Physical exercise impacts bone remodeling around bio-resorbable magnesium implants.

Physical exercise has been shown to induce positive reactions in bone healing but next to nothing is known about how it affects the nanostructure, in particular around implants. In this study, we established this link by using small-angle X-ray scattering tensor tomography (SASTT) to investigate nanostructural parameters in 3D such as mineral particle orientation and thickness. As a model system, rat femoral bone with a bio-resorbable implant (ultra-high purity magnesium) was used.

Cortical bone fracture analysis including the combined influence of osteon orientations, applied load and crack lengths: A numerical investigation.

Similar to how fiber orientation affects composite materials, osteon orientation affects the elasticity and fracture behavior of cortical bone. The objective of this work is to predict the combined effect of orientations of the osteon, applied load, and various crack lengths on the fracture characteristics of cortical bone. Orthotropic modeling and analyses of cortical bone were carried out using the linear-elastic fracture mechanics (LEFM) based extended finite element method (XFEM).

The influence of geographical location on moisture distribution in wood cross sections: a numerical simulation study using Austria as an example.

Unlabelled: Wood constantly interacts with the surrounding, locally varying climate, leading to changes in the moisture content. Advanced simulation tools can predict the two-dimensional moisture distributions caused by these changing climate conditions within wood cross sections over time. However, there is a notable absence of systematic simulation results for diverse climatic conditions and various wood cross sections.

Mechanical properties of additively manufactured lattice structures composed of zirconia and hydroxyapatite ceramics.

Ceramic lattices hold great potential for bone scaffolds to facilitate bone regeneration and integration of native tissue with medical implants. While there have been several studies on additive manufacturing of ceramics and their osseointegrative and osteoconductive properties, there is a lack of a comprehensive examination of their mechanical behavior. Therefore, the aim of this study was to assess the mechanical properties of different additively manufactured ceramic lattice structures under different loading conditions and their overall ability to mimic bone tissue properties.

Dynamic microvilli sculpt bristles at nanometric scale.

Organisms generate shapes across size scales. Whereas patterning and morphogenesis of macroscopic tissues has been extensively studied, the principles underlying the formation of micrometric and submicrometric structures remain largely enigmatic. Individual cells of polychaete annelids, so-called chaetoblasts, are associated with the generation of chitinous bristles of highly stereotypic geometry.

Influence of obesity on load-transfer mechanism, contact mechanics, and longevity of cemented acetabular cup.

Objective: This investigation aimed to assess the impact of obesity on the load-transfer mechanism, longevity, and contact mechanics of cemented acetabular cups.

Methods: Three obesity scenarios were considered: obese case-I (100-110 kg), obese case-II (120-130 kg), and obese case-III (140-150 kg). Utilising six finite element models, the effects of different bodyweights on load transfer, contact mechanics, and cup longevity during normal walking conditions were assessed.

Prediction of moisture-induced cracks in wooden cross sections using finite element simulations.

Unlabelled: Wood absorbs and desorbs moisture due to its hygroscopic behavior, leading to moisture gradients in timber elements as well as swelling and shrinkage. These processes are constrained due to the orthotropic material properties of wood, leading to moisture-induced stresses, which can cause crack initiation and propagation. A significant amount of the damage in timber constructions indoors can be related to changes of the moisture content (MC).

Characterisation of thermally treated beech and birch by means of quasi-static tests and ultrasonic waves.

Wood, being renewable and highly abundant material, with excellent high specific strength and stiffness, has received increasing attention to be used in high performance applications such as the structural element of a battery case in an electric vehicle. For a successful implementation of wood in the automotive sector, it is, therefore, crucial to understand the behaviour of wood during and after temperature exposure and in the event of fire with the presence/absence of oxygen. In this study, the mechanical properties of thermally modified and unmodified European beech and birch in air and nitrogen environments at six different treatment intensities were characterised using compression tests, tensile tests, shear tests and Poisson's ratio tests.

Strength of a cement-based dental material: Early age testing and first micromechanical modeling at mature age.

The compressive strength evolution of 37 centigrade-cured Biodentine, a cement-based dental material, is quantified experimentally by crushing cylindrical specimens with length-to-diameter ratios amounting to 1.84 and 1.34, respectively, at nine different material ages ranging from 1 h to 28 days.

Multiscale micromechanics modeling of plant fibers: upscaling of stiffness and elastic limits from cellulose nanofibrils to technical fibers.

The mechanical properties of natural fibers, as used to produce sustainable biocomposites, vary significantly-both among different plant species and also within a single species. All plants, however, share a common microstructural fingerprint. They are built up by only a handful of constituents, most importantly cellulose.

Computational modeling of multiple myeloma interactions with resident bone marrow cells.

The interaction of multiple myeloma with bone marrow resident cells plays a key role in tumor progression and the development of drug resistance. The tumor cell response involves contact-mediated and paracrine interactions. The heterogeneity of myeloma cells and bone marrow cells makes it difficult to reproduce this environment in in-vitro experiments.

About prestretch in homogenized constrained mixture models simulating growth and remodeling in patient-specific aortic geometries.

Evolution of mechanical and structural properties in the Ascending Thoracic Aorta (ATA) is the results of complex mechanobiological processes. In this work, we address some numerical challenges in order to elaborate computational models of these processes. For that, we extend the state of the art of homogenized constrained mixture (hCM) models.

Historic Timber Roof Structure Reconstruction through Automated Analysis of Point Clouds.

We present a set of methods to improve the automation of the parametric 3D modeling of historic roof structures using terrestrial laser scanning (TLS) point clouds. The final product of the TLS point clouds consist of 3D representation of all objects, which were visible during the scanning, including structural elements, wooden walking ways and rails, roof cover and the ground; thus, a new method was applied to detect and exclude the roof cover points. On the interior roof points, a region-growing segmentation-based beam side face searching approach was extended with an additional method that splits complex segments into linear sub-segments.

On a remarkable geometric-mechanical synergism based on a novel linear eigenvalue problem.

The vertices of two specific eigenvectors, obtained from a novel linear eigenvalue problem, describe two curves on the surface of an -dimensional unit hypersphere. denotes the number of degrees of freedom in the framework of structural analysis by the Finite Element Method. The radii of curvature of these two curves are 0 and 1.

Fiber Rearrangement and Matrix Compression in Soft Tissues: Multiscale Hypoelasticity and Application to Tendon.

It is widely accepted that the nonlinear macroscopic mechanical behavior of soft tissue is governed by fiber straightening and re-orientation. Here, we provide a quantitative assessment of this phenomenon, by means of a continuum micromechanics approach. Given the negligibly small bending stiffness of crimped fibers, the latter are represented through a number of hypoelastic straight fiber phases with different orientations, being embedded into a hypoelastic matrix phase.

Micromechanics of dental cement paste.

Biodentine is a calcium silicate/calcium carbonate/zirconium dioxide/water-based dental replacement biomaterial, significantly outperforming the stiffness and hardness properties of chemically similar construction cement pastes. We here report the first systematic micromechanical investigation of Biodentine, combining grid nanoindentation with ultrasonic testing and micromechanical modeling. Histograms of nanoindentation-probed hardness and elastic modulus, comprising more than 5700 values each, are very well represented by the superposition of three log-normal distributions (LNDs).

Parameter reduction, sensitivity studies, and correlation analyses applied to a mechanobiologically regulated bone cell population model of the bone metabolism.

When striving for reconstructing and predicting bone remodeling processes by means of mathematical models, cell population models have become a popular option. From a conceptual point of view, these models are able to take into account an arbitrary amount of regulatory mechanisms driving the development of bone cells and their activities. However, in most cases, the models include a large number of parameters; and most of those parameters cannot be measured, which certainly compromises the credibility of cell population models.

"Variances" and "in-variances" in hierarchical porosity and composition, across femoral tissues from cow, horse, ostrich, emu, pig, rabbit, and frog.

It is very well known that bone is a hierarchically organized material produced by bone cells residing in the fluid environments filling (larger) vascular pores and (smaller) lacunar pores. The extracellular space consists of hydroxyapatite crystals, collagen type I molecules, and water with non-collageneous organics. It is less known to which extent the associated quantities (mineral, organic, and water concentrations; vascular, lacunar, and extracellular porosities) vary across species, organs, and ages.

Application-oriented fundamental research on concrete and reinforced concrete structures: selected findings from an Austro-Chinese research project.

In this paper, the significance of application-oriented fundamental research on concrete and reinforced concrete structures for progress regarding practical applications to structural design is addressed based on four examples. They were treated in a joint research project of Vienna University of Technology and Tongji University. The first topic refers to sudden heating or cooling of concrete structures, the second one to high-dynamic strength of specimens made of cementitious materials, the third one to structural analysis of segmental tunnel rings used in mechanized tunneling, and the fourth one to serviceability and ultimate limit states of concrete hinges used in integral bridge construction.

Mathematical modeling of COVID-19 fatality trends: Death kinetics law versus infection-to-death delay rule.

The COVID-19 pandemic has world-widely motivated numerous attempts to properly adjust classical epidemiological models, namely those of the SEIR-type, to the spreading characteristics of the novel Corona virus. In this context, the fundamental structure of the differential equations making up the SEIR models has remained largely unaltered-presuming that COVID-19 may be just "another epidemic". We here take an alternative approach, by investigating the relevance of one key ingredient of the SEIR models, namely the death kinetics law.

Study of the combined effects of PTH treatment and mechanical loading in postmenopausal osteoporosis using a new mechanistic PK-PD model.

One of only a few approved and available anabolic treatments for severe osteoporosis is daily injections of PTH (1-34). This drug has a specific dual action which can act either anabolically or catabolically depending on the type of administration, i.e.

Mandibular biomechanics after marginal resection: Correspondences of simulated volumetric strain and skeletal resorption.

Serious mandibular diseases such as tumor or osteonecrosis often require segmental or marginal mandibulectomy, the latter with improved outcome thanks to preserved mandibular continuity. Nevertheless, gradual osteolytic and/or osteosclerotic skeletal changes frequently indicate repetitive resections. Based on the fundamental adaptivity of bone to mechanical loads, the question arose whether resection-related anatomical alterations trigger relevant pathological skeletal adaptations.

Multiscale Thermoelastic Analysis of the Thermal Expansion Coefficient and of Microscopic Thermal Stresses of Mature Concrete.

The thermal expansion coefficient and the microscopic thermal stresses of mature concrete depend on its microstructural composition and the internal relative humidity. This dependence is determined by means of thermoelastic multiscale analysis of concrete. The underlying multiscale model enables two types of scale transition.

On a nonlinear hybrid method for multiscale analysis of a bearing-capacity test of a real-scale segmental tunnel ring.

A nonlinear hybrid method is developed for multiscale analysis of a bearing-capacity test of a real-scale segmental tunnel ring subjected to point loads. The structural analysis consists of two parts. Part I refers to modeling of bending-induced tensile cracking of the segments, resulting from the external loading.