Cells concept first proposed

Although the principle was first proposed in 1839, making a practical fuel cell eluded scientists for a centuiy and a half The concept is simple, but the chemistry is difficult. A hydrogen fuel cell must cleanly convert H2 into H3 O at one electrode and cleanly convert O2 into OH at the other electrode. In addition, the fuel cell must contain a medium that allows these ions to diffuse and combine stoichiometrically. 

DNA has two broad functions replication and expression. First, DNA must be able to replicate itself so that the information coded into its primary structure is transmitted faithfully to progeny cells. Second, this information must be expressed in some useful way. The method for this expression is through RNA intermediaries, which in turn act as templates for the synthesis of every protein in the body. The relationships of DNA to RNA and to protein are often expressed in a graphic syllogism called the central dogma. The concept was proposed by Crick in 1958 and was revised in 1970 to accommodate the discovery of the RNA-dependent DNA polymerase. Crick s original theory suggested that the flow of information was always from RNA to protein and could not be reversed, yet it allowed for the possibility of DNA synthesis from RNA. 

An alternative SOFC configuration, based on the corrugated monolithic concept, was first proposed by the Argonne National Laboratories (Fee et al, 1986). The design is shown schematically in Fig. 11.26(h). The cells incorporate two triple layer subassemblies each prepared by... 

In the quest to improve fuel cell performance, the concept of fuel cell reactions requiring a three-phase interface was first proposed by Grove. In his initial experiment, he noticed that the reaction sped up when the three-phase area was large. In 1923, Schmid [7] developed the first gas diffusion electrode, which significantly increased the electrode active surface area and revolutionized fuel cell electrodes. The electrode contained a coarse-pore graphite gas-side layer and a fine porous platinum electrolyte layer. 

These observations led to the concept of a unit cell. Haiiy was able to build realistic models of calcite crystals by stacking rhombohedral building blocks of uniform size (each with interfacial angles of 75°). Clearly, the interfacial angles are important dimensions of the exteriors of crystals. The Law of the Constancy of Interfacial Angles was first proposed by Steno. It states that in all crystals of a givpn... 

As the NADH is oxidized, the electrons released are removed by specific carriers, and the protons are transported from cytoplasm to outside the cell. Removal of H+ causes an increase in the nmnber of OH ions inside the membrane. These conditions result in a proton gradient (pH gradient) across the membrane. This gradient of potential energy, termed as proton motive force, can be used to do useful work. This potential energy is captured by the cell by a series of complex membrane-bound enzymes, known as the ATPase in the process called oxidative phosphorylation. In 1961, the concept of proton gradient was first proposed as chemiosmotic theory by Peter Mitchell of England, who won the Nobel Prize for this scientific contribution. 

Another interesting application of the lithium-ion battery concept has been applied to the Sn02/LiNio gCog 2O2 electrodic couple [92]. Convertible oxides, and tin oxide in particular, first proposed as alternative anode materials by the Japanese Fuji Photo Film Company [93, 94], are presently the object of considerable attention in the lithium-ion battery community [95-98]. When negatively polarised in a lithium cell, tin oxide first undergoes an irreversible reaction shown in Equation 7.10. 

Whereas most of the work discussed so far in this essay has dealt with the synthesis of well-defined biochemical species supporting the theory of chemical evolution as first proposed by A. I. Oparin, one of Oparin s major concerns has been to develop a hypothesis of precellular evolution and to experimentally demonstrate that specific biochemical reactions can occur within simulated precellular entities (coacervates). In an elegant experiment, using polynucleotide phosphorylase in coacervate droplets and the appropriate substrate in the external medium, he showed a continuous uptake of the substrate, a rapid internal synthesis of polynucleotides and a continuous release of phosphate to the external environment. His more recent concepts on evolution of probionts and the origin of cells were presented at the 4th International Conference on the Origin of Life held in Barcelona, Spain, in 1973. Experimental models involving microspheres made of polymers of amino acids have been developed by S. W. Fox and coworkers > and other investigators. 

The concept of cell encapsulation was first proposed by Chang [119] in the early 1950s. A primary requirement of microcapsule-surrounding membranes are that they are amenable to the diffusion of nutrients (e.g., glucose) and molecules such as oxygen and growth factors essential for cell survival [120]. Twenty years later, Lim and Sun presented the first implantable alginate-poly(L-lysine) PEC... 

We can recognize four main periods in the history of the study of aqueous solutions. Each period starts with one or more basic discoveries or advances in theoretical understanding. The first period, from about 1800 to 1890, was triggered by the discovery of the electrolysis of water followed by the investigation of other electrolysis reactions and electrochemical cells. Developments during this period are associated with names such as Davy, Faraday, Gay-Lussac, Hittorf, Ostwald, and Kohlrausch. The distinction between electrolytes and nonelectrolytes was made, the laws of electrolysis were quantitatively formulated, the electrical conductivity of electrolyte solutions was studied, and the concept of independent ions in solutions was proposed. 

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