Die Verwendung von Radionukliden für Diffusionsuntersuchungen in Ein- und Mehrphasensystemen. Eine methodische Übersicht (Zusammenfassender Bericht)

Durch die Anwendung radioaktiver Nuklide ist die Untersuchung von Selbstdiffusionsvorgängen möglich geworden.

Diffusionsprozesse stellen Vorgänge dar, bei denen Substanzen in Richtung des Ausgleiches von Konzentrationsdifferenzen in verschiedenen Teilen einer oder verschiedener Phasen transportiert werden. Die ungeordnete Wärmebewegung von Stoffteilchen geht dann makroskopisch betrachtet in eine geordnete, gerichtete Bewegung über, wenn Konzentrationsgradienten – oder genauer: Gradienten des chemischen Potentials – in dem betreffenden Gebiet anliegen. Die nach Beendigung des Prozesses eingestellte Gleichgewichtsverteilung entspricht einem Minimum an freier Energie im Diffusionssystem. Bei der Selbstdiffusion findet ebenfallseine selbständige und kontinuierliche Vermischung der Teilchen in Festkörpern, Flüssigkeiten und Gasen als Resultat der Wärmebewegung statt, nur mit dem Unterschied, daß keine Konzentrationsgefälle im streng thermodynamischen Sinne vorliegen; im Resultat tritt ein Ausgleich der isotopcn Zusammensetzung des Systems ein.

Die Untersuchungen von Diffusions- und Selbstdiffusionsvorgängen in Festkörpern, speziell von Gitter- und Korngrenzendiffusion, geben z. B. die Möglichkeit, Rückschlüsse auf das Strukturgefüge, auf interatomare bzw.     

NMR Experiments on Ion Permeation in Irradiated Model Membranes

In aqueous solutions of sonicated egg-lecithin vesicles (5 weight-%) the ¹H-NMR parameters line width, area, and chemical shift of the signal of the (CH₃)₃N⁺ group were determined in dependence on the dose of gamma radiation (0 … 12 kGy). The application of curopium ions made it possible, by means of a line shape analysis, to calculate these parameters for the inside as well as for the outside lipid layer.

With increasing ⁶⁰Co-radiation dose the line widths increase linearly. The line width for the outside lipid layer increases significantly more rapidly than for the inside layer. This fact allows us to conclude that there exists a preferred radiation damage of the outside lipid layer. The asymmetry may he a consequence of an indirect radiation action mediated by the radicals of the water radiolysis.

From the temporal change of the NMR parameters information can be obtained about the radiation action on transport processes in the vesicles. Beginning at a threshold value (approx. 5 kGy) the permeation of the En^{+ ++} ions to the (CH₃)₃N⁺ head groups previously not accessible increases significantly.     

Reduzierung des Störstrahlungseinflusses bei der Elementanalyse nach dem (n, γ)-Verfahren mit Neutronengenerator

Bei der Elementanaylse mittels Szintillalionsspektrometrie im Ausgangskanal der (n, γ)-Reaktion tritt ein hoher Linienuntergrund auf. Dieser Untergrund lafit läβt herabsetzen durch Puhung des Neutronengenerators (Plasyna-Pulsung), zweckmäβige Dimensionierung der Meβanordnung und Optimierung des Meβzeilintervalls.     

Radioactive contamination of the atmosphere of Cairo,Egypt, from the Fukushima Dai-ichi nuclear plant accident

Radioactive contamination in air dust particles of Cairo atmosphere from the Fukushima accident was detected by the gamma-ray spectroscopy technique. Analysis of the spectra obtained by using an High-Purity Germanium detector showed that there were some traces of ¹³¹I and ^{134, 137}Cs. Estimate and study of concentration of those radionuclides were done over a period of about 5 months after the accident. Comparison with corresponding results in different countries all over the world has been performed.     

Über die Möglichkeit einer strahlenchemischen Reinigung von Abwässern,die Dodezylbenzolsulfonat und Nonylphelylpolyglykoläther enthalten

Es wurde die Möglichkeit des strahlenchemischen Abbaus einiger Detergenzien untersucht, die in Abwässern enthalten sind. Es wurde festgestellt, daß von den oberflächenaktiven Substanzen (OFAS) die den Hauptteil der aktiven Substanz der Detergenzien darstellen, die ionogenen (z. B. Dodezylbenzolsulfonat) bei verhältnismäßig niedrigeren Dosen zersetzt werden als die nichtionogenen (z. B. Nonylphenylpolyglykoläther). Bei gleicher Konzentration beider Stoffe bewirken Dosen in der Größenordnung von 5 bis 6 kGy einen höheren Grad des Abbaus bei Dodezylbenzolsulfonat als Dosen von 10 bis 20 kGy beim Nonylphenylpolyglykoläther. Versuche mit realen Abwässern, die die Präparate ?Biopon”, ?Alkasuper” und ?Kitka” enthalten, bestätigen die erkannte Gesetzmäßigkeit und zeigen die Perspektive eines strahlenchemischen Abbaus für die Reinigung von Abwässern, die ionogenc OFAS enthalten.     

The interpretation of radiation damage experiments on gold

The paper shows that the conclusions drawn from recent experiments on electron irradiation of gold at about 100° K should be reversed, i.e. that these experiments speak against the free thermally activated migration of interstitials at the irradiation temperature. It is shown that this viewpoint is in agreement with several related experiments, which may all be interpreted by a dynamic propagation of crowdions over distances between 1000 Å and 2000 Å. At intermediate and high defect concentrations the dynamic propagation mechanism is suppressed.     

Hg ION implantation in silicon: Lattice disorder created and hg atom lattice location

Abstract

The lattice disorder produced by 42-keV and 75-keV Hg ions implanted in Silicon at room temperature and the lattice location of the Hg atoms were studied by means of the channeling technique with a 2.0 MeV ⁴He⁺ beam. The damage produced was found to increase linearly with ion dose until a saturation value, connected to the ion range, is reached. The number of Si atoms displaced for Hg ion implanted was evaluated and compared with the theoretical expectation. The substitutional Hg fraction is connected to the disorder produced: the replacement mechanism is discussed.     

Dose rate effect of gamma on JFET transistors

Dose rate effects on the noise characteristics of gamma-irradiated junction field effect transistors (JFETs) are presented. The dose rate varied between 0.5 and 19 kGy/h at a constant radiation dose of 600 kGy. Neither obvious nor non-general relationship was identified between noise and dose rate along the total dose rate range. Nevertheless, some explanations have been provided about the resulting effects when the total range was studied, as some partial ranges corresponded to low, medium and high dose rates. This explanation is based on the gamma interaction process in JFET structure and the electronic noise resulted.     

Understanding the concepts of proportion and ratio among grade nine students in Malaysia

The purpose of the study was to investigate the concepts of ratio and proportion constructed by grade nine students by investigating grade nine students proportional reasoning schemes and procedures on three types of tasks: missing value, numerical comparison and qualitative reasoning. Comparisons among the different categories were made and the strategies used in solving these problems were identified. The relationship between student grades on a national examination and their knowledge of proportional reasoning was determined. The results of the quantitative analysis indicated that students performed generally well on the missing value tasks but their scores on the numerical comparison and qualitative tasks were much lower. The results indicate that only a small percentage of students who did well on the national exams were able to solve complex proportional problems and the grades obtained were not indicative of their knowledge of ratio and proportion. The difficulty experienced by the ninth graders indicated that students frequently used additive reasoning, that is a comparison of two numbers by subtraction rather than division. It appears that students cannot begin to understand the functional and scalar relationship inherent in a proportion until they first develop multiplicative reasoning.