Some Unsolved Problems

Arthur E. Humphrey, Some Unsolved Problems of Biotechnology... 

The alkali metal suboxides are well understood in terms of formation, structure, and properties, yet we still face some unsolved problems that will also be addressed in the following. In contrast, the first suboxide of barium came to light only recently [24], and one has to see whether this compound is the tip of another iceberg, as turned out to be the case with the subnitrides of alkaline earth metals. 

G. C. Bond, Supported metal catalysts—Some unsolved problems. Chem. Soc. Rev. 20, 441-475 (1991). 

Kirman, Lyle. 1988. "Some Unsolved Problems in Close Loop Nickel Recovery."... 

If the analysis of fatty acid methyl esters gives a large amount of information on the composition of fats, there remain some unsolved problems, related to the two major flaws of the approach. The transesterification of TGs derived from polyunsatured acids is not always quantitative. A more important and general problem is that the method does not provide any information regarding the actual composition of the TGs. 

By careful choice of reactants this technique, because of its simplicity, can lead to an understanding of some unsolved problems associated with graft copolymerizations. 

Sonochemical reactors can be used to degrade a variety of contaminants in aqueous solution, including some very harmful and recalcitrant compounds such as chlorinated hydrocarbons. The scale-up of these reactors in order to meet industrial needs (i.e., faster rates and high volume processes) is the present challenge in the development of the technique. The many advantages of the technique, described in this chapter, will surely encourage researchers and engineers to face some unsolved problems in the future, in order to provide alternatives to conventional waste treatment. 

The X-ray ED formalism, which is closely connected to the theory of atoms in molecules, is still evolving and there are some unsolved problems. Thus, it appears that in simple inorganic structure the multipole model may be nonunique. ... 

In the theory of electric properties of molecular systems in degenerate electronic states some unsolved problems remain. First, the problem of intermolecular interactions considering the degeneracy of the electronic states of the interacting molecules has not been solved completely. In this case, besides the lowering of the multipolarity of the interaction described in this paper, one can expect an essential contribution of anisotropic induction and dispersion interactions to different virial correction to the equations of state, refraction, and other electric characteristics of matter. 

Kubie, L. S. Some unsolved problems of the scientific career, American Scientist 42, 111 (1954). 

J3.2 Supported metal catalysts some unsolved problems... 

The aim of the present review is first to summarize what is known about the primary radiation induced defects in nucleic acid constituents from detailed EPR/ENDOR experiments, then to explore the use of theoretical calculations to assist in making free radical assignments. The theoretical calculations include estimates of spin densities and isotropic and anisotropic hyperfine couplings which can be compared with the experimental results. In many cases the theoretical and experimental results agree rather well. In other cases there are discrepancies between the theoretical and experimental results. The successes and failures of DFT to calculate spin densities and hyperfine couplings of more than twenty primary radiation induced radicals observed in the nucleobases are discussed. Some unsolved problems and suggestions for future work are also discussed. 

---