Anti-Corrosion performance of a new silane coating for corrosion protection of AZ31 Magnesium alloy in Hank’s solution

Mg alloys can be used as bioresorsable metallic implants. However, the high corrosion rate of magnesium alloys has limited their biomedical applications. Although Mg ions are essential to the human body, an excess may cause undesirable health effects. Therefore, surface treatments are required to enhance the corrosion resistance of magnesium parts, decreasing its rate to biocompatible levels and allowing its safe application as bioresorbable metallic implants. The application of biocompatible silane coatings is envisaged as a suitable strategy for retarding the corrosion process of magnesium alloys. In the current work, a new glycidoxypropyltrimethoxysilane (GPTMS) based coating was tested on AZ31 magnesium substrates subjected to different surface conditioning procedures before coating deposition. The surface conditioning included a short etching with hydrofluoric acid (HF) or a dc polarisation in alkaline electrolyte. The silane coated samples were immersed in Hank's solution and the protective performance of the coating was studied through electrochemical impedance spectroscopy (EIS). The EIS data was treated by new equivalent circuit models and the results revealed that the surface conditioning process plays a key role in the effectiveness of the silane coating. The HF treated samples led to the highest impedance values and delayed the coating degradation, compared to the mechanically polished samples or to those submitted to dc polarisation.

Prevention of electrocardiographic and histopathologic alterations in the murine model of Chagas' disease by preinoculation of an attenuated Trypanosoma cruzi strain

The effects of infection with Trypanosoma cruzi on the electrocardiographic tracings of mice were studied in 4.groups of animals: (1) normal; (2) infected with a pathogenic T. cruzi strain (TS COB); (3) immunized with 3 intraperitoneal inocula of 10(6) attenuated T. cruzi epimastigotes (TCC) and (4) immunized-infected, which sequentially received the treatments of groups 3 and 2. Infection and protection were confirmed by xenodiagnosis and histopathology. Isolated alterations such as extrasystolia, 1st degree atrioventricular block, arrhythmia and ST elevation were observed in normal as well as infected mice. However, tracings taken repeatedly on each mouse over a 293 day period revealed a set of alterations which were more frequently seen in infected (14/22) than in normal (4/27) animals (p = 0.00048). These alterations consisted of supraventricular tachycardia, sinus bradycardia and persisting, first degree AV blocks, often associated to pacemaker changes. Inoculation of attenuated T. cruzi (group 3) did not increase these alterations (2/27 mice) but significantly prevented their development after challenge with the pathogenic strain (1/19 versus 14/22 mice, p = 0.000095). Thus, preimmunization reduced not only parasitemia but also a pathogenic consequence of T. cruzi infection. This evidence is relevant for immunoprevention studies against Chagas' disease.

"In-vitro" corrosion behaviour of the magnesium alloy with Al and Zn (AZ31) protected with a biodegradable polycaprolactone coating loaded with hydroxyapatite and cephalexin

Mg alloys are very susceptible to corrosion in physiological media. This behaviour limits its widespread use in biomedical applications as bioresorbable implants, but it can be controlled by applying protective coatings. On one hand, coatings must delay and control the degradation process of the bare alloy and, on the other hand, they must be functional and biocompatible. In this study a biocompatible polycaprolactone (PCL) coating was functionalised with nano hydroxyapatite (HA) particles for enhanced biocompatibility and with an antibiotic, cephalexin, for anti-bacterial purposes and applied on the AZ31 alloy. The chemical composition and the surface morphology of the coated samples, before and after the corrosion tests, were studied by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDX) and Raman. The results showed that the presence of additives induced the formation of agglomerates and defects in the coating that resulted in the formation of pores during immersion in Hanks' solution. The corrosion resistance of the coated samples was studied in Hank's solution by electrochemical impedance spectroscopy (EIS). The results evidenced that all the coatings can provide corrosion protection of the bare alloy. However, in the presence of the additives, corrosion protection decreased. The wetting behaviour of the coating was evaluated by the static contact angle method and it was found that the presence of both hydroxyapatite and cephalexin increased the hydrophilic behaviour of the surface. The results showed that it is possible to tailor a composite coating that can store an antibiotic and nano hydroxyapatite particles, while allowing to control the in-vitro corrosion degradation of the bioresorbable Mg alloy AZ31. (C) 2015 Elsevier Ltd. All rights reserved.

Biofunctional composite coating architectures based on polycaprolactone and nanohydroxyapatite for controlled corrosion activity and enhanced biocompatibility of magnesium AZ31 alloy

In this work a biofunctional composite coating architecture for controlled corrosion activity and enhanced cellular adhesion of AZ31 Mg alloys is proposed. The composite coating consists of a polycaprolactone (PCL) matrix modified with nanohydroxyapatite (HA) applied over a nanometric layer of polyetherimide (PEI). The protective properties of the coating were studied by electrochemical impedance spectroscopy (EIS), a non-disturbing technique, and the coating morphology was investigated by field emission scanning electron microscopy (FE-SEM). The results show that the composite coating protects the AZ31 substrate. The barrier properties of the coating can be optimized by changing the PCL concentration. The presence of nanohydroxyapatite particles influences the coating morphology and decreases the corrosion resistance. The biocompatibility was assessed by studying the response of osteoblastic cells on coated samples through resazurin assay, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The results show that the polycaprolactone to hydroxyapatite ratio affects the cell behavior and that the presence of hydroxyapatite induces high osteoblastic differentiation. (C) 2014 Elsevier B.V. All rights reserved.

Chronic disease prevention and health promotion. Public policies and social network analysis of the hospitals services and oyhers health and social organizations to support joint action for children with diabetes

Comunicação apresentada na 18th Conference International of Health Promotion Hospitals & Health Services "Tackling causes and consequences of inequalities in health: contributions of health services and the HPH network", em Manchester de 14-16 de april de 2010

Study of a 9th century silver earrings set from Mikulčice: corrosion, conservation and maintenance

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Conservação e Restauro

A study on metallurgy and corrosion of ancient copper-based artefacts from the portuguese territory

Dissertação apresentada para a obtenção do Grau de Doutor em Conservação e Restauro, especialidade Ciências da Conservação, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

A reliability-based measure of robustness for concrete structures subjected to corrosion

This work is a contribution to the definition and assessment of structural robustness. Special emphasis is given to reliability of reinforced concrete structures under corrosion of longitudinal reinforcement. On this communication several authors’ proposals in order to define and measure structural robustness are analyzed and discussed. The probabilistic based robustness index is defined, considering the reliability index decreasing for all possible damage levels. Damage is considered as the corrosion level of the longitudinal reinforcement in terms of rebar weight loss. Damage produces changes in both cross sectional area of rebar and bond strength. The proposed methodology is illustrated by means of an application example. In order to consider the impact of reinforcement corrosion on failure probability growth, an advanced methodology based on the strong discontinuities approach and an isotropic continuum damage model for concrete is adopted. The methodology consist on a two-step analysis: on the first step an analysis of the cross section is performed in order to capture phenomena such as expansion of the reinforcement due to the corrosion products accumulation and damage and cracking in the reinforcement surrounding concrete; on the second step a 2D deteriorated structural model is built with the results obtained on the first step of the analysis. The referred methodology combined with a Monte Carlo simulation is then used to compute the failure probability and the reliability index of the structure for different corrosion levels. Finally, structural robustness is assessed using the proposed probabilistic index.

HIV Voluntary Testing among Portuguese Women Attending Family Planning Clinics: Implications for HIV Prevention Education and Testing

Objectives: The aim of this article is to analyze the factors associated with HIV testing among 767 sexually active women. Methods: Participants were administered several self-report questionnaires that assessed behavioral and psychosocial measures. Results: Overall, 59.8% of the participants reported ever having tested for HIV. Results show that higher levels of education, being pregnant or having been pregnant, concern about AIDS, AIDS knowledge, self-efficacy in condom negotiation and perception of no risk in partner significantly predicted the likelihood of testing among women. Attending the mass was negatively associated with HIV testing. Conclusions: These findings provide information that can be used in the development of a focused gender sensitive HIV prevention program to increase HIV testing.

OCCUPATIONAL EXPOSURES TO BODY FLUIDS AND BEHAVIORS REGARDING THEIR PREVENTION AND POST-EXPOSURE AMONG MEDICAL AND NURSING STUDENTS AT A BRAZILIAN PUBLIC UNIVERSITY

A cross-sectional study was conducted to assess the frequencies and characteristics of occupational exposures among medical and nursing students at a Brazilian public university, in addition to their prevention and post-exposure behavior. During the second semester of 2010, a self-administered semi-structured questionnaire was completed by 253/320 (79.1%) medical students of the clinical course and 149/200 (74.5%) nursing students who were already performing practical activities. Among medical students, 53 (20.9%) suffered 73 injuries, which mainly occurred while performing extra-curricular activities (32.9%), with cutting and piercing objects (56.2%), in the emergency room (39.7%), and as a result of lack of technical preparation or distraction (54.8%). Among nursing students, 27 (18.1%) suffered 37 injuries, which mainly occurred with hollow needles (67.6%) in the operating room or wards (72.2%), and as a result of lack of technical preparation or distraction (62.1%). Among medical and nursing students, respectively, 96.4% and 48% were dissatisfied with the instructions on previously received exposure prevention; 48% and 18% did not always use personal protective equipment; 67.6% and 16.8% recapped used needles; 49.3% and 35.1% did not bother to find out the source patient's serological results post-exposure; and 1.4% and 18.9% officially reported injuries. In conclusion, this study found high frequencies of exposures among the assessed students, inadequate practices in prevention and post-exposure, and, consequently, the need for training in “standard precautions” to prevent such exposures.

YELLOW FEVER PREVENTION STRATEGIES AWARENESS AMONG HIV-INFECTED PATIENTS IN SÃO PAULO, BRAZIL

Introduction: Vaccination is the main preventive strategy against Yellow Fever (YF), which is a public health concern in Brazil. However, HIV-infected patients might have insufficient knowledge regarding YF, YF prevention, and vaccines in general. Methods: In this questionnaire-based study, data from 158 HIV-infected individuals were addressed in three distinct outpatient clinics in São Paulo. Information was collected on demographic and clinical characteristics, as well as patients' knowledge of vaccines, YF and YF preventive strategies. In addition, individual YF vaccine recommendations and vaccine status were investigated. Results: Although most participants adequately ascertain the vaccine as the main prevention strategy against YF, few participants were aware of the severity and lack of specific treatment for YF. Discrepancy in YF vaccine (patients who should have taken the vaccine, but did not) was observed in 18.8% of participants. Conclusion: YF is an important and preventable public health concern, and these results demonstrate that more information is necessary for the HIV-infected population.

Caraterização das propriedades macânicas e de fratura de um adesivo estrutural de alta ductilidade

As juntas adesivas são uma alternativa viável para substituir ligações comuns como as mecânicas ou soldadas, devido a diversas vantagens como a possibilidade de união de materiais de natureza diferente, maior leveza, menores custos inerentes ao fabrico e ainda prevenção da corrosão galvânica que pode ocorrer nas ligações entre dois materiais metálicos diferentes. A resistência de uma junta depende, para um determinado tipo de solicitação imposta, da distribuição de tensões no interior da junta. Por outro lado, a geometria das juntas, as propriedades mecânicas dos adesivos e os componentes a ligar vão influenciar a distribuição de tensões. O carregamento nas camadas adesivas de uma junta poderá induzir tensões de tração, compressão, corte, arrancamento ou clivagem, ou ainda uma combinação de duas ou mais destas componentes. O objetivo da presente dissertação é a caraterização completa de um adesivo estrutural de alta ductilidade recentemente lançado no mercado (SikaPower® -4720), para facilitar o projeto e otimização de juntas adesivas ligadas com o mesmo. São quatro os ensaios a realizar: ensaios à tração de provetes maciços (também denominados de bulk), ensaios ao corte com a geometria Thick Adherend Shear Test, ensaios Double-Cantilever Beam e ainda ensaios End-Notched Flexure. Com a realização dos ensaios referidos, são determinadas as propriedades essenciais à caraterização mecânica e de fratura do adesivo. Os resultados obtidos para cada ensaio resultaram em propriedades medidas com elevada repetibilidade, da mesma maneira que se revelaram de acordo com os dados disponibilizados pelo fabricante, sempre que estes estavam disponíveis.

Economic Evaluation of Ticagrelor for Secondary Prevention Following Acute Coronary Syndromes

INTRODUCTION AND OBJECTIVES: To estimate the cost-effectiveness and cost-utility of ticagrelor in the treatment of patients with acute coronary syndromes (unstable angina or myocardial infarction with or without ST-segment elevation), including patients treated medically and those undergoing percutaneous coronary intervention or coronary artery bypass grafting. METHODS: A short-term decision tree and a long-term Markov model were used to simulate the evolution of patients' life-cycles. Clinical effectiveness data were collected from the PLATO trial and resource use data were obtained from the Hospital de Santa Marta database, disease-related group legislation and the literature. RESULTS: Ticagrelor provides increases of 0.1276 life years and 0.1106 quality-adjusted life years (QALYs) per patient. From a societal perspective these clinical gains entail an increase in expenditure of €610. Thus the incremental cost per life year saved is €4780 and the incremental cost per QALY is €5517. CONCLUSIONS: The simulation results show that ticagrelor reduces events compared to clopidogrel. The costs of ticagrelor are partially offset by lower costs arising from events prevented. The use of ticagrelor in clinical practice is therefore cost-effective compared to generic clopidogrel.

Adhesion Prevention in Laparoscopic Surgery

Adhesions have important consequences for patients, surgeons, and health services. Peritonealtissue injury can be prevented by using careful surgical techniques. A large number of antiadhesion products have been used experimentally and clinically to prevent postoperative adhesions. Methods: The current author reviewed the surgical literature published about epidemiology, pathogenesis, and various prevention strategies of adhesion formation. Results: Meticulous surgery is essential to reduce unnecessary morbidity and mortality rates from these untoward effects of surgery. Several preventive agents against postoperative peritoneal adhesions have been investigated. Bioresorbable membranes are site-specific antiadhesion products but may be more difficult to use laparoscopically. Liquids and gels have the advantage of more-widespread areas of action and increased ease of use, particularly during laparoscopic operations. Effective pharmacologic agents that can reduce release of proinflammatory cytokines or activate peritoneal fibrinolysis are under development. Their results are encouraging but most of them are contradictory. Conclusions: Many modalities are being studied to reduce this risk; despite initial promising results of different measures in postoperative adhesion prevention, none of them have become standard applications. With the current state of knowledge, preclinical or clinical studies are still necessary to evaluate the effectiveness of the several proposed prevention strategies for avoiding postoperative peritoneal adhesions.

Exploring motor neuron degeneration in ALS - prevention by glycoursodeoxycholic acid and signaling to microglia

Dissertação para obtenção do Grau de Mestre em Genética Molecular e Biomedicina