Pumping diffusion

An essential requirement for diffusion of Na+ ions is the creation of a concentration gradient for sodium between the filtrate and intracellular fluid of the epithelial cells. This is accomplished by the active transport ofNa+ ions through the basolateral membrane of the epithelial cells (see Figure 19.4). Sodium is moved across this basolateral membrane and into the interstitial fluid surrounding the tubule by the Na+, K+-ATPase pump. As a result, the concentration of Na+ ions within the epithelial cells is reduced, facilitating the diffusion of Na+ ions into the cells across the luminal membrane. Potassium ions transported into the epithelial cells as a result of this pump diffuse back into the interstitial fluid (proximal tubule and Loop of Henle) or into the tubular lumen for excretion in the urine (distal tubule and collecting duct). 

Figure 18.1 Diagram of the glass vacuum line showing the major components mechanical pumps, diffusion pump, vacuum gauge, main vacuum manifold, and purge valve.

Check pumping system to be sure it is achieving a good vacuum. If necessary, correct problem with fore pump, diffusion pump, or cold trap. 

A. Typical Systems. A simple system for the transfer of samples to an infrared gas cell or to a NMR sample tube consists of a fore pump, diffusion pump, trap, and manifold (Fig. 5.1). At the other extreme is a general-purpose chemical vacuum line, which permits the separation of volatile compounds, transfer of noncondensable gases, and storage of reactive gases and solvents (Fig. 5.2). When attack of stopcock grease is a serious problem, grease-free de-... 

The reaction was studied in a laboratory assembled high-vacuum system (see Figures 9.8 and 9.9), consisting of two vacuum circuits, one for the evacuation of the evaporation chamber and the other for the evacuation of the gas introduction system [119,122,123], Figure 9.8 shows the fore pump, diffusion pumps, cold traps, ionization manometer, and the metal evaporation chamber [119]. The evaporation was carried out al / = 10 6 Torr, with the help of a thread helicoidal filament made of a wolfram (W) wire of 0.5mm diameter and 10cm length [119]. The whole vacuum system was coupled with a mass spectrometer, Hitachi RMU-6D, in order to follow the reaction kinetics [119,122,123] (see Figure 9.9). The procedures followed in order to study the reaction were as follows ... 

The most common problem with hydrocarbon diffusion pump oil is its fractionation into multivapor pressure components. As pump oil breaks down, it develops both lower and higher vapor-pressure characteristics. Oils with high vapor pressures can potentially drift into the system, although they are more likely to be effectively removed from the system by being trapped in the alembics of the central vertical tube, in the cold trap between the system and the diffusion pump, or in the cold trap between the diffusion pump and the mechanical pump. If not trapped, they are free to travel into the vacuum line itself or into the mechanical pump. Diffusion pump oils that collect in a mechanical pump are not likely to have any significant performance effects (as opposed to the degrading effects of mechanical pump oil collected in diffusion pumps). 

Liquid-nitrogen cold traps stop condensable vapors from traveling between mechanical pumps, diffusion pumps, and the rest of the system. They also protect the helium leak detector from possibly contaminating materials (such as silicon-based diffusion pump oil). 

N02), a 2 ohm 10 W resistor, five female AC plugs, chassis mount (for the mechanical pumps, diffusion pump heater, CuO tube heater, etc.), five tineon lamps, 125 V, 0.3 W, five SPST 10 A power switches, a fuse holder, an amphenol 5 pin hex chassis mount female connector (to receive male connector with wires from alligator clips attached to leads on Toepler pump), a 6 foot power cord,... 

Figure 7-13. A fore pump - diffusion pump combination (Courtesy - Van Waters Rogers Scientific Co., McGaw Park, IL)...

High vacuum (0.1 Pa-ca. 0.001 Pa) Pump combination for example two stage positive displacement pump+ diffusion pump or single stage positive displacement pump +oil ejector + diffusion pump Molecular distillation (open path, short path distillation) Cup molecular distillator Rotary molecular distillator Film molecular distillator Centrifugal molecular distillator... 

The jet pump diffuser is welded to the core shroud support plate and designed to recover static head from the available kinetic energy. 

Types of chemical mixers (a) pump diffusion, (b) static,... 

Figure 2-10 Singie-blade mechanical mixer 21 Figure 2-11 Types of chemical mixers (a) pump diffusion, (b) static, (c) venturi 22...

Vacuum pump, diffusion pump (DP) A compression-type vacuum pump that operates by the collision of heavy vapor molecules with the gas molecules to be pumped, giving the gas molecules a preferential velocity toward the high pressure stages of the pump. Also called a Diff pump or Vapor jet pump. 

Oil-Sealed Rotary Pumps Turbomolecular Pumps Diffusion Pumps Cold Traps Sorption Pumps Ion Pumps Manifolds... 

Hot Diffusion Pumps. Diffusion pumps are very hot, and anyone working around them should be careful to avoid contact with them and to keep the area around them clear of flammable objects. 

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