abstract: The objective of this research is to develop a biocompatible scaffold based on dextran and poly acrylic acid (PAA) with the potential to be used for soft tissue repair. In this thesis, physical and chemical properties of the scaffold were investigated. The scaffolds were made using electrospinning and cross-linked under high temperature. After heat treatment, Scanning Electron Microscope (SEM) was used to observe the structures of these scaffolds. Fourier transform infrared spectroscopy (FTIR) was used to measure the cross-linking level of scaffold samples given different times of heat treatment by detecting and comparing the newly formed ester bonds. Single-walled carbon nanotubes (SWCNT) were added to enhance the mechanical properties of dextran-PAA scaffolds. Attachment of NIH-3T3 fibroblast cells to the scaffold and the response upon implantation into rabbit vaginal tissue were also evaluated to investigate the performance of SWCNT dextran-PAA scaffold. SEM was then used to characterize morphology of fibroblast cells and rabbit tissues. The results suggest that SWCNT could enhance cell attachment, distribution and spreading performance of dextran-PAA scaffold. / Dissertation/Thesis / Masters Thesis Bioengineering 2014

Jet Electrochemical Machining (Jet-ECM) is a manufacturing technique that applies a free electrolyte jet to generate the desired shapes [1]. Since the principle of the technique is the same as other techniques of Electrochemical Machining where the material removal takes place based on the anodic dissolution of workpiece, the working distance, which is the distance between nozzle’s front surface and the workpiece surface, is one important parameter of the process. The working distance affects the current density and consequently the geometry removal. The control of the working distance can be done based on the data gathered before and during machining by surface measurement [2]. This measurement usually is done by using electrostatic probing to detect a limited amount of points of the initial workpiece surface. Since electrostatic probing is comparatively slow, laser triangulation represents an alternative technique to detect a larger amount of points before machining within significantly shorter time [3]. In addition to electrostatic probing and laser triangulation, the actual working distance can be measured during the machining process to realize constant working distance. This can be done by detecting electrical signals like the actual total current. This method can be combined with pre-machining measurement by laser triangulation in order to ensure the prevention of any collision between the nozzle and the workpiece. In this study, on-machine metrology techniques for measuring the working gap as well as current measurements will be compared. Besides, the advantages and disadvantages of these techniques will be systematized. In further studies, the possibility of combining the techniques will be investigated to enhance Jet-ECM with more accurate measurement techniques.

In Electrochemical Machining (ECM), where the material removal takes place based on the anodic dissolution of the workpiece material, the working distance is one of the most important parameters. Especially in Jet Electrochemical Machining (Jet-ECM), where a micro nozzle is moved over the initial surface of the workpiece in order to apply an electrolytic free jet to produce the desired shapes, the distance between the nozzle and the workpiece becomes even more important. On the one hand a small working distance is aspired to achieve high current densities resulting in a high efficiency of the process. On the other hand the working distance needs to be large enough to avoid damages on the micro nozzle caused by electrical discharges or mechanical contact. Hence, the adjustment of the working gap is essential to realize a precise, effective and secure Jet-ECM process. The control of the gap size is done based on the data gathered before machining by surface measurement. Until now, the initial surface has been detected by electrostatic probing through moving the nozzle stepwise to the work piece surface and detect the voltage drop between the nozzle and the work piece. With this strategy, only a limited number of points can be detected within adequate time. Hence, in most cases only three points of the initial surface are detected in order to adjust the working distance according to the planar inclination of the workpiece. The coordinates of the three detected points are used to calculate the normal vector of the initial surface. In recent studies, another strategy was analysed, which is realized by dividing the surface into smaller areas and respectively calculating the normal vector of each area in order to obtain more accurate data of the initial surface. A further strategy is to use probing along the machining path of the tool and to gather the coordinates of a number of points along the path. The above mentioned methods usually do not ensure the precise control of the gap size especially for the surfaces with complex geometry with locally confined convex and concave shapes and are highly affected by the size of the probe. In this study, the application of a laser scanner is investigated for the measurement of the workpiece surface before machining to gather the required data for the adjustment of the working distance during Jet-EC machining of complicated surfaces.

Philosophiae Doctor - PhD / A phenomenological philosophy underlies this research study which attempts to understand clinicians’ perception and understanding of an electronic patient record (EPR) system currently operational at a hospital in the Western Cape Province in South Africa (SA). Healthcare is a human right, thus patient records contain critical data and mostly paper-based in many SA hospitals. Clinicians are the EPR primary users and their attitude in its use is important for its success. This study explores, identifies and determines clinicians’ cognitive attributes towards EPR with a technology use framework developed. An initial quantitative approach was applied but unsuccessful due to low sample size. A pilot study was then conducted using 11 respondents. Purposive sampling was first initiated then snowball introduced later to improve the sample size qualitatively. Interviews were administered to 15 clinicians and tape recorded. Narrative content analysis was used as the preferred analysis technique because of the advantage of gaining direct information from study participants, unobtrusive and a nonreactive way to study the phenomenon of interest. Research findings tested 12 propositions and found high impact relationships between attitude (ATT) and each listed theme namely: perceived usefulness (PU), perceived ease of use (PEOU), complexity (COM), facilitating condition (FC), use behaviour (USE). Use behaviour had high impact relationships with storage (STO) and retrieval (RET). There were moderate impact relationships between PU and USE; PEOU and PU; RA and ATT; job fit (JF) and ATT; USE and share (SHA). The implication here is that any EPR system to be implemented should be tested using this framework to ascertain its usefulness and fit with a hospital's objectives and users expectations. By so doing, anticipated problems can be mitigated against and resolved before implementation. The study contributes to the information system (IS) body of knowledge through the technology use framework. The framework is for adoption by hospital management and its use by clinicians where EPR is operational. Traditional IS frameworks can be adopted for hospitals about to implement EPR because of the relevance of the "intent to use" theme.

The chondroitin sulphate proteoglycan (CSPG) versican forms complexes with hyaluronan (HA), which are essential in a range of functions including cellular proliferation and migration. Four isoforms of versican result from alternative splicing. Furthermore, biological roles have been identified for the proteolytic cleavage product of versican which contains the N-terminal G1 hyaluronan binding domain. All of these versican forms have different tightly regulated tissue expression profiles. Consequently, impaired regulation is associated with a number of disease pathologies. For example the largest variants (V0/V1) have been shown to be negative indicators of disease outcome in a number of malignant cancers and are a marker of disease progression in atherosclerosis. Interestingly, the smaller versican isoform V3 which lacks CS chains has been demonstrated to have the potential to reverse disease associated phenotypes. The motivation for carrying out the work in this thesis was to try and gain a better understanding of how versican functions on a molecular scale. In this regard, the first aim was to investigate the structure of the hyaluronan binding region of versican using a construct called VG1. The structure of VG1 was analysed in the presence and absence of hyaluronan oligomers. This revealed an insight into the multi-modular structure of the versican hyaluronan binding region and demonstrated that on binding to HA, VG1 under goes a conformational change. Furthermore, the interaction between VG1 and longer lengths of hyaluronan (pHA) was investigated. This demonstrated that when VG1 binds to pHA it is does so with positive cooperativity, packing very close to neighbouring VG1 molecules along a chain of HA. One consequence of this interaction was to reorganise pHA into a helical conformation, an organisation that was confirmed by a number of solution phase techniques. The effect of this reorganisation of pHA by VG1 on HA/CD44 interactions was also assessed. Previously the interaction between CD44 (a cell surface hyaluronan receptor) and long chains of HA (>30 kDa) was shown to be irreversible; however we demonstrate that VG1 can reverse this. Furthermore, a TSG-6 enhanced CD44/interaction was also completely reversed by the addition of VG1. This provides an indication that a functional hierarchy of hyaluronan binding proteins may exist which could have important implications in understanding the function of hyaluronan complexes. Currently, we do not know whether intact versican molecules could interact with HA in the same way as VG1. However, preliminary data suggests that the CS-containing variants (i.e. V0, V1 and V2) would not, whereas V3 and versican fragments could. This work provides an exciting mechanistic insight into the function of versican variants and their breakdown products.

Enterprise document management has been in a long-term progress. Not long ago only files and folders were enough for enterprise document management, but nowadays most of enterprise documents are in the electronic form. The electronisation of enterprise documents has carried simplified manipulation, but it has also caused disorderliness in many cases. Systems called Document managament system (DMS) bring support for better management of electronic enterprise documents. This diploma thesis deals with the implementation of DMS into the environment of a specific company where it is designed to support effective function concerning enterprise document management.

Le mélanome cutané est le cancer de la peau le plus agressif de par sa grande plasticité phénotypique, son fort caractère métastatique et sa résistance aux traitements. L’émergence d’inhibiteurs ciblant la forme mutée de la kinase BRAF (BRAF V600E) a produit des réponses thérapeutiques spectaculaires, malheureusement suivies par l’apparition rapide de résistances secondaires très agressives. La compréhension des mécanismes cellulaires et moléculaires impliqués dans ces résistances constitue donc un prérequis indispensable à l’amélioration de ces thérapies ciblées. A côté des altérations intrinsèques au mélanome, les interactions entre les cellules malignes et leur microenvironnement favorisent la survie tumorale et contribuent à la résistance aux thérapies. En particulier, la matrice extracellulaire (MEC), qui constitue un réseau dynamique de macromolécules de composition et de propriétés physico-chimiques variables, influence l’architecture des tissus tumoraux, l’invasion et la réponse aux traitements. De façon importante, l’acquisition par les cellules de mélanome d’un phénotype mésenchymateux invasif a été décrite comme un mécanisme d’échappement aux thérapies ciblant la mutation oncogénique de BRAF. Dans ce contexte, l’objectif de mon travail de thèse a été de préciser le rôle de cette signature phénotypique sur les propriétés bio-mécaniques des cellules de mélanome et la réponse aux thérapies ciblées. Dans la première partie de ma thèse, j’ai observé que les cellules résistantes présentant un phénotype invasif mésenchymateux produisent, assemblent et remodèlent une matrice ayant des propriétés mécaniques et biochimiques proches de myofibroblastes. Ce phénotype est associé à une activation de la voie YAP/TAZ et une mécano-sensibilité amplifiée. La caractérisation par spectrométrie de masse du matrisome des cellules résistantes a révélé la présence abondante de protéines matricielles comme la Fibronectine, le Collagène 1(I) et la THBS1 mais également de protéines de réticulation du collagène comme LOXL2 et TGM2. Nos données montrent aussi que ces modifications sont conférées de novo par un traitement aux inhibiteurs de BRAF ou de MEK dans des cellules de mélanome mutées BRAF in vitro, et que chez la souris le traitement au Vémurafénib de cellules de mélanome xénogreffées induit l’assemblage de fibres de collagène associé à une rigidification tumorale. Finalement, j’ai pu montrer que la matrice produite par les cellules mésenchymales résistantes protège les cellules de mélanome naïves des effets anti-prolifératifs liées à l’inhibition de BRAF ou MEK. Dans une deuxième partie de ma thèse, je me suis intéressée à la protéine de réticulation du collagène de la famille des lysyl oxidases (LOX), LOXL2 exprimée par les cellules mésenchymales résistantes. Nos analyses bioinformatiques et biochimiques montrent que l'expression de cette enzyme est fortement associée à la signature invasive MITFlow AXLhigh des mélanomes. En utilisant des approches d'interférence à ARN, j'ai aussi montré que la suppression de LOXL2 dans les cellules de mélanome invasif diminue la migration cellulaire et augmente la prolifération cellulaire in vitro et in vivo, suggérant un rôle de LOXL2 dans la transition phénotypique du mélanome. Dans l’ensemble, mes travaux de thèse révèlent un rôle paradoxal de l’inhibition de la voie MAPK qui induit des changements du phénotype tumoral associés à la production autonome par la cellule maligne d’une MEC pathologique capable d'altérer le comportement cellulaire et la réponse au traitement. Cet environnement matriciel 'sanctuaire', associée à une intense hétérogénéité tumorale, pourrait jouer un rôle majeur dans le développement et l'émergence des résistances thérapeutiques du mélanome. Ces résultats permettent une meilleure compréhension du rôle de la MEC du mélanome et devraient proposer de nouvelles pistes pour améliorer les traitements. / Cutaneous melanoma remains one of the most challenging and difficult cancers to treat because of its high plasticity, metastatic potential and resistance to treatment. New therapies targeting oncogenic BRAFV600E mutation have shown remarkable clinical efficacy. However, drug resistance invariably develops. Thus, the need for improving existing therapies remains critical. Recent studies have indicated that tumor resistance arises from the tumor microenvironment in which the extracellular matrix (ECM) is a determinant factor. Here, we found that BRAF inhibitor (BRAFi)-resistant melanoma cells, but not BRAFi-sensitive cells display an increased mechanosensitivity associated with a capacity to produce and remodel a 3D ECM displaying increased levels of matrix proteins such as fibronectin (FN) and collagen fibers. Interestingly, our results show that this 3D ECM is able to protect therapy-sensitive cells from the anti-proliferative effects of MAPKi. In addition, short exposures of naive melanoma cells to MAPKi augment matrix proteins production and assembly in vitro and in vivo. This 3D ECM also promotes drug tolerance within BRAFi sensitive cells. In conclusion, our results suggest that a subset of resistance to MAPK targeted therapies is associated with the production by melanoma cells of a pathological fibrotic matrisome that may affect cell behavior and therapeutic response.

Thesis ( M.Sc.(Agricultural Economics)) --University of Limpopo, 2019. / Potato is perceived as an excellent crop in the fight against hunger and poverty. The recent high potato price in South Africa has pushed the vegetable out of reach of the poorest of the poor. The study attempts to analyse potato price volatility in South Africa and furthermore assess how various factors were responsible for the recent potato price volatility. Quarterly data for potato price, number of hectares planted, rainfall and temperature levels from 2006q1 to 2017q4 was collected from various sources and were used for analysis. The total observation of 48. The volatility in the series was determined by performing ARCH/GARCH model. GARCH model indicates an evidence of GARCH effect in the series, meaning that GARCH model influences potato price volatility in South Africa. The Johansen cointegration used both trace and eigenvalue to test the existence of a long run relationship between potato price and various variables. The cointegration results were positive indicating that there exists long run relationship amongst variables. The study further used Johansen cointegration as well as standard error to determine the number of cointegrating variables in the long run. The results indicated that the number of hectares planted and rainfall level have significant relationship with potato price. Wald tests was used to check whether the past values of number of hectares planted and rainfall level influenced the current value of potato price. The Walt test results concluded that there is no evidence of short run causality running from number of hectares planted and rainfall level to potato price. In the study, ECM model was used to forecast the potato price fluctuation in South Africa. The study recommends that farmers need to engage in contract market so as to minimize the risk of potato price volatility. The Department of Agriculture should forecast agricultural commodities price volatility and make information accessible to the farmers so that they are able to adopt strategies that will assist them to overcome crisis.

The main aim of this paper are models of Li-Ion storage batteries made and simulated in ANSYS Fluent software. Various ways of simulations are discussed with main aim on ECM method and how its numerical model is computed. A process of getting information and required data from real battery to be compared with simulation results by EIS method is also discussed. These results are then compared with results from ANSYS Fluent.

This master thesis deals with the efficiency improvement proposal of the deburring technology of the edge of the holes intersection inside of the given part. In the introductory chapter it deals with the introduction of Česká zbrojovka a.s. company, where the creation of this thesis took place. The definition of the fire guns, some of the special products of the CZUB a.s. company and the description of the given part are following. The third chapter contains the description of the current manufacturing process. In the second part the proposals of the possible technologies are listed along with their current state. In the end a technical-economic evaluation is accomplished.