über die Struktur aus der Gasphase kondensierter Schichten aus CH2-Kettenmolekeln

Zusammenfassung Die Struktur von Schichten aus CH₂-Kettenmolekeln (n-Paraffine und Abbauprodukte von Poly?thylen), die aus der Dampfphase bei Auff?ngertemperaturen zwischen −180 und +150 ‡C kondensiert wurden, wurde mit Hilfe der UR-Absorption untersucht. Bei Kondensationstemperaturen, die ungef?hr gleich oder h?her als der Schmelzpunkt der Substanzen sind, tritt auf frischen NaCl-Spaltfl?chen eine Epitaxie auf. Da das Aufwachsgesetz dieser Epitaxie bekannt ist, konnte bei den untersuchten Schichten aus der Winkelabh?ngigkeit des Absorptionsverh?ltnisses des 725 cm⁻¹-Dubletts die Gr?\e des kristallin orientierten, des kristallin nicht orientierten und des amorphen Anteils bestimmt werden. Abbauprodukte von Poly?thylen, die bei +150 ‡C auf frischen NaCl-Spaltfl?chen kondensiert wurden, haben einen kristallin orientierten Anteil von 82%. Schichten, die bei Temperaturen unterhalb des Schmelzpunktes der Substanzen kondensiert werden, haben bei Zimmertemperatur von der Unterlage unabh?ngige Texturorientierungen. Es konnten drei Typen von Texturorientierungen unterschieden werden. Zwischen dem Typ dieser bei Zimmertemperatur vorliegenden Texturorientierung und dem vorher bei der Kondensationstemperatur entstehenden Aufbau der Schichten besteht ein eindeutiger Zusammenhang.

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Summary By infrared spectroscopy the structure of films of CH₂-chain molecules (n-paraffins and degradation products of polyethylene) condensed between −180 ‡C and +150 ‡C has been studied. If the condensation temperature is approximately equal to or higher than the melting point of the sample, epitaxy is observed on fresh NaCl cleavage surfaces. Since the orientation of the crystallites by epitaxy on NaCl is well known, it was possible to determine the amounts of crystalline oriented, crystalline but not oriented and amorphous parts in the condensed films by a study of angular dependence of the absorption ratio of the 725 cm⁻¹ dublett lines. Degradation products of polyethylene condensed at +150‡C on fresh NaCl cleavage surfaces show a crystalline oriented part of 82%. If the condensation temperature is below the melting point, the films show texture orientations which are independent from the sublayer. We found three different types of this orientation. There is a correlation between the type of texture orientation observed at room temperature and the structure of the films found at the condensation temperature previously.

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Herrn Professor Dr.K.- H. Hellwege danke ich wieder fur die Anregung zu der Arbeit und für zahlreiche Diskussionen. Ferner danke ich der Forschungsgesellschaft Kunststoffe e. V. für die Unterstützung der Arbeit und der Fa. Shell, Amsterdam, für die überlassung von n-Paraffinen.     

Synthesis,Base Pairing,and Structural Transitions of Oligodeoxyribonucleotides Containing 8-Aza-2′-deoxyguanosine

The synthesis of oligonucleotides containing 8-aza-2′-deoxyguanosine (z⁸G_d; 1 ) or its N⁸-regioisomer z⁸G_d^* ( 2 ) instead of 2′-deoxyguanosine (G_d) is described. For this purpose, the NH₂ group of 1 and 2 was protected with a (dimethylamino)methylidene residue (→ 5, 6 ), a 4,4′-dimethoxytrityl group was introduced at 5′-OH (→ 7, 8 ), and the phosphonates 3a and 4 as well as the phosphoramidite 3b were prepared. These building blocks were used in solid-phase oligonucleotide synthesis. The oligonucleotides were characterized by enzymatic hydrolysis and melting curves (T_m values). The thermodynamic data of the oligomers 12–15 indicate that duplexes were stabilized when 1 was replacing G_d. The aggregation of d(T-G-G-G-G-T) ( 18 ) was studied by RP 18 HPLC, gel electrophoresis and CD spectroscopy and compared with that of oligonucleotides containing an increasing number of z⁸G_d residues instead of G_d. Similarly to [d(C-G)]₃ ( 12a ), the hexamer d(C-z⁸G-C-z⁸G-C-G) ( 14 ) underwent salt-dependent B-Z transition.     

A note on the QCD corrections to forward-backward asymmetries of heavy-quark jets inZ decays

The measurement of the forward-backward asymmetries of heavy quarks provides one of the most precise determinations of sin² _W inZ decays. We discuss in detail the one-loop QCD radiative corrections to these asymmetries. Results are given for single heavy-quark jet asymmetries and asymmetries of the thrust axis, as well as for heavy-quark two-jet final states.     

QCD corrections to charm quark production in deep-inelastic neutrino scattering

We evaluate theO(_s) corrections to weak, charged current production of charm quarks. For perturbative subtractions and parton densities in the deep inelastic scheme the residual corrections to p and charm production structure functionsF ₂,F ₃ andF _L are presented. The consequences of these corrections with respect to they dependence of the cross section is discussed.Supported by Bundesministerium für Forschung und Technologie. 05 5HH91P (8), Bonn, FRG     

Development of the Tetron Model

The main features of the tetron model of elementary particles are discussed in the light of recent developments, in particular the formation of strong and electroweak vector bosons and a microscopic understanding of how the observed tetrahedral symmetry of the fermion spectrum may arise.     

Alkoholergiebigkeit von Getreide und Kartoffeln

Analytical and Bioanalytical Chemistry -     

Regularized total least squares based on the nonlinear Arnoldi method

A computational approach for solving regularized total least squares problems via a sequence of quadratic eigenvalue problems has recently been introduced by Sima, Van Huffel, and Golub. Combining this approach with the nonlinear Arnoldi method and reusing information from all previous quadratic eigenvalue problems, together with an early update of search spaces we arrive at a very efficient method for large regularized total least squares problems. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cartan Geometries and Dynamics

We show how some basic dynamical ideas can be brought to bear on the study of Cartan geometries. In our main results, we give conditions for certain types of Cartan geometries to have constant curvature. We also consider ergodic actions of `higher-rank' semisimple groups on bundles supporting (not necessarily invariant) Cartan connections and show that these are `standard locally homogeneous' actions provided that some noncompact 1-parameter subgroup `preserves' a Cartan geometry.