Murine Axial Compression Tibial Loading Model to Study Bone Mechanobiology:Implementing the Model and Reporting Results

In vivo tibial loading in mice is increasingly used to study bone adaptation and mechanotransduction. To achieve standardized and defined experimental conditions, loading parameters and animal-related factors must be considered when performing in vivo loading studies. In this review we discuss these loading and animal-related experimental conditions, present methods to assess bone adaptation, and suggest reporting guidelines. This review originated from presentations by each of the authors at the workshop “Developing Best Practices for Mouse Models of In Vivo Loading” during the Preclinical Models Section at the Orthopaedic Research Society Annual Meeting, San Diego, CA, March 2017. Following the meeting, the authors engaged in detailed discussions with consideration of relevant literature. The guidelines and recommendations in this review are provided to help researchers perform in vivo loading experiments in mice, and thus further our knowledge of bone adaptation and the mechanisms involved in mechanotransduction

Cancellous bone and theropod dinosaur locomotion. Part I—an examination of cancellous bone architecture in the hindlimb bones of theropods

This paper is the first of a three-part series that investigates the architecture of cancellous (‘spongy’) bone in the main hindlimb bones of theropod dinosaurs, and uses cancellous bone architectural patterns to infer locomotor biomechanics in extinct non-avian species. Cancellous bone is widely known to be highly sensitive to its mechanical environment, and has previously been used to infer locomotor biomechanics in extinct tetrapod vertebrates, especially primates. Despite great promise, cancellous bone architecture has remained little utilized for investigating locomotion in many other extinct vertebrate groups, such as dinosaurs. Documentation and quantification of architectural patterns across a whole bone, and across multiple bones, can provide much information on cancellous bone architectural patterns and variation across species. Additionally, this also lends itself to analysis of the musculoskeletal biomechanical factors involved in a direct, mechanistic fashion. On this premise, computed tomographic and image analysis techniques were used to describe and analyse the three-dimensional architecture of cancellous bone in the main hindlimb bones of theropod dinosaurs for the first time. A comprehensive survey across many extant and extinct species is produced, identifying several patterns of similarity and contrast between groups. For instance, more stemward non-avian theropods (e.g. ceratosaurs and tyrannosaurids) exhibit cancellous bone architectures more comparable to that present in humans, whereas species more closely related to birds (e.g. paravians) exhibit architectural patterns bearing greater similarity to those of extant birds. Many of the observed patterns may be linked to particular aspects of locomotor biomechanics, such as the degree of hip or knee flexion during stance and gait. A further important observation is the abundance of markedly oblique trabeculae in the diaphyses of the femur and tibia of birds, which in large species produces spiralling patterns along the endosteal surface. Not only do these observations provide new insight into theropod anatomy and behaviour, they also provide the foundation for mechanistic testing of locomotor hypotheses via musculoskeletal biomechanical modelling

Machining-induced thermal damage in cortical bone: necrosis and micro-mechanical integrity

In bone cutting, the tissue is exposed to necrosis due to temperature elevation, which can significantly influence postoperative results in orthopaedic surgeries. This damage is usually revealed through histological analysis to show the necrotic extent; however, this technique does not capture mechanical damage, which is essential for a full material integrity assessment. Here, with micro-mechanics, it is demonstrated that machining-induced damage in bone extends beyond the necrotic region. Drilling with different conditions was performed on ex-vivo bovine cortical bone, inducing different damage degrees. Micro-pillar compression tests were performed in the machined sub-surface to identify changes in properties and failure modes caused by drilling. It was revealed that at high cutting temperatures, the bone near the machined surface suffers from lower modulus (−42%), strength (−41%) and brittle behaviour, whereas the bulk bone remains undamaged with pristine properties and ductile behaviour. Histology was also performed to evaluate necrosis and, surprisingly, it was found that the brittle and weaker bone layer is more than three times larger when compared to the necrotic layer, clearly showing that the drilling thermo-mechanical effect could affect not only biologically, but also micro-mechanically. Consequently, these results reveal another kind of bone damage that has so far been neglected

The influence of vehicle parameters on curve resistance for various track parameters

Tato práce se zabývá problematikou jízdy a postavení železničních vozidel v oblouku koleje a odporu z jízdy obloukem koleje. První část práce se věnuje teoretickému rozboru jízdy obloukem, popisem odporu při jízdě obloukem, popisem parametrů vozidla a trati majících vliv na odpor z jízdy obloukem. Dále je popsána Heumannova metoda, která se problematikou jízdy obloukem zabývá. V druhé části je popsán a znázorněn graficko-početní postup řešení postavení vozidla v oblouku koleje a zjištění velikostí řídících sil. Tato původní metoda rozšířena o numerickou metodu, pomocí níž jsme schopni zobrazovat závislost odporu z jízdy obloukem na požadovaných parametrech vozidla a trati.This work deals with the issue of driving and the positioning of railway vehicles on curved tracks and the resistance of driving around curves. The first part of the work focuses on the theoretical analysis of driving around curves, describing the resistance encountered during curve driving, and outlining the parameters of the vehicle and track that affect the resistance of driving around curves. Additionally, the Heumann method, which deals with the issue of driving around curves, is described. In the second part, a graphical-computational procedure for solving the positioning of the vehicle on curved tracks and determining the magnitudes of the controlling forces is described and illustrated. This original method is expanded by a numerical method, through which we are able to display the dependence of the resistance of driving around curves on the desired parameters of the vehicle and track.Dopravní fakulta Jana PerneraStudent přednesl obhajobu bakalářské práce. Jeho projev byl velmi dobrý. Student dále zodpověděl všechny dotazy vedoucího práce, oponenta práce a členů komise. Dokončená práce s úspěšnou obhajobo

Hodnocení vlivu výsypky lomu Obránců míru na dobývání a údržbu důlních děl na Dole Centrum v SHD v revírech Humboldt - západ II.

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