination of residual stresses requires the knowledge of stress-free lattice spacing a priori. For multiple-pass dissimilar metal welds common to nuclear reactor pipeline systems, the stress-free lattice parameter is a complex function of position due to the chemistry inhomogeneity in the weld region and can be challenging to determine experimentally. This paper presents a new approach to calculate the residual stress field in dissimilar welds without the use of stress-free lattice parameter. The theoretical basis takes advantage of the fact that the normal component of welding residual stresses is typically small for thin plate or pipe welds. The applicability of the new approach is examined and justified in a multi-pass dissimilar metal weld consisting of a stainless steel plate and a nickel alloy filler metal. The level of uncertainties associated with this new approach is assessed. Neutron diffraction experiment is carried out to measure the lattice spacing at various locations in the dissimilar weld. A comb-shaped specimen, electro-discharge machined from a companion weld, is used to determine the stress-free lattice spacing. The calculated results from the new approach are consistent with those from the conventional approach. The new approach is found to be a practical method for determining the two in-plane residual stress components in thin plate or pipe dissimilar metal welds.

  11. Mechanical Properties and Microstructure of Dissimilar Friction Stir Welds of 11Cr-Ferritic/Martensitic Steel to 316 Stainless Steel

    Science.gov (United States)

    Sato, Yutaka S.; Kokawa, Hiroyuki; Fujii, Hiromichi T.; Yano, Yasuhide; Sekio, Yoshihiro

    2015-12-01

    Dissimilar joints between ferritic and austenitic steels are of interest for selected applications in next generation fast reactors. In this study, dissimilar friction-stir welding of an 11 pct Cr ferritic/martensitic steel to a 316 austenitic stainless steel was attempted and the mechanical properties and microstructure of the resulting welds were examined. Friction-stir welding produces a stir zone without macroscopic weld-defects, but the two dissimilar steels are not intermixed. The two dissimilar steels are interleaved along a sharp zigzagging interface in the stir zone. During small-sized tensile testing of the stir zone, this sharp interface did not act as a fracture site. Furthermore, the microstructure of the stir zone was refined in both the ferritic/martensitic steel and the 316 stainless steel resulting in improved mechanical properties over the adjacent base material regions. This study demonstrates that friction-stir welding can produce welds between dissimilar steels that contain no macroscopic weld-defects and display suitable mechanical properties.

  12. Dynamic response of AFM cantilevers to dissimilar functionalized silica surfaces in aqueous electrolyte solutions.

    Science.gov (United States)

    Wu, Yan; Misra, Sambit; Karacor, M Basar; Prakash, Shaurya; Shannon, Mark A

    2010-11-16

    The dynamic response of an oscillating microcantilever with a gold-coated tip interacting with dissimilar functionalized silica surfaces was studied in electrolyte solutions with pH ranging from 4 to 9. Silica surfaces were chemically modified, yielding dissimilar surfaces with -Br, -NH(2), and -CH(3) functional group terminations. The relative hydrophobicity of the surfaces was characterized by contact angle measurements. The surface charge of the functionalized surfaces was first probed with commonly used static AFM measurements and serves as a reference to the dynamic response data. The amplitude and phase of the cantilever oscillation were monitored and used to calculate the effective interaction stiffness and damping coefficient, which relate to the electrical double layer interactions and also to distance-dependent hydrodynamic damping at the solid/water interface. The data for the dynamic response of the AFM over silica surfaces as a function of chemical functionalization and electrolyte pH show that the effective stiffness has a distinctive dependence on the surface charge of functionalized silica surfaces. The hydrodynamic damping also correlates strongly with the relative hydrophobicity of the surface. The data reported here indicate that interfacial properties can be strongly affected by changing the chemical composition of surfaces.

  13. Investigation on Mechanical Properties of 9%Cr/CrMoV Dissimilar Steels Welded Joint

    Science.gov (United States)

    Liu, Xia; Lu, Fenggui; Yang, Renjie; Wang, Peng; Xu, Xiaojin; Huo, Xin

    2015-04-01

    Advanced 9%Cr steel with good heat resistance and CrMoV with good toughness were chosen as candidate materials to fabricate combined rotor for steam turbine operating at over 620 °C. But the great difference in base metals properties presents a challenge in achieving sound defect-free joint with optimal properties in dissimilar welded rotor. In this paper, appropriate selection of filler metal, welding parameters, and post-weld heat treatment was combined to successfully weld 1100-mm-diameter 9%Cr/CrMoV dissimilar experimental rotor through ultra-narrow gap submerge arc welding. Some properties such as hardness, low-cycle fatigue (LCF), and high-cycle fatigue (HCF) combined with microstructural characterization qualify the integrity of the weld. Microstructural analysis indicated the presence of high-temperature tempered martensite as the phase responsible for the improved properties obtained in the weld. The Coffin-Manson parameters were obtained by fitting the data in LCF test, while the conditional fatigue strength was derived from the HCF test based on S-N curve. Analysis of hardness profile showed that the lowest value occurred at heat-affected zone adjacent to base metal which represents the appropriate location of fracture for the samples after LCF and HCF tests.

  14. Twin Support Vector Machine for Multiple Instance Learning Based on Bag Dissimilarities

    Directory of Open Access Journals (Sweden)

    Divya Tomar

    2016-01-01

    Full Text Available In multiple instance learning (MIL framework, an object is represented by a set of instances referred to as bag. A positive class label is assigned to a bag if it contains at least one positive instance; otherwise a bag is labeled with negative class label. Therefore, the task of MIL is to learn a classifier at bag level rather than at instance level. Traditional supervised learning approaches cannot be applied directly in such kind of situation. In this study, we represent each bag by a vector of its dissimilarities to the other existing bags in the training dataset and propose a multiple instance learning based Twin Support Vector Machine (MIL-TWSVM classifier. We have used different ways to represent the dissimilarity between two bags and performed a comparative analysis of them. The experimental results on ten benchmark MIL datasets demonstrate that the proposed MIL-TWSVM classifier is computationally inexpensive and competitive with state-of-the-art approaches. The significance of the experimental results has been tested by using Friedman statistic and Nemenyi post hoc tests.

  15. Three-Dimensional Thermomechanical Simulation and Experimental Validation on Failure of Dissimilar Material Welds

    Science.gov (United States)

    Santosh, R.; Das, S. K.; Das, G.; Korody, J.; Kumar, S.; Singh, P. K.; Ghosh, M.

    2016-07-01

    Dissimilar material weld joints, consisting of low-alloy steel and 304LN austenitic stainless steel (SS), have critical application in boiling water reactors in the nuclear industry. It was predicted that phase transformation adjacent to the fusion boundary and stress distribution across the transition joint play a key role in the structural degeneration of these welds. Quantitatively, to evaluate their contribution, two different joints were considered. One was fabricated with buttering material 309L SS (M/S Mishra Dhatu Nigam Limited, Hyderabad, India), and the other was produced with buttering material IN182 (M/S Mishra Dhatu Nigam Limited, Hyderabad, India). Base materials remained the same for both. Thermomechanical simulation on dissimilar material welds was performed using finite-element modeling to predict the thermal effect and stress prone area. Temperature-dependent thermal and structural properties were considered for simulation. Simulation results were compared with microstructural characteristics, and data were obtained from the in-situ tensile test. Simulation results exhibited that stress was at maximum in the buttering material and made the zone weaker with respect to adjacent areas. During the validation of results, it was observed that failure occurred through buttering material and endorsed the inference. The variation in mechanical properties of the two welds was explained considering the effect of thermal state and stress distribution.

  16. Electroelastic field induced by thin interface electrodes between two bonded dissimilar piezoelectric ceramics

    Institute of Scientific and Technical Information of China (English)

    LI; Xianfang

    2006-01-01

    The electroelastic analysis of multiple collinear electrodes embedded at the interface of two bonded dissimilar piezoelectric ceramics is made. Within the framework of linear piezoelectricity, the Fourier transform technique is applied to reducing the problem to a singular integral equation with Cauchy kernel. Two particular cases are especially emphasized. For a single interface electrode, the electroelastic field is obtained in the entire plane of a two-phase piezoelectric composite in terms of elementary functions. For two collinear interface electrodes of equal length, a closed-form solution is determined along the interface. Obtained results reveal that near the electrode edges, the induced electroelastic field exhibits a square-root singularity, and the oscillatory singularity does not occur for arbitrary two piezoelectric ceramics poled in the same or opposite directions normal to the interface. Across the electrode, the normal component of stress is continuous, while that of strain exhibits a jump, implying strain incompatibility due to the mismatch of the material properties of two dissimilar poled ceramics.

  17. Processing and Optimization of Dissimilar Friction Stir Welding of AA 2219 and AA 7039 Alloys

    Science.gov (United States)

    Venkateswarlu, D.; Nageswara rao, P.; Mahapatra, M. M.; Harsha, S. P.; Mandal, N. R.

    2015-12-01

    The present paper discusses the optimization of dissimilar friction stir welding of AA 2219 and AA 7039 alloys with respect to tool design issues including microstructural study of weld. The optimized ultimate tensile strength was ~280 MPa, and % elongation was ~11.5. It was observed that the extent of tool shoulder flat surface and tool rotational speed influenced the weld quality significantly. A mathematical model was also developed using response surface regression analysis to predict the effects of tool geometry and process variables on dissimilar AA 2219 and AA 7039 alloys welds. The microstructure evolution and mechanical properties were investigated by employing electron backscatter diffraction technique, Vickers microhardness, and tensile testing, respectively. The microstructural observations indicated that the grain size obtained at advancing side (AA 2219 alloy side) was much finer compared to the retreating side (AA 7039 alloy side). Hardness distribution in the stir zone was inhomogeneous, which might be due to inadequate mixing of weld zone material. The hardness values observed at the weld zone were lower than that in the base materials.

  18. Inertia Friction Welding Dissimilar Nickel-Based Superalloys Alloy 720Li to IN718

    Science.gov (United States)

    Huang, Z. W.; Li, H. Y.; Preuss, M.; Karadge, M.; Bowen, P.; Bray, S.; Baxter, G.

    2007-07-01

    This article describes a comprehensive microstructural characterization of an inertia friction welded joint between nickel-based superalloys 720Li and IN718. The investigation has been carried out on both as-welded and postweld heat-treated conditions. The detailed metallographic analysis has enabled the relation of hardness profiles across inertia-welded alloy 720Li to IN718 and morphological changes of the precipitates present. The work demonstrates that inertia friction welding (IFW) 720Li to IN718 results in a weld free of micropores and microcracks and no significant chemical migration across the weld line. However, substantial differences in terms of grain structure and precipitation phase distribution variations are observed on each side of the dissimilar weld. The high γ‧ volume fraction alloy 720Li exhibits a wider heat-affected zone than the mainly γ‧‧ strengthened IN718. Alloy 720Li displays only a small hardness trough near the weld line in the as-welded condition due to the depletion of γ‧, while γ″-strengthened IN718 shows a soft precipitation-free weld region. Postweld heat treatment (PWHT) of the dissimilar weld at 760 °C, a typical annealing temperature for alloy 720Li, results in an overmatch of the heat-affected zone in both sides of the weld. The comparison of the as-welded and postweld heat-treated condition also reveals that IN718 is in an overaged condition after the stress relief treatment.

  19. Numerical investigation on stress corrosion cracking behavior of dissimilar weld joints in pressurized water reactor plants

    Directory of Open Access Journals (Sweden)

    Lingyan Zhao

    2014-07-01

    Full Text Available There have been incidents recently where stress corrosion cracking (SCC observed in the dissimilar metal weld (DMW joints connecting the reactor pressure vessel (RPV nozzle with the hot leg pipe. Due to the complex microstructure and mechanical heterogeneity in the weld region, dissimilar metal weld joints are more susceptible to SCC than the bulk steels in the simulated high temperature water environment of pressurized water reactor (PWR. Tensile residual stress (RS, in addition to operating loads, has a great contribution to SCC crack growth. Limited experimental conditions, varied influence factors and diverging experimental data make it difficult to accurately predict the SCC behavior of DMW joints with complex geometry, material configuration, operating loads and crack shape. Based on the film slip/dissolution oxidation model and elastic-plastic finite element method (EPFEM, an approach is developed to quantitatively predict the SCC growth rate of a RPV outlet nozzle DMW joint. Moreover, this approach is expected to be a pre-analytical tool for SCC experiment of DMW joints in PWR primary water environment.

  20. Effects of stress on human mating preferences: stressed individuals prefer dissimilar mates

    Science.gov (United States)

    Lass-Hennemann, Johanna; Deuter, Christian E.; Kuehl, Linn K.; Schulz, André; Blumenthal, Terry D.; Schachinger, Hartmut

    2010-01-01

    Although humans usually prefer mates that resemble themselves, mating preferences can vary with context. Stress has been shown to alter mating preferences in animals, but the effects of stress on human mating preferences are unknown. Here, we investigated whether stress alters men's preference for self-resembling mates. Participants first underwent a cold-pressor test (stress induction) or a control procedure. Then, participants viewed either neutral pictures or pictures of erotic female nudes whose facial characteristics were computer-modified to resemble either the participant or another participant, or were not modified, while startle eyeblink responses were elicited by noise probes. Erotic pictures were rated as being pleasant, and reduced startle magnitude compared with neutral pictures. In the control group, startle magnitude was smaller during foreground presentation of photographs of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to self-resembling mates. In the stress group, startle magnitude was larger during foreground presentation of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to dissimilar mates. Our findings show that stress affects human mating preferences: unstressed individuals showed the expected preference for similar mates, but stressed individuals seem to prefer dissimilar mates. PMID:20219732

  1. Dissimilar Arc Welding of Advanced High-Strength Car-Body Steel Sheets

    Science.gov (United States)

    Russo Spena, P.; D'Aiuto, F.; Matteis, P.; Scavino, G.

    2014-11-01

    A widespread usage of new advanced TWIP steel grades for the fabrication of car-body parts is conditional on the employment of appropriate welding methods, especially if dissimilar welding must be performed with other automotive steel grades. Therefore, the microstructural features and the mechanical response of dissimilar butt weld seams of TWIP and 22MnB5 steel sheets after metal-active-gas arc welding are examined. The microstructural and mechanical characterization of the welded joints was carried out by optical metallography, microhardness and tensile testing, and fractographic examination. The heat-affected zone on the TWIP side was fully austenitic and the only detectable effect was grain coarsening, while on the 22MnB5 side it exhibited newly formed martensite and tempered martensite. The welded tensile specimens exhibited a much larger deformation on the TWIP steel side than on the 22MnB5. The fracture generally occurred at the interface between the fusion zone and the heat-affected zones, with the fractures surfaces being predominantly ductile. The ultimate tensile strength of the butt joints was about 25% lower than that of the TWIP steel.

  2. Behavior of a crack within a Dissimilar Metal Weld Part by using an Overlay Weld

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kang Soo; Lee, Ho Jin; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-05-15

    In recent years, the dissimilar metal welds, Alloy 82/182 welds, used to connect the stainless steel piping and low alloy steel or carbon steel components in a nuclear reactor piping system have experienced a cracking due to a primary water stress corrosion (PWSCC).It is well known that one reason for the cracking is the residual stress by the weld. But, it is difficult to estimate the weld residual stress exactly due to the many parameters for the welding process. In this paper, a Butt model weld specimen was manufactured and the residual stresses of the weld specimen were measured by the X-Ray method and a Hole Drilling Technique. These results were compared with the results of the Butt FEM Model to confirm the confidence of the FEM input. Also, an analysis of the Crack FEM models made by the ABAQUS Code was performed to estimate the behavior of a crack within a Dissimilar Metal Weld Part (DMWP) when an overlay weld on the DMWP was done.

  3. Hydrogen Assisted Crack in Dissimilar Metal Welds for Subsea Service under Cathodic Protection

    Science.gov (United States)

    Bourgeois, Desmond

    Dissimilar metal welds (DMWs) are routinely used in the oil and gas industries for structural joining of high strength steels in order to eliminate the need for post weld heat treatment (PWHT) after field welding. There have been reported catastrophic failures in these DMWs, particularly the AISI 8630 steel - Alloy 625 DMW combination, during subsea service while under cathodic protection (CP). This is due to local embrittlement that occurs in susceptible microstructures that are present at the weld fusion boundary region. This type of cracking is known as hydrogen assisted cracking (HAC) and it is influenced by base/filler metal combination, and welding and PWHT procedures. DMWs of two material combinations (8630 steel -- Alloy 625 and F22 steel -- Alloy 625), produced with two welding procedures (BS1 and BS3) in as welded and PWHT conditions were investigated in this study. The main objectives included: 1) evaluation of the effect of materials composition, welding and PWHT procedures on the gradients of composition, microstructure, and properties in the dissimilar transition region and on the susceptibility to HAC; 2) investigation of the influence of microstructure on the HAC failure mechanism and identification of microstructural constituents acting as crack nucleation and propagation sites; 3) assessment of the applicability of two-step PWHT to improve the resistance to HAC in DMWs; 4) establishment of non-failure criterion for the delayed hydrogen cracking test (DHCT) that is applicable for qualification of DMWs for subsea service under cathodic protection (CP).

  4. Caracterização e dissimilaridade entre populações de cenoura Characterization and dissimilarity among carrot populations

    Directory of Open Access Journals (Sweden)

    Giovani O da Silva

    2013-03-01

    Full Text Available Verificou-se a efetividade de caracteres fenotípicos na caracterização e dissimilaridade, bem como a distância genética entre populações melhoradas e cultivares de cenoura. Os experimentos foram conduzidos na Embrapa Hortaliças, Distrito Federal. Seis genótipos de cenoura, sendo três populações melhoradas (712467, 712473 e 712464, e três cultivares (Brasília, BRS Esplanada e BRS Planalto pertencentes ao grupo Brasília, foram avaliadas nas safras de verão de 2007/2008, 2008/2009, 2009/2010. Os experimentos foram instalados em delineamento de blocos ao acaso com duas repetições e parcelas de 1 m² de área útil. Aos 100 dias após semeio, foram colhidas 25 raízes por parcela e avaliadas individualmente para diâmetro do xilema da raiz, e para caracteres que fazem parte dos descritores mínimos para registro e proteção de cultivares de cenoura. Foram realizadas estimativas de repetibilidade e número de avaliações necessárias para caracterizar as populações, a dissimilaridade fenotípica e genotípica entre as populações, e os coeficientes de determinação (R² de acordo com diferente número de avaliações. Verificou-se que, com exceção do caractere formato de ponta da raiz, os demais caracteres estudados, que fazem parte dos descritores mínimos de cenoura, não são eficientes para ambos os processos de caracterização e discriminação de populações de cenoura pertencentes ao grupo Brasília. Não são esperados grandes efeitos heteróticos ao serem cruzados os genótipos de processamento BRS Esplanada e 712464. Para as populações de mesa avaliadas, é possível obter efeitos heteróticos apenas quando utilizada a cultivar Brasília nos cruzamentos.The effectiveness of phenotypic characters for characterization and evaluation of dissimilarity, and the genetic distance among improved carrot populations and cultivars were observed. The essays were carried out in Brasília, Brazil. Three improved carrot

  5. Microstructures and properties analysis of dissimilar metal joint in the friction stir welded copper to aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    Wang Xijing; Zhang Zhongke; Da Chaobing; Li Jing

    2007-01-01

    This paper mainly concentrated on the feasibility of friction stir welding of dissimilar metal of aluminum alloy to copper (T2) and a preliminary analysis of welding parameters influencing on the microstructures and properties of joint was carried out. The results indicated that the thickness of workpiece played an important role in the welding parameters which could succeed in the friction stir welding of dissimilar metal of copper to aluminum alloy, and the parameters were proved to be a narrow choice. The interfacial region between copper and aluminum in the dissimilar joint was not uniformly mixed, constituted with part of incomplete mixing zone, complete mixing zone, dispersion zone and the most region's boundary was obvious. Meantime a kind banded structure with inhomogeneous width was formed. The intermetallic compounds generated during friction stir welding in the interfacial region were mainly Cu9Al4 , Al2Cu etc, and their hardness was higher than others.

  6. Joint analysis of phenotypic and molecular diversity provides new insights on the genetic variability of the Brazilian physic nut germplasm bank.

    Science.gov (United States)

    Alves, Alexandre Alonso; Bhering, Leonardo Lopes; Rosado, Tatiana Barbosa; Laviola, Bruno Galvêas; Formighieri, Eduardo Fernandes; Cruz, Cosme Damião

    2013-09-01

    The genetic variability of the Brazilian physic nut (Jatropha curcas) germplasm bank (117 accessions) was assessed using a combination of phenotypic and molecular data. The joint dissimilarity matrix showed moderate correlation with the original matrices of phenotypic and molecular data. However, the correlation between the phenotypic dissimilarity matrix and the genotypic dissimilarity matrix was low. This finding indicated that molecular markers (RAPD and SSR) did not adequately sample the genomic regions that were relevant for phenotypic differentiation of the accessions. The dissimilarity values of the joint dissimilarity matrix were used to measure phenotypic + molecular diversity. This diversity varied from 0 to 1.29 among the 117 accessions, with an average dissimilarity among genotypes of 0.51. Joint analysis of phenotypic and molecular diversity indicated that the genetic diversity of the physic nut germplasm was 156% and 64% higher than the diversity estimated from phenotypic and molecular data, respectively. These results show that Jatropha genetic variability in Brazil is not as limited as previously thought.

  7. Exploring the Structure of Spatial Representations.

    Directory of Open Access Journals (Sweden)

    Tamas Madl

    Full Text Available It has been suggested that the map-like representations that support human spatial memory are fragmented into sub-maps with local reference frames, rather than being unitary and global. However, the principles underlying the structure of these 'cognitive maps' are not well understood. We propose that the structure of the representations of navigation space arises from clustering within individual psychological spaces, i.e. from a process that groups together objects that are close in these spaces. Building on the ideas of representational geometry and similarity-based representations in cognitive science, we formulate methods for learning dissimilarity functions (metrics characterizing participants' psychological spaces. We show that these learned metrics, together with a probabilistic model of clustering based on the Bayesian cognition paradigm, allow prediction of participants' cognitive map structures in advance. Apart from insights into spatial representation learning in human cognition, these methods could facilitate novel computational tools capable of using human-like spatial concepts. We also compare several features influencing spatial memory structure, including spatial distance, visual similarity and functional similarity, and report strong correlations between these dimensions and the grouping probability in participants' spatial representations, providing further support for clustering in spatial memory.

  8. Spectral methods for spatial resolution improvement of digital images

    Institute of Scientific and Technical Information of China (English)

    郝鹏威; 徐冠华; 朱重光

    1999-01-01

    A general matrix formula is proposed for signal spectral aliasing of various or mutual resolution, the concept of spectral aliasing matrix is introduced, and some general spectral methods for spatial resolution improvement from multiframes of undersampled digital images are discussed. A simplified iterative method of parallel row-action projection for spectral de-aliasing is also given. The method can be applied to multiframe images with various spatial resolution,relative displacement, dissimilar point spread function, different image radiance, and additive random noise. Some experiments with a resolution test pattern and an image of vertical fin performed the convergence and the effectiveness of the algorithms.

  9. Combination of laser keyhole and conduction welding: Dissimilar laser welding of niobium and Ti-6Al-4V

    Science.gov (United States)

    Torkamany, M. J.; Malek Ghaini, F.; Poursalehi, R.; Kaplan, A. F. H.

    2016-04-01

    Pulsed Nd:YAG laser welding of pure niobium plate to titanium alloy Ti-6Al-4V sheet in butt joint is studied regarding the laser/metal interaction modes. To obtain the optimized process parameters in dissimilar welding of Ti-6Al-4V/Nb, the melting ratio of laser beam energy for each weld counterpart is evaluated experimentally. Different laser welding modes of keyhole and conduction are predicted regarding the absorbed energy from the similar laser pulses on each weld counterpart. Laser keyhole and conduction welding were observed simultaneously through direct visualization of laser interaction with dissimilar metals using High Speed Imaging (HSI) system.

  10. Spatial Databases

    Science.gov (United States)

    2007-09-19

    for a city . Spatial attributes are used to define the spatial location and extent of spatial objects [35]. The spatial attributes of a spatial object...regarding both geometry and thematic differentiation. It can be used to model 2.5D data (e.g., digital terrain model), as well as 3D data ( walkable ...within a city , if the coverage area of a wireless antenna is considered to be the visible area, then the union of coverage areas of all the antennas in

  11. Premature failure of dissimilar metal weld joint at intermediate temperature superheater tube

    Directory of Open Access Journals (Sweden)

    Mohammed Al Hajri

    2015-04-01

    Full Text Available Dissimilar metal weld (DMW joint between alloyed steel (AS and stainless steel (SS failed at one of intermediate temperature superheater (ITSH tube in steam/power generation plant boiler. The premature failure was detected after a relatively short time of operation (8 years where the crack propagated circumferentially from AS side through the ITSH tube. Apart from physical examination, microstructural studies based on optical microscopy, SEM and EDX analysis were performed. The results of the investigation point out the limitation of Carbides precipitation at the alloyed steel/welding interface. This is synonym of creep stage I involvement in the failure of ITSH. Improper post-welding operation and bending moment are considered as root causes of the premature failure.

  12. Fracture analysis of a functionally graded interfacial zone between two dissimilar homogeneous materials

    Institute of Scientific and Technical Information of China (English)

    CHENG Zhanqi; ZHONG Zheng

    2006-01-01

    In this paper the plane elasticity problem for a functionally graded interfacial zone containing a crack between two dissimilar homogeneous materials has been considered. It is assumed that in the interfacial zone the reciprocal of the shear modulus is a linear function of the coordinate, while Possion's ratio keeps constant. By utilizing the Fourier transformation technique and the transfer matrix method, the mixed boundary problem is reduced to a system of singular integral equations that are solved numerically.The influences of the geometric parameters and the graded parameter on the stress intensity factors are investigated. The numerical results show that the graded parameters,the thickness of interfacial zone, the crack size and location have significant effects on the stress intensity factors.

  13. A Family of Uniform Strain Tetrahedral Elements and a Method for Connecting Dissimilar Finite Element Meshes

    Energy Technology Data Exchange (ETDEWEB)

    Dohrmann, C.R.; Heinstein, M.W.; Jung, J.; Key, S.W.

    1999-01-01

    This report documents a collection of papers on a family of uniform strain tetrahedral finite elements and their connection to different element types. Also included in the report are two papers which address the general problem of connecting dissimilar meshes in two and three dimensions. Much of the work presented here was motivated by the development of the tetrahedral element described in the report "A Suitable Low-Order, Eight-Node Tetrahedral Finite Element For Solids," by S. W. Key {ital et al.}, SAND98-0756, March 1998. Two basic issues addressed by the papers are: (1) the performance of alternative tetrahedral elements with uniform strain and enhanced uniform strain formulations, and (2) the proper connection of tetrahedral and other element types when two meshes are "tied" together to represent a single continuous domain.

  14. Fine structure at the diffusion welded interface of Fe3Al/Q235 dissimilar materials

    Indian Academy of Sciences (India)

    Wang Juan; Li Yajiang; Wu Huiqiang

    2001-12-01

    The interface of Fe3Al/Q235 dissimilar materials joint, which was made by vacuum diffusion welding, combines excellently. There are Fe3Al, FeAl phases and -Fe (Al) solid solution at the interface of Fe3Al/Q235. Aluminum content decreases from 28% to 1.5% and corresponding phase changes from Fe3Al with DO3 type body centred cubic (bcc) structure to -Fe (Al) solid solution with B2 type bcc structure. All phases are present in sub-grain structure level and there is no obvious brittle phases or micro-defects such as pores and cracks at the interface of Fe3Al/Q235 diffusion joint.

  15. Study on laser welding of stainless steel/copper dissimilar materials

    Science.gov (United States)

    Besnea, D.; Dontu, O.; Avram, M.; Spânu, A.; Rizescu, C.; Pascu, T.

    2016-08-01

    In this paper stainless steel/copper laser welding was investigated by controlling the processing parameters like welding speed and laser power. Welding the dissimilar materials of stainless steel and copper presents a series of problems. Differences in the physical properties of the two metals, including the melting point, thermal conductivity and thermal dilatation are the main reasons for obtaining an inappropriate laser welding bead. Particularly, the laser welding process of copper is complex because of the very high reflectivity of cooper and in almost situations it requires a specific surface pre-treatment. The main objective of the study conducted in this work was to laser weld a structure used in pressure measuring and control equipments. In order to satisfy the conditions imposed by the sensor manufacturer, the difficulty of obtaining flawless joints was represented by the very small dimensions of the parts to be welded especially of the elastic spiral thickness made of steel.

  16. Interface crack problems for mode Ⅱ of double dissimilar orthotropic composite materials

    Institute of Scientific and Technical Information of China (English)

    Wei-yang YANG; Shao-qin ZHANG; Jun-lin LI; Yu-lan MA

    2009-01-01

    The fracture problems near the interface crack tip for mode Ⅱ of double dissimilar orthotropic composite materials are studied. The mechanical models of interface crack for mode Ⅱ are given. By translating the governing equations into the generalized bi-harmonic equations,the stress functions containing two stress singularity exponents are derived with the help of a complex function method. Based on the boundary conditions,a system of non-homogeneous linear equations is found. Two real stress singularity exponents are determined be solving this system under appropriate conditions about himaterial engineering parameters. According to the uniqueness theorem of limit,both the formulae of stress intensity factors and theoretical solutions of stress field near the interface crack tip are derived. When the two orthotropic materials are the same,the stress singularity exponents,stress intensity factors and stresses for mode Ⅱ crack of the orthotropic single material are obtained.

  17. Evaluation of Laser Braze-welded Dissimilar Al-Cu Joints

    Science.gov (United States)

    Schmalen, Pascal; Plapper, Peter

    The thermal joining of Aluminum and Copper is a promising technology towards automotive battery manufacturing. The dissimilar metals Al-Cu are difficult to weld due to their different physicochemical characteristics and the formation of intermetallic compounds (IMC), which have reduced mechanical and electric properties. There is a critical thickness of the IMCs where the favored mechanical properties of the base material can be preserved. The laser braze welding principle uses a position and power oscillated laser-beam to reduce the energy input and the intermixture of both materials and therefore achieves minimized IMCs thickness. The evaluation of the weld seam is important to improve the joint performance and enhance the welding process. This paper is focused on the characterization and quantification of the IMCs. Mechanical, electrical and metallurgical methods are presented and performed on Al1050 and SF-Cu joints and precise weld criteria are developed.

  18. Phased array ultrasonic testing of dissimilar metal welds using geometric based referencing delay law technique

    Science.gov (United States)

    Han, Taeyoung; Schubert, Frank; Hillmann, Susanne; Meyendorf, Norbert

    2015-03-01

    Phased array ultrasonic testing (PAUT) techniques are widely used for the non-destructive testing (NDT) of austenitic welds to find defects like cracks. However, the propagation of ultrasound waves through the austenitic material is intricate due to its inhomogeneous and anisotropic nature. Such a characteristic leads beam path distorted which causes the signal to be misinterpreted. By employing a reference block which is cutout from the mockup of which the structure is a dissimilar metal weld (DMW), a new method of PAUT named as Referencing Delay Law Technique (RDLT) is introduced. With the RDLT, full matrix capture (FMC) was used for data acquisition. To reconstruct the images, total focusing method (TFM) was used. After the focal laws were calculated, PAUT was then performed. As a result, the flaws are more precisely positioned with significantly increased signal-to-noise ratio (SNR).

  19. Evaluating the Upset Protrusion Joining (UPJ) Method to Join magnesium Castings to Dissimilar Metals

    Energy Technology Data Exchange (ETDEWEB)

    Logan, Stephen D. [FCA US LLC

    2015-08-19

    This presentation discusses advantages and best practices for incorporating magnesium in automotive component applications to achieve substantial mass reduction, as well as some of the key challenges with respect to joining, coating, and galvanic corrosion, before providing an introduction and status update of the U.S. Department of Energy and Department of Defense jointly sponsored Upset Protrusion Joining (UPJ) process development and evaluation project. This update includes sharing performance results of a benchmark evaluation of the self-pierce riveting (SPR) process for joining dissimilar magnesium (Mg) to aluminum (Al) materials in four unique coating configurations before introducing the UPJ concept and comparing performance results of the joints made with the UPJ process to those made with the SPR process.

  20. Can Dissimilar Users Contribute to Accuracy and Diversity of Personalized Recommendation?

    Science.gov (United States)

    Zeng, Wei; Shang, Ming-Sheng; Zhang, Qian-Ming; Lü, Linyuan; Zhou, Tao

    Recommender systems are becoming a popular and important set of personalization techniques that assist individual users with navigating through the rapidly growing amount of information. A good recommender system should be able to not only find out the objects preferred by users, but also help users in discovering their personalized tastes. The former corresponds to high accuracy of the recommendation, while the latter to high diversity. A big challenge is to design an algorithm that provides both highly accurate and diverse recommendation. Traditional recommendation algorithms only take into account the contributions of similar users, thus, they tend to recommend popular items for users ignoring the diversity of recommendations. In this paper, we propose a recommendation algorithm by considering both the effects of similar and dissimilar users under the framework of collaborative filtering. Extensive analyses on three datasets, namely MovieLens, Netflix and Amazon, show that our method performs much better than the standard collaborative filtering algorithm for both accuracy and diversity.

  1. Fatigue Behaviors of Self-Piercing Rivets Joining Similar and Dissimilar Sheet Metals

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2007-01-01

    This paper summarizes the fatigue test results of self-piercing rivet (SPR) joints between similar and dissimilar sheet metals. The influences of material grades, material thickness, piercing direction and the use of structural adhesive on the rivet samples’ fatigue behaviors were investigated. Fatigue test results indicate that SPR joints have superior fatigue strength than resistance spot weld (RSW) joints for the same material combinations. The application of structure adhesive also significantly enhances the fatigue strength of the joint samples; this is particularly true for the lap shear loading configuration. In addition, different piercing directions for SPR joints have a noticeable effect on the static and fatigue strength of the joints. The joint fatigue results presented in this paper can offer design engineers with the durability data for SPR joints with these material combinations. Moreover, it will provide manufacturing engineers with some insights on the effects of different manufacturing parameters on the strength and durability of these joints.

  2. Fretting Behavior of SPR Joining Dissimilar Sheets of Titanium and Copper Alloys

    Directory of Open Access Journals (Sweden)

    Xiaocong He

    2016-12-01

    Full Text Available The fretting performance of self-piercing riveting joining dissimilar sheets in TA1 titanium alloy and H62 copper alloy was studied in this paper. Load-controlled cyclic fatigue tests were carried out using a sine waveform and in tension-tension mode. Scanning electron microscopy and energy-dispersive X-ray techniques were employed to analyze the fretting failure mechanisms of the joints. The experimental results showed that there was extremely severe fretting at the contact interfaces of rivet and sheet materials for the joints at relatively high loads levels. Moreover, the severe fretting in the region on the locked sheet in contact with the rivet was the major cause of the broken locked sheet for the joints at low load level.

  3. SEMI-WEIGHT FUNCTION METHOD ON COMPUTATION OF STRESS INTENSITY FACTORS IN DISSIMILAR MATERIALS

    Institute of Scientific and Technical Information of China (English)

    马开平; 柳春图

    2004-01-01

    Semi-weight function method is developed to solve the plane problem of two bonded dissimilar materials containing a crack along the bond. From equilibrium equation,stress and strain relationship, conditions of continuity across interface and free crack surface, the stress and displacementfields were obtained. The eigenvalue of these fields is lambda. Semi-weight functions were obtained as virtual displacement and stress fields with eigenvalue-lambda. Integral expression of fracture parameters, KⅠ and KⅡ, were obtained from reciprocal work theorem with semi-weight functions and approximate displacement and stress values on any integral path around crack tip. The calculation results of applications show that the semi-weight function method is a simple, convenient and high precision calculation method.

  4. Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

    Science.gov (United States)

    Juan, Pierre-Alexandre; Dingreville, Rémi

    2017-02-01

    Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive "interferences" are directly affected by the interface structure and its elastic response. This general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.

  5. Convincing similar and dissimilar others: the power of language abstraction in political communication.

    Science.gov (United States)

    Menegatti, Michela; Rubini, Monica

    2013-05-01

    Three studies examined the production of political messages and their persuasive impact on recipients as a function of speaker-audience similarity. The first two studies found support for the hypothesis that political leaders (Study 1) and party activists (Study 2) formulate more abstract messages when the audience is politically similar to them than when the audience is dissimilar or heterogeneous. The third study examined the persuasive impact of message abstractness versus concreteness. We predicted and found that abstract messages are more effective in convincing an audience whose political positions are similar to the speaker's and concrete messages are more effective in convincing an audience whose political positions differ from the speaker's or are heterogeneous. Implications of these findings for the relation between language and social cognition are discussed.

  6. Numerical simulation of dissimilar metal welding and its verification for determination of residual stresses

    Directory of Open Access Journals (Sweden)

    Sz. Szávai

    2016-03-01

    Full Text Available This paper summarizes the results of the through-thickness residual stress distributions on dissimilar metal weld (DMW mock-up. DMWs, as welded joints between ferritic steels and either austenitic stainless steels or nickel-based alloys, are commonly found in piping systems of NPPs as well as in other industrial plants. The welding of the mock-up is simulated by the 3D finite element model using temperature and phase dependent material properties. The commercial finite element code MSC.Marc is used to obtain the numerical results by implementing the Goldak’s double ellipsoidal shaped weld heat source and combined convection radiation boundary conditions. Residual stress measurements are performed on welded joints to validate the simulation results. The validated residual stress distributions can be used for the life time assessment and failure mode predictions of the welded joints.

  7. Microstructures and electrochemical behaviors of the friction stir welding dissimilar weld.

    Science.gov (United States)

    Shen, Changbin; Zhang, Jiayan; Ge, Jiping

    2011-06-01

    By using optical microscope, the microstructures of 5083/6082 friction stir welding (FSW) weld and parent materials were analyzed. Meanwhile, at ambient temperature and in 0.2 mol/L NaHS03 and 0.6 mol/L NaCl solutionby gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation, the electrochemical behavior of 5083/6082 friction stir welding weld and parent materials were comparatively investigated by gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation. The results indicated that at given processing parameters, the anti-corrosion property of the dissimilar weld was superior to those of the 5083 and 6082 parent materials.

  8. Microstructural and electrochemical characterization of a thin-section dissimilar stainless steel weld joint

    Energy Technology Data Exchange (ETDEWEB)

    Bala Srinivasan, P. [Institute of Materials Research, GKSS-Forschungszentrum Geesthacht GmbH, D 21502, Geesthacht (Germany)], E-mail: bala.srinivasan@gkss.de; Satish Kumar, M.P. [Mabani Steel, Ras Al Khaimah (United Arab Emirates)

    2009-05-15

    A dissimilar weld joint consisting of an austenitic stainless steel (ASS) and a martensitic stainless steel (MSS) was obtained under optimized welding conditions by autogenous gas tungsten arc welding technique. The weld metal was found to be dual-phased, and was constituted with an austenite matrix containing interdendritic ferrite of about 3-8 EFN, with over-matching mechanical properties. Electrochemical behaviour assessment of the composite zone comprising the weld metal, HAZ of both ASS and MSS showed different general corrosion behaviour in neutral and acidic chloride solutions. However, in both the electrolytes, the pitting susceptibility of this region was the highest, and the MSSHAZ of this composite zone was the observed to be more vulnerable to localized damage.

  9. CHARACTERISATION OF SPOT WELD GROWTH ON DISSIMILAR JOINTS WITH DIFFERENT THICKNESSES

    Directory of Open Access Journals (Sweden)

    Nachimani Charde

    2012-06-01

    Full Text Available A sound weld from spot welding is what most manufacturers desire and prefer for mechanical assemblies in their systems. The robustness is mainly attributed to the joining mechanism of mechanical parts. This paper focuses on the effect of parametric changes for dissimilar joints using 304 austenitic stainless steel and carbon steel of two different thicknesses. A pneumatic-based spot welder was used to accomplish the entire welding process. The parameters varied during the experiments are the welding current and welding time, while the electrode pressing force and electrode tip size are kept constant. The welding process began from a poor weld and moved on to a better weld by increasing the process parameters. However, this study is limited to the basic parametric variation to find the optimum parametric setup for 1 and 2 mm base metals. The welded specimens are subjected to tensile, hardness and metallurgical tests to characterise the spot weld growth for both thicknesses.

  10. Weld Metallurgy and Mechanical Properties of High Manganese Ultra-high Strength Steel Dissimilar Welds

    Science.gov (United States)

    Dahmen, Martin; Lindner, Stefan; Monfort, Damien; Petring, Dirk

    The increasing demand for ultra-high strength steels in vehicle manufacturing leads to the application of new alloys. This poses a challenge on joining especially by fusion welding. A stainless high manganese steel sheet with excellent strength and deformation properties stands in the centre of the development. Similar and dissimilar welds with a metastable austenitic steel and a hot formed martensitic stainless steel were performed. An investigation of the mixing effects on the local microstructure and the hardness delivers the metallurgical features of the welds. Despite of carbon contents above 0.4 wt.% none of the welds have shown cracks. Mechanical properties drawn from tensile tests deliver high breaking forces enabling a high stiffness of the joints. The results show the potential for the application of laser beam welding for joining in assembly of structural parts.

  11. Ultrasonic Transducer Design for the Axial Flaw Detection of Dissimilar Metal Weld

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Byung Sik; Kim, Yong Sik; Yang, Seung Han [Korea Hydro and Nuclear Power Central Research Institute, Daejeon (Korea, Republic of)

    2011-10-15

    Dissimilar metal welds in nuclear power plant are known as very susceptible to PWSCC flaws, and periodically inspected by the qualified inspector and qualified procedure during in-service inspection period. According to field survey data, the majority of their DMWs are located on tapered nozzle or adjacent to a tapered component. These types of configurations restrict examination access and also limit examination volume coverage. Additionally, circumferential scan for axially oriented flaw is very difficult to detect located on tapered surface because the transducer can't receive flaw response from reflector for miss-orientation. To overcome this miss-orientation, it is necessary adapt skewed ultrasonic transducer accommodate tapered surface. The skewed refracted longitudinal ultrasonic transducer designed by modeling and manufactured from the modelling result for axial flaw detection. Experimental results showed that the skewed refracted longitudinal ultrasonic transducer get higher flaw response than non-skewed refracted longitudinal ultrasonic transducer.

  12. Development of dissimilar metal transition joint by hot roll bonding technique

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, Takayuki; Takeda, Seiichiro; Tanaka, Yasumasa (Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works); Ogawa, Kazuhiro; Nakasuji, Kazuyuki; Ikenaga, Yoshiaki

    1994-12-01

    Metallurgically bonded transition joints which enable to connect reprocessing equipments made of superior corrosion resistant valve metals (Ti-5Ta, Zr or Ti) with stainless steel piping is needed for nuclear fuel reprocessing plants. The authors have developed dissimilar metal transition joints between stainless steel and Ti-5Ta, Zr or Ti with an insert metal of Ta by the hot roll bonding process, using the newly developed mill called 'rotary reduction mill'. In the R and D program, appropriate bonding conditions in the manufacturing process of the joints were established. This report presents the structure of transition joints and the manufacturing process by the hot roll bonding technique. Then, the evaluation of mechanical and corrosion properties and the results of demonstration test of joints for practical use are described. (author).

  13. Development of dissimilar metal transition joint by hot roll bonding technique

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, Takayuki; Takeuchi, Masayuki; Takeda, Seiichiro; Shikakura, Sakae [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works; Ogawa, Kazuhiro; Nakasuji, Kazuyuki; Kajimura, Haruhiko

    1995-12-01

    Metallurgically bonded transition joints which enable to connect reprocessing equipments made of superior corrosion resistant valve metals (Ti-5Ta, Zr or Ti) with stainless steel piping is needed for nuclear fuel reprocessing plants. The authors have developed dissimilar metal transition joints between stainless steel and Ti-5Ta, Zr or Ti with an insert metal of Ta by the hot roll bonding process, using the newly developed mill called `rotary reduction mill`. In the R and D program, appropriate bonding conditions in the manufacturing process of the joints were established. This report presents the structure of transition joints and the manufacturing process by hot roll bonding technique. Then, the evaluation of mechanical and corrosion properties and the results of demonstration test of joints for practical use are described. (author).

  14. Finite Element Modeling of the Inertia Friction Welding of Dissimilar High-Strength Steels

    Science.gov (United States)

    Bennett, C. J.; Attallah, M. M.; Preuss, M.; Shipway, P. H.; Hyde, T. H.; Bray, S.

    2013-11-01

    Finite element (FE) process modeling of inertia friction welding between dissimilar high-strength steels, AerMet® 100 and SCMV, has been carried out using the DEFORM™-2D (v10.0) software. This model was validated against experimental data collected for a test weld performed between the materials; this included process data such as upset and rotational velocities as well as thermal data collected during the process using embedded thermocouples. The as-welded hoop residual stress from the FE model was also compared with experimental measurements taken on the welded component using synchrotron X-ray and neutron diffraction techniques. The modeling work considered the solid-state phase transformations which occur in the steels, and the trends in the residual stress data were well replicated by the model.

  15. Schottky diode via dielectrophoretic assembly of reduced graphene oxide sheets between dissimilar metal contacts

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Muhammad R; Joung, Daeha; Khondaker, Saiful I, E-mail: saiful@mail.ucf.edu [Nanoscience Technology Center, School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, FL 32826 (United States)

    2011-03-15

    We demonstrate the fabrication of reduced graphene oxide (RGO) Schottky diodes via dielectrophoretic (DEP) assembly of RGO between two dissimilar metal contacts. Titanium (Ti) was used to make a Schottky contact, while palladium (Pd) was used to make an Ohmic contact. From the current-voltage characteristics, we obtain rectifying behavior with a rectification ratio of up to 600. The ideality factor was high (4.9), possibly due to the presence of a large number of defects in the RGO sheets. The forward biased turn-on voltage was 1 V, whereas the reverse biased breakdown voltage was -3.1 V, which improved further upon mild annealing at 200 deg. C and can be attributed to an increase in the work function of RGO due to annealing.

  16. Analysis of Dissimilar Material Defect Based on Eddy Current Conductivity Testing

    Science.gov (United States)

    Zhang, Xiaofan; Li, Lifu

    In this experiment, the conductivity distribution of lack of penetration (LOP) in friction stir welding (FSW) of dissimilar materials has been tested, and has been compared with the conductivity distribution of the same kind of material, by using eddy current conductivity meter. CZ state and M state LY12 aluminum alloy has been studied. The results show that when the depth of LOP is small, the conductivity of M state is the highest, the conductivity decreases gradually to the weld center, reduce to the minimum until reach the CZ state base metal. When the depth of LOP is larger, the conductivity of the weld center decreases sharply with the depth of LOP increases gradually. Scilicet, the larger the depth of LOP, the lower the conductivity. The conductivity distribution of other areas is similar to the distribution when the depth of LOP is small.

  17. Implication of Genetic Deletion of Wdr13 in Mice: Mild Anxiety, Better Performance in Spatial Memory Task, With Upregulation of Multiple Synaptic Proteins

    Directory of Open Access Journals (Sweden)

    Shiladitya Mitra

    2016-08-01

    Full Text Available WDR13 expresses from the X chromosome and has a highly conserved coding sequence. There have been multiple associations of WDR13 with memory. However, its detailed function in context of brain and behavior remains unknown. We characterized the behavioral phenotype of two months old male mice lacking the homologue of WDR13 gene (Wdr13-/0. Taking cue from analysis of its expression in the brain, we chose hippocampus for molecular studies to delineate its function. Wdr13-/0 mice spent less time in the central area of the open field test and with the novel object in novel object recognition test as compared to the wild-type. However, these mice didn’t show any significant changes in total time spent in arms or frequency of arm entries in elevated plus maze. In the absence of Wdr13, there was a significant upregulation of synaptic proteins, viz., SYN1, RAB3A, CAMK2A etc accompanied with increased spine density of hippocampal CA1 neurons and better spatial memory in mice as measured by increased time spent in target quadrant of Morris water maze during probe test. Parallel study from our lab has established c-JUN, ER α/ β and HDAC 1,3,7 as interacting partners of WDR13. WDR13 represses transcription from AP1 (c-JUN responsive and ERE (Estrogen Receptor Element promoters. We hypothesized that absence of Wdr13 would resulted in de-regulated expression of a number of genes including multiple synaptic genes leading to the observed phenotype. Knocking down Wdr13 in Neuro2a cell lines led to increased transcripts of Camk2a and Nrxn2 consistent with in-vivo results. Summarily, our data provides functional evidence for the role of Wdr13 in brain.

  18. Numerical investigation of ductile crack growth behavior in a dissimilar metal welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H.T. [MOE Key Laboratory of Pressurized System and Safety, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China); Wang, G.Z., E-mail: gzwang@ecust.edu.cn [MOE Key Laboratory of Pressurized System and Safety, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China); Xuan, F.Z.; Tu, S.T. [MOE Key Laboratory of Pressurized System and Safety, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2011-08-15

    Highlights: > Ductile crack growth behavior in a dissimilar metal welded joint was simulated. > Interface crack growth tends to deviate into material with lower yield stress. > Crack locations and mismatches affect local stress-strain distribution. > Local stress-strain leads to different crack growth resistances and paths. - Abstract: In this paper, the finite element method (FEM) based on GTN model is used to investigate the ductile crack growth behavior in single edge-notched bend (SENB) specimens of a dissimilar metal welded joint (DMWJ) composed of four materials in the primary systems of nuclear power plants. The J-{Delta}a resistance curves, crack growth paths and local stress-strain distributions in front of crack tips are calculated for eight initial cracks with different locations in the DMWJ and four cracks in the four homogenous materials. The results show that the initial cracks with different locations in the DMWJ have different crack growth resistances and growth paths. When the initial crack lies in the centers of the weld Alloy182 and buttering Alloy82, the crack-tip plastic and damage zones are symmetrical, and the crack grow path is nearly straight along the initial crack plane. But for the interface cracks between materials and near interface cracks, the crack-tip plastic and damage zones are asymmetric, and the crack growth path has significant deviation phenomenon. The crack growth tends to deviate into the material whose yield stress is lower between the two materials on both sides of the interface. The different initial crack locations and mismatches in yield stress and work hardening between different materials in the DMWJ affect the local stress triaxiality and plastic strain distributions in front of crack tips, and lead to different ductile crack growth resistances and growth paths. For the accurate integrity assessment for the DMWJ, the fracture toughness data and resistance curves for the initial cracks with different locations in the

  19. Thermal Aging Effects on Heat Affected Zone of Alloy 600 in Dissimilar Metal Weld

    Energy Technology Data Exchange (ETDEWEB)

    Ham, Jun Hyuk; Choi, Kyoung Joon; Yoo, Seung Chang; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of)

    2016-05-15

    Dissimilar metal weld (DMW), consists of Alloy 600, Alloy 182, and A508 Gr.3, is now being widely used as the reactor pressure vessel penetration nozzle and the steam generator tubing material for pressurized water reactors (PWR) because of its mechanical property, thermal expansion coefficient, and corrosion resistance. The heat affected zone (HAZ) on Alloy 600 which is formed by welding process is critical to crack. According to G.A. Young et al. crack growth rates (CGR) in the Alloy 600 HAZ were about 30 times faster than those in the Alloy 600 base metal tested under the same conditions [3]. And according to Z.P. Lu et al. CGR in the Alloy 600 HAZ can be more than 20 times higher than that in its base metal. To predict the life time of components, there is a model which can calculate the effective degradation years (EDYs) of the material as a function of operating temperature. This study was conducted to investigate how thermal aging affects the hardness of dissimilar metal weld from the fusion boundary to Alloy 600 base metal and the residual strain at Alloy 600 heat affected zone. Following conclusions can be drawn from this study. The hardness, measured by Vickers hardness tester, peaked near the fusion boundary between Alloy 182 and Alloy 600, and it decreases as the picked point goes to Alloy 600 base metal. Even though the formation of precipitate such as Cr carbide, thermal aging doesn't affect the value and the tendency of hardness because of reduced residual stress. According to kernel average misorientation mapping, residual strain decreases when the material thermally aged. And finally, in 30 years simulated specimen, the high residual strain almost disappears. Therefore, the influence of residual strain on primary water stress corrosion cracking can be diminished when the material undergoes thermal aging.

  20. Investigations on tunneling and kissing bond defects in FSW joints for dissimilar aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Noor Zaman, E-mail: noor_0315@yahoo.com [Department of Mechanical Engineering, Jamia Millia Islamia (A Central University), New Delhi (India); Siddiquee, Arshad Noor; Khan, Zahid A. [Department of Mechanical Engineering, Jamia Millia Islamia (A Central University), New Delhi (India); Shihab, Suha K. [Department of Mechanical Engineering, Engineering College, Diyala University, Diyala (Iraq)

    2015-11-05

    In this paper an attempt has been made to investigate the effect of two Friction Stir Welding (FSW) parameters i.e. tool pin offset and tool plunge depth on the formation of defects such as tunnel (tunneling defect) and kissing bond (KB) during welding of dissimilar aluminum alloys. 4.75 mm thick plates of AA5083-H116 and AA6063-T6 were welded using a novel work-fixture developed in-house which, apart from clamping the plated also imparted continuous variation of offset on both side of the faying line. The tunneling defect was modeled as a function of offset and plunge depth. The welds were characterised using optical microscopy (OM), scanning electron microscopy (SEM) and mechanical testing. The causes of such defects have been analyzed and discussed and recommendations have been made to prevent their occurrence. The findings of the study have revealed that the tunneling defects are formed at all offset (including zero offset) values towards stronger material (advancing side). And the cross-section of the tunnel varied with the amount of offset. Further, KBs are formed at the interface for all pin offset values except 0.5 mm towards weaker material and high plunge depth resulting in the poor mechanical properties. - Highlights: • Two dissimilar aluminum alloys are welded using FSW. • Formation of kissing bond and tunneling defects are investigated. • Defects are formed at pin offsets towards stronger material and also without offset. • The size of tunnel reduces significantly by increasing the plunge depth. • Tool pin offset towards weaker material prevent tunneling defects.

  1. Spatial cognition

    Science.gov (United States)

    Kaiser, Mary Kister; Remington, Roger

    1988-01-01

    Spatial cognition is the ability to reason about geometric relationships in the real (or a metaphorical) world based on one or more internal representations of those relationships. The study of spatial cognition is concerned with the representation of spatial knowledge, and our ability to manipulate these representations to solve spatial problems. Spatial cognition is utilized most critically when direct perceptual cues are absent or impoverished. Examples are provided of how human spatial cognitive abilities impact on three areas of space station operator performance: orientation, path planning, and data base management. A videotape provides demonstrations of relevant phenomena (e.g., the importance of orientation for recognition of complex, configural forms). The presentation is represented by abstract and overhead visuals only.

  2. Influence of genetic strain and access to litter on spatial distribution of 4 strains of laying hens in an aviary system.

    Science.gov (United States)

    Ali, A B A; Campbell, D L M; Karcher, D M; Siegford, J M

    2016-11-01

    Many laying hen producers are transitioning from conventional cages to new housing systems including multi-tier aviaries. Aviary resources, such as litter areas, are intended to encourage hens' expression of natural behaviors to improve their welfare. Little research has examined the influence of laying hen strain on distribution and behavior inside aviaries, yet differences could influence a strain's suitability for an aviary design. This research examined how laying hens of 4 strains (Hy-Line Brown [HB], Bovans Brown [BB], DeKalb White [DW], and Hy-Line W36) distributed themselves among 3 enclosed aviary tiers and 2 litter areas at peak lay (25 to 28 wk of age) and after gaining access to litter on the floor (26 wk). Observations of hens' spatial distribution were conducted immediately before and after, and 3 wk after hens gained access to litter. More HB and BB hens were in upper tiers in morning compared to DW and W36 (all P ≤ 0.05). However, DW and W36 hens roosted in upper tiers in larger numbers than HB and BB during evening (all P ≤ 0.05). More DW and W36 hens were on litter compared to BB and HB, particularly when litter was first accessible (all P ≤ 0.05). The number of hens on litter increased over time for all strains (P ≤ 0.06). White hens on litter occupied open areas in higher numbers (P ≤ 0.05), while more brown hens occupied litter under the aviary after acclimation (P ≤ 0.05). In the dark period, W36 and DW hens were present in higher numbers in upper tiers than HB and BB, while HB and BB showed higher tier-to-tier movement than DW and W36 (P ≤ 0.05). In general, more white hens roosted higher at night and explored litter sooner, while more brown hens were near or in nests in the morning and moved at night. Distinct strain differences indicate that attention should be paid to the match between configuration of the aviary design and strain of laying hen.

  3. Influence of genetic strain and access to litter on spatial distribution of 4 strains of laying hens in an aviary system1

    Science.gov (United States)

    Ali, A. B. A.; Campbell, D. L. M.; Karcher, D. M.; Siegford, J. M.

    2016-01-01

    Many laying hen producers are transitioning from conventional cages to new housing systems including multi-tier aviaries. Aviary resources, such as litter areas, are intended to encourage hens’ expression of natural behaviors to improve their welfare. Little research has examined the influence of laying hen strain on distribution and behavior inside aviaries, yet differences could influence a strain's suitability for an aviary design. This research examined how laying hens of 4 strains (Hy-Line Brown [HB], Bovans Brown [BB], DeKalb White [DW], and Hy-Line W36) distributed themselves among 3 enclosed aviary tiers and 2 litter areas at peak lay (25 to 28 wk of age) and after gaining access to litter on the floor (26 wk). Observations of hens’ spatial distribution were conducted immediately before and after, and 3 wk after hens gained access to litter. More HB and BB hens were in upper tiers in morning compared to DW and W36 (all P ≤ 0.05). However, DW and W36 hens roosted in upper tiers in larger numbers than HB and BB during evening (all P ≤ 0.05). More DW and W36 hens were on litter compared to BB and HB, particularly when litter was first accessible (all P ≤ 0.05). The number of hens on litter increased over time for all strains (P ≤ 0.06). White hens on litter occupied open areas in higher numbers (P ≤ 0.05), while more brown hens occupied litter under the aviary after acclimation (P ≤ 0.05). In the dark period, W36 and DW hens were present in higher numbers in upper tiers than HB and BB, while HB and BB showed higher tier-to-tier movement than DW and W36 (P ≤ 0.05). In general, more white hens roosted higher at night and explored litter sooner, while more brown hens were near or in nests in the morning and moved at night. Distinct strain differences indicate that attention should be paid to the match between configuration of the aviary design and strain of laying hen. PMID:27444438

  4. Relations between perceptual and conceptual scope: how global versus local processing fits a focus on similarity versus dissimilarity

    NARCIS (Netherlands)

    Förster, J.

    2009-01-01

    Nine studies showed a bidirectional link (a) between a global processing style and generation of similarities and (b) between a local processing style and generation of dissimilarities. In Experiments 1-4, participants were primed with global versus local perception styles and then asked to work on

  5. A Latent Class Multidimensional Scaling Model for Two-Way One-Mode Continuous Rating Dissimilarity Data

    Science.gov (United States)

    Vera, J. Fernando; Macias, Rodrigo; Heiser, Willem J.

    2009-01-01

    In this paper, we propose a cluster-MDS model for two-way one-mode continuous rating dissimilarity data. The model aims at partitioning the objects into classes and simultaneously representing the cluster centers in a low-dimensional space. Under the normal distribution assumption, a latent class model is developed in terms of the set of…

  6. 3D similarity-dissimilarity plot for high dimensional data visualization in the context of biomedical pattern classification.

    Science.gov (United States)

    Arif, Muhammad; Basalamah, Saleh

    2013-06-01

    In real life biomedical classification applications, it is difficult to visualize the feature space due to high dimensionality of the feature space. In this paper, we have proposed 3D similarity-dissimilarity plot to project the high dimensional space to a three dimensional space in which important information about the feature space can be extracted in the context of pattern classification. In this plot it is possible to visualize good data points (data points near to their own class as compared to other classes) and bad data points (data points far away from their own class) and outlier points (data points away from both their own class and other classes). Hence separation of classes can easily be visualized. Density of the data points near each other can provide some useful information about the compactness of the clusters within certain class. Moreover, an index called percentage of data points above the similarity-dissimilarity line (PAS) is proposed which is the fraction of data points above the similarity-dissimilarity line. Several synthetic and real life biomedical datasets are used to show the effectiveness of the proposed 3D similarity-dissimilarity plot.

  7. From the Fear of Death to the Fear of "Dissimilar Other": A Research in Elementary School Classrooms

    Science.gov (United States)

    Leondari, A.; Magos, K.; Oikonomou, A.

    2014-01-01

    Social stereotyping and prejudice constitute pressing societal problems and have many causes. Terror Management Theory offers a compelling and heavily researched account of individuals' reactions towards "dissimilar others" when faced with thoughts of mortality. Building from previous research with adult samples, the present study aimed…

  8. Global and Local Mechanical Properties and Microstructure of Friction Stir Welds with Dissimilar Materials and/or Thicknesses

    NARCIS (Netherlands)

    Zadpoor, A.A.; Sinke, J.; Benedictus, R.

    2010-01-01

    This article studies the properties of a wide range of friction-stir-welded joints with dissimilar aluminum alloys or thicknesses. Two aluminum alloys, namely, 2024-T3 and 7075-T6, are selected for the study and are welded in ten different combinations of alloys and thicknesses. The welding paramete

  9. Global and Local Mechanical Properties and Microstructure of Friction Stir Welds with Dissimilar Materials and/or Thicknesses

    NARCIS (Netherlands)

    Zadpoor, A.A.; Sinke, J.; Benedictus, R.

    2010-01-01

    This article studies the properties of a wide range of friction-stir-welded joints with dissimilar aluminum alloys or thicknesses. Two aluminum alloys, namely, 2024-T3 and 7075-T6, are selected for the study and are welded in ten different combinations of alloys and thicknesses. The welding

  10. Individual differences in commitment to value-based beliefs and the amplification of perceived belief dissimilarity effects.

    Science.gov (United States)

    Maxwell-Smith, Matthew A; Seligman, Clive; Conway, Paul; Cheung, Irene

    2015-04-01

    The commitment to beliefs (CTB) framework (Maxwell-Smith & Esses, 2012) proposes that there are individual differences in the extent to which people generally follow beliefs that are a reflection of their values. The current research hypothesized that CTB would amplify the effects of perceived belief dissimilarity or incompatibility, such that individuals higher in CTB would display more pronounced reactions to belief-relevant groups, events, or individuals seen as incompatible with their value-based beliefs. We tested our hypothesis in three studies that assessed participants' CTB and their perceptions of belief dissimilarity or incompatibility with regard to other religious groups (Study 1), political parties during a national election (Study 2), and their romantic partner (Study 3). CTB amplified the effects of perceived belief dissimilarity or incompatibility on people's biases toward other religious groups, voting intentions and behavior in a national election, and their evaluative and behavioral responses toward their romantic partner. These results collectively suggest that perceptions of belief dissimilarity or incompatibility are particularly important cues for individuals with higher levels of CTB as they encounter other people or events that are relevant to their beliefs.

  11. The Effect of Similarity/Dissimilarity of Race and Personal Interests on Empathy and Altruism in Second Graders.

    Science.gov (United States)

    Panofsky, Anne D.

    The experiment reported in this dissertation investigated the effect of similarity/dissimilarity of race and personal interests on empathy and altruism in second graders. It was hypothesized that white children would empathize more with other white children than with black children. It was also hypothesized that white children would empathize more…

  12. Material flow analysis in dissimilar friction stir welding of AA2024 and Ti6Al4V butt joints

    Directory of Open Access Journals (Sweden)

    BuffaGianluca

    2016-01-01

    Full Text Available The complex material flow occurring during the weld of dissimilar AA2024 to Ti6Al4V butt and lap joints was highlighted through a dedicated numerical model able to take into account the effects of the different materials as well as the phase transformation of the used titanium alloy.

  13. Spatial variation in genetic diversity and natural selection on the thrombospondin-related adhesive protein locus of Plasmodium vivax (PvTRAP.

    Directory of Open Access Journals (Sweden)

    Rattiporn Kosuwin

    Full Text Available Thrombospondin-related adhesive protein (TRAP of malaria parasites is essential for sporozoite motility and invasions into mosquito's salivary gland and vertebrate's hepatocyte; thereby, it is a promising target for pre-erythrocytic vaccine. TRAP of Plasmodium vivax (PvTRAP exhibits sequence heterogeneity among isolates, an issue relevant to vaccine development. To gain insights into variation in the complete PvTRAP sequences of parasites in Thailand, 114 vivax malaria patients were recruited in 2006-2007 from 4 major endemic provinces bordering Myanmar (Tak in the northwest, n = 30 and Prachuap Khirikhan in the southwest, n = 25, Cambodia (Chanthaburi in the east, n = 29 and Malaysia (Yala and Narathiwat in the south, n = 30. In total, 26 amino acid substitutions were detected and 9 of which were novel, resulting in 44 distinct haplotypes. Haplotype and nucleotide diversities were lowest in southern P. vivax population while higher levels of diversities were observed in other populations. Evidences of positive selection on PvTRAP were demonstrated in domains II and IV and purifying selection in domains I, II and VI. Genetic differentiation was significant between each population except that between populations bordering Myanmar where transmigration was common. Regression analysis of pairwise linearized Fst and geographic distance suggests that P. vivax populations in Thailand have been isolated by distance. Sequence diversity of PvTRAP seems to be temporally stable over one decade in Tak province based on comparison of isolates collected in 1996 (n = 36 and 2006-2007. Besides natural selection, evidences of intragenic recombination have been supported in this study that could maintain and further generate diversity in this locus. It remains to be investigated whether amino acid substitutions in PvTRAP could influence host immune responses although several predicted variant T cell epitopes drastically altered the epitope

  14. EFFECT OF CARBON MIGRATION ON CREEP PROPERTIES OF Cr5Mo DISSIMILAR WELDED JOINTS WITH Ni-BASED AND AUSTENITIC WELD METAL

    Institute of Scientific and Technical Information of China (English)

    J.M. Gong; Y. Jiang; S.T. Tu

    2004-01-01

    In this paper, the effect of carbon migration on creep properties of Cr5Mo dissimilar welded joints with Ni-based (Inconel 182) and Cr23Ni13 (A302) austenitic weld metal was investigated. Carbon migration near the weld metal/ferritic steel interface of Cr5Mo dissimilar welded joints was analyzed by aging method. Local creep deformations of the dissimilar welded joints were measured by a long-term local creep deformation measuring technique. The creep rupture testing was performed for Cr5Mo dissimilar welded joints with Inconel 182 and A302 weld metal. The research results show that the maximum creep strain rate occurs in the decarburized zone located on heat affect zone (HAZ) of Cr5Mo ferritic steel. The creep rupture life of Cr5Mo dissimilar welded joints with A302 weld metal decreases due to carbon migration and is about 50% of that welded with Inconel 182 weld metal.

  15. Effect of width of repair welding on stress distribution of dissimilar metal butt weld of nuclear piping

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Won Shik; Lee, Hwee Seung; Huh, Nam Su [Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of)

    2013-10-15

    In the present work, the welding residual stress due to repair welding and the stress redistribution behavior due to primary pressure are investigated via 2-dimensional non-linear finite element analyses. In particular, the effect of repair welding width on stress distribution is emphasized. Although, large tensile residual stresses are produced at the PWSCC sensitive region due to repair welding, these stresses are highly reduced due to stress redistribution caused by primary load. Based on the present finite element results, it has been revealed that the effect of width of repair welding on stress distribution is not significant. In the past few years, many numerical and experimental works have been made to assess a structural integrity of cracked components subjected to primary water stress corrosion cracking in dissimilar metal weld (DMW) using Alloys 82/182 in nuclear industries worldwide. These works include a prediction of weld residual stresses in dissimilar metal weld by either numerical or experimental works since an accurate estimation of residual stress distribution in dissimilar metal weld is the most important element for integrity assessment of components subjected to primary water stress corrosion cracking. During an actual welding process, in general, a repair welding is often performed when a defect indication is detected during post-welding inspection. It has been revealed that such a repair welding could lead to higher tensile residual stress in dissimilar metal weld, which is detrimental to the crack growth due to primary water stress corrosion cracking. Thus, the prediction of residual stress considering a repair welding is needed, and then many efforts were made on this issue. In the present work, the effect of width of repair welding on stress distribution of dissimilar metal butt weld of nuclear piping is evaluated based on the detailed 2-dimensional non-linear finite element analyses. For this purpose, the welding residual stress due to

  16. Non-metric multidimensional performance indicator scaling reveals seasonal and team dissimilarity within the National Rugby League.

    Science.gov (United States)

    Woods, Carl T; Robertson, Sam; Sinclair, Wade H; Collier, Neil French

    2017-06-22

    Analysing the dissimilarity of seasonal and team profiles within elite sport may reveal the evolutionary dynamics of game-play, while highlighting the similarity of individual team profiles. This study analysed seasonal and team dissimilarity within the National Rugby League (NRL) between the 2005 to 2016 seasons. Longitudinal. Total seasonal values for 15 performance indicators were collected for every NRL team over the analysed period (n=190 observations). Non-metric multidimensional scaling was used to reveal seasonal and team dissimilarity. Compared to the 2005 to 2011 seasons, the 2012 to 2016 seasons were in a state of flux, with a relative dissimilarity in the positioning of team profiles on the ordination surface. There was an abrupt change in performance indicator characteristics following the 2012 season, with the 2014 season reflecting a large increase in the total count of 'all run metres' (d=1.21; 90% CI=0.56-1.83), 'kick return metres' (d=2.99; 90% CI=2.12-3.84) and decrease in 'missed tackles' (d=-2.43; 90% CI=-3.19 to -1.64) and 'tackle breaks' (d=-2.41; 90% CI=-3.17 to -1.62). Interpretation of team ordination plots showed that certain teams evolved in (dis)similar ways over the analysed period. It appears that NRL match-types evolved following the 2012 season and are in a current state of flux. The modification of coaching tactics and rule changes may have contributed to these observations. Coaches could use these results when designing prospective game strategies in the NRL. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  17. Genetic Discrimination

    Science.gov (United States)

    ... in Genetics Archive Regulation of Genetic Tests Genetic Discrimination Overview Many Americans fear that participating in research ... I) and employment (Title II). Read more Genetic Discrimination and Other Laws Genetic Discrimination and Other Laws ...

  18. Spatializing Time

    DEFF Research Database (Denmark)

    Thomsen, Bodil Marie Stavning

    2011-01-01

    The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations.......The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations....

  19. Spatializing Time

    DEFF Research Database (Denmark)

    2011-01-01

    The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations.......The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations....

  20. Multiple Spectral-Spatial Classification Approach for Hyperspectral Data

    Science.gov (United States)

    Tarabalka, Yuliya; Benediktsson, Jon Atli; Chanussot, Jocelyn; Tilton, James C.

    2010-01-01

    A .new multiple classifier approach for spectral-spatial classification of hyperspectral images is proposed. Several classifiers are used independently to classify an image. For every pixel, if all the classifiers have assigned this pixel to the same class, the pixel is kept as a marker, i.e., a seed of the spatial region, with the corresponding class label. We propose to use spectral-spatial classifiers at the preliminary step of the marker selection procedure, each of them combining the results of a pixel-wise classification and a segmentation map. Different segmentation methods based on dissimilar principles lead to different classification results. Furthermore, a minimum spanning forest is built, where each tree is rooted on a classification -driven marker and forms a region in the spectral -spatial classification: map. Experimental results are presented for two hyperspectral airborne images. The proposed method significantly improves classification accuracies, when compared to previously proposed classification techniques.

  1. Residual Stresses in Inertia-Friction-Welded Dissimilar High-Strength Steels

    Science.gov (United States)

    Moat, R. J.; Hughes, D. J.; Steuwer, A.; Iqbal, N.; Preuss, M.; Bray, S. E.; Rawson, M.

    2009-09-01

    The welding of dissimilar alloys is seen increasingly as a way forward to improve efficiencies in modern aeroengines, because it allows one to tailor varying material property demands across a component. Dissimilar inertia friction welding (IFW) of two high-strength steels, Aermet 100 and S/CMV, has been identified as a possible joint for rotating gas turbine components and the resulting welds are investigated in this article. In order to understand the impact of the welding process and predict the life expectancy of such structures, a detailed understanding of the residual stress fields present in the welded component is needed. By combining energy-dispersive synchrotron X-ray diffraction (EDSXRD) and neutron diffraction, it has been possible to map the variations in lattice spacing of the ferritic phase on both sides of two tubular Aermet 100-S/CMV inertia friction welds (as-welded and postweld heat-treated condition) with a wall thickness of 37 mm. Laboratory-based XRD measurements were required to take into account the variation in the strain-free d-spacing across the weld region. It was found that, in the heat-affected zone (HAZ) slightly away from the weld line, residual stress fields showed tensile stresses increasing most dramatically in the hoop direction toward the weld line. Closer to the weld line, in the plastically affected zone, a sharp drop in the residual stresses was observed on both sides, although more dramatically in the S/CMV. In addition to residual stress mapping, synchrotron XRD measurements were carried out to map microstructural changes in thin slices cut from the welds. By studying the diffraction peak asymmetry of the 200- α diffraction peak, it was possible to demonstrate that a martensitic phase transformation in the S/CMV is responsible for the significant stress reduction close to the weld line. The postweld heat treatment (PWHT) chosen to avoid any overaging of the Aermet 100 and to temper the S/CMV martensite resulted in little

  2. Nano-structural and Nano-chemical analysis of dissimilar metal weld interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kyoung Joon; Shin, Sang Hoon; Kim, Jong Jin; Jung, Ju Ang; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2012-05-15

    Dissimilar Metal Welds (DMWs) is generally applied to nuclear power plants for manufacturing and machining in structural components such as reactor pressure vessels and pressurizer nozzles. Alloy 152 is used frequently as filler metal in the manufacture of the DMW in light water reactors to join the low alloy steel pressure vessel nozzles and steam generator nozzles to nickel-based wrought alloy or austenitic stainless steel components. However, in recent years cracking phenomena has been observed in the welded joints. Concerns have been raised to the integrity and reliability in the joint transition zone due to the high susceptibility of the heat affected zone (HAZ) and the fusion boundary (FB) to stress corrosion cracking in combination with thermal aging. Since the material microstructure and chemical composition are key parameters affecting the stress corrosion cracking, improving the understanding of stress corrosion cracking at the FB region requires fundamental understanding of the unique microstructure of the FB region in DMW. Despite the potential degradation and consequent risk in the DMW, there is still a lack of the fundamental understanding of microstructure in the FB region, in particular the region containing unidentified band structures near the FB. The scale of the microstructure in modern metallic materials is becoming increasingly smaller. The 3-dimensional atom probe tomography (3D APT) has a truly quantitative analytical capability to characterize nanometer scale particles in metallic materials, thus its application to the microstructural analysis in multi-component metallic materials provides critical information on the mechanism of nanoscale microstructural evolution. The 3D APT is a microscope that allows the reconstruction of 3D 'atom maps'. These reconstructions can be interrogated and interpreted to determine the nanoscale chemistry of the material. Therefore, the current study is aiming at the establishment of detail procedure

  3. Numerical Simulation of Similar and Dissimilar Materials Welding Process; Quantifications of Temperature, Stress, Strain and Deformation

    Directory of Open Access Journals (Sweden)

    Ranjit Shrestha

    2015-02-01

    Full Text Available In the present paper, 3 Dimensional welding simulation was carried out in the FE software ANSYS in order to predict temperature, stress, strain and deformation in the joining of similar and dissimilar materials. The numerical simulation shows that temperature exceeds well above the melting temperature of the substrate material in the welding region. It is found that, higher residual stress is distributed in the weld bead area and surrounding heat affected zone. The stress and strain distribution patterns in the specimen showed that both tended to concentrate at or near points of application of thermal load, and were generally not uniform in these areas. It is also found that Stress and strain were concentrated at corners, edges, and other areas of abrupt change in the shape of the specimen and was also not uniform where the cross-section of the structure changed suddenly, and had large gradients at localized points. The deformation was found maximum at the beginning and the end of welding direction (Y-axis and minimum at the ends of X-axis as they are simply supported in both ends. In addition, among the six different cases of similar and dissimilar materials (S40C+S40C, STS304+STS304, STS316L+STS316L, S40C+STS304, S40C+STS316L, STS304+STS316L, the minimum temperature was found in S40C+STS304 whereas the maximum temperature was S40C+STS316L; the minimum stress was found in case of S40C+STS304 and maximum stress was found in 40C+STS316L; the minimum strain was found in case of S40C+STS304 and maximum strain was found in STS304+STS304; the minimum deformation was found in S40C+S40C and maximum in S40C+STS316L.The prediction show qualitative good agreement with the experimental results found in the literature and hence it was confirmed that the method of finite elements has proved to be successful for proper design analysis.

  4. On combining image-based and ontological semantic dissimilarities for medical image retrieval applications.

    Science.gov (United States)

    Kurtz, Camille; Depeursinge, Adrien; Napel, Sandy; Beaulieu, Christopher F; Rubin, Daniel L

    2014-10-01

    Computer-assisted image retrieval applications can assist radiologists by identifying similar images in archives as a means to providing decision support. In the classical case, images are described using low-level features extracted from their contents, and an appropriate distance is used to find the best matches in the feature space. However, using low-level image features to fully capture the visual appearance of diseases is challenging and the semantic gap between these features and the high-level visual concepts in radiology may impair the system performance. To deal with this issue, the use of semantic terms to provide high-level descriptions of radiological image contents has recently been advocated. Nevertheless, most of the existing semantic image retrieval strategies are limited by two factors: they require manual annotation of the images using semantic terms and they ignore the intrinsic visual and semantic relationships between these annotations during the comparison of the images. Based on these considerations, we propose an image retrieval framework based on semantic features that relies on two main strategies: (1) automatic "soft" prediction of ontological terms that describe the image contents from multi-scale Riesz wavelets and (2) retrieval of similar images by evaluating the similarity between their annotations using a new term dissimilarity measure, which takes into account both image-based and ontological term relations. The combination of these strategies provides a means of accurately retrieving similar images in databases based on image annotations and can be considered as a potential solution to the semantic gap problem. We validated this approach in the context of the retrieval of liver lesions from computed tomographic (CT) images and annotated with semantic terms of the RadLex ontology. The relevance of the retrieval results was assessed using two protocols: evaluation relative to a dissimilarity reference standard defined for pairs of

  5. Citizen science: A new perspective to advance spatial pattern evaluation in hydrology.

    Science.gov (United States)

    Koch, Julian; Stisen, Simon

    2017-01-01

    Citizen science opens new pathways that can complement traditional scientific practice. Intuition and reasoning often make humans more effective than computer algorithms in various realms of problem solving. In particular, a simple visual comparison of spatial patterns is a task where humans are often considered to be more reliable than computer algorithms. However, in practice, science still largely depends on computer based solutions, which inevitably gives benefits such as speed and the possibility to automatize processes. However, the human vision can be harnessed to evaluate the reliability of algorithms which are tailored to quantify similarity in spatial patterns. We established a citizen science project to employ the human perception to rate similarity and dissimilarity between simulated spatial patterns of several scenarios of a hydrological catchment model. In total, the turnout counts more than 2500 volunteers that provided over 43000 classifications of 1095 individual subjects. We investigate the capability of a set of advanced statistical performance metrics to mimic the human perception to distinguish between similarity and dissimilarity. Results suggest that more complex metrics are not necessarily better at emulating the human perception, but clearly provide auxiliary information that is valuable for model diagnostics. The metrics clearly differ in their ability to unambiguously distinguish between similar and dissimilar patterns which is regarded a key feature of a reliable metric. The obtained dataset can provide an insightful benchmark to the community to test novel spatial metrics.

  6. Citizen science: A new perspective to advance spatial pattern evaluation in hydrology

    Science.gov (United States)

    Stisen, Simon

    2017-01-01

    Citizen science opens new pathways that can complement traditional scientific practice. Intuition and reasoning often make humans more effective than computer algorithms in various realms of problem solving. In particular, a simple visual comparison of spatial patterns is a task where humans are often considered to be more reliable than computer algorithms. However, in practice, science still largely depends on computer based solutions, which inevitably gives benefits such as speed and the possibility to automatize processes. However, the human vision can be harnessed to evaluate the reliability of algorithms which are tailored to quantify similarity in spatial patterns. We established a citizen science project to employ the human perception to rate similarity and dissimilarity between simulated spatial patterns of several scenarios of a hydrological catchment model. In total, the turnout counts more than 2500 volunteers that provided over 43000 classifications of 1095 individual subjects. We investigate the capability of a set of advanced statistical performance metrics to mimic the human perception to distinguish between similarity and dissimilarity. Results suggest that more complex metrics are not necessarily better at emulating the human perception, but clearly provide auxiliary information that is valuable for model diagnostics. The metrics clearly differ in their ability to unambiguously distinguish between similar and dissimilar patterns which is regarded a key feature of a reliable metric. The obtained dataset can provide an insightful benchmark to the community to test novel spatial metrics. PMID:28558050

  7. Evidence that pairing with genetically similar mates is maladaptive in a monogamous bird

    Science.gov (United States)

    Mulard, Hervé; Danchin, E.; Talbot, S.L.; Ramey, A.M.; Hatch, Shyla A.; White, J.F.; Helfenstein, F.; Wagner, R.H.

    2009-01-01

    Background. Evidence of multiple genetic criteria of mate choice is accumulating in numerous taxa. In many species, females have been shown to pair with genetically dissimilar mates or with extra-pair partners that are more genetically compatible than their social mates, thereby increasing their offsprings' heterozygosity which often correlates with offspring fitness. While most studies have focused on genetically promiscuous species, few studies have addressed genetically monogamous species, in which mate choice tends to be mutual. Results. Here, we used microsatellite markers to assess individual global heterozygosity and genetic similarity of pairs in a socially and genetically monogamous seabird, the black-legged kittiwake Rissa tridactyla. We found that pairs were more genetically dissimilar than expected by chance. We also identified fitness costs of breeding with genetically similar partners: (i) genetic similarity of pairs was negatively correlated with the number of chicks hatched, and (ii) offspring heterozygosity was positively correlated with growth rate and survival. Conclusion. These findings provide evidence that breeders in a genetically monogamous species may avoid the fitness costs of reproducing with a genetically similar mate. In such species that lack the opportunity to obtain extra-pair fertilizations, mate choice may therefore be under high selective pressure. ?? 2009 Mulard et al; licensee BioMed Central Ltd.

  8. Evidence that pairing with genetically similar mates is maladaptive in a monogamous bird

    Directory of Open Access Journals (Sweden)

    Ramey Andrew M

    2009-06-01

    Full Text Available Abstract Background Evidence of multiple genetic criteria of mate choice is accumulating in numerous taxa. In many species, females have been shown to pair with genetically dissimilar mates or with extra-pair partners that are more genetically compatible than their social mates, thereby increasing their offsprings' heterozygosity which often correlates with offspring fitness. While most studies have focused on genetically promiscuous species, few studies have addressed genetically monogamous species, in which mate choice tends to be mutual. Results Here, we used microsatellite markers to assess individual global heterozygosity and genetic similarity of pairs in a socially and genetically monogamous seabird, the black-legged kittiwake Rissa tridactyla. We found that pairs were more genetically dissimilar than expected by chance. We also identified fitness costs of breeding with genetically similar partners: (i genetic similarity of pairs was negatively correlated with the number of chicks hatched, and (ii offspring heterozygosity was positively correlated with growth rate and survival. Conclusion These findings provide evidence that breeders in a genetically monogamous species may avoid the fitness costs of reproducing with a genetically similar mate. In such species that lack the opportunity to obtain extra-pair fertilizations, mate choice may therefore be under high selective pressure.

  9. Exploring perception and annoyance due to wind turbine noise in dissimilar living environments

    Energy Technology Data Exchange (ETDEWEB)

    Pedersen, Eja; Persson Waye, Kerstin

    2006-07-01

    A cross-sectional study with the aim to explore differences in perception and annoyance between dissimilar living environments was carried out in seven different geographical areas in Sweden 2005. Responses to wind turbine noise were measured using a questionnaire (response rate: 58.4%; 765 respondents) and outdoor A-weighted sound pressure levels were calculated for each respondent. The result indicated that the proportion of people hearing and being annoyed by noise from wind turbines was higher among those who could see one or more wind turbines compared to among those who could not see any turbine at all sound levels. When comparing agricultural areas with suburban areas, a tendency towards higher degrees of perception and annoyance in the agricultural areas was observed. The differences could be due to (i) shortcomings of the sound propagation calculations not taking local barriers into account, (ii) variation in background sound pressure levels between agricultural and suburban areas, (iii) the variation in visibility of the wind turbines influencing the rate of noise annoyance and (iiii) resident's personal values of their living environment due to the level of urbanization of the areas (e.g. rural versus suburban)

  10. A study of weld quality in ultrasonic spot welding of similar and dissimilar metals

    Science.gov (United States)

    Al-Sarraf, Z.; Lucas, M.

    2012-08-01

    Several difficulties are faced in joining thinner sheets of similar and dissimilar materials from fusion welding processes such as resistance welding and laser welding. Ultrasonic metal welding overcomes many of these difficulties by using high frequency vibration and applied pressure to create a solid-state weld. Ultrasonic metal welding is an effective technique in joining small components, such as in wire bonding, but is also capable of joining thicker sheet, depending on the control of welding conditions. This study presents the design, characterisation and test of a lateral-drive ultrasonic metal welding device. The ultrasonic welding horn is modelled using finite element analysis and its vibration behaviour is characterised experimentally to ensure ultrasonic energy is delivered to the weld coupon. The welding stack and fixtures are then designed and mounted on a test machine to allow a series of experiments to be conducted for various welding and ultrasonic parameters. Weld strength is subsequently analysed using tensile-shear tests. Control of the vibration amplitude profile through the weld cycle is used to enhance weld strength and quality, providing an opportunity to reduce part marking. Optical microscopic examination and scanning electron microscopy (SEM) were employed to investigate the weld quality. The results show how the weld quality is particularly sensitive to the combination of clamping force and vibration amplitude of the welding tip.

  11. Dissimilar Physiological and Perceptual Responses Between Sprint Interval Training and High-Intensity Interval Training.

    Science.gov (United States)

    Wood, Kimberly M; Olive, Brittany; LaValle, Kaylyn; Thompson, Heather; Greer, Kevin; Astorino, Todd A

    2016-01-01

    High-intensity interval training (HIIT) and sprint interval training (SIT) elicit similar cardiovascular and metabolic adaptations vs. endurance training. No study, however, has investigated acute physiological changes during HIIT vs. SIT. This study compared acute changes in heart rate (HR), blood lactate concentration (BLa), oxygen uptake (VO2), affect, and rating of perceived exertion (RPE) during HIIT and SIT. Active adults (4 women and 8 men, age = 24.2 ± 6.2 years) initially performed a VO2max test to determine workload for both sessions on the cycle ergometer, whose order was randomized. Sprint interval training consisted of 8 bouts of 30 seconds of all-out cycling at 130% of maximum Watts (Wmax). High-intensity interval training consisted of eight 60-second bouts at 85% Wmax. Heart rate, VO2, BLa, affect, and RPE were continuously assessed throughout exercise. Repeated-measures analysis of variance revealed a significant difference between HIIT and SIT for VO2 (p HIIT (209.3 ± 40.3 kcal) vs. SIT (193.5 ± 39.6 kcal). During HIIT, subjects burned significantly more calories and reported lower perceived exertion than SIT. The higher VO2 and lower BLa in HIIT vs. SIT reflected dissimilar metabolic perturbation between regimens, which may elicit unique long-term adaptations. If an individual is seeking to burn slightly more calories, maintain a higher oxygen uptake, and perceive less exertion during exercise, HIIT is the recommended routine.

  12. Microstructure and Tensile Behavior of Laser Arc Hybrid Welded Dissimilar Al and Ti Alloys

    Directory of Open Access Journals (Sweden)

    Ming Gao

    2014-02-01

    Full Text Available Fiber laser-cold metal transfer arc hybrid welding was developed to welding-braze dissimilar Al and Ti alloys in butt configuration. Microstructure, interface properties, tensile behavior, and their relationships were investigated in detail. The results show the cross-weld tensile strength of the joints is up to 213 MPa, 95.5% of same Al weld. The optimal range of heat input for accepted joints was obtained as 83–98 J·mm−1. Within this range, the joint is stronger than 200 MPa and fractures in weld metal, or else, it becomes weaker and fractures at the intermetallic compounds (IMCs layer. The IMCs layer of an accepted joint is usually thin and continuous, which is about 1μm-thick and only consists of TiAl2 due to fast solidification rate. However, the IMCs layer at the top corner of fusion zone/Ti substrate is easily thickened with increasing heat input. This thickened IMCs layer consists of a wide TiAl3 layer close to FZ and a thin TiAl2 layer close to Ti substrate. Furthermore, both bead shape formation and interface growth were discussed by laser-arc interaction and melt flow. Tensile behavior was summarized by interface properties.

  13. Simulation Based Investigation of Focusing Phased Array Ultrasound in Dissimilar Metal Welds

    Directory of Open Access Journals (Sweden)

    Hun-Hee Kim

    2016-02-01

    Full Text Available Flaws at dissimilar metal welds (DMWs, such as reactor coolant systems components, Control Rod Drive Mechanism (CRDM, Bottom Mounted Instrumentation (BMI etc., in nuclear power plants have been found. Notably, primary water stress corrosion cracking (PWSCC in the DMWs could cause significant reliability problems at nuclear power plants. Therefore, phased array ultrasound is widely used for inspecting surface break cracks and stress corrosion cracks in DMWs. However, inspection of DMWs using phased array ultrasound has a relatively low probability of detection of cracks, because the crystalline structure of welds causes distortion and splitting of the ultrasonic beams which propagates anisotropic medium. Therefore, advanced evaluation techniques of phased array ultrasound are needed for improvement in the probability of detection of flaws in DMWs. Thus, in this study, an investigation of focusing and steering phased array ultrasound in DMWs was carried out using a time reversal technique, and an adaptive focusing technique based on finite element method (FEM simulation. Also, evaluation of focusing performance of three different focusing techniques was performed by comparing amplitude of phased array ultrasonic signals scattered from the targeted flaw with three different time delays.

  14. Dissimilar metals TIG welding-brazing of aluminum alloy to galvanized steel

    Institute of Scientific and Technical Information of China (English)

    San-bao LIN; Jian-ling SONG; Guang-chao MA; Chun-li YANG

    2009-01-01

    Dissimilar metals TIG welding-brazing of aluminum alloy to galvanized steel was investigated, and the wettability and spreadability of aluminum filler metal on the steel surface were analyzed. The resultant joint was characterized in order to determine the brittle intermetallic compound (IMC) in the interfacial layer, and the mechan-ical property of the joint was tested. The results show that the zinc coated layer can improve the wettability and spreadability of liquid aluminum filler metal on the surface of the steel, and the wetting angle can reach less than 20°. The lap joint has a dual characteristic and can be divided into a welding part on the aluminum side and a brazing part on the steel side. The interfacial IMC layer in the steel side is about 9.0 μm in thickness, which transfers from (α-Al + FeAl3) in the welded seam side to (Fe2Al5+ FeAl2) and (FeAl2+ FeAl) in the steel side. The crystal grain of the welded seam is obviously larger in size in the aluminum side. The local incomplete brazing is found at the root of the lap joint, which weakens the property of the joint. The fracture of the joint occurs at the root and the average tensile strength reaches 90 MPa.

  15. Surprising dissimilarities in a newly formed pair of 'identical twin' stars.

    Science.gov (United States)

    Stassun, Keivan G; Mathieu, Robert D; Cargile, Phillip A; Aarnio, Alicia N; Stempels, Eric; Geller, Aaron

    2008-06-19

    The mass and chemical composition of a star are the primary determinants of its basic physical properties-radius, temperature and luminosity-and how those properties evolve with time. Accordingly, two stars born at the same time, from the same natal material and with the same mass, are 'identical twins,' and as such might be expected to possess identical physical attributes. We have discovered in the Orion nebula a pair of stellar twins in a newborn binary star system. Each star in the binary has a mass of 0.41 +/- 0.01 solar masses, identical to within 2 per cent. Here we report that these twin stars have surface temperatures differing by approximately 300 K ( approximately 10 per cent) and luminosities differing by approximately 50 per cent, both at high confidence level. Preliminary results indicate that the stars' radii also differ, by 5-10 per cent. These surprising dissimilarities suggest that one of the twins may have been delayed by several hundred thousand years in its formation relative to its sibling. Such a delay could only have been detected in a very young, definitively equal-mass binary system. Our findings reveal cosmic limits on the age synchronization of young binary stars, often used as tests for the age calibrations of star-formation models.

  16. Effect of Shoulder Size on Weld Properties of Dissimilar Metal Friction Stir Welds

    Science.gov (United States)

    Akinlabi, E. T.

    2012-07-01

    This article reports a research study that shows the effect of shoulder diameter size on the resulting weld properties of dissimilar friction stir welds between 5754 aluminum alloy (AA) and C11000 copper (Cu). Welds were produced using three different shoulder diameter tools: 15, 18, and 25 mm by varying the rotational speed between 600 and 1200 rpm and the traverse speed between 50 and 300 mm/min to achieve the best result. Each parameter combination was chosen to represent different heat input conditions (low, intermediates and high). The welds were characterized through microstructural evaluation, tensile testing, microhardness measurements, x-ray diffraction analysis, and electrical resistivity. Microstructural evaluation of the welds revealed that the welds produced consisted of all the friction stir welding (FSW) microstructure zones with organized flow lines comprising mixture layers of aluminum (Al) and copper (Cu) at the Stir Zones. The average Ultimate Tensile Strength (UTS) of the welds considered ranged from 178 to 208 MPa. Higher Vickers microhardness values were measured at the joint interfaces of all the welds because of the presence of intermetallic compounds in these regions. The x-ray diffraction analysis revealed the presence of Al4Cu9 and Al2Cu intermetallics at the interfacial regions, and low electrical resistivities were obtained at the joint interfaces. An optimized parameter setting for FSW of Al and Cu was obtained at the weld produced at 950 rpm and 50 mm/min with the 18-mm shoulder diameter tool.

  17. Conformational similarities and dissimilarities between the stereoisomeric forms of endomorphin-2.

    Science.gov (United States)

    Leitgeb, Balázs

    2012-03-01

    In this study, taking into account both the l-d and cis-trans isomerisms, a comprehensive structural characterization and a comparative conformational analysis were performed on the 32 stereoisomeric forms of opioid tetrapeptide, endomorphin-2. For all stereoisomers, the Φ-Ψ and χ conformational spaces were explored, in the course of which the conformational distributions, as well as the rotamer states of aromatic side chains were characterized in detail. Furthermore, the typical β- and γ-turn structures, as well as the characteristic intramolecular interactions (i.e., H-bonds, aromatic-aromatic and proline-aromatic interplays) were determined. The afore-mentioned structural and conformational features identified for each stereoisomeric form were compared with one another, considering all 32 stereoisomers. The results obtained from this comparative study indicated that both similarities and dissimilarities could be observed between the stereoisomeric forms, with regard to their structural and conformational properties. This theoretical work supplied several valuable observations concerning the effects of both l-d and cis-trans isomerisms on the three-dimensional structure of parent peptide and its stereoisomers. Nevertheless, in the course of this structural investigation, it was clarified how the structural and conformational features of stereoisomeric forms differed from one another.

  18. THE ELASTIC FIELD CASED BY TWO INCLUSIONS WITH UNI-FORM DILATATIONAL EIGENSTRAINS IN DISSIMILAR MEDIA

    Institute of Scientific and Technical Information of China (English)

    YU; Jia-huan(

    2001-01-01

    [1]Guell D L, Dundurs J. Further results on center of dilatation and residual stresses in joined elastic half-spaces[A]. Developments in theoretical and applied mechanics, Vol.3 [C]. Oxford: Pergamon Press, Oxford,1967.105~115.[2]Mindlin R D, Cheng D H. Thermoealstic stress in the semi-infinite solid[J]. J Appl Phys, 1950,21:931~933.[3]Seo T, Mura T. The elastic field in a half space due to ellipsoidal inclusions with uniform dilatational eigenstrains[J].J Appl Mech,1979,46:568~572.[4]Yu H Y, Sandy S C. Thermoelastic stresses in bimaterials[J]. Phil Mag A, 1992,65:1049~1064.[5]Korsunsky A M. An axisymmetric inclusion in one of two perfectly bonded dissimilar elastic half[J]. J Appl Mech, 1998,64:697~700.[6]Walpole L J. An elastci singularity in joined half spaces[J]. Int J Engng Sci, 1996,34(6):619~638.

  19. Effect of Interfacial Reaction on the Mechanical Performance of Steel to Aluminum Dissimilar Ultrasonic Spot Welds

    Science.gov (United States)

    Xu, Lei; Wang, Li; Chen, Ying-Chun; Robson, Joe D.; Prangnell, Philip B.

    2016-01-01

    The early stages of formation of intermetallic compounds (IMC) have been investigated in dissimilar aluminum to steel welds, manufactured by high power (2.5 kW) ultrasonic spot welding (USW). To better understand the influence of alloy composition, welds were produced between a low-carbon steel (DC04) and two different aluminum alloys (6111 and 7055). The joint strengths were measured in lap shear tests and the formation and growth behavior of IMCs at the weld interface were characterized by electron microscopy, for welding times from 0.2 to 2.4 seconds. With the material combinations studied, the η (Fe2Al5) intermetallic phase was found to form first, very rapidly in the initial stage of welding, with a discontinuous island morphology. Continuous layers of η and then θ (FeAl3) phase were subsequently seen to develop on extending the welding time to greater than 0.7 second. The IMC layer formed in the DC04-AA7055 combination grew thicker than for the DC04-AA6111 welds, despite both weld sets having near identical thermal histories. Zinc was also found to be dissolved in the IMC phases when welding with the AA7055 alloy. After post-weld aging of the aluminum alloy, fracture in the lap shear tests always occurred along the joint interface; however, the DC04-AA6111 welds had higher fracture energy than the DC04-AA7055 combination.

  20. A Numerical Simulation for Dissimilar Aluminum Alloys Joined by Friction Stir Welding

    Science.gov (United States)

    Hamilton, Carter; Kopyściański, Mateusz; Węglowska, Aleksandra; Dymek, Stanisław; Pietras, Adam

    2016-09-01

    Dissimilar aluminum alloy sheets of 2017A-T451 and 7075-T651 (6 mm thickness) were friction stir welded in a butt weld configuration. A numerical simulation of the joining process was developed to visualize the material flow patterns and temperature distribution and to correlate the microstructure to the hardness behavior. Due to the complementary downward flow of surface material into the workpiece thickness and upward flow of mid-plane and bottom-plane material, the weld nugget is composed of alternating layers of 7075 and 2017A. These layers have unique temperature histories depending on the material's initial location within the cross section; therefore, they also have distinctive precipitate distributions. Supersaturated surface material flows into the process zone and forms a core in which GP zones reprecipitate upon cooling. Mid-plane and bottom-plane material flow toward the workpiece surface and encompass the surface material core. Within this region, the weld temperatures overage the equilibrium θ phase in 2017A, decreasing the hardness, and at the same time, dissolve the equilibrium η/ T phase in the 7075, leading to reprecipitation of GP zones upon cooling and a hardness recovery.

  1. Active fault tolerant control for vertical tail damaged aircraft with dissimilar redundant actuation system

    Institute of Scientific and Technical Information of China (English)

    Wang Jun; Wang Shaoping; Wang Xingjian; Shi Cun; Mileta M. Tomovic

    2016-01-01

    This paper proposes an active fault-tolerant control strategy for an aircraft with dissim-ilar redundant actuation system (DRAS) that has suffered from vertical tail damage. A damage degree coefficient based on the effective vertical tail area is introduced to parameterize the damaged flight dynamic model. The nonlinear relationship between the damage degree coefficient and the corresponding stability derivatives is considered. Furthermore, the performance degradation of new input channel with electro-hydrostatic actuator (EHA) is also taken into account in the dam-aged flight dynamic model. Based on the accurate damaged flight dynamic model, a composite method of linear quadratic regulator (LQR) integrating model reference adaptive control (MRAC) is proposed to reconfigure the fault-tolerant control law. The numerical simulation results validate the effectiveness of the proposed fault-tolerant control strategy with accurate flight dynamic model. The results also indicate that aircraft with DRAS has better fault-tolerant control ability than the traditional ones when the vertical tail suffers from serious damage.

  2. Numerical Simulation of the Inertia Friction Welding Process of Dissimilar Materials

    Science.gov (United States)

    El-Hadek, Medhat A.

    2014-12-01

    Three-dimensional axisymmetric finite element analyses have been performed to analyze the coupled thermo-mechanical oscillatory transient problem of friction welding of two dissimilar hollow cylinders. The analysis included the effect of conduction and convection heat transfer implementing three independent variables specifically the welding time, the rotational velocity, and the thrust pressure. Experimental evaluation of the non-linear copper and Aluminum 6061 stress-strain responses, the thermal conductivities, and the specific heat coefficients were conducted using an environmental-controlled compartment for at least four different temperatures. These results were incorporated in the finite element model calculating a real joint transient temperature distribution and a full field view of the residual stresses in weldment. Variables of angular rotational velocity of (200, 400, and 600 rpm), thrust pressure of (10E5, 10E6, and 10E7 Pa), and total welding time of (1, 2, and 4 seconds) were used in the model simulation. The optimum welding conditions were selected using Taguchi method. Finally, the deformation shape predicted by the finite element simulations was compared to the deformations obtained by the experimental results.

  3. Does health status explain gender dissimilarity in healthcare use among older adults?

    Directory of Open Access Journals (Sweden)

    Sandhi Maria Barreto

    2006-02-01

    Full Text Available This study investigates the extent to which gender dissimilarity in healthcare use in later life is explained by variation in health and social-economic statuses. It is based on a nationwide sample in Brazil of 12,757 men and 16,186 women aged 60+ years. Individuals with great difficulties or unable to perform at least one daily living activity and/or to walk 100m were classified as "established disability". Those who had interrupted their activities in the previous 15 days because of a health problem were regarded as "temporarily disabled". The remaining we classified as "healthy". These categories were analyzed by multinomial logistic regression, taking "healthy" as the reference category. Prevalences of established disability were 6% among men and 11% among women. Temporary disabilities were 7.9% and 10.1%, respectively. Poor health status was associated with increased use of healthcare among men and women, but men and women differed significantly in relation to use pattern after adjustment for age, health status, and income. Older women were greater consumers of outpatient services and older men of inpatient care.

  4. Environmentally assisted cracking behavior of dissimilar metal weldments in simulated BWR coolant environments

    Science.gov (United States)

    Huang, J. Y.; Chiang, M. F.; Jeng, S. L.; Huang, J. S.; Kuo, R. C.

    2013-01-01

    The environmentally assisted cracking behavior of dissimilar metal (DM) welds, including Alloy 52-A 508 and Alloy 82-A508, under simulated BWR coolant conditions was studied. Effects of postweld heat treatment and sulfur content of the base metal on the corrosion fatigue and SCC growth rates of DM welds were evaluated. The crack growth rates for the DM weld heat-treated at 621 °C for 24 h were observed to be faster than those for the as-welded. But the DM weld heat-treated at 621 °C for 8 h + 400 °C for 200 h showed better SCC resistance than the as-welded. The longer the heat treatment at 621 °C, the higher the chromium carbides density along the grain boundary was observed. Sulfur could diffuse out of the base metal and segregate along the grain boundaries of the dilution zone, leading to weakening the grain boundary strength and the SCC resistance of the Alloy 52-A508 weld.

  5. Creep behaviour and microstructural evolution in P23/P91 dissimilar welds

    Energy Technology Data Exchange (ETDEWEB)

    Vodarek, V. [Technical Univ. of Ostrava (Czech Republic); Kubon, Z.; Strilkova, L. [MATERIALS AND METALLURGICAL RESEARCH Ltd., Ostrava (Czech Republic); Hainsworth, S.V. [Leicester Univ. (United Kingdom). Dept. of Engineering

    2010-07-01

    The structural integrity of welded components operated at elevated temperatures is of key importance in power plant applications. Long-term creep exposure of dissimilar welds is accompanied by redistribution of interstitial elements which strongly affects microstructural evolution in the vicinity of the fusion zone between low and high alloy materials. This paper summarises results of studies on creep rupture properties and minor phase evolution in the P23/P71 heterogeneous welds duing creep exposure at 500, 550 and 600 C for durations exceeding 60 000 hours. The composition of filler material in Weld A corresponded to that of P91 steel, whilst for Weld B the low alloy filler material of P23 type composition was used. Results of creep rupture tests on the cross weld specimens are close to, or slightly below, the lower limit of the {+-}20% scatter band around the standardized curve for creep strength of the P23 steel. Experimental data on microstructural evolution have been compared with results of thermodynamic and kinetic simulations. The predicted minor phase evolution close to the P23/P91 interface was confirmed by microstructural investigations. Some differences between calculations and experimental studies were found for the P23 steel. It was demonstrated that undissolved fine MX particles in the partly decarburized zone of the P23 (WM23) steel significantly delayed recrystallization of the bainitic matrix. (orig.)

  6. Tree diversity promotes functional dissimilarity and maintains functional richness despite species loss in predator assemblages.

    Science.gov (United States)

    Schuldt, Andreas; Bruelheide, Helge; Durka, Walter; Michalski, Stefan G; Purschke, Oliver; Assmann, Thorsten

    2014-02-01

    The effects of species loss on ecosystems depend on the community's functional diversity (FD). However, how FD responds to environmental changes is poorly understood. This applies particularly to higher trophic levels, which regulate many ecosystem processes and are strongly affected by human-induced environmental changes. We analyzed how functional richness (FRic), evenness (FEve), and divergence (FDiv) of important generalist predators-epigeic spiders-are affected by changes in woody plant species richness, plant phylogenetic diversity, and stand age in highly diverse subtropical forests in China. FEve and FDiv of spiders increased with plant richness and stand age. FRic remained on a constant level despite decreasing spider species richness with increasing plant species richness. Plant phylogenetic diversity had no consistent effect on spider FD. The results contrast with the negative effect of diversity on spider species richness and suggest that functional redundancy among spiders decreased with increasing plant richness through non-random species loss. Moreover, increasing functional dissimilarity within spider assemblages with increasing plant richness indicates that the abundance distribution of predators in functional trait space affects ecological functions independent of predator species richness or the available trait space. While plant diversity is generally hypothesized to positively affect predators, our results only support this hypothesis for FD-and here particularly for trait distributions within the overall functional trait space-and not for patterns in species richness. Understanding the way predator assemblages affect ecosystem functions in such highly diverse, natural ecosystems thus requires explicit consideration of FD and its relationship with species richness.

  7. Modeling of reliability and performance assessment of a dissimilar redundancy actuation system with failure monitoring

    Institute of Scientific and Technical Information of China (English)

    Wang Shaoping; Cui Xiaoyu; Shi Jian; Mileta M. Tomovic; Jiao Zongxia

    2016-01-01

    Actuation system is a vital system in an aircraft, providing the force necessary to move flight control surfaces. The system has a significant influence on the overall aircraft performance and its safety. In order to further increase already high reliability and safety, Airbus has imple-mented a dissimilar redundancy actuation system (DRAS) in its aircraft. The DRAS consists of a hydraulic actuation system (HAS) and an electro-hydrostatic actuation system (EHAS), in which the HAS utilizes a hydraulic source (HS) to move the control surface and the EHAS utilizes an elec-trical supply (ES) to provide the motion force. This paper focuses on the performance degradation processes and fault monitoring strategies of the DRAS, establishes its reliability model based on the generalized stochastic Petri nets (GSPN), and carries out a reliability assessment considering the fault monitoring coverage rate and the false alarm rate. The results indicate that the proposed reli-ability model of the DRAS, considering the fault monitoring, can express its fault logical relation and redundancy degradation process and identify potential safety hazards.

  8. Structural integrity analyses for preemptive weld overlay on the dissimilar metal weld of a pressurizer nozzle

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Chin-Cheng, E-mail: cchuang@iner.gov.tw [Institute of Nuclear Energy Research, Taiwan (China); Liu, Ru-Feng [Institute of Nuclear Energy Research, Taiwan (China)

    2012-02-15

    This paper presents structural integrity analyses for preemptive weld overlay on the dissimilar metal weld (DMW) of a pressurizer nozzle in a pressurized water reactor (PWR). Based on MRP-169 and ASME Code Case N-504-2, weld overlay sizing calculation, residual stress improvement, shrinkage evaluation, fatigue crack growth and fatigue usage analysis are performed. The weld overlay procedure has to be confirmed to improve the residual stresses around the inside surface of DMW. The residual compressive stress distribution is thus addressed to be resistant to subsequent primary water stress corrosion cracking (PWSCC) initiation and further crack growth. To ensure the structural integrity of the original attached piping system, the measured displacement is transformed to temperature gradient to simulate the shrinkage after overlay and is used to determine the post weld distortion and stress situation. Further, the conservative postulated surface cracks are assumed in the DMW for fatigue crack growth analysis with system design cycles. The stress limits and cumulative fatigue usages of the pressurizer nozzle with overlay are also evaluated to meet ASME Code, Section III. Based on the present results, the structural integrity of the pressurizer nozzle with preemptive weld overlay is shown.

  9. Studies of residual stress measurement and analysis techniques for a PWR dissimilar weld joint

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Naoki, E-mail: naoki2_ogawa@mhi.co.jp [Mitsubishi Heavy Industries, Ltd., 2-1-1, Shinhama, Arai-cho, Takasago 676-8686 (Japan); Muroya, Itaru; Iwamoto, Youichi; Ohta, Takahiro; Ochi, Mayumi; Hojo, Kiminobu [Mitsubishi Heavy Industries, Ltd., 2-1-1, Shinhama, Arai-cho, Takasago 676-8686 (Japan); Ogawa, Kazuo [Japan Nuclear Energy Safety Organization, 3-17-1, Toranomon, Minato-ku, Tokyo 105-0001 (Japan)

    2012-02-15

    For evaluation of the PWSCC crack propagation behavior, a test model was produced using the same fabrication process of Japanese PWR plants and the stress distribution change was measured during a fabrication process such as a hydrostatic test, welding a main coolant pipe to the stainless steel safe end and an operation condition test. For confirmation of validity of the numerical estimation method of the stress distribution, FE analysis was performed to calculate the stress distributions for each fabrication process. From the validation procedure, a standard residual stress evaluation method was established. Furthermore for consideration of characteristics of PWSCC's propagation behavior of the dissimilar welding joint of the safe end nozzles, the influence coefficients at the deepest point for the stress intensity factors of axial cracks with large aspect ratio a/c (crack depth/half of surface crack length) was prepared. The crack shape was assumed a rectangular shape and the stress intensity factors at the deepest point of the crack were calculated with change of crack depth using FE analysis. By using these stress distribution and influence coefficients, a behavior of a PWSCC crack propagation at the safe end nozzles can be estimated easily and rationally.

  10. Residual stress measurements in the dissimilar metal weld in pressurizer safety nozzle of nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Wagner R.C.; Rabello, Emerson G.; Mansur, Tanius R.; Scaldaferri, Denis H.B.; Paula, Raphael G., E-mail: wrcc@cdtn.br, E-mail: egr@cdtn.br, E-mail: tanius@cdtn.br, E-mail: dhbs@cdtn.br, E-mail: tanius@cdtn.br, E-mail: raphaelmecanica@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Souto, Joao P.R.S.; Carvalho Junior, Ideir T., E-mail: joprocha@yahoo.com.br, E-mail: ideir_engenharia@yahoo.com.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Metalurgica

    2013-07-01

    Weld residual stresses have a large influence on the behavior of cracking that could possibly occur under normal operation of components. In case of an unfavorable environment, both stainless steel and nickel-based weld materials can be susceptible to stress-corrosion cracking (SCC). Stress corrosion cracks were found in dissimilar metal welds of some pressurized water reactor (PWR) nuclear plants. In the nuclear reactor primary circuit the presence of tensile residual stress and corrosive environment leads to so-called Primary Water Stress Corrosion Cracking (PWSCC). The PWSCC is a major safety concern in the nuclear power industry worldwide. PWSCC usually occurs on the inner surface of weld regions which come into contact with pressurized high temperature water coolant. However, it is very difficult to measure the residual stress on the inner surfaces of pipes or nozzles because of inaccessibility. A mock-up of weld parts of a pressurizer safety nozzle was fabricated. The mock-up was composed of three parts: an ASTM A508 C13 nozzle, an ASTM A276 F316L stainless steel safe-end, an AISI 316L stainless steel pipe and different filler metals of nickel alloy 82/182 and AISI 316L. This work presents the results of measurements of residual strain from the outer surface of the mock-up welded in base metals and filler metals by hole-drilling strain-gage method of stress relaxation. (author)

  11. A round-robin analysis of temperature and residual stresses in dissimilar metal weld

    Energy Technology Data Exchange (ETDEWEB)

    Song, Min Sup; Kang, Sun Ye; Park, June Soo; Sohn, Gap Heon [Korea Power Engineering Company, Inc., Daejeon (Korea, Republic of)

    2008-07-01

    DMWs are common feature of the PWR in the welded connections between carbon steel and stainless steel piping. The nickel-based weld metal, Alloy 82/182, is used for welding the dissimilar metals and is known to be susceptible to PWSCC. A round-robin program has been implemented to benchmark the numerical simulation of the transient temperature and weld residual stresses in the DMWs. To solve the round-robin problem related to pressurizer safety and relief nozzle, the thermal elasto-plastic analysis is performed in the DMW by using the FEM. The welding includes both the DMW of the nozzle to safe-end and the SMW of the safe-end and piping. Major results of the analyses are discussed: The axial and circumferential residual stresses are found to be -88MPa(225MPa) and -38MPa(293MPa) on the inner surface of the DMW; where the values in parenthesis are the residual stresses after the DMW. Thermo-mechanical interaction by the SMW has a significant effect on the residual stress fields in the DMW.

  12. Local fracture properties and dissimilar weld integrity in nuclear power plants

    Science.gov (United States)

    Wang, Guozhen; Wang, Haitao; Xuan, Fuzhen; Tu, Shantung; Liu, Changjun

    2013-09-01

    In this paper, the local fracture properties in a Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316 L stainless steel in nuclear power plants were investigated by using the single-edge notched bend (SENB) specimens, and their use in integrity assessment of DMWJ structures was analyzed. The results show that the local fracture resistance in the DMWJ is determined by local fracture mechanism, and which is mainly related to the microstructures and local strength mismatches of materials at the crack locations. The initial cracks always grow towards the materials with lower strength, and the crack path deviation is mainly controlled by the local strength mismatch. If the local fracture properties could not be used for cracks in the heat affected zones (HAZs), interface and near interface zones, the use of the fracture properties ( J-resistance curves) of base metals or weld metals following present codes will unavoidably produce non-conservative (unsafe) or excessive conservative assessment results. In most cases, the assessment results will be potentially unsafe. Therefore, it is recommended to obtain and use local mechanical and fracture properties in the integrity assessment of DMWJs.

  13. Spot Welding Parameter Optimization to Improve Weld Characteristics for Dissimilar Metals

    Directory of Open Access Journals (Sweden)

    Aravinthan Arumugam

    2015-01-01

    Full Text Available Abstract Resistance spot welding is a process which is widely used in the automotive industry to join steel parts of various thicknesses and types. The current practice in the automotive industry in determining the welding schedule which will be used in the welding process is based on welding table or experiences. This however may not be the optimum welding schedule that will give the best spot weld quality. This work concentrates on the parameter optimization when spot welding steels with dissimilar thickness and type using Grey Based Taguchi Method. The experimentation in this work used a L9 orthogonal array with three factors with each factor having three levels. The three factors used are welding current weld time and electrode force. The three weld characteristics that were optimized are weld strength weld nugget diameter and weld indentation. The analysis of variance ANOVA that was carried out showed that welding current gave the most significant contribution in the optimum welding schedule. The comparison test that was carried out to compare the current welding schedule and the optimum welding schedule showed distinct improvement in the increase of weld diameter and weld strengthas well as decrease in electrode indentation.

  14. Experimental analysis of dissimilar metal weld joint: Ferritic to austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Rathod, Dinesh W., E-mail: dineshvrathod@gmail.com [Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi 110016 (India); Pandey, Sunil [Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi 110016 (India); Singh, P.K. [Bhabha Atomic Research Centre, Mumbai 400085 (India); Prasad, Rajesh [Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2015-07-15

    The dissimilar metal weld (DMW) joint between SA508Gr.3Cl.1 ferritic steel and SS304LN using Inconel 82/182 consumables was required in the nuclear power plants. The joint integrity assessment of these welds requires mechanical and metallurgical properties evaluation in weldment regions. The joint was subjected to 100% radiography test and bend test and transverse tensile test. Welding and testing were carried out as per the requirements of ASME Sec-IX and acceptance criteria as per ASME Sec-III. The transverse tensile test results indicated the failure from the weld metal although it satisfies the minimum strength requirement of the ASME requirements; therefore, the DMW joint was analyzed in detail. Straight bead deposition technique, fine slag inclusion, less reliable radiograph technique, plastic instability stress, yield strength ratio and metallurgical deteriorations have been contributed to failure of the DMW joint from the weld region. In the present work, the factors contributing to the fracture from weld metal have been discussed and analyzed.

  15. Development of ultrasonic testing method of dissimilar metal transition joints by hot roll bonding

    Energy Technology Data Exchange (ETDEWEB)

    Hoshino, Ikuji; Fujisawa, Kazuo; Yamaguchi, Hisao [Sumitomo Metal Industries Ltd., Osaka (Japan); Nagai, Takayuki; Takeda, Seiichiro

    1996-03-01

    An ultrasonic inspection method for detection of debonding in a clad pipe was investigated. The clad pipe is composed of outer side stainless steel (SUS), inner side titanium alloy (Ti) and intermediate tantalum foil (Ta) 0.05 to 0.2mm in thickness. The clad pipe is machined to dissimilar metal transition tubular joints which are used in a nuclear fuel reprocessing plant. The ultrasonic echoes from sound bonding and debonding areas were calculated by combining echoes from SUS-Ta and Ti-Ta interfaces, and multiple reflection echoes in Ta foil, considering the reflection coefficient at each interface. The influence of multiple reflection echoes in Ta foil was also evaluated. The effects of center frequency and band width of ultrasonic pulse and inspection direction were analysed from the calculation results. The effect of inspection direction considering the pipe shift was also evaluated from the experiment. The determinations showed that inspection from the inner side of a pipe with a broad frequency band probe of 12 to 20 MHz is optimum. A test specimen with artificial defects 1 mm in diameter and specimens with a debonding area made by rolling oxidized material were inspected by the determined test condition. Findings allowed discrimination of the echoes from debonding boundaries from those from sound bonding boundaries. (author).

  16. Evidence for Submarine Groundwater Discharge into the Black Sea—Investigation of Two Dissimilar Geographical Settings

    Directory of Open Access Journals (Sweden)

    Michael Schubert

    2017-06-01

    Full Text Available The sustainable management of coastal marine environments requires a comprehensive understanding of the processes related to material transport from land to coastal sea. Besides surface water discharge (e.g., rivers and storm drains, submarine groundwater discharge (SGD plays a key role since it provides a major pathway for solute and particulate transport of contaminants and nutrients, both having considerable potential to cause deterioration of the overall ecological status of coastal environments. The aim of the presented study was the investigation of SGD in two exemplary and dissimilar areas at the Black Sea coast, one in the west (Romania and one in the east (Georgia. The approach included the assessment of the geological/geographical setting regarding the potential of SGD occurrence, the use of environmental tracer data (222Rn, δ18O, δ2H, salinity, and the evaluation of sea surface temperature patterns near the coastline using satellite data. Besides the individual site specific results, the study revealed that a combined evaluation of tracer data and satellite based information allows SGD localization with satisfying precision. A downscaling approach starting with large scale satellite data is generally recommended, continuing with medium scale tracer patterns and ending with local spot sampling.

  17. Software architecture for a kinematically dissimilar master-slave telethesis for exploring rehabilitation applications

    Science.gov (United States)

    Wunderlich, Joseph; Chen, Shoupu; Pino, D.; Rahman, Tariq; Harwin, William S.

    1993-12-01

    A person with limited arm and hand function could benefit from technology based on teleoperation principles, particularly where the mechanism provides proprioceptive-like information to the operator giving an idea of the forces encountered in the environment and the positions of the slave r