Multiple-quantum-well GaInAs/GaInAsP tapered broad-area amplifierswith monolithically integrated waveguide lens for high-powerapplications

A 1.48-μm tapered broad-area semiconductor laser amplifier with a monolithically integrated waveguide lens as demonstrated. The gain saturation characteristics of the tapered amplifier were examined. A maximum output power of 300 mW and a 3-dB saturation power of 200 mW under quasi-CW conditions were obtained from the amplifier without the waveguide lens. Output power of 200 mW was obtained with a broad emission spectrum of ~30 nm when the device was used as a superluminescent diode. The amplified output was focused to a single lobe by the monolithically integrated aspheric waveguide lens, which may be useful for efficient coupling of the output into a single-mode fiber     

A 2.5-V active low-pass filter using all-n-p-n Gilbert cells with a1-Vp-p range

This paper describes the design and measured results of an all-n-p-n low-voltage (2.5 V), low-current (1 mA), large-swing (1 V_p-p), low-distortion (-53 dB, 1 V_p-p) active filter using a conventional bipolar process. The transconductors for the filter are composed of Gilbert cell transconductors. Distortion has been improved by feedback circuits without increasing the supply voltage and without using p-n-p transistors. The filter is a gyrator-capacitor type third-order Butterworth low-pass filter with a nominal cutoff frequency of 192 kHz. A voltage scaling technique has been applied directly to the gyrator-capacitor filter. This has improved the signal-to-noise ratio by 3 dB. Simulation results indicated that a fast operation up to tens of MHz is possible with a standard bipolar process, as the signal path is composed only of n-p-n transistors     

Compressive properties of single-filament carbon fibres

Compressive properties of mesophase pitch-based carbon fibres (NT-20, NT-40 and NT-60) were measured using the tensile recoil test and the elastica loop test. The NT-40 fibre with a 400 GPa tensile modulus showed a smaller loop compressive yield strain and a larger recoil compressive strength compared to these values obtained from the longitudinal compression test on its unidirectional composites. Further, the recoil compressive strength of this fibre was higher than that of PAN-based carbon fibre with a corresponding modulus. Under the ideal conditions in the tensile recoil test, the strain energy was conserved before and after recoil, and the initial tensile stress and the recoil compressive stress do not coincide when fibre stress-strain behaviour is non-linear, and the non-linearity in compression and in tension is different. The difference between the composite compressive strength and the recoil compressive strength of NT-40 was quantitatively explained by taking account of the fibre compressive stress-strain non-linear relation. The difference between the loop compressive yield strain and the composite compressive strain to failure was also explained by this non-linearity.     

Distribution of nociceptive neurons in the ventrobasal complex of macaque thalamus

Crystal structures of glutamine phosphoribosylpyrophosphate (PRPP) amidotransferase from Escherichia coli have been determined to 2.0-A resolution in the absence of ligands, and to 2.5-A resolution with the feedback inhibitor AMP bound to the PRPP catalytic site. Glutamine PRPP amidotransferase (GPATase) employs separate catalytic domains to abstract nitrogen from the amide of glutamine and to transfer nitrogen to the acceptor substrate PRPP. The unliganded and AMP-bound structures, which are essentially identical, are interpreted as the inhibited form of the enzyme because the two active sites are disconnected and the PRPP active site is solvent exposed. The structures were compared with a previously reported 3.0-A structure of the homologous Bacillus subtilis enzyme (Smith JL et al., 1994, Science 264:1427-1433). The comparison indicates a pattern of conservation of peptide structures involved with catalysis and variability in enzyme regulatory functions. Control of glutaminase activity, communication between the active sites, and regulation by feedback inhibitors are addressed differently by E. coli and B. subtilis GPATases. The E. coli enzyme is a prototype for the metal-free GPATases, whereas the B. subtilis enzyme represents the metal-containing enzymes. The structure of the E. coli enzyme suggests that a common ancestor of the two enzyme subfamilies may have included an Fe-S cluster.     

Reducing the minimum load and NOx emissions for lignite-fired boiler by applying a stable-flame concept

For the purpose of improving the load range and NO_x emission level of lignite-fired power plants, a new combustion technology, called NR-LE burners (NO_x Reduction-Load Extension), has been developed in co-operation between Babcock-Hitachi and Fortum. A single-burner combustion test was performed in Japan with this new NR-LE type burner using Czech lignite. Adapting the flame-stabilization ring and a special additional air-nozzle resulted in achieving a stable flame, which enables:

• The burner minimum load to be less than 50% (Boiler load: 30–40%)

• Low NO_x emissions of less than 200 mg/m³ (6% O₂, dry base)

The first commercial full-scale application of the NR-LE burner was by the IPP power producer in the Czech Republic (Sokolovská Uhelná, a.s. at Vresová Unit2 boiler with steam parameters 325 t/h, 535 °C, 13.5 MPa). The commissioning test runs of the new burners were carried out during September to October 2001. The boiler is now in commercial operation, with (i) a 30% minimum load without supplementary fuel, and (ii) lower NO_x emission levels.     

Design and fabrication of GaAs-GaAlAs micromachined tunable filter with thermal strain control

In this paper, we present the design and fabrication of a novel GaAlAs-GaAs micromachined vertical cavity filter with a thermal strain control layer for wide wavelength tuning. The integration of a thermal strain control layer and heating element enables wavelength tuning induced by heating. The proposed tunable filter under thermal tuning operation provides us large tuning range over conventional micromachined tunable filters using electrostatic force. The calculated result shows a possibility of large continuous tuning range of over 100 nm. We fabricated a micromachined GaAlAs-GaAs vertical cavity filter with a strain control layer. The temperature dependence of the filter can be freely controlled either with temperature insensitive operation or with an enhanced temperature dependence, which depends on the thickness of the thermal strain control layer. We demonstrate a thermal wavelength tuning of 53 nm with a low tuning voltage of 6.1 V for the first time.     

Zinc levels in rice and in soil according to the soil types of Japan, Indonesia, and China

Sustained myocardial ischemia with angina pectoris, electrocardiographic changes and subsequent non-Q-wave infarctions has been reported during percutaneous transluminal rotational atherectomy of complex coronary lesions. The purpose of this study was to evaluate the effect of rotational atherectomy on regional myocardial perfusion as assessed by serial 99mTc-sestamibi SPECT imaging with semiquantitative tracer uptake analysis. METHODS: Twenty-nine consecutive patients with anginal symptoms, complex coronary lesions (all Type B and Type C) and preserved left ventricular function were studied using resting 99mTc-sestamibi SPECT before rotational atherectomy, during and 2 days after the procedure. For semiquantitative computerized analysis, the left ventricular myocardium was divided into 24 regions, and regional perfusion was expressed as percentage of maximal sestamibi uptake. RESULTS: Visual analysis of scintigraphic images revealed transient perfusion defects corresponding to the revascularized vessel in 26 of 29 patients, whereas three patients had no transient hypoperfusion. During rotational atherectomy, perfusion decreased significantly (>2 s.d. below normal mean) in 3.1 +/- 2.4 regions (range 1-10). Perfusion in the territory of the revascularized vessel was 75% +/- 11% at baseline, decreased to 67% +/- 12% during rotational atherectomy (p < 0.001) and normalized again after rotational atherectomy to 78% +/- 8% (p < 0.001). Similarly, perfusion in the region with the maximal reduction decreased from 74% +/- 15% at baseline to 55% +/- 14% (p < 0.001) during the procedure and returned to 74% +/- 16% (p < 0.001) following the intervention. In calcified stenoses, the extent of perfusion defects was larger as compared to noncalcified (4.2 +/- 2.5 versus 2.3 +/- 2.0 regions/patient, p < 0.05). CONCLUSION: During rotational atherectomy, myocardial hypoperfusion occurs. The transient nature of this perfusion defect can be demonstrated and quantified by serial 99mTc SPECT. This model may prove useful to assess the effects of pharmacological approaches to reducing myocardial hypoperfusion during coronary rotational atherectomy.     

A folded-type integrated-optic spectrum analyzer using butt-coupled chirped grating lenses

A folded-type integrated-optic spectrum analyzer (IOSA) using reflection-type chirped grating lenses butt-coupled to a LiNbO3waveguide Bragg cell is presented. The lenses can be easily fabricated by the well-established planar process, and the IOSA has good performance as well as a reduced device length. The spectrum analyzer function of 4.0 MHz resolution in 95-345 MHz RF frequency range is demonstrated.