The effect of interstitial fluid on the machining behaviour of cortical bone

Bone machining research is usually conducted ex-vivo with standard laboratory equipment, implying mostly that the cutting process takes place in dry state. While these studies are useful for understanding the bone cutting process, they cannot represent the real clinical cutting condition due to the disregard of internal irrigation (i.e., interstitial fluid and blood within the tissue's vascular porosities). As bone possesses ca. 20 % water, internal irrigation can influence the bone's properties (e.g., shear strength, friction coefficient) and alter the cutting mechanism and surface deformation (e.g., crack formation, smearing). Hence, to study the ex-vivo bone cutting process in an internally irrigated state, a novel machining and pumping setup is proposed here, which enables a scenario closer to a surgical condition than the traditional dry machining method. Cutting tests demonstrated that portions of bone near the fluid-filled porosities possess shear strength and friction coefficient gradients due to the bone's permeability. This resulted in machining forces and necrosis up to 52 % and 55 % lower than in dry bone, respectively. A cutting forces model was developed considering the internal irrigation condition and the randomness and anisotropy of the tissue. Moreover, it was found that internal irrigation can change the chip formation mechanism and induce minimised surface morphological damage due to the minimised friction between the tool and the cutting surface in near-porosity sites. This research highlights the importance of conducting bone machining research with the consideration of internal irrigation, an imperative aspect to more realistically mimic surgical scenarios in a laboratory environment

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

Uso de un sistema de ahorro de agua para conservar ecosistemas para el recurso hídrico

En la región noroeste de la república mexicana, zona fronteriza entre México y Estados Unidos (EE.UU.), se está evaluando una posible problemática de la escasa cantidad de agua que México recibe de su vecino del norte, proveniente del Río Colorado (RC). En ocasiones, México recibe agua contaminada por agroquímicos debido a que ese recurso hídrico proviene del lavado de tierras estadounidenses. Además, Estados Unidos propuso revestir el Canal Todo Americano (CTA), lo que ha generado una disminución en los mantos acuíferos del valle de Mexicali, generando preocupación en autoridades y la población. Esto ha conllevado a deteriorar ecosistemas y con ello presentarse cambios de clima que incrementan los niveles de humedad relativa (HR) y temperatura, que genera corrosión y pérdidas económicas, y reducción de la competitividad en la industria electrónica de la región

Regional temperature control in ceramic injection moulding: an approach based on cooling rate optimisation

The injection moulding of ceramic components with uneven wall thickness presents challenges due to differential cooling rates developing in the injected parts, which cause premature solidification of the feedstock at thin features and lead to detrimental defects , worsening in components from green to sintered states. To cope with this, suitable mould thermal control approaches have to be selected and validated, as current control methods are based on the achievement of a uniform cavity surface temperature, which is not tailored to such complex geometries. In this work, a novel thermal control system is proposed, based on regional mould temperatures, implemented with the use of Peltier modules, which locally and independently heat and cool different cavity features according to their thickness. The regional temperature profiles are optimised over time with the use of a coupled Finite Element-Particle Swarm Optimisation (FE-PSO), to achieve uniform cooling rates throughout the moulded components. The performance of this approach is compared to both constant ambient mould temperature and Rapid Heat Cycle Moulding (RHCM) techniques, which instead aim at achieving uniform temperatures throughout the mould cavity surface. Results show that the novel proposed method, based on regional temperature control and uniform cooling rates, promotes the simultaneous solidification of features with a 10-times difference in surface-to-volume ratio. Due to this, in terms of components quality, the novel method brings the advantages 1 of higher dimensional control and reduction of differential shrinkage compared to the other analysed approaches, thus increasing the capability to use injection moulding to manufacture ceramic components characterised by non-uniform wall thickness

Costameric integrin and sarcoglycan protein levels are altered in a Drosophila model for Limb-girdle muscular dystrophy type 2H

Mutations in two different domains of the ubiquitously expressed TRIM32 protein give rise to two clinically separate diseases, one of which is Limb-girdle muscular dystrophy type 2H (LGMD2H). Uncovering the muscle-specific role of TRIM32 in LGMD2H pathogenesis has proven difficult, as neurogenic phenotypes, independent of LGMD2H pathology, are present in TRIM32 KO mice. We previously established a platform to study LGMD2H pathogenesis using Drosophila melanogaster as a model. Here we show that LGMD2H disease-causing mutations in the NHL domain are molecularly and structurally conserved between fly and human TRIM32. Furthermore, transgenic expression of a subset of myopathic alleles (R394H, D487N, and 520fs) induce myofibril abnormalities, altered nuclear morphology, and reduced TRIM32 protein levels, mimicking phenotypes in patients afflicted with LGMD2H. Intriguingly, we also report for the first time that the protein levels of βPS integrin and sarcoglycan δ, both core components of costameres, are elevated in TRIM32 disease-causing alleles. Similarly, murine myoblasts overexpressing a catalytically inactive TRIM32 mutant aberrantly accumulate α- and β-dystroglycan and α-sarcoglycan. We speculate that the stoichiometric loss of costamere components disrupts costamere complexes to promote muscle degeneration

Social functioning of survivors of child sexual abuse: an analysis of childhood experiences and long-term effects

This study provided preliminary reliability and validity data for a measure of characteristics of child sexual abuse which may impair social development, and examined the relationship of these variables to adult functioning. Participants were 56 undergraduate psychology students reporting a history of child sexual abuse. The research measure was the Social Sequelae of Sexual Abuse (SSSA) scale (Gameros & Harter, 1996). Adult psychological functioning was evaluated using the Trauma Symptom Checklist-40 (TSC-40), and social functioning was measured with the Social Adjustment Scale-Self Report (SAS-SR). The SSSA demonstrated good reliability and validity, comparing favorably with similar measures developed by other researchers. It significantly predicted TSC-40 scores, accounting for 27% of the variance, but did not significantly predict social functioning

On the importance of stochasticity of composite workpiece structures for post-processing operations: An analysis of errors on fixturing problems

As woven composites have attracted the attention of high-value industries, their broader implementation should be supported by an enhanced understating of the impact that their characteristic uneven surface has on high-precision post-processing operations (e.g. machining). Here, this gap is addressed by analysing the positioning error (i.e. linear/angular deviations from a reference) of woven composite workpieces prior post-processing operations. A bespoke model, tailored to simulate large stochastic surfaces, is presented and employed to construct several realistic “virtual workpieces” to study the interactions between the woven surface of the composite and the locating elements of a work-holding fixture. Results show that positioning errors are considerably reduced by improving the fixture’s geometric design, highlighting for the first time the crucial effect that the workpiece’s uneven surface has on post-processing operations. The versatility of the model allows its use on other applications where understanding this effect is critical (e.g. gripping during mechanical testing)