ABSTRACT
The reciprocating action of the external environment gradually reduces the mechanical properties and water stability of original heritage buildings, resulting in the gradual loss of their cultural value. In this paper, the adobe for the construction of raw soil and cultural relics in western Henan is taken as the research object. The local plain soil is used as the raw material, and the adobe samples are prepared with modified materials such as quicklime and sodium methyl silicate, in order to improve its mechanical properties and water stability. The degree of correlation between the compressive strength, capillary water absorption, pH value, particle size distribution, and the electrical conductivity of modified raw adobe, as well as the modification mechanism of the microstructure, was studied. The results show that the addition of quicklime and sodium methyl silicate can enhance the compressive strength and water resistance of the modified raw adobe, and the optimum dosage is 1.5% sodium methyl silicate; with the increase of the curing age, the compressive strength of the single-mixed quicklime sample, the single mixed sodium methyl silicate samples, and the composite sample were increased by 1.94 times, 12.6 times and 2.61 times, respectively, compared with the plain soil samples, and with the increase of compressive strength, the pH, conductivity and capillary water absorption of the samples decreased continuously. It is evident from the particle gradation test and SEM images that the internal pores of the samples in the modified group become smaller, and the particle structure of the sample doped with sodium methyl silicate is the densest. The results of the study provide support for the restoration of the soil and cultural-relic buildings.
ABSTRACT
OBJECTIVE: To evaluate the risk factors of colorectal cancer in China. METHODS: The results of 14 case-control studies from 1988 to 2000 were analyzed by means of Meta-analysis. The total numbers of cases and controls were 5034 and 5205 respectively. Dersimonian and Laird random effective models were applied in processing data. RESULTS: Light physical activities and dietary fibers were protective factors (pooled OR<0.8); while histories of fecal mucohemorrhage, chronic diarrhea and bowel polyps were highly associated with colorecatal cancer (pooled OR >4) The stratified results indicated that there were probably some differences between OR values of some factors if using different sources of cases and controls or using different data from the north and south of China. CONCLUSION: Risks of colorectal cancer are significantly associated with the histories of intestinal diseases or relative symptoms, fatty food, psychic attack and family history of cancers. The light physical activities and dietary fibers are probably protective factors.