Uncertainty functions, a compact way of summarising or specifying the behaviour of analytical systems

Analytical chemists can advantageously use an uncertainty function to describe the performance of an analytical system in terms of the standard uncertainty or standard deviation as a function of the concentration of the analyte. This “characteristic function” is useful for estimating uncertainty at a new concentration. A similar function can be used to prescribe the uncertainty that is regarded as fit for purpose for a particular application. This “fitness function” is useful in setting standards of accuracy in proficiency tests and similar exercises without revealing the concentration of the analyte. In combination, these two functions provide a rational basis for method selection.     

Single-Round DNA Aptamer Selection by Combined Use of Capillary Electrophoresis and Next Generation Sequencing: An Aptaomics Approach for Identifying Unique Functional Protein-Binding DNA Aptamers

In DNA aptamer selection, existing methods do not discriminate aptamer sequences based on their binding affinity and function and the reproducibility of the selection is often poor, even for the selection of well-known aptamers like those that bind the commonly used model protein thrombin. In the present study, a novel single-round selection method (SR-CE selection) was developed by combining capillary electrophoresis (CE) with next generation sequencing. Using SR-CE selection, a successful semi-quantitative and semi-comprehensive aptamer selection for thrombin was demonstrated with high reproducibility for the first time. Selection rules based on dissociation equilibria and kinetics were devised to obtain families of analogous sequences. Selected sequences of the same family were shown to bind thrombin with high affinity. Furthermore, data acquired from SR-CE selection was mined by creating sub-libraries that were categorized by the functionality of the aptamers (e. g., pre-organized aptamers versus structure-induced aptamers). Using this approach, a novel fluorescent molecular recognition sensor for thrombin with nanomolar detection limits was discovered. Thus, in this proof-of-concept report, we have demonstrated the potential of a “DNA Aptaomics” approach to systematically design functional aptamers as well as to obtain high affinity aptamers.     

可见-近红外光谱技术结合递归变量选择算法对土壤全氮与有机质含量测定研究

应用可见-近红外光谱技术进行定量分析时,变量选择起着十分重要的作用。不同土壤样品之间的预测机制可能存在很大差异,当待测样品出现新的特征信息时,基于建模集选择的特征变量不一定能够很好地代表待测样品的有效信息,继续采用原有特征变量建模就易导致预测误差增大。该研究采用递归变量选择方法在预测过程中递归更新土壤全氮与有机质的特征变量,以保持预测模型的鲁棒性;比较了偏最小二乘法(PLS),递归偏最小二乘法(RPLS)和不同递归变量选择方法,如： 变量投影重要性与RPLS相结合(VIP-RPLS), VIP-RPLS, 无信息变量消除法与PLS相结合(UVE-PLS)对于土壤全氮与有机质含量的预测效果。所用195份土壤样品来自浙江省文成县8个乡镇的农田。土壤样品随机分成两部分,一部分作为建模集包含120份样品,另一部分作为预测集包含75份样品。结果表明： VIP-RPLS建立的模型对于预测土壤全氮与有机质含量取得了最优的结果,获得的决定系数(R2)分别为0.85与0.86,获得的预测相对分析误差(RPD)分别为2.6%与2.7%。说明VIP-RPLS通过不断更新模型的特征变量,能够捕获新加入到建模集样品的有效信息。相比于本研究中的其他方法,VIP-RPLS对于土壤全氮与有机质含量具有更高的预测精度。     

近红外高光谱图像结合CARS算法对鸭梨SSC含量定量测定

高光谱数据量大、 维数高且原始光谱噪声明显、 散射严重等特征导致光谱建模时关键波长变量提取困难。 基于此,提出采用竞争性自适应重加权算法(CARS)对近红外高光谱数据进行关键变量选择。 鸭梨作为研究对象。 采用决定系数r2、 预测均方根误差RMSEP和验证集标准偏差和预测集标准偏差的比值RPD值进行模型性能评估。 基于选择的关键变量建立PLS模型(CARS-PLS)与全光谱变量建立的PLS模型进行比较发现CARS-PLS模型仅仅使用原始变量中15.6%的信息获得了比全变量PLS模型更好的鸭梨SSC含量预测结果,r2_pre,RMSEP和RPD分别为0.908 2,0.312 0和3.300 5。 进一步与基于蒙特卡罗无信息变量MC-UVE和遗传算法(GA)获得的特征变量建立的PLS模型比较发现,CARS不仅可以去除原始光谱数据中的无信息变量,同时也能够对共线性的变量进行压缩去除,该方法能够有效地用于高光谱数据变量的选择。 结果表明,近红外高光谱技术结合CARS-PLS模型能够用于鸭梨可溶性固形物SSC含量的定量预测。 从而为基于近红外高光谱技术预测水果内部品质的研究提供了参考。     

多阶段应急决策的方案链选择方法

针对多阶段不同情景下多指标多任务的应急决策问题,提出了一种方案链选择方法。在该方法中,首先给出了决策方案链的概念,并对多阶段多指标多任务的应急决策问题进行了描述;然后根据相邻阶段的子方案之间的相容性,构建了相容性关系矩阵;进一步地,在考虑相邻阶段子方案之间相容性的情形下,以各阶段的子方案的综合评价值最大为目标,建立了应急决策的方案链选择的优化模型。通过求解模型,得到应急决策的最优方案链。最后,通过一个算例说明了该方法的可行性和有效性。     

EXISTENCE PROBLEMS OF ADDITIVE SELECTION MAPS FOR ANOTHER TYPE SUBADDITIVE SET-VALUED MAP

In this paper,we consider the following subadditive set-valued map F:X → P 0 (Y):F r ∑ i=1 x i + s ∑ j=1 x r+ j rF r ∑ i=1 x i r + sF s ∑ j=1 x r+ j s, x i ∈ X,i=1,2,,r + s,where r and s are two natural numbers.And we discuss the existence and unique problem of additive selection maps for the above set-valued map.     

一种基于约束的指针程序路径选择方法

动态符号执行是对程序进行安全性分析的重要技术.在动态符号执行过程中,存在着符号地址,系统调用,路径选择等问题.针对符号地址导致的别名分析问题,本文提出了一种基于约束的指针分析方法,对程序进行过程内的指向分析,并对指针分析过程引入约束条件,产生可以进行路径选择的测试用例,以提高指针分析的精度.在国内首款某型号商用编译器的开发过程中实现了该方法,实验结果表明,该方法可以准确地分析C语言测试用例,缩短用例测试的时间.     

Molecular Dynamic Simulation on the Absorbing Process of Isolating and Coating of α-olefin Drag Reducing Polymer

The absorbing process in isolating and coating process of α-olefin drag reducing polymer was studied by molecular dynamic simulation method, on basis of coating theory of α-olefin drag reducing polymer particles with polyurethane as coating material. The distributions of sodium laurate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate on the surface of α-olefin drag reducing polymer particles were almost the same, but the bending degrees of them were obviously different. The bending degree of SLA molecules was greater than those of the other two surfactant molecules. Simulation results of absorbing and accu-mulating structure showed that, though hydrophobic properties of surfactant molecules were almost the same, water density around long chain sulfonate sodium was bigger than that around alkyl sulfate sodium. This property goes against useful absorbing and accumulating on the surface of α-olefin drag reducing polymer particles; simulation results of interactions of different surfactant and multiple hydroxyl compounds on surface of particles showed that, interactions of different surfactant and one kind of multiple hydroxyl compound were similar to those of one kind of surfactant and different multiple hydroxyl compounds. These two contrast types of interactions also exhibited the differences of absorbing distribution and closing degrees to surface of particles. The sequence of closing degrees was derived from sim-ulation; control step of addition polymerization interaction in coating process was absorbing mass transfer process, so the more closed to surface of particle the multiple hydroxyl com-pounds were, the easier interactions with isocyanate were. Simulation results represented the compatibility relationship between surfactant and multiple hydroxyl compounds. The isolating and coating processes of α-olefin drag reducing polymer were further understood on molecule and atom level through above simulation research, and based on the simulation, a referenced theoretical basis was provided for practical optimal selection and experimental preparation of α-olefin drag reducing polymer particles suspension isolation agent.     

汶川地震地表破裂影响带调查与建筑场地避让宽度探讨

5.12汶川Ms8.0级地震沿龙门山中央断裂带形成长度约270km的地表破裂带,破裂带垂直和水平位移一般为1.0～5.0m,最大可达9.8m。在地表破裂带附近,建筑物破坏严重。笔者系统调查了龙门山中央断裂带地表破裂的垂直和水平位移以及地震地表破裂影响带宽度,并采用物探测试方法对部分影响带宽度进行了验证。统计结果表明,汶川地震地表破裂影响带宽度主要集中在16～60m,影响带宽度（D）与垂直位移（H）具有较好的线性关系,即D=10.11H+16.0。对于逆冲性质为主的地震地表破裂而言,上盘影响带宽度与下盘的比值一般为3：1～2：1,据此可确定地表破裂带上、下盘的避让带宽度。笔者根据现场调查并借鉴国外经验提出,上盘避让宽度下限一般不应低于15m,下盘避让宽度下限不应低于10m。本项研究对于汶川地震灾后重建场地选址具有重要的实际意义。
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基于选择性模型组合的三维荧光光谱水质分析方法

为提高三维荧光光谱水质分析的精度,提出一种选择性模型组合方法,采用相关系数法对三维荧光光谱激发波长进行选择,并将被选中的激发波长下的荧光发射光谱水质分析子模型采用岭回归法进行模型组合,得到对水质指标的组合模型。以一组总有机碳(TOC)范围在3.41～125.35 mg·L-1,化学需氧量(COD)范围在22.80～330.60 mg·L-1的32个地表水和城市生活污水水样做为研究对象,对其三维荧光光谱220～400 nm范围内的10个激发波长采用上述方法进行选择,分别针对TOC和COD指标筛选出260,280,400 nm和220,280,400 nm各3个激发波长。采用部分最小二乘方法建立上述激发波长下荧光发射光谱水质分析子模型,根据岭回归法计算各子模型的组合系数,分别得到对TOC和COD指标的组合模型。实验结果表明：采用该方法得到的组合模型对TOC和COD两种指标的预测误差均方根(RMSEP)相比精度最高的单一荧光发射光谱子模型分别减小了15.4%和17.5%,相比未经模型选择的组合模型分别减小了6.1%和10.9%。