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Sample records for range-wide demographic expansion

  1. Recent range-wide demographic expansion in a Taiwan endemic montane bird, Steere's Liocichla (Liocichla steerii)

    PubMed Central

    2010-01-01

    Background The subtropical island of Taiwan is an area of high endemism and a complex topographic environment. Phylogeographic studies indicate that vicariance caused by Taiwan's mountains has subdivided many taxa into genetic phylogroups. We used mitochondrial DNA sequences and nuclear microsatellites to test whether the evolutionary history of an endemic montane bird, Steere's Liocichla (Liocichla steerii), fit the general vicariant paradigm for a montane organism. Results We found that while mountains appear to channel gene flow they are not a significant barrier for Steere's Liocichla. Recent demographic expansion was evident, and genetic diversity was relatively high across the island, suggesting expansion from multiple areas rather than a few isolated refugia. Ecological niche modeling corroborated the molecular results and suggested that populations of Steere's Liocichla are connected by climatically suitable habitat and that there was less suitable habitat during the Last Glacial Maximum. Conclusions Genetic and ecological niche modeling data corroborate a single history--Steere's Liocichla was at lower density during the Last Glacial Maximum and has subsequently expanded in population density. We suggest that such a range-wide density expansion might be an overlooked cause for the genetic patterns of demographic expansion that are regularly reported. We find significant differences among some populations in FST indices and an admixture analysis. Though both of these results are often used to suggest conservation action, we affirm that statistically significant results are not necessarily biologically meaningful and we urge caution when interpreting highly polymorphic data such as microsatellites. PMID:20219124

  2. Testing the abundant center model using range-wide demographic surveys of two coastal dune plants.

    PubMed

    Samis, Karen E; Eckert, Christopher G

    2007-07-01

    It is widely accepted that species are most abundant at the center of their geographic ranges and become progressively rarer toward range limits. Although the abundant center model (ACM) has rarely been tested with range-wide surveys, it influences much thinking about the ecology and evolution of species' distributions. We tested ACM predictions using two unrelated but ecologically similar plants, Camissonia cheiranthifolia and Abronia umbellata. We intensively sampled both throughout their one-dimensional distributions within the Pacific coastal dunes of North America, from northern Baja California, Mexico, to southern Oregon, USA. Data from > 1100 herbarium specimens indicated that these limits have been stable for at least the last 100 years. Range-wide field surveys detected C. cheiranthifolia at 87% of 124 sites and A. umbellata at 54% of 113 sites, but site occupancy did not decline significantly toward range limits for either species. Permutation analysis did not detect a significant fit of geographical variation in local density to the ACM. Mean density did not correlate negatively with mean individual performance (plant size or number of seeds/plant), probably because both species occur at low densities. Although size and seeds per plant varied widely, central populations tended to have the highest values for size only. For C. cheiranthifolia, we observed asymmetry in the pattern of variation between the northern and southern halves of the range consistent with the long-standing prediction that range limits are imposed by different ecological factors in different parts of the geographical distribution. However, these asymmetries were difficult to interpret and likely reflect evolutionary differentiation as well as plastic responses to ecological variation. Both density and seeds per plant contributed to variation in seed production per unit area. In C. cheiranthifolia only, sites with highest seed production tended to occur at the range center, as

  3. Range-wide multilocus phylogeography of the red fox reveals ancient continental divergence, minimal genomic exchange and distinct demographic histories.

    PubMed

    Statham, Mark J; Murdoch, James; Janecka, Jan; Aubry, Keith B; Edwards, Ceiridwen J; Soulsbury, Carl D; Berry, Oliver; Wang, Zhenghuan; Harrison, David; Pearch, Malcolm; Tomsett, Louise; Chupasko, Judith; Sacks, Benjamin N

    2014-10-01

    Widely distributed taxa provide an opportunity to compare biogeographic responses to climatic fluctuations on multiple continents and to investigate speciation. We conducted the most geographically and genomically comprehensive study to date of the red fox (Vulpes vulpes), the world's most widely distributed wild terrestrial carnivore. Analyses of 697 bp of mitochondrial sequence in ~1000 individuals suggested an ancient Middle Eastern origin for all extant red foxes and a 400 kya (SD = 139 kya) origin of the primary North American (Nearctic) clade. Demographic analyses indicated a major expansion in Eurasia during the last glaciation (~50 kya), coinciding with a previously described secondary transfer of a single matriline (Holarctic) to North America. In contrast, North American matrilines (including the transferred portion of Holarctic clade) exhibited no signatures of expansion until the end of the Pleistocene (~12 kya). Analyses of 11 autosomal loci from a subset of foxes supported the colonization time frame suggested by mtDNA (and the fossil record) but, in contrast, reflected no detectable secondary transfer, resulting in the most fundamental genomic division of red foxes at the Bering Strait. Endemic continental Y-chromosome clades further supported this pattern. Thus, intercontinental genomic exchange was overall very limited, consistent with long-term reproductive isolation since the initial colonization of North America. Based on continental divergence times in other carnivoran species pairs, our findings support a model of peripatric speciation and are consistent with the previous classification of the North American red fox as a distinct species, V. fulva.

  4. Targeted capture sequencing in Whitebark pine reveals range-wide demographic and adaptive patterns despite challenges of a large, repetitive genome

    Treesearch

    John V. Syring; Jacob A. Tennessen; Tara N. Jennings; Jill Wegrzyn; Camille Scelfo-Dalbey; Richard Cronn

    2016-01-01

    Whitebark pine (Pinus albicaulis) inhabits an expansive range in western North America, and it is a keystone species of subalpine environments. Whitebark is susceptible to multiple threats – climate change, white pine blister rust, mountain pine beetle, and fire exclusion – and it is suffering significant mortality range-wide, prompting the tree to be listed as ‘...

  5. Targeted Capture Sequencing in Whitebark Pine Reveals Range-Wide Demographic and Adaptive Patterns Despite Challenges of a Large, Repetitive Genome

    PubMed Central

    Syring, John V.; Tennessen, Jacob A.; Jennings, Tara N.; Wegrzyn, Jill; Scelfo-Dalbey, Camille; Cronn, Richard

    2016-01-01

    Whitebark pine (Pinus albicaulis) inhabits an expansive range in western North America, and it is a keystone species of subalpine environments. Whitebark is susceptible to multiple threats – climate change, white pine blister rust, mountain pine beetle, and fire exclusion – and it is suffering significant mortality range-wide, prompting the tree to be listed as ‘globally endangered’ by the International Union for Conservation of Nature and ‘endangered’ by the Canadian government. Conservation collections (in situ and ex situ) are being initiated to preserve the genetic legacy of the species. Reliable, transferrable, and highly variable genetic markers are essential for quantifying the genetic profiles of seed collections relative to natural stands, and ensuring the completeness of conservation collections. We evaluated the use of hybridization-based target capture to enrich specific genomic regions from the 27 GB genome of whitebark pine, and to evaluate genetic variation across loci, trees, and geography. Probes were designed to capture 7,849 distinct genes, and screening was performed on 48 trees. Despite the inclusion of repetitive elements in the probe pool, the resulting dataset provided information on 4,452 genes and 32% of targeted positions (528,873 bp), and we were able to identify 12,390 segregating sites from 47 trees. Variations reveal strong geographic trends in heterozygosity and allelic richness, with trees from the southern Cascade and Sierra Range showing the greatest distinctiveness and differentiation. Our results show that even under non-optimal conditions (low enrichment efficiency; inclusion of repetitive elements in baits), targeted enrichment produces high quality, codominant genotypes from large genomes. The resulting data can be readily integrated into management and gene conservation activities for whitebark pine, and have the potential to be applied to other members of 5-needle pine group (Pinus subsect. Quinquefolia) due to

  6. Targeted Capture Sequencing in Whitebark Pine Reveals Range-Wide Demographic and Adaptive Patterns Despite Challenges of a Large, Repetitive Genome.

    PubMed

    Syring, John V; Tennessen, Jacob A; Jennings, Tara N; Wegrzyn, Jill; Scelfo-Dalbey, Camille; Cronn, Richard

    2016-01-01

    Whitebark pine (Pinus albicaulis) inhabits an expansive range in western North America, and it is a keystone species of subalpine environments. Whitebark is susceptible to multiple threats - climate change, white pine blister rust, mountain pine beetle, and fire exclusion - and it is suffering significant mortality range-wide, prompting the tree to be listed as 'globally endangered' by the International Union for Conservation of Nature and 'endangered' by the Canadian government. Conservation collections (in situ and ex situ) are being initiated to preserve the genetic legacy of the species. Reliable, transferrable, and highly variable genetic markers are essential for quantifying the genetic profiles of seed collections relative to natural stands, and ensuring the completeness of conservation collections. We evaluated the use of hybridization-based target capture to enrich specific genomic regions from the 27 GB genome of whitebark pine, and to evaluate genetic variation across loci, trees, and geography. Probes were designed to capture 7,849 distinct genes, and screening was performed on 48 trees. Despite the inclusion of repetitive elements in the probe pool, the resulting dataset provided information on 4,452 genes and 32% of targeted positions (528,873 bp), and we were able to identify 12,390 segregating sites from 47 trees. Variations reveal strong geographic trends in heterozygosity and allelic richness, with trees from the southern Cascade and Sierra Range showing the greatest distinctiveness and differentiation. Our results show that even under non-optimal conditions (low enrichment efficiency; inclusion of repetitive elements in baits), targeted enrichment produces high quality, codominant genotypes from large genomes. The resulting data can be readily integrated into management and gene conservation activities for whitebark pine, and have the potential to be applied to other members of 5-needle pine group (Pinus subsect. Quinquefolia) due to their

  7. Rapid, global demographic expansions after the origins of agriculture.

    PubMed

    Gignoux, Christopher R; Henn, Brenna M; Mountain, Joanna L

    2011-04-12

    The invention of agriculture is widely assumed to have driven recent human population growth. However, direct genetic evidence for population growth after independent agricultural origins has been elusive. We estimated population sizes through time from a set of globally distributed whole mitochondrial genomes, after separating lineages associated with agricultural populations from those associated with hunter-gatherers. The coalescent-based analysis revealed strong evidence for distinct demographic expansions in Europe, southeastern Asia, and sub-Saharan Africa within the past 10,000 y. Estimates of the timing of population growth based on genetic data correspond neatly to dates for the initial origins of agriculture derived from archaeological evidence. Comparisons of rates of population growth through time reveal that the invention of agriculture facilitated a fivefold increase in population growth relative to more ancient expansions of hunter-gatherers.

  8. Rapid, global demographic expansions after the origins of agriculture

    PubMed Central

    Gignoux, Christopher R.; Henn, Brenna M.; Mountain, Joanna L.

    2011-01-01

    The invention of agriculture is widely assumed to have driven recent human population growth. However, direct genetic evidence for population growth after independent agricultural origins has been elusive. We estimated population sizes through time from a set of globally distributed whole mitochondrial genomes, after separating lineages associated with agricultural populations from those associated with hunter-gatherers. The coalescent-based analysis revealed strong evidence for distinct demographic expansions in Europe, southeastern Asia, and sub-Saharan Africa within the past 10,000 y. Estimates of the timing of population growth based on genetic data correspond neatly to dates for the initial origins of agriculture derived from archaeological evidence. Comparisons of rates of population growth through time reveal that the invention of agriculture facilitated a fivefold increase in population growth relative to more ancient expansions of hunter-gatherers. PMID:21444824

  9. Range-wide success of red-cockaded woodpecker translocations.

    SciTech Connect

    Edwards, John W; Costa, Ralph

    2004-12-31

    Edwards, John W.; Costa, Ralph. 2004. Range-wide success of red-cockaded woodpecker translocations. In: Red-cockaded woodpecker; Road to Recovery. Proceedings of the 4th Red-cockaded woodpecker Symposium. Ralph Costa and Susan J. Daniels, eds. Savannah, Georgia. January, 2003. Chapter 6. Translocation. Pp 307-311. Abstract: Red-cockaded woodpeckers (Picoides borealis) have declined range-wide during the past century, suffering from habitat loss and the effects of fire exclusion in older southern pine forests. Red-cockaded woodpecker translocations are a potentially important tool in conservation efforts to reestablish red-cockaded woodpeckers in areas from which they have been extirpated. Currently, translocations are critical in ongoing efforts to save and restore the many existing small populations. We examined the effects of demographic and environmental factors on the range-wide success of translocations between 1989 and 1995.

  10. Final Range Wide Environmental Impact Statement

    DTIC Science & Technology

    2001-07-01

    Pollution Emission Factors AP-42 and Maricopa and Pima counties air documentation applicable to Arizona (U.S. Environmental Protection Agency, 1985...from northern Yuma County in 1983 , YPG became centered in both counties . The City of Yuma is the largest urban center in the region. More than 99...Number of Pages 190 FINAL RANGE WIDE ENVIRONMENTAL IMPACT STATEMENT U.S. Army Yuma Proving Ground Yuma and La Paz Counties , Arizona Prepared for U.S

  11. [The indigenous population. Demographic expansion of ethnic groups].

    PubMed

    Valdes De Montano, L M

    1989-01-01

    Analysis of the vital statistics of the 450 Mexican municipios in which 70% or more of the population speak indigenous languages permits a rough analysis of the demographic behavior of 23 different ethnic groups. Statistics of government departments dealing with indigenous affairs and the various indigenous organizations created since the 1970s provide other estimates of the size of the indigenous population. The census indicated a population of 5,181,038 speakers of indigenous languages aged 5 or older in 1980. The public administration estimated the 1980 indigenous population at 10 million, and the indigenous organizations estimated 12 to 18 million in 1980 and 15 million in 1989. Census and vital statistics data indicate that each indigenous group has had unique patterns of mortality and fertility in the past 30 years. Mortality declined significantly in some groups, but fertility overall has not declined to the same extent. In 1970 and 1980 respectively for the sample as a whole, the average crude birth rates were 42.4 and 37.3/1000 and the average crude death rates were 13.8 and 8.2/1000. The average annual growth rate was estimated at 2.9% for both years. 1980 growth rates ranged from 3.5% for the Maya and Mixtec to a low of 0.5% for the Tzotzil.

  12. Molecular evidence for a recent demographic expansion in the puma (Puma concolor) (Mammalia, Felidae).

    PubMed

    Matte, Eunice M; Castilho, Camila S; Miotto, Renata A; Sana, Denis A; Johnson, Warren E; O'Brien, Stephen J; de Freitas, Thales R O; Eizirik, Eduardo

    2013-12-01

    The puma is an iconic predator that ranges throughout the Americas, occupying diverse habitats. Previous phylogeographic analyses have revealed that it exhibits moderate levels of genetic structure across its range, with few of the classically recognized subspecies being supported as distinct demographic units. Moreover, most of the species' molecular diversity was found to be in South America. To further investigate the phylogeographic structure and demographic history of pumas we analyzed mtDNA sequences from 186 individuals sampled throughout their range, with emphasis on South America. Our objectives were to refine the phylogeographic assessment within South America and to investigate the demographic history of pumas using a coalescent approach. Our results extend previous phylogeographic findings, reassessing the delimitation of historical population units in South America and demonstrating that this species experienced a considerable demographic expansion in the Holocene, ca. 8,000 years ago. Our analyses indicate that this expansion occurred in South America, prior to the hypothesized re-colonization of North America, which was therefore inferred to be even more recent. The estimated demographic history supports the interpretation that pumas suffered a severe demographic decline in the Late Pleistocene throughout their distribution, followed by population expansion and re-colonization of the range, initiating from South America.

  13. Molecular evidence for a recent demographic expansion in the puma (Puma concolor) (Mammalia, Felidae)

    PubMed Central

    Matte, Eunice M.; Castilho, Camila S.; Miotto, Renata A.; Sana, Denis A.; Johnson, Warren E.; O’Brien, Stephen J.; de Freitas, Thales R. O.; Eizirik, Eduardo

    2013-01-01

    The puma is an iconic predator that ranges throughout the Americas, occupying diverse habitats. Previous phylogeographic analyses have revealed that it exhibits moderate levels of genetic structure across its range, with few of the classically recognized subspecies being supported as distinct demographic units. Moreover, most of the species’ molecular diversity was found to be in South America. To further investigate the phylogeographic structure and demographic history of pumas we analyzed mtDNA sequences from 186 individuals sampled throughout their range, with emphasis on South America. Our objectives were to refine the phylogeographic assessment within South America and to investigate the demographic history of pumas using a coalescent approach. Our results extend previous phylogeographic findings, reassessing the delimitation of historical population units in South America and demonstrating that this species experienced a considerable demographic expansion in the Holocene, ca. 8,000 years ago. Our analyses indicate that this expansion occurred in South America, prior to the hypothesized re-colonization of North America, which was therefore inferred to be even more recent. The estimated demographic history supports the interpretation that pumas suffered a severe demographic decline in the Late Pleistocene throughout their distribution, followed by population expansion and re-colonization of the range, initiating from South America. PMID:24385863

  14. Population expansions dominate demographic histories of endemic and widespread Pacific reef fishes

    PubMed Central

    Delrieu-Trottin, Erwan; Mona, Stefano; Maynard, Jeffrey; Neglia, Valentina; Veuille, Michel; Planes, Serge

    2017-01-01

    Despite the unique nature of endemic species, their origin and population history remain poorly studied. We investigated the population history of 28 coral reef fish species, close related, from the Gambier and Marquesas Islands, from five families, with range size varying from widespread to small-range endemic. We analyzed both mitochondrial and nuclear sequence data using neutrality test and Bayesian analysis (EBSP and ABC). We found evidence for demographic expansions for most species (24 of 28), irrespective of range size, reproduction strategy or archipelago. The timing of the expansions varied greatly among species, from 8,000 to 2,000,000 years ago. The typical hypothesis for reef fish that links population expansions to the Last Glacial Maximum fit for 14 of the 24 demographic expansions. We propose two evolutionary processes that could lead to expansions older than the LGM: (a) we are retrieving the signature of an old colonization process for widespread, large-range endemic and paleoendemic species or (b) speciation; the expansion reflects the birth of the species for neoendemic species. We show for the first time that the demographic histories of endemic and widespread reef fish are not distinctly different and suggest that a number of processes drive endemism. PMID:28091580

  15. Population expansions dominate demographic histories of endemic and widespread Pacific reef fishes.

    PubMed

    Delrieu-Trottin, Erwan; Mona, Stefano; Maynard, Jeffrey; Neglia, Valentina; Veuille, Michel; Planes, Serge

    2017-01-16

    Despite the unique nature of endemic species, their origin and population history remain poorly studied. We investigated the population history of 28 coral reef fish species, close related, from the Gambier and Marquesas Islands, from five families, with range size varying from widespread to small-range endemic. We analyzed both mitochondrial and nuclear sequence data using neutrality test and Bayesian analysis (EBSP and ABC). We found evidence for demographic expansions for most species (24 of 28), irrespective of range size, reproduction strategy or archipelago. The timing of the expansions varied greatly among species, from 8,000 to 2,000,000 years ago. The typical hypothesis for reef fish that links population expansions to the Last Glacial Maximum fit for 14 of the 24 demographic expansions. We propose two evolutionary processes that could lead to expansions older than the LGM: (a) we are retrieving the signature of an old colonization process for widespread, large-range endemic and paleoendemic species or (b) speciation; the expansion reflects the birth of the species for neoendemic species. We show for the first time that the demographic histories of endemic and widespread reef fish are not distinctly different and suggest that a number of processes drive endemism.

  16. Population expansions dominate demographic histories of endemic and widespread Pacific reef fishes

    NASA Astrophysics Data System (ADS)

    Delrieu-Trottin, Erwan; Mona, Stefano; Maynard, Jeffrey; Neglia, Valentina; Veuille, Michel; Planes, Serge

    2017-01-01

    Despite the unique nature of endemic species, their origin and population history remain poorly studied. We investigated the population history of 28 coral reef fish species, close related, from the Gambier and Marquesas Islands, from five families, with range size varying from widespread to small-range endemic. We analyzed both mitochondrial and nuclear sequence data using neutrality test and Bayesian analysis (EBSP and ABC). We found evidence for demographic expansions for most species (24 of 28), irrespective of range size, reproduction strategy or archipelago. The timing of the expansions varied greatly among species, from 8,000 to 2,000,000 years ago. The typical hypothesis for reef fish that links population expansions to the Last Glacial Maximum fit for 14 of the 24 demographic expansions. We propose two evolutionary processes that could lead to expansions older than the LGM: (a) we are retrieving the signature of an old colonization process for widespread, large-range endemic and paleoendemic species or (b) speciation; the expansion reflects the birth of the species for neoendemic species. We show for the first time that the demographic histories of endemic and widespread reef fish are not distinctly different and suggest that a number of processes drive endemism.

  17. Population resequencing of European mitochondrial genomes highlights sex-bias in Bronze Age demographic expansions.

    PubMed

    Batini, Chiara; Hallast, Pille; Vågene, Åshild J; Zadik, Daniel; Eriksen, Heidi A; Pamjav, Horolma; Sajantila, Antti; Wetton, Jon H; Jobling, Mark A

    2017-09-21

    Interpretations of genetic data concerning the prehistory of Europe have long been a subject of great debate, but increasing amounts of ancient and modern DNA data are now providing new and more informative evidence. Y-chromosome resequencing studies in Europe have highlighted the prevalence of recent expansions of male lineages, and focused interest on the Bronze Age as a period of cultural and demographic change. These findings contrast with phylogeographic studies based on mitochondrial DNA (mtDNA), which have been interpreted as supporting expansions from glacial refugia. Here we have undertaken a population-based resequencing of complete mitochondrial genomes in Europe and the Middle East, in 340 samples from 17 populations for which Y-chromosome sequence data are also available. Demographic reconstructions show no signal of Bronze Age expansion, but evidence of Paleolithic expansions in all populations except the Saami, and with an absence of detectable geographical pattern. In agreement with previous inference from modern and ancient DNA data, the unbiased comparison between the mtDNA and Y-chromosome population datasets emphasizes the sex-biased nature of recent demographic transitions in Europe.

  18. Appropriate homoplasy metrics in linked SSRs to predict an underestimation of demographic expansion times.

    PubMed

    Ortega-Del Vecchyo, Diego; Piñero, Daniel; Jardón-Barbolla, Lev; van Heerwaarden, Joost

    2017-09-11

    Homoplasy affects demographic inference estimates. This effect has been recognized and corrective methods have been developed. However, no studies so far have defined what homoplasy metrics best describe the effects on demographic inference, or have attempted to estimate such metrics in real data. Here we study how homoplasy in chloroplast microsatellites (cpSSR) affects inference of population expansion time. cpSSRs are popular markers for inferring historical demography in plants due to their high mutation rate and limited recombination. In cpSSRs, homoplasy is usually quantified as the probability that two markers or haplotypes that are identical by state are not identical by descent (Homoplasy index, P). Here we propose a new measure of multi-locus homoplasy in linked SSR called Distance Homoplasy (DH), which measures the proportion of pairwise differences not observed due to homoplasy, and we compare it to P and its per cpSSR locus average, which we call Mean Size Homoplasy (MSH). We use simulations and analytical derivations to show that, out of the three homoplasy metrics analyzed, MSH and DH are more correlated to changes in the population expansion time and to the underestimation of that demographic parameter using cpSSR. We perform simulations to show that Approximate Bayesian Computation (ABC) can be used to obtain reasonable estimates of MSH and DH. Finally, we use ABC to estimate the expansion time, MSH and DH from a chloroplast SSR dataset in Pinus caribaea. To our knowledge, this is the first time that homoplasy has been estimated in population genetic data. We show that MSH and DH should be used to quantify how homoplasy affects estimates of population expansion time. We also demonstrate how ABC provides a methodology to estimate homoplasy in population genetic data.

  19. Postglacial range shift and demographic expansion of the marine intertidal snail Batillaria attramentaria

    PubMed Central

    Ho, Phuong-Thao; Kwan, Ye-Seul; Kim, Boa; Won, Yong-Jin

    2015-01-01

    To address the impacts of past climate changes, particularly since the last glacial period, on the history of the distribution and demography of marine species, we investigated the evolutionary and demographic responses of the intertidal batillariid gastropod, Batillaria attramentaria, to these changes, using the snail as a model species in the northwest Pacific. We applied phylogeographic and divergence population genetic approaches to mitochondrial COI sequences from B. attramentaria. To cover much of its distributional range, 197 individuals collected throughout Korea and 507 publically available sequences (mostly from Japan) were used. Finally, a Bayesian skyline plot (BSP) method was applied to reconstruct the demographic history of this species. We found four differentiated geographic groups around Korea, confirming the presence of two distinct, geographically subdivided haplogroups on the Japanese coastlines along the bifurcated routes of the warm Tsushima and Kuroshio Currents. These two haplogroups were estimated to have begun to split approximately 400,000 years ago. Population divergence analysis supported the hypothesis that the Yellow Sea was populated by a northward range expansion of a small fraction of founders that split from a southern ancestral population since the last glacial maximum (LGM: 26,000–19,000 years ago), when the southern area became re-submerged. BSP analyses on six geographically and genetically defined groups in Korea and Japan consistently demonstrated that each group has exponentially increased approximately since the LGM. This study resolved the phylogeography of B. attramentaria as a series of events connected over space and time; while paleoceanographic conditions determining the connectivity of neighboring seas in East Asia are responsible for the vicariance of this species, the postglacial sea-level rise and warming temperatures have played a crucial role in rapid range shifts and broad demographic expansions of its

  20. Postglacial range shift and demographic expansion of the marine intertidal snail Batillaria attramentaria.

    PubMed

    Ho, Phuong-Thao; Kwan, Ye-Seul; Kim, Boa; Won, Yong-Jin

    2015-01-01

    To address the impacts of past climate changes, particularly since the last glacial period, on the history of the distribution and demography of marine species, we investigated the evolutionary and demographic responses of the intertidal batillariid gastropod, Batillaria attramentaria, to these changes, using the snail as a model species in the northwest Pacific. We applied phylogeographic and divergence population genetic approaches to mitochondrial COI sequences from B. attramentaria. To cover much of its distributional range, 197 individuals collected throughout Korea and 507 publically available sequences (mostly from Japan) were used. Finally, a Bayesian skyline plot (BSP) method was applied to reconstruct the demographic history of this species. We found four differentiated geographic groups around Korea, confirming the presence of two distinct, geographically subdivided haplogroups on the Japanese coastlines along the bifurcated routes of the warm Tsushima and Kuroshio Currents. These two haplogroups were estimated to have begun to split approximately 400,000 years ago. Population divergence analysis supported the hypothesis that the Yellow Sea was populated by a northward range expansion of a small fraction of founders that split from a southern ancestral population since the last glacial maximum (LGM: 26,000-19,000 years ago), when the southern area became re-submerged. BSP analyses on six geographically and genetically defined groups in Korea and Japan consistently demonstrated that each group has exponentially increased approximately since the LGM. This study resolved the phylogeography of B. attramentaria as a series of events connected over space and time; while paleoceanographic conditions determining the connectivity of neighboring seas in East Asia are responsible for the vicariance of this species, the postglacial sea-level rise and warming temperatures have played a crucial role in rapid range shifts and broad demographic expansions of its

  1. Demographic expansions in South America: enlightening a complex scenario with genetic and linguistic data.

    PubMed

    Ramallo, Virginia; Bisso-Machado, Rafael; Bravi, Claudio; Coble, Michael D; Salzano, Francisco M; Hünemeier, Tábita; Bortolini, Maria Cátira

    2013-03-01

    Native Americans are characterized by specific and unique patterns of genetic and cultural/linguistic diversities, and this information has been used to understand patterns of geographic dispersion, and the relationship between these peoples. Particularly interesting are the Tupi and Je speaker dispersions. At present, a large number of individuals speak languages of these two stocks; for instance, Tupi-Guarani is one of the official languages in Paraguay, Bolivia, and the Mercosul economic block. Although the Tupi expansion can be compared in importance to the Bantu migration in Africa, little is known about this event relative to others. Equal and even deeper gaps exist concerning the Je-speakers' expansion. This study aims to elucidate some aspects of these successful expansions. To meet this purpose, we analyzed Native American mtDNA complete control region from nine different populations and included HVS-I sequences available in the literature, resulting in a total of 1,176 samples investigated. Evolutionary relationships were explored through median-joining networks and genetic/geographic/linguistic correlations with Mantel tests and spatial autocorrelation analyses. Both Tupi and Je showed general traces of ancient or more recent fission-fusion processes, but a very different pattern of demographic expansion. Tupi populations displayed a classical isolation-by-distance pattern, while Je groups presented an intricate and nonlinear mode of dispersion. We suggest that the collective memory and other cultural processes could be important factors influencing the fission-fusion events, which likely contributed to the genetic structure, evolution, and dispersion of Native American populations.

  2. Low genetic diversity and recent demographic expansion in the red starfish Echinaster sepositus (Retzius 1816).

    PubMed

    Garcia-Cisneros, Alex; Palacín, Creu; Ben Khadra, Yousra; Pérez-Portela, Rocío

    2016-09-15

    Understanding the phylogeography and genetic structure of populations and the processes responsible of patterns therein is crucial for evaluating the vulnerability of marine species and developing management strategies. In this study, we explore how past climatic events and ongoing oceanographic and demographic processes have shaped the genetic structure and diversity of the Atlanto-Mediterranean red starfish Echinaster sepositus. The species is relatively abundant in some areas of the Mediterranean Sea, but some populations have dramatically decreased over recent years due to direct extraction for ornamental aquariums and souvenir industries. Analyses across most of the distribution range of the species based on the mitochondrial cytochrome c oxidase subunit I gene and eight microsatellite loci revealed very low intraspecific genetic diversity. The species showed a weak genetic structure within marine basins despite the a priori low dispersal potential of its lecithotrophic larva. Our results also revealed a very recent demographic expansion across the distribution range of the species. The genetic data presented here indicate that the species might be highly vulnerable, due to its low intraspecific genetic diversity.

  3. Low genetic diversity and recent demographic expansion in the red starfish Echinaster sepositus (Retzius 1816)

    PubMed Central

    Garcia-Cisneros, Alex; Palacín, Creu; Ben Khadra, Yousra; Pérez-Portela, Rocío

    2016-01-01

    Understanding the phylogeography and genetic structure of populations and the processes responsible of patterns therein is crucial for evaluating the vulnerability of marine species and developing management strategies. In this study, we explore how past climatic events and ongoing oceanographic and demographic processes have shaped the genetic structure and diversity of the Atlanto-Mediterranean red starfish Echinaster sepositus. The species is relatively abundant in some areas of the Mediterranean Sea, but some populations have dramatically decreased over recent years due to direct extraction for ornamental aquariums and souvenir industries. Analyses across most of the distribution range of the species based on the mitochondrial cytochrome c oxidase subunit I gene and eight microsatellite loci revealed very low intraspecific genetic diversity. The species showed a weak genetic structure within marine basins despite the a priori low dispersal potential of its lecithotrophic larva. Our results also revealed a very recent demographic expansion across the distribution range of the species. The genetic data presented here indicate that the species might be highly vulnerable, due to its low intraspecific genetic diversity. PMID:27627860

  4. Microsatellite data show recent demographic expansions in sedentary but not in nomadic human populations in Africa and Eurasia.

    PubMed

    Aimé, Carla; Verdu, Paul; Ségurel, Laure; Martinez-Cruz, Begoña; Hegay, Tatyana; Heyer, Evelyne; Austerlitz, Frédéric

    2014-10-01

    The transition from hunting and gathering to plant and animal domestication was one of the most important cultural and technological revolutions in human history. According to archeologists and paleoanthropologists, this transition triggered major demographic expansions. However, few genetic studies have found traces of Neolithic expansions in the current repartition of genetic polymorphism, pointing rather toward Paleolithic expansions. Here, we used microsatellite autosomal data to investigate the past demographic history of 87 African and Eurasian human populations with contrasted lifestyles (nomadic hunter-gatherers, semi-nomadic herders and sedentary farmers). Likely due to the combination of a higher mutation rate and the possibility to analyze several loci as independent replicates of the coalescent process, the analysis of microsatellite data allowed us to infer more recent expansions than previous genetic studies, potentially resulting from the Neolithic transition. Despite the variability in their location and environment, we found consistent expansions for all sedentary farmers, while we inferred constant population sizes for all hunter-gatherers and most herders that could result from constraints linked to a nomadic or semi-nomadic lifestyle and/or competition for land between herders and farmers. As an exception, we inferred expansions for Central Asian herders. This might be linked with the arid environment of this area that may have been more favorable to nomadic herders than to sedentary farmers. Alternatively, current Central Asian herders may descent from populations who have first experienced a transition from hunter-gathering to sedentary agropastoralism, and then a second transition to nomadic herding.

  5. Urban Change: Understanding how expansion and densification relate to demographic change and their implications for climate change.

    NASA Astrophysics Data System (ADS)

    Balk, D.; Jones, B.; Liu, Z.; Nghiem, S. V.; Pesaresi, M.

    2015-12-01

    Urbanization is the most demographic significant trend of the 21st century particularly in Asia. Characterizing it in a spatial context is difficult given the moderate resolution data provided by traditional sources of demographic data. Previous work on Saigon has shown by using these data together that much more about the correlates and potential consequences of change in the form and expansion of urban change can be learned than with a single data source alone. In this paper, we expand our analysis to two other much different urban and socioeconomic settings: Dhaka and Beijing. Particularly, where the demographic and socioeconomic indicators of change are too infrequent to capture annual change, use of satellites in combination with demographic data may be especially useful for capturing change in exurban and periurban areas, or in smaller cities within larger urban agglomerations. Using spatial regression techniques, we estimate statistical relationships between remotely sensed data sets to assess the ability demographic changes to predict urban changes as detected by two different satellite measures of change 2000-2010 in Dhaka, Saigon, and Beijing. We then predict socioeconomic outcomes associated with emissions and vulnerability proxies. We use two much different types of satellite data -- the Dense Sample Method (DSM) analysis of the NASA scatterometer data and new built-up area data from the Global Human Settlement Layer of the JRC - which respectively proxy for increases in building heights (vertical expansion) and impervious surface-type changes (horizontal expansion). These different data products help us to better understand the evolution of the built environment and urban form, while the underlying demographic data provide information regarding composition of urban population change, at different levels of economic development, built-upness, and population density. Combining these types of data yields important, high resolution spatial information that

  6. Quaternary range and demographic expansion of Liolaemus darwinii (Squamata: Liolaemidae) in the Monte Desert of Central Argentina using Bayesian phylogeography and ecological niche modelling.

    PubMed

    Camargo, Arley; Werneck, Fernanda P; Morando, Mariana; Sites, Jack W; Avila, Luciano J

    2013-08-01

    Until recently, most phylogeographic approaches have been unable to distinguish between demographic and range expansion processes, making it difficult to test for the possibility of range expansion without population growth and vice versa. In this study, we applied a Bayesian phylogeographic approach to reconstruct both demographic and range expansion in the lizard Liolaemus darwinii of the Monte Desert in Central Argentina, during the Late Quaternary. Based on analysis of 14 anonymous nuclear loci and the cytochrome b mitochondrial DNA gene, we detected signals of demographic expansion starting at ~55 ka based on Bayesian Skyline and Skyride Plots. In contrast, Bayesian relaxed models of spatial diffusion suggested that range expansion occurred only between ~95 and 55 ka, and more recently, diffusion rates were very low during demographic expansion. The possibility of population growth without substantial range expansion could account for the shared patterns of demographic expansion during the Last Glacial Maxima (OIS 2 and 4) in fish, small mammals and other lizards of the Monte Desert. We found substantial variation in diffusion rates over time, and very high rates during the range expansion phase, consistent with a rapidly advancing expansion front towards the southeast shown by palaeo-distribution models. Furthermore, the estimated diffusion rates are congruent with observed dispersal rates of lizards in field conditions and therefore provide additional confidence to the temporal scale of inferred phylogeographic patterns. Our study highlights how the integration of phylogeography with palaeo-distribution models can shed light on both demographic and range expansion processes and their potential causes.

  7. Molecular Evidence of Demographic Expansion of the Chagas Disease Vector Triatoma dimidiata (Hemiptera, Reduviidae, Triatominae) in Colombia

    PubMed Central

    Gómez-Palacio, Andrés; Triana, Omar

    2014-01-01

    Background Triatoma dimidiata is one of the most significant vectors of Chagas disease in Central America and Colombia, and, as in most species, its pattern of genetic variation within and among populations is strongly affected by its phylogeographic history. A putative origin from Central America has been proposed for Colombian populations, and high genetic differentiation among three biographically different population groups has recently been evidenced. Analyses based on putatively neutral markers provide data from which past events, such as population expansions and colonization, can be inferred. We analyzed the genealogies of the nicotinamide adenine dinucleotide dehydrogenase 4 (ND4) and the cytochrome oxidase subunit 1-mitochondrial genes, as well as partial nuclear ITS-2 DNA sequences obtained across most of the eco-geographical range in Colombia, to assess the population structure and demographic factors that may explain the geographical distribution of T. dimidiata in this country. Results The population structure results support a significant association between genetic divergence and the eco-geographical location of population groups, suggesting that clear signals of demographic expansion can explain the geographical distribution of haplotypes of population groups. Additionally, empirical date estimation of the event suggests that the population's expansion can be placed after the emergence of the Panama Isthmus, and that it was possibly followed by a population fragmentation process, perhaps resulting from local adaptation accomplished by orographic factors such as geographical isolation. Conclusion Inferences about the historical population processes in Colombian T. dimidiata populations are generally in accordance with population expansions that may have been accomplished by two important biotic and orographic events such as the Great American Interchange and the uplift of the eastern range of the Andes mountains in central Colombia. PMID:24625572

  8. Molecular evidence of demographic expansion of the chagas disease vector Triatoma dimidiata (Hemiptera, Reduviidae, Triatominae) in Colombia.

    PubMed

    Gómez-Palacio, Andrés; Triana, Omar

    2014-03-01

    Triatoma dimidiata is one of the most significant vectors of Chagas disease in Central America and Colombia, and, as in most species, its pattern of genetic variation within and among populations is strongly affected by its phylogeographic history. A putative origin from Central America has been proposed for Colombian populations, and high genetic differentiation among three biographically different population groups has recently been evidenced. Analyses based on putatively neutral markers provide data from which past events, such as population expansions and colonization, can be inferred. We analyzed the genealogies of the nicotinamide adenine dinucleotide dehydrogenase 4 (ND4) and the cytochrome oxidase subunit 1-mitochondrial genes, as well as partial nuclear ITS-2 DNA sequences obtained across most of the eco-geographical range in Colombia, to assess the population structure and demographic factors that may explain the geographical distribution of T. dimidiata in this country. The population structure results support a significant association between genetic divergence and the eco-geographical location of population groups, suggesting that clear signals of demographic expansion can explain the geographical distribution of haplotypes of population groups. Additionally, empirical date estimation of the event suggests that the population's expansion can be placed after the emergence of the Panama Isthmus, and that it was possibly followed by a population fragmentation process, perhaps resulting from local adaptation accomplished by orographic factors such as geographical isolation. Inferences about the historical population processes in Colombian T. dimidiata populations are generally in accordance with population expansions that may have been accomplished by two important biotic and orographic events such as the Great American Interchange and the uplift of the eastern range of the Andes mountains in central Colombia.

  9. Genetic signals of demographic expansion in Downy Woodpecker (Picoides pubescens) after the last North American glacial maximum.

    PubMed

    Pulgarín-R, Paulo C; Burg, Theresa M

    2012-01-01

    The glacial cycles of the Pleistocene have been recognized as important, large-scale historical processes that strongly influenced the demographic patterns and genetic structure of many species. Here we present evidence of a postglacial expansion for the Downy Woodpecker (Picoides pubescens), a common member of the forest bird communities in North America with a continental distribution. DNA sequences from the mitochondrial tRNA-Lys, and ATPase 6 and 8 genes, and microsatellite data from seven variable loci were combined with a species distribution model (SDM) to infer possible historical scenarios for this species after the last glacial maximum. Analyses of Downy Woodpeckers from 23 geographic areas suggested little differentiation, shallow genealogical relationships, and limited population structure across the species' range. Microsatellites, which have higher resolution and are able to detect recent differences, revealed two geographic groups where populations along the eastern edge of the Rocky Mountains (Montana, Utah, Colorado, and southern Alberta) were genetically isolated from the rest of the sampled populations. Mitochondrial DNA, an important marker to detect historical patterns, recovered only one group. However, populations in Idaho and southeast BC contained high haplotype diversity and, in general were characterized by the absence of the most common mtDNA haplotype. The SDM suggested several areas in the southern US as containing suitable Downy Woodpecker habitat during the LGM. The lack of considerable geographic structure and the starburst haplotype network, combined with several population genetic tests, suggest a scenario of demographic expansion during the last part of Pleistocene and early Holocene.

  10. Genetic Signals of Demographic Expansion in Downy Woodpecker (Picoides pubescens) after the Last North American Glacial Maximum

    PubMed Central

    Pulgarín-R, Paulo C.; Burg, Theresa M.

    2012-01-01

    The glacial cycles of the Pleistocene have been recognized as important, large-scale historical processes that strongly influenced the demographic patterns and genetic structure of many species. Here we present evidence of a postglacial expansion for the Downy Woodpecker (Picoides pubescens), a common member of the forest bird communities in North America with a continental distribution. DNA sequences from the mitochondrial tRNA-Lys, and ATPase 6 and 8 genes, and microsatellite data from seven variable loci were combined with a species distribution model (SDM) to infer possible historical scenarios for this species after the last glacial maximum. Analyses of Downy Woodpeckers from 23 geographic areas suggested little differentiation, shallow genealogical relationships, and limited population structure across the species’ range. Microsatellites, which have higher resolution and are able to detect recent differences, revealed two geographic groups where populations along the eastern edge of the Rocky Mountains (Montana, Utah, Colorado, and southern Alberta) were genetically isolated from the rest of the sampled populations. Mitochondrial DNA, an important marker to detect historical patterns, recovered only one group. However, populations in Idaho and southeast BC contained high haplotype diversity and, in general were characterized by the absence of the most common mtDNA haplotype. The SDM suggested several areas in the southern US as containing suitable Downy Woodpecker habitat during the LGM. The lack of considerable geographic structure and the starburst haplotype network, combined with several population genetic tests, suggest a scenario of demographic expansion during the last part of Pleistocene and early Holocene. PMID:22792306

  11. Pleistocene glaciations, demographic expansion and subsequent isolation promoted morphological heterogeneity: A phylogeographic study of the alpine Rosa sericea complex (Rosaceae)

    PubMed Central

    Gao, Yun-Dong; Zhang, Yu; Gao, Xin-Fen; Zhu, Zhang-Ming

    2015-01-01

    While most temperate plants probably underwent glacial constriction to refugia and interglacial expansion, another type of interglacial refugia might have existed to maintain alpine plants during warm periods. To test this hypothesis, we applied phylogeographic methods to 763 individuals (62 populations) which belong to 7 taxonomically difficult species of the Rosa sericea complex distributed in alpine regions of the temperate and subtropical zones in eastern Asia. We used three chloroplast (cp) DNA fragments (trnL-trnF, ndhF-rpl32 and ndhJ-trnF) approximately 3,100 bp and nuclear microsatellite (nSSR) on eight sites to determine whether cold tolerant plants experienced expansion during the Pleistocene. The neutral test and mismatch distribution analysis (MDA) indicated that whole populations and major lineages of the Qinghai-Tibet Plateau (QTP) underwent expansion during the middle to late Pleistocene. Environmental niche modeling (ENM) indicates more suitable habitats during the Last Glacial Maximum (LGM) than at present. We concluded that the demographic history of R. sericea, which diverged in the middle Pleistocene, was mostly affected by climatic oscillations instead of by geographical barriers. The low genetic divergence, as well as the weak phylogenetic structure in the R. sericea complex both support treating this complex as a single taxon. PMID:26123942

  12. Population panmixia and the Pleistocene demographic expansion of spotty belly greenling Hexagrammos agrammus in the East Sea and Northwest Pacific

    NASA Astrophysics Data System (ADS)

    Habib, Kazi Ahsan; Jeong, Dageum; Myoung, Jung-Goo; Lee, Youn-Ho

    2015-06-01

    The population genetic structure and historical demography of spotty belly greenling, Hexagrammos agrammus, which has limited distribution in the Northwest Pacific, was assessed with partial sequences of the mitochondrial DNA (mtDNA) cytochrome b and the control region (D-loop). A total of 103 individuals were collected from four sites located at the Korea Strait (Southern coast of Korea) and the East coast of Korea and two places in the Pacific coast of Japan. For all the populations, nucleotide diversities were low (0.006-0.009) while the haplotype diversities were as high as 0.92 to 0.97, indicating that the fish has undergone a recent population expansion after experiencing bottleneck. Star-shaped patterns of haplotype networks as well as the significant negative values of Tajima's D and Fu's F S corroborate the recent population expansion. Mismatch distribution analysis reveals that the demographic expansion of the species started during the 2nd half of the Middle Pleistocene Series approximately 141,000-406,000 years ago. Hierarchical analysis of molecular variance (AMOVA), the pairwise population statistics ( F ST), and the exact test of haplotype differentiation demonstrate no significant genetic differentiation among populations investigated, suggesting that spotty belly greenling is panmictic in the East Sea and the Pacific coast of Japan.

  13. The demographic benefits of belligerence and bravery: defeated group repopulation or victorious group size expansion?

    PubMed

    Lehmann, Laurent

    2011-01-01

    Intraspecific coalitional aggression between groups of individuals is a widespread trait in the animal world. It occurs in invertebrates and vertebrates, and is prevalent in humans. What are the conditions under which coalitional aggression evolves in natural populations? In this article, I develop a mathematical model delineating conditions where natural selection can favor the coevolution of belligerence and bravery between small-scale societies. Belligerence increases an actor's group probability of trying to conquer another group and bravery increase the actors's group probability of defeating an attacked group. The model takes into account two different types of demographic scenarios that may lead to the coevolution of belligerence and bravery. Under the first, the fitness benefits driving the coevolution of belligerence and bravery come through the repopulation of defeated groups by fission of victorious ones. Under the second demographic scenario, the fitness benefits come through a temporary increase in the local carrying capacity of victorious groups, after transfer of resources from defeated groups to victorious ones. The analysis of the model suggests that the selective pressures on belligerence and bravery are stronger when defeated groups can be repopulated by victorious ones. The analysis also suggests that, depending on the shape of the contest success function, costly bravery can evolve in groups of any size.

  14. Explosive demographic expansion by dreissenid bivalves as a possible result of astronomical forcing

    NASA Astrophysics Data System (ADS)

    Harzhauser, M.; Mandic, O.; Kern, A. K.; Piller, W. E.; Neubauer, T. A.; Albrecht, C.; Wilke, T.

    2013-07-01

    Human induced range expansions of invasive dreissenid bivalves are of great concern. However, the underlying biological processes are only poorly understood, partly due to the lack of information on natural expansion events. Here we use the extinct bivalve species Sinucongeria primiformis as a model organism for testing natural (i.e. non-Anthropocene) blooms of dreissenid species in a lacustrine system of Lake Pannon during the Tortonian (~10.5 Myr; Late Miocene). 600 samples from a consecutive core were evaluated for the relative abundance of this pavement-forming mollusc, which cover about 8 millennia of Late Miocene time with a decadal resolution. Our data indicate that the settlement by bivalves in the offshore environment was limited mainly by bottom water oxygenation, which follows predictable and repetitive patterns through time. These population fluctuations might be related to solar cycles: successful dreissenid settlement is re-occurring in a frequency known as the lower and upper Gleissberg cycles with a 50-80 and 90-120 yr period. These cycles appear to control regional wind patterns, which are directly linked to water mixing of the lake. This is modulated by the even more prominent 500 yr cycle, which seems to be the most important pacemaker for Lake Pannon hydrology.

  15. Explosive demographic expansion by dreissenid bivalves as a possible result of astronomical forcing

    NASA Astrophysics Data System (ADS)

    Harzhauser, M.; Mandic, O.; Kern, A. K.; Piller, W. E.; Neubauer, T. A.; Albrecht, C.; Wilke, T.

    2013-12-01

    Human induced range expansions of invasive dreissenid bivalves are of great concern. However, the underlying biological processes are only poorly understood, partly due to the lack of information on natural expansion events. Here we use the extinct bivalve species Sinucongeria primiformis as a model organism for testing natural (i.e. pre-Anthropocene) blooms of dreissenid species in a lacustrine system of Lake Pannon during the Tortonian (~ 10.5 Myr; late Miocene). A total of 600 samples from a consecutive core were evaluated for the relative abundance of this pavement-forming mollusc, which cover about eight millennia of late Miocene time with a decadal resolution. Our data indicate that the settlement by bivalves in the offshore environment was limited mainly by bottom water oxygenation, which follows predictable and repetitive patterns through time. These population fluctuations might be related to solar cycles: successful dreissenid settlement is recurring in a frequency known as the lower and upper Gleissberg cycles with 50-80 and 90-120 yr periods. These cycles appear to control regional wind patterns, which are directly linked to water mixing of the lake. This is modulated by the even more prominent 500 yr cycle, which seems to be the most important pacemaker for Lake Pannon hydrology.

  16. Range-wide Determinants of Plague Distribution in North America

    PubMed Central

    Maher, Sean P.; Ellis, Christine; Gage, Kenneth L.; Enscore, Russell E.; Peterson, A. Townsend

    2010-01-01

    Plague, caused by the bacterium Yersinia pestis, is established across western North America, and yet little is known of what determines the broad-scale dimensions of its overall range. We tested whether its North American distribution represents a composite of individual host–plague associations (the “Host Niche Hypothesis”), or whether mammal hosts become infected only at sites overlapping ecological conditions appropriate for plague transmission and maintenance (the “Plague Niche Hypothesis”). We took advantage of a novel data set summarizing plague records in wild mammals newly digitized from paper-based records at the Centers for Disease Control and Prevention to develop range-wide tests of ecological niche similarity between mammal host niches and plague-infected host niches. Results indicate that plague infections occur under circumstances distinct from the broader ecological distribution of hosts, and that plague-infected niches are similar among hosts; hence, evidence coincides with the predictions of the Plague Niche Hypothesis, and contrasts with those of the Host Niche Hypothesis. The “plague niche” is likely driven by ecological requirements of vector flea species. PMID:20889857

  17. Range-Wide Snow Leopard Phylogeography Supports Three Subspecies.

    PubMed

    Janecka, Jan E; Zhang, Yuguang; Li, Diqiang; Munkhtsog, Bariushaa; Bayaraa, Munkhtsog; Galsandorj, Naranbaatar; Wangchuk, Tshewang R; Karmacharya, Dibesh; Li, Juan; Lu, Zhi; Uulu, Kubanychbek Zhumabai; Gaur, Ajay; Kumar, Satish; Kumar, Kesav; Hussain, Shafqat; Muhammad, Ghulam; Jevit, Matthew; Hacker, Charlotte; Burger, Pamela; Wultsch, Claudia; Janecka, Mary J; Helgen, Kristofer; Murphy, William J; Jackson, Rodney

    2017-09-01

    The snow leopard, Panthera uncia, is an elusive high-altitude specialist that inhabits vast, inaccessible habitat across Asia. We conducted the first range-wide genetic assessment of snow leopards based on noninvasive scat surveys. Thirty-three microsatellites were genotyped and a total of 683 bp of mitochondrial DNA sequenced in 70 individuals. Snow leopards exhibited low genetic diversity at microsatellites (AN = 5.8, HO = 0.433, HE = 0.568), virtually no mtDNA variation, and underwent a bottleneck in the Holocene (∼8000 years ago) coinciding with increased temperatures, precipitation, and upward treeline shift in the Tibetan Plateau. Multiple analyses supported 3 primary genetic clusters: (1) Northern (the Altai region), (2) Central (core Himalaya and Tibetan Plateau), and (3) Western (Tian Shan, Pamir, trans-Himalaya regions). Accordingly, we recognize 3 subspecies, Panthera uncia irbis (Northern group), Panthera uncia uncia (Western group), and Panthera uncia uncioides (Central group) based upon genetic distinctness, low levels of admixture, unambiguous population assignment, and geographic separation. The patterns of variation were consistent with desert-basin "barrier effects" of the Gobi isolating the northern subspecies (Mongolia), and the trans-Himalaya dividing the central (Qinghai, Tibet, Bhutan, and Nepal) and western subspecies (India, Pakistan, Tajikistan, and Kyrgyzstan). Hierarchical Bayesian clustering analysis revealed additional subdivision into a minimum of 6 proposed management units: western Mongolia, southern Mongolia, Tian Shan, Pamir-Himalaya, Tibet-Himalaya, and Qinghai, with spatial autocorrelation suggesting potential connectivity by dispersing individuals up to ∼400 km. We provide a foundation for global conservation of snow leopard subspecies, and set the stage for in-depth landscape genetics and genomic studies. © The American Genetic Association 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  18. Range-wide phenotypic and genetic differentiation in wild sunflower.

    PubMed

    McAssey, Edward V; Corbi, Jonathan; Burke, John M

    2016-11-10

    Divergent phenotypes and genotypes are key signals for identifying the targets of natural selection in locally adapted populations. Here, we used a combination of common garden phenotyping for a variety of growth, plant architecture, and seed traits, along with single-nucleotide polymorphism (SNP) genotyping to characterize range-wide patterns of diversity in 15 populations of wild sunflower (Helianthus annuus L.) sampled along a latitudinal gradient in central North America. We analyzed geographic patterns of phenotypic diversity, quantified levels of within-population SNP diversity, and also determined the extent of population structure across the range of this species. We then used these data to identify significantly over-differentiated loci as indicators of genomic regions that likely contribute to local adaptation. Traits including flowering time, plant height, and seed oil composition (i.e., percentage of saturated fatty acids) were significantly correlated with latitude, and thus differentiated northern vs. southern populations. Average pairwise FST was found to be 0.21, and a STRUCTURE analysis identified two significant clusters that largely separated northern and southern individuals. The significant FST outliers included a SNP in HaFT2, a flowering time gene that has been previously shown to co-localize with flowering time QTL, and which exhibits a known cline in gene expression. Latitudinal differentiation in both phenotypic traits and SNP allele frequencies is observed across wild sunflower populations in central North America. Such differentiation may play an important adaptive role across the range of this species, and could facilitate adaptation to a changing climate.

  19. A high-resolution genetic signature of demographic and spatial expansion in epizootic rabies virus

    PubMed Central

    Biek, Roman; Henderson, J. Caroline; Waller, Lance A.; Rupprecht, Charles E.; Real, Leslie A.

    2007-01-01

    Emerging pathogens potentially undergo rapid evolution while expanding in population size and geographic range during the course of invasion, yet it is generally difficult to demonstrate how these processes interact. Our analysis of a 30-yr data set covering a large-scale rabies virus outbreak among North American raccoons reveals the long lasting effect of the initial infection wave in determining how viral populations are genetically structured in space. We further find that coalescent-based estimates derived from the genetic data yielded an amazingly accurate reconstruction of the known spatial and demographic dynamics of the virus over time. Our study demonstrates the combined evolutionary and population dynamic processes characterizing the spread of pathogen after its introduction into a fully susceptible host population. Furthermore, the results provide important insights regarding the spatial scale of rabies persistence and validate the use of coalescent approaches for uncovering even relatively complex population histories. Such approaches will be of increasing relevance for understanding the epidemiology of emerging zoonotic diseases in a landscape context. PMID:17470818

  20. Range-wide patterns of greater sage-grouse persistence

    USGS Publications Warehouse

    Aldridge, C.L.; Nielsen, S.E.; Beyer, H.L.; Boyce, M.S.; Connelly, J.W.; Knick, S.T.; Schroeder, M.A.

    2008-01-01

    population growth and peripherality of populations. However, future range loss may relate less to historical mechanisms and more to recent changes in land use and habitat condition, including energy developments and invasions by non-native species such as cheatgrass (Bromus tectorum) and West Nile virus. In conjunction with local measures of population performance, landscape-scale predictions of future range loss may be useful for prioritizing management and protection. Our results suggest that initial conservation efforts should focus on maintaining large expanses of sagebrush habitat, enhancing quality of existing habitats, and increasing habitat connectivity.

  1. Demographic history, current expansion and future management challenges of wild boar populations in the Balkans and Europe.

    PubMed

    Veličković, N; Ferreira, E; Djan, M; Ernst, M; Obreht Vidaković, D; Monaco, A; Fonseca, C

    2016-11-01

    Wild boar (Sus scrofa), one of the most widespread wildlife species, has entered a stage of continuous growth in Europe, and could even be considered a pest species. We analysed microsatellite variability in 723 wild boars from across Europe, including the northern Dinaric Balkans. Our aims were: (1) to define the population structure of wild boars in the Balkans and its relation with other European populations; (2) to estimate effective populations sizes, levels of intra- and inter-population diversity, inbreeding migration and gene flow patterns; (3) to test subpopulations for bottlenecks; (4) to interpret these results in light of current knowledge about the demographic history of wild boars in Europe; and (5) to discuss the relevance of these findings for management and conservation. Strong population structuring was observed and 14 subpopulations were revealed. High genetic diversity was found, and besides the well-known identity of the Italian populations of Sardinia and Castelporziano, we bring new insights into other potential relevant, refugial populations such as Littoral Slovenia, South Portugal, North-western Iberia and an entire cluster in the Balkans. There was evidence of gene flow going from these refugial subpopulations towards less peripheral and more admixed subpopulations. Recent population bottlenecks and expansions were detected, mostly in the peninsular refuge subpopulations. The results are consistent with the fluctuations of wild boar numbers in Europe since the beginning of the twentieth century. These results should be taken into account in future conservation and management plans for wild boar populations in Europe.

  2. Purifying selection and demographic expansion affect sequence diversity of the ligand-binding domain of a glutamate-gated chloride channel gene of Haemonchus placei.

    PubMed

    Mes, Ted H M

    2004-04-01

    Ninety-five genomic sequences of the ligand-binding domain of glutamate-gated chloride channel genes of three populations of the parasitic nematode H. placei were evaluated for patterns of diversity, demography, and selection. These genes code for subunits of ion channels, which are involved in the mode of action of the most commonly used antiparasitic drugs, the macrocyclic lactones. An extremely high frequency of unique segregating sites in exons and introns was observed, with significantly negative neutrality tests in each population for noncoding, synonymous, and nonsynonymous sites. Several tests indicated that support for balancing selection, positive selection, and hitchhiking was lacking. McDonald-Kreitman tests using H. contortus or C. elegans as an outgroup revealed an extreme excess of replacement polymorphism, consistent with weak purifying selection. Although these tests agree that negative selection may explain the excess of replacement changes, an alternative interpretation is required for the significantly negative Fu and Li's D statistics based on silent and noncoding sites. These include homogeneous forces such as background selection and demographic expansion. The lack of population subdivision and the negative values of Tajima's D for this outbreeding parasitic nematode render background selection less likely than demographic expansion. Comparison of D statistics based on different site types using neutral coalescent simulations supported this interpretation. Although this statistic was more negative for nonsynonymous sites than for synonymous sites, most comparisons of the D statistic were not significantly different between mutation classes. A few significant site comparisons were also consistent with demographic expansion, because the observed test statistic ( D(neutral) - D(selected)) were low relative to the neutral expectations. Finally, previous mitochondrial studies also identified a demographic expansion of this parasitic nematode

  3. Range-wide population genetic structure of the Caribbean sea fan coral, Gorgonia ventalina.

    PubMed

    Andras, Jason P; Rypien, Krystal L; Harvell, Catherine D

    2013-01-01

    The population structure of benthic marine organisms is of central relevance to the conservation and management of these often threatened species, as well as to the accurate understanding of their ecological and evolutionary dynamics. A growing body of evidence suggests that marine populations can be structured over short distances despite theoretically high dispersal potential. Yet the proposed mechanisms governing this structure vary, and existing empirical population genetic evidence is of insufficient taxonomic and geographic scope to allow for strong general inferences. Here, we describe the range-wide population genetic structure of an ecologically important Caribbean octocoral, Gorgonia ventalina. Genetic differentiation was positively correlated with geographic distance and negatively correlated with oceanographically modelled dispersal probability throughout the range. Although we observed admixture across hundreds of kilometres, estimated dispersal was low, and populations were differentiated across distances <2 km. These results suggest that populations of G. ventalina may be evolutionarily coupled via gene flow but are largely demographically independent. Observed patterns of differentiation corroborate biogeographic breaks found in other taxa (e.g. an east/west divide near Puerto Rico), and also identify population divides not discussed in previous studies (e.g. the Yucatan Channel). High genotypic diversity and absence of clonemates indicate that sex is the primary reproductive mode for G. ventalina. A comparative analysis of the population structure of G. ventalina and its dinoflagellate symbiont, Symbiodinium, indicates that the dispersal of these symbiotic partners is not coupled, and symbiont transmission occurs horizontally.

  4. Range-wide Yangtze freshwater dolphin expedition: The last chance to see Baiji?

    PubMed

    Wang, Kexiong; Wang, Ding; Zhang, Xianfeng; Pfluger, August; Barrett, Leigh

    2006-10-01

    the main stream of the river, and in captivity, has to be considered urgently as the short-term goal of ex situ strategies. Since the abundance of porpoises is higher than that of the Baiji, we have first established breeding populations of them in the semi-natural reserves and in captivity. But, considering the extremely low density of Baiji in the river, an immediate range-wide Yangtze Baiji survey is an urgent need for locating and capturing sufficient Baiji for successfully establishing a breeding population of them in semi-natural reserves. Two semi-natural reserves (in Shishou, Hubei Province, and Tongling, Anhui Province) have been set up along the river in order to establish breeding populations of the Baiji and the porpoises. So far, several small groups of porpoises that were caught in the main stream of the river have successively been introduced into the semi-natural reserves. Under careful management, these animals in both of the semi-natural reserves not only survive, but can also reproduce naturally and successfully. At least one or three calves were born in each reserve each year. Additionally, a breeding group of porpoises is being established at the Baiji Dolphinarium at the Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan. There are presently four adults and one calf living in the Dolphinarium. The calf, born in July, 2005, is the first captive bred Yangtze Finless Porpoise in the world. In preparation for the range-wide Yangtze cetacean survey, a 9-day pilot expedition on the river near Wuhan was conducted in March, 2006, in order to develop methods for locating the Baiji. No Baiji were expected to be seen in such a short period but about 40 porpoise sightings were observed. Results of the pilot survey indicated that traditional visual and acoustical survey methods for cetaceans should be adapted to find the elusive Baiji in the river. Currently, the range-wide Yangtze cetacean survey is in preparation. The survey will cover over 1

  5. Genetic Signatures of Demographic Changes in an Avian Top Predator during the Last Century: Bottlenecks and Expansions of the Eurasian Eagle Owl in the Iberian Peninsula

    PubMed Central

    Graciá, Eva; Ortego, Joaquín; Godoy, José Antonio; Pérez-García, Juan Manuel; Blanco, Guillermo; del Mar Delgado, María; Penteriani, Vincenzo; Almodóvar, Irene; Botella, Francisco; Sánchez-Zapata, José Antonio

    2015-01-01

    The study of the demographic history of species can help to understand the negative impact of recent population declines in organisms of conservation concern. Here, we use neutral molecular markers to explore the genetic consequences of the recent population decline and posterior recovery of the Eurasian eagle owl (Bubo bubo) in the Iberian Peninsula. During the last century, the species was the object of extermination programs, suffering direct persecution by hunters until the 70’s. Moreover, during the last decades the eagle owl was severely impacted by increased mortality due to electrocution and the decline of its main prey species, the European rabbit (Oryctolagus cuniculus). In recent times, the decrease of direct persecution and the implementation of some conservation schemes have allowed the species’ demographic recovery. Yet, it remains unknown to which extent the past population decline and the later expansion have influenced the current species’ pattern of genetic diversity. We used eight microsatellite markers to genotype 235 eagle owls from ten Spanish subpopulations and analyse the presence of genetic signatures attributable to the recent population fluctuations experienced by the species. We found moderate levels of differentiation among the studied subpopulations and Bayesian analyses revealed the existence of three genetic clusters that grouped subpopulations from central, south-western and south-eastern Spain. The observed genetic structure could have resulted from recent human-induced population fragmentation, a patchy distribution of prey populations and/or the philopatric behaviour and habitat selection of the species. We detected an old population bottleneck, which occurred approximately 10,000 years ago, and significant signatures of recent demographic expansions. However, we did not find genetic signatures for a recent bottleneck, which may indicate that population declines were not severe enough to leave detectable signals on the

  6. Genetic Signatures of Demographic Changes in an Avian Top Predator during the Last Century: Bottlenecks and Expansions of the Eurasian Eagle Owl in the Iberian Peninsula.

    PubMed

    Graciá, Eva; Ortego, Joaquín; Godoy, José Antonio; Pérez-García, Juan Manuel; Blanco, Guillermo; Delgado, María del Mar; Penteriani, Vincenzo; Almodóvar, Irene; Botella, Francisco; Sánchez-Zapata, José Antonio

    2015-01-01

    The study of the demographic history of species can help to understand the negative impact of recent population declines in organisms of conservation concern. Here, we use neutral molecular markers to explore the genetic consequences of the recent population decline and posterior recovery of the Eurasian eagle owl (Bubo bubo) in the Iberian Peninsula. During the last century, the species was the object of extermination programs, suffering direct persecution by hunters until the 70's. Moreover, during the last decades the eagle owl was severely impacted by increased mortality due to electrocution and the decline of its main prey species, the European rabbit (Oryctolagus cuniculus). In recent times, the decrease of direct persecution and the implementation of some conservation schemes have allowed the species' demographic recovery. Yet, it remains unknown to which extent the past population decline and the later expansion have influenced the current species' pattern of genetic diversity. We used eight microsatellite markers to genotype 235 eagle owls from ten Spanish subpopulations and analyse the presence of genetic signatures attributable to the recent population fluctuations experienced by the species. We found moderate levels of differentiation among the studied subpopulations and Bayesian analyses revealed the existence of three genetic clusters that grouped subpopulations from central, south-western and south-eastern Spain. The observed genetic structure could have resulted from recent human-induced population fragmentation, a patchy distribution of prey populations and/or the philopatric behaviour and habitat selection of the species. We detected an old population bottleneck, which occurred approximately 10,000 years ago, and significant signatures of recent demographic expansions. However, we did not find genetic signatures for a recent bottleneck, which may indicate that population declines were not severe enough to leave detectable signals on the species

  7. Demographic inference using spectral methods on SNP data, with an analysis of the human out-of-Africa expansion.

    PubMed

    Lukic, Sergio; Hey, Jody

    2012-10-01

    We present an implementation of a recently introduced method for estimating the allele-frequency spectrum under the diffusion approximation. For single-nucleotide polymorphism (SNP) frequency data from multiple populations, the method computes numerical solutions to the allele-frequency spectrum (AFS) under a complex model that includes population splitting events, migration, population expansion, and admixture. The solution to the diffusion partial differential equation (PDE) that mimics the evolutionary process is found by means of truncated polynomial expansions. In the absence of gene flow, our computation of frequency spectra yields exact results. The results are compared to those that use a finite-difference method and to forward diffusion simulations. In general, all the methods yield comparable results, although the polynomial-based approach is the most accurate in the weak-migration limit. Also, the economical use of memory attained by the polynomial expansions makes the study of models with four populations possible for the first time. The method was applied to a four-population model of the human expansion out of Africa and the peopling of the Americas, using the Environmental Genome Project (EGP) SNP database. Although our confidence intervals largely overlapped previous analyses of these data, some were significantly different. In particular, estimates of migration among African, European, and Asian populations were considerably lower than those in a previous study and the estimated time of migration out of Africa was earlier. The estimated time of founding of a human population outside of Africa was 52,000 years (95% confidence interval: 36,000-80,800 years).

  8. Demographic Inference Using Spectral Methods on SNP Data, with an Analysis of the Human Out-of-Africa Expansion

    PubMed Central

    Lukić, Sergio; Hey, Jody

    2012-01-01

    We present an implementation of a recently introduced method for estimating the allele-frequency spectrum under the diffusion approximation. For single-nucleotide polymorphism (SNP) frequency data from multiple populations, the method computes numerical solutions to the allele-frequency spectrum (AFS) under a complex model that includes population splitting events, migration, population expansion, and admixture. The solution to the diffusion partial differential equation (PDE) that mimics the evolutionary process is found by means of truncated polynomial expansions. In the absence of gene flow, our computation of frequency spectra yields exact results. The results are compared to those that use a finite-difference method and to forward diffusion simulations. In general, all the methods yield comparable results, although the polynomial-based approach is the most accurate in the weak-migration limit. Also, the economical use of memory attained by the polynomial expansions makes the study of models with four populations possible for the first time. The method was applied to a four-population model of the human expansion out of Africa and the peopling of the Americas, using the Environmental Genome Project (EGP) SNP database. Although our confidence intervals largely overlapped previous analyses of these data, some were significantly different. In particular, estimates of migration among African, European, and Asian populations were considerably lower than those in a previous study and the estimated time of migration out of Africa was earlier. The estimated time of founding of a human population outside of Africa was 52,000 years (95% confidence interval: 36,000–80,800 years). PMID:22865734

  9. Range-wide multilocus phylogeography of the red fox reveals ancient continental divergence, minimal genomic exchange and distinct demographic histories

    Treesearch

    Mark J. Statham; James Murdoch; Jan Janecka; Keith B. Aubry; Ceiridwen J. Edwards; Carl D. Soulsbury; Oliver Berry; Zhenghuan Wang; David Harrison; Malcolm Pearch; Louise Tomsett; Judith Chupasko; Benjamin N. Sacks

    2014-01-01

    Widely distributed taxa provide an opportunity to compare biogeographic responses to climatic fluctuations on multiple continents and to investigate speciation. We conducted the most geographically and genomically comprehensive study to date of the red fox (Vulpes vulpes), the world’s most widely distributed wild terrestrial carnivore. Analyses of 697 bp of...

  10. A range-wide synthesis and timeline for phylogeographic events in the red fox (Vulpes vulpes).

    PubMed

    Kutschera, Verena E; Lecomte, Nicolas; Janke, Axel; Selva, Nuria; Sokolov, Alexander A; Haun, Timm; Steyer, Katharina; Nowak, Carsten; Hailer, Frank

    2013-06-05

    Many boreo-temperate mammals have a Pleistocene fossil record throughout Eurasia and North America, but only few have a contemporary distribution that spans this large area. Examples of Holarctic-distributed carnivores are the brown bear, grey wolf, and red fox, all three ecological generalists with large dispersal capacity and a high adaptive flexibility. While the two former have been examined extensively across their ranges, no phylogeographic study of the red fox has been conducted across its entire Holarctic range. Moreover, no study included samples from central Asia, leaving a large sampling gap in the middle of the Eurasian landmass. Here we provide the first mitochondrial DNA sequence data of red foxes from central Asia (Siberia), and new sequences from several European populations. In a range-wide synthesis of 729 red fox mitochondrial control region sequences, including 677 previously published and 52 newly obtained sequences, this manuscript describes the pattern and timing of major phylogeographic events in red foxes, using a Bayesian coalescence approach with multiple fossil tip and root calibration points. In a 335 bp alignment we found in total 175 unique haplotypes. All newly sequenced individuals belonged to the previously described Holarctic lineage. Our analyses confirmed the presence of three Nearctic- and two Japan-restricted lineages that were formed since the Mid/Late Pleistocene. The phylogeographic history of red foxes is highly similar to that previously described for grey wolves and brown bears, indicating that climatic fluctuations and habitat changes since the Pleistocene had similar effects on these highly mobile generalist species. All three species originally diversified in Eurasia and later colonized North America and Japan. North American lineages persisted through the last glacial maximum south of the ice sheets, meeting more recent colonizers from Beringia during postglacial expansion into the northern Nearctic. Both brown

  11. A range-wide synthesis and timeline for phylogeographic events in the red fox (Vulpes vulpes)

    PubMed Central

    2013-01-01

    Background Many boreo-temperate mammals have a Pleistocene fossil record throughout Eurasia and North America, but only few have a contemporary distribution that spans this large area. Examples of Holarctic-distributed carnivores are the brown bear, grey wolf, and red fox, all three ecological generalists with large dispersal capacity and a high adaptive flexibility. While the two former have been examined extensively across their ranges, no phylogeographic study of the red fox has been conducted across its entire Holarctic range. Moreover, no study included samples from central Asia, leaving a large sampling gap in the middle of the Eurasian landmass. Results Here we provide the first mitochondrial DNA sequence data of red foxes from central Asia (Siberia), and new sequences from several European populations. In a range-wide synthesis of 729 red fox mitochondrial control region sequences, including 677 previously published and 52 newly obtained sequences, this manuscript describes the pattern and timing of major phylogeographic events in red foxes, using a Bayesian coalescence approach with multiple fossil tip and root calibration points. In a 335 bp alignment we found in total 175 unique haplotypes. All newly sequenced individuals belonged to the previously described Holarctic lineage. Our analyses confirmed the presence of three Nearctic- and two Japan-restricted lineages that were formed since the Mid/Late Pleistocene. Conclusions The phylogeographic history of red foxes is highly similar to that previously described for grey wolves and brown bears, indicating that climatic fluctuations and habitat changes since the Pleistocene had similar effects on these highly mobile generalist species. All three species originally diversified in Eurasia and later colonized North America and Japan. North American lineages persisted through the last glacial maximum south of the ice sheets, meeting more recent colonizers from Beringia during postglacial expansion into the

  12. Evolutionary history of a widespread Indo-Pacific goby: the role of Pleistocene sea-level changes on demographic contraction/expansion dynamics.

    PubMed

    Hoareau, Thierry Bernard; Boissin, Emilie; Berrebi, Patrick

    2012-01-01

    Compared to endemics, widespread species are of particular interest to retrace recent evolutionary history. These species have a large population size which provides a clearer genetic signature of past events. Moreover, their wide geographic range increases the potential occurrence of evolutionary events (expansion, divergence, etc.). Here, we used several coalescent-based methods to disentangle the evolutionary history of a widespread amphidromous goby (Sicyopterus lagocephalus), in the light of sea-level variations during the Pleistocene. Using 75 samples recovered from three biogeographic regions (Western Indian Ocean, Melanesia and Polynesia), we analysed a portion of the cytochromeb gene and confirmed three major haplogroups, each specific to a region. Furthermore, we found that: (1) the Melanesian haplogroup was the oldest while the two peripheral regions hosted daughter haplogroups; (2) two centrifugal colonisation events occurred from Melanesia to the periphery, each synchronised with periods of strong paleo-ENSO episodes; (3) the demographic contraction-expansion events were linked to Pleistocene sea-level changes; (4) Melanesia and Polynesia acted as efficient refuges during the Last Glacial Maximum. These results highlight the importance of studying widespread species to better understand the role of climate changes and paleo-oceanography on the evolution of biodiversity. Copyright © 2011 Elsevier Inc. All rights reserved.

  13. Diversification in subtropical mountains: phylogeography, Pleistocene demographic expansion, and evolution of polyphenic mandibles in Taiwanese stag beetle, Lucanus formosanus.

    PubMed

    Huang, Jen-Pan; Lin, Chung-Ping

    2010-12-01

    Pleistocene glacial oscillations have had profound impacts on the historical population dynamics of extant species. However, the genetic consequences of past climatic changes depend largely on the latitude and topography of the regions in question. This study investigates the effect of Pleistocene glacial periods and the Central Mountain Range on the phylogeography, historical demography, and phenotypic differentiation of a montane forest-dwelling stag beetle, Lucanus formosanus (Coleoptera: Lucanidae), which exhibits extensive mandible variations across mountain ranges in subtropical Taiwan. Analyses of mitochondrial (cox1) and nuclear (wg) loci reveal that L. formosanus originated nearly 1.6 million years ago (Mya) in the early Pleistocene period and consisted of geographically overlapping Alishan and Widespread clades. A drastic population expansion starting approximately 0.2 Mya in the Widespread clade likely resulted from altitudinal range shift of the temperate forests, which was closely tied to the arrival of the Riss glacial period in the late Middle Pleistocene. A ring-like pattern of historical gene flow among neighboring populations in the vicinity of the Central Mountain Range indicates that the mountains constitute a strong vicariant barrier to the east-west gene flow of L. formosanus populations. A geographic cline of decreasing mandible size from central to north and south, and onto southeast of Taiwan is inconsistent with the low overall phylogeographic structures. The degree of mandible variation does not correlate with the expected pattern of neutral evolution, indicating that the evolutionary diversification of this morphological weapon is most likely subject to sexual or natural selection. We hypothesize that the adaptive evolution of mandibles in L. formosanus is shaped largely by the habitat heterogeneity.

  14. Forecasting deforestation and carbon emissions in tropical developing countries facing demographic expansion: a case study in Madagascar.

    PubMed

    Vieilledent, Ghislain; Grinand, Clovis; Vaudry, Romuald

    2013-06-01

    Anthropogenic deforestation in tropical countries is responsible for a significant part of global carbon dioxide emissions in the atmosphere. To plan efficient climate change mitigation programs (such as REDD+, Reducing Emissions from Deforestation and forest Degradation), reliable forecasts of deforestation and carbon dioxide emissions are necessary. Although population density has been recognized as a key factor in tropical deforestation, current methods of prediction do not allow the population explosion that is occurring in many tropical developing countries to be taken into account. Here, we propose an innovative approach using novel computational and statistical tools, including R/GRASS scripts and the new phcfM R package, to model the intensity and location of deforestation including the effect of population density. We used the model to forecast anthropogenic deforestation and carbon dioxide emissions in five large study areas in the humid and spiny-dry forests of Madagascar. Using our approach, we were able to demonstrate that the current rapid population growth in Madagascar (+3.39% per year) will significantly increase the intensity of deforestation by 2030 (up to +1.17% per year in densely populated areas). We estimated the carbon dioxide emissions associated with the loss of aboveground biomass to be of 2.24 and 0.26 tons per hectare and per year in the humid and spiny-dry forest, respectively. Our models showed better predictive ability than previous deforestation models (the figure of merit ranged from 10 to 23). We recommend this approach to reduce the uncertainty associated with deforestation forecasts. We also underline the risk of an increase in the speed of deforestation in the short term in tropical developing countries undergoing rapid population expansion.

  15. Forecasting deforestation and carbon emissions in tropical developing countries facing demographic expansion: a case study in Madagascar

    PubMed Central

    Vieilledent, Ghislain; Grinand, Clovis; Vaudry, Romuald

    2013-01-01

    Anthropogenic deforestation in tropical countries is responsible for a significant part of global carbon dioxide emissions in the atmosphere. To plan efficient climate change mitigation programs (such as REDD+, Reducing Emissions from Deforestation and forest Degradation), reliable forecasts of deforestation and carbon dioxide emissions are necessary. Although population density has been recognized as a key factor in tropical deforestation, current methods of prediction do not allow the population explosion that is occurring in many tropical developing countries to be taken into account. Here, we propose an innovative approach using novel computational and statistical tools, including R/GRASS scripts and the new phcfM R package, to model the intensity and location of deforestation including the effect of population density. We used the model to forecast anthropogenic deforestation and carbon dioxide emissions in five large study areas in the humid and spiny-dry forests of Madagascar. Using our approach, we were able to demonstrate that the current rapid population growth in Madagascar (+3.39% per year) will significantly increase the intensity of deforestation by 2030 (up to +1.17% per year in densely populated areas). We estimated the carbon dioxide emissions associated with the loss of aboveground biomass to be of 2.24 and 0.26 tons per hectare and per year in the humid and spiny-dry forest, respectively. Our models showed better predictive ability than previous deforestation models (the figure of merit ranged from 10 to 23). We recommend this approach to reduce the uncertainty associated with deforestation forecasts. We also underline the risk of an increase in the speed of deforestation in the short term in tropical developing countries undergoing rapid population expansion. PMID:23789079

  16. New Mitochondrial and Nuclear Evidences Support Recent Demographic Expansion and an Atypical Phylogeographic Pattern in the Spittlebug Philaenus spumarius (Hemiptera, Aphrophoridae)

    PubMed Central

    Rodrigues, Ana S. B.; Silva, Sara E.; Marabuto, Eduardo; Silva, Diogo N.; Wilson, Mike R.; Thompson, Vinton; Yurtsever, Selçuk; Halkka, Antti; Borges, Paulo A. V.; Quartau, José A.; Paulo, Octávio S.; Seabra, Sofia G.

    2014-01-01

    Philaenus spumarius is a widespread insect species in the Holarctic region. Here, by focusing on the mtDNA gene COI but also using the COII and Cyt b genes and the nuclear gene EF-1α, we tried to explain how and when its current biogeographic pattern evolved by providing time estimates of the main demographic and evolutionary events and investigating its colonization patterns in and out of Eurasia. Evidence of recent divergence and expansion events at less than 0.5 Ma ago indicate that climate fluctuations in the Mid-Late Pleistocene were important in shaping the current phylogeographic pattern of the species. Data support a first split and differentiation of P. spumarius into two main mitochondrial lineages: the “western”, in the Mediterranean region and the “eastern”, in Anatolia/Caucasus. It also supports a following differentiation of the “western” lineage into two sub-lineages: the “western-Mediterranean”, in Iberia and the “eastern-Mediterranean” in the Balkans. The recent pattern seems to result from postglacial range expansion from Iberia and Caucasus/Anatolia, thus not following one of the four common paradigms. Unexpected patterns of recent gene-flow events between Mediterranean peninsulas, a close relationship between Iberia and North Africa, as well as high levels of genetic diversity being maintained in northern Europe were found. The mitochondrial pattern does not exactly match to the nuclear pattern suggesting that the current biogeographic pattern of P. spumarius may be the result of both secondary admixture and incomplete lineage sorting. The hypothesis of recent colonization of North America from both western and northern Europe is corroborated by our data and probably resulted from accidental human translocations. A probable British origin for the populations of the Azores and New Zealand was revealed, however, for the Azores the distribution of populations in high altitude native forests is somewhat puzzling and may imply a

  17. Simulating range-wide population and breeding habitat dynamics for an endangered woodland warbler in the face of uncertainty

    USGS Publications Warehouse

    Adam Duarte,; Hatfield, Jeffrey; Todd M. Swannack,; Michael R. J. Forstner,; M. Clay Green,; Floyd W. Weckerly,

    2015-01-01

    Population viability analyses provide a quantitative approach that seeks to predict the possible future status of a species of interest under different scenarios and, therefore, can be important components of large-scale species’ conservation programs. We created a model and simulated range-wide population and breeding habitat dynamics for an endangered woodland warbler, the golden-cheeked warbler (Setophaga chrysoparia). Habitat-transition probabilities were estimated across the warbler's breeding range by combining National Land Cover Database imagery with multistate modeling. Using these estimates, along with recently published demographic estimates, we examined if the species can remain viable into the future given the current conditions. Lastly, we evaluated if protecting a greater amount of habitat would increase the number of warblers that can be supported in the future by systematically increasing the amount of protected habitat and comparing the estimated terminal carrying capacity at the end of 50 years of simulated habitat change. The estimated habitat-transition probabilities supported the hypothesis that habitat transitions are unidirectional, whereby habitat is more likely to diminish than regenerate. The model results indicated population viability could be achieved under current conditions, depending on dispersal. However, there is considerable uncertainty associated with the population projections due to parametric uncertainty. Model results suggested that increasing the amount of protected lands would have a substantial impact on terminal carrying capacities at the end of a 50-year simulation. Notably, this study identifies the need for collecting the data required to estimate demographic parameters in relation to changes in habitat metrics and population density in multiple regions, and highlights the importance of establishing a common definition of what constitutes protected habitat, what management goals are suitable within those protected

  18. Spatiotemporal variation in range-wide Golden-cheeked Warbler habitat

    USGS Publications Warehouse

    Duarte, Adam; Jensen, Jennifer; Hatfield, Jeffrey S.; Weckerly, Floyd

    2013-01-01

    Habitat availability ultimately limits the distribution and abundance of wildlife species. Consequently, it is paramount to identify where wildlife habitat is and understand how it changes over time in order to implement large scale wildlife conservation plans. Yet, no work has quantified the degree of change in range-wide breeding habitat for the golden-cheeked warbler (Setophaga chrysoparia), despite the species being listed as endangered by the U.S. federal government. Thus, using available geographic information system (GIS) data and Landsat satellite imagery we quantified range-wide warbler breeding habitat change from 1999-2001 to 2010-2011. We detected a 29% reduction in total warbler breeding habitat and found that warbler breeding habitat was removed and became more fragmented at uneven rates across the warbler’s breeding range during this time period. This information will assist researchers and managers in prioritizing breeding habitat conservation efforts for the species and provide a foundation for more realistic carrying capacity scenarios when modeling golden-cheeked warbler populations over time. Additionally, this study highlights the need for future work centered on quantifying golden-cheeked warbler movement rates and distances in order to assess the degree of connectivity between increasingly fragmented habitat patches.

  19. Range-wide phylogeography and conservation genetics of a narrowly endemic stream salamander, Pachyhynobius shangchengensis (Caudata, Hynobiidae): implications for conservation.

    PubMed

    Pan, T; Wang, H; Hu, C-C; Shi, W-B; Zhao, K; Huang, X; Zhang, B-W

    2014-02-13

    The Shangcheng stout salamander (Pachyhynobius shangchengensis) is an endangered amphibian endemic to the Dabie Mountains, southeast China, and is currently threatened by habitat loss and illegal poaching. Here we used the mitochondrial DNA control region sequence (768 bp) to conduct a comprehensive investigation of genetic diversity, phylogeographic pattern, and demographic history of the species across its geographic distribution to assist its conservation. We concluded that the levels of genetic variation are relatively low in all four populations. Analysis of molecular variance indicated that the most likely phylogeographic pattern is [JGT] [KHJ] [TM, BYM]. Two distinct clades were identified in the phylogenetic tree of 28 haplotypes, corresponding to the two southern populations (TM, BYM) and two northern populations (JGT, KHJ). Significant population differentiation (FST) was detected among all populations. Among the four populations, historical demographic analyses (e.g., the g parameter, the Tajima D test, and the Fu Fs test) did not reveal definite information on population expansion except for the BYM population, which had undergone a strong population expansion event. Based on the analysis of a Bayesian skyline plot, the total population underwent a significant population fluctuation around 20 kya. This may have been triggered by the end of the last glacial maximum. In conclusion, the existence of three evolutionarily significant units (BMY-TM, KHJ, and JGT) and four management units (BMY, TM, KHJ, and JGT) is supported by our study.

  20. Australian SKA Pathfinder: A High-Dynamic Range Wide-Field of View Survey Telescope

    NASA Astrophysics Data System (ADS)

    DeBoer, D. R.; Gough, R. G.; Bunton, J. D.; Cornwell, T. J.; Beresford, R. J.; Johnston, S.; Feain, I. J.; Schinckel, A. E.; Jackson, C. A.; Kesteven, M. J.; Chippendale, A.; Hampson, G. A.; O'Sullivan, J. D.; Hay, S. G.; Jacka, C. E.; Sweetnam, T. W.; Storey, M. C.; Ball, L.; Boyle, B. J.

    2009-08-01

    The Australia SKA Pathfinder (ASKAP) is a new telescope under development as a world-class high-dynamic-range wide-field-of-view survey instrument. It will utilize focal plane phased array feeds on the 36 12-m antennas that will compose the array. The large amounts of data present a huge computing challenge, and ASKAP will store data products in an archive after near real-time pipeline processing. This powerful instrument will be deployed at a new radio-quiet observatory, the Murchison Radio-astronomy Observatory in the midwest region of Western Australia, to enable sensitive surveys of the entire sky to address some of the big questions in contemporary physics. As a pathfinder for the SKA, ASKAP will demonstrate field of view enhancement and computing/processing technology as well as the operation of a large-scale radio array in a remote and radio-quiet region of Australia.

  1. Range-wide assessment of livestock grazing across the sagebrush biome

    USGS Publications Warehouse

    Veblen, Kari E.; Pyke, David A.; Aldridge, Cameron L.; Casazza, Michael L.; Assal, Timothy J.; Farinha, Melissa A.

    2011-01-01

    Domestic livestock grazing occurs in virtually all sagebrush habitats and is a prominent disturbance factor. By affecting habitat condition and trend, grazing influences the resources required by, and thus, the distribution and abundance of sagebrush-obligate wildlife species (for example, sage-grouse Centrocercus spp.). Yet, the risks that livestock grazing may pose to these species and their habitats are not always clear. Although livestock grazing intensity and associated habitat condition may be known in many places at the local level, we have not yet been able to answer questions about use, condition, and trend at the landscape scale or at the range-wide scale for wildlife species. A great deal of information about grazing use, management regimes, and ecological condition exists at the local level (for individual livestock management units) under the oversight of organizations such as the Bureau of Land Management (BLM). However, the extent, quality, and types of existing data are unknown, which hinders the compilation, mapping, or analysis of these data. Once compiled, these data may be helpful for drawing conclusions about rangeland status, and we may be able to identify relationships between those data and wildlife habitat at the landscape scale. The overall objective of our study was to perform a range-wide assessment of livestock grazing effects (and the relevant supporting data) in sagebrush ecosystems managed by the BLM. Our assessments and analyses focused primarily on local-level management and data collected at the scale of BLM grazing allotments (that is, individual livestock management units). Specific objectives included the following: 1. Identify and refine existing range-wide datasets to be used for analyses of livestock grazing effects on sagebrush ecosystems. 2. Assess the extent, quality, and types of livestock grazing-related natural resource data collected by BLM range-wide (i.e., across allotments, districts and regions). 3. Compile and

  2. A projection of lesser prairie chicken (Tympanuchus pallidicinctus) populations range-wide

    USGS Publications Warehouse

    Cummings, Jonathan W.; Converse, Sarah J.; Moore, Clinton T.; Smith, David R.; Nichols, Clay T.; Allan, Nathan L.; O'Meilia, Chris M.

    2017-08-09

    We built a population viability analysis (PVA) model to predict future population status of the lesser prairie-chicken (Tympanuchus pallidicinctus, LEPC) in four ecoregions across the species’ range. The model results will be used in the U.S. Fish and Wildlife Service's (FWS) Species Status Assessment (SSA) for the LEPC. Our stochastic projection model combined demographic rate estimates from previously published literature with demographic rate estimates that integrate the influence of climate conditions. This LEPC PVA projects declining populations with estimated population growth rates well below 1 in each ecoregion regardless of habitat or climate change. These results are consistent with estimates of LEPC population growth rates derived from other demographic process models. Although the absolute magnitude of the decline is unlikely to be as low as modeling tools indicate, several different lines of evidence suggest LEPC populations are declining.

  3. Recommended methods for range-wide monitoring of prairie dogs in the United States

    USGS Publications Warehouse

    McDonald, Lyman L.; Stanley, Thomas R.; Otis, David L.; Biggins, Dean E.; Stevens, Patricia D.; Koprowski, John L.; Ballard, Warren

    2011-01-01

    One of the greatest challenges for conserving grassland, prairie scrub, and shrub-steppe ecosystems is maintaining prairie dog populations across the landscape. Of the four species of prairie dogs found in the United States, the Utah prairie dog (Cynomys parvidens) is listed under the Endangered Species Act (ESA) as threatened, the Gunnison's prairie dog (C. gunnisoni) is a candidate for listing in a portion of its range, and the black-tailed prairie dog (C. ludovicianus) and white-tailed prairie dog (C. leucurus) have each been petitioned for listing at least once in recent history. Although the U.S. Fish and Wildlife Service (USFWS) determined listing is not warranted for either the black-tailed prairie dog or white-tailed prairie dog, the petitions and associated reviews demonstrated the need for the States to monitor and manage for self-sustaining populations. In response to these findings, a multi-State conservation effort was initiated for the nonlisted species which included the following proposed actions: (1) completing an assessment of each prairie dog species in each State, (2) developing a range-wide monitoring protocol for each species using a statistically valid sampling procedure that would allow comparable analyses across States, and (3) monitoring prairie dog status every 3-5 years depending upon the species. To date, each State has completed an assessment and currently is monitoring prairie dog status; however, for some species, the inconsistency in survey methodology has made it difficult to compare data year-to-year or State-to-State. At the Prairie Dog Conservation Team meeting held in November 2008, there was discussion regarding the use of different methods to survey prairie dogs. A recommendation from this meeting was to convene a panel in a workshop-type forum and have the panel review the different methods being used and provide recommendations for range-wide monitoring protocols for each species of prairie dog. Consequently, the Western

  4. Range-wide genetic connectivity of the Hawaiian monk seal and implications for translocation.

    PubMed

    Schultz, Jennifer K; Baker, Jason D; Toonen, Robert J; Harting, Albert L; Bowen, Brian W

    2011-02-01

    The Hawaiian monk seal (Monachus schauinslandi) is one of the most critically endangered marine mammals. Less than 1200 individuals remain, and the species is declining at a rate of approximately 4% per year as a result of juvenile starvation, shark predation, and entanglement in marine debris. Some of these problems may be alleviated by translocation; however, if island breeding aggregates are effectively isolated subpopulations, moving individuals may disrupt local adaptations. In these circumstances, managers must balance the pragmatic need of increasing survival with theoretical concerns about genetic viability. To assess range-wide population structure of the Hawaiian monk seal, we examined an unprecedented, near-complete genetic inventory of the species (n =1897 seals, sampled over 14 years) at 18 microsatellite loci. Genetic variation was not spatially partitioned ((w) =-0.03, p = 1.0), and a Bayesian clustering method provided evidence of one panmictic population (K =1). Pairwise F(ST) comparisons (among 7 island aggregates over 14 annual cohorts) did not reveal temporally stable, spatial reproductive isolation. Our results coupled with long-term tag-resight data confirm seal movement and gene flow throughout the Hawaiian Archipelago. Thus, human-mediated translocation of seals among locations is not likely to result in genetic incompatibilities.

  5. Connectivity of wood thrush breeding, wintering, and migration sites based on range-wide tracking.

    PubMed

    Stanley, Calandra Q; McKinnon, Emily A; Fraser, Kevin C; Macpherson, Maggie P; Casbourn, Garth; Friesen, Lyle; Marra, Peter P; Studds, Colin; Ryder, T Brandt; Diggs, Nora E; Stutchbury, Bridget J M

    2015-02-01

    Many migratory animals are experiencing rapid population declines, but migration data with the geographic scope and resolution to quantify the complex network of movements between breeding and nonbreeding regions are often lacking. Determining the most frequently used migration routes and nonbreeding regions for a species is critical for understanding population dynamics and making effective conservation decisions. We tracked the migration of individual Wood Thrushes (Hylocichla mustelina) (n = 102) from across their range with light-level geolocators and, for the first time, quantified migration routes and wintering regions for distinct breeding populations. We identified regional and species-level migratory connectivity networks for this declining songbird by combining our tracking results with range-wide breeding abundance estimates and forest cover data. More than 50% of the species occupied the eastern wintering range (Honduras to Costa Rica), a region that includes only one-third of all wintering habitat and that is undergoing intensive deforestation. We estimated that half of all Wood Thrushes in North America migrate south through Florida in fall, whereas in spring approximately 73% funnel northward through a narrow span along the central U.S. Gulf Coast (88-93°W). Identifying migratory networks is a critical step for conservation of songbirds and we demonstrated with Wood Thrushes how it can highlight conservation hotspots for regional populations and species as a whole. © 2014 Society for Conservation Biology.

  6. Range-wide patterns of nuclear and chloroplast DNA diversity in Vriesea gigantea (Bromeliaceae), a neotropical forest species.

    PubMed

    Palma-Silva, C; Lexer, C; Paggi, G M; Barbará, T; Bered, F; Bodanese-Zanettini, M H

    2009-12-01

    The processes that have shaped the extraordinary species diversity in neotropical rainforests are poorly understood, and knowledge about the patterns of genetic diversity across species' ranges is scarce, in contrast to other regions of the globe. We have conducted a range-wide study of genetic diversity in a plant endemic to the Brazilian Atlantic Rainforest, Vriesea gigantea (Bromeliaceae), based on a combined data set of nuclear microsatellites and chloroplast (cp) DNA markers typed in 429 plants from 13 populations. The results indicate a strong negative correlation between genetic diversity and population latitude, consistent with historical forest expansion from the northern half of the present distribution range. A deep phylogeographic split exists between the Brazilian states of São Paulo and Rio de Janeiro at ca. 23 degrees S latitude, probably reflecting past population isolation within more than one glacial refuge during the climatic changes of the Pleistocene. A comparison of genetic structures at cpDNA and nuclear markers revealed a pollen/seed flow ratio of more than 3:1, thus indicating an important role of the pollinating animals (that is, bats) in shaping the population genetic structure of this species. Diversity was reduced for cpDNA markers in the island populations off the coast, and reduced diversity and increased differentiation were observed for both nuclear and cpDNA at the edges of the species' range. The link between patterns of genetic and species diversity supports the hypothesis that both were shaped by the same biogeographic processes, triggered by the climatic oscillations of the Pleistocene.

  7. Range-wide mtDNA phylogeography yields insights into the origins of Asian elephants.

    PubMed

    Vidya, T N C; Sukumar, Raman; Melnick, Don J

    2009-03-07

    Recent phylogeographic studies of the endangered Asian elephant (Elephas maximus) reveal two highly divergent mitochondrial DNA (mtDNA) lineages, an elucidation of which is central to understanding the species's evolution. Previous explanations for the divergent clades include introgression of mtDNA haplotypes between ancestral species, allopatric divergence of the clades between Sri Lanka or the Sunda region and the mainland, historical trade of elephants, and retention of divergent lineages due to large population sizes. However, these studies lacked data from India and Myanmar, which host approximately 70 per cent of all extant Asian elephants. In this paper, we analyse mtDNA sequence data from 534 Asian elephants across the species's range to explain the current distribution of the two divergent clades. Based on phylogenetic reconstructions, estimates of times of origin of clades, probable ancestral areas of origin inferred from dispersal-vicariance analyses and the available fossil record, we believe both clades originated from Elephas hysudricus. This probably occurred allopatrically in different glacial refugia, the alpha clade in the Myanmar region and the beta clade possibly in southern India-Sri Lanka, 1.6-2.1Myr ago. Results from nested clade and dispersal-vicariance analyses indicate a subsequent isolation and independent diversification of the beta clade in both Sri Lanka and the Sunda region, followed by northward expansion of the clade. We also find more recent population expansions in both clades based on mismatch distributions. We therefore suggest a contraction-expansion scenario during severe climatic oscillations of the Quaternary, with range expansions from different refugia during warmer interglacials leading to the varying geographical overlaps of the two mtDNA clades. We also demonstrate that trade in Asian elephants has not substantially altered the species's mtDNA population genetic structure.

  8. Range-wide mtDNA phylogeography yields insights into the origins of Asian elephants

    PubMed Central

    Vidya, T.N.C.; Sukumar, Raman; Melnick, Don J.

    2008-01-01

    Recent phylogeographic studies of the endangered Asian elephant (Elephas maximus) reveal two highly divergent mitochondrial DNA (mtDNA) lineages, an elucidation of which is central to understanding the species's evolution. Previous explanations for the divergent clades include introgression of mtDNA haplotypes between ancestral species, allopatric divergence of the clades between Sri Lanka or the Sunda region and the mainland, historical trade of elephants, and retention of divergent lineages due to large population sizes. However, these studies lacked data from India and Myanmar, which host approximately 70 per cent of all extant Asian elephants. In this paper, we analyse mtDNA sequence data from 534 Asian elephants across the species's range to explain the current distribution of the two divergent clades. Based on phylogenetic reconstructions, estimates of times of origin of clades, probable ancestral areas of origin inferred from dispersal–vicariance analyses and the available fossil record, we believe both clades originated from Elephas hysudricus. This probably occurred allopatrically in different glacial refugia, the α clade in the Myanmar region and the β clade possibly in southern India–Sri Lanka, 1.6–2.1 Myr ago. Results from nested clade and dispersal–vicariance analyses indicate a subsequent isolation and independent diversification of the β clade in both Sri Lanka and the Sunda region, followed by northward expansion of the clade. We also find more recent population expansions in both clades based on mismatch distributions. We therefore suggest a contraction–expansion scenario during severe climatic oscillations of the Quaternary, with range expansions from different refugia during warmer interglacials leading to the varying geographical overlaps of the two mtDNA clades. We also demonstrate that trade in Asian elephants has not substantially altered the species's mtDNA population genetic structure. PMID:19019786

  9. Assessing the umbrella value of a range-wide conservation network for jaguars (Panthera onca).

    PubMed

    Thornton, Daniel; Zeller, Kathy; Rondinini, Carlo; Boitani, Luigi; Crooks, Kevin; Burdeh, Christopher; Rabinowitz, Alan; Quigley, Howard

    2016-06-01

    Umbrella species are employed as conservation short-cuts for the design of reserves or reserve networks. However, empirical data on the effectiveness of umbrellas is equivocal, which has prevented more widespread application of this conservation strategy. We perform a novel, large-scale evaluation of umbrella species by assessing the potential umbrella value of a jaguar (Panthera onca) conservation network (consisting of viable populations and corridors) that extends from Mexico to Argentina. Using species richness, habitat quality, and fragmentation indices of ~1500 co-occurring mammal species, we show that jaguar populations and corridors overlap a substantial amount and percentage of high-quality habitat for co-occurring mammals and that the jaguar network performs better than random networks in protecting high-quality, interior habitat. Significantly, the effectiveness of the jaguar network as an umbrella would not have been noticeable had we focused on species richness as our sole metric of umbrella utility. Substantial inter-order variability existed, indicating the need for complementary conservation strategies for certain groups of mammals. We offer several reasons for the positive result we document, including the large spatial scale of our analysis and our focus on multiple metrics of umbrella effectiveness. Taken together, our results demonstrate that a regional, single-species conservation strategy can serve as an effective umbrella for the larger community and should help conserve viable populations and connectivity for a suite of co-occurring mammals. Current and future range-wide planning exercises for other large predators may therefore have important umbrella benefits.

  10. Assessing the umbrella value of a range-wide conservation network for jaguars (Panthera onca).

    PubMed

    Thornton, Daniel; Zeller, Kathy; Rondinini, Carlo; Boitani, Luigi; Crooks, Kevin; Burdett, Christopher; Rabinowitz, Alan; Quigley, Howard

    2016-06-01

    Umbrella species are employed as conservation short-cuts for the design of reserves or reserve networks. However, empirical data on the effectiveness of umbrellas is equivocal, which has prevented more widespread application of this conservation strategy. We perform a novel, large-scale evaluation of umbrella species by assessing the potential umbrella value of a jaguar (Panthera onca) conservation network (consisting of viable populations and corridors) that extends from Mexico to Argentina. Using species richness, habitat quality, and fragmentation indices of ~1500 co-occurring mammal species, we show that jaguar populations and corridors overlap a substantial amount and percentage of high-quality habitat for co-occurring mammals and that the jaguar network performs better than random networks in protecting high-quality, interior habitat. Significantly, the effectiveness of the jaguar network as an umbrella would not have been noticeable had we focused on species richness as our sole metric of umbrella utility. Substantial inter-order variability existed, indicating the need for complementary conservation strategies for certain groups of mammals. We offer several reasons for the positive result we document, including the large spatial scale of our analysis and our focus on multiple metrics of umbrella effectiveness. Taken together, our results demonstrate that a regional, single-species conservation strategy can serve as an effective umbrella for the larger community and should help conserve viable populations and connectivity for a suite of co-occurring mammals. Current and future range-wide planning exercises for other large predators may therefore have important umbrella benefits. © 2016 by the Ecological Society of America.

  11. Range-wide population genetics and variation in morph ratio in style-dimorphic Narcissus papyraceus.

    PubMed

    Simón-Porcar, Violeta I; Picó, F Xavier; Arroyo, Juan

    2015-03-01

    • Theoretical models state that natural selection and mating patterns account for floral morph ratio in style-polymorphic plants. However, the demographic history of populations can also influence variation in morph ratios. If so, we hypothesize an association between the morph ratios and the genetic structure across populations.• We used nuclear microsatellites to assess genetic variation and structure in populations of Narcissus papyraceus, a style-dimorphic plant whose floral morph ratios (L-morph to S-morph) gradually vary throughout its distribution range in the southwestern Mediterranean Basin. We implemented analyses to relate the genetic features of populations with their morph ratios.• We found greater frequencies of the S-morph in central populations and declining frequencies toward the periphery. This geographic pattern was not associated with the genetic structure of populations. Instead, we found two distinct genetic groups, mainly separated by the Strait of Gibraltar, with a mixture of morph ratios within each one. Overall, there was a weak genetic structure. Genetic diversity was greater in central and southern dimorphic populations than in northern L-monomorphic populations.• Altogether, our results do not support the hypothesis that the demographic history of populations can account for the observed geographical pattern of morph ratios in N. papyraceus. We suggest that adaptive processes shown in previous studies in the species are the main determinant of the existing variation in the morph composition of populations. © 2015 Botanical Society of America, Inc.

  12. Data resources for range-wide assessment of livestock grazing across the sagebrush biome

    USGS Publications Warehouse

    Assal, T.J.; Veblen, K.E.; Farinha, M.A.; Aldridge, C.L.; Casazza, M.L.; Pyke, D.A.

    2012-01-01

    The data contained in this series were compiled, modified, and analyzed for the U.S. Geological Survey (USGS) report "Range-Wide Assessment of Livestock Grazing Across the Sagebrush Biome." This report can be accessed through the USGS Publications Warehouse (online linkage: http://pubs.usgs.gov/of/2011/1263/). The dataset contains spatial and tabular data related to Bureau of Land Management (BLM) Grazing Allotments. We reviewed the BLM national grazing allotment spatial dataset available from the GeoCommunicator National Integrated Land System (NILS) website in 2007 (http://www.geocommunicator.gov). We identified several limitations in those data and learned that some BLM State and/or field offices had updated their spatial data to rectify these limitations, but maintained the data outside of NILS. We contacted appropriate BLM offices (State or field, 25 in all) to obtain the most recent data, assessed the data, established a data development protocol, and compiled data into a topologically enforced dataset throughout the area of interest for this project (that is, the pre-settlement distribution of Greater Sage-Grouse in the Western United States). The final database includes three spatial datasets: Allotments (BLM Grazing Allotments), OUT_Polygons (nonallotment polygons used to ensure topology), and Duplicate_Polygon_Allotments. See Appendix 1 of the aforementioned report for complete methods. The tabular data presented here consists of information synthesized by the Land Health Standard (LHS) analysis (Appendix 2), and data obtained from the BLM Rangeland Administration System (http://www.blm.gov/ras/). In 2008, available LHS data for all allotments in all regions were compiled by BLM in response to a Freedom of Information Act (FOIA) request made by a private organization. The BLM provided us with a copy of these data. These data provided three major types of information that were of interest: (1) date(s) (if any) of the most recent LHS evaluation for each

  13. Changing demographics affecting sprawl

    Treesearch

    John F. Dwyer; Susan I. Stewart

    1999-01-01

    Demographic changes including population growth, racial/ethnic diversity, aging, expansion of urban areas, and migration to rural areas can bring significant population increases in particular areas that may encourage sprawl. Areas where the pressures for sprawl are likely to be the greatest include the periphery of urban areas, popular retirement destinations, places...

  14. A phylogeographic, demographic and historical analysis of the short-tailed pit viper (Gloydius brevicaudus): evidence for early divergence and late expansion during the Pleistocene.

    PubMed

    Ding, Li; Gan, Xiao-Ni; He, Shun-Ping; Zhao, Er-Mi

    2011-05-01

    The impact of quaternary glaciation in eastern China on local fanua and flora has been a topic of considerable interest. We used mitochondrial DNA (mtDNA) sequence data and coalescent simulations to test two general biogeographic hypothesis related to the effects of Pleistocene climatic fluctuations for a widespread ophidian species (Gloydius brevicaudus) in eastern China and Korean Peninsula. The phylogenetic analysis revealed three major lineages, the southeast Coastal, Yangtze and North Lineages. The latter two are closely related and jointly form a continental lineage. Divergence dating and coalescent simulations indicate a Late Pliocene to Early Pleistocene divergence between lineages from the southeast coast and continental interior, followed by a mid-to-late Pleistocene divergence between lineages from the north and the middle-lower Yangtze Valley across East China, suggesting that all these lineages predated the last glacial maximum. An overlapping range between the two lineages within the continental lineage and a secondary contact associated with ecological transition zones on the margins of the North China Plain were also observed. These results show that vicariance patterns dominated the history of G. brevicaudus. Though the climatic events of the Pleistocene have had a marked effect on the historical distribution and intra-specific divergence of reptiles in China, coalescent and non-coalescent demographic analyses indicate that all lineages of G. brevicaudus seem not to have been adversely affected by glacial cycles during the Late Pleistocene, presumably because of an increase in the amount of climatically mild habitat in East Asia due to a decline in elevation and the development of monsoons since the Mid-End Pleistocene. © 2011 Blackwell Publishing Ltd.

  15. Southern montane populations did not contribute to the recolonization of West Siberian Plain by Siberian larch (Larix sibirica): a range-wide analysis of cytoplasmic markers.

    PubMed

    Semerikov, Vladimir L; Semerikova, Svetlana A; Polezhaeva, Maria A; Kosintsev, Pavel A; Lascoux, Martin

    2013-10-01

    While many species were confined to southern latitudes during the last glaciations, there has lately been mounting evidence that some of the most cold-tolerant species were actually able to survive close to the ice sheets. The contribution of these higher latitude outposts to the main recolonization thrust remains, however, untested. In the present study, we use the first range-wide survey of genetic diversity at cytoplasmic markers in Siberian larch (Larix sibirica; four mitochondrial (mt) DNA loci and five chloroplast (cp) DNA SSR loci) to (i) assess the relative contributions of southern and central areas to the current L. sibirica distribution range; and (ii) date the last major population expansion in both L. sibirica and adjacent Larix species. The geographic distribution of cpDNA variation was uninformative, but that of mitotypes clearly indicates that the southernmost populations, located in Mongolia and the Tien-Shan and Sayan Mountain ranges, had a very limited contribution to the current populations of the central and northern parts of the range. It also suggests that the contribution of the high latitude cryptic refugia was geographically limited and that most of the current West Siberian Plain larch populations likely originated in the foothills of the Sayan Mountains. Interestingly, the main population expansion detected through Approximate Bayesian Computation (ABC) in all four larch species investigated here pre-dates the LGM, with a mode in a range of 220,000-1,340,000 years BP. Hence, L. sibirica, like other major conifer species of the boreal forest, was strongly affected by climatic events pre-dating the Last Glacial Maximum.

  16. Using Range-Wide Abundance Modeling to Identify Key Conservation Areas for the Micro-Endemic Bolson Tortoise (Gopherus flavomarginatus)

    PubMed Central

    Ureña-Aranda, Cinthya A.; Rojas-Soto, Octavio; Martínez-Meyer, Enrique; Yáñez-Arenas, Carlos; Landgrave Ramírez, Rosario; Espinosa de los Monteros, Alejandro

    2015-01-01

    A widespread biogeographic pattern in nature is that population abundance is not uniform across the geographic range of species: most occurrence sites have relatively low numbers, whereas a few places contain orders of magnitude more individuals. The Bolson tortoise Gopherus flavomarginatus is endemic to a small region of the Chihuahuan Desert in Mexico, where habitat deterioration threatens this species with extinction. In this study we combined field burrows counts and the approach for modeling species abundance based on calculating the distance to the niche centroid to obtain range-wide abundance estimates. For the Bolson tortoise, we found a robust, negative relationship between observed burrows abundance and distance to the niche centroid, with a predictive capacity of 71%. Based on these results we identified four priority areas for the conservation of this microendemic and threatened tortoise. We conclude that this approach may be a useful approximation for identifying key areas for sampling and conservation efforts in elusive and rare species. PMID:26115482

  17. Using Range-Wide Abundance Modeling to Identify Key Conservation Areas for the Micro-Endemic Bolson Tortoise (Gopherus flavomarginatus).

    PubMed

    Ureña-Aranda, Cinthya A; Rojas-Soto, Octavio; Martínez-Meyer, Enrique; Yáñez-Arenas, Carlos; Landgrave Ramírez, Rosario; Espinosa de los Monteros, Alejandro

    2015-01-01

    A widespread biogeographic pattern in nature is that population abundance is not uniform across the geographic range of species: most occurrence sites have relatively low numbers, whereas a few places contain orders of magnitude more individuals. The Bolson tortoise Gopherus flavomarginatus is endemic to a small region of the Chihuahuan Desert in Mexico, where habitat deterioration threatens this species with extinction. In this study we combined field burrows counts and the approach for modeling species abundance based on calculating the distance to the niche centroid to obtain range-wide abundance estimates. For the Bolson tortoise, we found a robust, negative relationship between observed burrows abundance and distance to the niche centroid, with a predictive capacity of 71%. Based on these results we identified four priority areas for the conservation of this microendemic and threatened tortoise. We conclude that this approach may be a useful approximation for identifying key areas for sampling and conservation efforts in elusive and rare species.

  18. Conservation genetics of the alligator snapping turtle: cytonuclear evidence of range-wide bottleneck effects and unusually pronounced geographic structure

    USGS Publications Warehouse

    Echelle, A.A.; Hackler, J.C.; Lack, Justin B.; Ballard, S. R.; Roman, J.; Fox, S. F.; Leslie,, David M.; Van Den Bussche, Ronald A.

    2010-01-01

    A previous mtDNA study indicated that female-mediated gene flow was extremely rare among alligator snapping turtle populations in different drainages of the Gulf of Mexico. In this study, we used variation at seven microsatellite DNA loci to assess the possibility of male-mediated gene flow, we augmented the mtDNA survey with additional sampling of the large Mississippi River System, and we evaluated the hypothesis that the consistently low within-population mtDNA diversity reflects past population bottlenecks. The results show that dispersal between drainages of the Gulf of Mexico is rare (F STmsat  = 0.43, ΦSTmtDNA = 0.98). Past range-wide bottlenecks are indicated by several genetic signals, including low diversity for microsatellites (1.1–3.9 alleles/locus; H e = 0.06–0.53) and mtDNA (h = 0.00 for most drainages; π = 0.000–0.001). Microsatellite data reinforce the conclusion from mtDNA that the Suwannee River population might eventually be recognized as a distinct taxonomic unit. It was the only population showing fixation or near fixation for otherwise rare microsatellite alleles. Six evolutionarily significant units are recommended on the basis of reciprocal mtDNA monophyly and high levels of microsatellite DNA divergence.

  19. Plasticity in reproduction and growth among 52 range-wide populations of a Mediterranean conifer: adaptive responses to environmental stress.

    PubMed

    Santos-Del-Blanco, L; Bonser, S P; Valladares, F; Chambel, M R; Climent, J

    2013-09-01

    A plastic response towards enhanced reproduction is expected in stressful environments, but it is assumed to trade off against vegetative growth and efficiency in the use of available resources deployed in reproduction [reproductive efficiency (RE)]. Evidence supporting this expectation is scarce for plants, particularly for long-lived species. Forest trees such as Mediterranean pines provide ideal models to study the adaptive value of allocation to reproduction vs. vegetative growth given their among-population differentiation for adaptive traits and their remarkable capacity to cope with dry and low-fertility environments. We studied 52 range-wide Pinus halepensis populations planted into two environmentally contrasting sites during their initial reproductive stage. We investigated the effect of site, population and their interaction on vegetative growth, threshold size for female reproduction, reproductive-vegetative size relationships and RE. We quantified correlations among traits and environmental variables to identify allocation trade-offs and ecotypic trends. Genetic variation for plasticity was high for vegetative growth, whereas it was nonsignificant for reproduction. Size-corrected reproduction was enhanced in the more stressful site supporting the expectation for adverse conditions to elicit plastic responses in reproductive allometry. However, RE was unrelated with early reproductive investment. Our results followed theoretical predictions and support that phenotypic plasticity for reproduction is adaptive under stressful environments. Considering expectations of increased drought in the Mediterranean, we hypothesize that phenotypic plasticity together with natural selection on reproductive traits will play a relevant role in the future adaptation of forest tree species.

  20. Range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and Rana pretiosa) in northwestern North America

    USGS Publications Warehouse

    Funk, W.C.; Pearl, C.A.; Draheim, H.M.; Adams, M.J.; Mullins, T.D.; Haig, S.M.

    2008-01-01

    The dynamic geological and climatic history of northwestern North America has made it a focal region for phylogeography. We conducted a range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and Rana pretiosa) across its range in northwestern North America to understand its evolutionary history and the distribution of clades to inform conservation of R. pretiosa and Great Basin R. luteiventris, candidates for listing under the US Endangered Species Act. Mitochondrial DNA sequence data from a segment of the cytochrome b gene were obtained from 308 R. luteiventris and R. pretiosa from 96 sites. Phylogenetic analysis revealed one main R. pretiosa clade and three main R. luteiventris clades, two of which overlapped in southeastern Oregon. The three R. luteiventris clades were separated from each other by high levels of sequence divergence (average of 4.75-4.97%). Two divergent clades were also uncovered within the Great Basin. Low genetic variation in R. pretiosa and the southeastern Oregon clade of R. luteiventris suggests concern about their vulnerability to extinction. ?? 2008 Elsevier Inc.

  1. [Demographic perspectives].

    PubMed

    Parant, A

    1999-01-01

    This is a brief review of possible future developments in global population trends. The author notes that the world's population will number between 8 and 11 billion by the year 2050. Topics discussed include changes in the regional balance of population, changes in the age composition of the population, and demographic aging in Europe.

  2. Range-Wide Sex-Chromosome Sequence Similarity Supports Occasional XY Recombination in European Tree Frogs (Hyla arborea)

    PubMed Central

    Brelsford, Alan; Perrin, Nicolas

    2014-01-01

    In contrast with mammals and birds, most poikilothermic vertebrates feature structurally undifferentiated sex chromosomes, which may result either from frequent turnovers, or from occasional events of XY recombination. The latter mechanism was recently suggested to be responsible for sex-chromosome homomorphy in European tree frogs (Hyla arborea). However, no single case of male recombination has been identified in large-scale laboratory crosses, and populations from NW Europe consistently display sex-specific allelic frequencies with male-diagnostic alleles, suggesting the absence of recombination in their recent history. To address this apparent paradox, we extended the phylogeographic scope of investigations, by analyzing the sequences of three sex-linked markers throughout the whole species distribution. Refugial populations (southern Balkans and Adriatic coast) show a mix of X and Y alleles in haplotypic networks, and no more within-individual pairwise nucleotide differences in males than in females, testifying to recurrent XY recombination. In contrast, populations of NW Europe, which originated from a recent postglacial expansion, show a clear pattern of XY differentiation; the X and Y gametologs of the sex-linked gene Med15 present different alleles, likely fixed by drift on the front wave of expansions, and kept differentiated since. Our results support the view that sex-chromosome homomorphy in H. arborea is maintained by occasional or historical events of recombination; whether the frequency of these events indeed differs between populations remains to be clarified. PMID:24892652

  3. Range wide molecular data and niche modeling revealed the Pleistocene history of a global invader (Halyomorpha halys).

    PubMed

    Zhu, Geng-Ping; Ye, Zhen; Du, Juan; Zhang, Dan-Li; Zhen, Ya-hui; Zheng, Chen-guang; Zhao, Li; Li, Min; Bu, Wen-Jun

    2016-03-21

    Invasive species' Pleistocene history contains much information on its present population structure, dispersability and adaptability. In this study, the Pleistocene history of a global invasive pest (Brown Marmorated Stink Bug BMSB, Halyomorpha halys) was unveiled using the coupled approach of phylogeography and ecological niche modelling. Rangewide molecular data suggests that the Taiwan and other native populations had diverged in mid-Pleistocene. In mainland China, the native BMSB did not experience population contraction and divergence during last glacial, but persisted in interconnected populations. Combined Bayesian Skyline Plot (BSP) and niche modelling revealed a rapid expansion occurred during the transition of Last Inter Glacial (LIG) to Last Glacial Maximum (LGM). High genetic diversity and multi-reticular haplotypes network exist in the original sources populations of BMSB invasion in northern China. They were speculated to be colonized from the central China, with many derived haplotypes evolved to adapt the novel environment. The ENM future prediction suggest that BMSB may expand northward to higher latitudes in the US and Europe, because of its high invasive ability, together with the available suitable climate space there.

  4. Range wide molecular data and niche modeling revealed the Pleistocene history of a global invader (Halyomorpha halys)

    PubMed Central

    Zhu, Geng-Ping; Ye, Zhen; Du, Juan; Zhang, Dan-Li; Zhen, Ya-hui; Zheng, Chen-guang; Zhao, Li; Li, Min; Bu, Wen-Jun

    2016-01-01

    Invasive species’ Pleistocene history contains much information on its present population structure, dispersability and adaptability. In this study, the Pleistocene history of a global invasive pest (Brown Marmorated Stink Bug BMSB, Halyomorpha halys) was unveiled using the coupled approach of phylogeography and ecological niche modelling. Rangewide molecular data suggests that the Taiwan and other native populations had diverged in mid-Pleistocene. In mainland China, the native BMSB did not experience population contraction and divergence during last glacial, but persisted in interconnected populations. Combined Bayesian Skyline Plot (BSP) and niche modelling revealed a rapid expansion occurred during the transition of Last Inter Glacial (LIG) to Last Glacial Maximum (LGM). High genetic diversity and multi-reticular haplotypes network exist in the original sources populations of BMSB invasion in northern China. They were speculated to be colonized from the central China, with many derived haplotypes evolved to adapt the novel environment. The ENM future prediction suggest that BMSB may expand northward to higher latitudes in the US and Europe, because of its high invasive ability, together with the available suitable climate space there. PMID:26996353

  5. Range-wide genetic structure of maritime pine predates the last glacial maximum: evidence from nuclear DNA.

    PubMed

    Naydenov, Krassimir D; Alexandrov, Alexander; Matevski, Vlado; Vasilevski, Kole; Naydenov, Michel K; Gyuleva, Veselka; Carcaillet, Christopher; Wahid, Nadya; Kamary, Salim

    2014-02-01

    Using nuclear simple sequence repeats (nuSSRs), we determined the genetic variability in the natural distribution range of maritime pine (Pinus pinaster) in the western Mediterranean region. We analysed the role of global and significant climatic fluctuations in driving the evolutionary diversification of this species. We attempted to determine the impact of the last glacial maximum (LGM) and human activity on genetic variation and to identify the effect of bottlenecks, admixing, migration, time to the most recent common ancestor (TMRCA), and recent splits. A total of 972 individuals were analysed. The sample represented 27 natural populations from the western Mediterranean region, which encompasses most of the natural range of P. pinaster. Using eight nuSSRs, we analysed genetic diversity indices for each population and group of populations. We also examined the interpopulation structure by the frequency and distance method and investigated genetic barriers, signals of historical demographic fluctuations, phylogeographic structure, admixing, rate of mutation, migration, as well as testing the hypothesis of isolation by distance (IBD). Both cluster analyses showed similar population genetic structure with three genetic barriers that divided the samples into four large groups. Intensive migration was only detected during the period of the last glacial maximum (LGM), which permitted the mutation rate of the markers used to be calculated. The majority of the population was found to exhibit signs of a recent bottleneck and its timing showed a clear northeast-southwest geographic distribution. A clearly defined phylogeographic structure (Nst > Gst and Rst > Gst ) under IBD was established, and showed the highest divergence between groups of populations separated by physical barriers, such as the Strait of Gibraltar, the Mediterranean Sea and the Pyrenees. The high level of intergroup genetic differentiation (ΦIS = 20.26) was attributed to a long historical isolation

  6. Genomic diversity, population structure, and migration following rapid range expansion in the Balsam poplar, Populus balsamifera.

    PubMed

    Keller, Stephen R; Olson, Matthew S; Silim, Salim; Schroeder, William; Tiffin, Peter

    2010-03-01

    Rapid range expansions can cause pervasive changes in the genetic diversity and structure of populations. The postglacial history of the Balsam Poplar, Populus balsamifera, involved the colonization of most of northern North America, an area largely covered by continental ice sheets during the last glacial maximum. To characterize how this expansion shaped genomic diversity within and among populations, we developed 412 SNP markers that we assayed for a range-wide sample of 474 individuals sampled from 34 populations. We complemented the SNP data set with DNA sequence data from 11 nuclear loci from 94 individuals, and used coalescent analyses to estimate historical population size, demographic growth, and patterns of migration. Bayesian clustering identified three geographically separated demes found in the Northern, Central, and Eastern portions of the species' range. These demes varied significantly in nucleotide diversity, the abundance of private polymorphisms, and population substructure. Most measures supported the Central deme as descended from the primary refuge of diversity. Both SNPs and sequence data suggested recent population growth, and coalescent analyses of historical migration suggested a massive expansion from the Centre to the North and East. Collectively, these data demonstrate the strong influence that range expansions exert on genomic diversity, both within local populations and across the range. Our results suggest that an in-depth knowledge of nucleotide diversity following expansion requires sampling within multiple populations, and highlight the utility of combining insights from different data types in population genomic studies.

  7. The great human expansion.

    PubMed

    Henn, Brenna M; Cavalli-Sforza, L L; Feldman, Marcus W

    2012-10-30

    Genetic and paleoanthropological evidence is in accord that today's human population is the result of a great demic (demographic and geographic) expansion that began approximately 45,000 to 60,000 y ago in Africa and rapidly resulted in human occupation of almost all of the Earth's habitable regions. Genomic data from contemporary humans suggest that this expansion was accompanied by a continuous loss of genetic diversity, a result of what is called the "serial founder effect." In addition to genomic data, the serial founder effect model is now supported by the genetics of human parasites, morphology, and linguistics. This particular population history gave rise to the two defining features of genetic variation in humans: genomes from the substructured populations of Africa retain an exceptional number of unique variants, and there is a dramatic reduction in genetic diversity within populations living outside of Africa. These two patterns are relevant for medical genetic studies mapping genotypes to phenotypes and for inferring the power of natural selection in human history. It should be appreciated that the initial expansion and subsequent serial founder effect were determined by demographic and sociocultural factors associated with hunter-gatherer populations. How do we reconcile this major demic expansion with the population stability that followed for thousands years until the inventions of agriculture? We review advances in understanding the genetic diversity within Africa and the great human expansion out of Africa and offer hypotheses that can help to establish a more synthetic view of modern human evolution.

  8. Universal Expansion.

    ERIC Educational Resources Information Center

    McArdle, Heather K.

    1997-01-01

    Describes a week-long activity for general to honors-level students that addresses Hubble's law and the universal expansion theory. Uses a discrepant event-type activity to lead up to the abstract principles of the universal expansion theory. (JRH)

  9. Universal Expansion.

    ERIC Educational Resources Information Center

    McArdle, Heather K.

    1997-01-01

    Describes a week-long activity for general to honors-level students that addresses Hubble's law and the universal expansion theory. Uses a discrepant event-type activity to lead up to the abstract principles of the universal expansion theory. (JRH)

  10. The great human expansion

    PubMed Central

    Henn, Brenna M.; Cavalli-Sforza, L. L.; Feldman, Marcus W.

    2012-01-01

    Genetic and paleoanthropological evidence is in accord that today’s human population is the result of a great demic (demographic and geographic) expansion that began approximately 45,000 to 60,000 y ago in Africa and rapidly resulted in human occupation of almost all of the Earth’s habitable regions. Genomic data from contemporary humans suggest that this expansion was accompanied by a continuous loss of genetic diversity, a result of what is called the “serial founder effect.” In addition to genomic data, the serial founder effect model is now supported by the genetics of human parasites, morphology, and linguistics. This particular population history gave rise to the two defining features of genetic variation in humans: genomes from the substructured populations of Africa retain an exceptional number of unique variants, and there is a dramatic reduction in genetic diversity within populations living outside of Africa. These two patterns are relevant for medical genetic studies mapping genotypes to phenotypes and for inferring the power of natural selection in human history. It should be appreciated that the initial expansion and subsequent serial founder effect were determined by demographic and sociocultural factors associated with hunter-gatherer populations. How do we reconcile this major demic expansion with the population stability that followed for thousands years until the inventions of agriculture? We review advances in understanding the genetic diversity within Africa and the great human expansion out of Africa and offer hypotheses that can help to establish a more synthetic view of modern human evolution. PMID:23077256

  11. Low-speed wind-tunnel investigation of flight spoilers as trailing-vortex-alleviation devices on a medium range wide-body tri-jet airplane model

    NASA Technical Reports Server (NTRS)

    Croom, D. R.; Vogler, R. D.; Williams, G. M.

    1976-01-01

    An investigation was made in the V/STOL tunnel to determine, by the trailing wing sensor technique, the effectiveness of various segments of the existing flight spoilers on a medium range wide body tri-jet transport airplane model when they were deflected as trailing vortex alleviation devices. The four combinations of flight spoiler segments investigated were effective in reducing the induced rolling moment on the trailing wing model by as much as 15 to 60 percent at distances behind the transport model of from 3.9 to 19.6 transport wing spans, 19.6 spans being the downstream limit of distances used. Essentially all of the reduction in induced rolling moment on the trailing wing model was realized at a spoiler deflection of about 45 deg.

  12. Range-wide network of priority areas for greater sage-grouse - a design for conserving connected distributions or isolating individual zoos?

    USGS Publications Warehouse

    Crist, Michele R.; Knick, Steven T.; Hanser, Steven E.

    2015-09-08

    The network of areas delineated in 11 Western States for prioritizing management of greater sage-grouse (Centrocercus urophasianus) represents a grand experiment in conservation biology and reserve design. We used centrality metrics from social network theory to gain insights into how this priority area network might function. The network was highly centralized. Twenty of 188 priority areas accounted for 80 percent of the total centrality scores. These priority areas, characterized by large size and a central location in the range-wide distribution, are strongholds for greater sage-grouse populations and also might function as sources. Mid-ranking priority areas may serve as stepping stones because of their location between large central and smaller peripheral priority areas. The current network design and conservation strategy has risks. The contribution of almost one-half (n = 93) of the priority areas combined for less than 1 percent of the cumulative centrality scores for the network. These priority areas individually are likely too small to support viable sage-grouse populations within their boundary. Without habitat corridors to connect small priority areas either to larger priority areas or as a clustered group within the network, their isolation could lead to loss of sage-grouse within these regions of the network. 

  13. Range-wide network of priority areas for greater sage-grouse - a design for conserving connected distributions or isolating individual zoos?

    USGS Publications Warehouse

    Crist, Michele R.; Knick, Steven T.; Hanser, Steven E.

    2015-09-08

    The network of areas delineated in 11 Western States for prioritizing management of greater sage-grouse (Centrocercus urophasianus) represents a grand experiment in conservation biology and reserve design. We used centrality metrics from social network theory to gain insights into how this priority area network might function. The network was highly centralized. Twenty of 188 priority areas accounted for 80 percent of the total centrality scores. These priority areas, characterized by large size and a central location in the range-wide distribution, are strongholds for greater sage-grouse populations and also might function as sources. Mid-ranking priority areas may serve as stepping stones because of their location between large central and smaller peripheral priority areas. The current network design and conservation strategy has risks. The contribution of almost one-half (n = 93) of the priority areas combined for less than 1 percent of the cumulative centrality scores for the network. These priority areas individually are likely too small to support viable sage-grouse populations within their boundary. Without habitat corridors to connect small priority areas either to larger priority areas or as a clustered group within the network, their isolation could lead to loss of sage-grouse within these regions of the network. 

  14. Species associations and habitat influence the range-wide distribution of breeding Canada Geese (Branta canadensis interior) on Western Hudson Bay

    USGS Publications Warehouse

    Reiter, Matthew E.; Andersen, David E.; Raedeke, Andrew H.; Humburg, Dale D.

    2017-01-01

    Inter- and intra-specific interactions are potentially important factors influencing the distribution of populations. Aerial survey data, collected during range-wide breeding population surveys for Eastern Prairie Population (EPP) Canada Geese (Branta canadensis interior), 1987–2008, were evaluated to assess factors influencing their nesting distribution. Specifically, associations between nesting Lesser Snow Geese (Chen caerulescens caerulescens) and EPP Canada Geese were quantified; and changes in the spatial distribution of EPP Canada Geese were identified. Mixed-effects Poisson regression models of EPP Canada Goose nest counts were evaluated within a cross-validation framework. The total count of EPP Canada Goose nests varied moderately among years between 1987 and 2008 with no long-term trend; however, the total count of nesting Lesser Snow Geese generally increased. Three models containing factors related to previous EPP Canada Goose nest density (representing recruitment), distance to Hudson Bay (representing brood-habitat), nesting habitat type, and Lesser Snow Goose nest density (inter-specific associations) were the most accurate, improving prediction accuracy by 45% when compared to intercept-only models. EPP Canada Goose nest density varied by habitat type, was negatively associated with distance to coastal brood-rearing areas, and suggested density-dependent intra-specific effects on recruitment. However, a non-linear relationship between Lesser Snow and EPP Canada Goose nest density suggests that as nesting Lesser Snow Geese increase, EPP Canada Geese locally decline and subsequently the spatial distribution of EPP Canada Geese on western Hudson Bay has changed.

  15. Low speed wind tunnel investigation of flight spoilers as trailing-vortex-alleviation devices on an extended-range wide body tri-jet airplane model

    NASA Technical Reports Server (NTRS)

    Croom, D. R.; Vogler, R. D.; Thelander, J. A.

    1976-01-01

    An investigation was made in the Langley V/STOL tunnel to determine, by the trailing wing sensor technique, the effectiveness of various segments of the existing flight spoilers on an extended-range wide-body tri-jet transport airplane model when they were deflected as trailing-vortex-alleviation devices. On the transport model with the approach flap configuration, the four combinations of flight-spoiler segments investigated were effective in reducing the induced rolling moment on the trailing wing model by as much as 25 to 45 percent at downstream distances behind the transport model of 9.2 and 18.4 transport wing spans. On the transport airplane model with the landing flap configuration, the four combinations of flight-spoiler segments investigated were effective in reducing the induced rolling moment on the trailing wing model by as much as 35 to 60 percent at distances behind the transport model of from 3.7 to 18.4 transport wing spans, 18.4 spans being the downstream limit of distances used.

  16. Demographic compensation and tipping points in climate-induced range shifts.

    PubMed

    Doak, Daniel F; Morris, William F

    2010-10-21

    To persist, species are expected to shift their geographical ranges polewards or to higher elevations as the Earth's climate warms. However, although many species' ranges have shifted in historical times, many others have not, or have shifted only at the high-latitude or high-elevation limits, leading to range expansions rather than contractions. Given these idiosyncratic responses to climate warming, and their varied implications for species' vulnerability to climate change, a critical task is to understand why some species have not shifted their ranges, particularly at the equatorial or low-elevation limits, and whether such resilience will last as warming continues. Here we show that compensatory changes in demographic rates are buffering southern populations of two North American tundra plants against the negative effects of a warming climate, slowing their northward range shifts, but that this buffering is unlikely to continue indefinitely. Southern populations of both species showed lower survival and recruitment but higher growth of individual plants, possibly owing to longer, warmer growing seasons. Because of these and other compensatory changes, the population growth rates of southern populations are not at present lower than those of northern ones. However, continued warming may yet prove detrimental, as most demographic rates that improved in moderately warmer years declined in the warmest years, with the potential to drive future population declines. Our results emphasize the need for long-term, range-wide measurement of all population processes to detect demographic compensation and to identify nonlinear responses that may lead to sudden range shifts as climatic tipping points are exceeded.

  17. Demographics: people and markets.

    PubMed

    Merrick, T W; Tordella, S J

    1988-02-01

    The basics of demography are now basic to us business as well. Demographics combine demographic data with socioeconomic and geographic factors to help business and other managers know the market for their goods and services. This pamphlet explains market, product, and site analyses, discusses data sources and resources, and includes case studies involving major corporations. Post-war population trends have had an enormous impact on consumer and labor markets, bringing home to business the importance of taking advantage of demographic shifts. Advances in computerized access to data describing changes and increased consciousness of their economic significance has spurred the application of demographic knowledge by managers and the growth of the demographics information industry. The pamphlet describes the resources and methods of demographics including the creation and use of demographic data products.

  18. [Demographic profile of Venezuela].

    PubMed

    Quintero, I

    1984-04-01

    Sources of demographic data for Venezuela include 11 population censuses conducted between 1873-1981, birth and death registration statistics, and the household sample survey. The average annual rate of population growth increase from 2.8% between 1920-40 to 3-4% thereafter. The population at the 1961 census was 7.52 million. According to preliminary data from the 1981 census, the population of 14.57 million is growing at an annual rate of 2.8%. 41.2% of the population is under 15 years old, implying a huge demand for educational and health services, housing and employment. The dependency rate in 1980 was 81.3% for the country as a whole, 100.4% in rural areas, and 76.0% in urban areas. The young age structure means that the population will continue to grow even if natality rates decline. The crude natality rate was estimated at 47.3/1000 for 1950-55, 36.0 for 1970-75, and 32.9 for 1980-85. Some rural areas still have natality rates of over 47/1000. The total fertility rate declined from 6.5 in 1950-55 to 4.1 in 1980-85. The decline in the natality rate reflects improving quality of life, availability of family planning services, urbanization, and access of women to productive activities and educational centers. The mortality rate was 12.3/1000 in 1950-55, 9.1 in 1960-65, in 1970-75, and has been estimated at 5.5 for 1980-85. Some rural areas have mortality rates of 8.1. The infant mortality rate was 50.2/1000 in 1971 and 34.3 in 1980. Life expectancy at birth is about 69 years. During the 1920s, Venezuela unerwent expansion in infrastructure and technological utilization, generating rapid urbanization. 39.2% of the population was urban in 1941, compared to 78.8% in 1980. The significance of urbanization in Venezuela is due to the rapidity as well as the diffusion of the process. The household sample survey for the 2nd half of 1980 indicated a total of 8.16 million employed and an activity rate of 32.1% overall, 46.4% for males and 17.7% for females. The

  19. Demographics: People and Markets.

    ERIC Educational Resources Information Center

    Merrick, Thomas W.; Tordella, Stephen J.

    1988-01-01

    Population shifts directly affect the bottom line, so the basics of demography are now basic to business as well. Demographics combine demographic data with socioeconomic and geographic factors to help business and other managers know the market for the goods and services they offer. This guide explains market, product, and site analyses,…

  20. Dancing with Demographers.

    ERIC Educational Resources Information Center

    Robertson, Heather-Jane

    2000-01-01

    Demographic projections concerning the shortage of teachers in Canada, their pay scale, the feminization of teaching, the gender gap in salaries, and teacher autonomy have often been incorrect, or correct for the wrong reasons. Instead of relying on demographic predictions, teachers should contemplate who they really want to be professionally,…

  1. Demographics and the pension system.

    PubMed

    Livi Bacci, M

    1995-01-01

    "Italian demographic evolution closely resembles that of the other leading European countries, although with some distinctive features, such as a lower birth rate, more rapid population aging and fewer immigrants. Projections for the next two or three decades point to accelerating expansion of the aged population, especially of the very old, and a contraction of the working age population after the turn of the century. However, there are also unknowns involved in the demographic evolution of the aged population, turning on the speed of the decline in senile mortality in the decades to come and the possible effects on the health of the elderly population, hence on the demand for social services, considering among other things changing family patterns. There is broad agreement that the birth rate is now too low, that this could have serious long-run repercussions on relations between generations and on intergenerational transfers, and that there is room for social policy action to influence the reproductive choices of couples. This article examines several possible reproductive models and discusses the foundations for action and the potential policy contradictions." excerpt

  2. Expansion Microscopy

    PubMed Central

    Chen, Fei; Tillberg, Paul W.; Boyden, Edward S.

    2014-01-01

    In optical microscopy, fine structural details are resolved by using refraction to magnify images of a specimen. Here we report the discovery that, by synthesizing a swellable polymer network within a specimen, it can be physically expanded, resulting in physical magnification. By covalently anchoring specific labels located within the specimen directly to the polymer network, labels spaced closer than the optical diffraction limit can be isotropically separated and optically resolved, a process we call expansion microscopy (ExM). Thus, this process can be used to perform scalable super-resolution microscopy with diffraction-limited microscopes. We demonstrate ExM with effective ~70 nm lateral resolution in both cultured cells and brain tissue, performing three-color super-resolution imaging of ~107 μm3 of the mouse hippocampus with a conventional confocal microscope. PMID:25592419

  3. Thermal Expansion

    NASA Astrophysics Data System (ADS)

    Ventura, Guglielmo; Perfetti, Mauro

    All solid materials, when cooled to low temperatures experience a change in physical dimensions which called "thermal contraction" and is typically lower than 1 % in volume in the 4-300 K temperature range. Although the effect is small, it can have a heavy impact on the design of cryogenic devices. The thermal contraction of different materials may vary by as much as an order of magnitude: since cryogenic devices are constructed at room temperature with a lot of different materials, one of the major concerns is the effect of the different thermal contraction and the resulting thermal stress that may occur when two dissimilar materials are bonded together. In this chapter, theory of thermal contraction is reported in Sect. 1.2 . Section 1.3 is devoted to the phenomenon of negative thermal expansion and its applications.

  4. Demographic changes and nationalism.

    PubMed

    Vishnevskii, A G

    1995-01-01

    This article examines the different characteristics of the many peoples inhabiting what used to be the Soviet Union and communist Eastern Europe, including Yugoslavia. The differences among these nationalities, or ethnic groups, are illustrated using the example of demographic modernization, showing how different peoples have or have not passed through the demographic transition process. The author looks at ethnic differences in mortality, fertility, natural increase, and migration, as well as economic and social inequalities among ethnic groups. The prospects for inter-ethnic conflict are assessed.

  5. [Recent demographic trends].

    PubMed

    1984-01-01

    A review of demographic trends in Luxembourg in 1983 is presented. The most significant trend was a decline in the number of marriages to the lowest level since World War II. Topics covered include fertility, nuptiality and divorce, mortality, natural increase, migration, and adoptions. Selected vital statistics for the first six months of 1984 are also presented.

  6. [Recent demographic trends].

    PubMed

    1985-01-01

    The demographic situation in Luxembourg in 1984 is reviewed. Significant developments include a continuation of the decline in the number of marriages, a record number of divorces, and an increase in the number of births to those of Luxembourg nationality coupled with a decline in the foreign population.

  7. [Recent demographic trends].

    PubMed

    1986-01-01

    The demographic situation in Luxembourg in 1985 is reviewed. Separate consideration is given to fertility, nuptiality and divorce, mortality, and migration. Significant trends include the continued decline in fertility among the foreign population, a new peak in the number of divorces, and a decline in infant mortality to under 10 per 1,000 for the first time.

  8. Reassessing the Demographic Imperative

    ERIC Educational Resources Information Center

    Folts, W. Edward; Rosenberg, Edwin; Muir, Kenneth B.; Baumhover, Lorin A.

    2005-01-01

    For many years gerontologists have discussed the consequences of advances that have lengthened lives but have been less successful at improving the quality of those lives. While this debate continues, the resulting demographic shift in the age profile of the United States threatens to overwhelm our ability to care for those who most need…

  9. Changing Hispanic Demographics.

    ERIC Educational Resources Information Center

    McKay, Emily Gantz

    This report provides a demographic overview of Hispanics in the United States. Information was drawn largely from recent census figures. The following highlights are reported: (1) Hispanic Americans are the youngest and fastest growing minority group, but they are also more likely than non-Hispanics to drop out of school, be unemployed or…

  10. The Demographic Imperative

    ERIC Educational Resources Information Center

    Jordan, Stephen M.

    2009-01-01

    As the United States moves toward becoming a "minority-majority" country, what more can--and should--college presidents and governing boards do to provide low-income students and students of color with a pipeline to high-quality education? Ongoing discourse about shifting demographics locally and nationally must be built into…

  11. Youth Demographics. Fact Sheet

    ERIC Educational Resources Information Center

    Lopez, Mark Hugo; Marcelo, Karlo Barrios

    2006-01-01

    This fact sheet compares the numbers of 18-25 year-old residents and citizens by gender, race, ethnicity, geographic distribution, marital status, military status, unemployment, educational attainment, and assesses population trends from 1968-2006. It explores such demographic characteristics of young people using data from the March Annual…

  12. EJSCREEN Demographic Indicators 2015 Public

    EPA Pesticide Factsheets

    EJSCREEN uses demographic factors as very general indicators of a community's potential susceptibility to the types of environmental factors included in this screening tool. There are six demographic indicators: Demographic Index, Supplementary Demographic Index, Individuals under Age 5, Individuals over Age 64, Percent Low-Income, Linguistic Isolation, Percent Minority, and Less than High School Education.

  13. Human population growth and the demographic transition.

    PubMed

    Bongaarts, John

    2009-10-27

    The world and most regions and countries are experiencing unprecedentedly rapid demographic change. The most obvious example of this change is the huge expansion of human numbers: four billion have been added since 1950. Projections for the next half century expect a highly divergent world, with stagnation or potential decline in parts of the developed world and continued rapid growth in the least developed regions. Other demographic processes are also undergoing extraordinary change: women's fertility has dropped rapidly and life expectancy has risen to new highs. Past trends in fertility and mortality have led to very young populations in high fertility countries in the developing world and to increasingly older populations in the developed world. Contemporary societies are now at very different stages of their demographic transitions. This paper summarizes key trends in population size, fertility and mortality, and age structures during these transitions. The focus is on the century from 1950 to 2050, which covers the period of most rapid global demographic transformation.

  14. [Recent demographic trends].

    PubMed

    1983-01-01

    A review of demographic trends in Luxembourg in 1982 is presented. A decline in fertility, the first since 1977, is noted, together with an increase in divorce, as well as a negative migration balance for the first time since 1967. Topics covered include natural increase and migration, fertility, marriage and divorce, mortality, adoption, and legislation affecting the family. Special consideration is given to the mortality experience of those who were subjected to compulsory labor during World War II.

  15. [Reforms and demographic crisis].

    PubMed

    Velichkovskiĭ, B T

    2002-01-01

    During reformation years all basic medical and demographic indices have undergone negative changes in Russia. Since 1992 there has been a steady-state decrease in the population due to the fact that mortality rates are extremely greater than birth ones. In 2001, the Russian population reduced in number by nearly a million. The birth rates are twice less than that requires for a simple reproduction of generations. Extremely high death rates remain among the population, in able-bodied males. The main reasons for the demographic crisis are the negative consequences of the implemented reforms rather than the transition from traditional to the new present-day reproduction of the population. It is problematic now to correct the situation via active migration of Russian-speaking persons. This requires enormous funds to provide comers with jobs and dwelling. It is unreal to diminish annual departure of 100 thousand persons, mainly young educated professionals from the country, though it is joust not only a demographic, but a strategic problem. In 2001 there was a some rise in birth rates. But this is the most illusive way of solving the demographic crisis. Just in the USSR, the high educational level of the population, the socioeconomic emancipation of females and progress in medicine gave rise to the transition to the present-day reproduction of the population, which is characterized by low birth and death rates. So the population is unlikely to be replenished by high birth rates. The main way of overcoming the demographic crisis is to reduce mortality and not to allow young people to die prematurely. For this it is necessary to know the biological mechanisms responsible for extremely high mortality. It is most likely to be due to breakdown in the dynamic stereotype of higher nervous performance, as stated by I. P. Pavlov. Today it is insufficient to control alcoholism, traumatism, and smoking by healthy lifestyle propaganda in order to reduce death rates in Russian. All

  16. Building demographic literacy.

    PubMed

    Crews, K

    1993-01-01

    Students should get in the habit of seeking out the most current projections, estimates, or rates available. Since demographic measures change over time, publications based on the UN's world population projections from 1980 or 1990 may need to be supplemented using the UN's most current, 1992, projections. A 1989 Census Bureau report on the African American Population will not contain data from the 1990 Census or the 1992 Current Population Survey, conducted by the Census Bureau. Some groups collect data with advocacy in mind, as shown by the range of estimates of participants at the 1993 National March on Washington for Lesbian, Gay and Bi Equal Rights and Liberation. The organizers estimated that 1 million people participated; the US Park Police estimated 300,000; and the Washington Blade, a gay newspaper, reported 750,000. A seemingly innocuous choice of phrasing can change the meaning of demographic data. One commonly misreported concept is population doubling time which is not a prediction, but rather a concept designed to accent how fast a population is growing at the present time. At current rates, the population of India would double in size in 34 years, but it is more likely that growth rates will begin to slow down somewhat during that time. Older students may be encouraged to examine the assumptions behind population projections. The UN's long-range projection that world population will grow to 10 billion by 2050 is based on certain assumption about fertility and mortality during the period. With regard to the fastest growing US minority, Hispanics added the largest number of people to the US population during the 1980s, but Asians had the largest percent increase. The time to initiate demographic literacy is in the early grades of school.

  17. [INSEE's permanent demographic sample].

    PubMed

    Sautory, O

    1987-01-01

    This article discusses the permanent demographic sample survey developed by France's Institut National de la Statistique et des Etudes Economiques (INSEE), which has been in use in that country since the census of 1968. Approximately one percent of the metropolitan population of France was chosen for inclusion by birthdate. By adding data on marriage, births of children, change of residence, schooling, employment status, and death to each person's file, longitudinal studies of fertility, nuptiality, and mortality can be conducted. Two such studies are included as examples of how the permanent sample survey can be best put to use.

  18. Stochastic demographic forecasting.

    PubMed

    Lee, R D

    1992-11-01

    "This paper describes a particular approach to stochastic population forecasting, which is implemented for the U.S.A. through 2065. Statistical time series methods are combined with demographic models to produce plausible long run forecasts of vital rates, with probability distributions. The resulting mortality forecasts imply gains in future life expectancy that are roughly twice as large as those forecast by the Office of the Social Security Actuary.... Resulting stochastic forecasts of the elderly population, elderly dependency ratios, and payroll tax rates for health, education and pensions are presented."

  19. The demographic transition.

    PubMed

    Coale, A J

    1984-01-01

    Demographic transition is a set of changes in reproductive behavior that are experienced as a society is transformed from a traditional pre-industrial state to a highly developed, modernized structure. The transformation is the substitution of slow growth achieved with low fertility and mortality for slow growth maintained with relatively high fertility and mortality rates. Contrary to early descriptions of the transition, fertility in pre-modern societies was well below the maximum that might be attained. However, it was kept at moderate levels by customs (such as late marriage or prolonged breastfeeding) not related to the number of children already born. Fertility has been reduced during the demographic transition by the adoption of contraception as a deliberate means of avoiding additional births. An extensive study of the transition in Europe shows the absence of a simple link of fertility with education, proportion urban, infant mortality and other aspects of development. It also suggests the importance of such cultural factors as common customs associated with a common language, and the strength of religious traditions. Sufficient modernization nevertheless seems always to bring the transition to low fertility and mortality.

  20. China's demographic dilemma.

    PubMed

    1994-01-01

    China's population policies should take into account that further population declines between 1992 and the year 2000 will result in reducing the proportion of young people and increasing by two times the number of elderly over the age of 65 years. The aged population which was 1.2 billion in 1994 is expected to increase to 12.9% of total population. The expected increases in the elderly would make China the only country in the world, beside Japan with an expected elderly population comprising 20% of total population by 2025, ever to have such a high proportion of aged. China must decide whether it is more important to reduce population growth or secure a favorable ratio of working age persons to elderly dependents. With a high proportion of elderly in a population, there would be a need for social support from children for the elderly and increased expenditures for pensions, public health services, social welfare, and social relief. Griffith Feeney and Yuan Jianhua of the Beijing Institute of Information and Control in 1994 examined data from a 1992 national survey and found that fertility declined from 2.04 children per woman in 1990 to 1.65 children per woman in 1991, which is replacement level fertility. The reliability of the survey results has been questioned by Chinese demographers because of the change in national birth planning policy to the responsibility system among local, regional, and national political and administrative heads for family planning use. The study researchers conclude that, even with underreporting of 10% to 20%, the survey results indicate attainment of Chinese replacement level fertility. If policy continues to press for fertility decline, there would be unprecedented number of elderly and a tremendous population imbalance. Demographically, this form of age structure imbalance has never been experienced historically. The 1992 State Family Planning Commission survey results were substantiated by surveys conducted between 1982 and 1990

  1. Planet Demographics from Transits

    NASA Astrophysics Data System (ADS)

    Howard, Andrew

    2015-08-01

    From the demographics of planets detected by the Kepler mission, we have learned that there exists approximately one planet per star for planets larger than Earth orbiting inside of 1 AU. We have also learned the relative occurrence of these planets as a function of their orbital periods, sizes, and host star masses and metallicities. In this talk I will review the key statistical findings that the planet size distribution peaks in the range 1-3 times Earth-size, the orbital period distribution is characterized by a power-law cut off at short periods, small planets are more prevalent around small stars, and that approximately 20% of Sun-like stars hosts a planet 1-2 times Earth-size in a habitable zone. Looking forward, I will describe analysis of photometry from the K2 mission that is yielding initial planet discoveries and offering the opportunity to measure planet occurrence in widely separated regions of the galaxy. Finally, I will also discuss recent techniques to discover transiting planets in space-based photometry and to infer planet population properties from the ensemble of detected and non-detected transit signals.

  2. Relations between demographic parameters.

    PubMed

    Demetrius, L

    1979-05-01

    The mean life-expectancy e describes the average prospective life-time of an individual aged zero. This parameter can be explicitly described in terms of the survivorship distribution of the population. The Malthusian parameter r represents the asymptotic growth rate of a population. This parameter can be implicitly expressed in terms of the net-maternity distribution. The parameters e and r incompletely incorporate the age-specific fertility and mortality pattern of a population; distinct populations may have the same growth rate but different net-maternity functions; distinct populations may be characterized by the same mean life expectation but may have different survivorship distributions. This article analyzes a class of parameters called the entropy of a population (Demetrius, 1974a) which distinguishes between net-maternity functions with the same growth rate and also mortality distributions with the same mean life expectation. This class of parameters measures the convexity of the fertility and mortality distributions. This paper analyzes the relations between the entropy parameter and the standard demographic parameters.

  3. Demographics of Planetary Science

    NASA Astrophysics Data System (ADS)

    Bagenal, F.; White, S.

    2011-10-01

    A survey was sent out to university departments around the US that were thought to include faculty involved in planetary science research and/or offer planetary science undergraduate or graduate degrees. This is Part A of a study of the demographics of planetary science carried out by the American Institute of Physics (AIP) and sponsored by NASA's Planetary Science Division. Part B will be a survey of the planetary scientists with PhDs working in the US, to be carried out by the AIP in mid-2011. Starting on December 8th 2010 surveys were sent out by email to department chairs. A total of 48 departments responded between December 9th and April 8th . There is only U of Arizona that has a department that is called planetary sciences - the rest are combined with Earth sciences (14), astronomy (15), geology/geophysics (8), physics (7), atmospheric science (5), something else or combinations thereof. We present statistics from these 48 departments on faculty, researchers, graduate and undergraduate students.

  4. Different kinds of genetic markers permit inference of Paleolithic and Neolithic expansions in humans.

    PubMed

    Aimé, Carla; Austerlitz, Frédéric

    2017-02-01

    Recent population genetic studies have provided valuable insights on the demographic history of our species. However, some issues such as the dating of the first demographic expansions in human populations remain puzzling. Indeed, although a few genetic studies argued that the first human expansions were concomitant with the Neolithic transition, many others found signals of expansion events starting during the Palaeolithic. Here we performed a simulation study to show that these contradictory findings may result from the differences in the genetic markers used, especially if two successive expansion events occurred. For a large majority of replicates for each scenario tested, microsatellite data allow only detecting the recent expansion event in that case, whereas sequence data allow only detecting the ancient expansion. Combined with previous real data analyses, our results bring support to the ideas that (i) a first human expansions started during the Palaeolithic period, (ii) a second expansion event occurred later, concomitantly with the Neolithic transition.

  5. Rapid trait evolution drives increased speed and variance in experimental range expansions

    PubMed Central

    Weiss-Lehman, Christopher; Hufbauer, Ruth A; Melbourne, Brett A

    2017-01-01

    Range expansions are central to two ecological issues reshaping patterns of global biodiversity: biological invasions and climate change. Traditional theory considers range expansion as the outcome of the demographic processes of birth, death and dispersal, while ignoring the evolutionary implications of such processes. Recent research suggests evolution could also play a critical role in determining expansion speed but controlled experiments are lacking. Here we use flour beetles (Tribolium castaneum) to show experimentally that mean expansion speed and stochastic variation in speed are both increased by rapid evolution of traits at the expansion edge. We find that higher dispersal ability and lower intrinsic growth rates evolve at the expansion edge compared with spatially nonevolving controls. Furthermore, evolution of these traits is variable, leading to enhanced variance in speed among replicate population expansions. Our results demonstrate that evolutionary processes must be considered alongside demographic ones to better understand and predict range expansions. PMID:28128350

  6. Genetic consequences of population expansions and contractions in the common hippopotamus (Hippopotamus amphibius) since the Late Pleistocene.

    PubMed

    Stoffel, Céline; Dufresnes, Christophe; Okello, John B A; Noirard, Christian; Joly, Pierre; Nyakaana, Silvester; Muwanika, Vincent B; Alcala, Nicolas; Vuilleumier, Séverine; Siegismund, Hans R; Fumagalli, Luca

    2015-05-01

    Over the past two decades, an increasing amount of phylogeographic work has substantially improved our understanding of African biogeography, in particular the role played by Pleistocene pluvial-drought cycles on terrestrial vertebrates. However, still little is known on the evolutionary history of semi-aquatic animals, which faced tremendous challenges imposed by unpredictable availability of water resources. In this study, we investigate the Late Pleistocene history of the common hippopotamus (Hippopotamus amphibius), using mitochondrial and nuclear DNA sequence variation and range-wide sampling. We documented a global demographic and spatial expansion approximately 0.1-0.3 Myr ago, most likely associated with an episode of massive drainage overflow. These events presumably enabled a historical continent-wide gene flow among hippopotamus populations, and hence, no clear continental-scale genetic structuring remains. Nevertheless, present-day hippopotamus populations are genetically disconnected, probably as a result of the mid-Holocene aridification and contemporary anthropogenic pressures. This unique pattern contrasts with the biogeographic paradigms established for savannah-adapted ungulate mammals and should be further investigated in other water-associated taxa. Our study has important consequences for the conservation of the hippo, an emblematic but threatened species that requires specific protection to curtail its long-term decline. © 2015 John Wiley & Sons Ltd.

  7. Mitochondrial footprints of human expansions in Africa.

    PubMed Central

    Watson, E; Forster, P; Richards, M; Bandelt, H J

    1997-01-01

    mtDNA studies support an African origin for modern Eurasians, but expansion events within Africa have not previously been investigated. We have therefore analyzed 407 mtDNA control-region sequences from 13 African ethnic groups. A number of sequences (13%) were highly divergent and coalesced on the "mitochondrial Eve" in Africans. The remaining sequences also ultimately coalesced on this sequence but fell into four major clusters whose starlike phylogenies testify to demographic expansions. The oldest of these African expansions dates to approximately 60,000-80,000 years ago. Eurasian sequences are derived from essentially one sequence within this ancient cluster, even though a diverse mitochondrial pool was present in Africa at the time. PMID:9326335

  8. Demographic Trends: Impact on Schools

    ERIC Educational Resources Information Center

    Chong, Sylvia N. Y.; Cheah, Horn Mun

    2010-01-01

    Background: Singapore is experiencing great demographic change. These demographic trends show fewer young people and declining birth rates, greater longevity for ageing generations and an increase in the number of non-Singaporean residents. Statistics also show that more than half of the total population increase in the last decades was…

  9. Demographic perspectives on Saudi Arabia's development.

    PubMed

    Looney, R E

    1985-06-01

    Demographic movements likely to be taking place in Saudi Arabia were hypothesized on the basis of general knowledge. The discussion reports on population size, general Arab demographic patterns, general determinants of fertility, Arab fertility patterns, Saudi fertility patterns, mortality in general, mortality in the Middle East, mortality in Saudi Arabia, Saudi Arabian population growth, immigration, the changing composition of the work force, and third plan targets. Some doubt exists as to the size of Saudi Arabia's population, but there is little question that the total is growing rapidly. This expansion is taking place through stepped up immigration and a relatively high natural growth of indigenous Saudis, but statistics on population size, structure, and on the number of births and deaths leaves the magnitude of a number of important demographic trends in doubt. Yet, considerable evidence exists that several of the Arab countries in the region with fairly good demographic data are likely to have similar demographic patterns. In depth analysis of the demographic dynamics of these countries, particularly Jordan and Kuwait, identified several common elements bearing on several key parameters. Using what Saudi data is available and making comparisons with these neighboring countries, one can, based on expected levels of birth and death rates, indirectly infer the natural growth of Saudi Arabia's population. With several notable exceptions, Saudi Arabia's demographic patterns show a marked similarity to those experienced in the region as a whole. The average rate of population growth in both Saudi Arabia and the Arab region is about 3% a year and in both instances fertility rates are high. The demographic structure of these countries is characterized by the youthfulness of the population. In most of the Arab countries, the population aged 15 years or under accounts for over 48% of the population. The rate of the economically active population is low, ranging from

  10. [The demographic doctrines of Plato].

    PubMed

    Vilquin, E

    1982-01-01

    Plato has been invoked so often in discussions of population and so many different and contradictory attitudes toward population and demography have been attributed to him that it is necessary to examine his own works and their context in order to understand his true views of the subject. This article briefly examines Plato's demographic thought and its relation to the sociopolitical conditions and intellectual currents of his time and place. The major themes of his demographic work are viewed as outgrowths of the fundamental principles of platonic philosophy and ethics: perfect love, biological and spiritual fertility, procreation as a duty, eugenics, moderation and static equilibrium, the need for demographic legislation, and the justification for and methods of demographic policy. The demographic doctrines espoused in Plato's "Laws" and "The Republic" are then examined. Analysis of Plato's global demographic thought demonstrates how the implementation of perfectly logical means of improving the collective good through measures affecting social organization, legislation, and education resulted in the most totalitarian demographic doctrine ever enunciated. Thus for example, the necessity of harmonizing the ideal of platonic love with the biologic renewal of society led Plato to grant rulers absolute and exclusive power over the family, marriage, sexuality, procreation, and the life and death of infants.

  11. [Recent demographic trends in Luxembourg].

    PubMed

    1982-01-01

    Demographic trends in Luxembourg are reviewed for 1981. Sections are included on fertility; mortality; population change, including natural increase and migration; nuptiality and divorce; and family-related legislation. Preliminary data for the first half of 1982 are also included.

  12. [Contemporary demographic survey of Venezuela].

    PubMed

    Osorio, E

    1985-01-01

    Current demographic trends in Venezuela are reviewed, based on data from the 1981 census. Topics covered include population growth, age structure, family characteristics, school-age population, foreign population, spatial distribution, labor force, and housing.

  13. Demographic change and income distribution.

    PubMed

    Von Weizsacker, R K

    1989-03-01

    This paper examines the interactions between demographic change and income distribution, especially in the context of government. Starting from a simple, descriptive life-cycle model of individual income, this paper established an explicit link between the age composition of a population and the personal distribution of incomes. Demographic effects on income inequality are derived. Next, 2 income maintenance programs are introduced: a redistributive tax-transfer scheme and a pay-as-you-go financed state pension system. The resulting government budget constraints entail interrelations between fiscal and demographic variables, causing an additional, indirect demographic impact on the distribution. This is shown not only to change, but in some cases even to reverse the distributional incidence of demographic trends. The superimposition of different age structures on populations of otherwise identical characteristics is non-neutral with respect to income distribution: disregarding state interventions, population aging increases income inequality. This result may no longer generally hold if redistribution policies are taken into account. The paper provides an example of how indirect demographic effects may lead to a reversal of sign. In the absence of any government program, a higher ratio of pensioners to active workers raises income inequality. In the presence of a redistributive tax-transfer scheme and pay-as-you-go financed state pension system, a higher dependency ratio decreases income dispersion. The restoration of government budget equilibrium induces unintended distributional effects which put the incidence of demographic shifts in a different light. Varying important aging indicator with realistic forecast bounds leads to inequality fluctuations up to 35%. This illustrates the quantitative scale and hence the political importance of demographically caused inequality distortions.

  14. EJSCREEN Version 1, Demographic Data

    EPA Pesticide Factsheets

    This map service displays demographic data used in EJSCREEN. All demographic data were derived from American Community Survey 2006-2010 estimates. EJSCREEN is an environmental justice screening tool that provides EPA with a nationally consistent approach to screening for potential areas of EJ concern that may warrant further investigation. The EJ indexes are block group level results that combine multiple demographic factors with a single environmental variable (such as proximity to traffic) that can be used to help identify communities living with the greatest potential for negative environmental and health effects. The EJSCREEN tool is currently for internal EPA use only. It is anticipated that as users become accustomed to this new tool, individual programs within the Agency will develop program use guidelines and a community of practice will develop around them within the EPA Geoplatform. Users should keep in mind that screening tools are subject to substantial uncertainty in their demographic and environmental data, particularly when looking at small geographic areas, such as Census block groups. Data on the full range of environmental impacts and demographic factors in any given location are almost certainly not available directly through this tool, and its initial results should be supplemented with additional information and local knowledge before making any judgments about potential areas of EJ concern.

  15. Relating dispersal and range expansion of California sea otters.

    PubMed

    Krkosek, Martin; Lauzon-Guay, Jean-Sébastien; Lewis, Mark A

    2007-06-01

    Linking dispersal and range expansion of invasive species has long challenged theoretical and quantitative ecologists. Subtle differences in dispersal can yield large differences in geographic spread, with speeds ranging from constant to rapidly increasing. We developed a stage-structured integrodifference equation (IDE) model of the California sea otter range expansion that occurred between 1914 and 1986. The non-spatial model, a linear matrix population model, was coupled to a suite of candidate dispersal kernels to form stage-structured IDEs. Demographic and dispersal parameters were estimated independent of range expansion data. Using a single dispersal parameter, alpha, we examined how well these stage-structured IDEs related small scale demographic and dispersal processes with geographic population expansion. The parameter alpha was estimated by fitting the kernels to dispersal data and by fitting the IDE model to range expansion data. For all kernels, the alpha estimate from range expansion data fell within the 95% confidence intervals of the alpha estimate from dispersal data. The IDE models with exponentially bounded kernels predicted invasion velocities that were captured within the 95% confidence bounds on the observed northbound invasion velocity. However, the exponentially bounded kernels yielded range expansions that were in poor qualitative agreement with range expansion data. An IDE model with fat (exponentially unbounded) tails and accelerating spatial spread yielded the best qualitative match. This model explained 94% and 97% of the variation in northbound and southbound range expansions when fit to range expansion data. These otters may have been fat-tailed accelerating invaders or they may have followed a piece-wise linear spread first over kelp forests and then over sandy habitats. Further, habitat-specific dispersal data could resolve these explanations.

  16. Social demographic change and autism.

    PubMed

    Liu, Kayuet; Zerubavel, Noam; Bearman, Peter

    2010-05-01

    Parental age at child's birth--which has increased for U.S. children in the 1992-2000 birth cohorts--is strongly associated with an increased risk of autism. By turning a social demographic lens on the historical patterning of concordance among twin pairs, we identify a central mechanism for this association: de novo mutations, which are deletions, insertions, and duplications of DNA in the germ cells that are not present in the parents' DNA. Along the way, we show that a demographic eye on the rising prevalence of autism leads to three major discoveries. First, the estimated heritability of autism has been dramatically overstated. Second, heritability estimates can change over remarkably short periods of time because of increases in germ cell mutations. Third, social demographic change can yield genetic changes that, at the population level, combine to contribute to the increased prevalence of autism.

  17. Social Demographic Change and Autism

    PubMed Central

    LIU, KAYUET; ZERUBAVEL, NOAM; BEARMAN, PETER

    2010-01-01

    Parental age at child’s birth—which has increased for U.S. children in the 1992–2000 birth cohorts—is strongly associated with an increased risk of autism. By turning a social demographic lens on the historical patterning of concordance among twin pairs, we identify a central mechanism for this association: de novo mutations, which are deletions, insertions, and duplications of DNA in the germ cells that are not present in the parents’ DNA. Along the way, we show that a demographic eye on the rising prevalence of autism leads to three major discoveries. First, the estimated heritability of autism has been dramatically overstated. Second, heritability estimates can change over remarkably short periods of time because of increases in germ cell mutations. Third, social demographic change can yield genetic changes that, at the population level, combine to contribute to the increased prevalence of autism. PMID:20608100

  18. Thermal Expansion "Paradox."

    ERIC Educational Resources Information Center

    Fakhruddin, Hasan

    1993-01-01

    Describes a paradox in the equation for thermal expansion. If the calculations for heating a rod and subsequently cooling a rod are determined, the new length of the cool rod is shorter than expected. (PR)

  19. Pen Branch delta expansion

    SciTech Connect

    Nelson, E.A.; Christensen, E.J.; Mackey, H.E.; Sharitz, R.R.; Jensen, J.R.; Hodgson, M.E.

    1984-02-01

    Since 1954, cooling water discharges from K Reactor ({anti X} = 370 cfs {at} 59 C) to Pen Branch have altered vegetation and deposited sediment in the Savannah River Swamp forming the Pen Branch delta. Currently, the delta covers over 300 acres and continues to expand at a rate of about 16 acres/yr. Examination of delta expansion can provide important information on environmental impacts to wetlands exposed to elevated temperature and flow conditions. To assess the current status and predict future expansion of the Pen Branch delta, historic aerial photographs were analyzed using both basic photo interpretation and computer techniques to provide the following information: (1) past and current expansion rates; (2) location and changes of impacted areas; (3) total acreage presently affected. Delta acreage changes were then compared to historic reactor discharge temperature and flow data to see if expansion rate variations could be related to reactor operations.

  20. Weakly relativistic plasma expansion

    SciTech Connect

    Fermous, Rachid Djebli, Mourad

    2015-04-15

    Plasma expansion is an important physical process that takes place in laser interactions with solid targets. Within a self-similar model for the hydrodynamical multi-fluid equations, we investigated the expansion of both dense and under-dense plasmas. The weakly relativistic electrons are produced by ultra-intense laser pulses, while ions are supposed to be in a non-relativistic regime. Numerical investigations have shown that relativistic effects are important for under-dense plasma and are characterized by a finite ion front velocity. Dense plasma expansion is found to be governed mainly by quantum contributions in the fluid equations that originate from the degenerate pressure in addition to the nonlinear contributions from exchange and correlation potentials. The quantum degeneracy parameter profile provides clues to set the limit between under-dense and dense relativistic plasma expansions at a given density and temperature.

  1. Thermal Expansion "Paradox."

    ERIC Educational Resources Information Center

    Fakhruddin, Hasan

    1993-01-01

    Describes a paradox in the equation for thermal expansion. If the calculations for heating a rod and subsequently cooling a rod are determined, the new length of the cool rod is shorter than expected. (PR)

  2. Thermal-Expansion Measurement

    NASA Technical Reports Server (NTRS)

    Davis, J. H.; Rives, C.

    1985-01-01

    Precise stable laser system determines coefficients of thermal expansion. Dual-beam interferometer arrangement monitors changes in sample length as function of temperature by following changes inoptical path lengths.

  3. Optimal Electric Utility Expansion

    SciTech Connect

    1989-10-10

    SAGE-WASP is designed to find the optimal generation expansion policy for an electrical utility system. New units can be automatically selected from a user-supplied list of expansion candidates which can include hydroelectric and pumped storage projects. The existing system is modeled. The calculational procedure takes into account user restrictions to limit generation configurations to an area of economic interest. The optimization program reports whether the restrictions acted as a constraint on the solution. All expansion configurations considered are required to pass a user supplied reliability criterion. The discount rate and escalation rate are treated separately for each expansion candidate and for each fuel type. All expenditures are separated into local and foreign accounts, and a weighting factor can be applied to foreign expenditures.

  4. Expansion and contraction tension zones in western pinon-juniper woodlands under projected climate change

    Treesearch

    Jacob Gibson; Gretchen G. Moisen; Tracey S. Frescino; Thomas C. Jr. Edwards

    2012-01-01

    Populations of pinons and junipers across the interior west have been highly dynamic over the last two centuries, undergoing an overall expansion but punctuated with regional mortality. Accumulating demographic studies across the interior west indicate the drivers of expansion and contraction of populations are compounded by regional land use legacies, but have an...

  5. Grandparents today: a demographic profile.

    PubMed

    Szinovacz, M E

    1998-02-01

    This article presents a demographic profile of grandparents, using the National Survey of Families and Households. Specific dimensions of grandparenthood addressed include grandparents' survival, the timing of grandparenthood, grandparents' involvement in other roles, surrogate parenting, and stepgrandparents. The data indicate considerable heterogeneity among grandparents of different genders and races or ethnicities. They also suggest modifications in previous descriptions of modern grandparenthood.

  6. Grandparents Today: A Demographic Profile.

    ERIC Educational Resources Information Center

    Szinovacz, Maximiliane E.

    1998-01-01

    Utilizes the National Survey of Families and Households to present a demographic profile of grandparents. Examines grandparents' survival, timing of grandparenthood, grandparents' involvement in other roles, surrogate parenting, and stepgrandparents. Data indicate considerable heterogeneity among grandparents of different genders and ethnicities.…

  7. [Recent demographic trends in Luxembourg].

    PubMed

    1981-01-01

    Demographic trends in Luxembourg over the period 1970-1980 are reviewed. Data are presented separately ¿for the Luxembourg and foreign populations and cover fertility, mortality, natural increase, age and sex distribution, marriage and divorce, and family allowance legislation.

  8. Enrollment Management: Demographic Changes. Report.

    ERIC Educational Resources Information Center

    Gribbons, Barry C.; Meuschke, Daylene M.

    The Office of Institutional Development and Technology and the Public Information Office created this report that identifies several topics of research in order to inform marketing efforts associated with enrollment management. The report is based upon demographic studies done at the College of Canyons to measure things such as changes in the size…

  9. Are Demographics the Nation's Destiny?

    ERIC Educational Resources Information Center

    Glass, Gene V.

    2008-01-01

    In this article, the author discusses the demographic trends affecting America's public schools. As an expert on empirical evaluation of education, the author believes the major debates over vouchers, charter schools, bilingual education, and other issues are not really about preparing the next generation to compete with China or India, or about…

  10. The demographic situation in Croatia.

    PubMed

    Mrden, S; Friganovic, M

    1998-01-01

    "In this paper [the] authors discuss demographic features in Croatia [from] the [second] half of the 19th century till 1996, paying special attention to the period since [the] early fifties onwards. Beside...population migration, vital statistics, projections and population development programs have been analysed. It is possible to compare Croatia with some European countries...." (EXCERPT)

  11. Demographic Factors Affecting Faculty Salary.

    ERIC Educational Resources Information Center

    Webster, Allen L.

    1995-01-01

    Specific demographic attributes that influence salary at institutions of higher education were studied through data from 420 faculty members at 9 institutions. Results suggested that experience, publication rates, time at the institution, and possession of a terminal degree affected salary levels. The presence of salary compression was noted. (SLD)

  12. Demographic Challenges in America's Future.

    ERIC Educational Resources Information Center

    Butz, William P.; And Others

    This document examines trends in the United States population since World War II, and projects a scenario of how demographic and economic phenomena may evolve over the next several decades. The report is divided into five sections. Section 1 introduces the volume and discusses generally some of the effects of the nation's transition to zero…

  13. Demographic Modelling in Weed Biocontrol

    USDA-ARS?s Scientific Manuscript database

    Demographic matrix modeling of plant populations can be a powerful tool to identify key life stage transitions that contribute the most to population growth of an invasive plant and hence should be targeted for disruption. Therefore, this approach has the potential to guide the pre-release selection...

  14. Democratic constraints on demographic policy.

    PubMed

    Grigsby, J S

    1984-01-01

    The discussion compares the population policies adopted in Sweden during the 1930s to raise fertiity and the policies considered in the US during the 1970s in response to the high fertility experienced in the 1950s. Both sets of policies recommended increased availability of birth control, more liberal abortion laws, and greater employment opportunities for women. It becomes evident that the constraints imposed by a democratic system of government translate into policy recommendations that place individual freedom of choice and equal opportunity for all citizens as higher goals than any specific demographic target. Consequently, the population commissions of Sweden and the US made similar suggestions on how to resolve their opposite demographic problems. The demographic situations in the 2 nations were antipodal, and the countries also had very different social climates. This additional disparity was insufficient to counterbalance the apparently overwhelming influence of the democratic political systems in making virtually identical policy recommendations. Yet, the contrasting social climates of Sweden in 1935 and the US in 1970-72 may explain the different reactions each commission received. In terms of the responses by both citizens and government officials to the commissions' reports, the Swedish commission was more successful. Practically all of their recommendations were enthusiastically received and quickly adopted by the Swedish Riksdag. Yet, when the criterion for success becomes whether or not a demographic target was met, it increased in the 1940s and then dropped again while the same social policies were in effect. Even before the US commission began its study, fertility in the US had fallen and continues to remain low. These findings suggest that commissions in democratic countries will most likely never recommend dramatic measures in population policy. Thus, it is questionable whether such commissions in democratic nations will totally fulfill the

  15. Virial Expansion Bounds

    NASA Astrophysics Data System (ADS)

    Tate, Stephen James

    2013-10-01

    In the 1960s, the technique of using cluster expansion bounds in order to achieve bounds on the virial expansion was developed by Lebowitz and Penrose (J. Math. Phys. 5:841, 1964) and Ruelle (Statistical Mechanics: Rigorous Results. Benjamin, Elmsford, 1969). This technique is generalised to more recent cluster expansion bounds by Poghosyan and Ueltschi (J. Math. Phys. 50:053509, 2009), which are related to the work of Procacci (J. Stat. Phys. 129:171, 2007) and the tree-graph identity, detailed by Brydges (Phénomènes Critiques, Systèmes Aléatoires, Théories de Jauge. Les Houches 1984, pp. 129-183, 1986). The bounds achieved by Lebowitz and Penrose can also be sharpened by doing the actual optimisation and achieving expressions in terms of the Lambert W-function. The different bound from the cluster expansion shows some improvements for bounds on the convergence of the virial expansion in the case of positive potentials, which are allowed to have a hard core.

  16. Accelerating the loop expansion

    SciTech Connect

    Ingermanson, R.

    1986-07-29

    This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs.

  17. Emergence of Rapid Evolution from Demographic Stochasticity

    NASA Astrophysics Data System (ADS)

    Shih, Hong-Yan; Goldenfeld, Nigel

    2014-03-01

    The phenomenon of ``rapid evolution'' arises when genetic variation occurs fast enough to significantly change ecodynamics. Data from experiments with algae-rotifer system and bacteria-phage system show unusual dynamics when there are subpopulations of preys with different trait values, including predator-prey phase shifts near π (and distinct from the canonical value of π / 2) and so-called cryptic cycles, in which populations of preys remain constant while the predator population oscillates. Such phenomena have been modeled with deterministic differential equations containing empirical Michaelis-Menten kinetic terms and the unusual dynamics that is attributed to postulate complicated trade-off between sub-populations. Here we present a generic individual-level stochastic model of interacting populations that includes a subpopulation resistant to the predator but with metabolic cost. We solve this model by using a master equation approach, and by performing system size expansion, we find that antiphase and cryptic quasi-cycles can emerge from the combination of intrinsic demographic fluctuations and clonal mutations alone. These analytic results are then compared with Gillespie simulations, and the typical phase diagram of the system is calculated.

  18. Steppe expansion in Patagonia?

    NASA Astrophysics Data System (ADS)

    Veblen, Thomas T.; Markgraf, Vera

    1988-11-01

    Westward expansion of the Patagonian steppe and retrocession of Andean forests due to increasing aridity over the past one or two millennia has been a persistent theme in the ecological and paleoecological literature for at least half a century. New evidence from pollen profiles, tree-ring analysis, vegetation structure, and photographic and documentary historical sources does not show the expansion of the steppe. Instead, over the past century trees have invaded the steppe as a consequence mainly of human-induced changes in the fire regime, and trees have regenerated in forest areas that were heavily burnt at the onset of European colonization.

  19. Demographic Events and Evolutionary Forces Shaping European Genetic Diversity

    PubMed Central

    Veeramah, Krishna R.; Novembre, John

    2014-01-01

    Europeans have been the focus of some of the largest studies of genetic diversity in any species to date. Recent genome-wide data have reinforced the hypothesis that present-day European genetic diversity is strongly correlated with geography. The remaining challenge now is to understand more precisely how patterns of diversity in Europe reflect ancient demographic events such as postglacial expansions or the spread of farming. It is likely that recent advances in paleogenetics will give us some of these answers. There has also been progress in identifying specific segments of European genomes that reflect adaptations to selective pressures from the physical environment, disease, and dietary shifts. A growing understanding of how modern European genetic diversity has been shaped by demographic and evolutionary forces is not only of basic historical and anthropological interest but also aids genetic studies of disease. PMID:25059709

  20. Demographic events and evolutionary forces shaping European genetic diversity.

    PubMed

    Veeramah, Krishna R; Novembre, John

    2014-07-24

    Europeans have been the focus of some of the largest studies of genetic diversity in any species to date. Recent genome-wide data have reinforced the hypothesis that present-day European genetic diversity is strongly correlated with geography. The remaining challenge now is to understand more precisely how patterns of diversity in Europe reflect ancient demographic events such as postglacial expansions or the spread of farming. It is likely that recent advances in paleogenetics will give us some of these answers. There has also been progress in identifying specific segments of European genomes that reflect adaptations to selective pressures from the physical environment, disease, and dietary shifts. A growing understanding of how modern European genetic diversity has been shaped by demographic and evolutionary forces is not only of basic historical and anthropological interest but also aids genetic studies of disease. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

  1. Bet Hedging against Demographic Fluctuations

    NASA Astrophysics Data System (ADS)

    Xue, BingKan; Leibler, Stanislas

    2017-09-01

    Biological organisms have to cope with stochastic variations in both the external environment and the internal population dynamics. Theoretical studies and laboratory experiments suggest that population diversification could be an effective bet-hedging strategy for adaptation to varying environments. Here we show that bet hedging can also be effective against demographic fluctuations that pose a trade-off between growth and survival for populations even in a constant environment. A species can maximize its overall abundance in the long term by diversifying into coexisting subpopulations of both "fast-growing" and "better-surviving" individuals. Our model generalizes statistical physics models of birth-death processes to incorporate dispersal, during which new populations are founded, and can further incorporate variations of local environments. In this way, we unify different bet-hedging strategies against demographic and environmental variations as a general means of adaptation to both types of uncertainties in population growth.

  2. Sex and stochasticity affect range expansion of experimental invasions.

    PubMed

    Miller, Tom E X; Inouye, Brian D

    2013-03-01

    Understanding and predicting range expansion are key objectives in many basic and applied contexts. Among dioecious organisms, there is strong evidence for sex differences in dispersal, which could alter the sex ratio at the expansion's leading edge. However, demographic stochasticity could also affect leading-edge sex ratios, perhaps overwhelming sex-biased dispersal. We used insects in laboratory mesocosms to test the effects of sex-biased dispersal on range expansion, and a simulation model to explore interactive effects of sex-biased dispersal and demographic stochasticity. Sex-biased dispersal created spatial clines in the sex ratio, which influenced offspring production at the front and altered invasion velocity. Increasing female dispersal relative to males accelerated spread, despite the prediction that demographic stochasticity would weaken a signal of sex-biased dispersal. Our results provide the first experimental evidence for an influence of sex-biased dispersal on invasion velocity, highlighting the value of accounting for sex structure in studies of range expansion. © 2012 Blackwell Publishing Ltd/CNRS.

  3. A Special Trinomial Expansion

    ERIC Educational Resources Information Center

    Ayoub, Ayoub B.

    2006-01-01

    In this article, the author takes up the special trinomial (1 + x + x[squared])[superscript n] and shows that the coefficients of its expansion are entries of a Pascal-like triangle. He also shows how to calculate these entries recursively and explicitly. This article could be used in the classroom for enrichment. (Contains 1 table.)

  4. Static gas expansion cooler

    DOEpatents

    Guzek, J.C.; Lujan, R.A.

    1984-01-01

    Disclosed is a cooler for television cameras and other temperature sensitive equipment. The cooler uses compressed gas ehich is accelerated to a high velocity by passing it through flow passageways having nozzle portions which expand the gas. This acceleration and expansion causes the gas to undergo a decrease in temperature thereby cooling the cooler body and adjacent temperature sensitive equipment.

  5. Urban Expansion Study

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Under an Egyptian government contract, PADCO studies urban growth in the Nile Area. They were assisted by LANDSAT survey maps and measurements provided by TAC. TAC had classified the raw LANDSAT data and processed it into various categories to detail urban expansion. PADCO crews spot checked the results, and correlations were established.

  6. A Special Trinomial Expansion

    ERIC Educational Resources Information Center

    Ayoub, Ayoub B.

    2006-01-01

    In this article, the author takes up the special trinomial (1 + x + x[squared])[superscript n] and shows that the coefficients of its expansion are entries of a Pascal-like triangle. He also shows how to calculate these entries recursively and explicitly. This article could be used in the classroom for enrichment. (Contains 1 table.)

  7. Expansion of Pannes

    EPA Science Inventory

    For the Long Island, New Jersey, and southern New England region, one facet of marsh drowning as a result of accelerated sea level rise is the expansion of salt marsh ponds and pannes. Over the past century, marsh ponds and pannes have formed and expanded in areas of poor drainag...

  8. AUTO-EXPANSIVE FLOW

    EPA Science Inventory

    Physics suggests that the interplay of momentum, continuity, and geometry in outward radial flow must produce density and concomitant pressure reductions. In other words, this flow is intrinsically auto-expansive. It has been proposed that this process is the key to understanding...

  9. AUTO-EXPANSIVE FLOW

    EPA Science Inventory

    Physics suggests that the interplay of momentum, continuity, and geometry in outward radial flow must produce density and concomitant pressure reductions. In other words, this flow is intrinsically auto-expansive. It has been proposed that this process is the key to understanding...

  10. Expansion of Pannes

    EPA Science Inventory

    For the Long Island, New Jersey, and southern New England region, one facet of marsh drowning as a result of accelerated sea level rise is the expansion of salt marsh ponds and pannes. Over the past century, marsh ponds and pannes have formed and expanded in areas of poor drainag...

  11. [Population education. The school and demographic demographic knowledge].

    PubMed

    Camarena Cordova, R M

    1991-01-01

    Population education is recognized as a means of promoting changes in demographic behavior. Mexico's 1973 General Law of Population and its associated regulations assigned to education an important role in supporting the population policy. Inclusion of population content in curricular programs at the basic education level has been a major action. Content referring to sexuality, responsible parenthood, and human reproduction was introduced into the curriculum as part of the 1974 educational reform, and other topics such as family, health care, and environment were reformulated to emphasize their connection to demographic policy. The curricular change was important, but was not supported by later actions to enrich it and keep it up to date. The population education curriculum in basic education was never evaluated. Some studies of the knowledge and atti tudes of adolescents regarding sexuality, contraception, and reproduction have demonstrated the importance of the school as a channel of information but have also raised doubts about the quality and effectiveness of existing curricula. Other studies have found the population education content in primary texts to be too general, superficial, incomplete, and stereotyped in the treatment of some themes. The population education curriculum began to be reconsidered beginning in the mid-1980s. An interinstitutional group is now redefining and redesigning the population education materials that will be included in the plans, programs, and supporting material for basic education that will result from the current program for educational modernization. The relevance of these actions is obvious, despite their neglect by demographers. In the 1990-91 school year, 18.3 million children will be registered in primary and secondary schools, a figure representing 22.9% of the total 1990 population. In other words, over 20% of Mexicans will be potential recipients of population education.

  12. Impact of Sampling Schemes on Demographic Inference: An Empirical Study in Two Species with Different Mating Systems and Demographic Histories

    PubMed Central

    St. Onge, K. R.; Palmé, A. E.; Wright, S. I.; Lascoux, M.

    2012-01-01

    Most species have at least some level of genetic structure. Recent simulation studies have shown that it is important to consider population structure when sampling individuals to infer past population history. The relevance of the results of these computer simulations for empirical studies, however, remains unclear. In the present study, we use DNA sequence datasets collected from two closely related species with very different histories, the selfing species Capsella rubella and its outcrossing relative C. grandiflora, to assess the impact of different sampling strategies on summary statistics and the inference of historical demography. Sampling strategy did not strongly influence the mean values of Tajima’s D in either species, but it had some impact on the variance. The general conclusions about demographic history were comparable across sampling schemes even when resampled data were analyzed with approximate Bayesian computation (ABC). We used simulations to explore the effects of sampling scheme under different demographic models. We conclude that when sequences from modest numbers of loci (<60) are analyzed, the sampling strategy is generally of limited importance. The same is true under intermediate or high levels of gene flow (4Nm > 2–10) in models in which global expansion is combined with either local expansion or hierarchical population structure. Although we observe a less severe effect of sampling than predicted under some earlier simulation models, our results should not be seen as an encouragement to neglect this issue. In general, a good coverage of the natural range, both within and between populations, will be needed to obtain a reliable reconstruction of a species’s demographic history, and in fact, the effect of sampling scheme on polymorphism patterns may itself provide important information about demographic history. PMID:22870403

  13. Evolutionary shaping of demographic schedules

    PubMed Central

    Wachter, Kenneth W.; Steinsaltz, David; Evans, Steven N.

    2014-01-01

    Evolutionary processes of natural selection may be expected to leave their mark on age patterns of survival and reproduction. Demographic theory includes three main strands—mutation accumulation, stochastic vitality, and optimal life histories. This paper reviews the three strands and, concentrating on mutation accumulation, extends a mathematical result with broad implications concerning the effect of interactions between small age-specific effects of deleterious mutant alleles. Empirical data from genomic sequencing along with prospects for combining strands of theory hold hope for future progress. PMID:25024186

  14. Expansion tube test time predictions

    NASA Technical Reports Server (NTRS)

    Gourlay, Christopher M.

    1988-01-01

    The interaction of an interface between two gases and strong expansion is investigated and the effect on flow in an expansion tube is examined. Two mechanisms for the unsteady Pitot-pressure fluctuations found in the test section of an expansion tube are proposed. The first mechanism depends on the Rayleigh-Taylor instability of the driver-test gas interface in the presence of a strong expansion. The second mechanism depends on the reflection of the strong expansion from the interface. Predictions compare favorably with experimental results. The theory is expected to be independent of the absolute values of the initial expansion tube filling pressures.

  15. Bigravity from gradient expansion

    SciTech Connect

    Yamashita, Yasuho; Tanaka, Takahiro

    2016-05-04

    We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.

  16. Range expansion of mutualists

    NASA Astrophysics Data System (ADS)

    Muller, Melanie J. I.; Korolev, Kirill S.; Murray, Andrew W.; Nelson, David R.

    2012-02-01

    The expansion of a species into new territory is often strongly influenced by the presence of other species. This effect is particularly striking for the case of mutualistic species that enhance each other's proliferation. Examples range from major events in evolutionary history, such as the spread and diversification of flowering plants due to their mutualism with pollen-dispersing insects, to modern examples like the surface colonisation of multi-species microbial biofilms. Here, we investigate the spread of cross-feeding strains of the budding yeast Saccharomyces cerevisiae on an agar surface as a model system for expanding mutualists. Depending on the degree of mutualism, the two strains form distinctive spatial patterns during their range expansion. This change in spatial patterns can be understood as a phase transition within a stepping stone model generalized to two mutualistic species.

  17. The influence of interspecific interactions on species range expansion rates

    PubMed Central

    Svenning, Jens-Christian; Gravel, Dominique; Holt, Robert D.; Schurr, Frank M.; Thuiller, Wilfried; Münkemüller, Tamara; Schiffers, Katja H.; Dullinger, Stefan; Edwards, Thomas C.; Hickler, Thomas; Higgins, Steven I.; Nabel, Julia E. M. S.; Pagel, Jörn; Normand, Signe

    2014-01-01

    Ongoing and predicted global change makes understanding and predicting species’ range shifts an urgent scientific priority. Here, we provide a synthetic perspective on the so far poorly understood effects of interspecific interactions on range expansion rates. We present theoretical foundations for how interspecific interactions may modulate range expansion rates, consider examples from empirical studies of biological invasions and natural range expansions as well as process-based simulations, and discuss how interspecific interactions can be more broadly represented in process-based, spatiotemporally explicit range forecasts. Theory tells us that interspecific interactions affect expansion rates via alteration of local population growth rates and spatial displacement rates, but also via effects on other demographic parameters. The best empirical evidence for interspecific effects on expansion rates comes from studies of biological invasions. Notably, invasion studies indicate that competitive dominance and release from specialized enemies can enhance expansion rates. Studies of natural range expansions especially point to the potential for competition from resident species to reduce expansion rates. Overall, it is clear that interspecific interactions may have important consequences for range dynamics, but also that their effects have received too little attention to robustly generalize on their importance. We then discuss how interspecific interactions effects can be more widely incorporated in dynamic modeling of range expansions. Importantly, models must describe spatiotemporal variation in both local population dynamics and dispersal. Finally, we derive the following guidelines for when it is particularly important to explicitly represent interspecific interactions in dynamic range expansion forecasts: if most interacting species show correlated spatial or temporal trends in their effects on the target species, if the number of interacting species is low

  18. The influence of interspecific interactions on species range expansion rates

    USGS Publications Warehouse

    Svenning, Jens-Christian; Gravel, Dominique; Holt, Robert D.; Schurr, Frank M.; Thuiller, Wilfried; Münkemüller, Tamara; Schiffers, Katja H.; Dullinger, Stefan; Edwards, Thomas C.; Hickler, Thomas; Higgins, Steven I.; Nabel, Julia E.M.S.; Pagel, Jörn; Normand, Signe

    2014-01-01

    Ongoing and predicted global change makes understanding and predicting species’ range shifts an urgent scientific priority. Here, we provide a synthetic perspective on the so far poorly understood effects of interspecific interactions on range expansion rates. We present theoretical foundations for how interspecific interactions may modulate range expansion rates, consider examples from empirical studies of biological invasions and natural range expansions as well as process-based simulations, and discuss how interspecific interactions can be more broadly represented in process-based, spatiotemporally explicit range forecasts. Theory tells us that interspecific interactions affect expansion rates via alteration of local population growth rates and spatial displacement rates, but also via effects on other demographic parameters. The best empirical evidence for interspecific effects on expansion rates comes from studies of biological invasions. Notably, invasion studies indicate that competitive dominance and release from specialized enemies can enhance expansion rates. Studies of natural range expansions especially point to the potential for competition from resident species to reduce expansion rates. Overall, it is clear that interspecific interactions may have important consequences for range dynamics, but also that their effects have received too little attention to robustly generalize on their importance. We then discuss how interspecific interactions effects can be more widely incorporated in dynamic modeling of range expansions. Importantly, models must describe spatiotemporal variation in both local population dynamics and dispersal. Finally, we derive the following guidelines for when it is particularly important to explicitly represent interspecific interactions in dynamic range expansion forecasts: if most interacting species show correlated spatial or temporal trends in their effects on the target species, if the number of interacting species is low

  19. Alcohol Consumption in Demographic Subpopulations

    PubMed Central

    Delker, Erin; Brown, Qiana; Hasin, Deborah S.

    2016-01-01

    Alcohol consumption is common across subpopulations in the United States. However, the health burden associated with alcohol consumption varies across groups, including those defined by demographic characteristics such as age, race/ethnicity, and gender. Large national surveys, such as the National Epidemiologic Survey on Alcohol and Related Conditions and the National Survey on Drug Use and Health, found that young adults ages 18–25 were at particularly high risk of alcohol use disorder and unintentional injury caused by drinking. These surveys furthermore identified significant variability in alcohol consumption and its consequences among racial/ethnic groups. White respondents reported the highest prevalence of current alcohol consumption, whereas alcohol abuse and dependence were most prevalent among Native Americans. Native Americans and Blacks also were most vulnerable to alcohol-related health consequences. Even within ethnic groups, there was variability between and among different subpopulations. With respect to gender, men reported more alcohol consumption and binge drinking than women, especially in older cohorts. Men also were at greater risk of alcohol abuse and dependence, liver cirrhosis, homicide after alcohol consumption, and drinking and driving. Systematic identification and measurement of the variability across demographics will guide prevention and intervention efforts, as well as future research. PMID:27159807

  20. Our Demographically Divided World, Worldwatch Paper 74.

    ERIC Educational Resources Information Center

    Brown, Lester R.; Jacobson, Jodi L.

    Existing demographic analyses do not explain the negative relationship between population growth and life-support systems that are now emerging in scores of developing countries. The demographic transition, a theory first outlined by demographer Frank Notestein in 1945, classified all societies into one of three stages. Drawing heavily on the…

  1. Contrasting demographic histories of the neighboring bonobo and chimpanzee.

    PubMed

    Hvilsom, Christina; Carlsen, Frands; Heller, Rasmus; Jaffré, Nina; Siegismund, Hans R

    2014-01-01

    The Pleistocene epoch was a period of dramatic climate change that had profound impacts on the population sizes of many animal species. How these species were shaped by past events is often unclear, hindering our understanding of the population dynamics resulting in present day populations. We analyzed complete mitochondrial genomes representing all four recognized chimpanzee subspecies and the bonobo to infer the recent demographic history and used simulations to exclude a confounding effect of population structure. Our genus-wide Bayesian coalescent-based analysis revealed surprisingly dissimilar demographic histories of the chimpanzee subspecies and the bonobo, despite their overlapping habitat requirements. Whereas the central and eastern chimpanzee subspecies were inferred to have expanded tenfold between around 50,000 and 80,000 years ago and today, the population size of the neighboring bonobo remained constant. The changes in population size are likely linked to changes in habitat area due to climate oscillations during the late Pleistocene. Furthermore, the timing of population expansion for the rainforest-adapted chimpanzee is concurrent with the expansion of the savanna-adapted human, which could suggest a common response to changed climate conditions around 50,000-80,000 years ago.

  2. Thermal expansion of glassy polymers.

    PubMed

    Davy, K W; Braden, M

    1992-01-01

    The thermal expansion of a number of glassy polymers of interest in dentistry has been studied using a quartz dilatometer. In some cases, the expansion was linear and therefore the coefficient of thermal expansion readily determined. Other polymers exhibited non-linear behaviour and values appropriate to different temperature ranges are quoted. The linear coefficient of thermal expansion was, to a first approximation, a function of both the molar volume and van der Waal's volume of the repeating unit.

  3. Expansion: A Plan for Success.

    ERIC Educational Resources Information Center

    Callahan, A.P.

    This report provides selling brokers' guidelines for the successful expansion of their operations outlining a basic method of preparing an expansion plan. Topic headings are: The Pitfalls of Expansion (The Language of Business, Timely Financial Reporting, Regulatory Agencies of Government, Preoccupation with the Facade of Business, A Business Is a…

  4. Expansion: A Plan for Success.

    ERIC Educational Resources Information Center

    Callahan, A.P.

    This report provides selling brokers' guidelines for the successful expansion of their operations outlining a basic method of preparing an expansion plan. Topic headings are: The Pitfalls of Expansion (The Language of Business, Timely Financial Reporting, Regulatory Agencies of Government, Preoccupation with the Facade of Business, A Business Is a…

  5. Demographic parameters and natural selection.

    PubMed

    Demetrius, L

    1974-12-01

    This paper introduces two new demographic parameters, the entropy and the reproductive potential of a population. The entropy of a population measures the variability of the contribution of the different age classes to the stationary age distribution. The reproductive potential measures the mean of the contribution of the different age classes to the growth rate. Using a relation between these measures and the Malthusian parameter, it is shown that in a random mating population in Hardy-Weinberg equilibrium, and under slow selection, the rate of change of entropy is equal to the genetic variance in entropy minus the genetic covariance of entropy and reproductive potential. This result is an analogue of Fisher's fundamental theorem of natural selection.

  6. Exoplanet Demographics with Microlensing Surveys

    NASA Astrophysics Data System (ADS)

    Gaudi, B.

    2014-04-01

    Because of its unique sensitivity to low-mass, long-period, and free-floating planets, microlensing is an essential complement to our arsenal of planet detection methods. I motivate microlensing surveys for exoplanets, and in particular describe how they can be used to test models for planet formation, as well as inform our understanding of the frequency and potential habitability of low-mass planets located in the habitable zones of their host stars. I review results from current microlensing surveys, and then discuss expectations for next-generation experiments. I explain why a space-based mission is necessary to realize the full potential of microlensing. When combined with the results from complementary surveys such as Kepler, a space-based microlensing survey will yield a nearly complete picture of the demographics of planetary systems throughout the Galaxy.

  7. Demographic effects of scientific progress.

    PubMed

    Coale, A J

    1987-01-01

    This essay refutes the commonly held view that the demographic transition in the west occurred as a result of scientific progress, but admits that the drop in mortality in the developing world since 1950 is largely due to technology. Human populations have grown at about 0.05% annually for 10,000 years, until about 1750, when the rate grew to 0.5%, then to 0.7% after 1900, and to 2% in the 1960s. Looking at life expectancy, which was about 35 years in the 18th century and 40 in the 19th in Europe, as well as advances in treatment and prevention of the major killer diseases, it is apparent that death rates fell substantially well before any effective therapy or immunization was developed. This can be demonstrated for tuberculosis and smallpox. Probably, life-style changes such as wearing washable cotton clothing, bathing, and better nutrition contributed to longer life. Advances in the understanding of contagion and infection contributed toward eradication of typhoid and cholera after 1850. Hence, public health projects such as sewage and water systems, better housing and working conditions, helped stop typhoid and diarrhea and to prolong life generally. The decline in fertility documented in the west also took place before any scientific birth control methods were available: only folk methods such as withdrawal, and social methods such as later marriage were responsible. In the less developed world, death rates began to plummet after 1950, largely due to immunization, mosquito control and other advances in health technology. It is hoped that contraceptive technology, with methods unrelated to sexual behavior, will reduce births in parallel. In conclusion, although science may not have been responsible in detail for the demographic transition in the west, scientific ideas prompted new attitudes about social change and secularism, which may have played a role in lowering birth rates.

  8. Load regulating expansion fixture

    DOEpatents

    Wagner, L.M.; Strum, M.J.

    1998-12-15

    A free standing self contained device for bonding ultra thin metallic films, such as 0.001 inch beryllium foils is disclosed. The device will regulate to a predetermined load for solid state bonding when heated to a bonding temperature. The device includes a load regulating feature, whereby the expansion stresses generated for bonding are regulated and self adjusting. The load regulator comprises a pair of friction isolators with a plurality of annealed copper members located therebetween. The device, with the load regulator, will adjust to and maintain a stress level needed to successfully and economically complete a leak tight bond without damaging thin foils or other delicate components. 1 fig.

  9. Load regulating expansion fixture

    DOEpatents

    Wagner, Lawrence M.; Strum, Michael J.

    1998-01-01

    A free standing self contained device for bonding ultra thin metallic films, such as 0.001 inch beryllium foils. The device will regulate to a predetermined load for solid state bonding when heated to a bonding temperature. The device includes a load regulating feature, whereby the expansion stresses generated for bonding are regulated and self adjusting. The load regulator comprises a pair of friction isolators with a plurality of annealed copper members located therebetween. The device, with the load regulator, will adjust to and maintain a stress level needed to successfully and economically complete a leak tight bond without damaging thin foils or other delicate components.

  10. Expansion in condensates

    SciTech Connect

    Chakrabarti, J.; Sajjad Zahir, M.

    1985-03-01

    We show that the product of local current operators in quantum chromodynamics (QCD), when expanded in terms of condensates, such as psi-barpsi, G/sup a//sub munu/ G/sup a//sub munu/, psi-barGAMMA psipsi-barGAMMApsi, f/sub a/bcG/sup a//sub munu/G/sup b//sub nualpha/ x G/sup c//sub alphamu/, etc., yields a series in Planck's constant. This, however, provides no hint that the higher terms in such an expansion may be less significant.

  11. Thrust expansion engine

    NASA Astrophysics Data System (ADS)

    Zovko, Carl T.

    1993-03-01

    Break-up activity of water by injection of hot propellant gas into channels of a thrust expansion engine is suppressed to prevent rapid cooling of the gas utilizing one or more methods including injection of a secondary inflow of the propellant gas and/or the water under lower pressures into the channels, injection of a viscosity enhancer and/or surfactant into the inflow stream of the water, and restricting outflow of the water from the channels by means of convergent nozzles.

  12. Expansible quantum secret sharing network

    NASA Astrophysics Data System (ADS)

    Sun, Ying; Xu, Sheng-Wei; Chen, Xiu-Bo; Niu, Xin-Xin; Yang, Yi-Xian

    2013-08-01

    In the practical applications, member expansion is a usual demand during the development of a secret sharing network. However, there are few consideration and discussion on network expansibility in the existing quantum secret sharing schemes. We propose an expansible quantum secret sharing scheme with relatively simple and economical quantum resources and show how to split and reconstruct the quantum secret among an expansible user group in our scheme. Its trait, no requirement of any agent's assistant during the process of member expansion, can help to prevent potential menaces of insider cheating. We also give a discussion on the security of this scheme from three aspects.

  13. Genetic footprints reveal geographic patterns of expansion in Fennoscandian red foxes.

    PubMed

    Norén, Karin; Statham, Mark J; Ågren, Erik O; Isomursu, Marja; Flagstad, Øystein; Eide, Nina E; Berg, Thomas Bjørneboe G; Bech-Sanderhoff, Lene; Sacks, Benjamin N

    2015-09-01

    Population expansions of boreal species are among the most substantial ecological consequences of climate change, potentially transforming both structure and processes of northern ecosystems. Despite their importance, little is known about expansion dynamics of boreal species. Red foxes (Vulpes vulpes) are forecasted to become a keystone species in northern Europe, a process stemming from population expansions that began in the 19th century. To identify the relative roles of geographic and demographic factors and the sources of northern European red fox population expansion, we genotyped 21 microsatellite loci in modern and historical (1835-1941) Fennoscandian red foxes. Using Bayesian clustering and Bayesian inference of migration rates, we identified high connectivity and asymmetric migration rates across the region, consistent with source-sink dynamics, whereby more recently colonized sampling regions received immigrants from multiple sources. There were no clear clines in allele frequency or genetic diversity as would be expected from a unidirectional range expansion from south to north. Instead, migration inferences, demographic models and comparison to historical red fox genotypes suggested that the population expansion of the red fox is a consequence of dispersal from multiple sources, as well as in situ demographic growth. Together, these findings provide a rare glimpse into the anatomy of a boreal range expansion and enable informed predictions about future changes in boreal communities. © 2015 John Wiley & Sons Ltd.

  14. Demographic studies of extrasolar planets

    NASA Astrophysics Data System (ADS)

    Morton, Timothy

    Uncovering the demographics of extrasolar planets is crucial to understanding the processes of their formation and evolution. In this thesis, we present four studies that contribute to this end, three of which relate to NASA's Kepler mission, which has revolutionized the field of exoplanets in the last few years. In the pre-Kepler study, we investigate a sample of exoplanet spin-orbit measurements---measurements of the inclination of a planet's orbit relative to the spin axis of its host star---to determine whether a dominant planet migration channel can be identified, and at what confidence. Applying methods of Bayesian model comparison to distinguish between the predictions of several different migration models, we find that the data strongly favor a two-mode migration scenario combining planet-planet scattering and disk migration over a single-mode Kozai migration scenario. While we test only the predictions of particular Kozai and scattering migration models in this work, these methods may be used to test the predictions of any other spin-orbit misaligning mechanism. We then present two studies addressing astrophysical false positives in Kepler data. The Kepler mission has identified thousands of transiting planet candidates, and only relatively few have yet been dynamically confirmed as bona fide planets, with only a handful more even conceivably amenable to future dynamical confirmation. As a result, the ability to draw detailed conclusions about the diversity of exoplanet systems from Kepler detections relies critically on understanding the probability that any individual candidate might be a false positive. We show that a typical a priori false positive probability for a well-vetted Kepler candidate is only about 5-10%, enabling confidence in demographic studies that treat candidates as true planets. We also present a detailed procedure that can be used to securely and efficiently validate any individual transit candidate using detailed information of the

  15. Domestication and human demographic history in South America.

    PubMed

    Perez, S Ivan; Postillone, María Bárbara; Rindel, Diego

    2017-05-01

    The early groups of hunter-gatherers who peopled South America faced significant ecological changes in their trophic niche for a relatively short period after the initial peopling. In particular, the incorporation of cultigens during the Holocene led to a wider trophic niche and probably to an increased carrying capacity of the environment. Here, we study the relationship between the incorporation of domestic resources during the Holocene and the demographic dynamics of human populations at a regional scale in South America. We employ mitochondrial DNA (mtDNA), radiocarbon data and Bayesian methods to estimate differences in population size, human occupation and explore the demographic changes of human populations in three regions (i.e., South-Central Andes, Northwest, and South Patagonia). We also use archaeological evidence to infer the main diet changes in these regions. The absolute population size during the later Late Holocene was fifteen times larger in the South-Central Andes than in Northwest Patagonia, and two times larger in the latter region than in South Patagonia. The South-Central Andes display the earlier and more abrupt population growth, beginning about 9000 years BP, whereas Northwest Patagonia exhibits a more slow growth, beginning about 7000-7500 years BP. South Patagonia represents a later and slower population increase. In this work we uncovered a well-supported pattern of the demographic change in the populations from South-Central Andes and Patagonia, obtained on the basis of different data and quantitative approaches, which suggests that the incorporation of domestic resources was paramount for the demographic expansion of these populations during the Holocene. © 2017 Wiley Periodicals, Inc.

  16. [Population and crisis. Economic inflexibility or demographic subordination].

    PubMed

    Morelos, J B

    1989-01-01

    Much speculation, fact-based and subjective, has centered on the links between population and economic crisis, and between population and progress. In the past, famines directly affected the size and dynamics of population in affected regions, and such cycles inspired theories that regarded subsistence as the adjustment mechanism for demographic regimes. Population has alternatively been viewed as a crucial factor of production and a force for modernization and progress. After World War I and the Great Depression, many economists believed that population growth would be indispensable for renewing economic expansion. The favorable view of population growth in Mexico led to measures to repatriate emigrants, attract immigrants, and improve health conditions. The gross national product grew by around 6.0% annually on average between 1940 and 1960, and the per capita GNP by about 3%. Demographic dynamics acquired momentum by the 1960s, with high growth rates, a young age structure, considerable demographic inertia, and relative predominance of the urban population. Indications began to appear that a primarily economic solution to achieving full development would be unlikely. The polarization of development, distributive insufficiency, distortions in exchange relations for agricultural products, and incorporation of inappropriate technologies were factors decreasing the ability of the economy to respond adequately to population demands. National development was insufficient to meet growing demographic pressures in the labor market, educational system, housing, and urban services. The adjustment programs reduced even further the flexibility of the government to respond to pressures. Expectations for the future have been seriously compromised by the fall of real incomes.

  17. Demographic consequences of climate change and land cover help explain a history of extirpations and range contraction in a declining snake species.

    PubMed

    Pomara, Lars Y; LeDee, Olivia E; Martin, Karl J; Zuckerberg, Benjamin

    2014-07-01

    Developing conservation strategies for threatened species increasingly requires understanding vulnerabilities to climate change, in terms of both demographic sensitivities to climatic and other environmental factors, and exposure to variability in those factors over time and space. We conducted a range-wide, spatially explicit climate change vulnerability assessment for Eastern Massasauga (Sistrurus catenatus), a declining endemic species in a region showing strong environmental change. Using active season and winter adult survival estimates derived from 17 data sets throughout the species' range, we identified demographic sensitivities to winter drought, maximum precipitation during the summer, and the proportion of the surrounding landscape dominated by agricultural and urban land cover. Each of these factors was negatively associated with active season adult survival rates in binomial generalized linear models. We then used these relationships to back-cast adult survival with dynamic climate variables from 1950 to 2008 using spatially explicit demographic models. Demographic models for 189 population locations predicted known extant and extirpated populations well (AUC = 0.75), and models based on climate and land cover variables were superior to models incorporating either of those effects independently. These results suggest that increasing frequencies and severities of extreme events, including drought and flooding, have been important drivers of the long-term spatiotemporal variation in a demographic rate. We provide evidence that this variation reflects nonadaptive sensitivity to climatic stressors, which are contributing to long-term demographic decline and range contraction for a species of high-conservation concern. Range-wide demographic modeling facilitated an understanding of spatial shifts in climatic suitability and exposure, allowing the identification of important climate refugia for a dispersal-limited species. Climate change vulnerability

  18. The demographics of unfunded pensions.

    PubMed

    Keyfitz, N

    1985-01-01

    The performance of pay-as-you-go old-age insurance under different demographic conditions can be estimated from a metric consisting of the implicit rate of return to successive cohorts. The author shows a positive return for the prospective population over the next few years, but for cohorts born after the end of the century returns will become sharply negative. A decline in returns is typical of pay-as-you-go schemes as they mature, and a change to negative returns is typical in particular as the birth rate falls under fixed economic conditions. The return can be kept positive by greatly increased fertility or immigration. Taking labor-force participation rates into account, and supposing entitlement independent of contribution, gives much larger negative rates of return, however. The main calculations considered here are for schemes with a constant pension. If the contribution rather than the pension is kept constant then the disparities between cohorts with respect to their returns are smaller, and although the negative returns for future generations then set in earlier they are smaller. The conclusions of the paper are broadly applicable to any population that showed a baby boom after World War II and replacement-level or lower fertility subsequently.

  19. MtDNA analysis of global populations support that major population expansions began before Neolithic Time

    NASA Astrophysics Data System (ADS)

    Zheng, Hong-Xiang; Yan, Shi; Qin, Zhen-Dong; Jin, Li

    2012-10-01

    Agriculture resulted in extensive population growths and human activities. However, whether major human expansions started after Neolithic Time still remained controversial. With the benefit of 1000 Genome Project, we were able to analyze a total of 910 samples from 11 populations in Africa, Europe and Americas. From these random samples, we identified the expansion lineages and reconstructed the historical demographic variations. In all the three continents, we found that most major lineage expansions (11 out of 15 star lineages in Africa, all autochthonous lineages in Europe and America) coalesced before the first appearance of agriculture. Furthermore, major population expansions were estimated after Last Glacial Maximum but before Neolithic Time, also corresponding to the result of major lineage expansions. Considering results in current and previous study, global mtDNA evidence showed that rising temperature after Last Glacial Maximum offered amiable environments and might be the most important factor for prehistorical human expansions.

  20. Optical imaging. Expansion microscopy.

    PubMed

    Chen, Fei; Tillberg, Paul W; Boyden, Edward S

    2015-01-30

    In optical microscopy, fine structural details are resolved by using refraction to magnify images of a specimen. We discovered that by synthesizing a swellable polymer network within a specimen, it can be physically expanded, resulting in physical magnification. By covalently anchoring specific labels located within the specimen directly to the polymer network, labels spaced closer than the optical diffraction limit can be isotropically separated and optically resolved, a process we call expansion microscopy (ExM). Thus, this process can be used to perform scalable superresolution microscopy with diffraction-limited microscopes. We demonstrate ExM with apparent ~70-nanometer lateral resolution in both cultured cells and brain tissue, performing three-color superresolution imaging of ~10(7) cubic micrometers of the mouse hippocampus with a conventional confocal microscope.

  1. Cryogenic expansion machine

    DOEpatents

    Pallaver, Carl B.; Morgan, Michael W.

    1978-01-01

    A cryogenic expansion engine includes intake and exhaust poppet valves each controlled by a cam having adjustable dwell, the valve seats for the valves being threaded inserts in the valve block. Each cam includes a cam base and a ring-shaped cam insert disposed at an exterior corner of the cam base, the cam base and cam insert being generally circular but including an enlarged cam dwell, the circumferential configuration of the cam base and cam dwell being identical, the cam insert being rotatable with respect to the cam base. GI CONTRACTUAL ORIGIN OF THE INVENTION The invention described herein was made in the course of, or under, a contract with the UNITED STATES ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION.

  2. The Security Dynamics of Demographic Factors

    DTIC Science & Technology

    2000-01-01

    in the public domain. The principal aim of this report is to provide a framework for understanding the influence of demographic factors on...This report presents a framework for understanding the implications of global demographic trends for international and U.S. national Security. One of...its goals is to spark discussion between demographers and national security analysts. The document should be of interest to security analysts

  3. Australian Defence Force Demographic Data and Challenges

    DTIC Science & Technology

    2001-10-01

    AUSTRALIAN DEFENCE FORCE DEMOGRAPHIC DATA AND CHALLENGES Directorate of Strategic Personnel Planning and Research DSPPR Technical Note 10/2001...DATE 00 OCT 2001 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Australian Defence Force Demographic Data and Challenges 5a...Prescribed by ANSI Std Z39-18 AUSTRALIAN DEFENCE FORCE DEMOGRAPHIC DATA AND CHALLENGES The findings and views expressed in this report are the results

  4. The Importance of Demographic Data in Astronomy

    NASA Astrophysics Data System (ADS)

    Elmegreen, Debra M.

    2014-01-01

    The most effective astronomical workforce will be one that comprises a diverse and inclusive community. The “New Worlds, New Horizons in Astronomy and Astrophysics” Decadal Survey, with input from its Infrastructure Study Group on Demographics, provided an overview of recent demographic trends. Demographics in astronomy have undergone significant changes over the past two generations in several, but not all, categories. Maintaining records of demographics regarding age, gender, and minority status, as well as trends by discipline and career choices, is vital in planning for the future training and employment of astronomers.

  5. Demographic disequilibrium caused by canopy gap expansion and recruitment failure triggers forest cover loss

    Treesearch

    Martin Barrette; Louis Bélanger; Louis De Grandpré; Alejandro A. Royo

    2017-01-01

    In the absence of large-scale stand replacing disturbances, boreal forests can remain in the old-growth stage over time because of a dynamic equilibrium between small-scale mortality and regeneration processes. Although this gap paradigm has been a cornerstone of forest dynamics theory and practice for decades, evidence suggests that it could be disrupted, threatening...

  6. Evidence for the Postconquest Demographic Collapse of the Americas in Historical CO2 Levels

    NASA Astrophysics Data System (ADS)

    Mannstein, H.; Faust, F. X.

    2008-12-01

    In this talk we promote the hypothesis that the massive demographic collapse of the native populations of the Americas triggered by the European colonization brought about the abandonment of large expanses of agricultural fields soon recovered by forests, which in due turn fixed atmospheric CO2 in significant quantities. This hypothesis is supported by measurements of atmospheric CO2 levels in ice cores from Law Dome, Antarctica. Changing the focus from paleoclimate to global population dynamics and using the same causal chain, the measured drop in historic atmospheric CO2 levels can also be looked upon as further, strong evidence for the postconquest demographic collapse of the Americas.

  7. Indicator Expansion with Analysis Pipeline

    DTIC Science & Technology

    2015-01-13

    2014 Carnegie Mellon University Indicator Expansion with Analysis Pipeline Dan Ruef 1/13/15 Report Documentation Page Form ApprovedOMB No. 0704...4. TITLE AND SUBTITLE Indicator Expansion with Analysis Pipeline 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...Mellon®, CERT® and FloCon® are registered marks of Carnegie Mellon University. DM-0002067 3 Definition “Indicator expansion is a process of using one or

  8. The Intrinsic Demographics of Blazars

    NASA Astrophysics Data System (ADS)

    Urry, C. Megan; Mao, Peiyuan; Brandt, Timothy D.

    2017-08-01

    Blazar surveys over the past three decades have revealed a range of spectral energy distributions (SEDs), with large systematic differences depending on survey wavelength. This means blazar samples suffer from strong selection effects. To date there has been no agreement on how to infer intrinsic population demographics from these samples, with a key issue being whether blazar jet power is related to the shape of the spectral energy distribution. We investigate this issue using Monte Carlo simulations of BL Lac and flat-spectrum radio quasar populations. We rule out the hypothesis that the SED shape is not linked to luminosity, as the simulated samples in that case disagree strongly with observed surveys. This means that the low-power blazars found primarily in X-ray surveys must be more common than the high-power blazars found primarily in radio surveys. Given an intrinsic correlation between luminosity and SED shape, our simulations predict distributions of flux, redshift, luminosity, and spectral index consistent with existing surveys. We also show that the observed evolution of X-ray-selected blazars, as measured through the average V/Vmax ratio, appears to be negative even when the underlying evolution is actually mildly positive. The apparent negative evolution of X-ray bright BL Lacs is a selection effect caused by redshifting a steeply falling UV-to-X-ray spectrum out of the X-ray band. As this conclusion would suggest, our simulations also show that the deeper the X-ray flux limit and/or the lower the frequency of the synchrotron peak in the SED, the less negative the apparent evolution.

  9. Relativistic Sommerfeld Low Temperature Expansion

    NASA Astrophysics Data System (ADS)

    Lourenço, O.; Dutra, M.; Delfino, A.; Sá Martins, J. S.

    We derive a relativistic Sommerfeld expansion for thermodynamic quantities in many-body fermionic systems. The expansion is used to generate the equation of state of the Walecka model and its isotherms. We find that these results are in good agreement with numerical calculations, even when the expansion is truncated at its lowest order, in the low temperature regime, defined by T/xf ≪ 1. Although the interesting region near the liquid-gas phase transition is excluded by this criterion, the expansion may still find usefulness in the study of very cold nuclear matter systems, such as neutron stars.

  10. Burial Ground Expansion Hydrogeologic Characterization

    SciTech Connect

    Gaughan , T.F.

    1999-02-26

    Sirrine Environmental Consultants provided technical oversight of the installation of eighteen groundwater monitoring wells and six exploratory borings around the location of the Burial Ground Expansion.

  11. Demographic Aspects of the Black Community.

    ERIC Educational Resources Information Center

    Kiser, Clyde V.

    1970-01-01

    This volume contains the Proceedings of the Conference on "Demographic Aspects of the Black Community," held in 1969, and organized by the Milbank Memorial Fund. The Conference was held with the belief that knowledge of demographic characteristics and trends of the black community is essential to better understanding of various problems of the…

  12. Changing School Demographics: The New Baby Boom.

    ERIC Educational Resources Information Center

    Lake, Sara

    This paper addresses the demographic and socioeconomic effects on schools of the "new baby boom," consisting of school-age children of the original "baby boomers." The effects of this second-generation demographic trend include a higher proportion of minority students (since the decline in marriage and birth rates among baby…

  13. The State Economic, Demographic & Fiscal Handbook 1993.

    ERIC Educational Resources Information Center

    Baer, David; Cohen, Lee

    This handbook is an easy-to-use reference book for policymakers, public officials, and policy analysts, as well as anyone else who may need up-to-date information about state economic, demographic, and fiscal data. The book includes data on demographics, poverty rates, per capita state personal income, state and local tax rates, and state and…

  14. Demographics and Education: The 20 Richest Countries

    ERIC Educational Resources Information Center

    Marchant, Gregory J.; Johnson, Jessica J.

    2012-01-01

    This paper explores the PISA [Programme for International Student Assessment] achievement of twenty countries in light of some of their demographic differences. SES [student socioeconomic status], nuclear family, gender, home language, and native status were predictive of achievement for every country. Demographics accounted for as little as 8…

  15. The Unaddressed Costs of Changing Student Demographics

    ERIC Educational Resources Information Center

    Kaplan, Leslie S.; Owings, William A.

    2013-01-01

    This article discusses the impact of changing student demographics on financing education and on our national wellbeing. We begin by examining the research of current student demographics and their relationship to learning and education costs. We then calculate a 1% cost factor from the average per-pupil expenditure based on the 2011 "Digest…

  16. Bias and ignorance in demographic perception.

    PubMed

    Landy, D; Guay, B; Marghetis, T

    2017-08-31

    When it comes to knowledge of demographic facts, misinformation appears to be the norm. Americans massively overestimate the proportions of their fellow citizens who are immigrants, Muslim, LGBTQ, and Latino, but underestimate those who are White or Christian. Previous explanations of these estimation errors have invoked topic-specific mechanisms such as xenophobia or media bias. We reconsidered this pattern of errors in the light of more than 30 years of research on the psychological processes involved in proportion estimation and decision-making under uncertainty. In two publicly available datasets featuring demographic estimates from 14 countries, we found that proportion estimates of national demographics correspond closely to what is found in laboratory studies of quantitative estimates more generally. Biases in demographic estimation, therefore, are part of a very general pattern of human psychology-independent of the particular topic or demographic under consideration-that explains most of the error in estimates of the size of politically salient populations. By situating demographic estimates within a broader understanding of general quantity estimation, these results demand reevaluation of both topic-specific misinformation about demographic facts and topic-specific explanations of demographic ignorance, such as media bias and xenophobia.

  17. The Unaddressed Costs of Changing Student Demographics

    ERIC Educational Resources Information Center

    Kaplan, Leslie S.; Owings, William A.

    2013-01-01

    This article discusses the impact of changing student demographics on financing education and on our national wellbeing. We begin by examining the research of current student demographics and their relationship to learning and education costs. We then calculate a 1% cost factor from the average per-pupil expenditure based on the 2011 "Digest…

  18. Lifelong Learning and Demographics: A Japanese Perspective

    ERIC Educational Resources Information Center

    Ogawa, Seiko

    2005-01-01

    This paper explores the social dimension of lifelong learning from the perspective of demographics, with particular focus on the issue of the birth of fewer children, which has become one of the most important current social issues in Japanese society. When considering the relationship between lifelong learning and demographics, the issues arising…

  19. Lifelong Learning and Demographics: A Japanese Perspective

    ERIC Educational Resources Information Center

    Ogawa, Seiko

    2005-01-01

    This paper explores the social dimension of lifelong learning from the perspective of demographics, with particular focus on the issue of the birth of fewer children, which has become one of the most important current social issues in Japanese society. When considering the relationship between lifelong learning and demographics, the issues arising…

  20. [The Brazilian population: demographic and spatial dynamics].

    PubMed

    Bret, B; Le Gauffey, Y; Thery, H; Waniez, P

    1984-01-01

    Recent demographic trends in Brazil are reviewed. A continuing decline in fertility is noted as the demographic transition proceeds. The differences by region and between rural and urban areas are considered. Attention is also paid to differences in spatial distribution and to internal migration.

  1. Singularity Expansion Method

    NASA Astrophysics Data System (ADS)

    Riggs, Lloyd Stephen

    In this work the transient currents induced on an arbitrary system of thin linear scatterers by an electromagnetic plane wave are solved by using an electric field integral equation (EFIE) formulation. The transient analysis is carried out using the singularity expansion method (SEM). The general analysis developed here is useful for assessing the vulnerability of military aircraft to a nuclear generated electromagnetic pulse (EMP). It is also useful as a modal synthesis tool in the analysis and design of frequency selective surfaces (FSS). SEM parameters for a variety of thin cylindrical geometries have been computed. Specifically, SEM poles, modes, coupling coefficients, and transient currents are given for the two and three element planar array. Poles and modes for planar arrays with a larger number (as many as eight) of identical equally spaced elements are also considered. SEM pole-mode results are given for identical parallel elements with ends located at the vertices of a regular N-agon. Pole-mode patterns are found for symmetric (and slightly perturbed) single junction N-arm elements and for the five junction Jerusalem cross. The Jerusalem cross element has been used extensively in FSS.

  2. Expansive Northern Volcanic Plains

    NASA Image and Video Library

    2015-04-16

    Mercury northern region is dominated by expansive smooth plains, created by huge amounts of volcanic material flooding across Mercury surface in the past, as seen by NASA MESSENGER spacecraft. The volcanic lava flows buried craters, leaving only traces of their rims visible. Such craters are called ghost craters, and there are many visible in this image, including a large one near the center. Wrinkle ridges cross this scene and small troughs are visible regionally within ghost craters, formed as a result of the lava cooling. The northern plains are often described as smooth since their surface has fewer impact craters and thus has been less battered by such events. This indicates that these volcanic plains are younger than Mercury's rougher surfaces. Instrument: Mercury Dual Imaging System (MDIS) Center Latitude: 60.31° N Center Longitude: 36.87° E Scale: The large ghost crater at the center of the image is approximately 103 kilometers (64 miles) in diameter http://photojournal.jpl.nasa.gov/catalog/PIA19415

  3. Lattice harmonics expansion revisited

    NASA Astrophysics Data System (ADS)

    Kontrym-Sznajd, G.; Holas, A.

    2017-04-01

    The main subject of the work is to provide the most effective way of determining the expansion of some quantities into orthogonal polynomials, when these quantities are known only along some limited number of sampling directions. By comparing the commonly used Houston method with the method based on the orthogonality relation, some relationships, which define the applicability and correctness of these methods, are demonstrated. They are verified for various sets of sampling directions applicable for expanding quantities having the full symmetry of the Brillouin zone of cubic and non-cubic lattices. All results clearly show that the Houston method is always better than the orthogonality-relation one. For the cubic symmetry we present a few sets of special directions (SDs) showing how their construction and, next, a proper application depend on the choice of various sets of lattice harmonics. SDs are important mainly for experimentalists who want to reconstruct anisotropic quantities from their measurements, performed at a limited number of sampling directions.

  4. Local Adaptation Interacts with Expansion Load during Range Expansion: Maladaptation Reduces Expansion Load.

    PubMed

    Gilbert, Kimberly J; Sharp, Nathaniel P; Angert, Amy L; Conte, Gina L; Draghi, Jeremy A; Guillaume, Frédéric; Hargreaves, Anna L; Matthey-Doret, Remi; Whitlock, Michael C

    2017-04-01

    The biotic and abiotic factors that facilitate or hinder species range expansions are many and complex. We examine the impact of two genetic processes and their interaction on fitness at expanding range edges: local maladaptation resulting from the presence of an environmental gradient and expansion load resulting from increased genetic drift at the range edge. Results from spatially explicit simulations indicate that the presence of an environmental gradient during range expansion reduces expansion load; conversely, increasing expansion load allows only locally adapted populations to persist at the range edge. Increased maladaptation reduces the speed of range expansion, resulting in less genetic drift at the expanding front and more immigration from the range center, therefore reducing expansion load at the range edge. These results may have ramifications for species being forced to shift their ranges because of climate change or other anthropogenic changes. If rapidly changing climate leads to faster expansion as populations track their shifting climatic optima, populations may suffer increased expansion load beyond previous expectations.

  5. A Demographic Perspective on Family Change

    PubMed Central

    Bianchi, Suzanne M.

    2014-01-01

    Demographic analysis seeks to understand how individual microlevel decisions about child-bearing, marriage and partnering, geographic mobility, and behaviors that influence health and longevity aggregate to macrolevel population trends and differentials in fertility, mortality and migration. In this review, I first discuss theoretical perspectives—classic demographic transition theory, the perspective of the “second demographic transition,” the spread of developmental idealism—that inform demographers’ understanding of macrolevel population change. Then, I turn to a discussion of the role that demographically informed data collection has played in illuminating family change since the mid-20th century in the United States. Finally, I discuss ways in which demographic theory and data collection might inform future areas of family research, particularly in the area of intergenerational family relationships and new and emerging family forms. PMID:26078785

  6. [Contemplations on demographic theories (author's transl)].

    PubMed

    Maier, W

    1979-03-01

    All demographic theories make statements on the relationship between population developments and economic developments. The demographic teachings of Adam Smith, Thomas Robert Malthus, and Karl Marx are embedded in their specific economic theories and contain ideologic statements which are not detrimental to demographic and economic sciences but a stimulus for research. The demographic theories which developed with the onset of the industrial revolution of the 19th century are all sceptical of too high populations independent of their analysis of the market mechanisms or of capitalistic production relationships. This has remained unchanged to date. The statistical evaluation of the 1980's underlines this problem. The reproductive behaviour and demographic theory of a highly industrialized economy can not be based on experience alone but must also be based on rational findings. The rejection of the prestige value of children on the reproductive behaviour which is independent of circumstances must be recognized.

  7. Demographic training and research in Africa.

    PubMed

    Igun, A A

    1976-09-01

    The state of demographic data in Africa is reviewed in this paper along with constraints affecting the collection of adequate demographic information. An evaluation is made of the present situation and efforts to rectify the shortage of demographic personnel in the UN sponsored subregional demographic institutes, including an outline of the course program. The effort and progress being made in similar training programs at the University of Ife, Nigeria, is also examined. Obstacles to the collection of demographic data are classified as physical difficulties; administrative and official problems and difficulties; technical and staff problems; and sociocultural problems. A consensus has been reached on the inadequacy of past efforts in data collection and analysis in Africa. Special attention must be paid to the training of demographers. A comparison is made between demographers in developed countries who have their data collected for them and the African demographer who must be his own statistician, sociologist, anthropologist, and geographer to understand the biases his data are subject to. Training for African demographers should emphasize problems in data collection, data manipulation, and innovation in solving methodological problems. Type of personnel needed include teachers of demography, high level professionals, middle level professionals and low level workers. The training programs given by the Regional Institutes for Population Studies are a postgraduate diploma course, lasting 1 year and a Master's degree course for those who obtain the diploma. Subjects covered include substantive demography; technical demography; family planning, its development and evaluation; auxiliary subjects including mathematics, statistics, sampling and research methods; and complementary subjects e.g., economics, sociology, national planning, physiology of reproduction, and genetics. Short term research projects and a major research report are an integral part of the programs

  8. Isotropic Negative Thermal Expansion Metamaterials.

    PubMed

    Wu, Lingling; Li, Bo; Zhou, Ji

    2016-07-13

    Negative thermal expansion materials are important and desirable in science and engineering applications. However, natural materials with isotropic negative thermal expansion are rare and usually unsatisfied in performance. Here, we propose a novel method to achieve two- and three-dimensional negative thermal expansion metamaterials via antichiral structures. The two-dimensional metamaterial is constructed with unit cells that combine bimaterial strips and antichiral structures, while the three-dimensional metamaterial is fabricated by a multimaterial 3D printing process. Both experimental and simulation results display isotropic negative thermal expansion property of the samples. The effective coefficient of negative thermal expansion of the proposed models is demonstrated to be dependent on the difference between the thermal expansion coefficient of the component materials, as well as on the circular node radius and the ligament length in the antichiral structures. The measured value of the linear negative thermal expansion coefficient of the three-dimensional sample is among the largest achieved in experiments to date. Our findings provide an easy and practical approach to obtaining materials with tunable negative thermal expansion on any scale.

  9. Medicaid Participation among Liver Transplant Candidates after the Affordable Care Act Medicaid Expansion.

    PubMed

    Tumin, Dmitry; Beal, Eliza W; Mumtaz, Khalid; Hayes, Don; Tobias, Joseph D; Pawlik, Timothy M; Washburn, W Kenneth; Black, Sylvester M

    2017-08-01

    The 2014 Medicaid expansion in participating states increased insurance coverage among people with chronic health conditions, but its implications for access to surgical care remain unclear. We investigated how Medicaid expansion influenced the insurance status of candidates for liver transplantation (LT) and transplant center payor mix. Data on LT candidates aged 18 to 64 years, in 2012 to 2013 (pre-expansion) and 2014 to 2015 (post-expansion), were obtained from the United Network for Organ Sharing registry. Change between the 2 periods in the percent of LT candidates using Medicaid was compared between expansion and nonexpansion states. Multivariable logistic regression was used to determine how Medicaid expansion influenced individual LT candidates' likelihood of using Medicaid insurance. The study included 33,017 LT candidates, of whom 29,666 had complete data for multivariable analysis. Medicaid enrollment increased by 4% after Medicaid expansion in participating states. One-quarter of the transplant centers in these states experienced ≥10% increase in the proportion of LT candidates using Medicaid insurance. Multivariable analysis confirmed that Medicaid expansion was associated with increased odds of LT candidates using Medicaid insurance (odds ratio 1.49; 95% CI 1.34, 1.66; p < 0.001). However, the absolute number and demographic characteristics of patients listed for LT did not change in Medicaid expansion states during the post-expansion period. Candidates for LT became more likely to use Medicaid after the 2014 Medicaid expansion policy came into effect. Enactment of this policy did not appear to increase access to LT or address socioeconomic and demographic disparities in access to the LT wait list. Copyright © 2017 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

  10. On the Bantu expansion.

    PubMed

    Rowold, Daine J; Perez-Benedico, David; Stojkovic, Oliver; Garcia-Bertrand, Ralph; Herrera, Rene J

    2016-11-15

    Here we report the results of fine resolution Y chromosomal analyses (Y-SNP and Y-STR) of 267 Bantu-speaking males from three populations located in the southeast region of Africa. In an effort to determine the relative Y chromosomal affinities of these three genotyped populations, the findings are interpreted in the context of 74 geographically and ethnically targeted African reference populations representing four major ethno-linguistic groups (Afro-Asiatic, Niger Kordofanin, Khoisan and Pygmoid). In this investigation, we detected a general similarity in the Y chromosome lineages among the geographically dispersed Bantu-speaking populations suggesting a shared heritage and the shallow time depth of the Bantu Expansion. Also, micro-variations in the Bantu Y chromosomal composition across the continent highlight location-specific gene flow patterns with non-Bantu-speaking populations (Khoisan, Pygmy, Afro-Asiatic). Our Y chromosomal results also indicate that the three Bantu-speaking Southeast populations genotyped exhibit unique gene flow patterns involving Eurasian populations but fail to reveal a prevailing genetic affinity to East or Central African Bantu-speaking groups. In addition, the Y-SNP data underscores a longitudinal partitioning in sub-Sahara Africa of two R1b1 subgroups, R1b1-P25* (west) and R1b1a2-M269 (east). No evidence was observed linking the B2a haplogroup detected in the genotyped Southeast African Bantu-speaking populations to gene flow from contemporary Khoisan groups. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Modeling neolithic dispersal in central Europe: demographic implications.

    PubMed

    Galeta, Patrik; Sládek, Vladimír; Sosna, Daniel; Bruzek, Jaroslav

    2011-09-01

    On the basis of new examination of ancient DNA and craniometric analyses, Neolithic dispersal in Central Europe has been recently explained as reflecting colonization or at least a major influx of near eastern farmers. Given the fact that Neolithic dispersal in Central Europe was very rapid and extended into a large area, colonization would have to be associated with high population growth and fertility rates of an expanding Neolithic population. We built three demographic models to test whether the growth and fertility rates of Neolithic farmers were high enough to allow them to colonize Central Europe without admixture with foragers. The principle of the models is based on stochastic population projections. Our results demonstrate that colonization is an unlikely explanation for the Neolithic dispersal in Central Europe, as the majority of fertility and growth rate estimates obtained in all three models are higher than levels expected in the early Neolithic population. On the basis of our models, we derived that colonization would be possible only if (1) more than 37% of women survived to mean age at childbearing, (2) Neolithic expansion in Central Europe lasted more than 150 years, and (3) the population of farmers grew in the entire settled area. These settings, however, represent very favorable demographic conditions that seem unlikely given current archaeological and demographic evidence. Therefore, our results support the view that Neolithic dispersal in Central Europe involved admixture of expanding farmers with local foragers. We estimate that the admixture contribution from foragers may have been between 55% and 72%. 2011 Wiley-Liss, Inc.

  12. Better living through conifer removal: A demographic analysis of sage-grouse vital rates

    PubMed Central

    Hagen, Christian A.; Tack, Jason D.; Maestas, Jeremy D.; Naugle, David E.; Forbes, James T.; Reese, Kerry P.

    2017-01-01

    Sagebrush (Artemisia spp.) obligate wildlife species such as the imperiled greater sage-grouse (Centrocercus urophasianus) face numerous threats including altered ecosystem processes that have led to conifer expansion into shrub-steppe. Conifer removal is accelerating despite a lack of empirical evidence on grouse population response. Using a before-after-control-impact design at the landscape scale, we evaluated effects of conifer removal on two important demographic parameters, annual survival of females and nest survival, by monitoring 219 female sage-grouse and 225 nests in the northern Great Basin from 2010 to 2014. Estimates from the best treatment models showed positive trends in the treatment area relative to the control area resulting in an increase of 6.6% annual female survival and 18.8% nest survival relative to the control area by 2014. Using stochastic simulations of our estimates and published demographics, we estimated a 25% increase in the population growth rate in the treatment area relative to the control area. This is the first study to link sage-grouse demographics with conifer removal and supports recommendations to actively manage conifer expansion for sage-grouse conservation. Sage-grouse have become a primary catalyst for conservation funding to address conifer expansion in the West, and these findings have important implications for other ecosystem services being generated on the wings of species conservation. PMID:28333995

  13. Better living through conifer removal: A demographic analysis of sage-grouse vital rates.

    PubMed

    Severson, John P; Hagen, Christian A; Tack, Jason D; Maestas, Jeremy D; Naugle, David E; Forbes, James T; Reese, Kerry P

    2017-01-01

    Sagebrush (Artemisia spp.) obligate wildlife species such as the imperiled greater sage-grouse (Centrocercus urophasianus) face numerous threats including altered ecosystem processes that have led to conifer expansion into shrub-steppe. Conifer removal is accelerating despite a lack of empirical evidence on grouse population response. Using a before-after-control-impact design at the landscape scale, we evaluated effects of conifer removal on two important demographic parameters, annual survival of females and nest survival, by monitoring 219 female sage-grouse and 225 nests in the northern Great Basin from 2010 to 2014. Estimates from the best treatment models showed positive trends in the treatment area relative to the control area resulting in an increase of 6.6% annual female survival and 18.8% nest survival relative to the control area by 2014. Using stochastic simulations of our estimates and published demographics, we estimated a 25% increase in the population growth rate in the treatment area relative to the control area. This is the first study to link sage-grouse demographics with conifer removal and supports recommendations to actively manage conifer expansion for sage-grouse conservation. Sage-grouse have become a primary catalyst for conservation funding to address conifer expansion in the West, and these findings have important implications for other ecosystem services being generated on the wings of species conservation.

  14. Atom cooling by nonadiabatic expansion

    SciTech Connect

    Chen Xi; Muga, J. G.; Campo, A. del; Ruschhaupt, A.

    2009-12-15

    Motivated by the recent discovery that a reflecting wall moving with a square-root-in-time trajectory behaves as a universal stopper of classical particles regardless of their initial velocities, we compare linear-in-time and square-root-in-time expansions of a box to achieve efficient atom cooling. For the quantum single-atom wave functions studied the square-root-in-time expansion presents important advantages: asymptotically it leads to zero average energy whereas any linear-in-time (constant box-wall velocity) expansion leaves a nonzero residual energy, except in the limit of an infinitely slow expansion. For finite final times and box lengths we set a number of bounds and cooling principles which again confirm the superior performance of the square-root-in-time expansion, even more clearly for increasing excitation of the initial state. Breakdown of adiabaticity is generally fatal for cooling with the linear expansion but not so with the square-root-in-time expansion.

  15. Thermal Expansion of Polyurethane Foam

    NASA Technical Reports Server (NTRS)

    Lerch, Bradley A.; Sullivan, Roy M.

    2006-01-01

    Closed cell foams are often used for thermal insulation. In the case of the Space Shuttle, the External Tank uses several thermal protection systems to maintain the temperature of the cryogenic fuels. A few of these systems are polyurethane, closed cell foams. In an attempt to better understand the foam behavior on the tank, we are in the process of developing and improving thermal-mechanical models for the foams. These models will start at the microstructural level and progress to the overall structural behavior of the foams on the tank. One of the key properties for model characterization and verification is thermal expansion. Since the foam is not a material, but a structure, the modeling of the expansion is complex. It is also exacerbated by the anisoptropy of the material. During the spraying and foaming process, the cells become elongated in the rise direction and this imparts different properties in the rise direction than in the transverse directions. Our approach is to treat the foam as a two part structure consisting of the polymeric cell structure and the gas inside the cells. The polymeric skeleton has a thermal expansion of its own which is derived from the basic polymer chemistry. However, a major contributor to the thermal expansion is the volume change associated with the gas inside of the closed cells. As this gas expands it exerts pressure on the cell walls and changes the shape and size of the cells. The amount that this occurs depends on the elastic and viscoplastic properties of the polymer skeleton. The more compliant the polymeric skeleton, the more influence the gas pressure has on the expansion. An additional influence on the expansion process is that the polymeric skeleton begins to breakdown at elevated temperatures and releases additional gas species into the cell interiors, adding to the gas pressure. The fact that this is such a complex process makes thermal expansion ideal for testing the models. This report focuses on the thermal

  16. Micromechanics of expansive mechanisms in expansive cement concretes

    NASA Astrophysics Data System (ADS)

    Cohen, M. D.

    The kinetics of hydration were studied by monitoring the presence of various compounds by X-ray diffractometer, a chemical extraction method, and scanning electron microscope. These studies indicated that the rates of depletion of the expanding particles and sulfates are higher in the finer blends, which is why expansion stops earlier in these blends. It is shown that the double curvature phenomenon (strength-drop and sudden increase in the rate of expansion) is caused by mechanical failure (e.g., microcracking) of the matrix surrounding the expanding particles that are producing ettringite crystals. The theory of protective and partial protective coating is reviewed. A hypothesis is introduced which assumes that monosulfate is not formed immediately when ettringite stops forming but is preceded by an intermediate phase. Shrinkage studies show that expansive cements shrink more than portland cements. The results of these studies were used to develop a modified model of the expansive process. It was shown theoretically that the time of expansion is inversely proportional to the surface area of the expansive clinker and directly proportional to the amount of sulfate used.

  17. The Expansion of Adult Education and Training in Europe: Trends and Issues.

    ERIC Educational Resources Information Center

    Tuijnman, Albert C.

    1992-01-01

    Describes factors contributing to 1980s expansion of adult vocational education (AE) and training in Europe, reviewing demographic, economic, political, and social factors. Discusses ramifications of emerging decentralization in educational decision making. Examines potential conflict between emphasis on economic and labor market objectives of AE…

  18. Unemployment among Black Youths, Demographics, and Crime.

    ERIC Educational Resources Information Center

    Calvin, Allen D.

    1981-01-01

    Erroneous conclusions relating to the interrelationship among unemployment rates, demographics, and crime rates of Black youths are discussed. A reexamination of the data shows that crime by Black youths bears a close relationship with prevailing economic conditions. (Author/RC)

  19. The demographic work of Sir William Wilde.

    PubMed

    Froggatt, P

    2016-05-01

    This paper argues that Sir William Wilde was indeed a pioneering demographer. It also describes the unveiling of the plaque commemorating Sir William Wilde at his home, 1, Merrion Square, Dublin on the 28 October 1971.

  20. Unemployment among Black Youths, Demographics, and Crime.

    ERIC Educational Resources Information Center

    Calvin, Allen D.

    1981-01-01

    Erroneous conclusions relating to the interrelationship among unemployment rates, demographics, and crime rates of Black youths are discussed. A reexamination of the data shows that crime by Black youths bears a close relationship with prevailing economic conditions. (Author/RC)

  1. Demographic mechanisms underpinning genetic assimilation of remnant groups of a large carnivore.

    PubMed

    Mikle, Nate; Graves, Tabitha A; Kovach, Ryan; Kendall, Katherine C; Macleod, Amy C

    2016-09-28

    Current range expansions of large terrestrial carnivores are occurring following human-induced range contraction. Contractions are often incomplete, leaving small remnant groups in refugia throughout the former range. Little is known about the underlying ecological and evolutionary processes that influence how remnant groups are affected during range expansion. We used data from a spatially explicit, long-term genetic sampling effort of grizzly bears (Ursus arctos) in the Northern Continental Divide Ecosystem (NCDE), USA, to identify the demographic processes underlying spatial and temporal patterns of genetic diversity. We conducted parentage analysis to evaluate how reproductive success and dispersal contribute to spatio-temporal patterns of genetic diversity in remnant groups of grizzly bears existing in the southwestern (SW), southeastern (SE) and east-central (EC) regions of the NCDE. A few reproductively dominant individuals and local inbreeding caused low genetic diversity in peripheral regions that may have persisted for multiple generations before eroding rapidly (approx. one generation) during population expansion. Our results highlight that individual-level genetic and reproductive dynamics play critical roles during genetic assimilation, and show that spatial patterns of genetic diversity on the leading edge of an expansion may result from historical demographic patterns that are highly ephemeral.

  2. Demographic mechanisms underpinning genetic assimilation of remnant groups of a large carnivore

    USGS Publications Warehouse

    Mikle, Nathaniel; Graves, Tabitha A.; Kovach, Ryan P.; Kendall, Katherine C.; Macleod, Amy C.

    2016-01-01

    Current range expansions of large terrestrial carnivores are occurring following human-induced range contraction. Contractions are often incomplete, leaving small remnant groups in refugia throughout the former range. Little is known about the underlying ecological and evolutionary processes that influence how remnant groups are affected during range expansion. We used data from a spatially explicit, long-term genetic sampling effort of grizzly bears (Ursus arctos) in the Northern Continental Divide Ecosystem (NCDE), USA, to identify the demographic processes underlying spatial and temporal patterns of genetic diversity. We conducted parentage analysis to evaluate how reproductive success and dispersal contribute to spatio-temporal patterns of genetic diversity in remnant groups of grizzly bears existing in the southwestern (SW), southeastern (SE) and east-central (EC) regions of the NCDE. A few reproductively dominant individuals and local inbreeding caused low genetic diversity in peripheral regions that may have persisted for multiple generations before eroding rapidly (approx. one generation) during population expansion. Our results highlight that individual-level genetic and reproductive dynamics play critical roles during genetic assimilation, and show that spatial patterns of genetic diversity on the leading edge of an expansion may result from historical demographic patterns that are highly ephemeral.

  3. Estimates of expansion time scales

    NASA Astrophysics Data System (ADS)

    Jones, E. M.

    Monte Carlo simulations of the expansion of a spacefaring civilization show that descendants of that civilization should be found near virtually every useful star in the Galaxy in a time much less than the current age of the Galaxy. Only extreme assumptions about local population growth rates, emigration rates, or ship ranges can slow or halt an expansion. The apparent absence of extraterrestrials from the solar system suggests that no such civilization has arisen in the Galaxy.

  4. Multiplexing Prisms for Field Expansion.

    PubMed

    Peli, Eli; Jung, Jae-Hyun

    2017-08-01

    Prisms used for field expansion are limited by the optical scotoma at a prism apex (apical scotoma). For a patient with two functioning eyes, fitting prisms unilaterally allows the other eye to compensate for the apical scotoma. A monocular patient's field loss cannot be expanded with a conventional or Fresnel prism because of the apical scotoma. A newly invented optical device, the multiplexing prism (MxP), was developed to overcome the apical scotoma limitation in monocular field expansion. A Fresnel-prism-like device with alternating prism and flat elements superimposes shifted and see-through views, thus creating the (monocular) visual confusion required for field expansion and eliminating the apical scotoma. Several implementations are demonstrated and preliminarily evaluated for different monocular conditions with visual field loss. The field expansion of the MxP is compared with the effect of conventional prisms using calculated and measured perimetry. Field expansion without apical scotomas is shown to be effective for monocular patients with hemianopia or constricted peripheral field. The MxPs are shown to increase the nasal field for a patient with only one eye and for patients with bitemporal hemianopia. The MxPs placed at the far temporal field are shown to expand the normal visual field. The ability to control the contrast ratio between the two images is verified. A novel optical device is demonstrated to have the potential for field expansion technology in a variety of conditions. The devices may be inexpensive and can be constructed in a cosmetically acceptable format.

  5. Medicaid Expansion and ACA Repeal: Evidence From Ohio.

    PubMed

    Seiber, Eric E; Berman, Micah L

    2017-06-01

    To examine the health insurance coverage options for Medicaid expansion enrollees if the Affordable Care Act (ACA) is repealed, using evidence from Ohio, where more than half a million adults have enrolled in the state's Medicaid program through the ACA expansion. The Ohio Medicaid Assessment Survey interviewed 42 000 households in 2015. We report data from a unique battery of questions designed to identify insurance coverage immediately prior to Medicaid enrollment. Ninety-five percent of new Medicaid enrollees in Ohio did not have a private health insurance option immediately before enrollment. These new enrollees are predominantly older, low-income Whites with a high school education or less. Only 5% of new Medicaid enrollees were eligible for an employer-sponsored insurance plan to which they could potentially return in the case of repeal of the ACA. The vast majority of Medicaid expansion enrollees would have no plausible pathway to obtaining private-sector insurance if the ACA were repealed. Demographic similarities between the expansion population and 2016 exit polls suggest that coverage losses would fall disproportionately on members of the winning Republican coalition.

  6. Rock expansion caused by ultrasound

    NASA Astrophysics Data System (ADS)

    Hedberg, C.; Gray, A.

    2013-12-01

    It has during many years been reported that materials' elastic modulus decrease when exposed to influences like mechanical impacts, ultrasound, magnetic fields, electricity and even humidity. Non-perfect atomic structures like rocks, concrete, or damaged metals exhibit a larger effect. This softening has most often been recorded by wave resonance measurements. The motion towards equilibrium is slow - often taking hours or days, which is why the effect is called Slow Dynamics [1]. The question had been raised, if a material expansion also occurs. 'The most fundamental parameter to consider is the volume expansion predicted to occur when positive hole charge carriers become activated, causing a decrease of the electron density in the O2- sublattice of the rock-forming minerals. This decrease of electron density should affect essentially all physical parameters, including the volume.' [2]. A new type of configuration has measured expansion of a rock subjected to ultrasound. A PZT was used as a pressure sensor while the combined thickness of the rock sample and the PZT sensor was held fixed. The expansion increased the stress in both the rock and the PZT, which gave an out-put voltage from the PZT. Knowing its material properties then made it possible to calculate the rock expansion. The equivalent strain caused by the ultrasound was approximately 3 x 10-5. The temperature was monitored and accounted for during the tests and for the maximum expansion the increase was 0.7 C, which means the expansion is at least to some degree caused by heating of the material by the ultrasound. The fraction of bonds activated by ultrasound was estimated to be around 10-5. References: [1] Guyer, R.A., Johnson, P.A.: Nonlinear Mesoscopic Elasticity: The Complex Behaviour of Rocks, Soils, Concrete. Wiley-VCH 2009 [2] M.M. Freund, F.F. Freund, Manipulating the Toughness of Rocks through Electric Potentials, Final Report CIF 2011 Award NNX11AJ84A, NAS Ames 2012.

  7. Asymptotic Expansions, 1/Z Expansions, and the Critical Nuclear Charge

    NASA Astrophysics Data System (ADS)

    Drake, Gordon

    2014-03-01

    The quantum mechanical three-body problem defies analytic solution, and so computationally intensive approximation methods involving, for example, variational calculations with large correlated basis sets must be used. This talk will review recent work to explore the outer fringes of the quantum mechanical three-body problem for heliumlike atoms. Asymptotic expansions provide a surprisingly simple and accurate account of highly excited Rydberg states with high angular momentum. 1 / Z expansions, where Z is the nuclear charge, provide results for an entire isoelectronic sequence within a single calculation. Its radius of convergence is thought to be related to the critical nuclear charge Zc for a state to be bound. For Z expansions and the critical nuclear charge. Research suppoted by the Natural Sciences and Engineering Research Council of Canada, and by SHARCNET.

  8. Reconstructing the demographic history of orang-utans using Approximate Bayesian Computation.

    PubMed

    Nater, Alexander; Greminger, Maja P; Arora, Natasha; van Schaik, Carel P; Goossens, Benoit; Singleton, Ian; Verschoor, Ernst J; Warren, Kristin S; Krützen, Michael

    2015-01-01

    Investigating how different evolutionary forces have shaped patterns of DNA variation within and among species requires detailed knowledge of their demographic history. Orang-utans, whose distribution is currently restricted to the South-East Asian islands of Borneo (Pongo pygmaeus) and Sumatra (Pongo abelii), have likely experienced a complex demographic history, influenced by recurrent changes in climate and sea levels, volcanic activities and anthropogenic pressures. Using the most extensive sample set of wild orang-utans to date, we employed an Approximate Bayesian Computation (ABC) approach to test the fit of 12 different demographic scenarios to the observed patterns of variation in autosomal, X-chromosomal, mitochondrial and Y-chromosomal markers. In the best-fitting model, Sumatran orang-utans exhibit a deep split of populations north and south of Lake Toba, probably caused by multiple eruptions of the Toba volcano. In addition, we found signals for a strong decline in all Sumatran populations ~24 ka, probably associated with hunting by human colonizers. In contrast, Bornean orang-utans experienced a severe bottleneck ~135 ka, followed by a population expansion and substructuring starting ~82 ka, which we link to an expansion from a glacial refugium. We showed that orang-utans went through drastic changes in population size and connectedness, caused by recurrent contraction and expansion of rainforest habitat during Pleistocene glaciations and probably hunting by early humans. Our findings emphasize the fact that important aspects of the evolutionary past of species with complex demographic histories might remain obscured when applying overly simplified models.

  9. [Thoughts on demographic optimization in contemporary Poland].

    PubMed

    Oledzki, M

    1980-01-01

    This article presents the viewpoint of the Polish school of social policy of the Institute of Social Economy concerning the problem of optimization of demographic structures and processes in contemporary Poland. This school was created under the leadership of the outstanding sociologist Ludwik Krzywicki (1859-1941). The reasoning concerns, first of all, the scientific premises of the choice of criteria of demographic optimization examined and then there is a critical assessment of modern simplified approaches to the definition of optimum population. It also shows actual possibilities of demographic optimization and the complexity of analytical categories of socioeconomic processes which determine the development of the population in specific time and space. In conclusion, the theory of demographic optimization is regarded as a task too ambitious and perhaps even utopian in view of the assumptions needed for its satisfactory realization. This conclusion confirms the thesis contained in the handbook of demography by J.Z. Holzer published in 1970. The author considers, however, that the search for a theory of demographic optimization is still a task which mobilizes social sciences to an integration centered on demography and social policy. (author's)

  10. Identifying image preferences based on demographic attributes

    NASA Astrophysics Data System (ADS)

    Fedorovskaya, Elena A.; Lawrence, Daniel R.

    2014-02-01

    The intent of this study is to determine what sorts of images are considered more interesting by which demographic groups. Specifically, we attempt to identify images whose interestingness ratings are influenced by the demographic attribute of the viewer's gender. To that end, we use the data from an experiment where 18 participants (9 women and 9 men) rated several hundred images based on "visual interest" or preferences in viewing images. The images were selected to represent the consumer "photo-space" - typical categories of subject matter found in consumer photo collections. They were annotated using perceptual and semantic descriptors. In analyzing the image interestingness ratings, we apply a multivariate procedure known as forced classification, a feature of dual scaling, a discrete analogue of principal components analysis (similar to correspondence analysis). This particular analysis of ratings (i.e., ordered-choice or Likert) data enables the investigator to emphasize the effect of a specific item or collection of items. We focus on the influence of the demographic item of gender on the analysis, so that the solutions are essentially confined to subspaces spanned by the emphasized item. Using this technique, we can know definitively which images' ratings have been influenced by the demographic item of choice. Subsequently, images can be evaluated and linked, on one hand, to their perceptual and semantic descriptors, and, on the other hand, to the preferences associated with viewers' demographic attributes.

  11. Beyond the Castro: the role of demographics in the selection of gay and lesbian enclaves.

    PubMed

    Compton, D'Lane R; Baumle, Amanda K

    2012-01-01

    Although some qualitative research has noted differences in gay and lesbian enclaves based on characteristics such as race and sex, in this article, we draw upon quantitative data from the U.S. Census to demonstrate the manner in which enclave formation is affected by the interaction of sexual orientation and other demographic characteristics (such as sex, race, age, and income). We focus our attention on enclaves located in three counties in the San Francisco Bay Area: San Francisco County, Alameda County, and Sonoma County as one example. Even though these spaces fall within close proximity to one another and share similar geographic appeal, our analyses indicate that these enclaves are far from homogenous in terms of the demographic composition of their inhabitants. These quantitative analyses provide further support to past qualitative findings, as well as highlight additional distinctions in the manner in which demographics affect enclave selection. We supplement our demographic analyses with supporting field research and interviews, further highlighting both the variation and the commonalities of these enclaves. Overall, our findings promote an expansion of the understanding how intersecting demographic characteristics affect selection of a particular enclave and what may constitute a gay enclave.

  12. The demographic determinants of human microbiome health

    PubMed Central

    Estrela, Sylvie; Whiteley, Marvin; Brown, Sam P.

    2014-01-01

    The human microbiome is a vast reservoir of microbial diversity and increasingly recognized to play a fundamental role in human health. In polymicrobial communities, the presence of one species can modulate the demography (growth and distribution) of other species. These demographic impacts generate feedbacks in multi-species interactions, which can be magnified in spatially structured populations (e.g., host-associated communities). Here we argue that demographic feedbacks between species are central to microbiome development, shaping whether and how potential metabolic interactions come to be realized between expanding lineages of bacteria. Understanding how demographic feedbacks tune metabolic interactions and in turn shape microbiome structure and function is now a key challenge to our abilities to better manage microbiome health. PMID:25500524

  13. Demographic and affective covariates of pain.

    PubMed

    Garron, D C; Leavitt, F

    1979-11-01

    Relationships of four demographic variables and five affective variables to eight attributes of low back pain were investigated in 251 patients by stepwise, multivariate analysis. The demographic variables are age, sex, race, and education. The affective variables are state anxiety, trait anxiety anxiety, hostility, and depression. Seven of the pain variables are from the factorially derived Low Back Pain Questionnaire. The eighth pain variable is a self-estimate of intensity. Relationships among demographic and pain variables are small and unsystematic. Hostility has a small, systematically inverse relation to pain variables, supporting theories relating low back pain to inhibition of anger. Anxiety has a small positive relationship, and depression has no relationship to pain variables. In general, the small relationships indicate that the Low Back Pain Questionnaire provides descriptions of pain that are not confounded by social characteristics or current emotional states of patients.

  14. Demographic change and carbon dioxide emissions.

    PubMed

    O'Neill, Brian C; Liddle, Brant; Jiang, Leiwen; Smith, Kirk R; Pachauri, Shonali; Dalton, Michael; Fuchs, Regina

    2012-07-14

    Relations between demographic change and emissions of the major greenhouse gas carbon dioxide (CO(2)) have been studied from different perspectives, but most projections of future emissions only partly take demographic influences into account. We review two types of evidence for how CO(2) emissions from the use of fossil fuels are affected by demographic factors such as population growth or decline, ageing, urbanisation, and changes in household size. First, empirical analyses of historical trends tend to show that CO(2) emissions from energy use respond almost proportionately to changes in population size and that ageing and urbanisation have less than proportional but statistically significant effects. Second, scenario analyses show that alternative population growth paths could have substantial effects on global emissions of CO(2) several decades from now, and that ageing and urbanisation can have important effects in particular world regions. These results imply that policies that slow population growth would probably also have climate-related benefits.

  15. Thermal Expansion of Hafnium Carbide

    NASA Technical Reports Server (NTRS)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  16. Nonicosahedral pathways for capsid expansion

    NASA Astrophysics Data System (ADS)

    Cermelli, Paolo; Indelicato, Giuliana; Twarock, Reidun

    2013-09-01

    For a significant number of viruses a structural transition of the protein container that encapsulates the viral genome forms an important part of the life cycle and is a prerequisite for the particle becoming infectious. Despite many recent efforts the mechanism of this process is still not fully understood, and a complete characterization of the expansion pathways is still lacking. We present here a coarse-grained model that captures the essential features of the expansion process and allows us to investigate the conditions under which a viral capsid becomes unstable. Based on this model we demonstrate that the structural transitions in icosahedral viral capsids are likely to occur through a low-symmetry cascade of local expansion events spreading in a wavelike manner over the capsid surface.

  17. Mechanical waves during tissue expansion

    NASA Astrophysics Data System (ADS)

    Serra-Picamal, Xavier; Conte, Vito; Vincent, Romaric; Anon, Ester; Tambe, Dhananjay T.; Bazellieres, Elsa; Butler, James P.; Fredberg, Jeffrey J.; Trepat, Xavier

    2012-08-01

    The processes by which an organism develops its shape and heals wounds involve expansion of a monolayer sheet of cells. The mechanism underpinning this epithelial expansion remains obscure, despite the fact that its failure is known to contribute to several diseases, including carcinomas, which account for about 90% of all human cancers. Here, using the micropatterned epithelial monolayer as a model system, we report the discovery of a mechanical wave that propagates slowly to span the monolayer, traverses intercellular junctions in a cooperative manner and builds up differentials of mechanical stress. Essential features of this wave generation and propagation are captured by a minimal model based on sequential fronts of cytoskeletal reinforcement and fluidization. These findings establish a mechanism of long-range cell guidance, symmetry breaking and pattern formation during monolayer expansion.

  18. The demographic transition: model and reality.

    PubMed

    Alexandersson, G

    1981-01-01

    Observed exponential population growth curves are short-term parts of a logistic or S-curve in demography or a product-cycle curve in technology. All human populations have the ability to adjust their rates of growth, a fact recognized by the demographic transition model. The acceleration of world population growth that began after 1650 and became conspicuous after 1850 was largely confined to industrialized countries of European culture until after World War II, when the S-curve passed the inflection point. Many signs indicate that the decline in growth rates may become striking in the 1980s or 1990s. The demographic transition agrees with the logistic curve, and since the ultimate carrying capacity of the Earth is limited, represents an intelligent adaptation. The industrial countries with the longest statistical records, such as Sweden and Finland, evidence early efforts to control fertility. The demographic transition in Sweden lasted from 1815 to 1930 and occurred without government interference. A question for postindustrial western society is whether birth rates will be adjusted to the rising death rates expected as the population ages. Birth and death rates in most formulations of the demographic transition model are typical of Western Europe at the start of the transition process but are much too low for most countries of the world. Japan's demographic transition and that of several other Asian countries have occurred much more rapidly than those of Western Europe and have demonstrated not only that the demographic transition model was applicable but that the time span could be shortened by a factor of about 10 when government policy was substituted for spontaneous development. The Indian experience however shows that the shortening of the transition cannot be imposed from above. The demographic transition is well on its way in most of Asia and Latin America, but Africa and the Muslim countries of Asia have so far done little to restrain their high

  19. Demographic Challenges in America’s Future,

    DTIC Science & Technology

    1982-05-01

    of women are em- ployed, and if the opportunity cost of children is a sufficiently impor- tant factor in couples’ decisions, fertility rates may even...AD-A130 637 DEMOGRAPHIC CHALLENGES IN AMERICA’S FTTUREIU) RAND CORP / SANTA MONICA CA W ’P BUTZ ET AL. MAY 02 RAND/R 2911 RC seI-AD-E?5O 765...UNCLASSIFIED FIG 5/1 N OI liiie M~lD 1.0 4 *2.0 1111.25 lii I.4 . Ifln IIII~ - MICROCOPY RESOLUTION TEST CHART k&TONAL 9uREAU OF STAN0AROS -96 - A Demographic

  20. International Demographic Data Director. A Computerized Information Retrieval System for Demographic and Family Planning Data.

    ERIC Educational Resources Information Center

    Bargar, Martha

    Announced in this booklet is the availability of the International Demographic Data Directory (IDDD). The IDDD is designed to expedite the retrieval of demographic and family planning statistics for use by administrators, planners, and researchers. This guide describes the computerized system indicating the geographic scope of the data, subject…

  1. Expansion-based passive ranging

    NASA Technical Reports Server (NTRS)

    Barniv, Yair

    1993-01-01

    This paper describes a new technique of passive ranging which is based on utilizing the image-plane expansion experienced by every object as its distance from the sensor decreases. This technique belongs in the feature/object-based family. The motion and shape of a small window, assumed to be fully contained inside the boundaries of some object, is approximated by an affine transformation. The parameters of the transformation matrix are derived by initially comparing successive images, and progressively increasing the image time separation so as to achieve much larger triangulation baseline than currently possible. Depth is directly derived from the expansion part of the transformation. To a first approximation, image-plane expansion is independent of image-plane location with respect to the focus of expansion (FOE) and of platform maneuvers. Thus, an expansion-based method has the potential of providing a reliable range in the difficult image area around the FOE. In areas far from the FOE the shift parameters of the affine transformation can provide more accurate depth information than the expansion alone, and can thus be used similarly to the way they have been used in conjunction with the Inertial Navigation Unit (INU) and Kalman filtering. However, the performance of a shift-based algorithm, when the shifts are derived from the affine transformation, would be much improved compared to current algorithms because the shifts--as well as the other parameters--can be obtained between widely separated images. Thus, the main advantage of this new approach is that, allowing the tracked window to expand and rotate, in addition to moving laterally, enables one to correlate images over a very long time span which, in turn, translates into a large spatial baseline resulting in a proportionately higher depth accuracy.

  2. Expansion-based passive ranging

    NASA Technical Reports Server (NTRS)

    Barniv, Yair

    1993-01-01

    A new technique of passive ranging which is based on utilizing the image-plane expansion experienced by every object as its distance from the sensor decreases is described. This technique belongs in the feature/object-based family. The motion and shape of a small window, assumed to be fully contained inside the boundaries of some object, is approximated by an affine transformation. The parameters of the transformation matrix are derived by initially comparing successive images, and progressively increasing the image time separation so as to achieve much larger triangulation baseline than currently possible. Depth is directly derived from the expansion part of the transformation. To a first approximation, image-plane expansion is independent of image-plane location with respect to the focus of expansion (FOE) and of platform maneuvers. Thus, an expansion-based method has the potential of providing a reliable range in the difficult image area around the FOE. In areas far from the FOE the shift parameters of the affine transformation can provide more accurate depth information than the expansion alone, and can thus be used similarly to the way they were used in conjunction with the Inertial Navigation Unit (INU) and Kalman filtering. However, the performance of a shift-based algorithm, when the shifts are derived from the affine transformation, would be much improved compared to current algorithms because the shifts - as well as the other parameters - can be obtained between widely separated images. Thus, the main advantage of this new approach is that, allowing the tracked window to expand and rotate, in addition to moving laterally, enables one to correlate images over a very long time span which, in turn, translates into a large spatial baseline - resulting in a proportionately higher depth accuracy.

  3. Bearing-Mounting Concept Accommodates Thermal Expansion

    NASA Technical Reports Server (NTRS)

    Nespodzany, Robert; Davis, Toren S.

    1995-01-01

    Pins or splines allow radial expansion without slippage. Design concept for mounting rotary bearing accommodates differential thermal expansion between bearing and any structure(s) to which bearing connected. Prevents buildup of thermal stresses by allowing thermal expansion to occur freely but accommodating expansion in such way not to introduce looseness. Pin-in-slot configuration also maintains concentricity.

  4. 18 CFR 154.309 - Incremental expansions.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Incremental expansions... Changes § 154.309 Incremental expansions. (a) For every expansion for which incremental rates are charged... costs and revenues associated with the expansion, until the Commission authorizes the costs of the...

  5. 18 CFR 154.309 - Incremental expansions.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 18 Conservation of Power and Water Resources 1 2012-04-01 2012-04-01 false Incremental expansions... Changes § 154.309 Incremental expansions. (a) For every expansion for which incremental rates are charged... costs and revenues associated with the expansion, until the Commission authorizes the costs of the...

  6. 48 CFR 570.403 - Expansion requests.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 4 2011-10-01 2011-10-01 false Expansion requests. 570... Continued Space Requirements 570.403 Expansion requests. (a) If the expansion space is in the general scope... justification under FAR 6.3. (b) If the expansion space needed is outside the general scope of the lease, the...

  7. 32 CFR 169a.11 - Expansions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 1 2013-07-01 2013-07-01 false Expansions. 169a.11 Section 169a.11 National... PROGRAM PROCEDURES Procedures § 169a.11 Expansions. In cases where expansion of an in-house commercial activity is anticipated, a review of the entire commercial activity, including the proposed expansion...

  8. 32 CFR 169a.11 - Expansions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 1 2014-07-01 2014-07-01 false Expansions. 169a.11 Section 169a.11 National... PROGRAM PROCEDURES Procedures § 169a.11 Expansions. In cases where expansion of an in-house commercial activity is anticipated, a review of the entire commercial activity, including the proposed expansion...

  9. 48 CFR 570.403 - Expansion requests.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 4 2014-10-01 2014-10-01 false Expansion requests. 570... Continued Space Requirements 570.403 Expansion requests. (a) If the expansion space is in the general scope... justification under FAR 6.3. (b) If the expansion space needed is outside the general scope of the lease, the...

  10. 32 CFR 169a.11 - Expansions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 1 2010-07-01 2010-07-01 false Expansions. 169a.11 Section 169a.11 National... PROGRAM PROCEDURES Procedures § 169a.11 Expansions. In cases where expansion of an in-house commercial activity is anticipated, a review of the entire commercial activity, including the proposed expansion...

  11. 48 CFR 570.403 - Expansion requests.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 4 2013-10-01 2013-10-01 false Expansion requests. 570... Continued Space Requirements 570.403 Expansion requests. (a) If the expansion space is in the general scope... justification under FAR 6.3. (b) If the expansion space needed is outside the general scope of the lease, the...

  12. 32 CFR 169a.11 - Expansions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 1 2012-07-01 2012-07-01 false Expansions. 169a.11 Section 169a.11 National... PROGRAM PROCEDURES Procedures § 169a.11 Expansions. In cases where expansion of an in-house commercial activity is anticipated, a review of the entire commercial activity, including the proposed expansion...

  13. 48 CFR 570.403 - Expansion requests.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Expansion requests. 570... Continued Space Requirements 570.403 Expansion requests. (a) If the expansion space is in the general scope... FAR 6.3. (b) If the expansion space needed is outside the general scope of the lease, determine...

  14. 48 CFR 570.403 - Expansion requests.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 4 2012-10-01 2012-10-01 false Expansion requests. 570... Continued Space Requirements 570.403 Expansion requests. (a) If the expansion space is in the general scope... justification under FAR 6.3. (b) If the expansion space needed is outside the general scope of the lease, the...

  15. 18 CFR 154.309 - Incremental expansions.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 18 Conservation of Power and Water Resources 1 2014-04-01 2014-04-01 false Incremental expansions... Changes § 154.309 Incremental expansions. (a) For every expansion for which incremental rates are charged... costs and revenues associated with the expansion, until the Commission authorizes the costs of the...

  16. 18 CFR 154.309 - Incremental expansions.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 18 Conservation of Power and Water Resources 1 2013-04-01 2013-04-01 false Incremental expansions... Changes § 154.309 Incremental expansions. (a) For every expansion for which incremental rates are charged... costs and revenues associated with the expansion, until the Commission authorizes the costs of the...

  17. 32 CFR 169a.11 - Expansions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 1 2011-07-01 2011-07-01 false Expansions. 169a.11 Section 169a.11 National... PROGRAM PROCEDURES Procedures § 169a.11 Expansions. In cases where expansion of an in-house commercial activity is anticipated, a review of the entire commercial activity, including the proposed expansion...

  18. 18 CFR 154.309 - Incremental expansions.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 18 Conservation of Power and Water Resources 1 2011-04-01 2011-04-01 false Incremental expansions... Changes § 154.309 Incremental expansions. (a) For every expansion for which incremental rates are charged... costs and revenues associated with the expansion, until the Commission authorizes the costs of the...

  19. Relativistic effects on plasma expansion

    SciTech Connect

    Benkhelifa, El-Amine; Djebli, Mourad

    2014-07-15

    The expansion of electron-ion plasma is studied through a fully relativistic multi-fluids plasma model which includes thermal pressure, ambipolar electrostatic potential, and internal energy conversion. Numerical investigation, based on quasi-neutral assumption, is performed for three different regimes: nonrelativistic, weakly relativistic, and relativistic. Ions' front in weakly relativistic regime exhibits spiky structure associated with a break-down of quasi-neutrality at the expanding front. In the relativistic regime, ion velocity is found to reach a saturation limit which occurs at earlier stages of the expansion. This limit is enhanced by higher electron velocity.

  20. Shrub encroachment control by browsing: Targeting the right demographic process

    NASA Astrophysics Data System (ADS)

    da Silveira Pontes, Laíse; Magda, Danièle; Jarry, Marc; Gleizes, Benoît; Agreil, Cyril

    2012-11-01

    Exploring key demographic parameters for establishment and growth of shrub populations enables us to identify the life stages or plant organs that browsers need to consume to effectively influence shrub population dynamics. However, there is a lack of concrete knowledge on how browsing can efficiently meet this goal. We therefore tested the impact of different levels of browsing intensity on a key demographic parameter (survival of juveniles) of a major colonizing shrub species (broom, Cytisus scoparius) in order to control population growth, and designed a browsing management strategy focused on this target stage. Three browsing intensities, representing pertinent management practices, were simulated on juveniles (2 years old) in a broom population. Juvenile broom plants were either left untouched (control treatment; n = 126) or had 50% or 90% of their total edible stem biomass removed for "light-intensity browsing" (n = 127) and "high-intensity browsing" (n = 77) treatments, respectively. Survival and fecundity data were collected over 6 years. Standard matrix modeling was used to analyze the impact of browsing on changes in population growth rate (λ), and the results were 6.34 (control), 2.26 (light browsing) and 0.85 (heavy browsing). Therefore, the natural expansion of broom populations may be slowed by light browsing or even reversed by heavy browsing (λ < 1). This multi-year survey confirms that focusing browsing on juveniles is an efficient strategy for controlling broom dominance. Shrub control strategies should therefore target early-growth-stage populations and repeat the browsing strategy at the same intensity over several years to achieve cumulative effects.

  1. Demographic history and linkage disequilibrium in human populations.

    PubMed

    Laan, M; Pääbo, S

    1997-12-01

    In the human genome, linkage disequilibrium (LD)--the non-random association of alleles at chromosomal loci--has been studied mainly in regions surrounding disease genes on affected chromosomes. Consequently, little information is available on the distribution of LD across anonymous genomic regions in the general population. However, demographic history is expected to influence the extent of overall LD across the genome, so a population that has been of constant size will display higher levels of LD than a population that has expanded. In support of this, the extent of LD between anonymous loci on chromosome 4 in chimpanzees (as a model of a population of constant size) has been compared to that in Finns (as a model of an expanded population; refs 8,9) and found to exhibit more LD than in the latter population. In Europe, studies of mitochondrial (mt) DNA sequences have suggested that most populations have experienced expansion, whereas the Saami in northern Fenno-Scandinavia have been of constant size (Table 1). Thus, in northern Europe, populations with radically different demographic histories live in close geographic proximity to each other. We studied the allelic associations between anonymous microsatellite loci on the X chromosome in the Saami and neighbouring populations and found dramatically higher levels of LD in the Saami than in other populations in the region. This indicates that whereas recently expanded populations, such as the Finns, are well suited to map single disease genes affected by recent mutations, populations that have been of constant size, such as the Saami, may be much better suited to map genes for complex traits that are caused by older mutations.

  2. Removable Type Expansion Bolt Innovative Design

    NASA Astrophysics Data System (ADS)

    Wang, Feng-Lan; Zhang, Bo; Gao, Bo; Liu, Yan-Xin; Gao, Bo

    2016-05-01

    Expansion bolt is a kind of the most common things in our daily life. Currently, there are many kinds of expansion bolts in the market. However, they have some shortcomings that mainly contain underuse and unremovement but our innovation of design makes up for these shortcomings very well. Principle of working follows this: expansion tube is fixed outside of bolt, steel balls and expansion covers are fixed inside. Meanwhile, the steel balls have 120° with each other. When using it ,expansion cover is moved in the direction of its internal part. So the front part of expansion bolt cover is increasingly becoming big and steel halls is moved outside. Only in this way can it be fixed that steel balls make expansion tube expand. When removing them, expansion bolt is moved outside. So the front part of expansion bolt cover is gradually becoming small and steel balls moves inside, after expansion tube shrinks, we can detach them.

  3. The Thermal Expansion Of Feldspars

    NASA Astrophysics Data System (ADS)

    Hovis, G. L.; Medford, A.; Conlon, M.

    2009-12-01

    Hovis and others (1) investigated the thermal expansion of natural and synthetic AlSi3 feldspars and demonstrated that the coefficient of thermal expansion (α) decreases significantly, and linearly, with increasing room-temperature volume (VRT). In all such feldspars, therefore, chemical expansion limits thermal expansion. The scope of this work now has been broadened to include plagioclase and Ba-K feldspar crystalline solutions. X-ray powder diffraction data have been collected between room temperature and 925 °C on six plagioclase specimens ranging in composition from anorthite to oligoclase. When combined with thermal expansion data for albite (2,3,4) a steep linear trend of α as a function of VRT emerges, reflecting how small changes in composition dramatically affect expansion behavior. The thermal expansion data for five synthetic Ba-K feldspars ranging in composition from 20 to 100 mole percent celsian, combined with data for pure K-feldspar (3,4), show α-VRT relationships similar in nature to the plagioclase series, but with a slope and intercept different from the latter. Taken as a group all Al2Si2 feldspars, including anorthite and celsian from the present study along with Sr- (5) and Pb-feldspar (6) from other workers, show very limited thermal expansion that, unlike AlSi3 feldspars, has little dependence on the divalent-ion (or M-) site occupant. This apparently is due to the necessitated alternation of Al and Si in the tetrahedral sites of these minerals (7), which in turn locks the tetrahedral framework and makes the M-site occupant nearly irrelevant to expansion behavior. Indeed, in feldspar series with coupled chemical substitution it is the change away from a 1:1 Al:Si ratio that gives feldspars greater freedom to expand. Overall, the relationships among α, chemical composition, and room-temperature volume provide useful predictive tools for estimating feldspar thermal expansion and give insight into the controls of expansion behavior in

  4. A Demographic Profile of Cuban Americans.

    ERIC Educational Resources Information Center

    Boswell, Thomas D.

    This study offers a demographic profile of the U.S. Cuban population, using data from the decennial census and current population surveys. Part one estimates the number of Cuban Americans and describes their geographic distribution nationwide. Part two compares the socioeconomic characteristics (age, gender, educational attainment, income,…

  5. A Model for External Demographic Analysis.

    ERIC Educational Resources Information Center

    Hall, Barbara Ann

    A data-collection model is presented for the gathering of timely information on population demographic characteristics, as well as economic, educational, environmental, and social trends. First, the paper discusses the importance of anticipating internal and external changes and establishing priorities for resource allocation in the design of a…

  6. 5 CFR 841.404 - Demographic factors.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 2 2011-01-01 2011-01-01 false Demographic factors. 841.404 Section 841... factors. (a) The Office of Personnel Management (OPM) will consider the factors listed below in determining normal cost percentages. To the extent data are available for the factor by specific category of...

  7. The Demographics of Corporal Punishment in Texas

    ERIC Educational Resources Information Center

    Phillips, Stephanie

    2012-01-01

    This dissertation examined the student discipline policies of 1,025 Texas school districts, as well as data from the Texas Education Agency's Academic Excellence Indicator System in order to identify demographic patterns regarding corporal punishment policies in Texas schools. The study also studied the relationship between a district's corporal…

  8. State Differences: The Key to Demographics.

    ERIC Educational Resources Information Center

    Hodgkinson, Harold

    1999-01-01

    This companion piece to a 1997 article examines United States demographic trends, such as diversity by age, "race" and U.S. Census racial classifications, wealth, transiency, suburbanization and sprawl, and immigration, focusing on differences among states and metro regions. Nothing, including achievement scores, social services, and…

  9. Some Demographic Correlates of Changing Newspaper Circulation.

    ERIC Educational Resources Information Center

    Eberhard, Wallace B.

    There are varied opinions on the relationship between the circulation penetration of the American daily newspapers and certain demographic indicators. Previous studies have treated the growth of circulation figures by utilizing gross national data and have indicated the role newspaper circulation plays in defining the limits of major urban…

  10. Population Bulletin. Pakistan: A Demographic Report.

    ERIC Educational Resources Information Center

    Population Reference Bureau, Inc., Washington, DC.

    This report presents a brief history of Pakistan as a nation and reviews a number of demographic variables. Major topics discussed are population growth and shifts, urbanization, and labor characteristics and problems. Based on this information and projections, the report concludes with a discussion of the failure of family planning programs and…

  11. Economic and Demographic Predictors of Inclusive Education

    ERIC Educational Resources Information Center

    Cosier, Meghan E.; Causton-Theoharis, Julie

    2011-01-01

    This study investigated economic and demographic predictors of levels of inclusion of students with disabilities in 129 school districts. Multiple regression analysis was utilized to address the following research questions: (a) Is there a relationship between economic factors and percentage of highly included students with disabilities in general…

  12. Psychological and Demographic Correlates of Career Patterns

    ERIC Educational Resources Information Center

    Reitzle, Matthias; Korner, Astrid; Vondracek, Fred W.

    2009-01-01

    Recent years have witnessed a growing diversity of career patterns, resulting from the relative decline of stable employment. In the present study of 1368 employed and self-employed German adults career pattern diversity was assessed using nine pictograms. The goal was to identify psychological and demographic correlates of these patterns and to…

  13. State Differences: The Key to Demographics.

    ERIC Educational Resources Information Center

    Hodgkinson, Harold

    1999-01-01

    This companion piece to a 1997 article examines United States demographic trends, such as diversity by age, "race" and U.S. Census racial classifications, wealth, transiency, suburbanization and sprawl, and immigration, focusing on differences among states and metro regions. Nothing, including achievement scores, social services, and…

  14. Biosocial Models: Can Demographers Ignore Them?

    ERIC Educational Resources Information Center

    Casterline, John B.

    1995-01-01

    Accumulating empirical evidence documents the significant contribution of biological variables to the determination of social behaviors. More appropriate biosocial models may need to allow for causal relationships between biological and social determinants and for effects that are interactive, nonlinear, and discontinuous. Demographic surveys…

  15. Demographic Factors Related to Enrollment Projections. Draft.

    ERIC Educational Resources Information Center

    Pitruzzello, Philip

    School districts must analyze demographic data carefully if they hope to deal effectively with changing enrollment patterns. Sources of relevant data include local planning boards, utility companies, government records of vital statistics, carefully conducted school censuses, and municipal records of housing construction and property transfers.…

  16. A Model for External Demographic Analysis.

    ERIC Educational Resources Information Center

    Hall, Barbara Ann

    A data-collection model is presented for the gathering of timely information on population demographic characteristics, as well as economic, educational, environmental, and social trends. First, the paper discusses the importance of anticipating internal and external changes and establishing priorities for resource allocation in the design of a…

  17. Life Potential as a Basic Demographic Indicator

    ERIC Educational Resources Information Center

    Goerlich, Francisco J.; Soler, Angel

    2013-01-01

    This paper proposes an indicator that integrates life expectancy with the demographic structure of the population for a given society. By doing this, we have a simple indicator of mortality and aging combined, which could be very useful for developed societies. As is widely known, life expectancy at birth is independent of the demographic…

  18. Complexity and demographic stability in population models.

    PubMed

    Demetrius, Lloyd; Gundlach, Volker Matthias; Ochs, Gunter

    2004-05-01

    This article is concerned with relating the stability of a population, as defined by the rate of decay of fluctuations induced by demographic stochasticity, with its heterogeneity in age-specific birth and death rates. We invoke the theory of large deviations to establish a fluctuation theorem: The demographic stability of a population is positively correlated with evolutionary entropy, a measure of the variability in the age of reproducing individuals in the population. This theorem is exploited to predict certain correlations between ecological constraints and evolutionary trends in demographic stability, namely, (i) bounded growth constraints--a uni-directional increase in stability, (ii) unbounded growth constraints (large population size)--a uni-directional decrease in stability, (iii) unbounded growth constraints (small population size)--random, non-directional change in stability. These principles relating ecological constraints with trends in demographic stability are shown to be far reaching generalizations of the tenets derived from classical studies of stability in an evolutionary context. These results thus provide a new conceptual framework for explaining patterns of variation in population numbers observed in natural populations.

  19. Understanding China's Demographic Dividends and Labor Issue

    ERIC Educational Resources Information Center

    Peng, Xizhe

    2013-01-01

    One of the major concerns about the one-child policy is its negative impact on the current and future labor force in China. People have talked about the Lewis Turning Point and the end of demographic dividends. Some of these arguments, however, can be misleading. The working-age population (ages 15 to 59) can be treated as the potential labor…

  20. Understanding China's Demographic Dividends and Labor Issue

    ERIC Educational Resources Information Center

    Peng, Xizhe

    2013-01-01

    One of the major concerns about the one-child policy is its negative impact on the current and future labor force in China. People have talked about the Lewis Turning Point and the end of demographic dividends. Some of these arguments, however, can be misleading. The working-age population (ages 15 to 59) can be treated as the potential labor…

  1. Demographic Group Differences in Adolescents' Time Attitudes

    ERIC Educational Resources Information Center

    Andretta, James R.; Worrell, Frank C.; Mello, Zena R.; Dixson, Dante D.; Baik, Sharon H.

    2013-01-01

    In the present study, we examined demographic differences in time attitudes in a sample of 293 adolescents. Time attitudes were measured using the Adolescent Time Attitude Scale (Mello & Worrell, 2007; Worrell, Mello, & Buhl, 2011), which assesses positive and negative attitudes toward the past, the present, and the future. Generally, African…

  2. The Demographics of Corporal Punishment in Texas

    ERIC Educational Resources Information Center

    Phillips, Stephanie

    2012-01-01

    This dissertation examined the student discipline policies of 1,025 Texas school districts, as well as data from the Texas Education Agency's Academic Excellence Indicator System in order to identify demographic patterns regarding corporal punishment policies in Texas schools. The study also studied the relationship between a district's corporal…

  3. Demographic change in the northern forest

    Treesearch

    Kenneth M. Johnson; Susan I. Stewart; Miranda H. Mockrin

    2012-01-01

    The Northern Forest spans more than 26 million acres across Maine, New Hampshire, New York, and Vermont. With densely settled urban cores, sprawling suburbs, struggling industrial and forest products towns, fast growing recreational areas, and isolated rural villages, the region includes many of the diverse strands that together compose the demographic fabric of the...

  4. Demographic Group Differences in Adolescents' Time Attitudes

    ERIC Educational Resources Information Center

    Andretta, James R.; Worrell, Frank C.; Mello, Zena R.; Dixson, Dante D.; Baik, Sharon H.

    2013-01-01

    In the present study, we examined demographic differences in time attitudes in a sample of 293 adolescents. Time attitudes were measured using the Adolescent Time Attitude Scale (Mello & Worrell, 2007; Worrell, Mello, & Buhl, 2011), which assesses positive and negative attitudes toward the past, the present, and the future. Generally, African…

  5. Demographic Trends Affecting the Future Labor Force.

    ERIC Educational Resources Information Center

    Taeuber, Karl E.

    This report reviews recent population and manpower projections and examines how they take into account certain unexpected shifts in demographic, social, and economic behavior. It also assesses how well the particular circumstances, trends, and problems of the nation's major minority groups have been brought into the purview of the projection…

  6. Demographic and Lifestyle Variables Associated with Obesity

    ERIC Educational Resources Information Center

    Worthy, Sheri L.; Lokken, Kristine; Pilcher, Kenneth; Boeka, Abbe

    2010-01-01

    Objective: Overweight and obesity rates are associated with chronic diseases and higher rates of disability and continue to rise in the United States and worldwide. The purpose of this study was to build on past research and further investigate demographic and lifestyle variables associated with increased body mass index (BMI: kg/m[squared]).…

  7. Psychological and Demographic Correlates of Career Patterns

    ERIC Educational Resources Information Center

    Reitzle, Matthias; Korner, Astrid; Vondracek, Fred W.

    2009-01-01

    Recent years have witnessed a growing diversity of career patterns, resulting from the relative decline of stable employment. In the present study of 1368 employed and self-employed German adults career pattern diversity was assessed using nine pictograms. The goal was to identify psychological and demographic correlates of these patterns and to…

  8. Demographic and Lifestyle Variables Associated with Obesity

    ERIC Educational Resources Information Center

    Worthy, Sheri L.; Lokken, Kristine; Pilcher, Kenneth; Boeka, Abbe

    2010-01-01

    Objective: Overweight and obesity rates are associated with chronic diseases and higher rates of disability and continue to rise in the United States and worldwide. The purpose of this study was to build on past research and further investigate demographic and lifestyle variables associated with increased body mass index (BMI: kg/m[squared]).…

  9. Demographic monitoring of Wright fishhook cactus

    Treesearch

    Ronald J. Kass

    2001-01-01

    Wright fishhook cactus (Sclerocactus wrightiae Benson) is a small barrel cactus endemic to the San Rafael Swell in south-central Utah. It was listed as an endangered species in 1979 due to its small population size, threats of over-collecting, and development associated with oil and gas. Demographic monitoring was initiated in 1993 with the following objectives: to...

  10. Life Potential as a Basic Demographic Indicator

    ERIC Educational Resources Information Center

    Goerlich, Francisco J.; Soler, Angel

    2013-01-01

    This paper proposes an indicator that integrates life expectancy with the demographic structure of the population for a given society. By doing this, we have a simple indicator of mortality and aging combined, which could be very useful for developed societies. As is widely known, life expectancy at birth is independent of the demographic…

  11. Chapter 8: Demographic characteristics and population modeling

    Treesearch

    Scott H. Stoleson; Mary J. Whitfield; Mark K. Sogge

    2000-01-01

    An understanding of the basic demography of a species is necessary to estimate and evaluate population trends. The relative impact of different demographic parameters on growth rates can be assessed through a sensitivity analysis, in which different parameters are altered singly to assess the effect on population growth. Identification of critical parameters can allow...

  12. Expansive Openness in Teacher Practice

    ERIC Educational Resources Information Center

    Kimmons, Royce

    2016-01-01

    Background/Context: Previous work on the use of open educational resources in K-12 classrooms has generally focused on issues related to cost. The current study takes a more expansive view of openness that also accounts for adaptation and sharing in authentic classroom contexts. Purpose/Objective/Research Question/Focus of Study The study seeks to…

  13. Conversational Expansion in Young Children.

    ERIC Educational Resources Information Center

    Boynton, Kathleen Reardon; Henke, Lucy L.

    1978-01-01

    The importance of contextual influences to conversational competence development is emphasized. Included are one or more significant adults whose systematic patterns of feedback teach children rules of conversation while providing guided practice in the use of these rules. The role of expansion is examined as one of the common patterns of feedback…

  14. Clamshell Thermal-Expansion Bellows

    NASA Technical Reports Server (NTRS)

    Fesmire, J.; Moore, W. I.; Dipasquale, S. D.

    1993-01-01

    Improved bellows serves as thermal-expansion joint in vacuum-jacketed cyrogenic piping system. Made of Hastelloy C-22 and fabricated in field by welding two clam-shell-like half bellows. No protective paint or maintenance needed. Design modified to fit most thin-wall bellows.

  15. Evidence of local adaptation in the demographic response of American ginseng to interannual temperature variation.

    PubMed

    Souther, Sara; McGraw, James B

    2011-10-01

    Bioclimatic envelope models of species' responses to climate change are used to predict how species will respond to increasing temperatures. These models are frequently based on the assumption that the northern and southern boundaries of a species' range define its thermal niche. However, this assumption may be violated if populations are adapted to local temperature regimes and have evolved population-specific thermal optima. Considering the prevalence of local adaptation, the assumption of a species-wide thermal optimum may be violated for many species. We used spatially and temporally extensive demographic data for American ginseng (Panax quinquefolius L.) to examine range-wide variation in response of population growth rate (λ) to climatic factors. Our results suggest adaptation to local temperature, but not precipitation. For each population, λ was maximized when annual temperatures were similar to site-specific, long-term mean temperatures. Populations from disparate climatic zones responded differently to temperature variation, and there was a linear relation between population-level thermal optima and the 30-year mean temperature at each site. For species that are locally adapted to temperature, bioclimatic envelope models may underestimate the extent to which increasing temperatures will decrease population growth rate. Because any directional change from long-term mean temperatures will decrease population growth rates, all populations throughout a species' range will be adversely affected by temperature increase, not just populations at southern and low-elevation boundaries. Additionally, when a species' local thermal niche is narrower than its range-wide thermal niche, a smaller temperature increase than would be predicted by bioclimatic envelope approaches may be sufficient to decrease population growth. ©2011 Society for Conservation Biology.

  16. Effective Expansion: Balance between Shrinkage and Hygroscopic Expansion.

    PubMed

    Suiter, E A; Watson, L E; Tantbirojn, D; Lou, J S B; Versluis, A

    2016-05-01

    The purpose of this study was to investigate the relationship between hygroscopic expansion and polymerization shrinkage for compensation of polymerization shrinkage stresses in a restored tooth. One resin-modified glass-ionomer (RMGI) (Ketac Nano, 3M ESPE), 2 compomers (Dyract, Dentsply; Compoglass, Ivoclar), and a universal resin-based composite (Esthet•X HD, Dentsply) were tested. Volumetric change after polymerization ("total shrinkage") and during 4 wk of water storage at 37°C was measured using an optical method (n= 10). Post-gel shrinkage was measured during polymerization using a strain gauge method (n= 10). Extracted human molars with large mesio-occluso-distal slot preparations were restored with the tested restorative materials. Tooth surfaces at baseline (preparation), after restoration, and during 4 wk of 37°C water storage were scanned with an optical scanner to determine cuspal flexure (n= 8). Occlusal interface integrity was measured using dye penetration. Data were analyzed using analysis of variance and post hoc tests (significance level 0.05). All tested materials shrunk after polymerization. RMGI had the highest total shrinkage (4.65%) but lowest post-gel shrinkage (0.35%). Shrinkage values dropped significantly during storage in water but had not completely compensated polymerization shrinkage after 4 wk. All restored teeth initially exhibited inward (negative) cuspal flexure due to polymerization shrinkage. Cuspal flexure with the RMGI restoration was significantly less (-6.4 µm) than with the other materials (-12.1 to -14.1 µm). After 1 d, cuspal flexure reversed to +5.0 µm cuspal expansion with the RMGI and increased to +9.3 µm at 4 wk. After 4 wk, hygroscopic expansion compensated cuspal flexure in a compomer (Compoglass) and reduced flexure with Dyract and resin-based composite. Marginal integrity (93.7% intact restoration wall) was best for the Compoglass restorations and lowest (73.1%) for the RMGI restorations. Hygroscopic

  17. Phylogeography and demographic history of the neotropical otter (Lontra longicaudis).

    PubMed

    Trinca, Cristine S; de Thoisy, Benoit; Rosas, Fernando C W; Waldemarin, Helen F; Koepfli, Klaus-Peter; Vianna, Juliana A; Eizirik, Eduardo

    2012-07-01

    The Neotropical otter (Lontra longicaudis) is a medium-sized semiaquatic carnivore with a broad distribution in the Neotropical region. Despite being apparently common in many areas, it is one of the least known otters, and genetic studies on this species are scarce. Here, we have investigated its genetic diversity, population structure, and demographic history across a large portion of its geographic range by analyzing 1471 base pairs (bp) of mitochondrial DNA from 52 individuals. Our results indicate that L. longicaudis presents high levels of genetic diversity and a consistent phylogeographic pattern, suggesting the existence of at least 4 distinct evolutionary lineages in South America. The observed phylogeographic partitions are partially congruent with the subspecies classification previously proposed for this species. Coalescence-based analyses indicate that Neotropical otter mitochondrial DNA lineages have shared a rather recent common ancestor, approximately 0.5 Ma, and have subsequently diversified into the observed phylogroups. A consistent scenario of recent population expansion was identified in Eastern South America based on several complementary analyses of historical demography. The results obtained here provide novel insights on the evolutionary history of this largely unknown Neotropical mustelid and should be useful to design conservation and management policies on behalf of this species and its habitats.

  18. Geographical barriers and climate influence demographic history in narrowleaf cottonwoods

    PubMed Central

    Evans, L M; Allan, G J; DiFazio, S P; Slavov, G T; Wilder, J A; Floate, K D; Rood, S B; Whitham, T G

    2015-01-01

    Studies of genetic variation can clarify the role of geography and spatio-temporal variation of climate in shaping demography, particularly in temperate zone tree species with large latitudinal ranges. Here, we examined genetic variation in narrowleaf cottonwood, Populus angustifolia, a dominant riparian tree. Using multi-locus surveys of polymorphism in 363 individuals across the species' 1800 km latitudinal range, we found that, first, P. angustifolia has stronger neutral genetic structure than many forest trees (simple sequence repeat (SSR) FST=0.21), with major genetic groups corresponding to large apparent geographical barriers to gene flow. Second, using SSRs and putatively neutral sequenced loci, coalescent simulations indicated that populations diverged before the last glacial maximum (LGM), suggesting the presence of population structure before the LGM. Third, the LGM and subsequent warming appear to have had different influences on each of these distinct populations, with effective population size reduction in the southern extent of the range but major expansion in the north. These results are consistent with the hypothesis that climate and geographic barriers have jointly affected the demographic history of P. angustifolia, and point the importance of both factors as being instrumental in shaping genetic variation and structure in widespread forest trees. PMID:25585921

  19. Simulation of Demographic Change in Palestinian Territories

    NASA Astrophysics Data System (ADS)

    Sumour, M. A.; El-Astal, A. H.; Shabat, M. M.; Radwan, M. A.

    Mortality, birth rates and retirement play a major role in demographic changes. In most cases, mortality rates decreased in the past century without noticeable decrease in fertility rates, leading to a significant increase in population growth. In many poor countries like Palestinian Territories the number of births has fallen and the life expectancy increased. In this paper we concentrate on measuring, analyzing and extrapolating the age structure in Palestine a few decades ago into the future. A Fortran program has been designed and used for the simulation and analysis of our statistical data. This study of demographic change in Palestine has shown that Palestinians will have in future problems as the strongest age cohorts are the above-60-year olds. We therefore recommend the increase of both the retirement age and female employment.

  20. Population momentum across the demographic transition.

    PubMed

    Blue, Laura; Espenshade, Thomas J

    2011-01-01

    Population momentum is the main driver of global population growth today, and this makes an appreciation of momentum critical to understanding contemporary worldwide growth dynamics. This article traces population momentum along with two recently defined measures of momentum decomposed—stable and nonstable momentum—across the demographic transition. We use historical data and population projections from 16 countries to illustrate some previously ignored empirical regularities of the demographic transition in both the developed and the developing world. We also demonstrate the dynamic nature of stable and nonstable momentum, as changes in stable momentum lead to predictable changes in current and future nonstable momentum. These results suggest that momentum, which by definition is measured at a point in time, can also be considered as a process that unfolds over time.

  1. Global demographic trends and future carbon emissions.

    PubMed

    O'Neill, Brian C; Dalton, Michael; Fuchs, Regina; Jiang, Leiwen; Pachauri, Shonali; Zigova, Katarina

    2010-10-12

    Substantial changes in population size, age structure, and urbanization are expected in many parts of the world this century. Although such changes can affect energy use and greenhouse gas emissions, emissions scenario analyses have either left them out or treated them in a fragmentary or overly simplified manner. We carry out a comprehensive assessment of the implications of demographic change for global emissions of carbon dioxide. Using an energy-economic growth model that accounts for a range of demographic dynamics, we show that slowing population growth could provide 16-29% of the emissions reductions suggested to be necessary by 2050 to avoid dangerous climate change. We also find that aging and urbanization can substantially influence emissions in particular world regions.

  2. The spatial components of demographic change.

    PubMed

    Campisi, D

    1986-04-01

    "In recent years, fertility in developed countries has drastically fallen towards replacement levels, so that further changes play an increasing role in determining the dynamics of population systems. In this paper, the dynamics of multiregional populations are analyzed when occasional perturbations resulting from changes in social and economic conditions exist. A perturbation theory for population models is introduced and the increasing effect of changes in demographic rates in determining the spatial component of the multiregional population growth is shown." The author outlines the critical situations in which perturbations produce drastic demographic changes. Data for Italy are used to show the theory's usefulness in analyzing both short- and long-term effects of changes in vital rates.

  3. Demographic variables in coal miners’ safety attitude

    NASA Astrophysics Data System (ADS)

    Yin, Wen-wen; Wu, Xiang; Ci, Hui-Peng; Qin, Shu-Qi; Liu, Jia-Long

    2017-03-01

    To change unsafe behavior through adjusting people’s safety attitudes has become an important measure to prevent accidents. Demographic variables, as influential factors of safety attitude, are fundamental and essential for the research. This research does a questionnaire survey among coal mine industry workers, and makes variance analysis and correlation analysis of the results in light of age, length of working years, educational level and experiences of accidents. The results show that the coal miners’ age, length of working years and accident experiences correlate lowly with safety attitudes, and those older coal miners with longer working years have better safety attitude, as coal miners without experiences of accident do.However, educational level has nothing to do with the safety attitude. Therefore, during the process of safety management, coal miners with different demographic characteristics should be put more attention to.

  4. Global demographic trends and future carbon emissions

    PubMed Central

    O'Neill, Brian C.; Dalton, Michael; Fuchs, Regina; Jiang, Leiwen; Pachauri, Shonali; Zigova, Katarina

    2010-01-01

    Substantial changes in population size, age structure, and urbanization are expected in many parts of the world this century. Although such changes can affect energy use and greenhouse gas emissions, emissions scenario analyses have either left them out or treated them in a fragmentary or overly simplified manner. We carry out a comprehensive assessment of the implications of demographic change for global emissions of carbon dioxide. Using an energy–economic growth model that accounts for a range of demographic dynamics, we show that slowing population growth could provide 16–29% of the emissions reductions suggested to be necessary by 2050 to avoid dangerous climate change. We also find that aging and urbanization can substantially influence emissions in particular world regions. PMID:20937861

  5. New Approaches to Demographic Data Collection

    PubMed Central

    Treiman, Donald J.; Lu, Yao; Qi, Yaqiang

    2013-01-01

    As population scientists have expanded the range of topics they study, increasingly considering the interrelationship between population phenomena and social, economic, and health conditions, they have expanded the kinds of data collected and have brought to bear new data collection techniques and procedures, often borrowed from other fields. These new approaches to demographic data collection are the concern of this essay. We consider three main topics: new developments in sampling procedures; new developments in fieldwork procedures; and new developments in the kind of information collected in demographic and social surveys. We conclude with some comments on data sharing in the social research community and a list of major Chinese surveys publicly available to researchers. Where possible we illustrate our points with Chinese examples. PMID:23844330

  6. Exoplanet Demographics with WFIRST-AFTA

    NASA Astrophysics Data System (ADS)

    Gaudi, B. S.; WFIRST-AFTA Science Definition Team

    2014-01-01

    Measurements of the demographics of exoplanets over a broad range of planet and host-star properties provide fundamental empirical constraints on theories of planet formation and evolution. Because of its unique sensitivity to low-mass, long-period, and free-floating planets, microlensing is an essential complement to our arsenal of planet detection methods. I outline the expected returns of a microlensing survey with WFIRST-AFTA. When combined with the results from complementary surveys such as Kepler, WFIRST-AFTA will yield a nearly complete picture of the demographics of planetary systems throughout the Galaxy, providing fundamental tests of planet formation theories, and informing our understanding of the frequency and potential habitability of low mass planets located in the habitable zones of their host stars.

  7. Is the demographic dividend an education dividend?

    PubMed

    Crespo Cuaresma, Jesús; Lutz, Wolfgang; Sanderson, Warren

    2014-02-01

    The effect of changes in age structure on economic growth has been widely studied in the demography and population economics literature. The beneficial effect of changes in age structure after a decrease in fertility has become known as the "demographic dividend." In this article, we reassess the empirical evidence on the associations among economic growth, changes in age structure, labor force participation, and educational attainment. Using a global panel of countries, we find that after the effect of human capital dynamics is controlled for, no evidence exists that changes in age structure affect labor productivity. Our results imply that improvements in educational attainment are the key to explaining productivity and income growth and that a substantial portion of the demographic dividend is an education dividend.

  8. Independent Demographic Responses to Climate Change among Temperate and Tropical Milksnakes (Colubridae: Genus Lampropeltis)

    PubMed Central

    Ruane, Sara; Torres-Carvajal, Omar; Burbrink, Frank T.

    2015-01-01

    The effects of Late Quaternary climate change have been examined for many temperate New World taxa, but the impact of Pleistocene glacial cycles on Neotropical taxa is less well understood, specifically with respect to changes in population demography. Here, we examine historical demographic trends for six species of milksnake with representatives in both the temperate and tropical Americas to determine if species share responses to climate change as a taxon or by area (i.e., temperate versus tropical environments). Using a multilocus dataset, we test for the demographic signature of population expansion and decline using non-genealogical summary statistics, as well as coalescent-based methods. In addition, we determine whether range sizes are correlated with effective population sizes for milksnakes. Results indicate that there are no identifiable trends with respect to demographic response based on location, and that species responded to changing climates independently, with tropical taxa showing greater instability. There is also no correlation between range size and effective population size, with the largest population size belonging to the species with the smallest geographic distribution. Our study highlights the importance of not generalizing the demographic histories of taxa by region and further illustrates that the New World tropics may not have been a stable refuge during the Pleistocene. PMID:26083467

  9. Genomic sequencing of Plasmodium falciparum malaria parasites from Senegal reveals the demographic history of the population.

    PubMed

    Chang, Hsiao-Han; Park, Daniel J; Galinsky, Kevin J; Schaffner, Stephen F; Ndiaye, Daouda; Ndir, Omar; Mboup, Souleymane; Wiegand, Roger C; Volkman, Sarah K; Sabeti, Pardis C; Wirth, Dyann F; Neafsey, Daniel E; Hartl, Daniel L

    2012-11-01

    Malaria is a deadly disease that causes nearly one million deaths each year. To develop methods to control and eradicate malaria, it is important to understand the genetic basis of Plasmodium falciparum adaptations to antimalarial treatments and the human immune system while taking into account its demographic history. To study the demographic history and identify genes under selection more efficiently, we sequenced the complete genomes of 25 culture-adapted P. falciparum isolates from three sites in Senegal. We show that there is no significant population structure among these Senegal sampling sites. By fitting demographic models to the synonymous allele-frequency spectrum, we also estimated a major 60-fold population expansion of this parasite population ∼20,000-40,000 years ago. Using inferred demographic history as a null model for coalescent simulation, we identified candidate genes under selection, including genes identified before, such as pfcrt and PfAMA1, as well as new candidate genes. Interestingly, we also found selection against G/C to A/T changes that offsets the large mutational bias toward A/T, and two unusual patterns: similar synonymous and nonsynonymous allele-frequency spectra, and 18% of genes having a nonsynonymous-to-synonymous polymorphism ratio >1.

  10. Length distributions of identity by descent reveal fine-scale demographic history.

    PubMed

    Palamara, Pier Francesco; Lencz, Todd; Darvasi, Ariel; Pe'er, Itsik

    2012-11-02

    Data-driven studies of identity by descent (IBD) were recently enabled by high-resolution genomic data from large cohorts and scalable algorithms for IBD detection. Yet, haplotype sharing currently represents an underutilized source of information for population-genetics research. We present analytical results on the relationship between haplotype sharing across purportedly unrelated individuals and a population's demographic history. We express the distribution of IBD sharing across pairs of individuals for segments of arbitrary length as a function of the population's demography, and we derive an inference procedure to reconstruct such demographic history. The accuracy of the proposed reconstruction methodology was extensively tested on simulated data. We applied this methodology to two densely typed data sets: 500 Ashkenazi Jewish (AJ) individuals and 56 Kenyan Maasai (MKK) individuals (HapMap 3 data set). Reconstructing the demographic history of the AJ cohort, we recovered two subsequent population expansions, separated by a severe founder event, consistent with previous analysis of lower-throughput genetic data and historical accounts of AJ history. In the MKK cohort, high levels of cryptic relatedness were detected. The spectrum of IBD sharing is consistent with a demographic model in which several small-sized demes intermix through high migration rates and result in enrichment of shared long-range haplotypes. This scenario of historically structured demographies might explain the unexpected abundance of runs of homozygosity within several populations. Copyright © 2012 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  11. Evolving demographics of advanced dental education.

    PubMed

    Waldman, H Barry; Perlman, Steven P; Cinotti, Debra A

    2009-01-01

    The numbers of dental school graduates and students enrolled in post graduate programs have increased. Decreases are noted in the enrollment in Periodontics and Prosthodontics programs and a marked increase in the enrollment in Pediatric Dentistry programs. A review of these changes, by gender and race/ethnicity provides an overview of the future demographics of the profession. Some concerns regarding the future are considered.

  12. [Demographic characteristics of consumers in Indonesia?].

    PubMed

    Ananta, A

    1993-06-01

    "This paper presents a mosaic of business opportunities arising from the different demographic characteristics of the provinces in the western part of Indonesia. The author discusses the total number of population, density, and per capita income to [shed] some light on the volume of the market. He also presents the business impact of the [changes] in fertility, mortality, and the...life style of those aged 40-64." (SUMMARY IN ENG)

  13. The Demographic Transition: Causes and Consequences

    PubMed Central

    Galor, Oded

    2013-01-01

    This paper develops the theoretical foundations and the testable implications of the various mechanisms that have been proposed as possible triggers for the demographic transition. Moreover, it examines the empirical validity of each of the theories and their significance for the understanding of the transition from stagnation to growth. The analysis suggests that the rise in the demand for human capital in the process of development was the main trigger for the decline in fertility and the transition to modern growth PMID:25089157

  14. Different Approaches to Monitoring Local Demographic Change,

    DTIC Science & Technology

    1982-05-01

    1.254 Franklin 1.150 1.131 Schoharie 1.253 1.141 Fulton 1.317 1.260 Schuyler 0.959 0.927 Genesee 1.028 0.990 Seneca 0.978 0.943 Greene 1.574 1.528...Goldsmith, Harold F., and Elizabeth L. Unger. 1973. Social Area Analysis: Procedures and Illustrative Application Based Upon the Mental Health Demographic

  15. Lethality and Autonomous Systems: The Roboticist Demographic

    DTIC Science & Technology

    2008-01-01

    humanoid (22%), and other (23%); 9) Media Influence: only 18% said that media had a strong or very strong influence on their attitude to robots ...and whether certain emotions would be appropriate in a military robot . The Wars question was worded as follows: To what extent do you think ...Lethality and Autonomous Systems: The Roboticist Demographic Lilia V. Moshkina and Ronald C. Arkin Mobile Robot Laboratory, College of

  16. Multipole expansions and intense fields

    NASA Astrophysics Data System (ADS)

    Reiss, Howard R.

    1984-02-01

    In the context of two-body bound-state systems subjected to a plane-wave electromagnetic field, it is shown that high field intensity introduces a distinction between long-wavelength approximation and electric dipole approximation. This distinction is gauge dependent, since it is absent in Coulomb gauge, whereas in "completed" gauges of Göppert-Mayer type the presence of high field intensity makes electric quadrupole and magnetic dipole terms of importance equal to electric dipole at long wavelengths. Another consequence of high field intensity is that multipole expansions lose their utility in view of the equivalent importance of a number of low-order multipole terms and the appearance of large-magnitude terms which defy multipole categorization. This loss of the multipole expansion is gauge independent. Also gauge independent is another related consequence of high field intensity, which is the intimate coupling of center-of-mass and relative coordinate motions in a two-body system.

  17. [Tissue expansion under the cicatrix].

    PubMed

    Cai, Guo-Bin; Liu, Liu; Li, Tai-Ying; Zhang, Yi; Wang, Chun-Mei

    2005-09-01

    To investigate a more simple and effective method to repair cicatrix by tissue expansion. The dilator with the capacity of 80 - 500 ml was implanted into the subcutaneous pocket under the cicatrix. After dilating for one to two months, the dilator was taken out and the wound surface of the cicatrix was removed. The expanded skin flap was advanced or rotated to cover the defects. The procedure was used on 203 cases. The dilatation was achieved successfully in all the cases, followed by cicatrix removing and repair. The incision scar was not noticeable. Tissue expansion under the cicatrix has the advantages of safety, less trauma and less extra incisions. It is a reasonable choice to obtain more flexible surgical designs and more economical skin flap applications. It is suitable for most of the treatment for cicatrix.

  18. The Gradual Expansion Muscle Flap

    DTIC Science & Technology

    2014-01-01

    Biochem Cytol. 1961;9:493 495. 42. Sola OM, Christensen DL, Martin AW. Hypertrophy and hyperplasia of adult chicken anterior latissimus dorsi muscles ...TECHNICAL TRICK The Gradual Expansion Muscle Flap Michael J. Beltran, MD,* James A. Blair, MD,* Christopher R. Rathbone, PhD,† and Joseph R. Hsu, MD...acute shortening and angulation of the tibia and rotational muscle flap coverage and split thickness skin grafting of the soft tissue defect

  19. Expansive Cements and Their Use

    DTIC Science & Technology

    1972-10-01

    made available from the Office, Chief of Research and Development, Army, f- operation of the Concrete Technology Inxormation Aalysis Center (CTIAC...Ths is CTIAC Report No. 8. This report was prepared by Mr. George C. Hoff, Chief Materials Properties V Section of the Concrete iabcraLory, U. S. Army...compensating expansive cement concrete is to minimize cracking in concrete pavements and structures caused by drying shrinkage. The paper reviews the

  20. Stochastic game dynamics under demographic fluctuations

    PubMed Central

    Huang, Weini; Hauert, Christoph; Traulsen, Arne

    2015-01-01

    Frequency-dependent selection and demographic fluctuations play important roles in evolutionary and ecological processes. Under frequency-dependent selection, the average fitness of the population may increase or decrease based on interactions between individuals within the population. This should be reflected in fluctuations of the population size even in constant environments. Here, we propose a stochastic model that naturally combines these two evolutionary ingredients by assuming frequency-dependent competition between different types in an individual-based model. In contrast to previous game theoretic models, the carrying capacity of the population, and thus the population size, is determined by pairwise competition of individuals mediated by evolutionary games and demographic stochasticity. In the limit of infinite population size, the averaged stochastic dynamics is captured by deterministic competitive Lotka–Volterra equations. In small populations, demographic stochasticity may instead lead to the extinction of the entire population. Because the population size is driven by fitness in evolutionary games, a population of cooperators is less prone to go extinct than a population of defectors, whereas in the usual systems of fixed size the population would thrive regardless of its average payoff. PMID:26150518

  1. Entropy Based Modelling for Estimating Demographic Trends.

    PubMed

    Li, Guoqi; Zhao, Daxuan; Xu, Yi; Kuo, Shyh-Hao; Xu, Hai-Yan; Hu, Nan; Zhao, Guangshe; Monterola, Christopher

    2015-01-01

    In this paper, an entropy-based method is proposed to forecast the demographical changes of countries. We formulate the estimation of future demographical profiles as a constrained optimization problem, anchored on the empirically validated assumption that the entropy of age distribution is increasing in time. The procedure of the proposed method involves three stages, namely: 1) Prediction of the age distribution of a country's population based on an "age-structured population model"; 2) Estimation the age distribution of each individual household size with an entropy-based formulation based on an "individual household size model"; and 3) Estimation the number of each household size based on a "total household size model". The last stage is achieved by projecting the age distribution of the country's population (obtained in stage 1) onto the age distributions of individual household sizes (obtained in stage 2). The effectiveness of the proposed method is demonstrated by feeding real world data, and it is general and versatile enough to be extended to other time dependent demographic variables.

  2. Entropy Based Modelling for Estimating Demographic Trends

    PubMed Central

    Kuo, Shyh-Hao; Xu, Hai-Yan; Hu, Nan; Zhao, Guangshe; Monterola, Christopher

    2015-01-01

    In this paper, an entropy-based method is proposed to forecast the demographical changes of countries. We formulate the estimation of future demographical profiles as a constrained optimization problem, anchored on the empirically validated assumption that the entropy of age distribution is increasing in time. The procedure of the proposed method involves three stages, namely: 1) Prediction of the age distribution of a country’s population based on an “age-structured population model”; 2) Estimation the age distribution of each individual household size with an entropy-based formulation based on an “individual household size model”; and 3) Estimation the number of each household size based on a “total household size model”. The last stage is achieved by projecting the age distribution of the country’s population (obtained in stage 1) onto the age distributions of individual household sizes (obtained in stage 2). The effectiveness of the proposed method is demonstrated by feeding real world data, and it is general and versatile enough to be extended to other time dependent demographic variables. PMID:26382594

  3. Rural Household Demographics, Livelihoods and the Environment

    PubMed Central

    de Sherbinin, Alex; VanWey, Leah; McSweeney, Kendra; Aggarwal, Rimjhim; Barbieri, Alisson; Henry, Sabina; Hunter, Lori M.; Twine, Wayne

    2008-01-01

    This paper reviews and synthesizes findings from scholarly work on linkages among rural household demographics, livelihoods and the environment. Using the livelihood approach as an organizing framework, we examine evidence on the multiple pathways linking environmental variables and the following demographic variables: fertility, migration, morbidity and mortality, and lifecycles. Although the review draws on studies from the entire developing world, we find the majority of micro-level studies have been conducted in either marginal (mountainous or arid) or frontier environments, especially Amazonia. Though the linkages are mediated by many complex and often context-specific factors, there is strong evidence that dependence on natural resources intensifies when households lose human and social capital through adult morbidity and mortality, and qualified evidence for the influence of environmental factors on household decision-making regarding fertility and migration. Two decades of research on lifecycles and land-cover change at the farm level have yielded a number of insights about how households make use of different land-use and natural resource management strategies at different stages. A thread running throughout the review is the importance of managing risk through livelihood diversification, ensuring future income security, and culture-specific norms regarding appropriate and desirable activities and demographic responses. Recommendations for future research are provided. PMID:19190718

  4. Rural Household Demographics, Livelihoods and the Environment.

    PubMed

    de Sherbinin, Alex; Vanwey, Leah; McSweeney, Kendra; Aggarwal, Rimjhim; Barbieri, Alisson; Henry, Sabina; Hunter, Lori M; Twine, Wayne

    2008-02-01

    This paper reviews and synthesizes findings from scholarly work on linkages among rural household demographics, livelihoods and the environment. Using the livelihood approach as an organizing framework, we examine evidence on the multiple pathways linking environmental variables and the following demographic variables: fertility, migration, morbidity and mortality, and lifecycles. Although the review draws on studies from the entire developing world, we find the majority of micro-level studies have been conducted in either marginal (mountainous or arid) or frontier environments, especially Amazonia. Though the linkages are mediated by many complex and often context-specific factors, there is strong evidence that dependence on natural resources intensifies when households lose human and social capital through adult morbidity and mortality, and qualified evidence for the influence of environmental factors on household decision-making regarding fertility and migration. Two decades of research on lifecycles and land-cover change at the farm level have yielded a number of insights about how households make use of different land-use and natural resource management strategies at different stages. A thread running throughout the review is the importance of managing risk through livelihood diversification, ensuring future income security, and culture-specific norms regarding appropriate and desirable activities and demographic responses. Recommendations for future research are provided.

  5. Intelligent system to study demographic evolution

    NASA Astrophysics Data System (ADS)

    Rodrigues, M. de Fatima; Ramos, Carlos; Henriques, Pedro R.

    1999-02-01

    With three centuries of existence, the study of population's behavior implies the manipulation of large amounts of incomplete and imprecise data with high dimensionality. By virtue of its multidisciplinary character, the work in demography involves at least historicists, statisticians and computer scientists/programmers. Moreover, successful demographic analysis requires qualified experts, who have succeeded in analysing data through many views and relate different sources of information, including their personal knowledge of the epoch or regions under study. In this paper, we present an intelligent system to study demographic evolution (ISSDE). This system has a module based on on-line analytical processing (OLAP), which permits conducting multiple analysis, combining many data dimensions. It has a deductive database system, which allows the execution of elaborated queries through the database. It has another module for date treatment (generalization and/or reduction); and, at last, a data mining module to discover nontrivial relations hidden within data. We discover the data treatment procedure with two phases: data generalization and data reduction. In data generalization, utilizing knowledge about concept hierarchies and relevance of data, aggregation of attribute values is performed. In the data reduction phase, rough set theory is applied to compute the minimal attribute set. We highlight the advantages of combining attribute value generalization with rough set theory, to find a subset of attributes that lets the mining process discover more useful patterns, by providing results from the application of the C5.0 algorithm in a demographic relational database.

  6. Multiple scattering expansion with distortion

    NASA Astrophysics Data System (ADS)

    Tandy, P. C.; Thaler, R. M.

    1980-12-01

    A multiple scattering description of elastic scattering is formulated in terms of impulsive scatterings from single target nucleons and pairs of target nucleons. In this description, distortion effects on the projectile from the residual medium are also described by multiple scattering in terms of the same single and pair amplitudes. At the level of single scattering, this procedure yields the first order optical potential result of Kerman, McManus, and Thaler. When scattering from both single nucleons and pairs of nucleons is included, the method leads to a one-body integral equation which requires the physical projectile-nucleon and projectile-pair transition amplitudes as input. This input is similar, but not exactly equivalent to that required by the spectator expansion for the optical potential truncated at second order. A principal advantage of the present formulation is that there need be no explicit dependence upon the projection operator Q which projects off the target ground state. This feature introduces a scaling which appears to be a direct extension of the first order Kerman, McManus, and Thaler type of scaling. We follow up suggestions arising in the foregoing to show that the exact optical potential to second order in the spectator expansion can also be cast into a form having no explicit dependence upon Q, and requiring physical projectile-nucleon and projectile-pair transition amplitudes as input. NUCLEAR REACTIONS Multiple scattering from single nucleons, pairs of nucleons in nucleus. Distortion from residual medium. Optical potential. spectator expansion.

  7. Clinical grade expansion of MSCs.

    PubMed

    Capelli, C; Pedrini, O; Valgardsdottir, R; Da Roit, F; Golay, J; Introna, M

    2015-12-01

    Producing advanced therapy medicinal products (ATMP) according to Good Manufacturing Practice (GMP) guidelines represents a global challenge for the expansion of cells intended for human use. Mesenchymal stromal cells (MSCs) from different sources are one of the most actively developed cell type for a variety of clinical applications in cellular therapy. Complying with GMP means defining accurately both the production process and the release criteria required for a final safe product. We have here reported our manufacturing experience on 103 consecutive clinical-grade in vitro expansions of both bone marrow-derived and umbilical cord-derived mesenchymal stromal cells together with description of methods and reagents utilized in our Cell Factory. The same animal- and serum-free medium, additioned with human platelet lysate, has been used for all the expansions performed. This is the largest experience published so far with this alternative and clinical-grade reagent (compared to the traditional fetal bovine serum) and shows the feasibility and the reproducibility of the method. Indeed, we have been able to produce a sufficient number of MSCs to treat 57 patients so far, enrolled in 7 different experimental phase I/II protocols. Copyright © 2015 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.

  8. Femtosecond dynamics of cluster expansion

    NASA Astrophysics Data System (ADS)

    Gao, Xiaohui; Wang, Xiaoming; Shim, Bonggu; Arefiev, Alexey; Tushentsov, Mikhail; Breizman, Boris; Downer, Mike

    2010-03-01

    Noble gas clusters irradiated by intense ultrafast laser expand quickly and become typical plasma in picosecond time scale. During the expansion, the clustered plasma demonstrates unique optical properties such as strong absorption and positive contribution to the refractive index. Here we studied cluster expansion dynamics by fs-time-resolved refractive index and absorption measurements in cluster gas jets after ionization and heating by an intense pump pulse. The refractive index measured by frequency domain interferometry (FDI) shows the transient positive peak of refractive index due to clustered plasma. By separating it from the negative contribution of the monomer plasma, we are able to determine the cluster fraction. The absorption measured by a delayed probe shows the contribution from clusters of various sizes. The plasma resonances in the cluster explain the enhancement of the absorption in our isothermal expanding cluster model. The cluster size distribution can be determined. A complete understanding of the femtosecond dynamics of cluster expansion is essential in the accurate interpretation and control of laser-cluster experiments such as phase-matched harmonic generation in cluster medium.

  9. [The keys to the western demographic "miracle"].

    PubMed

    Burguiere, A

    1991-09-01

    Unlike most historical disciplines which had access to copious sources of data before refining their analytical methods, historical demography has almost simultaneously acquired data and developed rigorous analytical methods. French parish records did not attract detailed scrutiny until after World War II, but family reconstitution and other methods of exploitation were soon perfected. The continuing paradox of historical demography is that its statistical methods are rigorous but data remain sparse. Several dozen villages and a few cities have emerged from a vast obscurity but entire regions remain unexplored. Nonetheless, the study of preindustrial populations has progressed more in the past 20 years than has study of populations in the industrial era. Complex phenomena such as the fertility decline and incipient control of birth rates in late 18th century Europe have been studied or explained more adequately than has the inverse phenomenon, the baby boom of the 1940s. A major impetus to historical demography in Europe was the desire of demographers at the National Institute of Demographic Studies to understand Europe's fertility decline through knowledge of the mechanisms that initially caused it to occur. The diversity of apparent demographic models that have resulted from the works of historical demographers has caused various regional models to be proposed for France in the 17th and 18th centuries. It is clear from statistical analysis of available data that by the 18th century, fertility control was practiced by the mass of the French population, but the interpretation of this fact is problematic. The change in fertility behavior must reflect a deeper change in mentalities. The diffusion of contraception in the 18th century did not represent a transgression of the teachings of the Catholic Church as much as a change in attitudes toward life in which the future security of children was increasingly sought in education and improved living standards, and in

  10. Reconstruction of a beech population bottleneck using archival demographic information and Bayesian analysis of genetic data.

    PubMed

    Lander, Tonya A; Oddou-Muratorio, Sylvie; Prouillet-Leplat, Helene; Klein, Etienne K

    2011-12-01

    Range expansion and contraction has occurred in the history of most species and can seriously impact patterns of genetic diversity. Historical data about range change are rare and generally appropriate for studies at large scales, whereas the individual pollen and seed dispersal events that form the basis of geneflow and colonization generally occur at a local scale. In this study, we investigated range change in Fagus sylvatica on Mont Ventoux, France, using historical data from 1838 to the present and approximate Bayesian computation (ABC) analyses of genetic data. From the historical data, we identified a population minimum in 1845 and located remnant populations at least 200 years old. The ABC analysis selected a demographic scenario with three populations, corresponding to two remnant populations and one area of recent expansion. It also identified expansion from a smaller ancestral population but did not find that this expansion followed a population bottleneck, as suggested by the historical data. Despite a strong support to the selected scenario for our data set, the ABC approach showed a low power to discriminate among scenarios on average and a low ability to accurately estimate effective population sizes and divergence dates, probably due to the temporal scale of the study. This study provides an unusual opportunity to test ABC analysis in a system with a well-documented demographic history and identify discrepancies between the results of historical, classical population genetic and ABC analyses. The results also provide valuable insights into genetic processes at work at a fine spatial and temporal scale in range change and colonization.

  11. Estimating synchronous demographic changes across populations using hABC and its application for a herpetological community from northeastern Brazil.

    PubMed

    Gehara, Marcelo; Garda, Adrian A; Werneck, Fernanda P; Oliveira, Eliana F; da Fonseca, Emanuel M; Camurugi, Felipe; Magalhães, Felipe de M; Lanna, Flávia M; Sites, Jack W; Marques, Ricardo; Silveira-Filho, Ricardo; São Pedro, Vinícius A; Colli, Guarino R; Costa, Gabriel C; Burbrink, Frank T

    2017-09-01

    Many studies propose that Quaternary climatic cycles contracted and/or expanded the ranges of species and biomes. Strong expansion-contraction dynamics of biomes presume concerted demographic changes of associated fauna. The analysis of temporal concordance of demographic changes can be used to test the influence of Quaternary climate on diversification processes. Hierarchical approximate Bayesian computation (hABC) is a powerful and flexible approach that models genetic data from multiple species, and can be used to estimate the temporal concordance of demographic processes. Using available single-locus data, we can now perform large-scale analyses, both in terms of number of species and geographic scope. Here, we first compared the power of four alternative hABC models for a collection of single-locus data. We found that the model incorporating an a priori hypothesis about the timing of simultaneous demographic change had the best performance. Second, we applied the hABC models to a data set of seven squamate and four amphibian species occurring in the Seasonally Dry Tropical Forests (Caatinga) in northeastern Brazil, which, according to paleoclimatic evidence, experienced an increase in aridity during the Pleistocene. If this increase was important for the diversification of associated xeric-adapted species, simultaneous population expansions should be evident at the community level. We found a strong signal of synchronous population expansion in the Late Pleistocene, supporting the increase of the Caatinga during this time. This expansion likely enhanced the formation of communities adapted to high aridity and seasonality and caused regional extirpation of taxa adapted to wet forest. © 2017 John Wiley & Sons Ltd.

  12. Chemical recombination in an expansion tube

    NASA Technical Reports Server (NTRS)

    Bakos, Robert J.; Morgan, Richard G.

    1994-01-01

    The note describes the theoretical basis of chemical recombination in an expansion tube which simulates energy, Reynolds number, and stream chemistry at near-orbital velocities. Expansion tubes can satisfy ground-based hypersonic propulsion and aerothermal testing requirements.

  13. A Power Series Expansion and Its Applications

    ERIC Educational Resources Information Center

    Chen, Hongwei

    2006-01-01

    Using the power series solution of a differential equation and the computation of a parametric integral, two elementary proofs are given for the power series expansion of (arcsin x)[squared], as well as some applications of this expansion.

  14. A Power Series Expansion and Its Applications

    ERIC Educational Resources Information Center

    Chen, Hongwei

    2006-01-01

    Using the power series solution of a differential equation and the computation of a parametric integral, two elementary proofs are given for the power series expansion of (arcsin x)[squared], as well as some applications of this expansion.

  15. Nonlinear effects on composite laminate thermal expansion

    NASA Technical Reports Server (NTRS)

    Hashin, Z.; Rosen, B. W.; Pipes, R. B.

    1979-01-01

    Analyses of Graphite/Polyimide laminates shown that the thermomechanical strains cannot be separated into mechanical strain and free thermal expansion strain. Elastic properties and thermal expansion coefficients of unidirectional Graphite/Polyimide specimens were measured as a function of temperature to provide inputs for the analysis. The + or - 45 degrees symmetric Graphite/Polyimide laminates were tested to obtain free thermal expansion coefficients and thermal expansion coefficients under various uniaxial loads. The experimental results demonstrated the effects predicted by the analysis, namely dependence of thermal expansion coefficients on load, and anisotropy of thermal expansion under load. The significance of time dependence on thermal expansion was demonstrated by comparison of measured laminate free expansion coefficients with and without 15 day delay at intermediate temperature.

  16. Industrial trials of low-expansivity sawblades

    Treesearch

    Jeanne D. Danielson; Frank J. Worzala

    1992-01-01

    Low-expansivity alloys have the potential to reduce thermal instability of sawblades during the sawing operation. In preliminary industrial trials of sawblades made of low-expansivity alloy, sawing accuracy was improved 22 to 38 percent during normal sawing. When saws made of a low-expansivity alloy were operated with a large temperature gradient across the blade,...

  17. Mapping populations at risk: improving spatial demographic data for infectious disease modeling and metric derivation

    PubMed Central

    2012-01-01

    The use of Global Positioning Systems (GPS) and Geographical Information Systems (GIS) in disease surveys and reporting is becoming increasingly routine, enabling a better understanding of spatial epidemiology and the improvement of surveillance and control strategies. In turn, the greater availability of spatially referenced epidemiological data is driving the rapid expansion of disease mapping and spatial modeling methods, which are becoming increasingly detailed and sophisticated, with rigorous handling of uncertainties. This expansion has, however, not been matched by advancements in the development of spatial datasets of human population distribution that accompany disease maps or spatial models. Where risks are heterogeneous across population groups or space or dependent on transmission between individuals, spatial data on human population distributions and demographic structures are required to estimate infectious disease risks, burdens, and dynamics. The disease impact in terms of morbidity, mortality, and speed of spread varies substantially with demographic profiles, so that identifying the most exposed or affected populations becomes a key aspect of planning and targeting interventions. Subnational breakdowns of population counts by age and sex are routinely collected during national censuses and maintained in finer detail within microcensus data. Moreover, demographic and health surveys continue to collect representative and contemporary samples from clusters of communities in low-income countries where census data may be less detailed and not collected regularly. Together, these freely available datasets form a rich resource for quantifying and understanding the spatial variations in the sizes and distributions of those most at risk of disease in low income regions, yet at present, they remain unconnected data scattered across national statistical offices and websites. In this paper we discuss the deficiencies of existing spatial population datasets

  18. Demographics and treatment of the American family.

    PubMed

    Jojic, Mirjana; Raj, Abita; Wilkins, Kerry; Treadwell, Robyn; Caussade-Rodriguez, Eduardo; Blum, Joshua

    2012-04-01

    There have been numerous changes to the US family over the past several decades. Traditional family roles have changed, and the conception of what Americans consider a 'family' has likewise shifted with differing societal views regarding gender, gender roles, race, and ethnicity. This review examines demographics of the American family as well as a number of family therapies that have been historically and are presently used to treat family problems. We expect that with the changes present in US society, family therapies will need to continue to be sensitive and adaptive to these shifts in order to be effective.

  19. [Demographic development of Croatia, 1991-1994].

    PubMed

    Lajic, I

    1995-01-01

    "The demographic development of Croatia in the period 1991-1994, marked by... Serbian aggression, the state of ¿half-war', and the war in Bosnia and Hercegovina, should be described as irregular--its components being determined by the above conditions. This proves especially true concerning forced migrations and their past and future influence on population change. The paper analyzes the insufficiently studied topic of war mortality, as well as various dimensions of the refugee population. It also emphasizes several structural characteristics of the population, particularly its ethnic structure, and the population dynamics in the temporarily occupied territories." (EXCERPT)

  20. Patterns of demographic change in the Americas.

    PubMed

    Ubelaker, D H

    1992-06-01

    Considerable scholarly debate has focused on the nature of demographic change in the Americas before and after 1492. Recent research on human skeletal samples and related archeological materials suggests that morbidity and mortality were increasing throughout much of the Western Hemisphere before 1492 in response to increased population density, increased sedentism, and changing subsistence. The evidence suggests that after 1492 population reduction was caused not by continental pandemics but by localized or regional epidemics augmented by social and economic disruption. The twentieth century has witnessed remarkable Native American population recovery, fueled both by improvements in health care and changing definitions of "being Indian."

  1. [Demographic Dynamics and Educational Inequality in Mexico].

    PubMed

    Giorguli Saucedo, Silvia E; Vargas Valle, Eunice D; Ulloa, Viviana Salinas; Hubert, Celia; Potter, Joseph E

    This paper seeks to explore the link between educational processes and Mexico's demographic dynamic. In the tradition of thought on population and development, it has been hypothesized that the population growth rate, family size and migration influence the accumulation of human capital among the school-age population. This study explores the link between the academic performance of youth between the age of 14 and 23 and the youth dependency ratio, teenage fertility and internal and international migration, using data aggregated at the municipal level for the year 2000. The analysis uses indicators on the educational supply at the municipal level based on the administrative statistics of the Public Education Secretariat (SEP).

  2. Cosmic growth and expansion conjoined

    NASA Astrophysics Data System (ADS)

    Linder, Eric V.

    2017-01-01

    Cosmological measurements of both the expansion history and growth history have matured, and the two together provide an important test of general relativity. We consider their joint evolutionary track, showing that this has advantages in distinguishing cosmologies relative to considering them individually or at isolated redshifts. In particular, the joint comparison relaxes the shape degeneracy that makes fσ8(z) curves difficult to separate from the overall growth amplitude. The conjoined method further helps visualization of which combinations of redshift ranges provide the clearest discrimination. We examine standard dark energy cosmologies, modified gravity, and "stuttering" growth, each showing distinct signatures.

  3. Calculation of Turbulent Expansion Processes

    NASA Technical Reports Server (NTRS)

    Tollmien, Walter

    1945-01-01

    On the basis of certain formulas recently established by L. Prandtl for the turbulent interchange of momentum in stationary flows, various cases of "free turbulence" - that is, of flows without boundary walls - are treated in the present report. Prandtl puts the apparent shearing stress introduced by the turbulent momentum interchange. This present report deals first with the mixing of an air stream of uniform velocity with the adjacent still air, than with the expansion or diffusion of an air jet in the surrounding air space.

  4. Space nuclear system expansion joints

    NASA Technical Reports Server (NTRS)

    Whitaker, W. D.; Shimazki, T. T.

    1973-01-01

    The engineering, design, and fabrication status of the expansion joint unit (EJU) to be employed in the NaK primary coolant piping loop of the 5-kwe Reactor thermoelectric system are described. Four EJU's are needed in the NaK primary coolant piping loop. The four EJU's which will be identical, utilize bellows as the flexing member, are hermetically sealed, and provide double containment. The bellows are of a nested-formed design, and are to be constructed of 1-ply thickness of 0.010-in. Inconel 718. The EJU's provide a minimum piping load margin of safety of +0.22.

  5. Genetic variation reveals large-scale population expansion and migration during the expansion of Bantu-speaking peoples.

    PubMed

    Li, Sen; Schlebusch, Carina; Jakobsson, Mattias

    2014-10-22

    The majority of sub-Saharan Africans today speak a number of closely related languages collectively referred to as 'Bantu' languages. The current distribution of Bantu-speaking populations has been found to largely be a consequence of the movement of people rather than a diffusion of language alone. Linguistic and single marker genetic studies have generated various hypotheses regarding the timing and the routes of the Bantu expansion, but these hypotheses have not been thoroughly investigated. In this study, we re-analysed microsatellite markers typed for large number of African populations that-owing to their fast mutation rates-capture signatures of recent population history. We confirm the spread of west African people across most of sub-Saharan Africa and estimated the expansion of Bantu-speaking groups, using a Bayesian approach, to around 5600 years ago. We tested four different divergence models for Bantu-speaking populations with a distribution comprising three geographical regions in Africa. We found that the most likely model for the movement of the eastern branch of Bantu-speakers involves migration of Bantu-speaking groups to the east followed by migration to the south. This model, however, is only marginally more likely than other models, which might indicate direct movement from the west and/or significant gene flow with the western Branch of Bantu-speakers. Our study use multi-loci genetic data to explicitly investigate the timing and mode of the Bantu expansion and it demonstrates that west African groups rapidly expanded both in numbers and over a large geographical area, affirming the fact that the Bantu expansion was one of the most dramatic demographic events in human history.

  6. Genetic variation reveals large-scale population expansion and migration during the expansion of Bantu-speaking peoples

    PubMed Central

    Li, Sen; Schlebusch, Carina; Jakobsson, Mattias

    2014-01-01

    The majority of sub-Saharan Africans today speak a number of closely related languages collectively referred to as ‘Bantu’ languages. The current distribution of Bantu-speaking populations has been found to largely be a consequence of the movement of people rather than a diffusion of language alone. Linguistic and single marker genetic studies have generated various hypotheses regarding the timing and the routes of the Bantu expansion, but these hypotheses have not been thoroughly investigated. In this study, we re-analysed microsatellite markers typed for large number of African populations that—owing to their fast mutation rates—capture signatures of recent population history. We confirm the spread of west African people across most of sub-Saharan Africa and estimated the expansion of Bantu-speaking groups, using a Bayesian approach, to around 5600 years ago. We tested four different divergence models for Bantu-speaking populations with a distribution comprising three geographical regions in Africa. We found that the most likely model for the movement of the eastern branch of Bantu-speakers involves migration of Bantu-speaking groups to the east followed by migration to the south. This model, however, is only marginally more likely than other models, which might indicate direct movement from the west and/or significant gene flow with the western Branch of Bantu-speakers. Our study use multi-loci genetic data to explicitly investigate the timing and mode of the Bantu expansion and it demonstrates that west African groups rapidly expanded both in numbers and over a large geographical area, affirming the fact that the Bantu expansion was one of the most dramatic demographic events in human history. PMID:25209939

  7. Study of stellarator devices by expansion techniques

    SciTech Connect

    Johnson, J.L.; Boozer, A.H.; Koniges, A.E.; Kuo-Petravic, G.; Manickam, J.; Monticello, D.A.; Mynick, H.; Park, W.; Reiman, A.; Rewoldt, G.

    1984-09-01

    Expansion techniques have led to new tools for designing stellarators and interpreting experimental results. The stellarator expansion is coupled with Hamiltonian techniques to investigate the effect of plasma pressure on magnetic surface structure. An expansion for nonplanar-axis systems is described. A reduced-equation initial-value formalism is used to create three-dimensional heliac equilibria. A low-..beta.. expansion with an auxiliary expansion about the magnetic axis makes possible the determination of island widths in heliacs and allows analytic determination of the effect of equilibrium modifications associated with plasma pressure on radial transport.

  8. DEMOGRAPHIC UNCERTAINTY IN ECOLOGICAL RISK ASSESSMENTS. (R825347)

    EPA Science Inventory

    We built a Ricker's model incorporating demographic stochasticity to simulate the effects of demographic uncertainty on responses of gray-tailed vole (Microtus canicaudus) populations to pesticide applications. We constructed models with mark-recapture data collected from populat...

  9. DEMOGRAPHIC UNCERTAINTY IN ECOLOGICAL RISK ASSESSMENTS. (R825347)

    EPA Science Inventory

    We built a Ricker's model incorporating demographic stochasticity to simulate the effects of demographic uncertainty on responses of gray-tailed vole (Microtus canicaudus) populations to pesticide applications. We constructed models with mark-recapture data collected from populat...

  10. Can Establishment Success Be Determined through Demographic Parameters? A Case Study on Five Introduced Bird Species

    PubMed Central

    Sanz-Aguilar, Ana; Anadón, José D.; Edelaar, Pim; Carrete, Martina; Tella, José Luis

    2014-01-01

    The dominant criterion to determine when an introduced species is established relies on the maintenance of a self-sustaining population in the area of introduction, i.e. on the viability of the population from a demographic perspective. There is however a paucity of demographic studies on introduced species, and establishment success is thus generally determined by expert opinion without undertaking population viability analyses (PVAs). By means of an intensive five year capture-recapture monitoring program (involving >12,000 marked individuals) we studied the demography of five introduced passerine bird species in southern Spain which are established and have undergone a fast expansion over the last decades. We obtained useful estimates of demographic parameters (survival and reproduction) for one colonial species (Ploceus melanocephalus), confirming the long-term viability of its local population through PVAs. However, extremely low recapture rates prevented the estimation of survival parameters and population growth rates for widely distributed species with low local densities (Estrilda troglodytes and Amandava amandava) but also for highly abundant yet non-colonial species (Estrilda astrild and Euplectes afer). Therefore, determining the establishment success of introduced passerine species by demographic criteria alone may often be troublesome even when devoting much effort to field-work. Alternative quantitative methodologies such as the analysis of spatio-temporal species distributions complemented with expert opinion deserve thus their role in the assessment of establishment success of introduced species when estimates of demographic parameters are difficult to obtain, as is generally the case for non-colonial, highly mobile passerines. PMID:25333743

  11. Can establishment success be determined through demographic parameters? A case study on five introduced bird species.

    PubMed

    Sanz-Aguilar, Ana; Anadón, José D; Edelaar, Pim; Carrete, Martina; Tella, José Luis

    2014-01-01

    The dominant criterion to determine when an introduced species is established relies on the maintenance of a self-sustaining population in the area of introduction, i.e. on the viability of the population from a demographic perspective. There is however a paucity of demographic studies on introduced species, and establishment success is thus generally determined by expert opinion without undertaking population viability analyses (PVAs). By means of an intensive five year capture-recapture monitoring program (involving >12,000 marked individuals) we studied the demography of five introduced passerine bird species in southern Spain which are established and have undergone a fast expansion over the last decades. We obtained useful estimates of demographic parameters (survival and reproduction) for one colonial species (Ploceus melanocephalus), confirming the long-term viability of its local population through PVAs. However, extremely low recapture rates prevented the estimation of survival parameters and population growth rates for widely distributed species with low local densities (Estrilda troglodytes and Amandava amandava) but also for highly abundant yet non-colonial species (Estrilda astrild and Euplectes afer). Therefore, determining the establishment success of introduced passerine species by demographic criteria alone may often be troublesome even when devoting much effort to field-work. Alternative quantitative methodologies such as the analysis of spatio-temporal species distributions complemented with expert opinion deserve thus their role in the assessment of establishment success of introduced species when estimates of demographic parameters are difficult to obtain, as is generally the case for non-colonial, highly mobile passerines.

  12. Modeling and predicting community responses to events using cultural demographics

    NASA Astrophysics Data System (ADS)

    Jaenisch, Holger M.; Handley, James W.; Hicklen, Michael L.

    2007-04-01

    This paper describes a novel capability for modeling and predicting community responses to events (specifically military operations) related to demographics. Demographics in the form of words and/or numbers are used. As an example, State of Alabama annual demographic data for retail sales, auto registration, wholesale trade, shopping goods, and population were used; from which we determined a ranked estimate of the sensitivity of the demographic parameters on the cultural group response. Our algorithm and results are summarized in this paper.

  13. Demographic and Anthropometric Assessment of US Army Anthropometric Data Base

    DTIC Science & Technology

    1985-08-01

    demographics , because the demographic composition of the Army is influenced by many factors . Among these are: recruiting priorities, the state of the...34ST -I-BILAD TECHNICAL REPORT AD NATICK/TR-86/004 DEMOGRAPHIC AND ANTHROPOMETRIC ASSESSMENT OF US ARMY SANTHROPOMETRIC DATA BASE BY DTIC BRUCE...TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED Demographic and Anthropometric Assessment of Interim Report, Task I, eSeptember 1984 - April

  14. Demographic challenges across the European Union Member States.

    PubMed

    Megyesiová, Silvia; Hajduová, Zuzana

    2012-07-01

    The Member States of the European Union are undergoing major demographic changes; these changes are slow but significant. The demographic picture in the EU-27 is clearer: population growth is mainly the result of immigration, fertility is far below the replacement ratio, and the population is growing older, which will be a key demographic challenge in many Member States. All the actual demographic trends will have consequences for health care systems. Copyright 2012, SLACK Incorporated.

  15. Profile: Nanoro Health and Demographic Surveillance System.

    PubMed

    Derra, Karim; Rouamba, Eli; Kazienga, Adama; Ouedraogo, Sayouba; Tahita, Marc C; Sorgho, Hermann; Valea, Innocent; Tinto, Halidou

    2012-10-01

    The Nanoro Health and Demographic Surveillance System (HDSS), located in the rural centre of Burkina Faso, was established in 2009 by the Clinical Research Unit of Nanoro with the aim of providing a core framework for clinical trials and also to support the Burkina Faso health authorities in generating epidemiological data that can contribute to the setup and assessment of health interventions. In the baseline of initial census, 54 781 individuals were recorded of whom 56.1% are female. After the initial census, vital events such as pregnancies, births, migrations and deaths have been monitored, and data on individuals and household characteristics are updated during regular 4-monthly household visits. The available data are categorized into demographic, cultural, socio-economic and health information, and are used for monitoring and evaluation of population development issues. As a young site, our objective has been to strengthen our skills and knowledge and share new scientific experiences with INDEPTH and HDSS sites in Burkina Faso. In addition, all data produced by the Nanoro HDSS will be made publicly available through the INDEPTH data sharing system.

  16. The pitfalls of planning for demographic change.

    PubMed

    Stock, Gregory B

    2004-06-01

    As we begin to understand the biology of aging, it will be ever more tempting to try to plan for the social consequences of the coming biomedical interventions in this arena. However, this will remain a daunting task, because the larger consequences of the arrival of antiaging interventions will greatly depend on the relative character and timing of the specific procedures that emerge. Three basic classes of interventions are likely: ones that slow aging in adults, ones that reverse aging in adults, and embryonic interventions that modify the overall trajectory of human aging. The consequences of each will differ significantly in the time required before noticeable demographic shifts begin to manifest in the human population, and in the social and political changes the interventions evoke. The specific societal consequences generally will arrive long before the demographic ones, and will hinge on the technical details of the interventions themselves--their complexity, physiological targets, modes of delivery, costs, unpleasantness, and the character and frequency of side effects.

  17. Changing demographics: what to watch for.

    PubMed

    Morrison, P A

    1987-07-01

    Four broad demographic transformations: 1) the population's reconfiguration into smaller household units, especially those comprised of persons living alone; 2) changing employment patterns, notably the shift of married women into paid employment and the resulting proliferation of dual-earner families; 3) transformations in the population's age composition; and 4) the geography of growth in terms of regions that will gain or lose population--can be expected to have a profound impact on opportunities and challenges facing the business sector. The number of future households is projected to increase from 88.6 million in 1986 to 101.5 million by 1996. The sharpest gains will be among households headed by persons ranging in age from the late 30s to the early 50s. The fastest growth through the year 2000 is expected to occur in the Mountain states of the US. Business economists should be alert to these demographic analyses both to spot emerging growth markets and to identify long-term strategic issues, especially as the labor market changes. It will be increasingly important to differentiate time-sensitive from price-sensitive consumers.

  18. Demographic and health surveys: a profile.

    PubMed

    Corsi, Daniel J; Neuman, Melissa; Finlay, Jocelyn E; Subramanian, S V

    2012-12-01

    Demographic and Health Surveys (DHS) are comparable nationally representative household surveys that have been conducted in more than 85 countries worldwide since 1984. The DHS were initially designed to expand on demographic, fertility and family planning data collected in the World Fertility Surveys and Contraceptive Prevalence Surveys, and continue to provide an important resource for the monitoring of vital statistics and population health indicators in low- and middle-income countries. The DHS collect a wide range of objective and self-reported data with a strong focus on indicators of fertility, reproductive health, maternal and child health, mortality, nutrition and self-reported health behaviours among adults. Key advantages of the DHS include high response rates, national coverage, high quality interviewer training, standardized data collection procedures across countries and consistent content over time, allowing comparability across populations cross-sectionally and over time. Data from DHS facilitate epidemiological research focused on monitoring of prevalence, trends and inequalities. A variety of robust observational data analysis methods have been used, including cross-sectional designs, repeated cross-sectional designs, spatial and multilevel analyses, intra-household designs and cross-comparative analyses. In this profile, we present an overview of the DHS along with an introduction to the potential scope for these data in contributing to the field of micro- and macro-epidemiology. DHS datasets are available for researchers through MEASURE DHS at www.measuredhs.com.

  19. Incidence and Demographics of Childhood Ptosis

    PubMed Central

    Griepentrog, Gregory J.; Diehl, Nancy; Mohney, Brian G.

    2012-01-01

    Purpose To report the incidence and demographics of childhood ptosis diagnosed over a 40-year period in a well-defined population. Design Retrospective, population-based cohort study. Participants Patients (< 19 years) diagnosed with childhood ptosis as residents of Olmsted County, Minnesota, from January 1, 1965, through December 31, 2004 Methods The medical records of all potential patients identified by the Rochester Epidemiology Project were reviewed. Main Outcome Measures Calculated annual age- and sex-specific incidence rates and demographic information. Results A total of 107 children were diagnosed with ptosis during the 40-year period, yielding an incidence of 7.9/100,000 < 19 years (95% confidence interval [CI]: 6.4-9.5) of age. Ninety-six (89.7%) of the 107 were congenital in onset, 81 (75%) of which had simple congenital ptosis, yielding a birth prevalence of 1 in 842 births. A family history of childhood ptosis was present in twelve percent of queried patients with simple congenital ptosis. Three (4%) of the simple congenital ptosis cases were bilateral and 55 (68%) of the unilateral cases involved the left upper eyelid (95% CI: 57%-78%, p<0.001). Conclusion Childhood ptosis was diagnosed in 7.9 per 100,000 patients less than 19 years (95% CI: 6.4-9.5). Simple congenital ptosis was the most prevalent form, occurring in 1 in 842 births, and significantly more likely to involve the left side. PMID:21496927

  20. Socio-demographic Factors of Geriatric Depression

    PubMed Central

    Barua, Ankur; Ghosh, M. K.; Kar, N.; Basilio, M. A.

    2010-01-01

    Background: Depression is a common mental health problem in geriatric population and the overall prevalence rate of depression in this age group varies between 10 and 20%. Objective: To study the socio-demographic factors associated with depression in geriatric population. Materials and Methods: A systematic review was done on 74 community-based mental health surveys on depression in geriatric population, which were conducted in the continents of Asia, Europe, Australia, North America, and South America. All the studies were conducted between 1955 and 2005. The researchers had included only community-based cross-sectional surveys and some prospective studies that had not excluded depression on baseline. These studies were conducted on homogenous community of geriatric population in the world, who were selected by simple random sampling technique. A qualitative analysis was conducted to study the socio-demographic factors of depression. Results and Conclusion: The two non-modifiable risk factors found to be significantly associated with depression in geriatric population were “older age group” and “female gender”. However, the potentially modifiable risk factors for depression in the geriatric population were identified as low socioeconomic status, loss of spouse, living alone, chronic co-morbidities, cognitive impairment, bereavement and restricted activities of daily living (ADL). PMID:21716860

  1. Socio-demographic Factors of Geriatric Depression.

    PubMed

    Barua, Ankur; Ghosh, M K; Kar, N; Basilio, M A

    2010-07-01

    Depression is a common mental health problem in geriatric population and the overall prevalence rate of depression in this age group varies between 10 and 20%. To study the socio-demographic factors associated with depression in geriatric population. A systematic review was done on 74 community-based mental health surveys on depression in geriatric population, which were conducted in the continents of Asia, Europe, Australia, North America, and South America. All the studies were conducted between 1955 and 2005. The researchers had included only community-based cross-sectional surveys and some prospective studies that had not excluded depression on baseline. These studies were conducted on homogenous community of geriatric population in the world, who were selected by simple random sampling technique. A qualitative analysis was conducted to study the socio-demographic factors of depression. The two non-modifiable risk factors found to be significantly associated with depression in geriatric population were "older age group" and "female gender". However, the potentially modifiable risk factors for depression in the geriatric population were identified as low socioeconomic status, loss of spouse, living alone, chronic co-morbidities, cognitive impairment, bereavement and restricted activities of daily living (ADL).

  2. [Freedom in contraception: opinion of a demographer].

    PubMed

    Vincent, P

    1957-04-01

    Despite his belief, in common with that of most French demographers, that the French population is in danger of declining, this author favors legalized contraception in France. The Law of 1920 forbade contraceptive devices and propaganda. The author blamed many demographers for confusing demography with doctrine. He agreed, with a Catholic writer, that birth limitation is not necessarily synonymous with birth control i.e., use of contraceptives. Currently in France, people prefer coitus interruptus and spermicides, which they consider hygienic, but they dislike condoms and rarely use diaphragms, since it is illegal for physicians to prescribe them. The author's reasons for believing that legalizing contraception would have little impact on French population growth include: single people would use better methods, but then increase their sexual activity; young married couples are not motivated to use a secure method until they complete their families; diaphragms require premeditation and the spermidices are expensive, so they will probably not replace the Ogino rhythm method. People will probably continue to use coitus interruptus which is quute effective. Definite advantages of liberalized contraception will be reduced numbers of abortions, illegitimate births, adolescent pregnancies and forced marriages. He concludes that the principle advantage would be reversal of a hypocritical policy toward contraception.

  3. Demographic Characteristics of World Class Jamaican Sprinters

    PubMed Central

    Irving, Rachael; Charlton, Vilma; Morrison, Errol; Facey, Aldeam; Buchanan, Oral

    2013-01-01

    The dominance of Jamaican sprinters in international meets remains largely unexplained. Proposed explanations include demographics and favorable physiological characteristics. The aim of this study was to analyze the demographic characteristics of world class Jamaican sprinters. Questionnaires administered to 120 members of the Jamaican national team and 125 controls elicited information on place of birth, language, ethnicity, and distance and method of travel to school. Athletes were divided into three groups based on athletic disciplines: sprint (s: 100–400 m; n = 80), jump and throw (j/t: jump and throw; n = 25) and, middle distance (md: 800–3000 m; n = 15). Frequency differences between groups were assessed using chi-square tests. Regional or county distribution of sprint differed from that of middle distance (P < 0.001) but not from that of jump and throw athletes (P = 0.24) and that of controls (P = 0.59). Sprint athletes predominately originated from the Surrey county (s = 46%, j/t = 37%, md = 17, C = 53%), whilst middle distance athletes exhibited excess from the Middlesex county (md = 60%). The language distribution of all groups showed uniformity with a predominance of English. A higher proportion of middle distance and jump and throw athletes walked to school (md = 80%, j/t = 52%, s = 10%, and C = 12%) and travelled greater distances to school. In conclusion, Jamaica's success in sprinting may be related to environmental and social factors. PMID:24396303

  4. Demographic drivers of functional composition dynamics.

    PubMed

    Muscarella, Robert; Lohbeck, Madelon; Martínez-Ramos, Miguel; Poorter, Lourens; Rodríguez-Velázquez, Jorge Enrique; van Breugel, Michiel; Bongers, Frans

    2017-08-20

    Mechanisms of community assembly and ecosystem function are often analyzed using community-weighted mean trait values (CWMs). We present a novel conceptual framework to quantify the contribution of demographic processes (i.e., growth, recruitment, and mortality) to temporal changes in CWMs. We used this framework to analyze mechanisms of secondary succession in wet tropical forests in Mexico. Seed size increased over time, reflecting a trade-off between colonization by small seeds early in succession, to establishment by large seeds later in succession. Specific leaf area (SLA) and leaf phosphorus content decreased over time, reflecting a trade-off between fast growth early in succession vs. high survival late in succession. On average, CWM shifts were driven mainly (70%) by growth of surviving trees that comprise the bulk of standing biomass, then mortality (25%), and weakly by recruitment (5%). Trait shifts of growing and recruiting trees mirrored the CWM trait shifts, and traits of dying trees did not change during succession, indicating that these traits are important for recruitment and growth, but not for mortality, during the first 30 yr of succession. Identifying the demographic drivers of functional composition change links population dynamics to community change, and enhances insights into mechanisms of succession. © 2017 by the Ecological Society of America.

  5. Children with limb deficiencies: demographic characteristics.

    PubMed

    Al-Worikat, Abdel Fattah; Dameh, Walid

    2008-03-01

    The aim of this study is to determine the demographic data for amputations in children in relation of age, sex, level and cause of amputation. Data were collected from the records of amputees who attended the prosthetic clinic at the Royal Rehabilitation Center, King Hussein Medical Centre, Jordan, between 1 January 1995 and 31 December 2005. Demographic data (age, sex, level and cause of amputation) were analyzed. Some 120 children with different levels of amputation were included with mean age of 6.2 years. There were 64 (53.3%) males and 56 (46.7%) females. Male to female ratio was 1.15:1. The dominant level of amputation was trans-radial in 10 patients (15.62%) in the upper limb and trans-tibial in 18 patients (28.12%) in the lower limb. The dominant cause of amputation was congenital deficiency in 56 patients (46.67%) followed by trauma in 48 (40%). The results of this study presented greater similarities to others in the literature, congenital limb deficiency being the dominant cause of amputation in children. This study helps in planning the needs for materials and budgets for the treatment of amputee children in Jordan.

  6. Household demographic determinants of Ebola epidemic risk.

    PubMed

    Adams, Ben

    2016-03-07

    A salient characteristic of Ebola, and some other infectious diseases such as Tuberculosis, is intense transmission among small groups of cohabitants and relatively limited indiscriminate transmission in the wider population. Here we consider a mathematical model for an Ebola epidemic in a population structured into households of equal size. We show that household size, a fundamental demographic unit, is a critical factor that determines the vulnerability of a community to epidemics, and the effort required to control them. Our analysis is based on the household reproduction number, but we also consider the basic reproduction number, intrinsic growth rate and final epidemic size. We show that, when other epidemiological parameters are kept the same, all of these quantifications of epidemic growth and size are increased by larger households and more intense within-household transmission. We go on to model epidemic control by case detection and isolation followed by household quarantine. We show that, if household quarantine is ineffective, the critical probability with which cases must be detected to halt an epidemic increases significantly with each increment in household size and may be a very challenging target for communities composed of large households. Effective quarantine may, however, mitigate the detrimental impact of large household sizes. We conclude that communities composed of large households are fundamentally more vulnerable to epidemics of infectious diseases primarily transmitted by close contact, and any assessment of control strategies for these epidemics should take into account the demographic structure of the population. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Material Stock Demographics: Cars in Great Britain.

    PubMed

    Cabrera Serrenho, André; Allwood, Julian M

    2016-03-15

    Recent literature on material flow analysis has been focused on quantitative characterization of past material flows. Fewer analyses exist on past and prospective quantification of stocks of materials in-use. Some of these analyses explore the composition of products' stocks, but a focus on the characterization of material stocks and its relation with service delivery is often neglected. We propose the use of the methods of human demography to characterize material stocks, defined herein as stock demographics, exploring the insights that this approach could provide for the sustainable management of materials. We exemplify an application of stock demographics by characterizing the composition and service delivery of iron, steel, and aluminum stocks of cars in Great Britain, 2002-2012. The results show that in this period the stock has become heavier, it is traveling less, and it is idle for more time. The visualization of material stocks' dynamics demonstrates the pace of product replacement as a function of its usefulness and enables the formulation of policy interventions and the exploration of future trends.

  8. Imagination as expansion of experience.

    PubMed

    Zittoun, Tania; Cerchia, Frédéric

    2013-09-01

    This paper proposes a developmental view on imagination: from this perspective, imagination can be seen as triggered by some disrupting event, which generates a disjunction from the person's unfolding experience of the "real" world, and as unfolding as a loop, which eventually comes back to the actual experience. Examining recent and classical theorization of imagination in psychology, the paper opposes a deficitary view of imagination to an expansive notion of imagination. The paper explores Piaget, Vygotsky, Harris and Pelaprat & Cole consider: 1) What does provoke a "rupture" or disjunction? 2) What are the psychological processes involved in the imaginary loop? 3) What nourishes such processes? 4) What are the consequences of such imaginary loop, or what does it enable doing? The paper proposes to adopt an expansive view of imagination, as Vygotsky proposed-a perspective that has been under-explored empirically since his seminal work. To stimulate such sociocultural psychology of imagination, two empirical examples are provided, one showing how children make sense of metaphor in an experimental setting, the other showing a young person using a novel met at school as symbolic resource.

  9. Gyrification from constrained cortical expansion

    PubMed Central

    Tallinen, Tuomas; Chung, Jun Young; Biggins, John S.; Mahadevan, L.

    2014-01-01

    The exterior of the mammalian brain—the cerebral cortex—has a conserved layered structure whose thickness varies little across species. However, selection pressures over evolutionary time scales have led to cortices that have a large surface area to volume ratio in some organisms, with the result that the brain is strongly convoluted into sulci and gyri. Here we show that the gyrification can arise as a nonlinear consequence of a simple mechanical instability driven by tangential expansion of the gray matter constrained by the white matter. A physical mimic of the process using a layered swelling gel captures the essence of the mechanism, and numerical simulations of the brain treated as a soft solid lead to the formation of cusped sulci and smooth gyri similar to those in the brain. The resulting gyrification patterns are a function of relative cortical expansion and relative thickness (compared with brain size), and are consistent with observations of a wide range of brains, ranging from smooth to highly convoluted. Furthermore, this dependence on two simple geometric parameters that characterize the brain also allows us to qualitatively explain how variations in these parameters lead to anatomical anomalies in such situations as polymicrogyria, pachygyria, and lissencephalia. PMID:25136099

  10. High thermal expansion, sealing glass

    DOEpatents

    Brow, Richard K.; Kovacic, Larry

    1993-01-01

    A glass composition for hermetically sealing to high thermal expansion materials such as aluminum alloys, stainless steels, copper, and copper/beryllium alloys, which includes between about 10 and about 25 mole percent Na.sub.2 O, between about 10 and about 25 mole percent K.sub.2 O, between about 5 and about 15 mole percent Al.sub.2 O.sub.3, between about 35 and about 50 mole percent P.sub.2 O.sub.5 and between about 5 and about 15 mole percent of one of PbO, BaO, and mixtures thereof. The composition, which may also include between 0 and about 5 mole percent Fe.sub.2 O.sub.3 and between 0 and about 10 mole percent B.sub.2 O.sub.3, has a thermal expansion coefficient in a range of between about 160 and 210.times.10-7/.degree.C. and a dissolution rate in a range of between about 2.times.10.sup.- 7 and 2.times.10.sup.-9 g/cm.sup.2 -min. This composition is suitable to hermetically seal to metallic electrical components which will be subjected to humid environments over an extended period of time.

  11. High thermal expansion, sealing glass

    DOEpatents

    Brow, R.K.; Kovacic, L.

    1993-11-16

    A glass composition is described for hermetically sealing to high thermal expansion materials such as aluminum alloys, stainless steels, copper, and copper/beryllium alloys, which includes between about 10 and about 25 mole percent Na[sub 2]O, between about 10 and about 25 mole percent K[sub 2]O, between about 5 and about 15 mole percent Al[sub 2]O[sub 3], between about 35 and about 50 mole percent P[sub 2]O[sub 5] and between about 5 and about 15 mole percent of one of PbO, BaO, and mixtures thereof. The composition, which may also include between 0 and about 5 mole percent Fe[sub 2]O[sub 3] and between 0 and about 10 mole percent B[sub 2]O[sub 3], has a thermal expansion coefficient in a range of between about 160 and 210[times]10[sup [minus]7]/C and a dissolution rate in a range of between about 2[times]10[sup [minus]7] and 2[times]10[sup [minus]9]g/cm[sup 2]-min. This composition is suitable to hermetically seal to metallic electrical components which will be subjected to humid environments over an extended period of time.

  12. Social Security Disability: Demographic and Economic Characteristics of New Beneficiaries.

    DTIC Science & Technology

    1988-01-01

    your offices, we are providing information on the demographic , health, and economic conditions of social security disability insurance program...new survey in a subsequent report. SSA conducted its New Beneficiary Survey between October and December 1982, collecting a wide range of demographic ...retired beneficiaries and the general population. DEMOGRAPHIC AND EMPLOYMENT CHARACTERISTICS The disabled beneficiaries surveyed consisted of

  13. Understanding and Using Demographic Data: Terms and Measures.

    ERIC Educational Resources Information Center

    Lilley, Stephen

    This publication provides program planners and others with information and analytical tools for using demographic data in program planning, implementation, and evaluation. The report reviews the importance of demographic data and their relevance to programs and proper implementation of laws, discusses the collection of demographic information by…

  14. Fast algorithms for Quadrature by Expansion I: Globally valid expansions

    NASA Astrophysics Data System (ADS)

    Rachh, Manas; Klöckner, Andreas; O'Neil, Michael

    2017-09-01

    The use of integral equation methods for the efficient numerical solution of PDE boundary value problems requires two main tools: quadrature rules for the evaluation of layer potential integral operators with singular kernels, and fast algorithms for solving the resulting dense linear systems. Classically, these tools were developed separately. In this work, we present a unified numerical scheme based on coupling Quadrature by Expansion, a recent quadrature method, to a customized Fast Multipole Method (FMM) for the Helmholtz equation in two dimensions. The method allows the evaluation of layer potentials in linear-time complexity, anywhere in space, with a uniform, user-chosen level of accuracy as a black-box computational method. Providing this capability requires geometric and algorithmic considerations beyond the needs of standard FMMs as well as careful consideration of the accuracy of multipole translations. We illustrate the speed and accuracy of our method with various numerical examples.

  15. Mitochondrial Variation among the Aymara and the Signatures of Population Expansion in the Central Andes

    PubMed Central

    BATAI, KEN; WILLIAMS, SLOAN R.

    2015-01-01

    Objectives The exploitation of marine resources and intensive agriculture led to a marked population increase early in central Andean prehistory. Constant historic and prehistoric population movements also characterize this region. These features undoubtedly affected regional genetic variation, but the exact nature of these effects remains uncertain. Methods Mitochondrial DNA (mtDNA) hypervariable region I sequence variation in 61 Aymara individuals from La Paz, Bolivia, was analyzed and compared to sequences from 47 other South American populations to test hypotheses of whether increased female effective population size and gene flow influenced the mtDNA variation among central Andean populations. Results The Aymara and Quechua were genetically diverse showing evidence of population expansion and large effective population size, and a demographic expansion model fits the mtDNA variation found among central Andean populations well. Estimated migration rates and the results of AMOVA and multidimensional scaling analysis suggest that female gene flow was also an important factor, influencing genetic variation among the central Andeans as well as lowland populations from western South America. mtDNA variation in south central Andes correlated better with geographic proximity than with language, and fit a population continuity model. Conclusion The mtDNA data suggests that the central Andeans experienced population expansion, most likely because of rapid demographic expansion after introduction of intensive agriculture, but roles of female gene flow need to be further explored. PMID:24449040

  16. Demographics of Investigators Involved in OSSA-Funded Research

    NASA Technical Reports Server (NTRS)

    Stern, S. Alan; Konkel, Ronald; Habegger, Jay; Byerly, Radford, Jr.

    1991-01-01

    The birth of the U.S. civil space program and the subsequent, dramatic growth in the ranks of the space science research population occurred in the 1950s and 1960s'. The large, post- Sputnik/ Apollo buildup in space program manpower is now approximately one career-lifetime in the past. It is therefore natural to anticipate that a large fraction of the space program engineers, scientists, and managers who pioneered the early exploration of space are approaching retirement. Such a "retirement wave" bodes both a loss of manpower and, more fundamentally, a loss of experience from the civil-space manpower base. Such losses could play a critical role constraining in NASA's ability to expand or maintain its technical capabilities. If this indeed applies to the NASA space science research population, then the potential for problems is exacerbated by the anticipated growth in flight rates, data volume, and data-set diversity which will accompany the planned expansion in the OSSA science effort during the 1990s and 2000s. The purpose of this study was to describe the OSSA PI/Co-I population and to determine the degree to which the OSSA space science investigator population faces a retirement wave, and to estimate the future population of PIs in the 1990-2010 era. To conduct such a study, we investigated the present demographics of the PI and Co-1 population contained in the NASA/OSSA Announcement of Opportunity (AO) mailing list. PIs represent the "leadership" class of the OSSA scientific researcher population, and Co-Is represent one important, oncoming component of the "replacement" generation. Using the PI population data, we then make projection estimates of the future PI population from 1991 through 2010, under various NASA growth/PI demand scenarios.

  17. The Demographic Development of the First Farmers in Anatolia.

    PubMed

    Kılınç, Gülşah Merve; Omrak, Ayça; Özer, Füsun; Günther, Torsten; Büyükkarakaya, Ali Metin; Bıçakçı, Erhan; Baird, Douglas; Dönertaş, Handan Melike; Ghalichi, Ayshin; Yaka, Reyhan; Koptekin, Dilek; Açan, Sinan Can; Parvizi, Poorya; Krzewińska, Maja; Daskalaki, Evangelia A; Yüncü, Eren; Dağtaş, Nihan Dilşad; Fairbairn, Andrew; Pearson, Jessica; Mustafaoğlu, Gökhan; Erdal, Yılmaz Selim; Çakan, Yasin Gökhan; Togan, İnci; Somel, Mehmet; Storå, Jan; Jakobsson, Mattias; Götherström, Anders

    2016-10-10

    The archaeological documentation of the development of sedentary farming societies in Anatolia is not yet mirrored by a genetic understanding of the human populations involved, in contrast to the spread of farming in Europe [1-3]. Sedentary farming communities emerged in parts of the Fertile Crescent during the tenth millennium and early ninth millennium calibrated (cal) BC and had appeared in central Anatolia by 8300 cal BC [4]. Farming spread into west Anatolia by the early seventh millennium cal BC and quasi-synchronously into Europe, although the timing and process of this movement remain unclear. Using genome sequence data that we generated from nine central Anatolian Neolithic individuals, we studied the transition period from early Aceramic (Pre-Pottery) to the later Pottery Neolithic, when farming expanded west of the Fertile Crescent. We find that genetic diversity in the earliest farmers was conspicuously low, on a par with European foraging groups. With the advent of the Pottery Neolithic, genetic variation within societies reached levels later found in early European farmers. Our results confirm that the earliest Neolithic central Anatolians belonged to the same gene pool as the first Neolithic migrants spreading into Europe. Further, genetic affinities between later Anatolian farmers and fourth to third millennium BC Chalcolithic south Europeans suggest an additional wave of Anatolian migrants, after the initial Neolithic spread but before the Yamnaya-related migrations. We propose that the earliest farming societies demographically resembled foragers and that only after regional gene flow and rising heterogeneity did the farming population expansions into Europe occur. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  18. Kentucky Demographics: Demographic and Economic Impacts of Migration in Kentucky, 1975-80. No. 11.

    ERIC Educational Resources Information Center

    Price, Michael

    This analysis of demographic and economic impacts of migration compared samples of nonmigrants, inmigrants, and outmigrants for Kentucky from 1975 to 1980. Age, gender, race, birth place, educational attainment, income, and labor force characteristics were compared for the three groups. Inmigrants, including intrastate migrants, were compared on…

  19. Demographics: Diversity in More Forms. Student Demographics, Now and the Future.

    ERIC Educational Resources Information Center

    Windham, Patricia; And Others

    While demographic diversity among the student body has increased substantially over the past several decades, the academic, economic, and social diversity of students will play a greater part in upcoming staffing and faculty requirements at community colleges. Data from Tallahassee Community College (TCC), in Florida, from 1980 to 1994 indicate…

  20. Kentucky Demographics: Demographic and Economic Impacts of Migration in Kentucky, 1975-80. No. 11.

    ERIC Educational Resources Information Center

    Price, Michael

    This analysis of demographic and economic impacts of migration compared samples of nonmigrants, inmigrants, and outmigrants for Kentucky from 1975 to 1980. Age, gender, race, birth place, educational attainment, income, and labor force characteristics were compared for the three groups. Inmigrants, including intrastate migrants, were compared on…

  1. Study methods, recruitment, socio-demographic findings and demographic representativeness in the OPPERA study

    PubMed Central

    Slade, Gary D.; Bair, Eric; By, Kunthel; Mulkey, Flora; Baraian, Cristina; Rothwell, Rebecca; Reynolds, Maria; Miller, Vanessa; Gonzalez, Yoly; Gordon, Sharon; Ribeiro-Dasilva, Margarete; Lim, Pei Feng; Greenspan, Joel D; Dubner, Ron; Fillingim, Roger B; Diatchenko, Luda; Maixner, William; Dampier, Dawn; Knott, Charles; Ohrbach, Richard

    2011-01-01

    This paper describes methods used in the project “Orofacial Pain Prospective Evaluation and Risk Assessment” (OPPERA) and evaluates socio-demographic characteristics associated with temporomandibular disorders (TMD) in the OPPERA case-control study. Representativeness was investigated by comparing socio-demographic profiles of OPPERA participants with population census profiles of counties near study sites and by comparing age- and gender-associations with TMD in OPPERA and the 2007-09 US National Health Interview Survey. Volunteers aged 18-44 years were recruited at four US study sites: 3,263 people without TMD were enrolled into the prospective cohort study; 1,633 of them were selected as controls for the baseline case-control study. Cases were 185 volunteers with examiner-classified TMD. Distributions of some demographic characteristics among OPPERA participants differed from census profiles, although there was less difference in socio-economic profiles. Odds of TMD was associated with greater age in this 18-44 year range; females had three times the odds of TMD as males; and relative to non-Hispanic-Whites, other racial groups had one-fifth the odds of TMD. Age- and gender-associations with chronic TMD were strikingly similar to associations observed in the US population. Assessments of representativeness in this demographically diverse group of community volunteers suggest that OPPERA case-control findings have good internal validity. PMID:22074749

  2. Ensuring reliability in expansion schemes.

    PubMed

    Kamal-Uddin, Abu Sayed; Williams, Donald Leigh

    2005-01-01

    Existing electricity power supplies must serve, or be adapted to serve, the expansion of hospital buildings. With the existing power supply assets of many hospitals being up to 20 years old, assessing the security and reliability of the power system must be given appropriate priority to avoid unplanned outages due to overloads and equipment failures. It is imperative that adequate contingency is planned for essential and non-essential electricity circuits. This article describes the methodology undertaken, and the subsequent recommendations that were made, when evaluating the security and reliability of electricity power supplies to a number of major London hospitals. The methodology described aligns with the latest issue of NHS Estates HTM 2011 'Primary Electrical Infrastructure Emergency Electrical Services Design Guidance' (to which ERA Technology has contributed).

  3. Asymptotic expansions in nonlinear rotordynamics

    NASA Technical Reports Server (NTRS)

    Day, William B.

    1987-01-01

    This paper is an examination of special nonlinearities of the Jeffcott equations in rotordynamics. The immediate application of this analysis is directed toward understanding the excessive vibrations recorded in the LOX pump of the SSME during hot-firing ground testing. Deadband, side force, and rubbing are three possible sources of inducing nonlinearity in the Jeffcott equations. The present analysis initially reduces these problems to the same mathematical description. A special frequency, named the nonlinear natural frequency, is defined and used to develop the solutions of the nonlinear Jeffcott equations as singular asymptotic expansions. This nonlinear natural frequency, which is the ratio of the cross-stiffness and the damping, plays a major role in determining response frequencies.

  4. The energy expansions of evolution.

    PubMed

    Judson, Olivia P

    2017-04-28

    The history of the life-Earth system can be divided into five 'energetic' epochs, each featuring the evolution of life forms that can exploit a new source of energy. These sources are: geochemical energy, sunlight, oxygen, flesh and fire. The first two were present at the start, but oxygen, flesh and fire are all consequences of evolutionary events. Since no category of energy source has disappeared, this has, over time, resulted in an expanding realm of the sources of energy available to living organisms and a concomitant increase in the diversity and complexity of ecosystems. These energy expansions have also mediated the transformation of key aspects of the planetary environment, which have in turn mediated the future course of evolutionary change. Using energy as a lens thus illuminates patterns in the entwined histories of life and Earth, and may also provide a framework for considering the potential trajectories of life-planet systems elsewhere.

  5. Expansion of Physician Assistant Education.

    PubMed

    Cawley, James F; Eugene Jones, P; Miller, Anthony A; Orcutt, Venetia L

    2016-12-01

    Physician assistant (PA) educational programs were created in the 1960s to prepare a new type of health care practitioner. Physician assistant programs began as experiments in medical education, and later, they proved to be highly successful in preparing capable, flexible, and productive clinicians. The growth of PA educational programs in US medical education-stimulated by grants, public policy, and anticipated shortages of providers-has gone through 3 distinct phases. At present, such programs are in the midst of the third growth spurt that is expected to continue beyond 2020, as a large number of colleges and universities seek to sponsor PA programs and attain accreditation status. Characteristics of these new programs are described, and the implications of the current expansion of PA education are examined.

  6. 3D face analysis for demographic biometrics

    SciTech Connect

    Tokola, Ryan A; Mikkilineni, Aravind K; Boehnen, Chris Bensing

    2015-01-01

    Despite being increasingly easy to acquire, 3D data is rarely used for face-based biometrics applications beyond identification. Recent work in image-based demographic biometrics has enjoyed much success, but these approaches suffer from the well-known limitations of 2D representations, particularly variations in illumination, texture, and pose, as well as a fundamental inability to describe 3D shape. This paper shows that simple 3D shape features in a face-based coordinate system are capable of representing many biometric attributes without problem-specific models or specialized domain knowledge. The same feature vector achieves impressive results for problems as diverse as age estimation, gender classification, and race classification.

  7. Demographic group differences in adolescents' time attitudes.

    PubMed

    Andretta, James R; Worrell, Frank C; Mello, Zena R; Dixson, Dante D; Baik, Sharon H

    2013-04-01

    In the present study, we examined demographic differences in time attitudes in a sample of 293 adolescents. Time attitudes were measured using the Adolescent Time Attitude Scale (Mello & Worrell, 2007; Worrell, Mello, & Buhl, 2011), which assesses positive and negative attitudes toward the past, the present, and the future. Generally, African Americans and Asian Americans reported higher scores for negative time attitudes and lower scores for positive time attitudes than European Americans and Latinos, with medium sizes. Adolescents in the low socioeconomic status group reported a less favorable evaluation of their past than middle and high SES peers, but there were no meaningful differences in time attitudes by gender. Findings indicate that middle SES adolescents, high school juniors and seniors, Latinos, and European Americans had higher representation in positive time attitude clusters (i.e., Positives and Balanced) than high SES adolescents, high school freshmen and sophomores, and African Americans. Published by Elsevier Ltd.

  8. Fire victims: medical outcomes and demographic characteristics.

    PubMed Central

    Levine, M S; Radford, E P

    1977-01-01

    The medical outcomes and demographic characteristics of all victims of fires identified by The Baltimore Fire Department during a 14-month period in Baltimore City were studied. Fifty-nine per cent of victims suffered minor injuries, 25 per cent required hospitalization and 16 per cent were fatalities. The majority of survivable injuries were due to burns, while the majority of deaths were due to pulmonary injury and carbon monoxide intoxication. Deaths occurring at the scene of the fire or during the first 24 hours were predominantly due to carbon monoxide. Exposure to fires was more likely to result in deaths in the very young and very old. Evidence from autopsy protocols suggests that alcohol was a contributory factor. PMID:911020

  9. Demographics of the Short Period Comets

    NASA Astrophysics Data System (ADS)

    Grav, Tommy; Spahr, T.; Pan-STARRS Moving Object Processing Team

    2008-09-01

    The demographics of the short period comets is not very well understood. In order to create an accurate synthetic population of object to be used in the testing and prediction of the efficiency of the upcoming Pan-STARRS project, we have used two years of minor planet observations reported by the LINEAR survey to construct a model of the underlying cometary population. We find that the known population of Jupiter family comets are the visible portion of two populations, one with aphelia at Jupiter and another with aphelia at Saturn. Furthermore the population of small short period comets is found to be larger than previously thought. In this talk we present the synthetic model and its implication and prospects for science with Pan-STARRS and LSST.

  10. Demographic variation in nutrition knowledge in England

    PubMed Central

    Parmenter, K.; Waller, J.; Wardle, J.

    2000-01-01

    This paper describes a nutrition knowledge survey carried out on a cross-section of the adult population of England (n = 1040), looking at knowledge relating to current dietary recommendations, sources of nutrients, healthy food choices and diet–disease links. Serious gaps in knowledge about even the basic recommendations were discovered, and there was much confusion over the relationship between diet and disease. Significant differences in knowledge between socio-demographic groups were found, with men having poorer knowledge than women, and knowledge declining with lower educational level and socio-economic status. Possible reasons for these differences and implications for public education campaigns and socio-economic inequalities in health are discussed. PMID:10751375

  11. The Demographics of Women in Astronomy

    NASA Astrophysics Data System (ADS)

    Urry, M.; Marvel, K. B.; Blacker, B.

    1999-12-01

    To assess the status of women in astronomy we need data. How many women are astronomers? How does this percentage change with professional level? Do women have an advantage over men in hiring or other professional opportunities, or do men have the advantage, or is the playing field level? Using recent STScI and AAS surveys, I report the gender demographics in U.S. astronomy departments in 1999. Roughly 1/4 of astronomy graduate students are women, and this percentage decreases with rank, to 6% at the full professor level. Comparing to similar data from 1992, it appears that women fall behind men at the first transition, from graduate student to postdoc, but then keep pace with men in moving to faculty positions. (There is no sign that women advance more easily than men.) Interestingly, the percentage of women is slighly higher in the larger, better known institutions than in the profession as a whole.

  12. Demographic patterns and sustainable development in Ghana.

    PubMed

    Tawiah, E O

    1995-01-01

    There is a growing recognition that the present demographic patterns in sub-Saharan Africa, including Ghana, do not augur well for the achievement of sustainable development. Ghana is characterized by a youthful population, rapid population growth, uneven population distribution, high fertility, and rural-urban migration which has brought human numbers into collision with resources to sustain them. It is submitted that the issues discussed are equally applicable to the subregion as well. The estimated population in 1993 was about 16.4 million. The population of Ghana increased from 1970 to 1984 at a rate of growth of 2.6% per annum. The proliferation of small settlements has serious implications for sustainable development. Urban centers comprised about 12.9% of the total population in 1948, 23% in 1960, 28.3% in 1970, and 31.3% in 1984. The average woman in Ghana still has more than six children. The 1988 Ghana Demographic and Health Survey (GDHS) indicated that the median age at first marriage for women was 16.5 years. Contraceptive use is low in sub-Sahara Africa. Currently married women (15-49) currently using any modern method ranged from 1% in Burundi (1987) and Mali (1987) to 36% in Zimbabwe (1988/89). The rapid population growth in Ghana, coupled with the concentration of infrastructural facilities and job opportunities in the urban centers, has resulted in a massive rural-urban migration. Basic social facilities like health, water, housing, and electricity have been stretched to their breakpoints. The Government of Ghana initiated a major effort to put environmental issues on the priority agenda in March 1988. This led to the preparation of an Environmental Action Plan (EAP) in 1991 to address issues relating to the protection of the environment, but the need is still urgent to adopt relevant population policies as a basic strategy in sustainable development.

  13. Extraparenchymal neurocysticercosis: Demographic, clinicoradiological, and inflammatory features

    PubMed Central

    Marcin Sierra, Mariana; Arroyo, Mariana; Cadena Torres, May; Ramírez Cruz, Nancy; García Hernández, Fernando; Taboada, Diana; Galicia Martínez, Ángeles; Govezensky, Tzipe; Sciutto, Edda; Toledo, Andrea

    2017-01-01

    Background Extraparenchymal neurocysticercosis (ExPNCC), an infection caused by Taenia solium cysticerci that mainly occurs in the ventricular compartment (Ve) or the basal subarachnoid space (SAb), is more severe but less frequent and much less studied than parenchymal neurocysticercosis (ParNCC). Demographic, clinical, radiological, and lumbar cerebrospinal fluid features of patients affected by ExPNCC are herein described and compared with those of ParNCC patients. Methodology and principal findings 429 patients with a confirmed diagnosis of neurocysticercosis, attending the Instituto Nacional de Neurología y Neurocirugía, a tertiary reference center in Mexico City, from 2000 through 2014, were included. Demographic information, signs and symptoms, radiological patterns, and lumbar cerebrospinal fluid (CSF) laboratory values were retrieved from medical records for all patients. Data were statistically analyzed to assess potential differences depending on cyst location and to determine the effects of age and sex on the disease presentation. In total, 238 ExPNCC and 191 ParNCC patients were included. With respect to parenchymal cysts, extraparenchymal parasites were diagnosed at an older age (P = 0.002), chiefly caused intracranial hypertension (P < 0.0001), were more frequently multiple and vesicular (P < 0.0001), and CSF from these patients showed higher protein concentration and cell count (P < 0.0001). SAb patients were diagnosed at an older age than Ve patients, and showed more frequently seizures, vesicular cysticerci, and higher CSF cellularity. Gender and age modulated some traits of the disease. Conclusions This study evidenced clear clinical, radiological, and inflammatory differences between ExPNCC and ParNCC, and between SAb and Ve patients, and demonstrated that parasite location determines different pathological entities. PMID:28599004

  14. Extraparenchymal neurocysticercosis: Demographic, clinicoradiological, and inflammatory features.

    PubMed

    Marcin Sierra, Mariana; Arroyo, Mariana; Cadena Torres, May; Ramírez Cruz, Nancy; García Hernández, Fernando; Taboada, Diana; Galicia Martínez, Ángeles; Govezensky, Tzipe; Sciutto, Edda; Toledo, Andrea; Fleury, Agnès

    2017-06-01

    Extraparenchymal neurocysticercosis (ExPNCC), an infection caused by Taenia solium cysticerci that mainly occurs in the ventricular compartment (Ve) or the basal subarachnoid space (SAb), is more severe but less frequent and much less studied than parenchymal neurocysticercosis (ParNCC). Demographic, clinical, radiological, and lumbar cerebrospinal fluid features of patients affected by ExPNCC are herein described and compared with those of ParNCC patients. 429 patients with a confirmed diagnosis of neurocysticercosis, attending the Instituto Nacional de Neurología y Neurocirugía, a tertiary reference center in Mexico City, from 2000 through 2014, were included. Demographic information, signs and symptoms, radiological patterns, and lumbar cerebrospinal fluid (CSF) laboratory values were retrieved from medical records for all patients. Data were statistically analyzed to assess potential differences depending on cyst location and to determine the effects of age and sex on the disease presentation. In total, 238 ExPNCC and 191 ParNCC patients were included. With respect to parenchymal cysts, extraparenchymal parasites were diagnosed at an older age (P = 0.002), chiefly caused intracranial hypertension (P < 0.0001), were more frequently multiple and vesicular (P < 0.0001), and CSF from these patients showed higher protein concentration and cell count (P < 0.0001). SAb patients were diagnosed at an older age than Ve patients, and showed more frequently seizures, vesicular cysticerci, and higher CSF cellularity. Gender and age modulated some traits of the disease. This study evidenced clear clinical, radiological, and inflammatory differences between ExPNCC and ParNCC, and between SAb and Ve patients, and demonstrated that parasite location determines different pathological entities.

  15. Geriatric trauma: demographics, injuries, and mortality.

    PubMed

    Keller, Julie M; Sciadini, Marcus F; Sinclair, Elizabeth; O'Toole, Robert V

    2012-09-01

    To identify injuries that elderly sustain during high-energy trauma and determine which are associated with mortality. Retrospective review of prospectively collected database. Academic trauma center. Patients selected from database of all trauma admissions from January 2004 through June 2009. Study population consisted of patients directly admitted from scene of injury who sustained high-energy trauma with at least one orthopaedic injury and were 65 years or older (n = 597). Review of demographics, trauma markers, injuries, and disposition statuses. Statistical analysis using χ test, Student t test, and logistic regression analysis. The most common fractures were of the rib, distal radius, pelvic ring, facial bones, proximal humerus, clavicle, ankle, and sacrum. The injuries associated with the highest mortality rates were fractures of the cervical spine with neurological deficit (47%), at the C2 level (44%), and of the proximal femur (25%), pelvic ring (25%), clavicle (24%), and distal humerus (24%). The fractures significantly associated with mortality were fractures of the clavicle (P = 0.001), foot joints (P = 0.001), proximal humerus or shaft and head of the humerus (P = 0.002), sacroiliac joint (P = 0.004), and distal ulna (P = 0.002). Elderly patients present with significantly worse injuries, remain in the hospital longer, require greater use of resources after discharge, and die at 3 times the rate of the younger population. Although the high mortality rates associated with cervical spine, hip, and pelvic ring fractures were not unexpected, the injuries that were statistically associated with mortality were unexpected. Injuries such as clavicle fracture were statistically associated with mortality. As our population ages and becomes more active, the demographic may gain in clinical importance. Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

  16. Backstage at Broadway: a demographic study.

    PubMed

    Gehling, Drew; Sridharan, Shaum; Fritz, Mark; Friedmann, David R; Fang, Yixin; Amin, Milan R; Branski, Ryan C

    2014-05-01

    To provide insight into the demographics and vocal habits of current Broadway musical theater performers. Prospective, Questionnaire. Adult musical theater performers in Broadway Productions as defined by the League of American Theater Producers and the Actors' Equity Association were asked to complete a survey collecting demographic information, vocal health and habits, alcohol, tobacco, and drug use and information regarding their level of vocal comfort and threshold to miss performances based on their voice. Data were subjected to descriptive and statistical analysis based on sex and role type (lead vs. ensemble). One hundred thirty-five performers completed the survey from seven actively running shows. Ensemble members were younger and had not been in the business as long as performers in lead roles. Over 25% of respondents had been diagnosed with a vocal injury, yet the number of days missed per year due to voice problems was relatively low (1.7-4.7). Across all respondents, only approximately 54.8% reported consistently warming up before a performance and 7.4% reported consistently cooling down afterward. Nearly 91% of respondents reported regular alcohol consumption and tobacco use was 10.4%; 23.0% reported illicit drug use. This study marks the first time that vocal health has been addressed in this elite group of vocal professionals. The performer's low self-reported numbers of missed days is interesting particularly given that they appear to participate in harmful vocal health activities at the same rate as the general public. Copyright © 2014 The Voice Foundation. Published by Mosby, Inc. All rights reserved.

  17. Demographic variation and conservation of the narrow endemic plant Ranunculus weyleri

    NASA Astrophysics Data System (ADS)

    Cursach, Joana; Besnard, Aurélien; Rita, Juan; Fréville, Hélène

    2013-11-01

    Ranunculus weyleri is a narrow endemic protected plant from Majorca Island. It is known from only five populations located in two mountain areas 48 km apart. Using demographic data collected from 2007 to 2010, we assessed the demographic status of two populations - font des Coloms (FC) and talaia Moreia (TM) - using Integral Projection Models (IPMs). We showed that none of the two populations were declining under a deterministic model. Population FC was stable (λ = 1.026, CI95% = 0.965-1.093), while population TM showed sign of demographic expansion (λ = 1.113, CI95% = 1.032-1.219). Plant survival, flowering probability and the mean number of seedlings per floral peduncle were lower in TM, whereas growth and the number of floral peduncles per reproductive plant were lower in FC. Elasticity analyses showed that management strategies increasing plant survival and growth would be the most efficient to increase λ for both populations. Herbivory pressure by goats has been shown to be high in TM, resulting in high predation rate on floral peduncles. Controlling goat pressure may thus represent a promising management option, provided that we can demonstrate a negative impact of herbivory by goats on survival and growth which are the most critical parts of the life cycle in this species. Meanwhile, initiating a long-term monitoring is of crucial importance to get more insights into the relationships between environmental variation, plant performance and population dynamics.

  18. Multilocus Analyses Reveal Postglacial Demographic Shrinkage of Juniperus morrisonicola (Cupressaceae), a Dominant Alpine Species in Taiwan.

    PubMed

    Huang, Chi-Chun; Hsu, Tsai-Wen; Wang, Hao-Ven; Liu, Zin-Huang; Chen, Yi-Yen; Chiu, Chi-Te; Huang, Chao-Li; Hung, Kuo-Hsiang; Chiang, Tzen-Yuh

    2016-01-01

    Postglacial climate changes alter geographical distributions and diversity of species. Such ongoing changes often force species to migrate along the latitude/altitude. Altitudinal gradients represent assemblage of environmental, especially climatic, variable factors that influence the plant distributions. Global warming that triggered upward migrations has therefore impacted the alpine plants on an island. In this study, we examined the genetic structure of Juniperus morrisonicola, a dominant alpine species in Taiwan, and inferred historical, demographic dynamics based on multilocus analyses. Lower levels of genetic diversity in north indicated that populations at higher latitudes were vulnerable to climate change, possibly related to historical alpine glaciers. Neither organellar DNA nor nuclear genes displayed geographical subdivisions, indicating that populations were likely interconnected before migrating upward to isolated mountain peaks, providing low possibilities of seed/pollen dispersal across mountain ranges. Bayesian skyline plots suggested steady population growth of J. morrisonicola followed by recent demographic contraction. In contrast, most lower-elevation plants experienced recent demographic expansion as a result of global warming. The endemic alpine conifer may have experienced dramatic climate changes over the alternation of glacial and interglacial periods, as indicated by a trend showing decreasing genetic diversity with the altitudinal gradient, plus a fact of upward migration.

  19. Multilocus Analyses Reveal Postglacial Demographic Shrinkage of Juniperus morrisonicola (Cupressaceae), a Dominant Alpine Species in Taiwan

    PubMed Central

    Chiu, Chi-Te; Huang, Chao-Li; Hung, Kuo-Hsiang; Chiang, Tzen-Yuh

    2016-01-01

    Postglacial climate changes alter geographical distributions and diversity of species. Such ongoing changes often force species to migrate along the latitude/altitude. Altitudinal gradients represent assemblage of environmental, especially climatic, variable factors that influence the plant distributions. Global warming that triggered upward migrations has therefore impacted the alpine plants on an island. In this study, we examined the genetic structure of Juniperus morrisonicola, a dominant alpine species in Taiwan, and inferred historical, demographic dynamics based on multilocus analyses. Lower levels of genetic diversity in north indicated that populations at higher latitudes were vulnerable to climate change, possibly related to historical alpine glaciers. Neither organellar DNA nor nuclear genes displayed geographical subdivisions, indicating that populations were likely interconnected before migrating upward to isolated mountain peaks, providing low possibilities of seed/pollen dispersal across mountain ranges. Bayesian skyline plots suggested steady population growth of J. morrisonicola followed by recent demographic contraction. In contrast, most lower-elevation plants experienced recent demographic expansion as a result of global warming. The endemic alpine conifer may have experienced dramatic climate changes over the alternation of glacial and interglacial periods, as indicated by a trend showing decreasing genetic diversity with the altitudinal gradient, plus a fact of upward migration. PMID:27561108

  20. A new method for estimating the demographic history from DNA sequences: an importance sampling approach

    PubMed Central

    Ait Kaci Azzou, Sadoune; Larribe, Fabrice; Froda, Sorana

    2015-01-01

    The effective population size over time (demographic history) can be retraced from a sample of contemporary DNA sequences. In this paper, we propose a novel methodology based on importance sampling (IS) for exploring such demographic histories. Our starting point is the generalized skyline plot with the main difference being that our procedure, skywis plot, uses a large number of genealogies. The information provided by these genealogies is combined according to the IS weights. Thus, we compute a weighted average of the effective population sizes on specific time intervals (epochs), where the genealogies that agree more with the data are given more weight. We illustrate by a simulation study that the skywis plot correctly reconstructs the recent demographic history under the scenarios most commonly considered in the literature. In particular, our method can capture a change point in the effective population size, and its overall performance is comparable with the one of the bayesian skyline plot. We also introduce the case of serially sampled sequences and illustrate that it is possible to improve the performance of the skywis plot in the case of an exponential expansion of the effective population size. PMID:26300910

  1. Demographic estimation methods for plants with dormancy

    USGS Publications Warehouse

    Kery, M.; Gregg, K.B.

    2004-01-01

    Demographic studies in plants appear simple because unlike animals, plants do not run away. Plant individuals can be marked with, e.g., plastic tags, but often the coordinates of an individual may be sufficient to identify it. Vascular plants in temperate latitudes have a pronounced seasonal life–cycle, so most plant demographers survey their study plots once a year often during or shortly after flowering. Life–states are pervasive in plants, hence the results of a demographic study for an individual can be summarized in a familiar encounter history, such as 0VFVVF000. A zero means that an individual was not seen in a year and a letter denotes its state for years when it was seen aboveground. V and F here stand for vegetative and flowering states, respectively. Probabilities of survival and state transitions can then be obtained by mere counting.Problems arise when there is an unobservable dormant state, i.e., when plants may stay belowground for one or more growing seasons. Encounter histories such as 0VF00F000 may then occur where the meaning of zeroes becomes ambiguous. A zero can either mean a dead or a dormant plant. Various ad hoc methods in wide use among plant ecologists have made strong assumptions about when a zero should be equated to a dormant individual. These methods have never been compared among each other. In our talk and in Kéry et al. (submitted), we show that these ad hoc estimators provide spurious estimates of survival and should not be used.In contrast, if detection probabilities for aboveground plants are known or can be estimated, capturerecapture (CR) models can be used to estimate probabilities of survival and state–transitions and the fraction of the population that is dormant. We have used this approach in two studies of terrestrial orchids, Cleistes bifaria (Kéry et al., submitted) and Cypripedium reginae(Kéry & Gregg, submitted) in West Virginia, U.S.A. For Cleistes, our data comprised one population with a total of 620

  2. Population Genetic Structure and Demographic History of Atrina pectinata Based on Mitochondrial DNA and Microsatellite Markers

    PubMed Central

    Xue, Dong-Xiu; Wang, Hai-Yan; Zhang, Tao; Liu, Jin-Xian

    2014-01-01

    The pen shell, Atrina pectinata, is one of the commercial bivalves in East Asia and thought to be recently affected by anthropogenic pressure (habitat destruction and/or fishing pressure). Information on its population genetic structure is crucial for the conservation of A. pectinata. Considering its long pelagic larval duration and iteroparity with high fecundity, the genetic structure for A. pectinata could be expected to be weak at a fine scale. However, the unusual oceanography in the coasts of China and Korea suggests potential for restricted dispersal of pelagic larvae and geographical differentiation. In addition, environmental changes associated with Pleistocene sea level fluctuations on the East China Sea continental shelf may also have strongly influenced historical population demography and genetic diversity of marine organisms. Here, partial sequences of the mitochondrial Cytochrome c oxidase subunit I (COI) gene and seven microsatellite loci were used to estimate population genetic structure and demographic history of seven samples from Northern China coast and one sample from North Korea coast. Despite high levels of genetic diversity within samples, there was no genetic differentiation among samples from Northern China coast and low but significant genetic differentiation between some of the Chinese samples and the North Korean sample. A late Pleistocene population expansion, probably after the Last Glacial Maximum, was also demonstrated for A. pectinata samples. No recent genetic bottleneck was detected in any of the eight samples. We concluded that both historical recolonization (through population range expansion and demographic expansion in the late Pleistocene) and current gene flow (through larval dispersal) were responsible for the weak level of genetic structure detected in A. pectinata. PMID:24789175

  3. Potential (mis)match?: Marriage Markets amidst Socio-Demographic Change in India, 2005–2050

    PubMed Central

    Kashyap, Ridhi; Esteve, Albert; García-Román, Joan

    2015-01-01

    We explore the impact of socio-demographic change on marriage patterns in India by examining the hypothetical consequences of applying three sets of marriage pairing propensities – contemporary patterns by age, by age and education, and changing propensities that allow for greater educational homogamy and reduced educational asymmetries – to future population projections. Future population prospects for India indicate three trends that will impact marriage patterns: i) female-deficit in sex ratios at birth; ii) declining birth cohort size; iii) female educational expansion. Existing literature posits declining marriage rates for men arising from skewed sex ratios at birth (SRB) in India’s population. In addition to skewed SRBs, India’s population will experience female educational expansion in the coming decades. Female educational expansion and its impact on marriage patterns must be jointly considered with demographic changes, given educational differentials and asymmetries in union formation that exist in India, as across much of the world. We systematize contemporary pairing propensities using data from the 2005–2006 Indian National Family Health Survey and the 2004 Socio-Economic Survey and apply these and the third set of changing propensities to IIASA/VID multi-state population projections by educational attainment using an iterative longitudinal projection procedure. If today’s age patterns of marriage are viewed against age-sex population composition until 2050, men experience declining marriage prevalence. However, when education is included, women, particularly those with higher education experience a more salient rise in non-marriage. Significant changes in pairing patterns towards greater levels of educational homogamy and gender symmetry can counteract a marked rise in non-marriage. PMID:25604846

  4. A coupled phylogeographical and species distribution modelling approach recovers the demographical history of a Neotropical seasonally dry forest tree species.

    PubMed

    Collevatti, Rosane G; Terribile, Levi Carina; Lima-Ribeiro, Matheus S; Nabout, João C; de Oliveira, Guilherme; Rangel, Thiago F; Rabelo, Suelen G; Diniz-Filho, Jose A F

    2012-12-01

    We investigated here the demographical history of Tabebuia impetiginosa (Bignoniaceae) to understand the dynamics of the disjunct geographical distribution of South American seasonally dry forests (SDFs), based on coupling an ensemble approach encompassing hindcasting species distribution modelling and statistical phylogeographical analysis. We sampled 17 populations (280 individuals) in central Brazil and analysed the polymorphisms at chloroplast (trnS-trnG, psbA-trnH, and ycf6-trnC intergenic spacers) and nuclear (ITS nrDNA) genomes. Phylogenetic analyses based on median-joining network showed no haplotype sharing among population but strong evidence of incomplete lineage sorting. Coalescent analyses showed historical constant populations size, negligible gene flow among populations, and an ancient time to most recent common ancestor dated from ~4.7 ± 1.1 Myr BP. Most divergences dated from the Lower Pleistocene, and no signal of important population size reduction was found in coalescent tree and tests of demographical expansion. Demographical scenarios were built based on past geographical range dynamic models, using two a priori biogeographical hypotheses ('Pleistocene Arc' and 'Amazonian SDF expansion') and on two additional hypotheses suggested by the palaeodistribution modelling built with several algorithms for distribution modelling and palaeoclimatic data. The simulation of these demographical scenarios showed that the pattern of diversity found so far for T. impetiginosa is in consonance with a palaeodistribution expansion during the last glacial maximum (LGM, 21 kyr BP), strongly suggesting that the current disjunct distribution of T. impetiginosa in SDFs may represent a climatic relict of a once more wide distribution.

  5. Pressurized electrolysis stack with thermal expansion capability

    DOEpatents

    Bourgeois, Richard Scott

    2015-07-14

    The present techniques provide systems and methods for mounting an electrolyzer stack in an outer shell so as to allow for differential thermal expansion of the electrolyzer stack and shell. Generally, an electrolyzer stack may be formed from a material with a high coefficient of thermal expansion, while the shell may be formed from a material having a lower coefficient of thermal expansion. The differences between the coefficients of thermal expansion may lead to damage to the electrolyzer stack as the shell may restrain the thermal expansion of the electrolyzer stack. To allow for the differences in thermal expansion, the electrolyzer stack may be mounted within the shell leaving a space between the electrolyzer stack and shell. The space between the electrolyzer stack and the shell may be filled with a non-conductive fluid to further equalize pressure inside and outside of the electrolyzer stack.

  6. The use of mobile phones for demographic surveillance of mobile pastoralists and their animals in Chad: proof of principle.

    PubMed

    Jean-Richard, Vreni; Crump, Lisa; Moto Daugla, Doumagoum; Hattendorf, Jan; Schelling, Esther; Zinsstag, Jakob

    2014-01-01

    Demographic information is foundational for the planning and management of social programmes, in particular health services. The existing INDEPTH network surveillance sites are limited to coverage of sedentary populations. Including mobile populations in this approach would be expensive, time consuming and possibly low in accuracy. Very little is known about the demography of mobile pastoralists and their animals, so innovative approaches are urgently needed. To test and evaluate a mobile demographic surveillance system for mobile pastoralist households, including livestock herds, using mobile phones. Mobile pastoralist camps were monitored (10 for 12 months and 10 for 18 months) using biweekly mobile phone calls with camp leaders and their wives to conduct interviews about the households and livestock. The collected information was validated through personal visits, GPS data and a livestock demographic model. The study showed the feasibility of mobile phone surveillance for mobile pastoralist camps, providing usable, valid information on human and livestock population structures, pregnancy outcomes and herd dynamics, as well as migration patterns. The approach was low-cost and applicable with the existing local resources. Demographic surveillance in mobile populations is feasible using mobile phones. Expansion of the small-scale system into a full mobile demographic surveillance system is warranted and would likely lead to improved planning and provision of human and animal health care.

  7. The use of mobile phones for demographic surveillance of mobile pastoralists and their animals in Chad: proof of principle

    PubMed Central

    Jean-Richard, Vreni; Crump, Lisa; Daugla, Doumagoum Moto; Hattendorf, Jan; Schelling, Esther; Zinsstag, Jakob

    2014-01-01

    Background Demographic information is foundational for the planning and management of social programmes, in particular health services. The existing INDEPTH network surveillance sites are limited to coverage of sedentary populations. Including mobile populations in this approach would be expensive, time consuming and possibly low in accuracy. Very little is known about the demography of mobile pastoralists and their animals, so innovative approaches are urgently needed. Objective To test and evaluate a mobile demographic surveillance system for mobile pastoralist households, including livestock herds, using mobile phones. Design Mobile pastoralist camps were monitored (10 for 12 months and 10 for 18 months) using biweekly mobile phone calls with camp leaders and their wives to conduct interviews about the households and livestock. The collected information was validated through personal visits, GPS data and a livestock demographic model. Results The study showed the feasibility of mobile phone surveillance for mobile pastoralist camps, providing usable, valid information on human and livestock population structures, pregnancy outcomes and herd dynamics, as well as migration patterns. The approach was low-cost and applicable with the existing local resources. Conclusion Demographic surveillance in mobile populations is feasible using mobile phones. Expansion of the small-scale system into a full mobile demographic surveillance system is warranted and would likely lead to improved planning and provision of human and animal health care. PMID:24499744

  8. Microsatellite data support an early population expansion in Africa.

    PubMed

    Shriver, M D; Jin, L; Ferrell, R E; Deka, R

    1997-06-01

    We have developed a method for the analysis of microsatellite data that is useful in the elucidation of the demographic history of populations. This method, the PK distribution method of pairwise comparisons, is analogous to the mismatch distribution of sequence comparisons developed for the analysis of mitochondrial sequence data by Rodgers and Harpending and is defined as the distribution of the number of repeat unit differences between alleles when each allele in a sample is compared with every other allele in the sample. Using computer simulations of microsatellite loci, we show that the shape of the distribution of PK changes in a distinctive manner as a function either of time since population expansion or effective population size. Increases in both of these affect the PK distribution in a similar fashion leading to a change from a steep distribution with a Po peak to one with a nonzero peak. Analysis of three data sets from surveys of microsatellite loci in ethnographically defined populations reveals that most (9/12) of the African populations analyzed, but none of the 30 non-African populations showed PK distributions with nonzero peaks. These PK distributions indicate either an earlier expansion or a larger effective population size for African populations. This observation is consistent with the hypothesized African origin of modern human.

  9. Complications in tissue expansion: A logistic regression analysis for risk factors.

    PubMed

    Smolle, Christian; Tuca, Alexandru; Wurzer, Paul; Spendel, Stephanie M; Forbes, Abigail A; Spendel, Stephan; Schintler, Michael; Haxhija, Emir; Schwenzer-Zimmerer, Katja; Friedl, Herwig; Kamolz, Lars-Peter; Parvizi, Daryousch

    2017-09-01

    Tissue expansion is frequently used in reconstructive surgery. Although the surgical procedure is typically considered simple, reported complication rates of tissue expansions exceed 40%. There is little evidence concerning risk factors for complications in tissue expansion in body regions other than breast. The aim was to determine risk factors for complications in non-breast tissue expansion. 34 patients treated with subcutaneous tissue expanders between 2005 and 2014 were analyzed. Demographic data, body-mass index (BMI), mean arterial blood pressure (MAP), treatment indications, expansion site, previous expansion therapies in the same body region, smoking history, as well as expander characteristics (shape, volume, and filling mechanism) were ascertained. Complications were assessed and ranked according to severity based on the Clavien-Dindo classification. Binary logistic regression analysis adjusted for clinical characteristics was used. A p<0.05 was considered as statistically significant. Complications were observed in 26 out of 71 expanders analyzed (36.6%), of whom 10 led to therapy failure. Expanders used in the limbs, female gender, and high expander volume turned out as significant risk factors. Patients with both a high MAP and low BMI developed tissue necrosis significantly more often (p=0.002). The use of tissue expansion after a burn was not associated with an increased risk for complications. This is the first study revealing female gender and low BMI as risk factors in tissue expander surgery. Thus, careful patient selection is mandatory to avoid complications in tissue expansion. Burn patients do not develop complications more often. Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

  10. Hydration and Thermal Expansion in Anatase Nanoparticles.

    PubMed

    Zhu, He; Li, Qiang; Ren, Yang; Fan, Longlong; Chen, Jun; Deng, Jinxia; Xing, Xianran

    2016-08-01

    A tunable thermal expansion is reported in nanosized anatase by taking advantage of surface hydration. The coefficient of thermal expansion of 4 nm TiO2 along a-axis is negative with a hydrated surface and is positive without a hydrated surface. High-energy synchrotron X-ray pair distribution function analysis combined with ab initio calculations on the specific hydrated surface are carried out to reveal the local structure distortion that is responsible for the unusual negative thermal expansion.

  11. Hydration and Thermal Expansion in Anatase Nanoparticles

    SciTech Connect

    Zhu, He; Li, Qiang; Ren, Yang; Fan, Longlong; Chen, Jun; Deng, Jinxia; Xing, Xianran

    2016-06-06

    A tunable thermal expansion is reported in nanosized anatase by taking advantage of surface hydration. The coefficient of thermal expansion of 4 nm TiO2 along a-axis is negative with a hydrated surface and is positive without a hydrated surface. High-energy synchrotron X-ray pair distribution function analysis combined with ab initio calculations on the specific hydrated surface are carried out to reveal the local structure distortion that is responsible for the unusual negative thermal expansion.

  12. Anisotropic thermal expansion of strontium barium niobate

    NASA Astrophysics Data System (ADS)

    Qadri, Syed B.; Bellotti, Jeffrey A.; Garzarella, Anthony; Wu, Dong Ho

    2005-06-01

    Strontium barium niobate is a tungsten-bronze ferroelectric crystal having a tetragonal unit cell. Low-temperature x-ray diffraction studies were performed on a single crystal of Sr0.75Ba0.25Nb2O6 to determine the thermal expansivity along the a- and c-axes. Negative thermal expansion was observed along the c direction while a positive thermal expansion was measured along the a axis. The anisotropic thermal expansion behavior is explained as arising due to the geometry of the crystal structure.

  13. Cranial strains and malocclusion VIII: palatal expansion.

    PubMed

    James, Gavin; Strokon, Dennis

    2009-01-01

    Current techniques for palatal expansion are reviewed. Pre-treatment asymmetry of the palate and maxillary arch is shown to be almost universal and is not randomly distributed. The use of a symmetrical expansion appliance does not necessarily result in a symmetrical arch. ALF appliances provide a means of achieving orthopedic, symmetrical expansion of the palate by using very light force. This is demonstrated in seven subjects. It is argued that rapid palatal expansion is an inappropriate, potentially iatrogenic procedure which no longer has a place in the orthodontic armamentarium.

  14. Thermal expansion of L-ascorbic acid

    NASA Astrophysics Data System (ADS)

    Nicolaï, B.; Barrio, M.; Tamarit, J.-Ll.; Céolin, R.; Rietveld, I. B.

    2016-11-01

    The specific volume of vitamin C has been investigated by X-ray powder diffraction as a function of temperature from 110 K up to complete degradation around 440 K. Its thermal expansion is relatively small in comparison with other organic compounds with an expansivity αv of 1.2(3) × 10-4 K-1. The structure consists of strongly bound molecules in the ac plane through a dense network of hydrogen bonds. The thermal expansion is anisotropic. Along the b axis, the expansion has most leeway and is about 10 times larger than in the other directions.

  15. Thermal expansion of L-ascorbic acid

    NASA Astrophysics Data System (ADS)

    Nicolaï, B.; Barrio, M.; Tamarit, J.-Ll.; Céolin, R.; Rietveld, I. B.

    2017-04-01

    The specific volume of vitamin C has been investigated by X-ray powder diffraction as a function of temperature from 110 K up to complete degradation around 440 K. Its thermal expansion is relatively small in comparison with other organic compounds with an expansivity α v of 1.2(3) × 10-4 K-1. The structure consists of strongly bound molecules in the ac plane through a dense network of hydrogen bonds. The thermal expansion is anisotropic. Along the b axis, the expansion has most leeway and is about 10 times larger than in the other directions.

  16. Influence of spatial and temporal heterogeneities on the estimation of demographic parameters in a continuous population using individual microsatellite data.

    PubMed

    Leblois, Raphael; Rousset, François; Estoup, Arnaud

    2004-02-01

    Drift and migration disequilibrium are very common in animal and plant populations. Yet their impact on methods of estimation of demographic parameters was rarely evaluated especially in complex realistic population models. The effect of such disequilibria on the estimation of demographic parameters depends on the population model, the statistics, and the genetic markers used. Here we considered the estimation of the product Dsigma2 from individual microsatellite data, where D is the density of adults and sigma2 the average squared axial parent-offspring distance in a continuous population evolving under isolation by distance. A coalescence-based simulation algorithm was used to study the effect on Dsigma2 estimation of temporal and spatial fluctuations of demographic parameters. Estimation of present-time Dsigma2 values was found to be robust to temporal changes in dispersal, to density reduction, and to spatial expansions with constant density, even for relatively recent changes (i.e., a few tens of generations ago). By contrast, density increase in the recent past gave Dsigma2 estimations biased largely toward past demographic parameters values. The method was also robust to spatial heterogeneity in density and estimated local demographic parameters when the density is homogenous around the sampling area (e.g., on a surface that equals four times the sampling area). Hence, in the limit of the situations studied in this article, and with the exception of the case of density increase, temporal and spatial fluctuations of demographic parameters appear to have a limited influence on the estimation of local and present-time demographic parameters with the method studied.

  17. Internal diversification of mitochondrial haplogroup R0a reveals post-last glacial maximum demographic expansions in South Arabia.

    PubMed

    Cerný, Viktor; Mulligan, Connie J; Fernandes, Verónica; Silva, Nuno M; Alshamali, Farida; Non, Amy; Harich, Nourdin; Cherni, Lotfi; El Gaaied, Amel Ben Ammar; Al-Meeri, Ali; Pereira, Luísa

    2011-01-01

    Widespread interest in the first successful Out of Africa dispersal of modern humans ∼60-80 thousand years ago via a southern migration route has overshadowed the study of later periods of South Arabian prehistory. In this work, we show that the post-Last Glacial Maximum period of the past 20,000 years, during which climatic conditions were becoming more hospitable, has been a significant time in the formation of the extant genetic composition and population structure of this region. This conclusion is supported by the internal diversification displayed in the highly resolved phylogenetic tree of 89 whole mitochondrial genomes (71 being newly presented here) for haplogroup R0a-the most frequent and widespread haplogroup in Arabia. Additionally, two geographically specific clades (R0a1a1a and R0a2f1) have been identified in non-Arabic speaking peoples such as the Soqotri and Mahri living in the southern part of the Arabian Peninsula where a past refugium was identified by independent archaeological studies. Estimates of time to the most recent common ancestor of these lineages match the earliest archaeological evidence for seafaring activity in the peninsula in the sixth millennium BC.

  18. Impact of demographic policy on population growth.

    PubMed

    Podyashchikh, P

    1968-01-01

    Various bourgeois theories, including the reactionary Malthusianism and its variants, challenge the Marxist-Leninist revolutionary theory on the growth of population. Bourgeois science maintains that unchanging biological laws of proliferation form the foundation of social life. Malthus, in his "An Essay on the Principle of Population," contends that population increases in a geometric rate, while means of subsistence tend to increase only in an arithmetic rate: neither the way of production nor social conditions but this law of nature in control of proliferation had been the cause of overpopulation, which again leads to misery, hunger, and unemployment. From this follows the possible conclusion that the working classes should be concerned not about how to change the social order but how to reduce the number of childbirths. Progressive science views the laws of social life in a totally different way. Marxism-Leninism teaches that population size, despite the markedly important role played by it in historical progress, fails to represent that main force of social progress which determines the mode of production and of the distribution of material goods, but just the reverse: the mode of production determines the growth of population, the changes in its density and composition. Marxism-Leninism teaches that each historical stage of production (slavery, feudalism, capitalism) has its own special, historically valid demographic law. Bourgeois science maintains that humankind faces an absolute overpopulation caused by the means of production lagging behind the growth of population. Actually this is only a relative overpopulation due to the fact that capitalistic production is subjected to the interests of increasing capitalistic profit and not to those of meeting the demands of population. In socialist countries, production is incessantly developing and expanding, and employment of the entire productive population is ensured. Consequently, the problem of relative

  19. Magnetic Clouds: Global and local expansion

    NASA Astrophysics Data System (ADS)

    Gulisano, Adriana; Demoulin, Pascal; Soledad Nakwacki, Ms Maria; Dasso, Sergio; Emilia Ruiz, Maria

    Magnetic clouds (MCs) are magnetized objects forming flux ropes, which are expelled from the Sun and travel through the heliosphere, transporting important amounts of energy, mass, magnetic flux, and magnetic helicity from the Sun to the interplanetary medium. To know the detailed dynamical evolution of MCs is very useful to improve the knowledge of solar processes, for instance from linking a transient solar source with its interplanetary manifestation. During its travel, and mainly due to the decrease of the total (magnetic plus thermal) pressure in the surrounding solar wind, MCs are objects in expansion. However, the detailed magnetic structure and the dynamical evolution of MCs is still not fully known. Even the identification of their boundaries is an open question in some cases. In a previous work we have shown that from onepoint observations of the bulk velocity profile, it is possible to infer the 'local' expansion rate for a given MC, i.e., the expansion rate while the MC is observed by the spacecraft. By the another hand, and from the comparison of sizes for different MCs observed at different heliodistances, it is possible to quantify an 'average' expansion law (i.e., a global expansion). In this work, in order to study the variability of the 'local' expansion with respect to the 'average' expansion of MCs during their travel, we present results and a comparison between both approaches. We make a detailed study of one-point observations (magnetic and bulk velocity) using a set of MCs and we get the 'local' expansion rate for each studied event. We compare the obtained 'local' expansion rates with the 'average' expansion law, and also with the expansion rates for the stationary solar wind.

  20. Variation in insurance status by patient demographics and tumor site among nonelderly adult patients with cancer.

    PubMed

    Grant, Stephen R; Walker, Gary V; Guadagnolo, B Ashleigh; Koshy, Matthew; Allen, Pamela K; Mahmood, Usama

    2015-06-15

    In the United States, an estimated 48 million individuals live without health insurance. The purpose of the current study was to explore the Variation in insurance status by patient demographics and tumor site among nonelderly adult patients with cancer. A total of 688,794 patients aged 18 to 64 years who were diagnosed with one of the top 25 incident cancers (representing 95% of all cancer diagnoses) between 2007 and 2010 in the Surveillance, Epidemiology, and End Results (SEER) database were analyzed. Patient characteristics included age, race, sex, marital status, and rural or urban residence. County-level demographics included percent poverty level. Insurance status was defined as having non-Medicaid insurance, Medicaid coverage, or no insurance. On multivariate logistic regression analyses, younger age, male sex, nonwhite race, being unmarried, residence in counties with higher levels of poverty, and rural residence were associated with being uninsured versus having non-Medicaid insurance (all P <.001). The highest rates of non-Medicaid insurance were noted among patients with prostate cancer (92.3%), melanoma of the skin (92.5%), and thyroid cancer (89.5%), whereas the lowest rates of non-Medicaid insurance were observed among patients with cervical cancer (64.2%), liver cancer (67.9%), and stomach cancer (70.9%) (P <.001). Among uninsured individuals, the most prevalent cancers were lung cancer (14.9%), colorectal cancer (12.1%), and breast cancer (10.2%) (P <.001). Lung cancer caused the majority of cancer mortality in all insurance groups. Rates of insurance coverage vary greatly by demographics and by cancer type. The expansion of health insurance coverage would be expected to disproportionally benefit certain demographic populations and cancer types. © 2015 American Cancer Society.

  1. Health & Demographic Surveillance System Profile: The Nairobi Urban Health and Demographic Surveillance System (NUHDSS).

    PubMed

    Beguy, Donatien; Elung'ata, Patricia; Mberu, Blessing; Oduor, Clement; Wamukoya, Marylene; Nganyi, Bonface; Ezeh, Alex

    2015-04-01

    The Nairobi Urban Health and Demographic Surveillance System (NUHDSS) was the first urban-based longitudinal health and demographic surveillance platform in sub-Saharan Africa (SSA). The NUHDSS was established in 2002 to provide a platform to investigate the long-term social, economic and health consequences of urban residence, and to serve as a primary research tool for intervention and impact evaluation studies focusing on the needs of the urban poor in SSA. Since its inception, the NUHDSS has successfully followed every year a population of about 65,000 individuals in 24,000 households in two slum communities--Korogocho and Viwandani--in Nairobi, Kenya. Data collected include key demographic and health information (births, deaths including verbal autopsy, in- and out-migration, immunization) and other information that characterizes living conditions in the slums (livelihood opportunities, household amenities and possessions, type of housing etc.). In addition to the routine data, it has provided a robust platform for nesting several studies examining the challenges of rapid urbanization in SSA and associated health and poverty dynamics. NUHDSS data are shared through internal and external collaborations, in accordance with the Centre's guidelines for publications, data sharing.

  2. Health & Demographic Surveillance System Profile: Farafenni Health and Demographic Surveillance System in The Gambia.

    PubMed

    Jasseh, Momodou; Gomez, Pierre; Greenwood, Brian M; Howie, Stephen R C; Scott, Susana; Snell, Paul C; Bojang, Kalifa; Cham, Mamady; Corrah, Tumani; D'Alessandro, Umberto

    2015-06-01

    The Farafenni Health and Demographic Surveillance System (Farafenni HDSS) is located 170 km from the coast in a rural area of The Gambia, north of the River Gambia. It was set up in 1981 by the UK Medical Research Council Laboratories to generate demographic and health information required for the evaluation of a village-based, primary health care programme in 40 villages. Regular updates of demographic events and residency status have subsequently been conducted every 4 months. The surveillance area was extended in 2002 to include Farafenni Town and surrounding villages to support randomized, controlled trials. With over three decades of prospective surveillance, and through specific scientific investigations, the platform (population ≈ 50,000) has generated data on: morbidity and mortality due to malaria in children and during pregnancy; non-communicable disease among adults; reproductive health; and levels and trends in childhood and maternal mortality. Other information routinely collected includes causes of death through verbal autopsy, and household socioeconomic indicators. The current portfolio of the platform includes tracking Millennium Development Goal 4 (MDG4) attainments in rural Gambia and cause-of-death determination.

  3. [Poland's demographic and socio-economic problems].

    PubMed

    Secomski, K

    1984-01-01

    Population phenomena and processes are always the starting point for socioeconomic development planning. Thus it is necessary to properly coordinate the premises, goals, and directions of population and socioeconomic policies. This applies in particular to projections, programs, and development plans of the population, the economy, and society. Besides natural resources, human labor is the main factor in economic growth and its dynamics. Initially, abundant labor resources and their full use are of basic importance. Next, the quality of the human factor and the modern character of structural population, social, economic, and spatial changes become more important. These changes must be treated jointyl. Finally, the character and changing structure of human needs, society, and modernized economy should be taken into consideration. In order to meet these needs properly and with increasingly better methods, the development of the material base as well as the growth and structure of national ioncome must be coordinated accordingly. Also important are educational status and the culture of consumption. The growth of Poland's population and its structural changes require suitable changes with regard to the protective functions of the state and the implementation of new programs--in health care, education, housing, and environmental control. Appropriate research activities must be initiated in order to establish demographic and socioeconomic goals. (author's modified)

  4. Characterizing the Demographics of Exoplanet Bulk Compositions

    NASA Astrophysics Data System (ADS)

    Rogers, Leslie

    2013-10-01

    The Kepler Mission has discovered thousands of sub-Saturn-sized transiting planet candidates. Using planet interior structure models, we constrain the bulk compositions of the more than 50 known sub-Saturn-sized transiting planets with measured masses. Our model considers fully differentiated planets comprised of up to four layers: an iron core, a silicate mantle, a water mantle, and a gas envelope. We calculate the planet interior structure by integrating the coupled differential equations describing an evolving self-gravitating body, employing modern equations of state for the iron, silicates, water, and gas. For any individual planet, a wide range of compositions is consistent with the measured mass and radius. We consider the planets as an ensemble, and discuss how thermal evolution, mass loss, and observational biases sculpt the observed planet mass-radius-insolation distribution. Understanding these effects is crucial for constraining the demographics of small planet bulk compositions and for extracting signatures of the planet formation process from the accumulating census of transiting planets with dynamical confirmation.

  5. Demographics of Resonances in Exoplanetary Systems

    NASA Astrophysics Data System (ADS)

    Ragozzine, Darin; Conaway, James L.; MacDonald, Mariah G.; Sallee, Victor

    2016-10-01

    NASA's Kepler Space Telescope has identified ~700 systems of multiple transiting exoplanets containing ~1700 planets. Most of these multi-transiting systems have 3-5 planets small planets with periods of roughly 5-50 days and are known as Systems with Tightly-spaced Inner Planets (STIPs). These information-rich exoplanetary systems have precisely measured period ratios which allows for the identification and characterization of orbital mean motion resonances. Improved understanding of the resonant populations will reveal much about the formation and evolution of planetary systems. Lissauer, Ragozzine, et al. 2011 found that most Kepler systems were not in resonance, but that there was a small excess of planets wide of resonance. We present new analyses that rigorously identify the frequency of planets in multiple resonances (including three-body resonances) and thus identify many specific new results on the demographics of resonances. We also show that the apparent over-abundance of resonances can be attributed to a difference in inclinations (potentially from dissipation) with implications for the true underlying frequency of resonant systems. We compare the period ratio distribution of Kepler (corrected for inclination biases) to Radial Velocity (RV) surveys and conclude that RV systems are often missing small intermediate planets. This has serious implications for the completeness of RV identification of planets in STIPs.

  6. Demographic controls of future global fire risk

    NASA Astrophysics Data System (ADS)

    Knorr, W.; Arneth, A.; Jiang, L.

    2016-08-01

    Wildfires are an important component of terrestrial ecosystem ecology but also a major natural hazard to societies, and their frequency and spatial distribution must be better understood. At a given location, risk from wildfire is associated with the annual fraction of burned area, which is expected to increase in response to climate warming. Until recently, however, only a few global studies of future fire have considered the effects of other important global environmental change factors such as atmospheric CO2 levels and human activities, and how these influence fires in different regions. Here, we contrast the impact of climate change and increasing atmospheric CO2 content on burned area with that of demographic dynamics, using ensembles of climate simulations combined with historical and projected population changes under different socio-economic development pathways for 1901-2100. Historically, humans notably suppressed wildfires. For future scenarios, global burned area will continue to decline under a moderate emissions scenario, except for low population growth and fast urbanization, but start to increase again from around mid-century under high greenhouse gas emissions. Contrary to common perception, we find that human exposure to wildfires increases in the future mainly owing to projected population growth in areas with frequent wildfires, rather than by a general increase in burned area.

  7. Algeria. From demographic explosion to social rupture.

    PubMed

    Fargues, P

    1994-01-01

    Large families were the rule 20-30 years ago in the Maghrib and less than ten years ago in the Mashriq, with couples typically bearing 7-9 children over the course of their reproductive lives. The overall rate of total fertility, however, declined by more than 50% by the beginning of the 1990s. Rates of population growth in all Mediterranean Arab countries have actually started to decline. This stabilization of actual population growth does not, however, mean that the demand for social services will level off. Demand for health and education services increases with the decrease in the number of infants and children per family. In the years ahead, there will also be more jobs to create and houses to build, with additional future costs attributed less to an increase in numbers than to rising aspirations. The author discusses rural-urban and regional differentials in fertility, the political economy of fertility, social change and women's status, the rapid and wide-scale diffusion of formal education, and how demographic change has set the stage for horizontal competition between peers and vertical competition among generations.

  8. Demographic factors associated with bronchiolitis readmission.

    PubMed

    Riese, Jeffrey; McCulloh, Russell J; Koehn, Kristin L; Alverson, Brian K

    2014-05-01

    The goal of this study was to evaluate patient characteristics and medical management and their association with readmission in children with bronchiolitis. This retrospective chart review included children admitted with bronchiolitis to 2 children's hospitals. Reviewers selected charts based on International Classification of Diseases, Ninth Revision, diagnosis and collected information on demographic characteristics, treatment, diagnostic testing, length of stay, and adverse outcomes. Univariate analyses were used to identify risk factors associated with any-cause readmission in 4 weeks. A total of 1229 patients met inclusion criteria. Younger children were more likely to be readmitted within 4 weeks of discharge compared with older children (mean age: 4.5 vs 5.7 months; P = .005). Readmissions did not differ based on length of stay, and no medical intervention was associated with risk for readmission. Of patients readmitted from the large service area hospital, 57% lived ≤20 miles away, compared with 26.9% of those who were not readmitted (P = .03). Patients from the lowest income zip codes within the catchment area of the small service area hospital were more likely to be readmitted compared with patients from the highest income zip codes (7.8% vs 0%; P = .025). Overall, 6.4% of hospitalized patients with bronchiolitis were readmitted. Our data did not identify any inpatient medical management or modifiable risk factor associated with readmission.

  9. [Some demographic aspects associated with ectopic pregnancy].

    PubMed

    Guerrero-Martínez, Elly; Rivas-López, Radamés; Martínez-Escudero, Itzell Sarahid

    2014-02-01

    The determination techniques of chorionic gonadotropin and transvaginal high resolution ultrasound have revolutionized the diagnosis of ectopic pregnancy. Assess demographic aspects associated with ectopic pregnancy in Hospital Angeles del Pedregal over a 6 years period. Descriptive and retrospective study. We reviewed 143 clinical records from March 1, 2006 to January 31, 2013, with diagnosis of ectopic pregnancy discharge. The analyzed variables were: age, history of ectopic pregnancy, method of family planning, pelvic inflammatory disease, smoking, weeks of gestation, clinical picture, localization of ectopic pregnancy, treatment and complications. Were analyzed 143 cases, diagnosed and corroborated with histopathological study, of ectopic pregnancy in Hospital Angeles del Pedregal during the period from 2006 to 2012. The average age at which pregnancies occurred was 32.4 +/- 5.4 years; 89% of patients were over 25 years old. 35% were primigravidous and 51 women had previous caesarean, 31 abortion and 22 childbirth. 10% had history of ectopic pregnancy and 39% had 5 weeks gestation; 72% not used contraceptives, 30% were smokers, and only 2% had suffered pelvic inflammatory disease. Despite the technological advances the correct evaluation of risk factors is essential for the diagnosis of ectopic pregnancy.

  10. Comparative phylogeography of a coevolved community: concerted population expansions in Joshua trees and four yucca moths.

    PubMed

    Smith, Christopher Irwin; Tank, Shantel; Godsoe, William; Levenick, Jim; Strand, Eva; Esque, Todd; Pellmyr, Olle

    2011-01-01

    Comparative phylogeographic studies have had mixed success in identifying common phylogeographic patterns among co-distributed organisms. Whereas some have found broadly similar patterns across a diverse array of taxa, others have found that the histories of different species are more idiosyncratic than congruent. The variation in the results of comparative phylogeographic studies could indicate that the extent to which sympatrically-distributed organisms share common biogeographic histories varies depending on the strength and specificity of ecological interactions between them. To test this hypothesis, we examined demographic and phylogeographic patterns in a highly specialized, coevolved community--Joshua trees (Yucca brevifolia) and their associated yucca moths. This tightly-integrated, mutually interdependent community is known to have experienced significant range changes at the end of the last glacial period, so there is a strong a priori expectation that these organisms will show common signatures of demographic and distributional changes over time. Using a database of >5000 GPS records for Joshua trees, and multi-locus DNA sequence data from the Joshua tree and four species of yucca moth, we combined paleaodistribution modeling with coalescent-based analyses of demographic and phylgeographic history. We extensively evaluated the power of our methods to infer past population size and distributional changes by evaluating the effect of different inference procedures on our results, comparing our palaeodistribution models to Pleistocene-aged packrat midden records, and simulating DNA sequence data under a variety of alternative demographic histories. Together the results indicate that these organisms have shared a common history of population expansion, and that these expansions were broadly coincident in time. However, contrary to our expectations, none of our analyses indicated significant range or population size reductions at the end of the last glacial

  11. Comparative Phylogeography of a Coevolved Community: Concerted Population Expansions in Joshua Trees and Four Yucca Moths

    PubMed Central

    Smith, Christopher Irwin; Tank, Shantel; Godsoe, William; Levenick, Jim; Strand, Eva; Esque, Todd; Pellmyr, Olle

    2011-01-01

    Comparative phylogeographic studies have had mixed success in identifying common phylogeographic patterns among co-distributed organisms. Whereas some have found broadly similar patterns across a diverse array of taxa, others have found that the histories of different species are more idiosyncratic than congruent. The variation in the results of comparative phylogeographic studies could indicate that the extent to which sympatrically-distributed organisms share common biogeographic histories varies depending on the strength and specificity of ecological interactions between them. To test this hypothesis, we examined demographic and phylogeographic patterns in a highly specialized, coevolved community – Joshua trees (Yucca brevifolia) and their associated yucca moths. This tightly-integrated, mutually interdependent community is known to have experienced significant range changes at the end of the last glacial period, so there is a strong a priori expectation that these organisms will show common signatures of demographic and distributional changes over time. Using a database of >5000 GPS records for Joshua trees, and multi-locus DNA sequence data from the Joshua tree and four species of yucca moth, we combined paleaodistribution modeling with coalescent-based analyses of demographic and phylgeographic history. We extensively evaluated the power of our methods to infer past population size and distributional changes by evaluating the effect of different inference procedures on our results, comparing our palaeodistribution models to Pleistocene-aged packrat midden records, and simulating DNA sequence data under a variety of alternative demographic histories. Together the results indicate that these organisms have shared a common history of population expansion, and that these expansions were broadly coincident in time. However, contrary to our expectations, none of our analyses indicated significant range or population size reductions at the end of the last glacial

  12. Comparative phylogeography of a coevolved community: concerted population expansions in Joshua trees and four yucca moths

    USGS Publications Warehouse

    Smith, Christopher Irwin; Tank, Shantel; Godsoe, William; Levenick, Jim; Strand, Eva; Esque, Todd C.; Pellmyr, Olle

    2011-01-01

    Comparative phylogeographic studies have had mixed success in identifying common phylogeographic patterns among co-distributed organisms. Whereas some have found broadly similar patterns across a diverse array of taxa, others have found that the histories of different species are more idiosyncratic than congruent. The variation in the results of comparative phylogeographic studies could indicate that the extent to which sympatrically-distributed organisms share common biogeographic histories varies depending on the strength and specificity of ecological interactions between them. To test this hypothesis, we examined demographic and phylogeographic patterns in a highly specialized, coevolved community – Joshua trees (Yucca brevifolia) and their associated yucca moths. This tightly-integrated, mutually interdependent community is known to have experienced significant range changes at the end of the last glacial period, so there is a strong a priori expectation that these organisms will show common signatures of demographic and distributional changes over time. Using a database of >5000 GPS records for Joshua trees, and multi-locus DNA sequence data from the Joshua tree and four species of yucca moth, we combined paleaodistribution modeling with coalescent-based analyses of demographic and phylgeographic history. We extensively evaluated the power of our methods to infer past population size and distributional changes by evaluating the effect of different inference procedures on our results, comparing our palaeodistribution models to Pleistocene-aged packrat midden records, and simulating DNA sequence data under a variety of alternative demographic histories. Together the results indicate that these organisms have shared a common history of population expansion, and that these expansions were broadly coincident in time. However, contrary to our expectations, none of our analyses indicated significant range or population size reductions at the end of the last glacial

  13. Comparative phylogeography of a coevolved community: Concerted population expansions in Joshua trees and four Yucca moths

    USGS Publications Warehouse

    Smith, C.I.; Tank, S.; Godsoe, W.; Levenick, J.; Strand, Espen; Esque, T.; Pellmyr, O.

    2011-01-01

    Comparative phylogeographic studies have had mixed success in identifying common phylogeographic patterns among co-distributed organisms. Whereas some have found broadly similar patterns across a diverse array of taxa, others have found that the histories of different species are more idiosyncratic than congruent. The variation in the results of comparative phylogeographic studies could indicate that the extent to which sympatrically-distributed organisms share common biogeographic histories varies depending on the strength and specificity of ecological interactions between them. To test this hypothesis, we examined demographic and phylogeographic patterns in a highly specialized, coevolved community - Joshua trees (Yucca brevifolia) and their associated yucca moths. This tightly-integrated, mutually interdependent community is known to have experienced significant range changes at the end of the last glacial period, so there is a strong a priori expectation that these organisms will show common signatures of demographic and distributional changes over time. Using a database of >5000 GPS records for Joshua trees, and multi-locus DNA sequence data from the Joshua tree and four species of yucca moth, we combined paleaodistribution modeling with coalescent-based analyses of demographic and phylgeographic history. We extensively evaluated the power of our methods to infer past population size and distributional changes by evaluating the effect of different inference procedures on our results, comparing our palaeodistribution models to Pleistocene-aged packrat midden records, and simulating DNA sequence data under a variety of alternative demographic histories. Together the results indicate that these organisms have shared a common history of population expansion, and that these expansions were broadly coincident in time. However, contrary to our expectations, none of our analyses indicated significant range or population size reductions at the end of the last glacial

  14. Multipole expansion method for supernova neutrino oscillations

    SciTech Connect

    Duan, Huaiyu; Shalgar, Shashank E-mail: shashankshalgar@unm.edu

    2014-10-01

    We demonstrate a multipole expansion method to calculate collective neutrino oscillations in supernovae using the neutrino bulb model. We show that it is much more efficient to solve multi-angle neutrino oscillations in multipole basis than in angle basis. The multipole expansion method also provides interesting insights into multi-angle calculations that were accomplished previously in angle basis.

  15. Unitary expansion of the time evolution operator

    SciTech Connect

    Zagury, N.; Aragao, A.; Casanova, J.; Solano, E.

    2010-10-15

    We propose an expansion of the unitary evolution operator, associated with a given Schroedinger equation, in terms of a finite product of explicit unitary operators. In this manner, this unitary expansion can be truncated at the desired level of approximation, as shown in the given examples.

  16. Expansion techniques for collisionless stellar dynamical simulations

    SciTech Connect

    Meiron, Yohai; Li, Baile; Holley-Bockelmann, Kelly; Spurzem, Rainer

    2014-09-10

    We present graphics processing unit (GPU) implementations of two fast force calculation methods based on series expansions of the Poisson equation. One method is the self-consistent field (SCF) method, which is a Fourier-like expansion of the density field in some basis set; the other method is the multipole expansion (MEX) method, which is a Taylor-like expansion of the Green's function. MEX, which has been advocated in the past, has not gained as much popularity as SCF. Both are particle-field methods and optimized for collisionless galactic dynamics, but while SCF is a 'pure' expansion, MEX is an expansion in just the angular part; thus, MEX is capable of capturing radial structure easily, while SCF needs a large number of radial terms. We show that despite the expansion bias, these methods are more accurate than direct techniques for the same number of particles. The performance of our GPU code, which we call ETICS, is profiled and compared to a CPU implementation. On the tested GPU hardware, a full force calculation for one million particles took ∼0.1 s (depending on expansion cutoff), making simulations with as many as 10{sup 8} particles fast for a comparatively small number of nodes.

  17. 45 CFR 800.104 - Phased expansion.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 3 2013-10-01 2013-10-01 false Phased expansion. 800.104 Section 800.104 Public Welfare Regulations Relating to Public Welfare (Continued) OFFICE OF PERSONNEL MANAGEMENT MULTI-STATE PLAN PROGRAM Multi-State Plan Program Issuer Requirements § 800.104 Phased expansion. (a) Phase-in. OPM may...

  18. 45 CFR 800.104 - Phased expansion.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 45 Public Welfare 3 2014-10-01 2014-10-01 false Phased expansion. 800.104 Section 800.104 Public Welfare Regulations Relating to Public Welfare (Continued) OFFICE OF PERSONNEL MANAGEMENT MULTI-STATE PLAN PROGRAM Multi-State Plan Program Issuer Requirements § 800.104 Phased expansion. (a) Phase-in. OPM may...

  19. Earnings Returns to the British Education Expansion

    ERIC Educational Resources Information Center

    Devereux, Paul J.; Fan, Wen

    2011-01-01

    We study the effects of the large expansion in British educational attainment that took place for cohorts born between 1970 and 1975. Using the Quarterly Labour Force Survey, we find that the expansion caused men to increase education by about a year on average and gain about 8% higher wages; women obtained a slightly greater increase in education…

  20. Analysis of Performance Variation Using Query Expansion.

    ERIC Educational Resources Information Center

    Alemayehu, Nega

    2003-01-01

    Discussion of information retrieval performance evaluation focuses on a case study using a statistical repeated measures analysis of variance for testing the significance of factors, such as retrieval method and topic in retrieval performance variation. Analyses of the effect of query expansion on document ranking confirm that expansion affects…

  1. Analysis of Performance Variation Using Query Expansion.

    ERIC Educational Resources Information Center

    Alemayehu, Nega

    2003-01-01

    Discussion of information retrieval performance evaluation focuses on a case study using a statistical repeated measures analysis of variance for testing the significance of factors, such as retrieval method and topic in retrieval performance variation. Analyses of the effect of query expansion on document ranking confirm that expansion affects…

  2. Finnish Higher Education Expansion and Regional Policy

    ERIC Educational Resources Information Center

    Saarivirta, Toni

    2010-01-01

    This paper concentrates on the expansion of Finnish higher education between the 1960s and 1970s, exposes its background in the light of the policy decisions that were made, compares the unique features of this expansion with those of certain other countries, discusses the impact of the controlled "top down" governance of higher…

  3. Expansive Learning as Production of Community

    ERIC Educational Resources Information Center

    Morck, Line Lerche

    2010-01-01

    This article contributes a framework for analyzing learning as an expansive process in which persons come to partly transcend marginalization. Expansive learning is a kind of learning that partly transcends marginalization through changed participation and recognition by others of participants in their changed communities. This article draws on…

  4. A reduced volumetric expansion factor plot

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.

    1979-01-01

    A reduced volumetric expansion factor plot was constructed for simple fluids which is suitable for engineering computations in heat transfer. Volumetric expansion factors were found useful in correlating heat transfer data over a wide range of operating conditions including liquids, gases and the near critical region.

  5. A reduced volumetric expansion factor plot

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.

    1979-01-01

    A reduced volumetric expansion factor plot has been constructed for simple fluids which is suitable for engineering computations in heat transfer. Volumetric expansion factors have been found useful in correlating heat transfer data over a wide range of operating conditions including liquids, gases and the near critical region.

  6. Flash Expansion Threshold in Whirligig Swarms.

    PubMed

    Romey, William L; Lamb, Alicia R

    2015-01-01

    In the selfish herd hypothesis, prey animals move toward each other to avoid the likelihood of being selected by a predator. However, many grouped animals move away from each other the moment before a predator attacks. Very little is known about this phenomenon, called flash expansion, such as whether it is triggered by one individual or a threshold and how information is transferred between group members. We performed a controlled experiment with whirligig beetles in which the ratio of sighted to unsighted individuals was systematically varied and emergent flash expansion was measured. Specifically, we examined: the percentage of individuals in a group that startled, the resulting group area, and the longevity of the flash expansion. We found that one or two sighted beetles in a group of 24 was not enough to cause a flash expansion after a predator stimulus, but four sighted beetles usually initiated a flash expansion. Also, the more beetles that were sighted the larger the resulting group area and the longer duration of the flash expansion. We conclude that flash expansion is best described as a threshold event whose adaptive value is to prevent energetically costly false alarms while quickly mobilizing an emergent predator avoidance response. This is one of the first controlled experiments of flash expansion, an important emergent property that has applications to understanding collective motion in swarms, schools, flocks, and human crowds. Also, our study is a convincing demonstration of social contagion, how the actions of one individual can pass through a group.

  7. Finnish Higher Education Expansion and Regional Policy

    ERIC Educational Resources Information Center

    Saarivirta, Toni

    2010-01-01

    This paper concentrates on the expansion of Finnish higher education between the 1960s and 1970s, exposes its background in the light of the policy decisions that were made, compares the unique features of this expansion with those of certain other countries, discusses the impact of the controlled "top down" governance of higher…

  8. Earnings Returns to the British Education Expansion

    ERIC Educational Resources Information Center

    Devereux, Paul J.; Fan, Wen

    2011-01-01

    We study the effects of the large expansion in British educational attainment that took place for cohorts born between 1970 and 1975. Using the Quarterly Labour Force Survey, we find that the expansion caused men to increase education by about a year on average and gain about 8% higher wages; women obtained a slightly greater increase in education…

  9. The heavy quark expansion of QCD

    SciTech Connect

    Falk, A.F.

    1997-06-01

    These lectures contain an elementary introduction to heavy quark symmetry and the heavy quark expansion. Applications such as the expansion of heavy meson decay constants and the treatment of inclusive and exclusive semileptonic B decays are included. Heavy hadron production via nonperturbative fragmentation processes is also discussed. 54 refs., 7 figs.

  10. Expansive Learning as Production of Community

    ERIC Educational Resources Information Center

    Morck, Line Lerche

    2010-01-01

    This article contributes a framework for analyzing learning as an expansive process in which persons come to partly transcend marginalization. Expansive learning is a kind of learning that partly transcends marginalization through changed participation and recognition by others of participants in their changed communities. This article draws on…

  11. Series expansion of the modified Einstein Procedure

    Treesearch

    Seema Chandrakant Shah-Fairbank

    2009-01-01

    This study examines calculating total sediment discharge based on the Modified Einstein Procedure (MEP). A new procedure based on the Series Expansion of the Modified Einstein Procedure (SEMEP) has been developed. This procedure contains four main modifications to MEP. First, SEMEP solves the Einstein integrals quickly and accurately based on a series expansion. Next,...

  12. 76 FR 19746 - Approval for Subzone Expansion and Expansion of Manufacturing Authority; Foreign-Trade Subzone...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-08

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE Foreign-Trade Zones Board Approval for Subzone Expansion and Expansion of Manufacturing Authority; Foreign... Jefferson County Riverport Authority, grantee of Foreign-Trade Zone 29, has requested an expansion of the...

  13. 76 FR 75870 - Approval for Subzone Expansion and Expansion of Manufacturing Authority; Foreign-Trade Subzone...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE Foreign-Trade Zones Board Approval for Subzone Expansion and Expansion of Manufacturing Authority; Foreign... Louisiana Port Commission, grantee of Foreign- Trade Zone 124, has requested an expansion of the subzone and...

  14. The Impact of Educational Interventions by Socio-Demographic Attribute

    DTIC Science & Technology

    2008-07-10

    The Impact of Educational Interventions by Socio- Demographic Attribute Brian R. Hirshman, Michael Martin, Michael W. Bigrigg and...The Impact of Educational Interventions by Socio- Demographic Attribute 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...mechanisms have been added to Construct, and these attributes have been tied to socio- demographic sub-populations, it is now possible to examine the effects

  15. The Changing Demographic Profile of the United States

    DTIC Science & Technology

    2006-05-05

    Demographic Profile of the United States Updated May 5, 2006 Laura B. Shrestha Specialist in Demography Domestic Social Policy Division Report...TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE The Changing Demographic Profile of the United States 5a. CONTRACT NUMBER 5b. GRANT...unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 The Changing Demographic Profile of the United

  16. Behavioral, Psychological, and Demographic Predictors of Physical Fitness.

    DTIC Science & Technology

    1987-12-14

    psychological factors related to beliefs about fitness and weight control, and background/ demographic factors . These findings represent a successful attempt to...7AD-A192 697 BEHAVIORAL PSYCHOLOGICAL AND DEMOGRAPHIC PREDICTORS OF j PHYSICAL FITNESS(U) NAVAL HEALTH RESEARCH CENTER SAN DIEGO CA T L CONW~AY 1.4...DEC 87 NHRC-87-37 UNCLASSIFIED F/G 6/ie NL Illll i 11 .0 14w -W -- - -JCFILE Copy BEHAVIORALF PSYCHOLOGICAL, AND DEMOGRAPHIC - PREDICTORS OPPHYSICAL

  17. A Comparison of Breast Cancer Treatment Regimens by Demographic Characteristics

    DTIC Science & Technology

    1998-10-01

    Cancer Treatment Regimens by Demographic Characteristics PRINCIPAL INVESTIGATOR: Marianne E. Ulcickas Yood, M.P.H. CONTRACTING ORGANIZATION: Henry...NUMBERS A Comparison of Breast Cancer Treatment Regimens by Demographic Characteristics DAMD17-97-1-7302 6. AUTHOR(S) Marianne E. Ulcickas Yood, M.P.H. 7... Cancer Treatment Regimens by Demographic Characteristics (DAMD17-97-1-7302), Annual Report October, 1998 TABLE OF CONTENTS Introduction

  18. Low-thermal expansion infrared glass ceramics

    NASA Astrophysics Data System (ADS)

    Lam, Philip

    2009-05-01

    L2 Tech, Inc. is in development of an innovative infrared-transparent glass ceramic material with low-thermal expansion (<0.5 ppm/°C) and high thermal-shock resistance to be used as windows and domes for high speed flight. The material is an inorganic, non-porous glass ceramic, characterized by crystalline phases of evenly distributed nano-crystals in a residual glass phase. The major crystalline phase is zirconium tungstate (ZrW2O8) which has Negative Thermal Expansion (NTE). The glass phase is the infrared-transparent germanate glass which has positive thermal expansion (PTE). Then glass ceramic material has a balanced thermal expansion of near zero. The crystal structure is cubic and the thermal expansion of the glass ceramic is isotropic or equal in all directions.

  19. Expansion of Einstein-Yang-Mills amplitude

    NASA Astrophysics Data System (ADS)

    Fu, Chih-Hao; Du, Yi-Jian; Huang, Rijun; Feng, Bo

    2017-09-01

    In this paper, we study from various perspectives the expansion of tree level single trace Einstein-Yang-Mills amplitudes into linear combination of color-ordered Yang-Mills amplitudes. By applying the gauge invariance principle, a programable recursive construction is devised to expand EYM amplitude with arbitrary number of gravitons into EYM amplitudes with fewer gravitons. Based on this recursive technique we write down the complete expansion of any single trace EYM amplitude in the basis of color-order Yang-Mills amplitude. As a byproduct, an algorithm for constructing a polynomial form of the BCJ numerator for Yang-Mills amplitudes is also outlined in this paper. In addition, by applying BCFW recursion relation we show how to arrive at the same EYM amplitude expansion from the on-shell perspective. And we examine the EYM expansion using KLT relations and show how to evaluate the expansion coefficients efficiently.

  20. Business information query expansion through semantic network

    NASA Astrophysics Data System (ADS)

    Gong, Zhiguo; Muyeba, Maybin; Guo, Jingzhi

    2010-02-01

    In this article, we propose a method for business information query expansions. In our approach, hypernym/hyponymy and synonym relations in WordNet are used as the basic expansion rules. Then we use WordNet Lexical Chains and WordNet semantic similarity to assign terms in the same query into different groups with respect to their semantic similarities. For each group, we expand the highest terms in the WordNet hierarchies with hypernym and synonym, the lowest terms with hyponym and synonym and all other terms with only synonym. In this way, the contradictory caused by full expansion can be well controlled. Furthermore, we use collection-related term semantic network to further improve the expansion performance. And our experiment reveals that our solution for query expansion can improve the query performance dramatically.

  1. Evaluation of demographic history and neutral parameterization on the performance of FST outlier tests.

    PubMed

    Lotterhos, Katie E; Whitlock, Michael C

    2014-05-01

    F(ST) outlier tests are a potentially powerful way to detect genetic loci under spatially divergent selection. Unfortunately, the extent to which these tests are robust to nonequilibrium demographic histories has been understudied. We developed a landscape genetics simulator to test the effects of isolation by distance (IBD) and range expansion on FST outlier methods. We evaluated the two most commonly used methods for the identification of F(ST) outliers (FDIST2 and BayeScan, which assume samples are evolutionarily independent) and two recent methods (FLK and Bayenv2, which estimate and account for evolutionary nonindependence). Parameterization with a set of neutral loci ('neutral parameterization') always improved the performance of FLK and Bayenv2, while neutral parameterization caused FDIST2 to actually perform worse in the cases of IBD or range expansion. BayeScan was improved when the prior odds on neutrality was increased, regardless of the true odds in the data. On their best performance, however, the widely used methods had high false-positive rates for IBD and range expansion and were outperformed by methods that accounted for evolutionary nonindependence. In addition, default settings in FDIST2 and BayeScan resulted in many false positives suggesting balancing selection. However, all methods did very well if a large set of neutral loci is available to create empirical P-values. We conclude that in species that exhibit IBD or have undergone range expansion, many of the published FST outliers based on FDIST2 and BayeScan are probably false positives, but FLK and Bayenv2 show great promise for accurately identifying loci under spatially divergent selection.

  2. Evaluation of demographic history and neutral parameterization on the performance of FST outlier tests

    PubMed Central

    Lotterhos, Katie E; Whitlock, Michael C

    2014-01-01

    FST outlier tests are a potentially powerful way to detect genetic loci under spatially divergent selection. Unfortunately, the extent to which these tests are robust to nonequilibrium demographic histories has been understudied. We developed a landscape genetics simulator to test the effects of isolation by distance (IBD) and range expansion on FST outlier methods. We evaluated the two most commonly used methods for the identification of FST outliers (FDIST2 and BayeScan, which assume samples are evolutionarily independent) and two recent methods (FLK and Bayenv2, which estimate and account for evolutionary nonindependence). Parameterization with a set of neutral loci (‘neutral parameterization’) always improved the performance of FLK and Bayenv2, while neutral parameterization caused FDIST2 to actually perform worse in the cases of IBD or range expansion. BayeScan was improved when the prior odds on neutrality was increased, regardless of the true odds in the data. On their best performance, however, the widely used methods had high false-positive rates for IBD and range expansion and were outperformed by methods that accounted for evolutionary nonindependence. In addition, default settings in FDIST2 and BayeScan resulted in many false positives suggesting balancing selection. However, all methods did very well if a large set of neutral loci is available to create empirical P-values. We conclude that in species that exhibit IBD or have undergone range expansion, many of the published FST outliers based on FDIST2 and BayeScan are probably false positives, but FLK and Bayenv2 show great promise for accurately identifying loci under spatially divergent selection. PMID:24655127

  3. Population genetic structure of the Lyme disease vector Ixodes scapularis at an apparent spatial expansion front.

    PubMed

    Kelly, Rebecca R; Gaines, David; Gilliam, Will F; Brinkerhoff, R Jory

    2014-10-01

    Modeling and empirical evidence suggests that Lyme disease is undergoing geographic expansion from principal foci in the midwestern and northeastern United States. Virginia is at the southern edge of the current expansion zone and has seen dramatic rise in human Lyme disease cases since 2007, potentially owing to a recent increase in vector abundance. Ixodes scapularis is known throughout the eastern US but behavioral or physiological variation between northern and southern lineages might lead northern-variant ticks to more frequently parasitize humans. We hypothesized that recent spatial and numerical increase in Lyme disease cases is associated with demographic and/or spatial expansion of I. scapularis and that signals of these phenomena would be detectable and discernable in population genetic signals. In summer and fall 2011, we collected nymphal I. scapularis by drag sampling and adult I. scapularis from deer carcasses at hunting check stations at nine sites arranged along an east-west transect through central Virginia. We analyzed 16S mtDNA sequences data from up to 24 I. scapularis individuals collected from each site and detected a total of 24 haplotypes containing 29 segregating sites. We found no evidence for population genetic structure among these sites but we did find strong signals of both demographic and spatial expansion throughout our study system. We found two haplotypes (one individual each) representing a lineage of ticks that is only found in the southeastern United States, with the remaining individuals representing a less genetically diverse clade that is typical of the northern United States, but that has also been detected in the American South. Taken together, these results lead us to conclude that I. scapularis populations in Virginia are expanding and that this expansion may account for recent observed increases in Lyme disease. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Differential ventricular expansion in hydrocephalus.

    PubMed

    McAllister, J P; Chovan, P; Steiner, C P; Johnson, M J; Ayzman, I; Wood, A S; Tkach, J A; Hahn, J F; Luciano, M G

    1998-12-01

    In the large canine model of acquired obstructive hydrocephalus that we have developed recently, computer-assisted 3-dimensional morphometry has been performed on T1-weighted Spin Echo MRI images from adult dogs before and after the induction of hydrocephalus. To date, 7 hydrocephalic animals have been analyzed that survived 7-83 days (median = 54) after receiving injections of cyanoacrylate glue into the anterior fourth ventricle. Measurements were obtained from lateral, 3rd, and 4th ventricles. The volumes of the left and right lateral ventricles were symmetrical before and after induction. Mean lateral ventricle volume increased 424% from a baseline of 0.63 cc to a post-induction value of 3.30 cc (p < 0.01 with unpaired t-test). In contrast, the 3rd ventricle expanded 187% from a mean of 0.15 cc to 0.43 cc (p < 0.05). The combined volume of the lateral and 3rd ventricles increased 369% from a mean of 0.78 cc to 3.69 cc (p < 0.01). Evans' ratios, which are used routinely in the clinical setting, were also obtained from linear measurements of the lateral ventricle width divided by brain width at the level of the foramen of Monro. These values exhibited only a 94% increase from mean baseline ratios of 0.17 to post-induction ratios of 0.33 (p < 0.05). These findings indicate that in mechanically-induced obstructive hydrocephalus the relative expansion of the lateral ventricles is greater than that of the 3rd ventricle. In addition, volumetric measurements of the lateral and 3rd ventricles suggest that the extent of ventriculomegaly is 3-4 times greater than estimated by Evans' ratios.

  5. [The ecological limits to demographic growth].

    PubMed

    Raffestin, C

    1989-09-01

    Although most individuals are able to conceive of limitations on local resources, the idea that global resources are also potentially exhaustible appears harder to grasp. Not only are soil resources exhaustible, but the total vegetal biomass is ultimately limited by the fixed quantity of energy received from the sun. If the biomass is finite, the human population must also be finite. It would be very difficult to estimate the size of the human population that could be supported on earth because of the very different use of resources by different groups. Roughly 76% of the world's 5 billion persons live in the developing countries, and most of them weigh less heavily on the ecosystem as individuals than do persons living in the developed countries. Despite the difficulties of defining an ecologic limit on growth, the topic has held a certain fascination throughout history and various attempts have been made, most recently in 1972 with "The Limits of Growth". The question of ecological limits to growth is implicitly or explicitly posed in terms of 3 major problems: food resources, the physical capacity of ecosystems, and the territoriality of populations within ecosystems. The problem is made more complex by the fact that the objective of human societies compatible with resources. Soil erosion, inappropriate agricultural practices, pollution, the automobile and waste disposal are examples of technological aspects of society whose costs have not been rationally dealth with and which are not managed in a satisfactory manner in contemporary life. All economic and demographic growth carries with it bioecological degradation. The question of whether the earth is now overpopulated cannot be answered precisely. Nevertheless, the terrestrial ecosystem is in crisis; it is being degraded faster than it can be restored. There are no more free goods; air and water are not free.

  6. Demographic trends, population policy and public opinion.

    PubMed

    Palomba, R; Bonifazi, C; Menniti, A

    1989-01-01

    Findings are analyzed of the Instituto di Richerche solla poplazione survey carried out in Italy in 1987 which focused on: 1) those variables which may be indirectly affecting Italian's fertility intentions, and 2) the degree of acceptability of a global social policy i.e., one that is not only restricted to economic incentives to be offered to families. Data was obtained from a national sample of 1500 people between 18-49 years. Italians have a good awareness of demographic issues; 61% knew of the decline in marriages; 72% were aware of the increasing aging population; 50% viewed the fall in birth rate negatively; and 41% thought that population and fertility trends would remain at the present low level or would decrease even further (49%). The birth rate decline was contributed to economic reasons at both reasons at both a global and an individual level. The majority of people did not show any signs of prejudice toward immigrants; however, they did favor limiting the number of foreigners in general with the exception of political refugees. The majority were also in favor of helping 3rd World countries. Although Italians value their children and the parent-child relationship very highly, a reduction in the value of children with increasing educational level of the respondents was observed. 83% thought that couples should be allowed to have as many children as they wanted; 81% agreed that measures regarding contraceptive knowledge and availability should be improved; and 49% were in favor of measures to increase births. Regarding possible new policy measures, 50% were in full agreement on the development and increased efficiency of social services to enable women to go out to work. (author's modified)

  7. The demographics of military children and families.

    PubMed

    Clever, Molly; Segal, David R

    2013-01-01

    Since the advent of the all-volunteer force in the 1970s, marriage, parenthood, and family life have become commonplace in the U.S. military among enlisted personnel and officers alike, and military spouses and children now outnumber service members by a ratio of 1.4 to 1. Reviewing data from the government and from academic and nonacademic research, Molly Clever and David R. Segal find several trends that distinguish today's military families. Compared with civilians, for example, service members marry younger and start families earlier. Because of the requirements of their jobs, they move much more frequently than civilians do, and they are often separated from their families for months at a time. And despite steady increases since the 1970s in the percentage of women who serve, the armed forces are still overwhelmingly male, meaning that the majority of military parents are fathers. Despite these distinguishing trends, Clever and Segal's chief finding is that military families cannot be neatly pigeonholed. Instead, they are a strikingly diverse population with diverse needs. Within the military, demographic groups differ in important ways, and the service branches differ from one another as well. Military families themselves come in many forms, including not only the categories familiar from civilian life--two-parent, single-parent, and so on--but also, unique to the military, dual-service families in which both parents are service members. Moreover, military families' needs change over time as they move through personal and military transitions. Thus the best policies and programs to help military families and children are flexible and adaptable rather than rigidly structured.

  8. Genetic demographic networks: Mathematical model and applications.

    PubMed

    Kimmel, Marek; Wojdyła, Tomasz

    2016-10-01

    Recent improvement in the quality of genetic data obtained from extinct human populations and their ancestors encourages searching for answers to basic questions regarding human population history. The most common and successful are model-based approaches, in which genetic data are compared to the data obtained from the assumed demography model. Using such approach, it is possible to either validate or adjust assumed demography. Model fit to data can be obtained based on reverse-time coalescent simulations or forward-time simulations. In this paper we introduce a computational method based on mathematical equation that allows obtaining joint distributions of pairs of individuals under a specified demography model, each of them characterized by a genetic variant at a chosen locus. The two individuals are randomly sampled from either the same or two different populations. The model assumes three types of demographic events (split, merge and migration). Populations evolve according to the time-continuous Moran model with drift and Markov-process mutation. This latter process is described by the Lyapunov-type equation introduced by O'Brien and generalized in our previous works. Application of this equation constitutes an original contribution. In the result section of the paper we present sample applications of our model to both simulated and literature-based demographies. Among other we include a study of the Slavs-Balts-Finns genetic relationship, in which we model split and migrations between the Balts and Slavs. We also include another example that involves the migration rates between farmers and hunters-gatherers, based on modern and ancient DNA samples. This latter process was previously studied using coalescent simulations. Our results are in general agreement with the previous method, which provides validation of our approach. Although our model is not an alternative to simulation methods in the practical sense, it provides an algorithm to compute pairwise

  9. Febrile Seizure: Demographic Features and Causative Factors

    PubMed Central

    ESMAILI GOURABI, Hamed; BIDABADI, Elham; CHERAGHALIPOUR, Fatemeh; AARABI, Yasaman; SALAMAT, Fatemeh

    2012-01-01

    Objective Because of geographical and periodical variation, we prompted to determine the demographic features and causative factors for febrile seizure in Rasht. Materials & Methods In this cross-sectional study, all 6–month- to 6-year-old children with the diagnosis of febrile seizure admitted to 17 Shahrivar hospital in Rasht, from August, 2009 to August, 2010 were studied. Age, sex, family history of the disease, seizure types, body temperature upon admission and infectious causes of the fever were recorded. All statistical analysis was performed with SPSS software, version 16. Results Of the 214 children (mean age, 25.24±15.40 months), 124 were boys and 109 had a positive family history. Complex seizures were seen in 39 cases. In patients with a complex febrile seizure, 59% had the repetitive type, 20.5% had the focal type and 20.5% had more than 15 minutes duration of seizures. Most of the repetitive seizures (78.3%) occurred in patients under 2 years old; the difference between under and over 2-year-old patients was statistically significant. Study results did not show significant differences between the two genders for simple or complex seizures. The mean body temperature upon admission was 38.2±1.32◦C (38.31±0.82 degrees in boys and 38.04±1.78 in girls). Upper respiratory infections were seen in most patients (74.29%). All cases of lower respiratory infections were boys. There was a statistically significant difference between boys and girls in causes of fever. Conclusion Most of the children had a positive family history and the most common causative factor was upper respiratory infection. PMID:24665278

  10. The Epidemiology and Demographics of Hip Dysplasia

    PubMed Central

    Loder, Randall T.; Skopelja, Elaine N.

    2011-01-01

    The etiology of developmental dysplasia of the hip (DDH) is unknown. There are many insights, however, from epidemiologic/demographic information. A systematic medical literature review regarding DDH was performed. There is a predominance of left-sided (64.0%) and unilateral disease (63.4%). The incidence per 1000 live births ranges from 0.06 in Africans in Africa to 76.1 in Native Americans. There is significant variability in incidence within each racial group by geographic location. The incidence of clinical neonatal hip instability at birth ranges from 0.4 in Africans to 61.7 in Polish Caucasians. Predictors of DDH are breech presentation, positive family history, and gender (female). Children born premature, with low birth weights, or to multifetal pregnancies are somewhat protected from DDH. Certain HLA A, B, and D types demonstrate an increase in DDH. Chromosome 17q21 is strongly associated with DDH. Ligamentous laxity and abnormalities in collagen metabolism, estrogen metabolism, and pregnancy-associated pelvic instability are well-described associations with DDH. Many studies demonstrate an increase of DDH in the winter, both in the northern and southern hemispheres. Swaddling is strongly associated with DDH. Amniocentesis, premature labor, and massive radiation exposure may increase the risk of DDH. Associated conditions are congenital muscular torticollis and congenital foot deformities. The opposite hip is frequently abnormal when using rigorous radiographic assessments. The role of acetabular dysplasia and adult hip osteoarthritis is complex. Archeological studies demonstrate that the epidemiology of DDH may be changing. PMID:24977057

  11. Demographics of the European apicultural industry.

    PubMed

    Chauzat, Marie-Pierre; Cauquil, Laura; Roy, Lise; Franco, Stéphanie; Hendrikx, Pascal; Ribière-Chabert, Magali

    2013-01-01

    Over the last few years, many European and North American countries have reported a high rate of disorders (mortality, dwindling and disappearance) affecting honeybee colonies (Apis mellifera). Although beekeeping has become an increasingly professional activity in recent years, the beekeeping industry remains poorly documented in Europe. The European Union Reference Laboratory for Honeybee Health sent a detailed questionnaire to each Member State, in addition to Kosovo and Norway, to determine the demographics and state of their beekeeping industries. Based on data supplied by the National Reference Laboratory for honeybee diseases in each European country, a European database was created to describe the beekeeping industry including the number and types of beekeepers, operation size, industry production, and health (notifiable diseases, mortalities). The total number of beekeepers in Europe was estimated at 620,000. European honey production was evaluated at around 220,000 tons in 2010. The price of honey varied from 1.5 to 40 €/kg depending on the country and on the distribution network. The estimated colony winter mortality varied from 7 to 28% depending on the country and the origin of the data (institutional survey or beekeeping associations). This survey documents the high heterogeneity of the apicultural industry within the European Union. The high proportion of non-professional beekeepers and the small mean number of colonies per beekeeper were the only common characteristics at European level. The tremendous variation in European apicultural industries has implication for any comprehensive epidemiological or economic analysis of the industry. This variability needs to be taken into account for such analysis as well as for future policy development. The industry would be served if beekeeping registration was uniformly implemented across member states. Better information on the package bee and queen production would help in understanding the ability of

  12. Demographic features of subjects with congenital glaucoma

    PubMed Central

    Tamçelik, Nevbahar; Atalay, Eray; Bolukbasi, Selim; Çapar, Olgu; Ozkok, Ahmet

    2014-01-01

    Context: Congenital glaucoma is a potentially blinding ocular disease of the childhood. Identification of the possible associated risk factors and may be helpful for prevention or early detection of this public health problem. Aims: To demonstrate the demographic features of congenital glaucoma subjects. Setting and Design: The charts of congenital glaucoma patients referred to Tamcelik Glaucoma Center were retrospectively reviewed through the dates of 2000 and 2013. Materials and Methods: Analyzed data included diagnosis, age at first presentation, symptoms at first presentation, laterality of the disease, sex, presence of consanguinity, family history of congenital glaucoma, maturity of the fetus at delivery, and maternal age at conception. Statistical Analysis Used: Statistical Package for Social Sciences (SPSS) version 19.0 by IBM (SPSS Inc, Chicago, Illinois, USA) was used to compare the mean of continuous variables with Student's t-test and analysis of variance (ANOVA) and χ2 test was used to test differences in proportions of categorical variables. Results: The data of 600 eyes of 311 patients were analyzed. The distribution of primary and secondary congenital glaucoma among the patients were 63.3% (n = 197) and 36.7% (n = 114), respectively. Of the 311 patients, 57.2% (n = 178) were male and 42.8% (n = 133) were female. The overall frequency of bilateral disease was 92.3% (n = 287). Overall rate of consanguinity and positive family history was 45.3% (n = 141) and 21.2% (n = 66), respectively. Conclusions: Bilateral disease in this study was more common than previously reported studies. Positive family history was more frequent in primary congenital glaucoma although not statistically significant. PMID:24881602

  13. Foot Syndactyly: A Clinical and Demographic Analysis

    PubMed Central

    Kim, Jong Ho; Kim, Byung Jun

    2016-01-01

    Background Syndactyly of the foot is the second most common congenital foot anomaly. In East Asia, however, no large case study has been reported regarding the clinical features of isolated foot syndactyly. In this study, we report a review of 118 patients during the last 25 years. Methods We conducted a chart review of patients who underwent surgical correction for foot syndactyly between January 1990 and December 2014. Operations were performed with a dorsal triangular flap and a full-thickness skin graft. The demographics of included patients and their clinical features were evaluated. Surgical outcomes and complications were analyzed. Results Among 118 patients with 194 webs (155 feet), 111 patients showed nonsyndromic cases and 7 patients showed syndromic cases. In 80 unilateral cases (72.1%), the second web was the most frequently involved (37.5%), followed by the fourth (30%), the first (15%), the third (15%), the first and second in combination (1.3%), and the second and third in combination (1.3%). Among 31 bilateral cases, 2 cases were asymmetric. Among the remaining 29 symmetric bilateral cases, the second web was the most frequently involved (45.2%), followed by the first (22.6%), and the fourth (6.5%). No specific postoperative complications were observed, except in the case of 1 patient (0.51%) who required a secondary operation to correct web creep. Conclusions This retrospective clinical study of 118 patients with both unilateral and bilateral foot syndactyly revealed that the second web was the most frequently involved. In addition, complete division and tension-free wound closure with a full-thickness skin graft of sufficient size showed good postoperative results. PMID:27896188

  14. Demographics of the European Apicultural Industry

    PubMed Central

    Chauzat, Marie-Pierre; Cauquil, Laura; Roy, Lise; Franco, Stéphanie; Hendrikx, Pascal; Ribière-Chabert, Magali

    2013-01-01

    Over the last few years, many European and North American countries have reported a high rate of disorders (mortality, dwindling and disappearance) affecting honeybee colonies (Apis mellifera). Although beekeeping has become an increasingly professional activity in recent years, the beekeeping industry remains poorly documented in Europe. The European Union Reference Laboratory for Honeybee Health sent a detailed questionnaire to each Member State, in addition to Kosovo and Norway, to determine the demographics and state of their beekeeping industries. Based on data supplied by the National Reference Laboratory for honeybee diseases in each European country, a European database was created to describe the beekeeping industry including the number and types of beekeepers, operation size, industry production, and health (notifiable diseases, mortalities). The total number of beekeepers in Europe was estimated at 620 000. European honey production was evaluated at around 220 000 tons in 2010. The price of honey varied from 1.5 to 40 €/kg depending on the country and on the distribution network. The estimated colony winter mortality varied from 7 to 28% depending on the country and the origin of the data (institutional survey or beekeeping associations). This survey documents the high heterogeneity of the apicultural industry within the European Union. The high proportion of non-professional beekeepers and the small mean number of colonies per beekeeper were the only common characteristics at European level. The tremendous variation in European apicultural industries has implication for any comprehensive epidemiological or economic analysis of the industry. This variability needs to be taken into account for such analysis as well as for future policy development. The industry would be served if beekeeping registration was uniformly implemented across member states. Better information on the package bee and queen production would help in understanding the ability of

  15. Using demography and movement behavior to predict range expansion of the southern sea otter.

    USGS Publications Warehouse

    Tinker, M.T.; Doak, D.F.; Estes, J.A.

    2008-01-01

    In addition to forecasting population growth, basic demographic data combined with movement data provide a means for predicting rates of range expansion. Quantitative models of range expansion have rarely been applied to large vertebrates, although such tools could be useful for restoration and management of many threatened but recovering populations. Using the southern sea otter (Enhydra lutris nereis) as a case study, we utilized integro-difference equations in combination with a stage-structured projection matrix that incorporated spatial variation in dispersal and demography to make forecasts of population recovery and range recolonization. In addition to these basic predictions, we emphasize how to make these modeling predictions useful in a management context through the inclusion of parameter uncertainty and sensitivity analysis. Our models resulted in hind-cast (1989-2003) predictions of net population growth and range expansion that closely matched observed patterns. We next made projections of future range expansion and population growth, incorporating uncertainty in all model parameters, and explored the sensitivity of model predictions to variation in spatially explicit survival and dispersal rates. The predicted rate of southward range expansion (median = 5.2 km/yr) was sensitive to both dispersal and survival rates; elasticity analysis indicated that changes in adult survival would have the greatest potential effect on the rate of range expansion, while perturbation analysis showed that variation in subadult dispersal contributed most to variance in model predictions. Variation in survival and dispersal of females at the south end of the range contributed most of the variance in predicted southward range expansion. Our approach provides guidance for the acquisition of further data and a means of forecasting the consequence of specific management actions. Similar methods could aid in the management of other recovering populations.

  16. The Bantu expansion revisited: a new analysis of Y chromosome variation in Central Western Africa.

    PubMed

    Montano, Valeria; Ferri, Gianmarco; Marcari, Veronica; Batini, Chiara; Anyaele, Okorie; Destro-Bisol, Giovanni; Comas, David

    2011-07-01

    The current distribution of Bantu languages is commonly considered to be a consequence of a relatively recent population expansion (3-5kya) in Central Western Africa. While there is a substantial consensus regarding the centre of origin of Bantu languages (the Benue River Valley, between South East Nigeria and Western Cameroon), the identification of the area from where the population expansion actually started, the relation between the processes leading to the spread of languages and peoples and the relevance of local migratory events remain controversial. In order to shed new light on these aspects, we studied Y chromosome variation in a broad dataset of populations encompassing Nigeria, Cameroon, Gabon and Congo. Our results evidence an evolutionary scenario which is more complex than had been previously thought, pointing to a marked differentiation of Cameroonian populations from the rest of the dataset. In fact, in contrast with the current view of Bantu speakers as a homogeneous group of populations, we observed an unexpectedly high level of interpopulation genetic heterogeneity and highlighted previously undetected diversity for lineages associated with the diffusion of Bantu languages (E1b1a (M2) sub-branches). We also detected substantial differences in local demographic histories, which concord with the hypotheses regarding an early diffusion of Bantu languages into the forest area and a subsequent demographic expansion and migration towards eastern and western Africa. © 2011 Blackwell Publishing Ltd.

  17. Morphokinetics of human blastocyst expansion in vitro.

    PubMed

    Huang, T T F; Chinn, K; Kosasa, T; Ahn, H J; Kessel, B

    2016-12-01

    Time-lapse imaging offers new tools to study dynamic processes of development such as blastocyst formation and expansion. This study quantitatively describes expansion in human blastocysts from donated oocytes. Measurements of hourly interval rate of changes in the blastocoel cross-sectional area revealed oscillatory pulses having 2-4 h periodicities. Two types of oscillations were distinguished. An E-Type ('expansion') had positive peak and positive or slightly negative trough interval rate of change values, and these characterized most of the expansion period. A C-type ('contraction') represented an infrequent but notable contraction of the blastocoel with loss of blastocoel fluid. These were reversible within 2-4 h in both groups and followed by further expansion. Therefore, oscillatory pulses are an intrinsic property of the trophectoderm. The zona seems to variably dampen the amplitude of these pulses. Expansion kinetics were compared between blastocysts with known positive (KID+) or negative (KID-) implantation outcomes. Regression analysis suggests that expansion may be relatively restricted in KID- embryos blastulating at relatively later times. These data extend observations in other mammalian systems and may provide information useful for clinical selection algorithms. Copyright © 2016. Published by Elsevier Ltd.

  18. Giant negative thermal expansion in magnetic nanocrystals.

    PubMed

    Zheng, X G; Kubozono, H; Yamada, H; Kato, K; Ishiwata, Y; Xu, C N

    2008-12-01

    Most solids expand when they are heated, but a property known as negative thermal expansion has been observed in a number of materials, including the oxide ZrW2O8 (ref. 1) and the framework material ZnxCd1-x(CN)2 (refs 2,3). This unusual behaviour can be understood in terms of low-energy phonons, while the colossal values of both positive and negative thermal expansion recently observed in another framework material, Ag3[Co(CN)6], have been explained in terms of the geometric flexibility of its metal-cyanide-metal linkages. Thermal expansion can also be stopped in some magnetic transition metal alloys below their magnetic ordering temperature, a phenomenon known as the Invar effect, and the possibility of exploiting materials with tuneable positive or negative thermal expansion in industrial applications has led to intense interest in both the Invar effect and negative thermal expansion. Here we report the results of thermal expansion experiments on three magnetic nanocrystals-CuO, MnF2 and NiO-and find evidence for negative thermal expansion in both CuO and MnF2 below their magnetic ordering temperatures, but not in NiO. Larger particles of CuO and MnF2 also show prominent magnetostriction (that is, they change shape in response to an applied magnetic field), which results in significantly reduced thermal expansion below their magnetic ordering temperatures; this behaviour is not observed in NiO. We propose that the negative thermal expansion effect in CuO (which is four times larger than that observed in ZrW2O8) and MnF2 is a general property of nanoparticles in which there is strong coupling between magnetism and the crystal lattice.

  19. China's Demographic Challenge Requires an Integrated Coping Strategy

    ERIC Educational Resources Information Center

    Peng, Xizhe

    2013-01-01

    China has entered into a new stage of demographic dynamics whereby population-related challenges are more complicated than ever before. The current one-child policy should be modified. However, the anticipated impacts of such a policy change should not be over-exaggerated. China's demographic challenge requires an integrated coping strategy.…

  20. Some Emerging Demographic Issues on Australia's Teaching Academic Workforce

    ERIC Educational Resources Information Center

    Hugo, Graeme

    2005-01-01

    Like other OECD nations, Australia is facing a crisis in the academic staff of its universities over the next two decades. This is a function of several factors, among which demographic elements are especially significant. The academic workforce of Australia is characterized by three distinct demographic features--age heaping, a concentration in…