Performance estimation for indoor wireless systems using FDTD method

A three-dimensional implementation of the finite-difference time-domain method is used to estimate the down-link outage probability of a direct-sequence code division multiple access system operating in a multi-storey office building in the presence of co-channel interference. The numerical analysis is supported by experimental measurements and good agreement is found for the outage probability. Both simulation and measured results indicate that vertically aligned co-channel base stations have lower outage than a vertically staggered configuration, which is explained by examining the correlation between the desired and interfering signals

Angular independent frequency selective surfaces for interference control in indoor wireless environments

A study of electromagnetic wave propagation in buildings using a finite-difference time-domain algorithm has demonstrated that waves are incident on walls over a wide range of angles. If wall mounted frequency selective shielding is desired, it is argued that this behaviour requires shielding solutions that are angle insensitive. A simple single-layer annular ring frequency selective surface (which is relatively economic to fabricate) is shown to offer adequate angular stability of the transmission response, and is thus suitable for electromagnetic interference control in indoor wireless environment

Mast cells: the forgotten cells of renal fibrosis

Background/Aims—Mast cells, when activated, secrete a large number of fibrogenic factors and have been implicated in the development of fibrotic conditions of the liver, lung, and skin. There is evidence that renal fibrosis is closely linked with a chronic inflammatory cell infiltrate within the interstitium, but a potential role for mast cells in this process has yet to be defined. Therefore, the numbers of mast cells in normal and fibrotic kidneys with various pathologies were investigated. Methods—Mast cells were quantified in renal transplants showing acute and chronic rejection and cyclosporin toxicity, kidneys removed for chronic pyelonephritis, and renal biopsies from patients with IgA nephropathy, membranous nephropathy, and diabetic nephropathy. Mast cells were stained using two methods: acid toluidine blue detected less than 30% of the mast cells revealed by immunohistochemistry for mast cell tryptase. Results—Mast cells were scarce or absent in normal kidney (median, 1.6 mast cells/mm(2)) but numerous throughout the cortex and medulla in all specimens that showed fibrosis. They were almost entirely confined to the renal interstitium. Mast cells were present in large numbers in biopsies from patients with membranous nephropathy (median, 21.7 mast cells/mm(2)) and diabetic nephropathy (median, 29.2 mast cells/mm(2)), which were selected on the basis of showing chronic injury. In 24 unselected IgA nephropathy biopsies there was a close correlation between numbers of mast cells and the extent of interstitial fibrosis (r = 0.771; p < 0.0001). In renal transplant biopsies, mast cells were associated with allograft fibrosis in chronic rejection (median, 27.1 mast cells/mm(2)) and chronic cyclosporin toxicity (median, 10.6 mast cells/mm(2)) but not acute rejection (median, 2.7 mast cells/mm(2)) or acute cyclosporin toxicity (median, 2.0 mast cells/mm(2)). There was no detectable increase in mast cell numbers during acute rejection in those transplants that subsequently progressed to chronic rejection. In some biopsies the mast cells were largely intact, but in most cases some or all were degranulated. Conclusions—An increased number of mast cells is a consistent feature of renal fibrosis, whatever the underlying pathology, and the number of mast cells correlates with the extent of interstitial fibrosis. This suggests that mast cells might play a pathogenetic role in the fibrotic process. Key Words: mast cells • kidney • fibrosi