Investigation of the species-specific degradation behaviour of methylmercury and ethylmercury under microwave irradiation

The degradation behaviour of methylmercury (MeHg) under microwave irradiation is investigated, as is the (different) degradation behaviour of ethylmercury (EtHg) under similar irradiation. A simple and highly sensitive SPME-GC-pyrolysis-AFS system was used to analyse the aqueous MeHg and EtHg standard solutions after derivatization with sodium tetraphenylborate (NaBPh₄). Samples were irradiated in a microwave digester at microwave powers ranging from 20 to 160 W for durations of 2 to 10 min. The different tolerances towards microwave treatment of the two organomercury species were evident. Practically no degradation was experienced for MeHg for up to 8 minutes of irradiation at 120 W or for up to 4 minutes at 160 W. Significant analyte loss was observed for EtHg after 2 minutes at 40 W of microwave power. Awarded a Poster Prize on the occasion of the European Winter Conference on Plasma Spectrochemistry, February 2005, Budapest, Hungary     

FLASH INDUCED OSCILLATION OF THE LOW TEMPERATURE THERMOLUMINESCENCE BAND Zv IN CHLOROPLASTS

Using preilluminating flashes at 2°C prior to continuous excitation of isolated chloroplasts at -80°C, a period-four oscillation with maxima at the 0th, 4th and 8th flashes was observed in the amplitude of the thermoluminescence band Z_v. Inactivation of the water-splitting system by hydroxylamine- or Tris-treatments greatly diminished the Z_v band. On the other hand, its amplitude was not considerably affected by the addition of inhibitory concentration of DCMU. On the basis of the results, the possible origin of the Z_v band is discussed.     

Studies of UV photochemistry of psoralen and angelicin by infrared spectroscopy

The UV homodimerization reaction of psoralen and angelicin in crystalline thin layers has been investigated by means of transmission infrared and infrared ATR (attenuated total reflection) spectroscopy.

In the case of psoralen layers isoorientation was found. Dichroic ratios for several vibrational bands have been obtained. After irradiation, cis-syn photodimers were found for both psoralen and angelicin.     

Activation energies for nucleation and growth and critical cluster size dependence in JMAK analyses of kinetic Monte-Carlo simulations of precipitation

Kinetic Monte-Carlo (KMC) methods are used as an approach to simulate precipitation in Cu-alloyed bcc Fe. In order to characterize the process, transformed fractions, that is, the precipitated atoms, are related to Johnson-Mehl-Avrami-Kolmogorov theory. However, simulated data often deviate from corresponding fit curves and so does the resulting growth exponent when compared to theoretical expectations. Furthermore, some data may suggest the development of a metastable phase. In our study, we show that the characteristics of the transformed fraction and, as a consequence, the derived growth exponents sensitively depend on the number of atoms that are considered to form a particle and hence contribute to the transformed fraction. With a temperature dependence of the critical cluster size and additionally accounting for severe impingement of the particles, we obtain growth exponents which lie close to the expected range between n = 1.5 and n = 2.5 for pre-existing nuclei or continuous nucleation, respectively. From these, we obtain activation energies for nucleation and growth of precipitates. In this way, atomistic KMC simulations yield thermodynamical quantities, which can be valuable input parameters for larger length scale simulation methods, for example, for Phase Field Method simulations.     

Cinchona based squaramide catalysed enantioselective Michael addition of α-nitrophosphonates to aryl acrylates: enantioselective synthesis of quaternary α-aminophosphonates

Several cinchona based squaramide catalysts were applied to the asymmetric Michael addition of α-nitroethylphosphonates to acrylic acid aryl esters, resulting in high yields and enantioselectivities. The absolute configuration of one of the quaternary α-nitrophosphonate adducts was deduced from its experimental and calculated CD spectra. The adducts were reduced to their cyclic aminophosphonates by catalytic hydrogenation.     

Scope and Limitation for the Reaction of α,β-Unsaturated Carbonyl Compounds with Phosphorus Nucleophiles by Determination of the Half-Wave Potential

Abstract

During the formation of oxaphospholenes the phosphorus in the reagent gets oxidized and the double bond in the enones gets reduced.     

P-Mannich Reaction on Wool Fibre for Activation in Dyeing

Abstract

Chemical modification of wool by means of dimethyl phoaphitc and D-glucose results in an increase in dye pickup, while colour and light fastness properties did not decrease, in fact some features bccpme more favourable. Our invesigations showed that increase in fibre diameter occurred. which could rise the rate of dye penetration. Amino acid analysis of the treated wool sample h w e d a decrease in lysine and arginim content, which allows of supposing covalent bond formation betweecl dimcthyl phosphite, D-glucose and the amino and guanidino groups of wool.