Biomimetic Zirconia with Cactus-Inspired Meso-Scale Spikes and Nano-Trabeculae for Enhanced Bone Integration

Biomimetic design provides novel opportunities for enhancing and functionalizing biomaterials. Here we created a zirconia surface with cactus-inspired meso-scale spikes and bone-inspired nano-scale trabecular architecture and examined its biological activity in bone generation and integration. Crisscrossing laser etching successfully engraved 60 μm wide, cactus-inspired spikes on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) with 200–300 nm trabecular bone-inspired interwoven structures on the entire surface. The height of the spikes was varied from 20 to 80 μm for optimization. Average roughness (Sa) increased from 0.10 μm (polished smooth surface) to 18.14 μm (80 μm-high spikes), while the surface area increased by up to 4.43 times. The measured dimensions of the spikes almost perfectly correlated with their estimated dimensions (R² = 0.998). The dimensional error of forming the architecture was 1% as a coefficient of variation. Bone marrow-derived osteoblasts were cultured on a polished surface and on meso- and nano-scale hybrid textured surfaces with different spike heights. The osteoblastic differentiation was significantly promoted on the hybrid-textured surfaces compared with the polished surface, and among them the hybrid-textured surface with 40 μm-high spikes showed unparalleled performance. In vivo bone-implant integration also peaked when the hybrid-textured surface had 40 μm-high spikes. The relationships between the spike height and measures of osteoblast differentiation and the strength of bone and implant integration were non-linear. The controllable creation of meso- and nano-scale hybrid biomimetic surfaces established in this study may provide a novel technological platform and design strategy for future development of biomaterial surfaces to improve bone integration and regeneration.     

Effects of Neodymium Concentration on Optical Characteristics of Polycrystalline Nd:YAG Laser Materials

A neodymium-doped yttrium-aluminum garnet (Y₃A1₅O₁₂, YAG) (Nd:YAG) ceramic that contained 0.3–4.8 at.% neodymium additives and exhibited nearly the same optical properties as those of a single crystal was fabricated by a solid-state reaction method using high-purity powders. Although the integrated absorption intensity of the ²H_9/2+⁴F_5/2 bands simply increased as the neodymium concentration in the YAG ceramics decreased, the fluorescence intensity of the 2.4 at.% Nd:YAG ceramic was the strongest among Nd:YAG ceramics with various neodymium concentrations and a 0.9 at.% Nd:YAG single crystal. An oscillation experiment was performed on a continuous-wave (cw) laser with a diode-laser exciting system using those ceramics and the single crystal. The oscillation threshold and slope efficiency in that analysis were 309 mW and 28%, respectively, for the 1.1 at.% Nd:YAG ceramics and 356 mW and 40%, respectively, for the 2.4 at.% Nd:YAG ceramics. The lasing characteristics of the ceramics in the present work were superior to those of a 0.9 at.% Nd:YAG single crystal that was fabricated by the Czochralski (Cz) method.     

Densification of rare-earth (Lu, Gd, Nd)-doped alumina nanopowders obtained by a sol-gel route under seeding

Rare-earth (RE: Lu, Gd, Nd, 0.10 mol%)-doped alumina nanopowders were prepared by a new sol-gel route using polyhydroxoaluminum (PHA) and RECl₃ solutions under α-alumina (∼ 75 nm) seeding. Among the rare-earth dopants studied, Lu yields the most suitable nanopowders for low-temperature densification. The 0.10 mol% Lu-doped nanopowders, which were obtained at a calcination temperature of 900 °C under 5 mass% α-alumina seeding, consisted of ∼ 80-nm α-alumina particles and γ-alumina nanoparticles. Using these Lu-doped alumina nanopowders, fully densified alumina ceramics with a uniform microstructure composed of fine grains with an average size of 0.61 μm could be obtained at 1400 °C by pressureless sintering. Clearly, the Lu-doped nanopowders obtained here represent a viable option for fabricating dense, finer-grained alumina ceramics because an undoped sample with 5 mass% seeds gave a microstructure with an average grain size of 1.78 μm at 1400 °C.     

Fabrication of submicron alumina ceramics by pulse electric current sintering using M2+ (M = Mg,Ca, Ni)-doped alumina nanopowders

Dense submicron-grained alumina ceramics were fabricated by pulse electric current sintering (PECS) using M²⁺(M: Mg, Ca, Ni)-doped alumina nanopowders at 1250 °C under a uniaxial pressure of 80 MPa. The M²⁺-doped alumina nanopowders (0–0.10 mass%) were prepared through a new sol–gel route using high-purity polyhydroxoaluminum (PHA) and MCl₂ solutions as starting materials. The composite gels obtained were calcined at 900 °C and ground by planetary ball milling. The powders were re-calcined at 900 °C to increase the content of α-alumina particles, which act as seeding for low-temperature densification. Densification and microstructural development depend on the M²⁺ dopant species. Dense alumina ceramics (relative density ≥99.0%) thus obtained had a uniform microstructure composed of fine grains, where the average grain size developed for non-doped, Ni-doped, Mg-doped and Ca-doped samples was 0.67, 0.67, 0.47 and 0.30 μm, respectively, showing that Ca-doping is the most promising method for tailoring of nanocrystalline alumina ceramics.     

Preparation of novel porous solids from alumina-pillared fluorine micas by acid-treatment

New porous solids from alumina-pillared fluorine micas (APMs), which were obtained from synthetic Na-tetrasilicic fluorine mica [NaMg_2.5Si₄O₁₀F₂], were prepared by sulfuric acid-treatment under mild conditions at 25 °C. The products were investigated by XRD, ICP, SEM, TEM and N₂ adsorption–desorption isotherm at 77 K. XRD measurements indicated that the interlayer pillared structure having a large basal spacing collapsed during the early stages of the acid-treatment. ICP analyses indicated that Al³⁺ and Mg²⁺ ions were leached out from the pillared micas during the acid-treatment. The pore properties of the leached products were found to differ from those of the mother pillared micas: the acid leaching of the pillared micas leads to the formation of mesopores around 3.2 nm in diameter. The correlation between the change in pore properties and cation elution behavior suggests that the mesopore formation results from the leaching of Mg²⁺ ions from the octahedral sheet of the pillared micas. The leached products thus obtained retained the flaky morphology of the mother pillared micas. These results show that the mild acid-treatment using APMs provides a novel route for obtaining unique mesopore solids having the large particle sizes of the mother micas.     

A Nifedipine Coground Mixture with Sodium Deoxycholate. II. Dissolution Characteristics and Stability

Nifedipine is a poorly water soluble drug that demonstrates low bioavailability. In a previous study, a coground mixture of nifedipine with sodium deoxycholate (DCNa), a bile salt, immediately produced colloidal particles when dispersed in water. In this study, the effect of the weight fraction of DCNa, grinding time, dissolution media, and storage conditions on colloidal particle formation in solution was investigated. The coground mixture was prepared with a vibration rod mill, and its solid state was characterized using powder X-ray diffraction. A laser diffraction particle size analyzer was used to determine the particle size distribution curve in water. The size of particles formed in solution decreased with an increase in the weight fraction of DCNa and grinding time. A nifedipine-DCNa (1 : 2 w/w) mixture coground for 30 min was used in the experiments. Colloidal particle formation from the coground mixture was also observed in dissolution media of water and a pH 6.8 buffer solution at 37°C. Most precipitates passed through a filter with a pore size of 0.8 μm, but the particle size distribution in water was different from that in the pH 6.8 buffer solution. DCNa exhibited not only micellar solubilization for drug crystals, but also a retarding effect on drug crystal growth in a supersaturated solution. The latter effect could serve to form colloidal particles in solution. When stored under 75% relative humidity at 40°C for 1 month, the amorphous coground mixture crystallized, and the particle size in water markedly increased. Therefore, the weight fraction of DCNa, grinding time, dissolution media, and humidity during storage influence the dissolution characteristics of nifedipine from a coground mixture.     

Crystal growth of MgAlB14-type compounds using metal salts and some properties

LEAlB₁₄ (orthorhombic, Imam) (LE = Li, Mg) crystals were grown using metal salts (Li₂CO₃, LiF, LiI, MgO, MgF₂, MgI₂) and crystalline boron from a high-temperature aluminium metal flux. The growth conditions for growing LEAlB₁₄ were established using the starting mixtures of B/LE = 2.0, and Al metal was added to each mixture at a mass ratio of 1:15–20. LEAlB₁₄ crystals from the Al-self flux using metal salts could be obtained from all the different salts. The maximum dimensions of LiAlB₁₄ and MgAlB₁₄ crystals were approximately 18 and 12 mm for the crystals obtained from LiF and MgF₂. The unit-cell parameters of as-grown LEAlB₁₄ are as follows: for LiAlB₁₄, obtained from LiF, a = 0.5846 (2) nm, b = 0.8144 (2) nm, c = 1.0355 (3) nm, V = 0.4930 (2) nm³: for MgAlB₁₄, obtained from MgF₂, a = 0.5845 (2) nm, b = 0.8114 (2) nm, c = 1.0330 (3) nm, V = 0.4899 (3) nm³. Microhardness, oxidation resistance and magnetic susceptibility of these materials are described in detail.     

Researcher dynamics in the generation of emerging topics in life sciences and medicine

Understanding the driving forces that generate emerging topics (ETs or Emerging Research Topics) will assist in the sound development of science and technologies. In the present study, we aim to clarify the researcher dynamics of generating and developing ETs in life sciences and medicine over the past half-century by analyzing the pre-, contemporary-, and post-participation of researchers publishing articles containing the emerging keywords that are elements of ETs. Our results suggest that, while manpower needs for publication have increased, less manpower is actually required to generate ETs these days and that pre-participation in certain research topics has become important to generate regular ETs but not Nobel Prize-class ones. Finally, we discovered that, in this post-genomic era, those researchers who generate ETs also continue to focus on those fields. These trends illustrate a mode shift in the scientific practice of researchers that have generated and developed ETs over the last 50 years as well as highlight the significance of funding projects with high probabilities of generating high-impact ETs.

     

Microstructure and superconducting properties of rapidly-quenched copper-based alloys containing immiscible lead and bismuth elements

Copper-based superconducting alloys including finely dispersed f c c lead or h c p (Pb- Bi) particles in f c c copper matrix have been obtained by rapid quenching (Cu-M)_100-x Pb_x and (Cu-M)_100-x (Pb_0.6Bi_{0.4 x} (M = aluminium, silicon or tin;x < 10 at%) alloys containing immiscible elements such as lead and bismuth. The particle size and interparticle distance were about 30 to 130 nm and 20 to 200 nm for had particles and about 30 to 60 nm and 30 to 150 nm for (Pb- Bi) particles. The transition temperature,T _c, was in the range of 3.2 to 5.5 K for the Cu-M-Pb alloys and 6.2 to 6.3 K for the Cu-M-Pb-Bi alloys. Critical magnetic field,H _c2, and critical current density,J _c, for the later alloys were 0.47 to 0.93T at 4.2 K and 1.1 × 10⁵ to 2.7 × 10⁵ Am^–2 at zero applied field and 4.21 K. The mechanism of the appearance of such a soft-type superconductivity for the rapidly quenched copper-based alloys was discussed, and inferred to be due to the formation of a percolation path of a superconducting lead or Pb-Bi phase along the grain boundaries, sub-boundaries and/or tangled dislocations where the lead or Pb-Bi phase precipitated preferentially, rather than the proximity effect based on lead or Pb-Bi particles.     

Study on triazine thiols. IV. Action of triazine thiols and their metal salts to peroxide

Decomposition of t-butylhydroperoxide was retarded by triazine thiols and their zinc salts, but accelerated by the copper salts of triazine thiols as well as sulfur compounds such as dithiocarbamates and mercaptobenzothiazolates. Triazine thiols and their zine salts are effective antioxidants for polyethylene crosslinked with peroxide and containing copper, and for protecting epichlorohydrin vulcanizates against attack by “sour” or hydroperoxide-containing gasoline.