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Summary Selective Metal Powder Sintering is a ‘Material Accretion Manufacturing’ or ‘Rapid Prototyping’ process. It aims to be a manufacturing system to produce metallic parts with good mechanical properties. The present feasibility study addresses the basic binding mechanism to stuck powder particles together using a Nd:YAG laser. While conventional sintering occurs too slowly to be tackled by a scanning laser beam, preference went to liquid phase sintering. A Fe-Cu mixture gives promising results. Experiments reveal a large amount of parameters determining the process’ behaviour of liquid phase formation. Without precautions, the Fe powders tend to melt whilst Cu particles stay solid due to the high reflectivity of Cu for laser light. Three parameters seem to have important influence on the energy distribution between both metals: the particle diameter, reflectivity and mixture ratio. Simulations have been used to estimate settings for these parameters.
The synthesis of 4-benzoyloxy-5,5-difluoropentan-1-ol from ethyl difluoroacetate is described; its condensation with pyrimidine bases gave carbaacyclonucleosides. which were evaluated, and found inactive, in a large variety of antiviral assays.
No abstract is provided for this article.
Abstract With the aim of obtaining derivatives of the well established antiherpes compound 5‐ethyl‐2′‐deoxyuridine ( 1 ) (Aedurid©, EtUdR, EDU), which are more lipophilic and therapeutically superior, 5′‐ and 3′‐ester derivatives of 1 were synthesized. Tested in primary rabbit kidney cell cultures against various strains of herpes simplex type 1 (HSV‐1) and type 2 (HSV‐2), all EtUdR esters, with the exception of compounds 8 and 13 , proved almost as active as EtUdR itself, suggesting that they were readily hydrolized.
The generation of collision free NC-programs for multi-axis milling operations is a critical task, which leads to multi-axis milling machines being exploited below their full capacities. Today, CAM systems, generating the tool path, do not take the multi-axis machine movements into account. They generate a multi-axis tool path, described by a sequence of tool postures (tool tip+tool orientation), which is then converted by a NC-postprocessor to a machine specific NC-program. As the postprocessing is normally done in batch mode, the NC-programmer does not know how the machine will move and the chance for having collisions between (moving) machine components is often very high. The execution of a machine test run or the application of a machine simulation system (NC-simulation) is the only solution to inform the NC-programmer about possible machine collisions during operation. This paper describes a multi-axis tool path generation algorithm where the tool orientation is optimised to avoid machine collisions and at the same time to maximise the material removal rate along the tool track. To perform efficient collision avoidance, the tool path generation module (traditional CAM), the postprocessing (axes transformation) and machine simulation has been integrated into one system. Cutting tests have been carried out to define the allowable tool orientation changes for optimisation and collision avoidance without disturbing the surface quality. The developed multi-axis tool path generation algorithm is applicable for the machining of several part surfaces within one operation. This, together with tool path generation functionality to adapt the tool orientation for both, maximal material removal and avoidance of collisions between (moving) machine components, are the innovative aspects of the presented research work.
