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The variation in the lifetime of flash-excited gaseous benzophenone with pressure and temperature indicates that (1) self-quenching is a relatively inefficient process for the long-lived emission, ksq = 9 × 105 M?1 s?1 (estimated from solution data) at 25°C and 1.2 × 107 M?1 s?1 at 170°C and (2) the lifetime decreases with increasing temperature as a result of photochemical and photophysical decay pathways which have significant activation energies. The importance of diffusion to the walls on lifetime measurements is discussed. 相似文献
44.
Preparation of Stilbenyl Derivatives of Isoxazoles Schiff's bases derived from 3- and 5-(p-formylphenyl)-phenylisoxazoles and o- or p-chloroaniline are reacted with various p-tolyl substituted aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide or potassium t-but-oxide to yield the corresponding heterocyclic substituted stilbenes (‘Anil synthesis’). 5-[4-(Chlorphenylimino-methyl)phenyl]-phenylisoxazoles react less readily than the corresponding 3-isomers. 相似文献
45.
C. Matei D. Berger P. Marote S. Stoleriu J.P. Deloume 《Progress in Solid State Chemistry》2007,35(2-4):203-209
Lanthanum-based perovskites, LaMO3 (where M = Mn, Fe, Co, Ni), have been synthesised from lanthanum precursors and corresponding 3d transition metal salts in molten alkali metal nitrates or nitrites. The reactivity of eight precursors in three molten salts of different basicity was analysed. Single phase orthorhombic LaMnO3.11, and orthorhombic LaFeO3 have been obtained in molten NaNO2 at 723 K, for 2 h. LaCoO3 is also formed in molten nitrite, but an increase of basicity, by adding Na2O2, was necessary to obtain LaNiO3. The reaction systems were investigated by thermal analysis. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and specific surface area measurements (BET method) were used to characterise the synthesised nanopowders. 相似文献
46.
Pagel K Seeger K Seiwert B Villa A Mark AE Berger S Koksch B 《Organic & biomolecular chemistry》2005,3(7):1189-1194
We report here an advanced approach for the characterization of the folding pattern of a de novo designed antiparallel coiled coil peptide by high-resolution methods. Incorporation of two fluorescence labels at the C- and N-terminus of the peptide chain as well as modification of two hydrophobic core positions by Phe/[15N,13C]Leu enable the study of the folding characteristics and of distinct amino acid side chain interactions by fluorescence resonance energy transfer (FRET) and NMR spectroscopy. Results of both experiments reveal the antiparallel alignment of the helices and thus prove the design concept. This finding is also supported by molecular dynamics simulations. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in combination with NMR experiments was used for verification of the oligomerization equilibria of the coiled coil peptide. 相似文献
47.
Summary A sensitive method has been developed for analysis of trace amounts of arsenic in biological materials using the heteropoly blue method. The method employs a closed apparatus and a nitrogen atmosphere, and allows the detection of arsenic in ppm concentration using samples of 100 mg.
Presented at the 6th Annual Northeast Regional Meeting of the American Chemical Society, Burlington, Vermont, August 19, 1974. 相似文献
Zusammenfassung Eine empfindliche Methode zur Bestimmung von Arsenspuren in biologischem Material im Wege der Molybdänblaumethode wurde ausgearbeitet. Man arbeitet dabei in einer geschlossenen Apparatur in Stickstoffatmosphäre und kann so in 100-mg-Proben Arsenkonzentrationen in der Größenordnung von ppm bestimmen.
Presented at the 6th Annual Northeast Regional Meeting of the American Chemical Society, Burlington, Vermont, August 19, 1974. 相似文献
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Selman A. Berger 《Mikrochimica acta》1982,77(5-6):423-431
Summary A semi-automatic microliter sample injector with an 8-way motor-driven rotary valve was constructed for a conventional pneumatic nebulizer. After a 40-l sample was injected into an injection tee with a micro-syringe, nebulization and flushing the sample pathway with water followed by argon were automatically executed. An automatic peak detector/integrator was employed in each channel of a three-channel spectrometer for simultaneous multielement analysis. The relative standard deviation of the peak height for 1g Zr/ml was 1.7% and measuring time of one sample was about 1 min. Detection limits were 2 to 6 times higher than those in continuous feeding.
Halbautomatische Injektion von Mikroliter-Proben in ein induktiv gekoppeltes Plasma zwecks simultaner Multielementanalyse
Zusammenfassung Ein halbautomatischer Injektor für Mikroliterproben mit einem motorgetriebenen 8-Weg-Ventil für ein konventionelles Vernebelungsgerät wurde konstruiert. Nachdem eine 40-l-Probe mit einer Mikroinjektionsspritze in ein Injektions-T-Stück eingeführt ist, erfolgt automatisch Vernebelung, dann Spülung des Probenweges zunächst mit Wasser, dann mit Argon. Ein automatischer Spitzen-Detektor/Integrator in jedem der drei Kanäle des Spektrometers ermöglicht die gleichzeitige Multielementanalyse. Die rel. Standardabweichung der Spitzenhöhe für 1g Zr/ml betrug 1,7%, die Zeit für die Messung einer Probe ungefähr eine Minute. Die Nachweisgrenzen sind 2- bis 6mal höher als bei kontinuierlicher Zugabe.相似文献
50.
Selman A. Berger 《Mikrochimica acta》1984,84(3-4):275-282
Summary DbPH, a quadridentate chelating agent, was studied as a solvent extraction reagent for Cu(II), Co(II), and Ni(II). In all cases 11 complexes were extracted; however for Cu(II) and Co(II) ion-paired species exist, while for Ni(II) only neutral complexes were extracted. In all cases an extraction efficiency of 35–60% was observed unlike the greater than 90% observed for similar mono-hydrazone derivatives. The steric hindrance probably present in the bis adduct prevented a more efficient extraction.
Presented at the 18th Middle Atlantic Regional Meeting of the American Chemical Society, Newark, New Jersey, May 21, 1984. 相似文献
Diacetyl-bis-(2-pyridyl)hydrazon (DbPH) als Extraktionsmittel für Cu(ll), Co(II) und Ni(II)
Zusammenfassung DbPH bildet mit Cu(II), Co(II) und Ni(II) Komplexverbindungen im Verhältnis 11; diese sind für Cu und Co ionisierbar, im Falle des Ni läßt sich ein neutraler Komplex extrahieren. Die Extraktion erreicht jedenfalls nur 35–60% im Gegensatz zu mehr als 90% bei ähnlich gebauten Monohydrazon-Derivaten. Sterische Hinderung dürfte hierfür die Ursache sein.
Presented at the 18th Middle Atlantic Regional Meeting of the American Chemical Society, Newark, New Jersey, May 21, 1984. 相似文献