Ranking procedure based on mechanical, durability and thermal behavior of mortars with incorporation of phase change materials

Nowadays, considering the high variety of construction products, adequate material selection, based on their properties and function, becomes increasingly important. In this research, a ranking procedure developed by Czarnecki and Lukowski is applied in mortars with incorporation of phase change materials (PCM). The ranking procedure transforms experimental results of properties into one numerical value. The products can be classified according to their individual properties or even an optimized combination of different properties. The main purpose of this study was the ranking of mortars with incorporation of different contents of PCM based in different binders. Aerial lime, hydraulic lime, gypsum and cement were the binders studied. For each binder, three different mortars were developed. Reference mortars, mortars with incorporation of 40% of PCM and mortars with incorporation of 40% of PCM and 1% of fibers, were tested. Results show that the incorporation of PCM in mortars changes their global performance.

Projeto de produção de tubo elíptico em aço avançado de elevada resistência para uma serra de arco

Dissertação de mestrado integrado em Engenharia Mecânica

Biomaterials for cartilage tissue engineering under mechanical stimulus

Tese de Doutoramento em Ciências (Especialidade de Física)

Development of computational and experimental methods for biomass composition and evaluation of its impact in genome-scale models prediction

The use of genome-scale metabolic models has been rapidly increasing in fields such as metabolic engineering. An important part of a metabolic model is the biomass equation since this reaction will ultimately determine the predictive capacity of the model in terms of essentiality and flux distributions. Thus, in order to obtain a reliable metabolic model the biomass precursors and their coefficients must be as precise as possible. Ideally, determination of the biomass composition would be performed experimentally, but when no experimental data are available this is established by approximation to closely related organisms. Computational methods however, can extract some information from the genome such as amino acid and nucleotide compositions. The main objectives of this study were to compare the biomass composition of several organisms and to evaluate how biomass precursor coefficients affected the predictability of several genome-scale metabolic models by comparing predictions with experimental data in literature. For that, the biomass macromolecular composition was experimentally determined and the amino acid composition was both experimentally and computationally estimated for several organisms. Sensitivity analysis studies were also performed with the Escherichia coli iAF1260 metabolic model concerning specific growth rates and flux distributions. The results obtained suggest that the macromolecular composition is conserved among related organisms. Contrasting, experimental data for amino acid composition seem to have no similarities for related organisms. It was also observed that the impact of macromolecular composition on specific growth rates and flux distributions is larger than the impact of amino acid composition, even when data from closely related organisms are used.

Enzymatic treatments to improve mechanical properties and surface hydrophobicity of jute fiber membranes

Fiber membranes prepared from jute fragments can be valuable, low cost, and renewable. They have broad application prospects in packing bags, geotextiles, filters, and composite reinforcements. Traditionally, chemical adhesives have been used to improve the properties of jute fiber membranes. A series of new laccase, laccase/mediator systems, and multi-enzyme synergisms were attempted. After the laccase treatment of jute fragments, the mechanical properties and surface hydrophobicity of the produced fiber membranes increased because of the cross-coupling of lignins with ether bonds mediated by laccase. The optimum conditions were a buffer pH of 4.5 and an incubation temperature of 60 °C with 0.92 U/mL laccase for 3 h. Laccase/guaiacol and laccase/alkali lignin treatments resulted in remarkable increases in the mechanical properties; in contrast, the laccase/2,2-azino-bis-(3-ethylthiazoline-6-sulfonate) (ABTS) and laccase/2,6-dimethoxyphenol treatments led to a decrease. The laccase/ guaiacol system was favorable to the surface hydrophobicity of jute fiber membranes. However, the laccase/alkali lignin system had the opposite effect. Xylanase/laccase and cellulase/laccase combined treatments were able to enhance both the mechanical properties and the surface hydrophobicity of jute fiber membranes. Among these, cellulase/laccase treatment performed better; compared to mechanical properties, the surface hydrophobicity of the jute fiber membranes showed only a slight increase after the enzymatic multi-step processes.

Effects of protein-calorie restriction on mechanical function of hypertrophied cardiac muscle

OBJECTIVE: To assess the effect of food restriction (FR) on hypertrophied cardiac muscle in spontaneously hypertensive rats (SHR). METHODS: Isolated papillary muscle preparations of the left ventricle (LV) of 60-day-old SHR and of normotensive Wistar-Kyoto (WKY) rats were studied. The rats were fed either an unrestricted diet or FR diet (50% of the intake of the control diet) for 30 days. The mechanical function of the muscles was evaluated through monitoring isometric and isotonic contractions. RESULTS: FR caused: 1) reduction in the body weight and LV weight of SHR and WKY rats; 2) increase in the time to peak shortening and the time to peak developed tension (DT) in the hypertrophied myocardium of the SHR; 3) diverging changes in the mechanical function of the normal cardiac muscles of WKY rats with reduction in maximum velocity of isotonic shortening and of the time for DT to decrease 50% of its maximum value, and increase of the resting tension and of the rate of tension decline. CONCLUSION: Short-term FR causes prolongation of the contraction time of hypertrophied muscles and paradoxal changes in mechanical performance of normal cardiac fibers, with worsening of the shortening indices and of the resting tension, and improvement of the isometric relaxation.

Contact force models for multibody dynamics

"Series: Solid mechanics and its applications, vol. 226"

Clinical significance of in-hospital reocclusion after mechanical reperfusion and percutaneous transluminal coronary angioplasty for acute myocardial infarction

OBJECTIVE: To analyze the effects of in-hospital reocclusion of reperfused AMI culprit coronary arteries in mortality and to identify the predictors. METHODS: The present study comprises a sample of 155 patients with AMI who underwent successful mechanical reperfusion by direct coronary angioplasty and angiographic control during hospitalization or before discharge. Patients were classified into group A: reoccluded patients (n=30) and group B: non-reoccluded patients (n=125). RESULTS: We identified in-hospital reocclusion predictors and found a greater significance in mortality among reoccluded patients (23,3% x 1.6%; p=0.00004). Silent reocclusion or typical angina at reocclusion had a good prognosis. The independent predictors of in-hospital mortality were hypertension, multiarterial lesions, totally occluded AMI culprit lesions, failed redilatation, failed redilatation in comparison with no intention to redilate, no redilatation in comparison with no atempt to redilate, and reocclusion within the first 48 to 72 hours. The decision to redilate, independently of the result, led to a 50.0% reduction in hospital mortality (p=0.0366). CONCLUSION: In-hospital AMI culprit coronary artery reocclusion had an adverse effect similar to that reported in clinical studies with high mortality rates (23.3% x 1.6%; p=0.00004). The major contribution of this study is to recommend the reopening of reoccluded AMI culprit coronary arteries as a means for the management of coronary artery reocclusion.

On the frictional contacts in multibody system dynamics

"Series title: Computational methods in applied sciences, ISSN1871-3033, vol. 42"

Percutaneous mechanical mitral commissurotomy performed with a Cribier's metallic valvulotome. Initial results

OBJECTIVE: To evaluate the immediate results of percutaneous mechanical mitral commissurotomy. METHODS: Thirty patients underwent percutaneous mechanical mitral commissurotomy performed with a Cribier's metallic valvulotome from 8/11/99 to 2/4/00. Mean age was 30.7 years, and 73.3% were women. With regards to functional class, 63.3% were class III, and 36.7% were class IV. The echocardiographic score had a mean value of 7.5± 1.8. RESULTS: The mitral valve area increased from 0.97±0.15cm² to 2.16±0.50cm² (p>0.0001). The mean diastolic gradient decreased from 17.9±5.0mmHg to 3.2±1.4mmHg. The mean left atrial pressure decreased from 23.6±5.4mmHg to 8.6±3.1mmHg, (p>0.0001). Systolic pressure in the pulmonary artery decreased from 52.7±18.3mmHg to 32.2±7.4mmHg. Twenty-nine cases were successful. One patient developed severe mitral regurgitation. Interatrial septal defect was observed and one patient. One patient had cardiac tamponade due to left ventricular perforation. No deaths occurred. CONCLUSION: This method has proven to be safe and efficient in the treatment of rheumatic mitral stenosis. The potential advantage is that it can be used multiple times after sterilization, which decreases procedural costs significantly.

Mechanical versus biological aortic valve implants in the elderly. A comparison of early and mid-term results

OBJECTIVE: Our aim was to compare, in a non randomized study, the surgical outcome in elderly patients with mechanical (Group 1; n=83) and bioprosthetic valve implants (Group 2; n=136). METHODS: During a three year period, 219 patients >75 years underwent Aortic Valve Replacement. The groups matched according to age, sex, comorbidity, valve pathology and concomitant Coronary Artery Bypass Surgery. Follow-up was a total of 469 patient-years (mean follow-up 2.1 years, maximum 4,4 years). RESULTS: Operative mortality was zero and the overall early mortality was 2.3 % (within 30 days). Actuarial survival was 87.5 ± 4.0% and 66.1 ± 7.7% (NS) at 4 years in Group 1 and Group 2, respectively. Freedom from valve-related death was 88.9 ± 3.8% in Group 1 and 69.9±7.9% (NS) in Group 2 at 4 years. CONCLUSION: Aortic Valve Replacement in the elderly (>75 years) is a safe procedure even in cases where concomitant coronary artery revascularization is performed. Only a few anticoagulant-related complications were reported and this may indicate that selected groups of elderly patients with significant life expectancy may benefit from mechanical implants .

Insights on the mechanical behavior of keratin fibrils

Supplementary data associated with this article can be found,in the online version, at http://dx.doi.org/10.1016/j.ijbiomac.2016.05.018.

Evaluation of the marker of hypercoagulability prothrombin fragment F 1+2 in patients with mechanical or biological heart valve prostheses

OBJECTIVE: To investigate whether patients with heart valve prostheses and similar International Normalized Ratios (INR) have the same level of protection against thromboembolic events, that is, whether the anticoagulation intensity is related to the intensity of hypercoagulability supression. METHODS: INR and plasma levels of prothrombin fragment 1+2 (F1+2) were assessed in blood samples of 27 patients (7 with mechanical heart valves and 20 with biological heart valves) and 27 blood samples from healthy donors that were not taking any medication. RESULTS: Increased levels of F1+2 were observed in blood samples of 5 patients with heart valve prostheses taking warfarin. These findings reinforce the idea that even though patients may have INRs, within the therapeutic spectrum, they are not free from new thromboembolic events. CONCLUSION: Determination of the hypercoagulability marker F1+2 might result in greater efficacy and safety for the use of oral anticoagulants, resulting in improved quality of life for patients.

Assessment of factors that influence weaning from long-term mechanical ventilation after cardiac surgery

OBJECTIVE: To analyze parameters of respiratory system mechanics and oxygenation and cardiovascular alterations involved in weaning tracheostomized patients from long-term mechanical ventilation after cardiac surgery. METHODS: We studied 45 patients in their postoperative period of cardiac surgery, who required long-term mechanical ventilation for more than 10 days and had to undergo tracheostomy due to unsuccessful weaning from mechanical ventilation. The parameters of respiratory system mechanics, oxigenation and the following factors were analyzed: type of surgical procedure, presence of cardiac dysfunction, time of extracorporeal circulation, and presence of neurologic lesions. RESULTS: Of the 45 patients studied, successful weaning from mechanical ventilation was achieved in 22 patients, while the procedure was unsuccessful in 23 patients. No statistically significant difference was observed between the groups in regard to static pulmonary compliance (p=0.23), airway resistance (p=0.21), and the dead space/tidal volume ratio (p=0.54). No difference was also observed in regard to the variables PaO2/FiO2 ratio (p=0.86), rapid and superficial respiration index (p=0.48), and carbon dioxide arterial pressure (p=0.86). Cardiac dysfunction and time of extracorporeal circulation showed a significant difference. CONCLUSION: Data on respiratory system mechanics and oxygenation were not parameters for assessing the success or failure. Cardiac dysfunction and time of cardiopulmonary bypass, however, significantly interfered with the success in weaning patients from mechanical ventilation.

Left Atrial Volume Index and Prediction of Events in Acute Coronary Syndrome: Solar Registry

Background: According to some international studies, patients with acute coronary syndrome (ACS) and increased left atrial volume index (LAVI) have worse long-term prognosis. However, national Brazilian studies confirming this prediction are still lacking. Objective: To evaluate LAVI as a predictor of major cardiovascular events (MCE) in patients with ACS during a 365-day follow-up. Methods: Prospective cohort of 171 patients diagnosed with ACS whose LAVI was calculated within 48 hours after hospital admission. According to LAVI, two groups were categorized: normal LAVI (≤ 32 mL/m2) and increased LAVI (> 32 mL/m2). Both groups were compared regarding clinical and echocardiographic characteristics, in- and out-of-hospital outcomes, and occurrence of ECM in up to 365 days. Results: Increased LAVI was observed in 78 patients (45%), and was associated with older age, higher body mass index, hypertension, history of myocardial infarction and previous angioplasty, and lower creatinine clearance and ejection fraction. During hospitalization, acute pulmonary edema was more frequent in patients with increased LAVI (14.1% vs. 4.3%, p = 0.024). After discharge, the occurrence of combined outcome for MCE was higher (p = 0.001) in the group with increased LAVI (26%) as compared to the normal LAVI group (7%) [RR (95% CI) = 3.46 (1.54-7.73) vs. 0.80 (0.69-0.92)]. After Cox regression, increased LAVI increased the probability of MCE (HR = 3.08, 95% CI = 1.28-7.40, p = 0.012). Conclusion: Increased LAVI is an important predictor of MCE in a one-year follow-up.