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21.
Siegfried Kästner 《Colloid and polymer science》1961,178(1):24-35
Zusammenfassung Aufbauend auf den grundlegenden Untersuchungen vonKirkwood, Kirkwood undFuoss, Hammerle undKirkwood sowieErpenbeck undKirkwood werden die allgemeinen Grundgleichungen des mechanischen und dielektrischen Relaxationsverhaltens verdünnter und hochpolymerer
L?sungen abgeleitet.
Dabei wird unter Vernachl?ssigung von Valenz- und Deformationsschwingungen das ausN Atomen bestehende Makromolekül beliebiger chemischer Struktur und beliebigen Verzweigungsgrades durch ein Modell ersetzt,
das ausK≤N Kugeln besteht, wobei die geometrische Struktur des Makromoleküls streng nachgebildet wird. Die zugeh?rigenK Kraftgleichungen werden zun?chst als eine Vektorgleichung im 3K-dimensionlen vollst?ndigen Konfigurationsraum gedeutet und anschlie?end unter Einführung eines geeigneten Koordinatensystems
in denF-dimensionalen eigentlichen Konfigurationsraum projiziert, wobeiF die Zahl der Freiheitsgrade des Molekülmodells ist. Unter Verwendung der Kontinuit?tsgleichung gewinnt man daraus die Diffusionsgleichung,
durch welche die Wahrscheinlichkeitsdichte im eigentlichen Konfigurationsraum bestimmt ist. Wird diese Differentialgleichung
gel?st, so lassen sich die komplexe Viskosit?t und die komplexe Polarisation der hochpolymeren L?sung bestimmen.
Im Rahmen der Rechnung wird gezeigt, da? die vonErpenbeck undKirkwood für das zugrundeliegende Koordinatensystem geforderten Orthogonalit?tsbedingungen nicht notwendig sind. 相似文献
22.
Hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and dodecanoic acid are components of the trail pheromone of the ant species Lasius fuliginosus. The acids were extracted from the contents of the rectal ampullae and identified by the mass spectra and gas chromatographic retention times of the corresponding methyl esters. 相似文献
23.
24.
The multielement trace analytical method ‘total reflection X-ray fluorescence’ (TXRF) has become a successfully established method in the semiconductor industry, particularly, in the ultra trace element analysis of silicon wafer surfaces. TXRF applications can fulfill general industrial requirements on daily routine of monitoring wafer cleanliness up to 300 mm diameter under cleanroom conditions. Nowadays, TXRF and hyphenated TXRF methods such as ‘vapor phase decomposition (VPD)-TXRF’, i.e. TXRF with a preceding surface and acid digestion and preconcentration procedure, are automated routine techniques (‘wafer surface preparation system’, WSPS). A linear range from 108 to 1014 [atoms/cm2] for some elements is regularly controlled. Instrument uptime is higher than 90%. The method is not tedious and can automatically be operated for 24 h/7 days. Elements such as S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br, Sn, Sb, Ba and Pb are included in the software for standard peak search. The detection limits of recovered elements are between 1×1011 and 1×107 [atoms/cm2] depending upon X-ray excitation energy and the element of interest. For the determination of low Z elements, i.e. Na, Al and Mg, TXRF has also been extended but its implementation for routine analysis needs further research. At present, VPD-TXRF determination of light elements is viable in a range of 109 [atoms/cm2]. Novel detectors such as silicon drift detectors (SDD) with an active area of 5 mm2, 10 mm2 or 20 mm2, respectively, and multi-array detectors forming up to 70 mm2 are commercially available. The first SDD with 100 mm2 (!) area and integrated backside FET is working under laboratory conditions. Applications of and comparison with ICP-MS, HR-ICP-MS and SR-TXRF, an extension of TXRF capabilities with an extremely powerful energy source, are also reported. 相似文献
25.
Six known metabolites, two new isocoumarins 4 and 8, and one new highly substituted benzoic acid derivative 9 were isolated from the ethyl acetate culture extract of a fungal endophyte, Scytalidium sp. In addition, another new benzoic acid 10 with an unusual 1,2-dicarbonyl side chain was indirectly identified from its methylated derivatives 10a-10d. 相似文献
26.
Karappulli P. Balakrishnan Thomas A. Kaden Liselotte Siegfried Andreas D. Zuberbühler 《Helvetica chimica acta》1984,67(4):1060-1069
The complexation of Cu(I) and Cu(II) by a series of 12-, 14- and 16-membered macrocyclic ligands 1–6 containing the N2S2 donor set has been studied potentiometrically, spectrophotometrically and voltammetrically. In the case of Cu(II), mononuclear complexes CuL2+ with stability constants of 1010–1015 are formed. In addition, partially hydrolyzed species Cu(L)OH+ are observed at pH > 10 for the 12-membered ligands. For Cu(I), beside the specis CuL+ with stabilities of 1012–1014, the unexpected formation of protonated species CuLH2+ was detected. In contrast to the well-known general trends in coordination chemistry, the stability of these protonated species increases relative to that of the complexes with the neutral ligand when the ring size and concomitantly the distance between neighbouring donor atoms is decreased. From the stability constants of the Cu(I)- and Cu(II)-complexes the redox potentials have been calculated and are compared to the values of E1/2 obtained by cyclic voltammetry. Despite the identical donor set the Cu(II)/Cu(I) redox potentials of the complexes are spanning a range of 340 mV or six orders of magnitude in relative stability, reflecting the importance of subtle differences in steric requirements. 相似文献
27.
The kinetics of the on/off reaction of the amino group in the side chain of tetraazamacrocyclic Cu2+, Ni2+ and Co2+ complexes has been measured. The rate law k(obs)=k(0)+k(H)[H+]+k(OH)/[H+], the sum of the forward and reverse reaction, gives rise to u-shaped pH dependences from which the three rate constants can be determined. k(H) describes the proton assisted dissociation of the amino group bound to the metal ion and is roughly correlated to the equilibrium constant of the reaction. k(OH) is determined by the protonation constant of the free amino group and the rate constant describing the binding of the amino group to the metal ion. k(0) is composed of the rate constant for the opening of the chelate ring without proton assistance and the rate for the reactivity of the ammonium group in the formation of the chelate ring. Our results show that the rates of the opening and closing of the chelate ring are very little dependent on the nature of the metal ion. 相似文献
28.
Densities of aqueous solutions of a series of polymethonium chloride and bromide salts (CH3)3–N–(CH2)n–N–(CH3)3X2 have been measured at 25°C. Apparent molal volumes have been calculated, and methylene-group contributions to the limiting apparent molal volumes °v have been estimated. Constant values of the methylene-group contribution of 16.5 and 17.0 cm3-mole–1 were obtained for the bromide and chloride salts, respectively. These values are consistent with methylene-group contributions reported for other series of organic electrolytes. 相似文献
29.
Free-energy-perturbation theory from molecular dynamics calculations has been used to obtain the DeltaG of adjoining cavities' formation in water. The DeltaGs for systems with three, five and seven cavities are compared with that of a single cavity of the same volume, and found to be in good agreement. The conditions under which the analytical formulation of the energy of cavity formation proposed by Pierotti holds are discussed. The data for a single cavity have been tabulated and can lend themselves to a simple numerical implementation in standard quantum chemical packages, which can be used when high accuracy for DeltaG(cav) is required. 相似文献
30.
The rate of the reaction between ethyl tosylate and chloride as well as bromide ion has been measured in hexamethylphosphoric triamide in the presence of several counterions. Rate constants for the free ions at 25.0° are 14.4 mole?1 for chloride and 2.0 mole?1min?1 for bromide, both independent of the cation used. The equilibrium constants for ion pair dissociation of lithium-, ammonium- and tetra-n-butylammonium chloride are 3.97 × 10?2, 1.52 × 10?3 and 6.36 × 10?3 mole, and for the corresponding bromides 3.30 × 10?2, 9.65 × 10?3, and 9.62 × 10?3 mole. 相似文献