10,146 research outputs found
Uniform Representations for Syntax-Semantics Arbitration
Psychological investigations have led to considerable insight into the
working of the human language comprehension system. In this article, we look at
a set of principles derived from psychological findings to argue for a
particular organization of linguistic knowledge along with a particular
processing strategy and present a computational model of sentence processing
based on those principles. Many studies have shown that human sentence
comprehension is an incremental and interactive process in which semantic and
other higher-level information interacts with syntactic information to make
informed commitments as early as possible at a local ambiguity. Early
commitments may be made by using top-down guidance from knowledge of different
types, each of which must be applicable independently of others. Further
evidence from studies of error recovery and delayed decisions points toward an
arbitration mechanism for combining syntactic and semantic information in
resolving ambiguities. In order to account for all of the above, we propose
that all types of linguistic knowledge must be represented in a common form but
must be separable so that they can be applied independently of each other and
integrated at processing time by the arbitrator. We present such a uniform
representation and a computational model called COMPERE based on the
representation and the processing strategy.Comment: 7 pages, uses cogsci94.sty macr
Improved actions and asymptotic scaling in lattice Yang-Mills theory
Improved actions in SU(2) and SU(3) lattice gauge theories are investigated
with an emphasis on asymptotic scaling. A new scheme for tadpole improvement is
proposed. The standard but heuristic tadpole improvement emerges from a mean
field approximation from the new approach. Scaling is investigated by means of
the large distance static quark potential. Both, the generic and the new
tadpole scheme yield significant improvements on asymptotic scaling when
compared with loop improved actions. A study of the rotational symmetry
breaking terms, however, reveals that only the new improvement scheme
efficiently eliminates the leading irrelevant term from the action.Comment: minor modifications, improved presentatio
Socio-economic Impact in a Region in the Southern Part of Jutland by the Establishment of a Plant for Processing of Bio Ethanol
A cooperation between The Farmers Association of Southern Jutland, Institute of Food Economics Department of Environmental and Business Economics, USD, and Centre for Rural Development, hosting Leader+ Denmark This report is a translation of the original report in Danish: (Jørgensen, H. P. and K. H.-Gregersen: Estimerede økonomiske virkninger i Syd- og Sønderjyl-land ved etablering af et anlæg til fremstilling af bioethanol, September 2003).
Initial success of native grasses is contingent on multiple interactions among exotic grass competition, temporal priority, rainfall and site effects.
Ecological communities are increasingly being recognized as the products of contemporary drivers and historical legacies that are both biotic and abiotic. In an attempt to unravel multiple layers of ecological contingency, we manipulated (i) competition with exotic annual grasses, (ii) the timing of this competition (temporal priority in arrival/seeding times) and (iii) watering (simulated rainfall) in a restoration-style planting of native perennial grasses. In addition, we replicated this experiment simultaneously at three sites in north-central California. Native perennial grasses had 73-99 % less cover when planted with exotic annuals than when planted alone, but this reduction was greatly ameliorated by planting the natives 2 weeks prior to the exotics. In a drought year, irrigation significantly reduced benefits of early planting so that these benefits resembled those observed in a non-drought year. There were significant differences across the three sites (site effects and interactions) in (i) overall native cover, (ii) the response of natives to competition, (iii) the strength of the temporal priority effect and (iv) the degree to which supplemental watering reduced priority effects. These results reveal the strong multi-layered contingency that underlies even relatively simple communities
Having Your Cake and Eating It Too: Autonomy and Interaction in a Model of Sentence Processing
Is the human language understander a collection of modular processes
operating with relative autonomy, or is it a single integrated process? This
ongoing debate has polarized the language processing community, with two
fundamentally different types of model posited, and with each camp concluding
that the other is wrong. One camp puts forth a model with separate processors
and distinct knowledge sources to explain one body of data, and the other
proposes a model with a single processor and a homogeneous, monolithic
knowledge source to explain the other body of data. In this paper we argue that
a hybrid approach which combines a unified processor with separate knowledge
sources provides an explanation of both bodies of data, and we demonstrate the
feasibility of this approach with the computational model called COMPERE. We
believe that this approach brings the language processing community
significantly closer to offering human-like language processing systems.Comment: 7 pages, uses aaai.sty macr
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Parsing with parallelism : a spreading-activation model of inference processing during text understanding
The past decade of reseatch in Natural Language Processing has universally recognized that, since natural language input is almost always ambiguous with respect to its pragmatic implications, its syntactic parse, and even its lexical analysis (i.e., choice of correct word-sense for an ambiguous word), processing natural language input requires decisions about word meanings, syntactic structure, and pragmatic inferences. The lexical, syntactic, and pragmatic levels of inferencing are not as disparate as they have often been treated in both psychological and artificial intelligence research. In fact, these three levels of analysis interact to form a joint interpretation of text.ATLAST (A Three-level Language Analysis SysTem) is an implemented integration of human language understanding at the lexical, the syntactic, and the pragmatic levels. For psychological validity, ATLAST is based on results of experiments with human subjects. The ATLAST model uses a new architecture which was developed to incorporate three features: spreading activation memory, two-stage syntax, and parallel processing of syntax and semantics. It is also a new framework within which to interpret and tackle unsolved problems through implementation and experimentation
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STRATEGIST : a program that models strategy-driven and content-driven inference behavior
In the course of understanding a text, different readers use different inference strategies to guide their choice of interpretations of the events in the text. This is in contrast to previous computer models of understanding, which all use the content-driven inference. The separate strategies are theorized to be composed of the same component inference processes, but of different rules for application of the processes. The use of different strategies occasionally results in different results of new experimental data and a working computer program, called STRATEGIST, that models both strategy-drive and content-driven inference behavior. The rules which make up two of these strategies are presented
The Impact of Base Stacking on the Conformations and Electrostatics of Single-Stranded DNA
Single-stranded DNA (ssDNA) is notable for its interactions with ssDNA binding proteins (SSBs) during fundamentally important biological processes including DNA repair and replication. Previous work has begun to characterize the conformational and electrostatic properties of ssDNA in association with SSBs. However, the conformational distributions of free ssDNA have been difficult to determine. To capture the vast array of ssDNA conformations in solution, we pair small angle X-ray scattering with novel ensemble fitting methods, obtaining key parameters such as the size, shape and stacking character of strands with different sequences. Complementary ion counting measurements using inductively coupled plasma atomic emission spectroscopy are employed to determine the composition of the ion atmosphere at physiological ionic strength. Applying this combined approach to poly dA and poly dT, we find that the global properties of these sequences are very similar, despite having vastly different propensities for single-stranded helical stacking. These results suggest that a relatively simple mechanism for the binding of ssDNA to non-specific SSBs may be at play, which explains the disparity in binding affinities observed for these systems
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