Browsing by Issue Date, starting with "2002"
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- Ozone deposition modelling in a portuguese coastal zonePublication . Valinhas, Maria José; Borrego, Carlos; Barros, Nelson; Carvalho, Ana CristinaThe deposition of pollutants from the atmosphere to ecosystems is the cause of some present environmental problems: acidification, eutrophication and, indirectly, ground level ozone. Related with these issues is the critical loads/levels concept, widely accepted in Europe as basis for pollution control strategies. The knowledge of atmospheric pollutants deposition on ecosystems is needed to setup this methodology. This paper presents the parameterisation done in the deposition module of the system of models MAR IV which is adequate to simulate the transport, dispersion and removal of pollutants, including ozone production for mesoscale application. The ozone surface resistance (Rc) pararneterisation was applied to Lisbon region and the modelk performance was assessed with ozone deposition experimental data observed in the study area during the fieldwork LisbEx 97. The influence of parameterisation became evident with the good fit between modelled results and measured data. Based on an empirical method described by the Stockholm Environmental Institute report a Critical Load map, for non-forested areas, was calculated for Pomgal. The methodology is based on the kind of soil and its buffer capacity to acid compounds, The results show that around 70°/0of the country is in sensitive areas reinforcing the need for the application of this concept.
- Influence of traffic emissions estimation variability on urban air quality modellingPublication . Borrego, Carlos; Tchepel, Oxana; Monteiro, Alexandra; Barros, Nelson; Miranda, Ana IsabelThe main objective of this work is to analyse how uncertainties in emission data of nitrogen oxides (NOx) and volatile organic compounds (VOC), originated from road traffic, influence the model prediction of ozone (O3) concentration fields. Different methods to estimate emissions were applied and results were compared in order to obtain their variability. Based on these data, different emission scenarios were compiled for each pollutant considering the minimum and the maximum values of the estimated emission range. These scenarios were used as input to the MARIV mesoscale modelling system. Simulations have been performed for a summer day in the Northern Region of Portugal. The different approaches to estimate NOx and VOC traffic emissions show a significant variability of absolute values and of their spatial distribution. Comparison of modelling results obtained from the two scenarios presents a dissimilarity of 37% for ozone concentration fields as a response of the system to a variation in the input emission data of 63% for NOx and 59% for VOC. Far beyond all difficulties and approximations, the developed methodology to build up an emission data base shows to be consistent and an useful tool in order to turn applicable an air quality model. Nevertheless, the sensitivity of the model to input data should be considered when it is used as a decision support tool.
- A idade dos homens do poder: novos e velhos na burocracia de D. Afonso V (1439-1460)Publication . Freitas, Judite A. Gonçalves de; yes
- Cu2+-induced isoproterenol oxidation into isoprenochrome in adult rat calcium-tolerant cardiomyocytesPublication . Remião, Fernando; Carvalho, Márcia; Carmo, Helena; Carvalho, Félix; Bastos, Maria L.Sustained high levels of circulating catecholamines may induce cardiotoxicity. There is increasing evidence that this could result from catecholamine oxidation into aminochromes, which is catalyzed by transition metals. In fact, it has already been shown that copper-induced oxidation of the beta-agonist isoproterenol decreases the viability of isolated cardiomyocytes. Thus, the aim of this work was to contribute for the clarification of the mechanisms underlying the toxic effects of isoproterenol, Cu2+ and their concomitant effect in isolated rat cardiomyocytes. Freshly isolated calcium-tolerant cardiomyocytes from adult rat were incubated with 1 mM isoproterenol, 20 microM Cu2+ or with both during 4 h. Isoproterenol and its aminochrome (isoprenochrome), and reduced and oxidized glutathione were measured at each hour in the incubation medium and in the cells. The intracellular activities of the selenium-dependent glutathione peroxidase, glutathione reductase, and glutathione-S-transferase were determined after 4 h of incubation. Isoprenochrome was found in both cells and incubation medium in samples incubated with isoproterenol alone. However, in the isoproterenol plus Cu2+ samples, a greater depletion of isoproterenol accompanied by a proportional increase of isoprenochrome was observed. This higher ISO oxidation resulted in the depletion of intracellular glutathione and in the release of oxidized glutathione to the incubation medium. The content of total glutathione (intra- and extracellular) and the intracellular activity of the selenium-dependent glutathione peroxidase, glutathione reductase, and glutathione-S-transferase were also decreased in the isoproterenol plus Cu2+ samples. These results seem to indicate that the oxidative stress resulting from catecholamine/transition metal association may contribute to catecholamine cardiotoxicity.
- Imagens do Brasil na imprensa portuguesa de grande circulaçãoPublication . Sousa, Jorge PedroEste trabalho procura identificar e descrever as imagens atuais do Brasil projetadas em 1999 pela imprensa portuguesa de grande circulação, a partir de uma análise quantitativa do discurso. O autor salienta que, embora em números absolutos exista pouca informação sobre o Brasil na imprensa portuguesa, em termos relativos essa informação é relevante. Além disso, a informação sobre o Brasil na imprensa portuguesa tende a favorecer o Brasil e as relações Portugal-Brasil.
- Cloning of a peroxidase enzyme involved in the biosynthesis of pharmaceutically active terpenoid indole alkaloids in Catharanthus roseus (L.) G. DonPublication . Hilliou, F.; Costa, M.; Almeida, I.; Cardoso, I.L.; Leech, M.; Ros Barceló, A.; Sottomayor, M.
- A study of the optical properties of photopolymer Fabry-Perot microcavities by a dual-wavelength fibre optic architecturePublication . Heredero, Raquel L; Martin, Susana; Caleya, Ramón Fernández de; Lobo Ribeiro, Antonio B.; Araújo, Francisco M; Ferreira, Luís A; Santos, José Luís; Guerrero, HéctorWe present a novel method to study the behaviour of the optical properties of photopolymer materials with temperature. The photopolymer is deposited on the tip of optical fibres by dip coating to fabricate low-finesse Fabry–Perot microcavities. The signal processing technique utilized to interrogate the cavity is based on the generation of two quadrature phase-shifted interferometric signals using two Bragg fibre gratings. This technique enables the determination of the values of the thermo-optical coefficient and the linear coefficient of thermal expansion of the photopolymer. The effectiveness of the processing technique is also exploited in the study of the dependence of the temperature sensitivity on the cavity thickness.
- The measurement of coal porosity with different gasesPublication . Rodrigues, Cristina; Lemos de Sousa, M. J.Sorption processes can be used to study different characteristics of coal properties, such as gas content (coalbed methane potential of a deposit), gas diffusion, porosity, internal surface area, etc. Coal microstructure (porosity system) is relevant for gas flow behaviour in coal and, consequently, directly influences gas recovery from the coalbed. This paper addresses the determination of coal porosity (namely micro- and macroporosity) in relation to the molecular size of different gases. Experiments entailed a sorption process, which includes the direct method of determining the ‘‘void volume’’ of samples using different gases (helium, nitrogen, carbon dioxide, and methane). Because gas behaviour depends on pressure and temperature conditions, it is critical, in each case, to know the gas characteristics, especially the compressibility factor. The experimental conditions of the sorption process were as follows: temperature in the bath 35 ºC; sample with moisture equal to or greater than the moisture-holding capacity (MHC), particle size of sample less than 212 mm, and mass ca. 100 g. The present investigation was designed to confirm that when performing measurements of the coal void volume with helium and nitrogen, there are only small and insignificant changes in the volume determinations. Inducing great shrinkage and swelling effects in the coal molecular structure, carbon dioxide leads to ‘‘abnormal’’ negative values in coal void volume calculations, since the rate of sorbed and free gas is very high. In fact, when in contact with the coal structure, carbon dioxide is so strongly retained that the sorbed gas volume is much higher than the free gas volume. However, shrinkage and swelling effects in coal structure induced by carbon dioxide are fully reversible. Methane also induces shrinkage and swelling when in contact with coal molecular structure, but these effects, although smaller than those induced by carbon dioxide, are irreversible and increase the coal volume.
- A functional model of responsive suspension-feeding and growth in bivalve shellfish, configured and validated for the scallop Chlamys farreri during culture in ChinaPublication . Hawkins, Anthony; Duarte, Pedro; Fang, J. G.; Pascoe, Phillip; Zhang, J.; Zhang, X.; Zhu, M.A dynamic growth model is presented for the suspension-feeding scallop Chlamys farreri. The model is configured and validated for C. farreri cultured in Sungo Bay, China, using functional relations to simulate rapid and sensitive adjustments in feeding and metabolism as observed in response to the highly changeable environment there. Notable novel elements include resolving significant adjustments in the relative processing of living chlorophyll-rich phytoplankton organics, nonphytoplankton organics and the remaining inorganic matter during both differential retention on the gill and selective pre-ingestive rejection within pseudofaeces. We also include a facility to predict the energy content of non-phytoplankton organics. This is significant, for living phytoplankton contributed less than 20% towards suspended particulate organic matter within Sungo Bay. Further, the energy content of non-phytoplankton organics was very much more variable than for phytoplankton organics. Whether using that facility or assuming an average value for the energy content of non-phytoplankton organics, resolution of the relative processing of different particle types allows simulation of how the rates, organic compositions and energy contents of filtered, ingested and deposited matter change in response to differences in seawater temperature, seston availability and seston composition. Dependent relations predict rates of energy absorption, energy expenditure and excretion. By these means, our model replicates dynamic adjustments in feeding and metabolism across full ranges of relevant natural variability, and successfully simulates scallop growth from larvae or seed to harvestable size under different temporal and spatial scenarios of culture. This is an important advance compared with simpler models that do simulate responsive adjustments. Only by modelling the complex set of feedbacks, both positive and negative, whereby suspension feeding shellfish interact with ecosystem processes, can one realistically hope to assess environmental capacities for culture.
- Effect of 3,4-methylenedioxymethamphetamine ("ecstasy") on body temperature and liver antioxidant status in mice: influence of ambient temperaturePublication . Carvalho, Márcia; Carvalho, Félix; Remião, Fernando; Pereira, Maria de Lourdes; Pires-das-Neves, Ricardo; Bastos, Maria de LourdesThe consumption of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) is known to cause severe hyperthermia and liver damage in humans. The thermogenic response induced by MDMA is complex and partially determined by the prevailing ambient temperature (AT). This is of extreme importance since ecstasy is often consumed at "rave" parties, where dancing takes place in a warm environment, which may exacerbate the effect of MDMA on thermoregulation. In view of the fact that hyperthermia is a well-known pro-oxidant aggressive condition, its potential role in ecstasy-induced hepatocellular toxicity should be further studied. Thus, the present study was performed in order to evaluate the influence of AT on the effects of single administration of MDMA on body temperature and liver toxicity in Charles River mice. Animals were given an acute intraperitoneal dose of MDMA (5, 10 or 20 mg/kg) and placed in AT of 20+/-2 degrees C or 30+/-2 degrees C for 24 h. Body temperature was measured during the study using implanted transponders and a temperature probe reading device. Plasma and liver samples were used for biochemical analysis. Liver sections were also taken for histological examination. The parameters evaluated were (1) plasma levels of transaminases and alkaline phosphatase, (2) hepatic glutathione (GSH), (3) hepatic lipid peroxidation, (4) activity of hepatic antioxidant enzymes (catalase, glutathione peroxidase, glutathione reductase, glutathione- S-transferase, copper/zinc superoxide dismutase and manganese superoxide dismutase), and (5) liver histology. The hyperthermic response elicited by MDMA was clearly dose-related and potentiated by high AT. Administration of MDMA produced some evidence of oxidative stress, expressed as GSH depletion at both ATs studied, as well as by lipid peroxidation and decreased catalase activity at high AT. High AT, by itself, decreased glutathione peroxidase activity. Histological examination of the liver revealed abnormalities of a dose- and AT-dependent nature. These changes included vacuolation of the hepatocytes, presence of blood clots and loss of typical hepatic cord organisation. The results obtained in the present study suggest that oxidative stress plays a part in the first stage of MDMA-induced liver damage and that liver antioxidant status is aggravated by increased AT. Thus, these findings are in accordance with the hypothesis that high AT may potentiate ecstasy-induced hepatotoxicity by increasing body hyperthermia.