Confirmatory method for the determination of various acetylgestagens in animal kidney fat using liquid chromatography-tandem mass spectrometry

A confirmatory method has been developed and validated that allows for the simultaneous detection of medroxyprogesterone acetate (MPA), megestrol acetate (MGA), melengestrol acetate (MLA), chlormadinone acetate (CMA) and delmadinone acetate (DMA) in animal kidney fat using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The compounds were extracted from kidney fat using acetonitrile, defatted using a hexane wash and subsequent saponification. Extracts were then purified on Isolute CN solid-phase extraction cartridges and analysed by LC-MS/MS. The method was validated in animal kidney fat in accordance with the criteria defined in Commission Decision 2002/657/EC. The decision limit (CC) was calculated to be 0.12, 0.48, 0.40, 0.63 and 0.54 g kg-1, respectively, for MPA, MGA, MLA, DMA and CMA, with respective detection capability (CC) values of 0.20, 0.81, 0.68, 1.07 and 0.92 g kg-1. The measurement uncertainty of the method was estimated at 16, 16, 19, 27 and 26% for MPA, MGA, MLA, DMA and CMA, respectively. Fortifying kidney fat samples (n = 18) in three separate assays showed the accuracy of the method to be between 98 and 100%. The precision of the method, expressed as % RSD, for within-laboratory reproducibility at three levels of fortification (1, 1.5 and 2 g kg-1 for MPA, 5, 7.5 and 10 g kg-1 for MGA, MLA, DMA and CMA) was less than 5% for all analytes.

Development and validation of a method for the confirmation of halofuginone in chicken liver and eggs using electrospray tandem mass spectrometry

A method is described for the quantitative confirmation of halofuginone (HFG) residues in chicken liver and eggs. This method is based on LC coupled to positive ion electrospray MS-MS of the tissue extracts, prepared by trypsin digestion of the tissues followed by liquid-liquid extraction and final clean-up using Solid Phase Extraction (SPE). The [M+H](+) ion at m/z 416 is monitored along with four transitions at m/z 398, 138, 120 and 100. The method has been validated according to the draft EU criteria for the analysis of veterinary drug residues at 15, 30 and 45 mug kg (-1) in liver and 5, 15 and 50 mug kg (-1) in eggs. The new analytical limits, CCalpha and CCbeta were calculated for liver and were 35.4 and 43.6 mug kg (-1), respectively. (C) 2003 Elsevier Science B.V. All rights reserved.

A new method for estimating liquidity risk: Insights from a liquidity-adjusted CAPM framework

This paper proposes a new non-parametric method for estimating model-free, time-varying liquidity betas which builds on realized covariance and volatility theory. Working under a liquidity-adjusted CAPM framework we provide evidence that liquidity risk is a factor priced in the Greek stock market, mainly arising from the covariation of individual liquidity with local market liquidity, however, the level of liquidity seems to be an irrelevant variable in asset pricing. Our findings provide support to the notion that liquidity shocks transmitted across securities can cause market-wide effects and can have important implications for portfolio diversification strategies. ©2012 Elsevier B.V. All rights reserved.

Next generation planar waveguide detection of microcystins in freshwater and cyanobacterial extracts, utilising a novel lysis method for portable sample preparation and analysis

The study details the development of a fully validated, rapid and portable sensor based method for the on-site analysis of microcystins in freshwater samples. The process employs a novel lysis method for the mechanical lysis of cyanobacterial cells, with glass beads and a handheld frother in only 10min. The assay utilises an innovative planar waveguide device that, via an evanescent wave excites fluorescent probes, for amplification of signal in a competitive immunoassay, using an anti-microcystin monoclonal with cross-reactivity against the most common, and toxic variants. Validation of the assay showed the limit of detection (LOD) to be 0.78ngmL and the CCß to be 1ngmL. Robustness of the assay was demonstrated by intra- and inter-assay testing. Intra-assay analysis had % C.V.s between 8 and 26% and recoveries between 73 and 101%, with inter-assay analysis demonstrating % C.V.s between 5 and 14% and recoveries between 78 and 91%. Comparison with LC-MS/MS showed a high correlation (R=0.9954) between the calculated concentrations of 5 different Microcystis aeruginosa cultures for total microcystin content. Total microcystin content was ascertained by the individual measurement of free and cell-bound microcystins. Free microcystins can be measured to 1ngmL, and with a 10-fold concentration step in the intracellular microcystin protocol (which brings the sample within the range of the calibration curve), intracellular pools may be determined to 0.1ngmL. This allows the determination of microcystins at and below the World Health Organisation (WHO) guideline value of 1µgL. This sensor represents a major advancement in portable analysis capabilities and has the potential for numerous other applications.

High energy resolution fluorescence detection XANES - an in situ method to study the interaction of adsorbed molecules with metal catalysts in the liquid phase

The change in the Pt electronic structure following the adsorption of an a,ß-unsaturated aldehyde and ketone was followed by in situ HERFD-XANES in the liquid phase. The resulting shift in the Pt Fermi energy is in good agreement with the molecule adsorption energy trends calculated by DFT and provides insight into the reaction selectivity.

Production of a broad specificity antibody for the development and validation of an optical SPR screening method for free and intracellular microcystins and nodularin in cyanobacteria cultures

A highly sensitive broad specificity monoclonal antibody was produced and characterised for microcystin detection through the development of a rapid surface plasmon resonance (SPR) optical biosensor based immunoassay. The antibody displayed the following cross-reactivity: MC-LR 100%; MC-RR 108%; MC-YR 68%; MC-LA 69%; MC-LW 71%; MC-LF 68%; and Nodularin 94%. Microcystin-LR was covalently attached to a CM5 chip and with the monoclonal antibody was employed in a competitive 4min injection assay to detect total microcystins in water samples below the WHO recommended limit (1µg/L). A 'total microcystin' level was determined by measuring free and intracellular concentrations in cyanobacterial culture samples as this toxin is an endotoxin. Glass bead beating was used to lyse the cells as a rapid extraction procedure. This method was validated according to European Commission Decision 96/23/EC criteria. The method was proven to measure intracellular microcystin levels, the main source of the toxin, which often goes undetected by other analytical procedures and is advantageous in that it can be used for the monitoring of blooms to provide an early warning of toxicity. It was shown to be repeatable and reproducible, with recoveries from spiked samples ranging from 74 to 123%, and had % CVs below 10% for intra-assay analysis and 15% for inter-assay analysis. The detection capability of the assay was calculated as 0.5ng/mL for extracellular toxins and 0.05ng/mL for intracellular microcystins. A comparison of the SPR method with LC-MS/MS was achieved by testing six Microcystis aeruginosa cultures and this study yielded a correlation R(2) value of 0.9989.

A Spherical Array Approach for Simulation of Binaural Impulse Responses using the Finite Difference Time Domain Method

The finite difference time domain (FDTD) method has direct applications in musical instrument modeling, simulation of environmental acoustics, room acoustics and sound reproduction paradigms, all of which benefit from auralization. However, rendering binaural impulse responses from simulated
data is not straightforward to accomplish as the calculated pressure at FDTD grid nodes does not contain any directional information. This paper addresses this issue by introducing a spherical array to capture sound pressure on a finite difference grid, and decomposing it into a plane-wave density
function. Binaural impulse responses are then constructed in the spherical harmonics domain by combining the decomposed grid data with free field head-related transfer functions. The effects of designing a spherical array in a Cartesian grid are studied, and emphasis is given to the relationships
between array sampling and the spatial and spectral design parameters of several finite-difference
schemes.

Covariance Averaging for Improved Estimation and Portfolio Allocation

We propose a new method for estimating the covariance matrix of a multivariate time series of nancial returns. The method is based on estimating sample covariances from overlapping windows of observations which are then appropriately weighted to obtain the nal covariance estimate. We extend the idea of (model) covariance averaging o ered in the covariance shrinkage approach by means of greater ease of use, exibility and robustness in averaging information over different data segments. The suggested approach does not su er from the curse of dimensionality and can be used without problems of either approximation or any demand for numerical optimization.

State detection of bond wires in IGBT modules using eddy current pulsed thermography

Insulated gate bipolar transistor (IGBT) modules are important safety critical components in electrical power systems. Bond wire lift-off, a plastic deformation between wire bond and adjacent layers of a device caused by repeated power/thermal cycles, is the most common failure mechanism in IGBT modules. For the early detection and characterization of such failures, it is important to constantly detect or monitor the health state of IGBT modules, and the state of bond wires in particular. This paper introduces eddy current pulsed thermography (ECPT), a nondestructive evaluation technique, for the state detection and characterization of bond wire lift-off in IGBT modules. After the introduction of the experimental ECPT system, numerical simulation work is reported. The presented simulations are based on the 3-D electromagnetic-thermal coupling finite-element method and analyze transient temperature distribution within the bond wires. This paper illustrates the thermal patterns of bond wires using inductive heating with different wire statuses (lifted-off or well bonded) under two excitation conditions: nonuniform and uniform magnetic field excitations. Experimental results show that uniform excitation of healthy bonding wires, using a Helmholtz coil, provides the same eddy currents on each, while different eddy currents are seen on faulty wires. Both experimental and numerical results show that ECPT can be used for the detection and characterization of bond wires in power semiconductors through the analysis of the transient heating patterns of the wires. The main impact of this paper is that it is the first time electromagnetic induction thermography, so-called ECPT, has been employed on power/electronic devices. Because of its capability of contactless inspection of multiple wires in a single pass, and as such it opens a wide field of investigation in power/electronic devices for failure detection, performance characterization, and health monitoring. 

CLUSTER LEED - A VERY FAST METHOD FOR SURFACE-STRUCTURE DETERMINATION

A very fast method, cluster low-energy electron diffraction (LEED) is proposed for LEED I-V spectral analysis, in which three appproximations are introduced: the small-atom approximation, omission of the structure factors, and truncation of higher order ( > 2) scattering events. The method has been tested using a total of four sets of I-V spectra calculated by fully dynamic LEED for (i) the simple overlayer system, O on Ni{100}, and (ii) the reconstructed system, Cu on W{100}, and also one set of experimental data from W{100}-c(2 X 2)-Cu. In each case the correct structural parameters are recovered. It is suggested that for complex systems cluster LEED provides an efficient fast route to trial structures, which could be refined by automated tenser LEED.

Rapid, simple method for determining the porosity of mesoporous TiO2 films using a quartz crystal microbalance (QCM)

Two different mesoporous films of TiO2 were coated onto a QCM disc and fired at 450o C for 30 min. The first film was derived from a sol-gel paste that was popular in the early days of dye-sensitised solar cell, i.e. dssc, research, a TiO2(sg) film. The other was a commercial colloidal paste used to make examples of the current dssc cell; a TiO2(ds) film. A QCM was used to determine the mass of the TiO2 film deposited on each disc and the increase in the mass of the film when immersed in water/glycerol solutions with wt% values spanning the range 0-70%. The results of this work reveal that with both TiO2 mesoporous films the solution fills the film's pores and acts as a rigid mass, thereby allowing the porosity of each film to be calculated as: 59.1% and 71.6% for the TiO2(sg) and TiO2(ds) films, respectively. These results, coupled with surface area data, allowed the pore radii of the two films to be calculated as: 9.6 and 17.8 nm, respectively. This method is then simplified further, to just a few frequency measurements in water and only air to reveal the same porosity values. The value of the latter ‘one point’ method for making porosity measurements is discussed briefly.

Electron-impact ionization of diatomic molecules using a configuration-average distorted-wave method

Electron-impact ionization cross sections for diatomic molecules are calculated in a configuration-average distorted-wave method. Core bound orbitals for the molecular ion are calculated using a single-configuration self-consistent-field method based on a linear combination of Slater-type orbitals. The core bound orbitals are then transformed onto a two-dimensional (r,θ) numerical lattice from which a Hartree potential with local exchange is constructed. The single-particle Schrödinger equation is then solved for the valence bound orbital and continuum distorted-wave orbitals with S-matrix boundary conditions. Total cross section results for H2 and N2 are compared with those from semiempirical calculations and experimental measurements.

Electron-impact ionization of argon using the R-matrix with a pseudo-states method

Electron-impact ionization cross sections for argon are calculated using both non-perturbative R-matrix with pseudo-states (RMPS) and perturbative distorted-wave methods. At twice the ionization potential, the 3p(61)S ground-term cross section from a distorted-wave calculation is found to be a factor of 4 above crossed-beams experimental measurements, while with the inclusion of term-dependent continuum effects in the distorted-wave method, the perturbative cross section still remains almost a factor of 2 above experiment. In the case of ionization from the metastable 3p(5)4s(3)P term, the distorted-wave ionization cross section is also higher than the experimental cross section. On the other hand, the ground-term cross section determined from a nonperturbative RMPS calculation that includes 27 LS spectroscopic terms and another 282 LS pseudo-state terms to represent the high Rydberg states, and the target continuum is found to be in excellent agreement with experimental measurements, while the RMPS result is below the experimental cross section for ionization from the metastable term. We conclude that both continuum term dependence and interchannel coupling effects, which are included in the RMPS method, are important for ionization from the ground term, and interchannel coupling is also significant for ionization from the metastable term

New Method for the Estimation of Viscosity of Pure and Mixtures of Ionic Liquids Based on the UNIFAC–VISCO Model

A modified UNIFAC–VISCO group contribution method was developed for the correlation and prediction of viscosity of ionic liquids as a function of temperature at 0.1 MPa. In this original approach, cations and anions were regarded as peculiar molecular groups. The significance of this approach comes from the ability to calculate the viscosity of mixtures of ionic liquids as well as pure ionic liquids. Binary interaction parameters for selected cations and anions were determined by fitting the experimental viscosity data available in literature for selected ionic liquids. The temperature dependence on the viscosity of the cations and anions were fitted to a Vogel–Fulcher–Tamman behavior. Binary interaction parameters and VFT type fitting parameters were then used to determine the viscosity of pure and mixtures of ionic liquids with different combinations of cations and anions to ensure the validity of the prediction method. Consequently, the viscosities of binary ionic liquid mixtures were then calculated by using this prediction method. In this work, the viscosity data of pure ionic liquids and of binary mixtures of ionic liquids are successfully calculated from 293.15 K to 363.15 K at 0.1 MPa. All calculated viscosity data showed excellent agreement with experimental data with a relative absolute average deviation lower than 1.7%.

Photoionization of Co+ and electron-impact excitation of Co2 + using the Dirac R-matrix method

Modelling of massive stars and supernovae (SNe) plays a crucial role in understanding galaxies. From this modelling we can derive fundamental constraints on stellar evolution, mass-loss processes, mixing, and the products of nucleosynthesis. Proper account must be taken of all important processes that populate and depopulate the levels (collisional excitation, de-excitation, ionization, recombination, photoionization, bound–bound processes). For the analysis of Type Ia SNe and core collapse SNe (Types Ib, Ic and II) Fe group elements are particularly important. Unfortunately little data is currently available and most noticeably absent are the photoionization cross-sections for the Fe-peaks which have high abundances in SNe. Important interactions for both photoionization and electron-impact excitation are calculated using the relativistic Dirac atomic R-matrix codes (DARC) for low-ionization stages of Cobalt. All results are calculated up to photon energies of 45 eV and electron energies up to 20 eV. The wavefunction representation of Co III has been generated using GRASP0 by including the dominant 3d⁷, 3d⁶[4s, 4p], 3p⁴3d⁹ and 3p⁶3d⁹ configurations, resulting in 292 fine structure levels. Electron-impact collision strengths and Maxwellian averaged effective collision strengths across a wide range of astrophysically relevant temperatures are computed for Co III. In addition, statistically weighted level-resolved ground and metastable photoionization cross-sections are presented for Co II and compared directly with existing work.