Simulating the typical carbonation step in a mineral CO_2 sequestration, precipitated calcium carbonate(PCC) was prepared by bubbling CO_2 gas into a rich Ca solution. These carbonation reactions were conducted at thr...Simulating the typical carbonation step in a mineral CO_2 sequestration, precipitated calcium carbonate(PCC) was prepared by bubbling CO_2 gas into a rich Ca solution. These carbonation reactions were conducted at three p H ranges, namely 10.0–9.0, 9.0–8.0, and 8.0–7.0, in which temperature and CO_2 flow rate are additional experimental variables. The PCC obtained in experiments was examined by Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD). It was found that supersaturation determined by p H value and flow rate of CO_2 has significant influence on polymorph of PCC. Vaterite was preferably formed at high supersaturation, while dissolution of metastable vaterite and crystallization of calcite occurred at low supersaturation. High temperature is a critical factor for the formation of aragonite. At 70 °C, vaterite, calcite and aragonite were observed to coexist in PCC because transformation from vaterite to aragonite via calcite occurred at this temperature. Scanning electron microscopy(SEM) technology was performed on prepared PCC, and various morphologies consistent with polymorphs were observed.展开更多
In recent years, there has been an increasing interest in wood properties, because wood is a commonly used and advanced building material. In this paper, the effect of anatomical characters on the transverse fracture ...In recent years, there has been an increasing interest in wood properties, because wood is a commonly used and advanced building material. In this paper, the effect of anatomical characters on the transverse fracture properties of green wood was investigated. The specific fracture energy （Gf J/m2） of ash （Fraxinus excelsior）, cherry （Prunus avium） and birch （Betula pendula） was evaluated using double edge notched tensile tests. The tests were performed on both earlywood （EW） and latewood （LW） zones in both the radial-tangential （RT） and the tangential-radial （TR） crack propagation systems. Wood anatomy and the failure patterns of each species were also investigated using environmental scanning electron microscopy （ESEM） and light microscopy （LMC）. The results showed that the Gfof RT fracture systems was around 1.5 times greater than in the TR one, whereas there were no significant differences between EW and LW zones. ESEM micrographs showed that the RT fracture system had a rougher fracture surface, while the TR had a nearly smooth and fiat fracture surface. In particular, the wood ofF. excelsior was the toughest, because of its greater percentage of rays and homogenous distribution of ray cells, while P. avium and B. pendula showed a lower Gf due to their smaller percentage of rays with a distinctive arrangement of ray cells.展开更多
The spore morphology of 9 species of 3 genera of Chinese liverworts was studied by scanning electron microscopic observation. They are Riccia huebeneriana Lindenb., R. hantamensis Perold., R. cavernosa Hoffm., R. warn...The spore morphology of 9 species of 3 genera of Chinese liverworts was studied by scanning electron microscopic observation. They are Riccia huebeneriana Lindenb., R. hantamensis Perold., R. cavernosa Hoffm., R. warnstorfii Limpr. ex Warnst., R. frostii Aust., R. chinensis Herz., Asterella yoshinagana (Horik.) Horik., A. sanguinia L. et L., and Preissia quadrata (Scop.) Nees. There were evident morphological differences in spores among the above three genera. Difference of species morphology in the same genus was also observed. Therefore in the above genera and species the spore-wall ornamentation can be regarded as a criterion for taxonomic specificity. Meanwhile, slight difference in morphological characters of the same species collected from different sites was observed and reckoned to be an ecological adaptation.展开更多
Objectives To construct the cancellous bone explant model and a method of culturing these bone tissues in vitro, and to investigate the effect of mechanical load on growth of cancellous bone tissue in vtro. Methods C...Objectives To construct the cancellous bone explant model and a method of culturing these bone tissues in vitro, and to investigate the effect of mechanical load on growth of cancellous bone tissue in vtro. Methods Cancellous bone were extracted from rabbit femoral head and cut into I-ram-thick and 8-ram-diameter slices under sterile conditions. HE staining and scanning electron microscopy were employed to identify the histomorphology of the model after being cultured with a new dynamic load and circulating perfusion bioreactor system for 0, 3, 5, and 7 days, respectively. We built a three-dimensional model using microCT and analyzed the loading effects using finite element analysis. The model was subjected to mechanical load of 1000, 2000, 3000, and 4000 με respectively for 30 minutes per day. After 5 days of continuous stimuli, the activities of alkaline phosphatase （AKP） and tartrate-resistant acid phosphatase （TRAP） were detected. Apoptosis was analyzed by DNA ladder detection and caspase-3/8/9 activity detection. Results After being cultured for 3, 5, and 7 days, the bone explant model grew well. HE staining showed the apparent nucleus in cells at the each indicated time, and electron microscope revealed the living cells in the bone tissue. The activities of AKP and TRAP in the bone explant model under mechanical load of 3000 and 4000 με were significantly lower than those in the unstressed bone tissues （all P〈0.05）. DNA ladders were seen in the bone tissue under 3000 and 4000με mechanical load. Moreover, there was significant enhancement in the activities of caspase-3/8/9 in the mechanical stress group of 3000 and 4000 με （all P〈0.05）. Conclusions The cancellous bone explant model extracted from the rabbit femoral head could be alive at least for 7 days in the dynamic load and circulating perfusion bioreactor system, however, pathological mechanical load could affect the bone tissue growth by apoptosis in vitro. The differentiation of osteobiasts and osteoclasts might be inhibited after the model is stimulated by mechanical load of 3000 and 4000 με.展开更多
Tungsten carbide and zeolite nanocomposite was prepared by combining a mechanochemical approach with a reduction and carbonization approach,using natural zeolite and ammonia metatungstate as precursors.The sample was ...Tungsten carbide and zeolite nanocomposite was prepared by combining a mechanochemical approach with a reduction and carbonization approach,using natural zeolite and ammonia metatungstate as precursors.The sample was characterized by X-ray diffraction and scanning electron microscope.The results showed that the crystal phase of the sample is composed of zeolite,monotungsten carbide and bitungsten carbide.The mass percentage and the crystallite diameter of tungsten carbide change along with the reacted time.Its electrocatalytic activity was measured with a microelectrode system with three electrodes.The results show that its electrocatalytic property is related to its crystal phase and the mass percentage of tungsten carbide,and its electrocatalytic activity is connected with the property of electrolyte,in which it is measured.Synergistic effect between tungsten carbide and zeolite is found during electrocatalysis.展开更多
Eggshells are one of the most common and well-studied biomaterials in nature and exhibit unique properties of gas conduction. However, the morphologies of eggshells at the submicro-/nano-scale and their impact on eggs...Eggshells are one of the most common and well-studied biomaterials in nature and exhibit unique properties of gas conduction. However, the morphologies of eggshells at the submicro-/nano-scale and their impact on eggshell functions remain unclear. In this work, the architecture of hen＇s eggshell at different length scales has been systematically investigated by scanning electron microscopy （SEM） and environmental SEM （ESEM）. It is found that the skeleton of calcium carbonate （CaCO3） has hierarchical structures at nano- to micro-scales： primary nano-particles of -10 Fain loosely congregate giving a porous and rough texture, and compose the upper-level morphologies including submicro spheres, nano-rods, rhombohedral-cleavage pattern and slices, which are elaborately arranged in a surface layer, palisade layer and mammillary layer along the radial direction. Accordingly, the pore system exhibits a three-level hierarchy, namely nano-scale pores （between nano-rods and primary nano-particles）, submicro-scale pores （＂bubble pores＂） and micro-scale pores （opening of ＂gas pores＂）. Further investigation shows that hen＇s eggshell regulates gas conduction through adjusting the sizes and numbers of submicro-scale ＂bubble pores＂. Based on our observations, a new description of hen＇s eggshell is presented, which amends the conventional view of micro-scale, straight and permeating ＂gas pores＂, and reveals the role of hierarchical pores in gas conduction and contamination resistance.展开更多
Superabsorbent polymers(SAPs) as soil moisture conditioners have been increasingly used in agriculture, but conflicting results were reported regarding the effects of SAPs on crop growth. In this study, both laborator...Superabsorbent polymers(SAPs) as soil moisture conditioners have been increasingly used in agriculture, but conflicting results were reported regarding the effects of SAPs on crop growth. In this study, both laboratory cultivation and analysis were conducted to investigate the effects of different SAPs on the growth and physiology of crops under water-saving agricultural practices. Maize(Zea mays L.) seedlings were cultivated using distilled water or three different SAP hydrogels, sodium polyacrylate(SP), potassium polyacrylate(PP), and sodium polyacrylate embedded with phosphate rock powder(SPP), as growth media. Growth characteristics of the model plant and damage were assessed using scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results showed that both the SP and PP treatments had pronounced negative effect on the hydrogels of growth of maize seedlings. The SPP treatment appeared to facilitate the stem-leaf growth and had no obvious adverse effect on root growth. All the three hydrogel treatments caused varying degrees of damage to the organizational structure and cellular morphology of the roots, with the SP and PP treatments causing the most severe damage; the membrane system of root cells was damaged by both SP and PP treatments. An excessive accumulation of sodium and reduction of calcium occurred in the roots may be responsible for the observed damage to the cell membrane system, which, in turn, may have promoted the wilting of the cells.展开更多
基金Supported by the National Natural Science Foundation of China(41471412)
文摘Simulating the typical carbonation step in a mineral CO_2 sequestration, precipitated calcium carbonate(PCC) was prepared by bubbling CO_2 gas into a rich Ca solution. These carbonation reactions were conducted at three p H ranges, namely 10.0–9.0, 9.0–8.0, and 8.0–7.0, in which temperature and CO_2 flow rate are additional experimental variables. The PCC obtained in experiments was examined by Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD). It was found that supersaturation determined by p H value and flow rate of CO_2 has significant influence on polymorph of PCC. Vaterite was preferably formed at high supersaturation, while dissolution of metastable vaterite and crystallization of calcite occurred at low supersaturation. High temperature is a critical factor for the formation of aragonite. At 70 °C, vaterite, calcite and aragonite were observed to coexist in PCC because transformation from vaterite to aragonite via calcite occurred at this temperature. Scanning electron microscopy(SEM) technology was performed on prepared PCC, and various morphologies consistent with polymorphs were observed.
文摘In recent years, there has been an increasing interest in wood properties, because wood is a commonly used and advanced building material. In this paper, the effect of anatomical characters on the transverse fracture properties of green wood was investigated. The specific fracture energy （Gf J/m2） of ash （Fraxinus excelsior）, cherry （Prunus avium） and birch （Betula pendula） was evaluated using double edge notched tensile tests. The tests were performed on both earlywood （EW） and latewood （LW） zones in both the radial-tangential （RT） and the tangential-radial （TR） crack propagation systems. Wood anatomy and the failure patterns of each species were also investigated using environmental scanning electron microscopy （ESEM） and light microscopy （LMC）. The results showed that the Gfof RT fracture systems was around 1.5 times greater than in the TR one, whereas there were no significant differences between EW and LW zones. ESEM micrographs showed that the RT fracture system had a rougher fracture surface, while the TR had a nearly smooth and fiat fracture surface. In particular, the wood ofF. excelsior was the toughest, because of its greater percentage of rays and homogenous distribution of ray cells, while P. avium and B. pendula showed a lower Gf due to their smaller percentage of rays with a distinctive arrangement of ray cells.
文摘The spore morphology of 9 species of 3 genera of Chinese liverworts was studied by scanning electron microscopic observation. They are Riccia huebeneriana Lindenb., R. hantamensis Perold., R. cavernosa Hoffm., R. warnstorfii Limpr. ex Warnst., R. frostii Aust., R. chinensis Herz., Asterella yoshinagana (Horik.) Horik., A. sanguinia L. et L., and Preissia quadrata (Scop.) Nees. There were evident morphological differences in spores among the above three genera. Difference of species morphology in the same genus was also observed. Therefore in the above genera and species the spore-wall ornamentation can be regarded as a criterion for taxonomic specificity. Meanwhile, slight difference in morphological characters of the same species collected from different sites was observed and reckoned to be an ecological adaptation.
基金Supported by grants from the National Natural Science Foundation Key Project of China(10832012)the National Natural Science Foundation of China(31370942 and 11072266)
文摘Objectives To construct the cancellous bone explant model and a method of culturing these bone tissues in vitro, and to investigate the effect of mechanical load on growth of cancellous bone tissue in vtro. Methods Cancellous bone were extracted from rabbit femoral head and cut into I-ram-thick and 8-ram-diameter slices under sterile conditions. HE staining and scanning electron microscopy were employed to identify the histomorphology of the model after being cultured with a new dynamic load and circulating perfusion bioreactor system for 0, 3, 5, and 7 days, respectively. We built a three-dimensional model using microCT and analyzed the loading effects using finite element analysis. The model was subjected to mechanical load of 1000, 2000, 3000, and 4000 με respectively for 30 minutes per day. After 5 days of continuous stimuli, the activities of alkaline phosphatase （AKP） and tartrate-resistant acid phosphatase （TRAP） were detected. Apoptosis was analyzed by DNA ladder detection and caspase-3/8/9 activity detection. Results After being cultured for 3, 5, and 7 days, the bone explant model grew well. HE staining showed the apparent nucleus in cells at the each indicated time, and electron microscope revealed the living cells in the bone tissue. The activities of AKP and TRAP in the bone explant model under mechanical load of 3000 and 4000 με were significantly lower than those in the unstressed bone tissues （all P〈0.05）. DNA ladders were seen in the bone tissue under 3000 and 4000με mechanical load. Moreover, there was significant enhancement in the activities of caspase-3/8/9 in the mechanical stress group of 3000 and 4000 με （all P〈0.05）. Conclusions The cancellous bone explant model extracted from the rabbit femoral head could be alive at least for 7 days in the dynamic load and circulating perfusion bioreactor system, however, pathological mechanical load could affect the bone tissue growth by apoptosis in vitro. The differentiation of osteobiasts and osteoclasts might be inhibited after the model is stimulated by mechanical load of 3000 and 4000 με.
基金Supported by the National Natural Science Foundation of China (21173193)the Natural Science Foundation of Zhejiang Province (Y4080209, Y406094)the Science Plan of Zhejiang Province (2007F70039)
文摘Tungsten carbide and zeolite nanocomposite was prepared by combining a mechanochemical approach with a reduction and carbonization approach,using natural zeolite and ammonia metatungstate as precursors.The sample was characterized by X-ray diffraction and scanning electron microscope.The results showed that the crystal phase of the sample is composed of zeolite,monotungsten carbide and bitungsten carbide.The mass percentage and the crystallite diameter of tungsten carbide change along with the reacted time.Its electrocatalytic activity was measured with a microelectrode system with three electrodes.The results show that its electrocatalytic property is related to its crystal phase and the mass percentage of tungsten carbide,and its electrocatalytic activity is connected with the property of electrolyte,in which it is measured.Synergistic effect between tungsten carbide and zeolite is found during electrocatalysis.
文摘Eggshells are one of the most common and well-studied biomaterials in nature and exhibit unique properties of gas conduction. However, the morphologies of eggshells at the submicro-/nano-scale and their impact on eggshell functions remain unclear. In this work, the architecture of hen＇s eggshell at different length scales has been systematically investigated by scanning electron microscopy （SEM） and environmental SEM （ESEM）. It is found that the skeleton of calcium carbonate （CaCO3） has hierarchical structures at nano- to micro-scales： primary nano-particles of -10 Fain loosely congregate giving a porous and rough texture, and compose the upper-level morphologies including submicro spheres, nano-rods, rhombohedral-cleavage pattern and slices, which are elaborately arranged in a surface layer, palisade layer and mammillary layer along the radial direction. Accordingly, the pore system exhibits a three-level hierarchy, namely nano-scale pores （between nano-rods and primary nano-particles）, submicro-scale pores （＂bubble pores＂） and micro-scale pores （opening of ＂gas pores＂）. Further investigation shows that hen＇s eggshell regulates gas conduction through adjusting the sizes and numbers of submicro-scale ＂bubble pores＂. Based on our observations, a new description of hen＇s eggshell is presented, which amends the conventional view of micro-scale, straight and permeating ＂gas pores＂, and reveals the role of hierarchical pores in gas conduction and contamination resistance.
基金supported by the National Natural Science Foundation of China (Nos. 30600347 and 41071162)the Science and Technology Program of Guangzhou City, China (Nos. 201508030039 and 201604020074)
文摘Superabsorbent polymers(SAPs) as soil moisture conditioners have been increasingly used in agriculture, but conflicting results were reported regarding the effects of SAPs on crop growth. In this study, both laboratory cultivation and analysis were conducted to investigate the effects of different SAPs on the growth and physiology of crops under water-saving agricultural practices. Maize(Zea mays L.) seedlings were cultivated using distilled water or three different SAP hydrogels, sodium polyacrylate(SP), potassium polyacrylate(PP), and sodium polyacrylate embedded with phosphate rock powder(SPP), as growth media. Growth characteristics of the model plant and damage were assessed using scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results showed that both the SP and PP treatments had pronounced negative effect on the hydrogels of growth of maize seedlings. The SPP treatment appeared to facilitate the stem-leaf growth and had no obvious adverse effect on root growth. All the three hydrogel treatments caused varying degrees of damage to the organizational structure and cellular morphology of the roots, with the SP and PP treatments causing the most severe damage; the membrane system of root cells was damaged by both SP and PP treatments. An excessive accumulation of sodium and reduction of calcium occurred in the roots may be responsible for the observed damage to the cell membrane system, which, in turn, may have promoted the wilting of the cells.
