Pump, diffusion principal

Synaptic Clearance Antagonists. By preventing the removal of naturally-released transmitter from the region of its receptors, the effect of the neuromesssenger on the receiving cell will be prolonged and intensified. There are three principal routes by which neuromessengers are removed from the synaptic cleft (i) enzymatic destruction of the transmitter (e.g., acetylcholine (ACh) which is hydrolyzed in the synaptic cleft by acetylcholinesterase) (ii) uptake into pre- and post- synaptic cells by membrane-associated pumps that have substantial specificty for molecules they will carry (iii) diffusion away from the cleft. 

The principal types of vacuum pumps will be discussed in this section. The water aspirator is a crude but useful pump for many routine operations. Rotary oil pumps are used for pumping on refrigerant baths and as the forepump for backing low-pressure pumps. For most high-vacuum work, diffusion pumps are utilized to achieve pressures... 

There is, in principal, an alternative to the rotation of the disc, which is the rotation of the electrolyte. But just rotation of the electrolyte would not lead to similar diffusion conditions because the electrolyte, stopped at the walls of the cell, would develop a different radial flow profile. The generation of the same diffusion layer by rotation of the electrolyte was achieved by a special rotating pumping system as shown in Figure 5.24. ... 

The areas of application for these vacuum pumps are all within the rough and medium vacuum range, the principal vacuum range for chemistry processes. Only the short path and molecular distillation processes rely also high-vacuum pumps like the diffusion pump or even the turbomolecular pump (kinetic gas pumps). High-vacuum pumps are not covered in this book. For these refer to [2, 3]. 

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