Electron ionization and methane chemical ionization mass spectrometry study of some 2,2-disubstituted 1,3-dioxolanes, 1,3-dithiolanes, 1,3-oxathiolanes and 1,3-dioxanes. Gas-phase lactone and thiolactone formation

The electron ionization and methane chemical ionization mass spectra of some 2,2-disubstituted 1,3-dioxolanes, 1,3-dithiolanes and 1,3-oxathiolanes were studied. Especially, the effect of the length of the side chain in ring position 2 of these compounds and the ease of formation of possible lactone/thiolactone ion as a fragmentation product were examined. In addition, two 2,2-disubstituted 1,3-dioxanes were studied to see the effect of the bigger ring size. The formation of lactone ions was more favorable under methane chemical ionization than under electron ionization conditions. The structures of fragment ions and the ions generated from model compounds were carefully studied using both high- and low-energy collision-induced dissociation. Also ab initio molecular orbital calculations up to the HF/6–31G** level of theory for protonated 2-methyl-2-propanoic acid ethyl ester of 1,3-dioxolane, 1,3-oxathiolane and 1,3-dithiolane and for two isomeric bicyclic ions were carried out. The theoretical results obtained favor the formation of the lactone ion. Copyright © 2005 John Wiley & Sons, Ltd.     

Utilisation of customer feedback in a university hospital laboratory

The article describes the customer feedback system at a university hospital laboratory and the analysis of the feedback data from clinical customers in 2001–2006. The most common subject matters of the feedback were suspicion of the validity of laboratory results, delay in service and lacking test results, covering 82% of the 115 reports. The investigations of the cases revealed errors or defects in laboratory services in 81 cases. The most common errors or defects were erroneous test results (35 cases; 43%), delayed test results (24 cases; 30%) and lacking test results (15 cases; 18%). The most common underlying causes for a laboratory error or defect were unintended errors and non-compliance with operating instructions. Seventy-six percent of the feedback reports led to corrective actions. It is important to react to every instance of customer feedback and to find out possible errors or defects in the laboratory process. Uncovering the underlying causes makes adequate corrective and preventive actions possible.     

Identification of excited states in the T(z) = 1 nucleus (110)Xe: evidence for enhanced collectivity near the N=Z=50 double shell closure

Gamma-ray transitions have been identified for the first time in the extremely neutron-deficient (N=Z+2) nucleus (110)Xe, and the energies of the three lowest excited states in the ground-state band have been deduced. The results establish a breaking of the normal trend of increasing first excited 2(+) and 4(+) level energies as a function of the decreasing neutron number as the N=50 major shell gap is approached for the neutron-deficient Xe isotopes. This unusual feature is suggested to be an effect of enhanced collectivity, possibly arising from isoscalar n-p interactions becoming increasingly important close to the N=Z line.     

Chiral differentiation of some cyclic β‐amino acids by kinetic and fixed ligand methods

Differentiation of β ‐amino acid enantiomers with two chiral centres was investigated by kinetic method with trimeric metal‐bound complexes. Four enantiomeric pairs of β ‐amino acids were studied: cis‐(1R,2S)‐, cis‐(1S,2R)‐, trans‐(1R,2R)‐ and trans‐(1S,2S)‐2‐aminocyclopentanecarboxylic acids (cyclopentane β ‐amino acids), and cis‐(1R,2S)‐, cis‐(1S,2R)‐, trans‐(1R,2R)‐, and trans‐(1S,2S)‐2‐aminocyclohexanecarboxylic acids (cyclohexane β ‐amino acids). The results showed that the choice of metal ion (Cu²⁺, Ni²⁺) and chiral reference compound (α‐ and β ‐amino acids) had an effect on the enantioselectivity. Especially, aromaticity of the reference compound was noted to enhance the enantioselectivity. The fixed‐ligand kinetic method, a modification of the kinetic method, was then applied to the same β ‐amino acids, with dipeptides used as fixed ligands. With this method, dipeptide containing an aromatic side chain enhanced the enantioselectivity. Copyright © 2009 John Wiley & Sons, Ltd.     

连续波锁模P_r~（3＋）：YLF激光器

本文报导了采用氩离子激光器来泵浦Ｒｒ￣（３＋）：ＹＬＦ晶体，应用声光调制器实现了主动锁模；同时应用振动─高反射平面镜也实现了被动锁模，两种锁模均得到了ｐｓ光脉冲。据作者了解这是这种晶体材料的第一次锁模运转。     

Modeling of the Ion Exchange in Pulp Suspensions by Gibbs Energy Minimization

The ion exchange processes, which occur when two compartments of aqueous solutions separated by a semipermeable interface are placed in aqueous electrolyte solutions, were modeled using the multiphase Gibbs energy-minimization method. The Gibbs energy-minimization technique was applied for the ion-exchange system consisting of pulp fibers and the surrounding aqueous bulk solution. In such a system, the anionic acid groups inside the fibers cause an uneven distribution of ionic species between the solution within the fiber walls and the solution external to the fibers. The method was tested with four cation concentrations, which are naturally present in the fibers and whose partitioning between the fiber phase and the external solution phase has been described earlier. Although the Donnan distribution constant is not explicitly calculated in the Gibbs energy-minimization model, the results are consistent with the Donnan equilibrium theory. With the Gibbs energy-minimization multiphase model, the formation of solid precipitates can also be calculated.