Energy‐resolved mass spectrometry for differentiation of the fluorine substitution position on the phenyl ring of fluoromethcathinones

A reliable method for structural analysis is crucial for the forensic investigation of new psychoactive substances (NPSs). Towards this end, mass spectrometry is one of the most efficient and facile methods for the identification of NPSs. However, the differentiation among 2‐, 3‐, and 4‐fluoromethcathinones (o‐, m‐, and p‐FMCs), which are ring‐fluorinated positional isomers part of the major class of NPSs referred to as synthetic cathinones, remains a challenge. This is mostly due to their similar retention properties and nearly identical full scan mass spectra, which hinder their identification. In this study, we describe a novel and practical method for differentiating the fluorine substitution position on the phenyl ring of FMCs, based on energy‐resolved mass spectrometry (ERMS) using an electron ionization‐triple quadrupole mass spectrometer. ERMS measurements showed that the three FMC positional isomers exhibited differences in relative abundances of both the fluorophenyl cation (m/z 95) and the fluorobenzoyl cation (m/z 123). The logarithmic plots of the abundance ratio of these two cations (m/z 95 to m/z 123) as a function of the collision energy (CE) followed the order of o‐FMC < p‐FMC < m‐FMC at each CE, which allowed the three isomers to be unambiguously and reliably differentiated. The theoretical dissociation energy calculations confirmed the relationship obtained by ERMS analyses, and additional ERMS measurements of methylmethcathinone positional isomers showed that the differences in abundance among the FMCs were attributed to the differences in their collision‐induced dissociation reactivities arising from the halogen‐induced resonance effects on the phenyl ring. Moreover, the method for differentiation described herein was successfully applied to the actual samples containing seized drugs. We expect that the described methodology will also contribute significantly to the reliable and accurate structural identification of NPSs in the fields of therapeutic, clinical, and forensic toxicology.     

Analogue Realizations of Fractional-Order Controllers

An approach to the design of analogue circuits, implementingfractional-order controllers, is presented. The suggestedapproach is based on the use of continued fraction expansions;in the case of negative coefficients in a continued fractionexpansion, the use of negative impedance converters is proposed.Several possible methods for obtaining suitable rational appromixationsand continued fraction expansions are discussed. An exampleof realization of a fractional-order I controlleris presented and illustrated by obtained measurements.The suggested approach can be used for the control of veryfast processes, where the use of digital controllers isdifficult or impossible.     

大气光学湍流测量中平均时间和原始数据的筛选

 在使用温度脉动仪测量温度结构常数时，平均时间长度的选择会影响其测量结果。通过实际测量数据的分析和讨论，确定平均时间应该为10s左右，以得到真实可靠的结构常数。由于温度脉动仪在测量时会受到各种因素的影响，为了筛选掉不可靠的测量结果，提出了一种用温度脉动原始数据来对测量结果进行筛选的方法。该方法首先排除了实验纪录中的错误测量数据，其次对于异常的实验数据，如某一层结构常数数据的异常偏大或偏小，需要根据双点温差原始数据的频谱分析来确认数据是否正常，以进一步排除异常的测量结果，尽可能保证用以统计分析的数据真实可靠。     

The CRONE Suspension: Management of the Dilemma Comfort-Road Holding

The CRONE suspension, French acronym of suspension à Comportement Robuste dOrdre Non Entier, results from a traditional suspension system whose spring and damper are replaced by a mechanical and hydropneumatic system defined by a fractional (so-called non-integer) order force–displacement transfer function. ling, frequency-domain robust control design methodology, optimal approach, stability analysis and performance are presented in this paper.     

Full and partial differentiation of tris-1,1,1-(hydroxymethyl)ethane via direct and indirect methodology

Tris-1,1,1-(hydroxymethyl)ethane 1 was converted to a series of mono- and disubstituted derivatives. An indirect protocol for the differentiation of the alcohol groups was employed for the synthesis of partially and fully differentiated 1 containing a protected aldehyde unit. Complete differentiation of the alcohol groups was also achieved using a direct strategy (two steps from 1). The first synthesis of 1,3-dialdehydes derived from 1 is reported in two steps.     

Directions for computing truncated multivariate Taylor series

Efficient recurrence relations for computing arbitrary-order Taylor coefficients for any univariate function can be directly applied to a function of variables by fixing a direction in . After a sequence of directions, the multivariate Taylor coefficients or partial derivatives can be reconstructed or ``interpolated'. The sequence of univariate calculations is more efficient than multivariate methods, although previous work indicates a space cost for this savings and significant cost for the reconstruction. We completely eliminate this space cost and develop a much more efficient algorithm to perform the reconstruction. By appropriate choice of directions, the reconstruction reduces to a sequence of Lagrange polynomial interpolation problems in for which a divided difference algorithm computes the coefficients of a Newton form. Another algorithm collects like terms from the Newton form and returns the desired multivariate coefficients.

     

Determination of Phenolic Antioxidants in Spilled Aviation Fuels by Gas Chromatography-Mass Spectrometry

Summary A gas chromatography-mass spectrometric assay method was developed for the simultaneous determination of 2,6-di-tert-butylphenol (DTBP) and 2,4-dimethyl-6-tert-butylphenol (DMTBP) in aviation fuel. Extraction and purification were achieved with a solid phase extraction procedure using silica gel. Elution was performed with 30 mL of methylene chloride: pentane (2:3) following washing with 10 mL of n-pentane. The extract was concentrated to about 100 L and analyzed by GC-MS (SIM). The peaks had good chromatographic properties by using a semi-polar column (Innowax) and the extraction of these compounds from samples gave recoveries of about 87% for DTBP and about 75% for DMTBP with small variations. Method detection limits were 5.0 ng mL^–1 for DBMP and 7.0 ng mL^–1 for DMTBP. The method may be useful for spilled fuel type differentiation between kerosene and JP-8.     

Computation of the observer gain for extended Luenberger observers using automatic differentiation

For a given nonlinear system, the extended Luenberger observerprovides nearly exact error dynamics. In contrast to the normalform observer, the extended Luenberger observer exists evenif the associated integrability condition is violated. Up tonow, Lie derivatives and Lie brackets required by the designprocedure have been computed symbolically. Even for systemswith moderate size and complexity, one usually obtains extremelylarge expressions for the observer gain. The design of an extendedLuenberger observer based on symbolic differentiation is not feasible for complicated or large-scale systems. In this paperwe discuss a new approach to compute the observer gain. Ourapproach is based on a computation method for derivatives calledautomatic differentiation. In contrast to numeric differentiationby means of divided differences, automatic differentiationincurs no truncation errors.     

论Suslov误解和Holder缺陷

本文根据变分学的基本原理，从产生ｄ－δ交换性问题的根源出发，证明了Ｓｕｓｌｏｖ观点实际上是一种误解；还证明了Ｈｏｌｄｅｒ观点基本正确，但存在缺陷。本文的工作表明，微分运算ｄ和变分运算δ次序可以交换，这是变分学中的一个基本原理，这一基本原理也适用于非完整系统。