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151.
The cluster density function of independent percolation in ad-dimensional lattice is considered. For eachn, it is shown that(p) has finitenth leftderivative at critical probabilityp
c ifd is sufficiently large. This result agrees with the Bethe lattice approximation, where thenth one-sided derivative of(p) is bounded atp
c for alln. 相似文献
152.
153.
Gerhard Wendlberger Liljana Mladenova-Orlinova Walter Göhring Regina Scharf Erich Wünsch 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1297-1312
The synthesis of the tetratriacontapeptide amide corresponding to the revised primary structure of human big gastrin I is described. For this purpose the fragments were designed in view of the maximum use of those utilized in our previous synthesis of human big gastrin I according to the first sequence proposal. Consequently the key tripeptide-Pro-Pro-His- (sequence 7–9) was prepared in suitably protected form to be used as amino or carboxyl component for assembly of the segments 1–9 and 1–14, respectively. Final condensation of the latter nona- and tetradecapeptide derivatives with the C-terminal segments 10–34 and 15–34 via the azide and the dicyclohexylcarbodiimide/N-hydroxysuccinimide procedure, respectively, leads to crude fully protected human big gastrin I. Upon deprotection by exposure to trifluoroacetic acid in presence of ethanedithiol-(1,2) as scavanger, ion exchange chromatography and partition chromatography, the desired tetratriacontapeptide amide was isolated in satisfactory yield with a high degree of purity. The identical immunological behaviour of the synthetic material, if compared with that of natural human big gastrin I, represents ulterior strong evidence for the correctness of the newly proposed structure for this putative prohormonal form of the gastrins.
Kurzmitteilung:Wünsch E., Wendlberger G., Mladenova-Orlinova L., Göhring W., Jaeger E., Scharf R., Gregory R. A., Dockray G. J., Hoppe-Seyler's Z. Physiol. Chem.362, 179 (1981). 相似文献
154.
Walter Nielsch und Gerhard Böltz 《Fresenius' Journal of Analytical Chemistry》1954,143(3):168-172
Zusammenfassung Es wird gezeigt, daß die Bestimmung des Wismuts mit Thioharnstoff in bromwasserstoffsaurer Lösung auf photometrischem Wege mit dem Gerät ELKO II durchgeführt werden kann. Hierbei benutzt man zweckmäßig das Gerät mit der Glühlampe und Filter S 47 E oder den Quecksilberbrenner in Verbindung mit Filter Hg 436. Damit die Extinktion des gelbgefärbten Komplexes von der Thioharnstoffkonzentration unabhängig wird, muß die Lösung bei Benutzung des Filters S 45 E mindestens 10% Thiohamstoff, bei Benutzung des Filters Hg 436 mindestens 5% Thioharnstoff enthalten. Auch die Bromwasserstoffsäure übt einen Einfluß auf die Ausbildung der Extinktion aus. Wenn man die Messung mit dem Filter S 45 E durchführt und den Thioharnstoffgehalt mit 12% konstant hält, so darf die Bromwasserstoffkonzentration zwischen 1,2–9,2% betragen, um gleichbleibende Extinktionswerte zu erhalten. Benutzt man das Filter Hg 436 bei der gleichen Thioharnstoffkonzentration, so muß der Bromwasserstoffgehalt zwischen 3,0–7,5% liegen. Die Temperatur übt nur einen geringen Einfluß auf die Ausbildung des ThioharnstoffWismutkomplexes aus. Die Extinktion ist zeitunabhängig. Die Extinktionswerte ändern sich innerhalb 3 Std nach Zusammengeben der Reagenslösungen nicht. Das BEERsche Gesetz ist erfüllt. Das Verfahren besitzt erhebliche praktische Bedeutung, da sich sehr viele Metalllegierungen in denen Wismut zu bestimmen ist, mit Hilfe von Bromwasserstoffsäure und Brom sehr schnell lösen lassen. 相似文献
155.
Summary Quantitation of camphechlor/toxaphene in biological matrices like cod-liver oil or fish is difficult because it is a very complex mixture of alicyclic polychlorinated compounds. Furthermore, many toxaphene components are biotransformed and photodegraded and the complex mass spectral fragmentation pattern of HRGC/MSD (electron impact (EI)) cannot be used for quantitation at the g/g-level or below. The use of several indicator-peaks after ECD-detection using the technical standard mixture for calibration does not characterize the entire pattern in a biological sample. Two averaging integration methods that are based on the entire HRGC/ECD-pattern of toxaphene compounds after separation from the PCB congeneres by adsorption chromatography on silicagel, allow a fast and accurate quantitation of the mixture in biological samples, e.g. cod-liver oil. Biological degradation does not disturb the determination because the whole pattern of the complex mixture is considered instead of only a few compounds of the parent mixture which could be degraded or not. 相似文献
156.
Walter T. Smith John M. Patterson Albert C. Kovelesky 《Journal of heterocyclic chemistry》1990,27(3):549-550
Nitration of naphtho[2,3-c][1,2,5]thiadiazole gives the 5-nitro derivative in 61–66% yield. Chlorination of this product apparently gives an unstable addition product which loses hydrogen chloride on recrystallization to give 4-chloro-8-nitronaphtho[2,3-c][1,2,5]thiadiazole. Thus, naphtho[2,3-c][1,2,5]thiadiazole under nitrating conditions behaves as a 2-substituted naphthalene rather than as an anthracene analog. 相似文献
157.
158.
Determination of amino acids in a complex matrix without derivatization is advantageous, however, difficulties are found in both the detection and the separation of those compounds. In this study, a rapid and reliable LC-MS-MS method for the quantitation of underivatized amino acids in exocellular media was established. Injections were made directly after centrifugation of the samples, without further preparation. The separation of seven underivatized amino acids was achieved on a reversed-phase C18 column with pentadecafluorooctanoic acid as a volatile ion-pair reagent, and the specific detection of most amino acids was achieved by MS-MS of the specific transitions [M + H]+-->[M + H - 46]+. The calibration curves of all analytes were linear over the range of 1.0-1000 microg ml(-1) and the detection limits ranged from 0.1 to 5 ng ml(-1), with an injection volume of 20 microl. The inter-day and intra-day precisions ranged from 2.6 to 5.7% and 4.8 to 8.2%, respectively; the mean recoveries of the seven analytes were 81-104%, 91-107% and 93-101% respectively at the spiked level of 10, 40 and 200 microg ml(-1). A large number of fermentation samples were analysed using this method. The technique is simple, rapid, selective and sensitive, and shows potential for the high-throughput quantitation of amino acids from other biological matrices. 相似文献
159.
H.-J. Machulla A. Blocher M. Kuntzsch M. Piert R. Wei J.R. Grierson 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(3):843-846
[18F]FLT (3-deoxy-3-[18F]fluorothymidine) turned out to be a tracer particularly suitable for PET imaging of tumor proliferation because of lacking degradation in vivo. To facilitate clinical studies with [18F]FLT, we investigated two new easily accessible precursors, 2,3-anhydrothymidine (AThy) and 5-O-(4,4-dimethoxytriphenylmethyl)-2,3-anhydrothymidine (DMTThy), using a common approach for introducing the label with nucleophilic [18F]fluoride. Radiochemical yields were determined in dependence on substrate concentration, reaction time and temperature. In the case of AThy (10 mg), best FLT yields were 5.3%±1.2 (130 °C, 30 min). Labeling of DMTThy (10 mg) gave 14.3%±3.3 at 160 °C within 10 minutes. Starting with an aqueous solution of 20 GBq [18F]fluoride the new method allows to produce 1.3 GBq [18F]FLT within 90 minutes ready for intravenous injection. The new labeling procedures allow [18F]FLT synthesis without lengthy preparation of the precursor and with high reproducibility mandatory for clinical application. 相似文献
160.
Wei QH Zhang LY Yin GQ Shi LX Chen ZN 《Journal of the American Chemical Society》2004,126(32):9940-9941
Unusual AuI-AgI heterometallic complexes [Au5Ag8(mu-dppm)4{1,2,3-C6(C6H4R-4)3}(CCC6H4R-4)7]3+ (R = H 1, CH3 2, But 3) were isolated by reactions of polymeric silver arylacetylides (AgCCC6H4R-4)n with binuclear gold component [Au2(mu-dppm)2(MeCN)2]2+ (dppm = bis(diphenylphosphino)methane), in which cyclotrimerization of arylacetylide -CCC6H4R-4 affords trianion {1,2,3-C6(C6H4R-4)3}3- with an unprecedented mu5-bonding mode. Compounds 1(SbF6)3-3(SbF6)3 exhibit intense photoluminescence derived from an MLCT (Au5Ag8 --> CCC6H4R-4) transition, mixed with a metal cluster-centered excited states. 相似文献