A reliable and sensitive time-resolved fluorescent immunochromatographic assay (TRFICA) for ochratoxin A in agro-products

Immunochromatographic assays (ICAs) are considered as a suitable diagnostic tool for the detection of mycotoxins. Mycotoxins and especially, ochratoxin A are analytes with more demanding sensitivity requirements. To enhance the sensitivity of current immunochromatographic assays for ochratoxin A (OTA), a novel sensitive ICA was developed in this study. In the assay, microspheres enclosing fluorescent europium (III) [Eu(III)] nanoparticles (EuNPs) were used as a label for OTA monoclonal antibody (OTA-mAb) conjugation. Accordingly, assay was called time-resolved fluorescent immunochromatographic assay (TRFICA). The test strip was composed of three parts: a sample pad, nitrocellulose membrane and an absorbent pad. As for detection, a proper concentration of conjugated microspheres was pipetted into the microtube and sample extract was added to it. Then the strip was inserted into the tube and the fluid flow along the strip. The TRFICA results were obtained in 8 min and read by a portable TRFICA strip reader. The established method allows quantitative determination of OTA with limit of detection as low as 1.0 μg kg⁻¹ in the samples. For validation, spiked samples including wheat, maize, soybean and rice were respectively assayed by TRFICA and a standard high performance liquid chromatography equipped with a fluorescence detector (HPLC-FLD), and good agreement of results was obtained between two methods.     

强碱三元复合驱开采动态特点

以4个强碱三元复合驱工业性试验区为研究对象,研究了注采能力、综合含水率、采油速度、油层动用状况、采出化学剂变化以及结垢与乳化规律,将三元复合驱全过程划分为5个阶段.结果表明:注采能力在前置聚合物段塞大幅度下降,整体水平略低于相近地质条件的聚合物驱;油层动用程度明显增加,含水率下降幅度高于聚合物驱,采油速度是聚驱的2倍左右;采出化学剂顺序是聚合物、碱、表面活性剂;三元主段塞后期开始结垢,随着pH值的升高,由碳酸盐垢变为与硅垢的混合垢,保护段塞以后结垢减轻;含水率进入低值期采油井开始乳化,主段塞阶段随含水率升高乳化类型由油包水型转变为水包油型,副段塞阶段为水包油型乳化.     

一种社交网络群组间信息推荐的有效方法

群组间信息推荐是社交网络中人们传递和分享资讯的重要途径,然而获取精确的最优推荐方案需要指数级时间开销.为此,本文提出一种有效算法EAOORS(Efficient Algorithm for Obtaining Optimal Recommendation Solution),将该指数级时间开销问题等价归约为EST(Extended Steiner Tree,扩展Steiner树)问题,并在多项式时间复杂度内快速获取近似最优推荐方案.理论分析和仿真实验表明,本文所提的算法具有有效性和实用性.     

Social media usage and organizational performance: Reflections of Malaysian social media managers

Social media usage among organizations is growing tremendously. Organizations are now building and maintaining social media public pages to improve their social network salience, enhance interest in their organizations, and build relationships with the online public. The majority of the studies on social media usage are based on the individual perspective while some are from the organizational perspective. However, not many studies have investigated the actual impact of social media usage on organizational performance. Therefore, using the qualitative approach, this study investigates the various purposes of social media usage and its impact on organizational performance. This study however, focuses only on the social media managers’ views. The senior managers of six organizations that are using social media are interviewed from which we find that social media is used for various purposes in organizations, such as advertising and promotion, branding, information search, building customer relations and many more. The results also show that social media has a greater impact on the performance of organizations in terms of enhancement in customer relations and customer service activities, improvement in information accessibility and cost reduction in terms of marketing and customer service.     

等离子喷涂TiO2基涂层工艺参数优化研究

目的对TiO_2基涂层的等离子喷涂工艺参数进行优化。方法采用正交实验、基材温度采集并结合涂层微观形貌分析、能谱分析、结合强度试验、显微硬度测试等方法,研究了喷涂电流、喷涂距离、主气流量对涂层组织及性能的影响规律,并获得了优化的喷涂工艺参数。结果涂层分熔融区和部分熔融区,呈现双模结构的混合微观结构特征,截面形貌凹凸不平,并以机械结合为主。拉断后,涂层断裂面呈韧窝状,由陶瓷层到粘结层呈台阶状过渡,陶瓷层整体的内聚结合强度优于陶瓷层与粘结层结合界面的结合强度。涂层条带状夹杂随着粉末流到达基板的温度的增加而减少,对结合强度影响不显著,但对硬度影响较显著。等离子喷涂过程中,粉末流到达基板的温度在一定范围内时,涂层性能随着粉末流到达基板的温度的增加而增加,但粉末流到达基板的温度过大,涂层性能降低。结论获得最优涂层必须采用最优工艺参数,工艺参数对涂层综合性能的影响主次顺序为喷涂电流、喷涂距离、主气流量,得到的优化工艺参数为:喷涂电流350 A,喷涂距离110 mm,主气流量2100 L/h。     

1,5-环辛二烯氯化铱的HPLC法测定

建立了用高效液相色谱分析1,5-环辛二烯氯化铱纯度的方法。以C18色谱柱为固定相,以乙腈/水53/47 (V/V)溶液为流动相,检测波长为285 nm,可以获得满足1,5-环辛二烯氯化铱纯度测定要求的色谱图。在1,5-环辛二烯氯化铱浓度为0.224~0.336 mg/mL时,线性相关系数(r)为0.9993,样品加标回收率为99.13%~101.37%, 相对标准偏差为1.01%。     

An energy‐dissipating approach for adjacent retrofitted structures

The approach of positioning energy dissipaters between adjacent structures can effectively prevent the collision of two adjacent buildings. For adjacent retrofitted structures, an effective strengthening approach that involves implementing energy‐dissipation measures both between and within buildings is proposed. This paper is based on the actual Shanghai ShiMao International Plaza. To avoid having to strengthen most of the structural members, the strengthening measure of energy dissipation is selected because of its construction cost and time constraints. This approach involves replacing several dampers between the adjacent structures and adding viscous damping walls in the retrofitted structure to reduce the seismic response of the retrofitted structure back to the original level. Additionally, a practical calculating method for the equivalent additional damping ratio for the adjacent structures connected by energy dissipaters is proposed. The results show that the effect of energy dissipation in the retrofitted structure is prominent and that the goal of indirect strengthening is achieved. The strengthening approach of energy dissipation and the calculating method of the equivalent additional damping ratio for adjacent structures provide a reference for similar engineering designs.     

Influence of geotextile arrangement on seismic performance of mid-rise buildings subjected to MCE shaking

Geotextile layers make it possible to construct mid-rise buildings sitting on shallow foundations in unfavourable soil conditions; this study investigates how the arrangement of geotextiles affects the seismic performance of mid-rise buildings under Maximum Considered Earthquake (MCE) shaking. The geotextile arrangement considered here includes the stiffness (5000?kN/m – 12000?kN/m), the length with respect to width of the foundation (B) (1B – 4B), the number of geotextile layers (1 – 7 layers), and their spacing (250?mm – 1000?mm). FLAC3D is used for the numerical simulation and to carry out nonlinear dynamic analysis in the time domain, and an inelastic constitutive model is used to simulate the behaviour of the structure and the geotextile layers under seismic loads. Variations in the shear modulus of soil and the corresponding damping ratio with cyclic shear strain are considered using a hysteretic damping algorithm to model the reasonable dissipation of energy in the soil. The interface between the foundation and ground surface, including the material and geometrical nonlinearities, are used to capture any possible slide and uplift in the foundations. The results are presented with regard to the geotextile arrangement considered, and include the tensile force mobilised in the geotextile layers, the response spectra at the bedrock and ground surface, the shear force developed in the structure, the maximum rocking angle of the foundation, permanent foundation settlement, maximum lateral displacement and the maximum and residual inter-storey drifts. The results show that the geotextile layers close to the edges of the foundation sustained most of the stress induced by foundation rocking, and the geotextile arrangement has a significant influence on the seismic response of mid-rise buildings. Thus, to satisfy the seismic performance of buildings and to optimise the design of foundations reinforced with geotextiles, the stiffness, length, number and spacing of the geotextile layers should be designed with great care.     

寒冷地区用空气源热泵热水器准双级压缩循环特性研究

空气源热泵热水器在寒冷地区运行时会出现排气温度过高、制热性能弱等弊端,准双级压缩循环技术可有效改善其在寒冷地区的运行特性。采用带中压补气的转子压缩机,研制了以R410A为循环工质的空气源热泵热水器,试验研究了系统在寒冷地区低温环境下的制热性能。结果表明:带中压补气的空气源热泵热水器系统排气温度较无补气有所降低,当室外温度从7.0下降到-25.0℃时,与无补气系统相比,补气系统制热量提升了6.2%～15.5%,压缩机功率提升了2.8%～9.5%,COP_h提升了3.3%～9.6%。