A new data management concept for AES and SAM

The problem of interchangeability of surface analytical data is gaining increasing importance in multi-method surface analysis. There are various surface analytical instruments in different laboratories on several automation levels. For these instruments, which are controlled by computer systems working with company-specific software under various operating systems, a standardised data format is necessary to allow an exchange of data. Therefore, we are developing a software package for the transfer, archiving and editing of surface analytical data called MAXMIND (management and exchange of method independent data), which is based on public domain software products. It allows the storage of all available and necessary information on experimental conditions and all parameters specific for a number of analytical techniques such as AES, SAM, XPS, SIMS, STM and AFM. Additionally, all data concerning the sample-preparation and the state of the instrument are included in order to allow a well-founded evaluation of the data and improved reproducibility of the experiment. This concept is demonstrated in detail for the two Auger techniques AES (Auger Electron Spectroscopy) and SAM (Scanning Auger Microscopy).Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

1′,3′,3′-Trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline]: its thermal enantiomerization and the equilibration with its merocyanine

The enantiomers of the title compound, the important photochromic material (RS)-1b, have been enriched semipreparatively by liquid chromatography. As a consequence, we were able to determine the barrier of the thermal interconversion (R)-1b(S)-1b via time-dependent polarimetry, amounting to ΔG^≠=85.9 kJ/mol at 22.0°C in d⁶-DMSO (Table 2). The thermal equilibration of the corresponding merocyanine 2b was monitored in d⁶-DMSO by time-dependent ¹H NMR, resulting in ΔG₁^≠=102.8 and ΔG₂^≠=92.0 kJ/mol at 22°C (Table 1). This means that, starting from (RS)-1b, the opened isomer 2b is attained by a slow reaction (ΔG₁^≠=102.8 kJ/mol, Fig. 4). Therefore, the merocyanine 2b cannot be identified with the intermediate required for the fast process of C(sp³)–O bond cleavage (ΔG^≠=85.9 kJ/mol) upon the above enantiomerization of (RS)-1b. Apparently, these two thermal isomerizations (Fig. 4) are independent of each other. The structure of the unknown intermediate of the interconversion (R)-1b(S)-1b must therefore differ from the known one of merocyanine 2b.

Table 1. Equilibration between spiro compounds (RS)-1 and merocyanines 2 at 22°C, measured by time-dependent UV absorptions[3] for (RS)-1a2a and by time-dependent ¹H NMR intensities for the other compounds

Full-size table (8K)

C–H...O and C–H...N interactions in RNA structures

Small molecule studies indicate that C–H...X interactions (X: O,N) constitute weak H-bonds. We have performed a comprehensive analysis of their occurrence and geometry in RNA structures. Here, we report on statistical properties of the total set of interactions identified and discuss selected motifs. The distance/angle distribution of all interactions exhibits an excluded region where the allowed C–H...X angle range increases with an increasing H...X distance. The preferred short C–H...X interactions in RNA are backbone-backbone contacts between neighbour nucleotides. Distance/angle distributions generated for various interaction types can be used for error recognition and modelling. The axial C2′(H)...O4′ and C5′(H)...O2′ interactions connect two backbone segments and form a seven-membered ring that is specific for RNA. An AA base pair with one standard H-bond and one C–H...N interaction has been identified in various structures. Despite the occurrence of short C–H...X contacts their free energy contribution to RNA stability remains to be assessed. Received: 17 May 1998 / Accepted: 4 August 1998 / Published online: 2 November 1998     

Joseph covariance formula adaptation to Square-Root Sigma-Point Kalman filters

Nonlinear Dynamics - The development of a reliable Sense And Avoid (SAA) system is one of the limiting aspects for the integration into civil airspace of unmanned aerial vehicles, for which the...     

Visible-Light-Mediated Liberation and In Situ Conversion of Fluorophosgene

The first example for the photocatalytic generation of a highly electrophilic intermediate that is not based on radical reactivity is reported. The single-electron reduction of bench-stable and commercially available 4-(trifluoromethoxy)benzonitrile by an organic photosensitizer leads to its fragmentation into fluorophosgene and benzonitrile. The in situ generated fluorophosgene was used for the preparation of carbonates, carbamates, and urea derivatives in moderate to excellent yields via an intramolecular cyclization reaction. Transient spectroscopic investigations suggest the formation of a catalyst charge-transfer complex-dimer as the catalytic active species. Fluorophosgene as a highly reactive intermediate, was indirectly detected via its next downstream carbonyl fluoride intermediate by NMR. Furthermore, detailed NMR analyses provided a comprehensive reaction mechanism including a water dependent off-cycle equilibrium.     

Groups whose subgroups have small automizers

IfH is a subgroup of a groupG, theautomizer ofH inG is the group of all automorphisms ofH induced by elements of its normalizerN _G (H). the subgroupH is said to havesmall automizer ifAut _G (H)=Inn(H), i.e. ifN _G (H)=HC _G (H). This article is devoted to the study of groups for which many subgroups have small automizer. In Memoriam Valeria Fedri R. Brandl wishes to express his sincerest thanks for the warm hospitality offered by the Department of Mathematics of the University of Napoli “Federico II” for the time of writing this paper.     

Heavy ion induced desorption (HIID) mass spectrometry of Langmuir-Blodgett films built from CD-salts of fatty acids

Langmuir-Blodgett films made from cadmium salts of fatty acids have been analyzed by means of the heavy ion induced mass spectrometry in which megaelectronvolt ions are used to desorb sample specific molecules. The method is a useful tool for detecting incomplete salt formation at the subphase and the replacement of the original counter-ion by ions from the substrate surface. The method exhibits a depth sensitivity which can be varied between 2 to 14 layers depending on the energy loss of the heavy ion.