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Summary Experimental investigation shows that amorphous silica is converted into quartz through cristobalite under hydrothermal conditions. The rate of transformation, essentially dependent on the reaction temperature, was studied on the basis of quantitative analyses of quartz in the products, and the variation of quartz content was elucidated by taking the induction period into consideration. The transformation is a consecutive reaction involving two first‐order steps, from amorphous silica to low‐cristobalite and from low‐cristobalite to low‐quartz. Kinetic data such as the rate constants and the energy of activation are obtained. Mineralogical varieties of silica found in siliceous deposits suggest that the transformation probably takes place under natural conditions. Younger deposits contain amorphous silica or cristobalite, whereas older ones are invariably composed of quartz. By assuming that the transformation process observed experimentally holds in nature, kinetic data can be estimated. Since the process depends upon the thermal history, it is possible to follow the transformation process for a given model of a thermal history. An example of computed results is compared with the geological evidence, and it is concluded that the mineralogical variation of silica is accounted for by the transformation process. Zonal distribution of silica minerals apparently corresponds to that of zeolite minerals, and the transformation of silica is considered to occur during diagenesis. Evidently, almost all diagenetic facies represent intermediate stages on the way to the ultimate equilibrium. The cristobalite stage described in this paper belongs to one of these stages, and is referable to the early stage of diagenesis. It is suggested that silica minerals can be used as clues to understand a progressive change in diagenesis.

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The pathophysiology of canine gallbladder diseases, including biliary sludge, gallbladder mucoceles and gallstones, is poorly understood. This study aimed to evaluate the component of gallbladder contents and bacterial infection of the gallbladder in order to elucidate the pathophysiology of biliary sludge and gallbladder mucoceles. A total of 43 samples of canine gallbladder contents (biliary sludge, 21 and gallbladder mucoceles, 22) were subjected to component analysis by infrared spectroscopy, and the resultant infrared spectra were compared with that of swine mucin. Of the 43 samples, 41 were also evaluated by aerobic and anaerobic bacterial culture. The contents of 20 (95.2%) biliary sludge and 22 (100%) gallbladder mucocele samples exhibited similar infrared spectra as swine mucin. Although biliary sludge and gallbladder mucocele contents exhibited similar infrared spectra, one sample of biliary sludge (4.8%) was determined to be composed of proteins. The rate of bacterial infection of the gallbladder was 10.0% for biliary sludge and 14.3% for gallbladder mucoceles. Almost all of the identified bacterial species were intestinal flora. These results indicate that the principal components of gallbladder contents in both gallbladder mucoceles and biliary sludge are mucins and that both pathophysiologies exhibit low rates of bacterial infection of the gallbladder. Therefore, it is possible that gallbladder mucoceles and biliary sludge have the same pathophysiology, and, rather than being independent diseases, they could possibly represent a continuous disease. Thus, biliary sludge could be considered as the stage preceding the appearance of gallbladder mucoceles.

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Complete implementation of simple multidisciplinary prevention measures as a bundle can greatly decrease the incidence of DSWI.