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  • 1
    Electronic Resource
    Electronic Resource
    Photosensitizing activity of water- and lipid-soluble phthalocyanines on Escherichia coli (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 71 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Escherichia coli, as most Gram-negative bacteria, is insensitive to the photosensitizing action of both lipid-soluble Zinc-phthalocyanine (Zn-Pc) and water-soluble Zinc-mono/disulfonated phthalocyanine (Zn-PcS). Photosensitivity can be induced by alteration of the outer membrane, as obtained by either induction of competence or treatment with Tris-EDTA. Both phthalocyanines largely bind at the level of the cytoplasmic membrane; however, Zn-PcS shows a superior photosensitizing activity as compared with Zn-Pc. Biochemical analyses performed on irradiated cells suggest that the cytoplasmic membrane is an important target of the photoprocess, while DNA is not involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb03814.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Graph Rewriting, Constraint Solving and Tiles for Coordinating Distributed Systems (1999)
    Springer
    Applied categorical structures 7 (1999), S. 333-370 
    Details
    ISSN: 1572-9095
    Keywords: distributed systems ; graph rewriting ; constraints ; double categories ; coordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We describe an approach to modeling the dynamics of distributed systems. By distributed systems we mean systems consisting of concurrent processes communicating via shared ports and posing certain synchronization requirements, via the ports, to the adjacent processes. The basic idea is to use graphs to represent states of such systems, and graph rewriting to represent their evolution. The kind of graph rewriting we use is based on simple context-free productions which are, however, combined by means of a synchronization mechanism. This allows for a good level of expressivity in the system without sacrifying full distribution. To formally model this kind of graph rewriting, however, we do not adopt the classical graph rewriting style but a more general framework, called the tile model, which allows for a clear separation between sequential rewriting and synchronization. Then, since the problem of satisfying the synchronization requirements may be a complex combinatorial problem, we suggest exploiting existing techniques for constraint solving. This is based on the observation that the synchronization problem can be modeled as a (finite domain) constraint problem. In this respect, we propose to use both local consistency techniques, to remove the possible redundancies in a system state, and a distributed backtracking search algorithm, as used in distributed constraint solving. Our method has the following advantages: first, it provides a formal description of the way a distributed system evolves; second, it seems promising from the performance point of view, since the techniques we propose for combining productions have been proved to be very convenient in several cases; finally, the kind of system evolution we describe here is just a particular instance of what can be described by using the tile model in its most general form, thus suggesting the possibility of extending our approach to modeling more complex distributed systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008693303228
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  • 3
    Electronic Resource
    Electronic Resource
    Constraint Solving and Programming: What Next? (1997)
    Springer
    Constraints 2 (1997), S. 87-91 
    Details
    ISSN: 1572-9354
    Keywords: dynamic constraint problems ; constraint preferences ; constraint learning ; constraint programming ; semantics ; true concurrency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we advocate for more flexible and user-friendly constraint solving environments, as well as for constraint programming languages which have great expressive power while maintaining a formal semantics based on few crucial concepts. We cite some of our work in these directions and we hint at subjects of our future research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009757208585
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  • 4
    Electronic Resource
    Electronic Resource
    Constraint Retraction in CLP(FD): Formal Framework and Performance Results (1999)
    Springer
    Constraints 4 (1999), S. 5-42 
    Details
    ISSN: 1572-9354
    Keywords: constraint satisfaction ; constraint programming ; constraint retraction ; finite domains ; non-monotonicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Constraint retraction can be described, in general, as the possibility of deleting a previously stated piece of information. This is obviously very convenient in many programming frameworks, especially in those that involve some level of interaction between the user and the system, or also in those concerning rescheduling or replanning. Nevertheless, constraint retraction is usually not provided in current constraint programming environments. This is mainly due to its high complexity and also to its non-monotonic nature, which would make most of such systems much more complex to reason with. In this paper we avoid these problems by considering a specific constraint programming framework, called clpFD, that is, constraint logic programming (CLP) over finite domain (FD) constraints. We propose an algorithm which deletes a constraint from a set of FD constraints, while maintaining partial arc-consistency, which is usual in this programming framework. What is crucial is that the retraction operation we propose is incremental, in that it follows the chain of dependencies among variables which are set by the nature of the FD constraints, and by doing so it updates only the part of the constraint set which is affected by the deletion. We also detail how constraint retraction can be incorporated in the FD constraint solver and we evaluate its behavior within the clpFD system. Experimental results on usual benchmarks, on classes of problems of increasing connectivity, and also on a real-life problem show that in almost all cases the use of our retraction algorithm provides great speed-up with respect to standard methods while not slowing down the clpFD system when no retraction is performed. This provides the system with an efficient way of retracting constraints while not changing its performance when the user does not want to use this new feature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009893626769
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  • 5
    Electronic Resource
    Electronic Resource
    Contextual nets (1995)
    Springer
    Acta informatica 32 (1995), S. 545-596 
    Details
    ISSN: 1432-0525
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. We propose a new kind of nets, called contextual nets, where events may have both preconditions and postconditions, as in the classical case, and also positive or negative context conditions. Positive context conditions are to be interpreted as elements which are needed for the event to occur, but which are not affected by the occurring of the event. Instead, negative context conditions are elements which must not be present for the event to take place. The importance of an explicit representation of positive context elements is twofold. Firstly, it allows a faithful representation of systems where the notion of "reading without consuming" is commonly used, like database systems, concurrent constraint programming, or any computation framework based on shared memory. Secondly, it allows to specify directly and naturally a level of concurrency greater than in classical nets. In fact, two events with different preconditions but with the same positive context may occur both in any order and also simultaneously. It is important to note that no other formalism for specifying distributed systems has such feature, not even Petri nets, where the "read" operation does not exists and it is instead modelled through a "rewrite" operation (i.e., a loop), which however does not allow the simultaneous execution of two tasks which read the same resource. Of course a context situation may be simulated in classical nets by creating as many copies of the context as are the users, but this would lead to a very unrealistic (and also more costly) description of the real situation. Negative context conditions are instead very natural to use in systems or languages where negation is present. In this paper we provide contextual nets with two process-based semantics which both are able to represent all and only the computations of a net and express the correct level of true-concurrency. Moreover, we show that contact situations, as well as negative context conditions, do not add any additional power, and we investigate the relationship between contextual nets and classical nets in terms of their processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01178907
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  • 6
    Electronic Resource
    Electronic Resource
    Contextual nets (1995)
    Springer
    Acta informatica 32 (1995), S. 545-596 
    Details
    ISSN: 1432-0525
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We propose a new kind of nets, called contextual nets, where events may have both preconditions and postconditions, as in the classical case, and also positive or negative context conditions. Positive context conditions are to be interpreted as elements which are needed for the event to occur, but which are not affected by the occurring of the event. Instead, negative context conditions are elements which must not be present for the event to take place. The importance of an explicit representation of positive context elements is twofold. Firstly, it allows a faithful representation of systems where the notion of “reading without consuming” is commonly used, like database systems, concurrent constraint programming, or any computation framework based on shared memory. Secondly, it allows to specify directly and naturally a level of concurrency greater than in classical nets. In fact, two events with different preconditions but with the same positive context may occur both in any order and also simultaneously. It is important to note that no other formalism for specifying distributed systems has such feature, not even Petri nets, where the “read” operation does not exists and it is instead modelled through a “rewrite” operation (i.e., a loop), which however does not allow the simultaneous execution of two tasks which read the same resource. Of course a context situation may be simulated in classical nets by creating as many copies of the context as are the users, but this would lead to a very unrealistic (and also more costly) description of the real situation. Negative context conditions are instead very natural to use in systems or languages where negation is present. In this paper we provide contextual nets with two process-based semantics which both are able to represent all and only the computations of a net and express the correct level of true-concurrency. Moreover, we show that contact situations, as well as negative context conditions, do not add any additional power, and we investigate the relationship between contextual nets and classical nets in terms of their processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01178907
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  • 7
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    Dynamic consistency of fuzzy conditional temporal problems (2008)
    Springer
    Details
    Publication Date: 2008-11-15
    Print ISSN: 0956-5515
    Electronic ISSN: 1572-8145
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 8
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    Epitaxy of Nanocrystalline Silicon Carbide on Si(111) at Room Temperature (2012)
    American Chemical Society
    Details
    Publication Date: 2012-10-15
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 9
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    Influence of short-term low current dc aging on the electrical and optical properties of InGaN blue light-emitting diodes (2006)
    American Institute of Physics
    Details
    Publication Date: 2006-03-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Origin of the visible emission of black silicon microstructures (2015)
    American Institute of Physics
    Details
    Publication Date: 2015-07-13
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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