Synthesis, characterization, and crystal structures of n-alkyldiorganodithiophosphates RS2P(OC6H4)2

Treatment of KS₂P(OC₆H₄)₂ (1) with five n-alkyl halides afforded the stable n-alkyldithiophosphate compounds RS₂P(OC₆H₄)₂ (2–6). Single crystal X-ray analysis revealed that the PS₂ fragment in 1 displays an isobidentate coordination pattern; compounds 2–4 display a monodentate binding pattern. The crystal packing of title compounds is stabilized by cation-π, weak hydrogen bonding C–H---O, as well as aromatic non-bonded interactions.     

First Hydrolysis Constant of Lutetium (III) by Solvent Extraction

The solvent extraction method involving diglycolic acid (dicarboxy methyl ether) as a competitive ligand to lutetium and N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid (TES) as a buffer was used to study the hydrolysis of lutetium in 1 mol⋅dm⁻³ NaCl ionic strength at 303 K. Acid dissociation constants of H₂DG and TES were determined and the possible formation of lutetium–TES compounds was investigated. It was found that lutetium does not form compounds with TES under the experimental conditions. The solvent extraction method using ¹⁷⁷Lu as a tracer was applied and the first hydrolysis constant of lutetium was determined by means of the relationship of the equilibrium constant of the complex Lu(DG)⁺ in the absence and in the presence of hydrolysis. The value obtained was log ₁₀ β _Lu,H=−7.9±0.3.     

Spontaneous resolution under supramolecular control

The spontaneous resolution of enantiomers is an intriguing and important phenomenon in a number of research areas. Non-covalent interactions can play a key role in the process which can now be observed not only in crystals, but in liquid crystals, self-assembled monolayers, self-assembled fibres, and supramolecules self-assembled in solution. The evidence gathered in all of these areas is important for explaining the transfer of chirality from molecule to bulk, and in particular the spontaneous resolution of enantiomers.     

Feshbach resonance induced shock waves in Bose-Einstein condensates

We propose a method for generating shock waves in Bose-Einstein condensates by rapidly increasing the value of the nonlinear coefficient using Feshbach resonances. We show that in a cigar-shaped condensate there exist primary (transverse) and secondary (longitudinal) shock waves. We analyze how the shocks are generated in multidimensional scenarios and describe the related phenomenology.     

Structural instability of vortices in Bose-Einstein condensates

In this paper we study a gaseous Bose-Einstein condensate and show the following: (i) A minimum value of the interaction is needed for the existence of stable persistent currents. (ii) Vorticity is not a fundamental invariant of the system, as there exists a conservative mechanism which can destroy a vortex and change its sign. (iii) This mechanism is suppressed by strong interactions.     

Vortex revivals with trapped light

We predict that vortex dipoles nested in light beams trapped in graded-index media can undergo closed Berry trajectories, yielding periodic vortex annihilations and revivals along the light-propagation direction. The vortex revivals from vortex-free wave fronts are mediated by Freund stationary point bundles that carry the necessary Poincaré-Hopf indices. Vortex spiraling and spontaneous generation of circular-edge dislocations are also found to occur.     

Electrochemical characterization of a primary electrolytic conductivity cell at CENAM

Linear voltammetry and electrochemical impedance spectroscopy experiments were performed in order to obtain basic information about the electrochemical behavior of the primary cell of electrolytic conductivity at Centro Nacional de Metrología. Linear voltammetry shows that the amplitude of the sinusoidal perturbation must be smaller than 300 mV. Electrochemical impedance results indicate that optimal frequency interval extends from 5 to 0.6 kHz. Regarding sinusoidal signal amplitude, a lower bias with respect to electrolytic conductivity of an independent reference solution is obtained at 10 mV than at larger amplitudes; in addition, electrode integrity is improved.     

Activated carbon fibers with a high heteroatom content by chemical activation of PBO with phosphoric acid

The preparation of activated carbon fibers (ACFs) by phosphoric acid activation of poly(p-phenylene benzobisoxazole) (PBO) fibers was studied, with particular attention to the effects of impregnation ratio and carbonization temperature on porous texture. Phosphoric acid has a strong effect on PBO degradation, lowering the temperature range at which the decomposition takes place and changing the number of mass loss steps. Chemical analysis results indicated that activation with phosphoric acid increases the concentration of oxygenated surface groups; the resulting materials also exhibiting high nitrogen content. ACFs are obtained with extremely high yields; they have well-developed porosity restricted to the micropore and narrow mesopore range and with a significant concentration of phosphorus incorporated homogeneously in the form of functional groups. An increase in the impregnation ratio leads to increases in both pore volume and pore size, maximum values of surface area (1250 m(2)/g) and total pore volume (0.67 cm(3)/g) being attained at the highest impregnation ratio (210 wt % H(3)PO(4)) and lowest activation temperature (650 °C) used; the corresponding yield was as large as 83 wt %. The obtained surface areas and pore volumes were higher than those achieved in previous works by physical activation with CO(2) of PBO chars.     

Matrix Product States, Random Matrix Theory and the Principle of Maximum Entropy

Using random matrix techniques and the theory of Matrix Product States we show that reduced density matrices of quantum spin chains have generically maximum entropy.     

Joint System Quantum Descriptions Arising from Local Quantumness

We study the entropy flux in the stationary state of a finite one-dimensional sample ${\mathcal{S}}$ connected at its left and right ends to two infinitely extended reservoirs ${\mathcal{R}_{l/r}}$ at distinct (inverse) temperatures ${\beta_{l/r}}$ and chemical potentials ${\mu_{l/r}}$ . The sample is a free lattice Fermi gas confined to a box [0, L] with energy operator ${h_{\mathcal{S}, L}= - \Delta + v}$ . The Landauer-Büttiker formula expresses the steady state entropy flux in the coupled system ${\mathcal{R}_l + \mathcal{S} + \mathcal{R}_r}$ in terms of scattering data. We study the behaviour of this steady state entropy flux in the limit ${L \to \infty}$ and relate persistence of transport to norm bounds on the transfer matrices of the limiting half-line Schrödinger operator ${h_\mathcal{S}}$ .