Synthese, Aufbau und Eigenschaften käfigartiger vinyl- und allylsilylierter Kieselsäuren

Durch Umsatz des Tetramethylammoniumsilicats [N(CH3)4]8Si8O20 · 69 H2O mit Vinyldimethylchlorsilan (I) bzw. Divinyltetramethyldisiloxan oder Allydimethylchlorsilan wurden der Vinyldimethylsilylkieselsäureester [CH2CHCH2(CH3)2Si]8Si8O20 und Allyldimethylsilyl-kieselsäureester [CH2CHCH2(CH3)2Si]8Si8O20 erhalten. Mit Hilfe der Gaschromatographie, Massenspektroskopie sowie 1H-und 29Si-NMR wurden die Verbindungen charakterisiert und eine käfigartig aufgebaute Doppelvierring (D4R)-Struktur des Kieselsäuregerüsts nachgewiesen, an deren 8 terminalen O-Atomen des Kieselsäuregerüsts nachgewiesen, an deren 8 terminalen O-Atomen des Kieselsäuregerüsts Vinyldimethylsiyl- bzw. Allydimethylsilylgruppen gebunden sind. Durch Silylierung mit I und Trimethylchlorsilan sind in Abhängigkeit vom Mischungsverhältnis Vinyldimethylsilytrimethysily1-D4R-Kieselsäureester mit einer mittleren Anzahl ungesättigter Gruppen < 8 herzustellen

[(CH3)3Si]14Si7O21 - ein neuer cyclischer Kieselsäuretrimethylsilylester

Durch Trimethylsilylierung des Bariumchloridsilicates 2BaO - 3BaCl2 - 2SiO2 wurde ein bisher unbekannter Kieselsäuretrimethylsilylester hergestellt, der mit Hilfe der Kapillargaschromatographie, Massenspektroskopie29Si-NMR-Spektroskopie und Dünnschichtchromatographie charakterisiert wurde. Aus den Untersuchungen folgt für den Ester die Konstitution eines Cycloheptakieselsäuretrimethylsilylesters (Tetradecakistrimethylsiloxicycloheptasiloxan) der Formel [(CH3)3Si]14Si7O21. Die Verwendung des Esters als Standardsubstanz wird diskutiert

Influence of functional groups on the gas chromatographic retention behaviour of QM-siloxanes

The retention time sequences of QM-siloxane derivatives (derivatives of trimethylsilyl esters of silicic acids) of the formula QmM2m+2-nXn (X = H, Cl, C2H5O; m, n = 1,2,3) and of siloxane derivatives containing M, D and T groups were investigated by capillary gas chromatography. The investigation showed that in compounds of the same structural type the retention times increase in the order of the substituents H < Cl < C2H5O. A linear correlation between retention time and molecular weight was observed only within groups of QM derivatives of the same structural type. The retention sequence rule obtained from QM-siloxanes was modified so that it became valid for the investigated compounds, and so that it should be possible to identify unknown siloxane derivatives by the use of gas chromatography

Associative and Spatial Relationships in Thesaurus-based Retrieval

The OASIS (Ontologically Augmented Spatial Information System) project explores terminology systems for thematic and spatial access in digital library applications. A prototype implementation uses data from the Royal Commission on the Ancient and Historical Monuments of Scotland, together with the Getty AAT and TGN thesauri. This paper describes its integrated spatial and thematic schema and discusses novel approaches to the application of thesauri in spatial and thematic semantic distance measures. Semantic distance measures can underpin interactive and automatic query expansion techniques by ranking lists of candidate terms. We first illustrate how hierarchical spatial relationships can be used to provide more flexible retrieval for queries incorporating place names in applications employing online gazetteers and geographical thesauri. We then employ a set of experimental scenarios to investigate key issues affecting use of the associative (RT) thesaurus relationships in semantic distance measures. Previous work has noted the potential of RTs in thesaurus search aids but the problem of increased noise in result sets has been emphasised. Specialising RTs allows the possibility of dynamically linking RT type to query context. Results presented in this paper demonstrate the potential for filtering on the context of the RT link and on subtypes of RT relationships

Working Towards a Treat-to-Target Protocol in Juvenile Proliferative Lupus Nephritis - A Survey of Pediatric Rheumatologists and Nephrologists in Germany and Austria.

BackgroundTo describe treatment practices for juvenile proliferative lupus nephritis (LN) class III and IV of pediatric rheumatologists and nephrologists in Germany and Austria in preparation for a treat-to-target treatment protocol in LN.MethodsSurvey study by members of the Society for Pediatric and Adolescent Rheumatology (GKJR) and the German Society for Pediatric Nephrology (GPN) on diagnostics and (concomitant) therapy of LN.ResultsFifty-eight physicians completed the survey. Overall, there was a considerable heterogeneity regarding the suggested diagnostics and management of juvenile proliferative LN. Increased urinary protein excretion, either assessed by 24 h urine collection or spot urine (protein-creatinine ratio), and reduced estimated glomerular filtration rate were specified as important parameters for indication of kidney biopsy to diagnose proliferative LN and monitoring of therapy. Corticosteroids were generally proposed for induction and maintenance therapy, most often in conjunction with either mycophenolate mofetil (MMF) or cyclophosphamide (CP) as steroid-sparing immunosuppressants. MMF was clearly preferred over CP for induction therapy of LN class III, whereas CP and MMF were equally proposed for LN class IV. MMF was most often recommended for maintenance therapy in conjunction with oral corticosteroids and continued for at least 3 years and 1 year, respectively, after remission. Hydroxychloroquine was widely accepted as a concomitant measure followed by renin-angiotensin system inhibitors in cases of arterial hypertension and/or proteinuria.ConclusionThe majority of pediatric rheumatologists and nephrologists in Germany and Austria propose the use of corticosteroids, most often in combination with either MMF or CP, for treatment of proliferative LN in children. The considerable heterogeneity of responses supports the need for a treat-to-target protocol for juvenile proliferative LN between pediatric rheumatologists and nephrologists