Dissertations / Theses on the topic 'Migration and health'

There seems to be a gap in previous literature where economists and social scientists do not focus on factors driving emigration of health professionals between developed coun-tries. Although, there is a lot of literature that discusses emigration of health profession-als from developing towards developed countries, there are few previous studies of health professional emigration between developed to developed countries. This paper examines and analyzes factors which might be of importance in determining the direc-tion of emigration of health professionals between developed countries. The concept of health professionals in our study contains people with more than 3 years of education within the health and social welfare sector, not referring to any particular occupation such as nurses, doctors, dentist etc; or whether they are specialized in any area. This pa-per analyses factors that affect emigration of Swedish health professionals, using eco-nomic and social variables in a structured regression model. The results indicate that the percentage of Swedish health professionals is directly affected by factors of destination countries such as geographical proximity, GDP(PPP) per capita, income tax rate and co-workers encouraging development.

This secondary daa study, framed in social constructinism theory, descibes and analyses the "
pull"
factors influencing migration of health professionals developing to developed countries. 
The literature review sets the context withing which international migration takes place and explores relevant aspects of the G8, globalisation, and the gGeneral Agreement on Trade in Services. 
The research demonstrates that temprary or permanent internationsl migration occurs for employment or study purposes. 
It further confirms that, despite the lack of accurate data from African counties, the number of health professionals leaving th continent has increased significantly during the 1990's.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Cell migration is present in virtually all life processes, including fertilization, embryogenic development, immune response, wound healing, and tumor metastasis. To improve the treatment of diseases associated with these various life processes, it is important to understand the underlying mechanisms of cell migration involved. This often requires that we recreate the environment that leads to and supports the continuous migration of cells. Here, we present two engineering approaches toward such a goal, with the additional emphasis that cell migration can be conducted in the absence of fluid flow, a mechanical stimulus that is known to influence cell behaviors. We chose the primary human neutrophil, which is highly motile and sensitive to both fluid flow and chemoattraction, as the model cell type for all our studies.

In the first approach, we used fluid flow to create a linear and time-invariant gradient of chemoattractants to guide the migration of neutrophils. A thin and porous membrane was used to screen off the associated flow forces while still permitting the diffusion of the gradient to the neutrophils. We showed that the membrane-based system is capable of directing neutrophil migration without the bias from fluid flow, and allowed within minutes the exchange of media to label and wash the migrated neutrophils. To assess the reduction of flow forces enabled by the membrane, we developed an analytical model to predict the direction and the magnitude of flow within the system. The validity of the model was verified both experimentally and numerically with particle tracking and computational fluid mechanic (CFM) simulations. We also performed total internal reflection fluorescence (TIRF) microscopy to verify the preservation of the gradient after v its diffusion through the membrane.

In the second approach, we created immobilized gradients of the chemoattractant interleukin 8 (IL-8) and the intercellular adhesion molecule 1 (ICAM-1) in the attempt to guide neutrophil migration. A gradient of soluble factors is first established, and the resulting difference of concentration over space leads to a bias in the binding of the soluble factors unto the substrate, forming an immobilized gradient. The immobilization is mediated by a combination of different physicochemical linkages, including electrostatic attraction, protein/protein interactions, and covalent bonding. We showed through labeling with fluorescent antibody that the number of IL-8 or ICAM-1 immobilized in a given area could be controlled, and varied over distances to form different gradient profiles. We further showed that our immobilization procedure does not affect the ability of IL-8 and ICAM-1 to activate and bind the neutrophils. However, with all the immobilized gradients that we have created so far, none were able to effectively promote the directed migration of neutrophils in long distances. Additional work is therefore required to establish if an immobilized gradient of either IL-8 or ICAM-1 alone can direct the migration of neutrophils in long distances, and if it does, what are the required conditions. Currently, our efforts suggest that the membrane-based chemotaxis system is a more attainable platform for promoting a directed migration that is shear-free.

The presented thesis work offers many potential applications. The membrane-based chemotaxis system, which has the general structure of two compartments separated by a membrane, resembled many physiological structures, including bone marrow, blood vessel, blood-brain barrier, hepatic portal vein, nephron in the kidneys, and alveolus in vi the lungs, and therefore serves as a versatile platform for understanding the transport phenomenon and the biochemical signaling in the aforementioned tissues. With improvements, the membrane-based system can also host larger-scale cell culture for protein production and tissue engineering. The protocols established for the gradient immobilization also provided many valuable references. These include: 1. A 1^st order approximation of the reagents and the times required to fully saturate the substrate to be functionalized. 2. An automated image processing tool to measure the various parameters of cell motility. 3. A statistical framework to detect the presence of a directed migration. In theory, the standard operating procedures established are applicable to the surface functionalization with other peptides and proteins.

Lamb waves based ultrasonic testing has been studiedfor many years. However, conventional methods of generatingand collecting of Lamb waves usually require bulky instruments and manual interference, thus can not be applieddirectly for in-situ or in-service monitoring of thestructural health. Especially, the method of interpretingthe Lamb waves in an active structural health monitoring(SHM) system with built-in piezoelectric sensors/actuatorsis not available yet. The objective of this study was to propose and validate, through numerical simulation and experimental studies, the feasibility of adopting the geophysical migration method to interpret the ultrasonic Lamb wave signals for the purpose of realizing quantitative damage identification. A homogeneous isotropic plate with a surface-mountedlinear piezoelectric ceramic (PZT) disk array is studied as an example. The piezoelectric disks act as actuators to excite Lamb waves and also as sensors to receive the waves reflected from the structural anomaly in the plate. The migration technique, which is an advanced technique in geophysics to reverse the reflection wave field and to image the Earth interior, is then used to back-propagate the recorded wave signals and to visually image the damage in the plate. Mindlin plate theory is adopted to model the propagating waves, and a two-dimensional 2-6 order explicit finite difference algorithm is used to synthesize the reflection waves and to implement the migration process. The stability and accuracy criteria of the finite differencealgorithm when used in plate problems is discussed. An analytical solution is derived for the transient Lamb waves of an infinite plate subject to a point loading. This solution is used to verify the accuracy of the finite difference calculation. Both poststack and prestack migration are studied to propagate the reflection energy back to the damages. For the poststack migration, a one-way version of flexural wave equation is derived and the data pre-processing procedures before migration, such as muting direct arrival, deconvolution and stacking, are discussed. For prestack migration, an excitation-time imaging condition specifically for the migration of waves in a plate is introduced based on ray-tracing concepts and the asymptotic properties of flexural wave velocities and the migration is proceeded through the full-way wave equation. The results of numerical simulation show that the migration method possesses the capability of identifying multiple discrete damages without a priori assumption on the distribution pattern of the damages. Thus not only the existence but also the shape and the dimensions of the damages can be visually identified. An experimental apparatus is then set up to validate the conclusions drawn from the synthetic data. For calibration of the system, an analytical model of the waves in a plate incorporated with PZT sensors/actuators is developed. The agreement between the model calculated data and the measured data in the experiment shows that A0 mode Lamb waves are accurately generated and collected. Finally, the migration results from the reflection waves of an artificial damage in an arc shape recorded in the experiment are presented. It is shown that the existence of the damage could be correctly imaged through the migration process as it was shown in the numerical simulation.

The massive migration of rural labor to urban areas in China over the past few decades has created the largest labor flow in world history. The proportion of the residential population in rural areas decreased from 80% in the late 1970s to 44% in 2016. Due to institutional and practical constraints, whole family migration is often not feasible for most migrant families. As a result, 61 million children age 0-17 are estimated to be left behind in rural communities by at least one parent seeking employment elsewhere. These numbers reflect a major change in the family and community environment in which children are cared for. Parental migration brings about changes in family structure and dynamics, entails a trade-off between economic benefits and parenting inputs, such as parental supervision and emotional support. At community-level, large-scale selective migration leads to remarkable changes in community demographic composition, shifting sociocultural norms and aspirations, influencing community institutional resources and collective social capital.

Over the past few decades, the scientific literature examining the implications of this large-scale migration and split families on the well-being of children left-behind has proliferated. However, empirical evidence on the effect of parental migration on left-behind children’s well-being is mixed for China and other countries in the context of international migration. Few studies have attempted to reconcile the inconsistent findings by examining the moderator effect. Although the potential effects of migration on cognitive development of children in origin communities reflect both household- and community-level processes, few studies have examined how community-level migration affects child development. In addition, mostly focused on the well-being of school-aged children, very limited study has been conducted on parental migration and early childhood development in the first few years of children’s lives, especially in the domain of cognitive and behavioral outcomes. Moreover, most researches have relied on cross-sectional data, exploring the association between a contemporaneous measure of parental migration and statically measured child outcomes at one point in time, ignoring the potential impact of the timing, transition and cumulative exposure to parental migration/absence, and may also be prone to selection bias.

To bridge the gap, the first analysis examines the conditions that may influence the effect of parental migration on child self-rated health (SRH). The results suggest a relatively weak main effect, but this is due in part to the influence of moderating factors. Children are more likely to report a good health status when the economic return of migration is substantial, if they are from impoverished communities, or when mothers remained at home to provide care while the father migrated a short distance within the same province. The second analysis focuses on examining community migration effect. Findings suggest lower cognitive achievement in communities experiencing high migration intensity. Children living in very high migration intensity areas are expected to have 3.57- and 1.54-unit lower verbal and math scores, which are equivalent to 1.67 and 0.87 years of formal education respectively. A possible explanation for this effect is the change in demographic composition brought about by the outmigration of better-educated adults. Finally, applying growth curve modeling strategy, the third analysis examines parental migration and early childhood development trajectories and states, taking into account timing, transition and cumulative exposure to parental migration. Our findings indicate that while left-behind children are comparable in the prevalence of childhood illness, positive behaviors and preschool enrollment, two-parent migration has a detrimental effect on children’s linear growth, cognitive stimulation, and home environment. Lack of appropriate cognitive stimulation in the critical early years could have important implications for child cognitive development.