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Author Aiyangar, A.K.; Vivanco, J.; Au, A.G.; Anderson, P.A.; Smith, E.L.; Ploeg, H.L.
Title Dependence of Anisotropy of Human Lumbar Vertebral Trabecular Bone on Quantitative Computed Tomography-Based Apparent Density Type
Year 2014 Publication Journal Of Biomechanical Engineering-Transactions Of The Asme Abbreviated Journal J. Biomech. Eng.-Trans. ASME
Volume 136 Issue 9 Pages 10 pp
Keywords human lumbar vertebrae; trabecular bone; anisotropic ratio; transverse isotropy; elastic modulus-density relationship; strain-density relationship
Abstract Most studies investigating human lumbar vertebral trabecular bone (HVTB) mechanical property-density relationships have presented results for the superior-inferior (SI), or “ on-axis” direction. Equivalent, directly measured data from mechanical testing in the transverse (TR) direction are sparse and quantitative computed tomography (QCT) density-dependent variations in the anisotropy ratio of HVTB have not been adequately studied. The current study aimed to investigate the dependence of HVTB mechanical anisotropy ratio on QCT density by quantifying the empirical relationships between QCT-based apparent density of HVTB and its apparent compressive mechanical propertieselastic modulus (E-app), yield strength (sigma(y)), and yield strain (epsilon(y))-in the SI and TR directions for future clinical QCT-based continuum finite element modeling of HVTB. A total of 51 cylindrical cores (33 axial and 18 transverse) were extracted from four L1 human lumbar cadaveric vertebrae. Intact vertebrae were scanned in a clinical resolution computed tomography (CT) scanner prior to specimen extraction to obtain QCT density, rho(CT). Additionally, physically measured apparent density, computed as ash weight over wet, bulk volume, rho(app), showed significant correlation with rho(CT) [rho(CT) = 1.0568 x rho(app), r = 0.86]. Specimens were compression tested at room temperature using the Zetos bone loading and bioreactor system. Apparent elastic modulus (E-app) and yield strength (sigma(y)) were linearly related to the rho(CT) in the axial direction [E-SI = 1493.8 x (rho(CT)), r = 0.77, p < 0.01; sigma(Y,SI) = 6.9 x (rho(CT)) = 0.13, r = 0.76, p < 0.01] while a power-law relation provided the best fit in the transverse direction [E-TR 3349.1 x (rho(CT))(1.94), r = 0.89, p < 0.01; sigma(Y,TR) 18.81 x (rho(CT)) 1.83, r = 0.83, p < 0.01]. No significant correlation was found between epsilon(y) and rho(CT) in either direction. E-app and sigma(y) in the axial direction were larger compared to the transverse direction by a factor of 3.2 and 2.3, respectively, on average. Furthermore, the degree of anisotropy decreased with increasing density. Comparatively, epsilon(y) exhibited only a mild, but statistically significant anisotropy: transverse strains were larger than those in the axial direction by 30%, on average. Ability to map apparent mechanical properties in the transverse direction, in addition to the axial direction, from CT-based densitometric measures allows incorporation of transverse properties in finite element models based on clinical CT data, partially offsetting the inability of continuum models to accurately represent trabecular architectural variations.
Address [Aiyangar, Ameet K.] EMPA Swiss Fed Labs Mat Sci & Technol Dubendorf, Lab Mech Syst Engn 304, CH-8600 Dubendorf, Switzerland, Email: ameetaiyangar@gmail.com
Corporate Author Thesis
Publisher Asme Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0148-0731 ISBN Medium
Area Expedition Conference
Notes WOS:000340617700003 Approved
Call Number UAI @ eduardo.moreno @ Serial 401
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Author Lobos, F.; Goles, E.; Ruivo, E.L.P.; de Oliveira, P.P.B.; Montealegre, P.
Title Mining a Class of Decision Problems for One-dimensional Cellular Automata Type
Year 2018 Publication Journal Of Cellular Automata Abbreviated Journal J. Cell. Autom.
Volume 13 Issue 5-6 Pages 393-405
Keywords One-dimensional cellular automata; decision problems; density classification; parity problem
Abstract Cellular automata are locally defined, homogeneous dynamical systems, discrete in space, time and state variables. Within the context of one-dimensional, binary, cellular automata operating on cyclic configurations of odd length, we consider the general decision problem: if the initial configuration satisfies a given property, the lattice should converge to the fixed-point of all 1s ((1) over right arrow), or to (0) over right arrow, otherwise. Two problems in this category have been widely studied in the literature, the parity problem [1] and the density classification task [4]. We are interested in determining all cellular automata rules with neighborhood sizes of 2, 3, 4 and 5 cells (i.e., radius r of 0.5, 1, 1.5 and 2.5) that solve decision problems of the previous type. We have demonstrated a theorem that, for any given rule in those spaces, ensures the non existence of fixed points other than (0) over right arrow and (1) over right arrow for configurations of size larger than 2(2r), provided that the rule does not support different fixed points for any configuration with size smaller than or equal to 2(2r). In addition, we have a proposition that ensures the convergence to only (0) over right arrow or (1) over right arrow of any initial configuration, if the rule complies with given conditions. By means of theoretical and computational approaches, we determined that: for the rule spaces defined by radius 0.5 and r = 1, only 1 and 2 rules, respectively, converge to (1) over right arrow or (0) over right arrow, to any initial configuration, and both recognize the same language, and for the rule space defined by radius r = 1.5, 40 rules satisfy this condition and recognize 4 different languages. Finally, for the radius 2 space, out of the 4,294,967,296 different rules, we were able to significantly filter it out, down to 40,941 candidate rules. We hope such an extensive mining should unveil new decision problems of the type widely studied in the literature.
Address [Lobos, Fabiola; Goles, Eric; Montealegre, Pedro] Univ Adolfo Ibanez, Fac Ingn & Ciencias, Ave Diagonal Torres 2640, Santiago, Chile, Email: pp.balbi@gmail.com
Corporate Author Thesis
Publisher Old City Publishing Inc Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1557-5969 ISBN Medium
Area Expedition Conference
Notes WOS:000449762900002 Approved
Call Number UAI @ eduardo.moreno @ Serial 931
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Author Mahajan, S.M.; Asenjo, F.A.
Title Hot Fluids and Nonlinear Quantum Mechanics Type
Year 2015 Publication International Journal Of Theoretical Physics Abbreviated Journal Int. J. Theor. Phys.
Volume 54 Issue 5 Pages 1435-1449
Keywords Nonlinear quantum mechanics; Fluids; Temperature; High energy density physics
Abstract A hot relativistic fluid is viewed as a collection of quantum objects that represent interacting elementary particles. We present a conceptual framework for deriving nonlinear equations of motion obeyed by these hypothesized objects. A uniform phenomenological prescription, to affect the quantum transition from a corresponding classical system, is invoked to derive the nonlinear Schrodinger, Klein-Gordon, and Pauli-Schrodinger and Feynman-GellMaan equations. It is expected that the emergent hypothetical nonlinear quantum mechanics would advance, in a fundamental way, both the conceptual understanding and computational abilities, particularly, in the field of extremely high energy-density physics.
Address [Mahajan, Swadesh M.] Univ Texas Austin, Inst Fus Studies, Austin, TX 78712 USA, Email: mahajan@mail.utexas.edu;
Corporate Author Thesis
Publisher Springer/Plenum Publishers Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0020-7748 ISBN Medium
Area Expedition Conference
Notes WOS:000352858600004 Approved
Call Number UAI @ eduardo.moreno @ Serial 485
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Author Montalva-Medel, M.; de Oliveira, P.P.B.; Goles, E.
Title A portfolio of classification problems by one-dimensional cellular automata, over cyclic binary configurations and parallel update Type
Year 2018 Publication Natural Computing Abbreviated Journal Nat. Comput.
Volume 17 Issue 3 Pages 663-671
Keywords One-dimensional cellular automata; Classification problem; Decision problem; Language recognition; Density; Parity; Emergent computation
Abstract Decision problems addressed by cellular automata have been historically expressed either as determining whether initial configurations would belong to a given language, or as classifying the initial configurations according to a property in them. Unlike traditional approaches in language recognition, classification problems have typically relied upon cyclic configurations and fully paralell (two-way) update of the cells, which render the action of the cellular automaton relatively less controllable and difficult to analyse. Although the notion of cyclic languages have been studied in the wider realm of formal languages, only recently a more systematic attempt has come into play in respect to cellular automata with fully parallel update. With the goal of contributing to this effort, we propose a unified definition of classification problem for one-dimensional, binary cellular automata, from which various known problems are couched in and novel ones are defined, and analyse the solvability of the new problems. Such a unified perspective aims at increasing existing knowledge about classification problems by cellular automata over cyclic configurations and parallel update.
Address [Montalva-Medel, Marco; Goles, Eric] Univ Adolfo Ibanez, Ave Diagonal Torres 2640, Santiago, Chile, Email: marco.montalva@uai.cl
Corporate Author Thesis
Publisher Springer Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1567-7818 ISBN Medium
Area Expedition Conference
Notes WOS:000441986000016 Approved
Call Number UAI @ eduardo.moreno @ Serial 908
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Author Vivanco, J.F.; Burgers, T.A.; Garcia-Rodriguez, S.; Crookshank, M.; Kunz, M.; MacIntyre, N.J.; Harrison, M.M.; Bryant, J.T.; Sellens, R.W.; Ploeg, H.L.
Title Estimating the density of femoral head trabecular bone from hip fracture patients using computed tomography scan data Type
Year 2014 Publication Proceedings Of The Institution Of Mechanical Engineers Part H-Journal Of Engineering In Medicine Abbreviated Journal Proc. Inst. Mech. Eng. Part H-J. Eng. Med.
Volume 228 Issue 6 Pages 616-626
Keywords Computed tomography; femoral head; trabecular bone; bone density; X-ray attenuation
Abstract The purpose of this study was to compare computed tomography density (rho(CT)) obtained using typical clinical computed tomography scan parameters to ash density (rho(ash)), for the prediction of densities of femoral head trabecular bone from hip fracture patients. An experimental study was conducted to investigate the relationships between rho(ash) and rho(CT) and between each of these densities and rho(bulk) and rho(dry). Seven human femoral heads from hip fracture patients were computed tomography-scanned ex vivo, and 76 cylindrical trabecular bone specimens were collected. Computed tomography density was computed from computed tomography images by using a calibration Hounsfield units-based equation, whereas rho(bulk), rho(dry) and rho(ash) were determined experimentally. A large variation was found in the mean Hounsfield units of the bone cores (HUcore) with a constant bias from rho(CT) to rho(ash) of 42.5 mg/cm(3). Computed tomography and ash densities were linearly correlated (R-2 = 0.55, p < 0.001). It was demonstrated that rho(ash) provided a good estimate of rho(bulk) (R-2 = 0.78, p < 0.001) and is a strong predictor of rho(dry) (R-2 = 0.99, p < 0.001). In addition, the rho(CT) was linearly related to rho(bulk) (R-2 = 0.43, p < 0.001) and rho(dry) (R-2 = 0.56, p < 0.001). In conclusion, mineral density was an appropriate predictor of rho(bulk) and rho(dry), and rho(CT) was not a surrogate for rho(ash). There were linear relationships between rho(CT) and physical densities; however, following the experimental protocols of this study to determine rho(CT), considerable scatter was present in the rho(CT) relationships.
Address [Vivanco, Juan F.; Garcia-Rodriguez, Sylvana; Ploeg, Heidi-Lynn] Univ Wisconsin, Dept Mech Engn, Madison, WI 53706 USA, Email: ploeg@engr.wisc.edu
Corporate Author Thesis
Publisher Sage Publications Ltd Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0954-4119 ISBN Medium
Area Expedition Conference
Notes WOS:000338037000009 Approved
Call Number UAI @ eduardo.moreno @ Serial 383
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