Synthesis of a photoimmobilizable histidine polymer for surface modification

A novel photoreactive polymer with histidine polar groups was synthesized through the copolymerization of two types of methacrylic acid, one carrying histidine groups and the other carrying azidoaniline groups. The polymer was photoimmobilized on polyester disks for surface modification. The effect of the surface modification on the hydrophilic and biofouling properties was investigated. Static contact angle measurements showed that the polymeric surface was modified to be comparatively hydrophilic in the polymer‐immobilized region. Micropattern immobilization was carried out with a photolithographic method. Atomic force microscopy measurements showed that the polymer was formed on the disks in response to ultraviolet irradiation. Protein adsorption was reduced on the polymer‐immobilized regions, and in those regions, spreading and adhesion of mammalian cells were reduced in comparison with that in nonimmobilized regions. In conclusion, a novel histidine‐containing polymer was photoreactively immobilized on a conventional polymer surface, and it had reduced interaction with proteins and cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Transient phenomena of current and field distortion due to dynamics of packet‐like charges in LDPE films

Simultaneous measurements of space charge and external current were carried out using a PEA measurement system with an electrometer on the back of a grounding electrode in order to clarify the physical situation of a huge packet of positive space charges in LDPE films. A large number of positive charges from a semiconducting anode were accumulated at the interface between LDPE and an Al‐cathode at a mean applied field of 1.5 MV/cm and then finally disappeared. The results of simultaneous measurements showed that the external current kept a relatively high value during charge accumulation and further increased when the charges disappeared. Both the charge dynamics and the external current were restricted by addition of a low‐molecular‐weight paraffin wax, indicating that carrier transport was influenced by the microstructure of the polymer. The dynamics of the residual charges after short‐circuiting is also discussed. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(4): 10–17, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21256     

Effect of re-oxidation on dielectric properties in Ni-MLCC

The effect of re-oxidation treatment on the solubility of dopants and the dielectric properties of rare-earths (La, Ho) and V-substituted BaTiO₃ solid solutions, assuming the shell phase of X7R dielectrics, was investigated. Ho-V-substituted samples showed larger increase of the lattice parameter and T _c by re-oxidation treatment compared with La-V-substituted samples. Electron spin resonance measurements revealed that the oxidation of V³⁺ to V⁴⁺ or V⁵⁺ appeared in the range in which the increase of lattice parameter by re-oxidation treatment was observed. This suggests that the increase of T _c is due to the change of preferential occupational site of Ho ion from A-site to B-site, being accompanied with the oxidation of V³⁺. We also investigated the effect of re-oxidation treatment on the electrical properties and microstructure in Ni-MLCC samples, using rare-earths (La, Ho, Yb) and acceptors (Mn, V) doped BaTiO₃ based X7R dielectrics. The change in temperature characteristic of the dielectric constant by re-oxidation treatment was observed for the MLCC samples containing V with smaller content. In the case of Ho-V- and Yb-V-doped samples showed larger increase of the dielectric constant at around 120 °C compared with La-V-doped samples. The relationship between the microstructure and electrical properties of the MLCC sample was investigated by impedance measurement at elevated temperature.     

Effect of skimmed milk and its fractions on the inactivation of Escherichia coli K12 by high hydrostatic pressure treatment

We investigated the effects of skimmed milk and its protein fractions (casein, whey, globulin, and albumin) on the injury and inactivation of Escherichia coli K-12 by high hydrostatic pressure (HHP) treatment. The protective effect of skimmed milk on HHP-mediated inactivation and injury of E. coli increased with increases in the skimmed milk concentration. However, protein fractions derived from skimmed milk did not exhibit this protective effect. Microscopy analysis by DAPI/PI staining indicated that some cells were localized in the solid portion of skimmed milk, and some of these cells were alive. The coagulated fraction derived from the autoclaved whey fraction also showed a significant protective effect. We speculate that the solid portion in skimmed milk could provide the protective effect to bacterial cells.     

Surface passivation of the thin‐film LAPS with perhydropolysilazane‐derived silica treated by O2 plasma

Here, we describe a novel method for surface passivation of the thin‐film light addressable potentiometric sensor (LAPS). To form a uniform passivation layer, perhydropolysilazane (PHPS) was utilized as a spin‐coatable precursor of silica. After transformation of PHPS into silica by baking, we introduced an O₂ plasma treatment aiming for enhancement of the water resistance of the PHPS‐derived silica (PDS) film by completing the PHPS‐to‐silica conversion. To confirm the effect of the O₂ plasma treatment, the PDS film was deposited on a thin‐film LAPS electrode and tested by immersion in a cell culturing medium. The immersion test demonstrated that the plasma‐treated PDS film could keep the electrode stable longer than the untreated could. With the treated PSD film of 600 nm in thickness, a lifetime of the thin‐film LAPS was estimated at over 2 weeks, which is sufficient for cell culturing experiments. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Dimeric C34 Derivatives Linked through Disulfide Bridges as New HIV-1 Fusion Inhibitors

C34, a 34-mer fragment peptide, is contained in the HIV-1 envelope protein gp41. A dimeric derivative of C34 linked through a disulfide bridge at its C terminus was synthesized and found to display potent anti-HIV activity, comparable with that of a previously reported PEGylated dimer of C34REG. The reduction in the size of the linker moiety for dimerization was thus successful, and this result might shed some light on the mechanism of the suppression of six-helix bundle formation by these C34 dimeric derivatives. Addition of a Gly-Cys(CH₂CONH₂)-Gly-Gly motif at the N-terminal position of a C34 monomeric derivative significantly increased the anti-HIV-1 activity. This moiety functions as a new pharmacophore, and this might provide a useful insight into the design of potent HIV-1 fusion inhibitors.     

Methylcyclohexane production under fluctuating hydrogen flow rate conditions

Energy storage using liquid organic hydrogen carrier (LOHC) is a long-term method to store renewable energy with high hydrogen energy density. This study investigated a simple and low-cost system to produce methylcyclohexane (MCH) from toluene and hydrogen using fluctuating electric power, and developed its control method. In the current system, hydrogen generated by an alkaline water electrolyzer was directly supplied to hydrogenation reactors, where hydrogen purification equipment such as PSA and TSA is not installed to decrease costs. Hydrogen buffer tanks and compressors are not equipped. In order to enable MCH production using fluctuating electricity, a feed-forward toluene supply control method was developed and introduced to the system. The electrolyzer was operated under triangular waves and power generation patterns of photovoltaic cells and produced hydrogen with fluctuating flow rates up to 7.5 Nm³/h. Consequently, relatively high purity of MCH (more than 90% of MCH mole fraction) was successfully produced. Therefore, the simplified system has enough potential to produce MCH using fluctuating renewable electricity.     

Growth of β-Ga2O3 nanocolumns crossing perpendicularly each other on MgO (1 0 0) surface

β-Ga₂O₃ nanocolumns straightened and crossed perpendicularly each other were deposited on MgO (1 0 0) substrate by vapor phase transport method. Growth of the nanocolumns was examined at steps of 1000, 1050, and 1200 °C in elevation of source-boat temperature. We have drawn out the substrate from deposition-tube at each source-boat temperatures of 1000, 1050, and 1200 °C. Scanning electron microscopy of the sample with source-boat temperature of 1200 °C demonstrated that the straightened and elongated nanocolumns are crossing perpendicularly each other. Typical lengths of the nanocolumns were in the range of several hundreds nanometers below 1050 °C, and those of 1200 °C were in the range of ten to fifteen hundreds nanometers. Diameters of the nanocolumns stayed in the range of few hundreds nanometers, notwithstanding variation of the source temperature. X-ray diffraction and transmission electron microscopy with energy dispersive X-ray spectroscopy revealed that the nanocolumns are monoclinic β-Ga₂O₃ crystal, and the (4 0 0) plane of β-Ga₂O₃ nanocolumns is parallel to the (1 0 0) plane of MgO substrate.