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Search Results: 1 - 10 of 74 matches for " Tsegahun Asfaw "
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Antibiotic Resistant Bacteria from Treated and Untreated Hospital Wastewater at Ayder Referral Hospital, Mekelle, North Ethiopia  [PDF]
Tsegahun Asfaw, Letemichael Negash, Amlsha Kahsay, Yemane Weldu
Advances in Microbiology (AiM) , 2017, DOI: 10.4236/aim.2017.712067
Abstract: The widespread emergence of antibiotic resistance among bacterial pathogens has become one of the most serious challenges in Ethiopia. This study determined the prevalence and drug resistance patterns of bacterial pathogens isolated from treated and untreated wastewater released from Ayder Referral Hospital in Northern Ethiopia. A cross sectional study design was conducted from September-December, 2015 in wastewater released from Ayder referral hospital. A total of 40 composite samples were aseptically collected, transported and processed for enumeration of indicator organisms, bacteriological identification and susceptibility testing following standard procedure. Data obtained were entered and analyzed using SPSS version 20. Mean heterotrophic plate count, total coliform count, fecal coliform count and E. coli count were found to be 1.6 × 106 CFU/mL, 2.2 × 106 CFU/100 mL, 2.0 × 105 CFU/100 mL and 1.1 × 104 CFU/100 mL from treated wastewater respectively. Among the total samples 134 bacterial isolates were detected and [84 (62.7%)] were from untreated wastewater and [50 (37.3%)] were from treated wastewater. The most frequently isolated bacteria from untreated wastewater samples was Klebsiella spp [14 (16.7%)] followed by S. aureus [13 (15.5%)] and P. aeruginosa [12 (14.3%)], similarly in treated wastewater samples Klebsiella spp [10 (20%)], P. aeruginosa [8 (16%)] and S. aureus [8 (16%)] were frequently detected. The overall multi-drug resistance (MDR) in this study was [79/134 (79.1%)]. MDR from untreated wastewater sample was [64/84 (76.2%)] while from treated wastewater sample was [42/50 (84%)] and shows significant difference with (COR: 1.64, 95% CI: 1.15 - 3.29, P: 0.001). It is concluded that treated hospital wastewater contains large numbers of antibiotic resistant bacteria. Therefore, there should be continuous monitoring and evaluation of the effluent quality of the ponds and chlorination of the final effluent should be developed.
Woody Species Diversity and Structure of Agroforestry and Adjacent Land Uses in Dallo Mena District, South-East Ethiopia  [PDF]
Bikila Mengistu, Zebene Asfaw
Natural Resources (NR) , 2016, DOI: 10.4236/nr.2016.710044
Abstract: Sustainable farming practice that utilizes and conserves biodiversity, reducing negative impacts of agriculture on biodiversity and provides wood and energy to local community is a good solution to reduce deforestation and forest degradation. This study was carried out in Dallo Mena district of Bale zone to identify woody species diversity in homegarden agroforestry practices, shade grown coffee agroforestry practices and adjacent natural forest, and to show how land use and management practice determine the plant species diversity. The study site was selected based on spatial analogue approach. In each land use, a plots of 10 m × 10 m size was drown by using systematic sampling method following the transect line. A total of 36 sample plots were sampled along the transect line laid down inside each land uses. In each plot, woody species were counted and the diameter and height of trees and shrubs were measured. Based on this inventory a total of 39 woody plant species which are about 23, 10, 15 woody plant species were recorded from natural forest, shade grown coffee agroforestry and homegarden agroforestry practices respectively. These species were classified belonging to 24 families. The Shannon Wiener diversity index used to estimate species diversity ranged from 0.14 to 2.54 with a mean of 1.47. Also 21% woody species similarities were observed between those three land uses. The result shows that both agroforestry practices (shade grown coffee and home garden agroforestry practices) and adjacent natural forests are conserving several woody species diversity in its system.
Quantification of drought tolerance in Ethiopian common bean varieties  [PDF]
Asrat Asfaw, Matthew W. Blair
Agricultural Sciences (AS) , 2014, DOI: 10.4236/as.2014.52016
Abstract:

Understanding the level of drought tolerance of the varieties available in each country is of paramount importance for breeding common bean for drought adaptation. The goal of this study was to evaluate 25 common bean genotypes of which 24 were released/recommended varieties for production by farmers and one was a drought tolerant check. The genotypes were planted at two sites in Ethiopia, Hawasssa and Amaro, using variable sowing dates, one that was early to avoid drought and one that was late to expose the crop to drought. The experiments were repeated over two years in Hawassa and one year in Amaro. This resulted in treatments with high and low total seasonal rainfall and six environments for analysis. The impact of drought stress on the trait expression of the varieties was not uniform across traits assessed and varieties tested. The effect of drought on photosynthate translocation and partitioning traits was much greater than on yield component traits in the varieties studied. This indicating less breeding efforts has been made in improving the varieties ability to mobilize photosynthate to the developing grain as compared to the yield component traits. Drought tolerant varieties like Hawassa Dume maintained better photosynthate translocation and partitioning than the drought sensitive varieties like Brown Speckled bean. Hawassa Dume also showed better yield stability and performed well under both drought stress and nonstress conditions. Our results indicate the relevance of high levels of photosynthate translocation and partitioning as an effective selection objective for improving drought tolerance in common bean. The information generated on the drought tolerance of the available varieties should help in the design of a breeding strategy that incorporates adaptation traits with commercial characteristics preferred by common bean farmers for varieties to be grown in diverse environments.

Behavior of Bread Wheat (Triticum aestivum L.) Male Sterilized with Cytoplasmic-genetic and Chemical Systems and Their Impact in Hybrid Seed Production
Asfaw Adugna
Asian Journal of Plant Sciences , 2005,
Abstract: In this study the two pollination control systems, i.e. Cytoplasmic Male Sterility (CMS) and the use of Chemical Hybridizing Agents (CHA), were compared to discover their efficiency for the sterility reaction and their impacts in hybrid seed production. The result has shown that both systems were equally effective in their sterility performance. However, CHA resulted in reduced out crossing percentage due to female sterility, germination percentage and hundred seed weight of the hybrid seed due to toxicity. Overall the CMS system was better than the CHA system (based on the particular CHA used in this study) for attributes related to hybrid seed production.
Alternate Approaches in Deploying Genes for Disease Resistance in Crop Plants
Asfaw Adugna
Asian Journal of Plant Sciences , 2004,
Abstract: Plant breeders are much concerned about the durability of the resistance gene(s) that they are incorporating into the better performing backgrounds to tolerate biotic stresses. While resistance that is controlled by a single major gene (vertical resistance) is simple to achieve, the one controlled by poly genes (horizontal resistance) is not. There are a number of ways to make the non-durable resistance genes durable. Comprehensively, the exploitation of genes with known durability, the use of quantitative resistance and the use of gene deployment are suggested to be some of them that can lead to the better ways of achieving durability of resistance. There are also various approaches of deploying genes to achieve durability of resistance. Therefore, to realize durability of disease resistance genes in crop plants any one of the approaches that are dealt in this study can be used without compromising their economic feasibility.
Lateral phase separation of confined membranes
Mesfin Asfaw
Physics , 2010, DOI: 10.1142/S0217979211057864
Abstract: We consider membranes interacting via short, intermediate and long stickers. The effects of the intermediate stickers on the lateral phase separation of the membranes are studied via mean-field approximation. The critical potential depth of the stickers increases in the presence of the intermediate sticker. The lateral phase separation of the membrane thus suppressed by the intermediate stickers. Considering membranes interacting with short and long stickers, the effect of confinement on the phase behavior of the membranes is also investigated analytically.
Modeling an efficient Brownian heat engine
Mesfin Asfaw
Physics , 2008, DOI: 10.1140/epjb/e2008-00308-5
Abstract: We discuss the effect of subdividing the ratchet potential on the performance of a tiny Brownian heat engine that is modeled as a Brownian particle hopping in a viscous medium in a sawtooth potential (with or without load) assisted by alternately placed hot and cold heat baths along its path. We show that the velocity, the efficiency and the coefficient of performance of the refrigerator maximize when the sawtooth potential is subdivided into series of smaller connected barrier series. When the engine operates quasistatically, we analytically show that the efficiency of the engine can not approach the Carnot efficiency and, the coefficient of performance of the refrigerator is always less than the Carnot refrigerator due to the irreversible heat flow via the kinetic energy.
Thermally activated barrier crossing and stochastic resonance of a flexible polymer chain in a piecewise linear bistable potential
Mesfin Asfaw
Physics , 2010, DOI: 10.1103/PhysRevE.82.021111
Abstract: We study the stochastic resonance (SR) of a flexible polymer chain crossing over a piecewise linear bistable potential. The dependence of signal to noise ratio $SNR$ on noise intensity $D$, coupling constant $k$ and polymer length $N$ is studied via two state approximation. We find that the response of signal to the background noise strength is significant at optimum values of $D_{opt}$, $k_{opt}$ and $N_{opt}$ which suggests novel means of manipulating proteins or vesicles. Furthermore, the thermally activated barrier crossing rate $r_{k}$ for the flexible polymer chain is studied. We find that the crossing rate $r_{k}$ exhibits an optimal value at an optimal coupling constant $k_{opt}$; $k_{opt}$ decreases with $N$. As the chain length $N$ increases, the escape rate for the center of mass $r_{k}$ monotonously decreases. On the other hand, the crossing rate for the portion of polymer segment $r_s$ increases and saturates to a constant rate as $N$ steps up.
Thermally activated barrier crossing rate for a coupled system moving in a ratchet potential
Mesfin Asfaw
Physics , 2014,
Abstract: We explore the dependence of the thermally activated barrier crossing rate on various model parameters for a dimer that undergoes a Brownian motion on a piecewise linear bistable potential employing the method of adiabatic elimination of fast variable. By introducing a different model system and approaches than the previous works \cite{c4,c5}, not only we recapture the previous results but we further show that systematic elimination of the fast changing variable leads to an effective Kramers type potential. It is shown that for rigid dimer, the escape rate $R$ monotonously decreases with $k$. On the other hand, in the presence of time varying force, the signal to noise ratio (SNR) attains a pronounced peak at particular barrier height $U_{0}$.
Unbinding transitions of multicomponent membranes and strings
Mesfin Asfaw
Physics , 2007,
Abstract: We present a theory of unbinding transitions for membranes that interact via short and long receptor/ligand bonds. The detail of unbinding behavior of the membranes is governed by the binding energies and concentrations of receptors and ligands. We investigate the unbinding behavior of these membranes with Monte Carlo simulations and via a comparison with strings. We derive the scaling laws for strings analytically. The exact analytic results provide scaling estimate for membranes in the vicinity of the critical point.
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