Sample records for migration period high
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Periodic sediment shift in migrating ripples influences benthic microbial activity
Zlatanović, Sanja; Fabian, Jenny; Mendoza-Lera, Clara; Woodward, K. Benjamin; Premke, Katrin; Mutz, Michael
2017-06-01
Migrating bedforms have high levels of particulate organic matter and high rates of pore water exchange, causing them to be proposed as hot spots of carbon turnover in rivers. Yet, the shifting of sediments and associated mechanical disturbance within migrating bedforms, such as ripples, may stress and abrade microbial communities, reducing their activity. In a microcosm experiment, we replicated the mechanical disturbances caused by the periodic sediment shift within ripples under oligotrophic conditions. We assessed the effects on fungal and bacterial biomass ratio (F:B), microbial community respiration (CR), and bacterial production (BCP) and compared with stable undisturbed sediments. Interactions between periodic mechanical disturbance and sediment-associated particulate organic matter (POM) were tested by enriching sediments collected from migrating ripples with different qualities of POM (fish feces, leaf litter fragments and no addition treatments). F:B and BCP were affected by an interaction between mechanical disturbance and POM quality. Fish feces enriched sediments showed increased F:B and BCP compared to sediments with lower POM quality and responded with a decrease of F:B and BCP to sediment disturbance. In the other POM treatments F:B and BCP were not affected by disturbance. Microbial respiration was however reduced by mechanical disturbance to similar low activity levels regardless of POM qualities added, whereas fish feces enriched sediment showed short temporary boost of CR. With the worldwide proliferation of migrating sand ripples due to massive catchment erosion, suppressed mineralization of POM will increasingly affect stream metabolism, downstream transport of POM and carbon cycling from reach to catchment scale.
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Simulation of vacancy migration energy in Cu under high strain
International Nuclear Information System (INIS)
Sato, K.; Yoshiie, T.; Satoh, Y.; Xu, Q.; Kiritani, M.
2003-01-01
The activation energy for the migration of vacancies in Cu under high strain was calculated by computer simulation using static methods. The migration energy of vacancies was 0.98 eV in the absence of deformation. It varied with the migration direction and stress direction because the distance between a vacancy and its neighboring atoms changes by deformation. For example, the migration energy for the shortest migration distance was reduced to 9.6 and 39.4% of its initial value by 10% compression and 20% elongation, respectively, while that for the longest migration distance was raised to 171.7 by 20% elongation. If many vacancies are created during high-speed deformation, the lowering of migration energy enables vacancies to escape to sinks such as surfaces, even during the shorter deformation period. The critical strain rate above which the strain rate dependence of vacancy accumulation ceases to exist increases with the lowering of vacancy migration energy
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Vertebrate fauna of the Roman period, migrations period and Medieval period in Vojvodina (Serbia
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Radmanović Darko P.
2014-01-01
Full Text Available Based on current published and unpublished research results, a total of 16 vertebrate species members of mammal (Mammalia, bird (Aves and osteichthyes (Osteichthyes classes have been registered at 11 archaeological sites from the Roman Period in Vojvodina. Mammals dominate with 12 species and one genus, birds are present with 3 species, and osteichthyes with one. From the Migration Period, at 9 sites, 22 vertebrate species have been registered, of which 13 species and one genus of mammals, 4 species and one genus of birds, and 5 species from the Osteichthyes class. At 8 sites from the Medieval Period, 16 vertebrate species have been registered. Mammals are the most numerous class with 10 species and one genus, while birds are present with 4 species and one genus. Furthermore, two species of osteichthyes have also been registered.
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Tartakovsky, Eugene
2009-01-01
This article investigates the cultural identities of adolescent immigrants in the pre-migration period and during the first 3 years after immigration. The target population consists of high-school Jewish adolescents from Russia and Ukraine participating in an Israeli immigration program. In this program, Jewish adolescents immigrate to Israel…
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On the move: explaining migration patterns in Estonia during the transition period.
Tammaru, T; Sjoberg, O
1999-01-01
This paper attempts to explore the migration patterns during the transition period in Estonia. A structuration approach was used to analyze data from the Estonian Statistical Office collected in 1997. Findings show that for migration between urban and rural areas, work-related reasons have been the most important motivating factor in urban growth during the transition period. Also considered are the family and education. In relation to sociodemographic structure of the population, men cite work, while women count family-related reasons, as the main motive for migrating. As to nonregistration, the most significant reason relates to issues of ownership. Because migrants are living in rented housing, it is not possible for them to register even if they desire to do so. Other reasons include "temporary", associated with study and work; "juridical", bureaucratic matters; and "multiple places of residence". This analysis, however, is incomplete because the attitudes and patterns of behavior have only partially or perfunctorily been related to the dramatic changes that have occurred in Estonian society. Proper statistical data are needed to help examine trends at a more disaggregated spatial level.
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Migration and risk: net migration in marginal ecosystems and hazardous areas
International Nuclear Information System (INIS)
De Sherbinin, Alex; Levy, Marc; Adamo, Susana; MacManus, Kytt; Yetman, Greg; Mara, Valentina; Razafindrazay, Liana; Aichele, Cody; Pistolesi, Linda; Goodrich, Benjamin; Srebotnjak, Tanja
2012-01-01
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. (letter)
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Small flow rate can supply inwardly migrating shortest-period planets
Directory of Open Access Journals (Sweden)
Taylor S.F.
2013-04-01
Full Text Available The number of exoplanets found with periods as short as one day and less was surprising given how fast these planets had been expected to migrate into the star due to the tides raised on the star by planets at such close distances. It has been seen as improbable that we would find planets in such a small final fraction of their lives [1]. The favored solution has been that the tidal dissipation is much weaker than expected, which would mean that the final infall would be a larger fraction of the planets’ life. We find no reason, however, to exclude the explanation that a small number of planets are continuously sent migrating inwards such that these planets indeed are in the last fraction of their lives. Following the observation that the distribution of medium planets disfavors tidal dissipation being significantly weaker than has been found from observations of binary stars [2], we now show that the numbers of planets in such a “flow” of excess planets migrating inwards is low enough that even depletion of the three-day pileup is a plausible source. Then the shortest period occurrence distribution would be shaped by planets continuously being sent into the star, which may explain the depletion of the pileup in the Kepler field relative to the solar neighborhood [3]. Because Kepler observes above the galactic plan, [3] suggested the Kepler field may include an older population of stars. The tidal dissipation strength in stars due to giant planets may be not greatly weaker than it is in binary stars.
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Cyclic grain boundary migration during high temperature fatigue--I: microstructural observations
International Nuclear Information System (INIS)
Langdon, T.G.; Gifkins, R.S.
1983-01-01
Experiments were conducted on high purity lead at room temperature using reverse bending and torsion fatigue at low cyclic frequencies (less than or equal to1.50 Hz). Metallographic observations after testing show that there is a one-to-one correspondence between the markings from grain boundary migration and the number and pattern of cyclic loading, and this correspondence is maintained up to >100 cycles. Grain boundary sliding occurs in each cycle in addition to the migration, and this leads to the development of broad triple point folds. If the strain amplitude is maintained constant, it is shown that the average distance migrated in each cycle increases as the imposed frequency is decreased. The distance migrated is often exceptionally large in the first cycle of testing, and there is often a similar large initial displacement if the test is interrupted for periods of time from 1 to 24 h and then continued. For large grain sizes (greater than or equal to 2000μm), the migration markings may lead to a zig-zag pattern where the individual segments lie fairly close to 45 0 to the stress axis. A model is described which accounts for the one-to-one correspondence and which is consistent with a fine structure observed within the migration markings
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Dypvik, Eivind
2012-11-13
The vertical migration and diel feeding periodicity of the skinnycheek lanternfish (Benthosema pterotum) were studied by use of a hull-mounted 38 kHz echo sounder, ROV-deployments and net-sampling at two locations (∼24°48′N, ∼36°15′E and ∼21°27′N, ∼38°5′E) in the central Red Sea. The mesopelagic zone of the Red Sea represents an unusual environment with very high temperatures (∼22 °C) and low zooplankton concentrations (<10 individuals m−3 below 600 m). The skinnycheek lanternfish performed normal diel vertical migration from ∼500 to 750 m during daytime to the epipelagic zone (upper ∼200 m) at night. A strict feeding periodicity occurred; with the skinnycheek lanternfish foraging on zooplankton throughout the night, while rapidly digesting the preceding nocturnal meal in the warm mesopelagic region. We hypothesize that the constrained epipelagic distribution of zooplankton and the unusual warm waters of the Red Sea force the whole population to ascend and feed in epipelagic waters every night, as the prey-ration eaten each night is fully digested at mesopelagic depths during daytime.
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Small flow rate can supply inwardly migrating shortest-period planets
Taylor, Stuart F.
2013-01-01
The number of exoplanets found with periods as short as one day and less was surprising given how fast these planets had been expected to migrate into the star due to the tides raised on the star by planets at such close distances. It has been seen as improbable that we would find planets in such a small final fraction of their lives. The favored solution has been that the tidal dissipation is much weaker than expected, which would mean that the final infall would be a larger fraction of the ...
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Measuring International Migration in Azerbaijan
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Serhat Yüksel
2018-01-01
Full Text Available International migration significantly affects economic, social, cultural, and political factors of the country. Owing to this situation, it can be said that the reasons of international migration should be analyzed in order to control this problem. The purpose of this study is to determine the influencing factors of international migration in Azerbaijan. In this scope, annual data of 11 explanatory variables for the period of 1995–2015 was analyzed via Multivariate Adaptive Regression Splines (MARS method. According to the results of this analysis, it was identified that people prefer to move other countries in case of high unemployment rates. In addition, the results of the study show that population growth and high mortality rate increases the migration level. While considering these results, it was recommended that Azerbaijan should focus on these aspects to control international migration problem.
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The Migration of Researchers from Central Europe during the Transition Period
Czech Academy of Sciences Publication Activity Database
Bernard, Josef
2008-01-01
Roč. 40, č. 3 (2008), s. 191-214 ISSN 0049-1225 R&D Projects: GA MŠk 2E06015 Institutional research plan: CEZ:AV0Z70280505 Keywords : brain drain * researcher migration * highly qualified migrants Subject RIV: AO - Sociology, Demography Impact factor: 0.175, year: 2008
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Curtis, Katherine J; Fussell, Elizabeth; DeWaard, Jack
2015-08-01
Changes in the human migration systems of the Gulf of Mexico coastline counties affected by Hurricanes Katrina and Rita provide an example of how climate change may affect coastal populations. Crude climate change models predict a mass migration of "climate refugees," but an emerging literature on environmental migration suggests that most migration will be short-distance and short-duration within existing migration systems, with implications for the population recovery of disaster-stricken places. In this research, we derive a series of hypotheses on recovery migration predicting how the migration system of hurricane-affected coastline counties in the Gulf of Mexico was likely to have changed between the pre-disaster and the recovery periods. We test these hypotheses using data from the Internal Revenue Service on annual county-level migration flows, comparing the recovery period migration system (2007-2009) with the pre-disaster period (1999-2004). By observing county-to-county ties and flows, we find that recovery migration was strong: the migration system of the disaster-affected coastline counties became more spatially concentrated, while flows within it intensified and became more urbanized. Our analysis demonstrates how migration systems are likely to be affected by the more intense and frequent storms anticipated by climate change scenarios, with implications for the population recovery of disaster-affected places.
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The Migration of Highly Educated Asians: Brain Drain Boomerang.
Ong, Paul M.; And Others
1991-01-01
The heavy migration of highly educated Asians to the United States since the early 1970s is examined, noting advantages and disadvantages to the countries of origin and to the United States as well as the historical, educational, and economic factors causing this migration. It is concluded that, despite considerable loss, developing countries do…
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Dypvik, Eivind; Kaartvedt, Stein
2012-01-01
The vertical migration and diel feeding periodicity of the skinnycheek lanternfish (Benthosema pterotum) were studied by use of a hull-mounted 38 kHz echo sounder, ROV-deployments and net-sampling at two locations (∼24°48′N, ∼36°15′E and ∼21°27′N
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Directory of Open Access Journals (Sweden)
Milan Palát
2006-01-01
Full Text Available The paper presents partial findings obtained during the study of external migration according to countries in a defined territorial unit and time period. Applied methodical procedures of the statistical processing of empirical data make possible, in addition to the exact description of the proportion of selected country groups and aggregated particular countries on the total number of immigrants, emigrants and derived values of migration increases or decreases, also the description of developmental trends of the analysed time series of assessed events and point short-term extrapolation prediction.
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Fussell, Elizabeth; DeWaard, Jack
2015-01-01
Changes in the human migration systems of Hurricane Katrina- and Rita-affected Gulf of Mexico coastline counties provide an example of how climate change may affect coastal populations. Crude climate change models predict a mass migration of “climate refugees,” but an emerging literature on environmental migration suggests most migration will be short-distance and short-duration within existing migration systems, with implications for the population recovery of disaster-struck places. In this research, we derive a series of hypotheses on recovery migration predicting how the migration system of hurricane-affected coastline counties in the Gulf of Mexico was likely to have changed between the pre-disaster and the recovery periods. We test these hypotheses using data from the Internal Revenue Service on annual county-level migration flows, comparing the recovery period migration system (2007–2009) to the pre-disaster period (1999–2004). By observing county-to-county ties and flows we find that recovery migration was strong, as the migration system of the disaster-affected coastline counties became more spatially concentrated while flows within it intensified and became more urbanized. Our analysis demonstrates how migration systems are likely to be affected by the more intense and frequent storms anticipated by climate change scenarios with implications for the population recovery of disaster-affected places. PMID:26084982
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Lea, James S E; Wetherbee, Bradley M; Queiroz, Nuno; Burnie, Neil; Aming, Choy; Sousa, Lara L; Mucientes, Gonzalo R; Humphries, Nicolas E; Harvey, Guy M; Sims, David W; Shivji, Mahmood S
2015-06-09
Long-distance movements of animals are an important driver of population spatial dynamics and determine the extent of overlap with area-focused human activities, such as fishing. Despite global concerns of declining shark populations, a major limitation in assessments of population trends or spatial management options is the lack of information on their long-term migratory behaviour. For a large marine predator, the tiger shark Galeocerdo cuvier, we show from individuals satellite-tracked for multiple years (up to 1101 days) that adult males undertake annually repeated, round-trip migrations of over 7,500 km in the northwest Atlantic. Notably, these migrations occurred between the highly disparate ecosystems of Caribbean coral reef regions in winter and high latitude oceanic areas in summer, with strong, repeated philopatry to specific overwintering insular habitat. Partial migration also occurred, with smaller, immature individuals displaying reduced migration propensity. Foraging may be a putative motivation for these oceanic migrations, with summer behaviour showing higher path tortuosity at the oceanic range extremes. The predictable migratory patterns and use of highly divergent ecosystems shown by male tiger sharks appear broadly similar to migrations seen in birds, reptiles and mammals, and highlight opportunities for dynamic spatial management and conservation measures of highly mobile sharks.
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Repeated, long-distance migrations by a philopatric predator targeting highly contrasting ecosystems
Lea, James S. E.; Wetherbee, Bradley M.; Queiroz, Nuno; Burnie, Neil; Aming, Choy; Sousa, Lara L.; Mucientes, Gonzalo R.; Humphries, Nicolas E.; Harvey, Guy M.; Sims, David W.; Shivji, Mahmood S.
2015-06-01
Long-distance movements of animals are an important driver of population spatial dynamics and determine the extent of overlap with area-focused human activities, such as fishing. Despite global concerns of declining shark populations, a major limitation in assessments of population trends or spatial management options is the lack of information on their long-term migratory behaviour. For a large marine predator, the tiger shark Galeocerdo cuvier, we show from individuals satellite-tracked for multiple years (up to 1101 days) that adult males undertake annually repeated, round-trip migrations of over 7,500 km in the northwest Atlantic. Notably, these migrations occurred between the highly disparate ecosystems of Caribbean coral reef regions in winter and high latitude oceanic areas in summer, with strong, repeated philopatry to specific overwintering insular habitat. Partial migration also occurred, with smaller, immature individuals displaying reduced migration propensity. Foraging may be a putative motivation for these oceanic migrations, with summer behaviour showing higher path tortuosity at the oceanic range extremes. The predictable migratory patterns and use of highly divergent ecosystems shown by male tiger sharks appear broadly similar to migrations seen in birds, reptiles and mammals, and highlight opportunities for dynamic spatial management and conservation measures of highly mobile sharks.
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High glucose-mediated oxidative stress impairs cell migration.
Directory of Open Access Journals (Sweden)
Marcelo L Lamers
Full Text Available Deficient wound healing in diabetic patients is very frequent, but the cellular and molecular causes are poorly defined. In this study, we evaluate the hypothesis that high glucose concentrations inhibit cell migration. Using CHO.K1 cells, NIH-3T3 fibroblasts, mouse embryonic fibroblasts and primary skin fibroblasts from control and diabetic rats cultured in 5 mM D-glucose (low glucose, LG, 25 mM D-glucose (high glucose, HG or 25 mM L-glucose medium (osmotic control--OC, we analyzed the migration speed, protrusion stability, cell polarity, adhesion maturation and the activity of the small Rho GTPase Rac1. We also analyzed the effects of reactive oxygen species by incubating cells with the antioxidant N-Acetyl-Cysteine (NAC. We observed that HG conditions inhibited cell migration when compared to LG or OC. This inhibition resulted from impaired cell polarity, protrusion destabilization and inhibition of adhesion maturation. Conversely, Rac1 activity, which promotes protrusion and blocks adhesion maturation, was increased in HG conditions, thus providing a mechanistic basis for the HG phenotype. Most of the HG effects were partially or completely rescued by treatment with NAC. These findings demonstrate that HG impairs cell migration due to an increase in oxidative stress that causes polarity loss, deficient adhesion and protrusion. These alterations arise, in large part, from increased Rac1 activity and may contribute to the poor wound healing observed in diabetic patients.
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Repeat migration and disappointment.
Grant, E K; Vanderkamp, J
1986-01-01
This article investigates the determinants of repeat migration among the 44 regions of Canada, using information from a large micro-database which spans the period 1968 to 1971. The explanation of repeat migration probabilities is a difficult task, and this attempt is only partly successful. May of the explanatory variables are not significant, and the overall explanatory power of the equations is not high. In the area of personal characteristics, the variables related to age, sex, and marital status are generally significant and with expected signs. The distance variable has a strongly positive effect on onward move probabilities. Variables related to prior migration experience have an important impact that differs between return and onward probabilities. In particular, the occurrence of prior moves has a striking effect on the probability of onward migration. The variable representing disappointment, or relative success of the initial move, plays a significant role in explaining repeat migration probabilities. The disappointment variable represents the ratio of actural versus expected wage income in the year after the initial move, and its effect on both repeat migration probabilities is always negative and almost always highly significant. The repeat probabilities diminish after a year's stay in the destination region, but disappointment in the most recent year still has a bearing on the delayed repeat probabilities. While the quantitative impact of the disappointment variable is not large, it is difficult to draw comparisons since similar estimates are not available elsewhere.
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Individual Decisions to Migrate During Civil Conflict
Bohra-Mishra, Pratikshya; Massey, Douglas S.
2012-01-01
The existing literature on forced migration limits our understanding of how violence affects migration to competing destinations. This article adds to the literature on forced migration by studying how armed violence during a period of civil conflict in south-central Nepal influenced the likelihood of local, internal, and international migration. We find that violence has a nonlinear effect on migration, such that low to moderate levels of violence reduce the odds of movement, but when violence reaches high levels, the odds of movement increase. We also find that the effect of violence on mobility increases as the distance of the move increases. When we consider the influence of violence on microlevel decision-making, we find that the effects of individual and household-level determinants were mostly consistent with hypotheses derived from contemporary theories of voluntary migration and that no predictor of migration influenced the decision to migrate differently in the presence of violence. PMID:21541805
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International Nuclear Information System (INIS)
Altman, J.; Bayer, S.A.
1990-01-01
Methacrylate-embedded sections and short-survival thymidine radiograms of the hippocampal dentate gyrus were examined in perinatal and postnatal rats in order to trace the site of origin and migration of the precursors of granule cells and study the morphogenesis of the granular layer. The densely packed, spindle-shaped cells of the secondary dentate matrix (a derivative of the primary dentate neuroepithelium) stream in a subpial position towards the granular layer of the internal dentate limb during the perinatal and early postnatal periods. By an accretionary process, the crest of the granular layer forms on day E21 and on the subsequent days the granular layer of the internal dentate limb expands progressively in a lateral direction. Granule cells differentiation, as judged by the transformation of polymorph, darkly staining small cells into rounder, lightly staining larger granule cells, follows the same gradient from the external dentate limb to the internal dentate limb. The secondary dentate matrix is in a process of dissolution by day P5. This matrix is the source of what will later become the outer shell of the granular layer composed of early generated granule cells. The thicker inner shell of the granular layer, formed during the infantile and juvenile periods, derives from an intrinsic, tertiary germinal matrix. On day E22, the dentate migration of the secondary dentate matrix becomes partitioned into two components: (a) the subpial component of extradentate origin, referred to in this context as the first dentate migration, and (b) the second dentate migration. The latter is distributed in the basal polymorph layer throughout the entire dentate gyrus and is henceforth recognized as the tertiary dentate matrix. The tertiary dentate matrix is prominent between days P3 and P10
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Recovery Migration to the City of New Orleans after Hurricane Katrina: A Migration Systems Approach.
Fussell, Elizabeth; Curtis, Katherine J; Dewaard, Jack
2014-03-01
Hurricane Katrina's effect on the population of the City of New Orleans provides a model of how severe weather events, which are likely to increase in frequency and strength as the climate warms, might affect other large coastal cities. Our research focuses on changes in the migration system - defined as the system of ties between Orleans Parish and all other U.S. counties - between the pre-disaster (1999-2004) and recovery (2007-2009) periods. Using Internal Revenue Service county-to-county migration flow data, we find that in the recovery period Orleans Parish increased the number of migration ties with and received larger migration flows from nearby counties in the Gulf of Mexico coastal region, thereby spatially concentrating and intensifying the in-migration dimension of this predominantly urban system, while the out-migration dimension contracted and had smaller flows. We interpret these changes as the migration system relying on its strongest ties to nearby and less damaged counties to generate recovery in-migration.
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An economic analysis of migration in Mexico.
Greenwood, M J; Ladman, J R
1978-07-01
This paper analyzes internal migration in Mexico over the 1960-70 period. A model of the determinants of migration is specified and estimated for aggregated interstate migration flows. Results show that distance serves as a significant deterrent to migration, that higher destination earning levels are attractive to migrants, and that regions with high unemployment rates experience lower rates of inmigration. An unanticipated finding is that regions with higher earning levels have greater rates of outmigration. The data are disaggregated to examine separate migration relationships for each state. The results are that distance is a lesser deterrent for those migrants with more accessible alternatives, that higher earning levels reduce the deterring effects of distance, and that regions with higher earning levels have lower associated elasticities of migration. It is concluded that economic factors have played a crucial role in internal migration and thus in the changing occupational and geographic structure of the Mexican labor force.
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Internal migration in the USSR: 1897-1926.
Leasure, J W; Lewis, R A
1967-06-01
The purpose of this study is to describe and to analyze internal migration in the USSR primarily by the use of data from the 1926 census of the USSR. The article is divided into two parts. The first is devoted to a description of the aggregate and regional migration patterns based on place-of-birth data. The second is an analysis of these migration patterns, primarily in terms of economic differentials by guberniya. Because only limited income data are available for the period around1926 and because other economic data are scarce or unusable owing to boundary changes, census data on labor force distribution, literacy, and urbanization are used as substitute variables to approximate income differences.Migrationis a complex phenomenon related to a host of factors. The present study does not presume fully to explain migration in the USSR, but it does attempt to isolate differences in income and to relate these to the internal migration that occurred during this period. As a result of processing and analyzing an extensive array of data, we have shown that differences in income, derived indirectly from a variety of data, are closely related to internal migration in the USSR in the period prior to the 1926 census. There were striking similarities in respect to internal migration between the period prior to the 1897 census and the period prior to the1926 census. The chief areas of out-migration and in-migration were roughly the same,and migrants in both periods moved primarily to areas of higher income.
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Directory of Open Access Journals (Sweden)
Khrystyna FOGEL
2015-12-01
Full Text Available This article examines the consequences of the biggest round of EU Enlargement in 2004 on the labour migration flows from the new accession countries (A8 of the Eastern and Central Europe to Western Europe. The main focus of our research is the unique multistage nature of labour migration in the region. As a case study, we take labour migration from Poland to the United Kingdom and Germany and similar processes taking place in the labour migration from Ukraine to Poland. In particular, a new type of migration structure developed reflecting new features of integration stages of new EU Member States. This allows us to apprehend how this type of labour migration, within the multistage model, includes periods of time that take into account the inertia of labour movement. This article examines not only the character of A8 migration flows but also the potential drivers of this migration such as economic, institutional, etc. All processes are examined in the 2002 - 2011 time frame.
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A matter of months: High precision migration chronology of a Bronze Age female.
Directory of Open Access Journals (Sweden)
Karin Margarita Frei
Full Text Available 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.
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A matter of months: High precision migration chronology of a Bronze Age female
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
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The mechanism for migration in Poland.
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.
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Úbeda, Sara; Aznar, Margarita; Vera, Paula; Nerín, Cristina; Henríquez, Luis; Taborda, Laura; Restrepo, Claudia
2017-10-01
Most multilayer high barrier materials used in food packaging have a polyurethane adhesive layer in their structures. In order to assess the safety of these materials, it is important to determine the compounds intentionally added to the adhesives (IAS) as well as those non-intentionally added substances (NIAS). During the manufacture of polyurethane adhesives, some by-products can be formed, such as cyclic polyester oligomers coming from the reaction between dicarboxylic acids and glycols. Since these compounds are not listed in the Regulation 10/2011/EU, they should not be found in migration above 0.01 mg/kg of simulant. In this study two flexible multilayer packaging materials were used and migration was evaluated in simulant A (ethanol 10% v/v), simulant B (acetic acid 3% w/v) and simulant ethanol 95% v/v during 10 days at 60ºC. Identification and quantification of non-volatile compounds was carried out by UPLC-MS-QTOF. Most of migrants were oligomers such as cyclic polyesters and caprolactam oligomers. Overall migration and specific migration of adipic acid-diethylene glycol and phthalic acid-diethylene glycol were monitored over time and analysed by UPLC-MS-TQ. In most cases, ethanol 95% v/v was the simulant with the highest concentration values. Overall migration kinetics followed a similar pattern than specific migration kinetics.
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The design of the high energy physics massive data migration system
International Nuclear Information System (INIS)
Shi Jingyan; Zang Dongsong; Cheng Yaodong
2010-01-01
High energy physics is the typical data massive computing application due to its huge experiment data. For example, the amount of BESⅢ experiment data reaches to 4PB. Hierarchical storage system is adapted for the application in which disk array and tape library are used. It is quite important to migrate massive data from disk array to tape library. The article introduces the design and realization for the high performance data migration system between disk array and tape library. Besides, the system provides web page as the friendly user interface. (authors)
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Labor migration and risk aversion in less developed countries.
Katz, E; Stark, O
1986-01-01
"In this paper we question the pioneering work of Todaro, which states that rural-to-urban labor migration in less developed countries (LDCs) is an individual response to a higher urban expected income. We demonstrate that rural-to-urban labor migration is perfectly rational even if urban expected income is lower than rural income. We achieve this under a set of fairly stringent conditions: an individual decision-making entity, a one-period planning horizon, and global risk aversion. We obtain the result that a small chance of reaping a high reward is sufficient to trigger rural-to-urban labor migration." excerpt
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Gas migration characteristics of highly compacted bentonite ore
International Nuclear Information System (INIS)
Tanaka, Yukihisa; Hironaga, Michihiko
2010-01-01
In the current concept of repository for radioactive waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of dissolved gas inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Gas migration characteristics of highly compacted powdered bentonite are already reported by CRIEPI. In this report, gas migration characteristics of bentonite ore, which is a candidate for construction material of repository for radioactive waste, is investigated. The following conclusions are obtained through the results of the gas migration tests which are conducted in this study: 1) When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. By increasing the gas pressure more, gas breakthrough, which defined as a sudden and sharp increase in gas flow rate out of the specimen, occurs. Therefore gas migration mechanism of compacted bentonite ore is basically identical to that of compacted powdered bentonite. 2) Hydraulic conductivity measured after the gas breakthrough is somewhat smaller than that measured before the gas migration test. This fact means that it might be possible to neglect decline of the function of bentonite as engineered barrier caused by the gas breakthrough. These characteristics of compacted bentonite ore are identical to those of
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Determinants of spring migration departure decision in a bat.
Dechmann, Dina K N; Wikelski, M; Ellis-Soto, D; Safi, K; O'Mara, M Teague
2017-09-01
Migratory decisions in birds are closely tied to environmental cues and fat stores, but it remains unknown if the same variables trigger bat migration. To learn more about the rare phenomenon of bat migration, we studied departure decisions of female common noctules ( Nyctalus noctula ) in southern Germany. We did not find the fattening period that modulates departure decisions in birds. Female noctules departed after a regular evening foraging session, uniformly heading northeast. As the day of year increased, migratory decisions were based on the interactions among wind speed, wind direction and air pressure. As the migration season progressed, bats were likely to migrate on nights with higher air pressure and faster tail winds in the direction of travel, and also show high probability of migration on low-pressure nights with slow head winds. Common noctules thus monitor complex environmental conditions to find the optimal migration night. © 2017 The Authors.
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MIGRATION OF EXTRASOLAR PLANETS: EFFECTS FROM X-WIND ACCRETION DISKS
International Nuclear Information System (INIS)
Adams, Fred C.; Cai, Mike J.; Lizano, Susana
2009-01-01
Magnetic fields are dragged in from the interstellar medium during the gravitational collapse that forms star/disk systems. Consideration of mean field magnetohydrodynamics in these disks shows that magnetic effects produce sub-Keplerian rotation curves and truncate the inner disk. This Letter explores the ramifications of these predicted disk properties for the migration of extrasolar planets. Sub-Keplerian flow in gaseous disks drives a new migration mechanism for embedded planets and modifies the gap-opening processes for larger planets. This sub-Keplerian migration mechanism dominates over Type I migration for sufficiently small planets (m P ∼ + ) and/or close orbits (r ∼< 1 AU). Although the inclusion of sub-Keplerian torques shortens the total migration time by only a moderate amount, the mass accreted by migrating planetary cores is significantly reduced. Truncation of the inner disk edge (for typical system parameters) naturally explains final planetary orbits with periods P ∼ 4 days. Planets with shorter periods, P ∼ 2 days, can be explained by migration during FU-Orionis outbursts, when the mass accretion rate is high and the disk edge moves inward. Finally, the midplane density is greatly increased at the inner truncation point of the disk (the X-point); this enhancement, in conjunction with continuing flow of gas and solids through the region, supports the in situ formation of giant planets.
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Migration of the ThO2 kernels under the influence of a temperature gradient
International Nuclear Information System (INIS)
Smith, C.L.
1977-01-01
Biso-coated ThO 2 fertile fuel kernels will migrate up the thermal gradients imposed across coated particles during high-temperature gas-cooled reactor (HTGR) operation. Thorium dioxide kernel migration has been studied as a function of temperature (1290 to 1705 0 C) (1563 to 1978 K) and ThO 2 kernel burnup (0.9 to 5.8 percent FIMA) in out-of-pile postirradiation thermal gradient heating experiments. The studies were conducted to obtain descriptions of migration rates that will be used in core design studies to evaluate the impact of ThO 2 migration on fertile fuel performance in an operating HTGR and to define characteristics needed by any comprehensive model describing ThO 2 kernel migration. The kinetics data generated in these postirradiation studies are consistent with in-pile data collected by investigators at Oak Ridge National Laboratory, which supports use of the more precise postirradiation heating results in HTGR core design studies. Observations of intergranular carbon deposits on the cool side of migrating kernels support the assumption that the kinetics of kernel migration are controlled by solid-state diffusion within irradiated ThO 2 kernels. The migration is characterized by a period of no migration (incubation period), followed by migration at the equilibrium rate for ThO 2 . The incubation period decreases with increasing temperature and kernel burnup. The improved understanding of the kinetics of ThO 2 kernel migration provided by this work will contribute to an optimization of HTGR core design and an increased confidence in fuel performance predictions
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Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures
International Nuclear Information System (INIS)
Rutqvist, Jonny; Blanco-Martin, Laura; Molins, Sergi; Trebotich, David; Birkholzer, Jens
2015-01-01
In this report, we present FY2015 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. This is a combined milestone report related to milestone Salt R&D Milestone ''Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures'' (M3FT-15LB0818012) and the Salt Field Testing Milestone (M3FT-15LB0819022) to support the overall objectives of the salt field test planning.
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Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures
Energy Technology Data Exchange (ETDEWEB)
Rutqvist, Jonny [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Blanco-Martin, Laura [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Molins, Sergi [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Trebotich, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Birkholzer, Jens [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2015-09-01
In this report, we present FY2015 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. This is a combined milestone report related to milestone Salt R&D Milestone “Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures” (M3FT-15LB0818012) and the Salt Field Testing Milestone (M3FT-15LB0819022) to support the overall objectives of the salt field test planning.
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Hydraulic Characteristics of the Lower Snake River During Periods of Juvenile Fall Chinook Migration
Energy Technology Data Exchange (ETDEWEB)
Cook, Chris B.; Dibrani, Berhon; Richmond, Marshall C.; Bleich, Matthew D.; Titzler, P. Scott; Fu, Tao
2006-01-30
This report documents a four-year study to assess hydraulic conditions in the lower Snake River. The work was conducted for the Bonneville Power Administration, U.S. Department of Energy, by the Pacific Northwest National Laboratory. Cold water released from the Dworshak Reservoir hypolimnion during mid- to late-summer months cools the Clearwater River far below equilibrium temperature. The volume of released cold water augments the Clearwater River, and the combined total discharge is on the order of the Snake River discharge when the two rivers meet at their confluence near the upstream edge of Lower Granite Reservoir. With typical temperature differences between the Clearwater and Snake rivers of 10°C or more during July and August, the density difference between the two rivers during summer flow augmentation periods is sufficient to stratify Lower Granite Reservoir as well as the other three reservoirs downstream. Because cooling of the river is desirable for migrating juvenile fall Chinook salmon (Oncorhynchus tshawytscha) during this same time period, the amount of mixing and cold water entrained into Lower Granite Reservoir’s epilimnion at the Clearwater/Snake River confluence is of key biological importance to juvenile fall Chinook salmon. Data collected during this project indicates the three reservoirs downstream of Lower Granite also stratify as direct result of flow augmentation from Dworshak Reservoir. These four lower Snake reservoirs are also heavily influenced by wind forcing at the water’s surface, and during periods of low river discharge, often behave like a two-layer lake. During these periods of stratification, lower river discharge, and wind forcing, the water in the upper layer of the reservoir is held in place or moves slightly upstream. This upper layer is also exposed to surface heating and may warm up to temperatures close to equilibrium temperature. The depth of this upper warm layer and its direction of travel may also be of key
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Predator-prey interaction reveals local effects of high-altitude insect migration
High-altitude nocturnal insect migrations represent significant pulses of resources, yet are difficult to study and poorly understood. Predator-prey interactions, specifically migratory moth consumption by high-flying bats, potentially reveal flows of migratory insects across a landscape. In North...
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The Gravity of High-Skilled Migration Policies.
Czaika, Mathias; Parsons, Christopher R
2017-04-01
Combining unique, annual, bilateral data on labor flows of highly skilled immigrants for 10 OECD destinations between 2000 and 2012, with new databases comprising both unilateral and bilateral policy instruments, we present the first judicious cross-country assessment of policies aimed to attract and select high-skilled workers. Points-based systems are much more effective in attracting and selecting high-skilled migrants than requiring a job offer, labor market tests, and shortage lists. Offers of permanent residency, while attracting the highly skilled, overall reduce the human capital content of labor flows because they prove more attractive to non-high-skilled workers. Bilateral recognition of diploma and social security agreements foster greater flows of high-skilled workers and improve the skill selectivity of immigrant flows. Conversely, double taxation agreements deter high-skilled migrants, although they do not alter overall skill selectivity. Our results are robust to a variety of empirical specifications that account for destination-specific amenities, multilateral resistance to migration, and the endogeneity of immigration policies.
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Directory of Open Access Journals (Sweden)
Andrew Mamalis
Full Text Available Skin fibrosis is a significant medical problem that leads to a functional, aesthetic, and psychosocial impact on quality-of-life. Light-emitting diode-generated 633-nm red light (LED-RL is part of the visible light spectrum that is not known to cause DNA damage and is considered a safe, non-invasive, inexpensive, and portable potential alternative to ultraviolet phototherapy that may change the treatment paradigm of fibrotic skin disease.The goal of our study was to investigate the how reactive oxygen species (ROS free radicals generated by high fluence LED-RL inhibit the migration of skin fibroblasts, the main cell type involved in skin fibrosis. Fibroblast migration speed is increased in skin fibrosis, and we studied cellular migration speed of cultured human skin fibroblasts as a surrogate measure of high fluence LED-RL effect on fibroblast function. To ascertain the inhibitory role of LED-RL generated ROS on migration speed, we hypothesized that resveratrol, a potent antioxidant, could prevent the photoinhibitory effects of high fluence LED-RL on fibroblast migration speed.High fluence LED-RL generated ROS were measured by flow cytometry analysis using dihydrorhodamine (DHR. For purposes of comparison, we assessed the effects of ROS generated by hydrogen peroxide (H2O2 on fibroblast migration speed and the ability of resveratrol, a well known antioxidant, to prevent LED-RL and H2O2 generated ROS-associated changes in fibroblast migration speed. To determine whether resveratrol could prevent the high fluence LED-RL ROS-mediated photoinhibition of human skin fibroblast migration, treated cells were incubated with resveratrol at concentrations of 0.0001% and 0.001% for 24 hours, irradiated with high fluences LED-RL of 480, 640, and 800 J/cm2.High fluence LED-RL increases intracellular fibroblast ROS and decreases fibroblast migration speed. LED-RL at 480, 640 and 800 J/cm2 increased ROS levels to 132.8%, 151.0%, and 158.4% relative to matched
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A preliminary study of international migration of the Chinese people.
Zhu, G
1994-01-01
International Chinese migration has spanned five periods: 1) an initial period of random and short-term migration dating back to the Qing and Han dynasties; 2) a spontaneous period since the Sui and Tang dynasties along trade routes; 3) a transition period during the Ming dynasty and the early Qing dynasty with war, poverty, and population growth as push factors; 4) peak migration during the Opium War period due to economic depression, population pressure, and the "coolie" trade; and 5) continuous development between the 1920s and 1949. Migration tended to occur between Guangdong and Fujian provinces and other southeast Asian countries. Four factors were identified as necessary for international migration to occur: the origin of migration, the destination factor, the middle link factor, and the immigrant characteristics. The origins of early Chinese migration appeared in a country of political corruption, population pressure, a backward economy, and social chaos. The pull factors at destination end were demand for labor. The middle link was the short distance between Guangdong and Fujian provinces and southeast Asian countries and longstanding nongovernmental exchanges. Other links were the similarity of climate, similar racial features, cultural lifestyle similarities, and convenient transportation. The people in these two provinces had a history of migration and a personality suitable for the spirit of adventure. Peak migration occurred during the late Qing dynasty and during the continuous development period. Between 1840 and 1911 there were about 10 million Chinese immigrants and during 1911 and 1949 there were about 6 million. In general, over 20 million immigrated prior to 1949, of which about 50% migrated during the peak period, 33% during the continuous period, and 20% before 1840. This amounted to about 33% of European migration and two times African migration. 60% were from Guangdong, and 30% were from Fujian province, of whom most were from counties
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Bats on a Budget: Torpor-Assisted Migration Saves Time and Energy
McGuire, Liam P.; Jonasson, Kristin A.; Guglielmo, Christopher G.
2014-01-01
Bats and birds must balance time and energy budgets during migration. Migrating bats face similar physiological challenges to birds, but nocturnality creates special challenges for bats, such as a conflict between travelling and refueling, which many birds avoid by feeding in daylight and flying at night. As endothermic animals, bats and birds alike must expend substantial amounts of energy to maintain high body temperatures. For migratory birds refueling at stopovers, remaining euthermic during inactive periods reduces the net refuelling rate, thereby prolonging stopover duration and delaying subsequent movement. We hypothesized that bats could mitigate similar ambient-temperature dependent costs by using a torpor-assisted migration strategy. We studied silver-haired bats Lasionycteris noctivagans during autumn migration using a combination of respirometry and temperature-sensitive radiotelemetry to estimate energy costs incurred under ambient temperature conditions, and the energy that bats saved by using torpor during daytime roosting periods. All bats, regardless of sex, age, or body condition used torpor at stopover and saved up to 91% of the energy they would have expended to remain euthermic. Furthermore, bats modulated use of torpor depending on ambient temperature. By adjusting the time spent torpid, bats achieved a rate of energy expenditure independent of the ambient temperature encountered at stopover. By lowering body temperature during inactive periods, fuel stores are spared, reducing the need for refuelling. Optimal migration models consider trade-offs between time and energy. Heterothermy provides a physiological strategy that allows bats to conserve energy without paying a time penalty as they migrate. Although uncommon, some avian lineages are known to use heterothermy, and current theoretical models of migration may not be appropriate for these groups. We propose that thermoregulatory strategies should be an important consideration of future
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Navigational Strategies of Migrating Monarch Butterflies
2014-11-10
AFRL-OSR-VA-TR-2014-0339 NAVIGATIONAL STRATEGIES OF MIGRATING MONARCH BUTTERFLIES Steven Reppert UNIVERSITY OF MASSACHUSETTS Final Report 11/10/2014...Final Progress Statement to (Dr. Patrick Bradshaw) Contract/Grant Title: Navigational Strategies of Migrating Monarch Butterflies Contract...Grant #: FA9550-10-1-0480 Reporting Period: 01-Sept-10 to 31-Aug-14 Overview of accomplishments: Migrating monarch butterflies (Danaus
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Radiological and migration results of the DURALOC(R)-cup after two years
International Nuclear Information System (INIS)
Juen, F.
2000-10-01
In 1997 a study was conduced concerning 69 consecutive patients, all of whom consisted of DURALOC(R) series 100 acetabular components. The clinical, radiological and migrational aspect of each component was investigated 2 and 4 years postoperatively. In addition to this, a further 92 cups were analyzed in an identical manner, again 2 years after implantation. This therefore equated to a total of 161 investigated cups after a follow up interval of 2 years. In 144 of these cases the cup was combined with a cementless hydroxyapatite coated Spotorno shaft, with the remaining 17 involving a cemented Link-shaft (Lubinus SP II). A 28 mm Biolox(R) ceramic head was constant in all cases. Clinical data for each cup was collected via completion of a standard examination form, while acetabular migration, both vertical and horizontal, was measured on serial radiographs by the computer assisted EBRA method. From analyses of collected data, it was clearly shown that the clinical results remained very good over the 2- and 4-year-periods however, from radiological evidence it was indicated that for the period 3-4 years postoperatively, an increasing amount of radiolucencies around the cups were apparent. There was clearly no correlation between clinical and migration results. From the data taken from 106 migration curves, the mean total migration over the initial two-year-period was calculated to be 0.88 mm. From analysis of a further 56 migration curves, the mean total migration within 4 years of implantation was assessed to be 1.23 mm, however a decreasing speed of migration over the final 2-year-period was indicated. Our results demonstrate that statements relating to migration results of particular cups are more accurate after four years. However, statements about mean migration values are possible after two years. A migration speed of 1 mm total migration within the first 2 years after operation was predictive for radiological loosening of the cup after four years (p=0
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Levels and patterns of internal migration in Europe: A cohort perspective.
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.
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Migration of the Duraloc cup after 5 years.
Stihsen, Christoph; Pabinger, Christof; Radl, Roman; Rehak, Peter; Windhager, Reinhard
2008-12-01
The Duraloc cup is a frequently used metal-backed, porous-coated, hemispherical, press-fit acetabular component. Published data on loosening rates are contradictory. In this study we investigated migration patterns with computer-assisted Einzel-Bild-Roentgen-Analyse (EBRA) of 67 Duraloc 100 cups. Cup migration and clinical scores were analysed over a 5-year follow-up period. Median total migration of the Duraloc 100 cup was 1.21 mm at 5 years. Seventy-five percent of implants were radiologically stable at 2 years and 90% at 4 years. One cup loosened aseptically at 60 months, requiring revision. Cup diameters > or = 54 mm migrated significantly more than cups < 54 mm in diameter (p = 0.029 at 4 years). There was a significant correlation between high polyethylene wear and further migrating cups within the first post-operative year (p = 0.035 at 12 months). Our analysis revealed significantly higher wear in males (p = 0.029 at 4 years). Radiological loosening at two years could be calculated using receiver-operating characteristic curve analysis, and 1.2 mm as an adequate threshold value (sensitivity = 100%, specificity = 89%).
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Mitchell, Piers D; Anastasiou, Evilena; Syon, Danny
2011-12-01
The aim of this research is to highlight the role of ancient parasites as evidence for human migration in past populations. The material analysed was soil sediment from the excavation of a medieval cesspool in the city of Acre, in Israel. Archaeological stratigraphy and radiocarbon dating of a fragment of animal bone from the cesspool confirm its use in the 13th century CE, during the crusader period. At that time Acre was located in the Frankish Kingdom of Jerusalem. Soil samples from the cesspool were analysed and eggs of the roundworm (Ascaris lumbricoides) and fish tapeworm (Diphyllobothrium latum) were identified. The fish tapeworm has only been found in the mainland Near East once before, in a latrine of the crusader Order of St. John (Knights Hospitaller). It has been absent in all earlier cesspools, latrines and coprolites so far studied in the region. In contrast to its rarity in the Levant, the fish tapeworm was common in northern Europe during the medieval period. The presence of fish tapeworm eggs in a crusader period cesspool in Acre suggests its use by crusaders or pilgrims from northern Europe who travelled to the Levant carrying these parasites in their intestines. Copyright © 2011 Elsevier Inc. All rights reserved.
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International Nuclear Information System (INIS)
Zhou, Lang; Zhang, Huyuan; Yan, Ming; Chen, Hang; Zhang, Ming
2013-01-01
For the safety assessment of geological disposal of high-level radioactive waste (HLW), the migration of Eu(III) through compacted bentonite–sand mixtures was measured under expected repository conditions. Under the evaluated conditions, advection and dispersion is the dominant migration mechanism. The role of sorption on the retardation of migration was also evaluated. The hydraulic conductivities of compacted bentonite–sand mixtures were K=2.07×10 −10 –5.23×10 −10 cm/s, The sorption and diffusion of Eu(III) were examined using a flexible wall permeameter for a solute concentration of 2.0×10 −5 mol/l. The effective diffusion coefficients and apparent diffusion coefficients of Eu(III) in compacted bentonite–sand mixtures were in the range of 1.62×10 –12 –4.87×10 –12 m 2 /s, 1.44×10 –14 –9.41×10 –14 m 2 /s, respectively, which has a very important significance to forecast the relationship between migration length of Eu(III) in buffer/backfill material and time and provide a reference for the design of buffer/backfill material for HLW disposal in China. - Highlights: • The migration progress of Eu(III) in compacted bentonite–sand mixtures was researched. • The hydraulic conductivity of cominpacted bentonite–sand mixtures was measured. • The migration length of Eu(III) in buffer/backfill material after a certain period of time was forecasted
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Urbanization, Migration, Information
Directory of Open Access Journals (Sweden)
Konstantin Lidin
2016-05-01
Full Text Available In the contemporary world urbanization becomes a large-scale process. Huge flows of people migrate from poorer districts to the cities with a higher level of consumption. It takes migrants about 15-25 years to give up their traditional ascetic way of life. In this period the ‘new citizens’ try to arrange compact settlements with an archaic way of life, insanitary conditions, high criminogenity and an authoritative local self-government. The processes of formation and decay of the ascetic enclave are viewed through the example of the ‘Shanghai’ trading neighborhood in Irkutsk.
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International Nuclear Information System (INIS)
Nagao, Kakuhiro; Nakane, Sunao
1993-01-01
The experimental studies concerning temperature, moisture migration, and pore pressure of mass concrete mock-up specimens heated up to high temperature at 110degC to 600degC, were performed, so as to correctly estimate the moisture migration behaviour of concrete members subjected to high temperature, which is considered significantly influenced on physical properties of concrete. As a results, it is confirmed that the moisture migration behavior of concrete members can be explained by temperature and pore pressure, and indicate the characteristics both sealed condition (dissipation of moisture is prevented) and unsealed condition (dissipation of moisture occur). (author)
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PARENTAL AND SIBLING MIGRATION AND HIGH BLOOD PRESSURE AMONG RURAL CHILDREN IN CHINA.
Wen, Ming; Li, Kelin
2016-01-01
This study examines the associations between parental and sibling rural-to-urban migration and blood pressure (BP) of rural left-behind children (LBC) in rural China. Analysis was based on the 2000, 2004, 2006 and 2009 waves of longitudinal data from the China Health and Nutrition Survey, which is an ongoing prospective survey covering nine provinces with an individual-level response rate of 88%. Blood pressure levels were measured by trained examiners at three consecutive times on the same visit and the means of three measurements were used as the final BP values. An ordinal BP measure was then created using a recently validated age-sex-specified distribution for Chinese children and adolescents, distinguishing normal BP, pre-hypertension and hypertension. Random effect modelling was performed. Different migration circumstances play different roles in LBC's BP with mother-only and both-parent migration being particularly detrimental and father-only and sibling-only migration either having no association or a negative association with LBC's BP levels or odds of high BP. In conclusion, the link between family migration and left-behind children's blood pressure is complex, and depends on who is the person out-migrating.
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The accretion of migrating giant planets
Dürmann, Christoph; Kley, Wilhelm
2017-02-01
Aims: Most studies concerning the growth and evolution of massive planets focus either on their accretion or their migration only. In this work we study both processes concurrently to investigate how they might mutually affect one another. Methods: We modeled a two-dimensional disk with a steady accretion flow onto the central star and embedded a Jupiter mass planet at 5.2 au. The disk is locally isothermal and viscosity is modeled using a constant α. The planet is held on a fixed orbit for a few hundred orbits to allow the disk to adapt and carve a gap. After this period, the planet is released and free to move according to the gravitational interaction with the gas disk. The mass accretion onto the planet is modeled by removing a fraction of gas from the inner Hill sphere, and the removed mass and momentum can be added to the planet. Results: Our results show that a fast migrating planet is able to accrete more gas than a slower migrating planet. Utilizing a tracer fluid we analyzed the origin of the accreted gas originating predominantly from the inner disk for a fast migrating planet. In the case of slower migration, the fraction of gas from the outer disk increases. We also found that even for very high accretion rates, in some cases gas crosses the planetary gap from the inner to the outer disk. Our simulations show that the crossing of gas changes during the migration process as the migration rate slows down. Therefore, classical type II migration where the planet migrates with the viscous drift rate and no gas crosses the gap is no general process but may only occur for special parameters and at a certain time during the orbital evolution of the planet.
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Migration in the shearing sheet and estimates for young open cluster migration
Quillen, Alice C.; Nolting, Eric; Minchev, Ivan; De Silva, Gayandhi; Chiappini, Cristina
2018-04-01
Using tracer particles embedded in self-gravitating shearing sheet N-body simulations, we investigate the distance in guiding centre radius that stars or star clusters can migrate in a few orbital periods. The standard deviations of guiding centre distributions and maximum migration distances depend on the Toomre or critical wavelength and the contrast in mass surface density caused by spiral structure. Comparison between our simulations and estimated guiding radii for a few young supersolar metallicity open clusters, including NGC 6583, suggests that the contrast in mass surface density in the solar neighbourhood has standard deviation (in the surface density distribution) divided by mean of about 1/4 and larger than measured using COBE data by Drimmel and Spergel. Our estimate is consistent with a standard deviation of ˜0.07 dex in the metallicities measured from high-quality spectroscopic data for 38 young open clusters (<1 Gyr) with mean galactocentric radius 7-9 kpc.
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Moonlight Drives Ocean-Scale Mass Vertical Migration of Zooplankton during the Arctic Winter.
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.
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[East-West migration in Europe 1918-1992].
Fassmann, H; Munz, R
1995-03-01
"The paper [analyzes] available demographic data on international migration within and to Europe during the periods 1918-39 and 1945-92. The main focus is on the East-West dimension of this migration. In the inter-war period some 9.2 million people either left their countries as labour migrants or were displaced.... In the post-war period (1945-50) some 15.4 million people fled or were displaced within Europe. Most of them moved or were forced to move westwards.... In recent times the wars in Croatia and Bosnia as well as ethnic cleansing have led to the largest wave of refugees and displaced persons since 1945.... The paper argues that push and pull factors causing massive migration cannot...be contained by erecting new legislative barriers and deploying more armed guards against newcomers." (EXCERPT)
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Environmental concentration and migration of 129I
International Nuclear Information System (INIS)
Brauer, F.P.; Strebin, R.S. Jr.
1982-01-01
Local sources of 129 I suitable for study of migration in the environment are uranium ore bodies for long periods and nuclear fuel reprocessing operations for recent periods. Uranium ores produce 129 I from spontaneous and neutron-induced fission. Nuclear fuel reprocessing has resulted in releases of 129 I to both the atmosphere and the hydrosphere. The long-term fate of surface-deposited and groundwater 129 I was studied. Neutron activation analysis was used to measure the low levels of 129 I and natural 127 I in samples near and remote from nuclear fuel reprocessing facilities. Measurements were made on air samples, vegetation, soil, surface water, groundwater and uranium ore samples. Samples were collected both during reprocessing operations and after reprocessing activities had been discontinued for several years. The 129 I was found to accumulate in the top soil and litter layer. The surface concentrations of 129 I in forest communities were found to be several times higher than for nearby grass communities. The 129 I levels were found to persist in the environment after reprocessing activities had been discontinued. Measurable 129 I was found to be contained in uranium ore samples from a variety of locations and with a range of uranium concentrations. Thus ore bodies constitute a source of 129 I suitable for study of migration over long periods. Iodine-129 has entered surface and groundwater as the result of liquid and atmospheric discharges from nuclear fuel reprocessing facilities. The iodine in water samples was found to be anionic and travel with the water flow. Thus 129 I was found to provide high sensitivity for hydrology tracer studies and radioactivity migration surveillance. Once 129 I enters the hydrosphere it migrates with the water with little or no hold-up by exchange with cationic exchangers such as soil or silt
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Climate Change as Migration Driver from Rural and Urban Mexico
Hunter, Lori M.; Runfola, Daniel M.; Riosmena, Fernando
2015-01-01
Studies investigating migration as a response to climate variability have largely focused on rural locations to the exclusion of urban areas. This lack of urban focus is unfortunate given the sheer numbers of urban residents and continuing high levels of urbanization. To begin filling this empirical gap, this study investigates climate change impacts on U.S.-bound migration from rural and urban Mexico, 1986–1999. We employ geostatistical interpolation methods to construct two climate change indices, capturing warm and wet spell duration, based on daily temperature and precipitation readings for 214 weather stations across Mexico. In combination with detailed migration histories obtained from the Mexican Migration Project, we model the influence of climate change on household-level migration from 68 rural and 49 urban municipalities. Results from multilevel event-history models reveal that a temperature warming and excessive precipitation significantly increased international migration during the study period. However, climate change impacts on international migration is only observed for rural areas. Interactions reveal a causal pathway in which temperature (but not precipitation) influences migration patterns through employment in the agricultural sector. As such, climate-related international migration may decline with continued urbanization and the resulting reductions in direct dependence of households on rural agriculture. PMID:26692890
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Climate Change as Migration Driver from Rural and Urban Mexico.
Nawrotzki, Raphael J; Hunter, Lori M; Runfola, Daniel M; Riosmena, Fernando
2015-11-01
Studies investigating migration as a response to climate variability have largely focused on rural locations to the exclusion of urban areas. This lack of urban focus is unfortunate given the sheer numbers of urban residents and continuing high levels of urbanization. To begin filling this empirical gap, this study investigates climate change impacts on U.S.-bound migration from rural and urban Mexico, 1986-1999. We employ geostatistical interpolation methods to construct two climate change indices, capturing warm and wet spell duration, based on daily temperature and precipitation readings for 214 weather stations across Mexico. In combination with detailed migration histories obtained from the Mexican Migration Project, we model the influence of climate change on household-level migration from 68 rural and 49 urban municipalities. Results from multilevel event-history models reveal that a temperature warming and excessive precipitation significantly increased international migration during the study period. However, climate change impacts on international migration is only observed for rural areas. Interactions reveal a causal pathway in which temperature (but not precipitation) influences migration patterns through employment in the agricultural sector. As such, climate-related international migration may decline with continued urbanization and the resulting reductions in direct dependence of households on rural agriculture.
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Starks, Donna; Willoughby, Louisa
2015-01-01
Recent years have seen a backlash against multiculturalism in many Western countries and increasing calls to restrict migration and citizenship rights to those who can pass language tests. This paper explores the sentiment of high school students who were born and raised in Australia towards issues of language and migration, including the need for…
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The pulsed migration of hydrocarbons across inactive faults
Directory of Open Access Journals (Sweden)
S. D. Harris
1999-01-01
Full Text Available Geological fault zones are usually assumed to influence hydrocarbon migration either as high permeability zones which allow enhanced along- or across-fault flow or as barriers to the flow. An additional important migration process inducing along- or across-fault migration can be associated with dynamic pressure gradients. Such pressure gradients can be created by earthquake activity and are suggested here to allow migration along or across inactive faults which 'feel' the quake-related pressure changes; i.e. the migration barriers can be removed on inactive faults when activity takes place on an adjacent fault. In other words, a seal is viewed as a temporary retardation barrier which leaks when a fault related fluid pressure event enhances the buoyancy force and allows the entry pressure to be exceeded. This is in contrast to the usual model where a seal leaks because an increase in hydrocarbon column height raises the buoyancy force above the entry pressure of the fault rock. Under the new model hydrocarbons may migrate across the inactive fault zone for some time period during the earthquake cycle. Numerical models of this process are presented to demonstrate the impact of this mechanism and its role in filling traps bounded by sealed faults.
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OECD migration, welfare and skill selectivity
DEFF Research Database (Denmark)
Pedersen, Peder; Pytlikova, Mariola; Smith, Nina
into 27 OECD countries over the period of 12 years, 1989-2000. Using a fixed effects panel data model, we analyze the determinants of the migration flows during the latest decade. We study whether there are significant selectivity effects in international migration flows, i.e. whether the countries...
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Country-Specific Effects of Climate Variability on Human Migration
Gray, Clark; Wise, Erika
2016-01-01
Involuntary human migration is among the social outcomes of greatest concern in the current era of global climate change. Responding to this concern, a growing number of studies have investigated the consequences of short to medium-term climate variability for human migration using demographic and econometric approaches. These studies have provided important insights, but at the same time have been significantly limited by lack of expertise in the use of climate data, access to cross-national data on migration, and attention to model specification. To address these limitations, we link data on internal and international migration over a 6-year period from 9,812 origin households in Kenya, Uganda, Nigeria, Burkina Faso and Senegal to high-resolution gridded climate data from both station and satellite sources. Analyses of these data using several plausible specifications reveal that climate variability has country-specific effects on migration: Migration tends to increase with temperature anomalies in Uganda, tends to decrease with temperature anomalies in Kenya and Burkina Faso, and shows no consistent relationship with temperature in Nigeria and Senegal. Consistent with previous studies, precipitation shows weak and inconsistent relationships with migration across countries. These results challenge generalizing narratives that foresee a consistent migratory response to climate change across the globe. PMID:27092012
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Country-Specific Effects of Climate Variability on Human Migration.
Gray, Clark; Wise, Erika
2016-04-01
Involuntary human migration is among the social outcomes of greatest concern in the current era of global climate change. Responding to this concern, a growing number of studies have investigated the consequences of short to medium-term climate variability for human migration using demographic and econometric approaches. These studies have provided important insights, but at the same time have been significantly limited by lack of expertise in the use of climate data, access to cross-national data on migration, and attention to model specification. To address these limitations, we link data on internal and international migration over a 6-year period from 9,812 origin households in Kenya, Uganda, Nigeria, Burkina Faso and Senegal to high-resolution gridded climate data from both station and satellite sources. Analyses of these data using several plausible specifications reveal that climate variability has country-specific effects on migration: Migration tends to increase with temperature anomalies in Uganda, tends to decrease with temperature anomalies in Kenya and Burkina Faso, and shows no consistent relationship with temperature in Nigeria and Senegal. Consistent with previous studies, precipitation shows weak and inconsistent relationships with migration across countries. These results challenge generalizing narratives that foresee a consistent migratory response to climate change across the globe.
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SCANDINAVIAN MIGRATION IN THE VIKING AGE
Directory of Open Access Journals (Sweden)
Wladyslaw Duczko
2011-01-01
Full Text Available Movements of Scandinavians in period between late 8th AD to middle of 11th AD, called Viking Age, were combined military actions-piracy – and migrations with goal to colonize territories in the West Europe – mainly Insular world of Atlantic and British isles, but also in East Europe, among Finno-Ugrians and Slavs. This activity is seen as the recent, and last, of the Migration Period, the time of great movements of Germanic people in the 4th century AD.
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Harrington, Brian A.; Brown, S.; Corven, James; Bart, Jonathan
2002-01-01
Shorebirds are among the most highly migratory creatures on earth. Both the study of their ecology and ongoing efforts to conserve their populations must reflect this central aspect of their biology. Many species of shorebirds use migration and staging sites scattered throughout the hemisphere to complete their annual migrations between breeding areas and nonbreeding habitats (Morrison 1984). The vast distances between habitats they use pose significant challenges for studying their migration ecology. At the same time, the large number of political boundaries shorebirds cross during their epic migrations create parallel challenges for organizations working on their management and conservation.Nebel et al. (2002) represent a collaborative effort to understand the conservation implications of Western Sandpiper (Calidris mauri) migration ecology on a scale worthy of this highly migratory species. The data sets involved in the analysis come from four U.S. states, two Canadian provinces, and a total of five nations. Only by collaborating on this historic scale were the authors able to assemble the information necessary to understand important aspects of the migration ecology of this species, and the implications for conservation of the patterns they discovered.Collaborative approaches to shorebird migration ecology developed slowly over several decades. The same period also saw the creation of large-scale efforts to monitor and conserve shorebirds. This overview first traces the history of the study of migration ecology of shorebirds during that fertile period, and then describes the monitoring and protection efforts that have been developed in an attempt to address the enormous issues of scale posed by shorebird migration ecology and conservation.
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MIGRATIONS OF RELEASED SEISMIC ENERGY IN VARIOUS GEODYNAMIC CONDITIONS
Directory of Open Access Journals (Sweden)
A. V. Novopashina
2018-01-01
Full Text Available The properties of slow seismic activity migration have been revealed by the space-time analysis of the total earthquake energy (LgEsum. Our study of seismic activity covers the fragments of the Central Asian, Pacific and Alpine seismic belts: the Baikal rift system (BRS, Russia, the San Andreas fault zone (California, USA, the Christchurch fault (New Zealand, the North and East Anatolian faults (Turkey, the Philippine subduction zone, and the central fragment of the Mid-Atlantic oceanic ridge. The chains of LgEsum clusters mark the propagation of the maximum stresses front in the weaker crust areas, the zones of fault dynamic influence, and the regions of conjugated tectonic structures. The migration process is characterized by a periodicity, changes in direction, and similar modular values of the migration rates within a single fault segment (or a fault zone, which is probably related to the mechanical and rheological crust and upper mantle properties. The data analysis shows that a strong earthquake source may occur at a location wherein the front of seismic activity propagates with periodical changes in direction, and such a source can develop within a period that is multiple of the migration fluctuations, probably associated with the influence of external periodic factors. The main periods of migration fluctuations (2–4 years, and 9–13 years, in different ratios are present in the seismic regimes of different seismic belts. The migration rate, as well as the propagation velocity of the maximum stresses front, directly depends on the velocity of movements between the plates in the region.
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Directory of Open Access Journals (Sweden)
Katharine M. Donato
2015-02-01
Full Text Available In light of rising numbers of unaccompanied minors at the Mexico-US border in 2014, this article examines child migration from Mexico, Guatemala, El Salvador, Costa Rica, and Nicaragua. Using data from the Mexican and Latin American Migration Projects that permit us to go beyond simple descriptive analysis about children apprehended at the border, we investigate the extent to which children from these countries: (1 enter without legal authorization to do so; (2 are more likely to cross the border now than in the past; and (3 are tied to their parents’ migration. In theory, if immigration and refugee protections worked well for children and offered them legal pathways to reunify with their families, then we would expect low levels of unauthorized entry and no dramatic shifts over time. However, our examination of child migration shows that it is strongly linked to unauthorized entry, period of entry, and parents’ US experience.The findings show that the migration of children is closely linked to their parents’ migration history. Although the overall likelihood of a Mexican child making a first US trip is quite low, it is practically non-existent for children whose parents have no US experience. Thus, the increase in child migration from Central America, and the continued high levels of child migration from Mexico result from widespread migration networks and the United States’ long-standing reliance on the children’s parents as immigrant workers. The findings suggest that these children need protection in the form of family reunification and permanent legal status.
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A Life Course Approach to High-skilled Migration : Lived Experiences of Indians in the Netherlands
Kou, Anu; van Wissen, Leo; van Dijk, Jouke; Bailey, Ajay
2015-01-01
This article presents a framework which applies life course approach to high-skilled migration. By using the lens of the life course, migration behaviour is viewed not only in response to labour market triggers, but also in relation to other life domains such as education, employment and household.
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Migration from New EU Member Countries
DEFF Research Database (Denmark)
Pytlikova, Mariola
2007-01-01
The main purpose of the paper is to give predictions of the migration potential from the 7 new EU member countries to the EEA/EU-13 countries. Being able to analyze 'real' migration behavior from these particular countries over the period 1990-2000 helps me to avoid problems related to (double) o...
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The role of 'conservatism' in herring migrations
Corten, A.
2002-01-01
Herring (Clupea harengus) migrations tend to remain constant over periods of several years or even decades, despite environmental variation. When a migration pattern is changed, apparently in response to an environmental stimulus, the change in migratory behavior sometimes lasts longer than the
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Periodicity in Age-Resolved Populations
Esipov, Sergei
We discuss the interplay between the non-linear diffusion and age-resolved population dynamics. Depending on the age properties of collective migration the system may exhibit continuous joint expansion of all ages or continuous expansion with age segregation. Between these two obvious limiting regimes there is an interesting window of periodic expansion, which has been previously used by us in modeling bacterial colonies of Proteus mirabilis. In order to test whether the age-dependent collective migration leads to periodicity in other systems we performed a Fourier analysis of historical data on ethnic expansions and found multiple co-existing periods of activity.
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Low- and high-dose laser irradiation effects on cell migration and destruction
Layton, Elivia; Gallagher, Kyra A.; Zukerman, Sara; Stevens, Brianna; Zhou, Feifan; Liu, Hong; Chen, Wei R.
2018-02-01
Metastases are the cause of more than 90 percent of cancer-related deaths. Current treatment methods, including chemotherapy, radiation, and surgery, fail to target the metastases effectively. One potential treatment for metastatic cancer is laser immunotherapy (LIT). LIT combines the use of a photothermal laser with an immunoadjuvant, Glycated Chitosan (GC). GC combined with single-walled carbon nanotubes (SWNTs) has proven to be a viable alternative to traditional cancer treatment methods, when under irradiation of laser with appropriate wavelength. In this study, the effects of low dose and high dose laser irradiation on metastatic pancreatic cancer cell migration were observed. It was found that low dose irradiation increased the migration rate, but the high dose irradiation significantly decreased the migration rate of the cancer cells. When using LIT, the goal is to kill tumor cells and to prompt the correct immune response. If the tumor were irradiated with a low dose, it would promote metastasis. If the dose of irradiation were too high, it would destroy the entire tumor and the immune response would not recognize the tumor. Therefore, the laser dose plays an important role in LIT, particularly when using SWNT as light absorbing agent. Our results from this study will delineate the optimal laser irradiation dose for destroying tumor cells and at the same time preserve and release tumor antigens as a precursor of antitumor immune response.
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Rahim, Aisha
2014-01-01
Current Migration Studies literature in Europe can broadly be divided into two major strands. First is dominated by studies on the East-West migration of working class or asylum seeking, postcolonial ethnic groups and problems associated with their subsequent integration/assimilation into the host society. The second, more recent, strand of migration research is that of highly skilled professional migrants, usually hypermobile white men moving across highly-developed countries (for example wi...
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Buus, Simon; Lizondo, Maria; Hokland, Steffen; Rylander, Susanne; Pedersen, Erik M; Tanderup, Kari; Bentzen, Lise
To quantify needle migration and dosimetric impact in high-dose-rate brachytherapy for prostate cancer and propose a threshold for needle migration. Twenty-four high-risk prostate cancer patients treated with an HDR boost of 2 × 8.5 Gy were included. Patients received an MRI for planning (MRI1), before (MRI2), and after treatment (MRI3). Time from needle insertion to MRI3 was ∼3 hours. Needle migration was evaluated from coregistered images: MRI1-MRI2 and MRI1-MRI3. Dose volume histogram parameters from the treatment plan based on MRI1 were related to parameters based on needle positions in MRI2 or MRI3. Regression was used to model the average needle migration per implant and change in D90 clinical target volume, CTV prostate+3mm . The model fit was used for estimating the dosimetric impact in equivalent dose in 2 Gy fractions for dose levels of 6, 8.5, 10, 15, and 19 Gy. Needle migration was on average 2.2 ± 1.8 mm SD from MRI1-MRI2 and 5.0 ± 3.0 mm SD from MRI1-MRI3. D90 CTV prostate+3mm was robust toward average needle migration ≤3 mm, whereas for migration >3 mm D90 decreased by 4.5% per mm. A 3 mm of needle migration resulted in a decrease of 0.9, 1.7, 2.3, 4.8, and 7.6 equivalent dose in 2 Gy fractions for dose levels of 6, 8.5, 10, 15, and 19 Gy, respectively. Substantial needle migration in high-dose-rate brachytherapy occurs frequently in 1-3 hours following needle insertion. A 3-mm threshold of needle migration is proposed, but 2 mm may be considered for dose levels ≥15 Gy. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
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Japanese migration in contemporary Japan: economic segmentation and interprefectural migration.
Fukurai, H
1991-01-01
This paper examines the economic segmentation model in explaining 1985-86 Japanese interregional migration. The analysis takes advantage of statistical graphic techniques to illustrate the following substantive issues of interregional migration: (1) to examine whether economic segmentation significantly influences Japanese regional migration and (2) to explain socioeconomic characteristics of prefectures for both in- and out-migration. Analytic techniques include a latent structural equation (LISREL) methodology and statistical residual mapping. The residual dispersion patterns, for instance, suggest the extent to which socioeconomic and geopolitical variables explain migration differences by showing unique clusters of unexplained residuals. The analysis further points out that extraneous factors such as high residential land values, significant commuting populations, and regional-specific cultures and traditions need to be incorporated in the economic segmentation model in order to assess the extent of the model's reliability in explaining the pattern of interprefectural migration.
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Interregional migration in Indonesia. Macro, micro, and agent-based modelling approaches
Wajdi, N.
2017-01-01
This thesis aims to explain the dynamics of interregional migration in Indonesia in the 2000-2010 period and to project migration dynamics up to 2035. Four empirical studies presented in this thesis are interregional migration flows in Indonesia, migration and its relation to macro factors,
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Transnational Migration of Vietnamese Women in Asia | CRDI ...
International Development Research Centre (IDRC) Digital Library (Canada)
Over the last decade, Asia has witnessed rapid growth in the feminization of migration. For example, during that period, more than 100 000 Vietnamese women migrated to other countries to work and a similar ... University of Western Ontario.
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Transnational Migration of Vietnamese Women in Asia | IDRC ...
International Development Research Centre (IDRC) Digital Library (Canada)
Over the last decade, Asia has witnessed rapid growth in the feminization of migration. For example, during that period, more than 100 000 Vietnamese women migrated to other countries to work and a similar ... University of Western Ontario.
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Gender, marriage and migration : contemporary marriages between mainland China and Taiwan
Lu, Melody Chia-Wen
2008-01-01
This thesis investigates the highly complex issue of cross-border marriages between Mainland China and Taiwan in the period from early 1990 to 2004. The objectives of this research is to investigate three aspects of cross-border marriage migration: 1) factors and motivations for cross-border
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Migration strategies of Swan Geese Anser cygnoides from northeast Mongolia
Batbayar, Nyambayar; Takekawa, John Y.; Newman, Scott H.; Prosser, Diann J.; Natsagdorj, Tseveenmyadag; Xiao, Xiangming
2011-01-01
In 2006–2008, 25 Swan Geese Anser cygnoides were marked with solar-powered GPS satellite transmitters in northeast Mongolia to examine the timing and pathways of their migration. Most geese began their autumn migration in August, flying southeast toward a staging area at the Yalu River Estuary on the China-North Korea border. After staging for several weeks, the Swan Geese continued to their wintering grounds at wetlands along the Yangtze River Basin of eastern China in December. Spring migration commenced in late February, and the birds following either a same-route or loop migration to arrive at the breeding grounds in mid April. Swan Geese used a larger number of staging areas for a longer duration when they were north of 42°N latitude; they seemed to avoid staging for extended periods in the highly urbanised areas of eastern China. Further research should examine threats and disturbances to the geese in relation to human population growth and increasing urbanisation.
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EMPIRICAL REFLECTIONS ON MIGRATION PHENOMENON. MAJOR EFFECTS OF MIGRATION ON THE HUMAN CAPITAL
Directory of Open Access Journals (Sweden)
Simona BUTA
2013-12-01
Full Text Available The paper Empirical reflections on migration phenomenon. Major effects of migration on the human capital analyzes the migration flows of the workforce (as part of the human capital globally/regionally, especially the highly qualified workforce migration. The qualified manpower processes of attracting on the work market have not been always well understood and, in some cases, have generated a series of difficulties. This is the reason why we will focus on the „waste of brains” phenomenon, which appears when highly qualified individuals are neither employed in the source-country nor in the target country; and, if they are, their job is below their qualifications.
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Adverse effect of high migration stress on mental health during pregnancy: a case report.
Lecompte, Vanessa; Richard-Fortier, Zoé; Rousseau, Cécile
2017-02-01
Despite empirical evidence on the numerous consequences associated with high migration stress and mental health problems during pregnancy, a psychosocial stress assessment is rarely done, leaving it largely unaddressed. This case illustration sheds light on the common multiple risk factors related to migration stress that have to be taken into consideration when addressing perinatal mental health, and highlights the importance of obstetric appointments as a unique opportunity to assess psychosocial stress and mobilize interdisciplinary interventions.
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Migration Studies and Academic Research on International Migration Policies in Argentina
Directory of Open Access Journals (Sweden)
Eduardo Domenech
2017-05-01
Full Text Available This article approaches the historical development of the field of migratory studies in Argentina and makes a review of the academic production around the so - called "migratory policies." The systematization of these studies, historically placed on migration policies, aims to highlight some of the most significant contributions of the research during the last 30 years, to understand or explain various aspects and dimensions of the Argentinean migration policy. To achieve this, texts were selected that derived from empirical research that explicitly assume the migratory policies as the object of study, or whose themes and research problems adopt as a framework for discussion the policies and practices aimed at regulating migration and mobility in Argentina. The organization and presentation of these selected texts consider issues related to the interests and thematic concerns, disciplinary and analytical approaches, distinct periods, scales of analysis and sources of information.
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Innovative Visualizations Shed Light on Avian Nocturnal Migration
Shamoun-Baranes, J.; Farnsworth, A.; Aelterman, B.; Alves, J.A.; Azijn, K.; Bernstein, G.; Branco, S.; Desmet, P.; Dokter, A.M.; Horton, K.; Kelling, S.; Kelly, J.F.; Leijnse, H.; Rong, J.; Sheldon, D.; Van den Broeck, W.; Van Den Meersche, J.K.; Van Doren, B.M.; van Gasteren, H.
2016-01-01
Globally, billions of flying animals undergo seasonal migrations, many of which occur at night. The temporal and spatial scales at which migrations occur and our inability to directly observe these nocturnal movements makes monitoring and characterizing this critical period in migratory animals’
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Measurements of impurity migration in graphite at high temperatures using a proton microprobe
International Nuclear Information System (INIS)
Shroy, R.E.; Soo, P.; Sastre, C.A.; Schweiter, D.G.; Kraner, H.W.; Jones, K.W.
1978-01-01
The migration of fission products and other impurities through the graphite core of a High Temperature Gas Cooled Reactor is of prime importance in studies of reactor safety. Work in this area is being carried out in which graphite specimens are heated to temperatures up to 3800 0 C to induce migration of trace elements whose local concentrations are then measured with a proton microprobe. This instrument is a powerful device for such work because of its ability to determine concentrations at a part per million (ppm) level in a circular area as small as 10 μm while operating in an air environment. Studies show that Si, Ca, Cl, and Fe impurities in graphite migrate from hotter to cooler regions. Also Si, S, Cl, Ca, Fe, Mn, and Cr are observed to escape from the graphite and be deposited on cooler surfaces
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Population, migration and urbanization.
1982-06-01
Despite recent estimates that natural increase is becoming a more important component of urban growth than rural urban transfer (excess of inmigrants over outmigrants), the share of migration in the total population growth has been consistently increasing in both developed and developing countries. From a demographic perspective, the migration process involves 3 elements: an area of origin which the mover leaves and where he or she is considered an outmigrant; the destination or place of inmigration; and the period over which migration is measured. The 2 basic types of migration are internal and international. Internal migration consists of rural to urban migration, urban to urban migration, rural to rural migration, and urban to rural migration. Among these 4 types of migration various patterns or processes are followed. Migration may be direct when the migrant moves directly from the village to the city and stays there permanently. It can be circular migration, meaning that the migrant moves to the city when it is not planting season and returns to the village when he is needed on the farm. In stage migration the migrant makes a series of moves, each to a city closer to the largest or fastest growing city. Temporary migration may be 1 time or cyclical. The most dominant pattern of internal migration is rural urban. The contribution of migration to urbanization is evident. For example, the rapid urbanization and increase in urban growth from 1960-70 in the Republic of Korea can be attributed to net migration. In Asia the largest component of the population movement consists of individuals and groups moving from 1 rural location to another. Recently, because urban centers could no longer absorb the growing number of migrants from other places, there has been increased interest in the urban to rural population redistribution. This reverse migration also has come about due to slower rates of employment growth in the urban centers and improved economic opportunities
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Migrational polarization in high-current density molten salt electrochemical devices
Energy Technology Data Exchange (ETDEWEB)
Braunstein, J.; Vallet, C.E.
1977-01-01
Electrochemical flux equations based on the thermodynamics of irreversible processes have been derived in terms of experimental transport coefficients for binary molten salt mixtures analogous to those proposed for high temperature batteries and fuel cells. The equations and some numerical solutions indicate steady state composition gradients of significant magnitude. The effects of migrational separation must be considered along with other melt properties in the characterization of electrode behavior, melt composition, operating temperatures and differences of phase stability, wettability and other physicochemical properties at positive and negative electrodes of high current density devices with mixed electrolytes.
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Nuss bar migrations: occurrence and classification
International Nuclear Information System (INIS)
Binkovitz, Lauren E.; Binkovitz, Larry A.; Zendejas, Benjamin; Moir, Christopher R.
2016-01-01
Pectus excavatum results from dorsal deviation of the sternum causing narrowing of the anterior-posterior diameter of the chest. It can result in significant cosmetic deformities and cardiopulmonary compromise if severe. The Nuss procedure is a minimally invasive technique that involves placing a thin horizontally oriented metal bar below the dorsal sternal apex for correction of the pectus deformity. To identify the frequency and types of Nuss bar migrations, to present a new categorization of bar migrations, and to present examples of true migrations and pseudomigrations. We retrospectively reviewed the electronic medical records and all pertinent radiologic studies of 311 pediatric patients who underwent a Nuss procedure. We evaluated the frequency and type of bar migrations. Bar migration was demonstrated in 23 of 311 patients (7%) and occurred within a mean period of 26 days after surgery. Bar migrations were subjectively defined as deviation of the bar from the position demonstrated on the immediate postoperative radiographs and categorized as superior, inferior, rotation, lateral or flipped using a new classification system. Sixteen of the 23 migrations required re-operation. Nuss bar migration can be diagnosed with careful evaluation of serial radiographs. Nuss bar migration has a wide variety of appearances and requires exclusion of pseudomigration resulting from changes in patient positioning between radiologic examinations. (orig.)
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Nuss bar migrations: occurrence and classification
Energy Technology Data Exchange (ETDEWEB)
Binkovitz, Lauren E.; Binkovitz, Larry A. [Mayo Clinic, Department of Radiology, Rochester, MN (United States); Zendejas, Benjamin; Moir, Christopher R. [Mayo Clinic, Department of Surgery, Rochester, MN (United States)
2016-12-15
Pectus excavatum results from dorsal deviation of the sternum causing narrowing of the anterior-posterior diameter of the chest. It can result in significant cosmetic deformities and cardiopulmonary compromise if severe. The Nuss procedure is a minimally invasive technique that involves placing a thin horizontally oriented metal bar below the dorsal sternal apex for correction of the pectus deformity. To identify the frequency and types of Nuss bar migrations, to present a new categorization of bar migrations, and to present examples of true migrations and pseudomigrations. We retrospectively reviewed the electronic medical records and all pertinent radiologic studies of 311 pediatric patients who underwent a Nuss procedure. We evaluated the frequency and type of bar migrations. Bar migration was demonstrated in 23 of 311 patients (7%) and occurred within a mean period of 26 days after surgery. Bar migrations were subjectively defined as deviation of the bar from the position demonstrated on the immediate postoperative radiographs and categorized as superior, inferior, rotation, lateral or flipped using a new classification system. Sixteen of the 23 migrations required re-operation. Nuss bar migration can be diagnosed with careful evaluation of serial radiographs. Nuss bar migration has a wide variety of appearances and requires exclusion of pseudomigration resulting from changes in patient positioning between radiologic examinations. (orig.)
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de Haas, Hein; Fokkema, Tineke; Fihri, Mohamed Fassi
Different migration theories generate competing hypotheses with regard to determinants of return migration. While neoclassical migration theory associates migration to the failure to integrate at the destination, the new economics of labour migration sees return migration as the logical stage after migrants have earned sufficient assets and knowledge and to invest in their origin countries. The projected return is then likely to be postponed for sustained or indefinite periods if integration is unsuccessful. So, from an indication or result of integration failure return is rather seen as a measure of success. Drawing on recent survey data ( N = 2,832), this article tests these hypotheses by examining the main determinants of return intention among Moroccan migrants across Europe. The results indicate that structural integration through labour market participation, education and the maintenance of economic and social ties with receiving countries do not significantly affect return intentions. At the same time, investments and social ties to Morocco are positively related, and socio-cultural integration in receiving countries is negatively related to return migration intentions. The mixed results corroborate the idea that there is no uniform process of (return) migration and that competing theories might therefore be partly complementary.
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A STUDY ON THE INTERNAL MIGRATION FLOWS IN TURKEY: LOWRY HYPOTHESIS
Directory of Open Access Journals (Sweden)
FERHAT TOPBAŞ
2013-06-01
Full Text Available The purpose of this study is to re-examine Lowry hypothesis that were examined for Turkey in period of 1965–1980 by Gedik (1992 and period of 1985–1990 by Yamak and Küçükkale (2001 by using The Census of Population 1975, 1980, 1985, 1990 and 2000 in Turkey. For this reason, the relationships between in-migration and out-migration and net migration have investigated with population size, net migration rate and per capita income factors. Analysis that involve in all provinces called general model is not considered in social, economic and urban development factors. In addition, estimated restriction models that are considered urban development are involved population, net migration rate and per capita income factors. In conclusion we have exposed comparatively relationship between internal migration flows and urban development frame of estimated models.
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Analysis of Migration Flows of the Population of the Vologda Oblast Districts
Directory of Open Access Journals (Sweden)
Mikhail Mikhailovich Panov
2015-09-01
Full Text Available The article presents the research on the main directions and scale of migration in municipal districts of the Vologda Oblast and considers the main types of migration and the specifics of their statistical accounting. The data by Rosstat served as a basis upon which a general analysis of migration dynamics in the Vologda Oblast districts was carried out; and the article presents its periodization. Three main periods are defined: the “migration shock” of 1991–1999 after the collapse of the Soviet Union, the migration stability of 2000–2008 and the post-crisis rural out-migration that began in 2009 and is increasing year by year. At the same time, gross migration indicators have shown high sensitivity to significant socioeconomic change, in particular, to the economic crises of 1999 and 2008. The article describes the main age and gender characteristics of migrants, it has been determined that the most active migrants are girls aged 15–29, who move from rural to urban settlements. In general, it is the young people aged 15–34 who are most likely to migrate. The author has found out that most of the Vologda Oblast districts are characterized by a higher outflow of the population, which is in some places restrained by a relative migration attractiveness of a number of areas. The author has found out that most districts of the Oblast are characterized by a higher outflow of the population, which is sometimes restrained by relative migration attractiveness of some areas. The author highlights the region’s territories with the highest migration attraction; in the long run they can play the role of “growth points” in the region; these territories comprise Velikoustyugsky and Chagodoshchensky districts, as well as several districts of the central part of the Vologda Oblast – Ust-Kubinsky and Vologodsky. The author also points out the territories that suffered the most from out-migration: Kichmengsko-Gorodetsky, Vashkinsky
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Kenyon, Patricia M.
1993-01-01
Trace element concentrations and isotopic ratios are frequently used to study the behavior of high-temperature fluids in both metamorphic and igneous systems. Many theoretical formulations of the effects of fluid migration on trace elements have assumed instantaneous reequilibration between the migrating fluid and the solid material through which it is passing. This paper investigates the additional effects which arise when equilibration is not instantaneous due to a limited rate of diffusion in the solid, using an analytical steady state solution to a set of partial differential equations describing the exchange of trace elements between the fluid and the solid during the migration of the fluid.
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A probe into reasons for international migration in Fujian Province.
Zhu, G
1990-01-01
In this paper, the author discusses the extent of international migration from China's Fujian Province and considers the reasons behind the migration. The most recent estimates place China's overseas population at 22.1 million, 19 million (88%) of which are concentrated in Southeast Asia. According to the author's calculations, at least 7 million of the Chinese overseas population are of Fujian descent. Indonesia alone holds some 3.3 million Fujianese. Malaysia, Singapore, and the Philippines account for most of the remaining Fujianese overseas population. Having established the extent of international migration from the Fujian Province, the author attempts to establish the reasons behind it. The author first considers the historical origins of Fujianese international migration, from its early states (end century B.C.-17th century) to modern times *18-early 20th century) to the current period (1949-present). The author then examines the reasons behind the migration, primarily the social environment and individual behavior. Finally, the author provides categories of international migration, stressing that these categories often overlap or coincide. Most of the early migration was "spontaneous" -- essentially, an unplanned occurrence. During the modern period, most migration was "forced" by the contract labor system instituted by colonialists. Political and social upheaval also prompted "provoked" international migration. And following the Chinese Revolution, "free" migration allowed many to return home or to join relative abroad.
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Directory of Open Access Journals (Sweden)
Valentina Bizzarro
Full Text Available Deficient wound healing in diabetic patients is very frequent, but the cellular and molecular causes are poorly defined. In this study, we have evaluated whether Annexin A1 derived peptide Ac2-26 stimulates fibroblast migration in high glucose conditions. Using normal human skin fibroblasts WS1 in low glucose (LG or high glucose (HG we observed the enrichment of Annexin A1 protein at cell movement structures like lamellipodial extrusions and interestingly, a significant decrease in levels of the protein in HG conditions. The analysis of the translocation of Annexin A1 to cell membrane showed lower levels of Annexin A1 in both membrane pool and supernatants of WS1 cells treated with HG. Wound-healing assays using cell line transfected with Annexin A1 siRNAs indicated a slowing down in migration speed of cells suggesting that Annexin A1 has a role in the migration of WS1 cells. In order to analyze the role of extracellular Annexin A1 in cell migration, we have performed wound-healing assays using Ac2-26 showing that peptide was able to increase fibroblast cell migration in HG conditions. Experiments on the mobilization of intracellular calcium and analysis of p-ERK expression confirmed the activity of the FPR1 following stimulation with the peptide Ac2-26. A wound-healing assay on WS1 cells in the presence of the FPR agonist fMLP, of the FPR antagonist CsH and in the presence of Ac2-26 indicated that Annexin A1 influences fibroblast cell migration under HG conditions acting through FPR receptors whose expression was slightly increased in HG. In conclusion, these data demonstrate that (i Annexin A1 is involved in migration of WS1 cells, through interaction with FPRs; (ii N- terminal peptide of Annexin A1 Ac2-26 is able to stimulate direct migration of WS1 cells in high glucose treatment possibly due to the increased receptor expression observed in hyperglycemia conditions.
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Metropolitan migration and population growth in selected developing countries.
1983-01-01
The purpose of this article is to estimate the components of metropolitan population growth in selected developing countries during 1960-1970 period. The study examines population growth in 26 cities: 5 are in Africa, 8 in Asia, and 13 in Latin America, using data from national census publications. These cities in general are the political capitals of their countries, but some additional large cities were selected in Brazil, Mexico, and South Africa. All cities, at the beginning of the 1960-1970 decade had over 500,000 population; Accra, the only exception, reached this population level during the 1960s. Some cities had over 4 million residents in 1970. Net migration contributed about 37% to total metropolitan population growth; the remainder of the growth is attributable to natural increase. Migration has a much stronger impact on metropolitan growth than suggested by the above figure: 1) Several metropolitan areas, for various reasons, are unlikely to receive many migrants; without those cities, the share of metropolitan growth from net migration is 44%. 2) Estimates of the natural increase of migrants after their arrival in the metropolitan areas, when added to migration itself, changes the total contribution of migration to 49% in some metropolitan areas. 3) Even where net migration contributes a smaller proportion to metropolitan growth than natural increase, the rates of net migration are generally high and should be viewed in the context of rapid metropolitan population growth from natural increase alone. Finally, the paper also compares the components of metropolitan growth with the components of growth in the remaining urban areas. The results show that the metropolitan areas, in general, grow faster than the remaining urban areas, and that this more rapid growth is mostly due to a higher rate of net migration. Given the significance of migration for metropolitan growth, further investigations of the effects of these migration streams, particularly with
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Capturing the age and spatial structures of migration
Rogers, A; Raymer, J; Willekens, F
In this paper we model the structures found in the level (generation) and allocation (distribution) components of age-specific and origin-destination-specific migration flows. For the examples, we examine the regional migration patterns in the USA for four periods: 1955-60, 1965-70, 1975-80, and
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RSA migration of total knee replacements.
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.
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Circadian flight schedules in night-migrating birds caught on migration.
Coppack, Timothy; Becker, Simon F; Becker, Philipp J J
2008-12-23
Many species of migratory birds migrate in a series of solitary nocturnal flights. Between flights, they stop to rest and refuel for the next segment of their journey. The mechanism controlling this behaviour has long remained elusive. Here, we show that wild-caught migratory redstarts (Phoenicurus phoenicurus) are consistent in their flight scheduling. An advanced videographic system enabled us to determine the precise timing of flight activity in redstarts caught at a northern European stopover site during their return trip from Africa. Birds were held captive for three days in the absence of photoperiodic cues (constant dim light) and under permanent food availability. Despite the absence of external temporal cues, birds showed clear bimodal activity patterns: intense nocturnal activity alternating with diurnal foraging and resting periods. The onset of their migratory activity coincided with the time of local sunset and was individually consistent on consecutive nights. The data demonstrate that night-migrating birds are driven by autonomous circadian clocks entrained by sunset cues. This timekeeping system is probably the key factor in the overall control of nocturnal songbird migration.
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Migration and Extension of Solar Active Longitudinal Zones
Gyenge, N.; Baranyi, T.; Ludmány, A.
2014-02-01
Solar active longitudes show a characteristic migration pattern in the Carrington coordinate system if they can be identified at all. By following this migration, the longitudinal activity distribution around the center of the band can be determined. The half-width of the distribution is found to be varying in Cycles 21 - 23, and in some time intervals it was as narrow as 20 - 30 degrees. It was more extended around a maximum but it was also narrow when the activity jumped to the opposite longitude. Flux emergence exhibited a quasi-periodic variation within the active zone with a period of about 1.3 years. The path of the active-longitude migration does not support the view that it might be associated with the 11-year solar cycle. These results were obtained for a limited time interval of a few solar cycles and, bearing in mind uncertainties of the migration-path definition, are only indicative. For the major fraction of the dataset no systematic active longitudes were found. Sporadic migration of active longitudes was identified only for Cycles 21 - 22 in the northern hemisphere and Cycle 23 in the southern hemisphere.
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Emergent patterns of collective cell migration under tubular confinement.
Xi, Wang; Sonam, Surabhi; Beng Saw, Thuan; Ladoux, Benoit; Teck Lim, Chwee
2017-11-15
Collective epithelial behaviors are essential for the development of lumens in organs. However, conventional assays of planar systems fail to replicate cell cohorts of tubular structures that advance in concerted ways on out-of-plane curved and confined surfaces, such as ductal elongation in vivo. Here, we mimic such coordinated tissue migration by forming lumens of epithelial cell sheets inside microtubes of 1-10 cell lengths in diameter. We show that these cell tubes reproduce the physiological apical-basal polarity, and have actin alignment, cell orientation, tissue organization, and migration modes that depend on the extent of tubular confinement and/or curvature. In contrast to flat constraint, the cell sheets in a highly constricted smaller microtube demonstrate slow motion with periodic relaxation, but fast overall movement in large microtubes. Altogether, our findings provide insights into the emerging migratory modes for epithelial migration and growth under tubular confinement, which are reminiscent of the in vivo scenario.
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Migration of ThO2 kernels under the influence of a temperature gradient
International Nuclear Information System (INIS)
Smith, C.L.
1976-11-01
BISO coated ThO 2 fertile fuel kernels will migrate up the thermal gradients imposed across coated particles during HTGR operation. Thorium dioxide kernel migration has been studied as a function of temperature (1300 to 1700 0 C) and ThO 2 kernel burnup (0.9 to 5.8 percent FIMA) in out-of-pile, postirradiation thermal gradient heating experiments. The studies were conducted to obtain descriptions of migration rates that will be used in core design studies to evaluate the impact of ThO 2 migration on fertile fuel performance in an operating HTGR and to define characteristics needed by any comprehensive model describing ThO 2 kernel migration. The kinetics data generated in these postirradiation studies are consistent with in-pile data collected by investigators at Oak Ridge National Laboratory, which supports use of the more precise postirradiation heating results in HTGR core design studies. Observations of intergranular carbon deposits on the cool side of migrating kernels support the assumption that the kinetics of kernel migration are controlled by solid state diffusion within irradiated ThO 2 kernels. The migration is characterized by a period of no migration (incubation period) followed by migration at the equilibrium rate for ThO 2 . The incubation period decreases with increasing temperature and kernel burnup. The improved understanding of the kinetics of ThO 2 kernel migration provided by this work will contribute to an optimization of HTGR core design and an increased confidence in fuel performance predictions
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The migration function and the Todaro paradox.
Takagi, Y
1984-05-01
"The purpose of this paper is to present a microeconomic foundation of the migration function and to discuss the impact of an increase in the job creation rate on migration and urban unemployment. Each rural worker must estimate his expected urban income on the basis of his own expected numbers of both newly created jobs and migrants during the coming period. Workers whose expected urban income is greater than the rural one decide to migrate, while those who estimate smaller urban income stay on." The geographical focus is on developing countries. excerpt
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International Elderly Migration in Hungary
Directory of Open Access Journals (Sweden)
Sándor Illés
2006-06-01
Full Text Available The paper examines international elderly migration (IEM related to Hungary. Little effort has been made to investigate this increasingly important element of human migration in Central and Eastern Europe. The general objective of this study is to contribute to filling this gap. IEM is investigated using register-based data on migration flows, stocks and citizenship statistics. The analysis focuses on the time series but the paper also considers the historical context and the recent patterns of IEM. The aim of the research was fourfold. Firstly, we tried to establish when IEM related to Hungary began. Secondly, we detected the accelerating character of this phenomenon. Thirdly, we were able to identify the main macrofactors influencing the level of IEM. Fourthly, the main result of the study was that it allowed exploration of a Hungarian peculiarity. “Pension seeking” is one very distinctive feature of IEM and is in many ways a legacy of the state socialism period. Therefore, its emergence on such a large scale is the result of the transformation period. We suppose that pension-hunting type migration will be temporary in nature. Conclusions about the motivational structure of IEM are discussed with reference to policy implications in the light of the ageing population structure in Hungary.
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Migration characteristics of cobalt-60 through sandy soil in high pH solution
International Nuclear Information System (INIS)
Ohnuki, Toshihiko
1992-01-01
Migration characteristics of 60 Co through sandy soil in high pH solution has been investigated by both column and batch techniques. The association of 60 Co with the sandy soil and its components were studied by sequential extraction techniques. The concentration profile of 60 Co in the sandy soil column was composed of two exponential curves showing that 60 Co would consist of immobile and mobile fractions. The immobile 60 Co was retained by the sandy soil and was distributed near the top. Though the mobile 60 Co was little sorbed by soil and migrated through the soil column, maximum concentration of 60 Co in the effluents decreased slightly with increasing path length of the soil column. The sequential extraction of 60 Co from the sandy soil and from its components showed that 60 Co was sorbed by both manganese oxide and clay minerals. And manganese oxide is one of the responsible soil components for the observed decrease in the maximum concentration of 60 Co in the effluents. Although the content of manganese oxide in the sandy soil was 0.13%, manganese oxide is the important component to prevent from the migration of 60 Co in the high pH solution. (author)
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Inclusive growth?: Labour migration and poverty in India
Haan, Arjan
2011-01-01
textabstractThis paper discusses the relationship between labour migration and poverty in India. This is placed against the on-going debates on changes in patterns of employment and job creation in India, during the periods of economic liberalization, under the Inclusive Growth policies since 2004, and under the impact of the global financial crisis, and growing inequalities. The paper focuses on the migration patterns of deprived social groups, analyse whether migration form a routes out of ...
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Do American dippers obtain a survival benefit from altitudinal migration?
Green, David J; Whitehorne, Ivy B J; Middleton, Holly A; Morrissey, Christy A
2015-01-01
Studies of partial migrants provide an opportunity to assess the cost and benefits of migration. Previous work has demonstrated that sedentary American dippers (residents) have higher annual productivity than altitudinal migrants that move to higher elevations to breed. Here we use a ten-year (30 period) mark-recapture dataset to evaluate whether migrants offset their lower productivity with higher survival during the migration-breeding period when they occupy different habitat, or early and late-winter periods when they coexist with residents. Mark-recapture models provide no evidence that apparent monthly survival of migrants is higher than that of residents at any time of the year. The best-supported model suggests that monthly survival is higher in the migration-breeding period than winter periods. Another well-supported model suggested that residency conferred a survival benefit, and annual apparent survival (calculated from model weighted monthly apparent survival estimates using the Delta method) of residents (0.511 ± 0.038SE) was slightly higher than that of migrants (0.487 ± 0.032). Winter survival of American dippers was influenced by environmental conditions; monthly apparent survival increased as maximum daily flow rates increased and declined as winter temperatures became colder. However, we found no evidence that environmental conditions altered differences in winter survival of residents and migrants. Since migratory American dippers have lower productivity and slightly lower survival than residents our data suggests that partial migration is likely an outcome of competition for limited nest sites at low elevations, with less competitive individuals being forced to migrate to higher elevations in order to breed.
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Directory of Open Access Journals (Sweden)
Ji Young Oh
2018-04-01
Full Text Available Background/Aims: Glucose plays an important role in stem cell fate determination and behaviors. However, it is still not known how glucose contributes to the precise molecular mechanisms responsible for stem cell migration. Thus, we investigate the effect of glucose on the regulation of the human umbilical cord blood-derived mesenchymal stem cell (hUCB-MSC migration, and analyze the mechanism accompanied by this effect. Methods: Western blot analysis, wound healing migration assays, immunoprecipitation, and chromatin immunoprecipitation assay were performed to investigate the effect of high glucose on hUCB-MSC migration. Additionally, hUCB-MSC transplantation was performed in the mouse excisional wound splinting model. Results: High concentration glucose (25 mM elicits hUCB-MSC migration compared to normal glucose and high glucose-pretreated hUCB-MSC transplantation into the wound sites in mice also accelerates skin wound repair. We therefore elucidated the detailed mechanisms how high glucose induces hUCB-MSC migration. We showed that high glucose regulates E-cadherin repression through increased Snail and EZH2 expressions. And, we found high glucose-induced reactive oxygen species (ROS promotes two signaling; JNK which regulates γ–secretase leading to the cleavage of Notch proteins and PI3K/Akt signaling which enhances GSK-3β phosphorylation. High glucose-mediated JNK/Notch pathway regulates the expression of EZH2, and PI3K/Akt/GSK-3β pathway stimulates Snail stabilization, respectively. High glucose enhances the formation of EZH2/Snail/HDAC1 complex in the nucleus, which in turn causes E-cadherin repression. Conclusion: This study reveals that high glucose-induced ROS stimulates the migration of hUCB-MSC through E-cadherin repression via Snail and EZH2 signaling pathways.
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Cohort Measures of Internal Migration: Understanding Long-Term Trends.
Bernard, Aude
2017-12-01
Internal migration intensities fluctuate over time, but both migration levels and trends show great diversity. The dynamics underpinning these trends remain poorly understood because they are analyzed almost exclusively by applying period measures to cross-sectional data. This article proposes 10 cohort measures that can be applied to both prospective and retrospective data to systematically examine long-term trends. To demonstrate their benefits, the proposed measures are applied to retrospective survey data for England that provide residential histories from birth to age 50 for cohorts born between 1918 and 1957. The analysis reveals stable lifetime migration for men but increased lifetime migration for women associated with earlier ages at moving in adulthood and a compression of intervals between consecutive moves. The proposed cohort measures provide a more comprehensive picture of migration behavior and should be used to complement period measures in exploring long-term trends. Increasing availability of retrospective and longitudinal survey data means that researchers can now apply the proposed measures to a wide range of countries.
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Burn-Up Determination by High Resolution Gamma Spectrometry: Fission Product Migration Studies
Energy Technology Data Exchange (ETDEWEB)
Forsyth, R S; Blackadder, W H; Ronqvist, N
1967-04-15
The migration of solid fission products, in particular caesium and ruthenium, in high temperature oxide fuel can create a severe problem during the application of non-destructive burn-up methods employing gamma spectrometry, since caesium-137 is otherwise the most convenient long-lived burn-up monitor and ruthenium-106 can be used to distinguish between fissions in U-235 and Pu-239. As part of an experimental programme to develop burn-up methods, gamma scanning experiments have been performed on slices of irradiated UO{sub 2} pellets using a lithium-drifted germanium detector. The usefulness of the technique for migration studies has been demonstrated by comparing the fission product distribution curves across the specimen diameters with the microstructure of the specimens after polishing and etching.
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International Nuclear Information System (INIS)
Soares, Eufemia Paez; Saiki, Mitiko; Wiebeck, Helio
2005-01-01
In the present study a radiometric method was established to determine the migration of elements from food plastic packagings to a simulated acetic acid solution. This radiometric method consisted of irradiating plastic samples with neutrons at IEA-R1 nuclear reactor for a period of 16 hours under a neutron flux of 10 12 n cm -2 s -1 and, then to expose them to the element migration into a simulated solution. The radioactivity of the activated elements transferred to the solutions was measured to evaluate the migration. The experimental conditions were: time of exposure of 10 days at 40 deg C and 3% acetic acid solution was used as simulated solution, according to the procedure established by the National Agency of Sanitary Monitoring (ANVISA). The migration study was applied for plastic samples from soft drink and juice packagings. The results obtained indicated the migration of elements Co, Cr and Sb. The advantage of this methodology was no need to analyse the blank of simulantes, as well as the use of high purity simulated solutions. Besides, the method allows to evaluate the migration of the elements into the food content instead of simulated solution. The detention limits indicated high sensitivity of the radiometric method. (author)
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[The foundation of international migration policies in Latin America].
Marmora, L
1988-12-01
A government's international migration policies are intended to influence the size, composition, direction, destination, or integration of international migratory flows. The justification for migratory policies has been based on a series of themes that have had varied weights in different stages of Latin American history. Migrations as population settlement, the desired or undesired characteristics of migrants, the economic impact of migration, the role of migration in relations between countries, and the ethical dimensions of migratory movement have been the major policy issues. The 1st migration policies in Latin America saw international migration as a means of settling the colonies. After independence, migratory policies oriented toward massive settlement became common. Although the stated goals were to settle entire territories with immigrants, the usual result was to absorb immigrants in certain economic sectors with high demand for labor. In the colonial period both Spain and Portugal attempted to restrict immigration to the Catholic segment of their own populations. After independence, the criteria were liberalized somewhat but still reflected prejudices about the racial superiority of certain types of European immigration. The selection principals which appeared most clearly during the 19th century were overwhelmed to the extent that immigration was tranformed into provision of labor to meet unsatisfied needs for workers. Indiscriminate admissions and recourse to nontraditional elements such as Chinese and Japanese was strongest in countries needing labor for tropical agriculture or extractive industries. The economic argument that migration contributed to development was widespread economic argument that migration contributed to development was widespread in the 19th and early 20th centuries, but new rules were made to restrict immigration to protect local labor markets during the worldwide depression of the 1930s. In recent decades, migration policies
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Determinants of International Migration: The Nigerian Experience
Directory of Open Access Journals (Sweden)
Samuel Antwi Darkwah
2014-01-01
Full Text Available This paper examines some determinants of international migration in Nigeria using annual time series data spanning the period 1991–2011. Using ordinary least square regression method, the results indicate that the level of unemployment, migrants’ remittances and population growth are the key determinants of emigration from Nigeria to other countries, statistically significant at 0.01 level.In a country where unemployment rate is very high, this movement is likely to help in reducing pressures on the labour market. Migrants’ remittances might also help in alleviating poverty within households. Migrants’ remittance to Nigeria has surpassed both Foreign Direct Investment and Net Official Development Assistance inflows, making it one amongst the major sources of foreign earnings to Nigeria. Nigerians will continue to migrate to other parts of the world so long as the reasons or causes for their movement are not fully addressed i.e. if political and socioeconomic issues in the country do not improve. The Nigerian government should as a matter of urgency, create better jobs and conducive environment in order to stop people from migrating while at the same time encouraging its skilled labour abroad to return home to help in national development.
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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.
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DEFF Research Database (Denmark)
Olwig, Karen Fog
2015-01-01
a strong sense of agency and self-empowerment. In the post-WWII period, numerous Caribbean women trained in nursing at British hospitals that have been described as marred by race and gender related inequality and associated forms of exploitation. Yet, the nurses interviewed about this training emphasised......Youths from the Global South migrating for further education often face various forms of discrimination. This Caribbean case study discusses how conditions in the home country can provide a foundation for educational migration that helps the migrants overcome such obstacles and even develop...... in which it enabled these Caribbean women to stake out a new life for themselves....
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International Nuclear Information System (INIS)
Postma, R.W.
1991-01-01
Two lines form the southern North Sea, with known velocity inhomogeneities in the overburden, have been pre-stack depth migrated. The pre-stack depth migrations are compared with conventional processing, one with severe distortions and one with subtle distortions on the conventionally processed sections. The line with subtle distortions is also compared with post-stack depth migration. The results on both lines were very successful. Both have already influenced drilling decisions, and have caused a modification of structural interpretation in the respective areas. Wells have been drilled on each of the lines, and well tops confirm the results. In fact, conventional processing led to incorrect locations for the wells, both of which were dry holes. The depth migrated sections indicate the incorrect placement, and on one line reveals a much better drilling location. This paper reports that even though processing costs are high for pre-stack depth migration, appropriate use can save millions of dollars in dry-hole expense
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Centrifuge modelling - migration of radionuclides from engineered trenches
International Nuclear Information System (INIS)
Dean, E.T.R.; Schofield, A.N.
1991-12-01
This report provides an overview of some centrifuge small-scale physical model tests and 1g experimental and theoretical work relating to the sub-surface migration of a model pollutant (sodium chloride) from a notional prototype surface landfill of width 25 metres and depth 3 metres cut into a 20 metre deep layer of nominally uniform soil overlying a more permeable base layer. An introduction is given to the application of geotechnical centrifuge modelling techniques to pollutant migration studies. Experiments performed at 1/100th scale using the Cambridge 10 metre diameter Geotechnical Beam Centrifuge simulating transport through silt over prototype time periods of around 35 years, are summarised. Comparisons of data with calculations using early versions of the POLLUTE and MIGRATE computer codes are presented. An experiment at 1/400th scale using the new Cambridge Geotechnical Drum Centrifuge, involving transport through clay over a prototype time period of around 1000 years, is described. Potential future uses of centrifuge modelling techniques to simulate long-term migration through more complex hydrological environments are also discussed. (author)
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Do American dippers obtain a survival benefit from altitudinal migration?
Directory of Open Access Journals (Sweden)
David J Green
Full Text Available Studies of partial migrants provide an opportunity to assess the cost and benefits of migration. Previous work has demonstrated that sedentary American dippers (residents have higher annual productivity than altitudinal migrants that move to higher elevations to breed. Here we use a ten-year (30 period mark-recapture dataset to evaluate whether migrants offset their lower productivity with higher survival during the migration-breeding period when they occupy different habitat, or early and late-winter periods when they coexist with residents. Mark-recapture models provide no evidence that apparent monthly survival of migrants is higher than that of residents at any time of the year. The best-supported model suggests that monthly survival is higher in the migration-breeding period than winter periods. Another well-supported model suggested that residency conferred a survival benefit, and annual apparent survival (calculated from model weighted monthly apparent survival estimates using the Delta method of residents (0.511 ± 0.038SE was slightly higher than that of migrants (0.487 ± 0.032. Winter survival of American dippers was influenced by environmental conditions; monthly apparent survival increased as maximum daily flow rates increased and declined as winter temperatures became colder. However, we found no evidence that environmental conditions altered differences in winter survival of residents and migrants. Since migratory American dippers have lower productivity and slightly lower survival than residents our data suggests that partial migration is likely an outcome of competition for limited nest sites at low elevations, with less competitive individuals being forced to migrate to higher elevations in order to breed.
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Kane, H
1995-01-01
During the 1990s investment in prevention of international or internal migration declined, and crisis intervention increased. The budgets of the UN High Commissioner for Refugees and the UN Development Program remained about the same. The operating assumption is that war, persecution, famine, and environmental and social disintegration are inevitable. Future efforts should be directed to stabilizing populations through investment in sanitation, public health, preventive medicine, land tenure, environmental protection, and literacy. Forces pushing migration are likely to increase in the future. Forces include depletion of natural resources, income disparities, population pressure, and political disruption. The causes of migration are not constant. In the past, migration occurred during conquests, settlement, intermarriage, or religious conversion and was a collective movement. Current migration involves mass movement of individuals and the struggle to survive. There is new pressure to leave poor squatter settlements and the scarcities in land, water, and food. The slave trade between the 1500s and the 1800s linked continents, and only 2-3 million voluntarily crossed national borders. Involuntary migration began in the early 1800s when European feudal systems were in a decline, and people sought freedom. Official refugees, who satisfy the strict 1951 UN definition, increased from 15 million in 1980 to 23 million in 1990 but remained a small proportion of international migrants. Much of the mass movement occurs between developing countries. Migration to developed countries is accompanied by growing intolerance, which is misinformed. China practices a form of "population transfer" in Tibet in order to dilute Tibetan nationalism. Colonization of countries is a new less expensive form of control over territory. Eviction of minorities is another popular strategy in Iraq. Public works projects supported by foreign aid displace millions annually. War and civil conflicts
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Challenging issues in the study of fiscally-induced migration.
Winer, S L
1986-01-01
This paper reviews Shaw's book, INTERMETROPOLITAN MIGRATION IN CANADA, which provides new evidence concerning the link between fiscal structure and internal migration. Shaw bases his work on a valuable new migration series he has put together from census data: intermetropolitan flows from 1956-1981. The existence of censua data at 5-year intervals permits Shaw enough data to estimate migration equations separately for the periods before and after 1971. A comparison of the role of fiscal variables before and after 1971 is interesting because unemployment insurance, equalization payments, and provincial natural resource revenues probably became more important in determining regional differences in incomes after 1971 than in the 20 years prior to that. Shaw suspects that migration behavior has become less sensitive to traditional market variables such as wage differentials and more sensitive to other factors, including quality of life indicators since 1950. The author thinks that Shaw's conclusion cannot rest comfortably on estimating equations that omit fiscal variables. The overall role of wage differentials in determining observed migration patterns is the product of the coefficient on wage variables and the actual evolution of wages over the estimation period. Another problem with the methodology used to contrast pre- and post-1971 migration equations is the apparent neglect of statistical testing for shifts in coefficients on the traditional economic variables and for shifts in the coefficients on the fiscal variables. The strongest of the useful results from the study concern the role of unemployment insurance. The evidence that these have an influence on internal migration is now compelling. Shaw's book adds substantial weight to the view that variation in fiscal structure plays a significant role in determining internal migration patterns.
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Geochemical Processes Controlling Migration of High Level Wastes in Hanford's Vadose Zone
International Nuclear Information System (INIS)
Zachara, John M.; Serne, R. Jeffrey; Freshley, Mark D.; Mann, Frederick M.; Anderson, Frank J.; Wood, Marcus I.; Jones, Thomas E.; Myers, David A.
2007-01-01
High level nuclear wastes (HLW) from Hanford's plutonium reprocessing are stored in massive, buried, single-shell tanks in eighteen tank farms. The wastes were initially hot because of radioactive decay, and many exhibited extreme chemical character in terms of pH, salinity, and radionuclide concentration. At present, 67 of the 149 single shell tanks are suspected to have released over 1.9 million L of tank waste to the vadose zone, with most leak events occurring between 1950 and 1975. Boreholes have been placed through the largest vadose zone plumes to define the extent of contaminant migration, and to develop conceptual models of processes governing the transformation, retardation, and overall transport of tank waste residuals. Laboratory studies with sediments so collected have shown that ion exchange, precipitation and dissolution, and surface complexation reactions have occurred between the HLW and subsurface sediments moderating their chemical character, and retarding the migration of select contaminants. Processes suspected to facilitate the far-field migration of immobile radionuclides including stable aqueous complex formation and mobile colloids were found to be potentially operative, but unlikely to occur in the field, with the exception of cyanide-facilitated migration of 60Co. Fission product oxyanions are the most mobile of tank waste constituents because their adsorption is suppressed by large concentrations of waste anions; the vadose zone clay fraction is negative in surface charge; and, unlike Cr, their reduced forms are unstable in oxidizing environments. Reaction/process-based transport modeling is beginning to be used for predictions of future contaminant mobility and plume evolution
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Y chromosome evidence for Anglo-Saxon mass migration.
Weale, Michael E; Weiss, Deborah A; Jager, Rolf F; Bradman, Neil; Thomas, Mark G
2002-07-01
British history contains several periods of major cultural change. It remains controversial as to how much these periods coincided with substantial immigration from continental Europe, even for those that occurred most recently. In this study, we examine genetic data for evidence of male immigration at particular times into Central England and North Wales. To do this, we used 12 biallelic polymorphisms and six microsatellite markers to define high-resolution Y chromosome haplotypes in a sample of 313 males from seven towns located along an east-west transect from East Anglia to North Wales. The Central English towns were genetically very similar, whereas the two North Welsh towns differed significantly both from each other and from the Central English towns. When we compared our data with an additional 177 samples collected in Friesland and Norway, we found that the Central English and Frisian samples were statistically indistinguishable. Using novel population genetic models that incorporate both mass migration and continuous gene flow, we conclude that these striking patterns are best explained by a substantial migration of Anglo-Saxon Y chromosomes into Central England (contributing 50%-100% to the gene pool at that time) but not into North Wales.
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Second-Generation Outcomes of the Great Migration.
Alexander, J Trent; Leibbrand, Christine; Massey, Catherine; Tolnay, Stewart
2017-12-01
The mass migration of African Americans out of the South during the first two-thirds of the twentieth century represents one of the most significant internal migration flows in U.S. Those undertaking the Great Migration left the South in search of a better life, and their move transformed the cultural, social, and political dynamics of African American life specifically and U.S. society more generally. Recent research offers conflicting evidence regarding the migrants' success in translating their geographic mobility into economic mobility. Due in part to the lack of a large body of longitudinal data, almost all studies of the Great Migration have focused on the migrants themselves, usually over short periods of their working lives. Using longitudinally linked census data, we take a broader view, investigating the long-term economic and social effects of the Great Migration on the migrants' children. Our results reveal modest but statistically significant advantages in education, income, and poverty status for the African American children of the Great Migration relative to the children of southerners who remained in the South. In contrast, second-generation white migrants experienced few benefits from migrating relative to southern or northern stayers.
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Flexibility of continental navigation and migration in European mallards
DEFF Research Database (Denmark)
van Toor, Mariëlle L.; Hedenström, Anders; Waldenström, Jonas
2013-01-01
The ontogeny of continent-wide navigation mechanisms of the individual organism, despite being crucial for the understanding of animal movement and migration, is still poorly understood. Several previous studies, mainly conducted on passerines, indicate that inexperienced, juvenile birds may...... abilities. Here we tested whether immature mallard ducks correct for latitudinal displacement during fall migration within Europe. During two consecutive fall migration periods, we caught immature females on a stopover site in southeast Sweden, and translocated a group of them ca. 1,000 km to southern...... Germany. We followed the movements of the ducks via satellite GPS-tracking and observed their migration decisions during the fall and consecutive spring migration. The control animals released in Ottenby behaved as expected from banding recoveries: they continued migration during the winter and in spring...
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Migration, urban population growth and regional disparity in China
Renard, Mary-Françoise; Xu, Zelai; Zhu, Nong
2011-01-01
The main objective of this paper is to study the determinants of city population growth in China during the 1990s', as well as the determinants of migrations towards cities, which constitutes the main source of urban population growth in this period. A second objective is to identify regional differences in the urban growth and migrations, that is, whether urban growth and migration patterns are different between coastal and inland provinces. Additionally, we are interested in the differences...
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SHARPIN Regulates Uropod Detachment in Migrating Lymphocytes
Directory of Open Access Journals (Sweden)
Jeroen Pouwels
2013-11-01
Full Text Available SHARPIN-deficient mice display a multiorgan chronic inflammatory phenotype suggestive of altered leukocyte migration. We therefore studied the role of SHARPIN in lymphocyte adhesion, polarization, and migration. We found that SHARPIN localizes to the trailing edges (uropods of both mouse and human chemokine-activated lymphocytes migrating on intercellular adhesion molecule-1 (ICAM-1, which is one of the major endothelial ligands for migrating leukocytes. SHARPIN-deficient cells adhere better to ICAM-1 and show highly elongated tails when migrating. The increased tail lifetime in SHARPIN-deficient lymphocytes decreases the migration velocity. The adhesion, migration, and uropod defects in SHARPIN-deficient lymphocytes were rescued by reintroducing SHARPIN into the cells. Mechanistically, we show that SHARPIN interacts directly with lymphocyte-function-associated antigen-1 (LFA-1, a leukocyte counterreceptor for ICAM-1, and inhibits the expression of intermediate and high-affinity forms of LFA-1. Thus, SHARPIN controls lymphocyte migration by endogenously maintaining LFA-1 inactive to allow adjustable detachment of the uropods in polarized cells.
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Development of international labor migration in the dynamics of globalization processes
Directory of Open Access Journals (Sweden)
Rubinskaya Eteri, D.
2015-03-01
Full Text Available The current characteristics of international migration caused by the qualitative changes that occur in the global economy under influence of increasing globalization. The paper attempts to suggest periodization of the global economy development and to identify features of international labor migration occurred under the influence of deep changes in the world economy. During this period, the author identifies three stages in the formation of globalization, the transition criterion from one to other is the degree of world economy changes under the influence of the productive forces development and the major social and political transformations resulted in qualitative changes in the processes of international labor migration. At the same time in the context of globalization the place and role of international labor migration changes in the global economy system: migration becomes a means of promoting the globalization of countries and regions, the most important factor of demographic development and economic growth.
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Migration from a terrestrial network to a satellite network - Risks/constraints/payoffs
Homon, K. A.
The migration method is regarded as a straightforward approach to a customer's requirements while addressing the known constraints. The migration plan organizes, controls, and communicates the extensive number of tasks, schedules, technical details, and node-by-node conversion details using the selected migration method as its cornerstone. It is noted that a successful migration plan must also provide the flexibility and robustness necessary to handle the unforeseen changes that will occur over the three- to four-year migration period. A baseline network provides a solid structural underpinning for the migration plan.
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The role of fluid migration system in hydrocarbon accumulation in Maichen Sag, Beibuwan Basin
Liu, Hongyu; Yang, Jinxiu; Wu, Feng; Chen, Wei; Liu, Qianqian
2018-02-01
Fluid migration system is of great significance for hydrocarbon accumulation, including the primary migration and secondary migration. In this paper, the fluid migration system is analysed in Maichen Sag using seismic, well logging and core data. Results show that many factors control the hydrocarbon migration process, including hydrocarbon generation and expulsion period from source rocks, microfractures developed in the source rocks, the connected permeable sand bodies, the vertical faults cutting into/through the source rocks and related fault activity period. The spatial and temporal combination of these factors formed an effective network for hydrocarbon expulsion and accumulation, leading to the hydrocarbon reservoir distribution at present. Generally, a better understanding of the hydrocarbon migration system can explain the present status of hydrocarbon distribution, and help select future target zones for oil and gas exploration.
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Investigation on nuclide migration behaviors
International Nuclear Information System (INIS)
Baik, Minhoon; Park, Chungkyun; Kim, Seungsoo
2012-04-01
In this study, we investigated the properties of geochemical reactions and sorption of high-level radionuclides and highly-mobile radionuclides in deep geological disposal environments. We also analyzed the dissolution properties of pyro wastes and constructed databases for the geochemical reactions and sorption for the safety assessment of HLW disposal. Technologies for measuring diffusion depths of radionuclides through fracture surfaces and rock matrix were developed in KURT conditions and their diffusion properties were analyzed and evaluated. The combined reactions of radionuclide/mineral/microbe in deep disposal environments were investigated and the effects of microbe on the radionuclide migration and disposal system behaviors were evaluated. In-situ solute migration system and on-line monitoring system were installed in KURT and the migration and retardation behaviors of various solutes and their interaction with fracture-filling materials were investigated. Basic properties of KURT groundwater colloids were analyzed using various methods. In addition, in-situ colloid migration experiments through a rock fracture were carried out and the developed migration model was verified. We have participated in Colloid Formation and Migration (CFM) international joint project in GTS and obtained reliability for our research results by comparing research results each other
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Characteristics of meniscus progenitor cells migrated from injured meniscus.
Seol, Dongrim; Zhou, Cheng; Brouillette, Marc J; Song, Ino; Yu, Yin; Choe, Hyeong Hun; Lehman, Abigail D; Jang, Kee W; Fredericks, Douglas C; Laughlin, Barbara J; Martin, James A
2017-09-01
Serious meniscus injuries seldom heal and increase the risk for knee osteoarthritis; thus, there is a need to develop new reparative therapies. In that regard, stimulating tissue regeneration by autologous stem/progenitor cells has emerged as a promising new strategy. We showed previously that migratory chondrogenic progenitor cells (CPCs) were recruited to injured cartilage, where they showed a capability in situ tissue repair. Here, we tested the hypothesis that the meniscus contains a similar population of regenerative cells. Explant studies revealed that migrating cells were mainly confined to the red zone in normal menisci: However, these cells were capable of repopulating defects made in the white zone. In vivo, migrating cell numbers increased dramatically in damaged meniscus. Relative to non-migrating meniscus cells, migrating cells were more clonogenic, overexpressed progenitor cell markers, and included a larger side population. Gene expression profiling showed that the migrating population was more similar to CPCs than other meniscus cells. Finally, migrating cells equaled CPCs in chondrogenic potential, indicating a capacity for repair of the cartilaginous white zone of the meniscus. These findings demonstrate that, much as in articular cartilage, injuries to the meniscus mobilize an intrinsic progenitor cell population with strong reparative potential. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1966-1972, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
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Internal migration and household living conditions in Ethiopia
Directory of Open Access Journals (Sweden)
Blessing Uchenna Mberu
2006-06-01
Full Text Available Using the 1998 Migration, Gender and Health Survey in Five Regions of Ethiopia, and multivariate regression techniques, this paper examines the relationship between internal migration and household living conditions. The analysis finds significant living condition advantage of permanent and temporary migrants over non-migrants. These advantages are primarily linked to migration selectivity by education and non-agricultural income. Once the independent effects of these variables are controlled, no statistical significant independent association exists between migration status and living conditions. Government policies of resettlement in the 1980s and ethnic federalism of the 1990s may have engendered stress migration and exacerbated poor living outcomes for return migrants. The resort to migration and/or resettlement as an individual or government policy response to periodic unfavorable conditions in places of origin is not strongly supported by this analysis as the key to improved living conditions. Promoting higher education and opportunities for employment outside the agricultural sector are more likely to yield improved living conditions in Ethiopia.
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Avian influenza H5N1 viral and bird migration networks in Asia
Tian, Huaivu; Zhou, Sen; Dong, Lu; Van Boeckel, Thomas P.; Cui, Yujun; Newman, Scott H.; Takekawa, John Y.; Prosser, Diann J.; Xiao, Xiangming; Wu, Yarong; Cazelles, Bernard; Huang, Shanqian; Yang, Ruifu; Grenfell, Bryan T.; Xu, Bing
2015-01-01
The spatial spread of the highly pathogenic avian influenza virus H5N1 and its long-term persistence in Asia have resulted in avian influenza panzootics and enormous economic losses in the poultry sector. However, an understanding of the regional long-distance transmission and seasonal patterns of the virus is still lacking. In this study, we present a phylogeographic approach to reconstruct the viral migration network. We show that within each wild fowl migratory flyway, the timing of H5N1 outbreaks and viral migrations are closely associated, but little viral transmission was observed between the flyways. The bird migration network is shown to better reflect the observed viral gene sequence data than other networks and contributes to seasonal H5N1 epidemics in local regions and its large-scale transmission along flyways. These findings have potentially far-reaching consequences, improving our understanding of how bird migration drives the periodic reemergence of H5N1 in Asia.
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Reconstructing the migration patterns of late Pleistocene mammals from northern Florida, USA
Hoppe, Kathryn A.; Koch, Paul L.
2007-11-01
We used analyses of the strontium isotope ( 87Sr/ 86Sr) ratios of tooth enamel to reconstruct the migration patterns of fossil mammals collected along the Aucilla River in northern Florida. Specimens date to the late-glacial period and before the last glacial maximum (pre-LGM). Deer and tapir displayed low 87Sr/ 86Sr ratios that were similar to the ratios of Florida environments, which suggest that these taxa did not migrate long distance outside of the Florida region. Mastodons, mammoths, and equids all displayed a wide range of 87Sr/ 86Sr ratios. Some individuals in each taxon displayed low 87Sr/ 86Sr ratios that suggest they ranged locally, while other animals had high 87Sr/ 86Sr ratios that suggest they migrated long distances (> 150 km) outside of the Florida region. Mastodons were the only taxa from this region that provided enough well-dated specimens to compare changes in migration patterns over time. Pre-LGM mastodons displayed significantly lower 87Sr/ 86Sr ratios than late-glacial mastodons, which suggests that late-glacial mastodons from Florida migrated longer distances than their earlier counterparts. This change in movement patterns reflects temporal changes in regional vegetation patterns.
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The morphology and migration of transverse bars off the west-central Florida coast
Gelfenbaum, G.; Brooks, G.R.
2003-01-01
A series of migrating shore-normal sandbars with wavelengths of 75-120 m and heights up to 2 m have been identified off the northern tip of Anna Maria Island, a barrier island on the west-central Florida coast. Similar features have been described elsewhere since the 1930s and termed 'transverse bars'. The transverse bars identified off Anna Maria Island are found for about 3 km along the coast and extend 4 km offshore, well outside the normal surf-zone width. No cusps or any other associated beach expression is evident despite the fact that the bars come to within about 75 m of the beach. Sediments on the crests of the bars are a well-sorted fine quartz sand, whereas sediments in the troughs are a poorly sorted coarse carbonate shell hash. Historical aerial photographs and repeated high-resolution bathymetric surveys provide a means of quantifying the migration of the transverse bars. Analyses of orthorectified aerial photographs from the early 1940s through the mid 1990s clearly show movement or migration taking place in the bar field. In the 40-yr period from 1951 to 1991, the southern edge of the bar field moved 200-350 m to the south, with an average long-term migration rate of 8 m/yr. Repeated bathymetric surveys over an 8-month period give an average short-term migration rate of 21 m/yr to the south. Wave and current measurements suggest that southerly winds associated with the passage of cold fronts drive near-bed currents to the south that are strong enough to initiate sediment transport and cause the southerly migration of the transverse bars.
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Rella, Lorenzo; Fernandes Póvoa, Euclides E; Korswagen, Hendrik C
2016-04-01
During development, cell migration plays a central role in the formation of tissues and organs. Understanding the molecular mechanisms that drive and control these migrations is a key challenge in developmental biology that will provide important insights into disease processes, including cancer cell metastasis. In this article, we discuss the Caenorhabditis elegans Q neuroblasts and their descendants as a tool to study cell migration at single-cell resolution in vivo. The highly stereotypical migration of these cells provides a powerful system to study the dynamic cytoskeletal processes that drive migration as well as the evolutionarily conserved signaling pathways (including different Wnt signaling cascades) that guide the cells along their specific trajectories. Here, we provide an overview of what is currently known about Q neuroblast migration and highlight the live-cell imaging, genome editing, and quantitative gene expression techniques that have been developed to study this process. © 2016 Wiley Periodicals, Inc.
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Lombards on the move--an integrative study of the migration period cemetery at Szólád, Hungary.
Directory of Open Access Journals (Sweden)
Kurt W Alt
Full Text Available In 2005 to 2007 45 skeletons of adults and subadults were excavated at the Lombard period cemetery at Szólád (6th century A.D., Hungary. Embedded into the well-recorded historical context, the article presents the results obtained by an integrative investigation including anthropological, molecular genetic and isotopic (δ(15N, δ(13C, (87Sr/(86Sr analyses. Skeletal stress markers as well as traces of interpersonal violence were found to occur frequently. The mitochondrial DNA profiles revealed a heterogeneous spectrum of lineages that belong to the haplogroups H, U, J, HV, T2, I, and K, which are common in present-day Europe and in the Near East, while N1a and N1b are today quite rare. Evidence of possible direct maternal kinship was identified in only three pairs of individuals. According to enamel strontium isotope ratios, at least 31% of the individuals died at a location other than their birthplace and/or had moved during childhood. Based on the peculiar 87 Sr/86 Sr ratio distribution between females, males, and subadults in comparison to local vegetation and soil samples, we propose a three-phase model of group movement. An initial patrilocal group with narrower male but wider female Sr isotope distribution settled at Szólád, whilst the majority of subadults represented in the cemetery yielded a distinct Sr isotope signature. Owing to the virtual absence of Szólád-born adults in the cemetery, we may conclude that the settlement was abandoned after approx. one generation. Population heterogeneity is furthermore supported by the carbon and nitrogen isotope data. They indicate that a group of high-ranking men had access to larger shares of animal-derived food whilst a few individuals consumed remarkable amounts of millet. The inferred dynamics of the burial community are in agreement with hypotheses of a highly mobile lifestyle during the Migration Period and a short-term occupation of Pannonia by Lombard settlers as conveyed by written
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David, Alexandra; Barwinska-Malajowicz, Anna
2015-01-01
This paper deals with the migration motives of German and Polish final semester students and university graduates in the partner cities of Bielefeld (GER) and Rzeszów (PL), who are on the threshold of their professional careers. The survey presented here was motivated by the question: are the current migration motives of highly-skilled graduates…
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Records of Migration in the Exoplanet Configurations
Michtchenko, Tatiana A.; Rodriguez Colucci, A.; Tadeu Dos Santos, M.
2013-05-01
Abstract (2,250 Maximum Characters): When compared to our Solar System, many exoplanet systems exhibit quite unusual planet configurations; some of these are hot Jupiters, which orbit their central stars with periods of a few days, others are resonant systems composed of two or more planets with commensurable orbital periods. It has been suggested that these configurations can be the result of a migration processes originated by tidal interactions of the planets with disks and central stars. The process known as planet migration occurs due to dissipative forces which affect the planetary semi-major axes and cause the planets to move towards to, or away from, the central star. In this talk, we present possible signatures of planet migration in the distribution of the hot Jupiters and resonant exoplanet pairs. For this task, we develop a semi-analytical model to describe the evolution of the migrating planetary pair, based on the fundamental concepts of conservative and dissipative dynamics of the three-body problem. Our approach is based on an analysis of the energy and the orbital angular momentum exchange between the two-planet system and an external medium; thus no specific kind of dissipative forces needs to be invoked. We show that, under assumption that dissipation is weak and slow, the evolutionary routes of the migrating planets are traced by the stationary solutions of the conservative problem (Birkhoff, Dynamical systems, 1966). The ultimate convergence and the evolution of the system along one of these modes of motion are determined uniquely by the condition that the dissipation rate is sufficiently smaller than the roper frequencies of the system. We show that it is possible to reassemble the starting configurations and migration history of the systems on the basis of their final states, and consequently to constrain the parameters of the physical processes involved.
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Timing of pre-nuptial migration and leap-frog patterns in Yellow ...
African Journals Online (AJOL)
nuptial migration period, in parts of the wintering grounds most distant from the breeding area. Birds breeding at the highest latitudes are the latest to depart on prenuptial migration, and so can take advantage of this surge by extending their ...
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On bar growth and decay during interannual net offshore migration
Walstra, D.J.R.; Reniers, A.J.H.M.; Ranasinghe, R.; Roelvink, J.A.; Ruessink, B.G.
2012-01-01
Multiple bar systems often show a cyclic net offshore directed migration with return periods on the order of years. Generally, a bar is generated near the shoreline, grows in height and width, while migrating offshore before finally decaying at the seaward limit of the surf zone. Based on a
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Studies of Migration in Ecuador: From National Development to Mobilities
Directory of Open Access Journals (Sweden)
María Mercedes Eguiguren
2017-05-01
Full Text Available The article presents a review of the studies on migration in Ecuador during the period 1960-2016. It addresses the main debates that have marked these studies, the contexts of academic production, and the way in which migrations and their social and economic conditions have influenced the constitution and orientations of the field. Three stages go through the academic production: a first one where the internal migrations are approached from a spatial phenomena analysis; a second that deals with the links between agricultural transformations and migration; and a third that shows a transition from a resurgence of migration in the literature to recent studies on the diversification of mobilities in the country.
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Migration intentions among Portuguese junior doctors: Results from a survey.
Ramos, Pedro; Alves, Hélio
2017-12-01
Migration of health personnel during periods of economic crisis represents a challenge for policymakers in origin and destination countries. Portugal is going through a period of economic hardship and much has been speculated about an increase in junior doctors' migration during this period. Using a questionnaire administered to a sample of Portuguese junior doctors who were still in the general residency (1st-year after medical school), we aim at determining the prevalence of migration intentions among Portuguese junior doctors and to identify the most important drivers of career choice for those who are considering emigrating in the near future. In our sample, 55% of Portuguese junior doctors are considering working abroad in the coming 10 years. Several variables were associated with an intention to work abroad: female sex (odds ratio [OR] 0.559; 95% confidence interval [CI] 0.488-0.640), the National Medical Exam score (OR 0.978; 95% CI 0.961-0.996;), having studied abroad (OR 1.756; 95% CI 1.086-2.867) and considering income and research opportunities as key factors for future specialty choice (OR 1.356; 95% CI 1.132-1.626; OR 2.626; 95% CI 1.228-4.172). Our study warns of the shortages the country may face due to doctors' migration and the main factors behind migration intentions in Portugal. Developing physician retention strategies is a priority to appropriately address these factors. Copyright © 2017 Elsevier B.V. All rights reserved.
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Skilled migration and health outcomes in developing countries.
Uprety, Dambar
2018-04-30
Many studies have found that health outcomes decline when health professionals leave the country, but do such results remain consistent in gender- and income-disaggregated skilled migration? To help uncover explanations for such a pro-migration nature of health outcomes, the present study revisits this topic but allows for associations of skilled migration with mortality and life expectancy to differ between male and female, and between low- and high-income countries. Using a panel of 133 developing countries as source and 20 OECD countries as destination from 1980 to 2010 allowing the coefficient on emigration across different education levels to differ, the study finds the negative effect of high-skilled emigration on health outcomes. Such effect is more pronounced for high-skilled female migration than those for male and for low-income countries than for middle-and high-income countries. Results also show that such adverse effect is larger for African countries than non-African ones. However, the low-skilled migration appears to be insignificant to affect health outcomes in developing countries. Thus, skilled migration is detrimental to longevity in developing countries but unskilled migration is not.
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Population specific migration patterns of an European-Afrotropical songbird
DEFF Research Database (Denmark)
Pedersen, Lykke; Tøttrup, Anders P.; Thorup, Kasper
Every year, billions of songbirds migrate thousands of kilometres between the European and African continent. The fascinating behaviour of migration that we are witnessing today is assumed to have evolved through a series of dispersal events from Africa into Europe since the last glaciation period....... Recent technological advances are currently enabling us to track yet smaller songbirds throughout their migration cycle providing valuable insight into the life cycle of individual birds. However, direct tracking of migratory birds has so far mainly been conducted on single populations and our...... understanding of entire species migration systems is thus still limited. In this project we analyse the spatio-temporal migration schedule of Red-backed Shrikes, Lanius collurio, using tracking data from individuals originating from geographically distinct breeding populations (Scandinavia, the Netherlands...
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Nordic Migration and Integration Research
Pyrhönen, Niko; Martikainen, Tuomas; Leinonen, Johanna
2017-01-01
EXECUTIVE SUMMARY Migration and integration are currently highly contentious topics in political, public and scientific arenas, and will remain so in the near future. However, many common migration-related prejudices and inefficien¬cies in the integration of the migrant population are due to the lack of sound, tested and accessible scientific research. Therefore, the study of migration – by developing basic research and by properly resourcing novel methodological approaches and interventions ...
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Fitness consequences of timing of migration and breeding in cormorants.
Directory of Open Access Journals (Sweden)
Phillip Gienapp
Full Text Available In most bird species timing of breeding affects reproductive success whereby early breeding is favoured. In migratory species migration time, especially arrival at the breeding grounds, and breeding time are expected to be correlated. Consequently, migration time should also have fitness consequences. However, in contrast to breeding time, evidence for fitness consequences of migration time is much more limited. Climate change has been shown to negatively affect the synchrony between trophic levels thereby leading to directional selection on timing but again direct evidence in avian migration time is scarce. We here analysed fitness consequences of migration and breeding time in great cormorants and tested whether climate change has led to increased selection on timing using a long-term data set from a breeding colony on the island of Vorsø (Denmark. Reproductive success, measured as number of fledglings, correlated with breeding time and arrival time at the colony and declined during the season. This seasonal decline became steeper during the study period for both migration and breeding time and was positively correlated to winter/spring climate, i.e. selection was stronger after warmer winters/springs. However, the increasing selection pressure on timing seems to be unrelated to climate change as the climatic variables that were related to selection strength did not increase during the study period. There is indirect evidence that phenology or abundances of preferred prey species have changed which could have altered selection on timing of migration and breeding.
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Underlying mechanism of precursory activity from analysis of upward earthquake migration
Directory of Open Access Journals (Sweden)
O. A. Molchanov
2011-01-01
Full Text Available In this paper we analyse the upward earthquake hypocentral migration in the ten known subduction zones and discuss a possible mechanism of such migration. The total time of the migration appears to range from 2.5 to 10 years. It leads to the estimation of the average velocity Vz~ 60−300 km yr−1. It probably corresponds to the movement of the forcing agent like stress or deformation wave from depths of the upper mantle (600–700 km to the level of the lithosphere with subsequent initiation of fluid migration inside the crust to trigger shallow earthquakes. Averaged over all zones upward migration travel time is about 5 years (< Vz > ≈120 km yr−1 that coincides approximately with the period of characteristic temperature variation (El Nino and crustal seismic periodicity in the Pacific region. These findings are helpful for the study of the seismic precursors and analysis of earthquake triggering.
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Monitoring raptors post-breeding migration on the Elba island, Arcipelago Toscano; years 2005-2006
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Lorenzo Vanni
2012-09-01
Full Text Available Raptors post-reproductive migration was monitored over a two year period (2005-2006 in Arcipelago Toscano. This paper is a first attempt to analyze the migration patterns of the most abundant species (Circus aeruginosus, Pernis apivorus and Accipiter nisus, trying to define their timing and peak passage period.
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Ramos, Grasieli de Oliveira; Bernardi, Lisiane; Lauxen, Isabel; Sant’Ana Filho, Manoel; Horwitz, Alan Rick; Lamers, Marcelo Lazzaron
2016-01-01
Cell migration is regulated by adhesion to the extracellular matrix (ECM) through integrins and activation of small RhoGTPases, such as RhoA and Rac1, resulting in changes to actomyosin organization. During invasion, epithelial-derived tumor cells switch from laminin-enriched basal membrane to collagen and fibronectin-enriched connective tissue. How this switch affects the tumor migration is still unclear. We tested the hypothesis that ECM dictates the invasiveness of Oral Squamous Cell Carcinoma (OSCC). We analyzed the migratory properties of two OSCC lines, a low invasive cell line with high e-cadherin levels (Linv/HE-cad) or a highly invasive cell line with low e-cadherin levels (Hinv/LE-cad), plated on different ECM components. Compared to laminin, fibronectin induced non-directional collective migration and decreased RhoA activity in Linv/HE-cad OSCC. For Hinv/LE-cad OSCC, fibronectin increased Rac1 activity and induced smaller adhesions, resulting in a fast single cell migration in both 2D and 3D environments. Consistent with these observations, human OSCC biopsies exhibited similar changes in cell-ECM adhesion distribution at the invasive front of the tumor, where cells encounter fibronectin. Our results indicate that ECM composition might induce a switch from collective to single cell migration according to tumor invasiveness due to changes in cell-ECM adhesion and the resulting signaling pathways that alter actomyosin organization. PMID:26978651
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Directory of Open Access Journals (Sweden)
Grasieli de Oliveira Ramos
Full Text Available Cell migration is regulated by adhesion to the extracellular matrix (ECM through integrins and activation of small RhoGTPases, such as RhoA and Rac1, resulting in changes to actomyosin organization. During invasion, epithelial-derived tumor cells switch from laminin-enriched basal membrane to collagen and fibronectin-enriched connective tissue. How this switch affects the tumor migration is still unclear. We tested the hypothesis that ECM dictates the invasiveness of Oral Squamous Cell Carcinoma (OSCC. We analyzed the migratory properties of two OSCC lines, a low invasive cell line with high e-cadherin levels (Linv/HE-cad or a highly invasive cell line with low e-cadherin levels (Hinv/LE-cad, plated on different ECM components. Compared to laminin, fibronectin induced non-directional collective migration and decreased RhoA activity in Linv/HE-cad OSCC. For Hinv/LE-cad OSCC, fibronectin increased Rac1 activity and induced smaller adhesions, resulting in a fast single cell migration in both 2D and 3D environments. Consistent with these observations, human OSCC biopsies exhibited similar changes in cell-ECM adhesion distribution at the invasive front of the tumor, where cells encounter fibronectin. Our results indicate that ECM composition might induce a switch from collective to single cell migration according to tumor invasiveness due to changes in cell-ECM adhesion and the resulting signaling pathways that alter actomyosin organization.
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Studies of Migration in Ecuador: From National Development to Mobilities
María Mercedes Eguiguren
2017-01-01
The article presents a review of the studies on migration in Ecuador during the period 1960-2016. It addresses the main debates that have marked these studies, the contexts of academic production, and the way in which migrations and their social and economic conditions have influenced the constitution and orientations of the field. Three stages go through the academic production: a first one where the internal migrations are approached from a spatial phenomena analysis; a second that deals wi...
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26 CFR 1.679-6 - Outbound migrations of domestic trusts.
2010-04-01
... 26 Internal Revenue 8 2010-04-01 2010-04-01 false Outbound migrations of domestic trusts. 1.679-6 Section 1.679-6 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME.... Undistributed net income for periods prior to the migration is taken into account only for purposes of...
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Energy Technology Data Exchange (ETDEWEB)
Katzner, Todd [West Virginia Univ., Morgantown, WV (United States)
2014-06-15
The future of the US economy, our national security, and our environmental quality all depend on decreasing our reliance on foreign oil and on fossil fuels. An essential component of decreasing this reliance is the development of alternative energy sources. Wind power is among the most important alternative energy sources currently available, and the mid-Atlantic region is a primary focus for wind power development. In addition to being important to the development of wind power, the mid-Atlantic region holds a special responsibility for the conservation of the eastern North America's golden eagles (Aquila chrysaetos). This small population breeds in northeastern Canada, winters in the southern Appalachians, and nearly all of these birds pass through the mid-Atlantic region twice each year. Movement of these birds is not random and, particularly during spring and autumn, migrating golden eagles concentrate in a narrow 30-50 mile wide corridor in central Pennsylvania. Thus, because the fate of these rare birds may depend on responsible management of the habitat they use it is critical to use research to identify ways to mitigate prospective impacts on this and similar raptor species. The goal of this project was to develop high-resolution spatial risk maps showing migration corridors of and habitat use by eastern golden eagles in regions of high potential for wind development. To accomplish this, we first expanded existing models of raptor migration for the eastern USA to identify broad-scale migration patterns. We then used data from novel high-resolution tracking devices to discover routes of passage and detailed flight behavior of individual golden eagles throughout the eastern USA. Finally, we integrated these data and models to predict population-level migration patterns and individual eagle flight behavior on migration. We then used this information to build spatially explicit, probabilistic maps showing relative risk to birds from wind development. This
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Energy Technology Data Exchange (ETDEWEB)
Collins, J.L.
1981-01-01
The people of the southern Peruvian highlands have adapted to a condition of energy scarcity through seasonal migration to lowland areas. In the disrict of Sarata (a fictitious name for a real district on the northeastern shore of Lake Titicaca) people spend three to seven months of every year growing coffee in the Tambopata Valley of the eastern Andes. This migratory pattern, which is hundreds of years old, provides the context for an investigation of human adaptive processes. This study presents models of the flow of energy through high-altitude households and shows that energy is a limiting factor for the population. There are two periods when energy subsidies from lowland regions become crucial to the continued survival of highland households. These are the periods of peak growth and reproduction experienced by households early in their developmental cycles, and times of sharply lowered productivity caused by environmental crises such as drought or killing frosts. Seasonal migration provides the subsidies that households rely on during these periods.
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Indonesia's migration transition.
Hugo, G
1995-01-01
This article describes population movements in Indonesia in the context of rapid and marked social and economic change. Foreign investment in Indonesia is increasing, and global mass media is available to many households. Agriculture is being commercialized, and structural shifts are occurring in the economy. Educational levels are increasing, and women's role and status are shifting. Population migration has increased over the decades, both short and long distance, permanent and temporary, legal and illegal, and migration to and between urban areas. This article focuses specifically on rural-to-urban migration and international migration. Population settlements are dense in the agriculturally rich inner areas of Java, Bali, and Madura. Although the rate of growth of the gross domestic product was 6.8% annually during 1969-94, the World Bank ranked Indonesia as a low-income economy in 1992 because of the large population size. Income per capita is US $670. Indonesia is becoming a large exporter of labor to the Middle East, particularly women. The predominance of women as overseas contract workers is changing women's role and status in the family and is controversial due to the cases of mistreatment. Malaysia's high economic growth rate of over 8% per year means an additional 1.3 million foreign workers and technicians are needed. During the 1980s urban growth increased at a very rapid rate. Urban growth tended to occur along corridors and major transportation routes around urban areas. It is posited that most of the urban growth is due to rural-to-urban migration. Data limitations prevent an exact determination of the extent of rural-to-urban migration. More women are estimated to be involved in movements to cities during the 1980s compared to the 1970s. Recruiters and middlemen have played an important role in rural-to-urban migration and international migration.
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Emergence of long distance bird migrations: a new model integrating global climate changes
Louchart, Antoine
2008-12-01
During modern birds history, climatic and environmental conditions have evolved on wide scales. In a continuously changing world, landbirds annual migrations emerged and developed. However, models accounting for the origins of these avian migrations were formulated with static ecogeographic perspectives. Here I reviewed Cenozoic paleoclimatic and paleontological data relative to the palearctic paleotropical long distance (LD) migration system. This led to propose a new model for the origin of LD migrations, the ‘shifting home’ model (SHM). It is based on a dynamic perspective of climate evolution and may apply to the origins of most modern migrations. Non-migrant tropical African bird taxa were present at European latitudes during most of the Cenozoic. Their distribution limits shifted progressively toward modern tropical latitudes during periods of global cooling and increasing seasonality. In parallel, decreasing winter temperatures in the western Palearctic drove shifts of population winter ranges toward the equator. I propose that this induced the emergence of most short distance migrations, and in turn LD migrations. This model reconciliates ecologically tropical ancestry of most LD migrants with predominant winter range shifts, in accordance with requirements for heritable homing. In addition, it is more parsimonious than other non-exclusive models. Greater intrinsic plasticity of winter ranges implied by the SHM is supported by recently observed impacts of the present global warming on migrating birds. This may induce particular threats to some LD migrants. The ancestral, breeding homes of LD migrants were not ‘northern’ or ‘southern’ but shifted across high and middle latitudes while migrations emerged through winter range shifts themselves.
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Determinants of the Egyptian labour migration.
Kandil, M; Metwally, M
1992-03-01
The objective is to summarize the pattern of Egyptian migration to Arab oil-producing countries (AOPC), to review some factors that are important determinants of labor movement based on theory, and to empirically model the migration rate to AOPC and to Saudi Arabia. Factors are differentiated as to their relative importance. Push factors are the low wages, high inflation rate, and high population density in Egypt; pull factors are higher wages. It is predicted that an increase in income from destination countries has a significant positive impact on the migration rate. An increase in population density stimulates migration. An increase in inflation acts to increase out-migration with a 2-year lag, which accommodates departure preparation. Egypt's experience with labor migration is described for the pre-oil boom, and the post-oil boom. Several estimates of labor migration are given. Government policy toward migration is positive. Theory postulates migration to be determined by differences in the availability of labor, labor rewards between destination and origin, and the cost of migration. In the empirical model, push factors are population density, the current inflation rate, and the ratio of income/capita in AOPC to Egypt. The results indicate that the ratio of income/capita had a strong pull impact and population density had a strong push impact. The inflation rate has a positive impact with a lag estimated at 2 years. Prior to the Camp David Accord, there was a significant decrease in the number of Egyptian migrants due to political tension. The findings support the classical theory of factor mobility. The consequences of migration on the Egyptian economy have been adverse. Future models should disaggregate data because chronic shortages exist in some parts of the labor market. Manpower needs assessment would be helpful for policy makers.
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Adhesion and migration of cells responding to microtopography.
Estévez, Maruxa; Martínez, Elena; Yarwood, Stephen J; Dalby, Matthew J; Samitier, Josep
2015-05-01
It is known that cells respond strongly to microtopography. However, cellular mechanisms of response are unclear. Here, we study wild-type fibroblasts responding to 25 µm(2) posts and compare their response to that of FAK(-/-) fibroblasts and fibroblasts with PMA treatment to stimulate protein kinase C (PKC) and the small g-protein Rac. FAK knockout cells modulated adhesion number and size in a similar way to cells on topography; that is, they used more, smaller adhesions, but migration was almost completely stalled demonstrating the importance of FAK signaling in contact guidance and adhesion turnover. Little similarity, however, was observed to PKC stimulated cells and cells on the topography. Interestingly, with PKC stimulation the cell nuclei became highly deformable bringing focus on these surfaces to the study of metastasis. Surfaces that aid the study of cellular migration are important in developing understanding of mechanisms of wound healing and repair in aligned tissues such as ligament and tendon. © 2014 Wiley Periodicals, Inc.
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Vineetha, G.; Jyothibabu, R.; Madhu, N. V.; Kusum, K. K.; Sooria, P. M.; Shivaprasad, A.; Reny, P. D.; Deepak, M. P.
2015-01-01
in the tidal cycles, which differed from the general concepts of downward migration during ebb tide and upward migration during flood tide in estuarine systems. The weak currents during the slack period might have favored the effective vertical migration
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Hydrology/Radionuclide Migration Program and related research activities
International Nuclear Information System (INIS)
Jones, M.A.
1992-02-01
This report presents the results of technical studies conducted under the Hydrology/Radionuclide Migration Program (HRMP) at the Nevada Test Site (NTS) for the period of October 1, 1985 through September 30, 1986. The HRMP was initiated in 1973 as the Radionuclide Migration Program to study and better understand the hydrologic systems of the NTS and potential movement and rates of movement of radionuclides and other contaminants injected into these systems by underground nuclear testing
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Early incorporation of cell-derived cholesterol into pre-beta-migrating high-density lipoprotein
International Nuclear Information System (INIS)
Castro, G.R.; Fielding, C.J.
1988-01-01
Cultures of human skin fibroblasts were labeled to high cholesterol specific activity with [ 3 H]cholesterol and incubated briefly (1-3 min) with normal human plasma. The plasma was fractionated by two-dimensional agarose-polyacrylamide gel electrophoresis and the early appearance of cholesterol label among plasma lipoproteins determined. A major part of the label at 1-min incubation was in a pre-beta-migrating apo A-I lipoprotein fraction with a molecular weight of ca. 70,000. Label was enriched about 30-fold in this fraction relative to its content of apo A-I (1-2% of total apo A-I). The proportion of label in this lipoprotein was strongly correlated with its concentration in plasma. Further incubation (2 min) in the presence of unlabeled cells demonstrated transfer of label from this fraction to a higher molecular weight pre-beta apo A-I species, to low-density lipoprotein, and to the alpha-migrating apo A-I that made up the bulk (96%) of total apo A-I in plasma. The data suggest that a significant part of cell-derived cholesterol is transferred specifically to a pre-beta-migrating lipoprotein A-I species as part of a cholesterol transport transfer sequence in plasma
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TUnfold, an algorithm for correcting migration effects in high energy physics
Energy Technology Data Exchange (ETDEWEB)
Schmitt, Stefan
2012-07-15
TUnfold is a tool for correcting migration and background effects in high energy physics for multi-dimensional distributions. It is based on a least square fit with Tikhonov regularisation and an optional area constraint. For determining the strength of the regularisation parameter, the L-curve method and scans of global correlation coefficients are implemented. The algorithm supports background subtraction and error propagation of statistical and systematic uncertainties, in particular those originating from limited knowledge of the response matrix. The program is interfaced to the ROOT analysis framework.
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Return migration of highly skilled scientists and engineers to Morocco : return or circulation ?
Gaillard, A.M.; Gaillard, Jacques
2015-01-01
The qualification level of the emigrating Moroccans rose steadily in the 1990s, and especially since the year 2000. At present, an estimated 20 per cent of the highly qualified Moroccans live abroad. Student migration, which accounts for a large part of this 20 per cent, is contributing substantially to keeping this level high. For the last 20 years Morocco has been testing actions to mobilise and reconnect its S&T diaspora. The related special programmes and institutions are discussed and an...
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Uner, S
1988-01-01
This study is concerned with Turkish labor migration to Western Europe. Earlier and recent patterns of labor migration, characteristics of migrants by occupation, area of destination, and by geographical origins are discussed. Economic and demographic consequences of labor migration are also analyzed. It is estimated that Turkey's population will reach 73 million at the year 2000 with the present growth rate of 2.48% annually. Considering the efforts made to slow down the present high fertility rates and assuming that the decrease in labor force participation during 1970-1980 continues, the author concludes that the labor supply will increase with a growth rate of 2% annually for the next 13-15 years. Thus, the labor supply will reach 26.6 million people in the year 2000 from the 1980 level of 17.8 million. Assuming also that the income/employment elasticity of .25 which was observed throughout the period of 1960-1980 will not change until 2000, the annual growth rate of employment may be estimated as 1.5%. Thus, the number of people employed will reach 20 million in the year 1990 and 23.2 million in the year 2000. 8.8 million people will join the labor market as new entrants between 1980 and 2000. Only 6 million people out of 8.8 million will be employed. Thus, in the year 2000, it is estimated that 2.8 million new unemployed people will be added to the already open unemployment figure 1980 census data give the number of unemployed as .6 million people. Adding the 2.8 million new unemployed to this figure totals 3.4 million unemployed in 2000. The State Planning Organization's estimate of labor surplus for 1980 was 2.5 million people. When 2.8 million unemployed people are added to this figure, the labor surplus for the year 2000 reaches 5.3 million people.
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Globalization and formal sector migration in Brazil
Aguayo-Tellez, Ernesto; Muendler, Marc-Andreas; Poole, Jennifer Pamela
2008-01-01
We use novel linked employer–employee data to study the relationship between globalization and formal sector interstate migration for Brazil. We estimate the worker’s multichoice migration problem and document that previously unobserved employer covariates are significant predictors associated with migration flows. Our results provide support for the idea that globalization acts on internal migration through the growth of employment opportunities at locations with a high concentration of fore...
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Migration towards Windows 2000/XP
International Nuclear Information System (INIS)
Gal, J.
2004-01-01
The article deals with interesting technical solutions used in the project 'Migration towards Windows 2000/XP', which was introduced by the company AITEN, Plc for companies SE Plc, SEPS Plc and TEKO, Plc in the period 2002 and 2003. The contents of the project was migration of about 100 servers and more than 4 000 PC to the Windows 2000 and XP environs. The result of the project is a unified and documented system in the field of file, print and small application servers and PC. It has enabled to increase the system reliability and availability, to decrease the total costs for administration and operation and to establish the steady environs for users of the applications. (author)
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International Student Migration and Social Stratification in China
Xiang, Biao; Shen, Wei
2009-01-01
During the late 1990s China moved from a period of "wealth creation" that benefited the majority of the population to a period of "wealth concentration" that benefited a minority. This essay focuses on the role of international student migration from China to other countries in this process. In particular the authors delineate…
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Directory of Open Access Journals (Sweden)
Susanne Åkesson
Full Text Available The tracking of small avian migrants has only recently become possible by the use of small light-level geolocators, allowing the reconstruction of whole migration routes, as well as timing and speed of migration and identification of wintering areas. Such information is crucial for evaluating theories about migration strategies and pinpointing critical areas for migrants of potential conservation value. Here we report data about migration in the common swift, a highly aerial and long-distance migrating species for which only limited information based on ringing recoveries about migration routes and wintering areas is available. Six individuals were successfully tracked throughout a complete migration cycle from Sweden to Africa and back. The autumn migration followed a similar route in all individuals, with an initial southward movement through Europe followed by a more southwest-bound course through Western Sahara to Sub-Saharan stopovers, before a south-eastward approach to the final wintering areas in the Congo basin. After approximately six months at wintering sites, which shifted in three of the individuals, spring migration commenced in late April towards a restricted stopover area in West Africa in all but one individual that migrated directly towards north from the wintering area. The first part of spring migration involved a crossing of the Gulf of Guinea in those individuals that visited West Africa. Spring migration was generally wind assisted within Africa, while through Europe variable or head winds were encountered. The average detour at about 50% could be explained by the existence of key feeding sites and wind patterns. The common swift adopts a mixed fly-and-forage strategy, facilitated by its favourable aerodynamic design allowing for efficient use of fuel. This strategy allowed swifts to reach average migration speeds well above 300 km/day in spring, which is higher than possible for similar sized passerines. This study
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QUALIFIED VERSION OF MIGRATION: BRAIN DRAIN
Ayhan GENCLER
2009-01-01
Though globalization suggests an international exchange of people besides goods and capital, developed countries often tended to put forward some restrictions on the migration of workers from developed countries. However, there has been an increase in skilled international migration especially during the last two decades. Skilled international migration or brain drain points out the emigration of educated and highly skilled workers. It seems tha...
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Colloid migration in porous media
International Nuclear Information System (INIS)
Hunt, J.R.; McDowell-Boyer; Sitar, N.
1985-01-01
Retention of radionuclides for long periods near waste repositories depends upon multiple barriers, one of which is adsorption to immobile solid surfaces. Since small particles and colloidal matter have high adsorption capacities per unit mass and can be mobile in subsurface flows, colloidal transport of waste components requires analysis. Theories for predicting colloid migration through porous media have been developed in the filtration literature. The applicability of filtration theories for predicting particle and colloid transport. Emphasis is on suspended matter much smaller than pore sizes, where physical and chemical forces control migration rather than size dependent physical straining. In general, experimentally verifiable theories exist for particle filtration by clean media, and a sensitivity analysis is possible on particle and media properties and fluid flow rate. When particle aggregates accumulate within pores, media permeability decreases, resulting in flow field alteration and possible radionuclide isolation. An analysis of the limited experimental data available indicates that present theories cannot predict long-term colloid transport when permeability reduction occurs. The coupling of colloid attachment processes and the hydrologic flow processes requires more extensive laboratory field research than has currently been carried out. An emphasis on the fundamental mechanisms is necessary to enhance long-term predictability
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Volatile organic components migrating from plastic pipes (HDPE, PEX and PVC) into drinking water.
Skjevrak, Ingun; Due, Anne; Gjerstad, Karl Olav; Herikstad, Hallgeir
2003-04-01
High-density polyethylene pipes (HDPE), crossbonded polyethylene pipes (PEX) and polyvinyl chloride (PVC) pipes for drinking water were tested with respect to migration of volatile organic components (VOC) to water. The odour of water in contact with plastic pipes was assessed according to the quantitative threshold odour number (TON) concept. A major migrating component from HDPE pipes was 2,4-di-tert-butyl-phenol (2,4-DTBP) which is a known degradation product from antioxidants such as Irgafos 168(R). In addition, a range of esters, aldehydes, ketones, aromatic hydrocarbons and terpenoids were identified as migration products from HDPE pipes. Water in contact with HDPE pipes was assessed with respect to TON, and values > or =4 were determined for five out of seven brands of HDPE pipes. The total amount of VOC released to water during three successive test periods were fairly constant for the HDPE pipes. Corresponding migration tests carried out for PEX pipes showed that VOC migrated in significant amounts into the test water, and TON >/=5 of the test water were observed in all tests. Several of the migrated VOC were not identified. Oxygenates predominated the identified VOC in the test water from PEX pipes. Migration tests of PVC pipes revealed few volatile migrants in the test samples and no significant odour of the test water.
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Effort Estimation in BPMS Migration
Directory of Open Access Journals (Sweden)
Christopher Drews
2018-04-01
Full Text Available Usually Business Process Management Systems (BPMS are highly integrated in the IT of organizations and are at the core of their business. Thus, migrating from one BPMS solution to another is not a common task. However, there are forces that are pushing organizations to perform this step, e.g. maintenance costs of legacy BPMS or the need for additional functionality. Before the actual migration, the risk and the effort must be evaluated. This work provides a framework for effort estimation regarding the technical aspects of BPMS migration. The framework provides questions for BPMS comparison and an effort evaluation schema. The applicability of the framework is evaluated based on a simplified BPMS migration scenario.
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Does human migration affect international trade? A complex-network perspective.
Fagiolo, Giorgio; Mastrorillo, Marina
2014-01-01
This paper explores the relationships between international human migration and merchandise trade, using a complex-network approach. We firstly compare the topological structure of worldwide networks of human migration and bilateral trade over the period 1960-2000. Next, we ask whether the position of any pair of countries in the migration network affects their bilateral trade flows. We show that: (i) both weighted and binary versions of the networks of international migration and trade are strongly correlated; (ii) such correlations can be mostly explained by country economic/demographic size and geographical distance; and (iii) pairs of countries that are more central in the international-migration network trade more. Our findings suggest that bilateral trade between any two countries is not only affected by the presence of migrants from either countries but also by their relative embeddedness in the complex web of corridors making up the network of international human migration.
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Migration up and down the urban hierarchy and across the life course.
Plane, D A; Henrie, C J; Perry, M J
2005-10-25
In this article, we begin by reviewing the concept of step migration that originated in E. G. Ravenstein's seminal papers "The Laws of Migration" (1885, 1889). As a result of the forces of the Industrial Revolution underway in 19th century Great Britain, migrants moved from farms to villages, from villages to towns, from towns to county seats, and thence to large cities. Throughout much of the industrialization era in the United States, net population movements similarly were upward within the urban hierarchy, and step migration today remains widespread throughout much of the still developing world. Our investigations of recent data and trends, however, suggest that the latest U.S. migration-pattern regime is a strongly contrasting one. Many of the major movements in the system of internal (or domestic) migration are flows down the urban hierarchy, although we note highly differentiated patterns for persons and households at specific stages of the life course. We make use of the newly defined metropolitan and micropolitan Core-Based Statistical Areas (CBSAs) and a seven-level size typology to tabulate origin-destination-specific migration flow data from both Census 2000 and IRS tax-return administrative records for the period 1995-2000. We discuss the causes for net movements being either upward or downward in the national urban hierarchy, including the effects of spatially focused immigration, and movement preferences at various ages, including migration in young adulthood associated with entering and leaving college and the military, as well as moves characteristic of the stages of family formation, childrearing, and retirement.
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Climate shocks and rural-urban migration in Mexico: Exploring nonlinearities and thresholds
Nawrotzki, Raphael J.; DeWaard, Jack; Bakhtsiyarava, Maryia; Ha, Jasmine Trang
2016-01-01
Adverse climatic conditions may differentially drive human migration patterns between rural and urban areas, with implications for changes in population composition and density, access to infrastructure and resources, and the delivery of essential goods and services. However, there is little empirical evidence to support this notion. In this study, we investigate the relationship between climate shocks and migration between rural and urban areas within Mexico. We combine individual records from the 2000 and 2010 Mexican censuses (n=683,518) with high-resolution climate data from Terra Populus that are linked to census data at the municipality level (n=2,321). We measure climate shocks as monthly deviation from a 30-year (1961-1990) long-term climate normal period, and uncover important nonlinearities using quadratic and cubic specifications. Satellite-based measures of urban extents allow us to classify migrant-sending and migrant-receiving municipalities as rural or urban to examine four internal migration patterns: rural-urban, rural-rural, urban-urban, and urban-rural. Among our key findings, results from multilevel models reveal that each additional drought month increases the odds of rural-urban migration by 3.6%. In contrast, the relationship between heat months and rural-urban migration is nonlinear. After a threshold of ~34 heat months is surpassed, the relationship between heat months and rural-urban migration becomes positive and progressively increases in strength. Policy and programmatic interventions may therefore reduce climate induced rural-urban migration in Mexico through rural climate change adaptation initiatives, while also assisting rural migrants in finding employment and housing in urban areas to offset population impacts. PMID:28435176
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Specifics of external migration into the Pskov Oblast
Directory of Open Access Journals (Sweden)
Pavel Vladimirovich Vasilenko
2014-07-01
Full Text Available Modern scientists consider migration to be a tool that makes it possible to redistribute human capital, which is currently the most important resource. At that, of special interest are the peripheral regions of the country, including those with the cross-border status, where the influence of migration processes on the structure of population is most noticeable. The Pskov Oblast is currently the leader in Russia in terms of depopulation. Natural decline in the region’s population is only partially compensated by migration. In this regard, the role of migration in the solution of demographic issues of regional development is becoming more and more important. The article presents the analysis of migration processes in the Pskov Oblast in the post-Soviet period; the analysis is based on the processing of statistical data. The author attempts to explain the main trends in migration processes in the framework of the Pskov Oblast for the last 20 years. Informational base of the research is formed by the materials of Pskovstat. The research findings can be used in the drafting and adjustment of a concept for demographic development of the region
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Masaki Takenouchi
2001-01-01
Why did not mass migration from the Third World to the highly-developed countries occur before the Second World War? This is a simple but important question, since the preponderance of the migration from the "South" to the "North" is a main characteristic of the contemporary international migration. The orthodox explanations of migration based on the concept of the national economy as a unit of analysis do not give us clues to answer this question. Neither do these by the world-system approac...
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Kunimatsu, Ryo; Gunji, Hidemi; Tsuka, Yuji; Yoshimi, Yuki; Awada, Tetsuya; Sumi, Keisuke; Nakajima, Kengo; Kimura, Aya; Hiraki, Tomoka; Abe, Takaharu; Naoto, Hirose; Yanoshita, Makoto; Tanimoto, Kotaro
2018-01-04
Laser irradiation activates a range of cellular processes and can promote tissue repair. Here, we examined the effects of high-frequency near-infrared (NIR) diode laser irradiation on the proliferation and migration of mouse calvarial osteoblastic cells (MC3T3-E1). MC3T3-E1 cells were cultured and exposed to high-frequency (30 kHz) 910-nm diode laser irradiation at a dose of 0, 1.42, 2.85, 5.7, or 17.1 J/cm 2 . Cell proliferation was evaluated with BrdU and ATP concentration assays. Cell migration was analyzed by quantitative assessment of wound healing using the Incucyt ® ZOOM system. In addition, phosphorylation of mitogen-activated protein kinase (MAPK) family members including p38 mitogen-activated protein kinase (p38), stress-activated protein kinase/Jun-amino-terminal kinase (SAPK/JNK), and extracellular signal-regulated protein kinase (ERK)1/2) after laser irradiation was examined with western blotting. Compared to the control, cell proliferation was significantly increased by laser irradiation at a dose of 2.85, 5.7, or 17.1 J/cm 2 . Laser irradiation at a dose of 2.85 J/cm 2 induced MC3T3-E1 cells to migrate more rapidly than non-irradiated control cells. Irradiation with the high-frequency 910-nm diode laser at a dose of 2.85 J/cm 2 induced phosphorylation of MAPK/ERK1/2 15 and 30 min later. However, phosphorylation of p38 MAPK and SAPK/JNK was not changed by NIR diode laser irradiation at a dose of 2.85 J/cm 2 . Irradiation with a high-frequency NIR diode laser increased cell division and migration of MT3T3-E1 cells, possibly via MAPK/ERK signaling. These observations may be important for enhancing proliferation and migration of osteoblasts to improve regeneration of bone tissues.
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QUALIFIED VERSION OF MIGRATION: BRAIN DRAIN
Gencler, Ayhan
2009-01-01
Though globalization suggests an international exchange of people besides goods and capital, developed countries often tended to put forward some restrictions on the migration of workers from developed countries. However, there has been an increase in skilled international migration especially during the last two decades. Skilled international migration or brain drain points out the emigration of educated and highly skilled workers. It seems that, in general, developing or underdeveloped...
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Population Dynamics of Early Human Migration in Britain.
Directory of Open Access Journals (Sweden)
Mayank N Vahia
Full Text Available Early human migration is largely determined by geography and human needs. These are both deterministic parameters when small populations move into unoccupied areas where conflicts and large group dynamics are not important. The early period of human migration into the British Isles provides such a laboratory which, because of its relative geographical isolation, may allow some insights into the complex dynamics of early human migration and interaction.We developed a simulation code based on human affinity to habitable land, as defined by availability of water sources, altitude, and flatness of land, in choosing the path of migration. Movement of people on the British island over the prehistoric period from their initial entry points was simulated on the basis of data from the megalithic period. Topographical and hydro-shed data from satellite databases was used to define habitability, based on distance from water bodies, flatness of the terrain, and altitude above sea level. We simulated population movement based on assumptions of affinity for more habitable places, with the rate of movement tempered by existing populations. We compared results of our computer simulations with genetic data and show that our simulation can predict fairly accurately the points of contacts between different migratory paths. Such comparison also provides more detailed information about the path of peoples' movement over ~2000 years before the present era.We demonstrate an accurate method to simulate prehistoric movements of people based upon current topographical satellite data. Our findings are validated by recently-available genetic data. Our method may prove useful in determining early human population dynamics even when no genetic information is available.
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Jin, Wa; Bi, Wei-hong; Fu, Xing-hu; Fu, Guang-wei
2017-09-01
We report periodical rocking long period gratings (PR-LPGs) in PANDA fibers fabricated with CO2 laser. The PR-LPGs achieve very high coupling efficiency of 19 dB with 12 periods and a 3.5° twist angle in just one scanning cycle, which is much more effective than the conventional CO2 laser fabrication technique. This type of LPGs exhibits polarization-selective resonance dips which demonstrate different sensitivities to environmental parameters. The high temperature and external refractive index sensitivities are measured simultaneously, so it can be used as a wavelength-selective polarization filter and sensor.
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Norris, Anne E.; Aroian, Karen J.; Nickerson, David
2015-01-01
Background Competing theories exist regarding the importance of pre-migration trauma as compared to post-migration stressors and resources with respect to the risk to immigrant mental health. Objective To examine how type of pre-migration trauma, post-migration stressors, and post-migration resources differentially predict PTSD and MDD symptomatology in Arab immigrant women who have been exposed to pre-migration trauma. Design Descriptive; using multinomial logistic regression to explain membership in one of four groups: (a) PTSD only (n = 14); (b) major depressive disorder (MDD) (n = 162), (c) Co-Morbid PTSD-MDD (n = 148), (d) Subclinical Symptoms (n = 209). Results Post-immigration related stressors (as measured by the Demands of Immigration (DI)) had the strongest effect: Parameter estimates indicated that a unit increase in DI scores was associated with a nearly 17 fold increase in the likelihood of being in the Co-morbid relative to the Subclinical group, and a nearly 2.5 increase in the likelihood of being in the Co-Morbid relative to the MDD only group (p Arab immigrant women for depression and PTSD is important given high levels observed in this community based sample. PMID:21835819
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Migrating mule deer: effects of anthropogenically altered landscapes.
Directory of Open Access Journals (Sweden)
Patrick E Lendrum
Full Text Available Migration is an adaptive strategy that enables animals to enhance resource availability and reduce risk of predation at a broad geographic scale. Ungulate migrations generally occur along traditional routes, many of which have been disrupted by anthropogenic disturbances. Spring migration in ungulates is of particular importance for conservation planning, because it is closely coupled with timing of parturition. The degree to which oil and gas development affects migratory patterns, and whether ungulate migration is sufficiently plastic to compensate for such changes, warrants additional study to better understand this critical conservation issue.We studied timing and synchrony of departure from winter range and arrival to summer range of female mule deer (Odocoileus hemionus in northwestern Colorado, USA, which has one of the largest natural-gas reserves currently under development in North America. We hypothesized that in addition to local weather, plant phenology, and individual life-history characteristics, patterns of spring migration would be modified by disturbances associated with natural-gas extraction. We captured 205 adult female mule deer, equipped them with GPS collars, and observed patterns of spring migration during 2008-2010.Timing of spring migration was related to winter weather (particularly snow depth and access to emerging vegetation, which varied among years, but was highly synchronous across study areas within years. Additionally, timing of migration was influenced by the collective effects of anthropogenic disturbance, rate of travel, distance traveled, and body condition of adult females. Rates of travel were more rapid over shorter migration distances in areas of high natural-gas development resulting in the delayed departure, but early arrival for females migrating in areas with high development compared with less-developed areas. Such shifts in behavior could have consequences for timing of arrival on birthing areas
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Forced migration in childhood: Are there long-term health effects?
Directory of Open Access Journals (Sweden)
Jan M. Saarela
2016-12-01
Full Text Available Studies on the health of migrants have increased considerably in number in recent years, but little is still known about the long-term health effects associated with forced migration, and particularly for people who were forced to migrate as children. Data shortcomings together with the methodological challenges of studying migrant populations limit the ability to disentangle the roles of various factors that influence migrant health outcomes. Finland provides an unusual opportunity to study long-term health consequences associated with forced migration. During World War II, twelve per cent of the Finnish population was forced to leave the region nowadays referred to as Ceded Karelia. After the war, these Karelians could not return home because the area was relinquished to the Soviet Union. Using high quality, linked register-based data for the period 1988–2012, we investigate whether this forced migration had long-term health consequences for those who were forced to migrate as children. Comparison groups are non-displaced persons born on the adjacent side of the new border, and people born elsewhere in Finland. Health at ages 43–65 years is measured by receipt of sickness benefit, which is an indicator of short-term illness, and receipt of disability pension, which reflects long-term illness or permanent disability. All-cause and cause-specific mortality is analysed at ages 43–84 years. We find no support for the hypothesis that the traumatic event of being forced to migrate during childhood has long-term negative health consequences. The forced child migrants have lower odds for receipt of sickness benefit, and women also have lower odds for receipt of disability pension. The mortality results are largely driven by patterns specific for eastern-born populations of Finland. A likely reason behind the absence of negative health consequences is that these migrants seem to have integrated well into post-war Finnish society. Keywords
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International Nuclear Information System (INIS)
Soares, Eufemia Paez; Saki, Mitiko; Silva, Leonardo G.A.
2007-01-01
Brazilian plastic production for food packagings, in recent years, has grown in the same proportion as food consumption. Considering that the plastic manufacturing involves catalytic processes and the use of additives, when the foods are in direct contact with these materials, the components present in plastics may migrate to the food. The Brazilian Health Surveillance Agency (ANVISA) has established boundary-values of migrants as well as procedures to evaluate migration of elements and substances from plastic packaging to food. In this study elemental composition of poly (ethylene terephthalate) - PET - packaging and results of elemental migration were obtained. Instrumental Neutron Activation Analysis (INAA) was used to determine elemental concentrations in PET packagings and the radiometric method was applied for elemental migration determination. This radiometric method consisted of irradiating the PET samples with neutrons, followed by migration exposition and radioactivity measurement in food-simulated solution. Experimental conditions used for migration were 10 days exposure period at 40 deg C. Migration was evaluated for soft drink, juice and water PET packaging. The analytical results indicated that PET packagings contain Co and Sb and those elements are transferred to the simulated solutions. However, these migration results were lower than the maximum tolerance values established by ANVISA. The migration detection limits also indicated high sensitivity of the radiometric method. (author)
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The paradox of extreme high-altitude migration in bar-headed geese Anser indicus
Hawkes, L. A.; Balachandran, S.; Batbayar, N.; Butler, P. J.; Chua, B.; Douglas, D. C.; Frappell, P. B.; Hou, Y.; Milsom, W. K.; Newman, S. H.; Prosser, D. J.; Sathiyaselvam, P.; Scott, G. R.; Takekawa, J. Y.; Natsagdorj, T.; Wikelski, M.; Witt, M. J.; Yan, B.; Bishop, C. M.
2013-01-01
Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world's tallest mountains, the Himalayas, where partial pressure of oxygen is dramatically reduced while flight costs, in terms of rate of oxygen consumption, are greatly increased. Such a mismatch is paradoxical, and it is not clear why geese might fly higher than is absolutely necessary. In addition, direct empirical measurements of high-altitude flight are lacking. We test whether migrating bar-headed geese actually minimize flight altitude and make use of favourable winds to reduce flight costs. By tracking 91 geese, we show that these birds typically travel through the valleys of the Himalayas and not over the summits. We report maximum flight altitudes of 7290 m and 6540 m for southbound and northbound geese, respectively, but with 95 per cent of locations received from less than 5489 m. Geese travelled along a route that was 112 km longer than the great circle (shortest distance) route, with transit ground speeds suggesting that they rarely profited from tailwinds. Bar-headed geese from these eastern populations generally travel only as high as the terrain beneath them dictates and rarely in profitable winds. Nevertheless, their migration represents an enormous challenge in conditions where humans and other mammals are only able to operate at levels well below their sea-level maxima. PMID:23118436
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Migration characterization of Ga and In adatoms on dielectric surface in selective MOVPE
International Nuclear Information System (INIS)
Chen Wei-Jie; Han Xiao-Biao; Lin Jia-Li; Hu Guo-Heng; Liu Ming-Gang; Yang Yi-Bin; Chen Jie; Wu Zhi-Sheng; Zhang Bai-Jun; Liu Yang
2015-01-01
Migration characterizations of Ga and In adatoms on the dielectric surface in selective metal organic vapor phase epitaxy (MOVPE) were investigated. In the typical MOVPE environment, the selectivity of growth is preserved for GaN, and the growth rate of GaN micro-pyramids is sensitive to the period of the patterned SiO 2 mask. A surface migration induced model was adopted to figure out the effective migration length of Ga adatoms on the dielectric surface. Different from the growth of GaN, the selective area growth of InGaN on the patterned template would induce the deposition of InGaN polycrystalline particles on the patterned SiO 2 mask with a long period. It was demonstrated with a scanning electron microscope and energy dispersive spectroscopy that the In adatoms exhibit a shorter migration length on the dielectric surface. (paper)
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Energy Technology Data Exchange (ETDEWEB)
Lee, Eve J.; Chiang, Eugene, E-mail: evelee@berkeley.edu [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
2017-06-10
Sub-Neptunes around FGKM dwarfs are evenly distributed in log orbital period down to ∼10 days, but dwindle in number at shorter periods. Both the break at ∼10 days and the slope of the occurrence rate down to ∼1 day can be attributed to the truncation of protoplanetary disks by their host star magnetospheres at corotation. We demonstrate this by deriving planet occurrence rate profiles from empirical distributions of pre-main-sequence stellar rotation periods. Observed profiles are better reproduced when planets are distributed randomly in disks—as might be expected if planets formed in situ—rather than piled up near disk edges, as would be the case if they migrated in by disk torques. Planets can be brought from disk edges to ultra-short (<1 day) periods by asynchronous equilibrium tides raised on their stars. Tidal migration can account for how ultra-short-period planets are more widely spaced than their longer-period counterparts. Our picture provides a starting point for understanding why the sub-Neptune population drops at ∼10 days regardless of whether the host star is of type FGK or early M. We predict planet occurrence rates around A stars to also break at short periods, but at ∼1 day instead of ∼10 days because A stars rotate faster than stars with lower masses (this prediction presumes that the planetesimal building blocks of planets can drift inside the dust sublimation radius).
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International Nuclear Information System (INIS)
Lee, Eve J.; Chiang, Eugene
2017-01-01
Sub-Neptunes around FGKM dwarfs are evenly distributed in log orbital period down to ∼10 days, but dwindle in number at shorter periods. Both the break at ∼10 days and the slope of the occurrence rate down to ∼1 day can be attributed to the truncation of protoplanetary disks by their host star magnetospheres at corotation. We demonstrate this by deriving planet occurrence rate profiles from empirical distributions of pre-main-sequence stellar rotation periods. Observed profiles are better reproduced when planets are distributed randomly in disks—as might be expected if planets formed in situ—rather than piled up near disk edges, as would be the case if they migrated in by disk torques. Planets can be brought from disk edges to ultra-short (<1 day) periods by asynchronous equilibrium tides raised on their stars. Tidal migration can account for how ultra-short-period planets are more widely spaced than their longer-period counterparts. Our picture provides a starting point for understanding why the sub-Neptune population drops at ∼10 days regardless of whether the host star is of type FGK or early M. We predict planet occurrence rates around A stars to also break at short periods, but at ∼1 day instead of ∼10 days because A stars rotate faster than stars with lower masses (this prediction presumes that the planetesimal building blocks of planets can drift inside the dust sublimation radius).
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Does human migration affect international trade? A complex-network perspective.
Directory of Open Access Journals (Sweden)
Giorgio Fagiolo
Full Text Available This paper explores the relationships between international human migration and merchandise trade, using a complex-network approach. We firstly compare the topological structure of worldwide networks of human migration and bilateral trade over the period 1960-2000. Next, we ask whether the position of any pair of countries in the migration network affects their bilateral trade flows. We show that: (i both weighted and binary versions of the networks of international migration and trade are strongly correlated; (ii such correlations can be mostly explained by country economic/demographic size and geographical distance; and (iii pairs of countries that are more central in the international-migration network trade more. Our findings suggest that bilateral trade between any two countries is not only affected by the presence of migrants from either countries but also by their relative embeddedness in the complex web of corridors making up the network of international human migration.
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Staby, A; Rø stad, Anders; Kaartvedt, Stein
2011-01-01
. The data revealed known patterns as normal diel vertical migration (DVM), midnight sinking between dusk and dawn, and periods without migrations, as well as novel behaviours consisting of early morning ascents, reverse diel vertical migrations
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Energy Technology Data Exchange (ETDEWEB)
Assouline, F.
2001-07-01
3-D seismic imaging of complex geologic structures requires the use of pre-stack imaging techniques, the post-stack ones being unsuitable in that case. Indeed, pre-stack depth migration is a technique which allows to image accurately complex structures provided that we have at our disposal a subsurface velocity model accurate enough. The determination of this velocity model is thus a key element for seismic imaging, and to this end, migration velocity analysis methods have met considerable interest. The SMART method is a specific migration velocity analysis method: the singularity of this method is that it does not rely on any restrictive assumptions on the complexity of the velocity model to determine. The SMART method uses a detour through the pre-stack depth migrated domain for extracting multi-offset kinematic information hardly accessible in the time domain. Once achieved the interpretation of the pre-stack depth migrated seismic data, a kinematic de-migration technique of the interpreted events enables to obtain a consistent kinematic database (i.e. reflection travel-times). Then, the inversion of these travel-times, by means of reflection tomography, allows the determination of an accurate velocity model. To be able to really image geologic structures for which the 3-D feature is predominant, we have studied the implementation of migration velocity analysis in 3-D in the context of the SMART method, and more generally, we have developed techniques allowing to overcome the intrinsic difficulties in the 3-D aspects of seismic imaging. Indeed, although formally the SMART method can be directly applied to the case of 3-D complex structures, the feasibility of its implementation requires to choose well the imaging domain. Once this choice done, it is also necessary to conceive a method allowing, via the associated de-migration, to obtain the reflection travel-times. We first consider the offset domain which constitutes, still today, the strategy most usually used
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Pu, Y
1988-12-01
Based on quantitative analyses of the latest survey data and qualitative analyses of the demographic literature, this paper studies the course of international migration of Chinese people from Fujian Province during the period from the 1920s to 1949 when the People's Republic of China was founded. Migration to Southeast Asia is emphasized. Per capita arable land in Fujian Province was only 1.8 mu. in 1936. Far more arable land was available in Southeast Asian countries, and a lot of it was farmed far more productively. The period from the 1920s to 1949 was one of the most politically turbulent periods in Chinese history. Numerous wars took place during this period. 30% of the emigrants during this period went to join family members. Emigrants were not only informed about employment opportunities in the destination, they were also provided with transportation, accommodations, and even employment. This chain migration was influenced by the inertia of migration movements. Demographic theories describe patterns of migration, including primary, compulsory, promoting, free, and large-scale migration patterns. The international migration of Chinese from Fujian Province to Southeast Asia was a comprehensive process characterized by multiple patterns of migration. The process was influenced by many factors at both destination and origin, including the inertia principle. The major factors leading to emigration were poor living conditions at home, the attraction of the blood relationship, life-threatening political conditions, and the intention of seeking a better business environment, as well as the feedback effect of the previous migration process. Moreover, good transportation, a favorable natural environment, a large labor force, and political stability pulled emigrants to the Southeast Asian countries.
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Modification of meander migration by bank failures
Motta, D.; Langendoen, E. J.; Abad, J. D.; García, M. H.
2014-05-01
Meander migration and planform evolution depend on the resistance to erosion of the floodplain materials. To date, research to quantify meandering river adjustment has largely focused on resistance to erosion properties that vary horizontally. This paper evaluates the combined effect of horizontal and vertical floodplain material heterogeneity on meander migration by simulating fluvial erosion and cantilever and planar bank mass failure processes responsible for bank retreat. The impact of stream bank failures on meander migration is conceptualized in our RVR Meander model through a bank armoring factor associated with the dynamics of slump blocks produced by cantilever and planar failures. Simulation periods smaller than the time to cutoff are considered, such that all planform complexity is caused by bank erosion processes and floodplain heterogeneity and not by cutoff dynamics. Cantilever failure continuously affects meander migration, because it is primarily controlled by the fluvial erosion at the bank toe. Hence, it impacts migration rates and meander shapes through the horizontal and vertical distribution of erodibility of floodplain materials. Planar failures are more episodic. However, in floodplain areas characterized by less cohesive materials, they can affect meander evolution in a sustained way and produce preferential migration patterns. Model results show that besides the hydrodynamics, bed morphology and horizontal floodplain heterogeneity, floodplain stratigraphy can significantly affect meander evolution, both in terms of migration rates and planform shapes. Specifically, downstream meander migration can either increase or decrease with respect to the case of a homogeneous floodplain; lateral migration generally decreases as result of bank protection due to slump blocks; and the effect on bend skewness depends on the location and volumes of failed bank material caused by cantilever and planar failures along the bends, with possible achievement of
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International Nuclear Information System (INIS)
Chen Rui; Zhang Zhanshi
2014-01-01
Radionuclides released from waste can migrate from the repository to the rock and soil outside. On the other hand, nuclides also are retarded by the backfill material. Radionuclide migration is the main geochemical process of the waste disposal. This paper introduces various methods for radionuclide migration research, and give a brief analysis of the geochemical process of radionuclide migration. Finally, two of the most important processes of the radionuclide migration have been instanced. (authors)
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Carr, Sarah D.; Tankersley, Richard A.; Hench, James L.; Forward, Richard B.; Luettich, Richard A.
2004-08-01
Female blue crabs ( Callinectes sapidus Rathbun) migrate from low salinity estuarine regions to high salinity regions near the ocean to release larvae. During this migration, ovigerous females use ebb-tide transport, a vertical migratory behavior in which they ascend into the water column during ebb tides, to move seaward to larval release areas. In order to determine the relationship of ebb-tide vertical migrations to local currents and the influence of these vertical migrations on the horizontal transport of blue crabs in the estuary, ovigerous females with mature embryos (˜1-3 days from hatching) were tracked near Beaufort Inlet, North Carolina (USA), in July and August 2001 and 2002. Crabs were tagged and tracked using ultrasonic telemetry, and currents near the crabs were measured simultaneously with a shipboard acoustic Doppler current profiler. During the two seasons, eight crabs were successfully tracked for periods ranging from 3.9-37.0 h and for distances ranging from 1.9-10.6 km. All crabs migrated seaward during the tracking periods. Crabs moved episodically during all tidal phases with periods of movement on the order of minutes to an hour. They moved with local currents in terms of both speed and direction during ebb tides, consistent with ebb-tide transport, and moved down-estuary (seaward) in opposition to local currents during flood tides. The percentage of time that crabs were active was higher during night ebb tides than during day ebb tides or flood tides and increased with increasing ebb-tide current speed. Mean migratory speeds were 0.11, 0.04, 0.08 and 0.02 m s -1 during night ebb, night flood, day ebb and day flood tides, respectively, and net migratory speeds were on the order of 5 km day -1. Due to the episodic nature of the crabs' movements, the total distances that crabs traveled during ebb tides ranged from 10-40% of the distances that passive particles could have traveled under the same conditions.
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Energy Technology Data Exchange (ETDEWEB)
Cook, C.; Dibrani, B.; Richmond, M.; Bleich, M.; Titzler, P..; Fu, T. [Pacific Northwest National Laboratory
2006-01-01
This report documents a four-year study to assess hydraulic conditions in the lower Snake River. The work was conducted for the Bonneville Power Administration, U.S. Department of Energy, by the Pacific Northwest National Laboratory. Cold water released from the Dworshak Reservoir hypolimnion during mid- to late-summer months cools the Clearwater River far below equilibrium temperature. The volume of released cold water augments the Clearwater River, and the combined total discharge is on the order of the Snake River discharge when the two rivers meet at their confluence near the upstream edge of Lower Granite Reservoir. With typical temperature differences between the Clearwater and Snake rivers of 10 C or more during July and August, the density difference between the two rivers during summer flow augmentation periods is sufficient to stratify Lower Granite Reservoir as well as the other three reservoirs downstream. Because cooling of the river is desirable for migrating juvenile fall Chinook salmon (Oncorhynchus tshawytscha) during this same time period, the amount of mixing and cold water entrained into Lower Granite Reservoir's epilimnion at the Clearwater/Snake River confluence is of key biological importance. Data collected during this project indicates the three reservoirs downstream of Lower Granite also stratify as direct result of flow augmentation from Dworshak Reservoir. These four reservoirs are also heavily influenced by wind forcing at the water's surface and during periods of low river discharge often behave like a two-layer lake. During these periods of stratification, lower river discharge, and wind forcing, the water in the upper layer of the reservoir is held in place or moves slightly upstream. This upper layer is also exposed to surface heating and may warm up to temperatures close to equilibrium temperature. The thickness (depth) of this upper warm layer and its direction of travel may be of key biological importance to juvenile
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North-South Migration and Remittances in Ghana
African Journals Online (AJOL)
mobility and high rates of rural-urban migration and in recent times child migration .... after the migrant settles at the place of destination and his income profile starts rising .... the rural areas of Northern Ghana had little or no education. ... The poor educational infrastructure, lack of schools and teachers, high dropout rates.
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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.
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Hauser, Donna D W; Laidre, Kristin L; Stafford, Kathleen M; Stern, Harry L; Suydam, Robert S; Richard, Pierre R
2017-06-01
Migrations are often influenced by seasonal environmental gradients that are increasingly being altered by climate change. The consequences of rapid changes in Arctic sea ice have the potential to affect migrations of a number of marine species whose timing is temporally matched to seasonal sea ice cover. This topic has not been investigated for Pacific Arctic beluga whales (Delphinapterus leucas) that follow matrilineally maintained autumn migrations in the waters around Alaska and Russia. For the sympatric Eastern Chukchi Sea ('Chukchi') and Eastern Beaufort Sea ('Beaufort') beluga populations, we examined changes in autumn migration timing as related to delayed regional sea ice freeze-up since the 1990s, using two independent data sources (satellite telemetry data and passive acoustics) for both populations. We compared dates of migration between 'early' (1993-2002) and 'late' (2004-2012) tagging periods. During the late tagging period, Chukchi belugas had significantly delayed migrations (by 2 to >4 weeks, depending on location) from the Beaufort and Chukchi seas. Spatial analyses also revealed that departure from Beaufort Sea foraging regions by Chukchi whales was postponed in the late period. Chukchi beluga autumn migration timing occurred significantly later as regional sea ice freeze-up timing became later in the Beaufort, Chukchi, and Bering seas. In contrast, Beaufort belugas did not shift migration timing between periods, nor was migration timing related to freeze-up timing, other than for southward migration at the Bering Strait. Passive acoustic data from 2008 to 2014 provided independent and supplementary support for delayed migration from the Beaufort Sea (4 day yr -1 ) by Chukchi belugas. Here, we report the first phenological study examining beluga whale migrations within the context of their rapidly transforming Pacific Arctic ecosystem, suggesting flexible responses that may enable their persistence yet also complicate predictions of how
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Climate Variability and Human Migration in the Netherlands, 1865–1937
Jennings, Julia A.; Gray, Clark L.
2014-01-01
Human migration is frequently cited as a potential social outcome of climate change and variability, and these effects are often assumed to be stronger in the past when economies were less developed and markets more localized. Yet, few studies have used historical data to test the relationship between climate and migration directly. In addition, the results of recent studies that link demographic and climate data are not consistent with conventional narratives of displacement responses. Using longitudinal individual-level demographic data from the Historical Sample of the Netherlands (HSN) and climate data that cover the same period, we examine the effects of climate variability on migration using event history models. Only internal moves in the later period and for certain social groups are associated with negative climate conditions, and the strength and direction of the observed effects change over time. International moves decrease with extreme rainfall, suggesting that the complex relationships between climate and migration that have been observed for contemporary populations extend into the nineteenth century. PMID:25937689
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Trace interpolation by slant-stack migration
International Nuclear Information System (INIS)
Novotny, M.
1990-01-01
The slant-stack migration formula based on the radon transform is studied with respect to the depth steep Δz of wavefield extrapolation. It can be viewed as a generalized trace-interpolation procedure including wave extrapolation with an arbitrary step Δz. For Δz > 0 the formula yields the familiar plane-wave decomposition, while for Δz > 0 it provides a robust tool for migration transformation of spatially under sampled wavefields. Using the stationary phase method, it is shown that the slant-stack migration formula degenerates into the Rayleigh-Sommerfeld integral in the far-field approximation. Consequently, even a narrow slant-stack gather applied before the diffraction stack can significantly improve the representation of noisy data in the wavefield extrapolation process. The theory is applied to synthetic and field data to perform trace interpolation and dip reject filtration. The data examples presented prove that the radon interpolator works well in the dip range, including waves with mutual stepouts smaller than half the dominant period
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International Migration and its Effects on Family
Directory of Open Access Journals (Sweden)
Cornel Constantinescu
2008-03-01
Full Text Available The crises period that still cross Romania explain, between others, the apparition and development of international migration, after 1990. In a world marked by globalization, migration can not disappear, contrary, it grows bigger ant it remains an interesting subject in future. A study about migration consequences on family, specially on children’s personality left in the country, is justified because migration is a present phenomena in Romanian space at the beginning of the XXIth century. We try to analyse the effects of this phenomenon on family. Related to these goal we offer the conclusions obtained from a research realized in Campulung Muscel municipality, Arges county, on a lot of pupils that have parents left in foreign countries and the results to the investigation made in Pitesti municipality. The research showed that it is a relationship between children’s marks at school and parent’s leaving; children’s perceptions on parent’s leaving; identifies school’s interest level in diminution of the low school performance effects caused by this socio-economical phenomena.
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Directory of Open Access Journals (Sweden)
Snježana Mrđen
2004-03-01
Full Text Available The paper presents middle duration projections of Croatia’s population, until the year 2031, determined via the cohort-component method. It outlines eight variants derived from supposed hypotheses in regard to changing birth, migration and death rates. Differences in the variants are exclusively differences in birth and migration rates, since the assumptions in regard to the death rates are the same in all the variants. The corrected estimate of the population on January 1st 2001, according to the most recent census, served as the base population. The results of the projections indicate that in the next thirty years the overall and the natural population reduction of Croatia will continue, and at the end of the period (2031 the population will be demographically older than at the start (2001. The variants differ only in relation to the intensity (i.e. swiftness of the aging process, yet the direction remains the same. Thus, in the variant that assumes a positive migration balance, the process of aging would be somewhat slower. The only variant that assumes a constant proportion of young people (on the 2001 level, gradual demographic growth and at the end of the period a larger population than in 2001, is the variant based on a high birth rate and positive migration. The impact of migration is very important for future demographic processes. Namely, in the short run, migration cannot change the direction of demographic processes, but it can lessen already existing negative trends.
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Rural-urban migration: policy simulations in a dual economy model of Bangladesh.
Ahmed, S
1986-03-01
The process of rural-urban migration in Bangladesh is analyzed using a dual economy model. The focus is on the period 1976-1985. The main purpose of the paper is to examine alternative policies designed to reduce the level of such migration without adversely affecting the country's economy.
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QUALIFIED VERSION OF MIGRATION: BRAIN DRAIN
Directory of Open Access Journals (Sweden)
Ayhan GENCLER
2009-07-01
Full Text Available Though globalization suggests an international exchange of people besides goods and capital, developed countries often tended to put forward some restrictions on the migration of workers from developed countries. However, there has been an increase in skilled international migration especially during the last two decades. Skilled international migration or brain drain points out the emigration of educated and highly skilled workers. It seems that, in general, developing or underdeveloped countries experience the negative consequences of the brain drain and suffer from the decreases in their human capital. The paper explains the phenomenon of skilled international migration, or brain drain, and summarizes the main global trends in this area.
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Effects of particles on macrophage migration
International Nuclear Information System (INIS)
Mueller, H.L.; Robinson, B.; Muggenburg, B.A.; Guilmette, R.A.
1988-01-01
Random and directed migration of cells lavaged from the lungs of rats and dogs were studied in vitro using formyl-methionyl-leucyl-phenylalanine (FMLP) as a chemo attractant. Rats and dogs were intratracheally instilled with either saline (controls) or about 10 9 fluorescent polystyrene microspheres, and lungs were lavaged after 1 or 7 days. More rat cells than dog cells migrated at 1 day after both particle and saline instillations; at 7 days, only cells lavaged from rats after particle instillations showed enhanced migration abilities. FMLP caused a 1.5 to 2-fold enhancement compared to random migration in cell numbers counted on the lower sides of chemotactic membranes. Cells with low particle numbers were more likely to migrate than those with high numbers of ingested particles. (author)
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Rural migration in Nevada: Lincoln County
International Nuclear Information System (INIS)
Soden, D.L.; Carns, D.E.; Mosser, D.; Conary, J.S.; Ansell, J.P.
1993-01-01
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. The findings suggest that a serious out-migration problem in Lincoln County, and that the Yucca mountain project will likely affect decisions relating to migration patterns in the future
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Forced migration in childhood: are there long-term health effects?
Saarela, Jan M; Elo, Irma T
2016-12-01
Studies on the health of migrants have increased considerably in number in recent years, but little is still known about the long-term health effects associated with forced migration, and particularly for people who were forced to migrate as children. Data shortcomings together with the methodological challenges of studying migrant populations limit the ability to disentangle the roles of various factors that influence migrant health outcomes. Finland provides an unusual opportunity to study long-term health consequences associated with forced migration. During World War II, twelve per cent of the Finnish population was forced to leave the region nowadays referred to as Ceded Karelia. After the war, these Karelians could not return home because the area was relinquished to the Soviet Union. Using high quality, linked register-based data for the period 1988-2012, we investigate whether this forced migration had long-term health consequences for those who were forced to migrate as children. Comparison groups are non-displaced persons born on the adjacent side of the new border, and people born elsewhere in Finland. Health at ages 43-65 years is measured by receipt of sickness benefit, which is an indicator of short-term illness, and receipt of disability pension, which reflects long-term illness or permanent disability. All-cause and cause-specific mortality is analysed at ages 43-84 years. We find no support for the hypothesis that the traumatic event of being forced to migrate during childhood has long-term negative health consequences. The forced child migrants have lower odds for receipt of sickness benefit, and women also have lower odds for receipt of disability pension. The mortality results are largely driven by patterns specific for eastern-born populations of Finland. A likely reason behind the absence of negative health consequences is that these migrants seem to have integrated well into post-war Finnish society.
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ILO - International Migration Programme.
Boudraa, Miriam
2011-01-01
In a wide International Context characterised not only by the economical development but also by the social, cultural, political and individual development, we witness more and more to a exchange between the developed and the developing countries, which can be translated especially in the migration of the work force. In theory, all countries are either countries of origin either countries of transit or destination, and they are all responsible for the rights of migrant workers by promoting the rights, by monitoring and by preventing the abusive conditions. The process of migration of the workforce can be divided into three stages: the first coincides with the period prior to departure, the second is represented by the aftermath of the departure and the period of stay in the country of destination, the third stage corresponds to the return in the country of origin. The workers must be protected throughout this process by the international organizations that perform the catalytic role of communication and exchange between countries, for the only purpose of protecting the rights of immigrant and/or immigrants workers. The responsibility for the protection of workers is divided among the various players in the International Labour Organisation. Every country has to apply measures according to the international standards regarding workers' rights, standards that guide the various countries in the formulation and implementation of their policies and legislation. These standards are suggested by International Conventions, the ILO Conventions and other international instruments such as the human rights instrument. There has been a big step forward once the ILO Fundamental Conventions and Conventions on Migrant Workers where implemented and this implementation represented the use of the Guidelines "ILO Multilateral Framework on Labour Migration".
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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.
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Epidemic spread in coupled populations with seasonally varying migration rates
Muzyczyn, Adam; Shaw, Leah B.
2009-03-01
The H5N1 strain of avian influenza has spread worldwide, and this spread may be due to seasonal migration of birds and mixing of birds from different regions in the wintering grounds. We studied a multipatch model for avian influenza with seasonally varying migration rates. The bird population was divided into two spatially distinct patches, or subpopulations. Within each patch, the disease followed the SIR (susceptible-infected-recovered) model for epidemic spread. Migration rates were varied periodically, with a net flux toward the breeding grounds during the spring and towards the wintering grounds during the fall. The case of two symmetric patches reduced to single-patch SIR dynamics. However, asymmetry in the birth and contact rates in the breeding grounds and wintering grounds led to bifurcations to longer period orbits and chaotic dynamics. We studied the bifurcation structure of the model and the phase relationships between outbreaks in the two patches.
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Does migration matter? Job search outcomes for the unemployed.
Boehm, T P; Herzog, H W; Schlottmann, A M
1998-01-01
The US has long been characterized by its geographically mobile population, with workers historically seeking new or better jobs in different locales as dictated by either opportunity or necessity. It is now generally accepted that the main determinants of interregional labor force migration are differential employment growth and amenity-adjusted earnings. The authors investigate migration's effect upon labor market transitions. Specifically, transition rates out of unemployment to employment, and from nonparticipation to active job search are examined. A multistate model of the hazard rate is developed and estimated to facilitate this process. Study results strongly suggest that migration is both directly and indirectly associated with a successful transition to re-employment. Findings are based upon the analysis of longitudinal microdata drawn from the corrected 1987 panel of the Survey of Income and Program Participation. Monthly labor market histories used covered the period from January 1987 to March 1989, for a research population of 3814 heads of households involved in 6096 total months of employment, job searching, and nonparticipation over the 26-month study period.
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Wyman, M. T.; Kavet, R.; Klimley, A. P.
2016-02-01
There is an increasingly strong interest on a global scale in offshore renewable energy production and transportation. However, there is concern that the electromagnetic fields (EMF) produced by these underwater cables may alter the behavior and physiology of marine species. Despite this concern, few studies have investigated these effects in free-living species. In 2009, a 85 km long high-voltage DC (HVDC) power cable was placed within the San Francisco Bay, running parallel, then perpendicular to, the migration route of anadromous species moving from the inland river system to the oceans. In this study, we assess the impacts of this HVDC cable on the migration behaviors of EMF-sensitive fish, including juvenile salmonids (Chinook salmon, Oncorhynchus tshawytscha, and steelhead trout, Oncorhynchus mykiss) and adult green sturgeon, Acipenser medirostris. Acoustic telemetry techniques were used to track fish migration movements through the San Francisco Bay both before and after the cable was activated; individuals implanted with acoustic transmitters were detected on cross-channel hydrophone arrays at key locations in the system. Magnetic fields were surveyed and mapped at these locations using a transverse gradiometer, and models of the cable's magnetic field were developed that closely matched the empirically measured values. Here, we present our analyses on the relationships between migration-related behavioral metrics (e.g., percent of successful migrations, duration of migration, time spent near vs. far from cable location, etc.) and environmental parameters, such as cable activation and load level, local magnetic field levels, depth, and currents.
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Hoehn, Mathias; Küstermann, Ekkehard; Blunk, James; Wiedermann, Dirk; Trapp, Thorsten; Wecker, Stefan; Föcking, Melanie; Arnold, Heinz; Hescheler, Jürgen; Fleischmann, Bernd K.; Schwindt, Wolfram; Bührle, Christian
2002-01-01
In vivo monitoring of stem cells after grafting is essential for a better understanding of their migrational dynamics and differentiation processes and of their regeneration potential. Migration of endogenous or grafted stem cells and neurons has been described in vertebrate brain, both under normal conditions from the subventricular zone along the rostral migratory stream and under pathophysiological conditions, such as degeneration or focal cerebral ischemia. Those studies, however, relied on invasive analysis of brain sections in combination with appropriate staining techniques. Here, we demonstrate the observation of cell migration under in vivo conditions, allowing the monitoring of the cell dynamics within individual animals, and for a prolonged time. Embryonic stem (ES) cells, constitutively expressing the GFP, were labeled by a lipofection procedure with a MRI contrast agent and implanted into rat brains. Focal cerebral ischemia had been induced 2 weeks before implantation of ES cells into the healthy, contralateral hemisphere. MRI at 78-μm isotropic spatial resolution permitted the observation of the implanted cells with high contrast against the host tissue, and was confirmed by GFP registration. During 3 weeks, cells migrated along the corpus callosum to the ventricular walls, and massively populated the borderzone of the damaged brain tissue on the hemisphere opposite to the implantation sites. Our results indicate that ES cells have high migrational dynamics, targeted to the cerebral lesion area. The imaging approach is ideally suited for the noninvasive observation of cell migration, engraftment, and morphological differentiation at high spatial and temporal resolution. PMID:12444255
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SiMA: A simplified migration assay for analyzing neutrophil migration.
Weckmann, Markus; Becker, Tim; Nissen, Gyde; Pech, Martin; Kopp, Matthias V
2017-07-01
In lung inflammation, neutrophils are the first leukocytes migrating to an inflammatory site, eliminating pathogens by multiple mechanisms. The term "migration" describes several stages of neutrophil movement to reach the site of inflammation, of which the passage of the interstitium and basal membrane of the airway are necessary to reach the site of bronchial inflammation. Currently, several methods exist (e.g., Boyden Chamber, under-agarose assay, or microfluidic systems) to assess neutrophil mobility. However, these methods do not allow for parameterization on single cell level, that is, the individual neutrophil pathway analysis is still considered challenging. This study sought to develop a simplified yet flexible method to monitor and quantify neutrophil chemotaxis by utilizing commercially available tissue culture hardware, simple video microscopic equipment and highly standardized tracking. A chemotaxis 3D µ-slide (IBIDI) was used with different chemoattractants [interleukin-8 (IL-8), fMLP, and Leukotriene B4 (LTB 4 )] to attract neutrophils in different matrices like Fibronectin (FN) or human placental matrix. Migration was recorded for 60 min using phase contrast microscopy with an EVOS ® FL Cell Imaging System. The images were normalized and texture based image segmentation was used to generate neutrophil trajectories. Based on these spatio-temporal information a comprehensive parameter set is extracted from each time series describing the neutrophils motility, including velocity and directness and neutrophil chemotaxis. To characterize the latter one, a sector analysis was employed enabling the quantification of the neutrophils response to the chemoattractant. Using this hard- and software framework we were able to identify typical migration profiles of the chemoattractants IL-8, fMLP, and LTB 4 , the effect of the matrices FN versus HEM as well as the response to different medications (Prednisolone). Additionally, a comparison of four asthmatic and
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THE IMPACT OF THE “BEATEN PATH” MODEL ON ROMANIAN MIGRATION
Directory of Open Access Journals (Sweden)
Elena Raluca CRISTIAN
2015-08-01
Full Text Available The migrations process is influenced by a series of factors such as: degree of employment, migrant’s salary level in the origin and destination countries, age, gender, education and professional training, economic development, unemployment, prices and purchase power. The migrations flows originate especially from the poor or very poor countries, believed to be underprivileged, the migrant choosing, obviously, developed countries. International migration involves a series of effects and consequences (positive and negative for both countries involved - the origin and the destination - for undetermined periods of time.
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Spring Bird Migration Phenology in Eilat, Israel
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Reuven Yosef
2009-12-01
Full Text Available Analysis of the mean date of first captures and median arrival dates of spring migration for 34 species of birds at Eilat, Israel, revealed that the earlier a species migrates through Eilat, the greater is the inter-annual variation in the total time of its passage. Birds arrive during spring migration in Eilat in four structured and independent waves. The annual fluctuation in the initial arrival dates (initial capture dates and median dates (median date of all captures, not including recaptures, did not depend on the length of the migratory route. This implies that migrants crossing the Sahara desert depart from their winter quarters on different Julian days in different years. We suggest that negative correlations between the median date of the spring migration of early and late migrants depends upon the easterly (Hamsin wind period. Moreover, we believe that the phenology of all birds during spring migration in Eilat is possibly also determined by external factors such as weather conditions on the African continent or global climatic processes in the Northern hemisphere. Orphean Warblers (Sylvia hortensis show a strong positive correlation (rs=-0.502 of initial capture date with calendar years, whereas other species such as Barred Warbler (S. nisoria; rs = -0.391 and Spotted Flycatcher (Muscicapa striata; rs = -0.398 display an insignificant trend. The Dead Sea Sparrow (Passer moabiticus and Red-Backed Shrike (Lanius collurio are positively correlated regarding initial arrival date and medians of spring migration.
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Shen, Xiang; Dai, Bin; Xing, Yingbin; Yang, Luyun; Li, Haiqing; Li, Jinyan; Peng, Jingang
2018-05-08
We demonstrated a kind of long-period fiber grating (LPFG), which is manufactured with a thermal diffusion treatment. The LPFG was inscribed on an ultrahigh-numerical-aperture (UHNA) fiber, highly doped with Ge and P, which was able to easily diffuse at high temperatures within a few seconds. We analyzed how the elements diffused at a high temperature over 1300 °C in the UHNA fiber. Then we developed a periodically heated technology with a CO₂ laser, which was able to cause the diffusion of the elements to constitute the modulations of an LPFG. With this technology, there is little damage to the outer structure of the fiber, which is different from the traditional LPFG, as it is periodically tapered. Since the LPFG itself was manufactured under high temperature, it can withstand higher temperatures than traditional LPFGs. Furthermore, the LPFG presents a higher sensitivity to high temperature due to the large amount of Ge doping, which is approximately 100 pm/°C. In addition, the LPFG shows insensitivity to the changing of the environment’s refractive index and strain.
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Analysing migrations of Atlantic cod Gadus morhua in the north‐east Atlantic Ocean
DEFF Research Database (Denmark)
Neuenfeldt, S.; Righton, D.; Neat, F.
2013-01-01
The application of data storage tags bears the potential for a quantum leap in the research on fish migrations, because not only first-capture and recapture positions are known, but at least theoretically, the migration path during the period at large can be reconstructed. Position, however, cannot...
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Effects of labour migration on economic development during economic downturn and recovery
Directory of Open Access Journals (Sweden)
Milan Palát
2012-01-01
Full Text Available International labour migration is mainly promoted by economic interests. This paper focuses on the period before and after the economic crisis and puts together important facts regarding motivation to labour migration and provides explanations of its causes and impacts on the macroeconomic level. The economic explanation why is migration so severely restricted is that migration policies are essentially distributive tools, aiming at reducing negative effects of migration on wages and unemployment among natives and moreover, we may stress out the gradualist tendencies of migration and such migration restrictions can mitigate supply-side shocks that may negatively affect incomes or jobs of some specific groups. A partial objective of the practical part of the paper is to evaluate relationships between the rate of migration and selected economic indicators using adequate quantitative methods. While the correlation between the crude rate of net migration and the GDP per capita is very low, the existence of correlation between the crude rate of net migration and the unemployment rate is evident in the most of analysed countries. Statistical insignificance of correlation indices in some countries can be then attributed to structural problems of those economies.
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Compressed-sensing application - Pre-stack kirchhoff migration
Aldawood, Ali; Hoteit, Ibrahim; Alkhalifah, Tariq Ali
2013-01-01
Least-squares migration is a linearized form of waveform inversion that aims to enhance the spatial resolution of the subsurface reflectivity distribution and reduce the migration artifacts due to limited recording aperture, coarse sampling of sources and receivers, and low subsurface illumination. Least-squares migration, however, due to the nature of its minimization process, tends to produce smoothed and dispersed versions of the reflectivity of the subsurface. Assuming that the subsurface reflectivity distribution is sparse, we propose the addition of a non-quadratic L1-norm penalty term on the model space in the objective function. This aims to preserve the sparse nature of the subsurface reflectivity series and enhance resolution. We further use a compressed-sensing algorithm to solve the linear system, which utilizes the sparsity assumption to produce highly resolved migrated images. Thus, the Kirchhoff migration implementation is formulated as a Basis Pursuit denoise (BPDN) problem to obtain the sparse reflectivity model. Applications on synthetic data show that reflectivity models obtained using this compressed-sensing algorithm are highly accurate with optimal resolution.
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Spatial and temporal migration of a landfill leachate plume in alluvium
Masoner, Jason R.; Cozzarelli, Isabelle M.
2015-01-01
Leachate from unlined or leaky landfills can create groundwater contaminant plumes that last decades to centuries. Understanding the dynamics of leachate movement in space and time is essential for monitoring, planning and management, and assessment of risk to groundwater and surface-water resources. Over a 23.4-year period (1986–2010), the spatial extent of the Norman Landfill leachate plume increased at a rate of 7800 m2/year and expanded by 878 %, from an area of 20,800 m2 in 1986 to 203,400 m2 in 2010. A linear plume velocity of 40.2 m/year was calculated that compared favorably to a groundwater-seepage velocity of 55.2 m/year. Plume-scale hydraulic conductivity values representative of actual hydrogeological conditions in the alluvium ranged from 7.0 × 10−5 to 7.5 × 10−4 m/s, with a median of 2.0 × 10−4 m/s. Analyses of field-measured and calculated plume-scale hydraulic conductivity distributions indicate that the upper percentiles of field-measured values should be considered to assess rates of plume-scale migration, spreading, and biodegradation. A pattern of increasing Cl− concentrations during dry periods and decreasing Cl− concentrations during wet periods was observed in groundwater beneath the landfill. The opposite occurred in groundwater downgradient from the landfill; that is, Cl− concentrations in groundwater downgradient from the landfill decreased during dry periods and increased during wet periods. This pattern of changing Cl−concentrations in response to wet and dry periods indicates that the landfill retains or absorbs leachate during dry periods and produces lower concentrated leachate downgradient. During wet periods, the landfill receives more recharge which dilutes leachate in the landfill but increases leachate migration from the landfill and produces a more concentrated contaminant plume. This approach of quantifying plume expansion, migration, and concentration during variable hydrologic
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White-tailed deer migration and its role in wolf predation
Hoskinson, R.L.; Mech, L.D.
1976-01-01
Seventeen white-tailed deer (Odocoileus virginianus) were radio-tagged in winter yards and tracked for up to 17 months each (881 locations) from January 1973 through August 1974 in the central Superior National Forest of NE Minnesota following a drastic decline in deer numbers. Ten vyolves (Canis lupus) from 7 packs in the same area were radiotracked before and/or during the same period (703 locations). Deer had winter ranges averaging 26.4 ha. Spring migration took place from 26 March to 23 April and was related to loss of snow cover. Deer generally migrated ENE in straight-line distances of 10.0 to 38.0 km to summer ranges. Two fawns did not migrate. Arrival on summer ranges was between 19 April and 18 May, and summer ranges varied from 48.1 to 410.4 ha. Migration back to the same winter yards took place in early December, coincident with snow accumulation and low temperatures. Social grouping appeared strongest during migration and winter yarding. Survival of the radio-tagged deer was studied through 1 May 1975. Four deer were killed by wolves, one was poached, and one drowned. Mean age of the captured deer was 5.4 years and estimated minimum survival after capture was 2.6 years, giving an estimated total minimum survival of 8.0 years. This unusually high survival rate appeared to be related to the fact that both winter and summer ranges of these deer were situated along wolf-pack territory edges rather than in centers. In addition, most summer ranges of the radio-tagged deer were along major waterways where the deer could escape wolves.
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The Irish famine of 1740-1741: famine vulnerability and "climate migration"
Engler, S.; Mauelshagen, F.; Werner, J.; Luterbacher, J.
2013-05-01
The "Great Frost" of 1740 was one of the coldest winters of the eighteenth century and impacted many countries all over Europe. The years 1740-1741 have long been known as a period of general crisis caused by harvest failures, high prices for staple foods, and excess mortality. Vulnerabilities, coping capacities and adaptation processes varied considerably among different countries. This paper investigates the famine of 1740-1741 in Ireland applying a multi-indicator model developed specifically for the integration of an analysis of pre-famine vulnerability, the Famine Vulnerability Analysis Model (FVAM). Our focus is on Ireland, because famine has played a more outstanding role in Irish national history than in any other European country, due to the "Great Famine" of 1845-1852 and its long-term demographic effects. Our analysis shows that Ireland was already particularly vulnerable to famine in the first half of the eighteenth century. During and after the experience of hardship in 1740-1741, many Irish moved within Ireland or left the country entirely. We regard migration as a form of adaptation and argue that Irish migration in 1740-1741 should be considered as a case of climate-induced migration.
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Directory of Open Access Journals (Sweden)
Tilman Jakob Gaber
2013-06-01
Full Text Available Introduction: This article presents diagnostic rates for specific mental disorders in a German pediatric inpatient population over a period of 20 years with respect to migration background and socioeconomic status (SES. Methods: Diagnostic data were obtained over a period of 20 years from 8,904 patients who visited a child and adolescent psychiatry mental health service in Germany. Data from 5,985 diagnosed patients (ICD-9 and ICD-10 criteria were included with respect to gender, migration background, and SES. Results:Migration- and gender-specific effects were found for both periods of assessment. The group of boys with a migration background showed significantly higher rates of reactions to severe stress, adjustment disorders, and posttraumatic stress disorder compared to their male, non-migrant counterparts. Conversely, boys without a migration background showed a significantly higher percentage rate of hyperkinetic disorders than male migrants. Similar results were found for female migrants in the latter assessment period (ICD-10. In addition, female migrants showed lower rates of emotional disorders whose onset occurs in childhood compared to their non-migrant counterparts. Conclusions: Data from this investigation provide preliminary evidence that the prevalence of various psychiatric disorders in children and adolescents is influenced by migration background and SES.
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Melt migration modeling in partially molten upper mantle
Ghods, Abdolreza
The objective of this thesis is to investigate the importance of melt migration in shaping major characteristics of geological features associated with the partial melting of the upper mantle, such as sea-floor spreading, continental flood basalts and rifting. The partial melting produces permeable partially molten rocks and a buoyant low viscosity melt. Melt migrates through the partially molten rocks, and transfers mass and heat. Due to its much faster velocity and appreciable buoyancy, melt migration has the potential to modify dynamics of the upwelling partially molten plumes. I develop a 2-D, two-phase flow model and apply it to investigate effects of melt migration on the dynamics and melt generation of upwelling mantle plumes and focusing of melt migration beneath mid-ocean ridges. Melt migration changes distribution of the melt-retention buoyancy force and therefore affects the dynamics of the upwelling plume. This is investigated by modeling a plume with a constant initial melt of 10% where no further melting is considered. Melt migration polarizes melt-retention buoyancy force into high and low melt fraction regions at the top and bottom portions of the plume and therefore results in formation of a more slender and faster upwelling plume. Allowing the plume to melt as it ascends through the upper mantle also produces a slender and faster plume. It is shown that melt produced by decompressional melting of the plume migrates to the upper horizons of the plume, increases the upwelling velocity and thus, the volume of melt generated by the plume. Melt migration produces a plume which lacks the mushroom shape observed for the plume models without melt migration. Melt migration forms a high melt fraction layer beneath the sloping base of the impermeable oceanic lithosphere. Using realistic conditions of melting, freezing and melt extraction, I examine whether the high melt fraction layer is able to focus melt from a wide partial melting zone to a narrow region
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Reverse time migration by Krylov subspace reduced order modeling
Basir, Hadi Mahdavi; Javaherian, Abdolrahim; Shomali, Zaher Hossein; Firouz-Abadi, Roohollah Dehghani; Gholamy, Shaban Ali
2018-04-01
Imaging is a key step in seismic data processing. To date, a myriad of advanced pre-stack depth migration approaches have been developed; however, reverse time migration (RTM) is still considered as the high-end imaging algorithm. The main limitations associated with the performance cost of reverse time migration are the intensive computation of the forward and backward simulations, time consumption, and memory allocation related to imaging condition. Based on the reduced order modeling, we proposed an algorithm, which can be adapted to all the aforementioned factors. Our proposed method benefit from Krylov subspaces method to compute certain mode shapes of the velocity model computed by as an orthogonal base of reduced order modeling. Reverse time migration by reduced order modeling is helpful concerning the highly parallel computation and strongly reduces the memory requirement of reverse time migration. The synthetic model results showed that suggested method can decrease the computational costs of reverse time migration by several orders of magnitudes, compared with reverse time migration by finite element method.
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Migration in Deltas: An Integrated Analysis
Nicholls, Robert J.; Hutton, Craig W.; Lazar, Attila; Adger, W. Neil; Allan, Andrew; Arto, Inaki; Vincent, Katharine; Rahman, Munsur; Salehin, Mashfiqus; Sugata, Hazra; Ghosh, Tuhin; Codjoe, Sam; Appeaning-Addo, Kwasi
2017-04-01
Deltas and low-lying coastal regions have long been perceived as vulnerable to global sea-level rise, with the potential for mass displacement of exposed populations. The assumption of mass displacement of populations in deltas requires a comprehensive reassessment in the light of present and future migration in deltas, including the potential role of adaptation to influence these decisions. At present, deltas are subject to multiple drivers of environmental change and often have high population densities as they are accessible and productive ecosystems. Climate change, catchment management, subsidence and land cover change drive environmental change across all deltas. Populations in deltas are also highly mobile, with significant urbanization trends and the growth of large cities and mega-cities within or adjacent to deltas across Asia and Africa. Such migration is driven primarily by economic opportunity, yet environmental change in general, and climate change in particular, are likely to play an increasing direct and indirect role in future migration trends. The policy challenges centre on the role of migration within regional adaptation strategies to climate change; the protection of vulnerable populations; and the future of urban settlements within deltas. This paper reviews current knowledge on migration and adaptation to environmental change to discern specific issues pertinent to delta regions. It develops a new integrated methodology to assess present and future migration in deltas using the Volta delta in Ghana, Mahanadi delta in India and Ganges-Brahmaputra-Meghna delta across India and Bangladesh. The integrated method focuses on: biophysical changes and spatial distribution of vulnerability; demographic changes and migration decision-making using multiple methods and data; macro-economic trends and scenarios in the deltas; and the policies and governance structures that constrain and enable adaptation. The analysis is facilitated by a range of
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Brandsch, Rainer
2017-10-01
Migration modelling provides reliable migration estimates from food-contact materials (FCM) to food or food simulants based on mass-transfer parameters like diffusion and partition coefficients related to individual materials. In most cases, mass-transfer parameters are not readily available from the literature and for this reason are estimated with a given uncertainty. Historically, uncertainty was accounted for by introducing upper limit concepts first, turning out to be of limited applicability due to highly overestimated migration results. Probabilistic migration modelling gives the possibility to consider uncertainty of the mass-transfer parameters as well as other model inputs. With respect to a functional barrier, the most important parameters among others are the diffusion properties of the functional barrier and its thickness. A software tool that accepts distribution as inputs and is capable of applying Monte Carlo methods, i.e., random sampling from the input distributions of the relevant parameters (i.e., diffusion coefficient and layer thickness), predicts migration results with related uncertainty and confidence intervals. The capabilities of probabilistic migration modelling are presented in the view of three case studies (1) sensitivity analysis, (2) functional barrier efficiency and (3) validation by experimental testing. Based on the predicted migration by probabilistic migration modelling and related exposure estimates, safety evaluation of new materials in the context of existing or new packaging concepts is possible. Identifying associated migration risk and potential safety concerns in the early stage of packaging development is possible. Furthermore, dedicated material selection exhibiting required functional barrier efficiency under application conditions becomes feasible. Validation of the migration risk assessment by probabilistic migration modelling through a minimum of dedicated experimental testing is strongly recommended.
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Schweitzer, Robert D; Brough, Mark; Vromans, Lyn; Asic-Kobe, Mary
2011-04-01
This study documents the mental health status of people from Burmese refugee backgrounds recently arrived in Australia, then examines the contributions of gender, pre-migration and post-migration factors in predicting mental health. Structured interviews, including a demographic questionnaire, the Harvard Trauma Questionnaire, the Post-migration Living Difficulties Checklist and Hopkins Symptom Checklist assessed pre-migration trauma, post-migration living difficulties, depression, anxiety, somatization and traumatization symptoms in a sample of 70 adults across five Burmese ethnic groups. Substantial proportions of participants reported psychological distress in symptomatic ranges including: post-traumatic stress disorder (9%), anxiety (20%) and depression (36%), as well as significant symptoms of somatization (37%). Participants reported multiple and severe pre-migration traumas. Post-migration living difficulties of greatest concern included communication problems and worry about family not in Australia. Gender did not predict mental health. Level of exposure to traumatic events and post-migration living difficulties each made unique and relatively equal contributions to traumatization symptoms. Post-migration living difficulties made unique contributions to depression, anxiety and somatization symptoms. While exposure to traumatic events impacted on participants' mental well-being, post-migration living difficulties had greater salience in predicting mental health outcomes of people from Burmese refugee backgrounds. Reported rates of post-traumatic stress disorder symptoms were consistent with a large review of adults across seven western countries. High levels of somatization point to a nuanced expression of distress. Findings have implications for service provision in terms of implementing appropriate interventions to effectively meet the needs of this newly arrived group in Australia.
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Shi, D; Li, X; Chen, H; Che, N; Zhou, S; Lu, Z; Shi, S; Sun, L
2014-12-01
Some lines of evidence have demonstrated abnormalities of bone marrow mesenchymal stem cells (MSCs) in systemic lupus erythematosus (SLE) patients, characterized by defective phenotype of MSCs and slower growth with enhanced apoptosis and senescence. However, whether SLE MSCs demonstrate aberrant migration capacity or abnormalities in cytoskeleton are issues that remain poorly understood. In this study, we found that MSCs from SLE patients did show impairment in migration capacity as well as abnormalities in F-actin cytoskeleton, accompanied by a high level of intracellular reactive oxygen species (ROS). When normal MSCs were treated in vitro with H2O2, which increases intracellular ROS level as an oxidant, both reorganization of F-actin cytoskeleton and impairment of migration capability were observed. On the other hand, treatment with N-acetylcysteine (NAC), as an exogenous antioxidant, made F-actin more orderly and increased migration ratio in SLE MSCs. In addition, oral administration of NAC markedly reduced serum autoantibody levels and ameliorated lupus nephritis (LN) in MRL/lpr mice, partially reversing the abnormalities of MSCs. These results indicate that overpolymerization of F-actin cytoskeleton, which may be associated with high levels of ROS, causes impairment in the migration capacity of SLE MSCs and that oral administration of NAC may have potential therapeutic effects on MRL/lpr mice. Copyright © 2014 Elsevier Masson SAS. All rights reserved.
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Out of Africa: the importance of rivers as human migration corridors
Ramirez, J. A.; Coulthard, T. J.; Rogerson, M.; Barton, N.; Bruecher, T.
2013-12-01
The route and timing of Homo sapiens exiting Africa remains uncertain. Corridors leading out of Africa through the Sahara, the Nile Valley, and the Red Sea coast have been proposed as migration routes for anatomically modern humans 80,000-130,000 years ago. During this time climate conditions in the Sahara were wetter than present day, and monsoon rainfall fed rivers that flowed across the desert landscape. The location and timing of these rivers may have supported human migration northward from central Africa to the Mediterranean coast, and onwards to Europe or Asia. Here, we use palaeoclimate rainfall and a hydrological model to spatially simulate and quantitatively test the existence of three major rivers crossing the Sahara from south to north during the time of human migration. We provide evidence that, given realistic underlying climatology, the well-known Sahabi and Kufrah rivers very likely flowed across modern day Libya and reached the coast. More unexpectedly an additional river crossed the core of the Sahara through Algeria (Irharhar river) and flowed into the Chotts basin. The Irharhar river is unique, because it links locations in central Africa experiencing monsoon climates with temperate coastal Mediterranean environments where food and resources were likely abundant. From an ecological perspective, this little-known corridor may prove to be the most parsimonious migration route. Support for the Irharar as a viable migration corridor is provided by its geographic proximity to middle Stone Age archaeological artefacts found in North Africa. Our new, highly novel approach provides the first quantitative analysis of the likelihood that rivers occurred during the critical period of human migration out of Africa. Simulated probability of surface water in North Africa during the last interglacial and the location of tools and ornaments from the Middle Stone Age.
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Marriage, childbearing, and migration in Kyrgyzstan: Exploring interdependencies
Directory of Open Access Journals (Sweden)
Lesia Nedoluzhko
2010-02-01
Full Text Available In our study we investigate interdependencies between entry into a marital union, childbearing, and migration. We apply event-history techniques to retrospective data on women aged 18-29 from a survey conducted in northern Kyrgyzstan in 2005 to examine how these events can influence one another, with a special focus on the effects of duration of exposure. In addition we analyze the impact of some individual characteristics on the propensity to get married, to become a mother, and to migrate. In our analysis we account for several duration dependences ('clocks'. The results illustrate that months since marriage formation is the most important duration variable in the first-birth propensities model. Out-of-wedlock conception is associated with increased marriage risks. Migration is often a part of the family building process: high first-birth propensities of recent migrants as well as high migration risks among pregnant women are due to marriage-related migration.
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Migration of accreting giant planets
Crida, A.; Bitsch, B.; Raibaldi, A.
2016-12-01
We present the results of 2D hydro simulations of giant planets in proto-planetary discs, which accrete gas at a more or less high rate. First, starting from a solid core of 20 Earth masses, we show that as soon as the runaway accretion of gas turns on, the planet is saved from type I migration : the gap opening mass is reached before the planet is lost into its host star. Furthermore, gas accretion helps opening the gap in low mass discs. Consequently, if the accretion rate is limited to the disc supply, then the planet is already inside a gap and in type II migration. We further show that the type II migration of a Jupiter mass planet actually depends on its accretion rate. Only when the accretion is high do we retrieve the classical picture where no gas crosses the gap and the planet follows the disc spreading. These results impact our understanding of planet migration and planet population synthesis models. The e-poster presenting these results in French can be found here: L'e-poster présentant ces résultats en français est disponible à cette adresse: http://sf2a.eu/semaine-sf2a/2016/posterpdfs/156_179_49.pdf.
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Changes in timing of autumn migration in North European songbird populations
DEFF Research Database (Denmark)
Tøttrup, Anders Peter; Thorup, Kasper; Rahbek, Carsten
2006-01-01
Although studies of changes in the timing of passerine spring migration are numerous, less is known about timing of their autumn departure. We present phenological data on 22 species based on mist-netted birds caught on the Baltic island of Christiansø during autumn migration between 1976 and 1997...... departure (-0.0426 days year-1, P = 0.40). Testing the 12 species for which the entire migration period was included (thus excluding many long-distance migrants), we found an overall earlier departure (-0.18 days year-1, P = 0.007). Short-distance migrants tended to show earlier departure, while long...
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The impact of unemployment insurance benefits on the probability of migration of the unemployed.
Gose, E; Paul, C
1990-08-01
"By ignoring individual unemployment compensation benefits and conditions of job termination, past migration research has concluded that personal unemployment doubles the likelihood of interstate labor-force migration. Findings from the present study indicate that aggregating the unemployed, without adjusting for these two factors, overstates the probability of migration for the involuntarily unemployed benefit recipient and understates the likelihood of migration for the voluntarily unemployed benefit recipient. The results suggest that federal discretionary unemployment-compensation programs, which are implemented during recessionary periods, likely serve to retard out-migration of those who are involuntarily unemployed." Data are from a 1982 sample of unemployed U.S. workers. excerpt
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Did the ancient Egyptians migrate to ancient Nigeria?
Directory of Open Access Journals (Sweden)
Jock M. Agai
2014-01-01
Full Text Available Literatures concerning the history of West African peoples published from 1900 to 1970 debate�the possible migrations of the Egyptians into West Africa. Writers like Samuel Johnson and�Lucas Olumide believe that the ancient Egyptians penetrated through ancient Nigeria but Leo�Frobenius and Geoffrey Parrinder frowned at this opinion. Using the works of these early�20th century writers of West African history together with a Yoruba legend which teaches�about the origin of their earliest ancestor(s, this researcher investigates the theories that the�ancient Egyptians had contact with the ancient Nigerians and particularly with the Yorubas.Intradisciplinary and/or interdisciplinary implications: There is an existing ideology�amongst the Yorubas and other writers of Yoruba history that the original ancestors of�the Yorubas originated in ancient Egypt hence there was migration between Egypt and�Yorubaland. This researcher contends that even if there was migration between Egypt and�Nigeria, such migration did not take place during the predynastic and dynastic period as�speculated by some scholars. The subject is open for further research.
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Job transfers: a neglected aspect of migration in Malaysia.
Menon, R
1987-01-01
"This article examines the incidence of [job-related] transfers in Malaysia. The retrospective migration data from the Malaysia Family Life Survey [conducted in 1976-1977] are used to demonstrate that transfers comprise 18 percent of all migration in the country and that there has been a rise in the incidence of transfers over a 35 year period. Factors underlying this trend are outlined. Furthermore, significant differences in age, educational attainment and other characteristics between transferees and other types of migrants are identified and their implications discussed." excerpt
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Migration-driven diversity of super-Earth compositions
Raymond, Sean N.; Boulet, Thibault; Izidoro, Andre; Esteves, Leandro; Bitsch, Bertram
2018-06-01
A leading model for the origin of super-Earths proposes that planetary embryos migrate inward and pile up on close-in orbits. As large embryos are thought to preferentially form beyond the snow line, this naively predicts that most super-Earths should be very water-rich. Here we show that the shortest-period planets formed in the migration model are often purely rocky. The inward migration of icy embryos through the terrestrial zone accelerates the growth of rocky planets via resonant shepherding. We illustrate this process with a simulation that provided a match to the Kepler-36 system of two planets on close orbits with very different densities. In the simulation, two super-Earths formed in a Kepler-36-like configuration; the inner planet was pure rock while the outer one was ice-rich. We conclude from a suite of simulations that the feeding zones of close-in super-Earths are likely to be broad and disconnected from their final orbital radii.
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THE DETERMINANTS OF INTERNAL MIGRATION: THE CASE OFTURKEY
Directory of Open Access Journals (Sweden)
Ciler Sigeze
2016-07-01
Full Text Available This study investigates the determinants of the net migration statistics at regionallevel-1, consisting 12 regions, according to the Nomenclature of Units forTerritorial Statistics (NUTS of Turkey during the period 2008-2014 utilizingFeasible Generalized Least Squares. The results show that the coefficient ofpoverty variable found negative as consistent with literature. This finding suggeststhat migration movements are still one of the important strategies against poverty.In the study, the amount of exports and electricity per person used as a proxy forthe level of development of the regions foundsignificant and positive on the netmigration rate of the region. This result shows that the level of development of aregion is related to the net migration of that region in the same direction.Therefore, policy makers should implement policies on internal migrationmovements todecrease differences in income inequality and development levelsbetween regions.
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Realization of dynamic data migration and purge operations
International Nuclear Information System (INIS)
Wang Juan; Qiu Hongmao; Liu Junmin; Wang Xiaoming; Wang Hong; Zhong Bo; Lu Yuanlei; Xu Jin
2008-01-01
In the large scale real time data processing, with the time extend, the data in database system will be expanded, which declines the system capability. To solve the problem, this paper presents a method of migration and purge operations. New or updated database records within a specified time interval can be copied automatically from source database accounts to destination database accounts and the data in the source database will be deleted automatically after a specified period of time according to the rules using the method. The migration and purge operations have been realized in China National Data Center. (authors)
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Bacterial migration through punctured surgical gloves under real surgical conditions
Directory of Open Access Journals (Sweden)
Heidecke Claus-Dieter
2010-07-01
Full Text Available Abstract Background The aim of this study was to confirm recent results from a previous study focussing on the development of a method to measure the bacterial translocation through puncture holes in surgical gloves under real surgical conditions. Methods An established method was applied to detect bacterial migration from the operating site through the punctured glove. Biogel™ double-gloving surgical gloves were used during visceral surgeries over a 6-month period. A modified Gaschen-bag method was used to retrieve organisms from the inner glove, and thus-obtained bacteria were compared with micro-organisms detected by an intra-operative swab. Results In 20 consecutive procedures, 194 gloves (98 outer gloves, 96 inner gloves were examined. The rate of micro-perforations of the outer surgical glove was 10% with a median wearing time of 100 minutes (range: 20-175 minutes. Perforations occurred in 81% on the non-dominant hand, with the index finger most frequently (25% punctured. In six cases, bacterial migration could be demonstrated microbiologically. In 5% (5/98 of outer gloves and in 1% (1/96 of the inner gloves, bacterial migration through micro-perforations was observed. For gloves with detected micro-perforations (n = 10 outer layers, the calculated migration was 50% (n = 5. The minimum wearing time was 62 minutes, with a calculated median wearing time of 71 minutes. Conclusions This study confirms previous results that bacterial migration through unnoticed micro-perforations in surgical gloves does occur under real practical surgical conditions. Undetected perforation of surgical gloves occurs frequently. Bacterial migration from the patient through micro-perforations on the hand of surgeons was confirmed, limiting the protective barrier function of gloves if worn over longer periods.
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MRI of neuronal migration disorders
International Nuclear Information System (INIS)
Engelbrecht, V.
1996-01-01
Twenty-one MRI examinations of the brain were performed in 19 children with neuronal migration disorders. Multiplanar oriented spin-echo sequences were on a scanner with 1.5 T. In 8 children we performed an additional turbo-inversion recovery (TIR) sequence. Results of sonography or CT from five children were compared with MRI scans. Using the actual nomenclature, we found the following migration disorders: Lissencephaly (n=6), cobblestone lissencephaly with Walker-Warbung syndrome (WWS) (n=2), polymicrogyria and schizencephaly (n=2), focal heterotopia (n=5), diffuse heterotopie (n=2) and hemimegalencephaly (n=2). MRI was superior to CT and sonography in all children. Except for the two boys with WWS, the TIR sequence was the best to demonstrate the changes in migration disorder because of the high contrast between gray and white matter. We demonstrate the characteristic features of the different migration disorders and compare them with the existing literature. (orig.) [de
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The possibilities of compressed-sensing-based Kirchhoff prestack migration
Aldawood, Ali; Hoteit, Ibrahim; Alkhalifah, Tariq Ali
2014-01-01
An approximate subsurface reflectivity distribution of the earth is usually obtained through the migration process. However, conventional migration algorithms, including those based on the least-squares approach, yield structure descriptions that are slightly smeared and of low resolution caused by the common migration artifacts due to limited aperture, coarse sampling, band-limited source, and low subsurface illumination. To alleviate this problem, we use the fact that minimizing the L1-norm of a signal promotes its sparsity. Thus, we formulated the Kirchhoff migration problem as a compressed-sensing (CS) basis pursuit denoise problem to solve for highly focused migrated images compared with those obtained by standard and least-squares migration algorithms. The results of various subsurface reflectivity models revealed that solutions computed using the CS based migration provide a more accurate subsurface reflectivity location and amplitude. We applied the CS algorithm to image synthetic data from a fault model using dense and sparse acquisition geometries. Our results suggest that the proposed approach may still provide highly resolved images with a relatively small number of measurements. We also evaluated the robustness of the basis pursuit denoise algorithm in the presence of Gaussian random observational noise and in the case of imaging the recorded data with inaccurate migration velocities.
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The possibilities of compressed-sensing-based Kirchhoff prestack migration
Aldawood, Ali
2014-05-08
An approximate subsurface reflectivity distribution of the earth is usually obtained through the migration process. However, conventional migration algorithms, including those based on the least-squares approach, yield structure descriptions that are slightly smeared and of low resolution caused by the common migration artifacts due to limited aperture, coarse sampling, band-limited source, and low subsurface illumination. To alleviate this problem, we use the fact that minimizing the L1-norm of a signal promotes its sparsity. Thus, we formulated the Kirchhoff migration problem as a compressed-sensing (CS) basis pursuit denoise problem to solve for highly focused migrated images compared with those obtained by standard and least-squares migration algorithms. The results of various subsurface reflectivity models revealed that solutions computed using the CS based migration provide a more accurate subsurface reflectivity location and amplitude. We applied the CS algorithm to image synthetic data from a fault model using dense and sparse acquisition geometries. Our results suggest that the proposed approach may still provide highly resolved images with a relatively small number of measurements. We also evaluated the robustness of the basis pursuit denoise algorithm in the presence of Gaussian random observational noise and in the case of imaging the recorded data with inaccurate migration velocities.
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Least-squares migration of multisource data with a deblurring filter
Dai, Wei; Wang, Xin; Schuster, Gerard T.
2011-01-01
Least-squares migration (LSM) has been shown to be able to produce high-quality migration images, but its computational cost is considered to be too high for practical imaging. We have developed a multisource least-squares migration algorithm (MLSM) to increase the computational efficiency by using the blended sources processing technique. To expedite convergence, a multisource deblurring filter is used as a preconditioner to reduce the data residual. This MLSM algorithm is applicable with Kirchhoff migration, wave-equation migration, or reverse time migration, and the gain in computational efficiency depends on the choice of migration method. Numerical results with Kirchhoff LSM on the 2D SEG/EAGE salt model show that an accurate image is obtained by migrating a supergather of 320 phase-encoded shots. When the encoding functions are the same for every iteration, the input/output cost of MLSM is reduced by 320 times. Empirical results show that the crosstalk noise introduced by blended sources is more effectively reduced when the encoding functions are changed at every iteration. The analysis of signal-to-noise ratio (S/N) suggests that not too many iterations are needed to enhance the S/N to an acceptable level. Therefore, when implemented with wave-equation migration or reverse time migration methods, the MLSM algorithm can be more efficient than the conventional migration method. © 2011 Society of Exploration Geophysicists.
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Least-squares migration of multisource data with a deblurring filter
Dai, Wei
2011-09-01
Least-squares migration (LSM) has been shown to be able to produce high-quality migration images, but its computational cost is considered to be too high for practical imaging. We have developed a multisource least-squares migration algorithm (MLSM) to increase the computational efficiency by using the blended sources processing technique. To expedite convergence, a multisource deblurring filter is used as a preconditioner to reduce the data residual. This MLSM algorithm is applicable with Kirchhoff migration, wave-equation migration, or reverse time migration, and the gain in computational efficiency depends on the choice of migration method. Numerical results with Kirchhoff LSM on the 2D SEG/EAGE salt model show that an accurate image is obtained by migrating a supergather of 320 phase-encoded shots. When the encoding functions are the same for every iteration, the input/output cost of MLSM is reduced by 320 times. Empirical results show that the crosstalk noise introduced by blended sources is more effectively reduced when the encoding functions are changed at every iteration. The analysis of signal-to-noise ratio (S/N) suggests that not too many iterations are needed to enhance the S/N to an acceptable level. Therefore, when implemented with wave-equation migration or reverse time migration methods, the MLSM algorithm can be more efficient than the conventional migration method. © 2011 Society of Exploration Geophysicists.
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Domestic Diasporas And Trans-Border Migrations: The Implications ...
African Journals Online (AJOL)
While these migration existed in the pre-colonial period the relationships between the indigenes and non-indigenes or settlers were sometimes harmonious, the dynamics of colonial developments encouraged ethnic and communal competition for the control of socio-political and economic benefits arising from colonialism.
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Inclusive growth? : Labour migration and poverty in India
A. de Haan (Arjan)
2011-01-01
textabstractThis paper discusses the relationship between labour migration and poverty in India. This is placed against the on-going debates on changes in patterns of employment and job creation in India, during the periods of economic liberalization, under the Inclusive Growth policies since 2004,
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Directory of Open Access Journals (Sweden)
Zimovina E. P.
2014-05-01
Full Text Available This paper analyses the migration processes and their influence on the transformation of multiethnic population structure in the Kaliningrad region. The author uses official statistics (current statistics and census data, as well as interviews with the representatives of ethnic cultural associations as information sources. Special attention is paid to the migration features associated with different ethnic groups. The author identifies major reasons behind the incoming and outgoing movement of population. In the post-Soviet period the Kaliningrad region has experienced positive net migration. This active migration into the region has contributed to the development of “migration networks” and established a new basis for further population increase through migration. The article describes changes in the regional multiethnic population structure and identifies key factors behind them. It is concluded that migration has played the decisive role in the process of multiethnic population structure transformation in the Kaliningrad region in the post-Soviet period. The author views migration as a serious test for both the migrants and the receiving society. On the one hand, migrants have to adapt to a different national, cultural, and linguistic environment and look for the ways of successful integration into the receiving society. On the other hand, the receiving society also faces a serious transformation as a result of the changing population size and structure, the emergence of new elements in culture, rules of behaviour, and the development of new attitudes.
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Cabrera-Cruz, Sergio A; Smolinsky, Jaclyn A; Buler, Jeffrey J
2018-02-19
Excessive or misdirected artificial light at night (ALAN) produces light pollution that influences several aspects of the biology and ecology of birds, including disruption of circadian rhythms and disorientation during flight. Many migrating birds traverse large expanses of land twice every year at night when ALAN illuminates the sky. Considering the extensive and increasing encroachment of light pollution around the world, we evaluated the association of the annual mean ALAN intensity over land within the geographic ranges of 298 nocturnally migrating bird species with five factors: phase of annual cycle, mean distance between breeding and non-breeding ranges, range size, global hemisphere of range, and IUCN category of conservation concern. Light pollution within geographic ranges was relatively greater during the migration season, for shorter-distance migrants, for species with smaller ranges, and for species in the western hemisphere. Our results suggest that migratory birds may be subject to the effects of light pollution particularly during migration, the most critical stage in their annual cycle. We hope these results will spur further research on how light pollution affects not only migrating birds, but also other highly mobile animals throughout their annual cycle.
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Family migration and employment: the importance of migration history and gender.
Bailey, A J; Cooke, T J
1998-01-01
"This article uses event history data to specify a model of employment returns to initial migration, onward migration, and return migration among newly married persons in the U.S. Husbands are more likely to be full-time employed than wives, and being a parent reduces the employment odds among married women. Employment returns to repeated migration differ by gender, with more husbands full-time employed after onward migration and more wives full-time employed after return migration events. We interpret these empirical findings in the context of family migration theory, segmented labor market theory, and gender-based responsibilities." Data are from the National Longitudinal Survey of Youth from 1979 to 1991. excerpt
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Stark, Oded
2007-01-01
At least to some extent migration behavior is the outcome of a preference for migration. The pattern of migration as an outcome of a preference for migration depends on two key factors: imitation technology and migration feasibility. We show that these factors jointly determine the outcome of a preference for migration and we provide examples that illustrate how the prevalence and transmission of a migration-forming preference yield distinct migration patterns. In particular, the imitation of...
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SITE-94. Estimated rates of redox-front migration in granitic rocks
International Nuclear Information System (INIS)
Arthur, R.C.
1996-10-01
Analytical models for the rate of migration of oxidizing groundwaters are derived based on the stationary-state approximation to coupled fluid flow and water-rock interaction, and are constrained by molar concentrations of ferrous silicate, oxide, and sulfide minerals in the granites and associated fractures comprising the host rock beneath Aespoe. Model results indicate that small amounts of ferrous minerals in Aespoe granites and fractures will retard the downward migration of oxidizing conditions that could be generated by infiltration of glacial meltwaters during periods of glacial maxima and retreat. Calculated front velocities are retarded relative to Darcy fluxes observed in conductive fracture zones at Aespoe (0.3 to 3 m/y) by factors ranging from 10 -3 to 10 -4 . Corresponding times for the front to migrate 500 m vary from 5,100 to 4,400,000 years. Retardation efficiency depends on mineralogy and decreases in the order: fractures > altered granites > unaltered granite. The most conductive structures in these rocks are therefore the most efficient in limiting the rate of front migration. Periods of recharge during glaciation are comparable to times required for an oxidizing front to migrate to repository levels. This suggests an oxidizing front could reach repository depths during a single glacial-interglacial event. The persistence of oxidizing conditions could be relatively short lived, however, because reversal of flow conditions driven by the advance and retreat of ice sheets could cause reducing conditions to be restored. 27 refs
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The commercialization of migration.
Abrera-mangahas, M A
1989-01-01
International migration is not new to the Philippines. In the recent outflow of contract workers to the Middle East, there is a shift from individual and family initiated migrations to the more organized, highly commercial variety. While profit-taking intermediaries have played some role in the past, the increase in the number and influence of these intermediaries has altered the story of migration decision-making. In 1975, the signing of the bilateral labor agreement between the governments of Iran and the Philippines signalled the rising demand for Filipino contract workers. From 1970 to 1975, the number of Asian migrant workers in the Gulf countries rose from about 120,000 to 370,000. These figures rose dramatically to 3.3 million in 1985. The growing share of organized and commercialized migration has altered migration decision making. Primarily, intermediaries are able to broaden access to foreign job and high wage opportunities. Commercialization effectively raises the transaction costs for contract migration. Studies on recruitment costs and fees show that self-solicited foreign employment costs less than employment obtained through recruitment agents and intermediaries. The difference in the 2 prices is due, not only to overhead costs of intermediation, but more importantly to the rent exacted by agents from having job information and placement rights. In the Philippines in October 1987 the average placement fee was P8000, greatly exceeding the mandated maximum fee level of P5000. This average is understated because the computation includes the 17% who do not pay any fees. The widespread and popular view of recruitment intermediaries is negative, dominated by images of abuses and victims. Private intermediaries and the government bureaucracy need each other. Intermediaries need government; their consistent demand for incentives and protection is indicative. On the other hand, government expands its supervision of control of overseas employment via the
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Migration Decision-Making among Mexican Youth: Individual, Family, and Community Influences.
Tucker, Christine M; Torres-Pereda, Pilar; Minnis, Alexandra M; Bautista-Arredondo, Sergio A
2013-05-07
We explored migration decisions using in-depth, semi-structured interviews with male and female youth ages 14 to 24 (n=47) from two Mexican communities, one with high and one with low U.S. migration density. Half were return migrants and half were non-migrants with relatives in the U.S. Migrant and non-migrant youth expressed different preferences, especially in terms of education and their ability to wait for financial gain. Reasons for migration were mostly similar across the two communities; however, the perceived risk of the migration journey was higher in the low density migration community while perceived opportunities in Mexico were higher in the high density migration community. Reasons for return were related to youths' initial social and economic motivations for migration. A greater understanding of factors influencing migration decisions may provide insight into the vulnerability of immigrant youth along the journey, their adaptation process in the U.S., and their reintegration in Mexico.
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Innovative Visualizations Shed Light on Avian Nocturnal Migration.
Directory of Open Access Journals (Sweden)
Judy Shamoun-Baranes
Full Text Available Globally, billions of flying animals undergo seasonal migrations, many of which occur at night. The temporal and spatial scales at which migrations occur and our inability to directly observe these nocturnal movements makes monitoring and characterizing this critical period in migratory animals' life cycles difficult. Remote sensing, therefore, has played an important role in our understanding of large-scale nocturnal bird migrations. Weather surveillance radar networks in Europe and North America have great potential for long-term low-cost monitoring of bird migration at scales that have previously been impossible to achieve. Such long-term monitoring, however, poses a number of challenges for the ornithological and ecological communities: how does one take advantage of this vast data resource, integrate information across multiple sensors and large spatial and temporal scales, and visually represent the data for interpretation and dissemination, considering the dynamic nature of migration? We assembled an interdisciplinary team of ecologists, meteorologists, computer scientists, and graphic designers to develop two different flow visualizations, which are interactive and open source, in order to create novel representations of broad-front nocturnal bird migration to address a primary impediment to long-term, large-scale nocturnal migration monitoring. We have applied these visualization techniques to mass bird migration events recorded by two different weather surveillance radar networks covering regions in Europe and North America. These applications show the flexibility and portability of such an approach. The visualizations provide an intuitive representation of the scale and dynamics of these complex systems, are easily accessible for a broad interest group, and are biologically insightful. Additionally, they facilitate fundamental ecological research, conservation, mitigation of human-wildlife conflicts, improvement of meteorological
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Multi-source least-squares reverse time migration
Dai, Wei
2012-06-15
Least-squares migration has been shown to improve image quality compared to the conventional migration method, but its computational cost is often too high to be practical. In this paper, we develop two numerical schemes to implement least-squares migration with the reverse time migration method and the blended source processing technique to increase computation efficiency. By iterative migration of supergathers, which consist in a sum of many phase-encoded shots, the image quality is enhanced and the crosstalk noise associated with the encoded shots is reduced. Numerical tests on 2D HESS VTI data show that the multisource least-squares reverse time migration (LSRTM) algorithm suppresses migration artefacts, balances the amplitudes, improves image resolution and reduces crosstalk noise associated with the blended shot gathers. For this example, the multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with a comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution and fewer migration artefacts compared to conventional RTM. The empirical results suggest that multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with a similar or less computational cost. The caveat is that the LSRTM image is sensitive to large errors in the migration velocity model. © 2012 European Association of Geoscientists & Engineers.
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Multi-source least-squares reverse time migration
Dai, Wei; Fowler, Paul J.; Schuster, Gerard T.
2012-01-01
Least-squares migration has been shown to improve image quality compared to the conventional migration method, but its computational cost is often too high to be practical. In this paper, we develop two numerical schemes to implement least-squares migration with the reverse time migration method and the blended source processing technique to increase computation efficiency. By iterative migration of supergathers, which consist in a sum of many phase-encoded shots, the image quality is enhanced and the crosstalk noise associated with the encoded shots is reduced. Numerical tests on 2D HESS VTI data show that the multisource least-squares reverse time migration (LSRTM) algorithm suppresses migration artefacts, balances the amplitudes, improves image resolution and reduces crosstalk noise associated with the blended shot gathers. For this example, the multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with a comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution and fewer migration artefacts compared to conventional RTM. The empirical results suggest that multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with a similar or less computational cost. The caveat is that the LSRTM image is sensitive to large errors in the migration velocity model. © 2012 European Association of Geoscientists & Engineers.
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Twilight vertical migrations of zooplankton in a Chilean fjord
Valle-Levinson, Arnoldo; Castro, Leonardo; Cáceres, Mario; Pizarro, Oscar
2014-12-01
Time series of acoustic backscatter and vertical velocity profiles were obtained at three sites along a Chilean fjord with the purpose of determining dominant structures of vertical migrations of the sound scattering layer. Ancillary data obtained with stratified net samples indicated that the sound scattering layer may have been dominated by euphausiids and decapods. Therefore, distributions of acoustic backscatter anomalies and vertical velocities were attributed to vertical migrations of predominantly these organisms. Migration patterns were dominated by twilight excursions in which organisms swam toward the water surface at sunset, spent 100 m). This migration strategy can also be termed 'semidiel migration' as two double excursions were linked to light levels. The reasons for this twilight migration remain uncertain. But it is possible that the up and down motion around sunset was related to predation avoidance, hunger-satiation state, ontogeny, seaward transport evasion, or reaction to the environmental shock from the pycnocline, or a combination of all or some of them. In contrast, the sunrise double excursion was probably linked to feeding requirements by organisms that need to spend the day at great depth with no food available. This study demonstrated the existence of semidiel patterns throughout the fjord and through prolonged periods. In addition, identification of this pattern by acoustic backscatter was complemented by direct vertical velocity measurements. It is proposed that twilight vertical migration is a common strategy in Chilean fjords.
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Ernstoff, Alexi S; Fantke, Peter; Huang, Lei; Jolliet, Olivier
2017-11-01
Specialty software and simplified models are often used to estimate migration of potentially toxic chemicals from packaging into food. Current models, however, are not suitable for emerging applications in decision-support tools, e.g. in Life Cycle Assessment and risk-based screening and prioritization, which require rapid computation of accurate estimates for diverse scenarios. To fulfil this need, we develop an accurate and rapid (high-throughput) model that estimates the fraction of organic chemicals migrating from polymeric packaging materials into foods. Several hundred step-wise simulations optimised the model coefficients to cover a range of user-defined scenarios (e.g. temperature). The developed model, operationalised in a spreadsheet for future dissemination, nearly instantaneously estimates chemical migration, and has improved performance over commonly used model simplifications. When using measured diffusion coefficients the model accurately predicted (R 2 = 0.9, standard error (S e ) = 0.5) hundreds of empirical data points for various scenarios. Diffusion coefficient modelling, which determines the speed of chemical transfer from package to food, was a major contributor to uncertainty and dramatically decreased model performance (R 2 = 0.4, S e = 1). In all, this study provides a rapid migration modelling approach to estimate exposure to chemicals in food packaging for emerging screening and prioritization approaches. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Terrestrial planet formation in the presence of migrating super-Earths
International Nuclear Information System (INIS)
Izidoro, André; Morbidelli, Alessandro; Raymond, Sean N.
2014-01-01
Super-Earths with orbital periods less than 100 days are extremely abundant around Sun-like stars. It is unlikely that these planets formed at their current locations. Rather, they likely formed at large distances from the star and subsequently migrated inward. Here we use N-body simulations to study the effect of super-Earths on the accretion of rocky planets. In our simulations, one or more super-Earths migrate inward through a disk of planetary embryos and planetesimals embedded in a gaseous disk. We tested a wide range of migration speeds and configurations. Fast-migrating super-Earths (τ mig ∼ 0.01-0.1 Myr) only have a modest effect on the protoplanetary embryos and planetesimals. Sufficient material survives to form rocky, Earth-like planets on orbits exterior to the super-Earths'. In contrast, slowly migrating super-Earths shepherd rocky material interior to their orbits and strongly deplete the terrestrial planet-forming zone. In this situation any Earth-sized planets in the habitable zone are extremely volatile-rich and are therefore probably not Earth-like.
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Migration between the United States and Canada: a study of labour market adjustment.
Brox, J A
1983-01-01
"... The main purpose of this study is to examine population flows between Canada and the United States [from mid-1947 to mid-1972] in order to investigate the degree to which labour market adjustment is aided by such movements. [The author considers] several functional forms of the migration relationship in an attempt to empirically determine how the decision to migrate is formed. [He also compares the] results with those obtained by Courchene...for Canadian interprovincial migration in an effort to compare the effects of international and internal migration on labour market adjustment." It is found that "migration between the United States and Canada over the post-war period is an economic variable. In fact, [a] simple model employing differences in income levels and unemployment rates has been able to explain nearly ninety-five per cent of the variation in the migration rate." The author also notes that "although migration between Canada and the United States does occur in such a way as to aid labour market adjustment, it is not as efficient as internal migration." (summary in FRE, SPA) excerpt
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Climate Change, Agriculture and Migration: A Survey
Directory of Open Access Journals (Sweden)
Chiara Falco
2018-05-01
Full Text Available This paper proposes a selective review of the classical economics-based literature on climate change and migration, focusing on the extent to which agriculture might be considered a key mediating channel linking climate change to migration. Overall, climate change is expected to have large and negative effects on the global economy. These effects are even more evident whenever the economic sector considered is the agricultural one, particularly in developing countries. Hence, migration can be viewed as a specific form of adaptation implemented by individuals and households, enabling them to cope, among other things, with weather-induced risk. We show that the importance of agriculture emerges from both plenty of micro-level country studies and relatively few macro-level analyses using cross-sectional data over longer time periods. Thus, policy actions targeted to sustainable agriculture and rural development can both help tackle the challenges posed by climate change and create opportunities in the face of growing migration issues. However, we also stress that much of the current evidence is based on statistical associations that have nothing to do with causal inferences. This calls for the use of a more structural approach and more sophisticated research designs, enabling the researchers to better discriminate among different mechanisms concurrently at work. In addition, further research should be addressed to the role played by food security, a complex dimension largely missing in the current debates on climate change and migration.
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Migration, human capital, and growth in a globalized economy
Burzynski, Michal
2016-01-01
This thesis focuses on the implications of past, and hypothetical future movements of people for the prosperity of natives and residents living in the highly developed regions. The first Chapter discusses the welfare impact of migration in the OECD countries by analyzing recent migration flows (net migration between 2000 and 2010), and total stock of migrants in 2010. The importance of different channels, through which migration affects the wellbeing of stayers, is discussed. In the second Ch...
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Feeding habits, daily ration and vertical migration of the cape horse ...
African Journals Online (AJOL)
The feeding periodicity, rate of gut evacuation and vertical migration of horse mackerel were investigated from midwater and bottom trawl collections taken during five diel sampling periods between 1993 and 1995 at fixed positions on the South Coast. Horse mackerel feed only during the day, mostly in late afternoon prior ...
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Selection and network effects - Migration flows into OECD countries 1990-2000
DEFF Research Database (Denmark)
Pedersen, Peder J.; Pytlikova, Mariola; Smith, Nina
2008-01-01
This paper presents empirical evidence on immigration flows into the OECD countries during the period 1990-2000. Our results indicate that network effects are strong, but vary between different groups of welfare states and between countries according to the type of immigration policy being applie...... a major influence on the observed migration patterns until now. This may partly be explained by restrictive migration policies which may have dampened the potential selection effects....
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International Nuclear Information System (INIS)
Put, M.; Henrion, P.
1992-01-01
For the modelling of the migration of radionuclides in the Boom clay formation, the analytical code MICOF has been updated with a 3-dimensional analytical solution for discrete sources. the MICOF program is used for the calculation of the release of α and β emitters from the HIGH LEVEL RADIOACTIVE WASTES (HLW). A coherent conceptual model is developed which describes all the major physico-chemical phenomena influencing the migration of radionuclides in the Boom clay. The concept of the diffusion accessible porosity is introduced and included in the MICOF code. Different types of migration experiments are described with their advantages and disadvantages. The thermal impact of the HLW disposal in the stratified Boom clay formation has been evaluated by a finite element simulation of the coupled heat and mass transport equation. The results of the simulations show that under certain conditions thermal convection cells may form, but the convective heat transfer in the clay formation is negligible. 6 refs., 19 figs., 2 tabs., 5 appendices
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Student Migration Potential: The Case of Bulgaria
Valentina Makni
2011-01-01
Transnational student mobility is a major factor, which plays an ambiguous role in the dynamic process of international highly skilled migration. In this paper we try to attempt an approximate profile of the potential migrant student in Bulgaria, according to the migration incentives, intentions and expectations of highly educated young people from six reputable universities in the country. For this purpose a sample study is applied based on binary logistic regression analysis. Some of the co...
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The efficiency of interprovincial migration in Canada, 1961-1978.
Islam, M N
1983-05-01
A programming model is used to analyze the impact of the efficiency of migration flows on regional income disparities in Canada. A new method to measure such efficiency is presented in an attempt to show that occupations involving high-level skills and training have efficient migration patterns. The relationship between income differentials and internal migration is discussed.
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The future scenario for international labour migration.
Tassello, G
1989-01-01
The study of migration helps us to grasp the social evolution and the political and economic strategies required to meet the new economic trends. The issue of permanent or temporary migration, long debated in the 1960s, now tends to disappear. Migrants are compared more to commuters on the international labor markets. Besides the economic out-migration flows, there are also the refugee migrations or the ever present phenomenon of persons uprooted from their home country as a result of natural disasters and famine. The worldwide economic crisis in the 1970s, the recession affecting some industrialized countries which used to be traditional labor-importing countries have barred many potential immigrant workers from entering these countries. If, on 1 hand, the persistent high rate of unemployment due to the transformation of industry and the computerization process has caused the dismissal of numerous unskilled--mainly immigrants--on the other hand, it has created the exigency of highly qualified personnel. The children of the indigenous population are therefore favored because of their better scholastic training. A 2nd generation is now condemned to remain marginal even though they have been brought up to the ideals of social improvement and integration into higher standards of living. A highly dissatisfied category of young people is now an integral part of many labor-importing countries. Many industrial countries are flirting with zero population growth. Considering the demographic, economic, social, and political imbalances which exist and tend to grow, the world now has all the prerequisites for huge and prolonged migration flows originating from the South and moving almost exclusively toward the megacities and the industrial countries in the North. As long as technological as well as social inequalities persist, inner and international migration flows will continue. It is evident that the aim of many highly industrialized countries is the total ceasing of all
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Double path-integral migration velocity analysis: a real data example
International Nuclear Information System (INIS)
Costa, Jessé C; Schleicher, Jörg
2011-01-01
Path-integral imaging forms an image with no knowledge of the velocity model by summing over the migrated images obtained for a set of migration velocity models. Double path-integral imaging migration extracts the stationary velocities, i.e. those velocities at which common-image gathers align horizontally, as a byproduct. An application of the technique to a real data set demonstrates that quantitative information about the time migration velocity model can be determined by double path-integral migration velocity analysis. Migrated images using interpolations with different regularizations of the extracted velocities prove the high quality of the resulting time-migration velocity information. The so-obtained velocity model can then be used as a starting model for subsequent velocity analysis tools like migration tomography or other tomographic methods
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Rural migration in southern Nevada
International Nuclear Information System (INIS)
Mosser, D.; Soden, D.L.
1993-01-01
This study reviews the history of migration in two rural counties in Southern Nevada. It is part of a larger study about the impact of a proposed high-level nuclear waste repository on, in and out-migration patterns in the state. The historical record suggests a boom and bust economic cycle has predominated in the region for the past century creating conditions that should be taken into account, by decision makers, when ascertaining the long-term impacts of the proposed repository
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Effort Estimation in BPMS Migration
Drews, Christopher; Lantow, Birger
2018-01-01
Usually Business Process Management Systems (BPMS) are highly integrated in the IT of organizations and are at the core of their business. Thus, migrating from one BPMS solution to another is not a common task. However, there are forces that are pushing organizations to perform this step, e.g. maintenance costs of legacy BPMS or the need for additional functionality. Before the actual migration, the risk and the effort must be evaluated. This work provides a framework for effort estimation re...
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Migration and Ageing of the Island Population – Five Stories from Iž
Directory of Open Access Journals (Sweden)
Sanja Klempić
2002-12-01
Full Text Available The paper analyses population development on the island of Iž during the period from 1857 to 2001, with special focus on the role that migration has on the ageing of the population. The processes that effected the demographic picture of the island during the twentieth century were high war loses in two world wars and continuous migration. Depopulation on Iž began in 1921 and has persisted until today. According to the last census, 557 persons live on the island, which is half the number that was registered in the first census. The dominant demo-reproduction processes are depopulation and ageing. All indicators in regard to the age structure show a very old population. At the same time, there is a strong return migration flow of persons that have received pensions after having worked elsewhere, which further increases the percentage of elderly in the overall population. Apart from analysis of the demographic data, the aim of the paper was also to determine the existing models of return migration, based on the example of several typical migration experiences. The authors attempted to illustrate the effect of migration on the life cycle of the Iž’s older population through five typical island stories, collected in October 2001 while interviewing persons 60 or more years of age. If a major change does not occur in regard to the present trend of emigration of the younger population (creation of jobs, revival of economic activities that have a future on the island etc. and in the behaviour of younger islanders (both those living at present on the island and those living elsewhere who would accept such new programmes, Iž will remain in the group of islands that is threatened by further ageing and depopulation.
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A personality theory of U.S. migration geography.
Stetzer, F C
1985-01-01
"Neoclassical models of migration fail to account adequately for individual differences in propensity to migrate, rates of emigration from states and cities, and the generally high rates of population circulation common in the United States. This article proposes that migration propensity is related to an individual's personality. Using the facts that personality traits are generationally regenerative, both through inheritance and culture, and that the United States was settled in a series of migration waves from east to west, this theory predicts a spatial structuring of emigration rates which closely correspond to actual rates for states and major cities." excerpt
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Lowland-upland migration of sauropod dinosaurs during the Late Jurassic epoch.
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.
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International Nuclear Information System (INIS)
Rahmanian, Afsaneh; Knoll, Meinhard
2012-01-01
Highlights: ► We modify the doping front migration process. ► The migration velocity is controlled by a separate electrode. ► The process may be used in “best use before” labels. - Abstract: We demonstrate a new method of modifying the doping front migration process in multilayer structures, enabling the control of migration velocity. The presence of two interfaces in contact with the migration layer strongly affects the migration mechanism. Electrochemical switching of an electrode at one interface may be used to control the chemical doping front migration at the second interface. The process may be used to produce ultralow-cost devices acting as electronic “best use before” labels on food and drink or “use-by” labels on drugs. Control of the migration velocity may be used as a method for weighting storage conditions (i.e. opening of a package during the measurement period increases the migration velocity).
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Glaser, Rüdiger; Himmelsbach, Iso; Bösmeier, Annette
2017-11-01
This paper contributes to the ongoing debate on the extent to which climate and climatic change can have a negative impact on societies by triggering migration, or even contribute to conflict. It summarizes results from the transdisciplinary project Climate of migration (funded 2010-2014), whose innovative title was created by Franz Mauelshagen and Uwe Lübken. The overall goal of this project was to analyze the relation between climatic and socioeconomic parameters and major migration waves from southwest Germany to North America during the 19th century. The article assesses the extent to which climatic conditions triggered these migration waves. The century investigated was in general characterized by the Little Ice Age with three distinct cooling periods, causing major glacier advances in the alpine regions and numerous climatic extremes such as major floods, droughts and severe winter. Societal changes were tremendous, marked by the warfare during the Napoleonic era (until 1815), the abolition of serfdom (1817), the bourgeois revolution (1847/48), economic freedom (1862), the beginning of industrialization accompanied by large-scale rural-urban migration resulting in urban poverty, and finally by the foundation of the German Empire in 1871.The presented study is based on quantitative data and a qualitative, information-based discourse analysis. It considers climatic conditions as well as socioeconomic and political issues, leading to the hypothesis of a chain of effects ranging from unfavorable climatic conditions to a decrease in crop yields to rising cereal prices and finally to emigration. These circumstances were investigated extensively for the peak emigration years identified with each migration wave. Furthermore, the long-term relations between emigration and the prevailing climatic conditions, crop yields and cereal prices were statistically evaluated with a sequence of linear models which were significant with explanatory power between 22 and 38 %.
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In situ migration experiment in argillaceous formation
International Nuclear Information System (INIS)
Yoshida, Hidekazu
1990-01-01
International cooperative R and D has been performed within the five years framework of the bilateral agreement between PNC (Power Reactor and Nuclear Fuel Development Corporation) and SCK/CEN (Studiecentrum voor Kernergie/Centre D'etude de L'energie Nucleaire, Mol, Belgium) which is focused on 'The Migration Experiment in argillaceous formation.' This Tertiary argillaceous formation, called Boom clay, is located at about 230m depth in Mol-Dessel area, Belgium. The argillaceous rock is considered to have a high capability for retardation to radionuclides when they migrate in geosphere because of a high content of clay minerals and dissolved carbon-rich pore water. The main purpose of this collaboration work is to characterize the migration phenomena in sedimentary rock through understanding of the behaviour of radionuclides migration in the argillaceous formation. The present report describes the preliminary results of in situ one-dimensional migration experiment with labelled clay core emplaced in borehole under advective condition. In the experiment, radioactive tracer Sr-85 and Eu-152+154 have been used in order to determine the apparent dispersion coefficient and retardation factor of Boom clay. Finally, the following conclusions were obtained by in situ measurement and calculation based on a appropriate migration model; a) From the Sr-85 experiment, diffusive behavior is interpreted to be a dominant phenomena on radionuclides transportation. b) From the Eu-152+154 experiment, very small non-retarded fraction is observed. (author)
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Milestones of the history of modern Western theory of migration
Directory of Open Access Journals (Sweden)
A M Adediran
2015-12-01
Full Text Available The article outlines the key stages in the development of modern theory of migration following the historical sequence and continuity of its basic conceptual constructs’ formation. Although the author refers to the twentieth century as a chronological framework of the text, the narrative begins from the works of E. Ravenstein published at the end of the XIX century, for they laid the foundation for future theoretical studies on migration issues. In particular, many well-known scientists still use concepts “laws of migration” and “attracting and push factors of migration” proposed by Ravenstein claiming their timeless validity or, on the contrary, criticizing them for the loss of relevance in the new social and cultural realities. The author considers as milestones of the modern theory of migration the works of the representatives of Chicago school of sociology that enriched the conceptual apparatus of the analysis of migration processes and the typology of driving causes of migration; the works of S. Stouffer, G. Zipf, E. Lee and W. Lewis, W. Zelinsky and D. Massey. Finally, the article summarizes the objective trends in today’s global development that force scientists to introduce new accents in the study of migration processes, although upon closer inspection it turns out that all “new” ideas had already been formulated in early migration studies and just got a new sound in another historical period.
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International nurse migrations: Global trends
Directory of Open Access Journals (Sweden)
Ivković Marija
2011-01-01
Full Text Available This paper presents global trends of migration of nurses, as specific qualified personnel in high demand. In the last couple of decades, and especially in the last couple of years, many countries have faced the problem of insufficient healthcare workers, particularly nurses. Reasons for this occurrence might be found in the deficiencies of their education systems, as well as the population aging of northern and western countries. As a response to this deficiency, those countries have begun intensive recruitment of foreign qualified female healthcare workers, which has led to the point that nurse migration today presents a very intense, and by many accounts specific migration flow. Female migrating work force is often in pursuit of low-wage and lowqualified work. Nurse migration is actually an example of motion of qualified female migrants in pursuit for better employment opportunities. While such a way of filling up the vacant positions works for the “importing” countries as a temporary solution, departure of trained female personnel presents a significant loss for the originating countries. In this paper we pay special attention to the countries who are the main “importers”, but also to those who are “exporters” of nursing personnel, and to specific national strategies these countries have applied.
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Morphological constraints on changing avian migration phenology.
Møller, A P; Rubolini, D; Saino, N
2017-06-01
Many organisms at northern latitudes have responded to climate warming by advancing their spring phenology. Birds are known to show earlier timing of spring migration and reproduction in response to warmer springs. However, species show heterogeneous phenological responses to climate warming, with those that have not advanced or have delayed migration phenology experiencing population declines. Although some traits (such as migration distance) partly explain heterogeneity in phenological responses, the factors affecting interspecies differences in the responsiveness to climate warming have yet to be fully explored. In this comparative study, we investigate whether variation in wing aspect ratio (reflecting relative wing narrowness), an ecomorphological trait that is strongly associated with flight efficiency and migratory behaviour, affects the ability to advance timing of spring migration during 1960-2006 in a set of 80 European migratory bird species. Species with larger aspect ratio (longer and narrower wings) showed smaller advancement of timing of spring migration compared to species with smaller aspect ratio (shorter and wider wings) while controlling for phylogeny, migration distance and other life-history traits. In turn, migration distance positively predicted aspect ratio across species. Hence, species that are better adapted to migration appear to be more constrained in responding phenologically to rapid climate warming by advancing timing of spring migration. Our findings corroborate the idea that aspect ratio is a major evolutionary correlate of migration, and suggest that selection for energetically efficient flights, as reflected by high aspect ratio, may hinder phenotypically plastic/microevolutionary adjustments of migration phenology to ongoing climatic changes. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.
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Data and methods in the environment-migration nexus
DEFF Research Database (Denmark)
Eklund, Lina; Romankiewicz, Clemens; Brandt, Martin Stefan
2016-01-01
The relationship between environment and migration has gained increased attention since the 1990s when the Intergovernmental Panel on Climate Change projected climate change to become a major driver of human migration. Evaluations of this relationship include both quantitative and qualitative ass....... Several case studies base their results on data at very coarse resolutions that have undergone strong modifications and generalizations. We argue that scale-related shortcomings must be considered in all stages of environment-migration research....... assessments. This review article introduces the concept of scale to environment-migration research as an important methodological issue for the reliability of conclusions drawn. The review of case studies shows that scale issues are highly present in environment-migration research but rarely discussed...
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Vineetha, G.
2015-04-03
Monsoonal estuaries, located along the coastline of the Indian subcontinent, differ from other estuaries by their time dependence on the salinity characteristics. Effective sustenance and retention of the mesozooplankton community in the estuarine habitats is often determined by their dominant behavioral patterns: diel vertical migration (DVM) and tidal vertical migration (TVM). The modes of these endogenous rhythms often vary among estuaries based on the river runoff and tidal characteristics. The present study is a pioneering attempt to depict the vertical migration pattern of zooplankton along a diel and tidal scale in a tropical, microtidal, monsoonal estuary. We observed that in spite of the prominent asymmetry in the magnitude of the river runoff between the seasons, most of the zooplankton groups exhibited strong DVM, with a clear increase in biomass and abundance in surface waters during night. The peak increase in biomass and abundance at night always synchronized with the slack periods in the tidal cycles, which differed from the general concepts of downward migration during ebb tide and upward migration during flood tide in estuarine systems. The weak currents during the slack period might have favored the effective vertical migration of the mesozooplankton community in this monsoonal estuarine system. © 2015 Society of Wetland Scientists
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THE SEDUCTION OF MIGRATION WITH REGARD TO ROMANIAN WORKERS
Directory of Open Access Journals (Sweden)
Leca Irina
2015-07-01
Full Text Available The shock of the transition from a centralized type to a free market type economy and the fall of barriers with regard to migratory labor force in the countries of Central and Eastern Europe, after the fall of communist regimes in the early 1990s, have led to national companies modeling, producing a new configuration of Europe, under the banner of cooperation and common values. If in the case of Romania before 1989 we were dealing with migration restriction in the forthcoming period communism we are witnessing a massive flow of migration of the labor force, its own citizens leaving national territory in favor of establishing either temporary or definitive in Europe or in countries outside the European Union. The term migration has exceeded the strictly considered academic environment, becoming a popular subject, commonly used by the media and the population, but largely minimized by the Romanian political class. Given its particular importance on the socio-economic, cultural and political development, the purpose of this study is to get a better understanding of the magnitude of the Romanian migration and the causes that have led to its genesis and stimulation. Why people choose to emigrate, which are the motives which cause them to adopt this behavior, which are the countries of destination and which are the clichés faced by Romanian migrants there, what are the consequences of such a process, these are the questions to which we want to have an answer. Literature in the field, rigorous studies of visiting scientists from the various areas, the statistical data from the various publications by the National institute of Statistics and online media sources have been given a picture of the phenomenon being investigated, and which have been added to the data collected as a result of the application of a questionnaire in the Romanian community from the United Arab Emirates. This will highlight a reaction in the group, namely the run away from the
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Ibáñez, Carlos; Popa-Lisseanu, Ana G; Pastor-Beviá, David; García-Mudarra, Juan L; Juste, Javier
2016-10-01
Recently, several species of aerial-hawking bats have been found to prey on migrating songbirds, but details on this behaviour and its relevance for bird migration are still unclear. We sequenced avian DNA in feather-containing scats of the bird-feeding bat Nyctalus lasiopterus from Spain collected during bird migration seasons. We found very high prey diversity, with 31 bird species from eight families of Passeriformes, almost all of which were nocturnally flying sub-Saharan migrants. Moreover, species using tree hollows or nest boxes in the study area during migration periods were not present in the bats' diet, indicating that birds are solely captured on the wing during night-time passage. Additional to a generalist feeding strategy, we found that bats selected medium-sized bird species, thereby assumingly optimizing their energetic cost-benefit balance and injury risk. Surprisingly, bats preyed upon birds half their own body mass. This shows that the 5% prey to predator body mass ratio traditionally assumed for aerial hunting bats does not apply to this hunting strategy or even underestimates these animals' behavioural and mechanical abilities. Considering the bats' generalist feeding strategy and their large prey size range, we suggest that nocturnal bat predation may have influenced the evolution of bird migration strategies and behaviour. © 2016 John Wiley & Sons Ltd.
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Avian migrants adjust migration in response to environmental conditions en route
DEFF Research Database (Denmark)
Tøttrup, Anders P; Thorup, Kasper; Rainio, Kalle
2008-01-01
The onset of migration in birds is assumed to be primarily under endogenous control in long-distance migrants. Recently, climate changes appear to have been driving a rapid change in breeding area arrival. However, little is known about the climatic factors affecting migratory birds during...... covering the entire migration period every year from observatories located in the Middle East and northern Europe, we show that passage of the Sahara Desert is delayed and correlated with improved conditions in the wintering areas. By contrast, migrants travel more rapidly through Europe, and adjust...... the migration cycle, or whether recently reported phenological changes are caused by plastic behavioural responses or evolutionary change. Here, we investigate how environmental conditions in the wintering areas as well as en route towards breeding areas affect timing of migration. Using data from 1984 to 2004...
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Circular migration patterns and determinants in Nairobi slum settlements
Directory of Open Access Journals (Sweden)
Donatien Beguy
2010-09-01
Full Text Available This paper measures migration flows and determinants in two slum settlements in Nairobi City between 2003 and 2007. The results confirm the high intensity of migration with a quarter of the total slum population and a third of those aged 15-30 being renewed annually. A circular migration system is at play whereby the majority of slum dwellers are short-term migrants spending on average less than 3 years in the area. Migration is more intense during early adulthood (20-24, and despite very similar determinants across gender, mobility is more intense among women compared to men. The increasing feminization of migration is likely to change the face of slum settlements, resulting in more balanced sex ratios, in line with city-wide trends in Nairobi over the past half century. The high population turnover is due to the insecurity of livelihoods, tenure, and poor basic amenities and social services in slum settlements.
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Recent trends in human migrations: the case of the Venezuelan Andes.
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
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The Globalisation of migration
Milan Mesić
2002-01-01
The paper demonstrates that contemporary international migration is a constitutive part of the globalisation process. After defining the concepts of globalisation and the globalisation of migration, the author discusses six key themes, linking globalisation and international migration (“global cities”, the scale of migration; diversification of migration flows; globalisation of science and education; international migration and citizenship; emigrant communities and new identities). First, in ...
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Security and skills: the two key issues in health worker migration
Directory of Open Access Journals (Sweden)
Posy Bidwell
2014-07-01
Full Text Available Background: Migration of health workers from Africa continues to undermine the universal provision of quality health care. South Africa is an epicentre for migration – it exports more health workers to high-income countries than any other African country and imports health workers from its lower-income neighbours to fill the gap. Although an inter-governmental agreement in 2003 reduced the very high numbers migrating from South Africa to the United Kingdom, migration continues to other high-income English-speaking countries and few workers seem to return although the financial incentive to work abroad has lessened. A deeper understanding of reasons for migration from South Africa and post-migration experiences is therefore needed to underpin policy which is developed in order to improve retention within source countries and encourage return. Methods: Semi-structured interviews were conducted with 16 South African doctors and nurses who had migrated to the United Kingdom. Interviews explored factors influencing the decision to migrate and post-migration experiences. Results: Salary, career progression, and poor working conditions were not major push factors for migration. Many health workers reported that they had previously overcome these issues within the South African healthcare system by migrating to the private sector. Overwhelmingly, the major push factors were insecurity, high levels of crime, and racial tension. Although the wish to work and train in what was perceived to be a first-class care system was a pull factor to migrate to the United Kingdom, many were disappointed by the experience. Instead of obtaining new skills, many (particularly nurses felt they had become ‘de-skilled’. Many also felt that working conditions and opportunities for them in the UK National Health Service (NHS compared unfavourably with the private sector in South Africa. Conclusions: Migration from South Africa seems unlikely to diminish until the major
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Security and skills: the two key issues in health worker migration.
Bidwell, Posy; Laxmikanth, Pallavi; Blacklock, Claire; Hayward, Gail; Willcox, Merlin; Peersman, Wim; Moosa, Shabir; Mant, David
2014-01-01
Migration of health workers from Africa continues to undermine the universal provision of quality health care. South Africa is an epicentre for migration--it exports more health workers to high-income countries than any other African country and imports health workers from its lower-income neighbours to fill the gap. Although an inter-governmental agreement in 2003 reduced the very high numbers migrating from South Africa to the United Kingdom, migration continues to other high-income English-speaking countries and few workers seem to return although the financial incentive to work abroad has lessened. A deeper understanding of reasons for migration from South Africa and post-migration experiences is therefore needed to underpin policy which is developed in order to improve retention within source countries and encourage return. Semi-structured interviews were conducted with 16 South African doctors and nurses who had migrated to the United Kingdom. Interviews explored factors influencing the decision to migrate and post-migration experiences. Salary, career progression, and poor working conditions were not major push factors for migration. Many health workers reported that they had previously overcome these issues within the South African healthcare system by migrating to the private sector. Overwhelmingly, the major push factors were insecurity, high levels of crime, and racial tension. Although the wish to work and train in what was perceived to be a first-class care system was a pull factor to migrate to the United Kingdom, many were disappointed by the experience. Instead of obtaining new skills, many (particularly nurses) felt they had become 'de-skilled'. Many also felt that working conditions and opportunities for them in the UK National Health Service (NHS) compared unfavourably with the private sector in South Africa. Migration from South Africa seems unlikely to diminish until the major concerns over security, crime, and racial tensions are resolved
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DEFF Research Database (Denmark)
Bradshaw, J.; Song, X.J.; Shealy, J.R.
1992-01-01
We report growth of (InAs)1(AlAs)1 and (InAs)2(AlAs)2 strained layer superlattices by migration enhanced epitaxy. The samples were grown on InP (001) substrates and characterized by Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Satellite peaks in the x-ray data...... confirm the intended periodicity and indicate the presence of some disorder in the monolayer sample. The energies of the zone folded and quantum confined optic phonons are in reasonable agreement with calculations based on one-dimensional elastic continuum and linear chain models. Journal of Applied...
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Directory of Open Access Journals (Sweden)
Maarja Saar
2016-12-01
Full Text Available Recent studies on Eastern European migration argue that moving for self-development reasons is becoming increasingly common among this group. Furthermore, it is suggested that migration from the East is becoming individualised and less dependent on social surroundings. Nevertheless, most such results rely on interviews conducted among certain social groups, such as the young and highly skilled. Hence, the comparison between different social groups and their motivations is rarely provided and, therefore, the claims about increased individualisation might be premature. This article uses the Estonian Household Module Survey, including responses from 620 Estonians intending to migrate, to evaluate if migration flows are indeed becoming more individualised and less dependent on social surroundings. Using cluster analysis, three different groups — self-development, economic and life quality migrants — are formed, which are then tested using regression analysis to check for the influence of socio-demographic variables. The article concludes that socio-demographic variables such as gender, age, ethnicity, family status and socio-economic status are still relevant for migration intentions. Indeed, a new group of Eastern European migrants, mainly oriented towards self-development, is emerging; however, it is small and consists mostly of young, Estonian-speaking females. The results complicate the notions of free mobility and liquid migration from Eastern Europe and illustrate that there is a need to pay attention to the increasing group differences in these societies
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Migration and Remittances : Recent Developments and Outlook - Transit Migration
World Bank Group
2018-01-01
This Migration and Development Brief reports global trends in migration and remittance flows, as well as developments related to the Global Compact on Migration (GCM), and the Sustainable Development Goal (SDG) indicators for volume of remittances as percentage of gross domestic product (GDP) (SDG indicator 17.3.2), reducing remittance costs (SDG indicator 10.c.1) and recruitment costs (SD...
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Return Migration to Mexico: Does Health Matter?
Arenas, Erika; Goldman, Noreen; Pebley, Anne R; Teruel, Graciela
2015-12-01
We use data from three rounds of the Mexican Family Life Survey to examine whether migrants in the United States returning to Mexico in the period 2005-2012 have worse health than those remaining in the United States. Despite extensive interest by demographers in health-related selection, this has been a neglected area of study in the literature on U.S.-Mexico migration, and the few results to date have been contradictory and inconclusive. Using five self-reported health variables collected while migrants resided in the United States and subsequent migration history, we find direct evidence of higher probabilities of return migration for Mexican migrants in poor health as well as lower probabilities of return for migrants with improving health. These findings are robust to the inclusion of potential confounders reflecting the migrants' demographic characteristics, economic situation, family ties, and origin and destination characteristics. We anticipate that in the coming decade, health may become an even more salient issue in migrants' decisions about returning to Mexico, given the recent expansion in access to health insurance in Mexico.
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Riboflavin at high doses enhances lung cancer cell proliferation, invasion, and migration.
Yang, Hui-ting; Chao, Pei-chun; Yin, Mei-chin
2013-02-01
The influence of riboflavin (vitamin B(2) ) upon growth, invasion, and migration in non-small cell lung cancer cell lines was evaluated. Riboflavin at 1, 10, 25, 50, 100, 200, or 400 μmol/L was added into A549, H3255, or Calu-6 cells. The effects of this compound upon level and/or expression of reactive oxygen species (ROS), inflammatory cytokines, intercellular adhesion molecule (ICAM)-1, fibronectin, matrix metalloproteinase (MMP)-9, MMP-2, focal adhesion kinase (FAK), nuclear factor kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) were examined. Results showed that riboflavin at test doses did not affect the level of ROS and glutathione. Riboflavin at 200 and 400 μmol/L significantly enhanced cell growth in test lung cancer cell lines, and at 400 μmol/L significantly increased the release of interleukin-6, tumor necrosis factor-alpha, and vascular endothelial growth factor. This agent at 200 and 400 μmol/L also upregulated protein production of ICAM-1, fibronectin, MMP-9, MMP-2, NF-κB p50, p-p38 MAPK, and FAK; and at 400 μmol/L enhanced invasion and migration in test cell lines. These findings suggested that riboflavin at high doses might promote lung cancer progression. © 2013 Institute of Food Technologists®
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Modeling Coupled THMC Processes and Brine Migration in Salt at High Temperatures
Energy Technology Data Exchange (ETDEWEB)
Rutqvist, Jonny; Blanco Martin, Laura; Mukhopadhyay, Sumit; Houseworth, Jim; Birkholzer, Jens
2014-08-14
In this report, we present FY2014 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. LBNL’s work on the modeling of coupled THMC processes in salt was initiated in FY2012, focusing on exploring and demonstrating the capabilities of an existing LBNL modeling tool (TOUGH-FLAC) for simulating temperature-driven coupled flow and geomechanical processes in salt. This work includes development related to, and implementation of, essential capabilities, as well as testing the model against relevant information and published experimental data related to the fate and transport of water. we provide more details on the FY2014 work, first presenting updated tools and improvements made to the TOUGH-FLAC simulator, and the use of this updated tool in a new model simulation of long-term THM behavior within a generic repository in a salt formation. This is followed by the description of current benchmarking and validations efforts, including the TSDE experiment. We then present the current status in the development of constitutive relationships and the dual-continuum model for brine migration. We conclude with an outlook for FY2015, which will be much focused on model validation against field experiments and on the use of the model for the design studies related to a proposed heater experiment.
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Circular Migration and Young Child Malnutrition in Guatemala.
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…
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Landbird migration in the American West: Recent progress and future research directions
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.
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Migration and work-life balance in the periphery
Nørgaard, Helle
2013-01-01
This paper will address the potential of teleworking in relation to migration decisions to leave or stay in rural, peripheral locations. Various studies document long term patterns of migration from rural to urban areas but also urban-rural migration as well as significant differences between rural localities in regard to population growth or decline.Mobility is generally low in Denmark, decreases with age and is very low from age 50 whereas mobility is high when establishing family. Thus, mi...
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Vertical migration of motile phytoplankton chains through turbulence
Climent, Eric; Lovecchio, Salvatore; Durham, William; Stocker, Roman
2017-11-01
Daily, phytoplankton needs to migrate vertically from and towards the ocean surface to find nutrients such as dissolved oxygen. To travel through the water column they need to fight against gravity (by swimming) and fluid turbulence which can make their journey longer. It is often observed that cells migrate across the water column as chains. The first benefit to form chains is that micro-organisms sum up their thrust while reducing their drag. Therefore, upwards swimming is faster for chains in a quiescent fluid with steady vertical orientation. However, as chain length increases their tendency to periodically tumble in turbulent structures increases which reduces orientation stability and limits their capacity to swim upwards. The purpose of our study is to elaborate on this apparent contradiction. We carried out direct numerical simulations and physical analysis of the coupled system of homogeneous isotropic turbulence and chain trajectories through Lagrangian tracking. Formation of chains is indeed favorable for vertical migration through the upper layer of the ocean.
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She, Qianru; Wotherspoon, Terry
2013-12-01
Against the backdrop of demographic change and economic reconfiguration, recruiting international students, especially those at tertiary level, has drawn growing attention from advanced economies as part of a broad strategy to manage highly skilled migration. This comparative study focuses on three English speaking countries receiving international students: Canada, the United States, and the United Kingdom. International student policies, in particular entry and immigration regulations, and the trends in student mobility since the late 1990s are examined drawing on secondary data. By exploring the issue from the political economy perspectives, this study identifies distinct national strategies for managing student mobility, determines key factors shaping the environment of student migration in each nation, and addresses the deficiency of human capital theory in the analysis of global competition for high skills.
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Civil migration and risk assessment methodology
International Nuclear Information System (INIS)
Onishi, Y.; Brown, S.M.; Olsen, A.R.; Parkhurst, M.A.
1981-01-01
To provide a scientific basis for risk assessment and decision making, the Chemical Migration and Risk Assessment (CMRA) Methodology was developed to simulate overland and instream toxic containment migration and fate, and to predict the probability of acute and chronic impacts on aquatic biota. The simulation results indicated that the time between the pesticide application and the subsequent runoff producing event was the most important factor determining the amount of the alachlor. The study also revealed that sediment transport has important effects on contaminant migration when sediment concentrations in receiving streams are high or contaminants are highly susceptible to adsorption by sediment. Although the capabilities of the CMRA methodology were only partially tested in this study, the results demonstrate that methodology can be used as a scientific decision-making tool for toxic chemical regulations, a research tool to evaluate the relative significance of various transport and degradation phenomena, as well as a tool to examine the effectiveness of toxic chemical control practice
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International Nuclear Information System (INIS)
Domin, V.V.; Bondarenko, G.N.; Zheldakov, Yu.A.
1989-01-01
The role of organic substance dissolved (DOS) in radionuclide migration in the river water of the Kiev's water reservoir was considered. It was ascertained, that metal complexes with fulvic acids were stable and complexing properties of fulvic acids affected radionuclide migration. When DOS content increased sharply during the freshet period, radionuclide migration also increased. 8 refs.; 4 figs.; 3 tabs
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Peculiarities of International Migration of Population in Europe at the Present Stage
Directory of Open Access Journals (Sweden)
Iurchenko Svitlana A.
2017-06-01
Full Text Available Under conditions of globalization, international migration of population is steadily growing and significantly affects the socio-economic development of countries and regions. The aim of the article is to identify the features of international migration of population in Europe. The migration trends in the region and its subregions are analyzed. It is shown that Western Europe is leading according to the number of migrants residing on its territory, but the maximum growth of migrants for the period of 1990-2015 is observed in Southern Europe. The proportion of women and population of active age groups is increasing in the structure of migrants. In recent years the flow of refugees has increased. The impact of the migration crisis on the economies of the host countries is analyzed. Calculations of coefficients of multiple correlation demonstrated the level of dependence between the indicators of migration and GDP, population size, share of urban population. It is concluded that it is necessary to develop migration policies at different hierarchical levels.
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Latitudinal migration of sunspots based on the ESAI database
Zhang, Juan; Li, Fu-Yu; Feng, Wen
2018-01-01
The latitudinal migration of sunspots toward the equator, which implies there is propagation of the toroidal magnetic flux wave at the base of the solar convection zone, is one of the crucial observational bases for the solar dynamo to generate a magnetic field by shearing of the pre-existing poloidal magnetic field through differential rotation. The Extended time series of Solar Activity Indices (ESAI) elongated the Greenwich observation record of sunspots by several decades in the past. In this study, ESAI’s yearly mean latitude of sunspots in the northern and southern hemispheres during the years 1854 to 1985 is utilized to statistically test whether hemispherical latitudinal migration of sunspots in a solar cycle is linear or nonlinear. It is found that a quadratic function is statistically significantly better at describing hemispherical latitudinal migration of sunspots in a solar cycle than a linear function. In addition, the latitude migration velocity of sunspots in a solar cycle decreases as the cycle progresses, providing a particular constraint for solar dynamo models. Indeed, the butterfly wing pattern with a faster latitudinal migration rate should present stronger solar activity with a shorter cycle period, and it is located at higher latitudinal position, giving evidence to support the Babcock-Leighton dynamo mechanism.
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Kessel, Steven T; Hondorp, Darryl W; Holbrook, Christopher M; Boase, James C; Chiotti, Justin A; Thomas, Michael V; Wills, Todd C; Roseman, Edward F; 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 are 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 6 years (2011-2016), movements of 268 lake sturgeon in the HEC were continuously monitored across the Great Lakes using acoustic telemetry (10 years 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 assigned 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
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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
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Oceanic migration and spawning of anguillid eels.
Tsukamoto, K
2009-06-01
Many aspects of the life histories of anguillid eels have been revealed in recent decades, but the spawning migrations of their silver eels in the open ocean still remains poorly understood. This paper overviews what is known about the migration and spawning of anguillid species in the ocean. The factors that determine exactly when anguillid eels will begin their migrations are not known, although environmental influences such as lunar cycle, rainfall and river discharge seem to affect their patterns of movement as they migrate towards the ocean. Once in the ocean on their way to the spawning area, silver eels probably migrate in the upper few hundred metres, while reproductive maturation continues. Although involvement of a magnetic sense or olfactory cues seems probable, how they navigate or what routes they take are still a matter of speculation. There are few landmarks in the open ocean to define their spawning areas, other than oceanographic or geological features such as oceanic fronts or seamounts in some cases. Spawning of silver eels in the ocean has never been observed, but artificially matured eels of several species have exhibited similar spawning behaviours in the laboratory. Recent collections of mature adults and newly spawned preleptocephali in the spawning area of the Japanese eel Anguilla japonica have shown that spawning occurs during new moon periods in the North Equatorial Current region near the West Mariana Ridge. These data, however, show that the latitude of the spawning events can change among months and years depending on oceanographic conditions. Changes in spawning location of this and other anguillid species may affect their larval transport and survival, and appear to have the potential to influence recruitment success. A greater understanding of the spawning migration and the choice of spawning locations by silver eels is needed to help conserve declining anguillid species.
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Long-Term Trends in Marriage Timing and the Impact of Migration, the Netherlands (1650-1899
Directory of Open Access Journals (Sweden)
Charlotte Störmer
2017-12-01
Full Text Available The features of historical marriage patterns have been linked to debates in social and economic history about economic growth and female agency. However, there is a lack of empirical evidence on the demographics of marriage prior to the nineteenth century. Here, we study trends in sex-specific ages at first marriage, regional variation and the impact of migration on marital timing in the Netherlands in the period 1650-1900. We make use of two new large historical datasets, namely an aggregation of Dutch genealogies and the transcribed marriage banns of Amsterdam. This allows us to understand the features and developments of marriage ages from a long-term perspective in what is known as one of the core-areas of the so-called European Marriage Pattern. Our results show high marriage ages for both sexes from the beginning of our study period, increasing until the mid-19th century. A closer look at regional variation reveals clear differences between the provinces and between urban and rural settings with those in the western part of the country and in urban centers marrying earlier. Migrating individuals married on average later than non-migrating individuals both compared to men and women in the receiving community, as to the ‘stayers’ in the location of origin. As later marriage implies a reduction of the window of fertility, especially for women, our results suggest that migration and increasing regional mobility might have been an important driver of the demographic shift toward higher marriage ages and lower fertility in Europe between the 17th and 19th centuries.
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Siriwardhana, Chesmal; Stewart, Robert
2013-03-01
Forced internal displacement has been rising steadily, mainly due to conflict. Many internally displaced people (IDP) experience prolonged displacement. Global research evidence suggests that many of these IDP are at high risk for developing mental disorders, adding weight to the global burden of disease. However, individual and community resilience may act as protective factors. Return migration may be an option for some IDP populations, especially when conflicts end, although return migration may itself be associated with worse mental health. Limited evidence is available on effects of resettlement or return migration following prolonged forced internal displacement on mental health. Also, the role of resilience factors remains to be clarified following situations of prolonged displacement. The public health impact of internal displacement is not clearly understood. Epidemiological and interventional research in IDP mental health needs to look beyond medicalised models and encompass broader social and cultural aspects. The resilience factor should be integrated and explored more in mental health research among IDP and a clearly focused multidisciplinary approach is advocated.
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DEFF Research Database (Denmark)
Lundsgaard, Rasmus; Kontogeorgis, Georgios; Kristiansen, Jørgen K.
2009-01-01
soybean oil (ESBO) with regard to their migration from three different types of poly(vinyl chloride) into isooctane at 20, 40, and 60 degrees C. Diffusion coefficients derived from the experimental migration data were evaluated against diffusion coefficients estimated from a model based solely...
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IS WAGE A MANAGERIAL MOTIVATIONAL TOOL OR A MIGRATION DETERMINANT AMONG YOUNG PEOPLE?
Directory of Open Access Journals (Sweden)
MANCIU VENERA CRISTINA
2014-08-01
Full Text Available In recent years, the phenomenon of migration has intensified throughout the country, an increasing number of people choosing the path of foreign countries in the hope of a better life. It becomes a challenge for general managers in firms to retain those employees who have the skills needed to perform at a high level of performance the duties regarding work. The research conducted in this paper is a qualitative one, trying to provide an answer to the question stated in the title, ie if the current salary level practiced in Romania is a motivational factor for providing a valuable work, or on the contrary, is an element that lies at the basis of migration. The first part of the paper presents a theoretical point of view, presenting general aspects regarding the current economic context in terms of staff motivation, but also the general perspectives referring to the issue of migration. The final part presents a study that uses the focus group method in order to determine whether the young people in Caras Severin are susceptible to leaving the country for a higher wage level or would they consider this aspect for the following period of time.
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Underestimated Benefits from Periphery: Internal Migration and Subjective Well-being
Kopmann, Angela; Rehdanz, Katrin
2014-01-01
This paper is among the first to link internal migration and subjective well-being in developed countries. Economic theory predicts that individuals migrate towards urban agglomerations, if the potential gain in income is sufficient to cover costs. However, this narrow view cannot explain why migration exists also to the rural periphery. In our analysis, we investigate non-monetary benefits beyond economics from internal migration. Using highly disaggregated spatial information on people s mi...
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Multi-cellular logistics of collective cell migration.
Directory of Open Access Journals (Sweden)
Masataka Yamao
Full Text Available During development, the formation of biological networks (such as organs and neuronal networks is controlled by multicellular transportation phenomena based on cell migration. In multi-cellular systems, cellular locomotion is restricted by physical interactions with other cells in a crowded space, similar to passengers pushing others out of their way on a packed train. The motion of individual cells is intrinsically stochastic and may be viewed as a type of random walk. However, this walk takes place in a noisy environment because the cell interacts with its randomly moving neighbors. Despite this randomness and complexity, development is highly orchestrated and precisely regulated, following genetic (and even epigenetic blueprints. Although individual cell migration has long been studied, the manner in which stochasticity affects multi-cellular transportation within the precisely controlled process of development remains largely unknown. To explore the general principles underlying multicellular migration, we focus on the migration of neural crest cells, which migrate collectively and form streams. We introduce a mechanical model of multi-cellular migration. Simulations based on the model show that the migration mode depends on the relative strengths of the noise from migratory and non-migratory cells. Strong noise from migratory cells and weak noise from surrounding cells causes "collective migration," whereas strong noise from non-migratory cells causes "dispersive migration." Moreover, our theoretical analyses reveal that migratory cells attract each other over long distances, even without direct mechanical contacts. This effective interaction depends on the stochasticity of the migratory and non-migratory cells. On the basis of these findings, we propose that stochastic behavior at the single-cell level works effectively and precisely to achieve collective migration in multi-cellular systems.
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Emerging migration flows in a changing climate in dryland Africa
Kniveton, Dominic R.; Smith, Christopher D.; Black, Richard
2012-06-01
Fears of the movement of large numbers of people as a result of changes in the environment were first voiced in the 1980s (ref. ). Nearly thirty years later the numbers likely to migrate as a result of the impacts of climate change are still, at best, guesswork. Owing to the high prevalence of rainfed agriculture, many livelihoods in sub-Saharan African drylands are particularly vulnerable to changes in climate. One commonly adopted response strategy used by populations to deal with the resulting livelihood stress is migration. Here, we use an agent-based model developed around the theory of planned behaviour to explore how climate and demographic change, defined by the ENSEMBLES project and the United Nations Statistics Division of the Department of Economic and Social Affairs, combine to influence migration within and from Burkina Faso. The emergent migration patterns modelled support framing the nexus of climate change and migration as a complex adaptive system. Using this conceptual framework, we show that the extent of climate-change-related migration is likely to be highly nonlinear and the extent of this nonlinearity is dependent on population growth; therefore supporting migration policy interventions based on both demographic and climate change adaptation.
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Oceanic migration behaviour of tropical Pacific eels from Vanuatu
DEFF Research Database (Denmark)
Schabetsberger, R; Økland, F; Aarestrup, K
2013-01-01
Information on oceanic migrations and spawning areas of tropical Pacific freshwater eels (genus Anguilla) is very limited. Lake Letas and its single outflowing river, Mbe Solomul on Gaua Island, Vanuatu, were surveyed for large migrating individuals. Twenty-four Anguilla marmorata (87 to 142 cm),...... impact of the lunar cycle on the upper limit of migration depths was found in A. marmorata (full moon: 230 m, new moon: 170 m). These behaviours may be explained as a trade-off between predator avoidance and the necessity to maintain a sufficiently high metabolism for migration....
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Directory of Open Access Journals (Sweden)
Perticarrari A.
Full Text Available A comparison between two studies on diel vertical migration of two cyclopoid copepod species, in Lake Monte Alegre, undertaken in 1985/86 and 1999, revealed a change in their migratory behavior. In summer, during a period of marked stratification with low dissolved oxygen near the bottom, the organisms avoided the deepest layers, and migration was nocturnal or undetectable, in both periods. On other occasions, with partial or total circulation in the lake, a weak twilight migration of copepodites and adults in 1985 was replaced by the reverse in 1999. Differences were found among stages, with the weakest or undetectable migration being observed for nauplii. The migratory pattern change for copepodites and adults might be related with a recent predation pressure increase by Chaoborus larvae on copepods, after the virtual disappearance of their main cladoceran prey.
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Directory of Open Access Journals (Sweden)
Sanja Klempić Bogadi
2015-04-01
Full Text Available To mark the 30th anniversary of the publication of the journal Migracijske i etničke teme / Migration and Ethnic Themes (up to 2000 it was issued under the title Migration Themes: a Journal for Migration and Ethic Studies, we consider it important and necessary to provide an overview in one place of the papers published in the journal from its first issue in 1985 to the last one in 2014. The most important aim of this bibliography is to introduce the scientific and professional public, especially new researchers, to the topics covered by this journal as well as to enable easier access to the journal and its more convenient use. The bibliography is selective. It includes scientific papers (the original scientific paper, preliminary communication and review paper professional papers, conference papers, panel discussions, discussions, reviews and bibliographies, while reviews of books and periodicals (i.e. papers from the sections Books, Reviews, From Foreign Periodicals and Movie as well as Introductions, Memories, In Memoriam and Conference Reviews (from the sections Reviews and Conferences are not included. All the papers are available at Hrčak – Portal of Scientific Journals of Croatia. Given that all kinds of papers are not included, but primarily in order to provide its better examination and insight into published papers according to specific topics and dealing with various issues, as well as to provide easier and faster access, we have decided to make a subject bibliography, and not a chronological one. (On the occasion of the 10th anniversary of the Migration Themes journal, the chronological bibliography prepared by Josip Kumper was published in the 3-4/1994 issue. From the very first issue, migration and ethnicity have been the main themes represented in the journal, but the emphasis on the basic issues in previous papers, which involved external migration, internal migration, emigration and minorities/nationalities, have gradually
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International Nuclear Information System (INIS)
Hildebrand, S.T.; Carroll, R.J.
1993-01-01
A depth migration method is presented that used Radon-transformed common-source seismograms as input. It is shown that the Radon depth migration method can be extended to spatially varying velocity depth models by using asymptotic ray theory (ART) to construct wavefield continuation operators. These operators downward continue an incident receiver-array plane wave and an assumed point-source wavefield into the subsurface. The migration velocity model is constrain to have longer characteristic wavelengths than the dominant source wavelength such that the ART approximations for the continuation operators are valid. This method is used successfully to migrate two synthetic data examples: (1) a point diffractor, and (2) a dipping layer and syncline interface model. It is shown that the Radon migration method has a computational advantage over the standard Kirchhoff migration method in that fewer rays are computed in a main memory implementation
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The possibilities of compressed sensing based migration
Aldawood, Ali
2013-09-22
Linearized waveform inversion or Least-square migration helps reduce migration artifacts caused by limited acquisition aperture, coarse sampling of sources and receivers, and low subsurface illumination. However, leastsquare migration, based on L2-norm minimization of the misfit function, tends to produce a smeared (smoothed) depiction of the true subsurface reflectivity. Assuming that the subsurface reflectivity distribution is a sparse signal, we use a compressed-sensing (Basis Pursuit) algorithm to retrieve this sparse distribution from a small number of linear measurements. We applied a compressed-sensing algorithm to image a synthetic fault model using dense and sparse acquisition geometries. Tests on synthetic data demonstrate the ability of compressed-sensing to produce highly resolved migrated images. We, also, studied the robustness of the Basis Pursuit algorithm in the presence of Gaussian random noise.
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Migration from atolls as climate change adaptation
DEFF Research Database (Denmark)
Birk, Thomas Ladegaard Kümmel; Rasmussen, Kjeld
2014-01-01
to migration that reduce the efficacy of positive outcomes to both migrants and their home communities, including high transport costs and problems in gaining access to housing, employment and government services in urban destination areas. If it is accepted that voluntary migration may play a positive role...... that migration currently improves access to financial and social capital, reduces pressure on natural resources and makes island communities less vulnerable to extreme weather events and other shocks — all factors that contribute positively to adaptive capacity. It also shows that there are major barriers...... in adaptation to climate change in exposed atoll communities, addressing some of the barriers to migration seems logical. This may be done by efforts to stimulate migrant income opportunities, by improving migrant living conditions and by improving the transport services to the islands....
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The possibilities of compressed sensing based migration
Aldawood, Ali; Hoteit, Ibrahim; Alkhalifah, Tariq Ali
2013-01-01
Linearized waveform inversion or Least-square migration helps reduce migration artifacts caused by limited acquisition aperture, coarse sampling of sources and receivers, and low subsurface illumination. However, leastsquare migration, based on L2-norm minimization of the misfit function, tends to produce a smeared (smoothed) depiction of the true subsurface reflectivity. Assuming that the subsurface reflectivity distribution is a sparse signal, we use a compressed-sensing (Basis Pursuit) algorithm to retrieve this sparse distribution from a small number of linear measurements. We applied a compressed-sensing algorithm to image a synthetic fault model using dense and sparse acquisition geometries. Tests on synthetic data demonstrate the ability of compressed-sensing to produce highly resolved migrated images. We, also, studied the robustness of the Basis Pursuit algorithm in the presence of Gaussian random noise.
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Detection of cavity migration risks using radar interferometric time series
Chang, L.; Hanssen, R. F.
2012-12-01
, ERS-2, Envisat, and Radarsat-2, to investigate the dynamics (deformation) of the area. In particular we show, for the first time, shear-stress change distribution patterns within the structure of a building, over a period of close to 20 years. Time series analysis shows that deformation rates of ~4 mm/a could be detected for about 18 years, followed by a dramatic increase of up to 20 mm/a in the last period. These results imply that the driving mechanisms of the 2011 catastrophe have a very long lead time and are therefore likely due to a long-lasting gradual motion, such as the upward migration of a cavity. The analysis shows the collocation of the deformation location with relatively shallow near-horizontal mine shafts, suggesting that cavity migration has a high likelihood to be the driving mechanism of the collapse-sinkhole.
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Directory of Open Access Journals (Sweden)
Ewan Hunter
Full Text Available Crustaceans are key components of marine ecosystems which, like other exploited marine taxa, show seasonable patterns of distribution and activity, with consequences for their availability to capture by targeted fisheries. Despite concerns over the sustainability of crab fisheries worldwide, difficulties in observing crabs' behaviour over their annual cycles, and the timings and durations of reproduction, remain poorly understood. From the release of 128 mature female edible crabs tagged with electronic data storage tags (DSTs, we demonstrate predominantly westward migration in the English Channel. Eastern Channel crabs migrated further than western Channel crabs, while crabs released outside the Channel showed little or no migration. Individual migrations were punctuated by a 7-month hiatus, when crabs remained stationary, coincident with the main period of crab spawning and egg incubation. Incubation commenced earlier in the west, from late October onwards, and brooding locations, determined using tidal geolocation, occurred throughout the species range. With an overall return rate of 34%, our results demonstrate that previous reluctance to tag crabs with relatively high-cost DSTs for fear of loss following moulting is unfounded, and that DSTs can generate precise information with regards life-history metrics that would be unachievable using other conventional means.
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Directory of Open Access Journals (Sweden)
Shymanska K.V.
2017-03-01
Full Text Available The need for transformation of Ukraine's migration policy based on globalized world development trends and in response to the challenges of European integration transformations causes the need of researching the theoretical and methodological basis of migration studies, and the regulations of existing theories of international migration. The bibliometric analysis of scientific publications on international migration in cites indexes found that the recent researches on these problems acquire interdisciplinary character. It necessitates the transformation of migration study approaches basing on economic, social, institutional theories and concepts synthesis. The article is devoted to the study of theoretical regulations of existing international migration theories in the context of the evolution of scientists’ views on this phenomenon. The author found that the existing theories of international migration should be divided into three categories (microeconomic, macroeconomic, globalizational that contributes to their understanding in the context of implementation possibilities in migrational public administration practice. It allows to determine the theories which should be used for Ukrainian state migration policy constructing and eliminating or reducing the external migration negative effects.
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Seasonal associations with urban light pollution for nocturnally migrating bird populations.
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.
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The Irish famine of 1740–1741: famine vulnerability and "climate migration"
Directory of Open Access Journals (Sweden)
S. Engler
2013-05-01
Full Text Available The "Great Frost" of 1740 was one of the coldest winters of the eighteenth century and impacted many countries all over Europe. The years 1740–1741 have long been known as a period of general crisis caused by harvest failures, high prices for staple foods, and excess mortality. Vulnerabilities, coping capacities and adaptation processes varied considerably among different countries. This paper investigates the famine of 1740–1741 in Ireland applying a multi-indicator model developed specifically for the integration of an analysis of pre-famine vulnerability, the Famine Vulnerability Analysis Model (FVAM. Our focus is on Ireland, because famine has played a more outstanding role in Irish national history than in any other European country, due to the "Great Famine" of 1845–1852 and its long-term demographic effects. Our analysis shows that Ireland was already particularly vulnerable to famine in the first half of the eighteenth century. During and after the experience of hardship in 1740–1741, many Irish moved within Ireland or left the country entirely. We regard migration as a form of adaptation and argue that Irish migration in 1740–1741 should be considered as a case of climate-induced migration.
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Neuronal Migration and Neuronal Migration Disorder in Cerebral Cortex
SUN, Xue-Zhi; TAKAHASHI, Sentaro; GUI, Chun; ZHANG, Rui; KOGA, Kazuo; NOUYE, Minoru; MURATA, Yoshiharu
2002-01-01
Neuronal cell migration is one of the most significant features during cortical development. After final mitosis, neurons migrate from the ventricular zone into the cortical plate, and then establish neuronal lamina and settle onto the outermost layer, forming an "inside-out" gradient of maturation. Neuronal migration is guided by radial glial fibers and also needs proper receptors, ligands, and other unknown extracellular factors, requests local signaling (e.g. some emitted by the Cajal-Retz...
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Health Selection, Migration, and HIV Infection in Malawi.
Anglewicz, Philip; VanLandingham, Mark; Manda-Taylor, Lucinda; Kohler, Hans-Peter
2018-04-27
Despite its importance in studies of migrant health, selectivity of migrants-also known as migration health selection-has seldom been examined in sub-Saharan Africa (SSA). This neglect is problematic because several features of the context in which migration occurs in SSA-very high levels of HIV, in particular-differ from contextual features in regions that have been studied more thoroughly. To address this important gap, we use longitudinal panel data from Malawi to examine whether migrants differ from nonmigrants in pre-migration health, assessed via SF-12 measures of mental and physical health. In addition to overall health selection, we focus on three more-specific factors that may affect the relationship between migration and health: (1) whether migration health selection differs by destination (rural-rural, rural-town, and rural-urban), (2) whether HIV infection moderates the relationship between migration and health, and (3) whether circular migrants differ in pre-migration health status. We find evidence of the healthy migrant phenomenon in Malawi, where physically healthier individuals are more likely to move. This relationship varies by migration destination, with healthier rural migrants moving to urban and other rural areas. We also find interactions between HIV-infected status and health: HIV-infected women moving to cities are physically healthier than their nonmigrant counterparts.
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Japanese Migration and the Americas: An Introduction to the Study of Migration.
Mukai, Gary; Brunette, Rachel
This curriculum module introduces students to the study of migration, including a brief overview of some categories of migration and reasons why people migrate. As a case study, the module uses the Japanese migration experience in the United States, Peru, Brazil, Canada, Mexico, Argentina, Bolivia, and Paraguay. The module introduces students to…
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Random migration processes between two stochastic epidemic centers.
Sazonov, Igor; Kelbert, Mark; Gravenor, Michael B
2016-04-01
We consider the epidemic dynamics in stochastic interacting population centers coupled by random migration. Both the epidemic and the migration processes are modeled by Markov chains. We derive explicit formulae for the probability distribution of the migration process, and explore the dependence of outbreak patterns on initial parameters, population sizes and coupling parameters, using analytical and numerical methods. We show the importance of considering the movement of resident and visitor individuals separately. The mean field approximation for a general migration process is derived and an approximate method that allows the computation of statistical moments for networks with highly populated centers is proposed and tested numerically. Copyright © 2016 Elsevier Inc. All rights reserved.
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Stpiczynski, T
1986-10-01
Recent research on internal migration in Poland is reviewed. The basic sources of data, consisting of censuses or surveys, are first described. The author discusses the relationship between migration studies and other sectors of the national economy, and particularly the relationship between migration and income.
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The apparent and effective chloride migration coefficients obtained in migration tests
Spiesz, P.R.; Brouwers, H.J.H.
2013-01-01
The apparent (Dapp) and effective (Deff) migration coefficients obtained in chloride migration tests are investigated in this study. The presented Dapp profiles in concrete show that the apparent migration coefficient is strongly concentration-dependent. As demonstrated, the binding of chlorides is
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Alnafouri, A J; Franz, R
1999-10-01
As a consequence of an increasing awareness and findings about the technical and analytical difficulties related to the employment of triglycerides as fatty food simulants in migration testing, EU Directive 82/711/EEC on the basic rules of migration has been amended for the second time and adapted with the recent Commission Directive 97/48/EC. The major merit of this important amendment is to authorize alternative tests such as extraction tests and to allow substitute tests for the fat test with concrete indication of corresponding test conditions to be applied. As a novelty in food law compliance testing it authorizes a modified polyphenylene oxide (MPPO), well-known as Tenax, a thermostable and highly adsorptive porous polymer, as a 'solid' matrix to substitute fat simulant D at temperatures equal to or higher than 100 degrees C. In the study presented here, comparative migration testing--overall and specific--was carried out between fat simulants olive oil and 14C-labelled HB 307 and the substitute test media iso-octane, 95% ethanol and MPPO using polypropylene materials as examples at test temperatures of 100 degrees C to 120 degrees C and prescribed corresponding substitute test conditions. As a consequence, a number of conclusions were drawn which are relevant for overall and/or specific migration testing under the investigated test conditions. One of the major findings was that MPPO was generally more equivalent to the fat test than the other two substitute test media. The presence of volatile hydrocarbons in the test samples was found to play a crucial role with respect to the equivalence of the iso-octane-based substitute test. At high volatile concentrations in the test sample the iso-octane test underestimated the olive oil benchmark whereas low volatile concentrations led to satisfying equivalence. It is therefore recommended that the procedure is modified and GC-FID screening of the isooctane extract is carried out. As a logical consequence, the
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Directory of Open Access Journals (Sweden)
S. Strel'chenko
2016-01-01
Full Text Available This article examines the general trends of migration processes between the Russian Federation and the Republic of Belarus, briefly describes the main features of the socio-economic development and migration policy of the two countries, including in the context of their cooperation within the framework of the Eurasian Economic Union. The article defines the key directions of economic cooperation between Russia and Belarus on migration policies and the promotion of desirable forms of migration. The relevance of the topic chosen due to both diversity and unsystematic legal framework that regulates the various aspects of migration policy and the lack of established legal concepts of migration, the migration process and the migration policy. In addition, in recent years can be seen working mobility growth in the context of globalization, which creates conditions for employment are not only highly qualified professionals in the fields of finance, insurance, banking, communications, and migrant workers employed in agriculture, construction, landscaping, catering, hotel service.Methodology. In conducting this study the main sources of raw data served as the information contained in scientific, reference, periodical literature on the subject in question, including the sources in the "Internet" information and telecommunications network. The basis of methodological developments laid the comparative methods of analysis and synthesis of the available data.Conclusions / relevance. Supporters of immigration openness believes that the strengthening of migration one of the solutions to the demographic problems of Russia and the problem of replenishment of the labor market. Their opponents believe that immigration creates an excess supply in the labor market, allowing employers to permanently reduce the level of payment of labor and social security, working conditions deteriorate.Practical application of the results of this work will improve the forecasting and
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A foraging cost of migration for a partially migratory cyprinid fish
DEFF Research Database (Denmark)
Chapman, Ben B; Eriksen, Anders; Baktoft, Henrik
2013-01-01
Rutilus rutilus, which migrates from shallow lakes to streams during winter. By sampling fish from stream and lake habitats in the autumn and spring and measuring their stomach fullness and diet composition, we tested if migrating roach pay a cost of reduced foraging when migrating. Resident fish had...... fuller stomachs containing more high quality prey items than migrant fish. Hence, we document a feeding cost to migration in roach, which adds additional support for the validity of the p/g model of migration in freshwater systems....
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Directory of Open Access Journals (Sweden)
Zimovina E. P.
2014-06-01
Full Text Available This paper analyses the migration processes and their influence on the transformation of multiethnic population structure in the Kaliningrad region. The author uses official statistics (current statistics and census data, as well as interviews with the representatives of ethnic cultural associations as information sources. Special attention is paid to the migration features associated with different ethnic groups. The author identifies major reasons behind the incoming and outgoing movement of population. In the post-Soviet period the Kaliningrad region has experienced positive net migration. This active migration into the region has contributed to the development of “migration networks” and established a new basis for further population increase through migration. The article describes changes in the regional multiethnic population structure and identifies key factors behind them. It is concluded that migration has played the decisive role in the process of multiethnic population structure transformation in the Kaliningrad region in the post-Soviet period. The author views migration as a serious test for both the migrants and the receiving society. On the one hand, migrants have to adapt to a different national, cultural, and linguistic environment and look for the ways of successful integration into the receiving society. On the other hand, the receiving society also faces a serious transformation as a result of the changing population size and structure, the emergence of new elements in culture, rules of behaviour, and the development of new attitudes.
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A panel study of migration, self-selection and household real income.
Axelsson, R; Westerlund, O
1998-02-01
"The impact of migration on income for Swedish multi-adult households is examined using panel data pertaining to a sample of stable household constellations during the period 1980-1990. In contrast to previous studies, data on household disposable income is employed in estimating the income function. The empirical results indicate no significant effect on real disposable income from migration. In addition, the hypothesis of no self-selection, or zero correlation between the errors in the decision function and the income function, cannot be rejected." excerpt
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DEFF Research Database (Denmark)
Brücker, Herbert; Jahn, Elke J.
in a general equilibrium framework. For the empirical analysis we employ the IABS, a two percent sample of the German labor force. We find that the elasticity of the wage curve is particularly high for young workers and workers with a university degree, while it is low for older workers and workers...... Based on a wage curve approach we examine the labor market effects of migration in Germany. The wage curve relies on the assumption that wages respond to a change in the unemployment rate, albeit imperfectly. This allows one to derive the wage and employment effects of migration simultaneously...... with a vocational degree. The wage and employment effects of migration are moderate: a 1 percent increase in the German labor force through immigration increases the aggregate unemployment rate by less than 0.1 percentage points and reduces average wages by less 0.1 percent. While native workers benefit from...
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Re-thinking skilled international labour migration: world cities and banking organisations.
Beaverstock, J V
1994-08-01
"Highly skilled professional and managerial labour migration has become an important facet of the contemporary world economy. The operations of transnational corporations have created more opportunities for skilled migrants to work abroad.... There is a growing interest amongst economic geographers to examine this form of migration through an appreciation of global economic restructuring, labour market change and world cities. Consequently, this paper introduces a new conceptual framework...[which] is based on the rationale that world cities, and the patterns of labour market demand that exist within them, are of paramount importance in influencing highly skilled professional and managerial labour migration within the world economy. The author uses an example of highly skilled labour migration within the transnational banking sector [in London] to illustrate this new conceptual framework." excerpt
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Health care and patients' migration across Spanish regions.
Cantarero, David
2006-06-01
This paper analyses patient mobility across Spanish regions. A model of patient migration is specified and estimated using panel observations covering mobility and other main regional quality indicators over the period 1996-1999. Empirical results show that in Spain income and supply variables determines the quality of the service offered,, and that there is quality-driven mobility.
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Ding, Cheng-Zhi; Guo, Xu-Feng; Wang, Guo-Lei; Wang, Hong-Tao; Xu, Guang-Hui; Liu, Yuan-Yuan; Wu, Zhen-Jiang; Chen, Yu-Hang; Wang, Jiao; Wang, Wen-Guang
2018-01-24
Despite the growing number of studies exhibited an association of diabetes mellitus (DM) and lung cancer progression, the concrete mechanism of DM aggravating lung cancer has not been elucidated. This study was to investigate whether and how high glucose (HG) contribute to the proliferation and migration of non-small cell lung cancer (NSCLC) cells in vitro. In the present study, we confirmed that HG promoted the proliferation and migration of NSCLC cells, and also induced an anti-apoptosis effect on NSCLC cells. Moreover, HG inhibited the expression of GAS5 in NSCLC cells but elevated the protein level of TRIB3. GAS5 overexpression promoted the degradation of TRIB3 protein by ubiquitination and inhibited the HG induced-proliferation, anti-apoptosis and migration of NSCLC cells. Importantly, TRIB3 overexpression reversed the effects of GAS5 on the HG-treated NSCLC cells. Taken together, down-regulated GAS5 by HG significantly enhanced the proliferation, anti-apoptosis and migration in NSCLC cells through TRIB3, thus promoting the carcinogenesis of NSCLC. ©2018 The Author(s).
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Migration and the formation of systems of hot super-Earths and Neptunes
Terquem, Caroline; Papaloizou, John C. B.
2006-01-01
The existence of extrasolar planets with short orbital periods suggests that planetary migration induced by tidal interaction with the protoplanetary disk is important. Cores and terrestrial planets may undergo migration as they form. In this paper we investigate the evolution of a population of cores with initial masses in the range 0.1-1 earth mass embedded in a disk. Mutual interactions lead to orbit crossing and mergers, so that the cores grow during their evolution. Interaction with the ...
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Interrelationship of migration and housing in Slovakia
Directory of Open Access Journals (Sweden)
Peter Sika
2017-10-01
Full Text Available Labour mobility is one of the factors that positively influence the balance of the labor market and employment and thus, economic growth. Milton Friedman, in his speech (1968 to the American Economic Association, communicated that the natural rate of unemployment depends on the degree of labor mobility in the economy. In this article we examine the interdependencies between migration and housing in Slovak Republic. Most residents commute to work in Bratislava and Trnava regions and migration between the other regions is not as pronounced. Low migration of population in Slovak Republic is strongly affected by high percentage of private ownership in the housing sector, which is arresting work force trapped in unemployment. In regions of high unemployment it is also high percentage of dwellings owned by households, affecting possibility of employment in other regions, because they have insufficient income to procure reality in the area with availabale work places as there is no sector of rental housing assuch. Based on the forecasts of the house prices development this status in the next 5 years will not change.
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International Nuclear Information System (INIS)
Nakamura, Haruto; Tashiro, Shingo
1987-08-01
Researches on high-level waste management at the High Level Waste Management Laboratory and the Waste Safety Testing Facility Operation Division of the Japan Atomic Energy Research Institute in the fiscal year of 1986 are reviewed in the report. Topics in the three sections are as follows: 1) Non-radioactive research has been continued on Synroc irradiation and modellings of waste form leaching. 2) Research results are described in the section of Safety Evaluation for Geological Disposal on engineered barriers, field tests, safety assessment models, migration, natural analogue, seabed disposal and conceptual design of a repository. 3) Adsorption behaviour of plutonium on leach-containers and migration of leached cesium in a rock column are described in the section of Safety Examination of Vitrified Forms in the Hot Cells of WASTEF. (author)
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Williams, Nathalie E
Historically, legal, policy, and academic communities largely ascribed to a dichotomy between forced and voluntary migration, creating a black and white vision that was convenient for legal and policy purposes. More recently, discussions have begun addressing the possibility of mixed migration, acknowledging that there is likely a wide continuum between forced and voluntary, and most migrants likely move with some amount of compulsion and some volition, even during armed conflict. While the mixed migration hypothesis is well-received, empirical evidence is disparate and somewhat blunt at this point. In this article, I contribute a direct theoretical and causal pathway discussion of mixed migration. I also propose the complex mixed migration hypothesis, which argues that not only do non-conflict related factors influence migration during conflict, but they do so differently than during periods of relative peace. I empirically test both hypotheses in the context of the recent armed conflict in Nepal. Using detailed survey data and event history models, results provide strong evidence for both mixed migration and complex mixed migration during conflict hypotheses. These hypotheses and evidence suggest that armed conflict might have substantial impacts on long-term population growth and change, with significant relevance in both academic and policy spheres.
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The politicisation of migration
van der Brug, W.; D' Amato, G.; Berkhout, J.; Ruedin, D.
2015-01-01
Why are migration policies sometimes heavily contested and high on the political agenda? And why do they, at other moments and in other countries, hardly lead to much public debate? The entrance and settlement of migrants in Western Europe has prompted various political reactions. In some countries
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Reinventing US Internal Migration Studies in the Age of International Migration.
Ellis, Mark
2012-03-01
I argue that researchers have sidelined attention to issues raised by US internal migration as they shifted focus to the questions posed by the post-1960s rise in US immigration. In this paper, I offer some reasons about why immigration has garnered more attention and why there needs to be greater consideration of US internal migration and its significant and myriad social, economic, political, and cultural impacts. I offer three ideas for motivating more research into US internal geographic mobility that would foreground its empirical and conceptual connections to international migration. First, there should be more work on linked migration systems investigating the connections between internal and international flows. Second, the questions asked about immigrant social, cultural, and economic impacts and adaptations in host societies should also be asked about internal migrants. Third, and more generally, migration researchers should jettison the assumption that the national scale is the pre-eminent delimiter of migration types and processes. Some groups can move easily across borders; others are constrained in their moves within countries. These subnational scales and constraints will become more visible if migration research decentres the national from its theory and empirics.
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MANAGING MIGRATION: TURKISH PERSPECTIVE
Directory of Open Access Journals (Sweden)
İhsan GÜLAY
2018-04-01
Full Text Available Conducting migration studies is of vital importance to Turkey, a country which has been experiencing migration throughout history due to its “open doors policy”. The objective of this study is to evaluate the strategic management of migration in Turkey in order to deal with the issue of migration. The main focus of the study is Syrian migrants who sought refuge in Turkey due to the civil war that broke out in their country in April 2011. This study demonstrates the policies and processes followed by Turkey for Syrian migration flow in terms of the social acceptance and harmonisation of the migrants within a democratic environment. The study addresses some statistical facts and issues related to Syrian migration as it has become an integral part of daily life in Turkey. The study also reviews how human rights are protected in the migration process. The study will provide insights for developing sound strategic management policies for the migration issue.
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Return Migration among Elderly, Chronically Ill Bosnian Refugees
DEFF Research Database (Denmark)
Handlos, Line Neerup; Olwig, Karen Fog; Bygbjerg, Ib Christian
2015-01-01
Elderly migrants constitute a considerable share of global return migration; nevertheless, literature on the health aspects of the return migration among these migrants is still scarce. This study explores the significance of return migration among elderly, chronically ill Bosnian refugees from D...... of illness, health did matter. Viewed as physical, social and mental well-being in line with WHO's definition of health, health was indeed one of the most important factors when the decision to return was made....... that physical health, in the sense of the absence of illness and easy access to necessary health-care services and medicines, was not highly prioritized when the decision was made whether or not to return. However, if health is regarded more broadly as involving more than mere physical health and the absence......Elderly migrants constitute a considerable share of global return migration; nevertheless, literature on the health aspects of the return migration among these migrants is still scarce. This study explores the significance of return migration among elderly, chronically ill Bosnian refugees from...
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Modeling Quasi-Static and Fatigue-Driven Delamination Migration
De Carvalho, N. V.; Ratcliffe, J. G.; Chen, B. Y.; Pinho, S. T.; Baiz, P. M.; Tay, T. E.
2014-01-01
An approach was proposed and assessed for the high-fidelity modeling of progressive damage and failure in composite materials. It combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. Delamination, matrix cracking, and migration were captured failure and migration criteria based on fracture mechanics. Quasi-static and fatigue loading were modeled within the same overall framework. The methodology proposed was illustrated by simulating the delamination migration test, showing good agreement with the available experimental data.
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Effect of shear stress on the migration of hepatic stellate cells.
Sera, Toshihiro; Sumii, Tateki; Fujita, Ryosuke; Kudo, Susumu
2018-01-01
When the liver is damaged, hepatic stellate cells (HSCs) can change into an activated, highly migratory state. The migration of HSCs may be affected by shear stress due not only to sinusoidal flow but also by the flow in the space of Disse because this space is filled with blood plasma. In this study, we evaluated the effects of shear stress on HSC migration in a scratch-wound assay with a parallel flow chamber. At regions upstream of the wound area, the migration was inhibited by 0.6 Pa and promoted by 2.0 Pa shear stress, compared to the static condition. The platelet-derived growth factor (PDGF)-BB receptor, PDGFR-β, was expressed in all conditions and the differences were not significant. PDGF increased HSC migration, except at 0.6 Pa shear stress, which was still inhibited. These results indicate that another molecular factor, such as PDGFR-α, may act to inhibit the migration under low shear stress. At regions downstream of the wound area, the migration was smaller under shear stress than under the static condition, although the expression of PDGFR-β was significantly higher. In particular, the migration direction was opposite to the wound area under high shear stress; therefore, migration might be influenced by the intercellular environment. Our results indicate that HSC migration was influenced by shear stress intensity and the intercellular environment.
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The use of census migration data to approximate human movement patterns across temporal scales.
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.
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Globalising Chinese Migration: New Spaces, New Meanings
Directory of Open Access Journals (Sweden)
Pál Nyíri
2002-04-01
Full Text Available The paper reviews new trends in international migration from the People’s Republic of China in the last decade, focusing on two aspects: 1 The geographic expansion and merger of formerly distinct translocal migration flows into a global migration system. It includes the opening up of new migration spaces in Eastern Europe and Southeast Asia; increased mobility between destination countries; and increased interchange between different social strata of migrants, from students to illegal workers; 2 A shift in what the social and cultural meaning of migration is to the migrant, to non-migrants, and to elites, which can be described as “upgrading the migrant” (Wang,1998. Various discourses of migration have converged into a highly success-oriented discourse, which reduces the relevance of social background and path of migration. The People’s Republic of China imbues this discourse with tropes of patriotism and development. Concerning the first aspect, the paper problematises the distinction of flows of legal and illegal migrants, students, tourists, and workers, and calls for a holistic approach in studying the configuration of current migration from the PRC. Concerning the second aspect, the paper questions the persistent theory that the PRC as an entity supports emigration, and points out the conflicting interests of various levels and organisations within the state apparatus. At the same time, it recognises that the PRC, like other states, is currently enjoying a honeymoon with state-sanctioned transnationalism, in which migrants are often being more engaged into nation-building and enfranchised as political citizens than are rural non-migrants.
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Climate Shocks and Migration: An Agent-Based Modeling Approach
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
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International Nuclear Information System (INIS)
Carlsen, L.
1992-05-01
Migration chemistry, the influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour of pollutants in the environment, is an interplay between the actual natur of the pollutant and the characteristics of the environment, such as pH, redox conditions and organic matter content. The wide selection of possible pollutants in combination with varying geological media, as well as the operation of different chemical -, biochemical - and physico-chemical reactions compleactes the prediction of the influence of these processes on the mobility of pollutants. The report summarizes a wide range of potential pollutants in the terrestrial environment as well as a variety of chemical -, biochemical - and physico-chemical reactions, which can be expected to influence the migration behaviour, comprising diffusion, dispersion, convection, sorption/desorption, precipitation/dissolution, transformations/degradations, biochemical reactions and complex formation. The latter comprises the complexation of metal ions as well as non-polar organics to naturally occurring organic macromolecules. The influence of the single types of processes on the migration process is elucidated based on theoretical studies. The influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour is unambiguous, as the processes apparently control the transport of pollutants in the terrestrial environment. As the simple, conventional K D concept breaks down, it is suggested that the migration process should be described in terms of the alternative concepts chemical dispersion, average-elution-time and effective retention. (AB) (134 refs.)
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Gender and rural-urban migration in China.
Davin, D
1996-02-01
Many men and women in China are migrating in search of better economic opportunities. Young women who migrate to urban centers in search of opportunity may stay away from their home villages for several years. At some point, however, they are likely to return home. This article considers the effect which such circular migration is having upon gender relations in China. The author's argument is presented in sections on China's 1990 census, migration and the sexual division of labor, migration and child care, the influence of returning migrants, the influence of young female returnees, and the fertility of returnees. She speculates that the demands and expectations of young women who return to their villages after spending some time earning high wages in urban areas will be affected by urban norms. While their return may lead to initial conflict, it is likely that the women will retain greater personal autonomy from their urban experience. Their return is also likely to lead to a higher degree of material consumption in the rural areas. Present circular migration in China has the potential to return human and financial resources to the villages, thereby helping to prevent the urban-rural gap between economic, social, cultural, and educational factors from growing even wider.
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Ecological advantages of partial migration as a conditional strategy.
Vélez-Espino, Luis A; McLaughlin, Robert L; Robillard, Melissa
2013-05-01
Partial migration is a widespread phenomenon characterized by migrant and resident forms from the same population. In phenotypically plastic taxa with indeterminate growth, resident and migrant ecophenotypes can differ in size and life history traits in ways expected to maximize fitness in the different habitats they exploit. Studies of partial migration in different taxa have advocated either density-dependence or environmental stochasticity as explanations for partial migration. We used a demographic approach for a virtual Brook Trout population to demonstrate the ecological consequences of partial migration under interacting density dependence and environmental stochasticity. The maintenance of partial migration as a conditional strategy in species/populations where resident and migrant forms exhibit life history asymmetries provides ecological advantages. We show that density-dependent migration is expected to increase population fitness under constant environmental conditions or low environmental variation, but decreases population fitness under high environmental variation. These conditions favor intermediate levels of migration as an advantageous tactic. However, there are threshold rates of return migration below which partial migration is no longer a viable tactic. Our modeling approach also allowed the exploration of the distribution of the population by life stage and habitat in response to the strength of density dependence, costs of migration, and return rates, and demonstrated the importance of the conservation of ecophenotypes in partially migratory populations. Copyright © 2013 Elsevier Inc. All rights reserved.
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Hematopoietic stem cell migration and proliferation after Partial body irradiation
International Nuclear Information System (INIS)
Murata, Takashi; Utsumi, Makoto; Hotta, Tomomitsu; Yamada, Hideo
1983-01-01
Stem cell migration in hematopoietic recovery after partial body irradiation was investigated with special emphasis on the comparative roles of the bone marrow and the spleen. The number of CFU-S in circulation declined rapidly and reached zero within a day after irradiation, thereafter it increased gradually. This finding suggests the presence of two different phases of stem cell migration. One is a rapid migrating phase in which stem cells are released rapidly within a day after irradiation, and the other is a slow migrating phase. The result of split doses of local body irradiation experiments implicated a role for the spleen distinct from that of the bone marrow in the preferential distribution of stem cells early after irradiation. The cell kinetic study showed that the proliferation of CFU-S occurred actively in irradiated bone marrow and the spleens as compared to that in unirradiated control. But on Day 7 and on Day 10 after irradiation, the proliferation of CFU-S in shielded bone marrow did not occur as actively as those in irradiated areas. The results of our present studies suggest that the spleen is not only the storage pools of migrating stem cells but also the main site of active proliferation of CFU-S in the early period of hematopoietic regeneration. (author)
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Field migration rates of tidal meanders recapitulate fluvial morphodynamics
Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea
2018-02-01
The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths.
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Are Composers Different? Historical Evidence on Conflict-induced Migration (1816-1997)
DEFF Research Database (Denmark)
Borowiecki, Karol
2012-01-01
In this paper we explore whether, and to what extent, the incidence of war affects the migration intensity of 164 prominent classical composers born after 1800. We model the aggregate stock of composers in a country and find that periods of war correspond negatively with the number of artists. We...... also find that conflict-induced migration intensity is considerably higher for composers than for the overall population and demonstrate that the share of composers in the overall population drops due to the incidence of war. We further find that the observed outmigration substantially diminishes...
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Romanian migrants: their situation shortly after migration to the Netherlands
Mérove Gijsberts; Marcel Lubbers
2015-01-01
Original title: Roemeense migranten: De leefsituatie in Nederland kort na migratie What is the situation of Romanians who registered in the Netherlands in the initial period after their migration? This study looks among other things at their position on the labour market, their command of
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Modeling dissolution and volatilization of LNAPL sources migrating on the groundwater table.
Kim, Jeongkon; Corapcioglu, M Yavuz
2003-08-01
A vertically averaged two-dimensional model was developed to describe areal spreading and migration of light nonaqueous-phase liquids (LNAPLs) introduced into the subsurface by spills or leaks from underground storage tanks. The NAPL transport model was coupled with two-dimensional contaminant transport models to predict contamination of soil gas and groundwater resulting from a LNAPL migrating on the water table. Numerical solutions were obtained by using the finite-difference method. Simulations and sensitivity analyses were conducted with a LNAPL of pure benzene to study LNAPL migration and groundwater contamination. The model was applied to subsurface contamination by jet fuel. Results indicated that LNAPL migration were affected mostly by volatilization. The generation and movement of the dissolved plume was affected by the geology of the site and the free-product plume. Most of the spilled mass remained as a free LNAPL phase 20 years after the spill. The migration of LNAPL for such a long period resulted in the contamination of both groundwater and a large volume of soil.
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Religiosity and Migration Aspirations among Mexican Youth.
Hoffman, Steven; Marsiglia, Flavio Francisco; Ayers, Stephanie L
2015-02-01
International migration has become an important topic of discussion from a policy and humanitarian perspective. Part of the debate includes a renewed interest in understanding the factors that influence decisions about migration to the US among Mexican youth still residing in their country of origin. The purpose of this study was to advance knowledge specifically about internal and external religiosity and their influence on youths' migration aspirations. The data for this study were collected in 2007 from students enrolled in an alternative high school program located in the state of Guanajuato, Mexico. The findings indicated that as external religiosity increases, the desire to work or live in the USA decreases. Furthermore, as internal religiosity increases, the desire to work or live in the USA and plans to migrate increase. The results are interpreted and discussed in light of previous research on religious and cultural norm adherence.
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Madin, L. P.; Kremer, P.; Wiebe, P. H.; Purcell, J. E.; Horgan, E. H.; Nemazie, D. A.
2006-05-01
Sampling during four summers over a twenty-seven year period has documented dense populations of Salpa aspera in the Slope Water south of New England, northeastern United States. The salps demonstrated a strong pattern of diel vertical migration, moving to depth (mostly 600-800 m) during the day and aggregating in the epipelagic (salps measured were 5.7lm-2 in 1986 and 1.6lm-2 in 1993. Depending on the year, the sampled salp populations were calculated to clear between 8 and 74% of the upper 50 m during each 8 h night. Total fecal output for the same populations was estimated to be between 5 and 91mgCm-2night-1. These results, and other observations, suggest this region is a salp "hot spot", with swarms of S. aspera developing seasonally on a frequent basis.
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International Nuclear Information System (INIS)
Egorov, V.N.
1999-01-01
This report considers peculiarities of the mathematical description of radionuclides migration between water environment and biotic and abiotic components of the Black Sea ecosystems at different periods of averaging, from the time scale of metabolic processes, taking place in hydrobionts, to the large-scale description of radionuclides migration in the Black Sea
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Robotic Patterning a Superhydrophobic Surface for Collective Cell Migration Screening.
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
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Audibility of high harmonics in a periodic pulse
Duifhuis, H.
1970-01-01
A periodic pulse consisting of sufficiently narrow pulses has a frequency spectrum which contains all harmonics with equal amplitude. Owing to the limited resolving power of the hearing organ, only the low harmonics can be perceived separately. The high harmonics are heard together as one complex
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Countering inbreeding with migration 1. Migration from unrelated ...
African Journals Online (AJOL)
Ret:ieved 6 Octoher 1991; ut:cepted I8 Mur- 1995. The eff'ect of migration on inbreeding is moclelled fbr small populations with immigrants from a large unrelated population. Different migration rates and numbers fbr the two sexes are assumed, and a general recursion equation for inbreeding progress derived, which can ...
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The Globalisation of migration
Directory of Open Access Journals (Sweden)
Milan Mesić
2002-04-01
Full Text Available The paper demonstrates that contemporary international migration is a constitutive part of the globalisation process. After defining the concepts of globalisation and the globalisation of migration, the author discusses six key themes, linking globalisation and international migration (“global cities”, the scale of migration; diversification of migration flows; globalisation of science and education; international migration and citizenship; emigrant communities and new identities. First, in accordance with Saskia Sassen’s analysis, the author rejects the wide-spread notion that unqualified migrants have lost an (important role in »global cities«, i.e. in the centres of the new (global economy. Namely, the post-modern service sector cannot function without the support of a wide range of auxiliary unqualified workers. Second, a critical comparison with traditional overseas mass migration to the USA at the turn of the 19th and 20th centuries indicates that present international migration is, perhaps, less extensive – however it is important to take into consideration various limitations that previously did not exist, and thus the present migration potential is in really greater. Third, globalisation is more evident in a diversification of the forms of migration: the source area of migrants to the New World and Europe has expanded to include new regions in the world; new immigration areas have arisen (the Middle East, new industrial countries of the Far East, South Europe; intra-regional migration has intensified. Forth, globalisation is linked to an increased migration of experts and the pessimistic notion of a brain drain has been replaced by the optimistic idea of a brain gain. Fifth, contemporary international migration has been associated with a crisis of the national model of citizenship. Sixth, the interlinking of (migrant cultural communities regardless of distance and the physical proximity of cultural centres (the
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Large scale modulation of high frequency acoustic waves in periodic porous media.
Boutin, Claude; Rallu, Antoine; Hans, Stephane
2012-12-01
This paper deals with the description of the modulation at large scale of high frequency acoustic waves in gas saturated periodic porous media. High frequencies mean local dynamics at the pore scale and therefore absence of scale separation in the usual sense of homogenization. However, although the pressure is spatially varying in the pores (according to periodic eigenmodes), the mode amplitude can present a large scale modulation, thereby introducing another type of scale separation to which the asymptotic multi-scale procedure applies. The approach is first presented on a periodic network of inter-connected Helmholtz resonators. The equations governing the modulations carried by periodic eigenmodes, at frequencies close to their eigenfrequency, are derived. The number of cells on which the carrying periodic mode is defined is therefore a parameter of the modeling. In a second part, the asymptotic approach is developed for periodic porous media saturated by a perfect gas. Using the "multicells" periodic condition, one obtains the family of equations governing the amplitude modulation at large scale of high frequency waves. The significant difference between modulations of simple and multiple mode are evidenced and discussed. The features of the modulation (anisotropy, width of frequency band) are also analyzed.
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Impact of Migration upon a Receiving Country’s Economic Development
Directory of Open Access Journals (Sweden)
Sorin Manole
2017-08-01
Full Text Available Economic growth regarded as a mechanism to ensure a long-term balance through the optimal use of available resources, through the development of innovative potential, the creation and development of instruments generating economic growth and also an adequate distribution of income is influenced by many factors, including migration. This paper aims at highlighting the effects of migration upon the economic development of EU Member State receiving countries, starting from economic and social facts indicating a migration phenomenon that is ever increasing. In this regard, it has been thought appropriate to perform an analysis on how the migration phenomenon is perceived and an empirical study on the economic impact of migration on receiving countries of the European Union. Thus, a linear model has been used with panel data with specific fixed effects for cross section units, and the database has been made up of the values recorded for GDP per capita influence factors in the 28 EU Member States in the period 2008-2014. The results show that migration has positive effects upon economic development. We have chosen to use GDP per capita as a measure of economic growth starting from the EUROSTAT indicator system used to measure sustainable development, and also from the fact that the National Institute of Statistics in Romania uses GDP per capita as one of 18 indicators measuring the knowledge and economic and social development society.
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1998-01-01
This article presents the perspectives of UNAIDS and the International Organization for Migration (IOM) on migration and HIV/AIDS. It identifies research and action priorities and policy issues, and describes the current situation in major regions of the world. Migration is a process. Movement is enhanced by air transport, rising international trade, deregulation of trade practices, and opening of borders. Movements are restricted by laws and statutes. Denial to freely circulate and obtain asylum is associated with vulnerability to HIV infections. A UNAIDS policy paper in 1997 and IOM policy guidelines in 1988 affirm that refugees and asylum seekers should not be targeted for special measures due to HIV/AIDS. There is an urgent need to provide primary health services for migrants, voluntary counseling and testing, and more favorable conditions. Research is needed on the role of migration in the spread of HIV, the extent of migration, availability of health services, and options for HIV prevention. Research must be action-oriented and focused on vulnerability to HIV and risk taking behavior. There is substantial mobility in West and Central Africa, economic migration in South Africa, and nonvoluntary migration in Angola. Sex workers in southeast Asia contribute to the spread. The breakup of the USSR led to population shifts. Migrants in Central America and Mexico move north to the US where HIV prevalence is higher.
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Collinson, Mark A; Tollman, Stephen M; Kahn, Kathleen
2007-08-01
World population growth will be increasingly concentrated in the urban areas of the developing world; however, some scholars caution against the oversimplification of African urbanization noting that there may be "counter-urbanization" and a prevailing pattern of circular rural-urban migration. The aim of the paper is to examine the ongoing urban transition in South Africa in the post-apartheid period, and to consider the health and social policy implications of prevailing migration patterns. Two data sets were analysed, namely the South African national census of 2001 and the Agincourt health and demographic surveillance system. A settlement-type transition matrix was constructed on the national data to show how patterns of settlement have changed in a five-year period. Using the sub-district data, permanent and temporary migration was characterized, providing migration rates by age and sex, and showing the distribution of origins and destinations. The comparison of national and sub-district data highlight the following features: urban population growth, particularly in metropolitan areas, resulting from permanent and temporary migration; prevailing patterns of temporary, circular migration, and a changing gender balance in this form of migration; stepwise urbanization; and return migration from urban to rural areas. Policy concerns include: rural poverty exacerbated by labour migration; explosive conditions for the transmission of HIV; labour migrants returning to die in rural areas; and the challenges for health information created by chronically ill migrants returning to rural areas to convalesce. Lastly, suggestions are made on how to address the dearth of relevant population information for policy-making in the fields of migration, settlement change and health.
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Croatia’s Migration Potential – Micro-Analytic Aspects
Directory of Open Access Journals (Sweden)
Saša Božić
2005-06-01
Full Text Available The authors set criteria for the selection of a model for measuring migration potential; they select and apply such a model to Croatia and determine the practical and scientific relevance of the Croatian case, especially its significance for the improvement of the chosen model. The authors concentrate on the application of Heinz Fassmann’s and Christiane Hintermann’s micro-analytic model for the estimation of East-Central Europe’s migration potential. After applying this model, they estimate Croatia’s total migration potential at 12.5%, i.e. 460,000 persons older than fourteen. The probable migration potential is estimated at 2.5%, i.e. 92,000 and the real migration potential at 0.4% of the population above fourteen, i.e. 14,700 persons. In Croatian case as well, the younger population (which can still utilise its labour capacity, as well as unemployed, unmarried and highly educated persons, are more likely to consider emigration. The data show also that the regions with the lowest share in GNP have the highest percentage of potential migrants and not the regions which are geographically the closest to potential immigration countries. The authors stress the necessity to integrate migration potential research models. The explanatory assumptions of migration potential research models, based on place utility and subjective expected utility, often overlap when used to interpret the data. Furthermore, the Croatian case shows that personal migration experience and the analytical mezzo level must be considered in order to gain an understanding of the creation of migration preferences.
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Staby, A
2011-11-15
We studied the temporal dynamics in the vertical distribution of Maurolicus muelleri scattering layers (SL) by examining continuous acoustic recordings over a 15 mo period in Masfjorden, Norway, complemented by intermittent sampling campaigns. The data revealed known patterns as normal diel vertical migration (DVM), midnight sinking between dusk and dawn, and periods without migrations, as well as novel behaviours consisting of early morning ascents, reverse diel vertical migrations, and interrupted ascents in the evening. During the first autumn of the study, adult fish modified their normal DVM behaviour by suspending their migration in the evening, yet ascending toward the surface in the later part of the night to reach upper layers during dawn. This behaviour was not observed during the second autumn of the study. By mid- to end of November (1st autumn), adult fish had suspended the nocturnal ascent entirely, and in the subsequent period until the end of January, a fraction of the population rather performed limited reverse migrations, slightly shifting their vertical distribution upwards during the first part of the day. From January to March 2008, fish interrupted their evening ascent at apparently random intervals and returned to deeper waters, instead of completing a full ascent to the surface. Our study underlines the value of long-term recordings, with the results suggesting that M. muelleri has the capability of changing its behaviour in response to ontogeny and internal state (satiation and hunger) as well as to external stimuli.
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The role of migration-specific and migration-relevant policies in migrant decision-making in transit
Kuschminder - de Guerre, Katie; Koser, Khalid
2017-01-01
This paper examines the role of migration-specific and migration-relevant policies in migrant decision-making factors for onwards migration or stay in Greece and Turkey. In this paper we distinguish migration-specific policies from migration-relevant policies in transit and destination countries,
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[Haitian migration to Santo Domingo].
Latortue, P R
1985-01-01
This work examines the history of Haitian migration to the Dominican Republic, the central role of Haitian migration in Dominican society, working conditions of Haitian migrants in the Dominican Republic, and the relationship of the migration to economic development on the island of Hispaniola. Lack of data, the difficulty of measuring illegal movement, and the problem of defining Haitians in Santo Domingo have impeded understanding of migration to the Dominican Republic. It is believed by many authorities that Haitian migration to Santo Domingo is considerable and perhaps exceeds that to the US. Haitian migration to the Dominican Republic began after 1915 with the fall of the Haitian president, a worsening of economic conditions partly caused by stagnation in the agricultural sector, and the newly dominant role of the US in Haitian economic affairs. The Great Depression of the 1930s was a direct antecedent of the massacre of Haitians by Dominican police in which some 30 thousand persons were killed; the economic recession of the early 1980s has also caused an outburst of antiHaitian feeling in the Dominican Republic although 80% of laborers in the sugar industry are Haitians. Sugar is extremely important to the Dominican economy: in 1974, sugar covered 12% of cultivated land, produced 40% of foreign exchange earnings, and was responsable for 21% of taxable income. Dominicans however refuse to work in sugar plantations under the current technological. conditions and wage system. Although the government periodically demands the Dominicanization of the sugar work force, no such changes have been made. Sugar will probably continue to play a decisive role in the generation of foreign exchange despite introduction of more technologically advanced sectors which benefit from better prices in the international market. Possibilities of mechanizing sugar production in the Dominican Republic appear remote, and failure to modernize an important sector of the economy has
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Normal and abnormal neuronal migration in the developing cerebral cortex.
Sun, Xue-Zhi; Takahashi, Sentaro; Cui, Chun; Zhang, Rui; Sakata-Haga, Hiromi; Sawada, Kazuhiko; Fukui, Yoshihiro
2002-08-01
Neuronal migration is the critical cellular process which initiates histogenesis of cerebral cortex. Migration involves a series of complex cell interactions and transformation. After completing their final mitosis, neurons migrate from the ventricular zone into the cortical plate, and then establish neuronal lamina and settle onto the outermost layer, forming an "inside-out" gradient of maturation. This process is guided by radial glial fibers, requires proper receptors, ligands, other unknown extracellular factors, and local signaling to stop neuronal migration. This process is also highly sensitive to various physical, chemical and biological agents as well as to genetic mutations. Any disturbance of the normal process may result in neuronal migration disorder. Such neuronal migration disorder is believed as major cause of both gross brain malformation and more special cerebral structural and functional abnormalities in experimental animals and in humans. An increasing number of instructive studies on experimental models and several genetic model systems of neuronal migration disorder have established the foundation of cortex formation and provided deeper insights into the genetic and molecular mechanisms underlying normal and abnormal neuronal migration.
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Rural Education and Out-Migration: The Case of a Coastal Community
Corbett, Michael
2005-01-01
In this article, I report on findings from a case study examining the relationship between formal education and out-migration in a Canadian coastal community from the early 1960s to the late 1990s. Although high rates of village-level out-migration were chronic, most migration trajectories were short-range. Contrary to large-scale quantitative…
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Personal Networks and Migration Decision: The Case of Jamaican Brain Drain
Directory of Open Access Journals (Sweden)
Rosalyn NEGRÓN
2012-05-01
Full Text Available Brain drain is the phenomena where the most educated citizens of a country migrate to countries with better opportunities. This typically affects developing countries more negatively than developed countries. Given the close proximity to the US and the high standard of education of its citizens, Jamaica tends to be particularly hard hit by this brain drain. In this paper I examine intentions to migrate among skilled and educated Jamaicans. Specifically, I explore to what extent the composition of their personal network affects their decision to migrate. The data set consists of 62 university students, roughly half of who intended to migrate. Data were collected on 40 people that they knew, including information about social support provided by their social networks. The socioeconomic data about respondents did not predict intentions to migrate. However, students at Campion College, a prestigious high school linked to upper middle class status, were significantly more likely to express an interest in migration than students from other schools. Frequency of travel abroad was negatively related to intention to migrate for those that had traveled at least once. The proportion of network members that provided informational and career advice was significantly higher for those that intended to migrate. Implications of these findings for immigration policy in Jamaica and receiving countries are discussed.
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Spontaneous neutrophil migration patterns during sepsis after major burns.
Jones, Caroline N; Moore, Molly; Dimisko, Laurie; Alexander, Andrew; Ibrahim, Amir; Hassell, Bryan A; Warren, H Shaw; Tompkins, Ronald G; Fagan, Shawn P; Irimia, Daniel
2014-01-01
Finely tuned to respond quickly to infections, neutrophils have amazing abilities to migrate fast and efficiently towards sites of infection and inflammation. Although neutrophils ability to migrate is perturbed in patients after major burns, no correlations have yet been demonstrated between altered migration and higher rate of infections and sepsis in these patients when compared to healthy individuals. To probe if such correlations exist, we designed microfluidic devices to quantify the neutrophil migration phenotype with high precision. Inside these devices, moving neutrophils are confined in channels smaller than the neutrophils and forced to make directional decisions at bifurcations and around posts. We employed these devices to quantify neutrophil migration across 18 independent parameters in 74 blood samples from 13 patients with major burns and 3 healthy subjects. Blinded, retrospective analysis of clinical data and neutrophil migration parameters revealed that neutrophils isolated from blood samples collected during sepsis migrate spontaneously inside the microfluidic channels. The spontaneous neutrophil migration is a unique phenotype, typical for patients with major burns during sepsis and often observed one or two days before the diagnosis of sepsis is confirmed. The spontaneous neutrophil migration phenotype is rare in patients with major burns in the absence of sepsis, and is not encountered in healthy individuals. Our findings warrant further studies of neutrophils and their utility for early diagnosing and monitoring sepsis in patients after major burns.
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The effect of migration on family structures in sub-Saharan Africa.
Okoth-ogendo, H W
1989-06-01
This paper assesses the effect of migration or family structures in sub-Saharan Africa, especially the effect of emigration on the reproduction, production, and social stability of the family in areas of origin in the predominantly agrarian communities of East and Southern Africa. Migration in precolonial Africa usually occurred for 1 of the following reasons: 1) the search by communities for new habitats and opportunities; 2) as a community response to droughts, floods, environmental degradation, and similar disasters; and 3) as a result of internecine wars, civil strife, and general hostilities. Thus, because of the collective nature of early migrations, the family unit maintained a much greater degree of social cohesion. The effects of the rise of the modern state in Africa on migration include 1) spatial limits of collective migration were frozen, 2) the colonial boundaries did not always correspond to cultural divisions, 3) both migration within colonial boundaries and individual migration became dominant, and 4) cyclical migration began. The end of colonialism resulted in 1) difficulties in creating strong and internally coherent nation states because of the uncertainty of national borders and 2) more cyclical migrants. The effects of migration on reproduction in the family during the colonial period include 17 extremely low fertility rates, 2) widespread domestic instability, and 3) exacerbation of moral decadence. Contemporary patterns of emigration have been far less disruptive, due in part to increased personal mobility and migration of the complete reproductive unit. The effects of migration on production include 1) depletion of labor for production; 2) women had to assume production functions, together with all their other responsibilities; and 3) very little cash or goods were available for remittance to areas of origin. Production and productivity among rural African families will continue to suffer as long as plantations, mines, and urban centers
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Field-scale colloid migration experiments in a granite fracture
International Nuclear Information System (INIS)
Vilks, P.; Frost, L.H.; Bachinski, D.B.
1997-01-01
An understanding of particle migration in fractured rock, required to assess the potential for colloid-facilitated transport of radionuclides, can best be evaluated when the results of laboratory experiments are demonstrated in the field. Field-scale migration experiments with silica colloids were carried out at AECL's Underground Research Laboratory (URL), located in southern Manitoba, to develop the methodology for large-scale migration experiments and to determine whether colloid transport is possible over distances up to 17 m. In addition, these experiments were designed to evaluate the effects of flow rate and flow path geometry, and to determine whether colloid tracers could be used to provide additional information on subsurface transport to that provided by conservative tracers alone. The colloid migration studies were carried out as part of AECL's Transport Properties in Highly Fractured Rock Experiment, the objective of which was to develop and demonstrate methods for evaluating the solute transport characteristics of zones of highly fractured rock. The experiments were carried out within fracture zone 2 as two-well recirculating, two-well non-recirculating, and convergent flow tests, using injection rates of 5 and 101 min -1 . Silica colloids with a 20 nm size were used because they are potentially mobile due to their stability, small size and negative surface charge. The shapes of elution profiles for colloids and conservative tracers were similar, demonstrating that colloids can migrate over distances of 17 m. The local region of drawdown towards the URL shaft affected colloid migration and, to a lesser extent, conservative tracer migration within the flow field established by the two-well tracer tests. These results indicate that stable colloids, with sizes as small as 20 nm, have different migration properties from dissolved conservative tracers. (author)
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Partial diel migration: A facultative migration underpinned by long-term inter-individual variation.
Harrison, Philip M; Gutowsky, Lee F G; Martins, Eduardo G; Patterson, David A; Cooke, Steven J; Power, Michael
2017-09-01
The variations in migration that comprise partial diel migrations, putatively occur entirely as a consequence of behavioural flexibility. However, seasonal partial migrations are increasingly recognised to be mediated by a combination of reversible plasticity in response to environmental variation and individual variation due to genetic and environmental effects. Here, we test the hypothesis that while partial diel migration heterogeneity occurs primarily due to short-term within-individual flexibility in behaviour, long-term individual differences in migratory behaviour also underpin this migration variation. Specifically, we use a hierarchical behavioural reaction norm approach to partition within- and among-individual variation in depth use and diel plasticity in depth use, across short- and long-term time-scales, in a group of 47 burbot (Lota lota) tagged with depth-sensing acoustic telemetry transmitters. We found that within-individual variation at the among-dates-within-seasons and among-seasons scale, explained the dominant proportion of phenotypic variation. However, individuals also repeatedly differed in their expression of migration behaviour over the 2 year study duration. These results reveal that diel migration variation occurs primarily due to short-term within-individual flexibility in depth use and diel migration behaviour. However, repeatable individual differences also played a key role in mediating partial diel migration. These findings represent a significant advancement of our understanding of the mechanisms generating the important, yet poorly understood phenomena of partial diel migration. Moreover, given the pervasive occurrence of diel migrations across aquatic taxa, these findings indicate that individual differences have an important, yet previously unacknowledged role in structuring the temporal and vertical dynamics of aquatic ecosystems. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.
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The Spatio-Temporal Characteristics and Modeling Research of Inter-Provincial Migration in China
Directory of Open Access Journals (Sweden)
Xiaomei Fan
2018-02-01
Full Text Available The national census data during 1995 and 2000 and during 2005 and 2010 are selected in this paper to make an analysis of the spatio-temporal characteristics of the inter-provincial population migration in China. In addition, the general regression model, the extension regression model considering the historical dependent variable and the spatial lag model are established based on the gravity model to make the regression model on China’s inter-provincial population migration over two periods of time. The results show that: (1 the inter-provincial population migration increases rapidly in size with strong geographical proximity; (2 China’s inter-provincial population migration is still in the primary stage of the general process of population migration. In other words, the inter-provincial population emigration and immigration levels have increased greatly with the economic development; (3 Statistically, the inter-provincial population migration is negatively correlated with the level of economic development in the emigrant place and the migration distance and positively correlated with the level of economic development in the immigrant place and the population scale in the emigrant and immigrant places; and (4 The spatio-temporal factor is an important explanatory variable of population migration. The introduction of the historical dependent variable and the spatial lag factor can improve the regression effect of the gravity model greatly, and the historical variable and the spatial factor have strong explanatory power for the inter-provincial population migration.
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Representing Migration: Analysis of Media Portrayals of Syrian Migrant Women in Turkey
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Ruhdan Uzun
2017-06-01
Full Text Available The media coverage of women migrations has played an important role in shaping public opinion and governmental policies. This article aims at exploring the media portrayals of Syrian Migrant Women in Turkey. For this purpose, the research data were collected from the three Turkish online newspaper websites, Hürriyet, Birgün and Sabah, each of which has different editorial policy in representing migration, during one year period. The findings of quantitative content analysis of the news stories regarding Syrian migrant women would provide an understanding of the gender dimension of migration in Turkey. It concludes that Syrian Migrant Women in Turkey generally are reported on crime news and are framed as victims or perpetrators. However, the newspapers rarely report their hard living conditions.
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Influences of environmental cues, migration history and habitat familiarity on partial migration
DEFF Research Database (Denmark)
Skov, Christian; Aarestrup, Kim; Baktoft, Henrik
2010-01-01
The factors that drive partial migration in organisms are not fully understood. Roach (Rutilus rutilus), a freshwater fish, engage in partial migration where parts of populations switch between summer habitats in lakes and winter habitats in connected streams. To test if the partial migration trait...
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International Nuclear Information System (INIS)
Broster, B.E.; Pupek, D.
1997-01-01
The controlling factors in DNAPL (dense non-aqueous phase liquids) migration were studied. DNAPLs are anthropogenic hydrocarbon liquids that are denser than water and which persist in the subsurface for long periods of time. DNAPLs move under gravity as blobs through pores and fractures until they settle in depressions. A study at Sussex, New Brunswick, showed that dissolved perchloroethylene (PCE) as high as 28.0 microgram/l was detected within the upper aquifer and in concentrations to 1.6 microgram/l within the lower aquifer which served as the main source of municipal water supply. A dispersal plume was identified by contouring PCE concentrations from 72 samples of subsurface water. The shape of the dispersal plume showed that after an initial spill, PCE migration was influenced by a buried river channel cut into the middle aquitard. The study showed that the stratigraphy, conductivity and topography of the subsurface units were the controlling factors in DNAPL migration
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Hydrogen impurity in SrTiO3: structure, electronic properties and migration
International Nuclear Information System (INIS)
Villamagua, Luis; Barreto, Rafael; Procel, Luis Miguel; Stashans, Arvids
2007-01-01
The present paper reports a computational investigation of the geometry and electronic structure as well as the migration of a hydrogen impurity in the cubic SrTiO 3 crystal. The study is done using an approach based on the Hartree-Fock theory and developed for periodic systems. It is found that the H impurity forms the so-called OH group at the equilibrium. Analysis of electron density within the defective region implies the enhancement in covalent chemical bonding. A possible defect migration has been also investigated
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The Inuit cancer pattern--the influence of migration
DEFF Research Database (Denmark)
Boysen, T.; Friborg, J.; Andersen, Allan
2008-01-01
The Inuit cancer pattern is characterized by high frequencies of Epstein-Barr Virus (EBV)-associated carcinomas of the nasopharynx and salivary glands. The reasons are unknown, but genetic and environmental factors are believed to be involved. Using data from the well-defined Inuit population...... following migration to Denmark. The SIR was not generally influenced by duration of stay. The high risk of carcinoma of the nasopharynx and salivary glands observed in Inuit populations is maintained after migration to a low incidence area. This indicates that genetic factors or environmental factors acting...
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Conservation physiology of animal migration
Lennox, Robert J.; Chapman, Jacqueline M.; Souliere, Christopher M.; Tudorache, Christian; Wikelski, Martin; Metcalfe, Julian D.; Cooke, Steven J.
2016-01-01
Migration is a widespread phenomenon among many taxa. This complex behaviour enables animals to exploit many temporally productive and spatially discrete habitats to accrue various fitness benefits (e.g. growth, reproduction, predator avoidance). Human activities and global environmental change represent potential threats to migrating animals (from individuals to species), and research is underway to understand mechanisms that control migration and how migration responds to modern challenges. Focusing on behavioural and physiological aspects of migration can help to provide better understanding, management and conservation of migratory populations. Here, we highlight different physiological, behavioural and biomechanical aspects of animal migration that will help us to understand how migratory animals interact with current and future anthropogenic threats. We are in the early stages of a changing planet, and our understanding of how physiology is linked to the persistence of migratory animals is still developing; therefore, we regard the following questions as being central to the conservation physiology of animal migrations. Will climate change influence the energetic costs of migration? Will shifting temperatures change the annual clocks of migrating animals? Will anthropogenic influences have an effect on orientation during migration? Will increased anthropogenic alteration of migration stopover sites/migration corridors affect the stress physiology of migrating animals? Can physiological knowledge be used to identify strategies for facilitating the movement of animals? Our synthesis reveals that given the inherent challenges of migration, additional stressors derived from altered environments (e.g. climate change, physical habitat alteration, light pollution) or interaction with human infrastructure (e.g. wind or hydrokinetic turbines, dams) or activities (e.g. fisheries) could lead to long-term changes to migratory phenotypes. However, uncertainty remains
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Migration und Flucht als Forschungsthemen der Geographie - Eine Standortbestimmung
Pott, Andreas; Schmiz, Antonie
2018-03-01
The contribution at hand argues that migration, especially of refugees, has received growing recognition in public and academic debates in the past few years. It traces the reciprocal references to a highly dynamic research subject within migration scholarship, public discourse, and politics. It thereby highlights the value and risks of a space-related perspective. In addition to an outline of established and newly emerging research fields within geographic migration research, the contribution opens the debate on practical implications of the addressed topical challenges within the field.
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Migration of cesium-137 through sandy soil layer effect of fine silt on migration
International Nuclear Information System (INIS)
Ohnuki, Toshihiko; Wadachi, Yoshiki
1983-01-01
The migration of 137 Cs through sandy soil layer was studied with consideration of the migration of fine silt by column method. It was found that a portion of fine silt migrated through the soil layer accompanying with 137 Cs. The mathematical migration model of 137 Cs involved the migration of fine silt through such soil layer was presented. This model gave a good accordance between calculated concentration distribution curve in sandy soil layer and effluent curve and observed those. So, this model seems to be advanced one for evaluating migration of 137 Cs in sandy soil layer with silt. (author)
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The impact of rural-urban migration on child survival.
Brockerhoff, M
1994-10-01
Large rural-urban child mortality differentials in many developing countries suggest that rural families can improve their children's survival chances by leaving the countryside and settling in towns and cities. This study uses data from Demographic and Health Surveys in 17 countries to assess the impact of maternal rural-urban migration on the survival chances of children under age two in the late 1970s and 1980s. Results show that, before migration, children of migrant women had similar or slightly higher mortality risks than children of women who remained in the village. In the two-year period surrounding their mother's migration, their chances of dying increased sharply as a result of accompanying their mothers or being left behind, to levels well above those of rural and urban non-migrant children. Children born after migrants had settled in the urban area, however, gradually experienced much better survival chances than children of rural non-migrants, as well as lower mortality risks than migrants' children born in rural areas before migration. The study concludes that many disadvantaged urban children would probably have been much worse off had their mothers remained in the village, and that millions of children's lives may have been saved in the 1980s as a result of mothers moving to urban areas.
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South-South Migration and Remittances
Ratha, Dilip; Shaw, William
2007-01-01
South-South Migration and Remittances reports on preliminary results from an ongoing effort to improve data on bilateral migration stocks. It sets out some working hypotheses on the determinants and socioeconomic implications of South-South migration. Contrary to popular perception that migration is mostly a South-North phenomenon, South-South migration is large. Available data from nation...
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Agrawal, Sutapa; Taylor, Fiona C; Moser, Kath; Narayanan, Gitanjali; Kinra, Sanjay; Prabhakaran, Dorairaj; Reddy, Kolli Srinath; Davey Smith, George; Ebrahim, Shah
2015-01-01
Migration is suspected to increase the risk for psychological distress for those who enter a new cultural environment. We investigated the association between sociodemographic characteristics, premigratory and migratory factors and psychological distress in rural-to-urban migrants just after migration and after resettlement. Data from the cross-sectional sib-pair designed Indian Migration Study (IMS, 2005-2007) were used. The analysis focused on 2112 participants aged ≥18 years from the total IMS sample ( n = 7067) who reported being migrant. Psychological distress was assessed based on the responses of the 7-questions in a five-point scale, where the respondents were asked to report about their feelings now and also asked to recall these feelings when they first migrated. The associations were analyzed using multiple logistic regression models. High prevalence of psychological distress was found just after migration (7.3%; 95% confidence interval [CI]: 6.2-8.4) than after settlement (4.7%; 95% CI: 3.8-5.6). Push factors as a reason behind migration and not being able to adjust in the new environment were the main correlates of psychological distress among both the male and female migrants, just after migration. Rural-urban migration is a major phenomenon in India and given the impact of premigratory and migratory related stressors on mental health, early intervention could prevent the development of psychological distress among the migrants.
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Mironer, Y Eugene; Brown, Christopher; Satterthwaite, John R; Cohen, Mary; Tonder, Lisa M; Grumman, Steve
2004-01-01
Spinal cord stimulation (SCS) is a popular method of treatment of chronic pain. Unfortunately, migration of the lead continues to be a serious complication of this therapy. In an attempt to reduce lateral migration of the SCS lead, we performed a retrospective assessment of a new technique of percutaneous lead placement. This new method of "midline anchoring" of the lead using the plica mediana dorsalis was tested against conventional technique in a retrospective study involving 122 trials and 91 implants of SCS over a period of five years. The use of "midline anchoring" resulted in a decrease in lead migration from 23% to 6% after trial insertion and from 24% to 7% after implantation. We conclude that "midline anchoring" of the SCS lead is an effective method of preventing lead migration.
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Overexpression of Myo1e in mouse podocytes enhances cellular endocytosis, migration, and adhesion.
Jin, Xia; Wang, Wenjing; Mao, Jianhua; Shen, Huijun; Fu, Haidong; Wang, Xia; Gu, Weizhong; Liu, Aimin; Yu, Huimin; Shu, Qiang; Du, Lizhong
2014-02-01
Podocytes are a terminally differentiated and highly specialized cell type in the glomerulus that forms a crucial component of the glomerular filtration barrier. Recently, Myo1e was identified in the podocytes of glomeruli. Myo1e podocyte-specific knockout mice exhibit proteinuria, podocyte foot process effacement, glomerular basement membrane disorganization, signs of chronic renal injury, and kidney inflammation. After overexpression of Myo1e in a conditionally immortalized mouse podocyte cell line (MPC5), podocyte migration was evaluated via transwell assay, endocytosis was evaluated using FITC-transferrin, and adhesion was evaluated using a detachment assay after puromycin aminonucleoside treatment. Myo1e overexpression significantly increased the adherence of podocytes. ANOVA analysis indicated significant differences for cell adhesion between the overexpression and control groups (overexpression vs. control, t = 11.3199, P = 0.005; overexpression vs. negative control, t = 12.0570, P = 0.0006). Overexpression of Myo1e inhibited puromycin aminonucleoside-induced podocyte detachment, and the number of cells remaining on the bottom of the culture plate increased. Cell migration was enhanced in Myo1e-overexpressing podocytes in the transwell migration assay. Internalization of FITC-transferrin also increased in Myo1e-overexpressing podocytes relative to control cells. Overexpression of Myo1e can enhance podocyte migration ability, endocytosis, and attachment to the glomerular basement membrane. Restoration of Myo1e expression in podocytes may therefore strengthen their functional integrity against environmental and mechanical injury. © 2013 Wiley Periodicals, Inc.
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Economic, social and gender aspects of the international migration in Moldova
Directory of Open Access Journals (Sweden)
Dorin VACULOVSCHI
2016-06-01
Full Text Available International labor migration is one of the most marked phenomenon that characterize the current situation on the Moldovan labor market. Geographical and gender distribution in labor migration is largely determined by the type of work that provide migrant workers. Women migrate to provide domestic and care services abroad, delegating in the same time their responsibilities in this area to other people, leads to the constitution of so-called global care chains. Migration with the purpose of study in Moldova is accompanied by a negative phenomenon, of the departure of highly qualified specialists. International migration of highly skilled labor, known as "brain drain"clearly evokes a loss of intellectual capital. Moldova continues to be characterized as an origin country of human beings trafficking, being at lesser extent a country of transit of human trafficking victims from NIS countries to Europe. The lack of some measures from the Government on “human capital loss” problem will essentially reduce the chances of exit from the crisis.
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The use of census migration data to approximate human movement patterns across temporal scales.
Directory of Open Access Journals (Sweden)
Amy Wesolowski
Full Text Available 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.
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Basic Characteristics and Consequences of Migration Movements in Bosnia and Herzegovina
Directory of Open Access Journals (Sweden)
Alma Pobrić
2002-12-01
Full Text Available Migrations play a very important and significant cultural and historical role in Bosnia and Herzegovina. They have as a consequence brought economic and demographic changes and negative migration balance has been the main characteristic for a long period of time. Beside strong migration flows from Bosnian territory, internal population movements have also been very intensive, contributing to regional differences in population growth and leading to the development of immigration and emigration zones. At the same time, rural settlements have been registering a decline in population (some even ceasing to exist while municipal centers have increased in size. To make matters worse, population reproduction has become questionable. The number of municipalities with decreased population has grown by about 13 percent during 1953–1991 period. Between censuses in 1981 and 1991, the number of municipalities characterized by immigration declined whereas the number of those with emigration characteristics increased. Furthermore, as a result of war and related problems in Bosnia and Herzegovina from 1991 to 1999, only 24 municipalities now contain more inhabitants than they had in 1991. Also, the relationship between domiciled and displaced populations in municipalities is different, a fact which depends particularly on the administrative organization within the country.
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Studies of radiocaesium migration in soils with high organic matter content
International Nuclear Information System (INIS)
Zygmunt, J.; Chibowski, S.; Klimowicz, Z.
1997-01-01
This paper encloses results of field tests carried out on two types of organic soils. Activities of caesium, originating from global fallout as well as from Chernobyl power plant breakdown, were measured for these two soils. Radioactive caesium is present to a depth of 40 and 70 cm, in black soil and in peat, respectively, although the highest activity was found in the topmost layers. Caesium originating from the Chernobyl accident constitutes about 70% of the total activity in the 0-10 cm layers of soils. The vertical migration rates of caesium from both sources were also measured. In the case of peat soil the migration rate of the Chernobyl caesium as well as that from global fallout were found to be similar and amounted to 0.2 cm/year. In the case of black soil the differences were more pronounced (0.34 and 0.14 cm/year, respectively). (author)
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Internal wave-mediated shading causes frequent vertical migrations in fishes
Kaartvedt, Stein
2012-04-25
We provide evidence that internal waves cause frequent vertical migrations (FVM) in fishes. Acoustic data from the Benguela Current revealed that pelagic scattering layers of fish below ~140 m moved in opposite phases to internal waves, ascending ~20 m towards the wave trough and descending from the wave crest. At the trough, the downward displacement of upper waters and the upward migration of fish created an overlapping zone. Near-bottom fish correspondingly left the benthic boundary zone at the wave trough, ascending into an acoustic scattering layer likely consisting of zooplankton and then descending to the benthic boundary zone at the wave crest. We suggest that this vertical fish migration is a response to fluctuations in light intensity of 3 to 4 orders of magnitude caused by shading from a turbid surface layer that had chlorophyll a values of 3 to 4 mg m−3 and varied in thickness from ~15 to 50 m at a temporal scale corresponding to the internal wave period (30 min). This migration frequency thus is much higher than that of the common and widespread light-associated diel vertical migration. Vertical movements affect prey encounters, growth, and survival. We hypothesize that FVM increase the likelihood of prey encounters and the time for safe visual foraging among planktivorous fish, thereby contributing to efficient trophic transfer in major upwelling areas.
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Energy Technology Data Exchange (ETDEWEB)
Abbas, M., E-mail: micheline.abbas@ensiacet.fr [Laboratoire de Génie Chimique, Université de Toulouse INPT-UPS, 31030, Toulouse (France); CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Magaud, P. [CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Institut Clément Ader, Université de Toulouse UPS-INSA-ISAE-Mines Albi, 31400, Toulouse (France); Gao, Y. [Institut Clément Ader, Université de Toulouse UPS-INSA-ISAE-Mines Albi, 31400, Toulouse (France); Geoffroy, S. [CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Laboratoire Matériaux et Durabilité des Constructions, Université de Toulouse (France); UPS, INSA, 31077, Toulouse (France)
2014-12-15
The migration of neutrally buoyant finite sized particles in a Newtonian square channel flow is investigated in the limit of very low solid volumetric concentration, within a wide range of channel Reynolds numbers Re = [0.07-120]. In situ microscope measurements of particle distributions, taken far from the channel inlet (at a distance several thousand times the channel height), revealed that particles are preferentially located near the channel walls at Re > 10 and near the channel center at Re < 1. Whereas the cross-streamline particle motion is governed by inertia-induced lift forces at high inertia, it seems to be controlled by shear-induced particle interactions at low (but finite) Reynolds numbers, despite the low solid volume fraction (<1%). The transition between both regimes is observed in the range Re = [1-10]. In order to exclude the effect of multi-body interactions, the trajectories of single freely moving particles are calculated thanks to numerical simulations based on the force coupling method. With the deployed numerical tool, the complete particle trajectories are accessible within a reasonable computational time only in the inertial regime (Re > 10). In this regime, we show that (i) the particle undergoes cross-streamline migration followed by a cross-lateral migration (parallel to the wall) in agreement with previous observations, and (ii) the stable equilibrium positions are located at the midline of the channel faces while the diagonal equilibrium positions are unstable. At low flow inertia, the first instants of the numerical simulations (carried at Re = O(1)) reveal that the cross-streamline migration of a single particle is oriented towards the channel wall, suggesting that the particle preferential positions around the channel center, observed in the experiments, are rather due to multi-body interactions.
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International Nuclear Information System (INIS)
Abbas, M.; Magaud, P.; Gao, Y.; Geoffroy, S.
2014-01-01
The migration of neutrally buoyant finite sized particles in a Newtonian square channel flow is investigated in the limit of very low solid volumetric concentration, within a wide range of channel Reynolds numbers Re = [0.07-120]. In situ microscope measurements of particle distributions, taken far from the channel inlet (at a distance several thousand times the channel height), revealed that particles are preferentially located near the channel walls at Re > 10 and near the channel center at Re < 1. Whereas the cross-streamline particle motion is governed by inertia-induced lift forces at high inertia, it seems to be controlled by shear-induced particle interactions at low (but finite) Reynolds numbers, despite the low solid volume fraction (<1%). The transition between both regimes is observed in the range Re = [1-10]. In order to exclude the effect of multi-body interactions, the trajectories of single freely moving particles are calculated thanks to numerical simulations based on the force coupling method. With the deployed numerical tool, the complete particle trajectories are accessible within a reasonable computational time only in the inertial regime (Re > 10). In this regime, we show that (i) the particle undergoes cross-streamline migration followed by a cross-lateral migration (parallel to the wall) in agreement with previous observations, and (ii) the stable equilibrium positions are located at the midline of the channel faces while the diagonal equilibrium positions are unstable. At low flow inertia, the first instants of the numerical simulations (carried at Re = O(1)) reveal that the cross-streamline migration of a single particle is oriented towards the channel wall, suggesting that the particle preferential positions around the channel center, observed in the experiments, are rather due to multi-body interactions
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A Customizable Chamber for Measuring Cell Migration.
Chowdhury, Aniqa N; Vo, Huu Tri; Olang, Sharon; Mappus, Elliott; Peterson, Brian; Hlavac, Nora; Harvey, Tyler; Dean, Delphine
2017-03-12
Cell migration is a vital part of immune responses, growth, and wound healing. Cell migration is a complex process that involves interactions between cells, the extracellular matrix, and soluble and non-soluble chemical factors (e.g., chemoattractants). Standard methods for measuring the migration of cells, such as the Boyden chamber assay, work by counting cells on either side of a divider. These techniques are easy to use; however, they offer little geometric modification for different applications. In contrast, microfluidic devices can be used to observe cell migration with customizable concentration gradients of soluble factors 1 , 2 . However, methods for making microfluidics based assays can be difficult to learn. Here, we describe an easy method for creating cell culture chambers to measure cell migration in response to chemical concentration gradients. Our cell migration chamber method can create different linear concentration gradients in order to study cell migration for a variety of applications. This method is relatively easy to use and is typically performed by undergraduate students. The microchannel chamber was created by placing an acrylic insert in the shape of the final microchannel chamber well into a Petri dish. After this, poly(dimethylsiloxane) (PDMS) was poured on top of the insert. The PDMS was allowed to harden and then the insert was removed. This allowed for the creation of wells in any desired shape or size. Cells may be subsequently added to the microchannel chamber, and soluble agents can be added to one of the wells by soaking an agarose block in the desired agent. The agarose block is added to one of the wells, and time-lapse images can be taken of the microchannel chamber in order to quantify cell migration. Variations to this method can be made for a given application, making this method highly customizable.
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[Migration and urbanization in the Sahel. Consequences of the Sahelian migrations].
Traore, S
1997-10-01
The consequences of Sahelian migration are multiple and diverse. In rural areas there may be a loss of income in the short run and a reduced possibility of development in the long run. Apart from its implications for urban growth, Sahelian migration may have four series of consequences in the places of origin. In detaching peasants from their lands, migration may contribute to loss of appreciation and reverence for the lands. Attachment to the lands of the ancestors loses its meaning as soon as questions of survival or economic rationality are raised. Migration contributes to the restructuring of the societies of origin. Increasing monetarization of market relations and introduction of new needs create new norms that favor stronger integration into the world economy. Migration may cause a decline in production because of the loss of the most active population, and it changes the age and sex distribution of households and usually increases their dependency burden. The effects on fertility and mortality are less clear. The effects of migration on the zones of arrival in the Sahel depend on the type of area. Conflicts between natives and in-migrants are common in rural-rural migration. Degradation of land may result from the increased demands placed upon it. Migrants to cities in Africa, and especially in the Sahel, appear to conserve their cultural values and to transplant and reinterpret their village rules of solidarity.
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Jain, Ashali; Khalid, Maria; Qureshi, Muhammad M; Georgian-Smith, Dianne; Kaplan, Jonah A; Buch, Karen; Grinstaff, Mark W; Hirsch, Ariel E; Hines, Neely L; Anderson, Stephan W; Gallagher, Katherine M; Bates, David D B; Bloch, B Nicolas
2017-11-01
To evaluate breast biopsy marker migration in stereotactic core needle biopsy procedures and identify contributing factors. This retrospective study analyzed 268 stereotactic biopsy markers placed in 263 consecutive patients undergoing stereotactic biopsies using 9G vacuum-assisted devices from August 2010-July 2013. Mammograms were reviewed and factors contributing to marker migration were evaluated. Basic descriptive statistics were calculated and comparisons were performed based on radiographically-confirmed marker migration. Of the 268 placed stereotactic biopsy markers, 35 (13.1%) migrated ≥1 cm from their biopsy cavity. Range: 1-6 cm; mean (± SD): 2.35 ± 1.22 cm. Of the 35 migrated biopsy markers, 9 (25.7%) migrated ≥3.5 cm. Patient age, biopsy pathology, number of cores, and left versus right breast were not associated with migration status (P> 0.10). Global fatty breast density (P= 0.025) and biopsy in the inner region of breast (P = 0.031) were associated with marker migration. Superior biopsy approach (P= 0.025), locally heterogeneous breast density, and t-shaped biopsy markers (P= 0.035) were significant for no marker migration. Multiple factors were found to influence marker migration. An overall migration rate of 13% supports endeavors of research groups actively developing new biopsy marker designs for improved resistance to migration. • Breast biopsy marker migration is documented in 13% of 268 procedures. • Marker migration is affected by physical, biological, and pathological factors. • Breast density, marker shape, needle approach etc. affect migration. • Study demonstrates marker migration prevalence; marker design improvements are needed.
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Dynamic Quantification of Host Schwann Cell Migration into Peripheral Nerve Allografts
Whitlock, Elizabeth L.; Myckatyn, Terence M.; Tong, Alice Y.; Yee, Andrew; Yan, Ying; Magill, Christina K.; Johnson, Philip J.; Mackinnon, Susan E.
2010-01-01
Host Schwann cell (SC) migration into nerve allografts is the limiting factor in the duration of immunosuppression following peripheral nerve allotransplantation, and may be affected by different immunosuppressive regimens. Our objective was to compare SC migration patterns between clinical and experimental immunosuppression regimens both over time and at the harvest endpoint. Eighty mice that express GFP under the control of the Schwann cell specific S100 promoter were engrafted with allogeneic, nonfluorescent sciatic nerve grafts. Mice received immunosuppression with either tacrolimus (FK506), or experimental T-cell triple costimulation blockade (CSB), consisting of CTLA4-immunoglobulin fusion protein, anti-CD40 monoclonal antibody, and anti-inducible costimulator monoclonal antibody. Migration of GFP-expressing host SCs into wild-type allografts was assessed in vivo every 3 weeks until 15 weeks postoperatively, and explanted allografts were evaluated for immunohistochemical staining patterns to differentiate graft from host SCs. Immunosuppression with tacrolimus exhibited a plateau of SC migration, characterized by significant early migration (< 3 weeks) followed by a constant level of host SCs in the graft (15 weeks). At the endpoint, graft fluorescence was decreased relative to surrounding host nerve, and donor SCs persisted within the graft. CSB-treated mice displayed gradually increasing migration of host SCs into the graft, without the plateau noted in tacrolimus-treated mice, and also maintained a population of donor SCs at the 15-week endpoint. SC migration patterns are affected by immunosuppressant choice, particularly in the immediate postoperative period, and the use of a single treatment of CSB may allow for gradual population of nerve allografts with host SCs. PMID:20633557
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Directory of Open Access Journals (Sweden)
David A Lutz
Full Text Available Rapid 21st-century climate change may lead to large population decreases and extinction in tropical montane cloud forest species in the Andes. While prior research has focused on species migrations per se, ecotones may respond to different environmental factors than species. Even if species can migrate in response to climate change, if ecotones do not they can function as hard barriers to species migrations, making ecotone migrations central to understanding species persistence under scenarios of climate change. We examined a 42-year span of aerial photographs and high resolution satellite imagery to calculate migration rates of timberline--the grassland-forest ecotone-inside and outside of protected areas in the high Peruvian Andes. We found that timberline in protected areas was more likely to migrate upward in elevation than in areas with frequent cattle grazing and fire. However, rates in both protected (0.24 m yr(-1 and unprotected (0.05 m yr(-1 areas are only 0.5-2.3% of the rates needed to stay in equilibrium with projected climate by 2100. These ecotone migration rates are 12.5 to 110 times slower than the observed species migration rates within the same forest, suggesting a barrier to migration for mid- and high-elevation species. We anticipate that the ecotone will be a hard barrier to migration under future climate change, leading to drastic population and biodiversity losses in the region unless intensive management steps are taken.
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Human migration, protected areas, and conservation outreach in Tanzania.
Salerno, Jonathan D; Borgerhoff Mulder, Monique; Kefauver, Shawn C
2014-06-01
A recent discussion debates the extent of human in-migration around protected areas (PAs) in the tropics. One proposed argument is that rural migrants move to bordering areas to access conservation outreach benefits. A counter proposal maintains that PAs have largely negative effects on local populations and that outreach initiatives even if successful present insufficient benefits to drive in-migration. Using data from Tanzania, we examined merits of statistical tests and spatial methods used previously to evaluate migration near PAs and applied hierarchical modeling with appropriate controls for demographic and geographic factors to advance the debate. Areas bordering national parks in Tanzania did not have elevated rates of in-migration. Low baseline population density and high vegetation productivity with low interannual variation rather than conservation outreach explained observed migration patterns. More generally we argue that to produce results of conservation policy significance, analyses must be conducted at appropriate scales, and we caution against use of demographic data without appropriate controls when drawing conclusions about migration dynamics. © 2014 Society for Conservation Biology.
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The Spatial Structure of Planform Migration - Curvature Relation of Meandering Rivers
Guneralp, I.; Rhoads, B. L.
2005-12-01
of previous studies. Continuous curvature series can be related to measured rates of lateral migration to explore empirically the relationship between spatially extended curvature and local bend migration. The methodology is applied to a study reach along a highly sinuous section of the Embarras River in Illinois, USA, which contains double-headed asymmetrical loops. To identify patterns of channel planform and rates of lateral migration for a study reach along Embarrass River in central Illinois, geographical information systems analysis of historical aerial photography over a period from 1936 to 1998 was conducted. Results indicate that parametric cubic spline interpolation provides excellent characterization of the complex planforms and planform curvatures of meandering rivers. The findings also indicate that the spatial structure of migration rate-curvature relation may be more complex than a simple exponential distance-decay function. The study represents a first step toward unraveling the spatial structure of planform evolution of meandering rivers and for developing models of planform dynamics that accurately relate spatially extended patterns of channel curvature to local rates of lateral migration. Such knowledge is vital for improving the capacity to accurately predict planform change of meandering rivers.
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Language competition in a population of migrating agents
Lipowska, Dorota; Lipowski, Adam
2017-05-01
Influencing various aspects of human activity, migration is associated also with language formation. To examine the mutual interaction of these processes, we study a Naming Game with migrating agents. The dynamics of the model leads to formation of low-mobility clusters, which turns out to break the symmetry of the model: although the Naming Game remains symmetric, low-mobility languages are favored. High-mobility languages are gradually eliminated from the system, and the dynamics of language formation considerably slows down. Our model is too simple to explain in detail language competition of migrating human communities, but it certainly shows that languages of settlers are favored over nomadic ones.
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A highly specific test for periodicity
International Nuclear Information System (INIS)
Ansmann, Gerrit
2015-01-01
We present a method that allows to distinguish between nearly periodic and strictly periodic time series. To this purpose, we employ a conservative criterion for periodicity, namely, that the time series can be interpolated by a periodic function whose local extrema are also present in the time series. Our method is intended for the analysis of time series generated by deterministic time-continuous dynamical systems, where it can help telling periodic dynamics from chaotic or transient ones. We empirically investigate our method's performance and compare it to an approach based on marker events (or Poincaré sections). We demonstrate that our method is capable of detecting small deviations from periodicity and outperforms the marker-event-based approach in typical situations. Our method requires no adjustment of parameters to the individual time series, yields the period length with a precision that exceeds the sampling rate, and its runtime grows asymptotically linear with the length of the time series
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A highly specific test for periodicity
Energy Technology Data Exchange (ETDEWEB)
Ansmann, Gerrit, E-mail: gansmann@uni-bonn.de [Department of Epileptology, University of Bonn, Sigmund-Freud-Straße 25, 53105 Bonn (Germany); Helmholtz Institute for Radiation and Nuclear Physics, University of Bonn, Nussallee 14–16, 53115 Bonn (Germany); Interdisciplinary Center for Complex Systems, University of Bonn, Brühler Straße 7, 53175 Bonn (Germany)
2015-11-15
We present a method that allows to distinguish between nearly periodic and strictly periodic time series. To this purpose, we employ a conservative criterion for periodicity, namely, that the time series can be interpolated by a periodic function whose local extrema are also present in the time series. Our method is intended for the analysis of time series generated by deterministic time-continuous dynamical systems, where it can help telling periodic dynamics from chaotic or transient ones. We empirically investigate our method's performance and compare it to an approach based on marker events (or Poincaré sections). We demonstrate that our method is capable of detecting small deviations from periodicity and outperforms the marker-event-based approach in typical situations. Our method requires no adjustment of parameters to the individual time series, yields the period length with a precision that exceeds the sampling rate, and its runtime grows asymptotically linear with the length of the time series.
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Energy Technology Data Exchange (ETDEWEB)
Borgne, H.
2004-12-01
Seismic imaging is an important tool for ail exploration. From the filtered seismic traces and a subsurface velocity model, migration allows to localize the reflectors and to estimate physical properties of these interfaces. The subsurface is split up into a reference medium, corresponding to the low spatial frequencies (a smooth medium), and a perturbation medium, corresponding to the high spatial frequencies. The propagation of elastic waves in the medium of reference is modelled by the ray theory. The association of this theory with a principle of diffraction or reflection allows to take into account the high spatial frequencies: the Kirchhoff approach represents so the medium of perturbations with continuous surfaces, characterized by reflection coefficients. The target of the quantitative migration is to reconstruct this reflection coefficient, notably its behaviour according to the incidence angle. These information will open the way to seismic characterization of the reservoir domain, with. a stratigraphic inversion for instance. In order to improve the qualitative and quantitative migration results, one of the current challenges is to take into account the anisotropy of the subsurface. Taking into account rocks anisotropy in the imaging process of seismic data requires two improvements from the isotropic case. The first one roughly concerns the modelling aspect: an anisotropic propagator should be used to avoid a mis-positioning or bad focusing of the imaged reflectors. The second correction concerns the migration aspect: as anisotropy affects the reflectivity of subsurface, a specific anisotropic imaging formula should be applied in the migration kernel, in order to recover the correct A V A behavior of the subsurface reflectors, If the first correction is DOW made in most so-called anisotropic imaging algorithms, the second one is currently ignored. The first part of my work concerns theoretical aspects. 1 study first the preservation of amplitudes in the
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Learning from HIV: exploring migration and health in South Africa.
Vearey, Joanna
2012-01-01
Southern Africa is associated with high HIV prevalence and diverse population movements, including temporary, circular movements between rural and urban areas within countries (internal migration), and movements across borders (international migration). Whilst most migration in southern Africa is associated with the search for improved livelihood opportunities in urban areas a small--but significant--number of people are forced to migrate to escape persecution or civil war. This paper utilises recent empirical studies conducted in South Africa to explore linkages between migration into urban areas and health, focusing on HIV. It is shown that the relationship between migration and HIV is complex; that both internal and international migrants move to urban areas for reasons other than healthcare seeking; and that most migratory movements into urban areas involve the positive selection of healthy individuals. Whilst healthy migration has economic benefits for rural sending households, the data uncovers an important process of return migration (internally or across borders) in times of sickness, with the burden of care placed on the rural, sending household. There is an urgent need for a comprehensive response that maintains the health of migrants in urban areas, and provides support to rural areas in times of sickness.
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In-Vivo Imaging of Cell Migration Using Contrast Enhanced MRI and SVM Based Post-Processing.
Weis, Christian; Hess, Andreas; Budinsky, Lubos; Fabry, Ben
2015-01-01
The migration of cells within a living organism can be observed with magnetic resonance imaging (MRI) in combination with iron oxide nanoparticles as an intracellular contrast agent. This method, however, suffers from low sensitivity and specificty. Here, we developed a quantitative non-invasive in-vivo cell localization method using contrast enhanced multiparametric MRI and support vector machines (SVM) based post-processing. Imaging phantoms consisting of agarose with compartments containing different concentrations of cancer cells labeled with iron oxide nanoparticles were used to train and evaluate the SVM for cell localization. From the magnitude and phase data acquired with a series of T2*-weighted gradient-echo scans at different echo-times, we extracted features that are characteristic for the presence of superparamagnetic nanoparticles, in particular hyper- and hypointensities, relaxation rates, short-range phase perturbations, and perturbation dynamics. High detection quality was achieved by SVM analysis of the multiparametric feature-space. The in-vivo applicability was validated in animal studies. The SVM detected the presence of iron oxide nanoparticles in the imaging phantoms with high specificity and sensitivity with a detection limit of 30 labeled cells per mm3, corresponding to 19 μM of iron oxide. As proof-of-concept, we applied the method to follow the migration of labeled cancer cells injected in rats. The combination of iron oxide labeled cells, multiparametric MRI and a SVM based post processing provides high spatial resolution, specificity, and sensitivity, and is therefore suitable for non-invasive in-vivo cell detection and cell migration studies over prolonged time periods.
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de Haas, H.; Fokkema, T.; Fihri, M.F.
2015-01-01
Different migration theories generate competing hypotheses with regard to determinants of return migration. While neoclassical migration theory associates migration to the failure to integrate at the destination, the new economics of labour migration sees return migration as the logical stage after
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Thermal migration of iron implanted in aluminium at high doses
International Nuclear Information System (INIS)
Asundi, V.K.; Joshi, M.C.; Deb, S.K.; Soud, D.K.; Kulkarni, V.N.; Sundararaman, M.
1978-01-01
The anneal behaviour of the Fe-Al metastable system produced by implantation of Fe + ions at 30 keV has been reported. The implant concentrations between 18-42 at percent have been chosen, in order to exceed the normal solid solubility of Fe in Al by about three orders of magnitude. Isothermal annealing has been done under vacuum (55 x 10 -6 Torr) at 400deg C and 570 deg C. The iron depth profiles have been determined, by Rutherford backscattering of 2 MeV He + ions. It has been found that 1) as annealing proceeds, all specimens show rapid enhanced diffusion initially (upto about 30 m), followed by a much slower diffusion as iron ions migrate inwards (2) at implant concentrations 23 at percent, double peaks appear in iron depth profiles, followed by rapid migration of diffused iron towards surface and (3) at still higher anneal times, the out-diffused iron moves inward again. This kind of out-diffusion behaviour in a metallic system has not been reported earlier in the literature. Also, the presence of Fe 4 Al 13 has been identified as terminal phase, using x-ray diffraction techniques. (K.B.)
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Migration of phthalates on culture plates
DEFF Research Database (Denmark)
Frohnert Hansen, Juliana; Boas, Malene; Møller Brorson, Marianne
2016-01-01
-well culture plates are typically used to study phthalates in cell cultures. In a pilot study, we observed evidence of phthalate migration in 24-well culture plates. As this has not previously been described, we investigated the phenomenon in more detail. Primary human thyroid epithelial cell cultures (n = 8...... cultures) were exposed to either di-ethyl phthalate (DEP), di-n-butyl phthalate (DnBP), mono-n-butyl phthalate (MnBP) or di-(2-ethylhexyl) phthalate (DEHP). Measurement of phthalate metabolites by mass spectrometry demonstrated that the short-branched DEP was able to migrate to adjacent wells when added...... to cell culture plates. DnBP also seemed to be able to migrate, unlike the long-branched DEHP or the monoester MnBP which did not seem to have this ability. High background levels of phthalate metabolites were also observed, which might compromise results from low dose phthalate studies. In conclusion...
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Multiples least-squares reverse time migration
Zhang, Dongliang
2013-01-01
To enhance the image quality, we propose multiples least-squares reverse time migration (MLSRTM) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. Since each recorded trace is treated as a virtual source, knowledge of the source wavelet is not required. Numerical tests on synthetic data for the Sigsbee2B model and field data from Gulf of Mexico show that MLSRTM can improve the image quality by removing artifacts, balancing amplitudes, and suppressing crosstalk compared to standard migration of the free-surface multiples. The potential liability of this method is that multiples require several roundtrips between the reflector and the free surface, so that high frequencies in the multiples are attenuated compared to the primary reflections. This can lead to lower resolution in the migration image compared to that computed from primaries.
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Autumn crane migration and climate change in the Carpathian Basin
Directory of Open Access Journals (Sweden)
Végvári Zsolt
2015-12-01
Full Text Available Weekly counts of roosting cranes were conducted between 2006–2014 in all significant stopover sites of Common Cranes (Grus grus in Hungary, as an extension of the survey programme performed in Hortobágy National Park since 1994. As a result, I detected consistently asymmetrical migration phenologies in Hortobágy, indicating a superposition of several migration waves. Cranes used nearly 60 roost sites in Hortobágy with the largest ones situated in extensive fishponds. In contrast, cranes migrating in Körös-Maros National Park started to overwinter regularly, increasingly roosting in dry wetlands. In Kiskunság cranes tended to stage for shorter periods than in Körös-Maros, with the largest flocks to be observed in Lake Fehér of Szeged fishponds and additionally in a number of alkali lakes. Cranes observed in the Borsodi Mezőség region are considered satellite flocks staging in Hortobágy, as shown by irregular fluctuations.
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Shear-coupled grain-boundary migration dependence on normal strain/stress
Combe, N.; Mompiou, F.; Legros, M.
2017-08-01
In specific conditions, grain-boundary (GB) migration occurs in polycrystalline materials as an alternative vector of plasticity compared to the usual dislocation activity. The shear-coupled GB migration, the expected most efficient GB based mechanism, couples the GB motion to an applied shear stress. Stresses on GB in polycrystalline materials seldom have, however, a unique pure shear component. This work investigates the influence of a normal strain on the shear coupled migration of a Σ 13 (320 )[001 ] GB in a copper bicrystal using atomistic simulations. We show that the yield shear stress inducing the GB migration strongly depends on the applied normal stress. Beyond, the application of a normal stress on this GB qualitatively modifies the GB migration: while the Σ 13 (320 )[001 ] GB shear couples following the 〈110 〉 migration mode without normal stress, we report the observation of the 〈010 〉 mode under a sufficiently high tensile normal stress. Using the nudge elastic band method, we uncover the atomistic mechanism of this 〈010 〉 migration mode and energetically characterize it.
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International Nuclear Information System (INIS)
Muraoka, Susumu; Senoo, Muneaki; Kobayashi, Yoshii
1991-02-01
Research on high-level waste management at the Engineered Barrier Materials Laboratory, Environmental Geochemistry Laboratory and Environmental Radiochemistry Laboratory of the Department of Environmental Safety Research, JAERI in the fiscal year of 1989 are described. The topics are as follows: 1) As for waste forms and engineered barrier material, performance assessment studies on glass and ceramic forms, and corrosion test of carbon steel were continued. 2) In the safety evaluation study for geological disposal, chemical behavior of nuclide in water, nuclide migration and retardation in geosphere were studied. New microspectrometers was developed to analyze the chemical form in rocks. 3) Distribution and migration of uranium in uranium ore were examined as a natural analogue study. (author)
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Macrophage migration inhibitory factor as an incriminating agent in vitiligo.
Farag, Azza Gaber Antar; Hammam, Mostafa Ahmed; Habib, Mona SalahEldeen; Elnaidany, Nada Farag; Kamh, Mona Eaid
2018-03-01
Vitiligo is an autoimmune skin disorder in which the loss of melanocytes is mainly attributed to defective autoimmune mechanisms and, lately, there has been more emphasis on autoinflammatory mediators. Among these is the macrophage migration inhibitory factor, which is involved in many autoimmune skin diseases. However, little is known about the contribution of this factor to vitiligo vulgaris. To determine the hypothesized role of migration inhibitory factor in vitiligo via estimation of serum migration inhibitory factor levels and migration inhibitory factor mRNA concentrations in patients with vitiligo compared with healthy controls. We also aimed to assess whether there is a relationship between the values of serum migration inhibitory factor and/or migration inhibitory factor mRNA with disease duration, clinical type and severity in vitiligo patients. Evaluation of migration inhibitory factor serum level and migration inhibitory factor mRNA expression by ELISA and real-time PCR, respectively, were performed for 50 patients with different degrees of vitiligo severity and compared to 15 age- and gender-matched healthy volunteers as controls. There was a highly significant increase in serum migration inhibitory factor and migration inhibitory factor mRNA levels in vitiligo cases when compared to controls (pvitiligo patients, and each of them with duration and severity of vitiligo. In addition, patients with generalized vitiligo have significantly elevated serum migration inhibitory factor and mRNA levels than control subjects. Small number of investigated subjects. Migration inhibitory factor may have an active role in the development of vitiligo, and it may also be a useful index of disease severity. Consequently, migration inhibitory factor may be a new treatment target for vitiligo patients.
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Rural migration in Nevada: Lincoln County. Phase 1, 1992--1993
Energy Technology Data Exchange (ETDEWEB)
Soden, D.L.; Carns, D.E.; Mosser, D.; Conary, J.S.; Ansell, J.P.
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. 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.
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Field migration rates of tidal meanders recapitulate fluvial morphodynamics.
Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea
2018-02-13
The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths. Copyright © 2018 the Author(s). Published by PNAS.
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Directory of Open Access Journals (Sweden)
Nando Sigona
2012-06-01
Full Text Available The Arab Spring has not radically transformed migration patterns in the Mediterranean, and the label ‘migration crisis’ does not do justice to the composite and stratified reality.
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Immigration impacts on internal migration of the poor: 1990 census evidence for U.S. states.
Frey, W H
1995-09-01
"This article presents newly-available migration data from the 1990 U.S. census to assess immigration and internal migration components as they affect state poverty populations. New immigrant waves are heavily focused on only a few 'port-of-entry' states. It is suggested that these immigrants have begun to impact upon internal migration into and out of these 'high immigration states', and have also altered the national system of internal migration patterns. This article addresses three questions: How do the magnitudes of poverty population out-migration from high immigration states compare with those of other states? Is this out-migration selective on particular social and demographic groups? Is immigration a significant determinant of internal migration of the poor population? The results of this analysis are consistent with the view that recent, focused immigration is associated with out-migration among a state's poor longer-term residents." excerpt
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Migration Phenotype of Brain-Cancer Cells Predicts Patient Outcomes
Directory of Open Access Journals (Sweden)
Chris L. Smith
2016-06-01
Full Text Available Glioblastoma multiforme is a heterogeneous and infiltrative cancer with dismal prognosis. Studying the migratory behavior of tumor-derived cell populations can be informative, but it places a high premium on the precision of in vitro methods and the relevance of in vivo conditions. In particular, the analysis of 2D cell migration may not reflect invasion into 3D extracellular matrices in vivo. Here, we describe a method that allows time-resolved studies of primary cell migration with single-cell resolution on a fibrillar surface that closely mimics in vivo 3D migration. We used this platform to screen 14 patient-derived glioblastoma samples. We observed that the migratory phenotype of a subset of cells in response to platelet-derived growth factor was highly predictive of tumor location and recurrence in the clinic. Therefore, migratory phenotypic classifiers analyzed at the single-cell level in a patient-specific way can provide high diagnostic and prognostic value for invasive cancers.
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The evolution of immunity in relation to colonization and migration.
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.
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Human neutrophils facilitate tumor cell transendothelial migration.
LENUS (Irish Health Repository)
Wu, Q D
2012-02-03
Tumor cell extravasation plays a key role in tumor metastasis. However, the precise mechanisms by which tumor cells migrate through normal vascular endothelium remain unclear. In this study, using an in vitro transendothelial migration model, we show that human polymorphonuclear neutrophils (PMN) assist the human breast tumor cell line MDA-MB-231 to cross the endothelial barrier. We found that tumor-conditioned medium (TCM) downregulated PMN cytocidal function, delayed PMN apoptosis, and concomitantly upregulated PMN adhesion molecule expression. These PMN treated with TCM attached to tumor cells and facilitated tumor cell migration through different endothelial monolayers. In contrast, MDA-MB-231 cells alone did not transmigrate. FACScan analysis revealed that these tumor cells expressed high levels of intercellular adhesion molecule-1 (ICAM-1) but did not express CD11a, CD11b, or CD18. Blockage of CD11b and CD18 on PMN and of ICAM-1 on MDA-MB-231 cells significantly attenuated TCM-treated, PMN-mediated tumor cell migration. These tumor cells still possessed the ability to proliferate after PMN-assisted transmigration. These results indicate that TCM-treated PMN may serve as a carrier to assist tumor cell transendothelial migration and suggest that tumor cells can exploit PMN and alter their function to facilitate their extravasation.
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Production of freely-migrating defects during irradiation
International Nuclear Information System (INIS)
Rehn, L.E.; Okamoto, P.R.
1986-09-01
During irradiation at elevated temperatures, vacancy and interstitial defects that escape can produce several different types of microstructural changes. Hence the production rate of freely-migrating defects must be known as a function of irradiating particle species and energy before quantitative correlations can be made between microstructural changes. Our fundamental knowledge of freely-migrating defect production has increased substantially in recent years. Critical experimental findings that led to the improved understanding are reviewed in this paper. A strong similarity is found for the dependence of freely-migrating defect production on primary recoil energy as measured in a variety of metals and alloys by different authors. The efficiency for producing freely-migrating defects decreases much more strongly with increasing primary recoil energy than does the efficiency for creating stable defects at liquid helium temperatures. The stronger decrease can be understood in terms of additional intracascade recombination that results from the nonrandom distribution of defects existing in the primary damage state for high primary recoil energies. Although the existing data base is limited to fcc materials, the strong similarity in the reported investigations suggests that the same dependence of freely-migrating defect production on primary recoil energy may be characteristic of a wide variety of other alloy systems as well. 52 refs., 4 figs
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Migration = cloning; aliasiing
DEFF Research Database (Denmark)
Hüttel, Hans; Kleist, Josva; Nestmann, Uwe
1999-01-01
In Obliq, a lexically scoped, distributed, object-oriented programming language, object migration was suggested as the creation of a copy of an object’s state at the target site, followed by turning the object itself into an alias, also called surrogate, for the remote copy. We consider the creat......In Obliq, a lexically scoped, distributed, object-oriented programming language, object migration was suggested as the creation of a copy of an object’s state at the target site, followed by turning the object itself into an alias, also called surrogate, for the remote copy. We consider...... the creation of object surrogates as an abstraction of the abovementioned style of migration. We introduce Øjeblik, a distribution-free subset of Obliq, and provide three different configuration-style semantics, which only differ in the respective aliasing model. We show that two of the semantics, one of which...... matches Obliq’s implementation, render migration unsafe, while our new proposal for a third semantics is provably safe. Our work suggests a straightforward repair of Obliq’s aliasing model such that it allows programs to safely migrate objects....
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The Malaysian state's response to migration.
Pillai, P
1999-04-01
This paper aims to provide a profile of migration trends in Malaysia since 1970 and to analyze public policy on migration in the context of economic growth and the labor market. The discussion centers on the impact of the Asian financial crisis. There is long history of immigration to Malaysia. The development strategy of the 1970s and 1980s was to create more jobs and restructure employment to meet equity goals. Labor shortages on plantations and construction booms led to a more organized, sustained effort to import labor. Recession in the mid-1980s led to unemployment, but many Malaysians were unwilling to work on plantations, in construction, or in low paying jobs. Economic growth during 1987-96 was very high, and labor shortages spread to service and manufacturing sectors. Migration policy has shifted over the decades. Both the market and the government's promotion of export-based industrialization require access to low cost migrant labor. Public and official recognition of the large number of migrants was not made until 1995. The financial crisis in 1998 led to enforcement of a new migration policy on illegal migrants and greater outflow of migrants. The economic crisis has increased job and income inequities in the region; this encourages continued migration. It is argued that it would be best for Malaysia to maximize short-term gains while minimizing long-term economic, social, and political costs.
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Non-Migrating Tides, with Zonally Symmetric Component, Generated in the Mesosphere
Mayr, H. G.; Mengel, J. G.; Talaat, E. R.; Porter, H. S.; Hines, C. O.
2003-01-01
For comparison with measurements from the TIMED satellite and coordinated ground based observations, we discuss results from our Numerical Spectral Model (NSM) that incorporates the Doppler Spread Parameterization (Hines, 1997) for small-scale gravity waves (GWs). The NSM extends from the ground into the thermosphere and describes the major dynamical features of the atmosphere including the wave driven equatorial oscillations (QBO and SAO), and the seasonal variations of tides and planetary waves. With emphasis on the non-migrating tides, having periods of 24 and 12 hours, we discuss our modeling results that account for the classical migrating solar excitation sources only. As reported earlier, the NSM reproduces the observed seasonal variations and in particular the large equinoctial maxima in the amplitude of the migrating diurnal tide at altitudes around 90 km. Filtering of the tide by the zonal circulation and GW momentum deposition was identified as the cause. The GWs were also shown to produce a strong non-linear interaction between the diurnal and semi-diurnal tides. Confined largely to the mesosphere, the NSM produces through dynamical interactions a relatively large contribution of non-migrating tides. A striking feature is seen in the diurnal and semi-diurnal oscillations of the zonal mean (m = 0). Eastward propagating tides are also generated for zonal wave numbers m = 1 to 4. When the NSM is run without GWs, the amplitudes for the non-migrating tides, including m = 0, are generally small. Planetary wave interaction and non-linear coupling that involves the filtering of GWs and related height integration of dynamical features are discussed as possible mechanisms for generating these non-migrating tides in the NSM. As is the case for the solar migrating tides, the non-migrating tides reveal persistent seasonal variations. Under the influence of the QBO and SAO, interannual variations are produced.
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Tritium migration studies at the Nevada Test Site
International Nuclear Information System (INIS)
Schulz, R.K.; Weaver, M.O.
1993-05-01
Emanation of tritium from waste containers is a commonly known phenomenon. Release of tritium from buried waste packages was anticipated; therefore, a research program was developed to study both the rate of tritium release from buried containers and subsequent migration of tritium through soil. Migration of tritium away from low-level radioactive wastes buried in Area 5 of the Nevada Test Site was studied. Four distinct disposal events were investigated. The oldest burial event studied was a 1976 emplacement of 3.5 million curies of tritium in a shallow land burial trench. In another event, 248 thousand curies of tritium was disposed of in an overpack emplaced 6 m below the floor of a low-level waste disposal pit. Measurement of the emanation rate of tritium out of 55 gallon drums to the overpack was studied, and an annual doubling of the emanation rate over a seven year period, ending in 1990, was found. In a third study, upward tritium migration in the soil, resulting in releases in the atmosphere were observed in a greater confinement disposal test. Releases of tritium to the atmosphere were found to be insignificant. The fourth event consisted of burial of 2.2 million curies of tritium in a greater confinement disposal operation. Emanation of tritium from the buried containers has been increasing since disposal, but no significant migration was found four years following backfilling of the disposal hole
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Directory of Open Access Journals (Sweden)
Sergi Vidal
2017-01-01
Full Text Available Objective: Migration rates of dual-earner couples are lower than those of male-breadwinner couples. We revisit this issue using a cross-national comparative perspective and examine heterogeneity in the role of female employment in couple relocations. We propose a theoretical framework in which national levels of support for female employment and normative expectations about gender roles act as moderators of the relationship between couple type (i.e., dual-earner and male-breadwinner and family migration. Methods: We deploy discrete-time event history analyses of harmonised longitudinal data from four large-scale datasets from Australia, Britain, Germany, and Sweden, covering the 1992-2011 period. Results: Consistent with prior research, we find that male-breadwinner couples migrate more often than dual-earner couples in all countries, suggesting that traditional gender structures affecting family migration operate across very different contexts. We also find cross-country differences in the estimated effects of different sorts of absolute and relative partner resources on family migration. Conclusions: We take our results as preliminary evidence that national contexts can serve as moderators of the relationship between within-couple employment arrangements and family migration decisions. Contribution: Our study contributes to family migration literature by illustrating how cross-national comparisons are a valuable methodological approach to put prevailing micro-level explanations of the relationship between female employment and family migration in context.
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von Suchodoletz, Hans; Gärtner, Andreas; Hoth, Silvan; Umlauft, Josefine; Godoladze, Tea; Faust, Dominik
2015-04-01
Large-scale river channel migrations either in the form of avulsions or combing, i.e. progressive lateral migrations, are global phenomena during the Late Quaternary. Such channel migrations were triggered by tectonics, climate change, human activity or a combination of those factors. River channel migrations have the potential to cause significant human and economic losses. Thus, a more thorough knowledge about underlying causes and process rates is essential. Furthermore, such studies will elucidate the sensitivity or robustness of rivers to different external and internal forcing-agents, i.e. they help to identify the dominant drivers of regional landscape evolution. The Caucasus region is part of the active collision zone between the Africa-Arabian and the Eurasian plates, and is characterized by high current tectonic activity. Furthermore, significant environmental changes took place during the Late Quaternary, i.e. the shrinking or even disappearance of glaciers in the Greater and Lesser Caucasus or fundamental changes of the vegetation cover varying between woodland and grassland-dominated vegetation. The Kura River is the main gaining stream of the Transcaucasian Depression located between the Greater Caucasus Mountains in the north and the Lesser Caucasus Mountains in the south, and receives several tributaries from both mountain ranges. This study focusses on the middle course of the Kura River in eastern Georgia, SE of the city of Tbilisi. Integration of fluvial geomorphology, geochronology, heavy mineral analyses and seismo-tectonic analyses demonstrates that this part of the Kura River underwent large-scale channel migrations up to >10 km during Late Pleistocene and Holocene. It is interpreted that these movements followed both tectonic and climatic triggers: Whereas SW-ward migrations were caused by tectonic uplift in and SW-directed advance of the Kura fold and thrust belt as part of the Greater Caucasus, NE-ward migrations occurred during cold
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Matrix metalloproteinase-1 facilitates MSC migration via cleavage of IGF-2/IGFBP2 complex.
Guan, Shou P; Lam, Alan T L; Newman, Jennifer P; Chua, Kevin L M; Kok, Catherine Y L; Chong, Siao T; Chua, Melvin L K; Lam, Paula Y P
2018-01-01
The specific mechanism underlying the tumor tropism of human mesenchymal stem cells (MSCs) for cancer is not well defined. We previously showed that the migration potential of MSCs correlated with the expression and protease activity of matrix metalloproteinase (MMP)-1. Furthermore, highly tumor-tropic MSCs expressed higher levels of MMP-1 and insulin-like growth factor (IGF)-2 than poorly migrating MSCs. In this study, we examined the functional roles of IGF-2 and MMP-1 in mediating the tumor tropism of MSCs. Exogenous addition of either recombinant IGF-2 or MMP-1 could stimulate MSC migration. The correlation between IGF-2, MMP-1 expression, and MSC migration suggests that MMP-1 may play a role in regulating MSC migration via the IGF-2 signaling cascade. High concentrations of IGF binding proteins (IGFBPs) can inhibit IGF-stimulated functions by blocking its binding to its receptors and proteolysis of IGFBP is an important mechanism for the regulation of IGF signaling. We thus hypothesized that MMP-1 acts as an IGFBP2 proteinase, resulting in the cleavage of IGF-2/IGFBP2 complex and extracellular release of free IGF-2. Indeed, our results showed that conditioned media from highly migrating MSCs, which expressed high levels of MMP-1, cleaved the IGF-2/IGFBP2 complex. Taken together, these results showed that the MMP-1 secreted by highly tumor-tropic MSCs cleaved IGF-2/IGFBP2 complex. Free IGF-2 released from the complex may facilitate MSC migration toward tumor.
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Assessing the use of magnetic methods to monitor vertical migration of metal pollutants in soil
Sapkota, B.; Cioppa, M. T.
2010-12-01
In order to assess the use of magnetic methods to study and improve our understanding of the vertical migration behavior of metal pollutants in natural soil, a controlled experiment was performed during August-December 2009, near Belle River, Ontario. The soil is Quaternary in age, consisting primarily of glacial till (Tavistock Till) overlain by localized alluvium deposits of very recent origin. Groundcover vegetation is minimal, consisting only of various grasses. Eighteen PVC tubes (8” wide, 16” long) were inserted vertically into the ground as test capsules, in order to avoid contaminating the surrounding area. Magnetite powder (5µm) was distributed on the surface of the soil inside nine of the tubes (10 grams of magnetite/tube) to simulate anthropogenic contamination, while the others were used as controls. Magnetic Susceptibility (MS) measurements were used for both ongoing surface monitoring and pre- and post-treatment vertical migration assessment. The initial surface MS values in the contaminated tubes were one to two orders of magnitude larger than in the uncontaminated tubes. While the surficial MS remained fairly stable in uncontaminated soil, decreases of 15-60 % were observed in contaminated soil tubes. Susceptibility profiles from soil cores in the contaminated tubes show that the concentration of iron containing particles is highest at depths between 2-7 cm. Energy Dispersive Spectroscopy (EDS) analysis on layers with an enhanced magnetic signal showed high weight% of iron and oxygen, indicating the presence of iron minerals. Scanning Electron Microscopy (SEM) showed that the magnetite powder and the particles from the contaminated tubes had similar morphologies. These results suggest that the magnetite migrated downwards into the soil over the five month period, probably as a result of rainwater infiltration and vertical migration. Some of the soil profiles showed a small enhancement of magnetic signal at 17-18 cm, and SEM-EDS analysis shows
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DEFF Research Database (Denmark)
Petersen, Anne Ring
This book addresses a topic of increasing importance to artists, art historians and scholars of cultural studies, migration studies and international relations: migration as a profoundly transforming force that has remodelled artistic and art institutional practices across the world. It explores...... contemporary art's critical engagement with migration and globalisation as a key source for improving our understanding of how these processes transform identities, cultures, institutions and geopolitics. The author explores three interwoven issues of enduring interest: identity and belonging, institutional...
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Liu, Shengqiang; Wu, Ruofan; Huang, Jiang; Yu, Junsheng
2013-09-01
A voltage-controlled color-tunable and high-efficiency organic light-emitting diode (OLED) by inserting 16-nm N,N'-dicarbazolyl-3,5-benzene (mCP) interlayer between two complementary emitting layers (EMLs) was fabricated. The OLED emitted multicolor ranging from blue (77.4 cd/A @ 6 V), white (70.4 cd/A @ 7 V), to yellow (33.7 cd/A @ 9 V) with voltage variation. An equivalent model was proposed to reveal the color-tunable and high-efficiency emission of OLEDs, resulting from the swing of exciton bilateral migration zone near mCP/blue-EML interface. Also, the model was verified with a theoretical arithmetic using single-EML OLEDs to disclose the crucial role of mCP exciton adjusting layer.
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On the orientation dependent grain boundary migration in an Fe-6at.%Si alloy
International Nuclear Information System (INIS)
Lejcek, P.; Adamek, J.
1995-01-01
The [100]symmetrical tilt grain boundaries in an Fe-6at.%Si alloy were found to exhibit as pronounced anisotropy of activation enthalpy of migration characterized by its high values for special boundaries as compared to general ones. This rather surprising posing three main contributions to the migration enthalpy: intrinsic migration enthalpy, migration enthalpy resulting from grain boundary segregation, and migration enthalpy resulting from alloy mixing. It is shown that the differences in migration enthalpy of special and general grain boundaries in a concentrated alloy reflect the prevailing character of the intrinsic migration enthalpy over the weakened segregation effects. (orig.)
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Evolution of cooperation among game players with non-uniform migration scopes
International Nuclear Information System (INIS)
Zhang, Chunyan; Zhang, Jianlei; Xie, Guangming
2014-01-01
In social dilemmas, cooperation among randomly interacting individuals is often hard to achieve. The situation changes if migration takes place, where game structure jointly evolves with the migration from adverse neighborhoods. Here we introduce a framework combining migration with the individual heterogeneity of migration scopes. When faced with a gloomy outlook, some players prefer vacant sites within their adjacent neighborhoods, while others may migrate within the whole network, provided the sites are empty. Thus, we can make a thorough inquiry of the sustainability of cooperation in a spatially distributed population divided by these two groups, and all possible mixtures between them. Our main result is that small-scope migration and suitable population density can gear up high cooperation levels in the midst of dense populations structured by scale-free networks, while large-scope migration and sparsity favor the cooperator clustering among lattice-structured populations. In this sense, the conditions for the emergence of cooperation are prevailingly created by the spatial reciprocity, and migration also has enough potential to help cooperation to prevail in suitable combination of game parameters in dynamics (e.g., population density, the type of interaction structure and also the migration scope)
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A Study on the Nuclide Migration and Retardation Using Natural Barrier
International Nuclear Information System (INIS)
Baik, Min Hoon; Park, Chung Kyun; Kim, Seung Soo
2010-02-01
In this study, we investigated the properties of geochemical reactions and sorption of high-level radionuclides (U, Th, Am, and Np), constructed databases for the geochemical reactions and sorption of the high-level radionuclides, and developed application methodologies of the databases. For the investigation on the nuclide migration and retardation through fractured rocks in KURT, in-situ solute migration system and on-line monitoring system were installed. The migration and retardation behaviors of nuclides were investigated annually for non-sorbing, simply sorbing and multi-valent sorbing nuclides, respectively, and interactions with fracture-filling materials were also analyzed. Besides, researches difficult to perform in KURT were carried out in foreign underground research facilities as joint studies for nuclide and colloid migration. The results from domestic and foreign underground facilities were compared each other and the reliability of the domestic results were assured from this. Diffusion depths of high-level radionuclides into rock matrix were measured in KURT conditions and their diffusion properties were analyzed and evaluated. In addition, the effects of bio-mineralization and redox reactions of a nuclide and microbe on nuclide behaviors were carried out to study the effects of combined interactions between minerals and microbes on the radionuclide migration and retardation
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Migration of Co and Cs radionuclides through a loam soil column
International Nuclear Information System (INIS)
Syed Hakimi Sakuma bin Syed Ahmad; Shimooka, K.
1990-01-01
A soil column experiment was conducted to determine the migration of Co and Cs radionuclides through a loam soil. The different migration rates of the radionuclides at low and high concentrations were determined at pH 7. Retardation factor (Rf) both the radionuclides at low and high concentrations were determined by fitting adsorbed concentration distribution equations to observed values. The calculation shows that the Rf1=500 and Rf2=3 for Co at high and low concentrations, respectively. For Cs, the Rf1=600 and Rf2=5 at high and low concentrations, respectively. The results shows that major portions of both the radionuclides were adsorbed onto the soil layer at the top by ion exchange mechanism which resulted in the high retardation factor values. Minor portions had migrated downwards as insoluble cations, pseudocolloids and very fine silt particles resulting in the low retardation factor
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Time-domain least-squares migration using the Gaussian beam summation method
Yang, Jidong; Zhu, Hejun; McMechan, George; Yue, Yubo
2018-04-01
With a finite recording aperture, a limited source spectrum and unbalanced illumination, traditional imaging methods are insufficient to generate satisfactory depth profiles with high resolution and high amplitude fidelity. This is because traditional migration uses the adjoint operator of the forward modeling rather than the inverse operator. We propose a least-squares migration approach based on the time-domain Gaussian beam summation, which helps to balance subsurface illumination and improve image resolution. Based on the Born approximation for the isotropic acoustic wave equation, we derive a linear time-domain Gaussian beam modeling operator, which significantly reduces computational costs in comparison with the spectral method. Then, we formulate the corresponding adjoint Gaussian beam migration, as the gradient of an L2-norm waveform misfit function. An L1-norm regularization is introduced to the inversion to enhance the robustness of least-squares migration, and an approximated diagonal Hessian is used as a preconditioner to speed convergence. Synthetic and field data examples demonstrate that the proposed approach improves imaging resolution and amplitude fidelity in comparison with traditional Gaussian beam migration.
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Agricultural activity shapes the communication and migration patterns in Senegal
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.
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Catalan family companies with high growth during the crisis period
Directory of Open Access Journals (Sweden)
Nuria Arimany-Serrat
2016-11-01
Full Text Available Purpose: This study aims to analyze the financial and economic health of the Catalan family companies with high growth during the crisis period (2008-2013, as an engine of job creation and economic development of the territory, identifying the economic and financial characteristics. Design/methodology/approach: The data used comes from the financial statements of the high growth Catalan companies during the crisis period of 2008-2013, in particular it collects a sample of the 140 high growth Catalan companies where a 70% of them are family businesses, there is a financial and economic analysis using descriptive statistics of these family businesses with a regression model to achieve results and conclusions. Findings: During the 2008-2013 crisis, Catalan family companies with high growth that are mostly small businesses have a good economic and financial health, with moderate innovation and a great potential for survival. Research limitations/implications: It would be convenient to make the same study in similar territories where most of the companies are family businesses, in order to compare the financial and economic analysis, valuing the impact of these companies in the business. Practical implications: It allows valuing the projection of these kinds of family companies, mostly in Catalonia, in a financial and economic level, identifying if they have a proper financial strategy. Social implications: The results show that these companies have great financial and economic health and have a better response during a crisis period. Originality / value: The study shows that family businesses have moderate indebtedness and acceptable rendibility in the crisis period, although, since they are small businesses the lack of innovation and patents can lead to future problems.
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Siddesha, Jalahalli M; Valente, Anthony J; Sakamuri, Siva S V P; Gardner, Jason D; Delafontaine, Patrice; Noda, Makoto; Chandrasekar, Bysani
2014-07-01
The pathogenesis of cardiac fibrosis and adverse remodeling is thought to involve the ROS-dependent induction of inflammatory cytokines and matrix metalloproteinases (MMPs), and the activation and migration of cardiac fibroblasts (CF). Here we investigated the role of RECK (reversion-inducing-cysteine-rich protein with Kazal motifs), a unique membrane-anchored MMP regulator, on IL-18-induced CF migration, and the effect of acetylsalicylic acid (ASA) on this response. In a Matrigel invasion assay, IL-18-induced migration of primary mouse CF was dependent on both IKK/NF-κB- and JNK/AP-1-mediated MMP9 induction and Sp1-mediated RECK suppression, mechanisms that required Nox4-dependent H(2)O(2) generation. Notably, forced expression of RECK attenuated IL-18-induced MMP9 activation and CF migration. Further, therapeutic concentrations of ASA inhibited IL-18-induced H(2)O(2) generation, MMP9 activation, RECK suppression, and CF migration. The salicylic acid moiety of ASA similarly attenuated IL-18-induced CF migration. Thus, ASA may exert potential beneficial effect in cardiac fibrosis through multiple protective mechanisms. © 2013 Wiley Periodicals, Inc.
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Cell migration during heart regeneration in zebrafish.
Tahara, Naoyuki; Brush, Michael; Kawakami, Yasuhiko
2016-07-01
Zebrafish possess the remarkable ability to regenerate injured hearts as adults, which contrasts the very limited ability in mammals. Although very limited, mammalian hearts do in fact have measurable levels of cardiomyocyte regeneration. Therefore, elucidating mechanisms of zebrafish heart regeneration would provide information of naturally occurring regeneration to potentially apply to mammalian studies, in addition to addressing this biologically interesting phenomenon in itself. Studies over the past 13 years have identified processes and mechanisms of heart regeneration in zebrafish. After heart injury, pre-existing cardiomyocytes dedifferentiate, enter the cell cycle, and repair the injured myocardium. This process requires interaction with epicardial cells, endocardial cells, and vascular endothelial cells. Epicardial cells envelope the heart, while endocardial cells make up the inner lining of the heart. They provide paracrine signals to cardiomyocytes to regenerate the injured myocardium, which is vascularized during heart regeneration. In addition, accumulating results suggest that local migration of these major cardiac cell types have roles in heart regeneration. In this review, we summarize the characteristics of various heart injury methods used in the research community and regeneration of the major cardiac cell types. Then, we discuss local migration of these cardiac cell types and immune cells during heart regeneration. Developmental Dynamics 245:774-787, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
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Multisource Least-squares Reverse Time Migration
Dai, Wei
2012-12-01
Least-squares migration has been shown to be able to produce high quality migration images, but its computational cost is considered to be too high for practical imaging. In this dissertation, a multisource least-squares reverse time migration algorithm (LSRTM) is proposed to increase by up to 10 times the computational efficiency by utilizing the blended sources processing technique. There are three main chapters in this dissertation. In Chapter 2, the multisource LSRTM algorithm is implemented with random time-shift and random source polarity encoding functions. Numerical tests on the 2D HESS VTI data show that the multisource LSRTM algorithm suppresses migration artifacts, balances the amplitudes, improves image resolution, and reduces crosstalk noise associated with the blended shot gathers. For this example, multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution, and fewer migration artifacts compared to conventional RTM. The empirical results suggest that the multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with similar or less computational cost. The caveat is that LSRTM image is sensitive to large errors in the migration velocity model. In Chapter 3, the multisource LSRTM algorithm is implemented with frequency selection encoding strategy and applied to marine streamer data, for which traditional random encoding functions are not applicable. The frequency-selection encoding functions are delta functions in the frequency domain, so that all the encoded shots have unique non-overlapping frequency content. Therefore, the receivers can distinguish the wavefield from each shot according to the frequencies. With the frequency-selection encoding method, the computational efficiency of LSRTM is increased so that its cost is
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Gallagher, Brian K.; Piccoli, Philip M.; Secor, David H.
2018-01-01
Partial migration in complex life cycles allows environmental conditions experienced during one life-stage to interact with genetic thresholds and produce divergent spatial behaviors in the next stage. We evaluated partial migration over the entire life cycle of white perch, (Morone americana) within the Hudson River Estuary, combining otolith microchemistry, population demographics and environmental data analysis. Ecological carryover effects were used as a framework to test how environmental variation during the larval period influenced migration behaviors and growth characteristics in subsequent life-stages. Two annual cohorts of juveniles were classified based on whether they persisted in natal habitats (freshwater resident contingent) or dispersed into non-natal habitats (brackish water migratory contingent) as juveniles. The migratory contingent tended to hatch earlier and experience cooler temperatures as larvae, while the availability of zooplankton prey during the larval period appeared to influence growth dynamics before and after metamorphosis. Juvenile migration behaviors were reversible but usually persisted into adulthood. As juveniles, the consequences of partial migration on growth appeared to be modified by river flow, as demonstrated by the influence of a large storm event on feeding conditions in one of the study years. Migratory adults grew faster and attained larger maximum sizes, but may also experience higher rates of mortality. The interplay uncovered between life-stage transitions, conditional migration behaviors and habitat productivity throughout the life cycle shapes white perch population dynamics and will likely play an important role in responses to long-term environmental change.
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Migration and breeding biology of arctic terns in Greenland
DEFF Research Database (Denmark)
Egevang, Carsten
(Sandøen) in high-Arctic Northeast Greenland. The level of knowledge of the Arctic tern in Greenland before 2002 was to a large extent poor, with aspects of its biology being completely unknown in the Greenland population. This thesis presents novel findings for the Arctic tern, both on an international...... scale and on a national scale. The study on Arctic tern migration (Manus I) – the longest annual migration ever recorded in any animal – is a study with an international appeal. The study documented how Greenland and Iceland breeding terns conduct the roundtrip migration to the Weddell Sea in Antarctica...
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COLLINSON, MARK A.; TOLLMAN, STEPHEN M.; KAHN, KATHLEEN
2010-01-01
Background World population growth will be increasingly concentrated in the urban areas of the developing world; however, some scholars caution against the oversimplification of African urbanization noting that there may be “counter-urbanization” and a prevailing pattern of circular rural–urban migration. The aim of the paper is to examine the ongoing urban transition in South Africa in the post-apartheid period, and to consider the health and social policy implications of prevailing migration patterns. Methods Two data sets were analysed, namely the South African national census of 2001 and the Agincourt health and demographic surveillance system. A settlement-type transition matrix was constructed on the national data to show how patterns of settlement have changed in a five-year period. Using the sub-district data, permanent and temporary migration was characterized, providing migration rates by age and sex, and showing the distribution of origins and destinations. Findings The comparison of national and sub-district data highlight the following features: urban population growth, particularly in metropolitan areas, resulting from permanent and temporary migration; prevailing patterns of temporary, circular migration, and a changing gender balance in this form of migration; stepwise urbanization; and return migration from urban to rural areas. Conclusions Policy concerns include: rural poverty exacerbated by labour migration; explosive conditions for the transmission of HIV; labour migrants returning to die in rural areas; and the challenges for health information created by chronically ill migrants returning to rural areas to convalesce. Lastly, suggestions are made on how to address the dearth of relevant population information for policy-making in the fields of migration, settlement change and health. PMID:17676507
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Regional Redistribution and Migration
DEFF Research Database (Denmark)
Manasse, Paolo; Schultz, Christian
We study a model with free migration between a rich and a poor region. Since there is congestion, the rich region has an incentive to give the poor region a transfer in order to reduce immigration. Faced with free migration, the rich region voluntarily chooses a transfer, which turns out...... to be equal to that a social planner would choose. Provided migration occurs in equilibrium, this conclusion holds even in the presence of moderate mobility costs. However, large migration costs will lead to suboptimal transfers in the market solution...
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Database on gas migration tests through bentonite buffer material
International Nuclear Information System (INIS)
Tanai, Kenji
2009-02-01
Carbon steel is a candidate material for an overpack for geological disposal of high-level radioactive waste in Japan. The corrosion of the carbon steel overpack in aqueous solution under anoxic conditions will cause the generation of hydrogen gas, which may affect hydrological and mechanical properties of the bentonite buffer. To evaluate such an effect of gas generation, it is necessary to develop a model of gas migration through bentonite buffer material taking account of data obtained from experiments. The gas migration experiments under both unsaturated and saturated conditions have been carried out to clarify the fundamental characteristics of bentonite for gas migration. This report compiles the experimental data obtained from gas migration tests for buffer material which has been conducted by JAEA until December, 2007. A CD-ROM is attached as an appendix. (author)
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Periodically structured Si pillars for high-performing heterojunction photodetectors
Melvin David Kumar, M.; Yun, Ju-Hyung; Kim, Joondong
2015-03-01
A periodical array of silicon (Si) micro pillar structures was fabricated on Si substrates using PR etching process. Indium tin oxide (ITO) layer of 80 nm thickness was deposited over patterned Si substrates so as to make ITO/n-Si heterojunction devices. The influences of width and period of pillars on the optical and electrical properties of prepared devices were investigated. The surface morphology of the Si substrates revealed the uniform array of pillar structures. The 5/10 (width/period) Si pillar pattern reduced the optical reflectance to 6.5% from 17% which is of 5/7 pillar pattern. The current rectifying ratio was found higher for the device in which the pillars are situated in optimum periods. At both visible (600 nm) and near infrared (900 nm) range of wavelengths, the 5/7 and 5/10 pillar patterned device exhibited the better photoresponses which are suitable for making advanced photodetectors. This highly transmittance and photoresponsive pillar patterned Si substrates with an ITO layer would be a promising device for various photoelectric applications.
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Brine migration in hot-pressed polycrystalline sodium chloride
International Nuclear Information System (INIS)
Biggers, J.V.; Dayton, G.O.
1982-12-01
This report describes experiments designed to provide data on brine migration in polycrystalline salt. Polycrystalling samples of various grain sizes, density, and purity were prepared from several commercial-grade salts by hot-pressing. Three distinct experimental set-ups were used to place salt billets in an induced thermal gradient in contact with brine source. The test designs varied primarily in the way in which the thermal gradient was applied and monitored and the way in which brine migration was determined. All migration was in enclosed vessels which precluded visual observation of brine movement through the microstructure. Migration velocities were estimated either by the timed appearance of brine at the hot face of the sample, or by determination of the penetration distance of migration artifacts in the microstructure after tests of fixed duration. For various reasons both of these methods were subject to a large degree of error. Our results suggest, however, that the migration velocity in dense polycrystalline salt may be at least an order of magnitude greater than that suggested by single-crystal experiments. Microstructural analysis shows that brine prefers to migrate along paths of high crystalline activity such as grain and subgrain boundaries and is dispersed rather quickly in the microstructure. A series of tests were performed using various types of tracers in brine in order to flag migration paths and locate brine in the microstructure more decisively. These attempts failed and it appears that only the aqueous portion of the brine moves through the microstructure with the dissolved ions being lost and replaced rather quickly. This suggests the use of deuterium as a tracer in future work
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MR imaging of neuronal migration anomaly
International Nuclear Information System (INIS)
Hong, Hyun Sook; Choi, Eun Wan; Kim, Dae Ho; Chung, Moo Chan; Kwon, Kuy Hyang; Kim, Ki Jung
1991-01-01
Abnormalities of neuronal migration are characterized by anectopic location of neurons in the cerebral cortex. This broad group of anomalies includes agyria, pachygyria, schizencephaly, unilateral megalencephaly, and gray matter heterotopia. Patients with this anomaly present clinically with a variety of symptoms which are proportional to the extent of the brain involved. These abnormalities have characterized pathologically in vivo by sonography and CT scan. MR appears to be an imaging technique of choice in evaluating these anomalies because it is capable of exceptionally good differentiation between gray and white matter, high contrast resolution, multiplanar display of the anatomy, and lack of overlying bone artifac. The purpose of this paper is to describe the MR findings of neuronal migration anomaly. The results of our study support that MR appears to be the imaging method of choice for diagnosing migration anomalies and the primary screening method for infants or children who have seisure/and delayed development
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Chapman, Jason W; Reynolds, Don R; Wilson, Kenneth
2015-03-01
Myriad tiny insect species take to the air to engage in windborne migration, but entomology also has its 'charismatic megafauna' of butterflies, large moths, dragonflies and locusts. The spectacular migrations of large day-flying insects have long fascinated humankind, and since the advent of radar entomology much has been revealed about high-altitude night-time insect migrations. Over the last decade, there have been significant advances in insect migration research, which we review here. In particular, we highlight: (1) notable improvements in our understanding of lepidopteran navigation strategies, including the hitherto unsuspected capabilities of high-altitude migrants to select favourable winds and orientate adaptively, (2) progress in unravelling the neuronal mechanisms underlying sun compass orientation and in identifying the genetic complex underpinning key traits associated with migration behaviour and performance in the monarch butterfly, and (3) improvements in our knowledge of the multifaceted interactions between disease agents and insect migrants, in terms of direct effects on migration success and pathogen spread, and indirect effects on the evolution of migratory systems. We conclude by highlighting the progress that can be made through inter-phyla comparisons, and identify future research areas that will enhance our understanding of insect migration strategies within an eco-evolutionary perspective. © 2015 John Wiley & Sons Ltd/CNRS.
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International migration and educational assortative mating in Mexico and the United States.
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.
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Exploring the Role of Trade and Migrations in Nigeria-Ghana ...
African Journals Online (AJOL)
Of these facilitators of inter-group relations, the two most outstanding elements that defined their relations before and during the colonial period were trade and migrations. The basic theme of this paper is therefore to document the nature and form of this trade network facilitated largely by the Hausa's and Yoruba's of Nigeria ...
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Stopover habitats of spring migrating surf scoters in southeast Alaska
Lok, E.K.; Esler, Daniel; Takekawa, John Y.; De La Cruz, S.W.; Sean, Boyd W.; Nysewander, D.R.; Evenson, J.R.; Ward, D.H.
2011-01-01
Habitat conditions and nutrient reserve levels during spring migration have been suggested as important factors affecting population declines in waterfowl, emphasizing the need to identify key sites used during spring and understand habitat features and resource availability at stopover sites. We used satellite telemetry to identify stopover sites used by surf scoters migrating through southeast Alaska during spring. We then contrasted habitat features of these sites to those of random sites to determine habitat attributes corresponding to use by migrating scoters. We identified 14 stopover sites based on use by satellite tagged surf scoters from several wintering sites. We identified Lynn Canal as a particularly important stopover site for surf scoters originating throughout the Pacific winter range; approximately half of tagged coastally migrating surf scoters used this site, many for extended periods. Stopover sites were farther from the mainland coast and closer to herring spawn sites than random sites, whereas physical shoreline habitat attributes were generally poor predictors of site use. The geography and resource availability within southeast Alaska provides unique and potentially critical stopover habitat for spring migrating surf scoters. Our work identifies specific sites and habitat resources that deserve conservation and management consideration. Aggregations of birds are vulnerable to human activity impacts such as contaminant spills and resource management decisions. This information is of value to agencies and organizations responsible for emergency response planning, herring fisheries management, and bird and ecosystem conservation. Copyright ?? 2011 The Wildlife Society.
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Directory of Open Access Journals (Sweden)
Arzura Idris
2012-06-01
Full Text Available This paper analyzes the phenomenon of “forced migration” in Malaysia. It examines the nature of forced migration, the challenges faced by Malaysia, the policy responses and their impact on the country and upon the forced migrants. It considers forced migration as an event hosting multifaceted issues related and relevant to forced migrants and suggests that Malaysia has been preoccupied with the issue of forced migration movements. This is largely seen in various responses invoked from Malaysia due to “south-south forced migration movements.” These responses are, however, inadequate in terms of commitment to the international refugee regime. While Malaysia did respond to economic and migration challenges, the paper asserts that such efforts are futile if she ignores issues critical to forced migrants.
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Kanda, H.; Hashimoto, N.; Takahashi, H.
The phenomenon of grain boundary migration due to boundary diffusion via vacancies is a well-known process for recrystallization and grain growth during annealing. This phenomenon is known as diffusion-induced grain boundary migration (DIGM) and has been recognized in various binary systems. On the other hand, grain boundary migration often occurs under irradiation. Furthermore, such radiation-induced grain boundary migration (RIGM) gives rise to solute segregation. In order to investigate the RIGM mechanism and the interaction between solutes and point defects during the migration, stainless steel and Ni-Si model alloys were electron-irradiated using a HVEM. RIGM was often observed in stainless steels during irradiation. The migration rate of boundary varied, and three stages of the migration were recognized. At lower temperatures, incubation periods up to the occurrence of the boundary migration were observed prior to first stage. These behaviors were recognized particularly for lower solute containing alloys. From the relation between the migration rates at stage I and inverse temperatures, activation energies for the boundary migration were estimated. In comparison to the activation energy without irradiation, these values were very low. This suggests that the RIGM is caused by the flow of mixed-dumbbells toward the grain boundary. The interaction between solute and point defects and the effective defect concentration generating segregation will be discussed.
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Kim, W.; Kim, Y.; Min, D.; Oh, J.; Huh, C.; Kang, S.
2012-12-01
During last two decades, CO2 sequestration in the subsurface has been extensively studied and progressed as a direct tool to reduce CO2 emission. Commercial projects such as Sleipner, In Salah and Weyburn that inject more than one million tons of CO2 per year are operated actively as well as test projects such as Ketzin to study the behavior of CO2 and the monitoring techniques. Korea also began the CCS (CO2 capture and storage) project. One of the prospects for CO2 sequestration in Korea is the southwestern continental margin of Ulleung basin. To monitor the behavior of CO2 underground for the evaluation of stability and safety, several geophysical monitoring techniques should be applied. Among various geophysical monitoring techniques, seismic survey is considered as the most effective tool. To verify CO2 migration in the subsurface more effectively, seismic numerical simulation is an essential process. Furthermore, the efficiency of the seismic migration techniques should be investigated for various cases because numerical seismic simulation and migration test help us accurately interpret CO2 migration. In this study, we apply the reverse-time migration and Kirchhoff migration to synthetic seismic monitoring data generated for the simplified model based on the geological structures of Ulleung basin in Korea. Synthetic seismic monitoring data are generated for various cases of CO2 migration in the subsurface. From the seismic migration images, we can investigate CO2 diffusion patterns indirectly. From seismic monitoring simulation, it is noted that while the reverse-time migration generates clear subsurface images when subsurface structures are steeply dipping, Kirchhoff migration has an advantage in imaging horizontal-layered structures such as depositional sediments appearing in the continental shelf. The reverse-time migration and Kirchhoff migration present reliable subsurface images for the potential site characterized by stratigraphical traps. In case of
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Edelblute, Heather B; Clark, Sandra; Mann, Lilli; McKenney, Kathryn M; Bischof, Jason J; Kistler, Christine
2014-06-01
The migration of working-aged men from Mexico to the United States fractures the family-centered support structures typical of Latin America and contributes to high levels of depression in women left behind in migratory sending communities in Mexico. Mujeres en Solidaridad Apoyandose (MESA) was developed to improve depression in women through social support in a resource poor setting. MESA is a promotora intervention that trains women in the community to lead social support groups over a five-week period. The MESA curriculum uses a combination of cognitive behavioral theory techniques, psychoeducation, and social support activities aimed at alleviating or preventing depression in women. Results from this pilot efficacy study (n = 39) show that depressed participants at baseline experienced declines in depression as measured by the Center for Epidemiologic Studies Depression Scale at follow-up. Other findings demonstrate the complexity behind addressing social support and depression for women impacted by migration in different ways.
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International migration as a determinant of emergency caesarean.
Merry, Lisa; Semenic, Sonia; Gyorkos, Theresa W; Fraser, William; Small, Rhonda; Gagnon, Anita J
2016-10-01
High caesarean rates are of concern given associated risks. International migrant women (women born abroad) represent a substantial proportion of women giving birth in high-income countries (HICs) and face social conditions that may exacerbate childbearing health risks. Among migrant women, emergency rather than planned caesareans, tend to be more prevalent. This method of delivery can be stressful, physically harmful and result in an overall negative birth experience. Research establishing evidence of risk factors for emergency caesareans in migrants is insufficient. (1) Describe potential pathways (with a focus on modifiable factors) by which migration, using internationally recommended migration indicators: country of birth, length of time in country, fluency in receiving-country language, migration classification and ethnicity, may lead to emergency caesarean; and (2) propose a framework to guide future research for understanding "potentially preventable" emergency caesareans in migrant women living in HICs. "Potentially preventable" emergency caesareans in migrant women are likely due to several modifiable, interrelated factors pre-pregnancy, during pregnancy and during labour. Migration itself is a determinant and also shapes other determinants. Complications and ineffective labour progress and/or foetal distress and ultimately the decision to perform an emergency caesarean may be the result of poor health (i.e., physiological effects), lack of support and disempowerment (i.e., psychological effects) and sub-optimal care. Understanding the direct and indirect effects of migration on emergency caesarean is crucial so that targeted strategies can be developed and implemented for reducing unnecessary caesareans in this vulnerable population. Copyright © 2016 Australian College of Midwives. Published by Elsevier Ltd. All rights reserved.
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Rennie, Michael D.; Ebener, Mark P.; Wagner, Tyler
2012-01-01
Migration can be a behavioural response to poor or declining home range habitat quality and can occur when the costs of migration are overcome by the benefi ts of encountering higher-quality resources elsewhere. Despite dramatic ecosystem-level changes in the benthic food web of the Laurentian Great Lakes since the colonization of dreissenid mussels, coincident changes in condition and growth rates among benthivorous lake whitefi sh populations have been variable. We hypothesized that this variation could be in part mitigated by differences in migratory habits among populations, where increased migration distance can result in an increased probability of encountering high-quality habitat (relative to the home range). Results from four Great Lakes populations support this hypothesis; relative growth rates increased regularly with migration distance. The population with the largest average migration distance also had the least reduction in size-at-age during a period of signifi cant ecosystem change and among the highest estimated consumption and activity rates. In comparison, the population with the greatest declines in size-at-age was among the least mobile, demonstrating only moderate rates of consumption and activity. The least mobile population of lake whitefi sh was supported by a remnant Diporeia population and has experienced only moderate temporal growth declines. Our study provides evidence for the potential role of migration in mitigating the effects of ecosystem change on lake whitefi sh populations.
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International migration and unemployment in established member countries of the European Union
Directory of Open Access Journals (Sweden)
Milan Palát
2013-01-01
Full Text Available The objective of the paper is to evaluate relationships of the rate of migration and the unemployment rate in established member countries of the European Union covering also the period of the last financial and economic crisis and using statistical methods. To determine parameters of a regression function were used methods of regression and correlation analysis including testing the statistical significance. Nearly all countries (except Luxemburg and Austria show a negative linear relationship between tested indicators however not always statistically significant. Based on these results, the existence of correlation is evident between the crude rate of net migration and the unemployment rate in more than a half of the monitored countries. Calculated correlation indices show highly statistically significant results for typically immigrant’s destination countries, e.g. Germany, United Kingdom, Luxembourg, and Belgium but we can find statistically significant results also in countries which are facing enormous economic problems during the last financial and economic crisis, esp. in Ireland, Spain and Italy. With an exemption of Belgium, the selected type of regression function doesn’t play a role as it regards the statistical significance of correlation indices and the use of polynomials of higher degrees doesn’t improve those results significantly. The analysis of the crude rate of net migration and the unemployment rate presented in this paper can be further used and developed when other variables would be added to the model.
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Husky Oil's gas migration research effort: An update
International Nuclear Information System (INIS)
Schmitz, R.; Carlson, P.B.; Lorenz, G.D.; Watson, M.D.; Erno, B.P.
1993-01-01
Gas migration, which is the leakage of gas from outside the wellbore casings of oil and gas wells, has been recognized for many years as a problem but is still not clearly understood. It can exhibit itself as gas pressure on the surface casing, gas migrating through the soil surrounding the casing, or both. The phenomena is particularly visible in the Lloydminster area, in part due to the fact that well density is high and much of the land is under cultivation, making the effects on soil more evident. A research and development program has been initiated to determine the extent and impact of the problem and to identify technical solutions. The magnitude of the problem is discussed, indicating that 1 in 20 wells in Alberta has gas pressure on the surface casing. In the Lloydminster area, nearly half of all wells show indication of gas migration. Industry/regulatory action in the past is discussed, and the search for technical and business solutions is described. It is shown that methane leakage from gas migration is low, and emission from most gas migration wells is comparable to that generated by a typical dairy cow. 8 refs., 6 figs., 4 tabs
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Managing migration: the Brazilian case
Eduardo L. G. Rios-Neto
2005-01-01
The objective of this paper is to present the Brazilian migration experience and its relationship with migration management. The article is divided into three parts. First, it reviews some basic facts regarding Brazilian immigration and emigration processes. Second, it focuses on some policy and legal issues related to migration. Finally, it addresses five issues regarding migration management in Brazil.
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Directory of Open Access Journals (Sweden)
Piro Fredrik
2007-09-01
Full Text Available Abstract Background The association between area deprivation and health has mostly been examined in cross-sectional studies or prospective studies with short follow-up. These studies have rarely taken migration into account. This is a possible source of misclassification of exposure, i.e. an unknown number of study participants are attributed an exposure of area deprivation that they may have experienced too short for it to have any influence. The aim of this article was to examine to what extent associations between area deprivation and health outcomes were biased by recent migration. Methods Based on data from the Oslo Health Study, a cross-sectional study conducted in 2000 in Oslo, Norway, we used six health outcomes (self rated health, mental health, coronary heart disease, chronic obstructive pulmonary disease, smoking and exercise and considered migration nine years prior to the study conduct. Migration into Oslo, between the areas of Oslo, and the changes in area deprivation during the period were taken into account. Associations were investigated by multilevel logistic regression analyses. Results After adjustment for individual socio-demographic variables we found significant associations between area deprivation and all health outcomes. Accounting for migration into Oslo and between areas of Oslo did not change these associations much. However, the people who migrated into Oslo were younger and had lower prevalences of unfavourable health outcomes than those who were already living in Oslo. But since they were evenly distributed across the area deprivation quintiles, they had little influence on the associations between area deprivation and health. Evidence of selective migration within Oslo was weak, as both moving up and down in the deprivation hierarchy was associated with significantly worse health than not moving. Conclusion We have documented significant associations between area deprivation and health outcomes in Oslo after
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DEFF Research Database (Denmark)
Christiansen, Connie Carøe
2004-01-01
Migration og etnicitet er aktuelle og forbundne fænomener, idet migration øger berøringsfladerne mellem befolkningsgrupper. Etniciteter formes i takt med at grænser drages imellem disse grupper. Imod moderniserings-teoriernes forventning forsvandt etnicitet ikke som en traditionel eller oprindelig...... måde at skabe tilhørsforhold på; globalt set fremstår vor tid istedet som en "migrationens tidsalder", der tilsyneladende også er en tidsalder, hvor kulturelle særtræk, i form af etnicitet, udgør vigtige linjer, hvorefter grupper skilller sig ud fra hinanden. Både migration og etnicitet bringer fokus...... den finder sted i modtagerlandet, men nyere perspektiver på migration, som begreber om medborgerskab, transnationalisme og diaspora er eksponenter for, søger udover den nationalstatslige ramme og inddrager konsekvenserne af migrationen for afsenderlande....
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Persistent leatherback turtle migrations present opportunities for conservation.
Directory of Open Access Journals (Sweden)
George L Shillinger
2008-07-01
Full Text Available Effective transboundary conservation of highly migratory marine animals requires international management cooperation as well as clear scientific information about habitat use by these species. Populations of leatherback turtles (Dermochelys coriacea in the eastern Pacific have declined by >90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality. While research and conservation efforts on nesting beaches are ongoing, relatively little is known about this population of leatherbacks' oceanic habitat use and migration pathways. We present the largest multi-year (2004-2005, 2005-2006, and 2007 satellite tracking dataset (12,095 cumulative satellite tracking days collected for leatherback turtles. Forty-six females were electronically tagged during three field seasons at Playa Grande, Costa Rica, the largest extant nesting colony in the eastern Pacific. After completing nesting, the turtles headed southward, traversing the dynamic equatorial currents with rapid, directed movements. In contrast to the highly varied dispersal patterns seen in many other sea turtle populations, leatherbacks from Playa Grande traveled within a persistent migration corridor from Costa Rica, past the equator, and into the South Pacific Gyre, a vast, low-energy, low-productivity region. We describe the predictable effects of ocean currents on a leatherback migration corridor and characterize long-distance movements by the turtles in the eastern South Pacific. These data from high seas habitats will also elucidate potential areas for mitigating fisheries bycatch interactions. These findings directly inform existing multinational conservation frameworks and provide immediate regions in the migration corridor where conservation can be implemented. We identify high seas locations for focusing future conservation efforts within the leatherback dispersal zone in the South Pacific Gyre.
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Persistent Leatherback Turtle Migrations Present Opportunities for Conservation
Shillinger, George L; Palacios, Daniel M; Bailey, Helen; Bograd, Steven J; Swithenbank, Alan M; Gaspar, Philippe; Wallace, Bryan P; Spotila, James R; Paladino, Frank V; Piedra, Rotney; Eckert, Scott A; Block, Barbara A
2008-01-01
Effective transboundary conservation of highly migratory marine animals requires international management cooperation as well as clear scientific information about habitat use by these species. Populations of leatherback turtles (Dermochelys coriacea) in the eastern Pacific have declined by >90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality. While research and conservation efforts on nesting beaches are ongoing, relatively little is known about this population of leatherbacks' oceanic habitat use and migration pathways. We present the largest multi-year (2004–2005, 2005–2006, and 2007) satellite tracking dataset (12,095 cumulative satellite tracking days) collected for leatherback turtles. Forty-six females were electronically tagged during three field seasons at Playa Grande, Costa Rica, the largest extant nesting colony in the eastern Pacific. After completing nesting, the turtles headed southward, traversing the dynamic equatorial currents with rapid, directed movements. In contrast to the highly varied dispersal patterns seen in many other sea turtle populations, leatherbacks from Playa Grande traveled within a persistent migration corridor from Costa Rica, past the equator, and into the South Pacific Gyre, a vast, low-energy, low-productivity region. We describe the predictable effects of ocean currents on a leatherback migration corridor and characterize long-distance movements by the turtles in the eastern South Pacific. These data from high seas habitats will also elucidate potential areas for mitigating fisheries bycatch interactions. These findings directly inform existing multinational conservation frameworks and provide immediate regions in the migration corridor where conservation can be implemented. We identify high seas locations for focusing future conservation efforts within the leatherback dispersal zone in the South Pacific Gyre. PMID:18630987
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Internal migration in West Germany and implications for east-west salary convergence.
Decressin, J W
1994-01-01
"Using a simple model of gross migration [in West Germany], the paper shows that provided economic agents are sufficiently risk averse, migrational flows are likely to be procyclical. The econometric results confirm that flows are highly procyclical. They further indicate that changes in regional economic disparities significantly affect migrational flows. However, given the widening of regional disparities in the 1980s accompanied by a worsening in aggregate conditions, migration seems least effective in offsetting the differentiated impact of labor market shocks when it would be most useful. The paper concludes by applying the results to the issue of east-west migration and salary convergence." (SUMMARY IN GER) excerpt
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Kink structures induced in nickel-based single crystal superalloys by high-Z element migration
Energy Technology Data Exchange (ETDEWEB)
Sun, Fei; Zhang, Jianxin [Key Laboratory for Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Mao, Shengcheng [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Jiang, Ying [Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Feng, Qiang [National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Shen, Zhenju; Li, Jixue; Zhang, Ze [Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Han, Xiaodong [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)
2015-01-05
Highlights: • Innovative kink structures generate at the γ/γ′ interfaces in the crept superalloy. • Clusters of heavy elements congregate at the apex of the kinks. • Dislocation core absorbs hexagonal structural high-Z elements. - Abstract: Here, we investigate a new type of kink structure that is found at γ/γ′ interfaces in nickel-based single crystal superalloys. We studied these structures at the atomic and elemental level using aberration corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The core of the dislocation absorbs high-Z elements (i.e., Co and Re) that adopt hexagonal arrangements, and it extrudes elements (i.e., Ni and Al) that adopt face centered cubic (fcc) structures. High-Z elements (i.e., Ta and W) and Cr, which is a low-Z element, are stabilized in body centered cubic (bcc) arrangements; Cr tends to behave like Re. High-Z elements, which migrate and adopt a hexagonal structure, induce kink formation at γ/γ′ interfaces. This process must be analyzed to fully understand the kinetics and dynamics of creep in nickel-based single crystal superalloys.
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Silk Film Topography Directs Collective Epithelial Cell Migration
Rosenblatt, Mark I.
2012-01-01
The following study provides new insight into how surface topography dictates directed collective epithelial cell sheet growth through the guidance of individual cell movement. Collective cell behavior of migrating human corneal limbal-epithelial cell sheets were studied on highly biocompatible flat and micro-patterned silk film surfaces. The silk film edge topography guided the migratory direction of individual cells making up the collective epithelial sheet, which resulted in a 75% increase in total culture elongation. This was due to a 3-fold decrease in cell sheet migration rate efficiency for movement perpendicular to the topography edge. Individual cell migration direction is preferred in the parallel approach to the edge topography where localization of cytoskeletal proteins to the topography’s edge region is reduced, which results in the directed growth of the collective epithelial sheet. Findings indicate customized biomaterial surfaces may be created to direct both the migration rate and direction of tissue epithelialization. PMID:23185573
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Simulation of bentonite colloid migration through granite
International Nuclear Information System (INIS)
Rosicka, Dana; Hokr, Milan
2012-01-01
Document available in extended abstract form only. Full text of publication follows: Colloidal bentonite particles generate at the interface of buffer and host rock in spent nuclear fuel repository due to an erosion process and migrate through granite by the water flow. Stability of these colloids and their migration possibilities have been studied on account of radionuclide transport possibility as colloid could carry adsorbed radionuclides in groundwater through granite. That is why a simulation of bentonite colloid migration in the surrounding of a repository might be requested. According to chemical condition as ionic strength and pH, the colloidal particles coagulate into clusters and that influence the migration of particles. The coagulation kinetics of natural bentonite colloids were experimentally studied in many articles, for example by light scattering techniques. We created a model of coagulation of bentonite colloids and simulation of a chosen experiment with use of the multicomponent reactive transport equation. The coagulation model describes clustering of particles due to attractive van der Waals forces as result of collision of particles due to heat fluctuation and different velocity of particles during sedimentation and velocity gradient of water flow. Next, the model includes influence of repulsive electrostatic forces among colloidal particles leading to stability of particles provided high surface charge of colloids. In the model, each group of clusters is transported as one solution component and the kinetics of coagulation are implemented as reactions between the components: a shift of particles among groups of particles with similar migration properties, according to size of the clusters of colloids. The simulation of migration of bentonite colloid through granite using the coagulation model was calibrated according to experiment results. On the basis of the simulation, one can estimate the basic processes that occur during bentonite colloid
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Radionuclide migration in geological formations
International Nuclear Information System (INIS)
Barbreau, A.; Heremans, R.; Skytte Jensen, B.
1980-01-01
Radioactive waste disposal into geological formation is based on the capacity of rocks to confine radioactivity for a long period of time. Radionuclide migration from the repository to the environment depends on different mechanisms and phenomena whose two main ones are groundwater flow and the retention and ion-exchange property of rocks. Many studies are underway presently in EEC countries concerning hydrodynamic characteristics of deep geological formations as well as in radionuclide retention capacity and modelling. Important results have already been achieved which show the complexity of some phenomena and further studies shall principally be developed taking into account real conditions of the repository and its environment
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International Nuclear Information System (INIS)
Zeng Bing; Zhang Jinzhao; Wang Qing
2010-01-01
According to the relevant theory of thermodynamics, this presentation which based on the radon migration of the cluster theory has deduced ordinarily the ideal velocity period and displacement. The purpose was to establish the theoretical model of migration of radon and its daughters in the atmosphere in the ideal case, which would provide a underlying theoretical basis for the further research. (authors)
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Questions of migration and belonging: understandings of migration under neoliberalism in Ecuador.
Lawson, V
1999-01-01
This paper explores alternative understandings and experiences of migration under neoliberalism in Ecuador. Through the case study, the study examines migrants' multiple motivations for mobility and their ambivalence toward the process. Insights from the transnational migration literature were drawn in order to think through the implications of an increasingly contradictory context of economic modernization and its impact upon the sense of possibilities and belonging of migrants. In-depth interviews with urban-destined migrants in Ecuador were drawn to argue that mobility produces ambivalent development subjects. This argument is developed in three sections. First, the paper centers on the epistemological and theoretical basis for the relevance of migrant narratives in extending theorizations of migration. Second, in-depth interviews with migrants to Quito are drawn to explore migrants' sense of belonging and regional affiliation, identity formation through migration, and experiences of alienation and disruption in their lives. Lastly, this paper concludes with a retheorization of the role of migration places in the migrant identity construction.
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Borders in the South: Migration News in South Asia and the Pacific
Directory of Open Access Journals (Sweden)
Jahnnabi Das
2016-07-01
Full Text Available In the age of unprecedented movement of people, many migrants end up in the industrialized countries but originate from all over the world. A fuller picture of migration journalism thus warrants examining news from both the ‘source’ and ‘receiving’ countries of migration. However, most of the studies undertaken in this particular area deal with the issues from the perspectives of North America and Europe (i.e., ‘receiving’ countries, an approach which is inconsistent with the broad goal of comparative studies. The current study examines migration news from both the source and receiving countries. Given that South Asia and the Pacific are two regions that tend to be overlooked in the comparative studies literature, we studied the coverage of migration issues in six prominent English-language newspapers from six countries of these regions (Australia, Bangladesh, India, New Zealand, Pakistan and Sri Lanka over a four-month period in 2014. Our study utilized an exploratory frame analysis to determine whether, in line with several earlier studies, issues of migration are depicted as a crisis to be managed in the receiving countries. Moreover, we examined the emphasis attached to the subject matter by the source countries’ media. The findings suggest that the media frames in receiving countries are more diverse than expected. While newspapers in some countries follow the previously found crisis frame, others highlight the economic benefits of migration. Similarly, in the source countries, the frames are varied. Most newspapers portray migration as a problem to be solved, but some do focus on protecting the interests of the migrants.
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Singh, Kavita; Karunakara, Unni; Burnham, Gilbert; Hill, Kenneth
2005-11-01
Despite the large numbers of displaced persons and the often-lengthy periods of displacement, little is known about the impact of forced migration on long-term under-five mortality. This paper looks at the Brass Method (and adaptations of this method) and the Preceding Birth Technique in combination with a classification of women by their migration and reproductive histories, in order to study the impact of forced migration on under-five mortality. Data came from the Demography of Forced Migration Project, a study on mortality, fertility and violence in the refugee and host populations of Arua District, Uganda and Yei River District, Sudan. Results indicate that women who did not migrate in a situation of conflict and women who repatriated before the age of 15, had children with the highest under-five mortality rates compared with women who were currently refugees and women who repatriated after the age of 15.
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The European Crisis and Migration to Germany: Expectations and the Diversion of Migration Flows
Brücker, Herbert; Bertoli, Simone; Fernández-Huertas Moraga, Jesús
2013-01-01
The European crisis has diverted migration flows away from countries affected by the recession towards Germany. The diversion process creates a challenge for traditional discrete-choice models that assume that only bilateral factors account for dyadic migration rates. This paper shows how taking into account the sequential nature of migration decisions leads to write the bilateral migration rate as a function of expectations about the evolution of economic conditions in alternative destinatio...
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Hydrogen impurity in SrTiO{sub 3}: structure, electronic properties and migration
Energy Technology Data Exchange (ETDEWEB)
Villamagua, Luis [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Barreto, Rafael [Facultad de IngenierIa Civil, Escuela Politecnica Nacional, Apartado 14-01-2759, Quito (Ecuador); Procel, Luis Miguel [Departamento de Quimica, Colegio Politecnico, Universidad San Francisco de Quito, Apartado 17-12-841, Quito (Ecuador); Stashans, Arvids [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)
2007-03-15
The present paper reports a computational investigation of the geometry and electronic structure as well as the migration of a hydrogen impurity in the cubic SrTiO{sub 3} crystal. The study is done using an approach based on the Hartree-Fock theory and developed for periodic systems. It is found that the H impurity forms the so-called OH group at the equilibrium. Analysis of electron density within the defective region implies the enhancement in covalent chemical bonding. A possible defect migration has been also investigated.
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Income Inequality and Migration in Vietnam
NGUYEN, Tien Dung
2012-01-01
In this paper, we have analyzed the recent trends in income inequality, internal and international migrations and investigated the impact of migration on income distribution in Vietnam. Our analysis shows that the effects of migration on income inequality vary with different types of migration, depending on who migrate and where they migrate. Foreign remittances tend to flow toward more affluent households, and they increase income inequality. By contrast, domestic remittances accrue more to ...