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981.
Katharina Vollmayr Joseph D. Reger Manfred Scheucher Kurt Binder 《Zeitschrift für Physik B Condensed Matter》1993,91(1):113-125
We consider the rounding and shifting of a firstorder transition in a finited-dimensional hypercubicL
d geometry,L being the linear dimension of the system, and surface effects are avoided by periodic boundary conditions. We assume that upon lowering the temperature the system discontinuously goes to one ofq ordered states, such as it e.g. happens for the Potts model ind=3 forq3, with the correlation length of order parameter fluctuation staying finite at the transition. We then describe each of theseq ordered phases and the disordered phase forL by a properly weighted Gaussian. From this phenomenological ansatz for the total distribution of the order parameter, all moments of interest are calculated straight-forwardly. In particular, it is shown that forL exceeding a characteristic minimum sizeL
min the forthorder cumulantg
L
(T) exhibits a minimum atT
min>T
c, withT
min–T
cL
–d and the value of the cumulant and the minimum (g(T
min)) behaving asg(T
min)L
–d. All cumulantsg
L
(T) forL approximately intersect at a common crossing pointT
crossL
–2d, with a universal valueg(T
cross)=1–n/2q, wheren is the order parameter dimensionality. By searching for such a behavior in numerical simulation data, the first order character of a phase transition can be asserted. The usefulness of this approach is shown using data for theq=3,d=3 Potts ferromagnet. 相似文献
982.
Seeded beam expansions of high-temperature sodium vapour in helium, neon, argon, krypton and nitrogen carrier gases are examined. Photoionization coupled with mass spectroscopic detection is used to determine beam constituents. Contrary to non-seeded supersonic expansions, in which the abundance of sodium clusters observed decreases exponentially with increasing cluster size, large abundances of higher clusters (Nax, x ?65) are observed. Maxima centered at m/z = 161, m/z = 437 and m/z = 874 occur under certain conditions. 相似文献
983.
Petra Kindt Wolfgang Dölling Manfred Augustin 《Monatshefte für Chemie / Chemical Monthly》1989,120(10):871-878
Summary Dithiocarbamic acid esters1 with CH-acidic methylene group adjacent to nitrogen react in the system dimethylformamide +2 equivalent sodiumtert. butoxide with carbon disulphide yielding 1,3-thiazoline-2-thiones3. 2,5-Bis(alkylthio)-1,3,-thiazoles6 are available via dithiocarboxylation of isothiocyanate5. 相似文献
984.
985.
Iridoidglucosides from Leucocarpus perfoliatus G. DON . The known iridoid glucoside boschnalosid (1) was isolated from Leucocarpus perfoliatus in addition to the hitherto unknown yuheinosid, for which structure 2 was deduced. 相似文献
986.
Zusammenfassung Es wird eine Methode zur kolorimetrischen Bestimmung der Kristallviolettbase in benzolischen Lösungen beschrieben. Das Prinzip gründet sich auf der Salzbildung der farblosen Base mit der ebenfalls in Benzol löslichen Pikrinsäure. Dabei resultiert das tief blauviolett gefärbte KV-Pikrat, dessen Konzentration mit dem Spektralphotometer ermittelt wird.Mit 4 Abbildungen 相似文献
987.
Nicole Kunesch Yves Rolland Jacques Poisson P. L. Majumder R. Majumder A. Chatterjee Vincent C. Agwada Jorge Naranjo Manfred Hesse Hans Schmid 《Helvetica chimica acta》1977,60(8):2854-2859
The Structure of bis-indoline alkaloids of a novel type The structure of folicangine 4 , a bis-indoline alkaloid from the leaves of Voacanga africana, is obtained by correlation with voafolidine 3a and isovoafolidine 3b . It requires an ether bridge between the two parts of the molecule, as in subsessiline (amataine 5a ). Subsessiline-lactone, from the leaves of Voacanga thouarsii has structure 5b proved by correlation with 5a . The CD. curves of double-indole alkaloids of vobtusine type are given (Table 3). 相似文献
988.
Cr(III) complexes of tridendate imine and amine ligands with N, P, O, S donor atoms 1 and 2 have been prepared and tested as catalysts in the oligomerisation and polymerisation of ethylene giving excellent selectivity towards 1-hexene and polymerisation to polyethylene when activated with cocatalysts. X-ray structure analyses of the precatalysts 1a-c, 1i, and 2b are investigated. The metal-ligand binding in 1a and 1b is nearly the same, which leads to similar catalytic activities of these precatalysts. 相似文献
989.
990.
Let (A,M) be a noetherian local ring. For certain equimultiple ideals I in A we try to relate the Gorenstein property of the Rees algebran and of A itself. In particular we n0 treat the case of equimultiple prime ideals of height two and the case I=M. The results underscore a natural conjecture, s. Thm. 2.6. and 3.2. 相似文献