Probing for electrical inclusions with complex spherical waves

Let a physical body Ω in ?² or ?³ be given. Assume that the electric conductivity distribution inside Ω consists of conductive inclusions in a known smooth background. Further, assume that a subset Γ ? ?Ω is available for boundary measurements. It is proved using hyperbolic geometry that certain information about the location of the inclusions can be exactly recovered from static electric measurements on Γ. More precisely: given a ball B with center outside the convex hull of Ω and satisfying (B? ∩ ?Ω) ? Γ, boundary measurements on Γ with explicitly given Dirichlet data are enough to determine whether B intersects the inclusion. An approximate detection algorithm is introduced based on the theory. Numerical experiments in dimension two with simulated noisy data suggest that the algorithm finds the inclusion‐free domain near Γ and is robust against measurement noise. © 2007 Wiley Periodicals, Inc.     

Effect of post-metallization annealing on the ferroelectric properties of sol-gel derived PZT thin films

A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model.     

Construction of multiporphyrin arrays using ruthenium and rhodium coordination to phosphines

The synthesis of linear multiporphyrin arrays with mono- and bisphosphine-substituted porphyrins as ligand donors and ruthenium(II) or rhodium(III) porphyrins as ligand acceptors is described. With appropriate amounts of the building blocks mixed, linear dimeric and trimeric arrays have been synthesized and analyzed by (1)H NMR and (31)P NMR spectroscopy. The Ru/Rh acceptor porphyrins can be located either at the periphery or in the center of the array. Likewise, the monophosphine porphyrins can be positioned at the periphery, thus allowing a high degree of freedom in the overall composition of the arrays. This way, both donor and acceptor porphyrins can act as chain extenders or terminators. One of the trimeric complexes with two nickel and one ruthenium porphyrin has also been analyzed by X-ray crystallography. Attempts have also been made to synthesize higher order arrays by mixing appropriate amounts of the porphyrins; however, from the NMR data it cannot be concluded if monodisperse five, seven, or nine porphyrin arrays are present or if the solutions are composed of a statistical mixture of smaller and larger arrays.     

On Mercury(I) Oxo Compounds — Quasi‐Relativistic Computational and Experimental Studies

About 60 molecular species composed of up to 10 mercury atoms and of oxygen atoms and/or of some other elements or groups (such as halogen, OH₂, OH, H, alkali, NO₃) have been investigated quantum chemically. Different density functional approaches and the ab initio SCF‐MP2 method were applied, comparing different basis sets and different atomic core sizes. It is important not to treat the Hg 5s, p, d as inactive core shells, and to use sufficiently many polarization functions. The shape of the 〉O‐Hg‐Hg‐O〈 units is not favorable concerning the formation of lattices composed of Hg^I, O and OH only. Despite its bulkiness, the OHgHgO units can easily come into contact with each other and then disproportionate. This is prevented in the so‐called ternary M‐Hg^I oxides by the embedded oxometallate (oxoacidic) anions. Furthermore, the Hg^I and Hg^II oxide bond energies are less favorable towards the stability of Hg^I oxo compounds, as compared to Hg halidic or oxoacidic compounds. Both points are not promising concerning the search for Hg^I oxides/hydroxides, although the preparation of such compounds, including spacer groups, by topochemical reactions can still not be excluded. So far, experimental efforts towards the synthesis of such a new class of compounds have only demonstrated that Hg^II is strictly preferred over Hg^I in the formation of solids of binary Hg‐O or ternary A‐Hg‐O composition (A = electropositive metal such as alkali, in contrast to M = transition or semi‐metal). This is so even if compounds containing ‘electron rich Hg^δ— atoms’ (i.e. A‐Hg amalgams) are oxidized under mild conditions.     

Glycosylidene Carbenes. Part 9. Regioselective glycosidation of diols and triols: Intra- and intermolecular hydrogen bonds

Glycosidation of the myo-inositol derivatives 2 and 3 by the diazirine 1 yields 90% of a diastereoisomer pair of β-D -glycosides in a 1:1 ratio, i.e. 5/6 and 7/8 , respectively (Scheme 1). The crystal structure of 3 shows a strong intramolecular H-bond, which persists in solution, as indicated by FT-IR and ¹H-NMR spectra. Yields and diastereoselectivity are lower for the glycosidation of 24 by 1 (Scheme 3). The resulting 1,2- and 1,4-linked disaccharides 25–28 were isolated as their acetates 29–32 . The previously determined crystal structure of 24 shows no intramolecular H-bonds. The yield of the glycosidation of 24 , but not of 3 , depends upon the concentration, indicating that activation of 24 by intermolecular H-bonds is required. Glycosidation of 2 and 3 with the trichloroacetimidate 14 gave mixtures of four ( 5,6,15 , and 16 ), and six ( 7,8 , and 17–20 ) disaccharides, respectively (Scheme 2).     

Metallkomplexe des Hexamethyl-trisila-tetraphospha-nortricyclen P4 (Sime2)3

Transition Metal Complexes of the Hexamethyl-trisila-tetraphospha-nortricyclene P₄ (Sime ₂) ₃ P₄(Sime₂)₃ 1 reacts with Mo(CO)₆, Cr(CO)₅THF, and Mn(η-C₅H₅)(CO)₂THF to give crystalline complexes in which 1 functions as a monodentate ligand. In each compound one phophorus atom of the cyclotriphosphane ring coordinates to the metal atom. Using Mn(η-C₅H₅)(CO)₂THF, two different P atoms of the P₃ Cr(CO)₄ norbornadiene and 1 react, yielding the dimeric, red, crystalline compound (CO) ₄Cr[μ-P₄(Sime₂)₃]₂Cr(CO)₄. In this complex the two molecules of 1 are both bonded by two P atoms of the P ₃ ring to the two Cr(CO)₄ Units, forming a six-memered (CrP₂)₂ring.     

Formation and dissociation of the chloroethylene anions

Electron attachment spectroscopy is employed to study the formation of negative ions from the chloroethylenes. It is found that the resonances recently observed in the total electron scattering cross section are predominantly associated with the formation of Cl^?. Only in tetrachloroethylene is a long-lived parent negative ion observed.     

Eine neue Mikro- und Ultramikro-Bestimmung von Sauerstoff in organischen Verbindungen mit Hilfe eines W?rmeleitf?higkeitsdetektors

Zusammenfassung Zur Bestimmung des Sauerstoffs wird die organische Probe in Helium-Atmosphäre gecrackt; die sauerstoffhaltigen Crackprodukte werden über Kohle zu Kohlenmonoxid konvertiert. Um das Kohlenmonoxid von den übrigen Crackprodukten, wie H₂, N₂ und CH₄ abzutrennen, wird es zu Kohlendioxid oxydiert und danach an einem Molekularsieb bei 20° C durch Adsorption zurückgehalten; H₂, N₂ und CH₄ werden aus der Apparatur gespült. Sobald in der Probeleitung reines Spülgas auftritt, wird das adsorbierte Kohlendioxid durch Erhitzen desorbiert und im Detektor gemessen.

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Summary For the determination of oxygen the organic sample is cracked in helium atmosphere. Cracking products, containing oxygen, are converted to carbon monoxide by coal. For separation from the remaining cracking products (H₂, N₂, CH₄) carbon monoxide is oxidized and then adsorbed on molecular sieve 5A at 20°C; H₂, N₂ and CH₄ are flushed out. As soon as pure carrier gas flows through the sample pipe, carbon dioxide is desorbed by heating the molecular sieve and flushed to the detector.

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Es ist uns eine angenehme Pflicht, der Shell Austria AG., Wien, insbesondere Herrn Direktor Dipl.-Ing. R. Wallner, für die Gewährung eines Forschungsstipendiums an den einen von uns (E. W.) ergebenst zu danken.