Development of a measurement technique for ion distribution in an extended nanochannel by super-resolution-laser-induced fluorescence

Ion behavior confined in extended nanospace (10(1)-10(3) nm) is important for nanofluidics and nanochemistry with dominant surface effects. In this paper, we developed a new measurement technique of ion distribution in the nanochannel by super-resolution-laser-induced fluorescence. Stimulated emission depletion microscopy was used to achieve a spatial resolution of 87 nm higher than the diffraction limit. Fluorescein was used for ratiometric measurement of pH with two excitation wavelengths. The pH profile in a 2D nanochannel of 410 nm width and 405 nm depth was successfully measured at an uncertainty of 0.05. The excess protons, showing lower pH than the bulk, nonuniformly distributed in the nanochannel to cancel the negative charge of glass wall, especially when the electric double layer is thick compared to the channel size. The present study first revealed the ion distribution near the surface or in the nanochannel, which is directly related to the electric double layer. In addition, the obtained proton distribution is important to understand the nanoscale water structure between single molecules and continuum phase. This technique will greatly contribute to understanding the basic science in nanoscale and interfacial dynamics, which are strongly required to develop novel miniaturized systems for biochemical analysis and further applications.     

Neutron science and technology on J-PARC

This paper has briefly reviewed a history of neutron sources in Japan and highlighted the 1 MW JSNS (Japan Spallation Neutron Source), which is a central facility of the multi-purposed J-PARC (Japan Proton Accelerator Research Complex) to be completed in 2008. JSNS will provide worldwide users with most intense pulsed neutron beams available for a wide variety of fields ranging from fundamental research of material/life sciences to industrial/medical applications to open up a new era of science and technology.     

Eosinophilic proliferative pylephlebitis in the liver of Japanese beef cattle with fascioliasis

Intrahepatic pylephlebitis was detected in 17 Japanese beef cattle. Grossly, the intrahepatic vessels in the caudate lobe and/or in the periphery of the other hepatic lobes were thickened and protruded above the lobar surface. The vessel lumina were packed with white to red, waste thread-like contents. A few immature flukes were found in the bile ducts in 3 of the 7 cases with biliary thickening. Foci of hepatic necrosis and hemorrhage were scattered around the thickened vessels in 8 cases. Histologically, the interlobular veins were thickened due to severe intimal hyperplasia with endothelial proliferation and eosinophilic accumulation and medial hypertrophy, accompanied by fibrosis and eosinophilic infiltration in the portal areas. Hepatic tissues with necrosis and hemorrhage were surrounded by eosinophils and histiocytes including a granulomatous reaction. One immature fluke was detected in one of these regions of necrosis. Immunoperoxidase staining revealed that the small fluke, Kupffer cells, and histiocytes in the liver of all cases were positively stained with anti-Japanese Fasciola sp. antiserum. Enzyme-linked immunosorbent assay of the sera of 15 cases revealed that all were positive for the anti-Fasciola antibody. On the basis of these findings, the present cases were regarded as an atypical form of fascioliasis, characterized by eosinophilic proliferative pylephlebitis of the liver.     

Stereospecific synthesis of ditactic polymers

Summary Polymerizations of t-butyl crotonate (E-TBC) and t-butyl isocrotonate (Z-TBC) were carried out in toluene at-78°C using t-BuMgBr as initiator. E-TBC gave polymers, whereas Z-TBC did not. The dimer of E-TBC isolated from the polymerization mixture by means of GPC contained predominatly one of the four possible diastereomers. X-ray crystallographic determination showed that the predominant dimer was the erythro-diisotactic isomer. t-BuLi/Et₃Al polymerized effectively both E-TBC and Z-TBC in toluene. The poly(E-TBC)s prepared with t-BuMgBr and t-BuLi/Et₃Al were insoluble in toluene, THF, and chloroform, but soluble in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). Stereostructure of the poly(TBC)s was analyzed by the one- and two-dimensional NMR spectra measured in HFIP. The poly(E-TBC) prepared with t-BuMgBr was a 1:1 mixture of the erythro- and threo-diisotactic polymers with high stereoregularity. The poly(E-TBC) and poly(Z-TBC) obtained from the polymerizations with t-BuLi/Et₃Al were rich in disyndiotactic structure. Polymerization of TBCs with t-BuLi in toluene and THF was also studied.

---

     

A side-wall transfer-transistor cell (SWATT cell) for highlyreliable multi-level NAND EEPROMs

A multi-level NAND Flash memory cell, using a new Side-WAll Transfer-Transistor (SWATT) structure, has been developed for a high performance and low bit cost Flash EEPROM. With the SWATT cell, a relatively wide threshold voltage (V_th) distribution of about 1.1 V is sufficient for a 4-level memory cell in contrast to a narrow 0.6 V distribution that is required for a conventional 4-level NAND cell. The key technology that allows this wide V_th distribution is the Transfer Transistor which is located at the side wall of the Shallow Trench Isolation (STI) region and is connected in parallel with the floating gate transistor. During read, the Transfer Transistors of the unselected cells (connected in series with the selected cell) function as pass transistors. So, even if the V_th of the unselected floating gate transistor is higher than the control gate voltage, the unselected cell will be in the ON state. As a result, the V_th distribution of the floating gate transistor can be wider and the programming can be faster because the number of program/verify cycles can be reduced. Furthermore, the SWATT cell results in a very small cell size of 0.57 μm² for a 0.35 μm rule. Thus, the SWATT cell combines a small cell size with a multi-level scheme to realize a very low bit cost. This paper describes the process technology and the device performance of the SWATT cell, which can be used to realize NAND EEPROM's of 512 Mbit and beyond     

Direct computation of expected numbers of failures and repairs via integral equation approach

This paper develops a method for computing the expected number of failures and the expected number of repairs of a component in a prescribed time interval. Our method computes directly the above mentioned quantities without passing through a conventional step of calculating the unconditional failure and repair intensities over the corresponding time interval. Our method is constructed via integral equation formulation with its operator equation representation. It is shown that the expected number of failures and the expected number of repairs can be computed with the same precision of accuracy as that of the unconditional failure and repair intensities, which cannot be possible by a conventional approach.     

The Creep and Thermal Stability Characteristics of a Unidirectionally Solidified Al2O3/YAG Eutectic Composite

Compressive creep characteristics at 1773, 1873, and 1973 K, oxidation resistance over 1000 h at a temperature of 1973 K in ambient air, and the thermal stability characteristics at 1973 K in ambient air of a unidirectionally solidified Al2O3/YAG eutectic composite were evaluated. At a test temperature of 1873 K and a strain rate of 10–4/s, the compressive creep strength of a eutectic composite manufactured by the unidirectional solidification method is approximately 13 times higher than that of a sintered composite with the same chemical composition. The insite eutectic composite also showed greater thermal stability, with no change in mass after an exposure of 1000 hours at 1973 K in ambient air. The superior high-temperature characteristics are closely related to such factors as (1) the in-situ eutectic composite having a microstructure, in which single crystal Al2O3 and single crystal YAG are three-dimensionally and continuously connected and finely entangled without grain boundaries and (2) no amorphous phase is formed at the interface between the Al2O3 and the YAG phases.     

Direct conversion mechanism of fluorine-GIC into poly(carbon monofluoride), (CF)n

The reaction mechanisms of a stage-1 fluorine-graphite intercalation compound (GIC), C_2.5F, with 0.10 MPa of fluorine gas have been studied at 573-773 K. The original stage-1 structure of C_2.5F with semi-ionic C-F bonds and planar sp² carbon sheets is maintained in most part of the compound after the reaction at 573 K, although a large number of covalent C-F bonds are formed on the surface. This compound is partially or completely converted to poly(carbon monofluoride), (CF)_n, with covalent C-F bonds and puckered sp³ carbon sheets at 673 or 773 K, respectively. Single-phase (CF)_n obtained at 773 K possesses remarkably small BET specific surface area, 61 m²/g carbon, almost unchanged from the value of the precursor C_2.5F (69 m²/g carbon). In this reaction, the accommodation of fluorine atoms supplied from the atmosphere into the galleries of C_2.5F is facilitated by the rearrangement of originally intercalated fluorine atoms in the GIC, forming (CF)_n with fewer defects compared to those by the conventional direct fluorination of graphite.     

Lateral growth of GaAs on patterned {-1-1-1}B substrates for the fabrication of nano wires using metalorganic molecular beam epitaxy

We have grown GaAs nano wire structures (45 × 20 nm²) buried in AIAs layers by lateral metalorganic molecular beam epitaxy on the terraced sidewalls of mesa-grooved (-1-1-1)B substrates. The growth of GaAs occurred primarily on the sidewall of the mesa-grooves and not on the (-1-1-1)B surface for arsenic pressures greater than 2.0 × 10⁻³ Pa at a substrate temperature of 480°C. An (0-1-1) facet formation during the lateral epitaxy at the intersection region between the bottom (-1-1-1)B surface and the (1-2-2)A sidewall has been directly observed by real-time scanning microprobe reflection high-energy electron diffraction. The growth rate on the (0111) facet was estimated from the variation of its width with growth time.