The sub-micron sized YAG ： Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the p...The sub-micron sized YAG ： Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the pure YAG phase exists at a relatively lower sintering temperature of 1400 ℃. The smaller sizes of phosphors in the ranges of 1 - 3 μm are obtained due to the contribution of seeding effects of nano-sized alumina particles to strengthen each step of the processes. Both the excitation and emission spectra of photoluminescence of the phosphor obtained at 1400 ℃ meet well with the spectroscopic requirements of the WLED phosphors.展开更多
Background:The exclusion of tourist species from samples is important to avoid bias in community analyses.However,in practice,this is a very difficult task.The commonly used methods by researchers,when the habitat of ...Background:The exclusion of tourist species from samples is important to avoid bias in community analyses.However,in practice,this is a very difficult task.The commonly used methods by researchers,when the habitat of the species is not known,have several shortcomings:first,they exclude not only pseudo-rare species but also genuinely rare species;second,the results obtained with those methods depend on the abundance of the sampling;and third,they follow very subjective rules.The aims of this study were:(i)to propose a methodology to detect and exclude habitat-tourist species from the database used to carry out analyses in community ecology studies,(ii)to evaluate how the presence of habitat-tourist species affects the richness estimates,and(iii)to assess the effect of including juvenile spiders in the detection of tourist species and the effect of removing them from the richness estimates.Results:When the adult+juvenile dataset was considered,twenty-one habitat-tourist species were detected:8 in forest foliage,11 in forest leaf litter,and 2 in grassland.When habitat-tourist species were considered with this dataset,richness overestimation was significant in foliage and in leaf litter,and the final slopes of the richness estimation curves were significantly steeper in leaf litter.When only the adult dataset was considered,eight habitat-tourist species were detected:3 in forest foliage,4 in forest leaf litter,and just one in grassland.The inclusion of habitat-tourist species in this dataset showed an overestimation of richness,but this was not significant.Conclusions:The proposed methodology contributes to solving the problem of tourist species,which was recognized as one of the great problems in biodiversity studies.This study showed that common estimators overestimate species richness when habitat-tourist species are included,leading to erroneous conclusions.Besides,this research showed that the inclusion of juveniles(e.g.spiders)could improve the analysis outputs because it allowed the detection of more habitat-tourist species.展开更多
This work dealt with the computation of the mean activity coefficients of rare-earth halide aqueous solutions at 25℃, by means of the Quasi Random Lattice（QRL） model. The osmotic coefficients were then calculated c...This work dealt with the computation of the mean activity coefficients of rare-earth halide aqueous solutions at 25℃, by means of the Quasi Random Lattice（QRL） model. The osmotic coefficients were then calculated consistently, through the integration of the Gibbs-Duhem equation. Using of QRL was mainly motivated by its dependence on one parameter, given in the form of an electrolyte-dependent concentration, which was also the highest concentration at which the model could be applied. For all the electrolyte solutions here considered, this parameter was experimentally known and ranged from 1.5 to 2.2 mol/kg, at 25 ℃.Accordingly, rare- earth halide concentrations from strong dilution up to 2 mol/kg about could be considered without need for best-fit treatment in order to compute their osmotic and mean activity coefficients. The experimental knowledge about the parameter was an advantageous feature of QRL compared to existing literature models. Following a trend already observed with low charge electrolytes,a satisfactory agreement was obtained with the experimental values for all the investigated rare-earth chlorides and bromides. For the sake of compactness, in this work the considered rare-earth halides were all belonging to the P63/m space group in their crystalline（anhydrous） form.展开更多
Eu3+-activated Gd2(MoO4)3 pseudo-pompon-like red-emitting phosphors were prepared by solid-state method. The structure, morphology, and luminescent properties of these powder samples were investigated by X-ray diffrac...Eu3+-activated Gd2(MoO4)3 pseudo-pompon-like red-emitting phosphors were prepared by solid-state method. The structure, morphology, and luminescent properties of these powder samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fluorescent spectrophotometry, respectively. The as-obtained phosphors were single crystalline phase with orthorhombic unit cell. The particles of the powder samples had the length of 5-12 m and width of 3-7 m with flake shape and large surface area, which is suitable for manufacture of white LEDs. The phosphor could be efficiently excited by the incident light of 348-425 nm, well matched with the output wavelength of near-UV (In,Ga)N chip, and re-emitted an intense red light peaking at 615 nm. By combing this phosphor with a ~395 nm-emitting (In,Ga)N chip, a red LED was fabricated, so that the applicability of this novel phosphor to white LEDs was confirmed. It is considered to be an efficient red-emitting conversion phosphor for solid-state lighting based on (In,Ga)N LEDs.展开更多
文摘The sub-micron sized YAG ： Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the pure YAG phase exists at a relatively lower sintering temperature of 1400 ℃. The smaller sizes of phosphors in the ranges of 1 - 3 μm are obtained due to the contribution of seeding effects of nano-sized alumina particles to strengthen each step of the processes. Both the excitation and emission spectra of photoluminescence of the phosphor obtained at 1400 ℃ meet well with the spectroscopic requirements of the WLED phosphors.
基金This research was financed by project PI F 003/2015 of the SGCyT-UNNE(Argentina)by a CONICET doctoral fellowship awarded to the first author.
文摘Background:The exclusion of tourist species from samples is important to avoid bias in community analyses.However,in practice,this is a very difficult task.The commonly used methods by researchers,when the habitat of the species is not known,have several shortcomings:first,they exclude not only pseudo-rare species but also genuinely rare species;second,the results obtained with those methods depend on the abundance of the sampling;and third,they follow very subjective rules.The aims of this study were:(i)to propose a methodology to detect and exclude habitat-tourist species from the database used to carry out analyses in community ecology studies,(ii)to evaluate how the presence of habitat-tourist species affects the richness estimates,and(iii)to assess the effect of including juvenile spiders in the detection of tourist species and the effect of removing them from the richness estimates.Results:When the adult+juvenile dataset was considered,twenty-one habitat-tourist species were detected:8 in forest foliage,11 in forest leaf litter,and 2 in grassland.When habitat-tourist species were considered with this dataset,richness overestimation was significant in foliage and in leaf litter,and the final slopes of the richness estimation curves were significantly steeper in leaf litter.When only the adult dataset was considered,eight habitat-tourist species were detected:3 in forest foliage,4 in forest leaf litter,and just one in grassland.The inclusion of habitat-tourist species in this dataset showed an overestimation of richness,but this was not significant.Conclusions:The proposed methodology contributes to solving the problem of tourist species,which was recognized as one of the great problems in biodiversity studies.This study showed that common estimators overestimate species richness when habitat-tourist species are included,leading to erroneous conclusions.Besides,this research showed that the inclusion of juveniles(e.g.spiders)could improve the analysis outputs because it allowed the detection of more habitat-tourist species.
文摘This work dealt with the computation of the mean activity coefficients of rare-earth halide aqueous solutions at 25℃, by means of the Quasi Random Lattice（QRL） model. The osmotic coefficients were then calculated consistently, through the integration of the Gibbs-Duhem equation. Using of QRL was mainly motivated by its dependence on one parameter, given in the form of an electrolyte-dependent concentration, which was also the highest concentration at which the model could be applied. For all the electrolyte solutions here considered, this parameter was experimentally known and ranged from 1.5 to 2.2 mol/kg, at 25 ℃.Accordingly, rare- earth halide concentrations from strong dilution up to 2 mol/kg about could be considered without need for best-fit treatment in order to compute their osmotic and mean activity coefficients. The experimental knowledge about the parameter was an advantageous feature of QRL compared to existing literature models. Following a trend already observed with low charge electrolytes,a satisfactory agreement was obtained with the experimental values for all the investigated rare-earth chlorides and bromides. For the sake of compactness, in this work the considered rare-earth halides were all belonging to the P63/m space group in their crystalline（anhydrous） form.
基金Project supported by the Natural Science Research Project of the Jiangsu Higher Education Institutions (08KJD150014)the QingLan Project of the Jiangsu Province (2008)the Basic Research Fund of Jiangsu Teachers University of Technology (KYY09031)
文摘Eu3+-activated Gd2(MoO4)3 pseudo-pompon-like red-emitting phosphors were prepared by solid-state method. The structure, morphology, and luminescent properties of these powder samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fluorescent spectrophotometry, respectively. The as-obtained phosphors were single crystalline phase with orthorhombic unit cell. The particles of the powder samples had the length of 5-12 m and width of 3-7 m with flake shape and large surface area, which is suitable for manufacture of white LEDs. The phosphor could be efficiently excited by the incident light of 348-425 nm, well matched with the output wavelength of near-UV (In,Ga)N chip, and re-emitted an intense red light peaking at 615 nm. By combing this phosphor with a ~395 nm-emitting (In,Ga)N chip, a red LED was fabricated, so that the applicability of this novel phosphor to white LEDs was confirmed. It is considered to be an efficient red-emitting conversion phosphor for solid-state lighting based on (In,Ga)N LEDs.
