International legislation on trace elements as contaminants in food: a review

Environmental contaminants such as trace elements may be present in all foods. Foods, raw materials and ingredients for food production are to an increasing extent traded across borders. Hence, there is a need for international legislation on trace elements as contaminants in food. In 1961, the FAO and WHO established the Codex Alimentarius to elaborate international food legislation. Contaminants in food are handled by the Codex Committee for Food Additives and Contaminants (CCFAC). The Codex Alimentarius system for developing legislation concerning trace elements as contaminants in food is based upon the Codex General Standard for Contaminants and Toxins in Food (GSCTF). By October 2001, the principles for setting maximum limits (MLs) for contaminants in food are agreed, and work is in progress on MLs for trace elements such as lead and cadmium in the various food categories. The status for the proposals is presented and discussed. The EU Regulation 466/2001 of 8 March 2001 sets MLs for lead and cadmium in various foods. This regulation will apply from 5 April 2002. The EU regulation is more detailed but similar to the Codex draft standards for lead and cadmium in food. In future, legislators and administrators in the Codex and EU and analytical chemists will discuss how to use more and better analytical data as risk-management tools to protect public health. Trace elements' speciation is an important aspect of this discussion.     

Results from the monitoring of pesticide residues in fruit and vegetables on the Danish market, 2000-01

To check compliance with the maximum residue levels in foods and to monitor the residue levels to enable an evaluation of the exposure of the Danish population to pesticides, a monitoring programme for pesticides residues in fruit and vegetables was performed. Sampling plans were designed based on previous findings and on consumption data. Samples (n = 4404) of mainly fresh conventionally and organically grown fruit and vegetables were collected at wholesalers and importers and at food processing companies. Of the samples, 3% were frozen products and 5% organically grown. Of the samples, 34% were of Danish origin, with 66% from other countries. Two accredited laboratories performed analyses of the samples using capillary gas chromatography, liquid chromatography and a spectrophotometric method. Reporting levels were set at the lowest calibration level or at the limit of determination. Residues were found in 60% of the samples of fruit but in only 18% of the vegetable samples. Residues above the maximum residue levels were found in 6% of all samples of fruit and in 2% of the vegetable samples.     

Limits of Learning-Based Superresolution Algorithms

Learning-based superresolution (SR) is a popular SR technique that uses application dependent priors to infer the missing details in low resolution images (LRIs). However, their performance still deteriorates quickly when the magnification factor is only moderately large. This leads us to an important problem: “Do limits of learning-based SR algorithms exist?” This paper is the first attempt to shed some light on this problem when the SR algorithms are designed for general natural images. We first define an expected risk for the SR algorithms that is based on the root mean squared error between the superresolved images and the ground truth images. Then utilizing the statistics of general natural images, we derive a closed form estimate of the lower bound of the expected risk. The lower bound only involves the covariance matrix and the mean vector of the high resolution images (HRIs) and hence can be computed by sampling real images. We also investigate the sufficient number of samples to guarantee an accurate estimate of the lower bound. By computing the curve of the lower bound w.r.t. the magnification factor, we could estimate the limits of learning-based SR algorithms, at which the lower bound of the expected risk exceeds a relatively large threshold. We perform experiments to validate our theory. And based on our observations we conjecture that the limits may be independent of the size of either the LRIs or the HRIs.     

纳米电子技术

微电子技术引发了本世纪的信息革命。纳米科学技术将成为二十一世纪信息时代的核心和国际科学界和工程技术界关注的热点。     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

放射性废物管理与辐射防护新进展

本文探讨了近十年来辐射防护的研究进展对放射性废物管理特别是对放射性废物处置所产生的影响及进一步研究的课题。     

核电站选址的辐射安全准则和评价方法

核电站选址报告包括建核电站的可行性及其安全性的论证,涉及核地区的经济、交通、地质、地震、气象、水文、居民分布及活动等因素,是一个综合性的多学科的研究课题。本文从选址涉及的环境保护及其评价方法介绍了有关课题的研究现状和存在的问题,并提出了初步建议。本文强调了“事故树”的分析方法,并建议对扩散天气的分析也采用几率表述方法,以便能最终给出危险度与几率的关系。     

Quick Analysis Methods for Random Balance,Screening Experiments

A short expository account of random balance ia given, in which some different types of sampling are distinguished. As a quick significance test of effectiveness of single factors, a simple analysis of variance method is recommended. For the sake of sensitivity, it is suggested that the number of levels of quantitative factors should preferably be less than five. The degree of unbalance of a random balance design is studied, largely through an example, and a desirable upper bound is suggested for the number of levels of any factor, namely one eighth of the total number of observations.     

Forecasting Trending Time Series with Relative Growth Rate Models

Many annual time series in socioeconomic systems are steadily increasing functions of time. This paper deals with an empirical approach to analyzing and projecting such trending time series from models of relative growth rates or percent changes. A class of relative growth rate models is defined which includes the linear. exponential, modified exponential and logistic growth curves as special eases. Parameters are estimated for the most part by linear regression techniques since the, relative growth rates for this class of models are linear in the parameters. The ternd curve for each model is obtained by integration and approximate-confidence limits can be obtained for the forecasts of future series values.     

On the Distribution of Some Time Averages of Shot Noise

A shot noise X(t) is a superposition of impulses occurring at times tj, where the Tj follow a Poisson point process. For the case of a rectangular impulse function (height a, length b) the cumulant generating function of the sample mean M(T), (2), is obtained, also the mean and variance of the sample variance V(T), (3). This, together with the covariance of V and M, is used to calculate the standard error of the coefficient of dispersion V/M. An approximate distribution is conjectured for I(T) = V(T)/aM(T) and based on it, percentage points of this statistic are given. They could be used to test the hypothesis that a given noise is shot noise. An application to a textile problem is described.