863 resultados para nutrient mobility


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Les 21, 22 et 23 septembre 2006, le Département d’Études Françaises de l’Université de Turku (Finlande) a organisé une conférence internationale et bilingue (anglais et français) sur le thème de la mobilité académique ; le but de cette rencontre était de rendre possible la tenue d’un forum international et multidisciplinaire, susceptible d’être le siège de divers débats entre les différents acteurs de la mobilité académique (c’estàdire des étudiants, des chercheurs, des personnels enseignants et administratifs, etc.). Ainsi, ont été mis à contribution plus de cinquante intervenants, (tous issus de domaines aussi variés que la linguistique, les sciences de l’éducation, la didactique, l’anthropologie, la sociologie, la psychologie, l’histoire, la géographie, etc.) ainsi que cinq intervenants renommés1. La plupart des thèmes traités durant la conférence couvraient les champs suivants : l’organisation de la mobilité, les obstacles rencontrés par les candidats à la mobilité, l’intégration des étudiants en situation d’échange, le développement des programmes d’études, la mobilité virtuelle, l’apprentissage et l’enseignement des langues, la prise de cosncience interculturelle, le développement des compétences, la perception du système de mobilité académique et ses impacts sur la mobilité effective. L’intérêt du travail réalisé durant la conférence réside notamment dans le fait qu’il ne concentre pas uniquement des perspectives d’étudiants internationaux et en situation d’échange (comme c’est le cas de la plupart des travaux de recherche déjà menés sur ce sujet), mais aussi ceux d’autres corps : enseignants, chercheurs, etc. La contribution suivante contient un premier corpus de dixsept articles, répartis en trois sections : 1. Impacts de la mobilité étudiante ; 2. Formation en langues ; 3. Amélioration de la mobilité académique. À l’image de la conférence, la production qui suit est bilingue : huit des articles sont rédigés en français, et les neuf autres en anglais. Certains auteurs n’ont pas pu assister à la conférence mais ont tout de même souhaité apparaître dans cet ouvrage. Dans la première section de l’ouvrage, Sandrine Billaud tâche de mettre à jour les principaux obstacles à la mobilité étudiante en France (logement, organisation des universités, démarches administratives), et propose à ce sujet quelques pistes d’amélioration. Vient ensuite un article de Dominique Ulma, laquelle se penche sur la mobilité académique régnant au sein des Instituts Universitaires de Formation des Maîtres (IUFM) ; elle s’est tout particulièrement concentrée sur l’enthousiasme des stagiaires visàvis de la mobilité, et sur les bénéfices qu’apporte la mobilité Erasmus à ce type précis d’étudiant. Ensuite, dans un troisième article, Magali Hardoin s’interroge sur les potentialités éducationnelles de la mobilité des enseignantsstagiaires, et tâche de définir l’impact de celleci sur la construction de leur profil professionnel. Après cela arrive un groupe de trois articles, tous réalisés à bases d’observations faites dans l’enseignement supérieur espagnol, et qui traitent respectivement de la portée qu’a le programme de triple formation en langues européennes appliquées pour les étudiants en mobilité (Marián MorónMartín), des conséquences qu’occasionne la présence d’étudiants étrangers dans les classes de traductions (Dimitra Tsokaktsidu), et des réalités de l’intégration sur un campus espagnol d’étudiants américains en situation d’échange (Guadalupe Soriano Barabino). Le dernier article de la section, issu d’une étude sur la situation dans les institutions japonaises, fait état de la situation des programmes de doubles diplômes existant entre des établissements japonais et étrangers, et tente de voir quel est l’impact exact de tels programmes pour les institutions japonaises (Mihoko Teshigawara, Riichi Murakami and Yoneo Yano). La seconde section est elle consacrée à la relation entre apprentissage et enseignement des langues et mobilité académique. Dans un premier article, Martine Eisenbeis s’intéresse à des modules multimédia réalisés à base du film « L’auberge espagnole », de Cédric Klapish (2001), et destinés aux étudiants en mobilité désireux d’apprendre et/ou améliorer leur français par des méthodes moins classiques. Viennent ensuite les articles de Jeanine Gerbault et Sabine Ylönen, lesquels traitent d’un projet européen visant à supporter la mobilité étudiante par la création d’un programme multimédia de formation linguistique et culturelle pour les étudiants en situation de mobilité (le nom du projet est EUROMOBIL). Ensuite, un article de Pascal Schaller s’intéresse aux différents types d’activités que les étudiants en séjour à l’étranger expérimentent dans le cadre de leur formation en langue. Enfin, la section s’achève avec une contribution de Patricia KohlerBally, consacrée à un programme bilingue coordonné par l’Université de Fribourg (Suisse). La troisième et dernière section propose quelques pistes de réflexion destinées à améliorer la mobilité académique des étudiants et des enseignants ; dans ce cadre seront donc évoquées les questions de l’égalité face à la mobilité étudiante, de la préparation nécessitée par celleci, et de la prise de conscience interculturelle. Dans un premier chapitre, Javier Mato et Bego

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The interception of the rainfall by the forest canopy has great relevance to the nutrient geochemistry cycle in low fertility tropical soils under native or cultivated forests. However, little is known about the modification of the rainfall water quality and hydrological balance after interception by the canopies of eucalyptus under pure and mixed plantations with leguminous species, in Brazil. Samples of rainfall (RF), throughfall (TF) and stemflow (SF) were collected and analyzed in pure plantations of mangium (nitrogen fixing tree -NFT), guachapele (NFT) and eucalyptus (non-nitrogen fixing tree -NNFT) and in a mixed stand of guachapele and eucalyptus in Seropédica, State of Rio de Janeiro, Brazil. Nine stemflow collectors (in selected trees) and nine pluviometers were randomly disposed under each stand and three pluviometers were used to measure the incident rainfall during 5.5 months. Mangium conveyed 33.4% of the total rainfall for its stem. An estimative based on corrections for the average annual precipitation (1213 mm) indicated that the rainfall's contribution to the nutrient input (kg ha-1) was about 8.42; 0.95; 19.04; 6.74; 4.72 and 8.71 kg ha-1 of N-NH4+, P, K+, Ca+2, Mg+2 and Na+, respectively. Throughfall provided the largest contributions compared to the stemflow nutrient input. The largest inputs of N-NH4+ (15.03 kg ha-1) and K+ (179.43 kg ha-1) were observed under the guachapele crown. Large amounts of Na+ denote a high influence of the sea. Mangium was the most adapted species to water competitiveness. Comparatively to pure stand of eucalyptus, the mixed plantation intensifies the N, Ca and Mg leaching by the canopy, while the inputs of K and P were lower under these plantations.

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This study evaluated the contribution of agroforestry (AFS) and traditional systems to carbon sequestration and nutrient reserves in plants, litter and soil. The study was carried out in the semiarid region of Brazil in a long-term experiment on an experimental farm of the goat and sheep section of the Brazilian Agricultural Research Corporation (Embrapa). Two agroforestry systems were investigated: agrosilvopastoral (ASP) and forest-pasture areas (SP) as well as traditional agriculture management (TM), two areas left fallow after TM (six fallow years - F6 and nine fallow years - F9) and one area of preserved Caatinga vegetation (CAT). Soil, litter and plants were sampled from all areas and the contents of C, N, P, K, Ca and Mg per compartment determined. The AFS (ASP and SP) had higher nutrient stocks than the traditional and intermediate stocks compared to the preserved Caatinga. In the ASP, a relevant part of the nutrients extracted by crops is returned to the system by constant inputs of litter, weeding of herbaceous vegetation and cutting of the legume crops. After fallow periods of six and nine years, carbon and nutrient stocks in the compartments soil, litter and herbaceous plants were similar to those of the preserved Caatinga (CAT), but still lower than under natural conditions in the woody vegetation.

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We analyzed the nutritional composition and isotope ratios (C and N) of big-leaf mahogany (Swietenia macrophylla King) leaves in plantations established on contrasting soils and climates in Central America (State of Quintana Roo, Yucatán, México) and South America (State of Pará, Brazil). The objective was to determine the adaptability of this species to large differences in nutrient availability and rainfall regimes. Nutrient concentrations of leaves and soils were determined spectrophotometrically, and isotope ratios were measured using mass spectrometric techniques.In Pará soils were sandier, and acidic, receiving above 2000 mm of rain, whereas in Quintana Roo soils were predominantly clayey, with neutral to alkaline pH due to the underlying calcareous substrate, with about 1300 mm of rain. Leaf area/weight ratio was similar for both sites, but leaves from Quintana Roo were significantly smaller. Average N and K concentrations of adult leaves were similar, whereas Ca concentration was only slightly lower in Pará in spite of large differences in Ca availability. Leaves from this site had slightly higher P and lower Al concentrations. Differences in water use efficiency as measured by the natural abundance of 13C were negligible, the main effect of lower rainfall in Quintana Roo seemed to be a reduction in leaf area. The N isotope signature (δ15N) was more positive in Pará than in Quintana Roo, suggesting higher denitrification rates in the former. Results reveal a calciotrophic behavior and a remarkable capacity of mahogany to compensate for large differences in soil texture and nutrient availability.

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This study aimed to evaluate the spatial variability of leaf content of macro and micronutrients. The citrus plants orchard with 5 years of age, planted at regular intervals of 8 x 7 m, was managed under drip irrigation. Leaf samples were collected from each plant to be analyzed in the laboratory. Data were analyzed using the software R, version 2.5.1 Copyright (C) 2007, along with geostatistics package GeoR. All contents of macro and micronutrients studied were adjusted to normal distribution and showed spatial dependence.The best-fit models, based on the likelihood, for the macro and micronutrients were the spherical and matern. It is suggest for the macronutrients nitrogen, phosphorus, potassium, calcium, magnesium and sulfur the minimum distances between samples of 37; 58; 29; 63; 46 and 15 m respectively, while for the micronutrients boron, copper, iron, manganese and zinc, the distances suggests are 29; 9; 113; 35 and 14 m, respectively.

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The management of composting may influence the characteristics of the produced compounds. The experiment used three frequencies of plowing, combined with the conditions: with and without coverage of the composting patio, with and without the use of commercial inoculant, resulting in 12 furrows, installed on the Experimental Center of Agricultural Engineering (NEEA), of the STATE UNIVERSITY OF WEST PARANÁ (UNIOESTE), Campus of Cascavel city - state of Paraná (PR), in Brazil. The waste and quantities used in kg were: corn cob (7.5); hatchery residue (5); floater sludge (31); ash (1); wheat cleaning residue (120); wheat pre-cleaning residue (120); corn peel (7.5); solid fraction of wash trucks used to transport chickens (2); solid fraction of pig manure (1) and coal (5), totaling 300kg of natural matter. The aim of this study was to evaluate the influence of plowings, patio coverage and inoculation in losses of N, P, K, Ca, Mg, Na, Cu, Zn, Mn, Fe. The furrows plowed three times a week in the first month showed significant higher losses of N (p<0.05). The coverage of the composting patio influenced significantly the losses of N, K, Mg and Na (p<0.05). The produced compounds had a high agronomic value in relation to macro and micronutrients. It is recommended the use of patio coverage and plowing twice a week in the first month and once a week in the subsequent months for a compound with higher concentrations of nutrients.

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The objective of this study was to evaluate production of Sweet Grape mini tomato (Lycopersicum esculentum Mill.) using culture substrates and nutrient solution sewage effluent, applied by drip irrigation (fertigation). The experiment was conducted at the University of Goiás State (UEG-UnUCET), from June to November 2011 in Anápolis-GO, Brazil. The experimental design was a 2 x 3 factorial arrangement in a randomized complete block design with four repetitions. The plots were made by combining two nutrient solutions, effluent supplemented with mineral fertilizers (EcS); conventional nutrient solution (SnC); in addition three cultivation substrates: 60% of fine sand washed + 40% substrate composed by 20% coconut fiber plus 80% pine bark (S1); 20% coconut fiber and 80% pine bark (S2) and natural coconut fiber (S3). Sewage effluent were determined nitrate, calcium, potassium, manganese, total phosphate, total iron, magnesium, chloride, sulphate, boron, zinc and molybdenum. We evaluated average mass and average number of fruits per bunch, total fruit and total yield per plant. Statistical difference absence among tested solutions indicates sewage effluent can be used as an alternative source of nutrients in growing mini tomatoes in hydroponics.

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Chlorophenols have been classified as possible carcinogens for humans. Chlorophenols have been used as pesticides and wood preservatives. In Finland, during 1930 – 1980s, saw mills used KY-5 wood preservative that contained 2,4,6-TCP, 2,3,4,6-TeCP and PCP. Especially in Finland chlorophenols have entered the environment by leaking from contaminated grounds of old saw mills. Although chlorophenol concentrations found in environment do not cause acute concern, long term exposure can increase the risk of cancer. SPME is relatively cheap and simple sampling method, in which the sample extraction and concentration are performed in a single step. Solvents are not required in SPME. IMS is based on the detection of sample ion drift times. Based on the drift times, reduced mobilities are calculated, which are comparable despite the measurement conditions. SPME-IMS coupling has not been used earlier in the determination of chlorophenols from water samples. The scope of this work was to study, if SPME-IMS system is suitable for detecting chloro-phenols from water samples. The aim was to determine the most optimal extraction condi-tions, which were then applied to real water samples. Following detection limits were deter-mined: 2,4,6-TCP: 0.33 mg/l; 2,3,4,6-TeCP: 0.63 mg/l and PCP: 1.63 mg/l. Detection limits were high compared to the highest possible chlorophenol concentration that is allowed in Finnish drinking water, 10 μg/l. Detected concentrations from water sample differed from verified concentrations in the case of 2,3,4,6-TeCP by 4.6 % and in the case of 2,4,6-TCP by 48.4 %. Based on the results it can be said that SPME-IMS setup is suitable for preliminary analysis of mg/l chlorophenol concentrations from water samples.

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In this experiment, methods of total fecal collection (TFC) and internal markers (acid-insoluble ash - AIA, crude fiber - CF, and acid-detergent fiber - ADF) were compared for determination of the coefficients of apparent digestibility (CAD) for dry matter (DM), crude protein (CP), ether extract (EE), nitrogen-free extracts (NFE), and gross energy (GE) of commercial feline dry kibble for ocelots (Leopardus pardalis). Six adult animals, weighing 12.45±1.37 kg, gradually received experimental kibble in their usual diet until the beginning of the experiment and were submitted to an adaptation period ten days prior to the collection period. CAD obtained by TFC, AIA, CF, and ADF were, respectively, 73.7, 76.83, 62.01, and 46.03% for dry matter; 81.9, 84.8, 75.8, and 63.8% for crude protein; 85, 86.7, 78.5, and 69.1% for ether extract; 78.52, 79.55, 69.11, and 53.04% for nitrogen-free extracts; and 80.5, 82.2, 71.4, and 58.4% for gross energy. The AIA method showed to be efficient in determining coefficients of apparent digestibility and may contribute to investigations on the digestibility of diets for wild felines. In comparison to the items of ocelot's usual diet, the kibble used in this paper provided an adequate nutritional supply with reduced daily costs per animal.

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This work presents an application of the Mobility Approach to the analysis of the power flow through grillage-like structures. Such structures are usually found in offshore platforms, supporting large and heavy machines. Different wave kinds (longitudinal, flexural and torsional) were initially considered in the power flow analysis between two beams joined in L. Beams excited by an in-plane point force showed strong coupling between longitudinal-flexural waves, while that for out-of-plane point force excitation, flexural-torsional waves coupling represents the most important mechanism of energy transmission. The response determination of grillages by the mobility approach requires the structure to be separated into simple beam-like structural components. Equations for rotations and displacements at the joints of all beams are written for as mobility functions, and moments and forces acting at the joints. A system of equations relating all such internal forces and moments is obtained. This approach was applied to simple grillages. Response results showed good agreement when compared to those provided by Finite Elements.

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Ion mobility spectrometry (IMS) is a straightforward, low cost method for fast and sensitive determination of organic and inorganic analytes. Originally this portable technique was applied to the determination of gas phase compounds in security and military use. Nowadays, IMS has received increasing attention in environmental and biological analysis, and in food quality determination. This thesis consists of literature review of suitable sample preparation and introduction methods for liquid matrices applicable to IMS from its early development stages to date. Thermal desorption, solid phase microextraction (SPME) and membrane extraction were examined in experimental investigations of hazardous aquatic pollutants and potential pollutants. Also the effect of different natural waters on the extraction efficiency was studied, and the utilised IMS data processing methods are discussed. Parameters such as extraction and desorption temperatures, extraction time, SPME fibre depth, SPME fibre type and salt addition were examined for the studied sample preparation and introduction methods. The observed critical parameters were extracting material and temperature. The extraction methods showed time and cost effectiveness because sampling could be performed in single step procedures and from different natural water matrices within a few minutes. Based on these experimental and theoretical studies, the most suitable method to test in the automated monitoring system is membrane extraction. In future an IMS based early warning system for monitoring water pollutants could ensure the safe supply of drinking water. IMS can also be utilised for monitoring natural waters in cases of environmental leakage or chemical accidents. When combined with sophisticated sample introduction methods, IMS possesses the potential for both on-line and on-site identification of analytes in different water matrices.

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Eutrophication caused by anthropogenic nutrient pollution has become one of the most severe threats to water bodies. Nutrients enter water bodies from atmospheric precipitation, industrial and domestic wastewaters and surface runoff from agricultural and forest areas. As point pollution has been significantly reduced in developed countries in recent decades, agricultural non-point sources have been increasingly identified as the largest source of nutrient loading in water bodies. In this study, Lake Säkylän Pyhäjärvi and its catchment are studied as an example of a long-term, voluntary-based, co-operative model of lake and catchment management. Lake Pyhäjärvi is located in the centre of an intensive agricultural area in southwestern Finland. More than 20 professional fishermen operate in the lake area, and the lake is used as a drinking water source and for various recreational activities. Lake Pyhäjärvi is a good example of a large and shallow lake that suffers from eutrophication and is subject to measures to improve this undesired state under changing conditions. Climate change is one of the most important challenges faced by Lake Pyhäjärvi and other water bodies. The results show that climatic variation affects the amounts of runoff and nutrient loading and their timing during the year. The findings from the study area concerning warm winters and their influences on nutrient loading are in accordance with the IPCC scenarios of future climate change. In addition to nutrient reduction measures, the restoration of food chains (biomanipulation) is a key method in water quality management. The food-web structure in Lake Pyhäjärvi has, however, become disturbed due to mild winters, short ice cover and low fish catch. Ice cover that enables winter seining is extremely important to the water quality and ecosystem of Lake Pyhäjärvi, as the vendace stock is one of the key factors affecting the food web and the state of the lake. New methods for the reduction of nutrient loading and the treatment of runoff waters from agriculture, such as sand filters, were tested in field conditions. The results confirm that the filter technique is an applicable method for nutrient reduction, but further development is needed. The ability of sand filters to absorb nutrients can be improved with nutrient binding compounds, such as lime. Long-term hydrological, chemical and biological research and monitoring data on Lake Pyhäjärvi and its catchment provide a basis for water protection measures and improve our understanding of the complicated physical, chemical and biological interactions between the terrestrial and aquatic realms. In addition to measurements carried out in field conditions, Lake Pyhäjärvi and its catchment were studied using various modelling methods. In the calibration and validation of models, long-term and wide-ranging time series data proved to be valuable. Collaboration between researchers, modellers and local water managers further improves the reliability and usefulness of models. Lake Pyhäjärvi and its catchment can also be regarded as a good research laboratory from the point of view of the Baltic Sea. The main problem in both of them is eutrophication caused by excess nutrients, and nutrient loading has to be reduced – especially from agriculture. Mitigation measures are also similar in both cases.

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The effects of competition of six weed species on growth, nutrient concentration and nutrient content of coffee plant root system under greenhouse conditions were evaluated. Thirty days after coffee seedling transplantation into 12 L pots with soil level area of 6.5 dm². Weeds were transplanted or sowed in these pots, at densities of 0, 1, 2, 3, 4 and 5 plants per pot. The duration of competition (or weedy periods) from weed transplantation or emergence until plant harvesting, at the weed preflowering stage, were (in days): 77 (Bidens pilosa), 180 (Commelina diffusa), 82 (Leonurus sibiricus), 68 (Nicandra physaloides), 148 (Richardia brasiliensis) and 133 (Sida rhombifolia). Dry matter of coffee plants was linearly reduced with increasing B. pilosa and S. rhombifolia density, with pronounced effect of B. pilosa. C. diffusa was the only weed species whose increasing density in the pots did not diminish crop root dry matter. L. sibiricus, N. physaloides and R. brasiliensis reduced root dry matter of coffee plants by 75, 52 and 47%, respectively, as compared to the weed-free treatment, regardless of weed density. Under competition, even though weed species showed lower macronutrient concentration in the roots (except for P), they accumulated 4.2 (N), 12.3 (P), 4.3 (K), 5.5 (Ca), 7.6 (Mg) and 4.4 (S) times more nutrients in the roots than the coffee plants. Crop and weed nutrient concentration, as well as competition degrees greatly varied depending on both weed species and densities.