130 research outputs found
Functoriality in Finitary Vacuum Einstein Gravity and Free Yang-Mills Theories from an Abstract Differential Geometric Perspective
No full textWe continue ongoing research work on applying the homological algebraic
conceptual and technical machinery of Abstract Differential Geometry towards
formulating a finitary, causal and quantal version of vacuum Einstein
Lorentzian gravity and free Yang-Mills theories.Comment: This is an invited paper contribution to a Special Volume titled
`Physical Geometry: Unravelling the Weave of Quantum Geometry' in memory and
honour of Professor Anastasios Mallios, edited by Dr Elias Zafiris. Extended
latest version includes two Addenda and an Appendix at the bac
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
Finitary Čech-de Rham cohomology
No full textThe present paper continues (Mallios & Rapfis, International Journal of Theoretical Physics, 2001, 40, 1885) and studies the curved finitary spacetime sheaves of incidence algebras presented therein from a Čech cohomological perspective. In particular, we entertain the possibility of constructing a nontrivial de Rham complex on these finite dimensional algebra sheaves along the lines of the first author's axiomatic approach to differential geometry via the theory of vector and algebra sheaves (Mallios, Geometry of Vector Sheaves. An Axiomtic Approach to Differential Geometry, Vols. 1-2, Kluwer, Dordrecht, 1998a; Mathematica Japonica (International Plaza), 1998b, 48, 93). The upshot of this study is that important "classical" differential geometric constructions and results usually thought of as being intimately associated with C∞-smooth manifolds carry through, virtually unaltered, to the finitary-algebraic regime with the help of some quite universal, because abstract, ideas taken mainly from sheaf-cohomology as developed in Mallios (1998a,b). At the end of the paper, and due to the fact that the incidence algebras involved have been interpreted as quantum causal sets (Raptis, International Journal of Theoretical Physics, 2000, 39, 1233; Mallios & Rapfis, 2001), we discuss how these ideas may be used in certain aspects of current research on discrete Lorentzian quantum gravity
Abdominal Aortic Aneurysm Endovascular Repair: Profiling Postimplantation Morphometry and Hemodynamics with Image-Based Computational Fluid Dynamics
No full textRemodeling effects of carotid artery stenting versus endarterectomy with patch angioplasty in terms of morphology and hemodynamics
No full textBackground: Carotid endarterectomy (CEA) remains the first-line treatment option of symptomatic and asymptomatic carotid stenosis, while stenting (CAS) is reserved for selected patients at high surgical risk. Here, we compare the vascular remodeling process in CEA-and CAS-treated patients with respect to morphological and hemodynamic features, because of their possible engagement in carotid atherosclerosis. Methods: Twelve (12) patients were included, half with patched CEA and half with CAS. Pre-and post-operative 3D image-based models of the carotid bifurcation were anatomically characterized in terms of flare, tortuosity, and curvature. Individual computational fluid dynamics simulations allowed to quantify the postoperative hemodynamic milieu in terms of (1) wall shear stress and (2) helical flow. Results: Carotid flare increased in all cases, but a more marked increase emerged after CEA compared to CAS. Tortuosity and curvature increased after CEA but decreased after CAS. CEA patients presented with significantly higher postoperative tortuosity than CAS patients. CEA was associated with a worse (non-statistically significant) score in all flow disturbance indicators vs. CAS. Conclusion: The increased flare and tortuosity of the carotid bifurcation after CEA vs. CAS is a marked difference in the vascular remodeling process between the two modalities. CAS seems to induce a less pro-restenosis hemodynamic environment compared to CEA. The emerged differences stimulate further analysis on a larger cohort with long-term outcomes, to shed light on the clinical impact of the observations
Carotid artery endarterectomy vs. stenting: are there any relevant morphological and hemodynamic implications?
No full textMorphological and hemodynamic characterization of post endovascular AAA repair: comparison between two different commercial devices
No full textPatient-specific modelling for the assessment of the hemodynamics risk of failure in endovascular aneurysm repair
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