Design of Al-free and Al-based InGaAs/GaAs strained quantum well 980-nm pump lasers including thermal behavior effects on E/O characteristics

A 2D thermal simulator and a model to evaluate high power lasers characteristics have been developed. With these models it was possible to optimize cavity length of InGaAs/GaAs (Multiple) Quantum Well 980 nm lasers realized both with Al-based and Al-free confining layers. A comprehensive experimental investigation of the influence of cavity length and temperature on the laser emission wavelength has been performed. This allows a fine trimming of the devices to match the Erbium doped fiber absorption bandwidth

Disordering of InGaAs/GaAs strained quantum well structures induced by rare gas ion implantation

In this work we have investigated the effect of various implantation schemes on In(0.2)GaAs/GaAs/AlGaAs Single Quantum Well, where the implanted species are Argon and Helium, with doses in the range 1E12 to 1E14 at cm^2, at energy spanning 270 - 400 KeV and 30 to 50 KeV for Ar and He, respectively. Repetitive annealing processes were carried out between 735 and 870 degree(s)C and the interdiffusion was deduced by photoluminescence measurements. A maximum of 20 nm shift from He ion implanted Quantum Well with an high degree of reconstruction has been recorded, thus allowing the application of this disordering scheme for the realization of optoelectronic devices

Disordering of InGaAs/GaAs strained quantum well structures induced by rare gas ion implantation

In this work we have investigated the effect of various implantation schemes on In(0.2)GaAs/GaAs/AlGaAs Single Quantum Well, where the implanted species are Argon and Helium, with doses in the range 1E12 to 1E14 at cm^2, at energy spanning 270 - 400 KeV and 30 to 50 KeV for Ar and He, respectively. Repetitive annealing processes were carried out between 735 and 870 degree(s)C and the interdiffusion was deduced by photoluminescence measurements. A maximum of 20 nm shift from He ion implanted Quantum Well with an high degree of reconstruction has been recorded, thus allowing the application of this disordering scheme for the realization of optoelectronic devices

Rapid thermal annealing of Si implanted GaAs in Arsenic overpressure

A new method of rapid thermal annealing (RTA) in arsenic over­pressure using a high thermal mass reactor and a very low thermal mass sub­strate holder has been developed. Efficient activation of Si implantation has been obtained only with proper As overpressure. The design of the substrate holder allowed a very uniform activation of the implanted layers as well as a negligible formation of dislocation slips. This method of rapid thermal annealing was successfully applied to the fabrication of broadband 4-8 GHz MMIC amplifiers

MOCVD growth of GaAs-Ga1-xAlxAs structures for microwave MESFET's

MOCVD GaAs-Ga1-xAlxAs epitaxial structures to fabricate MESFET's have been successfully grown in a low pressure MOCVD system. The growth parameters were optimized to obtain very high uniform epitaxial layers (o - 2%). MESFET's were fabricated and the devices with heterobuffer layer showed good transconductance and linearity as compared to conventional GaAs buffered structures. A 7.7 dB gain was performed at Idss/2 at 18 GHz. However the breakdown voltage has to be improved by lowering the back­ground doping in the Ga1-xAlxAs buffer layer

The dose and quality program in mammography (DQM). Results of the study carried out in 20 Fruili-Venezia Giulia centers

Recently, 20 breast centers in Friuli Venezia Giulia have been investigated for the mammography optimization program known as DQM (Dose and Quality in Mammography). This was the second trial, the first one dating 1987-1988 and including only 10 centers. The chosen parameters were evaluated by means of a performance phantom containing 15 details, a Victoreen 660 ionizing camera, a star pattern and several plexiglass phantoms of different thickness. Statistical-methodological data were collected by means of a questionnaire. The results of the trial were communicated to each center as well as directions for future improvements. All centers were found to use mammographic equipment with a molybdenum anode and the film-screen combination; 18 center use grids daily, while 11 can perform direct radiographic magnification. Only 40% of the examined centers use a dedicated daylight printer. The overall quality of the radiographic image was seen to be acceptable, as 8 or more details of 15 hidden in the phantom were visualized, in 16 of 20 centers. The mean glandular dose was below the minimum threshold in all centers: in 45% of cases it was below 1.5 mGy. The setting of the automatic exposition control system was found to be poor, especially that of the adjustment related to breast thickness. Acceptability thresholds were met only by 31% of the examined centers (density variations < 20%). Notwithstanding the identification of areas where improvements can be made also from a methodological point of view, we can conclude that the quality provided by regional breast centers is definitely adequate. Good image quality and acceptable doses were observed in 80% of the centers. The results are significant and encouraging when compared with those from the first DQM trial carried out in our region, which confirms the value of periodical quality programs

Psoriasis and endothelins.

Background: Psoriasis is characterized by an abnormal proliferation and increased turnover of keratinocytes, the presence of acute and chronic inflammatory cells and microangiopathic changes. Endothelins are a family of peptides which have been investigated especially for their effects on the cardiovascular system. Recent studies have demonstrated their involvement also in human skin. Aim of the study: We evaluated the Endothelin-1 and 2 plasma levels in psoriatic patients, as endothelin-1 can be produced in vitro by keratinocytes and can stimulate the proliferation of fibroblasts as well as modify the skin microcirculation dynamics. Patients and methods: We studied 30 patients: 10 affected with psoriasis (PASI from 5 to 10), 10 affected with cardiovascular diseases and 10 healthy controls. The Endothelin-1 and 2 plasma levels were evaluated by radio-immunoassay procedure. Results: A significant increase in Endothelin-1 and 2 plasma levels was observed in the psoriatic patients, in comparison with the controls. Conclusions: Our data seem to suggest a possible relationship between psoriasis and increased plasma level of endothelin-1 and 2, though the possible role played in the pathogenesis of psoriasis needs further studies