3-Amino-thieno[2,3-b]furane und 3-Amino-thieno[3,2-b]furane

3-Amino-thieno[2,3-b]furans and 3-Amino-thieno[3,2-b]furans The O-alkylation of 2-hydroxy-thiophene-3-carbonitriles ( 1 ) with α-bromocarbonyl compounds yields the 2-alkoxy-thiophene-3-carbonitriles ( 2a–f ) among them 2-benzoylmethoxy-thiophene-3-carbonitriles ( 2a–c ) which undergo Thorpe-Ziegler-cyclization to form the 3-amino-2-benzoyl-thieno[2,3–b]furans ( 3 ) in low yields. The 2-acyl-3-amino-thieno[3,2–b]furans and ethyl 3-amino-thieno[3,2–b]furan-2-carboxylates ( 6 ) are synthesized in similar manner from 3-hydroxy-thiophene-2-carbonitriles ( 4 ) and α-halogencarbonyl compounds via 3-acylmethoxy- and 3-ethoxycarbonylmethoxy-thiophene-2-carbonitriles ( 5 ) with high yields.     

Towards to a system analytical and modelling approach for integration of ecological, hydrological, economical and social components of disturbed regions

As a consequence of surface coal mining, past landscapes within the Lusatian coal mining region were disturbed (land cover, forest, agro- and other ecosystems, geological material, hydrology), paralleled by strongly changed economic and socio-economic conditions (unemployment, emigration due to slowing down of mining activity in the region). The task is to restore the landscape and to improve the present state of the economic and socio-economic conditions, as well. Consented goal states for both the ecological and economic system in the region and consistent planning and management options (PMO) for such economic sectors, which are linked to natural resources (terrestrial, hydrological), are to be designed. They must be ecologically and economically evaluated, assessed and selected for real implementation.In order to handle such a complex problem, a comprehensive analysis of the whole system with subsequent multiscaled modelling efforts is needed. The final aim is to establish an interactive, effective, sufficiently simple decision support system for the actors in the disturbed region.The future responses of the landscape variables and the economical and social characteristics as an answer to economic sector PMO (e.g. PMO for control in agriculture, forestry, hydrology a.o.) can be approximately calculated, and subsequently evaluated and assessed by such an appropriately tailored simulation and decision support tool.In this study, the complex problem and the ecologic and economic system with its components are analysed and structured. Based on this, principles of stepwise model building and its usage (e.g. in if-than-simulation experiments as scenario analyses of the effects under changing non-modelled political and economical boundary conditions) toward an integrated approach are proposed.In this study, the present state of the disturbed region is described briefly (Section 1), and a rough scheme of the ecological and socio-economic structure of the region ( Section 2) as well as of the structure of the problem, which must be solved ( Section 3) and the role of the models in decision support ( Section 4) is outlined. In Section 5, the tasks of analysing and modelling of the components in the Lusatian coal mining region are derived, and in Section 6, the main steps in module building and its usage are briefly described. Finally, some conclusions are drawn.     

Schrifttumsberichte

Ohne Zusammenfassung     

Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate

Tricalcium silicate (Ca₃SiO₅) with a very small particle size of approximately 50 nm has been prepared and hydrated for a very short time (5 min) by two different modes in a paste experiment, using a water/solid-ratio of 1.20, and by hydration as a suspension employing a water/solid-ratio of 4000. A phase containing uncondensed silicate monomers close to hydrogen atoms (either hydroxyl groups or water molecules) was formed in both experiments. This phase is distinct from anhydrous tricalcium silicate and from the calcium-silicate-hydrate (C-S-H) phase, commonly identified as the hydration product of tricalcium silicate. In the paste experiment, approximately 79% of silicon atoms were present in the hydrated phase containing silicate monomers as determined from ²⁹Si{¹H} CP/MAS NMR. This result is used to show that the hydrated silicate monomers are part of a separate phase and that they cannot be attributed to a hydroxylated surface of tricalcium silicate after contact with water. The phase containing hydrated silicate monomers is metastable with respect to the C-S-H phase since it transforms into the latter in a half saturated calcium hydroxide solution. These data is used to emphasize that the hydration of tricalcium silicate proceeds in two consecutive steps. In the first reaction, an intermediate phase containing hydrated silicate monomers is formed which is subsequently transformed into C-S-H as the final hydration product in the second step. The introduction of an intermediate phase in calculations of the early hydration of tricalcium silicate can explain the presence of the induction period. It is shown that heterogeneous nucleation on appropriate crystal surfaces is able to reduce the length of the induction period and thus to accelerate the reaction of tricalcium silicate with water.     

MONITORING THE SURFACE TENSION OF REACTIVE EPOXY-AMINE SYSTEMS UNDER DIFFERENT ENVIRONMENTAL CONDITIONS

Two commercially available amine-cured epoxy resin formulations were studied under different environmental conditions with regard to the surface tension evolution using axisymmetric drop shape analysis (ADSA). By employing a new strategy, ADSA was used to monitor simultaneously the surface tension and the density of these reactive mixtures from sessile drops. The kinetics of the bulk reactions were quantified by Fourier transform infrared (FTIR) spectroscopy, and the changes in the molecular composition of the surface region were studied by X-ray photoelectron spectroscopy (XPS).

In both formulations, the surface tension values of the amine hardeners were lower than those of the epoxy resins. For one system, the surface tension of the mixture was similar to the surface tension of the hardener. In this case, the hardener migrates to the surface and determines the surface tension of the mixture, as could be proved by XPS measurements. In the other case, the surface region contained only a very small amount of nitrogen, indicating that the nitrogen-containing groups of the hardener were not enriched in the surface region of this mixture. Its surface tension was similar to that of the pure epoxy resin.

In a controlled argon atmosphere, the surface tension of the reactive epoxy-amine systems considered here changed very little as the curing reaction proceeded. The time-dependent changes of the surface tension of the mixtures were caused by environmental factors, particularly the presence of carbon dioxide and water. Such factors can produce complicated surface tension responses due to surface reactions with the amine hardener. The extent of these changes can be controlled by the migration of the hardener to the surface region.     

Stability of Dispersions

The importance of the production and application of disperse systems in industry is steadily growing, while colloidal systems surround us every day (for example foodstuffs, pharmaceuticals etc.). Understanding the forces and mechanisms of interaction allows the development of new materials and improvement of available systems. The stability of such systems is one of the central research points. One of the well‐known physical models of colloid stability is given by DLVO‐Theory. With this theory we have a tool to influence the stability of such dispersion systems. In this paper, electrokinetic methods are used to investigate interaction forces in disperse systems. The influence of pH‐value, electrolyte concentration and valency is shown with suitable examples. However, in some cases the DLVO‐model is not satisfactory, and reasons for this behavior will also be discussed.     

Zur Frage der Bewertung von Labor-Versuchsergebnissen über die Basidiomyceten-Resistenz der Holzarten

Numerous papers have been published in the last 50 years concerning the resistance of wood species against basidiomycetes. If only those papers are considered, which report on the resistance of timber used in moderate climates, a direct comparison is difficult. This paper describes the main parameters, which vary from test to test and influence the results of laboratory examinations as well as of field tests. It is furthermore shown that technical wording, used to describe the most commonly used durability classes, is not uniform.