A Refined Schwarz Lemma for the Spectral Nevanlinna-Pick Problem

The spectral Nevanlinna–Pick problem asks for necessary and sufficient conditions for the existence of a holomorphic map from the unit disc to the set of $n\times n$ complex matrices with spectral radius less than 1, that interpolates given data. Some versions of the Schwarz lemma, obtained by Ransford and Nokrane, and by Bharali, provide necessary conditions. We prove a refined version of their results, which makes it possible to treat problems with more than two interpolation points.     

Two new promelacacinidin dimers,including a novel flavanone-flavanol dimer characterized by a unique C(3)-C(4) linkage,from the heartwood of <Emphasis Type="Italic">Acacia nigrescens</Emphasis>

Two new promelacacinidin biflavonoids, mesquitol-(4α,5)-epimesquitol-4β-ol and a 3′,4′,7,8-tetrahydroxyflavanone(3,4)-ent-epimesquitol, were isolated among others from the heartwood of Acacia nigrescens. The flavanone derived dimer, characterized by a unique C(3) to C(4) bridge, which links the monomers via two stereogenic and sp³ hybridized C-atoms, is the prototype of a new subgroup of the flavonoid family. Assessment of the absolute configuration of all five stereogenic centers of this novel flavanone-derived biflavonoid was achieved by correlating the chiroptical properties of the benzoyl chromophore to the absolute configuration of C(2) of the flavanone moiety and hence the absolute stereochemistry of the other four chiral centers. Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 437–441, September–October, 2007. Dedicated to Prof. E. Malan, who initiated and supervised this research project, for a noteworthy contribution in the flavonoid field, and who has since retired.     

Nichtdistributive,modulare Polaritätsverbände

Ohne Zusammenfassung     

Laser removal of TiN coatings from WC micro-tools and in-process monitoring

Current environmental challenges require sustainable and extended use and re-use of materials. For example, the service life of engineering tooling can be extended by using thin film coatings such as titanium nitride (TiN). However, when errors arise in the coating process or when the tooling needs to be re-used it is necessary to remove the coating. Decoating is also useful when a large batch of cutting tools needs to be re-directed for a different application, which requires a new generation of coating. Existing technology uses chemical methods which are not environmentally friendly or ideal for selective removal. In this work, excimer laser striping of TiN from coated tungsten carbide (WC) micro-tools has been demonstrated as a viable alternative to chemical methods. Also, in order to raise the integrity of the decoating process and to make the process more accurate and reliable, two online monitoring systems were developed exploiting probe beam reflection (PBR) and laser plume emission spectroscopy (PES). The online monitoring system facilitated a simultaneous prediction of surface elements as coating layers are progressively removed and ensures better control over the laser irradiation process so as to avoid under or over stripping of the coating.     

Treillis Continus Et Treillis Completement Distributifs

Sans résumé     

Synthesis of indolizines and pyridinium ylids from 4,5-disubstituted α-picolines

New 1,3-diacetylindolizines were obtained from 4-phenyl- and 4-benzyl-2,5-dimethylpyridines; some transformations involving their acetyl groups were realized. The same pyridine bases were used in syntheses of pyridinium ylids. The transformations of the latter to indolizines were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 506–510, April, 1976.     

Synthesis of 4,5-dihydro-1,6:3,8-dimethano-1,3,6,8-benzotetrazecine

Three-component condensation of formaldehyde, o-phenylenediamine, and ethylenediamine gave for the first time 4,5-dihydro-1,6:3,8-dimethano-1,3,6,8-benzotetrazecine. Its structure was proved by X-ray diffraction analysis. A similar condensation of formaldehyde with a mixture of ethylenediamine and 1,2-diamino-4-methylbenzene yielded 10-methyl-4,5-dihydro-1,6:3,8-dimethano-1,3,6,8-benzotetrazecine and a condensation with a mixture of o-phenylenediamine and propane-1,2-diamine yielded 4-methyl-4,5-dihydro-1,6:3,8-dimethano-1,3,6,8-benzotetrazecine. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1544–1546, July, 2008.