Nanoanalysis by a high-resolution energy filtering transmission electron microscope

An energy-filtering transmission electron microscope with 300 kV acceleration voltage was developed and the spatial resolution of elemental distribution images was improved. Observing oxygen monolayers in Al(11)O(3)N(9), it was shown that the actual resolution attained is up to 0.5 nm. Surface plasmon loss images of silver particles were taken with a resolution of better than 0.4 nm. Furthermore, the sensitivity is sufficiently high to distinguish indium content differences of 2.5 atomic percent in In(x)Al(1-x)As. This performance is good enough to analyze elemental distribution with atomic-level resolution. Furthermore, since analysis with the energy-filtering microscope is easy and practical, nanoanalysis may come into wide use not only in academic fields but also in industry.     

Cathodoluminescence study of one-dimensional free-standing widegap-semiconductor nanostructures: GaN nanotubes, Si3N4 nanobelts and ZnS/Si nanowires

Luminescence properties of one-dimensional free-standing widegap-semiconductor nanostructures were characterized by means of cathodoluminescence (CL). GaN nanopipes, alpha-Si3N4 nanobelts and ZnS/Si nanowires were fabricated by a catalyst-free method, namely grown in an induction furnace from powders. After the observation of morphology by scanning electron microscopy as well as the confirmation of their crystal structures by transmission electron microscopy, their CL spectra and images were observed. The CL spectra mapping as well as the monochromatic CL imaging revealed the variation of the luminescence spectra of different nanowires as well as that along a single wire. These results revealed the optical features of nanostructures.     

Cytochemical detection of endogenous peroxidase in the intralobular ducts of hamster major salivary glands

Light and electron microscopic cytochemical investigation of endogenous peroxidase activity in the intralobular ducts of hamster major salivary glands was carried out using the diaminobenzidine-hydrogen peroxidase method. The peroxidase reaction product was localized in the nuclear envelope, the cisternae of the endoplasmic reticulum, the Golgi apparatus and secretory granules in both the intercalated duct cells and the striated duct light cells of all glands. These results suggest the ability of the intralobular duct cells to secrete peroxidase the same as that of acinar cells in hamster salivary glands.     

A genetically encoded fluorescent indicator capable of discriminating estrogen agonists from antagonists in living cells

A genetically encoded fluorescent indicator was developed for the detection and characterization of estrogen agonists and antagonists. Two different color mutants of green fluorescent protein were joined by a tandem fusion domain composed of LXXLL (L = leucine, X = any amino acid) motif from the nuclear receptor-box II of steroid receptor coactivator 1, a flexible linker sequence, and the estrogen receptor alpha ligand binding domain (ERalpha LBD). Monitoring real-time ligand-induced conformational change in the ERalpha LBD to recruit the LXXLL motif allowed screening of natural and synthetic estrogens in single living cells using fluorescence resonance energy-transfer technique. The indicator was named SCCoR (single cell-coactivator recruitment). The high sensitivity of the present indicator made it possible to distinguish between estrogen strong and weak agonists in a dose-dependent fashion, immediately after adding ligand to live cells. Discrimination of agonists from antagonists was efficiently achieved using the present study. The approach described here can be applied to develop biosensors for other hormone receptors as well.     

Development of alumina ceramics vacuum duct for the 3 GeV-RCS of the J-PARC project

An alumina ceramics vacuum duct has been developed for the 3 GeV-RCS of J-PARC project at JAERI. There are two types of alumina ceramics vacuum ducts needed, one being 1.5 m long with a circular cross-section for use in the quadrupole magnet, the other being 3.5 m long with a 15°, bend with a race-track cross-section for use in the dipole magnet. These ducts could be manufactured by joining several duct segments of 0.5-0.8 m in length by brazing. The alumina ceramic ducts have copper stripes on the outside surface to reduce the duct impedance. One of the ends of each stripe is connected to a titanium flange by way of a capacitor so to interrupt an eddy current circuit. The copper stripes are produced by an electroforming method in which a stripe pattern formed by Mo-Mn metallization is first sintered on the exterior surface and then overlaid by PR-electroformed copper (periodic current reversal electroforming method). In order to reduce emission of secondary electrons when protons or electrons strike the surface, TiN film is coated on the inside surface of the ducts.     

Surface grafting of artificial joints with a biocompatible polymer for preventing periprosthetic osteolysis

Periprosthetic osteolysis-bone loss in the vicinity of a prosthesis-is the most serious problem limiting the longevity of artificial joints. It is caused by bone-resorptive responses to wear particles originating from the articulating surface. This study investigated the effects of graft polymerization of our original biocompatible phospholipid polymer 2-methacryloyloxyethyl phosphorylcholine (MPC) onto the polyethylene surface. Mechanical studies using a hip-joint simulator revealed that the MPC grafting markedly decreased the friction and the amount of wear. Osteoclastic bone resorption induced by subperiosteal injection of particles onto mouse calvariae was abolished by the MPC grafting on particles. MPC-grafted particles were shown to be biologically inert by culture systems with respect to phagocytosis and resorptive cytokine secretion by macrophages, subsequent expression of receptor activator of NF-kappaB ligand in osteoblasts, and osteoclastogenesis from bone marrow cells. From the mechanical and biological advantages, we believe that our approach will make a major improvement in artificial joints by preventing periprosthetic osteolysis.     

Communication device to use an acceleration sensor for the seriously disabled

A communication device is proposed for use as an acceleration sensor for the seriously disabled. This device is mainly for disabled people with problems such as amyotrophic lateral sclerosis (ALS) or a cerebral infarction, who have communication difficulties because of a physical disability. A feature of this device is that the sensor can readily be mounted on the users body. The mounting of the sensor on the body is easy, unlike a conventional touch sensor. Another feature is that even though the physical disability of the user is serious, this device can be operated by slight movements of a part of the body. In addition, we have developed an adaptive word processing software for seriously disabled people. A feature of this software is that the arrangement and size of the buttons and the window on the display can be optimized based on the users physical ability. In a field test, we confirmed that our communication device incorporating this adaptive word processing software was applicable to disabled people.This work was presented in part at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003     

In situ electrical measurements and manipulation of B/N-doped C nanotubes in a high-resolution transmission electron microscope

B/N-doped multiwalled C nanotubes were electrically probed by means of a tungsten needle attached to a piezo-driven stage of a high-resolution transmission electron microscope holder. Two-terminal transport measurements were performed in a 'W needle-nanotube-ground' circuit. The I-V curves were recorded in situ while viewing the nanotubes in the imaging mode of the microscope. This allows us to trace nanotube array morphological changes under applied voltage (up to 50 V). Specific manipulation with nanotube assemblies was found to be possible under applied electrical field: attachment of a tiny nanotube bundle to the W needle and extraction of a given nanotube fragment from an entangled complex bunch were achieved. The electrically-probed B/N-doped C nanotubes exhibited alternating B-rich and C-rich B-C-N domains within tubular layers, as revealed by elemental mapping during energy-filtered TEM (Omega filter). At room temperature the nanostructures displayed resistivity (rho) of approximately 1.8 x 10(-5) omegam and linear I-V curves. The key role of a given contact between the probing needle and a nanotube during electrical measurements was particularly verified.     

Congruent melting of gallium nitride at 6 GPa and its application to single-crystal growth

The synthesis of large single crystals of GaN (gallium nitride) is a matter of great importance in optoelectronic devices for blue-light-emitting diodes and lasers. Although high-quality bulk single crystals of GaN suitable for substrates are desired, the standard method of cooling its stoichiometric melt has been unsuccessful for GaN because it decomposes into Ga and N(2) at high temperatures before its melting point. Here we report that applying high pressure completely prevents the decomposition and allows the stoichiometric melting of GaN. At pressures above 6.0 GPa, congruent melting of GaN occurred at about 2,220 degrees C, and decreasing the temperature allowed the GaN melt to crystallize to the original structure, which was confirmed by in situ X-ray diffraction. Single crystals of GaN were formed by cooling the melt slowly under high pressures and were recovered at ambient conditions.