Water mapping in hydrated soft materials

We present a method based on spatially resolved electron energy-loss spectroscopy in the cryo-STEM to map the spatial distribution of water in frozen-hydrated polymers. The spatial resolution is limited by the dose constraints imposed by radiation damage, and to stay within these constraints, the use of fine electron-probe sizes comes at the cost of reduced counts in the energy-loss spectra. Thus, at the resolution limit, the detection of isolated water-rich pixels or the identification of minor variations in water content across the specimen is complicated because one must distinguish significant fluctuations from noise. Here we develop a criterion with which to guide such a distinction. We characterize the intrinsic noise associated with spectral measurements under given illumination and acquisition conditions. We then use that noise in combination with scatter diagrams to threshold spectrum images and objectively identify statistically significant compositional fluctuations. We illustrate these ideas using a simulated spectrum dataset for a hypothetical blend of hydrophilic and hydrophobic homopolymers. We show that while a direct inspection of the water map may not allow any meaningful conclusions to be drawn, after applying the thresholding approach we can clearly identify the regions of the specimen that are rich in water. We also experimentally study a model blend system comprised of hydrophilic poly(vinyl pyrrolidone) (PVP) dispersed in a hydrophobic matrix of poly(styrene) (PS). By MLS fitting using damaged and undamaged PVP reference spectra, we determine that the critical dose characteristic of dry PVP is approximately 8000 e/nm2 using 200 keV incident electrons. Irradiating frozen-hydrated PVP gives rise to noticeable hydrogen evolution at doses of approximately 1500 e/nm2. To stay within this constraint we use doses of 400 e/nm2 and a pixel spacing in the spectrum imaging of 100 nm. In order to quantitatively map the water, PVP, and PS compositions, we measure their total inelastic scattering cross-sections. Direct inspection of the composition maps reveals the presence of large water-rich domains of the order of approximately 1 microm and the scatter-diagram thresholding approach identifies small water-rich domains one pixel in size.     

Advances in proteomics data analysis and display using an accurate mass and time tag approach

Proteomics has recently demonstrated utility for increasing the understanding of cellular processes on the molecular level as a component of systems biology approaches and for identifying potential biomarkers of various disease states. The large amount of data generated by utilizing high efficiency (e.g., chromatographic) separations coupled with high mass accuracy mass spectrometry for high-throughput proteomics analyses presents challenges related to data processing, analysis, and display. This review focuses on recent advances in nanoLC-FTICR-MS-based proteomics approaches and the accompanying data processing tools that have been developed to display and interpret the large volumes of data being produced.     

Electrodeposition of palladium-dotted nickel nanowire networks as a robust self-supported methanol electrooxidation catalyst

Journal of Materials Science - Mass activity and long-term stability are two major issues in current fuel cell catalyst designs. While supported catalysts normally suffer from poor long-term...     

Expanding the structural diversity of polyelectrolyte complexes and polyzwitterions

Charged (macro)molecules are essential components in natural materials and organisms; thus the rational design of biomimetic materials requires a holistic understanding of structure–property relationships in charged systems. We discuss recent progress in uncovering such relationships for polyzwitterions and polyelectrolyte complexes, with emphases on the synthetic strategies that were employed in systematic studies. For polyelectrolytes, discussion is confined to the effects that structural variations in polycation and polyanion structure have on the fundamental phase behavior of the corresponding polyelectrolyte complexes. In the field of polyzwitterions, both fundamental and applied properties are discussed in relation to chemical structure. Finally, we present an overview of promising chemistries that will expand the structural landscape of charged macromolecules with the aim of stimulating new research to further uncover and understand the fundamental design principles for these materials.     

The Absence and Importance of Operando Techniques for Metal‐Free Catalysts

Operando characterization techniques have played a crucial role in modern technological developments. In contrast to the experimental uncertainties introduced by ex situ techniques, the simultaneous measurement of desired sample characteristics and near‐realistic electrochemical testing provides a representative picture of the underlying physics. From Li‐ion batteries to metal‐based electrocatalysts, the insights offered by real‐time characterization data have enabled more efficient research programs. As an emerging class of catalyst, much of the mechanistic understanding of metal‐free electrocatalysts continues to be elusive in comparison to their metal‐based counterparts. However, there is a clear absence of operando characterization performed on metal‐free catalysts. Through the proper execution of operando techniques, it can be expected that metal‐free catalysts can achieve exceptional technological progress. Here, the motivation of using operando characterization techniques for metal‐free carbon‐based catalyst system is considered, followed by a discussion of the possibilities, difficulties and benefits of their applications.     

Effects of atmospheric ozone on microarray data quality

A data anomaly was observed that affected the uniformity and reproducibility of fluorescent signal across DNA microarrays. Results from experimental sets designed to identify potential causes (from microarray production to array scanning) indicated that the anomaly was linked to a batch process; further work allowed us to localize the effect to the posthybridization array stringency washes. Ozone levels were monitored and highly correlated with the batch effect. Controlled exposures of microarrays to ozone confirmed this factor as the root cause, and we present data that show susceptibility of a class of cyanine dyes (e.g., Cy5, Alexa 647) to ozone levels as low as 5-10 ppb for periods as short as 10-30 s. Other cyanine dyes (e.g., Cy3, Alexa 555) were not significantly affected until higher ozone levels (> 100 ppb). To address this environmental effect, laboratory ozone levels should be kept below 2 ppb (e.g., with filters in HVAC) to achieve high quality microarray data.     

The PumaPaint Project

The PumaPaint Project is an online robot that allows World Wide Web users to create original artwork. This paper describes the PumaPaint Project at two locations: the original site at Wilkes University and the site at Roger Williams University. Each site allows control of a PUMA robot equipped with four paintbrushes, jars of red, green, blue and yellow paint and white paper attached to a vertical easel. A Java interface executing within a web browser allows interactive control of the robot. This interface contains two windows showing live camera views of the easel and various controls for connecting to the robot, viewing the task status and controlling the painting task. The original site operated from June 1998 to March 2000 with approximately 25,000 unique-addressed machines downloading the interface to produce about 500 canvases. The new site has been in operation since August 2002. This paper discusses the author's experiences in operating the original site, and the motivation for and the challenges of reviving the site in its current location.     

Dennett Explained?: A Critical Study of Dahlbom's Dennett and His Critics

Minds and Machines -     

Measurement methods for LCoS displays

Abstract— Two measurement methods to characterize uniformity and the absolute cell gap of LCoS images will be reviewed. These are simple to use in a production environment and have allowed major improvements in manufacture to be achieved. For the purpose of this paper, the liquid‐crystal mode used is the 45° normally black mode.     

The nanocidal and antifeedant activities of titanium dioxide desiccant toward wool-digesting <Emphasis Type="Italic">Tineola bisselliella</Emphasis> moth larvae

The nanocidal and antifeedant activities of titanium dioxide nanoparticles (TiO₂) against the widespread pest of wool carpets, apparel, building insulation, and other wool textiles, Tineola bisselliella (common clothes moth), were investigated using an industry-recognized bioassay test, and a feeding preference test. Wool fabric was pre-treated with citric acid/sodium hypophosphite, TiO₂ applied, and then loosely bound TiO₂ was removed by ultrasound. A statistically significant (p < 0.05) increase in larval mortality was found using 1.7 % on mass of wool (omw) TiO₂, whereas levels as low as 0.1 % omw significantly reduced feeding. TiO₂ did not show any repellence in the feeding preference test. The TiO₂ was considerably less effective than the commercial insect-resist agent Lanacare FPL (Shamrock Group Ltd) was. This study extends understanding of entomotoxic nanocides on textiles to a new insect species and to new test methods, and further illustrates their potential for protecting wool textiles from keratinophagous insects.