This paper presents an approach to synthesis of gold nanoparticles with different morphologies and investigation of the relationship between morphologies and their optical properties.Spherical gold nanoparticles with ...This paper presents an approach to synthesis of gold nanoparticles with different morphologies and investigation of the relationship between morphologies and their optical properties.Spherical gold nanoparticles with different sizes are synthesized via reduction method.Using seed-mediated solution growth method,gold nanoparticles with shuttle,star and stick shapes can be obtained.The sizes and morphologies of the gold nanoparticles are characterized by transmission electron microscopy （TEM）.The characterization results illustrate the growth process of the gold nanoparticles with different morphologies.Absorption spectroscopy and Raman spectroscopy measurements are performed to demonstrate the relationship between the morphologies and optical properties.The results of Raman characterization show that the gold nanoparticles with different morphologies can be used to probe molecules with different concentrations.展开更多
Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investig...Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investigated by laboratory experiments under simulated industrial conditions.The results show that at higher temperature the variation period of particle size is shortened,while prolongs with more solid content.Particle size fluctuation amplitude reduces with the temperature rising but increases with the solid content increasing.Particle size distribution becomes more uniform by replenishing fine seeds,enabling the periodical fluctuation of Al(OH)3 particle size to be attenuated.Combining properly the additives with controlling the seed size is able to reduce the amplitude of periodical fluctuation and shorten the attenuation time.With unbalance of particle size distribution,the particles gradually become bigger,even inducing the decrease of the specific surface area of seeds,which is the major reason causing explosive attenuation of Al(OH)3 particles in seed precipitation process.展开更多
Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China s tropical areas that mainta...Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China s tropical areas that maintain fragments of primary forests, were studied to a) evaluate the effect of two common land use changes, conversion of forests to agricultural land or rubber tree plantation, on the dynamics of available P and total P in bulk soils as well as total P in particle size fractions; b) assess the rel…展开更多
AIM: To explore dendritic cells (DCs) multiple functions in immune modulation. METHODS: We used bone-marrow derived dendritic cells from BALB/c mice pulsed with pseudo particles from the hepatitis C virus to vaccinate...AIM: To explore dendritic cells (DCs) multiple functions in immune modulation. METHODS: We used bone-marrow derived dendritic cells from BALB/c mice pulsed with pseudo particles from the hepatitis C virus to vaccinate naive BALB/c mice. Hepatitis C virus (HCV) pseudo particles consist of the genotype 1b derived envelope proteins E1 and E2, covering a non-HCV core structure. Thus, not a single epitope, but the whole "viral surface" induces immunogenicity. For vaccination, mature and activated DC were injected subcutaneously twice. RESULTS: Humoral and cellular immune responses measured by enzyme-linked immunosorbent assay and interferon-gamma enzyme-linked immunosorbent spot test showed antibody production as well as T-cellsdirected against HCV. Furthermore, T-cell responses confi rmed two highly immunogenic regions in E1 and E2 outside the hypervariable region 1. CONCLUSION: Our results indicate dendritic cells as a promising vaccination model for HCV infection that should be evaluated further.展开更多
This paper is focused on the problem of the ability of seeding particles to follow the flow field. One of the most important factors influencing the resultant accuracy of the measurement is using the proper seeding pa...This paper is focused on the problem of the ability of seeding particles to follow the flow field. One of the most important factors influencing the resultant accuracy of the measurement is using the proper seeding particles for feeding the flow when measuring by PIV （Particle Image Velocimetry） method. The aim of the paper is to provide comprehensible instruction for choosing the proper type of seeding particles with regard to the flow characteristics and required measurement accuracy. The paper presents two methods with the help of which it is possible to determine the seeding particles＇ ability to follow the flow field. The first method is based on the direct calculation of the phase lag and amplitude ratio between the particle and the fluid. The calculation is based on solution of the BBO （Basset Boussinesq Oseen） equation for spherical particle. The other method results from the calculation of the particle time response, which defines the maximum frequency of disturbances, which are to be followed by the particle. In the conclusion, the method of choosing the seeding particles is proposed, depending on the required measurement accuracy.展开更多
Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds....Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds.Tensile tests,micro-hardness experiments,scanning electron microscopy and X-ray diffraction analysis were applied to studying the properties of welded joints.The joints with a travel speed of 50 mm/min and a rotation speed of 1000 r/min showed the best results.The presence of nano-sized SiC particles reduced the grain size of aluminum and copper in the stir zone(SZ)from 38.3 and 12.4μm to 12.9 and 5.1μm,respectively.The tensile strength of the joint in the presence of reinforcing SiC nano-particles was~240 MPa,which is~90%of that for the aluminum base.Furthermore,the highest microhardness of the weld zone was significantly increased from HV 160 to HV 320 upon the addition of SiC nano-particles.The results also showed that raising the heat generation in FSW joints increased the amount of Al_(4)Cu_(9) and Al_(2)Cu intermetallic compounds.展开更多
A highly crosslinked, monodispersed polystyrene（PS） particle was prepared by a seeded batch dispersion polymerization with a monomer absorption method. Prior to polymerization, 1,9 lam monodispersed PS seed particle...A highly crosslinked, monodispersed polystyrene（PS） particle was prepared by a seeded batch dispersion polymerization with a monomer absorption method. Prior to polymerization, 1,9 lam monodispersed PS seed particles were treated under an optimum condition of monomer absorption. The effects of divinylbenzebe（DVB） concentration and polymerization temperature were examined for styrene（in PS seed）/styrene（in the second stage） mass ratio of 1：1 in the medium range of EtOH/water mass ratio of 100/0-80/20 and 2.3 μm uniform crosslinked PS particles containing 15%-20% （mass fraction） DVB were prepared at 60-70 ℃. The results show that monomer absorption before the second stage of polymerization is more effective to prepare highly crosslinked monodispersed PS particles.展开更多
Gold nanoparticle （Au NP）@ZnO nanorod （NR） （Au@ZnO） hybrids with various ZnO：Au molar ratios were developed to enhance the generation of reactive oxygen species （ROS） in photodynamic therapy （PDT） applicati...Gold nanoparticle （Au NP）@ZnO nanorod （NR） （Au@ZnO） hybrids with various ZnO：Au molar ratios were developed to enhance the generation of reactive oxygen species （ROS） in photodynamic therapy （PDT） applications. Introducing a metal/semiconductor heterostructure interface between Au NPs and ZnO NRs modulated electron transfer under ultraviolet （UV） irradiation, which dramatically suppressed the electron-hole recombination in ZnO and simultaneously increased the amount of excited electrons with high energy at Au NP surfaces. Hence, the ROS yield of the nanohybrid was considerably improved over those of pristine Au NPs or ZnO NRs alone and demonstrated a ＂1 ＋ 1 〉 2 effect.＂ This enhancement was strengthened with increases in the proportion of Au in the hybrid. The results showed that the Au@ZnO nanohybrids with a ZnO：Au ratio of 20：1 generated the highest ROS yield because they had the largest interface area between Au and ZnO, which in turn led to the lowest cell viability for HeLa and C2C12 cells during PDT. Furthermore, both ROS generation and cell destruction were positively correlated with nanohybrid dosage. The Au@ZnO hybrid （20：1, 100 μg/mL） resulted in HeLa cell viability as low as 28% after UV exposure for 2 min, which indicated its promising potential to improve the therapeutic efficacy of PDT.展开更多
基金Merit-funded Science and Technology Project for Returned Oversea Scholars from Ministry of Human and Social Security of Shanxi provinceNatural Science Foundation for Young Scientists of Shanxi province(No.2011011020-2)Shanxi Province Foundation for Returness(No.2008062)
文摘This paper presents an approach to synthesis of gold nanoparticles with different morphologies and investigation of the relationship between morphologies and their optical properties.Spherical gold nanoparticles with different sizes are synthesized via reduction method.Using seed-mediated solution growth method,gold nanoparticles with shuttle,star and stick shapes can be obtained.The sizes and morphologies of the gold nanoparticles are characterized by transmission electron microscopy （TEM）.The characterization results illustrate the growth process of the gold nanoparticles with different morphologies.Absorption spectroscopy and Raman spectroscopy measurements are performed to demonstrate the relationship between the morphologies and optical properties.The results of Raman characterization show that the gold nanoparticles with different morphologies can be used to probe molecules with different concentrations.
基金Project(50804031) supported by the National Natural Science Foundation of China
文摘Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investigated by laboratory experiments under simulated industrial conditions.The results show that at higher temperature the variation period of particle size is shortened,while prolongs with more solid content.Particle size fluctuation amplitude reduces with the temperature rising but increases with the solid content increasing.Particle size distribution becomes more uniform by replenishing fine seeds,enabling the periodical fluctuation of Al(OH)3 particle size to be attenuated.Combining properly the additives with controlling the seed size is able to reduce the amplitude of periodical fluctuation and shorten the attenuation time.With unbalance of particle size distribution,the particles gradually become bigger,even inducing the decrease of the specific surface area of seeds,which is the major reason causing explosive attenuation of Al(OH)3 particles in seed precipitation process.
文摘Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China s tropical areas that maintain fragments of primary forests, were studied to a) evaluate the effect of two common land use changes, conversion of forests to agricultural land or rubber tree plantation, on the dynamics of available P and total P in bulk soils as well as total P in particle size fractions; b) assess the rel…
文摘AIM: To explore dendritic cells (DCs) multiple functions in immune modulation. METHODS: We used bone-marrow derived dendritic cells from BALB/c mice pulsed with pseudo particles from the hepatitis C virus to vaccinate naive BALB/c mice. Hepatitis C virus (HCV) pseudo particles consist of the genotype 1b derived envelope proteins E1 and E2, covering a non-HCV core structure. Thus, not a single epitope, but the whole "viral surface" induces immunogenicity. For vaccination, mature and activated DC were injected subcutaneously twice. RESULTS: Humoral and cellular immune responses measured by enzyme-linked immunosorbent assay and interferon-gamma enzyme-linked immunosorbent spot test showed antibody production as well as T-cellsdirected against HCV. Furthermore, T-cell responses confi rmed two highly immunogenic regions in E1 and E2 outside the hypervariable region 1. CONCLUSION: Our results indicate dendritic cells as a promising vaccination model for HCV infection that should be evaluated further.
文摘This paper is focused on the problem of the ability of seeding particles to follow the flow field. One of the most important factors influencing the resultant accuracy of the measurement is using the proper seeding particles for feeding the flow when measuring by PIV （Particle Image Velocimetry） method. The aim of the paper is to provide comprehensible instruction for choosing the proper type of seeding particles with regard to the flow characteristics and required measurement accuracy. The paper presents two methods with the help of which it is possible to determine the seeding particles＇ ability to follow the flow field. The first method is based on the direct calculation of the phase lag and amplitude ratio between the particle and the fluid. The calculation is based on solution of the BBO （Basset Boussinesq Oseen） equation for spherical particle. The other method results from the calculation of the particle time response, which defines the maximum frequency of disturbances, which are to be followed by the particle. In the conclusion, the method of choosing the seeding particles is proposed, depending on the required measurement accuracy.
文摘Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds.Tensile tests,micro-hardness experiments,scanning electron microscopy and X-ray diffraction analysis were applied to studying the properties of welded joints.The joints with a travel speed of 50 mm/min and a rotation speed of 1000 r/min showed the best results.The presence of nano-sized SiC particles reduced the grain size of aluminum and copper in the stir zone(SZ)from 38.3 and 12.4μm to 12.9 and 5.1μm,respectively.The tensile strength of the joint in the presence of reinforcing SiC nano-particles was~240 MPa,which is~90%of that for the aluminum base.Furthermore,the highest microhardness of the weld zone was significantly increased from HV 160 to HV 320 upon the addition of SiC nano-particles.The results also showed that raising the heat generation in FSW joints increased the amount of Al_(4)Cu_(9) and Al_(2)Cu intermetallic compounds.
基金the second stage of BK21 program for supporting a fellowship
文摘A highly crosslinked, monodispersed polystyrene（PS） particle was prepared by a seeded batch dispersion polymerization with a monomer absorption method. Prior to polymerization, 1,9 lam monodispersed PS seed particles were treated under an optimum condition of monomer absorption. The effects of divinylbenzebe（DVB） concentration and polymerization temperature were examined for styrene（in PS seed）/styrene（in the second stage） mass ratio of 1：1 in the medium range of EtOH/water mass ratio of 100/0-80/20 and 2.3 μm uniform crosslinked PS particles containing 15%-20% （mass fraction） DVB were prepared at 60-70 ℃. The results show that monomer absorption before the second stage of polymerization is more effective to prepare highly crosslinked monodispersed PS particles.
基金This work was supported by the National Basic Research Program of China （No. 2013CB932600）, the Major Project of International Cooperation and Exchanges （No. 2012DFA50990）, the Program of Introducing Talents of Discipline to Universities, the National Natural Science Foundation of China （Nos. 51232001, 51172022, 51372023, and 31371203）, the Research Fund of Co-Construction Program from Beijing Municipal Commission of Education, the Fundamental Research Funds for the Central Univer- sities, and the Program for Changjiang Scholars and Innovative Research Team in University.
文摘Gold nanoparticle （Au NP）@ZnO nanorod （NR） （Au@ZnO） hybrids with various ZnO：Au molar ratios were developed to enhance the generation of reactive oxygen species （ROS） in photodynamic therapy （PDT） applications. Introducing a metal/semiconductor heterostructure interface between Au NPs and ZnO NRs modulated electron transfer under ultraviolet （UV） irradiation, which dramatically suppressed the electron-hole recombination in ZnO and simultaneously increased the amount of excited electrons with high energy at Au NP surfaces. Hence, the ROS yield of the nanohybrid was considerably improved over those of pristine Au NPs or ZnO NRs alone and demonstrated a ＂1 ＋ 1 〉 2 effect.＂ This enhancement was strengthened with increases in the proportion of Au in the hybrid. The results showed that the Au@ZnO nanohybrids with a ZnO：Au ratio of 20：1 generated the highest ROS yield because they had the largest interface area between Au and ZnO, which in turn led to the lowest cell viability for HeLa and C2C12 cells during PDT. Furthermore, both ROS generation and cell destruction were positively correlated with nanohybrid dosage. The Au@ZnO hybrid （20：1, 100 μg/mL） resulted in HeLa cell viability as low as 28% after UV exposure for 2 min, which indicated its promising potential to improve the therapeutic efficacy of PDT.
