Reversible storage systems

Figure 6. A hypothetical scheme for the control of the number of active crossbridges in smooth muscle. Following the activation of a smooth muscle by an agonist, the concentrations of intermediates along the main route begins to build up transiently. This is shown by the thickened arrows. Also, cAMP is generated which is universally an inhibitor in smooth muscle. Cyclic AMP in turn combines with protein kinase A, which accounts for most of its action. The downstream mechanisms, however, are not well worked out and at least three possibilities are likely in different circumstances. First, protein kinase A is known to catalyze the phosphorylation of MLCK, once phosphorylated MLCK has a relatively lower affinity for Ca-calmodulin so that for a given concentration of Ca-calmodulin, the activation downstream is reduced. The law of mass action predicts that this inhibition should be reversed at high calcium concentrations. Other cAMP inhibitory mechanisms for which there is evidence include interference with the SR Ca storage system, and activation of a MLC phosphatase.

In recent years lithium - ion power sources have occupied one of the first places among other modem energy storage systems. Their functioning is based on the possibility of reversible intercalation of lithium ions in active materials (AM). Substances of tin are investigated often as negative materials for lithium-ion batteries. 

Another interesting lithium-based system is Li3N/Li2NH [53]. Lithium nitride can be hydrogenated to lithium imide and lithium hydride (5.4 wt% H2). The latter reaction can be used for reversible storage at 250°C. The formation of ammonia can be completely avoided by the addition of 1% TiCl3 to the system, which has the positive additional effect to improve the kinetics [54]. Very fast kinetics has been reported for a partially oxidized lithium nitride [55]. 

Waste heat from the fuel cell is used to reverse the reaction and release the fuel. In 2005 GM and Sandia National Laboratories launched a 10-million program to develop metal hydride storage systems based on sodium aluminum hydride. 

The QC is thermodynamically unstable relative to NBD, but a catalyst is needed to revert it to NBD. The reverse reaction of QC to NBD catalytically releases heat. The storage capacity of this is 21 kcal/mol. Since unsubstituted NBD has no absorption in visible region, a sensitizer such as aromatic ketones is required for the NBD isomerization by visible light. The efficiency and stability of various storage systems based on the photoisomerization were studied100b). 

The purple membrane is harvested semiindustrially from halobacteria mutants which are bred in fermenters. The BR is then embedded into a polymeric matrix of poly(vinyl alcohol) or polyacrylamide. The BR films manufactured in this way are used for different applications, preferably in holography, for example, as a reversible transient data storage system for optical information processing (159). Another example is real-time interferometry by using the property of BR films to integrate over time (160). BR has been proposed also as a two-photon memory material because of its unusually large two-photon cross section. 

Reversibility. Should the storage system be one that future generations can undo ... 

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