Centros - OPTICA | Documentos por Auto-Depósito
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- Sunlight-Driven AO7 Degradation with Perovskites (La,Ba)(Fe,Ti)O3 as Heterogeneous PhotocatalystsPublication . Rodrigues, Ana Sofia; Ciríaco, Lurdes; Pacheco, Maria José; Fernandes, Annabel; Mogo, Sandra; Lopes, AnaPerovskites of the (La,Ba)(Fe,Ti)O3 family were prepared, characterized, and utilized as heterogeneous photocatalysts, activated by natural sunlight, for environmental remediation of Acid Orange 7 (AO7) aqueous solutions. Catalysts were prepared by the ceramic (CM) and the complex polymerization (CP) methods and characterized by XRD, SEM, EDS, and band gap energy. It was found that catalytic properties depend on the synthesis method and annealing conditions. In the photocatalytic assays with sunlight, different AO7 initial concentrations and perovskite amounts were tested. During photocatalytic assays, AO7 and degradation products concentrations were followed by HPLC. Only photocatalysis with BaFeO3 -CM and BaTiO3 -CP presented AO7 removals higher than that observed for photolysis. However, photolysis leads to the formation of almost exclusively amino-naphthol and sulfanilic acid, whereas some of the perovskites utilized form lesstoxic compounds as degradation products, such as carboxylic acids (CA). Partial substitution of Ba by La in BaTiO3 -CM does not produce any change in the photocatalytic properties, but the replacement of Ti by Fe in the La0.1Ba0.9TiO3 leads to reduced AO7 removal rate, but with the formation of CAs. The best AO7 removal (92%) was obtained with BaFeO3 -CM (750 mg L−1 ), after 4 h of photocatalytic degradation with solar radiation
- A Two-Step Segmentation Method for Breast Ultrasound Masses Based on Multi-resolution AnalysisPublication . Rodrigues, Rafael; Braz, Rui; Pereira, Manuela; Moutinho, José; Pinheiro, Antonio M. G.Breast ultrasound images have several attractive properties that make them an interesting tool in breast cancer detection. However, their intrinsic high noise rate and low contrast turn mass detection and segmentation into a challenging task. In this article, a fully automated two-stage breast mass segmentation approach is proposed. In the initial stage, ultrasound images are segmented using support vector machine or discriminant analysis pixel classification with a multiresolution pixel descriptor. The features are extracted using non-linear diffusion, bandpass filtering and scale-variant mean curvature measures. A set of heuristic rules complement the initial segmentation stage, selecting the region of interest in a fully automated manner. In the second segmentation stage, refined segmentation of the area retrieved in the first stage is attempted, using two different techniques. The AdaBoost algorithm uses a descriptor based on scale-variant curvature measures and non-linear diffusion of the original image at lower scales, to improve the spatial accuracy of the ROI. Active contours use the segmentation results from the first stage as initial contours. Results for both proposed segmentation paths were promising, with normalized Dice similarity coefficients of 0.824 for AdaBoost and 0.813 for active contours. Recall rates were 79.6% for AdaBoost and 77.8% for active contours, whereas the precision rate was 89.3% for both methods.
- MPEG DASH - some QoE-based insights into the tradeoff between audio and video for live music concert streaming under congested network conditionsPublication . Rodrigues, Rafael; Pocta, Peter; Melvin, Hugh; Pereira, Manuela; Pinheiro, Antonio M. G.The rapid adoption of MPEG-DASH is testament to its core design principles that enable the client to make the informed decision relating to media encoding representations, based on network conditions, device type and preferences. Typically, the focus has mostly been on the different video quality representations rather than audio. However, for device types with small screens, the relative bandwidth budget difference allocated to the two streams may not be that large. This is especially the case if high quality audio is used, and in this scenario, we argue that increased focus should be given to the bit rate representations for audio. Arising from this, we have designed and implemented a subjective experiment to evaluate and analyses the possible effect of using different audio quality levels. In particular, we investigate the possibility of providing reduced audio quality so as to free up bandwidth for video under certain conditions. Thus, the experiment was implemented for live music concert scenarios transmitted over mobile networks, and we suggest that the results will be of significant interest to DASH content creators when considering bandwidth tradeoff between audio and video.
- New garment proposal for prevention of spreading Gram-negative bacteria resistant to carbapenem antibiotic class under hospital settingsPublication . Nogueira, Frederico; Gomes, Ana; Gouveia, Isabel C.Sensitive skin diseases, including atopic dermatitis, skin inflammation and bedsores, leave patients vulnerable under hospital setting. It is important for the development of a hospital gown with ‘‘soft hand’’ properties and at the same time as a protector against nosocomial infections. Klebsiella pneumoniae has developed resistance to antibiotics in the carbapenem antibiotic class, known as carbapenem-resistant K. pneumoniae (CRKP). CRKP is resistant to nearly all antibiotics and can kill up to 50% of infected patients. This work consisted in the development of a washable recycled silk fibroin-based gown covalently linked with an amino acid L-Cysteine(L-Cys), focused on prevention of K. pneumoniae establishment, proliferation and spreading to community, for use under hospital settings. With the growing problem of resistance to antibiotics and few new therapies on the horizon, gowns adsorbed with L-Cys show to function as a barrier to the establishment and proliferation of microorganisms, providing user protection from infectious disease. This gown was knitted at a rectilinear needle loom with a Jersey knit structure. Then it was cross-linked with L-Cys, subjected to laundry, and subsequently characterized by energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, contact angle, free energy of adhesion, scanning electron microscopy and transmission electron microscopy. Results presented a bactericidal effect against K. pneumoniae of 94.92% after three rinses and 88.88% after five washing cycles, with the few adhered bacteria with an altered and compromised morphology.
- Optimização da Técnica de Preparação de Amostras de Betões Refractários Auto-Escoantes de Alumina Sem Cimento Para Observação MicroscópicaPublication . Silva, Abílio P.; Gomes, Ana; Segadães, Ana Maria; Devezas, TessalenoA preparação de amostras para a observação de superfícies em microscopia requer um procedimento de corte, rectificação e polimento rigoroso que obedeça a requisitos sistemáticos de avaliação da qualidade superficial. Neste trabalho, um novo material constituído por 100% de alumina, mas de ingredientes (matriz e agregado) com características distintas obrigou, à implementação de uma nova receita de polimento e de realce dos contrastes entre os elementos estruturais presentes. Assim, apresenta-se um procedimento optimizado para a preparação das amostras de betões refractários auto-escoantes de alumina sem cimento para análise da microestrutura em microscópio metalográfico em complementaridade com o microscópio electrónico de varrimento.