323,859 research outputs found
Infected aneurysms of the carotid arteries after carotid endarterectomy
No full textRaptis, Spero ; Baker, Stephen R
Closing the loop: The role of audit in reducing groin complications associated with coronary angiography
No full textMcCleary, Alistair J. ; Raptis, Sper
Finitary topos for locally finite, causal and quantal vacuum einstein gravity
No full textThe pentalogy (Mallios, A. and Raptis, I. (2001). International Journal of Theoretical Physics 40, 1885; Mallios, A. and Raptis, I. (2002). International Journal of Theoretical Physics 41, 1857; Mallios, A. and Raptis, I. (2003).International Journal of Theoretical Physics 42, 1479; Mallios, A. and Raptis, I. (2004). 'paper-book'/research monograph); I. Raptis (2005). International Journal of Theoretical Physics (to appear)is brought to its categorical climax by organizing the curved finitary spacetime sheaves of quantumcausal sets involved therein, on which a finitary (:locally finite), singularity-free, background manifold independent and geometrically prequantized version of the gravitational vacuum Einstein field equations were seen to hold, into a topos structure [InlineMediaObject not available: see fulltext.]. We show that the category of finitary differential triads [InlineMediaObject not available: see fulltext.] is a finitary instance of an elementary topos proper in the original sense dueto Lawvere and Tierney. We present in the light of Abstract Differential Geometry (ADG) a Grothendieck-type of generalization of Sorkin's finitary substitutes of continuous spacetime manifoldtopologies, the latter's topological refinement inverse systems of locally finite coverings and their associated coarse graining sieves, the upshot being that [InlineMediaObject not available: see fulltext.] is also a finitary example of a Grothendieck topos. In the process, we discover that the subobject classifier Ω fcq of [InlineMediaObject not available: see fulltext.] is a Heyting algebra type of object, thus we infer that the internal logic of our finitary topos is intuitionistic, as expected. We also introduce the new notion of 'finitary differential geometric morphism' which, as befits ADG, gives a differential geometric slant to Sorkin's purely topological acts of refinement (:coarse graining). Based on finitary differential geometric morphisms regarded as natural transformations of the relevant sheaf categories, we observe that the functorial ADG-theoretic version of the principle of general covariance of GeneralRelativity is preserved under topological refinement. The paper closes with a thorough discussion of four future routes we could take in order to further develop our topos-theoretic perspective on ADG-gravity along certain categorical trends in current quantum gravity research. © Springer Science+Business Media, LLC 2007
Finitary-algebraic 'resolution' of the inner Schwarzschild singularity
No full textA 'resolution' of the interior singularity of the spherically symmetric Schwarzschild solution of the Einstein equations for the gravitational field of a point-particle is carried out entirely and solely by finitistic and algebraic means. To this end, the background differential spacetime manifold and, in extenso, Differential Calculus-free purely algebraic (:sheaf-theoretic) conceptual and technical machinery of Abstract Differential Geometry (ADG) is employed. As in previous works [Mallios, A. and Raptis, I. (2001). Finitary spacetime sheaves of quantum causal sets: Curving quantum causality. International Journal of Theoretical Physics, 40, 1885 [gr-qc/0102097]; Mallios, A. and Raptis, I. (2002). Finitary Čech-de Rham cohomology. International Journal of Theoretical Physics, 41, 1857 [gr-qc/0110033]; Mallios, A. and Raptis, I. (2003). Finitary, causal and quantal vacuum Einstein gravity. International Journal of Theoretical Physics 42, 1479 [gr-qc/0209048]], which this paper continues, the starting point for the present application of ADG is Sorkin's finitary (:locally finite) poset (:partially ordered set) substitutes of continuous manifolds in their Gel'fand-dual picture in terms of discrete differential incidence algebras and the finitary spacetime sheaves thereof. It is shown that the Einstein equations hold not only at the finitary poset level of 'discrete events,' but also at a suitable 'classical spacetime continuum limit' of the said finitary sheaves and the associated differential triads that they define ADG-theoretically. The upshot of this is two-fold: On the one hand, the field equations are seen to hold when only finitely many events or 'degrees of freedom' of the gravitational field are involved, so that no infinity or uncontrollable divergence of the latter arises at all in our inherently finitistic-algebraic scenario. On the other hand, the law of gravity-still modelled in ADG by a differential equation proper-does not break down in any (differential geometric) sense in the vicinity of the locus of the point-mass as it is traditionally maintained in the usual manifold-based analysis of spacetime singularities in General Relativity (GR). At the end, some brief remarks are made on the potential import of ADG-theoretic ideas in developing a genuinely background-independent Quantum Gravity (QG). A brief comparison between the 'resolution' proposed here and a recent resolution of the inner Schwarzschild singularity by Loop QG means concludes the paper. © 2006 Springer Science+Business Media, Inc
CONFIRMATORY FACTOR ANALYSIS AND ESTIMATOR COMPARISON OF TWO SHORT FORMS OF AN IRRATIONAL AND RATIONAL BELIEFS SCALE Author(s): Joanne Raptis
No full textThe present study examined two abbreviated versions of the Attitudes and Beliefs Scale-2 (ABS-2) to compare their factor structure and ability to achieve model fit to the data. The original scale, a measure of irrational and rational beliefs as defined by REBT theory, was designed with 72 items reflecting irrational and rational beliefs and each involving one of four cognitive processes and one of three content areas. The ABS-2 had been criticized for its length and the inconsistency of findings regarding its factor structure. Two groups of researchers independently created short forms of the ABS-2 using 24 of the original items. One scale used the items with the highest factor loadings, while the other also prioritized maintaining balance across all dimensions. To also explore the effects of using different estimators, the authors ran Confirmatory Factor Analyses (CFAs) for each short form twice, once using the Maximum Likelihood Robust (MLR) estimator and once using Diagonally Weighted Least Squares (DWLS). The sample consisted of over 1500 participants that included university students, psychotherapy outpatients, and individuals in a drug rehabilitation program. Results showed that both scales yielded virtually equal and excellent fit indices when using the DWLS estimator but not when using MLR. The model with the best fit was an eight-factor bifactor model with factors for the irrational and rational cognitive processes and a general factor. Two other models also yielded especially excellent fit, including a two-factor bifactor model for irrationality and rationality as well as a second-order model with items loading on either one of the four irrational cognitive processes and then a second-order irrationality factor or on one of the four rational cognitive processes and a second-order rationality factor. Ultimately, the results suggest that the assessment can provide meaningful subscales for scores of the total, irrationality, rationality, cognitive processes, and content domains. Additionally, the findings highlight the importance of critically considering one’s data and selecting an appropriate estimator as opposed to relying on default settings. Implications for the assessment of irrational and rational beliefs, furthering REBT research, and targeting treatment to client presentation across the three dimensions are discussed
Characterization of polymer layers for silicon micromachined bilayer chemical sensors using white light interferometry
No full textThe swelling behavior of polymer layers used in silicon micromachined bilayer structures is studied using white light interferometry. The study focuses on poly-hydroxy-ethyl-methacrylate (PHEMA) films and their behavior in terms of film expansion, response time and sensitivity upon exposure to methanol and ethanol vapors. Thin films of PHEMA exhibit higher relative swelling than thicker films, in the presence of methanol, as well as lower diffusion coefficients corresponding to higher response times. © 2005 Published by Elsevier B.V
Efficacy of balloon angioplasty of the superficial femoral artery and popliteal artery in the relief of leg ischemia
No full textBrendan Stanley, Benjamin Teague, Spero Raptis, David James Taylor, Michael Berc
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
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
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