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Watzinger, Andrea, Melanie Hager, Thomas Reichenauer, Gerhard Soja, and 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, no. 3 (April 16, 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, and J. Rudolph. "Method for the determination of concentration and stable carbon isotope ratios of atmospheric phenols." Atmospheric Measurement Techniques 6, no. 11 (November 5, 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, and J. Rudolph. "Method for the determination of concentration and stable carbon isotope ratios of atmospheric phenols." Atmospheric Measurement Techniques Discussions 6, no. 3 (May 28, 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, and Dominique P. Frueh. "Using delayed decoupling to attenuate residual signals in editing filters." Magnetic Resonance 2, no. 1 (June 21, 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, no. 10 (May 29, 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, and 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, and J. Rudolph. "Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric PM." Atmospheric Measurement Techniques Discussions 4, no. 3 (May 25, 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, and J. Rudolph. "Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric particulate matter." Atmospheric Measurement Techniques 4, no. 11 (November 16, 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, and Doru C. Lupascu. "Yttrium Oxide Freeze-Casts: Target Materials for Radioactive Ion Beams." Materials 14, no. 11 (May 27, 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, and 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, no. 11 (June 4, 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.
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Hüls, Matthias C., Pieter M. Grootes, and Marie-Josée Nadeau. "How Clean is Ultrafiltration Cleaning of Bone Collagen?" Radiocarbon 49, no. 2 (2007): 193–200. http://dx.doi.org/10.1017/s0033822200042119.
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As part of our bone dating development, we have tested the ultrafiltration of bone gelatin using 2 different filters—Vivaspin 20™ (VS20), a polyethersulfone, and Vivaspin 15R™ (VS15R), a cellulose, both with a 30,000 molecular weight cutoff—and bone collagen from dated samples ranging in age from 1.5 to >50 kyr BP. A direct accelerator mass spectrometry (AMS) measurement yielded radiocarbon concentrations of ∼0.5 pMC (∼42 kyr) for the polyethersulfone, ∼14.4–17.5 pMC (∼15.6–14 kyr) for the cellulose, and ∼107.4 pMC for the glycerin. The filters were cleaned before use similar to the Oxford protocol (Bronk Ramsey et al. 2004), and a series of freeze-dried archaeological bone gelatin samples and a modern pig-skin gelatin were passed through VS20 and VS15R filters (Vivascience™). We recovered both the eluent (<30-kD fraction) and the liquid that stayed above the filter (>30 kD) in order to obtain a carbon mass and isotope balance. While the >30-kD collagen fraction that is usually selected for AMS analysis does not appear to be significantly contaminated, measurements show significant age differences between the eluent <30 kD and the unfiltered bone collagen, indicating that, despite cleaning, both glycerin and filter still give off contaminants in the eluent. Ultrafiltration with young collagen from pig skin generally confirms these results for the <30-kD fraction but also shows the possibility of small contaminations in the >30-kD fraction. Until a contamination with filter carbon of the >30-kD collagen fraction can be excluded, we would recommend caution in the use of ultrafiltration for cleaning bone collagen with VS20 or VS15R ultrafilters.
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Kaiser, J., T. Röckmann, C. A. M. Brenninkmeijer, and P. J. Crutzen. "Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis." Atmospheric Chemistry and Physics Discussions 2, no. 5 (October 28, 2002): 1735–63. http://dx.doi.org/10.5194/acpd-2-1735-2002.
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Abstract. In previous reports on isotopic fractionation in the ultraviolet photolysis of nitrous oxide (N2O) only enrichments of heavy isotopes in the remaining N2O fraction have been found. However, most direct photolysis experiments have been performed at wavelengths far from the absorption maximum at 182 nm. Here we present high-precision measurements of the 15N and 18O fractionation constants (e) in photolysis at 185 nm. Small, but statistically robust depletions of heavy isotopes for the terminal atoms in the linear N2O molecule are found. This means that the absorption cross sections s(15N14N16O) and s(14N218O) are larger than s(14N216O) at this specific wavelength. In contrast, the central N atom becomes enriched in 15N. The corresponding fractionation constants (±1 standard deviation) are 15e1 = s(15N14N16O)/s(14N216O) - 1 = (3.7 ± 0.2)%o 18e = s(14N218O)/s(14N216O) - 1 = (4.5 ± 0.2)%o and 15e2 = s(\\chem{14N15N16O)/s(14N216O) - 1 = (-18.6 ± 0.5) %o To our knowledge, this is the first documented case of such a heavy isotope depletion in the photolysis of N2O which supports theoretical models and pioneering vacuum ultraviolet spectroscopic measurements of 15N substituted N2O species that predict fluctuations of e around zero in this spectral region (Selwyn and Johnston, 1981). Such a variability in isotopic fractionation could have consequences for atmospheric models of N2O isotopes since actinic flux varies also strongly over narrow wavelength regions between 175 and 200 nm due to the Schumann-Runge bands of oxygen. However, the spacing between maxima and minima of the fractionation constants and of the actinic flux differ by two orders of magnitude in the wavelength domain. The wavelength dependence of fractionation constants in N2O photolysis can thus be approximated by a linear fit with negligible consequences on the actual value of the spectrally averaged fractionation constant. In order to establish this linear fit, additional measurements at wavelengths other than 185 nm were made using broadband light sources, namely D2, Hg/Xe and Sb lamps. The latter lamp was used in conjunction with various interference filters to shift the peak photolysis rate to longer wavelengths. From these experiments and existing data in the literature, a comprehensive picture of the wavelength dependence of N2O photolysis is created.
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Kaiser, J., T. Röckmann, C. A. M. Brenninkmeijer, and P. J. Crutzen. "Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis." Atmospheric Chemistry and Physics 3, no. 2 (March 21, 2003): 303–13. http://dx.doi.org/10.5194/acp-3-303-2003.
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Abstract. In previous reports on isotopic fractionation in the ultraviolet photolysis of nitrous oxide (N2O) only enrichments of heavy isotopes in the remaining N2O fraction have been found. However, most direct photolysis experiments have been performed at wavelengths far from the absorption maximum at 182 nm. Here we present high-precision measurements of the 15N and 18O fractionation constants (ε) in photolysis at 185 nm. Small, but statistically robust depletions of heavy isotopes for the terminal atoms in the linear N2O molecule are found. This means that the absorption cross sections σ(15N 14N 16O) and σ(14N218O) are larger than σ(14N216O) at this specific wavelength. In contrast, the central N atom becomes enriched in 15N. The corresponding fractionation constants (±1 standard deviation) are 15ε1 = σ(15N 14N 16O)/σ(14N2 16O) - 1 = (3.7±0.2) %o 18ε = σ(14N218O)/σ(14N216O) - 1 = (4.5±0.2) %o and 15ε2 = σ(14N 15N 16O)/σ(14N216O) - 1 = (-18.6±0.5) %o To our knowledge, this is the first documented case of such a heavy isotope depletion in the photolysis of N2O which supports theoretical models and pioneering vacuum ultraviolet spectroscopic measurements of 15N substituted N2O species that predict fluctuations of ε around zero in this spectral region (Selwyn and Johnston, 1981). Such a variability in isotopic fractionation could have consequences for atmospheric models of N2O isotopes since actinic flux varies also strongly over narrow wavelength regions between 175 and 200 nm due to the Schumann-Runge bands of oxygen. However, the spacing between maxima and minima of the fractionation constants and of the actinic flux differ by two orders of magnitude in the wavelength domain. The wavelength dependence of fractionation constants in N2O photolysis can thus be approximated by a linear fit with negligible consequences on the actual value of the spectrally averaged fractionation constant. In order to establish this linear fit, additional measurements at wavelengths other than 185 nm were made using broadband light sources, namely D2, Hg/Xe and Sb lamps. The latter lamp was used in conjunction with various interference filters to shift the peak photolysis rate to longer wavelengths. From these experiments and existing data in the literature, a comprehensive picture of the wavelength dependence of N2O photolysis near room-temperature is created.
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Wooten, E. W., R. K. Dua, G. D. Dotson, and R. W. Woodard. "Homo- and Heteronuclear Multiple-Quantum Filters for Measurement of NMR Isotope Shifts." Journal of Magnetic Resonance, Series A 107, no. 1 (March 1994): 50–55. http://dx.doi.org/10.1006/jmra.1994.1046.
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Maki, Sorua L., Melissa B. Riley, and Nihal C. Rajapakse. "Gibberellin Status of Spectral Filter-grown Chrysanthemum Plants." HortScience 31, no. 4 (August 1996): 581c—581. http://dx.doi.org/10.21273/hortsci.31.4.581c.
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Endogenous gibberellins of chrysanthemum [Dendranthema ×grandiflorum (Ramat)] cv. Bright Golden Anne were characterized in apices from plants grown under control and CuSO4 spectral filters. Expanding shoots were separated into young expanding leaves and apices. Methanolic extracts of young expanding leaves were purified by solvent partitioning, PVPP column chromatography and reversed-phase high performance liquid chromatography. Two bioactive regions corresponding to the HPLC retention times of GA1 and GA19 standards were detected in fractions using the recently-developed non-dwarf rice bioassay. Di-deuterated internal standards of GA12, GA53, GA19, GA20, and GA1 were added to similar extracts of shoot apices. The presence of endogenous GA53, GA19, GA20, and GA1 in chrysanthemum apices was confirmed by isotope dilution using gas chromatography-mass spectrometry-selected ion monitoring and Kovats retention indices. In a preliminary quantification study, GA20 and GA1 levels were found to be higher in apices from plants grown under control filters while GA19 levels were higher in apices grown under CuSO4 filters. The possibility that light transmitted through CuSO4 filters alters gibberellin levels in shoot apices is discussed.
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Hieftje, Gary M., James H. Barnes, Ole A. Grøn, Andrew M. Leach, Denise M. McClenathan, Steven J. Ray, David A. Solyom, William C. Wetzel, M. Bonner Denton, and David W. Koppenaal. "Evolution and revolution in instrumentation for plasma-source mass spectrometry." Pure and Applied Chemistry 73, no. 10 (October 1, 2001): 1579–88. http://dx.doi.org/10.1351/pac200173101579.
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Plasma-source mass spectrometry, usually in the form of inductively coupled plasma mass spectrometry (ICP-MS), has matured into a widely accepted method for ultra-trace multielemental analysis. However, the method exhibits shortcomings. For example, it does not provide adequate precision for isotope ratio measurements if many isotopes are to be determined. Moreover, isobaric overlaps (spectral interferences) can be very troublesome in some situations. Similarly, matrix interferences can adversely affect many determinations. Yet, it is in the area of high-speed transient measurements that ICP-MS perhaps suffers its greatest weakness. When sampling devices such as flow injection, laser ablation, electrothermal vaporization, or chromatography are employed, the user must choose between broad elemental or isotopic coverage and signal-to-noise ratio (S/N). In turn, compromised S/N means lower precision or poorer detection limits. Here, new instrumentation aimed at overcoming these limitations will be described. One system, based on a time-of-flight mass spectrometer, provides excellent detection limits, resolving power better than commercial quadrupole mass filters, precision of at least 0.02% rsd in a ratioing mode, and extraordinarily high speed for use with transient sampling devices. The second instrument is based on a sector-field mass spectrometer but, unlike other such units, is equipped with a focal-plane array detector. So equipped, the system can detect a broad mass range at once.
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De Los Ríos, K., C. Méndez-García, S. Padilla, C. Solís, E. Chávez, A. Huerta, and L. Acosta. "Characterization of the LEMA isotope separator to measure concentrations of 10Be from atmospheric filters." Journal of Physics: Conference Series 1078 (August 2018): 012009. http://dx.doi.org/10.1088/1742-6596/1078/1/012009.
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Otting, Gottfried, and Kurt Wüthrich. "Heteronuclear filters in two-dimensional [1H, 1H]-NMR spectroscopy: combined use with isotope labelling for studies of macromolecular conformation and intermolecular interactions." Quarterly Reviews of Biophysics 23, no. 1 (February 1990): 39–96. http://dx.doi.org/10.1017/s0033583500005412.
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The use of heteronuclear filters enables the editing of complex 1H nuclear magnetic resonance (NMR) spectra into simplified subspectra containing a lesser number of resonance lines, which are then more easily amenable to detailed spectral analysis. This editing is based on the creation of heteronuclear two-spin or multiple-spin coherence and discrimination between protons that do or do not participate in these heteronuclear coherences. In principle, heteronuclear editing can be used in conjunction with one-dimensional or multidimensional 1H-NMR experiments for studies of a wide variety of low-molecular-weight compounds or macromolecular systems, and is implicitely applied in a wide range of heteronuclear NMR experiments with proton detection (e.g. Bax et al. 1983; Griffey & Redfield, 1987). In the present article we shall focus on the use of heteronuclear filters in two-dimensional (2D) [1H, 1H]-NMR experiments. The selection of the material covered was primarily motivated by its impact on the practice of protein structure determination in solution, and on NMR studies of intermolecular interactions with biological macromolecules. Section 2 surveys potential applications of heteronuclear filters in this area. The remainder of the article is devoted to an introduction of the theoretical principles used in heteronuclear filters, and to a detailed description of the experimental implementation of these measurements. In writing the review we tried to minimize redundancy with the recent article in Quarterly Review of Biophysics by Griffey & Redfield (1987) and to concentrate on experiments that were introduced during the period 1986–9.
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Bühler, Janica C., Carla Roesch, Moritz Kirschner, Louise Sime, Max D. Holloway, and Kira Rehfeld. "Comparison of the oxygen isotope signatures in speleothem records and iHadCM3 model simulations for the last millennium." Climate of the Past 17, no. 3 (May 5, 2021): 985–1004. http://dx.doi.org/10.5194/cp-17-985-2021.
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Abstract. Improving the understanding of changes in the mean and variability of climate variables as well as their interrelation is crucial for reliable climate change projections. Comparisons between general circulation models and paleoclimate archives using indirect proxies for temperature or precipitation have been used to test and validate the capability of climate models to represent climate changes. The oxygen isotopic ratio δ18O, a proxy for many different climate variables, is routinely measured in speleothem samples at decadal or higher resolution, and single specimens can cover full glacial–interglacial cycles. The calcium carbonate cave deposits are precisely dateable and provide well preserved (semi-)continuous albeit multivariate climate signals in the lower and mid-latitudes, where the measured δ18O in the mineral does not directly represent temperature or precipitation. Therefore, speleothems represent suitable archives to assess climate model abilities to simulate climate variability beyond the timescales covered by meteorological observations (101–102 years). Here, we present three transient isotope-enabled simulations from the Hadley Center Climate Model version 3 (iHadCM3) covering the last millennium (850–1850 CE) and compare them to a large global dataset of speleothem δ18O records from the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database version 2 (Comas-Bru et al., 2020b). We systematically evaluate offsets in mean and variance of simulated δ18O and test for the main climate drivers recorded in δ18O for individual records or regions. The time-mean spatial offsets between the simulated δ18O and the speleothem data are fairly small. However, using robust filters and spectral analysis, we show that the observed archive-based variability of δ18O is lower than simulated by iHadCM3 on decadal and higher on centennial timescales. Most of this difference can likely be attributed to the records' lower temporal resolution and averaging or smoothing processes affecting the δ18O signal, e.g., through soil water residence times. Using cross-correlation analyses at site level and modeled grid-box level, we find evidence for highly variable but generally low signal-to-noise ratios in the proxy data. This points to a high influence of cave-internal processes and regional climate particularities and could suggest low regional representativity of individual sites. Long-range strong positive correlations dominate the speleothem correlation network but are much weaker in the simulation. One reason for this could lie in a lack of long-term internal climate variability in these model simulations, which could be tested by repeating similar comparisons with other isotope-enabled climate models and paleoclimate databases.
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HINKLE, S., J. BOHLKE, and L. FISHER. "Mass balance and isotope effects during nitrogen transport through septic tank systems with packed-bed (sand) filters." Science of The Total Environment 407, no. 1 (December 15, 2008): 324–32. http://dx.doi.org/10.1016/j.scitotenv.2008.08.036.
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Haig, Sarah-Jane, Melanie Schirmer, Rosalinda D'Amore, Joseph Gibbs, Robert L. Davies, Gavin Collins, and Christopher Quince. "Stable-isotope probing and metagenomics reveal predation by protozoa drives E. coli removal in slow sand filters." ISME Journal 9, no. 4 (October 3, 2014): 797–808. http://dx.doi.org/10.1038/ismej.2014.175.
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Frederiksen, Hanne, Ole Nielsen, Niels E. Skakkebaek, Anders Juul, and Anna-Maria Andersson. "UV filters analyzed by isotope diluted TurboFlow-LC–MS/MS in urine from Danish children and adolescents." International Journal of Hygiene and Environmental Health 220, no. 2 (March 2017): 244–53. http://dx.doi.org/10.1016/j.ijheh.2016.08.005.
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Mitsui, Takaya, Yasuhiko Imai, Ryo Masuda, Makoto Seto, and Ko Mibu. "57Fe polarization-dependent synchrotron Mössbauer spectroscopy using a diamond phase plate and an iron borate nuclear Bragg monochromator." Journal of Synchrotron Radiation 22, no. 2 (February 14, 2015): 427–35. http://dx.doi.org/10.1107/s1600577514028306.
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Energy-domain57Fe polarization-dependent synchrotron radiation Mössbauer spectroscopy was developed by using a diamond X-ray phase plate and an iron borate nuclear Bragg monochromator. The former controls the polarization of the incident synchrotron radiation X-rays and the latter filters the57Fe-Mössbauer radiation with a narrow bandwidth of ∼3.4 Γ0(Γ0≃ 4.7 neV: natural linewidth of the57Fe nucleus) from the broadband synchrotron radiation. The developed nuclear diffraction optics allowed57Fe-Mössbauer studies to be performed with various polarization states,i.e.linear polarization, circular polarization and non-polarization. In this paper, the spectrometer system, beam characterization, performance-test experiments and a grazing-incidence Mössbauer measurement of an isotope-enriched (57Fe: 95%) iron thin film are described.
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CERUTTI, STEFANO, CHARLES MENEVEAU, and OMAR M. KNIO. "Spectral and hyper eddy viscosity in high-Reynolds-number turbulence." Journal of Fluid Mechanics 421 (October 25, 2000): 307–38. http://dx.doi.org/10.1017/s0022112000001671.
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For the purpose of studying the spectral properties of energy transfer between large and small scales in high-Reynolds-number turbulence, we measure the longitudinal subgrid-scale (SGS) dissipation spectrum, defined as the co-spectrum of the SGS stress and filtered strain-rate tensors. An array of four closely spaced X-wire probes enables us to approximate a two-dimensional box filter by averaging over different probe locations (cross-stream filtering) and in time (streamwise filtering using Taylor's hypothesis). We analyse data taken at the centreline of a cylinder wake at Reynolds numbers up to Rλ ∼ 450. Using the assumption of local isotropy, the longitudinal SGS stress and filtered strain-rate co-spectrum is transformed into a radial co-spectrum, which allows us to evaluate the spectral eddy viscosity, v(k, kΔ). In agreement with classical two-point closure predictions, for graded filters, the spectral eddy viscosity deduced from the box-filtered data decreases near the filter wavenumber kΔ. When using a spectral cutoff filter in the streamwise direction (with a box-filter in the cross-stream direction) a cusp behaviour near the filter scale is observed. In physical space, certain features of a wavenumber-dependent eddy viscosity can be approximated by a combination of a regular and a hyper-viscosity term. A hyper-viscous term is also suggested from considering equilibrium between production and SGS dissipation of resolved enstrophy. Assuming local isotropy, the dimensionless coefficient of the hyper-viscous term can be related to the skewness coefficient of filtered velocity gradients. The skewness is measured from the X-wire array and from direct numerical simulation of isotropic turbulence. The results show that the hyper-viscosity coefficient is negative for graded filters and positive for spectral filters. These trends are in agreement with the spectral eddy viscosity measured directly from the SGS stress–strain rate co-spectrum. The results provide significant support, now at high Reynolds numbers, for the ability of classical two-point closures to predict general trends of mean energy transfer in locally isotropic turbulence.
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Chambon, Amalia, Esben Klinkby, Leif Emås, and Bent Lauritzen. "Assessment of shutdown dose rates at the ESS target cooling system using SCALE6.2." Journal of Neutron Research 22, no. 2-3 (October 20, 2020): 309–18. http://dx.doi.org/10.3233/jnr-190136.
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The production of high-energy neutrons at the European Spallation Source through the spallation process may cause an erosion of the tungsten target. The eroded particles could be released into the target helium cooling system which contains four kind of filters. Among them, the auxiliary filters called “getters” are designed to capture volatile elements and remaining dust. In this work, the ORNL’s SCALE6.2 modelling and simulation suite for nuclear safety analysis is applied to assess shutdown dose rates and determine if added shielding and/or robotic arms are needed for their maintenance. SCALE6.2 is well adapted to treat this problem as it allows for isotope selection regarding source term calculation. Dose rates are determined by an ORIGEN2 source term and a MAVRIC shielding sequence calculation. As SCALE6.2 is non-standard software for ESS, the results are verified against MCNP, which is the baseline tool for neutronics analysis at ESS. Dose rate calculations show that additional shielding and/or robot arm are not needed to remove the getters after 3 months of cooling time, following 5400 h of operation at 5 MW beam power. At a distance of 1 mm from the getter, the dose rate is 0.2 mSv/h in the most conservative estimation.
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Maki, Sonja L., and Nihal C. Rajapakse. "GIBBERELLIN PHYSIOLOGY OF SPECTRAL FILTER-GROWN CHRYSANTHEMUM PLANTS." HortScience 31, no. 5 (September 1996): 752b—752. http://dx.doi.org/10.21273/hortsci.31.5.752b.
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Endogenous gibberellins of chrysanthemum [Dendrathema×grandiflorum (Ramat) cv. Bright Golden Anne] were characterized in preparation for quantification of endogenous gibberellins in apices under control and CuSO4 spectral filters. Expanding shoots were separated into young expanding leaves and apices. Methanolic extracts of young expanding leaves were purified by solvent partitioning, PVPP column chromatography, and reversed-phase high performance liquid chromatography. Two bioactive regions corresponding to the HPLC retention times of GA and GA19 standards were detected in fractions using the recently developed non-dwarf rice bioassay. Dideuterated internal standards of GA12, GA53, GA19, GA20, and GA1 were added to similar extracts of shoot apices. The presence of endogenous GA53, GA19, GA20, and GA1 in chrysanthemum apices was confirmed by isotope dilution using gas chromatography–mass spectrometry-selected ion monitoring and Kovats retention indices. Ions for the deuterated internal standard of GA12 were detected, but not for endogenous GA12. The above results demonstrate that the early 13-hydroxylation pathway operates in chrysanthemum.
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Gennett, Judith A., and Ethan L. Grossman. "Oxygen and Carbon Isotope Trends in a Late Glacial-Holocene Pollen Site in Wyoming, U.S.A." Géographie physique et Quaternaire 40, no. 2 (December 4, 2007): 161–69. http://dx.doi.org/10.7202/032636ar.
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ABSTRACT Stable isotope studies of North American Late Glacial and Holocene lake sediments are few. Previous studies of pollen sites in Indiana, South Dakota, and the Great Lakes area show low δ18O values during deglaciation, rising to a Hypsithermal peak, and provide paleoenvironmental reconstructions similar to those obtained from pollen studies. Blacktail Pond, located in Douglas fir steppe in northern Yellowstone National Park, Wyoming, is one of the highest elevation lakes (2018 m) yet studied with both pollen and stable isotopes. Analyses of marls yield low oxygen and carbon isotope values at the base of the core probably due to meltwater influx at 12,500 to 14,000 BP. Tundra vegetation persisted for about an additional 1,500 years following the end of meltwater input. Later, more enriched isotope values fluctuate due to the high sensitivity of Blacktail Pond to evaporation and CO2 exchange because of its shallow depth. These processes result in a covariance between δ13C and δ18O related to the residence time of water in the pond; they exert a primary control on the isotopic composition of the Holocene marl. It may be possible to filter the data for residence time effects and extract additional paleoenvironmental information based on the offsets of isotopic data from the δ13C-δ18O trend for a particular pollen zone.
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Vieira, Nancy E., and Alfred L. Yergey. "Extraction of Serum and Urine Calcium with Ion Exchange Membrane Filters for Isotope Enrichment Determination Using Thermal Ionization Mass Spectrometry." Analytical Chemistry 67, no. 22 (November 1995): 4217–19. http://dx.doi.org/10.1021/ac00118a028.
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Doi, Hideyuki, Yasuhiro Takemon, Taichi Ohta, Yuko Ishida, and Eisuke Kikuchi. "Effects of reach-scale canopy cover on trophic pathways of caddisfly larvae in a Japanese mountain stream." Marine and Freshwater Research 58, no. 9 (2007): 811. http://dx.doi.org/10.1071/mf07067.
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Differences in trophic pathways between reaches with and without tree canopy cover above the channel were assessed using stable isotopes in a 1.4-km stretch of the Kamo River, Japan. The trophic pathways of two larval trichopteran species, a grazer (Goera joponica, Goeridae) inhabiting stone surfaces and a net-spinning filter-feeder (Stenopsyche marmorata, Stenopsychidae) inhabiting interstices of the stony stream bottom, were estimated using carbon and nitrogen isotopes in reaches with and without canopy cover in winter. The δ13C values of G. japonica were similar to those of periphyton at each station, suggesting that G. japonica is a grazer on periphyton. A significant positive correlation between carbon isotope values of S. marmorata and benthic particulate organic matter (BPOM) indicated that BPOM varied in composition according to the amount of solar energy within a reach. In addition, there was a significant positive correlation between carbon isotope values of filter-feeders and the periphytic algal contribution to BPOM using an isotope mixing model, indicating that the main food source of the filter feeders was derived from the in situ periphytic algae in open reaches and from a terrestrial source in canopy-covered reaches.
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Deein, G., W. Thimdee, and K. Matsunaga. "Bioavailable colloidal iron in river water originated from the forest." Marine and Freshwater Research 53, no. 1 (2002): 43. http://dx.doi.org/10.1071/mf00145.
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In samples of water from five sites on the Shukunohe, Ohno and Kunebetsu rivers, Japan, most of the filterable iron (<0.45 m) was colloidal iron (0.45–0.025 m). There was a correlation between dissolved iron and colloidal iron; both are assumed to be associated with humic substances, since the carbon isotope ratio of colloidal organic substances on glass-fibre filters corresponded to the ratio of mountain humic soil. In culture experiments, the freshwater phytoplankton Melosira granulata var. angustissima f. spiralis grew rapidly in a medium containing colloidal iron, to a maximum of ~250 000 cells mL–1. However, there was little growth with amorphous colloidal iron and no growth in control medium containing ~0.1 M dissolved Fe. In a multispecies phytoplankton culture, colloidal iron also promoted growth, with a maximum of ~60 g Chl-a L–1. These results indicated the bioavailability of colloidal iron.
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Ussher, Simon J., Ivan Petrov, Christophe R. Quétel, and Paul J. Worsfold. "Validation of a portable flow injection - chemiluminescence (FI-CL) method for the determination of dissolved iron in Atlantic open ocean and shelf waters by comparison with isotope dilution - inductively coupled plasma mass spectrometry (ID-ICPMS)." Environmental Chemistry 7, no. 2 (2010): 139. http://dx.doi.org/10.1071/en09092.
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Environmental context. The importance of iron as a limiting micronutrient for primary production in the marine environment and its complex marine biogeochemical cycle necessitate accurate methods for the determination of iron in seawater. Current analytical challenges include the detection of trace concentrations (sub-nanomolar) and the high potential for contamination and matrix interferences. To improve confidence in dissolved iron data, intercomparison exercises of commonly used analytical methods are required that demonstrate their applicability to different water masses. Abstract. A blind intercomparison exercise was carried out to validate a well documented, portable flow injection–chemiluminescence (FI-CL) method for the determination of iron in seawater. This was done by the analysis of a variety of filtered Atlantic Ocean samples using FI-CL and a potential primary method of measurement, isotope dilution–inductively coupled plasma mass spectrometry (ID-ICPMS). To investigate the effect of the seawater matrix at various concentrations of iron, samples were collected at various depths (0–200 m) from different water masses (European Continental Shelf, the South Atlantic Ocean) and filtered through both 0.02- and 0.2-μm pore size filters. The exercise was conducted under controlled conditions using the same bottles transported between laboratories to avoid between-bottle inhomogeneity. The results generally showed good agreement between the two methods for dissolved iron over the concentration range 0.15 to 2.1 nM. However, some samples were not in agreement according to estimated uncertainties and this was attributed to random errors arising from contamination during sample handling and matrix effects (i.e. variable interferences) rather than systematic errors.
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Jacinthe, P. A., R. Lal, and L. B. Owens. "Application of stable isotope analysis to quantify the retention of eroded carbon in grass filters at the North Appalachian experimental watersheds." Geoderma 148, no. 3-4 (January 2009): 405–12. http://dx.doi.org/10.1016/j.geoderma.2008.11.013.
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Cheng, Jie, Xiaojian Kong, Shucheng Liu, Dandan Che, Zhiwei Sun, Guoliang Li, Meiling Ping, Jingpu Tang, and Jinmao You. "Determination of Ultraviolet Filters in Domestic Wastewater by LC–MS Coupled with Polydopamine-Based Magnetic Solid-Phase Extraction and Isotope-Coded Derivatization." Chromatographia 81, no. 12 (November 7, 2018): 1673–84. http://dx.doi.org/10.1007/s10337-018-3650-x.
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Ternon, Eva, and Imma Tolosa. "Comprehensive analytical methodology to determine hydrocarbons in marine waters using extraction disks coupled to glass fiber filters and compound-specific isotope analyses." Journal of Chromatography A 1404 (July 2015): 10–20. http://dx.doi.org/10.1016/j.chroma.2015.05.029.
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Guerrieri, Rossella, Pamela Templer, and Federico Magnani. "Canopy Exchange and Modification of Nitrogen Fluxes in Forest Ecosystems." Current Forestry Reports 7, no. 3 (August 24, 2021): 115–37. http://dx.doi.org/10.1007/s40725-021-00141-y.
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Abstract Purpose of Review We provide an overview of the main processes occurring during the interactions between atmospheric nitrogen and forest canopies, by bringing together what we have learned in recent decades, identifying knowledge gaps, and how they can be addressed with future research thanks to new technologies and approaches. Recent Findings There is mounting evidence that tree canopies retain a significant percentage of incoming atmospheric nitrogen, a process involving not only foliage, but also branches, microbes, and epiphytes (and their associated micro-environments). A number of studies have demonstrated that some of the retained nitrogen can be assimilated by foliage, but more studies are needed to better quantify its contribution to plant metabolism and how these fluxes vary across different forest types. By merging different approaches (e.g., next-generation sequence analyzes and stable isotopes, particularly oxygen isotope ratios) it is now possible to unveil the highly diverse microbial communities hidden in forest canopies and their ability to process atmospheric nitrogen through processes such as nitrification and nitrogen fixation. Future work should address the contribution of both foliar nitrogen uptake and biological transformations within forest canopies to whole ecosystem nitrogen cycling budgets. Summary Scientists have studied for decades the role of forest canopies in altering nitrogen derived from atmospheric inputs before they reach the forest floor, showing that tree canopies are not just passive filters for precipitation water and dissolved nutrients. We now have the technological capability to go beyond an understanding of tree canopy itself to better elucidate its role as sink or source of nutrients, as well as the epiphytes and microbial communities hidden within them.
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von Blume, Julia, Juan M. Duran, Elena Forlanelli, Anne-Marie Alleaume, Mikhail Egorov, Roman Polishchuk, Henrik Molina, and Vivek Malhotra. "Actin remodeling by ADF/cofilin is required for cargo sorting at the trans-Golgi network." Journal of Cell Biology 187, no. 7 (December 21, 2009): 1055–69. http://dx.doi.org/10.1083/jcb.200908040.
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Knockdown of the actin-severing protein actin-depolymerizing factor (ADF)/cofilin inhibited export of an exogenously expressed soluble secretory protein from Golgi membranes in Drosophila melanogaster and mammalian tissue culture cells. A stable isotope labeling by amino acids in cell culture mass spectrometry–based protein profiling revealed that a large number of endogenous secretory proteins in mammalian cells were not secreted upon ADF/cofilin knockdown. Although many secretory proteins were retained, a Golgi-resident protein and a lysosomal hydrolase were aberrantly secreted upon ADF/cofilin knockdown. Overall, our findings indicate that inactivation of ADF/cofilin perturbed the sorting of a subset of both soluble and integral membrane proteins at the trans-Golgi network (TGN). We suggest that ADF/cofilin-dependent actin trimming generates a sorting domain at the TGN, which filters secretory cargo for export, and that uncontrolled growth of this domain causes missorting of proteins. This type of actin-dependent compartmentalization and filtering of secretory cargo at the TGN by ADF/cofilin could explain sorting of proteins that are destined to the cell surface.
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Siflinger-Birnboim, A., P. J. Del Vecchio, J. A. Cooper, and A. B. Malik. "Transendothelial albumin flux: evidence against asymmetric transport." Journal of Applied Physiology 61, no. 6 (December 1, 1986): 2035–39. http://dx.doi.org/10.1152/jappl.1986.61.6.2035.
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We examined the recent proposition (Circ. Res. 57: 903–905, 1985) that the interstitium-to-luminal transport of albumin is an active phenomenon. Studies were made using cultured bovine and sheep pulmonary-artery endothelial cells. The transendothelial 125I-albumin flux from the luminal-to-abluminal side was compared with the flux from the abluminal-to-luminal side. The endothelial cells were grown to confluence on gelatinized-polycarbonated filters separating the abluminal from the luminal compartments. The albumin concentration in each compartment was 1 g/100 ml to equalize the oncotic pressure gradients. The effect of hydrostatic pressure was eliminated by maintaining equal fluid levels in both compartments. The transendothelial albumin flux across the monolayer was measured by adding the 125I-albumin tracer either on the luminal or the abluminal side. A double-isotope method was also used to study bidirectional transendothelial flux of albumin at the same time for the same cultured endothelium. The results indicated that albumin flux from the luminal-to-abluminal side was equal to the flux from the abluminal-to-luminal side. Both bovine and sheep pulmonary artery endothelial cells in culture behave symmetrically for albumin, suggesting that albumin is not actively transported from the interstitium to the lumen.
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Doi, Hideyuki, Kwang-Hyeon Chang, and Shin-ichi Nakano. "Nitrogen and carbon isotope fractionations of zooplankton consumers in ponds: potential effects of seston C:N stoichiometry." Marine and Freshwater Research 62, no. 1 (2011): 66. http://dx.doi.org/10.1071/mf10090.
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C : N stoichiometry in food sources is known to influence nitrogen isotope fractionation of consumers, but the relationship between C : N stoichiometry and isotope fractionation has never been tested in the field. In this study, we investigated the effects of the C : N ratio of food sources on nitrogen and carbon isotope fractionation (Δδ15N and Δδ13C) of consumers, using zooplankton communities in 15 ponds in Japan. The fractionation variations we found contradicted the assumption of a 3.4‰ enrichment in δ15N of consumers per trophic level. However, the negative relationships between Δδ15N of filter-feeding zooplankton and the C : N ratio of seston supported the isotope homeostasis hypothesis, which predicts isotopic homeostasis of consumers to vary with respect to their body nutrient composition. The Δδ15N of Eodiaptomus sp. and cyclopoid copepods did not correlate with the C : N ratio of the seston. Further studies should pay attention to the isotope fractionation of consumers in the field, especially given the increased use of isotope fractionation to elucidate the structure of natural food webs.
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Zwolińska, Elżbieta, and Monika Ciężka. "Geochemical and isotopic analyses of PM10 in Lower Silesia - preeliminary data." Contemporary Trends in Geoscience 2, no. 1 (September 1, 2013): 101–5. http://dx.doi.org/10.2478/ctg-2014-0015.
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Abstract The main aim of the study was to determine the origin of particulate air pollution in Lower Silesia. Samples of PM10 dust were collected on quartz filters Whatman QM-A by employees of Voivodship Inspectorate for Environmental Protection (VIEP) in Wroclaw in 2011. As a pilot researches in Lower Silesia were selected two monitoring points of VIEP: (i) Osieczow and (ii) Zgorzelec. Air sampling point in Osieczow is a point of regional background and it is an excellent reference base for the analyses of PM10 in Lower Silesia. The aim of monitoring in this point is to assess the exposure of ecosystems to air pollution. Sampling point in Zgorzelec reflects the urban background and the measurements will be compared, in the future, to the results of the sampling points investigated the impact of industry and local transport on air quality in the whole Lower Silesia. For further geochemical and isotopic analyses were selected 25 samples from each sampling point, average every two weeks measurement. The concentration of PM10 dust for Osieczow ranged from 7 μg∙m-3 (11.10.2011r.) to 89 μg∙m-3 (4.03.2011r.) with an average of 24 μg∙m-3 and for Zgorzelec between 10 μg∙m-3 (11.10.2011r.) and 85 μg∙m-3 (9.11.2011r.) with an average of 26 μg∙m-3. The mean percentage contribution of carbon in PM10 samples from Osieczow was 47%, while in Zgorzelec 42%. The obtained values of δ03C (PM10) in Osieczow varied from -31.1‰ (5.02.2011r.) to -25.5‰ (26.10.2011r.) with an average of -27.6‰, whereas in Zgorzelec between -28.6‰ (15.07.2011r.) and -25.2‰ (6.01.2011r.) with an average of -26.8‰. At the current stage of research is clearly discernible the different carbon isotope record in the material dust (qualitative information), despite the identical range of concentrations of PM10 in both analysed points (quantitative information). This confirms the appropriateness of the choice both research method and monitoring points.
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Klemp, Joseph B. "Damping Characteristics of Horizontal Laplacian Diffusion Filters." Monthly Weather Review 145, no. 11 (November 2017): 4365–79. http://dx.doi.org/10.1175/mwr-d-17-0015.1.
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Horizontally diffusive computational damping terms are frequently employed in 3D atmospheric simulation models to enhance stability and to suppress small-scale noise. In configuring these filters, it is desirable that damping effects are concentrated on the smaller-scale disturbances close to the grid scale and that the dissipation is spatially isotropic. On Cartesian meshes, the isotropy of the damping can vary greatly depending on the numerical formulation of the horizontal filter. The most isotropic behavior appears to result from recursive application of a 2D Laplacian that combines both along-axis and diagonal contributions. Also, the recursive application of 1D Laplacians in each coordinate direction provides better isotropy than the recursive application of the 2D Laplacian represented with a five-point operator. Increased isotropy also permits a larger maximum diffusivity, which may be beneficial in certain filter applications. On hexagonal and triangular meshes, Laplacian operators exhibit excellent isotropy, owing to the more isotropic nature of the meshes. However, previous research has established that straightforward application of the Laplacian may yield a diffusion operator that damps both resolved physical modes and unresolved high-wavenumber (aliased) modes, but it does not converge to the proper analytic behavior. Special averaging is then required to recover an accurate representation for the Laplacian. A consequence of this averaging is that the resulting filters do not act on the aliased modes (the checkerboard mode in particular) and thus employing the unaveraged diffusion operators may be preferable. The damping characteristics and stability constraints are derived for both the unaveraged and averaged Laplacian filters for C-grid staggering on these meshes.
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McCann, M. T., M. M. Thompson, I. C. Gueron, and M. Tuchman. "Quantification of orotic acid in dried filter-paper urine samples by stable isotope dilution." Clinical Chemistry 41, no. 5 (May 1, 1995): 739–43. http://dx.doi.org/10.1093/clinchem/41.5.739.
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Abstract A rapid, sensitive, and specific method for quantification of orotic acid from dried filter-paper urine samples is described. The method involves stable isotope dilution with 1,3-[15N2]orotic acid analysis by gas chromatography-mass spectrometry. The assay is sufficiently sensitive to be used with solvent extraction techniques commonly used for urinary organic acid analysis. Extraction efficiencies of both native and isotopic orotic acid from dried filter paper and from water were 31% and 28%, respectively. The concentration of orotic acid in dried filter-paper urine specimens from 50 healthy controls was 1.1 +/- 0.67 (mean +/- SD) mmol/mol of urinary creatinine. The same 50 urine samples, analyzed directly from a 5-mL aliquot of liquid urine, gave values of 0.93 +/- 0.51. The correlation coefficient between the results obtained by the two different collection methods was 0.87. Age-related reference values in filter-paper samples are also reported. The concentrations, which are normalized to urinary creatinine, decrease with age. This method is applicable to rapid screening for urea cycle disorders and may also be used for carrier testing of ornithine transcarbamylase deficiency.
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AVAKYAN, S. V., E. P. ANDREEV, I. M. AFANAS'EV, N. B. LEONOV, M. L. LEBEDINSKAYA, A. V. SAVUSHKIN, A. E. SEROVA, E. V. KUVALDIN, and N. A. VORONIN. "A SPACE SOLAR PATROL APPARATUS FOR PHOTOMETRIC MEASUREMENTS AT A PHOTON-ENERGY RANGE OF 8 eV TO 8 keV." Surface Review and Letters 09, no. 01 (February 2002): 491–96. http://dx.doi.org/10.1142/s0218625x02002531.
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At the Vavilov State Optical Institute (SOI) a special apparatus and a methodology have been developed which enable one to measure absolute fluxes from the full disk of the Sun in the VUV, the EUV and the soft X-ray spectral ranges (0.14–157 nm). The apparatus allows one to carry out absolute spectral measurements using simultaneous operation of the radiometer and spectrometers. The radiometer is equipped with a special disk on which several filters are fitted (foils, thin films and crystals). This enables one to carry out measurements in the spectral range of 0.14–157 nm. The EUV grating spectrometer with normal incidence provides five spectral channels with a channel width of 35 nm each for measurements in the spectral range under 155 nm. The spectral range of 1.8–60 nm can be covered by a soft X-ray grazing grating spectrometer. All instruments are equipped with the same detectors, namely with the open secondary electron multipliers (SEM) with photocathodes made of BeO which were developed at the SOI. This photocathode has a good sensitivity in the spectral range under 150 nm and its sensitivity falls practically down to zero at wavelengths greater than 160 nm. The SEM has a high amplification (up to 108) and is stable to atmospheric influence. The stability of the SEM could be controlled by the radiation of the isotope 55 Fe (0.2 nm). There are plans to use this complex for mutual calibration of various synchrotron sources. Moreover it is planned to launch the Space Solar Patrol mission at the Russian Module of the International Space Station.
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Buchardt, Bjørn, and Marianne Vasard Nielsen. "Comparison of organic geochemical and palynofacies methods: Example from the Upper Triassic Gassum Formation in Denmark." Bulletin of the Geological Society of Denmark 38 (February 19, 1991): 267–77. http://dx.doi.org/10.37570/bgsd-1990-38-23.
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Copenhagen, February 19th, 1991. Disseminated organic matter from the · Upper Triassic to Lower Jurassic Gassum Formation in the Gassum-1 deep well has been analyzed by palynological and organic geochemical methods. Tue paper compares the effects of the different preparation methods on the organic matter. The kerogen isolation process (demineralisation by HF) is found to cause major changes in the Rock-Eva! parameters, but not in carbon isotope composition of organic matter. Tm.,- and HI-values determined from kerogen concentrates are more consistent with the palynofacies data than those determined from whole rock samples. The differences are ascribed to analytical problems when dealing with low-TOC whole rock samples. Palynofacies data obtained from unfiltered and filtered kerogen concentrates demonstrate a variable loss of amorphous organic matter during filtration ( up to 1()()%). Other palynomorph distributions are not seriously affected by filtration. The loss in amorphous organic matter has no influence on the Rock-Eva! data and carbon isotope composition. Comparison of polynofacies and carbon isotope data identifies three organic matter sources with characteristic isotopic composition.
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Savard, Martine M., Amanda S. Cole, Robert Vet, and Anna Smirnoff. "The Δ<sup>17</sup>O and <i>δ</i><sup>18</sup>O values of atmospheric nitrates simultaneously collected downwind of anthropogenic sources – implications for polluted air masses." Atmospheric Chemistry and Physics 18, no. 14 (July 20, 2018): 10373–89. http://dx.doi.org/10.5194/acp-18-10373-2018.
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Abstract. There are clear motivations for better understanding the atmospheric processes that transform nitrogen (N) oxides (NOx) emitted from anthropogenic sources into nitrates (NO3-), two of them being that NO3- contributes to acidification and eutrophication of terrestrial and aquatic ecosystems, and particulate nitrate may play a role in climate dynamics. For these reasons, oxygen isotope delta values (δ18O, Δ17O) are frequently applied to infer the chemical pathways leading to the observed mass-independent isotopic anomalies from interaction with 17O-rich ozone (O3). Recent laboratory experiments suggest that the isotopic equilibrium between NO2 (the main precursor of NO3-) and O3 may take long enough under certain field conditions that nitrates may be formed near emission sources with lower isotopic values than those formed further downwind. Indeed, previously published field measurements of oxygen isotopes in NO3- in precipitation (wNO3-) and in particulate (pNO3-) samples suggest that abnormally low isotopic values might characterize polluted air masses. However, none of the air studies have deployed systems allowing collection of samples specific to anthropogenic sources in order to avoid shifts in isotopic signature due to changing wind directions, or separately characterized gaseous HNO3 with Δ17O values. Here we have used a wind-sector-based, multi-stage filter sampling system and precipitation collector to simultaneously sample HNO3 and pNO3-, and co-collect wNO3-. The nitrates are from various distances (<1 to >125 km) downwind of different anthropogenic emitters, and consequently from varying time lapses after emission. The separate collection of nitrates shows that the HNO3 δ18O ranges are distinct from those of w- and pNO3-. Interestingly, the Δ17O differences between pNO3- and HNO3 shift from positive during cold sampling periods to negative during warm periods. The low pNO3-Δ17O values observed during warm periods may partly derive from the involvement of 17O-depleted peroxy radicals (RO2) oxidizing NO during that season. Another possibility is that nitrates derive from NOx that has not yet reached isotopic equilibrium with O3. However, these mechanisms, individually or together, cannot explain the observed pNO3 minus HNO3 isotopic changes. We propose differences in dry depositional rates, faster for HNO3, as a mechanism for the observed shifts. Larger proportions of pNO3- formed via the N2O5 pathway would explain the opposite fall–winter patterns. Our results show that the separate HNO3, wNO3- and pNO3- isotopic signals can be used to further our understanding of NOx oxidation and deposition. Future research should investigate all tropospheric nitrate species as well as NOx to refine our understanding of nitrate distribution worldwide and to develop effective emission reduction strategies.
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He, Baofeng, Haibo Zheng, Ruizhao Yang, and Zhaoyao Shi. "Study on the Performances of an Approximating Spline Filter Based on the ADRF Function in Surface Roughness Evaluation." Applied Sciences 11, no. 2 (January 14, 2021): 761. http://dx.doi.org/10.3390/app11020761.
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Isotropy is an important feature of an area filter in the three-dimensional surface roughness evaluation. First, the transmission characteristic deviation between the approximating spline filter and the Gaussian filter is reduced by cascading approximating. Second, the approximating spline filter is superimposed on the orthogonal direction to obtain an isotropic areal filter. Then, four direct methods for the solving approximating spline matrix are applied. Based on the profile filtering and areal filtering, the computational efficiency and accuracy are compared. The experimental results show that the improved square root method (LDLT decomposition) combines both computational efficiency and filtering precision, and is a good choice for solving the approximating spline matrix. Finally, six kinds of robust approximating spline filters are constructed. Taking the output value of robust Gaussian regression filter (RGRF) as reference, and the honing profile and step surface with deep valley characteristics were used as test surfaces to compare their robustness and iteration time. The experimental results show that the approximating spline filter based on the ADRF function has the shortest iteration times, while its roughness is close to the robust Gaussian regression filter.
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Huang, Lin, Wendy Zhang, Guaciara M. Santos, Blanca T. Rodríguez, Sandra R. Holden, Vincent Vetro, and Claudia I. Czimczik. "Application of the ECT9 protocol for radiocarbon-based source apportionment of carbonaceous aerosols." Atmospheric Measurement Techniques 14, no. 5 (May 17, 2021): 3481–500. http://dx.doi.org/10.5194/amt-14-3481-2021.
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Abstract. Carbonaceous aerosol is mainly composed of organic carbon (OC) and elemental carbon (EC). Both OC and EC originate from a variety of emission sources. Radiocarbon (14C) analysis can be used to apportion bulk aerosol, OC, and EC into their sources. However, such analyses require the physical separation of OC and EC. Here, we apply of ECT9 protocol to physically isolate OC and EC for 14C analysis and evaluate its effectiveness. Several reference materials are selected, including two pure OC (fossil “adipic acid” and contemporary “sucrose”), two pure EC (fossil “regal black” and “C1150”), and three complex materials containing contemporary and/or fossil OC and EC (“rice char”, NIST urban dust standards “SRM1649a” and “SRM8785”, i.e., fine fraction of resuspended SRM1649a on filters). The pure materials were measured for their OC, EC, and total carbon (TC) mass fractions and corresponding carbon isotopes to evaluate the uncertainty of the procedure. The average accuracy of TC mass, determined via volumetric injection of a sucrose solution, was approximately 5 %. Ratios of EC/TC and OC/TC were highly reproducible, with analytical precisions better than 2 % for all reference materials, ranging in size from 20 to 100 µg C. Consensus values were reached for all pure reference materials for both δ13C and fraction modern (F14C), with an uncertainty of < 0.3 ‰ and approximately 5 %, respectively. The procedure introduced 1.3 ± 0.6 µg of extraneous carbon, an amount compatible to that of the Swiss_4S protocol. In addition, OC and EC were isolated from mixtures of pure contemporary OC (sucrose) with pure fossil EC (regal black) and fossil OC (adipic acid) with contemporary EC (rice char EC) to evaluate the effectiveness of OC and EC separation. Consensus F14C values were reached for all OC (∼ 5–30 µg) and EC (∼ 10–60 µg) fractions with an uncertainty of ∼ 5 % on average. We found that the ECT9 protocol efficiently isolates OC or EC from complex mixtures. Based on δ13C measurements, the average contribution of charred OC to EC is likely less than 3 % when the OC loading amount is less than 30 µg C. Charring was further assessed by evaluating thermograms of various materials, including aerosol samples collected in the Arctic and from tailpipes of gasoline or diesel engines. These data demonstrate that the ECT9 method effectively removes pyrolyzed OC. Thus, the ECT9 protocol, initially developed for concentration and stable isotope measurements of OC and EC, is suitable for 14C-based apportionment studies, including µg C-sized samples from arctic environments.
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Gonnella, Nina, Mengfen Lin, Michael J. Shapiro, James R. Wareing, and Xiaolu Zhang. "Isotope-Filtered Affinity NMR." Journal of Magnetic Resonance 131, no. 2 (April 1998): 336–38. http://dx.doi.org/10.1006/jmre.1997.1376.
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Hobson, Keith A., Mark L. Gloutney, and H. Lisle Gibbs. "Preservation of blood and tissue samples for stable-carbon and stable-nitrogen isotope analysis." Canadian Journal of Zoology 75, no. 10 (October 1, 1997): 1720–23. http://dx.doi.org/10.1139/z97-799.
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Researchers engaged in collecting animal material for stable-carbon and stable-nitrogen isotope analysis are frequently faced with the need to preserve tissues prior to transportation to the laboratory. In many cases, freezing is not possible in the field, so we investigated the potential of several techniques for preserving tissues for this purpose. We also included preservation techniques used for DNA analyses in order to evaluate how they might alter δ13C and δ15N values in tissues and, ultimately, whether archived DNA samples could be used for stable-isotope assay. Tissues included blood and pectoral muscle from quail (Coturnix coturnix japonica) and blood from sheep (Ovis aries). Preservation techniques for blood included freeze-drying (control), drying on precombusted glass-fibre filter paper, and storing in 70% ethanol, 10% buffered formalin, ABI lysis buffer, and Queen's lysis buffer. After 8 weeks, the use of both lysis buffers and formalin resulted in significant depletion of 13C and 15N in blood. Values for samples dried on glass-fibre filter paper or stored in 70% ethanol did not differ significantly from those for the control. Muscle tissue was freeze-dried (control) or stored in 70% ethanol, 10% buffered formalin, or DMSO solution. Both the DMSO and formalin treatments resulted in significant depletion of 13C and 15N compared with the control. Only the 70% ethanol treatment did not result in changes to either isotope ratio in muscle. Where freezing is not possible, we recommend that blood samples be dried or stored in 70% ethanol. Our study provides an estimate of isotopic correction factors that may be applied to tissues archived for DNA analysis or stored in formalin.
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Chen, Guo, Karl Auerswald, and Hans Schnyder. "<sup>2</sup>H and <sup>18</sup>O depletion of water close to organic surfaces." Biogeosciences 13, no. 10 (June 1, 2016): 3175–86. http://dx.doi.org/10.5194/bg-13-3175-2016.
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Abstract. Hydrophilic surfaces influence the structure of water close to them and may thus affect the isotope composition of water. Such an effect should be relevant and detectable for materials with large surface areas and low water contents. The relationship between the volumetric solid : water ratio and the isotopic fractionation between adsorbed water and unconfined water was investigated for the materials silage, hay, organic soil (litter), filter paper, cotton, casein and flour. Each of these materials was equilibrated via the gas phase with unconfined water of known isotopic composition to quantify the isotopic difference between adsorbed water and unconfined water. Across all materials, isotopic fractionation was significant (p<0.05) and negative (on average −0.91 ± 0.22 ‰ for 18∕16O and −20.6 ± 2.4 ‰ for 2∕1H at an average solid : water ratio of 0.9). The observed isotopic fractionation was not caused by solutes, volatiles or old water because the fractionation did not disappear for washed or oven-dried silage, the isotopic fractionation was also found in filter paper and cotton, and the fractionation was independent of the isotopic composition of the unconfined water. Isotopic fractionation became linearly more negative with increasing volumetric solid : water ratio and even exceeded −4 ‰ for 18∕16O and −44 ‰ for 2∕1H. This fractionation behaviour could be modelled by assuming two water layers: a thin layer that is in direct contact and influenced by the surface of the solid and a second layer of varying thickness depending on the total moisture content that is in equilibrium with the surrounding vapour. When we applied the model to soil water under grassland, the soil water extracted from 7 and 20 cm depth was significantly closer to local meteoric water than without correction for the surface effect. This study has major implications for the interpretation of the isotopic composition of water extracted from organic matter, especially when the volumetric solid : water ratio is larger than 0.5 or for processes occurring at the solid–water interface.
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Perga, Marie-Elodie, Martin Kainz, and Asit Mazumder. "Terrestrial carbon contribution to lake food webs: could the classical stable isotope approach be misleading?" Canadian Journal of Fisheries and Aquatic Sciences 65, no. 12 (December 2008): 2719–27. http://dx.doi.org/10.1139/f08-172.
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Carbon stable isotope analyses have been widely used to estimate terrestrial carbon contribution to lake secondary production. In such approaches, phytoplankton is tacitly assumed as a single, isotopically homogenous source. Such assumption might be valid if (i) zooplankton do not feed selectively on specific algal taxa within bulk phytoplankton, or (ii) although zooplankton do feed selectively, the variability in the δ13C values amongst the different algal taxa is small compared with the variability between the δ13C values of bulk phytoplankton and terrestrial end-members. In a summer field study of six coastal lakes of British Columbia, Canada, we tested these assumptions using gut pigments and stable isotope measures on zooplankton and particulate organic matter. Results revealed that filter-feeding cladocerans positively selected cryptophytes, shown to be substantially 13C-enriched compared with bulk phytoplankton and even with the terrestrial end-member. Comparing a classical two-source mixing model and a model that accounted for algal isotopic heterogeneity, we showed that the use of a classical two-source model can result in an overestimation of terrestrial contribution to zooplankton secondary production.