Densities, refractive indices and speeds of sound of the ternary mixtures (dimethyl carbonate + methanol + ethanol) and (dimethyl carbonate + methanol + 1-propanol) at T=298.15 K

Density, refractive index and speed of sound at T=298.15 K and atmospheric pressure have been measured over the entire composition range for (dimethyl carbonate (DMC) + methanol + ethanol) and (DMC + methanol + 1-propanol). Excess molar volumes, changes of refractive index on mixing and deviations in isentropic compressibility for the above systems have been calculated. The calculated quantities are further fitted to the Cibulka equation to estimate the ternary fitting parameters. Standard deviations from the regression lines are shown.     

Excess Molar Volumes,Viscosities and Speeds of Sound of the Ternary Mixture 1-Heptanol (1) + Tetrachloroethylene (2) + Methylcyclohexane (3) at 298.15 K

Densities (ρ), viscosities (η) and speeds of sound (u) of the ternary mixture (1-heptanol + tetrachloroethylene + methylcyclohexane) and the corresponding binary mixtures (1-heptanol + tetrachloroethylene), (1-heptanol + methylcyclohexane) and (tetrachloroethylene + methylcyclohexane) at 298.15 K were measured over the whole composition range. The data obtained are used to calculate the excess molar volumes (V ^E), excess isobaric thermal expansivities (α ^E), viscosity deviations (Δη), excess Gibbs energies of activation of viscous flow (ΔG ^*E) and excess isentropic compressibilities (κ _S ^E) of the binary and ternary mixtures. The data from the binary systems were fitted by the Redlich–Kister equation whereas the best correlation method for the ternary system was found using the Nagata equation. Viscosities, speeds of sound and isentropic compressibilities of the binary and ternary mixtures have been correlated by means of several empirical and semi-empirical equations. The best correlation method for viscosities of binary systems is found using the Iulan et al. equation and for the ternary system using the Heric and McAllister equations. The best correlation method for the speeds of sound and isentropic compressibilities of the binary system (1-heptanol + methylcyclohexane) is found using IMR (Van Deal ideal mixing relation) and for the binary system (tetrachloroethylene + methylcyclohexane) it is found using the NR (Nomoto relation) and for the binary system (1-heptanol + tetrachloroethylene) and the ternary system (1-heptanol + trichloroethylene + methylcyclohexane) it is obtained from the FLT (Jacobson free length theory).     

Thermodynamic interactions in binary mixtures of anisole with ethanol, propan-1-ol, propan-2-ol, butan-1-ol, pentan-1-ol, and 3-methylbutan-1-ol at T = (298.15, 303.15, and 308.15) K

In this paper, excess thermodynamic functions have been computed from the measured values of density, viscosity, and refractive index at T = (298.15, 303.15, and 308.15) K, ultrasonic velocity at T = 298.15 K over the entire mixture composition range of (anisole with ethanol, propan-1-ol, propan-2-ol, butan-1-ol, pentan-1-ol, or 3-methyl butan-1-ol). Excess molar volume, V^E has been calculated from densities, whereas deviations in viscosity, Δη, were computed from the measured viscosities. From ultrasonic velocities, isentropic compressibilities were calculated, from which deviations in isentropic compressibility, Δk_s have been computed. Lorenz-Lorentz mixture rule was used to compute molar refractivity, R from refractivity index data and from these data, deviations in molar refractivity, ΔR have been computed. Computed thermodynamic quantities have been fitted to Redlich and Kister polynomial equation to derive the coefficients and standard errors between experimental and predicted quantities. Intermolecular interactions between anisole and alkanols have been studied based on the computed excess thermodynamic quantities.     

Application of acoustic methods for a non-destructive evaluation of the elastic properties of several typologies of materials

In solid phase materials, differently from what happens in the fluid phase, elastic waves propagate both through longitudinal and transverse waves. From the speed of propagation of longitudinal and transverse waves, it is possible to evaluate important elastic properties of the solids under study, namely the Young’s modulus, the Poisson’s coefficient, the bulk modulus and the shear modulus. This work suggests an accurate method for measuring wave propagation speeds in homogeneous and non-homogeneous materials with the purpose to evaluate their mechanical properties and the associated uncertainty.First of all, to assess the performance of the proposed methodology, based on the “pulse-echo” technique, in terms of accuracy and precision, measurements of wave propagation speeds have been carried out, in atmospheric conditions, in well-known homogeneous and isotropic materials, such as copper, aluminum, stainless steel and also polymethyl methacrylate (Plexiglas®), Teflon® and optical glass BK7. These results were compared with the values reported in literature (if present), showing how published speed of sound data are very disperse and not so reliable owing to the lack of a precise uncertainty evaluation and of the temperature value associated to the measurement. Then, the same experimental apparatus was used for measuring speed of sound as a function of temperature (from 274.15 to 313.15 K) for 304 stainless steel and oxygen free copper, showing a good accuracy of the results also for temperature conditions far from ambient. Finally, the same procedure was applied to a non-homogeneous solid, obtaining some very preliminary results in typical mediterranean building material, as Carrara marble.     

Volumetric behaviour of the (2,2,4-trimethylpentane + methylbenzene + butan-1-ol) ternary system and its binary sub-systems within the temperature range (298.15–328.15) K

Densities and speeds of sound of the (2,2,4-trimethylpentane + methylbenzene + butan-1-ol) ternary system as well as all its binary sub-systems were measured at four temperatures, namely 298.15 K, 308.15 K, 318.15 K, and 328.15 K at atmospheric pressure by a vibrating-tube densimeter DSA 5000. The binary (isooctane + toluene) system was studied previously. Excess quantities (molar volume, adiabatic compressibility, and isobaric thermal expansivity) of the mixtures studied were calculated from the experimental densities and speed of sounds. The excess molar volume data were correlated using the Redlich–Kister equation. Both the positive and S-shaped excess molar volume curves were found for the systems studied. The excess molar volumes versus concentration of binary systems differed in the shape and temperature dependence. The experimental binary data were compared with literature data. The experimental excess molar volumes were analyzed by means of the Extended Real Associated Solution (ERAS) model. The experimental data and the ERAS model can help to estimate real behaviour of the systems studied.     

电子在蛋白质分子中的迁移机理及其特性

ATP水解作用所释放的能量能引起蛋白质分子中额外电子的激发,其激发与氨基酸残基晶格畸变相互作用,使额外电子自陷成孤子,这孤子在附着有供体(D)和受体(A)的蛋白质分子中运动时,由于孤子与供体电子的相互作用而"自局域"在孤子上进行迁移,从而可把电子供给受体.使用作者提出的孤子理论研究了这种迁移的特征,计算了在这种非平衡态过程中由孤子迁移电子的速率和动能系数,得到了一些有趣的结果,揭示了这种迁移的本质,求得了迁移的大小.     

Phase diagram of speed gradient model with an on-ramp

In this paper, phase transitions are investigated in speed gradient model with an on-ramp. Phase diagrams of traffic flow composed of manually driven vehicles and adaptive cruise control (ACC) vehicles are studied, respectively. The traffic flow composed of ACC vehicles is modeled by enhancing propagation speed of small disturbance. The phase diagram of traffic flow composed of manually driven vehicles is similar to that in previous works, in which such states as pinned localized cluster (PLC), moving localized cluster (MLC), triggered stop-and-go traffic (TSG), oscillatory congested traffic (OCT), and homogeneous congested traffic (HCT) are reproduced. In the phase diagram of traffic flow composed of ACC vehicles, traffic stability is enhanced and such states as PLC, MLC, and TSG disappear. Furthermore, some interesting phenomena, such as stationary OCT upstream of on-ramp and appearance of second OCT in HCT, are identified.     

Ultrasound-assisted of alkali chloride separation using bulk ionic liquid membrane

An ultrasonic-assisted separation of alkali chloride (LiCl, NaCl, and KCl) salts have been carried out using of an hydrophobic ionic liquid membrane (ILM). The ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and tributyl phosphate mixture have been used as ILM. An ultrasonic probe with different frequencies (25, 100, and 250) kHz have been applied as source of ultrasound generator with different times of sonication (2, 5, and 10) min in three phases system containing feed, ILM, and receiver in osmotic U-shaped tube. Also, 250, 500, and 1000 ppm of the feed (alkali chloride) concentration have been used to separate. The frequency of 250 kHz with higher sonication time provides optimum condition for separation of LiCl with lower feed concentration. The thermodynamic properties such as density and speed of sound and the related thermodynamic properties have been calculated to optimize ILM composition (x_IL = 0.45) for ultrasound-separation.     

Prediction of sound velocity and compressibility via molecular simulation at fixed entropy

A molecular-level simulation route is proposed to compute the isentropic thermodynamic properties in a fluid system by Monte Carlo simulation at fixed entropy. The method involves computation of the pressure response of a system to an infinitesimal change in system density by introduction of a single molecule, while retaining the system volume as well as the absolute molar entropy. The probability for accepting a change in temperature during the Monte Carlo moves was weighted against the argument proposed by Smith et al. [W.R. Smith, M. Lísal, I. Nezbeda, Chem. Phys. Lett. 426 (2006) 436–440]. Application to fluid argon has confirmed superior accuracy for the technique within the gas state to yield results within 1.2% of the measured values for the range of thermodynamic conditions investigated.     

High-efficiency hydrophilic interaction chromatography by coupling 25 cm × 4.6 mm ID × 5 μm silica columns and operation at 80 °C

Recently, hydrophilic interaction chromatography (HILIC) has emerged as a valuable orthogonal tool to reversed-phase liquid chromatography (RP-LC) as it allows for resolution of highly polar ionisable compounds. The relationships between separation efficiency, column length and speed of analysis for 4.6 mm ID × 5 μm silica particle columns in HILIC are demonstrated using kinetic plots. The kinetic plots constructed for conventional pressure systems operating at 350 bar and at 30 °C and 80 °C are confirmed using experimental data for different column lengths. Efficiencies of more than 130,000 theoretical plates could be achieved by connecting up to six columns of 25 cm. As expected, a significant gain in analysis speed without loss of efficiency could be obtained by operating at 80 °C compared to 30 °C. The advantages of using long columns in HILIC in combination with elevated column temperature for the pharmaceutical industry are illustrated using test mixtures comprised of commercially available ionisable compounds (including some containing functional groups with potential genotoxic typical structural alerts) as well as real polar ionisable pharmaceuticals.