Improvement of the Correlative AFM and ToF-SIMS Approach Using an Empirical Sputter Model for 3D Chemical Characterization

Technological progress has spurred the development of increasingly sophisticated analytical devices. The full characterization of structures in terms of sample volume and composition is now highly complex. Here, a highly improved solution for 3D characterization of samples, based on an advanced method for 3D data correction, is proposed. Traditionally, secondary ion mass spectrometry (SIMS) provides the chemical distribution of sample surfaces. Combining successive sputtering with 2D surface projections enables a 3D volume rendering to be generated. However, surface topography can distort the volume rendering by necessitating the projection of a nonflat surface onto a planar image. Moreover, the sputtering is highly dependent on the probed material. Local variation of composition affects the sputter yield and the beam-induced roughness, which in turn alters the 3D render. To circumvent these drawbacks, the correlation of atomic force microscopy (AFM) with SIMS has been proposed in previous studies as a solution for the 3D chemical characterization. To extend the applicability of this approach, we have developed a methodology using AFM–time-of-flight (ToF)-SIMS combined with an empirical sputter model, “dynamic-model-based volume correction”, to universally correct 3D structures. First, the simulation of 3D structures highlighted the great advantages of this new approach compared with classical methods. Then, we explored the applicability of this new correction to two types of samples, a patterned metallic multilayer and a diblock copolymer film presenting surface asperities. In both cases, the dynamic-model-based volume correction produced an accurate 3D reconstruction of the sample volume and composition. The combination of AFM–SIMS with the dynamic-model-based volume correction improves the understanding of the surface characteristics. Beyond the useful 3D chemical information provided by dynamic-model-based volume correction, the approach permits us to enhance the correlation of chemical information from spectroscopic techniques with the physical properties obtained by AFM

Tuning Plasmon Resonance in Magnetoplasmonic Nanochains by Controlling Polarization and Interparticle Distance for Simple Preparation of Optical Filters

Magnetoplasmonic Fe₃O₄-coated Ag nanoparticles (NPs) are assembled in large scale (18 × 18 mm²) in order to observe unique modulation of plasmonic coupling and optical tunable application via both external magnetic field and the combination of magnetic dipole and electrostatic interactions of particle–particle and particle–substrate. These large nanochains film exhibits outstanding tunability of plasmonic resonance from visible to near-infrared range by controlling the polarization angle and interparticle distance (IPD). The enormous spectral shift mainly originated from far-field rather than near-field coupling of Ag cores because of the sufficiently large separation between them in which Fe₃O₄ shell acts as spacer. This tunable magnetoplasmonic film can be applicable in the field of anisotropic optical waveguides, tunable optical filter, and nanoscale sensing platform

Anti-cancerous/Anti-bacterial Activities of Allicin Generated In situ from Diastereo Pure Alliins by Alliinase.

Aims: To facilitate allicin generation in-situ from pure diastereomers of alliin by enzymatic reaction of alliinase and assess its anti-cancerous/anti-bacterial activities. Study Design: Chemical synthesis and in-vitro assay of anti-cancerous/anti-bacterial activities. Place and Duration of Study: Protein Research Laboratory, Research Resources Center, University of Illinois at Chicago, between February 2014 and February 2015. Methodology: Cancer cell viability assay MTT assay, bacterial plate-diffusion growth inhibition assay, and flow cytometry cell cycle analysis have been used to demonstrate the anticancerous/anti-pathogen activities of the in-situ allicin. Diastereomers of alliin are produced by H2O2 oxidation of deoxyalliin, which is prepared by mixing L-cysteine and allyl bromide. Deoxyalliin and diastereomers of alliin are purified to high purity with repeated fractional crystallization. In addition, fluorenylmethyloxycarbonyl (Fmoc) protected alliin and alliin methyl ester are synthesized and purified with RP-HPLC to test the importance of amino and carboxyl groups of alliin in alliinase enzymatic reaction. Alliinase is produced by a simple and effective method from an aqueous garlic extract Results: Results from spectrophotometric alliinase activity assay indicate that (+)-L-alliin is more reactive toward alliinase than (-)-L-alliin, and both amino and carboxyl groups of the cysteine portion of alliin are critical in alliinase enzymatic reaction. Results from cancer cell viability assay MTT assay, bacterial plate-diffusion growth inhibition, and flow cytometry cell cycle analysis confirm that the in-situ allicin is as active as allicin purified from aqueous garlic extract or allicin synthesized chemically in a dose-dependent manner. Conclusion: We describe here facile pathways to synthesize diastereomerically pure alliins and isolate allinase. The in-situ allicin conversed from alliin by allinase is very active. The data obtained here provide useful information on the design of the in-situ allicin strategy

Additional file 1: Table S1. of Concordance of oral HPV prevalence between patients with oropharyngeal cancer and their partners

Demographics, exposure, and HPV-related disease history among all evaluable participants enrolled versus those who were excluded from the final analysis. (DOCX 16 kb

HO[subscript x] observations over West Africa during AMMA: impact of isoprene and NO[subscript x]

Aircraft OH and HO[subscript 2] measurements made over West Africa during the AMMA field campaign in summer 2006 have been investigated using a box model constrained to observations of long-lived species and physical parameters. "Good" agreement was found for HO[subscript 2] (modelled to observed gradient of 1.23 ± 0.11). However, the model significantly overpredicts OH concentrations. The reasons for this are not clear, but may reflect instrumental instabilities affecting the OH measurements. Within the model, HO[subscript x] concentrations in West Africa are controlled by relatively simple photochemistry, with production dominated by ozone photolysis and reaction of O([superscript 1]D) with water vapour, and loss processes dominated by HO[subscript 2] + HO[subscript 2] and HO[subscript 2] + RO[subscript 2]. Isoprene chemistry was found to influence forested regions. In contrast to several recent field studies in very low NO[subscript x] and high isoprene environments, we do not observe any dependence of model success for HO[subscript 2] on isoprene and attribute this to efficient recycling of HO[subscript x] through RO[subscript 2] + NO reactions under the moderate NO[subscript x] concentrations (5–300 ppt NO in the boundary layer, median 76 ppt) encountered during AMMA. This suggests that some of the problems with understanding the impact of isoprene on atmospheric composition may be limited to the extreme low range of NO[subscript x] concentrations