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Abstract  

As a consequence of their excellent barrier properties vinyl chloride/vinylidene chloride copolymers have long been prominent in the flexible packaging market. While these polymers possess a number of superior characteristics, they tend to undergo thermally- induced degradative dehydrochlorination at process temperatures. This degradation must be controlled to permit processing of the polymers. Three series of N-substituted maleimides (N-alkyl-, N-aralkyl, and N-aryl) have been synthesized, characterized spectroscopically, and evaluated as potential stabilizers for a standard vinyl chloride/vinylidene chloride (85 mass%) copolymer. As surface blends with the polymer, these compounds are ineffective as stabilizers. However, significant stabilization may be achieved by pretreatment of the polymer with N-substituted maleimides. The most effective stabilization of the polymer is afforded by N-aralkyl- or N-arylmaleimides, most notably, N-benzylmaleimide and N-p-methoxyphenylmaleimide.

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A new, least-squares optimization method with interpolation is devised to fit skeletal vibrational heat capacities to the two parameters θ1 and θ3 in the Tarasov function used for heat capacity calculations of linear macromolecules. When heat capacities are available in the proper temperature range, θ1 and θ3 can be determined uniquely in a single computer run. Appended to our Advanced THermal Analysis System (ATHAS), this new method offers an improvement in analyzing heat capacity data and facilitates the systematic study of the physical significance of θ1 and θ3 values for all polymers and related molecules of the ATHAS data bank.

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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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Summary  

The organometallic precursor fac-[99mTc(CO)3(H2O)3]+ was reacted with N-ethoxy, N-ethyl dithiocarbamate (NOET) in phosphate buffered saline (pH 7.4) at room temperature for 30 minutes to produce the 99mTc(CO)3-NOET complex. The radiochemical purity (RCP) of the product was over 90% as measured by thin layer chromatography (TLC). No decomposition of the complex at room temperature (RT) was observed over a period of 6 hours. Its partition coefficient indicated that it was a lipophilic complex. The biodistribution comparison in mice of the 99mTc(CO)3-NOET complex and the 99mTcN-NOET complex showed that the former had a lower heart and brain uptake as compared to that of the latter, suggesting the incorporation of the [99mTc(CO)3]+ core into the NOET ligand does not improve the biological features as a myocardial imaging agent.

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Abstract  

External-beam PIXE was used for the non-destructive analysis of early glasses unearthed from the tombs of Warring States (475–221BC) and Han Dynasty (BC 206–AD 220) in south China. It was found that these glasses were basically attributed to PbO—BaO—SiO2 system and K2O—SiO2 system. The results from the cluster analysis showed that some glasses had exactly the same recipe. The source of the K2O flux and the correlation between PbO and BaO are discussed. Some archeological information is revealed.

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Abstract  

In this paper the dependence of build-up233U,232U,233Pa and fission products from ThO2 irradiated in HFETR on integral thermal neutron fluxes and neutron spectra have been investigated. The yields of all above nuclides in ThO2 increase with the increase of integral thermal neutron fluxes at different neutron spectra. The values of233U/232Th increase with the increases of th and decreases with the increase of fast/thermal neutron ratios ( f/ th). The values of232U/233U increase with the increase of both th and f/ th ratio. The amount of fission products relative to original irradiated thorium decreases with the increase of f/ th ratios. These results could be used to evaluate the behaviour of thorium-based nuclear fuel in reactor.

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Journal of Thermal Analysis and Calorimetry
Authors:
A. Boller
,
I. Okazaki
,
K. Ishikiriyama
,
G. Zhang
, and
B. Wunderlich

Abstract  

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on the symmetry of the twin calorimeters. This symmetry is of particular importance for the temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. Three different DSC instruments capable of modulation have been calibrated for asymmetry using standard non-modulated measurements and a simple method is described that avoids potentially large errors when using the reversing heat capacity as the measured quantity. It consists of overcompensating the temperature-dependent asymmetry by increasing the mass of the sample pan.

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Abstract  

According to the theoretical basis of thermokinetics, the integral and differential thermokinetic equations of opposing reactions have been derived, and a novel thermokinetic research method, the characteristic parameter method for opposing reactions which taking place in a batch conduction calorimeter under isothermal condition, has been proposed in this paper. Only needing the characteristic thermoanalytical data corresponding to tm and 2tm from the same curve, the rate constants of forward and backward reactions and equilibrium constant can be calculated simultaneously with this method. In order to test the validity of this method, the proton-transfer reactions of nitroethane with ammonia at 15 and 25°C, and with trihydroxymethyl aminomethane (Tris) at 15 and 30°C have been studied, respectively. The results of rate constants and equilibrium constants calculated with this method are in agreement with those in the literature. Therefore, the characteristic parameter method for opposing reaction is believed to be correct.

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Thermodynamic investigation of several natural polyols

Part III. Heat capacities and thermodynamic properties of erythritol

Journal of Thermal Analysis and Calorimetry
Authors:
B. Tong
,
Z. Tan
,
J. Zhang
, and
S. Wang

Abstract  

The low-temperature heat capacity C p,m of erythritol (C4H10O4, CAS 149-32-6) was precisely measured in the temperature range from 80 to 410 K by means of a small sample automated adiabatic calorimeter. A solid-liquid phase transition was found at T=390.254 K from the experimental C p-T curve. The molar enthalpy and entropy of this transition were determined to be 37.92±0.19 kJ mol−1 and 97.17±0.49 J K−1 mol−1, respectively. The thermodynamic functions [H T-H 298.15] and [S T-S 298.15], were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The standard molar enthalpy of combustion and the standard molar enthalpy of formation of the compound have been determined: Δc H m 0(C4H10O4, cr)= −2102.90±1.56 kJ mol−1 and Δf H m 0(C4H10O4, cr)= − 900.29±0.84 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement with those obtained from heat capacity measurements.

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Abstract  

A novel thermokinetic research method for determination of rate constants of simple-order reaction in batch conduction calorimeter under isothermal condition, the characteristic parameter method, is proposed in this paper. Only needing the characteristic time parameter tm obtained from the measured thermoanalytical curve, the kinetic parameters of reactions studied can be calculated conveniently with this method. The saponifications of ethyl propionate and ethyl acetate in aqueous ethanol solvent, the polymerization of acrylamide in aqueous solution, the ring opening reaction of epichlorohydrin with hydrobromic acid have been studied. The experimental results indicate that the characteristic parameter method for simple-order reaction is correct.

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