Synthesis and characterization of metal ions containing hydroxyapatite microparticles with high specific surface area

Zinc and/or iron ions containing hydroxyapatite (HA) microparticles, which had twice as high specific surface area and higher pore volumes compared with the pure HA, were fabricated by a spray drying method; the zinc and/or iron ions were incorporated into the constitutional nanocrystals with below 20 nm in size in preparing. The small amount of carbonate ions was substituted in the phosphate group. The particle sizes were distributed in the range of 1 to 20 microm in diameter and its averaged size was approximately 6 microm. The microparticles with a spherical shape showed a single phase of HA and, after treated at higher temperature than 800 degrees C, had the high crystallite HA and the other phase of metal oxide such as ZnO or Fe2O3. The microparticles with higher specific surface area will be applicable for the drug delivery carriers of proteins.     

Drug-supported microparticles of calcium carbonate nanocrystals and its covering with hydroxyapatite

Drug-supported spherical microparticles with below 3 microm in diameter of calcium carbonate (CC) nanocrystals were precipitated by a complex decomposition method from Na2CO3 and CaCl2 solutions with hydrocortisone phosphate (HyC). The HyC was completely incorporated into the microparticles and was adsorbed on the surface of nanocrystals. The crystal phases of vaterite and calcite were controlled by the addition of magnesium ions. Spherical microparticles of calcite cores and petal-shaped hydroxyapatite (HAp) outer layers were fabricated by soaking calcite into the SBF, or a supersaturated solution of phosphate ions to enhance the crystal growth of HAp.     

Encapsulation of hemoglobin in mesoporous silica (FSM)-enhanced thermal stability and resistance to denaturants

Hemoblogin (Hb), which is a typical oligomeric protein, was introduced into the pores of mesoporous silica (FSM: folded-sheet mesoporous material) that had a diameter of 7.5 nm. Soret CD spectra of Hb-FSM-7.5 conjugates showed a peak that was identical to that of free Hb. This suggests that Hb retained its highly ordered structure in the mesoporous silica. In addition, the UV-visible absorption spectrum showed that Hb had an increased resistance to heat denaturation in the silica. Even after heat treatment at 85 degrees C, Hb-FSM-7.5 retained its ligand-binding activity. The stability of Hb-FSM-7.5 was examined further by measuring its peroxidase-like activity. Encapsulation of Hb resulted in the retention of activity in the presence of high NaCl or Gdn-HCl levels. This suggests that encapsulation prevented dissociation and denaturing. Thus, it seems that the mesopores created a favorable environment for the oligomeric protein to perform its function, even under harsh conditions.     

Chemically fixed nurse cells for culturing murine or primate embryonic stem cells

In current and past practice, murine or primate embryonic stem (ES) cells are usually cultured on live nurse cells for growth that keeps the cells in an undifferentiated state. It is troublesome, however, to prepare nurse cells for each cell culture and it is difficult to completely remove the nurse cells when they are transferred. In this study, mouse and monkey ES cells were therefore grown on chemically fixed mouse embryonic fibroblast (MEF) or human amniotic epithelial (HAE) cells. MEF cells were fixed by incubation in a glutaraldehyde or formaldehyde solution. HAE cells were immortalized by transfection of hTERT and chemically fixed with the same reagents. When mouse ES cells were cultured on these chemically fixed cells, the mouse ES cells grew well and expressed alkaline phosphatase, SSEA-1, and Oct-3/4 as their markers, indicating their undifferentiated state. The monkey ES cells also grew well and expressed alkaline phosphatase, SSEA-4, and Oct-4 as their markers, indicating their undifferentiated state. Freeze-drying HAE or MEF cells did not change their ability to support the undifferentiated growth of ES cells. Additionally, the chemically fixed cells could be utilized repeatedly in the culture of ES cells. These results demonstrate that chemically fixed nurse cells are useful for the maintenance of ES cells in an undifferentiated state in culture.     

Fluorinated ethylene carbonate as electrolyte additive for rechargeable Na batteries

Fluoroethylene carbonate is an efficient electrolyte additive to improve the reversibility of electrochemical sodium insertion for hard-carbon and NaNi(1/2)Mn(1/2)O(2) electrodes in aprotic Na cells. The additive is also capable of the electrochemical deposition/dissolution of metallic Na with higher reversibility because of improved passivation and suppression of side reactions between Na metal and propylene carbonate solution containing Na salts.     

Electrochemical Na Insertion and Solid Electrolyte Interphase for Hard‐Carbon Electrodes and Application to Na‐Ion Batteries

Recently, lithium‐ion batteries have been attracting more interest for use in automotive applications. Lithium resources are confirmed to be unevenly distributed in South America, and the cost of the lithium raw materials has roughly doubled from the first practical application in 1991 to the present and is increasing due to global demand for lithium‐ion accumulators. Since the electrochemical equivalent and standard potential of sodium are the most advantageous after lithium, sodium based energy storage is of great interest to realize lithium‐free high energy and high voltage batteries. However, to the best of our knowledge, there have been no successful reports on electrochemical sodium insertion materials for battery applications; the major challenge is the negative electrode and its passivation. In this study, we achieve high capacity and excellent reversibility sodium‐insertion performance of hard‐carbon and layered NaNi_0.5Mn_0.5O₂ electrodes in propylene carbonate electrolyte solutions. The structural change and passivation for hard‐carbon are investigated to study the reversible sodium insertion. The 3‐volt secondary Na‐ion battery possessing environmental and cost friendliness, Na⁺‐shuttlecock hard‐carbon/NaNi_0.5Mn_0.5O₂ cell, demonstrates steady cycling performance as next generation secondary batteries and an alternative to Li‐ion batteries.     

Production of Solar-grade Silicon by Halidothermic Reduction of Silicon Tetrachloride

To develop a new production process for solar-grade Si, a fundamental study on halidothermic reduction based on the subhalide reduction of SiCl₄ by Al subchloride reductant was carried out at 1273 K (1000 °C). Aluminum subchloride reductant was produced by reacting AlCl₃ vapor with metallic Al. Silicon tetrachloride was reduced to Si in a gas-phase reaction by vapors of Al subchloride reductant. Silicon deposits produced in the halidothermic reduction were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray fluorescence (XRF). The Al content in the Si deposits was no more than 0.5 at pct. The Si deposits have a fibrous or hexagonal columnar morphology with diameters ranging from 100 nm to several tens of microns. The reaction was discussed by comparison with the results of the conventional aluminothermic reduction of SiCl₄. Moreover, the halidothermic reduction reactions were analyzed from thermodynamical viewpoints. This study demonstrates the feasibility of a halidothermic reduction for producing solar-grade Si with high productivity.     

Position Dependence of SS304 and Iron Phases in Welded Specimen by Neutron Diffraction and Bragg-Edge Transmission Method

We investigated the nondestructive examination method by neutron scattering. A welded plate of SS304 (fcc) and iron (bcc) was investigated using neutron diffraction and the Bragg-edge transmission method. We tried to clear the positions of the welded area, SS304 phase, and iron phase and to determine the lattice spacing. The determined value of d ₁₁₁ for SS304 is 2.07471(8) Å using neutron diffraction. With Bragg-edge transmission, it is possible to collect the information of a specimen as two-dimensional (2-D) images using a 2-D position sensitive detector at a pulse neutron source. The determined d ₁₁₁ of SS304 phase indicates between 2.0745(8) and 2.0752(9) Å depending on the measurement points using Bragg-edge transmission. The same tendency was also seen in iron phase. The determined d ₁₁₀ of the iron phase is 2.02802(1) Å using neutron diffraction. The determined d ₁₁₀ of iron phase indicates between 2.0266(7) and 2.0321(13) Å using Bragg-edge transmission. The determined d using diffraction exists within that of Bragg-edge transmission. In order to clarify the position dependency of the phase and lattice spacing, the combined diffraction and Bragg-edge transmission is effective.     

Efficient growth of multi-walled carbon nanotubes by continuous-wave laser vaporization of graphite containing B4C

Multi-walled carbon nanotubes (MWCNTs), 7–70 nm thick and up to 30 μm long, were efficiently grown by room-temperature continuous-wave laser vaporization of a graphite target containing B₄C in an ambient Ar gas. Adjusting the boron content in the target and Ar gas pressure resulted in a maximum fraction of ∼60% of MWCNTs in the deposits. The straightness of the MWCNTs and graphene layers with an interlayer spacing of ∼0.35 nm indicated that the degree of graphitization was fairly high in the grown MWCNTs. However, the features of D, G, and 2D bands in the Raman spectrum of a deposit suggested boron doping in the MWCNTs. An apparent Young’s modulus of a grown MWCNT was measured to be 0.68 TPa and comparable to those of heat-treated vapor grown carbon nanofibers. MWCNTs are thought to grow on molten boron carbide particles acting as seeds at high temperatures of up to ∼2400 °C.