Biogrouting is a new ground improvement method that has been studied in recent years. This method involves mainly the use of a microbially induced calcite precipitation process to bind soil particles to increase the strength or to fill in the pores of soil or joints of rock for seepage control. There are two major challenges in the use of biogrout for seepage control through rock joints. The first is how to inject the biogrout solutions, and the second is to understand the mechanisms for the formation of calcite under seepage flow. In this paper, a study on the injection of biogrout solution and the formation of precipitates along a circular 1D flow channel is presented. To minimize the influence of flow, a new one-phase injection method to inject bacterial solution and cementation agents simultaneously was adopted in this study. Factors affecting the formation and distribution of precipitates along the flow channel such as flow velocity, flow rate, and aperture of flow channel were investigated. The experimental results indicated that less calcite was precipitated at locations further away from the injection point due to depletion of the reactants’ concentrations along the flow path. Using the one-phase injection method, the bacterial activity had a major effect on the accumulation of the calcite on the inner surface of the flow channel. The total calcite precipitated on the surface of the flow channel increased slightly with increasing bacterial activity or flow rate. An equation to predict the distance travelled by the biosolution has been derived based on the testing results.
Perciformes, the largest order of vertebrates with 20 suborders, is the most diverse fish order that dominates vertebrate
ocean life. The complete mitochondrial control region (CR) of Trichiurus japonicus (Trichiuridae, Scombroidei) and Pampus sp. (Stromateidae, Stromateoidei) were amplified and sequenced. Together with data from GenBank, the tandem repeats in the
mitochondrial CR from 48 species, which covered nine suborders of Perciformes, are reported in this study. The tandem repeats
tend to be long in the suborder Percoidei and Stromateoidei. The identical repeats in 21 species of Cichlidae suggest a common
origin and have existed before species divergence. Larimichthys crocea shows tandem repeats instead of the typical structure of the central conserved sequence blocks, which was first reported
in Perciformes and vertebrates. This might have resulted from interruption of the polymerase activity during the H-strand
synthesis. The four broader patterns presented here for the tandem repeats, including those in both the 5′ and 3′ ends, only
in the either 5′ or 3′ end, and in the central conserved domain of the control region, will be useful for understanding the
evolution of species. 相似文献
The ability of several ab initio models to predict experimental 29Si-NMR chemical shift is examined. The shielding values of trimethylsilyl chloride (A), t-butyldimethylsilyl chloride (B)
and allytrimethylsilane (C) are calculated by GIAO, CSGT and IGAIM methods, using HF/6–31G*, B3LYP/6-31G*, HF/6–311+G**, B3LYP/6–311+G** and MPW1PW91/6–311+G** models respectively. The 29Si chemical shifts calculated by GIAO method using HF/6–311+G** model are highly in agreement with those obtained experimentally. All of the models above reproduce the trends of chemical
shifts in all cases studied, suggesting that the models are of practical value. 相似文献