Occurrence of Ti3+ and Fe2+ in Mullite

Electron paramagnetic studies showed that Ti³⁺ and Fe²⁺ occur in mullites taken from a refractory material which was fused-cast under a reducing atmosphere. Exposure of the mullite samples to temperatures >1600°C caused oxidation of Ti³⁺ and Fe²⁺ to Ti⁴⁺ and Fe³⁺, respectively.     

Charakterisierung niedermolekularer Zinkspezies in handelsüblichen pflanzlichen Lebensmitteln

In six different ordinary vegetables, namely kohlrabi, Chinese cabbage, chard, leek, spinach and Jerusalem artichoke, zinc was mainly found as low molecular weight species. In the present study, these important zinc compounds are further investigated. The determinations of the metal are performed by ET-AAS. The zinc complexes of all vegetables are anionic at pH 8.0 and show similar elution behaviour in gel permeation and anion exchange chromatography. Consequently, a great resemblance in structure between the low molecular weight zinc species from the different vegetables can be supposed. Exemplary, the zinc complexes of kohlrabi and Chinese cabbage are further examined. In more purified samples of these vegetables compared to zinc neither stoichiometric amounts of free protein amino acids nor nicotianamine, free malic acid, citric acid or phytic acid have been detected. Mainly glutamic acid is found in molar excess to zinc after acid hydrolysis in both cases. The cysteine contents of both zinc-binding fractions are very low. Conclusively, the wellknown γ-glutamylcysteinyl-glycines (phytochelatines) can not be responsible for the bonding of zinc in both ordinary vegetables. We suppose that zinc in kohlrabi and Chinese cabbage is bound to a glutamic acid derivative unknown as yet, possibly a malic acid ester.     

Comparison of different techniques for the observation of the lamellar texture of isotactic polypropylene: TEM of surface replicas,TEM after staining,and SFM

Summary In the present study three different techniques have been employed to observe the lamellar texture of isotactic polypropylene (iPP) crystallized from the melt under the influence of shearing: (a) Transmission electron microscopy (TEM) of surface replicas of permanganically etched samples (b) TEM of thin sections of Ruthenium-oxide stained samples and (c) Scanning force microscopy (SFM) in contact mode of permanganically etched samples. The aim was to assess their relative merits in terms of practicability, resolution and type of information.     

Organische und anorganische Ionenaustauscher zur heterogen katalysierten Alkylierung von Aromaten

Organic and inorganic ion exchangers as catalysts for the heterogeneous alkylation of aromatics . Ion exchangers has advantages over low molecular for use in industrial alkylation reactions. The reactivity and selectivity behaviour of the polymeric catalysts were found to be markedly influenced by the structure of the polymeric matrix as well as the type and number of the functional groups. In this connection many similarities between inorganic ion exchangers (zeolites) and organic ion exchange resins were detected.     

Are all photon radiations similar in large absorbers?--a comparison of electron spectra

Conventional X rays, i.e. X rays generating voltage between roughly 150 and 300 kV, are used in many radio-diagnostic procedures and also in radiobiological experiments. They release less energetic and, therefore, more densely ionising electrons than the high-energy gamma rays from 60Co or from the A bombs. Accordingly, they are considered to be somewhat more effective, especially at low doses. Various radiobiological studies, especially studies on chromosome aberrations have confirmed this assumption, but epidemiological investigations, e.g. the comparison of the excess relative risk for mammary cancer in the X-ray exposed patients and in the gamma-ray exposed A bomb survivors, have not demonstrated a similar difference. In view of the missing epidemiological evidence and largely for the reasons of practicality in radiation protection, the ICRP has recommended the radiation weighting factor unity equally for all photon radiations. However, in the discussion preceding the 2005 Recommendations of the ICRP, the issue remains controversial. In a recent paper, Harder et al. argue--with reference to an assessment by the German Radiation Protection Commission (SSK)--that the use of the same weighting factor for different photon energies can be justified more directly. For high-energy incident photons, they present the degraded photon spectra at different depths in a phantom, and they conclude that much of the difference between high-energy gamma rays and conventional X rays disappears in a large phantom. The present assessment, which is more direct, compares the spectra of electrons released (through pair production, Compton effect and photo effect) in a small and in a very large receptor for the incident photons of 150 keV, 1 MeV and 6 MeV. For the 1 Mev and 6 MeV photons, there is a substantial shift towards smaller electron energies in the large receptor, but the electron spectra remain much harder than those from the 150 keV incident photons. Furthermore, it is seen--in agreement with earlier conclusions by Straume--that for the broad gamma-ray spectrum from the A bombs there is no shift at all to lower energies within the body, but rather some degree of hardening of the radiation. The assumption that distinct differences between high-energy gamma rays and conventional X rays are restricted to small samples must, thus, be rejected. The attribution of the same effective quality factor or radiation weighting factor to all photon energies remains, therefore, an issue that is based on the considerations beyond dosimetry.     

Measurement of the detective quantum efficiency (DQE) of digital X-ray detectors according to the novel standard IEC 62220-1

A mobile measurement facility which complies with IEC 62220-1 has been set up to determine the detective quantum efficiency (DQE) of digital X-ray detector systems. Exemplary measurements were performed for two similar CR detector systems, a CsI-based indirect detector and an Se-based direct detector. The standardised radiation quality RQA 5 was applied for measurement and for three of these systems RQA 9 was also applied. A pronounced dependence of DQE on radiation quality was observed for the direct detector, where the DQEs for RQA 5 and RQA 9 differ by a factor of approximately 2. The uncertainty (95% confidence interval) associated with the measured DQE values is within 0.01 and 0.04 depending on, for example, the spatial frequency. Thus, it has been demonstrated that the DQE can be measured accurately and reliably with the accuracy required by the international standard IEC 62220-1. It is now possible to objectively measure and compare DQE values of digital X-ray detector systems.     

Characterization of a hazardous eyeliner (kohl) by confocal Raman microscopy

A new method of analyzing kohl, a cosmetic eyeliner, using confocal Raman microscopy is reported. This technique offers an important alternative to conventional spectroscopic techniques that provide elemental/atomic composition. Raman spectra of three kohl samples have been measured between 150 and 3000 cm(-1) at room temperature. The main component of two kohl samples was found to be lead(II) sulfide (PbS). Kohl is used as a traditional cosmetic and remedy in the Middle East, Far East, and Northern Africa. Since kohl products contain very high concentrations of lead, they constitute a risk for public health, particularly for children.