<p>Water is the most consumed foodstuff around the world. Therefore it is very important to analyze possible faecal contamination of water, and Enterococci are an indicator for that. They are also used as an indicator for possible faecal contamination in food. Normally you find Enterococci in the intestines of humans and animals, but Enterococci can also give infections like urinary tract infection.</p><p>In this study, varying number of colonies and colours of Enterococci on different media were evaluated. The purpose was to investigate if three different methods would give the same numbers of colonies. Another interesting perspective was to investigate if one medium could be used for two methods. Membrane filter techniques and surface spreading techniques were used to detect Enterococci. These methods were compared with a most probable number method.</p><p>None of the strains showed an optimal result on all media, however one medium, ChromoCult, showed good results for all investigated strains.</p>

Water is the most consumed foodstuff around the world. Therefore it is very important to analyze possible faecal contamination of water, and Enterococci are an indicator for that. They are also used as an indicator for possible faecal contamination in food. Normally you find Enterococci in the intestines of humans and animals, but Enterococci can also give infections like urinary tract infection. In this study, varying number of colonies and colours of Enterococci on different media were evaluated. The purpose was to investigate if three different methods would give the same numbers of colonies. Another interesting perspective was to investigate if one medium could be used for two methods. Membrane filter techniques and surface spreading techniques were used to detect Enterococci. These methods were compared with a most probable number method. None of the strains showed an optimal result on all media, however one medium, ChromoCult, showed good results for all investigated strains.

Le carbure de silicium est un semiconducteur prometteur pour les applications en électronique de température et de haute puissance. La croissance de SiC a été améliorée continuellement pendant les derniers années mais la connaissance des processus à la surface pendant la croissance est encore faible. Dans cette thèse ces processus sont étudiés par l’analyse de la croissance initiale de cristaux non désorientés. Le processus qui limite la vitesse de croissance est déterminé. L’étude des germes observés occasionnellement permet d’avoir un aperçu des barrières Ehrlich-Schwoebel existantes et, de plus, d’estimer l’ordre de grandeur de la longueur de diffusion à la surface. Pour la première fois les lois de croissance de spirales sont systématiquement analysées sur la face silicium et la face carbone du SiC. L’influence d’un domaine limité et du chevauchement de champs de diffusion sur la forme des spirales et les lois de croissance sont analysées par des simulations. Sur les spirales de la face carbone, une nouvelle structure de marches est observée. La bicouche supérieure se dissocie à certaines conditions définies et reproductibles. Les conditions expérimentales sont clairement identifiées et une analyse de cette nouvelle structure est effectuée. / Silicon carbide is a promising semiconductor for high temperature and power electronics. Its growth process has been refined continuously in the last years but there is still little knowledge on the surface processes taking place during growth. This thesis is dealing with these processes by analysing the initial growth of on-axis crystals. The growth rate limiting step of the physical vapour transport technique is determined. The study of nuclei occasionally observed gives insight on the present Ehrlich-Schwoebel barriers and allows furthermore to estimate the order of magnitude of the surface diffusion length. For the first time the growth laws of spirals on both Si- and C- face SiC surfaces are systematically analysed. Simulations are performed in order to check the influence of a limited domain size and overlapping diffusion fields on the spiral shapes and growth laws. A novel spiral step structure is observed on C-face spirals. The top bilayer dissociates under certain and reproducible conditions. The experimental parameters are reported and further analysis of this new step structure is performed.