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  • Author or Editor: G. Zhang x
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Abstract  

In an ongoing effort to understand the thermodynamic properties of proteins, ovalbumin, lactoglobulin, lysozyme are studied by adiabatic and differential scanning calorimetry over wide temperature ranges. The heat capacities of the samples in their pure, solid states are linked to an approximate vibrational spectrum with the ATHAS analysis that makes use of known group vibrations and a set of parameters, Θ1 and Θ3, of the Tarasov function for the skeletal vibrations. Good agreement is found between experiment and calculation with rms errors mostly within ±3%. The analyses were also carried out with an empirical addition scheme using data from polypeptides of naturally occurring amino acids. Due to space limitation, only selected results are reported.

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Abstract  

The concept of crystallization dynamics method evaluating the miscibility of binary blend system including crystalline component was proposed. Three characteristic rates, nucleation, crystal growth rates (N*, G*) and growth rate of conformation (G c*) were used to evaluate the miscibility of PVDF/at-PMMA and PVDF/iso-PMMA by the simultaneous DSC-FTIR. N*, G* and G c* depended remarkably on both temperature and blend fraction (ϕPMMA) for PVDF/at-PMMA system, which indicated the miscible system. PVDF/iso-PMMA showed small ϕPMMA dependency of N*, G* and G c*, was estimated the immiscible system. The ΔT/T m 0 values, corresponding to Gibbs energy required to attend the constant G* and G c*, evaluated from G* and G c* showed the good linear relationships with different slope. The experimental results suggested that the concentration fluctuation existed in PVDF/iso-PMMA system.

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Abstract  

The crystallization dynamics of Nylon 66/Nylon 6 blends, the crystalline/crystalline polymer blends, was analyzed by DSC under isothermal conditions. The crystal growth rate (G) and the nucleation rate (N) depended on both the degree of supercooling (ΔT) and the blend mass fraction (ϕ). The ΔT /T m 0 values obtained at the fixed G, which corresponded to the chemical potential difference of molecules between liquid and crystal states, and the surface free energy parameters evaluated from G and N depended on ϕ for blends. The results suggested that Nylon 66/Nylon 6 blends with ϕN66≥0.80 or ϕN66≤0.15 are miscible.

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Abstract  

Highly oriented single crystal antimony nanowire arrays have been synthesized within anodic aluminum oxide (AAO) template by pulsed electrodeposition. Thermal behavior and oxidation analysis of the antimony nanowires have been investigated by means of thermogravimetry and differential scanning calorimetry in Ar and air atmosphere, respectively. Compared to bulk antimony, the antimony nanowires exhibit a lower sublimation temperature at 496.4°C. Evident oxidation of the Sb nanowires occurs at 429.8°C in air atmosphere and α-Sb2O4 nanowires have been obtained as the oxidation product. The results indicate that the sublimation and the oxidation of the antimony nanowires in the AAO template is a slow multi-step process. The present results are of relevance when processing antimony nanowries for thermoelectric applications at high temperatures.

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Abstract  

Thermal behaviors of two mixed-ligand complexes, [Ni(PMPP-SAL)(Py)3] and [Cu(PMPP-SAL)Py]·MeOH, (PMPP-SAL=1-phenyl-3-methyl-4-(salicylidene hydrazide)-propenylidene-pyrazolone-5, Py=pyridine), were studied by TG-DTG-DTA in dynamic air atmosphere. The complexes show the loss of pyridine molecule is followed by the decomposition of the PMPP-SAL anion and give respective metal oxides as residues. Meanwhile, the Ozawa-Flynn-Wall model-free analyses and multivariate non-linear regressions were applied to perform single and overall steps optimization. Kinetic parameters were given and the most probable mechanism functions were suggested in this study.

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Abstract  

The free-radical bulk polymerization of 2,2-dinitro-1-butyl-acrylate (DNBA) in the presence of 2,2′-azobisisobutyronitrile (AIBN) as the initiator was investigated by DSC in the non-isothermal mode. Kissinger and Ozawa methods were applied to determine the activation energy (E a) and the reaction order of free-radical polymerization. The results showed that the temperature of exothermic polymerization peaks increased with increasing the heating rate. The reaction order of non-isothermal polymerization of DNBA in the presence of AIBN is approximately 1. The average activation energy (92.91±1.88 kJ mol −1) obtained was smaller slightly than the value of E a=96.82 kJ mol−1 found with the Barrett method.

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Abstract  

2,2-dinitropropyl acrylate (DNPA), 2,2-dinitrobutyl acrylate (DNBA) and 2,2-dinitrobutyl methacrylate (DNBMA) were synthesized and the kinetics of their free-radical polymerization in the presence of 2,2′-azobisisobutyronitrile (AIBN) were investigated by DSC in the non-isothermal mode. The kinetics of the free-radical polymerization as estimated by the Kissinger and Ozawa methods showed that the reaction is disfavoured by increasing steric hindrance around the acrylyl double bond. The rate constants calculated from the activation parameters showed the structural dependency. The polymerization kinetics revealed that the polymerizability of three monomers decreased due to the presence of substituent methyl groups on the acrylyl double bond and 2,2-dinitrobutyl on ester group. Thus, the polymerization tendency increased in the order DNPA>DNBA>DNBMA.

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Abstract  

A series of UO2 2+ complex with monoamide ligand was isolated. The complexes have been characterized with the aid of 13C and 1HNMR spectroscopic studies. The result shows that the amide ligand directly coordinates to the uranyl(VI) ion through its carbonyl group. The change of the value of the chemical shift due to the complexation has been discussed.

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Summary  

Single aerosol particles were analyzed in the ambient air of the center of Shanghai by scanning proton microprobe to obtain characteristic X-ray spectra (micro-PIXE) which were considered to be the fingerprints of these aerosol particles. The origin of the lead-containing particles was identified by the combination of the micro-PIXE spectra with pattern recognition technique. It was found that the most of the lead-containing particles were derived from vehicle exhaust, coal combustion and soil dust.

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Abstract  

A simple direct labeling method was used to synthesize the iodinated ultrafine polystyrene particles. The assay of X-ray photoelectron spectroscopy (XPS) as well as Fourier-transform infrared (FT-IR) spectroscopy indicated the formation of stable covalent bond to aryl group of the polymer particles. The purified radioiodinated product was incubated with serum of rat, and then evaluated by in vitro stability test. The result showed that these synthesized ultrafine polystyrene particles were unmetabolized at 2 hours post-exposure, indicating the potential useful application of this labeled polymer particles as a promising probe in biomedical sciences.

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