170,174 research outputs found
Independence and conservativity results for intuitionistic set theory
No full textThere are two main parts to this thesis. The first part will deal with some independence results. In 1979, Lifschitz in [13] introduced a realizability interpretation
for Heyting's arithmetic, HA, that could differentiate between Church's thesis with uniqueness condition, CT0!, and the general form of Church's thesis, CT0. The objective here is to extend Lifschitz' realizability to intuitionistic Zermelo-Fraenkel set theory with two sorts, IZFN. In addition to separating Church's thesis with uniqueness condition from its general form in intuitionistic set theory, I also obtain several interesting
corollaries. The interpretation repudiates a weak form of countable choice, ACN2, asserting that every countable family of inhabited subsets of {0,1} has a choice function.
The second part will be concerned with Constructive Zermelo-Fraenkel Set Theory and other intuitionistic set theories augmented by various principles, notably choice principles. It will be shown that the addition of these (choice) principles does not change the stock of provable arithmetical theorems.
This type of conservativity result has its roots in a theorem of Goodman[9] who showed that Heyting arithmetic in all nite types augmented by the axiom of choice for all levels is conservative over HA. The technique I employ here to obtain such results for intuitionistic set theories, however, owes a lot to a paper by Beeson published in 1979. In [2] he showed how to construe Goodman's Theorem as the composition of two interpretations, namely relativized realizability and forcing. In this thesis, I adopt the same
approach and employ it to a plethora of intuitionistic set theories
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Temperature and magnetic field dependencies of Condon domain phase in Lifschitz-Kosevich-Shoenberg approximation
No full textThe temperature and magnetic field behavior of non-uniform diamagnetic phase of strongly correlated electron gas at the conditions of the dHvA effect is analyzed. It is shown that in the framework of Lifschitz-Kosevich-Shoenberg approximation the magnetic induction splitting, as well as the range of existence of Condon domains, are characterized by strong dependencies on temperature, magnetic field and impurities of the sample. (c) 2006 Elsevier Ltd. All rights reserved
Temperature and magnetic field dependencies of Condon domain phase in Lifschitz-Kosevich-Shoenberg approximation
No full textThe temperature and magnetic field behavior of non-uniform diamagnetic
phase of strongly correlated electron gas at the conditions of the dHvA
effect is analyzed. It is shown that in the framework of
Lifschitz-Kosevich-Shoenberg approximation the magnetic induction
splitting, as well as the range of existence of Condon domains, are
characterized by strong dependencies on temperature, magnetic field and
impurities of the sample. (c) 2006 Elsevier Ltd. All rights reserved
A Generalized Gelfond-Lifschitz Transformation for Logic Programs with Abstract Constraints
No full textWe present a generalized Gelfond-Lifschitz transformation in order to define stable models for a logic program with arbitrary abstract constraints on sets (c-atoms). The generalization is based on a formal semantics and a novel abstract representation of c-atoms, as opposed to the commonly used power set form representation. In many cases, the abstract representation of a c-atom results in a substantial reduction of size from its power set form representation. We show that any c-atom A =(Ad,Ac) in the body of a clause can be characterized using its satisfiable sets, so that given an interpretation I the c-atom can be handled simply by introducing a special atom θA together with a new clause θA ← A1,..., An for each satisfiable set {A1,..., An} of A. We also prove that the latest fixpoint approach presented by Son et al. and our approach using the generalized Gelfond-Lifschitz transformation are semantically equivalent in the sense that they define the same set of stable models
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A library of general-purpose action descriptions
No full texttextAn important idea in knowledge representation is that of libraries of reusable knowledge components. The goal of this research is to apply this idea to action description languages. An action language may be used to specify the effects and preconditions of actions, and serves to describe “transition systems” -- directed graphs with the vertices representing the states of an action domain and the edges representing the transitions that are caused by performing actions (or by the passage of time). Many actions can be described as special cases of other actions. (For example, pushing, carrying, going can all be described as special cases of moving things around.) However, descriptions of action domains in existing action languages describe the effects of all actions from scratch, which leads to common aspects of different domains getting reinvented over and over. In this dissertation we first developed a method for defining actions in terms of other actions, in the action language C+, a language with a rich set of features for describing action domains. This provided a theoretical basis for developing a library of general-purpose action descriptions and influenced the design of the Modular Action Description (MAD) language [Lifschitz and Ren, 2006], the semantics of which is based on C+. We extended the original MAD language in several ways, both in the syntactic dimension and in the semantic dimension, and developed an implementation of this extended language. The extended semantics not only provides new features but also addresses some shortcomings of the original semantics, which were identified during the course of our research. The implemented system was used to develop a library of basic MAD modules, each describing a group of general commonsense facts related to actions. Several action domains from the knowledge representation literature were formalized using the library of basic action descriptions. The availability of the library led to the representations being much simpler than before and also enabled us to recognize structural similarities of seemingly quite different domains.Computer Scienc
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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