A new boundary of the mapping class group

Based on the action of the mapping class group on the space of measured foliations, we construct a new boundary of the mapping class group and study the structure of this boundary. As an application, for any point in Teichmuller space, we consider the orbit of this point under the action of the mapping class group and describe the closure of this orbit in the Thurston compactification and the Gardiner-Masur compactification of Teichmuller space. We also construct some new points in the Gardiner-Masur boundary of Teichmuller space.Comment: To appear in Acta Mathematica Sinica, English Serie

A NEW COMPACTIFICATION OF TEICHMÜLLER SPACE

We construct a new compactification of Teichmüller space. We prove that this new compactification is finer than the Gardiner–Masur compactification of Teichmüller space and the action of the mapping class group on Teichmüller space extends continuously to this new compactification. We also construct some special points in the new boundary. The construction of the new compactification is based on the Hubbard-Masur theorem, which states that there is an one-to-one corresponding between holomorphic differentials and measured foliations

Asymptotic properties of maximum likelihood estimators for determinantal point processes

We obtain the almost sure consistency and the Berry-Esseen type bound of the maximum likelihood estimator for determinantal point processes (DPPs), completing and extending previous work initiated in Brunel, Moitra, Rigollet, and Urschel [BMRU17]. We also give explicit formula and a detailed discussion for the maximum likelihood estimator for blocked determinantal matrix of two by two submatrices and compare it with the frequency method

Synthesis of N,N-Diethyldithiocarbamate Nitrile Ethyl and the Chelating Behaviors with Metal Ions

The N,N-diethyldithiocarbamate nitrile ethyl (NND) was the nonionic polar collector, and it can synthesize the NND in dimethyl sulfoxide solvent. This method can effectively reduce the reaction intensity and the coefficient of the synthetic risk. The purity of NND which we synthesized is 94.23%, and the yield is 91.06%. UV analysis shows that the characteristic absorption peak wavelength of the NND is 276 nm, and its absorbance is 0.901. Based on the interaction of NND + Mn+ (Mn+ = Fe3+, Cu2+, Zn2+, Pb2+) and the quantum chemical calculation analysis of the NND and ethyl xanthate, we can conclude that the flotation performance of NND should be better than that of ethyl xanthate

How does the conversion of land cover to urban use affect net primary productivity? A case study in Shenzhen city, China

China has made great economic achievements since the Reform and Opening policy implementation. Shenzhen as the representative city has experienced rapid urbanization and population growth. Urbanization strongly changes the nature of the land surface and has a large influence on the regional ecosystems. In the process of urbanization, fertile cropland and original forest are often destroyed. It is important to regularly monitor the effect of urbanization on the natural environment so as to allow us to control the encroachment to a reasonable extent. Net primary productivity (NPP) is an important productivity indicator of the ecosystem. We obtained land covers from Landsat TM images to quantify urbanization of Shenzhen between 1999 and 2005. We used the Moderate Resolution Imaging Spectroradiometer (MODIS-based) Normalized Difference Vegetation Index (NDVI) data, Landsat-based land cover map, meteorological data and other field data to drive the CASA productivity model and obtain net primary productivity for the study area. Finally, we estimated the effect of urban sprawl on regional NPP. The study on Landsat-based land cover maps indicated that a move towards urban is the most significant landscape change in Shenzhen City and urbanization has irreversibly transformed about 20.21% of Shenzhen's surface during 1999–2005. NPP loss mainly resulted from urbanization during 1999–2005 and totaled to 321.51 Gg of carbon, an average annual reduction of 45.93 Gg of carbon. For every square km of Shenzhen area, NPP was on average reduced by 0.0017 Gg of carbon during 1999–2005. The loss of NPP is equivalent to a reduction in absorption of 520.85 Gg CO2 and release of 385.81 Gg O2, so urbanization has a large influence on the regional net primary productivity.China has made great economic achievements since the Reform and Opening policy implementation. Shenzhen as the representative city has experienced rapid urbanization and population growth. Urbanization strongly changes the nature of the land surface and has a large influence on the regional ecosystems. In the process of urbanization, fertile cropland and original forest are often destroyed. It is important to regularly monitor the effect of urbanization on the natural environment so as to allow us to control the encroachment to a reasonable extent. Net primary productivity (NPP) is an important productivity indicator of the ecosystem. We obtained land covers from Landsat TM images to quantify urbanization of Shenzhen between 1999 and 2005. We used the Moderate Resolution Imaging Spectroradiometer (MODIS-based) Normalized Difference Vegetation Index (NDVI) data, Landsat-based land cover map, meteorological data and other field data to drive the CASA productivity model and obtain net primary productivity for the study area. Finally, we estimated the effect of urban sprawl on regional NPP. The study on Landsat-based land cover maps indicated that a move towards urban is the most significant landscape change in Shenzhen City and urbanization has irreversibly transformed about 20.21% of Shenzhen's surface during 1999-2005. NPP loss mainly resulted from urbanization during 1999-2005 and totaled to 321.51 Gg of carbon, an average annual reduction of 45.93 Gg of carbon. For every square km of Shenzhen area, NPP was on average reduced by 0.0017 Gg of carbon during 1999-2005. The loss of NPP is equivalent to a reduction in absorption of 520.85 Gg CO(2) and release of 385.81 Gg O(2), so urbanization has a large influence on the regional net primary productivity. (C) 2009 Elsevier B.V. All rights reserved

Modelling net primary productivity of terrestrial ecosystems in East Asia based on an improved CASA ecosystem model

By using a land cover map, normalized difference vegetation index (NDVI) data sets, monthly meteorological data and observed net primary productivity (NPP) data, we have improved the method of estimating light use efficiency (LUE) for different biomes and soil moisture coefficients in the Carnegie-Ames-Stanford Approach ( CASA) ecosystem model. Based on this improved model we produced an annual NPP map ( in 1999) for the East Asia region located at 10-70 degrees N, 70-170 degrees E ( about 19.66% of the terrestrial surface of the Earth). The results show that the mean NPP for the study area in 1999 was 374.12 g carbon ( C) m(-2) year(-1) and the total NPP was 1.096 x 10(14) kg C year(-1), making up 17.51-18.39% of the global NPP. Comparison between the estimated NPP obtained from this improved CASA ecosystem model and the observed NPP obtained from two NPP databases indicates that the estimated NPP is close to the observed NPP, with an average error of 5.15% for the study region. We used two different land cover maps of China to drive the improved CASA model by keeping other inputs unchanged to determine how the classification accuracy of the land cover map affects the estimated NPP, and the results indicate that an accurate land cover map is important for obtaining an accurate and reliable estimate of NPP for some regions, especially for a particular biome.By using a land cover map, normalized difference vegetation index (NDVI) data sets, monthly meteorological data and observed net primary productivity (NPP) data, we have improved the method of estimating light use efficiency (LUE) for different biomes and soil moisture coefficients in the Carnegie-Ames-Stanford Approach ( CASA) ecosystem model. Based on this improved model we produced an annual NPP map ( in 1999) for the East Asia region located at 10-70 degrees N, 70-170 degrees E ( about 19.66% of the terrestrial surface of the Earth). The results show that the mean NPP for the study area in 1999 was 374.12 g carbon ( C) m(-2) year(-1) and the total NPP was 1.096 x 10(14) kg C year(-1), making up 17.51-18.39% of the global NPP. Comparison between the estimated NPP obtained from this improved CASA ecosystem model and the observed NPP obtained from two NPP databases indicates that the estimated NPP is close to the observed NPP, with an average error of 5.15% for the study region. We used two different land cover maps of China to drive the improved CASA model by keeping other inputs unchanged to determine how the classification accuracy of the land cover map affects the estimated NPP, and the results indicate that an accurate land cover map is important for obtaining an accurate and reliable estimate of NPP for some regions, especially for a particular biome

Effect of grain size distribution on the shear band thickness evolution in sand

Triaxial experiments were conducted on granular materials presenting uniform, graded and fractal particle distributions in order to investigate how the broadness of the distribution affects the phenomenon of strain localisation. The shear band thickness evolution is assessed by digital image correlation (DIC) using three cameras placed at different angles around a transparent triaxial cell. From the field of deformation, Gaussian distributions have made it possible to fit the data satisfactorily and determine the shear band width evolution. The latter exhibits a rapid decrease in the softening regime until a residual value is reached in all cases. In the conditions of the experiments, it is shown that the residual shear band thickness scales with the mean grain size and the ratio between the two increases with the broadness of the distribution. Samples with uniform distribution exhibit an average residual thickness of ∼ 10D50, samples with graded distribution exhibit an average residual thickness of ∼ 12·5D50 and samples with fractal distribution exhibit an average residual thickness of ∼ 17D50