AIM:To evaluate the safety and efficacy of partially covered self-expandable metallic stents(SEMSs)in benign pyloric obstruction.METHODS:We retrospectively analyzed data from 10consecutive patients with peptic ulcer-r...AIM:To evaluate the safety and efficacy of partially covered self-expandable metallic stents(SEMSs)in benign pyloric obstruction.METHODS:We retrospectively analyzed data from 10consecutive patients with peptic ulcer-related pyloric obstructive symptoms(gastric outlet obstruction scoring system(GOOSS)score of 1)between March 2012and September 2013.The patients were referred to and managed by partially covered SEMS insertion in our tertiary academic center.We assessed the technical success,symptom improvement,and adverse events after stenting.RESULTS:Early symptoms were improved just 3 d after SEMS placement in all 10 patients.The GOOSS score of all patients improved from 1 to 3.There were no serious immediate adverse events.The overall rate of being symptom free was 90%at a median of 11mo of follow-up(range:4-43 mo).Five patients were managed by a rescue SEMS because of failure of previous endoscopic balloon dilatation.Among them,four patients had sustained symptom improvement after the SEMS procedure.During the follow-up period,migration of the SEMS was observed in two patients(20.0%),both of whom had previous endoscopic balloon dilatation before SEMS insertion.CONCLUSION:Despite the small number in this study,partially covered SEMSs showed a favorable and safe outcome in the treatment of na?ve benign pyloric obstruction and in salvage treatment after balloon dilatation failure.展开更多
Some monosubstituted Keggin or Dawson anions nave been reporten by Hill to be "remarkably effective" catalysts for the epoxidation of alkenes, Hill, Finke and Neumann reported respectively that the transitio...Some monosubstituted Keggin or Dawson anions nave been reporten by Hill to be "remarkably effective" catalysts for the epoxidation of alkenes, Hill, Finke and Neumann reported respectively that the transition metal monosubstituted heteropolyanions [PW;O;M(H;O)]";, [P;W;O;M(L)]"- and [SiW;O;Ru(H;O)];have an ability to catalyze the epoxidation of alkenes. And the undecatungstotitanates with one kind of transition metal have展开更多
The hybrid metal-organic framework [(CH3)2NH2]Fe(HCOO)3 with a perovskite-like structure exhibits a variety of unusual magnetic behaviors at low temperatures. While the long-distance super-exchange through the Fe-...The hybrid metal-organic framework [(CH3)2NH2]Fe(HCOO)3 with a perovskite-like structure exhibits a variety of unusual magnetic behaviors at low temperatures. While the long-distance super-exchange through the Fe-(Y-CH-O- Fe exchange path leads to a canted antiferromagnetic ordering at TN - 19 K, a second transition of magnetic blocking develops at TB- 9 K. The stair-shaped magnetization hysteresis loops below TB resemble the behaviors of resonant quantum tunneling of magnetization in single-molecular quantum magnets. Moreover, the magnetic relaxation also exhibits several features of resonant quantum relaxation, such as the exponential law with a single characteristic relaxation time, and the nonmonotonic dependence of relaxation rate on the applied magnetic field with a much faster relaxation around the resonant fields. The origin of quantum tunneling behaviors in the [(CH3)2NH2]Fe(HCOO)3 metal-organic framework is discussed in terms of magnetic phase separation due to the modification of hydrogen bonding on the long-distance super-exchange interaction.展开更多
Synoptic patterns identified by an automated procedure employing principal- component analysis and a two-stage cluster analysis, and backward trajectory analysis clustered by the HYSPLIT4.9 model were used to examine ...Synoptic patterns identified by an automated procedure employing principal- component analysis and a two-stage cluster analysis, and backward trajectory analysis clustered by the HYSPLIT4.9 model were used to examine air quality patterns over¨ Uru¨mqi, China, one of the most heavily polluted cities in the world. Six synoptic patterns representing different atmospheric circulation patterns and air-mass characteristics were classified during the winter heating periods from 2001 to 2008, and seven trajectory clusters representing different paths of air masses arriving at ürümqi were calculated during the winter heating periods from 2005 to 2008. Then air quality was evaluated using these two approaches, and significant variations were found across both synoptic patterns and trajectory clusters. The heaviest air-pollution episodes occurred when ürümqi was either in an extremely cold, strong anticyclone or at the front of a migrating cyclone. Both conditions were characterized by with light winds, cold, wet surface air, and relatively dry upper air. ürümqi was predominately influenced by air masses from the southwest and from local areas. Air pollution index (API) levels were highest for air masses originating from the southwest with a longer path or for the local area, because of transport from semi-desert/desert regions by strong winds and because of local heavy pollution emissions, respectively. The interactions between these two analytical approaches showed that poor diffusion conditions, together with local circulation, enhanced air pollution, besides, regional air-mass transport caused by strong winds contributed to serious air quality under relatively good diffusion conditions.展开更多
Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years ...Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years but ceased in 2000, in Magu Town, Guizhou Province, China were selected to examine Pb, Zn, and Cd concentrations and their fractionation along a distance gradient from a zinc smelter, and to study the possible e?ects of Pb, Zn, and Cd accumulation on soil microorganisms by comparing with a reference soil located at a downwind distance of 10 km from the zinc smelter. Soils within 1.5 km of the zinc smelter accumulated high levels of heavy metals Zn (508 mg kg-1), Pb (95.6 mg kg-1), and Cd (5.98 mg kg-1) with low ratios of Zn/Cd (59.1-115) and Pb/Cd (12.4-23.4). Composite pollution indices (CPIs) of surface soils (2.52-15.2) were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. The saturation degree of metals (SDM) in soils within 1.5 km of the smelter (averaging 1.25) was six times higher than that of the reference soils (0.209). A smaller soil microbial biomass was found more frequently in metal accumulated soils (85.1-438 μg C g-1) than in reference soils (497 μg C g-1), and a negative correlation (P < 0.01) of soil microbial biomass carbon to organic carbon ratio (Cmic/Corg) with SDM was observed. Microbial consumption of carbon sources was more rapid in contaminated soils than in reference soils, and a shift in the substrate utilization pattern was apparent and was negatively correlated with SDM (R = -0.773, P < 0.01). Consequently, dust deposited Pb, Zn, and Cd in soils from zinc smelting were readily mobilized, and were detrimental to soil quality mainly in respect of microbial biomass.展开更多
A physiological strain of microorganism - Azotobacter sp. has been adopted as an indicator to detect the toxicity of heavy metals in soils. The concentration of heavy metals to which Azotobacter sp. was behaving initi...A physiological strain of microorganism - Azotobacter sp. has been adopted as an indicator to detect the toxicity of heavy metals in soils. The concentration of heavy metals to which Azotobacter sp. was behaving initially to have the resistance to heavy metals is defined as the critical poisoning concentration. The method of physiological threshold adopted can have a quantitative determination with reproducible results. The determined critical poisoning concentration is basically consistent with the results of heavy metals and arsenic toxicities to the bacteria reported recently in literatures. Total 9 typical soils, including 6 zonal soils and 3 purple soils, in the whole country were determined for the toxicities of 5 heavy metals and arsenic to Azotobacter sp. that resulted in 48 critical poisoning concentrations.展开更多
In the process of high-k films fabrication, a novel multi deposition multi annealing (MDMA) technique is introduced to replace simple post deposition annealing. The leakage current decreases with the increase of the...In the process of high-k films fabrication, a novel multi deposition multi annealing (MDMA) technique is introduced to replace simple post deposition annealing. The leakage current decreases with the increase of the post deposition annealing (PDA) times. The equivalent oxide thickness (EOT) decreases when the annealing time(s) change from 1 to 2. Furthermore, the characteristics of SILC (stress-induced leakage current) for an ultra-thin SiO2/HfO2 gate dielectric stack are studied systematically. The increase of the PDA time(s) from 1 to 2 can decrease the defect and defect generation rate in the HK layer. However, increasing the PDA times to 4 and 7 may introduce too much oxygen, therefore the type of oxygen vacancy changes.展开更多
<img src="Edit_bdc7d851-e537-40df-990c-d678defa9648.png" alt="" />(M = Au, Ag, Cu;<span lang="EN-US" style="font-size:9pt;font-family:"color:black;"><i>n&...<img src="Edit_bdc7d851-e537-40df-990c-d678defa9648.png" alt="" />(M = Au, Ag, Cu;<span lang="EN-US" style="font-size:9pt;font-family:"color:black;"><i>n</i></span>= 1, 2, 3) clusters were used as a cluster model to study the activation of oxygen molecules on single-atom catalysts. Structures of <img src="Edit_bb84deb7-e24a-4777-a2f6-a1621ddd2afc.png" alt="" /> clusters were studied by density functional calculations with global optimization. For each <span style="font-family:"color:black;white-space:normal;"><i>n</i></span>, the most stable structures are quite similar for different metal types, and the oxygen molecule prefers to be adsorbed onto M atoms. It is found that the activation degree of oxygen is higher on clusters with non-noble metal Cu than that of Ag or Au containing clusters, by comparing the changes of O-O bond length and vibrational frequency, natural charge population analysis, Fuzzy bond order analysis, and energy barriers of O<sub>2</sub> dissociation. CO oxidation was used as a probe reaction to study the reactivity of Cu-containing clusters, and it is found that the reactivity decreases with the increase of the size of silicon-oxygen clusters. Our results give a new aspect to understand the reaction mechanism of non-precious metal single-atom catalyst for oxygen activation with high efficiency.展开更多
文摘AIM:To evaluate the safety and efficacy of partially covered self-expandable metallic stents(SEMSs)in benign pyloric obstruction.METHODS:We retrospectively analyzed data from 10consecutive patients with peptic ulcer-related pyloric obstructive symptoms(gastric outlet obstruction scoring system(GOOSS)score of 1)between March 2012and September 2013.The patients were referred to and managed by partially covered SEMS insertion in our tertiary academic center.We assessed the technical success,symptom improvement,and adverse events after stenting.RESULTS:Early symptoms were improved just 3 d after SEMS placement in all 10 patients.The GOOSS score of all patients improved from 1 to 3.There were no serious immediate adverse events.The overall rate of being symptom free was 90%at a median of 11mo of follow-up(range:4-43 mo).Five patients were managed by a rescue SEMS because of failure of previous endoscopic balloon dilatation.Among them,four patients had sustained symptom improvement after the SEMS procedure.During the follow-up period,migration of the SEMS was observed in two patients(20.0%),both of whom had previous endoscopic balloon dilatation before SEMS insertion.CONCLUSION:Despite the small number in this study,partially covered SEMSs showed a favorable and safe outcome in the treatment of na?ve benign pyloric obstruction and in salvage treatment after balloon dilatation failure.
基金Supported by the National Natural Science Foundation of ChinaLaboratory of Apphed spectroscopy
文摘Some monosubstituted Keggin or Dawson anions nave been reporten by Hill to be "remarkably effective" catalysts for the epoxidation of alkenes, Hill, Finke and Neumann reported respectively that the transition metal monosubstituted heteropolyanions [PW;O;M(H;O)]";, [P;W;O;M(L)]"- and [SiW;O;Ru(H;O)];have an ability to catalyze the epoxidation of alkenes. And the undecatungstotitanates with one kind of transition metal have
基金supported by the National Natural Science Foundation of China(Grant Nos.11227405,51371192,and 51371193)the Chinese Academy of Sciences(Grant No.XDB07030200)
文摘The hybrid metal-organic framework [(CH3)2NH2]Fe(HCOO)3 with a perovskite-like structure exhibits a variety of unusual magnetic behaviors at low temperatures. While the long-distance super-exchange through the Fe-(Y-CH-O- Fe exchange path leads to a canted antiferromagnetic ordering at TN - 19 K, a second transition of magnetic blocking develops at TB- 9 K. The stair-shaped magnetization hysteresis loops below TB resemble the behaviors of resonant quantum tunneling of magnetization in single-molecular quantum magnets. Moreover, the magnetic relaxation also exhibits several features of resonant quantum relaxation, such as the exponential law with a single characteristic relaxation time, and the nonmonotonic dependence of relaxation rate on the applied magnetic field with a much faster relaxation around the resonant fields. The origin of quantum tunneling behaviors in the [(CH3)2NH2]Fe(HCOO)3 metal-organic framework is discussed in terms of magnetic phase separation due to the modification of hydrogen bonding on the long-distance super-exchange interaction.
基金supported by the National Basic Research Program (also called 973 Program) of China (Grant No 2007CB407303)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No KZCX2-YW-Q02-03)
文摘Synoptic patterns identified by an automated procedure employing principal- component analysis and a two-stage cluster analysis, and backward trajectory analysis clustered by the HYSPLIT4.9 model were used to examine air quality patterns over¨ Uru¨mqi, China, one of the most heavily polluted cities in the world. Six synoptic patterns representing different atmospheric circulation patterns and air-mass characteristics were classified during the winter heating periods from 2001 to 2008, and seven trajectory clusters representing different paths of air masses arriving at ürümqi were calculated during the winter heating periods from 2005 to 2008. Then air quality was evaluated using these two approaches, and significant variations were found across both synoptic patterns and trajectory clusters. The heaviest air-pollution episodes occurred when ürümqi was either in an extremely cold, strong anticyclone or at the front of a migrating cyclone. Both conditions were characterized by with light winds, cold, wet surface air, and relatively dry upper air. ürümqi was predominately influenced by air masses from the southwest and from local areas. Air pollution index (API) levels were highest for air masses originating from the southwest with a longer path or for the local area, because of transport from semi-desert/desert regions by strong winds and because of local heavy pollution emissions, respectively. The interactions between these two analytical approaches showed that poor diffusion conditions, together with local circulation, enhanced air pollution, besides, regional air-mass transport caused by strong winds contributed to serious air quality under relatively good diffusion conditions.
基金Project supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KZCX2-105)the "Light in Western China" Program of the Chinese Academy of Sciences and Guizhou Province, and the National Natural Science Foundation of China (No.40473049)
文摘Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years but ceased in 2000, in Magu Town, Guizhou Province, China were selected to examine Pb, Zn, and Cd concentrations and their fractionation along a distance gradient from a zinc smelter, and to study the possible e?ects of Pb, Zn, and Cd accumulation on soil microorganisms by comparing with a reference soil located at a downwind distance of 10 km from the zinc smelter. Soils within 1.5 km of the zinc smelter accumulated high levels of heavy metals Zn (508 mg kg-1), Pb (95.6 mg kg-1), and Cd (5.98 mg kg-1) with low ratios of Zn/Cd (59.1-115) and Pb/Cd (12.4-23.4). Composite pollution indices (CPIs) of surface soils (2.52-15.2) were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. The saturation degree of metals (SDM) in soils within 1.5 km of the smelter (averaging 1.25) was six times higher than that of the reference soils (0.209). A smaller soil microbial biomass was found more frequently in metal accumulated soils (85.1-438 μg C g-1) than in reference soils (497 μg C g-1), and a negative correlation (P < 0.01) of soil microbial biomass carbon to organic carbon ratio (Cmic/Corg) with SDM was observed. Microbial consumption of carbon sources was more rapid in contaminated soils than in reference soils, and a shift in the substrate utilization pattern was apparent and was negatively correlated with SDM (R = -0.773, P < 0.01). Consequently, dust deposited Pb, Zn, and Cd in soils from zinc smelting were readily mobilized, and were detrimental to soil quality mainly in respect of microbial biomass.
文摘A physiological strain of microorganism - Azotobacter sp. has been adopted as an indicator to detect the toxicity of heavy metals in soils. The concentration of heavy metals to which Azotobacter sp. was behaving initially to have the resistance to heavy metals is defined as the critical poisoning concentration. The method of physiological threshold adopted can have a quantitative determination with reproducible results. The determined critical poisoning concentration is basically consistent with the results of heavy metals and arsenic toxicities to the bacteria reported recently in literatures. Total 9 typical soils, including 6 zonal soils and 3 purple soils, in the whole country were determined for the toxicities of 5 heavy metals and arsenic to Azotobacter sp. that resulted in 48 critical poisoning concentrations.
基金supported by the National High Technology Research and Development Program of China(Grant No.2015AA016501)the National Natural Science Foundation of China(Grant No.61306129)
文摘In the process of high-k films fabrication, a novel multi deposition multi annealing (MDMA) technique is introduced to replace simple post deposition annealing. The leakage current decreases with the increase of the post deposition annealing (PDA) times. The equivalent oxide thickness (EOT) decreases when the annealing time(s) change from 1 to 2. Furthermore, the characteristics of SILC (stress-induced leakage current) for an ultra-thin SiO2/HfO2 gate dielectric stack are studied systematically. The increase of the PDA time(s) from 1 to 2 can decrease the defect and defect generation rate in the HK layer. However, increasing the PDA times to 4 and 7 may introduce too much oxygen, therefore the type of oxygen vacancy changes.
文摘<img src="Edit_bdc7d851-e537-40df-990c-d678defa9648.png" alt="" />(M = Au, Ag, Cu;<span lang="EN-US" style="font-size:9pt;font-family:"color:black;"><i>n</i></span>= 1, 2, 3) clusters were used as a cluster model to study the activation of oxygen molecules on single-atom catalysts. Structures of <img src="Edit_bb84deb7-e24a-4777-a2f6-a1621ddd2afc.png" alt="" /> clusters were studied by density functional calculations with global optimization. For each <span style="font-family:"color:black;white-space:normal;"><i>n</i></span>, the most stable structures are quite similar for different metal types, and the oxygen molecule prefers to be adsorbed onto M atoms. It is found that the activation degree of oxygen is higher on clusters with non-noble metal Cu than that of Ag or Au containing clusters, by comparing the changes of O-O bond length and vibrational frequency, natural charge population analysis, Fuzzy bond order analysis, and energy barriers of O<sub>2</sub> dissociation. CO oxidation was used as a probe reaction to study the reactivity of Cu-containing clusters, and it is found that the reactivity decreases with the increase of the size of silicon-oxygen clusters. Our results give a new aspect to understand the reaction mechanism of non-precious metal single-atom catalyst for oxygen activation with high efficiency.