Low-power performance of 0.5-μm JFET for low-cost MMIC's inpersonal communications

The low-power microwave performance of an enhancement-mode ion-implanted GaAs JFET is reported. A 0.5-μm×100-μm E-JFET with a threshold voltage of V_th=0.3 V achieved a maximum DC transconductance of g_m=489 mS/mm at V _ds=1.5 V and I_ds=18 mA. Operating at 0.5 mW of power with V_ds=0.5 V and I_ds =1 mA, the best device on a 3-in wafer achieved a noise figure of 0.8 dB with an associated gain of 9.6 dB measured at 4 GHz. Across a 3-in wafer the average noise figure was F_min=1.2 dB and the average associated gain was G_a=9.8 dB for 15 devices measured. These results demonstrate that the E-JFET is an excellent choice for low-power personal communication applications     

10-Gb/s low-input-power SOA-PLC hybrid integrated wavelength converter and its 8-slot unit

We achieved successful low-input-power (-10 dBm) wavelength conversion at 10 Gb/s by using a hybrid integrated cross-phase modulation wavelength converter (XPM-WC). The input CW power was also -10 dBm and the total current was only 215 mA, and no signal preamplifiers were used. From the relationship between the eye-opening ratio and the injection current to the SOA, we clarified the optimal current condition for low-input-power operation. The XPM-WC consists of a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA), which is mounted on a planar lightwave circuit (PLC) platform. We also fabricated an 8-slot unit. XPM-WC modules are inserted in every slot and can operate independently. Stable and uniform low-input-power operation is confirmed in all slots.     

An economic and energy analysis on bio-hydrogen fuel using a gasification process

Recently, in Japan, recycling technologies have been developed using waste biomass material. Waste biomass is traded in the waste materials market between users and a third-party, who receives a fee for processing them. This study is an environmental and economic analysis of a biomass energy system, which can produce hydrogen fuel for fuel cells (purity of 99.99%) as an example of an environmental business model. The experimental apparatus was made based on the moving-bed gasifier by the German company, DM2 Inc., and the hydrogen gas yield was measured. Finally, the economic viability of the future hydrogen business was estimated.The experimental results obtained gave the gas concentration of 57.5% in a Steam/Carbon ratio of 1.40 at 900 °C.Assuming the plant scale of 10 t/d, the production amount of hydrogen gas would be 21.3 kg/h. Based on the law concerning waste processing in Japan, a sizeable amount of waste biomass could be expected. Therefore, if the processing fee which is paid to the group (contractor) ranges between 5.0 and 10.0 $/t, and if the whole investment cost is 6 million dollars and the depreciation period is 15 years, the bio-hydrogen production cost using the experimental data would be 5.75–7.86 $/kg-H₂ without receiving related subsidies. In a one-third grant proportion, the cost would become 4.60–6.72 $/kg-H₂.     

Reforming of Methane with Carbon Dioxide over a Catalyst Consisting of Ruthenium Metal and Cerium Oxide Supported on Mordenite

Reforming of CH₄ with CO₂ proceeds at 400 °C over a catalyst consisting of ruthenium metal and CeO₂ highly dispersed on mordenite. The catalyst, Ru-CeO₂/MZ, is highly active for the reforming of CH₄ under the conditions at which a carbon formation reaction is thermodynamically apt to take place. The reforming selectively forms H₂ and CO. An increase in the weight of the catalyst resulting from carbon deposits was scarcely observed. IR spectra for the catalyst indicate that the reforming proceeds via the formation of the intermediate species such as Ru-CO and Ru-CH_x on the surface of ruthenium. The data of H₂ adsorption support the idea that ruthenium is highly dispersed in Ru-CeO₂/MZ.     

Determination of power reflectivity of quasi-graded distributedBragg reflectors using stopband width

The authors examine the reflectivity of the quasi-graded distributed Bragg reflector using the stopband width. The stopband width of about 1000 Å for a reflectivity of about 99% is able to be measured with an accuracy of ± 1 Å. Thus, the reflectivity is determined with high accuracy from the stopband width. It is found that the quasi-graded distributed Bragg reflector is a high-quality reflector with high reflectivity and low resistance     

Low-frequency dispersion of transconductance in GaAs JFETs andMESFETs with an ion-implanted channel layer

An analytical model of low-frequency dispersion of transconductanced in GaAs FETs which have nonuniform profiles of carrier concentration and mobility is reported. The frequency dependence of surface charge density is incorporated into the model as a variation in the source resistance of the FETs. The model explains the low-frequency dispersion of transconductance in GaAs p-n junction FETs (JFETs) and metal-semiconductor FETs (MESFETs), both of which have a channel layer formed by ion implantation. It is suggested that the low-frequency dispersion of transconductance can be attributed to the charge exchange which occurs with the surface states in GaAs FETs     

Cloning and sequencing of the Sphingomonas (Pseudomonas) paucimobilis gene essential for the O demethylation of vanillate and syringate

A growing body of evidence supports the existence of a tissue-based renin-angiotensin system (RAS) in the vasculature, but the functional capacity of vascular RAS was not investigated in humans. In 28 normotensive healthy control subjects, the metabolism of angiotensins through vascular tissue was investigated in normal, low, and high sodium diets by the measurement of arterial-venous gradient of endogenous angiotensin (Ang) I and Ang II in two different vascular beds (forearm and leg), combined with the study of 125I-Ang I and 125I-Ang II kinetics. In normal sodium diet subjects, forearm vascular tissue extracted 36+/-6% of 125I-Ang I and 30+/-5% of 125I-Ang II and added 14.9+/-5.1 fmol x 100 mL(-1) x min(-1) of de novo formed Ang I and 6.2+/-2.8 fmol x 100 mL(-1) x min(-1) of Ang II to antecubital venous blood. Fractional conversion of 125I-Ang I through forearm vascular tissue was about 12%. Low sodium diet increased (P<.01) plasma renin activity, whereas de novo Ang I and Ang II formation by forearm vascular tissue became undetectable. Angiotensin degradation (33+/-7% for Ang I and 30+/-7% for Ang II) was unchanged, and vascular fractional conversion of 125I-Ang I decreased from 12% to 6% (P<.01). In high sodium diet subjects, plasma renin activity decreased, and de novo Ang I and Ang II formation by forearm vascular tissue increased to 22 and 14 fmol x 100 mL(-1) x min(-1), respectively (P<.01). Angiotensin degradation did not significantly change, whereas fractional conversion of 125I-Ang I increased from 12% to 20% (P<.01). Leg vascular tissue functional activities of RAS paralleled those of forearm vascular tissue both at baseline and during different sodium intake. These results provide consistent evidence for the existence of a functional tissue-based RAS in vascular tissue of humans. The opposite changes of plasma renin activity and vascular angiotensin formation indicate that vascular RAS is independent from but related to circulating RAS.     

Reproducibility of spasm in patients with long-term remission of vasospastic angina by medical treatment

No single musculoskeletal disorder has generated more passionate discussion than bone osteonecrosis. Surprisingly, its physiopathogenesis remains largely unknown despite in-depth studies. Its treatment is still debated, and its wide range of clinical manifestations which vary from totally asymptomatic to the catastrophic event of irreversible epiphyseal collapse remains a fascinating question for the clinicians (1-4). Magnetic Resonance (MR) imaging has given a large tribute to the discussion during the last decade by allowing detection of marrow infarcts at a presymptomatic period of the disease, thus providing data on its natural history. Unfortunately, MR imaging has also contributed to increase the confusion among various epiphyseal disorders. The aim of the current paper is to provide an overview of the current knowledge of imaging features by stressing accepted data and delineating blind areas.     

Structural analysis of β-form poly(p-xylyene) starting from a high-resolution image

The crystal structure of β-form poly(p-xylylene) is analysed starting from a high-resolution image of a single crystal of this polymer. The high-resolution image corresponding to the projection of molecules onto the ab-plane along the chain axis shows clearly the mutual position of each molecule in a unit cell. The molecules are aligned wavily in the direction along the a-axis and the rough positions of their centres in a unit cell can be determined from the image. The refinement of the structure is carried out by the usual least-squares method using the intensities of electron and X-ray diffractions. The space group of the β-form is trigonal, P3, and the lattice dimensions are a=2.052 nm, c=0.655 nm and γ=120°. The unit cell contains 16 molecules and one of them is considered to occupy statistically one of three equivalent orientations so as to satisfy the P3 symmetry.