Far-infrared radiation response of antenna-coupled quantum-effect devices

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 227-238).by Rolf A. Wyss.Ph.D

Traveling-Wave Photomixers Based On Noncollinear Optical/Terahertz Phase-Matching

Traveling-wave THz photomixers based on angle-tuned optical/THz phase-matching are experimentally demonstrated. A dc-biased coplanar stripline terminated by a planar antenna is fabricated on low-temperature-grown GaAs. A distributed area between the striplines is illuminated by two noncollinear laser beams which generate interference fringes accompanied by THz waves. The velocity of the optical fringe is matched to the THz-wave velocity in the stripline by tuning the incident angle of the laser beams. The device can handle the laser power over 300 mW and provides the THz output of ~0.1 µW with the 3-dB bandwidth of 2 THz. The experimental results show that traveling-wave photomixers have the potential to surpass conventional small area designs

Design and characterization of optical-THz phase-matched traveling-wave photomixers

Design and characterization of optical-THz phase-matched traveling-wave photomixers for difference-frequency generation of THz waves are presented. A de-biased coplanar stripline fabricated on low-temperature-grown GaAs is illuminated by two non-collinear laser beams which generate moving interference fringes that are accompanied by THz waves. By tuning the offset angle between the two laser beams, the velocity of the interference fringe can be matched to the phase velocity of the THz wave in the coplanar stripline. The generated THz waves are radiated into free space by the antenna at the termination of the stripline. Enhancement of the output power was clearly observed when the phase-matching condition was satisfied. The output power spectrum has a 3-dB bandwidth of 2 THz and rolls off as ~9 dB/Oct which is determined by the frequency dependent attenuation in the stripline, while the bandwidth of conventional photomixer design has the limitation by the RC time constant due to the electrode capacitance. The device can handle the laser power of over 380 mW, which is 5 times higher than the maximum power handring capability of conventional small area devices. The results show that the traveling-wave photomixers have the potential to surpass small area designs, especially at higher frequencies over I THz, owing to their great thermal dissipation capability and capacitance-free wide bandwidth

A traveling-wave THz photomixer based on angle-tuned phase matching

A traveling-wave THz photomixer based on a free-space optical-THz phase-matching scheme is proposed. A dc-biased coplanar strip line fabricated on low-temperature-grown GaAs serves as the active area of the device, and is illuminated by two noncollinear laser beams which generate interference fringes that are accompanied by THz waves. The device with the laser-power-handling capability over 300 mW and a 3-dB bandwidth of 1.8 THz was experimentally demonstrated. The results show that traveling-wave photomixers have the potential to surpass small-area designs

Stellenverlust und Lohneinbusse durch die Globalisierung? Eine Fallstudie

In Medien und Öffentlichkeit ist die Meinung, dass die infolge von Globalisierung und Strukturwandel frei- gesetzten Arbeitskräfte zu den Verlierern der Globalisierung gehörten, weit verbreitet. Gemäss Handelsthe- orie muss dem allerdings nicht so sein. Schliesslich führt die Globalisierung nicht nur zu Stellenab-, sondern auch zu Stellenaufbau und somit zu neuen Chancen auf dem Arbeitsmarkt. Von diesen Chancen könnten auch die infolge von Globalisierung und Strukturwandel freigesetzten Arbeitskräfte profitieren. Auf Basis von sechs Firmenfallstudien (Bombardier, Calida, Ciba, Clariant, Lego, Roche) analysiert diese Studie für die Schweiz erstmals die Beschäftigungs- und Lohneffekte von Arbeitskräften, die ihre Stelle infolge von Globalisierung und Strukturwandel verloren haben. Die Studie zeigt, (i) dass die Wahrnehmung der freige- setzten Arbeitskräfte als Verlierer der Globalisierung nur bedingt mit der Realität übereinstimmt. Viele der Betroffenen finden eine neue Anstellung zu gleich hohem oder gar höherem Lohn. Für ältere und niedrig qualifizierte Arbeitskräfte ist das Risiko indessen hoch, aufgrund der Freisetzung deutlich schlechter gestellt zu werden. Entsprechend sollten die Anpassungskosten von Globalisierung und Strukturwandel nicht trivia- lisiert werden. Der Vergleich zum Ausland zeigt allerdings, (ii) dass diese Anpassungskosten in der Schweiz deutlich tiefer sind. Konkret tragen freigesetzte Arbeitskräfte in der Schweiz ein deutlich tieferes Risiko, von Lohneinbussen oder Arbeitslosigkeit betroffen zu sein, als entsprechende Arbeitskräfte in den USA und Europa. �

Deliberation and Identity Rules : The Effect of Anonymity, Pseudonyms and Real-Name Requirements on the Cognitive Complexity of Online News Comments

How do identity rules influence online deliberation? We address this question by drawing on a data set of 45 million comments on news articles on the Huffington Post from January 2013 to May 2015. At the beginning of this period, the site allowed commenting under what we call non-durable pseudonyms. In December 2013, Huffington Post moved to regulate its forum by requiring users to authenticate their accounts. And in June 2014, Huffington Post outsourced commenting to Facebook altogether, approximating a ‘real-name’ environment. We find a significant increase in the cognitive complexity of comments (a proxy for one aspect of deliberative quality) during the middle phase, followed by a decrease following the shift to real-name commenting through Facebook. Our findings challenge the terms of the apparently simple trade-off between the goods and bads of anonymous and real-name environments and point to the potential value of durable pseudonymity in the context of online discussion

Rat reproductive performance following photodynamic therapy with topically administered Photofrin

A rat animal model was used for comparing the photodynamic efficacy of two formulations of topically administered Photofrin in the uterus: 0.7 mg/kg Photofrin and 0.7 mg/kg Photofrin + 4% Azone, a penetrationenhancing agent. Uterine structure and reproductive performance were evaluated following illumination with 80 J/cm2 of 630 nm light. Fluorescence microscopy was employed to determine drug localization in frozen uterine sections at various times after drug administration. Functionality studies demonstrated a significant reduction in the number of implantations per treated uterine horn compared to controls. The mean number of implantations decreased systematically on increasing the interval between Photofrin administration and light application. At 72 h, 0.88 ± 0.52 gestational sacs per rat were recorded with Photofrin therapy, compared with 8.1 ± 1.12 (P = 0.01) on the untreated side, indicating nearly complete loss of reproductive capability. Similar results were achieved after only 3 h treatment with Photofrin + Azone (0.38 ± 0.26 sacs per rat versus 7.5 ± 1.07 on the untreated side; P = 0.01). This indicates that the effect of Photofrin can be enhanced either by extending the drug incubation period from 3 to 72 h or by adding the penetration-enhancing drug Azone. Fluorescence pharmacokinetic studies suggest that both forms of topically administered Photofrin are diffusely distributed throughout the endometrium at virtually the same rate. However, Azone may enhance the selectivity of photodynamic therapy by facilitating drug targeting to critical endometrial structure

High-Frequency (> 100 GHz) Electronic Devices

Contains reports on five research projects and a list of publications.MIT Lincoln LaboratoryNational Aeronautics and Space Administration Grant NAG2-693National Science Foundation Grant ECS 91-09330Defense Advanced Research Projects Agency Contract MDA972-90-C-0021U.S. Army - Research Office Grant DAAL03-92-G-025

High-Frequency (> 100 GHz) Electronic Devices

Contains reports on four research projects, the research facility and a list of publications.Defense Advanced Research Projects Agency Contract MDA972-90-C-0021National Aeronautics and Space Administration Grant NAG2-693National Science Foundation Grant ECS 91-0933

High-Frequency (> 100 GHz) and High-Speed (< 1 ps) Electronic Devices

Contains reports on six research projects and a list of publications.MIT Research Laboratory of Electronics Postdoctoral FellowshipNational Science Foundation Grant DMR 90-22933MIT Lincoln Laboratory Advanced Concept ProgramAdvanced Research Projects Agency Contract MDA972-90-C-0021MIT Lincoln LaboratoryNational Aeronautics and Space Administration Grant NAG2-693U.S. Army Research Office Grant DAAL03-92-G-025