Reactions of At//+, Ato.H2O, AtCl
and AtBr2 with the pseudohalogenides tricyanomethanide and azide are described. Information on the compound formation of astatine with C/CN/
could be obtained on the basis of electromigration investigations under variation of the conditions /composition of the electrolyte, pH, exchange reactions of ligands/. For the reaction: [At/H2O/C/CN/3]+C/CN/
[At/C/CN/3/2]+H2O at 301 K and u=0.075 mol.l–1 K2=/675±25/ [1.mol–1] and uo=–/3.50±0.10/×10–4 [cm2.s–1.V–1]. According to this astatine/I/-tricyanomethanide is classified between AtI
. First investigations in azid-containing systems confirm the formation of astatine/I/-azide-compounds. Their composition is probably At/N3/
. There is no dependence of the ion mobility of astatine/I/-azide in the investigated range on azide concentration which is due to its high stability.
Authors:R. Dreyer, I. Dreyer, S. Fischer, H. Hartmann, and F. Rösch
The formation of cationic astatine compounds with thiourea, thiourea derivatives and some N-acylthioureas was investigated in aqueous solutions. The ion mobilities in free electrolytes were determined for the detection of carrier-free astatine compounds and their characterization. Informations about the stability of this group of compounds could be given after investigations in the presence of halogenide and pseudo halogenide ions /Cl–, Br–, I–, SCN–/. First results on the reaction of At//+ with thiourea derivatives and N-acylthioureas in acid and neutral solutions are reported. The cationic astatine compound formation with representatives of this group is shown.
Authors:S. Fischer, R. Dreyer, H. Hussein, M. Weber, and H. Hartmann
The formation of cationic astatine /I/-coordination compounds with selenium-containing neutral ligands is described. The detection of compound formation and first physico-chemical data on the characterization of this new group of At/I/-compounds were obtained by investigation of their electromigration behaviour in free electrolytes. Se-donors coordinate more strongly to At/I/ than ligands containing carbamide and thiocarbamide. This fact is proved by electromigrational studies on the exchange of N,N-ethyleneselenocarbamide, respectively N,N-ethylenethiocarbamide with iodide.
Authors:Ch. Krueger, B. Gorski, A. Novgorodov, and S. Fischer
The selectivity of trioctylphosphineoxide /TOPO/ with respect to rare earths and sc was used to develop a single step separation method for43–48Sc from transition metals irradiated with high energy protons /660 MeV/. The target material serves as a salting-out agent in the described extraction-separation technique. Rapid and quantitative recovery of scandium is achieved using extraction chromatography. Radiochemically pure carrier-free Sc was separated from the following irradiated metals: Cr, Mn, Ni, Cu and Zn.
Authors:R. Ludwig, S. Fischer, H. Hussein, M. Frind, and R. Dreyer
The ion mobilities of [211At] At(I) in dependence on thiourea (tu) concentration, iodide concentration and a mixture of both ligands were measured by the electromigration method in free electrolytes. An equilibrium model was developed for the characterization of electromigration curves which permitted the calculation of stability constants and ion mobilities of the complexes [AtI], [AtI2]–, [Attu]+, [Attu2]+ and [AtItu] existing in these solutions. Ethanol and water served as solvents. The temperature was 298 K and the ionic strength was about 0.05 mol/dm3.
Authors:G. Wunderlich, S. Fischer, R. Dreyer, and W. Franke
A simple and rapid method for labelling proteins with211At by means of a 1,4-diaminobenzene link is described. 1,4-diaminobenzene is transformed into the diazonium salt and subsequently reactions of both211At and proteins with the diazonium salt take place simultaneously. For possibly high yields of astatized protein an appropriate temperature of 273 K was found. The results demonstrate the difference between the reaction mechanisms of iodine and astatine with proteins.
Authors:S. Gerdung, M. Pöllot, P. Fischer, R. Grillmaier, and P. Müller
The aim of the study reported in this paper was to derive factors describing the translocation of radiocesium from the green
plant parts to the crop. Wheat, rye and potatoes were contaminated and harvested at different growth stages to allow the assessment
of the contamination of the crop with known date of the radioactive deposition. At harvest, the cesium concentrations in the
crop, the green plant parts (i.e., straw without ears) and the roots were measured. The results show that the contamination
of the crop depends strongly on the date of134Cs application and on the type of plants. The highest translocation was observed when cesium was applied during flowering.
Authors:S. Bojcsev, A. Almási, H. Simon, P. Perjési, and Emil Fischer
In the extrahepatic drug metabolism the intestinal tract can play an important role. These experiments were designed to study the biotransformation of p-nitrophenol (PNP) in the small intestine in the rat. Various segments of the small intestine (proximal and distal jejunum, terminal ileum) were perfused with isotonic solution in vivo containing different concentrations of PNP (20–100–500–1000 μM) and the concentrations of metabolites (PNP-G: p-nitrophenol glucuronide, PNP-S: p-nitrophenol sulfate) were determined in the perfusion medium. It was found a decreasing tendency in the glucuronidation from the proximal to distal segment of the small intestine: e.g. 430 nmol, 240 nmol, and 100 nmol PNP-G appeared in the perfusion medium in the proximal, distal jejunum and in the terminal ileum, respectively, when 500 μM PNP was luminally perfused for 90 minutes. Similar ratio was found at the luminal perfusion of other PNP-concentrations, too. Luminal appearance of sulfoconjugate of PNP was considerably lower and no clear gradient tendency in the formation of PNP-S could be detected in the small intestine from the proximal to distal segment. Our results show that there are considerable differences in drug metabolism in various segments of the small intestine. We have found a gradient conjugating activity from proximal to distal segment of small intestine in the glucuronidation of PNP.
Authors:T. Lipovics, S. Czakó, I. Kelemen, and A. Fischer
A newly developed technique is presented to estimate site specific seismic failure frequencies of several types of storage tanks. Seismic failure is a failure event triggered by an earthquake leading to material release and serious damages. The present method is based on the convolution of site specific seismic hazard curves and component dependent fragility curves. Fragility curves are calculated with the help of probit coefficients originated from the analysis of historical data of earthquake damage. The calculation considers only the filling level, pressure and the damage state of storage tanks, and neglects the shape, volume, material and other parameters. Determination of seismic failure frequencies for storage tanks is done for three different Hungarian plant sites (Paks, Püspökszilágy, Csömör) using seismic hazard curves. In contrast of the simplifications the obtained frequency values represent a conservative estimation of failure frequencies triggered by earthquakes, and in comparison to international failure data the calculated values indicate significant frequencies. Therefore, the results imply that despite of the moderate seismic activity in Hungary, the effects of earthquakes on major-accident hazards should be considered in quantitative risk assessment.