Micro-drilling of monocrystalline silicon using a cutting tool

The micro-drilling of monocrystalline silicon using a cutting tool was tested with the aim of fabricating three-dimensional and high aspect ratio micro-shapes. Micro-tools with a D-shaped cross-section and cutting edge radius of 0.5 μm were fabricated by wire electrodischarge grinding (WEDG). The results showed that, with a depth of cut of 0.1 μm, ductile-regime cutting was realized, and that a tool clearance angle larger than 0° was necessary to prevent fractures at the hole entrance. The smallest machinable hole was of 6.7 μm diameter, which is the smallest not just in the present study, but of all holes drilled using a cutting tool so far. Furthermore, an aspect ratio of more than four was obtained in the drilling of a 22 μm diameter and 90 μm deep hole.     

Evaluation of temperature distribution in steel balls induced by friction generated during tribotest against diamond like carbon coatings

Temperature rise in carbon steel (SUJ2-ASTM E52100) and stainless steel (SUS440C-ASTM 440C) balls sliding against diamond like carbon was evaluated using thermal simulation. On the premise that most of the friction energy was consumed as friction heat, the temperature distribution in the steel balls was simulated by ANSYS thermal conduction analysis using the friction energy measured by the ball on disc test. The interior temperatures of the steel balls were also monitored by a thermocouple during the tribotest. The simulation data, calibrated by the heat partition rate based on the Peclet number, were compared to the experiment data, and good accordance of both data was demonstrated.     

Proposal of preliminary device model and scaling scheme of cross-current tetrode SOI MOSFET aiming at low-energy circuit applications

This paper describes a preliminary attempt with a semi-analytical model and a scaling scheme of the cross-current tetrode (XCT) silicon-on-insulator (SOI) MOSFET aiming at low energy-dissipation circuit applications. The channel-current model for XCT MOSFET is separated into an intrinsic MOSFET part and a parasitic junction-gate field-effect transistor (JFET) part. Models for MOSFET and JFET are proposed by taking the potential coupling between MOSFET and JFET. The later part of the paper introduces experiments on the original SOI nMOSFET and XCT nMOSFET. This paper stresses the fundamental operations and features of the XCT device structure. Calculation results of I-V characteristics from the semi-analytical model are compared with the measurement values. It is shown that the proposed model reproduces the measured values successfully. In addition, design guidelines for XCT devices and scaling issues are discussed from the viewpoint of performance control aiming at low energy-dissipation circuit applications. Finally, preliminary circuit simulation results of XCT CMOS devices are revealed to demonstrate the definite low-energy performance.     

Electrical discharge machining of submicron holes using ultrasmall-diameter electrodes

We have carried out the electrical discharge machining (EDM) of submicron holes using ultrasmall-diameter electrodes. Two types of electrode were used: tungsten electrodes fabricated by the combination of wire electrodischarge grinding and electrochemical machining, and silicon electrodes originally designed as probes for scanning probe microscopes. The diameters of the former and latter were 1 μm or less, and less than 0.15 μm, respectively. Holes were drilled using a relaxation-type pulse generator at an open-circuit voltage of less than or equal to 20 V with the machine's stray capacitance as the only capacitance. Using tungsten electrodes, holes of less than 1 μm in diameter and more than 1 μm in depth were successfully drilled. A 1.3-μm-wide slot was also fabricated by drilling many holes with a small pitch. It was possible to drill holes of approximately 0.5 μm diameter using silicon electrodes because the electrode diameter was less than those of the tungsten electrodes. These holes have the smallest reported diameter for holes drilled by EDM, indicating the possibility of submicron- and nanoscale machining by EDM.     

Fabrication and cutting performance of cemented tungsten carbide micro-cutting tools

We have developed cemented tungsten carbide (CTC) micro-cutting tools of 3 μm diameter by electrical discharge machining (EDM). Microdrilling and micromilling were carried out using the developed tools, and their cutting performance was investigated. Cutting was performed in free-cutting brass plates. Ultrasonic oscillation was employed to lower the cutting resistance. As a result, holes and a slot of 3 μm depth were successfully fabricated using tools made of CTC with 0.6 μm grain size, indicating that successful cutting with 3 μm-diameter tools was accomplished for the first time. Furthermore, CTC with 90 nm grain size was used as a tool material to improve the tool breakage resistance and tool form accuracy. The drilling performance of tools made of this ultrafine-grain-sized CTC was also investigated and found to exhibit a considerably improved average tool life.     

Effects of fullerene addition on the carbonization of synthetic naphthalene isotropic pitch

The toluene soluble fraction of fullerene soot, consisting of C₆₀ and C₇₀ and other fullerenes, was co-carbonized with synthesized isotropic pitch derived from naphthalene. Mixtures of fullerene and pitch gave carbons in higher yield than expected from their single carbonizations at fullerene contents <30 wt%. The fullerenes suppressed the expansion of the pitch during carbonizations, and changed the optical textures of resultant carbons. At levels of addition of fullerenes <30 wt%, no fullerenes could be detected in resultant carbons by spectroscopy, but were detected as spheres of ca. 10–20 nm diameter in the carbons by TEM. It is considered that fullerenes remove hydrogen from the naphthenic structures of the pitch and so alter carbonization characteristics. Hydrogenation breaks the spheroidal fullerene framework.     

Cloning of a Sphingomonas paucimobilis SYK-6 gene encoding a novel oxygenase that cleaves lignin-related biphenyl and characterization of the enzyme

Sphingomonas paucimobilis SYK-6 transforms 2,2'-dihydroxy-3,3'-dimethoxy-5,5'-dicarboxybiphenyl (DDVA), a lignin-related biphenyl compound, to 5-carboxyvanillic acid via 2,2',3-trihydroxy-3'-methoxy-5,5'-dicarboxybiphenyl (OH-DDVA) as an intermediate (15). The ring fission of OH-DDVA is an essential step in the DDVA degradative pathway. A 15-kb EcoRI fragment isolated from the cosmid library complemented the growth deficiency of a mutant on OH-DDVA. Subcloning and deletion analysis showed that a 1.4-kb DNA fragment included the gene responsible for the ring fission of OH-DDVA. An open reading frame encoding 334 amino acids was identified and designated ligZ. The deduced amino acid sequence of LigZ had 18 to 21% identity with the class III extradiol dioxygenase family, including the beta subunit (LigB) of protocatechuate 4,5-dioxygenase of SYK-6 (Y. Noda, S. Nishikawa, K.-I. Shiozuka, H. Kadokura, H. Nakajima, K. Yano, Y. Katayama, N. Morohoshi, T. Haraguchi, and M. Yamasaki, J. Bacteriol. 172:2704-2709, 1990), catechol 2,3-dioxygenase I (MpcI) of Alcaligenes eutrophus JMP222 (M. Kabisch and P. Fortnagel, Nucleic Acids Res. 18:3405-3406, 1990), the catalytic subunit of the meta-cleavage enzyme (CarBb) for 2'-aminobiphenyl-2,3-diol from Pseudomonas sp. strain CA10 (S. I. Sato, N. Ouchiyama, T. Kimura, H. Nojiri, H. Yamane, and T. Omori, J. Bacteriol. 179:4841-4849, 1997), and 2,3-dihydroxyphenylpropionate 1,2-dioxygenase (MhpB) of Escherichia coli (E. L. Spence, M. Kawamukai, J. Sanvoisin, H. Braven, and T. D. H. Bugg, J. Bacteriol. 178:5249-5256, 1996). The ring fission product formed from OH-DDVA by LigZ developed a yellow color with an absorption maximum at 455 nm, suggesting meta cleavage. Thus, LigZ was concluded to be a ring cleavage extradiol dioxygenase. LigZ activity was detected only for OH-DDVA and 2,2',3,3'-tetrahydroxy-5,5'-dicarboxybiphenyl and was dependent on the ferrous ion.     

Aneurysm of the membranous ventricular septum with ventricular septal defect, mitral and tricuspid insufficiency

Bile acids are known to promote colon carcinogenesis. However, there is one study showing that ursodeoxycholic acid (UDCA) supplemented in the diet at the concentration of 0.4% prevented azoxymethane-induced rat colon tumorigenesis. The aim of our study was to explore the inhibitory effect of a much smaller dose of UDCA on colon carcinogenesis in rats. One hundred 7-week-old F344 rats were given 2 mg of N-methylnitrosourea 3 times a week for 3 weeks by intrarectal instillation, and were fed a 0% (control), 0.4% or 0.08% UDCA-supplemented diet for the next 27 weeks. All the rats were killed and examined for tumor development at week 30. The tumor incidence and number were significantly lower and smaller, respectively, in the UDCA-fed rats than in the control rats: 40% and 36% vs. 68%; 0.5 +/- 0.1 (mean +/- SEM) and 0.4 +/- 0.1 vs. 1.0 +/- 0.2. All the tumors were located in the distal half of the colon and were plaque-shaped or polypoid, being well-differentiated adenocarcinomas restricted to the mucosa or submucosa. Bile acids in the feces and the blood obtained at weeks 20 and 30, respectively, were analyzed by HPLC. A significant increase of UDCA was confirmed in both the feces and the blood of the UDCA-fed rats compared with the control rats. The results suggest that the continuous feeding of a small dose of UDCA may prevent colon carcinogenesis.     

A 400-MHz random-cycle dual-port interleaved DRAM (D/sup 2/RAM) with standard CMOS Process

This paper describes a standard CMOS process based on embedded DRAM macro with dual-port interleaved DRAM architecture (D/sup 2/RAM), which is suitable for the leading edge CMOS LSIs with both high-speed and large-scale memories on a chip. This macro exploits three key technologies: fully sense-signal-loss compensating technology based on the whole detailed noise element breakdowns, the novel striped trench capacitor (STC) cell, and the write-before-sensing (WBS) circuit by decoded write-bus. A 400-MHz random cycle access has been verified for D/sup 2/RAM fabricated by a 0.15-/spl mu/m standard CMOS process.     

Bradykinin-induced vasodilation of human coronary arteries in vivo: role of nitric oxide and angiotensin-converting enzyme

Voltage-clamped GABA(A fast) and GABA(A slow) inhibitory postsynaptic currents (IPSCs) were selectively elicited in hippocampal area CA1 pyramidal neurons. Clinically relevant concentrations of halothane (1.2 vol.%) prolonged both GABA(A fast) and GABA(A slow) IPSC decay times approximately 2.5 fold, while having little to no effect on current amplitudes or rise times. Current-voltage analysis revealed that IPSC reversal potentials (-70 to -75 mV) remained constant in the presence of halothane. Under control conditions, GABA(A slow) IPSC decay times increased linearly with membrane depolarization, and this IPSC decay time voltage dependence was not significantly altered by halothane. These results confirm the existence of separable GABA(A fast) and GABA(A slow) IPSCs in hippocampus, and further elucidate the effects of halothane on these currents.