Linear regression model with generalized new symmetric error distribution

Linear models play a dominant role in analyzing several data sets arising at places like agricultural experiments, space experiments, biological experiments, financial modeling and a wide range other practical problems. One of the major strings in the development of the regression model is the assumption of the error. It is often assumed that the random error of the linear regression model is normally distributed. In numerous situations, however, it is nearly impossible to find a data set that satisfies the normality assumption due to various reasons, such as multivariate skewed and/or heavy-tailed distributions. This problem has been addressed by specifying a different parametric distribution family for the error terms. In this paper, a linear regression model with generalized new symmetric errors is developed and analyzed. The Maximum Likelihood (ML) estimators of the model parameters are derived and their properties with respect to the generalized new symmetric distributed errors are discussed. Simulations were carried out to study the performance of the proposed model with that of Gaussian errors and found that the proposed model perform well when the variables are platykurtic. Some applications of the developed model are also pointed.    Key Words: Generalized new symmetric distribution, Regression model, Simulatio

Prevalence of group B Streptococcus colonization among pregnant women attending antenatal clinic of Hawassa Health Center, Hawassa, Ethiopia

Background: Group B streptococcus (GBS) or Streptococcus agalactiae are members of the normal flora of the female genital tract. GBS has become the major cause of bacterial infections in the peri-natal period, includingbacteraemia, amnionitis, endometritis, and urinary tract infection in pregnant women as well as sepsis and meningitis in neonates and young infants. Infection of the new born may be acquired by the intra-amniotic route or directly during passage through the birth canal.Objectives: This study was undertaken to determine the prevalence of group B Streptococcus (GBS) colonization and to analyze related risk factors among pregnant women attending the antenatal clinic of Hawassa Health centre, Adare Hospital Hawassa, Ethiopia.Methods: A total of 139 pregnant women were screened for GBS  colonization between May and June 2010. Standard microbiological methods were used to isolate and identify GBS from vaginal and ano-rectal swabs obtained from study subjects. An antimicrobial susceptibility test was performed for all GBS isolates according to the criteria of the Clinical and laboratory Standards Institute (CLSI) by disk diffusion method.Results: A total of 29 out of 139 (20.9%) pregnant women were colonized by GBS. No statistically significant association was observed for GBS colonization with any of socio-demographic characteristics of the study subjects including age, occupation, type of contraceptive used, parity, number of antenatal clinic visits. All GBS strains were susceptible to penicillin, ampicillin, vancomycin and gentamicin. Resistance was observed against erythromycin (6.9%), tetracycline (48.2%), ceftriaxone (10.3%), chloramphenicol (51.7%), ciprofloxacin (13.8%) and norfloxacin(10.3%).Conclusion: This study showed that prevalence of GBS colonization was 20.9% among the study subjects. The finding of this study was comparable with findings reported from developed and developing countries. However,further epidemiological investigations should be done in different parts of the country in order to know the actual GBS colonization rate in pregnant women and to consider the use of intra-partum antibiotics prophylaxis for prevention of early onset GBS-neonatal diseases.[Ethiop. J. Health Dev. 2012;26(1):36-42

Multilocus sequence and microsatellite identification of intra-specific hybrids and ancestor-like donors among natural Ethiopian isolates of Leishmania donovani.

Protozoan parasites of the genus Leishmania (Kinetoplastida: Trypanosomatidae) cause widespread and devastating human diseases. Visceral leishmaniasis is endemic in Ethiopia where it has also been responsible for fatal epidemics. It is postulated that genetic exchange in Leishmania has implications for heterosis (hybrid vigour), spread of virulent strains, resistance to chemotherapeutics, and exploitation of different hosts and vectors. Here we analyse 11 natural Ethiopian Leishmania donovani isolates consisting of four putative hybrids, seven parent-like isolates and over 90 derived biological clones. We apply a novel combination of high resolution multilocus microsatellite typing (five loci) and multilocus sequence typing (four loci) that together distinguish parent-like and hybrid L. donovani strains. Results indicate that the four isolates (and their associated biological clones) are genetic hybrids, not the results of mixed infections, each possessing heterozygous markers consistent with inheritance of divergent alleles from genetically distinct Ethiopian L. donovani lineages. The allelic profiles of the putative hybrids may have arisen from a single hybridisation event followed by inbreeding or gene conversion, or alternatively from two or more hybridisation events. Mitochondrial sequencing showed uniparental maxicircle inheritance for all of the hybrids, each possessing a single mitochondrial genotype. Fluorescence activated cell sorting analysis of DNA content demonstrated that all hybrids and their associated clones were diploid. Together the data imply that intra-specific genetic exchange is a recurrent feature of natural L. donovani populations, with substantial implications for the phyloepidemiology of Leishmania

Absorbable versus silk sutures for surgical treatment of trachomatous trichiasis in Ethiopia: a randomised controlled trial.

BACKGROUND: Trachoma causes blindness through an anatomical abnormality called trichiasis (lashes touching the eye). Trichiasis can recur after corrective surgery. We tested the hypothesis that using absorbable sutures instead of silk sutures might reduce the risk of recurrent disease among patients with major trichiasis in a randomised trial. METHODS AND FINDINGS: 1,300 individuals with major trichiasis from rural villages in the Amhara Region of Ethiopia were recruited and assigned (1:1) by computer-generated randomisation sequence to receive trichiasis surgery using either an absorbable suture (polyglactin-910) or silk sutures (removed at 7-10 days) in an otherwise identical surgical technique. Participants were examined every 6 months for 2 years by clinicians masked to allocation. The primary outcome measure was recurrent trichiasis (≥one lash touching the eye) at 1 year. There was no difference in prevalence of recurrent trichiasis at 1 year (114 [18.2%] in the absorbable suture group versus 120 [19.7%] in the silk suture group; odds ratio = 0.90, 95% CI 0.68-1.20). The two groups also did not differ in terms of corneal opacification, visual acuity, conjunctival inflammation, and surgical complications. CONCLUSIONS: There was no evidence that use of absorbable polyglactin-910 sutures was associated with a lower prevalence of trichiasis recurrence at 1 year postsurgery than silk sutures. However, from a programmatic perspective, polyglactin-910 offers the major advantage that patients do not have to be seen soon after surgery for suture removal. The postoperative review after surgery using absorbable polyglactin-910 sutures can be delayed for 3-6 months, which might allow us to better determine whether a patient needs additional surgery. TRIAL REGISTRATION: ClinicalTrials.gov NCT00522860

Feeding your soil-nurturing the people

United States Agency for International Developmen

Decision support tools for fertilizer recommendation

United States Agency for International Developmen

Reprint of Glass compositions and tempo of post-17 ka eruptions from the Afar Triangle recorded in sediments from lakes Ashenge and Hayk, Ethiopia

Numerous volcanoes in the Afar Triangle and adjacent Ethiopian Rift Valley have erupted during the Quaternary, depositing volcanic ash (tephra) horizons that have provided crucial chronology for archaeological sites in eastern Africa. However, late Pleistocene and Holocene tephras have hitherto been largely unstudied and the more recent volcanic history of Ethiopia remains poorly constrained. Here, we use sediments from lakes Ashenge and Hayk (Ethiopian Highlands) to construct the first <17 cal ka BP tephrostratigraphy for the Afar Triangle. The tephra record reveals 21 visible and crypto-tephra layers, and our new database of major and trace element glass compositions will aid the future identification of these tephra layers from proximal to distal locations. Tephra compositions include comendites, pantellerites and minor peraluminous and metaluminous rhyolites. Variable and distinct glass compositions of the tephra layers indicate they may have been erupted from as many as seven volcanoes, most likely located in the Afar Triangle. Between 15.3?1.6 cal. ka BP, explosive eruptions occurred at a return period of <1000 years. The majority of tephras are dated at 7.5?1.6 cal. ka BP, possibly reflecting a peak in regional volcanic activity. These findings demonstrate the potential and necessity for further study to construct a comprehensive tephra framework. Such tephrostratigraphic work will support the understanding of volcanic hazards in this rapidly developing regionpublishersversionPeer reviewe

Natural resource management: Africa RISING science, innovations and technologies with scaling potential from the Ethiopian highlands

United States Agency for International Developmen

Genomic analysis of natural intra-specific hybrids among Ethiopian isolates of Leishmania donovani.

Parasites of the genus Leishmania (Kinetoplastida: Trypanosomatidae) cause widespread and devastating human diseases. Visceral leishmaniasis due to Leishmania donovani is endemic in Ethiopia where it has also been responsible for major epidemics. The presence of hybrid genotypes has been widely reported in surveys of natural populations, genetic variation reported in a number of Leishmania species, and the extant capacity for genetic exchange demonstrated in laboratory experiments. However, patterns of recombination and the evolutionary history of admixture that produced these hybrid populations remain unclear. Here, we use whole-genome sequence data to investigate Ethiopian L. donovani isolates previously characterized as hybrids by microsatellite and multi-locus sequencing. To date there is only one previous study on a natural population of Leishmania hybrids based on whole-genome sequences. We propose that these hybrids originate from recombination between two different lineages of Ethiopian L. donovani occurring in the same region. Patterns of inheritance are more complex than previously reported with multiple, apparently independent, origins from similar parents that include backcrossing with parental types. Analysis indicates that hybrids are representative of at least three different histories. Furthermore, isolates were highly polysomic at the level of chromosomes with differences between parasites recovered from a recrudescent infection from a previously treated individual. The results demonstrate that recombination is a significant feature of natural populations and contributes to the growing body of data that shows how recombination, and gene flow, shape natural populations of Leishmania

Recurring types of variability and transitions in the ∼620 kyr record of climate change from the Chew Bahir basin, southern Ethiopia

The Chew Bahir Drilling Project (CBDP) aims to test possible linkages between climate and hominin evolution in Africa through the analysis of sediment cores that have recorded environmental changes in the Chew Bahir basin (CHB). In this statistical project we used recurrence plots (RPs) together with a recurrence quantification analysis (RQA) to distinguish two types of variability and transitions in the Chew Bahir aridity record and compare them with the ODP Site 967 wetness index from the eastern Mediterranean. The first type of variability is one of slow variations with cycles of ∼20 kyr, reminiscent of the Earth's precession cycle, and subharmonics of this orbital cycle. In addition to these cyclical wet-dry fluctuations in the area, extreme events often occur, i.e. short wet or dry episodes, lasting for several centuries or even millennia, and rapid transitions between these wet and dry episodes. The second type of variability is characterized by relatively low variation on orbital time scales, but significant century-millennium-scale variations with progressively increasing frequencies. Within this type of variability there are extremely fast transitions between dry and wet within a few decades or years, in contrast to those within Type 1 with transitions over several hundreds of years. Type 1 variability probably reflects the influence of precessional forcing in the lower latitudes at times with maximum values of the long (400 kyr) eccentricity cycle of the Earth's orbit around the sun, with the tendency towards extreme events. Type 2 variability seems to be linked with minimum values of this cycle. There does not seem to be a systematic correlation between Type 1 or Type 2 variability with atmospheric CO2 concentration. The different types of variability and the transitions between those types had important effects on the availability of water, and could have transformed eastern Africa's environment considerably, which would have had important implications for the shaping of the habitat of H. sapiens and the direct ancestors of this species