Analysis of a cavity-backed annular slot antenna with one pointshorted

Analysis of a cavity-backed annular slot antenna with one point shorted is performed experimentally and theoretically. Resonance frequencies, bandwidths, and radiation patterns are studied with respect to slot width, cavity depth, and slot shorting position. In the theoretical analysis, the method of moments is applied to find the magnet current on the slot, and the Green's function for the field inside the cavity has been newly derived. By selecting a slot shorting position, circular polarization, and a bandwidth of more than 10%, the voltage standing-wave ratio (VSWR) ⩽2 for the input impedance is obtained     

Oligonucleotide-based gene therapy for cardiovascular disease

Gene therapy is emerging as a potential strategy for the treatment of cardiovascular disease such as restenosis after angioplasty, vascular bypass graft occlusion, transplant coronary vasculopathy, homozygous familial hypercholesterolemia and cystic fibrosis, for which no known effective therapy exists. Gene therapy requires efficient in vivo gene transfer technology. During the past decade, many gene transfer methods including viral transfer techniques have been developed, and some are being applied clinically in human gene therapy studies. Molecular biology and pathophysiology of the cardiovascular system have started to emerge, and the time is ripe for the introduction of gene therapy to the management of cardiovascular disorders. In this review, we have focused on the future potential of oligonucleotide-based gene therapy for the treatment of cardiovascular disease.     

Effects of calcium cations incorporated into magnesium vanadates on the redox behaviors and the catalytic activities for the oxidative dehydrogenation of propane

The influence of the incorporation of Ca²⁺ into MgV₂O₆, Mg₂V₂O₇ and Mg₃V₂O₈ on the catalytic activities for the oxidative dehydrogenation of propane and the mobility of lattice oxygen in those catalysts has been investigated. On Mg₂V₂O₇ and Mg₃V₂O₈ incorporated with Ca²⁺, the selectivity to propylene evidently increased with increasing the content of Ca²⁺ in those catalysts. A decrease of the conversion of propane was observed on Ca²⁺-added Mg₂V₂O₇ with increasing Ca²⁺-content; while on Ca²⁺-added Mg₃V₂O₈, no dependence on the Ca²⁺-content was observed. The incorporation of Ca²⁺ was rather insensitive to both the selectivity and the conversion on Ca²⁺-added MgV₂O₆. In order to examine the mobility of lattice oxygen in those catalysts, those catalysts were employed for the oxidative dehydrogenation in the absence of oxygen for 2.25 h, followed by the addition of gaseous oxygen into the feedstream. After the addition of gaseous oxygen under the present conditions, oxygen in the effluent was detected at 9, 3.5 and 2 min with Mg₂V₂O₇ incorporated with Ca²⁺ at these Ca/(Mg + Ca) ratios: 0, 0.05 and 0.1. The times were 1.4, 2 and 4 min with Mg₃V₂O₈ incorporated with Ca²⁺ as Mg₂V₂O₇. However, no oxygen was detected with MgV₂O₆ incorporated with Ca²⁺ even 15 min after the addition of the gaseous oxygen. The present results reveal that the mobility of the lattice oxygen in those catalysts is strongly influenced by the amount of Ca²⁺ incorporated, resulting in significant effects on the activities for the oxidative dehydrogenation of propane. ⁵¹V MAS NMR was also employed for the observation of redox behaviors of vanadium species in those catalysts during the reaction.     

Measurements of 220 GHz atmospheric opacity on Mt. Fuji with a radiometer/radome system

We measured atmospheric opacity at 220 GHz at the summit of Mt. Fuji (alt. 3776 m) about one year in order to explore a feasibility of submillimeter-wave astronomical observations. For this purpose, a 220 GHz radiometer system enclosed in a radome (51×51×62 cm³) has been developed. The 220 GHz opacity was lower than 0.06 for a significant fraction (～ 45 %) of time from November 1994 to March 1995. Diurnal variation of the opacity at the summit of Mt. Fuji is so small that continuous observation at submillimeter-wave is possible through day and night. Yearly variation of the opacity is studied from water vapor pressure data measured at the weather station for the past 3 years. To prevent accumulation of ice and snow on the Gore-Tex membrane in the radome, the outer membrane was supplied with a thermal flux of 0.63 kW m^?2 and the adjacent metal radome surfaces were supplied with a flux of ～0.9 kW m^?2. We evaluate from the 220 GHz transmission data that this heat flux is sufficient to keep the membrane on the radome free of ice and snow during 83 % of the time in 5 winter months. The summit of Mt. Fuji appears to be a promising site for submillimeter-wave observations.     

Patterning of CVD diamond films by seeding and their field emission properties

Selective seeding for growing diamond on Si substrates was performed by conventional lithography using photoresist mixed with fine diamond particles. The selectivity was improved by filtering the diamond powder-photoresist mixture and carrying out reactive ion etching of patterned substrates. As a result, a selectivity up to 2.0 × 10² or higher was achieved. The resolution was of the order of 1 μm. Field emission from diamonds prepared using this selective growth method was observed without any postgrowth treatment. The measured current vs. voltage plot of a diode showed a rectifying characteristic. Under a forward bias, a current of about 15 μA was obtained at about 570 V, with a turn-on voltage of about 480 V. The emission current was comparable with that which had been observed for Si field emitter tips.     

Influence of pulmonic position on durability of bioprosthetic heart valves

BACKGROUND: The insertion of bioprosthetic valves into the pulmonic position is not performed commonly because of uncertainty concerning the necessity and durability of such valves. METHODS: We reviewed the long-term outcome of 10 patients who underwent pulmonary valve replacement with bioprostheses between March 1985 and March 1997. A Carpentier-Edwards supraannular bioprosthesis was used in 7 patients, a Hancock II bioprosthesis was used in 2 patients, and a Carpentier-Edwards pericardial bioprosthesis was used in 1 patient. The mean patient age at the time of pulmonary valve replacement was 38.9 +/- 16.3 years (range, 15 to 63 years). The diagnoses were pulmonary valvular regurgitation after corrective surgery for tetralogy of Fallot in 7 patients, right ventricular outflow tract stenosis and absent right pulmonary artery combined with a double-outlet right ventricle in 1 patient, pulmonary valvular regurgitation with pulmonary artery dilatation in 1 patient, and aortic valve stenosis treated with our modification of the Ross procedure using a pulmonary bioprosthesis in 1 patient. Survivors were followed up for a mean of 5 years and 5 months. RESULTS: One patient underwent reoperation because of infective endocarditis of the bioprosthesis. No bioprosthetic valve dysfunction has been observed on Doppler echocardiography during a maximum follow-up period of 12.2 years, except in the patient who underwent replacement at 15 years of age. CONCLUSIONS: Bioprostheses in the pulmonic position are durable in adult patients because they face a minimal hemodynamic load, but they may undergo early leaflet degeneration in younger patients.     

The characterization of electrodeposited Zn-SiO2 composites before and after corrosion test

The microstructure of electrodeposited Zn-SiO₂ composites before and after corrosion tests has been studied by using scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. As-deposited Zn-SiO₂ composites are composed of SiO₂-rich and SiO₂-poor phases. After a wet and dry cyclic corrosion test, including NaCl solution spray, zinc hydroxychloride is formed on the SiO₂-rich phase which surrounds the uncorroded SiO₂-poor phase. Zinc hydroxide, zinc oxide and zinc hydroxychloride are also formed on the surface of the Zn-SiO₂ composites. The high corrosion resistance of the composites is attributed to the formation of protective corrosion products in the composite layer supported by SiO₂.     

Controlled beam dry etching of InP by using Br2-N2 Gas

Indium phosphide dry etching is carried out using a reactive beam extracted from a Br₂-N₂ gas discharge plasma. Keeping the N₂ gas pressure constant at 0.23 mTorr, the Br₂ gas pressure was varied from 0 to 0.1 mTorr and the sample temperature was varied from 40 to 200°C. The etched shapes and etching rates are investigated in terms of the etching beam composition. Two distinct types of etching mechanisms come into play depending on the Br₂ gas pressure. Smooth vertical side walls and a temperature independent etching rate can be obtained at a Br₂ gas pressure of 0.04 mTorr or less and a temperature above 100°C, where the etching is induced by the ambient Br₂ gas species and N₂ beam. Undercut etching with a temperature dependent etching rate is seen at a Br₂ gas pressure of 0.07 mTorr or higher, where the etching beam contains both N₂ and Br₂ gas species. Neutralized Br species generated by the discharge of the Br₂ gas are shown to form the undercut. A waveguide corner mirror with a loss of less than 1 dB is made by using an etching beam with no neutralized Br species.     

Basic experimental results of liquid CO2 injection intothe deep ocean

CO₂ disposal in the deep ocean is expected to be an effective option for mitigating the increase in CO₂ on the earth. The authors have investigated the behaviour of liquid CO₂ using test facilities which can simulate the pressure and temperature of the deep ocean. Phase equilibrium data of the CO₂ -seawater system and the conditions of CO₂ clathrate formation were confirmed. In addition, the authors measured the pH value of seawater saturated with CO₂ at high pressure. The data presented in this paper are considered indispensable for evaluating the possibility of CO₂ disposal in the deep ocean     

A compact programming environment for microprocessor-based controllers

To write a reliable program in an assembly language for microprocessor-based controller, we introduce data abstraction facility into an assembly language. For this purpose, we has designed and implemented ADT-RASM86 and its symbolic debugger. This paper presents the figure of the system and describes how the system is effective for writing a reliable program for microprocessors.