A group theoretic approach to shear-free radiating stars

A systematic analysis of the junction condition, relating the radial pressure with the heat flow in a shear-free relativistic radiating star, is undertaken. This is a highly nonlinear partial differential equation in general. We obtain the Lie point symmetries that leave the boundary condition invariant. Using a linear combination of the symmetries, we transform the junction condition into ordinary differential equations. We present several new exact solutions to the junction condition. In each case we can identify the exact solution with a Lie point generator. Some of the solutions obtained satisfy the linear barotropic equation of state. As a special case we regain conformally flat models which were found previously. Our analysis highlights the interplay between Lie algebras, nonlinear differential equations and application to relativistic astrophysics.Comment: 11 pages, Submitted for publication, minor revision

HOW GOOD ARE INPUT DEMAND MODELS USED IN PREVIOUS STUDIES NOW?

Demand and Price Analysis,

THE DEMAND FOR FERTILIZER

Crop Production/Industries, Demand and Price Analysis,

THE DEMAND FOR FARM MACHINERY

Demand and Price Analysis, Farm Management,

THE DEMAND FOR HIRED FARM LABOR

Labor and Human Capital,

Seroepidemiology of hepatitis B virus in Addis Ababa Ethiopia: transmission patterns and vaccine control

A community-based seroepidemiological survey of Addis Ababa, Ethiopia was conducted in 1994 to inform on the transmission dynamics and control of hepatitis B virus (HBV) infection. Venous blood from 4736 individuals under 50 years of age from 1262 households, selected using stratified cluster-sampling, was screened for HBV markers using commercial ELISAs. HBsAg prevalence was 7% (95% CI 6–8), higher in males (9%; 7–10) than females (5%; 4–6). HBeAg prevalence in HBsAg positives was 23% (18–29), and less than 1% of women of childbearing age were HBeAg positive. Overall HBV seroprevalence (any marker), rose steadily with age to over 70% in 40–49 year olds, indicating significant childhood and adult transmission. Estimated instantaneous incidence was 3–4/100 susceptibles/year, higher in males than females in 0–4 year olds, and peaking in early childhood and young adults. The age at which 50% had evidence of infection was around 20 years, and the herd immunity threshold is approximated at 63–77%. Addis Ababa is of intermediate-high HBV endemicity, with negligible perinatal transmission. Our main findings are the identification of a significant difference between males and females in the age-acquisition of HBV infection, and marked differences between age groups in HBV incidence rates. These results should target future research studies of underlying risk factors. Furthermore, we generate a crude estimate of the level of coverage of HBV vaccine that would be required to eliminate the virus from the study population

Production and characterization of biodiesel and glycerine pellet from macroalgae strain: Cladophora glomerata

Biodiesel was prepared by extracting oil from Cladophora glomerata green algae followed by transesterification of the oil using NaOH as a catalyst. The algae Oil extraction was carried out using two different techniques (Soxhlet and refluxing) and similar oil yield was obtained (23-24%). The resulting biodiesel showed desirable physical and chemical properties. Specific gravity, acid value, iodine value, ash content and calorific value of the algae biodiesel were within the specification of American Society for Testing and Materials (ASTM) and European Standards (EN). The analysis of fatty acid methyl ester composition revealed, 63, 27 and 10% for 9-octadecodenoic, hexadeconic and octadeconoic acid methyl ester, respectively. From the production line, two waste streams (glycerol and residual biomass) were combined to form a glycerine pellet. The measured energy content of the glycerine pellet was found to be comparable with firewood. Therefore, C. glomerata could potentially be utilized for the production of both biodiesel and glycerine pellet with no net waste in the transesterification process.                     KEY WORDS: Algae oil, Biodiesel, Transesterification, Glycerine pellet, Macroalgae, Cladophora glomerata   Bull. Chem. Soc. Ethiop. 2020, 34(2), 249-258 DOI: https://dx.doi.org/10.4314/bcse.v34i2.

Intermittent Urinary Retention Secondary to a Cervical Leiomyoma

A rare case of intemittent acute urinary retention secondary to impacted posteriorly sited cervical fibroid in a 34 year old nulliparous woman is deescribed. She presented with a two year history of progressive lower abdominal swelling and a one year history of recurrent urinary retention. She had a preoperative diagnosis of impacted posteriorly sited uterine leiomyoma with anterior displacement of the cervix. At laparotomy however, a huge intramural cervical fibroid was found in the posterior part of the cervix measuring 14cm? 12cm extending superiorly to the lower uterine segment and inferiorly into the pouch of Douglas. It completely filled the pelvis and displaced the cervix anteriorly. The uterus was of normal size. A myomectomy with excision of the fibroid was performed. Urinary retention completelyresolved after surgery