The microscopic investigation of structures of moving flux lines by neutron and muon techniques

We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux lines in low T _c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors.     

Three-dimensional visualization of protein expression in mouse brain structures using imaging mass spectrometry

We have developed a method to visualize matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) data aligned with optically determinable tissue structures in three dimensions. Details of the methodology are exemplified using the 3-D reconstruction of myelin basic protein (MBP) in the corpus callosum of a mouse brain. In this procedure, optical images obtained from serial coronal sections are first aligned to each other to reconstruct a surface of the corpus callosum from segmented contours of the aligned images. The MALDI IMS data are then coregistered to the optical images and superimposed into the surface to create the final 3-D visualization. Correlating proteomic data with anatomical structures provides a more comprehensive understanding of healthy and pathological brain functions, and holds promise to be utilized in more complex anatomical arrangements.     

Thioflavin T hydroxylation at basic pH and its effect on amyloid fibril detection

The fluorescent dye thioflavin T (ThT) is commonly used for in situ amyloid fibril detection. In this work, we focused on the spectroscopic properties and chemical stability of ThT in aqueous solution as a function of pH, temperature, and dye concentration. A reversible hydroxylation process occurs in alkaline solutions, which was characterized using a combination of UV-vis absorption spectroscopy, proton NMR, and density functional theory (DFT). On the basis of these studies, we propose a chemical structure for the hydroxylated form. Finally, by means of fluorescence spectroscopy, ThT hydroxylation effects on in situ amyloid detection have been investigated, providing new insights on the efficiency of the ThT assay for quantitative fibril evaluation at basic pH.     

Speciation measurements of uranium in alkaline waters using diffusive gradients in thin films technique

This work investigated the application of diffusive gradients in thin films technique (DGT) to uranium speciation measurements in natural water. Two binding phases were examined, a commercially available affinity membrane, Whatman DE 81 (DE 81), with amino binding functional groups and the conventionally used Chelex 100 beads imbedded polyacrylamide hydrogel (Chelex) with iminodiacetate functional groups. The DGT devices assembled with the binding phases of DE 81 (DE 81 DGT) and Chelex gel (Chelex DGT) were tested both in synthetic river water solutions and in local river water. DE 81 DGT and Chelex DGT measured 80% and 75% of the total uranium in synthetic river water solution, respectively, and measured 73% and 60% of the total uranium in St. Lawrence River, Canada, respectively. The binding properties of the DE 81 membrane and Chelex gel for uranium, and the diffusion of uranyl complexes in the polyacrylamide gel (PAM) were also studied.     

Influence of Cyclodextrins on the Kinetics of Oxidation of Amino Acids and BSA by Hydrazyl Radicals

The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin.     

Condensation reaction in the bandpass reaction cell improves sensitivity for uranium,thorium, neodymium and praseodymium measurements

Condensation reactions in the bandpass reaction cell or dynamic reaction cell (DRC) were used for the determination of actinides and lanthanides such as uranium, thorium, neodymium and praseodymium. These elements react with oxygen reagent gas in the dynamic reaction cell of the ELAN DRC II instrument to give mono- and/or dioxo cationic species (UO₂⁺, ThO⁺, NdO⁺ and PrO⁺, respectively). Increasing the oxygen flow rate in the dynamic reaction cell leads to the rapid decrease of the singly charged metal ions accompanied by the fast increase in the intensity of the oxide ion. This phenomenon is used to improve considerably the sensitivity of ICP-MS instruments equipped with a dynamic reaction cell for actinides and lanthanides. Estimated detection limits (EDL) obtained in this work for uranium, thorium, neodymium-144 and praseodymium are 0.022, 1.0, 0.045, and 0.10 ng L^–1, respectively. The detection limit for uranium measured in the standard (vented) mode of an ELAN DRC II was found to be 0.22 ng L^–1, which is an order of magnitude higher compared to the pressurized mode.     

Combination of LC-ICP-MS, LC-MS and NMR for investigation of the oxidative degradation of selenomethionine

Selenomethionine (SeMet) was oxidized by heating an acidic solution with hydrogen peroxide. Samples were taken before and during the oxidation process. The oxidation products were separated by cation exchange chromatography followed by ICP-MS detection to identify the selenium containing compounds as well as electrospray ionization MS detection to determine the masses of the degradation products. Furthermore, the samples were analyzed by ⁷⁷Se-NMR. The first appearing degradation product was selenomethionine selenoxide, which was converted via the deaminated selenoxide to methane seleninic acid and selenite.