Multielement determination of major elements in polymer additives by microwave induced plasma atomic emission spectrometry after microwave digestion

A method for multielement determination of major elements in polymer additives by microwave induced plasma atomic emission spectrometry (MIP-AES) has been elaborated. Microwave digestion with nitric acid was selected for sample preparation because of its speed and versatility. Sodium nitrate was added to the digestion mixture in order to reduce phosphorus losses. The precision obtained varied between 2 and 4.5% depending on the element determined. The accuracy of the method was studied by analyzing the Spex 5-element oil standard. The method was applied to a variety of commercial and in-house prepared compositions.     

Darwin and mass-velocity relativistic corrections in non-Born-Oppenheimer variational calculations

The Pauli approach to account for the mass-velocity and Darwin relativistic corrections has been applied to the formalism for quantum mechanical molecular calculations that does not assume the Born-Oppenheimer (BO) approximation regarding separability of the electronic and nuclear motions in molecular systems. The corrections are determined using the first order perturbation theory and are derived for the non-BO wave function of a diatomic system expressed in terms of explicitly correlated Gaussian functions with premultipliers in the form of even powers of the internuclear distance. As a numerical example we used calculations of the transition energies for pure vibrational states of the HD(+) ion.     

The Standard Model in noncommutative geometry: fundamental fermions as internal forms

Given the algebra, Hilbert space H, grading and real structure of the finite spectral triple of the Standard Model, we classify all possible Dirac operators such that H is a self-Morita equivalence bimodule for the associated Clifford algebra.     

Electronic Nose Differentiation between Quercus robur Acorns Infected by Pathogenic Oomycetes Phytophthora plurivora and Pythium intermedium

Identification of the presence of pathogenic oomycetes in infected plant material proved possible using an electronic nose, giving hope for a tool to assist nurseries and quarantine services. Previously, species of Phytophthora plurivora and Pythium intermedium have been successfully distinguished in germinated acorns of English oak Quercus robur L. Chemical compound analyses performed by HS-SPME/GC-MS (Headspace Solid-Phase Microextraction/Gas Chromatography–Mass Spectrometry) revealed the presence of volatile antifungal molecules produced by oak seedlings belonging to terpenes and alkanes. Compounds characteristic only of Phytophthora plurivora or Pythium intermedium were also found. Methylcarveol occurred when germinated acorns were infected with Pythium, while neophytadiene (isomer 2 and 3) occurred only when infected with Phytophthora. Moreover, isopentanol was found in acorns infected with Phytophthora, while in control, isopentyl vinyl ether was not observed anywhere else. Among the numerous volatile compounds, isopentanol only occurred in acorns infected with Phytophthora and methylcarveol in acorns infected with Pythium.     

Reaction of diethylhydroxyborane with trialkylaluminium

The reaction of diethylhydroxyborane with trialkylaluminium has been studied. Trialkylboranes and diethyltriisobutyldialuminium dioxide were isolated and characterized. A two-stage mechanism is proposed for the formation.     

The contribution of surface effects to the surface photovoltage dependence on temperature for the real Si(111) surface

The dependences of the surface photovoltage and photoconductivity on temperature (in the range of 300–430 K) for the real p- and n-type Si(111) surface have been measured. The results of the experiments have shown the strong influence of the surface treatment (etching in HF solution or baking in vacuum) on the temperature dependences of the surface photovoltage and photoconductivity. Good qualitative agreement has been obtained between experimental and theoretical plots of the surface photovoltage as a function of temperature calculated on the basis of the Lile theory.     

High-pressure (2+2)cycloaddition of toluene-4-sulphonyl isocyanate to glycals

High-pressure (2+2)cycloaddition of toluene-4-sulphonyl isocyanate to glycals is examined. Reactions proceed regiospecifically to afford single products in case of all 3-substituted glycals. Upon heating or even after standing at room temperature adducts undergo retro-addition to give starting glycals. Various aspects of the cycloaddition are discussed, especially ret-ro-reaction and rearrangement of β-lactams to α,β-unsaturated amides.     

A free particle in noncommutative space-time

By examining some known wave equations it is shown that the dynamics of a free quantum particle in a slightly noncommutative space-time is equivalent to that of a charged particle moving in a self-generated (weak) electromagnetic field.Presented at the 5th International Colloquium on Quantum Groups: Quantum Groups and Integrable Systems, Prague, 20–22 June 1996.     

Theoretical modeling of the nonenzymatic solvolysis of CMP-NeuAc in an acidic environment

A density-functional-theory investigation of the nonenzymatic solvolysis of the cytydine 5′-monophosphate N-acetylneuraminic acid and its derivatives in the acidic environment is presented. The theoretical calculations of the second stage of the reaction mechanism are in agreement with the hypothesis of a dissociative oxocarbenium-like transition state with proton transfer as a key part of the reaction. The geometries of the transition states of the reactions yielding -methyl and β-methyl glycosides are essentially different. This study provides new theoretical data that can be helpful in elucidating the mechanism of the carbohydrates hydrolysis as well as other reactions catalyzed by the glycosyltransferases.     

Polarization of Molecular ions in NaTCNQ and TTF. TCNQ Crtstals

Self-consistent electrostatic intersite potentials and atomic charges have been calculated. Lattice cohesion energy for NaTCNQ has been reproduced when polarization of TCNQ- anion in the lattice was taken into account.