Changes in the regional hydroclimate of the Midwest United States between the 6-kBP and current climate

This study used the NCAR Mesoscale Model version 5 release 3 (MM5v3) to simulate the climate of North America at 6000 years before present (6-kBP), and also tested the ability of the model in simulating the paleo-climate, which is significantly different from the present and partially verifiable. It also compared the paleo-climate simulations with the present and investigated the impact of changes in insolation, CO2 concentration, and vegetation on climate. To limit the influence of GCM bias on the simulations, the study used NCEP-DOE reanalysis II data for both 6-kBP and current climates. The present study differs from previous paleo-climate simulation, because it used a regional model instead of GCM, and also included differences in vegetation between the climates, which were ignored in the previous studies. The simulation results are compared with proxy records and paleo-climate simulation from General Circulation Models (GCM).;Results from the study show that MM5v3 is capable of simulating the paleo-climate. The simulated changes between the present and the 6-kBP climates are consistent with the proxy records and lake level data. The regional land-atmosphere interaction and the feedbacks better represented in MM5v3 than in GCM; hence the study obtained improved simulations for the Midwest, US. This study suggests that given realistic initial and lateral boundary conditions, MM5v3 is capable of simulating details of climates (past or future) that differ from present.;The simulated 6-kBP precipitation over Midwest is less than the present, but the evaporation is higher, resulting in negative precipitation minus evaporation (P-E). This is consistent with observed low lake level at 6-kBP over the region, but was not captured by previous GCM studies. However, analysis of the results reveals that less transport of moisture to the Midwest at 6-kBP caused the lower precipitation. Sensitivity tests show that a change in insolation influences both temperature and precipitation; a change in vegetation affects precipitation; but changes in CO2 produce less significant changes in temperature and precipitation

Enhancement of photo-conversion efficiency of organic solar cells by plasmon resonance effect

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015.Organic Photovoltaic (OPVs) is a promising alternative technology to provide clean and inexhaustible energy due to their excellent optoelectronic properties of the active polymer blends. The organic polymers have low weight, tunable electrical and optical properties besides being relatively insensitive to film imperfections which in the long run enable low-cost high-throughput roll-to-roll processing. However, their photo-conversion efficiency (PCE) and instability to air remains their greatest drawback as these preclude their commercialization. Indeed the highest power-conversion efficiency reported in literature is between 10-12 % compared to their inorganic counterparts (40 %). Therefore there is great need for improvement to make them competitive with grid parity. In this thesis, the major factors limiting the efficiency of organic solar cells such as light absorption, exciton diffusion and dissociation as well as charge collection are investigated and discussed. Despite the high thickness dependent absorption coefficients (>105 cm-1) within the visible spectrum the materials exhibit short exciton diffusion lengths (10-20 nm) which limit the optimal active layer thickness to a few nanometers. Improving optical absorption within this thickness forms the basis of this project. We report the use of surface Plasmons synthesized by both thermal evaporation and Radio Frequency (RF) magnetron sputtering system to tune and enhance optical absorption and scattering using the surface Plasmon resonance effect. The NPs were annealed at various temperatures and for different times to reconstruct and modify their shapes, sizes as well as the inter-particle distance (coverage). Stability is of paramount importance in organic semiconductor devices. Serious degradation in air constrains their applications potential. The study further investigates the mechanisms that determine the stability of organic photovoltaic devices. Our results depict the degradation mechanisms and their circumvention through the use of high mobility pentacene to improve stability

The Role of the “Path” and the “Container” Image Schemas in Political Discourse in Kenya

The study of conceptual interaction has attracted the attention of many scholars in Cognitive Linguistics. Primarily, the analysis has focused on the role of image-schemas in the construction of metaphors. This study explores the PATH and the CONTAINER image-schemas and the role they play in conceptual formation of metaphors in political discourse in Kenya. The study presents the PATH and its subsidiary image schemas of Verticality, Process and Force-Motion and the CONTAINER image-schema and the subsidiary image-schemas of Excess and In-Out. The analysis reveals that both the PATH and the CONTAINER image-schemas structure the relationship between the source domains (journey and container) and the target domain (politics) by activating subsidiary image-schemas in metaphors of politics in Kenya. The study further reveals that image-schemas provide the axiological value (positive or negative) of metaphorical expressions in political discourse. A positive political environment is a key ingredient for green growth and knowledge economy. The study contributes to the field of metaphor in political discourse by examining the politicians’ conceptualization of politics as a journey, which consists of four structural elements (a source, a destination, contiguous locations which connect the source and the destination and a direction) and as a container, which consists of an interior, an exterior and a boundary. The study used the Conceptual Metaphor Theory (CMT) as a tool to establish conceptual metaphors used during the 2005 Draft Constitution referendum campaigns in Kenya and the Image-Schema Theory to account for the presence of image-schemas in political discourse in Kenya. Lakoff and Johnson’s (1980) Conceptual Metaphor Theory is the locus classicus of the image schema theory

How does mine tailings slurry solids concentration affect stability of dam embankment slope?

In view of many past failures of tailings storage facilities, practising engineers have been analysing current design guidelines for different elements of these facilities, including for tailings dams. In this paper, an attempt is made to investigate how varying tailings slurry solids concentration ((Formula presented.)) affects the stability of tailings dam embankment slope. To achieve this, elaborate two-dimensional limit equilibrium and finite element simulations were conducted and a steady-state seepage analysis was performed so as to obtain accurate free surface water flux through the slope. Initially, numerical analyses were performed for the downstream embankment slope when no material is retained upstream. Subsequently, with all parameters kept constant, the same slope was then checked when water is retained upstream, and finally for varying slurry solids concentration. Special attention was paid to the boundary between sedimentation and consolidation, defined as the solids concentration limit beyond which effective stresses start to develop. From the stability analyses performed, it is found that the factor of safety of embankment slope varies nonlinearly with total unit weight of the slurry. For coal tailings slurry, factor of safety reduced from 1.24 when water is retained to 1.15 when tailings slurry with (Formula presented.) = 60% is retained, representing a drop by 7.3%

Linkages between Rural Poverty and Land Use in Nyando and Muhoroni Sub Counties Kenya

This study examined the relationship between rural poverty and land use among households in Nyando and Muhoroni Sub counties in Kenya. A Cross-sectional research design involving use of both systematic random sampling and purposive sampling was used in this study. Primary data was obtained using structured questionnaires to interview a minimum of 250 household heads from the two sub counties in Western Kenya. Data analysis involved the use of descriptive statistics. The Pearson product moment correlation (r) was used to determine the strength of the linkages between rural poverty and land use. The results showed that the Maize was by far the most dominant crop grown by 95.6 percent of the households compared to other different land use practices. In addition, results also indicated a significant relationship between rural poverty and land use in the two sub counties. The study therefore concludes that policies that increase households awareness on efficient and practical land use patterns that will help them break the vicious cycle of poverty given their diminishing sizes of land. Keywords: Rural Poverty, Land Use, land tenure, Nyando, Muhoron

The Influence of Agricultural Land Use on Household Food Security Situation in Kisii Central Sub-County, Kenya

Food security is a situation where people have access to sufficient, stable and safe food to meet their dietary needs for an active and healthy life. The aim of this paper is to determine the influence of agricultural land use on household food security situation in Kisii Central sub-county, Kenya. A sample of 209 households was picked from three sub-Locations within the three main agro-ecological zones of the study area. A structured questionnaire was used to collect the required data from household heads. Assessment of household food security status was based on experienced-based method. Agricultural land use was categorized into food crop, cash crop, fruits and vegetables and natural pasture and/or napier grass. The influence of agricultural land use on household food security situation was analyzed using the Pearson’s Chi-square test. Data analysis showed that 77.5% of the sampled households were food secure while 22.5% were not. About (65%) of the agricultural land was allocated to food crops, 25% to cash crops and the remaining proportion was left for other agricultural land uses. Cash crop (0.000) and natural pasture and/or napier grass (0.002) were found to have a significant influence on household food security while food crop (0.228) and fruits and vegetables (0.192) did not. The study recommends that more efficient ways of utilizing the land resource through increased use of high quality seeds and fertilizers to increase productivity. Investment in projects that enhance commercialization of small-scale farming in order to generate household income should be promoted. Keywords: Agricultural land use, Household food security, Kisii Central

The Impact of Socio-Economic Characteristics on Cash and Food Crop Production: Implications on Household Food Situation in Kisii Central Sub-County, Kenya

Socio-economic characteristics of households have significant implications on decisions related to utilization of household farms in order to meet food and non-food needs. This paper aims to establish the impact of socio-economic characteristics on cash and food production and the resultant household food situation in Kisii Central sub-County, Kenya. A structured questionnaire was used to collect data from 209 household heads drawn from three sub-Locations with the highest population density within the LM1, UM1 and LM2 agro-ecological zones. Data on gender and education level of the household heads, household size, farm size and household income was collected. The cash and food crop production data collected was the number of households involved in their production and the amount of land allocated to each activity. Assessment of the food situation was based on self-report by household heads in relation to levels of food availability within a period of one year. Descriptive and inferential techniques were used in data analysis and in particular, Pearson’s Chi-square test was used to analyze the impact of socio-economic characteristics on cash and food crop production and household food situation. The level of education of the household head (0.021) and household income (0.019) had significant impact on the food situation of households engaged in both cash and food crop production. Farm size had an impact on households engaged in food crop production (0.001). Most households were found to be food secure (77.5%). This study recommends that rural populations be encouraged to acquire formal education. Household income levels should also be enhanced through investment in value addition and establishment of cottage industries. Keywords: Cash and food crop production, Household socio-economic characteristics, Food situatio

Evaluation of the seasonal predictive potential of RegCM2 from a 10-year simulation

Regional climate models have been used in the past to project future climate changes on regional scales. Evaluation of model skill in predicting current climate is important for correct interpretation, determination of bounds of confidence and hence mitigation or adaptation strategies based on these projections. In this study RegCM2 was evaluated using various statistical assessment tools. Model output from the 10-year PIRCS runs, the NCEP/NCAR reanalysis, the Higgins, CMAP and VEMAP precipitation data sets for 1979-88 inclusive, and UNH/GRDC runoff were used. The results of bias score, simple bias and SOM analysis showed that RegCM2 has a large precipitation deficit in the south central United States in late fall and early winter. Compared to Higgins, the model identifies the rainy events well but the magnitudes are smaller. Bias in model variances of filtered 500 hPa height fields was generally less than 10%, and the storm tracks were not displaced in comparison to reanalysis. Similar model and reanalysis precipitation patterns, however, occurred with different model 500 hPa circulation patterns. Deficit in model precipitable water during spring and fall was about 10%; hence the dry bias was not due to shortage in atmospheric moisture. Using the water balance equations for both the earth and atmosphere to estimate subsurface water storage from simulated values of various terms, we estimated time dependent and time averaged errors in evapotranspiration. On the annual average the precipitation deficit was dominated by errors in convergence, while in fall evapotranspiration error was dominant. Insufficient evapotranspiration caused by inadequate soil moisture and hence higher soil and stomatal resistance, or insufficient evaporation from the sub-grid inland water bodies in this region arising from errors in land cover specifications are most likely responsible for the precipitation deficit. An examination of the land use specification and sensitivity studies in which the surface moisture availability and surface roughness are varied are suggested to examine the effects of land surface specification on evapotranspiration and hence the precipitation deficit

Access to Water among Slum Dwellers in Nakuru Town, Kenya: Lessons from Kaptembwa Location

Majority of urban residents in sub-Saharan Africa live in slums often characterised by lack of basic services such as water and sewerage.  With increasing pressures due to population growth, aging infrastructure, climate change, coupled with an unsustainable conventional water management, cities and urban areas in sub-Saharan African countries are facing enormous difficulties and will experience huge challenges in future in efficiently managing the scarce and increasingly unreliable water resources. This paper examines the level of access to water among slum dwellers in Nakuru town, Kaptembwo location, Kenya. The guiding questions the paper addresses are: (1) What is the level of households’ access to water? and (2) Has NAWASSCO met the demand for water by residents? A descriptive survey design was used and structured questionnaire administered to 280 households to collect the requisite data. Data was analyzed using descriptive statistical techniques and statistical software (SPSS) version 20. Results show that only 65.6% of the basic water requirements of the residents are met and that only 25% of the households access the minimum recommended 50 l/c/d. The low levels of investment in water infrastructure is the major explanatory reason for reduced access to water services. The paper shows that the domestic water supply in Kaptembwo is quite low according to the international standards. This situation is attributed to poor and inefficient water distribution system, unreliable and irrational rationing system, and poor management of water delivery services by NAWASSCO. This paper thus recommends that NAWASSCO should improve its distribution network and related infrastructure in order to facilitate adequate and reliable water provision to the study area. Other strategies including roof-harvesting and collection of run-off water if properly planned and managed could increase the water supply situation in the study area. Keywords: Access, water services, water supply, slums, household, water infrastructur

Roles of Local Governance Institutions and Promotion of Urban Agriculture Practices in Western Kenya

The role of local government institution and especially institutional structures and political culture often shape government performance including livelihood supporting activities such as Urban Agriculture (UA). The changing population pattern orchestrated by the spread of urbanization has resulted into a rise in poverty and food demand, necessitating UA. However, there seem to be limited documentation with regard to how local governance institutions influence and promote UA practices. The purpose of the study was to assess how roles of local governance institutions influence promotion of urban agriculture practices in Western Kenya. The specific objectives were to investigate the influence of economic, social and environmental roles of institutions, and the relationship between county government institutions roles and urban agriculture practice. Cross sectional survey design was adopted on a target population of 440 urban farmers (Eldoret: N=137; Kakamega: N=145; Kisumu: N=158) identified through the assistance of County Agricultural officers in the three towns. A sample size of 205 respondents (Eldoret=63; Kakamega=68; Kisumu=74) was obtained using stratified technique. Questionnaire and Key Informant interviews were used for data collection. Inferential statistics using Pearson Product Moment Correlation Coefficient was used in data analysis. Results showed that the department of agriculture, livestock and fisheries was the most important institution on promotion of urban agriculture in Kisumu (40.0%), Kakamega (42.2%) and Eldoret (64.8%). There was there was a moderate positive correlation (n=205; r =.532; p <.05) between role of county government institutions and UA practices which was statistically significant