Chemical structure of composites derived from poly(silicic acid) and 2‐hydroxyethylmethacrylate

Organic–inorganic hybrids from 2‐hydroxyethylmethacrylate (HEMA) and poly(silicic acid)s were prepared and characterized. The molecular architecture of the inorganic phase was studied with ²⁹Si NMR spectroscopy, and the effect of acid concentration and reaction time on the properties of poly(silicic acid) were elucidated. Interactions between phases were studied with NMR spectroscopy and gel permeation chromatography, and the coexistence and connectivity of the two phases were investigated. Contrary to previous assumptions, evidence was found that indicated that the organic and inorganic phases of this class of sol–gel materials were not covalently linked. The curing process was studied by infrared spectroscopy, by which the disappearance of terminal double bonds of HEMA monomer were monitored. Thermogravimetric analysis profiles showed that the inorganic phase content was about 10 wt %, and it was varied slightly by changes in the molar ratio of the components. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1342–1352, 2001     

Sensitive voltammetric determination of xanthinol nicotinate at a carbon nanotubes-ionic liquid gel modified electrode

The electrochemistry of xanthinol nicotinate(Xan) was studied by cyclic voltammetry at a glassy carbon electrode modified by a gel containing multi-walled carbon nanotubes(MWNTs) and room-temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate(BMTMPF_6).The modified electrode exhibited good promotion to the electrochemical oxidation of Xan and an ultrasensitive electrochemical method was proposed for the determination of Xan.This method was successfully applied to the determination of...     

A Chiral Lanthanide Tag for Stable and Rigid Attachment to Single Cysteine Residues in Proteins for NMR,EPR and Time-Resolved Luminescence Studies

A lanthanide-binding tag site-specifically attached to a protein presents a tool to probe the protein by multiple spectroscopic techniques, including nuclear magnetic resonance, electron paramagnetic resonance and time-resolved luminescence spectroscopy. Here a new stable chiral Ln^III tag, referred to as C12 , is presented for spontaneous and quantitative reaction with a cysteine residue to generate a stable thioether bond. The synthetic protocol of the tag is relatively straightforward, and the tag is stable for storage and shipping. It displays greatly enhanced reactivity towards selenocysteine, opening a route towards selective tagging of selenocysteine in proteins containing cysteine residues. Loaded with Tb^III or Tm^III ions, the C12 tag readily generates pseudocontact shifts (PCS) in protein NMR spectra. It produces a relatively rigid tether between lanthanide and protein, which is beneficial for interpretation of the PCSs by single magnetic susceptibility anisotropy tensors, and it is suitable for measuring distance distributions in double electron–electron resonance experiments. Upon reaction with cysteine or other thiol compounds, the Tb^III complex exhibits a 100-fold enhancement in luminescence quantum yield, affording a highly sensitive turn-on luminescence probe for time-resolved FRET assays and enzyme reaction monitoring.     

Continuous Cohomology of Permutation Groups on Profinite Modules

ABSTRACT

Model theorists have made use of low-dimensional continuous cohomology of infinite permutation groups on profinite modules, see Ahlbrandt and Ziegler (1991 Ahlbrandt , G. , Ziegler , M. ( 1991 ). What's so special about (?/4?)^ω? Archive for Math. Logic 31 : 115 – 132 . [CSA] [Crossref] , [Google Scholar]), Evans (1997b Evans , D. M. ( 1997b ). Computation of first cohomology groups of finite covers . J. Algebra 193 : 214 – 238 . [CSA] [CROSSREF] [Crossref], [Web of Science ®] , [Google Scholar]), Evans et al. (1997 Evans , D. M. , Ivanov , A. A. , Macpherson , H. D. ( 1997 ). Finite covers . In: Evans , D. M. , ed. Model Theory of Groups and Automorphism Groups . London Mathematical Society Lecture Notes 244 . Cambridge : Cambridge Univ Press , pp. 1 – 72 .[Crossref] , [Google Scholar]), and Hodges and Pillay (1994 Hodges , W. , Pillay , A. ( 1994 ). Cohomology of structures and some problems of Ahlbrandt and Ziegler . J. London Math. Soc. 50 ( 2 ): 1 – 16 . [CSA] [Crossref] , [Google Scholar]), for example. We expand the module category in order to widen the cohomological toolkit. For an important class of groups we use these tools to establish criteria for finiteness of cohomology.     

Development of an X-ray computed tomography (CT) system with sparse sources: application to three-phase pipe flow visualization

This paper describes the application of a two-beam X-ray computed tomography (CT) system to multiphase (gas–oil–water) flow measurement. Two high-voltage (160 keV) X-ray sources are used to penetrate a 4-in. (101.6 mm ID) pipeline. A rotating filter wheel mechanism is employed to alternately “harden” and “soften” the X-ray spectra to provide discrimination between the three phases. Because this system offers only two projections, conventional back-projection algorithms are ineffective and thus a new reconstruction technique has been developed. A matrix equation is formed, to which additional “smoothing equations” are added to compensate for the lack of projection data. The tomographic result is obtained by computing an inverse matrix. This is a one-off computation and the inverse is stored for repeated use; reconstructed images from synthesized data demonstrate the effectiveness of this technique. Three-phase tomographic images of a horizontal slug flow are presented, which clearly show the mixing of oil and water layers within the slug body. The relevance of this work to the offshore oil and gas industry is summarized.     

Implementation of a rapid and automated high performance liquid chromatography method development strategy for pharmaceutical drug candidates

A comprehensive, fully automated strategy is demonstrated for HPLC-UV chromatographic method development using ChromSword optimization software. The strategy involves: (1) the automated screening of various column and mobile phase combinations, (2) rational selection of the best starting conditions; and (3) subsequent automated method development to generate optimized separation methods. Pharmaceutical compounds were applied to solve problematic drug impurity separations. ChromSword software automates the screening, optimization, and documentation steps thus reducing the method development time. The strategy was compared to a manual method development approach showing the automated method strategy affords better selectivity in a shorter time.     

Mileage bands in freight transportation

Contract carriers in the trucking industry are known to offer shippers a per mile rate that decreases stepwise as the shipper’s route lengthens, with a mileage band designated for each rate. While the use of quantity-based pricing discounts in supply chains has been well studied, there has been no research on how shippers should route under such a pricing scheme or how carriers should set such bands. In this paper, we provide methods for both. Route construction is complicated by the fact that the per mile rate cannot be determined until after the route has been created. With this consideration, we develop a model of this problem and then an algorithm for solving it that assists the shipper in constructing the lowest cost route. It is beneficial for the shipper to extend the length of certain routes to incur a lower per mile cost, and we find that most of these routes can be constructed to equal any mileage required to receive the lower rate. As an extended route generates unnecessary expense and energy use for the carrier, theoretical and analytical insights provide guidelines for a carrier to use in developing better mileage bands. These guidelines assist a carrier in constructing bands that maximize profit and minimize the cost associated with a shipper extending a route.