Phenol in waste water threatens human health and is difficultly to be decomposed by nature.Efficient degradation of high-loaded phenol in water under mild condition is still a great challenge.Herein,ionic liquids with...Phenol in waste water threatens human health and is difficultly to be decomposed by nature.Efficient degradation of high-loaded phenol in water under mild condition is still a great challenge.Herein,ionic liquids with tungstate anion were designed and prepared.It was found that dodecyltrimethylammonium tungstate could catalyzed degradation of phenol into gases and water thoroughly at 323 k in 8 h.Tungstate anion revealed good catalytic oxidative activity and long carbon chain group connecting with cation of ionic liquids enriched phenol around catalysts,which induced the complete degradation of phenol at mild conditions.Increasing the amounts of hydrogen peroxide benefited to the total degradation of phenol.In addition,the ionic liquid could be reused for its excellent thermal stability.Our work provided a different strategy to treat waste water containing phenol efficiently.展开更多
Visible-light-responsive ternary metal tungstate(MWO_4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including ...Visible-light-responsive ternary metal tungstate(MWO_4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost,eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron–hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO_4-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO_4-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalyticactivities of MWO_4-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO_4-based photocatalysts.展开更多
An unusual inorganic-organic hybrid hexatungstate complex [Cu(phen)3][W6O19] 1 (C36H24 CuN6O19W6, Mr = 2011.20) was hydrothermally synthesized and characterized by single- crystal X-ray diffraction, IR spectrum, UV-VI...An unusual inorganic-organic hybrid hexatungstate complex [Cu(phen)3][W6O19] 1 (C36H24 CuN6O19W6, Mr = 2011.20) was hydrothermally synthesized and characterized by single- crystal X-ray diffraction, IR spectrum, UV-VIS spectrum and elemental analyses. This compound crystallizes in the monoclinic system, space group C2/c with a = 19.1005(11), b = 11.2585(11), c = 20.2867(15) , β = 102.177(2)o, V = 4264.4 3, μ(MoKa) = 16.691 mm–1, Dc = 3.133 g/cm3, Z = 4, F(000) = 3628, the final R = 0.0338 and wR = 0.0798 for 4090 observed reflections with I > 2σ(I). The result of structure determination shows that the crystal structure is constructed from [W6O19]2– cluster anions and [Cu(phen)3]2+ complex fragments, which are held together into a three-dimen- sional network through hydrogen-bonding interactions.展开更多
The crystals of NaLn（WO4）<sub>2</sub>（Ln=La,Pr,Nd）are grown from a melt of LiCl-Na<sub>2</sub>WO<sub>4</sub> flux by slowcooling method.The chemical analysis data show that the ...The crystals of NaLn（WO4）<sub>2</sub>（Ln=La,Pr,Nd）are grown from a melt of LiCl-Na<sub>2</sub>WO<sub>4</sub> flux by slowcooling method.The chemical analysis data show that the crystals are NaLa（WO<sub>4</sub>）<sub>2</sub>,NaPr（WO4）<sub>2</sub> andNaNd（WO<sub>4</sub>）<sub>2</sub> respectively.The structures of the crystals are ascertained that they belong to scheelite structureof the tetragonal system with a space group of 14<sub>1</sub>/a.The lattice parameters of the crystals have beencalculated.It is found that the cell volume of NaLn（WO<sub>4</sub>）<sub>2</sub> crystals decrease with a decrease of Ln<sup>3+</sup>radius.The bond distances and their angles in NaLa（WO<sub>4</sub>）<sub>2</sub> and NaNd（WO<sub>4</sub>）<sub>2</sub> are given.It is found that inaccordance with the decrease of ionic radii of Ln<sup>3+</sup>due to increase of atomic number,the bond distances betweenLn-O,Ln-Ln and W-O decrease regularly.The infrared spectra of NaLn（WO<sub>4</sub>）<sub>2</sub> are measured.Thetetrahedra characteristic absorptions of WO<sub>4</sub><sup>2-</sup>are shown.The sensitization of host lattice is observed from theexcitation and fluorescent spectra of NaLa（WO<sub>4</sub>）<sub>2</sub> and NaPr（WO<sub>4</sub>）<sub>2</sub>.展开更多
AIM: To evaluate the effect of sodium tungstate on visual evoked potentials(VEPs) in diabetic rats.· METHODS: Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic r...AIM: To evaluate the effect of sodium tungstate on visual evoked potentials(VEPs) in diabetic rats.· METHODS: Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic rats treated with sodium tungstate. Diabetes was induced by single intraperitoneal injection of streptozotocin(50 mg/kg). Sodium tungstate [40 mg/(kg·d)]was administered for 12 wk and then VEPs were recorded.Additionally, thiobarbituric acid reactive substance(TBARS) levels were measured in brain tissues.·RESULTS: The latencies of P1, N1, P2, N2 and P3 waves were significantly prolonged in diabetic rats compared with control group. Diabetes mellitus caused an increase in the lipid peroxidation process that was accompanied by changes in VEPs. However, prolonged latencies of VEPs for all components returned to control levels in sodium tungstate-treated group. The treatment of sodium tungstate significantly decreased brain TBARS levels and depleted the prolonged latencies of VEP components compared with diabetic control group.· CONCLUSION: Sodium tungstate shows protective effects on visual pathway in diabetic rats, and it can be worthy of further study for potential use.展开更多
The 10 at.% Er3+-doped KYb(WO4)2(KEr0.1Yb0.9(WO4)2) laser crystal with dimensions up to 25 mm×15 mm×10 mm was grown by the Kyropoulos method.The crystal structure was identified as β-KEr0.1Yb0.9(WO4)2 by XR...The 10 at.% Er3+-doped KYb(WO4)2(KEr0.1Yb0.9(WO4)2) laser crystal with dimensions up to 25 mm×15 mm×10 mm was grown by the Kyropoulos method.The crystal structure was identified as β-KEr0.1Yb0.9(WO4)2 by XRD analysis.Through TG-DTA curves,the melting point and transition point of the crystal were determined to be 1058 and 1031 °C,respectively.Infrared spectrum and Raman spectrum were measured,and the vibration frequencies of infrared and Raman active modes for the crystal were assigned.The absorption cross section is 3.1×10-20 cm2 at chief peak of 981 nm with the absorption line width of 26 nm.Based on the Judd-Ofelt theory,the intensity parameters ?λ(λ=2,4,6) calculated were:?2=16.34×10-20 cm2,?4=4.18×10-20 cm2,and ?6=1.26×10-20 cm2.There was a strong emission peak near 1533 nm and the emission line width at the main peak at 1533 nm run up to 55 nm with the emission cross section of 3.47×10-20 cm2 .These optical parameters indicated the potential of this crystal used as an excellent laser material for 1540 nm nearby human-eye safe.展开更多
The expanded industrial experiments were conducted with practical industfial liquor to separate free alkali from sodium tungstate solution by electrolysis with canon-exchange membrane. Experimental results show that o...The expanded industrial experiments were conducted with practical industfial liquor to separate free alkali from sodium tungstate solution by electrolysis with canon-exchange membrane. Experimental results show that on the condition that the temperature is 50-55℃ and the current density is 1000 A/m2, the single electrolysis cell is operated stably and 80% free-alkali in mass fraction is separated from the anode feed liquor of sodium tungstate, with electric ef- ficiency up to more than 88% and the unit energy consumption E lower than 1900 kWh/t; while three electfolysis cells in series are operated, under the condition that the temperature is 60-65 ℃ and the current density is 1000 A/m2, the elec- tric efficiency can reach higher than 88% and the unit energy consumption E can be lower than 2250 kWh/t.展开更多
Solvent – free Mortar-pestle (grinding) and microwave-assisted nitration reactions (MWANR’s) underwent smoothly in the presence of group V and VI metal salts with high regio-selectivity for anilides, moderately- and...Solvent – free Mortar-pestle (grinding) and microwave-assisted nitration reactions (MWANR’s) underwent smoothly in the presence of group V and VI metal salts with high regio-selectivity for anilides, moderately- and non-activated aro-matic compounds. The reactions were conducted under solvent-free conditions, which afforded good to excellent yields. The observed reaction times in MW assisted conditions are in the range of only few minutes.展开更多
Whereas the light yield of PWO crystal can be significantly improved by doping with either of F- and Sb3+, effects of heavily co-doping with by F-+Sb3+, F-+Ca2+, and F-+Ca2++Sb3+, respectively, on the properties of PW...Whereas the light yield of PWO crystal can be significantly improved by doping with either of F- and Sb3+, effects of heavily co-doping with by F-+Sb3+, F-+Ca2+, and F-+Ca2++Sb3+, respectively, on the properties of PWO scintillation crystals, including optical transmission, luminescence and light yield were studied. The result indicates that co-doping with three dopants, F-+Ca2++Sb3+, is a more effective measure than doping with single dopant F- for the improvement of scintillation properties of PWO crystals, including light yield.展开更多
Xiao Liansheng Wang Wei Zhang Qixiu Gong Bofan Cao Jiashu (Department of Metallurgical Science and Engineering, Central South University of Technology, Changsha 410083, China) Abstrac By measuring the electrode polari...Xiao Liansheng Wang Wei Zhang Qixiu Gong Bofan Cao Jiashu (Department of Metallurgical Science and Engineering, Central South University of Technology, Changsha 410083, China) Abstrac By measuring the electrode polarization curves of many kinds of materials and life spans of electrodes through intensifying electrolysis in the process, the appropriate electrode materials for different stages of electrolysis of sodium tungstate solution with membrane have been selected The effects of the electrodes with different shapes on electrolysis have been investigated. The result shows that network electrode is more suitable to electrolysis of sodium tungstate solution.展开更多
The present paper reports new results regarding the addition of pseudo-boehmite as a binder during the synthesis of shaped Pt/WO_(3)-ZrO_(2)-Al_(2)O_(3) (PtWZA) catalysts. Binder shaping can noticeably influence not o...The present paper reports new results regarding the addition of pseudo-boehmite as a binder during the synthesis of shaped Pt/WO_(3)-ZrO_(2)-Al_(2)O_(3) (PtWZA) catalysts. Binder shaping can noticeably influence not only the structure and acidity of catalyst and improve its catalytic performance with regard to n-heptane isomerization, but the mechanical strength of the catalyst. A suitable binder content can improve the isomerization activity or selectivity by changing the acidity of PtWZA. The influence of the binder content depends on the WO_(3) content of the catalyst. PtWZA catalysts that contain 5%-15% binder on a dry basis exhibit favorable isomerization performance that depends on WO_(3) content. Suitable catalysts include Pt20WZ5A and Pt30WZ15A, which provide conversions of approximately 80%-90% and a selectivity of 90%. These new findings enrich researcher knowledge of the effect of the binder on the catalyst shaping process and are useful in the production of industrial catalysts.展开更多
A series of uniform single-phase spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors were prepared via a microwave hydrothermal method by using trisodium citrate dehydrate as surfactant.The phase structure,morphology an...A series of uniform single-phase spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors were prepared via a microwave hydrothermal method by using trisodium citrate dehydrate as surfactant.The phase structure,morphology and photoluminescence properties were measured by powder X-ray diffraction,scanning electron microscope and fluorescence spectrometer,respectively.The results show that uniform spherical microcrystals with diameters in the range of 2–4μm are obtained.And the phase and morphology of samples are not significantly changed by doping rare earth(RE^(3+))ions.Under the excitation wavelength of 356 and 365 nm,the samples BaWO 4:0.03Dy^(3+),yTm^(3+)can emit cold white light.In order to lower the correlated color temperature(CCT)to get a warm white light,the Eu^(3+)ions were doped into BaWO 4:0.03Dy^(3+),0.01Tm^(3+).Especially,under the excitation of 365 nm,BaWO 4:0.03Dy^(3+),0.01Tm^(3+),0.03Eu^(3+)phosphor shew a bright warm white light with color coordi-nate of(0.4013,0.3629)and CCT of 3288 K.Moreover,in the BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors,the energy transfer mechanism among Dy^(3+),Tm^(3+)and Eu^(3+)ions have been discussed and the change of electron structures have been calculated by first-principles calculations.The results shew that the uniform single-phase spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors could be favorable candidates in warm white LEDs.展开更多
The structure of Tb∶Mo∶PbWO4 crystals was investigated by Raman spectra and the results showed that the spectra were varied differently by doping dopants in different ranges of shift. Rotation-vibration, curving-vib...The structure of Tb∶Mo∶PbWO4 crystals was investigated by Raman spectra and the results showed that the spectra were varied differently by doping dopants in different ranges of shift. Rotation-vibration, curving-vibration and non-symmetrical stretching-vibration had been investigated on the spectra. Rotation-vibration intensity of [WO4]2-group is weakened and curving-vibration intensity is undergirded; low Mo6+ doping enhances the intensity of non-symmetrical stretching-vibration, with the concentration of Mo6+ increasing, the intensity is weakened. So it could be inferred that Tb3+ ion replaced the vacancy of Pb, when achieving at a certain concentration, Tb3+ ion would substitute for the lattice of Pb2+, Mo6+ ion would substitute for W lattice and generate [MoO4]2-new group, these are the main reason for the properties changing. Furthermore it could suggest that the impurity ions doped in tetrahedral positions, strongly affect the electron-phonon coupling in [WO4]2-, which makes the intensities of the vibration changed regularly.展开更多
In high energy physics experiments,large arrays of scintillation crystals have b een used in electromagnetic calorimeters for precision measurements of photons a nd electrons.The large crystal calorimeters and their u...In high energy physics experiments,large arrays of scintillation crystals have b een used in electromagnetic calorimeters for precision measurements of photons a nd electrons.The large crystal calorimeters and their use has been a key factor in the high energy physics programs.Table 1 lists parameters of crystal calorime ter projects of the past (Crystal Ball),present(L3) and future (CMS) in high ene rgy physics.In future high energy collider,however,scintillating crysta ls face a new challenge:the radiation damage caused by the increased background radiation level.It would reach about 1000 rad/day for lead tungstate (PbWO 4) crystal at LHC.Lead tungstate is a new fast and dense scintillating crystal and has been s elected as scintillator for the construction of calorimeter in CMS experiment of Large Hadron Collider (LHC) at CERN(European Organization for Nuclear Research ) next century.82000 large sized PWO scintillating crystals will be assembled in the calorimeter of the CMS experiment,and they will be produced both in China a nd in Russia from now until to 2004.展开更多
Barium tungstate of homogeneous double cone structure was synthesized by microwave synthesis method with sodium tungstate, barium nitrate as raw materials, polyethylene glycol (PEG2000) as surfactant. The as-prepared ...Barium tungstate of homogeneous double cone structure was synthesized by microwave synthesis method with sodium tungstate, barium nitrate as raw materials, polyethylene glycol (PEG2000) as surfactant. The as-prepared sample was characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM) and photoluminescence spectrum (PL). The XRD Pattern showed that the samples are scheelite structure of BaWO4. The SEM image showed that the majority of as-prepared sample is a double cone structure, and some particles are attached to it. The length of most of the double cone is 10 μm. PL spectra showed that as-prepared sample had strong luminescence properties, and it had purity green emission at 495 nm and 521 nm. The effects of different surface active agent on the luminescence properties were studied. The results showed that when PEG2000 is as surfactant, the luminescence intensity of as-prepared sample was maximum.展开更多
Anabaena variabilis ATCC 29413 has two distinct nitrogenases that function in heterocysts, a conventional Mo-nitrogenase and an alternative V-nitrogenase. Synthesis of these two enzymes was repressed in cells growing ...Anabaena variabilis ATCC 29413 has two distinct nitrogenases that function in heterocysts, a conventional Mo-nitrogenase and an alternative V-nitrogenase. Synthesis of these two enzymes was repressed in cells growing with a source of fixed nitrogen, such as ammonium;however, the V-nitrogenase was also repressed by Mo. Expression of the V-nitrogenase which was not affected by V and expression of the Mo-nitrogenase was not affected by the presence or absence of either Mo or V. In the absence of both Mo and V in an environment lacking fixed nitrogen, cells became starved for both metals;however, low levels of nitrogen fixation and slow growth persisted. A mutant lacking the V-nitrogenase was still able to grow very slowly in Mo-and V-free medium;however, loss of the Mo-nitrogenase in a nifDK1 mutant abolished the residual growth, suggesting that only the Mo-nitrogenase functioned under these conditions to support slow growth. The addition of vanadate, molybdate, or tungstate, which is transported by the molybdate transporter, to cells starved for these metals resulted in an increase in nitrogenase activity within two hours after the addition of the metal and this increase required new protein synthesis. While tungstate functioned about as well as vanadate in supporting acetylene reduction, the cells were not able to grow any better with tungstate than with no added metal. A mutant lacking the V-nitrogenase showed no increase in nitrogenase activity upon addition of tungstate, suggesting that the V-nitrogenase was able to incorporate tungstate. Tungstate was able to substitute for molybdate in repressing transcription of a Mo-transport gene, but it did not repress transcription of the vnfH gene, which was repressed by Mo. The availability of Mo and V plays an important role in controlling whether the Mo-or the V-nitrogenase is used for nitrogen fixation.展开更多
Copper Tungstate-Graphene Oxide nano composites have been successfully applied as excellent catalysts for the photocatalytic degradation with Methylene blue and Malachite green dyes under visible light irradiation. A ...Copper Tungstate-Graphene Oxide nano composites have been successfully applied as excellent catalysts for the photocatalytic degradation with Methylene blue and Malachite green dyes under visible light irradiation. A facile?solid state metathesis synthesis of copper tungstate (CuWO4) followed by ball milling and subsequent preparation of copper tungstate-graphene oxide?(CuWO4-GO) nano composite using a colloidal blending process and its application as a visible light photocatalyst for the degradation of Malachite green and Methylene blue dyes. The morphology and composition of copper tungstate (CuWO4) nano composite have been characterized using X-Ray Diffraction (XRD), UV-Visible Diffuse Reflectance Spectra (UV-DRS), Raman Spectra, Field Emission Scanning Electron Microscopy (FESEM)-EDS and UV Visible Spectroscopy. It shows a band gap value of 2.13 eV, an increase in range and intensity of light absorption and the reduction of electron-hole pair recombination in CuWO4 with the introducing of GO on to it.展开更多
基金financially supported by the National Natural Science Foundation of China(21875265,22293015,22121002)。
文摘Phenol in waste water threatens human health and is difficultly to be decomposed by nature.Efficient degradation of high-loaded phenol in water under mild condition is still a great challenge.Herein,ionic liquids with tungstate anion were designed and prepared.It was found that dodecyltrimethylammonium tungstate could catalyzed degradation of phenol into gases and water thoroughly at 323 k in 8 h.Tungstate anion revealed good catalytic oxidative activity and long carbon chain group connecting with cation of ionic liquids enriched phenol around catalysts,which induced the complete degradation of phenol at mild conditions.Increasing the amounts of hydrogen peroxide benefited to the total degradation of phenol.In addition,the ionic liquid could be reused for its excellent thermal stability.Our work provided a different strategy to treat waste water containing phenol efficiently.
基金support of NSFC 51702284Fundamental Research Funds for the Central Universities (112109*172210171)+2 种基金the Startup Foundation for Hundred-Talent Program of Zhejiang University (112100-193820101/001/022)support of the NSFC 21501138the Science Research Foundation of Wuhan Institute of Technology (K201513)
文摘Visible-light-responsive ternary metal tungstate(MWO_4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost,eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron–hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO_4-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO_4-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalyticactivities of MWO_4-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO_4-based photocatalysts.
文摘An unusual inorganic-organic hybrid hexatungstate complex [Cu(phen)3][W6O19] 1 (C36H24 CuN6O19W6, Mr = 2011.20) was hydrothermally synthesized and characterized by single- crystal X-ray diffraction, IR spectrum, UV-VIS spectrum and elemental analyses. This compound crystallizes in the monoclinic system, space group C2/c with a = 19.1005(11), b = 11.2585(11), c = 20.2867(15) , β = 102.177(2)o, V = 4264.4 3, μ(MoKa) = 16.691 mm–1, Dc = 3.133 g/cm3, Z = 4, F(000) = 3628, the final R = 0.0338 and wR = 0.0798 for 4090 observed reflections with I > 2σ(I). The result of structure determination shows that the crystal structure is constructed from [W6O19]2– cluster anions and [Cu(phen)3]2+ complex fragments, which are held together into a three-dimen- sional network through hydrogen-bonding interactions.
文摘The crystals of NaLn（WO4）<sub>2</sub>（Ln=La,Pr,Nd）are grown from a melt of LiCl-Na<sub>2</sub>WO<sub>4</sub> flux by slowcooling method.The chemical analysis data show that the crystals are NaLa（WO<sub>4</sub>）<sub>2</sub>,NaPr（WO4）<sub>2</sub> andNaNd（WO<sub>4</sub>）<sub>2</sub> respectively.The structures of the crystals are ascertained that they belong to scheelite structureof the tetragonal system with a space group of 14<sub>1</sub>/a.The lattice parameters of the crystals have beencalculated.It is found that the cell volume of NaLn（WO<sub>4</sub>）<sub>2</sub> crystals decrease with a decrease of Ln<sup>3+</sup>radius.The bond distances and their angles in NaLa（WO<sub>4</sub>）<sub>2</sub> and NaNd（WO<sub>4</sub>）<sub>2</sub> are given.It is found that inaccordance with the decrease of ionic radii of Ln<sup>3+</sup>due to increase of atomic number,the bond distances betweenLn-O,Ln-Ln and W-O decrease regularly.The infrared spectra of NaLn（WO<sub>4</sub>）<sub>2</sub> are measured.Thetetrahedra characteristic absorptions of WO<sub>4</sub><sup>2-</sup>are shown.The sensitization of host lattice is observed from theexcitation and fluorescent spectra of NaLa（WO<sub>4</sub>）<sub>2</sub> and NaPr（WO<sub>4</sub>）<sub>2</sub>.
基金Supported by the Research Foundation of Akdeniz University, Turkey
文摘AIM: To evaluate the effect of sodium tungstate on visual evoked potentials(VEPs) in diabetic rats.· METHODS: Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic rats treated with sodium tungstate. Diabetes was induced by single intraperitoneal injection of streptozotocin(50 mg/kg). Sodium tungstate [40 mg/(kg·d)]was administered for 12 wk and then VEPs were recorded.Additionally, thiobarbituric acid reactive substance(TBARS) levels were measured in brain tissues.·RESULTS: The latencies of P1, N1, P2, N2 and P3 waves were significantly prolonged in diabetic rats compared with control group. Diabetes mellitus caused an increase in the lipid peroxidation process that was accompanied by changes in VEPs. However, prolonged latencies of VEPs for all components returned to control levels in sodium tungstate-treated group. The treatment of sodium tungstate significantly decreased brain TBARS levels and depleted the prolonged latencies of VEP components compared with diabetic control group.· CONCLUSION: Sodium tungstate shows protective effects on visual pathway in diabetic rats, and it can be worthy of further study for potential use.
基金supported by Jilin Provincial Education Department (2009JYT15)Jilin Provincial Science and Technology Department (20090709)Changchun Science and Technology Bureau (2009110)
文摘The 10 at.% Er3+-doped KYb(WO4)2(KEr0.1Yb0.9(WO4)2) laser crystal with dimensions up to 25 mm×15 mm×10 mm was grown by the Kyropoulos method.The crystal structure was identified as β-KEr0.1Yb0.9(WO4)2 by XRD analysis.Through TG-DTA curves,the melting point and transition point of the crystal were determined to be 1058 and 1031 °C,respectively.Infrared spectrum and Raman spectrum were measured,and the vibration frequencies of infrared and Raman active modes for the crystal were assigned.The absorption cross section is 3.1×10-20 cm2 at chief peak of 981 nm with the absorption line width of 26 nm.Based on the Judd-Ofelt theory,the intensity parameters ?λ(λ=2,4,6) calculated were:?2=16.34×10-20 cm2,?4=4.18×10-20 cm2,and ?6=1.26×10-20 cm2.There was a strong emission peak near 1533 nm and the emission line width at the main peak at 1533 nm run up to 55 nm with the emission cross section of 3.47×10-20 cm2 .These optical parameters indicated the potential of this crystal used as an excellent laser material for 1540 nm nearby human-eye safe.
文摘The expanded industrial experiments were conducted with practical industfial liquor to separate free alkali from sodium tungstate solution by electrolysis with canon-exchange membrane. Experimental results show that on the condition that the temperature is 50-55℃ and the current density is 1000 A/m2, the single electrolysis cell is operated stably and 80% free-alkali in mass fraction is separated from the anode feed liquor of sodium tungstate, with electric ef- ficiency up to more than 88% and the unit energy consumption E lower than 1900 kWh/t; while three electfolysis cells in series are operated, under the condition that the temperature is 60-65 ℃ and the current density is 1000 A/m2, the elec- tric efficiency can reach higher than 88% and the unit energy consumption E can be lower than 2250 kWh/t.
文摘Solvent – free Mortar-pestle (grinding) and microwave-assisted nitration reactions (MWANR’s) underwent smoothly in the presence of group V and VI metal salts with high regio-selectivity for anilides, moderately- and non-activated aro-matic compounds. The reactions were conducted under solvent-free conditions, which afforded good to excellent yields. The observed reaction times in MW assisted conditions are in the range of only few minutes.
文摘Whereas the light yield of PWO crystal can be significantly improved by doping with either of F- and Sb3+, effects of heavily co-doping with by F-+Sb3+, F-+Ca2+, and F-+Ca2++Sb3+, respectively, on the properties of PWO scintillation crystals, including optical transmission, luminescence and light yield were studied. The result indicates that co-doping with three dopants, F-+Ca2++Sb3+, is a more effective measure than doping with single dopant F- for the improvement of scintillation properties of PWO crystals, including light yield.
文摘Xiao Liansheng Wang Wei Zhang Qixiu Gong Bofan Cao Jiashu (Department of Metallurgical Science and Engineering, Central South University of Technology, Changsha 410083, China) Abstrac By measuring the electrode polarization curves of many kinds of materials and life spans of electrodes through intensifying electrolysis in the process, the appropriate electrode materials for different stages of electrolysis of sodium tungstate solution with membrane have been selected The effects of the electrodes with different shapes on electrolysis have been investigated. The result shows that network electrode is more suitable to electrolysis of sodium tungstate solution.
基金financial support from the National Natural Science Foundation of P. R. China (21103049)
文摘The present paper reports new results regarding the addition of pseudo-boehmite as a binder during the synthesis of shaped Pt/WO_(3)-ZrO_(2)-Al_(2)O_(3) (PtWZA) catalysts. Binder shaping can noticeably influence not only the structure and acidity of catalyst and improve its catalytic performance with regard to n-heptane isomerization, but the mechanical strength of the catalyst. A suitable binder content can improve the isomerization activity or selectivity by changing the acidity of PtWZA. The influence of the binder content depends on the WO_(3) content of the catalyst. PtWZA catalysts that contain 5%-15% binder on a dry basis exhibit favorable isomerization performance that depends on WO_(3) content. Suitable catalysts include Pt20WZ5A and Pt30WZ15A, which provide conversions of approximately 80%-90% and a selectivity of 90%. These new findings enrich researcher knowledge of the effect of the binder on the catalyst shaping process and are useful in the production of industrial catalysts.
基金This work was supported by Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions.
文摘A series of uniform single-phase spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors were prepared via a microwave hydrothermal method by using trisodium citrate dehydrate as surfactant.The phase structure,morphology and photoluminescence properties were measured by powder X-ray diffraction,scanning electron microscope and fluorescence spectrometer,respectively.The results show that uniform spherical microcrystals with diameters in the range of 2–4μm are obtained.And the phase and morphology of samples are not significantly changed by doping rare earth(RE^(3+))ions.Under the excitation wavelength of 356 and 365 nm,the samples BaWO 4:0.03Dy^(3+),yTm^(3+)can emit cold white light.In order to lower the correlated color temperature(CCT)to get a warm white light,the Eu^(3+)ions were doped into BaWO 4:0.03Dy^(3+),0.01Tm^(3+).Especially,under the excitation of 365 nm,BaWO 4:0.03Dy^(3+),0.01Tm^(3+),0.03Eu^(3+)phosphor shew a bright warm white light with color coordi-nate of(0.4013,0.3629)and CCT of 3288 K.Moreover,in the BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors,the energy transfer mechanism among Dy^(3+),Tm^(3+)and Eu^(3+)ions have been discussed and the change of electron structures have been calculated by first-principles calculations.The results shew that the uniform single-phase spherical BaWO 4:Dy^(3+),Tm^(3+),Eu^(3+)phosphors could be favorable candidates in warm white LEDs.
文摘The structure of Tb∶Mo∶PbWO4 crystals was investigated by Raman spectra and the results showed that the spectra were varied differently by doping dopants in different ranges of shift. Rotation-vibration, curving-vibration and non-symmetrical stretching-vibration had been investigated on the spectra. Rotation-vibration intensity of [WO4]2-group is weakened and curving-vibration intensity is undergirded; low Mo6+ doping enhances the intensity of non-symmetrical stretching-vibration, with the concentration of Mo6+ increasing, the intensity is weakened. So it could be inferred that Tb3+ ion replaced the vacancy of Pb, when achieving at a certain concentration, Tb3+ ion would substitute for the lattice of Pb2+, Mo6+ ion would substitute for W lattice and generate [MoO4]2-new group, these are the main reason for the properties changing. Furthermore it could suggest that the impurity ions doped in tetrahedral positions, strongly affect the electron-phonon coupling in [WO4]2-, which makes the intensities of the vibration changed regularly.
文摘In high energy physics experiments,large arrays of scintillation crystals have b een used in electromagnetic calorimeters for precision measurements of photons a nd electrons.The large crystal calorimeters and their use has been a key factor in the high energy physics programs.Table 1 lists parameters of crystal calorime ter projects of the past (Crystal Ball),present(L3) and future (CMS) in high ene rgy physics.In future high energy collider,however,scintillating crysta ls face a new challenge:the radiation damage caused by the increased background radiation level.It would reach about 1000 rad/day for lead tungstate (PbWO 4) crystal at LHC.Lead tungstate is a new fast and dense scintillating crystal and has been s elected as scintillator for the construction of calorimeter in CMS experiment of Large Hadron Collider (LHC) at CERN(European Organization for Nuclear Research ) next century.82000 large sized PWO scintillating crystals will be assembled in the calorimeter of the CMS experiment,and they will be produced both in China a nd in Russia from now until to 2004.
文摘Barium tungstate of homogeneous double cone structure was synthesized by microwave synthesis method with sodium tungstate, barium nitrate as raw materials, polyethylene glycol (PEG2000) as surfactant. The as-prepared sample was characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM) and photoluminescence spectrum (PL). The XRD Pattern showed that the samples are scheelite structure of BaWO4. The SEM image showed that the majority of as-prepared sample is a double cone structure, and some particles are attached to it. The length of most of the double cone is 10 μm. PL spectra showed that as-prepared sample had strong luminescence properties, and it had purity green emission at 495 nm and 521 nm. The effects of different surface active agent on the luminescence properties were studied. The results showed that when PEG2000 is as surfactant, the luminescence intensity of as-prepared sample was maximum.
文摘Anabaena variabilis ATCC 29413 has two distinct nitrogenases that function in heterocysts, a conventional Mo-nitrogenase and an alternative V-nitrogenase. Synthesis of these two enzymes was repressed in cells growing with a source of fixed nitrogen, such as ammonium;however, the V-nitrogenase was also repressed by Mo. Expression of the V-nitrogenase which was not affected by V and expression of the Mo-nitrogenase was not affected by the presence or absence of either Mo or V. In the absence of both Mo and V in an environment lacking fixed nitrogen, cells became starved for both metals;however, low levels of nitrogen fixation and slow growth persisted. A mutant lacking the V-nitrogenase was still able to grow very slowly in Mo-and V-free medium;however, loss of the Mo-nitrogenase in a nifDK1 mutant abolished the residual growth, suggesting that only the Mo-nitrogenase functioned under these conditions to support slow growth. The addition of vanadate, molybdate, or tungstate, which is transported by the molybdate transporter, to cells starved for these metals resulted in an increase in nitrogenase activity within two hours after the addition of the metal and this increase required new protein synthesis. While tungstate functioned about as well as vanadate in supporting acetylene reduction, the cells were not able to grow any better with tungstate than with no added metal. A mutant lacking the V-nitrogenase showed no increase in nitrogenase activity upon addition of tungstate, suggesting that the V-nitrogenase was able to incorporate tungstate. Tungstate was able to substitute for molybdate in repressing transcription of a Mo-transport gene, but it did not repress transcription of the vnfH gene, which was repressed by Mo. The availability of Mo and V plays an important role in controlling whether the Mo-or the V-nitrogenase is used for nitrogen fixation.
文摘Copper Tungstate-Graphene Oxide nano composites have been successfully applied as excellent catalysts for the photocatalytic degradation with Methylene blue and Malachite green dyes under visible light irradiation. A facile?solid state metathesis synthesis of copper tungstate (CuWO4) followed by ball milling and subsequent preparation of copper tungstate-graphene oxide?(CuWO4-GO) nano composite using a colloidal blending process and its application as a visible light photocatalyst for the degradation of Malachite green and Methylene blue dyes. The morphology and composition of copper tungstate (CuWO4) nano composite have been characterized using X-Ray Diffraction (XRD), UV-Visible Diffuse Reflectance Spectra (UV-DRS), Raman Spectra, Field Emission Scanning Electron Microscopy (FESEM)-EDS and UV Visible Spectroscopy. It shows a band gap value of 2.13 eV, an increase in range and intensity of light absorption and the reduction of electron-hole pair recombination in CuWO4 with the introducing of GO on to it.
