Electron sponges

A salient feature of NADP+ is its net positive charge, so it can act somewhat like an electron sponge. 

Table 1. Some important examples of homometallic TMC with electron-sponge behavior. ...

Table 4. HTMCC with electron-sponge features (only redox changes with chemical and electrochemical reversibility have been taken into account E° in V, relative to the SCE). 

Arsenate also carries a second kind of danger. Because it is bigger than phosphorus, arsenic has more room to carry extra electrons. In a cell, arsenate absorbs electrons like an electronic sponge, and this sabotages the cell s electron balance. Arsenate sheds its electrons randomly, and these extra electrons react powerfully with molecules, especially oxygen. Random reactions shred the cell like interior shrapnel. In an experiment in which yeast cells were fed arsenic, when the electronic balance was disrupted, the DNA fragmented like a dropped egg. Arsenic also pushes proteins out of shape by interfering with their sulfur atoms. 

Textile uses are a relatively stable area and consist of the lamination of polyester foams to textile products, usually by flame lamination or electronic heat sealing techniques. Flexible or semirigid foams are used in engineered packaging in the form of special slab material. Flexible foams are also used to make filters (reticulated foam), sponges, scmbbers, fabric softener carriers, squeegees, paint appHcators, and directly appHed foam carpet backing. 

Refining. KroU-process hafnium sponge and electrowon hafnium do not meet the performance requirements for the two principal uses of hafnium metal. Eurther purification is accompHshed by the van Arkel-de Boer, ie, iodide bar, process (18) and by electron beam melting. 

Impurities KroU process sponge Electrowon crystals Refined from KroU Electron beam ingot sponge Iodide bar... 

The vanadium alloy is purified and consoHdated by one of two procedures, as shown in the flow diagram of the entire aluminothermic reduction process presented in Figure 1. In one procedure, the brittle alloy is cmshed and heated in a vacuum at 1790°C to sublime most of the aluminum, oxygen, and other impurities. The aluminum faciHtates removal of the oxygen, which is the feature that makes this process superior to the calcium process. Further purification and consoHdation of the metal is accompHshed by electron-beam melting of pressed compacts of the vanadium sponge. 

Impurity Sponge Electron-beam melted First melt Second... 

The complex of the following destmctive and nondestmctive analytical methods was used for studying the composition of sponges inductively coupled plasma mass-spectrometry (ICP-MS), X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and atomic absorption spectrometry (AAS). Techniques of sample preparation were developed for each method and their metrological characteristics were defined. Relative standard deviations for all the elements did not exceed 0.25 within detection limit. The accuracy of techniques elaborated was checked with the method of additions and control methods of analysis. 

In any case, it is interesting to note that catalytic efficacy has been observed with nano- or mesoporous gold sponges [99-101, 145] suggesting that neither a discrete particle nor an oxide support is actually a fundamental requirement for catalysis. An alternative mechanism invokes the nanoscale structural effect noted in Section 7.2.2, and proposes that the catalytic effect of nanoscale gold structures is simply due to the presence of a large proportion of lowly-coordinated surface atoms, which would have their own, local electronic configurations suitable for the reaction to be catalyzed [34, 49,146] A recent and readily available study by Hvolbaek et al. [4] summarizes the support for this alternate view. 

Finally, it may be pointed out that none of the rare metals can be smelted directly from the ore. The concentrate must first be converted to a pure chemical compound which is utilized as the raw material for the production of the metal. The refractory rare metals are often obtained in the form of a powder or sponge. They are consolidated and refined by powder metallurgy techniques or by arc melting or by electron beam melting. In fact, the current refractory rare metals technology has been crucially dependent on the development of vacuum metallurgical techniques and processes. 

Fig. 3.25.1. Porous structure of collagen sponge produced by freezing in a cryogenic bath at -25 °C and subsequently freeze dried (scanning electron microscope, white bar = 1 mm) (from 13.67]).

An inflammable PE sponge that does not release any toxic gas when in contact with fire has been developed by Sanwa Kako Co.Ltd. The inner side of the polyethylene is chemically coated with a flame retardant using electron beam technology. The material is claimed to be suitable for use in car seats, furniture and cushions. Commercial production of the material is planned for late 1993. This abstract includes all the information contained in the original article. 

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