QuEChERS结合液相色谱-串联质谱法快速测定鸡肉中磺胺类残留

采用QuEChERS方法提取和净化鸡肉样品,建立测定磺胺类12种兽药残留的液相色谱-串联质谱(LC-MS/MS)检测方法。样品经乙腈和缓冲盐包SBEQ-CA8802-B提取,提取液经净化管净化后取上清液,旋转蒸发仪减压蒸干,溶解过膜,在电喷雾离子源多反应监测(MRM)模式下进行测定,基质外标法定量。结果表明,12种磺胺类药物测定方法的线性范围为0.01~0.20μg·kg^-1,线性相关系数r均大于0.999,定量检出限为0.02~0.12μg·kg^-1,10μg·kg^-1添加范围的平均回收率为87.6%~101.0%,相对标准偏差为3.53%~11.60%。该方法操作简单,净化效果好,灵敏度高,能够快速有效地检测鸡肉中的磺胺类药物残留。     

Knowledge Types in Technology

Starting with the distinction of natural science, engineering science ("technology") and engineering practice ("technics"), the paper will stress the difference between technological and technical knowledge. The first part will discuss the relationship between science and technology, arguing that technology is a genuine type of knowledge rather than "applied science". In technics, however, even technological laws, as transformations of scientific laws, cover a certain part of knowledge only. The greater part of technical knowledge includes technical know-how, functional rules, structural rules, and socio-technological understanding, which is just developing in our times. The classification of knowledge types will be used for determining which kind of knowledge may seem appropriate to general technological education.     

The effect of spillovers on the provision of local public goods

This paper analyzes the provision of local public goods with positive spillovers across jurisdictions. If spillovers are symmetric, the non-cooperative game played by jurisdictions admits a unique equilibrium, and an increase in spillovers reduces the total provision of public goods. Smaller jurisdictions always reduce their contribution, but larger jurisdictions can increase their contribution. When spillovers are asymmetric, equilibrium is unique if spillovers are low, while multiple equilibria exist for high spillover values. In the case of two jurisdictions, an increase in the flow of spillovers to one jurisdiction benefits agents from that jurisdiction but harms agents in the other jurisdiction. Beyond the case of two jurisdictions, the effect of changes in spillovers cannot be signed. An increase in the spillovers flowing to a jurisdiction can actually result in an increase in the supply of public goods by that jurisdiction and harm agents residing in it, while benefiting agents in the other jurisdictions. The results of the paper reveal the complexity of interactions that will plague the design of institutions for multijurisdictional local public good economies with spillovers.      

Regional Shifts in Pork Production: Implications for Competition and Food Safety

U.S. pork production and processing is consolidating in larger, more economically efficient units, and shifting from the Midwest into the Southeast. A regional model of farm supply and processing demand shows that smaller Midwest operations can survive only if processing capacity remains concentrated in that region. Salmonella incidence is higher in the Southeast and on larger farms. Restricting salmonella incidence in hogs delivered for processing to the minimum feasible level would increase total industry costs by 3%, due to increased production and delivery costs. It would also increase the comparative advantage of farms and processing firms in the Midwest.     

Agrarian Change and Labour Supply in Turkey, 1950–1980

Agrarian structures based on small peasant property can have two opposite kinds of impact on urban wages. In the first type, stable smallholder farming bringing high returns puts upward pressure on wages. In the second type, smallholder farming that does not bring sufficient returns leads to semi‐proletarianization in which workers' access to rural sources of income functions as wage subsidy and puts downward pressure on wages. This paper argues that the situation in Turkey between 1950 and 1980 fits the second type. By pointing out the factors that changed the attitude of the migrant labourers towards class struggle from relative passivity to increasing militancy, it suggests that instead of the rural ties of the emerging working class, the main reason behind the dramatic rise in urban wages in Turkey in the 1960s and 1970s was the working‐class struggle throughout the period.     

基于改进F-N曲线的滑坡可接受风险水平研究

滑坡灾害的可接受风险水平是滑坡领域的重要研究内容之一,它常常用F-N曲线直观地表示风险频率与后果之间的关系,然而这种传统方法的参数由人为确定,主观性强,缺乏理论依据,且同一个参数不能适用多个地区和风险.以滑坡灾害的相关规范为依据,用风险矩阵的方法做衔接,绘制出3种决策态度下的滑坡灾害可接受风险的F-N曲线.相比传统的方法,改进后的F-N曲线避免了以上缺陷,使得滑坡灾害可接受风险水平的确定更加精准,同时该方法也可运用到其他领域的相关规范,来研究其可接受风险水平.     

Packages with Cartoon Trade Characters Versus Advertising: An Empirical Examination of Preschoolers' Food Preferences

The present study examines mainly the comparison between child-appeal packages and TV advertising and suggests that packages with cartoon trade characters play a more effective role compared to TV advertising in preschoolers' food preferences.

Preschoolers who watched a cartoon film CD embedded with commercials (the treatment group) and who watched the same CD without commercials (the control group) selected the chocolate wafer with a cartoon trade character (73.6% vs. 26.3%) rather than the advertised one.     

Privatization and the economic performance of Irish Sugar/Greencore

As one of Ireland’s largest agribusiness companies, the Irish Sugar company played a key role in the country’s economic development in the twentieth century. The company was privatized in 1991 (under the new name Greencore) and has since transformed from a largely commodity-based agribusiness into an international convenience food company. This article analyses the financial and economic performance of the company in the 10 years before and after privatization. It finds that the change from public to private ownership was not strongly associated with improved financial performance and productivity as the company had experienced rapid growth and improvement in the pre-privatization period. These findings run counter to perspectives such as public choice theory that suggest a positive relationship between privatization and company performance. Performance in the post-privatization period was strongly influenced by greater exposure to market forces in the company’s expanding food division; however, it is surprising that this greater competition did not translate into improved overall performance.