IN-SITU ALLOYING PROCESS OF TI6AL4V-xCU STRUCTURES BY DIRECT METAL LASER SINTERING

Published Conference ProceedingsIn this paper the fabrication of in-situ Ti6Al4V-xCu alloy structures by DMLS are investigated. Ti6Al4V is a commonly used biomedical alloy because of it suitable mechanical and biocompatible properties. Copper is a proven anti-bacterial agent and in small amounts is not toxic to the human body. Ti6Al4V-xCu implants can be constructed to have a biocompatible structure with copper additions to reduce the risk of bacterial infection and implant failure. Infection at the bone–implant interface is the most probable reason for implant failure directly after implantation. Ti6Al4V powder was mixed with Cu powder to form a master alloy. Optimal process parameters need to be established for in-situ alloying of Ti6Al4V-xCu to form dense parts with suitable surface quality. The effect of laser scanning speeds and hatch distance on surface characteristics was investigated. The surface roughness, chemical composition and distribution of Cu near the surface and within the synthesized layer, as well as micro hardness were considered. A rescanning strategy was employed and showed improved alloy homogeneity and surface quality

Manufacturing, microstructure and mechanical properties of selective laser melted Ti6Al4V-Cu

Conference ProceedingsTi6Al4V is a commonly used biomedical alloy because of its suitable mechanical and biocompatible properties. Infection at the bone–implant interface is the most probable reason for implant failure directly after implantation. Copper is a proven anti-bacterial agent and in small amounts is not toxic to the human body. Copper additions reduce the risk of bacterial infection and implant failure. Thus advanced implants can be constructed to have a biocompatibility and antibacterial properties. Optimal process parameters are needed to be established for in-situ alloying of Ti6Al4V-Cu to form dense parts with suitable mechanical properties. The effect of laser scanning speeds and hatch distance on morphology of single layers was investigated. The surface roughness, chemical composition and distribution of Cu near the surface and within the synthesized layer, as well as micro hardness were considered. An employed rescanning strategy showed improved alloy homogeneity and surface quality. On the base of these data 3D samples were produced. Microstructure and mechanical properties of as-built parts were analysed

Interactions between skeletal muscle myoblasts and their extracellular matrix revealed by a serum free culture system

Decellularisation of skeletal muscle provides a system to study the interactions of myoblasts with muscle extracellular matrix (ECM). This study describes the efficient decellularisation of quadriceps muscle with the retention of matrix components and the use of this matrix for myoblast proliferation and differentiation under serum free culture conditions. Three decellularisation approaches were examined; the most effective was phospholipase A2 treatment, which removed cellular material while maximizing the retention of ECM components. Decellularised muscle matrices were then solubilized and used as substrates for C2C12 mouse myoblast serum free cultures. The muscle matrix supported myoblast proliferation and differentiation equally as well as collagen and fibronectin. Immunofluorescence analyses revealed that myoblasts seeded on muscle matrix and fibronectin differentiated to form long, well-aligned myotubes, while myoblasts seeded on collagen were less organized. qPCR analyses showed a time dependent increase in genes involved in skeletal muscle differentiation and suggested that muscle-derived matrix may stimulate an increased rate of differentiation compared to collagen and fibronectin. Decellularized whole muscle three-dimensional scaffolds also supported cell adhesion and spreading, with myoblasts aligning along specific tracts of matrix proteins within the scaffolds. Thus, under serum free conditions, intact acellular muscle matrices provided cues to direct myoblast adhesion and migration. In addition, myoblasts were shown to rapidly secrete and organise their own matrix glycoproteins to create a localized ECM microenvironment. This serum free culture system has revealed that the correct muscle ECM facilitates more rapid cell organisation and differentiation than single matrix glycoprotein substrates

Evaluating the spatial transferability and temporal repeatability of remote sensing-based lake water quality retrieval algorithms at the European scale:a meta-analysis approach

Many studies have shown the considerable potential for the application of remote-sensing-based methods for deriving estimates of lake water quality. However, the reliable application of these methods across time and space is complicated by the diversity of lake types, sensor configuration, and the multitude of different algorithms proposed. This study tested one operational and 46 empirical algorithms sourced from the peer-reviewed literature that have individually shown potential for estimating lake water quality properties in the form of chlorophyll-a (algal biomass) and Secchi disc depth (SDD) (water transparency) in independent studies. Nearly half (19) of the algorithms were unsuitable for use with the remote-sensing data available for this study. The remaining 28 were assessed using the Terra/Aqua satellite archive to identify the best performing algorithms in terms of accuracy and transferability within the period 2001–2004 in four test lakes, namely Vänern, Vättern, Geneva, and Balaton. These lakes represent the broad continuum of large European lake types, varying in terms of eco-region (latitude/longitude and altitude), morphology, mixing regime, and trophic status. All algorithms were tested for each lake separately and combined to assess the degree of their applicability in ecologically different sites. None of the algorithms assessed in this study exhibited promise when all four lakes were combined into a single data set and most algorithms performed poorly even for specific lake types. A chlorophyll-a retrieval algorithm originally developed for eutrophic lakes showed the most promising results (R2 = 0.59) in oligotrophic lakes. Two SDD retrieval algorithms, one originally developed for turbid lakes and the other for lakes with various characteristics, exhibited promising results in relatively less turbid lakes (R2 = 0.62 and 0.76, respectively). The results presented here highlight the complexity associated with remotely sensed lake water quality estimates and the high degree of uncertainty due to various limitations, including the lake water optical properties and the choice of methods

Dynamic magnetic resonance imaging in assessing lung function in adolescent idiopathic scoliosis: a pilot study of comparison before and after posterior spinal fusion

<p>Abstract</p> <p>Background</p> <p>Restrictive impairment is the commonest reported pulmonary deficit in AIS, which improves following surgical operation. However, exact mechanism of how improvement is brought about is unknown. Dynamic fast breath-hold (BH)-MR imaging is a recent advance which provides direct quantitative visual assessment of pulmonary function. By using above technique, change in lung volume, chest wall and diaphragmatic motion in AIS patients before and six months after posterior spinal fusion surgery were measured.</p> <p>Methods</p> <p>16 patients with severe right-sided predominant thoracic scoliosis (standing Cobb's angle 50° -82°, mean 60°) received posterior spinal fusion without thoracoplasty were recruited into this study. BH-MR sequences were used to obtain coronal images of the whole chest during full inspiration and expiration. The following measurements were assessed: (1) inspiratory, expiratory and change in lung volume; (2) change in anteroposterior (AP) and transverse (TS) diameter of the chest wall at two levels: carina and apex (3) change in diaphragmatic heights. The changes in parameters before and after operation were compared using Wilcoxon signed ranks test. Patients were also asked to score their breathing effort before and after operation using a scale of 1–9 with ascending order of effort. The degree of spinal surgical correction at three planes was also assessed by reformatted MR images and correction rate of Cobb's angle was calculated.</p> <p>Results</p> <p>The individual or total inspiratory and expiratory volume showed slight but insignificant increase after operation. There was significantly increase in bilateral TS chest wall movement at carina level and increase in bilateral diaphragmatic movements between inspiration and expiration. The AP chest wall movements, however, did not significantly change.</p> <p>The median breathing effort after operation was lower than that before operation (p < 0.05).</p> <p>There was significant reduction in coronal Cobb's angle after operation but the change in sagittal and axial angle at scoliosis apex was not significant.</p> <p>Conclusion</p> <p>There is improvement of lateral chest wall and diaphragmatic motions in AIS patients six months after posterior spinal fusion, associated with subjective symptomatic improvement. Lung volumes however, do not significantly change after operation. BH-MR is novel non-invasive method for long term post operative assessment of pulmonary function in AIS patients.</p

A systematic review of dedicated models of care for emergency urological patients

Available online 26 June 2020Objective: To systematically evaluate the spectrum of models providing dedicated resources for emergency urological patients (EUPs). Methods: A search of Cochrane, Embase, Medline and grey literature from January 1, 2000 to March 26, 2019 was performed using methods pre-published on PROSPERO. Reporting followed Preferred Reporting Items for Systematic Review and meta-analysis guidelines. Eligible studies were articles or abstracts published in English describing dedicated models of care for EUPs, which reported at least one secondary outcome. Studies were excluded if they examined pathways dedicated only to single presentations, such as torsion, or outpatient solutions, such as rapid access clinics. The primary outcome was the spectrum of models. Secondary outcomes were time-to-theatre, length of stay, complications and cost. Results: Seven studies were identified, totalling 487 patients. Six studies were conference abstracts, while one study was of full-text length but published in grey literature. Four distinct models were described. These included consultant urologists allocated solely to the care of EUPs (“Acute Urological Unit”) or dedicated registrars or operating theatres (“Hybrid structures”). In some services, EUPs bypassed emergency department assessment and were referred directly to urology (“Urological Assessment Unit”) or were managed by other dedicated means. Allocating services to EUPs was associated with reduced time-to-theatre, length of stay and hospital cost, and improved supervision of junior medical staff. Conclusion: Multiple dedicated models of care exist for EUPs. Low-level evidence suggests these may improve outcomes for patients, staff and hospitals. Higher quality studies are required to explore patient outcomes and minimum requirements to establish these models.Ned Kinnear, Matheesha Herath, Dylan Barnett, Derek Hennessey, Christopher Dobbins, Tarik Sammour, James Moor

Combinatorial localized dissolution analysis : application to acid-induced dissolution of dental enamel and the effect of surface treatments

A combination of scanning electrochemical cell microscopy (SECCM) and atomic force microscopy (AFM) is used to quantitatively study the acid-induced dissolution of dental enamel. A micron-scale liquid meniscus formed at the end of a dual barrelled pipette, which constitutes the SECCM probe, is brought into contact with the enamel surface for a defined period. Dissolution occurs at the interface of the meniscus and the enamel surface, under conditions of well-defined mass transport, creating etch pits that are then analysed via AFM. This technique is applied to bovine dental enamel, and the effect of various treatments of the enamel surface on acid dissolution (1 mM HNO3) is studied. The treatments investigated are zinc ions, fluoride ions and the two combined. A finite element method (FEM) simulation of SECCM mass transport and interfacial reactivity, allows the intrinsic rate constant for acid-induced dissolution to be quantitatively determined. The dissolution of enamel, in terms of Ca2+ flux (jCa2+), is first order with respect to the interfacial proton concentration and given by the following rate law: jCa2+=k0[H+], with k0=0.099±0.008 cm s−1. Treating the enamel with either fluoride or zinc ions slows the dissolution rate, although in this model system the partly protective barrier only extends around 10–20 nm into the enamel surface, so that after a period of a few seconds dissolution of modified surfaces tends towards that of native enamel. A combination of both treatments exhibits the greatest protection to the enamel surface, but the effect is again transient

Evolution of prolate molecular clouds at H II boundaries - II. Formation of BRCs of asymmetrical morphology

A systematic investigation on the evolution of a prolate cloud at an H II boundary is conducted using smoothed particle hydrodynamics in order to understand the mechanism for a variety of irregular morphological structures found at the boundaries of various H II regions. The prolate molecular clouds in this investigation are set with their semimajor axes at inclinations between 0° and 90° to a plane-parallel ionizing radiation flux. A set of four parameters, the number density n, the ratio of major to minor axis γ, the inclination angle Φ and the incident flux FEUV, are used to define the initial state of the simulated clouds. The dependence of the evolution of a prolate cloud under radiation-driven implosion (RDI) on each of the four parameters is investigated. It is found that (i) in addition to the well-studied standard type A, B or C bright-rimmed clouds (BRCs), many other types such as asymmetrical BRCs, filamentary structures and irregular horse-head structures could also be developed at H II boundaries with only simple initial conditions; (ii) the final morphological structures are very sensitive to the four initial parameters, especially to the initial density and the inclination; (iii) the previously defined ionizing radiation penetration depth can still be used as a good indicator of the final morphology. Based on the simulation results, the formation time-scales and masses of the early RDI-triggered star formation from clouds of different initial conditions are also estimated. Finally a unified mechanism for the various morphological structures found in many different H II boundaries is suggested

Tuberculosis research in South Africa over the past 30 years: From bench to bedside

The South African Medical Research Council Centre for Tuberculosis Research has a rich history of high-impact research that has influenced our understating of this hyper-epidemic which is further exacerbated by the emergence and spread of drug-resistant forms of the disease. This review aims to summarise the past 30 years of research conducted in the Centre which has influenced the way that tuberculosis (TB) is diagnosed and treated. The review includes the development of new technologies for rapid screening of people with probable TB and the repurposing of human diagnostics for wildlife conservation