- Hydrothermal growth and morphology evolution of CePO4 aggregates by a complexing method
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A facile hydrothermal route assisted by Na2H2EDTA (ethylenediaminetetraacetic acid disodium) has been successfully developed to prepare uniform cerium phosphate (CePO4) aggregates with different morphologies, such as peanut-like and spindle-like. It was found that the as-prepared uniform CePO4 aggregates were constructed with many nearly parallel aligned nanorods. The molar ratio of EDTA/Ce3+, solution pH and reaction time had great influences on the morphologies and sizes of the CePO4 samples. In our process of synthesis, Na2H2EDTA played important roles as complexing reagent and inducing agent on the formation of CePO4 aggregates. The possible growth mechanism for CePO4 aggregates was presented. Ce0.9Tb0.1PO4 aggregates with different morphologies were also prepared and their photoluminescence properties were characterized.
- Ma, Lin,Chen, Wei-Xiang,Zheng, Yi-Fan,Xu, Zhu-De
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- Cerium phosphate nanotubes: Synthesis, valence state, and optical properties
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A strong blue emission is observed for hybrid Ce3+/Ce 4+ cerium phosphate nanotubes, whereas Ce3+ phosphate nanowires exhibit a characteristic double-peak UV luminescence (see picture). These cerium phosphate systems were obtained by annealing novel cerium(IV) phosphate nanotubes at different temperatures.
- Tang, Chengchun,Bando, Yoshio,Golberg, Dmitri,Ma, Renzhi
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- The synthesis and thermal stability of CaKCe(PO4)2 phosphate. Phase equilibria in the CaKPO4-CePO4 system
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The compound CaKCe(PO4)2 was obtained using respectively the ceramic method, the Pechini method and the hydrothermal method. The low-temperature (Pechini and hydrothermal) methods yielded homogenous powders with a crystallite size up to 24 nm. The compound has a hexagonal structure with parameters of an elementary cell: a = b = 7.0468(8) ? and c = 6.4367(0) ?. The CaKCe(PO4)2 phosphate occurs in one polymorphic form. A phase equilibrium diagram of the CaKPO 4-CePO4 system has been established on the basis of XRD, DTA/DSC/TGA results. The initial phosphates were found to form one intermediate compound, CaKCe(PO4)2, with molar ratio CaKPO 4:CePO4 = 1:1, melting incongruently at a temperature of 1530 °C according to the reaction: CaKCe(PO4)2(cr) → CePO4(cr) + L. At a temperature of 1440 °C an eutectic was found to be present in the CaKPO4-CePO4 system at x(CePO4) = 0.25.
- Matraszek, Aleksandra,Szczygie?, Irena,Znamierowska, Teresa
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- Synthesis and characterization of mixed-morphology CePO4 nanoparticles
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Cerium phosphate nanoparticles with diameters of 10-180 nm were synthesized by a variety of solution techniques. X-ray diffraction (XRD) determined the crystalline phase(s) present in each sample. Population, shift, and spin-lattice relaxation 31P solid-state nuclear magnetic resonance (NMR) measurements accounted for all the 31P nuclei expected in each sample, and were able to distinguish between phosphorous nuclei in different environments and phases. Transmission electron microscopy (TEM) characterized the morphology and crystallinity of the powder samples as well as of the sintered compacts of the powders. In conjunction with TEM, energy-dispersive spectroscopy (EDS) provided a measure of the composition of the bulk intergranular regions within each CePO4 sample. The presence of an amorphous, phosphate-rich intergranular phase was found in those samples prepared by dissolution of ceria in H3PO4 under various conditions.
- Karpowich,Wilcke,Yu, Rong,Harley,Reimer,De Jonghe
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- Epitaxial synthesis of uniform cerium phosphate one-dimensional nanocable heterostructures with improved luminescence
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Uniform CePO4@LaPO4 and CePO4:Tb 3+@LaPO4 one-dimensional single-crystalline nanocable heterostructures with highly enhanced photoluminescent emission have been synthesized via a mild and simple hydrothermal approach. The resulting one-dimensional single-crystalline nanocable heterostructures have smooth and uniform LaPO4 sheaths, which is of great significance in effectively eliminating surface trap-states and suppressing the energy quenching in energy-transfer processes. The photoluminescence results for these one-dimensional nanocable heterostructures illustrate that the uniform LaPO 4 sheaths remarkably increase the luminescent efficiency. ? 2005 American Chemical Society.
- Bu, Wenbo,Hua, Zile,Chen, Hangrong,Shi, Jianlin
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- Synthesis of cerium orthophosphates with monazite and rhabdophane structure from phosphoric acid solutions in the presence of hydrogen peroxide
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It has been proposed to conduct the synthesis of cerium(III) orthophosphates by reacting cerium(IV) compounds with hydrogen peroxide in the presence of concentrated orthophosphoric acid at ambient temperature. It has been shown that the reaction of H
- Skogareva,Shekunova,Baranchikov,Yapryntsev,Sadovnikov,Ryumin,Minaeva,Ivanov
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- Vapour phase O-alkylation of phenol over alkali promoted rare earth metal phosphates
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The vapor phase synthesis of anisole by O-alkylation of phenol with methanol was studied over lanthanum, cerium, samarium, and antimony phosphate catalysts promoted with cesium hydroxide. The activity and selectivity trends on various catalysts followed the same pattern with temperature. The formation of some side products with traces of CO and CO2 were rarely noted at higher temperatures. The cesium promoted samarium phosphate showed maximum product yield (83%). The cesium promoter decreased the C-alkylation products and enhanced the O-alkylation product selectivity. The total amount of ammonia desorbed in the case of samarium was much higher than that of the Cs-Sm sample. A substantial decrease in the quantity of ammonia desorbed in the case of Cs-Sm catalyst indicated that the Cs promoter highly influenced the surface acidity of Sm-phosphate catalyst. Cs promoter had major influence on the strong acid sites of the catalyst.
- Reddy,Sarala Devi,Giridhar
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- Systematic Synthesis and Characterization of Single-Crystal Lanthanide Orthophosphate Nanowires
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A simple hydrothermal method has been developed for the systematic synthesis of lanthanide orthophosphate crystals with different crystalline phases and morphologies. It has been shown that pure LnPO4 compounds change structure with decreasing Ln ionic radius: i.e., the orthophosphates from Ho to Lu as well as Y exist only in the tetragonal zircon (xenotime) structure, while the orthophosphates from La to Dy exist in the hexagonal structure under hydrothermal treatment. The obtained hexagonal structured lanthanide orthophosphate LnPO4 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) products have a wirelike morphology. In contrast, tetragonal LnPO 4 (Ln = Ho, Er, Tm, Yb, Lu, Y) samples prepared under the same experimental conditions consist of nanoparticles. The obtained hexagonal LnPO4 (Ln = La → Tb) can convert to the monoclinic monazite structured products, and their morphologies remained the same after calcination at 900 °C in air (Hexagonal DyPO4 is an exceptional case, it transformed to tetragonal DyPO4 by calcination), while the tetragonal structure for (Ho→ Lu, Y)PO4 remains unchanged by calcination. The resulting LnPO4 (Ln = La → Dy) products consist almost entirely of nanowires/nanorods with diameters of 5-120 nm and lengths ranging from several hundreds of nanometers to several micrometers. Europium doped LaPO4 nanowires were also prepared, and their photoluminescent properties were reported. The optical absorption spectrum of CePO4 nanowires was measured and showed some differences from that of bulk CePO4 materials. The possible growth mechanism of lanthanide phosphate nanowires was explored in detail. X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, electron diffraction, infrared absorption spectra, X-ray photoelectron spectroscopy, optical absorption spectra, and photoluminescence spectra have been employed to characterize these materials.
- Fang, Yue-Ping,Xu, An-Wu,Song, Rui-Qi,Zhang, Hua-Xin,You, Li-Ping,Yu, Jimmy C.,Liu, Han-Qin
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- Facile sonochemical synthesis and photoluminescent properties of lanthanide orthophosphate nanoparticles
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Uniform lanthanide orthophosphate LnPO4 (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho) nanoparticles have been systematically synthesized via a facile, fast, efficient ultrasonic irradiation of inorganic salt aqueous solution under ambient conditi
- Yu, Cuicui,Yu, Min,Li, Chunxia,Liu, Xiaoming,Yang, Jun,Yang, Piaoping,Lin, Jun
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- Decomposition of chlorofluorocarbons over metal phosphate catalysis. II. Origin of the stability of AlPO4 and the location of CE as a promoter
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Aluminum-phosphate catalysts prepared from aqueous solution of Al(NO3)36H2O and H3PO4 in acidic condition are effective for hydrolysis of CCl2F2. Active species of the AlPO4 catalysts were studied and it was found that not Al(PO3)3 but pure AlPO4 was active. AlPO4 was amorphous when calcined at 1000°C for 5 h. But a slight crystallization of AlPO4 took place after the reaction at 400°C for 1000 h. Crystallization of AlPO4 proceeded only in the presence of both CCl2F2 and water vapor. Replacement of 5-10 at.% of Al in AlPO4 by Ce increased the catalytic activity without changing the selectivity. The Ce-promoted catalysts were composed of the mixture of AlPO4 and CePO4. The compositions of the catalysts were the same as those of parent liquor in preparation and it was almost uniform in the surface and the bulk. AlPO4 in the Ce-promoted AlPO4 catalyst was partially crystallized after the calcination at 1000°C for 5 h. (C) 2000 Elsevier Science B.V.
- Takita, Yusaku,Wakamatsu, Hironori,Li, Gong-Liang,Moro-Oka, Yoshihiko,Nishiguchi, Hiroyasu,Ishihara, Tatsumi
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- Precipitation coating of rare-earth orthophosphates on woven ceramic fibers-effect of rare-earth cation on coating morphology and coated fiber strength
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Monazite (La, Ce, Nd, and GdPO4) and xenotime (Tb, Dy, and YPO4) coatings were deposited on woven Nextel 610 and 720 fibers by heterogeneous precipitation from a rare-earth citrate/ phosphoric acid precursor. Coating phases and microstructure were characterized by SEMand TEM, and coated fiber strength was measured after heat treatment at 1200°C for 2 h. Coated fiber strength increased with decreasing ionic radius of the rareearth cation in the monazite and xenotime coatings, and correlates with the high-temperature weight loss and the densification rate of the coatings. Dense coatings with trapped porosity and high weight loss at a high temperature degrade fiber strength the most. The degradation is consistent with stress corrosion driven by thermal residual stress from coating precursor decomposition products trapped in the coating at a high temperature.
- Fair, Geoff E.,Hay, Randall S.,Boakye, Emmanuel E.
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- Characterization and thermal behavior of amorphous rare earth phosphates
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Amorphous cerium and terbium pyrophosphates were synthesized by precipitation method at 353K. The characterization of these amorphous phosphates was carried out by using X-ray powder diffraction (XRD), thermal gravimetric and differential thermal analysis (TG-DTA), Fourier-transformed infrared spectroscopy (FT-IR), and Raman spectroscopy, especially focusing on the thermal behavior dependence on the calcination temperatures. The amorphous state of the as-prepared cerium phosphate was stable up to 723K, and it crystallized at 773K to form a mixture of cerium pyrophosphate (CeP2O7) and cerium orthophosphate (CePO4). Heating at higher temperatures accelerates the phase change from pyrophosphate to orthophosphate accompanying the formation of metaphosphate (CeP3O9), and above 1173K, only a single phase of CePO4 was obtained. In the case of terbium phosphate, crystallization of amorphous phase occurred at 973K to produce a mixture of TbPO4 and Tb2P4O13. The Tb2P4O13 phase decomposed into TbP 3O9 and TbPO4 at 1673K, and these compounds remained even after the calcination at 1873K.
- Hirai, Hidekazu,Masui, Toshiyuki,Imanaka, Nobuhito,Adachi, Gin-ya
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- Hydrothermal synthesis and luminescent properties of novel ordered sphere CePO4 hierarchical architectures
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The ordered-sphere CePO4 hierarchical architectures have been successfully synthesized by a simple hydrothermal method through the controlled growth of the CePO4 nanorods and self-assemble hierarchical structure under various reactio
- Yang, Mei,You, Hongpeng,Zheng, Yuhua,Liu, Kai,Jia, Guang,Song, Yanhua,Huang, Yeju,Zhang, Lihui,Zhang, Hongjie
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- Hydrothermal synthesis of ultraviolet-emitting cerium phosphate single-crystal nanowires
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Cerium phosphate single-crystalline nanowires with a narrow distribution of diameters have been successfully synthesized by a mild and simple hydrothermal approach. Photoluminescence of cerium phosphate single-crystalline nanowires show that these nanowires can emit ultraviolet laser light.
- Bu, Wen-Bo,Hua, Zi-Le,Chen, Hang-Rong,Zhang, Ling-Xia,Shi, Jian-Lin
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- Mixed valence cerium substitution in Gd2-xCexTi2O7+δ pyrochlores
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Pyrochlore-type oxides having the formula Gd1.6Ce0.4Ti2O7+δδ have been synthesized by ceramic and co-precipitation methods and annealed at 1300 °C under different environments. Rietveld refinement of powder X-ray diffraction (XRD)patterns indicated that the products adopt the pyrochlore-type oxide structure with Ce ions substituting for Gd ions. Analysis of Ce 3d X-ray photoelectron spectroscopy (XPS)spectra confirmed the presence of both Ce3+ and Ce4+, which was corroborated by analysis of Ce L3-edge X-ray absorption near edge spectroscopy (XANES)spectra. Incorporation of Ce4+ imparts disorder on the Ti octahedra as observed by analysis of Ti K-edge XANES spectra. Due to the presence of Ce4+ in the A-site of the pyrochlore-type structure, oxygen is likely intercalated into the vacant anion 8b site to charge balance the system. This intercalation results in an increase of the average Ti coordination number from 6 to between 6 and 7, which leads to the formula unit being better represented as Gd1.6Ce0.4Ti2O7+δδ.
- Beam, Jeremiah C.,Hehn, Atikin G.,Grosvenor, Andrew P.
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- Optical and structural characterisation of pure and Pr3+ doped LaPO4 and CePO4 nanocrystals
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The rod- and stick-shaped nanocrystalline cerium and lanthanum orthophosphates, pure and Pr3+ doped, have been synthesised by the hydrothermal method in acidic (pH 1) or alkaline (pH 11) environment. Subsequent calcination of as-obtained powder
- MacAlik,Tomaszewski,Matraszek,Szczygie?,Solarz,Godlewska,Sobczyk,Hanuza
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- Ni/(rare earth phosphate) as a new effective catalyst for autothermal reforming of methane
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The stability of metal phosphate during H2 reduction is one of the critical factors that determine the catalytic behavior of Ni/(metal phosphate) in CH4 autothermal reforming. Ni/(rare earth phosphate), particularly Ni/(Gd, Ce, or ErPO4), has been found to be a new family of effective catalysts. Copyright
- Nagaoka, Katsutoshi,Eiraku, Toshikazu,Nishiguchi, Hiroyasu,Takita, Yusaku
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- Synthesis and characterization of the first organically templated layered cerium phosphate fluoride: [(CH2)2(NH3) 2]0.5[CeIVF3(HPO4)]
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A novel organically templated layered cerium phosphate fluoride [(CH 2)2(NH3)2]0.5[Ce IVF3(HPO4)] has been synthesized by hydrothermal synthesis technology, and characterized by means of single-crystal X-ray diffraction. Its unique layered structure is based on a network of novel CeO3F5 polyhedral and PO4 tetrahedral. The [NH3(CH2)2NH3]+ cations contact with the adjacent layers via hydrogen bonds to compensate the negative charge of the inorganic framework.
- Yu, Ranbo,Wang, Dan,Ishiwata, Shintaro,Saito, Takashi,Azuma, Masaki,Takano, Mikio,Chen, Yunfa,Li, Jinghai
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- Thermal conductivity of monazite-Type REPO4 (RE=La, Ce, Nd, Sm, Eu, Gd)
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Low-thermal conductivity ceramics in monazite-type REPO4 (RE=La, Ce, Nd, Sm, Eu, Gd) ceramics are expected to have potential in structural (refractories, thermal insulator) and nuclear applications. To this end, the present study determines the
- Du, Aibing,Wan, Chunlei,Qu, Zhixue,Pan, Wei
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- Two-phase synthesis of Fe doped cerium phosphate ultra-fine nanocrystals for efficient oxygen evolution
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It is very important and challenging to develop electrocatalysts with high performance and economic benefits. In this work, ultra-fine Fe doped CePO4 nanocrystals (Fe-CePO4) were prepared by a simple two-step hydrothermal synthesis method under mild conditions, combining the advantages of the PO43- group, easy hydroxylation of metal sites, convenient oxygen ion transfer due to the polyvalent nature of cerium ions, and a high charge transfer rate due to the doping of the second metal. The combination of these advantages improves the conductivity of the Fe-CePO4 electrocatalyst, makes it exhibit a faster charge transfer ability and shows excellent OER performance, with only 197 mV and 253 mV overpotentials at current densities of 10 mA cm-2 and 100 mA cm-2, an ultra-small Tafel slope of 52.4 mV dec-1 and a high turnover frequency (TOF) of 7.67 s-1 at 1.50 V. This synthesis method of ultrafine nanocrystals and the combination of the advantages of various groups in this work provide ideas and insights for the subsequent preparation of efficient and economical electrocatalysts. This journal is
- Cao, Lixin,Dong, Bohua,Gao, Rongjie,Li, Yanxin,Su, Ge,Wang, Ruonan,Zhou, Rui
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p. 2609 - 2617
(2022/02/22)
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- Preparation of two different crystal structures of cerous phosphate as solid acid catalysts: Their different catalytic performance in the aldol condensation reaction between furfural and acetone
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Liquid fuel intermediates can be produced via aldol condensation reactions through furan aldehydes and ketones driven from biomass. It was found that cerous phosphate (CP) with two different crystal structures (hexagonal and monoclinic structure), which was tailored by different hydrothermal temperature (120 °C for the hexagonal structure and 180 °C for the monoclinic structure) and calcination temperature (900 °C for the monoclinic structure) as a solid acid catalyst, exhibit high catalytic performance in aldol condensation between furfural and acetone. The CP with hexagonal structure gave 89.1% conversion of furfural with 42% yield of 4-(2-furyl)-3-buten-2-one (FAc) and 17.5% of yield of 1,5-di-2-furanyl-1,4-pentadien-3-one (F2Ac), much higher than CP with monoclinic structure. However, both furfural conversion and aldol product yield increased from 82.3% to 96% and from 50.5% to 68.4%, respectively, for CP with the monoclinic structure after calcination owing to the higher amount of acid of catalyst after calcination but decreased continuously for CP with hexagonal structure after calcination because of its rapidly reduced BET surface area and total pore volume. The results indicated that calcination affects significantly the physical-chemical properties of CP catalysts, which influence subsequently the catalytic performance in the aldol condensation reaction. Recycling experiments showed that the catalytic performance after five number runs for CP with monoclinic structure after calcination was acceptable but was not ideal for CP with hexagonal structure owing to its poor hydrothermal stability.
- Li, Wenzhi,Su, Mingxue,Yang, Tao,Zhang, Tingwei,Ma, Qiaozhi,Li, Song,Huang, Qifu
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p. 16919 - 16928
(2019/06/24)
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- METHOD FOR PRODUCTION OF ACROLEIN
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There is provided a process for producing acrolein, which makes it possible to obtain acrolein in high yield by dehydration of glycerin. Glycerin is allowed to coexist with a catalyst containing a rare earth metal salt crystal of phosphoric acid, thereby dehydrating the glycerin, wherein the crystal is obtained by calcining a solid which is formed by allowing a liquid containing water and a hydroxide of the rare earth metal and/or a dehydration condensate of the hydroxide to contain phosphate ions.
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(2010/03/31)
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- Composite shaped bodies and methods for their production and use
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Shaped, composite bodies are provided. One portion of the shaped bodies comprises an RPR-derived porous inorganic material, preferably a calcium phosphate. Another portion of the composite bodies is a different solid material, preferably metal, glass, ceramic or polymeric. The shaped bodies are especially suitable for orthopaedic and other surgical use.
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(2008/06/13)
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