Vibration control with shape-memory alloys in civil engineering structures

Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Doutor em Engenharia Civil

Determination of Microcystin-LR in waters in the subnanomolar range by sol–gel imprinted polymers on solid contact electrodes

The present work reports new sensors for the direct determination of Microcystin-LR (MC-LR) in environmental waters. Both selective membrane and solid contact were optimized to ensure suitable analytical features in potentiometric transduction. The sensing layer consisted of Imprinted Sol–Gel (ISG) materials capable of establishing surface interactions with MC-LR. Non-Imprinted Sol–Gel (NISG) membranes were used as negative control. The effects of an ionic lipophilic additive, time of sol–gel polymerization, time of extraction of MC-LR from the sensitive layer, and pH were also studied. The solid contact was made of carbon, aluminium, titanium, copper or nickel/chromium alloys (80 : 20 or 90 : 10). The best ISG sensor had a carbon solid contact and displayed average slopes of 211.3 mV per decade, with detection limits of 7.3 1010 M, corresponding to 0.75 mg L1 . It showed linear responses in the range of 7.7 1010 to 1.9 109 M of MC-LR (corresponding to 0.77–2.00 mg L1 ), thus including the limiting value for MC-LR in waters (1.0 mg L1 ). The potentiometric-selectivity coefficients were assessed by the matched potential method for ionic species regularly found in waters up to their limiting levels. Chloride (Cl) showed limited interference while aluminium (Al3+), ammonium (NH4 + ), magnesium (Mg2+), manganese (Mn2+), sodium (Na+ ), and sulfate (SO4 2) were unable to cause the required potential change. Spiked solutions were tested with the proposed sensor. The relative errors and standard deviation obtained confirmed the accuracy and precision of the method. It also offered the advantages of low cost, portability, easy operation and suitability for adaptation to flow methods.

Development and implementation of strategies for the incorporation of reinforcing elements in aluminium alloys by solid state processing

Dissertação para obtenção do Grau de Mestre em Engenharia Mecânica

Correlation between the mechanical cycling behavior and microstructure in laser welded joints using NiTi memory shape alloys

Dissertação para obtenção do Grau de Mestre em Engenharia de Materiais

Magnesium – association with inflammation and renal disease in systemic lupus erythematosus

Introduction: Recent studies suggest that magnesium deficiency may play a role in inflammation. In diabetes and cardio-vascular diseases, conditions with a component of chronic inflammation, C–reactive protein levels are higher and associated with low serum magnesium. The objective of this study is to evaluate serum magnesium levels in patients with systemic lupus erythematosus and its potential association with inflammation and renal manifestations. Methods: All patients with systemic lupus erythematosus followed in a Systemic Immune Diseases Unit, from January 2012 until January 2014, were included in this cross sectional analysis. Patients with infection, neoplasia, liver failure and chronic kidney disease (stage > 3) were excluded. Clinical information and laboratory results (serum magnesium, C-reactive protein, erythrocyte sedimentation rate, serum creatinine and spot urine test) were collected. A multivariate analysis was performed to explore possible predictive factors for hypomagnesaemia. Results: One hundred and two patients were included (94.1% female, 21-86 years). 33.4% had hypertension, 8.8% had diabetes and 20.6% had hypomagnesaemia (< 1.8mg/dL). There were no significant differences between the inflammatory parameters of patients with hypomagnesaemia or normomagnesaemia. Serum magnesium was significantly lower with increasing comorbidities (p = 0.01). Leukocyturia was significantly higher in the hypomagnesaemia group (p = 0.03) and haematuria had a negative correlation with serum magnesium (-0.23, p < 0.05). Multivariate analysis showed that patients with hypertension and diabetes had higher risk of hypomagnesaemia: OR 42.29 (95% CI, 1.43-1249.31). Leukocyturia was also individually and independently associated with hypomagnesaemia: OR 8.37 (95% CI, 1.40-49.97). Conclusion: The presence of hypomagnesaemia in our patients with systemic lupus erythematosus was high. There was no association between the levels of serum magnesium and the inflammatory parameters. Increasing comorbidities and leukocyturia were independent predictors of lower serum magnesium. Finally, the association of leukocyturia and haematuria with lower serum magnesium may suggest a relationship with a higher disease activity.

Friction surfacing of aluminium alloys

Dissertação para a obtenção do grau de Mestre em Engenharia Mecânica

Chemical and physical attributes and calcium, magnesium, potassium, and phosphorus in the soil of murundu fields in Brazil

Fields of murundus (FM) are wetlands that provide numerous ecosystem services. The objectives of this study were to evaluate the chemical [organic carbon (OC), P, K+, Ca2+, Mg2+, Al3+ and H+Al] and physical [texture and bulk density (Bd)] soil attributes and calculate the organic matter (OM) and nutrient stock (P, Ca, Mg, and K) in soils of FM located in the Guapore River basin in Mato Grosso. Thirty-six sampling points were selected, and soil samples were collected from two environments: the murundu and plain area surrounding (PAS). At each sampling point, mini trenches of 0.5 × 0.5 × 0.4 m were opened and disturbed and undisturbed soil samples were collected at depths of 0-0.1, 0.1-0.2, and 0.2-0.4 m. In the Principal Component Analysis the variables H+Al (49%) and OM (4%) were associated with the F1 component and sand content (47%) with the F2 component. The FM had lower pH values and higher concentrations of K+, P, and H+Al than PAS at all depths (p < 0.05). Additionally, FM stocked up to 433, 360, 205, and 11 kg ha-1 of Ca, Mg, K, and P, respectively, for up to a depth of 0.2 m. The murundu stored two times more K and three times more P than that in the PAS. Our results show that the FM has high sand content and Bd greater than 1.5 Mg m-3, high acidity, low OC content, and low nutrient concentrations. Thus, special care must be taken to preserve FM such that human intervention does not trigger environmental imbalances.

Late Outcome of a Randomized Study on Oral Magnesium for Premature Complexes

Background:Ventricular and supraventricular premature complexes (PC) are frequent and usually symptomatic. According to a previous study, magnesium pidolate (MgP) administration to symptomatic patients can improve the PC density and symptoms.Objective:To assess the late follow-up of that clinical intervention in patients treated with MgP or placebo.Methods:In the first phase of the study, 90 symptomatic and consecutive patients with PC were randomized (double-blind) to receive either MgP or placebo for 30 days. Monthly follow-up visits were conducted for 15 months to assess symptoms and control electrolytes. 24-hour Holter was performed twice, regardless of symptoms, or whenever symptoms were present. In the second phase of the study, relapsing patients, who had received MgP or placebo (crossing-over) in the first phase, were treated with MgP according to the same protocol.Results:Of the 45 patients initially treated with MgP, 17 (37.8%) relapsed during the 15-month follow-up, and the relapse time varied. Relapsing patients treated again had a statistically significant reduction in the PC density of 138.25/hour (p < 0.001). The crossing-over patients reduced it by 247/hour (p < 0.001). Patients who did not relapse, had a low PC frequency (3 PC/hour). Retreated patients had a 76.5% improvement in symptom, and crossing-over patients, 71.4%.Conclusion:Some patients on MgP had relapse of symptoms and PC, indicating that MgP is neither a definitive nor a curative treatment for late follow-up. However, improvement in the PC frequency and symptoms was observed in the second phase of treatment, similar to the response in the first phase of treatment.

Modelling the influence of microstructure on elastic properties and tensile damage behaviour of Mo-base silicide alloys

Mo-Si-B alloys, Real microstructures, Voronoi structures, Microstructural characterization, Modelling and finite element simulations, Effective material properties, Damage and Crack growth, tensile strength, fracture toughness

Métabolisme du magnésium pour le clinicien : une mise au point actuelle et simple [Magnesium metabolism for clinical practioner : an up to date review]

La mesure de la fraction libre du magnésium circulant est désormais possible grâce aux électrodes sélectives. Lors d'une déplétion magnésique l'enquête étiologique est orientée par la comparaison de la magnésiurie et de la magnésémie. Les syndromes de Bortter, ou alcaloses hypokaliémiques d'origine rénale, sont des tubulopathies primitives définies par des signes simples: tension artérielle normale; alcalose hypokaliémiques; excrétion rénale conservée des chlorures et recherche de diurétiques négative dans les urines. Grâce à la mesure de la magnésémie et de la calciurie on distingue au moins deux alcaloses hypokaliémiques d'origine rénale, la maladie de Gitelman et le syndrome de Bartter au sens strict.

Effect of magnesium sulphate and L-tryptophan and genotype on the feed intake, behaviour and meat quality of pigs

Sixty-nine entire male pigs with different halothane genotype (homozygous halothane positive – nn –, n=36; and homozygous halothane negative – NN-, n=33) were fed with a supplementation of magnesium sulphate (Mg) and/or L-tryptophan (Trp) in the diet for 5 days before slaughter. Animals were housed individually and were submitted to stressful ante mortem conditions (mixed in the lorry according to treatments and transported 1 hour on rough roads). Individual feed intake was recorded during the 5-d treatment. At the abattoir, pig behaviour was assessed in the raceway to the stunning system and during the stunning period by exposure to CO2. Muscle pH, colour, water holding capacity, texture and cathepsin activities were determined to assess meat quality. The number of pigs with an individual feed intake lower than 2 kg/d was significantly different among diets (P&0.05; Control: 8.7 %; Mg&Trp: 43.5 %; Trp: 17.4 %) and they were considered to have inadequate supplement intake. During the ante mortem period, 15.2 % of pigs included in the experiment died, and this percentage decreased to 8.7 % in those pigs with a feed intake & 2kg/day, all of them from the stress-sensitive pigs (nn). In general, no differences were observed in the behaviour of pigs along the corridor leading to the stunning system and inside the CO2 stunning system. During the stunning procedure, Trp diet showed shorter periods of muscular excitation than control and Mg&Trp diets. The combination of a stressful ante mortem treatment and Mg&Trp supplementation led to carcasses with high incidence of severe skin lesions. Different meat quality results were found when considering all pigs or considering only those with adequate supplement intake. In this later case, Trp increased pH45 (6.15) vs Control diet (5.96) in the Longissimus thoracis (LT) muscle (P&0.05) and pH at 24h (Trp: 5.59 vs C: 5.47) led to a higher incidence of dark, firm and exudative (DFD) traits in SM muscle (P&0.05). Genotype affected negatively all the meat quality traits. Seventy-five percent of LT and 60.0 % of the SM muscles from nn pigs were classified as pale, soft and exudative (PSE), while none of the NN pigs showed these traits (P&0.0001). No significant differences were found between genotypes on the incidence of DFD meat. Due to the negative effects observed in the Mg&Trp group in feed intake and carcass quality, the utilization of a mixture of magnesium sulphate and tryptophan is not recommended.

Effect of magnesium chloride and guanidinum chloride on the extraction of components of extracellular matrix from chicken cartilage

In order to evaluate the effect of chaotropic agents on proteoglycan and non-collagenous proteins, chicken xiphoid cartilage was treated with guanidine-HCI and MgCl2 in different concentrations (1M to 5M), and different periods of time (12, 24, 48 and 72hr). The maximum yield of uronic acid was obtained with 3M MgCl2 (73.3 per cent). Concentrations of 4M and 5M of MgCl2 showed that much less uronic acid was removed, 55.3 per cent and 38.1 respectively. Extraction with 3M MgCl2 and 3M guanidine-HCl resulted better efficiency when performed for 48 hr. Analysis by SDS-PAGE of the extracts obtained with guanidine-HCl and MgCl, in different concentrations pointed out that most components are equally removed with the two solvents, showing that the extraction with MgCl2 is an alternative assay to remove non-collagenous proteins from extracellular matrix.