PbS/epoxy resin nanocomposite prepared by a novel method

PbS/epoxy resin nanocomposite is prepared by a novel method. The epoxy resin microemulsion is taken as a microreactor for the formation of PbS nanocrystals. After the reaction, the collected epoxy proved to be a composite with nano-PbS embedded in. The morphological observation of cured PbS/epoxy resin nanocomposite by tunnel electronic microscopy (TEM) indicates that the PbS nanocrystals are dispersed in cured epoxy resin matrix homogenously. X-ray diffraction (XRD) and TEM were used to characterize the PbS nanocrystals.     

2010—2020年中国大陆副溶血性弧菌引发食源性疾病暴发调查

目的 分析2010—2020年中国大陆副溶血性弧菌引起的食源性疾病暴发事件的流行病学特征,获得其发生时间和地区的分布特点以及引发事件的场所、高危食品和危险因素。方法 对我国食源性疾病暴发监测系统收集的2010—2020年副溶血性弧菌引起的食源性疾病暴发资料进行统计分析。结果 2010—2020年共上报副溶血性弧菌引起的食源性疾病暴发事件1 772起,累计发病27 212人,住院5 944人,死亡2人。发生高峰时间是7～9月。发达地区发病率（28.8例/百万人）高于不发达地区（8.2例/百万人）,沿海地区发病率（31.7例/百万人）高于内陆地区（9.2例/百万人）。病因食品以水产食品（61.2%）、肉类食品（25.3%）为主。发生场所以宾馆饭店占比最高,占49.6%。污染环节主要是烹饪水产食品时未充分烧熟煮透,加工即食肉类食品和蔬菜类食品时生熟交叉污染。结论 应重点加强餐饮服务场所中水产食品和肉类食品的加工、储存等环节监管,降低副溶血性弧菌导致食源性疾病发病的风险。     

总膳食研究在人群膳食暴露评估中的应用

本文通过介绍总膳食研究实施的方法步骤,阐明其在食品安全风险评估中,尤其是在人群膳食暴露评估中的应用进展。     

陶瓷食具容器卫生标准中重金属分析方法的改进研究

目的对GB/T5009.62—2003《陶瓷食具容器卫生标准的分析方法》进行修订和补充,并为修订GB13121—1991《陶瓷食具容器卫生标准》提供技术支持。方法建议在新修订的GB/T5009.62中保留火焰原子吸收光谱法(FAAS);删除双硫腙比色法(DSMP);增加电感耦合等离子体质谱法(ICP-MS)和石墨炉原子吸收光谱法(GFAAS)。通过开展方法学研究和实验室间比对实验,优化了ICP-MS和GFAAS的检测条件和技术参数。结果采用ICP-MS和GFAAS测定陶瓷食具容器中铅溶出量的定量限(LOQ)分别为1.0和2.5μg/L;测定镉溶出量的定量限(LOQ)均为0.1μg/L;测定铅的实验室间加标回收率为89.0%～114%(ICP-MS)和88.2%～110%(GFAAS);测定镉的实验室间加标回收率为86.2%～94.0%(ICP-MS)和90.0%～108%(GFAAS)。应用ICP-MS和GFAAS对60份产地不同的陶瓷食具容器样品进行铅、镉溶出量检测,经配对样品t检验计算表明结果差异无统计学意义。结论采用ICP-MS和GFAAS测定痕量铅、镉是目前最先进的分析技术,具有很高的灵敏度和准确度。ICP-MS可同时检测陶瓷食具容器中各种金属离子的溶出迁移情况。鉴于新修订的GB/T13121会对不同生产工艺和类型的产品分别制定更严格的铅、镉溶出限量指标,故将以上两种分析技术引入GB/T5009.62十分必要。     

A 12-month longitudinal study of Listeria monocytogenes contamination and persistence in pork retail markets in China

Listeria monocytogenes is a foodborne pathogen frequently isolated from raw pork meat. This study was designed to investigate the prevalence and molecular characteristics of L. monocytogenes in raw pork from open markets in China. The survey was conducted monthly over a 12-month period in Zigong, China. L. monocytogenes was isolated from 262 of 1641 samples collected (16.0%) including minced meat samples (131/608, 21.5%), pork pieces samples (111/857, 13.0%) and environmental swabs (20/176, 11.4%). The isolation rates in spring and winter were significantly higher than those in summer and autumn (X² = 68.85, P < 0.05). All isolates were subjected to serotyping, multi-locus sequence typing (MLST) and AscI pulsed-field gel electrophoresis (PFGE). The 262 isolates were subtyped into five serotypes: 1/2b (43.1%), 1/2c (35.5%), 1/2a (19.1%), 4b (1.1%), 3a (1.1%); 20 sequence types (STs) with four most frequent STs, being ST9 (35.9%), ST87 (19.8%), ST3 (16.0%) and ST8 (14.1%); and 39 pulsotypes (PTs) with PT4 (26.3%), PT30 (14.5%) and PT11 (12.6%) being most frequent. Two primary pulsotypes from pork pieces were previously isolated from clinical listeriosis cases in the local hospitals. The six markets from different districts differed in the level of contamination and strain types. Persistent contamination of L. monocytogenes was found in the markets especially in meat mincers, which were found to be one likely source of continuous cross contamination. These findings will help develop strategies to reduce L. monocytogenes contamination in open markets for better public health control and prevention of foodborne L. monocytogenes infections.     

Field emission from nano-cluster carbon films

Field emission has been reported to occur at much lower fields in carbon based thin film systems than from any other material systems. The emission has been shown to depend on the various material parameters, but whichever carbon based system is used, it is found that emission occurs at localised sites rather than uniformly over the entire surface. Carbon films with mixed sp³/sp² bonding, like nanocrystalline diamond and nanocluster graphitic films emit at lower fields with a higher emission site density than single-phase films. The sp² cluster size in any carbon film can be altered during deposition, but it is easier to control nanocluster size by post-deposition annealing. Annealing increases the sp² cluster size embedded in a sp³ matrix until the sp³ matrix disappears completely and the film transforms into nanocrystalline graphite. To distinguish the effects of the sp² cluster size from other material parameters, a series of different carbon films were annealed post-deposition and the sp² cluster size was measured using visible Raman. Field emission was then measured at a vacuum of 10⁻⁸ mbar on all films using a parallel plate configuration. It was found that the field emission for all films tested depended upon the clustering of the sp² phase and this effect dominates the effects of the other parameters, such as chemical composition, surface termination, sp³ content or conductivity. The optimum size of the sp² was of the order of 1 nm for all systems tested. We believe that field emission occurs form the localised conducting, predominantly sp² bonded regions, which provideds the large field enhancement required for effective emission.     

Prevalence and antimicrobial resistance of Listeria species isolated from milk and dairy products in Iran

The objective of this study was to determine the prevalence of Listeria spp. in milk and dairy products in Isfahan province, Iran. From March 2007 to September 2009, a total of 594 samples of various milk and dairy products were obtained from randomly selected retail stores. Using conventional bacteriologic method, 55 samples (9.3%) were positive for Listeria spp. The highest prevalence of Listeria was found in raw sheep milk samples (22.6%), followed by cheese samples (18.9%). The most species recovered was Listeria innocua (58.2%); the remaining isolates were Listeria monocytogenes (32.7%) and Listeria seeligari (9.1%). Overall, 54 Listeria isolates (98.2%) were resistant to one or more antimicrobial agents. Resistance to nalidixic acid was the most common finding (96.4%). All Listeria isolates were susceptible to vancomycin. The results of this study indicate the potential risk of infection with Listeria in people consuming raw and unpasteurized milk and dairy products.     

建立适合我国国情的抗菌纺织品标准体系的认识与实践

本文结合编制FZ/T73023-2006《抗菌针织品》行业标准的实践、简要说明了对国内外纺织品抗菌性能的测试方法及抗菌纺织品的安全性要求的认识;围绕维护人体皮肤微生态平衡的要求,简要介绍了如何确定符合我国国情的抗菌产品标准相关参数的实践过程;最后,简要阐明了该标准的先进性和创新性及对我国抗菌纺织品标准体系建立的推动作用。     

广东省市售纯牛奶营养标签标示现状调查

通过对纯牛奶样品营养标签的调查分析,了解广东省市售纯牛奶营养标签的现状。方法 采集广州、深圳、茂名、清远、梅州5个城市的市售纯牛奶样品,对其营养标签进行分析。结果 全部68份纯牛奶样品,均标示了能量和核心营养素含量值,但个别纯牛奶样品分别存在未标注营养素参考值(NRV)的百分比、未使用我国营养标签要求的能量与营养素单位、钠含量单位错标成毫升等营养标签标注不规范的问题。结论 GB 28050—2011《食品安全国家标准 预包装食品营养标签通则》自2013年1月实施以来,在规范营养标签方面取得了较大成效,但纯牛奶样品营养标签现状揭示的问题表明,相关部门仍需加大宣传力度,指导企业和食品进口商按照标准要求正确标示营养标签。     

频率匹配Hald模型在非伤寒沙门菌感染散发病例归因中的应用研究

目的 探索频率匹配模型在食源性致病菌食物归因中的应用,识别导致我国某省2016—2020年非伤寒沙门菌（NTS）感染散发病例的主要食物来源,为精准防控提供科学依据。方法 通过食源性疾病监测报告系统和食品污染物风险监测系统收集并整理患者和食物来源NTS血清型数据,采用Hald模型,纳入病例和食物共有的血清型开展归因分析。结果 NTS感染散发病例归因于畜肉的比例最高,为35.67%,其中猪肉的贡献比例高达22.37%;其次是蛋及蛋制品,归因比例为33.83%;归因于禽肉和水产动物的比例分别是19.28%和11.22%。通过归因识别发现单相鼠伤寒可能是导致该省NTS病例的优势血清型。结论 采用Hald模型获得猪肉是某省NTS感染散发病例的重要病因食品,为该省NTS的污染控制提供了线索,为应用频率匹配模型解决散发病例归因问题提供了范式,该模型可拓展应用于对其他省份感染散发病例的归因研究。