Preclinical assessment procedures for wound dressings have been established with the clinical situation in mind, taking into account the important parameters of tensile mechanical properties, conformability to body surfaces, water vapour transmission rate (WVTR) and gaseous transmission (GTR) to 0₂ and CO₂. The mechanical (tensile) properties, the WVTR and the GTR's are measured by modified international standards. These are ASTM D882-81, ASTM E96-81 and BS 2782 respectively. The mechanical test is basically a uniaxial test taken to failure, from which the stress-strain characteristics and the ultimate strength of the material are determined. The WVTR is determined by measuring the rate of water loss from a container, covered with the dressing being evaluated, under controlled humidity conditions. Gaseous transmission, to both oxygen and carbon dioxide, is determined by the British Standard Vacuum technique. This method was used only for the assessment of the hydrophobic dressings. A liquid to gas technique was employed to assess the hydrophilic (water containing) dressings in respect to their transmission characteristics. Conformability is measured by an inflation test. At a pressure of 40 mmHg, a radius of curvature is calculated from the incremental change in height of the central point of a disc of the material under test. Viscoelastic tests were carried out to determine if any of the materials showed viscoelastic behaviour. These properties are of importance in the application of pretensioned dressings. A series of commercial and experimental materials were evaluated using the techniques described above. Some of the materials were assessed as a bi-laminate form, with a Mefix (adhesive bandage) top layer. Such a layer generally proved beneficial with regard to their possible clinical performance. Clinical studies were carried out for both in situ water vapour transmission and conformability. Such studies were carried out to provide a correlation between the laboratory and clinical situations. By providing an indication of possible clinical problems, preclinical assessment is of importance to clinicians and manufacturers.

With bandgap ranging from 1.74 to 2.67eV depending on composition, the ternary alloy (ZnCd)Se is an interesting system for optoelectronic applications. The main purpose of the work reported in this thesis was to characterise some of the electrical properties of crystals of Zn(_x) Cd(_1-x) Se and to assess the " potential in CdSe/Cu(_2)Se and zn(_x)Cd(_1-x)Se/Cu(_2)Se photovoltaic cells. Single crystals of this ternary compound have been grown from the vapour phase using two different methods. With each technique boules of graded composition were produced with the Cd/Zn ratio decreasing towards the end that was last to grow. The variation in composition was determined using atomic absorption spectroscopy and energy dispersive X-ray analysis. Lattice Parameters were determined using X-ray diffractometry and were found to vary linearly with composition over a wide range. This study showed that for x < 0.5 the crystal adopts the hexagonal Wurtzite structure, changing to the cubic sphalerite for higher values of x. The variation is bandgap energy with composition was determined for single crystals of Zn(_x)Cd(1-x)Se at 300K and 9OK and shows that the bandgap changes quadratically in x for x < 0.6. The barrier heights of Aūzn cd(_1-x)sc (x < 0.45) Schottky diodes were calculated from forward I-V characteristics, C-V and photoelectric measurements were also carried out. A good linear relationship with composition was obtained for barrier heights measured by the Photoelectric method. Deep levels were also investigated in these diodes using Photocapacitance, which revealed the presence of two dominant levels having activation energies of 0.4 - 0.5 eV and 0.9 - 1.0 eV (referred to the valence bandedge) that were independent of the composition The second part of the thesis described an investigation into CdSe/CU(_2)Se and Zn(_x)Cd(_1-x)Se/CU(_2)Se (x < 0,4) devices that had been prepared on orientated single crystal substrates by a chemiplating technique. Reflection high energy diffraction (RHEED) showed that the structure of the CU(_2)Se layer took the cubic modification. Cells formed on as-grown low resistivity substrates exhibited no rectification. However good Photovoltaic properties were produced by heating the devices in air or Argon at 200 C, However, for cells formed on higher resistivity CdSe, the resultant devices showed a Photovoltaic effect without any heat treatment. The Photovoltaic output characteristics were measured under simulated AMI illumination. The properties of the Photovoltaic cells prepared on Zn(_x)Cd(1-x)Se single crystals are closely related to those of devices fabricated on CdSe substrates. Cells formed on CdSe were found to have higher short circuit current densities (J(_sc)), but lower open circuit voltage (V(oc)) than those produced on the mixed Zn(_x)Cd(_1-x)Se crystal substrates. Thus the open circuit voltage was increased with zinc content to 420 mv with a Zng(_0.4)Cd(_0.6)Se based cell. However, there was a considerable decrease in the short circuit current. The characterisation of these cells has revealed the main threshold in all the devices Indicated a dominant level with an activation energy of between 1.0 and 1.1 eV with respect to the conduction band in both CdSe and Zn(_x)Cd(_1-x)Se.

The purpose of the study was to conduct documented research on two of the recently designed teaching methods of high school chemistry, the Chemical Education Material Study (CHEM Study) and the Chemical Bond Approach (CBA). An attempt was made to answer certain questions concerning differences in the two methods.

Rammed Concrete is a material study of an old building technique called rammed concrete and its predecessor rammed earth. Rammed earth is a technique used for constructing foundations, floors, and walls with the use of natural materials. It can be found all around the world and is commonly known by its French name “Pisé” from piser which means “to stamp, pound”. In short, earth is extracted from the ground and compacted in layers inside a formwork. Rammed earth structures can be traced all the way back to ancient China, with parts of the Great Wall and Han Dynasty watchtowers utilizing this technique. An updated version of rammed earth also known as rammed concrete, was developed in 1820 by Francois Martin Lebrun. It replaces the clay as its binder with cement. Resulting in a more robust construction, making it more resistant to rain and snow. However, at the beginning of the 20th century, reinforced concrete was introduced and just like anything else deemed less superior – the technique was slowly forgotten and rarely used, at least not for another 100 years. This thesis explores the idea of whether we could build with this technique in a contemporary context.

Continuous improvements are an integral part for the development of everyday life. These improvements do not only ascertain financial gain but also lessening the environmental impact. The purpose of this study is to gain a deeper understanding of the design process and the decisions required to achieve an optimal design with respect to weight reduction, while retaining the required strength. The study will also investigate the choice of material. This will be done through material and design studies, along with strength calculations of the product in question. The conclusion from this study is that it is possible to save a certain percentage of the material used, while keeping the strength, form, fit and function intact. The material study provided with a recommendation of the zinc alloy ZA-8. It is an alloy with a good combination of great strength, low density and price.

Västergarn is a medieval settlement situated on the west coast of the island of Gotland in the Baltic Sea. It has for a long time been the focus of study for researchers due to its cultural heritage in regards of its church, rampart and archaeological remains of a settlement dating to the Early Middle Ages. The University of Uppsala conducted excavations at the site during 2005–2013 which have led to large amounts of archaeological material which enabled several theses being written about the place. This thesis aims to study metal dress accessories from Västergarn and the people behind these artifacts who lived there during the early medieval period. Gender identity, ethnicity and cultural belonging will be addressed. The main part of the thesis focuses on typology and chronology. This will be achieved by a morphological study of the material. In addition to this, an ArcGis study is conducted to study distribution patterns in the settlement. The conclusion is that dress accessories allow different conclusions on the population of Västergarn. In terms of gender, it is argued that both men and women were present, albeit artefacts of male gender dominate the assemblages. The majority of the material in terms of ethnicity and cultural identity can be attributed to a Gotlandic tradition, while some dress accessories seem to come from abroad, to the Slavonic areas and other regions in the Baltic Sea. Also, oriental influences can be seen, mainly in regard to the decorated belt mounts. in conclusion, the result of this thesis indicates that two separate groups, both Gotlanders and non-Gotlanders were active in Västergarn during the early Middle Ages which is visible in the two churches, the Baltic ware pottery and the form of dress accessories people wore at the time.