Simultaneous determination of radioactive halogen isotopes and 99Tc

The purpose of this study was to develop a simplified method for simultaneous determination of radiologically important halogen isotopes and 99Tc from different types of samples like environmental, biological and waste samples. Due to their long half-lives (longer than 105 years) they play important role in the nuclear cycle, especially in environmental monitoring and protection.For a rapid response in the evaluation of 129I, 36Cl and 99Tc contamination levels of these samples it is advantageous to combine the existing individual methods. According to the present procedure, iodine, chlorine and technetium are separated selectively from the same sample aliquot followed by the ß-spectrometry of the purified fractions. Increased sensitivities can be achieved by neutron activation (NA) especially in the case of 129I.Our work intends to solve the problem by combining the well-known hot acidic distillation method for iodine separation with the organic extraction process characteristic for technetium separation. The major objective of the work was to separate the disturbing halides from iodine. For this purpose a selective oxidant was applied.For the sample destruction and fractionated distillation an air flow-through installation was used with hot concentrated sulphuric and nitric acids. The trap for iodine contained 3 M NaOH solution. After iodine separation the trap was exchanged for a new one containing the same solution for trapping chlorine or bromine with an addition of 0.01 M KMnO4 solution as an oxidative agent. As expected, the main part of technetium was contained in the acidic residue after distillation. Tc purification was performed by organic extraction with TBP and TEVA column

Impairments of probabilistic response reversal and passive avoidance following catecholamine depletion

Catecholamines, particularly dopamine, have been implicated in various aspects of the reward function including the ability to learn through reinforcement and to modify flexibly responses to changing reinforcement contingencies. We examined the impact of catecholamine depletion (CD) achieved by oral administration of alpha-methyl-paratyrosine (AMPT) on probabilistic reversal learning and passive avoidance (PA) in 15 female subjects with major depressive disorder in full remission (RMDD) and 12 healthy female controls. The CD did not affect significantly the acquisition phase of the reversal learning task. However, CD selectively impaired reversal of the 80-20 contingency pair. In the PA learning task, CD was associated with reduced responding toward rewarding stimuli, although the RMDD and control subjects did not differ regarding these CD-induced changes in reward processing. Interestingly, the performance decrement produced by AMPT on both of these tasks was associated with the level of decreased metabolism in the perigenual anterior cingulate cortex. In an additional examination using the affective Stroop task we found evidence for impaired executive attention as a trait abnormality in MDD. In conclusion, this study showed specific effects of CD on the processing of reward-related stimuli in humans and confirms earlier investigations that show impairments of executive attention as a neuropsychological trait in affective illness