Probing Electronic Correlations in Actinide Materials Using Multipolar Transitions

We report nonresonant inelastic x-ray scattering from the semi-core 5d levels of several actinide compounds. Dipole-forbidden, high-multipole features form a rich bound-state spectrum dependent on valence electron configuration and spin-orbit and Coulomb interactions. Cross-material comparisons, together with the anomalously high Coulomb screening required for agreement between atomic multiplet theory and experiment, demonstrate sensitivity to the neighboring electronic environment, such as is needed to address long-standing questions of electronic localization and bonding in 5f compounds.Comment: LA-UR 09-0782

An Old Tool Reexamined: Using the Star Power Simulation to Teach Social Inequality

This study examined the effectiveness of the Star Power simulation for teaching stratification and inequality to students of the net generation. The data for this study were obtained through the use of survey methodology and content analysis of 126 course papers from introductory sociology classes. Papers were analyzed for identification and application of class concepts, recommendation of the simulation, and perceived value of the simulation as a learning tool. Analysis of data revealed 100 percent of students found Star Power worthwhile, and 98 percent recommended it be used in future classes. The most common concepts students linked with their simulation experience were inequality, stratification, and social structure. Finally, six themes were identified illustrating students’ perceived value of the simulation

Les filtres à zéolite en assainissement collectif. Etat des lieux et analyse du fonctionnement

Au cours des dernières années, le Cemagref a déjà été conduit à contribuer à la réalisation de plusieurs états de l'art spécifiques à certaines filières d'épuration, notamment : Le lagunage naturel. L'étude, parue en 1997, a été conduite en étroite collaboration avec les agences de l'eau, les Satese et l'Ecole Nationale de la Santé Publiques. Le traitement statistique des données recueillies a amené, entre autres, à modifier les règles de conception de cette filière : modification de la taille du 1er bassin et suppression de l'usage des macrophytes. Les filtres plantés de roseaux à flux vertical. L'étude, parue en 2004, a été conduite en étroite collaboration avec les agences de l'eau, les Satese et l'université de Chambéry. Le traitement statistique des données a notamment conduit à confirmer le dimensionnement de la filière dans le cas général et à affiner le dimensionnement dans le cas d'une sensibilité particulière du milieu au paramètre azote. Le Cemagref a réalisé la présente étude sur "les filtres à zéolite installés en assainissement collectif" à la suite d'une sollicitation de l'Association des Maires Ruraux de France (AMRF) et après l'interpellation directe par des maîtres d'ouvrage, des Conseils Généraux et des maîtres d'oeuvre sur la façon de remédier à des dysfonctionnements qu'ils ont pu constater sur un certain nombre d'installations de ce type. Cette étude a été réalisée avec le soutien financier de l'Office National de l'Eau et des Milieux Aquatiques (ONEMA) et de l'AMRF. Elle s'est fixé plusieurs objectifs : avoir une vision précise de l'étendue du parc, cerner les difficultés rencontrées sur ces dispositifs, qualifier les sources des difficultés si elles s'avéraient confirmées et enfin envisager des solutions pour y remédier lorsque cela serait possible. L'étude s'est déroulée en 2 phases : Tout d'abord, un état des lieux exhaustif du développement de la filière et de son fonctionnement a été réalisé au niveau national. Pour ce faire, la participation de tous les SATESE ou de leurs homologues a été sollicitée afin de recueillir le plus grand nombre d'informations possible sur les dispositifs en place. L'enquête a porté sur TOUS les dispositifs, qu'ils soient considérés en fonctionnement satisfaisant ou non.Dans un deuxième temps, l'étude s'est concentrée sur l'identification des conditions dans lesquelles les dysfonctionnements se manifestent, afin d'envisager des solutions qui pourraient être mises en oeuvre pour résoudre ou réduire les difficultés rencontrées

Structural and spectroscopic characterization of an einsteinium complex.

The transplutonium elements (atomic numbers 95-103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to transplutonium elements. Furthermore, understanding the properties of these heavy elements has been restricted by their scarcity and radioactivity. This is especially true for einsteinium (Es), the heaviest element on the periodic table that can currently be generated in quantities sufficient to enable classical macroscale studies1. Here we characterize a coordination complex of einsteinium, using less than 200 nanograms of 254Es (with half-life of 275.7(5) days), with an organic hydroxypyridinone-based chelating ligand. X-ray absorption spectroscopic and structural studies are used to determine the energy of the L3-edge and a bond distance of einsteinium. Photophysical measurements show antenna sensitization of EsIII luminescence; they also reveal a hypsochromic shift on metal complexation, which had not previously been observed in lower-atomic-number actinide elements. These findings are indicative of an intermediate spin-orbit coupling scheme in which j-j coupling (whereby single-electron orbital angular momentum and spin are first coupled to form a total angular momentum, j) prevails over Russell-Saunders coupling. Together with previous actinide complexation studies2, our results highlight the need to continue studying the unusual behaviour of the actinide elements, especially those that are scarce and short-lived

Vanadium Bisimide Bonding Investigated by X‑ray Crystallography, ⁵¹V and ¹³C Nuclear Magnetic Resonance Spectroscopy, and V L_3,2-Edge X‑ray Absorption Near-Edge Structure Spectroscopy

Syntheses of neutral halide and aryl vanadium bisimides are described. Treatment of VCl₂(N<i>t</i>Bu)­[NTMS­(N^<i>t</i>Bu)], <b>2</b>, with PMe₃, PEt₃, PMe₂Ph, or pyridine gave vanadium bisimides via TMSCl elimination in good yield: VCl­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>3</b>, VCl­(PEt₃)₂(N^<i>t</i>Bu)₂ <b>4</b>, VCl­(PMe₂Ph)₂(N^<i>t</i>Bu)₂ <b>5</b>, and VCl­(Py)₂(N^<i>t</i>Bu)₂ <b>6</b>. The halide series (Cl–I) was synthesized by use of TMSBr and TMSI to give VBr­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>7</b> and VI­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>8</b>. The phenyl derivative was obtained by reaction of <b>3</b> with MgPh₂ to give VPh­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>9</b>. These neutral complexes are compared to the previously reported cationic bisimides [V­(PMe₃)₃(N^<i>t</i>Bu)₂]­[Al­(PFTB)₄] <b>10</b>, [V­(PEt₃)₂(N^<i>t</i>Bu)₂]­[Al­(PFTB)₄] <b>11</b>, and [V­(DMAP)­(PEt₃)₂(N^<i>t</i>Bu)₂]­[Al­(PFTB)₄] <b>12</b> (DMAP = dimethylaminopyridine, PFTB = perfluoro-<i>tert</i>-butoxide). Characterization of the complexes by X-ray diffraction, ¹³C NMR, ⁵¹V NMR, and V L_3,2-edge X-ray absorption near-edge structure (XANES) spectroscopy provides a description of the electronic structure in comparison to group 6 bisimides and the bent metallocene analogues. The electronic structure is dominated by π bonding to the imides, and localization of electron density at the nitrogen atoms of the imides is dictated by the cone angle and donating ability of the axial neutral supporting ligands. This phenomenon is clearly seen in the sensitivity of ⁵¹V NMR shift, ¹³C NMR Δδ_αβ, and L₃-edge energy to the nature of the supporting phosphine ligand, which defines the parameters for designing cationic group 5 bisimides that would be capable of breaking stronger σ bonds. Conversely, all three methods show little dependence on the variable equatorial halide ligand. Furthermore, this analysis allows for quantification of the electronic differences between vanadium bisimides and the structurally analogous mixed Cp/imide system CpV­(N^<i>t</i>Bu)­X₂ (Cp = C₅H₅^1–)

Vanadium Bisimide Bonding Investigated by X‑ray Crystallography, ⁵¹V and ¹³C Nuclear Magnetic Resonance Spectroscopy, and V L_3,2-Edge X‑ray Absorption Near-Edge Structure Spectroscopy

Syntheses of neutral halide and aryl vanadium bisimides are described. Treatment of VCl₂(N<i>t</i>Bu)­[NTMS­(N^<i>t</i>Bu)], <b>2</b>, with PMe₃, PEt₃, PMe₂Ph, or pyridine gave vanadium bisimides via TMSCl elimination in good yield: VCl­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>3</b>, VCl­(PEt₃)₂(N^<i>t</i>Bu)₂ <b>4</b>, VCl­(PMe₂Ph)₂(N^<i>t</i>Bu)₂ <b>5</b>, and VCl­(Py)₂(N^<i>t</i>Bu)₂ <b>6</b>. The halide series (Cl–I) was synthesized by use of TMSBr and TMSI to give VBr­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>7</b> and VI­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>8</b>. The phenyl derivative was obtained by reaction of <b>3</b> with MgPh₂ to give VPh­(PMe₃)₂(N^<i>t</i>Bu)₂ <b>9</b>. These neutral complexes are compared to the previously reported cationic bisimides [V­(PMe₃)₃(N^<i>t</i>Bu)₂]­[Al­(PFTB)₄] <b>10</b>, [V­(PEt₃)₂(N^<i>t</i>Bu)₂]­[Al­(PFTB)₄] <b>11</b>, and [V­(DMAP)­(PEt₃)₂(N^<i>t</i>Bu)₂]­[Al­(PFTB)₄] <b>12</b> (DMAP = dimethylaminopyridine, PFTB = perfluoro-<i>tert</i>-butoxide). Characterization of the complexes by X-ray diffraction, ¹³C NMR, ⁵¹V NMR, and V L_3,2-edge X-ray absorption near-edge structure (XANES) spectroscopy provides a description of the electronic structure in comparison to group 6 bisimides and the bent metallocene analogues. The electronic structure is dominated by π bonding to the imides, and localization of electron density at the nitrogen atoms of the imides is dictated by the cone angle and donating ability of the axial neutral supporting ligands. This phenomenon is clearly seen in the sensitivity of ⁵¹V NMR shift, ¹³C NMR Δδ_αβ, and L₃-edge energy to the nature of the supporting phosphine ligand, which defines the parameters for designing cationic group 5 bisimides that would be capable of breaking stronger σ bonds. Conversely, all three methods show little dependence on the variable equatorial halide ligand. Furthermore, this analysis allows for quantification of the electronic differences between vanadium bisimides and the structurally analogous mixed Cp/imide system CpV­(N^<i>t</i>Bu)­X₂ (Cp = C₅H₅^1–)