Electrically driven systems

A possible explanation for the differences observed in rat could be the use of animals under basal conditions vs electrically-driven systems and/or different receptor densities for different strains. Certainly, histamine H3-receptors are not homogeneously distributed along the rat vascular system, as they were found in some districts, like pulmonary microvessels (Danko et al., 1994), portal vein (Smit et al., 1997) or tail artery (Godlewski et al., 1997b), but not in vena cava (Schneider et al., 1991). 

Fig.l Schematic representation of the flow profiles obtained with the same capillary column connected to an electric-driven system (a) and to a pressure-driven system (b). Arrows indicate flow velocity vectors. 

By comparing the two Equations 5.3 and 5.5, it can be seen that the linear velocity u is proportional to dp in a pressure-driven system while it is independent of the particle diameter in an electrically driven system. Since plate height values are generally lowered as a result of using small diameter particles, it is possible in electrically driven systems to use very small diameter packing materials and still maintain high linear velocities to yield rapid and very efficient separations. 

Additionally, it is important to realize that deformations at an N1 phase transition occur locally, on the level of a small volume of the material in the micrometer range. To observe the unique properties of LCEs on a macroscopic scale, the mesogens have to be aligned uniformly over the whole sample, yielding an LC monodomain or, at least, a sample with a well-defined overall director pattern (see Chap. 1). Thus, the use of LCEs as actuators always requires a step to orient the sample prior to final crosslinking [184]. Consequently, we will discuss first the influence of different preparation strategies on the orientation step, focusing on materials for actuator applications (Sect. 1.1). This sectimi will be followed by a discussion of properties needed for application. We will examine temperature-driven actuators (Sect. 2) and electrically driven systems (Sect. 3). 

A series of papers have described light modulators based on the temperature driven shrinkage of colored N-isopropylacrylamide in a second gel matrix [178, 183, 184]. As the colored particles expand at lower temperature, they extract water from the surrounding matrix and occupy most of the volume, thus cutting off light transmission (Figure 1.9). Clearly, an electrically driven system based on temperature or pH change could be constructed. 

Thus, there are significant differences between enantioseparations in pressure-driven and electrically driven systems. On the one hand, these differences make the techniques complimentary. This is an advantage. On the other hand, the rules and dependencies observed in one technique should be applied to the other with some care in order to avoid mistakes in the interpretations of the experimental results. 

By modification to the control logic of the valve, and using analogue outputs from the robot control, this valve can be changed from providing preset levels of flow to continuously variable control and is therefore comparable to the electrically driven systems. 

The secondaiy ejector systems used for removing air require steam pressures of 2,5 bar or greater. When the available steam pressure is lower than this, an electrically driven vacuum pump is used for either the final secondaiy ejector or for the entire secondaiy group. The secondary ejectors normally require 0,2-0,3 kg/h of steam per kW of refrigeration capacity,... 

Data from an existing collection system were analyzed for failure modes and distribution. The results of Pareto analyses indicate the principal causes of failure. A few values of mean times to maintenance action (MTBM) are given for ethylene plant pumps (85 electric driven centrifugal pumps over a 19-month period), and ethylbenzene-styrene monomer plant equipment from 10 months data 4 gas compressors, 3 screw conveyors, 121 pumps, and 235 other items... 

The lubricating oil system for a turbine is very important and is nearly always provided with a dual pumping arrangement. One pump can be driven directly off the turbine shaft and the other by separate electric motor or steam turbine. In another arrangement, one pump can be separately electric driven and the other separately steam turbine driven. Twin coolers are often provided in the dual system to... 

The adequacy of continuous pumping of wells should be considered because wells are often of limited capacity. These systems are normally used as backup fire water or for refilling tanks and reservoirs. Also, most well pumps are only electrically driven, requiring special electrical feed requirements. 

The reliability of the power supply should be determined, taking into account the frequency of power outages and extent of interruption. Consideration should be given to connecting electrically driven fire water pumps to the emergency power system, where one exists. 

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