Numerical implementation of generalized Coddington equations for ophthalmic lens design

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Microbial load and microflora of weaning foods obtained from pediatric outpatients in Addis Ababa

Abstract: One hundred samples of feeding bottle contents from outpatient infants visiting four public clinics in Addis Ababa were analyzed for their microbial load and microflora. Forty-nine percent of the infants were female. The educational status of the mothers was illiterate (21%), elementary-level education (27%), and high-school level education and above (52%). Ingredients of the feeding bottles consisted of six different types and about 60% of the studied infants consumed cow's milk. Over 50% of the mothers used the same bottle throughout the day to feed the child and only 9% used three or more bottles interchangeably. High levels of bacterial contamination were observed in all samples with counts ranging between 1.6x105 and 9.9x108 cfu/ml of bottle content. Cow's milk and cereal gruel were the most heavily contaminated ones. A total of 366 bacterial strains belonging to 12 genera were isolated from feeding bottle contents. The dominant isolates were coliforms (31.2%), followed by staphylococci (30.1%), Bacillus spp. (19.1%), and micrococci (14.2%). Of the factory-produced weaning food samples (30), only nine were contaminated with over 102 cfu/g or ml. Possible sources of high contamination could be poorly cleaned and frequently re-used utensils, contamination during refilling and feeding bottles themselves. Findings of this study indicated the need for educating mothers on hygienic handling of infant food. The importance of thorough cleaning of feeding bottles and avoiding post-cooking contamination during storing the cooked foods should be stressed. [Ethiop. J. Health Dev. 1998;12(2):141-147

Patient Safety Culture Status and Its Predictors among Healthcare Workers

Good patient safety culture of healthcare professionals brings about fine consequences for patients. This study, therefore, aimed in evaluating the current status and predictors of safety culture among healthcare workers in Mekelle Zone hospitals, Tigray, Northern Ethiopia. A cross-sectional survey was conducted among 325 healthcare workers in three hospitals of Mekelle city from February to May, 2017. Simple random sampling technique was employed to select study subjects. Data was analyzed using SPSS. Logistic regression was used to determine the predictors of patient safety culture among healthcare workers at 95% confidence level and 5% level of significance. Statistical significance was set at p <0.05. Of the 325 Healthcare workers, 21.6% rated the culture of patient safety as satisfactory and 78.4% rated as unsatisfactory. Old aged healthcare workers (AOR=21.9, 95% of CI: 2.51-61.69) and ‘hospital management support for patient safety’ (AOR=2.68, 95% CI=1.06-6.79) were strong predictor of satisfactory patient safety culture. Satisfactory patient safety culture grade obtained was only 21.6%, indicating that health care professionals are not delivering patient centered service and there is a lot of work to be done in the hospitals to improve culture of patient safety among healthcare workers.

Study on the prevalence of bovine fasciolosis in and around Bahir Dar, Ethiopia

A cross sectional study aimed at determining the prevalence and type of common Fasciola species in cattle was conducted in and around Bahir Dar from November 2008- March 2009. The study was based on post-mortem inspection of livers of slaughtered animals at Bahir Dar municipality abattoir and coprological examination using sedimentation technique on fecal samples collected from animals of Bahir Dar and surrounding areas. Out of 413 livers inspected, 165 (39.95%) were positive for Fasciola species. F. hepatica was found to be the most prevalent species in cattle of the study area (89.70%). About 3.63% were positive for F. gigantica and 6.67% were harboring mixed infections. Likewise, out of 384 fecal samples examined 141 (36.72) were positive for the presence of Fasciola eggs. Risk factors such as locality, body condition and sex didn’t show any effect on the prevalence of infections (P>0.05). However, breed and age group revealed significant disparity (P<0.05) as greater magnitude of infections were detected in exotic breed and young age group, respectively. In view of the current result, fasciolosis could be considered as a major problem in Bahir Dar and surrounding areas as the ecological factors and management conditions are suitable both for the snail intermediate host and the parasite to be maintained. Strategic treatments need to be implemented at appropriate timing with the aim of reducing worm burden from infected animals and preclude pasture contamination. Integrated control approaches involving livestock owners has to be implemented in reducing the population and activity of snail intermediate hosts to enable maximization of long-term returns from such endemic areas.Key words: Abattoir, Bovine, Bahir Dar, Coprology, Fasciola, Prevalence

Moving towards the maximum speed in stepping motors by means of enlarging the bandwidth of the current controller

This paper pursues to maximise the mechanical speed when using stepping motors (SM) without position sensors in order to achieve a rapid-response manufacturing whenever any equipment based on such electrical machines is involved. The novelty of this paper is the fact that not only the bandwidth of the current controllers is improved for such maximization of the SM mechanical speed, as traditionally done in previous works, but also a comprehensive approach has been addressed. Such global approach starts justifying why the traditional PI controller is not sufficient and it includes the analytical tuning of the current controllers, considering implementation tiny issues (but of paramount importance) such as the delays caused by the processor and the sample and hold current measurements. It is proved and justified that this previously mentioned issues, which are often omitted, play a crucial role when trying to maximise the speed of the SM, since the electrical fundamental frequencies of the SM move close to the sampling frequency. Therefore, the analytical process to tune and implement the current controllers will have to be done in discrete-time domain, i.e. using the Z transform and treating the SM drive as a sampled data system. Experimental waveforms and results based on real prototypes will prove the validity of the entire research. Finally, a real case-study based on Printed Circuit Board (PCB) prototyping machine which is composed by two stepper machines, is fully reported. Such PCB prototype is the fruitful collaboration between the University (research institution) and a private company (industry). © 2016 Elsevier LtdPeer ReviewedPostprint (author's final draft

Comparison of two stabilizingsystems of steel structure including the effect of earthquake design

Master's thesis in Civil and structural engineering (BYG508