Theoretical Challenge

Lequeux F and Candau S J 1997 Struotural properties of wormlike mioelles Theoretical Challenges in the Dynamics of Complex Fluids ed MoLeish (Dordreoht Kluwer) pp 181-90... 

Theoretical challenges were changing dramatically during the seventies with the advent of ever more powerful computational devices. Accurate calculations became feasible for reasonably large systems and the opportunity... 

Tailoring block copolymers with three or more distinct type of blocks creates more exciting possibilities of exquisite self-assembly. The possible combination of block sequence, composition, and block molecular weight provides an enormous space for the creation of new morphologies. In multiblock copolymer with selective solvents, the dramatic expansion of parameter space poses both experimental and theoretical challenges. However, there has been very limited systematic research on the phase behavior of triblock copolymers and triblock copolymer-containing selective solvents. In the future an important aspect in the fabrication of nanomaterials by bottom-up approach would be to understand, control, and manipulate the self-assembly of phase-segregated system and to know how the selective solvent present affects the phase behavior and structure offered by amphiphilic block copolymers. 

The spin dynamics of solids whose primary or sole nuclear interactions (ignoring the omnipresent Zeeman and isotropic chemical shift terms) are dipolar interactions among a very large number of nuclei present interpretive and theoretical challenges... 

For an isotropic phase there are no differences between surface energy and surface tension. However, for crystals, which are anisotropic in nature, the relationship between these two quantities is significant and also theoretically challenging, see e.g. the recent review by Rusanov [2],... 

These authors conclude that the problem of internal solvation is still an experimental and theoretical challenge GB measurements for this type of molecules of low volatility are not always in good agreement194. Molecular orbital calculations may help to solve the difficult experimental problems, but they have to take into account conformational isomerisms and the prototropic tautomerisms of the amidine and guanidine moieties. In light of the above discussion, the proton affinities deduced from the experimental GB values should be based on accurate estimations of the entropy of cyclization 86. 

Cates M (1997) In McLeish T (ed) Theoretical challenges in the dynamics of complex fluids. Kluwer, Dordrecht... 

We anticipate that continued development of minimalist models, in conjunction with more efficient multi-reference approaches and a wider array of benchmark curves, will result in a better understanding of the theoretical challenges of bond breaking processes and increased ability of electronic structure theory to model them. 

This is probably the key heterogeneous reaction for Antarctic stratospheric ozone depletion, and serves as a useful focus for the discussion of the theoretical challenges that must be addressed in dealing with fairly complex chemistry in a complex environment, challenges enlivened — as will be seen below — by the evident chemical involvement of the ice surface environment. 

UV/vis spectra. The accurate characterisation of excited states, however, poses formidable conceptual and theoretical challenges. 

There is considerable evidence experimentally and theoretically that the kinetics and the thermodynamic behavior of deeply supercooled liquids, which are far away from equilibrium, are intricately linked [1-7,9,13,14,16-18,23,25, 26,32-34,37-105]. Although precise theoretical description of this connection is a major unsolved theoretical challenge, three key experimental and theoretical advances have provided novel insights into the decisive role played by thermodynamic factors in glass-forming liquids [37,38,52,54—56] ... 

In practice, spin is as real as mass and charge, and routinely measured spectroscopically by the techniques of electron and nuclear magnetic resonance. These measurements are done under widely different conditions and with minor interference between the two phenomena. As implied by the terminology, atomic spin is of two different types - separately associated with the nucleus and extranuclear electrons respectively. The theoretical challenge is how to describe these two independent rotations within the same body. 

Positronium still presents rather formidable theoretical challenges [39], since it is a relativistic two-body system which cannot be approximated by the motion of a particle of reduced mass in a fixed Coulomb potential. In addition, QED calculations must include annihilation terms. First laser measurements of the 1S-2S two-photon transition frequency in positronium [40] give a result about five standard deviation lower than the theoretical predictions, after taking a recalibration of the tellurium reference line into account [41]. On the other hand, as yet uncalculated higher order terms could well account for this discrepancy. 

The absorption spectrum of benzophenone is characterized by two distinct and broad bands [127], a weak n-Tr band and a strong tt-tt band. The n-Tr band suffers a shift of around 2200 cm 1 when going from n-hexane to water, while the tt—tt band is shifted by nearly -1600cm. The description of these distinct solvatochromic shifts is therefore a good theoretical challenge. 

It should also be frankly acknowledged here that there are a variety of theoretical challenges associated with these problems that are not highlighted at all in this chapter. These range from formulation questions involving quantum versus classical issues in calculating rates (see, for example, Chapter 16) to the quantum chemical electronic structure issues of solute intramolecular force fields. These and other difficulties certainly impede the theoretical ability to confidently predict VET rates and mechanisms, but not the desire to try. 

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