Design and fabrication of RESURF MOSFETs on 4H-SiC(0001), (112~0), and 6H-SiC(0001)

Design and fabrication of lateral SiC reduced surface field (RESURF) MOSFETs have been investigated. The doping concentration (dose) of the RESURF and lightly doped drain regions has been optimized to reduce the electric field crowding at the drain edge or in the gate oxide by using device simulation. The optimum oxidation condition depends on the polytype: N/sub 2/O oxidation at 1300/spl deg/C seems to be suitable for 4H-SiC, and dry O/sub 2/ oxidation at 1250/spl deg/C for 6H-SiC. The average inversion-channel mobility is 22, 78, and 68 cm/sup 2//Vs for 4H-SiC(0001), (112~0), and 6H-SiC(0001) MOSFETs, respectively. RESURF MOSFETs have been fabricated on 10-/spl mu/m-thick p-type 4H-SiC(0001), (112~0), and 6H-SiC(0001) epilayers with an acceptor concentration of 1/spl times/10/sup 16/ cm/sup -3/. A 6H-SiC(0001) RESURF MOSFET with a 3-/spl mu/m channel length exhibits a high breakdown voltage of 1620 V and an on-resistance of 234 m/spl Omega//spl middot/cm/sup 2/. A 4H-SiC(112~0) RESURF MOSFET shows the characteristics of 1230 V-138 m/spl Omega//spl middot/cm/sup 2/.     

Noncontact Material Identification and Distance Measurement Using Effective Capacitance With CdS Cells

We propose a novel noncontact sensing method for material identification and for detection of the distance between the sensor and the surface of a material by using its electrical and optical properties. In the proposed method, capacitance between the terminals of a pair of CdS cells, called the effective capacitance, is measured, and several capacitance values are obtained by changing the emission strength of the light emitting diode, thus changing the resistance value of the CdS cells. From these values, it is possible to identify the materials and to detect the distance between the CdS cells and the material. In this paper, we compare four kinds of effective capacitance measurement methods using a pair of CdS cells and describe the proposed measurement method. In addition, this paper discusses the measurement accuracy of effective capacitance values in the proposed method and demonstrates its ability to identify six material samples-clear, white, and black acrylic, clear vinyl chloride, brown bakelite, and aluminum-and to detect the distance between the CdS cells and the material.     

Correlates and prognosis in relation to intellectual dysfunction in a community-residing elderly population

To estimate the risk factors for intellectual dysfunction and examine its prognosis in a community-residing (non-institutionalized) elderly population, a randomly selected sample of 1,473 elderly people aged 65 years and over living in S city, Osaka Prefecture, was studied in October 1992, and data were obtained from 1,383, a response rate of 93.9%. A cohort of 1,383 was followed for 42 months and follow-up was completed for 1,300 (94.0%). The main results were as follows: 1) The prevalence of intellectual dysfunction did not differ significantly between sexes, and there was an increasing prevalence of intellectual dysfunction with age in both sexes. The prevalence of severe intellectual dysfunction was found to increase highly at age 85 and over. 2) By univariate analysis, odds ratios for age older than 75 years, low Activities of Daily Living (ADL), urinary and fecal incontinence, and no participation in social activities were significantly higher than 1 in any level of mild, moderate, and severe intellectual dysfunction. In the multivariate analysis using logistic regression, age older than 75 years and urinary and fecal incontinence showed significant higher odds ratios than 1 for severe intellectual dysfunction, and low ADL and treatment for hypertension also showed significant higher odds ratios than 1 for moderate intellectual dysfunction. 3) From analysis using the Kaplan-Meier method, the cumulative survival rates decreased with a decline in intellectual functioning in both age groups of 65-74 and 75 years and older. 4) Application of the Cox proportional hazards model resulted in adjusted hazard ratio for severe intellectual dysfunction of 1.79 (95% confidence interval, 1.02-3.12), controlling for other factors such as sex, age, general health status, incontinence and social activities.     

Monocarbonyl compounds from catalytic decomposition of autoxidized unsaturated fatty acid esters

Monocarbonyl compounds formed by the decomposition of autoxidized triolein, methyl linolenate, and methyl arachidonate were converted into their 2,4-dinitrophenylhydrazone derivatives and analyzed by thin layer and paper chromatographies. From decomposition of autoxidized triolein with acid-washed Fuller’s earth alkanals were the only monocarbonyl products found, whereas, with metal catalysts or heat, 2-alkenals were the primary products. Autoxidized methyl linolenate and methyl arachidonate decomposed with metal catalysts or heat yielded 23–55% of 2,4-alkadienals but minor amounts with acid-washed Fuller’s earth. The differences in distribution of monocarbonyl products were attributed to a selective course of scission of the hydroperoxides that depended upon the conditions of decomposition.     

Estimation of a nonvisible field-of-view mobile target incorporating optical and acoustic sensors

This paper presents a nonvisible field-of-view (NFOV) target estimation approach that incorporates optical and acoustic sensors. An optical sensor can accurately localize a target in its field-of-view whereas the acoustic sensor could estimate the target location over a much larger space, but only with limited accuracy. A recursive Bayesian estimation framework where observations of the optical and acoustic sensors are probabilistically treated and fused is proposed in this paper. A technique to construct the observation likelihood when two microphones are used as the acoustic sensor is also described. The proposed technique derives and stores the interaural level difference of observations from the two microphones for different target positions in advance and constructs the likelihood through correlation. A parametric study of the proposed acoustic sensing technique in a controlled test environment, and experiments with an NFOV target in an actual indoor environment are presented to demonstrate the capability of the proposed technique.     

Calcium ion as a second messenger for o-nitrophenylsulfenyl-adrenocorticotropin (NPS-ACTH) and ACTH in bovine adrenal steroidogenesis

o-Nitrophenyl sulfenyl-modified ACTH (NPS-ACTH) stimulated steroidogenesis acutely in bovine fasciculata-reticularis cells without increase in cellular cAMP synthesis. Application of NPS-ACTH to the cultured cells induced Ca2+ signals in individual cells as detected by video-enhanced microscopic fluorescence measurements. The percentage of Ca2+ signaling cells corresponded well with the increase of steroidogenesis induced by NPS-ACTH below 1 nM. Treatment of the cells with nicardipine, a Ca2+ channel blocker, suppressed the Ca2+ signals except for the transient increase just after the addition of NPS-ACTH and also blocked completely the stimulative effect on the steroidogenesis of NPS-ACTH below 1 nM. At a dosage of NPS-ACTH higher than 10 nM, the stimulative effect of steroidogenesis was partly suppressed by nicardipine and also by AA-861, a lipoxygenase inhibitor. The action of NPS-ACTH might be mediated by both Ca2+ and lipoxygenase metabolite(s) of arachidonic acid as dual second messengers. The effect of ACTH in pM range on the steroidogenesis was suppressed completely by the treatment with nicardipine and AA-861 at the same time, indicating that the action was mediated by both Ca2+ and the lipoxygenase metabolite(s) but not by cAMP. cAMP plays a significant role as a second messenger for ACTH action only at ACTH concentrations greater than 10 pM.     

HRTEM study of new series of oxycarbonitrate superconductors (Cu,C,N)Sr2Ca(n - 1)Cu(n)O(y) (n = 1-6)

Arrangements of Cu and anion groups (CO3 and NO3) in the charge-reservoir (CR) blocks of a series of new oxycarbonitrate superconductors (Cu,C,N)Sr2Ca(n - 1)Cu(n)O(y) (n = 1-6) were examined by means of electron diffraction and high-resolution transmission electron microscopy (HRTEM). The first three members with n = 1-3 [Tc = 33 K (n = 1), 91 K (n = 2), 90 K (n = 3)] show the 4a0-type superstructures with periodic arrangements, [-Cu-X-X-X-Cu-X-X-X-Cu-] (X = CO3, NO3), in the CR blocks. The third member (n = 3) partly contains the 2a0-type of superstructure with [-Cu-X-Cu-X-Cu] in the CR blocks. The fourth member with n = 4 (Tc = 113 K) contains only the 2a0-type of superstructure. The higher members, with n = 5 (Tc = 65 K) and n = 6 (Tc = 52 K), show no evidence of ordering in the CR blocks, suggesting random arrangements of Cu and anion groups.     

Fabrication of silicon nitride nanoceramics—Powder preparation and sintering: A review

Fine-grained silicon nitride ceramics were investigated mainly for their high-strain-rate plasticity. The preparation and densification of fine silicon nitride powder were reviewed. Commercial sub-micrometer powder was used as raw powder in the “as-received” state and then used after being ground and undergoing classification operation. Chemical vapor deposition and plasma processes were used for fabricating nanopowder because a further reduction in grain size caused by grinding had limitations. More recently, nanopowder has also been obtained by high-energy milling. This process in principle is the same as conventional planetary milling. For densification, primarily hot pressing was performed, although a similar process known as spark plasma sintering (SPS) has also recently been used. One of the advantages of SPS is its high heating rate. The high heating rate is advantageous because it reduces sintering time, achieving densification without grain growth. We prepared silicon nitride nanopowder by high-energy milling and then obtained nanoceramics by densifying the nanopowder by SPS.