Development of a digital freeprogrammable function generator for high precision double motion Mössbauer-drives

Construction and use of a function generator are presented. The flexible outline allows a high precision control for all required velocity profiles.     

Advantages of Odd Random Phase Multisine Electrochemical Impedance Measurements

Electrochemical impedance spectroscopy (EIS) is a powerful technique to study electrochemical processes and to perform screening tasks. Recently an integrated measuring and modeling methodology for EIS based on a multisine excitation signal was developed. A key issue in this methodology is the data analysis, allowing us to rapidly quantify the reliability of the measured data. In this paper, a comparison is made between classical single‐sine and the proposed multisine measurements on the same system. The fitting of the impedance data obtained by single‐or multisine excitation and using different weighting factors is also discussed. In addition to the advantages reported in earlier work, it is concluded that, of all investigated frequencies, the odd random phase multisine excitation yields the highest quality data in the shortest measurement time.     

IRMPD spectroscopy of anionic group II metal nitrate cluster ions

Anionic group II metal nitrate clusters of the formula [M₂(NO₃)₅]⁻, where M₂ = Mg₂, MgCa, Ca₂, and Sr₂, are investigated by infrared multiple photon dissociation (IRMPD) spectroscopy to obtain vibrational spectra in the mid-IR region. The IR spectra are dominated by the symmetric and the antisymmetric nitrate stretches, with the latter split into high and low-frequency components due to the distortion of nitrate anion symmetry by interactions with the cation. Density functional theory (DFT) is used to predict geometries and vibrational spectra for comparison to the experimental spectra. Calculations yield two stable isomers: the first one contains two terminal nitrate anions on each cation and a single bridging nitrate (“mono-bridging”), while the second structure features a single terminal nitrate on each cation with three bridging nitrate ligands (“tri-bridging”). The tri-bridging isomer is calculated to be lower in energy than the mono-bridging one for all species. Theoretical spectra of the tri-bridging structure provide a better qualitative match to the experimental infrared spectra of [Mg₂(NO₃)₅]⁻ and [MgCa(NO₃)₅]⁻. However, the profile of the low-frequency ν ₃ band for the Mg₂ complex suggests a third possible isomer not predicted by theory. The IRMPD spectra of the Ca₂ and Sr₂ complexes are better reconciled by a weighted summation of the spectra of both isomers suggesting that a mixture of structures is present.     

A performance comparison of k<Subscript>0</Subscript>-based ENAA and NAA in the (K,Th, U) radiation dose rate assessment for the luminescence dating of sediments

Summary Recently, in our laboratory an intercomparison was made of methods for the annual radiation dose determination (assessed from direct radiation counting and/or from the measurement of the K, Th and U contents) applied to luminescence dating of loess and sand sediment, whereby the emphasis was put on their precision and accuracy. Although these properties are important, the duration of the measurement is also a practically relevant aspect. Indeed, direct alpha, beta and gamma-counting can last a week or more, and the determination of K, Th and U via NAA can take up to three weeks to enable proper gamma-ray spectrometry of the long-lived ²³³ Th/²³³Pa. Therefore, in the present work the performance of k₀-based epiCd-NAA (ENAA, with irradiation under a cadmium cover) when applied to sediments is compared to k₀-NAA. As concluded, with the use of k₀-ENAA the analysis turnaround time could be considerably reduced from ~3 weeks to ~ 2.5days, while maintaining satisfactory accuracy, precision and determination sensitivity.     

Copper-mediated N- and O-arylations with arylboronic acids in a continuous flow microreactor: a new avenue for efficient scalability

A continuous flow procedure has been elaborated for the copper(II)-mediated N- and O-arylation of a range of compounds with arylboronic acids using a commercial microreactor setup. The compounds could be continuously generated in good yields paving the way for efficient scalability.     

Quantification of testosterone undecanoate in human hair by liquid chromatography–tandem mass spectrometry

Testosterone undecanoate (T‐C11) can be used by athletes in order to improve performance. After oral intake, T‐C11 is rapidly metabolized, hampering discrimination between exogenous and endogenous testosterone. A possible alternative is to detect the intact ester in hair. A method based on liquid chromatography–tandem mass spectrometry was developed for the determination of T‐C11 in hair. The sample procedure consisted of digestion of 200 mg of pulverized hair with tris(2‐carboxyethyl)phosphine hydrochloride and liquid–liquid extraction with n‐pentane. Several parameters such as the mobile phase, the ionization source and the washing step were optimized. The method was validated at different spiked levels obtaining satisfactory values for accuracy (between 92 and 102%) with relative standard deviations lower than 7% and a limit of detection of 0.2 ng/g. The applicability of the method was checked by the analysis of three samples from patients using T‐C11. A peak for the analyte was detected in all samples with concentrations between 0.4 and 8.4 ng/g. Copyright © 2009 John Wiley & Sons, Ltd.     

Gamow-Teller strength in the β+ decay of104In

Theβ-strength function of¹⁰⁴Cd is studied in theβ ⁺/EC decay of mass-separated¹⁰⁴In. The determination of theβ ⁺ feeding and theβ ⁺/β ⁺EC ratio is the result of the simultaneous measurement of beta and gamma rays in one semiconductor beta-spectrometer. Information on the strength function near theQ _EC value is obtained from the detection of high-energyγ rays. The total observedβ strength amounts up to 10% of the Extreme Single-Particle Shell Model value. A strong enhancement in theβ ⁺/EC feeding to a group of levels around 5.6 MeV shows the influence of the Gamow-Teller Resonance.