Siemens gradient system

Step gradients. The Siemens step-gradient system is shown in Fig, 6. Two solvents, A and B, are contained in two 220-nil holding coils (b, c), connected... 

LDC gradient master and Siemens Sill gradient system, some concave, linear or convex curves are pre-selected. They generally correspond to the following equations ... 

The number of different curves is B (Siemens), 9 (Spectra-Physics, LDC), 11 (DuPont, Waters) or infinite (Micromeritics and Perkin-Elraer) as the curvature can be selected continuously. In the last instance, the curvature selected must be read precisely in order to obtain good reproducibility. Although the curves are pre-selected, it is often possible to obtain complex gradient shapes, as at any time the programme can be stopped and a new curve selected. With the Orlita gradient system, only a linear gradient is available. However, an external control is possible. 

Many high-pressure liquid chromatographs include a gradient elution system. With the exception of the Siemens and Spectra-Physics systems, only two-.solvent gradient can be made with these devices, All systems that are able to give a continuous gradient also permit operation under isocratic conditions with a mixture of the two solvents of constant composition. 

There are only four installed human brain PET-MR imagers in the world at this moment. The PET insert is inside the magnet covered by the gradient coil. Data acquisition can be done separately or simultaneously by using two separate computers. The platform of the PET insert is the same as in the latest version of Siemens Inveon animal PET system. The MR imager is Siemens 3T TRIO. 

---