The concept of structure–soil–structure dynamic interaction was introduced, and the research methods were discussed. Based on several documents, a systematic summary of the history and status of the structure–soil–structure dynamic interaction research that considers adjacent structures was proposed as a reference for researchers. This study is in the initial stage, given its complexity and excessive simplification of the model for soil and structures, and should be carried forward for its significance. An attempt was made to summarize the common major computer programs in this area of study. Furthermore, the advantages, disadvantages, and applicability of such programs were discussed. The existing problems and the future research trend in this field were also examined. 相似文献
According to the known sequence of iron stress-induced gene (isiAB operon), we cloned its 1.5 kb fragment by PCR, and used this fragment as integration homologous fragment. After several steps of subcloning donor DNA into theisiAB fragment, a donor plasmid pZL which could be integrated into the chromosomal DNA ofSynechococcus sp. PCC7942 was constructed. In order to express the heterologous gene at a high level through the integration platform system, we constructed the donor DNA by the following steps. We cloned the strong promoter (240 bp) of heat shock genegroESL operon fromSynechococcus sp. PCC7942 by PCR. Then subcloned the multiple cloning sites (MCS),rbcS polyA into the downstream of thegroESL promoter. The kanamycin resistance gene, as the marker gene, was also subcloned into the donor DNA. Thus, in the donor plasmid pZL, the integration homologous fragment and several expression elements, such asgroESL promoter, MCS,rbcS polyA terminator and kanamycin resistance gene, were all included.
After naturally transformed and introduced the donor plasmid pZL intoSynechococcus sp. PCC7942, as in the pZL, the donor DNA sequence is flanked by two DNA fragments (0.4 kb and 0.7 kb) homologous to theisiAB fragment ofSynechococcus sp. PCC7942, the homologous DNA can recombine with the chromosomal DNA. After screening by kanamycin, the transformants which integrated the heterologous DNA were selected. The efficiency of transformation is about 1×10−6. By southern blot analysis, it was confirmed that the donor DNA had been integrated into the chromosomal DNA ofSynechococcus sp. PCC7942, located on the site of theisiAB gene, and can be replicated with the chromosomal DNA.
At ambient conditions, witherite is the stable form of BaCO3 and has the aragonite structure with space group Pmcn. Above ~10 GPa, BaCO3 adopts a post-aragonite structure with space group Pmmn. High-pressure and high-temperature synchrotron X-ray diffraction experiments were used to study the stability and equation of state of post-aragonite BaCO3, which remained stable to the highest experimental P–T conditions of 150 GPa and 2,000 K. We obtained a bulk modulus K0 = 88(2) GPa with $K'$ = 4.8(3) and V0 = 128.1(5) Å3 using a third-order Birch-Murnaghan fit to the 300 K experimental data. We also carried out density functional theory (DFT) calculations of enthalpy (H) of two structures of BaCO3 relative to the enthalpy of the post-aragonite phase. In agreement with previous studies and the current experiments, the calculations show aragonite to post-aragonite phase transitions at ~8 GPa. We also tested a potential high-pressure post–post-aragonite structure (space group C2221) featuring four-fold coordination of oxygen around carbon. In agreement with previous DFT studies, ΔH between the C2221 structure and post-aragonite (Pmmn) decreases with pressure, but the Pmmn structure remains energetically favorable to pressures greater than 200 GPa. We conclude that post–post-aragonite phase transformations of carbonates do not follow systematic trends observed for post-aragonite transitions governed solely by the ionic radii of their metal cations. 相似文献
Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectral version of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）, focusing on the eastern Antarctica （EA） continent in austral summer. First, we evaluated the ability of the model to simulate the EA surface cooling, and found the model can successfully reproduce the cooling trend of the EA surface, as well as the circulation change circling the South Pole in the past 30 years. Second, we compared the two experiments and discovered that the ozone depletion causes the cooling trend and strengthens the circumpolar westerly flow. We further investigated the causes of the EA surface cooling associated with the ozone hole and found two major contributors. The first is the ozone-hole direct radiation effect （DRE） upon the surface that happens because the decrease of the downward longwave （LW） radiation overcomes the increase of the downward shortwave （SW） radiation under clear sky. The second is the cloud radiation effect （CRE） induced by ozone depletion, which happens because the decreased downward SW radiation overcomes the increased downward LW radiation in the case of increased cloud. Although the CRE is theoretically opposite to the DRE, their final net effect makes comparable contributions to the EA surface cooling. Compared with the surface radiation budget, the surface heat flux budgets have a much smaller contribution. We additionally note that the CRE is basically ascribed to the circulation change. 相似文献
