Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relati...Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relationship between erosion and the productivity of purple soils has not been well studied.The purpose of this research was to determine if soil depth,which is dependent on the rate of erosion,has an influence on crop yield and growth.Plot and pot experiments at different soil depths were performed.Results indicate that soils from different parental materials had different growth features and crop yields due to the differential fertility of the derived soils.The yield reduction rate increases exponentially with the depth of eroded soil(level of erosion).The yield reduction rate per unit eroded soil horizon(10 cm) is approximately 10.5% for maize and wheat.展开更多
Objective： To study biomechanical changes of newly formed bones 24 weeks after repairing large defects of long bones of goats using heterogeneous deproteinated bone （DPB） prepared by modified methods as an engineer...Objective： To study biomechanical changes of newly formed bones 24 weeks after repairing large defects of long bones of goats using heterogeneous deproteinated bone （DPB） prepared by modified methods as an engineering scaffold. Methods： According to a fully randomized design, 18 goats were evenly divided into three groups： normal bone control group （Group A）, autologous bone group （Group B） and experimental group （Group C）. Each goat in Groups B and C were subjected to the periosteum and bone defect at middle-lower part of the right tibia （20% of the whole tibia in length）, followed by autologous bone or DPB plus autolognus MSCs ＋ rhBMP2 implantation, respectively and semi- ring slot fixation; while goats in Group A did not perform osteotomy. At 24 weeks after surgery, biomechanical tests were carried out on the tibias. Results： At 24 weeks after surgery, the results of anticompression test on tibias in three groups were recorded by a functional recorder presented as linear pressure-deformation curve. The shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values were 10.74 MPa±1.23 MPa, 10. 11 MPa±1.35 MPa and 10.22 MPa±1.32 MPa and fracture compression rates were 26.82%±0.87%, 27.17%±0.75% and 28.22%±1.12% in Groups A, B and C, respectively. Comparisons of anti-compression ultimate pressures and fracture compression rates among three groups demonstrated no significant difference （PAB=0.415, PBC=0.494）. Three-point antibend test on tibias was recorded as load-deformation curves, and the shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values of the anti-bend test were 481.52 N±12.45 N, 478.34 N±14.68 N and 475.62 N±13.41 N and the fracture bend rates were 2.62 mm±0.12 mm, 2.61 mm±0.15 mm and 2.81 mm±0.13 mm in Groups A, B and C, respectively. There was no significant difference between groups （PAB=0.7, PBc=0.448）. The ultimate anti-torsion torque values were 6.55 N.mi-0.25 N.m, 6.34 N＇m^0.18 N＇m and 6.42 N＇m^0.21 N＇m and fracture torsion rates were 29.51°±1.64°, 28.88±1.46° and 28.81°±1.33° in Groups A, B and C, respectively. There was no significant difference between groups （PAB=0.123, PBc=0.346）. Conclusions： The biomechanical characteristics of newly formed bones from heterogeneous DPB for repairing large segmental long bone defect are comparable to those of normal bones and autologous bones. DPB has the potential for clinical usage as bone graft material.展开更多
基金the National Natural Science Foundation Committee (Grant No.40971168)the National 973 Program(2007CB407206)
文摘Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relationship between erosion and the productivity of purple soils has not been well studied.The purpose of this research was to determine if soil depth,which is dependent on the rate of erosion,has an influence on crop yield and growth.Plot and pot experiments at different soil depths were performed.Results indicate that soils from different parental materials had different growth features and crop yields due to the differential fertility of the derived soils.The yield reduction rate increases exponentially with the depth of eroded soil(level of erosion).The yield reduction rate per unit eroded soil horizon(10 cm) is approximately 10.5% for maize and wheat.
文摘Objective： To study biomechanical changes of newly formed bones 24 weeks after repairing large defects of long bones of goats using heterogeneous deproteinated bone （DPB） prepared by modified methods as an engineering scaffold. Methods： According to a fully randomized design, 18 goats were evenly divided into three groups： normal bone control group （Group A）, autologous bone group （Group B） and experimental group （Group C）. Each goat in Groups B and C were subjected to the periosteum and bone defect at middle-lower part of the right tibia （20% of the whole tibia in length）, followed by autologous bone or DPB plus autolognus MSCs ＋ rhBMP2 implantation, respectively and semi- ring slot fixation; while goats in Group A did not perform osteotomy. At 24 weeks after surgery, biomechanical tests were carried out on the tibias. Results： At 24 weeks after surgery, the results of anticompression test on tibias in three groups were recorded by a functional recorder presented as linear pressure-deformation curve. The shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values were 10.74 MPa±1.23 MPa, 10. 11 MPa±1.35 MPa and 10.22 MPa±1.32 MPa and fracture compression rates were 26.82%±0.87%, 27.17%±0.75% and 28.22%±1.12% in Groups A, B and C, respectively. Comparisons of anti-compression ultimate pressures and fracture compression rates among three groups demonstrated no significant difference （PAB=0.415, PBC=0.494）. Three-point antibend test on tibias was recorded as load-deformation curves, and the shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values of the anti-bend test were 481.52 N±12.45 N, 478.34 N±14.68 N and 475.62 N±13.41 N and the fracture bend rates were 2.62 mm±0.12 mm, 2.61 mm±0.15 mm and 2.81 mm±0.13 mm in Groups A, B and C, respectively. There was no significant difference between groups （PAB=0.7, PBc=0.448）. The ultimate anti-torsion torque values were 6.55 N.mi-0.25 N.m, 6.34 N＇m^0.18 N＇m and 6.42 N＇m^0.21 N＇m and fracture torsion rates were 29.51°±1.64°, 28.88±1.46° and 28.81°±1.33° in Groups A, B and C, respectively. There was no significant difference between groups （PAB=0.123, PBc=0.346）. Conclusions： The biomechanical characteristics of newly formed bones from heterogeneous DPB for repairing large segmental long bone defect are comparable to those of normal bones and autologous bones. DPB has the potential for clinical usage as bone graft material.
