Electrochemical synthesis and characterization of bilayers of poly(O-aminophenol)/ polypyrrole/lignin composites for enhanced charge storage in supercapacitors

Using simple electrosynthesis methods a single and bilayer of conducting polymers, polypyrrole and poly(o-aminophenol) with biopolymer lignin hybrid composites were formed on gold electrodes. The specific capacitance of the single polymer-lignin composite value of 400 F/g obtained from galvanostatic charge-discharge experiment at 1 A/g is improved to a value of 514 F/g in the bilayer polymer-lignin composite systems. The charge capacity is also improved from 61 mAh/g to 121 mAh/g by forming a bilayer of conducting polymers.  Moreover, the charge retention during self-discharge is improved in the bilayer system. KEY WORDS: Supercapacitors, Conducting polymers, Lignin Bull. Chem. Soc. Ethiop. 2016, 30(1), 153-160. DOI: http://dx.doi.org/10.4314/bcse.v30i1.1

Electrocatalytic reduction of oxygen at vapor phase polymerized poly(3,4-ethylene- dioxidethiophene) modified glassy carbon electrode

We successfully polymerized poly(3,4-ethylenedioxidethiophene) by vapor phase polymerization technique on rotating glassy carbon disk electrode. The catalytic activity of this electrode towards oxygen reduction reaction was investigated and showed remarkable activity. Rotating disk voltammetry was used to study the kinetics of oxygen reduction reaction by plotting Levich, Koutecky Levich and Tafel plots. It was found that the reduction was mixed diffusion and kinetic controlled. The O2 reduction underwent through four electron transfer reaction. The Tafel slope was obtained as 55 mV/dec. The limiting current density was higher by a factor of more than 103 times the exchange current density.KEYWORDS: Poly(3,4-ethylenedioxidethiophene), Vapor phase polymerization, Oxygen reduction, Glassy carbon electrode Bull. Chem. Soc. Ethiop. 2012, 26(3), 449-454.DOI: http://dx.doi.org/10.4314/bcse.v26i3.1

Collective radiation dose from diagnostic x-ray examination in nine public hospitals in Addis Ababa, Ethiopia

Background: Medical x-ray exposures have the largest man made source of population exposure to ionizing radiation in different countries. Recent developments in medical imaging have led to rapid increases in a number of high dose xray examinations performed with significant consequences for individual patient doses and for collective dose to the population as a whole. It is therefore important in each country to make regular assessments of the magnitude of these large doses.Objectives: To calculate collective dose of the population as a result of radiation dose from diagnostic x-rays, thereby to estimate the annual incidence of cancer which would be reduced by the use of rare earth intensifying screen.Methods: Data on the number of diagnostic procedures using x-ray examination in year 2007 in nine governmental hospitals, excluding military hospitals, by body site were collected in Addis Ababa. The number of examinations of specific body site was multiplied by the average effective dose per examination to get the collective dose over the population. Based on International Commission on Radiological Protection (ICRP) the fatality risk of fatal cancers (5% per Sv) was estimated.Results: In this study, the annual collective dose over the population is 31.21manSv (0.0.42mSv per person). Based on ICRP fatality risk of 500 fatal cancers per 10,000 man-sieverts (5% per Sv), estimation of incidence of fatal cancers cases in year 2007 was 2 cases half of which can be reduced by adoption of rare earth screens.Conclusion: Although the use of ionizing radiation for diagnostic medical procedures is an acceptable part of modern medicine, there is also the potential for inappropriate use and unnecessary radiation dose to the patient, so the request of radiography must be justified. It is estimated that the adoption of rare earth screen technology might reduce the annual incidence of cancer which would be fatal after an average latency period of 18.4 years by half, hence this research recommended adopting rare earth screen technology in Ethiopia. [Ethiop. J. Health Dev. 2010;24(2):140-144

Childhood limb fracture at Tikur Anbessa Specialised Hospital (TASH), Addis Ababa, Ethiopia

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Voltammetric determination of nicotine in cigarette tobacco at electrochemically activated glassy carbon electrode

The electrochemical behavior of nicotine was investigated using cyclic and square wave voltammetric techniques. Electrochemical activation of glassy carbon electrode significantly increased the oxidation peak current of nicotine compared to the bare glassy carbon. At the activated glassy carbon electrode, the square wave voltammetry of nicotine revealed an oxidation peak at +838 mV (vs. SCE) in phosphate buffer solution of pH 7. Under optimized conditions, the linear range (R2 = 0.998) and detection limit (3σ) for nicotine determination were found to be 1-200 µM and 0.7 µM, respectively. The method was successfully applied for the determination of nicotine in two brands of commercial cigarettes and acceptable recovery values of 97-108% were found. KEY WORDS: Nicotine, Activated glassy carbon, Square wave voltammetry, Cigarette Bull. Chem. Soc. Ethiop. 2013, 27(3), 321-328.DOI: http://dx.doi.org/10.4314/bcse.v27i3.

Amino-substituted naphthalene sulfonic acid/graphene composite as metal -free catalysts for oxygen reduction reactions

Composites of reduced graphene oxide (rGO) and conducting polymers synthesized from 8-amino-2-naphthalene sulfonic acid (8-ANSA), 5-amino-1-naphthalene sulfonic acid (5-ANSA), 2-amino-1-naphthalene sulfonic acid (2-ANSA), and 4-amino-1-naphthalene sulfonic (4-ANSA) were prepared for use as an electrocatalyst in oxygen reduction reaction (ORR). The electrocatalytic activities were examined in oxygen saturated 0.1 M KOH solution using cyclic and linear sweep voltammetry. The best performing polymer composite was found to be GC/poly(8-ANSA)/rGO, with an enhanced electrocatalytic activity over the rGO only and poly(8-ANSA) only films. More than 100 mV positive shift in the onset potential and 1.6 times increase in current density were observed. The catalytic activity of 2-ANSA, 4-ANSA, 5-ANSA, and 8-ANSA was also validated by density functional theory (DFT). Our calculations predict a much better catalytic activity for 8-ANSA than that of 2-ANSA, 4-ANSA, and 5-ANSA.               KEY WORDS: Poly(amino naphthalene sulfonic acid), Reduced graphene oxide, Oxygen reduction reaction, Electrocatalyst Bull. Chem. Soc. Ethiop. 2019, 33(2), 359-372.DOI: https://dx.doi.org/10.4314/bcse.v33i2.1

X-ray film reject rate analysis at eight selected government hospitals in Addis Ababa, Ethiopia, 2010

Background: Improper practices in radiography that lead to possible repeating of procedures predispose patients for additional cost, more waiting time, and excess dose of ionizing radiation, leading to various dose dependent and dose independent health problems including cancer. In the face of such problems and the scarcity of resources, improvingthe quality and efficiency of radiology services is imperative.Objective: The purpose of this research was to identify the main causes of film faults as well as the pattern and magnitude of film rejection.Methods: Using a prospective cross-sectional hospital based approach; eight public hospitals were selected in Addis Ababa through convenience sampling. Adult and pediatrics radiographs with film faults were reviewed using a standardized checklist of common causes of reject. The collected data were then entered into a database for analysis using descriptive statistics.Results: Reject rate was calculated in eight governmental hospitals across all plain film examinations. The overall reject rate was 374 (3.1 %) in 12,165 x-ray exposures. Total reject rate by hospital showed 10.5% for Zewditu and 1.53% and 1.87% for Tikur Anbessa Specialized Hospital (TASH) and the Police Hospital, respectively.Conclusions: Rejected films were found to have been caused by numerous factors including poor technical judgment, patient motion, and poor supervision of staff. Hence, strategies need to be developed within medical imaging departments to improve the situation.[Ethiop. J. Health Dev. 2012;26(1):54-59

Adsorption of Pb(II) ions from aqueous solution using lignin from Hagenia abyssinica

The adsorption of lead(II) ions from aqueous solution onto alkali lignin extracted from Hagenia abyssinica was investigated by electrochemical methods. The effect of solution pH, lignin dosage and contact time were investigated at room temperature in a batch system. Adsorption equilibrium was approached within 80 min. The adsorption kinetics data were described by pseudo-second-order kinetics model, while the equilibrium data were well fitted using the Freundlich model. A maximum adsorption capacity was found to be 80.41 mg g-1 of the dry weight of lignin

Etiological spectrum and treatment outcome of Obstructive jaundice at a University teaching Hospital in northwestern Tanzania: A diagnostic and therapeutic challenges

Obstructive jaundice poses diagnostic and therapeutic challenges to general surgeons practicing in resource-limited countries. This study was undertaken to highlight the etiological spectrum, treatment outcome of obstructive jaundice in our setting and to identify prognostic factors for morbidity and mortality. This was a descriptive prospective study which was conducted at Bugando Medical Centre between July 2006 and June 2010. All patients with a clinical diagnosis of obstructive jaundice were, after informed consent for the study, consecutively enrolled into the study. Data were collected using a pre-tested structured questionnaire and analyzed using SPSS computer software version 11.5. A total of 116 patients were studied. Females outnumbered males by a ratio of 1.3:1. Patients with malignant obstructive jaundice were older than those of benign type. Ca head of pancreas was the commonest malignant cause of jaundice where as choledocholithiasis was the commonest benign cause. Abdominal ultrasound was the only diagnostic imaging done in all patients and revealed dilated intra and extra-hepatic ducts, common bile stones and abdominal masses in 56.2%, 78.9%, 58.1% and 72.4% of the cases respectively. A total of 110 (94.8%) patients underwent surgical treatment and the remaining 6 (5.2%) patients were unfit for surgery. The complication rate was 22.4% mainly surgical site infections. The mean hospital stay and mortality rate were 14.54 days and 15.5% respectively. A low haematocrit and presence of postoperative sepsis were the main predictors of the hospital stay (P < 0.001), whereas age > 60 years, prolonged duration of jaundice, malignant causes and presence of postoperative complications mainly sepsis significantly predicted mortality (P < 0.001). Obstructive jaundice in our setting is more prevalent in females and the cause is mostly malignant. The result of this study suggests that early diagnosis and treatment plays an important role in the prognosis of patients with obstructive jaundice