663 research outputs found

    Standards for photoluminescence quantum yield measurements in solution

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    The use of visual information in intercepting moving objects

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    In this thesis. we investigated the use of visual information in intercepting moving objects. We have tried to determine which sources of visual information are used in guiding different aspects of the intercepting action. There are many interception tasks that each have their own kind of action and their own potentially useful visual infonnation. For example. in catching balls you may have to run. whereas that is generally not necessary in hitting running spiders. The fact that the object that you want to intercept 'gets bigger' as it approaches you might be a useful source of information in catching balls. In contrast. this information is less useful in hitting spiders that run across a walL as their movement direction is not mainly towards your eyes. We thus looked at different tasks. which implied different kinds of action and different kinds of valuable information. An important aspect that all interception tasks have in common. is that one has to anticipate the movement of the target during one's own planning and moving. It is not possible to successfully intercept a moving target by determining the target's position and subsequently moving there. because by the time you arrive at the determined position. the target has already moved to somewhere else. It is poorly understood how this problem is solved

    Organocatalytic Fluorogenic Synthesis of Chromenes

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    Two fluorescent derivatives of 2-amino-3-carbonitrile-4H-chromene were synthesized by means of a fluorogenic Michael addition of dimedone to dicyano alkene labeled BODIPY derivatives. Different organocatalysts were used in different conditions to obtain compounds 3 and 4 in good yield (up to 65% and 85 and moderate enantiomeric excess (51% and 41% ee, respectively). This work provides the first example of an enantioselective organocatalytic conversion combined with fluorogenesis

    Computation of some parameters of Lie geometries

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    Local recognition of Tits geometries of classical type

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