The sulfate-methane interface is an important biogeochemical identification interface for the areas with high methane flux and containing gas hydrate. Above the sulfate-methane interface, the sulfate concentration in ...The sulfate-methane interface is an important biogeochemical identification interface for the areas with high methane flux and containing gas hydrate. Above the sulfate-methane interface, the sulfate concentration in the sediment is consumed progressively for the decomposition of the organic matter and anaerobic methane oxidation. Below the sulfate-methane interface, the methane concentration increases continuously with the depth. Based on the variation characters of the sulfate and methane concentration around the sulfate-methane interface, it is feasible to estimate the intensity of the methane flux, and thereafter to infer the possible occurrence of gas hydrate. The geochemical data of the pore water taken from the northern slope of the South China Sea show the sulfate-methane interface is relatively shallow, which indicates that this area has the high methane flux. It is considered that the high methane flux is most probably caused by the occurrence of underlying gas hydrate in the northern slope of the South China Sea.展开更多
[Objective] The aim of this study was to investigate the effects of salt stress on cell expansion in Arabidopsis thaliana rosette leaves.[Method] Arabidopsis seedlings were treated by sodium chloride at the concentrat...[Objective] The aim of this study was to investigate the effects of salt stress on cell expansion in Arabidopsis thaliana rosette leaves.[Method] Arabidopsis seedlings were treated by sodium chloride at the concentration of 0,100 or 150 mmol/L. At the 7th and 14th d of treatment,with nail enamel printing mark method and computer software,the leaf blades area and abaxial epidermal pavement cells area was measured and compared using statistical analysis in Excel. [Result] The growth of Arabidopsis rosette leaves was inhibited under salt stress. Leaves treated for 7 or 14 d expanded less compared with controls. The salt-mediated decrease in leaf expansion is associated with a decrease in abaxial pavement cell expansion. [Conclusion] The decreased leaf and epidermal cell expansion under salt stress is the most important characteristic of plant physiological response to salt stress.展开更多
The mechanism of the cycloaddition reaction of forming a silicic bis-heterocyclic compound between singlet dimethylmethylenesilylene (Me2C=Si:) and ethene has been investigated with the CCSD(T)//MP2/6-31G* metho...The mechanism of the cycloaddition reaction of forming a silicic bis-heterocyclic compound between singlet dimethylmethylenesilylene (Me2C=Si:) and ethene has been investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that, this reaction has one dominant channel. The presented rule of this dominant channel: the 3p unoccupied orbital of Si in dimethylmethylenesilylene and the π orbital of ethene forming the π→p donor-acceptor bond, resulting in the formation of three-membered ring intermediate (INT1); INT1 then isomerizes to a four-membered ring silylene (P2), which is driven by ring-enlargement effect; due to sp3 hybridization of Si atom in P2, P2 further combines with ethene to form a silicic bis-heterocyclic compound.展开更多
The mesoporous hydroxyapatite (HA) was synthesized by hydrothermal method utilizing cationic surfactant cetyltrimethylammonium bromide (CTAB) as template. The crystalline phase, morphology and porous structure wer...The mesoporous hydroxyapatite (HA) was synthesized by hydrothermal method utilizing cationic surfactant cetyltrimethylammonium bromide (CTAB) as template. The crystalline phase, morphology and porous structure were characterized respectively by different detecting techniques. The results reveal that the particles are highly crystalline hydroxyapatite phase. The surfactant has little influence on the morphology of the crystals, but affects the porous structure obviously. The sample without CTAB has a low surface area not exceeding 33 m^2/g, and no distinct pores can be observed by TEM. While the samples obtained with the surfactant get better parameters. Numerous open-ended pores centered at 2-7 nm spread unequally on the surface of the hydroxyapatite nanorods. The N2 adsorption-desorption experiments show type IV isotherms with distinct hysteresis loops, illustrating the presence of mesoporous structure. When the mole ratio of CTAB to HA is 1:2, the sample has the largest surface area of 97.1 m^2/g and pore volume of 0.466 cm^3/g.展开更多
Objective] This study was conducted to optimize cameI ia seed sheI fer-mentation conditions for ceI uIase production by Trichoderma koningi using response surface methodoIogy. [Method] Fermentation conditions for ceI ...Objective] This study was conducted to optimize cameI ia seed sheI fer-mentation conditions for ceI uIase production by Trichoderma koningi using response surface methodoIogy. [Method] Fermentation conditions for ceI uIase production from Trichoderma koningi were optimized with response surface method (RSM) by taking carboxymethyI ceI uIase (CMCase) activity as a response indicator. Three factors that affecting CMCase activity were screened out using singIe factor test among pretreatment methods of raw material, nitrogen sources, initial pH values, inocuIum voIume, fermentation time and voIume of Iiquid medium, they were fermentation time, initial pH value, and voIume of Iiquid medium. The optimum conditions of fer-mentation and interaction of the three factors were determined through Box-Behnken design and regression analysis using Design-Expert software. [Result] Pretreatment of cameI ia seed sheI with alkaline was most conducive to CMCase production. The use of 0.2% (NH4)2SO4 as nitrogen source, inocuIum size of 5%, initial pH value of 5.8 and voIume of Iiquid medium at 22 mI were the best fermentation conditions for maximizing CMCase production by T. koningi from cameI ia seed sheI . Under these conditions, 179.15 U/mI of CMCase was obtalned after 5 d of fermentation, which was improved by 24.52% compared with the maximum CMCase activity of singIe factor test. [Conclusion] The resuIts wiI provide some references for use of cameI ia seed sheI and ceI uIase production.展开更多
Mechanism of the cycloadditional formaldehyde has been investigated reaction between singlet with MP2/6-31G^* method, dichloro-germylidene and including geometry optimization, vibrational analysis and energies for t...Mechanism of the cycloadditional formaldehyde has been investigated reaction between singlet with MP2/6-31G^* method, dichloro-germylidene and including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. From the potential energy profile, we predict that the cyeloaddition reaction between singlet dichloro-germylidene and formaldehyde has two competitive dominant reaction pathways, going with the formation of two side products (INT3 and INT4), simultaneously. Both of the two competitive reactions consist of two steps, two reactants firstly form a three-membered ring intermediate INT1 and a twisted four-membered ring intermediate INT2, respectively, both of which are barrier-free exothermic reactions of 41.5 and 72.3 kJ/mol; then INT1 isomerizes to a four-membered ring product P1 via transition state TS1, and INT2 isomerizes to a chlorine-traasfer product P2 via transition state TS2, with the barriers of 2.9 and 0.3 kJ/mol, respectively. Simultaneously, P1 and INT2 further react with formaldehyde to form INT3 and INT4, respectively, which are also barrier-free exothermic reaction of 74.9 and 88.1 kJ/mol.展开更多
Electrochemical conversion of CO2 into fuel has been regarded as a promising approach to achieve the global carbon cycle.Herein,we report an efficient cobalt catalyst with a unique flower-like morphology synthesized b...Electrochemical conversion of CO2 into fuel has been regarded as a promising approach to achieve the global carbon cycle.Herein,we report an efficient cobalt catalyst with a unique flower-like morphology synthesized by a green and facile hydrothermal method,in which n-butylamine is used as the capping agent.The resultant catalyst shows superior electrocatalytic activity toward CO2 electroreduction,which is highly selective for generating formate with a Faraday efficiency of 63.4%.Electrochemical analysis reveals that the oxide on the surface is essential for the electrocatalysis of the CO2 reduction reaction.Cyclic voltammograms further suggest that this catalyst is highly active for the oxidation of reduced product,and can thus be seen as a bifunctional catalyst.展开更多
The shape impact of nanostructured ceria on the dispersion of Pd species was investigated by analyzing the atomic configuration and the bonding environment of Pd species over spherical and cubic ceria particles,using ...The shape impact of nanostructured ceria on the dispersion of Pd species was investigated by analyzing the atomic configuration and the bonding environment of Pd species over spherical and cubic ceria particles,using STEM and XPS.Amorphous Pd particles of about 2.0 nm,with a substantial amount of tiny Pd species,dispersed on spherical ceria,primarily due to the enriched surface oxygen vacancies that bonded the Pd species tightly.While faceted Pd particles of about 2.9 nm located on cubic ceria with distinct interfaces where Pd atoms embedded into the ceria lattice.The crystalline Pd particles on ceria cubes were highly active and stable for methane combustion that occurred on the metal surface via a facile PdO/Pd redox cycle;while the amorphous Pd particles on spherical ceria particles were featured by a significantly higher activity and stability towards CO oxidation,where the Pd-ceria interface served as the active sites.展开更多
To optimize the electronic structure of photocatalyst,a facile one‐step approach is developed for the simultaneous realization of Zn‐doping and surface oxygen vacancies(SOVs)formation on SnO_(2).The Zn‐doped SnO_(2...To optimize the electronic structure of photocatalyst,a facile one‐step approach is developed for the simultaneous realization of Zn‐doping and surface oxygen vacancies(SOVs)formation on SnO_(2).The Zn‐doped SnO_(2)with abundant SOVs exhibits efficient and stable performance for photocatalytic degradation of toluene under both low and high relative humidity.Experimental and theoretical calculations results show that the synergistic effects of Zn‐doping and SOVs on SnO_(2)can considerably boost the charge transfer and separation efficiency.Utilizing the in situ DRIFTS and theoretical calculations methods,it is revealed that the benzene ring of toluene is opened at benzoic acid on the SnO_(2)surface and selectively at benzaldehyde on the Zn‐doped SnO_(2)surface.This implies that Zn‐doped SnO_(2)photocatalysts shorten the pathway of toluene degradation,and toxic intermediates can be significantly inhibited.This work could provide a promising and sustainable route for safe and efficient removal of aromatic VOCs with photocatalytic technology.展开更多
Bimetallic Pt-based catalysts have been extensively investigated to enhance the performance of direct methanol fuel cells(DMFCs) because CO, a by-product, reduces the activity of the pure Pt catalysts. Herein, we synt...Bimetallic Pt-based catalysts have been extensively investigated to enhance the performance of direct methanol fuel cells(DMFCs) because CO, a by-product, reduces the activity of the pure Pt catalysts. Herein, we synthesized Pt-Pb hexagonal nanoplates as a model catalyst for the methanol oxidation reaction(MOR) and further controlled the Pt and Pb distributions on the surface of the nanoplates through acetic acid(HAc) treatment. As a result, we obtained Pt-Pb nanoplates and HAc-treated Pt-Pb nanoplates with homogeneous and heterogeneous distributions of the Pt-Pb alloy surfaces, respectively. We showed that the MOR activity and stability of the Pt-Pb nanoplates improved compared to those of the HAc-treated Pt-Pb nanoplates, mainly due to the enhanced CO tolerance and the modified electronic structure of Pt under the influence of the oxophilic Pb.展开更多
CeO2,Ce1–xZrxO2,and Ce1–xYxO2–δ(x=0.25,0.50,0.75,and 1.00)have been rapidly synthesized to estimate their catalytic behavior in decomposing CH3SH.The role of oxygen vacancies,and the relationship between the oxyge...CeO2,Ce1–xZrxO2,and Ce1–xYxO2–δ(x=0.25,0.50,0.75,and 1.00)have been rapidly synthesized to estimate their catalytic behavior in decomposing CH3SH.The role of oxygen vacancies,and the relationship between the oxygen species and catalytic properties of CeO2 and Zr‐doped and Y‐doped ceria‐based materials are investigated in detail.Combining the observed catalytic performance with the characterization results,it can be deemed that surface lattice oxygen plays a critical role in methanethiol catalytic conversion over cerium oxides.Ce0.75Zr0.25O2 shows higher catalytic activity for CH3SH decomposition due to the large amount of surface lattice oxygen,readily available oxygen species,and excellent redox properties.Ce0.75Y0.25O2–δdisplays better catalytic stability owing to the greater number of oxygen vacancies that would promote bulk lattice oxygen migration to the surface of the catalyst in order to replenish surface lattice oxygen.In addition,the results show that the difference in chemical valence between Ce and the heteroatoms would strongly influence the amount of surface lattice oxygen as well as the mobility of bulk‐phase oxygen in these catalysts,thus affecting their activity and stability.展开更多
As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive,...As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive, rapid, and environmentally friendly surface-enhanced Raman spectroscopy method (SERS) was developed for the determination of trace amount of amitraz in honey with the use of silver nanorod (AgNR) array substrate. The AgNR array substrate fabricated by an oblique angle deposition technique exhibited an excellent SERS activity with an enhancement factor of -10^7. Density function theory was employed to assign the characteristic peak of amitraz. The detection of amitraz was further explored and amitraz in honey at concentrations as low as 0.08 mg/kg can be identified. Specifically, partial least square regression analysis was employed to correlate the SERS spectra in full-wavelength with Camitraz to afford a multiple-quantitative amitraz predicting model. Preliminary results show that the predicted concentrations of amitraz in honey samples are in good agreement with their real concentrations. Compared with the conventional univariate quantitative model based on single peak’s intensity, the proposed multiple-quantitative predicting model integrates all the characteristic peaks of amitraz, thus offering an improved detecting accuracy and anti-interference ability.展开更多
A broadband infrared surface sum frequency generation vibrational spectroscopy (SFG-VS) and an in situ UV excitation setup devoted to studying surface photocatalysis have been constructed. With a home-made compact h...A broadband infrared surface sum frequency generation vibrational spectroscopy (SFG-VS) and an in situ UV excitation setup devoted to studying surface photocatalysis have been constructed. With a home-made compact high vacuum cell, organic contaminants on TiO2 thin film surface prepared by RF magnetron sputtering were in situ removed under 266 nm irradiation in 10 kPa 02 atmosphere. We obtained the methanol spectrum in the CH3 stretching vibration region on TiO2 surface with changing the methanol pressure at room temperature. Features of both molecular and dissociative methanol, methoxy, adsorbed on this surface were resolved. The CH3 symmetric stretching vibration frequency and Fermi resonance of molecular methanol is red-shifted by about 6-8 cm-1 from low to high coverage. Moreover, the recombination of dissociative methanol and H on Surfaces in vacuum was also observed. Our results suggest two equilibria exist: between molecular methanol in the gas phase and that on surfaces, and between molecular methanol and dissociative methanol on surfaces.展开更多
A general expression of the dynamic surface adsorption [Г(t)] on the expanding spherical surface was derived by solving the corresponding diffusion equation under different initial and boundary conditions. Differen...A general expression of the dynamic surface adsorption [Г(t)] on the expanding spherical surface was derived by solving the corresponding diffusion equation under different initial and boundary conditions. Different from the result of the still spherical surface, two factors (smaller than 1) appeared in the equation for the short time adsorption. Using the derived results, the adsorption kinetics of aqueous decanoyl-N-methylglucamine (Mega-10) solution was studied. In the short time region (t→0), a good agreement of experimental results with the theory was reached and the adsorption was controlled by diffusion.展开更多
The jumbo flying squid(Dosidicus gigas) population was surveyed with the help of Chinese squid jigging vessels off the Costa Rica Dome(4°–11°N, 90°–100°W) in 2009 and 2010. The daily catch of D. ...The jumbo flying squid(Dosidicus gigas) population was surveyed with the help of Chinese squid jigging vessels off the Costa Rica Dome(4°–11°N, 90°–100°W) in 2009 and 2010. The daily catch of D. gigas in the two survey cruises ranged from 0 to 5.5 t and was mostly obtained from the areas bounded by 6°–9°N and 91°–94°W and by 6°30′–7°30′N and 96°–97°W. The sea surface temperature in the areas yielding the most catch ranged from 27.5 to 29℃. The sex ratio of the total catch was 3.75:1(female: male). The mantle length of the squid ranged from 211 to 355 mm(male) and from 204 to 429 mm(female) with an average of 297.9 and 306.7 mm, respectively. In the relationship of the mantle length(mm) and body weight(g) of the squid, there was no significant difference between sexes. The female and male were at a similar maturity, and most individuals are maturing or have matured with a few females being spent. The size(mantle length) and age at the first sexual maturity were 297 mm and 195 d in females, and less than 211 mm and 130 d in males, respectively. Most of the sampled stomachs(70.6%) had no food remains. The major preys of the squids were fish, cephalopods and crustaceans, with the most abundant Myctophum orientale and D. gigas. The preys in more than 65% of the non-empty sampled stomachs evidenced the cannibalism of D. gigas. The results improved current understanding of the fishery biology of D. gigas off the Costa Rica Dome, which may facilitate the assessment and management of relative fishery resources.展开更多
Recent trend for the control of insect pests has been towards the use of substances of plant origin. Reductionin fertility was determined in red flour beetle, Tribolium castaneum (Herbst.) by Nerium indicum Millleav...Recent trend for the control of insect pests has been towards the use of substances of plant origin. Reductionin fertility was determined in red flour beetle, Tribolium castaneum (Herbst.) by Nerium indicum Millleaves extract compared with coopex applied by contact method under laboratory condition. When adults were placed on filter paper treated With 7.86, 9.43, 11.01, 12.58 and 14.15 μL/cm2 doses of N. indicum leaves extract, fertility was 154 ± 15.2, 139 ± 15.0, 126 ± 6.0, 89 ± 12.2 and 72 ± 13.6 larvae/pair, compared with untreated and controls fertility (233 ± 16.0 and 190 ± 15.1 larvae/pair, respectively). However, the reduction in fertility was 33.2 ± 6.4%, 39.7 ± 3.7%, 45.7 ± 2.9%, 58.0 ± 4.4% and 66.3 ± 5.1% by the same doses ofN. indicum extract. Moreover, adults treated with the same doses of coopex with the same method, fertility was 160 ± 14.6, 154 ± 9.3, 140 ± 11.2, 113 ± 7.5 and 71 ±- 4.8 larvae/pair, compared with controls fertility (211 ± 8.5 larvae/pair), respectively. Furthermore, reduction in fertility was 24.3 ± 5.2%, 30.2 ± 6.4%, 37.2 ± 8.0%, 51.3 ± 1.4% and 58.8 ± 4.7% by the same doses of coopex. Minimum fertility was found in August and maximum was in July in both, N. indicum extract and coopex treated batches. The trend of reduction in fertility was the same in both N. indicum leaves extract and coopex, i.e., it was increased gradually from lower to higher doses. Nerium indicum leaves extract reduced fertility significantly compared with coopex.展开更多
Nowadays, by the increasing attention to environment and high rate of fuel production, recycling of purge gas as reactant to a reactor is highly considered. In this study, it is proposed that the purge gases of methan...Nowadays, by the increasing attention to environment and high rate of fuel production, recycling of purge gas as reactant to a reactor is highly considered. In this study, it is proposed that the purge gases of methanol production unit, which are approximately15.018 t·h^(-1) in the largest methanol production complexes in the world, can be recycled to the reactor and utilized for increasing the production rate. Purge gas streams contain 63% hydrogen,20% carbon monoxide and carbon dioxide as reactants and 17% nitrogen and methane as inert. The recycling effect of beneficial components on methanol production rate has been investigated in this study. Simulation results show that methanol production enhances by recycling just hydrogen, carbon dioxide and carbon monoxide which is an effective configuration among the others. It is named as Desired Recycle Configuration(DRC) in this study. The optimum fraction of returning purge gas is calculated via one dimensional modeling of process and Response Surface Methodology(RSM) is applied to maximize the methanol flow rate and minimize the carbon dioxide flow rate. Simulation results illustrate that methanol flow rate increases by 0.106% in DRC compared to Conventional Recycle Configuration(CRC) which therefore shows the superiority of applying DRC to CRC.展开更多
A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely u...A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.展开更多
文摘The sulfate-methane interface is an important biogeochemical identification interface for the areas with high methane flux and containing gas hydrate. Above the sulfate-methane interface, the sulfate concentration in the sediment is consumed progressively for the decomposition of the organic matter and anaerobic methane oxidation. Below the sulfate-methane interface, the methane concentration increases continuously with the depth. Based on the variation characters of the sulfate and methane concentration around the sulfate-methane interface, it is feasible to estimate the intensity of the methane flux, and thereafter to infer the possible occurrence of gas hydrate. The geochemical data of the pore water taken from the northern slope of the South China Sea show the sulfate-methane interface is relatively shallow, which indicates that this area has the high methane flux. It is considered that the high methane flux is most probably caused by the occurrence of underlying gas hydrate in the northern slope of the South China Sea.
文摘[Objective] The aim of this study was to investigate the effects of salt stress on cell expansion in Arabidopsis thaliana rosette leaves.[Method] Arabidopsis seedlings were treated by sodium chloride at the concentration of 0,100 or 150 mmol/L. At the 7th and 14th d of treatment,with nail enamel printing mark method and computer software,the leaf blades area and abaxial epidermal pavement cells area was measured and compared using statistical analysis in Excel. [Result] The growth of Arabidopsis rosette leaves was inhibited under salt stress. Leaves treated for 7 or 14 d expanded less compared with controls. The salt-mediated decrease in leaf expansion is associated with a decrease in abaxial pavement cell expansion. [Conclusion] The decreased leaf and epidermal cell expansion under salt stress is the most important characteristic of plant physiological response to salt stress.
文摘The mechanism of the cycloaddition reaction of forming a silicic bis-heterocyclic compound between singlet dimethylmethylenesilylene (Me2C=Si:) and ethene has been investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that, this reaction has one dominant channel. The presented rule of this dominant channel: the 3p unoccupied orbital of Si in dimethylmethylenesilylene and the π orbital of ethene forming the π→p donor-acceptor bond, resulting in the formation of three-membered ring intermediate (INT1); INT1 then isomerizes to a four-membered ring silylene (P2), which is driven by ring-enlargement effect; due to sp3 hybridization of Si atom in P2, P2 further combines with ethene to form a silicic bis-heterocyclic compound.
基金Projects(51102285,81170912)supported by the National Natural Science Foundation of ChinaProject supported by the Open Foundation of State Key Laboratory of Powder Metallurgy,China
文摘The mesoporous hydroxyapatite (HA) was synthesized by hydrothermal method utilizing cationic surfactant cetyltrimethylammonium bromide (CTAB) as template. The crystalline phase, morphology and porous structure were characterized respectively by different detecting techniques. The results reveal that the particles are highly crystalline hydroxyapatite phase. The surfactant has little influence on the morphology of the crystals, but affects the porous structure obviously. The sample without CTAB has a low surface area not exceeding 33 m^2/g, and no distinct pores can be observed by TEM. While the samples obtained with the surfactant get better parameters. Numerous open-ended pores centered at 2-7 nm spread unequally on the surface of the hydroxyapatite nanorods. The N2 adsorption-desorption experiments show type IV isotherms with distinct hysteresis loops, illustrating the presence of mesoporous structure. When the mole ratio of CTAB to HA is 1:2, the sample has the largest surface area of 97.1 m^2/g and pore volume of 0.466 cm^3/g.
基金Supported by National High-tech R&D Program of China(863 Program,2013AA102-107)~~
文摘Objective] This study was conducted to optimize cameI ia seed sheI fer-mentation conditions for ceI uIase production by Trichoderma koningi using response surface methodoIogy. [Method] Fermentation conditions for ceI uIase production from Trichoderma koningi were optimized with response surface method (RSM) by taking carboxymethyI ceI uIase (CMCase) activity as a response indicator. Three factors that affecting CMCase activity were screened out using singIe factor test among pretreatment methods of raw material, nitrogen sources, initial pH values, inocuIum voIume, fermentation time and voIume of Iiquid medium, they were fermentation time, initial pH value, and voIume of Iiquid medium. The optimum conditions of fer-mentation and interaction of the three factors were determined through Box-Behnken design and regression analysis using Design-Expert software. [Result] Pretreatment of cameI ia seed sheI with alkaline was most conducive to CMCase production. The use of 0.2% (NH4)2SO4 as nitrogen source, inocuIum size of 5%, initial pH value of 5.8 and voIume of Iiquid medium at 22 mI were the best fermentation conditions for maximizing CMCase production by T. koningi from cameI ia seed sheI . Under these conditions, 179.15 U/mI of CMCase was obtalned after 5 d of fermentation, which was improved by 24.52% compared with the maximum CMCase activity of singIe factor test. [Conclusion] The resuIts wiI provide some references for use of cameI ia seed sheI and ceI uIase production.
文摘Mechanism of the cycloadditional formaldehyde has been investigated reaction between singlet with MP2/6-31G^* method, dichloro-germylidene and including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. From the potential energy profile, we predict that the cyeloaddition reaction between singlet dichloro-germylidene and formaldehyde has two competitive dominant reaction pathways, going with the formation of two side products (INT3 and INT4), simultaneously. Both of the two competitive reactions consist of two steps, two reactants firstly form a three-membered ring intermediate INT1 and a twisted four-membered ring intermediate INT2, respectively, both of which are barrier-free exothermic reactions of 41.5 and 72.3 kJ/mol; then INT1 isomerizes to a four-membered ring product P1 via transition state TS1, and INT2 isomerizes to a chlorine-traasfer product P2 via transition state TS2, with the barriers of 2.9 and 0.3 kJ/mol, respectively. Simultaneously, P1 and INT2 further react with formaldehyde to form INT3 and INT4, respectively, which are also barrier-free exothermic reaction of 74.9 and 88.1 kJ/mol.
文摘Electrochemical conversion of CO2 into fuel has been regarded as a promising approach to achieve the global carbon cycle.Herein,we report an efficient cobalt catalyst with a unique flower-like morphology synthesized by a green and facile hydrothermal method,in which n-butylamine is used as the capping agent.The resultant catalyst shows superior electrocatalytic activity toward CO2 electroreduction,which is highly selective for generating formate with a Faraday efficiency of 63.4%.Electrochemical analysis reveals that the oxide on the surface is essential for the electrocatalysis of the CO2 reduction reaction.Cyclic voltammograms further suggest that this catalyst is highly active for the oxidation of reduced product,and can thus be seen as a bifunctional catalyst.
文摘The shape impact of nanostructured ceria on the dispersion of Pd species was investigated by analyzing the atomic configuration and the bonding environment of Pd species over spherical and cubic ceria particles,using STEM and XPS.Amorphous Pd particles of about 2.0 nm,with a substantial amount of tiny Pd species,dispersed on spherical ceria,primarily due to the enriched surface oxygen vacancies that bonded the Pd species tightly.While faceted Pd particles of about 2.9 nm located on cubic ceria with distinct interfaces where Pd atoms embedded into the ceria lattice.The crystalline Pd particles on ceria cubes were highly active and stable for methane combustion that occurred on the metal surface via a facile PdO/Pd redox cycle;while the amorphous Pd particles on spherical ceria particles were featured by a significantly higher activity and stability towards CO oxidation,where the Pd-ceria interface served as the active sites.
文摘To optimize the electronic structure of photocatalyst,a facile one‐step approach is developed for the simultaneous realization of Zn‐doping and surface oxygen vacancies(SOVs)formation on SnO_(2).The Zn‐doped SnO_(2)with abundant SOVs exhibits efficient and stable performance for photocatalytic degradation of toluene under both low and high relative humidity.Experimental and theoretical calculations results show that the synergistic effects of Zn‐doping and SOVs on SnO_(2)can considerably boost the charge transfer and separation efficiency.Utilizing the in situ DRIFTS and theoretical calculations methods,it is revealed that the benzene ring of toluene is opened at benzoic acid on the SnO_(2)surface and selectively at benzaldehyde on the Zn‐doped SnO_(2)surface.This implies that Zn‐doped SnO_(2)photocatalysts shorten the pathway of toluene degradation,and toxic intermediates can be significantly inhibited.This work could provide a promising and sustainable route for safe and efficient removal of aromatic VOCs with photocatalytic technology.
文摘Bimetallic Pt-based catalysts have been extensively investigated to enhance the performance of direct methanol fuel cells(DMFCs) because CO, a by-product, reduces the activity of the pure Pt catalysts. Herein, we synthesized Pt-Pb hexagonal nanoplates as a model catalyst for the methanol oxidation reaction(MOR) and further controlled the Pt and Pb distributions on the surface of the nanoplates through acetic acid(HAc) treatment. As a result, we obtained Pt-Pb nanoplates and HAc-treated Pt-Pb nanoplates with homogeneous and heterogeneous distributions of the Pt-Pb alloy surfaces, respectively. We showed that the MOR activity and stability of the Pt-Pb nanoplates improved compared to those of the HAc-treated Pt-Pb nanoplates, mainly due to the enhanced CO tolerance and the modified electronic structure of Pt under the influence of the oxophilic Pb.
基金supported by the National Natural Science Foundation of China (21667016, 21267011, U1402233)~~
文摘CeO2,Ce1–xZrxO2,and Ce1–xYxO2–δ(x=0.25,0.50,0.75,and 1.00)have been rapidly synthesized to estimate their catalytic behavior in decomposing CH3SH.The role of oxygen vacancies,and the relationship between the oxygen species and catalytic properties of CeO2 and Zr‐doped and Y‐doped ceria‐based materials are investigated in detail.Combining the observed catalytic performance with the characterization results,it can be deemed that surface lattice oxygen plays a critical role in methanethiol catalytic conversion over cerium oxides.Ce0.75Zr0.25O2 shows higher catalytic activity for CH3SH decomposition due to the large amount of surface lattice oxygen,readily available oxygen species,and excellent redox properties.Ce0.75Y0.25O2–δdisplays better catalytic stability owing to the greater number of oxygen vacancies that would promote bulk lattice oxygen migration to the surface of the catalyst in order to replenish surface lattice oxygen.In addition,the results show that the difference in chemical valence between Ce and the heteroatoms would strongly influence the amount of surface lattice oxygen as well as the mobility of bulk‐phase oxygen in these catalysts,thus affecting their activity and stability.
基金supported by the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province (No.16KJB510009 and No.17KJB510017)Jiangsu Province Natural Science Foundation of China (BK20150228)
文摘As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive, rapid, and environmentally friendly surface-enhanced Raman spectroscopy method (SERS) was developed for the determination of trace amount of amitraz in honey with the use of silver nanorod (AgNR) array substrate. The AgNR array substrate fabricated by an oblique angle deposition technique exhibited an excellent SERS activity with an enhancement factor of -10^7. Density function theory was employed to assign the characteristic peak of amitraz. The detection of amitraz was further explored and amitraz in honey at concentrations as low as 0.08 mg/kg can be identified. Specifically, partial least square regression analysis was employed to correlate the SERS spectra in full-wavelength with Camitraz to afford a multiple-quantitative amitraz predicting model. Preliminary results show that the predicted concentrations of amitraz in honey samples are in good agreement with their real concentrations. Compared with the conventional univariate quantitative model based on single peak’s intensity, the proposed multiple-quantitative predicting model integrates all the characteristic peaks of amitraz, thus offering an improved detecting accuracy and anti-interference ability.
基金This work was supported by the National Ba- sic Research Program of China (No.2013CB834600) and the National Natural Science Foundation of China (No.II27002/B030403, No.II290162/A040106, and No.21322310/B030402).
文摘A broadband infrared surface sum frequency generation vibrational spectroscopy (SFG-VS) and an in situ UV excitation setup devoted to studying surface photocatalysis have been constructed. With a home-made compact high vacuum cell, organic contaminants on TiO2 thin film surface prepared by RF magnetron sputtering were in situ removed under 266 nm irradiation in 10 kPa 02 atmosphere. We obtained the methanol spectrum in the CH3 stretching vibration region on TiO2 surface with changing the methanol pressure at room temperature. Features of both molecular and dissociative methanol, methoxy, adsorbed on this surface were resolved. The CH3 symmetric stretching vibration frequency and Fermi resonance of molecular methanol is red-shifted by about 6-8 cm-1 from low to high coverage. Moreover, the recombination of dissociative methanol and H on Surfaces in vacuum was also observed. Our results suggest two equilibria exist: between molecular methanol in the gas phase and that on surfaces, and between molecular methanol and dissociative methanol on surfaces.
基金Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars (D4200111).
文摘A general expression of the dynamic surface adsorption [Г(t)] on the expanding spherical surface was derived by solving the corresponding diffusion equation under different initial and boundary conditions. Different from the result of the still spherical surface, two factors (smaller than 1) appeared in the equation for the short time adsorption. Using the derived results, the adsorption kinetics of aqueous decanoyl-N-methylglucamine (Mega-10) solution was studied. In the short time region (t→0), a good agreement of experimental results with the theory was reached and the adsorption was controlled by diffusion.
基金the supports of the two scientific surveys made by Fenghui No 16 and Zhe Yunyu No 807funded by National Nature Science Foundation of China (NSFC 41276156)+5 种基金National High-tech R&D Program of China (863 Program 2012AA092303)Project of Shanghai science and technology innovation (12231203900)Industrialization program of National Development and Reform Commission (2159999)Shanghai Leading Academic Discipline Projectsupported by National Distant-water Fisheries Engineering Research Center
文摘The jumbo flying squid(Dosidicus gigas) population was surveyed with the help of Chinese squid jigging vessels off the Costa Rica Dome(4°–11°N, 90°–100°W) in 2009 and 2010. The daily catch of D. gigas in the two survey cruises ranged from 0 to 5.5 t and was mostly obtained from the areas bounded by 6°–9°N and 91°–94°W and by 6°30′–7°30′N and 96°–97°W. The sea surface temperature in the areas yielding the most catch ranged from 27.5 to 29℃. The sex ratio of the total catch was 3.75:1(female: male). The mantle length of the squid ranged from 211 to 355 mm(male) and from 204 to 429 mm(female) with an average of 297.9 and 306.7 mm, respectively. In the relationship of the mantle length(mm) and body weight(g) of the squid, there was no significant difference between sexes. The female and male were at a similar maturity, and most individuals are maturing or have matured with a few females being spent. The size(mantle length) and age at the first sexual maturity were 297 mm and 195 d in females, and less than 211 mm and 130 d in males, respectively. Most of the sampled stomachs(70.6%) had no food remains. The major preys of the squids were fish, cephalopods and crustaceans, with the most abundant Myctophum orientale and D. gigas. The preys in more than 65% of the non-empty sampled stomachs evidenced the cannibalism of D. gigas. The results improved current understanding of the fishery biology of D. gigas off the Costa Rica Dome, which may facilitate the assessment and management of relative fishery resources.
文摘Recent trend for the control of insect pests has been towards the use of substances of plant origin. Reductionin fertility was determined in red flour beetle, Tribolium castaneum (Herbst.) by Nerium indicum Millleaves extract compared with coopex applied by contact method under laboratory condition. When adults were placed on filter paper treated With 7.86, 9.43, 11.01, 12.58 and 14.15 μL/cm2 doses of N. indicum leaves extract, fertility was 154 ± 15.2, 139 ± 15.0, 126 ± 6.0, 89 ± 12.2 and 72 ± 13.6 larvae/pair, compared with untreated and controls fertility (233 ± 16.0 and 190 ± 15.1 larvae/pair, respectively). However, the reduction in fertility was 33.2 ± 6.4%, 39.7 ± 3.7%, 45.7 ± 2.9%, 58.0 ± 4.4% and 66.3 ± 5.1% by the same doses ofN. indicum extract. Moreover, adults treated with the same doses of coopex with the same method, fertility was 160 ± 14.6, 154 ± 9.3, 140 ± 11.2, 113 ± 7.5 and 71 ±- 4.8 larvae/pair, compared with controls fertility (211 ± 8.5 larvae/pair), respectively. Furthermore, reduction in fertility was 24.3 ± 5.2%, 30.2 ± 6.4%, 37.2 ± 8.0%, 51.3 ± 1.4% and 58.8 ± 4.7% by the same doses of coopex. Minimum fertility was found in August and maximum was in July in both, N. indicum extract and coopex treated batches. The trend of reduction in fertility was the same in both N. indicum leaves extract and coopex, i.e., it was increased gradually from lower to higher doses. Nerium indicum leaves extract reduced fertility significantly compared with coopex.
文摘Nowadays, by the increasing attention to environment and high rate of fuel production, recycling of purge gas as reactant to a reactor is highly considered. In this study, it is proposed that the purge gases of methanol production unit, which are approximately15.018 t·h^(-1) in the largest methanol production complexes in the world, can be recycled to the reactor and utilized for increasing the production rate. Purge gas streams contain 63% hydrogen,20% carbon monoxide and carbon dioxide as reactants and 17% nitrogen and methane as inert. The recycling effect of beneficial components on methanol production rate has been investigated in this study. Simulation results show that methanol production enhances by recycling just hydrogen, carbon dioxide and carbon monoxide which is an effective configuration among the others. It is named as Desired Recycle Configuration(DRC) in this study. The optimum fraction of returning purge gas is calculated via one dimensional modeling of process and Response Surface Methodology(RSM) is applied to maximize the methanol flow rate and minimize the carbon dioxide flow rate. Simulation results illustrate that methanol flow rate increases by 0.106% in DRC compared to Conventional Recycle Configuration(CRC) which therefore shows the superiority of applying DRC to CRC.
基金the National High Technology Research and Development Program of China (863 Program,Grant No.2007AA11Z130)
文摘A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.