bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass spectral studies of perfluorooctane sulfonate derivatives separated by high‐resolution gas chromatography
Authors: Langlois Ingrid , Berger Urs , Zencak Zdenek , Oehme Michael 
Published: October 2007

AbstractThe mass spectral characteristics of perfluorooctane sulfonate (PFOS, C8F17SO) isomers present in technical PFOS were obtained using high‐resolution gas chromatography (HRGC) combined with mass spectrometry (MS). To make PFOS amenable to HRGC separation, a simple derivatization procedure was developed. The method involved the conversion of PFOS into the iso‐propyl ester using iso‐propanol as the derivatization reagent under acidic conditions. Mass spectra were generated employing electron ionization (EI) and negative chemical ionization (NCI). Interpretation of fragment ions was possible due to the use of deuterium‐labeled iso‐propanol as derivatization reagent, which induced mass shifts in the electron ionization (EI) and negative chemical ionization (NCI) mass spectra. HRMS allowed the accurate mass measurement of important EI fragments and confirmed the derivatization reaction as well as the proposed fragmentation pathway involving rearrangement. Moreover, the high resolution provided by HRGC enabled the separation of eleven PFOS isomers present in the technical product. This is an improvement over the previously reported high‐performance liquid chromatography (HPLC) separation. A complete identification of all isomers was not possible due to lack of pure reference materials. Finally, the developed derivatization procedure was successfully applied to perfluoroalkyl carboxylates (PFCA) and corresponding fragmentation involving rearrangement of the derivatized PFCA was observed. The described qualitative derivatization offers a promising alternative technique for the separation and identification of isomers of perfluoroalkyl sulfonates and carboxylates by HRGC/MS. Copyright © 2007 John Wiley & Sons, Ltd.
Capillary hydrophilic interaction chromatography/mass spectrometry for simultaneous determination of multiple neurotransmitters in primate cerebral cortex
Authors: Zhang Xiaozhe , Rauch Alexander , Lee Han , Xiao Hongbin , Rainer Gregor , Logothetis Nikos K. 
Published: October 2007

AbstractA diverse array of neurotransmitters and neuromodulators control and affect brain function. A profound understanding of the signaling pathways and the neural circuits underlying behavior is therefore likely to require the tracking of concentration changes of active neurochemicals. In the present study, we demonstrate the feasibility of a method allowing the simultaneous determination of the concentrations of six neurotransmitters: acetylcholine, serotonin, dopamine, γ‐aminobutyric acid (GABA), glutamate and aspartate, in the extracellular brain fluid (EBF). We used hydrophilic interaction chromatography (HILIC) coupled to tandem mass spectrometry (MS/MS) to analyze the EBF from the monkey brain. A push‐pull sampling method was used to collect EBF from the prefrontal cortex (PFC) of conscious monkeys at flow rates in the range of low nL/min. The detection limits of acetylcholine, serotonin, dopamine, GABA, glutamate and aspartate were 0.015, 0.15, 0.3, 1.2, 6 and 15 femtomoles, respectively, allowing us to quantitatively determine the concentrations of these six neurotransmitters simultaneously from 500 nL in vivo samples. We conclude that HILIC/MS/MS combined with the push‐pull sampling method represents a sensitive technique for simultaneous monitoring of neurotransmitters from EBF samples. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of the impact of some experimental procedures on different phosphopeptide enrichment techniques
Authors: Jensen Søren S. , Larsen Martin R. 
Published: October 2007

AbstractThe complete characterization of phosphorylated proteins requires an efficient procedure for the enrichment of phosphopeptides from amongst a complicated peptide mixture. The sensitivity of the traditional immobilized metal affinity chromatography (IMAC) approach is severely affected by various buffers, detergents and other reagents normally utilized in biochemical and cell biological procedures, and thus pre‐purification steps such as reversed‐phase chromatography is required prior to phosphopeptide enrichment. Here we evaluate the use of different ‘non‐phosphopeptide‐excluding compounds’ in the loading buffer for titanium dioxide (TiO2) chromatography and show that TiO2 is more robust and tolerant towards many reagents, including salts, detergents and other low molecular mass molecules, than conventional IMAC. In addition, we show that the inclusion of various detergents can enhance the efficiency of this enrichment method, as phosphopeptides that otherwise adhere to plastic surfaces can be efficiently solubilized and subsequently purified. The TiO2 chromatography technique is also compared to zirconium dioxide chromatography for phosphopeptide enrichment. Copyright © 2007 John Wiley & Sons, Ltd.
The combined use of thermal desorption and selected ion flow tube mass spectrometry for the quantification of xylene and toluene in air
Authors: Ross Brian M. , Vermeulen Natasha 
Published: October 2007

AbstractThermal desorption (TD) is commonly employed for volatile chemical analysis, it being the method of choice for occupational health and safety monitoring. TD allows for offline capture of volatiles onto a solid sorbent followed by desorption and analysis at a later time. Although TD is routinely used in conjunction with gas chromatography (TD‐GC), the assay throughput is low and requires the use of gas standards for quantification. Another technique increasingly employed for volatile chemical analysis, selected ion flow tube mass spectrometry (SIFT‐MS), is capable of real‐time absolute (i.e. without calibration standards) quantification of volatile chemicals present at single digit parts per billion or higher concentrations. SIFT‐MS is, however, normally used for online direct analysis of gas samples rather than offline collection and analysis. The goal of this study was to determine whether a combination of TD and SIFT‐MS could be used to quantify volatile compounds, specifically xylene and toluene, more rapidly than TD‐GC and without the need for calibration standards. SIFT‐MS was able to quantify xylene and toluene levels within 45 s of desorption. Due to the robustness of the SIFT‐MS analysis in the presence of water vapour and other major components of air, the purging of tubes usually required to remove these constituents during the TD cycle was not required, therefore reducing the TD cycle time. Comparing the quantity of xylene and toluene applied to the TD tube with the absolute levels quantified by SIFT‐MS subsequent to desorption suggested a recovery of over 95% of the applied compound. We conclude that the combination of TD and SIFT‐MS allows more rapid and accurate quantification of xylene and toluene (compared with TD‐GC) to be achieved without the need for calibration standards, features which may be advantageous in applications requiring rapid analysis and high throughput. Copyright © 2007 John Wiley & Sons, Ltd.
High‐field asymmetric waveform ion mobility spectrometry coupled with liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐FAIMS‐MS/MS) multi‐component bioanalytical method development, performance evaluation and demonstration of the constancy of the compensation voltage with change of mobile phase composition or flow rate
Authors: Wu Steven T. , Xia Yuan‐Qing , Jemal Mohammed 
Published: October 2007

AbstractThe feasibility of developing a multi‐component bioanalytical method using high‐field asymmetric waveform ion mobility spectrometry coupled with liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐FAIMS‐MS/MS) is demonstrated using nefazodone and its two metabolites as model compounds. The performance of the bioanalytical method for the three analytes, with three different compensation voltage (CV) values, is assessed using standard curves and quality control samples, which exhibited good accuracy, precision and ruggedness. The number of analytes with different CV values that can be quantitated simultaneously depends on the acquisition cycle time, which is a function of the FAIMS residence time (fixed), chromatographic peak width and selected reaction monitoring (SRM) dwell time. It is established that CV, the FAIMS selectivity parameter, is reproducible for at least 16 h, thus ensuring the constancy of the CV during a large‐batch sample analysis. It is also established that change in mobile phase composition or of flow rate does not cause a shift in CV. Thus, CV values determined from a CV scan via infusion of a sample can be used for an LC/ESI‐FAIMS‐M/MS method based on isocratic or gradient elution. Copyright © 2007 John Wiley & Sons, Ltd.
Multimarket contact and sales growth: evidence from insurance
Authors: Greve Henrich R. 
Published: October 2007

AbstractResearch on pricing, profits, and firm survival has shown that multimarket contact causes mutual forbearance against competition, but has not considered the consequences of imperfect observability of competitive moves. Here, predictions are developed to explain how mutual forbearance occurs—but sometimes fails—in markets with imperfect observability. Mutual forbearance means that firms do not seek to take market share from each other through price cuts or nonprice competition, and thus that sales grow at uniform rates. Firms defect from mutual forbearance, and hence have higher sales growth, if the potential rewards are high and the likelihood of being discovered is low. This theory is tested on a panel of firms operating in the Norwegian general insurance industry. The evidence suggests that sales growth is most rapid in firms that do not meet many multimarket competitors in a given market and firms that are economically troubled. Growing or highly concentrated markets have higher heterogeneity of growth rates. Copyright © 2007 John Wiley & Sons, Ltd.
Empirical‐based recovery and maintenance of input error‐correction features
Authors: Ngo Minh Ngoc , Tan Hee Beng Kuan 
Published: October 2007

AbstractMost information systems deal with inputs submitted from their external environments. In such systems, input validation is often incorporated to reject erroneous inputs. Unfortunately, many input errors cannot be detected automatically and therefore result in errors in the effects raised by the system. Therefore, the provision of input error‐correction features (IECFs) to correct these erroneous effects is critical. However, recovery and maintenance of these features are complicated, tedious and error prone because there are many possible input errors during user interaction with the system; each input error, in turn, might result in several erroneous effects. Through empirical study, we have discovered some interesting control flow graph patterns with regard to the implementation of IECFs in information systems. Motivated by these initial findings, in this paper, we propose an approach to the automated recovery of IECFs by realizing these patterns from the source code. On the basis of the recovered information, we further propose a decomposition‐slicing technique to aid the maintenance of these features without interfering with other parts of the system. A case study has been conducted to show the usefulness of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.
Fetal ductus venosus, middle cerebral artery and umbilical artery flow responses to uterine contractions in growth‐restricted human pregnancies
Authors: Fu J. , Olofsson P. 
Published: October 2007

AbstractObjectiveTo explore fetal ductus venosus (DV) flow velocity changes relative to umbilical artery (UA) blood flow and brain‐sparing flow (BSF) during uterine contractions.MethodsForty‐five term fetuses suspected of having growth restriction were exposed to an oxytocin challenge test (OCT) with simultaneous Doppler velocimetry in the UA, middle cerebral artery (MCA) and DV. Basal BSF was defined as a MCA‐to‐UA pulsatility index (PI) ratio of < 1.08, and de novo BSF as a decrease in MCA‐PI of ≥ 1 SD (equivalent to a value of 0.24 units) during the OCT.ResultsBasal DV flow velocities were lower in the BSF group (n = 7) than they were in the non‐BSF group (n = 38). During the OCT, DV flow velocity parameters changed in neither group but MCA‐PI decreased in the non‐BSF group. A crude de novo BSF was not associated with DV flow velocity changes, but when UA‐PI changes were considered, a serial relationship was found between decreased UA‐PI, increased DV flow velocity, and decreased MCA‐PI. When UA‐PI increased, the MCA‐PI still decreased (though not significantly) but DV flow velocity parameters remained unchanged.ConclusionsEstablished fetal BSF is associated with low DV flow velocities, but in an acute sequence there might be two contrasting courses along which BSF develops: one with an increase and one with a decrease in the UA vascular flow resistance. In the former situation the DV flow velocity increases, while in the latter situation the role of the DV in the acute redistribution of fetal blood flow is unclear. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Numerical optimization of the Voith‐Schneider® Propeller
Authors: Jürgens D. , Palm M. , Singer S. , Urban K. 
Published: October 2007

AbstractThe Voith‐Schneider® Propeller (VSP) is an efficient ship propeller that was invented by Ernst Leo Schneider (1894–1975) in 1927. It is a complex propeller having several parameters determining the behavior of the VSP. One of them is the Blade Steering Curve (BSC) which describes the angle of a propeller blade for a time instant. We investigate the choice of this BSC in order to optimize the efficiency of the VSP. We use numerical optimization and Computational Fluid Dynamics (CFD), in particular the Vortex‐Lattice Method for the optimization and Finite Volume Method for validation. We obtain a significant improvement of 4.8%.
Mathematical and physical interpretation of the solution to the initial–boundary value problem in linear hyperbolic thermoelasticity theory
Authors: Gawinecki J.A. , Sikorska B. , Nakamura G. , Rafa J. 
Published: October 2007

AbstractA new system of equations describing a thermoelastic medium in three‐dimensional space is considered. Such a system also describes the propagation of heat with finite speed.We consider the initial‐boundary value problem (with the boundary condition of Lamb's type) for this system of equations. Using the modified Cagniard‐de Hoop method we construct an explicit solution of this problem.Based on the constructed solution of the above mentioned problem, we describe the type of waves which propagate in the thermoelastic medium and the domain of their propagation.The main role in our considerations is played by the physical interpetation of the singular and branch points of the integrands in the corresponding Fourier integrals.The values of the singular and branch points and their localization on the complex plane are responsible for the velocities of the thermoelastic waves and for the type of such waves.The analysis of these singularities has allowed for the physical intepretation of the solution.Namely, new kind of waves in a thermoelastic medium have been discovered:frontal waves of the Schmidt's typesurface waves of the Rayleigh's typeWe have determined the exact geometric description of the wave surfaces and the character of their origin. We provided the quantitative characterization of the field of temperature, as well.
On Riemann problems and front tracking for a model of sedimentation of polydisperse suspensions
Authors: Berres S. , Bürger R. 
Published: October 2007

AbstractThis paper analyses a continuum model of the sedimentation of polydisperse suspensions, where the volume concentrations of the solids species are the sought unknowns. This leads to systems of conservation laws which are non‐genuinely nonlinear (“non‐convex”) in the sense that they are only piecewise genuinely nonlinear. The solution of a Riemann problem is represented as a concatenation of elementary waves, where the linear degeneracy requires using the Liu entropy condition. After a general description of the composition of elementary waves, an algorithm for the computational construction is given. The solution of the Riemann problem is then utilized as a problem‐adapted building block of a front tracking method. For the model of bidisperse suspensions, Riemann problems are classified by the location of the left and right state in the phase space of unknown variables. The front tracking method is applied to solve the initial value problem of a first‐order hyperbolic 2 × 2 system of conservation laws describing the settling of a bidisperse suspension. The solution obtained by front tracking is compared with results obtained by an experiment and a finite difference scheme.
Appell‐Hamel dynamical system: a nonlinear test of the Chetaev and the vakonomic model
Authors: Xu S.‐S. , Li S.‐M. , Berakdar J. 
Published: October 2007

AbstractWe contrast the results of the Chetaev and vakonomic models of nonholonomic mechanics when applied to the nonholonomically constrainted Appell‐Hamel dynamical system with a nonvanishing constant force parallel to the tangent direction of the wheel. We find that the Chetaev result is compatible with Newton‐Euler solution while the vakonomic model yields results inconsistent with the predictions of the Newton‐Euler mechanics.
Von Kármán equations with uncertain input data and the worst scenario method
Authors: Hlaváček I. 
Published: October 2007

AbstractA general coercive boundary value problem for the von Kármán system is considered. Both the perpendicular and in‐plane loading of the plate is uncertain, being contained in some compact set of admissible input data. Then the worst scenario problem is defined, taking the possible nonuniqueness of the solution of the von Kármán system into consideration. A proof is presented for the existence of the worst scenario.
Calculation of eigenfrequencies for rectangular free orthotropic plates – An overview
Authors: Hurlebaus S. 
Published: October 2007

AbstractIn this paper, the free transverse vibrations of rectangular orthotropic plates with completely free boundary conditions are considered. Some methodologies for calculating the eigenfrequencies and eigenmodes, based on the classical thin plate theory are presented in a comparative overview. The advantages and disadvantages of these methodologies are discussed for an orthotropic plate application with specific material and geometric properties.
Exact analytical solutions for steady three-dimensional inviscid vortical flows
Authors: BHATTACHARYA S. 
Published: October 2007

Vortical flows with an axial (z-axis) swirl and a toroidal circulation (in the (rho,z)-plane) can be observed in a wide range of fluid mechanical phenomena such as flow around rotary machines or natural vortices like tornadoes and hurricanes. In this paper, we obtain exact analytical solutions for a general class of steady systems with such three-dimensional circulating structures. Assuming incompressible ideal fluid, a general single-variable equation, known as the Squire–Long equation, can be constructed which can uniquely describe the velocity fields with steady axial and toroidal circulations. In this paper, we consider the case where this type of flow can be analysed by solving a linear homogeneous partial differential equation. The derived equation resembles the governing equation of the hydrogen problem. As a result, we obtain a quantization relation which is similar to the expression for the quantized energy states in a hydrogen atom.For circulating flows, this formalism provides a complete set of orthogonal basis functions which are regular and localized. Hence, each of the basis solutions can be used as a simplified model for a realistic phenomenon. Moreover, an arbitrary circulating field can be expanded in terms of these orthogonal functions. Such an expansion can be potentially useful in the study of more general vortices. As illustrations, we present a few examples where we solve the linear homogeneous equation to analyse fluid mechanical systems which can be models for circulating flow in confined geometry. First, we consider three-dimensional vortices confined between two parallel planar walls. Our examples include flows between two infinite planar walls, inside and outside a vertical cylinder bounded at the ends by horizontal plates, and in an axially confined annular region. Then we describe the special way in which the basis functions should be superposed so that a complicated steady velocity-field with three-dimensional vortical structures can be constructed. Two such cases are discussed to indicate that the derived solutions can be used for complicated fluid mechanical modelling.
Proximal bodies in hypersonic flow
Authors: LAURENCE STUART J. , DEITERDING R. , HORNUNG G. 
Published: October 2007

Hypersonic flows involving two or more bodies travelling in close proximity to one another are encountered in several important situations. The present work seeks to explore one aspect of the resulting flow problem by investigating the forces experienced by a secondary body when it is within the domain of influence of a primary body travelling at hypersonic speeds.An analytical methodology based on the blast wave analogy is developed and used to predict the secondary force coefficients for simple geometries in both two and three dimensions. When the secondary body is entirely inside the primary shocked region, the nature of the lateral force coefficient is found to depend strongly on the relative size of the two bodies. For two spheres, the methodology predicts that the secondary body will experience an exclusively attractive lateral force if the secondary diameter is larger than one-sixth of the primary diameter. The analytical results are compared with those from numerical simulations and reasonable agreement is observed if an appropriate normalization for the relative lateral displacement of the two bodies is used.Results from a series of experiments in the T5 hypervelocity shock tunnel are also presented and compared with perfect-gas numerical simulations, with good agreement. A new force-measurement technique for short-duration hypersonic facilities, enabling the experimental simulation of the proximal bodies problem, is described. This technique provides two independent means of measurement, and the agreement observed between the two gives a further degree of confidence in the results obtained.
Early Meiji Policies Towards the Ryukyus and the Taiwanese Aboriginal Territories
Authors: MIZUNO NORIHITO 
Published: October 2007

AbstractThis article focuses on Meiji Japan's policies towards the Ryukyus and the Taiwanese aboriginal territories in the early 1870s. The Meiji Government incorporated the Ryukyus by abolishing the kingdom in 1872 and sent expeditionary forces to the Taiwanese aboriginal territories on the pretext of the massacre of the shipwrecked Ryukyuans by the aboriginal tribes in 1874. Many Japanese and non-Japanese historians have argued that Japan started aggression on China by annexing its tributary state and invading its territories. In this article, I contend that the Ryukyu–Taiwan policies in the early Meiji period grew out of Japanese concerns over national security and prestige in a Western-dominated international environment but had no intention to secure Japan's independence and to aggrandise its national prestige by encroaching on China's territorial sovereignty.