Escherichia coli O157:H7 outbreak linked to raw milk cheese in Quebec, Canada: use of exact probability calculation and casecase study approaches to foodborne outbreak investigation

The analytical studies used to investigate foodborne outbreak are mostly case-control or retrospective cohort studies. However, these studies can be complex to perform and susceptible to biases. This article addresses basic principles of epidemiology, probability, and the use of case-case design to identify the source of an Escherichia coli O157:H7 outbreak linked to raw milk cheese consumption in Quebec, Canada; a small number of cases with the same pulsed-field gel electrophoresis (PFGE) profile were involved. Between 4 December 2008 and 15 January 2009, a cumulative total of 16 E. coli O157:H7 cases with the same PFGE profile were reported to Quebec public health authorities. Among the first six cases reported, three had consumed raw milk cheese from the same producer (cheese A). Raw milk cheese is consumed by about 2 % of the Quebec population. By using the exact probability calculation, it was found that a significantly higher proportion of E. coli O157:H7 cases (with the specific PFGE profile) than expected had consumed cheese A (P < 0.001). These computations were updated during the course of the investigation to include subsequent cases and gave the same results. A case-case study corroborated this result. This article considers alternative statistical and epidemiological approaches to investigate a foodborne outbreak-in particular with an exact probability calculation and case-case comparisons. This approach could offer a fast and inexpensive alternative to regular case-control studies to target public health actions, particularly during a foodborne outbreak.     

漆酶在染整加工中的应用

介绍了漆酶的理化性能和催化机理,综合评述了漆酶在纺织纤维改性、漂白、水洗后处理及染色废水脱色中的应用。漆酶应用于染色织物皂洗过程中,不仅能有效降低污水的色度值,进行自清洁处理,减轻印染污水处理的负担,同时又可取代常规的皂洗剂,去除浮色,提高织物的色牢度,有利于纺织品清洁生产和节能减排。     

圆柱滚子轴承外圈轴向温度分布研究

以圆柱滚子轴承为研究对象,建立了轴承外圈滚道的局部传热模型,用热流网络法分析了轴承外圈的轴向温度分布情况。通过算例分析了不同工况对外圈轴向温度分布的影响,结果显示轴承外圈温度随着转速和载荷的增大而增大,外圈表面温度沿轴向分布相差不大。     

基于AMESim的液粘调速离合器PID控制特性研究(英文)

为了准确模拟液粘调速离合器电液比例闭环控制特性,使系统能达到稳定转速的目的,基于AMESim仿真软件构建液粘调速离合器PID闭环控制系统仿真模型。采用Ziegler-Nichols整定法确定了PID参数,研究了液粘调速离合器闭环控制系统输出响应特性,分析了PID参数对输出特性的影响。结果表明,该方法能准确地模拟液粘调速离合器PID闭环控制输出响应特性,PID参数对系统输出响应特性和转速稳定性均有较大的影响。通过PID闭环控制系统,液粘调速离合器可以达到恒转速控制,得到的仿真结果为控制器的设计提供了参考依据。     

Controlling nickel silicide phase formation by Si implantation damage

In the context of fabrication process of contacts in CMOS integrated circuits, we studied the effect of implantation-induced damage on the Ni silicide phase formation sequence. The device layers of Silicon-on-insulator samples were implanted with 30 or 60 keV Si ions at several fluences up to amorphization. Next, 10 or 30 nm Ni layers were deposited. The monitoring of annealing treatments was achieved with time-resolved X-ray diffraction (XRD) technique. Rutherford Backscattering Spectrometry and pole figure XRD were also used to characterize some intermediate phase formations. We show the existence of an implantation threshold (1 ions/nm²) from where the silicidation behaviour changes significantly, the formation temperature of the disilicide namely shifting abruptly from 800 to 450 °C. It is also found that the monosilicide formation onset temperature for the thinner Ni deposits increases linearly by about 30 °C with the amount of damage.     

皖南地区荷塘组页岩气成藏条件及有利区预测

通过野外实地观察、样品采集及系列实验分析发现,皖南下扬子区下寒武统荷塘组页岩在研究区内分布广泛,沉积厚度大(约60~360 m),有机质丰度高(达0.5%~7.2%),热演化程度较高(Ro为2.0%~5.5%),达高-过成熟阶段晚期,具有较好的生烃潜力;储集层孔隙度平均为0.716%,为游离气提供了一定的储存空间,等温吸附实验测得吸附气含量平均为0.443 cm3/g,表明研究区页岩具有较强的吸附能力。通过综合研究认为,石台—黟县—泾县—宁国一带为今后的有利勘探区,分布面积约9 100 km2.     

Cathodic electrodeposition of cerium-based oxides on carbon steel from concentrated cerium nitrate solutions: Part I. Electrochemical and analytical characterisation

In this work the elaboration by cathodic electrodeposition of cerium-based oxides on carbon steel from relatively concentrated cerium nitrate solutions is investigated. In particular, the study presented here (Part I) focuses on the electrochemical and analytical characterisation of the films and on the correlations between the electrochemical features and the characteristics of the layers. The effect of other parameters such as concentration, temperature, pH and additives to improve the behaviour of the film against corrosion will be investigated in part II of the study.The electrochemical characterisation will reveal that Ce(IV)–steel interactions can be responsible for some weak electrochemical waves appearing in the cyclic voltammograms that often are attributed to oxygen or nitrates reduction. This results from the oxidation of Ce(III) solutions to Ce(IV) in contact with air. Furthermore, the deposits strongly depend on the applied current density. Low current densities do not render fully covering deposits on the steel and a carbonated green rust will appear. On the contrary, the increase of the current density leads to denser layers of relatively small crystallite size that readily covers the steel surface. The deposits have a needle-like morphology and the Ce content achieves a plateau of about 20–22 at.%. However, a significant network of cracks appears probably occurring during the deposition process itself. The differential scanning calorimetry (DSC) results indicate that the deposits are not fully crystalline after 550 °C in contrast with the X-ray diffraction (XRD) patterns that unambiguously show a fluorite-type CeO₂ phase whose crystallite size decreases with increasing the current density. The rinsing medium also brings about different features of the films. Rinsing with water allows to incorporate more nitrates and to adsorb CO₂ than when rinsing with ethanol. However, R-OH bonds will be trapped in the latter.     

Performance of different fermentation methods and the effect of their duration on the quality of raw cocoa beans

This study aims to compare the effect of three cocoa fermentation methods and their duration on raw cocoa quality. Results showed a decrease in percentage of physical quality defects on fermentation method. Cocoa fermented for 4 days presented higher percentage of purple beans reached 45% and about 10% of slaty beans than cocoa fermented for 6 days whatever the process. Fermentation duration did not influence the mouldy beans that were around 1%. Formation of brown beans increased from 16% to 50% depending on the fermentation duration and process. Using wooden boxes allowed higher percentage of 77%–90% brown beans than others materials. Acidity of cocoa decreased on fermentation duration but beans treated in boxes were significantly (P = 0.05) acidic from 1.40 and 3.07 meq of NaOH g^?1. Fungal population did not vary in number depending both on the duration and the fermentation method with rates that ranged from 3.32 × 10⁷ to 8.63 × 10⁷ CFU g^?1.     

Influence of the microstructure of gums on the mechanical properties of silicone high consistency rubbers

This paper is devoted to the characterization and processing of high molar mass vinyl‐bearing polysiloxanes in high consistency silicone rubber (HCR) formulations. The molar masses of five different polydimethylsiloxane gums, bearing vinyl groups at the ends and along their chains, were evaluated by size exclusion chromatography and rheometry. ²⁹Si and ¹H NMR spectroscopy allowed the precise determination of the vinyl content and of the distribution in the different polymers. Typical HCRs formulated from these gums were heat‐cured to process silicone rubber materials that were then tested mechanically. The macromolecular properties were correlated to the final material network structure. The amount of reactive vinyl moieties, rather than their distribution along or at the end of chains, is a key parameter to tailor the material mechanical properties. © 2016 Society of Chemical Industry