The catalytic epoxidation of olefin was investigated on two copper complex-modified molybdenum oxides with a 3D supramolecular structure, [Cu（bipy）]4[Mo15O47].2H2O （1） and [Cu1（bix）][（Cu1bix） （δ-MoVl8O26）0....The catalytic epoxidation of olefin was investigated on two copper complex-modified molybdenum oxides with a 3D supramolecular structure, [Cu（bipy）]4[Mo15O47].2H2O （1） and [Cu1（bix）][（Cu1bix） （δ-MoVl8O26）0.5] （2） （bipy = 4,4＇-bipyridine, bix = 1,4-bis（imidazole-1-ylmethyl）benzene）. Both compounds were catalytically active and stable for the epoxidation of cyclooctene, 1-octene, and styrene with tert-butyl hydroperoxide （t-BuOOH） as oxidant. The excellent catalytic performance was attributed to the presence of stable coordination bonds between the molybdenum oxide and copper complex, which resulted in the formation of easily accessible Mo species with high electropositivity. In addition, the copper complex also acted as an active site for the activation of t-BuOOH, thus im- proving these copper complex-modified polyoxometalates.展开更多
Although clustering is a convenient framework to enable traffic control and service support in Mobile Ad hoc NETworks （MANETs）, it is seldom adopted in practice due to the additional traffic overhead it leads to for...Although clustering is a convenient framework to enable traffic control and service support in Mobile Ad hoc NETworks （MANETs）, it is seldom adopted in practice due to the additional traffic overhead it leads to for the resource limited ad hoc network. In order to address this problem, we proposed a loop-based approach to combine clustering and routing. By employing loop topologies, topology information is disseminated with a loop instead of a single node, which provides better robustness, and the nature of a loop that there are two paths between each pair of nodes within a loop composed of setup procedure, regular procedure and emergent route recovering. suggests smart route recovery strategy. Our approach is recovery procedure to achieve clustering, routing and展开更多
In this paper detailed studies of the cyclic voltammetry(CV) of trinuclear metal cluster compounds [M_3O_2(O_2CCH_3,)6(H,O),j z+ (M,=Mo3,MoW2,W3) are reported.The result of CV shows that they are similar to each other...In this paper detailed studies of the cyclic voltammetry(CV) of trinuclear metal cluster compounds [M_3O_2(O_2CCH_3,)6(H,O),j z+ (M,=Mo3,MoW2,W3) are reported.The result of CV shows that they are similar to each other.There are a reversible redox peak near-0. 48 V and an irreversible reduced peak near-1.10 V in the scan range of + l.0 V to l. 5 V.It implies that the M_3O_2,clusters might gain one electron to be further reduced.But the two-electron-reduced product of M_3O_2 clusters are instable.The theoretical calculations(EHMO) agree well with the result of the CV experiment.展开更多
The title compound 〔(PPh 3)(CH 3COS) 2NiB 10 H 10 〕·0.4(C 5H 12 ) has been synthesized by the reaction of 〔NiCl 2(PPh 3) 2〕, closo 〔B 10 H 10 〕 2- and CH 3COSH in CH 2Cl 2 solution. It was recrystallized fr...The title compound 〔(PPh 3)(CH 3COS) 2NiB 10 H 10 〕·0.4(C 5H 12 ) has been synthesized by the reaction of 〔NiCl 2(PPh 3) 2〕, closo 〔B 10 H 10 〕 2- and CH 3COSH in CH 2Cl 2 solution. It was recrystallized from n pentane/CH 2Cl 2 solution and its structure was determined by X ray diffraction analysis. The crystal is triclinic, space group P1, M r= 618.23, with a=10.049(1), b=12.638(2), c=14.077(2) , α=110.13(1), β=87.65(1), γ=96.01(1)°, V=1669.3(4) 3, D c =1.230 g/cm 3, Z=2, λ (Mo Kα )=0.71073 , μ =7.76 cm -1 , F (000)=642. The final refinement is converged with R =0.042 (5986 observed reflections with I≥2σ(I)), wR 2 =0.151. The cluster is a nido eleven vertex {NiB 10 } cage with the Ni atom in the open NiB 4 face. Cyclizations resulting in two five membered rings, Ni(7)-S(1)-C(1)-O(1)-B(2) and Ni(7)-S(2)-C(2)-O(2)-B(3), have occurred.展开更多
The chiral cluster RuCoMo（CO）8 （μ3-Se）C5H4C （O）C6H4C （O）OCH3was synthesizgd by the thermal reaction of the precursor （μ3-Se）RuCo2（Co）9 with ’thefunctionally substituted cyclopentadienyl tricarbonyl meta...The chiral cluster RuCoMo（CO）8 （μ3-Se）C5H4C （O）C6H4C （O）OCH3was synthesizgd by the thermal reaction of the precursor （μ3-Se）RuCo2（Co）9 with ’thefunctionally substituted cyclopentadienyl tricarbonyl metal complex anions [Mo（CO）3（η5-C5H4） C （O）C6H4C （O） OCH3]- in THF. It was characterized by C/H elementalanalysis, IR, 1H/13C-NMR and MS （FAB）, and its crystal structure has also beensolved by single-crystal X-ray diffraction. Crystal data: Mr=786. 23, triclinic, spacegroup P1, a =8. 200（2）, b= 19. 631 （7）, c=7.997（2） , a=92. 50（2）, β=108. 66 （2）, γ=88. 97（2）°, V= 1218. 5（6） , Z=2, Dc=2. 143g/cm3, F（000） =756. 00, μ= 33. 44cm-1, the final R =0. 054 and R.= 0. 077 for 2644 observationswith （I≥3.0σ（I） ）.展开更多
We report a comprehensive theoretical investigation of the catalytic reaction mechanisms of propene epoxidation on gold nanoclusters using density functional theory （DFT）. We have shown that water acts as a catalyti...We report a comprehensive theoretical investigation of the catalytic reaction mechanisms of propene epoxidation on gold nanoclusters using density functional theory （DFT）. We have shown that water acts as a catalytic promoter for propene epoxidation on gold catalysts. Even without reducible supports, hydroperoxyl （OOH） and hydroxyl （OH） radicals are readily formed on small-size gold clusters from co-adsorbed H20 and 02, with energy barriers as low as 4-6 kcal/mol （1 cal = 4.186 J）. Propene epoxidation occurs easily through reactions between C3H6 and the weakened O-O bond of the OOH radicals on the surfaces of gold clusters.展开更多
Measuring the low-energy ions in the Earth's magnetotail lobes is difficult, because a spacecraft becomes positively charged in a sunlit and tenuous plasma environment. Recent studies have introduced a new method,...Measuring the low-energy ions in the Earth's magnetotail lobes is difficult, because a spacecraft becomes positively charged in a sunlit and tenuous plasma environment. Recent studies have introduced a new method, making use of the positive electric potential on the Cluster spacecraft, to measure the low-energy ions(less than a few tens of electronvolts) in the polar caps/magnetotail lobes in the years 2001–2010. With the measured velocities, we are able to study the trajectories of these low-energy ions. Particle tracing has been used in previous studies, confirming that ions of ionospheric origin are the dominant contributor to the ion population in the Earth's magnetotail lobes. In this work, we continue to study the source of low-energy ions measured in the lobes. We found that not all of the low-energy ions in the lobes come directly from the ionosphere. Particle tracing infers that some of the low-energy ions start to move tailward from the cusp/near-cusp region with a zero parallel velocity. In the following, we refer to these low-energy ions as stagnant low-energy ions. On the other hand, the in situ measurements by Cluster show a population of low-energy ions in the cusp/near-cusp region with pitch angles near 90°(i.e., no significant parallel velocity).The locations of stagnant low-energy ions are determined by particle tracing and in situ measurements. Similar ion energies and spatial distributions determined by these two methods confirm the presence of the stagnant low-energy ion population.展开更多
Currently adopted cross-linking methods in rubber industry are suffering from variable persistent issues, including the utilization of toxic curing packages, release of volatile organic compounds (VOCs) and difficulti...Currently adopted cross-linking methods in rubber industry are suffering from variable persistent issues, including the utilization of toxic curing packages, release of volatile organic compounds (VOCs) and difficulties in the recycling of end-of-life materials. It is of great importance to explore a green cross-linking strategy in the area. Herein, we report a new ‘‘green" strategy based on hydrolyzable ester cross-links for cross-linking diene-typed elastomers. As a proof of concept, a commercial carboxylated nitrile rubber (XNBR) is efficiently cross-linked by a bio-based agent, epoxidized soybean oil (ESO), without any toxic additives. ESO exhibits an excellent plasticization effect and excellent scorch safety for XNBR. The crosslinking density and mechanical properties of the ESO-cured XNBR can be manipulated in a wide range by changing simply varying the content of ESO. In addition, zinc oxide (Zn O) performs as a catalyst to accelerate the epoxide opening reaction and improve the cross-linking efficiency, serving as reinforcement points to enhance the overall mechanical properties of the ESO-cured XNBR. Furthermore, the end-oflife elastomer materials demonstrate a closed-loop recovery by selectively cleaving the ester bonds, resulting in very high recovery of the mechanical performance of the recycled composites. This strategy provides an unprecedented green avenue to cross-link diene elastomers and a cost-effective approach to further recycle the obtained cross-linked elastomers at high efficiency.展开更多
Zebra mussel Dreissena polymorpha is a Ponto-Caspian species invasive in Europe and North America, with great environmental impact. It lives byssally attached to hard substrata in large aggregations, which is often ex...Zebra mussel Dreissena polymorpha is a Ponto-Caspian species invasive in Europe and North America, with great environmental impact. It lives byssally attached to hard substrata in large aggregations, which is often explained by its preferences for conspecifics, though direct evidence for such preferences has been rather limited so far. We studied the reactions of zebra mussels to con- specifics, hypothesizing that they may either be attracted to one another or form aggregations only in the absence of alternative attachment sites, in Experiment 1, we tested mussel tendency to detach from existing druses depending on druse size （2-25 individuals） and substratum type （soft： sand; hard： glass）. Mussels detached significantly more often on the hard substratum and from larger druses compared to soft substratum and smaller druses, respectively. This indicates that mussels tended to avoid conspecifics at high density, particularly when alternative substratum was available. In Experiment 2, we tested the responses of single mussels to distant （3 or 15cm） conspecifics （0, 3, 15 individuals per 2.51 tank） on the sandy substratum. The presence of conspecifics, regardless of their distance and density, resulted in single unattached mussels staying more often in their initial positions. Mussels did not move preferentially towards or away from the conspecifics. Thus, even on unsuitable substratum mussels were not attracted by conspecifics and probably exhibited an avoidance reaction by reducing their movement. This suggests that dense mussel aggregations are formed due to the lack of available alternative attachment sites rather than due to their preferences for conspecifics.展开更多
基金supported by the National Natural Science Foundation of China(21173100 and 21320102001)~~
文摘The catalytic epoxidation of olefin was investigated on two copper complex-modified molybdenum oxides with a 3D supramolecular structure, [Cu（bipy）]4[Mo15O47].2H2O （1） and [Cu1（bix）][（Cu1bix） （δ-MoVl8O26）0.5] （2） （bipy = 4,4＇-bipyridine, bix = 1,4-bis（imidazole-1-ylmethyl）benzene）. Both compounds were catalytically active and stable for the epoxidation of cyclooctene, 1-octene, and styrene with tert-butyl hydroperoxide （t-BuOOH） as oxidant. The excellent catalytic performance was attributed to the presence of stable coordination bonds between the molybdenum oxide and copper complex, which resulted in the formation of easily accessible Mo species with high electropositivity. In addition, the copper complex also acted as an active site for the activation of t-BuOOH, thus im- proving these copper complex-modified polyoxometalates.
基金Supported in part by 863-2002AA103011-5, Shanghai Municipal R&D Foundation (No.035107008), and LG-KAIST-FUDAN International Cooperation Project.
文摘Although clustering is a convenient framework to enable traffic control and service support in Mobile Ad hoc NETworks （MANETs）, it is seldom adopted in practice due to the additional traffic overhead it leads to for the resource limited ad hoc network. In order to address this problem, we proposed a loop-based approach to combine clustering and routing. By employing loop topologies, topology information is disseminated with a loop instead of a single node, which provides better robustness, and the nature of a loop that there are two paths between each pair of nodes within a loop composed of setup procedure, regular procedure and emergent route recovering. suggests smart route recovery strategy. Our approach is recovery procedure to achieve clustering, routing and
文摘In this paper detailed studies of the cyclic voltammetry(CV) of trinuclear metal cluster compounds [M_3O_2(O_2CCH_3,)6(H,O),j z+ (M,=Mo3,MoW2,W3) are reported.The result of CV shows that they are similar to each other.There are a reversible redox peak near-0. 48 V and an irreversible reduced peak near-1.10 V in the scan range of + l.0 V to l. 5 V.It implies that the M_3O_2,clusters might gain one electron to be further reduced.But the two-electron-reduced product of M_3O_2 clusters are instable.The theoretical calculations(EHMO) agree well with the result of the CV experiment.
文摘The title compound 〔(PPh 3)(CH 3COS) 2NiB 10 H 10 〕·0.4(C 5H 12 ) has been synthesized by the reaction of 〔NiCl 2(PPh 3) 2〕, closo 〔B 10 H 10 〕 2- and CH 3COSH in CH 2Cl 2 solution. It was recrystallized from n pentane/CH 2Cl 2 solution and its structure was determined by X ray diffraction analysis. The crystal is triclinic, space group P1, M r= 618.23, with a=10.049(1), b=12.638(2), c=14.077(2) , α=110.13(1), β=87.65(1), γ=96.01(1)°, V=1669.3(4) 3, D c =1.230 g/cm 3, Z=2, λ (Mo Kα )=0.71073 , μ =7.76 cm -1 , F (000)=642. The final refinement is converged with R =0.042 (5986 observed reflections with I≥2σ(I)), wR 2 =0.151. The cluster is a nido eleven vertex {NiB 10 } cage with the Ni atom in the open NiB 4 face. Cyclizations resulting in two five membered rings, Ni(7)-S(1)-C(1)-O(1)-B(2) and Ni(7)-S(2)-C(2)-O(2)-B(3), have occurred.
文摘The chiral cluster RuCoMo（CO）8 （μ3-Se）C5H4C （O）C6H4C （O）OCH3was synthesizgd by the thermal reaction of the precursor （μ3-Se）RuCo2（Co）9 with ’thefunctionally substituted cyclopentadienyl tricarbonyl metal complex anions [Mo（CO）3（η5-C5H4） C （O）C6H4C （O） OCH3]- in THF. It was characterized by C/H elementalanalysis, IR, 1H/13C-NMR and MS （FAB）, and its crystal structure has also beensolved by single-crystal X-ray diffraction. Crystal data: Mr=786. 23, triclinic, spacegroup P1, a =8. 200（2）, b= 19. 631 （7）, c=7.997（2） , a=92. 50（2）, β=108. 66 （2）, γ=88. 97（2）°, V= 1218. 5（6） , Z=2, Dc=2. 143g/cm3, F（000） =756. 00, μ= 33. 44cm-1, the final R =0. 054 and R.= 0. 077 for 2644 observationswith （I≥3.0σ（I） ）.
文摘We report a comprehensive theoretical investigation of the catalytic reaction mechanisms of propene epoxidation on gold nanoclusters using density functional theory （DFT）. We have shown that water acts as a catalytic promoter for propene epoxidation on gold catalysts. Even without reducible supports, hydroperoxyl （OOH） and hydroxyl （OH） radicals are readily formed on small-size gold clusters from co-adsorbed H20 and 02, with energy barriers as low as 4-6 kcal/mol （1 cal = 4.186 J）. Propene epoxidation occurs easily through reactions between C3H6 and the weakened O-O bond of the OOH radicals on the surfaces of gold clusters.
基金supported by DLR (Grant No. 50 OC 1401)supported by the National Natural Science Foundation of China (Grant Nos. 41525016, 41474155, 41661164034)Lunar and Planetary Science Laboratory, Macao University of Science and Technology-Partner Laboratory of Key Laboratory of Lunar and Deep Space Exploration, Chinese Academy of Sciences (Grant No. 039/2013/A2)
文摘Measuring the low-energy ions in the Earth's magnetotail lobes is difficult, because a spacecraft becomes positively charged in a sunlit and tenuous plasma environment. Recent studies have introduced a new method, making use of the positive electric potential on the Cluster spacecraft, to measure the low-energy ions(less than a few tens of electronvolts) in the polar caps/magnetotail lobes in the years 2001–2010. With the measured velocities, we are able to study the trajectories of these low-energy ions. Particle tracing has been used in previous studies, confirming that ions of ionospheric origin are the dominant contributor to the ion population in the Earth's magnetotail lobes. In this work, we continue to study the source of low-energy ions measured in the lobes. We found that not all of the low-energy ions in the lobes come directly from the ionosphere. Particle tracing infers that some of the low-energy ions start to move tailward from the cusp/near-cusp region with a zero parallel velocity. In the following, we refer to these low-energy ions as stagnant low-energy ions. On the other hand, the in situ measurements by Cluster show a population of low-energy ions in the cusp/near-cusp region with pitch angles near 90°(i.e., no significant parallel velocity).The locations of stagnant low-energy ions are determined by particle tracing and in situ measurements. Similar ion energies and spatial distributions determined by these two methods confirm the presence of the stagnant low-energy ion population.
基金This work was supported by the National Natural Science Foundation of China(NSFC,51790501 and 51825303),the Basic Science Center Program of NSFC(51988102)the National Key Research and Development Program of China(2017YFB0306900 and 2017YFB0306904)the Beijing Advanced Innovation Center for Soft Matter Science and Engineering
文摘Currently adopted cross-linking methods in rubber industry are suffering from variable persistent issues, including the utilization of toxic curing packages, release of volatile organic compounds (VOCs) and difficulties in the recycling of end-of-life materials. It is of great importance to explore a green cross-linking strategy in the area. Herein, we report a new ‘‘green" strategy based on hydrolyzable ester cross-links for cross-linking diene-typed elastomers. As a proof of concept, a commercial carboxylated nitrile rubber (XNBR) is efficiently cross-linked by a bio-based agent, epoxidized soybean oil (ESO), without any toxic additives. ESO exhibits an excellent plasticization effect and excellent scorch safety for XNBR. The crosslinking density and mechanical properties of the ESO-cured XNBR can be manipulated in a wide range by changing simply varying the content of ESO. In addition, zinc oxide (Zn O) performs as a catalyst to accelerate the epoxide opening reaction and improve the cross-linking efficiency, serving as reinforcement points to enhance the overall mechanical properties of the ESO-cured XNBR. Furthermore, the end-oflife elastomer materials demonstrate a closed-loop recovery by selectively cleaving the ester bonds, resulting in very high recovery of the mechanical performance of the recycled composites. This strategy provides an unprecedented green avenue to cross-link diene elastomers and a cost-effective approach to further recycle the obtained cross-linked elastomers at high efficiency.
文摘Zebra mussel Dreissena polymorpha is a Ponto-Caspian species invasive in Europe and North America, with great environmental impact. It lives byssally attached to hard substrata in large aggregations, which is often explained by its preferences for conspecifics, though direct evidence for such preferences has been rather limited so far. We studied the reactions of zebra mussels to con- specifics, hypothesizing that they may either be attracted to one another or form aggregations only in the absence of alternative attachment sites, in Experiment 1, we tested mussel tendency to detach from existing druses depending on druse size （2-25 individuals） and substratum type （soft： sand; hard： glass）. Mussels detached significantly more often on the hard substratum and from larger druses compared to soft substratum and smaller druses, respectively. This indicates that mussels tended to avoid conspecifics at high density, particularly when alternative substratum was available. In Experiment 2, we tested the responses of single mussels to distant （3 or 15cm） conspecifics （0, 3, 15 individuals per 2.51 tank） on the sandy substratum. The presence of conspecifics, regardless of their distance and density, resulted in single unattached mussels staying more often in their initial positions. Mussels did not move preferentially towards or away from the conspecifics. Thus, even on unsuitable substratum mussels were not attracted by conspecifics and probably exhibited an avoidance reaction by reducing their movement. This suggests that dense mussel aggregations are formed due to the lack of available alternative attachment sites rather than due to their preferences for conspecifics.
