RESUMEN
AIMS: To gain an understanding of the environmental factors that affect the growth of the bacterium Sporosarcina pasteurii, the metabolism of the bacterium and the calcium carbonate precipitation induced by this bacterium to optimally implement the biological treatment process, microbial induced calcium carbonate precipitation (MICP), in situ. METHODS AND RESULTS: Soil column and batch tests were used to assess the effect of likely subsurface environmental factors on the MICP treatment process. Microbial growth and mineral precipitation were evaluated in freshwater and seawater. Environmental conditions that may influence the ureolytic activity of the bacteria, such as ammonium concentration and oxygen availability, as well as the ureolytic activities of viable and lysed cells were assessed. Treatment formulation and injection rate, as well as soil particle characteristics are other factors that were evaluated for impact on uniform induction of cementation within the soils. CONCLUSIONS: The results of the study presented herein indicate that the biological treatment process is equally robust over a wide range of soil types, concentrations of ammonium chloride and salinities ranging from distilled water to full seawater; on the time scale of an hour, it is not diminished by the absence of oxygen or lysis of cells containing the urease enzyme. SIGNIFICANCE AND IMPACT OF STUDY: This study advances the biological treatment process MICP towards field implementation by addressing key environmental hurdles faced with during the upscaling process.
Asunto(s)
Carbonato de Calcio/química , Microbiología del Suelo , Sporosarcina/crecimiento & desarrollo , Precipitación Química , Medios de Cultivo/química , Agua Dulce/química , Agua Dulce/microbiología , Agua de Mar/química , Agua de Mar/microbiología , Suelo/química , Sporosarcina/metabolismo , Urea/análisis , Ureasa/metabolismoRESUMEN
Burst fractures were created in the spines of twelve dairy calves and the mechanism of indirect canal clearance studied. The spines were reduced posturally and divided in to four subsets--control, and subsets in which either the posterior longitudinal ligament (PLL), the PLL and annulus, or posterior osteoligmentous structures were sectioned. The specimens were then instrumented and further reduction obtained through application of extension and distraction forces. Statistically significant reduction of the intracanal burst fragment occurred even if the PLL or PLL and annulus were incompetent but did not occur in that group in which the posterolateral complex had been sectioned.