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Phys Rev E ; 95(6-2): 069902, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28709253


This corrects the article DOI: 10.1103/PhysRevE.95.052901.

Phys Rev E ; 95(5-1): 052901, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28618587


Inspired by dynamic similarity in fluid systems, we have derived a general dimensionless form for locomotion in granular materials, which is validated in experiments and discrete element method (DEM) simulations. The form instructs how to scale size, mass, and driving parameters in order to relate dynamic behaviors of different locomotors in the same granular media. The scaling can be derived by assuming intrusion forces arise from resistive force theory or equivalently by assuming the granular material behaves as a continuum obeying a frictional yield criterion. The scalings are experimentally confirmed using pairs of wheels of various shapes and sizes under many driving conditions in a common sand bed. We discuss why the two models provide such a robust set of scaling laws even though they neglect a number of the complexities of granular rheology. Motivated by potential extraplanetary applications, the dimensionless form also implies a way to predict wheel performance in one ambient gravity based on tests in a different ambient gravity. We confirm this using DEM simulations, which show that scaling relations are satisfied over an array of driving modes even when gravity differs between scaled tests.

Dalton Trans ; 40(16): 4284-90, 2011 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-21394331


The self-assembly of a carbonylpyridine-based heptadentate ligand with Ln(III) results in the formation of triangular trinuclear europium complexes, which exhibit interesting luminescent properties in the solid state and in solution. With a view to developing multimodal responsive systems, we report here the preparation and characterisation of analogous complexes with Gd(III). The X-ray crystal structure of Gd(3)L2(3) indeed reveals the isostructurality with the Eu(III) complexes. A combination of (1)H NMRD and variable temperature studies yields the parameters elucidating the exchange of coordinated water and relaxivity properties. Conveniently, the competitive spectrophotometric titrations with EDTA and NTA are used to determine the thermodynamic stability constants of the europium complexes in aqueous media. In addition, the exchange reaction with EDTA is monitored with NMR and fluorimetry. The interactions of the Eu(III) trinuclear complex with some potentially interfering ligands are qualitatively investigated by means of luminescence titrations.

Elementos da Série dos Lantanídeos/química , Ácidos Carboxílicos/química , Cristalografia por Raios X , Ácido Edético/química , Espectroscopia de Ressonância Magnética , Magnetismo , Modelos Moleculares , Conformação Molecular , Termodinâmica
Chaos ; 20(1): 017507, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20370297


Ridges in the state space distribution of finite-time Lyapunov exponents can be used to locate dynamical boundaries. We describe a method for obtaining dynamical boundaries using only trajectories reconstructed from time series, expanding on the current approach which requires a vector field in the phase space. We analyze problems in musculoskeletal biomechanics, considered as exemplars of a class of experimental systems that contain separatrix features. Particular focus is given to postural control and balance, considering both models and experimental data. Our success in determining the boundary between recovery and failure in human balance activities suggests this approach will provide new robust stability measures, as well as measures of fall risk, that currently are not available and may have benefits for the analysis and prevention of low back pain and falls leading to injury, both of which affect a significant portion of the population.

Fenômenos Biomecânicos , Biofísica/métodos , Acidentes por Quedas , Algoritmos , Simulação por Computador , Interpretação Estatística de Dados , Humanos , Modelos Biológicos , Equilíbrio Postural , Postura , Reprodutibilidade dos Testes , Caminhada , Suporte de Carga/fisiologia