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Determination of Catechol by Cetyltrimethylammonium Bromide Functionalized Graphene Modified Electrode
Get PDFA simple and sensitive electrochemical sensor was prepared by using electrodeposition of the cetyltrimethylammonium Bromide (CTMAB ) functionalized Graphene (GR) on the glassy carbon electrode (GCE) to determine Catechol (CC) in water. The performance of the CTMAB functionalized GR sensor was studied and the analysis conditions of the CC were optimized. The experimental results showed that, compared with bare GCE, the redox peak current of CC on the modified electrode was obviously enhanced. Under the optimized conditions, the oxidation and reduction peak current all showed a good linear relationship with the concentration of CC from 5μmol/L to 1000 μmol/L. The detection limit of oxidation peak is 2.92 μmol/L, and that of reduction peak is 2.44 μmol/L. The recovery was founded to be in the range of 92.70 %~101.80 %. Moreover, the sensor could be used for the determination of CC in real samples with satisfactory results. And the mechanism of the sensitization of CC detected by CTMAB-GR modified GCE was discussed preliminarily
Morphological Structure, Physicochemical Properties Analysis and Application in Processing Vermicelli of the Kidney Bean Starch Grown in Qianjiang, China
Get PDF The structure, morphology, physicochemical properties and potential use in vermicelli of kidney bean starch, grown in Qianjiang, China, were carried out. Results pointed out that the scanning electron micrographs revealed the presence of kidney or ovoid- to globose-shaped granules and with a diameter ranging from 5 to 50 μm. And the kidney bean starch exhibited an A-type X-ray diffraction pattern. The freeze-thaw stability was poor that the rate of water release was only 41.90%. But the thermal stability and cold stability were good and it showed a C- type Brabender viscosity curve. Besides, the kidney bean vermicelli was prepared by the optimized process. The viscosity and swelling of kidney bean vermicelli were less than mung bean vermicelli, which lead to the acceptable unable to equal to mung bean vermicelli. But considering the price and big cooking loss, weak tensile strength and weak shear strength of other starch vermicelli, the kidney bean starch vermicelli still has important application value
Arc Erosion Behaviors of Ag-GNPs Electrical Contact Materials Fabricated with Different Graphene Nanoplates Content
Get PDFIn order to clarify the arc erosion behavior of Ag-GNPs electrical contact materials, Ag-GNPs electrical contact materials with different graphene nanoplates content from 0.5wt.% to 2.0wt.% were prepared by powder metallurgy. The microstructure, density, and electrical conductivity were investigated in detail. The weight loss, surface morphologies of the Ag-GNPs materials after arc erosion were characterized, and the arc erosion mechanism of Ag-GNPs materials was discussed. The experimental results show that high GNPs content decreases the densities and electrical conductivity of the Ag-GNPs materials. The Ag-GNPs electrical contact material with 1.5wt.%GNPs presents the best anti-arc erosion performance, which has the lowest weight loss and shallowest arc erosion pits after arc erosion under DC 25V/15A
Synthesis and structural characterization of CuAl2O4 spinel with an unusual cation distribution
Get PDFA CuAl2O4 spinel with unusual cation distribution has been synthesized for the first time by the solid phase reaction of copper hydroxide and pseudo-boehmite with both stoichiometric (Cu/Al = 1/2) and non-stoichiometric (Cu/Al = 1/3) ratios. Instead of characterizing one cation for the determination of cations distribution as generally performed in previous literatures, both cations in the synthesized spinel have been characterized with 27Al NMR for Al ions and EXAFS for Cu ions, respectively. The characterization data reveal that nearly all Al3+ ions are octahedrally coordinated while most Cu2+ occupy the tetrahedral sites, giving a (Cu0.8)[Cu0.2Al2]O4 spinel which has been supported by the Rietveld refinement. The unusual cation distribution, which has been rarely reported before, presents abnormal site occupancies in Cu-Al spinel oxide. Hence, the findings of this work may invoke further explorations on other spinel oxides for targeting novel distinctive properties and applications
Uncertainties Brought by Weight Assignment in Ecosystem Health Modelling
Get PDFWeight assignment is the most important step in ecosystem health modelling. However, few researches were conducted to test the uncertainties brought by weighting methods in ecosystem health modelling. In this research, aimed to test the rationality and uncertainties brought by objective weighting methods, we made a comparison between different objective weighting methods (Entropy, Variation coefficient, Mean square error, Critic). We found that (1) the weights assigned by different objective method are quite different; (2) the variation of sample size does not exert significant influences on weight assignment. However, the weight of indicator has the tendency of increasing or decreasing with the increment of sample size; (3) the weights assigned by these four objective methods were not able to reflect the actual relative importance of indicators. Therefore, we don't advise to use objective weighting method as the sole approach to assign the weight of indicator in ecosystem health modelling
Oviposition sequence of non-pollinating fig wasps associated with Ficus benjamina in China
Get PDFFig-fig wasp mutualisms are exploited by non-pollinating fig wasps (NPFWs). In most cases, NPFWs oviposit into ovaries of female flowers from outside syconia. In this study, the oviposition sequence of externally ovipositing non-pollinating fig wasps associated with Ficus benjamina were studied by direct observation, yellow sticky board and manipulation experiments in Xishuangbanna, southwest of China. The results showed that (i) Different genera of wasps showed a temporal partition in oviposition sequence among NPFWs. Acophila, Sycobia and Walkerella wasps colonized syconia in pre-female phase, while Micronisa, Philotrypesis and Sycoscapter oviposited in the interfloral phase. Further, NPFWs of the same genus also showed difference ovposition period. (ii) Different genera of wasps exhibited various strategies of resource exploitation. Acophila, Sycobia and Walkerella wasps were gallers, while Philotrypesis wasps should be inquiline. However, only the galler species Walkerella sp.2 had significant negative effective on pollinator and seed
Comparison of Aromatic Compounds in Pitaya Wine on Different Columns
Get PDFThe aroma components of pitaya wine was enriched by headspace solid-phase microextraction (HS-SPME). The chromatographic separation was performed on two kinds of polar columns, respectively. GC-MS was used to detect and compare the aroma components. Differences between the separation of aroma components of pitaya wine by polar column HP-5MS and polar column CP-Wax. The results showed that there were significant differences between the two columns in the determination of the aroma components of pitaya wine. The main aroma compounds measured by HP-5MS column had many more types and contents than the CP-Wax column
Application of Polypyrrole (Ppy) nanofibers in Solid Phase Extraction of samples before the determination of vitamin B families in infant powder
Get PDFIn this study, a kind of core/sheath Polystyrene/Polypyrrole (PS/PPy) electrospun nanofibers was prepared and used as the solid phase extraction (SPE) adsorbent. Primary extraction of target analytes, three kinds of vitamin B (VB2, riboflavin; VB9, folic acid; VB12, cobalamin), was carried out by loading samples onto the column along with appointed boric acid compound reagent, and then the column should also be rinsed with the same reagent solution before elution. The boric acid compound was applied as complexing reagent to retain as much of three analytes as possible on the column based on the multi interaction between three vitamins and the boronate affinity reagent, thus improving hydrophobicity of targets and adsorption efficiency through loading and rinsing steps. Analytical parameters include linearity r2> 0.99; limit of detection (LOD) ranged from 0.05 to 0.093μg/ml; Intraday and Interday precision of the method, 0.59%-12.1% and 0.64%-14.5%, respectively; the spiked extraction recoveries ranged from 84.9% to 111.7% in the infant powder samples. A Ppy nanofibers SPE column coupled with HPLC-UV was established for assay of elements in infant powder. The levels of three vitamin Bs in three brands of real milk powder samples were determined and the results were compared with the prescription. Results showed that the analysis method in the paper were reliable to be used in the determination of vitamin B families in infant powder
Design of Fuzzy Cognitive Model of Mutual Influence and Connectivity of Innovative Technologies
Get PDFThe article is devoted to research and development of fuzzy cognitive model of mutual influence and connectivity of innovative technologies on the basis of synthesis of interdisciplinary research strategies - foresight methods based on logically transparent mechanisms of interpretation of the solution, expert weighting methods and neutrosophic cognitive maps. Neutrosophic cognitive map of mutual influence and connectivity of innovative technologies is constructed on the basis of data on the nature and intensity of these interactions, allowing to calculate the degree of influence of one or several concepts (technologies), taking into account their state, on the target indicator, and also calculate the fixed state of the concept system. The results of experimental verification and the multiplicative effect of the developed model on the data of expert surveys are described, under conditions of transition to the 6th technological order
On the Stress State of the Semi-Strip with a Longitudinal Crack
Get PDFThe stress state of the elastic semi-strip is investigated in the paper. The lateral sides of the semi-strip are fixed and the semi-strip's short edge is under the mechanical load. The longitudinal crack is located inside the semi-strip. The problem is reduced to the one-dimensional problem with the help of Fourier sin-, cos- transformation, which was applied directly to the Lame's equilibrium equations and the boundary conditions. The one-dimensional problem is formulated is a vector form. Its solution is constructed with the help of the matrix differential calculation and the Green matrix-function, which was constructed in the bilinear form. The solution of the problem is reduced to the solving of three singular integral equations. The first equation in this system contains two fixed singularities in its kernel. To consider them the corresponding transcendental equation is constructed, and its roots are found. The special generalized method is applied to solve the system of singular integral equations. The stress intensity factors are calculated