SINET: Ethiopian Journal of Science最新文献

{"title":"Electric field induced and enhanced magnetic properties of multiferroic material (BiFeO3)","authors":"A. Mebrahtu","doi":"10.4314/sinet.v45i2.1","DOIUrl":"https://doi.org/10.4314/sinet.v45i2.1","url":null,"abstract":"In this research work, enhancement and induction of magnetization and other related properties of ferro-electromagnet is reported. The ascertained enhancement and induction is supported by the Hamiltonian composed of itinerant electrons, localized electrons, and their mutual interactions. Using double time temperature dependent Green’s function formalism and equation of motion, the study exhibited the effect of external electric field that can induce and enhance the magnetization and other related parameters of the material. The expressions for spin wave energy, magnetization, magnetic susceptibility, and heat capacity of the system have been obtained and influenced by the action of an external electric field. These enhanced and induced functional responses of this material will present an opportunity to create and implement thin film devices that actively couple the magnetic and ferroelectric order parameters. The results obtained in this work are in a good agreement with the previous theoretical and experimental findings.","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133096741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectral problem for the Laplacian and a selfadjoint nonlinear elliptic boundary value problem","authors":"Natnael Gezahegn, Tadesse Abdi","doi":"10.4314/sinet.v45i2.8","DOIUrl":"https://doi.org/10.4314/sinet.v45i2.8","url":null,"abstract":"In this paper, we present some connections between the spectral problem, \u0000−Δu(x) = λ1u(x) in Ω,u(x) = 0 on ∂Ω \u0000and selfadjoint boundary value problem, \u0000Δu(x) − λ1u(x) + g(x, u(x)) = h(x) in Ω,u(x) = 0 on ∂Ω, \u0000where λ1 is the smallest eigenvalue of −∆, Ω ⊆ Rn is a bounded domain, h ∈ L2(Ω) and the nonlinear function g is a Caratheodory function satisfying a growth condition. We initially investigate the existence of solutions for the spectral problem by considering the selfadjoint boundary value problem. The selfadjoint boundary value problem is then considered for both existence and estimation results. We use degree argument in order to show that the selfadjoint boundary value problem has a solution instead of the Landesman-Lazer condition or the monotonocity assumption on the second argument of the function g. \u0000In this paper, we present some connections between the spectral problem, \u0000and selfadjoint boundary value problem, \u0000where λ1 is the smallest eigenvalue of −∆, Ω ⊆ Rn is a bounded domain, h ∈ L2(Ω) and the nonlinear function g is a Caratheodory function satisfying a growth condition. We initially investigate the existence of solutions for the spectral problem by considering the selfadjoint boundary value problem. The selfadjoint boundary value problem is then considered for both existence and estimation results. We use degree argument in order to show that the selfadjoint boundary value problem has a solution instead of the Landesman-Lazer condition or the monotonocity assumption on the second argument of the function g.","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128447902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Population dynamics of the Nile tilapia (Oreochromis niloticus L. 1758) stock in Lake Langeno, Ethiopia","authors":"G. Tesfaye, Gashaw Tesfaye, A. Getahun, Z. Tadesse, Getinet Workiye","doi":"10.4314/sinet.v45i2.5","DOIUrl":"https://doi.org/10.4314/sinet.v45i2.5","url":null,"abstract":"Nile tilapia, Oreochromis niloticus, is a widely distributed and economically most import fish species in Ethiopia. Effective management is essential to sustain their fisheries and the benefits for the local communities. However, little is known about the population dynamics of the Nile tilapia stock in Lake Langeno. Vital parameters of its population were determined using length frequency data collected from 5,949 specimens ranging from 8.5 to 35.7 cm total length (tl). These specimens were collected from August 2017to July 2018. The population parameters were determined using the elefan I routine in FiSAT software. Estimated von Bertalanffy growth parameters were asymptotic length (L∞) = 35.70 cm, growth curvature (K) = 0.32 yr-1, age at length zero (to) = -0.49, and growth performance index (Փ') = 2.61. Instantaneous total mortality (Z), natural mortality (M), and fishing mortality (F) rates were determined from length-converted catch curve and empirical models, respectively, and their values obtained were Z = 2.31 yr-1, M = 0.82 and F =1.56 yr-1, respectively. The exploitation rate (E) of Nile tilapia computed from its mortality rates was 0.67 yr-1, suggesting state of overfishing. The size at first capture (Lc) was estimated at 14.0 cm which is much lower than the size at first maturity (Lm=16.62 cm), which further substantiated the state of overfishing. The results of the study are very useful for fishery managers and scientists who wish to manage and further explore the Nile tilapia stock in Lake Langeno.","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125942496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distribution of benthic macroinvertebrates in relation to physicochemical parameters and macrophyte cover in the Ketar River, Ethiopia","authors":"Yadesa Chibsa, S. Mengistou, D. Kifle","doi":"10.4314/sinet.v45i2.6","DOIUrl":"https://doi.org/10.4314/sinet.v45i2.6","url":null,"abstract":"The aim of this study was to determine the effects of physicochemical parameters and macrophyte on the macroinvertebrate assemblages in the Ketar River, which drains into Lake Ziway. Six sampling sites were selected along the river stretch and samples were collected from December to April 2017/2018 based on the method outlined in Ontario Benthos Biomonitoring Network Protocol Manual. A total of 5,450 individuals comprised of one class, 7 orders, and 23 families were collected during the study period. Hemiptera families were the predominant taxa and contributed the largest percentage of the total samples followed by the Coleoptera. Notonectidae and Corixidae shared the highest total abundance. This study confirmed that the sites covered with macrophytes were significantly different from the substrate both in taxa richness and total abundance (P < 0.05). Redundancy Analysis revealed that pH, Temperature, electric conductivity, DO, NO2, NO3, NH4, SiO2 and TP were the most important variables explaining the variation in macroinvertebrate assemblage patterns. The mean Shannon diversity index also indicated that the sites covered by the macrophyte stand had a significantly higher value than the sites sampled from the substrate, which implies that macrophytes support abundant, and promoting the diversity of macroinvertebrates. Thus, the conservation of macrophytes can enhance the conservation of macroinvertebrates along the course of the river, besides the role of macrophyte in sediment trapping and reducing sedimentation buildup in Lake Ziway.","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123673543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimization of Neochetina eichhorniae Warner and Neochetina bruchi Hustache for the management of water hyacinth, Eichhornia crassipes (Mart.) Solms in the Central Rift Valley lakes through the use of different nutrient levels in Ethiopia","authors":"Tatek Kassu, E. Getu, Diriba Muleta","doi":"10.4314/sinet.v45i2.7","DOIUrl":"https://doi.org/10.4314/sinet.v45i2.7","url":null,"abstract":"Water hyacinth, Eichhornia crassipes (Mart.) Solms, is an alien invasive weed in Ethiopia that has been established in freshwater bodies. Eichhornia crassipes negatively affects water transportation, fishing and biodiversity among others. Hence, implementation of eco-friendly management option such as biological control is a mandatory. The weevils, Neochetina eichhorniae Warner and N. bruchi Hustache, are the principal biocontrol agents against E. crassipes in their native ranges and have been introduced to Ethiopia for the management of the weed. The weevils and their host are affected by the nitrate and phosphate contents of the water body. Thus, this study was conducted to investigate the effect of N. bruchi and N. eichhorniae in relation to water nutrient contents in the management of E. crassipes. The experiment was conducted in a randomized complete block design with three replications in a 4x4x3 factorial arrangement. Eight weeks after the treatments’ application, the population of the weevils and E. crassipes growth parameters were recorded. The larval population was significantly (p < 0.05) affected only by the interaction effect of N. bruchi and the nutrient levels. Among the treatments, the highest mean number of larvae was found on the plants given high and medium nutrient levels. There was also a significant interaction (p < 0.05) between the two weevils adult density. The mean number of emerged adult density of the weevils increased with increasing nutrient levels. The nutrients and weevils exhibited a significant interaction effect on E. crassipes leaf scarring and petiole tunnel. Leaf scarring at the highest weevil density and nutrient level was sixfold greater than that at the lower nutrient level and weevil density. The tunnel length of the weed was threefold higher at the highest nutrient level regardless of the weevil density. The growth parameters of E. crassipes were found to be greater at high nutrient level, except for the mean number of flowers. Conversely, the growth parameters showed a non-uniform trend with the increasing density of the weevils. The current result suggests reduction in E. crassipes could be achieved by lowering the water nutrient levels and use of N. bruchi and N. eichhorniae. \u0000 ","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121617201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrology and geochemistry of bimodal volcanic rocks of Southern Lake Hayk area, northwestern Ethiopian plateau: implication for their petrogenesis","authors":"Getie Berlie, Dereje Dereje, Mohammed A. Assen","doi":"10.4314/sinet.v45i2.3","DOIUrl":"https://doi.org/10.4314/sinet.v45i2.3","url":null,"abstract":"This study presents and integrates field, petrological, and whole-rock geochemical (major and trace elements) data of the volcanic rocks from the Lake Hayk area to understand their petrogenesis. The study area's major lithological components include lower and upper basalt, rhyolitic lava, rhyolitic tuff, rhyolitic ignimbrite, and unwelded tuff. Petrographic analysis suggests that felsic rocks are dominated by quartz and well-developed sanidine (K-feldspar) phenocrysts with glassy groundmass, whereas mafic volcanic products are characterized by aphyric to porphyritic textures with the olivine and plagioclase dominant phenocryst. The area constitutes bimodal composition of flood basaltic to rhyolitic rock with scarce intermediate composition. Basalts have low Rb/Nb = 0.5-0.58, La/Nb = 0.88-1.06 and high TiO2 = 2.08-3.04, basaltic andecite have higher Rb/Nb =2.7, La/Nb = 1.81 and low TiO2= 1.96 and rhyolite Rb/Nb = 0.97-1.69, La/Nb = 0.51-1.08 and lower TiO2 = 0.41- 0.71.The positive Ba and negative K anomalies testify amphibole mantle source. The basalts are characterized by low CaO/Al2O3 ratios (0.71–0.97) and relatively less fractionated and flat hree patterns with (TbN/YbN = 1.75-2.33) chondritic values. This suggests a mantle source mostly containing spinel rather than garnet. Rhyolites are characterized by a steep negative correlation in bivariate plots of MgO, Fe2O3, TiO, and CaO against SiO2 and positive anomaly of Ta with slight Nb trough.  This suggests that Fractional Crystallization is the major process for the genesis of rhyolitic rocks, rather than crustal contribution, partial melting, and assimilation, producing rhyolitic rocks. \u0000 ","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124911876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geographical and population diversity of African honeybees, Apismellifera L. (Hymenoptera: Apidae): A review","authors":"G. Legesse, E. Getu","doi":"10.4314/sinet.v45i2.9","DOIUrl":"https://doi.org/10.4314/sinet.v45i2.9","url":null,"abstract":"This review was prepared to summarize the information on geographic and genetic diversity of Apismellifera L. of African honeybees and the progresses made through time and applications of various advanced tools in their taxonomy at subspecies level. African honeybees have developed distinct morphology, behavior and physiology as they evolved in tropical favorable climate. The variations among the African honeybee populations have helped to produce geographic subspecies based on the morphological characteristics. However, the introduction of molecular taxonomic tools has come up with discrepancies in the number of subspecies and lineages, and subspecies composition of evolutionary lineages in Africa and other parts of the world. It has also brought up controversies in the evolutionary history of A. mellifera reporting different location as the center of origin of the species at different times: Asia, Africa and Europe. It is not only the tools that are used, but also the genetic variations within subspecies, within colonies in an apiary site and within individuals of the same colony temporally are the factors for continually appearing discrepancies. Natural hybridization between populations of adjacent subspecies along the geographic transition zones and introgression of genes through introduction of colonies that is mainly driven by human demand for desirable traits of honeybees have been among the challenges for discrimination of honeybee subspecies. Therefore, in future genetic diversity and taxonomic investigations, considering these natural variations at subspecies level and developing standardized and integrated procedures from sampling to analysis methods would help to produce generally recognized data base that is critically important to resolve the problem of inconsistencies in taxonomy and nomenclature of  honeybee subspecies of Arica and elsewhere. \u0000 ","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127525612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determining regions of higher extinction risk occurrences in South African cycads","authors":"Bamigboye Samuel O.","doi":"10.4314/sinet.v45i1.10","DOIUrl":"https://doi.org/10.4314/sinet.v45i1.10","url":null,"abstract":"Extinction crisis in South African cycads has been very high in recent times. This study used comprehensive distribution records of cycads that occurred in South Africa.  The records obtained from the South African national herbarium named South African National Biodiversity Institute (sanbi) through the herbarium sheets were used to determine the regions of higher extinction crisis in South Africa. The threat status of the herbarium taxa was obtained from iucn 2019 version and was analysed. Threats to these taxa were extracted from iucn and the numbers of taxa facing each threat were determined to unravel the prominent threats. The herbarium records were used to construct a species distribution map for all the cycads in South Africa and another map for Critically Endangered and Extinct South African cycads. This study revealed that regions of high species richness for South African cycads are not the same as regions with highly threatened and extinct South African cycads. Prominent threats found in this plant group are also the major threats causing extinction crisis in the highly threatened and extinct cycads that occurs in few provinces in South Africa. This study therefore recommends that conservation efforts for South African cycads should be intensified in the hotspots of highly threatened and extinct South African cycads identified in this study to further mitigate extinction crisis of South African cycads.","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121530523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"User resistance in post enterprise resource planning implementation phase","authors":"Temtim Assefa Temtim Assefa","doi":"10.4314/sinet.v45i1.4","DOIUrl":"https://doi.org/10.4314/sinet.v45i1.4","url":null,"abstract":"User resistance in post Enterprise Resource Planning (erp) implementation phase is one of the main causes for failure of erp systems. Existing research identified different factors that cause erp failure in the post erp implementation phase. However, existing research is fragmented without strong theoretical base. The main objective of this study is to identify factors that cause user resistance in the post erp implementation phase using innovation resistance theory as a theoretical lens. The study used causal research design as a research method. Data was collected using Google’s online form. The empirical data from this research revealed that risk barriers and usability barriers as main factors that increase user resistance in the post erp implementation phase. The research also developed and validated data collection instruments to use innovation resistance theory for empirical investigation of user resistance in the post erp implementation phase for other researchers. It has also practical implication for managers what intervention to undertake so as to increase success of erp system implementation.","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126244033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Population density, feeding and, reproductive ecology of rodents from Alemsaga Priority State Forest and adjacent farmlands","authors":"B. Takele, Mesele Yihune, A. Bekele","doi":"10.4314/sinet.v45i1.7","DOIUrl":"https://doi.org/10.4314/sinet.v45i1.7","url":null,"abstract":"A study on population density, feeding, and reproductive ecology of rodents from Alemsaga Priority State Forest and the adjacent farmlands was conducted from July 2018-September 2020. Live and snap traps were used for capturing rodents from the study area. The Capture-Mark-Release method was employed to estimate the population size and respective density of rodents. Snap traps were used to capture rodents for body measurement and stomach content analysis. Embryo count was carried out from 64 pregnant females. Data were computed using descriptive statistics and compared with chi-square. Lophuromys simensis, Arvicanthis abyssinicus, Desmomys harringtoni, Mastomys natalensis, Stenocephalemys albipes, Rattus rattus, Arvicanthis dembeensis, Mus musculus, and Acomys cahrinus were recorded from the six habitats. The result indicated that a total of 1140 and 171 individuals were trapped in the study area with live and snap traps, respectively. The average population density of rodents was 47.4 h-1. The highest density was recorded in bushland habitat (75.1 h-l) while the least was in Carissa land (32.2h-l). In terms of species, L. simensis showed the highest density (111.65 h-l) whereas A. cahrinus was the lowest (1.7 ha-1). The overall densities of rodents were 224.82 ha-1 and 162.93 ha-1 during the wet and dry seasons, respectively. The total rodent biomass in the study area was 160,495 g. The number of embryos counted ranged from 4-12 and 2-8 during the wet and dry seasons, respectively. However, there was no statistical significance between the two seasons (χ2 = 0.74, df=1, p> 0.05). Plant matters constituted a higher proportion of stomach contents (64.4%) compared to animal matters (13.2%). Generally, Alemsaga State Forest harbors rodent species with high density and biomass. Proper conservation of the area will contribute to the betterment of species density and biomass.","PeriodicalId":275075,"journal":{"name":"SINET: Ethiopian Journal of Science","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126955445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}