The local meteoric water line (MWL) has been established from north to south of the Tibetan Plateau based on the measured results of δD and δ18O in precipitation and river water, and the relationship between MWL and...The local meteoric water line (MWL) has been established from north to south of the Tibetan Plateau based on the measured results of δD and δ18O in precipitation and river water, and the relationship between MWL and moisture origins discussed. The spatial and seasonal variations ofd in precipitation and river water on the Tibetan Plateau have been studied. Results show that the spatial and seasonal variations ofd between north and south of the Tanggula Mountains are related to different moisture origins and water recycling.展开更多
In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex...In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex （LCC） and the residual lignin from kraft pulp （KP） and sulfite pulp （SP） were isolated and analyzed by Fourier transform infrared （FTIR） spectrum and ^13C nuclear magnetic resonance （NMR）. The most diagnostic peaks were assigned and the differences were discussed. The spectral patterns reveal that triploid P tomentosa shows the specific features of hardwood from temperate areas, but in the spectrum of FTIR, the strength ratio orAl270 cm^-1 to A1226 cm^-1 is 0.88, higher than the average of hardwood from temperate areas, which will make the lignin delignification more difficult during pulping and bleaching. The LCC from triploid P tomentosa is mainly composed of xyloglucan and glucuronic acid, and other glucides have much lower ratio. In LCC FTIR, there are three peaks at 1 427, 1 329 and 1 046 cm^-1, indicating that both semi-cellulose and cellulose could exist in LCC, and that there might be relationships between cellulose and lignin. Compared with the residual lignin from KP and SP, the condensed structure in KP is more than that in SP.展开更多
The Structural nature of Tctracctron sinense MWL is characterized by means of Chemical analysis.GC,IR,’H NMR and <sup>C</sup>（13） NMR spectra.The researches indicated that the MWL is of guaiacyl—syring...The Structural nature of Tctracctron sinense MWL is characterized by means of Chemical analysis.GC,IR,’H NMR and <sup>C</sup>（13） NMR spectra.The researches indicated that the MWL is of guaiacyl—syringyl type.The main connective form between structural units is β—O—4aryl ether bonds.The quantity of β—O—4 and 5—5 substructures is 0.53/C<sub>9</sub> and 0.06/C<sub>9</sub>,respectively.The alipatic and phenolic hydroxy contents are respectively.The OCH<sub>3</sub> content is estimated by <sup>C</sup>（13）NMR is spectrum （1.14/C<sub>9</sub>）,which is con-sistent with chemical method（1.11/C<sub>9</sub>） The degree of condensetion of the MWL is 0.51/C<sub>9</sub>（from ’HNMR）,which is consistent with the result from <sup>C</sup>（13）NMR.展开更多
According to calculation on available data, higher δ18O exists in atmospheric precipitation of southeastern and northwestern part of China, and the lower in Northeast China and the southern QinghaiTibet Plateau. In C...According to calculation on available data, higher δ18O exists in atmospheric precipitation of southeastern and northwestern part of China, and the lower in Northeast China and the southern QinghaiTibet Plateau. In China temperature effect appears mainly in the inner continent of midhigh latitudes and the amount effect appears in southeastern coastal regions, the YunnanGuizhou Plateau and QinghaiTibet Plateau where the influence of monsoon climate is obvious. The meteoric water lines (MWLs) of different regions are of certain divergence, which is closely related to the stable isotopic fractionations of the two processes, namely the evaporation of origins and the precipitating of vapor.展开更多
We report a demonstration of a fast wavelength tunable source (TWS) based on the laser diode array coupled to the arrayed waveguide grating (AWG) multiplexer. The switching and optical characteristics of TWS make it a...We report a demonstration of a fast wavelength tunable source (TWS) based on the laser diode array coupled to the arrayed waveguide grating (AWG) multiplexer. The switching and optical characteristics of TWS make it a candidate for implementing the wavelength-division space switch fabric for an optical packet/burst switching.展开更多
本文研究了竹子原料及其磺化机浆 MWL 的结构特性,并把两者进行对比。发现竹料制成浆后,木素中的-OCH_3,侧链羧基含量降低,酚 OH 含量增加,木素发生了较大裂解,其分子量有很大减小,多分散性增大,木素中酯键连接的 H 单元制成浆后有部分...本文研究了竹子原料及其磺化机浆 MWL 的结构特性,并把两者进行对比。发现竹料制成浆后,木素中的-OCH_3,侧链羧基含量降低,酚 OH 含量增加,木素发生了较大裂解,其分子量有很大减小,多分散性增大,木素中酯键连接的 H 单元制成浆后有部分水解,但木素中存在非酯(?)连接的 H 单元,它们即使在皂化后也不水解,残留于木素中的糖主要是阿拉伯糖木聚糖,也有一定量的甘露糖、半乳糖、葡萄糖。竹料制成浆后,木素残留糖中的甘露糖消失,葡萄糖有较大减小,说明残留糖中的木糖、阿拉伯糖、半乳糖与木素有较牢固的连接存在。展开更多
基金Acknowledgements This work was supported by the National Nature Science Foundation of China (Grant No.49671021)
文摘The local meteoric water line (MWL) has been established from north to south of the Tibetan Plateau based on the measured results of δD and δ18O in precipitation and river water, and the relationship between MWL and moisture origins discussed. The spatial and seasonal variations ofd in precipitation and river water on the Tibetan Plateau have been studied. Results show that the spatial and seasonal variations ofd between north and south of the Tanggula Mountains are related to different moisture origins and water recycling.
文摘In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex （LCC） and the residual lignin from kraft pulp （KP） and sulfite pulp （SP） were isolated and analyzed by Fourier transform infrared （FTIR） spectrum and ^13C nuclear magnetic resonance （NMR）. The most diagnostic peaks were assigned and the differences were discussed. The spectral patterns reveal that triploid P tomentosa shows the specific features of hardwood from temperate areas, but in the spectrum of FTIR, the strength ratio orAl270 cm^-1 to A1226 cm^-1 is 0.88, higher than the average of hardwood from temperate areas, which will make the lignin delignification more difficult during pulping and bleaching. The LCC from triploid P tomentosa is mainly composed of xyloglucan and glucuronic acid, and other glucides have much lower ratio. In LCC FTIR, there are three peaks at 1 427, 1 329 and 1 046 cm^-1, indicating that both semi-cellulose and cellulose could exist in LCC, and that there might be relationships between cellulose and lignin. Compared with the residual lignin from KP and SP, the condensed structure in KP is more than that in SP.
文摘The Structural nature of Tctracctron sinense MWL is characterized by means of Chemical analysis.GC,IR,’H NMR and <sup>C</sup>（13） NMR spectra.The researches indicated that the MWL is of guaiacyl—syringyl type.The main connective form between structural units is β—O—4aryl ether bonds.The quantity of β—O—4 and 5—5 substructures is 0.53/C<sub>9</sub> and 0.06/C<sub>9</sub>,respectively.The alipatic and phenolic hydroxy contents are respectively.The OCH<sub>3</sub> content is estimated by <sup>C</sup>（13）NMR is spectrum （1.14/C<sub>9</sub>）,which is con-sistent with chemical method（1.11/C<sub>9</sub>） The degree of condensetion of the MWL is 0.51/C<sub>9</sub>（from ’HNMR）,which is consistent with the result from <sup>C</sup>（13）NMR.
文摘According to calculation on available data, higher δ18O exists in atmospheric precipitation of southeastern and northwestern part of China, and the lower in Northeast China and the southern QinghaiTibet Plateau. In China temperature effect appears mainly in the inner continent of midhigh latitudes and the amount effect appears in southeastern coastal regions, the YunnanGuizhou Plateau and QinghaiTibet Plateau where the influence of monsoon climate is obvious. The meteoric water lines (MWLs) of different regions are of certain divergence, which is closely related to the stable isotopic fractionations of the two processes, namely the evaporation of origins and the precipitating of vapor.
文摘We report a demonstration of a fast wavelength tunable source (TWS) based on the laser diode array coupled to the arrayed waveguide grating (AWG) multiplexer. The switching and optical characteristics of TWS make it a candidate for implementing the wavelength-division space switch fabric for an optical packet/burst switching.
文摘本文研究了竹子原料及其磺化机浆 MWL 的结构特性,并把两者进行对比。发现竹料制成浆后,木素中的-OCH_3,侧链羧基含量降低,酚 OH 含量增加,木素发生了较大裂解,其分子量有很大减小,多分散性增大,木素中酯键连接的 H 单元制成浆后有部分水解,但木素中存在非酯(?)连接的 H 单元,它们即使在皂化后也不水解,残留于木素中的糖主要是阿拉伯糖木聚糖,也有一定量的甘露糖、半乳糖、葡萄糖。竹料制成浆后,木素残留糖中的甘露糖消失,葡萄糖有较大减小,说明残留糖中的木糖、阿拉伯糖、半乳糖与木素有较牢固的连接存在。
