bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quadriceps muscle endurance in patients with chronic obstructive pulmonary disease
Authors: Hul Alex Van'T , Harlaar Jaap , Gosselink Rik , Hollander Peter , Postmus Piet , Kwakkel Gert 
Published: January 2004

AbstractThe purpose of this study was to compare quadriceps muscle strength (maximal voluntary contraction, MVC), endurance (TLIM), and dynamic work capacity (WLIM) in 89 patients (57 men and 32 women) with chronic obstructive pulmonary disease (COPD) to 31 healthy controls (20 men and 11 women). Compared with the healthy subjects, COPD patients demonstrated statistically significant (P < 0.05) lower values for MVC, TLIM and WLIM. The MVC was 20–30% lower, whereas TLIM and WLIM were 70–80% lower in the patients. Stepwise multiple regression analysis revealed that pulmonary function variables contributed only partially to the explanation of variance in MVC, TLIM, and WLIM. Our results indicate that in patients with COPD, quadriceps muscle endurance and dynamic work capacity are impaired to a greater extent than is quadriceps muscle strength. For rehabilitation purposes, the findings may lead to more specific exercise programs, further enhancing rehabilitation outcomes in terms of functional abilities and social participation. Muscle Nerve 29: 267–274, 2004
Electrodiagnostic services in the United States
Authors: Dillingham Timothy R. , Pezzin Liliana E. , Rice J. Bradford 
Published: January 2004

AbstractTo identify patterns of service provision in the United States, electrodiagnostic encounters were characterized by analyzing data from the 1998 MarketScan Commercial Claims & Encounters Database (The MEDSTAT Group). Electrodiagnostic‐related claims were identified using CPT codes for nerve conduction studies, electromyography, and somatosensory evoked potentials. Over 130,000 electrodiagnostic claims representing 48,207 separate electrodiagnostic encounters were identified. Neurologists accounted for the highest percentage of physician providers (23.6%), followed closely by physiatrists (22%). Physiatrists performed the services at a higher rate than any other provider (886.3 studies per 100 practicing physiatrists). Electrodiagnostic encounters by nonphysician providers accounted for 16.9% of all studies. Physical therapists were the dominant nonphysician providers of electrodiagnostic services (9.3%), followed by podiatrists (5.5%). Physician providers had a median of three claims per encounter compared with one claim per encounter for nonphysician providers. The relatively large proportion of studies conducted by nonphysicians, as well as their limited extent of testing, raises concerns about the quality of care for these patients. These quality issues should be addressed in future studies. Muscle Nerve 29: 198–204, 2004
A coupling of multi‐zone curved Galerkin BEM with finite elements for independently modelled sub‐domains with non‐matching nodes in elasticity
Authors: Ganguly S. , Layton J. B. , Balakrishna C. 
Published: January 2004

AbstractWhen the different parts of a structure are modelled independently by BEM or FEM methods, it is sometimes necessary to put the parts together without remeshing of the nodes along the part interfaces. Frequently the nodes do not match along the interface. In this work, the symmetric Galerkin multi‐zone curved boundary element is a fully symmetric formulation and is the method used for the boundary element part. For BEM–FEM coupling it is then necessary to interpolate the tractions in‐between the non‐matching nodes for the FEM part. Finally, the coupling is achieved by transforming the finite element domains to equivalent boundary element domains in a block symmetric formulation. This system is then coupled with a boundary element domain with non‐matching nodes in‐between. Copyright © 2004 John Wiley & Sons, Ltd.
Perfectly matched layers for transient elastodynamics of unbounded domains
Authors: Basu Ushnish , Chopra Anil K. 
Published: January 2004

AbstractOne approach to the numerical solution of a wave equation on an unbounded domain uses a bounded domain surrounded by an absorbing boundary or layer that absorbs waves propagating outward from the bounded domain. A perfectly matched layer (PML) is an unphysical absorbing layer model for linear wave equations that absorbs, almost perfectly, outgoing waves of all non‐tangential angles‐of‐incidence and of all non‐zero frequencies. In a recent work [Computer Methods in Applied Mechanics and Engineering 2003; 192: 1337–1375], the authors presented, inter alia, time‐harmonic governing equations of PMLs for anti‐plane and for plane‐strain motion of (visco‐) elastic media. This paper presents (a) corresponding time‐domain, displacement‐based governing equations of these PMLs and (b) displacement‐based finite element implementations of these equations, suitable for direct transient analysis. The finite element implementation of the anti‐plane PML is found to be symmetric, whereas that of the plane‐strain PML is not. Numerical results are presented for the anti‐plane motion of a semi‐infinite layer on a rigid base, and for the classical soil–structure interaction problems of a rigid strip‐footing on (i) a half‐plane, (ii) a layer on a half‐plane, and (iii) a layer on a rigid base. These results demonstrate the high accuracy achievable by PML models even with small bounded domains. Copyright © 2004 John Wiley & Sons, Ltd.
XFEM for direct evaluation of mixed mode SIFs in homogeneous and bi‐materials
Authors: Liu X. Y. , Xiao Q. Z. , Karihaloo B. L. 
Published: January 2004

AbstractThe extended finite element method (XFEM) is improved to directly evaluate mixed mode stress intensity factors (SIFs) without extra post‐processing, for homogeneous materials as well as for bimaterials. This is achieved by enriching the finite element (FE) approximation of the nodes surrounding the crack tip with not only the first term but also the higher order terms of the crack tip asymptotic field using a partition of unity method (PUM). The crack faces behind the tip(s) are modelled independently of the mesh by displacement jump functions. The additional coefficients corresponding to the enrichments at the nodes of the elements surrounding the crack tip are forced to be equal by a penalty function method, thus ensuring that the displacement approximations reduce to the actual asymptotic fields adjacent to the crack tip. The numerical results so obtained are in excellent agreement with analytical and numerical results available in the literature. Copyright © 2004 John Wiley & Sons, Ltd.
Combined extended and superimposed finite element method for cracks
Authors: Lee Sang‐Ho , Song Jeong‐Hoon , Yoon Young‐Cheol , Zi Goangseup , Belytschko Ted 
Published: January 2004

AbstractA combination of the extended finite element method (XFEM) and the mesh superposition method (s‐version FEM) for modelling of stationary and growing cracks is presented. The near‐tip field is modelled by superimposed quarter point elements on an overlaid mesh and the rest of the discontinuity is implicitly described by a step function on partition of unity. The two displacement fields are matched through a transition region. The method can robustly deal with stationary crack and crack growth. It simplifies the numerical integration of the weak form in the Galerkin method as compared to the s‐version FEM. Numerical experiments are provided to demonstrate the effectiveness and robustness of the proposed method. Copyright © 2004 John Wiley & Sons, Ltd.
The computation of the J integral with the traction boundary integral equation
Authors: Chen Songying , Wang Leqin , Jiao Lei 
Published: January 2004

AbstractThe solutions of the displacement boundary integral equation (BIE) are not uniquely determined in certain types of boundary conditions. Traction boundary integral equations that have unique solutions in these traction and mixed boundary cases are established. For two‐dimensional linear elasticity problems, the divergence‐free property of the traction boundary integral equation is established. By applying Stokes' theorem, unknown tractions or displacements can be reduced to computation of traction integral potential functions at the boundary points. The same is true of the J integral: it is divergence‐free and the evaluation of the J integral can be inverted into the computation of the J integral potential functions at the boundary points of the cracked body. The J integral can be expressed as the linear combination of the tractions and displacements from the traction BIE on the boundary of the cracked body. Numerical integrals are not needed at all. Selected examples are presented to demonstrate the validity of the traction boundary integral and J integral. Copyright © 2004 John Wiley & Sons, Ltd.
Theoretical study of magnetic coupling interaction in terephthalato‐bridged Ni(II) binuclear systems
Authors: Bi Siwei , Liu Chengbu 
Published: January 2004

AbstractThe density functional theory combined with broken‐symmetry approach has been successfully extended into the study of the long‐range weak coupling interaction in a binuclear Ni(II) complex bridged by terephthalate dianion. The calculated magnetic coupling constant (−0.27 cm−1) is well in agreement with the experimental one (−0.33 cm−1). The relative magnitude of the energies of different spin states has been obtained. The spin delocalization and spin polarization occur between two Ni(II) ions, based on the analysis of the spin density distribution. Weak antiferromagnetic behavior in such a system may result from the competition between spin delocalization and spin polarization where the former is dominant. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Structural analysis of certain linear operators representing chemical network systems via the existence and uniqueness theorems of spectral resolution VII
Authors: Arimoto Shigeru , Spivakovsky Mark , Ohno Hiromu , Zizler Peter , Zuidwijk Rob A. , Taylor Keith F. , Yamabe Tokio , Mezey Paul G. 
Published: January 2004

AbstractThe present Part VII of this series of articles is a direct extension of Part VI, where (1) fundamental methodology in the repeat space theory (RST) and (2) frontier electron theory of reactivity indices were theoretically linked. This part presents an estimate of the size of the regular index set, which was a central notion in Part VI, and two new theorems that are simpler and more powerful than the main theorem in Part VI. The main theorem in this part enables one to globally contextualize the Generalized Alpha Existence Theorem (a theorem essential in the RST and proved in Part V) and the μ Existence Theorem (derived from the main theorem in Part VI) into the star algebra structure of the generalized repeat space 𝒳r(q, d). © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Critical evaluation of the bond order concept with application to thermal hydrogen shifts
Authors: Buck Henk 
Published: January 2004

AbstractSince Coulson introduced the concept of bond order into the molecular orbital theory its significance has been proven as an important tool for the discussion and calculation of bond strength and bond length. On studying simple π‐conjugated odd‐ and even‐membered carbonhydrogen systems in an open and cyclic geometry, it could be shown that the use of the concept of bond order with respect to bond length in geometric representations for ground or transition states must be handled with caution. This has been concluded from a theoretical study of Okajima and Imafuku on chlorine and hydrogen thermal shifts in (cyclo)pentadiene and cycloheptatriene compounds. The results of their calculations and our previous calculations on the [1,5]‐H shift in cis‐1,3‐pentadiene following a suprafacial transition state compared with a shift of the migrating hydrogen in the plane of the carbon skeleton ask for a critical evaluation. The impact on the result of the π systems under investigation and on the results of others will be disclosed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Combinatorical analysis of the Rayleigh–Schrödinger perturbation theory based on a circular scale of time
Authors: Olszewski S. 
Published: January 2004

AbstractContractions of events examined on a circular scale of time have been applied to combinatorical analysis of the Rayleigh–Schrödinger (RS) perturbation theory. The main practical aim of the analysis was to split any of the RS perturbation terms for energy belonging to an order N into product of RS energy terms belonging to perturbation orders N′, N″, N‴ … lower than N. Solely the perturbation of a nondegenerate state is examined. The analysis is illustrated by the whole ensemble of the RS perturbation terms entering the perturbation orders N = 8, 9, and 10 taken as examples. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Unitarily invariant decomposition of arbitrary Hermitian matrices of physical interest
Authors: Alcoba Diego R. 
Published: January 2004

AbstractThe aim of this article is to report a unitarily invariant decomposition of arbitrary Hermitian second‐order matrices. For the particular cases of antisymmetrical and symmetrical Hermitian second‐order matrices this decomposition reduces to the unitarily invariant decompositions of antisymmetrical and symmetrical Hermitian second‐order matrices reported by Coleman, A. J. In: Erdahl, R. M., ed. Reduced Density Operators with Applications to Physical and Chemical Systems II, Queen's Paper in Pure and Applied Mathematics, vol. 40; Queen's University: Kingston, Ontario, 1974 and Sun et al. Int J Quantum Chem 1984, 25, 1045, respectively. An illustration of physical interest is reported. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Matrix‐assisted laser desorption/ionization mass spectrometry for the evaluation of the C‐terminal lysine distribution of a recombinant monoclonal antibody
Authors: Lazar Alexandru C. , Kloczewiak Marek A. , Mazsaroff Istvan 
Published: January 2004

AbstractRecombinant monoclonal antibodies produced using mammalian cell lines contain multiple chemical modifications. One specific modification resides on the C‐terminus of the heavy chain. Enzymes inside the cell can cleave the C‐terminal lysine from the heavy‐chain molecules, and variants with and without C‐terminal lysine can be produced. In order to fully characterize the protein, there is a need for analytical methods that are able to account for the different product variants. Conventional analytical methods used for the measurement of the distribution of the two different variants are based on chemical or enzymatic degradation of the protein followed by chromatographic separation of the degradation products. Chromatographic separations with gradient elution have long run times, and analyses of multiple samples are time‐consuming. This paper reports development of a novel method for the determination of the relative amounts of the two C‐terminal heavy‐chain variants based on matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) measurements of the cyanogen bromide degraded recombinant monoclonal antibody products. The distribution of the variants is determined from the MALDI‐TOF mass spectra by measuring the peak areas of the two C‐terminal peptides. The assay was used for the assessment of the C‐terminal lysine distribution in different development lots. The method was able to differentiate between the products obtained using the same cell line as well as between products obtained from different cell lines. Copyright © 2004 John Wiley & Sons, Ltd.
Continuous‐flow isotope analysis of the deuterium/hydrogen ratio in atmospheric hydrogen
Authors: Rhee Tae Siek , Mak John , Röckmann Thomas , Brenninkmeijer Carl A. M. 
Published: January 2004

AbstractA convenient method is described for analyzing the deuterium/hydrogen (D/H) ratio of atmospheric molecular hydrogen (H2) based on mass spectrometric isotope‐ratio monitoring. The method requires small amounts of air (∼300 mL STP), is operated on‐line, and comprises four steps: (1) the condensation of the air matrix at ∼40 K; (2) the collection of the non‐condensed components of the air sample (H2, Ne, He, and traces of N2) in a 5 Å molecular sieves pre‐concentration trap at ∼63 K; (3) gas chromatographic purification of H2 in a flow of He; and (4) quantification of the D/H ratio in an isotope‐ratio mass spectrometer. The precision of the determination of the D/H ratio is better than 2‰, which is comparable to, or better than, that obtained by conventional duel‐inlet off‐line analysis. There are, however, discrepancies relative to the D/H ratios determined by conventional duel‐inlet analysis. This is due to differences in peak shape between reference and sample air, depending on the amount of H2 injected. Consequently, calibration runs are required. After the calibration of the system, we obtained an accuracy of 1.5‰, so that the accumulated uncertainty is estimated to be less than 4‰. The method also allows determination of the H2 concentration, with an uncertainty estimated to be 2%. Copyright © 2004 John Wiley & Sons, Ltd.
Using dual‐bacterial denitrification to improve δ15N determinations of nitrates containing mass‐independent 17O
Authors: Coplen T. B. , Böhlke J. K. , Casciotti K. L. 
Published: January 2004

AbstractThe bacterial denitrification method for isotopic analysis of nitrate using N2O generated from Pseudomonas aureofaciens may overestimate δ15N values by as much as 1–2‰ for samples containing atmospheric nitrate because of mass‐independent 17O variations in such samples. By analyzing such samples for δ15N and δ18O using the denitrifier Pseudomonas chlororaphis, one obtains nearly correct δ15N values because oxygen in N2O generated by P. chlororaphis is primarily derived from H2O. The difference between the apparent δ15N value determined with P. aureofaciens and that determined with P. chlororaphis, assuming mass‐dependent oxygen isotopic fractionation, reflects the amount of mass‐independent 17O in a nitrate sample. By interspersing nitrate isotopic reference materials having substantially different δ18O values with samples, one can normalize oxygen isotope ratios and determine the fractions of oxygen in N2O derived from the nitrate and from water with each denitrifier. This information can be used to improve δ15N values of nitrates having excess 17O. The same analyses also yield estimates of the magnitude of 17O excess in the nitrate (expressed as Δ17O) that may be useful in some environmental studies. The 1‐σ uncertainties of δ15N, δ18O and Δ17O measurements are ±0.2, ±0.3 and ±5‰, respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of derivatized and underivatized theanine enantiomers by high‐performance liquid chromatography/atmospheric pressure ionization‐mass spectrometry
Authors: Desai Meera J. , Armstrong Daniel W. 
Published: January 2004

AbstractTheanine, a naturally occurring non‐proteinic amino acid found in tea leaves, has demonstrated wide‐ranging physiological activity, from lowering blood pressure to enhancing the anti‐tumor activity of chemotherapeutic drugs. The chiral nature of theanine suggests that enantiospecificity plays a significant role in its various pharmacological functions. Using the Chirobiotic T (teicoplanin) chiral stationary phase, native and derivatized theanine enantiomers were separated and detected via high‐performance liquid chromatography (HPLC) coupled to atmospheric pressure ionization mass spectrometry (API‐MS). With the use of flow rates compatible with each ionization source, native theanine standards achieved excellent sensitivity and detection limits (10 ng/mL) for both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). Optimum sensitivity and detection limits for derivatized theanine standards were achieved using ESI‐MS. The enantiomeric composition of six commercially available L‐theanine samples was evaluated using the high‐flow APCI‐MS method and confirmed with photodiode array detection. Five of the six products contained significant amounts of D‐theanine. Only one product, SunTheanine®, appeared to contain only the L‐theanine enantiomer. Copyright © 2004 John Wiley & Sons, Ltd.
Comparison of mono‐ and polyatomic primary ions for the characterization of organic dye overlayers with static secondary ion mass spectrometry
Authors: Lenaerts Jens , Vaeck Luc Van , Gijbels Renaat , Luppen Jaymes Van 
Published: January 2004

AbstractOrganic carbocyanine dye coatings have been analyzed by time‐of‐flight static secondary ion mass spectrometry (TOF‐S‐SIMS) using three types of primary ions: Ga+ operating at 25 keV, and Xe+ and SF5+ both operating at 9 keV. Secondary ion yields obtained with these three primary ions have been compared for coatings with different layer thickness, varying from (sub)‐monolayer to multilayers, on different substrates (Si, Ag and AgBr cubic microcrystals). For (sub)‐monolayers deposited on Ag, Xe+ and SF5+ primary ions generate similar precursor ion intensities, but with Ga+ slightly lower precursor ion intensities were obtained. Thick coatings on Ag as well as mono‐ and multilayers on Si produce the highest precursor and fragment ion intensities with the polyatomic primary ion. The yield difference between SF5+ and Xe+ can reach a factor of 6. In comparison with Ga+, yield enhancements by up to a factor of 180 are observed with SF5+. For the mass spectrometric analysis of dye layers on AgBr microcrystals, SF5+ again proves to be the primary ion of choice. Copyright © 2004 John Wiley & Sons, Ltd.
Simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene using high‐performance liquid chromatography/hybrid quadrupole time‐of‐flight mass spectrometry
Authors: Marchese Stefano , Curini Roberta , Gentili Alessandra , Perret Daniela , Rocca Lucia Mainero 
Published: January 2004

AbstractA simple and rapid method using reversed‐phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene in human urine specimens and standard solutions is described. A hybrid quadrupole/time‐of‐flight (QqTOF) mass spectrometer was compared for the determination of metabolite of aromatic solvents in urine samples. The metabolites selected were: trans,trans‐muconic acid, hippuric acid, o‐, m‐ and p‐methylhippuric acid and phenylglyoxylic acid. The compounds were well separated from each other on narrow‐bore 1‐mm i.d. reversed‐phase LC C‐18 columns. Average recoveries for loading 100 μL of urine samples varied from 88–110% and the quantification limits were less than 30 ng/mL for each analyte (3 ng/mL for trans,trans‐muconic acid). The qualitative information obtained (mass accuracy, resolution and full‐scan spectra) with the QqTOF mass spectrometer allows a secure identification of analytes in biological matrices. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and electrospray ionization mass spectra of AZT/d4T boranophosphates
Authors: Lin Changxue , Fu Hua , Zhao Yufen 
Published: January 2004

AbstractNew anti‐HIV prodrugs, conjugates of AZT and d4T with boranophosphates, were prepared by the H‐phosphonate method. Their structures were determined by negative ion electrospray ionization mass spectrometry (ESI‐MS) in conjunction with tandem mass spectrometry (MS/MS). The fragmentation pathways were investigated, and most of the fragment ions contained the boranophosphate or phosphinate group. Copyright © 2004 John Wiley & Sons, Ltd.