A dual-RPA based lateral flow strip for sensitive,on-site detection of CP4-EPSPS and Cry1Ab/Ac genes in genetically modified crops

Traditional transgenic detection methods require high test conditions and struggle to be both sensitive and efficient.In this study,a one-tube dual recombinase polymerase amplification(RPA)reaction system for CP4-EPSPS and Cry1Ab/Ac was proposed and combined with a lateral flow immunochromatographic assay,named“Dual-RPA-LFD”,to visualize the dual detection of genetically modified(GM)crops.In which,the herbicide tolerance gene CP4-EPSPS and the insect resistance gene Cry1Ab/Ac were selected as targets taking into account the current status of the most widespread application of insect resistance and herbicide tolerance traits and their stacked traits.Gradient diluted plasmids,transgenic standards,and actual samples were used as templates to conduct sensitivity,specificity,and practicality assays,respectively.The constructed method achieved the visual detection of plasmid at levels as low as 100 copies,demonstrating its high sensitivity.In addition,good applicability to transgenic samples was observed,with no cross-interference between two test lines and no influence from other genes.In conclusion,this strategy achieved the expected purpose of simultaneous detection of the two popular targets in GM crops within 20 min at 37°C in a rapid,equipmentfree field manner,providing a new alternative for rapid screening for transgenic assays in the field.

Comparative Studies on Detection of Antibodies against Infectious Bursal Disease Virus with Test Strips and Agar Gel Immunodiffusion Method

[Objective] This study aimed to compare the detection results of antibodies against infectious bursal disease virus with test strips and agar gel immunodiffusion method. [Method] Antibodies against infectious bursal disease virus in chicken serum were detected using test strips developed in our laboratory, and the results were comparad^with that using traditional agar diffusion method. [Result] The comparative study of the two methods showed that the sensitivity of test strips was eight times over agar gel immunodiffusion; test strips showed higher detection rate in the deter- mination test of 216 clinical samples, with high specificity, easy preservation, and simple and rapid operation, thereby being more suitable for the monitoring of clinical antibodies. [Conclusion] Test strips could replace the existing serological methods, having great promotion and application value in antibody monitoring.

Seismic responses of the steel-strip reinforced soil retaining wall with full-height rigid facing from shaking table test

To investigate the seismic response of the steel-strip reinforced soil retaining wall with fullheight rigid facing in terms of the acceleration in the backfill, dynamic earth pressure in the backfill, the displacements on the facing and the dynamic reinforcement strain distribution under different peak acceleration, a large 1-g shaking table test was performed on a reduced-scale reinforced-earth retaining wall model. It was observed that the acceleration response in non-strip region is greater than that in potential fracture region which is similar with the stability region under small earthquake,while the acceleration response in potential fracture region is greater than that in stability region in middle-upper of the wall under moderately strong earthquakes. The potential failure model of the rigid wall is rotating around the wall toe. It also was discovered that the Fourier spectra produced by the inputting white noises after seismic wave presents double peaks, rather than original single peak, and the frequency of the second peak trends to increase with increasing the PGA(peak ground amplitude) of the excitation which is greater than 0.4 g. Additionally,the non-liner distribution of strip strain along the strips was observed, and the distribution trend was not constant in different row. Soil pressure peak value in stability region is larger than that in potential fracture region. The wall was effective under 0.1 g-0.3 g seismic wave according to the analyses of the facing displacement and relative density. Also, it was discovered that the potential failure surface is corresponds to that in design code, but the area is larger. The results from the study can provide guidance for a more rational design of reinforced earth retaining walls with full-height rigid facing in the earthquake zone.

Strip loading test theory and equipment development

One of the important issues for geotechnical engineers is the characterization of soil properties such as cohesion and internal friction angle by means of soil testing. A new experimental method of soil characterization based on the surface displacement of strip loaded soils is proposed. The theory to relate the soil deformation/displacement to soil strength properties is presented and compared with a series of conventional soil characterization techniques with direct shear tests. The proposed/developed strip loading tests provide reasonably accurate results compared with traditional direct shear tests. The new strip loading physical simulation and testing devices are helpful for understanding soil strength concepts and also provide an effective bridge connecting with engineering mechanics and foundation engineering courses instructions wherein derivation of bearing capacity theory equations is based on the same MohrCoulomb soil strength parameters. The advantages, limitations, and use of the strip loading modeling/testing technique in engineering education and further more in depth researches are discussed in the concluding remarks part.

An Immunochromatographic Strip Test for Rapid Detection of Antibodies against Porcine Circovirus Type 2

Porcine cimovirus type 2 (PCV2) infection causes huge economic losses, but no serological method is available for batch detection of field samples. The aim of the study was to develop a method for large-batch detection of PCV2 infection. Colloidal gold-labeled staphylococcal protein A (SPA) was sprayed on glass fibers to prepare a conjugate pad. The recombinant ORF2 protein of PCV2 was blotted on the test line of the nitrocellulose (NC) membrane, and pig IgG was streaked on the control line of the NC membrane. Then, the immunochromatographic strip was used for detection of antibodies against PCV2. The results show that the strip test was simple and the results could be determined within 10 min with naked eyes. The test strip was highly specific for pig serum against PCV2 and no cross-reaction with pig serum against other pathogens was observed. The test strip had close similarity with ELISA. Storage at RT for 6 months did not affect the specificity and sensitivity obviously. A total of 324 clinical pig sera were detected by both ELISA and the developed test strip, and the coincidence was 98.77%. Therefore, the developed immunochromatographic strip is specific, sensitive, stable, fast and simple, and it is suitable for on-site detection of antibodies against PCV2.

Evaluation of the immunochromatographic strip test for the rapid diagnosis of antenatal syphilis in women in Eldoret,Kenya

Objective： This study compared the performance of the immunochromatographic strip （ICS） to the Venereal Disease Research Laboratory （VDRL） test and Treponema pallidum haemagglutination assay （TPHA） at a primary health care setting. Methods： The study group was comprised of 150 females randomly drawn from a population of pregnant women attending their first antenatal visit or follow-up visits at West Maternity Hospital in Eldoret Kenya, but without a previous syphilis test during that pregnancy. On-site VDRL, ICS and TPHA tests were performed and immediate treatment provided where appropriate. The performance of the three tests was compared, Results： The sero-prevalence of syphilis as determined by the VDRL test was 3%. There was no significant difference between the ICS and the VDRL test （P 〉 0.05）. The sensitivity and specificity of the ICS test were 80% and 98.6% respectively, while the negative predictive value （NPV） and positive predictive value （PPV） were both 100%. On the other hand, the sensitivity and specificity of the VDRL test were 66.7% and 99.3%, while the NPV and PPV were 80% and 98.6% respectively. The Treponema pallidum haemagglutination assay was used as a reference test and had sensitivity, specificity, NPV and PPV of 100%. Conclusion： The diagnostic accuracy of the ICS compared favorably with theVDRL gold standard. The use of the ICS in Kenya can improve the diagnosis of syphilis in health facilities both with and without laboratories and allow community health care workers to make a rapid diagnosis of the disease, and consequently make immediate therapeutic decisions.

''Blue Dream Pregnancy Test Strip''For Detecting Early Pregnancy

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Determination of the Friction Coefficient in the Flat Strip Drawing Test

Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.

Testing of Anti-stripping Property of Friction Spun Core Yarn

Friction spun core yarn has two components: filament core and staple fiber sheath. Under axial rubbing action, the failure mode of the core yarn is the stripping of the sheath from the core. This paper introduces a method to test the anti - stripping property of the core yarn. With a modified Universal Testing Machine, the stripping resistance of friction spun core yarn can be continuously measured. Some factors Influencing the measurements are discussed in detail. The testing results are compared with those from a Y731 Yarn Abrasion Tester and fur - ther confirmed by weaving practice.

基于实车路试的高速公路减速标线运行效果研究

为探寻高速公路减速标线设置对小客车的纵向运行特性的影响,明确减速标线的减速效果,以G50沪渝高速重庆段的3处减速标线区段为对象,开展了实车驾驶试验,采集了自然驾驶状态下的车辆速度、加速度和轨迹等数据,对比分析了车辆经过3处减速标线区段时的速度整体特征、幅值分布和变化模式;同时分析了纵向减速度变化特征;根据速度与加速度的组合示意图和纵向减速标线设置区段内速度的最大降幅、起止点的速度差异性,评价了减速标线的实施效果。结果表明:由于道路线形条件不同,3处减速标线区段的车辆行驶速度整体特征和变化模式存在差异,其中弯坡组合路段车辆速度存在波动,分为“近匀速—减速—加速—稳定—加速”的五阶段变化模式;减速度中位值和85%位值分别为0.123 m/s^(2)、0.225 m/s^(2)、0.185 m/s^(2)和0.346 m/s^(2)、0.513 m/s^(2)、0.489 m/s^(2)。减速标线主要有两方面作用效果:能够使车辆运行车速显著降低,或能够抑制车辆速度增加的趋势。研究成果为高速公路减速标线有效性评价及安全改善提供了基础数据支持。

水产品中甲醛快速显色试纸的构筑与应用

为实现水产品中甲醛含量的现场快速检测,本研究基于溶胶-凝胶法将高碘酸钾、乙二胺四乙酸二钠(EDTA-2Na)构筑于滤纸表面,制得纳米显色前体物;利用4-氨基-3-联氨-5-巯基-1,2,4-三氮杂茂(AHMT)甲醛显色反应原理,使甲醛与AHMT在纳米显色前体物表面富集缩合并经高碘酸钾氧化,最终形成蓝紫色纳米显色复合物;通过自行开发的SHotPic 1.0软件分析试纸显色程度,快速得到待测水产品中的甲醛含量。结果表明,甲醛含量与试纸显色深浅呈线性关系,相关系数达0.9719;纳米显色复合物在底物富集效应及纳米限域效应共同作用下显色蓝移并加深;试纸显色后经软件半定量可快速检测样品中甲醛含量,最低检出限为0.34 mg·kg^(-1)。本研究可为新型纳米显色剂开发和食品中有害化合物的快速直读显色分析提供理论指导和实践参考。

张力作用下柔性带钢模态灵敏度理论分析及试验研究

卷到卷工艺的产品正向薄和宽的方向发展,其柔性特征导致的振动特性变化需深入研究。针对弹性支撑的运动带钢,建立了面外振动的动力学模型,分析了模态频率灵敏度影响因子;搭建了试验平台,针对柔性带模态试验提出了力锤的选择方法。开展了张力作用下的不同宽厚比带钢模态试验,并建立了数值仿真模型。有限元与试验结果对比说明了有限元模型有效性。定量分析了不同张力下宽度、厚度对带钢模态灵敏度的影响,及张力对不同带钢模态灵敏度的影响。结果表明不同宽度、厚度变化m=2阶模态灵敏度影响较大且随宽度、厚度增大而增大,其余四阶模态灵敏度接近于0;不同张力下n=3阶的模态灵敏度是n=2阶的两倍均随张力的增大而增大,更薄更宽带钢的(2,2)和(2,3)阶模态频率对张力变化的灵敏度更高。

减蛋综合征病毒抗体胶体金免疫层析试纸条的研制及初步应用

为建立快速检测减蛋综合征病毒(EDSV)抗体的方法,基于EDSV的Fiber蛋白,制备快速检测EDSV抗体的免疫层析试纸条,为养禽业提供针对病原微生物的感染预警及免疫评估。利用胶体金标记EDSV Fiber蛋白抗原为探针,将羊抗鸡IgG和抗Fiber蛋白的抗体包被到硝酸纤维膜上,分别作为质控线和检测线,对家禽EDSV抗体水平进行监测。结果表明,制备的EDSV免疫层析试纸条具有高度特异性,与其他家禽病毒抗体无交叉反应,仅与EDSV抗体反应,在试纸条上产生可见的检测线;并且制备的试纸条具有高度稳定性,在室温条件下可至少保存6个月。应用制备的检测EDSV抗体的免疫层析试纸条对从河南、安徽、山东等地养鸡场采集的576份鸡血清样本检测,与血凝抑制试验(HI)结果进行平行比较,二者的Kappa值为0.878,具有良好一致性。综上,制备的检测ESDV抗体的免疫层析试纸条具有高度的特异性、敏感性、稳定性和易操作性,对EDSV抗体的临床检测具有实际应用价值。

基于紫胶红素的靶标有色化免疫层析试纸条联检大肠杆菌O157∶H7和沙门氏菌

为摆脱免疫层析试纸条对配对抗体的依赖,文章设计了一种新型靶标有色化免疫层析试纸条,使用紫胶红素和十二合水硫酸铝钾媒染剂,通过先媒后染的方法,实现了免疫层析试纸条的“可视化”。验证结果显示,该试纸条对大肠杆菌O157∶H7和沙门氏菌的检测限均达到了106 CFU/mL;同时,与常见食源性致病菌间不存在交叉反应,在鸡胸肉、鸡蛋、牛奶等食品基质中能够在增菌9 h内检出。文章成功设计了一种操作简单、检测成本低,更易国产化的快速检测免疫层析试纸条,为后续免疫层析试纸条的设计提供了新思路。

阳极溶出伏安法便携式重金属分析仪性能测试方法研究

阳极溶出伏安法便携式重金属分析仪被广泛应用于水体、土壤、食品、固态物质的重金属含量检测。除镉、铅、铜外,使用该分析仪检测砷、汞、锌、铬、锰、镍、锡、铊、铁、钴、硒、银、碲、金、铋等重金属时,需选择合适的计量性能测试项目及测试方法。同时,JJF 2037-2023《便携式溶出伏安法重金属检测仪校准规范》对测量镉、铅、铜元素的便携式溶出伏安法重金属检测仪的计量特性及校准方法做出了要求。

小比尺条形基础承载力模型试验的尺寸效应研究

开展小比尺模型试验是土力学承载力研究中的重要方法,但小比尺模型的尺寸效应会影响试验的定量结果,导致小比尺试验一般仅能用于定性研究。在饱和砂土地基中开展了20组条形基础承载力的小比尺模型试验,通过改变基础尺寸、埋深以及砂土的密实度研究承载力的变化,进而引入离散元分析方法,采用抗转动模型模拟砂土颗粒的力学行为,对条形基础承载力试验进行模拟,从微观角度揭示小比尺模型试验尺寸效应的来源和对宏观承载力的影响规律。研究结果表明,饱和砂土地基密实度与基础埋深越大,小比尺实试验的尺寸效应越明显,尺寸效应的产生是应力水平变化、破坏模式改变以及渐进破坏程度综合作用的结果。

弗氏柠檬酸杆菌RPA-LFD快速检测方法的建立及应用

为建立一种针对弗氏柠檬酸杆菌(Citrobacter freundii)敏感性高、特异性强的临床快速检测方法,根据该菌定居因子基因cfa的保守序列,设计特异性引物,采用重组酶聚合酶扩增技术(recombinase polymerase amplification,RPA),并结合琼脂糖凝胶电泳(AGE)和侧流层析试纸条(LFD)方法进行反应条件的优化及特异性与灵敏度的检测。结果表明:本研究中所建立的弗氏柠檬酸杆菌重组酶聚合酶扩增结合侧向流动试纸条(RPA-LFD)快速检测方法,在38℃条件下扩增20 min后,能特异性地检测到弗氏柠檬酸杆菌,对弗氏柠檬酸杆菌纯培养物和基因组DNA的最小检出限分别为1.5×102 CFU/mL和200 fg/μL,是常规PCR(cfa引物)检测灵敏度(20 pg/μL)的100倍;利用所建立的RPA-LFD法与常规PCR同时检测杂交鲟攻毒试验样本,两种方法的检测结果一致。研究表明,本研究中建立的弗氏柠檬酸杆菌RPA-LFD方法,操作简便、反应迅速、特异性好、灵敏度高,并且不需要昂贵的仪器,该方法可为未来弗氏柠檬酸杆菌细菌性疾病的早期诊断提供更有效的技术支持。

一种检测砷(Ⅲ)的适配体试纸条

利用三明治夹心法构建基于适配体胶体金的试纸条,目的在于开发切实可行的As(Ⅲ)检测应用装置。通过As(Ⅲ)与金标适配体的特异性结合,将其截留在试纸条检测线处。纳米金作为显色材料,其颗粒直径为(13±1)nm。经过优化反应条件,选择Satorius CN 140作为硝酸纤维素膜,控制线上捕获探针链霉亲和素与生物素的最佳比例为1∶4,对应的划线浓度为10μmol/L。检测线上1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐与N-羟基琥珀酰亚胺的最优比例为1∶3,金标适配体最优浓度为0.5μmol/L。在最佳反应条件下,观察试纸条的显色结果,颜色响应信号与砷浓度形成很好的梯度关系,检测限为0.1μmol/L。本试纸条对As(Ⅲ)具有高度的特异性,并且稳定性良好。其检测成本不足1元,可满足低收入地区普通人群实时检测As(Ⅲ)的要求。

农药残留快速检测试纸条的研制及应用

简单快速地筛查有机磷和氨基甲酸酯类农药残留对食品安全具有重要意义。采用酶抑制法,以重氮固红RC盐为指示剂、乙酸吲哚酚为乙酰胆碱酯酶(AChE)底物,设计开发了一种一步式快速检测试纸条。该试纸条底部为塑料胶板,上面依次粘贴样品垫、酶垫、阻滞垫、底物垫、吸附垫和固定有重氮固红RC盐的硝酸纤维素(NC)膜,通过检测区域颜色的变化可以实现农药残留的定性或定量分析,操作方法简单快捷。不同农药的检出限分别如下:马拉硫磷为0.6 mg·L^(-1),氧化乐果为0.4 mg·L^(-1),乙酰甲胺磷为1.3 mg·L^(-1),敌敌畏为0.1 mg·L^(-1),呋喃丹为0.1 mg·L^(-1),涕灭威为0.07 mg·L^(-1),且在实际果蔬样品检测中显示出良好的重现性和高灵敏度。

碳化钒免疫层析法检测玉米中T-2毒素

旨在构建一种碳化钒免疫层析试纸条,用于现场灵敏检测玉米中T-2毒素。通过超声辅助-液相剥离法合成碳化钒纳米片(vanadium carbide nanosheets,VCNSs),与T-2单克隆抗体(T-2 monoclonal antibody,T-2-mAb)偶联标记,作为信号探针。基于竞争原理,样品中的T-2毒素与检测线(T线)上T-2抗原竞争结合黑色的VCNSs-mAb探针,试纸条T线读值与T-2毒素质量浓度呈反比。以空白试纸条T线显色情况(信号读值>800,MD-600金标读数仪检测)和0.5、1.5 ng/mL T-2毒素的抑制率为优化指标,获得最佳实验条件,建立标准曲线。结果表明:该方法检测T-2毒素的线性范围在0.14~0.78 ng/mL之间、视觉检出限为0.25 ng/mL、消线值为1.5 ng/mL、半抑制浓度为0.344 ng/mL,灵敏度较传统胶体金试纸条提高了5.6倍。此外,该方法与其他5种常见真菌毒素均无交叉反应。针对玉米样品进行真实检测,回收率在92.8%~117.2%之间、变异系数均小于9.13%、检出限为5.06μg/kg。综上所述,该方法具有操作简便、快速灵敏和成本低等优点,为谷物中T-2的检测提供一定的现场快速检测技术。