995 resultados para pollen sources


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The impact of urban waste-water and non-point nitrate discharges in estuarine and near-shore coastal waters are analyzed. The study is focused on the effects of applying the European directives 91/271/EEC and 91/676/EEC to these systems. 4 Portuguese estuaries and two coastal lagoons with different characteristics are studied. A modelling system is applied and calibrated in each system. Three nitrate load scenarios are examined. It is shown that the morphologic and hydrodynamic characteristics of the domain largely control the ecological processes in these systems. The primary production limitation factors are split into “biologic” and “hydrodynamic” components. The physical limitation due to hydrodynamic and residence time is the most important factor. The combined limitation of “biologic” factors (temperature, light and nutrients availability) control productivity only in the systems where physical limitation is not important.

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Lorsqu'il est question de l'impact du sport sur le développement de jeunes adolescents' c'est généralement en fonction de leurs comportements. Toutefois, lorsqu'il s'agit d'évaluer l'influence de la pratique sportive sur le développement scolaire et professionnel des élèves-athlètes, nombreux sont les gens qui voient le sport comme une distraction notable à l'engagement et à la poursuite de leurs études. Pourtant nous remarquons, depuis quelques années, l'apparition et la multiplication de programmes d'études voulant favoriser à la fois la réussite scolaire ainsi que la réussite sportive de jeunes athlètes. Conformément aux propos de Boute, Lepert, Syndiqué et Taupin (1981), nous croyons que les programmes Sport-études concrétisent deux idées (et deux désirs) qui mûrissaient depuis longtemps: l'idée qu'il n'est pas nécessaire d'abandonner ses études pour se consacrer à un sport, et plus important, l'idée qu'il n'est pas nécessaire d'abandonner le sport pour mener à bien ses études secondaires. Selon cette perspective, il serait logique de penser que les programmes scolaires misant sur la combinaison des études et de la pratique du sport de haut niveau s'associent à des caractéristiques particulières notamment, en ce qui à trait à leur motivation au regard de leur projet professionnel. Notre étude vise donc à identifier les sources spécifiques de motivation des élèves inscrits aux programmes Sport-études et régulier à l'ordre d'enseignement secondaire et de vérifier l'existence possible de différences entre ces deux groupes de sujets. Ce mémoire se divise en trois parties. La première partie vise à exposer la problématique de notre recherche. Nous identifions d'abord notre problème de recherche en dressant un portrait général de la situation actuelle des jeunes à l'ordre d'enseignement secondaire puis nous traitons du rôle qu'occupe l'orientation quant à la motivation des élèves au regard de leurs études. À cela s'ajoute l'examen d'une littérature appropriée aux élèves-athlètes et aux sources de motivation particulières qui leur sont attribuées. Nous présentons ensuite le cadre théorique de notre recherche en analysant les concepts de motivation et de développement de carrière. Nous complétons cette partie par l'étude de certaines recherches et expériences en lien avec notre problématique et nous démontrons la pertinence de notre recherche avant d'identifier les objectifs poursuivis. En ce qui à trait à la deuxième partie de notre étude, elle concerne la méthodologie. Nous présentons dans cette section les principales démarches utilisées afin de rencontrer nos objectifs de recherche. Il s'agit entre autres de l'instrument de mesure retenu, les sujets sélectionnés, du déroulement de l'expérience, de la présentation des programmes Sport-études, des limites de notre recherche et des techniques statistiques employées pour analyser et interpréter les résultats obtenus. Quant à la troisième partie, elle contient essentiellement les données obtenues au cours de notre recherche. Dans un premier temps, nous dégageons un portrait général des sources de motivation au regard de la carrière des élèves inscrits aux programmes réguliers et Sport-études. Puis, dans un deuxième temps, nous essayons de dégager les particularités du profil motivationnel de ces élèves en fonction du programme d'études auquel ils sont inscrits. Enfin, quelques implications possibles de nos résultats pour la pratique de l'orientation professionnelle font l'objet de la conclusion de ce mémoire.

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Depuis une trentaine d' années, les nouveaux enseignants sont confrontés à des conditions d'insertion difficiles, notamment en raison de la précarité professionnelle. Ce contexte peut affecter de différentes manières le développement et la mobilisation des compétences, processus qui sont en relation avec le développement du sentiment d'efficacité personnelle (SEP) face à l'enseignement. Le SEP étant considéré comme une ressource essentielle pour agir avec compétence, s'engager dans les tâches et persévérer dans la profession enseignante, nous avons consacré notre recherche doctorale à ce sujet. Pour la méthodologie, la recherche a fait appel à des entrevues semi-structurées auprès de 15 enseignantes et enseignants, à une liste de contrôle permettant aux participants de cibler les sources de leur SEP, et enfin à la technique des incidents critiques pour faire évoquer des expériences mettant en relief le déploiement du SEP en contexte de pratique. Les résultats de la recherche montrent que le SEP se développe premièrement, au cours de la formation initiale grâce à la formation théorique et surtout aux stages. Deuxièmement, durant la phase d'insertion professionnelle par la mobilisation réussie des compétences acquises en formation initiale, par l'expérience d'enseignement, les conditions d'insertion facilitantes, la formation continue et l'apport des différents acteurs du milieu scolaire et universitaire, notamment à travers le soutien social, la rétroaction, la collaboration, la reconnaissance et la confiance témoignées. Les résultats indiquent également que ceux et celles qui se sentent efficaces surmontent mieux les difficultés de l'insertion, prennent davantage d'initiatives, innovent dans leur pratiques et obtiennent de meilleures performances dans les tâches attribuées. Notre étude contribue à apporter une nouvelle perspective dans la compréhension du SEP basée sur de véritables expériences d'enseignants débutants du secondaire, fait découvrir les possibilités sur lesquelles les programmes de formation et les mesures d' insertion pourraient s'appuyer et enfin, permet d'enrichir la problématique de l'insertion en enseignement.

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Tourism sector in Algarve region is the main engine of regional economy. Although frequently, tourism is considered as a low – moderate innovative sector, tourism competitiveness is still highly dependent on specific features of a Regional Innovation Platform, highlighting the crucial importance of knowledge creation and diffusion, learning, cooperative and collaborative interaction that may evolve to a Regional Innovation System (RIS). Studies of Local Knowledge Spillovers have been frequently focused on empirical evidence provided by regions highly related with manufacturing sectors. Considering a case study in Tourism Algarve Region, emphasizing a theoretical character on the analysis of these areas and using a qualitative methodology, the goal of this study was to provide preliminary evidence of the main sources and vehicles of regional knowledge spillovers used by tourism enterprises. Main information has been obtained using primary information collected from 20 interviews over main stakeholders regarding regional private and public sector. Primary information was complemented with secondary information, a deeply and extensive bibliography revision and also statistical information. Results show that, on the one hand, main sources of knowledge used by micro and small tourism enterprises are human resources and formal and informal networks. On the other hand, large tourism companies are weakly related with regional sources using mainly internal company and economic group resources to generate innovation activities. Regional innovation platform shows clear weaknesses on linkages and coordinated initiatives to promote and support innovation performance of firms hampering to increase tourism competitiveness and regional development.

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This work describes the synthesis of nanosized metal sulfides and respective SiO2 and/or TiO2 composites in high yield via a straightforward process, under ambient conditions (temperature and pressure), by adding to aqueous metals a nutrient solution containing biologically generated sulfide from sulfate-reducing bacteria (SRB). The nanoparticles‘ (NPs) morphological properties were shown not to be markedly altered by the SRB growth media composition neither by the presence of bacterial cells. We further extended the work carried out, using the effluent of a bioremediation system previously established. The process results in the synthesis of added value products obtained from metal rich effluents, such as Acid Mine Drainage (AMD), when associated with the bioremediation process. Precipitation of metals using sulfide allows for the possibility of selective recovery, as different metal sulfides possess different solubilities. We have evaluated the selective precipitation of CuS, ZnS and FeS as nanosized metal sulfides. Again, we have also tested the precipitation of these metal sulfides in the presence of support structures, such as SiO2. Studies were carried out using both artificial and real solutions in a continuous bioremediation system. We found that this method allowed for a highly selective precipitation of copper and a lower selectivity in the precipitation of zinc and iron, though all metals were efficiently removed (>93% removal). This research has also demonstrated the potential of ZnS-TiO2 nanocomposites as catalysts in the photodegradation of organic pollutants using the cationic dye, Safranin-T, as a model contaminant. The influence of the catalyst amount, initial pH and dye concentration were also evaluated. Finally, the efficiency of the precipitates as catalysts in sunlight mediated photodegradation was investigated, using different volumes of dye-contaminated water (150 mL and 10 L). This work demonstrates that all tested composites have the potential to be used as photocatalysts for the degradation of Safranin-T.

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Background Birch pollen is highly allergic and has the potential for episodically long range transport. Such episodes will in general occur out of the main pollen season. During that time allergy patients are unprotected and high pollen concentrations will therefore have a full allergenic impact. Objective To show that Denmark obtains significant quantities of birch pollen from Poland or Germany before the local trees start to flower. Methods Simultaneous observations of pollen concentrations and phenology in the potential source area in Poland as well as in Denmark were performed in 2006. The Danish pollen records from 2000-2006 were analysed for possible long range transport episodes and analysed with trajectories in combination with a birch tree source map. Results In 2006 high pollen concentrations were observed in Denmark with bi-hourly concentrations above 500 grains/ m3 before the local trees began to flower. Poland was identified as a source region. The analysis of the historical pollen record from Copenhagen shows significant pre-seasonal pollen episodes almost every year from 2000-2006. In all episodes trajectory analysis identified Germany or Poland as source regions. Conclusion Denmark obtains significant pre-seasonal quantities of birch pollen from either Poland or Germany almost every year. Forecasting of birch pollen quantities relevant to allergy patients must therefore take into account long-range transport. This cannot be based on measured concentrations in Denmark. The most effective way to improve the current Danish pollen forecasts is to extend the current forecasts with atmospheric transport models that take into account pollen emission and transport from countries such as Germany and Poland. Unless long range transport is taken into account pre-seasonal pollen episodes will have a full allergic impact, as the allergy patients in general will be unprotected during that time.

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Daily average Alnus pollen counts (1996-2005) from Worcester (UK) and Poznań (Poland) were examined with the aim of assessing the regional importance of Alnus pollen as an aeroallergen. The average number of Alnus pollen grains recorded annually at Poznań was more than 2.5 times that of Worcester. Furthermore, daily average Alnus pollen counts exceeded the thresholds of 100, 500 and 1,000 grains/m3 more times at Poznań than Worcester. Skin prick test results (1996-2005) and allergen-specific IgE(asIgE) measurements using the CAP (Pharmacia) system (2002-2005), were supplied by the Allergic Diseases Diagnostic Centre in Poznań. The annual number of positive skin prick tests to Alnus pollen allergens was significantly related (p<0.05) to seasonal variations in the magnitude of the Alnus pollen catch recorded at Poznań (r=0.70). The symptoms of patients with positive skin prick tests to Alnus pollen allergens were: 51% pollinosis, 43% atopic dermatitis, 4% asthma, 1% chronic urticaria and 1% eczema. On a scale of 0-6, 20.5% of patients examined for serum asIgE in relation to Alnus pollen allergens had asIgE measurements in classes 5 and 6. Alnus pollen is generally considered to be mildly allergenic. However, the amount of Alnus pollen released into the atmosphere in places such as Poznań may increase its impact on the population and make it one of the more important aeroallergens present.

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Previous work on Betula spp. (birch) in the UK and at five sites in Europe has shown that pollen seasons for this taxon have tended to become earlier by about 5–10 days per decade in most regions investigated over the last 30 years. This pattern has been linked to the trend to warmer winters and springs in recent years. However, little work has been done to investigate the changes in the pollen seasons for the early flowering trees. Several of these, such as Alnus spp. and Corylus spp., have allergens, which cross-react with those of Betula spp., and so have a priming effect on allergic people. This paper investigates pollen seasons for Alnus spp. and Corylus spp. for the years 1996–2005 at Worcester, in the West Midlands, United Kingdom. Pollen data for daily average counts were collected using a Burkard volumetric trap sited on the exposed roof of a three-storey building. The climate is western maritime. Meteorological data for daily temperatures (maximum and minimum) and rainfall were obtained from the local monitoring sites. The local area up to approximately 10 km surrounding the site is mostly level terrain with some undulating hills and valleys. The local vegetation is mixed farmland and deciduous woodland. The pollen seasons for the two taxa investigated are typically late December or early January to late March. Various ways of defining the start and end of the pollen seasons were considered for these taxa, but the most useful was the 1% method whereby the season is deemed to have started when 1% of the total catch is achieved and to have ended when 99% is reached. The cumulative catches (in grains/m3) for Alnus spp. varied from 698 (2001) to 3,467 (2004). For Corylus spp., they varied from 65 (2001) to 4,933 (2004). The start dates for Alnus spp. showed 39 days difference in the 10 years (earliest 2000 day 21, latest 1996 day 60). The end dates differed by 26 days and the length of season differed by 15 days. The last 4 years in the set had notably higher cumulative counts than the first 2, but there was no trend towards earlier starts. For Corylus spp. start days also differed by 39 days (earliest 1999 day 5, latest 1996 day 44). The end date differed by 35 days and length of season by 26 days. Cumulative counts and lengths of season showed a distinct pattern of alternative high (long) and low (short) years. There is some evidence of a synchronous pattern for Alnus spp.. These patterns show some significant correlations with temperature and rainfall through the autumn, winter and early spring, and some relationships with growth degree 4s and chill units, but the series is too short to discern trends. The analysis has provided insight to the variation in the seasons for these early flowering trees and will form a basis for future work on building predictive models for these taxa.

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A 30-day ahead forecast method has been developed for grass pollen at north London. The total period of the grass pollen season is covered by eight multiple regression models, each covering a 10-day period running consecutively from 21st May to 8th August. This means that three models were used for each 30-day forecast. The forecast models were produced using grass pollen and environmental data from 1961-1999 and tested on data from 2000 and 2002. Model accuracy was judged in two ways: the number of times the forecast model was able to successfully predict the severity (relative to the 1961-1999 dataset as a whole) of grass pollen counts in each of the eight forecast periods on a scale of one to four; and the number of times the forecast model was able to predict whether grass pollen counts were higher or lower than the mean. The models achieved 62.5% accuracy in both assessment years when predicting the relative severity of grass pollen counts on a scale of one to four, which equates to six of the eight 10-day periods being forecast correctly. The models attained 87.5% and 100% accuracy in 2000 and 2002 respectively when predicting whether grass pollen counts would be higher or lower than the mean. Attempting to predict pollen counts during distinct 10-day periods throughout the grass pollen season is a novel approach. The models also employed original methodology in the use of winter averages of the North Atlantic Oscillation to forecast 10-day means of allergenic pollen counts.

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A number of media outlets now issue medium-range (~7 day) weather forecasts on a regular basis. It is therefore logical that aerobiologists should attempt to produce medium-range forecasts for allergenic pollen that cover the same time period as the weather forecasts. The objective of this study is to construct a medium-range (< 7 day) forecast model for grass pollen at north London. The forecast models were produced using regression analysis based on grass pollen and meteorological data from 1990-1999 and tested on data from 2000 and 2002. The modelling process was improved by dividing the grass pollen season into three periods; the pre-peak, peak and post peak periods of grass pollen release. The forecast consisted of five regression models. Two simple linear regression models predicting the start and end date of the peak period, and three multiple regression models forecasting daily average grass pollen counts in the pre-peak, peak and post-peak periods. Overall the forecast models achieved 62% accuracy in 2000 and 47% in 2002, reflecting the fact that the 2002 grass pollen season was of a higher magnitude than any of the other seasons included in the analysis. This study has the potential to make a notable contribution to the field of aerobiology. Winter averages of the North Atlantic Oscillation were used to predict certain characteristics of the grass pollen season, which presents an important advance in aerobiological work. The ability to predict allergenic pollen counts for a period between five and seven days will benefit allergy sufferers. Furthermore, medium-range forecasts for allergenic pollen will be of assistance to the medical profession, including allergists planning treatment and physicians scheduling clinical trials.

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Trajectory analysis is a valuable tool that has been used before in aerobiological studies, to investigate the movement of airborne pollen. This study has employed back-trajectories to examine the four highest grass pollen episodes at Worcester, during the 2001 grass pollen season. The results have shown that the highest grass pollen counts of the 2001 season were reached when air masses arrived from a westerly direction. Back-trajectory analysis has a limited value to forecasters because the method is retrospective and cannot be employed directly for forecasting. However, when used in conjunction with meteorological data this technique can be used to examine high magnitude events in order to identify conditions that lead to high pollen counts.

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Spatial and temporal variations in daily grass pollen counts and weather variables are described for two regions with different bio-geographical and climatic regimes, southern Spain and the United Kingdom. Daily average grass pollen counts are considered from six pollen-monitoring sites, three in southern Spain (Ciudad Real, Córdoba and Priego) and three in the United Kingdom (Edinburgh, Worcester and Cambridge). Analysis shows that rainfall and maximum temperatures are important factors controlling the magnitude of the grass pollen season in both southern Spain and the United Kingdom, and that the strength and direction of the influence exerted by these variables varies with geographical location and time.

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Geographical and temporal variations in the start dates of grass pollen seasons are described for selected sites of the European Pollen Information Service. Daily average grass pollen counts are derived from Network sites in Finland, the Netherlands, Denmark, United Kingdom, Austria, Italy and Spain, giving a broad longitudinal transect over Western Europe. The study is part of a larger project that also examines annual and regional variations in the severity, timing of the peak and duration of the grass pollen seasons. For several sites, data are available for over twenty years enabling long term trends to be discerned. The analyses show notable contrasts in the progression of the seasons annually with differing lag times occurring between southern and northern sites in various years depending on the weather conditions. The patterns identified provide some insight into geographical differences and temporal trends in the incidence of pollinosis. The paper discusses the main difficulties involved in this type of analysis and notes possibilities for using data from the European Pollen Information service to construct pan European predictive models for pollen seasons.

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Two of the most frequently used methods of pollen counting on slides from Hirst type traps are evaluated in this paper: the transverse traverse method and the longitudinal traverse method. The study was carried out during June–July 1996 and 1997 on slides from a trap at Worcester, UK. Three pollen types were selected for this purpose: Poaceae, Urticaceae and Quercus. The statistical results show that the daily concentrations followed similar trends (p < 0.01, R-values between 0.78–0.96) with both methods during the two years, although the counts were slightly higher using the longitudinal traverses method. Significant differences were observed, however, when the distribution of the concentrations during 24 hour sampling periods was considered. For more detailed analysis, the daily counts obtained with both methods were correlated with the total number of pollen grains for the taxon over the whole slide, in two different situations: high and low concentrations of pollen in the atmosphere. In the case of high concentrations, the counts for all three taxa with both methods are significantly correlated with the total pollen count. In the samples with low concentrations, the Poaceae and Urticaceae counts with both methods are significantly correlated with the total counts, but none of Quercus counts are. Consideration of the results indicates that both methods give a reasonable approximation to the count derived from the slide as a whole. More studies need be done to explore the comparability of counting methods in order to work towards a Universal Methodology in Aeropalynology.

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Recent epidemics of acute asthma have caused speculation that, if their causes were known, early warnings might be feasible. In particular, some epidemics seemed to be associated with thunderstorms. We wondered what risk factors predicting epidemics could be identified. Daily asthma admissions counts during 1987-1994, for two age groups (0-14 yrs and > or = 15 yrs), were measured using the Hospital Episodes System (HES). Epidemics were defined as combinations of date, age group and English Regional Health Authority (RHA) with exceptionally high asthma admission counts compared to the predictions of a log-linear autoregression model. They were compared with control days 1 week before and afterwards, regarding seven meteorological variables and 5 day average pollen counts for four species. Fifty six asthma epidemics were identified. The mean density of sferics (lightning flashes), temperature and rainfall on epidemic days were greater than those on control days. High sferics densities were overrepresented in epidemics. Simultaneously high sferics and grass pollen further increased the probability of an epidemic, but only to 15% (95% confidence interval 2-45%). Two thirds of epidemics were not preceded by thunderstorms. Thunderstorms and high grass pollen levels precede asthma epidemics more often than expected by chance. However, most epidemics are not associated with thunderstorms or unusual weather conditions, and most thunderstorms, even following high grass pollen levels, do not precede epidemics. An early warning system based on the indicators examined here would, therefore, detect few epidemics and generate an unacceptably high rate of false alarms.