Validation of qPCR method for enterococci quantification at Toronto beaches: Application for rapid recreational water monitoring

Rapid quantitative PCR-based methods for enterococci monitoring can allow public health authorities to make more timely beach posting decisions. However, qPCR methods must be assessed for proposed sites as locale-specific factors may affect DNA recovery or qPCR inhibition. We assessed the feasibility of the USEPA 1609.1 qPCR-based (Enterococcus) method at two urban Toronto beaches and three recreational areas at nearby river mouths in parallel with culture-based methods on the same water samples. A strong positive correlation was observed between the Enterococcus qPCR method and culturing-based quantification methods for E. coli and enterococci at both beaches and two river mouth areas. One river, known to be highly sewage-impacted, did not yield DNA suitable for qPCR analyses. qPCR results from biological replicates were strongly correlated and showed coefficients of variation as low as or lower than culture-based methods. With respect to Beach Action Value exceedances, the USEPA 1609.1 qPCR method provided an 80–90% level of agreement with E. coli enumeration results and >90% with enterococci enumeration. Results indicated that if recreational water locations and sampling conditions met the requirements of the USEPA 1609.1 qPCR method, the method can meet or exceed all quality control requirements and provide water quality results within 3.5 h for diverse recreational water settings around the City of Toronto.     

农药沉积利用率喷雾指示剂诱惑红的酶标仪测定方法

诱惑红是一种水溶性染料,近年来被用作农药沉积利用率测定的指示剂。诱惑红的检测方法为高效液相色谱法和分光光度法。高效液相色谱法需要专门的分析仪器,且价格昂贵,可见分光光度计法操作繁琐,试剂用量大,耗时长,均不适宜田间快速高效测定。笔者发展了诱惑红的酶标仪测定方法,简单高效,可批量检测多个样品,且准确度和精密度高,线性关系良好,514 nm检测波长下不受其他农药影响,并应用于玉米无人飞机喷雾场景下农药雾滴在玉米冠层的沉积利用率测定。     

Microstructure–mechanical property relationship in an Al–Mg alloy processed by constrained groove pressing-cross route

The constrained groove pressing-cross route process was implemented on a commercially annealed AA5052 alloy at room temperature, with up to two passes (strain of ～4.64) along the rolling direction and transverse direction. The results showed the formation of an ultrafine-grained structure with an average sub-grain/cell size in the 300–500?nm range. The indentation hardness and tensile strength increased significantly, up to ～75 and 105%, respectively, and became more homogenous with a uniform and isotropic trend, as compared to the annealed alloy. According to the Hall–Petch and Taylor models used, grain refinement and increasing dislocation density were proposed as the main strengthening mechanisms. Fractographic studies revealed a ductile-fracture behaviour, with a dimpled structure proportional to the UFG structure.     

Detection and analysis of triterpenic compounds in apple extracts

A new technique for the rapid detection and analysis of triterpenic compounds in apple extracts using HPLC was developed and validated. The main advantage of this technique is the short duration of the analysis – this makes this technique superior to others currently applied for the routine HPLC analysis of triterpenic compounds. The developed, optimized, and validated technique was used for the evaluation of triterpenic compounds in samples of different cultivars of apples, their peels, and flesh. In total, four triterpenic compounds were isolated and identified. Ursolic acid was the dominant compound in all the tested apple samples. The highest amounts of triterpenic compounds were detected in the peels of the ‘Lodel’ apple cultivar, and thus apples of this cultivar may be potentially useful for the isolation of individual compounds and the production of functional food and dietary supplements.     

固体碳直接还原钢铁厂含锌固废的理论与实践

 钢铁厂内的含锌固废数量巨大，同时富含铁、碳等元素，是可循环再利用的二次资源。通过固体碳直接还原ZnO和FeO的热力学分析，发现在非标准状态下，ZnO的还原条件要优于FeO。为此，在实验室条件下设计了含锌固废在不同温度和时间下的还原试验，发现在还原温度为1 423 K、还原时间为15 min以上时，脱锌率可达到90%，而铁的金属化率需要在1 573 K时才能接近90%；在还原温度低于1 423 K时，还原时间对脱锌率的影响较大；在还原温度高于1 473 K时，还原温度对脱锌率影响较小，同时脱锌率可达到95%。这些结果对国内当前处理含锌固废主要工艺(回转窑、转底炉)的操作制度设置具有重要的参考价值，也为如何选择合理的工艺路线，以低投入、低运营成本实现含锌固废的再利用提供了理论依据。     

南水北调中线水源区浮游植物群落结构 及其生物多样性

为探究南水北调中线水源区丹江口水库浮游植物群落结构变化及其生物多样性，于 2014—2015 年对丹江 口水库进行为期 1 年的调查和分析。发现浮游植物共 8 门 76 属 101 种，其中，绿藻门、蓝藻门及硅藻门占总种数 90.10%，绿藻门种类数最多（45 种），其次是蓝藻门（26 种）和硅藻门（20 种）。浮游植物群落结构随季节变化有所 不同：夏秋季节生物量明显高于冬春季节；优势种在冬季以颗粒直链藻、颗粒直链藻极狭变种、铜绿微囊藻和小 环藻为主，春季以球衣藻、薄甲藻属及小环藻为主，夏季以简单颤藻、单胞衣藻原变种和球衣藻为主，秋季以类颤 藻鱼腥藻、简单颤藻、球衣藻和小环藻为主。应用 Shannon-Wiener 多样性指数 H′、Pielou 均匀度指数 J′、Margalef 丰富度指数 Dm评价水质结果表明：丹江口水库夏秋季水体营养化程度更高。典型对应分析表明：水温、透明度、 总氮、总磷等是影响浮游植物群落结构的主要环境因子，夏秋季受温度影响蓝藻、绿藻数量逐渐增多，一定程度 上增加了受水区生态变化风险。本研究可为南水北调中线水源区丹江口水库生态环境变化及生物迁移风险提供 数据支持。     

Improved magnetic and electromagnetic absorption properties of xSrFe12O19/(1−x)NiFe2O4 composites

xSrFe₁₂O₁₉/(1−x)NiFe₂O₄ composites (0 ≤ x ≤ 1.0) were synthesized by using a conventional solid-state synthetic route. The results show that magnetic hysteresis loops of the xSrFe₁₂O₁₉/(1−x)NiFe₂O₄ composites are similar to those of individual component ferrites, except for the 0.1SrFe₁₂O₁₉/0.9NiFe₂O₄ and 0.3SrFe₁₂O₁₉/0.7NiFe₂O₄, suggesting that the hard/soft magnetic phases are well exchange-coupled. The saturation magnetization, coercivity, and remanent magnetization of the xSrFe₁₂O₁₉/(1−x)NiFe₂O₄ composites are increased with increasing content of SrFe₁₂O₁₉, with maximal values of 42.1 Am² kg⁻¹, 78.7 kA m⁻¹, 17.2 Am² kg⁻¹, respectively, as the content x is about 0.5. They are higher than those of the individual components, implying that interface coupling is present in the magnetic composites. The coercivity and remanent magnetization of the composites are increased initially with increasing sintering temperature and then show a downward tendency. For the component SrFe₁₂O₁₉ and NiFe₂O₄, the minimum reflection losses are −12.5 dB and −18.3 dB at match thicknesses of 2.5 mm and 2 mm, respectively. Compared with those of the component SrFe₁₂O₁₉ and NiFe₂O₄, the microwave absorption performances of the xSrFe₁₂O₁₉/(1−x)NiFe₂O₄ composites are improved remarkably, especially for the samples of x = 0.3 and x = 0.9. The minimum reflection losses values of the 0.3SrFe₁₂O₁₉/0.7NiFe₂O₄ composite are −31.6 dB (12.7 GHz) and −20.2 dB (13 GHz), while those of the 0.9SrFe₁₂O₁₉/0.1NiFe₂O₄ composites are −23.7 dB (16.3 GHz) and −33.5 dB (15.8 GHz), as the matching thicknesses are 2.5 mm and 2 mm, respectively. Therefore, the xSrFe₁₂O₁₉/(1−x)NiFe₂O₄ composites could be used as potential microwave absorption materials.     

基于哈希链的软件定义网络路径安全

针对软件定义网络中，控制器无法保证下发的网络策略能够在转发设备上得到正确执行的安全问题，提出一种新的转发路径监控安全方案。首先以控制器的全局视图能力为基础，设计了基于OpenFlow协议的路径凭据交互处理机制；然后采用哈希链和消息验证码作为生成和处理转发路径凭据信息的关键技术；最后在此基础上，对Ryu控制器和Open vSwitch开源交换机进行深度优化，添加相应处理流程，建立轻量级的路径安全机制。测试结果表明，该机制能够有效保证数据转发路径安全，吞吐量消耗比SDN数据层可信转发方案（SDNsec）降低20%以上，更适用于路径复杂的网络环境，但时延和CPU使用率的浮动超过15%，有待进一步优化。     

航班恢复问题的迭代局部搜索算法

在恶劣天气和机械故障等原因造成航班不能按照原计划执行时，航空公司需要采取相应的措施对航班进行恢复。本文基于经典的资源指派模型，综合考虑了调整时间、换机、联程拉直、取消航班和调机5种恢复策略，提出一种以最小化加权成本为优化目标的航班恢复模型，并设计一种迭代局部搜索算法。首先用构造-修复启发式方法构造可行解，然后从该初始解出发，在飞机路线对的邻域中进行局部搜索。当陷入局部最优后，对解进行扰动，然后从扰动后的解重新出发进行局部搜索。为了提高搜索效率，同时降低陷入局部最优解的概率，局部搜索过程采用模拟退火算法。实例结果表明，本文提出的模型及算法能够在短时间内对受到影响的大规模航班计划进行恢复。     

Evaluation and validation of an automatic jaw movement recorder (RumiWatch) for ingestive and rumination behaviors of dairy cows during grazing and supplementation

Observation of ingestive and rumination behaviors of dairy cows may assist in detecting diseases, controlling reproductive status, and estimating intake. However, direct observation of cows on pasture is time consuming and can be difficult to realize. Consequently, different systems have been developed to automatically record behavioral characteristics; among them is the RumiWatch System (RWS; Itin and Hoch GmbH, Liestal, Switzerland). Until now, the RWS has not been thoroughly validated under grazing conditions. The aim of the current study was to validate the RWS, against direct observation, in measuring ingestive and rumination behaviors of dairy cows during grazing and supplementation in the barn. A further objective was to examine whether it is possible to refine the algorithm used by the evaluation software RumiWatch Converter 0.7.3.2 to improve the accuracy of the RWS. The data were collected from an experiment carried out with 18 lactating Holstein cows in a crossover block design including 3 treatments and 3 measuring periods. All cows grazed night and day, 19 h/d, and were either unsupplemented or supplemented, with chopped whole-plant corn silage, or chopped whole-plant corn silage mixed with a protein concentrate. During the measuring periods, cows were equipped with the RumiWatch Halter, and their ingestive and rumination behaviors were recorded concurrently by the RumiWatch Halter and by direct observation (690 × 10 min). Comparison of concurrently measured data shows that the RWS detected jaw movements reliably, but classification errors occurred. A low relative prediction error of ≤0.10 for the number of rumination boluses, rumination chews, and total eating chews was found. A high relative prediction error of >0.10 was found for the number of prehension bites and time spent in prehension and eating. Both converter versions performed equally well in differentiating ingestive and rumination behaviors when cows were supplemented in the barn or when grazing and supplementation activities were combined. For grazing cows, with no supplementation, more reliable results for the total number of eating chews, rumination chews, prehension bites, and time spent in these activities were obtained, by using the RumiWatch Converter 0.7.3.11. In light of these findings, further research is warranted to improve the accuracy of the RWS and to allow a differentiation between mastication chews and prehension bites while eating.