AbstractAn experimental program investigating the potential of fiber-reinforced polymers (FRPs) as a strengthening option for glulam beams subjected to simulated blast loads was undertaken. A total ...of four different retrofit configurations were investigated along with a fifth alternative for restoring previously damaged beams. Increases in resistance and maximum deflection in the range of 1.35–1.66 and 1.3–1.62, respectively, were obtained when FRP tension laminates with and without confinement were used. Partial-length and full-length confinement prevented premature debonding and significantly altered the failure mode from simple tension failure to a combination of brash tension and compression failure while limiting the damage to a small region. The results also showed that the addition of FRP contributed to an increase of 1.17 in the tensile failure strain relative to the unretrofitted beams. A material predictive model that accounts for strain-rate effects was developed using experimental stress–strain relationships determined from coupon tests. The proposed model compared well with resistance curves obtained from full-scale testing of glulam beam elements subjected to simulated blast loading.
AbstractA material predictive model that accounts for strain-rate effects and captures the effect of variable axial load on the dynamic response of glulam structural members subjected to combined ...lateral-blast and axial loading is developed and validated using experimental data for full-scale blast tests on beam and column specimens. Composite resistance curves, which capture the loss in axial load as the column displaces laterally, were shown to corroborate well with the measured axial-load time history and resistance curves. It was also found that the columns’ resistance can be obtained using an equivalent lateral-load approach when experimentally measured displacement, pressure, reaction, and axial-load time histories are considered. The model was also capable of predicting the maximum displacement and time to maximum displacement with reasonable accuracy.
Hundreds of studies have been devoted to the search for the ideal architecture for bone scaffold. Despite these efforts, results are often contradictory, and rules derived from these studies are ...accordingly vague. In fact, there is enough evidence to postulate that ideal scaffold architecture does not exist. The aim of this document is to explain this statement and review new approaches to decipher the existing but complex link between scaffold architecture and
in vivo response.
L’estimation du nombre de patients qui seront atteints de fibrillation atriale en 2030 en Europe est comprise entre 14 et 17 millions. Une personne sur quatre d’âge moyen en Europe aura développé ...cette arythmie à la fin de sa vie. Avec une prévalence aux alentours de 3 % chez l’adulte, cette prévalence augmente chez le sujet âgé, l’hypertendu, l’insuffisant cardiaque, le coronarien, le valvulaire, l’obèse l’insuffisant rénal et le diabétique. L’augmentation de prévalence peut être attribuée à la fois à une meilleure détection des formes silencieuses mais aussi au vieillissement de la population et à l’augmentation des conditions prédisposant à la fibrillation atriale. Concernant les mécanismes, la fibrillation atriale raccourcit la durée du potentiel d’action principalement par la sous-expression des courants entrants calciques et la surexpression de certains courants potassiques. Les sources focales au sein des veines pulmonaires peuvent déclencher la fibrillation atriale puisque leur suppression par ablation peut faire régresser l’arythmie. Ces mécanismes focaux peuvent inclure à la fois des activités déclenchées et de la rentrée locale. Les hypothèses de propagation d’ondes multiples ou de rotors ont été étayées par différents modèles à l’origine de la fibrillation atriale. Les sources focales peuvent aussi induire une propagation fibrillatoire qui vient obscurcir le mécanisme intime de la fibrillation. Enfin des facteurs extérieurs comme des pathologies cardiaques structurelles, l’hypertension peut-être le diabète mais également la fibrillation atriale elle-même peuvent induire un modelage structurel de l’atrium en activant le dépôt de tissu conjonctif et l’activation de fibroblastes. Ce remodelage structurel induit une dissociation électrique entre les faisceaux musculaires et des anomalies locales de conduction favorisant la perpétuation de l’arythmie. Chez certains patients ce remodelage structurel survient avant même les premiers épisodes de fibrillation atriale.
By 2030, 14–17 millions of atrial fibrillation patients are anticipated in the European Union. One in four middle-aged adults in European countries or USA will develop atrial fibrillation. Estimates suggest a prevalence of 3% in adults with a greater prevalence with increasing age, hypertension, diabetes, obesity, heart failure, coronary artery disease, valvular heart disease and chronic kidney disease. The increase in atrial fibrillation prevalence may be attributed to a better detection of silent forms as well as to the aging of the population and to increasing conditions predisposing to atrial fibrillation. About its mechanisms, atrial fibrillation shortens the action potential duration mainly through the down-regulation of calcium currents together with an up-regulation of some potassium currents. Focal sources located into the pulmonary veins may trigger atrial fibrillation and their ablation may suppress this arrhythmia. These focal sources both include reentrant mechanisms and triggered activity with after-depolarizations. The multiple wavelets hypothesis has been documented in several animal models at the origin of atrial fibrillation. Fibrillatory conduction may also occur from focal sources. Finally additional factors like cardiac diseases, hypertension or diabetes induce a slow but progressive process of structural remodeling in the atrium, with activation of fibroblasts, enhanced connective tissue deposition and fibrosis. This structural remodeling results in electrical dissociation of muscle bundles and local conduction disorders leading to reentry and perpetuation of the arrhythmia. In somes patients this remodeling occurs even before the onset of atrial fibrillation.
Starting from the quantum-phase-estimate (QPE) algorithm, a method is proposed to construct entangled states that describe correlated many-body systems on quantum computers. Using operators for which ...the discrete set of eigenvalues is known, the QPE approach is followed by measurements that serve as projectors on the entangled states. These states can then be used as inputs for further quantum or hybrid quantum-classical processing. When the operator is associated with a symmetry of the Hamiltonian, the approach can be seen as a quantum-computer formulation of symmetry breaking followed by symmetry restoration. The method, called discrete spectra assisted, is applied to superfluid systems. By using the blocking technique adapted to qubits, the full spectra of a pairing Hamiltonian is obtained.
Bone has a capability to repair itself when it is fractured. Repair involves the generation of intermediate tissues, such as fibrous connective tissue, cartilage and woven bone, before final bone ...healing can occur. The intermediate tissues serve to stabilise the mechanical environment and provide a scaffold for differentiation of new tissues. The repair process is fundamentally affected by mechanical loading and by the geometric configuration of the fracture fragments. Biomechanical analyses of fracture healing have previously computed the stress distribution within the callus and identified the components of the stress tensor favouring or inhibiting differentiation of particular tissue phenotypes. In this paper, a biphasic poroelastic finite element model of a fracture callus is used to
simulate the time-course of tissue differentiation during fracture healing. The simulation begins with granulation tissue (post-inflammation phase) and finishes with bone resorption. The biomechanical regulatory model assumes that tissue differentiation is controlled by a combination of shear strain and fluid flow acting within the tissue. High shear strain and fluid flows are assumed to deform the precoursor cells stimulating formation of fibrous connective tissue, lower levels stimulate formation of cartilage, and lower again allows ossification. This mechano-regulatory scheme was tested by simulating healing in fractures with different gap sizes and loading magnitudes. The appearance and disappearance of the various tissues found in a callus was similar to histological observation. The effect of gap size and loading magnitude on the rate of reduction of the interfragmentary strain was sufficiently close to confirm the hypothesis that tissue differentiation phenomena could be governed by the proposed mechano-regulation model.
•Unidirectional GFRP improves the behaviour of studs and light-frame walls.•Simple tension GFRP reinforcement did not increase the ductility (i.e., brittle).•U-shaped GFRP reinforcements resulted in ...ductility ratios ranging 1.4–3.9.•Weaker specimens experienced greater increases when reinforced with GFRP.•Four GFRP reinforced walls were subjected to simulated blast loading.
An experimental program was undertaken to investigate the flexural performance of forty-eight unreinforced and glass fibre-reinforced polymer (GFRP) reinforced Spruce-Pine-Fir No. 2 grade individual wood studs. In general, it was found that the GFRP contributed to reducing the damage region, especially when both reinforcement and confinement were utilized. The simple tension reinforcement did not provide any significant improvement to the post-peak behaviour and resulting in a brittle failure, similar to that observed in the unreinforced studs. Other reinforcement options, particularly those consisting of U-shaped reinforcement on the tension face with and without confinement, significantly increased the average flexural strength and stiffness of the stud by a factor of 2.4 and 1.8 times those obtained in the unreinforced studs, respectively. Significant ductility ratios, in the range of 1.4–3.9, were also observed in these reinforced configurations. Weaker specimens experienced greater increases in strength and reduction in variability when reinforced. Based on these observations, six full-scale light-frame stud walls reinforced with FRP were tested dynamically under simulated blast loading. The results showed that the walls reinforced with FRP performed better and had relatively less damage while dissipating, on average, twice the energy dissipated by the unreinforced walls. The observed failure modes of the reinforced walls were consistent with the static failure modes of the individual reinforced studs.
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