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Biomedical subjects

Yoshio Bando

Publications and source records attributed to Yoshio Bando.

At least 37 records · Page 2Linked to original sources
PubMed2006

Morphology-controlled synthesis of ZnO nanostructures by a simple round-to-round metal vapor deposition route.

One-dimensional ZnO nanostructures with different morphologies have been successfully synthesized through a simple round-to-round metal vapor deposition route at 550 degrees C with a zinc powder covered indium film as the source material. The structures and morphologies of the products were characterized in detail by using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Studies found that the morphology of the products can be easily tuned from one experimental round to another. Possible growth mechanisms for the formation of one-dimensional ZnO nanostructures with different morphologies are discussed. Photoluminescence studies show that there are sharp UV emission and broad defect-related green emissions for the products obtained in all experimental rounds. Relative intensity of the UV emission to defect-related emissions gradually increased from one experimental round to another.

Journal Article↗
PubMed2006

Purification of boron nitride nanotubes through polymer wrapping.

An effective method was proposed to remove obstinate boron nitride phase impurities in boron nitride nanotubes (BNNTs). The method is based on strong interactions between BNNTs and a conjugated polymer wrapping them and significant weight and size difference between BNNTs and impurities. The as-grown samples and purified samples were compared through detailed characterization, using scanning electron microscopy, transmission electron microscopy, and Raman and Fourier transformed infrared spectroscopy. The results reveal that impurities are effectively removed and resultant BNNTs possess perfect crystallization.

Journal Article↗
PubMed2006

Regeneration of the abdominal postganglionic sympathetic system.

The abdominal sympathetic system is unique in that its postganglionic axons do not directly innervate gastrointestinal smooth muscle layers but exert their effects through the enteric nervous system. The purpose of the present study was to examine the ability of neurons in abdominal sympathetic ganglia to regenerate after axonal injury and to determine whether reinnervation occurs after the removal of ganglia. Axons from the celiac ganglion and superior mesenteric ganglion complex (CG/SMG) of adult female BALB/c mice were crushed or the ganglion complex was removed. Immunohistochemistry, western blotting and in situ hybridization were performed to examine the changes in tyrosine hydroxylase (TH) and growth-associated protein 43 (GAP-43) in the duodenum and the sympathetic ganglia. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling and injection of the tracer dye, fluorogold were also performed. After crushing the nerve, TH in the duodenum disappeared and reappeared within 90 days. In the CG/SMG, TH decreased and increased as in the duodenum, while the expression of GAP-43 changed in the opposite direction. Nerve crushing caused cell death to limited number of neurons in the CG/SMG. The removal of CG/SMG decreased TH in the duodenum and stomach, but 180 days later TH-positive innervation was recovered. Fluorogold injection revealed that the inferior mesenteric ganglion reinnervated the stomach. Therefore, postganglionic sympathetic nerves in the abdomen are able to regenerate and reinnervation occurs even after the removal of sympathetic ganglia.

Abdomen↗
PubMed2006

Room-temperature ferromagnetism in doped face-centered cubic fe nanoparticles.

The magnetism of Fe and its alloys has been at the center of scientific and technological interest for decades. Along with the ferromagnetic nature of body-centered cubic Fe, the magnetic properties of face-centered cubic (fcc) Fe have attracted much attention. It is well known that fcc Fe is thermodynamically unstable at ambient conditions and not ferromagnetic. Contrary to what is known, we report that elongated nanoparticles of fcc Fe, grown within graphitic nanotubes, remain structurally stable and appear ferromagnetic at room temperature. The magnetic moment (2+/-0.5 microB) in these nanoparticles and the hyperfine fields for two different components of 57Fe (33 and 21 T), measured by Mössbauer spectroscopy, are explained by carbon interstitials in the expanded fcc Fe lattice, that is, FeC(x) where x approximately 0.10, which result in the formation of a dominant Fe4C stoichiometry. First-principles calculations suggest that the ferromagnetism observed in the fcc Fe is related to both lattice expansion and charge transfer between iron and carbon. The understanding of strain- and dopant-induced ferromagnetism in the fcc Fe could lead to the development of new fcc Fe-based alloys for magnetic applications.

Crystallization↗
PubMed2006

Carbon nanotubes as nanoreactors for fabrication of single-crystalline Mg3N2 nanowires.

Due to fast decomposition of Mg3N2 in the presence of water in the atmosphere (Mg3N2+6H2O-->3Mg(OH)2+2NH3), the synthesis of single-crystalline Mg3N2 nanowires has been a challenge. Here, we demonstrate that carbon nanotubes may serve as nanoreactors for a simple thermal reaction process resulting in the first fabrication of high-quality, large-yield, single-crystalline Mg3N2 nanowires. The Mg3N2 nanowires are homogeneously sheathed over their entire lengths with very thin graphitic carbon tubular layers, which effectively prevent their decomposition (even when the samples are put into water or exposed to atmosphere for several months). We have systematically analyzed for the first time the Mg3N2 nanomaterial by means of transmission electron microscopy (TEM), high-resolution TEM, and electron diffraction. Successful fabrication of carbon sheath protected Mg3N2 nanowires may promote further experimental studies on their crystal structures and properties.

Adsorption↗
PubMed2006

Field nanoemitters: ultrathin BN nanosheets protruding from Si3N4 nanowires.

Field emitters in nanoscale are important in micro/nanoelectronic devices. Here, we report a large scale synthesis and effective field emission of field nanoemitters. The integrated nanostructures of ultrathin BN nanosheets aligned on Si3N4 nanowires are prepared through a two-stage process. Si3N4 nanowires were previously synthesized through heating Si powder at 1500 degrees C under a N2 atmosphere. Ultrathin BN nanosheets were then deposited on Si3N4 nanowires by heating a homemade B-N-O precursor under a N2/NH3 atmosphere. The as-prepared nanofilaments act as cold electron emitters displaying excellent field emission performance owing to the untrathin and sharp edges of the protruding BN nanosheets.

Journal Article↗
PubMed2005

Immobilization of proteins on boron nitride nanotubes.

We report for the first time that proteins are immobilized on boron nitride nanotubes. It is found that there is a natural affinity of a protein to BNNT; this means that it can be immobilized on BNNT directly, without usage of an additional coupling reagent. For the most effective immobilization, noncovalently functionalized BNNTs should be used. The effect of immobilization was studied using high-resolution transmission electron microscopy and energy dispersion spectroscopy.

Boron Compounds↗
PubMed2005

Tubular configurations and structure-dependent anisotropic strains in GaS multi-walled sub-microtubes.

Bending strains and bonding structures of GaS multiwalled submicrotubes have been examined by transmission electron microscopy. Experimental observations reveal that the strain involved in building the GaS tubes is more complicated than the theoretical prediction and appears anisotropic and dependent on the tubular configurations. The armchair tube bears a larger lattice compression than the zigzag tube. The hexagonal GaS semiconducting compound degrades its crystal symmetry upon bending, leading to the anisotropy of the bonding structures. Curving of GaS sheets to form tubes is found to be dominated by the structures and electrostatic fields on the sheet surface, which eventually gives a well-controlled tubular structure showing preferred zigzag and close-to-zigzag configurations. Finally, interlayer packing structures of multiwalled tubes are examined.

Journal Article↗
PubMed2005

Porous BCN nanotubular fibers: growth and spatially resolved cathodoluminescence.

Porous boron carbonitride nanotubular fibers with BCN stoichiometry and homogeneous B, C, and N species distribution were fabricated via the CVD method. Spatially resolved cathodoluminescence measurements on individual nanostructures revealed intense ultraviolet emission centered at 319 nm, suggesting the characteristics of a semiconductor with a band gap of 3.89 eV. It is believed that the present nanostructures may have a variety of applications in ultraviolet optical devices, hydrogen storage systems, and field emission apparatus.

Journal Article↗
PubMed2005

Perfectly dissolved boron nitride nanotubes due to polymer wrapping.

We report for the first time that boron nitride nanotubes (BNNTs) may be dissolved in organic solvents by wrapping them with a polymer. Transmission electron microscopy and cathodoluminescence studies indicate the strong pi-pi interactions between BNNTs and the polymer. A band gap ranging from 5.2 to 5.5 eV was documented for the BNNTs independent of their geometrical characteristics by using ultraviolet-visible absorption experiments on composite films and thin BNNT films prepared from solutions.

Journal Article↗
PubMed2005

Involvement of neuropsin in the pathogenesis of experimental autoimmune encephalomyelitis.

Inflammation, demyelination, and axonal damage of the central nervous system (CNS) are major pathological features of multiple sclerosis (MS). Proteolytic digestion of the blood-brain barrier and myelin protein by serine proteases is known to contribute to the development and progression of MS. Neuropsin, a serine protease, has a role in neuronal plasticity, and its expression has been shown to be upregulated in response to injury to the CNS. To determine the possible involvement of neuropsin in demyelinating diseases of the CNS, we examined its expression in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a recognized animal model for MS. Neuropsin mRNA expression was induced in the spinal cord white matter of mice with EAE. Combined in situ hybridization and immunohistochemistry demonstrated that most of the cells expressing neuropsin mRNA showed immunoreactivity for CNPase, a cell-specific marker for oligodendrocytes. Mice lacking neuropsin (neuropsin-/-) exhibited an altered EAE progression characterized by delayed onset and progression of clinical symptoms as compared to wild-type mice. Neuropsin-/- mice also showed attenuated demyelination and delayed oligodendroglial death early during the course of EAE. These observations suggest that neuropsin is involved in the pathogenesis of EAE mediated by demyelination and oligodendroglial death.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2005

Double-helix structure in multiwall boron nitride nanotubes.

A new nanotube structural form is reported that resembles a double helix in multiwall boron nitride nanotubes (MW-BNNT) grown by a carbon-free chemical-vapor-deposition process as documented by evidence obtained by transmission electron diffraction and microscopy. The double-helix structure is found in MW-BNNTs exhibiting the same chirality in its different walls. The MW-BNNTs deviate from the structure of ideal nested coaxial cylindrical tubes. Most significantly, bright- and dark-field electron imaging reveals regular zigzag dark and bright spots on the side walls of the nanotubes. The repeating distance between the bright, or dark, spots is related to the chiral angle of the nanotube. Electron diffraction patterns recorded from individual nanotubes show additional diffraction spots belonging to the 201 zone axes, which are not allowed in a perfectly cylindrical nanotube. These additional diffraction spots become asymmetrical as smaller sections of the nanotube are probed. A series of diffraction patterns recorded along the tube axis showed that the imperfections giving rise to these spots move in a regular fashion around the circumference of the tube. It is shown that all experimental evidence supports the structure model of two helices; one is polygonal in cross section and highly crystalline and the other is circular and less ordered. It is further suggested that the double-helix structure is a result of stronger wall-wall interactions associated with the ionic bonding in boron nitride.

Journal Article↗
PubMed2005

Needlelike bicrystalline GaN nanowires with excellent field emission properties.

Large-yield and crystalline GaN nanowires have been synthesized on a Si substrate via a simple thermal evaporation process. The majority of the GaN nanowires has bicrystalline structures with a needlelike shape, a triangular prism morphology, and a uniform diameter of approximately 100 nm. Field-emission measurements show that the bicrystalline GaN nanowires with sharp tips have a lower turn-on field of approximately 7.5 V/microm and are good candidates for low-cost and large-area electron emitters. It is believed that the excellent filed emission property is attributed to the bicrystalline structure defects and sharp tips.

Journal Article↗
PubMed2005

Liquid gallium columns sheathed with carbon: Bulk synthesis and manipulation.

It is impossible to fabricate isolated gallium nanomaterials due to the low melting point of Ga (29.8 degrees C) and its high reactivity. We report the bulk synthesis of uniform liquid Ga columns encapsulated into carbon nanotubes through high-temperature chemical reaction between Ga and CH4. The diameter of filled Ga liquid columns is approximately 25 nm, and their length is up to several micrometers. The thickness of the carbon sheaths is approximately 6 nm. Simultaneous condensation of a Ga vapor and carbon clusters results in the generation of Ga-filled carbon nanotubes. A convergent 300 kV electron beam generated in a field emission high-resolution electron microscope is demonstrated to be a powerful tool for delicate manipulation of the liquid Ga nanocolumns: they can be gently joined, cut, and sealed within carbon nanotubes. The self-organization of a carbon sheath during the electron-beam irradiation is discussed. The electron-beam irradiation may also become a decent tool for Ga-filled carbon nanotube thermometer calibration.

Journal Article↗