African Journals Online
SINET: Ethiopian Journal of Science

Vol. 24, No. 1 (June 2001)
ABSTRACTS

ON THE EQUATION XY = Z (Y - X2) OVER 
A UNIQUE FACTORIZATION DOMAIN

Yismaw Alemu

Department of Mathematics, Faculty of Science, Addis Ababa University
PO Box 1176, Addis Ababa, Ethiopia, E-mail: [email protected] 


ABSTRACT: The article gives the parametric solutions of xy = z(y - x2) over any unique factorization domain. An application of the obtained characterization to Diophantine equations is demonstrated.


THE EFFICIENCY OF OLS ESTIMATOR IN THE LINEAR
REGRESSION MODEL WITH SPATIALLY CORRELATED ERRORS

Butte Gotu

Department of Statistics, Faculty of Science, Addis Ababa University
PO Box 1176, Addis Ababa, Ethiopia, E-mail: [email protected] 


ABSTRACT: Bounds for the efficiency of ordinary least squares estimator relative to generalized least squares estimator in the linear regression model with first-order spatial error process are given.

Key words/phrases: Efficiency, generalized least squares, ordinary least squares, spatial error process, spatial correlation

GROWTH PERFORMANCE OF CROSSBRED DAIRY CATTLE
AT ASELLA LIVESTOCK FARM, ARSI ETHIOPIA

Abdinasir Ibrahim 1,* and Eskil Brännäng 2

1 Awassa College of Agriculture, PO Box 5, Awassa, Ethiopia

2 Dept of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Box 7023, S-75007 Uppsala, Sweden 


ABSTRACT: Genetic and non-genetic factors affecting growth traits and growth performance at 50% and 75% upgrading levels were studied, in the Arsi highland, Ethiopia. The traits studied were: weight at birth, 6, 12, 18, 24 and 36 months. The analyses were carried out using Harvey's Mixed Model Least-squares and Maximum Likelihood Computer Program. The breed groups compared were: 1/2 Friesian 1/2 Arsi (F1FA), 1/2 Friesian 1/2 Zebu (F1FZ), 1/2 Friesian 1/4 Jersey 1/4 Arsi (F(JxA)), 3/4 Friesian 1/4 Arsi (75%FA) and 3/4 Friesian 1/4 Zebu (75%FZ). The 75% FA were significantly heavier than F1FA at birth, 6 and 30 months. No significant differences were found between F1FZ and 75%FZ at all ages. The differences between F(JxA) and F1FA were not significant except at 6 months. The 75% FA were significantly heavier than the F(JxA) at birth, 30 and 36 months. However, 75% FA were significantly lighter than 75% FZ at 12 and 36 months. No significant effect of sex were observed at birth, though males were slightly heavier. Parity of the dam did not show significant influence on body weight except at birth and 24 months. Year of birth of the calf did not have significant effect except at 12 months. The effect of season of birth was significant at birth and 12 months. Animals born during the main rains were the heaviest at birth. Heritability estimates for weights at birth, 6, 12, 18 and 24 months were: 0.20-0.15, 0.14-0.23, 0.04-0.21, 0.68-0.34 and 0.33-0.29, respectively. From the results obtained, it may be concluded that the management and feeding conditions at Asella Livestock Farm would warrant the limitation of upgrading level to 50% exotic inheritance. The smaller weights for the three-breed crosses, i.e., (F(JxA), may be advantageous to the smallholder, as such animal could be maintained by smallholder farmers as they have lower maintenance requirement as compared to the larger animals.

Key words/phrases: Crossbred, dairy cattle, growth, heritability

SURFACE KINETIC TEMPERATURE MAPPING USING  SATELLITE SPECTRAL DATA IN CENTRAL MAIN  ETHIOPIAN RIFT AND ADJACENT HIGHLANDS

Tenalem Ayenew

Department of Geology and Geophysics, Faculty of Science, Addis Ababa University
PO Box 1176, Addis Ababa, Ethiopia, E-mail: [email protected] 


ABSTRACT: Remotely sensed thermal-infrared spectral data can be used to derive surface temperature of any object if the optical and thermal properties are known. In this study TM band six has been used to assess the spatial variability of the kinetic temperature of the central Ethiopian rift lakes and adjacent highlands. NOAA-AVHRR data have been used to understand the relative differences of the monthly lake surface kinetic temperatures. The result revealed that despite the limited topographic differences of the rift lakes and their proximity, the surface kinetic temperature difference is high, mainly due to groundwater and surface water fluxes. From thermal signature analysis two hot springs below the lake bed of Ziway were discovered. The various hot springs around three of the lakes have limited role in the overall water budget of these lakes as compared to the total surface water and cold groundwater fluxes. Temperature from the land surface shows also large variations with altitude and land cover types. 

Key words/phrases: Kinetic temperature, rift lakes, spectral data, thematic mapper, thermal infra-red


EPITHERMAL GOLD OCCURRENCES IN THE LAKES DISTRICT OF THE MAIN ETHIOPIAN RIFT AND TENDAHO AREA OF THE AFAR RIFT: DISCOVERY OF A METALLOGENIC PROVINCE

Solomon Tadesse

Department of Geology and Geophysics, Faculty of Science, Addis Ababa 
University, PO Box 1176, Addis Ababa, Ethiopia, E-mail: [email protected] 


ABSTRACT: Plio-Quaternary volcanic products cover a large part of the Main Ethiopian Rift (MER). Epithermal gold occurrences related to Quaternary volcanics are at present being closely studied for their precious metal potential. Low sulphidation (Adularia-sericite-type) occurrences have been found. Analyses of 579 core and cutting samples collected for the purpose of exploratory geothermal studies from a number of localities (Gedemsa, Aluto and Corbetti calderas MER, and the Tendaho graben; Afar) were analyzed for gold. The results showed concentration of gold ranging from 100 ppb to 440 ppb. Values ranging between 200 and 300 ppb are very common. The overall characteristics of the known ore occurrences and the evolution of the Quaternary central volcanoes within the MER, and related epithermal processes seem to delineate an individual, homogeneous metallogenic province. A new field of investigation on epithermal ore occurrences which are unusual for the present Ethiopian metallogenic scenery is probably emerging. A study of these phenomena, in light of recent acquisitions in metallogenic knowledge, could be of interest not only for further scientific studies but also for new possibilities in mining activity. This study presents the occurrences of epithermal gold mineralization in the MER, the only one of its kind so far reported in the East African Rift System.

Key words/phrases: Caldera, epithermal gold, metallogeny, Plio-Quaternary, rift volcanics 

Short communication

THE IMPACT OF UNCONTROLLED WASTE DISPOSAL ON SURFACE WATER QUALITY IN ADDIS ABABA, ETHIOPIA

Tamiru Alemayehu

Department of Geology and Geophysics, Faculty of Science, Addis Ababa University PO Box 1176, Addis Ababa, Ethiopia, E-mail: [email protected] 


ABSTRACT: The main threat to the surface water quality in Addis Ababa is environmental pollution derived from domestic and industrial activities. Due to the inadequacy of controlled waste management strategies and waste treatment plants, people are forced to discharge wastes both on open surface and within water bodies. Uncontrolled (improper) waste disposal has deteriorated the quality of surface water (streams, rivers, reservoirs) by changing the chemical, physical and organoleptic properties of water. Chemical analyses of surface and shallow groundwater samples taken at various points along streams and different springs show that the level of unwanted chemical constituents such as nitrate and chromium, for example, are higher than the background level. Among the main causes are poor economy and lack of proper waste disposal systems that lead the residents to dump wastes illegally within the water bodies. Important measures to alleviate the problem are to develop the environmental awareness of the residents, proper control on industries, establishment of a widespread waste collection system and improved landfill technology.

Key words/phrases: Addis Ababa, Akaki river, toxic substances, uncontrolled waste disposal, water quality 

Short communication

TEST OF ENDOTHELIAL MONOLAYER INTEGRITY IN THE PRESENCE OR ABSENCE OF ENDOTOXIN AND ANTI-TNF-a MONOCLONAL ANTIBODIES

Andualem Mossie 1, Stefan Eriksson 2, 
Hassen Taha Sherief 3,** and Legesse Zerihun 3

1 Department of Physiology, Jimma Health Science Institute 
PO Box 378, Jimma, Ethiopia

2 Department of Physiology and Pharmacology, Karolinska Institute
Post address 171 77, Stockholm, Sweden

3 Department of Physiology, Faculty of Medicine
PO Box 9086, Addis Ababa, Ethiopia


ABSTRACT: Monolayer cultures of human umbilical vein endothelial cells were established and tested for the effects of endotoxin treatment and anti-TNF-a monoclonal antibodies following endotoxin treatment on albumin permeability and electrical conductance. Application of 40 -g(ml)-1 of endotoxin on human umbilical cord endothelial cell culture monolayer increased transendothelial albumin permeability significantly (P<0.001) and decreased transendothelial electrical resistances significantly (P<0.001). When 10 -g(ml)-1 of anti-TNF-a monoclonal antibodies was added after endotoxin, the effects of the latter on albumin permeability and electrical resistance were significantly decreased (P<0.001). This suggested that the monolayer sheet can be disturbed by endotoxin-induced TNF-a from endothelial cells. TNF-a can disintegrate the endothelial cell monolayer during septicemia. This can be abrogated using anti-TNF-a monoclonal antibodies.

Key words/phrases: Anti-TNF-a monoclonal antibodies, electrical resistance, endothelial monolayer, endotoxin, permeability


Short communication

THE SYNERGISTIC EFFECTS OF METARHIZIUM ANISOPLIAE (METSCHIKOFF) WITH THE ACYL UREA INSECTICIDES TEFLUBENZURON AND DIFLUBENZURON FOR SCHISTOCERCA GREGARIA (ORTHOPTERA: ACRIDIDAE)

Emiru Seyoum

Department of Biology, Faculty of Science, Addis Ababa University
PO Box 1176, Addis Ababa, Ethiopia, E-mail: [email protected] 


ABSTRACT: The acyl urea insecticide teflubenzuron (=Nomolt -) caused loss of appetite, ecdysial failure and eventual death in 4th instar Schistocerca gregaria. The entomopathogenic fungus Metarhizium anisopliae also caused mortality due to mycosis among nymphs of the locust. Enhanced mortality occurred following dual application of the growth regulator and the fungus, which at one combination was synergistic. In another experiment, the fungus was exposed to cuticle treated with acetone (the carrier for the insecticide). This reduced the effectiveness of the fungus. An ultrastructural study showed the effect of the joint application of another acyl urea diflubenzuron (= Dimlin-) and Metarhizium anisopliae on locust cuticle. Disruption of the lamellae pattern was observed in some areas of cuticle. This is consistent with localised disruption of chitin synthesized during treatment with Dimlin. This compound, that has a short half-life in the locust, was applied to the food at 5 day interval over a 15 day period. Clearing zones in the cuticle around penetrant hyphae suggested action of cuticle degrading fungal enzymes. These zones were more extensive around gyphae in Dimlin-affected cuticle suggesting possible enhanced hydrolysis of cuticle protein by fungal proteases in the absence of chitin.

Key words/phrases: Diflubenzuron, Metarhizium anisopliae, Schistocerca gregaria, teflubenzuron 

Feature article

LAKE AFDERA: A THREATENED SALINE LAKE IN ETHIOPIA

Abebe Getahun

Department of Biology, Faculty of Science, Addis Ababa University
PO Box 1176, Addis Ababa, Ethiopia, E-mail: [email protected] 


ABSTRACT: Lake Afdera is a saline lake located in the Afar region, Northern Ethiopia. Because of its inaccessibility it is one of the least studied lakes of the country. It supports life including three species of fish of which two are endemic. Recently, reports are coming out that this lake is used for salt extraction. This paper gives some insight on the most probable dangers on the ecology of the lake if such activity is allowed to take place before environmental impact assessment was conducted.

Key words/phrases: Afdera, conservation, Ethiopia, fishes, saline lake 

Feature article

TWIN CARBON ARC TORCH

David A. Skelskey

Don Bosco Technical School, PO Box 8, Makelle, Ethiopia


ABSTRACT: A simple twin carbon arc torch has been manufactured for the developing world from local materials and applied to brazing and heating in order to offer an alternative to the much more expensive oxyacetylene torch and to the usually environmentally degrading use of charcoal.

Key words/phrases: Arc, brazing, carbon electrode, plasma, torch