Experimental assessment of the reflection of passive multimodeinterference couplers

Integration of semiconductor amplifiers in integrated optical circuits is presently possible. Reflections inside these circuits are undesirable for they can cause unwanted oscillations. The reflection properties of integrated passive multimode interference (MMI)-couplers have been experimentally determined     

First InP-based reconfigurable integrated add-drop multiplexer

A four-channel reconfigurable integrated add-drop multiplexer on InP-substrate is reported. The device consists of a 5/spl times/5 PHASAR demultiplexer integrated with Mach-Zehnder interferometer electrooptical switches. Total device size is 3/spl times/6 mm/sup 2/. All routing configurations of four wavelengths have been demonstrated. Crosstalk values are better than -20 dB. On-chip loss for the dropped or added signals and for the signals coupled from the input to the output port are lower than 7 and 11 dB, respectively.     

Isolation and partial purification of mannose-specific agglutinin from brewer's yeast involved in flocculation

Yeast cell-agglutinating activity, designated agglutinin (possible lectin), was isolated from cell walls of both non-flocculent and flocculent brewer's yeast cells. Agglutinin-mediated aggregation of yeast cells in a manner similar to flocculation with respect to specific mannose-sensitivity, pH-dependence and calcium-dependence. Agglutinating activity was found to be heat-stable and protease-insensitive. Furthermore, addition of agglutinin to flocculent cells strongly stimulated the flocculation ability of the cells, whereas addition to non-flocculent cells rendered these cells weakly flocculent. Agglutinin was found to be released from flocculent cells during the course of a flocculation assay, but not from non-flocculent cells. Presence of mannose during the assay inhibited release of agglutinin. Our results suggest that (i) mannose-specific agglutinin is continuously synthesized during growth of brewer's yeast cells, (ii) agglutinin is present in cell walls of non-flocculent cells but is unable to bind its ligand on other cells, and (iii) the ability of yeast cells to flocculate in a flocculation assay depends, among other factors, on release of agglutinin from the cells. A 10-kDa polypeptide might represent one form of agglutinin.     

A Low-Cost Multichannel Preamplifier for Physiological Signals

A preamplifier for physiological signals (ECG, EMG, etc.) is described for general use in mnltichannel applications. The limited number of components made it possible to implement eight channels on one Eurocard printed circuit board (160 x 100 mm) and 64 channels in a 9.5 in cabinet in a cost-effective manner (about $ 50 per channel). The use of a monolithic instrumentation amplifier based on the current feedback principle resulted in high dc suppression combined with excellent noise performance and high common mode rejection. A second-order Butterworth low-pass filter was implemented using switched capacitor circuits, so that in a multichannel setup the rolloff frequency of all channels can be (digitally) controlled by one clock frequency.     

Cardiac asystole post-exercise: a report of two cases

Two patients are described with reproducible cardiac asystole post-exercise. No structural heart disease was demonstrable. At autonomic function testing no abnormal responses were noted. Also, head-up tilt tests were normal. However, electrophysiologic testing and heart rate variability during 24-h Holter monitoring were indicative of a high vagal tone in both patients. The findings suggest that post-exertional asystole may not be due solely to a vasovagal mechanism; excessive rebound vagotonia per se may also play a role.     

Characterization of the movement of polypyrrole–dodecylbenzenesulfonate–perchlorate/tape artificial muscles. Faradaic control of reactive artificial molecular motors and muscles

In this paper, we characterize polypyrrole–DBS–ClO₄/tape bilayers with prevalent interchange of cations, while acting as macroscopic bending artificial muscles in aqueous solution. The electrochemical origin of their movement is described by linear equations deduced from the driving Faraday's laws. We demonstrate that the engineering parameters for macroscopic bending movement rates, the direction of the movement, described angles, and final positions of the electrochemical motors, are under control of the involved current, the direction of the current flow and the consumed charge, which means under Faradaic control of the conducting polymer composition. The linear equations describing both movement rate and position were obtained. The specific (per unit of polypyrrole weight in the muscle) driving current (A g⁻¹), the specific driving charge (C s⁻¹ g⁻¹) or the specific counter-ion composition variation (mol s⁻¹ g⁻¹) are directly related to the actuator angular movement (rad s⁻¹ A⁻¹), whatever the muscle dimensions or the working polypyrrole weight in the device.