Kinetics of the brominated alkyl radical (CHBr2, CH3CHBr) reactions with NO2 in the temperature range 250–480 K

The gas‐phase kinetics of CHBr₂ + NO₂ and CH₃CHBr + NO₂ reactions have been studied in direct time resolved measurements using a tubular flow reactor coupled to a photoionization mass spectrometer. The radicals were generated by pulsed laser photolysis of bromoform and 1,1‐dibromoethane at 248 nm. The subsequent decays of the radical concentrations were monitored as a function of [NO₂] under pseudo–first‐order conditions. The rate coefficients of both reactions are independent of bath gas (He) pressure and display negative temperature dependence under the conditions of 2–6 Torr pressure (He) and 250–480 K. The obtained bimolecular rate coefficients are k(CHBr₂ + NO₂) = (9.8 ± 0.4) × 10^?12 (T/300 K)^{?1.65 ± 0.18} cm³ s^?1 (288–483 K) and k(CH₃CHBr + NO₂) = (2.27 ± 0.06) × 10^?11 (T/300 K)^{?1.28 ± 0.11} cm³ s^?1 (250–483 K), with the uncertainties given as one standard error. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are ±25%. The reaction products identified were CBr₂O for the CHBr₂ + NO₂ reaction and CHBrO and CH₃CHO with minor amounts of CH₃ for the CH₃CHBr + NO₂ reaction, respectively. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 767–777, 2012     

Thermodynamically based fictitious crack/interface model for general normal and shear loading

For small deformations a crack/interface model that considers general 3D normal and shear loading is proposed. It involves elasticity, plasticity and damage and it is thermodynamically based. An essential feature of the model is its consistency with the concepts behind the fictitious crack model. In particular, no crack deformation occurs before the crack is initiated and when a crack has just been initiated the proposed model provides an unloading stiffness that is infinitely large. For the same set of parameters, it is demonstrated that the proposed model is able to provide predictions that are in close agreement with experimental data for concrete for a wide range of loading situations.     

Thermo-mechanically coupled model of diffusionless phase transformation in austenitic steel

A constitutive model of thermo-mechanically coupled finite strain plasticity considering martensitic phase transformation is presented. The model is formulated within a thermodynamic framework, giving a physically sound format where the thermodynamic mechanical and chemical forces that drive the phase transformation are conveniently identifiable. The phase fraction is treated through an internal variable approach and the first law of thermodynamics allows a consistent treatment of the internal heat generation due to dissipation of inelastic work. The model is calibrated against experimental data on a Ni–Cr steel of AISI304-type, allowing illustrative simulations to be performed. It becomes clear that the thermal effects considered in the present formulation have a significant impact on the material behavior. This is seen, not least, in the effects found on forming limit diagrams, also considered in the present paper.     

Inverse boundary spectral problem for non–selfadjoint maxwells–s equations with incomplete data

The inverse boundary spectral problem for selfadjoint Maxwell–s equations is to reconstruct unknown coefficient functions in Maxwell– equations from the knowledge of the boundary spectral data, i.e. fromt eh eigenvalues and the boudnary value of the eigenfunctions. Since the spectrum of non–selfadjoint Maxwell–s operator consists of normal eigenvalues and an interval, the complete boundary spectral data can be defind only in a very complicated way. In this article we show that the coefficients can be reconstructed from incomplete data, that is, from the large eigenvalues and the boundary values of the generalized eigenfunctions. Particularly, we do not need the nfinit–dimensional data corresponding to the non–discrete spectrum.     

2,3,6,7,10,11‐Hexahydroxytriphenylene tetrahydrate: a new form of an important starting material for supramolecular chemistry and covalent organic frameworks

In the title compound, C₁₈H₁₂O₆·4H₂O, the 2,3,6,7,10,11‐hexahydroxytriphenylene molecule is located on a twofold axis and two water molecules occupy general positions. The compound forms (4,4) two‐dimensional nets via hydrogen bonds between neighbouring hexahydroxytriphenylene molecules, somewhat similar to the cyclopentanone solvates but distinctively different from the monohydrate form. Hydrogen bonds to water molecules connect these layers to form a complicated three‐dimensional net, supported also by strong π–π stacking.     

Metal‐Mediated [2+3] Cycloaddition of Nitrones to Palladium‐Bound Isonitriles

[2+3] Cycloadditions! The metal‐mediated [2+3] cycloaddition of acyclic [^?O⁺N(R²)?(H)R³] and nonaromatic cyclic nitrones [^?O⁺N^a?CHCH₂CH₂C^bMe₂(N^a? C^b)] to palladium‐bound isonitriles cis‐[PdCl₂(C?NR)₂] proceeds under mild conditions to furnish novel heterocyclic carbene complexes, which then undergo N? O bond rupture to give imino complexes and free isocyanates (see scheme).

     

Data analysis programs for comprehensive two-dimensional chromatography

User-friendly and easy-to-use laboratory-written programs for visualisation and interpretation of comprehensive two-dimensional chromatographic data were developed. The programs that are not tied to any particular commercial instrument, and data obtained either by comprehensive two-dimensional liquid (LC × LC) or gas (GC × GC) chromatography can be analysed. Operations of the programs allow visualisation of 2D and 3D plots, comparison of two 2D plots at a time, as well as determination of retention times and peak heights and volumes.