Rapid acquisition strategy for functional T1ρ mapping of the brain

Functional T1ρ mapping has been proposed as a method to assess pH and metabolism dynamics in the brain with high spatial and temporal resolution. The purpose of this work is to describe and evaluate a variant of the spin-locked echo-planar imaging sequence for functional T1ρ mapping at 3 T. The proposed sequence rapidly acquires a time series of T1ρ maps with 4.0 second temporal resolution and 10 slices of volumetric coverage. Simulation, phantom, and in vivo experiments are used to evaluate many aspects of the sequence and its implementation including fidelity of measured T1ρ dynamics, potential confounds to the T1ρ response, imaging parameter tradeoffs, time series analysis approaches, and differences compared to blood oxygen level dependent functional magnetic resonance imaging. It is shown that the high temporal resolution and volumetric coverage of the sequence are obtained with some expense including underestimation of the T1ρ response, sensitivity to T1 dynamics, and reduced signal-to-noise ratio. In vivo studies using a flashing checkerboard functional magnetic resonance imaging paradigm suggest differences between T1ρ and blood oxygen level dependent activation patterns. Possible sources of the functional T1ρ response and potential sequence improvements are discussed. The capability of T1ρ to map whole-brain pH and metabolism dynamics with high temporal and spatial resolution is potentially unique and warrants further investigation and development.     

Microstructural effects in non linear stratified composites

In this paper, we analyze the microstructural effects on non linear elastic and periodic composites within the framework of asymptotic homogenization. We assume that the constitutive laws of the individual constituents derive from strain potentials. The microstructural effects are incorporated by considering the higher order terms, which come from the asymptotic series expansion. The complete solution at any order requires the resolution of a chain of cell problems in which the source terms depend on the solution at the lower order. The influence of these terms on the macroscopic response of the non linear composite is evaluated in the particular case of a stratified microstructure. The analytic solutions of the cell problems at the first and second order are provided for arbitrary local strain–stress laws which derive from potentials. As classically, the non-linear dependence on the applied macroscopic strain is retrieved for the solution at the first order. It is proved that the second order term in the expansion series also exhibits a non linear dependence with the macroscopic strain but linearly depends on the gradient of macroscopic strain. As a consequence, the macroscopic potential obtained by homogenization is a quadratic function of the macroscopic strain gradient when the expansion series is truncated at the second order. This model generalizes the well known first strain gradient elasticity theory to the case of non linear elastic material. The influence of the non local correctors on the macroscopic potential is investigated in the case of power law elasticity under macroscopic plane strain or antiplane conditions.     

Interprotein Electron Transfer between FeS-Protein Nanowires and Oxygen-Tolerant NiFe Hydrogenase

Self-assembled redox protein nanowires have been exploited as efficient electron shuttles for an oxygen-tolerant hydrogenase. An intra/inter-protein electron transfer chain has been achieved between the iron-sulfur centers of rubredoxin and the FeS cluster of [NiFe] hydrogenases. [NiFe] Hydrogenases entrapped in the intricated matrix of metalloprotein nanowires achieve a stable, mediated bioelectrocatalytic oxidation of H₂ at low-overpotential.     

Reversible Single Molecular Switch Operating at 300 K on a Surface

A single 4‐pyridylazobenzene molecule is observed at room temperature on a Si(111)‐B surface by using scanning tunnel microscopy. The reversible conformational switching of this molecule is induced by tunneling electrons and observed at room temperature. This process is based on an intramolecular rotation of a single phenyl group without isomerization of the N?N double bond.     

Catalytic reduction of U(VI) to U(IV) using hydrogen with platinum loaded on alumina and silica

During the reprocessing of spent nuclear fuel, uranium (U) and plutonium (Pu) are together extracted by employing tri-n-butyl phosphate (TBP)/dodecane mixture and their partitioning is achieved by adding uranous nitrate. The partitioning agent, uranous is conventionally produced by the electrolytic reduction of uranyl nitrate. An alternate route for the reduction of U from (VI) to (IV) using hydrogen (H₂) as reductant was developed using platinum (Pt) based catalyst. Improvements in the development of the catalyst have been carried out in order to reduce the requirement of Pt without affecting the reduction performance. Experiments using 2 wt% Pt loaded on alumina beads and alumina powder have been performed and results are discussed. As the catalyst supported on alumina was found to be unstable in acidic environment, Pt loaded on silica powder has also been developed. Pt loaded on alumina and silica substrates have been tried to envisage the reduction behaviour using H₂ as reductant in presence of hydrazine nitrate which acts as U(IV) stabiliser as well as reductant. Parametric studies have been carried out to optimise the process parameters namely pressure, temperature, U concentration, free acidity, hydrazine concentration and catalyst to U (C/U) ratio. 2 wt% Pt loaded on silica has been selected for further scale up studies for making uranous.     

Syntheses of C-5-spirocyclic C-glycoside SGLT2 inhibitors

Several syntheses of C-5-spirocycle-containing C-glycosides are discussed. A multigram-scale synthesis capitalizing on a one-pot aldol-Cannizzaro sequence is described. Spiro oxetane formation using an unprotected penta-ol C-glycoside as substrate is also exemplified. Functional assessment of these compounds for potency and selectivity was evaluated at human SGLT2 and SGLT1.