Lichenoid contact dermatitis from the ink of a red pen]

So what is all this fuss about computers and the year 2000? Is it really a doomsday scenario? How will it affect us? This short article seeks to explain the problem and its significance to the medical illustration profession.     

Direction finding in IEEE802.11 wireless networks

A novel direction-finding method for stations of IEEE802.11 wireless local area networks is presented in this paper. The method uses a switched beam array for determining the direction of arrival of the incident electromagnetic field in a time efficient way and associates certain medium access control (MAC) layer functions with different radiation patterns of the switched antenna array, in order to determine the proper orientation of directional beams on both entities of a communication link. The application of the proposed method to an IEEE802.11 wireless network is presented and it is depicted how the method improves the network performance without requiring any modifications to the existing MAC protocol.     

Spatial multiplexing via antenna switching

A simple scheme for spatially multiplexing two BPSK signals using a switched antenna system with a single RF chain, a shared RF-DC cable and a shared RF-DC feeding circuit is proposed. The idea is to modulate the first BPSK substream to one of the two array elements while exciting the second element parasitically by the field of the first one. The second substream is encoded in such a way to control which of the two elements will be driven. Decorrelating the two BPSK signals at the transmitter side is achieved by mapping the signals onto a set of orthogonal functions while the matching impedance of the two antenna elements is optimized for the maximum outage rate by maximizing the matching efficiency and minimizing the power imbalance between the basis functions, simultaneously.     

On the Link Performance of a Proposed Compact Antenna System

In this paper we consider an antenna system, that consists of one active and one parasitic antenna element. Different antenna patterns may be created by loading the parasitic element with appropriate reactive impedances on each symbol period. We demonstrate the performance of a communication link that uses the proposed antenna system at the transmitter and two omnidirectional antennas at the receiver. The Arimoto-Blahut algorithm is used to find the capacity achieving distribution on the channel symbols. The capacity of the antenna system is compared to the capacity obtained by a single transmitter antenna.     

Influence des ions sur le pouvoir hydratant de l'ure e: e tude sur peau de porc ex vivo

This study deals with the influence of ions (NaCl and MgSO4) in a W/O emulsion containing 10% urea. Moisturization kinetics are assessed by corneometry on pig skin ex vivo. The formula's influence on urea penetration is measured by infrared spectrometry with an ATR device and the stripping method. Corneometry and spectroscopy were chosen to record simultaneously the hydratation levels and urea localization into superficial cell layers. Urea crystallization after evaporation of emulsions and aqueous solutions is described. Results show that urea does not hydrate nor penetrate when applied to the skin through an aqueous gel. In a W/O emulsion, sodium chloride increases the ability of urea to moisturize without improving penetration. In vitro urea crystallization is disturbed by sodium chloride or magnesium sulphate for solutions and emulsions. This stabilization by ions is correlated with good moisturization values. The stabilization of urea in the solute state provided by ions increases its water epidermal binding capacity without enhancing penetration.     

Comparison of analytical techniques for dynamic trace metal speciation in natural freshwaters

Several techniques for speciation analysis of Cu, Zn, Cd, Pb, and Ni are used in freshwater systems and compared with respect to their performance and to the metal species detected. The analytical techniques comprise the following: (i) diffusion gradients in thin-film gels (DGT); (ii) gel integrated microelectrodes combined to voltammetric in situ profiling system (GIME-VIP); (iii) stripping chronopotentiometry (SCP); (iv) flow-through and hollow fiber permeation liquid membranes (FTPLM and HFPLM); (v) Donnan membrane technique (DMT); (vi) competitive ligand-exchange/stripping voltammetry (CLE-SV). All methods could be used both under hardwater and under softwater conditions, although in some cases problems with detection limits were encountered at the low total concentrations. The detected Cu, Cd, and Pb concentrations decreased in the order DGT > or = GIME-VIP > or = FTPLM > or = HFPLM approximately = DMT (>CLE-SV for Cd), detected Zn decreased as DGT > or = GIME-VIP and Ni as DGT > DMT, in agreement with the known dynamic features of these techniques. Techniques involving in situ measurements (GIME-VIP) or in situ exposure (DGT, DMT, and HFPLM) appear to be appropriate in avoiding artifacts which may occur during sampling and sample handling.