Fabrication of Co-W Alloy/Multiwalled Carbon Nanotube Composite Films by Electrodeposition for Improved Frictional Properties

Co-W alloy/multiwalled carbon nanotube (MWCNT) composite films were fabricated using an electrodeposition technique and their microstructures were characterized. A citrate bath was used as the Co-W alloy/MWCNT composite plating bath. A compact Co-W alloy/MWCNT composite film having uniform distribution of MWCNTs without cracks was electrodeposited by adjusting the pH and current density. Frictional properties of the Co-W alloy/MWCNT composite film were evaluated using a ball-on-disk method at room temperature as well as at elevated temperatures (similar to 300 degrees C) without any lubricant. The coefficient of friction of the Co-W alloy/MWCNT composite film was clearly lower than that of a Co-W alloy film with the same tungsten content at room temperature. The coefficient of friction of the Co-W alloy/MWCNT composite film increased with increasing temperature. However, the coefficient of friction of the Co-W alloy/MWCNT composite film was lower than that of a Co-W alloy film with the same tungsten content at elevated temperatures.ArticleECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY. 2(11):M39-M43 (2013)journal articl

Field emission properties of cobalt/multiwalled carbon nanotube composite films fabricated by electrodeposition

Carbon nanotubes (CNT) are promising for use as field emitters. CNT field emitters in which CNTs are attached to a cathode by a metal are highly suitable structures for CNT field emitters. In this study, Co/CNT composite films were fabricated by composite plating for use as field emitters. Four types of multiwalled CNTs (MWCNTs) with different sizes were used as CNT field emitters. The microstructures, electrical conductivity, and field emission properties of the composite films were evaluated. Co/MWCNT composite films were fabricated with homogeneous distributions of relatively large MWCNTs, whereas small MWCNTs tended to form aggregates in the films. The Co/MWCNT composite films, which had lower electrical conductivities than pure cobalt film, exhibited clear field emission. The Co/MWCNT composite films had field emission electric fields in the range of 1.6-1.9 V mu m(-1) at an emission current density of 10 nAcm(-2).ArticleAPPLIED SURFACE SCIENCE. 280:957-961 (2013)journal articl

Frictional and wear properties of cobalt/multiwalled carbon nanotube composite films formed by electrodeposition

Carbon nanotubes (CNTs) have solid lubricity due to their unique structure, and as such, CNT composites are also expected to exhibit superior tribological properties. In this study, Co/CNT composite films were fabricated using a composite electrodeposition technique, and their tribological properties were investigated. Three different sizes of multiwalled carbon nanotubes (MWCNTs) were used as the CNTs in this study. The microstructures of the composite films were examined using scanning electron microscopy. Frictional and wear properties were examined using a ball-on-disk method without any lubricants at room temperature and at high temperatures (100-500 degrees C). The Co/MWCNT composite films had lower coefficients of friction than a cobalt film at room temperature. In contrast, the coefficients of friction of the Co/MWCNT composite film at high temperature became higher than that at room temperature and slightly lower than that of a cobalt film. These results are likely related to the formation of cobalt oxides on the surface and the heat dissipation of the MWCNTs.ArticleSURFACE & COATINGS TECHNOLOGY. 235:204-211 (2013)journal articl

Aplidin (plitidepsin) is a novel anti-myeloma agent with potent anti-resorptive activity mediated by direct effects on osteoclasts

Despite recent progress in its treatment, Multiple Myeloma (MM) remains incurable and its associated bone disease persists even after complete remission. Thus, identification of new therapeutic agents that simultaneously suppress MM growth and protect bone is an unmet need. Herein, we examined the effects of Aplidin, a novel anti-cancer marine-derived compound, on MM and bone cells. In vitro, Aplidin potently inhibited MM cell growth and induced apoptosis, effects that were enhanced by dexamethasone (Dex) and bortezomib (Btz). Aplidin modestly reduced osteocyte/osteoblast viability and decreased osteoblast mineralization, effects that were enhanced by Dex and partially prevented by Btz. Further, Aplidin markedly decreased osteoclast precursor numbers and differentiation, and reduced mature osteoclast number and resorption activity. Moreover, Aplidin reduced Dex-induced osteoclast differentiation and further decreased osteoclast number when combined with Btz. Lastly, Aplidin alone, or suboptimal doses of Aplidin combined with Dex or Btz, decreased tumor growth and bone resorption in ex vivo bone organ cultures that reproduce the 3D-organization and the cellular diversity of the MM/bone marrow niche. These results demonstrate that Aplidin has potent anti-myeloma and anti-resorptive properties, and enhances proteasome inhibitors blockade of MM growth and bone destruction

TGF-β in jaw tumor fluids induces RANKL expression in stromal fibroblasts

Odontogenic tumors and cysts, arising in the jawbones, grow by resorption and destruction of the jawbones. However, mechanisms underlying bone resorption by odontogenic tumors/cysts remain unclear. Odontogenic tumors/cysts comprise odontogenic epithelial cells and stromal fibroblasts, which originate from the developing tooth germ. It has been demonstrated that odontogenic epithelial cells of the developing tooth germ induce osteoclastogenesis to prevent the tooth germ from invading the developing bone to maintain its structure in developing bones. Thus, we hypothesized that odontogenic epithelial cells of odontogenic tumors/cysts induce osteoclast formation, which plays potential roles in tumor/cyst outgrowth into the jawbone. The purpose of this study was to examine osteoclastogenesis by cytokines, focusing on transforming growth factor-β (TGF-β), produced by odontogenic epithelial cells. We observed two pathways for receptor activator of NF-κB ligand (RANKL) induction by keratocystic odontogenic tumor fluid: the cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) pathway through interleukin-1α (IL-1α) signaling and non-COX-2/PGE2 pathway through TGF-β receptor signaling. TGF-β1 and IL-1α produced by odontogenic tumors/cysts induced osteoclastogenesis directly in the osteoclast precursor cells and indirectly via increased RANKL induction in the stroma

Frictional and wear properties of cobalt/multiwalled carbon nanotube composite films formed by electrodeposition

Carbon nanotubes (CNTs) have solid lubricity due to their unique structure, and as such, CNT composites are also expected to exhibit superior tribological properties. In this study, Co/CNT composite films were fabricated using a composite electrodeposition technique, and their tribological properties were investigated. Three different sizes of multiwalled carbon nanotubes (MWCNTs) were used as the CNTs in this study. The microstructures of the composite films were examined using scanning electron microscopy. Frictional and wear properties were examined using a ball-on-disk method without any lubricants at room temperature and at high temperatures (100-500 degrees C). The Co/MWCNT composite films had lower coefficients of friction than a cobalt film at room temperature. In contrast, the coefficients of friction of the Co/MWCNT composite film at high temperature became higher than that at room temperature and slightly lower than that of a cobalt film. These results are likely related to the formation of cobalt oxides on the surface and the heat dissipation of the MWCNTs.ArticleSURFACE & COATINGS TECHNOLOGY. 235:204-211 (2013)journal articl

Increased S1P expression in osteoclasts enhances bone formation in an animal model of Paget's disease

Paget's disease (PD) is characterized by increased numbers of abnormal osteoclasts (OCLs) that drive exuberant bone formation, but the mechanisms responsible for the increased bone formation remain unclear. We previously reported that OCLs from 70% of PD patients express measles virus nucleocapsid protein (MVNP), and that transgenic mice with targeted expression of MVNP in OCLs (MVNP mice) develop bone lesions and abnormal OCLs characteristic of PD. In this report, we examined if OCL-derived sphingosine-1-phosphate (S1P) contributed to the abnormal bone formation in PD, since OCL-derived S1P can act as a coupling factor to increase normal bone formation via binding S1P-receptor-3 (S1PR3) on osteoblasts (OBs). We report that OCLs from MVNP mice and PD patients expressed high levels of sphingosine kinase-1 (SphK-1) compared with wild-type (WT) mouse and normal donor OCLs. SphK-1 production by MVNP-OCLs was interleukin-6 (IL-6)-dependent since OCLs from MVNP/IL-6-/- mice expressed lower levels of SphK-1. Immunohistochemistry of bone biopsies from a normal donor, a PD patient, WT and MVNP mice confirmed increased expression levels of SphK-1 in OCLs and S1PR3 in OBs of the PD patient and MVNP mice compared with normal donor and WT mice. Further, MVNP-OCLs cocultured with OBs from MVNP or WT mice increased OB-S1PR3 expression and enhanced expression of OB differentiation markers in MVNP-OBs precursors compared with WT-OBs, which was mediated by IL-6 and insulin-like growth factor 1 secreted by MVNP-OCLs. Finally, the addition of an S1PR3 antagonist (VPC23019) to WT or MVNP-OBs treated with WT and MVNP-OCL-conditioned media (CM) blocked enhanced OB differentiation of MVNP-OBs treated with MVNP-OCL-CM. In contrast, the addition of the SIPR3 agonist, VPC24191, to the cultures enhanced osterix and Col-1A expression in MVNP-OBs treated with MVNP-OCL-CM compared with WT-OBs treated with WT-OCL-CM. These results suggest that IL-6 produced by PD-OCLs increases S1P in OCLs and S1PR3 on OBs, to increase bone formation in PD