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[en] The doctoral thesis explains methods and experiments for post-factum detection of radiation-induced alterations of DNA. There are various manifestations of such alterations. Ionizing radiation can directly alter the bases and/or sugar component, or can indirectly induce DNA damage by way of forming water radicals. Both mechanisms result in base derivatives, released for some part from the DNA strand, or formed by alterations of the 2-deoxyribose, inducing strand breaks ( single and double strand breaks). The first part of the thesis explains the approach applying GC-MS for detection of radiation-induced base derivatives, using herring sperm DNA as a model DNA. Some typical types of base derivatives were identified (thymine glycol, 5-hydroxycytosine).Some base derivatives were also found in DNA samples derived from poultry meat. These base derivatives are known to be indicators of food processing with ionizing radiation, but surprisingly were also found in non-irradiated controls, although in minor amounts. The second part discusses the identification of strand breaks applying the pused-field gel electrophoresis. This method is capable of producing evidence that irradiation markedly enhances the short-chain DNA molecules as compared to non-irradiated controls. DNA molecules of a size of approx. 2.2 million base pairs are almost completely broken into short-chain fragments. The method reliably detects radiation treatments down to 1500 Gy, even if applied long ago. (orig./MG)
[de]
Die vorliegende Arbeit ist ein Versuch, strahlenbehandelte Lebensmittel ueber Veraenderungen an der DNA nachzuweisen. Diese Veraenderungen koennen sich unterschiedlich manifestieren. Zum einen koennen die ionisierenden Strahlen direkt die Basen und/oder die Zuckerkomponente veraendern. Zum anderen koennen ionisierende Strahlen indirekt ueber gebildete Wasserradikale die DNA schaedigen. In beiden Faellen entstehen modifizierte Basen, die zum Teil aus dem DNA-Strang freigesetz werden und es entstehen modifizierte Base, die zum Teil aus den DNA-Strang freigesetzt werden und es entstehen Veraenderungen an der Zuckerkomponente 2-Desoxyribose, die einen Strangbruch zur Folge haben (Einzelstrang- und/oder Doppelstrangbrueche). Der erste Teil der Arbeit beschaeftigt sich mit der gaschromatographischen Analyse (GC-MS) von strahleninduzierten Basenveraenderungen. Als Modell-DNA diente zunaechst Heringssperma-DNA. In der bestrahlten Probe zeigten sich einige typische Vertreter von strahleninduzierten Basen-Derivaten (Thyminglykol, 5-Hydroxycytosin). Auch in der DNA aus Gefluegelfleisch wurden einige Basen-Derivate nachgewiesen. Interessant ist jedoch die Tatsache, dass diese Basen-Derivate, die bislang als Marker fuer eine Strahlenbehandlung galten, in geringen Mengen auch in unbestrahlten Proben identifiziert werden konnten. Das zweite Kapitel umfasst die Analytik von Strangbruechen mit Hilfe der gepulsten Gelelektrophorese. Mit dieser Methode kann der Nachweis erbracht werden, dass infolge einer Bestrahlung der Anteil an kurzkettigen DNA-Molekuelen im Vergleich zu unbehandelten Proben deutlich zunimmt. DNA-Molekuele mit einer Groesse von ca. 2.2 Mbp (2.2 Millionen Basenpaare) werden durch eine Bestrahlung fast vollstaendig zu kurzkettigen Bruchstuecken abgebaut. Mit dieser Methode koennen Bestrahlungen ab 1500 Gy eindeutig nachgewiesen werden, auch wenn die Bestrahlung bereits einige Zeit zurueckliegt. (orig./MG)Source
Berichte aus der Chemie; 1994; 164 p; Shaker; Aachen (Germany); ISBN 3-86111-938-2; 
; Diss. (Dr.rer.nat.).
; Diss. (Dr.rer.nat.).
[en] The program STRUCTNRA for the simulation of ion beam analysis charged particle spectra from arbitrary two-dimensional distributions of materials is described. The code is validated by comparison to experimental backscattering data from a silicon grating on tantalum at different orientations and incident angles. Simulated spectra for several types of rough thin layers and a chessboard-like arrangement of materials as example for a multi-phase agglomerate material are presented. Ambiguities between back-scattering spectra from two-dimensional and one-dimensional sample structures are discussed.
Journal
Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 371; p. 90-96
; CODEN NIMBEU; v. 371; p. 90-96
[en] The influence of surface roughness on Rutherford backscattering spectroscopy (RBS) spectra has been studied experimentally and by computer simulation with the SIMNRA code. Rough thin films are described by a distribution of film thicknesses, while rough substrates are approximated by a distribution of local inclination angles. Correlation effects of surface roughness are neglected. Rough film effects can be calculated for RBS including non-Rutherford scattering, nuclear reaction analysis and elastic recoil detection analysis. The results of simulation calculations show good agreement with experimental data. For thin films of high Z elements on rough substrates additionally plural scattering plays an important role
Journal
Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 194(2); p. 177-186
; CODEN NIMBEU; v. 194(2); p. 177-186
No abstract available
Journal
[en] SIMNRA is an analytical code for the simulation of ion beam analysis energy spectra obtained by Rutherford backscattering, non-Rutherford scattering, elastic recoil detection analysis, and nuclear reaction analysis. Improvements of the simulation physics in SIMNRA version 7 include among others the skewness of all energy spread distributions, improved handling of scattering or reaction cross-sections with structure, generalized layer roughness, and sample porosity
Journal
Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 332; p. 176-180
; CODEN NIMBEU; v. 332; p. 176-180
[en] The composition of co-deposited carbon-silicon layers (a-C:Si:D) with varying Si concentrations and their removal by heating in air were investigated using MeV ion beam techniques. The ion-induced release of D due to the analysing beam (1.2 MeV 3He) was determined. The removal rates of D and C by heating in air increase strongly at temperatures around 550 K for a-C:D layers. With increasing Si content, these temperatures rise to above 650 K for layers with Si concentrations larger than 0.2 Si/(Si+C). The C removal rate is always lower than the D removal rate. Si is not removed by this method. The observed properties of the layers are compared with those of hard and soft a-C:D films
Journal
[en] Rutherford backscattering spectra have been calculated with a parallel version of TRIM.SP for 0.5 and 1 MeV 4He normally on a target consisting of about 100 nm Au on Si. The calculated energy distributions are compared with experimental distributions and with those calculated with SIMNRA including double scattering. The contributions of plural scattering on the distributions are determined
Journal
Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 153(1-4); p. 337-344
; CODEN NIMBEU; v. 153(1-4); p. 337-344
[en] Whether the People's Republic of China may develop to an economical super-government in future depends on the amount of power and resources of this land. The security of power supply is in an extremely prominent position in the Agenda of the Chinese government. Under this aspect the author of the contribution under consideration reports on the power policy of China. The main aspects of this contribution are: (a) Trends of power consumption, productions and imports of power; (b) Power political targets, measures and instruments of China; (c) Characteristics, national and international impacts of the power policy of China. Due to the economical activities of the chinese oil industry worldwide as well as due to the increasing dependence from imports of petroleum and natural oil, China becomes a global player. Thus, one may expect an intensification of Beijing's economical activities with an increased military component. Nevertheless, the power policy of China is an important factor in the global competition according to fossil resources. In order to understand the future behaviour of China's power policy, one may have to take notice of the strategies relating the power policy and relating to foreign affairs. Furthermore, trends and problematic areas concerning the securitization of the power supply in the national area have to be observed
Source
[en] The backscattering cross-sections for 6Li and 7Li ions scattered from natural carbon have been measured in the energy range 1.7-5.5 MeV at a laboratory scattering angle of 165 deg. The threshold energies above which Rutherford backscattering becomes invalid are 3700 keV for 6Li and 3520 keV for 7Li. Above these thresholds the cross-sections decrease below Rutherford, while the background due to nuclear reactions increases strongly. The measured threshold energies are compared to theoretical predictions. The cross-section data are presented in tabular and graphical form
Journal
Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 183(3-4); p. 221-226
; CODEN NIMBEU; v. 183(3-4); p. 221-226
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