Laboratory test procedures to predict the thermal behaviour of concrete.

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of PhilosophyThe cracking of mass and structural concrete due to thermal stress is a major problem in the concrete construction industry. Concrete will crack when the thermal stress exceeds tbe tensile strength of the concrete, Decisions on the type of concrete mix, cooling facilities and construction techniques to be used in the erection of a concrete structure can only be made if the thermal behaviour and strength of the concrete can be predicted during hydration. This thesis describes the development of a low cost, computer controlled, adiabatic calorimeter to determine tlte heat of hydration and a probe to determine the thermal conductivity or concrere samples. The main thrust of this thesis is the development of the thermal conductivity probe which, for the first time, can measure the thermal conductivity of concrete through all stages of hydration. A thermal model was also developed to verify the results, and the use of the calorimeter for temperature matched curing tests is also discussed. Results, obtained from the test procedures described, will provide far more accurate predictions of the temperatures in concrete structures than was possible in the past.Andrew Chakane 201

Post exercise sauna bathing is an effective method of heat acclimating middle distance and endurance runners

This study investigated whether post-exercise sauna bathing can effectively heat acclimate middle distance and endurance runners. 16 runners (age 20 ± 2 years, BMI 21.3kg/m² ± 1.2kg/m², 11 females: 5 males) performed a heat tolerance test (HTT, 30 minutes running at 9kph, 2% incline; 40°C, 40%RH) pre, 3 weeks and 7 weeks after heat acclimation (HA; 30-minutes post-exercise sauna bathing (105-108°C) 3±1 times per week) or control. Measures included rectal temperature, skin temperature, sweat loss, heart rate, and forearm blood flow. Perceptual responses (perceived exertion, thermal comfort and thermal sensation) were also recorded. 3 week cohort: (n = 16, 10 Sauna, 6 Control). Following HA, sauna participants showed significantly reduced core temperature (p = .023), skin temperature (p = .020), HR (p = .020), increased sweat sensitivity (p = .032) and improved perceptual responses (all p = <.01) during the HTT. Controls saw no significant changes in any measure. 7 week cohort: (n = 7, 5 Sauna, 2 Control). Core temperature (p = <.01), skin temperature (p = .03), exercising heart rate (p = .017) and perceptual measures (all p= <.01) during the HTT were further reduced in sauna participants. Additionally post-exercise forearm blood flow and forearm blood flow sensitivity decreased from pre-intervention to 7 weeks (p = .015 and p = .008 respectively). Controls saw no significant changes in any measure. This study found 3 weeks of post-exercise sauna bathing to be an effective heat acclimation strategy. Data from the 7-week cohort shows some evidence that continuing HA from 3 weeks to 7 weeks results in further adaptation

Electropalatography for articulation disorders associated with cleft palate

Cleft palate is the most common congenital deformity of the face. It could affect speech acquisition, resulting in articulation errors that could persist into adulthood. Electropalatography (EPG) has been used in speech therapy with individuals who have articulation problems that are unresponsive to "standard treatment" procedures

A publicly available vessel segmentation algorithm for SLO images

Background and Objective: Infra-red scanning laser ophthalmoscope (IRSLO) images are akin to colour fundus photographs in displaying the posterior pole and retinal vasculature fine detail. While there are many trained networks readily available for retinal vessel segmentation in colour fundus photographs, none cater to IRSLO images. Accordingly, we aimed to develop (and release as open source) a vessel segmentation algorithm tailored specifically to IRSLO images. Materials and Methods: We used 23 expertly annotated IRSLO images from the RAVIR dataset, combined with 7 additional images annotated in-house. We trained a U-Net (convolutional neural network) to label pixels as 'vessel' or 'background'. Results: On an unseen test set (4 images), our model achieved an AUC of 0.981, and an AUPRC of 0.815. Upon thresholding, it achieved a sensitivity of 0.844, a specificity of 0.983, and an F1 score of 0.857. Conclusion: We have made our automatic segmentation algorithm publicly available and easy to use. Researchers can use the generated vessel maps to compute metrics such as fractal dimension and vessel density.Comment: 9 pages, 4 figure

The fluvial history of the lower Vaal River catchment

Cosmogenic nuclide burial dating was used to determine the age of ancient alluvial terrace deposits in the lower Vaal River catchment, and thus provide an absolute fluvial chronology. A poor chronological framework has been the primary shortcoming of previous fluvial history studies as there was no accurate way to evaluate or correlate the proposed driving mechanisms with the fluvial events themselves. Cosmogenic nuclide burial dating has shown that there have been three periods, each of both river incision and alluvial gravels and fines aggradation, in the Pliocene. Burial dating determined that periods of bedrock incision have occurred relatively rapidly over short periods of time, following lengthy periods of net aggradation. It has been proposed that the lower Vaal River catchment provided the ideal situation for rapid bedrock incision to pro- ceed sporadically. The Vaal River in its lower reaches is largely confined to pre-Karoo valleys that are filled with soft, easily erodible Karoo rocks. When these rocks are at least partially exposed along the river channel/valley, rapid bedrock erosion and incision occurs through the action of saltating resistant clasts abrading the channel. It has been argued that these incision events oc- cur only when suitable climatic conditions develop that allow for the complete erosion of alluvial gravel deposits lining the Vaal River channel/valley (i.e. fre- quent and large formative discharges are needed to achieve this). Periods of gravel aggradation have been attributed to an increase in coarse sediment sup- ply, primarily through the erosion of older alluvial deposits in the valley during periods of reduced vegetation cover. Periods of fine sediment aggradation are the net result of a reduction in the capacity of formative discharges, a direct result of a drying climate. It is thus apparent that climate change has played the most important role in controlling the fluvial evolution of the Vaal River. Climate controls fluvial events by determining the Vaal River’s net transport ability. Various combinations of changes in transport and erosion potentials, in both the river and surrounding landscape, have resulted in varying fluvial outcomes. In conclusion, the fluvial evolution of the lower Vaal River catch- ment is unique due to a number of aspects. The structure of the pre-Karoo surface and readily available resistant clasts from older terrace deposits and tillite, in conjunction with climate change, have proved crucial in shaping the Vaal River’s fluvial history

Food cost and availability in a rural setting in Australia

Introduction: The burden of chronic diseases is rapidly increasing worldwide. In&nbsp; Australia rural populations have a greater burden of disease. Chronic diseases are largely preventable with diet as a key risk factor. With respect to diet-related chronic disease, dietary risk may be due to poor food access, namely, poor availability and/or the high cost of healthy food. It is likely that poor food access is an issue in rural areas. Objective: To assess food access in rural south-west (SW) Victoria, Australia.Methods: A total of 53 supermarkets and grocery stores in 42 towns participated in a survey of food cost and availability in the rural area of SW Victoria. The survey assessed availability and cost of a Healthy Food Access Basket (HFAB) which was designed to meet the nutritional needs of a family of 6 for 2 weeks.Results: Seventy-two percent of the eligible shops in SW Victoria were surveyed. The study found that the complete HFAB was significantly more likely to be available in a town with a chain-owned store (p&lt;0.00). The complete HFAB was less likely to be available from an independently owned store in a town with only one grocery shop (p&lt;0.004). The average cost of the HFAB across SW Victoria was AU380.30 ± 25.10 (mean &plusmn; SD). There was a mean range in difference of cost of the HFAB of $36.92. In particular, high variability was found in the cost of fruits and vegetables.Conclusions: Cost and availability of healthy food may be compromised in rural areas. Implications: Improvements in food access in rural areas could reduce the high burden of disease suffered by rural communities.<br /

Adaptabilidad de la fibra de basalto a fijadores óseos

El cuerpo humano tiene la sorprendente capacidad de regenerar el tejido dañado de un hueso fracturado. A esta cualidad hay que añadirle el hecho de que los huesos evolucionan adaptándose a las solicitaciones mecánicas a las que se encuentran sometidos. Esta virtud, consecuencia de la evolución de la naturaleza hacia estructuras optimizadas, deriva en el deseo de emular e imitar estas estructuras por parte de la ciencia e ingeniería. Es el caso de los materiales de los fijadores óseos utilizados para el tratamiento de fracturas, y en los que predominan actualmente los metales como el acero inoxidable o el titanio. En el caso de los materiales compuestos, cuyo comportamiento mecánico se asemeja al hueso mucho más que los materiales metálicos, puede residir la próxima generación de fijadores más flexibles. La fibra de carbono ya se emplea con éxito para el tratamiento de muchos tipos de fracturas, pero materiales como los compuestos de fibra de basalto suponen un salto más allá al tener unas propiedades mecánicas más afines al hueso, especialmente por su módulo de Young en la dirección de la fibra. En este trabajo, se desarrollan en primer lugar los conceptos necesarios para comprender la preferencia por materiales de los fijadores cuyas propiedades mecánicas se asemejen a las del hueso. Para ello es necesario estudiar la biomecánica ósea, los procesos biológicos que tienen lugar durante la reparación ósea, los fundamentos de los fijadores óseos y las propiedades de los biomateriales. Una vez desarrollados estos conceptos, se fabricarán una serie de laminados de fibra de basalto-epoxy para realizar una caracterización mecánica y evaluar sus propiedades. El análisis de los resultados obtenidos en los ensayos permitirá establecer un principio de valoración de la viabilidad del material para su aplicación en fijadores óseos.The human body has the extraordinary capacity of regenerating the damaged tissue of a fractured bone. To this virtue it must be added the fact that bone’s mechanical properties evolve adapting themselves to the loads to which they are submitted. This circumstance, consequence of the evolution of nature towards optimized structures, derives on science and engineering’s desire of emulating and imitating these forms. It is the case of the materials used in bone internal fixation, nowadays dominated by metals like stainless steel or titanium alloys. In the case of composite materials, whose mechanical behaivour is much closer to that of bones than metals, can be found the next generation of flexible plates for bone fixation. Carbon fiber has already been used successfully as a bone implant material, but other fibers such as basalt may be a better alternative as their mechanical properties are far more similar to those of bone, especially for their Young’s modulus in the fiber direction. In this work, all concepts necessary to comprehend the preference for mechanically bone-like fixator materials are developed. For this purpose, it is necessary to study the biomechanics of bone, the biological processes related to bone healing, the fundaments of bone fixation and the definition of biomaterial’s properties. Once all this has been clarified, a basalt fiber-epoxy laminate will be fabricated to make a mechanical characterization and evaluate its properties. The analysis of the results will allow us to establish a primary assessment of the viability of basalt fibers for their use in bone internal fixation.Universidad de Sevilla. Grado en Ingeniería de Tecnologías Industriale

Outcomes of ventriculoperitoneal shunt insertion in the management of idiopathic intracranial hypertension in children

Purpose The ventriculoperitoneal (VP) shunt has become the procedure of choice for treatment of idiopathic intracranial hypertension (IIH). We aimed to assess the efficacy of frameless stereotactic placement of VP shunts for the management of medically resistant IIH in children and to assess the role of gender and obesity in the aetiology of the condition. Methods This is a retrospective analysis of the case notes of 10 patients treated surgically at the University Hospital of Wales in Cardiff, from May 2006 to September 2012. Results VP shunts were successful in relieving headache, papilloedema and stabilising vision. No sex predilection was identified, and increased BMI was a feature throughout the population, regardless of age. Conclusions Neuronavigated VP shunt insertion is an effective mode of treatment for medically resistant IIH in children. The aetiological picture in children does not seem to be dominated by obesity, as in adults. Literature on childhood IIH is sparse, and larger scale, comparative studies would be of benefit to treating clinicians

Low-Temperature Wafer-Scale Deposition of Continuous 2D SnS2 Films

Semiconducting 2D materials, such as SnS2, hold immense potential for many applications ranging from electronics to catalysis. However, deposition of few-layer SnS2 films has remained a great challenge. Herein, continuous wafer-scale 2D SnS2 films with accurately controlled thickness (2 to 10 monolayers) are realized by combining a new atomic layer deposition process with low-temperature (250 degrees C) postdeposition annealing. Uniform coating of large-area and 3D substrates is demonstrated owing to the unique self-limiting growth mechanism of atomic layer deposition. Detailed characterization confirms the 1T-type crystal structure and composition, smoothness, and continuity of the SnS2 films. A two-stage deposition process is also introduced to improve the texture of the films. Successful deposition of continuous, high-quality SnS2 films at low temperatures constitutes a crucial step toward various applications of 2D semiconductors.Peer reviewe