Search results for "Biomechanical"
showing 10 items of 524 documents
On the biomechanical function of scaffolds for engineering load-bearing soft tissues
2009
Replacement or regeneration of load-bearing soft tissues has long been the impetus for the development of bioactive materials. While maturing, current efforts continue to be confounded by our lack of understanding of the intricate multi-scale hierarchical arrangements and interactions typically found in native tissues. The current state of the art in biomaterial processing enables a degree of controllable microstructure that can be used for the development of model systems to deduce fundamental biological implications of matrix morphologies on cell function. Furthermore, the development of computational frameworks which allow for the simulation of experimentally derived observations represe…
A neural network approach to movement pattern analysis.
2004
Movements are time-dependent processes and so can be modelled by time-series of coordinates: E.g., each articulation has geometric coordinates; the set of the coordinates of the relevant articulations build a high-dimensional configuration. These configurations--or "patterns"--give reason for analysing movements by means of neural networks: The Kohonen Feature Map (KFM) is a special type of neural network, which (after having been coined by training with appropriate pattern samples) is able to recognize single patterns as members of pattern clusters. This way, for example, the particular configurations of a given movement can be identified as belonging to respective configuration clusters, …
A new interpretation and practical aspects of the direct-methods modulus sum function. VIII
2001
Since the first publication of the direct-methods modulus sum function [Rius (1993). Acta Cryst. A49, 406-409], the application of this function to a variety of situations has been shown in a series of seven subsequent papers. In this way, much experience about this function and its practical use has been gained. It is thought by the authors that it is now the right moment to publish a more complete study of this function which also considers most of this practical knowledge. The first part of the study relates, thanks to a new interpretation, this function to other existing phase-refinement functions, while the second shows, with the help of test calculations on a selection of crystal stru…
Ocean acidification bends the mermaid's wineglass
2015
Ocean acidification lowers the saturation state of calcium carbonate, decreasing net calcification and compromising the skeletons of organisms such as corals, molluscs and algae. These calcified structures can protect organisms from predation and improve access to light, nutrients and dispersive currents. While some species (such as urchins, corals and mussels) survive with decreased calcification, they can suffer from inferior mechanical performance. Here, we used cantilever beam theory to test the hypothesis that decreased calcification would impair the mechanical performance of the green alga Acetabularia acetabulum along a CO 2 gradient created by volcanic seeps off Vulcano, Italy. Cal…
Mussels as a model system for integrative ecomechanics.
2015
Copyright © 2015 by Annual Reviews. All rights reserved. Mussels form dense aggregations that dominate temperate rocky shores, and they are key aquaculture species worldwide. Coastal environments are dynamic across a broad range of spatial and temporal scales, and their changing abiotic conditions affect mussel populations in a variety of ways, including altering their investments in structures, physiological processes, growth, and reproduction. Here, we describe four categories of ecomechanical models (biochemical, mechanical, energetic, and population) that we have developed to describe specific aspects of mussel biology, ranging from byssal attachment to energetics, population growth, an…
Joined effects of pennation angle and tendon compliance on fibre length in isometric contractions: a simulation study.
1998
The main purpose of this study was to investigate the joined behaviours of tendon and pennation angle during maximal isometric contractions. A musculotendon model of the human soleus muscle was simulated as a function of ankle joint position, which determines the soleus length. Analysis of the respective values of tendon length and pennation angle for various musculotendon lengths showed that the primary effects of tendon elasticity and pennation angle variation were to reduce the fibre length variations by absorption of the musculotendon lengthening. The efficiency of this reduction process was the highest at short soleus lengths and principally related to tendon length variations. Finally…
Ricci-flow based conformal mapping of the proximal femur to identify exercise loading effects.
2018
AbstractThe causal relationship between habitual loading and adaptive response in bone morphology is commonly explored by analysing the spatial distribution of mechanically relevant features. In this study, 3D distribution of features in the proximal femur of 91 female athletes (5 exercise loading groups representing habitual loading) is contrasted with 20 controls. A femur specific Ricci-flow based conformal mapping procedure was developed for establishing correspondence among the periosteal surfaces. The procedure leverages the invariance of the conformal mapping method to isometric shape differences to align surfaces in the 2D parametric domain, to produce dense correspondences across an…
Subcellular localization and characterization of nitric oxide synthase(s) in endothelial cells: physiological implications.
1994
Endothelial cells (EC) contain a constitutive Ca2+/calmodulin-dependent nitric oxide (NO) synthase (cNOS) which plays an important role in the local control of vascular tone. We compared the subcellular distribution of this enzyme in cultured and freshly isolated pig EC by determination of specific cNOS activity and immunoblot analysis. Similar studies were also performed with cultured and freshly isolated bovine and cultured human EC. Enzyme activity was predominantly (> 70%) associated with the particulate fraction of all EC types tested and was highest in freshly isolated porcine EC. Both specific cNOS activity and immunoreactivity were substantially higher (> 3-fold) in th…
Seven Mathematical Models of Hemorrhagic Shock
2021
Although mathematical modelling of pressure-flow dynamics in the cardiocirculatory system has a lengthy history, readily finding the appropriate model for the experimental situation at hand is often a challenge in and of itself. An ideal model would be relatively easy to use and reliable, besides being ethically acceptable. Furthermore, it would address the pathogenic features of the cardiovascular disease that one seeks to investigate. No universally valid model has been identified, even though a host of models have been developed. The object of this review is to describe several of the most relevant mathematical models of the cardiovascular system: the physiological features of circulator…
Biomechanics of human ascending aorta and aneurysm rupture risk assessment
2021
Ascending aortic aneurysms (AsAA) and aortic dissections are life-threatening cardiovascular diseases. The main criteria for determining surgical intervention of AsAA are the maximum diameter or the increasing annual rate of the aneurysm. The mortality of the untreated aortic dissection can be 21% to 74%, depending on the delay of hospital admission.Our study aims to characterize the biomechanical properties of the ascending aorta and propose a patient-specific approach to assess the risks of rupture. The purpose of this PhD work is multifold.On the one hand, biaxial tensile tests were performed on AsAA samples obtained from one hundred patients with surgery of AsAA. The impact on the diffe…