Two-dimensional covalent organic frameworks(2D COFs)feature extendedπ-conjugation and ordered stacking sequence,showing great promise for high-performance photocatalysis.Periodic atomic frameworks of 2D COFs facilita...Two-dimensional covalent organic frameworks(2D COFs)feature extendedπ-conjugation and ordered stacking sequence,showing great promise for high-performance photocatalysis.Periodic atomic frameworks of 2D COFs facilitate the in-plane photogenerated charge transfer,but the precise ordered alignment is limited due to the non-covalentπ-stacking of COF layers,accordingly hindering out-of-plane transfer kinetics.Herein,we address a chiral induction method to construct a parallelly superimposed stacking chiral COF ultrathin shell on the support of SiO_(2) microsphere.Compared to the achiral COF analogues,the chiral COF shell with the parallel AA-stacking structure is more conducive to enhance the built-in electric field and accumulates photogenerated electrons for the rapid migration,thereby affording superior photocatalytic performance in hydrogen evolution from water splitting.Taking the simplest ketoenamine-linked chiral COF as a shell of SiO_(2) particle,the resulting composite exhibits an impressive hydrogen evolution rate of 107.1 mmol g^(-1)h^(-1)along with the apparent quantum efficiency of 14.31% at 475 nm.Furthermore,the composite photocatalysts could be fabricated into a film device,displaying a remarkable photocatalytic performance of 178.0 mmol m^(-2)h^(-1)for hydrogen evolution.Our work underpins the surface engineering of organic photocatalysts and illustrates the significance of COF stacking structures in regulating electronic properties.展开更多
In order to improve the destruction efficiency of dioxins and also for developing new dioxin control technology, the destruction mechanisms of 2,3,7,8-tetrachlorodihenzo-p-dioxin （2,3,7,8-TCDD） by O3 and NO3, were i...In order to improve the destruction efficiency of dioxins and also for developing new dioxin control technology, the destruction mechanisms of 2,3,7,8-tetrachlorodihenzo-p-dioxin （2,3,7,8-TCDD） by O3 and NO3, were investigated employing quantum chemical calculations. For involved reactions, the microcosmic reaction processes were analyzed and depicted in detail based on geometry optimizations made by the B3LYP/6-31G（d） method. At the same time, the reaction activation energies were also calculated at the MP2/6- 311G（d,p）//B3LYP/6-31G（d） level. Configuration analysis indicated that 2,3,7,8-TCDD could be destroyed by 03 and NO3 in two different ways. The destruction of 2,3,7,8-TCDD by 03 proceeded via the addition of 03 and the cleavage of C=C while the destruction of 2,3,7,8-TCDD by NO3 proceeded via the substitution of chlorine by NO3. Calculated results show that, the activation energy of the destruction reaction of 2,3,7,8-TCDD by NO3 （267.48 kJ/mol） is much larger than that of the destruction reaction of 2,3,7,8-TCDD by O3 （51.20 kJ/mol）. This indicated that the destruction of 2,3,7,8-TCDD by 03 is much more efficient than that of 2,3,7,8-TCDD by NO3. The reason why the activation energy for the destruction reaction of 2,3,7,8-TCDD by NO3 is so large, is also discussed.展开更多
AIM: In patients with liver cirrhosis and portal hypertension, portal hypertensive colopathy is thought to be an important cause of lower gastrointestinal hemorrhage. In this study, we evaluated the prevalence of colo...AIM: In patients with liver cirrhosis and portal hypertension, portal hypertensive colopathy is thought to be an important cause of lower gastrointestinal hemorrhage. In this study, we evaluated the prevalence of colonic mucosal changes in patients with liver cirrhosis and its clinical significance. METHODS: We evaluated the colonoscopic findings and liver function of 47 patients with liver cirrhosis over a 6-year period. The main cause of liver cirrhosis was post-viral hepatitis (68%) related to hepatitis B (6%) or C (62%) infection. All patients underwent upper gastrointestinal endoscopy to examine the presence of esophageal varices, cardiac varices, and congestive gastropathy, as well as a full colonoscopy to observe changes in colonic mucosa. Portal hypertensive colopathy was defined endoscopically in patients with vascular ectasia, redness, and blue vein. Vascular ectasia was classified into two types: type 1, solitary vascular ectasia; and type 2, diffuse vascular ectasia. RESULTS: Overall portal hypertensive colopathy was present in 31 patients (66%), including solitary vascular ectasia in 17 patients (36%), diffuse vascular ectasia in 20 patients (42%), redness in 10 patients (21%) and blue vein in 6 patients (12%). As the Child-Pugh class increased in severity, the prevalence of portal hypertensive colopathy rose. Child-Pugh class B and C were significantly associated with portal hypertensive colopathy. Portal hypertensive gastropathy, esophageal varices, ascites and hepatocellular carcinoma were not related to occurrence of portal hypertensive colopathy. Platelet count was significantly associated with portal hypertensive colopathy, but prothrombin time, serum albumin level, total bilirubin level and serum ALT level were not related to occurrence of portal hypertensive colopathy. CONCLUSION: As the Child-Pugh class worsens and platelet count decreases, the prevalence of portal hypertensive colopathy increases in patients with liver cirrhosis. A colonoscopic examination in patients with liver cirrhosis is indicated, especially those with worsening Child-Pugh class and/or decreasing platelet count, to prevent complications such as lower gastrointestinal bleeding.展开更多
To evaluate the operation comfortability in the master-slave robotic minimally invasive surgery(MIS), an optimal function was built with two operation comfortability decided indices, i.e., the center distance and volu...To evaluate the operation comfortability in the master-slave robotic minimally invasive surgery(MIS), an optimal function was built with two operation comfortability decided indices, i.e., the center distance and volume contact ratio. Two verifying experiments on Phantom Desktop and Micro Hand S were conducted. Experimental results show that the operation effect at the optimal relative location is better than that at the random location, which means that the optimal function constructed in this paper is effective in optimizing the operation comfortability.展开更多
文摘Two-dimensional covalent organic frameworks(2D COFs)feature extendedπ-conjugation and ordered stacking sequence,showing great promise for high-performance photocatalysis.Periodic atomic frameworks of 2D COFs facilitate the in-plane photogenerated charge transfer,but the precise ordered alignment is limited due to the non-covalentπ-stacking of COF layers,accordingly hindering out-of-plane transfer kinetics.Herein,we address a chiral induction method to construct a parallelly superimposed stacking chiral COF ultrathin shell on the support of SiO_(2) microsphere.Compared to the achiral COF analogues,the chiral COF shell with the parallel AA-stacking structure is more conducive to enhance the built-in electric field and accumulates photogenerated electrons for the rapid migration,thereby affording superior photocatalytic performance in hydrogen evolution from water splitting.Taking the simplest ketoenamine-linked chiral COF as a shell of SiO_(2) particle,the resulting composite exhibits an impressive hydrogen evolution rate of 107.1 mmol g^(-1)h^(-1)along with the apparent quantum efficiency of 14.31% at 475 nm.Furthermore,the composite photocatalysts could be fabricated into a film device,displaying a remarkable photocatalytic performance of 178.0 mmol m^(-2)h^(-1)for hydrogen evolution.Our work underpins the surface engineering of organic photocatalysts and illustrates the significance of COF stacking structures in regulating electronic properties.
文摘In order to improve the destruction efficiency of dioxins and also for developing new dioxin control technology, the destruction mechanisms of 2,3,7,8-tetrachlorodihenzo-p-dioxin （2,3,7,8-TCDD） by O3 and NO3, were investigated employing quantum chemical calculations. For involved reactions, the microcosmic reaction processes were analyzed and depicted in detail based on geometry optimizations made by the B3LYP/6-31G（d） method. At the same time, the reaction activation energies were also calculated at the MP2/6- 311G（d,p）//B3LYP/6-31G（d） level. Configuration analysis indicated that 2,3,7,8-TCDD could be destroyed by 03 and NO3 in two different ways. The destruction of 2,3,7,8-TCDD by 03 proceeded via the addition of 03 and the cleavage of C=C while the destruction of 2,3,7,8-TCDD by NO3 proceeded via the substitution of chlorine by NO3. Calculated results show that, the activation energy of the destruction reaction of 2,3,7,8-TCDD by NO3 （267.48 kJ/mol） is much larger than that of the destruction reaction of 2,3,7,8-TCDD by O3 （51.20 kJ/mol）. This indicated that the destruction of 2,3,7,8-TCDD by 03 is much more efficient than that of 2,3,7,8-TCDD by NO3. The reason why the activation energy for the destruction reaction of 2,3,7,8-TCDD by NO3 is so large, is also discussed.
文摘AIM: In patients with liver cirrhosis and portal hypertension, portal hypertensive colopathy is thought to be an important cause of lower gastrointestinal hemorrhage. In this study, we evaluated the prevalence of colonic mucosal changes in patients with liver cirrhosis and its clinical significance. METHODS: We evaluated the colonoscopic findings and liver function of 47 patients with liver cirrhosis over a 6-year period. The main cause of liver cirrhosis was post-viral hepatitis (68%) related to hepatitis B (6%) or C (62%) infection. All patients underwent upper gastrointestinal endoscopy to examine the presence of esophageal varices, cardiac varices, and congestive gastropathy, as well as a full colonoscopy to observe changes in colonic mucosa. Portal hypertensive colopathy was defined endoscopically in patients with vascular ectasia, redness, and blue vein. Vascular ectasia was classified into two types: type 1, solitary vascular ectasia; and type 2, diffuse vascular ectasia. RESULTS: Overall portal hypertensive colopathy was present in 31 patients (66%), including solitary vascular ectasia in 17 patients (36%), diffuse vascular ectasia in 20 patients (42%), redness in 10 patients (21%) and blue vein in 6 patients (12%). As the Child-Pugh class increased in severity, the prevalence of portal hypertensive colopathy rose. Child-Pugh class B and C were significantly associated with portal hypertensive colopathy. Portal hypertensive gastropathy, esophageal varices, ascites and hepatocellular carcinoma were not related to occurrence of portal hypertensive colopathy. Platelet count was significantly associated with portal hypertensive colopathy, but prothrombin time, serum albumin level, total bilirubin level and serum ALT level were not related to occurrence of portal hypertensive colopathy. CONCLUSION: As the Child-Pugh class worsens and platelet count decreases, the prevalence of portal hypertensive colopathy increases in patients with liver cirrhosis. A colonoscopic examination in patients with liver cirrhosis is indicated, especially those with worsening Child-Pugh class and/or decreasing platelet count, to prevent complications such as lower gastrointestinal bleeding.
基金Supported by the National High Technology Research and Development Program of China("863" Program,No.2012AA02A606)the Research Project of State Key Laboratory of Mechanical System and Vibration(MSV201412)
文摘To evaluate the operation comfortability in the master-slave robotic minimally invasive surgery(MIS), an optimal function was built with two operation comfortability decided indices, i.e., the center distance and volume contact ratio. Two verifying experiments on Phantom Desktop and Micro Hand S were conducted. Experimental results show that the operation effect at the optimal relative location is better than that at the random location, which means that the optimal function constructed in this paper is effective in optimizing the operation comfortability.
