High-resolution spectroscopy of bacteriochlorin in n-alkane host crystals at 4.2 K

Site-selection spectroscopy of free-base bacteriochlorin (7,8,17,18-tetrahydroporphin) in n-hexane, n-octane and n-decane at 4.2 K are reported. The vibrational frequencies of the ground state, and first and second excited singlet states were determined from the fluorescence and excitation spectra. Low-frequency modes were observed, from which the angle of reorientation of the Molecule upon excitation is estimated (< 1.5°).     

Pitfalls in the determination of optical homogeneous linewidths in amorphous systems by hole-burning. Influence of the structure of the host

An analysis is given of the conditions requires for the determination of the optical homogeneous linewidth (Γ_hom) in an organic glass from hole-burning experiments, in particular as regards laser power and detection method. The influence of the structure of polymer hosis on Γ_hom of free-base porphin as guest is studied with respect to solvents and size of polymer sidegroups.     

A simple and sensitive assay for the quantitative analysis of paclitaxel and metabolites in human plasma using liquid chromatography/tandem mass spectrometry

A sensitive and specific LC-MS/MS assay for the determination of paclitaxel and its 3'p- and 6-alpha-hydroxy metabolites is presented. A 200 microL plasma aliquot was spiked with a 13C6-labeled paclitaxel internal standard and extracted with 1.0 mL tert-butylmethylether. Dried extracts were reconstituted in 0.1 M ammonium acetate-acetonitrile (1:1, v/v) and 25 microL volumes were injected onto the HPLC system. Separation was performed on a 150 x 2.1 mm C18 column using an alkaline eluent (10 mm ammonium hydroxide-methanol, 30:70, v/v). Detection was performed by positive ion electrospray followed by tandem mass spectrometry. The assay quantifies a range for paclitaxel from 0.25 to 1000 ng/mL and metabolites from 0.25 to 100 ng/mL using 200 microL human plasma samples. Validation results demonstrate that paclitaxel and metabolite concentrations can be accurately and precisely quantified in human plasma. This assay is now used to support clinical pharmacologic studies with paclitaxel.     

A software controllable time-gain-compensation amplifier board for VMEbus systems

A new time-gain-compensation (TGC) amplifier has been designed and built. It has flexible and unambiguous TGC-amplification by software steering through digital control and synchronization of this amplification to the clock of the analogue-to-digital converter. It has been built on a single VMEbus board, and enables control of the RF signal as a function of time for ultrasound propagation in layered attenuating media.     

Study of DyFe12−xMx compounds by57Fe and161Dy Mössbauer spectroscopy

DyFe_12?xM_x (M=Si,Ti,Cr) were studied with⁵⁷Fe and¹⁶¹Dy Mössbauer spectroscopy. The deduced coupling constants J_RFe of these compounds are about equal. It is found that Si is substituting one particular Fe-site, while Cr is substituting Fe randomly. In DyFe₁₀Si₂ two Fe-sites favour a c-axis anisotropy, while the third one favours the basal plane.     

A Kalman filter for calibration,evaluation of unknown samples and quality control in drifting systems : Part 1. Theory and Simulations

The suitability of a Kalman filter for processing slowly varying parameters of a linear calibration graph is described. After calibration, the recursive algorithm predicts the changing parameters in time, which are used for the evaluation of unknown samples. With a preselected precision of the final results as a proper analytical goal, one may decide successively either to do another unknown sample or to calibrate again. The application of the proposed algorithm is demonstrated with a simulated example based on realistic data.