Variable diameter

P. H. (1977). Vesicles of variable diameter prepared by a modified injection method. Biochemistry, 16, 3932-3935. 

J. A. McGuire and E. H. Piepmeier, The characterisation and simplex optimisation of a variable-diameter, multi-electrode, direct current plasma for atomic emission spectroscopy. Can. J. Appl. Spectrosc., 36(6), 1991, 127-139. 

Figure 36. Conversion of an asymmetric square pyramid (top left) into its mirror image (top right) along a chiral pathway. Four spheres with different but variable diameters are centered at the vertices of the square base. The spheres labeled a and b shrink and expand, respectively, until their diameters are switched. This is followed by a similar switch in the diameters of spheres c and d.

ELECTRONIC STRUCTURE OF CARBON NANOTUBES OF VARIABLE DIAMETER... 

Abstract. Equilibrium configurations, total energy, heat of formation, energies of HOMO and LUMO orbitals, density of one-electron states (DOS) of open and semi open carbon nanotubes of variable diameter such types as (6,6)+(6,0), (5,5)+(5,0) and (6,0)+(5,0) are determined in frames of semi-empirical quantum chemistry PM3-method. 

Keywords junctions of carbon nanotubes, variable diameter, molecular simulations, quantum-chemical calculations, modeling. 

The (n,n)+(n,0) nanotubes of variable diameter can be considered as the result of junction of CNTs with two different types of conductivity metallic (n,n) CNT and semiconductor (n,0) CNT with forbidden gap near 0.5-1.5 eV. However, the nanotubes of variable diameter are rather the insulators with forbidden gap about 2.5-4 eV. 

We consider also the nanotubes of variable diameter of such type as (n+l,0)+(n,0). On the boundary between (n+1,0) and (n,0) tubes only one 7-members and one 5-members cycles are created. The axes of (n+1,0) and (n,0) tubes are parallel but they don t coincide, therefore the axis symmetry of junctions in whole is absent. 

The results of our calculations are in a reasonable accordance with the data of recently papers [3-5] devoted to research of the same problems. It s clear that nanotubes of variable diameter of such kind must possess anisotropic conductivity and therefore can be used as switching elements in future nanodevices [6-7]. 

The results of semi-empirical PM3 calculations confirm the possibility of existence of the different types of nanotubes of variable diameter. 

One of the simplest ways of extending this single-pore model is to assume that variations in the size of pore spaces can be represented by a variable-diameter assembly of such pores, referred to as a parallel bundle of pores. An example is shown in Fig. 3, for a variation of the model applied to a supported zeolite cracking catalyst. In this example [10] the zeolite pores are simply configured along the pore walls, so that the parallel bundle represents the Si/Alumina-support pore spaces. 

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