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Dynamic monitoring of soil moisture by remote sensing can play a significant role in agricultural production, weather research, and ecological environment evaluation. In recent years, continuous attention has been focused on the thought that soil moisture information can be extracted from multi-dimensional spectral feature space. A variety of soil moisture monitoring indices have been put forward in succession based on the spectral feature space, and some of them have gotten widespread attention and application such as PDI (perpendicular drought index), an simple, effective, and feasible index which has been developed based on red and near infrared spectral feature space and applied in many areas. However, the majority of these indices are devised without considering the influence of mixed pixels, which makes the effect of soil moisture estimation worse in vegetation-covered areas than in bare areas. Aiming at the problem of accuracy degradation for PDI monitoring in vegetation-covered areas, this study thoroughly analyzed the distribution of vegetation-soil pixels in Nir-Red spectral feature space, and figured out the distribution characteristics of PDI monitoring error under vegetation coverage. By taking PVI (perpendicular vegetable index) as vegetation coverage characterization, we tried to improve the PDI model in the PVI-PDI two-dimensional feature space and developed a new index (vegetation adjusted perpendicular drought index, VAPDI) theoretically suitable for vegetation coverage. Then, we used the measured soil moisture data in the study area in the Mingan Town, Bayinnaoer city of the Inner Mongolia autonomous region, China to compare and validate the PDI and VAPDI. Results showed that the coefficient of determination between the PDI and measured soil moisture were 0.630, 0.504, 0.571 and 0.543 respectively in 4 vegetation cover types (bare soil, wheat stubble, potato, and cowpea), and the coefficient of determination between the VAPDI and measured data were 0.599, 0.523, 0.602, and 0.585, respectively. The accuracy of the VAPDI was higher than the PDI in vegetation areas, and the advantage of VAPDI on monitoring accuracy increased gradually with the increase of vegetation coverage degree. Therefore, the overall effect of the VAPDI was better than that of the PDI in farmland vegetation areas. The comparison of space distribution of the PDI and VAPDI also indicated that the VAPDI does a better job in distinguishing the differences of soil moisture. The VAPDI index with clear physical meaning is simple and practical, which implies a good application prospect in the aspect of the mesoscale soil moisture inversion by remote sensing. The research can provide valuable information for method selection and error analysis in farmland soil moisture monitoring by remote sensing. [ABSTRACT FROM AUTHOR]

Fumed silica is prepared by flame pyrolysis, where silicon halide is combusted in an oxygen-hydrogen flame, resulting in finely dispersed and thermally stable silicon dioxide. Because of its unique physical and chemical properties, including high porosity, large pore volumes, large specific area, and high chemical activity, fumed silica is widely used in rubbers, plastics, adhesives, paints, and printing inks for reinforcement, as well as in thixotropy, anti-setting, and anti-sagging applications. These functional properties of fumed silica are related to the silanol group on its surface. However, there is no accurate and convenient test method to determine the silanol group content on the surface of fumed silica. This work explores a novel method to determine the silanol group content on the surface of fumed silica by chemical reaction-headspace gas chromatography (HS-GC). Theoretically, by this method, the silanol group can rapidly react with the Grignard reagent and generate methane, the amount of which can be determined accurately by GC analysis. GC analysis was conducted using a headspace flask as a closed reactor to transform the silanol group into a volatile component through a chemical reaction, so as to realize the accurate determination of silica hydroxyl. The amount of methane produced in the reaction was directly proportional to the content of silanol groups on the surface of fumed silica. Therefore, the silanol group content was calculated using the chemical reaction equation. Before the experiment, fumed silica was dried for 2 h in an oven at 105 ℃ to remove adsorbed moisture. The dried fumed silica sample was then reacted with the Grignard reagent dispersed in toluene in an airtight reaction bottle. Toluene was used as a dispersion agent to promote contact and reaction between the fumed silica sample and Grignard reagent. The methane produced by the reaction was injected into a gas chromatograph for separation and further detected using a flame ionization detector (FID). Methane was quantified from the peak areas of the GC signals using the external standard method, and the silanol content in the sample was obtained. Simultaneously, factors influencing the outcome of the method, such as the dosage of the Grignard reagent and reaction time with it, were optimized by a comparison test. Accordingly, 2.0 mL of 0.3 mol/L Grignard reagent and a reaction time of 15 min were found to be optimal for testing. The test results showed that there was good linear correlation between the content of the silanol group and the GC signals, with a correlation coefficient of 0.9990. The limit of detection was 0.30 mg/g, and the limit of quantification was 1.00 mg/g. The relative standard deviation of reproducibility was less than 3%. Based on an interlaboratory test conducted by four laboratories on five samples with different silanol group contents, the repeatability limit ( r ) was less than 2.5%, and the reproducibility limit ( R ) was less than 6.5%. Compared with the traditional chemical method, the method involving HS-GC presents distinct advantages in terms of lower reagent consumption, high sensitivity, good stability, and reliability. It is suitable for the rapid detection of the silanol group content on the surface of fumed silica, and can aid in the quality control of fumed silica during its production and application. This method has important theoretical and practical significance for developing accurate methods to determine silica hydroxyl in the silicon industry for standards and the optimization of industrial technology. This study serves as a foundation to standardize and promote the rapid development of silicon material-related industries.

Objective: To investigate the correlation of the levels of interleukin-8 (IL-8) and IL-6 in the prostatic fluid with serum levels of serum prostate-specific antigen (PSA) in patients with benign prostatic hyperplasia (BPH) complicated by prostatitis., Methods: A series of 211 patients undergoing surgery of BPH were divided into BPH group (n=75) and BPH with prostatitis group (n=136) according to the white blood cell count in the prostatic fluid. The clinical and laboratory findings were compared between the two groups, and stepwise regression analysis was used to assess the association of IL-8 and IL-6 with serum PSA level., Results: No significant differences were found in age, BMI, blood pressure, blood glucose, blood lipids, IPSS score, PSA-Ratio, or prostate volume between the two groups (P<0.05). The patients with prostatitis had significantly increased serum PSA and prostate fluid IL-8 and IL-6 levels compared with those without prostatitis (P<0.001). Multiple linear regression analysis showed that IL-8 and IL-6 levels and white blood cell count in the prostatic fluid were all positively correlated with serum PSA level., Conclusion: Prostatitis is an important risk factor for elevated serum PSA level in patients with BPH, and both IL-8 and IL-6 levels in the prostatic fluid are correlated with serum PSA level.