An outbreak of Proteus mirabilis food poisoning associated with eating stewed pork balls in brown sauce, Beijing

We report an outbreak of food poisoning that occurred in August 2008 in a group of 13 persons who ate Stewed Pork Balls in Brown Sauce in Beijing. Epidemiology investigation and case-control analysis indicated that the Stewed Pork Balls in Brown Sauce was the source of food poisoning (OR 3.34, 95% CI 1.30–8.65). With the different measurements including API 20E and PCR, Dienes typing and PFGE, Proteus mirabilis was identified as a contributor to this matter, which evaluated by analyzing the collectives, which derived from contaminated food, patients, cook handlers and waiter. So this is the first report that P. mirabilis as a culprit resulted in food poisoning in Beijing.     

Salmonella isolated from the slaughterhouses and correlation with pork contamination in free market

This study surveyed the distribution, antimicrobial susceptibility profiles and serotype of Salmonella isolated from three slaughterhouses, and performed molecular typing on these isolates, to understand the relationship between strains of Salmonella obtained from the pork production chain in Yangzhou, China. Samples from slaughtered pigs and the slaughtering environment were collected from three slaughterhouses in Yangzhou, Jiangsu province, from October 2012 to July 2013. The positive identification rates of Salmonella in slaughtered pigs and the environmental samples were 46.6% and 48.8%, respectively. The prevalence of Salmonella in slaughterhouses were affected by seasonal factors and reached the peak in summer. Among the Salmonella serovars identified, S. Derby was most prevalent in slaughterhouses, but other serovars like S. Typhimurium, S. Meleagridis and S. Anatum were also widespread. Antimicrobial susceptibility testing revealed that 32 and 131 different MDR patterns were found among the strains from the environment and slaughtered pig samples, respectively. Fifty-six isolates of S. Derby and 16 strains of S. Typhimurium were characterized by the technique of pulsed-field gel electrophoresis (PFGE) using the restriction enzyme Xba I. 35 and 11 PFGE patterns were generated among the selected isolates. Four isolates of S. Derby isolates with the same pattern (PF26) were isolated from cooling water, evisceration and carcass, suggesting that cross contamination occurred between the environment and the slaughtered pigs. Six S. Typhimurium in cluster 1 with the same ST type (ST19) came from different parts of the slaughtered pig, which could have occurred because of horizontal transmissions along the slaughtering process. The same PFGE patterns of Salmonella were found in both samples from carcasses in the slaughterhouse and in the Yangzhou pork market, proving that Salmonella had spread from the slaughterhouse to the pork market. In conclusion, our study demonstrate that serious cross contamination occurred in Yangzhou slaughterhouses and can contribute Salmonella contamination in pork sold in the local public market.     

应用SPSS软件分析石油污染土壤微生态环境

为了对石油污染土壤进行更加有效的生物修复,应用统计分析软件SPSS分析石油污染土壤微生态环境构成要素间的典型相关性,优化提高微生物生长代谢的环境条件,并运用变性梯度凝胶电泳(DGGE)技术考察石油污染对土壤微生物群落结构及多样性的影响。结果表明,土壤中有效的氮、磷质量分数,含水率和石油污染程度是石油降解菌生长繁殖的限制因素,因此在生物修复过程中,投加适量的氮、磷营养,适当地提高土壤含水率会增加降解菌数量,可以提高石油污染土壤的修复效率;石油污染土壤中存在常见的石油烃降解菌;石油污染一定程度上使微生物种群趋于单一化和功能化,微生物种群多样性降低。通过上述研究可为调控和优化石油污染土壤的微生态环境以及识别优势群落提供客观可靠的技术依据。     

油田水中有机酸的高效毛细管电泳分离

以两种背景电解质体系分别对油田水有机酸进行了毛细管电泳分离分析。在电解质体中，由于各有机酸阴离子的有效迁移率不同，在强地场中迁移速率不同，从而使各有机酸阴离子获得分离。     

鄂尔多斯盆地吴起-高桥地区延长组重排类藿烷分布特征及成因探讨

鄂尔多斯盆地吴起-高桥地区三叠系延长组长7-长9段烃源岩中检测出异常高丰度的重排类藿烷化合物。通过对不同层段烃源岩生物标志化合物特征的对比和探讨,对研究区烃源岩进行了分类并对其成因机制进行了分析。GC-MS分析结果表明：研究区源岩中含17α（H）-重排藿烷、早洗脱重排藿烷以及18α（H）-新藿烷（Ts和C₂₉Ts）这3个系列重排藿烷类化合物。根据重排藿烷相对丰度存在的差异,可以将烃源岩划为以17α（H）-C₃₀藿烷（C₃₀H）为主峰,以17α（H）-C₃₀重排藿烷（C₃₀*）为主峰和以18α（H）-C₂₇新藿烷（Ts）为主峰的3种类型。此外,早洗脱重排藿烷常与高丰度的17α（H）-重排藿烷以及18α（H）-新藿烷相伴出现,且这3类重排藿烷富集的烃源岩中同时富含重排甾烷和重排补身烷,说明重排类化合物的形成可能受控于相似的机制。各项地球化学参数的对比分析表明,高黏土含量、氧化性淡水沉积环境和以陆源植物为主的母质来源更利于烃源岩中高丰度重排类藿烷化合物的形成,较高的热成熟度促进藿烷重排反应的发生,但要考虑高成熟度下化合物裂解速率不同而造成的含量差异。     

溶剂梯度淋洗法表征无规共聚聚丙烯管材专用树脂

采用溶剂梯度淋洗法(SGEF)对无规共聚聚丙烯管材专用树脂(PPR)进行了结构分级,用凝胶渗透色谱仪及核磁共振波谱仪分析了级分试样的相对分子质量及乙烯含量,并对级分加和后的相对分子质量分布与未分级的原样进行了对比,探讨了SGEF方法的可行性。得到的数据在一定程度上可以定量地给出PPR中乙烯的分布情况。     

PE塑料的综合性能及PE管在燃气管网中的应用

文章介绍了一种常用的耐蚀非金属材料─聚乙烯（PE）材料的物理机械性能、抗震性能和耐腐蚀性能。并简要地阐述了PE管在燃气管网系统中的特点及设计与安装。同时也对PE管在燃气工业中的现状与前景作了一个简单的探讨。本文可供城市燃气设计、施工人员参考。     

中国与煤成气相关的大型、特大型气田分布特征及启示

与煤成气相关的大型、特大型气田是中国天然气储量的主体。中国含煤盆地众多,但是只有少数大、中型含煤盆地具有形成大型、特大型气田的地质条件。含煤岩系沉积后的构造地质环境对形成煤成气藏的影响更为重要。生气高峰期及成藏期越晚,越快、越有利于含煤盆地转化成为含气（油）盆地,越有利于形成大型、特大型煤成气田。以类前陆型、克拉通内坳陷型及陆缘断陷型含煤-含气（油）盆地勘探前景最好。鄂尔多斯盆地,四川盆地中部、西部和东北部,塔里木盆地北部（库车坳陷）,东海盆地西湖凹陷,莺琼盆地,柴达木盆地北部和三湖区,准噶尔盆地北部和南部,松辽盆地深部及南海北部深水区等含煤盆地,仍然是21世纪近、中期中国天然气储、产量保持快速增长的重点地区。     

盐浓度对交联聚合物线团形态的影响

用核孔膜过滤法 (过滤体积对过滤时间作图 )、动态光散射法 (DLS)和扫描电镜法 (SEM )研究了交联反应前后盐 (NaCl)浓度变化对低浓度HPAM与AlCit形成的交联聚合物溶液 (LPS)中交联聚合物线团 (LPC)形态的影响。所用HPAM相对分子质量 1.1× 10 7～ 1.4× 10 7,LPS中HPAM与Al的质量比 2 0∶1,HPAM浓度 0 .1或 0 .2 g/L ,交联反应温度 40℃ ,时间 7天。实验结果表明 :①LPC的平均水力半径Rh(DLS测定值 )随交联反应时盐浓度的增大先减小后增大 ,盐浓度由 0 .5 g/L增加到 2 g/L时Rh 由 45 0nm迅速减小到 2 5 0nm ,盐浓度增加到 2 0 g/L时Rh达到最小值 16 0nm ,此后随盐浓度的继续增加Rh 有所增大 ;盐浓度 0 .5和 2 .0 g/L时Rh 的SEM测定值分别为45 0和 2 5 0nm ,与DLS结果一致。②交联反应完成后改变LPS的盐浓度 ,也可改变LPC的Rh 值 ,但改变幅度较小 ;盐浓度 0 .5 g/L时形成的LPS ,当盐浓度增加至 2 g/L时 ,Rh 值由 45 0nm减小至 35 9nm ,大于盐浓度 2 g/L时形成的LPS的Rh 值 (2 46nm) ;盐浓度 2 g/L时形成的LPS ,当盐浓度减少至 0 .5 g/L时 ,Rh 值由 2 46nm增大至32 6nm ,小于盐浓度 0 .5g/L时形成的LPS的Rh 值 (4 5 0nm)。用盐浓度改变引起LPC水化层厚度改变 ,线团收缩或舒张解释盐浓度改变时Rh 测定值的     

实沸点蒸馏前后高酸重质原油的石油酸分布表征

The molecular transformations of carboxylic acids in heavy acidic SL crude before and after true boiling point distillation were examined by ultra-high resolution negative-ion electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）. The acid class （heteroatom number）, type （z numbers） and carbon number distributions were positively characterized. It was found out that the total acid number （TAN） of SL crude decreased after true boiling point distillation, and the abundance of O2 class in mass spectra was also found to be reduced from 67.6% to 34.5% in SL TBP mixed crude as measured by MS spectra, indicating to a potential carboxylic acid decomposition. However, it was interesting that the carboxylic acids type distribution in both oils was almost the same although their relative abundance in SL TBP mixed crude turned to be much lower, suggesting that various petroleum carboxylic acid types have the similar thermal decomposition reaction behavior. Furthermore, for each O2 type of acids in SL TBP mixed crude, the abundance of carboxylic acids with carbon number higher than 35 was reduced greatly, especially for those with carbon number higher than 60, the mass peaks of which were nearly totally removed, indicating that the large carboxylic acid molecules in heavy fractions decomposedmore significantly because of longer heating time during the true boiling point distillation process. As a result, the reduction ofTAN may be caused by the thermal decomposition of carboxylic acids especially those with high carbon number, suggesting that quick distillation or much lower pressure is required to avoid the thermal decomposition.     

Prevalence and antimicrobial resistance of Salmonella isolated from an integrated broiler chicken supply chain in Qingdao,China

The present study analyzed the prevalence and antimicrobial resistance of Salmonella along an integrated broiler chicken supply chain. A total of 172 Salmonella isolates were recovered from 1148 samples collected from four sample sources (breeder farms, broiler farms, abattoir, and retail markets), representing nine production stages. These Salmonella isolates were examined for antimicrobial susceptibility to 12 different antimicrobial agents using a disk diffusion assay. Among them, 168 were identified as six different serotypes of Salmonella enterica. The predominant serotype was S. Enteritidis (n = 116), followed by S. Infantis (n = 18), S. Gueuletapee (n = 16), S. Derby (n = 12), S. Meleagridis (n = 4), and S. London (n = 2). The remaining four isolates were serogroup-untypeable. A majority of the 172 isolates (96.51%) was resistant to one or more antibiotics and 61.05% of the Salmonella isolates showed a multidrug resistance phenotype. Statistical analysis indicated the one risk product stage for Salmonella contamination occurred in the sample source at the abattoir, specifically the stage of Carcasses after chilling. The majority of S. Enteritidis isolates shared the same pulsed-field gel electrophoresis (PFGE) cluster, suggesting that the S. Enteritidis strain might spread along the broiler chicken supply chain. The prevalence and antimicrobial resistance of Salmonella in different production stages suggest the importance of controlling Salmonella in the broiler chicken supply chain for public health, underlying the need for improved measures of reducing carcass contamination in abattoirs and the appropriate use of antimicrobials in broiler flocks.     

Determination of melamine in infant formulas by fluorescence quenching based on the functionalized Au nanoclusters

An environmentally benign and cost-effective assay was developed for the fast determination of melamine (MA) with tiopronin-stabilized gold nanoclusters (TPN-AuNCs) as a fluorophore. The TPN-protected gold nanoclusters which exhibit strong fluorescence emission were prepared by a simple one-vessel procedure. Upon addition of melamine to TPN-AuNCs, a dramatic decrease in their fluorescence intensity was observed, attributing to the electrostatic attraction between the MA and the surface of the TPN-AuNCs which induces the aggregation of TPN-AuNCs. Parameters affecting the detection of MA were investigated including pH, amount of TPN-AuNCs, temperature as well as reaction time. Under the optimized experimental conditions, trace amounts of MA could be analyzed based on the reduction in the fluorescence intensity of TPN-AuNCs. A linear relationship was established at concentrations ranging from 0.09 μM to 100 μM. The detection limit at 32 nM was achieved for this method. The developed method has been successfully applied to the determination of MA in several spiked infant formulas samples purchased from a local supermarket. Excellent recoveries at 92.0–102.2% and precision (RSD: 1.14–2.80%) were attained, respectively, which confirmed the great potential of tiopronin-stabilized gold nanoclusters toward practical measurement of melamine in infant formulas of samples.