高效液相色谱法测定食品接触材料中甲醛迁移量

在本次实验中主要使用高效液相色谱法分析食品接触材料中甲醛迁移量。选用4%乙酸、10%乙醇、20%乙醇、50%乙醇及精炼玉米油5种食品模拟物作为研究对象,将其与甲醛进行浸泡后使用高效液相色谱法测定。首先需要向测试物中加入2,4-二硝基苯肼,然后与浸泡液中的甲醛反应生成2,4-二硝基苯腙,以C18色谱柱为分离柱,以甲醇-水(6+4)溶液为流动相进行等度洗脱,检测波长为355nm。试验结果表明,当甲醛质量浓度为0.01～40.0mg/kg时呈现线性特征,然后对空白样品做加标回收试验,测得回收率数值为98.5%～101.2%,且相对标准偏差(n=10)均不大于1.1%。应用该方法检测甲醛迁移量有着较好的效果,且从检定结果发现,相同使用条件下,酸性模拟物中含有的甲醛迁移量相对较大;在接触相同食品模拟物时,如果接触的时间越长迁移量随之增加,如果接触时温度越高,迁移量随之增加。     

仔猪致病性大肠杆菌的分离鉴定和药敏试验

从患病死亡仔猪肝脏中分离纯化所得一株细菌，经染色镜检、培养形状观察和生化鉴定、致病性试验，最终被鉴定为致病性大肠杆菌。利用该菌株对临床常用9种抗菌药物进行了药敏试验，药敏结果显示该菌对氟苯尼考、多粘菌素、痢菌净敏感：对卡那霉素、强力霉素、环丙沙星中度敏感；对阿莫西林、链霉素磺胺甲基异恶唑耐药。使用痢菌净、氟苯尼考有效控制了病情。     

金属食品接触材料中5种重金属元素的迁移量检测分析

本文参考现有国标方法及国内外标准对市售金属食品接触材料中5种金属元素(镉、铅、铬、锌、镍)的迁移量水平进行评估研究。本研究以体积分数4%乙酸作为食品模拟物,利用电感耦合等离子体发射光谱法(Inductively Coupled Plasma Optical Emission Spectrometer,ICP-OES)测定食品用金属制品中5种金属元素迁移量。该方法的线性范围在0.01～1.00 mg·L^-1,检出限在0.001～0.010 mg·L^-1,重复性测定相对偏差(n=6)在2.1%～5.6%,加标回收率在90.0%～112.5%。对60批次市售食品用金属餐具金属元素迁移量水平测定结果表明,5种金属元素在不同样品中迁移水平不同,这与其在金属餐具中的含量有关。5种元素的迁移量均符合国家标准要求,表明目前市售金属食品接触材料产品整体质量水平较高,产品质量较安全。     

高谷维素米糠油双相萃取脱酸精炼工艺研究

对比研究碱炼脱酸、乙醇单相萃取脱酸和乙醇-正己烷双相萃取脱酸3种脱酸工艺对米糠油脱酸以及谷维素保存效果的影响.研究结果表明:碱炼脱酸后的米糠油中谷维素含量仅为0.38%,谷维素保留率23_3%,酸价降低至1.762mgKOH/g;乙醇单相萃取脱酸后的米糠油中谷维素含量为1.32%,谷维素保留80.9%,酸价降低至1.184mgKOH/g;乙醇-正己烷双相萃取脱酸后的米糠油中谷维素含量达到1.57%,谷维素保留率96.3%,酸价降低至0.237mgKOH/g.研究结果对生产富含谷维素的营养米糠油具有现实的指导意义.     

苦荞口服液的研制

试验以苦荞作为原料,研究苦荞黄酮提取过程中超声波时间、乙醇浓度、料液比、超声波温度对黄酮提取率的影响,通过正交试验研究出最佳苦荞口服液调配工艺。实验表明黄酮最佳提取条件为:超声波时间25 min、乙醇浓度80%、料液比1∶20、超声波温度45℃,此时黄酮的提取率最高,利用最佳提取条件进行苦荞黄酮提取分离,确定调配工艺黄酮浓缩液添加量为80%、安赛蜜添加量为0.25%、木糖醇添加量为5%、山梨酸添加量为0.025%,纯净水补足,此时口味最佳。     

响应面优化微波协同双水相体系提取咖啡豆中绿原酸的工艺研究

为优化提取云南小粒咖啡豆中绿原酸的工艺条件,以微波辅助低级醇双水相提取体系,对云南小粒咖啡豆中的绿原酸进行提取研究。分别研究了乙醇体积分数、磷酸氢二钾质量浓度、料液比、微波功率和微波时间对咖啡豆中绿原酸提取率的影响程度,采用响应面法优化提取工艺,得到云南小粒咖啡豆中绿原酸的最佳提取工艺条件为乙醇体积分数为76.98%,磷酸氢二钾质量浓度为0.14 g·mL-1,料液比为1∶54.97(g∶mL),微波功率为280 W,微波时间为15.48 s,绿原酸提取率为4.54%,与预测值4.55%相近。     

铝箔餐盒中铍、铅、砷、铬、镉、汞6种金属元素迁移量的研究

在测定体积分数分别为4%乙酸溶液、10%乙酸溶液、10%乙醇溶液的不同条件下,采用电感耦合等离子体质谱法对6组铝箔餐盒中6种金属元素迁移量以及6种金属元素的含量进行测定。结果表明,各元素在0～50μg·L^-1时线性关系良好,相关系数大于0.995,加标回收率为88.5%～98.1%,各元素的检出限为0.002～1.000μg·L^-1。6组铝箔餐盒中6种金属元素在不同条件下的迁移量不同,主要与铝箔餐盒对应原材料铝箔中各元素的含量有关。非正确长期使用铝箔餐盒势必对人们的身体健康造成危害,存在安全风险。     

凭祥市生态敏感性评价研究

通过选取主要生态敏感性因子(海拔、坡度、坡向、植被指数、水域距离)进行GIS叠加分析,并将叠加分析后结果分为高度敏感、较高敏感、中度敏感区、较低敏感和低度敏感5个等级。研究结果显示凭祥市生态质量较好,高敏感在空间分布存在小聚集特征,低度敏感面积为54.72 km²(8.48%),较低敏感面积为156.09 km²(24.18%),中度敏感面积为223.33 km²(34.59%),较高敏感面积为139.73km²(21.64%),高度敏感面积为71.73km²(11.11%)。提出了凭祥市西南部地区建立生态保护缓冲区和生态保护重点区,对接生态与经济发展空间的建议。     

高效液相色谱法检测贡梨中甲基硫菌灵及其代谢物多菌灵残留量

本实验采用高效液相色谱法测定贡梨中甲基硫菌灵及其代谢物多菌灵残留量。结果表明,甲基硫菌灵及其代谢物多菌灵在0.2～50.0μg·kg^-1线性关系良好,相关系数R²均大于0.999。甲基硫菌灵和多菌灵的平均回收率分别为93.3%～100.2%和94.5%～99.1%,RSD分别为1.8%～2.4%和1.9%～2.9%。该方法优越、快速、灵敏,适用于贡梨中甲基硫菌灵和多菌灵的快速筛查和定量检测。     

淮安市婴幼儿食品肠杆菌检测及耐药性研究

目的：了解淮安市2023年市场在售74批婴幼儿食品中肠杆菌携带情况以及耐药性。方法：随机购买淮安市市场婴幼儿产品共74批,尽量购买不同品牌和不同产地的样品作为研究样本,参考《食品安全国家标准食品微生物学检验沙门氏菌检验》（GB 4789.4—2016）用全自动鉴定药敏分析仪检测细菌对不同药物的敏感以及耐药情况。结果：74批婴幼儿食品中肠杆菌共检出2株阴沟肠杆菌、1株肺炎克雷伯杆菌和1株阪崎肠杆菌,肠杆菌总检出率为5.4%。在19种药物耐药试验中,上述检出菌对15种药物敏感,对头孢唑林、氨苄青霉素、氨苄青霉素-舒巴坦、阿莫西林克拉维酸盐的敏感率分别为50.0%、75.0%、50.0%和75.0%。结论：淮安市市场在售的部分婴幼儿食品检出肠杆菌,对β内酰胺类药物存在明显的耐药情况,应引起相关部门的重视。     

The Migration of Young Adults from Non-Metropolitan Counties

This article examines young adult migration from non-metropolitan counties to either different non-metropolitan counties or to metropolitan areas. The results show that expected gains in initial earnings provide young entrants to the labor force with a marked incentive to migrate from their non-metropolitan counties of origin. Initial earnings gains stem, in part, from higher returns to schooling in both metropolitan areas and other non-metropolitan counties. The propensity to migrate is also sensitive to the costs of migration, which, in turn, are correlated with paternal education and the local presence of extended family.     

花生红衣原花青素纯化工艺研究

为探究花生红衣中原花青素的纯化条件,本研究通过静态吸附和解吸试验对8种型号大孔树脂进行选择,再经动态吸附和解吸试验得出最优纯化条件。结果表明,大孔树脂最佳型号为D4020,得出最佳纯化条件为:上样流速1 mL·min^-1,上样浓度1.5 mg·mL^-1,洗脱液为40%乙醇,洗脱流速1 mL·min^-1,最终所得纯化物纯度达97.35%±1.58%。     

Employment Growth, Worker Mobility, and Rural Economic Development

A county-level labor market model is estimated for North Carolina. The model accounts for inter-county commuting, migration, and within-county adjustments to labor demand shocks. Econometric results indicate that most employment growth (70–80%) during the 1980s was accommodated by changes in commuting flows. Evidence is also presented indicating that labor force growth—and, by extension, population growth and associated fiscal impacts—in rural counties is sensitive to employment growth in nearby urban counties. These results highlight two opposing forces related to spatial spillovers that are usually neglected in analyses of the economic and fiscal impacts of employment growth.     

Does labor migration affect rural land transfer? Evidence from China

Land transfer in rural areas and labor migration from rural areas to cities are both becoming common in China due to the increasing development of the non-agricultural sector resulting from rapid urbanization. Many rural labours who migrated to cities left their land in rural areas, and in most cases, this land was abandoned. To make full use of abandoned land in rural areas, the central government in China has formulated policies to promote rural land transfer, but rural land transfer still lags far behind labor migration in China. Drivers of rural land transfer still need to be explored. In addition, the labor migration scale shows dynamic features as the labor migration of more family members is substituted for that of individuals recent years. Thus, the phased feature of household labor migration should be taken into consideration to examine the phased influence of the labor migration scale on rural land transfer. Considering the probability threshold effect of the impact of labor migration on rural land transfer, a threshold model was used to perform the empirical analysis. Based on the threshold model and CHARLS 2015 data, this study empirically analysed the impact of the labor migration scale on rural land transfer. On the national level, labor migration will significantly promote rural land transfer if it is less than or equal to 0.125, but when it is greater than 0.125, its impact on land transfer is not significant. On the basis of the spatial differentiation of rural land transfer, four regions were divided to do the regional threshold regression analysis. On the regional level, the thresholds of labor migration scale of the central region, the east region and the west region are 0.112, 0.221 and 0.133 respectively, and there is no threshold in the north region. The results show that labor migration have a phased impact on rural land transfer in China and policies should be targeted to different labor migration phases and different regions.     

纸吸管中铝元素迁移量的风险分析与评估

目的:研究我国市售纸吸管产品中铝元素的迁移情况,并进行风险分析与评估.方法:随机购买市场流通环节的纸吸管,采用电感耦合等离子发射光谱法测定迁移试验所得浸泡液中铝元素的迁移量,分别按照欧盟和美国的风险评估方法进行评价.结果:26批纸吸管样品的铝元素特定迁移结果均超过欧盟食品接触用塑料材料及制品法规中铝元素的特定迁移限量,...     

Analysis of an Emerging Market: Can Methyl Iodide Substitute for Methyl Bromide?

Recent amendments to the Montreal Protocol specify a 100% reduction in methyl bromide consumption in all developed countries by the year 2005 (except for 'critical uses'). In this paper we consider one possible chemical substitute to methyl bromide, methyl iodide, that until recently has received little attention as a potential alternative. We examine the viability of methyl iodide using information from studies of the economic benefits of methyl bromide to California agricultural producers and of methyl iodide effectiveness in pre-plant fumigation experiments, and from an assessment of the world market for iodine.     

微观家庭视角下库区移民适应状况及影响因素基于长江上游库区385户移民数据的实证分析

[目的]探究微观家庭视角下长江上游库区移民适应状况及影响因素,并提出提高移民适应的策略为政策制定提供参考。[方法]文章基于移民适应分析框架,运用二元Logit模型与统计分析法,分析影响移民适应的因素与移民适应状况及差异、不同适应状况的移民特征异质性。[结果]发现户主特征(户主年龄、民族、受教育程度、健康状况)与移民适应没有显著关系;家庭特征(是否负债、是否受灾),经济因素(人均可支配收入、主要收入来源、土地面积),政治因素(是否有党员干部、意见受重视程度、政策满意度、政治参与度),文化因素(语言异同、身份认同)与库区移民适应有着密切的关系;目前长江上游库区移民的总体适应比仅68%,岷江、金沙江、雅砻江等三大支流适应比分别为71.0%,68.3%,65.8%;适应的移民家庭的人均纯收入和耕地面积分别比不适应的移民家庭多1 815.01元、0.24hm~2。[结论]长江上游库区移民总体适应状况不佳,岷江、金沙江、雅砻江等三大支流适应状况存在差异,不同适应状况的移民特征也存在显著异质性。移民适应的状况是多因素影响的结果,因此移民适应政策的制定需要综合考虑,实现政策效益最大化。     

压煤村庄搬迁与"挂钩流转"政策相结合时的问题及对策研究——以兖州市为例

研究目的:在建设用地指标异常紧张的情况下,为顺利推进压煤村庄搬迁提供途径。研究方法:资料综合分析法、对比法和实证分析法。研究结果:压煤村庄搬迁与"挂钩流转"政策相结合时存在4大难题,提出了解决方法。研究结论:压煤村庄搬迁与"挂钩流转"政策相结合是可行的。但应适当放宽周转指标归还时间和对耕地数量质量的要求,优先开采能复垦出耕地的村庄下的煤炭资源,尽快归还挂钩周转指标。     

The Methyl Bromide Ban: Economic Impacts on the California Strawberry Industry

California strawberry production accounts for 18% of total methyl bromide use in U.S. agriculture. Under the Montreal Protocol, methyl bromide was slated to be banned in the United States in 2005. A critical use exemption was obtained for U.S. agriculture for 2005 and 2006, but the phaseout of methyl bromide continues. We examine the ban's effects on the California strawberry industry, and on individual production regions in the state. Under the most likely scenario, industry revenue will decline by 6–17% due to the ban. The effects will differ by region, due to seasonal differences in demand and production, and the possibility of increased foreign competition.