Browsing by Author "Nunes, S."
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- Ascorbic acid and flavanone glycosides in citrus: Relationship with antioxidant activityPublication . Miguel, Maria Graça; Duarte, Amílcar; Nunes, S.; Sustelo, V.; Martins, D.; Dandlen, S. A.The effects of cultivar and orchard on the content of ascorbic acid and flavanone glycosides as well as on the antioxidant activity of citrus juices were studied. Ascorbic acid and flavanone glycosides were determined using HPLC method. For antiradicalar activity evaluation, TAEC and ORAC methods were used. Citrus of 'Valencia late' from Faro and 'D. Joao' presented the highest levels of hesperidin in contrast to the citrus of 'Valencia late' from Silves with 0.4 mg/ml, a value closer to those of Navel oranges 'Navelate' and 'Lanelate'. Citrus of 'Valencia late' from Silves and 'D. Joao' presented the lowest levels of narirutin. 'Ortanique' and 'Encore' cultivars were poorer in ascorbic acid compared with the oranges. When the TEAC method was used for the determination of antioxidant activity, 'Valencia late' from Faro presented the best activity. A good relation was observed between antiradical activity measured through the TEAC method and the amount of ascorbic acids in samples. None relation was found between the levels of flavanones and antiradical activity. When the ORAC method was applied, the best activity was found for 'Navelate' and 'Encore' samples and practically none relation between this method and the amounts of ascorbic acid and flavanones was found.
- Building the what and where systems: multi-scale lines, edges and keypointsPublication . Rodrigues, J. M. F.; Almeida, D.; Nunes, S.; Lam, Roberto; du Buf, J. M. H.Computer vision for realtime applications requires tremendous computational power because all images must be processed from the first to the last pixel. Ac tive vision by probing specific objects on the basis of already acquired context may lead to a significant reduction of processing. This idea is based on a few concepts from our visual cortex (Rensink, Visual Cogn. 7, 17-42, 2000): (1) our physical surround can be seen as memory, i.e. there is no need to construct detailed and complete maps, (2) the bandwidth of the what and where systems is limited, i.e. only one object can be probed at any time, and (3) bottom-up, low-level feature extraction is complemented by top-down hypothesis testing, i.e. there is a rapid convergence of activities in dendritic/axonal connections.
- Fine arts edutainment: the amateur painterPublication . Almeida, D.; Carvalho, Brito; Rodrigues, J. M. F.; du Buf, J. M. H.; Nunes, S.A new scheme for painterly rendering (NPR) has been developed. This scheme is based on visual perception, in particular themulti-scale line/edge representation in the visual cortex. The Amateur Painter (TAP) is the user interface on top of the rendering scheme. It allows to (semi)automatically create paintings from photographs, with different types of brush strokes and colour manipulations. In contrast to similar painting tools, TAP has a set of menus that reflects the procedure followed by a normal painter. In addition, menus and options have been designed such that they are very intuitive, avoiding a jungle of sub-menus with options from image processing that children and laymen do not understand. Our goal is to create a tool that is extremely easy to use, with the possibility that the user becomes interested in painting techniques, styles, and fine arts in general.
- Influence of citric acid, ascorbic acid and calcium lactate applications on the shelf life of minimally processed horticultural productsPublication . Rodrigues, D.; Miguel, Maria Graça; Dandlen, S.; Nunes, S.; Antunes, Maria DulceThe market share of minimally processed fruits and vegetables has continuously increased in the past years due to consumer life style. These products have high expectations regarding quality and shelf-life. The objective of the present work was to evaluate the effect of additives applied externally after cutting in fresh-cut kiwifruit, pears, strawberries, tomatoes, and peppers. Fruit were washed in water, cut longitudinally in quarters and dipped in solutions of 2% citric acid, 2% ascorbic acid or 2% calcium lactate. Subsequently, fruit were packed in plastic trays, covered with 15 mu m thick polyethylene film and stored at 4 degrees C for 9 d. At intervals of 0, 3, 6 and 9 d, measurements of firmness and total phenolics content were performed. Calcium lactate was efficient in maintaining firmness in most fresh-cut fruit. Total phenolics content were higher in kiwifruit, strawberries and peppers than in pears and tomatoes. Ascorbic acid was the most efficient dip to maintain or increase the total phenolics content of the fresh-cut fruit studied.
- Object categorisations using templates constructed from multi-scale line and edge representationsPublication . Nunes, S.; Almeida, D.; Rodrigues, J. M. F.; du Buf, J. M. H.Object categorisation is linked to detection, segregation and recognition. In the visual system, these processes are achieved in the ventral \what"and dorsal \where"pathways [3], with bottom-up feature extractions in areas V1, V2, V4 and IT (what) in parallel with top-down attention from PP via MT to V2 and V1 (where). The latter is steered by object templates in memory, i.e. in prefrontal cortex with a what component in PF46v and a where component in PF46d.
- Painterly rendering using human visionPublication . du Buf, J. M. H.; Rodrigues, J. M. F.; Nunes, S.; Almeida, D.; Brito, Vera; Carvalho, J.Painterly rendering has been linked to computer vision, but we propose to link it to human vision because perception and painting are two processes that are interwoven. Recent progress in developing computational models allows to establish this link. We show that completely automatic rendering can be obtained by applying four image representations in the visual system: (1) colour constancy can be used to correct colours, (2) coarse background brightness in combination with colour coding in cytochrome-oxidase blobs can be used to create a background with a big brush, (3) the multi-scale line and edge representation provides a very natural way to render fi ner brush strokes, and (4) the multi-scale keypoint representation serves to create saliency maps for Focus-of-Attention, and FoA can be used to render important structures. Basic processes are described, renderings are shown, and important ideas for future research are discussed.
- Perception-based painterly rendering: funcionality and interface designPublication . Nunes, S.; Almeida, D.; Brito, Vera; Carvalho, J.; Rodrigues, J. M. F.; du Buf, J. M. H.Painterly rendering (non-photorealistic rendering or NPR) aims at translating photographs into paintings with discrete brush strokes, simulating certain techniques (im- or expressionism) and media (oil or watercolour). Recently, our research into visual perception and models of processes in the visual cortex resulted in a new rendering scheme, in which detected lines and edges at different scales are translated into brush strokes of different sizes. In order to prepare a version which is suitable for many users, including children, the design of the interface in terms of window and menu system is very important. Discussions with artists and non-artists led to three design criteria: (1) the interface must reflect the procedures and possibilities that real painters follow and use, (2) it must be based on only one window, and (3) the menu system must be very simple, avoiding a jungle of menus and sub-menus. This paper explains the interface that has been developed.
- Phenols and antioxidant activity of hydro-alcoholic extracts of propolis from Algarve, South of PortugalPublication . Miguel, Maria Graça; Nunes, S.; Dandlen, S. A.; Antunes, Maria DulcePropolis is a natural honeybee product known to be beneficial for human health, with a complex chemical composition, highly dependent on the collection site. The objective of the present research was to evaluate phenols and antioxidant activity of propolis samples collected in three main areas of Algarve, South of Portugal. Water revealed to be less effective for extracting phenolic compounds from propolis than the methanol and water/ethanol. The last two were good extraction solvents of phenols. Nevertheless water/ethanol was the solvent chosen because it was able to extract phenols in considerable amounts being less toxic than methanol. In spring, higher amounts of phenols (total phenols, flavones, flavonols, flavanones and dihydroflavonols) were detected in hydro-alcoholic extracts of propolis than in winter. Among the three main areas of Algarve where samples were collected, those from Barrocal had the highest levels of polyphenols, independent on the season (winter or spring). Within each area, the levels of phenols changed according to the zone. Concerning antioxidant activity, samples from Barrocal presented better radical scavenging abilities than those from the remaining areas, independent on the antioxidant method and collection season. Such results correlated closely with the levels of total phenols, flavones and flavonols in samples. (C) 2010 Elsevier Ltd. All rights reserved.
- Phenols, flavonoids and antioxidant activity of aqueous and methanolic extracts of propolis (Apis mellifera L.) from Algarve, South PortugalPublication . Miguel, Maria Graça; Nunes, S.; Dandlen, S. A; Cavaco, A. M.; Antunes, Maria DulcePropolis is a resinous substance collected by honeybees to seal honeycomb, which has been used in folk medicine due to its antimicrobial and antioxidant properties. In the present study, water and methanol were used to extract phenols and flavonoids from propolis collected in thirteen different areas in the Algarve region during the winter and spring. The ABTS(center dot+), DPPH center dot, and O-2(center dot-) scavenging capacity, and metal chelating activity were also evaluated in the propolis samples. Methanol was more effective than water in extracting total phenols (2.93-8.76 mg/mL) (0.93-2.81 mg/mL). Flavones and flavonols were also better extracted with methanol (1.28-2.76 mg/mL) than with water (0.031-0.019 mg/mL). The free radical scavenging activity, ABTS (IC50 = 0.006-0.036 mg/mL), DPPH (IC50 = 0.007-0.069 mg/mL) and superoxide (IC50 = 0.001-0.053 mg/mL), of the samples was also higher in methanolic extracts. The capacity for chelating metal ions was higher in aqueous extracts (41.11-82.35%) than in the methanolic ones (4.33-29.68%). Propolis from three locations of Algarve region were richer in phenols and had better capacity for scavenging free ABTS and DPPH radicals than the remaining samples. These places are part of a specific zone of Algarve known as Barrocal.