background and aims: in spite of a long tradition of fruit-tree growing in all provinces of iran, information on pear (pyrus communis) tree viruses is scant. in order to identify of the nature of the virus like symptoms and decline in pear trees, we carried out a survey for the occurrence of four important viruses. materials and methods: leaf samples of pear showing virus like symptoms were col...

Spot patterns, whereby the activator field becomes spatially localized near certain dynamically-evolving discrete spatial locations in a bounded multi-dimensional domain, is a common occurrence for two-component reaction-diffusion (RD) systems in the singular limit of a large diffusivity ratio. In previous studies of 2-D localized spot patterns for various specific well-known RD systems, the do...

Background and Aims: In spite of a long tradition of fruit-tree growing in all provinces of Iran, information on pear (Pyrus communis) tree viruses is scant. In order to identify of the nature of the virus like symptoms and decline in pear trees, we carried out a survey for the occurrence of four important viruses. Materials and Methods: Leaf samples of pear showing virus like symptoms wer...

A key question in cytokinesis is how the plane of cell division is positioned within the cell. Although a number of cytokinesis factors involved in formation of the actomyosin contractile ring have been identified, little is known about how these factors are localized and assembled at the cell-division site. Cells of the fission yeast Schizosaccharomyces pombe divide using a medial actomyosin r...

We propose an eecient dynamic load balancing scheme in cellular networks for managing tele-traac hot spot in which channel demand exceed a certain threshold. A hot spot, depicted as a stack of hexagonaìRings' of cells, is classiied as complete if all cells within it are hot. The rings containing only cold cells outside the hot spot are called`Peripheral Rings'. Our load balancing scheme migrate...

A modified Fresnel zone plate that can produce an approximate Gaussian focal spot is proposed for the focusing and imaging of soft x rays and extreme ultraviolet radiation. The selection conditions for the positions and the widths of the concentric open rings are analytically presented. The focal spot size can be much smaller than the width of the narrowest open ring, and the sidelobes and the ...

An electrons and holes of indirect excitons in semiconductor coupled quantum wells are localized in different wells and as the result the excitons have long lifetime. Such system present interest for study of exciton condensation phenomena [1]. Recently interesting experiments were fulfilled for indirect excitons in AlGaAs and InGaAs crystals with coupled quantum wells. In works [2, 3, 4, 5, 6,...

Multi-spot optics are applied for process parallelizing if the demand on throughput in mass production rises or large areas of material have to be processed. We investigate the usage of microlens arrays as multifunctional elements for forming an arbitrary shaped laser beam into a spot-, a ring-spotor a line-array pattern. It can be shown that the intensity distribution of each spot is equal to ...