Alkali Uranyl Borates: Bond Length, Equatorial Coordination and 5f States

Three uranyl borates, UO2B2O4, LiUO2BO3 and NaUO2BO3, have been prepared by solid state syntheses. The influence of the crystallographic structure on the splitting of the empty 5f and 6d states have been probed using High Energy Resolved Fluorescence Detected X-ray Absorption Spectroscopy (HERFD-XAS) at the uranium M4-edge and L3-edge respectively. We demonstrate that the 5f splitting is increased by the decrease of the uranyl U-Oax distance, which in turn correlates with an increased bond covalency. This is correlated to the equatorial coordination change of the uranium. The role of the alkalis as charge compensating the axial oxygen of the uranyl is discussed.

Dibenzothiophene Hydrodesulfurization over P-CoMo on Sol-Gel Alumina Modified by La Addition. Effect of Rare-Earth Content

Alumina-lanthana (La at 1, 3, or 5 wt%) supports were prepared by sol-gel from Al alkoxide sol where La(NO3)3 was added. Annealed (550 °C) xerogels were characterized by N2 physisorption, thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy- energy dispersive spectroscopy (SEM-EDS), CO2-adsorption studied in IR region, Raman and ultraviolet-vis (UV-vis) spectroscopies. The texture of amorphous binary matrices of high La dispersion was adequate to applications in catalysts for middle distillates hydrodesulfurization (HDS). Generally, the amount and strength of surface basic sites increased with La content in solids. Mo (at 2.8 at. nm−2) and Co (at Co/(Co+Mo) = 0.3) were deposited over carriers by one-pot simultaneous impregnation in the presence of PO43− (P2O5/(NiO+MoO3) = 0.2 mass ratio). Calcined (400 °C) Co-Mo-P impregnated precursors had decreased basicity as to that of corresponding carriers, suggesting strong La-deposited species interaction. As La content in carriers increased Mo=O Raman stretching vibrations shifted to lower wave-numbers (949 to 935 cm−1) suggesting octahedral molybdates coordination change to tetrahedral. Although La at the lowest concentration (1 wt%) enhanced dibenzothiophene, HDS (~38% higher as to the Al2O3-supported formulation) desulfurization was significantly diminished at augmented content. Presence of hardly sulfidable tetrahedral Mo originated during impregnation at basic conditions in pores of La-modified carriers seemed to dictate observed behavior. Rare earth content in formulations enhanced selectivity to biphenyl.

Inter-joint and temporal coordination change in very slow walking

PurposeVery slow walking has been suggested to be a distinctively different motor behavior than walking at comfortable gait speeds. While kinematic and spatiotemporal gait parameters are known to scale with gait speed, inter-joint coordination during swing remains consistent, at least across comfortable speeds. The purpose of this study was to determine whether coordination patterns serving limb clearance and shortening differ with very slow walking, providing additional support for the premise that very slow walking represents a unique motor behavior.MethodsWe assessed nine healthy adults walking overground at their self-selected speed and two-to-three progressively slower speeds. We collected lower extremity kinematics with 3D motion analysis and quantified joint motion contributions to limb clearance and shortening. We investigated changes in coordination using linear mixed models to determine magnitude and timing differences of joint influence across walking speeds.ResultsHip and knee influences serving limb clearance reduced considerably with slower walking speeds. Similarly, knee influence on limb shortening reduced with very slow walking. Importantly, ankle influence remained unchanged across gait speeds for limb shortening and reduced subtly for limb clearance. Temporally, joint influences on limb clearance varied across walking speeds. Specifically, the temporal order of peak hip and knee influences reversed between comfortable and very slow walking. For limb shortening the timing of ankle influence remained unchanged while the timing of knee influence occurred later in the gait cycle for slower walking speeds.ConclusionsOur results demonstrate temporal coordination and the relative joint contributions serving limb clearance and shortening differ with very slow walking providing additional evidence that slow walking may be a behavior distinct from walking at comfortable speeds.

Triggering Cu-coordination change in Cu(ii)-Ala-His-His by external ligands

A switch in copper(ii)-coordination between the two motifs Xxx-Zzz-His (ATCUN) and Xxx-His in the hybride peptide Ala-His-His is induced by adding a ligand such as imidazole.

Lanthanide-induced conformational change of methanol dehydrogenase involving coordination change of cofactor pyrroloquinoline quinone

Classical molecular dynamics simulations combined with fragment molecular orbital calculations were employed to rationalize the enzymatic activities of MDH carrying different lanthanides.