bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of high‐ and low‐resolution electrospray ionization mass spectrometry for the analysis of naphthenic acid mixtures in oil sands process water
Authors: Martin Jonathan W. , Han Xiumei , Peru Kerry M. , Headley John V. 
Published: May 2008

AbstractThe oil sands regions of Northern Alberta, Canada, contain an estimated 1.7 trillion barrels of oil in the form of bitumen, representing the second largest deposit of crude oil in the world. A rapidly expanding industry extracts surface‐mined bitumen using alkaline hot water, resulting in large volumes of oil sands process water (OSPW) that must be contained on site due to toxicity. The toxicity has largely been attributed to naphthenic acids (NAs), a complex mixture of naturally occurring aliphatic and (poly‐)alicyclic carboxylic acids. Research has increasingly focused on the environmental fate and remediation of OSPW NAs, but an understanding of these processes necessitates an analytical method that can accurately characterize and quantify NA mixtures. Here we report results of an interlaboratory comparison for the analysis of pure commercial NAs and environmental OSPW NAs using direct injection electrospray ionization mass spectrometry (ESI‐MS) and high‐pressure liquid chromatography/high‐resolution mass spectrometry (HPLC/HRMS). Both methods provided very similar characterization of pure commercial NA mixture; however, the m/z selectivity of HPLC/HRMS was essential to prevent substantial false‐positive detections and misclassifications in OSPW NA mixtures. For a range of concentrations encompassing those found in OSPW (10–100 mg/L), both methods produced linear response, although concentrations of commercial NAs above 50 mg/L resulted in slight non‐linearity by HPLC/HRMS. A three‐fold lower response factor for total OSPW NAs by HPLC/HRMS was largely attributable to other organic compounds in the OSPW, including hydroxylated NAs, which may explain the substantial misclassification by ESI‐MS. For the quantitative analysis of unknown OSPW samples, both methods yielded total NA concentrations that correlated with results from Fourier transform infrared (FTIR), but the coefficients of determination were not high. Quantification by either MS method should therefore be considered semi‐quantitative at best, albeit either method has substantial value in environmental fate experiments where relative concentration changes are the desired endpoints rather than absolute concentrations. Copyright © 2008 John Wiley & Sons, Ltd.
Grain‐scale heterogeneities in the stable carbon and oxygen isotopic compositions of the international standard calcite materials (NBS 19, NBS 18, IAEA‐CO‐1, and IAEA‐CO‐8)
Authors: Ishimura Toyoho , Tsunogai Urumu , Nakagawa Fumiko 
Published: May 2008

AbstractWe determined grain‐scale heterogeneities (from 6 to 88 µg) in the stable carbon and oxygen isotopic compositions (δ13C and δ18O) of the international standard calcite materials (NBS 19, NBS 18, IAEA‐CO‐1, and IAEA‐CO‐8) using a continuous‐flow isotope ratio mass spectrometry (CF‐IRMS) system that realizes a simultaneous determination of the δ13C and the δ18O values with standard deviations (S.D.) of less than 0.05‰ for CO2 gas. Based on the S.D. of the δ13C and δ18O values determined for CO2 gases evolved from the different grains of the same calcite material, we found that NBS 19, IAEA‐CO‐1, and IEAE‐CO‐8 were homogeneous for δ13C (less than 0.10‰ S.D.), and that only NBS 19 was homogeneous for δ18O (less than 0.14‰ S.D.). On the level of single grains, we found that both IAEA‐CO‐1 and IAEA‐CO‐8 were heterogeneous for δ18O (1.46‰ and 0.76‰ S.D., respectively), and that NBS 18 was heterogeneous for both δ13C and δ18O (0.34‰ and 0.54‰ S.D., respectively). Closer inspection of NBS 18 grains revealed that the highly deviated isotopic compositions were limited to the colored grains. By excluding such colored grains, we could also obtain the homogeneous δ13C and δ18O values (less than 0.18‰ and less than 0.16‰ S.D., respectively) for NBS 18. We conclude that NBS 19, IAEA‐CO‐1, or pure grains in NBS 18 are suitable to be used as the standard reference material for δ13C, and that either NBS 19 or pure grains in NBS 18 are suitable to be used as the reference material for δ18O during the grain‐scale isotopic analyses of calcite. Copyright © 2008 John Wiley & Sons, Ltd.
Determination of disulfide bond patterns in laminin β1 chain N‐terminal domains by nano‐high‐performance liquid chromatography/matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight mass spectrometry
Authors: Kalkhof Stefan , Haehn Sebastian , Ihling Christian , Paulsson Mats , Smyth Neil , Sinz Andrea 
Published: May 2008

AbstractThe disulfide bonding patterns in the N‐terminal (LN) domains of the basement membrane protein laminin β1 have not been investigated so far. We report an in‐depth mass spectrometric analysis using offline nano‐high‐performance liquid chromatography/matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight mass spectrometry (nano‐HPLC/MALDI‐TOF/TOF‐MS) for determining the disulfide bond patterns in the LN‐domain of recombinant mouse laminin β1 chain for the first time. Mass spectra were recorded and the putatively disulfide‐linked peptides were subjected to LIFT‐TOF/TOF‐MS to confirm the disulfide bond. Screening the fragment ion mass spectra of disulfide‐linked peptides for characteristic 66‐amu patterns (34 u +32 u), arising from symmetric and asymmetric cleavage of disulfide bonds, facilitated their identification. Using various enzymes for proteolytic digestion of a recombinant laminin β1 chain N‐terminal protein fragment, a linear bonding pattern of the eight cysteine residues in the LN‐domain of the laminin β1 chain was observed with a (1‐2, 3‐4, 5‐6, 7‐8) connectivity of cysteines. The identical disulfide‐bonding pattern was found in E4, the N‐terminal laminin β1 chain fragment derived by elastase digestion of mouse tumor laminin‐111, confirming that this pattern also occurs in native laminin. Copyright © 2008 John Wiley & Sons, Ltd.
Identification of the related substances of tilmicosin by liquid chromatography/ion trap mass spectrometry
Authors: Stoev Georgi , Nazarov Valeri 
Published: May 2008

AbstractStructures of seven impurities of the veterinary drug tilmicosin have been elucidated by multiple fragmentation with ion trap tandem mass spectrometry. All related compounds possess the main lactone ring of tilmicosin. The differences in their structures are due to the hydroxyl, mycaminose, 3,5‐dimethylpiperidine and mycinose groups connected to C3, C5, C6, C14 of the lactone ring, respectively. The following compounds of the impurity profile of tilmicosin were identified: B – tilmicosin with a hydroxyl group at C3; C – tilmicosin without a methyl group at the N‐atom connected to C3 of the mycaminose ring; D – tilmicosin with a hydroxyl group at C6 of the mycaminose ring; E – tilmicosin with a methoxy group at C3, F – desmicosin; G – 20‐dihydrodesmicosin; and H – tilmicosin without a mycaminose ring. Isomers of the compounds B, C, D, E and H were identified by their mass chromatograms and retention times. The concentrations of the impurities varied in the range of 0.1% to 2.9%. Copyright © 2008 John Wiley & Sons, Ltd.
Two‐pulse delayed 532‐nm laser ionization of metals using collinear sub‐threshold beams
Authors: Alcántara José F. , Vadillo José M. , Laserna J. Javier 
Published: May 2008

AbstractTwo frequency‐doubled Nd:YAG lasers collinearly aligned were used to ionize different metals at specific interpulse delays. The beams were independently operated in order to attain full control over the energy. Each laser beam was always set at fluences below the ionization threshold and an evaluation of the effect that the interpulse delay has on the material ionization and the LIMS signal was performed. The different metallic targets studied (Cu, Si, Al, Ti, Fe, 314 AISI stainless steel) exhibit a characteristic ionization feature consisting of a clear enhancement in the ionization yield at interpulse delays around 60 ns when analyzed as pure foils. In addition, an improvement in the spectral resolution is observed at the specific interpulse delay. Our results indicate that proper control of the energy allows optimization of the different steps in the ionization process and they suggest that the effect of the first laser pulse impinging on the surface enhances the way in which the second pulse interacts with the solid. Copyright © 2008 John Wiley & Sons, Ltd.
Succinylmonocholine analytics as an example for selectivity problems in high‐performance liquid chromatography/tandem mass spectrometry, and resulting implications for analytical toxicology
Authors: Kuepper Uta , Musshoff Frank , Madea Burkhard 
Published: May 2008

AbstractThe determination and quantitation of drugs in biological matrices using high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) is becoming increasingly popular in analytical toxicology, while at the same time a growing awareness for the limits of this technique can be observed. Our group previously developed a rapid HPLC/ESI‐MS/MS method for the detection and quantitation of succinylcholine (SUX) and succinylmonocholine (SMC) using ion‐pairing extraction of samples with subsequent separation by gradient chromatography on a Synergi Hydro RP C18 column (4 µm, 150 × 2 mm). Identification of analytes was achieved in the multiple reaction monitoring (MRM) mode, using two characteristic ion transitions each, the respective analytes' retention time as well as co‐elution of stable isotopic analogues.In both native serum as well as urine an interference with the main MRM transition of SMC was found to co‐elute with this analyte, thus severely compromising the identification and quantitation of this target analyte. The interference was further shown to be eliminated from serum and urine by exposure to alkaline conditions and hence proven to share a key physicochemical property with SMC. The observed absence of the second and third most intense ion transitions of SMC in the unknown substance was the only useful distinction between both compounds.The detailed presentation of selectivity problems encountered during method development is intended to initiate further discussion on this yet underrepresented issue in HPLC/MS/MS. The present work emphasizes the need to monitor more than just one ion transition to confidently rule out signal interferences, ensure correct analyte identification as well as quantitation, and thus avoid false‐positive results. In this context, the employment of minor MRM transitions for the quantitation and identification of a given analyte is presented as a satisfactory solution to HPLC/MS/MS selectivity problems, and proposed as a possible alternative to previously published approaches. Copyright © 2008 John Wiley & Sons, Ltd.
Atomic force microscopy application for degradation diagnostics in library heritage
Authors: Coluzza Carlo , Bicchieri Marina , Monti Michela , Piantanida Giovanna , Sodo Armida 
Published: May 2008

AbstractAtomic Force Microscopy was used on pure cotton cellulose paper to characterize the relationship between surface topographies and cellulose degradation patterns. Whatman N.1 chromatography paper and Fabriano Umbria paper artificially aged with different procedures and then naturally aged‐were evaluated together with a sample from an original book. Evidence is found of a clear distinction between surface heights distribution of chiefly oxidised samples with respect to those where hydrolysis is the dominant process. In both cases, deteriorated paper shows surface features well different from the paper in good preservation state, in agreement to results from previous experiments. This is a first step that could open the way to AFM application as a qualitative diagnostic tool for library materials. The only way to achieve such a goal is to extend the experimentation to a wider population of paper samples, so to improve the statistical evaluation. Copyright © 2008 John Wiley & Sons, Ltd.
Mesoporous Silica Nanoparticles Improve Magnetic Labeling Efficiency in Human Stem Cells
Authors: Liu Hon‐Man , Wu Si‐Han , Lu Chen‐Wen , Yao Ming , Hsiao Jong‐Kai , Hung Yann , Lin Yu‐Shen , Mou Chung‐Yuan , Yang Chung‐Shi , Huang Dong‐Ming , Chen Yao‐Chang 
Published: May 2008

AbstractTumblerlike magnetic/fluorescein isothiocyanate (FITC)‐labeled mesoporous silica nanoparticles, Mag‐Dye@MSNs, have been developed, which are composed of silica‐coated core–shell superparamagnetic iron oxide (SPIO@SiO2) nanoparticles co‐condensed with FITC‐incorporated mesoporous silica. Mag‐Dye@MSNs can label human mesenchymal stem cells (hMSCs) through endocytosis efficiently for magnetic resonance imaging (MRI) in vitro and in vivo, as manifested by using a clinical 1.5‐T MRI system with requirements of simultaneous low incubation dosage of iron, low detection cell numbers, and short incubation time. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes and osteocytes, which can still be readily detected by MRI. Moreover, a higher MRI signal intensity decrease is observed in Mag‐Dye@MSN‐treated cells than in SPIO@SiO2‐treated cells. This is the first report that MCM‐41‐type MSNs are advantageous to cellular uptake, as manifested by a higher labeling efficiency of Mag‐Dye@MSNs than SPIO@SiO2.
A SERS‐Active Nanocrystalline Pd Substrate and its Nanopatterning Leading to Biochip Fabrication
Authors: Bhuvana Thiruvelu , Kulkarni Giridhar U. 
Published: May 2008

AbstractNanocrystalline metallic Pd films have been produced by thermolysis of Pd hexadecanethiolate deposited on a Si surface. The particle size was in the range of 50–60 nm based on electron and atomic force microscopy. The Pd surface produced was found to be surface‐enhanced Raman scattering (SERS) active with an enhancement factor of ≈105. The electron‐resist behavior of Pd thiolate is exploited in conceptualizing a prototype chip with patterned Pd regions that are SERS active, called “SERS bits”, which host different biomolecules.
Fluorescent Bionanoprobes to Characterize Cytoadhesion and Cytoinvasion
Authors: Fillafer Christian , Friedl Daniela S. , Wirth Michael , Gabor Franz 
Published: May 2008

AbstractTo overcome current limitations in diagnostic imaging and targeted drug delivery, a highly versatile tool is presented that can be used to representatively investigate the effects of submicroparticles intended for the use in biological systems. An effective approach to render colloids trackable is developed by stable attachment of the fluorescent probe BODIPY 493/503 (BOD: 4,4‐difluoro‐1,3,5,7,8‐pentamethyl‐4‐bora‐3a,4a‐diaza‐s‐indacene) to a biodegradable and biocompatible particle core matrix. BOD submicroparticles are shown to be stable, can be surface modified, and exhibit high fluorescence emission. Upon conjugation with human serum albumin (nonspecific) and wheat germ agglutinin (biorecognitive) as model ligands explicit differences are found in the cytoadhesive and cytoinvasive characteristics of the submicroparticles using Caco‐2 cells. These results demonstrate the potency of BOD‐labeled colloids as a versatile analytical platform for a multifaceted investigation of cell‐particle interactions in biological systems.
Frictional contact models with local compliance: semismooth formulation
Authors: Pang J.‐S. 
Published: May 2008

AbstractA complementarity‐based, 3‐dimensional frictional contact model with local compliance and damping was introduced in the Ph.D. thesis [45] and the paper [47] and was subsequently studied extensively in [31, 49]. In this paper, we examine a variant of this model where there is no damping in the normal contact forces but there is coupled stiffness between the normal and tangential forces via body deformations. We show that this frictional contact model admits a formulation as an ordinary differential equation with a boundedly Lipschitz continuous, albeit implicitly defined, semismooth right‐hand side with global linear growth. Several major consequences follow from such a formulation: (a) existence and uniqueness of a continuously differentiable solution trajectory originated from an arbitrary initial state, (b) finite contact forces that are semismooth functions of the system state, (c) semismooth dependence of the trajectory on the initial state, and (d) convergence of a shooting method for solving two‐point boundary problems. The derived results are valid for both a dynamic model and a quasistatic model, the latter being one in which inertia effects are ignored, and for a broad class of friction cones that include the well‐known quadratic Coulomb cone and its polygonal approximations. Part II of this work establishes the absence of Zeno states in such a frictional contact model.
An inverse problem for a linear Schrödinger equation in the presence of inhomogeneities of small volumes
Authors: Khelifi A. 
Published: May 2008

AbstractIn this paper we prove that the knowledge of the partial (on part of the boundary) dynamic boundary measurements for the Schrödinger equation on any open subset Γ of the boundary determines uniquely the potential. Using a global Carleman estimate, we also derive a stability result with appropriate norms provided that Γ satisfies a suitable geometrical condition.
Spectrum of an operator arising elastic system with local K‐V damping
Authors: Xu G.Q. , Mastorakis N.E. 
Published: May 2008

AbstractIn this paper, we analyze the spectrum of an operator arising in elastic system with local K‐V damping, whose vibration is modelled as the Euler–Bernoulli beam. Suppose that the beam is clamped at both ends, at its internal bonded a patch made of smart material that produces the Kelvin–Voigt damping. Our aim is to study the spectrum of the operator determined by such a system. By a detail analysis, we show that the spectrum consists of the point spectrum and continuous spectrum, in which the point spectrum is a denumerable set, and the continuous spectrum is a segment on the real axis. Under certain conditions, the continuous spectrum is possibly the whole half line, and also degenerates possibly one point. For a special case, we give the asymptotic expression of the point spectrum.
Oscillations of a magneto‐sensitive elastic sphere
Authors: Altenbach H. , Brigadnov I.A. , Eremeyev V.A. 
Published: May 2008

AbstractMagneto‐sensitive (MS) or magnetorheological (MR) elastomers are smart materials whose mechanical properties change instantly by the application of a magnetic field. MS elastomers are widely used in the practice as elements of MEMS (sensors, actuators, etc.), for example, in medical devices. The behavior of MS elastomers under time‐dependent magnetic field is a complex process and till now is not investigated in all details. Here we present the statements of the dynamic boundary‐value problem of a MS elastomer and demonstrate the special features of the dynamic behavior of such system. As an example both the nonlinear and the linear oscillations of a MS elastic sphere are considered. The control of radially symmetric oscillations of MS elastic sphere by a homogeneous magnetic field is investigated. The presented results can be used for control and generation of radially symmetric acoustic waves using magnetic field excitation.
Homotopy analysis of unsteady boundary‐layer flow started impulsively from rest along a symmetric wedge
Authors: Xu H. , Pop I. 
Published: May 2008

AbstractAn investigation of the velocity boundary‐layer growth resulting from an impulsively started wedge is presented in this paper. By introducing a new set of scaled coordinates, the governing equations describing the impulsively set into motion Falkner‐Skan flows is transformed to a partial differential equation but the number of independent variables are reduced from three to two. Note that the new time scaling avoids the appearance of the singularity resulting from the logarithmic function ln(1‐ξ), thus reducing the difficulties of computations. Analytical approximations for the momentum boundary layer are obtained, which are valid for all time. The results are then matched numerically using the Keller‐Box method.
Energy integral in fracture mechanics (J‐integral) and Gauss‐Bonnet Theorem
Authors: Yamasaki K. , Nagahama H. 
Published: May 2008

AbstractThe J‐integral (a path‐independent energy integral) formalism is the standard method of analyzing nonlinear fracture mechanics. It is shown that the energy density of deformation fields in terms of the homotopy operator corresponds to the J‐integral for dislocation‐disclination fields and gives the force on dislocation‐disclination fields as a physical interpretation. The continuum theory of defects gives a natural framework for understanding the topological aspects of the J‐integral. This geometric interpretation gives that the J‐integral is an alternative expression of the well‐known theorem in differential geometry, i.e., the Gauss‐Bonnet theorem (with genus = 1). The geometrical expression of the J‐integral shows that the Eshelby's energy‐momentum (the physical quantity of the material space) is closely related to the Einstein 3‐form (the geometric objects of the material space).
Application of Continuum Damage Mechanics in discontinuous crack formation: Forward extrusion chevron predictions
Authors: Soyarslan C. , Tekkaya A.E. , Akyuz U. 
Published: May 2008

AbstractMaterializing Continuum Damage Mechanics (CDM), numerical modeling of discrete internal cracks, namely central bursts, in direct forward extrusion process is presented. Accordingly, in a thermodynamically consistent setting, a local Lemaitre variant damage model with quasi‐unilateral evolution is coupled with hyperelastic‐plasticity. The formulations are constructed in the principal axes where simultaneous local integration schemes are efficiently developed. To this end, the framework is implemented as ABAQUS/VUMAT subroutine to be used in an explicit FE solution scheme, and utilized in direct forward extrusion simulations for bearing steel, 100Cr6. Discontinuous cracks are obtained with the element deletion procedure, where the elements reaching the critical damage value are removed from the mesh. The periodicity of the cracks shows well accordance with the experimental facts. The investigations reveal that, application of the quasi‐unilateral conditions together with the crack closure parameter has an indispensable effect on the damage accumulation zones by determining their internal or superficial character.
Fatty acids—Synthetic or agrichemical
Authors: Fineberg Herbert 
Published: May 2008

Abstract and SummaryThe cost of producing fatty acids from agricultural products and the cost of producing them from petroleum and natural gas both depend heavily on the cost and availability of energy. The costs of the agrichemical acids and of the petrochemical acids will probably increase at the same rate in the future. Therefore, the choice of which one to use will depend at least as much on chemical composition and performance as on price.