Use of Cyclodextrins as An Environmentally Friendly Extracting Agent in Organic Aged-contaminated Soil Remediation

The removal of Polycyclic Aromatic Hydrocarbons (PAHs) from soil using pure water is quite ineffective due to␣their low aqueous solubility. Most of present processes are based on organic cosolvents or surfactants, leading to potential environmental hazard. Addition of cyclodextrin (CD) in aqueous washing solutions has been shown to␣increase the removal efficiency several times, while being non-toxic agents. Herein are investigated the effectiveness of cyclodextrins to remove PAHs occurring in industrially aged-contaminated soil. β-cyclodextrin (BCD), hydroxypropyl-β-cyclodextrin (HPCD) and methyl-β-cyclodextrin (MCD) solutions were used for soil flushing in column test or batch experiments to evaluate some influent parameters that can significantly increase the removal efficiency. The process parameters chosen were CD concentration, ratio of washing solution volume to soil weight, and temperature of washing solution. These parameters were found to have a significant and almost linear effect on PAHs removal from the contaminated soil, except the temperature where no significant enhancement in PAHs extraction was observed for temperature range from 5 to 35 °C. Removal capacity of HPCD and MCD was higher than BCD one. The PAHs extraction enhancement factor compared to water was about 200.     

Thermal Behaviour of Anhydrous α-, β- and γ-Cyclodextrin at Low Temperature

Heat capacities of anhydrous -and -cyclodextrin were measured by adiabaticcalorimetry between 10 K and 300 K. The thermalbehaviour of the two compounds exhibits significantdifferences. -Cyclodextrin shows an anomalousexcess heat capacity in the entire region between 70 Kand 210 K. In the case of -cyclodextrin, anendothermic effect is observed at 240K. This effect isanalysed through the study of the correspondingentropy change and discussed in terms ofintramolecular organization.Using the known heat capacity values of anhydrous-CD, a comparative analysis has been developed.For each cyclodextrin, the average behaviour of abound -D-glucopyranose has been calculated andcompared. From a thermodynamic point of view, thedegree of organization of the dehydrated macrocycliccompounds could be expressed as-CD -CD -CD.     

Vicinal alkylation of olefins,regio- and stereoselective addition of [CM + CN] units to cyclopentadiene.

Adducts of alkyl(phenylthio)ketenes to cyclopentadiene are cleaved with KOH-t-BuOK with retention of configuration at three centers. This observation broadens the synthetic potential of the method of vicinal alkylation of olefins. This method has been used for the vicinal addition of [C_m + C_n] units to cyclopentadiene.     

Self-similar solutions for the Schrödinger map equation

We study in this article the equivariant Schrödinger map equation in dimension 2, from the Euclidean plane to the sphere. A family of self-similar solutions is constructed; this provides an example of regularity breakdown for the Schrödinger map. These solutions do not have finite energy, and hence do not fit into the usual framework for solutions. For data of infinite energy but small in some norm, we build up associated global solutions.     

Electronic and magnetic structure of the undoped two and three-leg ladder cuprates in an itinerant electrons model

We study the electronic and magnetic structure of the undoped ideal two and three-leg ladder cuprates by assuming a moderate on site coulombic repulsion. This analysis is an extension of the Fermi liquids studies proposed for the CuO₂ plane in view to explain the high T_c superconductivity and the competition with the antiferromagnetic phase. At zero doping, the quasi-one-dimensionality of the structure results in SDW correlations with different (commensurate) vectors according to the number of legs, which contrasts with the predictions made from the Heisenberg model. At mean field, and for n = 3 (Sr₂Cu₃O₅), we predict a magnetic ordered state, detected by μSr and NMR measurements with critical temperatures consistent with our assumptions on the physical parameters, the modulation vector being .The presence of several bands at the Fermi level explains why there is no observable gap in the static susceptibility measurements. For n = 2, we predict a gap consistent with experimental Curie susceptibility. But the expected magnetic instability is detected only in La₂Cu₂O₅, where the interladder coupling is stronger. In every case the one-dimensional van Hove singularities are far from the Fermi level, making difficult the obtaining of high T_c superconductivity. Received 3 June 1998     

Vortex Filament Solutions of the Navier-Stokes Equations

We consider solutions of the Navier-Stokes equations in 3d with vortex filament initial data of arbitrary circulation, that is, initial vorticity given by a divergence-free vector-valued measure of arbitrary mass supported on a smooth curve. First, we prove global well-posedness for perturbations of the Oseen vortex column in scaling-critical spaces. Second, we prove local well-posedness (in a sense to be made precise) when the filament is a smooth, closed, non-self-intersecting curve. Besides their physical interest, these results are the first to give well-posedness in a neighborhood of large self-similar solutions of 3d Navier-Stokes, as well as solutions that are locally approximately self-similar. © 2023 Wiley Periodicals LLC.     

Insights into the mechanism of the site-selective sequential palladium-catalyzed cross-coupling reactions of dibromothiophenes/dibromothiazoles and arylboronic acids. Synthesis of PPARbeta/delta agonists

A reactivity study, aided by NMR spectroscopy, allowed a mechanistic rationale to be postulated for the palladium-catalyzed regioselective coupling of arylboronic acid (and arylstannane where feasible) at the position next to the sulfur atom in functionalized dibromothiophenes and dibromothiazoles. The analysis of the NMR spectra (using 19F from the boronic acid CF3 group and 31P from the phosphine of the catalyst as probes) of the entire reaction starting from the dibromoheterocycles allowed the qualitative proposal that the transmetalation is the rate-limiting step for both sequential substitution processes. The extremely facile oxidative addition at the C-Br bond next to the sulfur atom of the heterocycle instead determines the positional selectivity. An additional Stille reaction then replaced the second halogen, providing the trisubstituted heterocyclic scaffolds of PPAR ligands, which displayed PPARbeta/delta agonist activity, as revealed by reporter assays in living cells.