A formal implementation of the Fowler-Nodheim equation to emission characteristics of diamond coated cold cathodes gives values of the work function which depend on surface curvature of the coating, thus making it incorrect. Experiments with diamond coated Si tips having different coating radii have shown, that their emissivity depends on the radius of the Si tip rather than on the radius of th...

We consider generation of a perfect optical vortex by three elements: (i) amplitude-phase element with its transmission being proportional to the Bessel function, (ii) optimal element with the transmission proportional to the sign of the Bessel function, and (3) helical axicon. Maximal intensity of light on the ring is shown to be achieved by using the optimal element. Thickness of the light ri...

The conchoid surface G of a given surface F with respect to a point O is roughly speaking the surface obtained by increasing the radius function of F with respect to O by a constant d. This paper studies real rational ruled surfaces in this context and proves that their conchoid surfaces possess real rational parameterizations, independently on the position of O. Thus any rational ruled surface...

Let An denote the number of objects of some type of “size” n, and let Cn denote the number of these objects which are connected. It is often the case that there is a relation between a generating function of the Cn’s and a generating function of the An’s. Wright showed that if limn→∞Cn/An = 1, then the radius of convergence of these generating functions must be zero. In this paper we prove that...

the center (periphery) of a graph is the set of vertices with minimum (maximum)eccentricity. in this paper, the structure of centers and peripheries of some classes ofcomposite graphs are determined. the relations between eccentricity, radius and diameterof such composite graphs are also investigated. as an application we determinethe center and periphery of some chemical graphs such as nanotor...

We present NICMOS NIC3 observations of the Galactic globular cluster NGC288, taken South East at 2.4 times the cluster’s half-light radius in the J and H bands. We have detected the cluster main sequence down to J ≃ 25 and H ≃ 24. The corresponding luminosity function covers the range 3 < MH < 9 and peaks at MH ≃ 6.8. The theoretical tracks of Baraffe et al. (1997) at [Fe/H ] = −1.3 give a mass...

abstract  background: resection of the distal end of the radius is indicated in the treatment  of locally aggressive primary benign and malignant bone tumors. the aim of this study  was to evaluate the technique of osteoarticular allograft reconstruction of the distal radius after wide excision of a giant-cell tumor.  methods: we analyzed 15 patients retrospectively who had reconstruction of th...