Axiomatizations of the Euclidean compromise solution

A multicriteria optimization problem is one of choosing an alternative that optimizes several—possibly conflicting—objective functions simultaneously. The utopia point of a multicriteria optimization problem is the vector that specifies for each objective function the most favorable feasible value. The Euclidean compromise solution in multicriteria optimization is a solution that selects from a feasible set the alternative such that its vector of criteria values has minimal Euclidean distance to the utopia point. This paper provides several axiomatic characterizations of the Euclidean compromise solution that are based on consistency properties.     

Microscale Fracture Toughness of Bismuth Doped Copper Bicrystals Using Double Edge Notched Microtensile Tests

The availability of focused ion beam (FIB) milling, nanoindentation, and microelectromechanical systems (MEMS) based test platforms has enabled small-scale mechanical testing to become an increasingly popular approach for measuring material properties. While great emphasis has been placed on measuring plastic properties at the micro- and nanoscale [1, 2], an area that has received significantly less consideration is the measurement of fracture toughness. A technique for performing small-scale, in situ fracture toughness tests using double edge notched tensile (DENT) specimens has been developed and used to measure a nearly 40 % reduction in toughness associated with the addition of Bi to the grain boundary of a Cu bicrystal. That Bi embrittles Cu grain boundaries is well known [3–10], however, as shown herein, the DENT technique offers certain advantages over existing boundary fracture tests, especially when used with ductile materials.     

Atomic absorption with ultracold atoms

Recent advances in laser-atom cooling techniques and diode-laser technology now allow one to conduct an idealised atomic absorption experiment comprising a sample of ultracold, quasi-stationary absorbing atoms and a source of near-monochromatic resonant light. Under such conditions, the atomic absorption coefficient at line centre is independent of the oscillator strength of the atomic resonance line. This offers the prospect of ‘oscillator-strength-free’ atomic absorption spectroscopy in which the absorption signal is equally large for both strong and weak (closed) transitions of the same wavelength and in which absolute atomic absorption could be performed without knowledge of the oscillator strength. Moreover, the resolution and sensitivity for a given atom density are greatly enhanced, typically by approximately three orders of magnitude (and even more for weak transitions), compared with conventional flame or graphite-furnace atomic absorption. We describe an atomic absorption experiment based on samples of ultracold, laser-cooled caesium atoms and a narrow-bandwidth diode laser source that approximates the idealised conditions for oscillator-strength-free atomic absorption. The absorption measurements are used to determine the number density and temperature (approx. 6 μK) of the sample of ultracold atoms. Some of the technical obstacles that would have to be overcome before samples of ultracold atoms and diode laser sources could be used in analytical atomic absorption spectroscopy are discussed.     

Raman spectroscopy of dipyrrins: nonresonant,resonant and surface‐enhanced cross‐sections and enhancement factors

Detailed studies of the mechanism of surface‐enhanced (resonance) Raman spectroscopy (SE(R)RS), and its applications, place a number of demands on the properties of SERS scatterers. With large Raman cross‐sections, versatile synthetic chemistry and complete lack of fluorescence, free dipyrrins meet these demands but the Raman and SE(R)RS spectroscopy of free dipyrrins is largely unknown. The first study of the Raman spectroscopy of free dipyrrins is therefore presented in this work. The nonresonant Raman, resonant Raman and surface‐enhanced Raman spectra of a typical meso aryl‐substituted‐dipyrrin are reported. Absolute differential cross‐sections are obtained for excitation wavelengths in the near infrared and visible region, in solution phase and for dipyrrin adsorbed on the surface of silver nanoparticles. Raman enhancement factors for SERRS and resonance Raman are calculated from the observed differential cross‐sections. The magnitudes of the resonantly enhanced cross‐sections are similar to those recently reported for strong SERS dyes such as Rhodamine 6G and Crystal Violet. Free dipyrrins offer the advantages of existing SERS dyes but without the drawback of strong fluorescence. Free dipyrrins should therefore find applications in all areas of Raman spectroscopy including fundamental studies of the mechanisms of SERS and bioanalytical and environmental applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Application of Fragment Screening and Merging to the Discovery of Inhibitors of the Mycobacterium tuberculosis Cytochrome P450 CYP121

Pieces of the puzzle: The first fragment-based approach was used to target cytochrome?P450 enzymes (CYPs) for drug development. The experiments provide new insights into the binding site of the essential Mycobacterium tuberculosis CYP121 enzyme, and resulted in a promising novel lead compound based on fragment merging.     

Analysis of residual trifluoroacetic acid in a phosphate-buffered saline matrix by ion chromatography with suppressed conductivity detection

As part of the formulation of a cell-based pharmaceutical product, cells were harvested from mice and incubated in a cocktail containing cell culture media and high levels of trifluoroacetic acid (TFA). The cells were washed with a phosphate-buffered saline solution to remove residual cell culture media and other reagents before the cells were infused back into the mice from which they originated. Because of the potentially toxic nature of the TFA, the cells were washed multiple times and the final wash was monitored for residual TFA in order to demonstrate the efficient removal of the reagent before the cell product could be reintroduced into the test animal. This report describes the method that was developed incorporating anion-exchange chromatography with suppressed conductivity detection for the analysis of residual TFA (down to 50 ng/ml) in the presence of high concentrations of phosphate and chloride interferences. The ultimate sensitivity of the method was improved by selectively removing halide anions using a silver cartridge before sample analysis. The method proved to be rugged and reproducible enough to be validated and used to monitor residual TFA levels in cell washes in support of an acute toxicological study. Results demonstrating the method’s sensitivity, selectivity, precision and linearity were reported.     

Transport and time dependent small angle X‐ray morphology in metal cation and polymer modified perfluorocarbon ionomers

Transport and absorption in metal cation exchanged and polyvinylpyrrolidone (PVP) modified Nafion® films were studied by various techniques. To understand the microscopic basis for permeation, time resolved small angle X‐ray scattering (SAXS) was used to characterize the ionic domain morphology while films were exposed to vapors of water, dimethyl methylphosphonate (DMMP), or triethyl phosphate. Macroscopic weight uptake studies of DMMP vapor into PVP‐Nafion® were also used to help explain the SAXS absorption studies and DMMP permeation properties. The SAXS results were correlated with macroscopic permeation rates of DMMP, Soman, and water through several different membranes. To provide additional basis for the SAXS derived morphologies, tapping‐mode AFM was also used to image the 3–5 nm diameter ionic domains. A goal for protective suit applications is to find films with a balance of high moisture permeation rate for comfort, and low DMMP permeation. The best balance of properties in this context was found with PVP‐ and zirconyl‐modified films. In another extreme, the permeation rates of both water and DMMP through cesium‐modified Nafion® were low. SAXS studies were used to explain this where the ionic domains of cesium‐modified Nafion® did not “expand” when exposed to DMMP or water vapor. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 284–298, 2009     

Representations of the Banach algebra ℓ1(S)

Communicated by N. R. Reilly     

Implementation of the chemical reaction interface mass spectrometry technique on a Hewlett-Packard mass-selective detector

A microwave-powered chemical reaction interface has been installed in a Hewlett-Packard gas chromatograph-mass spectrometer (GC-MS) system (5890 IT gas chromatograph-S971 mass-selective detector). The technical details and optimization strategies are discussed. The evaluation of this new setup is presented, showing detection limits of 1 ng of ¹³C-, ¹⁵N-, and Cl-containing compounds with signal-to-noise ratios greater than or egual to 3. Selective detection was evaluated with a urine sample from a dog dosed with ¹⁵N₃-midazolam that had been previously analyzed by using a differentially pumped research-level quadrupole mass spectrometer. The results show that the detection of ¹⁵N and Cl remains highly selective and the mass-selective detector gives comparable sensitivity to the larger instrument when the latter is operating over a conventional mass range. The capability for chemical reaction interface mass spectrometry can be easily accomplished with an inexpensive GC-MS system.