Thickness scaling limitation factors of ONO interpoly dielectricfor nonvolatile memory devices

This paper describes the scaling limitation factors of ONO interpoly dielectric thickness, mainly considering the charge retention capability and threshold voltage stability for nonvolatile memory cell transistors with a stacked-gate structure, based on experimental results. For good intrinsic charge retention capability, either the top- or bottom-oxide thickness should be greater than around 6 nm. On the other hand, a thicker top oxide structure is preferable to minimize degradation due to defects. It has been confirmed that a 3.2 nm bottom-oxide shows detectable threshold voltage instability, but 4 nm does not. Effective oxide thickness scaling down to around 13 nm should be possible for flash memory devices with a quarter-micron design rule     

Polyhedral assembly of a membrane protein in its three-dimensional crystal

A novel ordered assemblage of bacteriorhodopsin, a transmembrane protein functioning as a light-driven proton pump, is found in its three-dimensional crystal. Atomic force microscope images of the crystal surface reveal that spherical protein clusters with a diameter of approximately 50 nm are hexagonally close-packed. Electron micrographs of mechanically disintegrated crystals show that the inside of the protein cluster is filled with the mother liquor. The crystal is made up of hollow protein clusters. When disintegrated crystals are illuminated in the presence of a lipophilic anion, a significant alkalization of the external medium occurs. This result indicates that the protein cluster contains native lipids and that the cytoplasmic side of the protein faces the external medium. X-ray diffraction patterns and the observed diameter of the spherical shell suggest that approximately 200 bacteriorhodopsin trimers are aligned on a polyhedral surface lattice. Another remarkable feature of the spherical assemblies of bacteriorhodopsin is that they fuse with each other at low ionic strength and occasionally form a tubular or doughnut-like structure. The concept of membrane protein polymorphism is introduced on the basis of these observations, and it is used to describe the dynamic structure of some other biological membranes.     

Preferred orientation of crystallite in carbons heat-treated under high pressure

A soft carbon and a hard carbon which were prepared from Polyvinylchloride and phenolformaldehyde resin, respectively, both by carbonizing to about 700°C, were obtained as sintered cakes by heat-treatment up to about 1800°C under the quasihydrostatic pressure of 5 kbar. Preferred orientation of crystallites relative to the compressing direction in these cakes was determined by X-ray difraction technique by using the (004) or (002) diffraction line. The soft carbon showed remarkable preferred orientation of crystallites, but the degree of orientation was dependent only a little on heat-treatment temperature (HTT). At 1200°C under 5 kbar, the hard carbon gave a sintered cake which had no appreciably preferred orientation. The degree of preferred orientation of crystallites in the cake of the hard carbon greatly increased with the increase in HTT. The difference in the dependence of preferred orientation of crystallites in the soft and hard carbons on HTT was interpreted by referring to the texture of the original carbons.     

System efficiency of a water-splitting system synthesized by photochemical and thermoelectric conversion of solar energy

Valuable hybrid systems for hydrogen production by solar energy have been developed and the system efficiency has been estimated and discussed from various points of view. In order to decompose water into hydrogen and oxygen without the consumption of additional reactants, a steady stream of the reacting materials must be maintained in consecutive reaction processes and if the system has a rate determining step extra energy should be supplied to promote the reaction. In the Yokohama Mark 5 Process, the efficiency of the thermoelectric device is as low as 5 %; however, the overall efficiency of hydrogen production can be raised to 20 % by addition of extra electric power.The energetics of a hybrid system combining photochemical, thermochemical and electrochemical reactions have also been discussed.     

Effect of water on permeation,diffusion, and solution of gases in cellophane

The laminate method for studying the permeability and diffusivity of moistened cellophane to gases is described and the humidity dependence of the transport parameters for H₂, He, and Ne is presented. In the relative humidity region of about 0% to 60%, a small increase in the permeability was observed, which is caused by a comparatively small increase in the diffusivity owing to the plasticizing effect of sorbed water and a decrease in the solubility. On the other hand, an extremely large increase in the permeability observed in the relative humidity region above 60% is mainly based on the diffusion coefficient of gas enhanced by the swelling effect of sorbed water. The presence of a minimum in the solubility–relative humidity curves has been confirmed and is discussed.     

Ozone-Based Decomposition of Main Endocrine Disruption Chemicals in Sewage Effluent

In order to decompose endocrine disruption chemicals (EDCs) in sewage effluent, ozone based oxidation of nonylphenol (NP), bisphenol A (BPA) and 17β-estradiol (E2) was investigated. Experimental results showed that these EDCs were decomposed easily even in the presence of other organic substances of TOC 5 mg/L. The simulation using kinetic constants obtained from the experiments indicated that these EDCs in sewage effluent were removed to below the detection limit with an amount of ozone consumed less than 0.5 mg/L. Ozonation also reduced the estrogenic activity and the aquatic acute toxicity of these EDCs solution. From these results it was concluded that ozonation was very effective in decomposing these EDCs in sewage effluent.     

Single application extracorporeal shock wave lithotripsy is the first choice for patients with pancreatic duct stones

OBJECTIVES: We performed extracorporeal shock wave lithotripsy (ESWL) as the treatment of first choice on 32 chronic pancreatitis patients with main pancreatic duct (MPD) stones prospectively to establish more convenient and safer treatment. METHODS: All patients were treated in a prone position, and shock waves were discharged from the ventral side. ESWL was performed once or twice a week, and no other treatments before ESWL had been applied. RESULTS: Disintegration of all MPD stones to 3 mm or less in diameter could be achieved in all treated patients. Complete clearance of the stones was obtained in 24 patients (75%) without the necessity of endoscopic extraction of fragments. Reduction of MPD diameters after ESWL was statistically significant (p < 0.01). Epigastric and/or back pain complaints before ESWL were completely alleviated in 79% (periods of follow-up: 16-63 months, mean 44), and the pancreatic exocrine function also improved in 61%. No severe complications occurred in any of the patients. CONCLUSIONS: ESWL, which is comparatively easy to perform, is a safe and efficient approach that changes endoscopy's status as an indispensable pretreatment. Therefore, ESWL can be recommended as the first choice treatment for patients with chronic pancreatitis accompanied by MPD stones that should be tried before consideration of either surgical or endoscopic procedures.     

Contrast echo imaging on the breast and thyroid cancers

The utility of ultrasound color Doppler flow mapping imaging for the differential diagnosis on the breast and thyroid tumors had already reported in 1991. Ultrasound contrast agent, SH/TA 508 (Levovist; Schering AG, Germany), had already finished clinical trials in Japan and reported the result phase II, III. On the breast and thyroid lesions, the utility of this contrast agent are safety and usefulness for the accurate diagnosis by the ultrasound color Doppler examination. Throughout of these clinical trials, a quit new ultrasound Doppler imaging methods had been developed, Harmonic Imaging and acoustic emission mode. As the result, ultrasound contrast agent is useful not only for the conventional color Doppler diagnosis but also for the developing of new diagnostic imaging methods.     

Lipase-catalyzed resolution of 1-hydroxymethyl-2-methylferrocene

±-1-Hydroxymethyl-2-methylferrocene was optically resolved by transesterification with lipases using vinyl esters such as vinyl butyrate, vinyl caproate, vinyl octanoate and vinyl decanoate, as acyl donors.