The induction of quantum beats by hyperfine interactions in radical-ion pair recombination

Quantum beats were detected in the recombination of spin-correlated radical-ion pairs. These beats are induced by singlet-triplet transitions in a pair due to hyperfine interactions. Singlet radical-ion pairs were generated by radiolysis of hydrocarbons involving acceptors of electrons and holes. The singlet pair recombination was detected by the luminescence of the product (singlet-excited molecules). The beat frequencies measured for (tetramethylethylene) ⁺/(paraterphenyl-d₁₄)-and (durene)⁺/(paraterphenyl-d₁₄)^? pairs correspond to the hfi constants in the cation radicals. The character of the beats differ in high and zero magnetic fields and their shape depends upon the solvent.     

A preliminary matrix‐assisted laser desorption/ionization time‐of‐flight approach for the characterization of Italian lentil varieties

Matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) was used in this study to obtain protein fingerprints of seven different lentil varieties, to characterize their differences and similarities. Two different matrices have been tested in order to obtain reproducible and significant mass spectra. Extraction with water containing 0.1% of trifluoroacetic acid has been used as preparative step to obtain hydrophilic protein samples of lentil seeds. The obtained MALDI protein profiles identified clear differences between the seven studied lentil varieties. Moreover, considering the high complexity of the obtained MALDI spectra, multivariate techniques of data analysis were employed to find further classification details. These multivariate analyses confirmed the possibility of a clear classification of the seven lentil varieties, indicating that the proposed procedure can be a valid taxonomic tool, and a method to certify the origin of lentils, useful for high added value lentils (Italian lentils). Copyright © 2010 John Wiley & Sons, Ltd.     

Eine einfache Methode zur Berechnung des Viskosit?tsgrades von Mineral?lmischungen

Ohne Zusammenfassung     

Proficiency testing in analytical chemistry, microbiology, and laboratory medicine – working group discussions on current status, problems, and future directions

Working group (WG) discussions on proficiency testing (PT) held at the joint Eurachem/ EQALM workshop, Borås, Sweden, 24–26 September 2000 are summarized. The discussions focused on aspects of PT and accreditation (WG 1), general aspects of PT in analytical chemistry (WG 2), microbiology (WG 3), and laboratory medicine (WG 4), incorporation of measurement uncertainty into PT schemes (WG 5), international harmonization of PT schemes (WG 6), and the role of PT in the international structure of chemical measurement (WG 7). Current status, problems and future directions are identified. Each WG contained a majority of participants experienced in the subject being covered by that WG, and a few participants with different expertise. This was done to promote cross-fertilization of ideas between sectors, a key objective of the workshop. The WG issues reflected the content of the keynote lectures and some issues were covered from different perspectives by more than one group.     

The influence of hemicellulose on fibril aggregation of kraft pulp fibres as revealed by FE-SEM and CP/MAS 13C-NMR

Three Norway spruce pulps were produced using different kraft pulping methods, in order to obtain large differences in cellulose and hemicellulose proportions at a similar lignin content. The hemicellulose content in the three pulps varied between 10% and 22%. The aim of the study was to evaluate the influence of cellulose and hemicellulose on fibre ultrastructure and correlate this with the differences observed in the mechanical properties between the pulps. The ultrastructure of the pulp fibres were studied using Field Emission Scanning Electron Microscopy (FE-SEM) and Solid-State Cross Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (CP/MAS ¹³C-NMR) in combination with spectral fitting. CP/MAS ¹³C-NMR measured the average bulk properties of the pulp fibres, while FE-SEM allowed for observations on the ultrastructure of fibre surfaces. The ultrastructure of the fibres varied with varying hemicellulose content. The pulp with a high hemicellulose content had a porous surface structure. In fibres with a low hemicellulose content, the fibril aggregates (macrofibrils) formed a much more compact surface structure. With CP/MAS ¹³C-NMR this change was reflected by an increase in average fibril aggregate width with decreasing hemicellulose content. Results from FE-SEM and CP/MAS ¹³C-NMR correlated well. The changes recorded in ultrastructure may explain the very different mechanical properties reported previously for pulps with different hemicellulose content.     

Coarse-grained description ofq-deformation top and t-j model

From RTT relations the integrable Hamiltonian of the trigonometric Goryachev-Chaplygin gyrostat is established, which can be reduced to the Hamiltonian of t-j model by using multi-fermion realization ofSU _q(2) algebra and average-field approximation. Project supported in part by the National Natural Science Foundation of China (Grant No. 19377102).