Impact of non-ideal transport modeling on supercritical flow simulation

The simulation of a supercritical fluid flow requires sophisticated models for real gas thermodynamic and non-ideal phenomena. They both are presently addressed through the simulation of a non-reacting and reacting high pressure H₂/O₂ splitter-plate configuration. In particular, the diffusion velocity of species is evaluated through the gradient of chemical potential (${\mathbf{d}}_l^{\text{NI}}=X_l{\left(?{\mu }_l\right)}_T$) expressed with the Peng–Robinson equation of state, or with the classical low-pressure approach ${\mathbf{d}}_l^{\mathrm{I}}=?X_l,$ which only uses the gradient of the lth species molar fraction, X_l. In addition, the high pressure binary diffusion coefficients are estimated by the correction of Kurochkin et al. or with the Takahashi approach. The results for the non-reaction case are consistent with the literature for mean and rms values using ${\mathbf{d}}_l^{\mathrm{I}}$. The use of ${\mathbf{d}}_l^{\text{NI}}$ has a limited impact but the temperature profiles become steeper. In the reactive case, the two approaches lead to a difference of 50 K on the average temperature just downstream of the injector and about 100 K further downstream. A non-ideal transport is then required for the modeling of supercritical flow simulation.     

A tandem ionic liquid-based dispersive microextraction method using in-syringe air-assisted vesicle system for rapid determination of lead and cadmium in artificial sweat extract of facial cosmetic products

In the present study an innovative tandem ionic liquid-based dispersive microextraction method using an in-syringe air-assisted vesicle system was developed to determine the ultra-trace levels of lead (Pb^II) and cadmium (Cd^II) ions in synthetic sweat extract of branded and nonbranded facial cosmetic products. This method is based on injecting 2-amino-3-sulfhydrylpropanoic acid (l -cysteine) (as an eco-friendly chelating agent), hexafluorophosphate ion [PF₆⁻] (as an ion pair agent) and 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM] [PF₆] (as an acceptor phase) into the synthetic sweat extract of facial cosmetic products (branded and nonbranded). The acceleration of the dispersion process was carried out by rapid pressure in the syringe through the back-and-forth movement of plunger. The sediment phase was removed following centrifugation, and then hydrophobic complexes of analyte were back-extracted into HNO₃ and finally injected into a flame atomic absorption spectrometer. Several factors were systematically optimized. The validity of the methodology was tested by analyzing spiked known standards of both metals in a real sample. The proposed method was applied to the artificial sweat extracts of face makeup products, indicating how much toxic metals from different cosmetics are directly absorbed into skin.     

Synthesis of non-symmetrical 3,5-diamidobenzyl amines, ethers and sulfides

A straightforward synthesis of non-symmetrical 3,5-diamidobenzyl amines, ethers and sulfides starting from 3,5-dinitrobenzoic acid is reported. Functionalization of the benzylic position is only achieved after formation of the two amides, otherwise benzylic hydrogenolysis occurs during nitro group reduction.     

Double-exchange ferromagnetism in the partially-filled one-dimensional Kondo lattice model

We investigate the incompletely saturated ferromagnetic phase which occurs at strong-coupling in the partially-filled one-dimensional (1D) Kondo lattice model. The double-exchange interaction responsible for the ferromagnetic ordering is absent in dilute Kondo systems, and is a missing element in nearly all theoretical treatments of the model. We discuss how: 1) double-exchange arises in the system, even though the Kondo coupling is antiferromagnetic, and show that at strong-coupling it favors an alignment of the spins of unpaired localized moments; and 2) how this determines the ground-state phase diagram, and properties of the localized moments.     

Mössbauer study of elemental substitution in Nd18Fe76B6 alloy

Fe-rich Nd-Fe-B permanent magnetic materials are of great technological interest because of their superior magnetic properties such as coercivity and large energy products. These properties can be further enhanced by the substitution of Nd or Fe. We are presenting the results of atomic replacement of iron by Ga, Dy, Nb and Si, in the base material N₁₈Fe_{7 6}B₆, obtained by Mössbauer spectroscopy. It is observed that the net magnetization decreases for all compositions with the substitution of these elements.     

Dipotassium maleate with boric acid

In the title compound, poly[(μ₃‐boric acid)‐μ₄‐maleato‐dipotassium], [K₂(C₄H₂O₄){B(OH)₃}]_n, there are two independent K⁺ cations, one bonded to seven O atoms (three from boric acid and four from maleate), and the other eight‐coordinate via three boric acid and four maleate O atoms and a weak η¹‐type coordination to the C=C bond of the maleate central C atoms. Hydrogen bonding links the boric acid ligands and maleate dianions, completing the packing structure.