Qualitative By-Product Identification of Plasma-Assisted TCE Abatement by Mass Spectrometry and Fourier-Transform Infrared Spectroscopy

In this study, the formation of by-products resulting from the decomposition of trichloroethylene with a negative DC glow discharge has been investigated. By combining the qualitative data from mass spectrometry and Fourier-transform infrared spectroscopy, the formation of phosgene, dichloroacetylchloride and trichloroacetaldehyde have been confirmed as incomplete oxidation products. Hydrogen chloride, chlorine, carbon monoxide and carbon dioxide were also detected. Also, formation of ozone was found in the outlet stream. Based on this information, it is possible to chose an appropriate catalyst to combine with non thermal plasma. In this way emission of harmful, incomplete oxidation products can be further reduced at a lower energy cost.     

Application of a novel type of adiabatic scanning calorimeter for high-resolution thermal data near the melting point of gallium

A novel type of adiabatic scanning calorimeter (ASC) based on Peltier elements (PEs) is used to obtain high-resolution enthalpy and heat capacity data on the melting transition of gallium. The accuracy of the specific heat capacity and specific enthalpy is about 2 %, for a sub-mK temperature resolution. The simultaneously determined equilibrium specific heat capacity and specific enthalpy are used to determine the heat of fusion and the purity. In addition, the use of the PE-based ASC as a classical heat step calorimeter and as a constant rate (DSC-type) calorimeter is discussed. A comparison of the ASC results with literature data and DSC data shows the advantages of ASC for the study of phase transitions.     

Saccharin

Ohne Zusammenfassung     

Zur Unterscheidung des Formaldehyds von Azetaldehyd

Ohne Zusammenfassung     

Temperature dependence of the radiative recombination coefficient in GaAs---(Al, Ga)As quantum wells

The temperature dependence of the radiative recombination coefficient of GaAs---(Al,Ga)As quantum wells grown by MO-VPE was investigated. This was done by measuring the minority carrier lifetime as deduced from photoluminescence decay. The experimental lifetime varies as T^a, where a equals 1.1 for small well thicknesses (66Å) and increases gradually to 1.4 for a well thickness of 300Å. This is in good agreement with simple theoretical considerations.     

Pinpointing a Mechanistic Switch Between Ketoreduction and “Ene” Reduction in Short‐Chain Dehydrogenases/Reductases

Three enzymes of the Mentha essential oil biosynthetic pathway are highly homologous, namely the ketoreductases (?)‐menthone:(?)‐menthol reductase and (?)‐menthone:(+)‐neomenthol reductase, and the “ene” reductase isopiperitenone reductase. We identified a rare catalytic residue substitution in the last two, and performed comparative crystal structure analyses and residue‐swapping mutagenesis to investigate whether this determines the reaction outcome. The result was a complete loss of native activity and a switch between ene reduction and ketoreduction. This suggests the importance of a catalytic glutamate vs. tyrosine residue in determining the outcome of the reduction of α,β‐unsaturated alkenes, due to the substrate occupying different binding conformations, and possibly also to the relative acidities of the two residues. This simple switch in mechanism by a single amino acid substitution could potentially generate a large number of de novo ene reductases.     

Intercalation ofn-alkylamines into α-titanium phosphate from aqueous solutions

The intercalation reactions betweenn-alkylamines and -titanium phosphate in aqueous media have been investigated. The compounds with the maximum intercalation have the formula -Ti(HOPO₃)₂ · 2 C _n H _2n+1 NH₂ · H₂O (n=1–10). Defined crystalline phases with lower amine content are described, the general formula being -Ti(HOPO₃)₂ · _m C _n H _2n+1 NH₂ ·pH₂O (m=1.0 1.3, 1.5, 1.7). Whenm=1.0 then-alkylamines form a monomolecular layer. Whenm>1.0 the layer is bimolecular. The inclination angle and the packing density of then-alkylamines in the interlayer space is determined.     

Temperature dependence of the electrical conductivity of imidazolium ionic liquids

The electrical conductivities of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids and of 1-hexyl-3-methylimidazolium ionic liquids with different anions were determined in the temperature range between 123 and 393 K on the basis of dielectric measurements in the frequency range from 1 to 10(7) Hz. Most of the ionic liquids form a glass and the conductivity values obey the Vogel-Fulcher-Tammann equation. The glass transition temperatures are increasing with increasing length of the alkyl chain. The fragility is weakly dependent on the alkyl chain length but is highly sensitive to the structure of the anion.     

Surface charge model of a carbon nanotube: self-consistent field from Thomas-Fermi theory

A model of a C nanotube is set up and solved self-consistently by numerical methods using the Thomas-Fermi statistical approach to treat the C 2s and 2p valence electrons. In the model presented here the C⁴⁺ ions are ‘smeared out’ uniformly over the surface of an infinitely long cylinder of radius R_t. Analytic forms of the self-consistent field are also presented far from the axis of the infinite tube, and well into its interior.