Showing papers by "Jiandong Ye published in 2009"

Alginate/poly (lactic-co-glycolic acid)/calcium phosphate cement scaffold with oriented pore structure for bone tissue engineering.

Abstract: In this study, the alginate/calcium phosphate cement (CPC) scaffolds with oriented pore structure were fabricated by unidirectional freeze casting and poly (lactic-co-glycolic acid) (PLGA) was used to infiltrate into the macropores to strengthen the scaffolds. By modifying the liquid to powder ratio, the porosity and pore size of the alginate/CPC scaffold could be controlled. At the liquid to powder (L/P) ratio of 3.25, scaffolds possessing open directional macropores and a total porosity of 89.24% could be achieved. The size of the tubule-like macropores could reach 100-200 mum in their radial dimension and more than 1000 mum in the axial one, with macropores well-regulated arrayed. Increasing the L/P ratio would significantly decrease the mechanical strength of alginate/CPC scaffolds. The compressive strength and toughness of scaffolds could be greatly improved via PLGA reinforcement. Three mechanisms of PLGA reinforcement ran as follows: participating in the external load, strengthening the matrix, and patching the defects of CPC pores wall. Alginate/PLGA/CPC scaffold preserved the open directional macropores and might be a potential scaffold for bone tissue engineering.

Raman-active Fröhlich optical phonon mode in arsenic implanted ZnO

Abstract: This work was supported by the Singapore Agency for Science, Technology and Research A*STAR, under SERC Grant No. 0521260095.

Suppression of compensation from nitrogen and carbon related defects for p-type N-doped ZnO

Abstract: In this letter, the authors performed a comprehensive study on suppression mechanism of compensation from nitrogen and carbon related complex defects in N-doped ZnO grown by metal-organic chemical vapor deposition. The chemical bonding information of donorlike substitutional complex defects, (NN)O and (NC)O, were restrained with low N/O ratio, leading to the conduction type conversion. High epitaxial temperature has more suppressing effect on the formation of desired acceptor NO than that of (NC)O, as evident by the decreasing hole concentration. Upon utilization of such suppression effect, this study provides a promising route to realize p-type ZnO.

Synthesis and property of a novel calcium phosphate cement

Abstract: The beta-cyclodextrins (beta-CDs) and amorphous calcium phosphate were used to prepare a novel calcium phosphate cement (CPC) after mechanochemical activation. Under the mechanochemical treatment, hydrogen bonding formed between beta-CD molecules, which induced strong interaction among beta-CD molecules in aqueous solution, thus conferring good antiwashout property for CPC. After mechanochemical treatment, the solubility of beta-CD was increased and so beta-CD showed different behaviors within and on the outer surface of CPC. During the setting process, when beta-CD was injected it flowed to the surface of CPC, forming a beta-CD film on the surface of CPC; inside the cement, the hydration reaction of calcium phosphates was not affected. Moreover, the antiwashout CPC with beta-CD also showed good mechanical setting, rheological properties, and injectability. The novel CPC was supposed to be developed as a good injectable bone substitute material in the clinical application.

Nanoscale band gap spectroscopy on ZnO and GaN-based compounds with a monochromated electron microscope

Abstract: Monochromated low-loss EELS (electron energy-loss spectroscopy) is explored as an analytical technique for nanoscale mapping of the electronic band gap energy on arsenic-implanted ZnO, CdZnO, and InGaN compounds. Its accuracy is confirmed independently with Raman spectroscopy. From a ternary compound, the relationship between the band gap energy and the chemical composition is determined, a powerful application of low-loss EELS. The effects of electron beam delocalization are discussed using examples from In0.25Ga0.75N quantum wells.

Surfactant effect of arsenic doping on modification of ZnO (0001) growth kinetics

Abstract: The effect of arsenic doping on the growth kinetics of ZnO during metalorganic vapor phase epitaxy has been investigated. Arsenic was found to segregate to the growth surface and facilitate layer-by-layer growth. Such surfactant enhances the lateral expansion of the terraces preferential along [1¯1¯20] direction and also reduces the screw lattice distortion. Arsenic is expected to reduce the total surface energy and diffusion barrier of oxygen adatoms, hence producing Zn-rich surface condition on the growth front, in which two-dimensional growth is thermodynamically and kinetically favored. The origin of tiny hexagonal pits formed on the wide terrace is discussed in terms of the modified step-bunching mechanism.

Anti-collapsibility calcium phosphate cement, preparation method and application thereof

Abstract: The invention belongs to the technical field of medical bone injury restoration materials, in particular discloses anti-collapsibility calcium phosphate cement, as well as a preparation method and the application thereof. The anti-collapsibility calcium phosphate cement is prepared by uniformly mixing 2-10 percent of beta-cyclodextrin or derivates thereof by mass percentage with 90-98 percent of common calcium phosphate cement by mass percentage. The invention successfully applies the beta-cyclodextrin or the derivates thereof to the common calcium phosphate cement for the first time, not only remarkably improves the anti-collapsibility performance of original calcium phosphate cement, but also keeps the original curing characteristics of the original calcium phosphate cement and improves the mechanical performance requirements thereof, effectively improves the success rate of operations, widens the application fields of the beta-cyclodextrin or the derivates thereof and enables the calcium phosphate cement to have wider application prospects.

Enhanced Vertical Light Extraction From Ultrathin Amorphous Si–Si $_{3}$ N $_{4}$ Multilayers With Photonic Crystal Patterns

Abstract: We have investigated the significant enhancement of light extraction from amorphous Si-Si3N4 multiple-quantum-well structures, in which two-dimensional hexagonal-lattice air-hole photonic crystals (PCs) were integrated. The vertical spectral integrated intensity of light emission around 674 nm was enhanced up to times due to strong coupling to the inherent leaky modes or radiation modes near Gamma point of PC's band structure. The experimental observations also suggested that coupling to leaky modes should be more beneficial for light extraction enhancement.

Control of Crystallinity of Hydrated Products in a Calcium Phosphate Cement

Abstract: A novel calcium phosphate cement (CPC) was prepared by dry-mechanochemical rout in this work. With the different crystallinity, the CPC showed the different degradation ratio after setting. The degradation ratio of CPC was characterized by the calcium ion-dissolving ratio in deionized water after different soaking time. With the increment of crystallinity, the setting times of CPC were prolonged, and the different mechanical property of CPC were obtained. This novel CPC was supposed to match the new bone ingrowth in vivo and have the potential application in orthopedic surgery for filling non-load-bearing bone defects.

Exothermal Behavior during the Hydration of the PCCP+DCPA System Cement

Abstract: Exothermal behavior is always present during the hydration of cements. The biocompatibility and curing effect of a bone cement is in close relationship with its exothermal behavior. The exothermal behavior in the hydration process of the partially crystallized calcium phosphate (PCCP)+dicalcium phosphate anhydrate (DCPA) system cement was studied in this article. The results show that with the decrease of the particle size of DCPA, the heat release rate was greatly increased; whereas, with the decrease of the particle size of PCCP, the heat release rate was not obviously altered. The heat release in the hydration process of the PCCP+DCPA system cement was only 137 J/g, which was quite smaller than that of the tetracalcium phosphate (TTCP)+dicalcium phosphate dihydrate (DPCD) system cement, and the temperature increase was very small for this cement.