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  • 1
    Electronic Resource
    Electronic Resource
    Determination of Silver in Minerals and Ores by Neutron Activation Analysis and High Resolution Gamma Spectrometry. (1966)
    s.l. : American Chemical Society
    Analytical chemistry 38 (1966), S. 432-434 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60235a014
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  • 2
    Electronic Resource
    Electronic Resource
    Radioactive Determination of the Relative Abundance of the Isotope K40 in Terrestrial and Meteoritic Potassium1 (1941)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 63 (1941), S. 1203-1205 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01850a012
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  • 3
    Electronic Resource
    Electronic Resource
    Application of stable isotopes in environmental tracer studies – Measurement of monomethylmercury (CH3Hg+) by isotope dilution ICP-MS and detection of species transformation (1997)
    Springer
    Fresenius' journal of analytical chemistry 358 (1997), S. 378-385 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The monovalent cation monomethylmercury (CH3Hg+) was determined in certified reference materials by isotope dilution GC/ICP-MS and good agreement between measured and certified values has been found. The use of enriched stable isotopes with subsequent detection by ICP-MS is a powerful tracer technique to study dynamic environmental processes. For the first time, it was possible to monitor opposite processes like Hg2+ methylation and CH3Hg+ demethylation at ambient tracer levels simultaneously in the same sample. A scheme for calculating the formation of new species from stable tracers used in environmental studies is presented. The sensitivity of stable tracer methods is superior to traditional tracer or radiotracer techniques. In case of mercury methylation, where the generation of a new compound is monitored, the limit of detection depends only on the precision of the isotope ratio measurements and the concentration of the ambient CH3Hg+ already present in the sample, not on the absolute detection limit of the GC/ICP-MS technique used for analyzing CH3Hg+. A 0.25% change in concentration of CH3Hg+ is detectable. In the case of CH3Hg+ demethylation, where the decrease of the added tracer is monitored, the detection limit again depends on the precision of the isotope ratio measurement and the ambient CH3Hg+ concentration but additionally on the amount of the added tracer as well. A decrease in the CH3Hg+ level of 2% of the added tracer is detectable. The validity of the calculation scheme was tested and no difference was found between individually measured isotope concentrations and calculated concentrations from solutions with multiple stable tracers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050433
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of artifactual formation of monomethylmercury (CH3Hg+) in environmental samples using stable Hg2+ isotopes with ICP-MS detection: Calculation of contents applying species specific isotope addition (1997)
    Springer
    Fresenius' journal of analytical chemistry 358 (1997), S. 363-370 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Various extraction techniques, as distillation, acid and alkaline extraction, have been tested with regard to their potential to form a monomethylmercury (CH3Hg+) artifact from inorganic Hg during sample preparation. Hg2+ has been added to different reference materials in the form of enriched stable tracers and the formation of new methylmercury from that tracer has been analyzed by HPLC/ICP-MS and GC/ICP-MS. Both techniques gave comparable results. In particular, the distillation technique was prone to artifact formation. The resulting overestimation of methylmercury in sediments was as high as 80%. Artifact formation in hair, liver and algae samples was less significant, though still observable. Fish muscle tissue showed no artifact formation upon distillation, but some of the inorganic tracer was converted to methylmercury during alkaline extraction. Acid extraction of sediments resulted in low artifact formation rates. Fractionated measurements of sediment distillates revealed high methylmercury formation rates towards the end of the distillation process when acid concentrations in the solution are highest. A technique for correction of the measured apparent methylmercury content applying species specific isotope addition (SSIA) is proposed and the calculation scheme is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050431
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of elevated carbon dioxide on green leaf tissue and leaf litter quality in an intact Mojave Desert ecosystem (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The effects of elevated carbon dioxide (CO2) on plant litter are critical determinants of ecosystem feedback to changing atmospheric CO2 concentrations. We measured concentrations of nitrogen (N) and carbon (C) and calculated C : N ratios of green leaves of two desert perennial shrubs, and the same quality parameters plus lignin and cellulose content of leaf litter from four shrub species exposed to elevated CO2 (FACE technology; Hendrey & Kimball, 1994) for 3 years in an intact Mojave Desert ecosystem. Shrubs tested were Larrea tridentata, Lycium pallidum, Lycium andersonii and Ambrosia dumosa. We calculated resorption efficiency from green tissue and leaf litter N data and measured lignin and cellulose content in litter in the last year study. Green leaves of L. tridentata grown under elevated CO2 had significantly lower N concentrations and higher C : N ratios than shrubs grown in ambient conditions in 1999 (P 〈 0.05). Lycium pallidum green leaves grown under elevated CO2 had significantly lower N concentrations and higher C : N ratios than shrubs grown under ambient conditions in 2000 (P 〈 0.05). There was no CO2 effect on C content of either species. We found no effect of CO2 on N or C content, C : N ratios, or lignin or cellulose concentrations in leaf litter of L. tridentata, L. pallidum, L. andersonii, or A. dumosa. There was no significant effect of CO2 on estimates of shrub resorption efficiency. There was a seasonal effect on green tissue and litter tissue quality for L. tridentata, with lower tissue N content in summer than in spring or winter months. These data suggest that any productivity increases with elevated CO2 in desert ecosystems may not be limited by lower leaf litter quality and that resorption efficiency calculations are best performed on an individual leaf basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00608.x
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  • 6
    Electronic Resource
    Electronic Resource
    Poisson's Ratio and Related Properties for Compounded Rubber. (1923)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 15 (1923), S. 1015-1018 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie50166a011
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  • 7
    Electronic Resource
    Electronic Resource
    Nitrogen isotope composition of tomato (Lycopersicon esculentum Mill. cv. T-5) grown under ammonium or nitrate nutrition (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Studies that quantify plant δ15N often assume that fractionation during nitrogen uptake and intra-plant variation in δ15N are minimal. We tested both assumptions by growing tomato (Lycopersicon esculetum Mill. cv. T-5) at NH4+ or NO−3 concentrations typical of those found in the soil. Fractionation did not occur with uptake; whole-plant δ15N was not significantly different from source δ15 N for plants grown on either nitrogen form. No intra-plant variation in δ15N was observed for plants grown with NH+4. In contrast. δ15N of leaves was as much as 5.8% greater than that of roots for plants grown with NO−3. The contrasting patterns of intra-plant variation are probably caused by different assimilation patterns. NH+4 is assimilated immediately in the root, so organic nitrogen in the shoot and root is the product of a single assimilation event. NO−3 assimilation can occur in shoots and roots. Fractionation during assimilation caused the δ15N of NO−3 to become enriched relative to organic nitrogen; the δ15N of NO−3 was 11.1 and 12.9% greater than the δ15N of organic nitrogen in leaves and roots, respectively. Leaf δ15N may therefore be greater than that of roots because the NO−3 available for assimilation in leaves originates from a NO−3 pool that was previously exposed to nitrate assimilation in the root.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00010.x
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  • 8
    Electronic Resource
    Electronic Resource
    Osmotic relations of the drought-tolerant shrub Artemisia tridentata in response to water stress (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Turgor maintenance, solute content and recovery from water stress were examined in the drought-tolerant shrub Artemisia tridentata. Predawn water potentials of shrubs receiving supplemental water remained above −2 MPa throughout summer, while predawn water potentials of untreated shrubs decreased to −5 MPa. Osmotic potentials decreased in conjunction with water potentials maintaining turgor pressures above 0 MPa. The decreases in osmotic potentials were not the result of osmotic adjustment (i.e. solute accumulation). Leaf solute contents decreased during drought, but leaf water volumes decreased more than 75% from spring to summer, thereby passively concentrating solutes within the leaves. The maintenance of positive turgor pressures despite decreases in leaf water volumes is consistent with other studies of species with elastic cell walls. Inorganic ion, organic acid, and carbohydrate contents of leaves declined during drought. The only solutes accumulating in leaves of A. tridentata with water stress were proline and a cyclitol, both considered compatible solutes. Total and osmotic potentials recovered rapidly following rewatering of shrubs; solute contents did not change except for a decrease in proline. Maintaining turgor through the passive concentration of solutes may be advantageous compared to synthesis of new solutes for osmotic adjustment in arid environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb01457.x
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of nitrogen source and concentration on nitrogen isotopic discrimination in two barley genotypes (Hordeum vulgare L.) (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The occurrence of nitrogen isotope discrimination with absorption and assimilation of nitrate (NO3–) and ammonium (NH4+) was investigated using two genotypes of barley, Hordeum vulgare L. cv. Steptoe and Az12 : Az70, the latter of which lacks the characterized nitrate reductase isozymes. Plants were grown under two situations: a closed system with limited nitrogen or an open system with unlimited nitrogen, to elucidate the conditions and processes that influence discrimination. There was no discrimination observed for Az12 : Az70 when supplied with limited nitrogen. Discrimination was observed for Steptoe seedlings at high external NO3– concentrations, but not with low NO3– when assimilation is probably rapid and complete. The same pattern was observed for Steptoe when NH4+ was supplied; indicating that for both nitrogen forms discrimination is dependent upon the presence of the assimilatory enzyme and the external concentration. The implications of this study are that both internal (assimilatory enzyme distribution) and external (source concentration) factors may have a larger impact on tissue δ 15N than the form of nitrogen utilized. This suggests that tissue δ 15N may not always be a reliable indicator of a plant's integrated nitrogen nutrition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2003.01066.x
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  • 10
    Electronic Resource
    Electronic Resource
    Rehydration-induced changes in pressure-volume relationships of Artemisia tridentata Nutt. ssp. tridentata (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Pressure-volume measurements were made on Artemisia tridentata Nutt. ssp. tridentata samples rehydrated for 0, 1.5, 3, 6 or 24 h. Increasing rehydration time caused a significant increase in osmotic potential at turgor loss, cell elasiticity, and the relative water content at turgor loss, and a significant decrease in pressure potential at saturation. Osmotic potential at saturation was changed significantly by rehydration, but no consistent trend was observed. The symplastic water fraction did not differ significantly among treatments. The increase in the osmotic potential at turgor loss did not correspond with decreasing cell elasticity or synthesis of solutes. Instead, the leaf solute content remained constant suggesting a redistribution of solutes between the symplast and apoplast. Using non-rehydrated samples for pressure-volume analysis introduced errors in estimates of the symplastic water fraction, osmotic potential at full turgor, and the relative water content at turgor loss. These errors are due to uncertainties in the determination of saturated weights.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1990.tb01322.x
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