Poisoning of aldol condensation reaction with H2O on acid catalysts

The effect of chemisorbing water on three catalysts previously evaluated in the acetone condensation reaction has been studied. The active sites in that reaction are Lewis acid sites present either on the surface of alumina or of nonframework alumina in zeolites. These sites are poisoned by water and the reaction rate decreases at the pace of the loss of Lewis sites. The stoichiometry of the poisoning reactions is one water molecule per site on alumina and two water molecules per site on nonframework alumina. This revised version was published online in July 2006 with corrections to the Cover Date.     

苏州市一起疑似类志贺邻单胞菌引起的食物中毒调查与分析

目的分析2019年6月苏州市某幼儿园食物中毒的原因,了解病原菌的基因分型和耐药谱情况。方法通过问卷调查、电话访谈,查阅医院就诊记录、餐厅订餐记录等主动搜索病例,开展病例个案调查和现场卫生学调查,采集相关样品进行实验室检测。以分离培养,质谱快速鉴定,VITEK-2 Compact全自动细菌鉴定仪生化鉴定进行鉴定分析,脉冲场电泳(pulsed-field gel electrophoresis,PFGE)进行基因分型,药敏试验采用微量肉汤稀释法。结果共搜索到17位病例(包括确诊病例4人),临床表现为腹痛、腹泻等胃肠道不适症状,均无头痛、发热等其他不适症状。6月20日中餐为可疑餐次,此外无其他共同饮食史。现场共采集47份样本(包括菜品、环境样本和肛拭子),其中4份学生肛拭子检出类志贺邻单胞菌。PFGE分型结果显示其中3株菌100%同源,属于同一型别,另一株菌与其差异较大,属于不同型别。对14种抗生素的药敏分析显示,3株菌(同一型别)除对氨苄西林耐药外还对甲氧苄胺嘧啶/磺胺甲噁唑耐药,对其它抗生素均敏感。另1株菌对氨苄西林耐药,对其它抗生素均敏感。结论此次事件很可能是一起由类志贺邻单胞菌引起的食物中毒,并且可能来源于不同的传染源。     

一起由沙门氏菌和金黄色葡萄球菌混合引起的食物中毒病原分析

目的对引起食物中毒相关样品进行病原菌的分离、鉴定和耐药分析。方法参照GB 4789系列标准的方法流程对采集的食物样本进行沙门氏菌、金黄色葡萄球菌、志贺氏菌、副溶血弧菌和单核细胞增生李斯特氏菌共5项致病菌指标检测,按照纸片扩散法(K-B法)进行药敏实验。结果从食物中毒样品中检出肠炎沙门氏菌、金黄色葡萄球菌,确定为二者混合感染引起的食物中毒。药敏结果显示肠炎沙门氏菌对多数抗生素敏感,金黄色葡萄球菌耐药性强,对链霉素、头孢噻肟、氯霉素、红霉素有一定的耐药性。结论本起事件是由肠炎沙门氏菌和金黄色葡萄球菌混合感染引起的食物中毒事件,建议食品卫生监管人员应加强对餐饮环节的监督引导,避免类似事件发生。     

The deactivation effect of Na2O and NaCl on CeO2–TiO2 catalysts for selective catalytic reduction of NO with NH3

The effect of Na₂O and NaCl on CeO₂–TiO₂ catalyst for the selective catalytic reduction of NO with NH₃ was investigated with BET, XRD, XPS, NH₃-TPD, H₂-TPR, in-situ DRIFT and catalytic activity measurements. The results showed that both Na species could deactivate the CeO₂–TiO₂ catalyst and Na₂O had a stronger effect than NaCl. The more serious deactivation by Na₂O could be ascribed to smaller surface area, fewer surface Ce³⁺ and chemical adsorbed oxygen, lower surface acidity, and worse reducibility. The introduction of NaCl and Na₂O facilitated the formation of new surface NO_x adspecies, but were inactive in NH₃-SCR reaction. The adsorption of NH₃ were inhibited. The NH₃-SCR reaction over the CeO₂–TiO₂ catalyst was governed by both E-R and L-H mechanisms. The introduction of NaCl and Na₂O didn't change the NH₃-SCR reaction mechanisms.     

Simulation of Fluctuating Populations of Microorganisms and Macroorganisms with Models Having a Normal Random Variate Term

Fluctuating populations of micro- and macroorganisms play a major role in the stability and safety of food and agricultural products. In recent years such populations have been described by ‘chaotic’ models, most notably the discrete logistic function. This model's major limitations, however, are that it implies determinism and that it can account for neither population explosions nor extinction. Consequently, it is suggested that in order to simulate realistic population histories, the growth rate constant, r, in the original discrete logistic function X_n+1=rX_n(1-X_n) can be replaced by a randomly varying term, r_n. The latter can be defined as r_n=r₀ exp(kZ_rn) where r₀ is a characteristic constant, Z_rn a normal random variate produced by a normally distributed random number generator and k its chosen standard deviation. Theoretically, the magnitude of such r_n (and its corresponding X_n) can be anywhere in the range 0<X_n<∞. However, the magnitude of k can be selected so that X_n>1 is a very rare event. In the special case of widely fluctuating populations dominated by random factors, the model can be replaced by N_n/N₀=exp(k′Z_rn), where N₀ is a characteristic number. In this form the model can account for occasional aperiodic population explosions, and if a lower limit to a viable number is also set (eg N/N₀>0·01), for extinction events as well. The flexibility of the two models is demonstrated with simulated population evolution patterns of different kinds. © 1997 SCI.     

2012—2017年云南省有毒动植物中毒事件分析

目的 探讨2012—2017年云南省有毒动植物中毒事件的发生规律和特点,为制定预防和控制措施提供依据。方法 对2012—2017年云南省报告的有毒动植物中毒事件资料建立数据库,并按时间、地区、场所、中毒因素等进行统计分析。结果 共报告有毒动植物中毒事件530起,发病4 147人,死亡64人。第四季度为发病高峰,报告起数、发病人数和死亡人数分别占全年总数的30.8%(163/530)、37.4%(1 553/4 147)和50.0%(32/64);有毒植物中毒事件报告起数较多的州(市)为楚雄州、大理州、玉溪市,占总数的44.2%(212/480);有毒动物中毒报告起数较多的州(市)为迪庆州、怒江州、保山市,占总数的80.0%(40/50)。家庭中毒报告起数、发病人数和死亡人数最多,分别占总数的63.6%(337/530)、40.3%(1 672/4 147)和89.1%(57/64)。引起有毒动物中毒事件的食物主要是蜂蛹(7.9%,42/530),引起有毒植物中毒事件的食物前5位依次为乌头(30.2%,160/530)、四季豆(29.2%,155/530)、蓖麻子(5.3%,28/530)、蜂蜜(3.8%,20/530)和油桐(3.6%,19/530)。结论 云南省有毒动植物中毒问题突出,应完善食物中毒的应急处理体系,广泛宣传有毒动植物中毒的预防知识,以有效地减少云南省中毒事件的发生。     

松花粉对铅中毒小鼠学习和记忆障碍的改善作用

目的：探讨松花粉对铅致中毒小鼠学习和记忆障碍的改善作用。方法：建立小鼠铅中毒模型,用松花粉灌胃进行实验性治疗。持续6 周后,检测小鼠的学习记忆成绩,以及脑组织MDA含量和单胺氧化酶（monoamineoxidase,MAO）、谷胱甘肽过氧化物酶（glutathione peroxidase,GSH-Px）、超氧化物歧化酶（superoxidedismutase,SOD）的活性。结果：与对照组相比,模型组小鼠的学习、记忆能力下降（P＜0.05或P＜0.01）,MDA含量、MAO活性升高（P＜0.05或P＜0.01）,GSH-Px、SOD活性降低（P＜0.05）;与模型组相比,松花粉组小鼠的学习、记忆能力又不同程度的得到恢复（P＜0.05）,MDA含量、MAO活性降低（P＜0.05）,GSH-Px、SOD活性升高（P＜0.05）。结论：铅可降低小鼠的学习、记忆能力,而松花粉对铅导致的小鼠学习和记忆障碍有一定的改善作用。     

ITO靶材的毒化机理研究现状

为了更好的了解ITO靶材的毒化机理,分别介绍了磁控溅射技术制备薄膜的基本原理,综述了ITO靶材在溅射过程中的毒化机理研究的现状,分析了影响ITO靶材毒化现象可能的原因,详细介绍了现阶段3种解决ITO靶材毒化现象的方法:不同工艺制备ITO靶材的影响、最佳Sn掺杂量和其他元素的掺杂等的影响以及溅射工艺的影响,指出了他们各自缓解ITO靶材毒化现象的原理。并且展望了未来解决我国ITO靶材毒化问题的发展方向。为我国ITO靶材的发展提供一定的参考。     

Tungsten carbide as supports for Pt electrocatalysts with improved CO tolerance in methanol oxidation

One anti-CO-poisoning Pt-WC/C catalyst for methanol electro-oxidation is prepared in this work, through depositing platinum on tungsten carbide support using an intermittent microwave heating (IMH) method. The catalyst presents an improved methanol oxidation performance evidenced by a negative shift in onset potential, and increase of peak current density, compared with a commercial Pt/C one. CO stripping experiments indicate that the adsorbed CO is able to be oxidized and removed from the Pt-WC/C catalyst more easily, attesting the enhanced capability of anti-poisoning to CO-like species. Theoretical calculation further provides evidence that the surface electronic structure in Pt-WC/C and Pt/C catalysts is likely different. WC supports could lead to much stronger negative electronic property, which is beneficial for avoiding CO adsorption on the Pt-WC/C catalyst. In the mean time, the electron donating effect generated by WC supports also promotes the ability to oxidize the adsorbed CO-like species on catalysts. In good agreement with experimental results, the theoretical calculation proves the anti-CO-poisoning nature of the Pt-WC/C catalyst, and well explains the origin of the improvement in the electrochemical catalytic performance for effectively accelerating the oxidation of CO to CO₂ in methanol oxidation.     

The effect of low concentrations of CO on H2 adsorption and activation on Pt/C: Part 2—In the presence of H2O vapor

CO affects H₂ activation on supported Pt in the catalyst layers of a PEMFC and significantly degrades overall fuel cell performance. This paper establishes a more fundamental understanding of the effect of humidity on CO poisoning of Pt/C at typical fuel cell conditions (80 °C, 2 atm). In this work, direct measurements of hydrogen surface concentration on Pt/C were performed utilizing an H₂-D₂ switch with Ar purge (HDSAP). The presence of water vapor decreased the rate of CO adsorption on Pt, but had very little effect on the resulting CO surface coverage on Pt_S (θ_CO) at steady-state. The steady-state θ_COs at 80 °C for Pt exposed to H₂ (PH₂=1 atm) and a mixture of H₂/H₂O (1 atm H₂, 10%RH) were 0.70 and 0.66 ML, respectively. Furthermore, total strongly bound surface hydrogen measured after exposure to H₂/H₂O was, surprisingly, the sum of the exchangeable surface hydrogen contributed by each component, even in the presence of CO. In the absence of any evidence for strong chemisorption of H₂O on the carbon support with/without Pt, this additive nature and seemingly lack of interaction from the co-adsorption of H₂ and H₂O on Pt may be explained by the repulsion of strongly adsorbed H₂O to the stepped-terrace interface at high coverages of surface hydrogen.