Transesterification between methyl-butyrate and 1-butanol in nonaqueous systems was catalyzed by porcine pancreatic lipase which was immobilized on cross- linked polystyrene. Organic solvents, substrate concentration,...Transesterification between methyl-butyrate and 1-butanol in nonaqueous systems was catalyzed by porcine pancreatic lipase which was immobilized on cross- linked polystyrene. Organic solvents, substrate concentration, contents of water and other parameters which affect the immobilized enzyme activity were studied. Lipase immobilized on hydrophobic crosslinked polystyrene can reduce its diffusion limit in the reaction. It was found that the activity of immobilized lipase in organic systems was two times as high as that of free lipase.展开更多
The interference imaging spectroradiometer (IIM) onboard the first lunar satellite of China "Chang'E-1" can now provide approximately global high spectral and spatial resolution reflectance spectra of th...The interference imaging spectroradiometer (IIM) onboard the first lunar satellite of China "Chang'E-1" can now provide approximately global high spectral and spatial resolution reflectance spectra of the Moon. It is the essential instrument with which to accomplish one of the four missions of the first lunar satellite of China. As the current data provided by the Lunar Exploration Program Center and National Astronomical Observatories (NAOC) are not reflectance and the sensor response is inhomogeneous in the line direction,users can not use the current data directly. Moreover,due to the narrow band range,IIM data cannot cover the absorption peak of the mafic minerals of the Moon completely,which limits its ability for identifying minerals. The main objective of this study is to describe the methods for absolute calibration,correction and acquiring the absorption center of minerals for IIM data. The results from our study show that in the space domain the sensor response decreases toward the left,and in the spectral domain the response of the longer bands is more inhomogeneous than that of the shorter bands. After the calibration and correction,the reflectance of IIM matches the earth-based telescopic spectra well,which suggests the possible use of the processed data in the geological research. A high correlation was found between the absorption center and the wavelength at which the first derivative equals 0,i.e.,the so-called Stagnation Point in the mathematical sense. In the end,we show a preliminary applied study of the two craters with diameter larger than 35 km using the calibrated data. The spectra of IIM data show that the lunar crust has compositional diversity within the km scale. Pure anorthosite may be found on the wall and floor of the Aristarchus crater with the map of absorption center,which indicates that anorthosite is ubiquitously present within the lunar crust. IIM,with its capacity to acquire lunar composition at the regional and global scale,will contribute to the research of lunar origin and evolution.展开更多
SIN(Space Information Network)has recently emerged as a promising approach to solving the collaboration difficulty among current space programs.However,because of the SIN’s large scale,high component complexity,and d...SIN(Space Information Network)has recently emerged as a promising approach to solving the collaboration difficulty among current space programs.However,because of the SIN’s large scale,high component complexity,and dynamic characteristics,designing a proper SIN architecture is challenging.Firstly,we propose a novel SIN architecture,which is composed of GEO(Geostationary Earth Orbit)satellites as backbone network nodes,LEO(Low Earth Orbit)or other types of satellites as enhanced coverage nodes,and high-altitude platforms to meet the service requirements of emergency or hot-spot applications.Unlike most existing studies,the proposed architecture is AS(Autonomous-System)based.We decouple the complex SIN into simpler sub-networks using a hierarchical AS model.Then,we propose a topology control algorithm to minimize the time delay among sub-AS networks.We prove that the proposed algorithm achieves logical k-connectivity provided that the original physical topology has k-connectivity.Simulation results validate the theoretic analysis and effectiveness of the algorithm.展开更多
文摘Transesterification between methyl-butyrate and 1-butanol in nonaqueous systems was catalyzed by porcine pancreatic lipase which was immobilized on cross- linked polystyrene. Organic solvents, substrate concentration, contents of water and other parameters which affect the immobilized enzyme activity were studied. Lipase immobilized on hydrophobic crosslinked polystyrene can reduce its diffusion limit in the reaction. It was found that the activity of immobilized lipase in organic systems was two times as high as that of free lipase.
基金Supported by the Macao Science and Technology Development Fund (Grant No. 003/2008/A1)
文摘The interference imaging spectroradiometer (IIM) onboard the first lunar satellite of China "Chang'E-1" can now provide approximately global high spectral and spatial resolution reflectance spectra of the Moon. It is the essential instrument with which to accomplish one of the four missions of the first lunar satellite of China. As the current data provided by the Lunar Exploration Program Center and National Astronomical Observatories (NAOC) are not reflectance and the sensor response is inhomogeneous in the line direction,users can not use the current data directly. Moreover,due to the narrow band range,IIM data cannot cover the absorption peak of the mafic minerals of the Moon completely,which limits its ability for identifying minerals. The main objective of this study is to describe the methods for absolute calibration,correction and acquiring the absorption center of minerals for IIM data. The results from our study show that in the space domain the sensor response decreases toward the left,and in the spectral domain the response of the longer bands is more inhomogeneous than that of the shorter bands. After the calibration and correction,the reflectance of IIM matches the earth-based telescopic spectra well,which suggests the possible use of the processed data in the geological research. A high correlation was found between the absorption center and the wavelength at which the first derivative equals 0,i.e.,the so-called Stagnation Point in the mathematical sense. In the end,we show a preliminary applied study of the two craters with diameter larger than 35 km using the calibrated data. The spectra of IIM data show that the lunar crust has compositional diversity within the km scale. Pure anorthosite may be found on the wall and floor of the Aristarchus crater with the map of absorption center,which indicates that anorthosite is ubiquitously present within the lunar crust. IIM,with its capacity to acquire lunar composition at the regional and global scale,will contribute to the research of lunar origin and evolution.
基金supported by the National Natural Science Foundation of China(Nos.91338201,91438109,61401507).
文摘SIN(Space Information Network)has recently emerged as a promising approach to solving the collaboration difficulty among current space programs.However,because of the SIN’s large scale,high component complexity,and dynamic characteristics,designing a proper SIN architecture is challenging.Firstly,we propose a novel SIN architecture,which is composed of GEO(Geostationary Earth Orbit)satellites as backbone network nodes,LEO(Low Earth Orbit)or other types of satellites as enhanced coverage nodes,and high-altitude platforms to meet the service requirements of emergency or hot-spot applications.Unlike most existing studies,the proposed architecture is AS(Autonomous-System)based.We decouple the complex SIN into simpler sub-networks using a hierarchical AS model.Then,we propose a topology control algorithm to minimize the time delay among sub-AS networks.We prove that the proposed algorithm achieves logical k-connectivity provided that the original physical topology has k-connectivity.Simulation results validate the theoretic analysis and effectiveness of the algorithm.
