Kai Tu | Chinese Academy of Sciences (original) (raw)

Papers by Kai Tu

Soft Matter, 2013

ABSTRACT Usually, it is very difficult to fabricate hydrogels from hydrophobic polyaniline (PANI)... more ABSTRACT Usually, it is very difficult to fabricate hydrogels from hydrophobic polyaniline (PANI). In the present work, an electromechanical PANI-cellulose hydrogel, for the first time, was prepared from a PANI-cellulose transparent solution dissolved in a NaOH-urea aqueous system at low temperature by cross-linking with epichlorohydrin. The composite hydrogels displayed a homogeneous macroporous structure, good miscibility, and excellent mechanical strength, as a result of the association of the PANI chains with the cellulose crosslinked networks held together by noncovalent interactions. Moreover, the hydrogels exhibited a continuous and linear crawling motion under a low applied electric field. The motion of the composite hydrogels was an acceleration process, reflecting the characteristics of a rapid electrical response. This work shows the great potential of a smart hydrogel for applications in the field of biomimetic materials.

Journal of the Meteorological Society of Japan, 2010

Changes in precipitation and its extremes in China were analyzed based on daily precipitation ser... more Changes in precipitation and its extremes in China were analyzed based on daily precipitation series from 1954 to 2006 at 740 stations. Indices of absolute extremes (e.g., heavy rains over 25 mm day À1 ), relative ones (e.g., events exceeding the 95th percentile for local sites and given time in a year), and parameters of fitted Generalized Extremes Value (GEV) distributions were investigated. Many of the precipitation and index series exhibited climatic jumps during the 1960s, around 1980 and in the 1990s. In particular, the widely-concerned drying process in North China was essentially formed by three drying jumps, indicating a stepwise weakening or southward retreating process of the East Asian summer monsoons during the second half of the 20th century. Changes in the atmospheric circulation in association with the regional drying jump around 1980 were analyzed based on the ECMWF 40 Years Re-Analysis (ERA-40) data available from 1958 to 2002. A significant phase shift was found in summer circulation indices and the northwestern Pacific Subtropical High during the late 1970s and the early 1980s. The drying jumps also led to abnormal variability in extreme rainfall events in the region, indicating that extreme events with higher intensity could happen in some years during recent decades than earlier, despite a decrease in the long-term mean precipitation.

Biomacromolecules, 2010

Heparin, a powerful anticoagulant used for the prophylaxis of both surgical and medical thrombosi... more Heparin, a powerful anticoagulant used for the prophylaxis of both surgical and medical thrombosis, was covalently incorporated into a supramolecular hydrogel network. For this attempt, heparin was first conjugated with amino-terminated poly(ethylene glycol) methyl ether by carbodiimide chemistry and then used to interact with α-cyclodextrin in aqueous solution. The rheological measurements and X-ray diffraction analyses were used to characterize the hydrogel formation. It was found that the gelation kinetics and hydrogel properties could be modulated by changing the amount of conjugated heparin or α-cyclodextrin. By circular dichroism analyses and in vitro release experiments, resultant hydrogel material was found to have a great potential as an injectable matrix for the encapsulation and sustained release of model protein drug (bovine serum albumin). By in vitro release, blood clotting, and hemolysis experiments, such a supramolecular hydrogel was also confirmed to have a controlled release profile for conjugated heparin and shows good anticoagulant and blood-compatible properties.

Advances in Atmospheric Sciences, 2011

... urban (•). Page 3. 410 CHANGES IN WIND SPEED IN BEIJING DURING 1960-2008 VOL. 28 are helpful ... more ... urban (•). Page 3. 410 CHANGES IN WIND SPEED IN BEIJING DURING 1960-2008 VOL. 28 are helpful for judging breakpoints in a series. Details of the method are available in the manual by Szen-timrey (1999, 2008). MASH ...

Advances in Atmospheric Sciences, 2011

Trends in the frequencies of four temperature extremes (the occurrence of warm days, cold days, w... more Trends in the frequencies of four temperature extremes (the occurrence of warm days, cold days, warm nights and cold nights) with respect to a modulated annual cycle (MAC), and those associated exclusively with weather-intraseasonal fluctuations (WIF) in eastern China were investigated based on an updated homogenized daily maximum and minimum temperature dataset for 1960-2008. The Ensemble Empirical Mode Decomposition (EEMD) method was used to isolate the WIF, MAC, and longer-term components from the temperature series. The annual, winter and summer occurrences of warm (cold) nights were found to have increased (decreased) significantly almost everywhere, while those of warm (cold) days have increased (decreased) in northern China (north of 40°N). However, the four temperature extremes associated exclusively with WIF for winter have decreased almost everywhere, while those for summer have decreased in the north but increased in the south. These characteristics agree with changes in the amplitude of WIF. In particular, winter WIF of maximum temperature tended to weaken almost everywhere, especially in eastern coastal areas (by 10%-20%); summer WIF tended to intensify in southern China by 10%-20%. It is notable that in northern China, the occurrence of * Corresponding author: YAN Zhongwei, yzw@tea.ac.cn Temperature Extremes and Weather-Intraseasonal Fluctuations 2 warm days has increased, even where that associated with WIF has decreased significantly. This suggests that the recent increasing frequency of warm extremes is due to a considerable rise in the mean temperature level, which surpasses the effect of the weakening weather fluctuations in northern China. , 2010: Trends in temperature extremes in association with weather-intraseasonal fluctuations in eastern China. Adv.

Acta Meteorologica Sinica, 2012

ABSTRACT Having provided an overview of the ideas of developing user-oriented interactive forecas... more ABSTRACT Having provided an overview of the ideas of developing user-oriented interactive forecast system (UIFS) emerging in recent years, the authors proposed an idealized framework of the new-generation meteorological system, which includes the initial user-end module for configuring the forecast target, the physical predictive and downscaling components, and an incessant assessing module in association with decision-making at the user-end. A case study was carried out with a focus on applying the TIGGE (THORPEX Interactive Grand Global Ensemble; THORPEX stands for The Observing System Research and Predictability Experiment) precipitation forecasts for the hydrological users in Linyi, a region richest in rivers and reservoirs in eastern China. The preliminary results exhibited great potential of improvement in applications of weather forecasts by combining the user-end information. Although the TIGGE results provided by existing national/ international operating models were independent from the user-end, the case study enlightened ways of establishing an iteratively self-improving UIFS involving user-orientation throughout the forecast process.

International Journal of Climatology

ABSTRACT

Soft Matter, 2013

ABSTRACT Usually, it is very difficult to fabricate hydrogels from hydrophobic polyaniline (PANI)... more ABSTRACT Usually, it is very difficult to fabricate hydrogels from hydrophobic polyaniline (PANI). In the present work, an electromechanical PANI-cellulose hydrogel, for the first time, was prepared from a PANI-cellulose transparent solution dissolved in a NaOH-urea aqueous system at low temperature by cross-linking with epichlorohydrin. The composite hydrogels displayed a homogeneous macroporous structure, good miscibility, and excellent mechanical strength, as a result of the association of the PANI chains with the cellulose crosslinked networks held together by noncovalent interactions. Moreover, the hydrogels exhibited a continuous and linear crawling motion under a low applied electric field. The motion of the composite hydrogels was an acceleration process, reflecting the characteristics of a rapid electrical response. This work shows the great potential of a smart hydrogel for applications in the field of biomimetic materials.

Journal of the Meteorological Society of Japan, 2010

Changes in precipitation and its extremes in China were analyzed based on daily precipitation ser... more Changes in precipitation and its extremes in China were analyzed based on daily precipitation series from 1954 to 2006 at 740 stations. Indices of absolute extremes (e.g., heavy rains over 25 mm day À1 ), relative ones (e.g., events exceeding the 95th percentile for local sites and given time in a year), and parameters of fitted Generalized Extremes Value (GEV) distributions were investigated. Many of the precipitation and index series exhibited climatic jumps during the 1960s, around 1980 and in the 1990s. In particular, the widely-concerned drying process in North China was essentially formed by three drying jumps, indicating a stepwise weakening or southward retreating process of the East Asian summer monsoons during the second half of the 20th century. Changes in the atmospheric circulation in association with the regional drying jump around 1980 were analyzed based on the ECMWF 40 Years Re-Analysis (ERA-40) data available from 1958 to 2002. A significant phase shift was found in summer circulation indices and the northwestern Pacific Subtropical High during the late 1970s and the early 1980s. The drying jumps also led to abnormal variability in extreme rainfall events in the region, indicating that extreme events with higher intensity could happen in some years during recent decades than earlier, despite a decrease in the long-term mean precipitation.

Biomacromolecules, 2010

Heparin, a powerful anticoagulant used for the prophylaxis of both surgical and medical thrombosi... more Heparin, a powerful anticoagulant used for the prophylaxis of both surgical and medical thrombosis, was covalently incorporated into a supramolecular hydrogel network. For this attempt, heparin was first conjugated with amino-terminated poly(ethylene glycol) methyl ether by carbodiimide chemistry and then used to interact with α-cyclodextrin in aqueous solution. The rheological measurements and X-ray diffraction analyses were used to characterize the hydrogel formation. It was found that the gelation kinetics and hydrogel properties could be modulated by changing the amount of conjugated heparin or α-cyclodextrin. By circular dichroism analyses and in vitro release experiments, resultant hydrogel material was found to have a great potential as an injectable matrix for the encapsulation and sustained release of model protein drug (bovine serum albumin). By in vitro release, blood clotting, and hemolysis experiments, such a supramolecular hydrogel was also confirmed to have a controlled release profile for conjugated heparin and shows good anticoagulant and blood-compatible properties.

Advances in Atmospheric Sciences, 2011

... urban (•). Page 3. 410 CHANGES IN WIND SPEED IN BEIJING DURING 1960-2008 VOL. 28 are helpful ... more ... urban (•). Page 3. 410 CHANGES IN WIND SPEED IN BEIJING DURING 1960-2008 VOL. 28 are helpful for judging breakpoints in a series. Details of the method are available in the manual by Szen-timrey (1999, 2008). MASH ...

Advances in Atmospheric Sciences, 2011

Trends in the frequencies of four temperature extremes (the occurrence of warm days, cold days, w... more Trends in the frequencies of four temperature extremes (the occurrence of warm days, cold days, warm nights and cold nights) with respect to a modulated annual cycle (MAC), and those associated exclusively with weather-intraseasonal fluctuations (WIF) in eastern China were investigated based on an updated homogenized daily maximum and minimum temperature dataset for 1960-2008. The Ensemble Empirical Mode Decomposition (EEMD) method was used to isolate the WIF, MAC, and longer-term components from the temperature series. The annual, winter and summer occurrences of warm (cold) nights were found to have increased (decreased) significantly almost everywhere, while those of warm (cold) days have increased (decreased) in northern China (north of 40°N). However, the four temperature extremes associated exclusively with WIF for winter have decreased almost everywhere, while those for summer have decreased in the north but increased in the south. These characteristics agree with changes in the amplitude of WIF. In particular, winter WIF of maximum temperature tended to weaken almost everywhere, especially in eastern coastal areas (by 10%-20%); summer WIF tended to intensify in southern China by 10%-20%. It is notable that in northern China, the occurrence of * Corresponding author: YAN Zhongwei, yzw@tea.ac.cn Temperature Extremes and Weather-Intraseasonal Fluctuations 2 warm days has increased, even where that associated with WIF has decreased significantly. This suggests that the recent increasing frequency of warm extremes is due to a considerable rise in the mean temperature level, which surpasses the effect of the weakening weather fluctuations in northern China. , 2010: Trends in temperature extremes in association with weather-intraseasonal fluctuations in eastern China. Adv.

Acta Meteorologica Sinica, 2012

ABSTRACT Having provided an overview of the ideas of developing user-oriented interactive forecas... more ABSTRACT Having provided an overview of the ideas of developing user-oriented interactive forecast system (UIFS) emerging in recent years, the authors proposed an idealized framework of the new-generation meteorological system, which includes the initial user-end module for configuring the forecast target, the physical predictive and downscaling components, and an incessant assessing module in association with decision-making at the user-end. A case study was carried out with a focus on applying the TIGGE (THORPEX Interactive Grand Global Ensemble; THORPEX stands for The Observing System Research and Predictability Experiment) precipitation forecasts for the hydrological users in Linyi, a region richest in rivers and reservoirs in eastern China. The preliminary results exhibited great potential of improvement in applications of weather forecasts by combining the user-end information. Although the TIGGE results provided by existing national/ international operating models were independent from the user-end, the case study enlightened ways of establishing an iteratively self-improving UIFS involving user-orientation throughout the forecast process.

International Journal of Climatology

ABSTRACT