An integrated strategy for the geographical origin traceability of Goji berries by antioxidants characteristic fingerprint based online ultra-performance liquid chromatography-2,2-diphenyl-1-picrylhydrazyl- photodiode array detector-mass spectrometry combined with multivariate statistics analysis

Goji berries are now becoming increasingly popular in the human diet due to their potential health benefits. Unscrupulous traders deliberately mislabel with certain origins to gain illegal profits, which seriously affected the consumers’ benefits. In this study, an online ultra-performance liquid chromatography-2,2-diphenyl-1 -picrylhydrazyl-photodiode array detector-electrospray ionization-quadrupole time of flight mass was developed for rapid screening and identification of the antioxidants from Goji berry; then, the antioxidants characteristic fingerprint was established and explored in the origins discrimination of Goji berries from China combined with multivariate statistics analysis. As a result, twenty-eight compounds were screened from Goji berry extract, 19 of which were identified by accurate molecular and ultraviolet information according to references. Principal components analysis and partial least squares discrimination analysis achieved the accurate classification from the four regions, eight compounds were selected as origin-related antioxidant markers with variable importance in projection >1 and one-way analysis of variance (P<0.05), including rutin, rutin di-hexose, P-coumaric acid tri-hexose, dicaffeoylquinic acid isomer, Quercetin-rhamno-di-hexoside, peak14, peak16, and peak27. This study provides a feasible strategy for the geographical origins discrimination of Goji berries based on antioxidant ingredients difference and will be helpful for improving the quality control level of Goji berries.     

Micro Electrical Impedance Spectroscopy (μEIS) Fabricated on the Curved Surface of a Fine Needle for Biotissue Discrimination

This work presents a novel micro electrical impedance spectroscopy (μEIS) technique that can measure and discriminate the electrical signal responses of biotissues in real time. An EoN (EIS‐on‐a‐needle), EIS on the surface of a fine needle (400 μm in diameter), was fabricated using a newly developed flexible photomask film. The base material of the photomask is parylene‐C, which allows uniform contact on the curved surface of the needle; thus, the designed electrode patterns of the photomask can be transferred onto the needle surface with a high resolution (2.95 % or less in dimensional error). To validate the developed EoN as an electrical sensor, ex vivo experiments with various biotissues—butchered pork (skin, fat, and muscle) and human breast tissues (normal and cancerous)—were conducted by measuring real‐time electrical impedance during a frequency sweep. The conductivities (relative permittivity) of the pork tissues were evaluated by electrical equivalent circuit analysis: 56.6 mS/m (37,800), 68.0 mS/m (74,755), and 74.9 mS/m (26,145) for the skin, fat, and muscle, respectively. Moreover, the normal and cancerous tissues were well distinguished by electrical resistance at 4.04 kHz for various cancer grades (Elston grades 1, 2, and 3). Analysis of the electrical impedance suggests that the EoN can be utilized to diagnose the physiological states of biotissues in clinical use.     

Neutron light output function and resolution investigation of the deuterated organic liquid scintillator EJ-315

In this paper we investigate the light response to fast neutrons and estimate the pulse height resolution of a deuterated liquid organic scintillator, EJ-315, considering the detector's non-linear light response to gamma-rays. Initially, collision data and a neutron beam trigger are recorded in coincidence mode, and incident neutron energy is calculated with a time-of-flight technique. Fast neutrons are further discriminated from gamma-ray background based on the scintillation material decay patterns using a pulse shape discrimination algorithm. A light response matrix composed of multiple neutron energy and their corresponding light outputs is derived. The pulse height resolution property of the EJ-315 is characterized utilizing the derivatives of the pulse height distributions with corrections of the measurements setup uncertainties. Additionally, the EJ-315's pulse height resolution is also characterized by comparing the smoothed derivatives of quasi-monoenergetic neutron pulse height distributions, given by the Peierls-formula-based analytic model, to match the measurement data. Results show rather consistent 10–13% pulse resolution for mono-energetic neutrons with kinetic energy above 2 MeV. The resolution decreases slightly with an increase in neutron energy indicating the improved resolution performance of EJ-315 in the higher energy events.     

Arbitrary-norm hyperplane separation by variable neighbourhood search

^** Email: alejandro.karam{at}hec.ca^*** Email: gilles.caporossi{at}gerad.ca^**** Email: pierre.hansen{at}gerad.ca We consider the problem of separating two sets of points ina Euclidean space with a hyperplane that minimizes the sum ofp-norm distances to the plane of points lying on the ‘wrong’side of the plane. A variable neighbourhood search heuristicis used to determine the plane coefficients. For a set of exampleswith L₁-norm, L₂-norm and L-norm, for which the exact solutioncan be computed, we show that our algorithm finds it in mostcases and gets good approximations in the others. The use ofour heuristic solutions for problems in these norms can dramaticallyaccelerate exact algorithms. Our method can be applied on verylarge instances that are intractable by exact algorithms. Sincethe proposed approach works for truly arbitrary norms (otherthan the traditional 1, 2 and ), we can explore for the firsttime the effects of the choice of p on the generalization propertiesof p-norm hyperplane separation.     

New approaches to chiral discrimination in coupling between molecules

Results in the coupling of chiral molecules are reviewed from elementary points of view and some new results are given. We show that interactions between chiral molecules can be treated by using molecular quantum electrodynamics in electric and magnetic dipole approximation in ways different from standard diagrammatic perturbation theory. The interactions are the dispersive coupling of ground-state chiral molecules and excitation transfer, with emphasis on chiral discrimination. For ground-state molecules the coupling is dealt with first by calculating the coupling, at all separation distances, of electric and magnetic dipoles induced in the two molecules by fluctuations in the vacuum radiation field. The second method is the response by one chiral molecule to the field generated by the other. Excitation transfer is treated as the response by the accepting ground-state molecule to the dipole field of the donor. A novel variant in finding the rate of excitation transfer is by using Poynting's theorem. Received: 17 June 1998 / Accepted: 6 October 1998 / Published online: 16 March 1999     

A “quasi‐flexible” automatic docking processing for studying stereoselective recognition mechanisms. Part I. Protocol validation

The main purpose of this work is the development and validation of a general scheme based on a systematic and automatic “quasi‐flexible” docking approach for studying stereoselective recognition mechanisms. To achieve our goals we explore the conformational and configurational space for small‐ or medium‐size flexible molecules in a systematic way, seeking a method that is both reasonably accurate and relatively fast from the computational point of view. In particular, we have developed a general computational protocol for the global molecular interaction evaluation (“Glob‐MolInE”) to efficiently explore the orientational and conformational space of flexible selectors and selectands used in modern chiral high‐performance liquid chromatography (HPLC); the enantioselective binding of the selector (S)‐N‐(3,5‐dinitrobenzoyl)‐leucine‐ n‐propylamide (S)‐ 1 towards the selectand N‐(2‐naphthyl)‐alanine methyl ester 2 has been studied; the global minimum obtained for the homochiral associate [S( 1 )/S( 2 )] (Pop. >99%) is very close (RMS≃0.20) to the crystallographically determined structure. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 515–530, 2000     

近红外光谱LASSO特征选择方法及其聚类分析应用研究

近红外光谱技术是一种通过分析样本的特征光谱数据,实现定性或定量分析的无损检测方法,特征数据的完整性和代表性决定了所建模型的性能,而现有分析方法只能实现光谱子区间特征筛选,导致分析模型稳定性差、且难以再优化。为实现近红外光谱区间高维数特征提取,有效提高近红外光谱定性分析模型的精度和稳定性,提出一种基于最小绝对收缩和选择算法(LASSO)的光谱特征筛选方法,并以我国特色高值外贸产品云南松茸为分析对象进行聚类应用研究,讨论了该方法对于高维光谱特征筛选的有效性、分析对比了LASSO筛选特征变量及主元分析(PCA)降维算法所建松茸真伪甄别及食用菌分类模型的预测精度及稳定性。通过调研发现,云南产鲜松茸因其独特外形易于分辨,而片状的干松茸失去其独有的外形特征,导致国内干松茸掺假事件屡禁不止。选取云南产松茸、杏鲍菇、老人头、姬松茸四种干样共166样本数据进行分析,采用光谱范围为900～1 700 nm的NIRQuest512型近红外光谱仪获得166×512维原始光谱数据,剔除异常数据后采用标准正态变换对光谱数据进行预处理。在此基础上,利用LASSO筛选出全光谱区间的特征变量,再使用Kennard-Stone法并结合典型线性(KNN)和非线性建模(BP)算法,构建松茸真伪甄别模型和食用菌分类模型,对两种模型进行盲样测试,并分析了LASSO与PCA算法的不同点,最后使用蒙特卡罗方法检测两种模型的稳定性。实验结果表明基于LASSO光谱特征选择的松茸真伪甄别模型和食用菌分类模型预测精度和稳定性均高于PCA方法,其中基于原始光谱数据所建真伪甄别模型的预测准确率为69.57% (BP)和60.87% (KNN),食用菌分类模型准确率为67.39% (BP)和65.22% (KNN),基于LASSO特征筛选的真伪甄别模型预测准确率分别达到100% (BP)和78.26% (KNN),食用菌分类模型预测准确率分别达到89.13% (BP)和80.43% (KNN),对两种模型进行10次蒙特卡罗实验,其结果平均值分别为99.93%和97.22%,由此可知,与PCA等数据降维算法相比,LASSO可实现全光谱区间的光谱特征选择和数据降维,有效地提高了近红外定性分析模型的预测性能,为近红外分析提供了一种新的特征筛选方法。     

利用水平阵模态域波束形成判别声源深度*

针对近水面声源和水下声源的深度判别问题,根据近水面声源难以激发低阶模态的物理现象,研究利用声源波数谱结构和波数位置的不同来分辨近水面声源和水下声源。通过采用MVDR的谱估计方法进行模态域波束形成,补偿水平阵各阵元之间各号简正波的相位差,获得主瓣窄、旁瓣低的声源信号波数谱。波数谱的波数位置与频率呈近似线性关系,水中声速剖面、海底参数、海深都会影响波数谱的具体结构和位置。此外,声源信号的到达角估计误差同样也会影响波数谱主瓣的位置估计。数值仿真结果表明,在浅海负跃层声速剖面条件下,可利用水平阵模态域波束形成判别声源深度,区分近水面声源和水下声源。     

硅探测器的数字化脉冲形状甄别

介绍了利用硅探测器的脉冲形状甄别进行粒子鉴别的原理。详细叙述了基于数字化方法的脉冲形状甄别的实现。采样频率和位数是数字化方法的两个重要参数。对于硅探测器信号,采用100 MS/s,12 bit的Digitizer可以满足脉冲形状甄别法对时间分辨的要求。同时对该方法粒子鉴别的特征和能量阈值做了简要的分析和对比。粒子背面入射硅探测器的所得的阈值低于正面入射的情况。例如对于氖周围的同位素,背面入射情况的阈值约为100 MeV,为正面入射情况下鉴别阈值的二分之一,相当与ΔE-E方法中ΔE探测器厚度约为60 μm情况下的阈值。最后定性讨论了硅探测器的电阻率不均匀性和沟道效应对粒子鉴别性能的影响。In this paper Pulse Shape Discrimination(PSD) for silicon detector has been briefly introduced. The emerging digital method successfully applied to detector signal processing makes digital PSD method one of the most promising particle identification methods. Sampling frequency and the number of bits are two key parameters of digital method. For silicon detector signal, adopting 100 Ms/s, 12 bit Digitizer can satisfy the time resolution requirement of PSD method. The identification characteristic and energy threshold of this method have been discussed and compared with both front injection and rear injection cases. Energy threshold with rear injection usually is much lower than that with front injection. For example, around for Neon isotope energy threshold with rear injection is about 100 MeV which is only half of the threshold with front injection, also equivalent to thickness of about 60 μm silicon detector threshold in ΔE-E method. At the end the impact of silicon detector's resistivity nonuniformity and channel effect on the identification capacity of PSD method has been discussed in detail.     

基于Pulic智力资本模型的上市公司财务危机预警研究

智力资本在知识经济时代对企业的发展至关重要.本文考察Pulic智力资本评测模型是否能够用于企业财务危机预警.首先基于2003年至2007年中国A股市场新增ST公司样本及配对样本的前三年数据对Pulic模型综合指标进行单变量分析证实了该模型的预警可行性,然后根据三项因素驱动指标分别运用多元判别、逻辑回归、神经网络和最小二乘支持向量机方法建立预警模型进行回判和外推.结果表明,Pulic模型在ST前两年具有较高的判断准确性,可以通过对智力资本的考察而预知企业未来的财务状况.