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Artigos de revistas sobre o assunto "Isotope filters"
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Watzinger, Andrea, Melanie Hager, Thomas Reichenauer, Gerhard Soja e Paul Kinner. "Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies". Biodegradation 32, n.º 3 (16 de abril de 2021): 343–59. http://dx.doi.org/10.1007/s10532-021-09942-1.
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AbstractMaintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO2 g−1 day−1) than in the expanded clay (1.0 µg CO2 g−1 day−1). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIEH = 1.072–1.500) and apparent decane biodegradation rates (k = − 0.017 to − 0.067 day−1) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.
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Saccon, M., R. Busca, C. Facca, L. Huang, S. Irei, A. Kornilova, D. Lane e J. Rudolph. "Method for the determination of concentration and stable carbon isotope ratios of atmospheric phenols". Atmospheric Measurement Techniques 6, n.º 11 (5 de novembro de 2013): 2965–74. http://dx.doi.org/10.5194/amt-6-2965-2013.
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Abstract. A method for the determination of the stable carbon isotopic composition of atmospheric nitrophenols in the gas and particulate phases is presented. It has been proposed to use the combination of concentration and isotope ratio measurements of precursor and product to test the applicability of results of laboratory studies to the atmosphere. Nitrophenols are suspected to be secondary products formed specifically from the photooxidation of volatile organic compounds. XAD-4TM resin was used as an adsorbent on quartz filters to sample ambient phenols using conventional high volume air samplers at York University in Toronto, Canada. Filters were extracted in acetonitrile, with a HPLC (high-performance liquid chromatography) clean-up step and a solid phase extraction step prior to derivatization with BSTFA (bis(trimethylsilyl) trifluoroacetamide). Concentration measurements were done with gas chromatography–mass spectrometry and gas chromatography–isotope ratio mass spectrometry was used for isotope ratio analysis. The technique presented allows for atmospheric compound-specific isotopic composition measurements for five semi-volatile phenols with an estimated accuracy of 0.3–0.5‰ at atmospheric concentrations exceeding 0.1 ng m−3 while the detection limits for concentration measurements are in the pg m−3 range. Isotopic fractionation throughout the entire extraction procedure and analysis was proven to be below the precision of the isotope ratio measurements. The method was tested by conducting ambient measurements from September to December 2011.
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Saccon, M., R. Busca, C. Facca, L. Huang, S. Irei, A. Kornilova, D. Lane e J. Rudolph. "Method for the determination of concentration and stable carbon isotope ratios of atmospheric phenols". Atmospheric Measurement Techniques Discussions 6, n.º 3 (28 de maio de 2013): 4705–33. http://dx.doi.org/10.5194/amtd-6-4705-2013.
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Abstract. A method for the determination of the stable carbon isotopic composition of atmospheric nitrophenols in the gas and particulate phases is presented. It has been proposed to use the combination of concentration and isotope ratio measurements of precursor and product to test the applicability of results of laboratory studies to the atmosphere. Nitrophenols are suspected to be secondary products formed specifically from the photooxidation of volatile organic compounds. XAD-4™ resin was used as an adsorbent on quartz filters to sample ambient phenols using conventional high-volume air samplers at York University in Toronto, Canada. Filters were extracted in acetonitrile, with a HPLC clean-up step and a solid phase extraction step prior to derivatization with BSTFA. Concentration measurements were done with gas chromatography-mass spectrometry and gas chromatography-isotope ratio mass spectrometry was used for isotope ratio analysis. The technique presented allows for atmospheric compound-specific isotopic composition measurements for five semi-volatile phenols with an estimated accuracy of 0.3‰ to 0.5‰ at atmospheric concentrations exceeding 0.1 ng m−3 while the detection limits for concentration measurements are in the pg m−3 range. Isotopic fractionation throughout the entire extraction procedure and analysis was proven to be below the precision of the isotope ratio measurements. The method was tested by conducting ambient measurements from September to December 2011.
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Marincin, Kenneth A., Indrani Pal e Dominique P. Frueh. "Using delayed decoupling to attenuate residual signals in editing filters". Magnetic Resonance 2, n.º 1 (21 de junho de 2021): 475–87. http://dx.doi.org/10.5194/mr-2-475-2021.
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Abstract. Isotope filtering methods are instrumental in biomolecular nuclear magnetic resonance (NMR) studies as they isolate signals of chemical moieties of interest within complex molecular assemblies. However, isotope filters suppress undesired signals of isotopically enriched molecules through scalar couplings, and variations in scalar couplings lead to imperfect suppressions, as occurs for aliphatic and aromatic moieties in proteins. Here, we show that signals that have escaped traditional filters can be attenuated with mitigated sensitivity losses for the desired signals of unlabeled moieties. The method uses a shared evolution between the detection and preceding preparation period to establish non-observable antiphase coherences and eliminates them through composite pulse decoupling. We demonstrate the method by isolating signals of an unlabeled post-translational modification tethered to an isotopically enriched protein.
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Meusinger, Carl, Ulrike Dusek, Stephanie M. King, Rupert Holzinger, Thomas Rosenørn, Peter Sperlich, Maxime Julien et al. "Chemical and isotopic composition of secondary organic aerosol generated by <i>α</i>-pinene ozonolysis". Atmospheric Chemistry and Physics 17, n.º 10 (29 de maio de 2017): 6373–91. http://dx.doi.org/10.5194/acp-17-6373-2017.
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Abstract. Secondary organic aerosol (SOA) plays a central role in air pollution and climate. However, the description of the sources and mechanisms leading to SOA is elusive despite decades of research. While stable isotope analysis is increasingly used to constrain sources of ambient aerosol, in many cases it is difficult to apply because neither the isotopic composition of aerosol precursors nor the fractionation of aerosol forming processes is well characterised. In this paper, SOA formation from ozonolysis of α-pinene – an important precursor and perhaps the best-known model system used in laboratory studies – was investigated using position-dependent and average determinations of 13C in α-pinene and advanced analysis of reaction products using thermal-desorption proton-transfer-reaction mass spectrometry (PTR-MS). The total carbon (TC) isotopic composition δ13C of the initial α-pinene was measured, and the δ13C of the specific carbon atom sites was determined using position-specific isotope analysis (PSIA). The PSIA analysis showed variations at individual positions from −6.9 to +10. 5 ‰ relative to the bulk composition. SOA was formed from α-pinene and ozone in a constant-flow chamber under dark, dry, and low-NOx conditions, with OH scavengers and in the absence of seed particles. The excess of ozone and long residence time in the flow chamber ensured that virtually all α-pinene had reacted. Product SOA was collected on two sequential quartz filters. The filters were analysed offline by heating them stepwise from 100 to 400 °C to desorb organic compounds that were (i) detected using PTR-MS for chemical analysis and to determine the O : C ratio, and (ii) converted to CO2 for 13C analysis. More than 400 ions in the mass range 39–800 Da were detected from the desorbed material and quantified using a PTR-MS. The largest amount desorbed at 150 °C. The O : C ratio of material from the front filter increased from 0.18 to 0.25 as the desorption temperature was raised from 100 to 250 °C. At temperatures above 250 °C, the O : C ratio of thermally desorbed material, presumably from oligomeric precursors, was constant. The observation of a number of components that occurred across the full range of desorption temperatures suggests that they are generated by thermal decomposition of oligomers. The isotopic composition of SOA was more or less independent of desorption temperature above 100 °C. TC analysis showed that SOA was enriched in 13C by 0.6–1.2 ‰ relative to the initial α-pinene. According to mass balance, gas-phase products will be depleted relative to the initial α-pinene. Accordingly, organic material on the back filters, which contain adsorbed gas-phase compounds, is depleted in 13C in TC by 0.7 ‰ relative to the initial α-pinene, and by 1.3 ‰ compared to SOA collected on the front filter. The observed difference in 13C between the gas and particle phases may arise from isotope-dependent changes in the branching ratios in the α-pinene + O3 reaction. Alternatively, some gas-phase products involve carbon atoms from highly enriched and depleted sites, as shown in the PSIA analysis, giving a non-kinetic origin to the observed fractionations. In either case, the present study suggests that the site-specific distribution of 13C in the source material itself governs the abundance of 13C in SOA.
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Neocleous, Andreas, George Azzopardi, Margot Kuitems, Andrea Scifo e Michael Dee. "Trainable Filters for the Identification of Anomalies in Cosmogenic Isotope Data". IEEE Access 7 (2019): 24585–92. http://dx.doi.org/10.1109/access.2019.2900123.
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Moukhtar, S., M. Saccon, A. Kornilova, S. Irei, L. Huang e J. Rudolph. "Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric PM". Atmospheric Measurement Techniques Discussions 4, n.º 3 (25 de maio de 2011): 3199–231. http://dx.doi.org/10.5194/amtd-4-3199-2011.
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Abstract. A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter (PM) is presented. It has been found in numerous laboratory studies that these compounds are photooxidation products of toluene in PM. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. PM was collected on quartz fibre filters using dichotomous high volume air samplers for PM 2.5. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography (HPLC) and solid phase extraction (SPE). The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyl)trifluoroacetamide (BSTFA), was added to the solution for Gas Chromatography/Mass Spectroscopy (GC/MS) analysis. The second half of the sample was stored at low temperature. When GC/MS analysis showed high enough concentrations the remaining sample was derivatized with BSTFA and analysed for stable isotope ratio using a Gas Chromatography/Isotope Ratio Mass Spectrometry (GC-IRMS). In all atmospheric PM samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol. Nevertheless, due to low pollution levels occurring in the rural area, no samples had concentrations high enough to perform stable carbon isotope composition measurements of the methylnitrophenols. Samples collected in the suburban area could be analysed for carbon stable isotope ratio using GC-IRMS. The procedure described in this paper provides a very sensitive and selective method for the analysis of methylnitrophenols in atmospheric PM at concentrations as low as 1 pg m−3. For accurate (within ±0.5‰) stable isotope ratio analysis significantly higher concentrations in the range of 100 pg m−3 or more are required.
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Moukhtar, S., M. Saccon, A. Kornilova, S. Irei, L. Huang e J. Rudolph. "Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric particulate matter". Atmospheric Measurement Techniques 4, n.º 11 (16 de novembro de 2011): 2453–64. http://dx.doi.org/10.5194/amt-4-2453-2011.
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Abstract. A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter is presented. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. Particulate matter was collected on quartz fibre filters using dichotomous high volume air samplers. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography and solid phase extraction. The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyl)trifluoroacetamide, was added for Gas Chromatography-Mass Spectrometry analysis. The second half of the sample was stored in a refrigerator. For samples with concentrations exceeding 1 ng μl−1, the second half of the sample was used for measurement of stable carbon isotope ratios by Gas Chromatography-Isotope Ratio Mass Spectrometry. The procedure described in this paper provides a method for the analysis of methylnitrophenols in atmospheric particulate matter at concentrations as low as 0.3 pg m−3 and for stable isotope ratios with an accuracy of better than ±0.5‰ for concentrations exceeding 100 pg m−3. In all atmospheric particulate matter samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol, with concentrations ranging from the low pg m−3 range in rural areas to more than 200 pg m−3 in some samples from a suburban location.
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Kröll, Eva, Miriana Vadalà, Juliana Schell, Simon Stegemann, Jochen Ballof, Sebastian Rothe e Doru C. Lupascu. "Yttrium Oxide Freeze-Casts: Target Materials for Radioactive Ion Beams". Materials 14, n.º 11 (27 de maio de 2021): 2864. http://dx.doi.org/10.3390/ma14112864.
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Highly porous yttrium oxide is fabricated as ion beam target material in order to produce radioactive ion beams via the Isotope Separation On Line (ISOL) method. Freeze casting allows the formation of an aligned pore structure in these target materials to improve the isotope release. Aqueous suspensions containing a solid loading of 10, 15, and 20 vol% were solidified with a unidirectional freeze-casting setup. The pore size and pore structure of the yttrium oxide freeze-casts are highly affected by the amount of solid loading. The porosity ranges from 72 to 84% and the crosslinking between the aligned channels increases with increasing solid loading. Thermal aging of the final target materials shows that an operation temperature of 1400 °C for 96 h has no significant effect on the microstructure. Thermo-mechanical calculation results, based on a FLUKA simulation, are compared to measured compressive strength and forecast the mechanical integrity of the target materials during operation. Even though they were developed for the particular purpose of the production of short-lived radioactive isotopes, the yttria freeze-cast scaffolds can serve multiple other purposes, such as catalyst support frameworks or high-temperature fume filters.
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Amiri, Neda, Roghayeh Ghahremaninezhad, Ofelia Rempillo, Travis W. Tokarek, Charles A. Odame-Ankrah, Hans D. Osthoff e Ann-Lise Norman. "Stable sulfur isotope measurements to trace the fate of SO<sub>2</sub> in the Athabasca oil sands region". Atmospheric Chemistry and Physics 18, n.º 11 (4 de junho de 2018): 7757–80. http://dx.doi.org/10.5194/acp-18-7757-2018.
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Abstract. Concentrations and δ34S values for SO2 and size-segregated sulfate aerosols were determined for air monitoring station 13 (AMS 13) at Fort MacKay in the Athabasca oil sands region, northeastern Alberta, Canada as part of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring (JOSM) campaign from 13 August to 5 September 2013. Sulfate aerosols and SO2 were collected on filters using a high-volume sampler, with 12 or 24 h time intervals. Sulfur dioxide (SO2) enriched in 34S was exhausted by a chemical ionization mass spectrometer (CIMS) operated at the measurement site and affected isotope samples for a portion of the sampling period. It was realized that this could be a useful tracer and samples collected were divided into two sets. The first set includes periods when the CIMS was not running (CIMS-OFF) and no 34SO2 was emitted. The second set is for periods when the CIMS was running (CIMS-ON) and 34SO2 was expected to affect SO2 and sulfate high-volume filter samples. δ34S values for sulfate aerosols with diameter D>0.49 µm during CIMS-OFF periods (no tracer 34SO2 present) indicate the sulfur isotope characteristics of secondary sulfate in the region. Such aerosols had δ34S values that were isotopically lighter (down to −5.3 ‰) than what was expected according to potential sulfur sources in the Athabasca oil sands region (+3.9 to +11.5 ‰). Lighter δ34S values for larger aerosol size fractions are contrary to expectations for primary unrefined sulfur from untreated oil sands (+6.4 ‰) mixed with secondary sulfate from SO2 oxidation and accompanied by isotope fractionation in gas phase reactions with OH or the aqueous phase by H2O2 or O3. Furthermore, analysis of 34S enhancements of sulfate and SO2 during CIMS-ON periods indicated rapid oxidation of SO2 from this local source at ground level on the surface of aerosols before reaching the high-volume sampler or on the collected aerosols on the filters in the high-volume sampler. Anti-correlations between δ34S values of dominantly secondary sulfate aerosols with D< 0.49 µm and the concentrations of Fe and Mn (r = −0.80 and r = −0.76, respectively) were observed, suggesting that SO2 was oxidized by a transition metal ion (TMI) catalyzed pathway involving O2 and Fe3+ and/or Mn2+, an oxidation pathway known to favor lighter sulfur isotopes. Correlations between SO2 to sulfate conversion ratio (F(s)) and the concentrations of α-pinene (r = 0.85), β-pinene (r = 0.87), and limonene (r = 0.82) during daytime suggests that SO2 oxidation by Criegee biradicals may be a potential oxidation pathway in the study region.
Teses / dissertações sobre o assunto "Isotope filters"
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Heikkinen, S. (Sami). "Some applications of RF-gradients and excitation sculpting in NMR spectroscopy". Doctoral thesis, University of Oulu, 1999. http://urn.fi/urn:isbn:9514252357.
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Abstract
RF-gradients produced utilizing RF-field inhomogenity of conventional receiver/transmitter coil of NMR-probe can be used to mimic the effects of B0-gradients. This is done by placing long inhomogenous pulse in between two 90° pulses of appropriate phases (z-rotation cluster). B0-gradient based excitation sculpting can be converted into RF-gradient version. Selective one-dimensional TOCSY and NOESY using RF-gradient based excitation sculpting are described. In addition, non-selective two-dimensional experiments, TOCSY and NOESY, with RF-gradient based coherence selection are presented. Excitation sculpting using BIRD or BIRDR as inversion element results in isotope filter. Pre-suppression of non-13C-bound protons using RF-gradient BIRD prior to HSQC enables recording of spectrum of comparable quality to B0-gradient selected HSQC. This is beneficial for spectrometers lacking B0-gradient capabilities. Excitation sculpting using BIRDR can be used efficiently as low-pass filter in HMBC experiment. Furthermore, simultaneous elimination of protons bound to 15N and 13C can be accomplished with BIRDR based method.
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Marchais, Violette. "Relations trophiques entre producteurs primaires et quatre consommateurs primaires benthiques dans un écosystème côtier tempéré". Thesis, Brest, 2014. http://www.theses.fr/2014BRES0111/document.
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Dans les zones euphotiques des écosystèmes côtiers, les producteurs primaires se développent à la fois dans l’espace pélagique (colonne d’eau) et benthique (sur ou près du fond). Dans ces écosystèmes, le couplage bentho-pélagique prend une place non négligeable qu’il convient d’étudier. Les consommateurs primaires benthiques en sont des acteurs à travers leur activité alimentaire. La relation trophique entre les différents producteurs primaires et les consommateurs primaires benthiques reste toutefois mal élucidée. Pour apporter des éléments d’informations, cette thèse s’est focalisée dans un premier temps sur la dynamique spatio-temporelle des producteurs primaires au sein de la matière organique particulaire en suspension (MOPS), notamment au niveau de l’interface eau-sédiment. Cette étude a permis de montrer une forte variation saisonnière de ce peuplement algal à toutes les profondeurs, mais également une importante contribution relative des diatomées benthiques dans la MOPS près du fond en hiver. Le second axe de recherche s’est concentré sur la relation trophique entre des consommateurs primaires benthiques (coquille Saint-Jacques, pétoncle noir, moule et ormeau) et les producteurs primaires présents dans la MOPS. L’analyse des isotopes stables dans les tissus mous des pétoncles noirs et des moules a indiqué une prédominance du phytoplancton assimilé et une potentielle contribution du microphytobenthos dans leur régime alimentaire (plus importante pour la moule), notamment en période hivernale et près du fond. Cependant, ces études ont mis en lumière l’effet du métabolisme sur les valeurs isotopiques dans les tissus mous. Un aspect novateur de cette thèse a été d’utiliser les exosquelettes des coquilles Saint-Jacques et des ormeaux pour caractériser leur régime alimentaire dans le milieu naturel, afin de s’affranchir des problèmes liés à l’utilisation des isotopes stables dans les tissus mous. Des études en conditions contrôlées ont validé l’intégration des sources d’alimentation à travers le carbone métabolique dans les carbonates de la coquille Saint-Jacques et la couleur de la coquille pour l’ormeau. Des études complémentaires doivent toutefois être menées. Enfin, une dernière étude s’est focalisée sur la capacité de la coquille Saint-Jacques à mettre en suspension les particules benthiques par leurs mouvements de valvesIn coastal euphotic areas, primary producers grow both in the pelagic (water column) and in the benthic zone (in or near the sediment). In these ecosystems, benthic-pelagic coupling is an important process which must be well described. Benthic primary consumers modify this coupling through their diet. Trophic relationships between primary producers and benthic primary consumers are not thoroughly understood. To gain additional information, this thesis was focused on the spatial and temporal dynamic of primary producers in suspended particulate organic matter (SPOM), especially at water-sediment interface. This study highlighted a seasonal variation of microalgal populations at all depths, and a relative dominance of benthic diatoms in SPOM near sediment and in winter. The second objective of the thesis was focused on the trophic relationships between benthic primary consumers (great scallop, black scallop, mussel and ormer) and primary producers in SPOM. Stable isotope analysis in soft tissues of black scallops and mussels showed a predominance of assimilated phytoplankton and the potential contribution of microphytobenthos in their diet (more important for mussel), especially in winter and near the sediment. However, this study highlighted the impact of metabolism on stable isotopic values of soft tissues. An innovative aspect of this thesis was the use of exoskeleton of great scallops and ormers to characterize their diet in natural environment and thus overcome problems related to the utilization of stable isotopes in soft tissues. Experiments in controlled conditions validated food sources integration through metabolic carbon in carbonates of great scallops and shell color for ormer but complementary studies are required on mollusk shell utilization. The last part of this thesis was focused on the ability of great scallops to achieve resuspension of benthic particles by valve movements
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Bell, Nicholle Georgina Anneke. "Molecular-scale characterisation of humic substances using isotope-filtered nD NMR spectroscopy". Thesis, University of Edinburgh, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716584.
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Humic substances (HS), the complex mixture of organic molecules produced by microbial and abiotic degradation of plant and animals residues, are the major components of organic matter in soil and natural waters. As such, they are vital to the integrity of soil, play important roles in nutrient biogeochemical cycling and determine the mobility and fate of both nutrients and contaminants. How HS enact their varied roles, however, is largely unknown due to the lack of comprehension of their molecular make-up. What is known is that they contain aromatic (e.g. phenols, condensed aromatics) and aliphatic (e.g. carbohydrates, lipids) molecules with prevailing carboxyl and hydroxyl functionalities. As for other complex chromatographically inseparable mixtures, high-resolution analytical techniques such as Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) as well as Nuclear Magnetic Resonance (NMR) spectroscopy have been applied to study HS composition at the molecular level. While FT-ICR MS can provide molecular formulae, it is only NMR that can unveil structures. Until now, however, very few unambiguous structures of individual molecules have emerged from standard NMR experiments. This is because purposely designed multidimensional NMR experiments are required to achieve ‘spectroscopic separation’ where chromatography fails. In this work, ‘spectroscopic separation’ was accomplished with the aid of chemical modification in the form of 13C methylation of COOH and OH groups. 13C containing tags allow the observation of signals only from molecules carrying these tags. In combination with purposelydesigned isotope-filtered NMR experiments, these tags act as spies reporting on their surrounding structure. This is achieved by utilising scalar and dipolar couplings to transfer the polarisation between protons and carbons of the 13CH3O groups and nuclei of the parent molecules. The necessary spectral resolution is attained using 3D/4D NMR experiments. This approach provides access to an array of correlated chemical shifts of HS molecules and represents a paradigm shift in the use of tags in investigations of complex mixtures: instead of focusing only on the tags, they are used to obtain structural information from the molecules they are attached to. The compounds at the centre of this investigation are the phenols of HS. These molecules are thought to be important in many of the key processes in organic matter rich soils, particularly peat. For example, their accumulation is thought to impair the activity of extracellular enzymes essential for the degradation of peat HS. Understanding the nature and source of phenols would provide a more fundamental framework for rationalising their role in peat, as well as other carbon rich soils. The developed methodology was initially tested on model mixtures containing 3 or 9 phenolic compounds before applying it to a operational fraction of HS, fulvic acid, extracted from a Scottish raised peat bog. For this fulvic acid, over 30 major phenolic molecules/moieties were identified, many of which can be directly traced to the flora prevalent in the vicinity of the sampling site. For the first time in 150 years of HS research, a novel analytical methodology has yielded unambiguous structural information, providing the first steps towards understanding the various roles of HS in natural systems.
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Manea, Vladimir. "Penning-trap mass measurements of exotic rubidium and gold isotopes for a mean-field study of pairing and quadrupole correlations". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112246/document.
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Les noyaux les plus complexes sont situés entre les nombres magiques et les médianes des espaces de valence, dans des régions connues pour les changements abrupts des observables nucléaires. Dans ces régions appelées de transition de forme, le paradigme nucléaire change entre la goutte liquide vibrationnelle et le rotor statique. Sauf quelques exceptions, les noyaux de ces régions sont radioactifs, avec des demi-vies qui chutent dans les millisecondes. Complémentaires aux propriétés des états excités à basse énergie, les énergies de liaison et les rayons de charge nucléaires sont parmi les observables les plus sensibles à ces changements de structure nucléaire. Dans ce travail, une étude du phénomène de transition de forme est effectuée, par des mesures de nucléides radioactifs produits dans le laboratoire ISOLDE au CERN. Les masses des isotopes de rubidium riches en neutrons 98-100Rb et des isotopes d’or riches en protons 180,185,188,190,191Au sont mesurées avec le spectromètre de masse de type Penning ISOLTRAP. La masse de 100Rb est déterminée pour la première fois. Des déviations significatives par rapport à la littérature sont trouvées pour les isotopes 188,190Au. Une nouvelle méthode expérimentale est présentée, utilisant un spectromètre de masse à multi-réflexion comme analyseur de faisceau pour la spectroscopie laser d’ionisation résonante. La nouvelle méthode donne la possibilité d’effectuer des études de structure hyperfine atomique avec ISOLTRAP, dont on peut extraire les rayons de charge et les moments électromagnétiques nucléairesThe most complex nuclei are situated between the magic and the mid-shell ones, in regions known for sudden changes of the trends of nuclear observables. These are the so-called shape-transition regions, where the nuclear paradigm changes from the vibrational liquid drop to the static rotor. With few exceptions, nuclei in these regions are radioactive, with half-lives dropping into the millisecond range.Complementing the information obtained from the low-lying excitation spectrum, nuclear binding energies and mean-square charge radii are among the observables most sensitive to these changes of nuclear structure. In the present work, a study of the shape-transition phenomenon is performed by measurements of radioactive nuclides produced by the ISOLDE facility at CERN. The masses of the neutron-rich rubidium isotopes 98−100Rb and of the neutron-deficient gold isotopes 180,185,188,190,191Au are determined using the Penning-trap mass spectrometer ISOLTRAP. The mass of 100Rb is determined for the first time. Significant deviations from the literature values are found for the isotopes 188,190Au. A new experimental method is presented, using a recently developed multi-reflection time-of-flight mass spectrometer as a beam-analysis tool for resonance-ionization laser spectroscopy. The new method opens the path to measurements of atomic hyperfine spectra with ISOLTRAP, from which charge radii and electromagnetic moments of radioactive nuclides can be extracted. The properties of the studied nuclides map the borders of two prominent regions of quadrupole deformation, which constrain the fine balance between pairing and quadrupole correlations in the nuclear ground states. This balance is studied by the Hartree-Fock- Bogoliubov (HFB) approach. The sensitivity of the shape-transition phenomenon to the strength of pairing correlations is demonstrated. In particular, the strong odd-even staggering of charge radii in the mercury isotopic chain is shown to result in the HFB approach from the fine interplay between pairing, quadrupole correlations and quasi-particle blocking
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Ambayi, Rudo. "The effect of reconstruction algorithms (iterative versus filtered backprojection) on the diagnosis of single pulmonary nodules using Thallium-201 and Technetium-99m MIBI SPECT". Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50144.
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Thesis (MScMed)--Stellenbosch University, 2004.Copy not signed by author.
ENGLISH ABSTRACT: This study involved 33 patients, 19 men and 14 women. The age range was wide (20-90 years) and median age was 57 years. These patients had a single pulmonary nodule (SPN) defined radiologically as a well defined, round or oval intrapulmonary lung lesion not associated with atelectasis or adenopathy on chest radiography or computed tomography. Patients were investigated with Tc-99m MIBI and TI-201 (25 patients) and with Tc-99m MIBI alone (8 patients). Single photon emission computed tomography images were reconstructed using both iterative reconstruction (Ordered Subsets - Expectation Maximisation: aSEM) and filtered backprojection (FBP), on the Hermes system. Transverse, coronal and sagittal slices were displayed on the screen using a grey scale. The aSEM and FBP images for each study were co-registered semi-automatically using the multimodality programme on the Hermes. The best slice for the lesion was chosen according to the best view used to locate the SPN on chest radiograph. Regions of interest (Ral) were drawn manually outside the outer margin of the detected lesion, first on the aSEM image. This was automatically mirrored on the co-registered FBP image. For most patients, the background was automatically mirrored horizontally on the contralateral side, again, first on the OSEM then automatically on the FBP image. Automatic vertical mirroring or manual horizontal mirroring was used when background was found to be in a visually 'hot' area like the heart or vertebrae. The average counts and standard deviation of the Ral and background were generated automatically. Semi-quantitative image analysis was done by calculating the signal-to-noise ratio (SNR) and tumour-to-background (TIB) ratio using the following formulae: SNR = Mean counts ROI(lesion) - Mean counts background Standard deviation background TIB rati.o = -M---e-a-n-'--c-o--u-n-'t-s- ROI(lesion) Mean counts background Detection was found to be the same for the two reconstruction algorithms, that is, every lesion detected by using OSEM could also be detected by using FBP. However lesion detection did differ between Tl-201 and Tc-99m-MIBI. Sensitivity and specificity were calculated for different thresholds of SNR and TIB ratios. Receiver operating characteristics (ROC) curves were drawn to represent the different sensitivities and specificities at each threshold. Tuberculosis (TB) was not included in this analysis as uptake of Tl-20l was found to be significantly high and comparable to that of malignant nodules. However the effect of OSEM and FBP on the 'positive' TB nodules was assessed separately. By calculating the area under the ROC curves, TI-201 using OSEM was shown to be more accurate at differentiating malignant nodules from benign ones than FBP. Although this difference was not statistically significant (p=0.1 0), there was a clear tendency. The two reconstruction algorithms were found to be almost equally accurate, when using Tc-99m-MIBI, the difference between them being considerably insignificant. In conclusion, it was shown that there is a tendency that OSEM outperforms FBP for studies using Tl-201 but not for Tc-99m-MIBI.
AFRIKAANSE OPSOMMING: Hierdie studie sluit 33 pasiënte in, 19 mans en 14 vroue. Die ouderdomme wissel tussen 20 en 90 jaar met 'n gemiddelde ouderdom van 57 jaar. Elkeen van die pasiënte het 'n enkel longnodule (SPN) op borskas X-straal en/of rekenaar tomografie getoon, wat radiologies gedefinieer word as 'n goed omskrewe, ronde of ovaal intrapulmonale longletsel wat nie met atelektase of adenopatie geassosieer is nie. Pasiënte is met Tc-99m MIDI en TI-201 (25 pasiënte) of slegs met Tc-99m MIBI (8 pasiënte) ondersoek. Enkelfoton emissie rekenaar tomografiese (EFERT) beelde is met beide iteratiewe rekonstruksie (Ordered Subsets - Expectation Maximisation: OSEM) en gefilterde terugprojeksie (FBP) met die Hermes sisteem gerekonstrueer. Transvers, koronale en sagittale snitte is in grysskaal op die sisteem vertoon. Die OSEM en FBP beelde vir elke studie is semi-outomaties gekoregistreer met behulp van die multimodaliteitsprogram op die Hermes. Die optimale snit vir elke letsel is gekies volgens die beste aansig op die borskas X-straalom die SPN te lokaliseer. Gebiede van belang (ROl) is met die hand buite-om die buitenste rand van die letsel getrek op die OSEM beeld en daarna outomaties in die ooreenstemmende area op die gekoregistreerde FPB beeld geplaas. Vir die meeste pasiënte is die agtergrond outomaties as horisontale spieëlbeeld op die kontralaterale kant geplaas, eers op die OSEM en dan outomaties op die FBP beeld. 'n Outomatiese vertikale spieëlbeeld of manuele horisontale verskuiwing van die agtergrondsarea is gedoen indien die agtergrond oorvleuel het met 'n 'warm' area soos die hart of werwels. Die gemiddelde tellings en standaardafwyking van die ROl en agtergrond is outomaties gegenereer. Semi-kwantitatiewe beeldanalise is gedoen deur berekening van die sein-tot-agtergrond verhouding (signal-to-noise ratio - SNR) en tumor-tot-agtergrond (TIB) verhouding met behulp van die volgende formules: SNR = gemiddelde tellings ROI(letsel) - gemiddelde tellings agtergrond Standaard afwyking van agtergrond TIB rati.o = -g=em--id-d-e-l-d-e--te=ll-in-g-s__R:_O-I(-le-t-s'e-l) gemiddelde tellings agtergrond Opsporing is soortgelyk bevind vir die twee rekonstruksie algoritmes, dit wil sê elke letselopgespoor met behulp van OSEM kon ook met FBP opgespoor word. Letselwaameming het egter verskil tussen TI-201 en Tc-99m-MIBI. Sensitiwiteit en spesifisiteit is vir verskillende drempels van SNR en TIB verhoudings bereken. 'Receiver operating characteristics' (ROC) kurwes is getrek om die verskillende sensitiwiteite en spesifisiteite by elke drempel te verteenwoordig. Tuberkulose (TB) is nie in hierdie analise ingesluit nie aangesien opname van Tl-201 beduidend hoog en vergelykbaar met die van maligne nodules was. Die effek van OSEM en FBP op die 'positiewe' TB nodules is egter apart beoordeel. Deur berekening van die area onder die ROC kurwes, is getoon dat OSEM van Tl-201 tomografiese data meer akkuraat as FBP was om maligne van benigne nodules te onderskei. Alhoewel hierdie verskil nie statisties betekenisvol was nie (p=0.10), is daar wel 'n duidelike neiging gevind. Die twee rekonstruksie algoritmes was byna ewe akkuraat wanneer Tc-99m-MIBI gebruik is, met duidelik geen betekenisvolle verskil tussen die algoritmes nie. Gevo lgtrekking In hierdie studie is dit getoon dat daar 'n neiging is dat OSEM beter vaar as FBP vir studies met tallium-201 maar nie vir Tc-99m-MIBI nie.
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Serve, Adrien. "Couche catalytiques conductrices ioniques pour filtre à particules autorégénérant". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1210/document.
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Les travaux s'inscrivent dans le développement de catalyseurs conducteurs ioniques à base de zircone stabilisée à l'oxyde d'yttrium (YSZ) pour l'oxydation des suies dans les filtres à particules (FAP) qui équipent les véhicules Diesel. L'oxydation de la suie sur YSZ a été observée à l'échelle nanométrique par microscopie électronique en transmission environnementale. La réaction d'oxydation se déroule à l'interface (20-40 nm) entre le catalyseur et la suie, l'activité étant liée au nombre de points de contact. Nous avons associé un vecteur d'oxygène mobile, l'argent, à YSZ. Les résultats montrent une synergie entre YSZ et les nanoparticules d'argent qui promeut l'activité notamment en cas de contact grossier avec la suie. Des expériences isotopiques d'échanges et d'oxydation ont démontré que l'argent active l'intégration de l'oxygène gazeux dans le réseau de YSZ. La caractérisation des propriétés physicochimiques des nanoparticules d'argent dispersées sur différents oxydes (une autre zircone yttriée aux propriétés différentes : YSZb, ZrO2, CeZrO2, SiO2) a permis de relier les performances catalytiques avec la teneur d'argent métallique en surface. Des tests de vieillissement hydrothermal ont montré que la formulation supportée sur YSZb présente une activité maintenue en contact médiocre avec la suie et une faible perte en argent. Des mini-FAPs imprégnés de catalyseur ont ensuite été testés sur un banc de gaz synthétiques capable de produire des particules de suie en suspension. L'activité des formulations catalytiques une fois mises en forme ainsi que leur capacité de filtration ont été évaluées. Un mini-FAP contenant la formulation Ag/YSZb oxyde les suies dès 350°C et s'auto-régénère (oxydation des suies plus rapide que leur collecte) dès 450°CThis study deals with the development of ionic conductive catalysts based on yttria-stabilized zirconia for soot oxidation in Diesel Particle Filter (DPF). Soot oxidation was observed at the nanoscale using Environmental Transmission Electron Microscopy. Reaction was shown to occur at the interface between YSZ and soot, ranging from 20 to 40 nm, and activity was related to the number of contact points between soot and catalyst. In order to promote activity, we associated to YSZ an oxygen carrier: silver, under the form of silver nanoparticles (AgNPs) scattered over YSZ surface. Results display a synergy between YSZ and AgNPs, allowing for the promotion of soot oxidation under poor contact conditions. Isotopic exchange and oxidation experiments demonstrated AgNPs promote oxygen integration into YSZ lattice. Characterizations of supported AgNPs over different oxides such as YSZb (displaying different properties than YSZ), ZrO2, SiO2, CeZrO2, indicate that the soot oxidation activity is related to the amount of metallic silver species on the oxide surface. Hydrothermal ageing tests indicate that Ag/YSZb formulation displays a stable activity in poor contact conditions and a low silver loss. Baby-DPF (1 inch diameter, 3 inches length) were impregnated with silver-supported catalysts and tested on a synthetic gas bench producing a gas stream containing suspended soot particles. Soot oxidation activity and filtration efficiency were measured. A baby-FAP containing the Ag/YSZb formulation was shown to oxide soot at a temperature as low as 350°C and to induce self-regeneration (soot oxidation overcoming the collection) at 450°C
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Cyrus, Mark Digby. "Use of stable isotope signatures in the macroalga Ecklonia maxima and the filter feeder Mytilus galloprovincialis to determine the extent of sewage dispersal from the Green Point outfall, South Africa". Bachelor's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/26664.
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Over the last decade natural abundances of stable isotopes ¹³C and ¹⁵N have been used to investigate the transport pathways of nutrients within aquatic ecosystems, and have contributed new understanding and knowledge to many aspects of ecology, which include tracking the spatial extents of nutrient discharges. In order to assess the uptake of nutrients from the Green Point sewage outfall in Cape Town South Africa, we selected a primary producer, the kelp Ecklonia maxima (for dissolved nutrients) and a filter-feeding organism, the blue mussel Mytilus galloprovincialis (for organic particulates). It was hypothesized that biota within close proximity of the outfall would have isotopic values (signatures) which were closer to the values recorded for sewage and that this signature would become weaker (more positive) with increasing distance from the outfall as the sewage would be diluted and dispersed. Results from our study indicated that the stable isotope abundances of biota near the outfall were significantly affected by sewage. Ecklonia maxima situated on the outfall itself had δ¹⁵N of 1.2±2.3‰, which was extremely depleted relative to our control (8.3±1.1‰), collected at Mauritzbaai. The δ¹⁵N recorded for raw sewage (0.4±0.4‰) was very similar to that of Ecklonia maxima situated on the outfall. Mytilus galloprovincialis were also affected by sewage organic matter however although the effects on the stable isotope abundances were less pronounced as they were relying on more than one source of food. The isotopic values recorded in this study demonstrated that sites which were in close proximity to the outfall and even those just within the study area were contaminated by sewage effluent. From this study we conclude that the δ¹⁵N signatures of Ecklonia maxima and Mytilus galloprovincialis in marine environments can provide a useful means of tracing sewage dispersal in well-mixed ocean conditions, where conventional methods may have failed to reveal the extent of dispersal.
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Lazareva, Olesya. "Constructed Wetland/Filter Basin System as a Prospective Pre-Treatment Option for Aquifer Storage and Recovery and a Potential Remedy for Elevated Arsenic". Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1697.
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The efficiency to improve the water quality of industrial and municipal wastewater in a constructed wetland/filter basin treatment system was investigated. The wetland system was constructed in a closed phosphate mine used for clay settling and sand tailings in Polk County, Florida. During 18-months of monitoring the chemical/microbiological composition of treated wetland water remained relatively constant, despite significant seasonal variations in temperature, rainfall and humidity. The following changes in water quality between input and output were observed: substantial decrease of water temperature (up to 10°C), reduction of As, SO4, F, Cl, NO3, NO2, Br, Na, K, Ca, and Mg, change in pH from 9 to 6.5-7, increase of H2S (up to 1060 micrograms/L), and a change from positive to negative ORP. There were no exceedances of the primary drinking water standards, volatile organic compounds, synthetic organic compounds, and radionuclides, but a number of exceedances for the secondary drinking water standards (Al, F, Fe, Mn, color, odor, total dissolved solids, and foaming agents). The concentration of fecal and total coliform bacteria in the wetland water was high, but subsequently reduced during filtration in the filter basin from 30 - 730 and 1000 - 7000 count/100 mL to < 2 and < 100 count/ 100 mL, respectively.
To resolve the complex hydrogeological conditions a combined isotope/chemical mass-balance approach was applied. The results were the following: (1) the composition of water in the wetland varied throughout the period of the study; (2) a change in isotopic composition along the wetland flow path; (3) the wetland contained mainly wastewater (88 - 100 %) during normal pumping operations; however, hurricanes and inconsistent pumping added low conductivity water directly and triggered enhanced groundwater inflow into the wetland of up to 78 %; (4) the composition of water in monitor wells was mostly groundwater dominated; however periodically seepage from a water body to the north was detected; and (5) seepage from adjacent water bodies into the wetland was not identified during operation, which would indicate a potential water loss from the wetland.
To test if the wetland system could be a prospective pre-treatment option for water used in aquifer storage and recovery (ASR) scenarios, a set of bench-scale leaching experiments was carried out using rocks from the Avon Park Formation, the Suwannee Limestone and the Ocala Limestone. Since As in the Floridan Aquifer was mainly present as an impurity in the mineral pyrite the elevated iron and sulfide concentrations in the wetland water were thought to prevent pyrite dissolution. The experiments which covered a range of redox conditions showed that the amount of As released from the aquifer matrix was not perfectly correlated with the bulk rock As concentration, nor the redox state of the water. The following important results were obtained: (1) the highest concentration of As was leached from the Avon Park Formation and the lowest - from the Suwannee Limestone, although the Ocala Limestone had the lowest bulk rock As; (2) minor to no As was released using native Floridan groundwater; (3) Tampa tap water, which chemically and physically resembled the ASR injection water, caused the As leaching of up to 27 micrograms/L, which was higher than the As drinking water standard; (4) the wetland and filter basin waters caused the highest release of As (up to 68 micrograms/L), which was unexpected because those water types were less oxygenated than Tampa tap water and thus should be less aggressive; (5) the in-situ filtration of the wetland water through a 0.2 micrometer membrane resulted in a reduction of As from 30 microgram/L to 16 microgram/L; and (5) the UV treatment significantly reduced both fecal and total coliform bacteria, but facilitated the increase of DO in initial waters, a change from negative to positive ORP, and the increase of As concentration in leachates.
The experiments confirmed that perturbations of native aquifer conditions caused the release of As from the Floridan aquifer matrix, although the reaction may not be as simple as the dissolution of pyrite by oxygen, but additionally governed by a complex set of factors including the ORP of the system, SO4²?/S², Fe³?/Fe²?, dissolved organic carbon and microbial activity. In addition, the trend of As leaching could be governed by a set of factors, such as the porosity and permeability of the aquifer matrix influencing the rate and degree of free water saturation, amount of pyrite to be exposed to the preferential water flow paths, limited surface reactivity of pyrite with favored reactions on fractured mineral surfaces, the concentration and the selective leaching of As from individual pyrite crystals.
To characterize and verify the geochemical processes in the column experiments, the Geochemist's Workbench reactive transport models (React and X1t) were developed. Results from the models correlated well to those from the column experiments and confirmed the following: (1) the water-rock reaction between the aquifer matrix and native groundwater was favorable for pyrite stability preventing the release of As into solution; (2) the injection of oxidizing surface water into reducing native groundwater caused a change in redox potential of the system thus promoting the dissolution of pyrite, and (3) 1D reactive transport model of water-rock reaction between the aquifer matrix and surface water indicated a diverse behavior of As along the column, such as the oxidative dissolution of pyrite, mobilization and simultaneous sorption of As onto neo-formed HFO, followed by the reductive dissolution of HFO and secondary release of adsorbed As, and the potential non-oxidative dissolution of pyrite contributing the additional source of As to the solution.
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Mons, Vincent. "Application de l'assimilation de données à la mécanique des fluides numérique : de la turbulence isotrope aux écoulements urbains". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066400/document.
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Dans cette thèse, l'application de l'assimilation de données (AD) à la MFN est étudiée, avec comme objectif global de contribuer à l'amélioration de la prévision numérique d'écoulements complexes. L'AD consiste à fusionner les outils de prévision numérique avec des données expérimentales afin d'améliorer l'estimation des paramètres d'entrée du code MFN. Les aspects méthodologiques de l'AD et son application pour des études physiques sont tous deux examinés dans cette thèse. Dans un premier temps, l'AD est utilisée pour une étude théorique de la turbulence de grille. Un modèle spectral pour les écoulements turbulents homogènes et anisotropes est également proposé. Plusieurs méthodes d'AD sont ensuite implémentées pour un code MFN et appliquées à la reconstruction d'écoulements instationnaires et compressibles en présence d'incertitudes sur des paramètres d'entrée de grandes dimensions afin d'évaluer les forces et faiblesses respectives de ces techniques. Des stratégies pour le placement optimal de réseaux de capteurs sont élaborées afin d'améliorer les performances du processus d'AD. Enfin, l'AD est appliquée à l'identification de sources de polluants et à la reconstruction de conditions météorologiques pour des écoulements en milieu urbain prédits par Simulation des Grandes EchellesIn this thesis, we investigate the use of various data assimilation (DA) techniques in the context of CFD, with the ultimate goal of enhancing the prediction of real-world flows. DA consists in merging numerical predictions and experimental observations in order to improve the estimation of the CFD solver inputs. Both methodological aspects of DA and its potential application to physics investigations are explored for various flow configurations. First, DA is considered for the theoretical analysis of grid turbulence decay. Fundamental aspects of anisotropic homogeneous turbulence are also investigated through spectral modelling. Various DA methodologies are deployed in conjunction with a Navier-Stokes solver and are assessed for the reconstruction of unsteady compressible flows with large control vectors. Sensor placement strategies are developed to enhance the performances of the DA process. Finally, a first application of DA to Large Eddy Simulations of full-scale urban flows is proposed with the aim of identifying source and wind parameters from concentration measurements
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Vallelonga, Paul Travis. "Measurement of Lead Isotopes in Snow and Ice from Law Dome and other sites in Antarctica to characterize the Lead and seek evidence of its origin". Curtin University of Technology, School of Applied Science, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14018.
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Human activities such as mining and smelting of lead (Pb) ores and combustion of alkyllead additives in gasoline have resulted in extensive global Pb pollution. Since the late 1960's studies of polar ice and snow have been undertaken to evaluate the extent of anthropogenic Pb emissions in recent times as well as to investigate changes in anthropogenic Pb emissions in the more distant past. The polar ice sheets have been used to investigate Pb pollution as they offer a long-term record of human activity located far from pollution sources and sample aerosol emissions on a hemispheric scale. Lead isotopes have been previously used to identify sources of Pb in polar snow and ice, while new evaluations of Pb isotopic compositions in aerosols and Pb ore bodies allow more thorough evaluations of anthropogenic Pb emissions. Lead isotopic compositions and Pb and Barium (Ba) concentrations have been measured in snow and ice core samples from Law Dome, East Antarctica, to produce a detailed pollution history between 1530 AD and 1989 AD. Such a record has been produced to evaluate changes in anthropogenic Pb emission levels and sources over the past 500 years, to determine when industrial (anthropogenic) activities first began to influence Antarctica and also to investigate natural Pb fluxes to Antarctica. Additional samples were also collected from Law Dome snow and ice cores to respectively investigate seasonal variations in Pb and Ba deposition, and the influence of the 1815 AD volcanic eruption of Tambora, Indonesia. All samples were measured by thermal ionisation mass spectrometry, for which techniques were developed to reliably analyse Pb isotopic compositions in Antarctic samples containing sub-picogram per gram concentrations of Pb.Particular attention was given to the quantity of Pb added to the samples during the decontamination and sample storage stages of the sample preparation process. These stages, including the use of a stainless steel chisel for the decontamination, contributed ~5.2 pg to the total sample analysed, amounting to a concentration increase of ~13 fg g-1. In comparison, the mass spectrometer ion source contributed typically 89 +/- 19 fg to the blank, however its influence depended upon the amount of Pb available for analysis and so had the greatest impact when small volumes of samples with a very low concentration were analysed. As a consequence of these careful investigations of the Pb blank contributions to the samples, the corrections made to the Pb isotopic ratios and concentrations measured are smaller than previously reported evaluations of Pb in Antarctica by thermal ionisation mass spectrometry. The data indicate that East Antarctica was relatively pristine until -1884 AD, after which the first influence of anthropogenic Pb in Law Dome is observed. "Natural", pre-industrial, background concentrations of Pb and Ba were - 0.4 pg/g and - 1.3 pg/g, respectively, with Pb isotopic compositions within the range 206Pb/207Pb = 1.20 - 1.25 and 208Pb/207Pb = 2.46 - 2.50 and an average rock and soil dust Pb contribution of 8-12%. A major pollution event was observed at Law Dome between 1884 and 1908 AD, elevating the Pb concentration fourfold and changing 206Pb/207Pb ratios in the ice to ~1.12. Based on Pb isotopic systematics and Pb emissions statistics, this was attributed to Pb mined at Broken Hill and smelted at Broken Hill and Port Pirie, Australia.
Anthropogenic Pb inputs to Law Dome were most significant from ~1900 to 1910 and from ~1960 to 1980. During the 20th century, Ba concentrations were consistently higher than "natural" levels. This was attributed to increased dust production, suggesting the influence of climate change and/or changes in land coverage with vegetation. Law Dome ice dated from 1814 AD to 1819 AD was analysed for Pb isotopes and Pb, Ba and Bismuth (Bi) concentrations to investigate the influence of the 1815 AD volcanic eruption of Tambora, Indonesia. The presence of volcanic debris in the core samples was observed from late-1816 AD to 1818 AD as an increase in sulphate concentrations and electrical conductivity of the ice. Barium concentrations were approximately three times higher than background levels from mid-1816 to mid1818, consistent with increased atmospheric loading of rock and soil dust, while enhanced Pb/Ba and Bi/Ba ratios, associated with deposition of volcanic debris, were observed at mid-1814 and from early-1817 to mid-1818. From the results, it appeared likely that Pb emitted from Tambora was removed from the atmosphere within the 1.6 year period required to transport aerosols to Antarctica. Increased Pb and Bi concentrations observed in Law Dome ice ~1818 AD were attributed to either increased heavy metal emissions from Mount Erebus, or increased fluxes of heavy metals to the Antarctic ice sheet resulting from climate and meteorological modifications following the Tambora eruption.
A non-continuous series of Law Dome snow core samples dating from 1980 to 9185 AD were analysed to investigate seasonal variations in the deposition of Pb and Ba. It was found that Pb and Ba at Law Dome do exhibit seasonal variations in deposition, with higher concentrations of Pb and Ba usually observed during Summer and lower concentrations of Pb and Ba usually observed during the Autumn and Spring seasons. At Law Dome, broad patterns of seasonal Pb and Ba deposition are evident however these appear to be punctuated by short-term deposition events or may even be composed of a continuum of short-term deposition events. This variability suggests that complex meteorological systems are responsible for the transport of Pb and Ba to Law Dome, and probably Antarctica in general.
Livros sobre o assunto "Isotope filters"
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Ellam, Rob. 4. Measuring isotopes. Oxford University Press, 2016. http://dx.doi.org/10.1093/actrade/9780198723622.003.0004.
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‘Measuring isotopes: counting the atoms’ explores how isotopes are measured. For stable isotopes, atoms of each isotope are counted using a mass spectrometer. This turns atoms into charged ions and separates them into the different isotopic species using a mass filter. Precise measurements of isotopic abundance can be achieved in a few minutes or hours. Mass spectrometry could be used for radioactive isotopes, but for short-lived isotopes, their low abundance often makes them difficult to detect. The alternative is to use nuclear spectroscopy or counting methods to detect the characteristic energy released by the radioactive decay of a particular isotope, but these can be much longer processes.
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Ellam, Rob. 6. Measuring isotopes. Oxford University Press, 2016. http://dx.doi.org/10.1093/actrade/9780198723622.003.0006.
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Mass spectrometers have become routine laboratory instruments in many disciplines. ‘Measuring isotopes: mass spectrometers’ concentrates on those used to quantify the abundance of different isotopes—gas source isotope ratio, thermal ionization, inductively coupled plasma, and secondary ion mass spectrometers. A mass spectrometer can be used to quantify the concentration of a particular element by monitoring an isotope of that element not overlapped by isotopes of other elements. All mass spectrometers have three essential components: an ion source, a mass filter, and a detector. There are two main types of detector: Faraday detectors measure large signals and a variant of photomultiplier tubes measures small isotope signals.
Capítulos de livros sobre o assunto "Isotope filters"
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Thomson, W. H., S. R. Hesslewood, J. Hepplewhite, K. Parker e B. Perrin. "Ionisation Chamber Measurements of I123 Using a Copper Filter". In Radioactive Isotopes in Clinical Medicine and Research, 231–36. Basel: Birkhäuser Basel, 1997. http://dx.doi.org/10.1007/978-3-0348-7772-5_34.
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Maschek, W., R. Pichler, H. Huber, M. Hatzl, F. Leisch e K. Kerschner. "Comparison of Filtered Back Projection with Iterative Reconstruction in TI-201 Scintigraphy". In Radioactive Isotopes in Clinical Medicine and Research, 463–66. Basel: Birkhäuser Basel, 1997. http://dx.doi.org/10.1007/978-3-0348-7772-5_75.
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Fesik, Stephen W., Robert T. Gampe, Edward T. Olejniczak, Jay R. Luly, Herman H. Stein e Todd W. Rockway. "Isotope-filtered proton NMR experiments for the conformational determination of peptides in solution and bound to biomacromolecules". In Peptides, 57–59. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-010-9595-2_14.
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WILLIAMS, DOUGLAS F., IAN LERCHE e W. E. FULL. "Filter and Deconvolution Methods". In Isotope Chronostratigraphy, 245–55. Elsevier, 1988. http://dx.doi.org/10.1016/b978-0-12-754560-8.50021-6.
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WILLIAMS, DOUGLAS F., IAN LERCHE e W. E. FULL. "Filter and Deconvolution Techniques". In Isotope Chronostratigraphy, 155–72. Elsevier, 1988. http://dx.doi.org/10.1016/b978-0-12-754560-8.50017-4.
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Gray, John S., e Michael Elliott. "The soft-sediment benthos in the ecosystem". In Ecology of Marine Sediments. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780198569015.003.0014.
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The benthos does not, of course, live in isolation from other parts of the ecosystem. Here we consider the roles that the benthos plays in the system and how the complex interactions that are found can be modelled using ecosystem models. First, we examine methods that allow us to establish food webs based not only on examining each species in the field and in laboratory feeding studies, but also using stable isotopes of carbon and nitrogen to ascertain the likely feeding mode of a species. It is relatively easy to determine the mode of feeding of some benthic organisms (see for example the excellent review of Fauchald and Jumars 1979, although this is now slightly dated and requires revision). Polychaetes have characteristic feeding structures, so one can determine from their morphology whether they are filter feeders, deposit feeders, or predators. Bivalves show similar morphological characteristics and it is easy to determine whether they are deposit or filter feeders. Some polychaetes have large jaws, e.g. the nereids, and one might assume that they are predators. Yet when Nereis vexillosa was studied in detail (Woodin 1977), it was found that it attached pieces of algae to its tube, which grew and were used for food, so-called ´gardening´. Nereids also are able to filter feed by creating a mucous bag and pumping water through their burrows, which filters the water; the mucous bag is then consumed. More recently, studies have shown varied and possibly opportunistic feeding by different benthic species; for example Christensen et al. (2000) showed how the suspension- and deposit-feeding abilities of nereids influenced sediment nutrient fluxes. These studies show that it is perhaps not so straightforward as once thought to interpret feeding mode simply from morphological features. The definition of functional groups and feeding guilds is increasingly used to help explain and interpret ecological functioning (e.g. Elliott et al. 2007 discuss the rationale behind functional groups). The eminent and immensely experienced benthic biologist Tom Pearson (2001) shows in detail that while the concept of functional groups gives us a greater understanding of the benthos, the idea is criticized by some as we do not have sufficient information about feeding types and modes of life of many benthic species.
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Cohen, Andrew S. "Geochemical Archives in Lake Deposits". In Paleolimnology. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195133530.003.0013.
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As we saw in chapter 4, the isotopic, elemental, or molecular constituents of a lake and its sediments reflect both external chemical inputs and the lake’s internal biogeochemical cycles. Lake sediment geochemistry is the product of interactions between these external inputs from watershed geology, groundwater, vegetation, and the airshed, and internal lake processes. Both external and internal inputs are heavily influenced by climate, and for the past few thousand years, human activities. With careful consideration of the various information filters affecting their records, geochemists can greatly broaden the scope of questions that can be addressed using paleolimnology. It is of critical importance when interpreting chemical data, that it be placed in the context of other sedimentological or paleontological archives. With modern, automated techniques, it is possible to amass large amounts of geochemical data in a relatively short time, data that can be compiled into deceptively ‘‘simple’’ geochemical profiles. Perhaps more than any other types of indicator, geochemical profiles are often interpreted as standalone records, without reference to petrographical, or even gross lithofacies information. Although it is tempting to read chemical stratigraphies as a direct record of inputs from a watershed or airshed, the signals are blurred by the whole host of messy, internal processes that we have already encountered in the hydroclimate filter: lag and residence time effects, reworking, particle and redox focusing, organismal uptake, and bioturbation. Lake deposits integrate local changes in source conditions, background sedimentation rates, and geochemical focusing processes (Engstrom and Swain, 1986). As a result, different locations within a lake may provide different geochemical histories, and interpretations of an integrated lake history must take into account these internal variations and their probable causes. This is always harder to do with paleolake deposits, where the original basin morphometry and hydrology is obscure. In this chapter we will also consider postdepositional information filters that affect geochemical archives, in particular bioturbation and diagenesis. Because many geochemical components of interest to paleolimnologists are bound to fine-grained particles, they can be readily mixed by bioturbation.
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Cohen, Andrew S. "The Chemical Environment of Lakes". In Paleolimnology. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195133530.003.0008.
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Understanding lake chemistry is critical for correctly interpreting the geochemical archives of lake deposits. Elemental and isotopic distributions in lakes are closely linked to external climatic and watershed processes. Solute concentrations regulate the distribution of organisms, and the precipitation or dissolution of mineral phases. Both fossils and minerals leave sedimentary archives, and when we can interpret aspects of ancient water chemistry from these records we may be able to reconstruct paleoclimate or prior human activity around the lake. Interpretation of isotopic records likewise requires an initial understanding of their behavior in lakes and the links between this behavior and external factors such as rainfall or nutrient discharge. Oxygen (O2) is the second most abundant component of the atmosphere (∼ 21%) after nitrogen (∼ 78%): Paleolimnological indicators of oxygenation at the sediment–water interface may provide clues as to the nature and frequency of water-column mixing, water depth, the lake’s trophic condition, and possibly climate. Thus, it is important to understand how oxygen is generated and consumed in lakes to properly interpret the oxygenation archives and filters. Oxygen is dissolved in lakes directly from air, and as a byproduct of photosynthesis by autotrophic organisms (multicellular plants, algae, and photosynthetic bacteria), greatly simplified as: . . . 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2 (4:1) . . . Photosynthesis is performed by both organisms on the lake floor (phytobenthos), and by floating algae and bacteria (phytoplankton). Molecular oxygen is lost from the water column through respiration, secondary oxidation of organic or inorganic compounds in the water column or sediments, or directly to the atmosphere following supersaturation. Oxygen concentrations in the water column are a function of productivity, respiration, temperature, and mixing, all of which vary both diurnally and seasonally within a lake, and because of climatic or morphometric differences between lakes. To understand this variation, it is useful to return to our examples at Junius Ponds #5 and #7. In dimictic Junius Pond #7, the water column just below the ice is well oxygenated during the winter, but is anoxic at the lake floor.
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Deudero, Salud, Ariadna Tor, Carme Alomar, Jose Maria, Piluca Sarriera e Andreu Blanco. "Integrated Multitrophic Aquaculture: Filter Feeders Bivalves as Efficient Reducers of Wastes Derived from Coastal Aquaculture Assessed with Stable Isotope Analyses". In Aquaculture and the Environment - A Shared Destiny. InTech, 2011. http://dx.doi.org/10.5772/28457.
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OTTING, G., e K. WÜTHRICH. "COMMUNICATIONS: Extended Heteronuclear Editing of 2D 1H NMR Spectra of Isotope-Labeled Proteins, Using the X(ω1, ω2) Double Half Filter". In NMR in Structural Biology, 402–10. WORLD SCIENTIFIC, 1995. http://dx.doi.org/10.1142/9789812795830_0032.
Texto completo da fonteTrabalhos de conferências sobre o assunto "Isotope filters"
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Newbound, T. D., A. N. Al-Nasser, M. P. Sang e W. J. Carrigan. "Recognition and Prevention of Distillate Fuel Emulsions". In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90030.
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This paper describes a case study involving chronic plugging of 5μm particulate filters in a gas turbine diesel fuel system in a Red Sea refinery. Rapid plugging of the filters was caused by water-in-diesel emulsions generated in diesel fuel supply tanks. Sludge with a wax-like appearance recovered from the 5 μm filters was, in fact, found to be composed of up to 50 percent water with no significant wax content. X-ray studies of the filter catch solids revealed a variety of iron oxide phases, sodium chloride, and high concentrations of sodium sulfate. Microbial cultures inoculated from storage tank ‘rag’ layers yielded moderate to high counts of general aerobic bacteria (GAB), moderate fungal cultures (yeast and molds) and low sulfate reducing bacteria (SRB). Elemental analysis of water in supply tanks where microbial activity was highest revealed ion concentrations similar to those found in Red Sea water. Sulfur isotope ratios in sulfate from filter catches suggest that much of the sulfate was derived from microbial metathesis of sulfur-bearing hydrocarbons. Frequent contamination of on-shore liquid hydrocarbon fuel tanks with sea water can cause corrosion and create a favorable environment for bacterial growth. Surfactant byproducts of microbial activity are capable of stabilizing emulsions, suspending water soluble salts such as sodium sulfate, and metals such as lead and copper. Copper is well known to promote gum formation, while all of these contaminants are potentially corrosive to gas turbine hot gas path components.
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Toadere, Florin, Nicoleta Tosa e Mihaela D. Lazar. "Functioning of the protective UV filters based on gold nanoparticles". In PROCESSES IN ISOTOPES AND MOLECULES (PIM 2011). AIP, 2012. http://dx.doi.org/10.1063/1.3681975.
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Cepraga, D. G., G. Cambi, M. Frisoni e D. Ene. "Cemented Containers Radiological Data From a Disused Uranium Mine Low-Level Waste Repository: A Calculated-Experiment Cross-Check for Data Verification and Validation". In ASME 2003 9th International Conference on Radioactive Waste Management and Environmental Remediation. ASMEDC, 2003. http://dx.doi.org/10.1115/icem2003-4516.
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Code validation problems involve calculation of experiments and a comparison experiment-calculation. Experimental data and physical properties of these systems are used to determine the range of applicability of the validation. Once a sequence-code of calculations has been validated, it has to be underlined that the comparison experimental-calculated results involving “complex systems” or “complex experimental measures” permits also a bi-lateral cross-check between the calculation scheme and the experimental procedures. The results of the testing and the validation effort related to the collection of information and measured data and the comparison between code results with experimental data coming from a “low-level waste” repository are presented in this paper. The Baita-Bihor repository, sited into former disused uranium mine in Transylvania, has been considered as the source of experimental data. The study was developed through the following steps: a) collection and processing of measured data (radioactivity content and dose rate), from the cemented containers of the Baita-Bihor repository; b) decay gamma source calculation by the ANITA-2000 code package (the input data for the calculations are the measured isotope activities for each container); c) decay gamma transport calculation by the SCALENEA-1 shielding Sn sequence approach (Nitawl-Xsdrnpm-Xsdose modules of the Scale 4.4a code system, using the Vitenea-J library, based on FENDL/E-2 data) to obtain dose rates on the surfaces and at various points outside the containers; d) comparison experimental-calculated dose rates, taking into account also the measurement uncertainties. The new version of the ANITA-2000 activation code package used makes possible to assess the behaviour of irradiated materials independently from the knowledge of the irradiation scenario but using only data on the isotope radioactive material composition. Radioactive waste disposed of at Baita Bihor repository consists of worn reactor parts, resins and filters, packing materials, mop heads, protective clothing, temporary floor coverings and tools, the sources normally generated during the day-to-day operation of research reactors, the remediation-treatment stations and the medicine and biological activities. The low and intermediate wastes are prepared for shipping and disposal in the treatment stations by confining them in a cement matrix inside 220 litre metallic drums. Each container consists of an iron cladding filled by concrete Portland. Radioisotope composition and radioactivity distributions inside the drum are measured. The gamma spectroscopy has been used for. The calibration technique was based on the assumption of a uniform distribution of the source activity in the drum and also of a uniform sample matrix. Dose rate measurements are done continuously, circularly, in the central plan on the surface of the drum and 1 m from the surface, in the air. A “stuffing factor” model has been adopted to simulate, for the calculation, the spatial distribution of the gamma sources in the concrete region. In order to guarantee a complete Quality Assurance for codes and procedures, a simulation of the radioactive containers to evaluate the dose rates was done also by using the Monte Carlo MCNP-4C code. Its calculation results are in a very good agreement with those obtained by the Sn approach (discrepancies are around 2%, using the spherical approximation).
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Wu, Tao, Weidong Chen, Erik Kerstel, Eric Fertein, Pascal Masselin, Xiaoming Gao, Johannes Koeth, Karl Rößner e Daniela Bruekner. "Real Time Determination of Water Isotope ratios by Laser Absorption Spectroscopy at 2.73 µm using Kalman Filter". In Laser Applications to Chemical, Security and Environmental Analysis. Washington, D.C.: OSA, 2010. http://dx.doi.org/10.1364/lacsea.2010.lmb5.
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Willems, M., P. Luycx, R. Gilis, C. I. Renard, H. Reyniers e J. M. Cuchet. "The HRA/SOLARIUM Project: Processing of Historical Waste". In ASME 2003 9th International Conference on Radioactive Waste Management and Environmental Remediation. ASMEDC, 2003. http://dx.doi.org/10.1115/icem2003-4732.
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Starting in 2003, Belgoprocess will proceed with the treatment and conditioning of some 200 m3 of widely varying high- and medium-level waste from earlier research and development work, to meet standard acceptance criteria for later disposal. The gross volume of primary and secondary packages amounts to 2,600 m3. The waste has been kept in decay storage for up to 30 years. The project was started in 1997. Operation of the various processing facilities will take 7–8 years. The overall volume of conditioned waste will be of the order of 800 m3. All conditioned waste will be stored in appropriate storage facilities onsite. In November 2002, a new processing facility has been constructed, the functional tests of the equipment have been performed and the start-up phase has been started. Several cells of the Pamela vitrification facility onsite will be adapted for the treatment of high-level and highly α-contaminated waste; low-level β/γ waste will be treated in the existing facility for super compaction and conditioning by embedding into cement (CILVA). The bulk of these waste, of which 95% are solids, the remainder consisting of mainly solidified liquids, have been produced between 1967 and 1988. They originate from various research programmes and reactor operation at the Belgian nuclear energy research centre SCK-CEN, isotope production, decontamination and dismantling operations. The waste is stored in 4800 primary packages, of which 700 contain 120 g (5.1012 Bq) radium. Half the radium inventory is present in 25 containers. The presence of radium in waste packages, resulting in the emission of radon gas, requires particular measurements. The total activity at the moment of production amounted to 18,811 TBq β/γ and 34.4 TBq α, with individual packages emitting up to 555 TBq β/γ and 2.2 TBq α. According to calculations, the β/γ activity has decreased to some 2,000 TBq, with individual packages up to 112 TBq. The extreme diversity of the waste is not only expressed in their radiological characteristics, but also in their chemical composition, physical state, the nature and condition of the packages. Radioactivity ranges between 0.01 mCi to 1,000 Ci per package. Some packages contain resins, Na, NaK and Al containing waste, poison rods, residues of fuel elements. Although most of the liquid waste are solidified, a small fraction — both aqueous and organic — still remains liquid. Primary packages may be plastic bags, metal boxes, wire gauze, La Cale`ne boxes; secondary packages may be steel drums and concrete containers. Solid waste may be sources, counters, nuclear fuel residues, filters, synthetic materials, metals, resins, granulates, rock, sludges, cables, glass, etc. Some 1000 primary packages are stored in a dry storage vault comprising 20 concrete cells, while 3800 primary packages are stored in some 2,000 concrete containers, on a concrete floor, surrounded by an earth bank to the height of the waste stacking and covered by a metal construction. At present, the annual production of similar waste amounts to 2 m3 divided over some 30 containers. Generally, the primary waste packages will be loaded in 80-1 drums (an average of 2 packages per drum), and compacted in a 150 ton hydraulic press. The pellets will be collected in 100 1 drums (an average of 3 pellets per drum). Low-level β/γ waste is transferred to the CILVA facility for further treatment, while the other 100-1 drums are filled up with sand and, in the case of radium-contaminated waste, tight-welded. Subsequently, the 100-1 drums are loaded into 400-1 drums and embedded into cement. Certain packages, for example solidified radium-contaminated liquids in welded metal containers, are conditioned as such in overpacks. Specific procedures will be established for the various non-standard waste, such as sources, control and poison rods, resins and filters, fuel residues. Highly active and/or heavily α-contaminated waste are transferred to the existing Pamela facility for treatment and conditioning. Ideally, gamma spectrometry measurements are carried out on the primary packages, but due to the extreme diversity of these packages, ranging from plastic bags containing cardboard to highly active steel valves, preference was given to measurements on the conditioned waste, or at least on already pre-compacted waste in the case of treatment in the 2,000 ton press of the CILVA facility. Thus tremendous problems of calibration can be largely avoided. All operations are remotely controlled. Transfers between buildings are carried out within appropriately shielded containers and secondary waste will be treated in existing facilities onsite. The new processing facility is being built partly over the dry storage vaults, in the immediate vicinity of the already covered storage area.
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Cheon, Donguk, Yoshihiro Iwata, Masabumi Miyabe e Shuichi Hasegawa. "Development of Bandpass Filtered External Cavity Diode Laser System for RIMS of Radioactive Strontium Isotopes". In Proceedings of the Second International Symposium on Radiation Detectors and Their Uses (ISRD2018). Journal of the Physical Society of Japan, 2019. http://dx.doi.org/10.7566/jpscp.24.011032.
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Willems, M., L. Krieckemans, P. Luycx e A. Meeus. "The HRA/Solarium Project: Processing of Widely Varying High- and Medium-Level Waste". In ASME 2001 8th International Conference on Radioactive Waste Management and Environmental Remediation. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/icem2001-1209.
Texto completo da fonteResumo:
Abstract Starting in 2002, Belgoprocess will proceed with the treatment and conditioning of some 200 m3 of widely varying high- and medium-level wastes from earlier research and development work, to meet standard acceptance criteria for later disposal. The gross volume of primary and secondary packages amounts to 2,600 m3. The wastes have been kept in decay storage for up to 30 years. The project was started in 1998. Operation of the various processing facilities will take 7–8 years. The overall volume of conditioned waste will be of the order of 800 m3. All conditioned waste will be stored in appropriate storage facilities onsite. At present (August, 2000), the construction of a new processing facility is in progress and the call for venders for the equipment has been sent out. Several cells of the Pamela vitrification facility onsite will be adapted for the treatment of high-level and highly α-contaminated wastes; low-level β/γ wastes will be treated in the existing facility for supercompaction and conditioning by embedding into cement (CILVA). The bulk of these wastes, of which 95% are solids, the remainder consisting of mainly solidified liquids, have been produced between 1967 and 1988. They originate from various research programmes and reactor operation at the Belgian nuclear energy research centre SCK•CEN, isotope production, decontamination and dismantling operations. The wastes are stored in 4800 primary packages, of which 700 contain 120 g (5.1012 Bq) radium. Half the radium inventory is present in 25 containers. The presence of radium in waste packages, resulting in the emission of radon gas, requires particular measurements and the welding of packages for storage, in order to allow a correct interpretation of alpha measurements onsite. The total activity at the moment of production amounted to 18,811 TBq β/γ and 34.4 TBq α, with individual packages emitting up to 555 TBq β/γ and 2.2 TBq α. According to calculations, the β/γ activity has decreased to some 2,000 TBq, with individual packages up to 112 TBq. The extreme diversity of the wastes is not only expressed in their radiological characteristics, but also in their chemical composition, physical state, the nature and condition of the packages. Radioactivity ranges between 0.01 mCi to 1,000 Ci per package. Some packages contain resins, Na, NaK and Al containing wastes, poison rods, residues of fuel elements. Although most of the liquid wastes are solidified, a small fraction — both aqueous and organic — still remains liquid. Primary packages may be plastic bags, metal boxes, wire gauze, La Calène boxes; secondary packages may be steel drums and concrete containers. Solid wastes may be sources, counters, control and poison rods, nuclear fuel residues, filters, synthetic materials, metals, resins, granulates, rock, sludges, cables, glass … Some 1000 primary packages are stored in a dry storage vault comprising 20 concrete cells, while 3800 primary packages are stored in some 2,000 concrete containers, on a concrete floor, surrounded by an earth bank to the height of the waste stacking and covered by a metal construction. At present, the annual production of similar wastes amounts to 2 m3 divided over some 30 containers. Generally, the primary waste packages will be loaded in 80 l drums (an average of 2 packages per drum), and compacted in a 150 t hydraulic press. The pellets will be collected in 100 l drums (an average of 3 pellets per drum). Low-level β/γ waste is transferred to the CILVA facility for further treatment, while the other 100 l drums are filled up with sand and, in the case of radium-contaminated wastes, tight-welded. Subsequently, the 100 l drums are loaded into 400 l drums and embedded into cement. Certain packages, for example solidified radium-contaminated liquids in welded metal containers, are conditioned as such in overpacks. Specific procedures will be established for the various non-standard wastes, such as sources, control and poison rods, resins and filters, fuel residues. The new processing facility is being built partly over the dry storage vaults, in the immediate vicinity of the already covered storage area. It comprises 1) feeder locks for the introduction of the various waste packages; 2) a dispatching cell in which the primary packages are loaded into 80 l drums; 3) the processing cell in which the 80 l drums are compacted and the pellets loaded into 100 l drums; and either sent to the CILVA facility (low-level β/γ wastes), or the Pamela facility (highly active and/or heavily α-contaminated), or further treated in 4) the transport area, in which radium and medium-level waste containing drums are conditioned into cement; 5) the measurement and characterisation cell, in which the conditioned waste is characterized by gamma spectrometry, and checked for compliance with maximum allowed surface contamination and dose rate in view of interim storage in the appropriate facilities onsite. Ideally, gamma spectrometry measurements are carried out on the primary packages, but due to the extreme diversity of these packages, ranging from plastic bags containing cardboard to highly active steel valves, preference was given to measurements on the conditioned wastes, or at least on already pre-compacted wastes in the case of treatment in the 2,000 t press of the CILVA facility. Thus tremendous problems of calibration can be largely avoided. All operations are remotely controlled. Transfers between buildings are carried out within appropriately shielded containers and secondary wastes will be treated in existing facilities onsite.
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Ishii, Tasuku, Daisuke Akiyama, Akira Kirishima, Nobuaki Sato e Tadashi Narabayashi. "Sorption of Radioactive Methyl Iodide by Silver Doped Zeolite for Filtered Venting System". In 2016 24th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icone24-60819.
Texto completo da fonteResumo:
Filtered containment venting system (FCVS) is an emergency response system for severe accident. FCVS reduces the pressure in reactor vessel and removes radioactive iodine and cesium. Recently, silver doped zeolite (AgX) has been attracting attentions since it is believed to remove over 99.99% of CH3I in the ventilation gas. However, the reliable data of AgX for CH3I sorption under expected severe accident conditions are still limited. Therefore, the sorption behavior of CH3I on AgX was investigated under several expected conditions. In this study, the CH3I labeled by 125I tracer was synthesized by isotope exchange reaction, and it was devoted for sorption experiment on AgX. Sorption experiment using stable CH3I was also conducted by the same procedure. From results of the sorption experiment, over 99.9% of 2.28g of CH3I were sorbed by 10g of AgX. After the sorption experiment, AgX samples were analyzed by powder X-ray diffraction (XRD) and SEM–EDX. These results indicated the distribution of Ag agreed with that of I in micro area of AgX. For the evaluation of apparent sorption capacity of AgX, breaking through experiment was carried out. The apparent sorption capacity of AgX for CH3I was determined as 0.25g / g (AgX) at 24°C. The breaking through experiment was also carried out for the evaluation of CH3I flux and humidity effects in the vent gas. The effect of temperature on the sorption capacity was also studied. When the flux of CH3I supply was increased from 1.09 × 10−4 to 2.33 × 10−4g/cm2s, apparent sorption capacity was unchanged (= 0.21g / g (AgX)). Besides, the apparent sorption capacity was unchanged in the humidity range of ∼0 % H2O to 0.01 % H2O, while it decreased to 0.19 g / g (AgX) at 3% H2O. When sorption temperature increased to 170 °C, the apparent sorption capacity also increased to 0.69 g / g (AgX).
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Misselwitz, F., C. Norden, S. P. Domogatsky, V. S. Repin e H. Heine. "INTERACTION OF PLATELETS WITH DIFFERENT ISOTYPES OF HUMAN COLLAGEN: THE COLLAGEN-RECEPTOR AND SIGNAL-RES-P0NSE COUPLING:". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644479.
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Platelet-collagen interaction is important in primary hemostasis and thrombosis. However, little is known about the interaction of platelets with genetically distinct collagen types I, III, IV, and V (Cl, ClII, CIV, CV) in their triple helical form. Here we report on the interaction of gel- filtered platelets with surfaces coated with monomeric collagen isotypes and the binding of 125-iodine-labeled Cl to platelets. It was shown that the binding of monomeric Cl is dose and time-dependent, saturable and specific, since it is competitively inhibited by unlabeled Cl, but not by unlabeled CV. Scatchard analysis reveals a receptor-class with a Kd of 2.5 x 10−8M. The result suggests that the different collagen isotypes may bind to platelets through various specific binding sites. Confirming that, we demonstrated, that interaction of platelets with collagen-coated surfaces is associated with the activation of different intra- and extracellular signal transduction systems: Initial attachment of discoid platelets to a CV-substrate does not induce neither synthesis of prostanoids nor changes of cyclic AMP-level. Adhesion and massive spreading of platelets on a CIV-substrate result in a decrease of stimulated cAMP-level without any synthesis of prostanoids. Only thrombus-formation during interaction of platelets with Cl- or CHI-coated surfaces is accompanied by a parallel decrease of cAMP and massive synthesis of platelet prostanoids. Additionally, it was shown that the stable prostacyclin analogue, carbacyc-lin, inhibited thrombus-formation and platelet spreading, whereas the PGH2/TXA2-receptor antagonists, 13-Azaprostanoic acid ana BM 13.177, completely inhibited thrombus-formation without any effect on platelet spreading.
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Gritzay, Olena O. "Total Cross Section and Self-Shielding Effects of the Cr-52 Isotope Measured at Kyiv Research Reactor Neutron-Filtered Beams". In INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY. AIP, 2005. http://dx.doi.org/10.1063/1.1945166.
Texto completo da fonteRelatórios de organizações sobre o assunto "Isotope filters"
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Campbell, D., e D. Trombino. FILTR: Flash Isotope Library and Training Resource. Office of Scientific and Technical Information (OSTI), julho de 2007. http://dx.doi.org/10.2172/921531.
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