A study was conducted to examine the natural regeneration of three dry forest species, Lysiloma divaricatum （Jacq.）, Tabebuia ochracea （Cham.） and Lonchocarpus minimiflorus （Donn. Sin.） over a three-year period ...A study was conducted to examine the natural regeneration of three dry forest species, Lysiloma divaricatum （Jacq.）, Tabebuia ochracea （Cham.） and Lonchocarpus minimiflorus （Donn. Sin.） over a three-year period and to analyze heterogeneity of regeneration in relationship to topographic slope and incidence of light in Chacocente Wildlife Reserve in Nicaragua. Permanent sample plots were established in 2001, and all individuals with height as low as 10 cm and diameter as large as 10 cm were recorded for three consecutive years from 2001 to 2003. The results show that the density of naturally regenerated individuals varied significantly among species, as well as over time. L. minimiflorus and T. ochracea had higher densities compared with L. divaricatum, and the net change in population density was slightly positive for T. ochracea only. Regeneration was more abundant in the gentle and steep slopes under partial exposure of the crown to sunlight, thus resulting in aggregated pattern of distribution, especially for L. minimiflorus and T. ochracea. We concluded that natural regeneration alone is not sufficient to maintain the desired number of stocks of these species, and an immediate restoration measure should be taken to assist the natural regeneration process.展开更多
Based on the low energy effective Hamiltonian with naive factorization, we calculate the branching ratios （BRs） and CP asymmetries （CPAs） for the twenty three double charm decays B/B8 → D（＊）D（＊） in both the...Based on the low energy effective Hamiltonian with naive factorization, we calculate the branching ratios （BRs） and CP asymmetries （CPAs） for the twenty three double charm decays B/B8 → D（＊）D（＊） in both the standard （s） （s） model （SM） and the minimal supergravity （mSUGRA） model. Within the considered parameter space, we find that （a） the theoretical predictions for the BRs, CPAs and the polarization fractions in the SM and the mSUGRA model are all consistent with the currently available data within ±2σ errors; （b） For all the considered decays, the supersymmetric contributions in the mSUGRA model are very small, less than 7% numerically. It may be difficult to observe so small SUSY contributions even at LHC.展开更多
In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean （Model for Prediction Across Scales） using a spherical centroidal voronoi tessellations developed jointly by the ...In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean （Model for Prediction Across Scales） using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z＊ vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy （RPE）, front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter 2＂, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number （HGRN）, Rea, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al. （2012）, i.e., MITocM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MIT6c and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexa- gon cell and the quadrilateral cell with the same resolution. Both the Zalesak （1979） flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy.展开更多
High quality gold nanorods （NRs） with a monodisperse size and aspect ratio are essential for many applications. Here, we describe how nearly monodisperse gold NRs can be separated from polydisperse samples using den...High quality gold nanorods （NRs） with a monodisperse size and aspect ratio are essential for many applications. Here, we describe how nearly monodisperse gold NRs can be separated from polydisperse samples using density gradient ultracentrifugation. Size and dimension analysis by transmission electron microscopy （TEM） and absorption spectroscopy revealed that the Au NRs were separated mainly as a function of their aspect ratio The surface-enhanced Raman scattering （SERS） activity of Au NRs with lower aspect ratio is notably stronger than that of NRs with higher aspect ratio under 633 nm laser excitation, due to the size-dependent absorption of the longitudinal plasmon band. The separation approach provides a method to improve the quality of NRs produced by large scale synthetic methods.展开更多
基金supported by the Swedish International Development Agency (Sida)
文摘A study was conducted to examine the natural regeneration of three dry forest species, Lysiloma divaricatum （Jacq.）, Tabebuia ochracea （Cham.） and Lonchocarpus minimiflorus （Donn. Sin.） over a three-year period and to analyze heterogeneity of regeneration in relationship to topographic slope and incidence of light in Chacocente Wildlife Reserve in Nicaragua. Permanent sample plots were established in 2001, and all individuals with height as low as 10 cm and diameter as large as 10 cm were recorded for three consecutive years from 2001 to 2003. The results show that the density of naturally regenerated individuals varied significantly among species, as well as over time. L. minimiflorus and T. ochracea had higher densities compared with L. divaricatum, and the net change in population density was slightly positive for T. ochracea only. Regeneration was more abundant in the gentle and steep slopes under partial exposure of the crown to sunlight, thus resulting in aggregated pattern of distribution, especially for L. minimiflorus and T. ochracea. We concluded that natural regeneration alone is not sufficient to maintain the desired number of stocks of these species, and an immediate restoration measure should be taken to assist the natural regeneration process.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10947020 and 11005033Foundation of Henan Educational Committee for Youth Backbone Scholars in Colleges and Universities+1 种基金the Natural Science Foundation of the Eduction Department of Henan Province under Grant No. 2010A140012Natural Science Foundation of Henan Province under Grant No. 102300410210
文摘Based on the low energy effective Hamiltonian with naive factorization, we calculate the branching ratios （BRs） and CP asymmetries （CPAs） for the twenty three double charm decays B/B8 → D（＊）D（＊） in both the standard （s） （s） model （SM） and the minimal supergravity （mSUGRA） model. Within the considered parameter space, we find that （a） the theoretical predictions for the BRs, CPAs and the polarization fractions in the SM and the mSUGRA model are all consistent with the currently available data within ±2σ errors; （b） For all the considered decays, the supersymmetric contributions in the mSUGRA model are very small, less than 7% numerically. It may be difficult to observe so small SUSY contributions even at LHC.
基金supported by the National Natural Science Foundation of China (Grant No.41175089)
文摘In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean （Model for Prediction Across Scales） using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z＊ vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy （RPE）, front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter 2＂, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number （HGRN）, Rea, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al. （2012）, i.e., MITocM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MIT6c and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexa- gon cell and the quadrilateral cell with the same resolution. Both the Zalesak （1979） flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy.
基金Acknowledgements This work was financially supported by the National Natural Science Foundation of China （NSFC）, Beijing Natural Science Foundation （No. 2102033）, the Programfor New Century Excellent Talents in Universities, and the 973 Program （No. 2009CB939801）.
文摘High quality gold nanorods （NRs） with a monodisperse size and aspect ratio are essential for many applications. Here, we describe how nearly monodisperse gold NRs can be separated from polydisperse samples using density gradient ultracentrifugation. Size and dimension analysis by transmission electron microscopy （TEM） and absorption spectroscopy revealed that the Au NRs were separated mainly as a function of their aspect ratio The surface-enhanced Raman scattering （SERS） activity of Au NRs with lower aspect ratio is notably stronger than that of NRs with higher aspect ratio under 633 nm laser excitation, due to the size-dependent absorption of the longitudinal plasmon band. The separation approach provides a method to improve the quality of NRs produced by large scale synthetic methods.
