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This thesis presents two applications of the incompleteness and one application of the imperfection of the market economy. The first application, Chapter 2, studies the decision making problem of an individual seeking to accumulate an optimal amount of human capital realizing that the wage income derived from the accumulated human capital is subject to incompletely insured uncertainty. In other words, the financial market that insures against wage income risk is not fully functional. We find that the individual's inability to diversify wage income risk tends to increase the need to accumulate more human capital in order to elevate wage path and compensate for the burden of its associated risk. This is particularly true when (i) the wage income risk is positively correlated with the rate-of-return risk in the financial market, resulting in an even greater risk burden to the individual, and (ii) the individual is more risk averse. There are two possibilities that no human capital is needed. The first possibility occurs when it is optimal to work as an unskilled worker because both the burden from wage income risk and the rate of return from education are low. The second possibility is the case where the risk burden is so high that the optimal time spent in school to acquire sufficient human capital to cover the risk is so long that the discounted rate of return from education is negative. In this case, the best strategy is to invest in financial assets alone and forfeit the opportunity to earn wage income - either as an educated or as an unskilled worker - to avoid its associated risk. Chapter 3 applies equilibrium unemployment theory with a frictional labor market to study the impact of immigration on the local labor market. Markets are imperfect in the sense that job matching takes time and recruitment is costly. We find that labor market outcomes of both the natives and existing immigrants depend crucially on how the economic surplus from successful matching is divided between the firms and the workers or, in other words, on the bargaining power of the workers. An arrival of immigrants with low bargaining power tends to benefit both the natives and the existing immigrants. A disparity between the two worker types in the matching efficiency also plays a major role. An inferior matching technology among the immigrants, interpreted here as reflecting their less established social network, lowers their wage rate and increases their unemployment rate. The natives are more likely to benefit from additional immigration than the existing immigrants and, when they do, the overall benefit can be decomposed into "job creation spillover" effect resulting from the immigrants' low bargaining power, and "job stealing" effect resulting from the immigrants' less efficient matching. The implications on the pattern of international migration flows are also discussed. In Chapter 4, a simple macroeconomic model is constructed and applied quantitatively to OECD countries, to analyze the effect of incomplete insurance on saving, growth and welfare in a closed economy. In this economy, precautionary saving motivated by uninsured idiosyncratic shocks raises growth rates but lowers risk-free returns. Welfare is measured by the sum of growth rates and risk-free rates of return, not growth rates alone. This welfare measure takes the negative impact of precautionary saving into consideration. Applied to the OECD data, three major results emerge: (i) the heterogeneous performance of growth and saving across the countries reflects different degrees of insurance incompleteness, (ii) since the externality of growth on productivity was very strong in the 1960's, the heavily constrained insurance market itself improves productivity by promoting growth, thereby enhancing welfare, (iii) while the externality of growth became weaker in the 1980's, the development of insurance markets lowered growth, but still contributed to a raise in welfare.

Invasive alien species (IAS) pose a serious threat to ecosystems and societies worldwide. Local ecological knowledge (LEK) is increasingly valued as a means of understanding environmental issues; however, its application in the context of IAS research has been limited. The overall objective of this study was to document the LEK of farmers and Weed Supervisors to gain insight into a recent IAS, Odontites serotina. I conducted semi-structured interviews with farmers and Weed Supervisors with O. serotina management experience. Results indicated that the socio-economic impacts for farmers were severe in affected rural communities. However, participants had developed promising control techniques, including the application of compost mulch. I used this LEK as well as data on species occurrence, environmental variables, and measures of propagule pressure to forecast the potential distribution of O. serotina across Manitoba. The risk map generated will be useful for guiding future monitoring and public outreach efforts.

Invasive alien species (IAS) pose a serious threat to ecosystems and societies worldwide. Local ecological knowledge (LEK) is increasingly valued as a means of understanding environmental issues; however, its application in the context of IAS research has been limited. The overall objective of this study was to document the LEK of farmers and Weed Supervisors to gain insight into a recent IAS, Odontites serotina. I conducted semi-structured interviews with farmers and Weed Supervisors with O. serotina management experience. Results indicated that the socio-economic impacts for farmers were severe in affected rural communities. However, participants had developed promising control techniques, including the application of compost mulch. I used this LEK as well as data on species occurrence, environmental variables, and measures of propagule pressure to forecast the potential distribution of O. serotina across Manitoba. The risk map generated will be useful for guiding future monitoring and public outreach efforts.

Objectius: Analitzar l’exposició a riscos psicosocials dels treballadors assalariats immigrants a Espanya comparant-la amb la dels espanyols i estudiar el paper dels riscos psicosocials en la relació entre la immigració i la salut mental. Mètodes: Estudi transversal realitzat per l’Institut Sindical de Treball, Ambient i Salut (ISTAS) entre el 2004 i el 2005 sobre una mostra representativa de població assalariada resident a Espanya. La informació s’obtingué a través d’un qüestionari estandarditzat administrat per entrevistador a domicili. La grandària de la mostra d’estudi fou de 7.555 treballadors, dels quals 6.868 eren espanyols i 687 eren immigrants. Per les exigències i la inseguretat, l’exposició es va definir segons el tercil més alt, mentre que per les altres dimensions, va ser definida segons el tercil més baix. La salut mental es dicotomitzà en bona i dolenta segons la mediana, que fou 76. Principals resultats: Els treballadors que estaven més exposats als riscos psicosocials van ser els immigrants manuals, especialment, en les baixes possibilitats de desenvolupament (PR: 2,87; IC95%: 2,44-3,73), i les dones immigrants, particularment en el baix control sobre els temps a disposició (PR: 1,72; IC95%: 1,55-1,91). Els treballadors immigrants amb elevades exigències quantitatives (PR: 1,46; IC95%: 1,34-1,59), elevades exigències emocionals (PR: 1,42; IC95%: 1,30-1,56), elevades exigències d’amagar emocions (PR:1,35; IC95%: 1,21-1,50), baixes possibilitats de desenvolupament (PR: 1,21; IC95%: 1,09-1,33), baixos nivells de suport social entre companys (PR: 1,41; IC95%: 1,30-1,53) i baixa estima (PR: 1,53; IC95%: 1,42-1,66) eren els treballadors que percebien pitjor salut mental. Conclusions: Els treballadors immigrants, especialment, els manuals i les dones, eren els més exposats a riscos psicosocials. Els treballadors més exposats als riscos psicosocials eren els que percebien pitjor salut mental. Per a millorar la salut mental dels treballadors, és necessari implementar mesures preventives per tal d’eradicar els riscos psicosocials, especialment dels grups més vulnerables. / Objetivos: Analizar la exposición a riesgos psicosociales de los trabajadores asalariados inmigrantes en España comparandola con la de los españoles y estudiar el papel de los riesgos psicosociales en la relación entre la inmigración y la salud mental. Métodos: Estudio transversal realizado por el Instituto Sindical de Trabajo, Ambiente y Salud (ISTAS) entre el 2004 y el 2005 sobre una muestra representativa de población asalariada residente en España. La información se obtuvo a través de un cuestionario estandardizado administrado por entrevistador en domicilio. El tamaño de la muestra de estudio fue de 7.555 trabajadores, de los cuales 6.868 eran españoles y 687 eran inmigrantes. Por las exigéncias y la inseguridad, la exposición se definió según el tercil màs alto, mientras que por las otras dimensiones, fue definida según el tercil más bajo. La salud mental se dicotomizó en buena y mala según la mediana, que fue 76. Principales resultados: Los trabajadores que estaban más expuestos a los riesgos psicosociales fueron los inmigrantes manuales, especialmente, en las bajas posibilidades de desarrollo (PR: 2,87; IC95%: 2,44-3,73), y las mujeres inmigrantes, particularmente en el bajo control sobre los tiempos a disposición (PR: 1,72; IC95%: 1,55-1,91). Los trabajadores inmigrantes con altas exigéncias cuantitativas (PR: 1,46; IC95%: 1,34-1,59), altas exigéncias emocionales (PR: 1,42; IC95%: 1,30-1,56), altas exigéncias de esconder emociones (PR: 1,35; IC95%: 1,21-1,50), bajas posibilidades de desarrollo (PR: 1,21; IC95%: 1,09-1,33), bajos niveles de apoyo social entre compañeros (PR: 1,41; IC95%: 1,30-1,53) y baja estima (PR: 1,53; IC95%: 1,42-1,66) fueron los trabajadores que percibieron peor salud mental. Conclusiones: Los trabajadores inmigrantes, especialmente, los manuales y las mujeres, eran los más expuestos a riesgos psicosociaels. Los trabajadores más expuestos a riesgos psicosociales eran los que percibieron peor salud mental. Para mejorar la salud mental de los trabajadores, es necesario implementar medidas preventivas para erradicar los riesgos psicosociales, especialmente de los grupos más vulnerables.

Thesis (M.B.A.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 120).

Made available in DSpace on 2016-06-02T19:32:05Z (GMT). No. of bitstreams: 1 4768.pdf: 6398545 bytes, checksum: da59eeea98c77e3bb13845ab8f838873 (MD5) Previous issue date: 2012-09-06 / Financiadora de Estudos e Projetos / The planet Earth is facing a serious crisis of the biodiversity loss. Often, human activities are responsible for biological invasions that alter significantly the various ecosystems and could lead to the extinction of native species. Dendrocephalus brasiliensis ( branconeta ) is a native freshwater Anostraca species, which has been studied and used in aquaculture to replace the brine shrimp originating from saline environments. Its occurrence in natural environments was recorded in Brazilian southeast and northeast regions, from the city of Urucuia-MG to Piauí State. However, there are records of its accidental introduction into fish ponds in São Paulo state, cities of Tabatinga and Arealva. The goal of this work is the study of the interactions of competition and predation / herbivory between D. brasiliensis and other planktonic species native of São Paulo in order to assess the possible impacts of a possible introduction of this species in natural environments where it does not occur originally. This study was conducted in an experimental system (10.000L tank) in Aquaculture Station of Department of Hydrobiology (EA-DHb), Federal University of São Carlos (UFSCar), São Carlos, SP, Brazil. Initially, the experimental tank was inoculated with the green algae Pseudokirchneriella subcapitata grown in laboratory. After the establishment of phytoplankton, zooplankton species were collected in limnic ecosystems of São Paulo state, in particular near São Carlos (June and July/2011), for the establishment of a zooplankton community in the experimental tank. Zooplankton succession in the tank was monitored for 133days before the introduction of branconeta. To evaluate the interaction of D. brasiliensis with other zooplankton species, the experimental tank was divided in two equal compartments that do not communicate to each other: one of them was kept with the original composition of the zooplankton, while in the other, cysts of the anostracean were introduced. In both experimental compartments samples were collected daily during 39 days, for quantitative and qualitative analyzes of zooplankton community, besides chlorophyll a, physical and chemical variables. The environmental variables were correlated to zooplankton groups using the statistical method of Canonical Correspondence Analysis (CCA). Numerical densities of Cladocera and Copepoda groups decreased in the presence of D. brasiliensis. We can conclude that the presence of D. brasiliensis does not exclude but significantly alters the composition and density of the plankton community. / O planeta Terra vem enfrentando a grave crise da perda da biodiversidade. Muitas vezes, as atividades humanas são responsáveis pelas invasões biológicas que alteram significativamente os vários ecossistemas, podendo levar à extinção espécies nativas. Dendrocephalus brasiliensis (branconeta) é uma espécie nativa de anostráceo dulcícola, que vem sendo estudada e utilizada na aquicultura, em substituição às artêmias originárias de ambientes salinos. Sua ocorrência em ambientes naturais foi registrada nas regiões sudeste e nordeste brasileira, a partir do município de Urucuia-MG até o Piauí. Entretanto, há registros de sua introdução acidental em pisciculturas localizadas no estado de São Paulo, municípios de Tabatinga e Arealva. O objetivo do presente trabalho é o estudo das interações de competição e de predação/herbivoria entre D. brasiliensis e outras espécies planctônicas nativas do estado de São Paulo, a fim de avaliar os possíveis impactos de uma eventual introdução dessa espécie em ambientes naturais onde a mesma não ocorra originalmente. Este estudo foi realizado em um sistema experimental (tanque de 10.000L) na Estação de Aquicultura do Departamento de Hidrobiologia (EA-DHb) da Universidade Federal de São Carlos (UFSCar), São Carlos, SP, Brasil. Inicialmente, o tanque experimental foi inoculado com a clorofícea Pseudokirchneriella subcapitata cultivada em laboratório. Logo após o estabelecimento do fitoplâncton, foram coletadas espécies de zooplâncton em ecossistemas límnicos do estado de São Paulo, em especial na região de São Carlos (junho e julho/2011) para o estabelecimento de uma comunidade zooplanctônica no tanque experimental. A sucessão zooplanctônica no tanque foi acompanhada por 133 dias antes da introdução da branconeta. Para a avaliação da interação de D. brasiliensis com outras espécies zooplanctônicas, o tanque experimental foi dividido em dois compartimentos iguais sem comunicação entre eles: em um deles foi mantida a composição zooplanctônica original, enquanto no outro foram introduzidos cistos do anostráceo. Em ambos os compartimentos experimentais foram recolhidas amostras diárias durante 39 dias, para análises quantitativas e qualitativas da comunidade zooplanctônica, além de variáveis físicas, químicas e clorofila a. As variáveis ambientais foram correlacionadas aos grupos zooplanctônicos através do método estatístico da Análise de Correspondência Canônica (CCA). As densidades numéricas dos grupos Cladocera e Copepoda diminuíram na presença de D. brasiliensis. Podemos concluir que a presença de D. brasiliensis não exclui, mas altera significativamente a composição e densidade da comunidade planctônica.

Made available in DSpace on 2016-06-02T19:32:14Z (GMT). No. of bitstreams: 1 6709.pdf: 4195083 bytes, checksum: 80992e3623fd375eb0fcff062a4c0f5d (MD5) Previous issue date: 2015-02-05 / Financiadora de Estudos e Projetos / Biological invasion is a threat to biodiversity, due to competition for resources between invaders and native organisms, decreasing the overall biodiversity. So, studies about the invasiveness of the ecossystems and invasion potential of exotic plants several environments must be taken to control this species. Hedychium coronarium, from the Himalayas, is an example of a high invasivisiness plant, taken to different places in the world, mainly due to ornamental uses. This study evaluated the development (height, diameter, birth and ramets mortality and internal rhyzome anatomy) of plants under different moisture contents, in in situ and in vitro experiments. We found the existence of plasticity for both vegetative ramets growth, and the internal rhyzome anatomy, which may contribute to the invasive potential of this plant. / A invasão biológica é uma ameaça à biodiversidade, já que ocorre competição por recursos entre organismos invasores e nativos, diminuindo a biodiversidade global. Assim, estudos sobre a invasão dos ecossistemas e potencial invasão de plantas exóticas em ambientes diversos devem ser realizados para que haja controle das espécies. Hedychium coronarium, proveniente do Himalaia, é um exemplo de planta com alta invasivisidade, levada a diferentes lugares do mundo, sobretudo devido ao potencial ornamental que fornece. O presente estudo avaliou o desenvolvimento (altura, diâmetro, nascimento, mortalidade dos rametas e anatomia interna do rizoma) da planta em ambientes com diferentes umidades, com experimentos in situ e in vitro. Foi encontrado indício de plasticidade, tanto em crescimento vegetativo dos rametas, quanto na anatomia interna dos rizomas, o que pode contribuir para a invasivisidade dessa planta.

The Akosombo Dam on the Volta River in Ghana was built in 1963 to provide cheap energy to fuel industry and to accelerate the economic growth of the country. It provides hydroelectric power, enhanced fishing and water transportation upstream, and improved opportunities for irrigated farming, especially in the lower reaches, and their attendant economic multiplier effects. A few years after the construction of this major dam, a rapid expansion of industrialization took place in Ghana. This brought about an exponential increase in demand for more electrical power. This led to the construction of a smaller dam at Akuse, downstream of the Akosomho Dam in 1981 and the formation of a headpond at Kpong. The impoundment of the river at the two sites (Akosombo and Kpong) caused an alteration in the existing ecological and biophysical processes in the river basin, including a slowing of the flow of the river, upstream and downstream. Changes in the natural processes, such as a reduction in the flow of the river and an increase in nutrient status of the water, resulted in an invasion of aquatic weeds, increasing the density of aquatic snails (intermediate hosts of schistosomiasis), silting and closure of the estuary, as well as other more subtle effects. The invasion of the river's main course and the dams by aquatic plants led to a corresponding reduction of navigable water both upstream and downstream. The aim of this thesis was to quantify the impact and control of waterweeds, especially water hyacinth, Eichhornia crassipes (Mart) Solms-Laubach (Pontederiaceae), in Ghana. A floral survey on the Kpong Headpond recorded 49 emergent, 12 free floating and I submerged aquatic plant species, many of which were indigenous, but the exotic or introduced water hyacinth was recorded at most of the sampling sites, and was the most abundant and had the biggest impact on the utilization of the water resource. Mats of water hyacinth served as substrates for other, indigenous species to grow out into the main channel of the headpond, including the intake point of the Kpong head works of the Ghana Water Company Limited (GWCL) and landing sites for boats. These mats resulted in a reduction of the fish (fin and shell) harvest, reducing the annual production to far below demand. Water hyacinth was also shown to have severe health implications. A survey of the Ministry of Health records showed that the prevalence of both urinary and intestinal schistosomiasis had risen significantly over time as the abundance of waterweeds, most notably water hyacinth, increased, and ranged between 70% and 75% but up to 100% in some lakeside communities. Based on the work done by an NGO on board the medical boat ("Onipa Nua "), losses in terms of money due to the effect on health of the aquatic weed infestations on the Volta River in 2006 amounted to US$ 620,000. Economic losses due to invasive alien aquatic weeds were also calculated on the Oti River Arm of Lake Volta. It was estimated that about US$2.3 million per annum would be lost to the Volta Lake Transport Company and individual boat transport operators if this section of the river were 100% covered by aquatic weeds (water hyacinth and Salvinia molesta D.S. Mitchell (Salviniaceae)). It was also estimated that US$327,038 was spent annually in monitoring and managing the weeds in the Oti River. Control interventions for aquatic weeds have been implemented in river systems in Ghana. The biological control agents Neochetina bruchi Hustache (Coleoptera, Curculionidae) and Neochetina eichhorniae Warner (Coleoptera, Curculionidae) have been used on water hyacinth infestations in the Oti River Arm of Lake Volta, the Tano River and the Lagoon complex in the south-western part of the country. Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) has been used to control salvinia, and Neohydronomous affinis Hustache (Coleoptera: Curculionidae) to control water lettuce, Pistia stratiotes Lilmaeus (Araceae) in the Tano River and Lagoon complex. Although these projects have been regarded as successful, they have relied on research from elsewhere in the world and no postrelease quantification has been conducted. In evaluating the impact of the biological control agents Neochetina bruchi and Neochetina eichhorniae weevils on water hyacinth infestations in the Tano River, fresh adult feeding scars were recorded as well as the numbers of adult weevils on each water hyacinth plant sampled at six sites. Despite being released in 1994, weevil numbers and resultant damage to plants in the Tano Lagoon was low in comparison to other regions of the world where these agents have been used. The main reason for this is that this lagoon floods seasonally, washing weevil-infested plants out to sea. Water hyacinth then re-infests the lagoon from seed and the weevil populations are low. To resolve this situation, two courses of action are proposed. The first is to mass rear the weevils along the shore of the lagoon and release them when the first seedlings recruit. The second proposal is that additional agents that have shorter lifecycies and are more mobile than the weevils should be released. To this end, the water hyacinth mirid, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) was imported from South Africa and released onto the Tano Lagoon in 2009. Retrospective laboratory host specificity trials were conducted on Neachetina eichharniae and Neachetina bruchi weevils 15 years after their release into Ghana to see if any variation in their host ranges had occurred. Considerable damage was inflicted on the E. crassipes leaves by the Neachetina weevils, while little feeding damage was recorded on both Heteranthera callifalia Kunth. (Pontederiaceae) and Eichharnia natans (P.Beauv.) Solms (Pontederiaceae). All the weevils introduced on H callifalia and E. natans died after the first week. This study served to confirm the host specificity and thereby the safety of these agents. Invasive alien aquatic macrophytes have negative impacts on the environment and economy of Ghana. The control of these weeds is essential to socioeconomic development and improved human health standards in riparian communities. Biological control offers a safe and sustainable control option, but requires diligent implementation. However, aquatic weed invasion is more typically a result of the anthropogenically induced eutrophication of water bodies, and this is the main issue that has to be addressed.