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  • Author: E. Schulte x
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Flash-x-ray-diffraction patterns (FXD) with an exposure time of 4 ns of NaCl single crystals compressed by plane shock waves are obtained at pressures of about 30 kbar. From the diffraction patterns the compression is determined and compared with Hugoniot data. During shock load the lattice shows an uniaxial compression. While in case of measurements at the free surface an observation time of only a few nanoseconds is available, this experimental set-up allows an observation time of two microseconds.

Bei der UV-Photolyse (λ= 254 nm) von 5-Joduracil (C =5·10-4 Mol/l) in wäßriger, sauerstoffgesättigter Lösung bildet sich als organisches Produkt nur Isodialursäure. Daneben entsteht elementares Jod. H2O2 wird nicht gefunden. Bei pH =1 (H2SO4) liegt neben dem elementaren Jod zusätzlich Jod in einer höheren Oxydationsstufe vor, das aus Jodid Jod frei macht und in dessen Gegenwart zugesetztes H2O2 rasch abgebaut wird. Unter besonderen Bedingungen wird nach der Photolyse bei pH =1 sehr wenig H2O2 gefunden, welches beim Stehenlassen rasch aus der Lösung verschwindet.

In Anwesenheit von Jodid (C=5·10-4 Mol/l) entsteht bei pH=3,5 (H2SO4) nur Isodialursäure und zwei Äquivalente Jod. Jod in einer anderen Wertigkeitsstufe wird nicht gefunden.

A reaction mechanism is presented for strand break formation in poly U induced by OH radicals in N2O/O2- saturated aqueous solution based on experimental results obtained with different methods

We report on the synthesis and the dielectric properties of four new unsymmetrically substituted diacetylenes: DNP/PU, DNP/4-MPU, DNP/DMPU and (+)-(R)- or (-)-(S)- DNP/MBU ((+)-/(-)- for dextro-/laevorotatory, (R)-/(S)-: Cahn-Ingold-Prelog notation for the asymmetric carbon atom). For (-)-(S)-DNP/MBU a pronounced temperature dependence of the permittivity is observed below the melting point. For thin polycrystalline pellets of (+)-(R)- DNP/MBU the poling characteristics are analysed in detail.

UV Photosylis (254 nm) of 5-iodouracil in aqueous, oxygenated solution in presence of KI, FeSO4, KBr and K2SO4 was investigated over a pH-range of 1—6. Uracil, isodialuric acid, and isobarbituric acid were identified as photoproducts.

At a constant pH-value (pH=1) at high KI-concentrations (10-1 mole/1) the main product is uracil. With decreasing KI-concentrations the yield of uracil decreases and isobarbituric acid appears as a photoproduct. On further decreasing KI-concentrations (< 10-2 mole/1) the yield of isobarbituric acid decreases and the formation of isodialuric acid commences.

UV Photolysis of iodouracil at constant KI-concentrations (10—1 mole/1) and increasing pH (pH = 1—6) yields similar results with one exception. At higher pH-values on account of isodialuric acid at least four further compounds are formed. The yield of these products increases with increasing pH value. Addition of KBr and K2SO4 has no effect on the product distribution.

The possible mechanisms for the formation of the reaction products are discussed.

UV-Photolysis of aqueous solution of 5-iodouracil in presence of oxygen and methanol leads quantitatively to isodialuric acid, uracil, formaldehyde, H2O2 and iodine. The yields of these products were determined as a function of methanol concentration. The results suggest that the primary step is the homolytic splitting of the C-I-bond. The reaction of the uracil radical with methanol gives uracil and a CH2OH-radical, and with oxygen isodialuric acid. The uracil radical reacts 24 times faster with oxygen than with methanol. The reaction of CH2OH-radical with oxygen gives formaldehyde and H2O2.