2,4,6-Tri-isopropylbenzenesulphonyl hydrazide: A convenient source of di-imide

2,4,6-Tri-isopropylbenzenesulphonyl hydrazide (TPSH, 3a) undergoes thermal decomposition in d₄-methanol solution at 35°, in the presence of triethylamine, at a rate ca. 380 times that of p-toluenesulphonyl hydrazide (2b). 3a has been found to be a convenient and effective hydrogenating agent for azobenzene and a number of olefins in methanol solution at 20° and in boiling ether and tetrahydrofuran solutions. Reductions in ether solution appear to be facilitated by the addition of base. 2,4,6-Trimethylbenzenesulphonyl hydrazide (MSH, 4a) undergoes thermal decomposition at a rate ca. 24 times that of 2b; 4a is also a useful hydrogenating agent.     

Exchange interaction during electron capture in Ar2+, K-collisions

During electron capture of Ar²⁺ from alkali atoms prevailingly Ar⁺ 4p states are occupied. While decaying they give rise to a spectrum which consists almost exclusively of 4p ? 4s and 4p ? 3d lines. The intensity of the lines turns out to be dependent on the Ar²⁺ projectile energy. At energies as low as 1 keV lines which belong to the Ar⁺ 3p ⁴(¹ D)n, l-system are by far the strongest. When increasing the projectile energy to 6 keV and above this system fades away and lines of the 3p ⁴(³ P)n, l-system appear. Considering that the primary beam consists constantly of 65% Ar²⁺ 3p ⁴ (³ P) and 35% Ar²⁺ 3p ³(¹ D) the strength surprises at which the 3p ⁴(¹ D)n, l system evolves from the electron capture. It is suggested that exchange interaction of the valence electron and one 3p-electron changes the 3p ⁴-core. Relative matrix elements for direct and exchange interaction of the valence electron and the 3p ⁴-core are calculated and used in a multi channel Landau Zener calculation. With this concept the measured spectra could be fitted by adopting only two parameters, namely one line strength and the ratio of the reduced matrix elements of direct and exchange interaction.     

General theory for flow optimisation of split-flow thin fractionation

Recently, magnetic split-flow thin (SPLITT) fractionation has been developed to separate macromolecules, colloids, cells and particles. However, the previous theory, developed for an infinitely long channel, needs to be improved to consider the flow transit regimes at both inlet and outlet. In this paper, we describe a new approach to optimising flow-rates for particle separation which considers the effect of flow transit region. Surprisingly, the critical particle migration velocities derived by the present theory are identical to the previous simplified theory. Therefore, the previous simplified theory may have wider application than might have been expected. As a test of our theory, a numerical simulation based on solving Navier-Stokes equations has also been carried out for a magnetic SPLITT device. The trajectory of a particle with the critical migration velocity is exactly as expected by our theory. Following experimental validation, this work will facilitate the design of new SPLITT fractionation systems with smaller aspect ratio.     

Kristallstruktur,Schwingungsspektren und Normalkoordinatenanalyse von (CH2py2)[Ru(NO)FCl4]

Crystal Structure, Vibrational Spectra, and Normal Coordinate Analysis of (CH₂py₂)[Ru(NO)FCl₄] By treatment of [Ru(NO)Cl₅]^2– with a BrF₃ saturated frigen solution in dichloromethane the complex [Ru(NO)FCl₄]^2– is formed, which can be separated from hydrolysis products by ion exchange chromatography on diethylaminoethyl cellulose. The X‐Ray structure determination on a single crystal of (CH₂py₂)[Ru(NO)FCl₄] · ¹/₂ (CH₃)₂CO (triclinic, space group P1, a = 9.416(2), b = 14.919(6), c = 15.127(3) Å, α = 61.86(3), β = 80.31(2), γ = 72.49(3)°, Z = 4) reveals, that the fluorine atom is trans positioned to the nitrosyl group. The low temperature IR and Raman spectra have been recorded of (n‐Bu₄N)₂[Ru(NO)FCl₄] and are assigned by normal coordinate analysis. A good agreement between observed and calculated frequencies is achieved. The valence force constants are f_d(NO) = 13.92, f_d(RuN) = 5.16, f_d(RuF) = 3.19 and f_d(RuCl) = 1.45 mdyn/Å. The ¹⁹F NMR spectra exhibits one singlet at –144.6 ppm.     

Finite element model updating for damage detection

In this contribution we derive the iterative finite element model updating algorithm. The ability of the method to detect the damage is verified by means of a simulation with a reference finite element model. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Finite deformation pseudo-elasticity of shape memory alloys – Constitutive modelling and finite element implementation

In this paper we suggest a new phenomenological material model for shape memory alloys. In contrast to many earlier concepts of this kind the present approach includes arbitrarily large deformations. The work is motivated by the requirement, also expressed by regulatory agencies, to carry out finite element simulations of NiTi stents. Depending on the quality of the numerical results it is possible to circumvent, at least partially, expensive experimental investigations. Stent structures are usually designed to significantly reduce their diameter during the insertion into a catheter. Thereby large rotations combined with moderate and large strains occur. In this process an agreement of numerical and experimental results is often hard to achieve. One of the reasons for this discrepancy is the use of unrealistic material models which mostly rely on the assumption of small strains. In the present paper we derive a new constitutive model which is no longer limited in this way. Further its efficient implementation into a finite element formulation is shown. One of the key issues in this regard is to fulfil “inelastic” incompressibility in each time increment. Here we suggest a new kind of exponential map where the exponential function is suitably computed by means of the spectral decomposition. A series expansion is completely avoided. Finite element simulations of stent structures show that the new concept is well appropriate to demanding finite element analyses as they occur in practically relevant problems.     

Modelling the Springback of Sheet Metals at Large Deformations

Sheet metal forming simulations are increasingly replacing traditional build-and-break prototyping because they provide a less expensive and more rapid way to speed up product design time while improving quality and performance. Sheet metal is subjected to stretching, bending and unbending during forming, and an accurate prediction of the formability and springback of the sheet necessitates the use of an appropriate constitutive model. Use of isotropic hardening alone has been identified as a source of inaccurate springback prediction. In order to be able to describe the cyclic hardening behaviour and the Bauschinger effect, a large-deformation elasto-plastic material model with non-linear kinematic hardening is discussed in the present work. The model is derived from a thermodynamical framework and is based on the multiplicative split of the deformation gradient. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Proof of Positive Definiteness of FI and Extended Finite Element Tearing and Interconnecting XFETI

We propose a mathematical theorem to prove the positive definiteness of the term FI used in Finite Element Tearing and Interconnecting introduced by Farhat [1]. Furthermore, we introduce a new idea to extend FETI to include non-self adjoint operators emerging from, for example, elastoplastic large deformation, non-associative plasticity or when coupling BEM and FEM [2]. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)