Gangliosides' analysis by MALDI-ion mobility MS

The combination of ion mobility with matrix-assisted laser desorption/ionization allows for the rapid separation and analysis of biomolecules in complex mixtures (such as tissue sections and cellular extracts), as isobaric lipid, peptide, and oligonucleotide molecular ions are pre-separated in the mobility cell before mass analysis. In this study, MALDI-IM MS is used to analyze gangliosides, a class of complex glycosphingolipids that has different degrees of sialylation. Both GD1a and GD1b, structural isomers, were studied to see the effects on gas-phase structure depending upon the localization of the sialic acids. A total ganglioside extract from mouse brain was also analyzed to measure the effectiveness of ion mobility to separate out the different ganglioside species in a complex mixture.     

The structure,composition, and dimensions of TiO<Subscript>2</Subscript> and ZnO nanomaterials in commercial sunscreens

TiO₂ and ZnO nanomaterials are widely used to block ultraviolet radiation in many skin care products, yet product labels do not specify their dimensions, shape, or composition. The absence of this basic information creates a data gap for both researchers and consumers alike. Here, we investigate the structural similarity of pigments derived from actual sunscreen products to nanocrystals which have been the subject of intense scrutiny in the nanotoxicity literature. TiO₂ and ZnO particles were isolated from eight out of nine commercial suncare products using three extraction methods. Their dimension, shape, crystal phase, surface area, and elemental composition were examined using transmission and scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller (BET) specific surface area analysis, energy dispersive X-ray and inductively coupled plasma optical emission spectroscopy. TiO₂ pigments were generally rutile nanocrystals (dimensions ~25 nm) with needle-like or near-spherical shapes. ZnO pigments were wurtzite rods with a short axes less than 40 nm and longer dimensions often in excess of 100 nm. We identify two commercial sources of TiO₂ and ZnO nanocrystals whose physical and chemical features are similar to the pigments found in sunscreens. These particular materials would be effective surrogates for the commercial product and could be used in studies of the health and environmental impacts of engineered nanomaterials contained in sunscreens.     

First evidence of resistive switching in polycrystalline GaV4S8 thin layers

Recently a new type of reversible and non‐volatile resistive switching was discovered in single crystals of Mott insulators AM₄X₈ (A = Ga, Ge; M = V, Nb, Ta; X = S, Se). Here we report on the first synthesis of thin layers (thicknesses in the 100 to 1000 nm range) of GaV₄S₈ by RF magnetron sputtering process. Energy dispersive spectroscopy, X‐ray diffraction and TEM analyses attest the high quality of polycrystalline GaV₄S₈ thin layers. Electrical measurements demonstrate that deposited GaV₄S₈ thin films exhibit a non‐volatile reversible resistive switching at room temperature with writing/erasing times of ～10 µs and a memory window (R_high – R_low)/ R_low > 33%. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Geometric distortion correction for echo planar images using nonrigid registration with spatially varying scale

One method used to correct geometric and intensity distortions in echo planar images is to register them to undistorted images via nonrigid deformations. However, some areas in the echo planar images are more distorted than others, thus suggesting the use of deformations whose characteristics are adapted spatially. In this article, we incorporate into our previously developed registration algorithm a spatially varying scale mechanism, which adapts the local scale properties of the transformation by means of a scale map. To compute the scale map, a technique is proposed that relies on an estimate of the expected deformation field. This estimate is generated using knowledge of the physical processes that induce distortions in echo planar images. We evaluate the method of spatially varying scale on both simulated and real data. We find that, in comparison with our earlier method using fixed scale, our new method finds deformation fields that are smoother and finds them faster without sacrificing accuracy.     

Axial coding in full-field microscopy using three-dimensional structured illumination implemented with no moving parts

We report a simple optical setup to produce both axial and lateral structured illumination through a single objective lens. With a minimum of six full-field images obtained without moving either the sample or the microscope objective, 100 nm diameter fluorescent beads can be localized axially with an accuracy of 50 nm in a 1.76-microm-thick layer. We show that this axial localization improvement can easily be combined with classical lateral structured illumination, so that lateral resolution enhancement by a factor of 2 is maintained.     

Clustering properties,Jack polynomials and unitary conformal field theories

Recently, Jack polynomials have been proposed as natural generalizations of Zk${\mathbb{Z}}_k$ Read–Rezayi states describing non-Abelian fractional quantum Hall systems. These polynomials are conjectured to be related to correlation functions of a class of W-conformal field theories based on the Lie algebra A_k−1$A_{k-1}$. These theories can be considered as non-unitary solutions of a more general series of CFTs with Zk${\mathbb{Z}}_k$ symmetry, the parafermionic theories. Starting from the observation that some parafermionic theories admit unitary solutions as well, we show, by computing the corresponding correlation functions, that these theories provide trial wavefunctions which satisfy the same clustering properties as the non-unitary ones. We show explicitly that, although the wavefunctions constructed by unitary CFTs cannot be expressed as a single Jack polynomial, they still show a fine structure where the mathematical properties of the Jack polynomials play a major role.     

A practical approach to the living polymerization of functionalized monomers: application to block copolymers and 3‐dimensional macromolecular architectures

The tolerance of living free radical procedures to reactive functional groups, coupled with their ability to prepare well‐defined random and block copolymers is demonstrated by the use of novel α‐hydrogen alkoxyamine derivatives instead of the traditional TEMPO‐based systems. This refinement in the nitroxide structure overcomes many limitations typically associated with TEMPO and has permitted a dramatic increase in the range of monomers, which can be polymerized under controlled conditions. The ability to prepare well‐defined multi‐arm star polymers from a variety of alkoxyamine terminated vinyl and non‐vinyl linear polymers are major benefits when compared to traditional living procedures, such as anionic polymerizations.     

Structure factor of a self-avoiding polymer chain at high momentum transfer

The molecular weight of a Gaussian polymer chain can be obtained from the intercept of the asymptote in a plot of the inverse structure factor 1/S(q) as a function of the square of the wave vector q². Using an ϵ expansion and scaling arguments, we show that in a good solvent the situation is more complex and that the molecular weight determination is difficult to justify. The corrections to the asymptotic behavior of the structure factor at large wave vector involve several terms that are difficult to separate experimentally. This is qualitatively explained by the nonuniform swelling of a polymer chain in a good solvent due to the existence of the chain ends.