ZrO2-Y2O3-Al2O3 nanocrystalline powders with different grain sizes have been synthesized using a chemical coprecipitation method. Nano-powders were compacted uniaxially and densified in a vacuum hot-pressing furnace. Density, pore size distribution, grain size and composition of the composites were determined by various techniques, including BET gas absorption, field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). It has been shown that the porosity, grain and pore size of the ceramics can be controlled by the initial powder size and sintering temperature. Fully densified ceramics with narrow grain size distribution in the range of 100 ∼ 500 nm could be obtained.
Background: Umbilical cord-derived mesenchymal stem cells (UC-MSCs) are considered to be multipotent mesenchymal stem cells that are easily induced to differentiate into functional osteoblasts both in vitro and in vivo. Osterix (Osx), a novel zinc-⃞nger-containing transcription factor of the Sp family, is required for osteoblast differentiation and bone formation.
Objective: We investigated the effect of Osx on the proliferation and osteogenic differentiation of the UC-MSCs.
Method: The primary UC-MSCs were isolated and cultured. An Osx-expressing plasmid (pEGFP-Osx) was constructed and transfected into UC-MSCs. Then expression of bone morphogenesis-related genes, proliferation rate, alkaline phosphatase activity, and mineralization were examined to evaluate the osteogenic potential of the Osx gene-modified UC-MSCs.
Result: UC-MSCs transfected with pEGFP-Osx exhibited apparent osteogenic differentiation as determined by increased activity of alkaline phosphatase, the formation of mineralized nodules and the expression of related osteoblastic genes.
Conclusion: These results confirmed the ability of Osx to enhance osteoblast differentiation of UC-MSCs in vitro, and the Osx gene-modified UC-MSCs are potential as novel cell resources of bone tissue engineering.
The present work was a study on global reaction rate of methanol synthesis. We measured experimentally the global reaction rate in the internal recycle gradientless reactor over catalyst SC309. The diffusion-reaction model of methanol synthesis was suggested. For model we chose the hydrogenation of CO and CO2 as key reaction. CO and CO2 were key components in our model. The internal diffusion effectiveness factors of CO and CO2 in the catalyst were calculated by the numerical integration. A comparison with the experiment showed that all the absolute values of the relative error were less than 10%. The simulation results showed that decreasing reaction temperature and catalyst diameter were conducive to reduce the influence of the internal diffusion on the methanol synthesis.
Zn0.7Co0.3(Ti1-xSnx)Nb2O8 (x = 0.1, 0.15, 0.2, 0.25, 0.3, 0.35) microwave ceramics were prepared by traditional solidstate reaction method. The influences of Sn substituted for Ti on the phase constitution, crystal structure and microwave dielectric properties of Zn0.7Co0.3(Ti1-xSnx)Nb2O8 ceramics were discussed. The XRD patterns revealed the main phase of ZnTiNb2O8 and little content of Zn0.17Ti0.5Nb0.33O2 secondary phase. With further substitution of Sn, the lattice constant, volume and apparent density of the ceramics increased, the ceramic structure reached a maximal compactness at x = 0.2 which was shown on SEM. Tremendous improvement of Q × f and a declining trend of Ɛr and τf were obtained with increasing x value. Appropriate substitution value (x = 0.10) would ensure excellent microwave dielectric properties (Ɛr = 34.1, Q × f = 40562 GHz, τf =-5 ppm/°C) of the ceramics sintered at 1080 °C.
PtSn/Al2O3 catalysts with a given loading of 1 wt% Pt and 1 wt% Sn were prepared by co-impregnation or successive impregnation with aqueous solutions of Pt, Sn precursors and a commercial alumina. The catalysts were characterized by N2 adsorption, H2-TPR (H2 temperature-programmed reduction), H2-pulse chemisorption, XPS (X-ray photoelectron spectroscopy) and CO-FTIR (Fourier transform infrared spectroscopy), and tested in the hydrogenation of acetic acid. The results showed that the preparation method affected both the chemical properties and their performance in the hydrogenation of acetic acid. Sn enrichment on the catalysts surface was observed on the co-impregnated catalyst and catalyst in which the Pt precursor had been loaded first. It was found that the modification of Pt was a function of the sequence of Sn addition as revealed by CO-FTIR. Co-impregnated catalyst showed the highest activity and ethanol selectivity.
To analyze the literature status and research hotspots of Science Citation Index (SCI)-related ostomy in the world and to provide references for scientific research and clinical work in the stoma care field.
Based on the Web of Science core database and its own analysis function, HistCite analysis software and Excel were used to study the published research about ostomy patients.
A total of 1,262 articles were published between 1910 and 2016 with the authors from 48 countries and regions, 1,347 research institutions, published in 321 journals, with 4,048 first authors and coauthors; globally, there was a trend of slow growth in the number of authors every year. The study in the USA was absolutely in the lead position, and Canada and Turkey were more active. China's circulation volume was the 15th in the world. The periodical that published most often was the Journal of Wound Ostomy and Continence Nursing The most interdisciplinary surgical studies were surgery and nursing, where these should be considered important. The most prolific author in the field was "Grant", and the highest cited article was entitled as "Living with a stoma: a review of the literature".
The related research of global stoma is constantly developing. The research hotspot is nursing before and after stoma surgery. China and the USA are leading countries in research. They should follow the recent trend to improve the depth and breadth of the research in the field.
The cost of growing triploid watermelon seedlings has increased due to their low-efficiency grafting. The first priority in growing seedless watermelon seedlings is increasing the grafted-plant and seed-utilization rates. This study aimed to improve the grafted-plant rate by screening the most suitable substrate formulation, optimizing water moisture in the substrate, and evaluating the effect of different scions to improve seed-utilization rate. Five combinations of substrate (S1 to S5) and seven relative humidity levels (45%, 50%, 55%, 60%, 65%, 70%, and 75%) were used. Three types of scions (yellow bud, Ts-1; two cotyledons did not unfold, Ts-2; and first true leaf appeared, Ts-3) were tested. Results showed that the combination of S1 exhibited the best seed-utilization rate which was 71.6%. Moreover, the most suitable water moisture in the substrate ranged from 50% to 55%. The usage of the scion from Ts-3 significantly increased the grafting survival, grafted plant and seed-utilization rates by 13.7%, 10.1% and 22%, respectively, compared with the conventional method. Our study suggested that the best time to use the scion and the rootstock was during the seedling stage when the first true leaf unfolded. The proposed method decreased the production cost of seedlings and significantly improved the efficiency of grafting procedures. The results of this work are applicable to the technique of growing seedlings and can thus guide growers of high-quality grafted plants of triploid watermelon.
The objective of this paper is to evaluate the self- healing properties of a commercially-available geosynthetic clay liner (GCL) using flexible-wall permeameter. The GCLs are produced by the same factory, but the contents of bentonite are different. Also the hydraulic conductivities (HC) of GCLs with no defect are different. In this study, specimens were completely saturated under the backpressure of 20 kPa before the test. Permeability tests were performed on GCL specimens with penetrating flaw and also on specimens permeated with distilled water and CaCl2 solutions. The test results were presented and discussed. Experimental results showed that the GCL with penetrating flaw did not exhibit complete self-healing in the case of flaw. After 120 days, the hydraulic conductivity increased by approximately an order of magnitude. In addition, CaCl2 solutions had a significant influence on the hydraulic conductivity. The research findings might be of interest to researchers and engineers who design liners for landfills and other liquid containment facilities
SiNO continuous fiber reinforced boron nitride (BN) wave-transparent composites (SiNOf/BN) have been fabricated by a precursor infiltration pyrolysis (PIP) method using borazine as the precursor. The densification behavior, microstructures, mechanical properties, and dielectric properties of the composites have been investigated. After four PIP cycles, the density of the composites had increased from 1.1 g·cm−3 to 1.81 g·cm−3. A flexural strength of 128.9 MPa and an elastic modulus of 23.5 GPa were achieved. The obtained composites have relatively high density and the fracture faces show distinct fiber pull-out and interface de-bonding features. The dielectric properties of the SiNOf/BN composites, including the dielectric constant of 3.61 and the dielectric loss angle tangent of 5.7×10−3, are excellent for application as wave-transparent materials.