Zur Bestimmung und Trennung des Chroms und zur Analyse von Chrom enthaltenden Substanzen

Ohne Zusammenfassung     

Ueber den forensisch-chemischen Nachweis mehrerer Pflanzenstoffe

Ohne Zusammenfassung     

Synthesis of new 1,2,4-triazolines and 1,3,4-thiadiazolines from bithioureas

2,4-Disubstituted thiosemicarbazides 1 react with acyl isothiocyanates to give bithioureas 2 , which by the action of sodium ethanolate cyclize to 1,2,4-triazoline-3-thiones 3 and 5 , respectively. Treatment of 2 with methyl iodide yields 1,3,4-thiadiazoline-2-imines 8 isomeric with 3 . Compound 8d undergoes a thermal induced DIMROTH rearrangement to give 3d in good yield.     

Factors affecting the capillary electrophoresis of ricin, a toxic glycoprotein

Conditions for the analysis of ricin with capillary electrophoresis were investigated. Uncoated and coated columns were tested with a variety of different buffer combinations which included different principal components, pH, ionic strength, and additives. Of the combinations tested, uncoated columns used with either zwitterionic salts or putrescine gave the best results. Multiple peaks were resolved with these conditions. Coated columns generally yielded between 1000 and 5000 plates with several buffer combinations. Ricin may be analyzed faster and with greater resolution with capillary electrophoresis employing untreated fused-silica columns than by using other chromatographic techniques.     

Determination of methylated globin and albumin for biomonitoring of exposure to methylating agents using HPLC with precolumn fluorescent derivatization

A new method has been developed for the quantitation of methylated blood proteins in persons exposed to methylating agents. Using different derivatizing agents, 9-fluorenylmethyl chloroformate was the most suitable with regard to both sensitivity and peak separation after subsequent HPLC. After optimization of the chromatographic conditions, two groups who worked with methyl bromide and a control group of non exposed persons were compared with regard to their adduct rates (S-methylcysteine) in the two blood proteins albumin and globin. Albumin and globin were isolated from whole blood samples. After total hydrolysis of the proteins with hydrochloric acid, an amino acid analysis was performed using HPLC with precolumn fluorescent derivatization. This method enabled a quantitation of methylated cysteine in the fmol range. Background levels of S-methylcysteine (15 nmol/g protein) in both albumin and globin were found in non-exposed control persons. Levels were up to 10 fold higher in exposed fumigators working with the methylating agent methyl bromide.     

Networks of complex neurons

Networks of formal binary neurons can be used to construct associative memory models. Given the fact that real neurons have more complex features we try to find if other cognitive functions can be modeled by adding new degrees of freedom to the formal neuron. We show that complex features can be represented by dynamically modifying the threshold of the neuron. We explain how this allows us to model phenomena of free associative transitions between memories, temporal segmentation of an input into its memory components, phase locking (binding) and short term memory.