Characteristic Thermogram Research Articles

The use of thermal analysis methods for conservation state determination of historical and/or cultural objects manufactured from lime tree wood

The TG, DTG and DSC methods were used for investigation of the thermo-oxidative degradation in static air atmosphere and oxygen flow of some sorts of lime tree wood (recent lime tree woods with different preparations, old lime tree woods extracted from some Romanian historical and/or cultural objects). At the progressive heating in the mentioned atmospheres, all the investigated materials exhibit three successive processes, associated with dehydration and two complex thermo-oxidative processes. Each analyzed material has a characteristic thermogram (TG, DTG and/or DSC curve) that can be considered a material “fingerprint”. It was pointed out that the following non-isothermal parameters can be used for distinction between a new and old lime tree wood: mass loss in the first process of thermo-oxidation, ratio between the mass losses in the first and the second processes of thermo-oxidation, the maximum rate of the first process of thermo-oxidation. Consequently, the certification of a patrimonial object manufactured from lime tree wood could be performed by applying the thermal analysis methods.

Calorimetry Outside the Box: A New Window into the Plasma Proteome

Differential scanning calorimetry provides a new window into the plasma proteome. Plasma from normal individuals yields a characteristic, reproducible thermogram that appears to represent the weighted sum of denaturation profiles of the most abundant constituent plasma proteins. Plasma from diseased individuals yields dramatically different signature thermograms. Thermograms from individuals suffering from rheumatoid arthritis, systemic lupus, and Lyme disease were measured. Each disease appears to have a distinctive and characteristic thermogram. The difference in thermograms between normal and diseased individuals is not caused by radical changes in the concentrations of the most abundant plasma proteins but rather appears to result from interaction of as yet unknown biomarkers with the major plasma proteins. These results signal a novel use for calorimetry as a diagnostic tool.

Physical, mechanical, and thermal properties of PVC/PMMA blends in relation to their morphologies

AbstractThe effect of blending poly (methyl methacrylate) (PMMA) in various proportions with suitably stabilized and plasticized poly (vinyl chloride) (PVC) was studied with reference to their physical, mechanical, and thermal properties. The resulting morphologies of the various blends were also studied to find a suitable explanation of these properties. The physical and mechanical properties of such polyblends revealed a substantial increase in toughness accompanied with unusual increase in modulus and ultimate tensile strength after an initial drop at the initial stages of PMMA incorporation compared to pure reference compound PVC. The toughening effect, however, undergoes a reduction with increasing proportion of PMMA but it never goes below that of pure PVC (reference compound) within the ranges of PMMA incorporation under study. The various polyblends exhibit the two‐stage degradation typical of PVC and all of them possess higher thermal stability as manifested in their characteristic thermograms. The softening characteristics imparted by PMMA were also reflected in their respective TMA curves. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2721–2730, 2004

Use of Thermal Analysis for Study of Characterisation of Multimetal Sulphides and Their Oxidation Behaviour

Although extensive literature is available on thermal analysis work describing oxidation behaviour of sulphide minerals this is mostly confined to simpler and often ideal systems. For technological purposes, a more complete characterisation of the natural metal sulphides and bulk concentrates is highly warranted. However, the oxidation reactions of these minerals are often complex. This is especially true for the oxidation of multimetal sulphides for which the characteristic thermograms are generally quite different from those for analytical grade reagents due to many pernicious interactions. This paper presents a comprehensive review of thermoanalytical studies on sulphide minerals and bulk concentrates. It also discusses possible uses of thermal analysis for understanding oxidation reactions during roasting and/or leaching.

Establishment of the Characteristic Thermogram Equation of Conduction Calorimeter

Establishment of the Characteristic Thermogram Equation of Conduction Calorimeter

Microcalorimetric investigations on Listeria

Sixty-one Listeria strains--Listeria monocytogenes (35 strains), Listeria ivanovii (8), Listeria innocua (7), Listeria welshimeri (6) and Listeria seeligeri (5)--were tested microcalorimetrically for their heat production upon growth in Columbia broth. Listeria ivanovii and Listeria seeligeri displayed different and quite characteristic thermograms. Listeria welshimeri, Listeria innocua and all but one of the Listeria monocytogenes strains showed similar microcalorimetric curves, which differed considerably from those of Listeria ivanovii and Listeria seeligeri.

Thermal decomposition characteristics in air and their relationship with electrochemical activity of different polymorphic forms of MnO2

Thermal decomposition characteristics of various synthetic MnO2 samples were studied with the help of DTA and TG in air. Each crystalline modification group produced its own characteristic thermogram which could be distinguished from the thermogram of other modifications. However, there were a few instances of overlapping, because some samples were not truly homogeneous and contained one or more polymorphic forms as impurities. The results indicate that relationships exist between electrochemical activity and DTA peak temperature for the loss of initial molecular water on the one hand, and DTA peak temperature for the decomposition of MnO2 to Mn2O3, on the other hand. The amount of combined water determined by the difference in weight loss at 400 and 200°C was found to be related to the electrochemical activity or depolarizing capacity of the samples.

The Influence of Processing Parameters on Food Protein Functionality I. Differential Scanning Calorimetry as an Indicator of Protein Denaturation

Heat denaturation of several proteins from plant sources was studied using differential scanning calorimetry (DSC). Differences in temperatures of denaturation (Td), overall thermal transitions (ΔH), and half band widths (HBW) were noted for these proteins, with oats having the highest Td (112°C) and ΔH (4.45 cal·g−1) and the lowest HBW (9.2°C). Vital gluten, on the other hand, did not exhibit a characteristic thermogram so these parameters could not be measured. Using fababean protein as a model system, heat denaturation was shown to be irreversible. The effect of pH on the heat stability of the fababean protein indicated decreases in Td and ΔH on either side of the isoelectric point to a situation where the protein was believed to be completely denatured if the pH were taken below pH 2.5 or above 11.5. The irreversibility of this phenomenon in the alkaline region was demonstrated by DSC of alkaline extracted, isoelectrically precipitated fababean protein isolates.

Identifying Scoliosis in the Adolescent with Thermography

Early diagnosis of adolescent idiopathic scoliosis is essential to prevent severe deformity. The accuracy of thermographic examination of the spine in the detection of minor degrees of curvature has been assessed in 125 asymptomatic young persons mean age 13.4 +/- 0.8 years who were also examined clinically and by spinal X-ray. Assessment of thermograms selected at random from the group of 154 young subjects showed that thermography has a sensitivity of 98.2% and a specificity of 91.0% in the identification of scoliosis when compared with radiography. Thermographic examination of the spine is simple, noninvasive and provides a permanent recording which is easily interpreted. It may provide an ideal method for use in large-scale prospective surveys. The criteria used to detect the thermographic abnormality associated with idiopathic scoliosis was derived from the spinal thermograms of 29 patients, mean age 10.25 +/- 4.65 years with known scoliosis, mean angle of curve 27 degrees +/- 12 degrees. In contrast to the thermal symmetry of the normal spine, all the thermograms of these patients show asymmetry, characteristically an increase in thermal emission on the concave aspect of the curve. Eight of the 16 patients with scoliosis with minor curves and a characteristic thermogram were not detected clinically. There were 25 asymmetrical thermograms in the asymptomatic group. Three of these patients had a simple postural defect, 5 had dorsal kyphosis and 16 had idiopathic scoliosis. Postural defects and kyphosis were readily recognized on clinical examination and did not produce the characteristic scoliotic thermogram.

Differential thermographic features of some crystalline biopolymers

AbstractCrystalline proteins, nucleic acids, nucleotides, and nucleosides have been examined by differential thermal analysis. Characteristic thermograms are illustrated for globular, serum, and blood plasma proteins, calf thymus DNA, sodium triticonucleate, sodium thymonucleate, sperm DNA, yeast RNA, adenosine‐3′‐phosphate, adenosine‐5′‐phosphate, disodium adenosine triphosphate, adenosine, and deoxyadenosine. A pronounced effect of moisture on the differential thermal properties of DNA has been observed. It is suggested that solid‐state denaturation is one of the prominent thermal effects recorded by the differential thermal analysis of proteins and nucleic acids.

Basic Dyestuffs in Clay Mineralogy

BASIC dyestufs are adsorbed on clay minerals by cation exchange reaction. The amount of dye adsorbed1 and the resulting colour transformations2 provide a possible basis for identifying clay minerals, but they are not very reliable. We have found that clay mineral–dye complexes exhibit characteristic thermograms and this method may possibly be applicable to the identification of clay mineral. Certain clay minerals which exhibit similar thermograms can be differentiated by the thermograms of their dye complexes.