2,521,847 research outputs found

    Quantum transport through a DNA wire in a dissipative environment

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    Electronic transport through DNA wires in the presence of a strong dissipative environment is investigated. We show that new bath-induced electronic states are formed within the bandgap. These states show up in the linear conductance spectrum as a temperature dependent background and lead to a crossover from tunneling to thermal activated behavior with increasing temperature. Depending on the strength of the electron-bath coupling, the conductance at the Fermi level can show a weak exponential or even an algebraic length dependence. Our results suggest a new environmental-induced transport mechanism. This might be relevant for the understanding of molecular conduction experiments in liquid solution, like those recently performed on poly(GC) oligomers in a water buffer (B. Xu et al., Nano Lett 4, 1105 (2004)).Comment: 5 pages, 3 figure

    Using Canonical Forms for Isomorphism Reduction in Graph-based Model Checking

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    Graph isomorphism checking can be used in graph-based model checking to achieve symmetry reduction. Instead of one-to-one comparing the graph representations of states, canonical forms of state graphs can be computed. These canonical forms can be used to store and compare states. However, computing a canonical form for a graph is computationally expensive. Whether computing a canonical representation for states and reducing the state space is more efficient than using canonical hashcodes for states and comparing states one-to-one is not a priori clear. In this paper these approaches to isomorphism reduction are described and a preliminary comparison is presented for checking isomorphism of pairs of graphs. An existing algorithm that does not compute a canonical form performs better that tools that do for graphs that are used in graph-based model checking. Computing canonical forms seems to scale better for larger graphs

    Issues on topics

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    The present volume contains papers that bear mainly on issues concerning the topic concept. This concept is of course very broad and diverse. Also, different views are expressed in this volume. Some authors concentrate on the status of topics and non-topics in so-called topic prominent languages (i.e. Chinese), others focus on the syntactic behavior of topical constituents in specific European languages (German, Greek, Romance languages). The last contribution tries to bring together the concept of discourse topic (a non-syntactic notion) and the concept of sentence topic, i.e. that type of topic that all the preceding papers are concerned with

    On topics today

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    This article surveys the state of so-called topic theory today. It charts its development through two generations of topic theorists. The first is constructed around three influential texts: Leonard Ratners seminal book that established the discipline in its own right, Classic music: expression, form and style (1980); Wye Allanbrooks. Rhythmic gesture in Mozart: Le nozze di Figaro and Don Giovanni (1983); and Kofi Agawus. Playing with signs: a semiotic interpretation of classical music (1991). The second comprises significant advances in topic theory essayed through two further pairs of texts: Robert Hattens Musical meaning in Beethoven: markedness, correlation, and interpretation (1994) and Interpreting musical gestures, topics, and tropes: Mozart, Beethoven, Schubert (2004); and Raymond Monelles Linguistics and semiotics in music (1992) and The sense of music: semiotic essays (2000). Topic Theory's role as the soft hermeneutic sub-field of music semiotics (relative to the harder, formalist practices of Nattiezs neutral level analysis) is portrayed here as navigating a number of treacherous polemical paths. These wend their way between referential style (expression) and structural syntax (form); historical reconstruction and hermeneutic construction; and heightened sensitivity to social meanings and imposed acts of creative interpretation. This existence of topic theory in a continuous dialogue between structural formalism and the semantics of expressive discourse is held responsible for its marginal position both to the dominant strains of contemporary postmodern musicology and to the dying embers of formalist analysis. The failure of topic theory to strike a fashionable text-context balance thus highlights why musicology continues to view semiotics with scepticism. Ratner presents his thesaurus of style labelssomewhat dubiouslyas the historically authentic ready-to-hand materials (types and styles) of eighteenth-century expressive musical rhetoric. But it is Agawus combination of this universe of topics with a Schenker-influenced beginning-middle-end paradigm that establishes the hallmark of first generation topic theory on which the first half of this paper focuses. Agawus delicate equation between extroversive and introversive semiosis is essayed as a pivotal turning point in topic theorys ability to transcend the mere passive ascription of rhetorical labels. Out of this equation, expressive meanings can ariseas much from the non-congruence, as the congruence, of signs and structure. Hatten's critique of Agawu for neglecting the full interpretative consequences of his signifieds is the springboard for his more hermeneutically replete brand of topic theory and the emergence of the second generation topic theorists. Hattens use of troping (a kind of musical metaphor), is one of many interpretative tools that are responsible for broadening the arena of topic theorysome of his others being: expressive genres, emergent meanings and markedness theory. These are deployed across a variety of musical parameters as Hattens attention increasingly turns to the prototypicality of topics in their euphoric and dysphoric states. Hattens interpretative work is shown to transcend historical reconstruction to comprise creative interpretation built on a much broader definition of expressive gestures, of which topics are only a constituent part. The article concludes with Monelles expos of the dubious historical underpinnings of Ratners topic theory foundations. This does not render this vibrant branch of semiotics redundant but, on the contrary, charts its future direction as one calling out for far deeper historical investigation and cultural criticism. Monelles enlightening forays into the more replete expressive meanings of such topics as the horse and pianto make this point abundantly clear. The future of topics today, if not musicology in general, is one of cultural criticism

    A Framework for collaborative writing with recording and post-meeting retrieval capabilities

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    From a HCI perspective, elucidating and supporting the context in which collaboration takes place is key to implementing successful collaborative systems. Synchronous collaborative writing usually takes place in contexts involving a “meeting” of some sort. Collaborative writing meetings can be face-to-face or, increasingly, remote Internet-based meetings. The latter presents software developers with the possibility of incorporating multimedia recording and information retrieval capabilities into the collaborative environment. The collaborative writing that ensues can be seen as an activity encompassing asynchronous as well as synchronous aspects. In order for revisions, information retrieval and other forms of post-meeting, asynchronous work to be effectively supported, the synchronous collaborative editor must be able to appropriately detect and record meeting metadata. This paper presents a collaborative editor that supports recording of user actions and explicit metadata production. Design and technical implications of introducing such capabilities are discussed with respect to document segmentation, consistency control, and awareness mechanisms