Chemometrics‐enhanced laser‐induced thermal emission detection of PETN and other explosives on various substrates

Infrared emissions (IREs) of samples of pentaerythritol tetranitrate (PETN) deposited as contamination residues on various substrates were measured to generate models for the detection and discrimination of the important nitrate ester from the emissions of the substrates. Mid‐infrared emissions were generated by heating the samples remotely using laser‐induced thermal emission (LITE). Chemometrics multivariate analysis techniques such as principal component analysis (PCA), soft independent modeling by class analogy (SIMCA), partial least squares‐discriminant analysis (PLS‐DA), support vector machines (SVMs), and neural network (NN) were employed to generate the models for the classification and discrimination of PETN IREs from substrate thermal emissions. PCA exhibited less variability for the LITE spectra of PETN/substrates. SIMCA was able to predict only 44.7% of all samples, while SVM proved to be the most effective statistical analysis routine, with a discrimination performance of 95%. PLS‐DA and NN achieved prediction accuracies of 94% and 88%, respectively. High sensitivity and specificity values were achieved for five of the seven substrates investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Criteria for the p-solvability and p-supersolvability of finite groups

Let A, K, and H be subgroups of a group G and K ≤ H. Then we say that A covers the pair (K, H) if AH = AK and avoids the pair (K, H) if A ∩ H = A ∩ K. A pair (K, H) in G is said to be maximal if K is a maximal subgroup of H. In the present paper, we study finite groups in which some subgroups cover or avoid distinguished systems of maximal pairs of these groups. In particular, generalizations of a series of known results on (partial) CAP-subgroups are obtained.     

Adsorption of water isotopomers H<Subscript>2</Subscript>O and D<Subscript>2</Subscript>O on hypercross-linked polystyrene MN-272

Adsorption of light and heavy water (H₂O and D₂O) on porous hypercross-linked polystyrene MN-272 was studied by gas chromatography. For the estimation of the properties of this polymer surface, n-alkanes (C6—C9), C_{6 6}, and polar compounds (CHCl₃, MeNO₂, MeCN, Me₂CO, EtCOOCH₃, Et₂O) were used as test adsorbates. The contributions of energies of dispersion and specific (donor-acceptor) intermolecular interactions to the total energy of adsorption were determined on the basis of experimental data on the retention of the sorbates. The electron-donor and electron-acceptor characteristics of the hypercross-linked polystyrene MN-272 surface were estimated. Hypercross-linked polystyrene MN-272 was found to be a weakly specific adsorbent with predomination of electron-donating properties. The adsorption isotherms of H₂O and D₂O were measured on this polymer at 50, 60, and 70 °C. The dependences of the isosteric heats of adsorption on the amount adsorbed were determined. The contribution of the energy of specific interactions to the total energy of adsorption for all polar adsorbates (except for acetone, light and heavy water) does not exceed 20%. Adsorption of H₂O on hypercross -linked polystyrene MN-272 is slightly weaker than that of D ₂O.     

HgBr2-CsPbBr3 and CsHgBr3-PbBr2 joins of the HgBr2-PbBr2-CsBr system

The HgBr₂-CsPbBr₃ (1) and CsHgBr₃-PbBr₂ (2) joins of the HgBr₂-PbBr₂-CsBr system are studied using differential thermal analysis (DTA) and X-ray powder diffraction. Both joins are non-quasi-binary. The primary phase fields, joint crystallization fields, and invariant temperatures are determined along these joins. X-ray powder diffraction results validate the diagrams mapped for these joins.     

Stochastic Dynamics of Flexible Systems with Motion Limiters

This paper presents an asymptotic analysis of the stochastic impact dynamics for a flexible structure with a unilateral rigid stop. The structure is modelled as an m.d.f. system in which one of the masses (the base) impacts on the stop. Assuming weak dissipation and weak coupling between the base and the secondary structure, we achieve the model reduction. Examination of the reduced model by the stochastic averaging method allows estimation of the statistical properties of the vibro-impact motion. A relationship between the responses of the secondary and primary structures is derived.     

One-pot synthesis of 1,5,3-oxathiazepanes via the three-component condensation of primary amines,formaldehyde and 2-mercaptoethanol

The three-component condensation reaction of primary amines, formaldehyde and 2-mercaptoethanol using salts of transition and rare earth metals as catalysts was developed to obtain a new 7-membered heterocyclic structural building block, 1,5,3-oxathiazepanes, in good to excellent yields. The structure of the heterocyclic fragment was confirmed by NMR spectroscopy.     

Sorption of boric acid by polymers containing dihydroxypropylamine fragments

Products of polymer-analogous transformations of chitosan, aminopolystyrene, and polyallylamine containing dihydroxypropylamine fragments were used as sorbents of boric acid. A dependence of their sorption properties on the structure of the main polymeric chain and its functionalization degree was found.     

Organosilicon synthesis of isocyanates: I. Synthesis of isocyanates of the furan, thiophene, and mono-and polyfluorophenyl series

A convenient synthesis of known and unknown isocyanates of the furan, thiophene, and mono-and polyfluorophenyl series, involving silylation of starting amines with hexamethyldisilazane or chlorotrimethylsilane, followed by phosgenation of the resulting N-silyl-substituted amines. An unusual high-temperature rearrangement of 3-(methoxycarbonyl)-4,5-dimethylthiophene-2-yl isocyanate into its 5-ethyl isomer. ortho-Fluorine substituent in anilines decreases the yield of isocyanates, whereas 2,3,5,6-tetrafluorophenyl isocyanate exists for only a short time as a 5% toluene solution.