Effect of the synthesis temperature of sodium nonatitanate on batch kinetics of strontium-ion adsorption from aqueous solution

Sodium titanate materials are promising inorganic ion exchangers for the adsorption of strontium from aqueous solutions. Sodium nonatitanate exhibits a layered structure consisting of titanate layers and exchangeable sodium ions between the layers. The materials used in this study include samples synthesized by a hydrothermal method at temperatures between 60 °C and 200 °C. Their structure, composition, and morphology were investigated with X-Ray diffraction measurements; thermogravimetric, compositional and surface area analyses, and scanning electron microscopy. The structure, composition, and morphology depended on the synthesis temperature. Batch kinetics experiments for the removal of strontium from aqueous solutions were performed, and the data were fitted by a pseudo-second-order reaction model and a diffusive model. The strontium extraction capacity also depended on the synthesis temperature and exhibited a maximum for samples synthesized at 100 °C. The sorption process occurs in one or two diffusion-controlled steps that also depend on the synthesis temperature. These diffusion-limited steps are the boundary-layer diffusion and intra-particle diffusion in the case of pure nonatitanate synthesized at temperatures lower than 170 °C, and only intra-particle diffusion in the case of nonatitanate synthesized at 200 °C.     

Identification of the finishing technique of an early eighteenth century musical instrument using FTIR spectromicroscopy

The study of varnishes from musical instruments presents the difficulty of analysing very thin layers of heterogeneous materials on samples most of which are generally brittle and difficult to prepare. Such study is crucial to the understanding of historical musical instrument varnishing practices since written sources before 1800 are very rare and not precise. Fourier-transform infrared (FTIR) spectroscopy and imaging methods were applied to identify the major chemical components within the build-up of the varnish layers on a cello made by one of the most prominent French violin-makers of the eighteenth century (Jacques Boquay, ca. 1680–1730). Two types of FTIR imaging methods were used: scanning with a synchrotron-based microscope and full-field imaging using a 2D imager with a conventional source. An interpretation of the results obtained from these studies on the Boquay cello is that the maker first applied a proteinaceous layer, probably gelatine-based animal glue. He later applied a second layer based on a mixture of a drying oil and diterpenic resin from Pinaceae sp. From an historical perspective, the results complement previous studies by describing a second technique used for musical instrument finishes at the beginning of the eighteenth century in Europe.     

Unprecedented Kinetic Inertness for a Mn2+-Bispidine Chelate: A Novel Structural Entry for Mn2+-Based Imaging Agents

The search for more biocompatible alternatives to Gd³⁺-based MRI agents, and the interest in ⁵²Mn for PET imaging call for ligands that form inert Mn²⁺ chelates. Given the labile nature of Mn²⁺, high inertness is challenging to achieve. The strongly preorganized structure of the 2,4-pyridyl-disubstituted bispidol ligand L₁ endows its Mn²⁺ complex with exceptional kinetic inertness. Indeed, MnL₁ did not show any dissociation for 140 days in the presence of 50 equiv. of Zn²⁺ (37 °C, pH 6), while recently reported potential MRI agents MnPyC3A and MnPC2A-EA have dissociation half-lives of 0.285 h and 54.4 h under similar conditions. In addition, the relaxivity of MnL₁ (4.28 mm ⁻¹ s⁻¹ at 25 °C, 20 MHz) is remarkable for a monohydrated, small Mn²⁺ chelate. In vivo MRI experiments in mice and determination of the tissue Mn content evidence rapid renal clearance of MnL₁. Additionally, L₁ could be radiolabeled with ⁵²Mn and the complex revealed good stability in biological media.     

A novel, facile route to beta-fluoroamines by hydrofluorination using superacid HF-SbF(5)

A range of unsaturated amines and sulfonamides were converted to beta-fluoro nitrogen analogues after hydrofluorination in superacid HF-SbF(5), based on the formation of highly reactive electrophilic intermediates.     

Synthesis and characterization of nickel nanoparticles dispersed in imidazolium ionic liquids

The diameter and size-distribution of Ni nanoparticles prepared by the decomposition of [bis(1,5-cyclooctadiene)nickel(0)] organometallic precursor dissolved in 1-alkyl-3-methylimidazolium N-bis(trifluoromethanesulfonyl) amide ionic liquids depend on the length of the alkyl side-chain of the imidazolium ring. The increase of the organization range order of the ionic liquid that increases with that of the alkyl side-chain (from n-butyl to n-hexadecyl) induces the formation of nanoparticles with a smaller diameter and size-distribution. The cubic fcc Ni nanoparticles with 4.9 +/- 0.9 to 5.9 +/- 1.4 nm in mean diameter and monomodal size-distribution thus prepared are probably composed of a small cap layer of NiO around a core of Ni metal. The contribution of the oxide layer also depends on the medium i.e. the metal oxide ratio increases in salts containing four to eight carbons on their side-chains and then decreases as the number of carbons increases. The Ni nanoparticles dispersed in the ionic liquids are active catalysts for the hydrogenation of olefins under relatively mild reaction conditions.     

Characterization of protein conjugates using capillary electrophoresis

With the aim of generating antibodies, a calix[4]arene-crown-6 was coupled to bovine serum albumin. For that purpose, a complete procedure to optimize and characterize the coupling of hydrophobic haptens based on capillary electrophoresis (CE) was developed. We demonstrated the existence of a polynomial relationship between the electrophoretic mobility (mu(ep)) and the hapten density. This correlation was used not only to study the coupling reaction in terms of optimization and kinetics but also to determine the average coupling molar ratio of any given conjugate. An estimation of the heterogeneity of these conjugates by simulation of experimental peaks was also proposed.     

Market Viability and Martingale Measures under Partial Information

We consider a financial market model with a single risky asset whose price process evolves according to a general jump-diffusion with locally bounded coefficients and where market participants have only access to a partial information flow. For any utility function, we prove that the partial information financial market is locally viable, in the sense that the optimal portfolio problem has a solution up to a stopping time, if and only if the (normalised) marginal utility of the terminal wealth generates a partial information equivalent martingale measure (PIEMM). This equivalence result is proved in a constructive way by relying on maximum principles for stochastic control problems under partial information. We then characterize a global notion of market viability in terms of partial information local martingale deflators (PILMDs). We illustrate our results by means of a simple example.     

Chaotic Dynamics Underlying Action Selection in Mice

In previous papers, we have established, through a functional analysis of the behavioral sequences recorded on laboratory mice over a twelve-hour period, the existence of two independent strategies of action selection. On the one hand, the choice of ultradian alternations of rest and activity bouts makes it possible for every mouse to maximize its net energy gain over a one-day or a one-night interval. On the other hand, the succession of acts performed within an activity bout might serve to precisely fit the metabolic needs of each animal, because the corresponding results present great inter-individual variability, with some mice increasing and others decreasing their net energy gain. To determine what kind of dynamic system could generate these successions of acts within an activity bout, we performed a nonlinear time series analysis of the energy costs related to the acts displayed by the mice during such a period. The results suggest that chaotic dynamics might be involved in action selection in mice. Thus, the variability mentioned above could be a consequence of the sensitive dependence on initial conditions associated with such dynamics, and would allow mice to rapidly adapt their metabolic needs to the ongoing situation.     

Optimal Stochastic Impulse Control with Delayed Reaction

We study impulse control problems of jump diffusions with delayed reaction. This means that there is a delay δ>0 between the time when a decision for intervention is taken and the time when the intervention is actually carried out. We show that under certain conditions this problem can be transformed into a sequence of iterated no-delay optimal stopping problems and there is an explicit relation between the solutions of these two problems. The results are illustrated by an example where the problem is to find the optimal times to increase the production capacity of a firm, assuming that there are transaction costs with each new order and the increase takes place δ time units after the (irreversible) order has been placed.