基于近红外光谱和化学计量学的驴肉鉴别方法研究

驴肉具有极高的食用价值,资源的缺乏使其价格持续走高,由此引发的欺骗和掺假亟待解决。选取了不同部位(脖子、肋板、后墩和腱子)的驴肉样品(n=167)及牛肉(n=47)、猪肉(n=51)和羊肉(n=32)样品在4 000~12 500cm-1光谱范围上建立了驴肉的近红外光谱鉴别模型。比较了马氏距离判别分析、簇类独立软模式分类法、最小二乘-支持向量机方法分别结合平滑(5点、15点及25点)、一阶和二阶微分、多元散射校正和标准归一化的光谱预处理方法对肉块样品及大中小三个不同粉碎粒径(7,5,3mm)肉糜样品的分类模型结果发现,原始光谱前11个主成分得分作为输入的马氏距离判别及前6个主成分作为输入的最小二乘-支持向量机肉块样品分类模型较优,校正集和预测集正确率分别为100%和98.96%;原始光谱前5个主成分作为输入的LS-SVM大粒径肉糜样品分类模型结果较优,校正集和预测集判别正确率为100%和97.53%;原始光谱前8个主成分得分作为输入的簇类独立软模式分类法中粒径肉糜样品分类模型结果较优,校正集和预测集的判别正确率均为100%;而对于小粒径肉糜样品,原始光谱前7主成分输入的马氏距离判别和前9主成分输入的簇类独立软模式分类法模型均得到了校正集和预测集100%的判别正确率。以上模型中的驴肉样品均得到了100%的判别正确率。研究结果表明,使用近红外光谱分析技术结合化学计量学方法鉴别驴肉是可行的。     

From Infrared Spectra to Macroscopic Mechanical Properties of sH Gas Hydrates through Atomistic Calculations

The vibrational characteristics of gas hydrates are key identifying molecular features of their structure and chemical composition. Density functional theory (DFT)-based IR spectra are one of the efficient tools that can be used to distinguish the vibrational signatures of gas hydrates. In this work, ab initio DFT-based IR technique is applied to analyze the vibrational and mechanical features of structure-H (sH) gas hydrate. IR spectra of different sH hydrates are obtained at 0 K at equilibrium and under applied pressure. Information about the main vibrational modes of sH hydrates and the factors that affect them such as guest type and pressure are revealed. The obtained IR spectra of sH gas hydrates agree with experimental/computational literature values. Hydrogen bond’s vibrational frequencies are used to determine the hydrate’s Young’s modulus which confirms the role of these bonds in defining sH hydrate’s elasticity. Vibrational frequencies depend on pressure and hydrate’s O···O interatomic distance. OH vibrational frequency shifts are related to the OH covalent bond length and present an indication of sH hydrate’s hydrogen bond strength. This work presents a new route to determine mechanical properties for sH hydrate based on IR spectra and contributes to the relatively small database of gas hydrates’ physical and vibrational properties.     

A methodology for modelling travel distances by Bias estimation

Round norms τl _p, p ∈ (1,2] and block norms have been utilised for modelling actual distances in transportation networks. A geometric setting will permit the establishment of a relationship between bias of the road network distance and trajectory deviations, which will be used to separate the set of origin-destination pairs into two samples and also to analyse each sample using regression, thus obtaining several types of estimators. What will be demonstrated in this paper is that these functions can be combined through either a weighted sum, or by means of the introduction of the expected distance concept applied to the bias, to obain distance predicting functions for the region considered.     

Extremal problems for convex polygons

Consider a convex polygon V _n with n sides, perimeter P _n , diameter D _n , area A _n , sum of distances between vertices S _n and width W _n . Minimizing or maximizing any of these quantities while fixing another defines 10 pairs of extremal polygon problems (one of which usually has a trivial solution or no solution at all). We survey research on these problems, which uses geometrical reasoning increasingly complemented by global optimization methods. Numerous open problems are mentioned, as well as series of test problems for global optimization and non-linear programming codes.     

Contravariant densities, complete distancesand relative fidelities for quantum channels

Introducing contravariant trace densities for quantum states, we restore one-to-one correspondencebetween quantum operations described by normal CP maps and their trace densities as Hermitian-positive operator-valued contravariant kernels. The CB-norm distance between two quantum operations is explicitly expressed in terms of these densities as the supremum over the input states. A larger C-distance is given as the natural norm distance for the channel densities, and another, Helinger type complete distance (CH distance), related to the minimax mean square fidelity optimization problem by purification of quantum channels, is also introduced and evaluated in terms of their contravariant trace densities. It is proved that the CH distance between two channels is equivalent to the CB distance. An operational meaning for these distances and relative complete fidelity for quantum channels is given in terms of quantum encodings producing optimal entanglements of quantum states for an opposite and output systems.     

Frequentistic approximations to Bayesian prevision of exchangeable random elements

Posterior and predictive distributions for m future trials, given the first n elements of an infinite exchangeable sequence ${\tilde{\xi }}_1,{\tilde{\xi }}_2,\dots$, are considered in a nonparametric Bayesian setting. The former distribution is compared to the unit mass at the empirical distribution ${\tilde{\mathfrak{e}}}_n:=\frac{1}{n}{\sum }_{i=1}^n{\delta }_{{\tilde{\xi }}_i}$ of the n past observations, while the latter is compared to the m-fold product ${\tilde{\mathfrak{e}}}_n^m$. Comparisons are made by means of distinguished probability distances inducing topologies that are equivalent to (or finer than) the topology of weak convergence of probability measures. After stating almost sure convergence to zero of these distances as n goes to infinity, the paper focuses on the analysis of the rate of approach to zero, so providing a quantitative evaluation of the approximation of posterior and predictive distributions through their frequentistic counterparts ${\delta }_{{\tilde{\mathfrak{e}}}_n}$ and ${\tilde{\mathfrak{e}}}_n^m$, respectively. Characteristic features of the present work, with respect to more common literature on Bayesian consistency, are: first, comparisons are made between entities which depend on the n past observation only; second, the approximations are studied under the actual (exchangeable) law of the ${\tilde{\xi }}_n$'s, and not under hypothetical product laws ${\mathfrak{p}}_0^{\infty }$, as ${\mathfrak{p}}_0$ varies among the admissible determinations of a random probability measure.     

19F Paramagnetic Relaxation Enhancement: A Valuable Tool for Distance Measurements in Proteins

Fluorine NMR paramagnetic relaxation enhancement was evaluated as a versatile approach for extracting distance information in selectively F‐labeled proteins. Proof of concept and initial applications are presented for the HIV‐inactivating lectin cyanovirin‐N. Single F atoms were introduced at the 4‐, 5‐, 6‐ or 7 positions of Trp49 and the 4‐position of Phe4, Phe54, and Phe80. The paramagnetic nitroxide spin label was attached to Cys residues that were placed into the protein at positions 50 or 52. ¹⁹F‐T₂ NMR spectra with different relaxation delays were recorded and the transverse ¹⁹F‐PRE rate, ¹⁹F‐Γ₂, was used to determine the average distance between the F nucleus and the paramagnetic center. Our data show that experimental ¹⁹F PRE‐based distances correspond to 0.93 of the ¹H_N‐PRE distances, in perfect agreement with the gyromagnetic γ¹⁹F/γ¹H ratio, thereby demonstrating that ¹⁹F PREs are excellent alternative parameters for quantitative distance measurements in selectively F‐labeled proteins.     

Convergence rate of a proximal multiplier algorithm for separable convex minimization

In this paper, we analyse the convergence rate of the proximal algorithm proposed by us in the article [A proximal multiplier method for separable convex minimization. Optimization. 2016; 65:501–537], which has been proposed to solve a separable convex minimization problem. We prove that, under mild assumptions, the primal-dual sequences of the algorithm converge linearly to the optimal solution for a class of proximal distances.     

X-Ray Studies of 2-Methyl-2-Propanol Solution in Cyclohexane

Abstract

Changes in the mean least intermolecular distances in a solution of 2-methyl-2-propanol in cyclohexane with increasing concentration of the former were found to be non-linear. Both in the range of low (0.005–0.04 molar fraction) and high (0.45–0.75 molar fraction) concentrations of the solutions studied local maxima of the mean least intermolecular distance were observed. In the range from 0.8 to 1 molar fraction the value of this parameter remained constant. Results obtained in this work prove the absence of the specific structural properties of a low concentration alcohol solution observed in other solvents. The occurrence of the local maxima proves that cyclohexane is a non-active solvent. Owing to this the molecules of the solute and the solvent assume positions ensuring homogeneity of the solvents.