具有变时滞的线性系统的α-稳定性分析

研究对具有多个时滞变化的连续时间线性系统的α-稳定性问题,给出了对于给定的线性时滞系统的所有极点分布在复平面的特定区域的充分条件.这个条件可以通过LMI(线性矩阵不等式)工具箱来解.同时研究设计一个状态反馈控制器,使得闭环系统是α-能稳定的,并且通过LMI的方法给出了控制器存在的条件和利用LMI的解给出了控制器的设计方法.最后给出了一个数值例子验证了结果的正确性.     

带有时滞和非线性不确定性的中立系统的鲁棒稳定性条件

研究一类带有时滞和非线性不确定性的不确定中立系统的鲁棒稳定性问题.通过选择适当的Lyapunov函数,使用Leibniz-Newton公式的变形,结合自由权矩阵思想,加入一些自由矩阵,并且利用线性矩阵不等式(LMI)技术,得到了新的带有时滞和非线性不确定性的中立系统的时滞依赖稳定性条件.最后,通过数值算例来验证此方法的可行性以及有效性.     

随机微分方程数值解的几乎必然稳定区域

从研究SDE数值解入手,证明了线性标量SDE的Euler-Maruyama方法数值解的几乎必然指数稳定的几个条件,并且找出了Euler-Maruyama方法数值解几乎必然指数稳定区域;通过与Saito和Mitsui研究的Euler-Maruyama方法数值解的均方稳定区域做比较,可以发现得到的几乎必然指数稳定区域更大,因此也是更有价值的.     

不确定离散时滞系统的鲁棒H_∞保成本控制

对一类同时具有状态时滞和输入时滞的不确定离散时滞系统, 基于Lyapunov稳定性理论和线性矩阵不等式(LMI)处理方法, 得到系统H∞保成本状态反馈控制律存在的一个充分条件, 并利用线性矩阵不等式的可行解给出H∞保成本状态反馈控制律的设计方法. 进而, 通过求解凸优化问题解决了系统最优鲁棒H∞保成本控制律的设计问题. 最后, 通过数值算例说明了该设计方法的可行性.     

集值映射不动点的连续本质连通区

本质解的方法被广泛应用于各种问题解的稳定性研究,其在研究Nash平衡、不动点的稳定性中起着重要的应用.探讨了集值映射不动点的稳定性.引入了上半连续非空紧凸值集值映射不动点集的连续本质集的概念,并证明了其存在性.即证明了每一上半连续非空紧凸值集值映射至少存在一个该映射不动点集的极小连续本质集,以及该极小连续本质集是连通的.     

一类非自治食物链模型的局部分歧

研究了一类具Beddington-DeAngelis(B-D)反应函数非自治的食物链模型.以确定时变环境的参数b为分歧参数.用单特征值分歧理论得到了周期解存在的条件,并运用Crandall-Rabinowitz定理证明了单种群分歧解的稳定性.     

酶法提取长枣红色素及其稳定性的研究

研究了从长枣中酶解醇提红色素的工艺条件及色素的稳定性,通过试验得最佳工艺参数为:料水比1:20(m/V),粉碎度60目,α-淀粉酶(110000U/g)添加量为1%,酶解温度50℃,酶解时间40min,酶解pH6,酶解液用3倍体积的80%乙醇浸提,此条件下长枣色素的得率为9.85%.同时又对长枣色素的稳定性进行了初步探讨,结果表明,该色素除了在强氧化剂H2O2和碱性条件下中稳定性较差外,在其他条件下均具有良好的稳定性.     

中立型广义系统的时滞依赖保性能控制

研究了不确定中立广义系统带有时变时滞的鲁棒保性能控制问题．基于Lyapunov函数的理论,并运用线性矩阵不等式（LMI）导出了该系统时滞依赖的保性能控制律存在的充分条件以及最小性能上界．最后,用一个数值算例来说明此方法的可行性．     

非线性中立型时滞随机微分方程数值解的指数稳定性

在非线性中立型时滞随机微分方程数值解的指数稳定性问题中,一般是将方程中的漂移项系数和扩散项系数分开设置增长性限制条件。为了降低对每个系数增长的限制,将非线性中立型时滞随机微分方程中的漂移项系数和扩散项系数联合考虑,即将两系数的限制在一个式子中,给出了非线性中立型时滞随机微分方程Euler-Maruyama(EM)方法数值解指数稳定性的一类充分性条件。结果显示,在给定的充分性条件下,对于任意初值,运用EM方法得到的非线性中立型时滞随机微分方程的数值解都是几乎处处渐近指数稳定的。     

3-维肿瘤模型解的非对称稳定性

肿瘤的非对称不稳定性,通常暗含肿瘤会浸润周围正常组织.为了研究一个考虑了细胞黏附力的未血管化3-维肿瘤的非对称稳定性,首先对该肿瘤模型球对称静止解增加了非对称扰动,应用Taylor展开,考虑了非对称扰动的线性化问题,即一个关于扰动的偏微分方程初值问题.然后利用球调和函数展开,研究了有关扰动的偏微分方程的变量分离形式的解,最后根据微分方程稳定性定理,在肿瘤静止半径没有限制或肿瘤静止半径小于1的情况下,得到了非对称扰动的稳定和不稳定的条件.     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the