Showing papers by "Helena I. S. Nogueira published in 2017"

Corrosion inhibition of copper in aqueous chloride solution by 1H-1,2,3-triazole and 1,2,4-triazole and their combinations: electrochemical, Raman and theoretical studies

Abstract: Triazoles are well-known organic corrosion inhibitors of copper. 1H-1,2,3-Triazole and 1,2,4-triazole, two very simple molecules with the only difference being the positions of the nitrogen atoms in the triazole ring, were studied in this work as corrosion inhibitors of copper in 50 mM NaCl solution using a set of electrochemical and analytical techniques. The results of electrochemical tests indicate that 1H-1,2,3-triazole exhibited superior inhibitor properties but could not suppress anodic copper dissolution at moderate anodic potentials (>+300 mV SCE), while 1,2,4-triazole, although it exhibited higher anodic currents, suppressed anodic copper dissolution at very anodic potentials. Density functional theory calculations were also performed to interpret the measured data and trends observed in the electrochemical studies. The computational studies considered either the inhibitors isolated in the gaseous phase or adsorbed onto Cu(111) surface models. From the calculations, the mechanisms of the inhibitive effects of both triazoles were established and plausible mechanisms of formation of the protective films on the Cu surface were proposed. The results of this study hold positive implications for research in the areas of catalysis, and copper content control in water purification systems.

Raman imaging studies on the adsorption of methylene blue species onto silver modified linen fibers

Abstract: We demonstrate in this research that surface-enhanced resonance Raman scattering combined with Raman imaging can be effectively used for analysis of distinct forms of organic dyes in antimicrobial Ag-loaded textile fibers. The potential of this approach, as a non-destructive characterization method of fabrics, was evaluated with Raman studies performed on the molecular forms of methylene blue (MB), used here as the organic dye model. On the basis of the surface-enhanced Raman scattering spectra of MB monomers and dimers, the Raman imaging of Ag-loaded linen fibers previously treated with MB solution was performed and then used for identification of the adsorbate species in distinct regions of the substrates. A semi-quantitative analysis is then performed by considering the area of the Raman bands ascribed to the MB molecular forms and image analysis applied to Raman images. Copyright © 2017 John Wiley & Sons, Ltd.

Waist‐to‐height ratio and its association with TV viewing in a sample of Portuguese children aged 7–9 years

Abstract: Introduction During the past decades, increased TV viewing and reduced physical activity (PA) levels may have contributed to the increased prevalence of pediatric obesity. This study aimed to analyze the association between TV viewing and central adiposity risk in Portuguese children. Methods The sample comprised 3987 children (1997 girls and 1990 boys) aged 7–9 years. Height, weight, and waist circumference (WC) were measured. Waist-to-height ratio (WHtR) was calculated as the ratio of waist/height with a cut-off of 0.5 used to define risk of abdominal obesity. WHtR does not depend on sex- or age-specific reference criteria. TV viewing and PA were assessed by questionnaire. Logistic regressions were used, with adjustments for age, PA, and parental education. Results This study revealed a positive significant association between central adiposity risk and sedentary behaviors in Portuguese boys. In addition, the final model showed an important inverse association between PA and the risk of abdominal obesity in both boys and girls (males: β = −0.01 95% CI, 0.99 to 1.00; females: β = −0.01; 95% CI, 0.99-1.00). Conclusion Findings revealed that associations between TV viewing and obesity risk could be highly influenced by socioeconomic factors. Future research should extend a similar design to children in other geographic contexts, and incorporate other behavioral variables in the statistical models, to confirm or not some of the aforementioned findings.

Luminescent carrageenan hydrogels containing lanthanopolyoxometalates

Abstract: In this research we have investigated the use of lanthanopolyoxometalates (LnPOM, K9[Ln(W5O18)2], Ln= Eu, Tb) as luminophores in thermosensitive polysacharides such as carrageenan hydrogels. We demonstrate that the LnPOM species retain the characteristic photoluminescence of the Ln(III) when incorporated in the gel matrix. Moreover, the strength of the carrageenan hydrogels increases by increasing the amount of LnPOM added, due to the effect of K+ as cross-linker, but without compromising the photoluminescent behaviour. The nanoscale homogeneity is crucial regarding applications of hydrogels responsive to external stimuli. This research shows that the final LnPOM loaded hydrogels are homogeneous as consequence of the diffusional behaviour of the luminophore species within the gel network. Therefore, we anticipate that the association of carrageenan hydrogels to luminescent lanthanopolyoxometalates might be of great relevance for optical devices and in particular for bioimaging techniques.

Defect concentration in nitrogen-doped graphene grown on Cu substrate: A thickness effect

Abstract: Tuning the band-gap of graphene is a current need for real device applications. Copper (Cu) as a substrate plays a crucial role in graphene deposition. Here we report the fabrication of in-situ nitrogen (N) doped graphene via chemical vapor deposition (CVD) technique and the effect of Cu substrate thickness on the growth mechanism. The ratio of intensities of G and D peaks was used to evaluate the defect concentration based on local activation model associated with the distortion of the crystal lattice due to incorporation of nitrogen atoms into graphene lattice. The results suggest that Cu substrate of 20 µm in thickness exhibits higher defect density (1.86×10 12 cm −2 ) as compared to both 10 and 25 µm thick substrates (1.23×10 12 cm −2 and 3.09×10 11 cm −2 , respectively). Furthermore, High Resolution -X-ray Photoelectron Spectroscopy (HR-XPS) precisely affirms ~0.4 at% of nitrogen intercalations in graphene. Our results show that the substitutional type of nitrogen doping dominates over the pyridinic configuration. In addition, X-ray diffraction (XRD) shows all the XRD peaks associated with carbon. However, the peak at ~24° is suppressed by the substrate peaks (Cu). These results suggest that nitrogen atoms can be efficiently incorporated into the graphene using thinner copper substrates, rather than the standard 25 µm ones. This is important for tailoring the properties by graphene required for microelectronic applications.

Patterns of lifestyle-related behaviors and parents’ overweight are associated with increased body adiposity in schoolchildren: a cross-sectional study in Portugal

Abstract: This study evaluated the association between lifestyle-related behavior patterns and weight status indicators in schoolchildren. Cross-sectional study includes nationally representative sample of Portuguese schoolchildren (6–9 years old; n = 10,258). Weight status was assessed using the body mass index (BMI) and waist circumference (WC). Principal component analysis was used to identify lifestyle-related behavior patterns. Multiple linear regression models were used to estimate the association between behavior patterns, BMI, and WC. Six lifestyle-related behavior patterns were identified: pattern 1: consuming iced tea and soft drinks ≥2 times/week, having a television (TV) in the bedroom, watching TV ≥2 h/day, and consuming <2 portions of fruits/day; pattern 2: parents and children remaining physically inactive during leisure time; pattern 3: consuming ≤1 portion of vegetables and milk/day; pattern 4: having parents with excess weight; pattern 5: consuming ≤3 daily meals and skipping breakfast; and pattern 6: not participating in physical education classes. After the adjustment, all of the patterns were associated with increased BMI z-score (P ≤ 0.02) and WC (P ≤ 0.03). Lifestyle-related behavior patterns were associated with an increased risk of excess weight and the central distribution of body fat. Taking a public health perspective toward preventing childhood obesity, special attention should be given to identify subgroups with simultaneous occurrence of multiple risk behaviors, which is useful for planning prevention programs.

Testing a Methodologic Approach to Territory Categorization Using Census Data

Abstract: The more traditional perspective in Geography views territory as a dichotomous reality of sociodemographic and biophysical characteristics yet, literature states that both territorial dimensions coexist and interact. The number of indicators for each territorial dimension is vast which makes the territory categorization a complex task. Despite it, territory categorization generates knowledge about the differences between territories that improve the planning process and make it more directed and strategic. This work main goal is to test a methodologic approach to categorize Lisbon Municipality area at the statistical section level, integrating information on the physical and social aspects. For this purpose, multivariate and complementary statistical analysis techniques will be used: Principal Component Analysis (applied to the physical and social aspects of the territory) and Hierarchical Classification Analysis (based in the factors extracted in the Principal Component Analysis). The resulting clusters will then be mapped and its distribution will be tested for spatial autocorrelation.