Non-volatile Components and Filamentary Morphology of Fresh Leaves of Zigui Simian Tea

To investigate the characteristics of quality formation of Simian tea, the non-volatile components, mineral elements and filamentary structure of fresh leaves from different positions of ‘Simian Tucha’ tea plants, endemic to Zigui, were analyzed using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), and scanning electron microscopy (SEM). The results showed that the non-volatile components were more abundant in the leaves with higher tenderness, with amino acids, alkaloids, catechins, and aroma glycosides being mainly concentrated in the first (L1) and second leaves (L2). Theanine, organic acids, and flavonoids were mainly concentrated in the third leaf (L3), while the content of non-volatile components in the older leaves was relatively lower. The accumulation of mineral elements greatly varied among tea leaves with different tenderness. The contents of nitrogen, phosphorus, potassium, zinc, and copper in L1 (32.41 mg/g, 4.53 mg/g, 15.65 mg/g, 45.45 μg/g, and 10.75 μg/g, respectively) and L2 (30.60 mg/g, 3.70 mg/g, 14.12 mg/g, 35.82 μg/g, 9.02 μg/g, respectively) were higher than those in older leaves. The contents of iron, manganese, and calcium were higher in mature leaves. Through SEM observation, it was found that the filamentary structure of Simian tea leaves consisted of two forms, triple-stranded coil and single-stranded coil, and was distributed in the internal thread or ringed vessels of the xylem in the vascular bundles in the midvein and lateral veins, and the number of filamentary structures was higher in the second, third and fourth leaves than that in buds and L1

Evaluation of Suitability for Green Tea Processing of Different Tea Cultivars Based on Multivariate Statistical Analysis

Principal component analysis (PCA) and multiple linear regression analysis (MLRA) were used to analyze and investigate the suitability of green tea for tea tree varieties in different tea cultivars. The fresh leaves of 63 tea cultivars planted in the same garden were processed into roasted green tea by the same method. The sensory and major physicochemical qualities (tea polyphenols, free amino acids, water extracts and chlorophyll) and the color (L*, a* and b*) of green tea were analyzed. To evaluate the suitability of the tested cultivars for green tea processing and its major influential factors, the data obtained were analyzed by PCA and MLRA. The results showed that the coefficient of variation (CV) of chlorophyll content in different cultivars was the highest (26.7%), followed by tea a* value (22.2%), sensory score for tea infusion color (17.1%) and sensory score for tea color (16.2%). A significant correlation was found between the polyphenol content of green tea and its color, tea infusion color and the color of infused tea leaves; between the chlorophyll content, |a*| and b* values of green tea and its color; between the chlorophyll content and |a*| value of green tea and the color of infused tea leaves; and between the |a*| and b* values of green tea and tea infusion color (P < 0.01). The PCA results showed that the contribution rate of the first five principal components (PCs) was 76.895%, and that of the first principal component was 31.918%, mainly pointing to the color quality. According to the evaluation model constructed based on the first five PCs, the top 10 cultivars were Zhongcha 108, Wuniuzao, Pingyangtezao, Mengshan 9, Soubeizhong, Fudingdabai, Jiukeng 16, Fudingdahao, Maolv, and Longjing 43. Using MLRA, the regression function between overall sensory score (Y) and |a*| value (x) was obtained as Y = 68.668 + 5.174x (R2 = 0.313) (P < 0.001). The top 10 varieties determined from this equation were highly consistent with the results of PCA, indicating that a* value is an important indicator for the evaluation of the suitability of tea cultivars for green tea processing

A repeating fast radio burst associated with a persistent radio source

The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4 and a compact persistent radio source5. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately 903−111+72 parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies2,6, far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications

Design and construction of an experimental setup for study of electron-ion collision and measurement of the cross sections for H- double ionisation and C+ single ionisation

Doctorat en Sciences physiques -- UCL, 199

Dual-UAV Collaborative High-Precision Passive Localization Method Based on Optoelectronic Platform

Utilizing the optical characteristics of the target for detection and localization does not require actively emitting signals and has the advantage of strong concealment. Once the optoelectronic platform mounted on the unmanned aerial vehicle (UAV) detects the target, the vector pointing to the target in the camera coordinate system can estimate the angle of arrival (AOA) of the target relative to the UAV in the Earth-centered Earth-fixed (ECEF) coordinate system through a series of rotation transformations. By employing two UAVs and the corresponding AOA measurements, passive localization of an unknown target is possible. To achieve high-precision target localization, this paper investigates the following three aspects. Firstly, two error transfer models are established to estimate the noise distributions of the AOA and the UAV position in the ECEF coordinate system. Next, to reduce estimation errors, a weighted least squares (WLS) estimator is designed. Theoretical analysis proves that the mean squared error (MSE) of the target position estimation can reach the Cramér–Rao lower bound (CRLB) under the condition of small noise. Finally, we study the optimal placement problem of two coplanar UAVs relative to the target based on the D-optimality criterion and provide explicit conclusions. Simulation experiments validate the effectiveness of the localization method

Different Withering Times Affect Sensory Qualities, Chemical Components, and Nutritional Characteristics of Black Tea

The present study emphasizes the effect of withering time set at 4 ± 0.5 h (WT4), 6 ± 0.5 h (WT6), 8 ± 0.5 h (WT8), 10 ± 0.5 h (WT10), and 12 ± 0.5 h (WT12) on the sensory qualities, chemical components, and nutritional characteristics of black tea. The sensory evaluation revealed high total quality scores at WT8 and WT10. Polysaccharides, amino acids, and soluble sugars significantly increased with an increase in withering time, and an apparent peak value was obtained at WT10. However, polyphenols, flavonoids, glycosides, organic acids, catechins, alkanoids, and theaflavins decreased with an increase in withering time. With an increase in withering time, the content of aromatic substances showed a trend of increasing first and then decreasing. The peaks of alcohols, aldehydes, and acids appeared at 10 ± 0.5 h, 10 ± 0.5 h, and 8 ± 0.5 h, respectively. The content of esters, ketones, and hydrocarbons showed a downward trend with an increase in withering time. Aroma analysis revealed that withering time could not exceed 10 ± 0.5 h. Black tea withered up to WT10 showed enhanced inhibition of α-glucosidase and α-amylase activity with good sensorial attributes. Glucose uptake inhibition capacity increased up 6 ± 0.5 h and then decreased, while antioxidant capacity decreased with an increase in withering time. The overall results show that the 8 ± 0.5 h to 10 ± 0.5 h withering time could improve black tea quality and nutritional characteristics

Study on taste quality formation and leaf conducting tissue changes in six types of tea during their manufacturing processes

This study fristly investigated the taste quality formation and leaf conducting tissue changes in six types of Chinese tea (green, black, oolong, yellow, white, and dark) made from Mingke No.1 variety. Non-targeted metabolomics showed the vital manufacturing processes (green tea-de-enzyming, black tea-fermenting, oolong tea-turning-over, yellow tea-yellowing, white tea-withering, and dark tea-pile-fermenting) were highly related to their unique taste formation, due to different fermentation degree in these processes. After drying, the retained phenolics, theanine, caffeine, and other substances significantly impacted each tea taste quality formation. Meanwhile, the tea leaf conducting tissue structure was significantly influenced by high processing temperature, and the change of its inner diameter was related to moisture loss during tea processing, as indicated by its significant different Raman characteristic peaks (mainly cellulose and lignin) in each key process. This study provides a reference for process optimization to improve tea quality

Rapid Determination of the Monosaccharide Composition and Contents in Tea Polysaccharides from Yingshuang Green Tea by Pre-Column Derivatization HPLC

A pre-column derivatization high-performance liquid chromatography (HPLC) method was developed and optimized to characterize and quantify the monosaccharides present in tea polysaccharides (TPS) isolated from Yingshuang green tea. TPS sample was hydrolyzed with trifluoroacetic acid, subjected to pre-column derivatization using 1-phenyl-3-methyl-5-pyrazolone (PMP), and separated on an Agilent TC-C18 column (4.6 mm × 250 mm, 5 μm) with UV detection at 250 nm. A mixture of ten PMP derivatives of standard monosaccharides (mannose, ribose, rhamnose, glucuronic acid, galacturonic acid, glucose, xylose, galactose, arabinose, and fucose) could be baseline separated within 20 min. Moreover, quantitative analysis of the component monosaccharides in Yingshuang green tea TPS was achieved, indicating the TPS consisted of mannose, ribose, rhamnose, glucuronic acid, galacturonic acid, glucose, xylose, galactose, and arabinose in the molar contents of 0.72, 0.78, 0.89, 0.13, 0.15, 0.36, 0.39, 0.36, 0.36, and 0.38 μM, respectively. Recovery efficiency for component monosaccharides from TPS ranged from 93.6 to 102.4% with RSD values lower than 2.5%. In conclusion, pre-column derivatization HPLC provides a rapid, reproducible, accurate, and quantitative method for analysis of the monosaccharide composition and contents in TPS, which may help to further explore the relationship between TPS monosaccharides isolated from different tea varieties and their biological activity