Ternary mixture MTBE+1-pentanol+nonane at 298.15 K and atmospheric pressure

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+nonane and for the involved binary mixture 1-pentanol+nonane. 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. Experimental data were also used to test several empirical expressions for estimating ternary properties from experimental binary results.     

Temperature dependence of thermophysical properties of octane+1-butanol system

The aim of this work is to complete our studies on physical properties of binary mixtures of alkane+1-alkanols. This work reports densities, refractive indices, speeds of sound and isentropic compressibilities of the mixture octane + 1-butanol at different temperatures, from 288.15 to 308.15 K. From the experimental values, the corresponding excess and deviation values were computed (excess molar volumes, changes of refractive index on mixing, changes of speed of sound on mixing and changes of isentropic compressibilities on mixing). The results were fitted to variable-degree polynomials. Excess molar volumes were compared with the predictions of Nitta-Chao Group Contribution Model. This revised version was published online in July 2006 with corrections to the Cover Date.     

Liquid chromatography–mass spectrometry methods for urinary biomarker detection in metabonomic studies with application to nutritional studies

The effects of sample preparation and chromatographic method differences on the classification and recovery of metabolic biomarkers from UPLC‐MS measurements on urine samples of humans exposed to different dietary interventions have been investigated. Eight volunteers consumed three high‐fat meals (rich in saturated, monounsaturated and polyunsaturated fatty acids, respectively) in randomized order with a washout period in between. For each participant, urine samples were obtained prior to and at three timed intervals after each meal. Samples were processed either by dilution (1 : 4) or by liquid–liquid extraction and then run under two different gradient conditions. For each analysis method, a total of 96 observations (eight participants, four time points, three diets) were measured. The total ion count chromatograms were analyzed using partial‐least‐squares discriminant analysis. All three dietary classes could be discriminated irrespective of sample preparation and chromatographic method. However, the main discriminating metabolites varied according to sample preparation, indicating that sample treatment and chromatographic conditions influence the ability to extract biomolecular information. Diluted samples showed higher m/z compounds (ca 400 u) while liquid–liquid extraction samples showed low m/z at the same retention time span. Optimized methods for metabolite identification (e.g. organic acids) were statistically inferior to global screening for mixed compound identification, confirming that multiple compound class‐based metabolic profiles are likely to give superior metabonomic (diagnostic) classification, although great care has to be taken in the interpretation in relation to matrix effects. Copyright © 2009 John Wiley & Sons, Ltd.     

Excess molar enthalpies of dichloropropane + <Emphasis Type="Italic">n</Emphasis>-alkane mixtures

We have determined the excess molar enthalpies H_\textm^\textE H_{\text{m}}^{\text{E}} at 298.15 K and normal atmospheric pressure for the binary mixtures containing dichloropropane and n-alkane [{xCH₂ClCHClCH₃ + (1−x) C _n H_2n+2 (n = 6, 8, 10, 12)} and {xCH₂ClCH₂CH₂Cl + (1−x) C _n H_2n+2 (n = 8, 10)}] using a Calvet microcalorimeter. The H_\textm^\textE H_{\text{m}}^{\text{E}} values for all the mixtures show endothermic behaviour for the whole composition range. The Redlich–Kister equation was used to correlated the experimental values. The experimental excess molar enthalpies were examined on basis of the DISQUAC group-contribution model and the UNIFAC group-contribution method using the version considered by Larsen et al. The experimental and calculated results are discussed in terms of molecular interactions and the proximity effect.     

Microcalorimetric study of the growth of <Emphasis Type="Italic">Enterococcus faecalis</Emphasis> in an enriched culture medium

Enterococcus faecalis is a Gram-positive bacteria, considered one of the most common causes of nosocomial infections. Bacterial cultures produce an exchange of energy as a result of the bacteria metabolisms. The rate of heat production is an adequate measure of the metabolic activity of the organisms and their constituent parts. Microorganisms produce small amounts of heat: 1–3 pW per cell. Although the heat produced by bacteria is very small, their exponential reproduction in a culture medium permits heat detection through microcalorimetry. In this study, we analyzed the microcalorimetric behavior of Enterococcus faecalis. A thermal Calvet microcalorimeter was used. The inside of the calorimeter contains two stainless steel cells (experimental and reference). Experiments were carried out at final concentrations of 10⁶,10⁵,10³, and 10 CFU/mL and a constant temperature of 309.65 K was maintained within the microcalorimeter. Recording the difference in calorific potential over time we obtained E. faecalis’s growth curves. Thermograms were analyzed mathematically allowing us to calculate the constant growth, generation time and the amount of heat exchanged over the culture time.     

Study on the effect of increasing the chain length of the alkanol in excess molar enthalpies of mixtures containing 2-methoxy-2-methylpropane, 1-alkanol,decane

Excess molar enthalpies for the ternary system {x₁ 2-methoxy-2-methylpropane + x₂ ethanol + (1 − x₁ − x₂) decane} and the involved binary mixture {x ethanol + (1 − x) decane} have been measured at the temperature of 298.15 K and atmospheric pressure, over the whole composition range. No experimental excess enthalpy values were found in the currently available literature for the ternary mixture under study. The results were fitted by means of different variable-degree polynomials. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The excess molar enthalpies for the binary and ternary system are positive over the whole range of composition. The binary mixture {x ethanol + (1 − x) decane} is asymmetric, with its maximum displace toward a high mole fraction of decane. The ternary contribution is also positive, and the representation is asymmetric.     

A Study of Excess Molar Enthalpies and Excess Molar Volumes of Binary Mixtures of 1-Chloropentane + 1-Alkanol (from 1-Butanol to 1-Octanol) at 25°C.

Excess molar enthalpies H ^E _mand excess molar volumes V ^E _m at 25°Cand normal atmospheric pressure for the binary mixtures 1-chloropentane + 1-alkanol(from 1-butanol to 1-octanol) have been determined using a Calvet microcalorimeterand from density measurements using a vibrating tube densimeter. The H ^E _m valuesfor all the mixtures are positive and V ^E _m values are positive or negative dependingon the mole fraction of the chloroalkane. Experimental H ^E _m results are comparedwith the predictions of UNIFAC group-contribution models proposed by Dang andTassios and by Larsen et al., and are discussed in terms of molecular interactions.     

Thermal conductivity and specific heat capacity measurements of Al2O3 nanofluids

Thermal conductivities and specific heat capacities of nanoparticles of Al₂O₃ dispersed in water and ethylene glycol as a function of the particle volume fraction and at temperatures between 298 and 338 K were measured. The steady-state coaxial cylinders method, using a C80D microcalorimeter (Setaram, France) equipped with special calorimetric vessels, was used for the thermal conductivities measurements. The heat capacities were measured with a Micro DSC II microcalorimeter (Setaram, France) with batch cells designed in our laboratory and the “scanning or continuous method.” The Hamilton–Crosser model properly accounts for the thermal conductivity of the studied nanofluids. Assuming that the nanoparticles and the base fluid are in thermal equilibrium, the experimental specific heat capacities of nanofluids are correctly justified.     

Microcalorimetric study of the growth of Enterococcus faecalis, Klebsiella pneumoniae and their mixtures in an enriched culture medium

In the last few years there has been a growing interest in microcalorimetric investigations of microbial processes. Microcalorimetry is a technique based on heat output of bacterial metabolism which can be applied to detect bacterial growth in a few hours. However, there are few studies that attempt to investigate the interactions between two or more bacteria. In this study, we researched the interaction relationship of Enterococcus faecalis and Klebsiella pneumoniae, which are important pathogens responsible for infections in humans. The measures were carried out using a Calvet microcalorimeter, that contains two stainless steel cells of approximately 10 cm³ (reference and experimental). Experiments were carried out at concentration of 10³ CFU mL^?1 and a constant temperature of 309.65 K. The differences in shape of the heat flow-time curves of E. faecalis and K. pneumoniae and their mixtures were compared. Curves of E. faecalis and K. pneumoniae and their mixtures were analyzed mathematically allowing to calculate thermokinetic parameters such as growth constant (k), generation time (G), detection time (t _d) and the amount of heat released (Q). The results revealed that when E. faecalis and K. pneumoniae were put together in the same proportion, the growth character of E. faecalis was not present, due to the inhibitory effects of K. pneumoniae on E. faecalis. Microcalorimetric investigations of microbial interactions is possible and promising.     

Study on volumetric measurement and correlations for MTBE+1-propanol+decane at 298.15 K and atmospheric pressure

Summary Experimental densities for the ternary mixture x₁MTBE+x₂1-propanol+(1-x₁-x₂)decane and the binary mixtures xMTBE +(1-x)1-propanol and x1-propanol+(1-x)decane have been measured at 298.15 K and atmospheric pressure, using a DMA 4500 Anton Paar densimeter. Excess molar volumes were determined from the densities of the pure liquids and mixtures. Attending to the symmetry of the studied mixtures, suitable fitting equations have been used in order to correlate adequately the experimental data. For the ternary mixture, experimental data were also used to test several empirical expressions for estimating ternary properties from experimental binary results.