Search

The ball bearing market is mature where there is a massive range of products available with new ones being developed all the time due to technological advancements. Additive Manufacturing (AM) provides a promising approach for developing oil-impregnated ball bearings. Oil impregnated bearings are critical for applications requiring smooth and low-friction motion. This study explores the feasibility of utilizing laser powder bed fusion (LPBF) technology to fabricate 304 stainless steel (304SS) samples with open pores, which can then be impregnated with a lubricant. To achieve this, 304SS powder was used, and optimum selective laser melting (SLM) printing parameters were altered to induce intentional pores. Initial screening of samples involved Archimedes density measurements and computed tomography (CT) scanning was conducted on a selected samples to assess their porosity levels. CT scan foam analysis results indicated a correlation between hatch spacing and porosity. Results revealed trends in cell volume and solidified scanning tracks thickness, indicating greater connectedness with larger pores. Synthesis of these findings could help in the development of efficient and reliable open pores that may find use in oil-impregnated self-lubricating ball bearings. [ABSTRACT FROM AUTHOR]

This study presents the development of a material selection decision support system for an automotive rooftop tent. The system uses five parameters of material cost, formability, corrosion resistance, tensile strength and hardness to optimize material choice from a list of aluminium alloy options. This was done before production via the deep drawing process can commence. The parameters were quantified using the average market prices for each alloy, product requirements obtained from the case study and the performance data that was obtained from the uniaxial tensile and hardness tests. These inputs were combined with the developed material selection framework and then programmed into a web-based decision support system for automated, data-driven material selection. The output presents the recommendation for the optimum material that balances cost-effectiveness and performance. The decision support system was successfully used to select the optimum alloy for the rooftop tent. Results show that AA1050 is the optimum material, providing weight reduction at the minimum achievable cost without compromising the product requirements for the rooftop tent. The decision support system is also scalable, and this allows it to be used with larger datasets for different products and processes in the future. [ABSTRACT FROM AUTHOR]

Haematocrit Levels is defined as the proportion, by volume, of the blood that consists of red blood cells. This study was conducted to model the progress of haematocrit levels over time in kidney patients after their transplant and to determine how the progress depends on the age and gender of the patient and other factors. This is a longitudinal study, and haematocrit level was considered as a response while the covariates were time, gender, age, cardio-vascular problem during the years preceding the transplantation, and rejection symptoms during the first three months after the transplantation took place of the patients. Different statistical methods such as, multivariate regression model, two stage analysis and linear mixed effects model were employed to explore the progress of haematocrit over time. Models revealed that haematocrit levels in kidney transplant patients evolve over time. Gender and Age of the patient have significant effect on the evolution of haematocrit levels. Males tend to have a high increase in haematocrit levels over time than females. With regards to age, haematocrit levels tend to increase with increasing age. Moreover, it was observed that experience of cardio-vascular problems before trandplant and rejection symptoms did not have a significant effect on the progress of haematicrit levels. The growth of Haematocrit levels evolve over time follows a quartic time effect. Change in haematocrit levels varies according to gender and age of the patient. Patients starting with low haematocrit levels tend to have a larger increase over time. [ABSTRACT FROM AUTHOR]

Barrier bednets (BBnets), regular bednets with a vertical insecticidal panel to target mosquitoes above the bednet roof, where they are most active, have the potential to improve existing Insecticidal Treated Bednets (ITNs), by reducing the quantity of insecticide required per net, reducing the toxic risks to those using the net, potentially increasing insecticide choice. We evaluated the performance of PermaNet 3.0 (P3) and untreated (Ut) bed nets with and without pyrethroid and piperonyl butoxide roof barriers in killing pyrethroid-resistant and susceptible Anopheles gambiae, simultaneously video-recording mosquito flight tracks. Bioassay results showed that treated roof barriers, particularly the longitudinal P3 barrier (P3L) could be an effective addition to a bed net: P3 + P3L were consistently significantly more effective than the reference P3 bednet while performance of untreated nets could be raised to equal that of the reference P3 following the addition of a P3 barrier. The BBnet's potential to augment existing bednets and enhance their performance is considered. [ABSTRACT FROM AUTHOR]

Monitoring the presence of commensal and pathogenic respiratory microorganisms is of critical global importance. However, community-based surveillance is difficult because nasopharyngeal swabs are uncomfortable and painful for a wide age range of participants. We designed a methodology for minimally invasive self-sampling at home and assessed its use for longitudinal monitoring of the oral, nasal and hand microbiota of adults and children within families. Healthy families with two adults and up to three children, living in and near Liverpool, United Kingdom, self-collected saliva, nasal lining fluid using synthetic absorptive matrices and hand swabs at home every two weeks for six months. Questionnaires were used to collect demographic and epidemiological data and assess feasibility and acceptability. Participants were invited to take part in an exit interview. Thirty-three families completed the study. Sampling using our approach was acceptable to 25/33 (76%) families, as sampling was fast (76%), easy (76%) and painless (60%). Saliva and hand sampling was acceptable to all participants of any age, whereas nasal sampling was accepted mostly by adults and children older than 5 years. Multi-niche self-sampling at home can be used by adults and children for longitudinal surveillance of respiratory microorganisms, providing key data for design of future studies. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) can be used to manufacture tool inserts with cooling channels conforming to the shape of the part to be produced. This results in shorter cycle times and improved quality. In the hot stamping industry, there is need to reduce cycle time and improve quality. The process differs from injection moulding since it involves larger tool inserts, high temperature and forces. In hot stamping tools, the cooling channels are in the form of straight drilled channels. These channels do not have the capacity to cool complex shaped parts consistently due to restrictions in machining. There is need for further studies on the design of hot stamping tools with AM-based cooling channels. The aim of this paper is to propose a method for designing hot stamping tools with conformal cooling channels. The method involves firstly evaluating the part to decide whether it is suitable for AM application, determining conformal cooling parameters and developing alternative layouts. This is followed by selection of the optimum layout and obtaining the cooling system parameters. [ABSTRACT FROM AUTHOR]

Conformal cooling channels introduced into manufacturing tools is fast becoming an industry standard, as it has proven to significantly reduce cycle time during operation. Introducing conformal cooling channels into a metal tool (such as a hot forming punch or injection moulding core) is a challenge on its own and often requires expertise in both additive and subtractive processes to execute efficiently. Another issue is that of the inherent constraints of both the additive and subtractive processes, which prohibit the effective use of these processes for manufacturing of specific tool designs. Thus, often a balance needs to be met, where a hybrid process is sought to utilise the advantages of both processes while limiting the disadvantages. This study suggests a viable process chain for manufacturing a large hybrid tool using milling and selective laser melting processes. A large (745 × 174 × 78.7 mm) hot forming punch with conformal cooling channels was produced by splitting the tool into four sections to fit into the build envelope of the M2 cusing machine from Concept Laser GmbH. Various considerations and challenges are highlighted. [ABSTRACT FROM AUTHOR]

The objective of the study was to examine strategies employed by farmers to mitigate the effects of drought on cattle production in communal rangelands of Zimbabwe. Data were collected from a total of 316 communal cattle farming households selected from semi-arid and sub-humid environments (158 each) using structured questionnaires. Farmers in sub-humid environments mostly resorted to controlled migration in search of pastures during drought whilst those in semi-arid environments mainly supplemented their cattle (P < 0.05). Travelling long distances to centralized water tanks was ranked first as a strategy to counter water shortage in sub-humid environments whilst in semi-arid environments farmers mostly resorted to use of boreholes (P < 0.05). Farmers in sub-humid environments were more than twice more likely to supplement their cattle than those in semi-arid environments (P < 0.05). Crop residues were the main type of feed used to supplement cattle during drought periods (P > 0.05). Mashona cattle were the most preferred breed (P > 0.05). Conformation traits were less preferred in both environments (P < 0.05). It was concluded that communal cattle producers in both environments use dietary supplementation with crop residues and controlled migration in search of pastures and water to mitigate drought effects. Given the shortcomings associated with drought mitigation strategies being used by communal cattle farmers, current findings suggest the need to design and implement sustainable strategies such as breeding cattle for drought resilience and selective supplementary feeding. [ABSTRACT FROM AUTHOR]

The occurrence of residual stresses in selective laser melting (SLM) presents challenges that limit the capability of the process to manufacture parts at industrial scale. These stresses can have irreversible effects such as warping and cracking of parts during and post manufacturing. One of the most important SLM parameters that should be controlled carefully in order to effectively manage residual stresses is the scanning strategy. This study presents an evaluation of four different scanning strategies, namely the island, successive, successive chessboard and least heat influence (LHI) scanning strategies with respect to their influence on residual stresses and distortions. All the scanning strategies were investigated by melting single tracks on tool steel substrates without powder. Measurement of residual stresses was performed on selected positions on the substrates before and after exposure to the laser beam using the x-ray diffraction technique. The successive chessboard scanning strategy was found to contribute to the least average residual stresses, and lowered residual stress by up to 40% relative to the default island scanning strategy. Further to this, the influence of the successive chessboard and island scanning strategies on distortions was evaluated. Similar to the residual stress findings, the successive chessboard contributed to lower form deviations compared to the island strategy. The scanning strategies were also evaluated based on their impact on total scanning times, with the successive chessboard strategy showing slightly lower scanning time than that for the island and LHI chessboard strategies. [ABSTRACT FROM AUTHOR]

A study was conducted to investigate the seroprevalence and associated risk factors of Chlamydia abortus infection in cattle and some selected wildlife species at selected interface areas at the periphery of the Great Limpopo Transfrontier Conservation Area in Zimbabwe. Three study sites were selected based on the type of livestock-wildlife interface, porous livestock-wildlife interface (unrestricted), non-porous livestock-wildlife interface (restricted by fencing), and livestock-wildlife non-interface (totally absent or control). Sera were collected from cattle aged ≥ 2 years representing both female and intact male. Sera were also collected from selected wild ungulates from Mabalauta (porous interface) and Chipinda Pools (non-interface) areas of the Gonarezhou National Park. Sera were tested for antibodies to Chlamydia abortus using a CFT. A X2 test was used to assess differences between categories and p < 0.05 was considered as significant. In cattle, the overall seroprevalence was 32.7% (327/1011; 95% CI 29.5-35.3). A significantly lower seroprevalence was recorded for the porous interface (24.2%) compared to the non-porous (42.5%) (p < 0.0001) and the non-interface (36.2%) (p = 0.001). Overall, the wet season recorded a significantly (p = 0.015) higher seroprevalence than the dry season. In wildlife, antibodies were detected in buffaloes (47.7%) and impalas (43.8%) but not in kudus. Buffaloes from Chipinda Pools (53.4%) had a significantly (p = 0.036) higher seroprevalence than those from Mabalauta (26.1%). The results established the presence of chlamydiosis in cattle and selected wildlife and that independent infections may be maintained in buffalo populations. Further studies are required to clarify chlamydiae circulating between cattle and wildlife. [ABSTRACT FROM AUTHOR]

This retrospective study aimed to assess the spatial and temporal distribution of anthrax and to identify risk areas in Zimbabwe. The data were extracted from the monthly and annual reports of the Division of Livestock Production and Veterinary Services for the period 1967 to 2006. The data were analyzed in relation to temporal and spatial factors. The hot-dry season was found to be significantly ( X = 847.8, P < 0.001) associated with the occurrence of anthrax in cattle, and the disease was found to be approximately three times more likely to occur during this season compared to other seasons. Anthrax outbreaks demonstrated a gradual temporal increase from an annual mean of three outbreaks for the 5-year period (1967-1971) to 42 for the 5-year period (2002-2006). Similarly, the data demonstrated a spatial increase in the number of districts affected by anthrax between 1967 and 2006, with 12 districts affected for the 10-year period (1967-1976) that expanded to 42 districts for the 10-year period (1997-2006). The majority of outbreaks (83.7%) were recorded in rural areas, and 11 districts were found to be at a higher risk than others. There is need to develop differential vaccination strategy, other control strategies and preventive recommendations to reduce anthrax in high-risk districts. In the medium- to low-risk districts, maintenance of effective surveillance systems and improvement of awareness is very important to detect and contain outbreaks early. [ABSTRACT FROM AUTHOR]

cross-sectional study was conducted to investigate seroprevalence of brucellosis and the associated risk factors in cattle from smallholder dairy farms in Gokwe, Marirangwe, Mushagashe, Nharira, Rusitu and Wedza areas of Zimbabwe. A total of 1,440 cattle from 203 herds were tested serially for Brucella antibodies using Rose Bengal test and the competitive ELISA. Weighted seroprevalence estimates were calculated and risk factors in individual cattle investigated using logistic regression analysis. The overall individual animal brucellosis seroprevalence was low, with mean of 5.6% (95% confidence interval (CI), 4.4%, 6.8%). Gokwe had the highest individual (12.6%; 95% CI, 3.9%, 21.4%) and herd-level (40.0%; 95% CI, 22.1%, 58.0%), while Wedza had the lowest individual (2.3%; 95% CI, 0%, 5.3%) and herd-level (8.0%; 95% CI, 0.0%, 18.9%) brucellosis seroprevalence, respectively. In individual cattle, the area of origin, age and history of abortion were independently associated with brucellosis seroprevalence. While the seroprevalence was independent of sex, it decreased with increasing age. Cattle 2-4 years old had higher odds (odds ratio (OR) = 3.2; 95% CI, 1.1%, 9.1%) of being seropositive compared to those >7 years. Cows with a history of abortion were more likely to be seropositive (OR = 7.9; 95% CI, 3.1, 20.1) than controls. In conclusion, the area-to-area variation of brucellosis may be linked to ecological factors and differences in management practices. The implementation of stamping out policy, bleeding and testing animals before movement and promoting the use self-contained units are likely to significantly reduce the public health risks associated with Brucella infections in cattle. [ABSTRACT FROM AUTHOR]

cross-sectional questionnaire-based study was conducted to assess milk producers' awareness of milk-borne zoonoses in selected smallholder and commercial dairy farms of Zimbabwe. The questionnaire was designed to obtain information on dairy breeds, milk production, dairy farmers' knowledge and awareness of zoonoses with particular emphasis on milk-borne zoonoses and farmers' behavioural practices that may lead to increased risk of milk-borne zoonoses transmission. A total of 119 dairy farmers were interviewed, and 41.5% were aware of milk-borne zoonoses with a significantly ( P < 0.01) higher percentage of commercial dairy farmers (65.0%) being aware compared to smallholder dairy farmers (36.7%). The behavioural practices of dairy farmers observed to increase the risk of milk-borne zoonoses transmission were; consumption of raw milk (68.1%), sale of raw milk to the local public (25.2%), lack of cooling facilities by smallholder farmers (98%), and no routine testing (84.9%) and medical check-ups (89.1%) for milk-borne zoonoses. General hygienic and disease control practices need to be integrated in the milk production process particularly at the smallholder level. Awareness, teaching and training programmes for smallholder dairy farmers can improve disease control in animals and reduce the public health risk of milk-borne zoonoses. [ABSTRACT FROM AUTHOR]

cross-sectional study was conducted between January 2007 and February 2008 to estimate seroprevalence of brucellosis and identify risk factors associated with Brucella infections in commercial cattle in three districts of Lusaka province (Chongwe, Luangwa, and Kafue; n = 849) and in one rural district from the Central province ( n = 48). A total of 897 serum samples were randomly collected from 55 farms along with animal-level data such as sex, age, and parity. Sera were screened for presence of anti- Brucella antibodies using the Rose Bengal test, and positive samples were confirmed using competitive enzyme-linked immunosorbent assay. At the animal level, seroprevalence was estimated at 7.9% (95% CI = 4.4–11.4%) in the Lusaka province and 18.7% (95% CI = 7.5–29.9%) for Chibombo district. Brucellosis seroprevalence varied according to district, with Chongwe district recording the highest compared to other districts. Seroprevalence also varied according to sex with bulls ( n = 96) having higher seroprevalence (12.5%; 95% CI = 3.8–21.1%) compared to females (8.1%; 95% CI = 4.6–11.6). Similarly, seroprevalence varied according to age groups, with the age category 1–4 years recording the highest (10.7%). The study recorded relatively low Brucella seroprevalence in commercial farms in Lusaka, compared to the traditional small-scale farms. We suggest that testing and stamping out of infected animals is likely to improve the situation and significantly reduce the public health risk associated with Brucella infections in animals. [ABSTRACT FROM AUTHOR]

Responses to tuberculin in Zebu cattle of the transhumant pastoral farming system in Karamoja region and Nakasongola district in the north-eastern and mid-central regions in Uganda, respectively, were investigated using a comparative intradermal tuberculin skin test. Of the 1864 cattle tested from 30 large units (superherds) in Karamoja and 7 herds in Nakasongola, a total of 28 animals from 19 herds (51.4%) tested positive. Inter-district tuberculin reactor prevalence variations seemed to be influenced by climate, with impact on both the management patterns and transmissibility of agent. High herd tuberculin reactor prevalence (51.4%) was attributed to widespread contacts and mixing of animals between herds. Low individual animal tuberculin test positivity (mean = 1.4%) was attributed to low transmissibility of the agent under the Karamoja climate, which is semi-arid, and to increased resistance due to non-specific response to environmental mycobacteria and natural selection, since there was no active control against bovine tuberculosis. Owing to similarities in management practices in Karamoja and widespread risk factors, it was difficult to identify which were more important, but variations in sources of drinking water pointed to provision of lake and borehole water during dry season as reducing the risk. Positive bovine tuberculin reactor prevalence and skin reactor status were related to age. [ABSTRACT FROM AUTHOR]

A cross-sectional study was performed in the livestock–wildlife interface areas of Lochinvar and Blue Lagoon National Parks and the non-interface area of Kazungula to determine the prevalence of antibodies to Brucella spp. in domestic ruminants and identify individual animal risk factors of infection. A total of 1245 cattle from 124 herds and 280 goats and sheep from 29 flocks were tested sequentially for Brucella antibodies using the Rose Bengal test (RBT) and competitive ELISA. In cattle, individual seroprevalence ranged from 14.1% to 28.1%, while herd sero–prevalence ranged from 46.2% to 74.0% in the three study areas. No goat or sheep tested positive for Brucella antibodies. Three types of cattle grazing strategies were encountered: locally grazed herds (LGH), transhumantly grazed herds (TGH) and river flood plain grazed herds (FGH). Brucella seroprevalence was seen to vary according to area and grazing strategy: Lochinvar and transhumant grazed herds recorded the highest figures, respectively. Age, sex and history of abortion were found to have independent effects on individual seroprevalence. This study establishes that brucellosis is endemic in domestic animals in the livestock–wildlife interface areas of Blue Lagoon and Lochinvar national parks and the disease is also present in Kazungula. We observed that type of grazing strategy had significant impact on cattle Brucella seroprevalence and that transhumant herds were at high risk of being infected. [ABSTRACT FROM AUTHOR]