Kilovolt Blumlein pulse generator with variable pulse duration and polarity

A Blumlein pulse generator which utilizes the superposition of electrical pulses launched from two individually switched pulse forming lines has been designed and tested. By using a power metal-oxide-semiconductor field-effect transistor as a switch on each end of the Blumlein line, we were able to generate pulses with amplitudes of 1 kV across a 100 Omega load. Pulse duration and polarity can be controlled by the temporal delay in the triggering of the two switches. Using this technique, we have demonstrated the generation of pulses with durations between 8 and 60 ns. The lower limit in pulse duration was determined by the switch closing time and the upper limit by the length of the pulse forming line. A further advantage of the concept is that pulse distortions caused by the non-negligible on-resistance of a line with a single switch can be eliminated by using switches with identical characteristics.     

EELS Spectrum‐Imaging for Boron Detection in Biological Cryofixed Tissues

Abstract

Boron imaging at the subcellular level in tissues is of prime importance to understand boron neutron capture therapy (BNCT) effects and to suggest ways to improve the efficiency of the treatments. In this paper, we present boron imaging in cryofixed biological tissues by electron energy loss spectroscopy (EELS), using the spectrum‐imaging acquisition mode. We performed boron imaging in tissues of mice who received boron compounds. We analysed cryosections of tumours, livers, and kidneys of infused mice. Our results point out the relevance of EELS for boron imaging and, particularly, in order to detect small accumulation areas. The data also point out the limitations of the technique and its complementarity with other imaging techniques. We discuss and illustrate the possibility for misinterpretation of EELS or electron spectroscopic imaging (ESI) data. We particularly focus on the problem of phosphorus for boron imaging.     

Juristen & Techniker

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Actuator saturation and anti-windup compensation in event-triggered control

Event-triggered control aims at reducing the communication load over the feedback link in networked control systems by sending information only if certain event conditions, which guarantee a desired control performance, are satisfied. This article investigates the consequences of actuator saturation on the behavior of the event-triggered control loop in terms of its stability and information exchange. Stability properties are derived using linear matrix inequalities (LMIs) which show how the stability of the event-triggered control loop depends on the selection of the event threshold. Moreover, it is shown that a lower bound on the minimum inter-event time exists being likewise affected by the event threshold. As actuator saturation might severely degrade the performance of the event-triggered closed-loop system, the scheme is extended by incorporating an anti-windup mechanism in order to overcome this problem. The results are illustrated by simulations and experiments.     

THERMAL RESPONSE OF SILICON CRYSTAL TO PICO-FEMTOSECOND HEAT PULSE BY MOLECULAR DYNAMICS

We investigate the thermal response of a silicon crystal irradiated by a pico-femto heat pulse by using molecular dynamics technique and a linear response theory–based statistical analysis. The thermal susceptibility is first defined in terms of computed quantities and then convoluted with time Gaussian temperature pulses. The qualitative difference between the responses to various pulse durations is explained and the results are compared to those of classical Fourier model. Non-Fourier behaviors are emphasized and a mean phonon relaxation time is identified.     

Saving energy in housing

As in many other countries it is only since the energy crisis that methods of house and apartment building in Austria have come under scrutiny in terms of energy conservation. This article, by the director of the Austrian Institute of Building Research, summarises studies carried out by the Institute which led to an energy saving programme that earned a State Prize for research work from the Austrian Ministry of Science.     

Understanding the influence of doping in efficient phosphorescent organic light-emitting diodes with an organic p–i–n homojunction

We report on the development and detailed investigation of highly efficient p–i–n phosphorescent organic light-emitting diodes (PhOLEDs) using 4,4′-bis(carbazol-9-yl)-biphenyl (CBP) as a single organic semiconductor matrix. Following optimization of doping concentration of both the phosphorescent emitter molecule and of the p- and n-type dopants, an external quantum efficiency (EQE) of 15% and a power efficiency (PE) of 28 lm/W are realized at a luminance of 1000 cd/m². These values are comparable to the state-of-the-art for conventional complex multilayered PhOLEDs. By analyzing the device characteristics (i.e. electroluminescence spectra, the current density–voltage behavior of single carrier devices, the transient electroluminescent decay, and the impedance spectroscopy response), we find that the device performance is closely linked to the charge carrier balance in the device, which in turn is governed by the interplay of the conductivities of the doped layers and the transport of each charge carrier species within the emitting layer.     

Understanding the Holocaust through The U.S. Holocaust Memorial Museum

The opening of the United States Holocaust Memorial Museum attracted significant attention in both the popular and the architectural press. This attention and the continuing large numbers of visitors to the Holocaust Museum raise significant questions involving both the paradoxes inherent in the museum as a building type and the particular difficulties in creating a museum specific to the Holocaust. This article addresses a single question: How do visitors come to understand the reality of the Holocaust as they pass through the museum? The focus is primarily on the exhibit sequence, although the building is also discussed. In particular, this article focuses on the question of the “distance” in time and context between the museum's visitors and those who were participants in the Holocaust. I argue that the psychological phenomenon described as “identification” is critical in overcoming this distance in the Holocaust Museum experience.