On Unsolved Problems

The answer depends on the person considering such questions. We recall an anecdote of asking our colleague organic chanist [46], Professor S. Borcid, after he has briefly explained what he has been doing, why it is so important. His answer was, If I know of something more important I would do that. That ought to be the rule in science, not the exception. 

So do we know of something more important than searching for additional molecular descriptors, improving the interpretation of our models, and similar questions Are there some giant problems in QSAR that deserve our attention And if there are, what are these problans One may expect that there are at least several highly important problans in any alive discipline of science because, if not, the discipline would be dead and not alive. To find than may not, however, be easy. 

What we may add to this is that in order to search and find important problems it may be for theoreticians very useful to speak to experimental scientists rather than only theoretical as the former ones tend to be closer to novelty. And the opposite is also true For experimental scientists, it may be very useful to speak to theoreticians, at least to become aware of the capabilities of the latest theoretical approaches. Be it experimental or theoretical, it is important to talk to otha scientists rather than continue to solve the problems that one knows how to solve  

The essence of the problem is identification of the molecular fragment whether a connection of disconnected atoms or atomic groups, which can be viewed as critical in determining molecular activity. 

An unsolved problem that we would like to mention and that we view as being rather important is to explore and find, if it exists, a counterpart of the pharmacophore in structure-property correlations. Let us refer to this counterpart as the physicophore, in the view that the structure-property relationship relates mostly to the physical properties of molecular physicochemical properties. Let us propose this formally as 

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M.Kaneko, 11th Symposium on Unsolved Problems of Polymer Chemistry, p.21 The society of Polymer Science, Japan, Tokyo (1976). 

A stimulating review on unsolved problems in isoquinoline biosynthesis has been published. ... 

Some more specific articles on unsolved problems in polymer crystallization can be found in the proceedings of three international discussion meetings (1979) Special issue of the Farad Disc Chem Soc 68 Dosiere M, ed (1993) Crystallization of Polymers. NATO ASI Series, C, Vol 405, Kluver Academic Publishers, Dordrecht, Netherlands (2002) Proceedings of the International Symposium on Polymer Crystallization in Mishima, Japan, June 9-12, partially published (2003) Journal of Macromolecular Science, Physics Ed, vol B42. 

Chemical graph theory has also an abundance of unsolved problems that challenge researchers. Not all the problems may be equally important for chemistry, but all require some imagination, some ingenuity, and some novelty, and all present considerable a challenge to novices as well as to old-timers. For a brief review on unsolved problems of chemical graph theory, consult articles by Randic et al. and Balaban. ... 

These unsolved problems can be addressed by detailed CMB experiments, which use soft El ionization for product detection and possibly also very low collision energies. In fact, by measuring the El efficiency curves for the C3H products it may be possible to obtain some information on which isomer is actually formed, because the IE of C-C3H is expected to be... 

The question of the elimination of water in polycondensation reactions still provides an unsolved problem. Solutions are being searched for in many laboratories, for example in Italy Paly6 and Zucchi from the University of Modena consider it possible that limited regions where liquid or supercritical CO2 phases were present could have existed on the young Earth. Such regions, with non-aqueous media, could have been particularly favourable for some prebiotic reactions, such as those involving the elimination of water. Experiments to study this hypothesis are planned (Paly6 and Zucchi, 2002 Holm and Andersson, 1998). 

Within the present model, we have many unsolved problems. Most of the present studies on 3D crystallization from the melt deal with the relatively short Cioo chain. The study of the much longer Ciooo chain is still preliminary we want to clarify more polymer-like behavior such as the reeling-in process of the chains. Since the polymers in the ideal melt are the ideal Gaussian and highly entangled, we need a much larger MD cell to accommodate such large polymers. 

Conspicuous by its absence is the question of calibration transfer, even though we consider it unsolved in the general sense, in that there is no single recipe or algorithm that is pretty much guaranteed to work in all (or at least a majority) of cases. Nevertheless, not only are many people working on the problem (so that it is hardly unaddressed ), but there have been many specific solutions developed over the years, albeit for particular calibration models on particular instruments. So we do not need to beat up on this one by ourselves. 

Instead of a theory to elucidate the important unsolved problems of chemistry, theoretical chemistry has become synonymous with what is also known as Quantum Chemistry. This discipline has patently failed to have any impact on the progress of mainstream chemistry. A new edition of the world s leading Physical Chemistry textbook [4] was published in the year that the Nobel prize was awarded to two quantum chemists, without mentioning either the subject of their work, nor the names of the laureates. Nevertheless, the teaching of chemistry, especially at the introductory level, continues in terms of handwaiving by reference to the same quantum chemistry, that never penetrates the surface of advanced quantum theory. 

How much detail does a student need to know and how much detail should a textbook then contain This is an almost unsolvable problem because of the diversity of students and their analytical needs. The majority of students will eventually move on into special fields in (bio)chemistry, molecular or systems biology or polymer chemistry. For them mass spectrometry will only be one of the commodities to help them solve their problems, which are defined by their field of activity, not the analytical technique. How much of the basics in mass spectrometry will they need to know Again, this depends on the problem at hand. For many a routine application of commercial instalments and the manufacturers manuals will suffice. However, if the problem is not routine the analytical technique cannot be either. Mass spectrometry is and, most probably, will remain a rather complex technique. To fully exploit its tremendous potential, but, equally important, to avoid its many pitfalls, a deeper understanding of the mechanisms and the technology will be mandatory. This book will, hopefully, help students to lay the basis for this expertise and, once the need arises, allow them to go back to the more specialized literature at a later time. It is in this sense that I hope this book will be a real help to many of them. 

This regioselectivity was originally one of the greatest unsolved problems in Diels-Alder reaction but with the application of FMO theory, it has now been solved satisfactorily. Calculations made on systems containing heteroatoms give a set of coefficients which account for the observed orientation. 

This paper may be regarded as a sequel to my second book on Cationic Polymerisation [1]. I have aimed here at providing a fairly detailed discussion of some theoretical aspects of the subject which is still (or perhaps now more than ever before) in Dainton s words rudis indigestaque moles (a crude and ill-digested, i.e., confused, mass) [2], I also intend to discuss specifically some of the problems raised by Mayo and Morton in their article Ionic Polymerization in the book Unsolved Problems in Polymer Science [3]. 

Theoretical considerations based upon a molecular approach to solvation are not yet very sophisticated. As in the case of ionic solvation, but even more markedly, the connection between properties of liquid mixtures and models on the level of molecular colculations is, despite all the progress made, an essentially unsolved problem. Even very crude approximative approaches utilizing for example the concept of pairwise additivity of intermolecular forces are not yet tractable, simply because extended potential hypersurfaces of dimeric molecular associations are lacking. A complete hypersurface describing the potential of two diatomics has already a dimensionality of six In this light, it is clear that advanced calculations are limited to very basic aspects of intermolecular interactions,... 

The pest control situation in California and Florida is reviewed, with particular attention to mechanical developments and the introduction of new fungicides and insecticides, such as the insoluble coppers and parathion, and the outstanding unsolved problems such as control for nematodes which will not injure the plant and the need for a systemic material which will control virus diseases. Emphasis is on needed lines of investigation. Pest control problems in Central America, the Caribbean Islands, and South America are discussed, with special reference to lack of suitable equipment and material because of dollar exchange problems. 

Post-harvest rots of avocado caused by fungal infection are an important but unsolved problem in quality control. Even with optimized post-harvest storage regimes about 20% of Hass avocado were found to be infected by postharvest rots in New Zealand. It is therefore surprising that no NMR/MRI investigations appear to have been reported on this quality factor. 

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