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The water extract contents, polyphenol compositions, total free amino acid contents, caffeine (CAF) contents, amino acid compositions and catechin compositions of spring and summer tea made from six varieties planted in Motuo, namely Tezao 213, Zhuyeqi, Zhongcha 302, Tieguanyin, Yinghong 9 and Fenghuang Dancong were determined and compared. The results indicated significant differences between spring and summer tea in all quality components except tea polyphenols. The average phenol/ammonia ratio of spring and summer tea was 4.60 and 7.99, respectively, indicating summer tea to be suitable for processing into green and black tea. Altogether 18 amino acids were detected in the six cultivars, and the contents of different groups of amino acid were in the decreasing order of umami amino acids > sweet amino acids > bitter amino acids > aromatic amino acids. The contents of umami and sweet amino acids in spring tea were significantly higher than those in summer tea. Correlation analysis revealed that the synthesis of various metabolites were highly correlated. Principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) showed that season had a more significant effect on tea metabolites than variety. A total of 16 compounds were identified as differential metabolites between spring and summer tea, including 7 amino acids, 8 catechins and CAF, which could be used as potential markers to distinguish spring and summer tea. This study provides a valuable reference for tea processing.

With the progress of technology, the high-speed gear transmission device, which is widely used in energy, petrochemical and other fields, develops towards the direction of high power, high line speed, high efficiency and lightweight. The herringbone gear is usually used in this kind of transmission device, and its dynamic particularity under high speed conditions has an important influence on the reliable operation of the equipment. Therefore, the model of herringbone gear transmission is established, the dynamic characteristics of various herringbone gear transmission are analyzed under the conditions of driving and load excitation, the dynamic simulation is carried out, and the product is tested. The results show that when the load is constant, the greater the angular speed of the gear, the greater the contact force on the gear and the higher the collision frequency. When the input speed increases from 500 r/min to 1 000 r/min and 1 488 r/min, the difference of velocity fluctuation amplitude is 2.27 rad/s, 4.76 rad/s and 9.37 rad/s respectively, and the maximum contact force is 1.87 times and 2.44 times of that under 500 r/min, respectively. The number of angular velocity fluctuation increases to 1.94 times and 2.94 times of the case of 500 r/min, respectively. When the load increases, the angular velocity fluctuation of driven gears decreases and the contact force increases. This study provides reference for the design of this kind of high speed transmission devices.

In order to study the factors affecting the transmission performance of the steering gear used in agricultural intelligent cars, a small steering gear model is established by RecurDyn. Within the allowable range of the circumferential backlash of each gear group, the changes of different circumferential backlash are obtained by adjusting the tooth thickness of the gear group. The simulation of acceleration, deceleration and forward and reverse rotation of the steering gear model shows that when the circumferential backlash is 0.130 mm, the accuracy of the output gear 8 of the steering gear is relatively high and the return error is small. This research provides a theoretical basis for solving the driving accuracy problem of a smart car.

BackgroundNuclear reactions have been crucial in the evolution of the universe since the big bang. The cross section of nuclear reaction that occurs during the early evolution of the star is extremely low, so it cannot be accurately measured in a ground laboratory. The China Jinping Underground Laboratory (CJPL), which is the deepest operational underground laboratory in the world, offers unique ultra-low background conditions that facilitate the direct evaluation of the nuclear reactions occurring during the early evolution of stars.PurposeAsymptotic giant branch (AGB) stars are thought to be the major contributor to Galactic fluorine production. However, the astronomical fluorine overabundance cannot be explained by using the current standard AGB models. Direct measurements of 19F(p,αγ)16O reactions can help solve this problem.MethodsExperiments were conducted on a high-current 400-kV JUNA (Jinping Underground laboratory for Nuclear Astrophysics) accelerator at the CJPL. A 4π BGO detector array was specially designed for the JUNA project.ResultsThe astrophysical S factors in the energy region of 72.4~188.8 keV were experimentally derived for the first time, covering the astrophysical Gamow window. The thermonuclear 19F(p,αγ)16O rate was determined at a low temperature of about 0.05 GK for astrophysical modeling. The present low-energy S factors significantly deviated from previous theoretical predictions, and the associated uncertainties were considerably reduced.

BackgroundHead and neck squamous cell carcinoma (HNSCC) is the sixth leading cause of cancer death in the US. The protein kinase D (PKD) family has emerged as a promising target for cancer therapy with PKD1 being most intensively studied; however, its role in HNSCC has not been investigated.MethodsThe expression of PKD was evaluated in human HNSCC by quantitative RT-PCR, Western blot and immunohistochemistry. Cell proliferation, wound healing, and matrigel invasion assays were performed upon siRNA-mediated knockdown of PKD1 in HNSCC cells, and subcutaneous xenograft mouse model was established by implantation of the stable doxycycline (Dox)-inducible PKD1 expression cell lines for analysis of tumorigenic activity in vivo.ResultsPKD1 was frequently downregulated in HNSCC cell lines at both transcript and protein levels. In human HNSCC tissues, PKD1 was significantly down-regulated in localized tumors and metastases, and in patient-paired tumor tissues as compared to their normal counterparts, which was in part due to epigenetic modification of the PRKD1 gene. The function of PKD1 in HNSCC was analyzed using stable doxycycline-inducible cell lines that express native or constitutive-active PKD1. Upon induction, the rate of proliferation, survival, migration and invasion of HNSCC cells did not differ significantly between the control and PKD1 overexpressing cells in the basal state, and depletion of endogenous PKD1 did not impact the proliferation of HNSCC cells. However, the median growth rate of the subcutaneous HNSCC tumor xenografts over time was elevated with PKD1 induction, and the final tumor weight was significantly increased in Dox-induced vs. the non-induced tumors. Moreover, induced expression of PKD1 promoted bombesin-induced cell proliferation of HNSCC and resulted in sustained ERK1/2 activation in response to gastrin-releasing peptide or bombesin stimulation, suggesting that PKD1 potentiates GRP/bombesin-induced mitogenic response through the activation of ERK1/2 in HSNCC cells.ConclusionsOur study has identified PKD1 as a frequently downregulated gene in HNSCC, and functionally, under certain cellular context, may play a role in GRP/bombesin-induced oncogenesis in HNSCC.

In this paper, the structure design and optimization of the column of the tree-shaped parking garage are carried out. The base dimensions are 2.4 m、0.7 m and 8.5 m respectively. The simplified model of column takes into account the axial stress caused by the total weight FN of each component and the bending stress caused by the suspended loading plate and the vehicle. The maximum stress is easy to occur at the root of the column. The calculated results are 63.06 MPa, less than allowable stress 117.5 MPa, maximum deflection 8.93 mm, much less than standard value 113.90 mm. In order to meet the requirements of strength and deflection displacement, the penalty function method is used to optimize the size of the main support of the column, and the optimized model is measured and compared with the software analysis. Under the same working condition, the stress change data at the root of the column are collected by the test instrument and compared with the software analysis. The stress at the same position is less than 10% of the deviation between the measured and the simulated analysis results. The design and analysis of column structure are carried out by combining finite element analysis with actual stress test, and the mixed penalty function method is used to optimize the column structure. The results show that the method is effective. It provides some means and reference for the analysis of this kind of project.

Collective teaching study for teachers in Chinese primary and secondary schools plays an important role in promoting the quality of basic education, and is a major characteristic of Chinese education. This paper looks at the collective study of teaching by Chinese teachers as a product of the historical and cultural traditions particular to China, and also incorporates historical sources to explain the origins, development, and formation of this tradition. The paper further discusses the challenges facing collective teaching study for Chinese teachers by analyzing the changes underlying modern Chinese society and culture. [This article was translated by Jeff Keller.]

Objective To study on preoperative diagnosis of papillary thyroid carcinoma (PTC) with Bethesda Ⅴ thyroid nodules retrospectively and to explore the differences of clinical parameters between Bethesda Ⅴ and Ⅵ thyroid nodules. Methods The clinical data of 430 patients were analyzed. Results Univariate analysis showed that there were significant differences of Bethesda Ⅴ nodules in nodule boundary, tumor size and echo between PTC group of 159 cases and benign group of 20 cases (P