Enantioselective Catalysis of the Aza-Cope Rearrangement by a Chiral Supramolecular Assembly

The chiral supramolecular catalyst Ga{sub 4}L{sub 6} [L = 1,5-bis(2,3-dihydroxybenzoylamino)naphthalene] is a molecular tetrahedron that catalyzes the 3-aza-Cope rearrangement of allyl enammonium cations. This catalysis is accomplished by preorganizing the substrate in a reactive conformation within the host. This work demonstrates that through the use of enantiopure assembly, its chiral cavity is capable of catalyzing the 3-aza-Cope rearrangement enantioselectively, with yields of 21-74% and enantiomeric excesses from 6 to 64% at 50 C. At lower temperatures, the enantioselectivity improved, reaching 78% ee at 5 C. This is the highest enantioselectivity to date induced by the chiral cavity of a supramolecular assembly

Incremental Development of Business Process Models

Abstract: The purpose of formal and so called semi-formal approaches to business process modeling is to provide a general technique for the development of workflow based information systems. For this, a concise and repeatable transformation of initial requirements into the final system must be achieved. Moreover, there is also a need for complex models to include justifications that explain the meaning and purpose of each component of the entire model. However, this is not sufficiently supported by current graphical methods. This paper therefore introduces a formal language for process modeling which allows incremental development, graphical visualization of the model, and adding justifications to the model.

Program transformations for distributed control system

This article focuses on programming support for the application area of distributed control systems. Program transformations are introduced to modify properties of distributed programs. Based on a specification-oriented version of CSP transformations are applied to solve standard problems of distributed programming. Equally transformations are used to map specification-oriented CSP-programs to implementation-oriented CSP-programs and further to specific targer environments. (orig.)Available from TIB Hannover: RO 6844(1994,13) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Schedulability criteria for age constraint processes in hard real-time systems

Real-time systems not only require the semantical correctness of their operations but also the availability of the computational results within some predefined time intervals. Static hard realtime scheduling has to construct an off-line schedule by interleaving all the required computations in a way that the application's time bounds are met. Processes are responsible to carry out the different computations. Depending on the application specific context they have to complete in time due to periodic contraints or age constraints. The paper presents two criteria for the existence of static schedules for sets of real-time processes and assesses their practical relevance in the scope of program development for real-time systems. This approach is based on a transformation from age constraint processes to periodic processes and derives a least upper bounds for the achievable load for age constraint processes is derived. (orig.)Available from TIB Hannover: RO 6844(1998,9) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Object Oriented Motion Estimation in Color Image Sequences

This paper describes a color region-based approach to motion estimation in color image sequences. The system is intended for robotic and vehicle guidance applications where the task is to detect and track moving objects in the scene. It belongs to the class of feature-based matching techniques and uses color regions, resulting from a prior color segmentation, as the matching primitives. In contrast to other regionbased approaches it takes into account the unavoidable variations in the segmentation by the extension of the matching model to multi matches

Abstract fairness and semantics

Fairness of a program execution, c, usually expresses that all objects which are sufficiently often enable have to occur also sufficiently often in c. There exists a well-known strong equivalence between fair program executions, #PI#_3"0-formulae, and convergence of initial program executions. However, these results cannot be applied to a study of 'fair semantics' of programs, as such a fair semantics is a #SIGMA#_1"1-formula in general. The main reason therefore is that a semantics does not tell which objects are enabled - only the actually occurring objects are usually seen in semantics. Here we study on a very abstract level some quite natural requirements for semantics s.t. fair semantics with invisible 'enabledness' can also be characterized with topological techniques. (orig.)Available from TIB Hannover: RO 6844(1995,16) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman