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BackgroundA novel coronavirus, SARS-CoV-2, was identified in December 2019, when the first cases were reported in Wuhan, China. The once-localized outbreak has since been declared a pandemic. As of April 24, 2020, there have been 2.7 million confirmed cases and nearly 200,000 deaths. Early warning systems using new technologies should be established to prevent or mitigate such events in the future. ObjectiveThis study aimed to explore the possibility of detecting the SARS-CoV-2 outbreak in 2019 using social media. MethodsWeChat Index is a data service that shows how frequently a specific keyword appears in posts, subscriptions, and search over the last 90 days on WeChat, the most popular Chinese social media app. We plotted daily WeChat Index results for keywords related to SARS-CoV-2 from November 17, 2019, to February 14, 2020. ResultsWeChat Index hits for “Feidian” (which means severe acute respiratory syndrome in Chinese) stayed at low levels until 16 days ahead of the local authority’s outbreak announcement on December 31, 2019, when the index increased significantly. The WeChat Index values persisted at relatively high levels from December 15 to 29, 2019, and rose rapidly on December 30, 2019, the day before the announcement. The WeChat Index hits also spiked for the keywords “SARS,” “coronavirus,” “novel coronavirus,” “shortness of breath,” “dyspnea,” and “diarrhea,” but these terms were not as meaningful for the early detection of the outbreak as the term “Feidian”. ConclusionsBy using retrospective infoveillance data from the WeChat Index, the SARS-CoV-2 outbreak in December 2019 could have been detected about two weeks before the outbreak announcement. WeChat may offer a new approach for the early detection of disease outbreaks.

Addressing the challenges of limited passability and adaptability encountered by existing pipe robots in navigating through tee and four-way junction pipes, This article designs a pipe robot based on the principle of metamorphism. This robot is designed with a variable number of linkages, constituting the core of its system structure. Through this innovative approach, it achieves movement in diverse types of pipelines by altering its own structural configuration. Kinematic analysis is conducted using both the Denavit-Hartenberg (D-H) method and screw theory, providing expressions for the forward kinematics in terms of the robot's positional and attitudinal states, as well as geometric solutions for the inverse kinematics. Simulations conducted in MATLAB and ADAMS software demonstrate consistent postural changes of the robot, validating its design and capabilities. Prototype experiments in a 500 mm diameter pipeline further confirm the robot's structural design rationality and its ability to navigate through tee and four-way junction pipes by altering its posture. The results indicate that this pipe robot effectively navigates through straight, vertical tee, and horizontal four-way junction pipes, offering a viable solution for efficiently maneuvering through complex pipeline junctions. [ABSTRACT FROM AUTHOR]

Tea standard samples are the benchmark for tea product quality control. Understanding the inherent differences in Chinese national standards for Lapsang Souchong black tea of different grades is crucial for the scientific development of tea standardization work. In this study, Lapsang Souchong black tea of different grades that meet Chinese national standards was selected as the research object. The aroma characteristics were comprehensively analyzed through sensory evaluation, electronic nose, and HS-SPME-GC-MS (headspace solid-phase microextraction gas chromatography–mass spectrometry). The findings indicate that the higher-grade Lapsang Souchong has a higher evaluation score. The results of electronic nose analysis indicate that the volatiles with differences in tea of different grades were mainly terpenoids and nitrogen oxides. The results of HS-SPME-GC-MS analysis show that the odor characteristics of the super-grade samples are mainly floral and fruity, and these substances mainly include D-Limonene, 3,7-dimethyl-1,6-octadien-3-ol and 3-Hydroxymandelic acid, and ethyl ester. The primary aroma characteristics of the first-grade samples are floral, sweet, woody, and green, with key contributing compounds including 2-Furanmethanol, 1-Octen-3-ol, and 5-ethenyltetrahydro-α,α,5-trimethyl-cis-, 4,5-di-epi-aristolochene. The main aroma characteristics of the second-grade samples are green, herbal scent, and fruity, and the main substances include 3,7-dimethyl-1,6-octadien-3-ol, 2,3-dimethylthiophene, Dihydroactinidiolide, and Naphthalene-1-methyl-7-(1-methylethyl)-. It is worth noting that the second-grade samples contain a large amount of phenolic substances, which are related to the smoking process during processing. This study lays a solid foundation for the preparation of tea standard samples and the construction of the tea standard system. [ABSTRACT FROM AUTHOR]

The stick-slip type actuator based on the stick-slip driving principle has the characteristics of simple structure, high precision, large travel and no electromagnetic interference. However, the stick-slip driving principle leads to the existence of the displacement backward phenomenon when it is driving in a single direction, which reduces the output performance of the driver. In order to solve the above problem, a stick-slip separated piezoelectric actuator with separable stator and actuator is designed by combining the advantages of lever mechanism and triangle mechanism in this paper, and theoretical calculations and simulations on the flexible hinged amplification mechanism are carried out. The prototype of the stick-slip separable piezoelectric actuator is made, and the output characteristics and speed characteristics of the actuator are experimentally tested to determine the optimum voltage and frequency values for practical operation. [ABSTRACT FROM AUTHOR]

A series of basic functional ionic liquids were prepared from 1, 4-diazabicyclo [2.2.2] octane (DABCO) with various halogenated hydrocarbons, then these functional ionic liquids were used as catalysts for the chemical fixation of CO2 into cyclic carbonates and the influence of the structure of the ionic liquids was investigated. The results showed that the N atom active center, types of anions and hydrogen bond of the catalyst play a key role in the cycloaddition reaction of CO2 with epoxides to cyclic carbonates. Under mild reaction conditions (T = 100 °C, 1 atm CO2), the ionic liquid [DABCO-CH2CH2CH2OH] I showed the best catalytic effect, which has notable advantages such as high catalytic activity, eco-friendly, ease of work-up and convenient reuse. [ABSTRACT FROM AUTHOR]

Customer referencing refers to the phenomenon of a firm intentionally revealing its customers so that the firm can obtain certification of the quality of its products. In this paper, we examine the association between customer referencing and firms' future product market performance. We find that firms that engage in customer referencing achieve better product market performance than those that do not, which is consistent with the notion that customer referencing, by certifying the referencing firm's product quality, enhances the firm's future product market performance. We also find that this positive association is stronger when the referenced customers are reputable and when the referencing firms have a greater need for certification. These results further affirm the certification role of customer referencing. Our study provides new insight into how certification via inter-organizational relationships can be an intangible marketing asset. [ABSTRACT FROM AUTHOR]

Exhaust sound quality is an important part of vehicle performance. In this paper, the sporty exhaust sound quality of an economical vehicle equipped with a 4-cylinder and 4-stroke engine is evaluated, analyzed, and improved under acceleration. Firstly, a sporty feeling evaluation method with engine speed divided is proposed, and the influence of exhaust sound order components on sporty exhaust sound is analyzed. The results show that while the A-weighted sound pressure level (ASPL) of Order 2 is lower and the ASPLs of Orders 4 and 6 are higher, the exhaust sound is sportier. Then, a hybrid predicted model of vehicle sporty exhaust sound under acceleration is established based on convolutional neural network (CNN) and support vector regression (SVR) algorithm. The relative errors between the predicted results of CNN-SVR hybrid model and the subjective evaluation results are limited within 2%, which indicates that the CNN-SVR hybrid prediction model achieves a high accuracy in assessing the sporty feeling of exhaust sound. Finally, considering the frequency ranges corresponding with the above order components under the practical accelerating condition, a strategy is proposed to enhance the sporty feeling of exhaust sound by reducing the sound energy within 100 Hz and increasing the sound energy within 100–450 Hz. Based on this strategy, a muffler with different structure is selected and installed on the economical vehicle, and the sporty feeling of exhaust sound is 0.63 points higher than before. [ABSTRACT FROM AUTHOR]

It is generally recognized that the quality differences in plant germplasm resources are genetically determined, and that only a good "pedigree" can have good quality. Ecological memory of plants and rhizosphere soil fungi provides a new perspective to understand this phenomenon. Here, we selected 45 tea tree germplasm resources and analyzed the rhizosphere soil fungi, nutrient content and tea quality. We found that the ecological memory of tea trees for soil fungi led to the recruitment and aggregation of dominant fungal populations that were similar across tea tree varieties, differing only in the number of fungi. We performed continuous simulation and validation to identify four characteristic fungal genera that determined the quality differences. Further analysis showed that the greater the recruitment and aggregation of Saitozyma and Archaeorhizomyces by tea trees, the greater the rejection of Chaetomium and Trechispora, the higher the available nutrient content in the soil and the better the tea quality. In summary, our study presents a new perspective, showing that ecological memory between tea trees and rhizosphere soil fungi leads to differences in plants' ability to recruit and aggregate characteristic fungi, which is one of the most important determinants of tea quality. The artificial inoculation of rhizosphere fungi may reconstruct the ecological memory of tea trees and substantially improve their quality. [ABSTRACT FROM AUTHOR]

There are obvious differences in quality between different varieties of the same plant, and it is not clear whether they can be effectively distinguished from each other from a bacterial point of view. In this study, 44 tea tree varieties (Camellia sinensis) were used to analyze the rhizosphere soil bacterial community using high-throughput sequencing technology, and five types of machine deep learning were used for modeling to obtain characteristic microorganisms that can effectively differentiate different varieties, and validation was performed. The relationship between characteristic microorganisms, soil nutrient transformation, and tea quality formation was further analyzed. It was found that 44 tea tree varieties were classified into two groups (group A and group B) and the characteristic bacteria that distinguished them came from 23 genera. Secondly, the content of rhizosphere soil available nutrients (available nitrogen, available phosphorus, and available potassium) and tea quality indexes (tea polyphenols, theanine, and caffeine) was significantly higher in group A than in group B. The classification result based on both was consistent with the above bacteria. This study provides a new insight and research methodology into the main reasons for the formation of quality differences among different varieties of the same plant. [ABSTRACT FROM AUTHOR]

Tea plant is an acidophilic plant, and soil pH has an important effect on the absorption and enrichment of elements, tea plant growth and quality. In this study, rhizosphere soils and leaves of tea plants from 30 tea plantations were collected to determine soil pH and multi-element content of soil and leaves of tea plants, to obtain and validate key elements that are enriched by pH affecting tea plants, and to analyze the effects of pH on the growth and quality of tea plants. The results showed that soil pH significantly affected the enrichment of 15 elements by tea plants, and the enrichment coefficients of 11 elements (C, Mg, Si, N, P, Mn, Sr, Cd, S, Ca and Sb) tended to increase significantly with the increase of soil pH, while the opposite was true for the other four elements (Cu, Rb, Ba and Al). TOPSIS analysis showed that soil pH had the greatest effect on tea plant enrichment of seven elements, namely N (100%), Mn (43.32%), C (39.22%), P (27.66%), Sr (15.30%), Mg (13.41%) and Ba (10.47%). Pot experiments with tea seedlings also verified that soil pH significantly affected the enrichment of tea leaves for seven key elements. Moreover, with the increase of soil pH, the growth indexes, photosynthesis indexes and quality indexes of tea seedlings showed a significant upward trend. Interaction analysis showed that the enhanced enrichment of N, Mn, C, P, Sr and Mg by tea plants was beneficial to increase the photosynthetic capacity of tea plants, promote the growth of tea plants and improve the quality of tea leaves. This study provides an important theoretical basis for the cultivation and management of tea plants. [ABSTRACT FROM AUTHOR]

Aviation mutagenesis is a breeding method for the rapid selection of superior plant varieties. In this study, rhizosphere soil chemical indexes, soil enzyme activities, and soil metabolites were measured in Dahongpao tea trees with aviation mutagenesis (TM) and without aviation mutagenesis (CK). The main soil metabolites distinguishing TM and CK and their relationships with soil chemical indexes and soil enzyme activities were analyzed and obtained. The results showed that there was no significant change in the rhizosphere soils' pH of TM tea trees compared to CK (p = 0.91), while all other chemical indexes of TM were significantly higher than CK (p < 0.05). In addition, the activities of enzymes related to soil nutrient cycling such as urease, protease, sucrase, acid phosphatase and cellulase, and enzymes related to soil antioxidants such as superoxide dismutase, catalase, peroxidase, and polyphenol oxidase were significantly increased (p < 0.05) in the rhizosphere soils of TM tea trees compared to CK. Soil metabolite analysis showed that the main soil metabolites distinguishing CK from TM were carbohydrates, nitrogen compounds, and amines. Of these, carbohydrates and nitrogen compounds were significantly positively correlated with soil chemical indexes and soil enzymes, whereas amine was significantly negatively correlated with soil chemical indexes such as organic matter, total nitrogen, total potassium, available nitrogen, available phosphorus; amine showed significant negative correlation with soil enzymes such as catalase, peroxidase, polyphenol oxidase, and urease. It can be seen that aviation mutagenesis is conducive to improving the ability of tea tree rhizosphere aggregation and transformation of soil nutrients, increasing the total amount of soil nutrients and the content of available nutrients, which is more conducive to promoting the uptake of nutrients by the tea tree, and thus promoting the growth of the tea tree. [ABSTRACT FROM AUTHOR]

The quality of the Dahongpao mother tree (Camellia sinensis) remains a mystery to this day. In this study, for the first time, the differences between the Dahongpao mother tree (MD) and Dahongpao cuttings (PD), in terms of odor characteristics and taste characteristics were analyzed by metabomics. The results showed that MD had stronger floral, fruity, green, and woody odor characteristics than PD, and that the contributions were mainly from dihydromyrcenol, methyl salicylate, 2-isobutylpyrazine, 1,6-dihydrocarveol, gamma-terpineol, and linalyl acetate. Further, fresh and brisk taste and mellowness taste characteristics of MD were significantly higher than PD, with contributions mainly from amino acids and derivatives and organic acids. Secondly, bitterness taste characteristics of PD were significantly higher than MD, with contributions from phenolic acids, flavones, and flavonols. This study preliminarily unraveled the legend of the superior quality of the Dahongpao mother tree, and also provided an important reference for the breeding of tea-tree cuttings. [ABSTRACT FROM AUTHOR]