Fabrication of nano/microfiber scaffolds using a combination of rapid prototyping and electrospinning systems

Tissue‐engineered scaffolds require an adequate three‐dimensional (3‐D) structure for cell growth and attachment. Solid freeform fabrication can provide the interconnected pore to induce the cell ingrowth, and electrospinning technique can make the nanofiber web with high surface for cell attachment. In this study, 3‐D polycaprolactone (PCL) scaffolds were fabricated using a rapid prototyping plotting system coupled with an electrospinning apparatus. Scanning electron micrographs showed that these hybrid scaffolds had a regular microfiber structure with interconnected pores and a nanofiber distribution appropriate for cell attachment. Scaffolds were seeded with MG63 cells for in vitro study and implanted in the tibia of rabbit for in vivo study. The resulting structure also facilitated cell adhesion, proliferation, and differentiation as evidenced by biochemical analyses and confocal microscopy. The hybrid scaffolds also exhibited good biocompatibility and osteoconductivity in animal studies. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Pyrolysis and co-pyrolysis of Laminaria japonica and polypropylene over mesoporous Al-SBA-15 catalyst

The catalytic co-pyrolysis of a seaweed biomass, Laminaria japonica, and a typical polymer material, polypropylene, was studied for the first time. A mesoporous material Al-SBA-15 was used as a catalyst. Pyrolysis experiments were conducted using a fixed-bed reactor and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). BET surface area, N₂ adsorption-desorption isotherms, and NH₃ temperature programmed desorption were measured to examine the catalyst characteristics. When only L. japonica was pyrolyzed, catalytic reforming slightly increased the gas yield and decreased the oil yield. The H₂O content in bio-oil was increased by catalytic reforming from 42.03 to 50.32 wt% due to the dehydration reaction occurring on the acid sites inside the large pores of Al-SBA-15. Acids, oxygenates, mono-aromatics, poly aromatic hydrocarbons, and phenolics were the main components of the bio-oil obtained from the pyrolysis of L. japonica. Upon catalytic reforming over Al-SBA-15, the main oxygenate species 1,4-anhydro-d-galactitol and 1,5-anhydro-d-manitol were completely removed. When L. japonica was co-pyrolyzed with polypropylene, the H₂O content in bio-oil was decreased dramatically (8.93 wt% in the case of catalytic co-pyrolysis), contributing to the improvement of the oil quality. A huge increase in the content of gasoline-range and diesel-range hydrocarbons in bio-oil was the most remarkable change that resulted from the co-pyrolysis with polypropylene, suggesting its potential as a transport fuel. The content of mono-aromatics with high economic value was also increased significantly by catalytic co-pyrolysis.     

Flavonoids from Machilus japonica Stems and Their Inhibitory Effects on LDL Oxidation

Stems of Machilus japonica were extracted with 80% aqueous methanol (MeOH) and the concentrated extract was successively extracted with ethyl acetate (EtOAc), normal butanol (n-BuOH), and water. Six flavonoids were isolated from the EtOAc fraction: (+)-taxifolin, afzelin, (−)-epicatechin, 5,3''-di-O-methyl-(−)-epicatechin, 5,7,3''-tri-O-methyl-(−)-epicatechin, and 5,7-di-O-methyl-3'',4''-methylenedioxyflavan-3-ol. The chemical structures were identified using spectroscopic data including NMR, mass spectrometry and infrared spectroscopy. This is the first report of isolation of these six compounds from M. japonica. The compounds were evaluated for their diphenyl picryl hydrazinyl scavenging activity and inhibitory effects on low-density lipoprotein oxidation. Compounds 1 and 3–6 exhibited DPPH antioxidant activity equivalent with that of ascorbic acid, with half maximal inhibitory concentration (IC₅₀) values of 0.16, 0.21, 0.17, 0.15 and 0.07 mM, respectively. The activity of compound 1 was similar to the positive control butylated hydroxytoluene, which had an IC₅₀ value of 1.9 µM, while compounds 3 and 5 showed little activity. Compounds 1, 3, and 5 exhibited LDL antioxidant activity with IC₅₀ values of 2.8, 7.1, and 4.6 µM, respectively.     

Microstructure and electrical conductivity of Mo/TiN composite powder for alkali metal thermal to electric converter electrodes

A Mo/TiN composite powder has been synthesized by a sol–gel method to improve the electrical performance and microstructural stability of the alkali metal thermal to electric converter electrode. The core (TiN)–shell (Mo) structure of the composite powder is confirmed by energy-dispersive X-ray spectroscopy and scanning electron microscopy. The composite powder is primarily composed of submicron (400–800 nm) particles that are coated on a core (>3–5 μm) particle. The Mo/TiN composite electrode exhibits high electrical conductivities of 1000 Scm⁻¹ at 300 °C and 260 Scm⁻¹ at 700  °C in an Ar atmosphere. The electrode exhibits excellent tolerance against grain growth during thermal cycling tests (R.T.↔800 °C), where the average growth rate of Mo grains in the Mo/TiN composite electrodes is controlled less than 0.5%/time (0.62→0.65 μm), while the growth rate in Mo electrodes is 306.7%/time (0.24→3.92 μm). It can be concluded that the Mo/TiN composite powder will suppress the degradation of the electrode and enhance the performance and durability of the unit cell at elevated temperatures.     

Sonochemical Synthesis and Characterization of A Nano-Rod Lead(II) Supramolecular, Three Dimensional Coordination Compound: New Precursor to Produce Pure Phase Nano-Sized Lead(II) Oxide

Nanorods of a lead(II) supramolecular three-dimensional (3D) coordination compound, [Pb(tfpb)₂]_n (1) (Htfpb?=?4,4,4-trifluoro-1-phenyl-1,3-butanedione), was prepared by the sonochemical method. The new nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction, elemental analyses and IR spectroscopy. A single-crystal structure of the compound showed that the coordination number of Pb(II) is eight with six O-donor atoms from the tfpb ligand and two F-donors from anionic ligands. The 3D supramolecular structure of 1 is realized by weak directional C–F···F–C and π–π stacking interactions. After calcination of nano-sized 1 at 500?°C, pure phase nano-sized lead(II) oxide is produced.     

Solvothermal Synthesis of a Nano-sized Aza-aromatic Base Adduct of a Cadmium(II) 4,4-Difluoro-1-phenyl-1,3-butandionate Coordination Compound

A new nano-structured cadmium(II) coordination compound, [Cd(phen)(dfpb)₂] (1) (phen?=?1,10-phenanthroline, dfpb?=?4,4-difluoro-1-phenyl-1,3-butandion), was synthesized by a solvothermal method and produced a coordination polymer in the nano-size range. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction elemental analysis and IR spectroscopy. Compound 1 was structurally characterised by single crystal X-ray diffraction. The single crystal structure shows a coordination number for the Cd ion of six with two N-donor atoms from the phen ligand and four O-donors from the two dfpb moieties. Self-assembly occurs by CH····F–C and π–π stacking interactions. The supramolecular features in these complexes are controlled by weak directional intermolecular interactions.     

Enhanced mechanical properties and pre-tension effects of polyurethane (PU) nanofiber filaments prepared by electrospinning and dry twisting

We studied the mechanical properties of polyurethane (PU) nanofiber filaments prepared by electrospinning and dry twisting, and compared them with those of the corresponding nonwoven PU nanofiber webs. The morphologies and mechanical properties of the nonwoven PU nanofiber webs and the corresponding PU nanofiber filaments were investigated by scanning electron microscopy (SEM) and through the use of a universal testing machine (UTM), respectively. The tensile strength and the Young’s modulus of the nanofiber filaments improved dramatically as the number of twists or the width of the nanofiber webs was increased compared with the nonwoven PU nanofibers. Moreover, it was found that applying pre-tension was an effective method of increasing the mechanical properties of PU nanofiber filaments.     

Influence of Y2O3 addition on electrical properties of β-SiC ceramics sintered in nitrogen atmosphere

The influence of Y₂O₃ addition on electrical properties of β-SiC ceramics has been investigated. Polycrystalline SiC samples obtained by hot-pressing SiC–Y₂O₃ powder mixtures in nitrogen (N) atmosphere contain Y₂O₃ clusters segregated between SiC grains. Y₂O₃ forms a Y–Si-oxycarbonitride phase during sintering by reacting with SiO₂ and SiC and by dissolution of N from the atmosphere; this induces N doping into the SiC grains during the process of grain growth. The SiC samples exhibit an electrical resistivity of ～10^?3 Ω cm and a carrier density of ～10²⁰ cm^?3, which are ascribed to donor states derived from N impurities. The increase in defect density with increasing Y₂O₃ content is likely to be a main limiting factor of the electrical conductivity of SiC ceramics.     

Effect of grain size on the mechanical properties and crack formation of HPFRCC containing deformed steel fibers

This research investigated the influence of sand grain size on the behavior of high-performance fiber-reinforced cementitious composites (HPFRCC). Four types of sand with different grain sizes were investigated using the same matrix composition containing 2.0% hooked and twisted fibers by volume. The compressive strength was significantly greater for the finer sand grains, despite little difference in the packing density. The better compressive strength was mainly due to the denser calcium silicate hydrate (CSH) resulting from an intensive pozzolanic reaction with the finer silica sand, rather than to an improvement in packing density. The interfacial bond strength of those fibers was notably improved, having favorable effects on the mechanical properties and multiple crack formation of HPFRCCs. Although both fibers showed superior properties in mortars with a finer sand grain, twisted fiber produced more sensitive behavior according to the sand grain size.