Piston-based systems

Both of these in situ devices use substantially less solution (volumes of solution samples for each kinetic run are usually of the order of a few cm3) than a typical piston-cylinder apparatus. The pill-box cell method has the advantage that the cell can be filled in an appropriate glove box for oxygen-sensitive samples or for nonaqueous solvent-based systems that are sensitive to moisture. Temperature control is exerted by fluid circulating through the metal block. 

We have used systems from simple pumps with an external low-pressure gradient generator (Lewis, 1979) to completely automated computer-based systems with pairs of multi-piston pumps as well as those in between for our work. All of them have been reasonably satisfactory. Although the automated systems are much more productive for analytical work, in our experience there is virtually no difference in productivity between the least and most expensive systems when biopolymer purification work is involved. Our tendency has been toward less expensive and less complicated systems because in oui ,laboratories, where several people are involved in protein work, it is much more productive to have as many systems as money will allow. Another factor that is important in choosing the appropriate H PLC system is the proximity of repair service in the area. 

With speed-controlled piston extruders, which imply a high definition of the signals, the micro-processor based systems are likely to represent the optimum technical solution at present. 

On the same idea, a piston-cylinder system can be built, e.g., based on the different complexation tendencies of /Z azobenzene into a diazapyrenilium cavity (Scheme 11.10) [15]. 

D radation of the endplate may affect PEMFC performance and durability. In some fuel cell stack assembhes, a pneumatic piston is installed adjacent to either one of the endplates. In such arrangements, the pneumatic piston uniformly apphes compressive force to the stack, which permits control of the compressive force apphed to the endplate. Unfortunately, the use of a pneumatic piston adds to the complexity of the fuel cell stack and can be a source of umeliability, with potentially adverse consequences if the piston-based compression system fails. For example, internal leakage may occur in the pneumatic system. 

Air is contained within a piston-cyHnder assembly, as shown in Figure E2.10A. The cross-sectional area of the piston is 0.01 m. Initially the piston is at 1 bar and 25 C, 10 cm above the base of the cylinder. In this state, the spring exerts no force on the piston. The system is then reversibly heated to 100°C. As the spring is compressed, it exerts a force on the piston according to ... 

To prevent/reduce the undesirable condensation in the pump, a small hole is drilled in the pump head to admit air or other process non-condensable gas (gas ballast) into the latter portion of the compression stroke. This occurs while the vapor being compressed is sealed off from the intake port by the piston. By reducing the partial pressure of the vapor s condensables, the condensation is avoided. Obviously, this can reduce the capacity of the pump, as the leakage past the seals allows the gas ballast to dilute the intake volume of base suction gas. For most process applications, the effect of this leakage is negligible, unless the vacuum system suction is below 1 torr [22]. 

Piston type aerosol system, 1 784 PIT (powder-in-tube) conductors, critical current density in, 23 833-834. See also PIT technique Pitch-based carbon fibers, 26 733-735 asbestos substitute, 3 314t compressive strength versus tensile modulus for, 26 742-743 Pitch-based fibers, 26 760 Pitch binders, 12 724-726 Pitchblende, 25 396-397 Pitch control, 10 304 Pitched blade turbine (PBT), 16 672 Pitches... 

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