An integrated laser blood flowmeter

We have constructed a very small and lightweight blood flowmeter using micromachining and surface mounting techniques for a wearable health monitoring system. The hybrid integrated structure of the optical system incorporates a InGaAsP-InP distributed feedback laser diode (DFB-LD) with a wavelength of 1310 nm, an edge-illuminated photodiode (PD) and a polyimide waveguide on silicon substrate (2 mm /spl times/ 3 mm). This integrated flowmeter can be positioned directly on the tissue and permits real-time monitoring of capillary microcirculation. In-vivo measurements of blood perfusion in a finger confirm the feasibility of the blood flowmeter.     

Effect of Annealing Ambient on the Self-Formation Mechanism of Diffusion Barrier Layers Used in Cu(Ti) Interconnects

Copper (titanium) [Cu(Ti)] films with low titanium (Ti) concentration were found to form thin Ti-rich barrier layers at the film/substrate interfaces after annealing, which is referred to as self-formation of the barrier layers. This Cu(Ti) alloy was one of the best candidates for interconnect materials used in next-generation ultra-large-scale integrated (ULSI) devices that require both very thin barrier layers and low-resistance interconnects. In the present paper, in order to investigate the influences of annealing ambient on resistivity and microstructure of the Cu alloys, the Cu(7.3at.%Ti) films were prepared on the SiO₂ substrates and annealed at 500°C in ultra-high vacuum (UHV) or argon (Ar) with a small amount of impurity oxygen. After annealing the film at 500°C in UHV, the resistivity was not reduced below 16 μΩ-cm. Intermetallic compounds of Cu₄Ti were observed to form in the films and believed to cause the high resistivity. However, after subsequently annealing in Ar, these compounds were found to decompose to form surface TiO _x and interfacial barrier layers, and the resistivity was reduced to 3.0 μΩ-cm. The present experiment suggested that oxygen reactive to titanium during annealing played an important role for both self-formation of the interfacial barrier layers and reduction of the interconnect resistivity.     

Optical frequency domain ranging by a frequency-shifted feedbacklaser

This paper describes the theoretical and experimental study of a new technique for optical frequency domain ranging (OFDR) by a frequency-shifted feedback (FSF) laser. In conventional OFDR, a frequency chirped single-mode laser is used as a light source to convert a distance into a beat frequency, and a tradeoff exists between measurement range and resolution. The FSF laser output consists of periodically generated chirped frequency components whose chirp rate is faster than 100 PHz/s (P=10¹⁵), By use of the FSF laser, the tradeoff is removed and long-distance high-resolution OFDR is realized In the experiment, a distance of 18.5 km was measured with a resolution of 20 mm     

Earth‐Abundant and Durable Nanoporous Catalyst for Exhaust‐Gas Conversion

Precious metals (Pt and Pd) and rare earth elements (Ce in the form of CeO₂) are typical materials for heterogeneous exhaust‐gas catalysts in automotive systems. However, their limited resources and high market‐driven prices are principal issues in realizing the path toward a more sustainable society. In this regard, herein, a nanoporous NiCuMnO catalyst, which is both abundant and durable, is synthesized by one‐step free dealloying. The catalyst thus developed exhibits catalytic activity and durability for NO reduction and CO oxidation. Microstructure characterization indicates a distinct structural feature: catalytically active Cu/CuO regions are tangled with a stable nanoporous NiMnO network after activation. The results obtained by in situ transmission electron microscopy during NO reduction clearly capture the unique reaction‐induced self‐transformation of the nanostructure. This finding can possibly pave the way for the design of new catalysts for the conversion of exhaust gas based on the element strategy.     

Statistics of Rain Attenuation and other Environmental Effects Associated with the BSE Satellite Down-Link at 12 GHz in Japan

Propagation measurements were carried out at 12 GHz on the down-link of the Japan's Medium-scale Broadcasting Satellite for Experimental Purpose (BSE), launched in 1978. Analyses of the measurements have revealed the statistics of rain attenuation and duration of fade at 12 GHz in various parts and climates of Japan, as well as other environmental effects such as degradation of reception quality due to snowfall on receiving antennae, reduction in carrier-to-noise ratio by solar noise interference and diffraction attenuation by obstacles. This paper describes the results which are useful for planning and operation of satellite broadcasting systems.     

Evaluation of the Parallel Conductor Theory for Measuring Human Limb Blood Flow by Electrical Admittance Plethysmography

We devised a compensation technique that measures the admittance change of a limb submerged in an electrolyte solution in a cylinder. Using this technique, we evaluated the accuracy of admittance plethysmography and the validity of the parallel-conductor model on which the theory of blood flow measurement by electrical admittance (or impedance) plethysmography is based. From a theoretical point of view, if a limb is regarded as a parallel-conductor model, the admittance change due to blood pooling following venous occlusion should disappear when the resistivity of the solution is equal to that of the blood.     

Jitter Accumulation for Periodic Pattern Signals

It is important to accurately evaluate and reduce jitter accumulation in long-haul digital repeatered lines. Jitter accumulation caused by random pattern signals has already been analyzed. However, periodic pattern signals such as pseudorandom signals are usually used to measure jitter accumulation. This paper describes the difference between the jitter accumulation for both signals and the necessary conditions to accurately estimate jitter accumulation for random pattern signals by using periodic pattern signals. First, it is shown theoretically that systematic jitter for periodic signals saturates, showing a ripple pattern. The limit of increase is determined by the ratio of tank bandwidth and pattern repetition frequency. Up to a certain number of regenerators determined by the ratio, systematic jitter increases in rough proportion to thesqrt{N}slope. It is also shown that the equation to estimate random pattern jitter accumulation is determined by the measured value for periodic pattern signals. Second, jitter characteristics are simulated by optical signal circulating experiments. The results are in agreement with the analysis. In addition, the reduction effects on periodic signal jitter accumulation caused by timing signal delay and nonlinearity of the limiter in the timing circuit are shown.     

Si hetero-bipolar transistor with a fluorine-doped SiC emitter anda thin, highly doped epitaxial base

The effect of fluorine doping on SiC/Si heterojunction bipolar transistors (HBTs) is studied. The film properties of the fluorine-doped SiC and device characteristics of an HBT using the SiC emitter and a 50-nm-thick, highly doped epitaxial base (10¹⁹/cm³) are presented. The current gain is improved from 15 to 80 by doping with fluorine. The current gain is four times larger than that of a conventional poly-Si emitter homo-transistor with the same base structure. In spite of the very thin base, the Early voltage is over 100 V. Forward-bias tunneling current was hardly seen at the emitter-base junction. The fluorine appears to terminate the dangling bonds. The results show the possibility of fabricating transistors with a very thin, highly doped base