Recent advances in scanning x-ray microscopy

A scanning x-ray microscope has been built at the Daresbury synchrotron radiation source and used to obtain images at soft x-ray wavelengths (～2–4 nm). The focusing element of the microscope is a zone plate, fabricated by a contamination writing process developed at King's College. Zone plates with the finest zone widths, and hence theoretical resolutions, below 20 nm have been fabricated in this way. The contamination material is carbon, and as such is unsuitable for high-efficiency focusing. In order to increase the zone plate efficiency, a shadowing pattern transfer process has been developed and used to replicate contamination lines with 25 nm widths into more suitable materials.     

Cover Image,Volume 67, Issue 9

The cover image, by Eneko Arrospide et al., is based on the Review Polymers beyond standard optical fibres ‐ fabrication of microstructured polymer optical fibres, DOI: 10.1002/pi.5602 .

     

Microcellular polymeric foams based on 1‐vinyl‐2‐pyrrolidone and butyl‐acrylate with tuned thermal conductivity

Microcellular polymers have been produced by ScCO₂ foaming, based on 1‐vinyl‐2‐pyrrolidone (VP) and butyl‐acrylate (BA). Three different copolymers were prepared, varying the compositions of VP and BA, following a simple radical polymerization process using an UV initiator. The samples a good foaming behavior and also excellent flexibility and handle ability, with expansion ratios between 1.53 and 1.72, and cell sizes in the microcellular range (below 5 µm). However, it was observed that the gas distribution and, consequently, the cellular structure inside the polymer foams was highly dependent on the VP and BA proportions, leading to very different thermal conductivity values, even for similar volume gas fraction values. These results were related to the copolymer nanostructuration, which seems to have an influence in the final pore structure, thus opening the possibility of designing microcellular foams with similar macroscopic characteristics but different thermal conductivity values. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45872.     

Use of in-stream reservoirs to reduce bacterial contamination of rural watersheds

An investigation into bacterial water quality problems was conducted on an interconnected stream and irrigation system within the Oldman River Basin of southern Alberta, Canada. Levels of indicator bacteria, including fecal coliforms, generic Escherichia coli and fecal streptococci, were repeatedly measured in streams and irrigation return canals of this river basin during the summer of 2001. Bacterial-loading segments of the irrigation/stream system were identified through a comparison of indicator bacteria levels in pairs of upstream and downstream sites. Mann-Whitney U-tests indicated that reservoirs significantly reduced bacterial counts. A temporal comparison of E. coli counts and river discharges suggested that these indicator bacteria do not originate from within in-stream sediments. Site-specific as well as cumulative inputs from a variety of non-point sources are likely to be responsible for the high downstream levels of indicator bacteria in this water system. The use of management practices such as in-stream reservoirs may significantly reduce contamination, and increase the quality of limited rural water supplies to allow their reuse and safe discharge into downstream water sources. The identification of bacteria-loading river/canal segments could also be used to prioritize restoration projects.     

Proteomic mapping of 4-hydroxynonenal protein modification sites by solid-phase hydrazide chemistry and mass spectrometry

The modification of proteins by the cytotoxic, reactive aldehyde 4-hydroxynonenal (HNE) is known to alter protein function and impair cellular mechanisms. In order to identify susceptible amino acid sites of HNE modification within complex biological mixtures by microcapillary liquid chromatography and linear ion trap tandem mass spectrometry, we have developed a solid-phase capture and release strategy that utilizes reversible hydrazide chemistry to enrich HNE-modified peptides. To maximize the detection of fragment ions diagnostic of HNE modification, both neutral loss-dependent acquisition of MS/MS/MS spectra and the pulsed Q dissociation operation mode were employed. When the solid-phase hydrazide enrichment strategy was applied to a yeast lysate treated with HNE, 125 distinct amino acid sites of HNE modification were mapped on 67 different proteins. The endogenous susceptibility of many of these proteins to HNE modification was demonstrated by analyzing HNE-treated yeast cell cultures with a complementary biotin hydrazide enrichment strategy. Further analysis revealed that the majority of amino acid sites susceptible to HNE modification were histidine residues, with most of these sites being flanked by basic amino acid residues, and predicted to be solvent exposed. These results demonstrate the effectiveness of this novel strategy as a general platform for proteome-scale identification of amino acid sites susceptible to HNE modification from within complex mixtures.     

Functionalized polymer foams as metal ion chelating agents with rapid complexation kinetics

Foams prepared from vinylbenzyl chloride and crosslinked with divinylbenzene were functionalized with trialkylphosphite and tetralkylvinylidene diphosphonate. It was determined that the foams could be uniformly functionalized. Batch studies with the functionalized foams show that high levels of metal ion complexation can be achieved. Foams may therefore offer an important alternative to beads for rapid complexation reactions due to their highly porous structure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1911–1916, 1998     

Motions,efforts, and actuations in constrained dynamic systems: A multilink closed chain example

The primary goal of this article is to examine various aspects of the motion–effort method for obtaining equations of motion and constraint of multibody systems. Gauge invariant transformations are used to recast the more commonly utilized dynamic equations into a dimensional gauge invariant form. Constraint elimination techniques based on singular value decompositions are then used to recast the invariant form of dynamic system equations into orthogonal sets of motion and effort equations. Desired motions and constraining efforts are partitioned into those ideally obtainable and unobtainable through the use of effort actuators. The actuation required to achieve these ideally obtainable constraining efforts and changes in motion are then found. The dynamic system performance resulting from the use of these ideal actuations is then evaluated. The method is compared to the more traditional augmented matrix, coordinate partitioning, and inverse dynamic solution approaches. A redundantly actuated multilinked closed chain linkage is used throughout the article as an example. ©1999 John Wiley & Sons, Inc.     

Who leads research productivity growth? Guidelines for R&D policy-makers

This paper evaluates to what extent policy-makers have been able to promote the creation and consolidation of comprehensive research groups that contribute to the implementation of a successful innovation system. Malmquist productivity indices are applied in the case of the Spanish Food Technology Program, finding that a large size and a comprehensive multi-dimensional research output are the key features of the leading groups exhibiting high efficiency and productivity levels. While identifying these groups as benchmarks, we conclude that the financial grants allocated by the program, typically aimed at small-sized and partially oriented research groups, have not succeeded in reorienting them in time so as to overcome their limitations. We suggest that this methodology offers relevant conclusions to policy evaluation methods, helping policy-makers to readapt and reorient policies and their associated means, most notably resource allocation (financial schemes), to better respond to the actual needs of research groups in their search for excellence (micro-level perspective), and to adapt future policy design to the achievement of medium-long term policy objectives (meso and macro-level).