Inelastic Behaviour Of Thin-Walled Circular Steel Tubular Columns Under Pushover And Cyclic Loading

Thin-walled circular steel tubular columns have been used as bridge piers widely around the globe because of their excellent seismic performance: ductility, strength, and energy dissipation capacity. This thesis investigates the inelastic behavior of thin-walled circular steel tubular columns with a uniform section and thin-walled circular steel columns with diaphragms. The loading protocol considered for this study is either pushover or cyclic lateral loading in the presence of a constant axial load. The effects of a pushover and cyclic lateral loading on the behavior of the thin-walled circular steel tubular bridge piers have been evaluated through analysis of failure mode, hysteresis curve, envelope curve, stiffness and strength degradation characteristic, and energy-dissipating capacity, including interaction effects of local buckling and flexural buckling, and post-buckling regimes. The analysis applies the finite element model (FEM) that considers the effect of both material and geometric nonlinearities. Also, in this research a comprehensive parametric study was carried out to investigate the effects of the key design parameters and namely are: the radius to thickness parameter (Rt), the column slenderness ratio parameter (λ), and the magnitude of axial load (P/Py). Finally, a series of proposed formulae for strength and ductility evaluation for thin-walled circular steel tubular columns are given

Assessing Economic Viability of Pasture Enterprise as Adaptation Strategy in Dry Land Ecosystems - A Case of Ijara, Kenya

To adapt to impacts of climate change and variability that outwit traditional coping mechanisms, communities in the semi-arid Ijara, spontaneously took to pasture enterprise strategy. The spontaneity translated into unclear costs and benefits that impeded management of the scarce resources. The study clarified costs and benefits by isolating them for analysis and measuring the strategies’ viability for adaptation. The objective was to measure costs incurred and benefits gained from avoided damages through adoption of the strategy at community farm-level. Costs-benefit-analysis was the design used, complemented by the financial market-driven 15% discounting rates and net present values. Also co-ordinated regional downscaling experiment models were used to ascertain climate performance and projection. Household questionnaire was administered to 240 sample size calculated from 9000 farmer population.  Fifty-seven per cent pastoralists had  embraced agro-pastoralism to incorporate on-farm rain-fed Sudan grass, whose input costs were US$1333/ha/season with estimated yields of 1.8 tons/ha of dry matter. Cash flow across three rain-fed seasons netted US$21390, US$45214 and US$67820 per hectare from one, two and three seasons respectively. Overall net present value was US$ 2000p.a. Equal to 50.5% agro-pastoralists produced fodder that cushioned against the high costs on inter-county importation.  Land size inadequacy and the communal tenure  upset 86.26% producers  whereas 47.5%  were concerned that drought raised production costs the most after that lack of skills 53.08%, feed deficit at 30.41%, and diseases 20.41% in that order. Overall benefits from the strategy exceeded costs, making the investment viable for adaptation. Going forward and considering the limited adaptation capacities, disease control and feed deficit costs, policies need to focus on formulating livestock improvement guidelines to include revitalizing traditional grazing management practices. Other pertinent investment opportunities include strategic value-chain linkages and infrastructure, promotion of rain-fed and irrigated fodder production technologies incorporating climate-smart water harvesting, supporting post-harvest feed reserves technologies, reviewing land tenure system and investing in local farmer-friendly weather data collection and application Keywords: Adaptation strategy, benefits and costs, climate change, pasture enterpris

Cascaded clinical mentoring improves health workers selfefficacy in provision of integrated HIV care in rural hospitals in Kenya

Objective: To evaluate cascaded clinical mentorship strategy on access and health-worker’s self-efficacy in delivery of integrated HIV services. Design: A cross sectional survey study design. Setting: Government health facilities in the Coastal region and City of Nairobi, Kenya. Participants: Nurses and clinical officers who were recipients of cascaded mentorship. Intervention: Training of volunteer health-workers on mentorship and the HIV care package by a team of master mentors followed by support to carry out mentorship among fellow health-workers. Outcome measure: Access to HIV services, and health-worker self-reported efficacy in delivering integrated HIV care services based on an anonymous standard self-administered tool that evaluated 9 domains of HIV care. Results: There was an exponential increase in mentorship services, 126 volunteer health-workers were trained, and they formed 22 multidisciplinary District teams who extended mentorship to 231 health facilities. In the 33 months a total of 5503 mentor visits and 7724 mentoring sessions were made. The evaluated 150 health workers self-reported significant improvement in all 9 domains of HIV care compared to baseline (p < 0.001). Health-workers were exposed to a mean of 6 mentor-ship sessions. On controlling for region and cadre of staff, number of mentor-ship sessions were significantly associated with increased competence in 7 of 9 fields (p< 0.01). Compared to volunteer mentors, mentorship and site visits by master mentors were five and twice more costly respectively. Conclusions: Cascaded HIV mentorship increased staff self-efficacy and access to HIV treatment services. The impact of this cascaded mentorship on patient outcomes should be evaluated

Evaluation of phytochemical, antioxidant and antibacterial activity of edible fruit extracts of Ziziphus abyssinica A. Rich

SUMMARY The conventional chemicals used in preservation of meat are perceived as harmful by health conscious consumers due to their potential toxicity. This has resulted in a general shift of preference to the use of traditional herbal remedies that are proven not to have any known negative effects. The pastoralists from West Pokot district use the fruit paste of Ziziphus abyssinica A. Rich for meat processing and preservation. However, the preservative mechanism of Z. abyssinica remains unknown. In the present study the aqueous and methanol extracts of the fruit paste of this herb, that is traditionally used by the Kenyan pastoralists of West Pokot for meat preservation, were subjected to qualitative phytochemical analysis using the Trease and Evans (1989) methods; antibacterial properties using agar-diffusion method with the test microorganisms Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans; antioxidant activity using stable radical 2, 2 diphenylpicrylhydrazyl (DPPH), and toxicity using brine shrimps lethality test. From each of the extracts, fractions containing 100 and 200mg/ml were used in all tests. Alkaloids, saponins, flavonoids and polyphenolics, condensed tannins, reducing compounds, sterols and steroids were detected. The diameter of bacterial colony growth inhibition at an extract concentration of between 100 and 200mg/ml ranged between 9 to 15mm. The minimum inhibitory concentration (MIC) of the aqueous extract ranged between 3.13 and 50mg/ml, while the LC 50 was 270µg/ml. The reducing activity presented as a percentage ranged between 90 -96%. The fruit extracts of Z. abyssinica were found to have highly potent antioxidant activity compared to the control sodium metabisulphite and the results lend scientific credence to justify the use of this plant in the preservation of meat

A longitudinal analysis of the vaginal microbiota and vaginal immune mediators in women from sub-Saharan Africa

In cross-sectional studies increased vaginal bacterial diversity has been associated with vaginal inflammation which can be detrimental for health. We describe longitudinal changes at 5 visits over 8 weeks in vaginal microbiota and immune mediators in African women. Women (N = 40) with a normal Nugent score at all visits had a stable lactobacilli dominated microbiota with prevailing Lactobacillus iners. Presence of prostate-specific antigen (proxy for recent sex) and being amenorrhoeic (due to progestin-injectable use), but not recent vaginal cleansing, were significantly associated with microbiota diversity and inflammation (controlled for menstrual cycle and other confounders). Women (N = 40) with incident bacterial vaginosis (Nugent 7-10) had significantly lower concentrations of lactobacilli and higher concentrations of Gardnerella vaginalis, Atopobium vaginae, and Prevotella bivia, at the incident visit and when concentrations of proinflammatory cytokines (IL-1β, IL-12p70) were increased and IP-10 and elafin were decreased. A higher 'composite-qPCR vaginal-health-score' was directly associated with decreased concentrations of proinflammatory cytokines (IL-1α, IL-8, IL-12(p70)) and increased IP-10. This longitudinal study confirms the inflammatory nature of vaginal dysbiosis and its association with recent vaginal sex and progestin-injectable use. A potential role for proinflammatory mediators and IP-10 in combination with the vaginal-health-score as predictive biomarkers for vaginal dysbiosis merits further investigation

Induction of humoral immune response to multiple recombinant Rhipicephalus appendiculatus antigens and their effect on tick feeding success and pathogen transmission

BACKGROUND: Rhipicephalus appendiculatus is the primary vector of Theileria parva, the etiological agent of East Coast fever (ECF), a devastating disease of cattle in sub-Saharan Africa. We hypothesized that a vaccine targeting tick proteins that are involved in attachment and feeding might affect feeding success and possibly reduce tick-borne transmission of T. parva. Here we report the evaluation of a multivalent vaccine cocktail of tick antigens for their ability to reduce R. appendiculatus feeding success and possibly reduce tick-transmission of T. parva in a natural host-tick-parasite challenge model. METHODS: Cattle were inoculated with a multivalent antigen cocktail containing recombinant tick protective antigen subolesin as well as two additional R. appendiculatus saliva antigens: the cement protein TRP64, and three different histamine binding proteins. The cocktail also contained the T. parva sporozoite antigen p67C. The effect of vaccination on the feeding success of nymphal and adult R. appendiculatus ticks was evaluated together with the effect on transmission of T. parva using a tick challenge model. RESULTS: To our knowledge, this is the first evaluation of the anti-tick effects of these antigens in the natural host-tick-parasite combination. In spite of evidence of strong immune responses to all of the antigens in the cocktail, vaccination with this combination of tick and parasite antigens did not appear to effect tick feeding success or reduce transmission of T. parva. CONCLUSION: The results of this study highlight the importance of early evaluation of anti-tick vaccine candidates in biologically relevant challenge systems using the natural tick-host-parasite combination

Clinical evaluation of Corridor disease in Bos indicus (Boran) cattle naturally infected with buffalo-derived Theileria parva

Corridor disease (CD) is a fatal condition of cattle caused by buffalo-derived Theileria parva. Unlike the related condition, East Coast fever, which results from infection with cattle-derived T. parva, CD has not been extensively studied. We describe in detail the clinical and laboratory findings in cattle naturally infected with buffalo-derived T. parva. Forty-six cattle were exposed to buffalo-derived T. parva under field conditions at the Ol Pejeta Conservancy, Kenya, between 2013 and 2018. The first signs of disease observed in all animals were nasal discharge (mean day of onset was 9 days post-exposure), enlarged lymph nodes (10 days post-exposure), and pyrexia (13.7 days post-exposure). Coughing and labored breathing were observed in more than 50% of animals (14 days post-exposure). Less commonly observed signs, corneal edema (22%) and diarrhea (11%), were observed later in the disease progression (19 days post-exposure). All infections were considered clinically severe, and 42 animals succumbed to infection. The mean time to death across all studies was 18.4 days. The mean time from onset of clinical signs to death was 9 days and from pyrexia to death was 4.8 days, indicating a relatively short duration of clinical illness. There were significant relationships between days to death and the days to first temperature (chi2 = 4.00, p = 0.046), and days to peak temperature (chi2 = 25.81, p = 0.001), animals with earlier onset pyrexia died sooner. These clinical indicators may be useful for assessing the severity of disease in the future. All infections were confirmed by the presence of macroschizonts in lymph node biopsies (mean time to parasitosis was 11 days). Piroplasms were detected in the blood of two animals (4%) and 20 (43%) animals seroconverted. In this study, we demonstrate the successful approach to an experimental field study for CD in cattle. We also describe the clinical progression of CD in naturally infected cattle, including the onset and severity of clinical signs and pathology. Laboratory diagnoses based on examination of blood samples are unreliable, and alternatives may not be available to cattle keepers. The rapid development of CD requires recognition of the clinical signs, which may be useful for early diagnosis of the disease and effective intervention for affected animals

Organic photovoltaic devices with enhanced efficiency processed from non-halogenated binary solvent blends

The development of processing routes to fabricate organic photovoltaic devices (OPVs) using non-halogenated solvents is a necessary step towards their eventual commercialisation. To address this issue, we have used Hansen solubility parameter analysis to identify a non-halogenated solvent blend based on a mixture of carbon disulphide and acetone. This solvent blend was then used to deposit a donor–acceptor polymer–fullerene thin-film that was then used as the active layer of bulk-heterojunction OPV. For the benchmark polymer:fullerene system PCDTBT:PC70BM, a power conversion efficiency of 6.75% was achieved; a 20% relative improvement over reference cells processed using the chlorinated-solvent chlorobenzene. Improvements in device efficiency are attributed to an increase in electron and hole conductivity resulting from enhanced fullerene crystallisation; a property that leads to enhanced device efficiency through improved charge extraction

Inherited tolerance in cattle to the apicomplexan protozoan Theileria parva is associated with decreased proliferation of parasite-infected lymphocytes

Theileria parva is the causative agent of East Coast fever and Corridor disease, which are fatal, economically important diseases of cattle in eastern, central and southern Africa. Improved methods of control of the diseases are urgently required. The parasite transforms host lymphocytes, resulting in a rapid, clonal expansion of infected cells. Resistance to the disease has long been reported in cattle from T. parva-endemic areas. We reveal here that first- and second-generation descendants of a single Bos indicus bull survived severe challenge with T. parva, (overall survival rate 57.3% compared to 8.7% for unrelated animals) in a series of five field studies. Tolerant cattle displayed a delayed and less severe parasitosis and febrile response than unrelated animals. The in vitro proliferation of cells from surviving cattle was much reduced compared to those from animals that succumbed to infection. Additionally, some pro-inflammatory cytokines such as IL1β, IL6, TNFα or TGFβ which are usually strongly expressed in susceptible animals and are known to regulate cell growth or motility, remain low in tolerant animals. This correlates with the reduced proliferation and less severe clinical reactions observed in tolerant cattle. The results show for the first time that the inherited tolerance to T. parva is associated with decreased proliferation of infected lymphocytes. The results are discussed in terms of whether the reduced proliferation is the result of a perturbation of the transformation mechanism induced in infected cells or is due to an innate immune response present in the tolerant cattle

tropiTree:an NGS-based EST-SSR resource for 24 tropical tree species

The development of genetic tools for non-model organisms has been hampered by cost, but advances in next-generation sequencing (NGS) have created new opportunities. In ecological research, this raises the prospect for developing molecular markers to simultaneously study important genetic processes such as gene flow in multiple non-model plant species within complex natural and anthropogenic landscapes. Here, we report the use of bar-coded multiplexed paired-end Illumina NGS for the de novo development of expressed sequence tag-derived simple sequence repeat (EST-SSR) markers at low cost for a range of 24 tree species. Each chosen tree species is important in complex tropical agroforestry systems where little is currently known about many genetic processes. An average of more than 5,000 EST-SSRs was identified for each of the 24 sequenced species, whereas prior to analysis 20 of the species had fewer than 100 nucleotide sequence citations. To make results available to potential users in a suitable format, we have developed an open-access, interactive online database, tropiTree (http://bioinf.hutton.ac.uk/tropiTree), which has a range of visualisation and search facilities, and which is a model for the efficient presentation and application of NGS data