116 research outputs found
Adverse birth outcome: a comparative analysis between cesarean section and vaginal delivery at Felegehiwot Referral Hospital, Northwest Ethiopia: a retrospective record review [Corrigendum]
No full textAbebe Eyowas F, Negasi AK, Aynalem GE, Worku AG. Pediatric Health, Medicine and Therapeutics. 2016;7:65–70On page 65 Abel Fekadu Dadi should have been listed as an author. The incorrect author list was:Fantu Abebe Eyowas1Ashebir Kidane Negasi1Gizachew Eyassu Aynalem1Abebaw Gebeyehu Worku2The correct author list should have been:Fantu Abebe Eyowas1Ashebir Kidane Negasi1Gizachew Eyassu Aynalem1Abebaw Gebeyehu Worku2Abel Fekadu Dadi2Read the original articl
Flexible two-piece distributions for right censored survival data
No full textAn important complexity in censored data is that only partial information on the variables of interest is observed. In recent years, a large family of asymmetric distributions and maximum likelihood estimation for the parameters in that family has been studied, in the complete data case. In this paper, we exploit the appealing family of quantile-based asymmetric distributions to obtain flexible distributions for modelling right censored survival data. The flexible distributions can be generated using a variety of symmetric distributions and monotonic link functions. The interesting feature of this family is that the location parameter coincides with an index-parameter quantile of the distribution. This family is also suitable to characterize different shapes of the hazard function (constant, increasing, decreasing, bathtub and upside-down bathtub or unimodal shapes). Statistical inference is done for the whole family of distributions. The parameter estimation is carried out by optimizing a non-differentiable likelihood function. The asymptotic properties of the estimators are established. The finite-sample performance of the proposed method and the impact of censorship are investigated via simulations. Finally, the methodology is illustrated on two real data examples (times to weaning in breast-fed data and German Breast Cancer data).sponsorship: The authors are grateful to the editor, and associate editor and reviewers for their valuable comments that led to an improvement of the manuscript. The second author gratefully acknowledge support from Research Grant FWO G0D6619N of the Flemish Science Foundation, and from the C16/20/002 project of the Research Fund KU Leuven. (Flemish Science Foundation|FWO G0D6619N, Research Fund KU Leuven|C16/20/002)status: Published onlin
A hybrid hazard-based model using two-piece distributions
No full textCox proportional hazards model is widely used to study the relationship between the survival time of an event and covariates. Its primary objective is parameter estimation assuming a constant relative hazard throughout the entire follow-up time. The baseline hazard is thus treated as a nuisance parameter. However, if the interest is to predict possible outcomes like specific quantiles of the distribution (e.g. median survival time), survival and hazard functions, it may be more convenient to use a parametric baseline distribution. Such a parametric model should however be flexible enough to allow for various shapes of e.g. the hazard function. In this paper we propose flexible hazard-based models for right censored data using a large class of two-piece asymmetric baseline distributions. The effect of covariates is characterized through timescale changes on hazard progression and on the relative hazard ratio; and can take three possible functional forms: parametric, semi-parametric (partly linear) and non-parametric. In the first case, the usual full likelihood estimation method is applied. In the semi-parametric and non-parametric settings a general profile (local) likelihood estimation approach is proposed. An extensive simulation study investigates the finite-sample performances of the proposed method. Its use in data analysis is illustrated in real data examples.The authors thank the reviewers for their valuable comments that led to an improvement
of the manuscript. The second author gratefully acknowledges support from Research Grant C16/20/002
project of the Research Fund KU Leuven
Stingless bee Meliponula Cockerell (Hymenoptera: Apidae: Meliponini) ground nest architecture and traditional knowledge on the use of honey in the Amhara Region, Northwest Ethiopia
No full textStingless bees constitute an important component of tropical ecosystems. The present study reports on the ground nest architecture of the Meliponula stingless bees, impact of agricultural activities on the stingless bee population and traditional use of stingless bee honey in three districts—Wegera, Libo Kemkem and Alepha—of the Amhara Region, Ethiopia. The ground nests were located with the help of indigenous knowledge. The parameters of the Meliponula ground nests were measured and compared with published data. The impact of agricultural activities and the use of stingless bee honey (locally known as tazima or tazma mar) in ethnomedicine were documented through interviewing local communities and briefly discussed. It has been noted that stingless bee honey is used locally as a treatment for both infectious and non-infectious conditions and as an effective pain-relief measure. However, the stingless bee populations in the Amhara Region are endangered by traditional agricultural practices and habitat destruction. It has been suggested that development of appropriate meliponiculture technology is most essential to conserve the stingless bee diversity in Ethiopia and to effectively utilize their honey for human benefit.
አብስትራክትንቦች ለሞቃታማ ሥነ ምህዳሮች ሙሉነት አስፈላጊ አካል ናቸው፡፡ የዚሀ ጥናት ዓላማ የሚያተኩርው የግብርና ሥራዎች እና በባህላዊ መንገድ የጣዝማ ማር አሰባስብ ዘዴ የሚያሳድረው ተጽዕኖ የመሬት ቅርፊት ሥነ-ሕንፃ ሰርተው በሚኖሩ ንቦች ላይ በተለይም በኢትዮጵያ፤ በአማራ ክልል በሚገኙ ሦስት ወረዳዎች ፦ ወገራ ፣ ሊቦ ከምከም እና አለፋ ናቸው:: በመሬት ውስጥ ጎጆ ሰርተው የሚገኙ ንቦችን በአገሬው ተወላጅ እውቀት በመታገዝ መራቢያቸውን ጎጆ በቀላሉ ማግኘት ተችሏል፡፡ ከጥናቱ የተገኘውን የንቦች የመሬት ቅርፊት ሥነ-ሕንፃ ይዘትና ባህሪያት በተለያዩ መለኪያዎች ተለክተው ከታተመው መረጃ ጋር ተነጻጽረዋል:: የግብርና እንቅስቃሴዎች እና በባህላዊ መንገድ የጣዝማ ንብ ማር አሰባስብ የሚያደርሰው ተፅእኖ ከአካባቢያዊ ማህበረሰቦች ጋር ቃለ-መጠይቅ ተደርጎ በአጭሩ ያመጣውን ችግር አስረድተዋል፡፡ የጣዝማ ንብ ማር በባህላዊ መድሐኒት አዋቂ ሰዎች ተላላፊ የሆኑና ያልሆኑ በሽታዎችን ለማከም እንዲሁም ውጤታማ የህመም ማስታገሻ ዘዴ ሆኖ እንደሚያገለግል ተገልጻል፡፡ ሆኖም በአማራ ክልል ውስጥ ባህላዊ የግብርና ሥራዎች እና የተፈጥሮ ሥነ-ምህዳር መዛባት የመሬት ቅርፊት ሥነ-ሕንፃ ሰርተው ለሚኖሩ ንብ ዝርያዎች ለመጥፋት መንስኤ መሆኑ ተርጋግጧል፡፡ በኢትዮጵያ ውስጥ የማይናቅ የንብ ብዝሃነትን ለማቆየት እና ማርቸውን ለሰው ልጅ ጥቅም ለማዋል ተገቢውን እንክብካቤ እና የማላመድ ባህል ልማት ቴክኖሎጂ እጅግ አስፈላጊ ነው ተብሏል::
To cite: Wondmeneh Jemberie, Worku Negash, Kassahun Alemu, Alemu Tarekegn, Malede Brhan & Nagappan Raja. 2020. Stingless bee Meliponula Cockerell (Hymenoptera: Apidae: Meliponini) ground nest architecture and traditional knowledge on the use of honey in the Amhara Region, Northwest Ethiopia. Israel Journal of Entomology 50 (1): 147–162.
DOI: 10.5281/zenodo.4588315urn:lsid:zoobank.org:pub:0F4D41F3-79E4-4E14-AAA2-33A1F05994F
Two-piece distribution based semi-parametric quantile regression for right censored data
No full textWidely used methods such as Cox proportional hazards, accelerated failure time, and Bennet proportional odds models do not model the quantiles directly, but rather allow to assess the influence of the covariates only on the location of the distribution. Quantile regression allows to assess the effects of covariates, not only on a location parameter (such as a mean or median) but also on specific percentiles of the conditional distribution. In recent years, a large family of flexible two-piece asymmetric distributions where the location parameter coincides with a specific quantile of the distribution has been studied. In a conditional (regression) setting the use of such a family of two-piece asymmetric distributions has only been investigated in the complete data case in the literature. In this paper, we propose a semi-parametric procedure to estimate the conditional quantile curves of two-piece asymmetric distributions based on right censored survival data. We use a local likelihood estimation technique in a multi-parameter functional form, via which the effect of a covariate on the location, scale, and index of the conditional survival distribution can be assessed. The finite sample performance of the estimators is investigated via simulations, and the methodology is illustrated on real data examples.The authors are grateful to an Associate Editor and two reviewers for their comments which led to an improvement of the manuscript. We thank the authors of Christou and Akritas (2019) to provide us with the R code to calculate their estimator in the SIQR model. The second author gratefully acknowledges support from Research Grant FWO G0D6619N of the Flemish Science Foundation, and from the C16/20/002 project of the Research Fund KU Leuven. The resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government
ABO and RH Blood Group Type Frequencies among Students from Different Ethnic Groups at Enchini Secondary School, West Shewa, Oromia Region, Ethiopia
No full textThe knowledge about ABO and Rh-D groups at individual and population levels is important for healthcare managements, clinical and genetic analyses. Ethiopia is working in archiving major events “Kunets” that have social and economic values. ABO blood groups and Rhfactor as biological characters and inheritance of genetic materials have major contributions to the “Kunets”. The study aimed to determine ABO and Rh-D blood groups distribution frequencies among 108 Amhara, 72 Gurage and 238 Oromo students at Enchini Secondary School. Each participant’s ABO and Rh-D blood types were determined by using agglutination reaction tests. In each study group, blood group O had the highest frequencies (38.39–41.18 %) whereas AB scored the least frequencies (6.30–10.18 %). Allele O scored the highest frequency (63.5‒64.2%) and allele B scored the least frequencies (17.0–18.2%). Rh+ had the higher frequencies (91.67‒94.12 %). The highest frequencies for O type (41.18%) and Rh+ (94.12%) were from Oromo students. The highest heterozygosity (54.65%) for ABO blood type was from Amhara students and the least (52.36%) was from Oromo students. All the differences between the observed and expected mean values of frequencies in the two blood system were not statistically significant at α = 0.05. The result would serve as a reference by lawyers in paternity suits, by police in forensic science, by anthropologists in the study of different populations, and for other studies and future utilities in health care planning and other needs or “Kunets” in the studied area
Application of mixed model and spatial analysis methods in multi-environmental and agricultural field trials.
No full textDoctor of Philosophy in Statistics. University of KwaZulu-Natal, Pietermaritzburg 2015.Agricultural experimentation involves selection of experimental materials,
selection of experimental units, planning of experiments, and collection of
relevant information, analysis and interpretation of the results. An overall
work of this thesis is on the importance, improvement and efficiency of variety
contrast by using linear mixed mode with spatial-variance covariance compare
to the usual ANOVA methods of analysis. A need of some considerations on the
recently widely usage of a bi-plot analysis of genotype plus genotype by
environment interaction (GEE) on the analysis of multi-environmental crop
trials. An application of some parametric bootstrap method for testing and
selecting multiplicative terms in GGE and AMMI models and to show some
statistical methods for handling missing data using multiple imputations
principal component and other deterministic approaches.
Multi-environment agricultural experiments are unbalanced because several
genotypes are not tested in some environments or missing of a
measurement from some plot during the experimental stage. A need for
imputation of the missing values sometimes is necessary. Multiple
imputation of missing data using the cross-validation by eigenvector method
and PCA methods are applied. We can see the advantage of these methods
having easy computational implementation, no need of any distributional or
structural assumptions and do not have any restrictions regarding the pattern
or mechanism of missing data in experiments.
Genotype by environment (G×E) interaction is associated with the differential
performance of genotypes tested at different locations and in different years,
and influences selection and recommendation of cultivars. Wheat genotypes
were evaluated in six environments to determine the G×E interactions and
stability of the genotypes. Additive main effects and multiplicative interactions
(AMMI) was conducted for grain yield of both year and it showed that grain
yield variation due to environments, genotypes and (G×E) were highly
significant. Stability for grain yield was determined using genotype plus
genotype by environment interaction (GGE) biplot analysis. The first two
principal components (PC1 and PC2) were used to create a 2-dimensional GGE
biplot. Which-won where pattern was based on six locations in the first and five
locations in the second year for all the twenty genotypes? The resulting pattern
is one realization among many possible outcomes, and its repeatability in the
second was different and a future year is quite unknown. A repeatability of
which won-where pattern over years is the necessary and sufficient condition
for mega-environment delineations and genotype recommendation.
The advantages of mixed models with spatial variance-covariance structures,
and direct implications of model choice on the inference of varietal
performance, ranking and testing based on two multi-environmental data sets
from realistic national trials. A model comparison with a ᵪ2-test for the trials in
the two data sets (wheat and barley data) suggested that selected spatial
variance-covariance structures fitted the data significantly better than the
ANOVA model. The forms of optimally-fitted spatial variance-covariance,
ranking and consistency ratio test were not the same from one trial (location) to
the other. Linear mixed models with single stage analysis including spatial
variance-covariance structure with a group factor of location on the random
model also improved the real genotype effect estimation and their ranking. The
model also improved varietal performance estimation because of its capacity to
handle additional sources of variation, location and genotype by location
(environment) interaction variation and accommodating of local stationary
trend. The knowledge and understanding of statistical methods for analysis of
multi-environmental data analysis is particularly important for plant breeders
and those who are working on the improvement of plant variety for proper
selection and decision making of the next level of improvement for country
agricultural development.Institute of Agricultural Research (EIAR) is acknowledged on p1039
Application of statistical multivariate techniques to wood quality data.
No full textThesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.Sappi is one of the leading producer and supplier of Eucalyptus pulp to the world market. It is also a great contributor to South Africa economy in terms of employment opportunity to the rural people through its large plantation and export earnings. Pulp mills production of quality wood pulp is mainly affected by the supply of non uniform raw material namely Eucalyptus tree supply from various plantations. Improvement in quality of the pulp depends directly on the improvement on the quality of the raw materials. Knowing factors which affect the pulp quality is important for tree breeders. Thus, the main objective of this research is first to determine which of the anatomical, chemical and pulp properties of wood are significant factors that affect pulp properties namely viscosity, brightness and yield. Secondly the study will also investigate the effect of the difference in plantation location and site quality, trees age and species type difference on viscosity, brightness and yield of wood pulp. In order to meet the above mentioned objectives, data for this research was obtained from Sappi’s P186 trial and other two published reports from the Council for Scientific and Industrial Research (CSIR). Principal component analysis, cluster analysis, multiple regression analysis and multivariate linear regression analysis were used. These statistical analysis methods were used to carry out mean comparison of pulp quality measurements based on viscosity, brightness and yield of trees of different age, location, site quality and hybrid type and the results indicate that these four factors (age, location, site quality and hybrid type) and some anatomical and chemical measurements (fibre lumen diameter, kappa number, total hemicelluloses and total lignin) have significant effect on pulp quality measurements
Variation and association analyses on morphological characters of linseed (<I>Linum usitatissimum</I> L.) in Ethiopia
No full textMorphological studies of linseed (Linum usitatissimum L.) of Ethiopia were undertaken in this study on 56 accessions collected from 10 administrative regions (former regions) classified into seven altitude classes. The seeds were planted during 2001 growing season in Bale-Goro wereda using randomized complete block design (RCBD) on three replications with the aim of investigating the morphological diversity in the accessions. Over the entire accession, except seed number per boll, all the characters showed significant variation. However, regional groups of linseed accessions showed insignificant variations only for secondary branches number per plant (SBP), days to flowering (DTF) and days to maturity (DTM) among themselves, and altitudinal groups of linseed accessions only for seed number per boll (SNB) and days to flowering (DTF). The analysis for coefficient of variation and cluster analysis showed that accessions from Gojam and Tigray were less diversified. About 53% of the total associations showed significant correlation and out of this 71% of the correlations were with the positive significant correlation coefficients. Cluster analysis indicates that accessions collected from the two extremes of altitude classes have variations for the studied traits. It is only Tigray Region that did not contribute member accession to cluster III, whereas Gondar and Bale regions contribute member accessions to 80% of clusters. Factor analysis showed that of the total variation (73.86%) 30.04% and 27.29% were accounted for by first and second principal components, respectively. The highest Shannon diversity index (0.322 ± 0.039) was recorded for boll size and Shannon diversity index for overall pooled mean was 0.223 ± 0.063.Keywords: cluster/factor analysis, diversity index, linseed accessions, morphological characters, variation/association SINET: Ethiopian Journal of Science Vol. 28(2) 2005: 129-14
Effect of Different Levels of Dried Sugar Cane Tops Inclusion on the Performance of Washera Sheep Fed Basal Diet of Grass Hay, Ethiopia
No full textCopyright: © 2015 Worku A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background: Ruminants feed largely on crop resides as their basal diet. Despite their vast use as a livestock feed, crop residues are naturally of low quality and do not fulfill the nutrient requirement of animals. Thus, the deficit in the basal feed of quantity can be covered with sugar cane tops that are potential feed for better performance of animals. This study aimed with to evaluate the effect of different level of Dried Sugar Can tops inclusion on carcass characteristics and Economic Feasibility of Washera sheep fed a basal diet of grass hay. Methodology: A study was conducted at Bure Agricultural Technical Vocational Educational Training (ATVET) College using twenty yearling Washera sheep with initial body weight (BW) of 18.15 ± 1.85 (mean ± SD). The experimental design was randomized complete block design, and sheep were blocked into five blocks of four animals based on their initial BW and randomly assigned to one of the treatments within a block. Treatments were hay ad libitum+100 g/head/d CM for T1 and an additional 120 g, 240 g and 360 g SCT per head/day on dry matter basis for T2, T3 and T4, respectively. The experiment consisted 90 days of Growth trials followed by evaluation of carcass components at the end
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