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Segregation Patterns (segregation + pattern)
Selected AbstractsSegregation patterns of AFLP markers in F1 hybrids of a cross between tetraploid and diploid species in the genus MalusPLANT BREEDING, Issue 4 2004Y. H. Li Abstract Malus xiaojinensis, one of the most important wild genotypes in the genus Malus, is resistant to a variety of stresses such as Fe deficiency chlorosis, drought and cold. However, lack of knowledge of its genetic background prevents using genetic analysis to study those agronomic traits and corresponding gene functions. Here, as the first step towards construction of the linkage map of M. xiaojinensis, genetic analysis of the F1 triploid hybrids (M. xiaojinensis × M. baccata) was performed with amplified fragment length polymorphism (AFLP) markers. Using 15 EcoRI- MseI primer combinations, 1110 AFLPs were identified, with 31.3% of M. xiaojinensis -, 12.7% of M. baccata-specific markers, 54.9% of common markers, and 1.2% of non-parental markers; 93.3% of the AFLP markers exhibit the expected segregation ratio. Thirty-two M. xiaojinensis -specific markers and 47 common markers display a 5 : 1 and 11:1 segregation ratios, respectively, suggesting that M. xiaojinensis is an autotetraploid, or at least an isosyndetic allotetraploid. [source] Analysis of the effect of particle size distributions on the fluid dynamic behavior and segregation patterns of fluidized, vibrated and vibrofluidized bedsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2007Roger Valeri Daleffe Abstract In this work, the effects of particle size distribution on the dynamics and segregation patterns in fluidized, vibrated and vibrofluidized beds were investigated. Four particle size distributions composed of glass spheres were tested: binary, flat, Gaussian and a reference one, all of them with a mean Sauter diameter equal to 2.18 × 10,3 m. The experimental setup consisted basically of a circular glass chamber with a height of 0.50 m and diameter of 0.114 m and was operated in different modes: as a fluidized bed (, = 0), or either as vibrated or vibrofluidized beds (, = 2). The pressure drops in the fluidized and vibrofluidized beds were not significantly affected by the particle size distributions. Well-defined segregation patterns were observed in fluidized and vibrated beds, with the small particles concentrated at the top and the large particles at the bottom in the fluidized bed, and with a reversed pattern in the vibrated bed. Segregation patterns in the vibrofluidized bed depended on the values of the vibration parameters. Segregation in vibrofluidized and vibrated beds was minimized by operating at high amplitudes of vibration. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Granular mixing and segregation in a horizontal rotating drum: A simulation study on the impact of rotational speed and fill levelAICHE JOURNAL, Issue 12 2008M. M. H. D. Arntz Abstract The rich phase behavior of granular beds of bidisperse hard spherical particles in a rotating horizontal drum is studied by Discrete Element Method (DEM) simulations. Several flow regimes and various forms of radial segregation, as well as mixing, are observed by systematically varying the operational parameters of the drum, i.e. fill level and angular velocity, over a wide range. Steady states after several dozen revolutions are summarized in two bed behavior diagrams, showing strong correlations between flow regime and segregation pattern. An entropy method quantifies the overall degree of mixing, while density and velocity plots are used to analyze the local properties of the granular bed. The percolation mechanism may provide a qualitative explanation for the distinct segregation processes, and for the transient mixing in nonradially segregated beds. Initially blockwise segregated beds are found to mix before radial segregation sets in. High fill fractions (>65%) show the most intense segregation. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Mechanisms influencing the evolution of resistance to Qo inhibitor fungicides,,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2002Ulrich Gisi Abstract Fungicides inhibiting the mitochondrial respiration of plant pathogens by binding to the cytochrome bc1 enzyme complex (complex III) at the Qo site (Qo inhibitors, QoIs) were first introduced to the market in 1996. After a short time period, isolates resistant to QoIs were detected in field populations of a range of important plant pathogens including Blumeria graminis Speer f sp tritici, Sphaerotheca fuliginea (Schlecht ex Fr) Poll, Plasmopara viticola (Berk & MA Curtis ex de Bary) Berl & de Toni, Pseudoperonospora cubensis (Berk & MA Curtis) Rost, Mycosphaerella fijiensis Morelet and Venturia inaequalis (Cooke) Wint. In most cases, resistance was conferred by a point mutation in the mitochondrial cytochrome b (cyt b) gene leading to an amino-acid change from glycine to alanine at position 143 (G143A), although additional mutations and mechanisms have been claimed in a number of organisms. Transformation of sensitive protoplasts of M fijiensis with a DNA fragment of a resistant M fijiensis isolate containing the mutation yielded fully resistant transformants, demonstrating that the G143A substitution may be the most powerful transversion in the cyt b gene conferring resistance. The G143A substitution is claimed not to affect the activity of the enzyme, suggesting that resistant individuals may not suffer from a significant fitness penalty, as was demonstrated in B graminis f sp tritici. It is not known whether this observation applies also for other pathogen species expressing the G143A substitution. Since fungal cells contain a large number of mitochondria, early mitotic events in the evolution of resistance to QoIs have to be considered, such as mutation frequency (claimed to be higher in mitochondrial than nuclear DNA), intracellular proliferation of mitochondria in the heteroplasmatic cell stage, and cell to cell donation of mutated mitochondria. Since the cyt b gene is located in the mitochondrial genome, inheritance of resistance in filamentous fungi is expected to be non-Mendelian and, therefore, in most species uniparental. In the isogamous fungus B graminis f sp tritici, crosses of sensitive and resistant parents yielded cleistothecia containing either sensitive or resistant ascospores and the segregation pattern for resistance in the F1 progeny population was 1:1. In the anisogamous fungus V inaequalis, donation of resistance was maternal and the segregation ratio 1:0. In random mating populations, the sex ratio (mating type distribution) is generally assumed to be 1:1. Therefore, the overall proportion of sensitive and resistant individuals in unselected populations is expected to be 1:1. Evolution of resistance to QoIs will depend mainly on early mitotic events; the selection process for resistant mutants in populations exposed to QoI treatments may follow mechanisms similar to those described for resistance controlled by single nuclear genes in other fungicide classes. It will remain important to understand how the mitochondrial nature of QoI resistance and factors such as mutation, recombination, selection and migration might influence the evolution of QoI resistance in different plant pathogens. © 2002 Society of Chemical Industry [source] Inheritance of reduced plant height in the sunflower line Dw 89PLANT BREEDING, Issue 5 2003L. Velasco Abstract The objective of the present research was to study the inheritance of reduced plant height in the sunflower line Dw 89. Plants of the cytoplasmic male sterile version of this line, cmsDw 89 (mean plant height of 47.4 cm) were crossed with plants of the restorer line RHA 271 (mean of 120.9 cm). F1 plants averaged 120.4 cm, which indicated dominance of standard over reduced plant height. F2 plants followed a segregation pattern of 1 : 15 (reduced : normal height), suggesting that reduced plant height in Dw 89 is controlled by alleles at two loci, designated Dw1 and Dw2. Class assignment in the F2 was confirmed through the evaluation of the F3 generation. Backcrosses to Dw 89 segregated with 1 : 3 (reduced : normal height) ratios, which confirmed the digenic inheritance of the trait. The evaluation of plant height distributions in F3 families suggested possible genetic interaction between the Dw1 and Dw2 loci. [source] An Economic Model of Friendship: Homophily, Minorities, and SegregationECONOMETRICA, Issue 4 2009Sergio Currarini We develop a model of friendship formation that sheds light on segregation patterns observed in social and economic networks. Individuals have types and see type-dependent benefits from friendships. We examine the properties of a steady-state equilibrium of a matching process of friendship formation. We use the model to understand three empirical patterns of friendship formation: (i) larger groups tend to form more same-type ties and fewer other-type ties than small groups, (ii) larger groups form more ties per capita, and (iii) all groups are biased towards same-type relative to demographics, with the most extreme bias coming from middle-sized groups. We show how these empirical observations can be generated by biases in preferences and biases in meetings. We also illustrate some welfare implications of the model. [source] Sex ratio, reproductive mode and genetic diversity in Triops cancriformisFRESHWATER BIOLOGY, Issue 7 2009THORID ZIEROLD Summary 1. Aquatic invertebrates display a wide array of alternative reproductive modes from apomixis to hermaphroditism and cyclical parthenogenesis. These have important effects on genetic diversity and population structure. Populations of the ,living fossil'Triops cancriformis display a range of sex ratios, and various reproductive modes are thought to underlie this variation. Using sex ratio information and histological analyses European populations have been inferred to be gonochoric (with separate males and females), selfing hermaphroditic and androdioecious, a rare reproductive mode in which selfing hermaphrodites coexist with variable proportions of males. In addition, some populations have been described as meiotic parthenogens. 2. Here we use population genetic analysis using microsatellite loci in populations with a range of sex ratios including a gonochoric population, and marker segregation patterns in heterozygote individuals reared in isolation, to clarify the reproductive mode in this species. 3. Our data show that populations in general have very low levels of genetic diversity. Non-gonochoric populations show lower genetic diversity, more heterozygote deficiencies, higher inbreeding coefficients and stronger linkage disequilibria than the gonochoric population. The maintenance of some heterozygosity in populations is consistent with some male influence in T. cancriformis populations, as would be expected from an androdioecious reproductive system. Results of marker segregation in eggs produced in isolation from non-gonochoric populations indicate that meiosis occurs and are consistent with two reproductive modes: selfing hermaphroditism and a type of ameiotic parthenogenesis. 4. Overall, our data indicate that androdioecy and selfing hermaphroditism are the most likely reproductive modes of non-gonochoric European Triops populations. Triops populations are strongly structured, suggesting high genetic drift and low levels of gene flow. [source] Divided Post-Soviet Small Cities?GEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 2 2004Kazakhstan, Residential Segregation, Urban Form in Leninogorsk, Zyryanovsk Abstract This paper maps and analyses ethnic and socio-economic residential segregation in two small post-Soviet mining and enrichment cities in Eastern Kazakhstan, Leninogorsk and Zyryanovsk. The study is based on data collected by the author in collaboration with the Eastern Kazakhstan oblast' statistical authority in an extensive questionnaire survey carried out during January 2001. The paper investigates the linkages between the physical spatial structure of small post-Soviet cities and the socio-spatial landscape that has unfolded in their context, and attempts to identify the principal factors that underlie the observed segregation patterns. [source] Vertical Social Differentiation in Athens: Alternative or Complement to Community Segregation?INTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 4 2001Thomas Maloutas Vertical social differentiation is presented in the recent literature as an important element of reduced segregation in South European cities, and the supporting evidence originates mainly from Athens. The authors of this article question the claim about the common form and function of vertical social differentiation across South Europe, as well as its opposition to community segregation, and try to reveal the specificity of the processes leading to its formation in Athens. Since the mid-1970s, the dominant process of urban growth in Athens has been middle-class suburbanization. This process has reinforced community segregation and, at the same time, has triggered a filtering-down process in wide areas around the CBD, formerly occupied by upper and mainly intermediate professional categories. Interclass vertical segregation has subsequently appeared in these areas, where intermediate professional categories and lower middle-class households are now predominant. The fact that these areas do not represent a real choice for any of their resident groups shows that this vertical cohabitation has been the unintended consequence of changing segregation patterns, and hardly the outcome or the corollary of a growing process of sociospatial homogenization. Dans les textes récents, la différenciation sociale verticale est présentée comme un facteur important dans la réduction de la ségrégation urbaine en Europe du Sud, les éléments probants provenant essentiellement d'Athènes. Cet article conteste l'idée que la différenciation sociale verticale ait une forme ou une fonction commune en Europe méridionale, et qu'elle entrave la ségrégation horizontale; de plus, il tente d'exposer la spécificité des processus qui conduisent à sa formation à Athènes. Depuis le milieu des années 1970, l'expansion urbaine de la capitale grecque se caractérise par l'implantation en banlieue des classes supérieurs et moyennes. Ce processus a renforcé la ségrégation dans les quartiers et, parallèlement, a déclenché un processus de filtrage vers le bas dans de vastes zones entourant l'hypercentre, précédemment occupées par des catégories de professionnels libéraux supérieures et surtout moyennes. Une ségrégation verticale interclasse est ensuite apparue dans ces quartiers, des catégories de libéraux moyennes et des ménages de la petite bourgeoisie y prédominant désormais. Or, quel que soit le groupe de résidents, ces zones ne représentent pas un choix réel; cette cohabitation verticale est donc bien la conséquence imprévue de la modification des schémas de ségrégation, plutôt que le résultat ou le corollaire d'une homogénéisation socio-spatiale accentuée. [source] Frequency of recombinant and nonrecombinant products of pericentric inversion of chromosome 1 in sperm nuclei of carrier: By FISH techniqueMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 1 2003Tahsin Yakut Abstract Meiotic segregation products of carriers with pericentric inversion are very important for assessing the risk of unbalanced forms and appropriate genetic counseling. We investigated the incidence of recombinant and nonrecombinant products of chromosome 1 with pericentric inversion, in the sperm nuclei of the carrier by using triple color fluorescence in situ hybridization (FISH). The centromere specific and telomere specific probes for chromosome 1 were used. In the segregation analysis, 1,636 sperm nuclei were analyzed; 82.5% of the sperms were including normal or inverted chromosome 1, and the dup(p)/del(q) and del(p)/dup(q) recombinant products in sperm nuclei of our carrier were 8.7 and 7.3%, respectively. The number of recombinant products may be dependent on the formation of an inversion loop, which the number of the formation of chiasmata results in the different number of normal/balanced and recombinant products. The use of FISH, using different probe combination, in sperm nuclei has proved to be an accurate approach to determine the meiotic segregation patterns and could help to better establish a reproductive prognosis and genetic counseling. Mol. Reprod. Dev. 66: 67,71, 2003. © 2003 Wiley-Liss, Inc. [source] Winners and losers in human-made habitats: interspecific competition outcomes in two Neotropical vulturesANIMAL CONSERVATION, Issue 4 2010M. Carrete Abstract Understanding the factors underlying species coexistence is a major focus in community ecology. When dealing with competition between native and exotic species, the competitive exclusion of the ,weaker' species can have consequences for biodiversity conservation. We examined interspecific interactions during foraging between black vultures Coragyps atratus and Andean condors Vultur gryphus in Southern Argentina. Previous studies suggest facilitatory interactions between them. However, in most parts of their distribution ranges, these species did not coexist until recently, when black vultures expanded their geographic range following human development. Thus, facilitatory processes or segregation patterns could not be fine-tuned enough to allow their coexistence. Our hypothesis is that black vultures and Andean condors compete for food resources, and that this competitive scenario can change depending on local species abundances and habitat humanization. We experimentally placed sheep carcasses in two habitats differing in degrees of humanization to study the foraging patterns in these species. Both species exploited carcasses with similar temporal patterns. However, the first to arrive and the dominant species were different in both habitats, according to their abundances. Although black vultures do not completely prevent the arrival of Andean condors to carcasses, they represent serious obstacles for feeding. Thus, while dominance hierarchy at carcasses could be related to body size, carcass consumption was determined by species abundance. Our results support the hypothesis that the expansion of a ,winning' species may trigger interspecific competition with other ,loser' species, with negative responses towards human activities when they became abundant. Although the results are not conclusive, invasion and extinction processes could be occurring and they can have serious consequences for the diversity (i.e. richness and evenness) of the New World scavenger guilds. [source] Female segregation patterns of the putative Y-chromosome-specific microsatellite markers INRA124 and INRA126 do not support their use for cattle population studiesANIMAL GENETICS, Issue 4 2009L. Pérez-Pardal Summary Here we tested the segregation and paternal compatibility of markers INRA124 and INRA126 on female DNA in 10 different cattle families, in order to clarify the usefulness of these microsatellites for the study of male-mediated population processes in cattle. Their performance was compared with that of four microsatellites located in the PAR-BTAY (UMN0108, UMN0803, UMN0929 and UMN0905) and another one male-specific microsatellite (INRA189). INRA124 and INRA126 amplified the same sized fragment in both sexes. Same size alleles were sequenced and the high homology found allowed us to rule out non-specific female amplification. INRA124 showed full parental compatibility, whilst the locus INRA126 showed 55% parental incompatibility. Based on these observations, it is recommended that markers INRA124 and INRA126 should not be used in studies to characterize male-mediated genetic events in cattle. [source] Analysis of the effect of particle size distributions on the fluid dynamic behavior and segregation patterns of fluidized, vibrated and vibrofluidized bedsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2007Roger Valeri Daleffe Abstract In this work, the effects of particle size distribution on the dynamics and segregation patterns in fluidized, vibrated and vibrofluidized beds were investigated. Four particle size distributions composed of glass spheres were tested: binary, flat, Gaussian and a reference one, all of them with a mean Sauter diameter equal to 2.18 × 10,3 m. The experimental setup consisted basically of a circular glass chamber with a height of 0.50 m and diameter of 0.114 m and was operated in different modes: as a fluidized bed (, = 0), or either as vibrated or vibrofluidized beds (, = 2). The pressure drops in the fluidized and vibrofluidized beds were not significantly affected by the particle size distributions. Well-defined segregation patterns were observed in fluidized and vibrated beds, with the small particles concentrated at the top and the large particles at the bottom in the fluidized bed, and with a reversed pattern in the vibrated bed. Segregation patterns in the vibrofluidized bed depended on the values of the vibration parameters. Segregation in vibrofluidized and vibrated beds was minimized by operating at high amplitudes of vibration. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||||||||