Since December 2019, a series of unexplained pneumonia cases have been reported in Hubei Province, China. Scientists have isolated a new type of coronavirus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2), which has been infected by the virus. The epidemic in China and many countries around the world has attracted global attention. This is the third type of coronavirus discovered after the severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome coronavirus (MERS-CoV). At present, many scholars have conducted a lot of research on it. This article focuses on SARS-CoV. The etiology, epidemiological characteristics, clinical manifestations, imaging examinations, laboratory examinations, diagnosis and treatment of CoV-2 are reviewed.
People infected with new coronavirus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) usually have respiratory symptoms as their typical manifestations. With the increase in the number of infections, studies have found that the prognosis of patients with cardiovascular disease is more serious than that of ordinary patients. Some patients have viral infection-related heart damage, which may be related to angiotensin-converting enzyme 2 (ACE2)-mediated SARS-CoV-2 infection. Appropriate application of myocardial protective drugs may help improve the prognosis of SARS-CoV-2 infection.
The new coronavirus (SARS-CoV-2) that broke out at the end of 2019 has caused more than 80,000 infections and more than 2,700 deaths worldwide (as of February 25, 2020). Although SARS-CoV-2 and the SARS-CoV that broke out in 2003 belong to the Coronavirus family and beta-coronavirus genus and have high similarities, the whole genome homology is about 79%, but the two have many aspects in terms of disease course and fatality rate. difference. So far, SARS-CoV-2 host (including natural host and intermediate host), transmission route, virulence variation, etc. still need to be clarified urgently. This article will briefly explain some of the above-mentioned scientific problems.
Objective: To investigate the drug of Bacillus licheniformis Capsule (BLC) to improve the high levels of cytokines and clinical prognosis in COVID-19 patients, and to provide the clinical evidence for gut microflora therapy in COVID-19.
针对国内秸秆压块机不能移至田间进行压块成型作业的现状,设计了利用75 kW轮式拖拉机进行牵引的移动式秸秆压块机.以水稻秸秆为原料,对移动式秸秆压块机进行生产试验研究,寻求作业参数对压块机压块成型影响规律和最优组合.采用3因素4水平二次正交旋转组合试验方法,以喂入辊转速、叶轮转速、环模主轴转速为影响因子,秸秆压块密度及生产率为评价指标,利用Design-Expert 8.0.6软件,对试验结果进行方差分析及响应面分析,建立了3个因子对评价指标影响的数学模型.结果表明:对秸秆压块密度的影响因素大小顺序为环模主轴转速、叶轮转速、喂入辊转速;对秸秆压块生产率的影响因素大小顺序为喂入辊转速、环模主轴转速、叶轮转速;当喂入辊转速为125.84 r·min-1、叶轮转速为776.05 r·min-1、环模主轴转速为169.16 r·min-1时,秸秆压块密度与生产率分别为1.153 g·cm-3,1135.87 kg·h-1,满足秸秆压块成型要求.
针对传统粮库监控效率不高、检测结果不准确的问题,提出了一种基于深度学习的粮库虫害实时监测预警系统(RMPS).该系统对粮库中常见几种害虫(米象、绣赤扁谷盗、赤拟谷盗)进行较大规模的样本采集,并使用卷积神经网络进行学习和训练,构建神经网络模型;通过新型采集器实时采集粮库内部图像信息,利用已训练的模型进行害虫种类和概率的检测;并将监测结果以web形式发布给手机客户端.在实验室条件下,搭建小型模拟粮仓,部署本系统进行试验.测试结果表明:RMPS从传统的定点定时监测转变成实时监测,并且将虫害检测准确率提升到90％;RMPS采用专门设计的采集器与移动客户端部署简单、方便,具有较高的实用性与扩展性.
利用水热法合成磁性水热炭(m-HTC)吸附剂,经X-射线衍射仪(XRD)、Zeta电位分析仪对吸附剂进行表征,通过试验探究吸附剂对水体中砷、氟的吸附特性.结果表明:投加量为2 g·L-1时,对砷、氟去除率达85％左右;去除率随pH变化而变化,随离子强度Is,吸附质初始质量浓度Co的增加而下降;不同温度下的等温线数据更符合Langmuir模型,温度升高有利于吸附,单独体系下砷、氟的最大吸附量qm分别为26.06和15.64 mg·g-1,共存体系下对砷、氟的qm分别为20.42和13.62 mg·g-1,砷、氟存在相互抑制的作用;动力学试验数据更符合准二级动力学方程,经5次循环,去除率下降,但从实际角度,具有可取性.
针对目前光催化中催化效率低的问题,采用溶胶-凝胶法及浸提技术,分别对玻璃片、纤维膜、钢丝网进行TiO2的固定化负载.通过微观形貌进行分析,利用亚甲基蓝为目标污染物,探究制备以及光催化工艺对Ti02催化降解性能的影响及其重复使用效果,结果表明:随着浸涂次数的增加,不同载体的表面TiO2薄膜的微观形貌有所变化,对亚甲基蓝的光催化降解率呈现先增大后稳定的趋势,降解率从大到小为玻璃片、纤维膜、钢丝网,薄膜最优镀膜次数分别为3,4,4次.采用玻璃片镀膜4次所制备的TiO2光催化降解率最高,4h紫外光降解率可达75.3％.
Considering the time-varying speed working conditions,the dynamic model was established by lumped-parameter method of planetary gear transmission system. The time-varying meshing stiffness was transformed into the function of meshing frequency by Fourier series. According to the simulation curve of rotation speed,the effect of variable speed on the time-varying meshing stiffness of gear pair was analyzed. The method of Runge-Kutta was applied to calculate the dynamic response of gears in transmission system. The experiment signal was analyzed based on the wind turbine gear box test bed,and the established dynamic model of wind turbine planetary gear under time-varying speed was verified.
目的:探讨铜绿假单胞菌(Pseudomonas aeruginosa,P.aeruginosa)亚胺培南异质性耐药的机制.方法:分别采用常规的KB法和MIC法检测310株铜绿假单胞菌对亚胺培南的敏感性,双纸片协同试验检测金属β-内酰胺酶,实时定量PCR实验检测外排泵基因MexAB和MexCD的表达水平,半定量结晶紫染色法检测生物膜的形成量,PCR扩增法检测细菌膜孔蛋白OPRD2基因是否缺失.结果:在临床分离的310株铜绿假单胞菌中,检出244株亚胺培南敏感菌株和66株非敏感菌株,244株中有36株铜绿假单胞菌对亚胺培南具有异质性耐药,总体检出率为11.6%.36株异质性耐药铜绿假单胞菌均不产生金属β-内酰胺酶,但高表达MexAB外排泵,且生物膜的形成量也较高,其中6株检出膜孔蛋白OPRD2基因缺失.结论:临床存在部分异质性耐药的铜绿假单胞菌,它们通过形成生物膜、高表达多重耐药外排泵基因和基因缺失等机制介导耐药.
目的:探讨低锌饮食对大鼠二次打击惊厥模型远期惊厥阈、死亡率和锌转运体3（Zn T3）的影响。方法:60只27日龄（P27）健康雄性SD大鼠随机分为4组,惊厥组和惊厥低锌饮食组在P27腹腔注射氯化锂、在P28腹腔注射匹罗卡品致惊厥持续状态模型,观察大鼠惊厥发作情况,将达到Ⅳ级及以上痫性发作的视为造模成功。对照组和低锌饮食组在相同时间腹腔注射生理盐水。致惊厥前2天（即P27、P28） 4组均予常锌饮食（锌44 mg/kg）喂养,致惊厥后（即P28后）对照组和惊厥组继续予常锌饮食喂养,而低锌饮食组和惊厥低锌饮食组予低锌饮食（锌2. 7 mg/kg）喂养。2周后予青霉素二次打击,记录大鼠首次出现惊厥发作的时间（惊厥阈）、死亡时间及死亡率,观察时间为1 h。观察结束后取各组大鼠皮层组织,蛋白质印迹法检测Zn T3的表达。结果:大鼠的持续惊厥模型诱导成功率为72. 5%（29/40）,死亡率为24. 1%（7/29）。惊厥第3天、5天、7天惊厥组、惊厥低锌饮食组体重明显低于对照组（P ＜0. 05）;惊厥第9天惊厥低锌饮食组体重明显低于对照组（P ＜0. 05）。惊厥组和惊厥低锌饮食组血清锌浓度均明显低于对照组（P ＜0. 05）。低锌饮食组、惊厥组、惊厥低锌饮食组惊厥阈明显低于对照组（P ＜0. 05）,惊厥低锌饮食组明显低于低锌饮食组和惊厥组（P ＜0. 05）。惊厥低锌饮食组生存时间明显低于对照组和低锌饮食组（χ~2分别为9. 994、6. 707,均P ＜0. 05）。对照组、低锌饮食组、惊厥组和惊厥低锌饮食组存活率分别为80%、60%、50%、20%,无统计学差异（P=0. 073）。低锌饮食组、惊厥组及惊厥低锌饮食组Zn T3蛋白表达明显低于对照组（P ＜0. 05）,惊厥低锌饮食组明显低于惊厥组和低锌饮食组（P ＜0. 05）。结论:惊厥可致大鼠血清锌浓度降低,缺锌膳食能增加惊厥后再次打击时惊厥发作的易感性,二者互为增强效应,这种现象可能是通过下调Zn T3的表达,破坏大脑锌稳态而导致。
To solve the soil heap problem before digging shovel of Panax notoginseng mechanical harvesting ,a new type of combined digging shovel with triangular plane shovel and soil crushing shovel was designed and investigated under the premise of not reducing harvest rate .The regression analysis and the response surface analysis were conducted by Design-Expert 8.0.6 Software.The structure and the optimum working parameters of the combined digging shovel were determined with shovel surface angle of 20°, buried gap angle of 12°and operation speed of 0.75 m· s-1 .The results of field experiment show that the yield rate is 98 .38%, and the correctness of regression model is verified to meet the operation requirements .The harvest effect comparison of the combined digging shovel with the common digging shovel shows that the combined digging shovel is more suitable for Panax notoginseng harvesting with better performance of harvest rate and problem solving of soil heap before digging shovel .
dimensional point cloud of dung beetle foreleg end tooth was identified and extracted from the stereomicroscope image to quantitatively analyze geometrical structure .The accuracy and the repeatability of the proposed method were verified .The results show that the outer edge profile of foreleg end tooth can be extracted from stereomicroscopy image with 669 ×727 pixels, and about 1500 outer edge contour points are obtained .The selection of different thresholds in the gray scale histogram range does not significantly alter the results of curve fitting .It is confirmed that compared to the traditional method , the digital image processing and computer vision analysis method is efficient and accurate to quantitatively analyze geometrical characteristic features of dung beetle foreleg end-tooth.
To investigate the effect of structure on the compressibility of peaty soil in Kunming,Yunnan, a series of one-dimensional compression tests were carried out for disturbed and undisturbed soil samples with depth from 16.5 to 17.0 m. The test results show that by drawing method,the pre-consolidation pressure is 91~105 kPa,and the over consolidation ratio is 0.71~0.82,which illuminates that the soil is in the under consolidated state. The consolidation yield stress of disturbed soil samples is only 60~72 kPa,which shows that the peaty soil has strong structure. Due to the influence of soil structure,the compression index of undisturbed soil samples is less than that of disturbed ones when the consolidation pressure is small. With the increasing of consolidation pressure,the structure of undisturbed soil samples is destroyed,and the compression index is gradually increased and exceeds that of disturbed soil samples. With the increasing of load,the compression amount increases sharply,and the consolidation coefficients of both undisturbed and disturbed soil samples show decreasing trend. The secondary consolidation coefficient is 0. 071 ~0. 101,and the secondary compression coefficient is 2.00% ~2.85%,which can be classified as a soil with high or very high secondary compressibility.
To solve the disadvantages of traditional Otsu algorithm with large computation and bad real-time performance,a new PSO+Otsu(S)segmentation method was proposed.The RGB color space was converted into HSV color space,and the S component image was extracted.A new updating strategy of inertia weight coefficient w was proposed for the basic particle swarm optimization algorithm,and the improved particle swarm optimization algorithm was used to search the optimal threshold.The optimal threshold was used as the threshold of Otsu algorithm,and the Otsu algorithm was used to segment the S component image.Finally,the segmentation image of lettuce leaf was obtained.The results show that the proposed segmentation method is not only suitable for single leaf image,but also suitable for canopy leaf image.When the algorithm is used to segment the single image of lettuce leaf and the canopy image of lettuce leaf,the program running times are 1 18 ms and 126 ms,and the iteration numbers are 6 and 5 times,respectively.Compared with the Otsu algorithm and the standard PSO +Otsu algorithm,the proposed algorithm can not only shorten program running time,but also improve the accuracy of image segmentation with better real-time performance.
To improve the feeding accuracy of basket transplanter and reduce the damage rate of root lump,the maximum deformation equation of root lump was established by contact mechanics,and the collision movement between tomato plug seedling and transplanter was observed by high speed camera. The results show that angular velocity,seedling angle of planting device and height of tomato plug seedling are the main impact factors on feeding accuracy and weight loss of root lump. When the transplantation frequencies are 45 plants·min-1and 50 plants·min-1,the orthogonal test is carried out with seedling angle and height of tomato plug seedling as factors to show that the overall rating of test result is good with seedling angles of 60°and 80°and heights of tomato plug seedling of 12 cm and 16 cm by the comprehensive score method. The field transplanting experiment illuminates that the test results are basically consistent with the orthogonal test. The feeding accuracy can be improved with reduced weight loss of root lump when the transplantation frequency is from 45 to 50 plants·min-1with seeding angle of 60°and tomato plug seedling height less than 16 cm.
To meet the demand of fruit farmers' timely grading of navel oranges,a set of navel orange postharvest field grading system was designed based on machine vision,which was composed of conveying system,visual system and sorting system.The size of navel orange,the number of surface defects and the defect area were detected by the proposed system.The fruit was automatically graded according to the predetermined comprehensive assessment standard.The experimental results show that the average detection time of single picture is less than 30 ms,and the detection error of size is less than 3％ with defect detection rate of 99％ and defect area detection error less than 7％.Compared with the traditional detection system,the proposed system has the advantages of high detection speed and compact design,which is suitable for in-filed grading of navel orange.
The swell-shrink grade of swelling soil was evaluated based on the cloud model, the improved analytic hierarchies process and the entropy weight method.The five evaluation indicators of liquid limit, swell-shrink total rate, plasticity index, natural moisture content and free swelling ratio were used to investigate 15 swelling soil samples.The cloud digital characteristics of each evaluation criterion were generated based on the swell-shrink grade classification standard, and each evaluation indicator cloud model was established.According to the calculated weights by component weighting method, the comprehensive certainties were obtained.The corresponding quality degree was determined as shrink and expansion grade of swelling soil.The cloud model results show good consistence with the results of certainty measurement method, matter-element extension model and approaching in variable weight.The cloud model method can provide reference for similar engineering problems with high classification accuracy.
Eco-medium device with layered medium was used to remove nitrogen (N )and phosphorus (P)of agricultural non-point source pollution (NPS)caused by rainfall runoff.The experiment results indicate that the system has significant removal efficiency of N and P.In the simulation of rainfall runoff formation under different rainfall intensity running for 0.5 h,1 h and 3 h,the removal rates of TN are 44.63% to 62.36%,38.59% to 54.74% and 29.69% to 51 .94%,and the removal rates of TP are 67.20% to 88.36%,56.08% to 81 .48% and 38.62% to 70.37%,respectively.The mass concentration of dissolved oxygen (DO)at the vertical direction is 0.23 to 5.61 mg·L-1 to provide ideal environment for microbial nitrification-denitrification.NH4 +-N removal is mainly completed by adsorption and microbiological nitrification in the layer of zeolite and ceramic.TN removal is pushed by denitrification in the middle and lower unit.TP removal is achieved by precipitation reaction of phosphate and metal elements in the limestone layer.
Based on the expansive ratio experiments of expansive soil under different loading conditions, the quantitative computing method of expansive potentiality was obtained for the expansive soil of tunnels in Baise in Guangxi province.The effects of time and compression force under different loadings on expansive ratio and expansive potentiality were investigated.The results indicate that the expansive potentiality is increased with the increasing of compression force,while the expansive ratio is decreased. The relationship between expansive ratio and pressure can be well represented by power function. Compared to low pressure,the expansive ratio and expansive potentiality are more sensitive to pressure change at high pressure.The variation trends of expansive ratio and expansive potentiality are basically the same with the increasing of pressure.After immersed for two hours,the growth rate of expansive ratio decreases with the increasing of pressure,and the variation trend remains stable in the following four hours.At the beginning of tests,the expansive potentialities of the same expansive soil are the same,and their differences are gradually increased with the increasing of time changes of soil particle distribution and moisture diffusion path by pressure force.The swelling characteristics of expansive soil can be well represented by expansive potentiality during the expansion process,and the trend of expansive potentiality with the variating of time and stress has the same significance with that of expansion rate.
