This study investigates the instability characteristics of dynamic disasters resulting from disruption caused by extracting resources underground. Utilizing the split Hopkinson pressure bar (SHPB) system, the dynamic ...This study investigates the instability characteristics of dynamic disasters resulting from disruption caused by extracting resources underground. Utilizing the split Hopkinson pressure bar (SHPB) system, the dynamic response mechanism of coal energy evolution is examined, and the energy instability criterion is established. The validity of the instability criterion is explored from the standpoint of damage progression. The results demonstrate that the energy conversion mechanism undergoes a fundamental alternation under impact disturbance. Moreover, the energy release rate as well as the energy dissipation rate undergo comparable changes across distinct levels of impact disturbance. The distinction between the energy release rate and the energy dissipation rate (DRD) increases as coal mass deformation grows. Prior to coal facing instability and failure, the DRD experienced an inflection point followed by a sharp decrease. In conjunction with the discussion on the damage evolution, the physical and mechanical significance of DRD remains clear, which can essentially describe the whole impact loading process. The phenomenon that the inflection point appears and DRD subsequently suddenly decreases can be employed as the energy criterion prior to the failure of instability. Furthermore, this paper provides significant reference for the prediction of dynamic instability of coal under dynamic disturbance.展开更多
Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the v...Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the video camera was used to record the deformation and failure process of rock.The distribution of meso-components in video images was then identified.The meso-components of rock failure precursors were also discussed.Moreover,a modified LSTM(long short-term memory method)based on SSA(sparrow search algorithm)was proposed to estimate the change of meso-components of rock failure precursor.It shows that the initiation and expansion of cracks are mainly caused by feldspar and quartz fracture,and when the quartz and feldspar exit the stress framework,rock failure occurs;the second large increase of crack area and the second large decrease of quartz or feldspar area may be used as a precursor of rock failure;the precursor time of rock failure based on meso-scopic components is about 4 s earlier than that observed by the naked eye;the modified LSTM network has the strongest estimation ability for quartz area change,followed by feldspar and biotite,and has the worst estimation ability for cracks;when using the modified LSTM network to predict the precursors of rock instability and failure,quartz and feldspar could be given priority.The results presented herein may provide reference in the investigation of rock failure mechanism.展开更多
Types and characteristics of gastric dysplasia werestudied histopathologically. Besides the adenomatous,cryptal and globoid dysplasias, regenerative type of gas-tric dysplasia was described, especially about its histo...Types and characteristics of gastric dysplasia werestudied histopathologically. Besides the adenomatous,cryptal and globoid dysplasias, regenerative type of gas-tric dysplasia was described, especially about its histo-pathological features and histogenesis. The peculiarityof this type of gastric dysplasia just coincided with thefindings of gastric mucosal changes found in the inhabitantsliving in Liaodong Panisula-a high incidence area ofgastric cancer. According to the epidemiologic and histo-pathologic studies on the inhabitants of Zhuanghe Countyof Liaodong Panisula, it was found that high salted foodse.g. the salted pork and fish etc. showed strongmutagenecity. The authors detected that these were therisk factors and might be the leading cause of the gastricmucosal erosions and following by epithelial regenerativechanges. Malignant changes were detected in the regene-rative dysplastic lesions in pathologic sections. Therefore,gastric mucosal regeneration should not be oper looked asa precursor of gastric cancer in some cases.展开更多
The anoxic decomposition and influence of carbon precursors on the properties of LiFePO_4/C prepared by using Fe_2O_3 were investigated.X-ray powder diffractometry,Fourier transform infrared spectroscopy(FTIR),scannin...The anoxic decomposition and influence of carbon precursors on the properties of LiFePO_4/C prepared by using Fe_2O_3 were investigated.X-ray powder diffractometry,Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM) and carbon content and charge–discharge tests were applied to the characterization of the as-synthesized cathodes.Partial carbon is lost in the anaerobic decomposition of organic precursors and a high hydrogen content leads to a high residual carbon rate.Pyromellitic anhydride and citric acid participate in reactions before and in ball-milling.All the chosen carbon precursors are capable of producing LiFePO_4 with high degree of crystallinity and purity.The carbon derived from α-D-glucose,pyromellitic anhydride,soluble starch,citric acid and polyacrylamide has a loose and porous texture in LiFePO_4/C which forms conduction on and between LiFePO_4 particles.LiFePO_4/C prepared by using α-D-glucose,pyromellitic anhydride,citric acid and sucrose exhibits appreciable electrochemical performance.Graphite alone is able to enhance the electrochemical performance of LiFePO_4 to a limited extent but incapable of preparing practical cathode.展开更多
Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coati...Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition(CVD)technique.Fiber/matrix debonding and relatively long fiber pullouts were observed on the fracture surfaces.Additionally,the flexural strength and elastic modulus of the composites with and without fiber/matrix interphase layer were investigated using three-point bending test and single-edge notched beam test.The results show that the fiber fraction and the porosity of 2D-SiC/SiC composites with and without coating are 27.2%(volume fraction)and 11.1%,and 40.7%(volume fraction)and 7.5%,respectively.And the flexural strength and elastic modulus of 2D-SiC/SiC composites with and without coating are 363.3 MPa and 127.8 GPa,and 180.2 MPa and 97.2 GPa,respectively.With a proper thickness,the coating can effectively adjust the fiber/matrix interface,thus causing a dramatic increase in the mechanical properties of the composites.展开更多
Electromagnetic signals may be a promising precursor to seismic activity which has been observed in many case studies in past decades.However,the correlation and causation between the electromagnetic signals and the s...Electromagnetic signals may be a promising precursor to seismic activity which has been observed in many case studies in past decades.However,the correlation and causation between the electromagnetic signals and the seismic activity are still unclear without intensive observation network.In order to find seismoelectromagnetic phenomenon,we deployed AETA(acoustic and electromagnetic testing all-in-one system),a high-density multi-component seismic monitoring system in the China Earthquake Science Experiment site(CESE,in Sichuan Province and Yunnan Province,China)and the capital circle(areas with a distance which is≤200 km from Beijing),to record electromagnetic and geo-acoustic data across 0.1 Hz−10 kHz.In the course of data collection,we discovered an electromagnetic waveform that occurs on a daily basis.Because the signal generally coincides with sunrise and sunset,we named this phenomenon the SRSS(Sunrise-Sunset)waveform.After conducting three statistical tests based on seismicity and SRSS,we determined that the SRSS waveform is roughly correlated with the onset of seismic activity.It generally occurs at the regions where seismicity occurs.This discovery might have significant implications with respect to the future of earthquake prediction.展开更多
In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepare...In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepared Fe2P2O7, Li2CO3 and glucose as raw materials, pure LiFePO4 and LiFePO4/C composite materials were respectively synthesized by solid state reaction at 700 ℃ in an argon atmosphere. X-ray diffractometry and scanning electron microscopy（SEM） were employed to characterize the as-prepared Fe2P2O7, LiFePO4 and LiFePO4/C. The as-prepared Fe2P2O7 crystallizes in the Cl space group and belongs to β-Fe2P2O7 for crystal phase. The particle size distribution of Fe2P2O7 observed by SEM is 0.4-3.0 μm. During the Li^＋ ion chemical intercalation, radical P2O7^4- is disrupted into two PO4^3- ions in the presence of O^2-, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO4/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.展开更多
From Octobet 1998 to January 1999,5 earthquakes ( M s≥5) occurred between Ninglang and Yanyuan counties (27°07′～27°12′N,100°40′～101°00′E area).They were situated in 140km southwest of the Xi...From Octobet 1998 to January 1999,5 earthquakes ( M s≥5) occurred between Ninglang and Yanyuan counties (27°07′～27°12′N,100°40′～101°00′E area).They were situated in 140km southwest of the Xichang.Among them,the largest one is M s 6 2 on November 19,1998.Based on small seismic data by the seismic remote sensing station of Xichang and the seismological station of Muli,and regional observation data,passing through careful observation and scientific analyses,we had made better forecasts before the earthquakes.That results obvious social benefits.By processing data of precursory earthquakes,such as,original observation data of total geomagnetic intensity from the station of Xichang,pressure capacitance stressometer and quartz horizaontal pendulum tiltmeter from the Xiaomiao station of Xichang,we summarized the sequence characteristics of the series earthquakes.The information about short\|term anomaly of gruond strain,total geomagnetic intensity and ground tilt before the earthquake is emphatically explained.展开更多
We have constructed a retroviral vector mediated mammalian cell expression system of the capsid precursor protein of foot-and-mouth disease virus(FMDV).The recombinant retroviral vector pBABEpuro-P1-2A-EGFP was constr...We have constructed a retroviral vector mediated mammalian cell expression system of the capsid precursor protein of foot-and-mouth disease virus(FMDV).The recombinant retroviral vector pBABEpuro-P1-2A-EGFP was constructed by sequentially inserting capsid precursor protein gene(P1) of FMDV and enhanced green fluorescent protein gene(EGFP) into pBABEpuro.The recombinant retroviral vector and the pVSV-G plasmid were co-transfected into packaging cells(GP2-293) by liposomemediated transduction to produce the pseudovirus.The pseudovirus was used to infect BHK-21 cells and resistant cells were screened with puromycin.Green fluorescent proteins were observed by fluorescence microscopy and expression of the capsid precursor protein gene of FMDV was detected by indirect immunofluorescence.The recombinant retroviral vector pBABEpuro-P1-2A-EGFP was constructed successfully.The capsid precursor protein of FMDV and green fluorescent protein were expressed in BHK-21 cells.The mammalian cell expression system for the capsid precursor protein of FMDV has been constructed successfully,which lays the foundation of development of a FMDV subunit vaccine.展开更多
In this article, spherical black spots-like selenium metal nanoparticles were synthesized. Accordingly, this experimental work proposed an innovative facile, green, one-step and solvent-free strategy to a large scale ...In this article, spherical black spots-like selenium metal nanoparticles were synthesized. Accordingly, this experimental work proposed an innovative facile, green, one-step and solvent-free strategy to a large scale synthesis of Se-NPs via thermal decomposition of green precursor. The Se(Ⅳ) L-glutamine precursor was prepared by solid state grinding using selenium(Ⅳ) tetrachloride, SeCl4, and L-glutamine for 2 hr without using any organic solvent. It was characterized by infrared spectroscopy, and micro analytical. The solid precursor compound was subsequently annealed in the muffle furnace at 300 ℃ for 3 hr in static air. Selenium NPs was resulted and well characterized using X-ray powder diffraction(XRD), FT-IR spectroscopy, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The FTIR and XRD data showed that the Se NPs is pure and has a good crystalline structure because no characteristic peaks of impurity were detected, while the SEM and TEM results showed that the obtained product is tiny, aggregated with spherical-like shape, narrow size distribution with an average size between 5~10 nm. Results show that the solid state thermal decomposition method is simple, eco-friendly, safe and suitable for preparation of SeNPs. This method can also be applied to synthesize nanoparticles pure metal and metal oxides.展开更多
The effects of polyurethane sponge pretreatment and slurry compositions on the slurry loading in precursor were discussed,and the performances of stainless steel foams prepared from precursors with different slurry lo...The effects of polyurethane sponge pretreatment and slurry compositions on the slurry loading in precursor were discussed,and the performances of stainless steel foams prepared from precursors with different slurry loadings and different particle sizes of the stainless steel powder were also investigated.The experimental results show that the pretreatment of sponge with alkaline solution is effective to reduce the jam of cells in precursor and ensure the slurry to uniformly distribute in sponge,and it is also an effective method for increasing the slurry loading in precursor;the mass fraction of additive A and solid content in slurry greatly affect the slurry loading in precursor,when they are kept in 9%-13% and 52%-75%,respectively,the stainless steel foam may hold excellent 3D open-cell network structure and uniform muscles;the particle size of the stainless steel powder and the slurry loading in precursor have great effects on the bending strength,apparent density and open porosity of stainless steel foam;when the stainless steel powder with particle size of 44 μm and slurry loading of 0.5 g/cm3 in precursor are used,a stainless steel foam can be obtained,which has open porosity of 81.2%,bending strength of about 51.76 MPa and apparent density of about 1.0 g/cm3.展开更多
Local segregation in Cu-In precursors and its effects on the element distribution and microstructures of selenized CuInSe2 thin films were investigated. Cu-In precursors with an ideal total mole ratio of Cu to In of 0...Local segregation in Cu-In precursors and its effects on the element distribution and microstructures of selenized CuInSe2 thin films were investigated. Cu-In precursors with an ideal total mole ratio of Cu to In of 0.92 were prepared by middle frequency alternating current magnetron sputtering with Cu-In alloy target, then CuInSe2 absorbers for solar cells were formed by selenization process in selenium atmosphere. Scanning electron microscope and energy dispersive X-ray spectroscope were used respectively to observe the surface morphologies and determine the compositions of both Cu-In precursors and CuInSe2 thin films. Their microstructures were characterized by X-ray diffractometry and Raman spectroscope. The results show that Cu-In precursors are mainly composed of (Cu11In9) phase with In-rich solid solution. Stoichiometric CuInSe2 thin films with a homogeneous element distribution and single chalcopyrite phase can be synthesized from a segregated Cu-In precursor film with an ideal total mole ratio of Cu to In of 0.92. CuInSe2 thin film shows P-type conductivity and its resistivity reaches 1.2×103Ω·cm.展开更多
In this paper, we investigate the precursors of large earthquakes in the eastern region of Taiwan by means of the reverse tracing of precursors. We discuss the parameters which are suitable for the seismic chains and ...In this paper, we investigate the precursors of large earthquakes in the eastern region of Taiwan by means of the reverse tracing of precursors. We discuss the parameters which are suitable for the seismic chains and intermedi- ate-term patterns in this region and obtain the threshold of the patterns. Applying the linear discriminate method to the intermediate-term patterns of seismic chains, we present an approach for exploring the precursors of large earthquakes. The results show that this method can reduce the false alarm rate for large earthquakes in this region, and the reverse tracing of precursors can be applied to the eastern region of Taiwan.展开更多
基金Projects(51934007,12072363,52004268) supported by the National Natural Science Foundation of ChinaProject(22KJD440002) supported by the Natural Science Fund for Colleges and Universities in Jiangsu Province,China。
文摘This study investigates the instability characteristics of dynamic disasters resulting from disruption caused by extracting resources underground. Utilizing the split Hopkinson pressure bar (SHPB) system, the dynamic response mechanism of coal energy evolution is examined, and the energy instability criterion is established. The validity of the instability criterion is explored from the standpoint of damage progression. The results demonstrate that the energy conversion mechanism undergoes a fundamental alternation under impact disturbance. Moreover, the energy release rate as well as the energy dissipation rate undergo comparable changes across distinct levels of impact disturbance. The distinction between the energy release rate and the energy dissipation rate (DRD) increases as coal mass deformation grows. Prior to coal facing instability and failure, the DRD experienced an inflection point followed by a sharp decrease. In conjunction with the discussion on the damage evolution, the physical and mechanical significance of DRD remains clear, which can essentially describe the whole impact loading process. The phenomenon that the inflection point appears and DRD subsequently suddenly decreases can be employed as the energy criterion prior to the failure of instability. Furthermore, this paper provides significant reference for the prediction of dynamic instability of coal under dynamic disturbance.
基金Project(41472254)supported by the National Natural Science Foundation of China。
文摘Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the video camera was used to record the deformation and failure process of rock.The distribution of meso-components in video images was then identified.The meso-components of rock failure precursors were also discussed.Moreover,a modified LSTM(long short-term memory method)based on SSA(sparrow search algorithm)was proposed to estimate the change of meso-components of rock failure precursor.It shows that the initiation and expansion of cracks are mainly caused by feldspar and quartz fracture,and when the quartz and feldspar exit the stress framework,rock failure occurs;the second large increase of crack area and the second large decrease of quartz or feldspar area may be used as a precursor of rock failure;the precursor time of rock failure based on meso-scopic components is about 4 s earlier than that observed by the naked eye;the modified LSTM network has the strongest estimation ability for quartz area change,followed by feldspar and biotite,and has the worst estimation ability for cracks;when using the modified LSTM network to predict the precursors of rock instability and failure,quartz and feldspar could be given priority.The results presented herein may provide reference in the investigation of rock failure mechanism.
基金This research was supported by the National "7.5" Research Grant on Cancer.
文摘Types and characteristics of gastric dysplasia werestudied histopathologically. Besides the adenomatous,cryptal and globoid dysplasias, regenerative type of gas-tric dysplasia was described, especially about its histo-pathological features and histogenesis. The peculiarityof this type of gastric dysplasia just coincided with thefindings of gastric mucosal changes found in the inhabitantsliving in Liaodong Panisula-a high incidence area ofgastric cancer. According to the epidemiologic and histo-pathologic studies on the inhabitants of Zhuanghe Countyof Liaodong Panisula, it was found that high salted foodse.g. the salted pork and fish etc. showed strongmutagenecity. The authors detected that these were therisk factors and might be the leading cause of the gastricmucosal erosions and following by epithelial regenerativechanges. Malignant changes were detected in the regene-rative dysplastic lesions in pathologic sections. Therefore,gastric mucosal regeneration should not be oper looked asa precursor of gastric cancer in some cases.
基金Project(2010ZC051)supported by Natural Science Foundation of Yunnan Province,ChinaProject(20140439)supported by Analysis and Testing Foundation of Kuming University of Science and Technology,ChinaProject(14118245)supported by the Starting Research Fund from Kunming University of Science and Technology,China
文摘The anoxic decomposition and influence of carbon precursors on the properties of LiFePO_4/C prepared by using Fe_2O_3 were investigated.X-ray powder diffractometry,Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM) and carbon content and charge–discharge tests were applied to the characterization of the as-synthesized cathodes.Partial carbon is lost in the anaerobic decomposition of organic precursors and a high hydrogen content leads to a high residual carbon rate.Pyromellitic anhydride and citric acid participate in reactions before and in ball-milling.All the chosen carbon precursors are capable of producing LiFePO_4 with high degree of crystallinity and purity.The carbon derived from α-D-glucose,pyromellitic anhydride,soluble starch,citric acid and polyacrylamide has a loose and porous texture in LiFePO_4/C which forms conduction on and between LiFePO_4 particles.LiFePO_4/C prepared by using α-D-glucose,pyromellitic anhydride,citric acid and sucrose exhibits appreciable electrochemical performance.Graphite alone is able to enhance the electrochemical performance of LiFePO_4 to a limited extent but incapable of preparing practical cathode.
基金Project(NCET-07-0228)support by the New Century Excellent Talents in University
文摘Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition(CVD)technique.Fiber/matrix debonding and relatively long fiber pullouts were observed on the fracture surfaces.Additionally,the flexural strength and elastic modulus of the composites with and without fiber/matrix interphase layer were investigated using three-point bending test and single-edge notched beam test.The results show that the fiber fraction and the porosity of 2D-SiC/SiC composites with and without coating are 27.2%(volume fraction)and 11.1%,and 40.7%(volume fraction)and 7.5%,respectively.And the flexural strength and elastic modulus of 2D-SiC/SiC composites with and without coating are 363.3 MPa and 127.8 GPa,and 180.2 MPa and 97.2 GPa,respectively.With a proper thickness,the coating can effectively adjust the fiber/matrix interface,thus causing a dramatic increase in the mechanical properties of the composites.
基金Projects(KJYY20170721151955849,JCYJ20190808161401653)supported by Fundamental Research Grant from Shenzhen Science&Technology,China。
文摘Electromagnetic signals may be a promising precursor to seismic activity which has been observed in many case studies in past decades.However,the correlation and causation between the electromagnetic signals and the seismic activity are still unclear without intensive observation network.In order to find seismoelectromagnetic phenomenon,we deployed AETA(acoustic and electromagnetic testing all-in-one system),a high-density multi-component seismic monitoring system in the China Earthquake Science Experiment site(CESE,in Sichuan Province and Yunnan Province,China)and the capital circle(areas with a distance which is≤200 km from Beijing),to record electromagnetic and geo-acoustic data across 0.1 Hz−10 kHz.In the course of data collection,we discovered an electromagnetic waveform that occurs on a daily basis.Because the signal generally coincides with sunrise and sunset,we named this phenomenon the SRSS(Sunrise-Sunset)waveform.After conducting three statistical tests based on seismicity and SRSS,we determined that the SRSS waveform is roughly correlated with the onset of seismic activity.It generally occurs at the regions where seismicity occurs.This discovery might have significant implications with respect to the future of earthquake prediction.
基金Project(50604018)supported by the National Natural Science Foundation of China
文摘In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepared Fe2P2O7, Li2CO3 and glucose as raw materials, pure LiFePO4 and LiFePO4/C composite materials were respectively synthesized by solid state reaction at 700 ℃ in an argon atmosphere. X-ray diffractometry and scanning electron microscopy（SEM） were employed to characterize the as-prepared Fe2P2O7, LiFePO4 and LiFePO4/C. The as-prepared Fe2P2O7 crystallizes in the Cl space group and belongs to β-Fe2P2O7 for crystal phase. The particle size distribution of Fe2P2O7 observed by SEM is 0.4-3.0 μm. During the Li^＋ ion chemical intercalation, radical P2O7^4- is disrupted into two PO4^3- ions in the presence of O^2-, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO4/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.
文摘From Octobet 1998 to January 1999,5 earthquakes ( M s≥5) occurred between Ninglang and Yanyuan counties (27°07′～27°12′N,100°40′～101°00′E area).They were situated in 140km southwest of the Xichang.Among them,the largest one is M s 6 2 on November 19,1998.Based on small seismic data by the seismic remote sensing station of Xichang and the seismological station of Muli,and regional observation data,passing through careful observation and scientific analyses,we had made better forecasts before the earthquakes.That results obvious social benefits.By processing data of precursory earthquakes,such as,original observation data of total geomagnetic intensity from the station of Xichang,pressure capacitance stressometer and quartz horizaontal pendulum tiltmeter from the Xiaomiao station of Xichang,we summarized the sequence characteristics of the series earthquakes.The information about short\|term anomaly of gruond strain,total geomagnetic intensity and ground tilt before the earthquake is emphatically explained.
基金supported by the National Programs for High Technology Research and Development of China (2006AA10A204)the Gansu Key Technologies R&D Program(ZGS-052-A41-0006-03)the Programs for Director Fund of Lanzhou Veterinary Research Institute
文摘We have constructed a retroviral vector mediated mammalian cell expression system of the capsid precursor protein of foot-and-mouth disease virus(FMDV).The recombinant retroviral vector pBABEpuro-P1-2A-EGFP was constructed by sequentially inserting capsid precursor protein gene(P1) of FMDV and enhanced green fluorescent protein gene(EGFP) into pBABEpuro.The recombinant retroviral vector and the pVSV-G plasmid were co-transfected into packaging cells(GP2-293) by liposomemediated transduction to produce the pseudovirus.The pseudovirus was used to infect BHK-21 cells and resistant cells were screened with puromycin.Green fluorescent proteins were observed by fluorescence microscopy and expression of the capsid precursor protein gene of FMDV was detected by indirect immunofluorescence.The recombinant retroviral vector pBABEpuro-P1-2A-EGFP was constructed successfully.The capsid precursor protein of FMDV and green fluorescent protein were expressed in BHK-21 cells.The mammalian cell expression system for the capsid precursor protein of FMDV has been constructed successfully,which lays the foundation of development of a FMDV subunit vaccine.
文摘In this article, spherical black spots-like selenium metal nanoparticles were synthesized. Accordingly, this experimental work proposed an innovative facile, green, one-step and solvent-free strategy to a large scale synthesis of Se-NPs via thermal decomposition of green precursor. The Se(Ⅳ) L-glutamine precursor was prepared by solid state grinding using selenium(Ⅳ) tetrachloride, SeCl4, and L-glutamine for 2 hr without using any organic solvent. It was characterized by infrared spectroscopy, and micro analytical. The solid precursor compound was subsequently annealed in the muffle furnace at 300 ℃ for 3 hr in static air. Selenium NPs was resulted and well characterized using X-ray powder diffraction(XRD), FT-IR spectroscopy, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The FTIR and XRD data showed that the Se NPs is pure and has a good crystalline structure because no characteristic peaks of impurity were detected, while the SEM and TEM results showed that the obtained product is tiny, aggregated with spherical-like shape, narrow size distribution with an average size between 5~10 nm. Results show that the solid state thermal decomposition method is simple, eco-friendly, safe and suitable for preparation of SeNPs. This method can also be applied to synthesize nanoparticles pure metal and metal oxides.
基金Project(06SK2011) supported by the Science and Technology Program of Hunan Province,China
文摘The effects of polyurethane sponge pretreatment and slurry compositions on the slurry loading in precursor were discussed,and the performances of stainless steel foams prepared from precursors with different slurry loadings and different particle sizes of the stainless steel powder were also investigated.The experimental results show that the pretreatment of sponge with alkaline solution is effective to reduce the jam of cells in precursor and ensure the slurry to uniformly distribute in sponge,and it is also an effective method for increasing the slurry loading in precursor;the mass fraction of additive A and solid content in slurry greatly affect the slurry loading in precursor,when they are kept in 9%-13% and 52%-75%,respectively,the stainless steel foam may hold excellent 3D open-cell network structure and uniform muscles;the particle size of the stainless steel powder and the slurry loading in precursor have great effects on the bending strength,apparent density and open porosity of stainless steel foam;when the stainless steel powder with particle size of 44 μm and slurry loading of 0.5 g/cm3 in precursor are used,a stainless steel foam can be obtained,which has open porosity of 81.2%,bending strength of about 51.76 MPa and apparent density of about 1.0 g/cm3.
基金Project(2004AA513023) supported by the National High Technology Research and Development Program of China
文摘Local segregation in Cu-In precursors and its effects on the element distribution and microstructures of selenized CuInSe2 thin films were investigated. Cu-In precursors with an ideal total mole ratio of Cu to In of 0.92 were prepared by middle frequency alternating current magnetron sputtering with Cu-In alloy target, then CuInSe2 absorbers for solar cells were formed by selenization process in selenium atmosphere. Scanning electron microscope and energy dispersive X-ray spectroscope were used respectively to observe the surface morphologies and determine the compositions of both Cu-In precursors and CuInSe2 thin films. Their microstructures were characterized by X-ray diffractometry and Raman spectroscope. The results show that Cu-In precursors are mainly composed of (Cu11In9) phase with In-rich solid solution. Stoichiometric CuInSe2 thin films with a homogeneous element distribution and single chalcopyrite phase can be synthesized from a segregated Cu-In precursor film with an ideal total mole ratio of Cu to In of 0.92. CuInSe2 thin film shows P-type conductivity and its resistivity reaches 1.2×103Ω·cm.
文摘In this paper, we investigate the precursors of large earthquakes in the eastern region of Taiwan by means of the reverse tracing of precursors. We discuss the parameters which are suitable for the seismic chains and intermedi- ate-term patterns in this region and obtain the threshold of the patterns. Applying the linear discriminate method to the intermediate-term patterns of seismic chains, we present an approach for exploring the precursors of large earthquakes. The results show that this method can reduce the false alarm rate for large earthquakes in this region, and the reverse tracing of precursors can be applied to the eastern region of Taiwan.
