Scratch and Wear Behaviour of Co-Cr-Mo Alloy in Ringer's Lactate Solution.

Cobalt-chromium-molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, together with electromagnetic stirring, to reduce its grain size. The samples were subjected to wear and scratch tests in simulated body fluid (Ringer's lactate solution). Since a reduction in grain size can influence the behaviour of the material, in terms of resistance and tribological response, four samples with different grain sizes were produced for use in our investigation of the behaviour of the alloy, in which we considered the friction coefficient, wear, and scratch resistance. The experiments were performed using a tribometer, with mean values for the friction coefficient, normal load, and tangential force acquired and recorded by the software. Spheres of Ti-6Al-4V and 316L steel were used as counterface materials. In addition, to elucidate the influence of grain size on the mechanical properties of the alloy, observations were conducted via scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The results showed changes in the structure, with a reduction in grain size from 5.51 to 0.79 mm. Using both spheres, the best results for the friction coefficient and wear volume corresponded to the sample with the smallest grain size of 0.79 mm. The friction coefficients obtained were 0.37 and 0.45, using the Ti-6Al-4V and 316L spheres, respectively. These results confirm that the best surface finish for Co-Cr-Mo alloy used as a biomedical implant is one with a smaller grain size, since this results in a lower friction coefficient and low wear.

Sputtering of micro-carbon-silver film (µC-Ag) for endotracheal tubes to mitigate respiratory infections.

Polyurethane (PU) substrates are biocompatible materials widely used to manufacture endotracheal tubes. However, in common with other biomedical materials, they are liable to the formation of microbial films. The occurrence of pneumonia in intubated patients treated at intensive care units often takes the form of ventilator-associated pneumonia (VAP). The issue relates to the translocation of pathogenic microorganisms that colonize the oropharyngeal mucosa, dental plaque, stomach, and sinuses. New protective materials can provide a more effective therapeutic approach to mitigating bacterial films. This work concerns microcrystalline carbon film containing dispersed silver nanoparticles (µC-Ag) deposited on PU substrates using a physical vapor deposition sputtering process. For the first time, carbon paper was used to produce a carbon target with holes exposing a silver disk positioned under the carbon paper, forming a single target for use in the sputtering system. The silver nanoparticles were well distributed in the carbon film. The adherence characteristics of the µC-Ag film were evaluated using a tape test technique, and electron dispersive x-ray mapping was performed to analyze the residual particles after the tape test. The microbicidal effect of the thin film was also investigated using speciesS. aureus, a pathogenic microorganism responsible for most infections of the lower respiratory tract involving VAP and ventilator-associated tracheobronchitis (VAT). The results demonstrated that µC-Ag films on PU substrates are promising materials for mitigating pathogenic microorganisms on endotracheal tubes.

Hospital infection control and occupational medicine services in the face of the COVID-19 pandemic in occupational health / Serviços de controle de infecção hospitalar e de medicina do trabalho no enfrentamento à pandemia de COVID-19 na saúde ocupacional

In this article, the actions developed by the Hospital Infection Control Service (HICS) and Occupational Medicine (OM) to face the COVID-19 pandemic and track cases of infection among employees of a large hospital in Belo Horizonte, Minas Gerais, Brazil. Training actions, guidelines on how to collect a swab sample, Code 19 (COVID-19) simulation, dressing/undressing, hand hygiene, the definition of flows, and the quantification of cases infected by COVID-19 among employees in care areas were highlighted. The engagement of HICS and OM in the prevention and promotion of health were fundamental to facing the pandemic. It is estimated that SARS-CoV-2 infection rates among staff at the study hospital were similar to those at other hospitals. The experience report is important for expanding knowledge about action planning in the context of a large hospital (AU).

Neste artigo, são relatadas as ações desenvolvidas pelo Serviço de Controle de Infecção Hospitalar (SCIH) e Medicina do Trabalho (MT) para o enfrentamento da pandemia de COVID-19 e rastreamento dos casos de infecção entre funcionários de um hospital de grande porte de Belo Horizonte, Minas Gerais, Brasil. Destacaram-se as ações de treinamentos, orientações de como coletar amostra de swab, simulação Código 19 (COVID-19), paramentação/desparamentação, higiene das mãos, definição de fluxos e quantificação dos casos infectados por COVID-19 entre funcionários de áreas assistenciais. O engajamento do SCIH e da MT na prevenção e promoção da saúde foi fundamental no enfrentamento da pandemia. Estima-se que os índices de infecção pelo SARS-CoV-2 entre os funcionários do hospital em estudo foram similares aos de outros hospitais. O relato de experiência é importante para a ampliação do conhecimento sobre o planejamento de ações no contexto de um hospital de grande porte (AU).

High-Tribological-Performance Polymer Nanocomposites: An Approach Based on the Superlubricity State of the Graphene Oxide Agglomerates.

Here, nanocomposites of high-molecular-weight polyethylene (HMWPE) and HMWPE-UHMWPE (80/20 wt.%) containing a low amount of multilayer graphene oxide (mGO) (≤0.1 wt.%) were produced via twin-screw extrusion to produce materials with a higher tribological performance than UHMWPE. Due to the high viscosity of both polymers, the nanocomposites presented a significant concentration of agglomerates. However, the mechanical (tensile) and tribological (volumetric loss) performances of the nanocomposites were superior to those of UHMWPE. The morphology of the nanocomposites was investigated using differential scanning calorimetry (DSC), microtomography, and transmission electron microscopy (TEM). The explanation for these results is based on the superlubricity phenomenon of mGO agglomerates. It was also shown that the well-exfoliated mGO also contained in the nanocomposite was of fundamental importance as a mechanical reinforcement for the polymer. Even with a high concentration of agglomerates, the nanocomposites displayed tribological properties superior to UHMWPE's (wear resistance up to 27% higher and friction coefficient up to 57% lower). Therefore, this manuscript brings a new exception to the rule, showing that agglomerates can act in a beneficial way to the mechanical properties of polymers, as long as the superlubricity phenomenon is present in the agglomerates contained in the polymer.