Disadvantages, potential

Cument methanol sufi rs from the fbOowing disadvantages Potential firrmaldehyde emissions Hitler cost per Btu Toxic to humans Low flame luminosity Vapor-phase ejq)bsivity Cob start difl uk (MlOO)... 

For each pair of interacting atoms (/r is their reduced mass), three parameters are needed D, (depth of the potential energy minimum, k (force constant of the par-tictilar bond), and l(, (reference bond length). The Morse ftinction will correctly allow the bond to dissociate, but has the disadvantage that it is computationally very expensive. Moreover, force fields arc normally not parameterized to handle bond dissociation. To circumvent these disadvantages, the Morse function is replaced by a simple harmonic potential, which describes bond stretching by Hooke s law (Eq. (20)). 

Additionally to and a third adjustable parameter a was introduced. For a-values between 14 and 15, a form very similar to the Lennard-Jones [12-6] potential can be obtained. The Buckingham type of potential has the disadvantage that it becomes attractive for very short interatomic distances. A Morse potential may also be used to model van der Waals interactions in a PEF, assuming that an adapted parameter set is available. 

The SCE has the advantage that the concentration of Ck, and, therefore, the potential of the electrode, remains constant even if the KCl solution partially evaporates. On the other hand, a significant disadvantage of the SCE is that the solubility of KCl is sensitive to a change in temperature. At higher temperatures the concentration of Ck increases, and the electrode s potential decreases. Eor example, the potential of... 

Another significant disadvantage of the patented process is the two large mnning seals involved in the main body of the filter as the vessel rotates around a stationary central arrangement this seal is another potential source of trouble. This version has Htde chance of commercial success and has been shelved in favor of a more conventional system of stationary vessel (16). 

Pyrolytic routes to hexafluorobenzene have also attracted attention but have not been commercialized. Pyrolysis of tribromofluoromethane [353-54-8] CBr F, at 630—640°C in a platinum tube gives hexafluorobenzene in 55% yield (251—253). The principal disadvantage of this process is the low weight yield of product 90% of the costly CBr F that is charged is lost as bromine. Of economic potential is the related copyrolysis of dichlorofluoromethane [754-34-0] and chlorofluoromethane [593-70-4] (254,255). 

Table 9 compares the most important properties of substrate materials based on BPA-PC, PMMA, and CPO (three different products) (216,217). The future will prove if the current disadvantages of CPO against BPA-PC regarding warp, processibiUty (melt viscosity), and especially cost can be alleviated. CycHc polyolefins (CPO) and, especially cycloolefin copolymers (COC) (218) and blends of cycloolefin copolymers with suitable engineering plastics have the potential to be interesting materials for substrate disks for optical data storage. 

Use of traveling wave tube (TWT) amplifiers at power levels of hundreds of watts has been proposed (54) for power appHcations, at least when the heating chamber is well shielded. The potential advantage is an improved uniformity of heating when a broad band of frequency is used, ie, excitation of many modes. Disadvantages are high cost and lower (<50%) efficiency of the TWT. 

Yeast. The advantages of expression in yeast include potentially high level production of proteins, the abiUty to have expressed proteins secreted into the media for ease of purification, and relatively low cost, easy scale-up. A disadvantage is that plasmid instabiUty may be a problem which can lead to low product yield. Whereas post-translational modification occurs in yeast, proteins are quite often hyperglycosylated. This is generally a problem with expression in Saccharomyces cerevisiae but not for the more recently used yeast host Pichiapastoris (25) (see Yeasts). 

ChemicalRecope . There are advantages and disadvantages to each of the base systems employed in sulfite pulping (see Table 4). Each has its own potential recovery systems except the calcium system, which is obsolete. Calcium-based Hquors can be burned, but scaling problems are severe, and conversion of the calcium sulfate to CaO is not economical. 

Single-crystal siHcon can also be grown from various fluxes and by a combination of electrolysis and fluxes at temperatures weU below the melting point of pure siHcon (16). The main disadvantages are the inclusion of the flux in the crystal and the poor crystal quaHty. Potential advantages are a decrease in growth temperature and purification during electrolysis. 

Solvent Extraction. Solvent extraction has widespread appHcation for uranium recovery from ores. In contrast to ion exchange, which is a batch process, solvent extraction can be operated in a continuous countercurrent-fiow manner. However, solvent extraction has a large disadvantage, owing to incomplete phase separation because of solubihty and the formation of emulsions. These effects, as well as solvent losses, result in financial losses and a potential pollution problem inherent in the disposal of spent leach solutions. For leach solutions with a concentration greater than 1 g U/L, solvent extraction is preferred. For low grade solutions with <1 g U/L and carbonate leach solutions, ion exchange is preferred (23). Solvent extraction has not proven economically useful for carbonate solutions. 

Like brines, alcohols were readily available and widely used as antifreeze Hquids in the early 1900s. Both methanol and ethanol offer exceUent heat transfer and efficient freeze point depression. However, the alcohols have the distinct disadvantage of their low boiling points. During the summer months when the engines operate hot, significant amounts of the alcohols are lost because of evaporation. These evaporative losses result in cosdy make-up requirements. Additionally, the alcohols have very low flash points and potentially flammable vapors. These safety concerns have, particularly in recent years, caused the use of alcohols to be completely discontinued for most heat-transfer systems. 

Another potential solution is the use of catalytic combustors, which produce extremely low levels of emissions by the use of combustion catalysts such as platinum. The main disadvantage of catalytic combustors, however, is thek high cost. 

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