Automated assignment of ionization states in broad‐mass matrix‐assisted laser desorption/ionization spectra of protein mixtures

A computational technique is presented for the automated assignment of the multiple charge and multimer states (ionization states) in the time‐of‐flight (TOF) domain for matrix‐assisted laser desorption/ionization (MALDI) spectra. Examples of the application of this technique include an improved, automatic calibration over the 2 to 70 kDa mass range and a reduced data redundancy after reconstruction of the molecular spectrum of only singly charged monomers. This method builds on our previously reported enhancement of broad‐mass signal detection, and includes two steps: (1) an automated correction of the instrumental acquisition initial time delay, and (2) a recursive TOF detection of multiple charge states and singly charged multimers of molecular [MH]⁺ ions over the entire record range, based on MALDI methods. The technique is tested using calibration mixtures and pooled serum quality control samples acquired along with clinical study data. The described automated procedure improves the analysis and dimension reduction of MS data for comparative proteomics applications. Copyright © 2009 John Wiley & Sons, Ltd.     

Reduction of FeO/Pt(1 1 1) thin films by exposure to atomic hydrogen

Using scanning tunneling microscopy (STM), X-ray photoemission spectroscopy (XPS) and density functional theory (DFT) calculations we have studied the reduction of ultra-thin films of FeO(1 1 1) grown on Pt(1 1 1) after exposure to atomic hydrogen at room temperature. A number of new ordered, partly-reduced FeO_x structures are identified and as a general trend we reveal that all the reduced FeO_x structures incorporate 2-fold coordinated Fe atoms as opposed to the original 3-fold coordinated Fe atoms in the FeO film. We find that when all the Fe atoms are 2-fold O-coordinated the FeO_x surface structure is resistant to further reduction at room temperature. We observe that water easily dissociates on the most heavily reduced FeO_x, structure in contrast to the initially inert FeO film, and reveal that it is possible to partially re-oxidize the FeO_x film by heating the surface slightly in the presence of water.     

The geometry and the analytic properties of isotropic multiresolution analysis

In this paper we investigate Isotropic Multiresolution Analysis (IMRA), isotropic refinable functions, and wavelets. The main results are the characterization of IMRAs in terms of the Lax–Wiener Theorem, and the characterization of isotropic refinable functions in terms of the support of their Fourier transform. As an immediate consequence of these results, there are no compactly supported (in the space domain) isotropic refinable functions in many dimensions. Next we study the approximation properties of IMRAs. Finally, we discuss the application of IMRA wavelets to 2D and 3D-texture segmentation in natural and biomedical images.     

The uses of diversity: non-crystalline arrays in microstructured optical fibres

Microstructured polymer optical fibres (mPOFs) can be more easily fabricated in unusual geometries than their silica counterparts, allowing a more diverse range of structures to be explored. We have used evolutionary algorithms to explore a variety of fibre structures, including non-periodic structures.     

Surface and subsurface hydrogen: adsorption properties on transition metals and near-surface alloys

Periodic, self-consistent DFT-GGA calculations are used to study the thermochemical properties of both surface and subsurface atomic hydrogen on a variety of pure metals and near-surface alloys (NSAs). For surface hydrogen on pure metals, calculated site preferences, adsorption geometries, vibrational frequencies, and binding energies are reported and are found to be in good agreement with available experimental data. On NSAs, defined as alloys wherein a solute is present near the surface of a host metal in a composition different from the bulk composition, surface hydrogen generally binds more weakly than it binds to the pure-metal components composing the alloys. Some of the NSAs even possess the unusual property of binding hydrogen as weakly as the noble metals while, at the same time, dissociating H(2) much more easily. On both NSAs and pure metals, formation of surface hydrogen is generally exothermic with respect to H(2)(g). In contrast, formation of subsurface hydrogen is typically endothermic with respect to gas-phase H(2) (the only exception to this general statement is found for pure Pd). As with surface H, subsurface H typically binds more weakly to NSAs than to the corresponding pure-metal components of the alloys. The diffusion barrier for hydrogen from surface to subsurface sites, however, is usually lower on NSAs compared to the pure-metal components, suggesting that population of subsurface sites may occur more rapidly on NSAs.     

On the dimension function of orthonormal wavelets

We announce the following result: Every orthonormal wavelet of is associated with a multiresolution analysis such that for the subspace the integral translates of a countable at most family of functions is a tight frame.

     

The initial oxidation of polycrystalline thorium

The initial oxidation of clean, polycrystalline α‐Th from background CO/CO₂ and saturation of the Th surface by O₂ has been examined by angle‐resolved Auger electron spectroscopy (ARAES) and time of flight secondary ion mass spectrometry (ToF‐SIMS). Following dissociative adsorption of very low doses of background CO/CO₂ (<1 L), the carbon surface population was dominant and spontaneously formed thorium carbide. The accompanying oxygen population increased at a rate roughly one‐third that of the carbon, suggesting simultaneous oxygen incorporation into the bulk. To further corroborate the surface kinetics of adsorbed oxygen, O₂ was admitted, following heating and sputter cleaning of the Th; some oxygen atoms continued to diffuse into the bulk until formation of stoichiometric ThO₂ at ～37 L. ARAES measurements showed an oxygen concentration gradient in the near‐surface region confirming rapid oxygen incorporation at low doses; however, once the surface is saturated, virtually no variation in the oxygen intensity is observed. AES and ToF‐SIMS depth profiling revealed complete oxide formation to a depth of 2 nm. Copyright © 2010 John Wiley & Sons, Ltd.     

Juxtaposition of Chemical and Mutation-Induced Developmental Defects in Zebrafish Reveal a Copper-Chelating Activity for Kalihinol F

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Mixed-metal Pt monolayer electrocatalysts with improved CO tolerance

Using a combination of periodic, self-consistent, density functional theory (DFT) calculations and CO-stripping voltammetry experiments, we have designed a new class of Pt-M bimetallic monolayer catalysts supported on a non-Pt metal, which exhibit improved stability against CO poisoning and might be suitable for proton-exchange membrane fuel cell anodes. These surfaces help in reducing the overpotential associated with anodic CO oxidation and minimize the amount of Pt used, thereby reducing materials cost. DFT calculations predict highly repulsive interactions between adsorbed CO molecules on these surfaces, leading to weaker binding and lower coverage of CO than on pure Pt, which in turn facilitates oxidative removal of CO from these catalytic surfaces.