Identification of an unknown b-agonist in feed by liquid chromatography/bioassay/quadrupole time-of-flight tandem mass spectrometry with accurate mass measurement.

A new approach to the search for residues of unknown growth promoting agents such as anabolic steroids and -agonists in feed is presented. Following primary extraction and clean-up, samples are separated using gradient liquid chromatography (LC). The effluent is split towards two identical 96-well fraction collectors and an optional electrospray quadrupole time-of-flight mass spectrometry (QTOFMS) system for accurate mass measurement. One 96-well plate is used for a bioassay (enzyme-immuno assay, receptor assay) and will detect the bioactivity and position of the relevant peak in the chromatogram. The positive well in the second 96-well plate is used for identification by LC/QTOFMS/MS. The value of this LC/bioassay/QTOFMS/MS methodology is highlighted by the finding and structure elucidation of a new -agonist in a feed extract.

Single feed low profile omnidirectional antenna with slant 45 degrees linear polarization

It is shown that a side-fed bifilar helix antenna with a single feed, can generate a slant 451 linearly polarized onmidirectional toroidal pattern. The antenna has a low profile and does not require a ground plane. The bifilar helix antenna provides slant 45 degrees polarization over a solid angle of almost 4 pi steradians as compared to a crossed dipole which generates a tilted 45 degrees linearly, polarized pattern only over a solid angle of 1.14 pi steradians. The computed results are validated by experimental data.

Analysis of the effect of finite d.c. blocking capacitance and finite d.c. feed inductance on the performance of inverse class-E amplifiers

The first analysis and synthesis equations for the newly introduced inverse Class-E amplifier when operated with a finite d.c. blocking capacitance and a finite d.c.-feed inductance are presented in the paper. Closed-form design equations are derived in order to establish the circuit component values required for optimum synthesis. Excellent agreement between numerical simulation results and theoretical prediction is obtained. It is shown that drain efficiency approaching 100 at a pre-specified output power level can be achieved as zero-current switching and zero-current derivative conditions are simultaneously satisfied. The proposed analysis offers the prospect for realistic MMIC implementation.