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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Stable carbon isotope ratio of polycyclic aromatic hydrocarbons (PAHs) in the environment: validation of isolation and stable carbon isotope analysis methods

Kim, Moon Koo 15 November 2004 (has links)
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, toxic contaminants that are released to the environment from various petrogenic and pyrogenic sources. In an effort to more clearly identify and trace sources of PAHs in the environment, purification and compound specific isotope analysis methods were developed to accurately measure the stable carbon isotope ratio of individual PAHs. Development of the method included improving accuracy and precision of the isotopic measurement by producing highly pure extracts using various chromatographic techniques. The method was refined by improving compound separations using purification techniques and high resolution chromatographic columns. The purification method consists of alumina/silica gel column chromatography, gel permeation chromatography and thin layer chromatography. The mean recovery of PAHs after the purification procedure was approximately 80 %. Sample purities after purification were verified by GC/FID and full scan mass spectrometry. To better resolve peaks and provide more accurate stable carbon isotope measurements, various gas chromatographic conditions were evaluated. The precision of the method ranged between 0.08 and 0.43 . The analytical protocols were evaluated to confirm compositional and stable isotopic integrity during purification and stable isotopic analysis. To confirm the utility of the purification and isotope analysis methods, various environmental samples from marine, land and lacustrine environments were analyzed. The isolates were analyzed for the composition and the stable carbon isotope ratios of PAHs. The stable carbon isotope ratio was measured by GC/IRMS and the results, along with quantitative compound compositions, were used to characterize and identify the contaminant sources. The sources of the PAHs in the study areas were differentiated by PAH molecular ratios and confirmed by stable carbon isotope ratios. This study confirms that compound specific isotope analysis of pollutants by GC/IRMS can be used to identify PAH sources in environmental samples. The study also confirms that the purification and stable carbon isotope analysis methods that were developed can be used to accurately measure the stable carbon isotope ratios of PAHs in environmental samples for the purpose of source identification. GC/IRMS measurement of stable isotopic compositions can be an effective fingerprinting method when used in conjunction with traditional molecular composition methods.
12

Isotope selective analysis of CO2 with tunable diode laser (TDL) spectroscopy in the NIR

Hörner, Gerald, Lau, Steffen, Kantor, Zoltan, Löhmannsröben, Hans-Gerd January 2004 (has links)
The performance of a home-built tunable diode laser (TDL) spectrometer, aimed at multi-line detection of carbon dioxide, has been evaluated and optimized. In the regime of the (30<SUP>0</SUP>1)<SUB>III</SUB> / (000) band of <SUP>12</SUP>CO<SUB>2</SUB> around 1.6 μm, the dominating isotope species <SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, and <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O were detected simultaneously without interference by water vapor. Detection limits in the range of few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. High sensitivity in conjunction with high precision —typically ±1‰ and ±6‰ for 3% and 0.7% of CO<SUB>2</SUB>, respectively— renders this experimental approach a promising analytical concept for isotope-ratio determination of carbon dioxide in soil and breath gas. For a moderate <SUP>12</SUP>CO<SUB>2</SUB> line, the pressure dependence of the line profile was characterized in detail, to account for pressure effects on sensitive measurements.
13

加速器質量分析計を用いた鉄製遺物の14C年代測定に関する基礎研究

NAKAMURA, Toshio, KONDO, Hiroki, 中村, 俊夫, 近藤, 宏樹 03 1900 (has links)
名古屋大学年代測定総合研究センターシンポジウム報告
14

Stable carbon isotope ratio of polycyclic aromatic hydrocarbons (PAHs) in the environment: validation of isolation and stable carbon isotope analysis methods

Kim, Moon Koo 15 November 2004 (has links)
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, toxic contaminants that are released to the environment from various petrogenic and pyrogenic sources. In an effort to more clearly identify and trace sources of PAHs in the environment, purification and compound specific isotope analysis methods were developed to accurately measure the stable carbon isotope ratio of individual PAHs. Development of the method included improving accuracy and precision of the isotopic measurement by producing highly pure extracts using various chromatographic techniques. The method was refined by improving compound separations using purification techniques and high resolution chromatographic columns. The purification method consists of alumina/silica gel column chromatography, gel permeation chromatography and thin layer chromatography. The mean recovery of PAHs after the purification procedure was approximately 80 %. Sample purities after purification were verified by GC/FID and full scan mass spectrometry. To better resolve peaks and provide more accurate stable carbon isotope measurements, various gas chromatographic conditions were evaluated. The precision of the method ranged between 0.08 and 0.43 . The analytical protocols were evaluated to confirm compositional and stable isotopic integrity during purification and stable isotopic analysis. To confirm the utility of the purification and isotope analysis methods, various environmental samples from marine, land and lacustrine environments were analyzed. The isolates were analyzed for the composition and the stable carbon isotope ratios of PAHs. The stable carbon isotope ratio was measured by GC/IRMS and the results, along with quantitative compound compositions, were used to characterize and identify the contaminant sources. The sources of the PAHs in the study areas were differentiated by PAH molecular ratios and confirmed by stable carbon isotope ratios. This study confirms that compound specific isotope analysis of pollutants by GC/IRMS can be used to identify PAH sources in environmental samples. The study also confirms that the purification and stable carbon isotope analysis methods that were developed can be used to accurately measure the stable carbon isotope ratios of PAHs in environmental samples for the purpose of source identification. GC/IRMS measurement of stable isotopic compositions can be an effective fingerprinting method when used in conjunction with traditional molecular composition methods.
15

Untersuchungen zur anwendung der isotopenrelations-technik bei nachbestrahlungsuntersuchungen und der uberwachung von spaltstoffen

MARZO, MARCO A.S. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:28:35Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:02Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IEA/T / Universidade Karlsruhe, Alemanha
16

Analise multielementar e isotopica em compostos de uranio por espectrometria de massa com fonte de plasma induzido ( ICPMS )

OLIVEIRA JUNIOR, OLIVIO P. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:44:24Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:23Z (GMT). No. of bitstreams: 1 06890.pdf: 3271433 bytes, checksum: 57399ce5f630231a9b2741455ed096f0 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
17

Uso da monitoracao ambiental como tecnica de identificacao de atividades de enriquecimento isotopico

BUCHMANN, JOSE H. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:44:34Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:11Z (GMT). No. of bitstreams: 1 06861.pdf: 8656275 bytes, checksum: 33d75be9bc7f27a315785b762567f56c (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
18

Contribuicao ao estudo da evaporacao de aguas naturais por meio de isotopos estaveis

TAKAKI, T. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:50:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:03Z (GMT). No. of bitstreams: 1 00385.pdf: 917455 bytes, checksum: 170691f120f1bd5b66fa48cba02fe1f6 (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
19

Aplicação de redes neurais artificiais na caracterização isotópica de tambores de rejeito radioativo

POTIENS JUNIOR, ADEMAR J. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:51:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:15Z (GMT). No. of bitstreams: 1 11135.pdf: 7189578 bytes, checksum: 2301b9d209a5d40ecb7cb637fe73b0f8 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
20

Determinacao da razao isotopica sup235U/sup238U em UFsub6 usando espectrometria de massa por quadrupolo

KUSAHARA, HELENA S. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:30:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:38Z (GMT). No. of bitstreams: 1 01293.pdf: 1218457 bytes, checksum: 4fc6334de8505695e9783162eebf4a08 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Energia Atomica - IEA

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