Unanswered Questions

The molecular mechanics calculations discussed so far have been concerned with predictions of the possible equilibrium geometries of molecules in vacuo and at OK. Because of the classical treatment, there is no zero-point energy (which is a pure quantum-mechanical effect), and so the molecules are completely at rest at 0 K. There are therefore two problems that I have carefully avoided. First of all, I have not treated dynamical processes. Neither have I mentioned the effect of temperature, and for that matter, how do molecules know the temperature Secondly, very few scientists are interested in isolated molecules in the gas phase. Chemical reactions usually take place in solution and so we should ask how to tackle the solvent. We will pick up these problems in future chapters. 

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New lonomer Types. There is a continuing interest in new ionomers within the academic community, since novel and unexpected phenomena are frequently being discovered. However, there are still many unanswered questions with respect to the ethylene ionomers, especially the influence of ionic bonding on crystalline stmcture. Continued study of these interesting polymers will close the gaps in knowledge of this area of polymer science. 

The hitherto unanswered question whether the chemically identical thujonas isolated from various essential oils are also physically identical, or whether they are physically isomeric, has now been decided by Wallach in the last-named sense. He has succeeded in establishing the presence of two and possibly of three thujones, although with regard to the third the more probable view is, that it represents a mixture of the other two. His examination has, moreover, proved that thuja oil contains essentially... 

Acetylene Ion. No evidence for the contribution of ion-molecule reactions originating with acetylene ion to product formation has been obtained to date. By analogy with the two preceding sections, we may assume that the third-order complex should dissociate at pressures below about 50 torr. Unfortunately, the nature of the dissociation products would make this process almost unrecognizable. The additional formation of hydrogen and hydrogen atoms would be hidden in the sizable excess of the production of these species in other primary acts while the methyl radical formation would probably be minor compared with that resulting from ethylene ion reactions. The fate of the acetylene ion remains an unanswered question in ethylene radiolysis. 

U.S. General Accounting Office. The Nation s Water Key Unanswered Questions about the Quality of Rivers and Streams, Rep. No. GAO/PE MD-86-6. Washington, D.C., 1986. 

The reviews collected in this book convey some of the themes recurrent in nano-colloid science self-assembly, constraction of supramolecular architecture, nanoconfmement and compartmentalization, measurement and control of interfacial forces, novel synthetic materials, and computer simulation. They also reveal the interaction of a spectrum of disciplines in which physics, chemistry, biology, and materials science intersect. Not only is the vast range of industrial and technological applications depicted, but it is also shown how this new way of thinking has generated exciting developments in fundamental science. Some of the chapters also skirt the frontiers, where there are still unanswered questions. 

Placebos Secrets, Revelations, and Unanswered Questions , Prevention ir Treatment 5 (2002b) n.p. 

The development and application of the CPHMD method demonstrate that simulations are capturing physical reality at increasing resolution. With the explosion in computing technologies, we are just at the beginning of a new era, where in silico experimentation becomes an indispensable complement to wet lab experiments in exploring unanswered questions related to a wide variety of biological and chemical processes. 

An unanswered question about adenosine is how this inhibitory neurotransmitter activates the ventrolateral preoptic area of the hypothalamus (VLPO), which contains a population of sleep-active neurons and is hypothesized to be... 

We have learned a great deal about comets in the intervening centuries, but there still remain some unanswered questions. 

A majority of biogenesis researchers seem to accept the RNA world, in spite of the many unanswered questions a world in which protein synthesis, coded by nucleic acids and catalysed by ribosomes, did not yet occur. Leslie Orgel, probably the most profound connoisseur of this difficult metier, calls attention to important consequences which follow from acceptance of the RNA world. In summary, Orgel discusses two possibilities ... 

The preceding treatment of the spin Hamiltonian terms in bulk semiconductors, where they are relatively-well understood, will provide a basis for the discussion of the NMR of nanocrystalline semiconductors in Sect. 4, since as a group they present special considerations and many unanswered questions remain. Section 5 will provide some general conclusions and suggest future promising avenues of NMR research in semiconductors. 

The use of a Fischer-Tropsch (FT) process to produce long-chain hydrocarbons is well known in industry, and achieving the desired selectivity from the FT reaction is crucial for the process to make economic sense. It is, however, well known that a one-alpha model does not describe the product spectrum well. From either a chemicals or fuels perspective, hydrocarbon selectivity in the FT process needs to be thoroughly understood in order to manipulate process conditions and allow the optimization of the required product yield to maximize the plant profitability. There are many unanswered questions regarding the selectivity of the iron-based low-temperature Fischer-Tropsch (Fe-LTFT) synthesis. 

During the past few years, experiment and theory have converged to a number of explicit answers regarding the location and electronic structure of hydrogen or muonium in semiconductors. Anomalous muonium, which had remained a puzzle for many years, now appears to be well understood in terms of the bond-center model. It is, oddly enough, normal muonium that still seems to pose some unanswered questions is it located at T itself or does it tunnel among various sites How does its rapid diffusion proceed ... 

Fig. 4-11). Interestingly, the larger amounts of P2 protein that are in myelin of some species correlate with increased widths of the major dense lines as determined by X-ray diffraction, and there appears to be substantially more P2 in large sheaths than small ones [4]. The large variation in the amount and distribution of the protein from species to species and sheath to sheath raises so far unanswered questions about its function. Its similarities to cytoplasmic proteins in other cells, whose functions appear to involve solubilization and transport of fatty acids and retinoids, suggest that it might function similarly in myelin assembly or turnover, but there is currently no direct experimental evidence to support this hypothesis. 

Unanswered questions with the use of adjuvant trastuzumab include optimal concurrent chemotherapy, optimal dose, schedule and duration of therapy, and use of other concurrent therapeutic modalities. 

While much is now known about the function, structure, and mechanism of PLCj,-, there remain numerous unanswered questions. For example, it is well documented that PLCSc preferentially hydrolyzes micellular substrates and monomeric substrates with longer acyl side chains. However, the basis for the discontinuity in the rate of hydrolysis that is observed at the critical micelle concentration of the substrate is unknown as is the reason for the increase in the Km for soluble substrates as the length of the acyl side chains decrease. What is... 

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