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Abstract  

Scintillation cocktail components were studied with regard to their impact on pulse decay discimination (PDD) and hence the separation of alpha from beta activity, using a Packard 2250 CA /. Di-isopropyl naphthalene (DIN) was found to be the most suitable solvent, both from safety considerations and also the fact that it acts in a very similar manner to naphthalene in stretching the pulses produced at the photomultiplier tube anode and hence enhancing the separation. Increasing the surfactant concentration and the use of dimethylanthracene (DMA) as secondary fluor degraded the cocktail's performance. PMT anode pulse shapes were found to be a useful indicator of PDD efficiency but could not give a quantitative guide.

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Abstract  

The activation energy associated with the glass transition relaxation of an epoxy system has been determined by using the three-point bending clamp provided in the recently introduced TA Instruments DMA 2980 dynamic mechanical analyzer. A mathematical expression showing the dependency of modulus measurements on the sample properties and test conditions has also been derived. The experimental results showed that the evaluation of activation energy is affected by the heating rate and test frequency, as well as the criterion by which the glass transition temperature (T g) is established. It has been found that the activation energy based on the loss tangent (tanδ) peak is more reliable than on the loss modulus (E 2) peak, as long as the dynamic test conditions do not cause excessive thermal lags.

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Determination of experimental excess molar properties for MTBE+1-propanol+octane

Analysis and comparison with different theoretical methods

Journal of Thermal Analysis and Calorimetry
Authors: M. M. Mato, S. M. Cebreiro, P. V. Verdes, J. L. Legido, and M. I. Paz Andrade

Summary Experimental excess molar enthalpies and densities have been measured for the ternary mixture x 1MTBE+x 21-propanol+(1-x 1-x 2)octane and the involved binary mixtures at 298.15 K and atmospheric pressure. In addition, excess molar volumes were determined from the densities of the pure liquids and mixtures. A standard Calvet microcalorimeter was employed to determine the excess molar enthalpies. Densities were measured using a DMA 4500 Anton Paar densimeter. The UNIFAC group contribution model (in the versions of Larsen et al., and Gmehling et al.) has been used to estimate excess enthalpies values. Experimental data were also used to test several empirical expressions for estimating ternary properties from experimental binary results.

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Summary Densities at 298.15 K and atmospheric pressure have been measured, using a DMA 4500 Anton Paar densimeter, for the ternary mixture methyl tert-butyl ether (MTBE)+1-pentanol+decane and for the involved binary mixtures MTBE+1-pentanol and 1-pentanol+decane. The excess molar volumes for the binary mixture MTBE+decane was reported in an earlier work [1]. In addition, excess molar volumes were determined from the densities of the pure liquids and mixtures. Suitable fitting equations have been used in order to correlate adequately the excess molar volumes. The empirical expressions of Kohler [18], Jacob and Fitzner [19], Colinet [20], Knobeloch and Schwartz [21], Tsao and Smith [22], Toop [23], Scatchard et al. [24], Hillert [25], Mathieson and Thynne [26] were applied to estimate ternary properties from binary results.

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Experimental and predicted excess molar volumes of the ternary system.

Tert-butylmethylether+1-propanol+heptane at 298.15 K

Journal of Thermal Analysis and Calorimetry
Authors: M. M. Mato, S. M. Cebreiro, P. V. Verdes, A. V. Pallas, J. L. Legido, and M. I. Paz Andrade

Summary Experimental excess molar volumes for the ternary system x 1MTBE+x 21-propanol+(1-x 1-x 2) heptane and the three involved binary mixtures have been determined at 298.15 K and atmospheric pressure. Excess molar volumes were determined from the densities of the pure liquids and mixtures, using a DMA 4500 Anton Paar densimeter. The ternary mixture shows maximum values around the binary mixture MTBE+heptane and minimum values for the mixture MTBE+propanol. The ternary contribution to the excess molar volume is negative, with the exception of a range located around the rich compositions of 1-propanol. Several empirical equations predicting ternary mixture properties from experimental binary mixtures have been applied.

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Abstract  

The dissolution enthalpies of glycine in aqueous solutions of acetamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylformamide, N,N-diethylformamide and N,N-diethylacetamide were measured at 298.15 K. The enthalpic pair interaction coefficients of glycine zwitterion-amide molecules were determined by using standard solution enthalpies of glycine in water and aqueous solutions of amides. The additivity of groups concept of Savage and Wood was used to estimate the contribution of each of the functional groups of the studied amides.

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Abstract  

The [InCl3(L)n] (where L is 2,2′-bipyridine (bipy), 2,2′-bipyridine N,N′-dioxide (bipyNO), N,N-dimethylacetamide (dma), urea (u), thiourea (tu) or 1,1,3,3-tetramethylthiourea (tmtu); n = 1.5, 3 or 4) were synthesized and characterized by melting points, elemental analysis, thermal analysis and IR spectroscopy. The enthalpies of dissolution of the adducts, Indium(III) chloride and ligands in 1.2 M aqueous HCl were measured and by using thermochemical cycles, the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reactions (Δr H θ), the standard enthalpies of formation (Δf H θ), the lattice standard enthalpies (ΔM H θ), and the standard enthalpies of decomposition (ΔD H θ).

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In the present study, we developed a simple, sensitive, and selective thin-layer chromatographic method for the detection and identification of amitraz using chloranil as chromogenic spray. In the first step, amitraz was hydrolized by using 10% sodium hydroxide solution in water to give dimethylaniline (DMA) and N-2,4-dimethylphenyl- N-methyl formamidine (DMPMF). The dimethylaniline further treated with chloranil in acetone gives blue spot. This spray reagent does not react with other organophosphorous, organochloro, carbamate, and synthetic pyrethroid insecticides. This reagent is sensitive and selective only to amitraz. The constituents of viscera (amino acids, peptides, and proteins) do not interfere with the test. The detection limit for amitraz is about 0.7 µg.

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Abstract  

Inorganic arsenic, MMA, DMA and arsenobetaine (As) were separated by the use of cation and anion exchange chromatography combined with neutron activation. Two complementary approaches were used: firstly, authentic, non-irradiated arsenic compounds, either singly or in mixtures, were separated and NAA of the fractions used as an element specific detection method. Secondly, the arsenic compounds were neutron irradiated under different conditions and for different times and the products separated and quantified. The76As labeled species (mono-, di and trimethylated) were then additionally used to calibrate and improve the column separations. Using the separations developed, arsenic species in samples of shrimps and the standard reference material DORM-1 were determined, after an extraction step, using ion exchange chromatography followed by INAA of the fractions collected.

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Journal of Thermal Analysis and Calorimetry
Authors: M. Mato, S. Cebreiro, J. Legido, and M. Paz Andrade

Abstract  

Experimental excess molar volumes for the ternary system {x 1MTBE+x 21-propanol+(1–x 1x 2)nonane} and the three involved binary mixtures have been determined at 298.15 K and atmospheric pressure. Excess molar volumes were determined from the densities of the pure liquids and mixtures, using a DMA 4500 Anton Paar densimeter. The ternary mixture shows maximum values around the binary mixture MTBE+nonane and minimum values for the mixture MTBE+propanol. The ternary contribution to the excess molar volume is negative, with the exception of a range located around the rich compositions of 1-propanol. Several empirical equations predicting ternary mixture properties from experimental binary mixtures have been applied.

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