Microporosity has a critical role in improving the osteogenesis of scaffolds for bone tissue engineering.Although the exact mechanism,by which it promotes new bone formation,is not well recognized yet,the related hypo...Microporosity has a critical role in improving the osteogenesis of scaffolds for bone tissue engineering.Although the exact mechanism,by which it promotes new bone formation,is not well recognized yet,the related hypothesis can be found in many previous studies.This review presents those possible mechanisms about how the microporosity enhances the osteogenic-related functions of cells in vitro and the osteogenic activity of scaffolds in vivo.In summary,the increased specific surface areas by microporosity can offer more protein adsorption sites and accelerate the release of degradation products,which facilitate the interactions between scaffolds and cells.Meanwhile,the unique surface properties of microporous scaffolds have a considerable effect on the protein adsorption.Moreover,capillary force generated by the microporosity can improve the attachment of bone-related cells on the scaffolds surface,and even make the cells achieve penetration into the micropores smaller than them.This review also pays attention to the relationship between the biological and mechanical properties of microporous scaffolds.Although lots of achievements have been obtained,there is still a lot of work to do,some of which has been proposed in the conclusions and perspectives part.展开更多
In order to study the effect of Zr modification and riser size on microporosity defect distributions in WE54 alloy sand castings, the microporosity volume percentage in Zr-free and Zr-containing WE54 alloy plate casti...In order to study the effect of Zr modification and riser size on microporosity defect distributions in WE54 alloy sand castings, the microporosity volume percentage in Zr-free and Zr-containing WE54 alloy plate castings was determined by density measurement based on Archimedes＇ principle, and the microstructure of the microporosity defects was observed by optical microscopy and scanning electron microscopy. Then by using Procast software, the Niyama criterion was calculated in order to investigate the validity of Niyama criterion on prediction of microporosity defects in WE54 alloy sand castings. It is found from the density measurement results that Zr addition does not affect the microporosity distributions in WE54 alloy castings. While the distribution area of microporosity defect in the plate castings decreases significantly as the riser size increases. Based on the experimental results, a riser selection principle for production of compact WE54 alloy castings is proposed that the solidification modulus of the riser should be greater than that of the casting by 30%, simply mr ≥ 1.3mc. By comparing the experimental and simulating results, it is found that the predicted microporosity regions by Niyama criterion agrees well with experimental results, and a critical Niyama value of 0.4 ℃0.5 s0.5 mm-1 is suggested for prediction of microporosity formation in WE54 alloy sand castings.展开更多
Polymers of intrinsic microporosity （PIMs） are a class of porous organic polymer （POP） that form microporous solids due to the inefficient packing of their rigid and contorted macromolecular chains. In contrast to...Polymers of intrinsic microporosity （PIMs） are a class of porous organic polymer （POP） that form microporous solids due to the inefficient packing of their rigid and contorted macromolecular chains. In contrast to other types of POP, PIMs are not comprised of a network of cross-linked covalent bonds so that they can be dissolved in organic solvents and processed into robust films, coatings or fibres. Here, over twelve years＇ accumulated research on the synthesis of PIMs is reviewed. To date, three types of polymerisation reaction have been used successfully to prepare PIMs of sufficient molecular mass to form robust self-standing films. These involve the formation of dibenzodioxin, Tr6ger＇s base and imide linkages between monomeric units. This rapid development of synthetic methods for preparing PIMs has been driven by their rich potential for numerous diverse applications and this synergistic relationship between synthesis and functionality is set to continue.展开更多
Two novel compounds, {[Co2（epda）2（4,4＇-bpy）（H20）z]＇3H20}n 1 and {[Co2（epda）2（bpe）（HzO）z]＇3HzO}n 2 （H2epda = 5-ethyl-pyridine-2,3-dicarboxylic acid, 4,4＇-bpy = 4,4＇-bipyridine and bpe = 1,2-di（4-pyri...Two novel compounds, {[Co2（epda）2（4,4＇-bpy）（H20）z]＇3H20}n 1 and {[Co2（epda）2（bpe）（HzO）z]＇3HzO}n 2 （H2epda = 5-ethyl-pyridine-2,3-dicarboxylic acid, 4,4＇-bpy = 4,4＇-bipyridine and bpe = 1,2-di（4-pyridyl）ethylene） were solvothermally synthesized and charac- terized by elemental analysis, IR spectroscopy, thermogravimetric analysis （TGA）, and single- crystal X-ray diffraction. Complex 1 is ofmonoclinic system, space group P21/c with a = 13.344（5）, b = 14.724（5）, c = 8.267（3） A, fl = 105.840（4）~, V= 1562.5（10） A3, Dc = 1.480 g/cm3, Mr = 375.19, Z = 4, F（000） = 712, gl = 1.121 mm-1, the final R = 0.0512 and wR = 0.1260 for 2890 observed reflections with I 〉 2σ（I）. 2 belongs to the monoclinic system, space group P21/c with a = 14.224（4）, b = 14.726（4）, c = 8.287（2） A,β = 99.696（4）°, V= 1711.1（9） A3, Dc = 1.402 g/cm3, Mr = 388.21, Z = 4, F（000） = 740, kt = 1.027 mm-1, the final R = 0.0354 and wR = 0.0862 for 12237 observed reflections with I 〉 2a（/）. Both complexes present intimately related structures featuring infinite Co-carboxylate layers of [Con（epda）（H20）]n pillared by 4,4＇-bpy （or bpe） molecule to produce the microporous frameworks, Unambiguously indicating that pore dimensions of the framework are regulated by the N,N＇-donor pillars.展开更多
基金the financial supports from the National Natural Science Foundation of China(Nos.31370959 and 31771042)National Key R&D Program of China(No.2017YFC1104703)+3 种基金Beijing Nova Programme Interdisciplinary Cooperation Project(No.xxjc201616)Fok Ying Tung Education Foundation(No.141039)State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KF201714)International Joint Research Center of Aerospace Biotechnology and Medical Engineering,Ministry of Science and Technology of China,and the 111 Project(No.B13003).
文摘Microporosity has a critical role in improving the osteogenesis of scaffolds for bone tissue engineering.Although the exact mechanism,by which it promotes new bone formation,is not well recognized yet,the related hypothesis can be found in many previous studies.This review presents those possible mechanisms about how the microporosity enhances the osteogenic-related functions of cells in vitro and the osteogenic activity of scaffolds in vivo.In summary,the increased specific surface areas by microporosity can offer more protein adsorption sites and accelerate the release of degradation products,which facilitate the interactions between scaffolds and cells.Meanwhile,the unique surface properties of microporous scaffolds have a considerable effect on the protein adsorption.Moreover,capillary force generated by the microporosity can improve the attachment of bone-related cells on the scaffolds surface,and even make the cells achieve penetration into the micropores smaller than them.This review also pays attention to the relationship between the biological and mechanical properties of microporous scaffolds.Although lots of achievements have been obtained,there is still a lot of work to do,some of which has been proposed in the conclusions and perspectives part.
基金supported by the National Basic Research Program of China(973 Program,No.2013CB632202)
文摘In order to study the effect of Zr modification and riser size on microporosity defect distributions in WE54 alloy sand castings, the microporosity volume percentage in Zr-free and Zr-containing WE54 alloy plate castings was determined by density measurement based on Archimedes＇ principle, and the microstructure of the microporosity defects was observed by optical microscopy and scanning electron microscopy. Then by using Procast software, the Niyama criterion was calculated in order to investigate the validity of Niyama criterion on prediction of microporosity defects in WE54 alloy sand castings. It is found from the density measurement results that Zr addition does not affect the microporosity distributions in WE54 alloy castings. While the distribution area of microporosity defect in the plate castings decreases significantly as the riser size increases. Based on the experimental results, a riser selection principle for production of compact WE54 alloy castings is proposed that the solidification modulus of the riser should be greater than that of the casting by 30%, simply mr ≥ 1.3mc. By comparing the experimental and simulating results, it is found that the predicted microporosity regions by Niyama criterion agrees well with experimental results, and a critical Niyama value of 0.4 ℃0.5 s0.5 mm-1 is suggested for prediction of microporosity formation in WE54 alloy sand castings.
文摘Polymers of intrinsic microporosity （PIMs） are a class of porous organic polymer （POP） that form microporous solids due to the inefficient packing of their rigid and contorted macromolecular chains. In contrast to other types of POP, PIMs are not comprised of a network of cross-linked covalent bonds so that they can be dissolved in organic solvents and processed into robust films, coatings or fibres. Here, over twelve years＇ accumulated research on the synthesis of PIMs is reviewed. To date, three types of polymerisation reaction have been used successfully to prepare PIMs of sufficient molecular mass to form robust self-standing films. These involve the formation of dibenzodioxin, Tr6ger＇s base and imide linkages between monomeric units. This rapid development of synthetic methods for preparing PIMs has been driven by their rich potential for numerous diverse applications and this synergistic relationship between synthesis and functionality is set to continue.
基金supported by the National Natural Science Foundation of China (Nos. 20971064 and 21071074)the Foundation for University Young Key Teacher by Henan Province (No. 2011GGJS-153)
文摘Two novel compounds, {[Co2（epda）2（4,4＇-bpy）（H20）z]＇3H20}n 1 and {[Co2（epda）2（bpe）（HzO）z]＇3HzO}n 2 （H2epda = 5-ethyl-pyridine-2,3-dicarboxylic acid, 4,4＇-bpy = 4,4＇-bipyridine and bpe = 1,2-di（4-pyridyl）ethylene） were solvothermally synthesized and charac- terized by elemental analysis, IR spectroscopy, thermogravimetric analysis （TGA）, and single- crystal X-ray diffraction. Complex 1 is ofmonoclinic system, space group P21/c with a = 13.344（5）, b = 14.724（5）, c = 8.267（3） A, fl = 105.840（4）~, V= 1562.5（10） A3, Dc = 1.480 g/cm3, Mr = 375.19, Z = 4, F（000） = 712, gl = 1.121 mm-1, the final R = 0.0512 and wR = 0.1260 for 2890 observed reflections with I 〉 2σ（I）. 2 belongs to the monoclinic system, space group P21/c with a = 14.224（4）, b = 14.726（4）, c = 8.287（2） A,β = 99.696（4）°, V= 1711.1（9） A3, Dc = 1.402 g/cm3, Mr = 388.21, Z = 4, F（000） = 740, kt = 1.027 mm-1, the final R = 0.0354 and wR = 0.0862 for 12237 observed reflections with I 〉 2a（/）. Both complexes present intimately related structures featuring infinite Co-carboxylate layers of [Con（epda）（H20）]n pillared by 4,4＇-bpy （or bpe） molecule to produce the microporous frameworks, Unambiguously indicating that pore dimensions of the framework are regulated by the N,N＇-donor pillars.
