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Steps in a minefield

Some kinetic aspects of thermal analysis

Journal of Thermal Analysis and Calorimetry
Author: M. Brown

Abstract  

This paper is a review of some of the controversial kinetic aspects of thermal analysis, starting from the ‘šesták questions’ posed in 1979 and looking at developments in some areas since that time. Aspects considered include: temperature programmes and variations, models and mechanisms, kinetic parameters, distinguishability and extent of fit of kinetic models, complementary evidence for kinetic models, the Arrhenius equation and the compensation effect. The value of the ideas of non-isothermal kinetics in chemical education is emphasized.

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The four new spray reagents (Benzoic acid and some of its parahaloderivatives) have been introduced. These reagents enable convenient and easy detection of amino acids on thin-layer chromatography plates by developing distinguishable colors with very high sensitivity.

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distinguishable change of the curve slope. The microstructural examination of the oxidized specimens showed that an oxide layer was formed in every case, which is composed of a mixed Cr–Fe oxide layer (inner layer with 62 wt% Fe, 20 wt% oxygen, and 18 wt% Cr) and

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higher with a breakthrough member in only 4 of 10 pairs. The percentage of times that an index for the breakthrough drug was higher than that of its corresponding pair, and related 95% CIs are presented in Table 5 . For the TJSI, distinguishability from

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Abstract  

Fingernails of pathologically diagnosed normal people, light esophageal epitheliosis patients, severe esophageal epitheliosis patients and esophageal cancer patients were irradiated and their elemental contents were determined by INAA. Multivariate statistical treatment of Ca, Cl, K. Mg, Se and Zn data shows that esophageal cancer patients are distinguishable from non-cancer patients. The accuracy computed by neural networks is greater than 80%.

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A new ligand has been synthesized by anchoring anthracene to l -methionine. The ligand enables easy identification of amino acids on thin-layer chromatography plates by developing distinguishable colors. This paper deals with the detailed synthesis, characterization, and application of the new ligand. Estimation of binding constants of this new ligand with different amino acids are also reported. A theoretical calculation ( Hartree-Fock ) has been performed to investigate interaction of the ligand with the amino acid.

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Adenoviral nucleic acid was detected by polymerase chain reaction (PCR) in formalin-fixed paraffin-embedded tissue samples of a cat that had suffered from disseminated adenovirus infection. The identity of the amplified products from the hexon and DNA-dependent DNA polymerase genes was confirmed by DNA sequencing. The sequences were clearly distinguishable from corresponding hexon and polymerase sequences of other mastadenoviruses, including human adenoviruses. These results suggest the possible existence of a distinct feline adenovirus.

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Abstract  

Crystallization of fat droplets in complex emulsions, which differed only by the initial structure of proteins, was studied by differential scanning calorimetry, before and after application of a whipping process. Upon cooling at 5 or 1°C min–1, the temperature needed to initiate fat crystallization was lower, and one more distinguishable crystallization peak was detected in emulsions containing caseins, in comparison with the emulsion containing pure whey proteins. Furthermore, the whipping process was accompanied by more protein depletion from the fat droplet surface, less resistance to coalescence, and a lower supercooling effect in the emulsion based on pure whey proteins.

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Abstract  

Fast neutron activation analysis (FNAA) was investigated as a possible on-site preliminary screening technique for metal contamination of soil. Two metals, Cu and Zn, were used in a laboratory setting to evaluate the possibility of detecting metal contamination of soil at or below the maximum permissible metal concentration in soil. Varying quantities of compounds of the selected metals were mixed into a prepared soil column for analysis of signal intensity as a function of concentration in the soil. Experiments were conducted with a sealed tube neutron generator and a germanium gamma-ray detector. Both metals produced signal levels distinguishable from background soil concentrations at the maximum permissible level.

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Abstract  

Neutron activation analysis, in combination with multivariate analysis of the generated data, was used for the chemical characterization of prehistoric pottery from the Greek islands of Thera, Melos (islands with similar geology) and Crete. The statistical procedure which proved that Theran pottery could be distinguishable from Melian, is described. This discrimination, attained for the first time, was mainly based on the concentrations of the trace elements Sm, Yb, Lu and Cr. Also, Cretan imports to both Thera and Melos were clearly separable from local wares.

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