Low-Friction Coatings of Zinc Oxide Synthesized by Optimization of Crystal Preferred Orientation

The crystal preferred orientation of zinc oxide (ZnO) coatings on stainless steel substrates was precisely controlled by a combinatorial sputter-coating system. ZnO coatings were analyzed by X-ray diffraction spectroscopy, and surface and interfacial cutting analysis methods. The frictional properties of the coatings in a vacuum, the atmosphere, oil of n-hexadecane, and oil doped with palmitic acid molecules were observed. Different frictional behaviors of the ZnO coatings were observed by varying the crystal preferred orientation. A low-friction coefficient as less as 0.2 was realized by ZnO coatings with uni- and multi-crystal orientation in all of those conditions. Inverse proportion of the friction coefficient to normal load was observed on ZnO coatings with bi-orientation of (002) and (103) in pure and palmitic acid doped oil.     

Low Frictional Coating of Copper Oxide with Preferred Crystal Orientation

Coating films of copper oxide were synthesized on stainless steel substrates with a r.f. magnetron sputter. The composition of the films could be controlled by changing a gas ratio of oxygen and argon in sputter plasma, which was analyzed with X-ray diffraction spectroscopy. Frictional property of the films in an atmospheric pressure and in an ultra high vacuum (UHV) was measured with a pin-on-disk vacuum tribometer. Frictional coefficients of the film as low as 0.03 and 0.05 were achieved in an atmospheric pressure and in UHV, respectively. It is therefore, expected that the films are applicable to smooth-drive movable materials for ultimate conditions such as UHV and high temperature.     

Suppression of Bone Necrosis around Tooth Extraction Socket in a MRONJ-like Mouse Model by E-rhBMP-2 Containing Artificial Bone Graft Administration

Medication-related osteonecrosis of the jaw (MRONJ) is related to impaired bone healing conditions in the maxillomandibular bone region as a complication of bisphosphonate intake. Although there are several hypotheses for the onset of MRONJ symptoms, one of the possible causes is the inhibition of bone turnover and blood supply leading to bone necrosis. The optimal treatment strategy for MRONJ has not been established either. BMP-2, a member of the TGF-β superfamily, is well known for regulating bone remodeling and homeostasis prenatally and postnatally. Therefore, the objectives of this study were to evaluate whether cyclophosphamide/zoledronate (CY/ZA) induces necrosis of the bone surrounding the tooth extraction socket, and to examine the therapeutic potential of BMP-2 in combination with the hard osteoinductive biomaterial, β-tricalcium phosphate (β-TCP), in the prevention and treatment of alveolar bone loss around the tooth extraction socket in MRONJ-like mice models. First, CY/ZA was intraperitoneally administered for three weeks, and alveolar bone necrosis was evaluated before and after tooth extraction. Next, the effect of BMP-2/β-TCP was investigated in both MRONJ-like prevention and treatment models. In the prevention model, CY/ZA was continuously administered for four weeks after BMP-2/β-TCP transplantation. In the treatment model, CY/ZA administration was suspended after transplantation of BMP-2/β-TCP. The results showed that CY/ZA induced a significant decrease in the number of empty lacunae, a sign of bone necrosis, in the alveolar bone around the tooth extraction socket after tooth extraction. Histological analysis showed a significant decrease in the necrotic alveolar bone around tooth extraction sockets in the BMP-2/β-TCP transplantation group compared to the non-transplanted control group in both MRONJ-like prevention and treatment models. However, bone mineral density, determined by micro-CT analysis, was significantly higher in the BMP-2/β-TCP transplanted group than in the control group in the prevention model only. These results clarified that alveolar bone necrosis around tooth extraction sockets can be induced after surgical intervention under CY/ZA administration. In addition, transplantation of BMP-2/β-TCP reduced the necrotic alveolar bone around the tooth extraction socket. Therefore, a combination of BMP-2/β-TCP could be an alternative approach for both prevention and treatment of MRONJ-like symptoms.     

Histidine Ligated Iron-Sulfur Peptides

Iron-sulfur clusters are thought to be ancient cofactors that could have played a role in early protometabolic systems. Thus far, redox active, prebiotically plausible iron-sulfur clusters have always contained cysteine ligands to the cluster. However, extant iron-sulfur proteins can be found to exploit other modes of binding, including ligation by histidine residues, as seen with [2Fe-2S] Rieske and MitoNEET proteins. Here, we investigated the ability of cysteine- and histidine-containing peptides to coordinate a mononuclear Fe²⁺ center and a [2Fe-2S] cluster and compare their properties with purified iron-sulfur proteins. The iron-sulfur peptides were characterized by UV-vis, circular dichroism, and paramagnetic NMR spectroscopies and cyclic voltammetry. Small (≤6 amino acids) peptides can coordinate [2Fe-2S] clusters through a combination of cysteine and histidine residues with similar reduction potentials as their corresponding proteins. Such complexes may have been important for early cell-like systems.     

Photocatalytic properties of titanium dioxide sputtered on a nanostructured substrate

The effective one-step physical approach is demonstrated for the fabrication of anatase titanium dioxide nanotubes through r.f. magnetron sputtering of TiO₂ on a highly ordered nanoporous anodic alumina template. The nanostructured TiO₂ benefited from the combination of unique properties of both the sputtering technique that provided well-controlled environment for the fabrication of anatase phase TiO₂ and the porous anodic alumina (PAA) that provided uniform and ordered nanopores. The photocatalytic properties of TiO₂ films were characterized following the degradation of methylene blue molecules under UV light irradiation. The photocatalytic activity of the nanostructured TiO₂ films has been found to be approximately twice higher in comparison with the flat TiO₂ films fabricated at the same conditions.     

Free radicals of phenothiazine and related compounds. III. Selective Chlorination of Phenothiazines with Copper(II) Chloride

The preferential introduction of chlorine atoms in position 1 of the phenothiazine ring by means of Cu(II) chloride is described.     

Frictional property with preferred crystal orientation of platinum oxide and palladium oxide coatings synthesized by combinatorial sputter coating system

The combinatorial sputter coating system (COSCOS) has been newly developed, that can fabricate various kinds of coatings under precisely controlled lots of conditions such as selection of sputter gas and gas pressure, gas partial pressure, r.f. power, substrate temperature, distance between a substrate and a target, etc. COSCOS can also control the crystal preferred orientation of coatings which strongly affect those frictional property. Platinum oxide and palladium oxide coatings were synthesized by COSCOS, then the crystal structure was analyzed with X-ray diffraction spectroscopy and frictional properties of the coatings were measured by a tribometer at an atmospheric pressure.