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Search Results: 1 - 10 of 20 matches for " Balder HAGERAATS "
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La construcción de la paz y la guerra contra el terrorismo: Conflicto de Intereses?
Relaciones Internacionales , 2008,
Abstract: La Guerra Global Contra el Terrorismo (GGCT) ha sido uno de los temas más importantes dentro de la política internacional. Hasta la fecha su impacto en la seguridad internacional ha sido abrumadoramente negativo. En un intento de analizar sus debilidades, los responsables políticos de Estados Unidos están incorporando cada vez más actividades de la Construcción de la Paz y conceptos similares a la GGCT. Esto es, en parte, una reacción a sus fracasos actuales, y refleja un entendimiento de la importancia a largo plazo de soluciones sostenibles. Sin embargo, la combinación de la GGCT y la Construcción de la Paz es peligrosa ya que amenaza con afectar a la efectividad y legitimidad de la última. La verdadera seguridad internacional requiere enfoques que no estén contaminados por la GGCT y debe frenar una mayor integración de la Construcción de la Paz y conceptos similares a sus doctrinas. Los casos de Afganistán y AFRICOM en la región del Sahel ilustran los problemas potenciales si la comunidad internacional fracasa a la hora de separar suficientemente los dos. The Global War on Terror (GWOT) has been one of the most important topics within International Relations in recent years. To date, it has had an overwhelmingly negative impact on international security. In order to address its current weaknesses, some US policymakers are beginning to incorporate Peacebuilding initiatives and other alternatives to the GWOT. In part, this is a reaction to the failures that have plagued the war, as well as an indication that there does exist an understanding of the need for long-term, sustainable solutions. However, the combination of these distinct tactics, the GWOT and Peacebuilding, is a dangerous maneuver as it may threaten the legitimacy and effectiveness of the latter. True international security requires an approach that is not tainted by the GWOT, and one that incorporates Peacebuilding along with other similar initiatives on a much greater scale. The case of Afghanistan and the establishment of AFRICOM in relation to the Sahel region both illustrate the potential problems likely to arise if the international community fails to separate the two activities.
Unary negation
Luc Segoufin,Balder ten Cate
Computer Science , 2013, DOI: 10.2168/LMCS-9(3:25)2013
Abstract: We study fragments of first-order logic and of least fixed point logic that allow only unary negation: negation of formulas with at most one free variable. These logics generalize many interesting known formalisms, including modal logic and the $\mu$-calculus, as well as conjunctive queries and monadic Datalog. We show that satisfiability and finite satisfiability are decidable for both fragments, and we pinpoint the complexity of satisfiability, finite satisfiability, and model checking. We also show that the unary negation fragment of first-order logic is model-theoretically very well behaved. In particular, it enjoys Craig Interpolation and the Projective Beth Property.
Modal languages for topology: expressivity and definability
Balder ten Cate,David Gabelaia,Dmitry Sustretov
Mathematics , 2006,
Abstract: In this paper we study the expressive power and definability for (extended) modal languages interpreted on topological spaces. We provide topological analogues of the van Benthem characterization theorem and the Goldblatt-Thomason definability theorem in terms of the well established first-order topological language $L_t$.
From weak to strong types of $L_E^1$-convergence by the Bocce-criterion
Erik J. Balder,Maria Girardi,Vincent Jalby
Mathematics , 1994,
Abstract: Necessary and sufficient oscillation conditions are given for a weakly convergent sequence (resp. relatively weakly compact set) in the Bochner-Lebesgue space $\l1$ to be norm convergent (resp. relatively norm compact), thus extending the known results for $\rl1$. Similarly, necessary and sufficient oscillation conditions are given to pass from weak to limited (and also to Pettis-norm) convergence in $\l1$. It is shown that tightness is a necessary and sufficient condition to pass from limited to strong convergence. Other implications between several modes of convergence in $\l1$ are also studied.
Queries with Guarded Negation (full version)
Vince Barany,Balder ten Cate,Martin Otto
Computer Science , 2012,
Abstract: A well-established and fundamental insight in database theory is that negation (also known as complementation) tends to make queries difficult to process and difficult to reason about. Many basic problems are decidable and admit practical algorithms in the case of unions of conjunctive queries, but become difficult or even undecidable when queries are allowed to contain negation. Inspired by recent results in finite model theory, we consider a restricted form of negation, guarded negation. We introduce a fragment of SQL, called GN-SQL, as well as a fragment of Datalog with stratified negation, called GN-Datalog, that allow only guarded negation, and we show that these query languages are computationally well behaved, in terms of testing query containment, query evaluation, open-world query answering, and boundedness. GN-SQL and GN-Datalog subsume a number of well known query languages and constraint languages, such as unions of conjunctive queries, monadic Datalog, and frontier-guarded tgds. In addition, an analysis of standard benchmark workloads shows that most usage of negation in SQL in practice is guarded negation.
Complete Axiomatizations of Fragments of Monadic Second-Order Logic on Finite Trees
Amélie Gheerbrant,Balder ten Cate
Computer Science , 2012, DOI: 10.2168/LMCS-8(4:12)2012
Abstract: We consider a specific class of tree structures that can represent basic structures in linguistics and computer science such as XML documents, parse trees, and treebanks, namely, finite node-labeled sibling-ordered trees. We present axiomatizations of the monadic second-order logic (MSO), monadic transitive closure logic (FO(TC1)) and monadic least fixed-point logic (FO(LFP1)) theories of this class of structures. These logics can express important properties such as reachability. Using model-theoretic techniques, we show by a uniform argument that these axiomatizations are complete, i.e., each formula that is valid on all finite trees is provable using our axioms. As a backdrop to our positive results, on arbitrary structures, the logics that we study are known to be non-recursively axiomatizable.
A note on the product homomorphism problem and CQ-definability
Balder ten Cate,Víctor Dalmau
Computer Science , 2012,
Abstract: The product homomorphism problem (PHP) takes as input a finite collection of relational structures A1, ..., An and another relational structure B, all over the same schema, and asks whether there is a homomorphism from the direct product A1 x ... x An to B. This problem is clearly solvable in non-deterministic exponential time. It follows from results in [1] that the problem is NExpTime-complete. The proof, based on a reduction from an exponential tiling problem, uses structures of bounded domain size but with relations of unbounded arity. In this note, we provide a self-contained proof of NExpTime-hardness of PHP, and we show that it holds already for directed graphs, as well as for structures of bounded arity with a bounded domain size (but without a bound on the number of relations). We also present an application to the CQ-definability problem (also known as the PP-definability problem). [1] Ross Willard. Testing expressibility is hard. In David Cohen, editor, CP, volume 6308 of Lecture Notes in Computer Science, pages 9-23. Springer, 2010.
Molecular Dynamics Simulation of the Crystallizable Fragment of IgG1—Insights for the Design of Fcabs
Balder Lai,Christoph Hasenhindl,Christian Obinger,Chris Oostenbrink
International Journal of Molecular Sciences , 2014, DOI: 10.3390/ijms15010438
Abstract: An interesting format in the development of therapeutic monoclonal antibodies uses the crystallizable fragment of IgG1 as starting scaffold. Engineering of its structural loops allows generation of an antigen binding site. However, this might impair the molecule’s conformational stability, which can be overcome by introducing stabilizing point mutations in the CH3 domains. These point mutations often affect the stability and unfolding behavior of both the CH2 and CH3 domains. In order to understand this cross-talk, molecular dynamics simulations of the domains of the Fc fragment of human IgG1 are reported. The structure of human IgG1-Fc obtained from X-ray crystallography is used as a starting point for simulations of the wild-type protein at two different pH values. The stabilizing effect of a single point mutation in the CH3 domain as well as the impact of the hinge region and the glycan tree structure connected to the CH2 domains is investigated. Regions of high local flexibility were identified as potential sites for engineering antigen binding sites. Obtained data are discussed with respect to the available X-ray structure of IgG1-Fc, directed evolution approaches that screen for stability and use of the scaffold IgG1-Fc in the design of antigen binding Fc proteins.
Question answering: from partitions to Prolog
Balder D. ten Cate,Chung-chieh Shan
Computer Science , 2002,
Abstract: We implement Groenendijk and Stokhof's partition semantics of questions in a simple question answering algorithm. The algorithm is sound, complete, and based on tableau theorem proving. The algorithm relies on a syntactic characterization of answerhood: Any answer to a question is equivalent to some formula built up only from instances of the question. We prove this characterization by translating the logic of interrogation to classical predicate logic and applying Craig's interpolation theorem.
The partition semantics of questions, syntactically
Chung-chieh Shan,Balder D. ten Cate
Computer Science , 2002,
Abstract: Groenendijk and Stokhof (1984, 1996; Groenendijk 1999) provide a logically attractive theory of the semantics of natural language questions, commonly referred to as the partition theory. Two central notions in this theory are entailment between questions and answerhood. For example, the question "Who is going to the party?" entails the question "Is John going to the party?", and "John is going to the party" counts as an answer to both. Groenendijk and Stokhof define these two notions in terms of partitions of a set of possible worlds. We provide a syntactic characterization of entailment between questions and answerhood . We show that answers are, in some sense, exactly those formulas that are built up from instances of the question. This result lets us compare the partition theory with other approaches to interrogation -- both linguistic analyses, such as Hamblin's and Karttunen's semantics, and computational systems, such as Prolog. Our comparison separates a notion of answerhood into three aspects: equivalence (when two questions or answers are interchangeable), atomic answers (what instances of a question count as answers), and compound answers (how answers compose).
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