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Abstract  

Temperature oscillation has been used in various applications of thermal analysis, such as relaxation, non-stoichiometry and chemical reactions. However, there are common essential points in these applications, and these are discussed in this short communication for further understanding significance of the temperature oscillation in thermal analysis.

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Abstract  

A small scale (100 mL) calorimeter is developed. It includes a glass vessel submerged in a thermostatic bath, a compensation electrical heater, and a control system. The typical operation mode consists on introducing the solvents and part of the reactants into the vessel, to stabilise a temperature of the bath (T j) some degrees below the desired process temperature (T p) and to adjust the reaction mass temperature (T r) to T p using the electrical heater. An oscillating set point is established for Tr, which produces an oscillating response of the applied compensation power (Q c). Finally, the rest of reactants are dosed to the vessel. A small deviation of T r and T p is observed. Even though it can be avoided improving the tuning of the controller, it can be useful for enhancing the calculation of the heat capacity of the reaction mixture (C P). The signals of T r, Q c and T j are processed on-line using the FFT (Fast Fourier Transform) method as the mathematical tool used to analyse the data obtained, producing accurate values of the heat evolved (Q c) by the process, the heat transfer coefficient (UA), and the heat capacity of the reaction mixture (C P).

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Daily body core temperature rhythm has been known to become blunted for several days following intra-abdominal implantation of biotelemetry transmitters in small rodents and about a week is required for re-establishment of stable body core temperature oscillation. In the present study carried out on mice it was found that a repetition of the same minor surgical intervention (laparotomy) several days apart could speed up the stabilization of body temperature oscillations. Melatonin supplied with the drinking water continuously was found to speed up the return of stable daily body temperature rhythm further on consecutive laparotomies, while daily injections of methylprednisolone resulted in some delay in the development of stable body core temperature oscillations. It is concluded that in C57BL/6 mice possessing low plasma levels of melatonin exhibit an adaptive response to repeated stresses influencing the dynamics of daily body temperature rhythm.

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Abstract  

Activation energies of ignition for the thermokinetic oscillations obtained during the heterogeneous catalytic oxidation of ethanol on Pd/Al2O3 in a dynamic calorimeter were obtained using the minimum values of the temperature oscillations. These activation energies of ignition are greater than the activation energies of the corresponding oscillations. The obtained results are discussed by assuming a PdOx redox cycle.

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Abstract  

Isothermal titration calorimetry (ITC) and reaction calorimetry (RC) have been used to construct the solid-liquid equilibrium line in ternary systems containing the solute to precipitate and an aqueous mixed solvent, and to study polymerization reactions under real process conditions, respectively. Phase diagrams have been established over the whole concentration range for some benzene substituted derivatives, including o-anisaldehyde, 1,3,5-trimethoxybenzene and vanillin, in {water + alcohol}mixtures at different temperatures. Acrylamide polymerization in aqueous solution using potassium permanganate/acid oxalic redox system as initiator was investigated on a homemade calorimeter, which works according to the isoperibolic mode. A Calvet type differential RC was used to illustrate the applicability of temperature oscillation calorimetry (TOC) for the evaluation of the heat transfer coefficient during the course of reaction.

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Palynological records helped to illuminate the past, but we show the take can be made much sharper when statistical analysis recognises the records' scale dependence. The latter is an unavoidable consequence of site selection, sediment sampling, and the samples' arrangement into time series by dating. To make provision for this in statistical analysis, scale has to be incorporated as one of the intrinsic variables. But by incorporating scale, the analysis will render the outcome not to be a single conclusion, the usual case in conventional statistics, but a multitude of conclusions each regarding the same set of response and forcing variables and each as valid at its own scale as any of the other conclusions at theirs. Thus, the central question for a usable Statistics is this: how to incorporate scale into the analysis and still have a unique conclusion. We address the methodological aspects and illustrate them by worked examples. We use 14 sites scattered across the globe. Interestingly, the analysis of these brought forth hitherto hidden aspects of the temporal synchronicity of change in palynological composition and concomitant atmospheric temperature oscillations that should greatly interest Ecology, as one critique put it, in the age of Global Change. The examples testify to a conceptual advance in laying open a very basic principle: the synchronicity's statistically strong formation specificity, dominantly positive (in frequency terms) for climate warming at sites in the currently humid, micro- and mesothermal zones, and negative in the currently arid and semi-arid zones. Our paper begins with an introduction to the terminology of multiscale analysis in Ecology, followed by data sources, the method we call canonical serial scaling, and objectives. A detailed discussion of data properties with special attention to error sources in palynology is provided. The method components discussed include the scalars of compositional transition and synchronicity, error dampening, stabilisation of the synchronicity scalar and its sign distribution, analysis of time shifted series, the use of deviation graphs, and pointers to help detect hotspots and other characteristic points of change on the time axis.

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. Thermochim Acta 2000 356 : 173 – 180 10.1016/S0040-6031(00)00517-7 . 4. Ozawa , T Further thoughts on temperature oscillation in thermal analysis . J Therm Anal Calorim 2003 73

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oscillations at ‘2&’ frequency. The temperature oscillations make the resistance of line heater vary at ‘2&’ frequency and consequently leading to voltage oscillations at ‘3&’ frequency. The thermal conductivity information of the underlying sample can be

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Journal of Thermal Analysis and Calorimetry
Authors: C. Gracia-Fernández, J. Tarrío-Saavedra, J. López-Beceiro, S. Gómez-Barreiro, S. Naya, and R. Artiaga

work is to investigate the ability of TMPDSC to evaluate the effect of pressure on the curing reaction of an epoxy system. TMDSC is a technique in which a sinusoidal temperature oscillation is superimposed upon a linear change in the underlying

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