Unique-spatial shape

The shape of the stable icosahedral clusters, [B,2H,2] " and C2B]qHj2, brings the possibility to build dendrimers having the cluster as the core, allowing for a maximum of 12 primary branches in a unique spatial disposition. Because the utility of the units is dependent on their functionaliza-tion,3 2 the introduction of functional groups is a necessary target. Substitution of the carbon-bound... 

This is a very unique situation for superconductivity, since in the previous experience inhomogeneity is almost always harmful to superconductivity. Why is the superconductivity in the cuprates so different While further research is clearly required to answer this puzzle, one possibility is that the spatial confinement produces the vibronic resonant state of phonon and charge that enhances HTSC [15,23], The benefit of spatial confinement on HTSC has been strongly advocated for some time by Phillips with the idea of filamental superconductivity [24] and more recently by Bianconi [25] as the shape resonance effect. In both cases the effect arises due to the enhancement of the local density of states (DOS). An additional, and possibly more central, effect of confinement is to reduce the group velocity of electrons and bring it comparable to the phonon velocity, thus... 

In addition to the repeat unit sequence, another area of current interest in polymer structural control (Fig. 1) may be the spatial or three-dimensional shapes of macromolecules. In fact, the recent development of star [181-184] and graft [185] polymers, as well as starburst dendrimers [126], arborols [186,187], and related multibranched or multiarmed polymers of unique and controlled topology, has been eliciting active interest among polymer scientists. In this section, let us consider the following macromolecules of unique topology for which living cationic polymerizations offers convenient synthetic methods that differ from the stepwise syntheses (polycondensation and polyaddition) [126,186,187]. 

A class of aluminosilicates called zeolites offer a number of chemical, physical, and structural characteristics that merit use as electrode modifiers (7,101-106). The chemical composition of zeolites is similar to that of clays however, zeohtes are three-dimensional aluminosilicate crystals rather than two-dimensional sheet structures. This distinction imparts unique chemical and physical properties that can be exploited for preconcentration, size and shape selectivity, and catalysis. However, molecules that can be incorporated into zeohtes are more limited due to spatial constraints of the zeolite cavity. 

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