Solubility behaviour, crystallisation kinetics and pour point : a comparison of linear alkane and triacyl glyceride solute/solvent mixtures

Mixtures of either a hydrocarbon wax in a hydrocarbon solvent or a long chain triacyl glyceride (TAG) in a TAG solvent show complex solubility boundary temperature hysteresis and precipitated crystal network formation leading to gelation. For these industrially-important systems, we show how the equilibrium solubility and its hysteresis, crystallisation kinetics and pour point temperature vary with solute concentration for representative examples of both hydrocarbon (n-tetracosane (C24) solute in n-heptane (C7) solvent) and TAG (tristearin (SSS) solute in tricaprylin (CCC) solvent) mixtures. The behaviour is modelled with good accuracy; thereby providing a useful aid to formulation and process optimisation

A model study of enhanced oil recovery by flooding with aqueous surfactant solution and comparison with theory

With the aim of elucidating the details of enhanced oil recovery by surfactant solution flooding, we have determined the detailed behavior of model systems consisting of a packed column of calcium carbonate particles as the porous rock, n-decane as the trapped oil, and aqueous solutions of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The AOT concentration was varied from zero to above the critical aggregation concentration (cac). The salt content of the aqueous solutions was varied to give systems of widely different, post-cac oil–water interfacial tensions. The systems were characterized in detail by measuring the permeability behavior of the packed columns, the adsorption isotherms of AOT from the water to the oil–water interface and to the water–calcium carbonate interface, and oil–water–calcium carbonate contact angles. Measurements of the percent oil recovery by pumping surfactant solutions into calcium carbonate-packed columns initially filled with oil were analyzed in terms of the characterization results. We show that the measured contact angles as a function of AOT concentration are in reasonable agreement with those calculated from values of the surface energy of the calcium carbonate–air surface plus the measured adsorption isotherms. Surfactant adsorption onto the calcium carbonate–water interface causes depletion of its aqueous-phase concentration, and we derive equations which enable the concentration of nonadsorbed surfactant within the packed column to be estimated from measured parameters. The percent oil recovery as a function of the surfactant concentration is determined solely by the oil–water–calcium carbonate contact angle for nonadsorbed surfactant concentrations less than the cac. For surfactant concentrations greater than the cac, additional oil removal occurs by a combination of solubilization and emulsification plus oil mobilization due to the low oil–water interfacial tension and a pumping pressure increase

Evidence for nodal superconductivity in LaFePO

In several iron-arsenide superconductors there is strong evidence for a fully gapped superconducting state consistent with either a conventional s-wave symmetry or an unusual $s_\pm$ state where there the gap changes sign between the electron and hole Fermi surface sheets. Here we report measurements of the penetration depth $\lambda(T)$ in very clean samples of the related iron-phosphide superconductor, LaFePO, at temperatures down to $\sim$ 100 mK. We find that $\lambda(T)$ varies almost perfectly linearly with $T$ strongly suggesting the presence of gap nodes in this compound. Taken together with other data, this suggests the gap function may not be generic to all pnictide superconductors

Lucerne Crown and Taproot Biomass Affected Early-Spring Canopy Expansion

Leaf area index (LAI) quantifies canopy expansion in crops and is used in lucerne (Medicago sativa L.) simulation models to predict daily PAR interception (PAR i). This then drives yield through radiation use efficiency (RUE) (Gosse et al., 1984). In perennial crops, like lucerne, the level of biomass stored in crown and taproot may affect canopy expansion in subsequent regrowth cycles (Avice et al., 1997). In temperate regions the impact of this is likely to be greatest in early-spring, when low temperatures delay development. The objective of the current research was to identify whether contrasting levels of winter biomass in crown and taproots affected LAI expansion in early-spring regrowth crops

RC J1148+0455 identification: gravitational lens or group of galaxies ?

The structure of the radio source RC B1146+052 of the ``Cold'' catalogue is investigated by data of the MIT-GB-VLA survey at 4850 MHz. This source belongs to the steep spectrum radio sources subsample of the RC catalogue. Its spectral index is $\alpha$ = -1.04. The optical image of this source obtained with 6m telescope is analysed. The radio source center is situated in a group of 8 galaxies of about 24$^m$ in the R-filter. The possible explanations of the complex structure of radio components are considered.Comment: 6 pages, 5 figures, uses psfig.sty. This was the poster as presented on Gamow Memorial Internat. Conference GMIC'99 "Early Universe: Cosmological Problems and Instrumental Technologies" in St.Petersburg, 23-27 Aug., 1999. Submitted to Proceedings to be published in A&A Transaction

Three dimensionality of pulsed second-sound waves in He II

Three dimensionality of 3D pulsed second sound wave in He II emitted from a finite size heater is experimentally investigated and theoretically studied based on two-fluid model in this study. The detailed propagation of 3D pulsed second sound wave is presented and reasonable agreement between the experimental and theoretical results is obtained. Heater size has a big influence on the profile of 3D second sound wave. The counterflow between the superfluid and normal fluid components becomes inverse in the rarefaction of 3D second sound wave. The amplitude of rarefaction decreases due to the interaction between second sound wave and quantized vortices, which explains the experimental results about second sound wave near [Phys. Rev. Lett. 73, 2480 (1994)]. The accumulation of dense quantized vortices in the vicinity of heater surface leads to the formation of a thermal boundary layer, and further increase of heating duration results in the occurrence of boiling phenomena. PACS numbers: 67.40.Pm 43.25.+y 67.40.BzComment: 30 pages, 9 figures. Physical Review B, Accepte

Model Study of Enhanced Oil Recovery by Flooding with Aqueous Solutions of Different Surfactants: How the Surface Chemical Properties of the Surfactants Relate to the Amount of Oil Recovered

© 2016 American Chemical Society. The main aim of this work is to establish how the fraction of oil recovered from an oil-filled calcite powder packed column by injection of aqueous surfactant solution depends on the phase behavior and surface chemical properties of the surfactant system. We have measured the phase behavior, the adsorption of surfactant to the oil-water, calcite-water, and calcite-oil interfaces, tensions, and contact angles for anionic, cationic, and nonionic surfactant/oil/aqueous phase systems. We show how the measured surface chemical properties can be used to approximately predict the fraction of oil recovered as a function of the volume and concentration of the surfactant solutions injected into the column. Measured and calculated plots of %oil recovery versus surfactant concentration show reasonably good agreement for the different surfactant systems. The experimentally validated model for oil recovery provides a sound basis for the rational selection of surfactant type and concentration to achieve maximum oil recovery based on laboratory measurements of the surface chemical properties of candidate surfactants

Adsorption of benzyldimethyldodecylammonium chloride onto stainless steel using the quartz crystal microbalance and the depletion methods: An optimisation study

The adsorption behaviour of benzyldimethyldodecylammonium chloride (C12BDMAC) corrosion inhibitor from aqueous solutions onto a stainless steel surface has been investigated using the quartz crystal microbalance (QCM) technique and the depletion-HPLC method. Three different experimental procedures were used to carry out the adsorption measurements using the QCM. The results revealed that the employed experimental procedure had a marked influence on both of the measured frequency and dissipation energy changes. Additionally, the measured changes in the normalized frequency and dissipation changes were found to be overtone-dependent. The adsorbed amounts determined by QCM were higher than those determined by depletion due to strong contributions from the bulk liquid properties. The direct application of the measured frequency shifts corresponding to the lowest dissipation changes, ?flowestD, in the Sauerbrey equation was effective in minimising these contributions within an acceptable experimental tolerance. A correction procedure, based on the Kanazawa equation, has been proposed and applied successfully to separate the contribution from the bulk effects to the calculated adsorbed mass. The adsorption isotherms obtained from the corrected frequency shifts and the depletion method were perfectly matched over the whole range of concentrations investigated

Muon content of ultra-high-energy air showers: Yakutsk data versus simulations

We analyse a sample of 33 extensive air showers (EAS) with estimated primary energies above 2\cdot 10^{19} eV and high-quality muon data recorded by the Yakutsk EAS array. We compare, event-by-event, the observed muon density to that expected from CORSIKA simulations for primary protons and iron, using SIBYLL and EPOS hadronic interaction models. The study suggests the presence of two distinct hadronic components, ``light'' and ``heavy''. Simulations with EPOS are in a good agreement with the expected composition in which the light component corresponds to protons and the heavy component to iron-like nuclei. With SYBILL, simulated muon densities for iron primaries are a factor of \sim 1.5 less than those observed for the heavy component, for the same electromagnetic signal. Assuming two-component proton-iron composition and the EPOS model, the fraction of protons with energies E>10^{19} eV is 0.52^{+0.19}_{-0.20} at 95% confidence level.Comment: 8 pages, 3 figures; v2: replaced with journal versio