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Abstract

The enthalpies of mixing of six kinds of amino acid (glycine, L-alanine, L-valine, L-serine, L-threonine, and L-proline) with glycerol in aqueous solutions and the enthalpies of diluting of amino acid and glycerol aqueous solutions have been determined by flow microcalorimetry at 298.15 K. Employing McMillan–Mayer theory, the enthalpies of mixing and diluting have been used to calculate heterogeneous enthalpic pairwise interaction coefficients (h xy) between amino acids and glycerol in aqueous solutions. Combining h xy values of amino acids with glycol in the previous study, the variations of the h xy values between amino acids and glycerol have been interpreted from the point of view of solute–solute interactions.

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The principle for the electro-generative simultaneous leaching (EGSL) is applied to simultaneous leaching of pyrite-MnO2 in this paper. A galvanic system for the bio-electro-generative simultaneous leaching (BEGSL) has been set up. The equation of electric quantity vs. time is used to study the effect of produced sulfur on electro-generative efficiency and quantity. It has been shown that the resistance decreased in the presence of Acidithiobacillus thiooxidans (A. thiooxidans) with the increase of electro-generative efficiency. The effects of temperature and grain size on rate of ferrous extraction from pyrite under the conditions of presence and absence of A. thiooxidans were studied, respectively. The changes in the extraction rate of Fe2+ as particle size in presence of A. thiooxidans were more evident than that in the absence, which indicated that the extraction in bio-electro-generative leaching was affected by particle size remarkably. Around the optimum culture temperature for A. thiooxidans, the bigger change in the conversion rate of Fe2+ was depending on temperature. The transferred charge in BEGSL including part of S0 to sulfate group in the presence of (A. thiooxidans) which is called as biologic electric quantity, and the ratio of biologic electric quantity reached to 58.10% in 72 h among the all-transferred charge.

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TG and DTA experiments were performed to investigate the biomass tar combustion behavior in coexistence of dolomite and mayenite at two different heating rates as 5 and 15°C min−1. Different reaction kinetic mechanisms with the classical Arrhenius model were used to treat TG data, and showed that the first-order combustion model fitted the data well. Three stages combustion model was proposed and applied for the calculation of kinetics parameters successfully. The starting temperature of high temperature combustion stage moved up near 100°C because of the coexistence catalysts, and the combustion amount of biomass of the stage also improved nearly 10 mass%. By calculation a uniform trend of decreasing activation energies was observed with the addition of dolomite and mayenite, and also greatly improved the amount and speed of tar combustion process.

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Abstract  

Enthalpies of dilution at 298.15 K of aqueous solutions of THF and 1,4-dioxane have been determined using flow microcalorimetry. The results obtained were used to determine the homotactic enthalpic interaction coefficients that characterize pair interactions of THF and 1,4-dioxane in aqueous solution. These are briefly discussed from the point of view of intermolecular interaction between the hydrated solute species.

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Abstract  

A novel AB2-type monomer diethyl 5-(4-hydroxyethoxyphenylazo)isophthalate for preparing hyperbranched azo polymers (HBPAZO) was synthesized. The monomer obtained was characterized by IR spectra, UV–Vis spectra, 1H NMR spectrum and C NMR spectrum. The TG-DTG/DTA curves show that the decomposition of the monomer proceeds in four steps. During the second-step decomposition, the mass loss occurs between 480.5 K and 579.0 K and the phenomena of condensing to HBPAZO for the melted monomer was found. So it is inferred that this temperature range is the best for polycondensation of the melted monomer, which is very important for synthesizing of HBPAZO.

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Abstract  

The thermal decomposition studies for two palladium(II) complexes Pd(apyr)2Cl2 and Pd(pmpa)Cl2 (apyr=1–aminopyrene and pmpa=N–(2–pyridylmethylene)–1–pyrenylamine) were carried out in pure nitrogen using TG-DTG techniques. The non-isothermal kinetic parameters for the two complexes were evaluated employing the method suggested by Málek, esták, Koga et al. Based on the above results, thermal behaviour of the complexes were carefully discussed, which showed that not only the parameters value, but also the decomposition pattern and mechanism for complex 1 are different from complex 2.

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The molar heat capacity C p,m of 1,2-cyclohexane dicarboxylic anhydride was measured in the temperature range from T=80 to 390 K with a small sample automated adiabatic calorimeter. The melting point T m, the molar enthalpy Δfus H m and the entropy Δfus S m of fusion for the compound were determined to be 303.80 K, 14.71 kJ mol−1 and 48.43 J K−1 mol−1, respectively. The thermodynamic functions [H T-H 273.15] and [S T-S 273.15] were derived in the temperature range from T=80 to 385 K with temperature interval of 5 K. The thermal stability of the compound was investigated by differential scanning calorimeter (DSC) and thermogravimetry (TG), when the process of the mass-loss was due to the evaporation, instead of its thermal decomposition.

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Cyanocobalamin (CNCbl), a kind of vitamin B12 (cobalamin, Cbl), which has a special binding capability to rapid dividing cells and proliferating tissue, especially tumors, has been modified and labeled by 99mTc. The optimal labeling condition was determined, and the biodistribution of 99mTc-DTPA-b-CNCbl both in normal mice and TA2 mice bearing MA891 mammary tumors were studied. 99mTc-DTPA-b-CNCbl showed low uptake and rapid clearance in nontarget tissues, and renal excretion. About 40% of uptake at 1 hour remained in the tumor at 12 hours p.i. The satisfying ratio of T/NT was acquired at 6 hours p.i.

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A rapid, simple, and practical high-performance liquid chromatographic method (HPLC) was developed and validated for the simultaneous determination of norephedrine (NME), norpseudoephedrine (NMP), ephedrine (E), pseudoephedrine (PE), and methylephedrine (ME) in traditional Chinese medicines (TCM) which contained Ephedrae Herba (Ephedra). This analysis could be accomplished within 12.5 min with an Alltima Phenyl Column by isocratic elution using a mixture of KH2PO4 (20 mM)-acetonitrile (96:4, v/v) as the mobile phase at a flow-rate of 0.6 mL min−1 and a wavelength of 210 nm. This method was successfully applied to quantify ephedra alkaloids in both Ma-xing-gan-shi decoction and Ephedra decoction. The concentration of total ephedra alkaloids (4.62 mg mL−1) in Ma-xing-gan-shi decoction was much lower than that (7.10 mg mL−1) in Ephedra decoction. Furthermore, the concentration of NME, NMP, E, PE, and ME was significantly lower in Ma-xing-gan-shi decoction than that in Ephedra decoction, respectively. The method was easily acceptable and would be popular with most analytical laboratories.

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A micellar high-performance liquid chromatography (HPLC) method has been described for simultaneous determination of ephedrine, pseudoephedrine, and methylephedrine in Ephedra Herb and two traditional Chinese preparations. The separation and determination of ephedrine, pseudoephedrine, and methylephedrine were performed using a mobile phase containing 1.75 × 10−1 mol·L−1 sodium dodecyl sulphate and 0.02 mol·L−1 potassium hydrogen phosphate with 10% (v/v) methanol at pH 3.0, running at 1.5 mL·min−1 by a Venusil XBP C18 (250 × 4.6 mm, 5 μm) column at 40 °C. The detected wavelength was set at 210 nm. The method was validated according to the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines. The main analytical parameters were linearity (r > 0.9990), intra- and inter-day precisions (relative standard deviation [RSD %], 0.33–1.63, and RSD %, 1.26–2.20, respectively), limit of quantifications [LOQs], and limit of detections [LODs] (2.6 × 10−4 and 7.8 × 10−5 mg·mL−1 for ephedrine, 6.8 × 10−4 and 2.0 × 10−4 mg·mL−1 for pseudoephedrine, and 5.0 × 10−4 and 1.5 × 10−4 mg·mL−1 for methylephedrine). RSDs of recoveries were <5.5% in the three samples. Based on the optimized chromatographic conditions and the eluted orders, a model of separation mechanism for the analytes was established. The results indicated that the proposed method was an accurate, “green” and cheap method.

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