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Applicability of Gravity Separation Method on the Ashashire Gold Ore Deposit from Benishangul Gumuz Region, Western Ethiopia

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International Journal of Nonferrous Metallurgy 2024年第2期11卷 21-31页

作者： Misganu Kabeta Mulugeta Sisay Cheru Goitom Gebreyohannes Berhe School of Chemical and Bio Engineering Center for Ethio-Mines Development AAiT Addis Ababa University Addis Ababa Ethiopia Mineral Industry Development Institute Ministry of Mines Addis Ababa Ethiopia School of Materials Science and Engineering Jimma Institute of Technology Jimma University Jimma Ethiopia College of Natural and Computational Sciences Mekelle University Mekelle Ethiopia

The study was conducted to determine the applicability of gravity separation method on the Ashashire gold ore deposit Benishangul gumuz region, western Ethiopia. The Ashashire composite was produced to provide sufficient mass for this study and experiment, including sample preparation, mineralogical analysis of gold and associated elements, gravity concentration, and data interpretation and analysis. During the study, a grind optimization was conducted on the composites sample with varying grind size to evaluate the effect of grind size on gold recovery. The ore was moderately ground to the standard grind size of 80%, passing 106 µm, 75 µm, 53 µm and this nominal size was selected for the preliminary assessment for concentration optimization for this deposit. The gravity testing comprised three-stage concentration using Knelson concentrator. High recovery of gold from the gravity concentrates was achieved from the second gravity concentration. Based on the laboratory experimental result analysis, a grind size of P80 75 µm is selected as optimal size for the Ashashire gold deposit. Increasing the grind size from P80 of 75 µm to 106 µm decreases the recovery rate from 75% to 54%, or decreasing the grind size from P80 of 75 µm to 53 µm decreases the gold recovery rate to 37%. The native gold grain in the ores is mostly associated with quartz and fine gold is closely associated with pyrite. According to analysis of the fire assay, chemical, and mineralogical data, only gold and telluride is commercially valuable elements in the ores. Predominantly gold was occurred in the native form of Au-Te. The sample subjected to gravity separation assayed about 2.6 g/t Au.

关键词： Ore Gangue Ashashire Gravity Method Gold Telluride Concentration Knelson

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Prevalence and associated risk factors for Salmonella enterica contamination of cow milk and cottage cheese in Ethiopia

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Food Safety and Risk 2023年第1期10卷 1-11页

作者： Bedassa, Abdi Nahusenay, Henok Asefa, Zerihun Sisay, Tesfaye Girmay, Gebrerufael Kovac, Jasna Vipham, Jessie L. Zewdu, Ashagrie Ethiopian Institute of Agricultural Research National Agricultural Biotechnology Research Center PO Box 249 Holeta Ethiopia Ethiopian Institute of Agricultural Research Megenagna Near Egziarab Church P.O.Box: 2003 Addis Ababa Ethiopia Ethiopian Institute of Agricultural Research Holeta Agricultural Research Centre PO Box 031 Holeta Ethiopia Institute of Biotechnology College of Natural and Computational Sciences New Graduate Building Addis Ababa University P.O. Box 1176 Addis Ababa Ethiopia Department of Food Science The Pennsylvania State University 437 Erickson Food Science Building University Park State College 16802 PA United States Department of Animal Sciences and Industry Kansas State University 247 Weber Hall Manhattan 66506 KS United States Center for Food Science and Nutrition Addis Ababa University New Graduate Building College of Natural Sciences P.O. Box 1176 Addis Ababa Ethiopia

Animal sourced foods, such as dairy products, are common sources of Salmonella enterica, a foodborne pathogen of increasing global concern, particularly in developing countries. In Ethiopia, most data on the prevalence of Salmonella in dairy products is highly varied and limited to a specific region or district. Furthermore, there is no data available on the risk factors for Salmonella contamination of cow milk and cottage cheese in Ethiopia. This study was therefore conducted to determine the presence of Salmonella throughout the Ethiopian dairy value chain and to identify risk factors for contamination with Salmonella. The study was carried out in three regions of Ethiopia, including Oromia, Southern Nations, Nationalities and Peoples, and Amhara during a dry season. A total 912 samples were collected from milk producers, collectors, processors, and retailers. Samples were tested for Salmonella using the ISO 6579-1: 2008 method, followed by PCR confirmation. Concurrent with sample collection, a survey was administered to study participants to identify risk factors associated with Salmonella contamination. Salmonella contamination was highest in raw milk samples at the production (19.7%) and at milk collection (21.3%) levels. No significant difference in the prevalence of Salmonella contamination among regions was detected (p > 0.05). Regional differences were apparent for cottage cheese, with the highest prevalence being in Oromia (6.3%). Identified risk factors included the temperature of water used for cow udder washing, the practice of mixing milk lots, the type of milk container, use of refrigeration, and milk filtration. These identified factors can be leveraged to develop targeted intervention strategies aimed at reducing the prevalence of Salmonella in milk and cottage cheese in Ethiopia. © 2023, The Author(s).

关键词： Cottage cheese Pasteurized milk Raw milk Risk factors Salmonella enterica

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Development of Suitable Magnetite–Diatomite Nanocomposite for Cd (Ii) Adsorptive Removal from Wastewater

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SSRN 2023年

作者： Lemessa Gusu, Gemechu Africa Center of Excellence for Water Management College of Natural and Computational Sciences Addis Ababa University Addis Ababa Ethiopia College of Natural and Computational Science Wollega University Nekemte Ethiopia

In this study, suitable nanocomposite materials were synthesized form magnetite precursor and diatomite via co-precipitation method. The efficiency of the materials in adsorbing Cd(II) from aqueous solutions was investigated in a batch experimental system. The physicochemical characteristics of the adsorbent were investigated through FTIR, XRD, BET, SEM-EDX, and VSM measurements. Box-Behnken design (BBD) was employed to optimize the most significant adsorption variables;initial pH, adsorbent dose (g), initial (Cd(II) concentration (mg), and contact time (min). Under the optimized conditions, a maximum adsorption capacity of 31.44 mg/g and a Cd(II) removal efficiency of 98.94 % were achieved. Isotherm studies indicated that the Temkin model provided the best fit for adsorption equilibrium compared to other models. In addition, the kinetic adsorption studies revealed that the pseudo-second-order model is the best fit model for the adsorption kinetic data. Moreover, thermodynamic studies suggested that the uptake of Cd (II) was exothermic and spontaneous under standard conditions. Furthermore, the magnetite-diatomite nanocomposite adsorbents exhibited good reusability and could be easily separated from the solution using an external magnet for recycling purposes. About 80 % of Cd(II) recovery was achieved when using HNO3 desorbing agents. This study demonstrates promising potential of magnetite-diatomite nanocomposite as a viable solution for remediation of Cd(II) contamination in diverse wastewater treatment scenarios. © 2023, The Authors. All rights reserved.

关键词： Nanocomposites

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BiVO4-Decorated Graphite Felt as Highly Efficient Negative Electrode for All-Vanadium Redox Flow Batteries

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ACS Applied Energy Materials 2023年第6期6卷 3301-3311页

作者： Kabtamu, Daniel Manaye Li, Yu-Zhen Bayeh, Anteneh Wodaje Ou, Yun-Ting Huang, Zih-Jhong Chiang, Tai-Chin Huang, Hsin-Chih Wang, Chen-Hao Department of Materials Science and Engineering National Taiwan University of Science and Technology Taipei106335 Taiwan Department of Chemistry Debre Berhan University Po. Box 445 Debre Berhan Ethiopia King George VI Street Addis Ababa1000 Ethiopia King George VI Street Addis Ababa1000 Ethiopia Global Development Engineering Program National Taiwan University of Science and Technology Taipei106335 Taiwan Research Center National Cheng Kung University Tainan70101 Taiwan Advanced Manufacturing Research Center National Taiwan University of Science and Technology Taipei106335 Taiwan

Recently, discovering high-performance electrocatalytic materials for vanadium redox flow batteries (VRFBs) has been one of the most crucial tasks. This paper details the successful fabrication of a low-cost platelike bismuth vanadate (BiVO4) material through a simple one-step hydrothermal route, employed as an electrocatalyst to adorn graphite felt (GF) for use as the negative electrode in VRFBs. The experimental results show that BiVO4-3h exhibits the optimal electrocatalytic activity and reversibility for the vanadium redox couples among all samples. The energy efficiency of the VRFB cell assembled with BiVO4-decorated GF as the negative electrode is found to be 75.42% at 100 mA cm-2, which is about 10.24% more efficient than that of the cell assembled with a heat-treated graphite felt (HT-GF) electrode. The possible reasons for the activity enhancement can be ascribed to the existence of oxygen vacancies in the BiVO4 lattice structure and the relatively high surface area of BiVO4, which provide more active sites for facilitating the vanadium redox reactions. Furthermore, the BiVO4-GF electrode obstructs the competitive irreversible hydrogen evolution reaction on the negative side of the cell, and it also has better wettability. Impressively, BiVO4-GF as the negative electrode shows good stability over 100 cycles. © 2023 American Chemical Society.

关键词： Electrocatalysts

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Petrogenesis and geotectonic setting of Berguda granitoids of Neoproterozoic Burji-Finchawa granite-gneiss complex, southern Ethiopia: implication for the cessation of subduction control magmatism in East African Orogeny

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Arabian Journal of Geosciences 2022年第8期15卷 1-16页

作者： Chekol, Takele Meshesha, Daniel Bululta, Utura Department of Geology College of Applied Science Addis Ababa Science and Technology University Addis Ababa Ethiopia Mineral Exploration Extraction and Processing Center of Excellence Addis Ababa Science and Technology University Addis Ababa Ethiopia Present Address: Geology Department College of Natural and Computational Science Bule Hora University Bule Hora Ethiopia

Major and trace element data are presented for Berguda granitoids within the Neoproterozoic basement rocks of southern Ethiopia, East African Orogeny. Geochemical and petrological constrains indicate the presence of two distinct types of granitoid rocks: (1) Wolena Bokosa granitoid (WBG) and (2) Hida Korma granitoid (HKG). WBG is granite in composition with high SiO2 content (73.38–79.38 wt.%) and wider Al2O3 values (10.68–14.81 wt.%). It has relatively high molecular values (ASI = 0.99–1.05) with low contents of CaO, MgO, Fe2O3, TiO2, and P2O5. WBG is shoshonitic to high-k calc-alkaline, Al-rich metaluminous, and more felsic I-type granitoid, whereas HKG is quartz-monzonite in composition (SiO2 = 65.31–68.26) with relatively low molecular values (ASI = 0.86–0.96) with high contents of CaO, MgO, Fe2O3, TiO2, and P2O5. HKG is also shoshonitic to high-k calc-alkaline, metaluminous, and more mafic I-type granitoid. The observed positive anomalies in Rb, Th, K, Pb, and Zr and negative anomalies of Sr, P, Ti, Nb, and Ta in both groups reflect the involvements of crustal materials in their petrogenesis. In terms of geodynamic setting, WBG is classified as volcanic arc (VAG) and syn-collisional (syn-COLG) granite and inferred as syn-orogenic, whereas the HKG is classified as within-plate granite (WPG) with post-orogenic emplacement. Furthermore, this study infers that the transition from syn-orogenic calcic-alkalic WBG to alkalic HKG magmatism is marking the cessation of subduction control magmatism of the East African Orogeny (EAO) at about 529 ± 11 Ma. The continuation of the magmatism after the cessation of subduction control magmatism is shown by emplacement of more alkalic post-orogenic HKG with volcanic arc chemical affinities possibly the effect of previous subduction process.

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Construction of Morpheme-Based Amharic Stopword List for Information Retrieval System 8th

Construction of Morpheme-Based Amharic Stopword List for Inf...

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8th EAI International Conference on Advancement of science and Technology, ICAST 2020

作者： Yeshambel, Tilahun Mothe, Josiane Assabie, Yaregal IT PhD Program Addis Ababa University Addis Ababa Ethiopia INSPE Univ. de Toulouse IRIT UMR5505 CNRS Toulouse France Department of Computer Science Addis Ababa University Addis Ababa Ethiopia

ISBN: (纸本)9783030806200

One of the major forms of pre-processing in information retrieval and many other text processing applications is filtering out stopwords. They are ignored by many retrieval systems during indexing and retrieval in order to enhance retrieval effectiveness and efficiency. The aim of this paper is to present the construction of morpheme-based Amharic stopwords and investigate their effect on information retrieval tasks. The stopword list is constructed based on the semantics of Amharic words and corpus statistics: frequency, mean, variance, and entropy parameters. The stopword list is evaluated using Lemur on Amharic information retrieval test collection. Removal of stopwords has shown significant impact on retrieval effectiveness, size of index and term weighting of non-stopwords. On the other hand, their presence in index and query negatively affects the retrieval effectiveness of Amharic retrieval system. The average precisions of retrieving with and without stopwords using language modeling on root-based approach are 0.24 and 0.70, respectively. © 2021, ICST Institute for Computer sciences, Social Informatics and Telecommunications Engineering.

关键词： Semantics

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Evaluation of Corpora, Resources and Tools for Amharic Information Retrieval 8th

Evaluation of Corpora, Resources and Tools for Amharic Infor...

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8th EAI International Conference on Advancement of science and Technology, ICAST 2020

ISBN: (纸本)9783030806200

Amharic is the working language of Ethiopia. It is the second-most commonly spoken Semitic language in the world next to Arabic. Amharic is morphologically complex and under-resourced, which poses tremendous challenges for natural language processing. The development of fully functional Amharic text processing applications is a non-trivial task for researchers and developers. Despite attempts to develop some applications, lack of standards in corpus collection and resource development resulted in the problem of interoperability. The aim of this paper is to present and evaluate the accessibility of Amharic corpora, resources and tools with the purpose of highlighting the status of Amharic language processing applications. We present available resources and linguistic tools, assess their usability and effectiveness, investigate the implications of the morphological complexity and put the way forward in the development of Amharic text processing applications. © 2021, ICST Institute for Computer sciences, Social Informatics and Telecommunications Engineering.

关键词： Text processing

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Investigation of Paper Based Microfluidic Analytical Device (Μpad) Using Bees Wax Printing for Quantitative Colorimetric Determination of Paracetamol (N-4-Hydroxyphenylacetamide) in Water Sample;Optimization Using Response Surface Methodology and Method Validation

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SSRN 2022年

作者： Nur, Nejat Mohammed Hussien, Ahmed MOHAMMED Solomon, Feleke Zewge Addis Ababa University Addis Ababa Ethiopia Department of Chemistry College of Natural and Computational Sciences Dire Dawa University Dire Dawa Ethiopia Center for Environmental Science College of Natural and Computational Sciences Addis Ababa University Addis Ababa Ethiopia Department of Chemistry College of Natural and Computational Sciences Addis Ababa University Addis Ababa Ethiopia

The detection and quantification of pharmaceutical compounds in various environmental matrices is still a challenge and difficult task because of pharmaceutical compounds are present in a very low quantities (ng- μg), and there are not yet any analytical methods that are rapid, cost effective and portable. The purpose of this study was to develop a paper based microfluidic analytical devices (μPADs) using bees wax printing method for the detection of paracetamol in water sample. Independent parameters (reaction time, concentration, reagent volume, length of channel) were optimized using response surface methodology based on the central composite design. Quadratic model was used to predict the efficiency of the μPADs. Sample solution containing paracetamol was determined quantitatively by the prepared μPADs with the support of image J software. μPADs showed successful detection of paracetamol in water sample from 1ppm to 5ppm with mean intensity ranges from 95.6 to 107.9 pixel. The maximum efficiency of detection was achieved, at a 5ppm sample concentration(A), 10 μL reagent volume (B), 10 min reaction time(C), and 2.01cm channel length(D) optimum conditions with 0.970 desirability. The limits of detection for paracetamol were 0.26 µg L−1. μPADs showed good linearity (R2 = 0.9955), accuracy (98.35-103.64), reproducibility (5-1), repeatability (3-0.01) limit of quantification (0.858) comparable to ICH guide line. Therefore, this study clearly demonstrated the promising of μPADs for quantitative colorimetric detection of paracetamol in water sample. © 2022, The Authors. All rights reserved.

关键词： Microfluidics

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Urinary 8-OHdG level is not affected by geography and trace elements in nail of residents of addis ababa: It is shaped by interactions between different social factors

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Toxicology Reports 2022年 9卷 1777-1787页

作者： Dessie, Bitew K. Mehari, Bewketu Tefera, Molla Osman, Mahlet Tsegaye, Yosef Gari, Sirak Robele Desta, Adey F. Melaku, Samuel Alamirew, Tena Goodson, Michaela L. Walsh, Claire L. Zeleke, Gete Mihret, Adane Ethiopian Institute of Water Resources Addis Ababa University Ethiopia Water and Land Resource Centre Addis Ababa University Addis Ababa Ethiopia College of Natural and Computational Sciences University of Gondar P.O.Box 196 Gondar Ethiopia Armauer Hansen Research Institute Addis Ababa Ethiopia Department of Microbial Cellular and Molecular Biology Addis Ababa University Ethiopia Department of Medical Laboratory Science Wollega University Ethiopia Department of Chemistry Columbus State University 4225 University Avenue Columbus 31907 GA United States Newcastle University Medicine Malaysia Johor Iskandar Puteri 79200 Malaysia School of Engineering Newcastle University Newcastle upon Tyne NE1 7RU United Kingdom

The objective of this study was to evaluate the association between exposure to heavy metals and oxidative DNA damage among residents living in the potentially more polluted downstream (Akaki-Kality) area of addis ababa, in comparison to the upstream area (Gullele). For this, 8-hydroxy-2′-deoxyguanosine (8-OHdG) was used as a biomarker for oxidative DNA damage and heavy metals (Fe, Zn, Mn, Cu, Ni, Cr, Pb, As) as indicators of exposure. The concentrations of heavy metals in nails were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES), and 8-OHdG in urine using Enzyme-Linked with Immunosorbent Assay (ELISA), from 95 residents of the two areas, upstream and downstream. The urinary 8-OHdG concentration was not significantly different (p = 0.05) between the two Sub-Cities, with mean of 18.50 ± 4.37 ng/mg Creatinine in Akaki-Kality and 17.30 ± 5.83 ng/mg Creatinine in Gullele. Also, there were no statistically significant (p = 0.05) difference among the different demographic groups according to gender, age, educational status, body mass index or habit of alcohol consumption. However, the interactions of sex with age, sex with alcohol consumption and alcohol consumption with education were found to affect the urinary 8-OHdG levels of residents of the two Sub-Cities. The mean concentrations (µg/g) of the elements were 488 and 1035 for Fe, 106 and 251 for Zn, 13.0 and 31.2 for Mn, 5.23 and 6.63 for Cu, 11.2 and 7.39 for Ni, 2.23 and 2.02 for Cr, 0.09 and 0.63 for Pb;and 0.16 and 0.25 for As, in nail samples from Akaki-Kality and Gullele, respectively. The determined concentrations of the heavy metals in nails were not significantly associated (p = 0.05) with the corresponding urinary levels of 8-OHdG. Hence, the observed 8-OHdG might have been caused by environmental exposure to toxic substances other than the analyzed heavy metals. © 2022

关键词： 8-OHdG addis ababa ELISA ICP-OES Oxidative DNA damage Trace element

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Antioxidant Activity of Flavonoids and Phenolic Acids from Dodonaea angustifolia Flower: HPLC Profile and PASS Prediction

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Journal of Chemistry 2023年第1期2023卷

作者： Tessema, Fekade Beshah Gonfa, Yilma Hunde Asfaw, Tilahun Belayneh Tadesse, Mesfin Getachew Bachheti, Rakesh Kumar Department of Industrial Chemistry Addis Ababa Science and Technology University Addis Ababa Ethiopia Department of Chemistry Faculty of Natural and Computational Science Woldia University Woldia Ethiopia Department of Chemistry Faculty of Natural and Computational Science Ambo University Ambo Ethiopia Department of Chemistry College of Natural and Computational Science Gondar University Gondar Ethiopia Centre of Excellence in Biotechnology and Bioprocess Addis Ababa Science and Technology University Addis Ababa Ethiopia

Background. Dodonaea angustifolia is a known medicinal plant across East Arica. The flower of D. angustifolia is not well investigated in terms of phytochemistry and biological activities. This study aims to investigate the presence of flavonoids and phenolic acids in the flower of D. angustifolia and its antioxidant activity. Methods. Preliminary phytochemical screening was carried out using the standard protocols. Antioxidant activity evaluation using DPPH assay and total phenol content (TPC) and total flavonoid content (TFC) determinations in the flower extract were compared with the values of the leaf extract. UHPLC-DAD analysis was managed to develop the profile of the flower extract. Prediction of biological activity spectra for substances (PASS) was done using an online server for antioxidant and related activities. Results. Preliminary phytochemical screening and TPC and TFC values confirmed the presence of flavonoids and phenolic acids. From the HPLC analysis of flavonoids, quercetin, myricetin, rutin, and phenolic acids such as chlorogenic acid, gallic acid, and syringic acid were detected and quantified. The biological activity spectrum was predicted for the detected and quantified polyphenols. Conclusions. D. angustifolia flower is a rich source of flavonoids and phenolic acids, which are extractable and can be checked for further biological activity. It was possible to identify and quantify phenolic compounds through HPLC analysis in the methanol extract of D. angustifolia flower. The PASS biological activity prediction results showed that there were stronger antioxidant activities for the identified flavonoids. Future work will emphasize the isolation and characterization of active principles responsible for bioactivity. © 2023 Fekade Beshah Tessema et al.

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