Self-assembled alkanethiol structures on gold: A further insight into the origins of structural rearrangement phenomena

Self-assembled structures of alkanethiols that have been deposited on gold from ethanolic solutions are susceptible to both chemical and physical changes: ethanol provides a medium for the formation of S-alkyl hydrogen thiocarbonates and related compounds via reaction with dissolved, atmospheric, CO₂. Deposition from ethanolic solutions results in multilayered structures incorporating these compounds, which at room temperature are susceptible to time-dependent structural rearrangement and molecular migration.     

Some methodological problems concerning nonisothermal kinetic analysis of heterogeneous solid–gas reactions

Isoconversional methods, those using only one curve α = α(T) (α is the conversion degree and T is the temperature), and invariant kinetic parameter method were applied to estimate the kinetic parameters from the following nonisothermal data: (1) simulated TG curves for a single reaction; (2) TG curves for thermal degradation of PVC; and (3) TG curves for the dehydration of CaC₂O₄·H₂O. The results obtained by applying various methods for the same system are compared and discussed. Finally, a procedure of kinetic analysis is suggested. Its application could lead to kinetic parameter values that can be used to predict either α = α(t) curves for other heating rates or α = α(T) curves for isothermal conditions. © 2001 John Wiley & Sons, Inc. Int J chem Kinet 33: 564–573, 2001     

Amplification of a cyclic mixed-metalloporphyrin tetramer from a dynamic combinatorial library through orthogonal metal coordination

A cyclic porphyrin tetramer, consisting of two bis-phosphine substituted zinc(II) porphyrin units and two Rh(III)TPP units, is selected and amplified virtually quantitatively from a dynamic combinatorial library using 4,4'-bipy as a scaffold and using orthogonal binding modes.     

Double-quantum dipolar recoupling at high magic-angle spinning rates

A full investigation of the possible homonuclear double-quantum recoupling sequences, based on the RN family of sequences with N < or = 20, is given. Several new RN sequences, R16(6)(5), R18(8)(5), and R18(10)(5), were applied at high magic-angle spinning rates and compared with theory. The R18(10)(5) technique can be used to recouple dipolar couplings at spinning rates up to 39 kHz, and the application of the sequence in an INADEQUATE experiment is shown for a spinning rate of 30 kHz.     

Contributions a l'etude cinetique des decompositions endothermiques dans des systemes solide-gaz,a l'aide des donnees thermogravimetriques

Résumé On a déterminé les paramètres cinétiques des réactions de décomposition de quelques combinaisons complexes des halogénures et pseudohalogénures de cobalt, nickel, manganèse, cuivre et cadmium, avec l'ammoniaque, la pyridine et des pyridines substituées. Pour les réactions d'ordre zéro, les valeurs des facteurs préexponentiels, calculées en considérant comme étape limitante la diffusion du composant volatil à travers la couche de la substance décomposée, concordent de façon satisfaisante avec celles déterminées expérimentalement.

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Kinetic parameters were determined for the decomposition reactions of some com plexes of cobalt, nickel, manganese, copper and cadmium halides and pseudohalides with ammonia, pyridine and substituted pyridines. For the zero order reactions, the values of the pre-exponential factors calculated assuming as limiting step the diffusion of the volatile component through the layer of the decomposed substance, are in satisfactory agreement with the experimental values.

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Zusammenfassung Es wurden die kinetischen Parameter der Zersetzungsreaktionen einiger Komplexe der Halogenide und Pseudohalogenide von Kobalt, Nickel, Mangan, Kupfer und Kadmium mit Ammoniak, Pyridin und substituiertem Pyridin bestimmt. Bei den Reaktionen von Null-Ordnung zeigten die preexponentiellen Koeffizienten, berechnet, indem für die limitierende Stufe die Diffusion des flüchtigen Bestandteils durch die Schicht der zersetzten Substanz betrachtet wurde, gute Übereinstimmung mit den experimentellen Werten.

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Die extremalität gewisser teichmüllerscher abbildungen des einheitskreises

Ohne Zusammenfassung