1,821 research outputs found

    On the decidability of homomorphism equivalence for languages

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    AbstractWe consider decision problems of the following type. Given a language L and two homomorphisms h1 and h2, one has to determine to what extent h1 and h2 agree on L. For instance, we say that h1 and h2 are equivalent on L if h1(ω) = h2(ω) holds for each ω Δ L. In our main theorem we present an algorithm for deciding whether two given homomorphisms are equivalent on a given context-free language. This result also gives an algorithm for deciding whether the translations defined by two deterministic gsm mappings agree on a given context-free language

    On almost cylindrical languages and the decidability of the D0L and PWD0L primitivity problems

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    AbstractPrimitive words and their properties have always been of fundamental importance in the study of formal language theory. Head and Lando in Periodic D0L Languages proposed the idea of deciding whether or not a given D0L language has the property that every word in it is a primitive word. After reducing the general problem to the case in which h is injective, it will be shown that primitivity is decidable when ((A)h)∗ is an almost cylindrical set. Moreover, in this case, it is shown that the set of words which generate primitive sequences (given a particular D0L scheme) is an algorithmically constructible context-sensitive language. An undecidability result for the PWD0L primitivity problem and decidability results for cases of the RWD0L primitivity problem are also given

    Watson-Crick walks and roads on DOL graphs

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    On test sets for checking morphism equivalence on languages with fair distribution of letters

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    AbstractA test set for a language L is a finite subset T of L with the property that each pair of morphisms that agrees on T also agrees on L. Some results concerning test sets for languages with fair distribution of letters are presented. The first result is that every D0L language with fair distribution of letters has a test set. The second result shows that every language L with fair distribution has a test set relative to morphisms g, h which have bounded balance on L. These results are generalizations of results of Culik II and KarhumÀki (1983)

    On the Ehrenfeucht conjecture for DOL languages

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    Mixing Metaphors: Voting, Dollars, and Campaign Finance Reform (Review Essay)

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    Reviewing, Bruce Ackerman & Ian Ayers, Voting with Dollars: A New Paradigm for Campaign Finance (2002

    Acta Cybernetica : Volume 14. Number 1.

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    Mens rea - Mistake of law & mistake of fact in German criminal law: A survey for international criminal tribunals

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    More than a decade has passed since the establishment of the two ad hoc Tribunals, however, the jurisprudence of both Tribunals evidence the inconsistency regarding the requisite mens rea standards for serious violations of international humanitarian law. Hence, a survey of the attitude taken towards the definition of the major facets of mens rea by the world major legal systems is of great significance with regard to the establishment of a unified concept for mens rea in international criminal law. Section I of this study examines some of the major judgments of the two ad hoc Tribunals where both Tribunals refers to national jurisdictions in order to clarify the mens rea required for the imposition of criminal responsibility for serious violations of international humanitarian law. Section II is a brief outline of the structure of the criminal offence in German criminal law. This is necessary since German criminal law does not follow the “offence analysis” scheme known in common law countries, but is based upon a three stage structure of the criminal offence. In Section III, the concept of intention (Vorsatz) in German criminal law is thoroughly discussed and analysed. This includes the discussion of dolus directus (first and second degree) as well as of dolus eventualis. Emphasis is put on the differentiation between dolus eventualis and negligence, since it reflects a highly debated issue in German criminal law. The concept of negligence will be outlined in Section IV. Given the fact that the German criminal law recognizes that mistake of law and mistake of fact (Tatbestandsirrtum, Verbotsirrtum) is not a separate doctrine, but part and parcel of the basic analysis of mens rea, these two basic types of mistake will be addressed in Section V. This includes the discussion of error in persona vel obiecto and aberratio ictus. Finally, the conclusion will be supported by some remarks and recommendations regarding the German law of intent and its influence on the development of international criminal law

    Exchange-dependent relaxation in the rotating frame for slow and intermediate exchange - modeling off-resonant spin-lock and chemical exchange saturation transfer

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    Chemical exchange observed by NMR saturation transfer (CEST) and spin-lock (SL) experiments provide an MRI contrast by indirect detection of exchanging protons. The determination of the relative concentrations and exchange rates is commonly achieved by numerical integration of the Bloch-McConnell equations. We derive an analytical solution of the Bloch-McConnell equations that describes the magnetization of coupled spin populations under radiofrequency irradiation.As CEST and off-resonant SL are equivalent, their steady-state magnetization and dynamics can be predicted by the same single eigenvalue: the longitudinal relaxation rate in the rotating frame R1rho. For the case of slowly exchanging systems, e.g. amide protons, the saturation of the small proton pool is affected by transverse relaxation (R2b). It turns out, that R2b is also significant for intermediate exchange, such as amine- or hydroxyl-exchange or paramagnetic CEST agents, if pools are only partially saturated. We propose a solution for R1rho that includes R2 of the exchanging pool by extending existing approaches, and verify it by numerical simulations. With the appropriate projection factors, we obtain an analytical solution for CEST and SL for nonzero R2 of the exchanging pool, whilst considering the dilution by direct water saturation across the entire Z-spectra. This allows the optimization of irradiation parameters and the quantification of pH-dependent exchange rates and metabolite concentrations. In addition, we propose evaluation methods that correct for concomitant direct saturation effects. It is shown that existing theoretical treatments for CEST are special cases of this approach
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