Multilevel description of the Rh isotopes in the interacting boson-fermion model

We present a multilevel calculation within the framework of the interacting boson-fermion model (IBFM-1) of the odd-mass ^101–109Rh isotopes. We calculate both positive- and negative-parity states of the same hamiltonian, starting from the $\text{1g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$, $\text{2p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, $\text{lf}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ and $\text{2d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ single-particle orbitals. We discuss energy spectra, electromagnetic E2 transition rates and one-nucleon transfer properties. We also discuss the influence of the $\text{1f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ orbital on the one-nucleon transfer properties. The results of the calculation for the negative-parity states are compared with the results of the $\text{U(}\text{6}\text{12}$) supersymmetry scheme of the interacting boson model.     

A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.     

Towards logistics systems parameter optimisation through the use of response surfaces

Logistics systems have to cope with uncertainties in demand, in lead times, in transport times, in availability of resources and in quality. Management decisions have to take these uncertainties into consideration. An evaluation of decisions may be done by means of simulation. However, not all stochastic phenomena are of equal importance. By design of simulation experiments and making use of response surfaces, the most important phenomena are detected and their influence on performance estimated. Once the influence of the phenomena is known, this knowledge may be used to determine the optimal values of some decision parameters. An illustration is given on how to use response surfaces in a real-world case. A model is built in a logistics modelling software. The decision parameters have to be optimised for a specific objective function. Experiments are run to estimate the response surface. The validity of the response surface with few observations is also tested.     

Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co_1.1−x Zn _x Ge_0.1Fe_1.2O₁ spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co²⁺ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.     

Quantitative determination of transferrin in cerebrospinal fluid using an enzyme linked immunosorbent assay

An enzyme linked immunosorbent assay (ELISA) based method for the determination of transferrin in cerebrospinal fluid (CSF) is described. This method allows transferrin determinations in ultra-small ( 5 L) sample volumes. The proposed method offers the possibility to determine transferrin at very low concentrations at which existing methodologies fail because of their insufficient detection limits. The accuracy of the proposed technique was validated by comparing the results of 20 CSF samples obtained by ELISA to those measured by nephelometry yielding mean ± SD values of 21.1±5 mg/L and 20.6 ± 6 mg/L, respectively (y = 1.13X – 2.97, r = 0.899). The interassay CV was below 10% whereas the detection limit was 2.9 g/L.     

HPLC-AAS hybrid technique for studying the speciation of trace metals (Al,Fe, Si,Hg) in biological fluids: A review of applications,recent experiences and perspectives

A method developed using the combination of HPLC and AAS enabling both qualitative and quantitative study of the protein binding and speciation of trace metals in biological fluids at clinical relevant levels is reviewed. The whole system was made metal-free by using polymer-based columns, column holders and tubing and by the insertion of a silica-based scavenger column placed immediately before the injection valve to selectively retain any trace of aluminum and iron originating from buffer solutions and recipients. ETAAS instrumental conditions were carefully selected to eliminate interferences secondary to the salt gradient elution. Particular attention was paid to the choice of HPLC columns. Protein recoveries varied between 95 and 105% and trace metal recoveries were close to 100%. Intra-assay and inter-assay CVs of the HPLC/AAS hybrid technique were below 10%. Because of its high sensitivity, the method can be used at clinically relevant concentrations and was applied successfully to study (i) the interaction between iron and aluminum for binding to transferrin, (ii) the influence of citrate on the transferrin binding of aluminum, (iii) the speciation of silicon in the serum of dialysis patients and (iv) the toxicity of mercury compounds in cell cultures.     

Ring transformation of 2-(haloalkyl)azetidines into 3,4-disubstituted pyrrolidines and piperidines

[reaction: see text] Reduction of 4-(haloalkyl)azetidin-2-ones with chloroalane (AlH(2)Cl) afforded new 2-(haloalkyl)azetidines in high yields. The latter compounds proved to be very useful starting materials for rearrangements toward stereospecifically defined five- and six-membered azaheterocycles, such as 3,4-cis-disubstituted pyrrolidines and piperidines. During these reactions, bicyclic azetidinium intermediates were formed which were ring opened by a variety of nucleophiles. Hereby, reactions proceeding via 1-azoniabicyclo[2.2.0]hexanes are reported for the first time.