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11.
Chromatographia - Ausgehend von den thermodynamischen Grundlagen wird die Siedepunktsabhängigkeit der Retentionszeiten diskutiert. Über eine Formel vonKlages, nach der sich das Quadrat... 相似文献
12.
Abe K Ahrens LA Amako K Aronson SH Beier EW Callas JL Cutts D Diwan M Durkin LS Gibbard BG Heagy SM Hedin D Hoftun JS Hurley M Kabe S Kurihara Y Lanou RE Mann AK Marx MD Murtagh MJ Nagashima Y Newcomer FM Shinkawa T Stern E Suzuki Y Terada S White DH Williams HH Yamaguchi Y 《Physical review letters》1987,58(7):636-639
13.
Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson H Bintinger DL Bobbink GJ Bolognese TS Bross AD Buchanan CD Buijs A Cain MP Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Eisner AM Enomoto R Erné FC Fujii T Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG Linde FL Lindsey CS Loken SC Lu A Lu X 《Physical review letters》1986,57(8):945-948
14.
Richard Partch Egon Matijevi Anthony W. Hodgson Barlow E. Aiken 《Journal of polymer science. Part A, Polymer chemistry》1983,21(4):961-967
A procedure was developed by which polymer colloids can be prepared by polymerizing aerosol droplets of monomers with an initiator in the vapor state. This work describes the formation of poly(p-tertiarybutylstyrene) particles by exposing the corresponding monomer droplets to trifluoromethanesulfonic acid. It was found that the monomer-to-initiator mass ratio is the critical factor in determining the uniformity and morphology of the particles. Under ideal conditions spheres of narrow size distribution are obtained. Otherwise porous particles or soft particles with whiskers may develop. The aerosol was prepared in a falling film generator, but other procedures for producing monomer droplets may be used. 相似文献
15.
Dr. David Lindsay Professor Egon Matijević Professor Josip P. Kratohvil 《Colloid and polymer science》1976,254(4):421-428
Summary The effects of dextran sulfates of different molecular weights and charge densities on the stability of positively and negatively charged silver bromide solsin statu nascendi have been studied by means of light scattering.The plots of scattering intensities of a positively charged sol against the concentration of the added dextran sulfates show one pronounced maximum, the position which is independent on the molecular weight of the polyelectrolyte used. The maximum shifts to lower polyion concentrations with dilution of the sol.The effect of polyanions on the stability of silver bromide sols of the same sign of charge were investigated as a function of molecular weight of the polymers, the sol concentration, the charge and the concentration of counterions, and the addition of methanol. Destabilization only occurred if sufficient amount of indifferent electrolyte was present in the system. However, the concentration of counterions necessary to produce a flocculation maximum was lower in the presence of the polyelectrolytes than in their absence. The results obtained were compared with the data on sols containing nonionic dextrans reported earlier.
5 figures and 1 table
Supported by the NSF Grant GP 42331 X.
A part of the Ph.D. Thesis by David Lindsay. 相似文献
Zusammenfassung Der Einfluß der Dextransulfate von verschiedenen Molekulargewichten und Ladungsdichten auf die Stabilität der positiv und negativ geladenen Silberbromid-Solein statu nascendi wurden durch Lichtstreuung untersucht. Wenn die Intensitäten der Lichtstreuung eines positiv geladenen Silberbromid-Sols gegen die Konzentration der zugesetzten DextranSulfate aufgetragen werden, tritt ein ausgeprägtes Maximum auf, dessen Lage von dem Molekulargewicht des angewandten Polyelektrolyten unabhängig ist. Bei Verdünnung des Sols wird das Maximum zur niedrigeren Konzentration des Polyanions verschoben.Der Einfluß der Polyanionen auf die Stabilität der Silberbromid-Sole mit gleichem Ladungsvorzeichen wurde in Abhängigkeit von dem Molekulargewicht des zugesetzten Dextransulfats, der Solkonzentration, der Ladung und Konzentration der Gegenionen und dem Zusatz von Methylalkohol untersucht. Destabilisierung wird nur in Anwesenheit einer genügenden Menge von Neutralelektrolyten in den untersuchten Systemen beobachtet. Die Konzentration der Gegenionen, die ein Flockungsmaximum verursachen, ist immer niedriger als die kritische Koagulationsmenge derselben Ionen für das gleiche Sol in Abwesenheit von Makroionen. Die Resultate wurden mit den Wechselwirkungen der Silberbromid-Sole mit nichtionogenen Dextranen verglichen, und der Mechanismus der Flockung durch Polyelektrolyte wurde diskutiert.
5 figures and 1 table
Supported by the NSF Grant GP 42331 X.
A part of the Ph.D. Thesis by David Lindsay. 相似文献
16.
Strerath M Cramer J Restle T Marx A 《Journal of the American Chemical Society》2002,124(38):11230-11231
DNA polymerase selectivity often varies significantly depending on the DNA polymerase. The origin of this varying error propensity is elusive. It is assumed that DNA polymerases form nucleotide binding pockets that differ in properties such as shape and tightness. We tested this prediction and studied HIV-1 RT by employment of size-augmented nucleotides and site-directed mutagenesis of the enzyme. New valuable insights into the mechanism of DNA polymerase fidelity were obtained. The presented study provides experimental evidence that variations of steric constraints within the nucleotide binding pocket of at least two DNA polymerases cause variations in nucleotide incorporation selectivity. Thus, our results support the concept of active site tightness as a causative in differential fidelity among DNA polymerases. 相似文献
17.
Ammonia and primary amines react with dimethyl 3-oxo-1,ω-alkanedioates to give cyclic,N-acylated enaminoesters. 相似文献
18.
Sabine Hanelt Birgit Braun Stefan Marx Hansjörg A. W. Schneider-Poetsch 《Photochemistry and photobiology》1992,56(5):751-758
We have sequenced cDNA and genomic clones coding for phytochrome of the fern Selaginella. On the amino acid level, this phytochrome shares sequence homologies with phytochromes of higher plants which range between 62 (phytochrome B of Arabidopsis) and 55 (56)% [phytochrome C of Arabidopsis (Avena)]. Introns in the Selaginella gene are short and occupy positions known from phytochrome sequences of higher plants. A rooted phylogenetic tree based on mutation distances puts Selaginella phytochrome closest to the hypothetical ancestor. A similar tree arises if the tree is constructed with partial sequences (about 200 amino acids) around the chromophore attachment site. An extension of this tree by sequences of other cryptogamic plants (Mougeotia, Ceratodon, Psilotum) shows all these sequences including those of the phytochromes B and C of Arabidopsis on a branch, well separated from the branch formed by phytochromes known to accumulate in etiolated plants. The rooted phytochrome phylogenetic tree, however, is difficult to reconcile with the fossil record. 相似文献
19.
Structural investigations of thin films of SiC, SiC with free silicon and various titanium suicides (TiSi2, TiSi and Ti5Si3) are described. The crystal phases have been identified using X-ray diffractometry. The growth of reaction products from surface reactions between silicon and deposited titanium can be observed.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
20.
Uniform, well-dispersed silver particles of various morphologies have been prepared by reducing highly acidic silver nitrate solutions with ascorbic acid in the presence of a sodium naphthalene sulfonate-formaldehyde copolymer as dispersing agent. By varying the temperature of the reaction, the free acid content, the addition rate of the reductant, and the aging time, both isometric and anisotropic silver particles could be obtained. It was found that the latter were formed by aggregation of nanosize subunits, which were identified by electron microscopy and X-ray diffractometry. 相似文献