A number of ancient charred paddies with a 14C dating of about 5900 a BP were recovered in the sixth excavation at Chuodun Site and are assigned to the Majiabang culture
(7–6 ka BP). To understand their formation mechanism, the ancient charred paddies were compared to modern paddies using FT-IR
spectrum and thermaogravimetric analysis. At the same time, modern charred paddies were made in helium by the laboratory method,
and the structural characteristics of them and the ancient ones were revealed using CP/MAS-13C-NMR. Our results show there are more aromatic moieties in ancient charred paddies compared to modern paddies. The aliphatic
components of modern charred paddies decrease continuously, accompanied by the accumulation of aromatic components, when the
duration and temperature of oxidation increase, and the structure buildings of modern charred paddies are more similar to
ancient ones. Given the planting manner of paddies during Majiabang culture period, these ancient charred paddies might be
a result of the original farming mode involving fire.
Supported by the National Natural Science Foundation of China (Grant No. 40571088) 相似文献
Granitic rocks usually exhibit strongly anisotropy due to pre-existing microcracks induced by long-term geological loadings.
The understanding of the rock anisotropy in mechanical properties is critical to a variety of rock engineering applications.
In this paper, Brazilian tests are conducted statically with a material testing machine and dynamically with a split Hopkinson
pressure bar system to measure both static and dynamic tensile strength of Barre granite. To understand the anisotropy in
tensile strength, samples are cored and labelled using the three principle directions of Barre granite to form six sample
groups. For dynamic tests, a pulse shaping technique is used to achieve dynamic equilibrium in the samples during the dynamic
test. The finite element method is then implemented to formulate equations that relate the failure load to the material tensile
strength by employing an orthotropic elastic material model. For samples in the same orientation group, the tensile strength
shows clear loading rate dependence. The tensile strengths also exhibit clear anisotropy under static loading while the anisotropy
diminishes as the loading rate increases, which may be due to the interaction of pre-existing microcracks. 相似文献
Geotechnical and Geological Engineering - The periodic reservoir water level (RWL) fluctuation on bank slopes during water impoundment in Three Gorges Reservoir (TGR) may lead to the reactivation... 相似文献
Microbes live throughout the soil profile. Microbial communities in subsurface horizons are impacted by a saltwater–freshwater transition zone formed by seawater intrusion (SWI) in coastal regions. The main purpose of this study is to explore the changes in microbial communities within the soil profile because of SWI. The study characterizes the depth-dependent distributions of bacterial and archaeal communities through high-throughput sequencing of 16S rRNA gene amplicons by collecting surface soil and deep core samples at nine soil depths in Longkou City, China. The results showed that although microbial communities were considerably impacted by SWI in both horizontal and vertical domains, the extent of these effects was variable. The soil depth strongly influenced the microbial communities, and the microbial diversity and community structure were significantly different (p < 0.05) at various depths. Compared with SWI, soil depth was a greater influencing factor for microbial diversity and community structure. Furthermore, soil microbial community structure was closely related to the environmental conditions, among which the most significant environmental factors were soil depth, pH, organic carbon, and total nitrogen.