Background: Women suffer from various distress and disturbances after menopause, including osteoporosis, a risk factor associated with multiple diseases. Altered gut microbiota has been implicated in postmenopausal osteoporosis. In this study, to understand gut microbiota signatures and fecal metabolite changes in postmenopausal women with osteoporosis, 108 postmenopausal women were recruited for intestinal microbiota and fecal metabolite detection. Among these participants, 98 patients, who met the inclusion criteria, were divided into postmenopausal osteoporosis (PMO) and non-postmenopausal osteoporosis (non-PMO) groups based on bone mineral density (BMD). The compositions of gut bacteria and fungi were examined by 16 S rRNA gene sequencing and ITS sequencing, respectively. Meanwhile, fecal metabolites were analyzed using liquid chromatography coupled with mass spectrometry (LC-MS). Results: We found that bacterial α-diversity and β-diversity were significantly altered in PMO compared to non-PMO patients. Interestingly, fungi composition showed larger changes, and the differences in β-diversity were more significant between PMO and non-PMO patients. Metabolomics analysis revealed that fecal metabolites, such as levulinic acid, N-Acetylneuraminic acid, and the corresponding signaling pathways were also changed significantly, especially in the alpha-Linolenic acid metabolism and selenocompound metabolism. The screened differential bacteria, fungi, and metabolites closely correlated with clinical findings between these two groups, for example, the bacterial genus, Fusobacterium, the fungal genus, Devriesia, and the metabolite, L-pipecolic acid, were significantly associated with BMD. Conclusions: Our findings indicated that there were remarkable changes in gut bacteria, fungi, and fecal metabolites in postmenopausal women, and such changes were notably correlated with patients’ BMD ​​and clinical findings. These correlations provide novel insights into the mechanism of PMO development, potential early diagnostic indicators, and new therapeutic approaches to improve bone health in postmenopausal women.

Accurate characterization of coal reservoir micro- and nanopores is crucial in evaluating coalbed methane storage and gas production capacity. In this work, 12 coal-bearing rock samples from the Jurassic Yan’an Formation, Longdong area, Ordos Basin were taken as research objects, and micro- and nanopore structures were characterized via scanning electron microscopy, high-pressure mercury pressure, low-temperature N₂ adsorption and low-pressure CO₂ adsorption experiments. The main factors controlling coal pore structure development and the influence of pore development on the gas content were studied by combining the reflectivity of specular samples from the research area, the pore microscopic composition and the pore gas content determined through industrial analyses and isothermal absorption experiments. The results show that the coal strata of the Yan’an coal mine are a very important gas source, and that the coal strata of the Yan’an Formation in the study area exhibit remarkable organic and clay mineral pore development accompanied by clear microfractures and clay mineral interlayer joints, which together optimize the coal gas storage conditions and form efficient microseepage pathways for gas. Coalstone, carbonaceous mudstone and mudstone show differential distributions in pore volume and specific surface area. The general trend is that coal rock is the best, carbonaceous mudstone is the second best, and mudstone is the weakest. The coal samples’ microporous properties are positively correlated with the coal sample composition for the specular group, whereas there is no clear correlation for the inert group. An increase in the moisture content of the air-dried matrix promotes adsorption pore development, leading to increases in the microporous volume and specific surface area. CH₄ adsorption in coal rock increases with increasing pressure, and the average maximum adsorption is approximately 8.13 m³/t. The limit of the amount of methane adsorbed by the coal samples, V_L, is positively correlated with the pore volume and specific surface area, indicating that the larger the pore volume is, the greater the amount of gas that can be adsorbed by the coal samples, and the larger the specific surface area is, the greater the amount of methane that can be adsorbed by the coal samples. The P_L value, pore volume and specific surface area are not correlated, indicating that there is no direct mathematical relationship between them.

In this study, an abundant 17 alpha(H)-diahopanes has been observed in the sediments from the seventh member of the Triassic Yanchang Formation in the central part of the Ordos Basin. The results show that the maturity has a minor contribution to the relative abundance of 17 alpha(H)-diahopanes as the maturity of the samples are similar and fall into a limited range in the selected samples from the study area. The C27-C29 regular steranes distributions of the samples are also similar and shaped a "V" pattern, indicating a mixture of aquatic organisms and terrigenous organic matter, which may be not responsible for the different 17 alpha(H)-diahopanes distributions. Mineral compositions indicate clay present in those samples with a distinctly enhanced abundance, which likely suggests that catalysis plays a critical role on the formation of arranged hopanes. Moreover, the relative contents of 17 alpha(H)-diahopanes appear to be affected by the depositional environment due to a positive correlation with those of gammacerane, indicating that a more reducing water body is more helpful for the formation of 17 alpha(H)-diahopanes, which is different from the conclusions in the previous studies. Therefore, the biomarker 17 alpha(H)-diahopane may be an effective indicator for oil-oil/source correlation in this study area.

This study aims to reveal the geochemical behavior characteristics of rare earth elements (REEs) in the process of seawater evaporation and concentration by analyzing the REEs and their variation characteristics in different stages of rocks from the rock system of carbonate-gypsum-salt (C-G-S system) of the Ordovician in the central-eastern Ordos Basin, China. The results indicate: despite the low overall content of REEs in the endogenous deposition process of the C-G-S system in this area, a relatively consistent REEs distribution pattern is still exhibited in different types of rocks formed in different stages of seawater evaporation and concentration, showing a relative enrichment of light rare earth elements (LREEs) and obvious negative europium (Eu) anomalies; and its REEs content is not directly related to the content of continental source detrital minerals. All this means that REEs do not enter the crystal structure of the main rock-forming minerals mainly in the form of isomorphous substitution during the mineral crystallization process but are more likely to aggregate in the form of extremely fine particles, exist in the lattice defects and mineral surfaces of the main rock-forming minerals, or be enclosed by subsequent growth of mineral crystals. Also, during the dolomitization transformation from limestone to dolomite, REEs undergo relatively significant outward migration.

Alkane-related parameters of oils obtained by both gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) were widely used in oil-source correlation. However, it is still unclear whether different detection methods will lead to significant differences in these parameters. The compositions of alkanes in Jurassic oils from the Sichuan Basin were investigated using GC analysis of whole-oil samples and saturated hydrocarbons and GC-MS analysis of saturated hydrocarbons. Comparative analyses of alkane-related parameters obtained by these detection methods were also performed in this study. n-Alkanes in the range nC3–nC35 were detected in oils using whole-oil GC analysis. By contrast, short-chain n-alkanes (nC3–nC13) were not detected by GC and GC-MS analysis of saturated hydrocarbons. The abundances of n-alkanes in the range nC14–nC16 were lower than those detected by whole-oil GC analysis. nC21–/nC22+ ratios and terrigenous/aquatic ratios (TAR = (nC27 + nC29 + nC31)/(nC15 + nC17 + nC19)) obtained by GC analysis of saturated hydrocarbons are similar to those obtained by m/z 85 mass chromatograms of GC-MS and show huge differences from those obtained by whole-oil GC analysis and total ion current of GC-MS. However, the differences between these ratios obtained by GC analysis of saturated hydrocarbons, m/z 85 mass chromatograms, and total ion current of GC-MS are systematic. Pristane/phytane (Pr/Ph) ratios obtained by GC analysis of saturated hydrocarbons exhibit little difference from those obtained by total ion current of GC-MS but show large differences from those obtained by whole-oil GC and m/z 85 mass chromatograms of GC-MS. While, the differences between Pr/Ph obtained by all these methods mentioned above are systematic and can be basically eliminated. Additionally, the different detection methods have no influence on carbon preference index, odd-to-even preference, Pr/nC17 and Ph/nC18.