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991.
Laiyan Bao 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1765-1771
Ammonium persulfate (APS), 2,2′‐azobis(amidinopropane) dihydrochloride (V50) and 4,4′‐azobis(4‐cyanovaleric acid) (ACVA) were utilized to prepare temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) microgels by precipitation polymerization under various reaction pH conditions. Their particle sizes and swelling ratios depended on the reaction pH due to the pH dependence on the ionization degree of the decomposed fragments originating from the initiators and their hydrophilicity‐hydrophobicity. The more hydrophobic initiator, under the reaction pH conditions used, could be partitioned to a greater extent into the microgel particles due to the hydrophobicity of PNIPAM chains at the reaction temperature, which led to a more cross‐linked structure inside the microgels resulting in their smaller swelling ratio. pH dependence of surface charge density of the microgels with amidino groups or carboxylic acid groups on their surfaces was evidenced by the variation of their zeta potentials as a function of pH. 相似文献
992.
Peng Zhang Wenzhe Wang Yingfang Zhou Gang Ruan Haiyang Yu Wenjuan Ji 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11-12):764-769
AbstractA novel cationic water-soluble monomer allyldimethylisooctylammonium bromide (ADIAB) containing a short-chain alkane was synthesized successfully. This monomer was copolymerized with acrylamide and sodium acrylate to produce hydrophobically modified polyacrylamide (HMPAM) using solution polymerization without surfactants. The structures of monomer ADIAB and HMPAM were characterized with infrared spectroscopy and nuclear magnetic resonance spectroscopy. Influence of preparation condition on viscosities of products was studied. The aqueous solution viscosity of the terpolymer was also investigated as functions of concentration, temperature and salinity. The results showed that when the temperature exceeds the 60?°C and NaCl concentration exceeds about 2000?mg/L, the temperature and salt tolerance characters of terpolymer were demonstrated. The enhanced oil recovery tests were initially carried out using homogeneous sandpack models. 相似文献
993.
Z. Y. Zhang B. Wu Y. H. Tang Z. X. Li Z. L. Sun L. Y. Chen Y. B. Ji C. H. Ma C. G. Huang 《Journal of Analytical Chemistry》2013,68(8):716-721
To characterize of the constituents in rat urine after oral administration of Radix Astragali decoction, a HPLC-DAD-MS/MS technique had been developed. Urine collected from 0 to 24 h, after administration, was purified using a C18 solid-phase extraction cartridge, and then detected by an on-line MS/MS detector. By comparing the retention times and MS/MS data with those obtained from authentic compounds and the published data, a total of 11 compounds including six flavonoids, one dipeptide, one triterpenoid and three of their metabolites in urine were identified. Compounds daidzein, genistein, quercetin, L-asparamide-D-phenylalanine, 4,2′,4′-trihydroxychalcone, Astragaloside-IV, daidzein sulfate, and kaempferol sulfate were for the first time detected by HPLC-MS/MS technique in urine. The present research results success-fully narrowed the range of effective constituents to be found in Astragalus membranaceus and would be useful for the following action mechanism research of this traditional Chinese medicine in treating various diseases. 相似文献
994.
H. Huang J. Wang J. Z. Fu L. Q. Wang H. Z. Zhao S. Y. Song L. X. Ji M. Jiang G. Bai G. A. Luo 《Journal of Analytical Chemistry》2013,68(4):348-356
An ultra performance liquid chromatographic method was used for the simultaneous identification and quantification of thirteen main components in Xuebijing Injection, including uridine, gallic acid, guanosine, danshensu, protocatechualdehyde, oxypaeoniflorin, hydroxysafflor yellow A, paeoniflorin, ferulic acid, safflor yellow A, senkyunolide I, senkyunolide H and salvianolic acid B. The chromatographic separation was performed on an Acquity UPLC BEH C18 column (1.7-μm, 2.1 × 100 mm, i.d.) with a gradient elution of acetonitrile and 0.2% acetic acid at a flow rate of 0.4 mL/min. The method was validated for linearity (r 2 > 0.9990), intra- and inter-day precision (RSD < 1.94%), accuracy (91.8–99.7%), recovery (96.8–103.8%), limits of detection (0.16–8.0 ng), and limits of quantification (0.54–26.8 ng). At least eight metabolites in prototype were found in rat plasma and urine after intravenous injection of 4 mL/kg doses of Xuebijing Injection. The proposed method could be utilized to qualify and control Xuebijing Injection to ensure its safety and efficacy in application. 相似文献
995.
Sang Gyo Seo Ji Hyun Yeo JI Hye Kim Ji-Beom Kim Tae-Joon Cho Dong Yeon Lee 《Experimental & molecular medicine》2013,45(11):e62
Non healing chronic wounds are difficult to treat in patients with diabetes and can result in severe medical problems for these patients and for society. Negative-pressure wound therapy (NPWT) has been adopted to treat intractable chronic wounds and has been reported to be effective. However, the mechanisms underlying the effects of this treatment have not been elucidated. To assess the vasculogenic effect of NPWT, we evaluated the systemic mobilization of endothelial progenitor cells (EPCs) during NPWT. Twenty-two of 29 consecutive patients who presented at the clinic of Seoul National Universty Hospital between December 2009 and November 2010 who underwent NPWT for diabetic foot infections or skin ulcers were included in this study. Peripheral blood samples were taken before NPWT (pre-NPWT) and 7–14 days after the initiation of NPWT (during-NPWT). Fluorescence-activated cell sorting (FACS) analysis showed that the number of cells in EPC-enriched fractions increased after NPWT, and the numbers of EPC colony forming units (CFUs) significantly increased during NPWT. We believe that NPWT is useful for treating patients with diabetic foot infections and skin ulcers, especially when these conditions are accompanied by peripheral arterial insufficiency. The systemic mobilization of EPCs during NPWT may be a mechanism for healing intractable wounds in diabetic patients with foot infections or skin defects via the formation of increased granulation tissue with numerous small blood vessels. 相似文献
996.
A novel, rapid and sensitive liquid chromatography/quadrupole linear ion trap mass spectrometry [LC‐ESI‐(QqLIT)MS/MS] method was developed and validated for the quantification of protopanaxadiol (PPD) in rat plasma. Oleanolic acid (OA) was used as internal standard (IS). A simple protein precipitation based on acetonitrile (ACN) was employed. Chromatographic separation was performed on a Sepax GP‐C18 column (50 × 2.1 mm, 5 μM) with a mobile phase consisting of ACN–water and 1.5 μM formic acid and 25 mM lithium acetate (90 : 10, v/v) at a flow rate of 0.4 ml/min for 3.0 min. Multiple‐reaction‐monitoring mode was performed using lithium adduct ion as precursor ion of m/z 467.5/449.4 and 455.6/407.4 for the drug and IS, respectively. Calibration curve was recovered over a concentration range of 0.5–100 ng/ml with a correlation coefficient >0.99. The limit of detection was 0.2 ng/ml in rat plasma for PPD. The results of the intraday and interday precision and accuracy studies were well within the acceptable limits. The validated method was successfully applied to investigate the pharmacokinetic study of PPD after intravenous and gavage administration to rat. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
997.
The effect of crystal structure on the thermal reactivity of CL-20 and its C4-bonded explosives 总被引:1,自引:0,他引:1
Qi-Long Yan Svatopluk Zeman Roman Svoboda Ahmed Elbeih Jiří Málek 《Journal of Thermal Analysis and Calorimetry》2013,112(2):837-849
The critical temperature and mechanism functions for thermal decomposition of ε-CL-20, RS-ε-CL-20, α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 were evaluated based on non-isothermal TG data. A two-step mechanism has been found for thermal decomposition of α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4, where the initial step is partly controlled by crystal structure of CL-20. The more reasonable mean activation energies could be obtained after peak separation for each individual steps. In fact, the activation energy for the post integrated process is almost equivalent with that of the second step, indicating that the total activation energy at the main decomposition process is dominated by thermolysis of CL-20 molecular. Besides, it has been found that the decomposition of C4 matrix does not affect the decomposition of normal ε-CL-20, resulting in identical activation energy and reaction model. However, the interaction between the C4 matrix and RS-ε-CL-20 is significant especially at the initial stage, where the activation energy of RS-ε-CL-20/C4 was overestimated before peak separation, while the activation energy for the second step due to thermolysis of CL-20 molecular is underestimated. The first decomposition step for α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 could be considered as autocatalytic process (AC model), whereas the second as JMA model, which is also applicable to that of pure ε-CL-20 and RS-ε-CL-20. Moreover, The critical temperatures of thermal explosion (T b) are obtained as 205.6, 205.5, 209.4, 214.4, and 227.5 °C for α-CL-20, ε-CL-20, RS-ε-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4, respectively. It proves that the C4 matrix could stabilize ε-CL-20 while the crystal form of CL-20 has little effect on its thermal stability. 相似文献
998.
A novel flame retardant (PSiN), containing silicon and nitrogen, was synthesized using N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602) and diphenylsilanediol through solution polycondesation and it was used together with potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) to prepare a flame-retardant system for polycarbonate (PC). The structure and thermal property of PSiN were characterized by Fourier transform infrared spectroscopy (FTIR), 1HNMR and thermogravimetric analysis (TG) tests. Flammability and thermal behaviors of PC/KSS/PSiN systems were estimated by limited oxygen index (LOI), cone calorimeter, vertical burning test (UL-94), and TG tests. The results showed that the flame retardancy and char residues of PC/KSS system were improved with the addition of PSiN. When 1 mass% PSiN and 0.5 mass% KSS were incorporated, the LOI value of PC was found to be 46, and class V-0 of the UL-94 test. Moreover, both the heat release rate and the total heat release of PC/KSS/1 mass% PSiN decreased compared with those of PC and PC/KSS systems. The microstructures observed by scanning electron microscopy and FTIR indicated that the surface of the char for PC/KSS/PSiN system hold a more cohesive and denser char structure when compared with the pure PC and PC/KSS system. 相似文献
999.
Yang Guo Wei Zhang Xing Zhou Tong Bao 《Journal of Thermal Analysis and Calorimetry》2013,113(2):787-791
Boron was chosen as fuel owing to its excellent thermodynamic values for combustion. The difficulty of the boron in combustion is the formation of a surface oxide layer, which postpones the combustion process, reducing the performance of the rocket engine. In this paper, magnesium boride was sintered as high-energy fuel as a substitute for boron. The combustion heat and efficiency of magnesium boride and boron were determined using oxygen bomb calorimeter. The combustion characteristics of magnesium boride were investigated by thermal analysis, chemical analysis, XRD, and EDS. Results show that the combustion performance of magnesium boride are better than that of amorphous boron in oxygenated environments. The evaporation of magnesium in magnesium boride combustion process prevent the formation of a closed oxide layer, leading to higher combustion efficiency. 相似文献
1000.
Effects of common synergistic agents on intumescent flame retardant polypropylene with a novel charring agent 总被引:1,自引:0,他引:1
In this article, the laboratory-made poly (p-ethylene terephthalamide) (PETA) was used as a novel charring agent and it combined with ammonium polyphosphate (APP) to prepare the intumescent flame retardant (IFR). For improving the flame-retardant efficiency of IFRs on polypropylene (PP), several general synergistic agents, such as common zinc oxide (Com-ZnO), nanometer structural zinc oxide (Nano-ZnO), zeolite 4A, and aluminum hypophosphite(Al(H2PO2)3), were added in composites of PP/IFR, and the synergistic effect was investigated by the limited oxygen index (LOI), the UL-94 (vertical flame) test, thermogravimetric analysis (TG), thermogravimetry-fourier transform infraredspectroscopy (TG-IR) test, and scanning electron microscopy (SEM). It indicated that the flame retardancy was significantly enhanced in terms of prompting the char formation of PETA and interaction between APP and synergistic agents. Overall, Al(H2PO2)3 was the most effective synergistic agent among them. TG-IR analysis showed that the addition of Al(H2PO2)3 could delay the release of NH3, and make the release of NH3 more smooth, which was useful to form a dense char. SEM presented that compact, continuous and good intumescent charring layers were observed in all PP/IFR systems with synergistic agent. 相似文献