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Application of Bayesian Method in Geology and Geochemistry
QIAN Hang, ZHANG Nan, TIAN Meng
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (6): 1201-1217.   DOI: 10.13209/j.0479-8023.2025.021
Abstract987)   HTML    PDF(pc) (902KB)(167)       Save
The introduction to Bayesian methods is presented from the perspective of inversion modeling, outlining the fundamental principles, computational techniques, development history, and current research status. Various methods and their applications across different fields of geology and geochemistry are analysed in detail. Finally, the future development directions and challenges are discussed.
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Preliminary Investigation on the Origin of Geoid Anomalies in the Tethys Tectonic Domain
YAN Peilong, ZHANG Nan
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (2): 403-410.   DOI: 10.13209/j.0479-8023.2025.011
Abstract1942)   HTML    PDF(pc) (12150KB)(1821)       Save
Regarding the large-scale gravity field response in the Tethyan tectonic domain, this work aims to connect specific wavelength of geoid anomaly with the mantle structure caused by Tethys evolution. To acheive this, spherical harmonic spectrum analysis and kernel analysis on global geoid are employed, and the global geoid is further calculated by forward modeling with the mantle structure obtained by global seismic tomography. Density structure in our geoid calculation is obtained by seismic tomography. Through spherical harmonic analysis of global geoid observation, the geoid anomalies of the Tethyan tectonic domain exhibit a spherical harmonic degree 7 wavelength scale. Analysis of geoid kernels provides initial constraints on the density source depth of Tethyan geoid anomalies. Finally, through global geodynamic numerical modeling, the degree 7 density anomaly at depths of 425–1000 km in the mantle corresponds well with the Tethyan geoid anomalies in the Indonesian, Burmese, Tibetan Plateau, and Zagros regions. Preliminarily, the observed degree 7 geoid anomalies indicate slab remnants in the central and eastern segments of the Tethys at depths of 425–1000 km in the mantle.
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Study on the Mechanism of Mantle Plume Production: Taking Ferrar as an Example
LIU Xiaoxu, DANG Zhuo, ZHANG Nan
Acta Scientiarum Naturalium Universitatis Pekinensis    2022, 58 (2): 234-240.   DOI: 10.13209/j.0479-8023.2022.018
Abstract2092)   HTML    PDF(pc) (3582KB)(1478)       Save
According to the mantle convection control equations, taking the Ferrar large igneous province (LIP) erupted at 180 Ma as an example, we used the 3D numerical simulation method and introduced Pangea supercontinent, large low shear velocity provinces (LLSVPs), subductions surrounding Pangea supercontinent to simulate mantle convection process. The evolution process of Ferrar LIP from the interior thermal boundary layer of the earth (such as the core-mantle boundary) and the related factors affecting the location of mantle plumes are discussed. The results show that the shape of LLSVPs and the distance between subduction zone and LLSVPs’ edge have great influence on the location of mantle plumes. The mantle plumes often rise from the position where the curvature of the LLSVPs’ edge is large, and gradually shift away from the LLSVPs’ edge with the increase of the distance between the subduction zone and the LLSVPs’ edge. The viscosity of the subduction zone affects the timing of the mantle plume emergence, but not the location of the mantle plume production. 
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Investigation on Biofilm-Forming Characteristics of the Nitrogenous Heterocyclic Compound-Degrading Bacteria in a Flow Cell System
XIONG Fuzhong, ZHANG Nan, WEN Donghui, LI Qilin
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (5): 907-916.   DOI: 10.13209/j.0479-8023.2020.060
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The flow cell system and confocal laser scanning microscopy were applied to investigate the characteristics of biofilm formed by the nitrogenous heterocyclic compound (NHC)-degrading bacteria under different environmental conditions. The results showed that increasing the initial inoculum density and prolonging the initial attachment time were beneficial to the adhesion and biofilm formation of the NHC-degrading bacteria on the surface of the substrate. When the flow rate of the medium was reduced, the biofilm became more homogeneous and formed more water channel structures. Moreover, the biofilm under different conditions presented a same phenomenon that the inner layer (near the surface) had a low ratio of living cells and the outer layer (distant from the surface) had a high ratio of living cells. Compared with the single-strain biofilm, the dual-strain biofilm had an advantage in thickness, surface coverage ratio and living cell ratio. The target NHC concentration also had a significant effect on the morphology and cell viability of the quinoline-degrading bacteria biofilm: at lower concentration of quinoline, the bacteria formed large and developed aggregates; while at higher concentration, the bacterial aggregates became much smaller and evenly dispersive. Besides, the ratio of living cells of the biofilm formed at lower concentration was remarkably higher than that at higher concentration.
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Effects of Environmental Factors on Degrading Bacterial Biofilm Formation
ZHANG Nan, XIONG Fuzhong, WEN Donghui, YU Cong, LI Qilin
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (2): 345-353.   DOI: 10.13209/j.0479-8023.2015.244
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The authors investigated how environmental factors (pH, temperature, incubation time and concentration of pollutants) effected three NHCs degrading strains’ biofilm forming. The results show significant effects of pH, temperature and incubation time on biofilm formation. The optimum environmental conditions for forming the maximum amount of biofilm is: pH=7, temperature 35°C, and incubation time 36 hours for BC026; pH=8, temperature 35°C, and incubation time 48 hours for BW001; and pH=7–9, temperature 40°C, and incubation time 36 hours for BW004. There is no significant impact on biofilm formation of any degrading bacterium exposed to 0–1600 mg/L of pollutant concentration.

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