扭振减振器对曲轴弯曲和纵向振动的影响研究

以一台多缸柴油机为例,采用结合有限元法(FEM)的多体系统仿真(MSS)方法,研究了扭转振动减振器振动对曲轴弯曲、纵向振动的影响;实验测量了有无扭振减振器时的曲轴自由端的弯曲和纵向振动,其与计算结果吻合得较好。     

Expression of cathepsin C and tumor necrosis factor-α in human coronary artery and their relationships with coronary heart disease

AIM To explore the possible mechanism of cathepsin C （CTSC） and tumor necrosis factor-α （TNF-α） in coronary heart disease （CHD） by detecting the protein expression of CTSC and TNF-α in human coronary artery tissue. METHODS The coronary artery tissues from 52 cases of CHD and 25 cases of accidental death without any heart disease in the Forensic Judicial Expertise Center of Guizhou Medical University from October 2018 to December 2019 were collected as CHD group and control group, respectively. The coronary artery stenosis and intimal plaque formation were examined by histopathology, the protein expression of CTSC and TNF-α was determined by Western blot, and the intracellular expression of CTSC and TNF-α was analyzed by immunohistochemical staining. RESULTS The results of HE staining showed that the intima of coronary artery in control group was smooth, and no thickening or stenosis was observed. In CHD group, the intima thickened irregularly, atherosclerotic plaques formed, the intima became thinner and the lumen showed eccentric stenosis in varying degrees （P<0.05）. The results of Western blot showed that the expression of CTSC and TNF-α in CHD group was significantly higher than that in control group （P<0.05）. Immunohistochemical staining showed that both CTSC and TNF-α were expressed in the cytoplasm of foam cells, and their positive expression was significantly higher than that in control group （P<0.05）. The results of Pearson moment correlation analysis showed that there was positive correlation between the expression of CTSC and TNF-α in CHD （r²=0.743, P<0.05）. CONCLUSION The up-regulated expression of CTSC in coronary artery tissue may promote the expression of TNF-α and affect the occurrence and development of CHD.     

Prior infection with antigenically heterologous low pathogenic avian influenza viruses interferes with the lethality of the H5 highly pathogenic strain in domestic ducks

Low and highly pathogenic avian influenza viruses (LPAIVs and HPAIVs, respectively) have been co-circulating in poultry populations in Asian, Middle Eastern, and African countries. In our avian-flu surveillance in Vietnamese domestic ducks, viral genes of LPAIV and HPAIV have been frequently detected in the same individual. To assess the influence of LPAIV on the pathogenicity of H5 HPAIV in domestic ducks, an experimental co-infection study was performed. One-week-old domestic ducks were inoculated intranasally and orally with phosphate-buffered saline (PBS) (control) or 10⁶ EID₅₀ of LPAIVs (A/duck/Vietnam/LBM678/2014 (H6N6) or A/Muscovy duck/Vietnam/LBM694/2014 (H9N2)). Seven days later, these ducks were inoculated with HPAIV (A/Muscovy duck/Vietnam/LBM808/2015 (H5N6)) in the same manner. The respective survival rates were 100% and 50% in ducks pre-infected with LBM694 or LBM678 strains and both higher than the survival of the control group (25%). The virus titers in oral/cloacal swabs of each LPAIV pre-inoculation group were significantly lower at 3–5 days post-HPAIV inoculation. Notably, almost no virus was detected in swabs from surviving individuals of the LBM678 pre-inoculation group. Antigenic cross-reactivity among the viruses was not observed in the neutralization test. These results suggest that pre-infection with LPAIV attenuates the pathogenicity of HPAIV in domestic ducks, which might be explained by innate and/or cell-mediated immunity induced by the initial infection with LPAIV.     

Synthesis and Anthelmintic Activity of 7-Hydroxy- 5-oxo-5H-thieno[3,2-b]pyran-6-carboxanilides and -6-thiocarboxanilides

7-Hydroxy-5-oxo-5H-thieno[3,2-b]pyran-6-carboxanilides and -6-thio-carboxanilides represent a novel series of anthelmintic compounds, with broad-spectrum activity against important parasitic nematodes in sheep and dogs. In particular, an improved efficacy against Trichostrongylus colubriformis in sheep over the related 3-carbamoyl-4-hydroxycoumarins has been noted. New synthetic routes to the key intermediate, 7-hydroxythieno[3,2-b]pyran-5-one, have been developed.     

余甘子果实维生素C动态积累规律研究

为研究不同品种余甘子果实维生素C含量差异和余甘子果实维生素C积累规律,本研究以6个品种余甘子果实为试材,比较不同时期余甘子果实维生素C含量的差异,描绘维生素C积累动态曲线。结果表明,余甘子果实维生素C含量丰富,适宜作为食品加工和保健品的开发利用;其中秋白品种维生素C含量最高,适宜作为加工和遗传育种的原材料;余甘子果实作为加工原材料适宜采收期为10月20日左右;维生素C 的积累分为快速积累阶段,缓慢积累阶段,下降阶段,稳定阶段4个阶段。     

A 13CO2 Enrichment Experiment to Study the Synthesis Pathways of Polyunsaturated Fatty Acids of the Haptophyte Tisochrysis lutea

The production of polyunsaturated fatty acids (PUFA) in Tisochrysis lutea was studied using the gradual incorporation of a ¹³C-enriched isotopic marker, ¹³CO₂, for 24 h during the exponential growth of the algae. The ¹³C enrichment of eleven fatty acids was followed to understand the synthetic pathways the most likely to form the essential polyunsaturated fatty acids 20:5n-3 (EPA) and 22:6n-3 (DHA) in T. lutea. The fatty acids 16:0, 18:1n-9 + 18:3n-3, 18:2n-6, and 22:5n-6 were the most enriched in ¹³C. On the contrary, 18:4n-3 and 18:5n-3 were the least enriched in ¹³C after long chain polyunsaturated fatty acids such as 20:5n-3 or 22:5n-3. The algae appeared to use different routes in parallel to form its polyunsaturated fatty acids. The use of the PKS pathway was hypothesized for polyunsaturated fatty acids with n-6 configuration (such as 22:5n-6) but might also exist for n-3 PUFA (especially 20:5n-3). With regard to the conventional n-3 PUFA pathway, Δ6 desaturation of 18:3n-3 appeared to be the most limiting step for T. lutea, “stopping” at the synthesis of 18:4n-3 and 18:5n-3. These two fatty acids were hypothesized to not undergo any further reaction of elongation and desaturation after being formed and were therefore considered “end-products”. To circumvent this limiting synthetic route, Tisochrysis lutea seemed to have developed an alternative route via Δ8 desaturation to produce longer chain fatty acids such as 20:5n-3 and 22:5n-3. 22:6n-3 presented a lower enrichment and appeared to be produced by a combination of different pathways: the conventional n-3 PUFA pathway by desaturation of 22:5n-3, the alternative route of ω-3 desaturase using 22:5n-6 as precursor, and possibly the PKS pathway. In this study, PKS synthesis looked particularly effective for producing long chain polyunsaturated fatty acids. The rate of enrichment of these compounds hypothetically synthesized by PKS is remarkably fast, making undetectable the ¹³C incorporation into their precursors. Finally, we identified a protein cluster gathering PKS sequences of proteins that are hypothesized allowing n-3 PUFA synthesis.     

浅谈5G推动下的农业现代化发展现状与前景

随着社会现代化的不断发展,越来越多的高新技术逐步问世,例如:云计算、大数据、人工智能、5G技术等.5G技术出现给人们生活带来了便利,同时也为各个产业的发展提供了强大动力.5G推动下的农业现代化发展就是结合5G技术当前发展状况和我国现阶段的农业现状,利用先进技术推动农业各方面发展进程.本文从"5G+农业"的角度出发,分析...     

基于改进YOLOv5算法的农田杂草检测

随着智慧农业技术和大田种植技术的不断发展,自动除草具有广阔的市场前景。关于除草剂自动喷洒的有效性,农田杂草的精准、快速地识别和定位是关键技术之一。基于此提出一种改进的YOLOv5算法实现农田杂草检测,该方法通过改进数据增强方式,提高模型泛化性;通过添加注意力机制,增强主干网络的特征提取能力;通过改进框回归损失函数,提升预测框的准确率。试验表明,在芝麻作物和多种杂草的复杂环境下,本文方法的检测平均精度均值mAP为90.6%,杂草的检测平均精度AP为90.2%,比YOLOv5s模型分别提高4.7%和2%。在本文试验环境下,单张图像检测时间为2.8 ms,可实现实时检测。该研究内容可以为农田智能除草设备提供参考。     

Performance and uncertainty analysis of a short-term climate reconstruction based on multi-source data in the Tianshan Mountains region,China

Short-term climate reconstruction, i.e., the reproduction of short-term(several decades) historical climatic time series based on the relationship between observed data and available longer-term reference data in a certain area, can extend the length of climatic time series and offset the shortage of observations. This can be used to assess regional climate change over a much longer time scale. Based on monthly grid climate data from a Coupled Model Inter-comparison Project phase 5(CMIP5) dataset for the period of 1850–2000, the Climatic Research Unit(CRU) dataset for the period of 1901–2000 and the observed data from 53 meteorological stations located in the Tianshan Mountains region(TMR) of China during the period of 1961–2011, we calibrated and validated monthly average temperature(MAT) and monthly accumulated precipitation(MAP) in the TMR using the delta, physical scaling(SP) and artificial neural network(ANN) methods. Performance and uncertainty during the calibration(1971–1999) and verification(1961–1970) periods were assessed and compared using traditional performance indices and a revised set pair analysis(RSPA) method. The calibration and verification processes were subjected to various sources of uncertainty due to the influence of different reconstructed variables, different data sources, and/or different methods used. According to traditional performance indices, both the CRU and CMIP5 datasets resulted in satisfactory calibrated and verified MAT time series at 53 meteorological stations and MAP time series at 20 meteorological stations using the delta and SP methods for the period of 1961–1999. However, the results differed from those obtained by the RSPA method. This showed that the CRU dataset produced a low degree of uncertainty(positive connection degree) during the calibration and verification of MAT using the delta and SP methods compared to the CMIP5 dataset. Overall, the calibrated and verified MAP had a high degree of uncertainty(negative connection degree) regardless of the dataset or reconstruction method used. Therefore, the reconstructed time series of MAT for the period of 1850(or 1901)–1960 based on the CRU and CMIP5 datasets using the delta and SP methods could be used for further study. The results of this study will be useful for short-term(several decades) regional climate reconstruction and longer-term(100 a or more) assessments of regional climate change.