Mechanical properties of resorbable PCL/FastOs® BG composite materials

Mestrado em Materiais e Dispositivos BiomédicosBioresorbable composites nowadays play an increasingly important role in the modern medicine, especially in orthopaedics for the fixation of bone fractures and tendons. Contrarily to the metallic counterparts, they prevent a second surgical operation to remove them, because they will be gradually integrated in the bone tissues. Finding ways to improve their physical and mechanical properties to better fit the intended specific conditions and environments has been a goal in many researches. It has already established that size, shape, aspect ratio and volume fraction of reinforcing particles are parameters which can effect on mechanical properties of a composite. The aim of this work is to investigate the effect of different proportion of particulate FastOs®BG Di70 bioactive glass filler on the mechanical properties of polycaprolactone (PCL) matrix. The selection of the PCL was based on its set of interesting properties, including the FDA approval for biomedical applications and the relatively low cost. The main drawbacks of PCL are related to its relatively hydrophobic nature and the slow degradation rate it undergoes in vivo (up to 3-4 years). The present work has a multifold purpose and aims at overcoming and/or mitigating the main identifies limitations of PCL, namely enhancing relevant mechanical properties, fastening the biodegradation rate in vivo, and turning the material bioactive. For this, FastOs®BG Di70 bioglass powder was selected as filler. This bioglass is characterised by a high biomineralisation rate in vitro, has a more hydrophilic character and higher Young modulus. The combination of PCL-FastOs®BG Di70 bioglass in different proportions is therefore expected to confer to the composites a more balanced set of properties for the intended applications. The mechanical properties of composites were assessed under different testing modes (tensile, compressive, oscillatory and torsional).Compósitos biorreabsorvíveis desempenham hoje em dia um papel cada vez mais importante na medicina moderna, especialmente em ortopedia para a fixação de fracturas ósseas e de tendões. Contrariamente aos dispositivos metálicos, eles evitam uma segunda intervenção cirúrgica para os remover, sendo gradualmente integrados nos tecidos ósseos. Encontrar maneiras de melhorar suas propriedades físicas e mecânicas para melhor atender as condições e ambientes específicos a que se destinam tem sido uma meta estabelecida em vários trabalhos de investigação. Com base nesses trabalhos, foi possível estabelecer que o tamanho, a forma e a razão de aspecto, bem como a fracção volúmica das partículas de reforço constituem os principais parâmetros que afectam as propriedades mecânicas de um compósito. O objectivo deste trabalho é investigar o efeito da adição de diferentes proporções de partículas do vidro bioativo FastOs®BG Di70 nas propriedades mecânicas de policaprolactona (PCL) usada como matriz. A selecção desta matriz foi baseada num conjunto de propriedades interessantes que possui, incluindo o facto de ter sido aprovada pela FDA para aplicações biomédicas e ser relativamente barata. As principais desvantagens da PCL estão relacionados com a sua natureza relativamente hidrofóbica, e com uma taxa de degradação lenta in vivo (até 3-4 anos). O presente trabalho tem uma finalidade múltipla e visa a superação e / ou mitigar as principais limitações identificadas para a PCL, ou seja, melhorar as propriedades mecânicas relevantes, acelerar a taxa de biodegradação in vivo, e tornar os materiais compósitos bioactivos. Para o efeito seleccionou-se o biovidro FastOs®BG Di70 na forma de pó como material de enchimento. Este biovidro é caracterizado por uma elevada taxa de biomineralização in vitro, tem um caracter mais hidrófilo e um módulo de elasticidade mais elevado. Assim, da combinação em proporções diferentes de PCL-FastOs®BG Di70, espera-se que resultem materiais compósitos com um conjunto mais equilibrado de propriedades para as aplicações almejadas. As propriedades mecânicas dos compósitos foram avaliadas sob diferentes modos de teste (de tração, compressão, torção e oscilatórios)

Global Air Quality and COVID-19 Pandemic : Do We Breathe Cleaner Air?

The global spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has challenged most countries worldwide. It was quickly recognized that reduced activities (lockdowns) during the Coronavirus Disease of 2019 (COVID-19) pandemic produced major changes in air quality. Our objective was to assess the impacts of COVID-19 lockdowns on groundlevel PM2.5, NO2, and O-3 concentrations on a global scale. We obtained data from 34 countries, 141 cities, and 458 air monitoring stations on 5 continents (few data from Africa). On a global average basis, a 34.0% reduction in NO2 concentration and a 15.0% reduction in PM2.5 were estimated during the strict lockdown period (until April 30, 2020). Global average O-3 concentration increased by 86.0% during this same period. Individual country and continent-wise comparisons have been made between lockdown and business-as-usual periods. Universally, NO2 was the pollutant most affected by the COVID-19 pandemic. These effects were likely because its emissions were from sources that were typically restricted (i.e., surface traffic and non-essential industries) by the lockdowns and its short lifetime in the atmosphere. Our results indicate that lockdown measures and resulting reduced emissions reduced exposure to most harmful pollutants and could provide global-scale health benefits. However, the increased O-3 may have substantially reduced those benefits and more detailed health assessments are required to accurately quantify the health gains. At the same, these restrictions were obtained at substantial economic costs and with other health issues (depression, suicide, spousal abuse, drug overdoses, etc.). Thus, any similar reductions in air pollution would need to be obtained without these extensive economic and other consequences produced by the imposed activity reductions.Peer reviewe

High-cocoa polyphenol-rich chocolate improves blood pressure in patients with diabetes and hypertension

BACKGROUND: The aim was to examine the effects of high-cocoa polyphenol-rich chocolate on lipid profiles, weight, blood pressure, glycemic control, and inflammation in individuals with Type 2 diabetes and hypertension. METHODS: Sixty individuals [32 in dark chocolate group (DCG) and 28 in white chocolate group (WCG)] with Type 2 diabetes on stable medication were enrolled in a randomized, placebo-controlled double-blind study. Subjects were randomized to consume 25 g DCG or WCG for 8 weeks. Changes in weight, blood pressure, glycemic control, lipid profile, and high sensitive C-reactive protein (hsCRP) were measured at the beginning and end of the intervention. This clinical trial was registered at the Iranian registry of clinical trials. RESULTS: In DCC group, compared with baseline, serum levels of Apo A-1 (P = 0.045) was increased and fasting blood sugar (FBS) (P = 0.027), hemoglobin A1c (HbA1c) (P = 0.025), Apo B (P = 0.012) and Log of hsCRP (P = 0.043) levels were decreased at the end of study. No changes were seen within the WCG in studied parameters. High polyphenol chocolate consumption compared to white chocolate resulted in significant decrease in of systolic (&minus;5.93 &plusmn; 6.25 vs. &minus;1.07 &plusmn; 7.97 mmHg, P = 0.004) and diastolic blood pressure (&minus;6.4 &plusmn; 6.25 vs. 0.17 &plusmn; 7.9 mmHg, P = 0.002), FBS (&minus;7.84 &plusmn; 19.15 vs. 4.00 &plusmn; 20.58 mg/dl, P = 0.019) over the course of 8 weeks of daily chocolate consumption neither weight nor body mass index and TG levels altered from baseline. CONCLUSION: High polyphenol chocolate is effective in improving TG levels in hypertensive patients with diabetes and decreasing blood pressure and FBS without affecting weight, inflammatory markers, insulin resistance or glycemic control. &nbsp;&nbsp; Normal 0 false false false EN-US X-NONE FA <!--[endif] --

Bi-layer glass-ceramic sealant for solid oxide fuel cells

A bi-layered concept of glass-ceramic (GC) sealant is proposed to overcome the challenges being faced by solid oxide fuel cells' (SOFCs). Two separated layers composed of glasses (Gd-0.3 and Sr-0.3) were prepared and deposited onto interconnect materials using a tape casting approach. After heat treating the bi-layered structure at 850 degrees C for 1-100 h, smooth and void free interfaces over the entire cross-section of joint were obtained. Micro-Raman analysis confirmed the presence of a higher amount of residual glassy phase in Gd-0.3 in comparison to Sr-0.3. The bi-layered GC showed good wetting and bonding ability to the Crofer22APU metallic plate. Slight increase of electrical conductivity with increasing annealing time was observed due to partial crystallization of the glass, but the overall conductivity levels of GC bi-layers were low enough to grant good electrical insulation. This set of relevant properties makes the investigated bi-layered sealants suitable for SOFC applications. (C) 2013 Elsevier Ltd. All rights reserved