Polymerisationskinetische Versuche mit α-Azoisobuttersäurenitril und Benzoylperoxyd an Styrol zur Aufklärung der Geschwindigkeit von Start- und Übertragungsreaktion

Zusammenfassung Die Geschwindigkeit des Zerfalls des -Azoisobuttersäurenitrils (AIBN) wird in Styrollösung bei 50 und 70° gemessen, ebenso die Geschwindigkeit der dadurch angeregten Polymerisation und die Grundviskosität der Polymerisate.Höchstens 72% der durch den Zerfall der Azoverbinding entstandenen Radikale werden zum Start der Polymerisation ausgenützt.Aus dem Vergleich zwischen der durch AIBN und der durch Peroxyde angeregten Polymerisation werden die Übertragungskonstanten für Benzoylperoxyd sowie einige andere Acylperoxyde berechnet.     

Field detachment of the negatively charged water dimer

Beams of Ar _m (H₂O) ₂ ^? ,m=0 to 4, are passed through an electric field and separated with a quadrupole mass spectrometer. Form<=2 the signal disappears at 31±1 kV/cm. Form=3 and 4 and larger (H₂O) _n ^? (n≧6) no field detachment is observed up to 40 kV/cm. The application of these results to the binding of excess electron in water clusters is discussed.     

An outline of the nuclear activation system at the Atominstitut

The process of nuclear activation analysis is rather complex compared to other analytical techniques. For improvement it is necessary to analyse performance of all individual components and to establish a list of requirements for further development of the system. The analysis of short-lived radionuclides offers a number of benefits to the analyst, but on the other hand calls for an analytical system, the organization of which is rather different from that of conventional NAA systems. This paper presents a summary of the Atominstituts nuclear activation system, its layout and organization. Sample preparation, activation, detection and computer action are described in their present form and in their intended future development.     

X-ray crystal structures of halogen containing nucleobase derivatives in unsolvated and DMSO solvated forms

A series of halogenated nucleobase derivatives 1–4 is reported to yield solvent-free (2) and DMSO solvated crystals (1, 3, 4) on the crystallization from DMSO with one of them (4) containing an additional molecule of water. The molecular and crystal structures are described and comparatively discussed with reference to previous results on related compounds. The molecule of 1 is planar, molecules of 2 and 3 show syn alignment with reference to the heterocyclic ring and common C2′-endo conformation of the ribose residue, while 4 is also syn aligned but C4′-exo in the sugar conformation. The packing structures reveal typical aggregations created via networks of hydrogen bonds. These involve conventional N–H···N, N–H···O and O–H···O interactions between nucleobase and ribose units as well as solvent molecules, additionally supported by weak C–H···O contacts but excluding the participation of halogen···halogen interactions as well as halogen···heteroatom contacts in the supramolecular structure formation.     

Kolmogorov-Smirnov two-sample test based on regression rank scores

We derive the two-sample Kolmogorov-Smirnov type test when a nuisance linear regression is present. The test is based on regression rank scores and provides a natural extension of the classical Kolmogorov-Smirnov test. Its asymptotic distributions under the hypothesis and the local alternatives coincide with those of the classical test. (Supplement to the special issue of Appl. Math. 53 (2008), No. 3) This work was supported by the Czech Science Foundation under Grant No. 201/05/H007 and by Research Project LC06024.