Switching mechanisms

The polymers are extensively used in telecommunications equipment, a major use being in telephone switching mechanisms. Polycarbonates now dominate the... 

Electrical properties of liquids and solids are sometimes crucially influenced by H bonding. The ionic mobility and conductance of H30 and OH in aqueous solutions are substantially greater than those of other univalent ions due to a proton-switch mechanism in the H-bonded associated solvent, water. For example, at 25°C the conductance of H3O+ and OH are 350 and 192ohm cm mol , whereas for other (viscosity-controlled) ions the values fall... 

H2SO4.Z2H2O, are known with = 1, 2, 3, 4 (mps 8.5", -39.5". -36.4" and -28.3% respectively). Other compounds in the H2O/SO3 system are H2S2O7 (mp 36") and H2S4O13 (mp 4"). Anhydrous H2SO4 is a remarkable compound with an unusually high dielectric constant, and a very high electrical conductivity which results from the ionic self-dissociation (autoprotolysis) of the compound coupled with a proton-switch mechanism for the rapid... 

The reaction mechanism presented here combines the evidence from X-ray structures (41,42) with elements of the affinity change mechanism (116) and of the catalytic switch mechanism (118). All electron transfer reactions occur between species when they are hydrogen bonded to each other therefore, electron transfer will be extremely rapid and most likely not rate limiting. 

Fig. 7 A molecular switch made of the leg of a legged Cu-porphyrin adsorbed on a Cu(211) surface, (a) An idealized version of such a molecular switch where the switching leg is exactly interconnected to two atomic wires in a Fig. la like configuration. The device resistance is maximum for a perpendicular = 0 conformation, (b) The real experimental device where the STM tip apex can be maintained at 0.7 nm or 0.9 nm separation between the tip and the surface in between the leg switching. In this case, the resistance is minimum for perpendicular to the Cu(211) surface = 0 conformation. The energetic of the switching mechanism can be calculated and the switching barrier height was also determined experimentally...

Thermoelectric flame failure detection Analog burner control systems Safety temperature cut-out Mechanical pressure switch Mechanic/pneumatic gas-air-ration control Thermoelectric flame supervision Thermal combustion products, discharge safety devices Electronic safety pilot Electronic burner control systems Electronic cut-out with NTC Electronic pressure sensor/transmitter Electronic gas-air-ration control with ionisation signal or 02 sensor Ionisation flame supervision Electronic combustions product discharge safety device... 

Valve-based modulators rely on flow switching mechanisms, and traditionally discrete (sub)sampling of effluent has been performed for subsequent separation on... 

M. Okamoto, T. Sakai, and K. Hayashi, Switching mechanism of a cyclic enzyme system role as a chemical diode, BioSystems, 21, 1-11 (1987). 

Alfassi, Z. B., and Benson, S. W., A simple empirical method for the estimation of activation energies in radical molecule metathesis reactions, Int. J. Chem. Kinetics S, 879 (1973). Allara, D. L., and Edelson, D., A computational analysis of a chemical switch mechanism. Catalysis-inhibition effects in a copper surface-catalyzed oxidation, J. Phys. Chem. 81, 2443 (1977). 

Polymerization of isobutylene, for example, may be explained in terms of this hydrogen switch mechanism by assuming that the hydrogen switch occurs between two molecules of the olefin ... 

Yang JJ, Pickett MD, Li X, Ohlberg DAA, Stewart DR, Williams RS (2008) Memristive switching mechanism for metal/oxide/metal nanodevices. Nat Nanotechnol 3 429-433... 

FIGURE 22. The active site of alkaline phosphatase (above) and an allosteric kinetic switch mechanism (below) for the regulatory function of the Mg + ions in controlling the conformation of the nonequivalent subunits (square and circle). Reprinted with permission from Reference 214. Copyright 2005 American Chemical Society... 

Fig. 5. On-off switching mechanism of drug release (Reproduced from J. Biomater. Sci. Polymer. Edn. [Ref. 49] through the courtesy of VSP BV)...

Other recent developments include crown ethers which contain potential switch mechanisms for complexation and transport. When photoresponsive chromophores are linked to crown ethers, ion binding can change on photoirradiation. The crown (120) is formed as its tram isomer with no alkali metal affinity, but photoirradiation gives a cis isomer capable of alkali metal complexation 500 this is an example of a reversible all or none ion-binding capability. A... 

Shepherd, P.R., Withers, D.J., Siddle, K. (1998) Phospho-inositide 3-kinase the key switch mechanism in insulin signalling. Biochem. J. 333, 471-490. 

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