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• 31. [Article] The morphological events during the self-reassembly of the sea urchin embryo in culture

  The gastrula of the sea urchin Strongylocentrotus purpuratus was dissociated into single cells. In culture these cells appeared apolar, but reassembled into quasi-normal embryos composed of structures ...

  Citation × Citation Citation Abstract Copy Title: The morphological events during the self-reassembly of the sea urchin embryo in culture Author: Hamada, Spencer Hiroshi The gastrula of the sea urchin Strongylocentrotus purpuratus was dissociated into single cells. In culture these cells appeared apolar, but reassembled into quasi-normal embryos composed of structures with polarized cells. In this study emphasis was placed on those morphological events coincident with the reestablishment of a polar orientation within the epithelial cells. Using both time-lapse dark-field-phase microscopy and electron microscopy, the major morphological events followed in detail include: (a) the migration of lysosome-like vesicles to specific margins within the epithelial cells; (b) the migration of the epithelial cells during the re-construction of the epithelium: and (c) the reformation of the cell junctions between the epithelial cells. Evidence indicates that: (1) The orientation resulting from the migration of the lysosome-like vesicles is transient and may not determine any lasting polarity of the epithelial cell. The sequential migration of the lysosome-like vesicles first to the epithelial cell to cell interface, then to the basal margin and finally to the apical margin of the epithelial cell was coincident with and apparently in response to the presence of cell debris often trapped at these sites. The Lysosome-like vesicles formed tight clusters along the epithelial cellular margins where phagocytosis of cell debris and resorption of specialized structures occurred. In contrast, the mesenchyme cell had smaller numbers of phagosomes and lysosome-like vesicles and was observed to participate to a more limited degree in phagocytosis and resorption. (2) The orientation resulting from the formation of a leading edge during the migration of the epithelial cell is transient. The sequence of cytological events associated with epithelial cell migration included the formation of: (a) hyaloplasmic blebs along the cell free margin; (b) filopodia and microvilli; and (c) lamellae with a number of lamellipodia at the leading edge. In contrast, the mesenchyme cell formed filopodia on a smaller scale and was observed to participate in migration only to a limited degree. Coincident with the cessation of epithelial cell migration was the enlargement of the lamella between the epithelial cells into a hyaloplasmic sheet which forms the blastocoel wall. Embryonic cells from reassembling aggregates were cultured as monolayers on glass treated with an adhesion enhancing factor derived from the incubation medium. Cords of cells, composed of both epithelial and mesenchyme cells migrate away from the aggregate and leave in their wake clusters of cells. Epithelial cells were found at the leading margins of these cell cords and were observed forming cytoplasmic blebs, filopodia and hyaloplasmic leading edges during the migration of the cell cord. No apparent coordinate orientation was detectable within the epithelial cells of the migrating cell cord or stationary cell cluster. A hypothesis is presented suggesting a role for resorption during epithelial cell migration. (3) Cell contacts formed during reaggregation become more adhesive as development proceeds. The sequence of fine structural events associated with cell contact formation include the formation of (a) a non--junctional cell apposition, which was characterized by parallel apposed membranes; (b) an incipient continuous junction, which was characterized by parallel apposed membranes; and (c) a continuous junction, which was characterized by the presence of an electron dense region both superjacent and subjacent to the plasma membrane at the site of the junction. The cell appositions between premigratory cells were easier to disrupt mechanically than the later forming continuous junctions. The forming continuous junction was first focal in extent and later zonal in girth around the apical margin of the epithelial cell. Concurrent with the formation of the strongly adhesive continuous junction by the lamella was a cessation of epithelial cell migration, followed by an expression of an apical-basal polarity within the epithelial cell. A hypothesis is presented suggesting a role for cell contacts during the coordinated orientation of the epithelia during the formation of the blastocoel wall. Title: The morphological events during the self-reassembly of the sea urchin embryo in culture Author: Hamada, Spencer Hiroshi The gastrula of the sea urchin Strongylocentrotus purpuratus was dissociated into single cells. In culture these cells appeared apolar, but reassembled into quasi-normal embryos composed of structures with polarized cells. In this study emphasis was placed on those morphological events coincident with the reestablishment of a polar orientation within the epithelial cells. Using both time-lapse dark-field-phase microscopy and electron microscopy, the major morphological events followed in detail include: (a) the migration of lysosome-like vesicles to specific margins within the epithelial cells; (b) the migration of the epithelial cells during the re-construction of the epithelium: and (c) the reformation of the cell junctions between the epithelial cells. Evidence indicates that: (1) The orientation resulting from the migration of the lysosome-like vesicles is transient and may not determine any lasting polarity of the epithelial cell. The sequential migration of the lysosome-like vesicles first to the epithelial cell to cell interface, then to the basal margin and finally to the apical margin of the epithelial cell was coincident with and apparently in response to the presence of cell debris often trapped at these sites. The Lysosome-like vesicles formed tight clusters along the epithelial cellular margins where phagocytosis of cell debris and resorption of specialized structures occurred. In contrast, the mesenchyme cell had smaller numbers of phagosomes and lysosome-like vesicles and was observed to participate to a more limited degree in phagocytosis and resorption. (2) The orientation resulting from the formation of a leading edge during the migration of the epithelial cell is transient. The sequence of cytological events associated with epithelial cell migration included the formation of: (a) hyaloplasmic blebs along the cell free margin; (b) filopodia and microvilli; and (c) lamellae with a number of lamellipodia at the leading edge. In contrast, the mesenchyme cell formed filopodia on a smaller scale and was observed to participate in migration only to a limited degree. Coincident with the cessation of epithelial cell migration was the enlargement of the lamella between the epithelial cells into a hyaloplasmic sheet which forms the blastocoel wall. Embryonic cells from reassembling aggregates were cultured as monolayers on glass treated with an adhesion enhancing factor derived from the incubation medium. Cords of cells, composed of both epithelial and mesenchyme cells migrate away from the aggregate and leave in their wake clusters of cells. Epithelial cells were found at the leading margins of these cell cords and were observed forming cytoplasmic blebs, filopodia and hyaloplasmic leading edges during the migration of the cell cord. No apparent coordinate orientation was detectable within the epithelial cells of the migrating cell cord or stationary cell cluster. A hypothesis is presented suggesting a role for resorption during epithelial cell migration. (3) Cell contacts formed during reaggregation become more adhesive as development proceeds. The sequence of fine structural events associated with cell contact formation include the formation of (a) a non--junctional cell apposition, which was characterized by parallel apposed membranes; (b) an incipient continuous junction, which was characterized by parallel apposed membranes; and (c) a continuous junction, which was characterized by the presence of an electron dense region both superjacent and subjacent to the plasma membrane at the site of the junction. The cell appositions between premigratory cells were easier to disrupt mechanically than the later forming continuous junctions. The forming continuous junction was first focal in extent and later zonal in girth around the apical margin of the epithelial cell. Concurrent with the formation of the strongly adhesive continuous junction by the lamella was a cessation of epithelial cell migration, followed by an expression of an apical-basal polarity within the epithelial cell. A hypothesis is presented suggesting a role for cell contacts during the coordinated orientation of the epithelia during the formation of the blastocoel wall. Close

• 32. [Article] Contribution of subyearling estuarine migrant coho salmon (Oncorhynchus kisutch) to spawning populations on the southern Oregon coast

  The typical coho salmon life history has been characterized by juvenile fish that spend their entire first year in freshwater habitats before migrating into estuaries as smolts. However, reports of early ...

  Citation × Citation Citation Abstract Copy Title: Contribution of subyearling estuarine migrant coho salmon (Oncorhynchus kisutch) to spawning populations on the southern Oregon coast Author: Nordholm, Katherine E. The typical coho salmon life history has been characterized by juvenile fish that spend their entire first year in freshwater habitats before migrating into estuaries as smolts. However, reports of early migrating coho fry (age 0), including migration downstream to estuarine habitats, date back to the 1960s. Until a few years ago, these individuals were considered to be displaced surplus fish with low chances of survival. Recent studies have suggested that subyearling estuarine migrating coho salmon could be an alternative life history in coastal populations, but their return as jacks or mature adults needed to be documented for this life history to be considered a viable strategy. The goal of our study was to track the return of spawning coho salmon that had been individually tagged in either estuarine or riverine nursery habitats, and determine return percentages for each life history strategy as well as independently verify the presence of subyearling estuarine migrating coho salmon through otolith analysis on spawning populations. We used Passive Integrated Transponder (PIT) tags to identify individual fish as they passed through a series of antennas deployed in two coastal lowland streams on the southern Oregon coast. Percentage return of estuary tagged parr (fish ≥ 60 mm tagged in spring and summer of their first year) was variable between years and streams. For the 2010 return year, subyearling estuarine migrants was 2.5 times higher than stream residents in Palouse Creek. Fork length at estuary entrance was reconstructed for one return year of spawning fish based on otolith Sr:Ca and Br:Ca. Four main life history strategies were identified based on their fork length at time of estuary/ocean entrance: early migrating fry (< 60 mm fork length), early migrating parr (60 - 70 mm fork length), early migrating parr that returned to freshwater before migrating as yearlings ("nomads"), and yearling migrating smolts (> 70 mm fork length). Overall, 30% (Larson Creek) to 42% (Palouse Creek) of the 2009 spawning run was made up of fish that displayed evidence of estuarine residence during their first year. This study confirms that subyearling estuarine migrating coho salmon survive to reproductive age and contribute to subsequent generations. The survival of this life history type likely varies between years with changing ocean and stream conditions. It is hypothesized that their life history serves as a "bet hedging" strategy that supports coastal populations in years of poor stream conditions. In the face of rising sea levels, this life history may represent a key to the future viability of coho salmon stocks in coastal watersheds. Title: Contribution of subyearling estuarine migrant coho salmon (Oncorhynchus kisutch) to spawning populations on the southern Oregon coast Author: Nordholm, Katherine E. The typical coho salmon life history has been characterized by juvenile fish that spend their entire first year in freshwater habitats before migrating into estuaries as smolts. However, reports of early migrating coho fry (age 0), including migration downstream to estuarine habitats, date back to the 1960s. Until a few years ago, these individuals were considered to be displaced surplus fish with low chances of survival. Recent studies have suggested that subyearling estuarine migrating coho salmon could be an alternative life history in coastal populations, but their return as jacks or mature adults needed to be documented for this life history to be considered a viable strategy. The goal of our study was to track the return of spawning coho salmon that had been individually tagged in either estuarine or riverine nursery habitats, and determine return percentages for each life history strategy as well as independently verify the presence of subyearling estuarine migrating coho salmon through otolith analysis on spawning populations. We used Passive Integrated Transponder (PIT) tags to identify individual fish as they passed through a series of antennas deployed in two coastal lowland streams on the southern Oregon coast. Percentage return of estuary tagged parr (fish ≥ 60 mm tagged in spring and summer of their first year) was variable between years and streams. For the 2010 return year, subyearling estuarine migrants was 2.5 times higher than stream residents in Palouse Creek. Fork length at estuary entrance was reconstructed for one return year of spawning fish based on otolith Sr:Ca and Br:Ca. Four main life history strategies were identified based on their fork length at time of estuary/ocean entrance: early migrating fry (< 60 mm fork length), early migrating parr (60 - 70 mm fork length), early migrating parr that returned to freshwater before migrating as yearlings ("nomads"), and yearling migrating smolts (> 70 mm fork length). Overall, 30% (Larson Creek) to 42% (Palouse Creek) of the 2009 spawning run was made up of fish that displayed evidence of estuarine residence during their first year. This study confirms that subyearling estuarine migrating coho salmon survive to reproductive age and contribute to subsequent generations. The survival of this life history type likely varies between years with changing ocean and stream conditions. It is hypothesized that their life history serves as a "bet hedging" strategy that supports coastal populations in years of poor stream conditions. In the face of rising sea levels, this life history may represent a key to the future viability of coho salmon stocks in coastal watersheds. Close

• 33. [Article] Women's Actions and Reactions to Male Migration: A Case Study of Women in San Juan Guelavía, Oaxaca, Mexico

  Using a mixed methods, interdisciplinary case study approach, this research project explores the benefits, risks, and challenges of male migration for women who reside in San Juan Guelavía, Oaxaca, Mexico. ...

  Citation × Citation Citation Abstract Copy Title: Women's Actions and Reactions to Male Migration: A Case Study of Women in San Juan Guelavía, Oaxaca, Mexico Author: Boyles, Julie Year: 2013 Using a mixed methods, interdisciplinary case study approach, this research project explores the benefits, risks, and challenges of male migration for women who reside in San Juan Guelavía, Oaxaca, Mexico. In a unique approach in the field of migration studies, this project considers not only women whose husbands have migrated--absent husbands--but also the impact of male migration on women whose husbands have returned as well as women whose husbands have never left--anchored husbands. Women with returned husbands and even women with anchored husbands feel the threat, worry, and fear that male migration could, at an unknown point in the future, fragment their family. This case study approach looks at how women's work responses are differentiated by husbands' migration status, by age, and by husband's control over women's activities. Women with absent husbands tend be income-producing women as well as women ages 35 to 50 far more than women 35 and under and 50 and over. With motherhood as a cultured priority of rural Mexican women, women's income-producing opportunities are primarily limited to options within the home or in venues that can accommodate their children until the children enter school. Although this case study showed little or no connection between male migration and educational attainment, substantial policy-worthy findings suggest that the lack of value that residents of San Juan Guelavía place on the local public high school curriculum negatively impacts educational attainment of children beyond middle school. Women's traditional and cultural emphasis of marriage for their daughters as well as their reluctance to expose daughters to the negative influences of the city sway the decisions that women make for their daughters. Title: Women's Actions and Reactions to Male Migration: A Case Study of Women in San Juan Guelavía, Oaxaca, Mexico Author: Boyles, Julie Year: 2013 Using a mixed methods, interdisciplinary case study approach, this research project explores the benefits, risks, and challenges of male migration for women who reside in San Juan Guelavía, Oaxaca, Mexico. In a unique approach in the field of migration studies, this project considers not only women whose husbands have migrated--absent husbands--but also the impact of male migration on women whose husbands have returned as well as women whose husbands have never left--anchored husbands. Women with returned husbands and even women with anchored husbands feel the threat, worry, and fear that male migration could, at an unknown point in the future, fragment their family. This case study approach looks at how women's work responses are differentiated by husbands' migration status, by age, and by husband's control over women's activities. Women with absent husbands tend be income-producing women as well as women ages 35 to 50 far more than women 35 and under and 50 and over. With motherhood as a cultured priority of rural Mexican women, women's income-producing opportunities are primarily limited to options within the home or in venues that can accommodate their children until the children enter school. Although this case study showed little or no connection between male migration and educational attainment, substantial policy-worthy findings suggest that the lack of value that residents of San Juan Guelavía place on the local public high school curriculum negatively impacts educational attainment of children beyond middle school. Women's traditional and cultural emphasis of marriage for their daughters as well as their reluctance to expose daughters to the negative influences of the city sway the decisions that women make for their daughters. Close

• 34. [Article] MIST: PVM with Transparent Migration and Checkpointing

  We are currently involved in research to enable PVM to take advantage of shared networks of workstations (NOWs) more effectively. In such a computing environment, it is important to utilize workstations ...

  Citation × Citation Citation Abstract Copy Title: MIST: PVM with Transparent Migration and Checkpointing Author: Casas, Jeremy, Clark, Dan, Galbiati, Phil, Konuru, Ravi, Otto, Steve, Prouty, Robert, Walpole, Jonathan Year: 1995 We are currently involved in research to enable PVM to take advantage of shared networks of workstations (NOWs) more effectively. In such a computing environment, it is important to utilize workstations unobtrusively and recover from machine failures. Towards this goal, we have enhanced PVM with transparent task migration, checkpointing, and global scheduling. These enhancements are part of the MIST project which takes an open systems approach in developing a cohesive, distributed parallel computing environment. This open systems approach promotes plug-and-play integration of independently developed modules, such as Condor, DQS, A VS, Prospero, XPVM, PIOUS, Ptools, etc. Transparent task migration, in conjunction with a global scheduler, facilitates the use of shared NOWs by allowing parallel jobs to unobtrusively utilize nodes that are currently unused. PVM tasks can be moved onto nodes that are otherwise idle, and moved off when the node is no longer free. Experiments show that migration performance is limited by the bandwidth of the underlying network. E.g. An 8 MB process migrates in 8 seconds on a 10 Mbps ethernet. We have implemented a global scheduler as a PVM resource manager which can take advantage of task migration to perform dynamic scheduling of tasks. Some extensions to the resource manager interface were required. The task migration mechanism also serves as the basis for transparent checkpointing, which is a common method for improving a system's fault tolerance. We have developed a PVM prototype that integrates checkpointing and migration. This paper presents an overview of the entire system, issues raised by this work, and discusses future plans. Title: MIST: PVM with Transparent Migration and Checkpointing Author: Casas, Jeremy, Clark, Dan, Galbiati, Phil, Konuru, Ravi, Otto, Steve, Prouty, Robert, Walpole, Jonathan Year: 1995 We are currently involved in research to enable PVM to take advantage of shared networks of workstations (NOWs) more effectively. In such a computing environment, it is important to utilize workstations unobtrusively and recover from machine failures. Towards this goal, we have enhanced PVM with transparent task migration, checkpointing, and global scheduling. These enhancements are part of the MIST project which takes an open systems approach in developing a cohesive, distributed parallel computing environment. This open systems approach promotes plug-and-play integration of independently developed modules, such as Condor, DQS, A VS, Prospero, XPVM, PIOUS, Ptools, etc. Transparent task migration, in conjunction with a global scheduler, facilitates the use of shared NOWs by allowing parallel jobs to unobtrusively utilize nodes that are currently unused. PVM tasks can be moved onto nodes that are otherwise idle, and moved off when the node is no longer free. Experiments show that migration performance is limited by the bandwidth of the underlying network. E.g. An 8 MB process migrates in 8 seconds on a 10 Mbps ethernet. We have implemented a global scheduler as a PVM resource manager which can take advantage of task migration to perform dynamic scheduling of tasks. Some extensions to the resource manager interface were required. The task migration mechanism also serves as the basis for transparent checkpointing, which is a common method for improving a system's fault tolerance. We have developed a PVM prototype that integrates checkpointing and migration. This paper presents an overview of the entire system, issues raised by this work, and discusses future plans. Close

• 35. [Article] Source of cobalt-60 and migrations of albacore off the west coast of north America

  Citation × Citation Citation Abstract Copy Title: Source of cobalt-60 and migrations of albacore off the west coast of north America Author: Pearcy, William G., Krygier, Earl E. Title: Source of cobalt-60 and migrations of albacore off the west coast of north America Author: Pearcy, William G., Krygier, Earl E. Close

• 36. [Article] Modeling carbohydrate ballasting by Trichodesmium spp.

  We report the development of a numerical model simulating vertical movement of the cyanobacterium Trichodesmium spp. Given a range of physiological parameters derived from the literature, resultant model ...

  Citation × Citation Citation Abstract Copy Title: Modeling carbohydrate ballasting by Trichodesmium spp. Author: Spitz, Yvette H., Letelier, Ricardo M., White, Angelicque E. We report the development of a numerical model simulating vertical movement of the cyanobacterium Trichodesmium spp. Given a range of physiological parameters derived from the literature, resultant model solutions allow us to explore the ecological significance of vertical migration by Trichodesmium colonies in a stratified oligotrophic oceanic system such as the North Pacific subtropical gyre (NPSG). Whereas the dominant type of model solution results in trapping of the migrating colony at the water surface, the next most frequent type of model solution is consistent with colony migration to the average depth of the phosphocline, followed by return to the upper euphotic zone, a scenario termed P-mining. Given the temporal phasing of these migrations, our results indicate that while Trichodesmium colonies could fulfill their entire P-quota in a single phosphoclinescale migration, the minimal colony size required for such a migration would be approximately 1000 μm in radius. Colonies of this size and larger have been observed in nature. However, neither the frequency of occurrence nor the relative size distributions of natural populations is known. Using published estimates of colony abundance at Station ALOHA (22° 45’ N, 158° 00’W, in the NPSG), we estimate that upward fluxes of P associated with Trichodesmium migration represent as much as 10% of the P-based export flux measured at this site. Inclusion of this simple model into coupled biophysical models should allow for better simulations of the vertical distribution of Trichodesmium biomass and thus improved representations of Trichodesmium productivity. Title: Modeling carbohydrate ballasting by Trichodesmium spp. Author: Spitz, Yvette H., Letelier, Ricardo M., White, Angelicque E. We report the development of a numerical model simulating vertical movement of the cyanobacterium Trichodesmium spp. Given a range of physiological parameters derived from the literature, resultant model solutions allow us to explore the ecological significance of vertical migration by Trichodesmium colonies in a stratified oligotrophic oceanic system such as the North Pacific subtropical gyre (NPSG). Whereas the dominant type of model solution results in trapping of the migrating colony at the water surface, the next most frequent type of model solution is consistent with colony migration to the average depth of the phosphocline, followed by return to the upper euphotic zone, a scenario termed P-mining. Given the temporal phasing of these migrations, our results indicate that while Trichodesmium colonies could fulfill their entire P-quota in a single phosphoclinescale migration, the minimal colony size required for such a migration would be approximately 1000 μm in radius. Colonies of this size and larger have been observed in nature. However, neither the frequency of occurrence nor the relative size distributions of natural populations is known. Using published estimates of colony abundance at Station ALOHA (22° 45’ N, 158° 00’W, in the NPSG), we estimate that upward fluxes of P associated with Trichodesmium migration represent as much as 10% of the P-based export flux measured at this site. Inclusion of this simple model into coupled biophysical models should allow for better simulations of the vertical distribution of Trichodesmium biomass and thus improved representations of Trichodesmium productivity. Close

• 37. [Article] Out-migration, income and poverty in nonmetropolitan America

  Why do rural households leave for urban places? And how does this decision affect their economic well-being? Rural places in the United States have higher poverty and unemployment rates and lower levels ...

  Citation × Citation Citation Abstract Copy Title: Out-migration, income and poverty in nonmetropolitan America Author: Marre, Alexander Why do rural households leave for urban places? And how does this decision affect their economic well-being? Rural places in the United States have higher poverty and unemployment rates and lower levels of educational attainment relative to urban places. Does leaving a rural place for a city offer a pathway out of poverty and to greater income? This dissertation examines these questions with data from the Panel Study of Income Dynamics. Four models of household economic outcomes are estimated for three periods: 1979 to 1985, 1985 to 1991, and 1991 to 1997. These models estimate the nonmetropolitan out-migration decision and the following economic outcomes: household poverty, cost-of-housing adjusted household poverty, household income, and cost-of-housing adjusted household income. All four models include an instrumental variable or variables to control for possible endogeneity between the migration decision and economic outcomes. Empirical results indicate that nonmetropolitan out-migration increased poverty risk in the 1979 to 1985 period, yet had no statistically significant effect on any economic outcome during the latter periods. Educational attainment was found to be a significant, in the statistical and economic sense, determinant of economic outcomes. These findings suggest that human capital and other individual and household characteristics explained household poverty risk and income from 1985 to 1997 and that migrating out of nonmetropolitan counties had no effect. The evidence from this study indicates that rural anti-poverty policy should focus on human capital development. It does not support place-based policy. Title: Out-migration, income and poverty in nonmetropolitan America Author: Marre, Alexander Why do rural households leave for urban places? And how does this decision affect their economic well-being? Rural places in the United States have higher poverty and unemployment rates and lower levels of educational attainment relative to urban places. Does leaving a rural place for a city offer a pathway out of poverty and to greater income? This dissertation examines these questions with data from the Panel Study of Income Dynamics. Four models of household economic outcomes are estimated for three periods: 1979 to 1985, 1985 to 1991, and 1991 to 1997. These models estimate the nonmetropolitan out-migration decision and the following economic outcomes: household poverty, cost-of-housing adjusted household poverty, household income, and cost-of-housing adjusted household income. All four models include an instrumental variable or variables to control for possible endogeneity between the migration decision and economic outcomes. Empirical results indicate that nonmetropolitan out-migration increased poverty risk in the 1979 to 1985 period, yet had no statistically significant effect on any economic outcome during the latter periods. Educational attainment was found to be a significant, in the statistical and economic sense, determinant of economic outcomes. These findings suggest that human capital and other individual and household characteristics explained household poverty risk and income from 1985 to 1997 and that migrating out of nonmetropolitan counties had no effect. The evidence from this study indicates that rural anti-poverty policy should focus on human capital development. It does not support place-based policy. Close

• 38. [Article] Passage of juvenile cutthroat trout and steelhead through retrofitted culverts

  Citation × Citation Citation Abstract Copy Title: Passage of juvenile cutthroat trout and steelhead through retrofitted culverts Author: McEnroe, Jeffrey R. Title: Passage of juvenile cutthroat trout and steelhead through retrofitted culverts Author: McEnroe, Jeffrey R. Close

• 39. [Article] Latino Immigrant Students: Exploring the Relationship between Migration Experience and Education Outcomes

  The purpose of this study was to contribute to the literature on the educational outcomes and protective factors (i.e., support systems) in the lives of Latino immigrant youth, with a special emphasis ...

  Citation × Citation Citation Abstract Copy Title: Latino Immigrant Students: Exploring the Relationship between Migration Experience and Education Outcomes Author: Ramos, Karina Year: 2015 The purpose of this study was to contribute to the literature on the educational outcomes and protective factors (i.e., support systems) in the lives of Latino immigrant youth, with a special emphasis on how these experiences relate to and are impacted by their migration experiences. Using the cultural-ecological theoretical framework and the Stages of Migration framework, this study utilized an existing data set to explore the relationships between migration stress, psychological distress, experiences of discrimination, and awareness of discrimination in relation to educational outcomes in a sample of 281 Latino immigrant youth. These relationships were then examined to see if they differed as a function of perceived support, gender, and school type (i.e., middle school versus high school). Structural equation modeling was utilized to test the hypothesized model that included migration stress, psychological distress, and education outcomes. The structural model showed very good fit. Results suggest that migration stress has a significant direct effect on psychological distress and on educational outcomes among Latino immigrant youth. Participants reporting high migration stress reported greater psychological distress and had poorer educational outcomes with respect to academic grades, educational aspirations, and educational expectations. Moderation testing indicated the structural model did not vary as a function of perceived support, gender, or school. Implications for research and practice are discussed. Title: Latino Immigrant Students: Exploring the Relationship between Migration Experience and Education Outcomes Author: Ramos, Karina Year: 2015 The purpose of this study was to contribute to the literature on the educational outcomes and protective factors (i.e., support systems) in the lives of Latino immigrant youth, with a special emphasis on how these experiences relate to and are impacted by their migration experiences. Using the cultural-ecological theoretical framework and the Stages of Migration framework, this study utilized an existing data set to explore the relationships between migration stress, psychological distress, experiences of discrimination, and awareness of discrimination in relation to educational outcomes in a sample of 281 Latino immigrant youth. These relationships were then examined to see if they differed as a function of perceived support, gender, and school type (i.e., middle school versus high school). Structural equation modeling was utilized to test the hypothesized model that included migration stress, psychological distress, and education outcomes. The structural model showed very good fit. Results suggest that migration stress has a significant direct effect on psychological distress and on educational outcomes among Latino immigrant youth. Participants reporting high migration stress reported greater psychological distress and had poorer educational outcomes with respect to academic grades, educational aspirations, and educational expectations. Moderation testing indicated the structural model did not vary as a function of perceived support, gender, or school. Implications for research and practice are discussed. Close

• 40. [Article] The horizontal distribution and vertical migrations of the limnetic zooplankton in Crater Lake, Oregon

  During the summers of 1967 and 1968 the horizontal distribution and did vertical migrations of zooplankton were studied within the unique environment of Crater Lake. Sampling of the horizontal distribution ...

  Citation × Citation Citation Abstract Copy Title: The horizontal distribution and vertical migrations of the limnetic zooplankton in Crater Lake, Oregon Author: Hoffman, F. Owen During the summers of 1967 and 1968 the horizontal distribution and did vertical migrations of zooplankton were studied within the unique environment of Crater Lake. Sampling of the horizontal distribution was done by towing plankton nets vertically in different locations. The vertical distribution was sampled by towing at different depths with a standard tow net and Miller samplers. During both summers, the greatest numbers of zooplankton were sampled in late August. Bosmina longispina was the most numerous zooplankter, while Daphnia pulex, insignificant in 1967, increased in abundance during 1968. The horizontal distribution of B. longispina was clumped, being consistently more abundant in some locations than others. D. pulex had a random, or near-uniform, distribution. Vertical migrations were not consistent and seem to occur only during certain times of the year. The depth of the maximum concentration of B. longispina was found to vary between distances of 12.5 and 25 m, and was located at depths of 75 to 50 m during the day and between 50 to 37.5 m at night. A few B. longispina, however, did migrate to the surface at night. On August 28 and 29, 1968, the entire adult population of D. pulex migrated from 62.5 m during the day to the surface at night. This migration appears to have reproductive advantages. Prior to this time, only a nocturnal scattering of a small portion of the total population of D. pulex occurred. Various ideas are given as to why these different migrations occurred, but based on the information that is presently available, any direct relationships between the variations of vertical migrations and environmental factors are difficult to make. Title: The horizontal distribution and vertical migrations of the limnetic zooplankton in Crater Lake, Oregon Author: Hoffman, F. Owen During the summers of 1967 and 1968 the horizontal distribution and did vertical migrations of zooplankton were studied within the unique environment of Crater Lake. Sampling of the horizontal distribution was done by towing plankton nets vertically in different locations. The vertical distribution was sampled by towing at different depths with a standard tow net and Miller samplers. During both summers, the greatest numbers of zooplankton were sampled in late August. Bosmina longispina was the most numerous zooplankter, while Daphnia pulex, insignificant in 1967, increased in abundance during 1968. The horizontal distribution of B. longispina was clumped, being consistently more abundant in some locations than others. D. pulex had a random, or near-uniform, distribution. Vertical migrations were not consistent and seem to occur only during certain times of the year. The depth of the maximum concentration of B. longispina was found to vary between distances of 12.5 and 25 m, and was located at depths of 75 to 50 m during the day and between 50 to 37.5 m at night. A few B. longispina, however, did migrate to the surface at night. On August 28 and 29, 1968, the entire adult population of D. pulex migrated from 62.5 m during the day to the surface at night. This migration appears to have reproductive advantages. Prior to this time, only a nocturnal scattering of a small portion of the total population of D. pulex occurred. Various ideas are given as to why these different migrations occurred, but based on the information that is presently available, any direct relationships between the variations of vertical migrations and environmental factors are difficult to make. Close