Propagation of a quasi-shear horizontal acoustic wave in Z-Xlithium niobate plates [and conductivity sensor application]

It is found that an acoustic wave which is nearly polarized in the shear horizontal (SH) direction can propagate along the X axis of a Z-cut lithium niobate plate if the ratio h/λ, where h=plate thickness and λ=acoustic wavelength, is less than about 0.5. Attractive properties of this quasi-SH wave include: (1) phase velocity nearly constant for all values of h/λ; (2) ability to propagate in contact with a liquid medium; and (3) electromechanical coupling coefficient as high as 0.15. These properties make the wave attractive for use in a variety of sensor and signal processing applications. An example of sensor applications is illustrated by using the wave to measure conductivity of liquids (aqueous KCl solution). The frequency of a 12-MHz quasi-SH mode oscillator fabricated on a 0.48 wavelength thick Z-X lithium niobate plate is found to vary by more than 80 kHz for variation in KCI concentration from 0 to 0.15%     

Potential difference and photovoltaic effect arising from distortion of the electron wave function in a GaAs quantum well with a thin AlGaAs barrier

This paper discusses changes in the spectrum and distortion of the electron wave function of a GaAs quantum well when a thin AlGaAs barrier is introduced into it. The potential difference generated across the quantum well by distortion of the electron wave function is calculated, along with its dependence on the position of the barrier in the quantum well. The photovoltaic response of the structure to optical intersubband excitations is also calculated, along with the role of wave function and electronic spectrum distortion as well as intersubband nonradiative transitions in generating this response. The suitability of a GaAs quantum well with a thin barrier for use as an infrared detector is considered. Fiz. Tekh. Poluprovodn. 32, 1246–1250 (October 1998)     

Tomsk complex for neutron-transmutation doping of silicon

All-Union Scientific-Research Institute of Nuclear Physics at the S. M. Kirov Tomsk Polytechnical University. Translated from Atomnaya énergiya, Vol. 79, No. 1, pp. 38–40, July, 1995.     

A microprocessor-based toggle-control lighting system

Analysis, design, practical consideration, and implementation of a microprocessor-based toggle-control lighting system are presented. The system is primarily configured with a power factor corrector (PFC), a square-wave voltage generator, a manually controlled toggle switch, and two relays. Toggling the toggle switch can select a different number of lamps in operation, resulting in a mutual dimming feature. A fluorescent lamp lighting system with this specific ballast gains the merits of lower system cost and more flexibilities in lighting fixture design, as compared to conventional systems     

The importance of electrochemistry-related etching in thegate-groove fabrication for InAlAs/InGaAs HFETs

For the first time, the surface metal on nonalloyed ohmic electrodes is found to significantly change the profiles of gate grooves, when resist openings are employed to monitor drain current during wet-chemical gate recess for sub-micron InAlAs/lnGaAs heterojunction field-effect transistors (HFETs). The surface metal of Ni enhances the etching rate in comparison with that in the absence of electrodes by a factor of 4 and 10, laterally and vertically, which is favorable to fabricate deep gate grooves with small side etching. The Pt surface metal, however, leads to preferential etching of InGaAs over InAlAs, which can be useful to realize large side etching. The existence of an electrochemistry-related etching component, which arises when the ohmic electrodes are present during recess etching, is considered to be responsible for these behaviors     

Leiomyomatosis peritonealis disseminata. Two case reports

AIM: To study the action of quercetin (Que) on inhibiting platelet aggregation. METHODS: Active oxygen free radicals produced by xanthine/xanthine oxidase (Xan/XO) reaction was used, platelet aggregation was determined by the turbidimetric method, and the Xan/XO oxyradicals generating reaction by luminol-dependent chemiluminescence (Che) method. RESULTS: Active oxygen free radicals enhanced the platelet aggregation induced by ADP 1.6 mumol.L-1. The rate of maximal aggregation increased from 29%-38% for ADP to 59%-70% for ADP + Xan/XO. The enhancement was abolished by the treatment of platelet-rich plasma (PRP) with Que 650 mumol.L-1 or hydrocortisone (Hyd) 900 mg.L-1. Both Que and Hyd scavenged the active oxyradicals in vitro. The Che was decreased by 75.7% (Que 4 mumol.L-1) and 79.0% (Hyd 900 mg.L-1) as compared with control. CONCLUSION: Active oxygen free radicals participated in the platelet aggregation, and scavenging oxyradicals by Que was one of mechanisms of inhibiting platelet aggregation.     

Analysis of a resonant-cavity enhanced GaAs/AlGaAs MSMphotodetector

The authors have developed a 2-D device simulator for heterostructure metal-semiconductor-metal (MSM) photodetectors. They have incorporated a model of multilayer optics into the simulator and used it to analyze the temporal response of a resonant-cavity enhanced heterostructure with a confining buffer layer and a distributed Bragg reflector (DBR). The authors show that through fine tuning the layer thicknesses, optical resonance enhancement of the light absorption can be obtained