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OALib Journal期刊

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Assessment of the Levels of Brominated Flame Retardants in Computers and Televisions in Selected Regions of Eritrea  [PDF]
Afewerki Tesfagabr, Tesfamichael Haile, Mussie Sium, Teame Tekleab
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1105061
Abstract:
During recent years, electronic waste (e-waste) around the world is growing at a fast rate and has become a matter of concern due to the presence of toxic brominated flame retardants (BFRs) and certain heavy metals. Currently, in Eritrea there is low awareness on the harmful effects of e-wastes, lack of proper storage facilities and no proper policy and legislative framework related to e-wastes. Thus, in most cases e-wastes still reside in homes, offices, and some are stored with other materials in different places. Therefore, the objective of the present study was to assess the levels of BFRs in obsolete as well as in lately imported computers and televisions using hand held hazardous substances analyzer—Genius 3000 XRF. The survey was done in selected regions of Eritrea and thus a total of 223 samples of computers and TVs from 78 different products were screened. Three readings at forty seconds were conducted for each sample and the average value was calculated. From 173 sampled computers, both oldest and lately imported products, different levels of Br were measured varying from the lowest detectable amount (0.3689 ppm) to the highest (87,821 ppm). Similarly, out of 50 screened old and new models of TVs various levels of Br were determined with minimum detectable level (1.5793 ppm) and highest level (80,916 ppm). The analysis displayed high levels of Br both in the obsolete and lately manufactured products. The concentration of Br didn’t show any consistency either to the product type or manufacturing time. This is a very first preliminary study conducted related to the levels of BFRs in electronic wastes in the country and thus in order to evaluate the environmental impacts and health hazards caused by BFRs and other toxic materials of e-wastes, further study using advanced analytical methods is mandatory.
Simulations of Nitrate Leaching from Sugarcane Farm in Metahara, Ethiopia, Using the LEACHN Model  [PDF]
Haile Arefayne Shishaye
Journal of Water Resource and Protection (JWARP) , 2015, DOI: 10.4236/jwarp.2015.78055
Abstract: Metahara is the largest sugarcane farm in Ethiopia. It produces around 120,000 tons of sugar per year. The farm has been facing some problems such as salinity and sodicity, which has been studied by different experts for several decades. However, the other universal problem of agricultural farms is nitrate leaching loss, which has never been studied in the site, owing to lack of resources and expertise. The amount of nitrate leaching from agricultural farms can be measured directly from drainage rates or estimated by using numerical models. Measurements of drainage flow can be done by using lysimeters, but normally it can be estimated from water balance calculations or from field measurements of hydraulic gradients and hydraulic conductivities. However, in reality, hydraulic conductivity is highly variable and measurements in the field can be very laborious. Moreover, predicting nitrate leaching losses by using numerical models from such data- poor study area is also another problem. Nevertheless, groundwater nitrate concentration of the farm is measured by using the UV screening and distillation methods. Using the experimental results as an input for the model calibration, the amount of nitrate leaching from the farm is predicted for a 47 years of simulation period using the LEACHN model. In this case, both the measured and predicted values of nitrate leaching losses show that there is no nitrate problem in the site. However, even though the likelihood of detecting nitrate contamination in the study area is low, potential anthropogenic nitrogen sources must be carefully managed, for it is better to be safe than regretful.
Learning from the Past for Future Policy: Approaches to Time-series Catch Data Reconstruction
D Tesfamichael, D Pauly
Western Indian Ocean Journal of Marine Science , 2011,
Abstract: Reliable time-series catch and effort data are fundamental for fisheries assessment and management; however, such data are usually not readily available. The Food and Agricultrual Organization (FAO) compiles statistical reports from its member countries, but their reliability is questionable. Several approaches were explored in this study for the reconstruction of time-series catch data using Red Sea fisheries as case studies, starting from 1950. Historical documents, published and unpublished reports, grey literature, databases, surveys, anecdotal information, interviews, and information on processed seafood products were used as sources. When reliable data were available for a number of years, they were used as anchor points to interpolate for missing data, based on transparent assumptions, which use the basic knowledge of the fisheries. Monte Carlo simulations were used to estimate uncertainty in estimates of the means and 95% confidence intervals. The results revealed that actual catches are up to nine times higher than those reported to the FAO. The resulting catch trends provide interesting historical records and important guidance for the development of future fisheries management policies on resource conservation for the benefit of coastal communities.
On-farm storage studies on sorghum and chickpea in Eritrea
A Haile
African Journal of Biotechnology , 2006,
Abstract: On-farm storage studies were conducted in Teraemini, Ashera and Hamelmalo sub-zones in Eritrea during 2004/2005, with the objective of finding the damages caused by storage pests under farmers’ situations. The studies were conducted on chickpea and sorghum and the treatments used were sand, small grain (taff, Eragrostis tef), vegetable oil and chemical (Malathox 1%). Data were collected every month on the number of eggs, number of holes, grain damage, weight loss and germination of the grains. The major storage pests observed during the studies were bruchids (Callosobruchus chinensis L.) on chickpea. Sorghum was attacked in storage by Angoumois grain moth (Sitotroga cerealella), weevils (Sitophilus spp), confused flour beetles (Tribolium spp), saw toothed grain beetles and mites. The populations of these pests were very low in the first three months. However, after three months of storage the population of the pests in all grains and locations increased very fast and caused high damage. The highest grain damages were recorded in the untreated control (check), sand and taff treatments. The weight loss for sorghum and chickpea in the untreated control (check) were 9.17 and 27.51%, respectively. Ash, oil and chemical treatments significantly lowered grain damage and weight loss in all the studies and locations. Ash and edible oils-treated grains had low or no storage pest problems in all the study sites
Analytic solutions of n-th order differential equations at a singular point
Brian Haile
Electronic Journal of Differential Equations , 2002,
Abstract: Necessary and sufficient conditions are be given for the existence of analytic solutions of the nonhomogeneous n-th order differential equation at a singular point. Let $L$ be a linear differential operator with coefficients analytic at zero. If $L^*$ denotes the operator conjugate to $L$, then we will show that the dimension of the kernel of $L$ is equal to the dimension of the kernel of $L^*$. Certain representation theorems from functional analysis will be used to describe the space of linear functionals that contain the kernel of $L^*$. These results will be used to derive a form of the Fredholm Alternative that will establish a link between the solvability of $Ly = g$ at a singular point and the kernel of $L^*$. The relationship between the roots of the indicial equation associated with $Ly=0$ and the kernel of $L^*$ will allow us to show that the kernel of $L^*$ is spanned by a set of polynomials.
A second eigenvalue bound for the Dirichlet Schrodinger equation wtih a radially symmetric potential
Craig Haile
Electronic Journal of Differential Equations , 2000,
Abstract: We study the time-independent Schrodinger equation with radially symmetric potential $k|x|^alpha$, $k ge 0$, $k in mathbb{R}, alpha ge 2$ on a bounded domain $Omega$ in $mathbb{R}^n$, $(n ge 2)$ with Dirichlet boundary conditions. In particular, we compare the eigenvalue $lambda_2(Omega)$ of the operator $-Delta + k |x|^alpha $ on $Omega$ with the eigenvalue $lambda_2(S_1)$ of the same operator $-Delta +kr^alpha$ on a ball $S_1$, where $S_1$ has radius such that the first eigenvalues are the same ($lambda_1(Omega) = lambda_1(S_1)$). The main result is to show $lambda_2(Omega) le lambda_2(S_1)$. We also give an extension of the main result to the case of a more general elliptic eigenvalue problem on a bounded domain $Omega$ with Dirichlet boundary conditions.
Nitrogen in combination with Desmodium intortum effectively suppress Striga asiatica in a sorghum Desmodium intercropping system
Carl Frederick Reinhardt,Niguse Tesfamichael
Journal of Agriculture and Rural Development in the Tropics and Subtropics , 2011,
Abstract: It is well known that the parasitic weed Striga asiatica (L.) Kuntze can be suppressed by Striga-tolerant sorghum (Sorghum bicolor L. Moench) cultivars, Desmodium intortum (Mill.) Urb. (greanleaf desmodium), and by fertilization with nitrogen. The study objective was the assessment of Striga control provided by integration of Desmodium density, timing of sorghum-Desmodium intercrop establishment, and nitrogen fertilization. Growth responses and yield of three sorghum cultivars were measured in three pot experiments. A soil naturally infested with Striga was used, and that part of the soil which served as uninfested control was chemically sterilised. Striga numbers and growth were affected significantly by sorghum cultivars, sorghum-Desmodium intercrop ratios, timing of the sorghum-Desmodium association, as well as by their interactions. Desmodium caused 100% suppression of Striga emergence when Desmodium was established in the 1:3 sorghum-Desmodium ratio at seeding of sorghum. Total control of Striga was also achieved with the 1:1 sorghum-Desmodium ratio when Desmodium was transplanted 30 days before sorghum seeding. However, these two treatments also caused significant reductions in sorghum yield. In contrast, 100% Striga control and a dramatic increase in sorghum yield were achieved with 100 kg N ha^{-1} in the 1:1 sorghum-Desmodium intercrop. Compatibility of sorghum and Desmodium was evident at the 1:1 sorghum-Desmodium intercrop established at sorghum seeding. Overall, the Ethiopian cultivars Meko and Abshir showed better agronomic performance and higher tolerance to Striga than the South African cultivar PAN 8564. It is recommended that the N × Desmodium × sorghum interaction be investigated under field conditions.
Chronic Alcohol Consumption and the Development of Skeletal Fluorosis in a Fluoride Endemic Area of the Ethiopian Rift Valley  [PDF]
Redda Tekle-Haimanot, Gebeyehu Haile
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.62020
Abstract:

This study compared the occurrence of skeletal fluorosis in chronic consumers of locally brewed alcoholic beverages and their matched controls in the Ethiopian Rift Valley. The study revealed that chronic alcohol consumers developed severe forms of crippling skeletal fluorosis quite early in life. The controls were either symptom-free or exhibited mild forms of the fluorosis. The study showed that crippling skeletal fluorosis was directly associated with the large volumes of the locally brewed beer and honey-mead consumption on a daily basis. Chemical analysis of the alcoholic beverages showed that high concentration of fluoride which was much higher than the fluoride in the water was used for the brewing process. From this study one would conclude that in communities residing in high fluoride areas, there should be awareness creation campaigns to point out the relationship of excessive consumption of locally brewed alcoholic drinks and skeletal fluorosis. Regulations should also be put in place to require producers of local alcoholic beverages to use low fluoride water for brewing.

Groundwater Recharge, Evapotranspiration and Surface Runoff Estimation Using WetSpass Modeling Method in Illala Catchment, Northern Ethiopia
A Teklebirhan, N Dessie, G Tesfamichael
Momona Ethiopian Journal of Science , 2012,
Abstract: Hydrometeorological information is important in planning and management of natural resources. The northern Ethiopia in general and Illala sub-basin in particular is lacking reliable information with regard to groundwater recharge, evapotranspiration and surface runoff. The main objective of the study is to estimate the distributed groundwater recharge, surface runoff and evapotranspiration amount of Illala sub basin using WetSpass modeling method. Long term mean hydrometeorological data and physical characteristics of the catchment such as land use/land cover, soil type, topography, groundwater level and slope are used as an input to the model. The mean annual groundwater recharge, evapotranspiration and runoff were found to be 66, 440 and 40mm respectively. Accordingly, recharge accounts for 12% of the precipitation while the rest 81% and 7% becomes evapotranspiration and surface runoff respectively. The study area is characterized by low groundwater recharge due to the presence of high evapotranspiration rate associated with high temperature, dry wind, low rainfall and relative humidity though it is a little bit large compared to some parts of the northern Ethiopia.
Effect of Particle Size on Effective Thermal Conductivity of Nanofluids
Aklilu Tesfamichael Baheta,Abraham D. Woldeyohannes
Asian Journal of Scientific Research , 2013,
Abstract: Experiments have demonstrated that when nanoparticles such Al2O3, Cu, TiO2 are added to traditional heat exchanger working fluids their thermal fluid properties changes. Especially, the effective thermal conductivity of the nanofluids increases. Different empirical models were suggested to predict there effective thermal conductivity based on experimental data. Effective thermal conductivity varies with size, shape, volume fraction of the nanoparticles and thermal conductivities of the particle and base fluid. Hence, this study investigates the effect of nanoparticles size, volume fraction and type of nanoparticles in water based nanofluids. Using interfacial shell concept, the Hamilton and Crosser model was modified to study the nanoparticles size effect. The modified model was compared with literature data and found under predict the effective thermal conductivity but follow the same trend. The result shows that as the nanoparticles size increases the thermal conductivity decreases. Cu water nanofluid gives better thermal conductivity than Al2O3 water nanofluid at a given particle volume fraction.
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