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.     

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.     

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.     

Why Machine Ethics?

Machine ethics, machine morality, artificial morality, and computational ethics are all terms for an emerging field of study that seeks to implement moral decision-making faculties in computers and robots. Machine ethics is not merely science fiction but a topic that requires serious consideration given the rapid emergence of increasingly complex autonomous software agents and robots. The authors introduce the issues shaping this new field of enquiry and describe issues regarding the development of artificial moral agents.This article is part of a special issue on Machine Ethics.     

APPLICATION OF MUD GAS DATA AND LEAKAGE PHENOMENA TO EVALUATE SEAL INTEGRITY OF POTENTIAL CO2 STORAGE SITES: A STUDY OF CHALK STRUCTURES IN THE DANISH CENTRAL GRABEN,NORTH SEA

Depleted chalk oilfields and chalk structures in the Danish Central Graben, North Sea, are potential CO₂ storage sites. In most of these fields, the main reservoir is the Upper Cretaceous – Danian Chalk Group and the Eocene – Miocene mudstones of the Horda and Lark Formations constitute the primary seal. In a few fields, the reservoir is composed of the Lower Cretaceous Tuxen and Sola Formations. Here the main seal is assumed to be the Chalk Group which however has poor gas sealing characteristics; the Horda and Lark Formations constitute an efficient secondary seal although they are quite high in the section. This study documents a workflow that may help to evaluate the seal integrity of the structures from an integration of mud gas data from wells with seismic data. Mud gas data provide detailed information about the distribution and types of gas (biogenic or thermogenic) throughout the seal section and overburden. The presence of higher carbon number gases (C₃–C₅, propane to pentane) in the seal indicates migration of thermogenic gas into the thermally immature sealing mudstones; whereas the dominance of C₁ (methane) and partly C₂ (ethane) likely reflects the presence of in situ generated biogenic gas in the mudstones, thus indicating that there are no seal integrity issues. The vertical thermogenic gas migration front has been determined, and a “traffic light” indicator system has been used for seal integrity evaluation. Where no or minor migration of thermogenic gas into the primary seal has occurred and a primary seal >30 m thick is present, the seal is considered to have good matrix seal integrity (green). If some significant thermogenic gas migration has occurred into the primary seal but more than 30 m of primary seal is present above the thermogenic gas migration front, the seal integrity is reduced (yellow). In structures where thermogenic gas migration is recorded through the primary seal and into the overburden, seal integrity is considered to be poor (red). In areas where significant leakage of thermogenic gas has occurred into the seal, high density, low porosity carbonate beds frequently occur encapsulated within the sealing mudstones and are interpreted to be composed of methane-derived authigenic carbonates (MDACs). Seismic data show that there is a convincing correlation between leakage as indicated from mud gas data and the presence of vertical wipe-out zones (gas chimneys), bright zones (gas-charged sediments or MDACs), and depressions (pockmarks). In general, potential CO₂ storage sites in the study area in tectonically inverted structures show good seal integrity, but this may locally be reduced and require additional analyses. Storage sites associated with salt diapirs generally show poor seal integrity and are likely to be poor candidates for CO₂ storage. In combination, mud gas and seismic data are therefore powerful tools to investigate (palaeo-) leakage phenomena and provide support for seal integrity evaluation at local to regional scales.     

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.