Nitrate | EPFL Graph Search

vignette|Vue planaire de la structure de l'ion nitrate. vignette|Vue en 3D de la structure de l'ion nitrate. vignette|Modèle boules et bâtonnets de la structure de l'ion nitrate. vignette|Niveaux de nitrates à la surface des océans. L'ion nitrate est l'ion polyatomique de formule chimique . En chimie, un nitrate est un composé associant cet anion à un ou plusieurs cations. Autrement dit, c'est un sel (nitrate de sodium, nitrate de potassium) ou un ester (nitrate d'éthyle, nitrate d'amyle, nitrate de cellulose) de l'acide nitrique. En minéralogie, les nitrates sont des minéraux dont la composition chimique est celle d'un nitrate (nitronatrite, gwihabaïte). Ils étaient autrefois appelés nitre ou salpêtre. Les nitrates sont indispensables aux écosystèmes, en étant un nutriment de première importance pour la croissance des végétaux et autres organismes autotrophes, car l'azote (N) est assimilé par ces organismes principalement par sa forme d'ion nitrate, loin devant l'ion ammonium dans

Novel Analytical Methods for Allergy-Related Studies

Mikaël Frossard

Managing and treating diseases require a deep understanding of the pathologies coupled with accurate diagnostic procedures. The constant development and improvement of bioanalytical methods reflect the need of diagnosis ameliorations with respect to accuracy, sensitivity and efficiency. The field of allergy diagnosis is a good example. Despite affecting almost a third of the population in western countries, allergies still present complex challenges for the physicians in terms of diagnosis and allergen characterization. This thesis presents novel analytical methods developed for the fast and personalized allergy component-resolved diagnosis (CRD), the allergen identification and quantification in food matrices and the characterization of allergen modifications, notably nitration. Immunomagnetic separation (IMS) was used to perform the allergy diagnosis at the molecular level by extracting the IgE antibodies from allergic patient blood sera and probing them against individual allergens and natural allergenic extracts. The fast and highly selective IMS procedure was coupled to matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry (MS) to identify accurately and with high sensitivity the proteins recognized as sensitizers by the patient antibodies. The developed CRD methods were successful to diagnose cowâs milk, egg, peanut and tree nuts allergies, allowing the resolution of several complex clinical cases. Additionally, precious information was collected for the cross-reactivity and cross-sensitization in peanut and tree nuts allergies using blood sera from the PronNut clinical study. Allergen nitration is one of the potential causes for the increase in allergy prevalence observed recently and requires thorough investigation. Herein, various nitrating agents were tested and compared for in vitro allergen nitration. After modifying allergens using two of the most efficient nitrating procedures, the nitration sites were identified by bottom-up proteomics (BUP) and compared to the known epitopes, bringing useful information and novel insights to the problem of correlation between protein nitration and allergenicity. The presence of a minute amount of allergens in a food product is responsible for potential life-threatening reactions in highly allergic patients and sensitive analytical methods are therefore required in food quality assessments. A proteomic-based method was used for the quality control of several food products suspected of causing severe reactions for peanut and hazelnut-allergic patients. Peptide markers were identified in a first screening of the food extracts by BUP using a high-resolution MS instrument. A standard addition method was then used to quantify peanut and hazelnut proteins by BUP using an untargeted âshotgunâ approach.

EPFL2020

Méthodologie de dimensionnement des zones de protection des captages d'eaux souterraines contre les polluants chimiques persistants

Thierry Bussard

This research proposes a general methodology allowing the delimitation of protection areas for abstracted groundwater against persistent chemical contaminants for the setting up of: (1) remediation programmes in the event of contamination and (2) prevention programmes, in a general way. Since such substances are mainly transported by water circulation, this approach suggests delineating protection areas on the basis of the complete groundwater flow cycle, from the surface of the catchment zone to the groundwater source itself. Areas with the highest contribution rate to the groundwater source will be protected first and foremost. The method under consideration is essentially applied to diffuse contaminants, such as pesticides or nitrates released by agriculture. If pollution is local, a standard method must be applied to treat the problem at the root. The methodology proposes the following steps, which start from the groundwater source and are widened, upstream, to the catchment zone: Identifying the aquifer portion that supplies the groundwater source. Defining, on the ground surface, the catchment zone of the groundwater source. Quantifying the recharge and discharge processes. Calculating the contribution to the groundwater abstraction rate of any point i on the catchment zone surface (Ci) by the following equation: Ci = Ii(1-ei)Pi [m/s] Ii : Infiltration of the precipitation or stream losses at point i [m/s]. ei : Discharge coefficient of water before reaching the main groundwater table (agricultural draining, perched water table, etc.), 0 ≤ e ≤ 1 [-]. Pi : Probability of a particle of water that reaches the groundwater table from point i at the surface going to the groundwater source, 0 ≤ P ≤ 1 [-]. Checking the results (water and mass balances). When the results are not satisfactory, the steps will have to be reiterated. Delineating protection areas (areas with the highest C will be primarily protected). With this approach, we propose not to confine ourselves taking the totality of the catchment zone as protection area against persistent contaminants (protection defined in most of the countries), but to define a smaller area of protection by selecting only the most contributive surfaces. As the acreage of the protection area can be considerably reduced, it will be possible to apply more severe regulations to it, which could never be done on the scale of the entire acreage of the catchment zone. Protection areas defined on this basis moreover allow target remediation solutions(1) which optimize the efficiency/cost ratio. They are, by their very concept, independent of the flux of contaminants at any given time and provide a tool for sustainable development and land planning. For each groundwater source, a rapid calculation based on the contribution field can be made to estimate the potential efficiency of the method and determine the remediation surface that is necessary to reduce contamination. In the same way, the effects of the potential development of the region can be evaluated. The contribution isoline that delimits the protection area can be proposed on the basis of this result. Three actual cases have been treated in order to test the method's applicability. The results are convincing in various porous or fractured aquifers. In the three sites, the results show that, with a similar remediation surface, remediation is more efficient when acting according to the concept of the methodology than when operating without spatial differentiation. ---------- (1) This study uses the concept of a "natural" remediation surface whereby contaminant leaching is reduced by a change in cultivation or in proceedings. The conversion of cultivated areas into meadows is, e.g., one of the most effective methods to reduce nitrates leaching.

EPFL2005