Sensitivity of trace gas abundances retrievals from infrared limb emission spectra to simplifying approximations in radiative transfer modelling

The accuracy of trace gas abundances retrieved from spectrally resolved infrared limb emission measurements relies, among other things, on the appropriate modelling of radiative transfer through the actual atmosphere. We quantify the mapping of several commonly applied simplifications in radiative transfer modelling on the trace gas abundances retrieval error at the example of the Michelson interferometer for passive atmospheric sounding (MIPAS)/environmental satellite (ENVISAT) space borne Fourier transform infra-red limb emission experiment. The Karlsruhe optimized and precise radiative transfer algorithm (KOPRA) which was used as a tool for this study will be introduced. KOPRA supports accurate modelling of the particular instrument requirements of MIPAS and the observation scenarios during the ENVISAT mission, in particular with respect to its viewing direction and its altitude coverage of the atmosphere. We show that disregarding of horizontal temperature inhomogeneities and non-local thermodynamic equilibrium effects, insufficient accuracy in modelling of field-of-view and apodisation effects, and disregarding individual profiles of isotopic species play the key roles in radiative transfer modelling and lead to systematic retrieval errors which can by far exceed the expected random retrieval error caused by measurement noise.     

A Helly theorem for geodesic convexity in strongly dismantlable graphs

A (finite or infinite) graph G is strongly dismantlable if its vertices can be linearly ordered x₀,…, x so that, for each ordinal β < , there exists a strictly increasing finite sequence (i_j)_{0 j n} of ordinals such that i₀ = β, i_n = and x_ij+1 is adjacent with x_ij and with all neighbors of x_ij in the subgraph ofG induced by {x_y: β γ }. We show that the Helly number for the geodesic convexity of such a graph equals its clique number. This generalizes a result of Bandelt and Mulder (1990) for dismantlable graphs. We also get an analogous equality dealing with infinite families of convex sets.     

Synthesis of a novel heterocyclic system: 8-Fluro- 1,2,3,4,4a,10a-hexahydro-5H-[1]benzopyrano[2,3-c]pyridin-5-ol

The Synthesis of the title compound is described and its structure elucidated by ¹H nmr spectroscopy.     

Beiträge zur Chemie der Pyrrolpigmente, 59. Mitt.

By investigation of bilatrienes-abc possessing a rigid tautomeric structure within their pyrromethene fragment, using¹³C-NMR spectroscopy, a criterion for the fixation of tautomerism was deduced: if there is a signal in the otherwise unoccupied shift region between 157 and 170 ppm corresponding to an azomethine fragment, tautomerism is fixed. If there is no signal in this region there is a rapidly equilibrating system of the two possible tautomers. This criterion may be used as well for natural substitution patterns. Moreover, assignment of the¹³C-signals by correlation with the easily assigned¹H-NMR signals establishes the position of the fixed tautomeric system. The criterion is applied as well to the 2,3-dihydrobilatrienes-abc where it is in accord with the results gained from a coupling criterion reported earlier.

     

Photo-stimulated CVD of SiNx for GaAs IC applications

The characteristics of silicon nitride deposited by a photo-enhanced CVD process have been investigated. The nitride films are used as inter metal insulator in GaAs ICs. For this application the step coverage is the most crucial aspect. The photo-CVD of SiN_x proves to be a surface determined deposition process, even in the case of undercutted structures. The insulation between first and second metallization was measured on a contact test structure with 1800 cross-overs. The insulating resistance in this structure is in the GΩ range even if the nitride is only 300 nm thick. A thickness uniformity of 4% for a batch of six 3 inch wafers and a reproducibility of 5% were obtained for 300 nm thick films, the intrinsic tensile stress being as small as 10⁷ to 10⁸ dyn/cm². The threshold voltage shift due to deposition was only -25 mV for MESFETs in GaAs ICs.     

Nouvelles syntheses de Me2SiCl2 et Me3SiCl

Partial reduction of MeSiCl₃ and Me₂SiCl₂ using CaH₂ or (TiH₂)_n at high temperature (300°C) leads to MeSiHCl₂ and Me₂SiHCl, respectively, in good yields but in low proportion. In the presence of AlCl₃ as catalyst the reaction affords Me₂SiCl₂ and Me₃SiCl, in yields higher than those previously observed in the absence of a reducing agent. These redistribution reactions involve MeSiHCl₂ and Me₂SiHCl as intermediates. Consequently Me₂SiHCl with or without Me₂SiCl₂ and Alcl₃ deposited on carbon black as catalyst can undergo disproportionation to give Me₃SiCl.