Reducing Huge Gyroscopic Eigenproblems by Automated Multi-level Substructuring

Simulating numerically the sound radiation of a rolling tire requires the solution of a very large and sparse gyroscopic eigenvalue problem. Taking advantage of the automated multi-level substructuring (AMLS) method it can be projected to a much smaller gyroscopic problem, the solution of which however is still quite costly since the eigenmodes are non-real and complex arithmetic is necessary. This paper discusses the application of AMLS to huge gyroscopic problems and the numerical solution of the AMLS reduction. A numerical example demonstrates the efficiency of AMLS.     

Sample preparation procedure for the determination of sulphur and trace metals in oil products by the ICP with a minitorch using emulsions

A quick sample preparation method was used for the determination of sulphur and trace metals in oil and oily products by the ICP with a minitorch. Stable aqueous emulsions of oils and oil products were made by using two kinds of emulsifiers (one with low sulphur content, the other sulfonated). Aqueous standard solutions can be used for the preparation of calibration solutions. The contents of S, Al, Cr, Cu, Fe, Mg, Ni and Pb in aqueous emulsions were determined and the results were in good agreement with the composition of oil standard solutions used for control analysis procedure.     

Accurate pKa determination for a heterogeneous group of organic molecules.

Single-molecule studies that allow to compute pKa values, proton affinities (gas-phase acidity/basicity) and the electrostatic energy of solvation have been performed for a heterogeneous set of 26 organic compounds. Quantum mechanical density functional theory (DFT) using the Becke-half&half and B3LYP functionals on optimized molecular geometries have been carried out to investigate the energetics of gas-phase protonation. The electrostatic contribution to the solvation energies of protonated and deprotonated compounds were calculated by solving the Poisson equation using atomic charges generated by fitting the electrostatic potential derived from the molecular wave functions in vacuum. The combination of gas-phase and electrostatic solvation energies by means of the thermodynamic cycle enabled us to compute pKa values for the 26 compounds, which cover six distinct chemical groups (carboxylic acids, benzoic acids, phenols, imides, pyridines and imidazoles). The computational procedure for determining pKa values is accurate and transferable with a root-mean-square deviation of 0.53 and 0.57 pKa units and a maximum error of 1.0 pKa and 1.3 pKa units for Becke-half&half and B3LYP DFT functionals, respectively.     

Total digestion of silicate containing matrices (plants,soil, sludges) using a pressure ashing device with PFA-vessels

A digestion procedure for silicate containing matrices like soil, sludge, etc. by using a commercially available pressure ashing device (Seif-Aufschlutechnik, Germany) with PFA (perfluoroalkoxy) sample vessels is described at the results for different matrix- and trace elements in different suitable certified standard reference materials. The advantages of this technique compared with the use of Teflon®-(PTFE, polytetrafluoroethylene) vessels and the open treatment in Pt-crucibles will be discussed.     

Potential cerebral perfusion agents. Synthesis and evaluation of berberine analogues

The synthesis and tissue distribution studies in rats of tetra[³H]-hydroberberine ([³H] 2 ) and 8-(p-[¹²⁵I]iodobenzyl)tetrahydroberberine ([¹²⁵I] 6 ) are described. Compound 2 was synthesized by sodium borohydride reduction of berberine hydrochloride ( 1 ). Treatment of berberine hydrochloride with p-bromo-benzylmagnesium bromide gave 8-(p-bromobenzyl)dihydroberberine ( 4 ) which after sodium borohydride reduction and iodine-125 bromine exchange gave [¹²⁵I] 6 . The unsubstituted tetrahydro compound [³H] 2 showed significantly higher brain uptake (2.2% dose/gm after 5 minutes) as compared to the corresponding 8-substituted derivative [¹²⁵I] 6 . Both radiolabeled compounds washed out from the brain relatively quickly.