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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.
1

Quantitative basis for component factors of gas flow proportional counting efficiencies

Nichols, Michael 21 August 2009 (has links)
Counting efficiencies were determined by empirical measurement and Monte Carlo simulation for carbon-14, strontium-89, strontium-90, and yttrium-90 standards counted by low-background gas flow proportional counter for strontium carbonate precipitates in the range from 3 to 33 mg cm⁻². The maximum beta particle energies range from 0.156 MeV for carbon-14 to 2.28 MeV for yttrium-90. The parameters for estimating the counting efficiency are summarized for sources with areal thickness of 14 mg cm⁻² and over the range in strontium carbonate areal thickness from 0.1 mg cm⁻² to 33 mg cm⁻². Uncertainty budgets providing estimates of the uncertainty, sources of variability in the calibration process, and the total expanded uncertainty are presented. Information is presented for the Monte Carlo simulation regarding the composition of the detector window, the energy excluded by the amplifier discriminator of the counting system, and the physical density of materials for this analytical process. The histogram normalization routine implemented within MCNP is described and found to bias the probability distribution for beta-particle energy spectra. The difference in the specification of the probability distribution for beta-particle energy spectra in ICRU 56 Appendix D and MCNP requirements are described and a correction for the bias introduced during the normalization process for beta spectra is provided. Counting efficiencies determined by empirical measurement and Monte Carlo simulations agree within the total expanded uncertainties of the measurements and the uncertainties of the Monte Carlo simulations.
2

A method for traceable protein quantification using isotope dilution ICP-MS and its application on the tau protein

Lemke, Nora 19 August 2022 (has links)
In dieser Arbeit wurde ein Verfahren zur rückführbaren Proteinquantifizierung unter Verwendung von Schwefelisotopenverdünnung mit induktiv gekoppelter Plasmamassenspektrometrie (ID-ICP-MS) entwickelt. Die Methode dient zur zuverlässigen Quantifizierung laborinterner Proteinstandards. Sie eignet sich nur zur Analyse reiner Proteine, deren Stöchiometrie bekannt ist, da die Proteinkonzentration aus dem Schwefelgehalt bestimmt wird. Nicht proteingebundener Schwefel wird durch Membranfiltration von der Proteinfraktion abgetrennt und mit ID-ICP-MS quantifiziert. Der Gesamtschwefelgehalt in der Probe wird ebenfalls mittels ID-ICP-MS quantifiziert und um die Menge an ungebundenem Schwefel korrigiert. Die Optimierung der Probenvorbereitung zeigte, dass ein Aufschluss die Unsicherheit des Ergebnisses verbessert. Für die Methodenentwicklung wurden ein zertifiziertes Rinderserumalbumin-Referenzmaterial (BSA), sowie ein kommerzielles Avidin verwendet. Die Bestimmung der Proteinmassenfraktionen und Unsicherheitsbudgets erfolgte nach Korrektur für den ungebundenen Schwefel (0,4 % für BSA, 30 % für Avidin). Die Methode wurde auf das Tau-Protein angewendet, das ein Biomarker für die sogenannten „Tauopathien“ ist – eine Gruppe neurodegenerativer Krankheiten, die die Alzheimer-Krankheit und die frontotemporale Demenz einschließen. Durch Verwendung eines isotopenangereicherten Spikes, der an das SI-System angebunden ist, wurde die metrologische Rückführbarkeit für den Massenanteil des Tau-Proteins erreicht. Dieser Tau-Standard wurde zur absoluten Quantifizierung toxischer transgener Tau-Spezies in der löslichen Hirnfraktion transgener Mäuse verwendet. Die entwickelte Methode ist für die rückführbare Quantifizierung von Proteinen zur Verwendung als Standards in der biologischen und medizinischen Forschung anwendbar. Sie zeigte eine ähnliche Präzision wie etablierte Verfahren, erforderte jedoch weniger Probenvorbereitung und keine spezies-spezifischen Standards. / In this work, a method for traceable protein quantification using sulphur isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) was developed. The method is intended for the reliable quantification of in-house protein standards. It is only suited for pure protein formulations for proteins of known stoichiometry because the protein concentration is determined from the sulphur content. Non-protein bound sulphur is separated from the protein fraction by membrane filtration and is quantified by ID-ICP-MS. The total sulphur content in the sample is as well quantified by ID-ICP-MS and corrected for the amount of non-protein bound sulphur. Optimisation of the sample preparation showed that digestion improves the uncertainty of the result. For method development, a certified reference material bovine serum albumin (BSA) and a commercial avidin were used. The protein mass fractions with full uncertainty budgets were determined after correction for unbound sulphur. The developed procedure was applied to the tau protein, which is a biomarker fort he so-called „tauopathies“ – a group of neurodegenerative diseases including Alzheimer’s disease and Frontotemporal dementia. By employing an isotopically enriched spike, which is linked to the SI system, full metrological traceability was achieved for the tau mass fraction. The mass fraction of (0.328 ± 0.036) g kg-1 for tau was determined by ID-ICP-MS and confirmed by amino acid analysis. This tau standard was used for the absolute quantification of toxic transgenic tau species in the soluble brain fraction of transgenic mice. The developed method is applicable for the traceable quantification of proteins for use as standards in biological and medical research. The precision of the method was similar to established absolute protein quantification procedures while requiring less sample preparation and no species-specific standards.

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