Impedance valve

Lurie, K.G., Coffen, R, Shultz, J., McKnite, S., Detloff, B., and Mulligan, K. Improving active compression-decompression cardiopulmonary resuscitation with an inspiratory impedance valve. Circulation, 92,1629-1632,1995. 

Isovolumic canine ventricular pressure curves, 8-5 ITV (inspiratory impedance valve) CPR, 18-10 Iwasa, K.H., 63-9... 

Water Water is a serious contaminant of hydraulic systems. Hydraulic fluids are adversely affected by dissolved, emulsified, or free water. Water contamination may result in the formation of ice, which impedes the operation of valves, actuators, and other moving parts. Water can also cause the formation of oxidation products and corrosion of metallic surfaces. 

The second valve controls a sample loop, 5 cm long and 1 mm in diameter, packed with dimethyloctadecyl reverse phase comprising of fairly coarse particles 100-120 im in diameter to reduce flow impedance. The sample pump is supplied via a two-way tap from either of two reservoirs, one containing pure water and the other, normal saline. The output of the pump can be used to either force the contents of the open loop sample tube through the packed loop, or to permit washing with an appropriate solvent. The separate pump is necessary to overcome the impedance of the packed loop. 

A simple and effective check valve which impedes the flow of mercury is seen in Figure 67, /. It consists of a small plunger floating on mercury, which is pushed into a seating when the mercury level rises. The plunger P is made by blowing an elongated bulb at the end of a... 

In a number of works, a potentiostatic regime has been used for the experimental and theoretical study of the anodization of aluminum and other valve metals.80 Upon the application of a constant potential step, Va, barrier-forming electrolytes are characterized by a sharp increase in the anodic current to a certain maximum. Both the slope and the maximum are determined by the impedance of the cell circuit. Subsequently, there is a continuous decrease in the anodic current, which is due to oxide growth. The decay of the anodic current can be described by the expression81... 

Figure 1. Diagram of apparatus (M) monomer reservoir (F) flow meter (VG) vacuum gage (mercury manometer) (E) electrode (T) liquid nitrogen trap (P) mechanical pump (V,) needle valve (Vt) stop valve (Vs) pressure control valve (OSC) discharge frequency oscillator (AMP) amplifier (1MC) impedance matching circuit...

Figure 10. Kleitz s reaction pathway model for solid-state gas-diffusion electrodes. Traditionally, losses in reversible work at an electrochemical interface can be described as a series of contiguous drops in electrical state along a current pathway, for example. A—E—B. However, if charge transfer at point E is limited by the availability of a neutral electroactive intermediate (in this case ad (b) sorbed oxygen at the interface), a thermodynamic (Nernstian) step in electrical state [d/j) develops, related to the displacement in concentration of that intermediate from equilibrium. In this way it is possible for irreversibilities along a current-independent pathway (in this case formation and transport of electroactive oxygen) to manifest themselves as electrical resistance. This type of chemical valve , as Kleitz calls it, may also involve a significant reservoir of intermediates that appears as a capacitance in transient measurements such as impedance. Portions of this image are adapted from ref 46. (Adapted with permission from ref 46. Copyright 1993 Rise National Laboratory, Denmark.)...

Second, contraptions used for external generation of reactive intermediates are often quite bulky, which may impede the mobility of the experiment. Such contraptions may render it difficult to investigate a sample by several different kinds of spectroscopy. In principle it is possible, with the aid of a gate valve mounted on the vacuum shroud, to construct devices that allow one to retract and detach the external source of a reactive intemediate after a matrix has been built, but the implementation of this strategy is technically quite challenging because high vacuum must be maintained at all times within the cryostat. 

Where chemical compatibility of the process fluid with the diaphragms or seals of the valve is questionable or where corrosion build-up can impede the actuation of the pilot. 

A third type of stenosis of a degenerative nature occurs in patients above 70 years of age in whom the commissures stay separated but the valve excursion is impeded at the base of the leaflets. Clinical symptoms may include syncope, dyspnea, or angina. Advanced stages of this disease can cause heart failure and sudden death. 

Maximum Working Pressure - (Pq) - The maximum working pressure of the detector determines the maximum impedance that can be permitted in post-detector conduits, valves or columns and is largely used in multidimensional analysis and superfluid chromatography. It is specified either in p.s.i or kg/m ... 

Although the data show a relationship between the ability of a surface to adsorb fibrinogen out of plasma, the plasma s inability to convert this fibrinogen, and the tendency of platelets to adhere, it does not confirm that adsorption of fibrinogen must precede adhesion of platelets to all kinds of surface, or that surfaces which adsorb fibrinogen under these conditions will be bad biomaterials in vivo as heart valves, blood vessels, or canulae, or ex vivo as artificial kidney membranes—even though the latter are most likely to be impeded by any adsorbate. 

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