Electric feed systems for liquid-propellant rockets

Liquid-propellant rocket feed systems based on electric pumps are compared with the more classical pressure-gas and turbopump systems. The design parameters entering in the definition of the system mass are highlighted, and a careful choice of the figures of merit is performed, in particular for the electric motors and batteries. Indeed, recent developments, taking into account new electric motors based on rare earth permanent magnets (neodymium-iron-boron) , and different lithium-based cells, show that the specific mass of the electric-pump system can be reduced to such an extent to make the proposed system competitive not only with the pressure-gas system but also with the turbopump one, at least for some applications such as small launchers and upper stage rockets. Further, electric motor and battery cell technologies currently under development could extend the proposed feed system convenience. Critical points related to electric-pump systems are also discussed

Sample preparation for peptides and proteins in biological matrices prior to liquid chromatography and capillary zone electrophoresis

The determination of peptides and proteins in a biological matrix normally includes a sample-preparation step to obtain a sample that can be injected into a separation system in such a way that peptides and proteins of interest can be determined qualitatively and/or quantitatively. This can be a rather challenging, labourious and/or time-consuming process. The extract obtained after sample preparation is further separated using a compatible separation system. Liquid chromatography (LC) is the generally applied technique for this purpose, but capillary zone electrophoresis (CZE) is an alternative, providing fast, versatile and efficient separations. In this review, the recent developments in the combination of sample-preparation procedures with LC and CZE, for the determination of peptides and proteins, will be discussed. Emphasis will be on purification from and determination in complex biological matrices (plasma, cell lysates, etc.) of these compounds and little attention will be paid to the proteomics area. Additional focus will be put on sample-preparation conditions, which can be 'hard' or 'soft', and on selectivity issues. Selectivity issues will be addressed in combination with the used separation technique and a comparison between LC and CZE will be made. © Springer-Verlag 2005