Apparent molar heat capacities of aqueous solutions of acetic,propanoic and succinic acids,sodium acetate and sodium propanoate from 300 to 525 K and a pressure of 28 MPa

The apparent molar heat capacities of dilute aqueous solutions of acetic, propanoic and succinic acid and sodium salts of the two monofunctional acids were measured at 300 Kp,2 ^o . After subtracting the heat capacity of a point mass, the remaining heat capacity was successfully decomposed into functional group contributions at all temperatures. Together with the results of our previous paper on alcohols and diols the heat capacity contributions of the CH₂, CH₃, OH, COOH, (COOH)₂, and COONa groups are now available and these allow reasonably accurate predictions of the heat capacities of all compounds composed of these groups in this temperature range.     

Group contributions to the infinite dilution partial molar volumes of alkanes, alcohols, and glycols in polar organic solvents

Densities of binary mixtures of polar organic solvents with alcohols were measured at 25‡C. The solvents studied were N,N-dimethylformamide, dimethylsulfoxide, and formamide while alcohols were butanol, pentanol, hexanol, and 1,4-butanediol. Density measurements of hydrocarbons (from pentane to dodecane and some heptane isomers) + N,N-dimethylformamide were also performed. From these data the apparent molar volumes of alcohols and hydrocarbons as functions of concentration were calculated. The standard partial molar volumes were obtained by extrapolation to infinite dilution and are discussed in terms of group contributions.     

Generalization of Carré equation

The present work offers new equations for phase evaluation in measurements. Several phase shifting equations with an arbitrary but constant phase shift between captured intensity signs are proposed. The equations are similarly derived as the so-called Carré equation. The idea is to develop a generalization of Carré equation that is not restricted to four images. Errors and random noise in the images cannot be eliminated, but the uncertainty due to their effects can be reduced by increasing the number of observations. An experimental analysis of the mistakes of the technique was made, as well as a detailed analysis of mistakes of the measurement. The advantages of the proposed equation are its precision in the measures taken, speed of processing and the immunity to noise in signs and images.     

Surface Tension, Heat Capacity, and Volume of Amphiphilic Compounds in Formamide Solutions

Density measurements of sodium dodecyl sulfate (SDS), sodium decyl sulfate (SDeS), sodium octyl sulfate(SOS), and sodium hexyl sulfate(SHS) in formamide (FA) as functions of the surfactant concentrations were carried out at 25°C. For SDS in FA, additional density measurements at 35 and 60°C and surface tension and specific heat capacity measurements at 25°C were also performed. From density and specific heat capacity data, the apparent molar volume and heat capacity of the surfactants as functions of concentration were calculated. The surface excess of SDS at the solution–air interface was also determined from the surface tension measurements using the Gibbs adsorption equation. Under our experimental conditions, none of the experimental results evidence micelle formation. In addition, volumetric studies of the hexanol–SDS–FA ternary system at 25°C evidence only interactions between the dispersed surfactant and alcohol.     

Mesure des chaleurs de Mélange de duex liquides,sans programmation des débits,avec le microcalorimètre picker à écoulement

A method is proposed for using the Picker microcalorimeter without programmation of the flow rates of the reactant liquids. From the measurements of the three systems (carbon tetrachloride+benzene, +n-heptane and +cyclopentane) it is shown that the excess enthalphy curves obtained point by point are better defined than those obtained directly in the scanning mode, especially in the dilute regions.     

Phase shifting technique using generalization of Carre algorithm with many images

The present work offers new algorithms for phase evaluation in optics measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity frames are proposed. The algorithms are derived similarly to the so called Carre algorithm. The idea is to develop a generalization of Carre that is not restricted to four images. Errors and random noise in the images cannot be eliminated, but the uncertainty due to its effects can be reduced by increasing the number of observations. The advantages of the proposed algorithm are its precision in the measures taken and immunity to noise in images.     

Excess heat capacities and excess volumes of binary liquid mixtures of chloroform with cyclic ethers at 298.15 K

Molar excess heat capacities at constant pressure, C^E_p, of binary liquid mixtures chloroform + oxolane, chloroform + 1,3-dioxolane, chloroform + oxane, and chloroform + 1,4-dioxane have been determined at 298.15 K from measurements of volumetric heat capacities in a Picker flow microcalorimeter. A precision of ±0.04 J K^?1 mole^? was achieved by using the stepwise procedure. Experimental molar excess heat capacities are compared with values derived from H^E results at different temperatures. Excess molar volumes, V^E, for the same systems at 298.15 K have been determined by measuring the density of the pure liquids and solutions with a high-precision digital flow densimeter.     

Enhancing the performance of a bistable energy harvesting device via the cross-entropy method

Nonlinear Dynamics - This work deals with the solution of a non-convex optimization problem to enhance the performance of an energy harvesting device, which involves a nonlinear objective function...     

Preparation and characterization of rhenium (I) tricarbonyl dithiocarbamate compounds; Re(CO)3(S2CNMe2)(L)

The title compounds were prepared in good yield by treatment of Re(CO)₅Cl or [Re(CO)₃(H₂O)₃]Br with sodium dimethyldithiocarbamate hydrate (NaS₂CNMe₂·H₂O) and a neutral ligand yielding eight Re(CO)₃(S₂CNMe₂)(L) derivatives: L = NH₃1, pyridine (py) 2, imidazole (im) 3, pyrazole (pz) 4, triphenylphospine (PPh₃) 5, 1,3,5-triaza-7-phosphaadamantane (PTA) 6, t-butyl isocyanide (t-BuNC) 7, and cyclohexyl isocyanide (CyNC) 8. The resulting new complexes were characterized by ¹H and ¹³C NMR and infrared spectroscopy. Each was also structurally elucidated by X-ray crystallography. General structural features in all eight compounds were similar. The orientation of the three single-faced ligands, py, im and pz, demonstrates an interaction with the filled π orbital of the dithiocarbamate. Compounds were tested for stability under conditions that mimic physiological conditions; 1-4 quickly decomposed, 7 and 8 decomposed over 24 h while 5 and 6 were stable.     

Conservative cross diffusions and pattern formation through relaxation

This paper is aimed at studying the formation of patches in a cross-diffusion system without reaction terms when the diffusion matrix can be negative but with positive self-diffusion. We prove existence results for small data and global a priori bounds in space–time Lebesgue spaces for a large class of ‘diffusion’ matrices. This result indicates that blow-up should occur on the gradient. One can tackle this issue using a relaxation system with global solutions and prove uniform a priori estimates. Our proofs are based on a duality argument à la M. Pierre which we extend to treat degeneracy and growth of the diffusion matrix.We also analyze the linearized instability of the relaxation system and a Turing type mechanism can occur. This gives the range of parameters and data for which instability may occur. Numerical simulations show that patterns arise indeed in this range and the solutions tend to exhibit patches with stiff gradients on bounded solutions, in accordance with the theory.