Plasma nitriding of AA2011 alloy and surface characterization by NDT techniques

Al-Cu alloys are widely used in the aerospace and automotive industries due to their high specific strength in some tempered conditions. However, due to poor corrosion and wear resistance, they are often anodized and/or painted. Plasma nitriding has been proposed as an alternative, though the developments in this technique are still in a recent stage for Al alloys. Electrical characterization techniques are well implemented NDTs in the industry because of good accuracy associated with lower cost, compared to other methods. Some, like eddy currents and 4-point probe techniques, are often used in coating inspection. The objective of this study was to perform Al nitriding at low temperatures to minimize the tempering initial condition damage and to assess the feasibility of eddy currents technique as a method for evaluating surface properties. The work developed can be divided in two stages. The first one was the process tuning, done at the Shibaura Institute of Technology, in Tokyo; and the second was the electrical characterization done in Faculdade de Ciências e Tecnologia, UNL. Low temperature nitriding of AA2011 alloy specimens was successfully achieved. Electrical conductivity results show that lift-off measurements by eddy currents testing can be related to surface properties.

Low coronary perfusion pressure is associated with endocardial fibrosis in a rat model of volume overload cardiac hypertrophy

Left ventricular hypertrophy following volume overload is regarded as an example of cardiac remodeling without increased fibrosis accumulation. However, infarction is associated with increased fibrosis within the noninfarcted, hypertrophied myocardium, particularly in the subendocardial regions. It is conceivable to suppose that, as also occurs postinfarction, low coronary driving pressure may also interfere with accumulation of myocardial fibrosis following aortocaval fistula. PURPOSE: To investigate the role of acute hemodynamic changes in subsequent deposition of cardiac fibrosis in response to aortocaval fistula. METHOD: Aortocaval fistula were created in 4 groups of Wistar rats that were followed over 4 and 8 weeks: aortocaval fistula 4 and aortocaval fistula 8 (10 rats each) and their respective controls (sham-operated controls - Sh), Sh4 and Sh8 (8 rats each). Hemodynamic measurements were performed 1 week after surgery. Hypertrophy and fibrosis were quantified by myocyte diameter and collagen volume fraction at the end of follow up. RESULT: Compared with Sh4 and Sh8, pulse pressure, left ventricular end-diastolic pressure, and +dP/dt were higher in aortocaval fistula 4 and aortocaval fistula 8, but -dP/dt was similar. Coronary driving pressure (mm Hg), used as an estimate of perfusion pressure, was lower in aortocaval fistula 8 (52.6 ± 4.1) than in Sh8 (100.8 ± 1.3), but comparable between aortocaval fistula 4 (50.0 ± 8.9) and Sh4 (84.8 ± 2.3). Myocyte diameter was greater in aortocaval fistula 8, whereas interstitial and subendocardial fibrosis were greater in aortocaval fistula 4 and aortocaval fistula 8. Coronary driving pressure correlated inversely and independently with subendocardial fibrosis (r² = .86, P <.001), whereas left ventricular systolic pressure (r² = 0.73, P = .004) and end-diastolic pressure (r² = 0.55, P = 012) correlated positively and independently with interstitial fibrosis. CONCLUSION: Coronary driving pressure falls and ventricular pressures increase early after aortocaval fistula and are associated with subsequent myocardial fibrosis deposition.

Influence of oxygen plasma treatment parameters on poly(vinylidene fluoride) electrospun fiber mats wettability

Electrospun poly(vinylidene fluoride) (PVDF) fiber mats find applications in an increasing number of areas, such as battery separators, filtration and detection membranes, due to their excellent properties. However, there are limitations due to the hydrophobic nature and low surface energy of PVDF. In this work, oxygen plasma treatment has been applied in order to modify the surface wettability of PVDF fiber mats and superhydrophilic PVDF electrospun membranes have been obtained. Further, plasma treatment does not significantly influences fiber average size (~400 ± 200 nm), morphology, electroactive -phase content (~80-85%) or the degree of crystallinity (Xc of 42 ± 2%), allowing to maintain the excellent physical-chemical characteristics of PVDF. Plasma treatment mainly induces surface chemistry modifications, such as the introduction of oxygen and release of fluorine atoms that significantly changes polymer membrane wettability by a reduction of the contact angle of the polymer fibers and an overall decrease of the surface tension of the membranes.

Erratum: Influence of oxygen plasma treatment parameters on poly(vinylidene fluoride) electrospun fiber mats wettability

Electrospun poly(vinylidene fluoride) (PVDF) fiber mats find applications in an increasing number of areas, such as battery separators, filtration and detection membranes, due to their excellent properties. However, there are limitations due to the hydrophobic nature and low surface energy of PVDF. In this work, oxygen plasma treatment has been applied in order to modify the surface wettability of PVDF fiber mats and superhydrophilic PVDF electrospun membranes have been obtained. Further, plasma treatment does not significantly influences fiber average size (~400 ± 200 nm), morphology, electroactive -phase content (~80-85%) or the degree of crystallinity (Xc of 42 ± 2%), allowing to maintain the excellent physical-chemical characteristics of PVDF. Plasma treatment mainly induces surface chemistry modifications, such as the introduction of oxygen and release of fluorine atoms that significantly changes polymer membrane wettability by a reduction of the contact angle of the polymer fibers and an overall decrease of the surface tension of the membranes.

Characterization of physical, mechanical and chemical properties of quiscal fibres : the influence of atmospheric DBD plasma treatment

This paper reports the first attempt of characterizing various physical, mechanical and chemical properties of Quiscal fibres, used by the native communities in Chile and investigating the influence of atmospheric dielectric barrier discharge plasma treatment on various properties such as diameter and linear density, fat, wax and impurity%, moisture regain, chemical elements and groups, thermal degradation, surface morphology, etc. According to the experimental observations, Quiscal fibre has lower tenacity than most of the technical grade natural fibres such as sisal, hemp, flax, etc., and plasma treatment at optimum dose improved its tenacity to the level of sisal fibres. Plasma treatment also reduced the amount of fat, wax and other foreign impurities present in Quiscal fibres as well as removed lignin and hemicellulose partially from the fibre structure. Plasma treatment led to functionalization of Quiscal fibre surface with chemical groups, as revealed from attenuated total reflection spectroscopy and also confirmed from the elemental analysis using energy dispersive Xray technique and pH and conductivity measurements of fibre aqueous extract. The wetting behavior of Quiscal fibre also improved considerably through plasma treatment. However, untreated and plasma treated Quiscal fibres showed similar thermal degradation behavior, except the final degradation stage, in which plasma treated fibres showed higher stability and incomplete degradation unlike the untreated fibres. The experimental results suggested that the plasma treated Quiscal fibres, like other technical grade natural fibres, can find potential application as reinforcement of composite materials for various industrial applications.

Effect of chemical and plasma DBD treatments on pseudostem plantain fiber properties

Las fibras del seudotallo de plátano (FSP) fueron modificadas mediante epiclorhidrina (EP), anhídrido acético (AA), y su combinación (AA_EP), y con plasma a tres descargas de barrera dieléctrica (DBD) 1, 3 y 6 kW min m-2. Las FSP tratadas y sin tratar fueron caracterizadas mediante espectroscopia infrarroja por la transformada de Fourier (FT-IR), termogravimetría (TGA), microscopía electrónica de barrido (SEM) y pruebas mecánicas de tensión y de humectabilidad. Los espectros FT-IR, las micrografías SEM, y el análisis TGA indicaron pérdidas de lignina, hemicelulosa, impurezas y ceras. Estos efectos en conjunto con las reacciones de grupos OH y -C-C-, con los tratamientos químicos y de plasma respectivamente, incrementaron la hidrofobicidad de las FSP tratadas. Los tratamientos químicos produjeron reacciones de esterificación, eterificación y entrecruzamiento de los grupos OH libres en las FSP, lo que hizo que mostraran mayor rigidez que las expuestas al plasma. Las micrografías SEM mostraron que las FSP expuestas al plasma quedaron con superficie más irregular y rugosa que la de las FSP tratadas químicamente. La humectabilidad de las fibras, medida mediante pruebas de ángulo de contacto, se redujo como consecuencia de ambos tratamientos, característica importante para un relleno en los materiales compuestos.

The spiny rat Proechimys guyannensis (Rodentia: Echimydae) fails to respond to intradermal inoculation with Leishmania (Viannia) braziliensis

Leishmaniasis a disease of worldwide occurrence is caused by protozoa of the Leishmania genus. In Brazil, Leishmania (Viannia) braziliensis is the main parasite responsible for the American cutaneous leishmaniasis. Main hosts of this protozoa are small wild mammals particularly marsupials and rodents. The aim of this study was to evaluate if spiny rat Proechimys guyannensis (Rodentia: Echimydae) has role in the cycle of the American cutaneous leishmaniasis caused by L. (V.) braziliensis. Thus, promastigotes (the flagellate stage) of Leishmania (Viannia) braziliensis were used to inoculate seven spiny rats (Proechimys guyannensis). After inoculated intradermal at the ear pinna, nose and plantar pad, the rats were monitored for 180 days. Tissue samples collected at 90 and 180 days from the rats proved to be negative for the presence of genetic material from the parasite. After euthanasia, the protozoa also failed to growth in culture medium containing tissue samples collected from the rats showing that there was no infection. These results fail to prove that spiny rat has a role in the cycle of the American cutaneous leishmaniasis caused by L. (V.) braziliensis.

Characterization of physical, mechanical and chemical properties of quiscal fibres: the influence of atmospheric dbd plasma treatment

This paper reports the first attempt of characterizing several physical, mechanical and chemical properties of Quiscal fibres, usually used by the native communities in Chile and on investigations concerning the influence of atmospheric dielectric barrier discharge (DBD) plasma treatment on various properties such as diameter and linear density, percent of impurity, moisture regain, chemical elements and groups, thermal degradation, surface morphology, among others.

Looking for mechanisms regulating lung growth in CDH: rat and human studies

Tese de Doutoramento em Ciências da Saúde

Lower NPAS3 expression during the later stages of abnormal lung development in rat congenital diaphragmatic hernia

Purpose Congenital diaphragmatic hernia (CDH) is characterized by a developmental defect in the diaphragm, pulmonary hypoplasia and pulmonary hypertension. NPAS3 is a PAS domain transcription factor regulating Drosophila tracheogenesis. NPAS3 null mice develop pulmonary hypoplasia in utero and die after birth due to respiratory failure. We aimed to evaluate NPAS3 expres- sion during normal and abnormal lung development due to CDH. Methods CDH was induced by administering 100 mg/ml nitrofen to time-pregnant dams on embryonic day (E) 9 of gestation. Lungs were isolated on E15, E18 and E21 and NPAS3 localization was determined by immunohisto- chemistry and quantified using Western blotting. Results We found that only E21 hypoplastic CDH lungs have reduced expression of NPAS3 in the terminal sac- cules. Western blotting confirmed the down-regulation of NPAS3 protein in the nitrofen-induced hypoplastic lungs. Conclusions We demonstrate for the first time that ni- trofen-induced hypoplastic CDH lungs have reduced NPAS3 expression in the terminal saccules during the later stages of abnormal lung development. Our findings suggest that NPAS3 is associated with pulmonary hypoplasia in CDH.

O estudo da aplicação de acabamentos funcionais de barreira UV em fibras previamente ativadas por plasma

Tese de Doutoramento Engenharia Têxtil

Stress induced risk-aversion is reverted by D2/D3 agonist in the rat

Stress exposure triggers cognitive and behavioral impairments that influence decision-making processes. Decisions under a context of uncertainty require complex reward-prediction processes that are known to be mediated by the mesocorticolimbic dopamine (DA) system in brain areas sensitive to the deleterious effects of chronic stress, in particular the orbitofrontal cortex (OFC). Using a decision-making task, we show that chronic stress biases risk-based decision-making to safer behaviors. This decision-making pattern is associated with an increased activation of the lateral part of the OFC and with morphological changes in pyramidal neurons specifically recruited by this task. Additionally, stress exposure induces a hypodopaminergic status accompanied by increased mRNA levels of the dopamine receptor type 2 (Drd2) in the OFC; importantly, treatment with a D2/D3 agonist quinpirole reverts the shift to safer behaviors induced by stress on risky decision-making. These results suggest that the brain mechanisms related to risk-based decision-making are altered after chronic stress, but can be modulated by manipulation of dopaminergic transmission.

Structural and functional characteristics of rat hearts with and without myocardial infarct. Initial experience with doppler echocardiography

OBJECTIVE: To assess by Doppler echocardiography the structural and functional alterations of rat heart with surgical induced extensive myocardial infarction. METHODS: Five weeks after surgical ligature of the left coronary artery, 38 Wistar-EPM rats of both sexes, 10 of them with extensive infarction, undergone anatomical and functional evaluation by Doppler echocardiography and then euthanized for anatomopathological analysis. RESULTS: Echocardiography was 100% sensible and specific to anatomopathological confirmed extensive miocardial infarction. Extensive infarction lead to dilatation of left ventricle (diastolic diameter: 0.89cm vs.0.64cm; systolic: 0.72cm vs. 0.33cm) and left atrium (0.55cm vs. 0.33cm); thinning of left ventricular anterior wall (systolic: 0.14cm vs. 0.23cm, diastolic: 0.11cm vs. 0.14cm); increased mitral E/ A wave relation (6.45 vs. 1.95). Signals of increased end diastolic ventricle pressure, B point in mitral valve tracing in 62.5% and signs of pulmonary hypertension straightening of pulmonary valve (90%) and notching of pulmonary systolic flow (60%) were observed in animals with extensive infarction. CONCLUSION: Doppler echocardiography has a high sensitivity and specificity for detection of chronic extensive infarction. Extensive infarction caused dilatation of left cardiac chambers and showed in Doppler signals of increased end diastolic left ventricular pressure and pulmonary artery pressure.

Plasma levels of immunoinflammatory markers in De Novo coronary atherosclerosis and coronary restenosis postangioplasty

OBJECTIVE: To compare circulating plasma levels of immunoinflammatory markers in patients with known de novo coronary artery disease and patients with postangioplasty restenosis. METHODS: Using enzymatic immunoabsorbent assay, we measured plasma levels of soluble interleukin-2 receptosr, tumor necrosis factor alpha, and soluble tumor necrosis alpha receptors I and II in 11 patients with restenosis postcoronary angioplasty (restenosis group), in 10 patients with primary atherosclerosis (de novo group) who were referred for coronary angiography because of stable or unstable angina, and in 9 healthy volunteers (control group). Levels of soluble interleukin-2 receptors were significantly higher in the de novo group compared with that in the restenosis and control groups. Levels were also higher in the restenosis group compared with that in the control group. Plasma levels of tumor necrosis alpha and receptor levels were significantly higher in the de novo group compared to with that in the restenosis and control groups, but levels in the restenosis group were not different from that in the controls. CONCLUSION: Coronary artery disease, either primary or secondary to restenosis, is associated with significant immunoinflammatory activity, which can be assessed by examining the extent of circulating plasma levels of inflammatory markers. Moreover, patients with de novo lesions appear to have increased inflammatory activity compared with patients with restenosis.

Acabamentos funcionais têxteis aplicados por estamparia digital em substratos têxteis ativados por plasma

Tese de Doutoramento em Engenharia Têxtil