Preparation of one-dimensional polymer films by modification of a hydroxymethylbenzene self-assembled monolayer on iron with alkyltriethoxysilanes for preventing iron corrosion

A self-assembled monolayer (SAM) of p-hydroxymethylbenzene HOCH₂C₆H₄ - (HOMB) moiety adsorbed on iron by the formation of a covalent bond between carbon and iron atoms was prepared by electrochemical derivatization of an iron electrode with p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH₂C₆H₄N₂BF₄. The electrode covered with the HOMB SAM was modified with alkyltriethoxysilanes C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18) to prepare a film of one-dimensional polymer. The protective ability of the polymer film was determined by polarization measurement of the covered electrode in an aerated 0.5 M NaCl solution. The ability was enhanced by modification of the HOMB SAM with C_nTES markedly. The iron surface coated with the one-dimensional polymer film of the HOMB SAM modified with C₈TES was characterized by contact angle measurement and FTIR reflection and X-ray photoelectron spectroscopies. The persistence in the protective ability of the polymer film against iron corrosion in 0.5 M NaCl may be associated with the strong adsorption via the covalent bond, revealed by electron-probe microanalysis.     

Cooperative behavior of various agents in dynamic environment

The multi-agent model is a model in which agents with limited ability cooperate each other to accomplish a goal. In this paper, we introduce a multi-agent model in which agents are created to imitate real ants. There are two different type of agents, each type of which has a particular task. We designed agents to communicate each other by using pheromone considering noise. On this model, we observed cooperative behavior of agents and evaluated conditions to make an order of behavior in the model.     

Cation Effect on the Binary and Ternary Phase Behaviors of Double-Tailed Methanesulfonate Amphiphiles

A series of symmetrical dialkyl methanesulfonate amphiphiles [DiC _n CHSO ₃ ] _m M (n = 6, 7, 8) with different counter cations (M^m+ = H⁺, Li⁺, Na⁺, K⁺, Cu²⁺, Zn²⁺, Mg²⁺, Ca²⁺, Sc³⁺) were synthesized in five steps. Their solubility and critical micelle concentration (CMC) in water were determined highlighting a huge effect of the chain length and the nature of the cation. The hydrophilic–lipophilic balance of the surfactants were assessed with the phase inversion temperature (PIT)-slope method based on the deviation from the PIT of the reference C₁₀E₄/n-octane/0.01 M NaCl_(aq) emulsion through addition of increasing amounts of the dialkyl methanesulfonates. The hydrophilicity of the surfactants was thus ranked in terms of dPIT/dx_sulfonate. A “cation” scan with the [DiC ₆ CHSO ₃ ] _m M /benzene/water systems at f_w = 0.5 was finally performed confirming the hydrophilicity ranking obtained with the PIT-slope method. It revealed that the [DiC ₆ CHSO ₃ ] ₂ Mg behaves as a “Balanced Surfactant” able to form spontaneously a three-phase microemulsion system (Winsor III) just in the presence of water and oil, in the same way as the catalytic surfactant dimethyldioctylammonium molybdate, which has the same PIT-slope.     

Residues important for the function of a multihelical DNA binding domain in the new transcription factor family of Cam and Tet repressors

We report that some prokaryotic repressors including CamR andTetR belong to the same family. CamR and TetR bind to DNA usinga multihelical DNA binding domain (DBD) at the N-termini ofthe proteins, while the C-termini are important for regulatingthe DNA binding in a manner dependent on their co-factors (camphorfor CamR, tetracycline for TetR). In all, 11 important aminoacid positions have been identified in the CamR DBD by the systematicsubstitution of residues by Ala. Of the 11 positions, 10 areeither buried in the core, and thus important for creating thehydrophobic environment, or exposed on the surface, and thusimportant for binding to DNA. The eleventh residue, Gly, seemsto be important for a loop structure. The DNA binding mode ofthis type of DBD and a general mechanism of regulating theirDNA binding are discussed in reference to the crystal structureof TetR [Hinrichs et al., (1994) Science, 264, 418–420].     

Self-assembled monolayers of p-toluene and p-hydroxymethylbenzene moieties adsorbed on iron by the formation of covalent bonds between carbon and iron atoms for protection of iron from corrosion

An iron electrode was modified by electrolytic reduction in deaerated acetonitrile solution of p-toluenediazonium tetrafluoroborate CH₃C₆H₄N₂BF₄ (TDFB) or p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH₂C₆H₄N₂BF₄ (HOTDFB) below 10 °C to form a self-assembled monolayer (SAM) of toluene CH₃C₆H₄- or hydroxymethylbenzene HOCH₂C₆H₄- (HOMB) moiety, probably adsorbed on the electrode by the formation of a covalent bond between carbon and iron atoms, as shown in references. The protective ability of the layer was examined by polarization measurement of the electrode in an aerated 0.5 M NaCl solution. The protective efficiencies of these two SAMs were not high, around 30%, a little higher than that of the toluenethiol CH₃C₆H₄SH SAM which was anchored on iron via a coordinate bond between sulfur and iron atoms. The iron surfaces modified with TDFB and HOTDFB were characterized by contact angle measurement, FTIR reflection spectroscopy and X-ray photoelectron spectroscopy. The persistence in protection of iron against corrosion by coverage with the HOMB SAM was confirmed by polarization measurements after immersion in 0.5 M NaCl for a long period of the time.     

Preparation of a two-dimensional polymer film on passivated iron by modification of a carboxylate ion self-assembled monolayer with alkyltriethoxysilanes for preventing passive film breakdown

The effect of an ultrathin, regularly arranged polymer film on prevention of passive film breakdown on iron in the presence of chloride ion was investigated. The film of two-dimensional polymer was prepared by modification of a 16-hydroxyhexadecanoate ion self-assembled monolayer adsorbed on a passivated iron electrode with 1,2-bis(triethoxysilyl)ethane(C₂H₅O)₃Si(CH₂)₂Si(OC₂H₅)₃ and octyltriethoxysilane C₈H₁₇Si(OC₂H₅)₃. The pitting potentials of the passivated electrodes bare and covered with the polymer film were determined by anodic polarization measurements in a borate buffer solution containing 0.1 M of Cl⁻. The pitting potential of the coated electrode was higher than that of the uncoated one, indicating prevention of passive film breakdown. No breakdown was observed over the potential range in the passive and transpassive regions by covering the passive film with the well-arranged two-dimensional polymer film. The film was characterized by X-ray photoelectron and FTIR reflection spectroscopies and measurement of the contact angle with a drop of water.     

Preparation of self-healing protective films on a zinc electrode treated in a cerium(III) nitrate solution and modified with sodium phosphate and cerium(III) nitrate

Self-healing protective films were prepared on a zinc electrode previously treated in a Ce(NO₃)₃ solution by modification with Na₃PO₄ and Ce(NO₃)₃. The protective and self-healing abilities of the films were examined by polarization measurements and observation of pit formation after the electrode was scratched with a knife-edge crosswise and immersed in oxygenated 0.5 M NaCl at 30 °C for many hours. Mechanisms of the protective and self-healing activities were discussed using X-ray photoelectron spectroscopy and electron-probe microanalysis. The protective and self-healing abilities of the films prepared on the zinc electrode by treatment in the Ce(NO₃)₃ solution and modification with Na₃PO₄ plus Ca(NO₃)₂, Mg(NO₃)₂, Zn(NO₃)₂ or Ce(NO₃)₃ were summarized.     

An application of the 2-nitrobenzenesulfenyl method to proteomic profiling of human colorectal carcinoma: A novel approach for biomarker discovery

In the development of novel biomarkers, the proteomic approach is advantageous because using it the cancer-associated proteins can be directly identified. We previously developed a 2-nitrobenzenesulfenyl (NBS) method to improve quantitative proteome analysis. Here, we applied this method to proteomic profiling of colorectal carcinoma (CRC) to identify novel proteins with altered expression in CRC. Each pair of tumor and normal tissue specimens from 12 CRC patients was analyzed, and approximately 5000 NBS-labeled paired peaks were quantified. Peaks with altered signal intensities (>1.5-fold) and occurring frequently in the samples (>70%) were selected, and 128 proteins were identified by MS/MS analyses as differentially expressed proteins in CRC tissues. Many proteins were newly revealed to be CRC related; 30 were reported in earlier studies of CRC. Six proteins that were up-regulated in CRC (ZYX, RAN, RCN1, AHCY, LGALS1, and VIM) were further characterized and validated by Western blot and immunohistochemistry. All six were found to be CRC-localized, either in cancer cells or in stroma cells near the cancer cells. These results indicate that the proteins identified in this study are novel candidates for CRC markers, and that the NBS method is useful in proteome mining to discover novel biomarkers.     

High-intensity multi-bunch beam generation by a photo-cathode RF gun

A multi-bunch photo-cathode RF gun system has been developed as an electron source for the production of intense quasi-monochromatic X-rays based on inverse Compton scattering. The desired multi-bunch beam is 100 bunches/pulse with a total charge of 500 nC and a bunch spacing of 2.8 ns. We modified the gun cavity of a ‘BNL-type IV’ RF gun to allow a CsTe cathode plug in the end plate. The system uses a four-dipole chicane beam line to allow the injection of laser light normal to the cathode surface. We compensate the gun cavity beam loading caused by the high-intensity multi-bunch electron beam by injecting the laser pulse before RF power has filled the cavity. We have achieved a total intensity of 220 nC in 100 bunches with a bunch-to-bunch energy spread under 1.3% (peak-to-peak). This paper concentrates on experiments to generate the high-intensity multi-bunch beam with compensation of the bunch-to-bunch energy spread due to heavy beam loading.     

Preparation of a crack-free rough titania coating on stainless steel mesh by electrophoretic deposition

TiO₂ (anatase) coating was prepared on stainless mesh by electrophoretic (EPD) process utilizing an isopropyl alcohol (IPA)-based suspension with submicron TiO₂ powder. When the deposition time was 30 s, a smooth thin coating was obtained. It remained crack-free even after sintering. Coating surface morphology was roughened by UV pre-illumination of the suspension. Photocatalytic decomposition of IPA to acetone and resultant electrochemical reaction at cathode during EPD provides heterogeneous deposition.