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Journal articleRosenberg N, Bull AMJ, 2018,
Simulating localised cellular inflammation and substrate properties in a strain energy density based bone remodelling algorithm for use in modelling trauma
, Computer Methods in Biomechanics and Biomedical Engineering, Vol: 21, Pages: 208-218, ISSN: 1025-5842Bone responds to mechanical stimulus and a range of pre-existing finite element models have been suggested to reproduce the internal physiological structure of bone. Inflammation effects are not included in these models, yet inflammation is a key component of bone repair in trauma. Therefore, a model is proposed and tested here that extends these methods to include parameters that could be considered to represent the behaviour of bone remodelling when influenced by inflammation. The proposed model regulates remodelling based on findings from recent studies into the nature of heterotopic ossification, the formation of heterotopic bone, which have revealed information about the nature of bone after high levels of trauma. These parameters include consideration of the distance from the zone of trauma, the density of mesenchymal stem cells, and substrate stiffness as a trigger for cells becoming osteogenic. The method is tested on a two-dimensional plate model and shows that the new extended algorithm can produce a range of structures depending on inputs that could be used in the future to replicate physiological scenarios.
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Journal articleEtard OE, Kegler M, Braiman C, et al., 2018,
Real-time decoding of selective attention from the human auditory brainstem response to continuous speech
, BioRxiv -
Journal articlearora H, nila A, Vitharana K, et al., 2017,
Microstructural consequences of blast lung injury characterised with digital volume correlation
, Frontiers in Materials, Vol: 4, ISSN: 2296-8016This study focuses on microstructural changes that occur within the mammalian lung when subject to blast and how these changes influence strain distributions within the tissue. Shock tube experiments were performed to generate the blast injured specimens (cadaveric Sprague-Dawley rats). Blast overpressures of 100 and 180 kPa were studied. Synchrotron tomography imaging was used to capture volumetric image data of lungs. Specimens were ventilated using a custom-built system to study multiple inflation pressures during each tomography scan. These data enabled the first digital volume correlation (DVC) measurements in lung tissue to be performed. Quantitative analysis was performed to describe the damaged architecture of the lung. No clear changes in the microstructure of the tissue morphology were observed due to controlled low- to moderate-level blast exposure. However, significant focal sites of injury were observed using DVC, which allowed the detection of bias and concentration in the patterns of strain level. Morphological analysis corroborated the findings, illustrating that the focal damage caused by a blast can give rise to diffuse influence across the tissue. It is important to characterize the non-instantly fatal doses of blast, given the transient nature of blast lung in the clinical setting. This research has highlighted the need for better understanding of focal injury and its zone of influence (alveolar interdependency and neighboring tissue burden as a result of focal injury). DVC techniques show great promise as a tool to advance this endeavor, providing a new perspective on lung mechanics after blast.
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Journal articleForte AE, Etard O, Reichenbach J, 2017,
The human auditory brainstem response to running speech reveals a subcortical mechanism for selective attention
, eLife, Vol: 6, ISSN: 2050-084XHumans excel at selectively listening to a target speaker in background noise such as competing voices. While the encoding of speech in the auditory cortex is modulated by selective attention, it remains debated whether such modulation occurs already in subcortical auditory structures. Investigating the contribution of the human brainstem to attention has, in particular, been hindered by the tiny amplitude of the brainstem response. Its measurement normally requires a large number of repetitions of the same short sound stimuli, which may lead to a loss of attention and to neural adaptation. Here we develop a mathematical method to measure the auditory brainstem response to running speech, an acoustic stimulus that does not repeat and that has a high ecological validity. We employ this method to assess the brainstem's activity when a subject listens to one of two competing speakers, and show that the brainstem response is consistently modulated by attention.
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Conference paperForte AE, Etard O, Reichenbach J, 2017,
Selective auditory attention modulates the human brainstem's response to running speech
, Basic Auditory Science 2017 -
Conference paperKegler M, Etard O, Forte AE, et al., 2017,
Complex statistical model for detecting the auditory brainstem response to natural speech and for decoding attention
, Basic Auditory Science 2017 -
Journal articleVillette CC, Phillips ATM, 2017,
Microscale poroelastic metamodel for efficient mesoscale bone remodelling simulations.
, Biomechanics and Modeling in Mechanobiology, Vol: 16, Pages: 2077-2091, ISSN: 1617-7940Bone functional tissue adaptation is a multiaspect physiological process driven by interrelated mechanical and biological stimuli which requires the combined activity of osteoclasts and osteoblasts. In previous work, the authors developed a phenomenological mesoscale structural modelling approach capable of predicting internal structure of the femur based on daily activity loading, which relied on the iterative update of the cross-sectional areas of truss and shell elements representative of trabecular and cortical bones, respectively. The objective of this study was to introduce trabecular reorientation in the phenomenological model at limited computational cost. To this aim, a metamodel derived from poroelastic microscale continuum simulations was used to predict the functional adaptation of a simplified proximal structural femur model. Clear smooth trabecular tracts are predicted to form in the regions corresponding to the main trabecular groups identified in literature, at minimal computational cost.
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Conference paperEtard, Reichenbach J, 2017,
EEG-measured correlates of comprehension in speech-in-noise listening
, Basic Auditory Science 2017 -
Journal articleSidiras C, Iliadou V, Nimatoudis I, et al., 2017,
Spoken word recognition enhancement due to preceding synchronized beats compared to unsynchronized or unrhythmic beats
, Frontiers in Neuroscience, Vol: 11, ISSN: 1662-4548The relation between rhythm and language has been investigated over the last decades, with evidence that these share overlapping perceptual mechanisms emerging from several different strands of research. The dynamic Attention Theory posits that neural entrainment to musical rhythm results in synchronized oscillations in attention, enhancing perception of other events occurring at the same rate. In this study, this prediction was tested in 10 year-old children by means of a psychoacoustic speech recognition in babble paradigm. It was hypothesized that rhythm effects evoked via a short isochronous sequence of beats would provide optimal word recognition in babble when beats and word are in sync. We compared speech recognition in babble performance in the presence of isochronous and in sync vs. non-isochronous or out of sync sequence of beats. Results showed that (a) word recognition was the best when rhythm and word were in sync, and (b) the effect was not uniform across syllables and gender of subjects. Our results suggest that pure tone beats affect speech recognition at early levels of sensory or phonemic processing.
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Conference paperForte AE, Etard O, Reichenbach J, 2017,
Complex Auditory-brainstem Response to the Fundamental Frequency of Continuous Natural Speech
, ARO 2017 -
Conference paperButler BJ, Sory DR, Nguyen T-TN, et al., 2017,
Characterization of Focal Muscle Compression Under Impact Loading
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Journal articleNolte D, Tsang CK, Zhang KY, et al., 2016,
Non-linear scaling of a musculoskeletal model of the lower limb using statistical shape models
, Journal of Biomechanics, Vol: 49, Pages: 3576-3581, ISSN: 1873-2380Accurate muscle geometry for musculoskeletal models is important to enable accurate subject-specific simulations. Commonly, linear scaling is used to obtain individualised muscle geometry. More advanced methods include non-linear scaling using segmented bone surfaces and manual or semi-automatic digitisation of muscle paths from medical images. In this study, a new scaling method combining non-linear scaling with reconstructions of bone surfaces using statistical shape modelling is presented. Statistical Shape Models (SSMs) of femur and tibia/fibula were used to reconstruct bone surfaces of nine subjects. Reference models were created by morphing manually digitised muscle paths to mean shapes of the SSMs using non-linear transformations and inter-subject variability was calculated. Subject-specific models of muscle attachment and via points were created from three reference models. The accuracy was evaluated by calculating the differences between the scaled and manually digitised models. The points defining the muscle paths showed large inter-subject variability at the thigh and shank – up to 26 mm; this was found to limit the accuracy of all studied scaling methods. Errors for the subject-specific muscle point reconstructions of the thigh could be decreased by 9% to 20% by using the non-linear scaling compared to a typical linear scaling method. We conclude that the proposed non-linear scaling method is more accurate than linear scaling methods. Thus, when combined with the ability to reconstruct bone surfaces from incomplete or scattered geometry data using statistical shape models our proposed method is an alternative to linear scaling methods.
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Journal articleGrigoriadis G, Newell N, Carpanen D, et al., 2016,
Material properties of the heel fat pad across strain rates
, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 65, Pages: 398-407, ISSN: 1751-6161The complex structural and material behaviour of the human heel fat pad determines the transmission of plantar loading to the lower limb across a wide range of loading scenarios; from locomotion to injurious incidents. The aim of this study was to quantify the hyper-viscoelastic material properties of the human heel fat pad across strains and strain rates. An inverse finite element (FE) optimisation algorithm was developed and used, in conjunction with quasi-static and dynamic tests performed to five cadaveric heel specimens, to derive specimen-specific and mean hyper-viscoelastic material models able to predict accurately the response of the tissue at compressive loading of strain rates up to 150 s−1. The mean behaviour was expressed by the quasi-linear viscoelastic (QLV) material formulation, combining the Yeoh material model (C10=0.1MPa, C30=7MPa, K=2GPa) and Prony׳s terms (A1=0.06, A2=0.77, A3=0.02 for τ1=1ms, τ2=10ms, τ3=10s). These new data help to understand better the functional anatomy and pathophysiology of the foot and ankle, develop biomimetic materials for tissue reconstruction, design of shoe, insole, and foot and ankle orthoses, and improve the predictive ability of computational models of the foot and ankle used to simulate daily activities or predict injuries at high rate injurious incidents such as road traffic accidents and underbody blast.
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Journal articleWebster C, Clasper J, Masouros S, 2016,
Pelvic Fracture and Posture at the time of injury: The potential for mitigation strategies and improving survivability
, BRITISH JOURNAL OF SURGERY, Vol: 103, Pages: 91-91, ISSN: 0007-1323 -
Journal articleWarren RL, Ramamoorthy S, Ciganovic N, et al., 2016,
Minimal basilar membrane motion in low-frequency hearing
, Proceedings of the National Academy of Sciences of the United States of America, Vol: 113, Pages: E4304-E4310, ISSN: 1091-6490Low-frequency hearing is critically important for speech and music perception, but no mechanical measurements have previously been available from inner ears with intact low-frequency parts. These regions of the cochlea may function in ways different from the extensively studied high-frequency regions, where the sensory outer hair cells produce force that greatly increases the sound-evoked vibrations of the basilar membrane. We used laser interferometry in vitro and optical coherence tomography in vivo to study the low-frequency part of the guinea pig cochlea, and found that sound stimulation caused motion of a minimal portion of the basilar membrane. Outside the region of peak movement, an exponential decline in motion amplitude occurred across the basilar membrane. The moving region had different dependence on stimulus frequency than the vibrations measured near the mechanosensitive stereocilia. This behavior differs substantially from the behavior found in the extensively studied high-frequency regions of the cochlea.
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Journal articleCampos-Pires R, Edge CJ, Dickinson R, 2016,
Argon: A Noble Foe for Subarachnoid Hemorrhage
, Critical Care Medicine, Vol: 44, Pages: 1456-1457, ISSN: 1530-0293 -
Journal articleDel Linz P, Wang Y, Hooper PA, et al., 2016,
Determining Material Response for Polyvinyl Butyral (PVB) in Blast Loading Situations
, Experimental Mechanics, Vol: 56, Pages: 1501-1517, ISSN: 1741-2765Protecting structures from the effect of blast loads requires the careful design of all building components. In this context, the mechanical properties of Polyvinyl Butyral (PVB) are of interest to designers as the membrane behaviour will affect the performance of laminated glass glazing when loaded by explosion pressure waves. This polymer behaves in a complex manner and is difficult to model over the wide range of strain rates relevant to blast analysis. In this study, data from experimental tests conducted at strain rates from 0.01 s−1 to 400 s−1 were used to develop material models accounting for the rate dependency of the material. Firstly, two models were derived assuming Prony series formulations. A reduced polynomial spring and a spring derived from the model proposed by Hoo Fatt and Ouyang were used. Two fits were produced for each of these models, one for low rate cases, up to 8 s−1, and one for high rate cases, from 20 s−1. Afterwards, a single model representing all rates was produced using a finite deformation viscoelastic model. This assumed two hyperelastic springs in parallel, one of which was in series with a non-linear damper. The results were compared with the experimental results, assessing the quality of the fits in the strain range of interest for blast loading situations. This should provide designers with the information to choose between the available models depending on their design needs.
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Journal articleBarnett-Vanes A, Sharrock A, Eftaxiopoulou T, et al., 2016,
CD43Lo classical monocytes participate in the cellular immune response to isolated primary blast lung injury
, Journal of Trauma and Acute Care Surgery, Vol: 81, Pages: 500-511, ISSN: 2163-0763BACKGROUND: Understanding of the cellular immune response to primary blast lung injury (PBLI) is limited, with only the neutrophil response well documented. Moreover, its impact on the immune response in distal organs remains poorly understood. In this study, a rodent model of isolated primary blast injury was used to investigate the acute cellular immune response to isolated PBLI in the circulation and lung; including the monocyte response, and investigate distal sub-acute immune effects in the spleen and liver 6hr after injury. METHODS: Rats were subjected to a shock wave (~135kPa overpressure, 2ms duration) inducing PBLI or sham procedure. Rat physiology was monitored and at 1, 3 and 6 hr thereafter blood, lung, and Broncho-alveolar lavage fluid (BALF) were collected and analysed by flow cytometry (FCM), ELISA and Histology. In addition, at 6hr spleen and liver were collected and analysed by FCM. RESULTS: Lung histology confirmed pulmonary barotrauma and inflammation. This was associated with rises in CXCL-1, IL-6, TNF-α and albumin protein in the BALF. Significant acute increases in blood and lung neutrophils and CD43Lo/His48Hi (classical) monocytes/macrophages were detected. No significant changes were seen in blood or lung 'non-classical' monocyte, NK, B or T Cells. In the BALF, significant increases were seen in neutrophils, CD43Lo monocyte-macrophages and MCP-1. Significant increases in CD43Lo and Hi monocyte-macrophages were detected in the spleen at 6hr. CONCLUSIONS: This study reveals a robust and selective response of CD43Lo/His48Hi (classical) monocytes - in addition to neutrophils - in blood and lung tissue following PBLI. An increase in monocyte-macrophages was also observed in the spleen at 6hr. This profile of immune cells in the blood and BALF could present a new research tool for translational studies seeking to monitor, assess or attenuate the immune response in blast injured patients. EVIDENCE: Experimental laboratory study.WC- 300.
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Conference paperCampos-Pires R, Armstrong SP, Sebastiani A, et al., 2016,
THE NOBLE GAS XENON REDUCES SECONDARY INJURYAND IMPROVES LONG-TERM LOCOMOTOR FUNCTION AFTER TRAUMATIC BRAIN INJURY IN RODENTS
, 27th International Symposium on Cerebral Blood Flow, Metabolism and Function / 12th International Conference on Quantification of Brain Function with PET, Publisher: SAGE PUBLICATIONS INC, Pages: 308-309, ISSN: 0271-678X -
Journal articleDel Linz P, Hooper PA, Arora H, et al., 2016,
Delamination properties of laminated glass windows subject to blast loading
, International Journal of Impact Engineering, Vol: 105, Pages: 39-53, ISSN: 1879-3509Delamination processes absorb significant amounts of energy in laminated glass windows when they are subjected to blast loads. Blast tests were performed previously and their results had been used to calculate the loads imposed on the support systems. In this research, the delamination process at realistic deformation rates was studied to understand the reaction force response obtained. Laboratory tensile tests were performed on pre-cracked laminated glass specimens to investigate their delamination behaviour. The experiments confirmed the presence of a plateau in the force-deflection graphs, suggesting that the delamination process absorbed significant energy. The experimental results were then employed to calibrate FEA models of the delamination process with the aim of estimating the delamination energy of the polyvinyl butyral (PVB) membrane and glass layers and its relationship with deformation speed. The delamination energies obtained through this research, if used with the appropriate PVB material model, are a valuable new tool new tool in the modelling and design of laminated glass façade structures.
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