Pumping method

Fig. 1. Pumping methods for lasers where is the pump light frequency and is the laser frequency, wavy lines represent radiationless transitions, and the dashed line collisions (a) optical pumping in three-level systems (b) optical pumping in four-level systems (c) pumping by electron impact and...

A third pumping method (Fig. Ic) uses an electrical discharge in a mixture of gases. It relies on electronic excitation of the first component of the gas mixture, so that those atoms are raised to an upper energy level. The two components are chosen so that there can be a resonant transfer of energy by collisions from the upper level of the first component to level 3 of the second component. Because there are no atoms in level 2, this produces a population inversion between level 3 and level 2. After laser emission, the atoms in the second component return to the ground state by collisions. 

Therefore, the single-pump method is commonly used only for smaller spills when the gasoline-water recovery rates are relatively low (e.g., less than 1892 L/h or 500 gal/h). 

Most contaminations of aquifers are a result of material being released above the saturated zone. The contaminant pumping method is limited to the cleanup of the saturated zone. Contaminants in the unsaturated zone can still be a source of future contamination. In situ bioremediation techniques can also be designed to clean up the unsaturated zone simultaneously. 

The contaminants in places where they are strongly adsorbed or where permeability is locally low, or where microcracks are developed in rocks, cannot be efficiently drawn out with water using the pumping method. 

Answer. There has been little effective interplay between experimental results obtained on single nanostructures grown as quantum-wells and studied by optical-pumping methods and those obtained on bulk nanoscale semiconductors by more conventional NMR approaches. However, this situation may change, since the former studies can provide information about the effects of, e.g., charge carriers or strain or compositional interfaces upon NMR parameters such as chemical and Knight shifts and EFGs in reasonably well-defined systems. 

Due to the large variety of laser materials and pumping methods, it is almost impossible to catalog all the laser devices that have been demonstrated up to date. However, we can make a classification of the laser systems based on the different types of active media. We will briefly comment on the basis and properties of some specific types of laser systems, which are representative of different laser schemes. 

The different pumping methods, such as the commonly used current injection or optical pumping electron beam pumping and avalanche breakdown have been studied in detail (for further refs, see and information has been obtained regarding the excitation probabilities of the different interband transitions. The very short laser pulses (less than 10 sec) obtained enable rapid processes and their time dependence to be studied. 

This technology is most advantageous in low-permeability soils, such as clay, where only a limited amount of groundwater can be withdrawn by traditional pumping methods. 

The other area in which projection of an unrestricted result has received attention is projected Mpller-Plesset perturbation theory, the PUMPn methods [31], where n is the order of the perturbation theory. In cases in which the UHF approximation is a poor starting point (considerable spin contamination, for example), the convergence of the MP perturbation expansion can be slow and/or erratic. The PUMP methods apply projection operators to the perturbation expansion, although usually not full projection but simply annihilation of the leading contaminants. This approach has met with mixed success again, it represents a rather expensive modification to a technique that was originally chosen partly for its economy — seldom a recipe for success. 

Dimroth, P (1986) Preparation, characterization, and reconstitution of oxaloac-etate decarboxylase from Klebsiella aerogenes, a sodium pump. Methods Enzymol 125, 530—540... 

In the syringe pump method, the halide and the alkene acceptor are typically refluxed in benzene and a solution of tributyltin hydride and AIBN in benzene is added slowly over a period of hours by syringe drive. The exact concentration of tin hydride is not known but it remains low, provided that the chain continues at a rate more rapid than syringe pump addition. Telomerization may intervene if the tin hydride concentration falls too low. To insure that the chain continues, it is important to use a reactive atom donor (to maximize the rate of step 1) and to insure that a constant source of initiator is present.91... 

The liquid pumping in the microfluidic chip is mostly achieved by using electro-osmotic flow (EOF) [324]. Other liquid pumping methods have also been employed for microfluidic flow. Flow has been employed for fraction collection and generation of concentration gradient. Laminar flow in the microfluidic channel allows liquid-liquid extraction and microfabrication to occur within the channels. Moreover, valving and mixing are needed in order to achieve a better flow control. All these microfluidic flow operations are further described in subsequent sections. 

The thermal effect is exploited to produce liquid pumping. For instance, a thermocapillary pump was constructed. The pumping method is based on surface-tension change due to local heating created by heaters fabricated on a Si-Pyrex chip. This method was used to pump reagents to perform successive PCR, gel electrophoresis, and detection [392,393],... 

Walker, G.M., Beebe, D.J., A passive pumping method for microfluidic devices. Labchip 2002, 2, 131-134. 

The carbanion pump method has been successfully applied for the preparation of different block copolymers including poly(ethylene oxide)-block-polystyrene, poly(ethylene oxide)-block-polystyrene-block-poly(ethylene oxide), poly(ethylene oxide)-block-poly(methyl methacrylate), poly(ethylene oxide)-block-poly(methylmethacry-late)-block-poly(ethylene oxide) (shown in Scheme 14), and poly(ferrocenyldimethylsilane)-block-(methyl methacrylate) <2004MI856, 2004MM1720, 2006MI(928)292>. 

Compound 103 was added slowly using syringe pump methods over 8 h. 

Weber, H.G., Glass, H.-J., Huber, R., Kompitsas, M., Schmidt, G. and zu Putlitz, G. (1974). Optical pumping method for studying nuclear-spin polarization in alkali dimers, Z. Physik, 268, 91-95. 

Although it may require special designs, pressure transfer does eliminate the problems that occur with gear pumping methods. Many resinous systems may be moved from their original drums by air pumps. Transfer distances should be short, and lines should be smooth and noncorrosive. In some instances, barrel warmers and heated lines may be required to reduce pressures required to transport materials. Under no circumstances should the same transfer equipment be used on different resins without complete and thorough cleaning. This will avoid the contamination of one resin system with the other. 

Alternatively, electroosmotic pumping could be used in this application. For generation of electroosmosis it is necessary to apply an electric voltage at both ends of the column. However, when we used electroosmotic flow instead of a pressurized pumping method, we encountered several problems. The hardest problem was evolution of gas at the electrode due to electrolysis. Elimination of this gas from the chromatographic system was one of the key challenges we faced in designing our system. 

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