搅拌棒吸附萃取技术及其在食品分析中的应用

作为20世纪90年代末发展起来的一种新型的样品前处理技术,搅拌棒吸附萃取具有灵敏度高、重现性好、不使用有机溶剂等优点,现已成功应用于环境、食品、生物等领域。综述了搅拌棒吸附萃取原理、发展状况及其在食品分析中的应用。     

基于自适应交叉、变异遗传算法的PID整定

提出了一种带有自适应交叉、变异算子的遗传算法，并把它应用到PID参数的整定当中，仿真结果表明，该方法提高了参数的优化性能，对控制系统具有良好的控制精度、动态性能和鲁棒性。     

基于遗传神经网络的郫县豆瓣有机酸提取工艺研究

针对郫县豆瓣有机酸最佳提取工艺问题,提出了一种高精度遗传神经网络优化方法,解决回归分析方法拟合度精度和准确性不高的现象。以郫县豆瓣有机酸提取量为性能指标,用中心组合试验数据训练遗传神经网络,当神经网络训练误差达到1.1862×10^-11时,神经网络算法输出数据与试验数据几乎完全拟合,平均相对误差为0%,而回归模型为0.822%,对比分析得出遗传神经网络算法的拟合精度和拟合优度均高于回归模型。用训练好的遗传神经网络算法对郫县豆瓣有机酸提取工艺条件进行优化,得到最佳提取工艺条件为:乙醇体积分数68.50%,料液比1∶20.44(g/mL),超声时间35.28min。此时有机酸提取量达到最大值15.19mg/g。该方法可为郫县豆瓣有机酸提取工艺提供试验参考,为制定更加完善的产品质量标准提供了数据支撑。     

行星齿轮减速器均载性能动态的优化设计

基于遗传算法搜索技术以及行星齿轮传动系统的弯扭耦合振动模型,完成某2K-H型行星齿轮减速器动态均载性能的优化设计。通过行星齿轮传动系统动力学响应的数值计算,确定对减速器均载性能影响较为显著的几个设计参数,结合工程中方便修改实现的原则,从中选择内、外啮合副的齿侧间隙作为优化设计变量。根据工程中齿侧间隙的许可取值范围,确定设计变量的搜索区间。经过遗传算法的搜索,最终获得一组内、外啮合副的最优齿侧间隙组合,数值试验证实在该组参数组合下行星齿轮减速器的均载性能有了明显改善。     

MATHEMATICAL FUNDAMENTALS TO DETERMINE THE KINETIC CONSTANTS OF FIRST-ORDER CONSECUTIVE REACTIONS

An accurate mathematical analysis of the trend of experimental data to determine the kinetic constants of consecutive reactions is important for further design and optimization studies. For this purpose, the kinetics of the consecutive reactions was evaluated for different cases, and an unconstrained minimization (optimization) problem was defined to determine the kinetic constants. Minimization of least square analysis was used with the Newton's multivariable optimization procedure. The solution method for the defined optimization problem and the effect of initial guess parameters were discussed in detail. The applied optimization algorithm was then tested with simulated and literature‐reported kinetic data. The algorithm was shown to converge under different situations, and it was concluded that knowing the mathematical fundamentals and using them through different optimization techniques would be a useful tool in the evaluation of experimental data.     

基于变长编码的遗传算法在纸卷切割中的应用

针对造纸生产中的纸卷切割问题，提出了一种基于变长编码求解纸卷切割问题的遗传算法。该算法实现简单、求解快速，应用于某造纸企业销售管理信息系统优化排产计划模块中运行效果良好。     

Role of biofilms in sorptive removal of steroidal hormones and 4-nonylphenol compounds from streams

Stream biofilms play an important role in geochemical processing of organic matter and nutrients, however, the significance of this matrix in sorbing trace organic contaminants is less understood. This study focused on the role of stream biofilms in sorbing steroidal hormones and 4-nonylphenol compounds from surface waters using biofilms colonized in situ on artificial substrata and subsequently transferred to the laboratory for controlled batch sorption experiments. Steroidal hormones and 4-nonylphenol compounds readily sorb to stream biofilms as indicated by organic matter partition coefficients (K(om), L kg(-1)) for 17β-estradiol (10(2.5-2.8) L kg(-1)), 17α-ethynylestradiol (10(2.5-2.9) L kg(-1)), 4-nonylphenol (10(3.4-4.6) L kg(-1)), 4-nonylphenolmonoethoxylate (10(3.5-4.0) L kg(-1)), and 4-nonylphenoldiethoxylate (10(3.9-4.3) L kg(-1)). Experiments using water quality differences to induce changes in the relative composition of periphyton and heterotrophic bacteria in the stream biofilm did not significantly affect the sorptive properties of the stream biofilm, providing additional evidence that stream biofilms will sorb trace organic compounds under of variety of environmental conditions. Because sorption of the target compounds to stream biofilms was linearly correlated with organic matter content, hydrophobic partition into organic matter appears to be the dominant mechanism. An analysis of 17β-estradiol and 4-nonylphenol hydrophobic partition into water, biofilm, sediment, and dissolved organic matter matrices at mass/volume ratios typical of smaller rivers showed that the relative importance of the stream biofilm as a sorptive matrix was comparable to bed sediments. Therefore, stream biofilms play a primary role in attenuating these compounds in surface waters. Because the stream biofilm represents the base of the stream ecosystem, accumulation of steroidal hormones and 4-nonylphenol compounds in the stream biofilm may be an exposure pathway for organisms in higher trophic levels.     

Quantification of solute-solute interactions using negligible-depletion solid-phase microextraction: measuring the affinity of estradiol to bulk organic matter

The interaction of trace organic contaminants with bulk organic matter has implications for the transport and behavior of organic trace contaminants within the aquatic environment as well as water and wastewater treatment processes. Partition coefficients (K(OM)) of the steroidal trace organic contaminant estradiol were quantified for environmentally relevant concentrations of bulk organic matter (12.5 mg C/L) using a full mass balance form of solid-phase microextraction (SPME). The results indicated that the method is successful and can be used at environmental concentrations. Estradiol had the greatest affinity for bulk organic matter that contained phenolic and benzoic acid ester groups, namely tannic acid, compared to organics containing predominately carboxylic functional groups. The solution chemistry (pH) was found to influence the interaction, as estradiol had a lower affinity for negatively charged and hydrophilic bulk organic matter. The partition coefficients determined using SPMEwere consistentwith partition coefficients derived using solubility enhancement and fluorescence quenching measurements, confirming that SPME is a powerful technique to quantify the affinity of estradiol for low concentrations of bulk organic matter and trace contaminants. Further, this novel method can be applied to a range of trace contaminants.     

Ab initio and in situ comparison of caffeine, triclosan, and triclocarban as indicators of sewage-derived microbes in surface waters

Three organic wastewater compounds (OWCs) were evaluated in theory and practice for their potential to trace sewage-derived microbial contaminants in surface waters. The underlying hypothesis was that hydrophobic OWCs outperform caffeine as a chemical tracer, due to their sorptive association with suspended microorganisms representing particulate organic carbon (POC). Modeling from first principles (ab initio) of OWC sorption to POC under environmental conditions suggested an increasing predictive power: caffeine (0.2% sorbed) < triclosan (9-60%; pH 6-9) < triclocarban (76%). Empirical evidence was obtained via analysis of surface water from three watersheds in a rural-to-urban gradient in Baltimore, MD. Mass spectrometric OWC detections were correlated to microbial plate counts for 40 monitoring sites along 14 streams, including multiple chronic sewage release sites and the local wastewater treatment plant. Consistent with ab initio calculations, correlation analyses of 104 observations for fecal coliforms, enterococci, and Escherichia coli in natural surface waters showed that the particle-active antimicrobials triclosan and triclocarban (R2 range, 0.45-0.55) were indeed superior to caffeine (0.16-0.37) for tracking of microbial indicators. It is concluded that chemical monitoring of microbial risks is more effective when using hydrophobic OWCs such as triclosan and triclocarban in place of, or in conjunction with, the traditional marker caffeine.     

改进遗传算法PID参数优化在流浆箱总压控制中的应用

稀释水水力式流浆箱的总压控制直接关系到纸张质量的好坏,传统的PID方法对于非线性、参数时变性和模型不确定性的对象控制精度较低。虽然传统遗传算法可以优化PID参数,提高精度,但是收敛速度慢,整定时间长,限制其在高速纸机控制中的应用。针对这些问题,本课题以纸机流浆箱总压控制为研究对象,采用改进的遗传算法来整定PID参数,通过优化交叉和变异算子、增加当前最优追踪策略以及改进收敛准则等方法来提高遗传算法的全局寻优能力和收敛速度。仿真结果表明,用改进的遗传算法整定后的流浆箱总压控制PID具有更快的响应速度和更好的鲁棒性。     

基于人群搜索自抗扰控制的放卷张力控制系统

针对轧染机放卷运行中张力波动的问题,提出将自抗扰控制(ADRC)与人群搜索算法(SOA)相结合进行张力控制的方法。通过分析放卷张力系统,建立放卷张力系统数学模型,采用自抗扰控制方法推导得到解耦模型,利用人群搜索算法对自抗扰控制器中的主要参数进行在线调整,并建立人群搜索自抗扰控制器。通过与PID控制器仿真实验对比表明,所建立的控制器能够使放卷张力系统实现解耦控制,保证放卷张力系统的恒张力稳定运行,并且提升了放卷张力系统的抗干扰性能。     

Multilayer packaging: Advances in preparation techniques and emerging food applications

In recent years, with advantages of versatility, functionality, and convenience, multilayer food packaging has gained significant interest. As a single entity, multilayer packaging combines the benefits of each monolayer in terms of enhanced barrier properties, mechanical integrity, and functional properties. Of late, apart from conventional approaches such as coextrusion and lamination, concepts of nanotechnology have been used in the preparation of composite multilayer films with improved physical, chemical, and functional characteristics. Further, emerging techniques such as ultraviolet and cold plasma treatments have been used in manufacturing films with enhanced performance through surface modifications. This work provides an up‐to‐date review on advancements in the preparation of multilayer films for food packaging applications. This includes critical considerations in design, risk of interaction between the package and the food, mathematical modeling and simulation, potential for scale‐up, and costs involved. The impact of in‐package processing is also explained considering cases of nonthermal processing and advanced thermal processing. Importantly, challenges associated with degradability and recycling multilayer packages and associated implications on sustainability have been discussed.     

Sorption of perfluorinated surfactants on sediments

The sorption of anionic perfluorochemical (PFC) surfactants of varying chain lengths to sediments was investigated using natural sediments of varying iron oxide and organic carbon content. Three classes of PFC surfactants were evaluated for sorptive potential: perfluorocarboxylates, perfluorosulfonates, and perfluorooctyl sulfonamide acetic acids. PFC surfactant sorption was influenced by both sediment-specific and solution-specific parameters. Sediment organic carbon, rather than sediment iron oxide content, was the dominant sediment-parameter affecting sorption, indicating the importance of hydrophobic interactions. However, sorption also increased with increasing solution [Ca2+] and decreasing pH, suggesting that electrostatic interactions play a role. Perfluorocarbon chain length was the dominant structural feature influencing sorption, with each CF2 moiety contributing 0.50-0.60 log units to the measured distribution coefficients. The sulfonate moiety contributed an additional 0.23 log units to the measured distribution coefficient, when compared to carboxylate analogs. In addition, the perfluorooctyl sulfonamide acetic acids demonstrated substantially stronger sorption than perfluorooctane sulfonate (PFOS). These data should prove useful for modeling the environmental fate of this class of contaminants.     

基因工程抗体在食品安全检测中应用进展研究

基因工程抗体是近年来发展起来的一种新型抗体,将其应用于食品安全检测是目前食品学科领域研究的热点之一。因基因工程抗体具有分子小、免疫原性低、可塑性强、成本低以及可大批量生产等诸多优点,所以在食品污染物检测方面具有潜在的巨大应用价值。本文综述了基因工程抗体的分类、对污染物的检测原理、展示技术以及目前基因工程抗体在食品污染物检测方面应用的一些最新进展和存在的不足之处。     

Bioremediation: a novel approach to food waste management

Bioremediation is a general concept that includes all those processes and actions that take place in order to biotransform an environment, already altered by contaminants, to its original status. Although the processes that can be used in order to achieve the desirable results vary, they still have the same principles; the use of microorganisms or their enzymes, that are either indigenous and are stimulated by the addition of nutrients or optimization of conditions, or are seeded into the soil. There are several advantages of the implementation of such methods but mainly they have to do with the lack of interference with the ecology of the ecosystem. This article presents general bioremediation principles and techniques along with representative examples of their use both in the laboratory and industry and the ways that they work and give results in the five main areas of the food industry where bioremediation is applicable. Although the application of bioremediation to the food industry is not new, developments in microbiology and genetic engineering have given a valuable instrument to scientists to deal with contaminants in the environment. Pesticides, herbicides, insecticides, cleaning chemicals and chemicals used in the food chain are among the new contaminants which have entered the biogeochemical cycles. Bioremediating methods transform the contaminants into substances that can be absorbed and used by the autotrophic organisms with no toxic effect on them.     

Theoretical considerations on the use of solid-phase microextraction with complex environmental samples

The equations governing the use of equilibrium solid-phase microextraction (SPME) for environmental samples with complex heterogeneous matrices were derived in terms of parameters commonly measured or estimated by environmental scientists. Parameterization of the SPME equations allowed for the a priori prediction of SPME performance as a function of analyte and sample properties as well as experimental conditions. A theoretical evaluation of SPME was performed for a broad range of realistic scenarios using calculated equilibrium partitioning parameters and the implications for practical applications were discussed. Potential pitfalls and errors in quantitative measurements were identified, and different approaches to SPME calibration were presented. The concept of an optimum minimum volume for the analysis of heterogeneous environmental samples was presented and fully developed. Data from three previous studies were used to validate the correctness of our theoretical framework; the agreement between the measured relative recoveries of a variety of hydrophobic organic chemicals and theoretical predictions was reasonable. The results of this study highlight the potential for SPME to be a valuable technique for the measurement of hydrophobic organic contaminants in complex environmental samples. The SPME technique appears to be especially well suited for samples with high solids-to-water ratios and/or large sample volumes. Examples of such applications include sediment interstitial water and in situ field measurements, respectively.     

虾蟹壳中甲壳素绿色提取技术研究进展

甲壳素的提取需经脱除蛋白质、矿物质、脂质和色素等工艺,酸碱法有成本高、环境危害等缺点,微生物发酵、酶法或基因工程等生物法绿色提取技术亟待研究。本文综述以虾蟹壳为原料,由传统化学法、生物法绿色提取技术的进展;分析微生物发酵、酶法及基因工程等生物法的优缺点,微生物生物转化及酶处理利用发酵产生的有机酸和蛋白酶,经济有效易实现大规模生产,提出微生物发酵法提取甲壳素具有产业化潜力;最后对遗传操作和代谢工程在近几年的进展也进行了讨论。以生物法绿色提取技术生产甲壳素既具备环境友好又具备高效性,具有重要的发展前景。     

Investigating the role of mineral-bound humic acid in phenanthrene sorption

Contaminant-soil interaction studies have indicated that physical conformation of organic matter atthe solid-aqueous interface is important in governing hydrophobic organic compound (HOC) sorption. To testthis, organo-clay complexes were constructed by coating montmorillonite and kaolinite with peat humic acid (PHA) in Na+ or Ca2+ dominated solutions with varying pH and ionic strength values. The solution conditions encouraged the dissolved PHA to adopt a "coiled" or "stretched" conformation prior to interacting with the clay mineral surface. Both kaolinite and montmorillonite organo-clay complexes exhibited higher phenanthrene sorption (Koc values) with decreasing pH, indicating that the coiled configuration provided more favorable sorption conditions. Evidence from 1H high-resolution magic angle spinning (HR-MAS) nuclear magnetic resonance (NMR) indicated that polymethylene groups were prevalent at the surface of the organo-clay complexes and may enhance sorptive interactions. Preferential sorption of polymethylene groups on kaolinite and aromatic compounds on montmorillonite may also contribute to the difference in phenanthrene sorption by PHA associated with these two types of clay. This study demonstrates the importance of solution conditions in the sorption of nonionic, hydrophobic organic contaminants and also provides evidence for the indirect role of clay minerals in sorption of contaminants at the soil-water interface.     

Are reductions in industrial organic contaminants emissions in rich countries achieved partly by export of toxic wastes?

Recent studies show that PCB (polychlorinated biphenyl) air concentrations remain surprisingly high in parts of Africa and Asia. These are regions where PCBs were never extensively used, but which are implicated as recipients of obsolete products and wastes containing PCBs and other industrial organic contaminants, such as halogenated flame retardants (HFRs). We hypothesize that there may be different trends in emissions across the globe, whereby emissions of some industrial organic contaminants may be decreasing faster in former use regions (due to emission reductions combined with uncontrolled export), at the expense of regions receiving these substances as obsolete products and wastes. We conclude that the potential for detrimental effects on the environment and human health due to long-range transport by air, water, or wastes should be of equal concern when managing and regulating industrial organic contaminants. This calls for a better integration of life-cycle approaches in the management and regulation of industrial organic contaminants in order to protect environmental and human health on a global scale. Yet, little remains known about the amounts of industrial organic contaminants exported outside former use regions as different types of wastes because of the often illicit nature of these operations.     

应用改进遗传算法的自动配棉模型优化与应用

针对配棉工艺具有多约束条件的特点和现有自动配棉的不足,提出将改进的遗传算法应用到线性规划优化求解问题中,通过改进遗传算法的初始种群生成策略、遗传算子和进化收敛条件,将配棉约束条件动态融合到种群进化过程中,在保证配棉约束条件的前提下,兼顾了求解的效率和有效性,以达到对自动配棉进行优化的目的。应用结果显示:用改进遗传算法对配棉模型的求解优于基本遗传算法,且配棉的各项指标值符合生产技术要求,在满足混棉质量的前提下,该方法能指导技术人员对候选棉和库存棉做出更合理的选择,有效降低了配棉成本。