Excess enthalpies of binary mixtures of 2-, 3-, 4-picoline+n-alkane (C6H14-C10H22) at 298.15 K. Comparison with theory

The molar excess enthalpies measured for binary mixtures of 2-, 3-, 4-picoline +n-alkane (C₆H₁₄-C₁₀H₂₂) at 298.15 K have been compared with the Prigogine-Flory-Patterson theory and the Extended Real Associated Solution model estimations.

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Zusammenfassung Die bei 298.15 K gemessenen molaren Zusatzenthalpien binärer Mischungen aus 2-,3-,4-Picolin und einemn-Alkan (C₆H₁₄-C₁₀H₂₂) wurden mit den nach der Prigonine-Flory-Patterson-Theorie und den nach dem erweiterten Modell real assoziierter Lösungen (ERAS) berechneten Weiten verglichen.

     

Identification of novel antitumor agents from mixture-based synthetic combinatorial libraries using cell-based assays

A new strategy is presented here which integrates combinatorial library technology with the antitumor in vitro screening system at the National Cancer Institute in the search for novel antitumor agents. Mixture-based synthetic combinatorial libraries (SCLs) representing hundreds of thousands to millions of individual compounds were screened against the cell-based assay, which evaluates compounds for their ability to inhibit the growth of 60 different human tumor cell lines. Five different SCLs, composed of peptides, peptidomimetics, polyamines or small molecules were first tested against three cell lines to identify the most active SCLs. Two SCLs, namely the N-perbenzylated pentamine and the N-acylated permethylated triamine, were deconvoluted to yield individual compounds having significant activities against the 60 tumor cell lines. Active compounds were tested in mice to determine the maximum tolerated dose, followed by in vivo testing in a hollow fiber assay. Using this strategy, three different compounds identified directly from SCLs are currently being evaluated in human tumor xenografts. This study demonstrates for the first time the use of in vitro cell-based assays to identify antitumor lead compounds from mixture-based combinatorial libraries.     

Pinning and long-time-scale behavior in traveling-wave convection

We study nonlinear traveling-wave (TW) and stationary states of convection in experiments in ethanol-water mixtures. While the TW phase velocity as a function of Rayleigh number has been recently shown to be in agreement with the predictions of theory and numerical calculations, we find that this velocity is temporally modulated at frequencies corresponding to the travel time of a single convection roll and of a roll pair past a point stationary in the convection cell. This modulation could be due to the pinning of the convection pattern by experimental inhomogeneities. For large Rayleigh numbers where stationary overturning convection is expected, we sometimes observe extremely slow unidirectional TW states. For larger Rayleigh numbers, this slow TW state starts and stops intermittently on a characteristic time scale of several days. The possible origin of these phenomena and their potential utility are discussed.     

Prediction of miscibility regions in ternary blends of poly(styrene-stat-acrylonitrile), poly(acrylonitrile-stat-methyl methacrylate), and poly(styrene-stat-methyl methacrylate)

The miscibilities of ternary copolymer blends prepared from poly(styrene-stat-acrylonitrile), poly(styrene-stat-methyl methacrylate), and poly(methyl methacrylate-stat-acrylonitrile) were predicted by calculating the interaction parameter, χ_blend, for various blend combinations, from the corresponding binary segmental interaction parameters estimated from previous work. Binodal and spinodal curves were calculated using the Flory-Huggins theory and it was observed that the most accurate estimate of the boundary between miscible and immiscible blends was given by the spinodal. It has also been demonstrated that in some of the ternary blends with fixed copolymer compositions the miscibility of the blend can be altered by changing the ratio of the three components in the mixture. Conditions for miscibility in this ternary system, and possibly a general feature of all such systems, are (a) that at least two of the binary interaction parameters χ_ij are less than the critical value χ_crit, while the third should not be too much larger, that is, one of the copolymers may act as a compatibilizer for the other two copolymers, (b) that the difference Δχ = /χ₁₂ ? χ₁₃/ is small. © 1992 John Wiley & Sons, Inc.     

Interaction enthalpy of lysozyme with vesicles

Negatively charged vesicles made of non-stoichiometric amounts of sodium dodecylsulfate and cetyltrimethylammonium bromide were characterised by physico-chemical methods. Interactions with lysozyme were examined by calorimetry. A remarkable heat effect is observed upon diluting the protein with the vesicular pseudo-solvent. The maximum ΔH_bind value occurs at complete vesicle charge neutralisation by the protein.     

Freezing points and related properties of electrolyte solutions. II. Mixtures of lithium chloride and sodium chloride in water

The freezing points of aqueous lithium chloride and its mixtures with sodium chloride have been measured from 0.1 to 1.5m. From these measurements, calorimetric enthalpies of mixing, and osmotic coefficients of the pure salts at 298°K, osmotic and activity coefficients of the mixtures have been calculated up to 6.0m at 298°K. Excellent agreement with the literature values is found over the entire range of composition. This method of computation is considered to be superior to the analysis of only isopiestic results in the calculation of activity coefficients in mixed electrolytes.     

Solution thermodynamics for alkoxy phenols in alcohol and in water-alcohol systems

Solubilities have been measured for m-alkoxyphenols in water-alcohol mixtures. The alcohols ranged from the co-solvent methanol to the co-solute 1-octanol, and each alcohol was present at the saturating concentration of 1-octanol in water viz. 0.00316M. Plots of sobubility vs. carbon number of the alcohols show discontinuities. Enthalpies of solution in these same solvent systems have also been measured. The enthalpies of solution and the derived enthalpies of transfer both support the observations on solubilities. The results are discussed on the basis of solvent-solute interactions and in terms of solute volumes.     

Activity coefficients of hexaamminecobalt(III) oxalate and hexacyanoferrate(III) in aqueous solutions of higher valent electrolytes at 25°C

The solubilities of hexaamminecobalt(III) oxalate and hexaamminecobalt(III) hexacyanoferrate(III) in aqueous solutions of different 1-2, 2-1 and 2-2 electrolytes were measured at 25°C. The results have been used to evaluate the relative activity coefficient of the saturating salts.     

Speed of sound and isentropic compressibilities of nonelectrolyte liquid mixtures. I. Binary mixtures containingp-dioxane

The speed of sound was measured for mixtures of p-dioxane with cyclohexane, n-hexane, benzene, toluene, carbon tetrachloride, chloroform, 1,1,2,2-tetrachloroethane, pentachloroethane and ethyl acetate over the whole mole fraction range at 30°C. These data were combined with densities and molar volumes to obtain isentropic compressibilities and Rao's molar sound functions. Excess isentropic compressibilities and excess speeds of sound have also been calculated. The behavior of the present mixtures is discussed in terms of possible molecular interactions and the Prigogine-Flory-Patterson theory of liquid mixtures.     

Effects of sodium concentration on the morphology and rheological behaviour of alkoxide-carboxylate co-ionomeric mixtures of phenoxy and ethylene terpolymers

Mixtures at various weight ratios of phenoxy (PH) and a terpolymer of ethylene tert. butyl acrylate-acrylic acid (EAA) were prepared in a Brabender Plasticorder in the presence of different amounts of sodium ethoxide (NaOEt). The mixtures were examined by SEM, DSC, and dynamic rheometry.While the crystallisation characteristics of EAA were affected only to a small extent by the addition of NAOEt, the corresponding mixtures with phenoxy acquired an increasingly more pronounced amorphous nature by increasing the concentration of NaOEt.SEM examinations revealed that the morphology of the mixtures became more homogeneous when NaOEt was present. This was manifested also by a change from dual relaxations to single relaxations in the Cole-Cole plots of the rheological data.