Systems Involving Differential Pumping

All molecular systems involved in Ca2+ homeostatic processes are regulated by Ca2+ itself, which operates numerous feedback loops. That is, increase in cytosolic Ca2+ concentration induces a Ca2+-dependent inactivation of voltage-operated plasmalemmal Ca2+ channels. Fluctuations in [Ca2+]L differentially regulate Ca2+ transport across the endomembrane elevation of [Ca2+]L increases the susceptibility of RyRs and InsP3Rs to activation, and inhibits the SERCAs when [Ca2+]L falls, the SERCA pumping is much activated, and the Ca2+ release channels are inhibited (Burdakov et al., 2005 Burdakov and Verkhratsky 2006). 

Hydrodynamic chromatography. This technique is related to SEC in that it attempts to separate species according to their size, but several orders of magnitude larger than those encountered in solution chromatography. The mechanisms involved in hydrodynamic chromatography are different to SEC, but the basic experimental system is similar pump, injector, column and detector. Special columns and data analysis software are required, and the detectors usually employed are a differential refractometer, ultraviolet photometer or LALLS. Chapter 10 is devoted to this technique and full details can be found there. 

In all vacuum systems, the pressure obtained is determined by the gas load and the effective pumping speed. In UHV systems at equilibrium, the predominant gas load arises from the outgassing of the internal surfaces. Although gas sources in vacuum systems have been discussed in Chapter 4, no differentiation was made between gas adsorbed on a surface and that absorbed within its structure. Various applications of UHV technology involve the use of vacuum systems that cannot be baked in situ and consideration of the choice of material for the vacuum envelope and also its surface treatment is critical. An important starting point for this is an understanding of the interaction of gas with materials. 

The sequence in the treatment of a core with a polymer gel system is similar to that just described and typically involves three steps. First, the initial permeability of the core sample is measured with brine. Then the core is treated with a polymer/crosslinker solution at a constant rate using a dual piston HPLC pump and a transfer cell (see Figure 5) while monitoring pressure with a differential pressure transducer. The core effluent is fractionated for analysis. This includes the determination of polymer and crosslinker concentration, the measurement of sample gelation tendencies, and the investigation of rock/polymer interactions. Finally, after a waiting period to allow gelation, the final permeability of the core is measured with brine to evaluate the effectiveness of the treatment. 

From now on the number of clusters involved in the Type I and Type II dissociation process will be called ni t) and ri2 i), respectively. The number of larger clusters, which are excited by the pump pulse and dissociate into the recorded mass channel, is characterized by a single simplifying function Hence, this extended fragmentation model leads to the following system of coupled differential equations ... 

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