Intermediate strain rate behavior of cancellous bone: From the lower to the higher strain rate

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Links between microstructural properties of cancellous bone and its mechanical response to different strain rates.

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Correlations between cancellous bone architecture and its dynamic behaviour

Previous studies showed that in vivo evaluation of the fracture risk of cancellous bone can be assessed by identifying the relationships between its microarchitecture description extracted from clinical imaging and its mechanical properties. The mechanical properties under dynamic loadings (with and without confinement) were obtained and compared to quasi-static ones. The architectural parameters of each specimen were extracted from pQCT images and split into four groups: geometry, topology, connectivity and anisotropy. Results show that architectural parameters are strong determinants of mechanical behaviour for the different applied boundary conditions.http://icills2014.org/wp-content/uploads/2014/01/Marrianne-Prot.pd

Les principes de la Gestalt et des proportions dérivées du nombre d'or comme outils créatifs pour la conception d'environnements intérieurs

Cette recherche présente l’étude d'un procédé conceptuel pouvant potentiellement être utilisé lors de la réalisation d’un projet de design d’intérieur pour générer des impacts spatiaux efficaces via des gestes simples. Ce sont donc principalement les designers d'intérieur qui peuvent bénéficier de la lecture de ce travail, mais également les autres disciplines du design d'espace. La simplicité et l’épuration des formes sont considérées dans ce travail comme une avenue possible pour réduire les ressources financières et matérielles requises et ainsi répondre aux enjeux budgétaires et écologiques des projets. Ensuite, pour favoriser l’émergence d’un design efficace et de qualité, cette recherche met de l'avant des savoirs théoriques et étudie comment des possibilités conceptuelles peuvent émerger ce ceux-ci lorsque des principes issus de la Gestalt et des proportions sont transplantés dans la volumétrie d'un espace physique. C’est par l’entremise d’une revue de projets existants construits, d’investigations exploratoires volumétriques et de mises en application digitales qu’il a été possible d’avoir une vision plus éclairée de la potentialité des principes à l’étude à favoriser la mise en place d’interventions de design efficaces. L’étude permet de constater que les principes issus de la Gestalt ont le potentiel d'influencer la perception (cognition) spatiale de l'usager, de favoriser la mise en place d’un design visuellement distingué ainsi que de définir et de structurer les espaces. Ensuite, l’étude permet de constater que l'utilisation des principes de proportions inspirés du nombre d'or favorise un design esthétiquement harmonieux et adapté à la morphologie de l’homme ainsi qu’une symbiose avec la nature. L'harmonie des proportions favorise un bien-être à l'occupant du lieu. Finalement, l'utilisation d'un système de proportion peut agir à titre de guide structurel pour la conception de compositions spatiales. Mots-clés : design d’intérieur, conception, spatialité, principes, Gestalt, proportion, nombre d’or, fonctionnalité, esthétisme, simplicit

What is the recommended size of a Volume of Interest for cancellous bone ? A skeleton-based study

The study of the bone fracture is an important issue for oste- oporosis and car safety. The behavior of cancellous bone is strongly linked to the micro-architecture, the strain rate (Prot et al. 2015), and the specimen size Harrison & McHugh 2010). Numerical models are used in order to simulate the viscoelas- tic behavior up to the point of fracture propagation in cancellous bone. Finite element method (FEM) models based on micro-CT scans are currently the most popular approach. However, the results are dependent on the specimen size and the mesh den- sity, in addition to which the fracture analysis is time-consum- ing (Hambli 2013). Moreover, the variable architecture within a typical specimen limits the minimum sample size that will still provide reasonable architectural parameter values in comparison with the full specimen size. Indeed, a BV/TV variation up to 20% was found in the same specimen (ϕ = 7.85 mm) (Stauber et al. 2014). Skeleton-based models have already shown a great poten- tial for the efficient simulation of bone behavior and fracture. Cancellous bone geometry is based on nodes, beams, and plates (Stauber & Müller 2006), which is straightforward to implement from a skeleton. In this study, the effect of the Volume of Interest (VOI) size, within a sample, on the evaluation of cancellous bone architec- tural parameters from the skeletonized model will be presented. The aim was to furnish recommendations for the sample size for further numerical simulations

Morpho-statistical description of networks through graph modelling and Bayesian inference

Collaborative graphs are relevant sources of information to understand behavioural tendencies of groups of individuals. Exponential Random Graph Models (ERGMs) are commonly used to analyze such social processes including dependencies between members of the group. Our approach considers a modified version of ERGMs, modeling the problem as an edge labelling one. The main difficulty is inference since the normalising constant involved in classical Markov Chain Monte Carlo (MCMC) approaches is not available in an analytic closed form. The main contribution is to use the recent ABC Shadow algorithm. This algorithm is built to sample from posterior distributions while avoiding the previously mentioned drawback. The proposed method is illustrated on real data sets provided by the Hal platform and provides new insights on self-organised collaborations among researchers

Fracture characterization in cancellous bone specimens via surface difference evaluation of 3D registered pre- and post-compression micro-CT scans

In recent years, increasingly stringent passenger vehicle safety requirements have led to a renewed interest in the fracture properties of bone. It has been shown that can- cellous bone architecture is strongly linked to its overall behavior (Follet et al. 2011; Prot et al. 2015). Micro- fracture mechanisms have been resolved by time- consuming direct microscopy (Prot et al. 2012) or by the use of calcein (Lambers et al. 2014; Hernandez et al. 2014). Furthermore, the application of CT scanners, along with the development of registration algorithms, has allowed separated portions of fractured specimen to be registered to the pre-compression scan so as to quantify the differ- ence between 3D shapes as a mean to characterize the fracture behavior (Tassani & Matsopoulos 2014). How- ever, this method is operator-dependent in the case of multiple fracture zone identification and requires suffi- cient deformation of the specimen to obtain distinct reg- istration sets. In addition, built-in micro-compression testers, developed by CT scanner manufacturers, are limited to loading at low levels of strain rate, which does not allow measurement over a range that is representative of daily life. The goal of this study was to identify distinct fracture patterns based on micro-CT scans of cancellous bone specimens, loaded over a large range of strain rates, without the need for specimens that have broken into separate pieces

Links between mechanical behavior of cancellous bone and its microstructural properties under dynamic loading

Previous studies show that in vivo assessment of fracture risk can be achieved by identifying the relationships between microarchitecture description from clinical imaging and mechanical properties. This study demonstrates that results obtained at low strain rates can be extrapolated to loadings with an order of magnitude similar to trauma such as car crashes. Cancellous bovine bone specimens were compressed under dynamic loadings (with and without confinement) and the mechanical response properties were identified, such as Young's modulus, ultimate stress, ultimate strain, and ultimate strain energy. Specimens were previously scanned with pQCT, and architectural and structural microstructure properties were identified, such as parameters of geometry, topology, connectivity and anisotropy. The usefulness of micro-architecture description studied was in agreement with statistics laws. Finally, the differences between dynamic confined and non-confined tests were assessed by the bone marrow influence and the cancellous bone response to different boundary conditions. Results indicate that architectural parameters, such as the bone volume fraction (BV/TV), are as strong determinants of mechanical response parameters as ultimate stress at high strain rates (p-valueo0.001). This study reveals that cancellous bone response at high strain rates, under different boundary conditions, can be predicted from the architectural parameters, and that these relations with mechanical properties can be used to make fracture risk prediction at a determined magnitude

Formation of Complexes at Plasmodesmata for Potyvirus Intercellular Movement Is Mediated by the Viral Protein P3N-PIPO

Intercellular transport of viruses through cytoplasmic connections, termed plasmodesmata (PD), is essential for systemic infection in plants by viruses. Previous genetic and ultrastructural data revealed that the potyvirus cyclindrical inclusion (CI) protein is directly involved in cell-to-cell movement, likely through the formation of conical structures anchored to and extended through PD. In this study, we demonstrate that plasmodesmatal localization of CI in N. benthamiana leaf cells is modulated by the recently discovered potyviral protein, P3N-PIPO, in a CI:P3N-PIPO ratio-dependent manner. We show that P3N-PIPO is a PD-located protein that physically interacts with CI in planta. The early secretory pathway, rather than the actomyosin motility system, is required for the delivery of P3N-PIPO and CI to PD. Moreover, CI mutations that disrupt virus cell-to-cell movement compromise PD-localization capacity. These data suggest that the CI and P3N-PIPO complex coordinates the formation of PD-associated structures that facilitate the intercellular movement of potyviruses in infected plants

Integrated immunovirological profiling validates plasma SARS-CoV-2 RNA as an early predictor of COVID-19 mortality.

peer reviewedDespite advances in COVID-19 management, identifying patients evolving toward death remains challenging. To identify early predictors of mortality within 60 days of symptom onset (DSO), we performed immunovirological assessments on plasma from 279 individuals. On samples collected at DSO11 in a discovery cohort, high severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA (vRNA), low receptor binding domain–specific immunoglobulin G and antibody-dependent cellular cytotoxicity, and elevated cytokines and tissue injury markers were strongly associated with mortality, including in patients on mechanical ventilation. A three-variable model of vRNA, with predefined adjustment by age and sex, robustly identified patients with fatal outcome (adjusted hazard ratio for log-transformed vRNA = 3.5). This model remained robust in independent validation and confirmation cohorts. Since plasma vRNA’s predictive accuracy was maintained at earlier time points, its quantitation can help us understand disease heterogeneity and identify patients who may benefit from new therapies