Dynamics of neutrophil migration in lymph nodes during infection

PubMed Central

Chtanova, Tatyana; Schaeffer, Marie; Han, Seong-Ji; van Dooren, Giel G.; Nollmann, Marcelo; Herzmark, Paul; Chan, Shiao Wei; Satija, Harshita; Camfield, Kristin; Aaron, Holly; Striepen, Boris; Robey, Ellen A.

2008-01-01

Summary While the signals that control neutrophil migration from the blood to sites of infection have been well characterized, little is known about their migration patterns within lymph nodes, or the strategies that neutrophils use to find their local sites of action. To address these questions, we used two-photon scanning laser microscopy (TPSLM) to examine neutrophil migration in intact lymph nodes during infection with an intracellular parasite, Toxoplasma gondii. We find that neutrophils form both small, transient or large, persistent swarms via a strikingly coordinated migration pattern. We provide evidence that cooperative action of neutrophils and parasite egress from host cells can trigger swarm formation. Neutrophil swarm formation coincides in space and time with the removal of macrophages that line the subcapsular sinus of the lymph node. Our data provide insights into the cellular mechanisms underlying neutrophil swarming and suggest new roles for neutrophils in shaping immune responses. PMID:18718768

Species-specific patterns of diel migration into the Oxygen Minimum Zone by euphausiids in the Humboldt Current Ecosystem

NASA Astrophysics Data System (ADS)

Antezana, Tarsicio

2009-12-01

A series of stratified bongo net samples taken over a 2 day period at ca. 18°S, about 20 nm off the coast of Peru, South America, suggest species-specific patterns of diel vertical migration into the Oxygen Minimum Zone (OMZ) of the Humboldt Current Ecosystem (HCE). The OMZ was the most dramatic feature of the water column and seemed to determine the extent of migration: Stylocheiron affine migrated only to the shallow oxycline; whereas Euphausia mucronata, Euphausia eximia, Euphausia distinguenda and Euphausia tenera migrated to the core of the OMZ; and Nematoscelis gracilis to beneath the core of the OMZ. Some differences were also found in the timing and duration of the ascent and descent, and residence times in shallow and deep layers. E. mucronata, N. gracilis and E. distinguenda displayed a normal descent during sunrise, and ascent during sunset. E. eximia and E. tenera also descended during sunrise but seemed to begin their ascent earlier in the afternoon and consequently shortened their deep residence times. S. affine showed the most extended residence times at the shallow layer and the shortest vertical displacement. Day and night vertical stratification and differences in the timing of migration into and out of the OMZ of the HCE suggest a community structure based on habitat partitioning whereby species avoided co-occurrence in time and space. Species-specific patterns of vertical stratification and migratory chronology are examined with regard to body and gill sizes, feeding adaptations of euphausiids, and potential food resources at the OMZ.

Rural migration and agrarian reform in Russia: a research note.

PubMed

Wegren, S K

1995-07-01

This study focuses primarily on trends in rural-urban migration in Russia and the former Soviet Union. "New data suggest that a historic shift in migration patterns is underway in Russia, a change that may have profound long-term effects on agrarian reform and the nature of the Russian countryside. We begin with a short review of past rural migration trends and the rural demographic situation, in part using archival data for an oblast in central Russia. We will then present new data on rural migration. Finally, we assess the implications of rural migratory trends for agrarian reform in Russia." excerpt

Genetic profiling links changing sea-ice to shifting beluga whale migration patterns

PubMed Central

Mahoney, Andrew R.; Suydam, Robert; Quakenbush, Lori; Whiting, Alex; Lowry, Lloyd; Harwood, Lois

2016-01-01

There is increasing concern over how Arctic fauna will adapt to climate related changes in sea-ice. We used long-term sighting and genetic data on beluga whales (Delphinapterus leucas) in conjunction with multi-decadal patterns of sea-ice in the Pacific Arctic to investigate the influence of sea-ice on spring migration and summer residency patterns. Substantial variations in sea-ice conditions were detected across seasons, years and sub-regions, revealing ice–ocean dynamics more complex than Arctic-wide trends suggest. This variation contrasted with a highly consistent pattern of migration and residency by several populations, indicating that belugas can accommodate widely varying sea-ice conditions to perpetuate philopatry to coastal migration destinations. However, a number of anomalous migration and residency events were detected and coincided with anomalous ice years, and in one case with an increase in killer whale (Orcinus orca) sightings and reported predation on beluga whales. The behavioural shifts were likely driven by changing sea-ice and associated changes in resource dispersion and predation risk. Continued reductions in sea-ice may result in increased predation at key aggregation areas and shifts in beluga whale behaviour with implications for population viability, ecosystem structure and the subsistence cultures that rely on them.

The spring migration of adult North American Ospreys

USGS Publications Warehouse

Martell, Mark S.; Bierregaard, Richard O.; Washburn, Brian E.; Elliott, John E.; Henny, Charles J.; Kennedy, Robert S.; MacLeod, Iain

2014-01-01

Most North American Ospreys (Pandion haliaetus) are migratory, breeding in northern latitudes and migrating long distances to and from their wintering grounds in the tropics. Although fall migration patterns of North American Ospreys have been described and studied, very little has been published about the spring migration of these birds. We used satellite telemetry to: (1) determine the characteristics (timing, duration, migratory routes) of spring migrations of Ospreys; (2) determine if differences in spring migration patterns existed between sexes and among three breeding populations (east coast, midwestern, and western); and (3) compare consecutive fall and spring migrations of individual Ospreys. The median dates for departure from the wintering grounds and arrival on the breeding grounds did not differ significantly between adult male and female Ospreys. Compared to their fall migrations, all male and all east coast Ospreys spent fewer days on migration, fewer days in stopover periods along the migration route, traveled shorter distances overall, and traveled farther (on average) each day during spring. In contrast, fall and spring migration characteristics of all female and western Ospreys were similar. Our findings suggest that, although sex and breeding location might influence the spring migration strategy used by individual Ospreys, both males and females minimize the time spent on migration to ensure a timely arrival on the breeding grounds to establish or defend a nesting territory.

Exploring Child Mortality Risks Associated with Diverse Patterns of Maternal Migration in Haiti

PubMed Central

Smith-Greenaway, Emily; Thomas, Kevin

2014-01-01

Internal migration is a salient dimension of adulthood in Haiti, particularly among women. Despite the prevalence of migration in Haiti, it remains unknown whether Haitian women’s diverse patterns of migration influence their children’s health and survival. In this paper, we introduce the concept of lateral (i.e., rural-to-rural, urban-to-urban) versus nonlateral (i.e., rural-to-urban, urban-to-rural) migration to describe how some patterns of mothers’ internal migration may be associated with particularly high mortality among children. We use the 2006 Haitian Demographic and Health Survey to estimate a series of discrete-time hazard models among 7,409 rural children and 3,864 urban children. We find that, compared with their peers with nonmigrant mothers, children born to lateral migrants generally experience lower mortality whereas those born to nonlateral migrants generally experience higher mortality. Although there are important distinctions across Haiti’s rural and urban contexts, these associations remain net of socioeconomic factors, suggesting they are not entirely attributable to migrant selection. Considering the timing of maternal migration uncovers even more variation in the child health implications of maternal migration; however, the results counter the standard disruption and adaptation perspective. Although future work is needed to identify the processes underlying the differential risk of child mortality across lateral versus nonlateral migrants, the study demonstrates that looking beyond rural-to-urban migration and considering the timing of maternal migration can provide a fuller, more complex understanding of migration’s association with child health. PMID:25506111

Nonautonomous Roles of MAB-5/Hox and the Secreted Basement Membrane Molecule SPON-1/F-Spondin in Caenorhabditis elegans Neuronal Migration.

PubMed

Josephson, Matthew P; Miltner, Adam M; Lundquist, Erik A

2016-08-01

Nervous system development and circuit formation requires neurons to migrate from their birthplaces to specific destinations.Migrating neurons detect extracellular cues that provide guidance information. In Caenorhabditis elegans, the Q right (QR) and Q left (QL) neuroblast descendants migrate long distances in opposite directions. The Hox gene lin-39 cell autonomously promotes anterior QR descendant migration, and mab-5/Hox cell autonomously promotes posterior QL descendant migration. Here we describe a nonautonomous role of mab-5 in regulating both QR and QL descendant migrations, a role masked by redundancy with lin-39 A third Hox gene, egl-5/Abdominal-B, also likely nonautonomously regulates Q descendant migrations. In the lin-39 mab-5 egl-5 triple mutant, little if any QR and QL descendant migration occurs. In addition to well-described roles of lin-39 and mab-5 in the Q descendants, our results suggest that lin-39, mab-5, and egl-5 might also pattern the posterior region of the animal for Q descendant migration. Previous studies showed that the spon-1 gene might be a target of MAB-5 in Q descendant migration. spon-1 encodes a secreted basement membrane molecule similar to vertebrate F-spondin. Here we show that spon-1 acts nonautonomously to control Q descendant migration, and might function as a permissive rather than instructive signal for cell migration. We find that increased levels of MAB-5 in body wall muscle (BWM) can drive the spon-1 promoter adjacent to the Q cells, and loss of spon-1 suppresses mab-5 gain of function. Thus, MAB-5 might nonautonomously control Q descendant migrations by patterning the posterior region of the animal to which Q cells respond. spon-1 expression from BWMs might be part of the posterior patterning necessary for directed Q descendant migration. Copyright © 2016 by the Genetics Society of America.

Nonautonomous Roles of MAB-5/Hox and the Secreted Basement Membrane Molecule SPON-1/F-Spondin in Caenorhabditis elegans Neuronal Migration

PubMed Central

Josephson, Matthew P.; Miltner, Adam M.; Lundquist, Erik A.

2016-01-01

Nervous system development and circuit formation requires neurons to migrate from their birthplaces to specific destinations.Migrating neurons detect extracellular cues that provide guidance information. In Caenorhabditis elegans, the Q right (QR) and Q left (QL) neuroblast descendants migrate long distances in opposite directions. The Hox gene lin-39 cell autonomously promotes anterior QR descendant migration, and mab-5/Hox cell autonomously promotes posterior QL descendant migration. Here we describe a nonautonomous role of mab-5 in regulating both QR and QL descendant migrations, a role masked by redundancy with lin-39. A third Hox gene, egl-5/Abdominal-B, also likely nonautonomously regulates Q descendant migrations. In the lin-39mab-5egl-5 triple mutant, little if any QR and QL descendant migration occurs. In addition to well-described roles of lin-39 and mab-5 in the Q descendants, our results suggest that lin-39, mab-5, and egl-5 might also pattern the posterior region of the animal for Q descendant migration. Previous studies showed that the spon-1 gene might be a target of MAB-5 in Q descendant migration. spon-1 encodes a secreted basement membrane molecule similar to vertebrate F-spondin. Here we show that spon-1 acts nonautonomously to control Q descendant migration, and might function as a permissive rather than instructive signal for cell migration. We find that increased levels of MAB-5 in body wall muscle (BWM) can drive the spon-1 promoter adjacent to the Q cells, and loss of spon-1 suppresses mab-5 gain of function. Thus, MAB-5 might nonautonomously control Q descendant migrations by patterning the posterior region of the animal to which Q cells respond. spon-1 expression from BWMs might be part of the posterior patterning necessary for directed Q descendant migration. PMID:27225683

Reconstructing the Timing and Dispersion Routes of HIV-1 Subtype B Epidemics in The Caribbean and Central America: A Phylogenetic Story

PubMed Central

Pagán, Israel; Holguín, África

2013-01-01

The Caribbean and Central America are among the regions with highest HIV-1B prevalence worldwide. Despite of this high virus burden, little is known about the timing and the migration patterns of HIV-1B in these regions. Migration is one of the major processes shaping the genetic structure of virus populations. Thus, reconstruction of epidemiological network may contribute to understand HIV-1B evolution and reduce virus prevalence. We have investigated the spatio-temporal dynamics of the HIV-1B epidemic in The Caribbean and Central America using 1,610 HIV-1B partial pol sequences from 13 Caribbean and 5 Central American countries. Timing of HIV-1B introduction and virus evolutionary rates, as well as the spatial genetic structure of the HIV-1B populations and the virus migration patterns were inferred. Results revealed that in The Caribbean and Central America most of the HIV-1B variability was generated since the 80 s. At odds with previous data suggesting that Haiti was the origin of the epidemic in The Caribbean, our reconstruction indicated that the virus could have been disseminated from Puerto Rico and Antigua. These two countries connected two distinguishable migration areas corresponding to the (mainly Spanish-colonized) Easter and (mainly British-colonized) Western islands, which indicates that virus migration patterns are determined by geographical barriers and by the movement of human populations among culturally related countries. Similar factors shaped the migration of HIV-1B in Central America. The HIV-1B population was significantly structured according to the country of origin, and the genetic diversity in each country was associated with the virus prevalence in both regions, which suggests that virus populations evolve mainly through genetic drift. Thus, our work contributes to the understanding of HIV-1B evolution and dispersion pattern in the Americas, and its relationship with the geography of the area and the movements of human populations. PMID:23874917

Dual impacts of climate change: forest migration and turnover through life history.

PubMed

Zhu, Kai; Woodall, Christopher W; Ghosh, Souparno; Gelfand, Alan E; Clark, James S

2014-01-01

Tree species are predicted to track future climate by shifting their geographic distributions, but climate-mediated migrations are not apparent in a recent continental-scale analysis. To better understand the mechanisms of a possible migration lag, we analyzed relative recruitment patterns by comparing juvenile and adult tree abundances in climate space. One would expect relative recruitment to be higher in cold and dry climates as a result of tree migration with juveniles located further poleward than adults. Alternatively, relative recruitment could be higher in warm and wet climates as a result of higher tree population turnover with increased temperature and precipitation. Using the USDA Forest Service's Forest Inventory and Analysis data at regional scales, we jointly modeled juvenile and adult abundance distributions for 65 tree species in climate space of the eastern United States. We directly compared the optimal climate conditions for juveniles and adults, identified the climates where each species has high relative recruitment, and synthesized relative recruitment patterns across species. Results suggest that for 77% and 83% of the tree species, juveniles have higher optimal temperature and optimal precipitation, respectively, than adults. Across species, the relative recruitment pattern is dominated by relatively more abundant juveniles than adults in warm and wet climates. These different abundance-climate responses through life history are consistent with faster population turnover and inconsistent with the geographic trend of large-scale tree migration. Taken together, this juvenile-adult analysis suggests that tree species might respond to climate change by having faster turnover as dynamics accelerate with longer growing seasons and higher temperatures, before there is evidence of poleward migration at biogeographic scales.

Migration out of 1930s Rural Eastern Oklahoma: Insights for Climate Change Research

ERIC Educational Resources Information Center

McLeman, Robert

2006-01-01

The question of how communities and individuals adapt to changing climatic conditions is of pressing concern to scientists and policymakers in light of the growing evidence that human activity has modified the Earth's climate. A number of authors have suggested that widespread changes in human settlement and migration patterns may occur in…

The evolution of immunity in relation to colonization and migration.

PubMed

O'Connor, Emily A; Cornwallis, Charlie K; Hasselquist, Dennis; Nilsson, Jan-Åke; Westerdahl, Helena

2018-05-01

Colonization and migration have a crucial effect on patterns of biodiversity, with disease predicted to play an important role in these processes. However, evidence of the effect of pathogens on broad patterns of colonization and migration is limited. Here, using phylogenetic analyses of 1,311 species of Afro-Palaearctic songbirds, we show that colonization events from regions of high (sub-Saharan Africa) to low (the Palaearctic) pathogen diversity were up to 20 times more frequent than the reverse, and that migration has evolved 3 times more frequently from African- as opposed to Palaearctic-resident species. We also found that resident species that colonized the Palaearctic from Africa, as well as African species that evolved long-distance migration to breed in the Palaearctic, have reduced diversity of key immune genes associated with pathogen recognition (major histocompatibility complex class I). These results suggest that changes in the pathogen community that occur during colonization and migration shape the evolution of the immune system, potentially by adjusting the trade-off between the benefits of extensive pathogen recognition and the costs of immunopathology that result from high major histocompatibility complex class I diversity.

Periodic Pattern Formation of Bacterial Colonies

NASA Astrophysics Data System (ADS)

Itoh, Hiroto; Wakita, Jun-ichi; Matsuyama, Tohey; Matsushita, Mitsugu

1999-04-01

We have experimentally investigated pattern formation of colonies ofbacterial species Proteus mirabilis, which is famous forforming concentric-ring-like colonies.The colony grows cyclically with the interface repeating an advance anda stop alternately on a surface of a solid agar medium.We distinguish three phases (initial lag phase, the followingmigration and consolidation phases that appear alternately) for the colony growth.When we cut a colony just behind a migrating front shortly after the migrationstarted, the migration ended earlier and the following consolidationlasted longer.However, the following cycles were not influenced by the cut, i.e., thephases of the migration and consolidation were not affected.Global chemical signals governing the colony formation from thecenter were not found to exist.We also quantitatively checked phase entrainment by letting two coloniescollide with each other and found that it does not take place in macroscopic scales.All these experimental results suggest that the most important factorfor the migration is the cell population density.

Migration patterns and movements of sandhill cranes wintering in central and southwestern Louisiana

USGS Publications Warehouse

King, Sammy L.; Pierce, Aaron R.; Hersey, Kent R.; Winstead, Nicholas; Hartup, Barry K.

2010-01-01

In this study we trapped wintering sandhill cranes (Grus canadensis) in Louisiana and fitted them with satellite transmitters to determine their migration routes. Four of the 6 sandhill cranes with validated locations and a terminus point used the Central Flyway for spring migration; 2 of these 4 (the only 2 for which we have data) also used the Central Flyway for fall migration. Two of the 6 birds used the Mississippi Flyway for spring migration. The results of this study suggest that reintroduced whooping cranes (G. americana) that intermix and migrate with sandhill cranes that winter in Louisiana may enter the Central Flyway. In addition, the Mississippi Flyway is a viable option to use as a migration route for whooping cranes if they are reintroduced in Louisiana.

Migration of moth species in a network of small islands.

PubMed

Nieminen, Marko

1996-12-01

Rapidly increasing fragmentation of natural landscapes decreases the ability of many species to reach the smaller and more isolated patches of habitat in a metapopulation. The densities of local populations of several moth species and the butterfly Hipparchia semele in a network of small islands, and the rates of inter-island movement and movement patterns, were investigated, to determine the factors affecting the rate and pattern of movements. The estimated population densities ranged from 0.001 to 0.2 individuals/m 2 . The observed emigration and immigration rates depended on island isolation and various traits of the species, with great variability in migration rates among species. Thin-bodied, slow-flying species did not move among the islands, whereas many robust, fast-flying species moved among the islands relatively frequently. Migration rate increased significantly with body size and was significantly higher in oligophagous than in polyphagous species, suggesting that these factors are important determinants of the migration rate of the species. Migration rate was low when the surface temperature of the sea was low, and a greater proportion of individuals emigrated from small than large patches of habitat. The migration distances of female noctuids were shorter than those of males and those of both sexes of the butterfly H. semele. The observed movement patterns are consistent with a metapopulation structure in most of the moth species.

Reorientation Timescales and Pattern Dynamics for Titan's Dunes: Does the Tail Wag the Dog or the Dragon?

NASA Astrophysics Data System (ADS)

Hayes, A. G.; Ewing, R. C.; Cassini Radar Science Team, T.

2011-12-01

Fields of bedform patterns persist across many orders of magnitude, from cm-scale sub-aqueous current ripples to km-scale aeolian dunes, and form with surprisingly little difference in expression despite a range of formative environments. Because of the remarkable similarity between and among patterns, extracting information about climate and environment from these patterns is a challenge. For example, crest orientation is not diagnostic of a particular flow regime; similar patterns form under many different flow configurations. On Titan, these challenges have played out with many attempts to reconcile dune-field patterns with modeled and expected wind regimes. We propose that thinking about the change in dune orientation, rather than the orientation itself, can provide new insights on the long-term stability of the dune-field patterns and the formative wind regime. In this work, we apply the re-orientation model presented by Werner and Kocurek [Geology, 1997] to the equatorial dune fields of Titan. We measure variations in pattern parameters (crest spacing, crest length and defect density, which is the number of defect pairs per total crest length) both within and between Titan's dune fields to describe pattern maturity and identify areas where changes in dune orientation are likely to occur (or may already be occurring). Measured defect densities are similar to Earth's largest linear dune fields, such as the Namib Sand Sea and the Simpson Desert. We use measured defect densities in the Werner and Kocurek model to estimate crestline reorientation rates. We find reorientation timescales varying from ten to a hundred thousand times the average migration timescale (time to migrate a bedform one meter, ~1 Titan year according to Tokano (Aeolian Research, 2010)). Well organized patterns have the longest reorientation time scales (~10^5 migration timescales), while the topographically or spatially isolated patches of dunes show the shortest reorientation times (~10^3 migration timescales). In addition, comparisons between spacing and defect density of Titan's dunes and some of the largest fields observed on Earth and Mars reveal that dune patterns on all three planets are geometrically similar, suggesting that growth and organization share common pattern dynamics. Our results suggest that Titan's dunes may react to gross bedform transport averaged over orbital timescales, relaxing the requirement that a single modern wind regime is required to produce the observed pattern.

Climate Shocks and the Timing of Migration from Mexico

PubMed Central

Nawrotzki, Raphael J.; DeWaard, Jack

2016-01-01

Although evidence is increasing that climate shocks influence human migration, it is unclear exactly when people migrate after a climate shock. A climate shock might be followed by an immediate migration response. Alternatively, migration, as an adaptive strategy of last resort, might be delayed and employed only after available in-situ (in-place) adaptive strategies are exhausted. In this paper, we explore the temporally lagged association between a climate shock and future migration. Using multilevel event-history models, we analyze the risk of Mexico-U.S. migration over a seven-year period after a climate shock. Consistent with a delayed response pattern, we find that the risk of migration is low immediately after a climate shock and increases as households pursue and cycle through in-situ adaptive strategies available to them. However, about three years after the climate shock, the risk of migration decreases, suggesting that households are eventually successful in adapting in-situ. PMID:27795604

Transoceanic migration, spatial dynamics, and population linkages of white sharks.

PubMed

Bonfil, Ramón; Meÿer, Michael; Scholl, Michael C; Johnson, Ryan; O'Brien, Shannon; Oosthuizen, Herman; Swanson, Stephan; Kotze, Deon; Paterson, Michael

2005-10-07

The large-scale spatial dynamics and population structure of marine top predators are poorly known. We present electronic tag and photographic identification data showing a complex suite of behavioral patterns in white sharks. These include coastal return migrations and the fastest known transoceanic return migration among swimming fauna, which provide direct evidence of a link between widely separated populations in South Africa and Australia. Transoceanic return migration involved a return to the original capture location, dives to depths of 980 meters, and the tolerance of water temperatures as low as 3.4 degrees C. These findings contradict previous ideas that female white sharks do not make transoceanic migrations, and they suggest natal homing behavior.

The Use of Census Migration Data to Approximate Human Movement Patterns across Temporal Scales

PubMed Central

Wesolowski, Amy; Buckee, Caroline O.; Pindolia, Deepa K.; Eagle, Nathan; Smith, David L.; Garcia, Andres J.; Tatem, Andrew J.

2013-01-01

Human movement plays a key role in economies and development, the delivery of services, and the spread of infectious diseases. However, it remains poorly quantified partly because reliable data are often lacking, particularly for low-income countries. The most widely available are migration data from human population censuses, which provide valuable information on relatively long timescale relocations across countries, but do not capture the shorter-scale patterns, trips less than a year, that make up the bulk of human movement. Census-derived migration data may provide valuable proxies for shorter-term movements however, as substantial migration between regions can be indicative of well connected places exhibiting high levels of movement at finer time scales, but this has never been examined in detail. Here, an extensive mobile phone usage data set for Kenya was processed to extract movements between counties in 2009 on weekly, monthly, and annual time scales and compared to data on change in residence from the national census conducted during the same time period. We find that the relative ordering across Kenyan counties for incoming, outgoing and between-county movements shows strong correlations. Moreover, the distributions of trip durations from both sources of data are similar, and a spatial interaction model fit to the data reveals the relationships of different parameters over a range of movement time scales. Significant relationships between census migration data and fine temporal scale movement patterns exist, and results suggest that census data can be used to approximate certain features of movement patterns across multiple temporal scales, extending the utility of census-derived migration data. PMID:23326367

Residency patterns of migrating sandpipers at a midcontinental stopover

USGS Publications Warehouse

Skagen, Susan K.; Knopf, Fritz L.

1994-01-01

Arctic-nesting shorebirds require several refueling stops during their long migrations between breeding grounds and Central and South American wintering areas. The protection of stopover habitats for transcontinental migrants depends on whether birds fly long distances between a few select sites or fly short distances and stop at several wetlands. Although the Great Plains historically provided a vast array of wetlands for use by migrants, wetland loss and conversion have reduced the availability of stopover sites in recent decades. In this study, we examined (1) residency periods, (2) fat dynamics, and (3) migration chronology of two shorebird species, the Semipalmated Sandpiper (Calidris pusilla) and White-rumped Sandpiper (C. fuscicollis) at Quivira National Wildlife Refuge (NWR), Kansas. Semipalmated Sandpipers had prolonged periods of species residency with overlapping arrivals and departures. Individual residency periods were highly variable and were unrelated to lipid reserves upon arrival. In contrast, White-rumped Sandpipers arrived and departed more synchronously. Birds that arrived in poor condition stayed longer than those with more body fat in 1991, but not in 1992. Wind direction did not influence patterns of departures of either species. We hypothesize that Semipalmated Sandpipers are ecologically eurytopic when migrating across the Great Plains in the spring. Highly variable patterns in arrival, residency, and lipid levels indicate that spring migration of this species is relaxed and opportunistic. White-rumped Sandpipers showed a pattern of reduced flexibility. Flight range estimates suggest that most birds require intermediate stopovers before reaching the breeding grounds. Interior wetlands appear to function as migration stopovers rather than staging areas for shorebirds.

Patterns in diurnal airspace use by migratory landbirds along an ecological barrier.

PubMed

Peterson, Anna C; Niemi, Gerald J; Johnson, Douglas H

2015-04-01

Migratory bird populations and survival are affected by conditions experienced during migration. While many studies and conservation and management efforts focus on terrestrial stoppage and staging areas, the aerial environment through which migrants move also is subjected to anthropogenic impacts with potential consequences to migratory movement and survival. During autumn migration, the northern coastline of Lake Superior acts as an ecological barrier for many landbirds migrating out of the boreal forests of North America. From 24 observation points, we assessed the diurnal movements of birds throughout autumn migration, 2008-2010, within a 210 × 10 km coastal region along the northern coast of Lake Superior. Several raptor species showed patterns in airspace associated with topographic features such as proximity to the coastline and presence of ridgelines. Funneling movement, commonly used to describe the concentration of raptors along a migratory diversion line that either prevents or enhances migration progress, occurred only for Bald and Golden Eagles. This suggests a "leaky" migration funnel for most migratory raptors (e.g., migrating birds exiting the purported migration corridor). Passerines migrating during the late season showed more spatial and temporal structure in airspace distribution than raptors did, including funneling and an association with airspace near the coast. We conclude that (1) the diurnal use of airspace by many migratory landbirds is patterned in space and time, (2) autumn count sites situated along ecological barriers substantially underestimate the number of raptors due to "leakage" out of these concentration areas, and (3) the magnitude and structure of diurnal passerine movements in airspace have been overlooked. The heavy and structured use of airspace by migratory landbirds, especially the airspace associated with anthropogenic development (e.g., buildings, towers, turbines) necessitates a shift in focus to airspace management and conservation attention for these animals.

Patterns in diurnal airspace use by migratory landbirds along an ecological barrier

USGS Publications Warehouse

Peterson, Anna C.; Niemi, Gerald J.; Johnson, Douglas H.

2015-01-01

Migratory bird populations and survival are affected by conditions experienced during migration. While many studies and conservation and management efforts focus on terrestrial stoppage and staging areas, the aerial environment through which migrants move also is subjected to anthropogenic impacts with potential consequences to migratory movement and survival. During autumn migration, the northern coastline of Lake Superior acts as an ecological barrier for many landbirds migrating out of the boreal forests of North America. From 24 observation points, we assessed the diurnal movements of birds throughout autumn migration, 2008-2010, within a 210 km by 10 km coastal region along the northern coast of Lake Superior. Several raptor species showed patterns in airspace associated with topographic features such as proximity to the coastline and presence of ridgelines. Funneling movement, commonly used to describe the concentration of raptors along a migratory diversion line that either prevents or enhances migration progress, occurred only for Bald and Golden Eagles. This suggests a "leaky" migration funnel for most migratory raptors (e.g., migrating birds exiting the purported migration corridor). Passerines migrating during the late season showed more spatial and temporal structure in airspace distribution than raptors, including funneling and an association with airspace near the coast. We conclude that a) the diurnal use of airspace by many migratory landbirds is patterned in space and time, b) autumn count sites situated along ecological barriers substantially underestimate the number of raptors due to 'leakage' out of these concentration areas, and c) the magnitude and structure of diurnal passerine movements in airspace have been overlooked. The heavy and structured use of airspace by migratory landbirds, especially the airspace associated with anthropogenic development (e.g., buildings, towers, turbines) necessitates a shift in focus to airspace management and conservation attention for these animals.

High migration rates shape the postglacial history of amphi-Atlantic bryophytes.

PubMed

Désamoré, Aurélie; Patiño, Jairo; Mardulyn, Patrick; Mcdaniel, Stuart F; Zanatta, Florian; Laenen, Benjamin; Vanderpoorten, Alain

2016-11-01

Paleontological evidence and current patterns of angiosperm species richness suggest that European biota experienced more severe bottlenecks than North American ones during the last glacial maximum. How well this pattern fits other plant species is less clear. Bryophytes offer a unique opportunity to contrast the impact of the last glacial maximum in North America and Europe because about 60% of the European bryoflora is shared with North America. Here, we use population genetic analyses based on approximate Bayesian computation on eight amphi-Atlantic species to test the hypothesis that North American populations were less impacted by the last glacial maximum, exhibiting higher levels of genetic diversity than European ones and ultimately serving as a refugium for the postglacial recolonization of Europe. In contrast with this hypothesis, the best-fit demographic model involved similar patterns of population size contractions, comparable levels of genetic diversity and balanced migration rates between European and North American populations. Our results thus suggest that bryophytes have experienced comparable demographic glacial histories on both sides of the Atlantic. Although a weak, but significant genetic structure was systematically recovered between European and North American populations, evidence for migration from and towards both continents suggests that amphi-Atlantic bryophyte population may function as a metapopulation network. Reconstructing the biogeographic history of either North American or European bryophyte populations therefore requires a large, trans-Atlantic geographic framework. © 2016 John Wiley & Sons Ltd.

Large scale patterns in vertical distribution and behaviour of mesopelagic scattering layers

NASA Astrophysics Data System (ADS)

Klevjer, T. A.; Irigoien, X.; Røstad, A.; Fraile-Nuez, E.; Benítez-Barrios, V. M.; Kaartvedt., S.

2016-01-01

Recent studies suggest that previous estimates of mesopelagic biomasses are severely biased, with the new, higher estimates underlining the need to unveil behaviourally mediated coupling between shallow and deep ocean habitats. We analysed vertical distribution and diel vertical migration (DVM) of mesopelagic acoustic scattering layers (SLs) recorded at 38 kHz across oceanographic regimes encountered during the circumglobal Malaspina expedition. Mesopelagic SLs were observed in all areas covered, but vertical distributions and DVM patterns varied markedly. The distribution of mesopelagic backscatter was deepest in the southern Indian Ocean (weighted mean daytime depth: WMD 590 m) and shallowest at the oxygen minimum zone in the eastern Pacific (WMD 350 m). DVM was evident in all areas covered, on average ~50% of mesopelagic backscatter made daily excursions from mesopelagic depths to shallow waters. There were marked differences in migrating proportions between the regions, ranging from ~20% in the Indian Ocean to ~90% in the Eastern Pacific. Overall the data suggest strong spatial gradients in mesopelagic DVM patterns, with implied ecological and biogeochemical consequences. Our results suggest that parts of this spatial variability can be explained by horizontal patterns in physical-chemical properties of water masses, such as oxygen, temperature and turbidity.

Large scale patterns in vertical distribution and behaviour of mesopelagic scattering layers.

PubMed

Klevjer, T A; Irigoien, X; Røstad, A; Fraile-Nuez, E; Benítez-Barrios, V M; Kaartvedt, S

2016-01-27

Recent studies suggest that previous estimates of mesopelagic biomasses are severely biased, with the new, higher estimates underlining the need to unveil behaviourally mediated coupling between shallow and deep ocean habitats. We analysed vertical distribution and diel vertical migration (DVM) of mesopelagic acoustic scattering layers (SLs) recorded at 38 kHz across oceanographic regimes encountered during the circumglobal Malaspina expedition. Mesopelagic SLs were observed in all areas covered, but vertical distributions and DVM patterns varied markedly. The distribution of mesopelagic backscatter was deepest in the southern Indian Ocean (weighted mean daytime depth: WMD 590 m) and shallowest at the oxygen minimum zone in the eastern Pacific (WMD 350 m). DVM was evident in all areas covered, on average ~50% of mesopelagic backscatter made daily excursions from mesopelagic depths to shallow waters. There were marked differences in migrating proportions between the regions, ranging from ~20% in the Indian Ocean to ~90% in the Eastern Pacific. Overall the data suggest strong spatial gradients in mesopelagic DVM patterns, with implied ecological and biogeochemical consequences. Our results suggest that parts of this spatial variability can be explained by horizontal patterns in physical-chemical properties of water masses, such as oxygen, temperature and turbidity.

Seasonal migrations of North Atlantic minke whales: novel insights from large-scale passive acoustic monitoring networks.

PubMed

Risch, Denise; Castellote, Manuel; Clark, Christopher W; Davis, Genevieve E; Dugan, Peter J; Hodge, Lynne Ew; Kumar, Anurag; Lucke, Klaus; Mellinger, David K; Nieukirk, Sharon L; Popescu, Cristian Marian; Ramp, Christian; Read, Andrew J; Rice, Aaron N; Silva, Monica A; Siebert, Ursula; Stafford, Kathleen M; Verdaat, Hans; Van Parijs, Sofie M

2014-01-01

Little is known about migration patterns and seasonal distribution away from coastal summer feeding habitats of many pelagic baleen whales. Recently, large-scale passive acoustic monitoring networks have become available to explore migration patterns and identify critical habitats of these species. North Atlantic minke whales (Balaenoptera acutorostrata) perform seasonal migrations between high latitude summer feeding and low latitude winter breeding grounds. While the distribution and abundance of the species has been studied across their summer range, data on migration and winter habitat are virtually missing. Acoustic recordings, from 16 different sites from across the North Atlantic, were analyzed to examine the seasonal and geographic variation in minke whale pulse train occurrence, infer information about migration routes and timing, and to identify possible winter habitats. Acoustic detections show that minke whales leave their winter grounds south of 30° N from March through early April. On their southward migration in autumn, minke whales leave waters north of 40° N from mid-October through early November. In the western North Atlantic spring migrants appear to track the warmer waters of the Gulf Stream along the continental shelf, while whales travel farther offshore in autumn. Abundant detections were found off the southeastern US and the Caribbean during winter. Minke whale pulse trains showed evidence of geographic variation, with longer pulse trains recorded south of 40° N. Very few pulse trains were recorded during summer in any of the datasets. This study highlights the feasibility of using acoustic monitoring networks to explore migration patterns of pelagic marine mammals. Results confirm the presence of minke whales off the southeastern US and the Caribbean during winter months. The absence of pulse train detections during summer suggests either that minke whales switch their vocal behaviour at this time of year, are absent from available recording sites or that variation in signal structure influenced automated detection. Alternatively, if pulse trains are produced in a reproductive context by males, these data may indicate their absence from the selected recording sites. Evidence of geographic variation in pulse train duration suggests different behavioural functions or use of these calls at different latitudes.

Migration of cemented femoral components after THR. Roentgen stereophotogrammetric analysis.

PubMed

Kiss, J; Murray, D W; Turner-Smith, A R; Bithell, J; Bulstrode, C J

1996-09-01

We studied the migration of 58 cemented Hinek femoral components for total hip replacement, using roentgen stereophotogrammetric analysis over four years. The implants migrated faster during the first year than subsequently, and the pattern of migration in the second period was very different. During the first year they subsided, tilted into varus and internally rotated. After this there was slow distal migration with no change in orientation. None of the prostheses has yet failed. The early migration is probably caused by resorption of bone damaged by surgical trauma or the heat generated by the polymerisation of bone cement. Later migration may be due to creep in the bone cement or the surrounding fibrous membrane. The prosthesis which we studied allows the preservation of some of the femoral neck, and comparison with published migration studies of the Charnley stem suggests that this decreases rotation and may help to prevent loosening.

The ethnic composition of migration in the former Soviet Union.

PubMed

Robertson, L R

1996-02-01

"This paper examines the impact of the disintegration of the Soviet Union on migration patterns within the newly independent states. Data on migration between Russia and the other 14 former Soviet republics are analyzed to reveal the magnitude and ethnic composition of migration after independence and to examine the assumption that Russians will tend to return to Russia, whereas members of other titular groups will emigrate to their respective newly independent states. The data suggest that nationalization not only pushes non-titular groups to emigrate from the former Soviet republics, but also pulls titular groups to immigrate to the newly independent states from Russia." excerpt

Singing behavior of fin whales in the Davis Strait with implications for mating, migration and foraging.

PubMed

Simon, Malene; Stafford, Kathleen M; Beedholm, Kristian; Lee, Craig M; Madsen, Peter T

2010-11-01

Most baleen whales undertake migrations between low-latitude breeding grounds and high-latitude feeding grounds. Though little is known about the timing of their migration from the Arctic, fin whales are assumed to undertake a similar migratory pattern. To address questions about habitat use and migrations, the acoustic activity of fin whales in Davis Strait, between Greenland and Canada, was monitored continuously for two years using three bottom-moored acoustic recorders. The acoustic power in the fin whale call frequencies peaked in November-December, showing that fin whales are present in Davis Strait much later in the year than previously expected. The closely timed peaks in song activity and conception time imply that not all fin whales migrate south to mate, but rather start mating at high latitudes rather than or before migrating. Singing activity was strongly linked to daylight hours, suggesting that fin whales might feed during the few daylight hours of the late fall and early Arctic winter. A negative correlation between the advancing sea ice front and power in fin whale frequencies indicates that future changes in sea ice conditions from global warming might change the distribution and migratory patterns of fin whales near the poles.

Moving Across Boundaries: Migration in South Africa, 1950–2000

PubMed Central

2013-01-01

Existing knowledge about historical patterns of black internal migration in South Africa is incomplete, primarily because of the lack of good life course studies as well as the apartheid government’s suppression and censoring of data. This article provides a comprehensive picture of historical internal migration patterns with an analysis of a unique individual retrospective life history data set. This sample of the black population, collected in 2000, is the only known nationally representative life history data for South Africa; it includes all residential moves for each individual during his/her lifetime. Various mobility outcomes are analyzed: moves within/across provinces, moves within/across rural and urban areas, forced moves, moves with a nuclear family, and individual moves. The results indicate that migration significantly increased among black South Africans during the last half of the twentieth century, and that this increase began before the Pass Laws were repealed in 1986 and well before the official end of apartheid in 1991 or the first free election in 1994. The timing of this increase in migration rates suggests that migration in defiance of the Pass Laws (albeit a dangerous and desperate proposition) was a way of life for many black South Africans. PMID:22956415

Moving across boundaries: migration in South Africa, 1950-2000.

PubMed

Reed, Holly E

2013-02-01

Existing knowledge about historical patterns of black internal migration in South Africa is incomplete, primarily because of the lack of good life course studies as well as the apartheid government's suppression and censoring of data. This article provides a comprehensive picture of historical internal migration patterns with an analysis of a unique individual retrospective life history data set. This sample of the black population, collected in 2000, is the only known nationally representative life history data for South Africa; it includes all residential moves for each individual during his/her lifetime. Various mobility outcomes are analyzed: moves within/across provinces, moves within/across rural and urban areas, forced moves, moves with a nuclear family, and individual moves. The results indicate that migration significantly increased among black South Africans during the last half of the twentieth century, and that this increase began before the Pass Laws were repealed in 1986 and well before the official end of apartheid in 1991 or the first free election in 1994. The timing of this increase in migration rates suggests that migration in defiance of the Pass Laws (albeit a dangerous and desperate proposition) was a way of life for many black South Africans.

"International Migration and Gender Discrimination among Children Left Behind"

PubMed

Antman, Francisca M

2011-05-01

This paper considers how international migration of the head of household affects the allocation of resources toward boys relative to girls within households remaining in the home country. I address the endogeneity of migration with a differences-in-differences style regression model that compares those households in which migrants have already returned home with those in which migrants are still away. The evidence suggests that while the head of household is away a greater fraction of resources are spent on girls relative to boys, but upon his return, this pattern is reversed.

Seasonally dynamic diel vertical migrations of Mysis diluviana, coregonine fishes, and siscowet lake trout in the pelagia of western Lake Superior

USGS Publications Warehouse

Ahrenstorff, Tyler D.; Hrabik, Thomas R.; Stockwell, Jason D.; Yule, Daniel L.; Sass, Greg G.

2011-01-01

Diel vertical migrations are common among many aquatic species and are often associated with changing light levels. The underlying mechanisms are generally attributed to optimizing foraging efficiency or growth rates and avoiding predation risk (μ). The objectives of this study were to (1) assess seasonal and interannual changes in vertical migration patterns of three trophic levels in the Lake Superior pelagic food web and (2) examine the mechanisms underlying the observed variability by using models of foraging, growth, and μ. Our results suggest that the opossum shrimp Mysis diluviana, kiyi Coregonus kiyi, and siscowet lake trout Salvelinus namaycush migrate concurrently during each season, but spring migrations are less extensive than summer and fall migrations. In comparison with M. diluviana, kiyis, and siscowets, the migrations by ciscoes C. artedi were not as deep in the water column during the day, regardless of season. Foraging potential and μ probably drive the movement patterns of M. diluviana, while our modeling results indicate that movements by kiyis and ciscoes are related to foraging opportunity and growth potential and receive a lesser influence from μ. The siscowet is an abundant apex predator in the pelagia of Lake Superior and probably undertakes vertical migrations in the water column to optimize foraging efficiency and growth. The concurrent vertical movement patterns of most species are likely to facilitate nutrient transport in this exceedingly oligotrophic ecosystem, and they demonstrate strong linkages between predators and prey. Fishery management strategies should use an ecosystem approach and should consider how altering the densities of long-lived top predators produces cascading effects on the nutrient cycling and energy flow in lower trophic levels.

Age-specific function of α5β1 integrin in microglial migration during early colonization of the developing mouse cortex.

PubMed

Smolders, Sophie Marie-Thérèse; Swinnen, Nina; Kessels, Sofie; Arnauts, Kaline; Smolders, Silke; Le Bras, Barbara; Rigo, Jean-Michel; Legendre, Pascal; Brône, Bert

2017-07-01

Microglia, the immune cells of the central nervous system, take part in brain development and homeostasis. They derive from primitive myeloid progenitors that originate in the yolk sac and colonize the brain mainly through intensive migration. During development, microglial migration speed declines which suggests that their interaction with the microenvironment changes. However, the matrix-cell interactions allowing dispersion within the parenchyma are unknown. Therefore, we aimed to better characterize the migration behavior and to assess the role of matrix-integrin interactions during microglial migration in the embryonic brain ex vivo. We focused on microglia-fibronectin interactions mediated through the fibronectin receptor α5β1 integrin because in vitro work indirectly suggested a role for this ligand-receptor pair. Using 2-photon time-lapse microscopy on acute ex vivo embryonic brain slices, we found that migration occurs in a saltatory pattern and is developmentally regulated. Most importantly, there is an age-specific function of the α5β1 integrin during microglial cortex colonization. At embryonic day (E) 13.5, α5β1 facilitates migration while from E15.5, it inhibits migration. These results indicate a developmentally regulated function of α5β1 integrin in microglial migration during colonization of the embryonic brain. © 2017 Wiley Periodicals, Inc.

Identification of tissues and patterning events required for distinct steps in early migration of zebrafish primordial germ cells.

PubMed

Weidinger, G; Wolke, U; Köprunner, M; Klinger, M; Raz, E

1999-12-01

In many organisms, the primordial germ cells have to migrate from the position where they are specified towards the developing gonad where they generate gametes. Extensive studies of the migration of primordial germ cells in Drosophila, mouse, chick and Xenopus have identified somatic tissues important for this process and demonstrated a role for specific molecules in directing the cells towards their target. In zebrafish, a unique situation is found in that the primordial germ cells, as marked by expression of vasa mRNA, are specified in random positions relative to the future embryonic axis. Hence, the migrating cells have to navigate towards their destination from various starting positions that differ among individual embryos. Here, we present a detailed description of the migration of the primordial germ cells during the first 24 hours of wild-type zebrafish embryonic development. We define six distinct steps of migration bringing the primordial germ cells from their random positions before gastrulation to form two cell clusters on either side of the midline by the end of the first day of development. To obtain information on the origin of the positional cues provided to the germ cells by somatic tissues during their migration, we analyzed the migration pattern in mutants, including spadetail, swirl, chordino, floating head, cloche, knypek and no isthmus. In mutants with defects in axial structures, paraxial mesoderm or dorsoventral patterning, we find that certain steps of the migration process are specifically affected. We show that the paraxial mesoderm is important for providing proper anteroposterior information to the migrating primordial germ cells and that these cells can respond to changes in the global dorsoventral coordinates. In certain mutants, we observe accumulation of ectopic cells in different regions of the embryo. These ectopic cells can retain both morphological and molecular characteristics of primordial germ cells, suggesting that, in zebrafish at the early stages tested, the vasa-expressing cells are committed to the germ cell lineage.

Reorientation Timescales and Pattern Dynamics for Titan's Dunes: Does the Tail Wag the Dog or the Dragon?

NASA Astrophysics Data System (ADS)

Ewing, R. C.; Hayes, A. G.; McCormick, C.; Ballard, C.; Troy, S. A.

2012-04-01

Fields of bedform patterns persist across many orders of magnitude, from cm-scale sub-aqueous current ripples to km-scale aeolian dunes, and form with surprisingly little difference in expression despite a range of formative environments. Because of the remarkable similarity among bedform patterns, extracting information about climate and environment from these patterns is a challenge. For example, crestline orientation is not diagnostic of a particular flow regime; similar patterns form under many different flow configurations. On Titan, these challenges have played out with many attempts to reconcile dune crestline orientation with modeled and expected wind regimes. We propose that thinking about the time-scale of the change in dune orientation, rather than the orientation itself, can provide new insights on the long-term stability of the dune-field patterns and the formative wind regime. In this work, we apply the crestline re-orientation model developed by Werner and Kocurek [Geology, 1997] to the equatorial dune fields of Titan. We use Cassini Synthetic Aperture Radar images processed through a de-noising algorithm recently developed by Lucas et al. [LPSC, 2012] to measure variations in pattern parameters (crest spacing, crest length and defect density, which is the number of defect pairs per total crest length) both within and between Titan's dune fields to describe pattern maturity and identify areas where changes in dune orientation are likely to occur (or may already be occurring). Measured defect densities are similar to Earth's largest linear dune fields, such as the Namib Sand Sea and the Simpson Desert. We use measured defect densities in the Werner and Kocurek model to estimate crestline reorientation rates. We find reorientation timescales varying from ten to a hundred thousand times the average migration timescale (time to migrate a bedform one meter, ~1 Titan year according to Tokano (Aeolian Research, 2010)). Well-organized patterns have the longest reorientation time scales (~105 migration timescales), while the topographically or spatially isolated patches of dunes show the shortest reorientation times (~103 migration timescales). In addition, comparisons between spacing and defect density reveal that the well-organized patterns plot along an expected trend with Earth and Mars' largest, well-organized fields. Patterns on Earth and Mars that have been degraded and broken by environmental change fall off this trend and similarly, so do the isolated dune patterns on Titan fall suggesting changing environmental conditions such as wind regime and/or sediment availability have influenced the dunes on Titan. Crestline orientations in these areas suggest star and crescentic (barchans) morphologies in addition to linear dunes. Our results suggest that Titan's dunes may react to gross bedform transport averaged over orbital timescales, relaxing the requirement that a single modern wind regime is necessary to produce the observed well-organized dune patterns. We find signals of environmental change within the smallest patterns suggesting that the dunes may be recently reoriented or are reorienting to one component of a longer timescale wind regime with a duty cycle that persists over many seasonal cycles.

Evidence for Patterns of Selective Urban Migration in the Greater Indus Valley (2600-1900 BC): A Lead and Strontium Isotope Mortuary Analysis

PubMed Central

Valentine, Benjamin; Kamenov, George D.; Kenoyer, Jonathan Mark; Shinde, Vasant; Mushrif-Tripathy, Veena; Otarola-Castillo, Erik; Krigbaum, John

2015-01-01

Just as modern nation-states struggle to manage the cultural and economic impacts of migration, ancient civilizations dealt with similar external pressures and set policies to regulate people’s movements. In one of the earliest urban societies, the Indus Civilization, mechanisms linking city populations to hinterland groups remain enigmatic in the absence of written documents. However, isotopic data from human tooth enamel associated with Harappa Phase (2600-1900 BC) cemetery burials at Harappa (Pakistan) and Farmana (India) provide individual biogeochemical life histories of migration. Strontium and lead isotope ratios allow us to reinterpret the Indus tradition of cemetery inhumation as part of a specific and highly regulated institution of migration. Intra-individual isotopic shifts are consistent with immigration from resource-rich hinterlands during childhood. Furthermore, mortuary populations formed over hundreds of years and composed almost entirely of first-generation immigrants suggest that inhumation was the final step in a process linking certain urban Indus communities to diverse hinterland groups. Additional multi disciplinary analyses are warranted to confirm inferred patterns of Indus mobility, but the available isotopic data suggest that efforts to classify and regulate human movement in the ancient Indus region likely helped structure socioeconomic integration across an ethnically diverse landscape. PMID:25923705

Evidence for Patterns of Selective Urban Migration in the Greater Indus Valley (2600-1900 BC): A Lead and Strontium Isotope Mortuary Analysis.

PubMed

Valentine, Benjamin; Kamenov, George D; Kenoyer, Jonathan Mark; Shinde, Vasant; Mushrif-Tripathy, Veena; Otarola-Castillo, Erik; Krigbaum, John

2015-01-01

Just as modern nation-states struggle to manage the cultural and economic impacts of migration, ancient civilizations dealt with similar external pressures and set policies to regulate people's movements. In one of the earliest urban societies, the Indus Civilization, mechanisms linking city populations to hinterland groups remain enigmatic in the absence of written documents. However, isotopic data from human tooth enamel associated with Harappa Phase (2600-1900 BC) cemetery burials at Harappa (Pakistan) and Farmana (India) provide individual biogeochemical life histories of migration. Strontium and lead isotope ratios allow us to reinterpret the Indus tradition of cemetery inhumation as part of a specific and highly regulated institution of migration. Intra-individual isotopic shifts are consistent with immigration from resource-rich hinterlands during childhood. Furthermore, mortuary populations formed over hundreds of years and composed almost entirely of first-generation immigrants suggest that inhumation was the final step in a process linking certain urban Indus communities to diverse hinterland groups. Additional multi disciplinary analyses are warranted to confirm inferred patterns of Indus mobility, but the available isotopic data suggest that efforts to classify and regulate human movement in the ancient Indus region likely helped structure socioeconomic integration across an ethnically diverse landscape.

Recent divergence, intercontinental dispersal and shared polymorphism are shaping the genetic structure of amphi-Atlantic peatmoss populations.

PubMed

Szövényi, P; Terracciano, S; Ricca, M; Giordano, S; Shaw, A J

2008-12-01

Several lines of evidence suggest that recent long-distance dispersal may have been important in the evolution of intercontinental distribution ranges of bryophytes. However, the absolute rate of intercontinental migration and its relative role in the development of certain distribution ranges is still poorly understood. To this end, the genetic structure of intercontinental populations of six peatmoss species showing an amphi-Atlantic distribution was investigated using microsatellite markers. Methods relying on the coalescent were applied (IM and MIGRATE) to understand the evolution of this distribution pattern in peatmosses. Intercontinental populations of the six peatmoss species were weakly albeit significantly differentiated (average F(ST) = 0.104). This suggests that the North Atlantic Ocean is acting as a barrier to gene flow even in bryophytes adapted to long-range dispersal. The im analysis suggested a relatively recent split of intercontinental populations dating back to the last two glacial periods (9000-289,000 years ago). In contrast to previous hypotheses, analyses indicated that both ongoing migration and ancestral polymorphism are important in explaining the intercontinental genetic similarity of peatmoss populations, but their relative contribution varies with species. Migration rates were significantly asymmetric towards America suggesting differential extinction of genotypes on the two continents or invasion of the American continent by European lineages. These results indicate that low genetic divergence of amphi-Atlantic populations is a general pattern across numerous flowering plants and bryophytes. However, in bryophytes, ongoing intercontinental gene flow and retained shared ancestral polymorphism must both be considered to explain the genetic similarity of intercontinental populations.

Rural migration in Nevada: Lincoln County. Phase 1, 1992--1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soden, D.L.; Carns, D.E.; Mosser, D.

1993-12-31

The principal objective of this project was to develop insight into the scope of migration of working age Nevadans out of their county of birth; including the collection of data on their skill levels, desire to out or in-migrate, interactions between families of migratory persons, and the impact that the proposed high-level nuclear waste repository at Yucca mountain might have on their individual, and collective, decisions to migrate and return. The initial phase of this project reported here was conducted in 1992 and 1993 in Lincoln County, Nevada, one of the counties designated as ``affected`` by the proposed repository program.more » The findings suggest that a serious out-migration problem exists in Lincoln County, and that the Yucca mountain project will likely affect decisions relating to migration patterns in the future.« less

Corridor- and stopover-use of the Hawaiian goose (Branta sandvicensis), an intratropical altitudinal migrant

USGS Publications Warehouse

Leopold, Christina R.; Hess, Steven C.

2014-01-01

We outfitted six male Hawaiian geese, or nene (Branta sandvicensis), with 45-g solar-powered satellite transmitters and collected four location coordinates d−1 from 2010 to 2012. We used 6193 coordinates to characterize migration corridors, habitat preferences and temporal patterns of displacement for 16 migration events with Brownian bridge utilization distributions (BBUD). We used 1552 coordinates to characterize stopovers from 37 shorter-distance movement events with 25% BBUDs. Two subpopulations used a well-defined common migration corridor spanning a broad gradient of elevation. Use of native-dominated subalpine shrubland was 2.81 times more likely than the availability of this land-cover type. The nene differed from other tropical and temperate-zone migrant birds in that: (1) migration distance and the number of stopovers were unrelated (Mann–Whitney test W = 241, P < 0.006), and; (2) individual movements were not unidirectional suggesting that social interactions may be more important than refuelling en route; but like other species, nene made more direct migrations with fewer stopovers in return to breeding areas (0.58 ± 0.50) than in migration away from breeding areas (1.64 ± 0.48). Our findings, combined with the direction and timing of migration, which is opposite that of most other intratropical migrants, suggest fundamentally different drivers of altitudinal migration.

Comparing internal migration across the countries of Latin America: A multidimensional approach

PubMed Central

Bernard, Aude; Rowe, Francisco; Bell, Martin; Ueffing, Philipp; Charles-Edwards, Elin

2017-01-01

While considerable progress has been made in understanding the way particular aspects of internal migration, such as its intensity, age profile and spatial impact, vary between countries around the world, little attention to date has been given to establishing how these dimensions of migration interact in different national settings. We use recently developed measures of internal migration that are scale-independent to compare the overall intensity, age composition, spatial impact, and distance profile of internal migration in 19 Latin American countries. Comparisons reveal substantial cross-national variation but cluster analysis suggests the different dimensions of migration evolve systematically to form a broad sequence characterised by low intensities, young ages at migration, unbalanced flows and high friction of distance at lower levels of development, trending to high intensities, an older age profile of migration, more closely balanced flows and lower friction of distance at later stages of development. However, the transition is not linear and local contingencies, such as international migration and political control, often distort the migration-development nexus, leading to unique migration patterns in individual national contexts. PMID:28328932

Large scale patterns in vertical distribution and behaviour of mesopelagic scattering layers

PubMed Central

Klevjer, T. A.; Irigoien, X.; Røstad, A.; Fraile-Nuez, E.; Benítez-Barrios, V. M.; Kaartvedt., S.

2016-01-01

Recent studies suggest that previous estimates of mesopelagic biomasses are severely biased, with the new, higher estimates underlining the need to unveil behaviourally mediated coupling between shallow and deep ocean habitats. We analysed vertical distribution and diel vertical migration (DVM) of mesopelagic acoustic scattering layers (SLs) recorded at 38 kHz across oceanographic regimes encountered during the circumglobal Malaspina expedition. Mesopelagic SLs were observed in all areas covered, but vertical distributions and DVM patterns varied markedly. The distribution of mesopelagic backscatter was deepest in the southern Indian Ocean (weighted mean daytime depth: WMD 590 m) and shallowest at the oxygen minimum zone in the eastern Pacific (WMD 350 m). DVM was evident in all areas covered, on average ~50% of mesopelagic backscatter made daily excursions from mesopelagic depths to shallow waters. There were marked differences in migrating proportions between the regions, ranging from ~20% in the Indian Ocean to ~90% in the Eastern Pacific. Overall the data suggest strong spatial gradients in mesopelagic DVM patterns, with implied ecological and biogeochemical consequences. Our results suggest that parts of this spatial variability can be explained by horizontal patterns in physical-chemical properties of water masses, such as oxygen, temperature and turbidity. PMID:26813333

“International Migration and Gender Discrimination among Children Left Behind”

PubMed Central

Antman, Francisca M.

2012-01-01

This paper considers how international migration of the head of household affects the allocation of resources toward boys relative to girls within households remaining in the home country. I address the endogeneity of migration with a differences-in-differences style regression model that compares those households in which migrants have already returned home with those in which migrants are still away. The evidence suggests that while the head of household is away a greater fraction of resources are spent on girls relative to boys, but upon his return, this pattern is reversed. PMID:23239896

Seasonal Movement and Distribution of Fluvial Adult Bull Trout in Selected Watersheds in the Mid-Columbia River and Snake River Basins

PubMed Central

Starcevich, Steven J.; Howell, Philip J.; Jacobs, Steven E.; Sankovich, Paul M.

2012-01-01

From 1997 to 2004, we used radio telemetry to investigate movement and distribution patterns of 206 adult fluvial bull trout (mean, 449 mm FL) from watersheds representing a wide range of habitat conditions in northeastern Oregon and southwestern Washington, a region for which there was little previous information about this species. Migrations between spawning and wintering locations were longest for fish from the Imnaha River (median, 89 km) and three Grande Ronde River tributaries, the Wenaha (56 km) and Lostine (41 km) rivers and Lookingglass Creek (47 km). Shorter migrations were observed in the John Day (8 km), Walla Walla (20 km) and Umatilla river (22 km) systems, where relatively extensive human alterations of the riverscape have been reported. From November through May, fish displayed station-keeping behavior within a narrow range (basin medians, 0.5–6.2 km). Prespawning migrations began after snowmelt-driven peak discharge and coincided with declining flows. Most postspawning migrations began by late September. Migration rates of individuals ranged from 0.1 to 10.7 km/day. Adults migrated to spawning grounds in consecutive years and displayed strong fidelity to previous spawning areas and winter locations. In the Grande Ronde River basin, most fish displayed an unusual fluvial pattern: After exiting the spawning tributary and entering a main stem river, individuals moved upstream to wintering habitat, often a substantial distance (maximum, 49 km). Our work provides additional evidence of a strong migratory capacity in fluvial bull trout, but the short migrations we observed suggest adult fluvial migration may be restricted in basins with substantial anthropogenic habitat alteration. More research into bull trout ecology in large river habitats is needed to improve our understanding of how adults establish migration patterns, what factors influence adult spatial distribution in winter, and how managers can protect and enhance fluvial populations. PMID:22655037

Temporal patterns in adult salmon migration timing across southeast Alaska

USGS Publications Warehouse

Kovach, Ryan P.; Ellison, Stephen; Pyare, Sanjay; Tallmon, David

2015-01-01

Pacific salmon migration timing can drive population productivity, ecosystem dynamics, and human harvest. Nevertheless, little is known about long-term variation in salmon migration timing for multiple species across broad regions. We used long-term data for five Pacific salmon species throughout rapidly warming southeast Alaska to describe long-term changes in salmon migration timing, interannual phenological synchrony, relationships between climatic variation and migratory timing, and to test whether long-term changes in migration timing are related to glaciation in headwater streams. Temporal changes in the median date of salmon migration timing varied widely across species. Most sockeye populations are migrating later over time (11 of 14), but pink, chum, and especially coho populations are migrating earlier than they did historically (16 of 19 combined). Temporal trends in duration and interannual variation in migration timing were highly variable across species and populations. The greatest temporal shifts in the median date of migration timing were correlated with decreases in the duration of migration timing, suggestive of a loss of phenotypic variation due to natural selection. Pairwise interannual correlations in migration timing varied widely but were generally positive, providing evidence for weak region-wide phenological synchrony. This synchrony is likely a function of climatic variation, as interannual variation in migration timing was related to climatic phenomenon operating at large- (Pacific decadal oscillation), moderate- (sea surface temperature), and local-scales (precipitation). Surprisingly, the presence or the absence of glaciers within a watershed was unrelated to long-term shifts in phenology. Overall, there was extensive heterogeneity in long-term patterns of migration timing throughout this climatically and geographically complex region, highlighting that future climatic change will likely have widely divergent impacts on salmon migration timing. Although salmon phenological diversity will complicate future predictions of migration timing, this variation likely acts as a major contributor to population and ecosystem resiliency in southeast Alaska.

The migrational patterns and developmental fates of glial precursors in the rat subventricular zone are temporally regulated.

PubMed

Levison, S W; Chuang, C; Abramson, B J; Goldman, J E

1993-11-01

Postnatal gliogenesis in the rodent forebrain was studied by infecting subventricular zone cells of either neonates or juvenile rats with replication-deficient retroviruses that encode reporter enzymes, enabling the migration and fate of these germinal zone cells to be traced over the ensuing several weeks. Neither neonatal nor juvenile subventricular zone cells migrated substantially along the rostral-caudal axis. Neonatal subventricular zone cells migrated dorsally and laterally into hemispheric gray and white matter and became both astrocytes and oligodendrocytes. Juvenile subventricular zone cells migrated into more medial areas of the subcortical white matter and on occasion appeared in the white matter of the contralateral hemisphere, but rarely migrated into the neocortex. Juvenile subventricular zone cells almost exclusively differentiated into oligodendrocytes. Thus, the migratory patterns and the developmental fates of subventricular zone cells change during the first 2 weeks of life. When either neonatal or juvenile subventricular zone cells were labeled in vivo and then removed and cultured, some generated homogeneous clones that contained either astrocytes with a 'type 1' phenotype or oligodendrocytes, but some generated heterogeneous clones that contained both glial types. These results provide additional evidence for a common progenitor for astrocytes and oligodendrocytes and strongly suggest that temporally and spatially regulated environmental signals control the destiny of glial progenitors during postnatal development.

Expression of Eag1 K+ channel and ErbBs in human pituitary adenomas: cytoskeleton arrangement patterns in cultured cells.

PubMed

del Pliego, Margarita González; Aguirre-Benítez, Elsa; Paisano-Cerón, Karina; Valdovinos-Ramírez, Irene; Rangel-Morales, Carlos; Rodríguez-Mata, Verónica; Solano-Agama, Carmen; Martín-Tapia, Dolores; de la Vega, María Teresa; Saldoval-Balanzario, Miguel; Camacho, Javier; Mendoza-Garrido, María Eugenia

2013-01-01

Pituitary adenomas can invade surrounded tissue, but the mechanism remains elusive. Ether à go-go-1 (Eag1) potassium channel and epidermal growth factor receptors (ErbB1 and ErbB2) have been associated to invasive phenotypes or poor prognosis in cancer patients. However, cells arrange their cytoskeleton in order to acquire a successful migration pattern. We have studied ErbBs and Eag1 expression, and cytoskeleton arrangements in 11 human pituitary adenomas. Eag1, ErbB1 and ErbB2 expression were studied by immunochemistry in tissue and cultured cells. The cytoskeleton arrangement was analyzed in cultured cells by immunofluorescence. Normal pituitary tissue showed ErbB2 expression and Eag1 only in few cells. However, Eag1 and ErbB2 were expressed in all the tumors analyzed. ErbB1 expression was observed variable and did not show specificity for a tumor characteristic. Cultured cells from micro- and macro-adenomas clinically functional organize their cytoskeleton suggesting a mesenchymal pattern, and a round leucocyte/amoeboid pattern from invasive clinically silent adenoma. Pituitary tumors over-express EGF receptors and the ErbB2 repeated expression suggests is a characteristic of adenomas. Eag 1 was express, in different extent, and could be a therapeutic target. The cytoskeleton arrangements observed suggest that pituitary tumor cells acquire different patterns: mesenchymal, and leucocyte/amoeboid, the last observed in the invasive adenomas. Amoeboid migration pattern has been associated with high invasion capacity.

A generalizable energetics-based model of avian migration to facilitate continental-scale waterbird conservation

USGS Publications Warehouse

Lonsdorf, Eric V.; Thogmartin, Wayne E.; Jacobi, Sarah; Coppen, Jorge; Davis, Amélie Y.; Fox, Timothy J.; Heglund, Patricia J.; Johnson, Rex; Jones, Tim; Kenow, Kevin P.; Lyons, James E.; Luke, Kirsten E.; Still, Shannon; Tavernia, Brian G.

2016-01-01

Conserving migratory birds is made especially difficult because of movement among spatially disparate locations across the annual cycle. In light of challenges presented by the scale and ecology of migratory birds, successful conservation requires integrating objectives, management, and monitoring across scales, from local management units to ecoregional and flyway administrative boundaries. We present an integrated approach using a spatially explicit energetic-based mechanistic bird migration model useful to conservation decision-making across disparate scales and locations. This model moves a mallard-like bird (Anas platyrhynchos), through spring and fall migration as a function of caloric gains and losses across a continental scale energy landscape. We predicted with this model that fall migration, where birds moved from breeding to wintering habitat, took a mean of 27.5 days of flight with a mean seasonal survivorship of 90.5% (95% CI = 89.2%, 91.9%) whereas spring migration took a mean of 23.5 days of flight with mean seasonal survivorship of 93.6% (95% CI = 92.5%, 94.7%). Sensitivity analyses suggested that survival during migration was sensitive to flight speed, flight cost, the amount of energy the animal could carry and the spatial pattern of energy availability, but generally insensitive to total energy availability per se. Nevertheless, continental patterns in the bird-use days occurred principally in relation to wetland cover and agricultural habitat in the fall. Bird-use days were highest in both spring and fall in the Mississippi Alluvial Valley and along the coast and near-shore environments of South Carolina. Spatial sensitivity analyses suggested that locations nearer to migratory endpoints were less important to survivorship; for instance, removing energy from a 1,036 km2 stopover site at a time from the Atlantic Flyway suggested coastal areas between New Jersey and North Carolina, including Chesapeake Bay and the North Carolina piedmont, are essential locations for efficient migration and increasing survivorship during spring migration but not locations in Ontario and Massachusetts. This sort of spatially explicit information may allow decision-makers to prioritize their conservation actions toward locations most influential to migratory success. Thus, this mechanistic model of avian migration provides a decision-analytic medium integrating the potential consequences of local actions to flyway-scale phenomena.

What are the evolutionary mechanisms explaining the similar species richness patterns in tropical mosses? Insights from the phylogeny of the pantropical genus Pelekium.

PubMed

Norhazrina, Nik; Vanderpoorten, Alain; Hedenäs, Lars; Patiño, Jairo

2016-12-01

As opposed to angiosperms, moss species richness is similar among tropical regions of the world, in line with the hypothesis that tropical bryophytes are extremely good dispersers. Here, we reconstructed the phylogeny of the pantropical moss genus Pelekium to test the hypothesis that high migration rates erase any difference in species richness among tropical regions. In contrast with this hypothesis, several species considered to have a pantropical range were resolved as a complex of species with a strong geographic structure. Consequently, a significant phylogeographical signal was found in the data, evidencing that cladogenetic diversification within regions takes place at a faster rate than intercontinental migration. The shape of the Pelekium phylogeny, along with the selection of a constant-rate model of diversification among species in the genus, suggests, however, that the cladogenetic speciation patterns observed in Pelekium are not comparable to some of the spectacular examples of tropical radiations reported in angiosperms. Rather, the results presented here point to the constant accumulation of diversity through time in Pelekium. This, combined with evidence for long-distance dispersal limitations in the genus, suggests that the similar patterns of species richness among tropical areas are better explained in terms of comparable rates of diversification across tropical regions than by the homogenization of species richness by recurrent migrations. Copyright © 2016 Elsevier Inc. All rights reserved.

Migrants in transit: the importance of monitoring HIV risk among migrant flows at the Mexico-US border.

PubMed

Martinez-Donate, Ana P; Hovell, Melbourne F; Rangel, Maria Gudelia; Zhang, Xiao; Sipan, Carol L; Magis-Rodriguez, Carlos; Gonzalez-Fagoaga, J Eduardo

2015-03-01

We conducted a probability-based survey of migrant flows traveling across the Mexico-US border, and we estimated HIV infection rates, risk behaviors, and contextual factors for migrants representing 5 distinct migration phases. Our results suggest that the influence of migration is not uniform across genders or risk factors. By considering the predeparture, transit, and interception phases of the migration process, our findings complement previous studies on HIV among Mexican migrants conducted at the destination and return phases. Monitoring HIV risk among this vulnerable transnational population is critical for better understanding patterns of risk at different points of the migration process and for informing the development of protection policies and programs.

Migrants in Transit: The Importance of Monitoring HIV Risk Among Migrant Flows at the Mexico–US Border

PubMed Central

Martinez-Donate, Ana P.; Hovell, Melbourne F.; Rangel, Maria Gudelia; Zhang, Xiao; Sipan, Carol L.; Magis-Rodriguez, Carlos; Gonzalez-Fagoaga, J. Eduardo

2015-01-01

We conducted a probability-based survey of migrant flows traveling across the Mexico–US border, and we estimated HIV infection rates, risk behaviors, and contextual factors for migrants representing 5 distinct migration phases. Our results suggest that the influence of migration is not uniform across genders or risk factors. By considering the predeparture, transit, and interception phases of the migration process, our findings complement previous studies on HIV among Mexican migrants conducted at the destination and return phases. Monitoring HIV risk among this vulnerable transnational population is critical for better understanding patterns of risk at different points of the migration process and for informing the development of protection policies and programs. PMID:25602882

A potential inhibitory function of draxin in regulating mouse trunk neural crest migration.

PubMed

Zhang, Sanbing; Su, Yuhong; Gao, Jinbao; Zhang, Chenbing; Tanaka, Hideaki

2017-01-01

Draxin is a repulsive axon guidance protein that plays important roles in the formation of three commissures in the central nervous system and dorsal interneuron 3 (dI3) in the chick spinal cord. In the present study, we report the expression pattern of mouse draxin in the embryonic mouse trunk spinal cord. In the presence of draxin, the longest net migration length of a migrating mouse trunk neural crest cell was significantly reduced. In addition, the relative number of apolar neural crest cells increased as the draxin treatment time increased. Draxin caused actin cytoskeleton rearrangement in the migrating trunk neural crest cells. Our data suggest that draxin may regulate mouse trunk neural crest cell migration by the rearrangement of cell actin cytoskeleton and by reducing the polarization activity of these cells subsequently.

Disentangling the Effects of Migration, Selection and Acculturation on Weight and Body Fat Distribution: Results from a Natural Experiment involving Vietnamese Americans, Returnees, and Never-leavers

PubMed Central

Fu, Hongyun; VanLandingham, Mark J.

2012-01-01

Objective We distinguish between selection and true migration effects on weight and body fat for Vietnamese immigrants; and examine the role of acculturation on these outcomes. Methods Data (n=703) were collected among three population-based samples of working-age Vietnamese immigrants, repatriated emigrants and never-migrated Vietnamese nationals. This allows for a decomposition exercise to separate the effects of migration effects from selection effects on body mass index (BMI) and waist-hip ratio (WHR). Results Immigrants are more likely to be overweight and to have high WHR, relative to both never-leavers and returnees, a pattern reflecting the importance of migration over selection. Among immigrants, coming to the US at a younger age is associated with higher BMI and WHR levels. And longer length of residence in the US is related to higher BMI. While higher Vietnamese language proficiency is related to a lower BMI level, being bilingual (proficient in both English and Vietnamese) is associated with lower risks for being overweight. Conclusions The distinct pattern of results suggests that more problematic weight status and fat distribution among Vietnamese immigrants relative to Vietnamese nationals are not artifacts of the types of persons choosing to emigrate, but rather are due to acculturation to American diet and lifestyles. While efforts to promote and maintain traditional patterns of diet and lifestyle are likely to help Vietnamese and other immigrants avoid the perils of American patterns, facilitating a bi-cultural orientation is perhaps the most realistic approach for preserving protective features of the culture of origin with regard to body weight and fat distribution. PMID:22427069

Changes in bird-migration patterns associated with human-induced mortality.

PubMed

Palacín, Carlos; Alonso, Juan C; Martín, Carlos A; Alonso, Javier A

2017-02-01

Many bird populations have recently changed their migratory behavior in response to alterations of the environment. We collected data over 16 years on male Great Bustards (Otis tarda), a species showing a partial migratory pattern (sedentary and migratory birds coexisting in the same breeding groups). We conducted population counts and radio tracked 180 individuals to examine differences in survival rates between migratory and sedentary individuals and evaluate possible effects of these differences on the migratory pattern of the population. Overall, 65% of individuals migrated and 35% did not. The average distance between breeding and postbreeding areas of migrant individuals was 89.9 km, and the longest average movement of sedentary males was 3.8 km. Breeding group and migration distance had no effect on survival. However, mortality of migrants was 2.4 to 3.5 times higher than mortality of sedentary birds. For marked males, collision with power lines was the main cause of death from unnatural causes (37.6% of all deaths), and migratory birds died in collisions with power lines more frequently than sedentary birds (21.3% vs 6.3%). The percentage of sedentary individuals increased from 17% in 1997 to 45% in 2012. These results were consistent with data collected from radio-tracked individuals: The proportion of migratory individuals decreased from 86% in 1997-1999 to 44% in 2006-2010. The observed decrease in the migratory tendency was not related to climatic changes (temperatures did not change over the study period) or improvements in habitat quality (dry cereal farmland area decreased in the main study area). Our findings suggest that human-induced mortality during migration may be an important factor shaping the migration patterns of species inhabiting humanized landscapes. © 2016 Society for Conservation Biology.

Sexual orientation, internal migration, and mental health during the transition to adulthood.

PubMed

Ueno, Koji; Vaghela, Preeti; Ritter, Lacey J

2014-12-01

Previous research has suggested that sexual minorities may have higher rates of migration than heterosexuals, indicating their effort to escape stigma in the currently residing areas. However, direct evidence for the migration pattern has been lacking, and mental health implications of such coping effort have been unclear. This study seeks to fill these gaps in the literature by analyzing the Add Health data, which include longitudinal measures of residential locations, sexual orientation, and mental health. The analysis focuses on the transition to adulthood, when the rate of internal migration peaks. Among women, sexual minorities have a higher rate of migration than heterosexuals, but men do not show such a difference. Sexual minorities show better mental health when they migrate to counties with higher proportions of people living in urban areas whereas heterosexuals do not show such an association. Among sexual minority men, migration to counties with higher population density and higher proportions of college-educated residents is also linked to better mental health. © American Sociological Association 2014.

Dcx Re-expression Reduces Subcortical Band Heterotopia and Seizure Threshold in an Animal Model of Neuronal Migration Disorder

PubMed Central

Manent, Jean-Bernard; Wang, Yu; Chang, YoonJeung; Paramasivam, Murugan; LoTurco, Joseph J

2009-01-01

Disorders of neuronal migration can lead to malformations of the cerebral neocortex that greatly increase the risk of seizures. It remains untested whether malformations caused by disorders in neuronal migration can be reduced by reactivating cellular migration, and whether such repair can decrease seizure risk. Here we show, in a rat model of subcortical band heterotopia (SBH) generated by in utero RNAi of Dcx, that aberrantly positioned neurons can be stimulated to migrate by re-expressing Dcx after birth. Re-starting migration in this way both reduces neocortical malformations and restores neuronal patterning. We find further that the capacity to reduce SBH has a critical period in early postnatal development. Moreover, intervention after birth reduces convulsant-induced seizure threshold to levels similar to that of malformation-free controls. These results suggest that disorders of neuronal migration may be eventually treatable by re-engaging developmental programs both to reduce the size of cortical malformations and to reduce seizure risk. PMID:19098909

Agrarian change and labour migration in the Sierra of Ecuador.

PubMed

Peek, P

1980-01-01

"Among the effects produced in the Sierra of Ecuador by the programme of land reforms launched in 1964 was a reduction in the incomes from small-scale farming. At the same time, the growth of productive employment in urban areas was insufficient to provide round-the-year work to the fast growing army of jobseekers. Analysis of the agrarian structure and migration patterns before and after 1964 suggests that it was primarily this combination of circumstances that produced a pronounced shift towards short-term rather than permanent migration, thereby providing industry and services with the labour they needed while avoiding the disadvantages of severe urban overpopulation." excerpt

Multiple functional units in the preattentive segmentation of speech in Japanese: evidence from word illusions.

PubMed

Nakamura, Miyoko; Kolinsky, Régine

2014-12-01

We explored the functional units of speech segmentation in Japanese using dichotic presentation and a detection task requiring no intentional sublexical analysis. Indeed, illusory perception of a target word might result from preattentive migration of phonemes, morae, or syllables from one ear to the other. In Experiment I, Japanese listeners detected targets presented in hiragana and/or kanji. Phoneme migrations did occur, suggesting that orthography-independent sublexical constituents play some role in segmentation. However, syllable and especially mora migrations were more numerous. This pattern of results was not observed in French speakers (Experiment 2), suggesting that it reflects native segmentation in Japanese. To control for the intervention of kanji representations (many words are written in kanji, and one kanji often corresponds to one syllable), in Experiment 3, Japanese listeners were presented with target loanwords that can be written only in katakana. Again, phoneme migrations occurred, while the first mora and syllable led to similar rates of illusory percepts. No migration occurred for the second, "special" mora (/J/ or/N/), probably because this constitutes the latter part of a heavy syllable. Overall, these findings suggest that multiple units, such as morae, syllables, and even phonemes, function independently of orthographic knowledge in Japanese preattentive speech segmentation.

Migration Related to Climate Change: Impact, Challenges and Proposed Policy Initiatives

NASA Astrophysics Data System (ADS)

Sarkar, A.

2015-12-01

Migration of human population possesses a great threat to human development and nation building. A significant cause for migration is due to change in climatic conditions and vulnerabilities associated with it. Our case study focuses on the consequent reason and impact of such migration in the coastal areas of West Bengal, India. The changes in rainfall pattern and the variation of temperature have been considered as parameters which have resulted in migration. It is worthy to note that the agricultural pattern has subsequently changed over the last two decades due to change in rainfall and temperature. India being an agriculture oriented economy, the changes in the meteorological variables have not only altered the rate of agricultural pattern but also the rate of migration. A proposed framework depicting relationship between changes in meteorological variables and the migration pattern, and an estimate of how the migration pattern is expected to change over the next century by utilizing the downscaled values of future rainfall and temperature has been analyzed. Moreover, various public policy frameworks has also been proposed through the study for addressing the challenges of migration related to climate change. The proposed public policy framework has been streamlined along the lines of various international treaties and conventions in order to integrate the policy initiatives through universalization of law and policy research.

Follow-the-leader cell migration requires biased cell-cell contact and local microenvironmental signals

NASA Astrophysics Data System (ADS)

Wynn, Michelle L.; Rupp, Paul; Trainor, Paul A.; Schnell, Santiago; Kulesa, Paul M.

2013-06-01

Directed cell migration often involves at least two types of cell motility that include multicellular streaming and chain migration. However, what is unclear is how cell contact dynamics and the distinct microenvironments through which cells travel influence the selection of one migratory mode or the other. The embryonic and highly invasive neural crest (NC) are an excellent model system to study this question since NC cells have been observed in vivo to display both of these types of cell motility. Here, we present data from tissue transplantation experiments in chick and in silico modeling that test our hypothesis that cell contact dynamics with each other and the microenvironment promote and sustain either multicellular stream or chain migration. We show that when premigratory cranial NC cells (at the pre-otic level) are transplanted into a more caudal region in the head (at the post-otic level), cells alter their characteristic stream behavior and migrate in chains. Similarly, post-otic NC cells migrate in streams after transplantation into the pre-otic hindbrain, suggesting that local microenvironmental signals dictate the mode of NC cell migration. Simulations of an agent-based model (ABM) that integrates the NC cell behavioral data predict that chain migration critically depends on the interplay of biased cell-cell contact and local microenvironment signals. Together, this integrated modeling and experimental approach suggests new experiments and offers a powerful tool to examine mechanisms that underlie complex cell migration patterns.

Geographic migration of black and white families over four generations.

PubMed

Sharkey, Patrick

2015-02-01

This article analyzes patterns of geographic migration of black and white American families over four consecutive generations. The analysis is based on a unique set of questions in the Panel Study of Income Dynamics (PSID) asking respondents about the counties and states in which their parents and grandparents were raised. Using this information along with the extensive geographic information available in the PSID survey, the article tracks the geographic locations of four generations of family members and considers the ways in which families and places are linked together over the course of a family's history. The patterns documented in the article are consistent with much of the demographic literature on the Great Migration of black Americans out of the South, but they reveal new insights into patterns of black migration after the Great Migration. In the most recent generation, black Americans have remained in place to a degree that is unique relative to the previous generation and relative to whites of the same generation. This new geographic immobility is the most pronounced change in black Americans' migration patterns after the Great Migration, and it is a pattern that has implications for the demography of black migration as well as the literature on racial inequality.

Sexually Dimorphic Patterns of Cell Proliferation in the Brain Are Linked to Seasonal Life-History Transitions in Red-Sided Garter Snakes.

PubMed

Lutterschmidt, Deborah I; Lucas, Ashley R; Karam, Ritta A; Nguyen, Vicky T; Rasmussen, Meghann R

2018-01-01

Seasonal rhythms in physiology and behavior are widespread across diverse taxonomic groups and may be mediated by seasonal changes in neurogenesis, including cell proliferation, migration, and differentiation. We examined if cell proliferation in the brain is associated with the seasonal life-history transition from spring breeding to migration and summer foraging in a free-ranging population of red-sided garter snakes ( Thamnophis sirtalis ) in Manitoba, Canada. We used the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) to label newly proliferated cells within the brain of adult snakes collected from the den during the mating season or from a road located along their migratory route. To assess rates of cell migration, we further categorized BrdU-labeled cells according to their location within the ventricular zone or parenchymal region of the nucleus sphericus (homolog of the amygdala), preoptic area/hypothalamus, septal nucleus, and cortex (homolog of the hippocampus). We found that cell proliferation and cell migration varied significantly with sex, the migratory status of snakes, and reproductive behavior in males. In most regions of interest, patterns of cell proliferation were sexually dimorphic, with males having significantly more BrdU-labeled cells than females prior to migration. However, during the initial stages of migration, females exhibited a significant increase in cell proliferation within the nucleus sphericus, hypothalamus, and septal nucleus, but not in any subregion of the cortex. In contrast, migrating males exhibited a significant increase in cell proliferation within the medial cortex but no other brain region. Because it is unlikely that the medial cortex plays a sexually dimorphic role in spatial memory during spring migration, we speculate that cell proliferation within the male medial cortex is associated with regulation of the hypothalamus-pituitary-adrenal axis. Finally, the only brain region where cell migration into the parenchymal region varied significantly with sex or migratory status was the hypothalamus. These results suggest that the migration of newly proliferated cells and/or the continued division of undifferentiated cells are activated earlier or to a greater extent in the hypothalamus. Our data suggest that sexually dimorphic changes in cell proliferation and cell migration in the adult brain may mediate sex differences in the timing of seasonal life-history transitions.

Sexually Dimorphic Patterns of Cell Proliferation in the Brain Are Linked to Seasonal Life-History Transitions in Red-Sided Garter Snakes

PubMed Central

Lutterschmidt, Deborah I.; Lucas, Ashley R.; Karam, Ritta A.; Nguyen, Vicky T.; Rasmussen, Meghann R.

2018-01-01

Seasonal rhythms in physiology and behavior are widespread across diverse taxonomic groups and may be mediated by seasonal changes in neurogenesis, including cell proliferation, migration, and differentiation. We examined if cell proliferation in the brain is associated with the seasonal life-history transition from spring breeding to migration and summer foraging in a free-ranging population of red-sided garter snakes (Thamnophis sirtalis) in Manitoba, Canada. We used the thymidine analog 5-bromo-2′-deoxyuridine (BrdU) to label newly proliferated cells within the brain of adult snakes collected from the den during the mating season or from a road located along their migratory route. To assess rates of cell migration, we further categorized BrdU-labeled cells according to their location within the ventricular zone or parenchymal region of the nucleus sphericus (homolog of the amygdala), preoptic area/hypothalamus, septal nucleus, and cortex (homolog of the hippocampus). We found that cell proliferation and cell migration varied significantly with sex, the migratory status of snakes, and reproductive behavior in males. In most regions of interest, patterns of cell proliferation were sexually dimorphic, with males having significantly more BrdU-labeled cells than females prior to migration. However, during the initial stages of migration, females exhibited a significant increase in cell proliferation within the nucleus sphericus, hypothalamus, and septal nucleus, but not in any subregion of the cortex. In contrast, migrating males exhibited a significant increase in cell proliferation within the medial cortex but no other brain region. Because it is unlikely that the medial cortex plays a sexually dimorphic role in spatial memory during spring migration, we speculate that cell proliferation within the male medial cortex is associated with regulation of the hypothalamus-pituitary-adrenal axis. Finally, the only brain region where cell migration into the parenchymal region varied significantly with sex or migratory status was the hypothalamus. These results suggest that the migration of newly proliferated cells and/or the continued division of undifferentiated cells are activated earlier or to a greater extent in the hypothalamus. Our data suggest that sexually dimorphic changes in cell proliferation and cell migration in the adult brain may mediate sex differences in the timing of seasonal life-history transitions.

A space oddity: geographic and specific modulation of migration in Eudyptes penguins.

PubMed

Thiebot, Jean-Baptiste; Cherel, Yves; Crawford, Robert J M; Makhado, Azwianewi B; Trathan, Philip N; Pinaud, David; Bost, Charles-André

2013-01-01

Post-breeding migration in land-based marine animals is thought to offset seasonal deterioration in foraging or other important environmental conditions at the breeding site. However the inter-breeding distribution of such animals may reflect not only their optimal habitat, but more subtle influences on an individual's migration path, including such factors as the intrinsic influence of each locality's paleoenvironment, thereby influencing animals' wintering distribution. In this study we investigated the influence of the regional marine environment on the migration patterns of a poorly known, but important seabird group. We studied the inter-breeding migration patterns in three species of Eudyptes penguins (E. chrysolophus, E. filholi and E. moseleyi), the main marine prey consumers amongst the World's seabirds. Using ultra-miniaturized logging devices (light-based geolocators) and satellite tags, we tracked 87 migrating individuals originating from 4 sites in the southern Indian Ocean (Marion, Crozet, Kerguelen and Amsterdam Islands) and modelled their wintering habitat using the MADIFA niche modelling technique. For each site, sympatric species followed a similar compass bearing during migration with consistent species-specific latitudinal shifts. Within each species, individuals breeding on different islands showed contrasting migration patterns but similar winter habitat preferences driven by sea-surface temperatures. Our results show that inter-breeding migration patterns in sibling penguin species depend primarily on the site of origin and secondly on the species. Such site-specific migration bearings, together with similar wintering habitat used by parapatrics, support the hypothesis that migration behaviour is affected by the intrinsic characteristics of each site. The paleo-oceanographic conditions (primarily, sea-surface temperatures) when the populations first colonized each of these sites may have been an important determinant of subsequent migration patterns. Based on previous chronological schemes of taxonomic radiation and geographical expansion of the genus Eudyptes, we propose a simple scenario to depict the chronological onset of contrasting migration patterns within this penguin group.

Geomagnetic imprinting predicts spatio-temporal variation in homing migration of pink and sockeye salmon

PubMed Central

Putman, Nathan F.; Jenkins, Erica S.; Michielsens, Catherine G. J.; Noakes, David L. G.

2014-01-01

Animals navigate using a variety of sensory cues, but how each is weighted during different phases of movement (e.g. dispersal, foraging, homing) is controversial. Here, we examine the geomagnetic and olfactory imprinting hypotheses of natal homing with datasets that recorded variation in the migratory routes of sockeye (Oncorhynchus nerka) and pink (Oncorhynchus gorbuscha) salmon returning from the Pacific Ocean to the Fraser River, British Columbia. Drift of the magnetic field (i.e. geomagnetic imprinting) uniquely accounted for 23.2% and 44.0% of the variation in migration routes for sockeye and pink salmon, respectively. Ocean circulation (i.e. olfactory imprinting) predicted 6.1% and 0.1% of the variation in sockeye and pink migration routes, respectively. Sea surface temperature (a variable influencing salmon distribution but not navigation, directly) accounted for 13.0% of the variation in sockeye migration but was unrelated to pink migration. These findings suggest that geomagnetic navigation plays an important role in long-distance homing in salmon and that consideration of navigation mechanisms can aid in the management of migratory fishes by better predicting movement patterns. Finally, given the diversity of animals that use the Earth's magnetic field for navigation, geomagnetic drift may provide a unifying explanation for spatio-temporal variation in the movement patterns of many species. PMID:25056214

Directional migration in the Hindu castes: inferences from mitochondrial, autosomal and Y-chromosomal data.

PubMed

Wooding, Stephen; Ostler, Christopher; Prasad, B V Ravi; Watkins, W Scott; Sung, Sandy; Bamshad, Mike; Jorde, Lynn B

2004-08-01

Genetic, ethnographic, and historical evidence suggests that the Hindu castes have been highly endogamous for several thousand years and that, when movement between castes does occur, it typically consists of females joining castes of higher social status. However, little is known about migration rates in these populations or the extent to which migration occurs between caste groups of low, middle, and high social status. To investigate these aspects of migration, we analyzed the largest collection of genetic markers collected to date in Hindu caste populations. These data included 45 newly typed autosomal short tandem repeat polymorphisms (STRPs), 411 bp of mitochondrial DNA sequence, and 43 Y-chromosomal single-nucleotide polymorphisms that were assayed in more than 200 individuals of known caste status sampled in Andrah Pradesh, in South India. Application of recently developed likelihood-based analyses to this dataset enabled us to obtain genetically derived estimates of intercaste migration rates. STRPs indicated migration rates of 1-2% per generation between high-, middle-, and low-status caste groups. We also found support for the hypothesis that rates of gene flow differ between maternally and paternally inherited genes. Migration rates were substantially higher in maternally than in paternally inherited markers. In addition, while prevailing patterns of migration involved movement between castes of similar rank, paternally inherited markers in the low-status castes were most likely to move into high-status castes. Our findings support earlier evidence that the caste system has been a significant, long-term source of population structuring in South Indian Hindu populations, and that patterns of migration differ between males and females. Copyright 2004 Springer-Verlag

Causes, trends, and policy of population migration and the floating population.

PubMed

Cai, F

1996-01-01

This study provides a discussion of migration theory, a description of the main characteristics of migrants and floating population in China, and a migration impact assessment and potential social policy directions. It is argued that the impetus for migration in China was the population distribution pattern and an uneven industrial structure that favored heavy industry. Another factor affecting migration is the gap in income between urban and rural areas, which has widened since reforms in the mid-1980s. The author finds the Todaro or the Harris-Todaro theories inappropriate for understanding migration in developing countries and flawed. Evidence about migrants' characteristics suggest that migration in China was part of a process governed by the laws of economic growth and market development. Legal migrants are defined as those who legally migrated according to the household registration system. China's development strategy during the 1950s relied on growth of capital-intensive heavy industry. The cost was underwritten by adoption of a price system that shifted the price of products in order to lower the cost of heavy industrial development. During 1952-78, agricultural output dropped sharply, but the employment structure changed very little and the rate of urbanization changed slightly. Regional inequality was obvious by 1978. As reform progressed, patterns emerged that favored eastern coastal development. Microlevel reform outdistanced macrolevel reform. Obstacles to migration were reduced: the breakup of the commune system and changes in the urban food supply system and housing. In 1990 there were 34.128 million migrants, of which 32.42% were interprovincial and 42.99% involved job-related shifts. In 1992, 8.1% of urban population were not registered; 94.909 million were floating population. Cities have established policies to match the size of the floating population to the current carrying capacity.

Brain-Derived Neurotrophic Factor Promotes Vasculature-Associated Migration of Neuronal Precursors toward the Ischemic Striatum

PubMed Central

Grade, Sofia; Weng, Yuan C.; Snapyan, Marina; Kriz, Jasna; Malva, João O.; Saghatelyan, Armen

2013-01-01

Stroke induces the recruitment of neuronal precursors from the subventricular zone (SVZ) into the ischemic striatum. In injured areas, de-routed neuroblasts use blood vessels as a physical scaffold to their migration, in a process that resembles the constitutive migration seen in the rostral migratory stream (RMS). The molecular mechanism underlying injury-induced vasculature-mediated migration of neuroblasts in the post-stroke striatum remains, however, elusive. Using adult mice we now demonstrate that endothelial cells in the ischemic striatum produce brain-derived neurotrophic factor (BDNF), a neurotrophin that promotes the vasculature-mediated migration of neuronal precursors in the RMS, and that recruited neuroblasts maintain expression of p75NTR, a low-affinity receptor for BDNF. Reactive astrocytes, which are widespread throughout the damaged area, ensheath blood vessels and express TrkB, a high-affinity receptor for BDNF. Despite the absence of BDNF mRNA, we observed strong BDNF immunolabeling in astrocytes, suggesting that these glial cells trap extracellular BDNF. Importantly, this pattern of expression is reminiscent of the adult RMS, where TrkB-expressing astrocytes bind and sequester vasculature-derived BDNF, leading to the entry of migrating cells into the stationary phase. Real-time imaging of cell migration in acute brain slices revealed a direct role for BDNF in promoting the migration of neuroblasts to ischemic areas. We also demonstrated that cells migrating in the ischemic striatum display higher exploratory behavior and longer stationary periods than cells migrating in the RMS. Our findings suggest that the mechanisms involved in the injury-induced vasculature-mediated migration of neuroblasts recapitulate, at least partially, those observed during constitutive migration in the RMS. PMID:23383048

Epitaxially grown collagen fibrils reveal diversity in contact guidance behavior among cancer cells.

PubMed

Wang, Juan; Petefish, Joseph W; Hillier, Andrew C; Schneider, Ian C

2015-01-01

Invasion of cancer cells into the surrounding tissue is an important step during cancer progression and is driven by cell migration. Cell migration can be random, but often it is directed by various cues such as aligned fibers composed of extracellular matrix (ECM), a process called contact guidance. During contact guidance, aligned fibers bias migration along the long axis of the fibers. These aligned fibers of ECM are commonly composed of type I collagen, an abundant structural protein around tumors. In this paper, we epitaxially grew several different patterns of organized type I collagen on mica and compared the morphology and contact guidance behavior of two invasive breast cancer cell lines (MDA-MB-231 and MTLn3 cells). Others have shown that these cells randomly migrate in qualitatively different ways. MDA-MB-231 cells exert large traction forces, tightly adhere to the ECM, and migrate with spindle-shaped morphology and thus adopt a mesenchymal mode of migration. MTLn3 cells exert small traction forces, loosely adhere to the ECM, and migrate with a more rounded morphology and thus adopt an amoeboid mode of migration. As the degree of alignment of type I collagen fibrils increases, cells become more elongated and engage in more directed contact guidance. MDA-MB-231 cells perceive the directional signal of highly aligned type I collagen fibrils with high fidelity, elongating to large extents and migrating directionally. Interestingly, behavior in MTLn3 cells differs. While highly aligned type I collagen fibril patterns facilitate spreading and random migration of MTLn3 cells, they do not support elongation or directed migration. Thus, different contact guidance cues bias cell migration differently and the fidelity of contact guidance is cell type dependent, suggesting that ECM alignment is a permissive cue for contact guidance, but requires a cell to have certain properties to interpret that cue.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y. B.; Budai, J. D.; Tischler, J. Z.

How boundaries surrounding recrystallization grains migrate through the 3D network of dislocation boundaries in deformed crystalline materials is unknown and critical for the resulting recrystallized crystalline materials. Furthermore, by using X-ray Laue diffraction microscopy, we show for the first time the migration pattern of a typical recrystallization boundary through a well-characterized deformation matrix. The data provide a unique possibility to investigate effects of both boundary misorientation and plane normal on the migration, information which cannot be accessed with any other techniques. Our results show that neither of these two parameters can explain the observed migration behavior. Instead we suggest thatmore » the subdivision of the deformed microstructure ahead of the boundary plays the dominant role. Our experimental observations challenge the assumptions of existing recrystallization theories, and set the stage for determination of mobilities of recrystallization boundaries.« less

Ontogenetic development of migration: Lagrangian drift trajectories suggest a new paradigm for sea turtles.

PubMed

Hays, Graeme C; Fossette, Sabrina; Katselidis, Kostas A; Mariani, Patrizio; Schofield, Gail

2010-09-06

Long distance migration occurs in a wide variety of taxa including birds, insects, fishes, mammals and reptiles. Here, we provide evidence for a new paradigm for the determinants of migration destination. As adults, sea turtles show fidelity to their natal nesting areas and then at the end of the breeding season may migrate to distant foraging sites. For a major rookery in the Mediterranean, we simulated hatchling drift by releasing 288 000 numerical particles in an area close to the nesting beaches. We show that the pattern of adult dispersion from the breeding area reflects the extent of passive dispersion that would be experienced by hatchlings. Hence, the prevailing oceanography around nesting areas may be crucial to the selection of foraging sites used by adult sea turtles. This environmental forcing may allow the rapid evolution of new migration destinations if ocean currents alter with climate change.

Boundary migration in a 3D deformed microstructure inside an opaque sample

DOE PAGES

Zhang, Y. B.; Budai, J. D.; Tischler, J. Z.; ...

2017-06-30

How boundaries surrounding recrystallization grains migrate through the 3D network of dislocation boundaries in deformed crystalline materials is unknown and critical for the resulting recrystallized crystalline materials. Furthermore, by using X-ray Laue diffraction microscopy, we show for the first time the migration pattern of a typical recrystallization boundary through a well-characterized deformation matrix. The data provide a unique possibility to investigate effects of both boundary misorientation and plane normal on the migration, information which cannot be accessed with any other techniques. Our results show that neither of these two parameters can explain the observed migration behavior. Instead we suggest thatmore » the subdivision of the deformed microstructure ahead of the boundary plays the dominant role. Our experimental observations challenge the assumptions of existing recrystallization theories, and set the stage for determination of mobilities of recrystallization boundaries.« less

Inter-Provincial Migration Intentions of Family Physicians in Canada: The Roles of Income and Community Characteristics

PubMed Central

Olfert, M. Rose

2015-01-01

The inter-provincial migration patterns of family physicians in Canada show that some provinces like Newfoundland and Saskatchewan experience persistent net out-migration, while others, including Ontario and British Columbia, are destinations more often than origins of migrants. Governments in provinces exhibiting net out-migration have responded with a number of incentive and recruitment programs. In this study, we investigate the determinants of the stated interprovincial migration intentions of 3,995 rural and urban family physicians in the 2010 wave of the National Physician Survey. We consider a range of physician characteristics, community attributes and working conditions. We find that in the intention to move, higher compensation has a modest effect, while the community characteristics have a consistently important influence. Our results suggest that policy and program designers should acknowledge the critical role of community-level living and working conditions in their family physician recruitment and retention efforts. PMID:26742116

How community organizations moderate the effect of armed conflict on migration in Nepal

PubMed Central

Williams, Nathalie E.

2013-01-01

This article describes an analytical study of systematic micro-level variability in migration during conflict. The study is based on a multi-dimensional model of individual out-migration that examines the economic, social, and political consequences of conflict and how community organizations condition the experience of these consequences and systematically alter migration patterns. A unique combination of detailed data on violent events and individual behaviours during the Maoist insurrection in Nepal and multi-level event-history models were used to empirically test the model. Results indicate that community organizations dampened the effect of conflict on out-migration by providing resources that helped people to cope with the danger as well as economic, social and political consequences of conflict. This evidence suggests a systematic redistribution of population, partially contingent upon specific resources available in each community, which will likely affect the socio-demographic context of post-conflict Nepal into the future. PMID:23356735

Ontogenetic development of migration: Lagrangian drift trajectories suggest a new paradigm for sea turtles

PubMed Central

Hays, Graeme C.; Fossette, Sabrina; Katselidis, Kostas A.; Mariani, Patrizio; Schofield, Gail

2010-01-01

Long distance migration occurs in a wide variety of taxa including birds, insects, fishes, mammals and reptiles. Here, we provide evidence for a new paradigm for the determinants of migration destination. As adults, sea turtles show fidelity to their natal nesting areas and then at the end of the breeding season may migrate to distant foraging sites. For a major rookery in the Mediterranean, we simulated hatchling drift by releasing 288 000 numerical particles in an area close to the nesting beaches. We show that the pattern of adult dispersion from the breeding area reflects the extent of passive dispersion that would be experienced by hatchlings. Hence, the prevailing oceanography around nesting areas may be crucial to the selection of foraging sites used by adult sea turtles. This environmental forcing may allow the rapid evolution of new migration destinations if ocean currents alter with climate change. PMID:20236958

International labour migration in the Asian-Pacific region: patterns, policies and economic implications.

PubMed

Athukorala, P

1993-11-01

"This paper reviews the literature on international labour migration from and within the Asian-Pacific region. It deals with patterns and characteristics of migration flows, government policies towards labour migration, and economic implications of labour migration for both labour-exporting and importing countries in the region. The indications are that, despite gradual slowing down of labour flows to the western industrial countries and the Middle East, labour migration will continue to be a major economic influence on surplus-labour countries in the region. As an integral part of the growth dynamism in the region, labour migration has now begun to take on a regional dimension, with immense implications for the process of industrial restructuring in high growth economies and the changing pattern of economic interdependence among countries." excerpt

MIGRATION OF COLLEGE AND UNIVERSITY STUDENTS, STATE OF WASHINGTON.

ERIC Educational Resources Information Center

GOSSMAN, CHARLES S.; AND OTHERS

TWO GENERAL ASPECTS OF COLLEGE AND UNIVERSITY STUDENT MIGRATION AS IT RELATES TO THE STATE OF WASHINGTON ARE DISCUSSED. THE FIRST ASPECT INCLUDES ANALYSIS OF MIGRATION PATTERNS IN ACCORDANCE WITH ENROLLMENT CATEGORIES AND TYPES OF INSTITUTIONS, DIFFERENTIAL VOLUMES AND PATTERNS OF MIGRATION FOR SPECIFIC COLLEGES AND UNIVERSITIES IN THE STATE, AND…

Migration of Tundra Swans (Cygnus columbianus) Wintering in Japan Using Satellite Tracking: Identification of the Eastern Palearctic Flyway.

PubMed

Chen, Wenbo; Doko, Tomoko; Fujita, Go; Hijikata, Naoya; Tokita, Ken-Ichi; Uchida, Kiyoshi; Konishi, Kan; Hiraoka, Emiko; Higuchi, Hiroyoshi

2016-02-01

Migration through the Eastern Palearctic (EP) flyway by tundra swans (Cygnus columbianus) has not been thoroughly documented. We satellite-tracked the migration of 16 tundra swans that winter in Japan. The objectives of this study were 1) to show the migration pattern of the EP flyway of tundra swans; 2) to compare this pattern with the migration pattern of whooper swans; and 3) to identify stopover sites that are important for these swans' conservation. Tundra swans were captured at Kutcharo Lake, Hokkaido, in 2009-2012 and satellite-tracked. A new method called the "MATCHED (Migratory Analytical Time Change Easy Detection) method" was developed. Based on median, the spring migration began on 18 April and ended on 27 May. Autumn migration began on 9 September and ended on 2 November. The median duration of the spring and autumn migrations were 48 and 50 days, respectively. The mean duration at one stopover site was 5.5 days and 6.8 days for the spring and autumn migrations, respectively. The number of stopover sites was 3.0 and 2.5 for the spring and autumn migrations, respectively. The mean travel distances for the spring and autumn migrations were 6471 and 6331 km, respectively. Seven migration routes passing Sakhalin, the Amur River, and/or Kamchatka were identified. There were 15, 32, and eight wintering, stopover, and breeding sites, respectively. The migration routes and staging areas of tundra swans partially overlap with those of whooper swans, whose migration patterns have been previously documented. The migration patterns of these two swan species that winter in Japan confirm the importance of the Amur River, Udyl' Lake, Shchastya Bay, Aniva Bay, zaliv Chayvo Lake, zal Piltun Lake, zaliv Baykal Lake, Kolyma River, Buyunda River, Sen-kyuyel' Lake, and northern coastal areas of the Sea of Okhotsk.

Phylogeography of the finless porpoise (genus Neophocaena): testing the stepwise divergence hypothesis in the northwestern Pacific.

PubMed

Lin, Wenzhi; Frère, Céline H; Karczmarski, Leszek; Xia, Jia; Gui, Duan; Wu, Yuping

2014-10-10

We used 344 mitochondrial control region (717 bp) sequences from the finless porpoise (genus Neophocaena) from the northwestern Pacific to investigate the extent and manner in which past climatic oscillations may have shaped patterns of genetic diversity for this marine mammal. Both SplitsTree and Analysis of Molecular Variance (AMOVA) revealed the presence of a deep divergence among N. phocaenoides in subtropical waters compared with N. asiaeorientalis in temperate waters. Results from Migrate-n indicated that migration increased along the continent during the early Pleistocene period. Migration increased, although to a lesser extent than that during the Pleistocene, along the marginal shelf in the Yellow/Bohai Sea during the Last Glacial Maximum (LGM) due to a shortening coastline. Our results suggest that the current patterns of genetic diversity of Neophocaena vary at a hierarchy on a temporal and spatial scale, and phylogeographic history should be taken into account when examining species population structure and taxonomy.

RSA migration of total knee replacements.

PubMed

Pijls, Bart G; Plevier, José W M; Nelissen, Rob G H H

2018-06-01

Purpose - We performed a systematic review and meta-analyses to evaluate the early and long-term migration patterns of tibial components of TKR of all known RSA studies. Methods - Migration pattern was defined as at least 2 postoperative RSA follow-up moments. Maximal total point motion (MTPM) at 6 weeks, 3 months, 6 months, 1 year, 2 years, 5 years, and 10 years were considered. Results - The literature search yielded 1,167 hits of which 53 studies were included, comprising 111 study groups and 2,470 knees. The majority of the early migration occurred in the first 6 months postoperatively followed by a period of stability, i.e., no or very little migration. Cemented and uncemented tibial components had different migration patterns. For cemented tibial components there was no difference in migration between all-poly and metal-backed components, between mobile bearing and fixed bearing, between cruciate retaining and posterior stabilized. Furthermore, no difference existed between TKR measured with model-based RSA or marker-based RSA methods. For uncemented TKR there was some variation in migration with the highest migration for uncoated TKR. Interpretation - The results from this meta-analysis on RSA migration of TKR are in line with both the survival analyses results from joint registries of these TKRs as well as revision rates results from meta-analyses, thus providing further proof for the association between early migration and late revision for loosening. The pooled migration patterns can be used both as benchmarks and for defining migration thresholds for future evaluation of new TKR.

The Great Migration and African-American Genomic Diversity

PubMed Central

Barakatt, Maxime; Gignoux, Christopher R.; Errington, Jacob; Blot, William J.; Bustamante, Carlos D.; Kenny, Eimear E.; Williams, Scott M.; Aldrich, Melinda C.; Gravel, Simon

2016-01-01

We present a comprehensive assessment of genomic diversity in the African-American population by studying three genotyped cohorts comprising 3,726 African-Americans from across the United States that provide a representative description of the population across all US states and socioeconomic status. An estimated 82.1% of ancestors to African-Americans lived in Africa prior to the advent of transatlantic travel, 16.7% in Europe, and 1.2% in the Americas, with increased African ancestry in the southern United States compared to the North and West. Combining demographic models of ancestry and those of relatedness suggests that admixture occurred predominantly in the South prior to the Civil War and that ancestry-biased migration is responsible for regional differences in ancestry. We find that recent migrations also caused a strong increase in genetic relatedness among geographically distant African-Americans. Long-range relatedness among African-Americans and between African-Americans and European-Americans thus track north- and west-bound migration routes followed during the Great Migration of the twentieth century. By contrast, short-range relatedness patterns suggest comparable mobility of ∼15–16km per generation for African-Americans and European-Americans, as estimated using a novel analytical model of isolation-by-distance. PMID:27232753

Limited geographical origin and global spread of sulfadoxine-resistant dhps alleles in Plasmodium falciparum populations.

PubMed

Mita, Toshihiro; Venkatesan, Meera; Ohashi, Jun; Culleton, Richard; Takahashi, Nobuyuki; Tsukahara, Takahiro; Ndounga, Mathieu; Dysoley, Lek; Endo, Hiroyoshi; Hombhanje, Francis; Ferreira, Marcelo U; Plowe, Christopher V; Tanabe, Kazuyuki

2011-12-15

Plasmodium falciparum malaria resistant to chloroquine and pyrimethamine originated in limited foci and migrated to Africa. It remains unresolved whether P. falciparum resistance to sulfadoxine, which is conferred by mutations in dihydropteroate synthase (DHPS), evolved following a similar pattern. The dhps locus of 893 P. falciparum isolates from 12 countries in Asia, the Pacific Islands, Africa, and South America was sequenced. Haplotypes of 6 microsatellite loci flanking the dhps locus were determined to define the genetic relationships among sulfadoxine-resistant lineages. Six distinct sulfadoxine-resistant lineages were identified. Highly resistant lineages appear to have originated only in Southeast Asia and South America. Two resistant lineages found throughout Southeast Asia have been introduced to East Africa, where they appear to have spread. The infrequent selection of parasites highly resistant to sulfadoxine and the subsequent migration of resistant lineages from Asia to Africa are similar to the patterns observed in chloroquine and pyrimethamine resistance. These findings strongly suggest that the global migration of resistant parasites has played a decisive role in the establishment of drug-resistant P. falciparum parasites, and that similar patterns may be anticipated for the spread of artemisinin resistance.

Tracking Mallards (Anas platyrhynchos) with GPS Satellite Transmitters Along Their Migration Route Through Northeast Asia.

PubMed

Shin, Jeong-Hwa; Lee, Ki-Sup; Kim, Seol-Hee; Hwang, Jong-Kyung; Woo, Chanjin; Kim, Jiyeon; Kim, Jung-Hyun; Suh, Jae-Hwa; Jeong, Jipseol; Wang, Seung-Jun; Chung, Hyen-Mi; Yu, Seung-do; Choi, Kyung-Hee; Mo, In-Pil

2016-05-01

In this study, Global Positioning System satellite transmitters were attached to three mallards (Anas platyrhynchos) wintering in South Korea to track their migration routes, stopover sites, breeding sites, and migration patterns. We successfully tracked only one mallard (no. 108917) from November 15, 2011, to November 29, 2013, and determined separate migration routes in two cases of spring migration and one case of fall migration. The mallard repeatedly migrated to the same final destination, even though the travel path varied. We identified six stopover sites: Hunhe River, Liaohe River, Yinma River, Yalu River, Songjeon Bay, and Dahuofang Reservoir in China and South Korea. The wintering sites of two migration cases were discovered to be identical (Gokgyo River in Asan, South Korea). The terminal sites, which were presumed to be breeding grounds, were the same in both cases (Hinggan League in Inner Mongolia Autonomous Region, China). On the basis of the migration routes identified in this study, we suggest that future efforts to control highly pathogenic avian influenza (HPAI) should not only include avian influenza surveillance but also implement flyway-based strategies, with regard to all countries affected by potential HPAI outbreaks.

Using Nocturnal Flight Calls to Assess the Fall Migration of Warblers and Sparrows along a Coastal Ecological Barrier

PubMed Central

Smith, Adam D.; Paton, Peter W. C.; McWilliams, Scott R.

2014-01-01

Atmospheric conditions fundamentally influence the timing, intensity, energetics, and geography of avian migration. While radar is typically used to infer the influence of weather on the magnitude and spatiotemporal patterns of nocturnal bird migration, monitoring the flight calls produced by many bird species during nocturnal migration represents an alternative methodology and provides information regarding the species composition of nocturnal migration. We used nocturnal flight call (NFC) recordings of at least 22 migratory songbirds (14 warbler and 8 sparrow species) during fall migration from eight sites along the mainland and island coasts of Rhode Island to evaluate five hypotheses regarding NFC detections. Patterns of warbler and sparrow NFC detections largely supported our expectations in that (1) NFC detections associated positively and strongly with wind conditions that influence the intensity of coastal bird migration and negatively with regional precipitation; (2) NFCs increased during conditions with reduced visibility (e.g., high cloud cover); (3) NFCs decreased with higher wind speeds, presumably due mostly to increased ambient noise; and (4) coastal mainland sites recorded five to nine times more NFCs, on average, than coastal nearshore or offshore island sites. However, we found little evidence that (5) nightly or intra-night patterns of NFCs reflected the well-documented latitudinal patterns of migrant abundance on an offshore island. Despite some potential complications in inferring migration intensity and species composition from NFC data, the acoustic monitoring of NFCs provides a viable and complementary methodology for exploring the spatiotemporal patterns of songbird migration as well as evaluating the atmospheric conditions that shape these patterns. PMID:24643060

Is there a step-wise migration in Nigeria? A case study of the migrational histories of migrants in Lagos.

PubMed

Afolayan, A A

1985-09-01

"The paper sets out to test whether or not the movement pattern of people in Nigeria is step-wise. It examines the spatial order in the country and the movement pattern of people. It then analyzes the survey data and tests for the validity of step-wise migration in the country. The findings show that step-wise migration cannot adequately describe all the patterns observed." The presence of large-scale circulatory migration between rural and urban areas is noted. Ways to decrease the pressure on Lagos by developing intermediate urban areas are considered. excerpt

Temporal patterns of migration and spawning of river herring in coastal Massachusetts

USGS Publications Warehouse

Rosset, Julianne; Roy, Allison; Gahagan, Benjamin I.; Whiteley, Andrew R.; Armstrong, Michael P.; Sheppard, John J.; Jordaan, Adrian

2017-01-01

Migrations of springtime Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, collectively referred to as river herring, are monitored in many rivers along the Atlantic coast to estimate population sizes. While these estimates give an indication of annual differences in the number of returning adults, links to the subsequent timing and duration of spawning and freshwater juvenile productivity remain equivocal. In this study, we captured juvenile river herring at night in 20 coastal Massachusetts lakes using a purse seine and extracted otoliths to derive daily fish ages and back-calculate spawn dates. Estimates of spawning dates were compared with fishway counts of migrating adults to assess differences in migration timing and the timing and duration of spawning. We observed a distinct delay between the beginning of the adult migration run and the start of spawning, ranging from 7 to 28 d across the 20 lakes. Spawning continued 13–48 d after adults stopped migrating into freshwater, further demonstrating a pronounced delay in spawning following migration. Across the study sites the duration of spawning (43–76 d) was longer but not related to the duration of migration (29–66 d). The extended spawning period is consistent with recent studies suggesting that Alewives are indeterminate spawners. The long duration in freshwater provides the opportunity for top-down (i.e., predation on zooplankton) and bottom-up (i.e., food for avian, fish, and other predators) effects, with implications for freshwater food webs and nutrient cycling. General patterns of spawn timing and duration can be incorporated into population models and used to estimate temporal changes in productivity associated with variable timing and density of spawning river herring in lakes.

Genomic diversity and phylogeography of norovirus in China.

PubMed

Qiao, Niu; Ren, He; Liu, Lei

2017-10-03

Little is known about the phylogeography of norovirus (NoV) in China. In norovirus, a clear understanding for the characteristics of tree topology, migration patterns and its demographic dynamics in viral circulation are needed to identify its prevalence trends, which can help us better prepare for its epidemics as well as develop useful control strategies. The aim of this study was to explore the genetic diversity, temporal distribution, demographic dynamics and migration patterns of NoV that circulated in China. Our analysis showed that two major genogroups, GI and GII, were identified in China, in which GII.3, GII.4 and GII.17 accounted for the majority with a total proportion around 70%. Our demography inference suggested that during the long-term migration process, NoV evolved into multiple lineages and then experienced a selective sweep, which reduced its genetic diversity. The phylogeography results suggested that the norovirus may have originated form the South China (Hong Kong and Guangdong), followed by multicenter direction outbreaks across the country. From these analyses, we indicate that domestic poultry trade and frequent communications of people from different regions have all contributed to the spread of the NoV in China. Together with recent advances in phylogeographic inference, our researches also provide powerful illustrations of how coalescent-based methods can extract adequate information in molecular epidemiology.

International migration network: Topology and modeling

NASA Astrophysics Data System (ADS)

Fagiolo, Giorgio; Mastrorillo, Marina

2013-07-01

This paper studies international migration from a complex-network perspective. We define the international migration network (IMN) as the weighted-directed graph where nodes are world countries and links account for the stock of migrants originated in a given country and living in another country at a given point in time. We characterize the binary and weighted architecture of the network and its evolution over time in the period 1960-2000. We find that the IMN is organized around a modular structure with a small-world binary pattern displaying disassortativity and high clustering, with power-law distributed weighted-network statistics. We also show that a parsimonious gravity model of migration can account for most of observed IMN topological structure. Overall, our results suggest that socioeconomic, geographical, and political factors are more important than local-network properties in shaping the structure of the IMN.

International migration network: topology and modeling.

PubMed

Fagiolo, Giorgio; Mastrorillo, Marina

2013-07-01

This paper studies international migration from a complex-network perspective. We define the international migration network (IMN) as the weighted-directed graph where nodes are world countries and links account for the stock of migrants originated in a given country and living in another country at a given point in time. We characterize the binary and weighted architecture of the network and its evolution over time in the period 1960-2000. We find that the IMN is organized around a modular structure with a small-world binary pattern displaying disassortativity and high clustering, with power-law distributed weighted-network statistics. We also show that a parsimonious gravity model of migration can account for most of observed IMN topological structure. Overall, our results suggest that socioeconomic, geographical, and political factors are more important than local-network properties in shaping the structure of the IMN.

Spatial pattern analysis of nuclear migration in remodelled muscles during Drosophila metamorphosis.

PubMed

Kuleesha; Feng, Lin; Wasser, Martin

2017-07-10

Many human muscle wasting diseases are associated with abnormal nuclear localization. During metamorphosis in Drosophila melanogaster, multi-nucleated larval dorsal abdominal muscles either undergo cell death or are remodeled to temporary adult muscles. Muscle remodeling is associated with anti-polar nuclear migration and atrophy during early pupation followed by polar migration and muscle growth during late pupation. Muscle remodeling is a useful model to study genes involved in myonuclear migration. Previously, we showed that loss of Cathepsin-L inhibited anti-polar movements, while knockdown of autophagy-related genes affected nuclear positioning along the medial axis in late metamorphosis. To compare the phenotypic effects of gene perturbations on nuclear migration more objectively, we developed new descriptors of myonuclear distribution. To obtain nuclear pattern features, we designed an algorithm to detect and track nuclear regions inside live muscles. Nuclear tracks were used to distinguish between fast moving nuclei associated with fragments of dead muscles (sarcolytes) and slow-moving nuclei inside remodelled muscles. Nuclear spatial pattern features, such as longitudinal (lonNS) and lateral nuclear spread (latNS), allowed us to compare nuclear migration during muscle remodelling in different genetic backgrounds. Anti-polar migration leads to a lonNS decrease. As expected, lack of myonuclear migration caused by the loss of Cp1 was correlated with a significantly lower lonNS decrease. Unexpectedly, the decrease in lonNS was significantly enhanced by Atg9, Atg5 and Atg18 silencing, indicating that the loss of autophagy promotes the migration and clustering of nuclei. Loss of autophagy also caused a scattering of nuclei along the lateral axis, leading to a two-row as opposed to single row distribution in control muscles. Increased latNS resulting from knockdown of Atg9 and Atg18 was correlated with increased muscle diameter, suggesting that the wider muscle fibre promotes lateral displacement of nuclei from the medial axis during polar migration. We developed new nuclear features to characterize the dynamics of nuclear distribution in time-lapse images of Drosophila metamorphosis. Image quantification improved our understanding of phenotypic abnormalities in nuclear distribution resulting from gene perturbations. Therefore, in vivo imaging and quantitative image analysis of Drosophila metamorphosis promise to provide novel insights into the relationship between muscle wasting and myonuclear positioning.

Influences of body size and environmental factors on autumn downstream migration of bull trout in the Boise River, Idaho

Treesearch

Lauri Monnot; Jason B. Dunham; Tammy Hoem; Peter Koetsier

2008-01-01

Many fishes migrate extensively through stream networks, yet patterns are commonly described only in terms of the origin and destination of migration (e.g., between natal and feeding habitats). To better understand patterns of migration in bull trout, Salvelinus confluentus we studied the influences of body size (total length [TL]) and environmental...

Zic3 is required in the migrating primitive streak for node morphogenesis and left–right patterning

PubMed Central

Sutherland, Mardi J.; Wang, Shuyun; Quinn, Malgorzata E.; Haaning, Allison; Ware, Stephanie M.

2013-01-01

In humans, loss-of-function mutations in ZIC3 cause isolated cardiovascular malformations and X-linked heterotaxy, a disorder with abnormal left–right asymmetry of organs. Zic3 null mice recapitulate the human heterotaxy phenotype but also have early gastrulation defects, axial patterning defects and neural tube defects complicating an assessment of the role of Zic3 in cardiac development. Zic3 is expressed ubiquitously during critical stages of left–right patterning but its later expression in the developing heart remains controversial and the molecular mechanism(s) by which it causes heterotaxy are unknown. To define the temporal and spatial requirements, for Zic3 in left–right patterning, we generated conditional Zic3 mice and Zic3-LacZ-BAC reporter mice. The latter provide compelling evidence that Zic3 is expressed in the mouse node and absent in the heart. Conditional deletion using T-Cre identifies a requirement for Zic3 in the primitive streak and migrating mesoderm for proper left–right patterning and cardiac development. In contrast, Zic3 is not required in heart progenitors or the cardiac compartment. In addition, the data demonstrate abnormal node morphogenesis in Zic3 null mice and identify similar node dysplasia when Zic3 was specifically deleted from the migrating mesoderm and primitive streak. These results define the temporal and spatial requirements for Zic3 in node morphogenesis, left–right patterning and cardiac development and suggest the possibility that a requirement for Zic3 in node ultrastructure underlies its role in heterotaxy and laterality disorders. PMID:23303524

Intermetropolitan Migration and the Rise of the Sunbelt.

ERIC Educational Resources Information Center

Watkins, Alfred J.

1978-01-01

Examines the historical patterns and components of the population flows that have contributed to recent metropolitan development in the sunbelt. Examines potential problems and fundamental contradictions inherent in both the continuation and cessation of the population influx. Suggests that these demographic and economic trends may seriously…

GEOGRAPHIC AND ENVIRONMENTAL CORRELATES OR REGIONAL POPULATION GENETIC STRUCTURE IN THE CENTRAL STONEROLLER (CAMPOSTOMA ANOMALUM)

EPA Science Inventory

Environmental factors that impact population sizes, migration rates, mutation rates or selective forces can leave lasting genetic imprints on patterns of intraspecific genetic variation. This suggests that measures of genetic diversity may be useful indicators of the condition o...

Geomagnetic imprinting predicts spatio-temporal variation in homing migration of pink and sockeye salmon.

PubMed

Putman, Nathan F; Jenkins, Erica S; Michielsens, Catherine G J; Noakes, David L G

2014-10-06

Animals navigate using a variety of sensory cues, but how each is weighted during different phases of movement (e.g. dispersal, foraging, homing) is controversial. Here, we examine the geomagnetic and olfactory imprinting hypotheses of natal homing with datasets that recorded variation in the migratory routes of sockeye (Oncorhynchus nerka) and pink (Oncorhynchus gorbuscha) salmon returning from the Pacific Ocean to the Fraser River, British Columbia. Drift of the magnetic field (i.e. geomagnetic imprinting) uniquely accounted for 23.2% and 44.0% of the variation in migration routes for sockeye and pink salmon, respectively. Ocean circulation (i.e. olfactory imprinting) predicted 6.1% and 0.1% of the variation in sockeye and pink migration routes, respectively. Sea surface temperature (a variable influencing salmon distribution but not navigation, directly) accounted for 13.0% of the variation in sockeye migration but was unrelated to pink migration. These findings suggest that geomagnetic navigation plays an important role in long-distance homing in salmon and that consideration of navigation mechanisms can aid in the management of migratory fishes by better predicting movement patterns. Finally, given the diversity of animals that use the Earth's magnetic field for navigation, geomagnetic drift may provide a unifying explanation for spatio-temporal variation in the movement patterns of many species. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Spatial Dynamics of the Blue Crab Spawning Stock in the Gulf of Mexico: Local Processes Driving Regional Patterns.

NASA Astrophysics Data System (ADS)

Darnell, M. Z.

2016-02-01

Female blue crabs undertake a critical spawning migration seaward, migrating from low-salinity mating habitat to high-salinity waters of the lower estuaries and coastal ocean, where larval survival is highest. This migration occurs primarily through ebb tide transport, driven by an endogenous circatidal rhythm in vertical swimming that is modulated by behavioral responses to environmental cues. Blue crabs are typically considered an estuarine species and fisheries are managed on a state-by-state basis. Yet recent evidence from state and regional fishery independent survey programs suggests that the spawning migration can take females substantial distances offshore (>150 km), and that offshore waters are important spawning grounds for female blue crabs in the Gulf of Mexico. This is especially true in areas where freshwater inflow is high, resulting in low estuarine and coastal salinities. In low-salinity, high-inflow areas (e.g., Louisiana), spawning occurs further offshore while in high-salinity, low-inflow areas (e.g., South Texas), spawning takes place primarily within the estuary. Regional patterns in spawning locations both inshore and offshore are driven by interactions between behavioral mechanisms and local oceanographic conditions during the spawning migration. These environmentally driven differences in spawning locations have implications for larval survival and population connectivity, and emphasize the need for interjurisdictional assessment and management of the blue crab spawning stock.

Type I interferon dependence of plasmacytoid dendritic cell activation and migration

PubMed Central

Asselin-Paturel, Carine; Brizard, Géraldine; Chemin, Karine; Boonstra, Andre; O'Garra, Anne; Vicari, Alain; Trinchieri, Giorgio

2005-01-01

Differential expression of Toll-like receptor (TLR) by conventional dendritic cells (cDCs) and plasmacytoid DC (pDCs) has been suggested to influence the type of immune response induced by microbial pathogens. In this study we show that, in vivo, cDCs and pDCs are equally activated by TLR4, -7, and -9 ligands. Type I interferon (IFN) was important for pDC activation in vivo in response to all three TLR ligands, whereas cDCs required type I IFN signaling only for TLR9- and partially for TLR7-mediated activation. Although TLR ligands induced in situ migration of spleen cDC into the T cell area, spleen pDCs formed clusters in the marginal zone and in the outer T cell area 6 h after injection of TLR9 and TLR7 ligands, respectively. In vivo treatment with TLR9 ligands decreased pDC ability to migrate ex vivo in response to IFN-induced CXCR3 ligands and increased their response to CCR7 ligands. Unlike cDCs, the migration pattern of pDCs required type I IFN for induction of CXCR3 ligands and responsiveness to CCR7 ligands. These data demonstrate that mouse pDCs differ from cDCs in the in vivo response to TLR ligands, in terms of pattern and type I IFN requirement for activation and migration. PMID:15795237

Self-organized mechano-chemical dynamics in amoeboid locomotion of Physarum fragments

NASA Astrophysics Data System (ADS)

Zhang, Shun; Guy, Robert D.; Lasheras, Juan C.; del Álamo, Juan C.

2017-05-01

The aim of this work is to quantify the spatio-temporal dynamics of flow-driven amoeboid locomotion in small (∼100 μm) fragments of the true slime mold Physarum polycephalum. In this model organism, cellular contraction drives intracellular flows, and these flows transport the chemical signals that regulate contraction in the first place. As a consequence of these non-linear interactions, a diversity of migratory behaviors can be observed in migrating Physarum fragments. To study these dynamics, we measure the spatio-temporal distributions of the velocities of the endoplasm and ectoplasm of each migrating fragment, the traction stresses it generates on the substratum, and the concentration of free intracellular calcium. Using these unprecedented experimental data, we classify migrating Physarum fragments according to their dynamics, finding that they often exhibit spontaneously coordinated waves of flow, contractility and chemical signaling. We show that Physarum fragments exhibiting symmetric spatio-temporal patterns of endoplasmic flow migrate significantly slower than fragments with asymmetric patterns. In addition, our joint measurements of ectoplasm velocity and traction stress at the substratum suggest that forward motion of the ectoplasm is enabled by a succession of stick-slip transitions, which we conjecture are also organized in the form of waves. Combining our experiments with a simplified convection-diffusion model, we show that the convective transport of calcium ions may be key for establishing and maintaining the spatio-temporal patterns of calcium concentration that regulate the generation of contractile forces.

Local adaptation and pronounced genetic differentiation in an extremophile fish, Poecilia mexicana, inhabiting a Mexican cave with toxic hydrogen sulphide.

PubMed

Plath, M; Hauswaldt, J S; Moll, K; Tobler, M; García De León, F J; Schlupp, I; Tiedemann, R

2007-03-01

We investigated genetic differentiation and migration patterns in a small livebearing fish, Poecilia mexicana, inhabiting a sulfidic Mexican limestone cave (Cueva del Azufre). We examined fish from three different cave chambers, the sulfidic surface creek draining the cave (El Azufre) and a nearby surface creek without the toxic hydrogen sulphide (Arroyo Cristal). Using microsatellite analysis of 10 unlinked loci, we found pronounced genetic differentiation among the three major habitats: Arroyo Cristal, El Azufre and the cave. Genetic differentiation was also found within the cave between different pools. An estimation of first-generation migrants suggests that (i) migration is unidirectional, out of the cave, and (ii) migration among different cave chambers occurs to some extent. We investigated if the pattern of genetic differentiation is also reflected in a morphological trait, eye size. Relatively large eyes were found in surface habitats, small eyes in the anterior cave chambers, and the smallest eyes were detected in the innermost cave chamber (XIII). This pattern shows some congruence with a previously proposed morphocline in eye size. However, our data do not support the proposed mechanism for this morphocline, namely that it would be maintained by migration from both directions into the middle cave chambers. This would have led to an increased variance in eye size in the middle cave chambers, which we did not find. Restricted gene flow between the cave and the surface can be explained by local adaptations to extreme environmental conditions, namely H2S and absence of light. Within the cave system, habitat properties are patchy, and genetic differentiation between cave chambers despite migration could indicate local adaptation at an even smaller scale.

Movement ecology of migration in turkey vultures

PubMed Central

Mandel, J. T.; Bildstein, K. L.; Bohrer, G.; Winkler, D. W.

2008-01-01

We develop individual-based movement ecology models (MEM) to explore turkey vulture (Cathartes aura) migration decisions at both hourly and daily scales. Vulture movements in 10 migration events were recorded with satellite-reporting GPS sensors, and flight behavior was observed visually, aided by on-the-ground VHF radio-tracking. We used the North American Regional Reanalysis dataset to obtain values for wind speed, turbulent kinetic energy (TKE), and cloud height and used a digital elevation model for a measure of terrain ruggedness. A turkey vulture fitted with a heart-rate logger during 124 h of flight during 38 contiguous days showed only a small increase in mean heart rate as distance traveled per day increased, which suggests that, unlike flapping, soaring flight does not lead to greatly increased metabolic costs. Data from 10 migrations for 724 hourly segments and 152 daily segments showed that vultures depended heavily upon high levels of TKE in the atmospheric boundary layer to increase flight distances and maintain preferred bearings at both hourly and daily scales. We suggest how the MEM can be extended to other spatial and temporal scales of avian migration. Our success in relating model-derived atmospheric variables to migration indicates the potential of using regional reanalysis data, as here, and potentially other regional, higher-resolution, atmospheric models in predicting changing movement patterns of soaring birds under various scenarios of climate and land use change. PMID:19060195

Robotic Patterning a Superhydrophobic Surface for Collective Cell Migration Screening.

PubMed

Pang, Yonggang; Yang, Jing; Hui, Zhixin; Grottkau, Brian E

2018-04-01

Collective cell migration, in which cells migrate as a group, is fundamental in many biological and pathological processes. There is increasing interest in studying the collective cell migration in high throughput. Cell scratching, insertion blocker, and gel-dissolving techniques are some methodologies used previously. However, these methods have the drawbacks of cell damage, substrate surface alteration, limitation in medium exchange, and solvent interference. The superhydrophobic surface, on which the water contact angle is greater than 150 degrees, has been recently utilized to generate patterned arrays. Independent cell culture areas can be generated on a substrate that functions the same as a conventional multiple well plate. However, so far there has been no report on superhydrophobic patterning for the study of cell migration. In this study, we report on the successful development of a robotically patterned superhydrophobic array for studying collective cell migration in high throughput. The array was developed on a rectangular single-well cell culture plate consisting of hydrophilic flat microwells separated by the superhydrophobic surface. The manufacturing process is robotic and includes patterning discrete protective masks to the substrate using 3D printing, robotic spray coating of silica nanoparticles, robotic mask removal, robotic mini silicone blocker patterning, automatic cell seeding, and liquid handling. Compared with a standard 96-well plate, our system increases the throughput by 2.25-fold and generates a cell-free area in each well non-destructively. Our system also demonstrates higher efficiency than conventional way of liquid handling using microwell plates, and shorter processing time than manual operating in migration assays. The superhydrophobic surface had no negative impact on cell viability. Using our system, we studied the collective migration of human umbilical vein endothelial cells and cancer cells using assays of endpoint quantification, dynamic cell tracking, and migration quantification following varied drug treatments. This system provides a versatile platform to study collective cell migration in high throughput for a broad range of applications.

Residence rule flexibility and descent groups dynamics shape uniparental genetic diversities in South East Asia.

PubMed

Ly, Goki; Alard, Bérénice; Laurent, Romain; Lafosse, Sophie; Toupance, Bruno; Monidarin, Chou; Diffloth, Gérard; Bourdier, Frédéric; Evrard, Olivier; Pavard, Samuel; Chaix, Raphaëlle

2018-03-01

Social organization plays a major role in shaping human population genetic diversity. In particular, matrilocal populations tend to exhibit less mitochondrial diversity than patrilocal populations, and the other way around for Y chromosome diversity. However, several studies have not replicated such findings. The objective of this study is to understand the reasons for such inconsistencies and further evaluate the influence of social organization on genetic diversity. We explored uniparental diversity patterns using mitochondrial HV1 sequences and 17 Y-linked short tandem repeats (STRs) in 12 populations (n = 619) from mainland South-East Asia exhibiting a wide range of social organizations, along with quantitative ethno-demographic information sampled at the individual level. MtDNA diversity was lower in matrilocal than in multilocal and patrilocal populations while Y chromosome diversity was similar among these social organizations. The reasons for such asymmetry at the genetic level were understood by quantifying sex-specific migration rates from our ethno-demographic data: while female migration rates varied between social organizations, male migration rates did not. This unexpected lack of difference in male migrations resulted from a higher flexibility in residence rule in patrilocal than in matrilocal populations. In addition, our data suggested an impact of clan fission process on uniparental genetic patterns. The observed lack of signature of patrilocality on Y chromosome patterns might be attributed to the higher residence flexibility in the studied patrilocal populations, thus providing a potential explanation for the apparent discrepancies between social and genetic structures. Altogether, this study highlights the need to quantify the actual residence and descent patterns to fit social to genetic structures. © 2018 Wiley Periodicals, Inc.

Health, Human Capital, and African American Migration Before 1910

PubMed Central

Logan, Trevon D.

2009-01-01

Using both IPUMS and the Colored Troops Sample of the Civil War Union Army Data, I estimate the effects of literacy and health on the migration propensities of African Americans from 1870 to 1910. I find that literacy and health shocks were strong predictors of migration and the stock of health was not. There were differential selection propensities based on slave status—former slaves were less likely to migrate given a specific health shock than free blacks. Counterfactuals suggest that as much as 35 percent of the difference in the mobility patterns of former slaves and free blacks is explained by differences in their human capital, and more than 20 percent of that difference is due to health alone. Overall, the selection effect of literacy on migration is reduced by one-tenth to one-third once health is controlled for. The low levels of human capital accumulation and rates of mobility for African Americans after the Civil War are partly explained by the poor health status of slaves and their immediate descendants. PMID:20161107

Inter-Provincial Migration Intentions of Family Physicians in Canada: The Roles of Income and Community Characteristics.

PubMed

Mou, Haizhen; Olfert, M Rose

2015-11-01

The inter-provincial migration patterns of family physicians in canada show that some provinces like newfoundland and saskatchewan experience persistent net out-migration, while others, including ontario and british columbia, are destinations more often than origins of migrants. Governments in provinces exhibiting net out-migration have responded with a number of incentive and recruitment programs. In this study, we investigate the determinants of the stated interprovincial migration intentions of 3,995 rural and urban family physicians in the 2010 wave of the national physician survey. We consider a range of physician characteristics, community attributes and working conditions. We find that in the intention to move, higher compensation has a modest effect, while the community characteristics have a consistently important influence. Our results suggest that policy and program designers should acknowledge the critical role of community-level living and working conditions in their family physician recruitment and retention efforts. Copyright © 2015 Longwoods Publishing.

Migration, Residential Mobility, and Poverty in Rural Pennsylvania.

ERIC Educational Resources Information Center

Schachter, Jason P.; Jensen, Leif; Cornwell, Gretchen T.

1998-01-01

In Pennsylvania, high-poverty nonmetro counties are attracting additional poor immigrants, especially the least educated, at the same time that college graduates are showing a net outmigration from rural areas. This pattern increases the strain on rural educational and social services. Survey results suggest that the poor move primarily for…

Impact of migration on new case detection rates in leprosy in Gudiyatham Taluk, Tamil Nadu, India.

PubMed

Samuel, P; Bushanam, J D R S; Ebenezer, M; Richard, J

2012-01-01

Migration of persons affected by leprosy was hinted at as early as 1929 (Bhaskara Rao 1930). All new cases of leprosy in Isfahan Province (Iran) were found to be migrants (Asilian et al 2005). Chudasama (2007) suspected increase in leprosy cases in Surat district to migration. These suggest migration contributes to new cases. This study was done to find out 1. Extent of migration among new cases, 2. Characteristics of migrants, 3. Occupational pattern 4.Reasons for migration. 5. Place of origin of migrants 6. Assimilation of migrants into the society. Trained staff collected information regarding migration using special questionnaire from all 222 new untreated cases from the field area of Community Health department during 2004 to 2008. Migrants were 10.4%. Distribution of place of residence, age, gender, marital status, education, mode of detection, Ridley-Jopling and MB/PB classifications of migrants were not significantly different from that of nonmigrants. Grade 2 deformities were more among migrants. All migrants found occupation. Mostly men migrated for job and women for joining their husbands. The role of migration in increasing the number of new cases cannot be minimized. Enhanced efforts should be made to provide adequate medical, health and rehabilitation services for them also.

Migration and Socio-Economic Change in Africa.

ERIC Educational Resources Information Center

Adepoju, Aderanti

1979-01-01

Explores determinants, characteristics, and patterns of migration in Africa and relates these factors to socioeconomic change processes. Influences of migration are evaluated as they relate to work conditions, land use, marriage and family patterns, life style, and new skills and experiences gained in formal and non-formal educational situations.…

Ancient Human Migrations to and through Jammu Kashmir- India were not of Males Exclusively.

PubMed

Sharma, Indu; Sharma, Varun; Khan, Akbar; Kumar, Parvinder; Rai, Ekta; Bamezai, Rameshwar N K; Vilar, Miguel; Sharma, Swarkar

2018-01-16

Jammu and Kashmir (J&K), the Northern most State of India, has been under-represented or altogether absent in most of the phylogenetic studies carried out in literature, despite its strategic location in the Himalayan region. Nonetheless, this region may have acted as a corridor to various migrations to and from mainland India, Eurasia or northeast Asia. The belief goes that most of the migrations post-late-Pleistocene were mainly male dominated, primarily associated with population invasions, where female migration may thus have been limited. To evaluate female-centered migration patterns in the region, we sequenced 83 complete mitochondrial genomes of unrelated individuals belonging to different ethnic groups from the state. We observed a high diversity in the studied maternal lineages, identifying 19 new maternal sub-haplogroups (HGs). High maternal diversity and our phylogenetic analyses suggest that the migrations post-Pleistocene were not strictly paternal, as described in the literature. These preliminary observations highlight the need to carry out an extensive study of the endogamous populations of the region to unravel many facts and find links in the peopling of India.

Primordial germ cells in the dorsal mesentery of the chicken embryo demonstrate left-right asymmetry and polarized distribution of the EMA1 epitope.

PubMed

Hen, Gideon; Friedman-Einat, Miriam; Sela-Donenfeld, Dalit

2014-05-01

Despite the importance of the chicken as a model system, our understanding of the development of chicken primordial germ cells (PGCs) is far from complete. Here we characterized the morphology of PGCs at different developmental stages, their migration pattern in the dorsal mesentery of the chicken embryo, and the distribution of the EMA1 epitope on PGCs. The spatial distribution of PGCs during their migration was characterized by immunofluorescence on whole-mounted chicken embryos and on paraffin sections, using EMA1 and chicken vasa homolog antibodies. While in the germinal crescent PGCs were rounded and only 25% of them were labeled by EMA1, often seen as a concentrated cluster on the cell surface, following extravasation and migration in the dorsal mesentery PGCs acquired an elongated morphology, and 90% exhibited EMA1 epitope, which was concentrated at the tip of the pseudopodia, at the contact sites between neighboring PGCs. Examination of PGC migration in the dorsal mesentery of Hamburger and Hamilton stage 20-22 embryos demonstrated a left-right asymmetry, as migration of cells toward the genital ridges was usually restricted to the right, rather than the left, side of the mesentery. Moreover, an examination of another group of cells that migrate through the dorsal mesentery, the enteric neural crest cells, revealed a similar preference for the right side of the mesentery, suggesting that the migratory pathway of PGCs is dictated by the mesentery itself. Our findings provide new insights into the migration pathway of PGCs in the dorsal mesentery, and suggest a link between EMA1, PGC migration and cell-cell interactions. These findings may contribute to a better understanding of the mechanism underlying migration of PGCs in avians. © 2014 Anatomical Society.

Gender and spatial population mobility in Iran.

PubMed

Hemmasi, M

1994-01-01

1976-1986 data from the National Census of Population and Housing were analyzed to examine the spatial patterns of internal migration of women and men in Iran within its Islamic patriarchal cultural system. The researcher also organized 1986 data into two interprovincial migration matrixes for men and women. Women were spatially as mobile as men (urban, 16.7% for men and 17% for women; rural, 8.4% and 8.9%, respectively). Gender spatial mobility patterns during the 10 years included: migration streams from nine provinces consistently led to Tehran province, most migration flows to Tehran and most other provinces originated from Khuzistan, East Azerbaijan province still continued to lose population (about 500,000), and out-flows generally originated from the provinces affected by the Iran-Iraq war and went to the central and eastern provinces. The strongest determinants of women's migration was men's migration ratio and the road distance between the origin and destination. Reasons for these strong associations were few employed women ( 10%), strong family ties, and traditional cultural values (e.g., women tend not to travel alone). So their migration patterns tended to be associational rather than autonomous. Despite the fact that internal migration patterns of men and women were the same, the causes, processes, and consequences of migration were still very gender-specific in Iran. There are no signs of change in the near future.

Mid-term migration analysis of a femoral short-stem prosthesis: a five-year EBRA-FCA-study.

PubMed

Freitag, Tobias; Fuchs, Michael; Woelfle-Roos, Julia V; Reichel, Heiko; Bieger, Ralf

2018-05-01

The objective of this study was to evaluate the mid-term migration pattern of a femoral short stem. Implant migration of 73 femoral short-stems was assessed by Ein-Bild-Roentgen-Analysis Femoral-Component-Analysis (EBRA-FCA) 5 years after surgery. Migration pattern of the whole group was analysed and compared to the migration pattern of implants "at risk" with a subsidence of more than 1.5 mm 2 years postoperative. Mean axial subsidence was 1.1 mm (-5.0 mm to 1.5 mm) after 60 months. There was a statistical significant axial migration until 2 years postoperative with settling thereafter. 2 years after surgery 18 of 73 Implants were classified "at risk." Nevertheless, all stems showed secondary stabilisation in the following period with no implant failure neither in the group of implants with early stabilisation nor the group with extensive early onset migration. In summary, even in the group of stems with more pronounced early subsidence, delayed settling occurred in all cases. The determination of a threshold of critical early femoral short stem subsidence is necessary because of the differing migration pattern described in this study with delayed settling of the Fitmore stem 2 years postoperatively compared to early settling within the first postoperative year described for conventional stems.

Labour migration and HIV epidemics in Africa.

PubMed

Decosas, J

1998-10-01

The profile of HIV infection in West Africa is linked to the regional pattern of labor migration. Areas of high HIV prevalence correspond closely to the destination and recruitment points of migrant workers. This correlation suggests that mobile populations have characteristics that make them more susceptible to HIV epidemics. The most plausible explanatory variables for the association of migration and epidemic HIV are deprived living conditions, disruption of social support, and dysfunctional social organization. Migration creates chronic gender imbalances in the reproductive age group. The general excess of females in the recruitment areas and excess of males at the destination erodes traditional community norms of behavior. Health service provision, including health education and condom marketing, does not address these key social factors. Small improvements in the physical and social environment of migrants and their communities of origin may result in greater benefits than any targeted service provision.

Fluctuations in Blood Marginal Zone B-Cell Frequencies May Reflect Migratory Patterns Associated with HIV-1 Disease Progression Status

PubMed Central

Poudrier, Johanne; Roger, Michel

2016-01-01

We have previously shown that overexpression of BLyS/BAFF was associated with increased relative frequencies of innate “precursor” marginal zone (MZ)-like B-cells in the blood of HIV-1-infected rapid and classic progressors. However, along with relatively normal BLyS/BAFF expression levels, these cells remain unaltered in elite-controllers (EC), rather, percentages of more mature MZ-like B-cells are decreased in the blood of these individuals. Fluctuations in frequencies of blood MZ-like B-cell populations may reflect migratory patterns associated with disease progression status, suggesting an important role for these cells in HIV-1 pathogenesis. We have therefore longitudinally measured plasma levels of B-tropic chemokines by ELISA-based technology as well as their ligands by flow-cytometry on blood B-cell populations of HIV-1-infected individuals with different rates of disease progression and uninfected controls. Migration potential of B-cell populations from these individuals were determined by chemotaxis assays. We found important modulations of CXCL13-CXCR5, CXCL12-CXCR4/CXCR7, CCL20-CCR6 and CCL25-CCR9 chemokine-axes and increased cell migration patterns in HIV progressors. Interestingly, frequencies of CCR6 expressing cells were significantly elevated within the precursor MZ-like population, consistent with increased migration in response to CCL20. Although we found little modulation of chemokine-axes in EC, cell migration was greater than that observed for uninfected controls, especially for MZ-like B-cells. Overall the immune response against HIV-1 may involve recruitment of MZ-like B-cells to peripheral sites. Moreover, our findings suggest that “regulated” attraction of these cells in a preserved BLyS/BAFF non-inflammatory environment, such as encountered in EC could be beneficial to the battle and even control of HIV. PMID:27203285

HIV transmission patterns among The Netherlands, Suriname, and The Netherlands Antilles: a molecular epidemiological study.

PubMed

Kramer, Merlijn A; Cornelissen, Marion; Paraskevis, Dimitrios; Prins, Maria; Coutinho, Roel A; van Sighem, Ard I; Sabajo, Lesley; Duits, Ashley J; Winkel, Cai N; Prins, Jan M; van der Ende, Marchina E; Kauffmann, Robert H; Op de Coul, Eline L

2011-02-01

We aimed to study patterns of HIV transmission among Suriname, The Netherlands Antilles, and The Netherlands. Fragments of env, gag, and pol genes of 55 HIV-infected Surinamese, Antillean, and Dutch heterosexuals living in The Netherlands and 72 HIV-infected heterosexuals living in Suriname and the Antilles were amplified and sequenced. We included 145 pol sequences of HIV-infected Surinamese, Antillean, and Dutch heterosexuals living in The Netherlands from an observational cohort. All sequences were phylogenetically analyzed by neighbor-joining. Additionally, HIV-1 mobility among ethnic groups was estimated. A phylogenetic tree of all pol sequences showed two Surinamese and three Antillean clusters of related strains, but no clustering between ethnic groups. Clusters included sequences of individuals living in Suriname and the Antilles as well as those who have migrated to The Netherlands. Similar clustering patterns were observed in env and gag. Analysis of HIV mobility among ethnic groups showed significantly lower migration between groups than expected under the hypothesis of panmixis, apart from higher HIV migration between Antilleans in The Netherlands and all other groups. Our study shows that HIV transmission mainly occurs within the ethnic group. This suggests that cultural factors could have a larger impact on HIV mobility than geographic distance.

Evidence of Partial Migration in a Large Coastal Predator: Opportunistic Foraging and Reproduction as Key Drivers?

PubMed Central

Espinoza, Mario; Heupel, Michelle R.; Tobin, Andrew J.; Simpfendorfer, Colin A.

2016-01-01

Understanding animal movement decisions that involve migration is critical for evaluating population connectivity, and thus persistence. Recent work on sharks has shown that often only a portion of the adult population will undertake migrations, while the rest may be resident in an area for long periods. Defining the extent to which adult sharks use specific habitats and their migratory behaviour is essential for assessing their risk of exposure to threats such as fishing and habitat degradation. The present study used acoustic telemetry to examine residency patterns and migratory behaviour of adult bull sharks (Carcharhinus leucas) along the East coast of Australia. Fifty-six VR2W acoustic receivers were used to monitor the movements of 33 bull sharks in the central Great Barrier Reef (GBR). Both males and females were detected year-round, but their abundance and residency peaked between September and December across years (2012–2014). High individual variability in reef use patterns was apparent, with some individuals leaving the array for long periods, whereas others (36%) exhibited medium (0.20–0.40) or high residency (> 0.50). A large portion of the population (51%) undertook migrations of up to 1,400 km to other coral reefs and/or inshore coastal habitats in Queensland and New South Wales. Most of these individuals (76%) were mature females, and the timing of migrations coincided with the austral summer (Dec-Feb). All migrating individuals (except one) returned to the central GBR, highlighting its importance as a potential foraging ground. Our findings suggest that adult bull sharks appear to be highly dependent on coral reef resources and provide evidence of partial migration, where only a portion of the female population undertook seasonal migrations potentially to give birth. Given that estuarine habitats face constant anthropogenic pressures, understanding partial migration and habitat connectivity of large coastal predators should be a priority for their management. PMID:26841110

Geomorphological Evidence Bearing on the Paired Compressional-Extensional Fronts of the Northern Apennines

NASA Astrophysics Data System (ADS)

Alvarez, W.

2001-12-01

The close association of compressional folding and extensional normal faulting in the Northern Apennines has long attracted the attention of geologists. Elter et al.(1) showed that an extensional front has been following along, about 100 km behind a NE-migrating compressional front. This puzzling tectonic pattern has most commonly been explained by delamination and rollback, but the identity of the delaminating unit has been controversial. Little attention has been paid to the question whether the migration of the paired tectonic fronts and the generation of structures has been episodic or steady state. Since most or all of the Northern Apennines has emerged from the sea in Neogene time, the drainage pattern of the Peninsula may provide evidence bearing on this question. At the latitude of Gubbio, many short, straight, parallel rivers flow northeast from the main drainage divide to the Adriatic Sea, cutting through large anticlines between the extensional and compressional fronts. Alvarez (2) showed that this pattern arose from a process suggested by Mazzanti and Trevisan (3), in which incipient anticlines, additions to the coastal plain, and downstream increments of the rivers formed synchronously at the advancing shoreline. Deeper and deeper gorges cutting higher and higher anticlines southwest from the Adriatic coast show that the eastern third of the Northern Apennines formed in a roughly steady-state process. From the Tyrrhenian coast to the drainage divide, grabens that formed behind the extensional front have produced a trellis pattern in the three master streams (Arno, Ombrone, Tiber). In the steady-state hypothesis, many short, straight, parallel streams - the former headwaters of the Adriatic rivers - would have been disrupted by graben formation and progressively (from SW to NE) added to the trellis pattern. Close to the extensional front, this disruption would have occurred only in Quaternary time, and one would predict that the abandoned headwater tracts would be recognizable. A few candidates are currently under investigation, but the predicted patterns are difficult to detect, and there is little to suggest that the present drainage divide has migrated. This suggests that the steady-state migration of topographic features does not extend back beyond Late Miocene or Early Pliocene time. This is supported by the fact that the Monte Nerone-Monte Catria anticline, forming the main Umbria-Marche Ridge, about 15 km east of Gubbio, is far more structurally elevated than any feature for 100 km to the west. Departure from steady-state topographic evolution may have been driven at the surface by km-scale sea level drawdown during the Messinian salinity crisis or by 100-m-scale Quaternary sea-level oscillations. Or the driver may have been at depth, e.g., duplexing or out-of-sequence thrusting, or episodic delamination. On the other hand, the model of migrating paired fronts, which has guided Apennine research for 25 years, might be in need of major revision. (1) Boll. Geofis. Teor. Appl. 17, p. 3, 1975. (2) Basin Res. 11, p. 267, 1999. (3) Geog. Fis. Din. Quat. 1, p. 55, 1978.

Clines in quantitative traits: The role of migration patterns and selection scenarios

PubMed Central

Geroldinger, Ludwig; Bürger, Reinhard

2015-01-01

The existence, uniqueness, and shape of clines in a quantitative trait under selection toward a spatially varying optimum is studied. The focus is on deterministic diploid two-locus n-deme models subject to various migration patterns and selection scenarios. Migration patterns may exhibit isolation by distance, as in the stepping-stone model, or random dispersal, as in the island model. The phenotypic optimum may change abruptly in a single environmental step, more gradually, or not at all. Symmetry assumptions are imposed on phenotypic optima and migration rates. We study clines in the mean, variance, and linkage disequilibrium (LD). Clines result from polymorphic equilibria. The possible equilibrium configurations are determined as functions of the migration rate. Whereas for weak migration, many polymorphic equilibria may be simultaneously stable, their number decreases with increasing migration rate. Also for intermediate migration rates polymorphic equilibria are in general not unique, however, for loci of equal effects the corresponding clines in the mean, variance, and LD are unique. For sufficiently strong migration, no polymorphism is maintained. Both migration pattern and selection scenario exert strong influence on the existence and shape of clines. The results for discrete demes are compared with those from models in which space varies continuously and dispersal is modeled by diffusion. Comparisons with previous studies, which investigated clines under neutrality or under linkage equilibrium, are performed. If there is no long-distance migration, the environment does not change abruptly, and linkage is not very tight, populations are almost everywhere close to linkage equilibrium. PMID:25446959

Seasonal changes in serum gonadal steroids associated with migration, mating, and nesting in the loggerhead sea turtle (Caretta caretta).

PubMed

Wibbels, T; Owens, D W; Limpus, C J; Reed, P C; Amoss, M S

1990-07-01

Adult male loggerhead sea turtles, Caretta caretta, exhibited a "prenuptial" spermatogenic cycle that was coincident with increased concentrations of serum testosterone (T). Serum T was high during the months when migration and mating have been recorded for males. In contrast to females, males appear to be annual breeders. Nine reproductively active female C. caretta (as verified through laparoscopy) were tagged with sonic transmitters and were repeatedly bled prior to migration. Four months prior to the nesting season, the ovaries of reproductively active females had hundreds of vitellogenic follicles of approximately 1.5 cm in diameter (i.e., half the size of ovulatory follicles). Approximately 4-6 weeks prior to migration from feeding grounds to mating and nesting areas, serum estradiol-17 beta (E2) concentrations increased significantly and remained high for approximately 4 weeks, suggesting a period of increased vitellogenesis. During a 1- to 2-week period prior to migration, serum E2 decreased significantly, while serum T concentrations increased (at least) until the time of migration. Serum T, E2, and progesterone (PRO) were elevated during nesting if a turtle was going to nest again during that nesting season. During the last nesting of a season, turtles had low serum concentrations of T, E2, and Pro. The prenuptial pattern of gonadal recrudescence and gonadal steroid production in both male and female C. caretta contrasts with those of many temperate freshwater turtles, and this type of reproductive pattern may have been facilitated by adaptation to a tropical marine environment.

The Reversal in Migration Patterns -- Some Rural Development Consequences.

ERIC Educational Resources Information Center

Ploch, Louis A.

The reversal in migration patterns in the 1970's resulting in a net population flow from metropolitan (urban) to nonmetropolitan (rural) areas may have a variety of rural development consequences. Sizeable population increase in rural communities which traditionally have experienced net out-migration or very slow increases is evident in Maine…

Migration Background Influences Consumption Patterns Based on Dietary Recommendations of Food Bank Users in Germany.

PubMed

Stroebele-Benschop, Nanette; Depa, Julia; Gyngell, Fiona; Müller, Annalena; Eleraky, Laila; Hilzendegen, Carolin

2018-03-29

People with low income tend to eat less balanced than people with higher income. This seems to be particularly the case for people with migration background. This cross-sectional study examined the relation of consumption patterns of 597 food bank users with different migration background in Germany. Questionnaires were distributed assessing sociodemographic information and consumption patterns. Analyses were conducted using binary logistic regressions. Models were controlled for age, gender, type of household and education. The group of German food bank users consumed fewer fruits and vegetables and less fish compared to all other groups with migration background (former USSR, Balkan region, Middle East). A significant predictor for fruit and vegetable consumption was migration status. Participants from the former USSR consumed less often SSBs compared to the other groups. Dietary recommendations for low income populations should take into consideration other aspects besides income such as migration status.

Southward autumn migration of waterfowl facilitates cross-continental transmission of the highly pathogenic avian influenza H5N1 virus

NASA Astrophysics Data System (ADS)

Xu, Yanjie; Gong, Peng; Wielstra, Ben; Si, Yali

2016-08-01

The highly pathogenic avian influenza subtype H5N1 (HPAI H5N1) is a worldwide zoonotic infectious disease, threatening humans, poultry and wild birds. The role of wild birds in the spread of HPAI H5N1 has previously been investigated by comparing disease spread patterns with bird migration routes. However, the different roles that the southward autumn and northward spring migration might play in virus transmission have hardly been explored. Using direction analysis, we analyze HPAI H5N1 transmission directions and angular concentration of currently circulating viral clades, and compare these with waterfowl seasonal migration directions along major waterfowl flyways. Out of 22 HPAI H5N1 transmission directions, 18 had both a southward direction and a relatively high concentration. Differences between disease transmission and waterfowl migration directions were significantly smaller for autumn than for spring migration. The four northward transmission directions were found along Asian flyways, where the initial epicenter of the virus was located. We suggest waterfowl first picked up the virus from East Asia, then brought it to the north via spring migration, and then spread it to other parts of world mainly by autumn migration. We emphasize waterfowl autumn migration plays a relatively important role in HPAI H5N1 transmission compared to spring migration.

Abundance, biomass, vertical migration and estimated development rate of the copepod Calanus finmarchicus in the southern Gulf of Maine during late spring

NASA Astrophysics Data System (ADS)

Durbin, Edward G.; Gilman, Sharon L.; Campbell, Robert G.; Durbin, Ann G.

Abundance, biomass, diel vertical migration and estimated in situ development in the copepod Calanus finmarchicus were investigated during late spring in 1988 and 1989 in the southern Gulf of Maine. This region is an important feeding ground for the planktivorous right whale, Eubalaena glacialis. The 1988 study took place during the declining spring bloom, with phytoplankton biomass variable, but relatively high. The 1989 study occurred after seasonal stratification, and phytoplankton biomass was low. During the 1988 cruise the dominant stage in C. finmarchicus shifted from C1-C2 to C4-C5. Stage durations during 1988 (4.0 days for C3 and 6.6 days for C4), estimated from the temporal change in stage distribution, were similar to maximal values observed in the laboratory. In contrast, during 1989 stages C4 and C5 were dominant throughout the study period and development rate was slow (estimated C4 stage duration about 24 days). Diel vertical migration patterns changed, from an absence of migration at the first two 1988 stations where younger stages predominated (C1-C3), to a very strong diel vertical migration at the later 1988 stations where stages C3-C3 predominated. This was not a simple ontogenetic change in migratory behavior since all copepodite stages at each station showed similar patterns. During 1989 dense aggregations of C. finmarchicus remained in the surface layer both day and night, and no diel vertical migration was observed. A small, nonmigratory population of late-stage C. finmarchicus was found at depth. Individual body size of these copepods was considerably greater than those found at the surface. Differences in development rate between years reflect differences in the food environment, brought about by seasonal hydrographic changes and the development of more intense stratification. Diel vertical migration patterns, however, did not show a simple relation with food availability, and it is suggested that predation may play an important role in regulating the behavior of the copepods.

The influence of rural-urban migration on migrant's fertility behavior in Cameroon.

PubMed

Lee, B S

1992-01-01

Preliminary analysis of Cameroon fertility data suggests that rural stayers do not have a significantly higher fertility than rural-urban migrants in contrast to hypotheses suggested in the literature. Bongaarts and Caldwell both suggest that modernization plays a role in African fertility and migration patterns by increasing exposure to childbearing. Supply constraints are changed by higher levels of education, short duration of postpartum abstinence, less prevalence of polygamy, and more stable marriages. The influence of relatives may be weaker and the fear of losing a husband greater, which influence earlier returns to sexual relations. Because the levels of fertility of stayers and movers may be equal does not suggest that movers do not adapt fertility to urban norms. Analysis was conducted with d ata from the 1978 Cameroon World Fertility Survey on 8219 women aged 15-54 years for rural nonmigrants, rural-rural migrants, and rural-urban migrants. Rural-urban migrants were found to be better educated, have fewer cases of infertility, and have more stable first marriages. Descriptive statistics are provided for migrants and nonmigrants. Cross classification analysis shows that fertility is not lower for women with higher education, even when migration status is controlled for. Multivariate regression results in an autoregressive model in a first difference form indicated that the fertility rate of rural-urban migrant women was significantly higher than that of rural staryers during the period of 5-9 years after migration. The urban effect acts to reduce migrants' fertility by about .13 births. Comparisons are made with Mexican and Korean migration behavior, which reflect decreased fertility after migration of 1.5 births and 2.6 births, respectively. The suggestion is that the fertility-increasing effect of supply conditions in Cameroon is significantly offset by the fertility-depressing adaptation effect of migration to urban areas. It is expected that eventually fertility will decline as economic development continues and women's educational levels increase. Stability in marriages will increase women's confidence needed to control fertility and contribute to the increased use of contraceptives.

Embryonic expression of endothelins and their receptors in lamprey and frog reveals stem vertebrate origins of complex Endothelin signaling

PubMed Central

Square, Tyler; Jandzik, David; Cattell, Maria; Hansen, Andrew; Medeiros, Daniel Meulemans

2016-01-01

Neural crest cells (NCCs) are highly patterned embryonic cells that migrate along stereotyped routes to give rise to a diverse array of adult tissues and cell types. Modern NCCs are thought to have evolved from migratory neural precursors with limited developmental potential and patterning. How this occurred is poorly understood. Endothelin signaling regulates several aspects of NCC development, including their migration, differentiation, and patterning. In jawed vertebrates, Endothelin signaling involves multiple functionally distinct ligands (Edns) and receptors (Ednrs) expressed in various NCC subpopulations. To test the potential role of endothelin signaling diversification in the evolution of modern, highly patterned NCC, we analyzed the expression of the complete set of endothelin ligands and receptors in the jawless vertebrate, the sea lamprey (Petromyzon marinus). To better understand ancestral features of gnathostome edn and ednr expression, we also analyzed all known Endothelin signaling components in the African clawed frog (Xenopus laevis). We found that the sea lamprey has a gnathsotome-like complement of edn and ednr duplicates, and these genes are expressed in patterns highly reminiscent of their gnathostome counterparts. Our results suggest that the duplication and specialization of vertebrate Endothelin signaling coincided with the appearance of highly patterned and multipotent NCCs in stem vertebrates. PMID:27677704

Do Rainfall Deficits Predict U.S.-bound Migration from Rural Mexico? Evidence from the Mexican Census

PubMed Central

Nawrotzki, Raphael J.; Riosmena, Fernando; Hunter, Lori M.

2013-01-01

Environmental and climatic changes have shaped human mobility for thousands of years and research on the migration-environment connection has proliferated in the past several years. Even so, little work has focused on Latin America or on international movement. Given rural Mexico’s dependency on primary sector activities involving various natural resources, and the existence of well-established transnational migrant networks, we investigate the association between rainfall patterns and U.S.-bound migration from rural locales, a topic of increasing policy relevance. The New Economics of Labor Migration (NELM) theory provides background, positing that migration represents a household-level risk management strategy. We use data from the year 2000 Mexican census for rural localities and socioeconomic and state-level precipitation data provided by the Mexican National Institute for Statistics and Geography. Multilevel models assess the impact of rainfall change on household-level international out-migration while controlling for relevant sociodemographic and economic factors. A decrease in precipitation is significantly associated with U.S.-bound migration, but only for dry Mexican states. This finding suggests that programs and policies aimed at reducing Mexico-U.S. migration should seek to diminish the climate/weather vulnerability of rural Mexican households, for example by supporting sustainable irrigation systems and subsidizing drought-resistant crops. PMID:23913999

Do Rainfall Deficits Predict U.S.-bound Migration from Rural Mexico? Evidence from the Mexican Census.

PubMed

Nawrotzki, Raphael J; Riosmena, Fernando; Hunter, Lori M

2013-02-01

Environmental and climatic changes have shaped human mobility for thousands of years and research on the migration-environment connection has proliferated in the past several years. Even so, little work has focused on Latin America or on international movement. Given rural Mexico's dependency on primary sector activities involving various natural resources, and the existence of well-established transnational migrant networks, we investigate the association between rainfall patterns and U.S.-bound migration from rural locales, a topic of increasing policy relevance. The New Economics of Labor Migration (NELM) theory provides background, positing that migration represents a household-level risk management strategy. We use data from the year 2000 Mexican census for rural localities and socioeconomic and state-level precipitation data provided by the Mexican National Institute for Statistics and Geography. Multilevel models assess the impact of rainfall change on household-level international out-migration while controlling for relevant sociodemographic and economic factors. A decrease in precipitation is significantly associated with U.S.-bound migration, but only for dry Mexican states. This finding suggests that programs and policies aimed at reducing Mexico-U.S. migration should seek to diminish the climate/weather vulnerability of rural Mexican households, for example by supporting sustainable irrigation systems and subsidizing drought-resistant crops.

International migration and educational assortative mating in Mexico and the United States.

PubMed

Choi, Kate H; Mare, Robert D

2012-05-01

This paper examines the relationship between migration and marriage by describing how the distributions of marital statuses and assortative mating patterns vary by individual and community experiences of migration. In Mexico, migrants and those living in areas with high levels of out-migration are more likely to be in heterogamous unions. This is because migration increases the relative attractiveness of single return migrants while disproportionately reducing the number of marriageable men in local marriage markets. In the United States, the odds of homogamy are lower for migrants compared with nonmigrants; however, they do not vary depending on the volume of migration in communities. Migrants are more likely than nonmigrants to "marry up" educationally because the relatively small size of this group compels them to expand their pool of potential spouses to include nonmigrants, who tend to be better educated than they are. Among migrants, the odds of marrying outside of one's education group increase the most among the least educated. In Mexican communities with high rates of out-migration, the odds of marrying outside of one's education group are highest among those with the highest level of education. These findings suggest that migration disrupts preferences and opportunities for homogamy by changing social arrangements and normative climates.

International Migration and Educational Assortative Mating in Mexico and the United States

PubMed Central

Mare, Robert D.

2014-01-01

This paper examines the relationship between migration and marriage by describing how the distributions of marital statuses and assortative mating patterns vary by individual and community experiences of migration. In Mexico, migrants and those living in areas with high levels of out-migration are more likely to be in heterogamous unions. This is because migration increases the relative attractiveness of single return migrants while disproportionately reducing the number of marriageable men in local marriage markets. In the United States, the odds of homogamy are lower for migrants compared with nonmigrants; however, they do not vary depending on the volume of migration in communities. Migrants are more likely than nonmigrants to “marry up” educationally because the relatively small size of this group compels them to expand their pool of potential spouses to include nonmigrants, who tend to be better educated than they are. Among migrants, the odds of marrying outside of one’s education group increase the most among the least educated. In Mexican communities with high rates of out-migration, the odds of marrying outside of one’s education group are highest among those with the highest level of education. These findings suggest that migration disrupts preferences and opportunities for homogamy by changing social arrangements and normative climates. PMID:22419447

Controls on drainage divide migration in the northern Sierras Pampeanas assessed through morphometric indicators

NASA Astrophysics Data System (ADS)

Seagren, E. G.; Schoenbohm, L. M.

2017-12-01

Drainage reorganization, primarily through progressive divide migration leading to discrete stream captures, is increasingly recognized as a common phenomenon during mountain-building events. This drainage rearrangement reflects complex interactions between tectonics, climate, and lithology, and can fundamentally change erosion and sedimentation patterns; therefore, determining the spatial extent and potential controls of divide migration is vital to understanding the topographic evolution of orogenic landscapes. Both geomorphic and morphometric evidence can be used to identify such drainage reorganization. The northern Sierras Pampeanas is an ideal location in which to study divide migration as limited glaciation and low out-of-channel erosion rates preserve evidence of reorganization. Additionally, several ranges in the region, such as Sierra de las Planchadas, exhibit geomorphic evidence of drainage rearrangement, including wind gaps and hairpin turns. Using ArcGIS, LSDTopoTools, and TopoToolbox, we conducted a systematic analysis of the spatial distribution of three morphometric indicators of divide migration: χ, Mx, and local headwater relief. Local `hotspots' undergoing drainage divide migration were identified using spatial autocorrelation and clustering methods - Gi* and Moran's I. Using spatial regression analysis, we assessed the potential controls of lithology, modern TRMM precipitation rates, and tectonics over divide migration. Preliminary results suggest broad westward migration of main drainage divides, following both the orographic precipitation gradient and regional slope.

International migration patterns of Red-throated Loons (Gavia stellata) from four breeding populations in Alaska

USGS Publications Warehouse

McCloskey, Sarah E.; Uher-Koch, Brian D.; Schmutz, Joel A.; Fondell, Thomas F.

2018-01-01

Identifying post-breeding migration and wintering distributions of migratory birds is important for understanding factors that may drive population dynamics. Red-throated Loons (Gavia stellata) are widely distributed across Alaska and currently have varying population trends, including some populations with recent periods of decline. To investigate population differentiation and the location of migration pathways and wintering areas, which may inform population trend patterns, we used satellite transmitters (n = 32) to describe migration patterns of four geographically separate breeding populations of Red-throated Loons in Alaska. On average (± SD) Red-throated Loons underwent long (6,288 ± 1,825 km) fall and spring migrations predominantly along coastlines. The most northern population (Arctic Coastal Plain) migrated westward to East Asia and traveled approximately 2,000 km farther to wintering sites than the three more southerly populations (Seward Peninsula, Yukon-Kuskokwim Delta, and Copper River Delta) which migrated south along the Pacific coast of North America. These migration paths are consistent with the hypothesis that Red-throated Loons from the Arctic Coastal Plain are exposed to contaminants in East Asia. The three more southerly breeding populations demonstrated a chain migration pattern in which the more northerly breeding populations generally wintered in more northerly latitudes. Collectively, the migration paths observed in this study demonstrate that some geographically distinct breeding populations overlap in wintering distribution while others use highly different wintering areas. Red-throated Loon population trends in Alaska may therefore be driven by a wide range of effects throughout the annual cycle.

Defective neuronal migration and inhibition of bipolar to multipolar transition of migrating neural cells by Mesoderm-Specific Transcript, Mest, in the developing mouse neocortex.

PubMed

Ji, Liting; Bishayee, Kausik; Sadra, Ali; Choi, Seunghyuk; Choi, Wooyul; Moon, Sungho; Jho, Eek-Hoon; Huh, Sung-Oh

2017-07-04

Brain developmental disorders such as lissencephaly can result from faulty neuronal migration and differentiation during the formation of the mammalian neocortex. The cerebral cortex is a modular structure, where developmentally, newborn neurons are generated as a neuro-epithelial sheet and subsequently differentiate, migrate and organize into their final positions in the cerebral cortical plate via a process involving both tangential and radial migration. The specific role of Mest, an imprinted gene, in neuronal migration has not been previously studied. In this work, we reduced expression of Mest with in utero electroporation of neuronal progenitors in the developing embryonic mouse neocortex. Reduction of Mest levels by shRNA significantly reduced the number of neurons migrating to the cortical plate. Also, Mest-knockdown disrupted the transition of bipolar neurons into multipolar neurons migrating out of the sub-ventricular zone region. The migrating neurons also adopted a more tangential migration pattern upon knockdown of the Mest message, losing their potential to attach to radial glia cells, required for radial migration. The differentiation and migration properties of neurons via Wnt-Akt signaling were affected by Mest changes. In addition, miR-335, encoded in a Mest gene intron, was identified as being responsible for blocking the default tangential migration of the neurons. Our results suggest that Mest and its intron product, miR-335, play important roles in neuronal migration with Mest regulating the morphological transition of primary neurons required in the formation of the mammalian neocortex. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Overcoming the Problems of Inconsistent International Migration data: A New Method Applied to Flows in Europe

PubMed Central

Raymer, James; van der Erf, Rob; van Wissen, Leo

2010-01-01

Due to differences in definitions and measurement methods, cross-country comparisons of international migration patterns are difficult and confusing. Emigration numbers reported by sending countries tend to differ from the corresponding immigration numbers reported by receiving countries. In this paper, a methodology is presented to achieve harmonised estimates of migration flows benchmarked to a specific definition of duration. This methodology accounts for both differences in definitions and the effects of measurement error due to, for example, under reporting and sampling fluctuations. More specifically, the differences between the two sets of reported data are overcome by estimating a set of adjustment factors for each country’s immigration and emigration data. The adjusted data take into account any special cases where the origin–destination patterns do not match the overall patterns. The new method for harmonising migration flows that we present is based on earlier efforts by Poulain (European Journal of Population, 9(4): 353–381 1993, Working Paper 12, joint ECE-Eurostat Work Session on Migration Statistics, Geneva, Switzerland 1999) and is illustrated for movements between 19 European countries from 2002 to 2007. The results represent a reliable and consistent set of international migration flows that can be used for understanding recent changes in migration patterns, as inputs into population projections and for developing evidence-based migration policies. PMID:21124647

Overcoming the Problems of Inconsistent International Migration data: A New Method Applied to Flows in Europe.

PubMed

de Beer, Joop; Raymer, James; van der Erf, Rob; van Wissen, Leo

2010-11-01

Due to differences in definitions and measurement methods, cross-country comparisons of international migration patterns are difficult and confusing. Emigration numbers reported by sending countries tend to differ from the corresponding immigration numbers reported by receiving countries. In this paper, a methodology is presented to achieve harmonised estimates of migration flows benchmarked to a specific definition of duration. This methodology accounts for both differences in definitions and the effects of measurement error due to, for example, under reporting and sampling fluctuations. More specifically, the differences between the two sets of reported data are overcome by estimating a set of adjustment factors for each country's immigration and emigration data. The adjusted data take into account any special cases where the origin-destination patterns do not match the overall patterns. The new method for harmonising migration flows that we present is based on earlier efforts by Poulain (European Journal of Population, 9(4): 353-381 1993, Working Paper 12, joint ECE-Eurostat Work Session on Migration Statistics, Geneva, Switzerland 1999) and is illustrated for movements between 19 European countries from 2002 to 2007. The results represent a reliable and consistent set of international migration flows that can be used for understanding recent changes in migration patterns, as inputs into population projections and for developing evidence-based migration policies.

bullwinkle and shark regulate dorsal-appendage morphogenesis in Drosophila oogenesis.

PubMed

Tran, David H; Berg, Celeste A

2003-12-01

bullwinkle (bwk) regulates embryonic anteroposterior patterning and, through a novel germline-to-soma signal, morphogenesis of the eggshell dorsal appendages. We screened for dominant modifiers of the bullwinkle mooseantler eggshell phenotype and identified shark, which encodes an SH2-domain, ankyrin-repeat tyrosine kinase. At the onset of dorsal-appendage formation, shark is expressed in a punctate pattern in the squamous stretch cells overlying the nurse cells. Confocal microscopy with cell-type-specific markers demonstrates that the stretch cells act as a substrate for the migrating dorsal-appendage-forming cells and extend cellular projections towards them. Mosaic analyses reveal that shark is required in follicle cells for cell migration and chorion deposition. Proper shark RNA expression in the stretch cells requires bwk activity, while restoration of shark expression in the stretch cells suppresses the bwk dorsal-appendage phenotype. These results suggest that shark plays an important downstream role in the bwk-signaling pathway. Candidate testing implicates Src42A in a similar role, suggesting conservation with a vertebrate signaling pathway involving non-receptor tyrosine kinases.

Does metabolic rate and evaporative water loss reflect differences in migratory strategy in sexually dimorphic hoverflies?

PubMed

Tomlinson, Sean; Menz, Myles H M

2015-12-01

A typical explanation for ecologically stable strategies that apply to only a proportion of a population, is bet hedging, where increased reproductive success offsets reduced reproductive rate. One such is partial migration, where only a proportion of a population moves seasonally to avoid inclement climatic conditions. Bet hedging may overlook unseen costs to maintain broad physiological resilience, implied by encountering a breadth of environmental conditions. We investigated the physiological correlates of partial migration by measuring standard metabolic rates, and rates of evaporative water loss, and then estimating upper and lower thermal tolerance in males and females of two hoverfly species, Episyrphus balteatus and Eristalis tenax. In central Europe, females of these species may either migrate or overwinter, whereas males may migrate south to the Mediterranean, but have not been found overwintering. Both species were sexually dimorphic; female Ep. balteatus were lighter than males, but female Er. tenax were heavier than males. While allometrically- corrected metabolic rate in both species increased with temperature, the most parsimonious models included no sex-specific differences in metabolic rate for either species. Evaporative water loss of both species also increased with temperature, but was higher for females of both species than males. Assuming that resting metabolism is congruent with the activity requirements of migration, highly consistent thermal tolerance and metabolic rate suggests that any given fly could migrate, although water loss patterns suggest that females may be less well-adapted to Mediterranean climates. We infer that partial migration probably results from the imperatives of their reproductive strategies. Copyright © 2015 Elsevier Inc. All rights reserved.

Genome scan of hybridizing sunflowers from Texas (Helianthus annuus and H. debilis) reveals asymmetric patterns of introgression and small islands of genomic differentiation.

PubMed

Scascitelli, M; Whitney, K D; Randell, R A; King, Matthew; Buerkle, C A; Rieseberg, L H

2010-02-01

Although the sexual transfer of genetic material between species (i.e. introgression) has been documented in many groups of plants and animals, genome-wide patterns of introgression are poorly understood. Is most of the genome permeable to interspecific gene flow, or is introgression typically restricted to a handful of genomic regions? Here, we assess the genomic extent and direction of introgression between three sunflowers from the south-central USA: the common sunflower, Helianthus annuus ssp. annuus; a near-endemic to Texas, Helianthus debilis ssp. cucumerifolius; and their putative hybrid derivative, thought to have recently colonized Texas, H. annuus ssp. texanus. Analyses of variation at 88 genetically mapped microsatellite loci revealed that long-term migration rates were high, genome-wide and asymmetric, with higher migration rates from H. annuus texanus into the two parental taxa than vice versa. These results imply a longer history of intermittent contact between H. debilis and H. annuus than previously believed, and that H. annuus texanus may serve as a bridge for the transfer of alleles between its parental taxa. They also contradict recent theory suggesting that introgression should predominantly be in the direction of the colonizing species. As in previous studies of hybridizing sunflower species, regions of genetic differentiation appear small, whether estimated in terms of FST or unidirectional migration rates. Estimates of recent immigration and admixture were inconsistent, depending on the type of analysis. At the individual locus level, one marker showed striking asymmetry in migration rates, a pattern consistent with tight linkage to a Bateson-Dobzhansky-Muller incompatibility.

Migration and risk: net migration in marginal ecosystems and hazardous areas

NASA Astrophysics Data System (ADS)

de Sherbinin, Alex; Levy, Marc; Adamo, Susana; MacManus, Kytt; Yetman, Greg; Mara, Valentina; Razafindrazay, Liana; Goodrich, Benjamin; Srebotnjak, Tanja; Aichele, Cody; Pistolesi, Linda

2012-12-01

The potential for altered ecosystems and extreme weather events in the context of climate change has raised questions concerning the role that migration plays in either increasing or reducing risks to society. Using modeled data on net migration over three decades from 1970 to 2000, we identify sensitive ecosystems and regions at high risk of climate hazards that have seen high levels of net in-migration and out-migration over the time period. This paper provides a literature review on migration related to ecosystems, briefly describes the methodology used to develop the estimates of net migration, then uses those data to describe the patterns of net migration for various ecosystems and high risk regions. The study finds that negative net migration generally occurs over large areas, reflecting its largely rural character, whereas areas of positive net migration are typically smaller, reflecting its largely urban character. The countries with largest population such as China and India tend to drive global results for all the ecosystems found in those countries. Results suggest that from 1970 to 2000, migrants in developing countries have tended to move out of marginal dryland and mountain ecosystems and out of drought-prone areas, and have moved towards coastal ecosystems and areas that are prone to floods and cyclones. For North America results are reversed for dryland and mountain ecosystems, which saw large net influxes of population in the period of record. Uncertainties and potential sources of error in these estimates are addressed.

Climate Vulnerability and Human Migration in Global Perspective

PubMed Central

Grecequet, Martina; DeWaard, Jack; Hellmann, Jessica J.; Abel, Guy J.

2018-01-01

The relationship between climate change and human migration is not homogenous and depends critically on the differential vulnerability of population and places. If places and populations are not vulnerable, or susceptible, to climate change, then the climate–migration relationship may not materialize. The key to understanding and, from a policy perspective, planning for whether and how climate change will impact future migration patterns is therefore knowledge of the link between climate vulnerability and migration. However, beyond specific case studies, little is known about this association in global perspective. We therefore provide a descriptive, country-level portrait of this relationship. We show that the negative association between climate vulnerability and international migration holds only for countries least vulnerable to climate change, which suggests the potential for trapped populations in more vulnerable countries. However, when analyzed separately by life supporting sector (food, water, health, ecosystem services, human habitat, and infrastructure) and vulnerability dimension (exposure, sensitivity, and adaptive capacity), we detect evidence of a relationship among more, but not the most, vulnerable countries. The bilateral (i.e., country-to-country) migration show that, on average, people move from countries of higher vulnerability to lower vulnerability, reducing global risk by 15%. This finding is consistent with the idea that migration is a climate adaptation strategy. Still, ~6% of bilateral migration is maladaptive with respect to climate change, with some movement toward countries with greater climate change vulnerability. PMID:29707262

Climate Vulnerability and Human Migration in Global Perspective.

PubMed

Grecequet, Martina; DeWaard, Jack; Hellmann, Jessica J; Abel, Guy J

2017-05-01

The relationship between climate change and human migration is not homogenous and depends critically on the differential vulnerability of population and places. If places and populations are not vulnerable, or susceptible, to climate change, then the climate-migration relationship may not materialize. The key to understanding and, from a policy perspective, planning for whether and how climate change will impact future migration patterns is therefore knowledge of the link between climate vulnerability and migration. However, beyond specific case studies, little is known about this association in global perspective. We therefore provide a descriptive, country-level portrait of this relationship. We show that the negative association between climate vulnerability and international migration holds only for countries least vulnerable to climate change, which suggests the potential for trapped populations in more vulnerable countries. However, when analyzed separately by life supporting sector (food, water, health, ecosystem services, human habitat, and infrastructure) and vulnerability dimension (exposure, sensitivity, and adaptive capacity), we detect evidence of a relationship among more, but not the most, vulnerable countries. The bilateral (i.e., country-to-country) migration show that, on average, people move from countries of higher vulnerability to lower vulnerability, reducing global risk by 15%. This finding is consistent with the idea that migration is a climate adaptation strategy. Still, ~6% of bilateral migration is maladaptive with respect to climate change, with some movement toward countries with greater climate change vulnerability.

A Comparison of Freshmen Who Attend College in Their Home Community and Freshmen Who Migrate to College.

ERIC Educational Resources Information Center

Fenske, Robert H.; Scott, Craig S.

This study of student migration patterns is based on the assumption that an important determinant of change in student migration patterns in recent years has been the increase in the number of two-year colleges. The present study utilizes data which makes possible an analysis of the relationship between student characteristics and their migration…

Wound Healing Is Defective in Mice Lacking Tetraspanin CD151

PubMed Central

Cowin, Allison J.; Adams, Damian; Geary, Sean M.; Wright, Mark D.; Jones, Jonathan C.R.; Ashman, Leonie K.

2010-01-01

The tetraspanin CD151 forms complexes in epithelial cell membranes with laminin-binding integrins α6 β4, α3 β1, and α6 β1, and modifies integrin-mediated cell migration in vitro. We demonstrate in this study that CD151 expression is upregulated in a distinct temporal and spatial pattern during wound healing, particularly in the migrating epidermal tongue at the wound edge, suggesting a role for CD151 in keratinocyte migration. We show that healing is significantly impaired in CD151-null mice, with wounds gaping wider at 7 days post-injury. The rate of re-epithelialization of the CD151-null wounds is adversely affected, with significantly less wound area being covered by migrating epidermal cells. Our studies reveal that although laminin levels are similar in wild-type and CD151-null wounds, the organization of the laminin in the basement membrane is impaired. Furthermore, upregulation of α6 and β4 integrin expression is adversely affected in CD151-null mice wounds. In contrast, we find no significant effect of CD151 gene knockout on α3 and β1 integrin expression in wound repair. We suggest that mice lacking the CD151 gene are defective in wound healing, primarily owing to impairment of the re-epithelialization process. This may be due to defective basement membrane formation and epithelial cell adhesion and migration. PMID:16410781

Scaling Relations for the Efficiency of Radial Migration in Disk Galaxies

NASA Astrophysics Data System (ADS)

Daniel, Kathryne J.

2018-01-01

Radial migration is frequently recognized as an internal, secular process that could play an important role in disk galaxy evolution. The driving mechanism for radial migration is transient spiral patterns, which rearrange the orbital angular momentum distribution of disk stars around corotation without causing kinematic heating. Should radial migration be an efficient process, it could cause a substantial fraction of disk stars to move large radial distances over the lifetime of the disk, thus having a significant impact on the disk’s kinematic, structural and chemical evolution. Observational and simulated data are consistent with radial migration being important for kinematically cold stellar populations and less so for populations with hot kinematics. I will present an analytic criterion that determines which stars are in orbits that could lead to radial migration. I will then show some scaling relations for the efficacy of radial migration that result from applying this analytic criterion to a series of models that have a variety of distribution functions and spiral patterns in systems with an assumed flat rotation curve. Most importantly, I will argue that these scaling relations can be used to place constraints on the efficiency of radial migration, where stronger spiral patterns and kinematically cold populations will lead to a higher fraction of stars in orbits that can lead to radial migration.

A Physics-Inspired Mechanistic Model of Migratory Movement Patterns in Birds.

PubMed

Revell, Christopher; Somveille, Marius

2017-08-29

In this paper, we introduce a mechanistic model of migratory movement patterns in birds, inspired by ideas and methods from physics. Previous studies have shed light on the factors influencing bird migration but have mainly relied on statistical correlative analysis of tracking data. Our novel method offers a bottom up explanation of population-level migratory movement patterns. It differs from previous mechanistic models of animal migration and enables predictions of pathways and destinations from a given starting location. We define an environmental potential landscape from environmental data and simulate bird movement within this landscape based on simple decision rules drawn from statistical mechanics. We explore the capacity of the model by qualitatively comparing simulation results to the non-breeding migration patterns of a seabird species, the Black-browed Albatross (Thalassarche melanophris). This minimal, two-parameter model was able to capture remarkably well the previously documented migration patterns of the Black-browed Albatross, with the best combination of parameter values conserved across multiple geographically separate populations. Our physics-inspired mechanistic model could be applied to other bird and highly-mobile species, improving our understanding of the relative importance of various factors driving migration and making predictions that could be useful for conservation.

Population Genetic Analysis Infers Migration Pathways of Phytophthora ramorum in US Nurseries

PubMed Central

Goss, Erica M.; Larsen, Meg; Chastagner, Gary A.; Givens, Donald R.; Grünwald, Niklaus J.

2009-01-01

Recently introduced, exotic plant pathogens may exhibit low genetic diversity and be limited to clonal reproduction. However, rapidly mutating molecular markers such as microsatellites can reveal genetic variation within these populations and be used to model putative migration patterns. Phytophthora ramorum is the exotic pathogen, discovered in the late 1990s, that is responsible for sudden oak death in California forests and ramorum blight of common ornamentals. The nursery trade has moved this pathogen from source populations on the West Coast to locations across the United States, thus risking introduction to other native forests. We examined the genetic diversity of P. ramorum in United States nurseries by microsatellite genotyping 279 isolates collected from 19 states between 2004 and 2007. Of the three known P. ramorum clonal lineages, the most common and genetically diverse lineage in the sample was NA1. Two eastward migration pathways were revealed in the clustering of NA1 isolates into two groups, one containing isolates from Connecticut, Oregon, and Washington and the other isolates from California and the remaining states. This finding is consistent with trace forward analyses conducted by the US Department of Agriculture's Animal and Plant Health Inspection Service. At the same time, genetic diversities in several states equaled those observed in California, Oregon, and Washington and two-thirds of multilocus genotypes exhibited limited geographic distributions, indicating that mutation was common during or subsequent to migration. Together, these data suggest that migration, rapid mutation, and genetic drift all play a role in structuring the genetic diversity of P. ramorum in US nurseries. This work demonstrates that fast-evolving genetic markers can be used to examine the evolutionary processes acting on recently introduced pathogens and to infer their putative migration patterns, thus showing promise for the application of forensics to plant pathogens. PMID:19774068

Cell migration without a lamellipodium: translation of actin dynamics into cell movement mediated by tropomyosin.

PubMed

Gupton, Stephanie L; Anderson, Karen L; Kole, Thomas P; Fischer, Robert S; Ponti, Aaron; Hitchcock-DeGregori, Sarah E; Danuser, Gaudenz; Fowler, Velia M; Wirtz, Denis; Hanein, Dorit; Waterman-Storer, Clare M

2005-02-14

The actin cytoskeleton is locally regulated for functional specializations for cell motility. Using quantitative fluorescent speckle microscopy (qFSM) of migrating epithelial cells, we previously defined two distinct F-actin networks based on their F-actin-binding proteins and distinct patterns of F-actin turnover and movement. The lamellipodium consists of a treadmilling F-actin array with rapid polymerization-dependent retrograde flow and contains high concentrations of Arp2/3 and ADF/cofilin, whereas the lamella exhibits spatially random punctae of F-actin assembly and disassembly with slow myosin-mediated retrograde flow and contains myosin II and tropomyosin (TM). In this paper, we microinjected skeletal muscle alphaTM into epithelial cells, and using qFSM, electron microscopy, and immunolocalization show that this inhibits functional lamellipodium formation. Cells with inhibited lamellipodia exhibit persistent leading edge protrusion and rapid cell migration. Inhibition of endogenous long TM isoforms alters protrusion persistence. Thus, cells can migrate with inhibited lamellipodia, and we suggest that TM is a major regulator of F-actin functional specialization in migrating cells.

Redefining the functional roles of the gastrointestinal migrating motor complex and motilin in small bacterial overgrowth and hunger signaling.

PubMed

Deloose, Eveline; Tack, Jan

2016-02-15

During the fasting state the upper gastrointestinal tract exhibits a specific periodic migrating contraction pattern that is known as the migrating motor complex (MMC). Three different phases can be distinguished during the MMC. Phase III of the MMC is the most active of the three and can start either in the stomach or small intestine. Historically this pattern was designated to be the housekeeper of the gut since disturbances in the pattern were associated with small intestinal bacterial overgrowth; however, its role in the involvement of hunger sensations was already hinted in the beginning of the 20th century by both Cannon (Cannon W, Washburn A. Am J Physiol 29: 441-454, 1912) and Carlson (Carlson A. The Control of Hunger in Health and Disease. Chicago, IL: Univ. of Chicago Press, 1916). The discovery of motilin in 1973 shed more light on the control mechanisms of the MMC. Motilin plasma levels fluctuate together with the phases of the MMC and induce phase III contractions with a gastric onset. Recent research suggests that these motilin-induced phase III contractions signal hunger in healthy subjects and that this system is disturbed in morbidly obese patients. This minireview describes the functions of the MMC in the gut and its regulatory role in controlling hunger sensations. Copyright © 2016 the American Physiological Society.

Molecular Detection of Hematozoa Infections in Tundra Swans Relative to Migration Patterns and Ecological Conditions at Breeding Grounds

PubMed Central

Ramey, Andrew M.; Ely, Craig R.; Schmutz, Joel A.; Pearce, John M.; Heard, Darryl J.

2012-01-01

Tundra swans (Cygnus columbianus) are broadly distributed in North America, use a wide variety of habitats, and exhibit diverse migration strategies. We investigated patterns of hematozoa infection in three populations of tundra swans that breed in Alaska using satellite tracking to infer host movement and molecular techniques to assess the prevalence and genetic diversity of parasites. We evaluated whether migratory patterns and environmental conditions at breeding areas explain the prevalence of blood parasites in migratory birds by contrasting the fit of competing models formulated in an occupancy modeling framework and calculating the detection probability of the top model using Akaike Information Criterion (AIC). We described genetic diversity of blood parasites in each population of swans by calculating the number of unique parasite haplotypes observed. Blood parasite infection was significantly different between populations of Alaska tundra swans, with the highest estimated prevalence occurring among birds occupying breeding areas with lower mean daily wind speeds and higher daily summer temperatures. Models including covariates of wind speed and temperature during summer months at breeding grounds better predicted hematozoa prevalence than those that included annual migration distance or duration. Genetic diversity of blood parasites in populations of tundra swans appeared to be relative to hematozoa prevalence. Our results suggest ecological conditions at breeding grounds may explain differences of hematozoa infection among populations of tundra swans that breed in Alaska. PMID:23049862

Molecular detection of hematozoa infections in tundra swans relative to migration patterns and ecological conditions at breeding grounds

USGS Publications Warehouse

Ramey, Andrew M.; Ely, Craig R.; Schmutz, Joel A.; Pearce, John M.; Heard, Darryl J.

2012-01-01

Tundra swans (Cygnus columbianus) are broadly distributed in North America, use a wide variety of habitats, and exhibit diverse migration strategies. We investigated patterns of hematozoa infection in three populations of tundra swans that breed in Alaska using satellite tracking to infer host movement and molecular techniques to assess the prevalence and genetic diversity of parasites. We evaluated whether migratory patterns and environmental conditions at breeding areas explain the prevalence of blood parasites in migratory birds by contrasting the fit of competing models formulated in an occupancy modeling framework and calculating the detection probability of the top model using Akaike Information Criterion (AIC). We described genetic diversity of blood parasites in each population of swans by calculating the number of unique parasite haplotypes observed. Blood parasite infection was significantly different between populations of Alaska tundra swans, with the highest estimated prevalence occurring among birds occupying breeding areas with lower mean daily wind speeds and higher daily summer temperatures. Models including covariates of wind speed and temperature during summer months at breeding grounds better predicted hematozoa prevalence than those that included annual migration distance or duration. Genetic diversity of blood parasites in populations of tundra swans appeared to be relative to hematozoa prevalence. Our results suggest ecological conditions at breeding grounds may explain differences of hematozoa infection among populations of tundra swans that breed in Alaska.

Molecular detection of hematozoa infections in tundra swans relative to migration patterns and ecological conditions at breeding grounds.

PubMed

Ramey, Andrew M; Ely, Craig R; Schmutz, Joel A; Pearce, John M; Heard, Darryl J

2012-01-01

Tundra swans (Cygnus columbianus) are broadly distributed in North America, use a wide variety of habitats, and exhibit diverse migration strategies. We investigated patterns of hematozoa infection in three populations of tundra swans that breed in Alaska using satellite tracking to infer host movement and molecular techniques to assess the prevalence and genetic diversity of parasites. We evaluated whether migratory patterns and environmental conditions at breeding areas explain the prevalence of blood parasites in migratory birds by contrasting the fit of competing models formulated in an occupancy modeling framework and calculating the detection probability of the top model using Akaike Information Criterion (AIC). We described genetic diversity of blood parasites in each population of swans by calculating the number of unique parasite haplotypes observed. Blood parasite infection was significantly different between populations of Alaska tundra swans, with the highest estimated prevalence occurring among birds occupying breeding areas with lower mean daily wind speeds and higher daily summer temperatures. Models including covariates of wind speed and temperature during summer months at breeding grounds better predicted hematozoa prevalence than those that included annual migration distance or duration. Genetic diversity of blood parasites in populations of tundra swans appeared to be relative to hematozoa prevalence. Our results suggest ecological conditions at breeding grounds may explain differences of hematozoa infection among populations of tundra swans that breed in Alaska.

Intercontinental spread of Asian-origin H5N8 to North America through Beringia by migratory birds

USDA-ARS?s Scientific Manuscript database

Phylogenetic analysis and understanding of the waterfowl migration patterns suggests that Eurasian H5N8 clade 2.3.4.4 viruses moved to the Russian Far East/Beringia via migratory birds in spring 2014, evolved into 2 subgroups and subsequently spread along different flyways during fall 2014 into Euro...

Effect of migration patterns on maternal genetic structure: a case of Tai-Kadai migration from China to Thailand.

PubMed

Kampuansai, Jatupol; Kutanan, Wibhu; Tassi, Francesca; Kaewgahya, Massupa; Ghirotto, Silvia; Kangwanpong, Daoroong

2017-02-01

The migration of the Tai-Kadai speaking people from southern China to northern Thailand over the past hundreds of years has revealed numerous patterns that have likely been influenced by routes, purposes and periods of time. To study the effects of different migration patterns on Tai-Kadai maternal genetic structure, mitochondrial DNA hypervariable region I sequences from the Yong and the Lue people having well-documented histories in northern Thailand were analyzed. Although the Yong and Lue people were historically close relatives who shared Xishuangbanna Dai ancestors, significant genetic differences have been observed among them. The Yong people who have been known to practice mass migration have exhibited a closer genetic affinity to their Dai ancestors than have the Lue people. Genetic heterogeneity and a sudden reduced effective population size within the Lue group is likely a direct result of the circumstances of the founder effect.

The Impact of Social Security on Return Migration among Latin American Elderly in the U.S.

PubMed Central

Vega, Alma

2014-01-01

International migration has long been considered the preserve of working-age adults. However, the rapid diversification of the elderly population calls for increased attention to the migration patterns of this group and its possible motivations. This study examines whether Latin American immigrants who are primary Social Security beneficiaries are more likely to return to their home countries during later life if they receive lower Social Security benefits. Using a regression discontinuity approach on restricted data from the U.S. Social Security Administration (N=1,515), this study presents the results of a natural experiment whereby the Social Security Administration unexpectedly lowered the Social Security benefits of the 1917-1921 birth cohorts due to a miscalculation in the benefit-calculation formula. Results suggest that approximately 10% of primary Social Security beneficiaries from Latin America born close to these dates return migrated, the probability of which was not affected by Social Security benefit levels. PMID:26279596

Wintering ecology of adult North American ospreys

USGS Publications Warehouse

Washburn, Brian E.; Martell, Mark S.; Bierregaard, Richard O.; Henny, Charles J.; Dorr, Brian S.; Olexa, Thomas J.

2014-01-01

North American Ospreys (Pandion haliaetus) typically migrate long distances to their wintering grounds in the tropics. Beyond the general distribution of their wintering range (i.e., the Caribbean, South America, and Central America), very little is known about the wintering ecology of these birds. We used satellite telemetry to determine the duration of wintering period, to examine the characteristics of wintering areas used by Ospreys, and to quantify space use and activity patterns of wintering Ospreys. Adult Ospreys migrated to wintering sites and exhibited high wintering site fidelity among years. Overall, Ospreys wintered on river systems (50.6%) more than on lakes (19.0%), and use of coastal areas was (30.4%) intermediate. Ospreys remained on their wintering grounds for an average of 154 d for males and 167 d for females. Locations of wintering Ospreys obtained via GPS-capable satellite telemetry suggest these birds move infrequently and their movements are very localized (i.e., 2 and 1.4 km2, respectively. Overall, our findings suggest wintering adult North American Ospreys are very sedentary, demonstrating a pattern of limited daily movements and high fidelity to a few select locations (presumably roosts). We suggest this wintering strategy might be effective for reducing the risk of mortality and maximizing energy conservation.

The Origin And Migration Of Primordial Germ Cells In Sturgeons

PubMed Central

Saito, Taiju; Pšenička, Martin; Goto, Rie; Adachi, Shinji; Inoue, Kunio; Arai, Katsutoshi; Yamaha, Etsuro

2014-01-01

Primordial germ cells (PGCs) arise elsewhere in the embryo and migrate into developing gonadal ridges during embryonic development. In several model animals, formation and migration patterns of PGCs have been studied, and it is known that these patterns vary. Sturgeons (genus Acipenser) have great potential for comparative and evolutionary studies of development. Sturgeons belong to the super class Actinoptergii, and their developmental pattern is similar to that of amphibians, although their phylogenetic position is an out-group to teleost fishes. Here, we reveal an injection technique for sturgeon eggs allowing visualization of germplasm and PGCs. Using this technique, we demonstrate that the PGCs are generated at the vegetal pole of the egg and they migrate on the yolky cell mass toward the gonadal ridge. We also provide evidence showing that PGCs are specified by inheritance of maternally supplied germplasm. Furthermore, we demonstrate that the migratory mechanism is well-conserved between sturgeon and other remotely related teleosts, such as goldfish, by a single PGCs transplantation (SPT) assay. The mode of PGCs specification in sturgeon is similar to that of anurans, but the migration pattern resembles that of teleosts. PMID:24505272

Mobility among youth in Rakai, Uganda: Trends, characteristics, and associations with behavioural risk factors for HIV

PubMed Central

Schuyler, Ashley C.; Edelstein, Zoe R.; Mathur, Sanyukta; Sekasanvu, Joseph; Nalugoda, Fred; Gray, Ronald; Wawer, Maria J.; Serwadda, David M.; Santelli, John S.

2015-01-01

Mobility, including migration and travel, influences risk of HIV. This study examined time trends and characteristics among mobile youth (15-24 years) in rural Uganda, and the relationship between mobility and risk factors for HIV. We used data from an annual household census and population-based cohort study in the Rakai district, Uganda. Data on in-migration and out-migration were collected among youth (15-24 years) from 43 communities from 1999-2011 (N=112,117 observations) and travel among youth residents from 2003-2008 (N=18,318 observations). Migration and travel were more common among young women than young men. One in five youth reported out-migration. Over time, out-migration increased among youth and in-migration remained largely stable. Primary reasons for migration included work, living with friends or family, and marriage. Recent travel within Uganda was common and increased slightly over time in teen women (15-19 years old), and young adult men and women (20-24 years old). Mobile youth were more likely to report HIV risk behaviours including: alcohol use, sexual experience, multiple partners, and inconsistent condom use. Our findings suggest that among rural Ugandan youth, mobility is increasingly common and associated with HIV risk factors. Knowledge of patterns and characteristics of a young, high-risk mobile population has important implications for HIV interventions. PMID:26313708

Substrate engagement of integrins α5β1 and αvβ3 is necessary, but not sufficient, for high directional persistence in migration on fibronectin

PubMed Central

Missirlis, Dimitris; Haraszti, Tamás; Scheele, Catharina v. C.; Wiegand, Tina; Diaz, Carolina; Neubauer, Stefanie; Rechenmacher, Florian; Kessler, Horst; Spatz, Joachim P.

2016-01-01

The interplay between specific integrin-mediated matrix adhesion and directional persistence in cell migration is not well understood. Here, we characterized fibroblast adhesion and migration on the extracellular matrix glycoproteins fibronectin and vitronectin, focusing on the role of α5β1 and αvβ3 integrins. Fibroblasts manifested high directional persistence in migration on fibronectin-, but not vitronectin-coated substrates, in a ligand density-dependent manner. Fibronectin stimulated α5β1-dependent organization of the actin cytoskeleton into oriented, ventral stress fibers, and assembly of dynamic, polarized protrusions, characterized as regions free of stress fibers and rich in nascent adhesions at their edge. Such protrusions correlated with persistent, local leading edge advancement, but were not sufficient, nor necessary for directional migration over longer times. Selective blocking of αvβ3 or α5β1 integrins using small molecule integrin antagonists reduced directional persistence on fibronectin, indicating integrin cooperativity in maintaining directionality. On the other hand, patterned substrates, designed to selectively engage either integrin, or their combination, were not sufficient to establish directional migration. Overall, our study demonstrates adhesive coating-dependent regulation of directional persistence in fibroblast migration and challenges the generality of the previously suggested role of β1 and β3 integrins in directional migration. PMID:26987342

Satellite tracking reveals novel migratory patterns and the importance of seamounts for endangered South Pacific humpback whales

PubMed Central

Garrigue, Claire; Clapham, Phillip J.; Geyer, Ygor; Kennedy, Amy S.; Zerbini, Alexandre N.

2015-01-01

The humpback whale population of New Caledonia appears to display a novel migratory pattern characterized by multiple directions, long migratory paths and frequent pauses over seamounts and other shallow geographical features. Using satellite-monitored radio tags, we tracked 34 whales for between 5 and 110 days, travelling between 270 and 8540 km on their southward migration from a breeding ground in southern New Caledonia. Mean migration speed was 3.53±2.22 km h−1, while movements within the breeding ground averaged 2.01±1.63 km h−1. The tag data demonstrate that seamounts play an important role as offshore habitats for this species. Whales displayed an intensive use of oceanic seamounts both in the breeding season and on migration. Seamounts probably serve multiple and important roles as breeding locations, resting areas, navigational landmarks or even supplemental feeding grounds for this species, which can be viewed as a transient component of the seamount communities. Satellite telemetry suggests that seamounts represent an overlooked cryptic habitat for the species. The frequent use by humpback whales of such remote locations has important implications for conservation and management. PMID:26716006

Satellite tracking reveals novel migratory patterns and the importance of seamounts for endangered South Pacific humpback whales.

PubMed

Garrigue, Claire; Clapham, Phillip J; Geyer, Ygor; Kennedy, Amy S; Zerbini, Alexandre N

2015-11-01

The humpback whale population of New Caledonia appears to display a novel migratory pattern characterized by multiple directions, long migratory paths and frequent pauses over seamounts and other shallow geographical features. Using satellite-monitored radio tags, we tracked 34 whales for between 5 and 110 days, travelling between 270 and 8540 km on their southward migration from a breeding ground in southern New Caledonia. Mean migration speed was 3.53±2.22 km h(-1), while movements within the breeding ground averaged 2.01±1.63 km h(-1). The tag data demonstrate that seamounts play an important role as offshore habitats for this species. Whales displayed an intensive use of oceanic seamounts both in the breeding season and on migration. Seamounts probably serve multiple and important roles as breeding locations, resting areas, navigational landmarks or even supplemental feeding grounds for this species, which can be viewed as a transient component of the seamount communities. Satellite telemetry suggests that seamounts represent an overlooked cryptic habitat for the species. The frequent use by humpback whales of such remote locations has important implications for conservation and management.

Fundamentals of capillary electrochromatography: migration behavior of ionized sample components.

PubMed

Xiang, Rong; Horváth, Csaba

2002-02-15

The mechanism of separating charged species by capillary electrochromatography (CEC) was modeled with the conditions of ideal/linear chromatography by using a simple random walk. The most novel aspect of the work rests with the assumption that in sufficiently high electric field ionized sample components can also migrate in the adsorbed state on the ionized surface of the stationary phase. This feature of CEC leads to the introduction of three dimensionless parameters: alpha, reduced mobility of a sample component with the electrosmotic mobility as the reference; beta, the CEC retention factor; and gamma, the ratio of the electrophoretic migration velocity and the velocity of surface electrodiffusion. Since the interplay of retentive and electrophoretic forces determines the overall migration velocity, the separation mechanism in CEC is governed by the relative importance of the above parameters. The model predicts conditions under which the features of the CEC system engender migration behavior that manifests itself in a relatively narrow elution window and in a gradient like elution pattern in the separation of peptides and proteins by using pro forma isocratic CEC. It is believed that such elution patterns, which resemble those obtained by the use of external gradient of the eluent, are brought about by the formation of an internal gradient in the CEC system that gave rise to concomitant peak compression. The peculiarities of CEC are discussed in the three operational modalities of the technique: co-current, countercurrent, and co-counter CEC. The results suggest that CEC, which is often called "liquid chromatography on electrophoretic platform" is an analytical tool with great potential in the separation of peptides and proteins.

Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea–Baltic Sea salinity gradient

PubMed Central

Sjöqvist, C; Godhe, A; Jonsson, P R; Sundqvist, L; Kremp, A

2015-01-01

Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea–Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30 psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea–Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone. PMID:25892181

EB Ford revisited: assessing the long-term stability of wing-spot patterns and population genetic structure of the meadow brown butterfly on the Isles of Scilly

PubMed Central

Baxter, S W; Hoffman, J I; Tregenza, T; Wedell, N; Hosken, D J

2017-01-01

Understanding selection in the wild remains a major aim of evolutionary ecology and work by Ford and colleagues on the meadow brown butterfly Maniola jurtina did much to ignite this agenda. A great deal of their work was conducted during the 1950s on the Isles of Scilly. They documented island-specific wing-spot patterns that remained consistent over about a decade, but patterns on some islands changed after environmental perturbation. It was suggested that these wing-spot patterns reflected island-specific selection and that there was little migration between islands. However, genetic studies to test the underlying assumption of restricted migration are lacking and it is also unknown whether the originally described wing-spot patterns have persisted over time. We therefore collected female butterflies from five of Ford's original study locations, including three large islands (St Mary's, St Martin's and Tresco) and two small islands (Tean and St Helen's). Wing-spot patterns had not changed appreciably over time on three of the islands (two large and one small), but were significantly different on the other two. Furthermore, analysis of 176 amplified fragment length polymorphisms revealed significant genome-wide differentiation among the five islands. Our findings are consistent with Ford's conclusions that despite the close proximity of these islands, there is restricted gene flow among them. PMID:27804964

Long-term in vivo single-cell tracking reveals the switch of migration patterns in adult-born juxtaglomerular cells of the mouse olfactory bulb

PubMed Central

Liang, Yajie; Li, Kaizhen; Riecken, Kristoffer; Maslyukov, Anatoliy; Gomez-Nicola, Diego; Kovalchuk, Yury; Fehse, Boris; Garaschuk, Olga

2016-01-01

The behavior of adult-born cells can be easily monitored in cell culture or in lower model organisms, but longitudinal observation of individual mammalian adult-born cells in their native microenvironment still proves to be a challenge. Here we have established an approach named optical cell positioning system for long-term in vivo single-cell tracking, which integrates red-green-blue cell labeling with repeated angiography. By combining this approach with in vivo two-photon imaging technique, we characterized the in vivo migration patterns of adult-born neurons in the olfactory bulb. In contrast to the traditional view of mere radial migration of adult-born cells within the bulb, we found that juxtaglomerular cells switch from radial migration to long distance lateral migration upon arrival in their destination layer. This unique long-distance lateral migration has characteristic temporal (stop-and-go) and spatial (migratory, unidirectional or multidirectional) patterns, with a clear cell age-dependent decrease in the migration speed. The active migration of adult-born cells coincides with the time period of initial fate determination and is likely to impact on the integration sites of adult-born cells, their odor responsiveness, as well as their survival rate. PMID:27174051

International migration patterns of physicians to the United States: a cross-national panel analysis.

PubMed

Hussey, Peter S

2007-12-01

To analyze the dynamics of physician international migration patterns and identify the countries deviating most from expected migration rates. A negative binomial log-linear model of physician migration to the United States from every other country was constructed using a panel of country-level data for years 1994-2000. The model was used to identify factors associated with physician migration and to identify countries with higher or lower rates of physician migration than expected. Physician migration varied with a country's GDP per capita in an inverse-U pattern, with highest migration rates from middle-income countries. The absence of medical schools, immigrant networks in the United States, medical instruction in English, proximity to the United States, and the lack of political and civil liberties were also associated with higher migration rates. Countries with higher-than-predicted migration rates included Iceland, Albania, Armenia, Dominica, Lebanon, Syria, the United Arab Emirates, and Bulgaria. Countries with lower-than-predicted migration rates included Mexico, Japan, Brazil, Zimbabwe, Mauritania, Portugal, Senegal, and France. This analysis shows that many of the most powerful factors associated with physician migration are difficult or impossible for countries to change through public policy. GDP per capita and proximity to the U.S. are two of the most powerful predictors of physician migration. Networks of immigrants in the U.S. and fewer political and civil liberties also put countries at higher risk for physician emigration. Several other factors that were associated with physician migration might be more easily amenable to policy intervention. These factors include the absence of a medical school and medical instruction in English. Policies addressing these factors would involve making several difficult tradeoffs, however. Other examples of policies that are effective in minimizing physician migration might be found by examining countries with lower-than-expected migration rates.

Interkinetic nuclear migration in the mouse embryonic ureteric epithelium: Possible implication for congenital anomalies of the kidney and urinary tract.

PubMed

Motoya, Tomoyuki; Ogawa, Noriko; Nitta, Tetsuya; Rafiq, Ashiq Mahmood; Jahan, Esrat; Furuya, Motohide; Matsumoto, Akihiro; Udagawa, Jun; Otani, Hiroki

2016-05-01

Interkinetic nuclear migration (INM) is a phenomenon in which progenitor cell nuclei migrate along the apico-basal axis of the pseudostratified epithelium, which is characterized by the presence of apical primary cilia, in synchrony with the cell cycle in a manner of apical mitosis. INM is suggested to regulate not only stem/progenitor cell proliferation/differentiation but also organ size and shape. INM has been reported in epithelia of both ectoderm and endoderm origin. We examined whether INM exists in the mesoderm-derived ureteric epithelium. At embryonic day (E) 11.5, E12.5 and E13.5, C57BL/6J mouse dams were injected with 5-bromo-2'-deoxyuridine (BrdU) and embryos were killed 1, 2, 4, 6, 8, 10 and 12 h later. We immunostained transverse sections of the ureter for BrdU, and measured the position of BrdU (+) nuclei in the ureteric epithelia along the apico-basal axis at each time point. We analyzed the distribution patterns of BrdU (+) nuclei in histograms using the multidimensional scaling. Changes in the nucleus distribution patterns suggested nucleus movement characteristic of INM in the ureteric epithelia, and the mode of INM varied throughout the ureter development. While apical primary cilia are related with INM by providing a centrosome for the apical mitosis, congenital anomalies of the kidney and urinary tract (CAKUT) include syndromes linked to primary ciliary dysfunction affecting epithelial tubular organs such as kidney, ureter, and brain. The present study showed that INM exists in the ureteric epithelium and suggests that INM may be related with the CAKUT etiology via primary ciliary protein function. © 2015 Japanese Teratology Society.

Conserved pattern of tangential neuronal migration during forebrain development.

PubMed

Métin, Christine; Alvarez, Chantal; Moudoux, David; Vitalis, Tania; Pieau, Claude; Molnár, Zoltán

2007-08-01

Origin, timing and direction of neuronal migration during brain development determine the distinct organization of adult structures. Changes in these processes might have driven the evolution of the forebrain in vertebrates. GABAergic neurons originate from the ganglionic eminence in mammals and migrate tangentially to the cortex. We are interested in differences and similarities in tangential migration patterns across corresponding telencephalic territories in mammals and reptiles. Using morphological criteria and expression patterns of Darpp-32, Tbr1, Nkx2.1 and Pax6 genes, we show in slice cultures of turtle embryos that early cohorts of tangentially migrating cells are released from the medial ganglionic eminence between stages 14 and 18. Additional populations migrate tangentially from the dorsal subpallium. Large cohorts of tangentially migrating neurons originate ventral to the dorsal ventricular ridge at stage 14 and from the lateral ganglionic eminence from stage 15. Release of GABAergic cells from these regions was investigated further in explant cultures. Tangential migration in turtle proceeds in a fashion similar to mammals. In chimeric slice culture and in ovo graft experiments, the tangentially migrating cells behaved according to the host environment - turtle cells responded to the available cues in mouse slices and mouse cells assumed characteristic migratory routes in turtle brains, indicating highly conserved embryonic signals between these distant species. Our study contributes to the evaluation of theories on the origin of the dorsal cortex and indicates that tangential migration is universal in mammals and sauropsids.

Proximate cues for a short-distance migratory species: An application of survival analysis

USGS Publications Warehouse

Meunier, J.; Song, R.; Lutz, R.S.; Andersen, D.E.; Doherty, K.E.; Bruggink, J.G.; Oppelt, E.

2008-01-01

Investigation of bird migration has often highlighted the importance of external factors in determining timing of migration However, little distinction has been made between short- and long-distance migrants and between local and flight birds (passage migrants) in describing migration chronology. In addition, measures of food abundance as a proximate factor influencing timing of migration are lacking in studies of migration chronology. To address the relationship between environmental variables and timing of migration we quantified the relative importance of proximate external factors on migration chronology of local American woodcock (Scolopax minor), a short distance migrant, using event-time analysis methods (survival analysis). We captured 1,094 woodcock local to our study sites in Michigan, Minnesota and Wisconsin (USA) during autumn 2002-2004 and documented 786 departure dates for these birds. Photoperiod appeared to provide an initial proximate cue for timing of departure. Moon phase was important in modifying timing of departure, which may serve as a navigational aid in piloting and possibly orientation. Local synoptic weather variables also contributed to timing of departure by changing the rate of departure from our study sites. We found no evidence that food availability influenced timing of woodcock departure. Our results suggest that woodcock use a conservative photoperiod-controlled strategy with proximate modifiers for timing of migration rather than relying on abundance of their primary food, earthworms. Managing harvest pressure on local birds by adjusting season lengths may be an effective management tool with consistent migration patterns from year to year based on photoperiod.

Genetic diversity and connectivity of the megamouth shark (Megachasma pelagios)

PubMed Central

Joung, Shoou Jeng; Yu, Chi-Ju; Hsu, Hua-Hsun; Tsai, Wen-Pei; Liu, Kwang Ming

2018-01-01

The megamouth shark (Megachasma pelagios) was described as a new species in 1983. Since then, only ca. 100 individuals have been observed or caught. Its horizontal migration, dispersal, and connectivity patterns are still unknown due to its rarity. Two genetic markers were used in this study to reveal its genetic diversity and connectivity pattern. This approach provides a proxy to indirectly measure gene flow between populations. Tissues from 27 megamouth sharks caught by drift nets off the Hualien coast (eastern Taiwan) were collected from 2013 to 2015. With two additional tissue samples from megamouths caught in Baja California, Mexico, and sequences obtained from GenBank, we were able to perform the first population genetic analyses of the megamouth shark. The mtDNA cox1 gene and a microsatellite (Loc 6) were sequenced and analyzed. Our results showed that there is no genetic structure in the megamouth shark, suggesting a possible panmictic population. Based on occurrence data, we also suggest that the Kuroshio region, including the Philippines, Taiwan, and Japan, may act as a passageway for megamouth sharks to reach their feeding grounds from April to August. Our results provide insights into the dispersal and connectivity of megamouth sharks. Future studies should focus on collecting more samples and conducting satellite tagging to better understand the global migration and connectivity pattern of the megamouth shark. PMID:29527411

Remotely sensed wind speed predicts soaring behaviour in a wide-ranging pelagic seabird.

PubMed

Gibb, Rory; Shoji, Akiko; Fayet, Annette L; Perrins, Chris M; Guilford, Tim; Freeman, Robin

2017-07-01

Global wind patterns affect flight strategies in many birds, including pelagic seabirds, many of which use wind-powered soaring to reduce energy costs during at-sea foraging trips and migration. Such long-distance movement patterns are underpinned by local interactions between wind conditions and flight behaviour, but these fine-scale relationships are far less well understood. Here we show that remotely sensed ocean wind speed and direction are highly significant predictors of soaring behaviour in a migratory pelagic seabird, the Manx shearwater ( Puffinus puffinus ). We used high-frequency GPS tracking data (10 Hz) and statistical behaviour state classification to identify two energetic modes in at-sea flight, corresponding to flap-like and soar-like flight. We show that soaring is significantly more likely to occur in tailwinds and crosswinds above a wind speed threshold of around 8 m s -1 , suggesting that these conditions enable birds to reduce metabolic costs by preferentially soaring over flapping. Our results suggest a behavioural mechanism by which wind conditions may shape foraging and migration ecology in pelagic seabirds, and thus indicate that shifts in wind patterns driven by climate change could impact this and other species. They also emphasize the emerging potential of high-frequency GPS biologgers to provide detailed quantitative insights into fine-scale flight behaviour in free-living animals. © 2017 The Author(s).

Biogeographical profiles of shorebird migration in midcontinental North America

USGS Publications Warehouse

Skagen, Susan K.; Sharpe, Peter B.; Waltermire, Robert G.; Dillon, M. Beth

1999-01-01

The biogeographic information described here will help identify the uniqueness of different regions of the plains to migrating shorebirds. Although shorebirds migrating along Atlantic and Pacific coastal areas are capable of long jumps between refueling stops, there is evidence that some species move short rather than long distances between refueling sites. Maps of distribution patterns and chronology accounts can lend insight towards understanding migration strategies of the different shorebird species.This report focuses on the distribution patterns of enroute migrants that refuel in interior wetlands during migration. We provide information on the spatial and temporal occurrence and habitat requirements for individual species and groups of species with the intent that this information be used in guiding management efforts.

Stripes and belly-spots – a review of pigment cell morphogenesis in vertebrates

PubMed Central

Kelsh, Robert N.; Harris, Melissa L.; Colanesi, Sarah; Erickson, Carol A.

2009-01-01

Pigment patterns in the integument have long-attracted attention from both scientists and non-scientists alike since their natural attractiveness combines with their excellence as models for the general problem of pattern formation. Pigment cells are formed from the neural crest and must migrate to reach their final locations. In this review, we focus on our current understanding of mechanisms underlying the control of pigment cell migration and patterning in diverse vertebrates. The model systems discussed here –chick, mouse, and zebrafish – each provide unique insights into the major morphogenetic events driving pigment pattern formation. In birds and mammals, melanoblasts must be specified before they can migrate on the dorsolateral pathway. Transmembrane receptors involved in guiding them onto this route include EphB2 and Ednrb2 in chick, and Kit in mouse. Terminal migration depends, in part, upon extracellular matrix reorganization by ADAMTS20. Invasion of the ectoderm, especially into the feather germ and hair follicles, requires specific signals that are beginning to be characterized. We summarize our current understanding of the mechanisms regulating melanoblast number and organization in the epidermis. We note the apparent differences in pigment pattern formation in poikilothermic vertebrates when compared with birds and mammals. With more pigment cell types, migration pathways are more complex and largely unexplored; nevertheless, a role for Kit signaling in melanophore migration is clear and indicates that at least some patterning mechanisms may be highly conserved. We summarize the multiple factors thought to contribute to zebrafish embryonic pigment pattern formation, highlighting a recent study identifying Sdf1a as one factor crucial for regulation of melanophore positioning. Finally, we discuss the mechanisms generating a second, metamorphic pigment pattern in adult fish, emphasizing recent studies strengthening the evidence that undifferentiated progenitor cells play a major role in generating adult pigment cells. PMID:18977309

Rural-Urban Migration in Colombia.

ERIC Educational Resources Information Center

Schultz, T. Paul

The rural-urban migration pattern in Colombia during the last 25 years has resulted in a population increase in urban areas from 30 to 52 percent of the total population. This study explores the causes of internal migration. Migration rates are estimated for various groups in the population to clarify who migrates and to where. A model of…

Migration, Acculturation and Environment: Determinants of Obesity among Iranian Migrants in Australia

PubMed Central

Delavari, Maryam; Sønderlund, Anders Larrabee; Mellor, David; Mohebbi, Mohammadreza; Swinburn, Boyd

2015-01-01

While migration from low- to high-income countries is typically associated with weight gain, the obesity risks of migration from middle-income countries are less certain. In addition to changes in behaviours and cultural orientation upon migration, analyses of changes in environments are needed to explain post-migration risks for obesity. The present study examines the interaction between obesity-related environmental factors and the pattern of migrant acculturation in a sample of 152 Iranian immigrants in Victoria, Australia. Weight measurements, demographics, physical activity levels and diet habits were also surveyed. The pattern of acculturation (relative integration, assimilation, separation or marginalization) was not related to body mass index, diet, or physical activity behaviours. Three relevant aspects of participants’ perception of the Australian environment (physically active environments, social pressure to be fit, unhealthy food environments) varied considerably by demographic characteristics, but only one (physically active environments) was related to a pattern of acculturation (assimilation). Overall, this research highlighted a number of key relationships between acculturation and obesity-related environments and behaviours for our study sample. Theoretical models on migration, culture and obesity need to include environmental factors. PMID:25648171

Geovisualization of Local and Regional Migration Using Web-mined Demographics

NASA Astrophysics Data System (ADS)

Schuermann, R. T.; Chow, T. E.

2014-11-01

The intent of this research was to augment and facilitate analyses, which gauges the feasibility of web-mined demographics to study spatio-temporal dynamics of migration. As a case study, we explored the spatio-temporal dynamics of Vietnamese Americans (VA) in Texas through geovisualization of mined demographic microdata from the World Wide Web. Based on string matching across all demographic attributes, including full name, address, date of birth, age and phone number, multiple records of the same entity (i.e. person) over time were resolved and reconciled into a database. Migration trajectories were geovisualized through animated sprites by connecting the different addresses associated with the same person and segmenting the trajectory into small fragments. Intra-metropolitan migration patterns appeared at the local scale within many metropolitan areas. At the scale of metropolitan area, varying degrees of immigration and emigration manifest different types of migration clusters. This paper presents a methodology incorporating GIS methods and cartographic design to produce geovisualization animation, enabling the cognitive identification of migration patterns at multiple scales. Identification of spatio-temporal patterns often stimulates further research to better understand the phenomenon and enhance subsequent modeling.

Climate Shocks and Migration: An Agent-Based Modeling Approach.

PubMed

Entwisle, Barbara; Williams, Nathalie E; Verdery, Ashton M; Rindfuss, Ronald R; Walsh, Stephen J; Malanson, George P; Mucha, Peter J; Frizzelle, Brian G; McDaniel, Philip M; Yao, Xiaozheng; Heumann, Benjamin W; Prasartkul, Pramote; Sawangdee, Yothin; Jampaklay, Aree

2016-09-01

This is a study of migration responses to climate shocks. We construct an agent-based model that incorporates dynamic linkages between demographic behaviors, such as migration, marriage, and births, and agriculture and land use, which depend on rainfall patterns. The rules and parameterization of our model are empirically derived from qualitative and quantitative analyses of a well-studied demographic field site, Nang Rong district, Northeast Thailand. With this model, we simulate patterns of migration under four weather regimes in a rice economy: 1) a reference, 'normal' scenario; 2) seven years of unusually wet weather; 3) seven years of unusually dry weather; and 4) seven years of extremely variable weather. Results show relatively small impacts on migration. Experiments with the model show that existing high migration rates and strong selection factors, which are unaffected by climate change, are likely responsible for the weak migration response.

Climate Shocks and Migration: An Agent-Based Modeling Approach

PubMed Central

Entwisle, Barbara; Williams, Nathalie E.; Verdery, Ashton M.; Rindfuss, Ronald R.; Walsh, Stephen J.; Malanson, George P.; Mucha, Peter J.; Frizzelle, Brian G.; McDaniel, Philip M.; Yao, Xiaozheng; Heumann, Benjamin W.; Prasartkul, Pramote; Sawangdee, Yothin; Jampaklay, Aree

2016-01-01

This is a study of migration responses to climate shocks. We construct an agent-based model that incorporates dynamic linkages between demographic behaviors, such as migration, marriage, and births, and agriculture and land use, which depend on rainfall patterns. The rules and parameterization of our model are empirically derived from qualitative and quantitative analyses of a well-studied demographic field site, Nang Rong district, Northeast Thailand. With this model, we simulate patterns of migration under four weather regimes in a rice economy: 1) a reference, ‘normal’ scenario; 2) seven years of unusually wet weather; 3) seven years of unusually dry weather; and 4) seven years of extremely variable weather. Results show relatively small impacts on migration. Experiments with the model show that existing high migration rates and strong selection factors, which are unaffected by climate change, are likely responsible for the weak migration response. PMID:27594725

Potential Hydrogeomechanical Impacts of Geological CO2 Sequestration

NASA Astrophysics Data System (ADS)

McPherson, B. J.; Haerer, D.; Han, W.; Heath, J.; Morse, J.

2006-12-01

Long-term sequestration of anthropogenic "greenhouse gases" such as CO2 is a proposed approach to managing climate change. Deep brine reservoirs in sedimentary basins are possible sites for sequestration, given their ubiquitous nature. We used a mathematical sedimentary basin model, including coupling of multiphase CO2-groundwater flow and rock deformation, to evaluate residence times in possible brine reservoir storage sites, migration patterns and rates away from such sites, and effects of CO2 injection on fluid pressures and rock strain. Study areas include the Uinta and Paradox basins of Utah, the San Juan basin of New Mexico, and the Permian basin of west Texas. Regional-scale hydrologic and mechanical properties, including the presence of fracture zones, were calibrated using laboratory and field data. Our initial results suggest that, in general, long-term (~100 years or more) sequestration in deep brine reservoirs is possible, if guided by robust structural and hydrologic data. However, specific processes must be addressed to characterize and minimize risks. In addition to CO2 migration from target sequestration reservoirs into other reservoirs or to the land surface, another environmental issue is displacement of brines into freshwater aquifers. We evaluated the potential for such unintended aquifer contamination by displacement of brines out of adjacent sealing layers such as marine shales. Results suggest that sustained injection of CO2 may incur significant brine displacement out of adjacent sealing layers, depending on the injection history, initial brine composition, and hydrologic properties of both reservoirs and seals. Model simulations also suggest that as injection-induced overpressures migrate, effective stresses may follow this migration under some conditions, as will associated rock strain. Such "strain migration" may lead to induced or reactivated fractures or faults, but can be controlled through reservoir engineering.

[The rural-urban nature and geographical nature of patterns of internal migration].

PubMed

Raczynski, D

1981-07-01

The rural-urban nature and geographical patterns of internal migration in Chile are studied. The magnitude, nature, and relative importance of rural-urban, interurban, inter-rural, and urban-rural movements in the country are examined, with a focus on the impact of internal migration on urbanization and on the demographic growth of cities and rural areas. Rural and urban differentials in propensity to migrate and in the capacity to attract and retain population are investigated using 1970 census data on migratory flows to and from the Santiago metropolitan area and those directed to other parts of the country.

Migration and the epidemiological transition: insights from the Agincourt sub-district of northeast South Africa

PubMed Central

Collinson, Mark A.; White, Michael J.; Bocquier, Philippe; McGarvey, Stephen T.; Afolabi, Sulaimon A.; Clark, Samuel J.; Kahn, Kathleen; Tollman, Stephen M.

2014-01-01

Background Migration and urbanization are central to sustainable development and health, but data on temporal trends in defined populations are scarce. Healthy men and women migrate because opportunities for employment and betterment are not equally distributed geographically. The disruption can result in unhealthy exposures and environments and income returns for the origin household. Objectives The objectives of the paper are to describe the patterns, levels, and trends of temporary migration in rural northeast South Africa; the mortality trends by cause category over the period 2000–2011; and the associations between temporary migration and mortality by broad cause of death categories. Method Longitudinal, Agincourt Health and Demographic Surveillance System data are used in a continuous, survival time, competing-risk model. Findings In rural, northeast South Africa, temporary migration, which involves migrants relocating mainly for work purposes and remaining linked to the rural household, is more important than age and sex in explaining variations in mortality, whatever the cause. In this setting, the changing relationship between temporary migration and communicable disease mortality is primarily affected by reduced exposure of the migrant to unhealthy conditions. The study suggests that the changing relationship between temporary migration and non-communicable disease mortality is mainly affected by increased livelihood benefits of longer duration migration. Conclusion Since temporary migration is not associated with communicable diseases only, public health policies should account for population mobility whatever the targeted health risk. There is a need to strengthen the rural health care system, because migrants tend to return to the rural households when they need health care. PMID:24848656

Migration and the epidemiological transition: insights from the Agincourt sub-district of northeast South Africa.

PubMed

Collinson, Mark A; White, Michael J; Bocquier, Philippe; McGarvey, Stephen T; Afolabi, Sulaimon A; Clark, Samuel J; Kahn, Kathleen; Tollman, Stephen M

2014-01-01

Migration and urbanization are central to sustainable development and health, but data on temporal trends in defined populations are scarce. Healthy men and women migrate because opportunities for employment and betterment are not equally distributed geographically. The disruption can result in unhealthy exposures and environments and income returns for the origin household. The objectives of the paper are to describe the patterns, levels, and trends of temporary migration in rural northeast South Africa; the mortality trends by cause category over the period 2000-2011; and the associations between temporary migration and mortality by broad cause of death categories. Longitudinal, Agincourt Health and Demographic Surveillance System data are used in a continuous, survival time, competing-risk model. In rural, northeast South Africa, temporary migration, which involves migrants relocating mainly for work purposes and remaining linked to the rural household, is more important than age and sex in explaining variations in mortality, whatever the cause. In this setting, the changing relationship between temporary migration and communicable disease mortality is primarily affected by reduced exposure of the migrant to unhealthy conditions. The study suggests that the changing relationship between temporary migration and non-communicable disease mortality is mainly affected by increased livelihood benefits of longer duration migration. Since temporary migration is not associated with communicable diseases only, public health policies should account for population mobility whatever the targeted health risk. There is a need to strengthen the rural health care system, because migrants tend to return to the rural households when they need health care.

Timing of seasonal migration in mule deer: effects of climate, plant phenology, and life-history characteristics

USGS Publications Warehouse

Monteith, Kevin L.; Bleich, Vernon C.; Stephenson, Thomas R.; Pierce, Beck M.; Conner, Mary M.; Klaver, Robert W.; Bowyer, R. Terry

2011-01-01

Phenological events of plants and animals are sensitive to climatic processes. Migration is a life-history event exhibited by most large herbivores living in seasonal environments, and is thought to occur in response to dynamics of forage and weather. Decisions regarding when to migrate, however, may be affected by differences in life-history characteristics of individuals. Long-term and intensive study of a population of mule deer (Odocoileus hemionus) in the Sierra Nevada, California, USA, allowed us to document patterns of migration during 11 years that encompassed a wide array of environmental conditions. We used two new techniques to properly account for interval-censored data and disentangle effects of broad-scale climate, local weather patterns, and plant phenology on seasonal patterns of migration, while incorporating effects of individual life-history characteristics. Timing of autumn migration varied substantially among individual deer, but was associated with the severity of winter weather, and in particular, snow depth and cold temperatures. Migratory responses to winter weather, however, were affected by age, nutritional condition, and summer residency of individual females. Old females and those in good nutritional condition risked encountering severe weather by delaying autumn migration, and were thus risk-prone with respect to the potential loss of foraging opportunities in deep snow compared with young females and those in poor nutritional condition. Females that summered on the west side of the crest of the Sierra Nevada delayed autumn migration relative to east-side females, which supports the influence of the local environment on timing of migration. In contrast, timing of spring migration was unrelated to individual life-history characteristics, was nearly twice as synchronous as autumn migration, differed among years, was related to the southern oscillation index, and was influenced by absolute snow depth and advancing phenology of plants. Plasticity in timing of migration in response to climatic conditions and plant phenology may be an adaptive behavioral strategy, which should reduce the detrimental effects of trophic mismatches between resources and other life-history events of large herbivores. Failure to consider effects of nutrition and other life-history traits may cloud interpretation of phenological patterns of mammals and conceal relationships associated with climate change.

SDN-1/syndecan regulates growth factor signaling in distal tip cell migrations in C. elegans.

PubMed

Schwabiuk, Megan; Coudiere, Ludivine; Merz, David C

2009-10-01

Mutations in the sdn-1/syndecan gene act as genetic enhancers of the ventral-to-dorsal distal tip cell (DTC) migration defects caused by a weak allele of the netrin receptor gene unc-5. The sdn-1(ev697) allele was identified in a genetic screen for enhancers of unc-5 DTC migration defects, and carried a nonsense mutation predicted to truncate the SDN-1 protein prior to the transmembrane domain. The enhancement of unc-5 caused by an sdn-1 mutation was rescued by expression of wild-type sdn-1 in the hypodermis or nervous system rather than the DTCs, indicating a cell non-autonomous function of sdn-1. The enhancement was also partially reversed by mutations in the egl-17/FGF or egl-20/Wnt genes, suggesting that sdn-1 affects UNC-5 function through a mis-regulation of signaling in growth factor pathways. egl-20 reporter constructs exhibited increased and mis-localized EGL-20 distribution in sdn-1 mutants compared to wild-type animals. Finally, using loss of function mutations, we show that egl-17/Fgf and egl-20/Wnt are partially redundant in regulating the migration pattern of the posterior DTC, as double mutants exhibit significant frequencies of defects in migration phases along both the anteroposterior and dorsoventral axes. Together these results suggest that SDN-1 affects UNC-5 function by regulating the proper extracellular distribution of growth factors.

Soaring Migratory Birds Avoid Wind Farm in the Isthmus of Tehuantepec, Southern Mexico

PubMed Central

Villegas-Patraca, Rafael; Cabrera-Cruz, Sergio A.; Herrera-Alsina, Leonel

2014-01-01

The number of wind farms operating in the Isthmus of Tehuantepec, southern Mexico, has rapidly increased in recent years; yet, this region serves as a major migration route for various soaring birds, including Turkey Vultures (Cathartes aura) and Swainson's Hawks (Buteo swainsoni). We analyzed the flight trajectories of soaring migrant birds passing the La Venta II wind farm during the two migratory seasons of 2011, to determine whether an avoidance pattern existed or not. We recorded three polar coordinates for the flight path of migrating soaring birds that were detected using marine radar, plotted the flight trajectories and estimated the number of trajectories that intersected the polygon defined by the wind turbines of La Venta II. Finally, we estimated the actual number of intersections per kilometer and compared this value with the null distributions obtained by running 10,000 simulations of our datasets. The observed number of intersections per kilometer fell within or beyond the lower end of the null distributions in the five models proposed for the fall season and in three of the four models proposed for the spring season. Flight trajectories had a non-random distribution around La Venta II, suggesting a strong avoidance pattern during fall and a possible avoidance pattern during spring. We suggest that a nearby ridgeline plays an important role in this pattern, an issue that may be incorporated into strategies to minimize the potential negative impacts of future wind farms on soaring birds. Studies evaluating these issues in the Isthmus of Tehuantepec have not been previously published; hence this work contributes important baseline information about the movement patterns of soaring birds and its relationship to wind farms in the region. PMID:24647442

Soaring migratory birds avoid wind farm in the Isthmus of Tehuantepec, southern Mexico.

PubMed

Villegas-Patraca, Rafael; Cabrera-Cruz, Sergio A; Herrera-Alsina, Leonel

2014-01-01

The number of wind farms operating in the Isthmus of Tehuantepec, southern Mexico, has rapidly increased in recent years; yet, this region serves as a major migration route for various soaring birds, including Turkey Vultures (Cathartes aura) and Swainson's Hawks (Buteo swainsoni). We analyzed the flight trajectories of soaring migrant birds passing the La Venta II wind farm during the two migratory seasons of 2011, to determine whether an avoidance pattern existed or not. We recorded three polar coordinates for the flight path of migrating soaring birds that were detected using marine radar, plotted the flight trajectories and estimated the number of trajectories that intersected the polygon defined by the wind turbines of La Venta II. Finally, we estimated the actual number of intersections per kilometer and compared this value with the null distributions obtained by running 10,000 simulations of our datasets. The observed number of intersections per kilometer fell within or beyond the lower end of the null distributions in the five models proposed for the fall season and in three of the four models proposed for the spring season. Flight trajectories had a non-random distribution around La Venta II, suggesting a strong avoidance pattern during fall and a possible avoidance pattern during spring. We suggest that a nearby ridgeline plays an important role in this pattern, an issue that may be incorporated into strategies to minimize the potential negative impacts of future wind farms on soaring birds. Studies evaluating these issues in the Isthmus of Tehuantepec have not been previously published; hence this work contributes important baseline information about the movement patterns of soaring birds and its relationship to wind farms in the region.

Agricultural activity shapes the communication and migration patterns in Senegal.

PubMed

Martin-Gutierrez, S; Borondo, J; Morales, A J; Losada, J C; Tarquis, A M; Benito, R M

2016-06-01

The communication and migration patterns of a country are shaped by its socioeconomic processes. The economy of Senegal is predominantly rural, as agriculture employs over 70% of the labor force. In this paper, we use mobile phone records to explore the impact of agricultural activity on the communication and mobility patterns of the inhabitants of Senegal. We find two peaks of phone calls activity emerging during the growing season. Moreover, during the harvest period, we detect an increase in the migration flows throughout the country. However, religious holidays also shape the mobility patterns of the Senegalese people. Hence, in the light of our results, agricultural activity and religious holidays are the primary drivers of mobility inside the country.

Agricultural activity shapes the communication and migration patterns in Senegal

NASA Astrophysics Data System (ADS)

Martin-Gutierrez, S.; Borondo, J.; Morales, A. J.; Losada, J. C.; Tarquis, A. M.; Benito, R. M.

2016-06-01

The communication and migration patterns of a country are shaped by its socioeconomic processes. The economy of Senegal is predominantly rural, as agriculture employs over 70% of the labor force. In this paper, we use mobile phone records to explore the impact of agricultural activity on the communication and mobility patterns of the inhabitants of Senegal. We find two peaks of phone calls activity emerging during the growing season. Moreover, during the harvest period, we detect an increase in the migration flows throughout the country. However, religious holidays also shape the mobility patterns of the Senegalese people. Hence, in the light of our results, agricultural activity and religious holidays are the primary drivers of mobility inside the country.

Gendered Patterns of Migration in Rural South Africa

PubMed Central

Camlin, Carol S.; Snow, Rachel C.; Hosegood, Victoria

2013-01-01

Gender is increasingly recognized as fundamental to understanding migration processes, causes and consequences. In South Africa, it is intrinsic to the social transformations fueling high levels of internal migration and complex forms of mobility. While female migration in Africa has often been characterized as less prevalent than male migration, and primarily related to marriage, in South Africa a feminization of internal migration is underway, fueled by women’s increasing labor market participation. In this paper, we report sex differences in patterns, trends and determinants of internal migration based on data collected in a demographic surveillance system between 2001 and 2006 in rural KwaZulu-Natal. We show that women were somewhat more likely than men to undertake any migration, but sex differences in migration trends differed by migration flow, with women more likely to migrate into the area than men, and men more likely to out-migrate. Out-migration was suppressed by marriage particularly for women, but most women were not married; both men’s and women’s out-migrations were undertaken mainly for purposes of employment. Over half of female out-migrations (versus 35% of male out-migrations) were to nearby rural areas. The findings highlight the high mobility of this population and the extent to which gender is intimately related to the processes determining migration. We consider the implications of these findings for the measurement of migration and mobility, in particular for health and social policy and research among highly mobile populations in southern Africa. PMID:25332690

Experience drives innovation of new migration patterns of whooping cranes in response to global change.

PubMed

Teitelbaum, Claire S; Converse, Sarah J; Fagan, William F; Böhning-Gaese, Katrin; O'Hara, Robert B; Lacy, Anne E; Mueller, Thomas

2016-09-06

Anthropogenic changes in climate and land use are driving changes in migration patterns of birds worldwide. Spatial changes in migration have been related to long-term temperature trends, but the intrinsic mechanisms by which migratory species adapt to environmental change remain largely unexplored. We show that, for a long-lived social species, older birds with more experience are critical for innovating new migration behaviours. Groups containing older, more experienced individuals establish new overwintering sites closer to the breeding grounds, leading to a rapid population-level shift in migration patterns. Furthermore, these new overwintering sites are in areas where changes in climate have increased temperatures and where food availability from agriculture is high, creating favourable conditions for overwintering. Our results reveal that the age structure of populations is critical for the behavioural mechanisms that allow species to adapt to global change, particularly for long-lived animals, where changes in behaviour can occur faster than evolution.

Experience drives innovation of new migration patterns of whooping cranes in response to global change

PubMed Central

Teitelbaum, Claire S.; Converse, Sarah J.; Fagan, William F.; Böhning-Gaese, Katrin; O'Hara, Robert B.; Lacy, Anne E.; Mueller, Thomas

2016-01-01

Anthropogenic changes in climate and land use are driving changes in migration patterns of birds worldwide. Spatial changes in migration have been related to long-term temperature trends, but the intrinsic mechanisms by which migratory species adapt to environmental change remain largely unexplored. We show that, for a long-lived social species, older birds with more experience are critical for innovating new migration behaviours. Groups containing older, more experienced individuals establish new overwintering sites closer to the breeding grounds, leading to a rapid population-level shift in migration patterns. Furthermore, these new overwintering sites are in areas where changes in climate have increased temperatures and where food availability from agriculture is high, creating favourable conditions for overwintering. Our results reveal that the age structure of populations is critical for the behavioural mechanisms that allow species to adapt to global change, particularly for long-lived animals, where changes in behaviour can occur faster than evolution. PMID:27597446

Experience drives innovation of new migration patterns of whooping cranes in response to global change

USGS Publications Warehouse

Teitelbaum, Claire S.; Converse, Sarah J.; Fagan, William F.; Böhning-Gaese, Katrin; O'Hara, Robert B.; Lacy, Anne E; Mueller, Thomas

2016-01-01

Anthropogenic changes in climate and land use are driving changes in migration patterns of birds worldwide. Spatial changes in migration have been related to long-term temperature trends, but the intrinsic mechanisms by which migratory species adapt to environmental change remain largely unexplored. We show that, for a long-lived social species, older birds with more experience are critical for innovating new migration behaviours. Groups containing older, more experienced individuals establish new overwintering sites closer to the breeding grounds, leading to a rapid population-level shift in migration patterns. Furthermore, these new overwintering sites are in areas where changes in climate have increased temperatures and where food availability from agriculture is high, creating favourable conditions for overwintering. Our results reveal that the age structure of populations is critical for the behavioural mechanisms that allow species to adapt to global change, particularly for long-lived animals, where changes in behaviour can occur faster than evolution.

Coalbed methane accumulation and dissipation patterns: A Case study of the Junggar Basin, NW China

NASA Astrophysics Data System (ADS)

Li, Xin; Fu, Xuehai; Yang, Xuesong; Ge, Yanyan; Quan, Fangkai

2018-07-01

The Junggar Basin is a potential replacement area of coalbed methane (CBM) development in China. To improve the efficiency of CBM exploration, we investigated CBM accumulation and dissipation patterns of coal profiles located in the northwestern, southern, eastern, and central Junggar Basin based on the following criteria: burial depth, hydrogeological zone, CBM origin, CBM phase, and CBM migration type. We identified four types of CBM accumulation patterns: (1) a self-sourcing CBM pattern containing adsorbed gas of biogenic origin from shallow-depth coal within a weak runoff zone; (2) an endogenic migration pattern containing adsorbed gas of thermogenic origin from the medium and deep coals within a stagnant zone; (3) an exogenic migration pattern containing adsorbed gas of thermogenic origin from deep coal within a stagnant zone; and (4) an exogenic migration pattern containing adsorbed and free gas of thermogenic origin from ultra-deep coal within a stagnant zone. We also identified two types of CBM dissipation patterns: (1) shallow-depth coal within a runoff zone with mixed origin CBM; and (2) shallow and medium-deep coal seams with mixed origin CBM. CBM migration in low-rank coals was more substantial than that adsorbed in high-rank coal. CBM in shallow coal could easily escape, in the absence of closed structures or hydrogeological seals. CBM reservoirs occurred in deep coal where oversaturated gas may accumulate. Future exploration should focus on gas-water sealing structures in shallow coalbeds. CBM that occurred in adsorbed and free phases and other unconventional natural gas dominated by free gas in the coal stratum should be co-explored and co-developed.

Influence of seasonal migration on geographic distribution of mitochondrial DNA haplotypes in humpback whales.

PubMed

Baker, C S; Palumbi, S R; Lambertsen, R H; Weinrich, M T; Calambokidis, J; O'Brien, S J

1990-03-15

Humpback whales (Megaptera novaeangliae) migrate nearly 10,000 km each year between summer feeding grounds in temperate or near-polar waters and winter breeding grounds in shallow tropical waters. Observations of marked individuals suggest that major oceanic populations of humpback whales are divided into a number of distinct seasonal subpopulations which are not separated by obvious geographic barriers. To test whether these observed patterns of distribution and migration are reflected in the genetic structure of populations, we looked for variation in the mitochondrial DNA of 84 individual humpback whales on different feeding and wintering grounds of the North Pacific and western North Atlantic oceans. On the basis of restriction-fragment analysis, we now report a marked segregation of mitochondrial DNA haplotypes among subpopulations as well as between the two oceans. We interpret this segregation to be the consequence of maternally directed fidelity to migratory destinations.

Genomic signals of migration and continuity in Britain before the Anglo-Saxons.

PubMed

Martiniano, Rui; Caffell, Anwen; Holst, Malin; Hunter-Mann, Kurt; Montgomery, Janet; Müldner, Gundula; McLaughlin, Russell L; Teasdale, Matthew D; van Rheenen, Wouter; Veldink, Jan H; van den Berg, Leonard H; Hardiman, Orla; Carroll, Maureen; Roskams, Steve; Oxley, John; Morgan, Colleen; Thomas, Mark G; Barnes, Ian; McDonnell, Christine; Collins, Matthew J; Bradley, Daniel G

2016-01-19

The purported migrations that have formed the peoples of Britain have been the focus of generations of scholarly controversy. However, this has not benefited from direct analyses of ancient genomes. Here we report nine ancient genomes (∼ 1 ×) of individuals from northern Britain: seven from a Roman era York cemetery, bookended by earlier Iron-Age and later Anglo-Saxon burials. Six of the Roman genomes show affinity with modern British Celtic populations, particularly Welsh, but significantly diverge from populations from Yorkshire and other eastern English samples. They also show similarity with the earlier Iron-Age genome, suggesting population continuity, but differ from the later Anglo-Saxon genome. This pattern concords with profound impact of migrations in the Anglo-Saxon period. Strikingly, one Roman skeleton shows a clear signal of exogenous origin, with affinities pointing towards the Middle East, confirming the cosmopolitan character of the Empire, even at its northernmost fringes.

Genomic signals of migration and continuity in Britain before the Anglo-Saxons

PubMed Central

Martiniano, Rui; Caffell, Anwen; Holst, Malin; Hunter-Mann, Kurt; Montgomery, Janet; Müldner, Gundula; McLaughlin, Russell L.; Teasdale, Matthew D.; van Rheenen, Wouter; Veldink, Jan H.; van den Berg, Leonard H.; Hardiman, Orla; Carroll, Maureen; Roskams, Steve; Oxley, John; Morgan, Colleen; Thomas, Mark G.; Barnes, Ian; McDonnell, Christine; Collins, Matthew J.; Bradley, Daniel G.

2016-01-01

The purported migrations that have formed the peoples of Britain have been the focus of generations of scholarly controversy. However, this has not benefited from direct analyses of ancient genomes. Here we report nine ancient genomes (∼1 ×) of individuals from northern Britain: seven from a Roman era York cemetery, bookended by earlier Iron-Age and later Anglo-Saxon burials. Six of the Roman genomes show affinity with modern British Celtic populations, particularly Welsh, but significantly diverge from populations from Yorkshire and other eastern English samples. They also show similarity with the earlier Iron-Age genome, suggesting population continuity, but differ from the later Anglo-Saxon genome. This pattern concords with profound impact of migrations in the Anglo-Saxon period. Strikingly, one Roman skeleton shows a clear signal of exogenous origin, with affinities pointing towards the Middle East, confirming the cosmopolitan character of the Empire, even at its northernmost fringes. PMID:26783717

Magneto-ionic control of interfacial magnetism

NASA Astrophysics Data System (ADS)

Bauer, Uwe; Yao, Lide; Tan, Aik Jun; Agrawal, Parnika; Emori, Satoru; Tuller, Harry L.; van Dijken, Sebastiaan; Beach, Geoffrey S. D.

2015-02-01

In metal/oxide heterostructures, rich chemical, electronic, magnetic and mechanical properties can emerge from interfacial chemistry and structure. The possibility to dynamically control interface characteristics with an electric field paves the way towards voltage control of these properties in solid-state devices. Here, we show that electrical switching of the interfacial oxidation state allows for voltage control of magnetic properties to an extent never before achieved through conventional magneto-electric coupling mechanisms. We directly observe in situ voltage-driven O2- migration in a Co/metal-oxide bilayer, which we use to toggle the interfacial magnetic anisotropy energy by >0.75 erg cm-2 at just 2 V. We exploit the thermally activated nature of ion migration to markedly increase the switching efficiency and to demonstrate reversible patterning of magnetic properties through local activation of ionic migration. These results suggest a path towards voltage-programmable materials based on solid-state switching of interface oxygen chemistry.

Social networks in the migration process: empirical evidence on chain migration in India.

PubMed

Banerjee, B

1983-01-01

This study, based on interviews with 1615 migrant heads of household in Delhi, was concerned with interactions between labor migrants and their urban-based contacts. 86% of the rural migrants reported having relatives and/or covillagers living in Delhi at the time of their arrival, and virtually all received some form of assistance from their contacts. A preference for assistance from relatives rather than covillagers was noted, suggesting that migrants regarded kinship bonds as stronger than village and caste ties. However, covillagers tended to be contacted if relatives failed to secure a job for the new migrants within a reasonable time. The moves of only 17% of the sample could be classified under delayed family migration (relocation of family members in lagged stages). The tendency for traditional norms to be relaxed in an urban setting is reflected in the finding that the places of origin of migrants and their urban-based relatives differed in about half the cases that involved assistance from relatives. In addition, 13% of migrants violated traditional norms by seeking assistance from female agnates and kin affinally linked through these women. The most common pattern of assistance provided by both relatives and covillagers included room, food, and job search; however, new migrants tended to prefer to obtain board and lodging from relatives. Migrants helped by primary male agnates were twice as likely to receive money as those helped by other relatives. A consequence of chain migration is the concentration of persons from the same village or kinship network in particular occupations. 36% of the wage employees in the sample had relatives and/or covillagers working for the same employer. This suggests that migration induced by urban-based contacts (accounting for 42% of the migration in this sample) will be low if the sectors in which job opportunities are expanding are dominated by nonmigrants. Given the prevalence of chain migration, the contribution of migration to urban unemployment is likely to be fairly low.

Patterns of migrating soaring migrants indicate attraction to marine wind farms

PubMed Central

Desholm, Mark; Heinänen, Stefan; Kahlert, Johnny A.; Laubek, Bjarke; Jensen, Niels Einar; Žydelis, Ramūnas; Jensen, Bo Præstegaard

2016-01-01

Monitoring of bird migration at marine wind farms has a short history, and unsurprisingly most studies have focused on the potential for collisions. Risk for population impacts may exist to soaring migrants such as raptors with K-strategic life-history characteristics. Soaring migrants display strong dependence on thermals and updrafts and an affinity to land areas and islands during their migration, a behaviour that creates corridors where raptors move across narrow straits and sounds and are attracted to islands. Several migration corridors for soaring birds overlap with the development regions for marine wind farms in NW Europe. However, no empirical data have yet been available on avoidance or attraction rates and behavioural reactions of soaring migrants to marine wind farms. Based on a post-construction monitoring study, we show that all raptor species displayed a significant attraction behaviour towards a wind farm. The modified migratory behaviour was also significantly different from the behaviour at nearby reference sites. The attraction was inversely related to distance to the wind farm and was primarily recorded during periods of adverse wind conditions. The attraction behaviour suggests that migrating raptor species are far more at risk of colliding with wind turbines at sea than hitherto assessed. PMID:28003522

Beyond Group-Threat: Temporal Dynamics of International Migration and Linkages to Anti-Foreigner Sentiment.

PubMed

DeWaard, Jack

2015-07-01

Prior research on the association between country-level patterns of international migration and anti-foreigner sentiment shows that larger foreign-born concentrations increase perceptions of threat among native-born individuals in receiving countries, which, in turn, give rise to exclusionary preferences. While recent work has assembled a list of limiting conditions that shape the strength of this association, I argue that these efforts are premature because they are based on a narrow way of conceptualising and measuring international migration. In contrast to concepts and measures privileging the size of the foreign-born population in receiving countries, I draw from other literatures highlighting the temporal dynamics of migration. In considering the role of the temporal dynamics of international migration in explaining variation in anti-foreigner sentiment, the question is whether and how the temporal stability of the foreign-born population in receiving countries matters. My results suggest that it does. The size and temporal stability of the foreign-born population play opposing roles in aggravating and ameliorating anti-foreigner sentiment, respectively, with each operating via different pathways at the individual level. My work thus breaks new ground by challenging existing theoretical constructs and operationalisations in the group-threat literature.

Internal and International Mobility as Adaptation to Climatic Variability in Contemporary Mexico: Evidence from the Integration of Census and Satellite Data.

PubMed

Leyk, Stefan; Runfola, Dan; Nawrotzki, Raphael J; Hunter, Lori M; Riosmena, Fernando

2017-08-01

Migration provides a strategy for rural Mexican households to cope with, or adapt to, weather events and climatic variability. Yet prior studies on "environmental migration" in this context have not examined the differences between choices of internal (domestic) or international movement. In addition, much of the prior work relied on very coarse spatial scales to operationalize the environmental variables such as rainfall patterns. To overcome these limitations, we use fine-grain rainfall estimates derived from NASA's Tropical Rainfall Measuring Mission (TRMM) satellite. The rainfall estimates are combined with Population and Agricultural Census information to examine associations between environmental changes and municipal rates of internal and international migration 2005-2010. Our findings suggest that municipal-level rainfall deficits relative to historical levels are an important predictor of both international and internal migration, especially in areas dependent on seasonal rainfall for crop productivity. Although our findings do not contradict results of prior studies using coarse spatial resolution, they offer clearer results and a more spatially nuanced examination of migration as related to social and environmental vulnerability and thus higher degrees of confidence.

February precipitation in the wintering grounds of the lesser whitethroat, Sylvia curruca: is it a cue for migration onset?

PubMed

Aloni, Irith; Markman, Shai; Ziv, Yaron

2017-02-01

Numerous studies report shifts in bird migration phenology, presumably owing to global warming. However, most studies focus on migration patterns in the Northern Hemisphere. In this study, we investigated associations between weather conditions in African wintering grounds of the lesser whitethroat, Sylvia curruca, and spring arrival time in Eilat, Israel. Using multivariate regression models, we analysed a 30-year dataset in order to examine correlations between median springtime arrival and 46 climate variables of the wintering quarters. The model obtained exhibited a highly statistical fit, involving mean precipitation in February and March with negative effects and number of wet days during November-February. February precipitation levels were also the major factor associated with the interquartile range of arrival time. Interestingly and contrary to published results, annual or seasonal precipitation showed no correlation with spring arrival time, nor did temperature. Moreover, winter in this region falls into dry season with negligible rainfall quantities. Hence, it is unlikely that precipitation effect on habitat productivity is a driving force of migration, as suggested by other studies. Instead, we propose that precipitation in February acts as a cue for the birds, indicating the approach of spring and migration time.

Beyond Group-Threat: Temporal Dynamics of International Migration and Linkages to Anti-Foreigner Sentiment

PubMed Central

DeWaard, Jack

2014-01-01

Prior research on the association between country-level patterns of international migration and anti-foreigner sentiment shows that larger foreign-born concentrations increase perceptions of threat among native-born individuals in receiving countries, which, in turn, give rise to exclusionary preferences. While recent work has assembled a list of limiting conditions that shape the strength of this association, I argue that these efforts are premature because they are based on a narrow way of conceptualising and measuring international migration. In contrast to concepts and measures privileging the size of the foreign-born population in receiving countries, I draw from other literatures highlighting the temporal dynamics of migration. In considering the role of the temporal dynamics of international migration in explaining variation in anti-foreigner sentiment, the question is whether and how the temporal stability of the foreign-born population in receiving countries matters. My results suggest that it does. The size and temporal stability of the foreign-born population play opposing roles in aggravating and ameliorating anti-foreigner sentiment, respectively, with each operating via different pathways at the individual level. My work thus breaks new ground by challenging existing theoretical constructs and operationalisations in the group-threat literature. PMID:26146481

Distribution and foraging patterns of common loons on Lake Michigan with implications for exposure to type E avian botulism

USGS Publications Warehouse

Kenow, Kevin P.; Houdek, Steven C.; Fara, Luke; Gray, Brian R.; Lubinski, Brian R.; Heard, Darryl J.; Meyer, Michael W.; Fox, Timothy J.; Kratt, Robert

2018-01-01

Common loons (Gavia immer) staging on the Great Lakes during fall migration are at risk to episodic outbreaks of type E botulism. Information on distribution, foraging patterns, and exposure routes of loons are needed for understanding the physical and ecological factors that contribute to avian botulism outbreaks. Aerial surveys were conducted to document the spatiotemporal distribution of common loons on Lake Michigan during falls 2011–2013. In addition, satellite telemetry and archival geolocator tags were used to determine the distribution and foraging patterns of individual common loons while using Lake Michigan during fall migration. Common loon distribution observed during aerial surveys and movements of individual radiomarked and/or geotagged loons suggest a seasonal pattern of use, with early fall use of Green Bay and northern Lake Michigan followed by a shift in distribution to southern Lake Michigan before moving on to wintering areas. Common loons tended to occupy offshore areas of Lake Michigan and, on average, spent the majority of daylight hours foraging. Dive depths were as deep as 60 m and dive characteristics suggested that loons were primarily foraging on benthic prey. A recent study concluded that round gobies (Neogobius melanostomus) are an important prey item of common loons and may be involved in transmission of botulinum neurotoxin type E. Loon distribution coincides with the distribution of dreissenid mussel biomass, an important food resource for round gobies. Our observations support speculation that energy transfer to higher trophic levels via gobies may occur in deep-water habitats, along with transfer of botulinum neurotoxin.

Seasonal associations with urban light pollution for nocturnally migrating bird populations.

PubMed

La Sorte, Frank A; Fink, Daniel; Buler, Jeffrey J; Farnsworth, Andrew; Cabrera-Cruz, Sergio A

2017-11-01

The spatial extent and intensity of artificial light at night (ALAN) has increased worldwide through the growth of urban environments. There is evidence that nocturnally migrating birds are attracted to ALAN, and there is evidence that nocturnally migrating bird populations are more likely to occur in urban areas during migration, especially in the autumn. Here, we test if urban sources of ALAN are responsible, at least in part, for these observed urban associations. We use weekly estimates of diurnal occurrence and relative abundance for 40 nocturnally migrating bird species that breed in forested environments in North America to assess how associations with distance to urban areas and ALAN are defined across the annual cycle. Migratory bird populations presented stronger than expected associations with shorter distances to urban areas during migration, and stronger than expected association with higher levels of ALAN outside and especially within urban areas during migration. These patterns were more pronounced during autumn migration, especially within urban areas. Outside of the two migration periods, migratory bird populations presented stronger than expected associations with longer distances to urban areas, especially during the nonbreeding season, and weaker than expected associations with the highest levels of ALAN outside and especially within urban areas. These findings suggest that ALAN is associated with higher levels of diurnal abundance along the boundaries and within the interior of urban areas during migration, especially in the autumn when juveniles are undertaking their first migration journey. These findings support the conclusion that urban sources of ALAN can broadly effect migratory behavior, emphasizing the need to better understand the implications of ALAN for migratory bird populations. © 2017 John Wiley & Sons Ltd.

Design modifications of the uncemented Furlong hip stem result in minor early subsidence but do not affect further stability: a randomized controlled RSA study with 5-year follow-up.

PubMed

Weber, Erik; Sundberg, Martin; Flivik, Gunnar

2014-12-01

Even small design modifications of uncemented hip stems may alter the postoperative 3-D migration pattern. The Furlong Active is an uncemented femoral stem which, in terms of design, is based on its precursor-the well-proven Furlong HAC-but has undergone several design changes. The collar has been removed on the Active stem along with the lateral fin; it is shorter and has more rounded edges in the proximal part. We compared the migration patterns of the uncemented Furlong HAC stem and the modified Furlong Active stem in a randomized, controlled trial over 5 years using radiostereometry (RSA). 50 patients with primary osteoarthritis were randomized to receive either the HAC stem or the Active stem. The patients underwent repeated RSA examinations (postoperatively, at 3 months, and after 1, 2, and 5 years) and conventional radiography, and they also filled out hip-specific questionnaires. During the first 3 months, the collarless Active stem subsided to a greater extent than the collar-fitted HAC stem (0.99 mm vs. 0.31 mm, p=0.05). There were, however, no other differences in movement measured by RSA or in clinical outcome between the 2 stems. After 3 months, both stem types had stabilized and almost no further migration was seen. The Active stem showed no signs of unfavorable migration. Our results suggest that the osseointegration is not compromised by the new design features.

Engineered three-dimensional microfluidic device for interrogating cell-cell interactions in the tumor microenvironment.

PubMed

Hockemeyer, K; Janetopoulos, C; Terekhov, A; Hofmeister, W; Vilgelm, A; Costa, Lino; Wikswo, J P; Richmond, A

2014-07-01

Stromal cells in the tumor microenvironment play a key role in the metastatic properties of a tumor. It is recognized that cancer-associated fibroblasts (CAFs) and endothelial cells secrete factors capable of influencing tumor cell migration into the blood or lymphatic vessels. We developed a microfluidic device that can be used to image the interactions between stromal cells and tumor cell spheroids in a three dimensional (3D) microenvironment while enabling external control of interstitial flow at an interface, which supports endothelial cells. The apparatus couples a 200-μm channel with a semicircular well to mimic the interface of a blood vessel with the stroma, and the design allows for visualization of the interactions of interstitial flow, endothelial cells, leukocytes, and fibroblasts with the tumor cells. We observed that normal tissue-associated fibroblasts (NAFs) contribute to the "single file" pattern of migration of tumor cells from the spheroid in the 3D microenvironment. In contrast, CAFs induce a rapid dispersion of tumor cells out of the spheroid with migration into the 3D matrix. Moreover, treatment of tumor spheroid cultures with the chemokine CXCL12 mimics the effect of the CAFs, resulting in similar patterns of dispersal of the tumor cells from the spheroid. Conversely, addition of CXCL12 to co-cultures of NAFs with tumor spheroids did not mimic the effects observed with CAF co-cultures, suggesting that NAFs produce factors that stabilize the tumor spheroids to reduce their migration in response to CXCL12.

Aspects of Migration in an Advanced Industrial Society.

ERIC Educational Resources Information Center

Wilson, Franklin D.

This paper evaluates the hypothesis that patterns of migration within and between the metropolitan and nonmetropolitan sectors and between regions, and migrant/nonmigrant differentials in education attainment during the 1935-1980 period of United States history reflect historical differences in socioeconomic development and settlement patterns.…

Breast Cancer Cell Colonization of the Human Bone Marrow Adipose Tissue Niche.

PubMed

Templeton, Zach S; Lie, Wen-Rong; Wang, Weiqi; Rosenberg-Hasson, Yael; Alluri, Rajiv V; Tamaresis, John S; Bachmann, Michael H; Lee, Kitty; Maloney, William J; Contag, Christopher H; King, Bonnie L

2015-12-01

Bone is a preferred site of breast cancer metastasis, suggesting the presence of tissue-specific features that attract and promote the outgrowth of breast cancer cells. We sought to identify parameters of human bone tissue associated with breast cancer cell osteotropism and colonization in the metastatic niche. Migration and colonization patterns of MDA-MB-231-fLuc-EGFP (luciferase-enhanced green fluorescence protein) and MCF-7-fLuc-EGFP breast cancer cells were studied in co-culture with cancellous bone tissue fragments isolated from 14 hip arthroplasties. Breast cancer cell migration into tissues and toward tissue-conditioned medium was measured in Transwell migration chambers using bioluminescence imaging and analyzed as a function of secreted factors measured by multiplex immunoassay. Patterns of breast cancer cell colonization were evaluated with fluorescence microscopy and immunohistochemistry. Enhanced MDA-MB-231-fLuc-EGFP breast cancer cell migration to bone-conditioned versus control medium was observed in 12/14 specimens (P = .0014) and correlated significantly with increasing levels of the adipokines/cytokines leptin (P = .006) and IL-1β (P = .001) in univariate and multivariate regression analyses. Fluorescence microscopy and immunohistochemistry of fragments underscored the extreme adiposity of adult human bone tissues and revealed extensive breast cancer cell colonization within the marrow adipose tissue compartment. Our results show that breast cancer cells migrate to human bone tissue-conditioned medium in association with increasing levels of leptin and IL-1β, and colonize the bone marrow adipose tissue compartment of cultured fragments. Bone marrow adipose tissue and its molecular signals may be important but understudied components of the breast cancer metastatic niche. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Migration: a Negative or a Positive Driver for Development? OECD Development Centre Policy Insights, No.29

ERIC Educational Resources Information Center

Katseli, Louka T.; Xenogiani, Theodora

2006-01-01

The effects of migration on development depend on who leaves, where they go, and how home countries adjust to their leaving. The authors advocate that migration patterns and the capacity to adjust are fundamental determinants of a migration-development nexus, and that migration and development policies are complements rather than substitutes. The…

The fine scale genetic structure of the British population

PubMed Central

Davison, Dan; Boumertit, Abdelhamid; Day, Tammy; Hutnik, Katarzyna; Royrvik, Ellen C; Cunliffe, Barry; Lawson, Daniel J; Falush, Daniel; Freeman, Colin; Pirinen, Matti; Myers, Simon; Robinson, Mark; Donnelly, Peter; Bodmer, Walter

2015-01-01

Summary Fine-scale genetic variation between human populations is interesting as a signature of historical demographic events and because of its potential for confounding disease studies. We use haplotype-based statistical methods to analyse genome-wide SNP data from a carefully chosen geographically diverse sample of 2,039 individuals from the United Kingdom (UK). This reveals a rich and detailed pattern of genetic differentiation with remarkable concordance between genetic clusters and geography. The regional genetic differentiation and differing patterns of shared ancestry with 6,209 individuals from across Europe carry clear signals of historical demographic events. We estimate the genetic contribution to SE England from Anglo-Saxon migrations to be under half, identify the regions not carrying genetic material from these migrations, suggest significant pre-Roman but post-Mesolithic movement into SE England from the Continent, and show that in non-Saxon parts of the UK there exist genetically differentiated subgroups rather than a general “Celtic” population. PMID:25788095

Elemental Mercury Diffusion Processes and Concentration at the Lunar Poles

NASA Technical Reports Server (NTRS)

Moxley, Frederick; Killen, Rosemary M.; Hurley, Dana M.

2011-01-01

In 2009, the Lyman Alpha Mapping Project (LAMP) spectrograph onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft made the first detection of element mercury (Hg) vapor in the lunar exosphere after the Lunar Crater Observing and Sensing Satellite (LCROSS) Centaur rocket impacted into the Cabeus crater in the southern polar region of the Moon. The lunar regolith core samples from the Apollo missions determined that Hg had a devolatilized pattern with a concentration gradient increasing with depth, in addition to a layered pattern suggesting multiple episodes of burial and volatile loss. Hg migration on the lunar surface resulted in cold trapping at the poles. We have modeled the rate at which indigenous Hg is lost from the regolith through diffusion out of lunar grains. We secondly modeled the migration of Hg vapor in the exosphere and estimated the rate of cold-trapping at the poles using a Monte Carlo technique. The Hg vapor may be lost from the exosphere via ionization, Jeans escape, or re-impact into the surface causing reabsorption.

Periodic Colony Formation of Bacteria Due to their Cell Reproduction and Movement

NASA Astrophysics Data System (ADS)

Itoh, H.; Wakita, J.; Watanabe, K.; Matsuyama, T.; Matsushita, M.

We have experimentally investigated periodic pattern formation produced by bacterial species Proteus mirabilis, which forms concentric-ring-like colonies by repeating migration and rest alternately on the surface of a solid agar medium. We distinguish three phases (initial lag phase, the following migration and consolidation phases that appear alternately) for the colony growth. Here we mainly used physical approaches in order to try to understand the formation of concentric-ring-like colonies, such as cutting the part of a colony during its growth. Global chemical signals governing the colony formation from the center were not found. We also checked phase entrainment quantitatively by letting two colonies collide with each other and confirmed that it does not take place in macroscopic scales. When we cut a colony just behind the migrating front shortly after the migration started, the migration ended earlier and the following consolidation lasted longer. However, the following cycles were not influenced by the cut, i.e., the following migration and consolidation phases were both found to return normal. The cut results in the stop of supply of cell population to the migrating front by internal waves. In fact the cell population on the new terrace during the first migration after the cut was less than that without cut. Furthermore, the cell population density was found to be recovered to the ordinary value by the end of the consolidation. All these experimental results suggest that the most important factor for the repetition of migration and consolidation phases is the cell population density.

Health professionals' migration in emerging market economies: patterns, causes and possible solutions.

PubMed

Nair, Manisha; Webster, Premila

2013-03-01

About a third of the countries affected by shortage of human resources for health are the emerging market economies (EMEs). The greatest shortage in absolute terms was found to be in India and Indonesia leading to health system crisis. This review identifies the patterns of migration of health workers, causes and possible solutions in these EMEs. A qualitative synthesis approach based on the 'critical review' and 'realist review' approaches to the literature review was used. The patterns of migration of health professionals' in the EMEs have led to two types of discrepancies between health needs and healthcare workers: (i) within country (rural-urban, public-private or government healthcare sector-private sector) and (ii) across countries (south to north). Factors that influence migration include lack of employment opportunities, appropriate work environment and wages in EMEs, growing demand in high-income countries due to demographic transition, favourable country policies for financial remittances by migrant workers and medical education system of EMEs. A range of successful national and international initiatives to address health workforce migration were identified. Measures to control migration should be country specific and designed in accordance with the push and pull factors existing in the EMEs.

Changing patterns of migration in Latin America: how can research develop intelligence for public health?

PubMed

Cabieses, Baltica; Tunstall, Helena; Pickett, Kate E; Gideon, Jasmine

2013-07-01

Migration patterns in Latin America have changed significantly in recent decades, particularly since the onset of global recession in 2007. These recent economic changes have highlighted and exacerbated the weakness of evidence from Latin America regarding migration-a crucial determinant of health. Migration patterns are constantly evolving in Latin America, but research on migration has not developed at the same speed. This article focuses on the need for better understanding of the living conditions and health of migrant populations in Latin America within the context of the recent global recession. The authors explain how new data on migrant well-being could be obtained through improved evidence from censuses and ongoing research surveys to 1) better inform policy-makers about the needs of migrant populations in Latin America and 2) help determine better ways of reaching undocumented immigrants. Longitudinal studies on immigrants in Latin America are essential for generating a better representation of migrant living conditions and health needs during the initial stages of immigration and over time. To help meet this need, the authors support the promotion of sustainable sources of data and evidence on the complex relationship between migration and health.

Migration history of air-breathing fishes reveals Neogene atmospheric circulation patterns

NASA Astrophysics Data System (ADS)

Böhme, M.

2004-05-01

The migration history of an air-breathing fish group (Channidae; snakehead fishes) is used for reconstructing Neogene Eurasian precipitation and atmospheric circulation patterns. The study shows that snakeheads are sensitive indicators of summer precipitation maxima in subtropical and temperate regions, and are present regularly if the wettest month exceeds 150 mm precipitation and 20 °C mean temperature. The analysis of 515 fossil freshwater fish deposits of the past 50 m.y. from Africa and Eurasia shows two continental-scale migration events from the snakeheads' center of origin in the south Himalayan region, events that can be related to changes in the Northern Hemisphere circulation pattern. The first migration, ca. 17.5 Ma, into western and central Eurasia may have been caused by a northward shift of the Intertropical Convergence Zone that brought western Eurasia under the influence of trade winds that produced a zonal and meridional precipitation gradient in Europe. During the second migration, between 8 and 4 Ma, into Africa and East Asia, snakeheads reached their present-day distribution. This migration could have been related to the intensification of the Asian monsoon that brought summer precipitation to their migratory pathways in East Africa Arabia and East Asia.

Age constraints for the present fault configuration in the Imperial Valley, California: Evidence for northwestward propagation of the Gulf of California rift system

NASA Technical Reports Server (NTRS)

Larsen, Shawn; Reilinger, Robert

1990-01-01

Releveling and other geophysical data for the Imperial Valley of southern California suggest the northern section of the Imperial-Brawley fault system, which includes the Mesquite Basin and Brawley Seismic Zone, is much younger than the 4 to 5 million year age of the valley itself. A minimum age of 3000 years is calculated for the northern segment of the Imperial fault from correlations between surface topography and geodetically observed seismic/interseismic vertical movements. Calculations of a maximum age of 80,000 years is based upon displacements in the crystalline basement along the Imperial fault, inferred from seismic refraction surveys. This young age supports recent interpretations of heat flow measurements, which also suggest that the current patterns of seismicity and faults in the Imperial Valley are not long lived. The current fault geometry and basement morphology suggest northwestward growth of the Imperial fault and migration of the Brawley Seismic Zone. It is suggested that this migration is a manifestation of the propagation of the Gulf of California rift system into the North American continent.

Vertical migrations of a deep-sea fish and its prey.

PubMed

Afonso, Pedro; McGinty, Niall; Graça, Gonçalo; Fontes, Jorge; Inácio, Mónica; Totland, Atle; Menezes, Gui

2014-01-01

It has been speculated that some deep-sea fishes can display large vertical migrations and likely doing so to explore the full suite of benthopelagic food resources, especially the pelagic organisms of the deep scattering layer (DSL). This would help explain the success of fishes residing at seamounts and the increased biodiversity found in these features of the open ocean. We combined active plus passive acoustic telemetry of blackspot seabream with in situ environmental and biological (backscattering) data collection at a seamount to verify if its behaviour is dominated by vertical movements as a response to temporal changes in environmental conditions and pelagic prey availability. We found that seabream extensively migrate up and down the water column, that these patterns are cyclic both in short-term (tidal, diel) as well as long-term (seasonal) scales, and that they partially match the availability of potential DSL prey components. Furthermore, the emerging pattern points to a more complex spatial behaviour than previously anticipated, suggesting a seasonal switch in the diel behaviour mode (benthic vs. pelagic) of seabream, which may reflect an adaptation to differences in prey availability. This study is the first to document the fine scale three-dimensional behaviour of a deep-sea fish residing at seamounts.

Sockeye salmon (Oncorhynchus nerka) return after an absence of nearly 90 years: A case of reversion to anadromy

USGS Publications Warehouse

Godbout, L.; Wood, C.C.; Withler, R.E.; Latham, S.; Nelson, R.J.; Wetzel, L.; Barnett-Johnson, R.; Grove, M.J.; Schmitt, A.K.; McKeegan, K.D.

2011-01-01

We document the recent reappearance of anadromous sockeye salmon (Oncorhynchus nerka) that were thought to have been extirpated by the construction of hydroelectric dams on the Coquitlam and Alouette rivers in British Columbia, Canada, in 1914 and 1927, respectively. Unexpected downstream migrations of juveniles during experimental water releases into both rivers in 2005 and 2006 preceded upstream return migrations of adults in 2007 and 2008. Genetic (microsatellite and mitochondrial DNA) markers and stable isotope (??34S and 87Sr/86Sr) patterns in otoliths confirm that both the juvenile downstream migrants and adult upstream migrants were progeny of nonanadromous sockeye salmon (kokanee) that inhabit Coquitlam and Alouette reservoirs. Low genetic diversity and evidence of genetic bottlenecks suggest that the kokanee populations in both reservoirs originated from relatively few anadromous individuals that residualized after downstream migration was largely prevented by the construction of dams. Once given an opportunity for upstream and downstream migration, both populations appear capable of reverting to a successful anadromous form, even after 25 generations.

Pre-migration Trauma Exposure and Psychological Distress for Asian American Immigrants: Linking the Pre- and Post-migration Contexts.

PubMed

Li, Miao; Anderson, James G

2016-08-01

Drawing on the life course perspective and the assumptive world theory, this paper examines whether pre-migration trauma exposure is associated with psychological distress through post-migration perceived discrimination for Asian American immigrants. The study is based on cross-sectional data from the National Latino and Asian American Study (N = 1639). Structural equation model is used to estimate the relationship between pre-migration trauma, post-migration perceived discrimination, and psychological distress. Additional models are estimated to explore possible variations across ethnic groups as well as across different types of pre-migration trauma experience. Pre-migration trauma exposure is associated with higher levels of psychological distress, both directly and indirectly through higher level of perceived discrimination, even after controlling for demographic/acculturative factors and post-migration trauma exposure. This pattern holds for the following sub-types of pre-migration trauma: political trauma, crime victimization, physical violence, accidental trauma, and relational trauma. Multi-group analyses show that this pattern holds for all Asian immigrant subgroups except the Vietnamese. Studies of immigrant mental health primarily focus on post-migration stressors. Few studies have considered the link between pre- and post-migration contexts in assessing mental health outcomes. The study illustrates the usefulness of bridging the pre- and post-migration context in identifying the mental health risks along the immigrant life course.

Probing Leader Cells in Endothelial Collective Migration by Plasma Lithography Geometric Confinement

PubMed Central

Yang, Yongliang; Jamilpour, Nima; Yao, Baoyin; Dean, Zachary S.; Riahi, Reza; Wong, Pak Kin

2016-01-01

When blood vessels are injured, leader cells emerge in the endothelium to heal the wound and restore the vasculature integrity. The characteristics of leader cells during endothelial collective migration under diverse physiological conditions, however, are poorly understood. Here we investigate the regulation and function of endothelial leader cells by plasma lithography geometric confinement generated. Endothelial leader cells display an aggressive phenotype, connect to follower cells via peripheral actin cables and discontinuous adherens junctions, and lead migrating clusters near the leading edge. Time-lapse microscopy, immunostaining, and particle image velocimetry reveal that the density of leader cells and the speed of migrating clusters are tightly regulated in a wide range of geometric patterns. By challenging the cells with converging, diverging and competing patterns, we show that the density of leader cells correlates with the size and coherence of the migrating clusters. Collectively, our data provide evidence that leader cells control endothelial collective migration by regualting the migrating clusters. PMID:26936382

Cellular automaton for migration in ecosystem: Application of traffic model to a predator-prey system

NASA Astrophysics Data System (ADS)

Nagatani, Takashi; Tainaka, Kei-ichi

2018-01-01

In most cases, physicists have studied the migration of biospecies by the use of random walk. In the present article, we apply cellular automaton of traffic model. For simplicity, we deal with an ecosystem contains a prey and predator, and use one-dimensional lattice with two layers. Preys stay on the first layer, but predators uni-directionally move on the second layer. The spatial and temporal evolution is numerically explored. It is shown that the migration has the important effect on populations of both prey and predator. Without migration, the phase transition between a prey-phase and coexisting-phase occurs. In contrast, the phase transition disappears by migration. This is because predator can survive due to migration. We find another phase transition for spatial distribution: in one phase, prey and predator form a stripe pattern of condensation and rarefaction, while in the other phase, they uniformly distribute. The self-organized stripe may be similar to the migration patterns in real ecosystems.

Use of NEXRAD to study shorebird migration in the Prairie Pothole region: A feasibility study

USGS Publications Warehouse

Melcher, Cynthia P.; Skagen, Susan K.; Randall, Lori

2006-01-01

An essential component of shorebird conservation is identifying, protecting, and managing high-priority stopover sites and migration habitats crucial to the long-term persistence of migrating shorebirds. Because of the tremendous variability in migrant shorebird occurrence patterns in the Prairie Pothole Region of the U.S. (Skagen 1997), it is labor- and cost-intensive to locate the majority of sites used heavily by shorebirds in any one migration period. Because WSR-88D (Weather Surveillance Radar – 1988 Doppler) or NEXRAD (NEXt generation weather RADar) has been useful for locating migrating birds and revealing migration patterns and important roosting sites of some species (e.g., Diehl and others 2003, Gauthreaux and Belser 2003), we undertook a pilot field study to determine wheTHER it also might be feasible to use NEXRAD for locating important stopover sites used by migrating shorebirds in the prairie potholes landscape. Coordinated efforts to advance the applicability of radar technology to bird conservation are underway (Ruth and others 2005).

Probing Leader Cells in Endothelial Collective Migration by Plasma Lithography Geometric Confinement.

PubMed

Yang, Yongliang; Jamilpour, Nima; Yao, Baoyin; Dean, Zachary S; Riahi, Reza; Wong, Pak Kin

2016-03-03

When blood vessels are injured, leader cells emerge in the endothelium to heal the wound and restore the vasculature integrity. The characteristics of leader cells during endothelial collective migration under diverse physiological conditions, however, are poorly understood. Here we investigate the regulation and function of endothelial leader cells by plasma lithography geometric confinement generated. Endothelial leader cells display an aggressive phenotype, connect to follower cells via peripheral actin cables and discontinuous adherens junctions, and lead migrating clusters near the leading edge. Time-lapse microscopy, immunostaining, and particle image velocimetry reveal that the density of leader cells and the speed of migrating clusters are tightly regulated in a wide range of geometric patterns. By challenging the cells with converging, diverging and competing patterns, we show that the density of leader cells correlates with the size and coherence of the migrating clusters. Collectively, our data provide evidence that leader cells control endothelial collective migration by regualting the migrating clusters.

Retention of CXCR4 in the endoplasmic reticulum blocks dissemination of a T cell hybridoma

PubMed Central

Zeelenberg, Ingrid S.; Stalle, Lisette Ruuls-Van; Roos, Ed

2001-01-01

The dissemination of T cell hybridomas to multiple nonhematopoietic tissues is blocked by pertussis toxin, suggesting the involvement of a chemokine. To study whether this chemokine is SDF-1, we employed a strategy proposed previously for gene therapy of AIDS, whereby the SDF-1 receptor CXCR4 (also a coreceptor for HIV) is retained in the endoplasmic reticulum (ER) and fails to reach the cell surface. We transfected SDF-1, carrying an ER retention sequence, into a T cell hybridoma. This altered chemokine is retained in the ER, where it binds CXCR4 and prevents the latter protein from reaching the surface. These cells failed to migrate toward SDF-1 or to invade fibroblast monolayers, although they could still migrate toward thymus and activation-regulated chemokine (TARC) and invade TARC-treated monolayers. Furthermore, the ability of the transfected cells to disseminate to multiple organs upon intravenous injection into mice was abolished. This dissemination reflects the in vivo migration patterns of activated and memory T cells into nonhematopoietic tissues, which is thus likely to depend on CXCR4. Attempts to block CXCR4 function as a therapy for AIDS may affect this migration with consequences for T cell function. Our results also suggest a decisive role for CXCR4 in the dissemination of hematopoietic malignancies expressing this receptor. PMID:11457880

Retention of CXCR4 in the endoplasmic reticulum blocks dissemination of a T cell hybridoma.

PubMed

Zeelenberg, I S; Ruuls-Van Stalle, L; Roos, E

2001-07-01

The dissemination of T cell hybridomas to multiple nonhematopoietic tissues is blocked by pertussis toxin, suggesting the involvement of a chemokine. To study whether this chemokine is SDF-1, we employed a strategy proposed previously for gene therapy of AIDS, whereby the SDF-1 receptor CXCR4 (also a coreceptor for HIV) is retained in the endoplasmic reticulum (ER) and fails to reach the cell surface. We transfected SDF-1, carrying an ER retention sequence, into a T cell hybridoma. This altered chemokine is retained in the ER, where it binds CXCR4 and prevents the latter protein from reaching the surface. These cells failed to migrate toward SDF-1 or to invade fibroblast monolayers, although they could still migrate toward thymus and activation-regulated chemokine (TARC) and invade TARC-treated monolayers. Furthermore, the ability of the transfected cells to disseminate to multiple organs upon intravenous injection into mice was abolished. This dissemination reflects the in vivo migration patterns of activated and memory T cells into nonhematopoietic tissues, which is thus likely to depend on CXCR4. Attempts to block CXCR4 function as a therapy for AIDS may affect this migration with consequences for T cell function. Our results also suggest a decisive role for CXCR4 in the dissemination of hematopoietic malignancies expressing this receptor.

Migration stopover ecology of western avian populations: A southwestern migration workshop

USGS Publications Warehouse

Skagen, Susan K.; Melcher, Cynthia P.; Hazelwood, Rob

2004-01-01

Workshop participants discussed a coordinated approach for addressing immediate research needs regarding migration patterns and crucial stopover sites and types. They envisioned a three­-tiered, coordinated approach: (1) long-term research to address effects of climate change and other large-scale patterns, (2) intensive, short-term survey and monitoring efforts using a stratified random design within habitats of interest to elucidate regional patterns of distribution and habitat use, and (3) research conducted at existing survey and banding sites to address more in-depth questions (e.g., rates of lipid deposition, microhabitat use, isotope analyses). There was considerable interest in developing common research proposals to blend the broad expertise represented at this workshop. A second meeting is recommended to build on the momentum of these discussions, to facilitate collaborations, and further the goals of integrated approaches to broadscale research on migration stopover ecology. 

Geographic variation in Bar-headed geese Anser indicus: connectivity of wintering and breeding grounds across a broad front

USGS Publications Warehouse

Takekawa, John Y.; Heath, Shane R.; Douglas, David C.; Perry, William M.; Javed, Sàlim; Newman, Scott H.; Suwal, Rajendra N.; Rahman, Asad R.; Choudhury, Binod C.; Prosser, Diann J.; Yan, Baoping; Hou, Yuansheng; Batbayar, Nyambayar; Natsagdorj, Tseveenmayadag; Bishop, Charles M.; Butler, Patrick J.; Frappell, Peter B.; Milsom, William K.; Scott, Graham R.; Hawkes, Lucy A.; Wikelski, Martin

2009-01-01

The connectivity and frequency of exchange between sub-populations of migratory birds is integral to understanding population dynamics over the entire species' range. True geese are highly philopatric and acquire lifetime mates during the winter, suggesting that the number of distinct sub-populations may be related to the number of distinct wintering areas. In the Bar-headed Goose Anser indicus, a species found exclusively in Central Asia, the connectivity between breeding and wintering areas is not well known. Their migration includes crossing a broad front of the Himalaya Cordillera, a significant barrier to migration for most birds. Many Bar-headed Geese fly to breeding areas on the Tibetan-Qinghai Plateau (TQP), the highest plateau in the world. From 2005-2008, 60 Bar-headed Geese were captured and marked with satellite transmitters in Nepal (n = 2), India (n = 6), China (n = 29), and Mongolia (n = 23) to examine their migration and distribution. Distinct differences were observed in their migration corridors and timing of movements, including an apparent leap-frog migration pattern for geese from Mongolia. Measurements of geese from Mongolia were larger than their counterparts from China, providing some evidence of morphological differences. Alteration of habitats in China, including the warming effects of climate change on glaciers increasing runoff to TQP wetlands, may be changing goose migration patterns and timing. With the exception of one individual, all geese from Qinghai Lake, China wintered in the southern TQP near Lhasa, and their increasing numbers in that region may be related to the effects of climate change and agricultural development. Thus, our findings document both morphological and geographical variation in sub-populations of Bar-headed Geese, but their resilience to environmental change may be lost if migratory short-stopping results in larger congregations restricted to a smaller number of wintering areas.

Geography of spring landbird migration through riparian habitats in southwestern North America

Treesearch

Susan K. Skagen; Jeffrey F. Kelly; Charles van Riper III; Richard L. Hutto; Deborah M. Finch; David J. Krueper; Cynthia P. Melcher

2005-01-01

Migration stopover resources, particularly riparian habitats, are critically important to landbirds migrating across the arid southwestern region of North America. To explore the effects of species biogeography and habitat affinity on spring migration patterns, we synthesized existing bird abundance and capture data collected in riparian habitats of the borderlands...

Women in Migration: A Third World Focus. Summary.

ERIC Educational Resources Information Center

International Center for Research on Women, Washington, DC.

A study of women in migration in Third World countries since 1960 reveals that, contrary to assumptions, more women are migrating autonomously from rural to urban areas in an often unsuccessful effort to improve their economic status. The results of the study of migration patterns in Africa, Asia, Central America, South America, and the Middle…

Migration from Rural Areas: Employment and Education. IIEP Seminar Paper: 26.

ERIC Educational Resources Information Center

Hallak, Jacques

Discussing migration and migration patterns in the third world, this paper asserts that the failure of plans for controlling rural to urban migration is due to: lack of knowledge about the phenomenon; the favor given to one-dimensional interpretations stressing certain aspects of urban economies; and the implicit assumptions underlying most…

Vaginal Epithelial Cell-Derived S100 Alarmins Induced by Candida albicans via Pattern Recognition Receptor Interactions Are Sufficient but Not Necessary for the Acute Neutrophil Response during Experimental Vaginal Candidiasis

PubMed Central

Yano, Junko; Palmer, Glen E.; Eberle, Karen E.; Peters, Brian M.; Vogl, Thomas; McKenzie, Andrew N.

2014-01-01

Vulvovaginal candidiasis (VVC), caused by Candida albicans, affects women worldwide. Animal and clinical studies suggest that the immunopathogenic inflammatory condition of VVC is initiated by S100 alarmins in response to C. albicans, which stimulate polymorphonuclear neutrophil (PMN) migration to the vagina. The purpose of this study was to extend previous in vitro data and determine the requirement for the alarmin S100A8 in the PMN response and to evaluate pattern recognition receptors (PRRs) that initiate the response. For the former, PMN migration was evaluated in vitro or in vivo in the presence or absence of S100 alarmins initiated by several approaches. For the latter, vaginal epithelial cells were evaluated for PRR expression and C. albicans-induced S100A8 and S100A9 mRNAs, followed by evaluation of the PMN response in inoculated PRR-deficient mice. Results revealed that, consistent with previously reported in vitro data, eukaryote-derived S100A8, but not prokaryote-derived recombinant S100A8, induced significant PMN chemotaxis in vivo. Conversely, a lack of biologically active S100A8 alarmin, achieved by antibody neutralization or by using S100A9−/− mice, had no effect on the PMN response in vivo. In PRR analyses, whereas Toll-like receptor 4 (TLR4)- and SIGNR1-deficient vaginal epithelial cells showed a dramatic reduction in C. albicans-induced S100A8/S100A9 mRNAs in vitro, inoculated mice deficient in these PRRs showed PMN migration similar to that in wild-type controls. These results suggest that S100A8 alarmin is sufficient, but not necessary, to induce PMN migration during VVC and that the vaginal PMN response to C. albicans involves PRRs in addition to SIGNR1 and TLR4, or other induction pathways. PMID:24478092

Vaginal epithelial cell-derived S100 alarmins induced by Candida albicans via pattern recognition receptor interactions are sufficient but not necessary for the acute neutrophil response during experimental vaginal candidiasis.

PubMed

Yano, Junko; Palmer, Glen E; Eberle, Karen E; Peters, Brian M; Vogl, Thomas; McKenzie, Andrew N; Fidel, Paul L

2014-02-01

Vulvovaginal candidiasis (VVC), caused by Candida albicans, affects women worldwide. Animal and clinical studies suggest that the immunopathogenic inflammatory condition of VVC is initiated by S100 alarmins in response to C. albicans, which stimulate polymorphonuclear neutrophil (PMN) migration to the vagina. The purpose of this study was to extend previous in vitro data and determine the requirement for the alarmin S100A8 in the PMN response and to evaluate pattern recognition receptors (PRRs) that initiate the response. For the former, PMN migration was evaluated in vitro or in vivo in the presence or absence of S100 alarmins initiated by several approaches. For the latter, vaginal epithelial cells were evaluated for PRR expression and C. albicans-induced S100A8 and S100A9 mRNAs, followed by evaluation of the PMN response in inoculated PRR-deficient mice. Results revealed that, consistent with previously reported in vitro data, eukaryote-derived S100A8, but not prokaryote-derived recombinant S100A8, induced significant PMN chemotaxis in vivo. Conversely, a lack of biologically active S100A8 alarmin, achieved by antibody neutralization or by using S100A9(-/-) mice, had no effect on the PMN response in vivo. In PRR analyses, whereas Toll-like receptor 4 (TLR4)- and SIGNR1-deficient vaginal epithelial cells showed a dramatic reduction in C. albicans-induced S100A8/S100A9 mRNAs in vitro, inoculated mice deficient in these PRRs showed PMN migration similar to that in wild-type controls. These results suggest that S100A8 alarmin is sufficient, but not necessary, to induce PMN migration during VVC and that the vaginal PMN response to C. albicans involves PRRs in addition to SIGNR1 and TLR4, or other induction pathways.

Small heat shock proteins are necessary for heart migration and laterality determination in zebrafish

PubMed Central

Lahvic, Jamie L.; Ji, Yongchang; Marin, Paloma; Zuflacht, Jonah P.; Springel, Mark W.; Wosen, Jonathan E.; Davis, Leigh; Hutson, Lara D.; Amack, Jeffrey D.; Marvin, Martha J.

2013-01-01

Small heat shock proteins (sHsps) regulate cellular functions not only under stress, but also during normal development, when they are expressed in organ-specific patterns. Here we demonstrate that two small heat shock proteins expressed in embryonic zebrafish heart, hspb7 and hspb12, have roles in the development of left-right asymmetry. In zebrafish, laterality is determined by the motility of cilia in Kupffer’s vesicle (KV), where hspb7 is expressed; knockdown of hspb7 causes laterality defects by disrupting the motility of these cilia. In embryos with reduced hspb7, the axonemes of KV cilia have a 9+0 structure, while control embyros have a predominately 9+2 structure. Reduction of either hspb7 or hspb12 alters the expression pattern of genes that propagate the signals that establish left-right asymmetry: the nodal-related gene southpaw (spaw) in the lateral plate mesoderm, and its downstream targets pitx2, lefty1 and lefty2. Partial depletion of hspb7 causes concordant heart, brain and visceral laterality defects, indicating that loss of KV cilia motility leads causes coordinated but randomized laterality. Reducing hspb12 leads to similar alterations in the expression of downstream laterality genes, but at a lower penetrance. Simultaneous reduction of hspb7 and hspb12 randomizes heart, brain and visceral laterality, suggesting that these two genes have partially redundant functions in the establishment of left-right asymmetry. In addition, both hspb7 and hspb12 are expressed in the precardiac mesoderm and in the yolk syncytial layer, which supports the migration and fusion of mesodermal cardiac precursors. In embryos in which the reduction of hspb7 or hspb12 was limited to the yolk, migration defects predominated, suggesting that the yolk expression of these genes rather than heart expression is responsible for the migration defects. PMID:24140541

The circle game: understanding physician migration patterns within Canada.

PubMed

Dauphinee, W Dale

2006-12-01

This report explores the movement of physicians to, from, and within Canada and identifies recurring patterns of migration. The primary position of the report is that physician movement is part of reality both internationally and within Canada, and that movement of Canadian-trained physicians creates a need for international medical graduates (IMGs) in "physician-losing" locations. The report's argument is based on data retrieved from public sources on aggregate physician practice patterns in Canada and analyzed for migration patterns. In addition, literature was reviewed on factors affecting the migration patterns being described.Canadian-educated physicians have tended to move from less prosperous to more prosperous provinces and from rural to urban areas; because of the resulting need, the physician-losing locales generally have the highest proportions of IMGs. Physicians traditionally have tended to emigrate from Canada to the United States, thus increasing Canadian demand for IMGs, but recently this movement has slowed and even reversed. In Canada, liberalized immigration policies for physicians combined with a shortage of postgraduate training positions to create a serious bottleneck early in the current decade. However, this problem is now being resolved. In summary, physician migration within Canada shows specific long-term patterns, and IMGs will be needed in underserved areas for years to come. Well-informed policies for workforce management are essential in Canada to ensure an adequate physician supply consisting mainly of Canadian-educated physicians but also including IMGs. A role for nonadvocacy groups such as the Educational Commission for Foreign Medical Graduates may be to help ensure that recruitment of physicians from developing countries follows accepted ethical principles.

Bird migration patterns in the arid southwest-Final report

USGS Publications Warehouse

Ruth, Janet M.; Felix, Rodney K.; Dieh, Robert H.

2010-01-01

To ensure full life-cycle conservation, we need to understand migrant behavior en route and how migrating species use stopover and migration aerohabitats. In the Southwest, birds traverse arid and mountainous landscapes in migration. Migrants are known to use riparian stopover habitats; we know less about how migrant density varies across the Southwest seasonally and annually, and how migrants use other habitat types during migratory stopover. Furthermore, we lack information about migrant flight altitudes, speeds, and directions of travel, and how these patterns vary seasonally and annually across the Southwest. Using weather surveillance radar data, we identified targets likely dominated by nocturnally migrating birds and determined their flight altitudes, speeds, directions over ground, and variations in abundance. Migrating or foraging bats likely are present across the region in some of these data, particularly in central Texas. We found that migrants flew at significantly lower altitudes and significantly higher speeds in spring than in fall. In all seasons migrants maintained seasonally appropriate directions of movement. We detected significant differences in vertical structure of migrant densities that varied both geographically within seasons and seasonally within sites. We also found that in fall there was a greater and more variable passage of migrants through the central part of the borderlands (New Mexico and west Texas); in spring there was some suggestion of greater and more variable passage of migrants in the eastern borderlands (central and south Texas). Such patterns are consistent with the existence of at least two migration systems through western North America and the use of different migration routes in spring and fall for at least some species. Using radar data and satellite land cover data, we determined the habitats with which migrants are associated during migration stopover. There were significant differences in bird densities among habitat types at all sites in at least one season. Upland forest habitat in parts of Arizona and New Mexico supported high migrant densities, especially in fall. Developed habitats in areas with little upland forest habitat also supported high migrant densities. Scrub/shrub and grassland habitats supported low to intermediate migrant densities, but because these habitat types dominate the region, they may support large numbers of migratory birds. This may be especially true for species that do not use forested habitats during migration. Target identity remains a challenge for radar-based studies. Presence of bats in the data complicates interpretation of some observations, particularly from central Texas. Based on our results it is simplistic to: (1) consider the arid west as a largely inhospitable landscape in which there are only relatively small oases of habitat that provide the resources needed by all migrants; (2) think of western riparian and upland forest habitat as supporting the majority of migrants in all cases; or (3) consider a particular habitat type unimportant migrant stopover habitat based solely on migrant densities.

Narrow-Front Loop Migration in a Population of the Common Cuckoo Cuculus canorus, as Revealed by Satellite Telemetry

PubMed Central

Willemoes, Mikkel; Strandberg, Roine; Klaassen, Raymond H. G.; Tøttrup, Anders P.; Vardanis, Yannis; Howey, Paul W.; Thorup, Kasper; Wikelski, Martin; Alerstam, Thomas

2014-01-01

Narrow migration corridors known in diurnal, social migrants such as raptors, storks and geese are thought to be caused by topographical leading line effects in combination with learning detailed routes across generations. Here, we document narrow-front migration in a nocturnal, solitary migrant, the common cuckoo Cuculus canorus, using satellite telemetry. We tracked the migration of adult cuckoos from the breeding grounds in southern Scandinavia (n = 8), to wintering sites in south-western Central Africa (n = 6) and back to the breeding grounds (n = 3). Migration patterns were very complex; in addition to the breeding and wintering sites, six different stopover sites were identified during the 16,000 km annual route that formed a large-scale clockwise loop. Despite this complexity, individuals showed surprisingly similar migration patterns, with very little variation between routes. We compared observed tracks with simulated routes based on vector orientation (with and without effects of barriers on orientation and survival). Observed distances between routes were often significantly smaller than expected if the routes were established on the basis of an innate vector orientation programme. Average distance between individuals in eastern Sahel after having migrated more than 5,000 km for example, was merely 164 km. This implies that more sophisticated inherent guiding mechanisms, possibly involving elements of intermediate goal area navigation or more elaborate external cues, are necessary to explain the complex narrow-front migration pattern observed for the cuckoos in this study. PMID:24421890

Spatio-temporal variability in movement, age, and growth of mountain whitefish (Prosopium williamsoni) in a river network based upon PIT tagging and otolith chemistry

USGS Publications Warehouse

Benjamin, Joseph R.; Wetzel, Lisa A.; Martens, Kyle D.; Larsen, Kimberly; Connolly, Patrick J.

2013-01-01

Connectivity of river networks and the movements among habitats can be critical for the life history of many fish species, and understanding of the patterns of movement is central to managing populations, communities, and the landscapes they use. We combined passive integrated transponder tagging over 4 years and strontium isotopes in otoliths to demonstrate that 25% of the mountain whitefish (Prosopium williamsoni) sampled moved between the Methow and Columbia rivers, Washington, USA. Seasonal migrations downstream from the Methow River to the Columbia River to overwinter occurred in autumn and upstream movements in the spring. We observed migration was common during the first year of life, with migrants being larger than nonmigrants. However, growth between migrants and nonmigrants was similar. Water temperature was positively related to the proportion of migrants and negatively related to the timing of migration, but neither was related to discharge. The broad spatio-temporal movements we observed suggest mountain whitefish, and likely other nonanadromous fish, require distant habitats and also suggests that management and conservation strategies to keep connectivity of large river networks are imperative.

Middle to Upper Jurassic sedimentary sequences and marine biota of the early Indian Ocean (Southwest Madagascar): some biostratigraphic, palaeoecologic and palaeobiogeographic conclusions

NASA Astrophysics Data System (ADS)

Mette, Wolfgang

2004-03-01

As part of an intradisciplinary project which was concerned with the early rifting processes between Madagascar and East Africa, the Middle to Upper Jurassic sedimentary sequences of the Morondava Basin in Southwest Madagascar has been investigated with respect to biostratigraphy, sedimentary facies and palaeoecology. The transgressive sedimentary sections in the Bajocian and Callovian-Oxfordian yield rich macro- and microfossil assemblages which improved the biostratigraphic framework and gave some important information about the palaeoenvironments. Palaeogeographic distribution patterns of the Bajocian ostracod Paradoxorhyncha are suggestive of a migration along the southern shores of Gondwana between Madagascar, Australia and South America. The Callovian ostracods show strong affinities to the Indian faunas, indicating existence of a free migration route for shallow marine benthic organisms between Madagascar and India. Significant faunal differences between Madagascar and Tanzania suggest a physical or environmental migration barrier between Madagascar and East Africa during the Callovian to Kimmeridgian interval. The Upper Jurassic ostracods from the northern and eastern margin of Gondwana show a very high degree of endemism and they can be assigned to two faunal provinces in North Gondwana (Arabia, Near East, North Africa) and South Gondwana (India, Madagascar, East Africa).

Mixed fluvial systems of Messak Sandstone, a deposit of Nubian lithofacies, southwestern Libya

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenz, J.C.

1987-05-01

The Messak Sandstone is a coarse to pebbly, tabular cross-bedded, Lower Cretaceous deposit of the widespread Nubian lithofacies. It was deposited at the northern edge of the Murzuq basin in southwestern Libya. Although the sedimentary record is predominantly one of braided fluvial systems, a common subfacies within the formation is interpreted to record the passage of straight-crested sand waves across laterally migrating point bars in sinuous rivers, similar to the pattern documented by Singh and Kumar on the modern Ganga and Yamuna Rivers. Because the sand waves were larger on the lower parts of the point bars, lateral migration createdmore » diagnostic thinning-upward, unidirectional cosets of tabular cross-beds as well as fining-upward, grain-size trends. Common, thick, interbedded claystones, deposited in associated paludal and lacustrine environments, and high variance in cross-bed dispersion patterns also suggest the local presence of sinuous fluvial systems within the overall braided regime. The Messak Sandstone contains some of the features that led Harms et al to propose an unconventional low-sinuosity fluvial environment for the Nubian lithofacies in Egypt, and the continuously high water levels of this model may explain channel-scale clay drapes and overturned cross-beds in the Messak. However, most of the Messak characteristics are incompatible with the low-sinuosity model, suggesting instead that the fluvial channels in the Murzuq basin alternated between braided and high-sinuosity patterns.« less

Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics.

PubMed

Cherry, Seth G; Derocher, Andrew E; Thiemann, Gregory W; Lunn, Nicholas J

2013-07-01

Understanding how seasonal environmental conditions affect the timing and distribution of synchronized animal movement patterns is a central issue in animal ecology. Migration, a behavioural adaptation to seasonal environmental fluctuations, is a fundamental part of the life history of numerous species. However, global climate change can alter the spatiotemporal distribution of resources and thus affect the seasonal movement patterns of migratory animals. We examined sea ice dynamics relative to migration patterns and seasonal geographical fidelity of an Arctic marine predator, the polar bear (Ursus maritimus). Polar bear movement patterns were quantified using satellite-linked telemetry data collected from collars deployed between 1991-1997 and 2004-2009. We showed that specific sea ice characteristics can predict the timing of seasonal polar bear migration on and off terrestrial refugia. In addition, fidelity to specific onshore regions during the ice-free period was predicted by the spatial pattern of sea ice break-up but not by the timing of break-up. The timing of migration showed a trend towards earlier arrival of polar bears on shore and later departure from land, which has been driven by climate-induced declines in the availability of sea ice. Changes to the timing of migration have resulted in polar bears spending progressively longer periods of time on land without access to sea ice and their marine mammal prey. The links between increased atmospheric temperatures, sea ice dynamics, and the migratory behaviour of an ice-dependent species emphasizes the importance of quantifying and monitoring relationships between migratory wildlife and environmental cues that may be altered by climate change. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

In Search of Lakshmi's Footprints: A Brief Study of the Use of Surface Design in India. Fulbright-Hays Summer Seminars Abroad, 1997 (India).

ERIC Educational Resources Information Center

Rasmussen, Marie

This paper provides a description of the use of surface design in India and how those patterns have migrated throughout India. This study is confined in interest to the use of design and pattern to convey religious symbolism and other auspicious meanings. The migration of pattern to various parts of India will change the name or the technique, but…

Understanding Historical Human Migration Patterns and Interbreeding (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

ScienceCinema

Willerslev, Eske

2018-02-14

Eske Willerslev from the University of Copenhagen on Understanding Historical Human Migration Patterns and Interbreeding Using the Ancient Genomes of a Palaeo-Eskimo and an Aboriginal Australian at the 7th Annual Genomics of Energy & Environment Meeting on March 21, 2012 in Walnut Creek, California.

Increased Flight Altitudes among Migrating Golden Eagles Suggest Turbine Avoidance at a Rocky Mountain Wind Installation

PubMed Central

Johnston, Naira N.; Bradley, James E.; Otter, Ken A.

2014-01-01

Potential wind-energy development in the eastern Rocky Mountain foothills of British Columbia, Canada, raises concerns due to its overlap with a golden eagle (Aquila chrysaetos) migration corridor. The Dokie 1 Wind Energy Project is the first development in this area and stands as a model for other projects in the area because of regional consistency in topographic orientation and weather patterns. We visually tracked golden eagles over three fall migration seasons (2009–2011), one pre- and two post-construction, to document eagle flight behaviour in relation to a ridge-top wind energy development. We estimated three-dimensional positions of eagles in space as they migrated through our study site. Flight tracks were then incorporated into GIS to ascertain flight altitudes for eagles that flew over the ridge-top area (or turbine string). Individual flight paths were designated to a category of collision-risk based on flight altitude (e.g. flights within rotor-swept height; ≤150 m above ground) and wind speed (winds sufficient for the spinning of turbines; >6.8 km/h at ground level). Eagles were less likely to fly over the ridge-top area within rotor-swept height (risk zone) as wind speed increased, but were more likely to make such crosses under headwinds and tailwinds compared to western crosswinds. Most importantly, we observed a smaller proportion of flights within the risk zone at wind speeds sufficient for the spinning of turbines (higher-risk flights) during post-construction compared to pre-construction, suggesting that eagles showed detection and avoidance of turbines during migration. PMID:24671199

Impact of Hurricanes and Nor'easters on a Migrating Inlet System

NASA Astrophysics Data System (ADS)

Hopkins, J.; Elgar, S.; Raubenheimer, B.

2016-12-01

After breaching in 2007, Katama Inlet, connecting Katama Bay to the Atlantic Ocean on the south shore of Martha's Vineyard, MA, migrated 2 km until it closed in 2015. Bathymetric surveys before and after Hurricanes Irene (2011) and Sandy (2012) indicate the strong waves and currents associated with these storms caused 2 m of erosion and deposition around the inlet mouth. The waves, currents, and bathymetric change observed during the hurricanes were used to validate the hydrodynamic and morphodynamic components of a Delft3D numerical model of the Martha's Vineyard coastline for storm (> 3 m wave heights) conditions. When driven with observed bathymetry and offshore waves, as well as simulated (WaveWatch3) winds and barometric pressures, the model reproduces the pattern and range of bathymetric change observed around the inlet. Model simulations of realistic (i.e., Irene and Sandy) and idealized storm conditions with a range of durations and wave conditions are used to test the relative importance of short-duration, high-intensity storms (hurricanes) and longer-duration, lower-intensity storms (nor'easters) on inlet migration. The simulations suggest that longer-duration, lower-intensity storms cause a higher range and variance in bathymetric change around the inlet than shorter-duration, higher-intensity storms. However, the simulations also suggest that the storm-induced migration of the inlet depends more on the wave direction at the peak of the storm than on the duration of the storm peak. The effect of storms on inlet migration over yearly time scales will be discussed. Funded by NSF, NOAA, ONR, and ASD(R&E).

Increased flight altitudes among migrating golden eagles suggest turbine avoidance at a Rocky Mountain wind installation.

PubMed

Johnston, Naira N; Bradley, James E; Otter, Ken A

2014-01-01

Potential wind-energy development in the eastern Rocky Mountain foothills of British Columbia, Canada, raises concerns due to its overlap with a golden eagle (Aquila chrysaetos) migration corridor. The Dokie 1 Wind Energy Project is the first development in this area and stands as a model for other projects in the area because of regional consistency in topographic orientation and weather patterns. We visually tracked golden eagles over three fall migration seasons (2009-2011), one pre- and two post-construction, to document eagle flight behaviour in relation to a ridge-top wind energy development. We estimated three-dimensional positions of eagles in space as they migrated through our study site. Flight tracks were then incorporated into GIS to ascertain flight altitudes for eagles that flew over the ridge-top area (or turbine string). Individual flight paths were designated to a category of collision-risk based on flight altitude (e.g. flights within rotor-swept height; ≤150 m above ground) and wind speed (winds sufficient for the spinning of turbines; >6.8 km/h at ground level). Eagles were less likely to fly over the ridge-top area within rotor-swept height (risk zone) as wind speed increased, but were more likely to make such crosses under headwinds and tailwinds compared to western crosswinds. Most importantly, we observed a smaller proportion of flights within the risk zone at wind speeds sufficient for the spinning of turbines (higher-risk flights) during post-construction compared to pre-construction, suggesting that eagles showed detection and avoidance of turbines during migration.

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

PubMed Central

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

2015-01-01

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

Seasonal effects of wind conditions on migration patterns of soaring American white pelican.

PubMed

Gutierrez Illan, Javier; Wang, Guiming; Cunningham, Fred L; King, D Tommy

2017-01-01

Energy and time expenditures are determinants of bird migration strategies. Soaring birds have developed migration strategies to minimize these costs, optimizing the use of all the available resources to facilitate their displacement. We analysed the effects of different wind factors (tailwind, turbulence, vertical updrafts) on the migratory flying strategies adopted by 24 satellite-tracked American white pelicans (Pelecanus erythrorhynchos) throughout spring and autumn in North America. We hypothesize that different wind conditions encountered along migration routes between spring and autumn induce pelicans to adopt different flying strategies and use of these wind resources. Using quantile regression and fine-scale atmospheric data, we found that the pelicans optimized the use of available wind resources, flying faster and more direct routes in spring than in autumn. They actively selected tailwinds in both spring and autumn displacements but relied on available updrafts predominantly in their spring migration, when they needed to arrive at the breeding regions. These effects varied depending on the flying speed of the pelicans. We found significant directional correlations between the pelican migration flights and wind direction. In light of our results, we suggest plasticity of migratory flight strategies by pelicans is likely to enhance their ability to cope with the effects of ongoing climate change and the alteration of wind regimes. Here, we also demonstrate the usefulness and applicability of quantile regression techniques to investigate complex ecological processes such as variable effects of atmospheric conditions on soaring migration.

Seasonal effects of wind conditions on migration patterns of soaring American white pelican

PubMed Central

Wang, Guiming; Cunningham, Fred L.; King, D. Tommy

2017-01-01

Energy and time expenditures are determinants of bird migration strategies. Soaring birds have developed migration strategies to minimize these costs, optimizing the use of all the available resources to facilitate their displacement. We analysed the effects of different wind factors (tailwind, turbulence, vertical updrafts) on the migratory flying strategies adopted by 24 satellite-tracked American white pelicans (Pelecanus erythrorhynchos) throughout spring and autumn in North America. We hypothesize that different wind conditions encountered along migration routes between spring and autumn induce pelicans to adopt different flying strategies and use of these wind resources. Using quantile regression and fine-scale atmospheric data, we found that the pelicans optimized the use of available wind resources, flying faster and more direct routes in spring than in autumn. They actively selected tailwinds in both spring and autumn displacements but relied on available updrafts predominantly in their spring migration, when they needed to arrive at the breeding regions. These effects varied depending on the flying speed of the pelicans. We found significant directional correlations between the pelican migration flights and wind direction. In light of our results, we suggest plasticity of migratory flight strategies by pelicans is likely to enhance their ability to cope with the effects of ongoing climate change and the alteration of wind regimes. Here, we also demonstrate the usefulness and applicability of quantile regression techniques to investigate complex ecological processes such as variable effects of atmospheric conditions on soaring migration. PMID:29065188

The Social and Economic Significance of Human Migration in the Western Region. Bulletin 859.

ERIC Educational Resources Information Center

Knop, Edward, Comp.; And Others

Because migration trends in the West and their consequences have sometimes served as indicators of what other regions can expect, it is important that such trends and effects be monitored and analyzed. This bulletin describes patterns of migration, assesses individual and family and social considerations in western migration, and discusses policy…

Impact of migration on fertility and abortion: evidence from the household and welfare study of Accra.

PubMed

Rokicki, Slawa; Montana, Livia; Fink, Günther

2014-12-01

Over the last few decades, total fertility rates, child morbidity, and child mortality rates have declined in most parts of sub-Saharan Africa. Among the most striking trends observed are the rapid rate of urbanization and the often remarkably large gaps in fertility between rural and urban areas. Although a large literature has highlighted the importance of migration and urbanization within countries' demographic transitions, relatively little is known regarding the impact of migration on migrants' reproductive health outcomes in general and abortion in particular. In this article, we use detailed pregnancy and migration histories collected as part of the Household and Welfare Study of Accra (HAWS) to examine the association between migration and pregnancy outcomes among women residing in the urban slums of Accra, Ghana. We find that the completed fertility patterns of lifetime Accra residents are remarkably similar to those of residents who migrated. Our results suggest that recent migrants have an increased risk of pregnancy but not an increased risk of live birth in the first years post-move compared with those who had never moved. This gap seems to be largely explained by an increased risk of miscarriage or abortion among recent migrants. Increasing access to contraceptives for recent migrants has the potential to reduce the incidence of unwanted pregnancies, lower the prevalence of unsafe abortion, and contribute to improved maternal health outcomes.

Amphioxus and lamprey AP-2 genes: implications for neural crest evolution and migration patterns

NASA Technical Reports Server (NTRS)

Meulemans, Daniel; Bronner-Fraser, Marianne

2002-01-01

The neural crest is a uniquely vertebrate cell type present in the most basal vertebrates, but not in cephalochordates. We have studied differences in regulation of the neural crest marker AP-2 across two evolutionary transitions: invertebrate to vertebrate, and agnathan to gnathostome. Isolation and comparison of amphioxus, lamprey and axolotl AP-2 reveals its extensive expansion in the vertebrate dorsal neural tube and pharyngeal arches, implying co-option of AP-2 genes by neural crest cells early in vertebrate evolution. Expression in non-neural ectoderm is a conserved feature in amphioxus and vertebrates, suggesting an ancient role for AP-2 genes in this tissue. There is also common expression in subsets of ventrolateral neurons in the anterior neural tube, consistent with a primitive role in brain development. Comparison of AP-2 expression in axolotl and lamprey suggests an elaboration of cranial neural crest patterning in gnathostomes. However, migration of AP-2-expressing neural crest cells medial to the pharyngeal arch mesoderm appears to be a primitive feature retained in all vertebrates. Because AP-2 has essential roles in cranial neural crest differentiation and proliferation, the co-option of AP-2 by neural crest cells in the vertebrate lineage was a potentially crucial event in vertebrate evolution.

Patterns of testosterone in three Nearctic-Neotropical migratory songbirds during spring passage.

PubMed

Covino, Kristen M; Morris, Sara R; Moore, Frank R

2015-12-01

Preparation for breeding may overlap extensively with vernal migration in long-distance migratory songbirds. Testosterone plays a central role in mediating this transition into breeding condition by facilitating changes to physiology and behavior. While changes in testosterone levels are well studied in captive migrants, these changes are less well known in free-living birds. We examined testosterone levels in free-living Nearctic-Neotropical migrants of three species during their vernal migration. Testosterone levels increased during the migratory period in males of all three species but significantly so in only two. Testosterone levels in females remained the same throughout their migration. Our results support the extensive overlap between vernal migration and breeding preparation in male songbirds. The pattern of testosterone changes during vernal migration is far from clear in females. Copyright © 2015 Elsevier Inc. All rights reserved.

A landscape scale decision support tool for monitoring bird and bat migration across Wisconsin

USGS Publications Warehouse

Suarez, Manuel J.; Heglund, Patricia J.; Kratt, Robert; Kirsch, Eileen

2008-01-01

This project was initiated to begin addressing the question, “Are there patterns in timing, location, and direction among migrating landbirds?” that have been at the forefront of discussion with our Federal, State, and County partners with regard to siting wind energy projects. Our goal was to explore the use of Nexrad weather data to see if examining 5 or more years’ worth of data would provide us with a sense of the general timing, movement patterns and habitat use by migrating landbirds.

Seismic patterns and migration history of submarine fan channels in deep-water area, Niger Delta, West Africa

NASA Astrophysics Data System (ADS)

Zhang, Guotao; Zhang, Shangfeng; Li, Yuan

2015-04-01

The channels of deep-water submarine fan under Niger delta slope are characterized by large dimensions special deposition positions and complex formation processes, its geographical location and sedimentary environment also hinder the research and exploration development. According to the strata slicing, RMS amplitude attribute and other techniques, we exhibit the platforms patterns of channels at different period, and based on the analysis of internal architecture and deformation history of channel-leveed systems, migration and evolution process of channel systems could be understood accurately. A great quantity of isolated channels develop in middle Miocene and aggrading streams in late Miocene, which generating because of large scale of turbidity caused by the drop of second order sea-level, which characterized by vertical accretion at smooth channel, while vertical accretion and lateral migration at bend. Evolution of channel systems can be divided into three stages: the initial erosion, erosion and filling alternately, and abandoned stage. With these three stages, the sinuosity of channel change from moderate to high, then decrease. Incision and filling of channels, being during the three development phases, is the driving force of meander-loops migration, which promote three kinds of migration patterns: lateral, down-system and combination migration. The research provides theoretical basis for high-precision prediction and evaluation of deep-water reservoir.

Genetic landscape of populations along the Silk Road: admixture and migration patterns.

PubMed

Mezzavilla, Massimo; Vozzi, Diego; Pirastu, Nicola; Girotto, Giorgia; d'Adamo, Pio; Gasparini, Paolo; Colonna, Vincenza

2014-12-05

The ancient Silk Road has been a trading route between Europe and Central Asia from the 2(nd) century BCE to the 15(th) century CE. While most populations on this route have been characterized, the genetic background of others remains poorly understood, and little is known about past migration patterns. The scientific expedition "Marco Polo" has recently collected genetic and phenotypic data in six regions (Georgia, Armenia, Azerbaijan, Uzbekistan, Kazakhstan, Tajikistan) along the Silk Road to study the genetics of a number of phenotypes. We characterized the genetic structure of these populations within a worldwide context. We observed a West-East subdivision albeit the existence of a genetic component shared within Central Asia and nearby populations from Europe and Near East. We observed a contribution of up to 50% from Europe and Asia to most of the populations that have been analyzed. The contribution from Asia dates back to ~25 generations and is limited to the Eastern Silk Road. Time and direction of this contribution are consistent with the Mongolian expansion era. We clarified the genetic structure of six populations from Central Asia and suggested a complex pattern of gene flow among them. We provided a map of migration events in time and space and we quantified exchanges among populations. Altogether these novel findings will support the future studies aimed at understanding the genetics of the phenotypes that have been collected during the Marco Polo campaign, they will provide insights into the history of these populations, and they will be useful to reconstruct the developments and events that have shaped modern Eurasians genomes.

Shifting Quaternary migration patterns in the Bahamian archipelago: Evidence from the Zamia pumila complex at the northern limits of the Caribbean island biodiversity hotspot.

PubMed

Salas-Leiva, Dayana E; Meerow, Alan W; Calonje, Michael; Francisco-Ortega, Javier; Griffith, M Patrick; Nakamura, Kyoko; Sánchez, Vanessa; Knowles, Lindy; Knowles, David

2017-05-01

The Bahamas archipelago is formed by young, tectonically stable carbonate banks that harbor direct geological evidence of global ice-volume changes. We sought to detect signatures of major changes on gene flow patterns and reconstruct the phylogeographic history of the monophyletic Zamia pumila complex across the Bahamas. Nuclear molecular markers with both high and low mutation rates were used to capture two different time scale signatures and test several gene flow and demographic hypotheses. Single-copy nuclear genes unveiled apparent ancestral admixture on Andros, suggesting a significant role of this island as main hub of diversity of the archipelago. We detected demographic and spatial expansion of the Zamia pumila complex on both paleo-provinces around the Piacenzian (Pliocene)/Gelasian (Pleistocene). Populations evidenced signatures of different migration models that have occurred at two different times. Populations on Long Island ( Z. lucayana ) may either represent a secondary colonization of the Bahamas by Zamia or a rapid and early-divergence event of at least one population on the Bahamas. Despite changes in migration patterns with global climate, expected heterozygosity with both marker systems remains within the range reported for cycads, but with significant levels of increased inbreeding detected by the microsatellites. This finding is likely associated with reduced gene flow between and within paleo-provinces, accompanied by genetic drift, as rising seas enforced isolation. Our study highlights the importance of the maintenance of the predominant direction of genetic exchange and the role of overseas dispersion among the islands during climate oscillations. © 2017 Botanical Society of America.

Spatio-temporal evolution of female lung cancer mortality in a region of Spain, is it worth taking migration into account?

PubMed

Zurriaga, Oscar; Vanaclocha, Hermelinda; Martinez-Beneito, Miguel A; Botella-Rocamora, Paloma

2008-01-31

The Comunitat Valenciana (CV) is a tourist region on the Mediterranean coast of Spain with a high rate of retirement migration. Lung cancer in women is the cancer mortality cause that has increased most in the CV during the period 1991 to 2000. Moreover, the geographical distribution of risk from this cause in the CV has been previously described and a non-homogenous pattern was determined. The present paper studies the spatio-temporal distribution of lung cancer mortality for women in the CV during the period 1987-2004, in order to gain some insight into the factors, such as migration, that have had an influence on these changes. A novel methodology, consisting of a Bayesian hierarchical model, is used in this paper. Such a model allows the handling of data with a very high disaggregation, while at the same time taking advantage of its spatial and temporal structure. The spatio-temporal pattern which was found points to geographical differences in the time trends of risk. In fact, the southern coastal side of the CV has had a higher increase in risk, coinciding with the settlement of a large foreign community in that area, mainly comprised of elderly people from the European Union. Migration has frequently been ignored as a risk factor in the description of the geographical risk of lung cancer and it is suggested that this factor should be considered, especially in tourist regions. The temporal component in disease mapping provides a more accurate depiction of risk factors acting on the population.

Genetic evidence of an East Asian origin and paleolithic northward migration of Y-chromosome haplogroup N.

PubMed

Shi, Hong; Qi, Xuebin; Zhong, Hua; Peng, Yi; Zhang, Xiaoming; Ma, Runlin Z; Su, Bing

2013-01-01

The Y-chromosome haplogroup N-M231 (Hg N) is distributed widely in eastern and central Asia, Siberia, as well as in eastern and northern Europe. Previous studies suggested a counterclockwise prehistoric migration of Hg N from eastern Asia to eastern and northern Europe. However, the root of this Y chromosome lineage and its detailed dispersal pattern across eastern Asia are still unclear. We analyzed haplogroup profiles and phylogeographic patterns of 1,570 Hg N individuals from 20,826 males in 359 populations across Eurasia. We first genotyped 6,371 males from 169 populations in China and Cambodia, and generated data of 360 Hg N individuals, and then combined published data on 1,210 Hg N individuals from Japanese, Southeast Asian, Siberian, European and Central Asian populations. The results showed that the sub-haplogroups of Hg N have a distinct geographical distribution. The highest Y-STR diversity of the ancestral Hg N sub-haplogroups was observed in the southern part of mainland East Asia, and further phylogeographic analyses supports an origin of Hg N in southern China. Combined with previous data, we propose that the early northward dispersal of Hg N started from southern China about 21 thousand years ago (kya), expanding into northern China 12-18 kya, and reaching further north to Siberia about 12-14 kya before a population expansion and westward migration into Central Asia and eastern/northern Europe around 8.0-10.0 kya. This northward migration of Hg N likewise coincides with retreating ice sheets after the Last Glacial Maximum (22-18 kya) in mainland East Asia.

Overexpression of Polysialylated Neural Cell Adhesion Molecule Improves the Migration Capacity of Induced Pluripotent Stem Cell-Derived Oligodendrocyte Precursors

PubMed Central

Czepiel, Marcin; Leicher, Lasse; Becker, Katja; Boddeke, Erik

2014-01-01

Cell replacement therapy aiming at the compensation of lost oligodendrocytes and restoration of myelination in acquired or congenital demyelination disorders has gained considerable interest since the discovery of induced pluripotent stem cells (iPSCs). Patient-derived iPSCs provide an inexhaustible source for transplantable autologous oligodendrocyte precursors (OPCs). The first transplantation studies in animal models for demyelination with iPSC-derived OPCs demonstrated their survival and remyelinating capacity, but also revealed their limited migration capacity. In the present study, we induced overexpression of the polysialylating enzyme sialyltransferase X (STX) in iPSC-derived OPCs to stimulate the production of polysialic acid-neuronal cell adhesion molecules (PSA-NCAMs), known to promote and facilitate the migration of OPCs. The STX-overexpressing iPSC-derived OPCs showed a normal differentiation and maturation pattern and were able to downregulate PSA-NCAMs when they became myelin-forming oligodendrocytes. After implantation in the demyelinated corpus callosum of cuprizone-fed mice, STX-expressing iPSC-derived OPCs demonstrated a significant increase in migration along the axons. Our findings suggest that the reach and efficacy of iPSC-derived OPC transplantation can be improved by stimulating the OPC migration potential via specific gene modulation. PMID:25069776

Patterns of migrating soaring migrants indicate attraction to marine wind farms.

PubMed

Skov, Henrik; Desholm, Mark; Heinänen, Stefan; Kahlert, Johnny A; Laubek, Bjarke; Jensen, Niels Einar; Žydelis, Ramūnas; Jensen, Bo Præstegaard

2016-12-01

Monitoring of bird migration at marine wind farms has a short history, and unsurprisingly most studies have focused on the potential for collisions. Risk for population impacts may exist to soaring migrants such as raptors with K-strategic life-history characteristics. Soaring migrants display strong dependence on thermals and updrafts and an affinity to land areas and islands during their migration, a behaviour that creates corridors where raptors move across narrow straits and sounds and are attracted to islands. Several migration corridors for soaring birds overlap with the development regions for marine wind farms in NW Europe. However, no empirical data have yet been available on avoidance or attraction rates and behavioural reactions of soaring migrants to marine wind farms. Based on a post-construction monitoring study, we show that all raptor species displayed a significant attraction behaviour towards a wind farm. The modified migratory behaviour was also significantly different from the behaviour at nearby reference sites. The attraction was inversely related to distance to the wind farm and was primarily recorded during periods of adverse wind conditions. The attraction behaviour suggests that migrating raptor species are far more at risk of colliding with wind turbines at sea than hitherto assessed. © 2016 The Author(s).

Travelling Careers: Overseas Migration Patterns in the Professional Lives of Women Attending Girton and Newnham before 1939

ERIC Educational Resources Information Center

Goodman, Joyce; Jacobs, Andrea; Kisby, Fiona; Loader, Helen

2011-01-01

This paper explores the migration patterns of women who studied at Girton and Newnham prior to 1939 through whom dissemination of knowledge and values flowed from Cambridge overseas. It also considers organisations that fostered women's mobility in empire, particularly the Colonial Intelligence League for Educated Women and the International…

An Analysis of Rural Manpower Migration Patterns in the South Plains Region of Texas.

ERIC Educational Resources Information Center

Stapleton, Richard C.

Because of declining prices for sorghum and cotton, increased operating costs, and reduction in the underground water level, opportunities for male high school graduates in the Southern Plains region have declined in recent years. The study collected data on migration patterns of males who graduated during the 1953-63 period by surveying high…

Identifying change in spatial accumulation of soil salinity in an inland river watershed, China.

PubMed

Wang, Yugang; Deng, Caiyun; Liu, Yan; Niu, Ziru; Li, Yan

2018-04-15

Soil salinity accumulation is strong in arid areas and it has become a serious environmental problem. Knowledge of the process and spatial changes of accumulated salinity in soil can provide an insight into the spatial patterns of soil salinity accumulation. This is especially useful for estimating the spatial transport of soil salinity at the watershed scale. This study aimed to identify spatial patterns of salt accumulation in the top 20cm soils in a typical inland watershed, the Sangong River watershed in arid northwest China, using geostatistics, spatial analysis technology and the Lorenz curve. The results showed that: (1) soil salt content had great spatial variability (coefficient variation >1.0) in both in 1982 and 2015, and about 56% of the studied area experienced transition the degree of soil salt content from one class to another during 1982-2015. (2) Lorenz curves describing the proportions of soil salinity accumulation (SSA) identified that the boundary between soil salinity migration and accumulation regions was 24.3m lower in 2015 than in 1982, suggesting a spatio-temporal inequality in loading of the soil salinity transport region, indicating significant migration of soil salinity from the upstream to the downstream watershed. (3) Regardless of migration or accumulation region, the mean value of SSA per unit area was 0.17kg/m 2 higher in 2015 than 1982 (p<0.01) and the increasing SSA per unit area in irrigated land significantly increased by 0.19kg/m 2 compared with the migration region. Dramatic accumulation of soil salinity in all land use types was clearly increased by 0.29kg/m 2 in this agricultural watershed during the studied period in the arid northwest of China. This study demonstrates the spatial patterns of soil salinity accumulation, which is particularly useful for estimating the spatial transport of soil salinity at the watershed scale. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluating methods to visualize patterns of genetic differentiation on a landscape.

PubMed

House, Geoffrey L; Hahn, Matthew W

2018-05-01

With advances in sequencing technology, research in the field of landscape genetics can now be conducted at unprecedented spatial and genomic scales. This has been especially evident when using sequence data to visualize patterns of genetic differentiation across a landscape due to demographic history, including changes in migration. Two recent model-based visualization methods that can highlight unusual patterns of genetic differentiation across a landscape, SpaceMix and EEMS, are increasingly used. While SpaceMix's model can infer long-distance migration, EEMS' model is more sensitive to short-distance changes in genetic differentiation, and it is unclear how these differences may affect their results in various situations. Here, we compare SpaceMix and EEMS side by side using landscape genetics simulations representing different migration scenarios. While both methods excel when patterns of simulated migration closely match their underlying models, they can produce either un-intuitive or misleading results when the simulated migration patterns match their models less well, and this may be difficult to assess in empirical data sets. We also introduce unbundled principal components (un-PC), a fast, model-free method to visualize patterns of genetic differentiation by combining principal components analysis (PCA), which is already used in many landscape genetics studies, with the locations of sampled individuals. Un-PC has characteristics of both SpaceMix and EEMS and works well with simulated and empirical data. Finally, we introduce msLandscape, a collection of tools that streamline the creation of customizable landscape-scale simulations using the popular coalescent simulator ms and conversion of the simulated data for use with un-PC, SpaceMix and EEMS. © 2017 John Wiley & Sons Ltd.

Migration speed and directionality switch of normal epithelial cells after TGF-β1-induced EMT (tEMT) on micro-structured polydimethylsiloxane (PDMS) substrates with variations in stiffness and topographic patterning.

PubMed

Wu, Tsung-Hsien; Li, Chia-Hui; Tang, Ming-Jer; Liang, Jen-I; Chen, Chia-Hsin; Yeh, Ming-Long

2013-10-01

The epithelial to mesenchymal transition (EMT) involves several physiological and pathological phenomena and endows cells with invasive and migratory properties. However, the effects of substrate stiffness and topography on the migration of cells before or after transforming growth factor-β1 (TGF-β1)-induced EMT (tEMT) are unknown. Herein, we seed control or tEMT NMuMG cells on the 2D patterns consisted of 1 μm or 5 μm line-widths and groove or cone patterns on either 2 MPa (1.96 ± 0.48 MPa) or 4 MPa (3.70 ± 0.74 MPa) polydimethylsiloxane (PDMS) substrates. After tEMT, the increased expression of α-SMA with vinculin in focal adhesion (FA) sites led to an acceleration of tEMT cell motility. On the 2 MPa substrate, the most influenced substrate was the 1 μm, cone-patterned substrate, where the tEMT cells' motility decelerated by 0.13 μm/min (36% slower than the cells on groove pattern). However, on the 5 μm, groove-patterned substrate, where the tEMT cells demonstrated the most rapid motility relative to the control cells, with an increment of 0.18 μm/min (100%). Among the different physical cues from substrate, the cone pattern could impede the migration speed of tEMT cells. Furthermore, we recommend the groove-patterned with a 5 μm line-width substrate as a useful tool to differentiate control and tEMT cells by migration speed.

Capitalist development and internal migration in Nigeria.

PubMed

Akor, R I; Mou, D

1986-12-01

The authors analyze internal migration trends in Nigeria by examining individual household strategies and how they have adapted to structural changes brought about by colonial rule and capitalist development. The first section of this article describes the structural changes that started the process of labor migration. The second section deals with post-independence industrialization and the consequent rural-urban migration. The final section analyzes the consequences of these migration patterns for urban growth and rural productivity.

Wind effects on the migration routes of trans-Saharan soaring raptors: geographical, seasonal, and interspecific variation

PubMed Central

Vidal-Mateo, Javier; Mellone, Ugo; López-López, Pascual; La Puente, Javier De; García-Ripollés, Clara; Bermejo, Ana; Urios, Vicente

2016-01-01

Abstract Wind is among the most important environmental factors shaping birds’ migration patterns. Birds must deal with the displacement caused by crosswinds and their behavior can vary according to different factors such as flight mode, migratory season, experience, and distance to goal areas. Here we analyze the relationship between wind and migratory movements of three raptor species which migrate by soaring–gliding flight: Egyptian vulture Neophron percnopterus, booted eagle Aquila pennata, and short-toed snake eagle Circaetus gallicus. We analyzed daily migratory segments (i.e., the path joining consecutive roosting locations) using data recorded by GPS satellite telemetry. Daily movements of Egyptian vultures and booted eagles were significantly affected by tailwinds during both autumn and spring migrations. In contrast, daily movements of short-toed eagles were only significantly affected by tailwinds during autumn migration. The effect of crosswinds was significant in all cases. Interestingly, Egyptian vultures and booted eagles showed latitudinal differences in their behavior: both species compensated more frequently at the onset of autumn migration and, at the end of the season when reaching their wintering areas, the proportion of drift segments was higher. In contrast, there was a higher drift at the onset of spring migration and a higher compensation at the end. Our results highlight the effect of wind patterns on the migratory routes of soaring raptors, with different outcomes in relation to species, season, and latitude, ultimately shaping the loop migration patterns that current tracking techniques are showing to be widespread in many long distance migrants. PMID:29491895

Circular Migration and Young Child Malnutrition in Guatemala.

ERIC Educational Resources Information Center

Teller, Charles H.; Butz, William P.

This paper examined the relationship between temporary migration and childhood malnutrition in Guatemala and questioned whether migration patterns or low socioeconomic status produced a special risk group. The study emphasized policy implications of high priorities placed on population redistribution in Latin American governments and the…

40 CFR 264.601 - Environmental performance standards.

Code of Federal Regulations, 2011 CFR

2011-07-01

... to migration of waste constituents in the ground water or subsurface environment, considering: (1... for migration through soil, liners, or other containing structures; (2) The hydrologic and geologic... users; (6) The patterns of land use in the -region; (7) The potential for deposition or migration of...

Integrative Mechanisms of Oriented Neuronal Migration in the Developing Brain

PubMed Central

Evsyukova, Irina; Plestant, Charlotte; Anton, E.S.

2014-01-01

The emergence of functional neuronal connectivity in the developing cerebral cortex depends on neuronal migration. This process enables appropriate positioning of neurons and the emergence of neuronal identity so that the correct patterns of functional synaptic connectivity between the right types and numbers of neurons can emerge. Delineating the complexities of neuronal migration is critical to our understanding of normal cerebral cortical formation and neurodevelopmental disorders resulting from neuronal migration defects. For the most part, the integrated cell biological basis of the complex behavior of oriented neuronal migration within the developing mammalian cerebral cortex remains an enigma. This review aims to analyze the integrative mechanisms that enable neurons to sense environmental guidance cues and translate them into oriented patterns of migration toward defined areas of the cerebral cortex. We discuss how signals emanating from different domains of neurons get integrated to control distinct aspects of migratory behavior and how different types of cortical neurons coordinate their migratory activities within the developing cerebral cortex to produce functionally critical laminar organization. PMID:23937349

Toward conservation of midcontinental shorebird migrations

USGS Publications Warehouse

Skagen, Susan K.; Knopf, Fritz L.

1993-01-01

Shorebirds represent a highly diverse group of species, many of which experience tremendous energy demands associated with long-distance migratory flights. Transcontinental migrants are dependant upon dynamic freshwater wetlands for stopover resources essential for replenishment of lipid reserves and completion of migration. Patterns of shorebird migration across midcontinental wetlands were detected from migration reports to American Birds and information provided by U.S. Fish and Wildlife Service national wildlife refuges. Patterns in species composition and abundance varied geographically, emphasizing the uniqueness of different regions to migrating shorebirds. Smaller species and neotropical migrants moved primarily across the Great Plains, whereas larger species and North American migrants predominated in assemblages in the intermountain west. Shorebirds were broadly dispersed in wetland habitats with dynamic water regimes. Whereas populations of shorebirds in coastal system appear to concentrate at sites of seasonally predictable and abundant food resources, we propose that transcontinental shorebirds disperse and use wetlands opportunistically. This migration system exemplifies the need for large-scale, coordinated regional management efforts that recognize the dynamic nature of ecosystem processes.

Migration and Vulnerability among Adolescents in Slum Areas of Addis Ababa, Ethiopia

ERIC Educational Resources Information Center

Erulkar, Annabel S.; Mekbib, Tekle-Ab; Simie, Negussie; Gulema, Tsehai

2006-01-01

Studies of urban rural migration often find the most likely migrants are adolescents and young people. Yet few studies have explored patterns of adolescent migration and the role of migration in transitions to adulthood. This study uses data from a population-based survey of over 1000 adolescents aged 10-19 in slum areas of Addis Ababa.…

Migration timing of female kokanee salmon Oncorhynchus nerka: diel patterns and effects of maturation state.

PubMed

Warren, M A; Morbey, Y E

2012-09-01

Diel patterns of migration and migration speed were compared between reproductive timing phenotypes in female kokanee salmon Oncorhynchus nerka. Females of varying degrees of reproductive maturation were captured on their migration route to the Meadow Creek Spawning Channel (British Columbia, Canada), were tagged with passive-integrated transponders (PIT tags) and were subsequently monitored with stationary receivers. Females showed crepuscular migration timing, with approximately equal detections at dawn and dusk. In particular, peaks of movement were associated with the appearance of the sun over the mountains in the east and the disappearance of the sun over the mountains in the west. Over 25 m, migration speed was 1·0 body lengths (measured as fork length; L(F)) s(-1) and did not depend on maturation state. Over 3 km, migration speed was much slower (0·2-0·3 L(F) s(-1)) than over the short distance, with less mature females migrating more slowly than more mature females. Less mature females appeared to be in less of a hurry to reach breeding areas compared with more mature females. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

Landbird migration in the American West: Recent progress and future research directions

USGS Publications Warehouse

Carlisle, J.D.; Skagen, S.K.; Kus, B.E.; van Riper, Charles; Paxton, K.L.; Kelly, J.F.

2009-01-01

Our knowledge of avian behaviors during the nonbreeding period still lags behind that of the breeding season, but the last decade has witnessed a proliferation in research that has yielded significant progress in understanding migration patterns of North American birds. And, although historically the great majority of migration research has been conducted in the eastern half of the continent, there has been much recent progress on aspects of avian migration in the West. In particular, expanded use of techniques such as radar, plasma metabolites, mist-netting, count surveys, stable isotopes, genetic data, and animal tracking, coupled with an increase in multi-investigator collaborations, have all contributed to this growth of knowledge. There is increasing recognition that migration is likely the most limiting time of year for migratory birds, increasing the importance of continuing to decipher patterns of stopover ecology, identifying critical stopover habitats, and documenting migration routes in the diverse and changing landscapes of the American West. Here, we review and briefly synthesize the latest findings and advances in avian migration and consider research needs to guide future research on migration in the West. ?? 2009 by The Cooper Ornithological Society. All rights reserved.

Seasonal and Diel Vocalization Patterns of Antarctic Blue Whale (Balaenoptera musculus intermedia) in the Southern Indian Ocean: A Multi-Year and Multi-Site Study.

PubMed

Leroy, Emmanuelle C; Samaran, Flore; Bonnel, Julien; Royer, Jean-Yves

2016-01-01

Passive acoustic monitoring is an efficient way to provide insights on the ecology of large whales. This approach allows for long-term and species-specific monitoring over large areas. In this study, we examined six years (2010 to 2015) of continuous acoustic recordings at up to seven different locations in the Central and Southern Indian Basin to assess the peak periods of presence, seasonality and migration movements of Antarctic blue whales (Balaenoptera musculus intermedia). An automated method is used to detect the Antarctic blue whale stereotyped call, known as Z-call. Detection results are analyzed in terms of distribution, seasonal presence and diel pattern of emission at each site. Z-calls are detected year-round at each site, except for one located in the equatorial Indian Ocean, and display highly seasonal distribution. This seasonality is stable across years for every site, but varies between sites. Z-calls are mainly detected during autumn and spring at the subantarctic locations, suggesting that these sites are on the Antarctic blue whale migration routes, and mostly during winter at the subtropical sites. In addition to these seasonal trends, there is a significant diel pattern in Z-call emission, with more Z-calls in daytime than in nighttime. This diel pattern may be related to the blue whale feeding ecology.

Seasonal and Diel Vocalization Patterns of Antarctic Blue Whale (Balaenoptera musculus intermedia) in the Southern Indian Ocean: A Multi-Year and Multi-Site Study

PubMed Central

Leroy, Emmanuelle C.; Samaran, Flore; Bonnel, Julien; Royer, Jean-Yves

2016-01-01

Passive acoustic monitoring is an efficient way to provide insights on the ecology of large whales. This approach allows for long-term and species-specific monitoring over large areas. In this study, we examined six years (2010 to 2015) of continuous acoustic recordings at up to seven different locations in the Central and Southern Indian Basin to assess the peak periods of presence, seasonality and migration movements of Antarctic blue whales (Balaenoptera musculus intermedia). An automated method is used to detect the Antarctic blue whale stereotyped call, known as Z-call. Detection results are analyzed in terms of distribution, seasonal presence and diel pattern of emission at each site. Z-calls are detected year-round at each site, except for one located in the equatorial Indian Ocean, and display highly seasonal distribution. This seasonality is stable across years for every site, but varies between sites. Z-calls are mainly detected during autumn and spring at the subantarctic locations, suggesting that these sites are on the Antarctic blue whale migration routes, and mostly during winter at the subtropical sites. In addition to these seasonal trends, there is a significant diel pattern in Z-call emission, with more Z-calls in daytime than in nighttime. This diel pattern may be related to the blue whale feeding ecology. PMID:27828976

FoxP2 protein levels regulate cell morphology changes and migration patterns in the vertebrate developing telencephalon.

PubMed

Garcia-Calero, Elena; Botella-Lopez, Arancha; Bahamonde, Olga; Perez-Balaguer, Ariadna; Martinez, Salvador

2016-07-01

In the mammalian telencephalon, part of the progenitor cells transition from multipolar to bipolar morphology as they invade the mantle zone. This associates with changing patterns of radial migration. However, the molecules implicated in these morphology transitions are not well known. In the present work, we analyzed the function of FoxP2 protein in this process during telencephalic development in vertebrates. We analyzed the expression of FoxP2 protein and its relation with cell morphology and migratory patterns in mouse and chicken developing striatum. We observed FoxP2 protein expressed in a gradient from the subventricular zone to the mantle layer in mice embryos. In the FoxP2 low domain cells showed multipolar migration. In the striatal mantle layer where FoxP2 protein expression is higher, cells showed locomoting migration and bipolar morphology. In contrast, FoxP2 showed a high and homogenous expression pattern in chicken striatum, thus bipolar morphology predominated. Elevation of FoxP2 in the striatal subventricular zone by in utero electroporation promoted bipolar morphology and impaired multipolar radial migration. In mouse cerebral cortex we obtained similar results. FoxP2 promotes transition from multipolar to bipolar morphology by means of gradiental expression in mouse striatum and cortex. Together these results indicate a role of FoxP2 differential expression in cell morphology control of the vertebrate telencephalon.

Boyfriends and booty calls: sexual partnership patterns among Canadian Aboriginal young people.

PubMed

Devries, Karen M; Free, Caroline J

2011-01-01

Sexual partnership patterns, forced sex, and condom non-use can contribute to STI risk, but little is known about these patterns among Aboriginal young people despite elevated STI risk in this group. We describe sexual relationship and condom use patterns among Canadian Aboriginal young people, and how these patterns relate to the socio-structural context as experienced by young people. We use data from in-depth individual interviews conducted in 2004 with 22 young people who reported ever having sex and who self-identified as Aboriginal in British Columbia, Canada. A thematic analysis is presented. Young people described a range of partnership patterns, including 'on-off' relationships which could have high rates of partner turnover but could sometimes be viewed as acceptable contexts for pregnancy, precluding condom use. Contextual elements beyond individual control appeared to contribute to these patterns. Migration between geographic locations was linked with risky partnership patterns, especially if it was linked with family instability or substance use problems. Sexual health interventions for this group must address partnership patterns in addition to promoting condom use. Survey research into 'migration' as a risk factor for STI transmission should consider reasons for migration. Interventions that address both individual level behaviour and the contextual elements that shape behaviour should be developed and tested.

Ancestral Polymorphisms and Sex-Biased Migration Shaped the Demographic History of Brown Bears and Polar Bears

PubMed Central

Nakagome, Shigeki; Mano, Shuhei; Hasegawa, Masami

2013-01-01

Recent studies have reported discordant gene trees in the evolution of brown bears and polar bears. Genealogical histories are different among independent nuclear loci and between biparentally inherited autosomal DNA (aDNA) and matrilineal mitochondrial DNA (mtDNA). Based on multi-locus genomic sequences from aDNA and mtDNA, we inferred the population demography of brown and polar bears and found that brown bears have 6 times (aDNA) or more than 14 times (mtDNA) larger population sizes than polar bears and that polar bear lineage is derived from within brown bear diversity. In brown bears, the effective population size ratio of mtDNA to aDNA was at least 0.62, which deviated from the expected value of 0.25, suggesting matriarchal population due to female philopatry and male-biased migration. These results emphasize that ancestral polymorphisms and sex-biased migration may have contributed to conflicting branching patterns in brown and polar bears across aDNA genes and mtDNA. PMID:24236053

Genomic Analyses Reveal the Influence of Geographic Origin, Migration, and Hybridization on Modern Dog Breed Development.

PubMed

Parker, Heidi G; Dreger, Dayna L; Rimbault, Maud; Davis, Brian W; Mullen, Alexandra B; Carpintero-Ramirez, Gretchen; Ostrander, Elaine A

2017-04-25

There are nearly 400 modern domestic dog breeds with a unique histories and genetic profiles. To track the genetic signatures of breed development, we have assembled the most diverse dataset of dog breeds, reflecting their extensive phenotypic variation and heritage. Combining genetic distance, migration, and genome-wide haplotype sharing analyses, we uncover geographic patterns of development and independent origins of common traits. Our analyses reveal the hybrid history of breeds and elucidate the effects of immigration, revealing for the first time a suggestion of New World dog within some modern breeds. Finally, we used cladistics and haplotype sharing to show that some common traits have arisen more than once in the history of the dog. These analyses characterize the complexities of breed development, resolving longstanding questions regarding individual breed origination, the effect of migration on geographically distinct breeds, and, by inference, transfer of trait and disease alleles among dog breeds. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Ancestral polymorphisms and sex-biased migration shaped the demographic history of brown bears and polar bears.

PubMed

Nakagome, Shigeki; Mano, Shuhei; Hasegawa, Masami

2013-01-01

Recent studies have reported discordant gene trees in the evolution of brown bears and polar bears. Genealogical histories are different among independent nuclear loci and between biparentally inherited autosomal DNA (aDNA) and matrilineal mitochondrial DNA (mtDNA). Based on multi-locus genomic sequences from aDNA and mtDNA, we inferred the population demography of brown and polar bears and found that brown bears have 6 times (aDNA) or more than 14 times (mtDNA) larger population sizes than polar bears and that polar bear lineage is derived from within brown bear diversity. In brown bears, the effective population size ratio of mtDNA to aDNA was at least 0.62, which deviated from the expected value of 0.25, suggesting matriarchal population due to female philopatry and male-biased migration. These results emphasize that ancestral polymorphisms and sex-biased migration may have contributed to conflicting branching patterns in brown and polar bears across aDNA genes and mtDNA.

Analysis of Peristaltic Waves & their Role in Migrating Physarum Plasmodia

NASA Astrophysics Data System (ADS)

Lewis, Owen; Guy, Robert

2017-11-01

The true slime mold Physarum polycephalum exhibits a vast array of sophisticated manipulations of its intracellular cytoplasm. Growing microplasmodia of physarum have been observed to adopt an elongated tadpole shape, then contract in a rhythmic, traveling wave pattern that resembles peristaltic pumping. This contraction drives a fast flow of non-gelated cytoplasm along the cell longitudinal axis. It has been hypothesized that this flow of cytoplasm is a driving factor in generating motility of the plasmodium. In this work, we use two different mathematical models to investigate how peristaltic pumping within physarum may be used to drive cellular motility. We compare the relative phase of flow and deformation waves predicted by both models to similar phase data collected from in vivo experiments using physarum plasmodia. Both models suggest that a mechanical asymmetry in the cell is required to reproduce the experimental observations. Such a mechanical asymmetry is also shown to increase the potential for cellular migration, as measured by both stress generation and migration velocity.

Global Migration Dynamics Underlie Evolution and Persistence of Human Influenza A (H3N2)

PubMed Central

Bedford, Trevor; Cobey, Sarah; Beerli, Peter; Pascual, Mercedes

2010-01-01

The global migration patterns of influenza viruses have profound implications for the evolutionary and epidemiological dynamics of the disease. We developed a novel approach to reconstruct the genetic history of human influenza A (H3N2) collected worldwide over 1998 to 2009 and used it to infer the global network of influenza transmission. Consistent with previous models, we find that China and Southeast Asia lie at the center of this global network. However, we also find that strains of influenza circulate outside of Asia for multiple seasons, persisting through dynamic migration between northern and southern regions. The USA acts as the primary hub of temperate transmission and, together with China and Southeast Asia, forms the trunk of influenza's evolutionary tree. These findings suggest that antiviral use outside of China and Southeast Asia may lead to the evolution of long-term local and potentially global antiviral resistance. Our results might also aid the design of surveillance efforts and of vaccines better tailored to different geographic regions. PMID:20523898

Genetic distinction between contiguous urban and rural multimammate mice in Tanzania despite gene flow.

PubMed

Gryseels, S; Goüy de Bellocq, J; Makundi, R; Vanmechelen, K; Broeckhove, J; Mazoch, V; Šumbera, R; Zima, J; Leirs, H; Baird, S J E

2016-10-01

Special conditions are required for genetic differentiation to arise at a local geographical scale in the face of gene flow. The Natal multimammate mouse, Mastomys natalensis, is the most widely distributed and abundant rodent in sub-Saharan Africa. A notorious agricultural pest and a natural host for many zoonotic diseases, it can live in close proximity to humans and appears to compete with other rodents for the synanthropic niche. We surveyed its population genetic structure across a 180-km transect in central Tanzania along which the landscape varied between agricultural land in a rural setting and natural woody vegetation, rivers, roads and a city (Morogoro). We sampled M. natalensis across 10 localities and genotyped 15 microsatellite loci from 515 individuals. Hierarchical STRUCTURE analyses show a K-invariant pattern distinguishing Morogoro suburbs (located in the centre of the transect) from nine surrounding rural localities. Landscape connectivity analyses in Circuitscape and comparison of rainfall patterns suggest that neither geographical isolation nor natural breeding asynchrony could explain the genetic differentiation of the urban population. Using the isolation-with-migration model implemented in IMa2, we inferred that a split between suburban and rural populations would have occurred recently (<150 years ago) with higher urban effective population density consistent with an urban source to rural sink of effective migration. The observed genetic differentiation of urban multimammate mice is striking given the uninterrupted distribution of the animal throughout the landscape and the high estimates of effective migration (2N e M = 3.0 and 29.7), suggesting a strong selection gradient across the urban boundary. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Evolutionary origin of the latitudinal diversity gradient in liverworts.

PubMed

Laenen, Benjamin; Patiño, Jairo; Hagborg, Anders; Désamoré, Aurélie; Wang, Jian; Jonathan Shaw, A; Goffinet, Bernard; Vanderpoorten, Alain

2018-06-08

A latitudinal diversity gradient towards the tropics appears as one most recurrent patterns in ecology, but the mechanisms underlying this pattern remain an area of controversy. In angiosperms, the tropical conservatism hypothesis proposes that most groups originated in the tropics and are adapted to a tropical climatic regime, and that relatively few species have evolved physiological adaptations to cold, dry or unpredictable climates. This mechanism is, however, unlikely to apply across land plants, and in particular, to liverworts, a group of about 7500 species, whose ability to withstand cold much better than their tracheophyte counterparts is at odds with the tropical conservatism hypothesis. Molecular dating, diversification rate analyses and ancestral area reconstructions were employed to explore the evolutionary mechanisms that account for the latitudinal diversity gradient in liverworts. As opposed to angiosperms, tropical liverwort genera are not older than their extra-tropical counterparts (median stem age of tropical and extra-tropical liverwort genera of 24.35±39.65 Ma and 39.57±49.07 Ma, respectively), weakening the 'time for speciation hypothesis'. Models of ancestral area reconstructions with equal migration rates between tropical and extra-tropical regions outperformed models with asymmetrical migration rates in either direction. The symmetry and intensity of migrations between tropical and extra-tropical regions suggested by the lack of resolution in ancestral area reconstructions towards the deepest nodes are at odds with the tropical niche conservatism hypothesis. In turn, tropical genera exhibited significantly higher net diversification rates than extra-tropical ones, suggesting that the observed latitudinal diversity gradient results from either higher extinction rates in extra-tropical lineages or higher speciation rates in the tropics. We discuss a series of experiments to help deciphering the underlying evolutionary mechanisms. Copyright © 2018. Published by Elsevier Inc.

Parabolic distribution of circumeastern Snake River Plain seismicity and latest Quaternary faulting: Migratory pattern and association with the Yellowstone hotspot

NASA Astrophysics Data System (ADS)

Anders, Mark H.; Geissman, John Wm.; Piety, Lucille A.; Sullivan, J. Timothy

1989-02-01

The Intermountain and Idaho seismic belts within Idaho, Wyoming, and Montana form an unusual parabolic pattern about the axis of the aseismic eastern Snake River Plain (SRP). This pattern is also reflected in the distribution of latest Quaternary normal faults. Several late Cenozoic normal faults that trend perpendicular to the axis of the eastern SRP extend from the aseismic region to the region of latest Quaternary faulting and seismicity. A study of the late Miocene to Holocene displacement history of one of these, the Grand Valley fault system in southeastern Idaho and western Wyoming, indicates that a locus of high displacement rates has migrated away from the eastern SRP to its present location in southern Star Valley in western Wyoming. In Swan Valley the studied area closest to the eastern SRP, isotopic ages, and paleomagnetic data for over 300 samples from 47 sites on well-exposed late Cenozoic volcanic rocks (the tuff of Spring Creek, the tuff of Heise, the Huckleberry Ridge tuff, the Pine Creek Basalt, and an older tuff thought to be the tuff of Cosgrove Road) are used to demonstrate differences in the displacement rate on the Grand Valley fault over the last ˜10 m.y. Tectonic tilts for these volcanic rocks are estimated by comparing the results of paleomagnetic analyses in Swan Valley to similar analyses of samples from undeformed volcanic rocks outside of Swan Valley. Basin geometry and tilt axes are established using seismic reflection profiles and field mapping. Combining these data with the tilt data makes it possible to calculate displacement rates during discrete temporal intervals. An average displacement rate of ˜1.8 mm/yr is calculated for the Grand Valley fault in Swan Valley between 4.4 and 2.0 Ma. In the subsequent 2.0-m.y. interval the rate dropped 2 orders of magnitude to ˜0.014 mm/yr; during the preceding 5.5-m.y. interval the displacement rate is ˜0.15 mm/yr, or about 1 order of magnitude less than the rate between 4.4 and 2.0 Ma. Mapping of fault scarps and unfaulted deposits along the Grand Valley fault system shows that latest Quaternary fault scarps are restricted to the portion farthest from the eastern SRP, the southern part of the Star Valley fault. Surface displacements estimated from scarp profiles and deposit ages estimated from soil development suggest a latest Quaternary displacement rate of 0.6-1.2 mm/yr for the southern portion of the Star Valley fault. Morphologic evidence suggests that this displacement rate persisted on the Star Valley fault throughout most of the Quaternary. The latest Quaternary displacement rate calculated for the southern portion of the Star Valley fault is similar to the rate calculated for Swan Valley during the interval from 2.0 to 4.4 Ma. This similarity, together with evidence for a low Quaternary displacement rate on the fault system in Swan Valley, suggests that the location of the highest displacement rate has migrated away from the eastern SRP. Other normal faults in southeastern Idaho, northwestern Wyoming, and southwestern Montana, while less well described than the Grand Valley fault system, exhibit a similar outward migrating pattern of increased fault activity followed by quiescence. Furthermore, a temporal and spatial relationship between fault activity and the 3.5 cm/yr northeastward track of the Yellowstone hotspot is observable on the Grand Valley fault system and on other north-northwest trending late Cenozoic faults that border the eastern SRP. The temporal and spatial relationship of Miocene to present high displacement rates for other circumeastern SRP faults and the observable outwardly migrating pattern of fault activity suggest that a similar parabolic distribution of seismicity and high displacement rates was symmetrically positioned about the former position of the hotspot. Moreover, the tandem migration of the hotspot and the parabolic distribution of increased fault activity and seismicity are closely followed by a parabolic-shaped "collapse shadow," or region of fault inactivity and aseismicity. We suggest that the outwardly migrating pattern of increased fault activity (active region) results from reduced integrated lithospheric strength caused by thermal effects of the hotspot. Conversely, the outwardly propagating quiescent region is the result of a reduction or "collapse" of crustal extension rates caused by increased integrated lithospheric strength. Lithospheric strength in this region is increased by addition of mafic materials at the base of the crust and at midcrustal levels. Although the strength of the mantle portion of the lithosphere is reduced, the increased strength of the crust results in a total integrated increase in lithospheric strength. Paradoxically, the surface heat flow data suggest that the region within the interior parabola has a higher heat flow (after accounting for the cooling effects of the eastern SRP aquifer) than the adjacent regions, yet the interior region exhibits significantly lower extension rates. It appears that in this region the surface heat flow is not a good predictor of rates of lithospheric extension.

[Ethnic dimension to migration in the Senegal river valley].

PubMed

Traore, S

1993-08-01

Studies of the factors determining migratory patterns in the Senegal River Valley usually stress the importance of economic factors related to colonial domination. But when cultural factors and the social relations governing them are examined in a comparative study of ethnic groups, distinct population subgroups may be revealed to have differential migratory patterns. The Soninka and the Poular, two groups highly affected by migration, were chosen for an analysis of the impact of specific historical experiences on migratory behavior. A historical analysis of colonial archives and anthropological and historical monographs and the 1982-83 "Survey of Migration in the Valley of the Senegal River" provided data. The survey indicated that Soninka and Poular migratory patterns differed from each other, but that both differed from the migratory patterns of all other ethnic groups in the region. Soninka migration is international and oriented primarily toward Europe. It has recently become more intense than that of the poular. The determinants of migration in the two groups appear related more to the structure of households than to lack of educational and health facilities or even of food at the village level. Pastoral life and its associated beliefs and religious ideology appear to have been the principal determinants of precolonial movement among the Poular, while Soninka migration responded more to competition over control of manpower. Itinerant commercial activity was coupled with use of slave labor to ensure food production. But the suppression of slavery and crises of subsistence aggravated by colonial policy provoked ever more distant migration, which found a focus in the French demand for labor after World War II. Migration as an alternative does not appear to have been as significant for the Poular until more recently, when subsistence agriculture and the sale of animals were no longer sufficient to cover monetary needs. Male migration among the Soninka is a consequence of the sexual division of labor in which men were primarily responsible for economic activity and the movement of women was controlled in the interests of social cohesion. The movement of young people is now related to the hopes of older family members for social and economic advancement.

The workforce for health in a globalized context--global shortages and international migration.

PubMed

Aluttis, Christoph; Bishaw, Tewabech; Frank, Martina W

2014-01-01

The 'crisis in human resources' in the health sector has been described as one of the most pressing global health issues of our time. The World Health Organization (WHO) estimates that the world faces a global shortage of almost 4.3 million doctors, midwives, nurses, and other healthcare professionals. A global undersupply of these threatens the quality and sustainability of health systems worldwide. This undersupply is concurrent with globalization and the resulting liberalization of markets, which allow health workers to offer their services in countries other than those of their origin. The opportunities of health workers to seek employment abroad has led to a complex migration pattern, characterized by a flow of health professionals from low- to high-income countries. This global migration pattern has sparked a broad international debate about the consequences for health systems worldwide, including questions about sustainability, justice, and global social accountabilities. This article provides a review of this phenomenon and gives an overview of the current scope of health workforce migration patterns. It further focuses on the scientific discourse regarding health workforce migration and its effects on both high- and low-income countries in an interdependent world. The article also reviews the internal and external factors that fuel health worker migration and illustrates how health workforce migration is a classic global health issue of our time. Accordingly, it elaborates on the international community's approach to solving the workforce crisis, focusing in particular on the WHO Code of Practice, established in 2010.

The workforce for health in a globalized context – global shortages and international migration

PubMed Central

Aluttis, Christoph; Bishaw, Tewabech; Frank, Martina W.

2014-01-01

The ‘crisis in human resources’ in the health sector has been described as one of the most pressing global health issues of our time. The World Health Organization (WHO) estimates that the world faces a global shortage of almost 4.3 million doctors, midwives, nurses, and other healthcare professionals. A global undersupply of these threatens the quality and sustainability of health systems worldwide. This undersupply is concurrent with globalization and the resulting liberalization of markets, which allow health workers to offer their services in countries other than those of their origin. The opportunities of health workers to seek employment abroad has led to a complex migration pattern, characterized by a flow of health professionals from low- to high-income countries. This global migration pattern has sparked a broad international debate about the consequences for health systems worldwide, including questions about sustainability, justice, and global social accountabilities. This article provides a review of this phenomenon and gives an overview of the current scope of health workforce migration patterns. It further focuses on the scientific discourse regarding health workforce migration and its effects on both high- and low-income countries in an interdependent world. The article also reviews the internal and external factors that fuel health worker migration and illustrates how health workforce migration is a classic global health issue of our time. Accordingly, it elaborates on the international community's approach to solving the workforce crisis, focusing in particular on the WHO Code of Practice, established in 2010. PMID:24560265

The dynamics of avian influenza in western Arctic snow geese: implications for annual and migratory infection patterns

USGS Publications Warehouse

Samuel, Michael D.; Hall, Jeffrey S.; Brown, Justin D.; Goldberg, Diana R.; Ip, Hon S.; Baranyuk, Vasily V.

2015-01-01

Wild water birds are the natural reservoir for low-pathogenic avian influenza viruses (AIV). However, our ability to investigate the epizootiology of AIV in these migratory populations is challenging, and despite intensive worldwide surveillance, remains poorly understood. We conducted a cross-sectional, retrospective analysis in Pacific Flyway lesser snow geese Chen caerulescens to investigate AIV serology and infection patterns. We collected nearly 3,000 sera samples from snow geese at 2 breeding colonies in Russia and Canada during 1993-1996 and swab samples from > 4,000 birds at wintering and migration areas in the United States during 2006-2011. We found seroprevalence and annual seroconversion varied considerably among years. Seroconversion and infection rates also differed between snow goose breeding colonies and wintering areas, suggesting that AIV exposure in this gregarious waterfowl species is likely occurring during several phases (migration, wintering and potentially breeding areas) of the annual cycle. We estimated AIV antibody persistence was longer (14 months) in female geese compared to males (6 months). This relatively long period of AIV antibody persistence suggests that subtype-specific serology may be an effective tool for detection of exposure to subtypes associated with highly-pathogenic AIV. Our study provides further evidence of high seroprevalence in Arctic goose populations, and estimates of annual AIV seroconversion and antibody persistence for North American waterfowl. We suggest future AIV studies include serology to help elucidate the epizootiological dynamics of AIV in wild bird populations.

The Adventures of the Gray Whale: An Integrated Approach to Learning about the Long Migration

ERIC Educational Resources Information Center

Britton, Stacey; Tippins, Deborah; Cajigal, Aris; Cox, Melissa; Cole, Gerri; Vazquez, Max; Trejo, Martha Cabrera; Guzman, Amelia

2010-01-01

Using migration as a springboard, students can begin to understand patterns of survival and interdependence that exist within nature, as well as humankind's role in modifying these patterns. This mini-unit involves a series of integrated activities designed to take middle school students (fifth through eighth grades) on a journey of the eastern…

Wave forecasting and longshore sediment transport gradients along a transgressive barrier island: Chandeleur Islands, Louisiana

NASA Astrophysics Data System (ADS)

Georgiou, Ioannis Y.; Schindler, Jennifer K.

2009-12-01

Louisiana barrier islands, such as the chain surrounding the southeast region of the state, are experiencing rapid loss of land area, shoreline erosion, and landward migration due to transgression and in-place drowning, and the landfall of several major hurricanes in the last decade. Observations of migration rates and overall impacts to these barrier islands are poorly understood since they do not respond in a traditional way, such as barrier rollover. This paper aims to verify how wave energy and potential longshore sediment transport trends have influenced the recent evolution of the Chandeleur Islands, by direct comparison with recent observations of migration and erosion trends. The Chandeleur Islands are characterized by a bidirectional transport system, with material moving from the central arc to the flanks. The longshore sediment transport along the barrier islands was calculated after propagation and transformation of waves to breaking (generated using observed winds), and through the use of a common longshore sediment transport formula. Seasonal variations in wind climate produced changes in the transport trends and gradients that agree with migration and rotation patterns observed for this barrier island system. Results suggest that wind dominance produces seasonal oscillations that cause an imbalance in the resulting transport gradients that over time are responsible for higher rates of transport in the northward direction. These results and data from other works verify the evolutionary model previously suggested, and qualitatively confirm the recent observations in asymmetric shoreline erosion.

Larval Transport and Its Association with Recruitment of Blue Crabs to Chesapeake Bay

DTIC Science & Technology

1989-01-01

conditions in the dependent fishing industry and making it difficult to optimize the yield through effective management. In part, successful management depends ...bibliography, can be found in Millikin and Williams (1984). After mating; the Chesapeake Bay blue crab females migrate to the higher salinity waters near the...similar pattern, and suggesting a similar cycle of environmental involvement. A physical mechanism for the retention of the larvae within sufficient

Occupation and urbanization of Roraima State, Brazil.

PubMed

Diniz, A

1997-01-01

The author examines settlement patterns and urbanization of the remote area of Roraima State, Brazil. "A survey conducted in the capital city, Boa Vista, provides information on migration histories and migrants' characteristics.... Current views of urbanization of the Amazon [region] are focused on the displacement factor that development and state geopolitics have upon rural settlements...." The author also suggests that more attention needs to be paid to the characteristics of migrants in the urban areas. (EXCERPT)

Butterfly Diagram and Activity Cycles in HR 1099

NASA Astrophysics Data System (ADS)

Berdyugina, Svetlana V.; Henry, Gregory W.

2007-04-01

We analyze photometric data of the active RS CVn-type star HR 1099 for the years 1975-2006 with an inversion technique and reveal the nature of two activity cycles of 15-16 yr and 5.3+/-0.1 yr duration. The 16 yr cycle is related to variations of the total spot area and is coupled with the differential rotation, while the 5.3 yr cycle is caused by the symmetric redistribution of the spotted area between the opposite stellar hemispheres (flip-flop cycle). We recover long-lived active regions comprising two active longitudes that migrate in the orbital reference frame with a variable rate because of the differential rotation along with changes in the mean spot latitudes. The migration pattern is periodic with the 16 yr cycle. Combining the longitudinal migration of the active regions with a previously measured differential rotation law, we recover the first stellar butterfly diagram without an assumption about spot shapes. We find that mean latitudes of active regions at opposite longitudes change antisymmetrically in the course of the 16 yr cycle: while one active region migrates to the pole, the other approaches the equator. This suggests a precession of the global magnetic field with respect to the stellar rotational axis.

Migration And wintering areas Of Glaucous-winged Gulls From south-central Alaska

USGS Publications Warehouse

Hatch, Scott A.; Gill, V.A.; Mulcahy, Daniel M.

2011-01-01

We used satellite telemetry to investigate the migration patterns and wintering areas of Glaucous-winged Gulls (Larus glaucescens) from Middleton Island, Alaska, where this species' population increased tenfold from the 1970s to the 1990s. Fall migration spanned 11 weeks, including numerous stopovers en route, apparently for feeding. Spring migration from wintering sites to Middleton Island was shorter (4 weeks) and more direct. One juvenile spent several months in southern Prince William Sound. An adult spent several months near Craig, southeast Alaska, while three others overwintered in southern British Columbia. For all four wintering adults use of refuse-disposal sites was evident or strongly suggested. Commensalism with humans may have contributed to the increase on Middleton, but a strong case can also be made for a competing explanation-regional recruitment of gulls to high-quality nesting habitat in Alaska created after the earthquake of 1964. An analysis of band returns reveals broad overlap in the wintering grounds of gulls from different Alaska colonies and of gulls banded on the west coast from British Columbia to California. The seasonal movement of many gulls from Alaska is decidedly migratory, whereas gulls from British Columbia, Washington, and Oregon disperse locally in winter.

Genetics of alkaline phosphatase of the small intestine of the house mouser (Mus musculus).

PubMed

Wilcox, F H

1983-08-01

Four inbred strains of mice exhibited either slow (PL/J), intermediate (DBA/2J, LP/J), or fast (SWR/J) rates of migration of duodenal alkaline phosphatase on cellulose acetate electrophoresis. Hybrids of these strains also had intermediate rates of migration regardless of the combination of strains used as parents. Strain differences were present in all regions of the small but not the large intestine. Crosses of the PL/J strain to hybrids between this strain and the other three strains gave a 1:1 segregation of the slow and intermediate patterns. The symbol Akp-3 is proposed for the locus responsible for the slower migration of the enzyme in this strain. Data from the LP/J X PL/J hybrid crossed with the PL/J strain showed linkage with two loci on chromosome 1 as follows: centromere--Idh-1--13.8 cM--Akp-3--8.9 +/- 2.6 cM--Pep-3. The available data do not reveal the genetic basis for the faster migration rate of the enzyme from the SWR/J strain, but a different response to neuraminidase and apparent nonlinkage to the Pep-3 locus suggest that a locus other than Akp-3 is responsible.

Adult Mouse Subventricular Zone Stem and Progenitor Cells Are Sessile and Epidermal Growth Factor Receptor Negatively Regulates Neuroblast Migration

PubMed Central

Kim, Yongsoo; Comte, Isabelle; Szabo, Gabor; Hockberger, Philip; Szele, Francis G.

2009-01-01

Background The adult subventricular zone (SVZ) contains stem and progenitor cells that generate neuroblasts throughout life. Although it is well accepted that SVZ neuroblasts are migratory, recent evidence suggests their progenitor cells may also exhibit motility. Since stem and progenitor cells are proliferative and multipotential, if they were also able to move would have important implications for SVZ neurogenesis and its potential for repair. Methodology/Principal Findings We studied whether SVZ stem and/or progenitor cells are motile in transgenic GFP+ slices with two photon time lapse microscopy and post hoc immunohistochemistry. We found that stem and progenitor cells; mGFAP-GFP+ cells, bright nestin-GFP+ cells and Mash1+ cells were stationary in the SVZ and rostral migratory stream (RMS). In our search for motile progenitor cells, we uncovered a population of motile βIII-tubulin+ neuroblasts that expressed low levels of epidermal growth factor receptor (EGFr). This was intriguing since EGFr drives proliferation in the SVZ and affects migration in other systems. Thus we examined the potential role of EGFr in modulating SVZ migration. Interestingly, EGFrlow neuroblasts moved slower and in more tortuous patterns than EGFr-negative neuroblasts. We next questioned whether EGFr stimulation affects SVZ cell migration by imaging Gad65-GFP+ neuroblasts in the presence of transforming growth factor alpha (TGF-α), an EGFr-selective agonist. Indeed, acute exposure to TGF-α decreased the percentage of motile cells by approximately 40%. Conclusions/Significance In summary, the present study directly shows that SVZ stem and progenitor cells are static, that EGFr is retained on some neuroblasts, and that EGFr stimulation negatively regulates migration. This result suggests an additional role for EGFr signaling in the SVZ. PMID:19956583

Fission-fusion and lineal effect: aspects of the population structure of the Semai Senoi of Malaysia.

PubMed

Fix, A G

1975-09-01

Analysis of histories and genealogies from seven relatively unacculturated, swidden-farming Semai settlements shows that the composition of local groups fluctuates through time. This instability is similar to a pattern which Neel and his colleagues have suggested is typical of primitive society, the fission-fusion model. In addition, the individuals comprising Semai fission groups are kinsmen which implies that the number of independent genomes represented is markedly less than the number of individual migrants (the lineal effect). Fission groups may form new villages or fuse with an established settlement. In either case, the genetic effects of such migration are more pronounced than would be expected on the basis of founder effect or random migration. Despite several conspicuous differences in social organization between the Semai and the South American Indians (e.g., bilateral vs. unilineal descent) whose population structure provided the empirical basis for the fission-fusion, lineal effect model, the basic similarities are striking. The Semai case thus lends support to the proposition that this pattern may be of some generality in technologically primitive populations.

Diel changes in the near-surface biomass of zooplankton and the carbon content of vertical migrants

NASA Astrophysics Data System (ADS)

Hays, Graeme C.; Harris, Roger P.; Head, Robert N.

Zooplankton biomass and the carbon content of vertical migrants were measured in the NE Atlantic (36.5°N, 19.2°W) between 11 and 18 July 1996 as part of the Plankton Reactivity in the Marine Environment (PRIME) programme. The increase in zooplankton biomass near the surface (0-100 m) at night compared to during the day suggested that diel vertical migration was an important feature at this site. For three species of vertically migrant copepods, Pleuromamma pisekii, P. gracilis and P. abdominalis, the carbon content of individuals collected at dusk was significantly less than for individuals collected at dawn, with this reduction being 6.2, 7.3 and 14.8%, respectively. This dawn-dusk reduction in carbon content is consistent with the diel pattern of feeding and fasting exhibited by vertical migrants and supports the suggestion that migrating zooplankton will cause an active export of carbon from the surface layers.

Contrasting patterns of population history and seed-mediated gene flow in two endemic Costa Rican oak species.

PubMed

Rodríguez-Correa, Hernando; Oyama, Ken; Quesada, Mauricio; Fuchs, Eric J; González-Rodríguez, Antonio

2018-03-02

Lower Central America is an important area to study recent population history and diversification of Neotropical species due to its complex and dynamic geology and climate. Phylogeographic studies in this region are few in comparison with other regions and even less for tree species. The aim of the present study was to characterize the phylogeographic structure in two partially co-distributed endemic oak species (Quercus costaricensis and Q. bumelioides) of the Costa Rican mountains using chloroplast short sequence repeats (cpSSRs), and to test for the effect of geological and palaeoclimatic processes on their population history. Genetic diversity and structure, haplotype networks, patterns of seed-mediated gene flow and historical demography were estimated for both species. Results suggested contrasting patterns. Quercus costaricensis exhibited high values of genetic diversity, a marked phylogeographic structure, a north-to-south genetic diversity gradient and evidence of a demographic expansion during the Quaternary. Quercus bumelioides did not show significant genetic structure and the haplotype network and historical demography estimates suggested a recent population expansion probably during the Pleistocene-Holocene transition. Phylogeographic structure of Q. costaricensis seems to be related to Pleistocene altitudinal migration due to its higher altitudinal distribution. Meanwhile, historical seed-mediated gene flow through the lower altitudinal distribution of Q. bumelioides may have promoted the homogenization of genetic variation. Population expansion and stable availability of suitable climatic areas in both species probably indicate that palaeoclimatic changes promoted downwards altitudinal migration and formation of continuous forests allowing oak species to expand their distribution into the Panamanian mountains during glacial stages.

Focal adhesion kinase is involved in mechanosensing during fibroblast migration

NASA Technical Reports Server (NTRS)

Wang, H. B.; Dembo, M.; Hanks, S. K.; Wang, Y.

2001-01-01

Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase localized at focal adhesions and is believed to mediate adhesion-stimulated effects. Although ablation of FAK impairs cell movement, it is not clear whether FAK might be involved in the guidance of cell migration, a role consistent with its putative regulatory function. We have transfected FAK-null fibroblasts with FAK gene under the control of the tetracycline repression system. Cells were cultured on flexible polyacrylamide substrates for the detection of traction forces and the application of mechanical stimulation. Compared with control cells expressing wild-type FAK, FAK-null cells showed a decrease in migration speed and directional persistence. In addition, whereas FAK-expressing cells responded to exerted forces by reorienting their movements and forming prominent focal adhesions, FAK-null cells failed to show such responses. Furthermore, FAK-null cells showed impaired responses to decreases in substrate flexibility, which causes control cells to generate weaker traction forces and migrate away from soft substrates. Cells expressing Y397F FAK, which cannot be phosphorylated at a key tyrosine site, showed similar defects in migration pattern and force-induced reorientation as did FAK-null cells. However, other aspects of F397-FAK cells, including the responses to substrate flexibility and the amplification of focal adhesions upon mechanical stimulation, were similar to that of control cells. Our results suggest that FAK plays an important role in the response of migrating cells to mechanical input. In addition, phosphorylation at Tyr-397 is required for some, but not all, of the functions of FAK in cell migration.

Do sexual risk behaviour, risk perception and testing behaviour differ across generations of migrants?

PubMed

Kramer, Merlijn A; van Veen, Maaike G; Op de Coul, Eline L M; Coutinho, Roel A; Prins, Maria

2014-02-01

Behaviour and related health outcomes of migrants have been suggested to shift towards the practices of the indigenous population of the host country. To investigate this, we studied generational differences in sexual behaviour between first- and second-generation migrants (FGMs and SGMs) in The Netherlands. In 2003-05, persons aged 16-70 years with origins in Surinam, the Antilles and Aruba were interviewed on their sexual behaviour in The Netherlands and their country of origin. The relationship of generation, age at migration and sexual behaviour was studied by multinomial logistic regression analyses. Generational differences were observed regarding concurrent partnerships, anal sex and history of sexually transmitted infection. Compared with FGMs who migrated at an age >25 years, those who migrated between 10 and 25 years of age were more likely to report concurrency [odds ratio (OR): 1.52, 95% confidence interval (CI): 1.14-2.04], whereas SGMs were less likely to report concurrency (OR: 0.65, 95% CI: 0.43-0.98). FGMs who migrated before the age of 10 were more likely to have had anal sex (OR: 1.90, 95% CI: 1.34-2.71) or a sexually transmitted infection diagnosis (OR: 1.80, 95% CI: 1.20-2.71) than those who had migrated at >25 years of age. Our study shows that not only SGMs but also FGMs who migrated at an early age tend to differ from the sexual patterns of FGMs who migrated at an older age. Generational differences in sexual behaviour could be explained by acculturation and increased identity with the values of the host country.

Variable detours in long-distance migration across ecological barriers and their relation to habitat availability at ground

PubMed Central

Hahn, Steffen; Emmenegger, Tamara; Lisovski, Simeon; Amrhein, Valentin; Zehtindjiev, Pavel; Liechti, Felix

2014-01-01

Migration detours, the spatial deviation from the shortest route, are a widespread phenomenon in migratory species, especially if barriers must be crossed. Moving longer distances causes additional efforts in energy and time, and to be adaptive, this should be counterbalanced by favorable condition en route. We compared migration patterns of nightingales that travelled along different flyways from their European breeding sites to the African nonbreeding sites. We tested for deviations from shortest routes and related the observed and expected routes to the habitat availability at ground during autumn and spring migration. All individuals flew detours of varying extent. Detours were largest and seasonally consistent in western flyway birds, whereas birds on the central and eastern flyways showed less detours during autumn migration, but large detours during spring migration (eastern flyway birds). Neither migration durations nor the time of arrival at destination were related to the lengths of detours. Arrival at the breeding site was nearly synchronous in birds flying different detours. Flying detours increased the potential availability of suitable broad-scale habitats en route only along the western flyway. Habitat availability on observed routes remained similar or even decreased for individuals flying detours on the central or the eastern flyway as compared to shortest routes. Thus, broad-scale habitat distribution may partially explain detour performance, but the weak detour-habitat association along central and eastern flyways suggests that other factors shape detour extent regionally. Prime candidate factors are the distribution of small suitable habitat patches at local scale as well as winds specific for the region and altitude. PMID:25505540

Spatial analysis of the regional variation of reproductive tract infections and spousal migration correlates in Nepal.

PubMed

Johnson, Derek C; Lhaki, Pema; Buehler Cherry, Charlotte; Kempf, Mirjam-Colette; Chamot, Eric; Vermund, Sten H; Shrestha, Sadeep

2017-05-30

Nepal has a diverse geographic landscape that could potentially create clustered subpopulations with regional socio-cultures that could result in differential health outcomes. With an alarming rise in married male populations migrating for work, it is possible that these migrants are engaged in risky sexual behaviour, putting their wives at risk for infectious disease outcomes, including reproductive tract infections (RTI), when they return home. The prevalence of male migration varies by geographic region in Nepal and this variation could potentially contribute to different RTI rates. Using a cross-sectional dataset (the 2011 Nepal Demographic and Health Survey) including 9607 married women, we investigated geospatial and socio-cultural factors associated with the symptoms of RTIs with a focus on the husbands' migration status. Choropleth maps were created to illustrate areas with high percentages of RTIs that correlated with migration patterns. Overall, 31.9% of the husbands were migrating for work. After adjusting for wealth, contraception use, age at first marriage, urban/rural status and husband's education, women whose husbands had been absent for a year or more in Nepal's Mid-West region (OR 1.93 95%, CI 1.02-3.67) or Far-West region (OR 2.89 95%, CI 1.24-6.73) were more likely to report RTI-like symptoms than others. Our results suggest a potential association between husbands' migration status and Nepali women reporting RTI symptoms by geographic regions. However, further research is needed to put this outcome on a stronger footing with respect to this under-studied population, specifically in the context of geographical variation.

When and where does mortality occur in migratory birds? Direct evidence from long-term satellite tracking of raptors.

PubMed

Klaassen, Raymond H G; Hake, Mikael; Strandberg, Roine; Koks, Ben J; Trierweiler, Christiane; Exo, Klaus-Michael; Bairlein, Franz; Alerstam, Thomas

2014-01-01

Information about when and where animals die is important to understand population regulation. In migratory animals, mortality might occur not only during the stationary periods (e.g. breeding and wintering) but also during the migration seasons. However, the relative importance of population limiting factors during different periods of the year remains poorly understood, and previous studies mainly relied on indirect evidence. Here, we provide direct evidence about when and where migrants die by identifying cases of confirmed and probable deaths in three species of long-distance migratory raptors tracked by satellite telemetry. We show that mortality rate was about six times higher during migration seasons than during stationary periods. However, total mortality was surprisingly similar between periods, which can be explained by the fact that risky migration periods are shorter than safer stationary periods. Nevertheless, more than half of the annual mortality occurred during migration. We also found spatiotemporal patterns in mortality: spring mortality occurred mainly in Africa in association with the crossing of the Sahara desert, while most mortality during autumn took place in Europe. Our results strongly suggest that events during the migration seasons have an important impact on the population dynamics of long-distance migrants. We speculate that mortality during spring migration may account for short-term annual variation in survival and population sizes, while mortality during autumn migration may be more important for long-term population regulation (through density-dependent effects). © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

Electro-migration of heavy metals in an aged electroplating contaminated soil affected by the coexisting hexavalent chromium.

PubMed

Zhang, Weihua; Zhuang, Luwen; Tong, Lizhi; Lo, Irene M C; Qiu, Rongliang

2012-02-01

Cr(VI) was often reported to oxidize soil organic matter at acidic environments due to its high ORP, probably thus changing cationic metal species bound to soil organic matter, and influencing their electro-migration patterns. However, such an effect on the electro-migration was not confirmed in most previous studies. Therefore, this study applied a fixed voltage direct current field on an aged electroplating contaminated clayed soil, with a special interest in the direct or indirect influence of Cr(VI) on the electro-migration of other coexisting metals. After 353 h electrokinetic process, 81% of Zn, 53% of Ni and 22% of Cu in the original soil were electro-migrated into the electrolyte, and most of the remaining concentrated near the cathode. The Cr(VI) oxidized some soil organic matter along its migration pathway, with a pronounced reaction occurred near the anode at low pHs. The resulting Cr(III) reversed its original movement, and migrated towards the cathode, leading to the occurrence of a second Cr concentration peak in the soil. Metal species analyses showed that the amount of metals bound to soil organic matter significantly decreased, while a substantial increase in the Cr species bound to Fe/Mn (hydro-)oxides was observed, suggesting an enhancement of cationic metal electro-migration by the reduction of Cr(VI) into Cr(III). However, the Cr(VI) may form some stable lead chromate precipitates, and in turn demobilize Pb in the soil, as the results showed a low Pb removal and an increase in its acid-extractable and residual fractions after electrokinetic remediation. Copyright © 2011 Elsevier Ltd. All rights reserved.

The challenges of the first migration: movement and behaviour of juvenile vs. adult white storks with insights regarding juvenile mortality.

PubMed

Rotics, Shay; Kaatz, Michael; Resheff, Yehezkel S; Turjeman, Sondra Feldman; Zurell, Damaris; Sapir, Nir; Eggers, Ute; Flack, Andrea; Fiedler, Wolfgang; Jeltsch, Florian; Wikelski, Martin; Nathan, Ran

2016-07-01

Migration conveys an immense challenge, especially for juvenile birds coping with enduring and risky journeys shortly after fledging. Accordingly, juveniles exhibit considerably lower survival rates compared to adults, particularly during migration. Juvenile white storks (Ciconia ciconia), which are known to rely on adults during their first fall migration presumably for navigational purposes, also display much lower annual survival than adults. Using detailed GPS and body acceleration data, we examined the patterns and potential causes of age-related differences in fall migration properties of white storks by comparing first-year juveniles and adults. We compared juvenile and adult parameters of movement, behaviour and energy expenditure (estimated from overall dynamic body acceleration) and placed this in the context of the juveniles' lower survival rate. Juveniles used flapping flight vs. soaring flight 23% more than adults and were estimated to expend 14% more energy during flight. Juveniles did not compensate for their higher flight costs by increased refuelling or resting during migration. When juveniles and adults migrated together in the same flock, the juvenile flew mostly behind the adult and was left behind when they separated. Juveniles showed greater improvement in flight efficiency throughout migration compared to adults which appears crucial because juveniles exhibiting higher flight costs suffered increased mortality. Our findings demonstrate the conflict between the juveniles' inferior flight skills and their urge to keep up with mixed adult-juvenile flocks. We suggest that increased flight costs are an important proximate cause of juvenile mortality in white storks and likely in other soaring migrants and that natural selection is operating on juvenile variation in flight efficiency. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Population mobility in Peninsular Malaysia.

PubMed

Jones, G W; Sidh, M S

1979-12-01

1970 census materials were used to analyze migration patterns in Peninsular Malaysia. Inter-state migration patterns were analyzed by comparing birth place and current place of residence data, and inter-district and intra-district migration patterns were assessed using information on previous and current place of residence. The proportion of inter-state migrants in the total population increased from 4.7%-10.9% from 1947-1970. 53% of the inter-state migrants were Malays, 33% were Chinese, and 13% were Indian. The states of Selangor and Pahang had the highest net migration gains and Perak had the highest number of out-migrants. Selangor attracted migrants because it was a major industrial, administrative and educational center. Migrants were attracted to Pahang because of recent efforts by the government to promote agricultural development in the state. Areas which showed a net migration loss were experiencing slow economic growth. 48.4% of the inter-state migrants migrated to either rural or suburban areas, 26% moved to cities with populations of 75,000 or more, and 26% moved to towns with populations of 1000-10,000. 48.6% of the inter-state migrants were females. When all types of internal migration were taken into account it was estimated that approximately 30% of the population had moved at some point in their life time. During the early 1900s, Peninsular Malaysia received many immigrants from China, India, and other countries, and the Chinese became the dominant group in many urban areas and in many economic sectors. In 1950 the government, fearing that the Malays would become a minority group in their own country, halted international immigration. The recent increase in internal migration has contributed toward equalizing the influence and power of the Chinese and the Malays in urban areas and in various economic sectors.

Rural-urban migration in a developing country: Botswana, Africa.

PubMed

Tarver, J D; Miller, H M

1987-01-01

Trends in internal migration in Botswana are analyzed, with a focus on rural-urban migration. Data are from the 1981 census and from a survey carried out in 1979. The authors note that even though the predominance of subsistence agriculture acts as a deterrent to rural-urban migration, it is probable that the total and percentage of people living in urban areas will increase. However, the magnitude and pattern of future migration will fluctuate over time as social and economic conditions change.

Different waves and directions of Neolithic migrations in the Armenian Highland.

PubMed

Hovhannisyan, Anahit; Khachatryan, Zaruhi; Haber, Marc; Hrechdakian, Peter; Karafet, Tatiana; Zalloua, Pierre; Yepiskoposyan, Levon

2014-01-01

The peopling of Europe and the nature of the Neolithic agricultural migration as a primary issue in the modern human colonization of the globe is still widely debated. At present, much uncertainty is associated with the reconstruction of the routes of migration for the first farmers from the Near East. In this context, hospitable climatic conditions and the key geographic position of the Armenian Highland suggest that it may have served as a conduit for several waves of expansion of the first agriculturalists from the Near East to Europe and the North Caucasus. Here, we assess Y-chromosomal distribution in six geographically distinct populations of Armenians that roughly represent the extent of historical Armenia. Using the general haplogroup structure and the specific lineages representing putative genetic markers of the Neolithic Revolution, haplogroups R1b1a2, J2, and G, we identify distinct patterns of genetic affinity between the populations of the Armenian Highland and the neighboring ones north and west from this area. Based on the results obtained, we suggest a new insight on the different routes and waves of Neolithic expansion of the first farmers through the Armenian Highland. We detected at least two principle migratory directions: (1) westward alongside the coastline of the Mediterranean Sea and (2) northward to the North Caucasus.

Matchmaker, Matchmaker, Make Me a Match: Migration of Populations via Marriages in the Past

NASA Astrophysics Data System (ADS)

Lee, Sang Hoon; Ffrancon, Robyn; Abrams, Daniel M.; Kim, Beom Jun; Porter, Mason A.

2014-10-01

The study of human mobility is both of fundamental importance and of great potential value. For example, it can be leveraged to facilitate efficient city planning and improve prevention strategies when faced with epidemics. The newfound wealth of rich sources of data—including banknote flows, mobile phone records, and transportation data—has led to an explosion of attempts to characterize modern human mobility. Unfortunately, the dearth of comparable historical data makes it much more difficult to study human mobility patterns from the past. In this paper, we present an analysis of long-term human migration, which is important for processes such as urbanization and the spread of ideas. We demonstrate that the data record from Korean family books (called "jokbo") can be used to estimate migration patterns via marriages from the past 750 years. We apply two generative models of long-term human mobility to quantify the relevance of geographical information to human marriage records in the data, and we find that the wide variety in the geographical distributions of the clans poses interesting challenges for the direct application of these models. Using the different geographical distributions of clans, we quantify the "ergodicity" of clans in terms of how widely and uniformly they have spread across Korea, and we compare these results to those obtained using surname data from the Czech Republic. To examine population flow in more detail, we also construct and examine a population-flow network between regions. Based on the correlation between ergodicity and migration in Korea, we identify two different types of migration patterns: diffusive and convective. We expect the analysis of diffusive versus convective effects in population flows to be widely applicable to the study of mobility and migration patterns across different cultures.

Uncovering patterns of spring migration in the monarch butterfly using stable isotopes and demographic models

NASA Astrophysics Data System (ADS)

Norris, R.; Miller, N.; Wassenaar, L.; Hobson, K.

2010-12-01

Each spring, millions of monarch butterflies (Danaus plexippus) migrate up to 3000 km from central Mexico to re-colonize eastern North America. However, despite centuries of research, the patterns of re-colonization are not well understood. We combined stable-hydrogen (δD) and -carbon (δ13C) isotope measurements with demographic models to test (1) whether individuals sampled in the northern part of the breeding range in the Great Lakes originate directly from Mexico or are second generation individuals born in the southern US and (2) to estimate whether populations on the eastern seaboard migrate longitudinally over the Appalachians or originate directly from the Gulf Coast. In the Great Lakes, we found that the majority of individuals were second-generation monarchs born in the Gulf Coast and Central regions of the US. However, 25% individuals originated directly from Mexico and we estimated that these individuals produced the majority of offspring born in the Great Lakes region during June. On the eastern seaboard, we found the majority of monarchs (88%) originated in the mid-west and Great Lakes regions, providing the first direct evidence that second generation monarchs born in June complete a (trans-) longitudinal migration across the Appalachian mountains. The remaining individuals (12%) originated from parents that migrated directly from the Gulf coast during early spring. Our results demonstrate how stable isotopes, when combined with ecological data, can provide insights into patterns of connectivity in migratory insects that have been impossible to test using conventional techniques. The migration patterns presented here have important implications for predicting future changes in population size and for developing effective conservation plans for this species.

The mechanism for migration in Poland.

PubMed

Rykiel, Z

1988-01-01

The author reviews neoclassical theories and models of migration. The mobility theory, which concerns the impact of local labor markets on migration, is discussed in the Polish context. A general model of the regional labor market and a multicausal model are developed to explain the patterns of internal migration. The period of a managed economy (1949-1980) is contrasted with the period since the implementation of a new economic system in 1983.

The fertility of internal migrants to Kinshasa.

PubMed

Anglewicz, Philip; Corker, Jamaica; Kayembe, Patrick

2017-01-01

The rapid population growth of many African cities has important implications for population health, yet little is known about factors contributing to increasing population, such as the fertility of internal migrants. We examine whether in-migrants to Kinshasa have different fertility patterns than lifetime Kinshasa residents, and identify characteristics of migrants that may explain differences in fertility. We also use detailed migration histories to examine whether fertility differs by features of migration. We use representative data from the PMA2020 Project for 2197 women in Kinshasa, including 340 women who moved to Kinshasa. We examine differences between migrants and non-migrants in fertility and other fertility-related characteristics. We also examine whether fertility differs by duration of residence in Kinshasa, number of lifetime moves, age at first migration, urban/rural classification of birthplace, and the distinction between intra-Kinshasa migration and migration to Kinshasa.. Migrants have significantly higher fertility than permanent Kinshasa residents, but the difference is relatively small in magnitude. This higher fertility appears due in part to patterns of contraceptive use among migrants. There is noteworthy heterogeneity among migrants: higher fertility among migrants is associated with longer duration in Kinshasa, more lifetime moves, urban-Kinshasa migration, older age at first migration, and moving to Kinshasa from outside (as opposed to intra-Kinshasa migration).

Tank Information System (tis): a Case Study in Migrating Web Mapping Application from Flex to Dojo for Arcgis Server and then to Open Source

NASA Astrophysics Data System (ADS)

Pulsani, B. R.

2017-11-01

Tank Information System is a web application which provides comprehensive information about minor irrigation tanks of Telangana State. As part of the program, a web mapping application using Flex and ArcGIS server was developed to make the data available to the public. In course of time as Flex be-came outdated, a migration of the client interface to the latest JavaScript based technologies was carried out. Initially, the Flex based application was migrated to ArcGIS JavaScript API using Dojo Toolkit. Both the client applications used published services from ArcGIS server. To check the migration pattern from proprietary to open source, the JavaScript based ArcGIS application was later migrated to OpenLayers and Dojo Toolkit which used published service from GeoServer. The migration pattern noticed in the study especially emphasizes upon the use of Dojo Toolkit and PostgreSQL database for ArcGIS server so that migration to open source could be performed effortlessly. The current ap-plication provides a case in study which could assist organizations in migrating their proprietary based ArcGIS web applications to open source. Furthermore, the study reveals cost benefits of adopting open source against commercial software's.

Developmental Patterns of Doublecortin Expression and White Matter Neuron Density in the Postnatal Primate Prefrontal Cortex and Schizophrenia

PubMed Central

Fung, Samantha J.; Joshi, Dipesh; Allen, Katherine M.; Sivagnanasundaram, Sinthuja; Rothmond, Debora A.; Saunders, Richard; Noble, Pamela L.; Webster, Maree J.; Shannon Weickert, Cynthia

2011-01-01

Postnatal neurogenesis occurs in the subventricular zone and dentate gyrus, and evidence suggests that new neurons may be present in additional regions of the mature primate brain, including the prefrontal cortex (PFC). Addition of new neurons to the PFC implies local generation of neurons or migration from areas such as the subventricular zone. We examined the putative contribution of new, migrating neurons to postnatal cortical development by determining the density of neurons in white matter subjacent to the cortex and measuring expression of doublecortin (DCX), a microtubule-associated protein involved in neuronal migration, in humans and rhesus macaques. We found a striking decline in DCX expression (human and macaque) and density of white matter neurons (humans) during infancy, consistent with the arrival of new neurons in the early postnatal cortex. Considering the expansion of the brain during this time, the decline in white matter neuron density does not necessarily indicate reduced total numbers of white matter neurons in early postnatal life. Furthermore, numerous cells in the white matter and deep grey matter were positive for the migration-associated glycoprotein polysialiated-neuronal cell adhesion molecule and GAD65/67, suggesting that immature migrating neurons in the adult may be GABAergic. We also examined DCX mRNA in the PFC of adult schizophrenia patients (n = 37) and matched controls (n = 37) and did not find any difference in DCX mRNA expression. However, we report a negative correlation between DCX mRNA expression and white matter neuron density in adult schizophrenia patients, in contrast to a positive correlation in human development where DCX mRNA and white matter neuron density are higher earlier in life. Accumulation of neurons in the white matter in schizophrenia would be congruent with a negative correlation between DCX mRNA and white matter neuron density and support the hypothesis of a migration deficit in schizophrenia. PMID:21966452

Recurrence of seismic migrations along the central California segment of the San Andreas fault system

USGS Publications Warehouse

Wood, M.D.; Allen, S.S.

1973-01-01

VERIFICATIONS of tectonic concepts1 concerning seafloor spreading are emerging in a manner that has direct bearing on earthquake prediction. Although the gross pattern of worldwide seismicity contributed to the formulation of the plate tectonic hypothesis, it is the space-time characteristics of this seismicity that may contribute more toward understanding the kinematics and dynamics of the driving mechanism long speculated to originate in the mantle. If the lithosphere is composed of plates that move essentially as rigid bodies, then there should be seismic edge effects associated with this movement. It is these interplate effects, especially seismic migration patterns, that we discuss here. The unidirectional propagation at constant velocity (80 km yr-1 east to west) for earthquakes (M???7.2) on the Antblian fault for the period 1939 to 1956 (ref. 2) is one of the earliest observations of such a phenomenon. Similar studies3,4 of the Alaska Aleutian seismic zone and certain regions of the west coast of South America suggest unidirectional and recurring migrations of earthquakes (M???7.7) occur in these areas. Between these two regions along the great transform faults of the west coast of North America, there is some evidence 5 for unidirectional, constant velocity and recurrent migration of great earthquakes. The small population of earthquakes (M>7.2) in Savage's investigation5 indicates a large spatial gap along the San Andreas system in central California from 1830 to 1970. Previous work on the seismicity of this gap in central California indicates that the recurrence curves remain relatively constant, independent of large earthquakes, for periods up to a century6. Recurrence intervals for earthquakes along the San Andreas Fault have been calculated empirically by Wallace7 on the basis of geological evidence, surface measurements and assumptions restricted to the surficial seismic layer. Here we examine the evidence for recurrence of seismic migrations along the San Andreas fault system of central California for earthquakes of magnitude M???5. ?? 1973 Nature Publishing Group.

Factors Impacting the Migration Paths of Humpback Whales, Megaptera novaeangliae, in Queensland, Australia

NASA Astrophysics Data System (ADS)

Lemckert, C. J.; Reinke, J.; Meynecke, O.

2016-02-01

Humpback whales, Megaptera novaeangliae, migrate annually from polar feeding grounds in summer to tropical breeding grounds in winter. Large scale migration patterns are quite well known; however, small scale distribution patterns and relationships with environmental conditions have received less attention. Protection from a range of threats, as well as predicting the effects of climate change, requires knowledge of preferred habitat and the reasons behind the preferences. East Australian humpback whales travel from the Southern Ocean, along the East Coast of Australia, to the Great Barrier Reef (or further) to breed. The East Australian coastal environment is dominated by the East Australian Current. This current carries warm water poleward from the tropics and is responsible for generating upwelling conditions on the coast and providing the majority of nutrients available for primary production. Sharp temperature changes develop at the border of the warm current and the cooler coastal and upwelled waters. This study investigates relationships between humpback whale distribution and environmental conditions (including bathymetry and remotely sensed sea surface temperature, as well as their gradients) on the Gold Coast and Hervey Bay, Australia. The Gold Coast is used primarily a migration route, but also provides a rest stop for mothers and calves on the return journey. Hervey Bay is used on the southern (return) migration for resting and socialising. Environmental preferences for these two will provide a comparison of the requirements for different habitat types. Initial outcomes of the study on the Gold Coast suggest a preference for cooler waters and in areas with a strong temperature gradient. The higher productivity in cooler upwelled water and fronts may provide the whales with a chance of opportunistic feeding, a rare occurrence on their prolonged journey. Following particular hydrodynamic features such as these, which generally run parallel to the shore, may also serve as a tool for navigation.

Changing patterns of clinical malaria since 1965 among a tea estate population located in the Kenyan highlands*

PubMed Central

Shanks, G. D.; Biomndo, K.; Hay, S. I.; Snow, R. W.

2012-01-01

The changing epidemiology of clinical malaria since 1965 among hospitalized patients was studied at a group of tea estates in the western highlands of Kenya. These data indicate recent dramatic increases in the numbers of malaria admissions (6·5 to 32·5% of all admissions), case fatality (1·3 to 6%) and patients originating from low-risk, highland areas (34 to 59%). Climate change, environmental management, population migration, and breakdown in health service provision seem unlikely explanations for this changing disease pattern. The coincident arrival of chloroquine resistance during the late 1980s in the sub-region suggests that drug resistance is a key factor in the current pattern and burden of malaria among this highland population. PMID:10974991

A model-based estimation of inter-prefectural migration of physicians within Japan and associated factors: A 20-year retrospective study.

PubMed

Okada, Naoki; Tanimoto, Tetsuya; Morita, Tomohiro; Higuchi, Asaka; Yoshida, Izumi; Kosugi, Kazuhiro; Maeda, Yuto; Nishikawa, Yoshitaka; Ozaki, Akihiko; Tsuda, Kenji; Mori, Jinichi; Ohnishi, Mutsuko; Ward, Larry Wesley; Narimatsu, Hiroto; Yuji, Koichiro; Kami, Masahiro

2018-06-01

Despite an increase in the number of physicians in Japan, misdistribution of physicians within the 47 prefectures remains a major issue. Migration of physicians among prefectures might partly explain the misdistribution. However, geographical differences and the magnitude of physicians' migration are unclear. The aim of this study was to estimate the extent of migration of physicians among prefectures and explore possible factors associated with physicians' migration patterns.Using a publicly available government database from 1995 to 2014, a quantitative estimation of physicians' migration after graduation from a medical school was performed. The inflow and outflow of physicians were ostensibly calculated in each prefecture based on the differences between the number of newly licensed physicians and the actual number of practicing physicians after an adjustment for the number of deceased or retired physicians. Simple and multiple linear regression analyses were conducted to examine socio-demographic background factors.During the 20-year study period, the mean annual numbers of newly licensed physicians, deceased or retired physicians, and increase in practicing physicians in the whole country were 7416, 3382, and 4034, respectively. Among the 47 prefectures, the median annual number of newly licensed physicians to 100,000 population ratio (PPR) was 6.4 (range 1.5-16.5), the median annual adjusted number of newly licensed physicians was 61 (range, -18 to 845; the negative and positive values denote outflow and inflow, respectively), whereas the median annual number of migrating physicians was 13 (range, -171 to 241). The minimum and maximum migration ratios observed were -68% and 245%, respectively. In the final regression model of the 8 variables examined, only "newly licensed PPR" remained significantly associated with physician's migration ratios.A significant inequality in the proportion of the migration of physicians among prefectures in Japan was observed. The multivariate analyses suggest that the newly licensed PPRs, and not from-rural-to-urban migration, might be one of the keys to explaining the migration ratios of physicians. The differences and magnitude of physicians' migration should be factored into mitigate misdistribution of physicians.

[Female migration and social change in Africa. The case of Kenya].

PubMed

Vorlaufer, K

1985-06-01

Causes of the recent increase in female rural-urban migration in Kenya are investigated. "Reasons for this additional migration-wave are to be found in a general weakening of traditional values and authorities, the increasing land shortage and the resulting population pressure in the rural areas, which are factors that do in fact force women to migrate to towns." Comparisons are made with male migration flows. Regional differences in migration patterns are also noted. The author concludes that the increase in female migration is not a result of greater emancipation of women but rather a symptom of increasing poverty among Kenya's female population. (SUMMARY IN ENG) excerpt

High Altitude Bird Migration at Temperate Latitudes: A Synoptic Perspective on Wind Assistance

PubMed Central

Dokter, Adriaan M.; Shamoun-Baranes, Judy; Kemp, Michael U.; Tijm, Sander; Holleman, Iwan

2013-01-01

At temperate latitudes the synoptic patterns of bird migration are strongly structured by the presence of cyclones and anticyclones, both in the horizontal and altitudinal dimensions. In certain synoptic conditions, birds may efficiently cross regions with opposing surface wind by choosing a higher flight altitude with more favourable wind. We observed migratory passerines at mid-latitudes that selected high altitude wind optima on particular nights, leading to the formation of structured migration layers at varying altitude up to 3 km. Using long-term vertical profiling of bird migration by C-band Doppler radar in the Netherlands, we find that such migration layers occur nearly exclusively during spring migration in the presence of a high-pressure system. A conceptual analytic framework providing insight into the synoptic patterns of wind assistance for migrants that includes the altitudinal dimension has so far been lacking. We present a simple model for a baroclinic atmosphere that relates vertical profiles of wind assistance to the pressure and temperature patterns occurring at temperate latitudes. We show how the magnitude and direction of the large scale horizontal temperature gradient affects the relative gain in wind assistance that migrants obtain through ascending. Temperature gradients typical for northerly high-pressure systems in spring are shown to cause high altitude wind optima in the easterly sectors of anticyclones, thereby explaining the frequent observations of high altitude migration in these synoptic conditions. Given the recurring synoptic arrangements of pressure systems across temperate continents, the opportunities for exploiting high altitude wind will differ between flyways, for example between easterly and westerly oceanic coasts. PMID:23300969

High altitude bird migration at temperate latitudes: a synoptic perspective on wind assistance.

PubMed

Dokter, Adriaan M; Shamoun-Baranes, Judy; Kemp, Michael U; Tijm, Sander; Holleman, Iwan

2013-01-01

At temperate latitudes the synoptic patterns of bird migration are strongly structured by the presence of cyclones and anticyclones, both in the horizontal and altitudinal dimensions. In certain synoptic conditions, birds may efficiently cross regions with opposing surface wind by choosing a higher flight altitude with more favourable wind. We observed migratory passerines at mid-latitudes that selected high altitude wind optima on particular nights, leading to the formation of structured migration layers at varying altitude up to 3 km. Using long-term vertical profiling of bird migration by C-band Doppler radar in the Netherlands, we find that such migration layers occur nearly exclusively during spring migration in the presence of a high-pressure system. A conceptual analytic framework providing insight into the synoptic patterns of wind assistance for migrants that includes the altitudinal dimension has so far been lacking. We present a simple model for a baroclinic atmosphere that relates vertical profiles of wind assistance to the pressure and temperature patterns occurring at temperate latitudes. We show how the magnitude and direction of the large scale horizontal temperature gradient affects the relative gain in wind assistance that migrants obtain through ascending. Temperature gradients typical for northerly high-pressure systems in spring are shown to cause high altitude wind optima in the easterly sectors of anticyclones, thereby explaining the frequent observations of high altitude migration in these synoptic conditions. Given the recurring synoptic arrangements of pressure systems across temperate continents, the opportunities for exploiting high altitude wind will differ between flyways, for example between easterly and westerly oceanic coasts.

Migration within China and from China to the USA: the effects of migration networks, selectivity, and the rural political economy in Fujian Province.

PubMed

Liang, Zai; Chunyu, Miao David

2013-07-01

This paper tests a new strategy for simultaneously studying internal migration within, and international migration from, China. Our theoretical discussion draws on ideas from migration-networks theory and studies of the transition to a market-oriented economy. Data collection is modelled on the Mexican Migration Project. We find that education is more important in initiating internal migration than international migration. Second, although the role of migration networks at a community level seems similar to that for Mexico-USA migration, the networks at a family level show a different pattern. Third, there is evidence that internal and international migration are competing options. Finally, we find that individuals with cadres (public officials) in the family are less likely to undertake internal migration, but more likely to participate in international migration, a finding that highlights the continuing significance of the cadres in coastal rural China.

Migration, Adjustment, and Integration of the Indian Into the Urban Environment.

ERIC Educational Resources Information Center

McCaskill, Donald N.

The migration, adjustment, and integration patterns of Canadian Indian and Metis families in an urban setting were studied. Data were collected in 1968 via a 64-item interview schedule administered to a sample of 71 families moving into the city of Winnepeg, Canada. Addressing the problems of migration, adjustment, and integration, analysis…

Patterning C. elegans: homeotic cluster genes, cell fates and cell migrations.

PubMed

Salser, S J; Kenyon, C

1994-05-01

Despite its simple body form, the nematode C. elegans expresses homeotic cluster genes similar to those of insects and vertebrates in the patterning of many cell types and tissues along the anteroposterior axis. In the ventral nerve cord, these genes program spatial patterns of cell death, fusion, division and neurotransmitter production; in migrating cells they regulate the direction and extent of movement. Nematode development permits an analysis at the cellular level of how homeotic cluster genes interact to specify cell fates, and how cell behavior can be regulated to assemble an organism.

A Simple Force-Motion Relation for Migrating Cells Revealed by Multipole Analysis of Traction Stress

PubMed Central

Tanimoto, Hirokazu; Sano, Masaki

2014-01-01

For biophysical understanding of cell motility, the relationship between mechanical force and cell migration must be uncovered, but it remains elusive. Since cells migrate at small scale in dissipative circumstances, the inertia force is negligible and all forces should cancel out. This implies that one must quantify the spatial pattern of the force instead of just the summation to elucidate the force-motion relation. Here, we introduced multipole analysis to quantify the traction stress dynamics of migrating cells. We measured the traction stress of Dictyostelium discoideum cells and investigated the lowest two moments, the force dipole and quadrupole moments, which reflect rotational and front-rear asymmetries of the stress field. We derived a simple force-motion relation in which cells migrate along the force dipole axis with a direction determined by the force quadrupole. Furthermore, as a complementary approach, we also investigated fine structures in the stress field that show front-rear asymmetric kinetics consistent with the multipole analysis. The tight force-motion relation enables us to predict cell migration only from the traction stress patterns. PMID:24411233

Activation of a C. elegans Antennapedia homologue in migrating cells controls their direction of migration.

PubMed

Salser, S J; Kenyon, C

1992-01-16

Anterior-posterior patterning in insects, vertebrates and nematodes involves members of conserved Antennapedia-class homeobox gene clusters (HOM-C) that are thought to give specific body regions their identities. The effects of these genes on region-specific body structures have been described extensively, particularly in Drosophila, but little is known about how HOM-C genes affect the behaviours of cells that migrate into their domains of function. In Caenorhabditis elegans, the Antennapedia-like HOM-C gene mab-5 not only specifies postembryonic fates of cells in a posterior body region, but also influences the migration of mesodermal and neural cells that move through this region. Here we show that as one neuroblast migrates into this posterior region, it switches on mab-5 gene expression; mab-5 then acts as a developmental switch to control the migratory behaviour of the neuroblast descendants. HOM-C genes can therefore not only direct region-specific patterns of cell division and differentiation, but can also act within migrating cells to programme region-specific migratory behaviour.

Eco-virological approach for assessing the role of wild birds in the spread of avian influenza H5N1 along the Central Asian Flyway.

PubMed

Newman, Scott H; Hill, Nichola J; Spragens, Kyle A; Janies, Daniel; Voronkin, Igor O; Prosser, Diann J; Yan, Baoping; Lei, Fumin; Batbayar, Nyambayar; Natsagdorj, Tseveenmyadag; Bishop, Charles M; Butler, Patrick J; Wikelski, Martin; Balachandran, Sivananinthaperumal; Mundkur, Taej; Douglas, David C; Takekawa, John Y

2012-01-01

A unique pattern of highly pathogenic avian influenza (HPAI) H5N1 outbreaks has emerged along the Central Asia Flyway, where infection of wild birds has been reported with steady frequency since 2005. We assessed the potential for two hosts of HPAI H5N1, the bar-headed goose (Anser indicus) and ruddy shelduck (Tadorna tadorna), to act as agents for virus dispersal along this 'thoroughfare'. We used an eco-virological approach to compare the migration of 141 birds marked with GPS satellite transmitters during 2005-2010 with: 1) the spatio-temporal patterns of poultry and wild bird outbreaks of HPAI H5N1, and 2) the trajectory of the virus in the outbreak region based on phylogeographic mapping. We found that biweekly utilization distributions (UDs) for 19.2% of bar-headed geese and 46.2% of ruddy shelduck were significantly associated with outbreaks. Ruddy shelduck showed highest correlation with poultry outbreaks owing to their wintering distribution in South Asia, where there is considerable opportunity for HPAI H5N1 spillover from poultry. Both species showed correlation with wild bird outbreaks during the spring migration, suggesting they may be involved in the northward movement of the virus. However, phylogeographic mapping of HPAI H5N1 clades 2.2 and 2.3 did not support dissemination of the virus in a northern direction along the migration corridor. In particular, two subclades (2.2.1 and 2.3.2) moved in a strictly southern direction in contrast to our spatio-temporal analysis of bird migration. Our attempt to reconcile the disciplines of wild bird ecology and HPAI H5N1 virology highlights prospects offered by both approaches as well as their limitations.

A matter of months: High precision migration chronology of a Bronze Age female

PubMed Central

Villa, Chiara; Jørkov, Marie Louise; Allentoft, Morten E.; Kaul, Flemming; Ethelberg, Per; Reiter, Samantha S.; Wilson, Andrew S.; Taube, Michelle; Olsen, Jesper; Lynnerup, Niels; Willerslev, Eske; Kristiansen, Kristian; Frei, Robert

2017-01-01

Establishing the age at which prehistoric individuals move away from their childhood residential location holds crucial information about the socio dynamics and mobility patterns in ancient societies. We present a novel combination of strontium isotope analyses performed on the over 3000 year old “Skrydstrup Woman” from Denmark, for whom we compiled a highly detailed month-scale model of her migration timeline. When combined with physical anthropological analyses this timeline can be related to the chronological age at which the residential location changed. We conducted a series of high-resolution strontium isotope analyses of hard and soft human tissues and combined these with anthropological investigations including CT-scanning and 3D visualizations. The Skrydstrup Woman lived during a pan-European period characterized by technical innovation and great social transformations stimulated by long-distance connections; consequently she represents an important part of both Danish and European prehistory. Our multidisciplinary study involves complementary biochemical, biomolecular and microscopy analyses of her scalp hair. Our results reveal that the Skrydstrup Woman was between 17–18 years old when she died, and that she moved from her place of origin -outside present day Denmark- to the Skrydstrup area in Denmark 47 to 42 months before she died. Hence, she was between 13 to 14 years old when she migrated to and resided in the area around Skrydstrup for the rest of her life. From an archaeological standpoint, this one-time and one-way movement of an elite female during the possible “age of marriageability” might suggest that she migrated with the aim of establishing an alliance between chiefdoms. Consequently, this detailed multidisciplinary investigation provides a novel tool to reconstruct high resolution chronology of individual mobility with the perspective of studying complex patterns of social and economic interaction in prehistory. PMID:28582402

A matter of months: High precision migration chronology of a Bronze Age female.

PubMed

Frei, Karin Margarita; Villa, Chiara; Jørkov, Marie Louise; Allentoft, Morten E; Kaul, Flemming; Ethelberg, Per; Reiter, Samantha S; Wilson, Andrew S; Taube, Michelle; Olsen, Jesper; Lynnerup, Niels; Willerslev, Eske; Kristiansen, Kristian; Frei, Robert

2017-01-01

Establishing the age at which prehistoric individuals move away from their childhood residential location holds crucial information about the socio dynamics and mobility patterns in ancient societies. We present a novel combination of strontium isotope analyses performed on the over 3000 year old "Skrydstrup Woman" from Denmark, for whom we compiled a highly detailed month-scale model of her migration timeline. When combined with physical anthropological analyses this timeline can be related to the chronological age at which the residential location changed. We conducted a series of high-resolution strontium isotope analyses of hard and soft human tissues and combined these with anthropological investigations including CT-scanning and 3D visualizations. The Skrydstrup Woman lived during a pan-European period characterized by technical innovation and great social transformations stimulated by long-distance connections; consequently she represents an important part of both Danish and European prehistory. Our multidisciplinary study involves complementary biochemical, biomolecular and microscopy analyses of her scalp hair. Our results reveal that the Skrydstrup Woman was between 17-18 years old when she died, and that she moved from her place of origin -outside present day Denmark- to the Skrydstrup area in Denmark 47 to 42 months before she died. Hence, she was between 13 to 14 years old when she migrated to and resided in the area around Skrydstrup for the rest of her life. From an archaeological standpoint, this one-time and one-way movement of an elite female during the possible "age of marriageability" might suggest that she migrated with the aim of establishing an alliance between chiefdoms. Consequently, this detailed multidisciplinary investigation provides a novel tool to reconstruct high resolution chronology of individual mobility with the perspective of studying complex patterns of social and economic interaction in prehistory.

Recent trends in human migrations: the case of the Venezuelan Andes.

PubMed

Suarez, M M; Torrealba, R

1982-01-01

Changes in world capitalism caused prices of traditional raw materials to fall and new energy demands to arise at the end of the 19th and beginning of the 20th century. The Andean countries witnessed the fall in the value of their exports and began to receive large flows of foreign investment in mining and industry. Consequently, urban economies were strengthened and demographic patterns were changed. This led to the internal migrations and to a process of social change. These consequences are summarized from relevant studies focusing on Ecuador, Colombia, and Venezuela. Since the 1960s a compendium of information has become available which highlights the causes of the migration, migration patterns, the composition of migratory movements, and the mechanisms that the migrant uses to establish himself/herself in the city. Preston (1969) distinguished 2 migratory patterns in Ecuador: rural to urban, with migratory flows from the rural areas to urban centers and new industrial cities that experienced development and high demand for unskilled labor at comparatively high wages: and rural to rural, based on the movement of population from depressed rural areas to other areas in which programs for colonization or commercial agriculture have been promoted. In a study of Colombia, McGreevey (1968) identifies the lack of cultivatable land, rural violence in certain departments, and other economic and family causes as the principal factors that induced migrations to the cities. The study emphasizes that the predominant model of movement relates to "fill in" migration. The spatial mobility of the Venezuelan Andean population was initially outlined in a voluminous report on economic and social problems of the region (1954). The study indicates that during the intercensal period 1941-50 cities grew much more rapidly than rural "municipos" and that the drive to find employment and earn a living were the most important motives in the movement of peasants to the cities. All of the studies identified that use demographic, economic, or phychosocial approaches have provided partial explanations of the current status of Andean migrations. The explanations they offer, by not transcending the current reality of the migrants, overlook the historical traits of internal migration. Migratory flows do not spring up suddenly. They result from specific socio-political circumstances which, when closely linked to demographic evidence, serve as a basis for understanding the process. Review of studies on internal migration in the Northern Andes, as presented here, reveals a series of distinguishing characteristics: there are 5 migratory patterns--rural to rural, rural to urban, urban to urban, seasonal worker migration, and return migration, and the predominant pattern has been rural to urban; the demographic data show the importance of rural migrants to urban growth in the region and a complementary loss of population in the rural areas; depopulation of the countryside has been selective; and there is a marked disparity in employment remuneration between rural and urban areas.

Interplay of migratory and division forces as a generic mechanism for stem cell patterns

NASA Astrophysics Data System (ADS)

Hannezo, Edouard; Coucke, Alice; Joanny, Jean-François

2016-02-01

In many adult tissues, stem cells and differentiated cells are not homogeneously distributed: stem cells are arranged in periodic "niches," and differentiated cells are constantly produced and migrate out of these niches. In this article, we provide a general theoretical framework to study mixtures of dividing and actively migrating particles, which we apply to biological tissues. We show in particular that the interplay between the stresses arising from active cell migration and stem cell division give rise to robust stem cell patterns. The instability of the tissue leads to spatial patterns which are either steady or oscillating in time. The wavelength of the instability has an order of magnitude consistent with the biological observations. We also discuss the implications of these results for future in vitro and in vivo experiments.

Spatial patterns of close relationships across the lifespan

NASA Astrophysics Data System (ADS)

Jo, Hang-Hyun; Saramäki, Jari; Dunbar, Robin I. M.; Kaski, Kimmo

2014-11-01

The dynamics of close relationships is important for understanding the migration patterns of individual life-courses. The bottom-up approach to this subject by social scientists has been limited by sample size, while the more recent top-down approach using large-scale datasets suffers from a lack of detail about the human individuals. We incorporate the geographic and demographic information of millions of mobile phone users with their communication patterns to study the dynamics of close relationships and its effect in their life-course migration. We demonstrate how the close age- and sex-biased dyadic relationships are correlated with the geographic proximity of the pair of individuals, e.g., young couples tend to live further from each other than old couples. In addition, we find that emotionally closer pairs are living geographically closer to each other. These findings imply that the life-course framework is crucial for understanding the complex dynamics of close relationships and their effect on the migration patterns of human individuals.

Migration patterns among Floridians with AIDS, 1993-2007: implications for HIV prevention and care.

PubMed

Trepka, Mary Jo; Fennie, Kristopher P; Pelletier, Valerie; Lutfi, Khaleeq; Lieb, Spencer; Maddox, Lorene M

2014-09-01

To characterize migration patterns among people diagnosed as having and who died of acquired immunodeficiency syndrome (AIDS) from 1993 to 2007 because migrating to a new community can disrupt human immunodeficiency virus/AIDS care delivery and patients' adherence to care and affect migrants' social services and healthcare needs. Florida AIDS surveillance data were used to describe patterns of migration among people diagnosed as having and who died of AIDS from 1993 to 2007. Individual and community characteristics were compared between residence at the time of AIDS diagnosis and residence at the time of death by type of migration. Of 31,816 people in the cohort, 2510 (7.9%) migrated to another county in Florida and 1306 (4.1%) migrated to another state. Interstate migrants were more likely to be men, 20 to 39 years old, non-Hispanic white, and born in the United States, to have had a transmission mode of injection drug use (IDU) or men who have sex with men with IDU (MSM&IDU), and to have been diagnosed before 1999. Intercounty migrants were more likely to be non-Hispanic white, younger than 60 years, have had a transmission mode of MSM, IDU, or MSM&IDU, have higher CD4 counts/percentages, and to have lived in areas with low levels of poverty or low physician density. There was a small net movement from urban to rural areas within the state. A sizable percentage of people, particularly younger people and people with a transmission mode of IDU and IDU&MSM, migrated at least once between the time of their AIDS diagnosis and death. This has important implications for care and treatment, as well as efforts to prevent the disease. Further research is needed to explore barriers and facilitators to access to care upon migration and to assess the need for programs to help people transfer their human immunodeficiency virus/AIDS care, ensuring continuity of care and adherence.

Patterns of Migration and Risks Associated with Leprosy among Migrants in Maranhão, Brazil

PubMed Central

Murto, Christine; Chammartin, Frédérique; Schwarz, Karolin; da Costa, Lea Marcia Melo; Kaplan, Charles; Heukelbach, Jorg

2013-01-01

Leprosy remains a public health problem in Brazil with new case incidence exceeding World Health Organization (WHO) goals in endemic clusters throughout the country. Migration can facilitate movement of disease between endemic and non-endemic areas, and has been considered a possible factor in continued leprosy incidence in Brazil. A study was conducted to investigate migration as a risk factor for leprosy. The study had three aims: (1) examine past five year migration as a risk factor for leprosy, (2) describe and compare geographic and temporal patterns of migration among past 5-year migrants with leprosy and a control group, and (3) examine social determinants of health associated with leprosy among past 5-year migrants. The study implemented a matched case-control design and analysis comparing individuals newly diagnosed with leprosy (n = 340) and a clinically unapparent control group (n = 340) without clinical signs of leprosy, matched for age, sex and location in four endemic municipalities in the state of Maranhão, northeastern Brazil. Fishers exact test was used to conduct bivariate analyses. A multivariate logistic regression analysis was employed to control for possible confounding variables. Eighty cases (23.5%) migrated 5-years prior to diagnosis, and 55 controls (16.2%) migrated 5-years prior to the corresponding case diagnosis. Past 5 year migration was found to be associated with leprosy (OR: 1.59; 95% CI 1.07–2.38; p = 0.02), and remained significantly associated with leprosy after controlling for leprosy contact in the family, household, and family/household contact. Poverty, as well as leprosy contact in the family, household and other leprosy contact, was associated with leprosy among past 5-year migrants in the bivariate analysis. Alcohol consumption was also associated with leprosy, a relevant risk factor in susceptibility to infection that should be explored in future research. Our findings provide insight into patterns of migration to localize focused control efforts in endemic areas with high population mobility. PMID:24040433

Migration and control of purple loosestrife (Lythrum salicaria L.) along highway corridors

NASA Astrophysics Data System (ADS)

Wilcox, Douglas A.

1989-05-01

The east-west density gradient and the pattern and mode of migration of the wetland exotic, purple loosestrife ( Lythrum salicaria L.), were assessed in a survey of populations along the New York State Thruway from Albany to Buffalo to determine if the highway corridor contributed to the spread of this species. During the peak flowering season of late July to early August, individual colonies of purple loosestrife were identified and categorized into three size classes in parallel belt transects consisting of the median strip and highway rights-of-way on the north and south sides of the road. Data were also collected on the presence of colonies adjacent to the corridor and on highway drainage patterns. Although a distinct east-west density gradient existed in the corridor, it corresponded to the gradient on adjacent lands and was greatly influenced by a major infestation at Montezuma National Wildlife Refuge. The disturbed highway corridor served as a migration route for purple loosestrife, but topographic features dictated that this migration was a short-distance rather than long-distance process. Ditch and culvert drainage patterns increased the ability of purple loosestrife to migrate to new wetland sites. Management strategies proposed to reduce the spread of this wetland threat include minimizing disturbance, pulling by hand, spraying with glyphosate, disking, and mowing.

Migration and control of purple loosestrife (Lythrum salicaria L.) along highway corridors

USGS Publications Warehouse

Wilcox, Douglas A.

1989-01-01

The east-west density gradient and the pattern and mode of migration of the wetland exotic, purple loosestrife (Lythrum salicaria L.), were assessed in a survey of populations along the New York State Thruway from Albany to Buffalo to determine if the highway corridor contributed to the spread of this species. During the peak flowering season of late July to early August, individual colonies of purple loosestrife were identified and categorized into three size classes in parallel belt transects consisting of the median strip and highway rights-of-way on the north and south sides of the road. Data were also collected on the presence of colonies adjacent to the corridor and on highway drainage patterns. Although a distinct east-west density gradient existed in the corridor, it corresponded to the gradient on adjacent lands and was greatly influenced by a major infestation at Montezuma National Wildlife Refuge. The disturbed highway corridor served as a migration route for purple loosestrife, but topographic features dictated that this migration was a short-distance rather than long-distance process. Ditch and culvert drainage patterns increased the ability of purple loosestrife to migrate to new wetland sites. Management strategies proposed to reduce the spread of this wetland threat include minimizing disturbance, pulling by hand, spraying with glyphosate, disking, and mowing.

Linkages between life history type and migration pathways in freshwater and marine environments for Chinook salmon, Oncorhynchus tshawytscha

NASA Astrophysics Data System (ADS)

Sharma, Rishi; Quinn, Thomas P.

2012-05-01

Chinook salmon, Oncorhynchus tshawytscha, are commonly categorized as ocean-type (migrating to the ocean in their first year of life) or stream-type (migrating after a full year in freshwater). These two forms have been hypothesized to display different ocean migration pathways; the former are hypothesized to migrate primarily on the continental shelf whereas the latter are hypothesized to migrate off the shelf to the open ocean. These differences in migration patterns have important implications for management, as fishing mortality rates are strongly influenced by ocean migration. Ocean-type Chinook salmon predominate in coastal rivers in the southern part of the species' range, whereas stream-type predominate in the interior and northerly rivers. This latitudinal gradient has confounded previous efforts to test the hypothesis regarding ocean migration pathways. To address this problem, we used a pair-wise design based on coded wire tagging data to compare the marine distributions of stream- and ocean-type Chinook salmon from a suite of rivers producing both forms. Both forms of Chinook salmon from the lower Columbia River, Oregon coast, lower Fraser River, and northern British Columbia rivers followed similar migration paths, contradicting the hypothesis. In contrast, recoveries of tagged Chinook salmon from the upper Columbia River, Snake River, and the upper Fraser River revealed migration patterns consistent with the hypothesis. These findings have important implications for our understanding of these life history types, and also for the conservation and management of declining, threatened, or endangered stream-type Chinook salmon populations in the US and Canada.

Changing patterns of migration in the Adriatic region.

PubMed

Schatzer, P

1988-06-01

International migration in the Adriatic countries of Albania, Greece, Italy, San Marino, and Yugoslavia is briefly examined using data from official and other published sources. The main types of migratory movements identified by the author within the region are "1) economically motivated migration (legal and clandestine); 2) immigration of refugees for resettlement; 3) immigration with the scope of final resettlement in a third country (transit movements); [and] 4) return migration by former emigrants." excerpt

China’s Internal Migration, Public Policies, and Economic Growth

DTIC Science & Technology

2012-12-01

Studying the internal migration of China since 1949, the overall effect of migration on economic performance has had a discernible impact both...positive and negative at different times. There are two distinct aspects: the actual migration patterns and their relative effects on the economy; and the ...domestic policies enacted by the PRC that directly prompted movements whether intentional or not. This thesis has led to the conclusion that it was the

Migration from printing inks in multilayer food packaging materials by GC-MS analysis and pattern recognition with chemometrics.

PubMed

Clemente, Isabel; Aznar, Margarita; Nerín, Cristina; Bosetti, Osvaldo

2016-01-01

Inks and varnishes used in food packaging multilayer materials can contain different substances that are potential migrants when packaging is in contact with food. Although printing inks are applied on the external layer, they can migrate due to set-off phenomena. In order to assess food safety, migration tests were performed from two materials sets: set A based on paper and set B based on PET; both contained inks. Migration was performed to four food simulants (EtOH 50%, isooctane, EtOH 95% and Tenax(®)) and the volatile compounds profile was analysed by GC-MS. The effect of presence/absence of inks and varnishes and also their position in the material was studied. A total of 149 volatile compounds were found in migration from set A and 156 from set B materials, some of them came from inks. Quantitative analysis and a principal component analysis were performed in order to identify patterns among sample groups.

Digital Plasmonic Patterning for Localized Tuning of Hydrogel Stiffness.

PubMed

Hribar, Kolin C; Choi, Yu Suk; Ondeck, Matthew; Engler, Adam J; Chen, Shaochen

2014-08-20

The mechanical properties of the extracellular matrix (ECM) can dictate cell fate in biological systems. In tissue engineering, varying the stiffness of hydrogels-water-swollen polymeric networks that act as ECM substrates-has previously been demonstrated to control cell migration, proliferation, and differentiation. Here, "digital plasmonic patterning" (DPP) is developed to mechanically alter a hydrogel encapsulated with gold nanorods using a near-infrared laser, according to a digital (computer-generated) pattern. DPP can provide orders of magnitude changes in stiffness, and can be tuned by laser intensity and speed of writing. In vitro cellular experiments using A7R5 smooth muscle cells confirm cell migration and alignment according to these patterns, making DPP a useful technique for mechanically patterning hydrogels for various biomedical applications.

Cadherins in cerebellar development: translation of embryonic patterning into mature functional compartmentalization.

PubMed

Redies, Christoph; Neudert, Franziska; Lin, Juntang

2011-09-01

Cadherins are cell adhesion molecules with multiple morphogenic functions in brain development, for example, in neuroblast migration and aggregation, axon navigation, neural circuit formation, and synaptogenesis. More than 100 members of the cadherin superfamily are expressed in the developing and mature brain. Most of the cadherins investigated, in particular classic cadherins and δ-protocadherins, are expressed in the cerebellum. For several cadherin subtypes, expression begins at early embryonic stages and persists until mature stages of cerebellar development. At intermediate stages, distinct Purkinje cell clusters exhibit unique rostrocaudal and mediolateral expression profiles for each cadherin. In the chicken, mouse, and other species, the Purkinje cell clusters are separated by intervening raphes of migrating granule cells. This pattern of Purkinje cell clusters/raphes is, at least in part, continuous with the parasagittal striping pattern that is apparent in the mature cerebellar cortex, for example, for zebrin II/aldolase C. Moreover, subregions of the deep cerebellar nuclei, vestibular nuclei and the olivary complex also express cadherins differentially. Neuroanatomical evidence suggests that the nuclear subregions and cortical domains that express the same cadherin subtype are connected to each other, to form neural subcircuits of the cerebellar system. Cadherins thus provide a molecular code that specifies not only embryonic structures but also functional cerebellar compartmentalization. By following the implementation of this code, it can be revealed how mature functional architecture emerges from embryonic patterning during cerebellar development. Dysfunction of some cadherins is associated with psychiatric diseases and developmental impairments and may also affect cerebellar function.

Don't Fence Me In: Free Meanders in a Confined River Valley

NASA Astrophysics Data System (ADS)

Eke, E. C.; Wilcock, P. R.

2015-12-01

The interaction between meandering river channels and inerodible valley walls provides a useful test of our ability to understand meander dynamics. In some cases, river meanders confined between valley walls display distinctive angular bends in a dynamic equilibrium such that their size and shape persist as the meander migrates. In other cases, meander geometry is more varied and changes as the meander migrates. The ratio of channel to valley width has been identified as a useful parameter for defining confined meanders, but is not sufficient to distinguish cases in which sharp angular bends are able to migrate with little change in geometry. Here, we examine the effect of water and sediment supply on the geometry of confined rivers in order to identify conditions under which meander geometry reaches a persistent dynamic equilibrium. Because channel width and meander geometry are closely related, we use a numerical meander model that allows for independent migration of both banks, thereby allowing channel width to vary in space and time. We hypothesize that confined meanders with persistent angular bends have smaller transport rates of bed material and that their migration is driven by erosion of the cutbank (bank-pull migration). When bed material supply is sufficiently large that point bar deposition drives meander migration (bar-push migration), confined meander bends have a larger radius of curvature and a geometry that varies as the meander migrates. We test this hypothesis using historical patterns of confined meander migration for rivers with different rates of sediment supply and bed material transport. Interpretation of the meander migration pattern is provided by the free-width meander migration model.

Measurement of Heavy Ion Irradiation Induced In-Plane Strain in Patterned Face-Centered-Cubic Metal Films: An in Situ Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, K. Y.; Chen, Y.; Li, J.

Nanocrystalline Ag, Cu, and Ni thin films and their coarse grained counterparts are patterned in this paper using focused ion beam and then irradiated by Kr ions within an electron microscope at room temperature. Irradiation induced in-plane strain of the films is measured by tracking the location of nanosized holes. The magnitude of the strain in all specimens is linearly dose-dependent and the strain rates of nanocrystalline metals are significantly greater as compared to that of the coarse grained metals. Finally, real-time microscopic observation suggests that substantial grain boundary migration and grain rotation are responsible for the significant in-plane strain.

Measurement of Heavy Ion Irradiation Induced In-Plane Strain in Patterned Face-Centered-Cubic Metal Films: An in Situ Study

DOE PAGES

Yu, K. Y.; Chen, Y.; Li, J.; ...

2016-11-28

Nanocrystalline Ag, Cu, and Ni thin films and their coarse grained counterparts are patterned in this paper using focused ion beam and then irradiated by Kr ions within an electron microscope at room temperature. Irradiation induced in-plane strain of the films is measured by tracking the location of nanosized holes. The magnitude of the strain in all specimens is linearly dose-dependent and the strain rates of nanocrystalline metals are significantly greater as compared to that of the coarse grained metals. Finally, real-time microscopic observation suggests that substantial grain boundary migration and grain rotation are responsible for the significant in-plane strain.

Poverty Catchments: Migration, Residential Mobility, and Population Turnover in Impoverished Rural Illinois Communities

ERIC Educational Resources Information Center

Foulkes, Matt; Newbold, K. Bruce

2008-01-01

Research has thoroughly documented how out-migration of the educated and skilled from rural areas leaves behind a poorer population and creates pockets of rural poverty. Recently, studies have recognized that the poor are also geographically mobile and that poverty migration patterns can reinforce rural poverty concentrations. In this process,…

Green migration into rural America: The new frontier of environmentalism?

Treesearch

Robert Emmet Jones; J. Mark Fly; James Talley; H. Ken Cordell

2003-01-01

This article proposes that shifts in rural population and economic growth patterns may help explain rising levels of support for environmental values in many rural areas. In particular, it assesses a model of "green migration" that assumes that domestic in-migration, with its impacts on the character and composition of rural communities, is one of the reasons...

Dual impacts of climate change: forest migration and turnover through life history

Treesearch

Kai Zhu; Christopher W. Woodall; Souparno Ghosh; Alan E. Gelfand; James S. Clark

2014-01-01

Tree species are predicted to track future climate by shifting their geographic distributions, but climate-mediated migrations are not apparent in a recent continental-scale analysis. To better understand the mechanisms of a possible migration lag, we analyzed relative recruitment patterns by comparing juvenile and adult tree abundances in climate space. One would...

Human Migration Patterns in Yemen and Implications for Reconstructing Prehistoric Population Movements

PubMed Central

Miró-Herrans, Aida T.; Al-Meeri, Ali; Mulligan, Connie J.

2014-01-01

Population migration has played an important role in human evolutionary history and in the patterning of human genetic variation. A deeper and empirically-based understanding of human migration dynamics is needed in order to interpret genetic and archaeological evidence and to accurately reconstruct the prehistoric processes that comprise human evolutionary history. Current empirical estimates of migration include either short time frames (i.e. within one generation) or partial knowledge about migration, such as proportion of migrants or distance of migration. An analysis of migration that includes both proportion of migrants and distance, and direction over multiple generations would better inform prehistoric reconstructions. To evaluate human migration, we use GPS coordinates from the place of residence of the Yemeni individuals sampled in our study, their birthplaces and their parents' and grandparents' birthplaces to calculate the proportion of migrants, as well as the distance and direction of migration events between each generation. We test for differences in these values between the generations and identify factors that influence the probability of migration. Our results show that the proportion and distance of migration between females and males is similar within generations. In contrast, the proportion and distance of migration is significantly lower in the grandparents' generation, most likely reflecting the decreasing effect of technology. Based on our results, we calculate the proportion of migration events (0.102) and mean and median distances of migration (96 km and 26 km) for the grandparent's generation to represent early times in human evolution. These estimates can serve to set parameter values of demographic models in model-based methods of prehistoric reconstruction, such as approximate Bayesian computation. Our study provides the first empirically-based estimates of human migration over multiple generations in a developing country and these estimates are intended to enable more precise reconstruction of the demographic processes that characterized human evolution. PMID:24759992

Bioelectric patterning during oogenesis: stage-specific distribution of membrane potentials, intracellular pH and ion-transport mechanisms in Drosophila ovarian follicles.

PubMed

Krüger, Julia; Bohrmann, Johannes

2015-01-16

Bioelectric phenomena have been found to exert influence on various developmental and regenerative processes. Little is known about their possible functions and the cellular mechanisms by which they might act during Drosophila oogenesis. In developing follicles, characteristic extracellular current patterns and membrane-potential changes in oocyte and nurse cells have been observed that partly depend on the exchange of protons, potassium ions and sodium ions. These bioelectric properties have been supposed to be related to various processes during oogenesis, e. g. pH-regulation, osmoregulation, cell communication, cell migration, cell proliferation, cell death, vitellogenesis and follicle growth. Analysing in detail the spatial distribution and activity of the relevant ion-transport mechanisms is expected to elucidate the roles that bioelectric phenomena play during oogenesis. To obtain an overview of bioelectric patterning along the longitudinal and transversal axes of the developing follicle, the spatial distributions of membrane potentials (Vmem), intracellular pH (pHi) and various membrane-channel proteins were studied systematically using fluorescent indicators, fluorescent inhibitors and antisera. During mid-vitellogenic stages 9 to 10B, characteristic, stage-specific Vmem-patterns in the follicle-cell epithelium as well as anteroposterior pHi-gradients in follicle cells and nurse cells were observed. Corresponding distribution patterns of proton pumps (V-ATPases), voltage-dependent L-type Ca(2+)-channels, amiloride-sensitive Na(+)-channels and Na(+),H(+)-exchangers (NHE) and gap-junction proteins (innexin 3) were detected. In particular, six morphologically distinguishable follicle-cell types are characterized on the bioelectric level by differences concerning Vmem and pHi as well as specific compositions of ion channels and carriers. Striking similarities between Vmem-patterns and activity patterns of voltage-dependent Ca(2+)-channels were found, suggesting a mechanism for transducing bioelectric signals into cellular responses. Moreover, gradients of electrical potential and pH were observed within single cells. Our data suggest that spatial patterning of Vmem, pHi and specific membrane-channel proteins results in bioelectric signals that are supposed to play important roles during oogenesis, e. g. by influencing spatial coordinates, regulating migration processes or modifying the cytoskeletal organization. Characteristic stage-specific changes of bioelectric activity in specialized cell types are correlated with various developmental processes.

Spatial genetic features of eastern oysters (Crassostrea virginica Gmelin) in the Gulf of Mexico: northward movement of a secondary contact zone.

PubMed

Anderson, Joel D; Karel, William J; Mace, Christopher E; Bartram, Brian L; Hare, Matthew P

2014-05-01

The eastern oyster (Crassostrea virginica Gmelin) is an economically and ecologically valuable marine bivalve occurring in the Gulf of Mexico. This study builds upon previous research that identified two divergent populations of eastern oysters in the western Gulf of Mexico. Allelic and genotypic patterns from 11 microsatellite markers were used to assess genetic structure and migration between the previously described oyster populations in Texas. The main findings are as follows: (1) there are two distinct populations (F ST = 0.392, P < 0.001) of oysters that overlap in the Corpus Christi/Aransas Bay estuarine complex in Texas, (2) the distribution of genotypes among individuals in the contact zone suggests limited hybridization between populations, (3) the variables of salinity, temperature, dissolved oxygen, turbidity and depth are not correlated with allele frequencies on reefs in the contact zone or when analyzed across Texas, and (4) there is little evidence of directional selection acting on the loci assayed here, although patterns at four markers suggested the influence of balancing selection based on outlier analyses. These results are consistent with long-term historical isolation between populations, followed by secondary contact. Recent hydrological changes in the area of secondary contact may be promoting migration in areas that were previously inhospitable to eastern oysters, and observed differences in the timing of spawning may limit hybridization between populations. Comparison of these findings with the results of an earlier study of oysters in Texas suggests that the secondary contact zone has shifted approximately 27 km north, in as little as a 23-year span.

Spatial genetic features of eastern oysters (Crassostrea virginica Gmelin) in the Gulf of Mexico: northward movement of a secondary contact zone

PubMed Central

Anderson, Joel D; Karel, William J; Mace, Christopher E; Bartram, Brian L; Hare, Matthew P

2014-01-01

The eastern oyster (Crassostrea virginica Gmelin) is an economically and ecologically valuable marine bivalve occurring in the Gulf of Mexico. This study builds upon previous research that identified two divergent populations of eastern oysters in the western Gulf of Mexico. Allelic and genotypic patterns from 11 microsatellite markers were used to assess genetic structure and migration between the previously described oyster populations in Texas. The main findings are as follows: (1) there are two distinct populations (FST = 0.392, P < 0.001) of oysters that overlap in the Corpus Christi/Aransas Bay estuarine complex in Texas, (2) the distribution of genotypes among individuals in the contact zone suggests limited hybridization between populations, (3) the variables of salinity, temperature, dissolved oxygen, turbidity and depth are not correlated with allele frequencies on reefs in the contact zone or when analyzed across Texas, and (4) there is little evidence of directional selection acting on the loci assayed here, although patterns at four markers suggested the influence of balancing selection based on outlier analyses. These results are consistent with long-term historical isolation between populations, followed by secondary contact. Recent hydrological changes in the area of secondary contact may be promoting migration in areas that were previously inhospitable to eastern oysters, and observed differences in the timing of spawning may limit hybridization between populations. Comparison of these findings with the results of an earlier study of oysters in Texas suggests that the secondary contact zone has shifted approximately 27 km north, in as little as a 23-year span. PMID:24967084

Temperature-induced physiological stress and reproductive characteristics of the migratory seahorse Hippocampus erectus during a thermal stress simulation.

PubMed

Qin, Geng; Johnson, Cara; Zhang, Yuan; Zhang, Huixian; Yin, Jianping; Miller, Glen; Turingan, Ralph G; Guisbert, Eric; Lin, Qiang

2018-05-15

Inshore-offshore migration occurs frequently in seahorse species either because of prey opportunities or because it is driven by reproduction, and variations in water temperature may dramatically change migratory seahorse behavior and physiology. The present study investigated the behavioral and physiological responses of the lined seahorse Hippocampus erectus under thermal stress and evaluated the potential effects of different temperatures on its reproduction. The results showed that the thermal tolerance of the seahorses was time dependent. Acute thermal stress (30°C, 2-10 hours) increased the basal metabolic rate (breathing rate) and the expression of stress response genes ( Hsp genes) significantly and further stimulated seahorse appetite. Chronic thermal treatment (30°C, 4 weeks) led to a persistently higher basal metabolic rate, higher stress response gene expression, and higher mortality, indicating that the seahorses could not acclimate to chronic thermal stress and might experience massive mortality due to excessive basal metabolic rates and stress damage. Additionally, no significant negative effects on gonad development or reproductive endocrine regulation genes were observed in response to chronic thermal stress, suggesting that seahorse reproductive behavior could adapt to higher-temperature conditions during migration and within seahorse breeding grounds. In conclusion, this simulation experiment indicated that temperature variations during inshore-offshore migration have no effect on reproduction but promote basal metabolic rates and stress responses significantly. Therefore, we suggest that the high observed tolerance of seahorse reproduction was in line with the inshore-offshore reproductive migration pattern of lined seahorse. © 2018. Published by The Company of Biologists Ltd.

Flyway-scale variation in plasma triglyceride levels as an index of refueling rate in spring-migrating western sandpipers (Calidris mauri)

USGS Publications Warehouse

Williams, T.D.; Warnock, N.; Takekawa, John Y.; Bishop, M.A.

2007-01-01

We combined radiotelemetry, plasma metabolite analyses, and macro-invertebrate prey sampling to investigate variation in putative fattening rates (estimated as plasma triglyceride levels) at the flyway scale in Western Sandpipers (Calidris mauri) migrating between Punta Banda, Mexico (31°N), and Hartney Bay, Alaska (60°N), a distance of 4,240 km. Birds were caught at a wintering site (San Francisco Bay) and eight stopover sites along this Pacific Flyway. Body mass was higher in females than in males at six sites, but variation was not correlated with latitude for either sex, and the relationship of change in mass by date within sites was uninformative with regard to possible latitudinal variation in fattening rates. At San Francisco Bay, triglyceride levels were higher in the spring than in the winter. Mean plasma triglyceride varied among stopover sites, and there was a significant linear trend of increasing triglyceride levels with latitude as birds migrated north. At San Francisco Bay, length of stay was negatively related to triglyceride levels. However, plasma triglyceride levels at wintering or initial stopover sites (San Francisco and Punta Banda) did not predict individual variation in subsequent rates of travel during migration. We found no significant relationship between triglyceride levels and prey biomass at different stopover sites, which suggests that the latitudinal pattern is not explained by latitudinal changes in food availability. Rather, we suggest that differences in physiology of migratory birds at southern versus northern stopover sites or behavioral differences may allow birds to sustain higher fattening rates closer to the breeding grounds.

Gas Migration Processes through the Gas Hydrate Stability Zone at Four-Way Closure Ridge Offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Kunath, P.; Chi, W. C.; Berndt, C.; Liu, C. S.

2016-12-01

We have used 3D P-Cable seismic data from Four-Way-Closure Ridge, a NW-SE trending anticlinal ridge within the lower slope domain of accretionary wedge, to investigate the geological constraints influencing the fluid migration pattern in the shallow marine sediments. In the seismic data, fluid migration feature manifests itself as high reflection layers of dipping strata, which originate underneath a bottom simulating reflector (BSR) and extend towards the seafloor. Shoaling of the BSR near fluid migration pathways indicates a focused fluid flux, perturbing the temperature field. Furthermore, seafloor video footage confirmed the presence of recent methane seepage above seismically imaged fluid migration pathways. We plan to test two hypotheses for the occurrence of these fluid migration pathways: 1) the extensional regime under the anticlinal ridge crest caused the initiation of localized fault zones, acting as fluid conduits in the gas hydrate stability zone (GHSZ). 2) sediment deformation induced by focused fluid flow and massive growth and dissolution of gas hydrate, similar to processes controlling the evolution of pockmarks on the Nigerian continental margin. We suggest that these processes may be responsible for the formation of a massive hydrate core in the crest of the anticline, as inferred from other geophysical datasets. Triggering process for fluid migration cannot be clearly defined. However, the existence of blind thrust faults may help to advect deep-seated fluids. This may be augmented by biogenic production of shallow gas underneath the ridge, where the excess of gas enables the coexistence of gas, water, and gas hydrate within the GHSZ. Fluid migration structures may exists because of the buoyancy of gas-bearing fluids. This study shows a potential model on how gas-bearing fluids migrate upward towards structural highs, which might occur in other anticlinal structures around the world. Keywords: P-Cable, gas-hydrate, fluid flow, fault-related fold, methane seepage

Comparative Study on Migration, Urbanization and Development in the ESCAP Region (RAS/P13/79). Rev. version.

PubMed

1982-01-01

Development of a study project by the UN Economic and Social Commission for Asia and the Pacific (ESCAP) on migration, urbanization, and development in the following countries is described: Indonesia, Malaysia, Pakistan, Philippines, Republic of Korea, Sri Lanka, and Thailand. The project's immediate goal is to assist decision makers in formulating population redistribution policies. It was recommended that ESCAP develop and test a migration questionnaire to assist member countries in undertaking surveys to study the interrelationships of migration and development. Upon completion of survey manuals to assist in the survey implementation, it was suggested that ESCAP run a series of in-country workshops to discuss the applications of survey results for policy formulation. A national migration survey will be taken in each country in the early 1980s in order to discern pattern and type of population mobility, factors that cause people to move or not to move, and the consequences of migration on places of origin and destination. A sample of 14,000 households in each country will be selected and 1 person of age 15-64 will be chosen as the respondent for each household. the following are some items which will be studied: 1) volume of migration streams within and between metropolitan areas and urban-rural areas; 2) decision making factors; 3) interactions between population movement and family structure, chages in fertility levels, employment, and education; 4) impact of agricultural systems on seasonal movements; 5) contributions of migrants to the cities; and 6) implications of international migration to and from the country. Leading family planning agencies will use these results to develop policy relating to population distribution, industry location, migration laws, regional economic planning, modern technology, and rural education. The management framework of the project is presented. After these results are published, government agencies can utilize them by incorporating direct questions on population movement into the national census, conducting demonstration projects to assess the impact of population movement programs, and training personnel.

Divergent migration within lake sturgeon (Acipenser fulvescens) populations: Multiple distinct patterns exist across an unrestricted migration corridor

USGS Publications Warehouse

Kessel, Steven T.; Hondorp, Darryl W.; Holbrook, Christopher; Boase, James C.; Chiotti, Justin A.; Thomas, Michael V.; Wills, Todd C.; Roseman, Edward; Drouin, Richard; Krueger, Charles C.

2018-01-01

Population structure, distribution, abundance, and dispersal arguably underpin the entire field of animal ecology, with consequences for regional species persistence, and provision of ecosystem services. Divergent migration behaviours among individuals or among populations is an important aspect of the ecology of highly-mobile animals, allowing populations to exploit spatially- or temporally-distributed food and space resources.This study investigated the spatial ecology of lake sturgeon (Acipenser fulvescens) within the barrier free Huron-Erie Corridor (HEC), which connects Lake Huron and Lake Erie of the North American Laurentian Great Lakes.Over six years (2011 – 2016), movements of 268 lake sturgeon in the HEC were continuously monitored across the Great Lakes using acoustic telemetry (10 yr battery life acoustic transmitters). Five distinct migration behaviours were identified with hierarchical cluster analysis, based on the phenology and duration of river and lake use.Lake sturgeon in the HEC were found to contain a high level of intraspecific divergent migration, including partial migration with the existence of residents. Specific behaviours included year-round river residency and multiple lake-migrant behaviours that involved movements between lakes and rivers. Over 85% of individuals were assign to migration behaviours as movements were consistently repeated over the study, which suggested migration behaviours were consistent and persistent in lake sturgeon. Differential use of specific rivers or lakes by acoustic-tagged lake sturgeon further subdivided individuals into 14 “contingents” (spatiotemporally segregated subgroups).Contingents associated with one river (Detroit or St. Clair) were rarely detected in the other river, which confirmed that lake sturgeon in the Detroit and St. Clair represent two semi-independent populations that could require separate management consideration for their conservation. The distribution of migration behaviours did not vary between populations, sexes, body size, or among release locations, which indicated that intrapopulation variability in migratory behaviour is a general feature of the spatial ecology of lake sturgeon in un-fragmented landscapes.

Trend of different molecular markers in the last decades for studying human migrations.

PubMed

Kundu, Sharbadeb; Ghosh, Sankar Kumar

2015-02-10

Anatomically modern humans are known to have widely migrated throughout history. Different scientific evidences suggest that the entire human population descended from just several thousand African migrants. About 85,000 years ago, the first wave of human migration was out of Africa, that followed the coasts through the Middle East, into Southern Asia via Sri Lanka, and in due course around Indonesia and into Australia. Another wave of migration between 40,000 and 12,000 years ago brought humans northward into Europe. However, the frozen north limited human expansion in Europe, and created a land bridge, "Bering land bridge", connecting Asia with North America about 25,000 years ago. Although fossil data give the most direct information about our past, it has certain anomalies. So, molecular archeologists are now using different molecular markers to trace the "most recent common ancestor" and also the migration pattern of modern humans. In this study, we have studied the trend of molecular markers and also the methodologies implemented in the last decades (2003-2014). From our observation, we can say that D-loop region of mtDNA and Y chromosome based markers are predominant. Nevertheless, mtDNA, especially the D-loop region, has some unique features, which makes it a more effective marker for tracing prehistoric footprints of modern human populations. Although, natural selection should also be taken into account in studying mtDNA based human migration. As per technology is concerned, Sanger sequencing is the major technique that is being used in almost all studies. But, the emergence of different cost-effective-and-easy-to-handle NGS platforms has increased its popularity over Sanger sequencing in studying human migration. Copyright © 2014. Published by Elsevier B.V.

Migrant children and migrants’ children: Nativity differences in school enrollment in Mexico and the United States

PubMed Central

Glick, Jennifer E.; Yabiku, Scott T.

2016-01-01

BACKGROUND The growing prevalence of migrant children in diverse contexts requires a reconsideration of the intergenerational consequences of migration. To understand how migration and duration of residence are associated with children’s schooling, we need more comparative work that can point to the similarities and differences in outcomes for children across contexts. OBJECTIVE This paper addresses the importance of nativity and duration of residence for children’s school enrollment on both sides of a binational migration system: The United States and Mexico. The analyses are designed to determine whether duration of residence has a similar association with school enrollment across these different settings. METHODS The analyses are based on nationally representative household data from the 2010 Mexican Census and the 2006–2010 American Community Survey. Logistic regression models compare school enrollment patterns of Mexican and U.S.-born children of Mexican origin in the United States and those of Mexican and U.S.-born children in Mexico. Interactions for nativity/duration of residence and age are also included. RESULTS The results demonstrate that, adjusting for household resources and household-level migration experience, Mexican-born children in the United States and U.S.-born children in Mexico, particularly those who arrived recently, lag behind in school enrollment. These differences are most pronounced at older ages. CONCLUSIONS The comparisons across migration contexts point to greater school attrition and non-enrollment among older, recent migrant youth, regardless of the context. The interactions suggest that recent migration is associated with lower schooling for youth who engage in migration at older ages in both the United States and Mexico. PMID:28077926

DHA-mediated regulation of lung cancer cell migration is not directly associated with Gelsolin or Vimentin expression.

PubMed

Ali, Mehboob; Heyob, Kathryn; Rogers, Lynette K

2016-06-15

Deaths associated with cancer metastasis have steadily increased making the need for newer, anti-metastatic therapeutics imparative. Gelsolin and vimentin, actin binding proteins expressed in metastatic tumors, participate in actin remodelling and regulate cell migration. Docosahexaenoic acid (DHA) limits cancer cell proliferation and adhesion but the mechanisms involved in reducing metastatic phenotypes are unknown. We aimed to investigate the effects of DHA on gelsolin and vimentin expression, and ultimately cell migration and proliferation, in this context. Non-invasive lung epithelial cells (MLE12) and invasive lung cancer cells (A549) were treated with DHA (30μmol/ml) or/and 8 bromo-cyclic adenosine monophosphate (8 Br-cAMP) (300μmol/ml) for 6 or 24h either before (pre-treatment) or after (post-treatment) plating in transwells. Migration was assessed by the number of cells that progressed through the transwell. Gelsolin and vimentin expression were measured by Western blot and confocal microscopy in cells, and by immunohistochemistry in human lung cancer biopsy samples. A significant decrease in cell migration was detected for A549 cells treated with DHA verses control but this same decrease was not seen in MLE12 cells. DHA and 8 Br-cAMP altered gelsolin and vimentin expression but no clear pattern of change was observed. Immunofluorescence staining indicated slightly higher vimentin expression in human lung tissue that was malignant compared to control. Collectively, our data indicate that DHA inhibits cancer cell migration and further suggests that vimentin and gelsolin may play secondary roles in cancer cell migration and proliferation, but are not the primary regulators. Copyright © 2016 Elsevier Inc. All rights reserved.

DHA-Mediated Regulation of Lung Cancer Cell Migration Is Not Directly Associated with Gelsolin or Vimentin Expression

PubMed Central

Ali, Mehboob; Heyob, Kathryn; Rogers, Lynette K.

2016-01-01

AIMS Deaths associated with cancer metastasis have steadily increased making the need for newer, anti-metastatic therapeutics imparative. Gelsolin and vimentin, actin binding proteins expressed in metastatic tumors, participate in actin remodelling and regulate cell migration. Docosahexaenoic acid (DHA) limits cancer cell proliferation and adhesion but the mechanisms involved in reducing metastatic phenotypes are unknown. We aimed to investigate the effects of DHA on gelsolin and vimentin expression, and ultimately cell migration and proliferation, in this context. MAIN METHODS Non-invasive lung epithelial cells (MLE12) and invasive lung cancer cells (A549) were treated with DHA (30 μmol/ml) or/and 8 bromo-cyclic adenosine monophosphate (8 Br-cAMP) (300 μmol/ml) for 6 or 24 h either before (pre-treatment) or after (post-treatment) plating in transwells. Migration was assessed by the number of cells that progressed through the transwell. Gelsolin and vimentin expression were measured by western blot and confocal microscopy in cells, and by immunohistochemistry in human lung cancer biospy samples. KEY FINDINGS A significant decrease in cell migration was detected for A549 cells treated with DHA verses control but this same decrease was not seen in MLE12 cells. DHA and 8 Br-cAMP altered gelsolin and vimentin expression but no clear pattern of change was observed. Immunoflorescence staining indicated slightly higher vimentin expression in human lung tissue that was malignant compared to control. SIGNIFICANCE Collectively, our data indicate that DHA inhibits cancer cell migration and further suggests that vimentin and gelsolin may play secondary roles in cancer cell migration and proliferation, but are not the primary regulators. PMID:27157519

Partial migration and transient coexistence of migrants and residents in animal populations.

PubMed

Singh, Navinder J; Leonardsson, Kjell

2014-01-01

Partial migration, whereby a proportion of the population migrates, is common across the animal kingdom. Much of the focus in the literature has been on trying to explain the underlying mechanisms for the coexistence of migrants and residents. In addition, there has been an increasing number of reports on the prevalence and frequency of partially migratory populations. One possible explanation for the occurrence of partial migration, which has received no attention in the literature, is that of 'transient coexistence' during the invasion phase of a superior behaviour. In this study we develop a theoretical basis for explaining partial migration as a transient coexistence and derive a method to predict the frequency of residents and migrants in partially migrating populations. This method is useful to predict the frequencies of migrants and residents in a small set of populations as a complementing hypothesis to 'an Evolutionary Stable Strategy (ESS)'. We use the logistic growth equation to derive a formula for predicting the frequencies of residents and migrants. We also use simulations and empirical data from white perch (Morone americana), moose (Alces alces) and red deer (Cervus elaphus) to demonstrate our approach. We show that the probability of detecting partial migration due to transient coexistence depends upon a minimum number of tracked or marked individuals for a given number of populations. Our approach provides a starting point in searching for explanations to the observed frequencies, by contrasting the observed pattern with both the predicted transient and the uniform random pattern. Aggregating such information on observed patterns (proportions of migrants and residents) may eventually lead to the development of a quantitative theory for the equilibrium (ESS) populations as well.

Chagas Disease, Migration and Community Settlement Patterns in Arequipa, Peru

PubMed Central

Gilman, Robert H.; Cornejo del Carpio, Juan G.; Naquira, Cesar; Bern, Caryn; Levy, Michael Z.

2009-01-01

Background Chagas disease is one of the most important neglected tropical diseases in the Americas. Vectorborne transmission of Chagas disease has been historically rare in urban settings. However, in marginal communities near the city of Arequipa, Peru, urban transmission cycles have become established. We examined the history of migration and settlement patterns in these communities, and their connections to Chagas disease transmission. Methodology/Principal Findings This was a qualitative study that employed focus group discussions and in-depth interviews. Five focus groups and 50 in-depth interviews were carried out with 94 community members from three shantytowns and two traditional towns near Arequipa, Peru. Focus groups utilized participatory methodologies to explore the community's mobility patterns and the historical and current presence of triatomine vectors. In-depth interviews based on event history calendars explored participants' migration patterns and experience with Chagas disease and vectors. Focus group data were analyzed using participatory analysis methodologies, and interview data were coded and analyzed using a grounded theory approach. Entomologic data were provided by an ongoing vector control campaign. We found that migrants to shantytowns in Arequipa were unlikely to have brought triatomines to the city upon arrival. Frequent seasonal moves, however, took shantytown residents to valleys surrounding Arequipa where vectors are prevalent. In addition, the pattern of settlement of shantytowns and the practice of raising domestic animals by residents creates a favorable environment for vector proliferation and dispersal. Finally, we uncovered a phenomenon of population loss and replacement by low-income migrants in one traditional town, which created the human settlement pattern of a new shantytown within this traditional community. Conclusions/Significance The pattern of human migration is therefore an important underlying determinant of Chagas disease risk in and around Arequipa. Frequent seasonal migration by residents of peri-urban shantytowns provides a path of entry of vectors into these communities. Changing demographic dynamics of traditional towns are also leading to favorable conditions for Chagas disease transmission. Control programs must include surveillance for infestation in communities assumed to be free of vectors. PMID:20016830

Selective Modulation of Integrin-mediated Cell Migration by Distinct ADAM Family MembersV⃞

PubMed Central

Huang, Jing; Bridges, Lance C.; White, Judith M.

2005-01-01

A disintegrin and a metalloprotease (ADAM) family members have been implicated in many biological processes. Although it is recognized that recombinant ADAM disintegrin domains can interact with integrins, little is known about ADAM-integrin interactions in cellular context. Here, we tested whether ADAMs can selectively regulate integrin-mediated cell migration. ADAMs were expressed in Chinese hamster ovary cells that express defined integrins (α4β1, α5β1, or both), and cell migration on full-length fibronectin or on its α4β1 or α5β1 binding fragments was studied. We found that ADAMs inhibit integrin-mediated cell migration in patterns dictated by the integrin binding profiles of their isolated disintegrin domains. ADAM12 inhibited cell migration mediated by the α4β1 but not the α5β1 integrin. ADAM17 had the reciprocal effect; it inhibited α5β1- but not α4β1-mediated cell migration. ADAM19 and ADAM33 inhibited migration mediated by both α4β1 and α5β1 integrins. A point mutation in the ADAM12 disintegrin loop partially reduced the inhibitory effect of ADAM12 on cell migration on the α4β1 binding fragment of fibronectin, whereas mutations that block metalloprotease activity had no effect. Our results indicate that distinct ADAMs can modulate cell migration mediated by specific integrins in a pattern dictated, at least in part, by their disintegrin domains. PMID:16079176

Clan-structured migration and phenotypic differentiation in the Jirels of Nepal.

PubMed

Williams-Blangero, S

1989-04-01

This paper examines the impact of clan-structured migration on the between-village differentiation of the Jirels, a tribal population of eastern Nepal. The Jirel population is geographically restricted to nine villages, all of which were sampled to some extent for this study. Data on five head measurements, stature, and digital ridge counts are utilized to illustrate the patterns of phenotypic variation. Multivariate statistical techniques are used to assess the extent to which clan membership and associated patterns of marital exchange influence the population structure of the Jirels. The phenotypic characteristics of randomly generated migrant sets are compared to those of the observed clan-structured sets, demonstrating the clan-related phenotypic nonrandomness of migrants. The results indicate that clan-structured migration may significantly influence the amount of between-village variation. Clan structure may be a significant factor in determining patterns of variation and should not be ignored in studies of microdifferentiation in tribal populations.

Patterning of Endothelial Cells and Mesenchymal Stem Cells by Laser-Assisted Bioprinting to Study Cell Migration.

PubMed

Bourget, Jean-Michel; Kérourédan, Olivia; Medina, Manuela; Rémy, Murielle; Thébaud, Noélie Brunehilde; Bareille, Reine; Chassande, Olivier; Amédée, Joëlle; Catros, Sylvain; Devillard, Raphaël

2016-01-01

Tissue engineering of large organs is currently limited by the lack of potent vascularization in vitro . Tissue-engineered bone grafts can be prevascularized in vitro using endothelial cells (ECs). The microvascular network architecture could be controlled by printing ECs following a specific pattern. Using laser-assisted bioprinting, we investigated the effect of distance between printed cell islets and the influence of coprinted mesenchymal cells on migration. When printed alone, ECs spread out evenly on the collagen hydrogel, regardless of the distance between cell islets. However, when printed in coculture with mesenchymal cells by laser-assisted bioprinting, they remained in the printed area. Therefore, the presence of mesenchymal cell is mandatory in order to create a pattern that will be conserved over time. This work describes an interesting approach to study cell migration that could be reproduced to study the effect of trophic factors.

Patterning of Endothelial Cells and Mesenchymal Stem Cells by Laser-Assisted Bioprinting to Study Cell Migration

PubMed Central

Medina, Manuela; Rémy, Murielle; Thébaud, Noélie Brunehilde; Bareille, Reine; Chassande, Olivier; Amédée, Joëlle; Catros, Sylvain

2016-01-01

Tissue engineering of large organs is currently limited by the lack of potent vascularization in vitro. Tissue-engineered bone grafts can be prevascularized in vitro using endothelial cells (ECs). The microvascular network architecture could be controlled by printing ECs following a specific pattern. Using laser-assisted bioprinting, we investigated the effect of distance between printed cell islets and the influence of coprinted mesenchymal cells on migration. When printed alone, ECs spread out evenly on the collagen hydrogel, regardless of the distance between cell islets. However, when printed in coculture with mesenchymal cells by laser-assisted bioprinting, they remained in the printed area. Therefore, the presence of mesenchymal cell is mandatory in order to create a pattern that will be conserved over time. This work describes an interesting approach to study cell migration that could be reproduced to study the effect of trophic factors. PMID:27833916

Prehistoric mitochondrial DNA of domesticate animals supports a 13th century exodus from the northern US southwest

PubMed Central

Judd, Kathleen; Monroe, Cara; Hilldorfer, Lindsay; Cordray, Connor; Schad, Rebecca; Reams, Erin

2017-01-01

The 13th century Puebloan depopulation of the Four Corners region of the US Southwest is an iconic episode in world prehistory. Studies of its causes, as well as its consequences, have a bearing not only on archaeological method and theory, but also social responses to climate change, the sociology of social movements, and contemporary patterns of cultural diversity. Previous research has debated the demographic scale, destinations, and impacts of Four Corners migrants. Much of this uncertainty stems from the substantial differences in material culture between the Four Corners vs. hypothesized destination areas. Comparable biological evidence has been difficult to obtain due to the complete departure of farmers from the Four Corners in the 13th century CE and restrictions on sampling human remains. As an alternative, patterns of genetic variation among domesticated species were used to address the role of migration in this collapse. We collected mitochondrial haplotypic data from dog (Canis lupus familiaris) and turkey (Meleagris gallopavo) remains from archaeological sites in the most densely-populated portion of the Four Corners region, and the most commonly proposed destination area for that population under migration scenarios. Results are consistent with a large-scale migration of humans, accompanied by their domestic turkeys, during the 13th century CE. These results support scenarios that suggest contemporary Pueblo peoples of the Northern Rio Grande are biological and cultural descendants of Four Corners populations. PMID:28746407

The role of Internal Solitary Waves on deep-water sedimentary processes: the case of up-slope migrating sediment waves off the Messina Strait

NASA Astrophysics Data System (ADS)

Droghei, Riccardo; Falcini, Federico; Martorelli, Eleonora; Salusti, Ettore; Sannino, Gianmaria; Santoleri, Rosalia; Chiocci, Francesco

2015-04-01

In the last decade joint marine geology and physical oceanography studies are demonstrating the inherited connection between deep-water sedimentary processes and dynamics of water masses in a fruitful exchange in which bedforms type and geometry highlight slow or periodic bottom current processes or event of and oceanography explains and predicts morphological and sedimentary pattern at the seafloor. We investigate the presence of an intriguing up-slope migrating and rotating sand waves observed off the north entrance of the Messina Strait by taking into account the main oceanographic process occurring in the Strait, namely the presence of tidal induced internal solitary waves (ISWs). We hypothesize that the observed deflected pattern of these sand waves is due to refraction of wave occurring at the LIW-MAW interface and that the motion of the grains is due to the increased particle velocity field during the passage of ISWs. We modeled their formations and compared the results with the observed geometries of the dune field. Our findings suggest an intrinsic relationship between the dune filed and the presence of internal solitary waves, and provide some insights about their dynamics and migration rate as in accordance with previous measurements and analysis. We believe that our work represents an innovative and promising link between the geological and oceanographic communities, and gives some insights on the role of ISWs on sedimentary process.

Livelihood Diversification through Migration among a Pastoral People: Contrasting Case Studies of Maasai in Northern Tanzania

PubMed Central

McCabe, J. Terrence; Smith, Nicole M.; Leslie, Paul W.; Telligman, Amy L.

2015-01-01

This paper brings together over two decades of research concerning the patterns and processes of livelihood diversification through migration among Maasai pastoralists and agro-pastoralists of northern Tanzania. Two case studies, one from the Ngorongoro Conservation Area and the other from the Simanjiro plains, jointly demonstrate the complexity of migration within a single ethnic group. We analyze the relationship between wealth and migration and examine some of the consequences of migration for building herds, expanding cultivation, and influencing political leadership. We further argue that migration in Maasai communities is becoming a cultural norm and not only a response to economic conditions. PMID:25745192

Counterintuitive migration patterns by Atlantic salmon Salmo salar smolts in a large lake.

PubMed

Honkanen, H M; Rodger, J R; Stephen, A; Adams, K; Freeman, J; Adams, C E

2018-06-21

What little is known about the seaward migration of Salmo salar smolt migration through standing waters indicates that it is both slow and results in high mortality rates, compared with riverine migration. This may be partly because smolts in lakes need to swim more actively and require more complex directional cues than they do in rivers. In this telemetry study of smolt migration through Loch Lomond, S. salar smolts made repeated movements in directions away from the outflowing river, which considerably increased migration time. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Modeling the Ebola zoonotic dynamics: Interplay between enviroclimatic factors and bat ecology

PubMed Central

Johnson, Kaylynn

2017-01-01

Understanding Ebola necessarily requires the characterization of the ecology of its main enzootic reservoir, i.e. bats, and its interplay with seasonal and enviroclimatic factors. Here we present a SIR compartmental model where we implement a bidirectional coupling between the available resources and the dynamics of the bat population in order to understand their migration patterns. Our compartmental modeling approach and simulations include transport terms to account for bats mobility and spatiotemporal climate variability. We hypothesize that environmental pressure is the main driving force for bats’ migration and our results reveal the appearance of sustained migratory waves of Ebola virus infected bats coupled to resources availability. Ultimately, our study can be relevant to predict hot spots of Ebola outbreaks in space and time and suggest conservation policies to mitigate the risk of spillovers. PMID:28604813

Ocean-wide Drivers of Migration Strategies and Their Influence on Population Breeding Performance in a Declining Seabird.

PubMed

Fayet, Annette L; Freeman, Robin; Anker-Nilssen, Tycho; Diamond, Antony; Erikstad, Kjell E; Fifield, Dave; Fitzsimmons, Michelle G; Hansen, Erpur S; Harris, Mike P; Jessopp, Mark; Kouwenberg, Amy-Lee; Kress, Steve; Mowat, Stephen; Perrins, Chris M; Petersen, Aevar; Petersen, Ib K; Reiertsen, Tone K; Robertson, Gregory J; Shannon, Paula; Sigurðsson, Ingvar A; Shoji, Akiko; Wanless, Sarah; Guilford, Tim

2017-12-18

Which factors shape animals' migration movements across large geographical scales, how different migratory strategies emerge between populations, and how these may affect population dynamics are central questions in the field of animal migration [1] that only large-scale studies of migration patterns across a species' range can answer [2]. To address these questions, we track the migration of 270 Atlantic puffins Fratercula arctica, a red-listed, declining seabird, across their entire breeding range. We investigate the role of demographic, geographical, and environmental variables in driving spatial and behavioral differences on an ocean-basin scale by measuring puffins' among-colony differences in migratory routes and day-to-day behavior (estimated with individual daily activity budgets and energy expenditure). We show that competition and local winter resource availability are important drivers of migratory movements, with birds from larger colonies or with poorer local winter conditions migrating further and visiting less-productive waters; this in turn led to differences in flight activity and energy expenditure. Other behavioral differences emerge with latitude, with foraging effort and energy expenditure increasing when birds winter further north in colder waters. Importantly, these ocean-wide migration patterns can ultimately be linked with breeding performance: colony productivity is negatively associated with wintering latitude, population size, and migration distance, which demonstrates the cost of competition and migration on future breeding and the link between non-breeding and breeding periods. Our results help us to understand the drivers of animal migration and have important implications for population dynamics and the conservation of migratory species. Copyright © 2017 Elsevier Ltd. All rights reserved.

Continental-scale, seasonal movements of a heterothermic migratory tree bat

USGS Publications Warehouse

Cryan, Paul M.; Stricker, Craig A.; Wunder, Michael B.

2014-01-01

Long-distance migration evolved independently in bats and unique migration behaviors are likely, but because of their cryptic lifestyles, many details remain unknown. North American hoary bats (Lasiurus cinereus cinereus) roost in trees year-round and probably migrate farther than any other bats, yet we still lack basic information about their migration patterns and wintering locations or strategies. This information is needed to better understand unprecedented fatality of hoary bats at wind turbines during autumn migration and to determine whether the species could be susceptible to an emerging disease affecting hibernating bats. Our aim was to infer probable seasonal movements of individual hoary bats to better understand their migration and seasonal distribution in North America. We analyzed the stable isotope values of non-exchangeable hydrogen in the keratin of bat hair and combined isotopic results with prior distributional information to derive relative probability density surfaces for the geographic origins of individuals. We then mapped probable directions and distances of seasonal movement. Results indicate that hoary bats summer across broad areas. In addition to assumed latitudinal migration, we uncovered evidence of longitudinal movement by hoary bats from inland summering grounds to coastal regions during autumn and winter. Coastal regions with nonfreezing temperatures may be important wintering areas for hoary bats. Hoary bats migrating through any particular area, such as a wind turbine facility in autumn, are likely to have originated from a broad expanse of summering grounds from which they have traveled in no recognizable order. Better characterizing migration patterns and wintering behaviors of hoary bats sheds light on the evolution of migration and provides context for conserving these migrants.

Changing drainage patterns within South Cascade Glacier, Washington, USA, 1964-1992

USGS Publications Warehouse

Fountain, A.G.; Vaughn, B.H.

1995-01-01

The theoretical patterns of water drainage are presented for South Cascade Glacier for four different years between 1964 and 1992, during which the glacier was thinning and receding. The theoretical pattern compares well, in a broad sense, with the flow pattern determined from tracer injections in 1986 and 1987. Differences between the patterns may result from the routing of surface meltwater in crevasses prior to entering the body of the glacier. The changing drainage pattern was caused by glacier thinning. The migration of a drainage divide eventually rerouted most of the surface meltwater from the main stream that drained the glacier in 1987 to another, formerly smaller, stream by 1992. On the basis of projected glacier thinning between 1992 and 1999, we predict that the drainage divide will continue to migrate across the glacier.

Empirical evaluation of predator-driven diel vertical migration in Lake Superior

USGS Publications Warehouse

Stockwell, J.D.; Hrabik, T.R.; Jensen, O.P.; Yule, D.L.; Balge, M.

2010-01-01

Recent studies on Lake Superior suggest that diel vertical migration (DVM) of prey (generalized Coregonus spp.) may be influenced by the density of predatory siscowet (Salvelinus namaycush). We empirically evaluated this hypothesis using data from acoustic, midwater trawl, and bottom trawl sampling at eight Lake Superior sites during three seasons in 2005 and a subset of sites in 2006. We expected the larger-bodied cisco (Coregonus artedi) to exhibit a shallower DVM compared with the smaller-bodied kiyi (Coregonus kiyi). Although DVM of kiyi and cisco were consistent with expectations of DVM as a size-dependent, predator-mediated process, we found no relationship between siscowet density and the magnitude of DVM of either coregonid. Cisco appear to have a size refuge from siscowet predation. Kiyi and siscowet co-occur in demersal habitat > 150 m during the day, where visual predation is unlikely, suggesting predator avoidance is not a factor in the daytime distribution of kiyi. Seasonal patterns of kiyi DVM were consistent with reported DVM of their primary prey Mysis relicta. Our results suggest that consideration of nonvisual foraging, rather than lightbased foraging theory (i.e., the antipredation window), is necessary to understand the processes driving DVM in deepwater systems.

Mental health is the most important factor influencing quality of life in elderly left behind when families migrate out of rural China.

PubMed

Xie, Jian-fei; Ding, Si-qing; Zhong, Zhu-qing; Yi, Qi-feng; Zeng, Sai-nan; Hu, Jun-hua; Zhou, Jian-da

2014-01-01

to investigate the quality of life and the associated factors on left behind elderly in rural China. the research was conducted cluster sampling to select 456 elderly left behind when family members migrated out of rural China to participate in a cross-sectional study by completing a general data questionnaire and Quality of Life questionnaire. 91.5% of the elderly requested psychological counseling and education. For the elderly, scores for mental health (39.56±13.73) were significantly lower compared with Chinese standard data (61.6±13.7) (P<0.001). Age, chronic disease type, gender, residence pattern and economic support from children were the main psychological factors influencing this population. mental health is the most important factor influencing quality of life of elderly left behind when family members migrated out of rural China. Our study suggested a need to widely establish a general practitioner team for psychological intervention for improving rural elderly people's Quality of Life level, especially in the psychological domain.

Migration of Sakhalin taimen (Parahucho perryi): Evidence of freshwater resident life history types

USGS Publications Warehouse

Zimmerman, C.E.; Rand, P.S.; Fukushima, M.; Zolotukhin, S.F.

2012-01-01

Sakhalin taimen (Parahucho perryi) range from the Russian Far East mainland along the Sea of Japan coast, and Sakhalin, Kuril, and Hokkaido Islands and are considered to primarily be an anadromous species. We used otolith strontium-to-calcium ratios (Sr/Ca) to determine the chronology of migration between freshwater and saltwater and identify migratory contingents of taimen collected from the Koppi River, Russia. In addition, we examined taimen from the Sarufutsu River, Japan and Tumnin River, Russia that were captured in marine waters. Transects of otolith Sr/Ca for the Sarufutsu River fish were consistent with patterns observed in anadromous salmonids. Two fish from the Tumnin River appeared to be recent migrants to saltwater and one fish was characterized by an otolith Sr/Ca transect consistent with marine migration. Using these transects as benchmarks, all Koppi River taimen were classified as freshwater residents. These findings suggest more work is needed to assess life history variability among locations and the role of freshwater productivity in controlling migratory behavior in taimen. ?? 2011 Springer Science+Business Media B.V. (outside the USA).

Seasonally-Dynamic Presence-Only Species Distribution Models for a Cryptic Migratory Bat Impacted by Wind Energy Development

PubMed Central

Hayes, Mark A.; Cryan, Paul M.; Wunder, Michael B.

2015-01-01

Understanding seasonal distribution and movement patterns of animals that migrate long distances is an essential part of monitoring and conserving their populations. Compared to migratory birds and other more conspicuous migrants, we know very little about the movement patterns of many migratory bats. Hoary bats (Lasiurus cinereus), a cryptic, wide-ranging, long-distance migrant, comprise a substantial proportion of the tens to hundreds of thousands of bat fatalities estimated to occur each year at wind turbines in North America. We created seasonally-dynamic species distribution models (SDMs) from 2,753 museum occurrence records collected over five decades in North America to better understand the seasonal geographic distributions of hoary bats. We used 5 SDM approaches: logistic regression, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy and consolidated outputs to generate ensemble maps. These maps represent the first formal hypotheses for sex- and season-specific hoary bat distributions. Our results suggest that North American hoary bats winter in regions with relatively long growing seasons where temperatures are moderated by proximity to oceans, and then move to the continental interior for the summer. SDMs suggested that hoary bats are most broadly distributed in autumn—the season when they are most susceptible to mortality from wind turbines; this season contains the greatest overlap between potentially suitable habitat and wind energy facilities. Comparing wind-turbine fatality data to model outputs could test many predictions, such as ‘risk from turbines is highest in habitats between hoary bat summering and wintering grounds’. Although future field studies are needed to validate the SDMs, this study generated well-justified and testable hypotheses of hoary bat migration patterns and seasonal distribution. PMID:26208098

Contrasting Patterns of Genetic Differentiation among Blackcaps (Sylvia atricapilla) with Divergent Migratory Orientations in Europe

PubMed Central

Mettler, Raeann; Schaefer, H. Martin; Chernetsov, Nikita; Fiedler, Wolfgang; Hobson, Keith A.; Ilieva, Mihaela; Imhof, Elisabeth; Johnsen, Arild; Renner, Swen C.; Rolshausen, Gregor; Serrano, David; Wesołowski, Tomasz; Segelbacher, Gernot

2013-01-01

Migratory divides are thought to facilitate behavioral, ecological, and genetic divergence among populations with different migratory routes. However, it is currently contentious how much genetic divergence is needed to maintain distinct migratory behavior across migratory divides. Here we investigate patterns of neutral genetic differentiation among Blackcap (Sylvia atricapilla) populations with different migratory strategies across Europe. We compare the level of genetic divergence of populations migrating to southwestern (SW) or southeastern (SE) wintering areas with birds wintering in the British Isles following a recently established northwesterly (NW) migration route. The migratory divide between SW and SE wintering areas can be interpreted as a result of a re-colonization process after the last glaciation. Thus we predicted greater levels of genetic differentiation among the SW/SE populations. However, a lack of genetic differentiation was found between SW and SE populations, suggesting that interbreeding likely occurs among Blackcaps with different migratory orientations across a large area; therefore the SW/SE migratory divide can be seen as diffuse, broad band and is, at best, a weak isolating barrier. Conversely, weak, albeit significant genetic differentiation was evident between NW and SW migrants breeding sympatrically in southern Germany, suggesting a stronger isolating mechanism may be acting in this population. Populations located within/near the SW/SE contact zone were the least genetically divergent from NW migrants, confirming NW migrants likely originated from within the contact zone. Significant isolation-by-distance was found among eastern Blackcap populations (i.e. SE migrants), but not among western populations (i.e. NW and SW migrants), revealing different patterns of genetic divergence among Blackcap populations in Europe. We discuss possible explanations for the genetic structure of European Blackcaps and how gene flow influences the persistence of divergent migratory behaviors. PMID:24278428

Seasonally-dynamic presence-only species distribution models for a cryptic migratory bat impacted by wind energy development

USGS Publications Warehouse

Hayes, Mark A.; Cryan, Paul M.; Wunder, Michael B.

2015-01-01

Understanding seasonal distribution and movement patterns of animals that migrate long distances is an essential part of monitoring and conserving their populations. Compared to migratory birds and other more conspicuous migrants, we know very little about the movement patterns of many migratory bats. Hoary bats (Lasiurus cinereus), a cryptic, wide-ranging, long-distance migrant, comprise a substantial proportion of the tens to hundreds of thousands of bat fatalities estimated to occur each year at wind turbines in North America. We created seasonally-dynamic species distribution models (SDMs) from 2,753 museum occurrence records collected over five decades in North America to better understand the seasonal geographic distributions of hoary bats. We used 5 SDM approaches: logistic regression, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy and consolidated outputs to generate ensemble maps. These maps represent the first formal hypotheses for sex- and season-specific hoary bat distributions. Our results suggest that North American hoary bats winter in regions with relatively long growing seasons where temperatures are moderated by proximity to oceans, and then move to the continental interior for the summer. SDMs suggested that hoary bats are most broadly distributed in autumn—the season when they are most susceptible to mortality from wind turbines; this season contains the greatest overlap between potentially suitable habitat and wind energy facilities. Comparing wind-turbine fatality data to model outputs could test many predictions, such as ‘risk from turbines is highest in habitats between hoary bat summering and wintering grounds’. Although future field studies are needed to validate the SDMs, this study generated well-justified and testable hypotheses of hoary bat migration patterns and seasonal distribution.

Seasonally-Dynamic Presence-Only Species Distribution Models for a Cryptic Migratory Bat Impacted by Wind Energy Development.

PubMed

Hayes, Mark A; Cryan, Paul M; Wunder, Michael B

2015-01-01

Understanding seasonal distribution and movement patterns of animals that migrate long distances is an essential part of monitoring and conserving their populations. Compared to migratory birds and other more conspicuous migrants, we know very little about the movement patterns of many migratory bats. Hoary bats (Lasiurus cinereus), a cryptic, wide-ranging, long-distance migrant, comprise a substantial proportion of the tens to hundreds of thousands of bat fatalities estimated to occur each year at wind turbines in North America. We created seasonally-dynamic species distribution models (SDMs) from 2,753 museum occurrence records collected over five decades in North America to better understand the seasonal geographic distributions of hoary bats. We used 5 SDM approaches: logistic regression, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy and consolidated outputs to generate ensemble maps. These maps represent the first formal hypotheses for sex- and season-specific hoary bat distributions. Our results suggest that North American hoary bats winter in regions with relatively long growing seasons where temperatures are moderated by proximity to oceans, and then move to the continental interior for the summer. SDMs suggested that hoary bats are most broadly distributed in autumn-the season when they are most susceptible to mortality from wind turbines; this season contains the greatest overlap between potentially suitable habitat and wind energy facilities. Comparing wind-turbine fatality data to model outputs could test many predictions, such as 'risk from turbines is highest in habitats between hoary bat summering and wintering grounds'. Although future field studies are needed to validate the SDMs, this study generated well-justified and testable hypotheses of hoary bat migration patterns and seasonal distribution.

Acculturation and other risk factors of depressive disorders in individuals with Turkish migration backgrounds.

PubMed

Janssen-Kallenberg, Hanna; Schulz, Holger; Kluge, Ulrike; Strehle, Jens; Wittchen, Hans-Ulrich; Wolfradt, Uwe; Koch-Gromus, Uwe; Heinz, Andreas; Mösko, Mike; Dingoyan, Demet

2017-07-19

Acculturation is a long-term, multi-dimensional process occurring when subjects of different cultures stay in continuous contact. Previous studies have suggested that elevated rates of depression among different migrant groups might be due to patterns of acculturation and migration related risk factors. This paper focused on prevalence rates of depressive disorders and related risk factors among individuals with Turkish migration backgrounds. A population-based sample of 662 individuals with Turkish migration backgrounds were interviewed by bilingual interviewers using a standardised diagnostic interview for DSM-IV-TR and ICD-10 diagnoses (CIDI DIA-X Version 2.8). Associations between 12-month prevalence rates of depressive disorders with potential risk factors were assessed, including gender, age, socioeconomic status, acculturation status and migration status. 12-month prevalence rates of any depressive disorder were 29.0%, 14.4% of major depressive disorder (MDD) and 14.7% of dysthymia. Older age and low socioeconomic status were most consistently related to higher risks of depressive disorders. Acculturation status showed associations with subtypes of depressive disorder. Associations differed between men and women. Symptom severity of MDD was linked to gender, with females being more affected by severe symptoms. The prevalence of depressive disorders is high in individuals with Turkish migration backgrounds, which can be partly explained by older age, low socioeconomic status and acculturation pressures. Only a limited number of risk factors were assessed. Acculturation in particular is a complex process which might not be sufficiently represented by the applied measures. Further risk factors have to be identified in representative samples of this migrant group.

Moonlight Drives Ocean-Scale Mass Vertical Migration of Zooplankton during the Arctic Winter.

PubMed

Last, Kim S; Hobbs, Laura; Berge, Jørgen; Brierley, Andrew S; Cottier, Finlo

2016-01-25

In extreme high-latitude marine environments that are without solar illumination in winter, light-mediated patterns of biological migration have historically been considered non-existent [1]. However, diel vertical migration (DVM) of zooplankton has been shown to occur even during the darkest part of the polar night, when illumination levels are exceptionally low [2, 3]. This paradox is, as yet, unexplained. Here, we present evidence of an unexpected uniform behavior across the entire Arctic, in fjord, shelf, slope and open sea, where vertical migrations of zooplankton are driven by lunar illumination. A shift from solar-day (24-hr period) to lunar-day (24.8-hr period) vertical migration takes place in winter when the moon rises above the horizon. Further, mass sinking of zooplankton from the surface waters and accumulation at a depth of ∼50 m occurs every 29.5 days in winter, coincident with the periods of full moon. Moonlight may enable predation of zooplankton by carnivorous zooplankters, fish, and birds now known to feed during the polar night [4]. Although primary production is almost nil at this time, lunar vertical migration (LVM) may facilitate monthly pulses of carbon remineralization, as they occur continuously in illuminated mesopelagic systems [5], due to community respiration of carnivorous and detritivorous zooplankton. The extent of LVM during the winter suggests that the behavior is highly conserved and adaptive and therefore needs to be considered as "baseline" zooplankton activity in a changing Arctic ocean [6-9]. VIDEO ABSTRACT. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Anguilla rostrata glass eel migration and recruitment in the estuary and Gulf of St Lawrence.

PubMed

Dutil, J-D; Dumont, P; Cairns, D K; Galbraith, P S; Verreault, G; Castonguay, M; Proulx, S

2009-06-01

This study describes catches of Anguilla rostrata glass eels and associated oceanographic conditions in the St Lawrence Estuary and Gulf. Ichthyoplankton survey data suggest that they enter the Gulf primarily in May, migrate at the surface at night, and disperse broadly once they have passed Cabot Strait. They arrive in estuaries beginning at about mid-June and through the month of July. Migration extends west up to Québec City, in the freshwater zone of the St Lawrence Estuary, 1000 km west of Cabot Strait. Anguilla rostrata glass eels travel between Cabot Strait and receiving estuaries at a straight-line ground speed of c. 10-15 km day(-1). Catches of fish per unit effort in estuaries in the St Lawrence system are much lower than those reported for the Atlantic coast of Canada. Low abundance of A. rostrata glass eels in the St Lawrence system may be due to cold surface temperatures during the migration period which decrease swimming capacity, long distances from the spawning ground to Cabot Strait and from Cabot Strait to the destination waters (especially the St Lawrence River), complex circulation patterns, and hypoxic conditions in bottom waters of the Laurentian Channel and the St Lawrence Estuary.

Trinucleate uterine epithelial cells as evidence for White-tail Deer trophoblast binucleate cell migration and as markers of placental binucleate cell dynamics in a variety of wild ruminants.

PubMed

Wooding, F B Peter; Osborn, David; Killian, Gary J

2018-02-01

The unicellular trophoblast epithelium of all ruminants so far investigated contains 15-20% binucleate cells with numerous secretory granules. Electron microscope (EM) studies of the domesticated cow, ewe, goat and deer species have established that these BNC migrate out of the trophoblast epithelium to fuse with the apposed maternal uterine epithelial cells or derivative to form fetomaternal tissue throughout pregnancy. However there is one careful EM study of the trophoblast of a wild ruminant, the White-tail deer, which found the usual number of BNC but no evidence of any migration or fusion. Since there are up to 200 species of wild ruminants, it was important to establish whether there really are two possible scenarios for BNC function. This paper reports a light microscope (LM) immunocytochemical study of cell dynamics in ruminant placentas using 1-2 mμ deresinated sections. The results clearly demonstrate that the White-tail deer and all of the other 15 (see Table 1) randomly selected wild ruminants show the same BNC migration and fusion pattern. These results suggest that this remarkable cellular behaviour is fundamental to the ruminant evolutionary success. Copyright © 2017 Elsevier Ltd. All rights reserved.

Migration and wintering areas of glaucous-winged Gulls from south-central Alaska

USGS Publications Warehouse

Hatch, Shyla A.; Gill, V.A.; Mulcahy, D.M.

2011-01-01

We used satellite telemetry to investigate the migration patterns and wintering areas of Glaucouswinged Gulls (Larus glaucescens) from Middleton Island, Alaska, where this species' population increased tenfold from the 1970s to the 1990s. Fall migration spanned 11 weeks, including numerous stopovers en route, apparently for feeding. Spring migration from wintering sites to Middleton Island was shorter (4 weeks) and more direct. One juvenile spent several months in southern Prince William Sound. An adult spent several months near Craig, southeast Alaska, while three others overwintered in southern British Columbia. For all four wintering adults use of refuse-disposal sites was evident or strongly suggested. Commensalism with humans may have contributed to the increase on Middleton, but a strong case can also be made for a competing explanation-regional recruitment of gulls to high-quality nesting habitat in Alaska created after the earthquake of 1964. An analysis of band returns reveals broad overlap in the wintering grounds of gulls from different Alaska colonies and of gulls banded on the west coast from British Columbia to California. The seasonal movement of many gulls from Alaska is decidedly migratory, whereas gulls from British Columbia, Washington, and Oregon disperse locally in winter. ?? The Cooper Ornithological Society 2011.

Lowland-upland migration of sauropod dinosaurs during the Late Jurassic epoch.

PubMed

Fricke, Henry C; Hencecroth, Justin; Hoerner, Marie E

2011-10-26

Sauropod dinosaurs were the largest vertebrates ever to walk the Earth, and as mega-herbivores they were important parts of terrestrial ecosystems. In the Late Jurassic-aged Morrison depositional basin of western North America, these animals occupied lowland river-floodplain settings characterized by a seasonally dry climate. Massive herbivores with high nutritional and water needs could periodically experience nutritional and water stress under these conditions, and thus the common occurrence of sauropods in this basin has remained a paradox. Energetic arguments and mammalian analogues have been used to suggest that migration allowed sauropods access to food and water resources over a wide region or during times of drought or both, but there has been no direct support for these hypotheses. Here we compare oxygen isotope ratios (δ(18)O) of tooth-enamel carbonate from the sauropod Camarasaurus with those of ancient soil, lake and wetland (that is, 'authigenic') carbonates that formed in lowland settings. We demonstrate that certain populations of these animals did in fact undertake seasonal migrations of several hundred kilometres from lowland to upland environments. This ability to describe patterns of sauropod movement will help to elucidate the role that migration played in the ecology and evolution of gigantism of these and associated dinosaurs.

Layer-specific gene expression in epileptogenic type II focal cortical dysplasia: normal-looking neurons reveal the presence of a hidden laminar organization

PubMed Central

2014-01-01

Background Type II focal cortical dysplasias (FCDs) are malformations of cortical development characterised by the disorganisation of the normal neocortical structure and the presence of dysmorphic neurons (DNs) and balloon cells (BCs). The pathogenesis of FCDs has not yet been clearly established, although a number of histopathological patterns and molecular findings suggest that they may be due to abnormal neuronal and glial proliferation and migration processes. In order to gain further insights into cortical layering disruption and investigate the origin of DNs and BCs, we used in situ RNA hybridisation of human surgical specimens with a neuropathologically definite diagnosis of Type IIa/b FCD and a panel of layer-specific genes (LSGs) whose expression covers all cortical layers. We also used anti-phospho-S6 ribosomal protein antibody to investigate mTOR pathway hyperactivation. Results LSGs were expressed in both normal and abnormal cells (BCs and DNs) but their distribution was different. Normal-looking neurons, which were visibly reduced in the core of the lesion, were apparently located in the appropriate cortical laminae thus indicating a partial laminar organisation. On the contrary, DNs and BCs, labelled with anti-phospho-S6 ribosomal protein antibody, were spread throughout the cortex without any apparent rule and showed a highly variable LSG expression pattern. Moreover, LSGs did not reveal any differences between Type IIa and IIb FCD. Conclusion These findings suggest the existence of hidden cortical lamination involving normal-looking neurons, which retain their ability to migrate correctly in the cortex, unlike DNs which, in addition to their morphological abnormalities and mTOR hyperactivation, show an altered migratory pattern. Taken together these data suggest that an external or environmental hit affecting selected precursor cells during the very early stages of cortical development may disrupt normal cortical development. PMID:24735483

Migration patterns of post-spawning Pacific herring in a subarctic sound

NASA Astrophysics Data System (ADS)

Bishop, Mary Anne; Eiler, John H.

2018-01-01

Understanding the distribution of Pacific herring (Clupea pallasii) can be challenging because spawning, feeding and overwintering may take place in different areas separated by 1000s of kilometers. Along the northern Gulf of Alaska, Pacific herring movements after spring spawning are largely unknown. During the fall and spring, herring have been seen moving from the Gulf of Alaska into Prince William Sound, a large embayment, suggesting that fish spawning in the Sound migrate out into the Gulf of Alaska. We acoustic-tagged 69 adult herring on spawning grounds in Prince William Sound during April 2013 to determine seasonal migratory patterns. We monitored departures from the spawning grounds as well as herring arrivals and movements between the major entrances connecting Prince William Sound and the Gulf of Alaska. Departures of herring from the spawning grounds coincided with cessation of major spawning events in the immediate area. After spawning, 43 of 69 tagged herring (62%) moved to the entrances of Prince William Sound over a span of 104 d, although most fish arrived within 10 d of their departure from the spawning grounds. A large proportion remained in these areas until mid-June, most likely foraging on the seasonal bloom of large, Neocalanus copepods. Pulses of tagged herring detected during September and October at Montague Strait suggest that some herring returned from the Gulf of Alaska. Intermittent detections at Montague Strait and the Port Bainbridge passages from September through early January (when the transmitters expired) indicate that herring schools are highly mobile and are overwintering in this area. The pattern of detections at the entrances to Prince William Sound suggest that some herring remain in the Gulf of Alaska until late winter. The results of this study confirm the connectivity between local herring stocks in Prince William Sound and the Gulf of Alaska.

Detecting Bedform Migration in Portsmouth Harbor, New Hampshire, USA on Relatively Short Spatial and Temporal Scales

NASA Astrophysics Data System (ADS)

Felzenberg, J. A.; Ward, L. G.; Rzhanov, Y.; Irish, J. D.; Mayer, L. A.

2008-12-01

Multibeam echosounder (MBES) systems have enjoyed recent popularity as a tool in bedform-migration studies due to their ability to produce high-resolution seafloor imagery with complete bottom coverage. Although shallow-water MBES systems may achieve decimeter-scale data resolution, the use of MBES to successfully detect and quantify bedform migration on short time-scales (days to weeks) where the migration distance is relatively small (< 1 m) remains limited by positioning uncertainty. In this study we evaluate short-term bedform migration and sediment transport in a bedform field at the entrance to Portsmouth Harbor, New Hampshire, USA. Bedform dynamics over 24-hour and multi-day periods were determined from high-resolution bathymetry (0.25 m grid resolution) acquired with a Kongsberg EM3002D MBES system. Position, heading and attitude data were acquired with an Applanix POS/MV system with integrated real-time kinematic GPS correctors, providing a horizontal positioning uncertainty of < 0.1 m at the GPS receiver. MBES surveys were conducted on June 8, 14 and 15 in 2007 and July 3 and 9 in 2008. Acoustic current meters were deployed at two stations within the survey area in 2008 to provide simultaneous observations of current velocities at a height of 1 m above the bottom. A new approach was developed and used for detecting and quantifying bedform migration from the bathymetry. Our approach utilizes a ridge-extraction algorithm to derive a binary map of dune-crest positions from the bathymetric surface, and then calculates the displacements of small (6.25 m2) subsets of dune crest. Preliminary results indicate that bedform migrations of ≥ 0.1 m were successfully resolved. Morphology of the bedform field is dominated by medium and large, two-dimensional, asymmetrical subaqueous dunes (0.4 to 0.8 m height, 8 to 16 m wavelength). Small, two-dimensional, ebb-oriented subaqueous dunes (0.3 m height, 5 m wavelength) line the eastern margin of the bedform field, which is adjacent to the channel thalweg. Initial analysis indicates that bedforms are active on 24-hour and multi-day cycles, with migrations of > 1.2 m observed on multi-day cycles. The highest bedform-migration rates are observed along the eastern margin where smaller dunes occur. In 2007 we observed a reciprocal pattern of bedform migration, in which dunes in the western half of the bedform field migrated in a net flood (northward) direction and dunes in the eastern half migrated in a net ebb (southward) direction. In 2008, the eastern dune population was still active and southward-migrating, though the western half of the bedform field appeared to be inactive. The observed pattern of bedform migration is supported by current-meter data from six tidal cycles (spring tidal conditions) during the 2008 experiment, which reveal a strong cross-channel difference in the flood and ebb currents. The data indicate ebb-current dominance in the eastern half of the study area and flood-current dominance in the western half of the study area. Individual bedforms cannot be tracked over the annual period (2007 to 2008) without a higher survey-repetition rate, suggesting that annual migration distances are comparable with or greater than the bedform wavelength, and/or that bedform morphology changes significantly over time-scales shorter than one year.

Influence of summer biogeography on wood warbler stopover abundance

Treesearch

Jeffrey F. Kelly; Rob Smith; Deborah M. Finch; Frank R. Moore; Wang Yong

1999-01-01

We evaluated the effect of summer biogeography of migrant wood warblers (Parulidae) on their stopover abundance. To characterize abundance patterns, we used mist-net capture data from spring and fall migration in the Middle Rio Grande Valley, New Mexico, spring migration on the Gulf Coast of Louisiana, and fall migration on the Gulf Coast of Alabama. To describe the...

Effects of Migration on Sending Countries: What Do We Know? OECD Development Centre Working Paper No. 250

ERIC Educational Resources Information Center

Katseli, Louka T.; Lucas, Robert E. B.; Xenogiani, Theodora

2006-01-01

This report evaluates the evidence on how migration may promote or hinder development in countries of origin, and explores possible win-win solutions for both sending and receiving countries. The analysis of recent OECD data of foreign-born nationals into Europe documents the presence of multiple migration patterns and reveals that the EU lags…

Migration in Thailand: A Twenty-Five-Year Review. Papers of the East-West Population Institute. No. 100.

ERIC Educational Resources Information Center

Goldstein, Sidney; Goldstein, Alice

Using data from the 1960, 1970, and 1980 censuses of Thailand, this paper explores the changing pattern of internal migration. Throughout the period, the census indicates a high degree of stability. Lifetime migration shows a slight rise in each period; recently it has risen in inter- as opposed to intra-regional movement. Five year…

A simple force-motion relation for migrating cells revealed by multipole analysis of traction stress.

PubMed

Tanimoto, Hirokazu; Sano, Masaki

2014-01-07

For biophysical understanding of cell motility, the relationship between mechanical force and cell migration must be uncovered, but it remains elusive. Since cells migrate at small scale in dissipative circumstances, the inertia force is negligible and all forces should cancel out. This implies that one must quantify the spatial pattern of the force instead of just the summation to elucidate the force-motion relation. Here, we introduced multipole analysis to quantify the traction stress dynamics of migrating cells. We measured the traction stress of Dictyostelium discoideum cells and investigated the lowest two moments, the force dipole and quadrupole moments, which reflect rotational and front-rear asymmetries of the stress field. We derived a simple force-motion relation in which cells migrate along the force dipole axis with a direction determined by the force quadrupole. Furthermore, as a complementary approach, we also investigated fine structures in the stress field that show front-rear asymmetric kinetics consistent with the multipole analysis. The tight force-motion relation enables us to predict cell migration only from the traction stress patterns. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

First description of autumn migration of Sooty Falcon Falco concolor from the United Arab Emirates to Madagascar using satellite telemetry

USGS Publications Warehouse

Javed, Sàlim; Douglas, David C.; Khan, Shahid Noor; Nazeer Shah, Junid; Ali Al Hammadi, Abdullah

2012-01-01

The movement and migration pattern of the 'Near Threatened' Sooty Falcon Falco concolor is poorly known. Sooty Falcons breed on the islands of the Arabian Gulf after arriving from their non-breeding areas that are mainly in Madagascar. In the first satellite tracking of the species we fitted a 9.5 g Argos solar powered transmitter on an adult breeding Sooty Falcon off the western coast of Abu Dhabi in the United Arab Emirates. The bird successfully undertook autumn migration to Madagascar, a known wintering area for the species. We document the Sooty Falcon's autumn migration route and stop-over sites. The adult Sooty Falcon initiated its migration at night and with tailwinds, and travelled mainly during daytime hours for 13 days over an inland route of more than 5,656 km. The three stop-over sites in East Africa were characterised by moderate to sparse shrub cover associated with potential sources of water. We discuss the migration pattern of the tracked bird in relation to importance of non-breeding areas for Sooty Falcons and recent declines in numbers in their breeding range.

Chicken HOXA3 Gene: Its Expression Pattern and Role in Branchial Nerve Precursor Cell Migration

PubMed Central

Watari-Goshima, Natsuko; Chisaka, Osamu

2011-01-01

In vertebrates, the proximal and distal sensory ganglia of the branchial nerves are derived from neural crest cells (NCCs) and placodes, respectively. We previously reported that in Hoxa3 knockout mouse embryos, NCCs and placode-derived cells of the glossopharyngeal nerve were defective in their migration. In this report, to determine the cell-type origin for this Hoxa3 knockout phenotype, we blocked the expression of the gene with antisense morpholino oligonucleotides (MO) specifically in either NCCs/neural tube or placodal cells of chicken embryos. Our results showed that HOXA3 function was required for the migration of the epibranchial placode-derived cells and that HOXA3 regulated this cell migration in both NCCs/neural tube and placodal cells. We also report that the expression pattern of chicken HOXA3 was slightly different from that of mouse Hoxa3. PMID:21278919

Evidence of sex-bias in gene expression in the brain transcriptome of two populations of rainbow trout (Oncorhynchus mykiss) with divergent life histories.

PubMed

Hale, Matthew C; McKinney, Garrett J; Thrower, Frank P; Nichols, Krista M

2018-01-01

Sex-bias in gene expression is a mechanism that can generate phenotypic variance between the sexes, however, relatively little is known about how patterns of sex-bias vary during development, and how variable sex-bias is between different populations. To that end, we measured sex-bias in gene expression in the brain transcriptome of rainbow trout (Oncorhynchus mykiss) during the first two years of development. Our sampling included from the fry stage through to when O. mykiss either migrate to the ocean or remain resident and undergo sexual maturation. Samples came from two F1 lines: One from migratory steelhead trout and one from resident rainbow trout. All samples were reared in a common garden environment and RNA sequencing (RNA-seq) was used to estimate patterns of gene expression. A total of 1,716 (4.6% of total) genes showed evidence of sex-bias in gene expression in at least one time point. The majority (96.7%) of sex-biased genes were differentially expressed during the second year of development, indicating that patterns of sex-bias in expression are tied to key developmental events, such as migration and sexual maturation. Mapping of differentially expressed genes to the O. mykiss genome revealed that the X chromosome is enriched for female upregulated genes, and this may indicate a lack of dosage compensation in rainbow trout. There were many more sex-biased genes in the migratory line than the resident line suggesting differences in patterns of gene expression in the brain between populations subjected to different forces of selection. Overall, our results suggest that there is considerable variation in the extent and identity of genes exhibiting sex-bias during the first two years of life. These differentially expressed genes may be connected to developmental differences between the sexes, and/or between adopting a resident or migratory life history.

Cohort and duration patterns among Asian immigrants: Comparing trends in obesity and self-rated health

PubMed Central

Ro, Annie; Geronimus, Arline; Bound, John; Griffith, Derek; Gee, Gilbert

2015-01-01

Many studies, but not all, suggest that immigrant health worsens with duration of residence in the U.S. Cohort effects may explain the inconsistent findings; not only are cohort effects confounded with duration, but the timing of entry into the US may also create qualitatively different migration experiences. The present study tests for duration and cohort patterns among Asian immigrants to the United States across six year-of-entry cohorts (pre-1980, 1981-1985, 1986-1990, 1991-1995, 1996-2000, 2001-2005). Data come from the Asian American sample (n=44,002) from the 1994-2009 waves of the National Health Interview Survey. The data show cohort differences for self-rated health, such that more recent cohorts showed improved baseline health compared to older cohorts. After accounting for cohorts, there was no significant change in self-rated health by duration. Older cohorts actually showed improving self-rated health with longer duration. Obesity showed the opposite pattern; there were no differences across cohorts, but duration in the United States correlated with higher obesity. These results imply that immigrant health is not simply an issue of duration and adaptation, but underscore the utility of considering cohorts as broader contexts of migration. Collectively, the results encourage future research that more carefully examines the etiological mechanisms that drive immigrant health. PMID:25879262

Exploring how residential mobility and migration influences teenage pregnancy in five rural communities in California: youth and adult perceptions.

PubMed

Lara, Diana; Decker, Martha J; Brindis, Claire D

2016-09-01

Teenage birth rates among young people aged 15-19 years in California, USA, have declined from 47 births per 1000 in 2000 to 24 per 1000 in 2013. Nevertheless, the US counties with the highest teenage birth rates are predominantly rural and have a high proportion of Latinos/as. We conducted 42 interviews with key stakeholders and 12 focus groups with 107 young people in five rural communities to better understand local migration patterns and their influence on intermediate and proximate variables of pregnancy, such as interaction with role models and barriers to access contraception. The migration patterns identified were: residential mobility due to seasonal jobs, residential mobility due to economic and housing changes and migration from other countries to California. These patterns affect young people and families' interactions with school and health systems and other community members, creating both opportunities and barriers to prevent risky sexual behaviours. In rural areas, residential mobility and migration to the USA interconnect. As a result, young people dually navigate the challenges of residential mobility, while also adapting to the dominant US culture. It is important to promote programmes that support the integration of immigrant youth to reduce their sense of isolation, as well as to assure access to sexual health education and reproductive health services.

Amphibian terrestrial habitat selection and movement patterns vary with annual life-history period

USGS Publications Warehouse

Groff, Luke A.; Calhoun, Aram J.K.; Loftin, Cynthia S.

2017-01-01

Identification of essential habitat is a fundamental component of amphibian conservation; however, species with complex life histories frequently move among habitats. To better understand dynamic habitat use, we evaluated Wood Frog (Lithobates sylvaticus (LeConte, 1825)) habitat selection and movement patterns during the spring migration and foraging periods and described the spatiotemporal variability of habitats used during all annual life-history periods. We radio-tracked 71 frogs in Maine during 2011–2013 and evaluated spring migration, foraging activity center (FAC), and within-FAC habitat selection. Telemetered frogs spent the greatest percentage of each field season in hibernacula (≥54.4%), followed by FACs (≥25.5%), migration habitat (≥16.9%), and breeding sites (≥4.5%). FACs ranged 49 – 1 335 m2 (568.0 ± 493.4 m2) and annual home ranges spanned 1 413 – 32 165 m2 (11 780.6 ± 12 506.1 m2). During spring migration, Wood Frogs exhibited different movement patterns (e.g., turn angles), selected different habitat features, and selected habitat features less consistently than while occupying FACs, indicating that the migration and foraging periods are ecologically distinct. Habitat-use studies that do not discriminate among annual life-history periods may obscure true ecological relationships and fail to identify essential habitat necessary for sustaining amphibian populations.

The impact of elite labour migration on the identification, selection and development of European soccer players.

PubMed

Maguire, J; Pearton, R

2000-09-01

In this study, we examined sociocultural aspects of the identification, selection and development of elite soccer players as part of wider processes of globalization, particularly worker migration. Patterns of migration were identified among the 704 players who comprised the national squads of the 32 nations contesting the finals of the 1998 World Cup in France. An analysis of the migration patterns within and between the six Confederations into which member nations of FIFA are grouped established the European Federation (UEFA) as soccer's core economy. The study is subsequently focused on Europe and, in particular, upon the import strategies of clubs in the four most popular destination countries - England, Germany, Italy and Spain. It is argued that, in light of European Union deregulation of worker migration between member states and, in particular, the Bosman judgement, European soccer is being reshaped. The identification and selection of elite players are producing migrant patterns that are seen increasingly to impact upon indigenous player development and, potentially, the viability and success of national teams. We argue that, although these developments are contoured in part by global economic factors, economic accounts alone do not provide an adequate understanding of them. A series of interrelated economic, political, cultural and social factors is at work. We conclude with a brief outline of the policy implications of the analysis.

Collective cell migration in development

PubMed Central

Scarpa, Elena

2016-01-01

During embryonic development, tissues undergo major rearrangements that lead to germ layer positioning, patterning, and organ morphogenesis. Often these morphogenetic movements are accomplished by the coordinated and cooperative migration of the constituent cells, referred to as collective cell migration. The molecular and biomechanical mechanisms underlying collective migration of developing tissues have been investigated in a variety of models, including border cell migration, tracheal branching, blood vessel sprouting, and the migration of the lateral line primordium, neural crest cells, or head mesendoderm. Here we review recent advances in understanding collective migration in these developmental models, focusing on the interaction between cells and guidance cues presented by the microenvironment and on the role of cell–cell adhesion in mechanical and behavioral coupling of cells within the collective. PMID:26783298

Soybean agglutinin binding to corneal endothelial cell surfaces disrupts in situ monolayer integrity and actin organization and interferes with wound repair.

PubMed

Gordon, Sheldon R; Wood, Meredith

2009-03-01

Rat corneal endothelium demonstrates cell-surface soybean agglutinin (SBA) binding during organ-culture or injury. When organ-cultured in medium containing SBA, the endothelial monolayer is disrupted because of cell-cell and cell-matrix alterations. SBA binding disorganizes the circumferential microfilament bundles (CMBs), an effect that is partially prevented by phallacidin preincubation. This disruption is reversible if tissues are returned to standard culture medium. Serum heightens SBA binding, whereas puromycin prevents it. Neither actinomycin D nor alpha-amanitin inhibits SBA binding, suggesting that SBA-binding protein(s) may be post-transcriptionally regulated. During injury-induced cell migration in the presence of SBA, cellular processes are blunted and fail to extend significantly outward. By 72 h post-injury, cells of SBA-treated tissues repopulate the wound but demonstrate little association with neighboring cells. Cells migrating in the presence of N-acetylgalactosamine appear normal but also fail to reassociate with other cells in the jury zone. Immunofluorescent staining for ZO-1 reveals punctuate patterns in cells of control tissues, whereas neither SBA- nor N-acetylgalactosamine-treated tissues exhibit ZO-1 staining. Terminal N-acetylgalactosamine removal fails to affect cell morphology, actin organization, or migration but prevents lectin binding. Our results suggest that SBA binding reflects the synthesis of a stress-induced protein(s) that may play a role in reestablishing cell-cell relationships during monolayer reorganization following injury.

Multilocus phylogeographic assessment of the California Mountain Kingsnake (Lampropeltis zonata) suggests alternative patterns of diversification for the California Floristic Province.

PubMed

Myers, E A; Rodríguez-Robles, J A; Denardo, D F; Staub, R E; Stropoli, A; Ruane, S; Burbrink, F T

2013-11-01

Phylogeographic inference can determine the timing of population divergence, historical demographic processes, patterns of migration, and when extended to multiple species, the history of communities. Single-locus analyses can mislead interpretations of the evolutionary history of taxa and comparative analyses. It is therefore important to revisit previous single-locus phylogeographic studies, particularly those that have been used to propose general patterns for regional biotas and the processes responsible for generating inferred patterns. Here, we employ a multilocus statistical approach to re-examine the phylogeography of Lampropeltis zonata. Using nonparametic and Bayesian species delimitation, we determined that there are two well-supported species within L. zonata. Ecological niche modelling supports the delimitation of these taxa, suggesting that the two species inhabit distinct climatic environments. Gene flow between the two taxa is low and appears to occur unidirectionally. Further, our data suggest that gene flow was mediated by females, a rare pattern in snakes. In contrast to previous analyses, we determined that the divergence between the two lineages occurred in the late Pliocene (c. 2.07 Ma). Spatially and temporally, the divergence of these lineages is associated with the inundation of central California by the Monterey Bay. The effective population sizes of the two species appear to have been unaffected by Pleistocene glaciation. Our increased sampling of loci for L. zonata, combined with previously published multilocus analyses of other sympatric species, suggests that previous conclusions reached by comparative phylogeographic studies conducted within the California Floristic Province should be reassessed. © 2013 John Wiley & Sons Ltd.

Cells as strain-cued automata

NASA Astrophysics Data System (ADS)

Cox, Brian N.; Snead, Malcolm L.

2016-02-01

We argue in favor of representing living cells as automata and review demonstrations that autonomous cells can form patterns by responding to local variations in the strain fields that arise from their individual or collective motions. An autonomous cell's response to strain stimuli is assumed to be effected by internally-generated, internally-powered forces, which generally move the cell in directions other than those implied by external energy gradients. Evidence of cells acting as strain-cued automata have been inferred from patterns observed in nature and from experiments conducted in vitro. Simulations that mimic particular cases of pattern forming share the idealization that cells are assumed to pass information among themselves solely via mechanical boundary conditions, i.e., the tractions and displacements present at their membranes. This assumption opens three mechanisms for pattern formation in large cell populations: wavelike behavior, kinematic feedback in cell motility that can lead to sliding and rotational patterns, and directed migration during invasions. Wavelike behavior among ameloblast cells during amelogenesis (the formation of dental enamel) has been inferred from enamel microstructure, while strain waves in populations of epithelial cells have been observed in vitro. One hypothesized kinematic feedback mechanism, "enhanced shear motility", accounts successfully for the spontaneous formation of layered patterns during amelogenesis in the mouse incisor. Directed migration is exemplified by a theory of invader cells that sense and respond to the strains they themselves create in the host population as they invade it: analysis shows that the strain fields contain positional information that could aid the formation of cell network structures, stabilizing the slender geometry of branches and helping govern the frequency of branch bifurcation and branch coalescence (the formation of closed networks). In simulations of pattern formation in homogeneous populations and network formation by invaders, morphological outcomes are governed by the ratio of the rates of two competing time dependent processes, one a migration velocity and the other a relaxation velocity related to the propagation of strain information. Relaxation velocities are approximately constant for different species and organs, whereas cell migration rates vary by three orders of magnitude. We conjecture that developmental processes use rapid cell migration to achieve certain outcomes, and slow migration to achieve others. We infer from analysis of host relaxation during network formation that a transition exists in the mechanical response of a host cell from animate to inanimate behavior when its strain changes at a rate that exceeds 10-4-10-3 s-1. The transition has previously been observed in experiments conducted in vitro.

The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound.

PubMed

Menze, Sebastian; Zitterbart, Daniel P; van Opzeeland, Ilse; Boebel, Olaf

2017-01-01

This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales ( Balaenoptera musculus intermedia ), fin whales ( Balaenoptera physalus ), Antarctic minke whales ( Balaenoptera bonaerensis ) and leopard seals ( Hydrurga leptonyx ). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.

Progressive Seismic Failure, Seismic Gap, and Great Seismic Risk across the Densely Populated North China Basin

NASA Astrophysics Data System (ADS)

Yin, A.; Yu, X.; Shen, Z.

2014-12-01

Although the seismically active North China basin has the most complete written records of pre-instrumentation earthquakes in the world, this information has not been fully utilized for assessing potential earthquake hazards of this densely populated region that hosts ~200 million people. In this study, we use the historical records to document the earthquake migration pattern and the existence of a 180-km seismic gap along the 600-km long right-slip Tangshan-Hejian-Cixian (THC) fault zone that cuts across the North China basin. The newly recognized seismic gap, which is centered at Tianjin with a population of 11 million people and ~120 km from Beijing (22 million people) and Tangshan (7 million people), has not been ruptured in the past 1000 years by M≥6 earthquakes. The seismic migration pattern in the past millennium suggests that the epicenters of major earthquakes have shifted towards this seismic gap along the THC fault, which implies that the 180- km gap could be the site of the next great earthquake with M≈7.6 if it is ruptured by a single event. Alternatively, the seismic gap may be explained by aseismic creeping or seismic strain transfer between active faults.

The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound

NASA Astrophysics Data System (ADS)

Menze, Sebastian; Zitterbart, Daniel P.; van Opzeeland, Ilse; Boebel, Olaf

2017-01-01

This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus), Antarctic minke whales (Balaenoptera bonaerensis) and leopard seals (Hydrurga leptonyx). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.

Genetic disruption of CYP26B1 severely affects development of neural crest derived head structures, but does not compromise hindbrain patterning.

PubMed

Maclean, Glenn; Dollé, Pascal; Petkovich, Martin

2009-03-01

Cyp26b1 encodes a cytochrome-P450 enzyme that catabolizes retinoic acid (RA), a vitamin A derived signaling molecule. We have examined Cyp26b1(-/-) mice and report that mutants exhibit numerous abnormalities in cranial neural crest cell derived tissues. At embryonic day (E) 18.5 Cyp26b1(-/-) animals exhibit a truncated mandible, abnormal tooth buds, reduced ossification of calvaria, and are missing structures of the maxilla and nasal process. Some of these abnormalities may be due to defects in formation of Meckel's cartilage, which is truncated with an unfused distal region at E14.5 in mutant animals. Despite the severe malformations, we did not detect any abnormalities in rhombomere segmentation, or in patterning and migration of anterior hindbrain derived neural crest cells. Abnormal migration of neural crest cells toward the posterior branchial arches was observed, which may underlie defects in larynx and hyoid development. These data suggest different periods of sensitivity of anterior and posterior hindbrain neural crest derivatives to elevated levels of RA in the absence of CYP26B1. (c) 2009 Wiley-Liss, Inc.

Estimating freshwater productivity, overwinter survival, and migration patterns of Klamath River Coho Salmon

USGS Publications Warehouse

Manhard, Christopher V.; Som, Nicholas A.; Perry, Russell W.; Faukner, Jimmy; Soto, Toz

2018-01-01

An area of great importance to resource management and conservation biology in the Klamath Basin is balancing water usage against the life history requirements of threatened Coho Salmon. One tool for addressing this topic is a freshwater dynamics model to forecast Coho Salmon productivity based on environmental inputs. Constructing such a forecasting tool requires local data to quantify the unique life history processes of Coho Salmon inhabiting this region. Here, we describe analytical methods for estimating a series of sub-models, each capturing a different life history process, which will eventually be synchronized as part of a freshwater dynamics model for Klamath River Coho Salmon. Specifically, we draw upon extensive population monitoring data collected in the basin to estimate models of freshwater productivity, overwinter survival, and migration patterns. Our models of freshwater productivity indicated that high summer temperatures and high winter flows can both adversely affect smolt production and that such relationships are more likely in tributaries with naturally regulated flows due to substantial intraannual environmental variation. Our models of overwinter survival demonstrated extensive variability in survival among years, but not among rearing locations, and demonstrated that a substantial proportion (~ 20%) of age-0+ fish emigrate from some rearing sites in the winter. Our models of migration patterns indicated that many age-0+ fish redistribute in the basin during the summer and winter. Further, we observed that these redistributions can entail long migrations in the mainstem where environmental stressors likely play a role in cueing refuge entry. Finally, our models of migration patterns indicated that changes in discharge are important in cueing the seaward migration of smolts, but that the nature of this behavioral response can differ dramatically between tributaries with naturally and artificially regulated flows. Collectively, these analyses demonstrate that environmental variation interacts with most phases of the freshwater life history of Klamath River Coho Salmon and that anthropogenic environmental variation can have a particularly large bearing on productivity.

Reconsidering residency: Characterization and conservation implications of complex migratory patterns of shortnose sturgeon (Acispenser brevirostrum)

USGS Publications Warehouse

Dionne, Phillip E.; Zydlewski, Gayle B.; Kinnison, Michael T.; Zydlewski, Joseph D.; Wippelhauser, Gail S.

2013-01-01

Efforts to conserve endangered species usually involve attempts to define and manage threats at the appropriate scale of population processes. In some species that scale is localized; in others, dispersal and migration link demic units within larger metapopulations. Current conservation strategies for endangered shortnose sturgeon (Acipenser brevirostrum) assume the species is river resident, with little to no movement between rivers. However we have found that shortnose sturgeon travel more than 130 km through coastal waters between the largest rivers in Maine. Indeed, acoustic telemetry shows that shortnose sturgeon enter six out of the seven acoustically monitored rivers we have monitored, with over 70% of tagged individuals undertaking coastal migrations between river systems. Four migration patterns were identified for shortnose sturgeon inhabiting the Penobscot River, Maine: river resident (28%), spring coastal emigrant (24%), fall coastal emigrant (33%), and summer coastal emigrant (15%). No shortnose sturgeon classified as maturing female exhibited a resident pattern, indicating differential migration. Traditional river-specific assessment and management of shortnose sturgeon could be better characterized using a broader metapopulation scale, at least in the Gulf of Maine, that accounts for diverse migratory strategies and the importance of migratory corridors as critical habitat.

[A study on feeding ecology and migration patterns of Dosidicus gigas off Peru using stable isotope analysis].

PubMed

Gong, Yi; Chen, Xin-jun; Li, Yun-kai; Han, Meng-jie

2015-09-01

As a pelagic cephalopod and one of the main target species of Chinese distant water fishery, jumbo squids (Dosidicus gigas) play a major role in the marine ecosystems of the eastern Pacific. Understanding the feeding ecology and migration patterns of jumbo squids is of importance for better utilizing the resources. The isotopic signatures of gladius, have been proved to be a powerful tool to reveal high resolution and ontogenic variations in individual foraging strategies of squids; which is an archival tissue with no elemental turnover after formation. In this study, the growth equation of gladius proostracum was established based on the age information determined by statolith. Gladius was cut successionally by the growth curve of gladius proostracum, the stable isotopic values of the gladius profiles were determined, and the feeding ecology and migration patterns of jumbo squids during its growth process were investigated. Results showed that the jumbo squids began to migrate after 180 days of postnatal, and their trophic levels tended to decrease throughout the life span. These results demonstrated the feasibility of using continuous sampling hard tissue to study the feeding ecology and habitat transfer of jumbo squids.

Neighborhood Foreclosures, Racial/Ethnic Transitions, and Residential Segregation

PubMed Central

Hall, Matthew; Crowder, Kyle; Spring, Amy

2015-01-01

In this article, we use data on virtually all foreclosure events between 2005 and 2009 to calculate neighborhood foreclosure rates for nearly all block groups in the United States to assess the impact of housing foreclosures on neighborhood racial/ethnic change and on broader patterns of racial residential segregation. We find that the foreclosure crisis was patterned strongly along racial lines: black, Latino, and racially integrated neighborhoods had exceptionally high foreclosure rates. Multilevel models of racial/ethnic change reveal that foreclosure concentrations were linked to declining shares of whites and expanding shares of black and Latino residents. Results further suggest that these compositional shifts were driven by both white population loss and minority growth, especially from racially mixed settings with high foreclosure rates. To explore the impact of these racially selective migration streams on patterns of residential segregation, we simulate racial segregation assuming that foreclosure rates remained at their 2005 levels throughout the crisis period. Our simulations suggest that the foreclosure crisis increased racial segregation between blacks and whites by 1.1 dissimilarity points, and between Latinos and whites by 2.2 dissimilarity points. PMID:26120142

Flow, Sediment Supply, and Channel Width Controls on Gravel Bedform Dynamics

NASA Astrophysics Data System (ADS)

Nelson, P. A.; Morgan, J. A.

2017-12-01

Heterogeneous, coarse-grained riverbeds often self-organize into migrating bedforms such as gravel dunes or bedload sheets. It has recently been suggested that sediment supply and the relative mobility of the bed surface sediment affects the type of bedforms that may be present in gravel-bed rivers; however, our understanding of gravel bedform dynamics remains well behind that of bedforms in sandy channels. Here, we present results from flume experiments in which we investigate how the formation and dynamics of gravel bedforms is affected by changes in discharge, sediment supply, and channel geometry. Experiments were conducted in a 1.1-m wide, 18-m long, sediment-feed flume. The initial bed material and the sediment feed mixture was composed of a sediment mixture ranging in size from 0.5-4 mm, with a median value of 3.6 mm. We used two channel geometries (a straight channel and a channel with sinusoidal width variations) and conducted three experimental runs for each geometry: 1) equilibrium sediment supply and steady flow, 2) equilibrium sediment supply and repeated hydrographs, and 3) doubled sediment supply and repeated hydrographs. During the experiments, low-amplitude, migrating bedforms developed and their dynamics were tracked both visually and via collection of repeated structure-from-motion topographic datasets. In the constant-width geometry, bedform amplitudes and migration rates were relatively constant under steady flow, but when subjected to repeated hydrographs the average bedform celerity decreased by about 50% and the amplitude of the bedforms increased and decreased with the changing flow rate. At twice the equilibrium sediment supply, the bedforms organized into an alternating pattern. This pattern was most pronounced at the lower flow rates, and became less stable at the higher discharges of the repeat hydrographs. Preliminary results suggest bedform celerity in the variable width geometry under steady flow and equilibrium sediment supply was half the celerity of the bedforms for the same conditions in the straight-walled geometry. These experiments suggest that variations in discharge, sediment supply, and channel geometry play an important role in the formation and dynamics of bedforms in gravel-bed rivers.

Primate archaeology reveals cultural transmission in wild chimpanzees (Pan troglodytes verus).

PubMed

Luncz, Lydia V; Wittig, Roman M; Boesch, Christophe

2015-11-19

Recovering evidence of past human activities enables us to recreate behaviour where direct observations are missing. Here, we apply archaeological methods to further investigate cultural transmission processes in percussive tool use among neighbouring chimpanzee communities in the Taï National Park, Côte d'Ivoire, West Africa. Differences in the selection of nut-cracking tools between neighbouring groups are maintained over time, despite frequent female transfer, which leads to persistent cultural diversity between chimpanzee groups. Through the recovery of used tools in the suggested natal territory of immigrants, we have been able to reconstruct the tool material selection of females prior to migration. In combination with direct observations of tool selection of local residents and immigrants after migration, we uncovered temporal changes in tool selection for immigrating females. After controlling for ecological differences between territories of immigrants and residents our data suggest that immigrants abandoned their previous tool preference and adopted the pattern of their new community, despite previous personal proficiency of the same foraging task. Our study adds to the growing body of knowledge on the importance of conformist tendencies in animals. © 2015 The Author(s).

Uridine adenosine tetraphosphate (Up{sub 4}A) is a strong inductor of smooth muscle cell migration via activation of the P2Y{sub 2} receptor and cross-communication to the PDGF receptor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiedon, Annette; Toelle, Markus; Bastine, Joschika

2012-01-20

Highlights: Black-Right-Pointing-Pointer Up{sub 4}A induces VSMC migration. Black-Right-Pointing-Pointer VSMC migration towards Up{sub 4}A involves P2Y{sub 2} activation. Black-Right-Pointing-Pointer Up{sub 4}A-induced VSMC migration is OPN-dependent. Black-Right-Pointing-Pointer Activation of ERK1/2 pathway is necessary for VSMC migration towards Up{sub 4}A. Black-Right-Pointing-Pointer Up{sub 4}A-directed VSMC migration cross-communicates with the PDGFR. -- Abstract: The recently discovered dinucleotide uridine adenosine tetraphosphate (Up{sub 4}A) was found in human plasma and characterized as endothelium-derived vasoconstrictive factor (EDCF). A further study revealed a positive correlation between Up{sub 4}A and vascular smooth muscle cell (VSMC) proliferation. Due to the dominant role of migration in the formation of atherosclerotic lesions ourmore » aim was to investigate the migration stimulating potential of Up{sub 4}A. Indeed, we found a strong chemoattractant effect of Up{sub 4}A on VSMC by using a modified Boyden chamber. This migration dramatically depends on osteopontin secretion (OPN) revealed by the reduction of the migration signal down to 23% during simultaneous incubation with an OPN-blocking antibody. Due to inhibitory patterns using specific and unspecific purinoreceptor inhibitors, Up{sub 4}A mediates it's migratory signal mainly via the P2Y{sub 2}. The signaling behind the receptor was investigated with luminex technique and revealed an activation of the extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway. By use of the specific PDGF receptor (PDGFR) inhibitor AG1296 and siRNA technique against PDGFR-{beta} we found a strongly reduced migration signal after Up{sub 4}A stimulation in the PDGFR-{beta} knockdown cells compared to control cells. In this study, we present substantiate data that Up{sub 4}A exhibits migration stimulating potential probably involving the signaling cascade of MEK1 and ERK1/2 as well as the matrix protein OPN. We further suggest that the initiation of the migration process occurs predominant through direct activation of the P2Y{sub 2} by Up{sub 4}A and via transactivation of the PDGFR.« less

High-intensity urban light installation dramatically alters nocturnal bird migration

PubMed Central

Horton, Kyle G.; Dokter, Adriaan M.; Klinck, Holger; Elbin, Susan B.

2017-01-01

Billions of nocturnally migrating birds move through increasingly photopolluted skies, relying on cues for navigation and orientation that artificial light at night (ALAN) can impair. However, no studies have quantified avian responses to powerful ground-based light sources in urban areas. We studied effects of ALAN on migrating birds by monitoring the beams of the National September 11 Memorial & Museum's “Tribute in Light” in New York, quantifying behavioral responses with radar and acoustic sensors and modeling disorientation and attraction with simulations. This single light source induced significant behavioral alterations in birds, even in good visibility conditions, in this heavily photopolluted environment, and to altitudes up to 4 km. We estimate that the installation influenced ≈1.1 million birds during our study period of 7 d over 7 y. When the installation was illuminated, birds aggregated in high densities, decreased flight speeds, followed circular flight paths, and vocalized frequently. Simulations revealed a high probability of disorientation and subsequent attraction for nearby birds, and bird densities near the installation exceeded magnitudes 20 times greater than surrounding baseline densities during each year’s observations. However, behavioral disruptions disappeared when lights were extinguished, suggesting that selective removal of light during nights with substantial bird migration is a viable strategy for minimizing potentially fatal interactions among ALAN, structures, and birds. Our results also highlight the value of additional studies describing behavioral patterns of nocturnally migrating birds in powerful lights in urban areas as well as conservation implications for such lighting installations. PMID:28973942

Activation of glial FGFRs is essential in glial migration, proliferation, and survival and in glia-neuron signaling during olfactory system development.

PubMed

Gibson, Nicholas J; Tolbert, Leslie P; Oland, Lynne A

2012-01-01

Development of the adult olfactory system of the moth Manduca sexta depends on reciprocal interactions between olfactory receptor neuron (ORN) axons growing in from the periphery and centrally-derived glial cells. Early-arriving ORN axons induce a subset of glial cells to proliferate and migrate to form an axon-sorting zone, in which later-arriving ORN axons will change their axonal neighbors and change their direction of outgrowth in order to travel with like axons to their target areas in the olfactory (antennal) lobe. These newly fasciculated axon bundles will terminate in protoglomeruli, the formation of which induces other glial cells to migrate to surround them. Glial cells do not migrate unless ORN axons are present, axons fail to fasciculate and target correctly without sufficient glial cells, and protoglomeruli are not maintained without a glial surround. We have shown previously that Epidermal Growth Factor receptors and the IgCAMs Neuroglian and Fasciclin II play a role in the ORN responses to glial cells. In the present work, we present evidence for the importance of glial Fibroblast Growth Factor receptors in glial migration, proliferation, and survival in this developing pathway. We also report changes in growth patterns of ORN axons and of the dendrites of olfactory (antennal lobe) neurons following blockade of glial FGFR activation that suggest that glial FGFR activation is important in reciprocal communication between neurons and glial cells.

Activation of Glial FGFRs Is Essential in Glial Migration, Proliferation, and Survival and in Glia-Neuron Signaling during Olfactory System Development

PubMed Central

Gibson, Nicholas J.; Tolbert, Leslie P.; Oland, Lynne A.

2012-01-01

Development of the adult olfactory system of the moth Manduca sexta depends on reciprocal interactions between olfactory receptor neuron (ORN) axons growing in from the periphery and centrally-derived glial cells. Early-arriving ORN axons induce a subset of glial cells to proliferate and migrate to form an axon-sorting zone, in which later-arriving ORN axons will change their axonal neighbors and change their direction of outgrowth in order to travel with like axons to their target areas in the olfactory (antennal) lobe. These newly fasciculated axon bundles will terminate in protoglomeruli, the formation of which induces other glial cells to migrate to surround them. Glial cells do not migrate unless ORN axons are present, axons fail to fasciculate and target correctly without sufficient glial cells, and protoglomeruli are not maintained without a glial surround. We have shown previously that Epidermal Growth Factor receptors and the IgCAMs Neuroglian and Fasciclin II play a role in the ORN responses to glial cells. In the present work, we present evidence for the importance of glial Fibroblast Growth Factor receptors in glial migration, proliferation, and survival in this developing pathway. We also report changes in growth patterns of ORN axons and of the dendrites of olfactory (antennal lobe) neurons following blockade of glial FGFR activation that suggest that glial FGFR activation is important in reciprocal communication between neurons and glial cells. PMID:22493675

Coastal Forests of the Gulf of Mexico: A Description and Some Thoughts on Their Conservation

Treesearch

W. C. Barrow; L. A. Johnson Randall; M. S. Woodrey; J. Cox; E. Ruelas I.; C. M. Riley; R. B. Hamilton; C. Eberly

2005-01-01

Millions of Nearctic-Neotropical landbirds move through the coastal forests of the Gulf of Mexico each spring and autumn as they migrate across and around the gulf. Migration routes in the gulf region are not static—they shift year to year and season to season according to prevailing wind patterns. Given the dynamic nature of migration routes, coastal forests...

Aboriginal Community Education Officers' Border Work: Culturally Safe Practices for Supporting Migrating Indigenous Students from Country into Urban and Semi-Rural Schools

ERIC Educational Resources Information Center

MacGill, Bindi

2012-01-01

Since 2001 there has been an increase in migration patterns by Indigenous families from remote communities to urban and semi-rural locations. Indigenous student emigration from remote Indigenous schools to urban and semi-rural schools is an emerging crisis as there are routinely inadequate service providers for Indigenous emigres. Migration away…

Temporal lobe dual pathology in malignant migrating partial seizures in infancy.

PubMed

Coppola, Giangennaro; Operto, Francesca Felicia; Auricchio, Gianfranca; D'Amico, Alessandra; Fortunato, Delia; Pascotto, Antonio

2007-06-01

A child had the characteristic clinical and EEG pattern of migrating partial seizures in infancy with left temporal lobe atrophy, hippocampal sclerosis and cortical-subcortical blurring. Seizures were drug-resistant, with recurring episodes of status epilepticus. The child developed microcephaly with arrest of psychomotor development. Focal brain lesions, in the context of migrating partial seizures, have not been previously reported.[Published with video sequences].

Domestic and International Climate Migration from Rural Mexico

PubMed Central

Nawrotzki, Raphael J.; Runfola, Daniel M.; Hunter, Lori M.; Riosmena, Fernando

2016-01-01

Evidence is increasing that climate change and variability may influence human migration patterns. However, there is less agreement regarding the type of migration streams most strongly impacted. This study tests whether climate change more strongly impacted international compared to domestic migration from rural Mexico during 1986-99. We employ eight temperature and precipitation-based climate change indices linked to detailed migration histories obtained from the Mexican Migration Project. Results from multilevel discrete-time event-history models challenge the assumption that climate-related migration will be predominantly short distance and domestic, but instead show that climate change more strongly impacted international moves from rural Mexico. The stronger climate impact on international migration may be explained by the self-insurance function of international migration, the presence of strong migrant networks, and climate-related changes in wage difference. While a warming in temperature increased international outmigration, higher levels of precipitation declined the odds of an international move. PMID:28439146

Domestic and International Climate Migration from Rural Mexico.

PubMed

Nawrotzki, Raphael J; Runfola, Daniel M; Hunter, Lori M; Riosmena, Fernando

2016-12-01

Evidence is increasing that climate change and variability may influence human migration patterns. However, there is less agreement regarding the type of migration streams most strongly impacted. This study tests whether climate change more strongly impacted international compared to domestic migration from rural Mexico during 1986-99. We employ eight temperature and precipitation-based climate change indices linked to detailed migration histories obtained from the Mexican Migration Project. Results from multilevel discrete-time event-history models challenge the assumption that climate-related migration will be predominantly short distance and domestic, but instead show that climate change more strongly impacted international moves from rural Mexico. The stronger climate impact on international migration may be explained by the self-insurance function of international migration, the presence of strong migrant networks, and climate-related changes in wage difference. While a warming in temperature increased international outmigration, higher levels of precipitation declined the odds of an international move.

Interspecific exchange of avian influenza virus genes in Alaska: The influence of trans-hemispheric migratory tendency and breeding ground sympatry

USGS Publications Warehouse

Pearce, John M.; Reeves, A.B.; Ramey, A.M.; Hupp, Jerry W.; Ip, Hon S.; Bertram, M.; Petrula, M.J.; Scotton, B.D.; Trust, K.A.; Meixell, Brandt W.; Runstadler, J.A.

2011-01-01

The movement and transmission of avian influenza viral strains via wild migratory birds may vary by host species as a result of migratory tendency and sympatry with other infected individuals. To examine the roles of host migratory tendency and species sympatry on the movement of Eurasian low-pathogenic avian influenza (LPAI) genes into North America, we characterized migratory patterns and LPAI viral genomic variation in mallards (Anas platyrhynchos) of Alaska in comparison with LPAI diversity of northern pintails (Anas acuta). A 50-year band-recovery data set suggests that unlike northern pintails, mallards rarely make trans-hemispheric migrations between Alaska and Eurasia. Concordantly, fewer (14.5%) of 62 LPAI isolates from mallards contained Eurasian gene segments compared to those from 97 northern pintails (35%), a species with greater inter-continental migratory tendency. Aerial survey and banding data suggest that mallards and northern pintails are largely sympatric throughout Alaska during the breeding season, promoting opportunities for interspecific transmission. Comparisons of full-genome isolates confirmed near-complete genetic homology (>99.5%) of seven viruses between mallards and northern pintails. This study found viral segments of Eurasian lineage at a higher frequency in mallards than previous studies, suggesting transmission from other avian species migrating inter-hemispherically or the common occurrence of endemic Alaskan viruses containing segments of Eurasian origin. We conclude that mallards are unlikely to transfer Asian-origin viruses directly to North America via Alaska but that they are likely infected with Asian-origin viruses via interspecific transfer from species with regular migrations to the Eastern Hemisphere.

Medical tourism's impacts on health worker migration in the Caribbean: five examples and their implications for global justice.

PubMed

Snyder, Jeremy; Crooks, Valorie A; Johnston, Rory; Adams, Krystyna; Whitmore, Rebecca

2015-01-01

Medical tourism is a practice where individuals cross international borders in order to access medical care. This practice can impact the global distribution of health workers by potentially reducing the emigration of health workers from destination countries for medical tourists and affecting the internal distribution of these workers. Little has been said, however, about the impacts of medical tourism on the immigration of health workers to medical tourism destinations. We discuss five patterns of medical tourism-driven health worker migration to medical tourism destinations: 1) long-term international migration; 2) long-term diasporic migration; 3) long-term migration and 'black sheep'; 4) short-term migration via time share; and 5) short-term migration via patient-provider dyad. These patterns of health worker migration have repercussions for global justice that include potential negative impacts on the following: 1) health worker training; 2) health worker distributions; 3) local provision of care; and 4) local economies. In order to address these potential negative impacts, policy makers in destination countries should work to ensure that changes in health worker training and licensure aimed at promoting the medical tourism sector are also supportive of the health needs of the domestic population. Policy makers in both source and destination countries should be aware of the effects of medical tourism on health worker flows both into and out of medical tourism destinations and work to ensure that the potential harms of these worker flows to both groups are mitigated.

Emigration flows from North Africa to Europe.

PubMed

Kassar, Hassène; Marzouk, Diaa; Anwar, Wagida A; Lakhoua, Chérifa; Hemminki, Kari; Khyatti, Meriem

2014-08-01

The region of North Africa (NA) represents a striking locality regarding migration with several migration patterns, namely emigration in the form of labour export to Europe and North America and, to a lesser extent, to the Arab Gulf area. The latter has increased enormously in the last decade because of the political instability in most of the NA countries. The aim of the present chapter was to explore the patterns of migration stocks and flows in NA countries, based on several websites, systematic review of journals, comparable data available by the United Nations and by the International Organization of Migration. The NA region has become an area of transit migration and labour migration. Emigrant flows from NA countries towards Europe and North America are increasing this decade more than towards the Arab Gulf countries after being replaced by Asian labour. The recent increase in the proportion of women among the migrant population is remarkable. Remittances sent by African migrants have become an important source of external finance for countries of origin. Transient and irregular migration to Egypt originates at the borders with Sudan, Palestine and Libya with destination to the Euro Mediterranean countries. In Tunisia and Morocco, irregular migrants originate from Sub-Saharan Africa to the northern borders. The NA countries serve as departure rather than destination countries, and migration flows to the Euro-Mediterranean countries through legal or illegal routes. © The Author 2014. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.

Medical tourism's impacts on health worker migration in the Caribbean: five examples and their implications for global justice

PubMed Central

Snyder, Jeremy; Crooks, Valorie A.; Johnston, Rory; Adams, Krystyna; Whitmore, Rebecca

2015-01-01

Medical tourism is a practice where individuals cross international borders in order to access medical care. This practice can impact the global distribution of health workers by potentially reducing the emigration of health workers from destination countries for medical tourists and affecting the internal distribution of these workers. Little has been said, however, about the impacts of medical tourism on the immigration of health workers to medical tourism destinations. We discuss five patterns of medical tourism-driven health worker migration to medical tourism destinations: 1) long-term international migration; 2) long-term diasporic migration; 3) long-term migration and ‘black sheep’; 4) short-term migration via time share; and 5) short-term migration via patient-provider dyad. These patterns of health worker migration have repercussions for global justice that include potential negative impacts on the following: 1) health worker training; 2) health worker distributions; 3) local provision of care; and 4) local economies. In order to address these potential negative impacts, policy makers in destination countries should work to ensure that changes in health worker training and licensure aimed at promoting the medical tourism sector are also supportive of the health needs of the domestic population. Policy makers in both source and destination countries should be aware of the effects of medical tourism on health worker flows both into and out of medical tourism destinations and work to ensure that the potential harms of these worker flows to both groups are mitigated. PMID:25865122

PET bottle use patterns and antimony migration into bottled water and soft drinks: the case of British and Nigerian bottles.

PubMed

Tukur, Aminu; Sharp, Liz; Stern, Ben; Tizaoui, Chedly; Benkreira, Hadj

2012-04-01

While antimony has been reported to migrate from PET bottles into contents, reports on bottled water and soft drinks usage and PET bottle reuse patterns are currently unavailable in the literature. Bottle use conditions and patterns are important determinants of antimony migration. In this work a survey assessing the pattern of bottle use and reuse in Britain and Nigeria was undertaken. The survey findings influenced the design of laboratory experiments that assessed the migration of antimony from PET bottles into water and soft drinks. Typical storage durations for bottled contents between purchase and opening for use were 7 days or less. However storage of up to one year was reported. Bottle reuse was high and similar for the two countries with reuse durations being higher in Nigeria. The antimony concentration in 32 PET bottle materials from Britain and Nigeria were similar and ranged between 177 and 310 mg kg(-1). For 47 freshly purchased British bottled contents antimony concentration ranged between 0.03 and 6.61 μg L(-1) with only one sample exceeding the EU acceptable limit. Concentrations of Cd, Ge, Zn, Al, Be, Ti, Co and Pb were also measured. At realistic temperatures of 40 and 60 °C antimony concentration in deionised water in bottles remained below the EU acceptable limit even after 48 h exposure. The limit was exceeded for most exposures at 80 °C. Concentration of antimony in some bottled contents exceeded the EU limit after 11 months of storage at room temperature. Bottle aging and increase in bottle volume were associated with decreased migration of antimony from bottles.

Short-chain chlorinated paraffins in the soils of two different Chinese cities: Occurrence, homologue patterns and vertical migration.

PubMed

Huang, Yumei; Chen, Laiguo; Feng, Yongbin; Ye, Zhixiang; He, Qiusheng; Feng, Qianhua; Qing, Xian; Liu, Ming; Gao, Bo

2016-07-01

Short-chain chlorinated paraffins (SCCPs) are candidate persistent organic pollutants (POPs) that are under review by the Stockholm Convention. China is currently the largest producer and consumer of chlorinated paraffins (CPs). To study the environmental behavior and fate of SCCPs in the soils of urban and suburban regions, the SCCP concentrations in 88 topsoils and 15 soil columns from land of different use types (e.g., woodland, vegetable field, paddy field and greenbelt) from Guangzhou and Chengdu have been determined. The SCCP concentrations in topsoils from Guangzhou (range: 1.45-25.5ngg(-1) dry weight (dw), average: 10.3ngg(-1) dw) were much higher than those from Chengdu (range: 0.218-3.26ngg(-1) dw, average: 1.43ngg(-1) dw). When compared to previously reported SCCP levels for topsoils from other areas, the SCCP concentrations measured in the present work were quite low. Much higher SCCP concentrations were observed in the greenbelt topsoils from Chengdu relative to the values measured from woodlands and vegetable and paddy fields. The composition profiles suggest that C10Cl6-10 and C11-13Cl6-8 were the major groups of SCCPs in topsoils from the woodlands and vegetable and paddy fields in Guangzhou and Chengdu. Vertical variations of the SCCP concentrations in the soil columns suggest that less chlorinated SCCPs (Cl5-6-SCCPs) are more capable of migrating to the deeper-layer soils than more chlorinated ones (Cl9-10-SCCPs). The SCCP concentrations displayed little dependence on organic matter (OM) for most topsoils (p>0.05), indicating that OM is not the controlling factor in the distribution of SCCPs in the soils. This study analyzed the occurrence, homologue patterns and vertical migration of SCCPs in the topsoils of two Chinese cities with different industrial structures and climate conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Migration in south Asia: an overview.

PubMed

Skeldon, R

1983-01-01

Past studies on migration patterns and flows in south Asia have been based on limited data. The present overview is based on a detailed study of census and survey data reaching back to the early 1950's. The study incorporates the thinking of several research scholars who have dealt with specialized areas of migration in individual countries, and in the region as a whole. The interrelationships between migration and development are considered in a final chapter, with special mention of future trends, associated with traditional practices and historical circumstances. Migration will be of great importance in the coming decades. The activities of "sons of soil" anti-migrant movements and anti-migrant legislation have had little, if any, effect on migration flows. As the population increases in villages and towns and jobs become scarce, migration is likely to become even more of a political issue. Less politically volatile is circulation between village and town or between villages, whereby the migrants can have access to resources in 2 or more places. This option may play a critical role in the continued survival of much of the population in the future. This has been perhaps the most important factor in explaining the relatively slow rate of urbanization in south Asia as it allowed the rural people to take advantage of the towns without causing a massive and permanent transfer of population. The numbers who practice this "bilocality" are therefore likely to increase and migrants will continue to make up more significant proportions of the urban populations than their contribution to urban growth would suggest owing to the importance of "turnover migration." However, this circulation is not a new phenomenon: India and the other countries of south Asia have been characterized by tremendous mobility of population through circulation for considerable time but both its volume, and the distances over which it occurs are likely to increase as these countries develop.

Compositional shifts in Costa Rican forests due to climate-driven species migrations.

PubMed

Feeley, Kenneth J; Hurtado, Johanna; Saatchi, Sassan; Silman, Miles R; Clark, David B

2013-11-01

Species are predicted to shift their distributions upslope or poleward in response to global warming. This prediction is supported by a growing number of studies documenting species migrations in temperate systems but remains poorly tested for tropical species, and especially for tropical plant species. We analyzed changes in tree species composition in a network of 10 annually censused 1-ha plots spanning an altitudinal gradient of 70-2800 m elevation in Costa Rica. Specifically, we combined plot data with herbarium records (accessed through GBIF) to test if the plots' community temperature scores (CTS, average thermal mean of constituent species weighted by basal area) have increased over the past decade as is predicted by climate-driven species migrations. In addition, we quantified the contributions of stem growth, recruitment, and mortality to the observed patterns. Supporting our a priori hypothesis of upward species migrations, we found that there have been consistent directional shifts in the composition of the plots, such that the relative abundance of lowland species, and hence CTS, increased in 90% of plots. The rate of the observed compositional shifts corresponds to a mean thermal migration rate (TMR) of 0.0065 °C yr(-1) (95% CI = 0.0005-0.0132 °C yr(-1) ). While the overall TMR is slower than predicted based on concurrent regional warming of 0.0167 °C yr(-1) , migrations were on pace with warming in 4 of the 10 plots. The observed shifts in composition were driven primarily by mortality events (i.e., the disproportionate death of highland vs. lowland species), suggesting that individuals of many tropical tree species will not be able to tolerate future warming and thus their persistence in the face of climate change will depend on successful migrations. Unfortunately, in Costa Rica and elsewhere, land area inevitably decreases at higher elevations; hence, even species that are able to migrate successfully will face heightened risks of extinction. © 2013 John Wiley & Sons Ltd.

Tempo-spatial analysis of Fennoscandian intraplate seismicity

NASA Astrophysics Data System (ADS)

Roberts, Roland; Lund, Björn

2017-04-01

Coupled spatial-temporal patterns of the occurrence of earthquakes in Fennoscandia are analysed using non-parametric methods. The occurrence of larger events is unambiguously and very strongly temporally clustered, with major implications for the assessment of seismic hazard in areas such as Fennoscandia. In addition, there is a clear pattern of geographical migration of activity. Data from the Swedish National Seismic Network and a collated international catalogue are analysed. Results show consistent patterns on different spatial and temporal scales. We are currently investigating these patterns in order to assess the statistical significance of the tempo-spatial patterns, and to what extent these may be consistent with stress transfer mechanism such as coulomb stress and pore fluid migration. Indications are that some further mechanism is necessary in order to explain the data, perhaps related to post-glacial uplift, which is up to 1cm/year.

Russian, Soviet, and post-Soviet scientific migration: history and patterns

NASA Astrophysics Data System (ADS)

Kojevnikov, Alexei

2011-03-01

Immigrant scientists from other European countries (predominantly German) were crucial in establishing the tradition of modern science in the Russian Empire of the 18th and 19th centuries. Since the 1860s, however, outgoing waves of scientific migration started originating in Russia, bringing important innovations to international science. The scale and patterns of migration varied greatly with the turbulent time. The talk will describe several landmark stages of the proceess and their cultural consequences: from opening higher education possibilities for women during the late 19th century, to post-1917 academic refugees and Soviet defectors, to the 1960s brain drain provoked by the launch of Sputnik, and to what can be called the first truly global scientific diaspora of Russophone scientists after 1990.

Intravital multiphoton imaging reveals multicellular streaming as a crucial component of in vivo cell migration in human breast tumors

PubMed Central

Patsialou, Antonia; Bravo-Cordero, Jose Javier; Wang, Yarong; Entenberg, David; Liu, Huiping; Clarke, Michael; Condeelis, John S.

2014-01-01

Metastasis is the main cause of death in breast cancer patients. Cell migration is an essential component of almost every step of the metastatic cascade, especially the early step of invasion inside the primary tumor. In this report, we have used intravital multiphoton microscopy to visualize the different migration patterns of human breast tumor cells in live primary tumors. We used xenograft tumors of MDA-MB-231 cells as well as a low passage xenograft tumor from orthotopically injected patient-derived breast tumor cells. Direct visualization of human tumor cells in vivo shows two patterns of high-speed migration inside primary tumors: a. single cells and b. multicellular streams (i.e., cells following each other in a single file but without cohesive cell junctions). Critically, we found that only streaming and not random migration of single cells was significantly correlated with proximity to vessels, with intravasation and with numbers of elevated circulating tumor cells in the bloodstream. Finally, although the two human tumors were derived from diverse genetic backgrounds, we found that their migratory tumor cells exhibited coordinated gene expression changes that led to the same end-phenotype of enhanced migration involving activating actin polymerization and myosin contraction. Our data are the first direct visualization and assessment of in vivo migration within a live patient-derived breast xenograft tumor. PMID:25013744

Outmigration patterns in development transition of rural areas.

PubMed

Kaistha, K C

1987-01-01

Using a broadened concept of migration, which includes circulatory migration and commuting, this paper maintains that the patterns of outmigration vary a great deal when the level of development of a rural area is treated as an independent variable. This study uses a stratified conditional sample of 192 households selected from 3 areas: 53 households from a low developed (LDL) area, 56 from a medium (MDL), and 83 from a high (HDL). Data were collected by personal observation, interview, and genealogical methods at both the household and individual level. The households are divided into 3 main categories: 1) non-migrating, 2) commuting only, and 3) migrating (which is further divided into migrating within and migrating outside the boundaries of the district). Results show that 1) 37.51% of household members neither commute nor have migrated outside the village; 2) using the narrow definition of migration, only 10% of males over age 15 migrate, while including commuting in the definition increases the percentage to 40; 3) proportions of non-migrating households decrease from 58.4% for the LDL, to 35.7% for the MDL, to 25.3% for the HDL area; 4) the proportion of commuting only households increases from 26.4% for the LDL, to 35.7% to the MDL, and 55.4% for the HDL area; 5) 15.2% of households in the LDL, 28.6% in the MDL, and 19.3% in the HDL area experience a permanent change in residence; 6) as development accelerates, the overall volume of outmigration increases; 7) the flow of migration from rural to rural areas is mostly limited to the MDL area, while cityward migration increasingly occurs on both LDL and HDL areas; 8) the median age of commuters increases with rising levels of development; and 9) almost all migrants from the LDL area are employed in low prestige occupations, most from the HDL area have higher prestige jobs, and those from the MDL area have both high and low prestige jobs.

Spatio-Temporal Migration Patterns of Pacific Salmon Smolts in Rivers and Coastal Marine Waters

PubMed Central

Melnychuk, Michael C.; Welch, David W.; Walters, Carl J.

2010-01-01

Background Migrations allow animals to find food resources, rearing habitats, or mates, but often impose considerable predation risk. Several behavioural strategies may reduce this risk, including faster travel speed and taking routes with shorter total distance. Descriptions of the natural range of variation in migration strategies among individuals and populations is necessary before the ecological consequences of such variation can be established. Methodology/Principal Findings Movements of tagged juvenile coho, steelhead, sockeye, and Chinook salmon were quantified using a large-scale acoustic tracking array in southern British Columbia, Canada. Smolts from 13 watersheds (49 watershed/species/year combinations) were tagged between 2004–2008 and combined into a mixed-effects model analysis of travel speed. During the downstream migration, steelhead were slower on average than other species, possibly related to freshwater residualization. During the migration through the Strait of Georgia, coho were slower than steelhead and sockeye, likely related to some degree of inshore summer residency. Hatchery-reared smolts were slower than wild smolts during the downstream migration, but after ocean entry, average speeds were similar. In small rivers, downstream travel speed increased with body length, but in the larger Fraser River and during the coastal migration, average speed was independent of body length. Smolts leaving rivers located towards the northern end of the Strait of Georgia ecosystem migrated strictly northwards after ocean entry, but those from rivers towards the southern end displayed split-route migration patterns within populations, with some moving southward. Conclusions/Significance Our results reveal a tremendous diversity of behavioural migration strategies used by juvenile salmon, across species, rearing histories, and habitats, as well as within individual populations. During the downstream migration, factors that had strong effects on travel speeds included species, wild or hatchery-rearing history, watershed size and, in smaller rivers, body length. During the coastal migration, travel speeds were only strongly affected by species differences. PMID:20886121

Explaining the Muslim employment gap in Western Europe: individual-level effects and ethno-religious penalties.

PubMed

Connor, Phillip; Koenig, Matthias

2015-01-01

It is well-documented that Muslims experience economic disadvantages in Western European labor markets. However, few studies comprehensively test individual-level explanations for the Muslim employment gap. Using data from the European Social Survey, this research note briefly examines the role of individual-level differences between Muslims and non-Muslims in mediating employment differences. Results reveal that human capital, migration background, religiosity, cultural values, and perceptions of discrimination jointly account for about 40% of the employment variance between Muslims and non-Muslims. Model specifications for first- and second-generation Muslim immigrants reveal a similar pattern, with migration background and perceived discrimination being of key relevance in mediating employment difference. While individual-level effects are indeed relevant, unexplained variance suggests that symbolic boundaries against Islam may still translate into tangible ethno-religious penalties. Copyright © 2014 Elsevier Inc. All rights reserved.

Inferring human history in East Asia from Y chromosomes.

PubMed

Wang, Chuan-Chao; Li, Hui

2013-06-03

East Asia harbors substantial genetic, physical, cultural and linguistic diversity, but the detailed structures and interrelationships of those aspects remain enigmatic. This question has begun to be addressed by a rapid accumulation of molecular anthropological studies of the populations in and around East Asia, especially by Y chromosome studies. The current Y chromosome evidence suggests multiple early migrations of modern humans from Africa via Southeast Asia to East Asia. After the initial settlements, the northward migrations during the Paleolithic Age shaped the genetic structure in East Asia. Subsequently, recent admixtures between Central Asian immigrants and northern East Asians enlarged the genetic divergence between southern and northern East Asia populations. Cultural practices, such as languages, agriculture, military affairs and social prestige, also have impacts on the genetic patterns in East Asia. Furthermore, application of Y chromosome analyses in the family genealogy studies offers successful showcases of the utility of genetics in studying the ancient history.

Mixed sediment beach processes: Kachemak Bay, Alaska

USGS Publications Warehouse

Ruggiero, P.; Adams, P.N.; Warrick, J.A.

2007-01-01

Mixed sediment beaches are morphologically distinct from and more complex than either sand or gravel only beaches. Three digital imaging techniques are employed to quantify surficial grain size and bedload sediment transport rates along the mixed sediment beaches of Kachemak Bay, Alaska. Applying digital imaging procedures originally developed for quickly and efficiently quantifying grain sizes of sand to coarse sediment classes gives promising results. Hundreds of grain size estimates lead to a quantitative characterization of the region's sediment at a significant reduction in cost and time as compared to traditional techniques. Both the sand and coarse fractions on this megatidal beach mobilize into self-organized bedforms that migrate alongshore with a seasonally reflecting the temporal pattern of the alongshore component of wave power. In contrast, the gravel bedforms also migrate in the cross-shore without significant seasonally suggesting that swash asymmetry is sufficient to mobilize the gravel even during low energy summer conditions. ?? 2007 ASCE.

Inferring human history in East Asia from Y chromosomes

PubMed Central

2013-01-01

East Asia harbors substantial genetic, physical, cultural and linguistic diversity, but the detailed structures and interrelationships of those aspects remain enigmatic. This question has begun to be addressed by a rapid accumulation of molecular anthropological studies of the populations in and around East Asia, especially by Y chromosome studies. The current Y chromosome evidence suggests multiple early migrations of modern humans from Africa via Southeast Asia to East Asia. After the initial settlements, the northward migrations during the Paleolithic Age shaped the genetic structure in East Asia. Subsequently, recent admixtures between Central Asian immigrants and northern East Asians enlarged the genetic divergence between southern and northern East Asia populations. Cultural practices, such as languages, agriculture, military affairs and social prestige, also have impacts on the genetic patterns in East Asia. Furthermore, application of Y chromosome analyses in the family genealogy studies offers successful showcases of the utility of genetics in studying the ancient history. PMID:23731529

MOR23 promotes muscle regeneration and regulates cell adhesion and migration

PubMed Central

Griffin, Christine A.; Kafadar, Kimberly A.; Pavlath, Grace K.

2009-01-01

Summary Odorant receptors (ORs) in the olfactory epithelium bind to volatile small molecules leading to the perception of smell. ORs are expressed in many tissues but their functions are largely unknown. We show multiple ORs display distinct mRNA expression patterns during myogenesis in vitro and muscle regeneration in vivo. Mouse OR23 (MOR23) expression is induced during muscle regeneration when muscle cells are extensively fusing and plays a key role in regulating migration and adhesion of muscle cells in vitro, two processes common during tissue repair. A soluble ligand for MOR23 is secreted by muscle cells in vitro and muscle tissue in vivo. MOR23 is necessary for proper skeletal muscle regeneration as loss of MOR23 leads to increased myofiber branching, commonly associated with muscular dystrophy. Together these data identify a functional role for an OR outside of the nose and suggest a larger role for ORs during tissue repair. PMID:19922870

Fish Research Project Oregon; Aspects of Life History and Production of Juvenile Oncorhynchus Mykiss in the Grande Ronde River Basin, Northeast Oregon, 1995-1999 Summary Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Dyke, Erick S.; Jonnasson, Brian C.; Carmichael, Richard W.

2001-07-01

Rotary screw traps, located at four sites in the Grande Ronde River basin, were used to characterize aspects of early life history exhibited by juvenile Onchorhychus mykiss during migration years 1995-99. The Lostine, Catherine Creek and upper Grande Ronde traps captured fish as they migrated out of spawning areas into valley rearing habitats. The Grande Ronde Valley trap captured fish as they left valley habitats downstream of Catherine Creek and upper Grande Ronde River rearing habitats. Dispersal downstream of spawning areas was most evident in fall and spring, but movement occurred during all seasons that the traps were fished. Seawardmore » migration occurred primarily in spring when O. mykiss smolts left overwintering area located in both spawning area and valley habitats. Migration patterns exhibited by O. mykiss suggest that Grande Ronde Valley habitats are used for overwintering and should be considered critical rearing habitat. We were unable to positively differentiate anadromous and resident forms of O. mykiss in the Grande Ronde River basin because both forms occur in our study area. The Grande Ronde Valley trap provided the best information on steelhead production in the basin because it fished below valley habitats where O. mykiss overwinter. Length frequency histograms of O. mykiss captured below upper spawning and rearing habitats showed a bimodal distribution regardless of the season of capture. Scale analyses suggested that each mode represents a different brood year. Length frequency histograms of O. mykiss captured in the Grande Ronde Valley trap were not bimodal, and primarily represented a size range consistent with other researchers' accounts of anadromous smolts.« less

Measuring Polycentricity of Mega-City Regions in China Based on the Intercity Migration Flows

NASA Astrophysics Data System (ADS)

Mu, Xiaoyan; Yeh, Anthony G. O.

2016-06-01

This paper uses the intercity migration flows to examine relations between Chinese cities, identify the important mega-city regions and measure each region's polycentricity from an interaction perspective. Data set contains the long-term residential migration trajectories of three million Sina weibo users across 345 cities. Cities with close connectivity deployed around one or several mega cities are identified as mega-city regions. Features of the mega-city regions are characterized by the strength of migration flows, density of connections, and regional migration patterns. The results show that the disparities exist in different mega-city regions; most mega-city regions are lack of polycentricity.

Digital modeling of radioactive and chemical waste transport in the aquifer underlying the Snake River Plain at the National Reactor Testing Station, Idaho

USGS Publications Warehouse

Robertson, J.B.

1974-01-01

Industrial and low-level radioactive liquid wastes at the National Reactor Testing Station (NRTS) in Idaho have been disposed to the Snake River Plain aquifer since 1952. Monitoring studies have indicated that tritium and chloride have dispersed over a 15-square mile (39-square kilometer) area of the aquifer in low but detectable concentrations and have only migrated as far as 5 miles (8 kilometers) downgradient from discharge points. The movement of cationic waste solutes, particularly 90Sr and 137Cs, has been significantly retarded due to sorption phenomena, principally ion exchange. 137Cs has shown no detectable migration in the aquifer and 90Sr has migrated only about 1.5 miles (2 kilometers) from the Idaho Chemical Processing Plant (ICPP) discharge well, and is detectable over an area of only 1.5 square miles ( 4 square kilometers) of the aquifer. Digital modeling techniques have been applied successfully to the analysis of the complex waste-transport system by utilizing numerical solution of the coupled equations of groundwater motion and mass transport. The model includes the effects of convective transport, flow divergence, two-dimensional hydraulic dispersion, radioactive decay, and reversible linear sorption. The hydraulic phase of the model uses the iterative, alternating direction, implicit finite-difference scheme to solve the groundwater flow equations, while the waste-transport phase uses a modified method of characteristics to solve the solute transport equations simulated by the model. The modeling results indicate that hydraulic dispersion (especially transverse) is a much more significant influence than previously suggested by earlier studies. The model has been used to estimate future waste migration patterns for varied assumed hydrological and waste conditions up through the year 2000. The hydraulic effects of recharge from the Big Lost River have an important (but not predominant) influence on the simulated future migration patterns. For the assumed conditions, the model indicates that detectable concentrations of waste chloride and tritium could move as much as 15 miles (24 kilometers) downgradient from the original discharge points by the year 2000. However, the model shows 90Sr moving only 2 to 3 miles (3 to 5 kilometers) downgradient in the same time. The model may also be used to estimate the effects of the various future waste disposal practices and hydrologic conditions on subsequent migration of waste products.

Convergent evolution in locomotory patterns of flying and swimming animals.

PubMed

Gleiss, Adrian C; Jorgensen, Salvador J; Liebsch, Nikolai; Sala, Juan E; Norman, Brad; Hays, Graeme C; Quintana, Flavio; Grundy, Edward; Campagna, Claudio; Trites, Andrew W; Block, Barbara A; Wilson, Rory P

2011-06-14

Locomotion is one of the major energetic costs faced by animals and various strategies have evolved to reduce its cost. Birds use interspersed periods of flapping and gliding to reduce the mechanical requirements of level flight while undergoing cyclical changes in flight altitude, known as undulating flight. Here we equipped free-ranging marine vertebrates with accelerometers and demonstrate that gait patterns resembling undulating flight occur in four marine vertebrate species comprising sharks and pinnipeds. Both sharks and pinnipeds display intermittent gliding interspersed with powered locomotion. We suggest, that the convergent use of similar gait patterns by distinct groups of animals points to universal physical and physiological principles that operate beyond taxonomic limits and shape common solutions to increase energetic efficiency. Energetically expensive large-scale migrations performed by many vertebrates provide common selection pressure for efficient locomotion, with potential for the convergence of locomotory strategies by a wide variety of species.

Migration of female construction labourers to Dhaka City, Bangladesh.

PubMed

Ahsan, R M

1997-03-01

The author analyzes migration patterns and processes of female construction workers in Dhaka City, Bangladesh, and considers the impact of this migration. "Interviews...reveal that the major goal of these female migrants, whose mobility and employment have traditionally been restricted, is to take responsibility in the struggle for livelihood.... Success of many migrations is linked with participation in construction work in the city. Employment in such activities is largely by women from male-headed households, indicating male support in the work, followed by females heading their own households." excerpt

Fractal analysis of narwhal space use patterns.

PubMed

Laidre, Kristin L; Heide-Jørgensen, Mads P; Logsdon, Miles L; Hobbs, Roderick C; Dietz, Rune; VanBlaricom, Glenn R

2004-01-01

Quantifying animal movement in response to a spatially and temporally heterogeneous environment is critical to understanding the structural and functional landscape influences on population viability. Generalities of landscape structure can easily be extended to the marine environment, as marine predators inhabit a patchy, dynamic system, which influences animal choice and behavior. An innovative use of the fractal measure of complexity, indexing the linearity of movement paths over replicate temporal scales, was applied to satellite tracking data collected from narwhals (Monodon monoceros) (n = 20) in West Greenland and the eastern Canadian high Arctic. Daily movements of individuals were obtained using polar orbiting satellites via the ARGOS data location and collection system. Geographic positions were filtered to obtain a daily good quality position for each whale. The length of total pathway was measured over seven different temporal length scales (step lengths), ranging from one day to one week, and a seasonal mean was calculated. Fractal dimension (D) was significantly different between seasons, highest during summer (D = 1.61, SE 0.04) and winter (D = 1.69, SE 0.06) when whales made convoluted movements in focal areas. Fractal dimension was lowest during fall (D = 1.34, SE 0.03) when whales were migrating south ahead of the forming sea ice. There were no significant effects of size category or sex on fractal dimension by season. The greater linearity of movement during the migration period suggests individuals do not intensively forage on patchy resources until they arrive at summer or winter sites. The highly convoluted movements observed during summer and winter suggest foraging or searching efforts in localized areas. Significant differences between the fractal dimensions on two separate wintering grounds in Baffin Bay suggest differential movement patterns in response to the dynamics of sea ice.

Keratinocyte response to immobilized growth factors for enhanced dermal wound healing

NASA Astrophysics Data System (ADS)

Stefonek-Puccinelli, Tracy Jane

Chronic wounds cost billions of dollars per year to treat and wound care is limited to ineffective and/or expensive options. Chronic wounds are characterized by a failure to reepithelialize, as well as deficiencies in growth factors, such as epidermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1), normally present during wound healing. Our system described herein begins to tackle the problems associated with designing bioactive materials for chronic wound healing applications. We show that we can induce accelerated keratinocyte migration with photo-immobilized EGF and further control migration speed through the culture of cells on different types of gradient patterns of EGF. We also successfully immobilized IGF-1 while retaining its bioactivity, and further showed it induces directed keratinocyte migration, although not as potently as immobilized EGF. Potential synergy between co-immobilized IGF-1 and EGF was also investigated, although EGF continued to dominate the cellular response, and no significant increase in cell migration was achieved via the addition of IGF-1 to the system. To further understand cellular response to our immobilized growth factors, we investigated keratinocyte signaling and function in response to changes in EGF presentation. It was found that immobilized and soluble EGF can play different, yet complementary, roles in regulating keratinocyte function. Specifically, keratinocytes responded to immobilized EGF with high EGF receptor (EGFR) activation, accompanied by low proliferation and high migratory activity. In contrast, keratinocytes treated with soluble EGF displayed a highly proliferative, rather than migratory, phenotype. We then transitioned our photo-immobilization techniques to materials that may be more suitable as a wound dressing, such as silk fibroin films. Silk fibroin is a natural fiber with many desirable qualities for a biomaterial including high strength and elasticity, biocompatibility, a beta-keratin structure which closely mimics human keratin, and ease of fabrication and modification. These silk films can also provide topographical cues via simple cast molding of any feature on the micron scale. This system allowed simultaneous presentation of topographic cues, inhibitory and/or synergistic, with our chemotactic cues. Our preliminary data suggest keratinocytes remain viable on silk fibroin films, and that these films can be patterned with immobilized EGF to induce keratinocyte migration.

Direct observation of localized radial oxygen migration in functioning tantalum oxide memristors

DOE PAGES

Kumar, Suhas; Graves, Catherine E.; Strachan, John Paul; ...

2016-02-02

Oxygen migration in tantalum oxide, a promising next-generation storage material, is studied using in operando x-ray absorption spectromicroscopy and is used to microphysically describe accelerated evolution of conduction channel and device failure. Furthermore, the resulting ring-like patterns of oxygen concentration are modeled using thermophoretic forces and Fick diffusion, establishing the critical role of temperature-activated oxygen migration that has been under question lately.

Appraisal of rural-urban migration determinants: a case study of Constantine, Algeria.

PubMed

Boukhemis, K; Zeghiche, A

1988-02-01

Despite some impressive achievements, Algerian planning strategy has neglected the spatial aspect of development, which has accelerated interregional migration and consequently has reinforced existing urban problems: 1) overcrowding, 2) the housing crisis, 3) unemployment, and 4) inadequate infrastructure services. It has become obvious that policy makers must take into account the major role of migration in balanced economic growth, and yet knowledge of migration patterns and processes is very limited in Algeria. Constantine's geographic location and role as a regional metropolis played an essential part in shaping migration flows. Up to 1966, Constantine's disproportionate growth was largely the result of massive migration. Since then, there has been a noticeable slowdown in migration, and natural increase has become the largest component of urban growth. This change reflects the government's development policies. Migration flows to Constantine have been deflected to the new industrial poles, which offer greater employment opportunities. More knowledge of migration is essential for an understanding of the factors that determine the rate and direction of migration flows.

Wild waterfowl migration and domestic duck density shape the epidemiology of highly pathogenic H5N8 influenza in the Republic of Korea

PubMed Central

Hill, Sarah C.; Lee, Youn-Jeong; Song, Byung-Min; Kang, Hyun-Mi; Lee, Eun-Kyoung; Hanna, Amanda; Gilbert, Marius; Brown, Ian H.; Pybus, Oliver G.

2015-01-01

Highly pathogenic avian influenza (HPAI) viruses threaten human and animal health yet their emergence is poorly understood, partly because sampling of the HPAI Asian-origin H5N1 lineage immediately after its identification in 1996 was comparatively sparse. The discovery of a novel H5N8 virus in 2013 provides a new opportunity to investigate HPAI emergence in greater detail. Here we investigate the origin and transmission of H5N8 in the Republic of Korea, the second country to report the new strain. We reconstruct viral spread using phylogeographic methods and interpret the results in the context of ecological data on poultry density, overwintering wild bird numbers, and bird migration patterns. Our results indicate that wild waterfowl migration and domestic duck density were important to H5N8 epidemiology. Specifically, we infer that H5N8 entered the Republic of Korea via Jeonbuk province, then spread rapidly among western provinces where densities of overwintering waterfowl and domestic ducks are higher, yet rarely persisted in eastern regions. The common ancestor of H5N8 in the Republic of Korea was estimated to have arrived during the peak of inward migration of overwintering birds. Recent virus isolations likely represent re-introductions via bird migration from an as-yet unsampled reservoir. Based on the limited data from outside the Republic of Korea, our data suggest that H5N8 may have entered Europe at least twice, and Asia at least three times from this reservoir, most likely carried by wild migrating birds. PMID:26079277

Uridine 5′-Triphosphate Promotes In Vitro Schwannoma Cell Migration through Matrix Metalloproteinase-2 Activation

PubMed Central

Martiañez, Tania; Segura, Mònica; Figueiro-Silva, Joana; Grijota-Martinez, Carmen; Trullas, Ramón; Casals, Núria

2014-01-01

In response to peripheral nerve injury, Schwann cells adopt a migratory phenotype and modify the extracellular matrix to make it permissive for cell migration and axonal re-growth. Uridine 5′-triphosphate (UTP) and other nucleotides are released during nerve injury and activate purinergic receptors expressed on the Schwann cell surface, but little is known about the involvement of purine signalling in wound healing. We studied the effect of UTP on Schwannoma cell migration and wound closure and the intracellular signaling pathways involved. We found that UTP treatment induced Schwannoma cell migration through activation of P2Y2 receptors and through the increase of extracellular matrix metalloproteinase-2 (MMP-2) activation and expression. Knockdown P2Y2 receptor or MMP-2 expression greatly reduced wound closure and MMP-2 activation induced by UTP. MMP-2 activation evoked by injury or UTP was also mediated by phosphorylation of all 3 major mitogen-activated protein kinases (MAPKs): JNK, ERK1/2, and p38. Inhibition of these MAPK pathways decreased both MMP-2 activation and cell migration. Interestingly, MAPK phosphorylation evoked by UTP exhibited a biphasic pattern, with an early transient phosphorylation 5 min after treatment, and a late and sustained phosphorylation that appeared at 6 h and lasted up to 24 h. Inhibition of MMP-2 activity selectively blocked the late, but not the transient, phase of MAPK activation. These results suggest that MMP-2 activation and late MAPK phosphorylation are part of a positive feedback mechanism to maintain the migratory phenotype for wound healing. In conclusion, our findings show that treatment with UTP stimulates in vitro Schwannoma cell migration and wound repair through a MMP-2-dependent mechanism via P2Y2 receptors and MAPK pathway activation. PMID:24905332

Wild waterfowl migration and domestic duck density shape the epidemiology of highly pathogenic H5N8 influenza in the Republic of Korea.

PubMed

Hill, Sarah C; Lee, Youn-Jeong; Song, Byung-Min; Kang, Hyun-Mi; Lee, Eun-Kyoung; Hanna, Amanda; Gilbert, Marius; Brown, Ian H; Pybus, Oliver G

2015-08-01

Highly pathogenic avian influenza (HPAI) viruses threaten human and animal health yet their emergence is poorly understood, partly because sampling of the HPAI Asian-origin H5N1 lineage immediately after its identification in 1996 was comparatively sparse. The discovery of a novel H5N8 virus in 2013 provides a new opportunity to investigate HPAI emergence in greater detail. Here we investigate the origin and transmission of H5N8 in the Republic of Korea, the second country to report the new strain. We reconstruct viral spread using phylogeographic methods and interpret the results in the context of ecological data on poultry density, overwintering wild bird numbers, and bird migration patterns. Our results indicate that wild waterfowl migration and domestic duck density were important to H5N8 epidemiology. Specifically, we infer that H5N8 entered the Republic of Korea via Jeonbuk province, then spread rapidly among western provinces where densities of overwintering waterfowl and domestic ducks are higher, yet rarely persisted in eastern regions. The common ancestor of H5N8 in the Republic of Korea was estimated to have arrived during the peak of inward migration of overwintering birds. Recent virus isolations likely represent re-introductions via bird migration from an as-yet unsampled reservoir. Based on the limited data from outside the Republic of Korea, our data suggest that H5N8 may have entered Europe at least twice, and Asia at least three times from this reservoir, most likely carried by wild migrating birds. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

β-Globin gene sequencing of hemoglobin Austin revises the historically reported electrophoretic migration pattern.

PubMed

Racsa, Lori D; Luu, Hung S; Park, Jason Y; Mitui, Midori; Timmons, Charles F

2014-06-01

Hemoglobin (Hb) Austin was defined in 1977, using amino acid sequencing of samples from 3 unrelated Mexican-Americans, as a substitution of serine for arginine at position 40 of the β-globin chain (Arg40Ser). Its electrophoretic migration on both cellulose acetate (pH 8.4) and citrate agar (pH 6.2) was reported between Hb F and Hb A, and this description persists in reference literature. OBJECTIVES.-To review the clinical features and redefine the diagnostic characteristics of Hb Austin. Eight samples from 6 unrelated individuals and 2 siblings, all with Hispanic surnames, were submitted for abnormal Hb identification between June 2010 and September 2011. High-performance liquid chromatography, isoelectric focusing (IEF), citrate agar electrophoresis, and bidirectional DNA sequencing of the entire β-globin gene were performed. DNA sequencing confirmed all 8 individuals to be heterozygous for Hb Austin (Arg40Ser). Retention time on high-performance liquid chromatography and migration on citrate agar electrophoresis were consistent with that identification. Migration on IEF, however, was not between Hb F and Hb A, as predicted from the report of cellulose acetate electrophoresis. By IEF, Hb Austin migrated anodal to ("faster than") Hb A. Hemoglobin Austin (Arg40Ser) appears on IEF as a "fast," anodally migrating, Hb variant, just as would be expected from its amino acid substitution. The cited historic report is, at best, not applicable to IEF and is probably erroneous. Our observation of 8 cases in 16 months suggests that this variant may be relatively common in some Hispanic populations, making its recognition important. Furthermore, gene sequencing is proving itself a powerful and reliable tool for definitive identification of Hb variants.

Differences in contraceptive use across generations of migration among women of Mexican origin.

PubMed

Wilson, Ellen K

2009-09-01

To explore differences in contraceptive use among women of Mexican origin across generations of migration. Logit models were used to assess contraceptive use among 1,830 women of Mexican origin in Cycles 5 (1995) and 6 (2002) of the National Survey of Family Growth (NSFG). Analyses were stratified by age. Initial models controlled for survey year and underlying differences across generations of migration in age and parity; subsequent models added a range of potential mediating variables. Models account for significant interactions between generation of migration and parity. Among women under age 30 who have not yet had any children, women in their twenties with parity 3 or more, and women 30 or older with parity 1 or 2, those born in the US are much more likely to use contraception than immigrant women. For other levels of parity, there are no significant differences in contraceptive use across generations of migration. Generational differences in marital status, socio-economic status, health insurance coverage, and catholic religiosity did little to mediate the association between generation of migration and contraceptive use. Among women of Mexican origin, patterns of contraceptive use among first-generation immigrants and women of generation 1.5 are similar to those of women in Mexico, with very low rates of contraceptive use among young women who have not yet had a child. Further research is needed to investigate the extent to which this pattern is due to fertility preferences, contraceptive access, or concerns about side effects and infertility. Patterns of contraceptive use appear to change more slowly with acculturation than many other factors, such as education, income, and work force participation.

A characterization of autumn nocturnal migration detected by weather surveillance radars in the northeastern USA.

PubMed

Farnsworth, Andrew; Van DOREN, Benjamin M; Hochachka, Wesley M; Sheldon, Daniel; Winner, Kevin; Irvine, Jed; Geevarghese, Jeffrey; Kelling, Steve

2016-04-01

Billions of birds migrate at night over North America each year. However, few studies have described the phenology of these movements, such as magnitudes, directions, and speeds, for more than one migration season and at regional scales. In this study, we characterize density, direction, and speed of nocturnally migrating birds using data from 13 weather surveillance radars in the autumns of 2010 and 2011 in the northeastern USA. After screening radar data to remove precipitation, we applied a recently developed algorithm for characterizing velocity profiles with previously developed methods to document bird migration. Many hourly radar scans contained windborne "contamination," and these scans also exhibited generally low overall reflectivities. Hourly scans dominated by birds showed nightly and seasonal patterns that differed markedly from those of low reflectivity scans. Bird migration occurred during many nights, but a smaller number of nights with large movements of birds defined regional nocturnal migration. Densities varied by date, time, and location but peaked in the second and third deciles of night during the autumn period when the most birds were migrating. Migration track (the direction to which birds moved) shifted within nights from south-southwesterly to southwesterly during the seasonal migration peaks; this shift was not consistent with a similar shift in wind direction. Migration speeds varied within nights, although not closely with wind speed. Airspeeds increased during the night; groundspeeds were highest between the second and third deciles of night, when the greatest density of birds was migrating. Airspeeds and groundspeeds increased during the fall season, although groundspeeds fluctuated considerably with prevailing winds. Significant positive correlations characterized relationships among bird densities at southern coastal radar stations and northern inland radar stations. The quantitative descriptions of broadscale nocturnal migration patterns presented here will be essential for biological and conservation applications. These descriptions help to define migration phenology in time and space, fill knowledge gaps in avian annual cycles, and are useful for monitoring long-term population trends of migrants. Furthermore, these descriptions will aid in assessing potential risks to migrants, particularly from structures with which birds collide and artificial lighting that disorients migrants.

Envisioning migration: Mathematics in both experimental analysis and modeling of cell behavior

PubMed Central

Zhang, Elizabeth R.; Wu, Lani F.; Altschuler, Steven J.

2013-01-01

The complex nature of cell migration highlights the power and challenges of applying mathematics to biological studies. Mathematics may be used to create model equations that recapitulate migration, which can predict phenomena not easily uncovered by experiments or intuition alone. Alternatively, mathematics may be applied to interpreting complex data sets with better resolution—potentially empowering scientists to discern subtle patterns amid the noise and heterogeneity typical of migrating cells. Iteration between these two methods is necessary in order to reveal connections within the cell migration signaling network, as well as to understand the behavior that arises from those connections. Here, we review recent quantitative analysis and mathematical modeling approaches to the cell migration problem. PMID:23660413

Envisioning migration: mathematics in both experimental analysis and modeling of cell behavior.

PubMed

Zhang, Elizabeth R; Wu, Lani F; Altschuler, Steven J

2013-10-01

The complex nature of cell migration highlights the power and challenges of applying mathematics to biological studies. Mathematics may be used to create model equations that recapitulate migration, which can predict phenomena not easily uncovered by experiments or intuition alone. Alternatively, mathematics may be applied to interpreting complex data sets with better resolution--potentially empowering scientists to discern subtle patterns amid the noise and heterogeneity typical of migrating cells. Iteration between these two methods is necessary in order to reveal connections within the cell migration signaling network, as well as to understand the behavior that arises from those connections. Here, we review recent quantitative analysis and mathematical modeling approaches to the cell migration problem. Copyright © 2013 Elsevier Ltd. All rights reserved.

Long-Distance Dispersal Shaped Patterns of Human Genetic Diversity in Eurasia

PubMed Central

Alves, Isabel; Arenas, Miguel; Currat, Mathias; Sramkova Hanulova, Anna; Sousa, Vitor C.; Ray, Nicolas; Excoffier, Laurent

2016-01-01

Most previous attempts at reconstructing the past history of human populations did not explicitly take geography into account or considered very simple scenarios of migration and ignored environmental information. However, it is likely that the last glacial maximum (LGM) affected the demography and the range of many species, including our own. Moreover, long-distance dispersal (LDD) may have been an important component of human migrations, allowing fast colonization of new territories and preserving high levels of genetic diversity. Here, we use a high-quality microsatellite data set genotyped in 22 populations to estimate the posterior probabilities of several scenarios for the settlement of the Old World by modern humans. We considered models ranging from a simple spatial expansion to others including LDD and a LGM-induced range contraction, as well as Neolithic demographic expansions. We find that scenarios with LDD are much better supported by data than models without LDD. Nevertheless, we show evidence that LDD events to empty habitats were strongly prevented during the settlement of Eurasia. This unexpected absence of LDD ahead of the colonization wave front could have been caused by an Allee effect, either due to intrinsic causes such as an inbreeding depression built during the expansion or due to extrinsic causes such as direct competition with archaic humans. Overall, our results suggest only a relatively limited effect of the LGM contraction on current patterns of human diversity. This is in clear contrast with the major role of LDD migrations, which have potentially contributed to the intermingled genetic structure of Eurasian populations. PMID:26637555

Evolution of salt and hydrocarbon migration: Sweet Lake area, Cameron Parish, Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spencer, J.A.; Sharpe, C.L.

The interpretation of seismic, gravity, and well data in northern Cameron Parish, Louisiana suggest that lateral salt flow has influenced the area`s structural evolution, depositional patterns, and hydrocarbon migration. Sweet Lake Field has produced over 46 MMBO and 15 BCFG from Middle Miocene deltaic sands. The structural closure is a downthrown anticline on a fault controlled by the underlying salt feature. Sweet Lake Field overlies an allochthonous salt mass that was probably once part of an ancestral salt ridge extending from Hackberry to Big Lake fields. Nine wells encountering top of salt and several seismic lines define a detached saltmore » feature underlying over twenty square miles at depths from 8500-18,000 ft. Salt withdrawal in the East Hackberry-Big Lake area influenced the depositional patterns of the Oligocene lower Hackberry channel systems. Progradation of thick Middle Oligocene Camerina (A) and Miogypsinoides sands into the area caused salt thinning and withdrawal resulting in the development and orientation of the large Marginulina-Miogypsinoides growth fault northwest of Sweet Lake. Additional evidence for the southeast trend of the salt is a well approximately two miles southeast of Sweet Lake which encountered salt at approximately 19,800 ft. High quality 2-D and 3-D seismic data will continue to enhance the regional understanding of the evolving salt structures in the onshore Gulf Coast and the local understanding of hydrocarbon migration. Additional examples of lateral salt flow will be recognized and some may prove to have subsalt hydrocarbon potential.« less

Temporal Changes in Stress Drop, Frictional Strength, and Earthquake Size Distribution in the 2011 Yamagata-Fukushima, NE Japan, Earthquake Swarm, Caused by Fluid Migration

NASA Astrophysics Data System (ADS)

Yoshida, Keisuke; Saito, Tatsuhiko; Urata, Yumi; Asano, Youichi; Hasegawa, Akira

2017-12-01

In this study, we investigated temporal variations in stress drop and b-value in the earthquake swarm that occurred at the Yamagata-Fukushima border, NE Japan, after the 2011 Tohoku-Oki earthquake. In this swarm, frictional strengths were estimated to have changed with time due to fluid diffusion. We first estimated the source spectra for 1,800 earthquakes with 2.0 ≤ MJMA < 3.0, by correcting the site-amplification and attenuation effects determined using both S waves and coda waves. We then determined corner frequency assuming the omega-square model and estimated stress drop for 1,693 earthquakes. We found that the estimated stress drops tended to have values of 1-4 MPa and that stress drops significantly changed with time. In particular, the estimated stress drops were very small at the beginning, and increased with time for 50 days. Similar temporal changes were obtained for b-value; the b-value was very high (b 2) at the beginning, and decreased with time, becoming approximately constant (b 1) after 50 days. Patterns of temporal changes in stress drop and b-value were similar to the patterns for frictional strength and earthquake occurrence rate, suggesting that the change in frictional strength due to migrating fluid not only triggered the swarm activity but also affected earthquake and seismicity characteristics. The estimated high Q-1 value, as well as the hypocenter migration, supports the presence of fluid, and its role in the generation and physical characteristics of the swarm.

Levels and patterns of internal migration in Europe: A cohort perspective.

PubMed

Bernard, Aude

2017-11-01

Europe displays important variations in the level of internal migration, with a clear spatial gradient of high mobility in northern and western Europe but lower mobility in the south and east. However, cross-national variation in levels of internal migration remains poorly understood, because it is analysed almost exclusively using cross-sectional data and period measures. This paper seeks to advance understanding of cross-national variation in migration levels in 14 European countries by drawing on a recently proposed suite of migration cohort measures, coupled with internationally comparable retrospective residential histories. It shows that differences in migration levels are mainly attributable to variation in the extent of repeat movement, which is underpinned by the differences in mean ages at first and last move that together delineate the average length of migration careers. Cohort analysis provides a robust foundation for exploring the demographic mechanisms underpinning variation in migration levels across countries and over time.

Transnational nurse migration: future directions for medical anthropological research.

PubMed

Prescott, Megan; Nichter, Mark

2014-04-01

Transnational nurse migration is a serious global health issue in which inequitably distributed shortages hinder health and development goals. This article selectively reviews the literature on nurse migration that has emerged from nursing, health planning, and the social sciences and offers productive directions for future anthropological research. The literature on global nurse migration has largely focused on push/pull economic logic and the concept of brain drain to understand the causes and effects of nurse migration. These concepts obscure political-economic, historical, and cultural factors that pattern nurse migration and influence the complex effects of nurse migration. Global nurse care chain analysis helps illuminate the numerous nodes in the production and migration of nurses, and management of this transnational process. Examples are provided from the Philippines and India to illustrate ways in which this analysis may be deepened, refined and rendered more critical by anthropological research. Copyright © 2014 Elsevier Ltd. All rights reserved.

Flight mode affects allometry of migration range in birds.

PubMed

Watanabe, Yuuki Y

2016-08-01

Billions of birds migrate to exploit seasonally available resources. The ranges of migration vary greatly among species, but the underlying mechanisms are poorly understood. I hypothesise that flight mode (flapping or soaring) and body mass affect migration range through their influence on flight energetics. Here, I compiled the tracks of migratory birds (196 species, weighing 12-10 350 g) recorded by electronic tags in the last few decades. In flapping birds, migration ranges decreased with body mass, as predicted from rapidly increasing flight cost with increasing body mass. The species with higher aspect ratio and lower wing loading had larger migration ranges. In soaring birds, migration ranges were mass-independent and larger than those of flapping birds, reflecting their low flight costs irrespective of body mass. This study demonstrates that many animal-tracking studies are now available to explore the general patterns and the underlying mechanisms of animal migration. © 2016 John Wiley & Sons Ltd/CNRS.

Digital Plasmonic Patterning for Localized Tuning of Hydrogel Stiffness

PubMed Central

Hribar, Kolin C.; Choi, Yu Suk; Ondeck, Matthew; Engler, Adam J.

2015-01-01

The mechanical properties of the extracellular matrix (ECM) can dictate cell fate in biological systems. In tissue engineering, varying the stiffness of hydrogels—water-swollen polymeric networks that act as ECM substrates—has previously been demonstrated to control cell migration, proliferation, and differentiation. Here, “digital plasmonic patterning” (DPP) is developed to mechanically alter a hydrogel encapsulated with gold nanorods using a near-infrared laser, according to a digital (computer-generated) pattern. DPP can provide orders of magnitude changes in stiffness, and can be tuned by laser intensity and speed of writing. In vitro cellular experiments using A7R5 smooth muscle cells confirm cell migration and alignment according to these patterns, making DPP a useful technique for mechanically patterning hydrogels for various biomedical applications. PMID:26120293

Sorted bedform pattern evolution: Persistence, destruction and self-organized intermittency

NASA Astrophysics Data System (ADS)

Goldstein, Evan B.; Murray, A. Brad; Coco, Giovanni

2011-12-01

We investigate the long-term evolution of inner continental shelf sorted bedform patterns. Numerical modeling suggests that a range of behaviors are possible, from pattern persistence to spatial-temporal intermittency. Sorted bedform persistence results from a robust sorting feedback that operates when the seabed features a sufficient concentration of coarse material. In the absence of storm events, pattern maturation processes such as defect dynamics and pattern migration tend to cause the burial of coarse material and excavation of fine material, leading to the fining of the active layer. Vertical sorting occurs until a critical state of active layer coarseness is reached. This critical state results in the local cessation of the sorting feedback, leading to a self-organized spatially intermittent pattern, a hallmark of observed sorted bedforms. Bedforms in shallow conditions and those subject to high wave climates may be temporally intermittent features as a result of increased wave orbital velocity during storms. Erosion, or deposition of bimodal sediment, similarly leads to a spatially intermittent pattern, with individual coarse domains exhibiting temporal intermittence. Recurring storm events cause coarsening of the seabed (strengthening the sorting feedback) and the development of large wavelength patterns. Cessation of storm events leads to the superposition of storm (large wavelength) and inter-storm (small wavelength) patterns and spatial heterogeneity of pattern modes.

IDENTIFYING AND PREDICTING DIVING PLUME BEHAVIOR AT GROUNDWATER SITES CONTAMINATED WITH MTBE: PART 2

EPA Science Inventory

As contaminant ground water flows downgradient from a release point, its movement is dictated by site geological conditions and hydraulics that may result in significant perpendicular contamination migration. This vertical migration pattern has been termed 'plume diving'. Under ...

Tuning cell adhesion by direct nanostructuring silicon into cell repulsive/adhesive patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Premnath, Priyatha, E-mail: priyatha.premnath@ryerson.ca; Tavangar, Amirhossein, E-mail: atavanga@ryerson.ca; Tan, Bo, E-mail: tanbo@ryerson.ca

2015-09-10

Developing platforms that allow tuning cell functionality through incorporating physical, chemical, or mechanical cues onto the material surfaces is one of the key challenges in research in the field of biomaterials. In this respect, various approaches have been proposed and numerous structures have been developed on a variety of materials. Most of these approaches, however, demand a multistep process or post-chemical treatment. Therefore, a simple approach would be desirable to develop bio-functionalized platforms for effectively modulating cell adhesion and consequently programming cell functionality without requiring any chemical or biological surface treatment. This study introduces a versatile yet simple laser approachmore » to structure silicon (Si) chips into cytophobic/cytophilic patterns in order to modulate cell adhesion and proliferation. These patterns are fabricated on platforms through direct laser processing of Si substrates, which renders a desired computer-generated configuration into patterns. We investigate the morphology, chemistry, and wettability of the platform surfaces. Subsequently, we study the functionality of the fabricated platforms on modulating cervical cancer cells (HeLa) behaviour. The results from in vitro studies suggest that the nanostructures efficiently repel HeLa cells and drive them to migrate onto untreated sites. The study of the morphology of the cells reveals that cells evade the cytophobic area by bending and changing direction. Additionally, cell patterning, cell directionality, cell channelling, and cell trapping are achieved by developing different platforms with specific patterns. The flexibility and controllability of this approach to effectively structure Si substrates to cell-repulsive and cell-adhesive patterns offer perceptible outlook for developing bio-functionalized platforms for a variety of biomedical devices. Moreover, this approach could pave the way for developing anti-cancer platforms that selectively repel cancer cells while favoring the adhesion of normal cells. - Highlights: • Si platforms with cytophobic/philic patterns were developed to program cell growth. • Both nanotopography and chemistry contributed to the cytophobic property. • Cytophobic zones efficiently repel and drive HeLa cells to migrate to adhesive sites. • The approach enables cell patterning, directionality, channelling, and trapping. • This approach paves the way for developing anti-cancer platforms.« less

Visualizing Human Migration Trhough Space and Time

NASA Astrophysics Data System (ADS)

Zambotti, G.; Guan, W.; Gest, J.

2015-07-01

Human migration has been an important activity in human societies since antiquity. Since 1890, approximately three percent of the world's population has lived outside of their country of origin. As globalization intensifies in the modern era, human migration persists even as governments seek to more stringently regulate flows. Understanding this phenomenon, its causes, processes and impacts often starts from measuring and visualizing its spatiotemporal patterns. This study builds a generic online platform for users to interactively visualize human migration through space and time. This entails quickly ingesting human migration data in plain text or tabular format; matching the records with pre-established geographic features such as administrative polygons; symbolizing the migration flow by circular arcs of varying color and weight based on the flow attributes; connecting the centroids of the origin and destination polygons; and allowing the user to select either an origin or a destination feature to display all flows in or out of that feature through time. The method was first developed using ArcGIS Server for world-wide cross-country migration, and later applied to visualizing domestic migration patterns within China between provinces, and between states in the United States, all through multiple years. The technical challenges of this study include simplifying the shapes of features to enhance user interaction, rendering performance and application scalability; enabling the temporal renderers to provide time-based rendering of features and the flow among them; and developing a responsive web design (RWD) application to provide an optimal viewing experience. The platform is available online for the public to use, and the methodology is easily adoptable to visualizing any flow, not only human migration but also the flow of goods, capital, disease, ideology, etc., between multiple origins and destinations across space and time.

Interspecific Comparison of the Performance of Soaring Migrants in Relation to Morphology, Meteorological Conditions and Migration Strategies

PubMed Central

Mellone, Ugo; Klaassen, Raymond H. G.; García-Ripollés, Clara; Limiñana, Ruben; López-López, Pascual; Pavón, Diego; Strandberg, Roine; Urios, Vicente; Vardakis, Michalis; Alerstam, Thomas

2012-01-01

Background Performance of migrating birds can be affected by a number of intrinsic and extrinsic factors like morphology, meteorological conditions and migration strategies. We compared travel speeds of four raptor species during their crossing of the Sahara desert. Focusing the analyses on this region allows us to compare different species under equivalent conditions in order to disentangle which factors affect migratory performance. Methodology/Principal Finding We tracked raptors using GPS satellite transmitters from Sweden, Spain and Italy, and evaluated their migratory performance at both an hourly and a daily scale. Hourly data (flight speed and altitude for intervals of two hours) were analyzed in relation to time of day, species and season, and daily data (distance between roosting sites) in relation to species, season, day length and tailwind support. Conclusions/Significance Despite a clear variation in morphology, interspecific differences were generally very small, and did only arise in spring, with long-distance migrants (>5000 km: osprey and Western marsh-harrier) being faster than species that migrate shorter distances (Egyptian vulture and short-toed eagle). Our results suggest that the most important factor explaining hourly variation in flight speed is time of day, while at a daily scale, tailwind support is the most important factor explaining variation in daily distance, raising new questions about the consequences of possible future changes in worldwide wind patterns. PMID:22768314

Isotope signatures in winter moulted feathers predict malaria prevalence in a breeding avian host.

PubMed

Yohannes, Elizabeth; Hansson, Bengt; Lee, Raymond W; Waldenström, Jonas; Westerdahl, Helena; Akesson, Mikael; Hasselquist, Dennis; Bensch, Staffan

2008-11-01

It is widely accepted that animal distribution and migration strategy might have co-evolved in relation to selection pressures exerted by parasites. Here, we first determined the prevalence and types of malaria blood parasites in a breeding population of great reed warblers Acrocephalus arundinaceus using PCR. Secondly, we tested for differences in individual feather stable isotope signatures (delta (13)C, delta (15)N, deltaD and delta (34)S) to investigate whether malaria infected and non-infected birds had occupied different areas in winter. We show that birds moulting in Afro-tropical habitats with significantly higher delta (13)C and delta (15)N but lower deltaD and delta(34)S values were more frequently infected with malaria parasites. Based on established patterns of isotopic distributions, our results indicate that moulting sites with higher incidence of malaria are generally drier and situated further to the north in West Africa than sites with lower incidence of malaria. Our findings are pertinent to the general hypothesis that animal distribution and particularly avian migration strategy might evolve in response to selection pressures exerted by parasites at different geographic scales. Tradeoffs between investment in energy demanding life history traits (e.g. migration and winter moult) and immune function are suggested to contribute to the particular choice of habitat during migration and at wintering sites.

Genetic Divergence of an Avian Endemic on the Californian Channel Islands

PubMed Central

Wilson, Amy G.; Chan, Yvonne; Taylor, Sabrina S.; Arcese, Peter

2015-01-01

The Californian Channel Islands are near–shore islands with high levels of endemism, but extensive habitat loss has contributed to the decline or extinction of several endemic taxa. A key parameter for understanding patterns of endemism and demography in island populations is the magnitude of inter–island dispersal. This paper estimates the extent of migration and genetic differentiation in three extant and two extinct populations of Channel Island song sparrows (Melospiza melodia graminea). Inter–island differentiation was substantial (G''ST: 0.14–0.37), with San Miguel Island having the highest genetic divergence and lowest migration rates. Santa Rosa and Santa Cruz Island populations were less diverged with higher migration rates. Genetic signals of past population declines were detected in all of the extant populations. The Channel Island populations were significantly diverged from mainland populations of M. m. heermanni (G''ST: 0.30–0.64). Ten mtDNA haplotypes were recovered across the extant and extinct Channel Island population samples. Two of the ten haplotypes were shared between the Northern and Southern Channel Islands, with one of these haplotypes being detected on the Californian mainland. Our results suggest that there is little contemporary migration between islands, consistent with early explanations of avian biogeography in the Channel Islands, and that song sparrow populations on the northern Channel Islands are demographically independent. PMID:26308717

Migration and diving behavior of Centrophorus squamosus in the NE Atlantic. Combining electronic tagging and Argo hydrography to infer deep ocean trajectories

NASA Astrophysics Data System (ADS)

Rodríguez-Cabello, Cristina; González-Pola, Cesar; Sánchez, Francisco

2016-09-01

A total of nine leafscale gulper sharks Centrophorus squamosus (Bonnaterre, 1788), were tagged with pop-up, satellite, archival, transmitting tags (PSAT) in the Marine Protected Area (MPA) of El Cachucho (Le Danois Bank) located in waters to the north of Spain, (NE Atlantic). Tags provided data on time, pressure and temperature that were used to examine movement patterns and diving behavior. Data collected from Argo floats in the study area have been used to devise a simple geolocation algorithm to infer the probable routes followed by this species. Tag release points revealed that C. squamosus moved both to the west (Galician waters) and to the north (Porcupine Bank) from the tagging area, suggesting well defined preferred pathways. The inferred trajectories indicated that sharks alternate periods constrained to specific geographical regions with quick and prompt movements covering large distances. Two sharks made conspicuous diurnal vertical migrations being at shallower depths around midnight and at maximum depths at midday, while other sharks did not make vertical migrations. Vertical movements were done smoothly and independently of the fish swimming long-distances or resting in the area. Overall results confirm that this species is highly migratory, supporting speeds of 20 nautical miles.day-1 and well capable to swim and make vertical migrations well above the abyssal plain.

Eco-virological approach for assessing the role of wild birds in the spread of avian influenza H5N1 along the central Asian flyway

USGS Publications Warehouse

Newman, Scott H.; Hill, Nichola J.; Spragens, Kyle A.; Janies, Daniel; Voronkin, Igor O.; Prosser, Diann J.; Yan, Baoping; Lei, Fumin; Batbayar, Nyambayar; Natsagdorj, Tseveenmyadag; Bishop, Charles M.; Butler, Patrick J.; Wikelski, Martin; Balachandran, Sivananinthaperumal; Mundkur, Taej; Douglas, David C.; Takekawa, John Y.

2012-01-01

A unique pattern of highly pathogenic avian influenza (HPAI) H5N1 outbreaks has emerged along the Central Asia Flyway, where infection of wild birds has been reported with steady frequency since 2005. We assessed the potential for two hosts of HPAI H5N1, the bar-headed goose (Anser indicus) and ruddy shelduck (Tadorna tadorna), to act as agents for virus dispersal along this ‘thoroughfare’. We used an eco-virological approach to compare the migration of 141 birds marked with GPS satellite transmitters during 2005–2010 with: 1) the spatio-temporal patterns of poultry and wild bird outbreaks of HPAI H5N1, and 2) the trajectory of the virus in the outbreak region based on phylogeographic mapping. We found that biweekly utilization distributions (UDs) for 19.2% of bar-headed geese and 46.2% of ruddy shelduck were significantly associated with outbreaks. Ruddy shelduck showed highest correlation with poultry outbreaks owing to their wintering distribution in South Asia, where there is considerable opportunity for HPAI H5N1 spillover from poultry. Both species showed correlation with wild bird outbreaks during the spring migration, suggesting they may be involved in the northward movement of the virus. However, phylogeographic mapping of HPAI H5N1 clades 2.2 and 2.3 did not support dissemination of the virus in a northern direction along the migration corridor. In particular, two subclades (2.2.1 and 2.3.2) moved in a strictly southern direction in contrast to our spatio-temporal analysis of bird migration. Our attempt to reconcile the disciplines of wild bird ecology and HPAI H5N1 virology highlights prospects offered by both approaches as well as their limitations.

Eco-Virological Approach for Assessing the Role of Wild Birds in the Spread of Avian Influenza H5N1 along the Central Asian Flyway

PubMed Central

Newman, Scott H.; Hill, Nichola J.; Spragens, Kyle A.; Janies, Daniel; Voronkin, Igor O.; Prosser, Diann J.; Yan, Baoping; Lei, Fumin; Batbayar, Nyambayar; Natsagdorj, Tseveenmyadag; Bishop, Charles M.; Butler, Patrick J.; Wikelski, Martin; Balachandran, Sivananinthaperumal; Mundkur, Taej; Douglas, David C.; Takekawa, John Y.

2012-01-01

A unique pattern of highly pathogenic avian influenza (HPAI) H5N1 outbreaks has emerged along the Central Asia Flyway, where infection of wild birds has been reported with steady frequency since 2005. We assessed the potential for two hosts of HPAI H5N1, the bar-headed goose (Anser indicus) and ruddy shelduck (Tadorna tadorna), to act as agents for virus dispersal along this ‘thoroughfare’. We used an eco-virological approach to compare the migration of 141 birds marked with GPS satellite transmitters during 2005–2010 with: 1) the spatio-temporal patterns of poultry and wild bird outbreaks of HPAI H5N1, and 2) the trajectory of the virus in the outbreak region based on phylogeographic mapping. We found that biweekly utilization distributions (UDs) for 19.2% of bar-headed geese and 46.2% of ruddy shelduck were significantly associated with outbreaks. Ruddy shelduck showed highest correlation with poultry outbreaks owing to their wintering distribution in South Asia, where there is considerable opportunity for HPAI H5N1 spillover from poultry. Both species showed correlation with wild bird outbreaks during the spring migration, suggesting they may be involved in the northward movement of the virus. However, phylogeographic mapping of HPAI H5N1 clades 2.2 and 2.3 did not support dissemination of the virus in a northern direction along the migration corridor. In particular, two subclades (2.2.1 and 2.3.2) moved in a strictly southern direction in contrast to our spatio-temporal analysis of bird migration. Our attempt to reconcile the disciplines of wild bird ecology and HPAI H5N1 virology highlights prospects offered by both approaches as well as their limitations. PMID:22347393

Implications of historical eruptive-vent migration on the northeast rift zone of Mauna Loa Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Lockwood, John P.

1990-07-01

Five times within the past 138 yr (1852, 1855-1856, 1880-1881, 1942, and 1984), lava flows from vents on the northeast rift zone of Mauna Loa Volcano have reached within a few kilometres of Hilo (the largest city on the Island of Hawaii). Most lavas erupted on this rift zone in historical time have traveled northeastward (toward Hilo), because their eruptive vents have been concentrated north of the rift zone's broad topographic axis. However, with few exceptions each successive historical eruption on the northeast rift zone has occurred farther southeast than the preceding one. Had the 1984 eruptive vents (the most southeasterly yet) opened less than 200 m farther southeast, the bulk of the 1984 lavas would have flowed away from Hilo. If this historical vent-migration pattern continues, the next eruption on the northeast rift zone could send lavas to the southeast, toward less populated areas. The historical Mauna Loa vent-migration patterns mimic the southeastern "younging" of the Hawaiian-Emperor volcanic chain and may be cryptically related to northwestward movement of the Pacific plate. Systematic temporal-spatial vent-migration patterns may characterize eruptive activity at other volcanoes with flank activity and should be considered as an aid to long-term prediction of eruption sites.