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Flame propagation over liquid alcohols

Part I. Experimental results

Journal of Thermal Analysis and Calorimetry
Authors:
E. Degroote
and
P. L. García Ybarra

Summary The different spreading regimes above liquid fuels have been experimentally described for a wide range of initial surface temperatures. Five different spreading regimes are observed. The flame spreading driving parameter has been found. The critical transition temperatures between these regimes have been characterized; they present common characteristics for the four alcohols (methanol, ethanol, propanol and butanol) used in the experiments. A preheating zone ahead of the flame (produced by thermocapillarity) has been observed. The initial surface temperature of the liquid fuel results to be a control parameter of flame spreading; therefore, it can be applied to improve fire safety conditions in fuel containers.

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Flame propagation over liquid alcohols

Part II. Steady propagation regimes

Journal of Thermal Analysis and Calorimetry
Authors:
E. Degroote
and
P. L. García Ybarra

Summary The different spreading regimes above liquid fuels have been experimentally characterized for surface temperatures close to the flash-point temperature. Two different spreading regimes are observed: for temperatures larger than some critical value, flame spreading velocity is well described by the De Ris solid fuel-like model. For temperature values lower than the critical one, a preheating thermocapillary region has been observed in the fuel, which can be described by a purely thermodynamic non-reactive model. The critical transition temperature has shown to present common characteristics for the four alcohols used in the experiments.

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Flame propagation over liquid alcohols

Part III. Pulsating regime

Journal of Thermal Analysis and Calorimetry
Authors:
E. Degroote
and
P. L. García Ybarra

Summary The pulsating regime of flame spreading liquid fuels has been experimentally characterized. The mechanism that produces this oscillating behavior has been proposed, that correlates very well with our experimental data. The existence of a preheated region preceding the flame has been found; the characteristic horizontal length has also been experimentally measured. The transition temperatures have been found to possess common features for all fuels and geometrical configurations used in our experiments that can be used to improve fire safety in fuel containers.

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Abstract  

99mTc hexakis (2-methoxyisobutylisonitrile) is a cationic complex useful as a myocardial perfusion agent. The synthesis of 2-methoxyisobutylisonitrile (MIBI) by a modified and improved procedure in a two-step process with an overall yield of 53% is described. The preparation of its copper and technetium-99m complexes is also presented.

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Abstract  

Polycrystalline titanium samples were oxidized in pure oxygen under a 75 torr pressure, at temperatures ranging from 400°C to 500°C, and for times up to 2 hrs. A similar treatment was applied to some single crystal samples, so as to show the relationship between the crystallite orientation and the oxidation rate. The oxide films were studied by means of radioanalytical techniques, such as nuclear microanalysis, electron diffraction and ESCA, in addition to most classical techniques such as optical and electron microscopy. The complementary side of these methods is showed. They permit us to determine the contamination of the metallic surface introduced by the polishing treatments, the oxidation rate at constant temperature, and the structure of the oxides which exists in the films. These ones are especially TiO2, Ti3O5, Ti2O3 and TiO.

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Abstract  

Thermogravimetry technique is useful to determine the thermal stability of vegetable oils. In this paper some vegetable oils obtained from brazilian Cerrado native plants were studied based on their high oleic acid content. Amburana, baru and pequi pulp oils presented higher yield of extraction compared to soybean oil. The thermal stability of oils in nitrogen was very close hence their fatty acid composition was very similar. Amburana and baru oils have major amount of unsaturated fatty acids, especially linoleic acid and pequi pulp oil has the highest short chain fatty acid content which can explain its lowest thermal stability in synthetic air.

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Studies of surface properties of Na- and La-montmorillonites

Thermogravimetry Q-TG, sorptometry, porosimetry and AFM methods

Journal of Thermal Analysis and Calorimetry
Authors:
P. Staszczuk
,
J. Bazan
,
M. Błachnio
,
D. Sternik
, and
N. Garcia

Abstract  

This paper presents possible applications of thermal analysis, sorptometry and porosimetry to study physico-chemical properties of Na- and La-montmorillonite samples, especially for determination of total surface heterogeneity. The quasi-isothermal thermogravimetric (Q-TG) mass loss and its first derivative (Q-DTG) curves with respect to temperature and time obtained during programmed liquid thermodesorption under quasi-isothermal conditions have been used to study adsorbed layers and heterogeneous properties of the Na- and La-montmorillonites. Calculations of the desorption energy distribution functions by analytical procedure using mass loss Q-TG and differential mass loss Q-DTG curves of thermodesorption under quasi-isothermal conditions of polar and non-polar liquid vapours preadsorbed on a material surface are presented. Parameters relating to porosity of samples were determined by sorptometry, mercury porosimetry and atomic force microscopy (AFM). From nitrogen sorption isotherms from sorptometry and porosimetry methods, the fractal dimensions of montmorillonites have been calculated. Moreover, a new approach is proposed to calculate fractal dimensions of materials obtained from Q-TG curve; this is compared with values obtained by the above methods. The total heterogeneous properties (energy distribution function and pore-size distribution functions) of samples studied were estimated. The radius and pore volume of the tested samples calculated on the basis of thermogravimetry, sorptometry and porosimetry techniques were compared and good correlations obtained.

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Summary The disposal of used automotive tires has caused many environmental and economical problems to most countries. We propose the use of rice husk as filler for increasing the value of recycled tire rubber. Thermal degradation of both components and their sintering mixtures is presented in this paper. Thermal decomposition of rice husk occurs in various steps in the temperature range between 150 and 550°C. This complex process is the result of the overlapping of thermal decomposition of the three major constituents common in all lignocellulosic materials, i.e., hemicellulose, lignin and cellulose. Hemicellulose is degraded at temperatures between 150 and 350°C, cellulose from 275 to 380°C and lignin from 250 to 550°C. The degradation process of major constituents of scrap tires or their composites is observed at temperatures between 150 and 550°C. For composites, the addition of rice husk (maximum 25%) produces an increase in the mass loss rate. This effect is higher as the amount of rice husk increases. However, the degradation initial temperature of elastomeric matrix is not affected with addition of rice husk. Apparent kinetic parameters were also studied by the isoconversional Friedman method. We observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed.

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Abstract  

The precipitation of uranyl ion with 2-hydroxy-1-naphthaldehyde /2H–1N=HL/ was studied. The solid complex /orange crystals/ was characterized by IR, UV-Vis spectra. Uranium was determined as U3O8 after calcination of the complex at 850°C /37.78% U experimental, 36.64% U calculated for C22H14O6U, UO2L2/. Using a statistical experimental design, the best conditions for quantitative precipitation were obtained. A gravimetric method for the determination of UO 2 2+ is proposed by weighing the complex after drying at 110°C.

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Bacillus subtilis natto is a potential source of fructooligosaccharides (FOS), which can be obtained by fermentation and may stimulate the growth of beneficial microorganisms in the colon representing a strategy to manipulate the intestinal microbiota acting as a prebiotic compound. The present study focuses on the ability of Lactobacillus ssp. strains to utilize FOS as a sole energy source. The results showed that FOS was equally good as glucose to provide energy source. The highest prebiotic activity score was obtained with Lactobacillus plantarum ATCC 14917 grown on FOS (0.526), followed by Lactobacillus casei (LC-1) (0.222). The lowest score was for Lactobacillus paracasei ATCC 27092 (−0.051). The results suggests that specific combinations of probiotic (L. plantarum ATCC 14917 and L. casei (LC-1)) and prebiotic (FOS) could be used as synbiotics in dairy and other foods.

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