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As one of the major agricultural production areas in the world, the United States (U.S.) Midwest plays a vital role in the global food supply and agricultural ecosystem services. Although significant efforts have been made in modeling the carbon cycle dynamics over this area, large uncertainty still exists in the previous simulations in terms of reproducing individual components of the carbon cycle and their responses to environmental variability. Here we evaluated the performance of an advanced agroecosystem model, ecosys, in simulating carbon budgets over the U.S. Midwest, considering both the magnitude of carbon flux/yield and its response to environmental (climate and soil) variability. We conducted model simulations and evaluations at 7 cropland eddy-covariance sites as well as over 293 counties of Illinois, Indiana, and Iowa in the U.S. Midwest. The site-level simulations showed that ecosys captured both the magnitude and seasonal patterns of carbon fluxes (i.e., net ecosystem carbon exchange (NEE), ecosystem gross primary production (GPP), and ecosystem respiration (Reco)), leaf area index (LAI), and dynamic plant carbon allocation processes, with R2 equal to 0.92, 0.87, 0.87, and 0.78 for GPP, NEE, Reco, and LAI, respectively across all the sites compared with the observations. For regional scale simulations, ecosys reproduced the spatial distribution and interannual variability of corn and soybean yields with the constraints of observed yields and a new remotely sensed GPP product, with R2 of multi-year averaged simulated and observed yield equal 0.83 and 0.80 for corn and soybean, respectively. The simulated responses of carbon cycle dynamics to environmental variability were consistent with that from the empirical observations at both site and regional scales. Our results demonstrated the applicability of ecosys in simulating the carbon cycle and soil carbon dynamics of the U.S. Midwestern agroecosystems under different climate and soil conditions.

The micro-discharge effect limits the development of high-frequency microwave power components to miniaturization and integration. Therefore, it has become a focus of research to effectively suppress the micro-discharge effect, increase the micro-discharge threshold, and strengthen the environmental stability of high-frequency microwave devices. In this study, different elemental ratios of carbon (C)/silver (Ag)/titanium (Ti) composite films were obtained by multi-target magnetron co-sputtering technology and then systematically analyzed for micro-discharge effects. When the doping ratio of C/Ag/Ti was 3.538/1/0.013, the corresponding maximum secondary electron emission coefficient (δmax) decreased to 1.01 owing to the suppression of secondary electron emission by the increase in the content of sp2 hybrid bond. The micro-discharge threshold of Ku band waveguide filters coated with moderate C/Ag/Ti composite films showed an optimal performance of 10 000−12 500 W, which was increased by approximately 20 times. Moreover, the microstructure of the composite films exhibited higher density and flatness with a tiny increase in the titanium doping ratio, representing good environmental stability. Thus, the effective suppression of the secondary electron emission yield, significant improvement in the micro-discharge threshold, and enhancement of the environment stability of microwave components could be realized simultaneously by reasonably controlling the content of titanium in silver and titanium co-doped carbon-based composite films. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of the refining process on the quality and sensory properties of snakehead fish oil, the physicochemical properties, fatty acid composition and volatile flavor composition during the refining process of crude fish oil extracted from snakehead viscera were evaluated. The results showed that the physicochemical properties of snakehead fish oil were significantly improved; the acid value, peroxide value, moisture content, volatile content, anisidine value and unsaponifiable matter content were significantly reduced, and the iodine value was increased. In total, 27 fatty acids were detected in snakehead fish oil, the major ones being oleic acid, linoleic acid, and palmitic acid. During the refining process, the number of fatty acids was almost unchanged, the contents of monounsaturated and polyunsaturated fatty acids increased, while a reverse trend was observed for the content of saturated fatty acids. Additionally, a total of 99 volatile compounds were detected during the refining process of snakehead fish oil, among which 14 compounds including 1-octen-3-ol, hexanal, nonanal, 2-heptenal, (E,Z)-2,6-nonadienal, 2,4-decadienal, and trans-2,4-decadienal were the key flavor substances of snakehead fish oil. These findings provide a theoretical basis and technical support for the deep processing and high-value utilization of snakehead fish visceral oil.

This study examined exosomal hepatitis B virus (HBV)-DNA levels in chronic HBV infection (CHB). Patients were grouped according to the European Association for the Study of the Liver classification (1: HBV-DNA-positive CHB, normal alanine aminotransferase [ALT]; 2: HBV-DNA-positive CHB, elevated ALT; 3: HBV-DNA-negative HBeAb-positive CHB, normal ALT; 4: HBV-DNA-positive HBeAg-negative HBeAb-positive CHB, elevated ALT; 5: HBV-DNA-negative, HBcAb-positive; 6: HBV-negative, normal ALT). Exosomes were isolated, comparative analysis of exosomes and serum HBV-DNA. The HBV-DNA content was lower in exosomes than in serum for groups 1, 2, and 4 (all P < 0.05). In the groups negative for serum HBV-DNA (groups 3 and 5), the exosomal HBV-DNA levels were higher than the serum HBV-DNA levels (all P < 0.05). The exosomal and serum HBV-DNA levels were correlated in groups 2 (R 2 = 0.84) and 4 (R 2 = 0.98). The exosomal HBV-DNA levels were correlated with total bilirubin (R 2 = 0.94), direct bilirubin (R 2 = 0.82), and indirect bilirubin (R 2 = 0.81) in group 5 (all P < 0.05). In patients with CHB and negative for serum HBV-DNA, exosomal HBV-DNA was detectable and could be used to monitor the treatment effects. Exosomal HBV-DNA could be used in patients with a high suspicion of HBV infection but negative for serum HBV-DNA.

The multiple mechanisms of entrepreneurial intention are still an open issue, and few have explored whether the relationship between entrepreneurial intention and proactive personality is influenced by entrepreneurial passion. This study aims to reveal the mediation role of entrepreneurial passion between proactive personality and entrepreneurial intention with the application of the classic structural equation modeling. A questionnaire survey was conducted on Chinese undergraduates and 647 questionnaires were collected for the further analysis. The main findings shed light on the mechanisms that underpin entrepreneurial passion and contribute to the growing body of knowledge on entrepreneurial intention and will raise implications for both academic entrepreneurial theory and practice.

A novel variable thickness scroll expander composed of involutes of circle with different base circle radii is proposed. The generating method of profile is discussed, the general equation of profile is given, and a series of geometric models of the variable thickness scroll expander are established. According to the established geometric model, the influence of control coefficient on the volume change of the variable thickness scroll expander is analyzed. In addition, the geometric models of the traditional equal constant thickness and variable thickness scroll expander are constructed, and the advantages and disadvantages of the geometric models are compared. The results show that the novel variable thickness scroll expander model not only has the advantages of the traditional variable thickness model, but also greatly reduces the amount of calculation. To a certain extent, it enriches the types of variable thickness scroll expanders and provides reference for the development of high-performance scroll expanders.