Aluminiumalkyle mit Heteroatomen. II [1]. Darstellung von Tris(3-trimethylsilyl-propyl)aluminium

Aluminium Alkyls with Heteroatoms. II. Preparation of Tris[(3-trimethylsilyl)-propyl]aluminium Tris[(3-trimethylsilyl)-propyl]aluminium is prepared by disproportionation and by an olefine displacement reaction in a circulation process. The reaction way is investigated with the aid of ¹H-n.m.r.- and i.r.-spectroscopy.     

ATM‐based wireless broadband access in the local loop

Broadband networks using wireless transmission techniques are a quick and flexible means of implementing subscriber access. Unoccupied frequency bands with sufficient bandwidth to allow the transmission of digital signals at very high bit rates are found only in the microwave bands. Because the path loss is fairly high at these frequencies, the diameter of radio cells is limited to a maximum of a few kilometres. This results in a microcellular system, which is best implemented in the form of a point‐to‐multipoint system, where one radio‐base station serves all subscribers registered in that radio cell. An interactive, broadband, ATM‐based radio local loop has undergone successful trials in Munich. Copyright © 2001 John Wiley & Sons, Ltd.     

Enhancing interference rejection of preamplified electrodes by automated gain adaption

The use of preamplified electrodes in electrocardiography (ECG) or electroencephalography (EEG) has a numbe of benefits, most importantly, the noise reduction through preamplification and the interference reduction through buffering (Fernandez and Pallas-Areny, 1997). Normally, preamplified electrodes are not used because the mismatch in amplification due to component tolerances leads to a reduced common mode rejection ration (CMRR) (Pallas-Areny and Webster, 1991). In this paper, we introduce a new technique to restore the CMRR. We do this by adapting the gain of the differential amplifier (DA) following the preamplified electrodes. The technique is based on measuring the transfer function of a chosen common mode signal. The gain of the DA is adjusted by a closed loop controller to maximize the CMRR. With this technique, there is no adverse effect on the ECG or EEG. In this way, the control loop can be operated continuously if needed.     

Stress-induced effects by the anodic oxide in ridge waveguide laserdiodes

This paper studies, both theoretically and experimentally, stress-induced effects on the lateral far-field behavior for ridge-type semiconductor laser diodes where anodic oxide is used for the definition of the stripe width. These effects consist of antiguiding under the stripe region, and of two positive waveguiding features near the stripe edges. For low-threshold devices, these effects may be more important than thermal effects, depending on the stress in the oxide. They put a lower limit on the built-in index guiding to be introduced by lateral etch outside the ridge region in order to maintain fundamental mode operation for wider stripes. The magnitude of these effects may be as large as Δn_ef=1×10^-3. An analytical mathematical model is deduced for computing stresses and strains for a certain ridge-shaped interface which bounds the elastic medium     

Next Generation ADC Massive Parallel Testing with Real Time Parameter Evaluation

The paper describes the implementation of a novel Analog-to-Digital-Converter (ADC) test technique for next generation low cost massive parallel ADC testing using a Field Programmable Gate Array (FPGA) on tester load board. The goal is to test the ADC which is embedded in an automotive micro controller with only pure digital tester sources. Therefore, the analog test stimulus for the ADC is generated by using ΔΣ-modulation technique off-line and analog filtering on load board. The digital test response is analyzed by a FPGA in real time by comparing the measured data with a reference signal. The modular concept of FPGA evaluation allows for quick and flexible reaction on changing production test requirements. Simply by reprogramming the FPGA with a new module there is no need of any hardware reconfigurations. Measurements with a high precision reference ADC in laboratory environment show that the method is ready for production.     

Predictive model for inactivation of Campylobacter spp. by heat and high hydrostatic pressure

Campylobacter represents one of the leading causes of foodborne enteritis. Poultry and its products frequently transmit the pathogen. The objective of the present study was to model predictively the short-term inactivation of Campylobacter in a ready-to-eat poultry product to develop an economic high-pressure treatment. We inactivated baroresistant strains of Campylobacter jejuni and Campylobacter coli, grown to stationary phase on nutrient agar and inoculated in poultry meat slurry, by heat and high hydrostatic pressure. Incubation at ambient pressure at 70 degrees C for 1 min and at 450 MPa at 15 degrees C for 30 s inactivated more than 6 log CFU of this foodborne pathogen per ml of poultry meat slurry. Thermal and pressure inactivation kinetics of C. coli and C. jejuni in poultry meat slurry were accurately described by a first-order kinetic model. A mathematical model was developed from 10 to 65 degrees C and from ambient to 500 MPa that predicts the reduction in numbers of Campylobacter in response to the combination of temperature, pressure, and treatment time. We suggest the high-pressure treatment of foods to avoid health risks caused by Campylobacter. The nonthermal short-term treatment of the examined food model system represents a successful step to an economic high-pressure procedure.