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261.
Zinc oxide-layered titanate nanohybrids with a 1 ratio 1 ordered heterostructure have been successfully synthesized by reassembling exfoliated titanate nanosheets in the sol solution of zinc acetate under hydrothermal conditions. 相似文献
262.
Let J be an abelian surface with a generic ample line bundle . For n≥1, the moduli space MJ(2,0,2n) of (1)-semistable sheaves F of rank 2 with Chern classes c1(F)=0, c2(F)=2n is a singular projective variety, endowed with a holomorphic symplectic structure on the smooth locus. In this paper, we
show that there does not exist a crepant resolution of MJ(2,0,2n) for n≥2. This certainly implies that there is no symplectic desingularization of MJ(2,0,2n) for n≥2.
Jaeyoo Choy was partially supported by KRF 2003-070-C00001
Young-Hoon Kiem was partially supported by a KOSEF grant R01-2003-000-11634-0. 相似文献
263.
Chin Chye Teo Swee Ngin Tan Jean Wan Hong Yong Choy Sin Hew Eng Shi Ong 《Journal of separation science》2009,32(4):613-622
An approach that combined green‐solvent methods of extraction with chromatographic chemical fingerprint and pattern recognition tools such as principal component analysis (PCA) was used to evaluate the quality of medicinal plants. Pressurized hot water extraction (PHWE) and microwave‐assisted extraction (MAE) were used and their extraction efficiencies to extract two bioactive compounds, namely stevioside (SV) and rebaudioside A (RA), from Stevia rebaudiana Bertoni (SB) under different cultivation conditions were compared. The proposed methods showed that SV and RA could be extracted from SB using pure water under optimized conditions. The extraction efficiency of the methods was observed to be higher or comparable to heating under reflux with water. The method precision (RSD, n = 6) was found to vary from 1.91 to 2.86% for the two different methods on different days. Compared to PHWE, MAE has higher extraction efficiency with shorter extraction time. MAE was also found to extract more chemical constituents and provide distinctive chemical fingerprints for quality control purposes. Thus, a combination of MAE with chromatographic chemical fingerprints and PCA provided a simple and rapid approach for the comparison and classification of medicinal plants from different growth conditions. Hence, the current work highlighted the importance of extraction method in chemical fingerprinting for the classification of medicinal plants from different cultivation conditions with the aid of pattern recognition tools used. 相似文献
264.
In this paper, the networks with optimal synchronizability are obtained using the local structure information. In scale-free networks, a node will be coupled by its neighbors with maximal degree among the neighbors if and only if the maximal degree is larger than its own degree. If the obtained coupled networks are connected, they are synchronization optimal networks. The connection probability of coupled networks is greatly affected by the average degree which usually increases with the average degree. This method could be further generalized by taking into account the degree of next-nearest neighbors, which will sharply increase the connection probability. Compared to the other proposed methods that obtain synchronization optimal networks, our method uses only local structure information and can hold the structure properties of the original scale-free networks to some extent. Our method may present a useful way to manipulate the synchronizability of real-world scale-free networks. 相似文献
265.
Liya Zhou Wallace C.H. Choy Jianxin Shi Menglian Gong T.I. Yuk 《Journal of solid state chemistry》2005,178(10):3004-3009
Vacuum ultraviolet (VUV) excitation and photoluminescent (PL) properties of Eu3+ and Tb3+ ion-doped aluminate phosphors, GdCaAl3O7:Eu3+ and GdCaAl3O7:Tb3+ have been investigated. X-ray diffraction (XRD) patterns indicate that the phosphor GdCaAl3O7 forms without impurity phase at 900 °C. Field emission scanning electron microscopy (FE-SEM) images show that the particle size of the phosphor is less than 3 μm. Upon excitation with VUV irradiation, the phosphors show a strong emission at around 619 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu3+, and at around 545 nm corresponding to the 5D4→7F5 transition of Tb3+. The results reveal that both GdCaAl3O7:RE3+ (RE=Eu, Tb) are potential candidates as red and green phosphors, respectively, for use in plasma display panel (PDP). 相似文献