Transit-time devices as local oscillators for frequencies above 100 GHz

Very promising preliminary experimental results have been obtained from GaAs IMPATT diodes at F-band frequencies (75 mW, 3.5 percent at 111.1 GHz and 20 mW, 1.4 percent at 120.6 GHz) and from GaAs TUNNETT diodes at W-band frequencies (26 mW, 1.6 percent at 87.2 GHz and 32 mW, 2.6 percent at 93.5 GHz). These results indicate that IMPATT, MITATT and TUNNETT diodes have the highest potential of delivering significant amounts of power at Terahertz frequencies. As shown recently, the noise performance of GaAs W-band IMPATT diodes can compete with that of Gunn devices. Since TUNNETT diodes take advantage of the quieter tunnel injection, they are expected to be especially suited for low-noise local oscillators. This paper will focus on the two different design principles for IMPATT and TUNNETT diodes, the material parameters involved in the design and some aspects of the present device technology. Single-drift flat-profile GaAs D-band IMPATT diodes had oscillations up to 129 GHz with 9 mW, 0.9 percent at 128.4 GHz. Single-drift GaAs TUNNETT diodes had oscillations up to 112.5 GHz with 16 mW and output power levels up to 33 mW and efficiencies up to 3.4 percent around 102 GHz. These results are the best reported so far from GaAs IMPATT and TUNNETT diodes

Microwave device investigations Semiannual progress report, 1 Oct. 1969 - 1 Apr. 1970

Beam-plasma interactions, cyclotron harmonic instability study, and millimeter and submillimeter wave detection by paramagnetic material

Microwave device investigations Semiannual progress report, 1 Apr. - 1 Oct. 1968

Beam-plasma interactions, cyclotron harmonic instabilities, harmonic generation in beam-plasma system, relativistic electron beam studies, and materials test

Microwave device investigations Semiannual progress report, 1 Apr. - 1 Oct. 1969

Summaries of progress in beam plasma interactions, paramagnetic and bulk semiconductor materials, and avalanche diode

Microwave device investigations Semiannual progress report, 1 Oct. 1968 - 1 Apr. 1969

Beam plasma amplification, harmonic generation, and coupling scheme

Frequency multiplication in high-energy electron beams Semiannual progress report, 1 Oct. 1967 - 31 Mar. 1968

Electron beam-plasma interactions, cyclotron harmonic instabilities, paramagnetic and semiconductor materials, and harmonic current generatio

Spanish validation of the revised depression attitude questionnaire (R-daq)

Purpose: The aim of the study was to develop and validate a Spanish version of the Revised Depression Attitude Questionnaire (R-DAQ). Methods: The R-DAQ was used as a baseline for the study. It was translated and tested to ensure the instrument was appropriate for the target population. 537 Ecuadorian healthcare professionals completed the revised Spanish version of the R-DAQ (SR-DAQ). Statistical and exploratory factor analyses were performed to examine construct validity, internal consistency, readability and floor and ceiling effects. Results: Three factors were obtained: “Professional confidence in depression care”; “Therapeutic optimism about depression”; and “Generalist perspective about depression occurrence, recognition, and management”. The internal consistency of the SR-DAQ was determined by means of Cronbach’s α coefficient, with values ranging between 0.61–0.8. The correlations with the English version reflected adequate validity. The model explained 39% of the variance. Subsequent analysis with a sample restricted to those who had received training in depression produced a model that explained 42% of the variance. Conclusion: The SR-DAQ meets the psychometric requirements for measuring depression attitude in a Spanish-speaking population and shows adequate internal consistency and validity

Induction Chemotherapy Followed by Concurrent Chemoradiation Therapy Versus Concurrent Chemoradiation Therapy Upfront in Locally Advanced Oral Cavity Cancer: Systematic Review and Meta-Analysis of Individual Data

Univ Sao Paulo, Hosp Siriolibanes, Dept Radiat Oncol, Sao Paulo, BrazilUniv Sao Paulo, Fac Med, Inst Canc Estado Sao Paulo, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med UNIFESP EPM, Brazilian Cochrane Ctr, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med UNIFESP EPM, Discipline Emergency Med & Evidence Based Med, Sao Paulo, BrazilHarvard Univ, Sch Med, Dana Farber Canc Inst, Dept Med Oncol, 44 Binney St, Boston, MA 02115 USABrigham & Womens Hosp, Dept Med, 75 Francis St, Boston, MA 02115 USAUniv Calif San Diego, La Jolla, CA 92093 USAHarvard Univ, Sch Med, Dana Farber Canc Inst, Head & Neck Oncol Program, 44 Binney St, Boston, MA 02115 USAAC Camargo Canc Ctr, Dept Head & Neck Surg & Otorhinolaryngol, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med UNIFESP EPM, Brazilian Cochrane Ctr, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med UNIFESP EPM, Discipline Emergency Med & Evidence Based Med, Sao Paulo, BrazilWeb of Scienc

Microwave device investigations

Several tasks were active during this report period: (1) noise modulation in avalanche-diode devices; (2) schottky-barrier microwave devices; (3) intermodulation products in IMPATT diode amplifiers; (4) harmonic generation using Read-diode varactors; and (5) fabrication of GaAs Schottky-barrier IMPATT diodes

Renormalization Group calculations with k|| dependent couplings in a ladder

We calculate the phase diagram of a ladder system, with a Hubbard interaction and an interchain coupling $t_\perp$. We use a Renormalization Group method, in a one loop expansion, introducing an original method to include $k_{||}$ dependence of couplings. We also classify the order parameters corresponding to ladder instabilities. We obtain different results, depending on whether we include $k_{||}$ dependence or not. When we do so, we observe a region with large antiferromagnetic fluctuations, in the vicinity of small $t_\perp$, followed by a superconducting region with a simultaneous divergence of the Spin Density Waves channel. We also investigate the effect of a non local backward interchain scattering : we observe, on one hand, the suppression of singlet superconductivity and of Spin Density Waves, and, on the other hand, the increase of Charge Density Waves and, for some values of $t_\perp$, of triplet superconductivity. Our results eventually show that $k_{||}$ is an influential variable in the Renormalization Group flow, for this kind of systems.Comment: 20 pages, 19 figures, accepted in Phys. Rev. B 71 v. 2