Design of an axial-flux generator for a small-scale wind electrolysis plant

Includes abstract.Includes bibliographical references (leaves [124]-128).The main objective of this study is the selection and design of a wind generator to meet electrolyser requirements. These are the hydrogen production rate, the power requirements and the operating temperature. This requires the analysis of the load, sizing and characterizing of an electrolyser and finally, the design of a wind generator that meets electrolyser requirements. A hybrid system that combines the use of hydrogen as an efficient form of energy storage, and the growing renewable energy (RE) industry is discussed in detail

HIGH FLUX DENSITY ROTATIONAL CORE LOSS MEASUREMENTS

Energy conversion processes involve losses. Specifically core losses, which are a result of the magnetization process in cored electrical energy conversion and storage devices. The cores are made of soft ferromagnetic materials that are easily magnetized and demagnetized. These soft magnetic cores, allow a reduction in size, higher energy storage density, and a reduction in magnetizing current, when compared to non-cored devices. The characterization of soft ferromagnetic materials is traditionally done under unidirectional pulsating fields, which is sufficient for single-phase transformers and inductors, where the cores are under pulsating fields. However, T-joints of three phase transformers and teeth-roots of rotating machine stator cores are exposed to two-dimensional rotational fields of higher core loss. Pulsating measurements are therefore insufficient in the characterization of soft ferromagnetic materials used in rotating electrical machines or in three phase transformers. In two-dimensional fields, the magnetization direction changes with time, tracing a flux density locus. This requires the measurement of tangential magnetic field and flux density components, hence the associated loss. This study proposes a two-dimensional rotational core loss tester for high flux density measurements up to about 2 T, at 60 Hz. Its frequency measurement range is from 60 Hz to 1 kHz. The initial sizing was done analytically, then implemented in three-dimensional finite element analysis, prototyped and experiments performed to verify its capability. It was validated by testing two 0.35 mm and 0.65 mm thick samples. Very high flux densities in the range of 2 T at 60 Hz were achieved in both samples. For the thinner sample, flux densities of 1.8 T and 1.6 T were measured at 400 Hz and 1 kHz, respectively, while for the thicker one, the range reduced to 1.7 T and 1.4 T, at 400 Hz and 1 kHz, respectively. The magnetizer also reproduced non-sinusoidal flux density waveforms, for flux densities less than or equal to 1.0 T, without any waveform control. The proposed rotational core loss setup will find application in the characterization of electrical steels, and generation of pulsating and rotational core loss data. This data can then be applied in core loss models, uprating of megawatt (MW) rated machines, transient and hotspots analysis, and in the design of higher power density machines, such as high-speed machines

Is Congruence a Predictor of Satisfaction with the Choice of Degree Program among University Students in Kenya

A lot of studies carried out in Kenya have examined the factors that lead to a student’s choice of degree program with most reports suggesting that parents and peers have significant influence. The extent to which the personal attributes lead to the choice of degree program has not been examined. This study examined congruence as a predictor of satisfaction with the choice of degree program. The Self Directed Search 4th Edition questionnaire by (Rosen, Holmberg, & Holland, 1994) and a satisfaction scale were used to gather information. The results indicated that majority of the students were satisfied with their choice of degree program. Congruence was found to be weak predictor of the choice of degree program (r=.04, n = 389, .433), and significantly negatively correlated with satisfaction with the degree program (r=-.099, n=389, p=.051). The study concluded that congruence is a predictor of choice of the degree program but not a strong predictor of satisfaction. Key words: Congruence, Satisfaction, and Choice of degree program

Effect of Sequence of Infection of Maize with Viruses Causing Maize Lethal Necrosis on Disease Development

Maize is the main staple food crop in Kenya. However, its production is constrained by maize lethal necrosis (MLN) disease, a result of dual infection of maize plants with Maize chlorotic mottle virus (MCMV) and a potyvirus Sugarcane mosaic virus (SCMV). In the field, infection by the two viruses is independent rather than occurring simultaneously since MCMV and SCMV are transmitted by different vectors. This study aimed at evaluating the effect of sequence of infection of maize by the two viruses causing MLN disease in the greenhouse. Two susceptible maize hybrids (DUMA 43 and H614D) were each infected with either of the two viruses first and later inoculated with the second virus. The plants were assessed for disease development weekly over a period of 2 months. Symptoms were significantly (p=0.05) more severe in maize plants initially infected with MCMV followed by SCMV, resulting in rapid death of plants compared to plants infected with SCMV followed by MCMV. The results indicate that severity of symptoms is influenced by the sequence of infection of maize plants with the causal agents of MLN disease. More remarkable was the synergism observed in maize plants pre-inoculated with SCMV followed by MCMV that had a slow manifestation of MLN disease symptoms. The results suggest that initial infection by SCMV may result in maize plants developing some levels of resistance resulting in initial suppression of MCMV infection. This study contributes to the understanding of resistance mechanisms exhibited by the plants during MLN disease development. Keywords: Maize, MCMV, SCMV, Synergism, Sequence of infection DOI: 10.7176/JNSR/9-8-06 Publication date: April 30th 201

Population Levels of Indigenous Bradyrhizobia Nodulating Promiscuous Soybean in two Kenyan Soils of the Semi-arid and Semi-humid Agroecological Zones

Soybeans grown in Africa have been selected to nodulate effectively with indigenous Bradyrhizobium spp. populations since Bradyrhizobium japonicum populations are considered absent or in very low numbers in African soils. The major objective of this study was to estimate total population of Bradyrhizobia specific to soybean in two agro-ecologically different study sites, Kiboko in Makueni District, Southeast Kenya (semi-arid to arid conditions) and Kaguru in Meru District, East Kenya (semi-humid climate) . The population of the indigenous rhizobia specific to soybeans was determined using the Most Probable Number (MPN) plant infection technique. In these experiments, the total Bradyrhizobia populations, the population sizes of taxonomically defined slow-growing Bradyrhizobia specific to soybean and the population sizes of Bradyrhizobia spp. specific to tropical Glycine Cross (TGx) varieties were determined for the two study sites. Cowpea, Vigna unguiculata, cultivar Ken Kunde I was used to estimate the total Bradyrhizobia spp. population. Clark soybean, Glycine max, was used to estimate the population sizes of taxonomically defined slow-growing Bradyrhizobia spp. specific to soybean while a TGx genotype, SB12-TGx1869-31E was used to determine the population sizes of Bradyrhizobia spp. specific to TGx varieties. The results of the MPN counts indicated that the total Bradyrhizobia population in Kiboko was between 2.59x104 and 1.89x105. The population size of taxonomically defined slowgrowing Bradyrhizobia in Kiboko was between 2.59x102 and 1.89x103 cells per gram of soil sample while the approximate Bradyrhizobia population specific to TGx genotype was between 7.81x102 and 5.67x103 cells per gram of soil. In Kaguru, the approximate total Bradyrhizobia population was between 1.04x102 and 7.56x103 cells per gram of soil. The population size of taxonomically defined slow-growing Bradyrhizobia was between 1.33x102 and 9.72x102 cells per gram of soil while the approximate Bradyrhizobia population specific toTGx genotype was between 2.37x102 and 1.73x103 per gram of soil. These populations were adequate to give satisfactory results on nodulation and nitrogen fixation in the two study sites

Mixed Goblet Cell Carcinoid-Adenocarcinoma: A Case Series

INTRODUCTION: Mixed goblet cell carcinoid-adenocarcinoma (GCC) tumors are a group of rare heterogenous neoplasms of the appendix accounting for \u3c 5% of all primary appendiceal tumors. They are characterized as an intermediate between classic carcinoid tumors and appendiceal adenocarcinomas, exhibiting both neuroendocrine and glandular/mucinous morphology that most commonly presents in Caucasian females in the fifth and sixth decades. We present three cases of mixed GCC presenting as acute appendicitis. CASE PRESENTATION: Case #1 A 65-year-old male presented with RLQ pain, nausea, emesis, and leukocytosis. CT of the abdomen revealed perforated appendicitis. The patient underwent a laparoscopic appendectomy. Pathology revealed a high-grade adenocarcinoma ex goblet cell carcinoid, signet ring type extending through the muscularis propria into the mesoappendix measuring \u3e3cm. The patient subsequently underwent a colonoscopy that revealed diverticulosis, but was otherwise normal. Patient then underwent a right hemicolectomy and partial omentectomy. Pathology revealed normal ileal, omental, and colonic tissue without evidence of carcinoma. 0/12 nodes were positive. Case #2 A 49-year-old male presented with periumbilical pain, nausea, emesis, and leukocytosis. CT of the abdomen revealed appendicitis. The patient underwent a laparoscopic appendectomy. Pathology revealed a high-grade, poorly differentiated, adenocarcinoma ex goblet cell carcinoid invading through the muscularis propria into the periappendiceal soft tissue measuring 1.5cm. The patient subsequently underwent a colonoscopy that revealed diverticulosis, but was otherwise normal. Patient then underwent a laparoscopic right hemicolectomy. Pathology revealed normal ileal and colonic mucosa without evidence of carcinoma. 0/14 nodes were positive. Case #3 A 70-year-old female presented with periumbilical pain. CT of the abdomen revealed appendicitis. The patient underwent a laparoscopic appendectomy. Pathology revealed a high-grade adenocarcinoma ex goblet cell carcinoid extending through the muscularis propria into the mesoappendix measuring 4cm. Patient then underwent an exploratory laparotomy with a right hemicolectomy. Pathology revealed normal ileal and colonic mucosa without evidence of carcinoma. 0/21 nodes were positive. CONCLUSION: Mixed GCC tumors are rare tumors that tend to present at an advanced stage and most commonly spread via direct extension. Surgical resection with a right hemi-colectomy after an appendectomy has been shown to improve the prognosis. HIPEC and adjuvant chemotherapy are other therapeutic options, but have not been shown to improve survival. In the current age of increasing rates of managing acute appendicitis non-operatively we strongly encourage surgical appendectomy in patients older than 45 years of age to avoid missing this important diagnosis and the opportunity to treat it in a timely manner

Exploring Partnerships between Academia and Disabled Persons’ Organisations: Lessons Learned from Collaborative Research in Africa

In this article, we discuss how our academic research on disability and international development in five African countries has benefited hugely from active collaboration with advocates, practitioners, and policymakers, ultimately ensuring that research evidence is used to inform policy and practice. Whilst building such partnerships is seen as good practice, it is particularly important when working on disability issues, as the clarion call of the disability movement, ‘nothing about us without us’, attests. This is not just a slogan. Without the active and critical engagement of disabled people – as researchers, participants, advocates – the evidence gathered would not have the same impact. This article discusses experiences from research in Liberia, Kenya, Uganda, Sierra Leone, and Zambia. It highlights the challenges and opportunities such partnerships can bring in achieving the goals of leaving no one behind and doing nothing without the active engagement and inclusion of persons with disabilities.Department for International Development (DFID)Economic and Social Research Council (ESRC

The pathogenicity of blood stream and central nervous system forms of Trypanosoma brucei rhodesiense trypanosomes in laboratory mice: a comparative study [version 2; peer review: 2 approved]

Background: Human African trypanosomiasis (HAT) develops in two stages namely early stage when trypanosomes are found in the blood and late stage when trypanosomes are found in the central nervous system (CNS). The two environments are different with CNS environment reported as being hostile to the trypanosomes than the blood environment. The clinical symptoms manifested by the disease in the two environments are different. Information on whether blood stream are pathologically different from CNS trypanosomes is lacking. This study undertook to compare the inter-isolate pathological differences caused by bloodstream forms (BSF) and central nervous system (CNS) of five Trypanosoma brucei rhodesiense (Tbr) isolates in Swiss white mice. Methods: Donor mice infected with each of the five isolates were euthanized at 21 days post infection (DPI) for recovery of BSF trypanosomes in heart blood and CNS trypanosomes in brain supernatants. Groups of Swiss white mice (n = 10) were then infected with BSF or CNS forms of each isolate and monitored for parasitaemia, packed cell volume (PCV), body weight, survivorship, trypanosome length, gross and histopathology characteristics. Results: Amplification of SRA gene prior to trypanosome morphology and pathogenicity studies confirmed all isolates as T. b. rhodesiense. At 21 DPI, CNS trypanosomes were predominantly long slender (LS) while BSF were a mixture of short stumpy and intermediate forms. The density of BSF trypanosomes was on average 2-3 log-scales greater than that of CNS trypanosomes with isolate KETRI 2656 having the highest CNS trypanosome density. Conclusions: The pathogenicity study revealed clear differences in the virulence/pathogenicity of the five (5) isolates but no distinct and consistent differences between CNS and BSF forms of the same isolate. We also identified KETRI 2656 as a suitable isolate for acute menigo- encephalitic studies

Complete genome sequences of dengue virus type 2 strains from Kilifi, Kenya

Dengue infection remains poorly characterized in Africa and little is known regarding its associated viral genetic diversity. Here, we report dengue virus type 2 (DENV-2) sequence data from 10 clinical samples, including 5 complete genome sequences of the cosmopolitan genotype, obtained from febrile adults seeking outpatient care in coastal Kenya

Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Kenyan blood donors.

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Africa is poorly described. The first case of SARS-CoV-2 in Kenya was reported on 12 March 2020, and an overwhelming number of cases and deaths were expected, but by 31 July 2020, there were only 20,636 cases and 341 deaths. However, the extent of SARS-CoV-2 exposure in the community remains unknown. We determined the prevalence of anti-SARS-CoV-2 immunoglobulin G among blood donors in Kenya in April-June 2020. Crude seroprevalence was 5.6% (174 of 3098). Population-weighted, test-performance-adjusted national seroprevalence was 4.3% (95% confidence interval, 2.9 to 5.8%) and was highest in urban counties Mombasa (8.0%), Nairobi (7.3%), and Kisumu (5.5%). SARS-CoV-2 exposure is more extensive than indicated by case-based surveillance, and these results will help guide the pandemic response in Kenya and across Africa