DTA was applied to investigate amorphous sulfur samples remelted at different temperatures T s. For the sample remelted at TI< 159 ~ an exothermic process I occurs in the range 30-40 ~ Transformation of orthorhombic to monoclinic sulfur, melting and polymerization of $8 rings was observed at higher temperatures. For the sample remelted at T I > 159 ~ a new, fast exothermic process II occurs at ambient temperature, follbwed by an exothermic process III at slightly higher temperature. The next, also exothermic process IV is detected in the vicinity of the melting point. The heats of the thermal effects for all the above-mentioned processes, and the part of sulfur insoluble in CS2, were determined. An attempt was made to evaluate the mechanism of the transformations.Durch rasche Abkfihlung einer Schwefelschmelze entsteht ein amorphes Produkt. Es enth/ilt viel Ss-Ringe (bis 94%), kleine Menge yon anderen Ringen (haupts/ichlich: S6-etwa 1%, S7-etwa 4%, Sg-etwa 0,5%, S12-etwa 0,4%) und Polymere S, (n = 1 000-12 000) [1-3], ffir die in dieser Arbeit die Annahme der Kettenstruktur zul/issig zu sein scheint [4,5]. Mit der Erh6hung der Schmelztemperatur T I yon 116 bis 243 ~ nimmt der Gehalt an Polymeren von 0,17 bis 40% zu [1]. Die Zunahme ist bei T I = 159 ~ sprunghaft, was durch die Polymerisation der SsRinge verursacht wird [2][3][4][5].Der amorphe Schwefel wander sich schon bei Zimmertemperatur exotherm in die rhombische Modifikation (S~) um [6], die aus regelm/issig angeordneten S8-Ringen besteht [7]. W/ihrend dieser Umwandlung sollten folgende Prozesse ablaufen:A) Die Umgestaltung der Ketten in unregelm/issig gebaute Ss'-Ringe:

We study bivariate stochastic recurrence equations (SREs) motivated by applications to GARCH(1, 1) processes. If coefficient matrices of SREs have strictly positive entries, then the Kesten result applies and it gives solutions with regularly varying tails. Moreover, the tail indices are the same for all coordinates. However, for applications, this framework is too restrictive. We study SREs when coefficients are triangular matrices and prove that the coordinates of the solution may exhibit regularly varying tails with different indices. We also specify each tail index together with its constant. The results are used to characterize regular variations of bivariate stationary GARCH(1, 1) processes.

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The angular correlation of annihilation photons (ACAP) for multilayer aluminium-aluminium oxide sandwich had been measured. The ACAP observed for the sandwich plane parallel to the annihilation spectrometer axis appeared to be broader than the one observed when the plane was perpendicular to the axis.