Integrated Circuits Based on 300 GHz fT Metamorphic HEMT Technology for Millimeter-Wave and Mixed-Signal Applications

Advanced circuits based on metamorphic HEMT (MHEMT)technologies on 4 ”GaAs substrates for both millimeter-wave,and mixed- signal applications are presented.Extrinsic cut-off frequencies of ft =293 GHz and fmax =337 GHz were achieved for a 70 nm gate length metamorphic HEMT echnology.The MMIC process obtains high yield on transistor and circuit level.Single-stage low-noise amplifiers demonstrate a small signal gain of 13 dB and a noise figure of 2.8 dB at 94 GHz.An amplifier MMIC developed for D-Band operation features a gain of 15 dB at 160 GHz.The achieved results are comparable to state- of-the-art InP-based HEMT technologies.In order to realize 80 Gbit/s digital circuits,a process with 100 nm gate length enhancement type HEMTs with a transit frequency of 200 GHz is used.Three metalization layers are available for interconnects.The parasitic capacitance of the interconnects is kept low by using BCB and plated air bridge technology.Based on this process,static and dynamic frequency dividers achieve a maximu toggle frequency of 70 GHz and 108 GHz,respectively

Im Fokus: „Atypische“ Beschäftigung breitet sich auch in Ostdeutschland aus

Der kräftige konjunkturelle Aufschwung im Zeitraum von 2005 bis Anfang 2008 wirkte sich auch auf den ostdeutschen Arbeitsmarkt positiv aus. Die Zahl der Erwerbstätigen stieg in diesem Zeitraum um 177 000 Personen bzw. 3,2%. In Westdeutschland nahm die Beschäftigung im gleichen Zeitraum um 3,9% zu. Der Zuwachs in Ostdeutschland ist insofern bemerkenswert, als im konjunkturellen Aufschwung zwischen 1998 und 2000 die Zahl der Erwerbstätigen nur in den Alten Ländern kräftig zunahm, während die deutliche Besserung der wirtschaftlichen Lage in Ostdeutschland spurlos am Arbeitsmarkt vorüberging. Dabei stellt sich die Frage, ob und in welchem Maß im jüngsten konjunkturellen Aufschwung der Beschäftigungsaufbau in Ostdeutschland durch die Ausweitung von Normalarbeitsverhältnissen oder durch die Ausdehnung von so genannten „atypischen“ Beschäftigungsverhältnissen erfolgte.

The 64 Mpixel wide field imager for the Wendelstein 2m Telescope: Design and Calibration

The Wendelstein Observatory of Ludwig Maximilians University of Munich has recently been upgraded with a modern 2m robotic telescope. One Nasmyth port of the telescope has been equipped with a wide-field corrector which preserves the excellent image quality (< 0.8" median seeing) of the site (Hopp et al. 2008) over a field of view of 0.7 degrees diameter. The available field is imaged by an optical imager (WWFI, the Wendelstein Wide Field Imager) built around a customized 2 $\times$ 2 mosaic of 4k $\times$ 4k 15 \mu m e2v CCDs from Spectral Instruments. This paper provides an overview of the design and the WWFI's performance. We summarize the system mechanics (including a structural analysis), the electronics (and its electromagnetic interference (EMI) protection) and the control software. We discuss in detail detector system parameters, i.e. gain and readout noise, quantum efficiency as well as charge transfer efficiency (CTE) and persistent charges. First on sky tests yield overall good predictability of system throughput based on lab measurements.Comment: 38 pages 19 Figures To be published in Springer Experimental Astronom

Flow-Enhanced Photothermal Spectroscopy

Photothermal spectroscopy (PTS) is a promising sensing technique for the measurement of gases and aerosols. PTS systems using a Fabry&ndash;P&eacute;rot interferometer (FPI) are considered particularly promising owing to their robustness and potential for miniaturization. However, limited information is available on viable procedures for signal improvement through parameter tuning. In our work, we use an FPI-based PTS configuration, in which the excitation laser irradiates the target collinearly to the flowing gas. We demonstrate that the generated thermal wave, and thus the signal intensity, is significantly affected by the ratio between excitation modulation frequency and gas flow velocity towards another. We provide an analytical model that predicts the signal intensity with particular considerations of these two parameter settings and validate the findings experimentally. The results reveal the existence of an optimal working regime, depending on the modulation frequency and flow velocity

Effects of Disorder on the Pressure-Induced Mott Transition in κ\kappa-BEDT-TTF)2_2Cu[N(CN)2_2]Cl

We present a study of the influence of disorder on the Mott metal-insulator transition for the organic charge-transfer salt $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Cl. To this end, disorder was introduced into the system in a controlled way by exposing the single crystals to x-ray irradiation. The crystals were then fine-tuned across the Mott transition by the application of continuously controllable He-gas pressure at low temperatures. Measurements of the thermal expansion and resistance show that the first-order character of the Mott transition prevails for low irradiation doses achieved by irradiation times up to 100 h. For these crystals with a moderate degree of disorder, we find a first-order transition line which ends in a second-order critical endpoint, akin to the pristine crystals. Compared to the latter, however, we observe a significant reduction of both, the critical pressure $p_c$ and the critical temperature $T_c$. This result is consistent with the theoretically-predicted formation of a soft Coulomb gap in the presence of strong correlations and small disorder. Furthermore, we demonstrate, similar to the observation for the pristine sample, that the Mott transition after 50 h of irradiation is accompanied by sizable lattice effects, the critical behavior of which can be well described by mean-field theory. Our results demonstrate that the character of the Mott transition remains essentially unchanged at a low disorder level. However, after an irradiation time of 150 h, no clear signatures of a discontinuous metal-insulator transition could be revealed anymore. These results suggest that, above a certain disorder level, the metal-insulator transition becomes a smeared first-order transition with some residual hysteresis.Comment: 20 pages, 7 figures, appeared in the Special Issue "Advances in Organic Conductors and Superconductors" of Crystal

A model of partial differential equations for HIV propagation in lymph nodes

Texto completo versión postprint de autor.-- PACS numbers: 02.30.Ks,02.30.Hq,87.18.Hf,87.19.XxA system of partial differential equations is used to model the dissemination of the Human Immunodeficiency Virus (HIV) in CD4+T cells within lymph nodes. Besides diffusion terms, the model also includes a time-delay dependence to describe the time lag required by the immunologic system to provide defenses to new virus strains. The resulting dynamics strongly depends on the properties of the invariant sets of the model, consisting of three fixed points related to the time independent and spatial homogeneous tissue configurations in healthy and infected states. A region in the parameter space is considered, for which the time dependence of the space averaged model variables follows the clinical pattern reported for infected patients: a short scale primary infection, followed by a long latency period of almost complete recovery and third phase characterized by damped oscillations around a value with large HIV counting. Depending on the value of the diffusion coefficient, the latency time increases with respect to that one obtained for the space homogeneous version of the model. It is found that same initial conditions lead to quite different spatial patterns, which depend strongly on the latency interval.This work was partially supported by the following Brazilian funding agencies: CAPES, FAPESB/PRONEX, CNPq and National Institute for Science and Technology/Complex Systems.Peer reviewe

„Arbeitsplatzausstattung“ und „Arbeitsplatzlücke“ nach Geschlechtern in Ost- und Westdeutschland

The paper investigates (a) the number and structure of available jobs by gender in East and West Germany, (b) the gap between the supply and demand of jobs by gender in both regions and (c) the reasons for the wider “job gap” in East Germany compared with West Germany. The paper uses data from the Regional National Accounts and the Federal Labor Office. The analysis shows no significant difference in the number of jobs per 1000 persons in working age between East and West Germany. For women, the East German economy offers more jobs. Nevertheless, the gap between labour demand and the supply of jobs is wider in East Germany. This is caused not only by problems concerning the production structure, but also by the significantly higher partizipation rate of women in the labor market. Reasons are the traditional behaviour of East German woman and – compared with West Germany – the considerably lower household income.employment, underemployment, labor demand, labor supply, East Germany, West Germany