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461.
A modified regularized algorithm for a semilinear space‐fractional backward diffusion problem 下载免费PDF全文
Xiaoying Jiang Dinghua Xu Qifeng Zhang 《Mathematical Methods in the Applied Sciences》2017,40(16):5996-6006
In this paper, we investigate a backward problem for a space‐fractional partial differential equation. The main purpose is to propose a modified regularization method for the inverse problem. The existence and the uniqueness for the modified regularized solution are proved. To derive the gradient of the optimization functional, the variational adjoint method is introduced, and hence, the unknown initial value is reconstructed. Finally, numerical examples are provided to show the effectiveness of the proposed algorithm. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
462.
Three-dimensional light-emitting diodes (LEDs) are the preferred light source for bulb lamps due to their 360° illumination. Addition curing silicone resins have usually been used to encapsulate LEDs. LED-filament encapsulation needs silicone resins having high thermal performance and thixotropy. Herein, a low refractive index and highly anti-thermal aging silicone oil was synthesized by hydrolysis and co-condensation method, and used to prepare an encapsulation material for high-power LED-filament. The cured silicone materials were characterized by thermogravimetric analysis (TGA) and thermal aging test under 180°C and 250°C. The results demonstrated that the thermal stability of the cured silicone resins with short-chain phenyl silicone as a crosslinker was higher than that with long-chain methyl silicone oil crosslinker. Owing to the excellent thermal stability, appropriate hardness, high transparency and photoelectric efficiency, this LED encapsulation material is a promising candidate for high-power LED package. 相似文献
463.
Graphene oxide coated capillary for the analysis of endocrine‐disrupting chemicals by open‐tubular capillary electrochromatography with amperometric detection 下载免费PDF全文
Xiaoying Jiang Yuehuang Jiang Guoyue Shi Tianshu Zhou 《Journal of separation science》2014,37(13):1671-1678
A graphene oxide‐coated capillary was fabricated by using 3‐aminopropyltriethoxysilane as the cross‐linking agent. It was used for the separation and detection of three endocrine‐disrupting chemicals, including bisphenol A, 4‐nonylphenol, and 4‐octylphenol by capillary electrochromatography. Due to the hydrophobicity, hydrogen bonding, and π–π interaction between graphene oxide and the analytes, the three analytes could be well separated in pH = 11.0, 20 mmol/L Na2B4O7‐NaOH/methanol mobile phase (50:50, v/v) within 950 s. After preconcentration, the detection limits were 6.7 × 10?10, 3.3 × 10?9, and 6.7 × 10?10 mol/L (S/N = 3) for bisphenol A, nonylphenol, and octylphenol, respectively. The developed method was successfully applied to the determination of the above analytes in water samples. The satisfactory result demonstrated that the graphene oxide coated capillary used in capillary electrochromatography with amperometric detection was convenient to prepare, highly stable, and had good reproducibility. 相似文献
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Optically Transparent Electrodes Modified with Sulfide Ion‐Covered CdS Quantum Dots for Sensitive Photoelectrochemical Detection of Sulfhydryl‐Containing Compounds 下载免费PDF全文
Xiaoying Wang Yunfei Long Angela Ramos Dianlu Jiang Xiaohua Ma Qinlu Lin Feimeng Zhou 《Electroanalysis》2015,27(8):1899-1905
A sensitive and selective photoelectrochemical sensor has been developed. Negatively charged, citrate‐capped CdS quantum dots (QDs) are assembled layer‐by‐layer onto indium tin oxide (ITO) electrodes precoated with positively charged poly(diallyldimethylammonium chloride). By exposing the modified photoelectrochemical electrodes to a Na2S solution, QDs can be covered with excess S2? ions. The weakly bound S2? ions are easily replaceable with a sulphydryl‐containing analyte, and the photocurrent decrease is proportional to the analyte concentration. The detection limit is 0.4 nM for cysteine with a linear range of 1.0–100.0 nM. The level of cysteine in human serum samples has been quantified. 相似文献
466.
Hua Y Wainhaus SB Yang Y Shen L Xiong Y Xu X Zhang F Bolton JL van Breemen RB 《Journal of the American Society for Mass Spectrometry》2001,12(1):80-87
Oxidized deoxynucleosides are widely used as biomarkers for DNA oxidation and oxidative stress assessment. Although gas chromatography mass spectrometry is widely used for the measurement of multiple DNA lesions, this approach requires complex sample preparation contributing to possible artifactual oxidation. To address these issues, a high performance liquid chromatography (HPLC)-tandem mass spectrometric (LC-MS/MS) method was developed to measure 8-hydroxy-2'-deoxyguanosine (8-OH-dG), 8-hydroxy-2'-deoxyadenosine (8-OH-dA), 2-hydroxy-2'-deoxyadenosine (2-OH-dA), thymidine glycol (TG), and 5-hydroxy-methyl-2'-deoxyuridine (HMDU) in DNA samples with fast sample preparation. In order to selectively monitor the product ions of these precursors with optimum sensitivity for use during quantitative LC-MS/MS analysis, unique and abundant fragment ions had to be identified during MS/MS with collision-induced dissociation (CID). Positive and negative ion electrospray tandem mass spectra with CID were compared for the analysis of these five oxidized deoxynucleosides. The most abundant fragment ions were usually formed by cleavage of the glycosidic bond in both positive and negative ion modes. However, in the negative ion electrospray tandem mass spectra of 8-OH-dG, 2-OH-dA, and 8-OH-dA, cleavage of two bonds within the sugar ring produced abundant S1 type ions with loss of a neutral molecule weighing 90 u, [M - H - 90]-. The signal-to-noise ratio was similar for negative and positive ion electrospray MS/MS except in the case of thymidine glycol where the signal-to-noise was 100 times greater in negative ionization mode. Therefore, negative ion electrospray tandem mass spectrometry with CID would be preferred to positive ion mode for the analysis of sets of oxidized deoxynucleosides that include thymidine glycol. Investigation of the fragmentation pathways indicated some new general rules for the fragmentation of negatively charged oxidized nucleosides. When purine nucleosides contain a hydroxyl group in the C8 position, an S1 type product ion will dominate the product ions due to a six-membered ring hydrogen transfer process. Finally, a new type of fragment ion formed by elimination of a neutral molecule weighing 48 (CO2H4) from the sugar moiety was observed for all three oxidized purine nucleosides. 相似文献
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Xiaoying Luo Hongye Zhang Zhengang Ke Cailing Wu Shien Guo Yunyan Wu Bo Yu Zhimin Liu 《中国科学:化学(英文版)》2018,(6)
Using mesoporous N-doped carbons(NCs)derived from glucose and melamine as the supports,a series of Pd/NC catalysts were prepared,in which Pd nanoparticles with average size2.0 nm were uniformly distributed on the supports.It was indicated that the resultant Pd/NC catalysts were effective for N-formylation of amines with CO_2and H_2in ethanol without any additives.Especially,the catalyst Pd/NC-800-6.9%containing quaternary N showed the best performance,affording a series of formylamides in good or even excellent yields.Further investigation reveals that the interaction between the Pd nanoparticles and quaternary nitrogen in the NC support was responsible for the good performance of the catalyst. 相似文献
470.
Hua Cheng Yan Jia Ling Wang Xiaoying Liu Guangrong Liu Li Li 《Natural product research》2016,30(1):58-64
A crude polysaccharide possessing antitumour, radiation-resistant and anti-ageing attributes was extracted from Tricholoma matsutake by water extraction and alcohol precipitation. From this crude polysaccharide, a homogeneous polysaccharide, TMP-5II, was successfully purified by Sephacryl S-300 column chromatography. The average molecular weight (Mw) of TMP-5II was 15.76 kDa. Monosaccharide analysis indicated that the homogeneous polysaccharide contained four different residues: d-glucose, d-galactose, d-mannose and d-fucose. Attenuated total reflectance infrared spectroscopy revealed characteristics typical of carbohydrate polymers and a peak typical of a β-type glycosidic bond. TMP-5II was selected for structural characterisation by nuclear magnetic resonance (NMR) analysis. According to 1H NMR, 13C NMR and two-dimensional-NMR analysis, TMP-5II contains two kinds of linkages, β and α, at a ratio of 4:1. Preliminary results indicated that the polysaccharide had (1-4)-beta-pyran glucose as the main chain, and a branched chain in the O-6 location with fucose (1-2) mannose (1-3)-alpha-pyran galactose. 相似文献