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Abstract  

The thermal behaviors of four organic solvents with/without LiPF6 were measured by C80 microcalorimeter at a 0.2�C min−1 heating rate. With the addition of 1 M LiPF6, the ethylene carbonate (EC) and propylene carbonate (PC) show the exothermic peaks at elevated temperature, which lessen their stabilities. The exothermic peak temperatures of EC and PC based LiPF6 solutions are at 212 and 223�C, respectively, in argon filled vessel. However, two endothermic peak temperatures were detected in diethyl carbonate (DEC) based LiPF6 solution at 182 and 252.5�C, respectively, in argon filled vessel. Dimethyl carbonate (DMC) based LiPF6 solution shows two endothermic peak temperatures at 68.5 and 187�C in argon filled vessel at elevated temperature. Consequently, it is concluded that LiPF6 play a key role in the thermal behavior of its organic solution.

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Using an ac calorimetric method, detailed behaviour of the heat capacity in dipalmitoyl-phosphatidylcholine-cholesterol system was studied in the cholesterol concentration less than 5 mol%. It was revealed that the heat capacity near the main transition was composed of at least four anomalies, i.e., multipeak took place in the heat capacity. This fact indicates that a simple theory explaining coexistence of two phases in two component systems does not work in the multipeak region. Then, relation between the multipeak heat capacity and the change of the ripple structure with the cholesterol concentration should be taken into account, when we consider thermodynamical behaviour of the systems.

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An improved ion-pairing reversed-phase high-performance liquid chromatography method coupled with evaporative light scattering detection (HPLC-ELSD) was developed to determine spectinomycin and its related substances in commercial samples. The method was validated in accordance with International Conference on Harmonization (ICH) guidelines. The specificity of the HPLC-ELSD method was similar to that of the European Pharmacopoeia (Ph. Eur.) method, and repeatability and robustness were markedly improved relative to other reported methods due to our empirical evaluation of separation columns. Indeed, it is a more specific assay of spectinomycin than traditional microbiological techniques. The HPLC-ELSD method was used to evaluate the impurity profiles of eight compounds in seven spectinomycin batches from five different companies. Liquid chromatography coupled with electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was employed to characterize the structures of these compounds. Though the HPLC-ELSD method was not as sensitive as the Ph. Eur. method, its limit of quantitation (LOQ) (0.16%) was lower than the disregard limit (0.3%) described by the Ph. Eur. 7.0. This suggests that the HPLC-ELSD method is appropriate for routine analysis of spectinomycin and its related substances.

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Abstract  

With the low permeability and high swelling property, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for a potential repository. The diffusion behaviors of HTO in GMZ bentonite were studied to obtain effective diffusion coefficient (D e) and accessible porosity (ε) by through- and out-diffusion experiments. A computer code named Fitting for diffusion coefficient (FDP) was used for the experimental data processing and theoretical modeling. The D e and ε values were (5.2–11.2) × 10−11 m2/s and 0.35–0.50 at dry density from 1,800 to 2,000 kg/m3, respectively. The D e values at 1,800 kg/m3 was a little higher than that of at 2,000 kg/m3, whereas the D e value at 1,600 kg/m3 was significantly higher (approximately twice) than that of at 1,800 and 2,000 kg/m3. It may be explained that the diffusion of HTO mainly occurred in the interlayer space for the highly compacted clay (dry density exceeding 1,300 kg/m3). 1,800 and 2,000 kg/m3 probably had similar interlayer space, whereas 1,600 kg/m3 had more. Both D e and ε values decreased with increasing dry density. For compacted bentonite, the relationship of D e and ε could be described by Archie’s law with exponent n = 4.5 ± 1.0.

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Abstract  

Thermal analysis on two new heterometallic sulfide clusters, [PPh4]2[WS3(CuBr)3]2 and [PPh4]2[MoS3(CuBr)3]2 (where PPh4=tetraphenyl phosphonium, =pentamethylcyclopenta- dienyl), was carried out using a simultaneous TG-DTA unit in an atmosphere of flowing nitrogen and at various heating rates. Supplemented using EDS method, their thermal behavior and properties, together with the composition of their intermediate product, were examined and discussed in connection with their distinctive molecular structure as a dianion, which provided some theoretically and practically significant information. Both clusters decomposed in a two-step mode, but without a stable new phase composed of Mo/W-Cu-S formed during their decomposition process as we expected. Based on TG-DTG data, four methods, i.e. Achar-Brindley-Sharp, Coats-Redfern, Kissinger and Flynn- Wall-Ozawa equation, were used to calculate the non-isothermal kinetic parameters and to determine the most probable mechanisms.

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Abstract  

A microcalorimetric technique based on the bacterial heat-output was explored to evaluate the effect of Mn(II) on Bacillus thuringiensis. The power-time curves of the growth metabolism of B. thuringiensis and the effect of Mn(II) on it were studied using an LKB-2277 BioActivity Monitor, ampoules method, at 28C. For evaluation of the results, the maximum peak-heat output power (P max) in the growth phase, the growth rate constants (k), the log phase heat effects (Q log ), and the total heat effect in 23 h (Q T) for B. thuringiensis were determined. Manganese has been regarded as the essential biological trace element. Mn(II) of different concentration have different effects on B. thuringiensis growth metabolism. High concentration (800-1600 μg mL-1) of Mn(II) can promote the growth of B. thuringiensis; low concentration (500-800 μg mL-1) can inhabit its growth.

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Abstract  

The effects of some kinds of metal ions used as chemical modifications on the thermal properties of the modified polyacrylonitrile (PAN) fibers were studied by DTA, TG, GC and cone calorimetry. The apparent activation energies for the decomposition of the unmodified and modified PAN fibers were determined using Kissinger equation and Broido equation.

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Journal of Thermal Analysis and Calorimetry
Authors: J. Yao, F. Wang, L. Tian, Y. Zhou, H. Chen, K. Chen, N. Gai, R. Zhuang, T. Maskow, B. Ceccanti, and G. Zaray

Abstract  

Using TAM III multi-channel calorimetry combined with direct microorganism counting (bacteria, actinomycetes and fungi) under laboratory conditions, we determined the microbial population count, resistance and activity toward cadmium (Cd(II)) and hexavalent chromium (Cr(VI)) toxicity in soil. The thermokinetic parameters, which can represent soil microbial activity, were calculated from power-time curves of soil microbial activity obtained by microcalorimetric measurement. Simultaneous application of the two methods showed that growth rate constant (k), peak-heat output power (P max) and the number of living microorganisms decreased with increasing concentration of Cd and Cr. The accumulation of Cr on E. coli was conducted by HPLC-ICP-MS. Cr6+ accumulation by Escherichia coli was increased steadily with increasing Cr6+ concentration. The results revealed that the change in some thermo-kinetic parameters could have good corresponding relationship with metal accumulation. Our work also suggests that microcalorimetry is a fast, simple, more sensitive, on-line and in vitro method that can be easily performed to study the toxicity of different species of heavy metals on microorganism compared to other biological methods, and can combine with other analytic methods to study the interaction mechanism between environmental toxicants and microbes.

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