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991.
Xiong Yin Catherine Choong Liang Hong Zhaolin Liu 《Journal of Solid State Electrochemistry》2006,10(8):643-650
This work reports a new design of asymmetric tubular oxygen-permeable ceramic membrane (OPCM) consisting of a porous Y2O3 stabilized ZrO2 (YSZ) tube (with ∼1 μm of pore diameters and 31% porosity) as the support and a gas-tight mixed conductive membrane. The
membrane has an interlocking structure composed of a host matrix, Ag(Pd) alloy (9:1 by wt) doped perovskite-type (LSM80, 90wt%), and the embedded constituent, pristine LSM80. The Ag(Pd) alloy component promotes not only electronic conductivity
and mechanical strength but also reduction of both porosity and pore sizes in the layer (∼10-μm-thick) where it dopes. The
porous structure in this layer could then be closed through a solution coating procedure by which ingress of an aqueous solution
containing stoichiometric nitrate salts of La3+, Mn3+, and Sr2+ to the pore channels takes place first and the mixture of nitrate salts left after drying is subjected to pyrolysis to generate
tri-metal oxides in situ. This is followed by calcinations at l,300 °C to consolidate the embedded trioxide and to cohere
them with the Ag(Pd)-LSM80 host matrix. The structure formed is dubbed LSM80(S)-Ag(Pd)-LSM80, which was confirmed gas-tight
by electron micrograph and N2 permeation test. Finally, we assess the chemical compatibility between LSM80 and YSZ at the sintering temperature by X-ray
diffraction and electrochemical impedance analysis. The oxygen permeation of the fabricated LSM80(S)-Ag(Pd)-LSM80-YSZ membrane
is within the temperature range of 600 to 900 °C. The tests reveal good compatibility between the LSM80 and YSZ and a reasonably
high oxygen permeation flux in association with this OPCM assembly. 相似文献
992.
Andrés H. Thomas Romina Cabrerizo Mariana Vignoni Rosa Erra-Balsells Franco M. Cabrerizo Alberto L. Capparelli 《Helvetica chimica acta》2006,89(6):1090-1104
The photochemistry of 6‐(hydroxymethyl)pterin (HPT; 1 ) in aqueous solution (pH 5–6) was investigated by irradiation at 350 nm at room temperature. The photochemical reactions of the acidic form 1a were followed by UV/VIS spectrophotometry, thin‐layer chromatography (TLC), high‐performance liquid chromatography (HPLC), and enzymatic methods for the determination of the superoxide anion radical (O ) and hydrogen peroxide (H2O2). When 1a is exposed to UV‐A radiation, the intermediates 4 and 4′ are formed reacting with O2 to yield 6‐formylpterin (FPT; 5 ) and 6‐carboxypterin (CPT; 6 ) under formation of O and H2O2 (Scheme 3). The quantum yields of the disappearance of HPT ( 1a ) and of the formation of the photoproducts 5 and 6 were determined. HPT was investigated for its efficiency in singlet‐oxygen (1O2) production in acidic aqueous solution. The corresponding quantum yield of 1O2 production (ΦΔ) was 0.15 ± 0.02, as measured by the 1O2 luminescence in the near‐IR (1270 nm) upon continuous excitation of the sensitizer. However, 1O2 does not participate in the actual photooxidation of HPT ( 1a ) to FPT ( 5 ) and CPT ( 6 ). 相似文献
993.
The sensitivity of contactless conductivity detection to amino acids, peptides and proteins in CE was studied for BGE solutions of different pH values. The LOD and analytical characteristics were compared for acidic and basic conditions and better results were in most cases found for buffers of low pH values. Linear dynamic ranges varied between two orders of magnitude for amino acids and peptides and three orders of magnitude for larger proteins. The concentration detection limits were found to be between 1.2 and 7.5 microM for the amino acids tested and for the larger molecules they varied between 2.6 microM for leucine enkephalin and 0.2 microM for HSA when using a buffer at pH 2.1. 相似文献
994.
Pasic A Koehler H Schaupp L Pieber TR Klimant I 《Analytical and bioanalytical chemistry》2006,386(5):1293-1302
A new microdialysis-based glucose-sensing system with an integrated fiber-optic hybrid sensor is presented. Design and dimensions
of the cell are adapted for its coupling with commercially available microdialysis techniques, thereby providing a new system
for continuous glucose monitoring. The glucose level is detected via oxygen consumption which occurs as a consequence of enzymatic
reaction between immobilized glucose oxidase and glucose. The use of gas-permeable Tygon tubing ensures complete and constant
air-saturation of the measuring fluid in the cell. Nevertheless, a reference oxygen optode is used to detect and to compensate
response changes caused by events like bacterial growth, temperature fluctuations, or failure of the peristaltic pump. In
contrast to widely used electrochemical sensors, the response of the microdialysis-based fiber-optic glucose sensor is highly
selective, making this sensor approach particularly advantageous for continuous glucose monitoring of patients in intensive
care units. The effects of flow rate, pH, temperature, and common interferences on the sensor response are presented and discussed
in detail. The sensor is evaluated in vitro using a 3-day continuous test in glucose-spiked plasma. The ability to measure
glucose in humans is demonstrated by coupling the flow-through cell and commercially available microdialysis catheter CMA60.
A 24-h monitoring test using this setup is successfully applied to a healthy volunteer. 相似文献
995.
Rosa AH Goveia D Bellin IC da Silva Lessa S Dias Filho NL de Magalhães Padilha P 《Analytical and bioanalytical chemistry》2006,386(7-8):2153-2160
A new procedure was developed for the in situ characterization of the lability of metal species in aquatic systems by using
a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified
with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined
in the laboratory to evaluate the influence of complexation time, mass of exchanger, pH, metal ions (Cu, Cd, Fe, Mn, and Ni),
and concentration of organic matter on the relative lability of metal species. It was found that the pH and kinetics strongly
influence the process of metal complexation by the DM-Cell-PAB system. At all pH levels, Cd, Mn, and Ni showed lower complexation
with Cell-PAB resin than Cu and Fe metals. Note that relative lability of metals complexed to aquatic humic substances (AHS)
in the presence of Cell-PAB resin showed the following order: Cu≅Fe≫Ni>Mn=Cd. The results presented here also indicate that
increasing the AHS concentration decreases the lability of metal species by shifting the equilibrium to AHS–metal complexes.
Our results indicate that the system under study offers an interesting alternative that can be applied to in situ experiments
for differentiation of labile and inert metal species in aquatic systems. 相似文献
996.
The geometry and the vibrational properties of missing row reconstructed O/Cu(0 0 1) and O/Ag(0 0 1) surfaces are investigated by means of density functional theory and density functional perturbation theory, using the local density and the generalized-gradient approximations. Our results predict very similar structural and vibrational properties for the two reconstructed surfaces. In the case of copper our calculations reproduce quite accurately the experimental results, while for the missing row reconstructed O/Ag(0 0 1) surface the agreement between theory and experiment is less satisfactory. 相似文献
997.
We report the observation of levels in the state of CH2 via optical–optical double resonance spectroscopy. Direct transitions between the lowest singlet state and the state are allowed by symmetry, but weak because they correspond to a two electron excitation in the single configuration approximation to the electronic wavefunction. The observed transitions involve sequential single photon absorptions at visible and near infrared wavelengths using state intermediate levels. Recent ab initio results (S.N. Yurchenko et al., J. Mol. Spectrosc. 208 (2001), 136) predicted the positions of some of the levels which are confirmed by the present results. The new spectra provide accurate energies for rotational levels in the , l = 0 level of the state. 相似文献
998.
讨论了非自治N种群Lotka-volterra竞争反馈控制模型,主要采用构造适当的Lyapunov泛函的方法,同时应用Barbalat引理得到了系统全局吸引的判别准则,而且给出了周期系统存在全局吸引的正周期解的充分条件,最后利用数值模拟验证了所得结论. 相似文献
999.
In the present article, two focal subjects, i.e., hydration of the NO and associated ion species in the Mg(NO3)2 solution are researched by using the ab initio method. Nitrate ions with the hydration number of 1–6 are optimized at the HF/6‐31+G* level. Their relative energies, binding energies, and v1‐NO frequencies are also presented. The investigation of the binding energies shows the hydration number is 3–6 in the solvent abundant environment. The associated species, including ion pairings, triple‐ and multiple‐ion clusters, are also optimized at the same level and their v1‐NO frequencies are calculated for comparing with the results in experiments. From the comparison, the new associated process via aqueous free ions → solvent‐shared ion pairings → solvent‐shared triple and multiple ion clusters → contact multiple ion clusters → amorphous crystal is proposed. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010 相似文献
1000.
Herein a water-soluble ‘click’ modified coumarin-based fluorescent probe for hydrogen peroxide is reported. This probe shows significant intensity increases (up to fivefold) in near-green fluorescence upon reaction with hydrogen peroxide, and good selectivity over other reactive oxygen species. 相似文献